JET PROPULSION BOAT

Abstract

A jet propulsion boat includes: a boat body; a jet water stream generation device that jets a jet water stream from the boat body to impart a propulsion force in a front-rear direction to the boat body; a steering device including a steering operator operated by a driver, and changes an orientation in a lateral direction of a propulsion force of the jet water stream generation device in response to an operation on the steering operator; an auxiliary propulsion device provided on the boat body to impart a propulsion force in a lateral direction to the boat body; and a control device that controls the auxiliary propulsion device based on an operation of the steering device.

Claims

1. A jet propulsion boat comprising: a boat body; a jet water stream generation device that jets a jet water stream from the boat body to impart a propulsion force in a front-rear direction to the boat body; a steering device including a steering operator operated by a driver, and changes an orientation in a lateral direction of a propulsion force of the jet water stream generation device in response to an operation on the steering operator; an auxiliary propulsion device provided on the boat body to impart a propulsion force in a lateral direction to the boat body; and a control device that controls the auxiliary propulsion device based on an operation of the steering device.

2. The jet propulsion boat according to claim 1, wherein the control device controls the auxiliary propulsion device based on an operation of the steering device and a state of the boat body.

3. The jet propulsion boat according to claim 2, wherein the control device drives the auxiliary propulsion device when an operation amount of the steering device is greater than a predetermined amount and the boat body is in a predetermined state.

4. The jet propulsion boat according to claim 1, wherein the control device controls the auxiliary propulsion device such that the orientation in the lateral direction of the propulsion force of the jet water stream generation device is same as an orientation in the lateral direction of the propulsion force of the auxiliary propulsion device.

5. The jet propulsion boat according to claim 1, wherein the control device controls the auxiliary propulsion device such that the orientation in the lateral direction of the propulsion force of the jet water stream generation device is opposite to an orientation in the lateral direction of the propulsion force of the auxiliary propulsion device.

6. The jet propulsion boat according to claim 1, wherein the control device increases the propulsion force of the auxiliary propulsion device as an operation amount of the steering device is large.

7. The jet propulsion boat according to claim 1, wherein the control device increases the propulsion force of the auxiliary propulsion device as the propulsion force of the jet water stream generation device is large.

8. The jet propulsion boat according to claim 1, comprising a throttle operator provided on the boat body and operated by the driver to increase or decrease the propulsion force of the jet water stream generation device, wherein when the boat body is traveling, the steering device is operating in a direction of turning the boat body to one side of the lateral direction, and an operation amount of the throttle operator is equal to or less than a predetermined determination operation amount, the control device drives the auxiliary propulsion device and controls the auxiliary propulsion device such that the propulsion force of the auxiliary propulsion device acts in a direction of turning the boat body to the one side of the lateral direction.

9. The jet propulsion boat according to claim 1, wherein the control device determines whether a predetermined stabilization condition is satisfied based on the operation of the steering device, and when the stabilization condition is satisfied, the control device controls the auxiliary propulsion device such that the propulsion force of the auxiliary propulsion device acts in a direction of stabilizing an attitude of the boat body.

10. The jet propulsion boat according to claim 9, wherein the stabilization condition includes a condition that a yaw rate of the boat body exceeds an allowable range set based on the operation of the steering device, and when the stabilization condition is satisfied, the control device drives the auxiliary propulsion device and controls the auxiliary propulsion device such that the yaw rate of the boat body falls within the allowable range.

11. The jet propulsion boat according to claim 9, wherein the stabilization condition includes a condition that a roll angle or a roll rate of the boat body exceeds a predetermined allowable range, and when the stabilization condition is satisfied, the control device drives the auxiliary propulsion device and controls the auxiliary propulsion device such that the roll angle or the roll rate exceeding the allowable range falls within the allowable range.

12. The jet propulsion boat according to claim 1, wherein the steering operator is pivotally operated in the lateral direction from a predetermined neutral position, and includes a detection device that detects an operation direction and an operation amount of the steering operator, and the control device controls the auxiliary propulsion device based on a detection result of the detection device.

13. The jet propulsion boat according to claim 1, wherein the control device switches a control mode of the jet water stream generation device between a plurality of modes, and controls the auxiliary propulsion device based on the operation of the steering device and a type of the control mode of the jet water stream generation device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a partially broken side view of a jet propulsion boat according to an embodiment of the present disclosure;

[0006] FIG. 2 is a plan view of the jet propulsion boat;

[0007] FIG. 3 is a schematic perspective view showing a periphery of a jet nozzle provided in the jet propulsion boat;

[0008] FIG. 4 is a schematic plan view showing the periphery of the jet nozzle;

[0009] FIG. 5 is a schematic view showing a motion of a boat body of the jet propulsion boat;

[0010] FIG. 6 is a schematic side view showing the periphery of the jet nozzle;

[0011] FIG. 7 is a plan cross-sectional view schematically showing a structure of an auxiliary propulsion device of the jet propulsion boat;

[0012] FIG. 8 is a functional block diagram showing a control system of the jet propulsion boat;

[0013] FIG. 9 is a display example of an image displayed on a display provided on the boat body of the jet propulsion boat;

[0014] FIG. 10 is a flowchart showing control content of a thruster motor when a first condition is satisfied;

[0015] FIG. 11 is a flowchart showing control content of the thruster motor when a second condition is satisfied;

[0016] FIG. 12 is a flowchart showing control content of the thruster motor when a third condition is satisfied;

[0017] FIG. 13 is a flowchart showing control content of the thruster motor when a fourth condition is satisfied;

[0018] FIG. 14 is a view schematically showing the motion of the boat body when the first condition is satisfied;

[0019] FIG. 15 is a view schematically showing the motion of the boat body when the second condition is satisfied;

[0020] FIG. 16 is a schematic view for describing actions and effects when the thruster motor is driven in association with satisfaction of the third condition; and

[0021] FIG. 17 is a view schematically showing the motion of the boat body when the fourth condition is satisfied.

DETAILED DESCRIPTION

[0022] Embodiments of a jet propulsion boat according to the present disclosure will be described below with reference to the drawings. In the following description, the front-rear direction of the boat body of the jet propulsion boat, specifically, the longitudinal direction of the boat body, the direction connecting the bow and the stern, is simply called the front-rear direction, and the bow side is called front and the stern side is called rear. The lateral direction of the boat body of the jet propulsion boat, specifically, a width direction of the boat body, the direction orthogonal to the front-rear direction and a vertical direction, is called the lateral direction. Note that the front-rear and lateral directions coincide with front-rear and lateral directions as viewed from the driver aboard the jet propulsion boat. Front, rear, left, and right direction indications in the drawings indicate directions defined as described above.

Configuration of Jet Propulsion Boat

[0023] FIG. 1 is a partially broken side view of a jet propulsion boat 1 according to an embodiment of the present disclosure, and FIG. 2 is a plan view of the jet propulsion boat 1. The jet propulsion boat 1 is a watercraft that jets a water stream rearward and moves on water in reaction to the water stream. In the present embodiment, the jet propulsion boat 1 is a straddle-type personal watercraft also called a PWC. For this reason, hereinafter, the jet propulsion boat 1 is abbreviated as the PWC 1.

[0024] The PWC 1 includes, as propulsion devices that impart a propulsion force to a boat body 10, a main propulsion device 2, and an auxiliary propulsion device 3 that imparts a propulsion force different from that of the main propulsion device 2 to the boat body 10. The main propulsion device 2 is an engine-type propulsion device and includes an engine 5 as a drive source. The auxiliary propulsion device 3 is an electric-type propulsion device and includes a thruster motor 59 including an electric motor as a drive source. Here, the main propulsion device 2 generates a propulsion force by drive of the engine 5. Hereinafter, drive/stop of the main propulsion device 2 is simply called drive/stop of the engine 5. By drive of the thruster motor 59, the auxiliary propulsion device 3 generates a propulsion force. Hereinafter, drive/stop of the auxiliary propulsion device 3 is simply called drive/stop of the thruster motor 59. Hereinafter, the propulsion force imparted to the boat body 10 by the main propulsion device 2 is called a main propulsion force, and the propulsion force imparted to the boat body 10 by the auxiliary propulsion device 3 is called an auxiliary propulsion force.

[0025] The boat body 10 includes a hull 11 and a deck 12 overlying the hull 11.

[0026] A front upper part of the deck 12 is provided with a steering handle 13 operated by a driver M. The steering handle 13 is pivotally supported by the boat body 10 in the lateral direction. Specifically, the steering handle 13 is allowed to pivot rightward and leftward from a neutral position shown in FIG. 2 about a pivotal axis X1 extending in the up-down direction. The steering handle 13 includes a pair of handlebars 13A and 13B having a bar shape provided at both left and right ends of the steering handle 13 and extending in the lateral direction. By gripping the handlebars 13A and 13B, the driver M can pivot the steering handle 13 about the pivotal axis X1. The neutral position is a position where the left and right handlebars 13A and 13B are substantially bilaterally symmetrical with respect to a center line O1 of the boat body 10. Hereinafter, as appropriate, pivoting of the steering handle 13 rightward, that is, clockwise is simply called pivoting rightward, and pivoting of the steering handle 13 leftward, that is, counterclockwise is simply called pivoting leftward.

[0027] As shown in FIG. 2, the steering handle 13 is provided with a throttle lever 21 and an engine start/stop switch 22, each of which is operated by the driver M. The deck 12 is provided with a shift lever 23 operated by the driver M. The throttle lever 21 is a device for changing mainly the output of the engine 5 and thus the main propulsion force. The start/stop switch 22 is a switch for starting the engine 5 in a stopped state and for stopping the engine 5 in a driven state. The shift lever 23 is a device for operating a reverse bucket 7 described later.

[0028] The steering handle 13 is provided with a start switch 24 operated by the driver M. The start switch 24 is a switch for bringing the boat body 10 into a navigable state. The start switch 24 includes a key cylinder, and is turned ON when a key is inserted into the key cylinder and is turned OFF when the key is removed. When the start switch 24 is turned ON, power feed from a battery 80 mounted on the boat body 10 is started to each electric device of the boat body 10. When the power feed is started, each device of the main propulsion device 2 including the engine 5 and the auxiliary propulsion device 3 can be driven, and the boat body 10 can be navigated.

[0029] A display 15 is disposed on the deck 12. The display 15 is a device that displays various types of information. The display 15 is a touchscreen-type display, and can perform various input operations on the display 15.

[0030] A seat 14 is disposed on the deck 12. The seat 14 is a seat on which the driver M who drives the PWC 1 is seated. The seat 14 may be a seat on which at least the driver M can be seated. That is, the seat 14 may be a multiple-passenger seat on which not only the driver M but also passengers can be seated, or may be a single-passenger seat on which only the driver M can be seated.

Main Propulsion Device

[0031] The main propulsion device 2 includes a jet pump 6 that jets water and the reverse bucket 7 disposed at an outlet of the jet pump 6. As described above, the main propulsion device 2 includes the engine 5 as a drive source. The jet pump 6 is driven by the engine 5 to jet water.

[0032] The engine 5 is an internal combustion engine. The engine 5 generates power for driving the jet pump 6. The engine 5 is, for example, a water-cooled four-stroke multicylinder engine using gasoline as fuel. The engine 5 is accommodated in an engine room ER formed inside the hull 11. The engine 5 includes, as an output shaft, a crankshaft 30 extending in the front-rear direction.

[0033] Although not shown, the engine 5 includes an engine body in which cylinders are formed and an intake passage for introducing intake air into the engine body. The engine 5 includes a throttle valve that is provided in the intake passage and adjusts an intake air amount, which is an amount of intake air to be introduced into the engine body. When an opening degree of the throttle valve decreases, the intake air amount is reduced. When the intake air amount is reduced, the amount of fuel supplied into the cylinders is also reduced. Due to this, when the opening degree of the throttle valve decreases, the output of the engine 5 decreases. When the output of the engine 5 decreases, the momentum of a jet water stream decreases, and the main propulsion force decreases.

[0034] The throttle lever 21 is a lever-type operation device that is movable in a direction of coming into contact with or separating from the handlebar 13B. The driver M can move the throttle lever 21 by gripping the handlebar 13B and the throttle lever 21. The throttle lever 21 is at a position farthest from the handlebar 13B in a non-operation state, and approaches the handlebar 13B when operated. Hereinafter, as appropriate, the position of the throttle lever 21 in the non-operation state is called a throttle off position. The throttle lever 21 being at the throttle off position is appropriately called that the throttle is off.

[0035] When the throttle is off in a state in which the engine 5 is started, the engine 5 is in a so-called idle state, and the output of the engine 5 is the minimum output that enables self-sustained rotation. The larger the operation amount with respect to the throttle lever 21, that is, the gripping amount of the throttle lever 21 that is the movement amount of the throttle lever 21 from the throttle off position, the larger the opening degree of the throttle valve. Due to this, the larger the operation amount with respect to the throttle lever 21, the larger the output and the main propulsion force of the engine 5. Hereinafter, as appropriate, the operation amount with respect to the throttle lever 21 is called an operation amount of the throttle lever 21.

[0036] The steering handle 13 is provided with a throttle position sensor SN1 that can detect the operation amount of the throttle lever 21. The opening degree of the throttle valve is changed in accordance with a detection result of the throttle position sensor SN1.

[0037] The boat body 10 includes an impeller passage 37. The impeller passage 37 is a passage having, as an inlet, a water intake 36 formed at the center in the lateral width direction of a bottom surface 11A of the hull 11. The impeller passage 37 is formed so as to penetrate a rear part of the hull 11 in the front-rear direction.

[0038] The jet pump 6 is disposed in the impeller passage 37. The jet pump 6 is a pump that generates a jet water stream. The jet pump 6 includes a pump shaft 31, a pump impeller 32, a Venturi nozzle 33, and a jet nozzle 34.

[0039] The pump shaft 31 is coaxially coupled to the rear end of the crankshaft 30. The driving force of the engine 5 is transmitted to the pump impeller 32 via the crankshaft 30 and the pump shaft 31. Upon receiving the driving force, the pump impeller 32 rotates about an axis and generates a rearward water stream.

[0040] The Venturi nozzle 33 and the jet nozzle 34 generate a jet water stream by pressurizing and accelerating the water sent from the pump impeller 32. The jet nozzle 34 is a nozzle having a jet port 35 opening rearward as an outlet of a jet water stream. The jet nozzle 34 is coupled to a rear end part of the Venturi nozzle 33. The jet water stream is jetted rearward from the jet port 35 of the jet nozzle 34. The rearward jet of the jet water stream imparts a propulsion force for the boat body 10 to move forward.

[0041] The jet nozzle 34 is disposed at the rear end part of the boat body 10 more rearward than a center of gravity G of the PWC 1. The center of gravity G of the PWC 1 is positioned in a region where the seat 14 is disposed. By this, the jet pump 6 and the jet nozzle 34 jet a jet water stream rearward from a position more rearward than the seat 14. The jet nozzle 34 is disposed on the center line O1 in the lateral direction of the boat body 10 in plan view. Due to this, the jet water stream is jetted rearward from the vicinity of a part positioned on the center line O1 in plan view of the rear end part of the boat body 10.

[0042] As described above, in the present embodiment, the engine 5 and the jet pump 6 impart the propulsion force in the front-rear direction to the boat body 10. The device including the engine 5 and the jet pump 6 corresponds to the jet water stream generation device in the present disclosure.

[0043] FIG. 3 is a schematic perspective view showing the periphery of the jet nozzle 34. FIG. 4 is a schematic plan view showing the periphery of the jet nozzle 34.

[0044] The jet nozzle 34 has a substantially cylindrical shape extending in the front-rear direction. The jet nozzle 34 is supported by the Venturi nozzle 33 and thus the boat body 10 so as to be swingable laterally. Specifically, a center part of left and right of a front end part of the jet nozzle 34 is immovably fixed to the Venturi nozzle 33. As indicated by a broken line, a solid line, and a chain line in FIG. 4, the jet nozzle 34 rotates about a rotation center line X2 passing through the left and right center of the front end part and extending in the up-down direction. When the jet nozzle 34 swings, the orientation of the jet port 35 and the jet direction of the jet water stream from the jet port 35 are changed to left and right.

[0045] Hereinafter, regarding the position of the jet nozzle 34, a position where the center axis of the jet nozzle 34 extends straight in the front-rear direction as indicated by the solid lines in FIGS. 2 and 4 and the jet port 35 opens straight rearward is called a basic position. Regarding the swinging direction of the jet nozzle 34, a case where the jet nozzle 34 swings so that the rear end of the jet nozzle 34 moves to the left as indicated by the solid line to the broken line in FIG. 4 is called swinging leftward, and a case where the jet nozzle 34 swings to the opposite side is called swinging rightward. Note that the jet nozzle 34 shown in FIG. 3 swings leftward from the basic position.

[0046] FIG. 5 is a plan view schematically showing the motion of the boat body 10 to which the main propulsion force directed forward is imparted. In a state where the jet nozzle 34 is in the basic position, the jet water stream is jetted substantially straight rearward from the boat body 10 as indicated by arrow Y11 in FIGS. 4 and 5. Due to this, as indicated by arrow Y21 in FIG. 5, the boat body 10 moves substantially straight forward. On the other hand, in a state where the jet nozzle 34 swings leftward from the basic position, as indicated by arrow Y12 in FIGS. 4 and 5, the jet water stream is jetted diagonally left rearward from the rear end part of the boat body 10. Due to this, a rightward and forward main propulsion force is imparted to the rear end part of the boat body 10. Therefore, at this time, as indicated by arrow Y22 in FIG. 5, the boat body 10 moves forward while turning leftward and moves diagonally left forward. In a state where the jet nozzle 34 swings rightward from the basic position, as indicated by arrow Y13 in FIGS. 4 and 5, the jet water stream is jetted diagonally right rearward from the boat body 10. Due to this, a leftward and forward main propulsion force is imparted to the rear end part of the boat body 10. Therefore, at this time, as indicated by arrow Y23 in FIG. 5, the boat body 10 moves forward while turning rightward and moves diagonally right forward.

[0047] The position of the jet nozzle 34 is changed by the steering handle 13. Specifically, in a state where the steering handle 13 is at the neutral position, the position of the jet nozzle 34 is the basic position. When the steering handle 13 is pivotally operated rightward with respect to the neutral position, the jet nozzle 34 is swung rightward from the basic position. When the steering handle 13 is pivotally operated leftward with respect to the neutral position, the jet nozzle 34 is swung leftward from the basic position. A swing amount of the jet nozzle 34 in the lateral direction with respect to the basic position increases as the pivot amount of the steering handle 13 with respect to the neutral position increases.

[0048] The steering handle 13 is provided with a steering angle sensor SN2 for detecting an operation state of the steering handle 13. The steering angle sensor SN2 detects the pivot direction of the steering handle 13 from the neutral position. The steering angle sensor SN2 detects a pivot amount from the neutral position of the steering handle 13, that is, a steering angle. The position of the jet nozzle 34 is changed based on the detection result of the steering angle sensor SN2.

[0049] The jet nozzle 34 is swung by an electric motor. This electric motor is controlled based on the detection result of the steering angle sensor SN2. Hereinafter, the electric motor that swings the jet nozzle 34 is called a nozzle motor 39. Specifically, an outer peripheral surface of the jet nozzle 34 is provided with a flange portion 34A protruding outward. A shaft 38 extending in the front-rear direction is coupled to this flange portion 34A. The nozzle motor 39 is coupled to the shaft 38 via a gear or the like. When the nozzle motor 39 is driven based on the detection result of the steering angle sensor SN2, the shaft 38 slides and moves in the front-rear direction. With the movement of the shaft 38, the jet nozzle 34 swings in the lateral direction.

[0050] As described above, in the present embodiment, the jet nozzle 34 is swung in the lateral direction by the steering handle 13, the steering angle sensor SN2, the nozzle motor 39, and the shaft 38, and the orientation in the lateral direction of the jet water stream, that is, the orientation in the lateral direction of the main propulsion force is changed. The mechanism including the steering handle 13, the steering angle sensor SN2, the nozzle motor 39, and the shaft 38 corresponds to the steering device of the present disclosure. The steering handle 13 corresponds to the steering operator of the present disclosure. The steering angle sensor SN2 corresponds to the detection deviceof the present disclosure.

[0051] Note that although not shown, the boat body 10 is also provided with a tilt mechanism that pivots the jet nozzle 34 in the up-down direction. At the time of execution of normal navigation control described later or the like, the jet nozzle 34 is appropriately pivoted in the up-down direction by this tilt mechanism.

[0052] FIG. 6 is a schematic side view showing the periphery of the jet nozzle 34. The reverse bucket 7 is a member movable between a reverse position and a forward position. The reverse position is a position where the reverse bucket 7 covers the jet port 35 of the jet nozzle 34 from the rear as indicated by the chain line in FIG. 6. The forward position is a position at which the jet port 35 is exposed as indicated by the broken line in FIG. 6. The position of the reverse bucket 7 is switched among the reverse position, the forward position, and a neutral position. The neutral position is an intermediate position between the forward position and the reverse position as indicated by the solid line in FIG. 6.

[0053] In a state where the reverse bucket 7 is in the forward position and the jet port 35 is exposed rearward, the jet water stream jetted from the jet port 35 is directed rearward as it is from the boat body 10. Due to this, in the state where the reverse bucket 7 is in the forward position, a forward propulsion force is imparted to the boat body 10 from the main propulsion device 2.

[0054] On the other hand, in a state where the reverse bucket 7 is in the reverse position and covers the jet port 35, the orientation of the jet water stream jetted from the jet port 35 is changed forward by the reverse bucket 7. Thus, in the state where the reverse bucket 7 is in the reverse position, a rearward propulsion force is imparted to the boat body 10 from the main propulsion device 2.

[0055] In a state where the reverse bucket 7 is in the neutral position, the jet water stream is distributed to the left and right. Due to this, in the state where the reverse bucket 7 is in the neutral position, neither forward nor rearward propulsion force is imparted to the boat body 10.

[0056] The position of the reverse bucket 7 is changed in accordance with an operation on the shift lever 23. Specifically, the shift lever 23 is supported by the boat body 10 in a state where the position thereof can be switched to three positions different from one another. In a state where the shift lever 23 is in a predetermined first position, the reverse bucket 7 is in the neutral position. In a state where the shift lever 23 is in a second position different from the first position, the reverse bucket 7 is in the forward position. In a state where the shift lever 23 is in a third position different from the first position and the second position, the reverse bucket 7 is in the reverse position.

[0057] The shift lever 23 is attached a shift position sensor SN3 that detects the position of the shift lever 23. The position of the reverse bucket 7 is changed based on the detection result of the shift position sensor SN3.

[0058] The reverse bucket 7 is pivoted in the up-down direction by an electric motor. This electric motor is controlled based on the detection result of the shift position sensor SN3. Hereinafter, the electric motor that drives the reverse bucket 7 is called a bucket motor 49. Specifically, a shaft 48 extending in the front-rear direction is coupled to the reverse bucket 7. The bucket motor 49 is coupled to this shaft 48 via a gear or the like. When the bucket motor 49 is driven based on the detection result of the shift position sensor SN3, the shaft 48 slides and moves in the front-rear direction. With the movement of the shaft 48, the reverse bucket 7 pivots in the up-down direction.

[0059] Here, although not shown, when the reverse bucket 7 is in the reverse position and the steering handle 13 is pivotally operated leftward with respect to the neutral position, the jet nozzle 34 is swung leftward from the basic position. In this state, a front-rear direction component of the jet water stream is reversed by the reverse bucket 7, and the jet water stream is directed diagonally left forward from the rear end part of the boat body 10. Due to this, a rightward and rearward main propulsion force is imparted to the rear end part of the boat body 10, and the boat body 10 moves diagonally right rearward with the stern as the head. When the reverse bucket 7 is in the reverse position and the steering handle 13 is pivotally operated rightward with respect to the neutral position, the jet nozzle 34 is swung rightward from the basic position. In this state, the jet water stream is directed diagonally right forward from the rear end part of the boat body 10. Due to this, a rightward and rearward main propulsion force is imparted to the rear end part of the boat body 10, and the boat body 10 moves diagonally left rearward with the stern as the head.

Auxiliary Propulsion Device

[0060] FIG. 7 is a plan cross-sectional view schematically showing the structure of the auxiliary propulsion device 3. The auxiliary propulsion device 3 is provided at a front part of the boat body 10. As shown in FIG. 1, the auxiliary propulsion device 3 is disposed more forward than the seat 14 and the center of gravity G of the PWC 1. As shown in FIG. 2, the auxiliary propulsion device 3 is disposed more upward than the center of gravity G of the PWC 1. The auxiliary propulsion device 3 generates an auxiliary water stream directed outward in the lateral direction from the front part of the boat body 10, that is, directed rightward or leftward. This auxiliary water stream imparts a propulsion force to the boat body 10 in the lateral direction, that is, the width direction of the boat body 10.

[0061] The auxiliary propulsion device 3 is a so-called electric thruster. The auxiliary propulsion device 3 includes a propeller shaft 51, an impeller 52, and a gear mechanism 53. As described above, the auxiliary propulsion device 3 includes the thruster motor 59 as a drive source.

[0062] The boat body 10 includes a water passage 55 in a position corresponding to the auxiliary propulsion device 3. The water passage 55 is a passage penetrating a front part of the hull 11 in the lateral direction. As shown in FIG. 7, the water passage 55 causes a left opening 55A opening on the left side surface of the front part of the hull 11 and a right opening 55B opening on the right side surface of the front part of the hull 11 to communicate with each other.

[0063] The thruster motor 59 is disposed inside the hull 11 more rearward than the water passage 55. The propeller shaft 51, the impeller 52, and the gear mechanism 53 are accommodated inside the water passage 55. The driving force of the thruster motor 59 is transmitted to the impeller 52 via the gear mechanism 53 and the propeller shaft 51 and rotates the impeller 52 about an axis. Specifically, the gear mechanism 53 is a bevel gear mechanism linked with an output shaft of the thruster motor 59. The propeller shaft 51 is a shaft coupling the gear mechanism 53 and the impeller 52. The rotation input from the thruster motor 59 to the gear mechanism 53 is changed in direction by 90 degrees and then transmitted to the impeller 52. Due to this, the impeller 52 rotates about an axis extending in the lateral direction.

[0064] The rotation of the impeller 52 causes water introduced into the water passage 55 to be jetted from one end (the left opening 55A or the right opening 55B) of the water passage 55. Due to this, the auxiliary water stream, which is a water stream along the lateral direction, is generated, and a propulsion force is imparted to the boat body 10.

[0065] The thruster motor 59 can rotate forward and backward. The orientation of the auxiliary water stream is switched by switching the rotation direction of the thruster motor 59. During the forward rotation of the thruster motor 59, a leftward auxiliary water stream is generated as indicated by arrow Y51 in FIG. 7. The leftward auxiliary water stream imparts a rightward propulsion force (auxiliary propulsion force) to the boat body 10 as indicated by arrow Y52. During the backward rotation of the thruster motor 59, a rightward auxiliary water stream is generated as indicated by arrow Y53 in FIG. 7. The rightward auxiliary water stream imparts a leftward propulsion force (auxiliary propulsion force) to the boat body 10 as indicated by arrow Y54.

[0066] The auxiliary water stream is generated more forward than the center of gravity G of the PWC 1. Due to this, when a leftward auxiliary water stream (Y51) is generated by the auxiliary propulsion device 3, the boat body 10 does not substantially move in the front-rear direction and turns rightward (clockwise), specifically, the bow moves rightward, as indicated by arrow Y55. On the contrary, when a rightward auxiliary water stream (Y53) is generated, the boat body 10 does not substantially move in the front-rear direction and turns leftward (counterclockwise), specifically, the bow moves leftward, as indicated by arrow Y56. This, the auxiliary propulsion device 3 is provided at a position shifted in the front-rear direction from the center of gravity G of the PWC 1, the position where the boat body 10 turns when the thruster motor 59 is driven in a state where the engine 5 is stopped.

[0067] The larger the output of the thruster motor 59 is, the stronger the flow rate, that is, the momentum of the auxiliary water stream is. The stronger the momentum of the auxiliary water stream is, the larger the auxiliary propulsion force, which is the propulsion force imparted to the boat body 10 by the auxiliary water stream, is.

Control System

[0068] A control system of the PWC 1 will be described. The boat body 10 is mounted with a control device 100 for controlling various devices mounted on the boat body 10. FIG. 8 is a functional block diagram showing the control system of the PWC 1. The control device 100 is a device including, as a main part, a microcomputer including a processor (CPU) that performs calculation and memories such as a ROM and a RAM.

[0069] The control device 100 is electrically connected to the throttle position sensor SN1, the steering angle sensor SN2, and the shift position sensor SN3. The detection result of the throttle position sensor SN1, that is, the operation amount of the throttle lever 21 is input to the control device 100. The detection result of the steering angle sensor SN2, that is, the steering angle and the pivot direction of the steering handle 13 are input to the control device 100. The detection result of the shift position sensor SN3, that is, the position of the shift lever 23 is input to the control device 100. The control device 100 is electrically connected to the start/stop switch 22. The control device 100 is electrically connected to the start switch 24. The control device 100 receives signals from these sensors SN1 to SN3 and the switches 22 and 24.

[0070] In the present embodiment, two types of keys, a normal key and an SLO key, are prepared as keys to be inserted into the key cylinder of the start switch 24. The start switch 24 transmits different signals to the control device 100 in accordance with the type of the inserted key. Note that SLO is an abbreviation for smart learning operation. Hereinafter, the key inserted into the key cylinder of the start switch 24 is appropriately called a key in use.

[0071] The boat body 10 is mounted with an IMU (inertial measurement unit) 92. The control device 100 is electrically connected to the IMU 92 and receives a signal from the IMU 92. The IMU 92 is an inertial measurement unit in which a three-axis gyro sensor and a three-axis acceleration sensor are combined. The IMU 92 detects angular velocities around three axes orthogonal to one another and accelerations in three-axis directions in the boat body 10.

[0072] The control device 100 is electrically connected to the display 15. The control device 100 receives a signal input to the display 15. FIG. 9 is a display example of an image displayed on the display 15.

[0073] A turn assist switch 25 is displayed on the display 15. The turn assist switch 25 is a switch for causing the control device 100 to execute turn assist control described later. For example, the turn assist switch 25 is switched to ON when a press operation is performed in an OFF state, and is switched to OFF when a press operation is performed in an ON state.

[0074] The control device 100 is electrically connected to the main propulsion device 2 and the auxiliary propulsion device 3. The control device 100 outputs control signals to the main propulsion device 2 and the auxiliary propulsion device 3 to control them. Specifically, the control device 100 controls each part of the engine 5 included in the main propulsion device 2, the jet nozzle 34 (nozzle motor 39), and the reverse bucket 7 (bucket motor 49). The control device 100 controls the thruster motor 59 included in the auxiliary propulsion device 3. The control device 100 outputs a control signal to the display 15.

[0075] The control device 100 functionally includes a determination unit 101, a position/speed specification unit 102, a display control unit 103, a main propulsion device control unit 111, and an auxiliary propulsion device control unit 112.

[0076] The determination unit 101 is a module that performs various determinations regarding control of the PWC 1. For example, the determination unit 101 determines whether the key in use is the normal key or the SLO key based on a signal from the start switch 24. The determination unit 101 determines whether or not first to fourth conditions described later are satisfied.

[0077] The position/speed specification unit 102 is a module that specifies the position of the PWC 1 and the navigation speed of the boat body 10. The position/speed specification unit 102 has a GPS function, and specifies the current position of the PWC 1 and the navigation speed of the boat body 10 based on a signal from an artificial satellite.

[0078] The display control unit 103 is a module that executes control related to display on the display 15. The display control unit 103 outputs a control signal to the display 15 to change display content and a display format of the display 15. The display control unit 103 changes a display format such as brightness of the switch 25 on the display 15 between a case of ON and a case of OFF so that the driver M can recognize whether the turn assist switch 25 is ON or OFF. As shown in FIG. 9, the display control unit 103 causes the display 15 to display a remaining amount D1 of the fuel, and a current position D2 of the PWC 1 and a navigation speed D3 of the boat body 10 specified by the position/speed specification unit 102, and the like.

[0079] The main propulsion device control unit 111 is a module that controls the main propulsion device 2. The main propulsion device control unit 111 outputs a control signal to elements such as a throttle valve, a fuel jet device, and an ignition plug included in the engine 5. The main propulsion device control unit 111 switches drive/stop of the engine 5 based on a signal from the start/stop switch 22.

[0080] When the engine 5 is driven, the main propulsion device control unit 111 changes the opening degree of the throttle valve based on the detection result of the throttle position sensor SN1. The main propulsion device control unit 111 changes the amount of fuel supplied to the cylinder of the engine 5 and the ignition timing in accordance with the opening degree of the throttle valve and the like.

[0081] The main propulsion device control unit 111 switches the control mode of the main propulsion device 2 between a normal mode and a beginner mode in accordance with the type of key in use. Specifically, when the determination unit 101 determines that the key in use is the normal key, the main propulsion device control unit 111 switches the control mode of the main propulsion device 2 to the normal mode. When the determination unit 101 determines that the key in use is the SLO key, the main propulsion device control unit 111 switches the control mode of the main propulsion device 2 to the beginner mode.

[0082] When the control mode is the beginner mode, the main propulsion device control unit 111 sets the output of the engine 5 to be smaller than the value in a case of the normal mode. Specifically, when the control mode is the beginner mode, the main propulsion device control unit 111 controls each part of the engine 5 so that the output of the engine 5 when the operation amount of the throttle lever 21 is maximized becomes smaller than the value in a case of the normal mode.

[0083] The main propulsion device control unit 111 outputs control signals to the nozzle motor 39 and the bucket motor 49. The main propulsion device control unit 111 changes the position of the jet nozzle 34 based on the detection result of the steering angle sensor SN2. The main propulsion device control unit 111 changes the position of the reverse bucket 7 based on the detection result of the shift position sensor SN3. As described above, when the positions of the jet nozzle 34 and the reverse bucket 7 change, the direction of the jet water stream and the direction of the main propulsion force change.

[0084] The auxiliary propulsion device control unit 112 outputs a control signal to the thruster motor 59. The auxiliary propulsion device control unit 112 switches between drive and stop of the thruster motor 59. The auxiliary propulsion device control unit 112 changes the orientation of the auxiliary water stream and the orientation of the auxiliary propulsion force by changing the rotation direction of the thruster motor 59.

[0085] The auxiliary propulsion device control unit 112 drives the thruster motor 59 when the determination unit 101 determines that a specific condition is satisfied. In the present embodiment, the first to fourth conditions are set as the specific conditions. These first to fourth conditions and the control performed on the thruster motor 59 when these conditions are satisfied will be described below.

First Condition

[0086] FIG. 10 is a flowchart showing specific content of the first condition and control content for the thruster motor 59 when the first condition is satisfied. The control device 100 repeatedly performs steps S1 to S10 in FIG. 10 at predetermined time intervals during a period in which the start switch 24 is ON.

[0087] First, the control device 100 determines whether or not the current navigation speed of the boat body 10 is equal to or greater than a first determination speed (step S1). The first determination speed is set to a value greater than 0 (zero) in advance and stored in the control device 100. In step S1, the navigation speed of the boat body 10 specified by the position/speed specification unit 102 at the time point of performing step S1 is used as the current navigation speed.

[0088] If the determination in step S1 is NO and the navigation speed of the boat body 10 is less than the first determination speed, the control device 100 proceeds to step S10, stops the thruster motor 59, and ends the process (returns to step S1). Note that in step S10, when the thruster motor 59 is already stopped at the time of performing step S10, the stop is maintained.

[0089] On the other hand, if the determination in step SI is YES and the navigation speed of the boat body 10 is equal to or greater than the first determination speed, the control device 100 then determines whether or not the engine 5 is being driven (step S2). The determination in step S2 is performed based on a signal from the start/stop switch 22, a signal from a sensor that detects the rotation speed of the engine 5 attached to the engine 5, or the like.

[0090] If the determination in step S2 is NO and the engine 5 is not being driven, the control device 100 proceeds to step S10, stops the thruster motor 59, and ends the process (returns to step S1).

[0091] On the other hand, if the determination in step S2 is YES and the engine 5 is being driven, the control device 100 then determines whether or not the operation amount of the throttle lever 21 is equal to or less than a predetermined throttle determination amount (step S3). The determination in step S3 is performed based on the detection result of the throttle position sensor SN1. In the present embodiment, the throttle determination amount is set to 0 (zero). That is, in step S3, it is determined whether or not the operation amount of the throttle lever 21 is 0 (zero) and the throttle is off.

[0092] If the determination in step S3 is NO and the operation amount of the throttle lever 21 is greater than the throttle determination amount, the control device 100 proceeds to step S10, stops the thruster motor 59, and ends the process (returns to step S1).

[0093] On the other hand, if the determination in step S3 is YES and the operation amount of the throttle lever 21 is equal to or less than the throttle determination amount, the control device 100 then determines whether or not the steering angle is greater than a first determination steering angle (step S4). The first determination steering angle is set in advance and stored in the control device 100. The determination in step S4 is performed based on the detection result of the steering angle sensor SN2. Here, the steering angle used in the determination in step S4 is an absolute value of the pivot amount from the neutral position of the steering handle 13. That is, in any of the left and right directions with respect to the neutral position, if the steering handle 13 is pivotally operated by an angle greater than the first determination steering angle from the neutral position, the determination in step S4 is YES.

[0094] If the determination in step S4 is NO and the steering angle is equal to or less than the first determination steering angle, the control device 100 proceeds to step S10, stops the thruster motor 59, and ends the process (returns to step S1).

[0095] On the other hand, if the determination in step S4 is YES and the steering angle is greater than the first determination steering angle, the control device 100 drives the thruster motor 59 (step S5).

[0096] The control device 100 determines whether or not the steering handle 13 is pivotally operated rightward with respect to the neutral position (step S6).

[0097] If the determination in step S6 is YES and the steering handle 13 is pivotally operated rightward with respect to the neutral position, the control device 100 rotates the thruster motor 59 forward (step S7). Due to this, an auxiliary propulsion force directed rightward, that is, in the same direction as the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10.

[0098] On the other hand, if the determination in step S6 is NO and the steering handle 13 is pivotally operated leftward with respect to the neutral position, the control device 100 rotates the thruster motor 59 backward (step S8). Due to this, an auxiliary propulsion force directed leftward, that is, in the same direction as the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10.

[0099] After step S7 or step S8, the control device 100 adjusts the driving force of the thruster motor 59 in accordance with the steering angle (step S9). Specifically, the control device 100 increases the output of the thruster motor 59 as the steering angle is large. Due to this, the larger the steering angle is, the larger the momentum of the auxiliary water stream and the auxiliary propulsion force are. After step S9, the control device 100 ends the process (returns to step S1).

[0100] Thus, the first condition for driving the thruster motor 59 is a condition that the navigation speed of the boat body 10 is equal to or greater than the first determination speed, the engine 5 is being driven, the operation amount of the throttle lever 21 is equal to or less than the throttle determination amount, and the steering angle is greater than the first determination steering angle. When this first condition is satisfied, the thruster motor 59 is driven. At this time, an auxiliary propulsion force in the same orientation as the pivot direction of the steering handle 13 in the lateral direction is imparted to the front part of the boat body 10.

Second Condition

[0101] FIG. 11 is a flowchart showing specific content of the second condition and control content for the thruster motor 59 when the second condition is satisfied. The control device 100 repeatedly performs steps S11 to S23 in FIG. 11 at predetermined time intervals during a period in which the start switch 24 is ON.

[0102] First, the control device 100 determines whether or not it is immediately after the start switch 24 is switched from OFF to ON (step S21). Specifically, the control device 100 determines that the start switch 24 is switched from OFF to ON when an elapsed time from when the start switch 24 is ON is within a predetermined time. The determination in step S11 is performed based on a signal from the start switch 24.

[0103] If the determination in step S11 is NO and it is not immediately after the start switch 24 is switched from OFF to ON, the control device 100 proceeds to step S24 without performing step S23.

[0104] On the other hand, if the determination in step S21 is YES and it is immediately after the start switch 24 is switched from OFF to ON, the control device 100 determines whether or not the key in use is the SLO key based on a signal from the start switch 24 (step S22).

[0105] If the determination in step S22 is NO and the key in use is the normal key, the control device 100 proceeds to step S24 without performing step S23. Note that if the determination in step S22 is NO, the operation mode of the main propulsion device 2 is the normal mode.

[0106] On the other hand, if the determination in step S22 is YES and the key in use is the SLO key, the control device 100 turns ON the turn assist switch 25 (step S23). Note that when step S23 is performed, the control device 100, specifically, the display control unit 103, sets the display format of the turn assist switch 25 on the display 15 to a format that enables the driver M to recognize that this is ON. Note that if the determination in step S22 is YES, the operation mode of the main propulsion device 2 is the beginner mode.

[0107] When the start switch 24 is OFF, the turn assist switch 25 is turned OFF. Due to this, immediately after the start switch 24 is switched from OFF to ON and when the key in use is the SLO key, the turn assist switch 25 is forcibly switched from OFF to ON along with the execution of step S13. Thus, in the present embodiment, switching of ON and OFF of the turn assist switch 25 is possible by the operation of the driver M on the display 15 as described above, and is also possible by a command from the control device 100. After step S23, the control device 100 proceeds to step S24.

[0108] In step S24, the control device 100 determines whether or not the turn assist switch 25 is ON.

[0109] Even when the turn assist switch 25 is forcibly turned ON by performing step S23, the turn assist switch 25 may be subsequently switched to OFF by the operation of the driver M. Even when step S23 is not performed because the key in use is the normal key, the turn assist switch 25 may be subsequently switched to ON by the driver M. Thus, step S24 is YES when step S23 is performed and then the driver M does not turn OFF the turn assist switch 25, or when step S13 is not performed and the driver M turns ON the turn assist switch 25.

[0110] If the determination in step S24 is NO and the turn assist switch 25 is OFF, the control device 100 proceeds to step S33, stops the thruster motor 59, and ends the process (returns to step S21). Note that in step S33, when the thruster motor 59 is already stopped at the time of performing step S33, the stop is maintained.

[0111] On the other hand, if the determination in step S24 is YES and the turn assist switch 25 is ON, the control device 100 determines whether or not the operation amount of the throttle lever 21 is greater than 0 (zero) and equal to or less than a second throttle determination amount (step S25). The second throttle determination amount is set in advance to a value greater than 0 and smaller than the maximum value of the operation amount of the throttle lever 21 and stored in the control device 100. The determination in step S25 is performed based on the detection result of the throttle position sensor SN1.

[0112] If the determination in step S25 is NO and the operation amount of the throttle lever 21 is 0 or greater than the second throttle determination amount, the control device 100 proceeds to step S33, stops the thruster motor 59, and ends the process (returns to step S21).

[0113] On the other hand, if the determination in step S25 is YES and the operation amount of the throttle lever 21 is greater than 0 (zero) and equal to or less than the second throttle determination amount, the control device 100 then determines whether or not the engine 5 is being driven (step S26). The determination in step S26 is performed similarly to step S2 described above.

[0114] If the determination in step S26 is NO and the engine 5 is not being driven, the control device 100 proceeds to step S33, stops the thruster motor 59, and ends the process (returns to step S21).

[0115] On the other hand, if the determination in step S26 is YES and the engine 5 is being driven, the control device 100 then determines whether or not the steering angle is greater than a second determination steering angle (step S27). The second determination steering angle is set in advance and stored in the control device 100. Similarly to step S4 described above, if the steering handle 13 is pivotally operated by an angle greater than the second determination steering angle from the neutral position regardless of the pivot direction of the steering handle 13, the determination in step S27 is YES.

[0116] If the determination in step S27 is NO and the steering angle is equal to or less than the second determination steering angle, the control device 100 proceeds to step S33, stops the thruster motor 59, and ends the process (returns to step S21).

[0117] On the other hand, if the determination in step S27 is YES and the steering angle is greater than the second determination steering angle, the control device 100 drives the thruster motor 59 (step S28).

[0118] The control device 100 determines whether or not the steering handle 13 is pivotally operated rightward with respect to the neutral position (step S29). This determination is performed based on the detection result of the steering angle sensor SN2.

[0119] If the determination in step S29 is YES and the steering handle 13 is pivotally operated rightward with respect to the neutral position, the control device 100 rotates the thruster motor 59 forward (step S30). Due to this, an auxiliary propulsion force directed rightward, that is, in the same direction as the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10.

[0120] On the other hand, if the determination in step S29 is NO and the steering handle 13 is pivotally operated leftward with respect to the neutral position, the control device 100 rotates the thruster motor 59 backward (step S31). Due to this, an auxiliary propulsion force directed leftward, that is, in the same direction as the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10.

[0121] After step S30 or step S31, the control device 100 adjusts the driving force of the thruster motor 59 in accordance with the main propulsion force (step S32). Specifically, the control device 100 increases the output of the thruster motor 59 as the output of the engine 5 is large. Due to this, the larger the main propulsion force is, the larger the momentum of the auxiliary water stream and the auxiliary propulsion force are. After step S32, the control device 100 ends the process (returns to step S21).

[0122] Thus, the second condition for driving the thruster motor 59 is a condition that the key in use is the SLO key and in a state where the turn assist switch 25 is not operated OFF, or the key in use is the normal key and in a state where the turn assist switch 25 is operated ON, the operation amount of the throttle lever 21 is greater than 0 (zero) and equal to or less than the second throttle determination amount, the engine 5 is being driven, and the steering angle is greater than the second determination steering angle. When this second condition is satisfied, the thruster motor 59 is driven. At this time, an auxiliary propulsion force in the same orientation as the pivot direction of the steering handle 13 in the lateral direction is imparted to the front part of the boat body 10. Here, when the second condition is satisfied, the operation amount of the throttle lever 21 is greater than 0. Therefore, when the second condition is satisfied, the main propulsion force is also imparted to the boat body 10. In the lateral direction, the pivot direction of the steering handle 13 and the jet direction of the jet water stream are the same. On the other hand, in the lateral direction, the jet direction of the jet water stream and the orientation of the main propulsion force are opposite, and the pivot direction of the steering handle 13 and the direction of the main propulsion force are opposite. Accordingly, when the second condition is satisfied, the orientation of the auxiliary propulsion force and the orientation of the main propulsion force are opposite in the lateral direction.

Third Condition

[0123] FIG. 12 is a flowchart showing specific content of the third condition and control content for the thruster motor 59 when the third condition is satisfied. The control device 100 repeatedly performs steps S41 to S49 in FIG. 12 at predetermined time intervals during a period in which the start switch 24 is ON.

[0124] First, the control device 100 determines whether or not the current navigation speed of the boat body 10 is equal to or greater than a third determination speed (step S41). The third determination speed is set to a value greater than 0 (zero) in advance and stored in the control device 100. In step S31, the navigation speed of the boat body 10 specified by the position/speed specification unit 102 at the time point of performing step S31 is used as the current navigation speed. In the present embodiment, the third determination speed is set to a speed greater than the maximum speed when the boat body 10 is moving backward, and step S41 is YES when the boat body 10 is moving forward.

[0125] If the determination in step S41 is NO and the navigation speed of the boat body 10 is less than the third determination speed, the control device 100 proceeds to step S49, stops the thruster motor 59, and ends the process (returns to step S41). Note that in step S49, when the thruster motor 59 is already stopped at the time of performing step S49, the stop is maintained.

[0126] On the other hand, if the determination in step S41 is YES and the navigation speed of the boat body 10 is equal to or greater than the third determination speed, the control device 100 then determines whether or not the engine 5 is being driven (step S42). The determination in step S42 is performed similarly to step S2 described above.

[0127] If the determination in step S42 is NO and the engine 5 is not being driven, the control device 100 proceeds to step S49, stops the thruster motor 59, and ends the process (returns to step S41).

[0128] On the other hand, if the determination in step S42 is YES and the engine 5 is being driven, the control device 100 then determines whether or not the steering angle is greater than a third determination steering angle (step S43). The third determination steering angle is set in advance and stored in the control device 100. Similarly to step S4, if the steering handle 13 is pivotally operated by an angle greater than the third determination steering angle from the neutral position regardless of the pivot direction of the steering handle 13, the determination in step S43 is YES.

[0129] If the determination in step S43 is NO and the steering angle is equal to or less than the third determination steering angle, the control device 100 proceeds to step S49, stops the thruster motor 59, and ends the process (returns to step S41).

[0130] On the other hand, if the determination in step S43 is YES and the steering angle is greater than the third determination steering angle, the control device 100 determines whether or not the current roll angle of the boat body 10 exceeds a predetermined determination angle (step S44). The roll angle is a rotation angle of the boat body 10 about a horizontal axis passing through the center of gravity G of the boat body 10. The determination angle is set in advance and stored in the control device 100. That is, in step S44, it is determined whether or not the roll angle of the boat body 10 exceeds an allowable range from 0 (zero) to equal to or less than a determination angle.

[0131] The determination in step S44 is performed based on a signal from the IMU 92. Specifically, in the present embodiment, the IMU 92 detects the angle of the boat body 10 about the horizontal axis passing through the center of gravity G of the boat body 10, and the control device 100 performs the determination in step S44 based on this detection result. Note that in step S44, when the boat body 10 rotates about the horizontal axis beyond the determination angle regardless of the rotation direction of the boat body 10, the determination in step S43 is YES.

[0132] If the determination in step S44 is NO and the roll angle of the boat body 10 is equal to or less than the determination angle, the control device 100 proceeds to step S49, stops the thruster motor 59, and ends the process (returns to step S41).

[0133] On the other hand, if the determination in step S44 is YES and the roll angle of the boat body 10 exceeds the determination angle, the control device 100 drives the thruster motor 59 (step S45).

[0134] The control device 100 determines whether or not the steering handle 13 is pivotally operated rightward with respect to the neutral position (step S46). The determination in step S46 is performed based on the detection result of the steering angle sensor SN2.

[0135] If the determination in step S46 is YES and the steering handle 13 is pivotally operated rightward with respect to the neutral position, the control device 100 rotates the thruster motor 59 backward (step S47). Due to this, a rightward auxiliary water stream is generated on the boat body 10, and an auxiliary propulsion force of leftward, that is, in a direction opposite to the pivot direction with respect to the neutral position of the steering handle is imparted to the boat body 10. On the other hand, if the determination in step S46 is NO and the steering handle 13 is pivotally operated leftward with respect to the neutral position, the control device 100 rotates the thruster motor 59 forward (step S48). Due to this, a leftward auxiliary water stream is generated on the boat body 10, and an auxiliary propulsion force of rightward, that is, in a direction opposite to the pivot direction with respect to the neutral position of the steering handle 13 is imparted to the boat body 10. After step S47 or step S48, the control device 100 ends the process (returns to step S41).

[0136] Thus, the third condition for driving the thruster motor 59 is a condition that the navigation speed of the boat body 10 is equal to or greater than the third determination speed, the engine 5 is being driven, the steering angle is greater than the third determination steering angle, and the roll angle of the boat body 10 exceeds the determination angle. When this third condition is satisfied, the thruster motor 59 is driven. At this time, an auxiliary propulsion force in a direction opposite to the pivot direction of the steering handle 13 is imparted to the boat body 10. As described above, the opening degree direction of the steering handle 13 and the direction of the main propulsion force are opposite. Accordingly, when the third condition is satisfied, the orientation of the auxiliary propulsion force and the orientation of the main propulsion force are the same in the lateral direction.

Fourth Condition

[0137] FIG. 13 is a flowchart showing specific content of the fourth condition and control content for the thruster motor 59 when the fourth condition is satisfied. The control device 100 repeatedly performs steps S51 to S60 in FIG. 13 at predetermined time intervals during a period in which the start switch 24 is ON.

[0138] First, the control device 100 determines whether or not the current navigation speed of the boat body 10 is equal to or greater than a fourth determination speed (step S51). The fourth determination speed is set to a value greater than 0 (zero) in advance and stored in the control device 100. In step S51, the navigation speed of the boat body 10 specified by the position/speed specification unit 102 at the time point of performing step S51 is used as the current navigation speed.

[0139] If the determination in step S51 is NO and the navigation speed of the boat body 10 is less than the fourth determination speed, the control device 100 proceeds to step S60, stops the thruster motor 59, and ends the process (returns to step S51). Note that in step S60, when the thruster motor 59 is already stopped at the time of performing step S60, the stop is maintained.

[0140] On the other hand, if the determination in step S51 is YES and the navigation speed of the boat body 10 is equal to or greater than the fourth determination speed, the control device 100 then determines whether or not the engine 5 is being driven (step S52). The determination in step S52 is performed similarly to step S2 described above.

[0141] If the determination in step S52 is NO and the engine 5 is not being driven, the control device 100 proceeds to step S60, stops the thruster motor 59, and ends the process (returns to step S51).

[0142] On the other hand, if the determination in step S52 is YES and the engine 5 is being driven, the control device 100 then determines whether or not the steering angle is greater than a fourth determination steering angle (step S53). The fourth determination steering angle is set in advance and stored in the control device 100. Similarly to step S4, if the steering handle 13 is pivotally operated by an angle greater than the third determination steering angle from the neutral position regardless of the pivot direction of the steering handle 13, the determination in step S53 is YES.

[0143] If the determination in step S53 is NO and the steering angle is equal to or less than the fourth determination steering angle, the control device 100 proceeds to step S60, stops the thruster motor 59, and ends the process (returns to step S51).

[0144] On the other hand, if the determination in step S53 is YES and the steering angle is greater than the fourth determination steering angle, the control device 100 sets a determination angular velocity to be used in the next step S55 (step S44). The determination angular velocity is an angle larger by a predetermined amount than a requested turning angular velocity, which is a turning angular velocity of the boat body 10 requested by the driver M. The control device 100 calculates the requested turning angular velocity based on the steering angle. The requested turning angular velocity is calculated to a larger value as the steering angle is larger. The control device 100 calculates, as a determination angular velocity, a value in which a predetermined amount is added to a calculated requested turning angular velocity.

[0145] After step S54, the control device 100 determines whether or not a current yaw rate of the boat body 10, that is, the angular velocity of the boat body 10 about a vertical axis passing through the center of gravity G of the boat body 10 exceeds the determination angular velocity (step S55). That is, in step S55, it is determined whether or not the yaw rate of the boat body 10 exceeds an allowable range of equal to or less than the determination angular velocity. This determination is performed based on a signal from the IMU 92.

[0146] If the determination in step S55 is NO and the yaw rate of the boat body 10 does not exceed the determination angular velocity, the control device 100 proceeds to step S60, stops the thruster motor 59, and ends the process (returns to step S51).

[0147] On the other hand, if the determination in step S55 is YES and the yaw rate of the boat body 10 exceeds the determination angular velocity, the control device 100 drives the thruster motor 59 (step S56). Note that the determination in step S56 is YES when the yaw rate of the boat body 10 exceeds a predetermined amount with respect to the requested turning angular velocity calculated from the steering angle. That is, when the determination in step S56 is YES, the boat body 10 is in a so-called oversteering state.

[0148] After step S56, the control device 100 determines whether or not the steering handle 13 is pivotally operated rightward with respect to the neutral position (step S57). The determination in step S57 is performed based on the detection result of the steering angle sensor SN2.

[0149] If the determination in step S57 is YES and the steering handle 13 is pivotally operated rightward with respect to the neutral position, the control device 100 rotates the thruster motor 59 backward (step S58). Due to this, an auxiliary propulsion force of leftward, that is, in a direction opposite to the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10. On the other hand, if the determination in step S56 is NO and the steering handle 13 is pivotally operated leftward with respect to the neutral position, the control device 100 rotates the thruster motor 59 forward (step S58). Due to this, an auxiliary propulsion force of rightward, that is, in a direction opposite to the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10. After step S58 or step S59, the control device 100 ends the process (returns to step S51).

[0150] Thus, the fourth condition for driving the thruster motor 59 is a condition that the navigation speed of the boat body 10 is equal to or greater than the fourth determination speed, the engine 5 is being driven, the steering angle is greater than the fourth determination steering angle, and the yaw rate of the boat body 10 exceeds the determination angular velocity. When this fourth condition is satisfied, the thruster motor 59 is driven. At this time, an auxiliary propulsion force in a direction opposite to the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10. As described above, the opening degree direction of the steering handle 13 and the direction of the main propulsion force are opposite. Accordingly, when the third condition is satisfied, the orientation of the auxiliary propulsion force and the orientation of the main propulsion force are the same in the lateral direction.

Actions and Effects

[0151] When the engine 5 is driven at a navigation speed of equal to or greater than the first determination speed, the operation amount of the throttle lever 21 is small, and the main propulsion force imparted to the boat body 10 is small, the boat body 10 is likely to travel by inertia. When the steering angle is greater than the first determination steering angle, it is highly possible that the driver M intends to turn the boat body 10 in the lateral direction. Therefore, the first condition is satisfied when the boat body 10 is likely to travel by inertia while it is highly possible that the driver M intends to turn the boat body 10 in the lateral direction, that is, when a turning force due to the main propulsion force does not act on the boat body 10.

[0152] In the above embodiment, when the first condition is satisfied, the thruster motor 59 is driven. When the first condition is satisfied, an auxiliary propulsion force in the same orientation as the pivot direction of the steering handle 13 with respect to the neutral position in the lateral direction is imparted to the front part of the boat body 10. Therefore, according to the above embodiment, it is possible to prevent the boat body 10 from traveling by inertia in a direction different from the direction intended by the driver M.

[0153] This will be specifically described with reference to FIG. 14. FIG. 14 is a view schematically showing the motion of the boat body 10 when the first condition is satisfied. FIG. 14 shows the motion of the boat body 10 when the engine 5 is driven and the boat body 10 is navigating forward at a navigation speed of equal to or greater than the first determination speed by the main propulsion force. In FIG. 14, the solid line indicates the motion of the boat body 10 according to the above embodiment. In FIG. 14, the chain line indicates the motion of the boat body 10 of a comparative example when the thruster motor 59 is not driven even when the first condition is satisfied. FIG. 14 shows the motion of the boat body 10 when the second condition is satisfied as the driver M releases the operation of the throttle lever 21 and the operation amount of the throttle lever 21 becomes 0 and the driver M pivotally operates leftward the steering handle 13 at an angle greater than the first determination steering angle at a point P11.

[0154] When the operation amount of the throttle lever 21 is 0, that is, when the throttle is off, the engine 5 is brought into the idle state. Due to this, the propulsion force of the boat body 10 by the jet water stream becomes substantially 0 (zero). When the propulsion force of the boat body 10 by the jet water stream is substantially 0, the traveling direction of the boat body 10 is substantially unchanged even if the orientation of jet nozzle 34 is changed. On the other hand, even if the propulsion force imparted to the boat body 10 is 0, when the navigation speed of the boat body 10 is great, the boat body 10 travels by inertia.

[0155] Therefore, in the comparative example, as indicated by the chain line in FIG. 14, even if the driver M pivotally operates the steering handle 13 at the point P11, the boat body 10 travels forward as it is by inertia. Thus, in the comparative example, the boat body 10 travels in a direction different from the operation direction of the steering handle 13, that is, the traveling direction intended by the driver M.

[0156] On the other hand, in the above embodiment, due to the first condition satisfied at the point P11, the thruster motor 59 is driven, and an auxiliary propulsion force F10 in the same orientation as the pivot direction with respect to the neutral position of the steering handle 13 in the lateral direction is imparted to the front part of the boat body 10. Therefore, in the above embodiment, as indicated by the solid line in FIG. 14, the boat body 10 can be turned leftward by the auxiliary propulsion force. Therefore, according to the above embodiment, the boat body 10 can be moved in the pivot direction of the steering handle 13, that is, the direction intended by the driver M.

[0157] Note that when an auxiliary propulsion force in the same orientation as the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10, this auxiliary propulsion force acts so as to turn the rear part of the boat body 10 in a direction opposite to the pivot direction of the steering handle 13. Here, when the boat body 10 is moving backward and the steering handle 13 is pivotally operated rightward, the driver M tries to move the stern of the boat body 10 diagonally left rearward. Here, when the boat body 10 is moving backward and the steering handle 13 is pivotally operated leftward, the driver M tries to move the stern of the boat body 10 diagonally right rearward. Therefore, when an auxiliary propulsion force in the same direction as the pivot direction of the steering handle 13 is imparted to the front part of the boat body 10, a force for moving the boat body 10 in the orientation intended by the driver M in the lateral direction is imparted from the auxiliary propulsion device 3 to the boat body 10 even during moving backward of the boat body 10. Therefore, according to the above embodiment, the boat body 10 can be moved in the pivot direction of the steering handle 13, that is, in the direction intended by the driver M both during moving forward and during moving backward of the boat body 10.

[0158] When the operation amount of the throttle lever 21 is equal to or less than the second throttle determination amount and is relatively small, the propulsion force of the jet water stream is small. Therefore, at this time, even if the orientation of the jet nozzle 34 is changed, a change amount in the traveling direction of the boat body 10 can be suppressed to be relatively small. On the other hand, when the steering angle is greater than the second determination steering angle, it is highly possible that the driver M intends to greatly change the traveling direction of the boat body 10. Therefore, the second condition is established at least when it is highly possible that the driver M intends to greatly change the traveling direction of the boat body 10 while a change in the orientation of the jet nozzle 34 results in a change in the traveling direction of the boat body 10 suppressed to be small. In the above embodiment, when the second condition is satisfied, the thruster motor 59 is driven. At this time, an auxiliary propulsion force in the same orientation as the pivot direction of the steering handle 13 with respect to the neutral position in the lateral direction is imparted to the front part of the boat body 10. Therefore, according to the above embodiment, the traveling direction of the boat body 10 can be greatly changed to match the intention of the driver M.

[0159] This will be specifically described with reference to FIG. 15. FIG. 15 is a view schematically showing the motion of the boat body 10 when the second condition is satisfied. FIG. 15 shows the motion of the boat body 10 when the turn assist switch 25 is ON, the engine 5 is driven, the operation amount of the throttle lever 21 is greater than 0 and equal to or less than the second throttle determination amount, and the boat body 10 is navigating forward by the propulsion force of the jet water stream. In FIG. 15, the solid line indicates the motion of the boat body 10 according to the above embodiment. In FIG. 15, the chain line indicates the motion of the boat body 10 of a comparative example when the thruster motor 59 is not driven even when the second condition is satisfied. FIG. 15 shows the motion of the boat body 10 when the second condition is satisfied as the driver M pivotally operates leftward the steering handle 13 at an angle greater than the second determination steering angle at a point P21.

[0160] If the steering handle 13 is pivoted, the orientation of the jet nozzle 34 is changed, whereby the traveling direction of the boat body 10 is changed. However, when the operation amount of the throttle lever 21 is small, the propulsion force of the jet water stream with respect to the boat body 10 is small. Therefore, even if the orientation of the jet nozzle 34 is changed, the change amount in the traveling direction of the boat body 10 can be suppressed to be small. Due to this, in the comparative example, as indicated by the chain line in FIG. 15, the traveling direction of the boat body 10 changes from forward to diagonally left frontward as the driver M pivots the steering handle 13 leftward at the point P21. However, in the comparative example, the movement amount in the left direction is suppressed to be small.

[0161] On the other hand, in the above embodiment, due to the second condition satisfied at the point P21, the thruster motor 59 is driven, and the auxiliary propulsion force in addition to the main propulsion force is imparted to the boat body 10. At this time, an auxiliary propulsion force F20 in in the same orientation as the pivot direction of the steering handle 13 with respect to the neutral position in the lateral direction, that is, the left direction is imparted to the front part of the boat body 10, and a leftward turning force is imparted to the boat body 10. Therefore, according to the above embodiment, as indicated by the solid line in FIG. 15, the orientation of the boat body 10 can be greatly changed to the left side, and the traveling direction of the boat body 10 can be changed to match the intention of the driver M.

[0162] Moreover, in the above embodiment, only when the turn assist switch 25 is ON, the second condition is satisfied and the thruster motor 59 is driven. Therefore, the driver M can select whether or not to use the auxiliary propulsion force in order to change the traveling direction of the boat body 10.

[0163] Note that similarly to when the first condition is satisfied, also when the second condition is satisfied, an auxiliary propulsion force in the same orientation as the pivot direction of the steering handle 13 in the lateral direction is imparted to the front part of the boat body 10. Therefore, according to the above embodiment, when the second condition is satisfied, the boat body 10 can be moved in the pivot direction of the steering handle 13, that is, in the direction intended by the driver M both during moving forward and during moving backward of the boat body 10, and the traveling direction of the boat body 10 can be changed to match the intention of the driver M.

[0164] In the above embodiment, the thruster motor 59 is driven as the third condition is satisfied. When the third condition is satisfied, an auxiliary propulsion force in a direction opposite to the pivot direction with respect to the neutral position of the steering handle 13 is imparted to the front part of the boat body 10. Therefore, according to the above embodiment, it is possible to suppress excessive tilting of the boat body 10 and stabilize the boat body 10.

[0165] This will be specifically described with reference to FIG. 16. FIG. 16 is a schematic view for describing actions and effects when the thruster motor 59 is driven in association with satisfaction of the third condition. FIG. 16 is a view of the boat body 10 as viewed from the rear. FIG. 16 shows that the steering handle 13 is pivotally operated leftward and the boat body 10 travels diagonally left forward as indicated by arrow Y30. Note that illustration of the driver M is omitted.

[0166] When the navigation speed of the boat body 10 is equal to or greater than the third determination speed, the engine 5 is driven, and the steering angle is greater than the third determination steering angle, that is, when the boat body 10 is traveling at a high speed by receiving the main propulsion force and the steering handle 13 is greatly pivotally operated, the boat body 10 tilts to a pivot direction side of the steering handle 13. In the example of FIG. 16, due to the steering handle 13 being pivotally operated leftward while the boat body 10 is moving forward, the boat body 10 tilts to the left side. In detail, the boat body 10 tilts such that its upper part falls to the left side. When the boat body 10 tilts in this manner and a tilting angle, that is, a roll angle of the boat body 10 is great, the boat body 10 is not stabilized and the driver M easily loses his balance.

[0167] On the contrary, in the above embodiment, the thruster motor 59 is driven when the navigation speed of the boat body 10 is equal to or greater than the third determination speed, the engine 5 is being driven, the steering angle is greater than the third determination steering angle, and the roll angle of the boat body 10 exceeds the determination angle. The thruster motor 59 imparts, to the boat body 10, an auxiliary propulsion force in a direction opposite to the pivot direction with respect to the neutral position of the steering handle 13. In the example of FIG. 16, an auxiliary propulsion force F30 of rightward is imparted to the boat body 10 from the auxiliary propulsion device 3.

[0168] Here, in the above embodiment, the auxiliary propulsion device 3 is positioned more upward than the center of gravity G of the boat body 10. Therefore, the propulsion force of the auxiliary propulsion device 3 causes a moment in a direction opposite to the tilting direction of the boat body 10 to act on the boat body 10. In the example of FIG. 16, the auxiliary propulsion force F30 of the auxiliary propulsion device 3 causes a moment M30 pivoting rightward the upper part of the boat body 10 to act on the boat body 10. Therefore, according to the above embodiment, the roll angle of the boat body 10 can be reduced to be equal to or less than the determination angle. In other words, the control device 100 controls the thruster motor 59 so that the roll angle of the boat body 10 is equal to or less than the determination angle, that is, within the allowable range from 0 (zero) to equal to or less than the determination angle. Thus, according to the above embodiment, the boat body 10 can be stabilized.

[0169] When the steering handle 13 is greatly pivotally operated while the boat body 10 is traveling at a high speed by receiving the main propulsion force, there is a possibility that the boat body 10 is brought into an oversteering state due to an influence of waves and wind. That is, even though the driver M operates the steering handle 13 so that the boat body 10 moves at a predetermined speed in the lateral direction, there is a possibility that the angle of the boat body 10 with respect to a turning direction, that is, the angular velocity becomes excessively larger than a level intended by the driver M, and the boat body 10 enters a turning center side relative to a course desired by the driver M.

[0170] On the contrary, in the above embodiment, the thruster motor 59 is driven when the fourth condition is satisfied that the navigation speed of the boat body 10 is equal to or greater than the fourth determination speed, the engine 5 is being driven, the steering angle is greater than the fourth determination steering angle, and the yaw rate exceeds the determination angular velocity. At this time, the thruster motor 59 imparts, to the front part of the boat body 10, an auxiliary propulsion force in a direction opposite to the pivot direction with respect to the neutral position of the steering handle 13. Therefore, according to the above embodiment, the boat body 10 can be stably turned.

[0171] This will be specifically described with reference to FIG. 17. FIG. 17 is a view schematically showing the motion of the boat body 10 when the fourth condition is satisfied. FIG. 17 shows the motion of the boat body 10 when the engine 5 is driven, the boat body 10 is navigating at a navigation speed of equal to or greater than the fourth determination speed by the main propulsion force, and the steering handle 13 is pivotally operated leftward with an operation amount of equal to or greater than a fourth steering angle. In FIG. 17, the solid line indicates the motion of the boat body 10 according to the above embodiment. The chain line and the broken line in FIG. 17 indicate the motion of the boat body 10 according to the comparative example. Specifically, the chain line in FIG. 17 indicates the motion of the boat body 10 when the oversteering does not occur and indicates the motion of the boat body 10 desired by the driver M. The broken line in FIG. 17 indicates the motion of the boat body 10 when the oversteering occurs and the thruster motor 59 is not driven even when the fourth condition is satisfied.

[0172] In the example of FIG. 17, the steering handle 13 is pivotally operated leftward so that the boat body 10 moves along a turning route L40 as indicated by the chain line. When the steering handle 13 is pivotally operated leftward in this manner, as indicated by the broken line in FIG. 17, there is a possibility that the boat body 10 is brought into an oversteering state where the boat body 10 deviates to the left side from the turning route L40 and greatly turns in the left direction. In the oversteering state, the traveling direction of the boat body 10 deviates from the direction requested by the driver M, and the course of the boat body 10 also greatly deviates from the desired turning route L40. On the contrary, in the above embodiment, when the fourth condition is satisfied in the oversteering state, an auxiliary propulsion force F40 in the direction opposite to the steering handle 13, that is, the auxiliary propulsion force F40 in the right direction is imparted to the front part of the boat body 10. This auxiliary propulsion force F40 causes a moment M40 pivoting rightward the front part of the boat body 10 to act on the boat body 10. Therefore, according to the above embodiment, it is possible to reduce the roll rate by increasing a turning diameter of the boat body 10. That is, according to the above embodiment, the roll rate of the boat body 10 can be made equal to or less than the determination angular velocity. In other words, the control device 100 controls the thruster motor 59 so that the roll rate of the boat body 10 is equal to or less than the determination angular velocity, that is, within the allowable range of equal to or less than the determination angular velocity. Thus, according to the above embodiment, the boat body 10 can be stabilized.

[0173] As described above, the first to fourth conditions, which are conditions for driving the thruster motor 59, include conditions that the steering angle is equal to or greater than a predetermined amount (the first determination steering angle, the second determination steering angle, the third determination steering angle, and the fourth determination steering angle), respectively. In steps S6 to S8, steps S19 to S21, steps S36 to S38, and steps S47 to S49, a driving direction of the thruster motor 59 is changed in accordance with the pivot direction of the steering handle 13. That is, in the above embodiment, drive/stop of the thruster motor 59 is switched and the rotation direction thereof is determined in response to an operation state of the steering handle 13. Therefore, the thruster motor 59 can be appropriately controlled in response to an operation situation of the steering handle 13, and the auxiliary propulsion force in addition to the main propulsion force can be appropriately imparted to the boat body 10.

[0174] In particular, when the first condition and the second condition are satisfied, the thruster motor 59 is driven such that the orientation same as the pivot direction of the steering handle 13, i.e., the orientation of the main propulsion force in the lateral direction and the orientation of the auxiliary propulsion force become the same, whereby the traveling direction of the boat body 10 can be made the direction that matches the operation state of the steering handle 13, i.e., the intention of the driver M.

[0175] When the third condition and the fourth condition are satisfied, the thruster motor 59 is driven such that the orientation of the main propulsion force in the direction opposite to the pivot direction of the steering handle 13, i.e., the lateral direction and the orientation of the auxiliary propulsion force become opposite to each other, whereby behavior of the boat body 10 can be stabilized.

[0176] Here, in the above embodiment, the steering angle and the pivot direction of the steering handle 13, that is, the operation state of the steering handle 13 corresponds to the operation of the steering device in the present disclosure. The steering angle corresponds to the operation amount of the steering device in the present disclosure. The first determination steering angle, the second determination steering angle, the third determination steering angle, and the fourth determination steering angle each correspond to the predetermined amount in the present disclosure. The third condition and the fourth condition each correspond to the stabilization condition in the present disclosure.

[0177] The first to fourth conditions respectively include a condition that the navigation speed is within a predetermined range (steps S1, S15, S31, and S41). That is, in the above embodiment, drive/stop of the thruster motor 59 is switched in response to the operation state of the steering handle 13 and the state of the boat body 10. Therefore, the thruster motor 59 can be appropriately controlled in response to the operation situation of the steering handle 13 and the state of the boat body 10, and the auxiliary propulsion force in addition to the main propulsion force can be appropriately imparted to the boat body 10.

[0178] When the first condition is satisfied, the output of the thruster motor 59 and thus the auxiliary propulsion force increase as the steering angle is large. When the steering angle is large, it is highly possible that the driver M desires to greatly change the traveling direction of the boat body 10. Therefore, according to the above embodiment, since a larger turning force can be imparted from the auxiliary propulsion device 3 to the boat body 10 when the steering angle is large, the traveling direction of the boat body 10 can be greatly changed in accordance with the intention of the driver M.

[0179] When the second condition is satisfied, the momentum of the auxiliary water stream and the auxiliary propulsion force are increased as the main propulsion force is large. When the main propulsion force is large, it is highly possible that the driver M desires to greatly change the traveling direction of the boat body 10. Therefore, according to the above embodiment, since a larger turning force can be imparted from the auxiliary propulsion device 3 to the boat body 10 when the main propulsion force is large, the traveling direction of the boat body 10 can be greatly changed in accordance with the intention of the driver M.

[0180] The fourth condition includes a condition that the key in use is the SLO key, and drive/stop of the thruster motor 59 is switched depending on whether or not the key in use is the SLO key. Here, depending on the key in use, the control mode of the main propulsion device 2 is switched between the normal mode and the beginner mode. Thus, drive/stop of the thruster motor 59 is switched depending on the type of the control mode of the main propulsion device 2. That is, according to the present embodiment, the auxiliary propulsion device 3 can be controlled in accordance with the control mode of the main propulsion device 2, and the state of the main propulsion device 2 and the state of the auxiliary propulsion device 3 can be made to correspond to each other.

Modifications

[0181] In the above embodiment, in steps S4, S17, S33, and S43, the pivot amount of the steering handle 13, which is the steering angle, detected by the steering angle sensor SN2 is compared with each determination steering angle. Alternatively, a parameter that changes in proportion to the pivot amount of the steering handle 13 may be used and compared with a predetermined amount. For example, the swing amount of the jet nozzle 34 from the basic position may be compared with the predetermined amount. Similarly, also in steps S6, S19, S36, and S47, determination may be performed using another parameter in place of the detection result of the steering angle sensor SN2.

[0182] In the above embodiment, the jet nozzle 34 is swung by the nozzle motor 39. Alternatively, by mechanically coupling the jet nozzle 34 and the steering handle 13, the jet nozzle 34 may be directly swung and operated by the steering handle 13. In this case, in steps S4, S17, S33, and S43, in place of comparison between the steering angle with each determination steering angle, a displacement amount or the like of a component connecting the steering handle 13 and the jet nozzle 34 may be compared with the predetermined amount. In steps S6, S19, S36, and S47, determination may be performed using the displacement amount or the like.

[0183] In the above embodiment, the throttle valve is opened/closed by a lever-type throttle lever. The specific configuration of an operation device that opens/closes the throttle valve is not limited to this. For example, this operation may be performed by a grip-type or button-type operation device.

[0184] In the above embodiment, the navigation speed of the boat body 10 is specified by a GPS function of the control device 100. The specific configuration for specifying the navigation speed of the boat body 10 is not limited to this. For example, the navigation speed may be specified based on a detection value of a sensor that detects the rotation speed of the engine 5. The navigation speed may be specified based on a detection value of a sensor incorporating a waterwheel.

[0185] The condition for driving the thruster motor 59 is not limited to the condition that the steering angle is equal to or larger than the determination steering angle as in the above embodiment. For example, the condition for driving the thruster motor 59 may include a condition that the change amount of the steering angle is equal to or greater than a predetermined value.

[0186] In the above embodiment, the case where the fourth condition includes a condition that the yaw rate exceeds the determination angular velocity, and the thruster motor 59 is driven when the boat body 10 is in the oversteering state has been described. Alternatively or additionally, the thruster motor 59 may be driven when the boat body 10 is in an understeering state. As specific control content in a case of driving the thruster motor 59 when the boat body 10 is in the understeering state, whether or not the yaw rate is less than a predetermined angular velocity may be determined in step S44 of the flowchart shown in FIG. 13. That is, whether the yaw rate exceeds an allowable range of equal to or greater than a predetermined angle may be determined. The rotation direction of the thruster motor 59 may be forward rotation in step S48 of the flowchart shown in FIG. 13, and the rotation direction of the thruster motor 59 may be backward rotation in step S49.

[0187] In the above embodiment, the case where the thruster motor 59 is driven when the roll angle exceeds the determination angle and the third condition is satisfied has been described. Alternatively or additionally, the thruster motor 59 may be configured to be driven when the roll rate exceeds a predetermined allowable range.

[0188] In the above embodiment, the case where the auxiliary propulsion device 3 is positioned more forward than the center of gravity G of the boat body 10 has been described, but the position in the front-rear direction of the auxiliary propulsion device 3 is not limited to this. Note that when the auxiliary propulsion device 3 is disposed more rearward than the center of gravity G of the boat body 10, that is, when the auxiliary propulsion device 3 is disposed on the same side as the side where the jet water stream is generated with respect to the center of gravity G in the front-rear direction, the rotation direction of the thruster motor 59 may be altered to the forward rotation in steps S7, S20, and S49 described above. Similarly, in steps S8, S21, and S48 described above, the rotation direction of the thruster motor 59 may be altered to the forward rotation.

[0189] In the above embodiment, the case where the auxiliary propulsion device 3 is positioned more upward than the center of gravity G of the boat body 10 has been described, but the position in the up-down direction of the auxiliary propulsion device 3 is not limited to this. Note that when the auxiliary propulsion device 3 is disposed more downward than the center of gravity G of the boat body 10, the rotation direction of the thruster motor 59 may be altered to the forward rotation in step S37 described above. Similarly, in step S38 described above, the rotation direction of the thruster motor 59 may be altered to the backward rotation.

[0190] An operator that can operate the thruster motor 59 may be provided separately from the steering handle 13. Hereinafter, this operator is called a second operator. That is, the thruster motor 59 may be controlled in response to the operation on the second operator regardless of the operation state of the steering handle 13. Specifically, drive and stop of the thruster motor 59 may be switched and the output may be changed in response to the operation on the second operator. Note that when the steering handle 13 is operated simultaneously with the second operator in the case of providing the second operator, the boat body 10 may be controlled based on one of the second operator and the steering handle 13. For example, when the steering handle 13 is operated simultaneously with the second operator, the steering handle 13 may be prioritized over the second operator. That is, the operation of the second operator may be invalidated, and the boat body 10 may be navigated based on the operation of the steering handle 13. Similarly, when the throttle lever 21 is operated simultaneously with the second operator, the boat body 10 may be controlled based on one of the second operator and the throttle lever 21. For example, when the throttle lever 21 is operated simultaneously with the second operator, the throttle lever 21 may be prioritized over the second operator. That is, the operation of the second operator may be invalidated, and the boat body 10 may be navigated based on the operation of the throttle lever 21. In place of or in addition to the steering handle 13 and the throttle lever 21, an operator prioritized over the second operator may be separately provided on the steering handle 13. Note that the second operator may include a so-called joystick, a dial-type switch, or a switch displayed on a display configured to be able to change the traveling direction of the boat body 10.

Summary

[0191] The above embodiment and modifications thereof include the following disclosure.

[0192] A jet propulsion boat according to one aspect of the present disclosure includes: a boat body; a jet water stream generation device that jets a jet water stream from the boat body to impart a propulsion force in a front-rear direction to the boat body; a steering device including a steering operator operated by a driver, and changes an orientation in a lateral direction of a propulsion force of the jet water stream generation device in response to an operation on the steering operator; an auxiliary propulsion device provided on the boat body to impart a propulsion force in a lateral direction to the boat body; and a control device that controls the auxiliary propulsion device based on an operation of the steering device.

[0193] According to the present disclosure, it is possible to perform drive assist of the driver by adding the propulsion force of the auxiliary propulsion device to the propulsion force of the jet water stream generation device. In particular, since the auxiliary propulsion device is controlled based on the operation of the steering device that changes the orientation of the propulsion force of the jet water stream generation device, the orientation and magnitude of the propulsion force of the auxiliary propulsion device can be made to correspond to the orientation and magnitude of the propulsion force of the jet water stream generation device.

[0194] Preferably, the control device controls the auxiliary propulsion device based on an operation of the steering device and a state of the boat body.

[0195] According to this aspect, more appropriate drive assist based on the operation of the steering device and the state of the boat body is possible.

[0196] Preferably, the control device drives the auxiliary propulsion device when an operation amount of the steering device exceeds a predetermined amount and the boat body is in a predetermined state.

[0197] According to this aspect, it is possible to perform drive assist when a request for drive assist is high, such as when the driver wants to greatly change the orientation of the boat body.

[0198] Preferably, the control device controls the auxiliary propulsion device such that the orientation in the lateral direction of the propulsion force of the jet water stream generation device is same as an orientation in the lateral direction of the propulsion force of the auxiliary propulsion device.

[0199] According to this aspect, the orientation of the boat body can be changed at an early stage or the behavior of the boat body can be stabilized by using the propulsion force of the auxiliary propulsion device.

[0200] Preferably, the control device controls the auxiliary propulsion device such that the orientation in the lateral direction of the propulsion force of the jet water stream generation device is opposite to an orientation in the lateral direction of the propulsion force of the auxiliary propulsion device.

[0201] According to this aspect, the orientation of the boat body can be changed at an early stage or the behavior of the boat body can be stabilized by using the propulsion force of the auxiliary propulsion device.

[0202] Preferably, the control device increases the propulsion force of the auxiliary propulsion device as an operation amount of the steering device is large.

[0203] According to this aspect, a larger propulsion force can be imparted to the boat body when the request for drive assist is high, such as when the driver wants to greatly change the orientation of the boat body. Therefore, drive assist can be performed more appropriately.

[0204] Preferably, the control device increases the propulsion force of the auxiliary propulsion device as the propulsion force of the jet water stream generation device is large.

[0205] According to this aspect, the propulsion force of the auxiliary propulsion device can be made to correspond to the propulsion force of the jet water stream generation device.

[0206] Preferably, the jet propulsion boat includes a throttle operator provided on the boat body and operated by the driver to increase or decrease the propulsion force of the jet water stream generation device, in which when the boat body is traveling, the steering device is operating in a direction of turning the boat body to one side of the lateral direction, and an operation amount of the throttle operator is equal to or less than a predetermined determination operation amount, the control device drives the auxiliary propulsion device and controls the auxiliary propulsion device such that the propulsion force of the auxiliary propulsion device acts in a direction of turning the boat body to the one side of the lateral direction.

[0207] According to this aspect, when the operation amount of the throttle operator is small and the propulsion force of the jet water stream generation device is small, the propulsion force of the auxiliary propulsion device can impart the propulsion force to the boat body, and the movement of the boat body can be promoted.

[0208] Preferably, the control device determines whether a predetermined stabilization condition is satisfied based on the operation of the steering device, and when the stabilization condition is satisfied, the control device controls the auxiliary propulsion device such that the propulsion force of the auxiliary propulsion device acts in a direction of stabilizing an attitude of the boat body.

[0209] According to this aspect, the boat body can be stabilized.

[0210] Preferably, the stabilization condition includes a condition that a yaw rate of the boat body exceeds an allowable range set based on the operation of the steering device, and when the stabilization condition is satisfied, the control device drives the auxiliary propulsion device and controls the auxiliary propulsion device such that the yaw rate of the boat body falls within the allowable range.

[0211] According to this aspect, the boat body can be stabilized by setting the yaw rate within the allowable range.

[0212] Preferably, the stabilization condition includes a condition that a roll angle or a roll rate of the boat body exceeds a predetermined allowable range, and when the stabilization condition is satisfied, the control device drives the auxiliary propulsion device and controls the auxiliary propulsion device such that the roll angle or the roll rate exceeding the allowable range falls within the allowable range.

[0213] According to this aspect, the boat body can be stabilized in the roll direction.

[0214] Preferably, the steering operator is pivotally operated in the lateral direction from a predetermined neutral position, and includes a detection device that detects an operation direction and an operation amount of the steering operator, and the control device controls the auxiliary propulsion device based on a detection result of the detection device.

[0215] According to this aspect, drive assist suitable for the operation situation of the driver with respect to the steering operator is possible.

[0216] Preferably, the control device switches an operation mode of the jet water stream generation device between a plurality of modes, and controls the auxiliary propulsion device based on the operation of the steering device and a type of the operation mode of the jet water stream generation device.

[0217] According to this aspect, drive assist corresponding to the driver's intention can be performed.