ELECTRIC PROPULSION MACHINE

Abstract

An electric propulsion machine for propelling a boat. The electric propulsion machine includes a motor provided in an upper portion of the electric propulsion machine, a propeller shaft provided in a lower portion of the electric propulsion machine, a propeller provided in the propeller shaft, a drive shaft extending in an upper-lower direction and configured to transmit rotation of the motor to the propeller shaft, and a first non-positive displacement pump provided in the propeller shaft and configured to supply cooling water to the motor, the cooling water cooling the motor.

Claims

1. An electric propulsion machine for propelling a boat, the electric propulsion machine comprising: a motor provided in an upper portion of the electric propulsion machine; a propeller shaft provided in a lower portion of the electric propulsion machine; a propeller provided in the propeller shaft; a drive shaft extending in an upper-lower direction and configured to transmit rotation of the motor to the propeller shaft; and a first non-positive displacement pump provided in the propeller shaft and configured to supply cooling water to the motor, the cooling water cooling the motor.

2. The electric propulsion machine according to claim 1, wherein the first non-positive displacement pump is provided at a front end side of the propeller shaft.

3. The electric propulsion machine according to claim 2, further comprising: a transfer passage configured to transfer the cooling water from the first non-positive displacement pump to the motor, wherein the transfer passage is provided in front of the drive shaft in the electric propulsion machine.

4. The electric propulsion machine according to claim 2, further comprising: a water intake port configured to take in water around the electric propulsion machine into the electric propulsion machine, wherein the water intake port is provided in front of the propeller shaft, and the first non-positive displacement pump faces the water intake port.

5. The electric propulsion machine according to claim 2, wherein the first non-positive displacement pump includes a pump shaft and an impeller, the impeller is provided at a front end portion of the pump shaft, and a rear end portion of the pump shaft is connected to a front end portion of the propeller shaft.

6. The electric propulsion machine according to claim 1, further comprising: a second non-positive displacement pump provided between the first non-positive displacement pump and the motor, and configured to transfer cooling water discharged from the first non-positive displacement pump to the motor.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0016] Exemplary embodiment(s) of the present invention will be described in detail based on the following figures, wherein:

[0017] FIG. 1 is an overall view illustrating an outboard motor that is a first embodiment of an electric propulsion machine of the present disclosure.

[0018] FIG. 2 is a cross-sectional view illustrating a lower portion of the outboard motor in FIG. 1.

[0019] FIG. 3 is an enlarged cross-sectional view of a portion where a water pump is provided in a lower portion of the outboard motor in FIG. 2.

[0020] FIG. 4 is a cross-sectional view illustrating a lower portion of an outboard motor that is a second embodiment of the electric propulsion machine of the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0021] An electric propulsion machine according to an embodiment of the present disclosure is an electric propulsion machine for propelling a boat and includes: a motor provided in an upper portion of the electric propulsion machine; a propeller shaft provided in a lower portion of the electric propulsion machine; a propeller provided in the propeller shaft; a drive shaft extending in an upper-lower direction and configured to transmit rotation of the motor to the propeller shaft; and a first non-positive displacement pump provided in the propeller shaft and configured to supply cooling water cooling the motor to the motor.

[0022] In the electric propulsion machine of the present embodiment, the pump is provided in the propeller shaft. In a state in which the electric propulsion machine is attached to the boat, the propeller shaft is located below a water surface, and the pump provided on the propeller shaft is also located below the water surface. Accordingly, it is possible to easily ensure priming of the pump, that is, it is possible to easily obtain a state in which the periphery of the impeller is filled with water at the start of driving of the pump. Therefore, it is possible to use a non-positive displacement pump that requires priming. The non-positive displacement pump is easily reduced in size as compared with a rotary volume change pump having a rubber impeller. Therefore, according to the electric propulsion machine of the present embodiment, it is possible to reduce the size of the electric propulsion machine by using the non-positive displacement pump.

[0023] In the electric propulsion machine of the present embodiment, the rotation of the motor is transmitted to the propeller shaft via the drive shaft. When the rotation direction of the motor is reversed, the rotation direction of the propeller shaft is reversed. The pump is provided on the propeller shaft and rotates integrally with the propeller shaft. When the rotation direction of the motor is reversed, the rotation direction of the impeller of the pump is also reversed. In a case where the pump is used in the manner that the rotation direction of the impeller is reversed, when the durability of the rotary volume change pump having the rubber impeller is compared to the durability of the non-positive displacement pump, the durability of the non-positive displacement pump is significantly higher. Therefore, according to the electric propulsion machine of the present embodiment using the non-positive displacement pump, it is possible to solve the above problem that the durability of the motor cooling pump decreases in the electric propulsion machine having a configuration in which the rotation direction of the motor is reversed.

Embodiment 1

[0024] Two embodiments of the electric propulsion machine of the present disclosure will be described with reference to FIGS. 1 to 4. In the description, when describing directions of the upper (Ud), the lower (Dd), the front (Fd), and the rear (Bd), please follow arrows drawn at the lower right of each figure.

[0025] FIG. 1 illustrates an outboard motor 1 that is a first embodiment of the electric propulsion machine of the present disclosure. FIG. 2 illustrates a cross section of a lower portion of the outboard motor 1 which is divided into two parts that are left and right parts along a plane passing through a center in the left-right direction of the outboard motor 1. FIG. 3 is an enlarged view of a portion where the water pump 22 is provided in the lower portion of the outboard motor 1 in FIG. 2.

[0026] The outboard motor 1 is a device configured to propel a boat and is attached to the boat. As illustrated in FIG. 1, the outboard motor 1 includes a motor 2 that is a power source configured to generate a propulsion force of a boat, a motor control device 3 configured to control driving of the motor 2, a propeller 4 configured to generate a propulsion force of the boat from the rotation of the motor 2, a propeller shaft 5 to which the propeller 4 is fixed, a drive shaft 6 configured to transmit the rotation of the motor 2 to the propeller shaft 5, and a gear mechanism 7 configured to transmit the rotation of the motor 2 to the propeller shaft 5 together with the drive shaft 6.

[0027] The motor 2 and the motor control device 3 are provided in an upper portion of the outboard motor 1 and located above the water surface in a state in which the outboard motor 1 is attached to the boat. The outboard motor 1 also includes an upper case 10. The motor 2 and the motor control device 3 are accommodated in the upper case 10.

[0028] The propeller 4, the propeller shaft 5, and the gear mechanism 7 are provided in the lower portion of the outboard motor 1, and are located below the water surface in the state in which the outboard motor 1 is attached to the boat. The propeller shaft 5 extends in a front-rear direction. The propeller 4 is fixed to a rear end portion of the propeller shaft 5. The outboard motor 1 also includes a lower case 11. A front portion of the propeller shaft 5 and the gear mechanism 7 are accommodated in the lower case 11. An anti-cavitation plate 12 is provided in the lower case 11.

[0029] The drive shaft 6 extends in an upper-lower direction from the motor 2 toward the propeller shaft 5. An upper portion of the drive shaft 6 is located inside the upper case 10. An upper end portion of the drive shaft 6 is connected to an output shaft of the motor 2. A lower portion of the drive shaft 6 is located in the lower case 11. A lower end portion of the drive shaft 6 is connected to the propeller shaft 5 via the gear mechanism 7. Specifically, the gear mechanism 7 includes a drive gear 8 and a driven gear 9. The drive gear 8 is fixed to the lower end portion of the drive shaft 6. The driven gear 9 is fixed to the front portion of the propeller shaft 5. The drive gear 8 and the driven gear 9 are bevel gears and mesh with each other.

[0030] The motor control device 3 includes, for example, an inverter configured to generate a drive current driving the motor 2, a host control unit configured to control the inverter in accordance with an operation input from the outside of the outboard motor 1, and the like. When driving the motor 2, the motor control device 3 selects the rotation direction of the motor 2 in response to the operation input from the outside of the outboard motor 1. Specifically, the motor control device 3 is configured to rotate the motor 2 in one direction in a case where the boat is moved forward, and is configured to rotate the motor 2 in the other direction in a case where the boat is moved backward. In a case where the motor 2 rotates in one direction under the control of the motor control device 3, the rotation of the motor 2 is transmitted from the output shaft to the drive shaft 6, and the drive shaft 6 rotates. Further, the rotation of the drive shaft 6 is transmitted to the propeller shaft 5 via the gear mechanism 7, causing the propeller shaft 5 and the propeller 4 to rotate forward. The forward rotation of the propeller 4 generates the propulsion force for moving the boat forward. In a case where the motor 2 rotates in the other direction under the control of the motor control device 3, the rotation is transmitted to the propeller shaft 5 via the drive shaft 6 and the gear mechanism 7, and the propeller shaft 5 and the propeller 4 rotate reversely. The reverse rotation of the propeller 4 generates a propulsion force for moving the boat backward.

[0031] Further, the outboard motor 1 is provided with a clamp bracket 13 that attaches the outboard motor 1 to a transom of the boat, and a swivel bracket 14 that connects the outboard motor 1 to the boat such that a horizontal direction of the propeller 4 with respect to the boat can be changed.

[0032] Further, the outboard motor 1 includes a water-cooling cooling mechanism 20 configured to cool the motor 2. The cooling mechanism 20 includes a water intake port 21 configured to take in water around the outboard motor 1 into the outboard motor 1 as cooling water, a water pump 22 configured to supply the cooling water taken in from the water intake port 21 to the motor 2, and a water jacket 30 configured to cool the motor 2 by making the cooling water flow to, for example, an outer peripheral portion of the motor 2.

[0033] The water pump 22 is a non-positive displacement pump, for example, a centrifugal pump. The water pump 22 is provided at a front end side of the propeller shaft 5. Specifically, as illustrated in FIG. 3, the water pump 22 includes a pump shaft 23 and an impeller 24. The pump shaft 23 extends in the front-rear direction. A rear end portion of the pump shaft 23 is connected to a front end portion of the propeller shaft 5. The impeller 24 is fixed to a front end portion of the pump shaft 23. The pump shaft 23 and the impeller 24 rotate integrally with the propeller shaft 5. A support member 25 that supports the front end portion of the propeller shaft 5 and the pump shaft 23 is provided in a front portion of a lower portion in the lower case 11. The front end portion of the propeller shaft 5 and the pump shaft 23 are rotatably supported by the support member 25 via bearings. A pump chamber 26 is formed in the front portion of the lower portion of the lower case 11 in front of the support member 25. The impeller 24 is disposed in the pump chamber 26. Further, a suction port 27 is formed in a front portion of the pump chamber 26. A discharge port 28 is formed in an upper portion of the pump chamber 26.

[0034] The water intake port 21 is provided in the front portion of the lower portion in the lower case 11. The water intake port 21 is disposed in front of the propeller shaft 5. The water intake port 21 is disposed in front of the water pump 22. Specifically, the water intake port 21 is disposed immediately in front of the pump chamber 26 and the impeller 24. The suction port 27 and the impeller 24 face the water intake port 21. A strainer for preventing dust or the like in water from entering the inside of the outboard motor 1 is provided in the water intake port 21. A water intake passage 29 is provided between the water intake port 21 and the suction port 27. The water intake passage 29 extends in the front-rear direction. The water intake passage 29 is extremely short, and the water intake port 21 and the suction port 27 are extremely close to each other.

[0035] As illustrated in FIG. 1, the water jacket 30 is provided in the motor 2. The water jacket 30 is implemented by, for example, a cooling water passage formed to cover the entire outer peripheral portion of the motor 2. A transfer passage 33 configured to transfer the cooling water from the water pump 22 to the water jacket 30 is provided between the discharge port 28 of the pump chamber 26 and the water jacket 30. The transfer passage 33 is provided in front of the drive shaft 6 in the outboard motor 1. A lower portion of the transfer passage 33 is disposed in the lower case 11 as illustrated in FIG. 2. A lower end portion of the transfer passage 33 is connected to the discharge port 28 of the pump chamber 26 as illustrated in FIG. 3. Further, an upper portion of the transfer passage 33 is disposed in the upper case 10 as illustrated in FIG. 1. An upper end portion of the transfer passage 33 is connected to a cooling water inlet 31 of the water jacket 30. A drain passage 34 configured to discharge the cooling water after flowing through the water jacket 30 to the outside of the outboard motor 1 is connected to a cooling water outlet 32 of the water jacket 30.

[0036] In the outboard motor 1, the pump chamber 26 is disposed right behind the water intake port 21, and the position of the pump chamber 26 and the position of the water intake port 21 are the same in the upper-lower direction. Therefore, in a case where the outboard motor 1 is attached to the boat and the water intake port 21 completely sinks in water, water around the outboard motor 1 naturally flows into the pump chamber 26 from the water intake port 21. As a result, the pump chamber 26 is filled with water, and the periphery of the impeller 24 is filled with water. In this way, in the outboard motor 1, the water intake port 21 is completely submerged in water, so that the priming of the water pump 22 is ensured.

[0037] Thereafter, when the motor 2 is driven and the propeller shaft 5 rotates, the impeller 24 of the water pump 22 rotates together with the propeller shaft 5. Water that has flowed from the water intake port 21 into the pump chamber 26 as the cooling water is fed to the water jacket 30 via the transfer passage 33 by the rotation of the impeller 24. The cooling water fed to the water jacket 30 flows through the inside of the water jacket 30. Accordingly, the motor 2 is cooled. The cooling water after flowing through the inside of the water jacket 30 is discharged to the outside of the outboard motor 1 from a discharge port provided in, for example, a boss portion of the propeller 4 via the drain passage 34.

[0038] Further, since a rotation direction of the impeller 24 of the water pump 22 is determined by a rotation direction of the propeller shaft 5, the rotation direction of the impeller 24 is opposite when the propeller shaft 5 rotates forward and when the propeller shaft 5 rotates reversely. However, the water pump 22 provided in the outboard motor 1 exhibits a suction capacity and a discharge capacity regardless of the rotation direction of the impeller 24.

[0039] Further, since the water intake port 21 is disposed immediately in front of the suction port 27 of the pump chamber 26, when the boat moves forward, water around the outboard motor 1 flows vigorously into the pump chamber 26 through the water intake port 21. The water pressure at this time assists in the direction of promoting the rotation of the impeller 24, and as a result, the smoothness of the flow of the cooling water from the water intake port 21 to the water jacket 30 is improved.

[0040] As described above, in the outboard motor 1 of the first embodiment of the present disclosure, the water pump 22 is provided on the propeller shaft 5. Since the water pump 22 is provided on the propeller shaft 5, the water pump 22 is located below the anti-cavitation plate 12, and when the outboard motor 1 is attached to the boat, the entire water pump 22 is located below the water surface. As a result, it is easy to ensure priming of the water pump 22. Therefore, in the outboard motor 1, the non-positive displacement pump that requires priming can be adopted as the water pump 22. The non-positive displacement pump is easily reduced in size as compared with the rotary volume change pump having the rubber impeller used in many boat propulsion machines in the related art. According to the outboard motor 1 of the present embodiment, it is possible to reduce the size of the outboard motor by using the non-positive displacement pump. Further, among the non-positive displacement pumps, the centrifugal pump has a simple structure and therefore has a small size and is lightweight. By using the centrifugal pump as the water pump 22, it is possible to promote size reduction and weight reduction of the outboard motor 1.

[0041] Further, in the outboard motor 1 of the present embodiment, the rotation direction of the impeller 24 is reversed in response to the switching of the rotation direction of the propeller 4. Generally, in the case where the pump is used in the manner that the rotation direction of the impeller is reversed, when the durability of the rotary volume change pump having the rubber impeller is compared to the durability of the non-positive displacement pump, the durability of the non-positive displacement pump is significantly higher. Therefore, according to the outboard motor 1 of the present embodiment using the non-positive displacement pump as the water pump 22, it is possible to solve the above problem that the durability of the motor cooling pump decreases in the electric propulsion machine having a configuration in which the rotation direction of the motor is reversed.

[0042] Further, in the outboard motor 1 of the present embodiment, the water pump 22 is provided in the front end side of the propeller shaft 5. By providing the water pump 22 at the front end side of the propeller shaft 5, the lower case 11 of the outboard motor 1 of the present embodiment can be prevented from becoming larger than a lower case of an outboard motor using an engine (internal combustion engine) while the water pump 22 is provided on the propeller shaft 5. That is, most of the outboard motors using the engine as the power source that generates the propulsion force of the boat include a shift device that switches the rotation direction of the propeller (see, for example, JP2012-144186A). Since it is difficult for the engine to reverse the rotation direction of a crankshaft, most of the outboard motors using the engine include a shift device, and the rotation direction of the propeller is switched by the shift device. Specifically, in the outboard motor using the engine as the power source, the gear mechanism is provided between the lower end portion of the drive shaft extending downward from the engine and the front portion of the propeller shaft. The gear mechanism includes the drive gear fixed to the lower end portion of the drive shaft, a forward gear that meshes with the drive gear and rotates in the forward direction by the rotation of the drive shaft, a reverse gear that meshes with the drive gear and rotates in the reverse direction by the rotation of the drive shaft, and a dog clutch that switches between connecting the forward gear to the propeller shaft to rotate the propeller shaft forward and connecting the reverse gear to the propeller shaft to rotate the propeller shaft reversely. The shift device controls the dog clutch according to an operation input for switching the rotation direction of the propeller and switches the rotation directions of the propeller shaft and the propeller. Generally, in the outboard motor using the engine, a portion to which an operation for switching the rotation direction of the propeller is input is the front portion of the upper portion of the outboard motor, and on the other hand, the dog clutch to be controlled by the shift device is disposed in the lower portion of the outboard motor. Therefore, the shift device includes a shift rod for transmitting the operation input for switching the rotation direction of the propeller to the dog clutch, and the shift rod extends in the upper-lower direction at a portion in front of the drive shaft in the outboard motor. Further, the shift device includes a shift slider that connects a lower end portion of the shift rod to the dog clutch, and the shift slider is provided at the front end side of the propeller shaft. In the outboard motor 1 of the present embodiment, the power source that generates the propulsion force of the boat is the motor 2, and the rotation direction of the propeller 4 is switched by switching the rotation direction of the motor 2 by the control of the motor control device 3. Therefore, the shift device is unnecessary in the outboard motor 1 of the present embodiment, and the shift device is not provided in the outboard motor 1 of the present embodiment. Therefore, the shift slider is not provided at the front end side of the propeller shaft 5. According to the outboard motor 1 of the present embodiment, since the water pump 22 is disposed at the front end side of the propeller shaft 5, a place where the shift slider of the shift device is disposed in the outboard motor using the engine can be used as the disposition place of the water pump 22. Further, by using a small non-positive displacement pump as the water pump 22, the water pump 22 can be disposed at the place without enlarging a space of the place where the shift slider of the shift device is provided in the outboard motor using the engine. Therefore, according to the outboard motor 1 of the present embodiment, the lower case 11 can be prevented from becoming larger than the lower case of the outboard motor using the engine while the water pump 22 is provided on the propeller shaft 5.

[0043] Further, the outboard motor 1 of the present embodiment includes the transfer passage 33 that transfers the cooling water from the water pump 22 to the water jacket 30 of the motor 2, and the transfer passage 33 is provided in front of the drive shaft 6 inside the outboard motor 1. According to the outboard motor 1 of the present embodiment, since the transfer passage 33 is disposed in front of the drive shaft 6 in the outboard motor 1, a place where the shift rod of the shift device is disposed in the outboard motor using the engine can be used as the disposition place of the transfer passage 33. Therefore, it is possible to prevent the lower case 11 of the outboard motor 1 of the present embodiment from becoming larger than the lower case of the outboard motor using the engine.

[0044] In the outboard motor 1 of the present embodiment, the water intake port 21 is provided in front of the propeller shaft 5, and the water pump 22 faces the water intake port 21. The suction port 27 of the pump chamber 26 in which the impeller 24 of the water pump 22 is disposed is disposed right behind the water intake port 21. According to this configuration, it is possible to make a distance between the water intake port 21 and the water pump 22 extremely short, and it is possible to easily take in water around the outboard motor 1 into the outboard motor 1 from the water pump 22 via the water intake port 21. Further, even if the suction capacity of the water pump 22 is low, the water around the outboard motor 1 can be sufficiently taken into the outboard motor 1 via the water intake port 21. Since the water intake port 21 and the pump chamber 26 are extremely close to each other, water around the outboard motor 1 flows extremely smoothly into the pump chamber 26 while the water pump 22 is stopped. As a result, water can be quickly filled in the pump chamber 26, and the priming of the water pump 22 can be quickly and reliably ensured. Further, since the water intake port 21 and the water pump 22 are extremely close to each other and the water intake port 21 is disposed in front of the water pump 22, when the boat moves forward, the water around the outboard motor 1 can flow vigorously from the water intake port 21 toward the water pump 22, and the pressure of the water can be used to promote the rotation of the impeller 24, thereby improving the smoothness of the flow of the cooling water from the water intake port 21 to the water jacket 30.

[0045] Further, in the outboard motor 1 of the present embodiment, the rear end portion of the pump shaft 23 of the water pump 22 is connected to the front end portion of the propeller shaft 5. According to this configuration, the rotation of the propeller shaft 5 can be transmitted to the impeller 24 of the water pump 22 provided at the front end side of the propeller shaft 5 by a simple structure.

Embodiment 2

[0046] FIG. 4 illustrates a cross section of a lower portion of an outboard motor 51 that is a second embodiment of the electric propulsion machine of the present disclosure. In the outboard motor 51 of the second embodiment illustrated in FIG. 4, the same components as those of the outboard motor 1 of the above first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified. The outboard motor 51 of the second embodiment is characterized in that another water pump 52 that transfers cooling water discharged from the water pump 22 to the water jacket 30 of the motor 2 is provided between the water pump 22 and the motor 2. In the following description of the second embodiment, the water pump 22 disposed right behind the water intake port 21 is referred to as a first water pump 22, and the water pump 52 disposed between the first water pump 22 and the motor 2 is referred to as a second water pump 52.

[0047] In FIG. 4, the second water pump 52 is a non-positive displacement pump, and is, for example, a mixed flow pump. The second water pump 52 is disposed at a rear stage of the first water pump 22 in the flow direction of the cooling water, and is disposed between the first water pump 22 and the water jacket 30 of the motor 2. Specifically, the second water pump 52 is disposed at a boundary portion between the upper case 10 and the lower case 11. The impeller 53 of the second water pump 52 is fixed to the drive shaft 6. Further, at the boundary between the upper case 10 and the lower case 11, a pump chamber 54 accommodating the impeller 53 of the second water pump 52 is provided on an outer periphery of the drive shaft 6. Further, a suction port 55 is provided in a lower portion of the pump chamber 54. A discharge port 56 is provided in an upper portion of the pump chamber 54.

[0048] Further, the outboard motor 1 of the above first embodiment is provided with the transfer passage 33 transferring the cooling water from the water pump 22 to the water jacket 30 of the motor 2. However, in the outboard motor 51 of the second embodiment, the transfer passage is divided into a lower transfer passage 57 connecting the first water pump 22 to the second water pump 52, and an upper transfer passage 58 connecting the second water pump 52 to the water jacket 30 of the motor 2. An introduction passage 59 is provided between an upper end portion of the lower transfer passage 57 and the suction port 55 of the pump chamber 54 to guide the cooling water flowing through the lower transfer passage 57 to the suction port 55.

[0049] When the motor 2 is driven, the drive shaft 6 and the propeller shaft 5 rotate respectively. The impeller 53 of the second water pump 52 rotates together with the drive shaft 6, and the impeller 24 of the first water pump 22 rotates together with the propeller shaft 5. As the impeller 24 of the first water pump 22 and the impeller 53 of the second water pump 52 rotate, the water taken in from the water intake port 21 flows as the cooling water sequentially through the pump chamber 26, the lower transfer passage 57, the introduction passage 59, the pump chamber 54, and the upper transfer passage 58, and is supplied to the water jacket 30. The cooling water supplied to the water jacket 30 flows in the water jacket 30. Accordingly, the motor 2 is cooled. The cooling water after flowing through the inside of the water jacket 30 is discharged to the outside of the outboard motor 1 from a discharge port provided in, for example, a boss portion of the propeller 4 via the drain passage 34.

[0050] The outboard motor 51 of the second embodiment of the present disclosure having the configuration has operational effects similar to those of the outboard motor 1 of the first embodiment of the present disclosure. That is, the second water pump 52 is a non-positive displacement pump, and the non-positive displacement pump is easily reduced in size as compared with a rotary volume change pump having a rubber impeller. Therefore, according to the outboard motor 51 of the second embodiment, even though the first water pump 22 and the second water pump 52 are provided, the outboard motor 1 can be reduced in size as compared with an outboard motor in the related art. Further, by making each of the first water pump 22 and the second water pump 52 as the non-positive displacement pump, it is possible to solve the above problem that the durability of the motor cooling pump decreases in the electric propulsion machine having the configuration in which the rotation direction of the motor 2 is reversed.

[0051] Further, since the outboard motor 51 of the second embodiment includes the second water pump 52, even when the discharge capacity of the first water pump 22 is low, the cooling water can be smoothly fed to the water jacket 30 of the motor 2 in cooperation with the first water pump 22 and the second water pump 52. Therefore, a small-sized pump having a low discharge capacity can be used as the first water pump 22, and the outboard motor 51 can be reduced in size. Further, since the first water pump 22 and the second water pump 52 are in cooperation with each other, the second water pump 52 can be reduced in size, which also makes it possible to reduce the size of the outboard motor 51.

[0052] Although the centrifugal pump is used as the water pump 22 in the above first embodiment and the mixed flow pump is used as the water pump 52 in the above second embodiment, the present disclosure is not limited thereto. Other types or models of non-positive displacement pumps may also be used as the water pump 22 or the water pump 52.

[0053] Further, in the above first embodiment, the case where the cooling water is supplied to the water jacket 30 of the motor 2 from the water pump 22 to cool the motor 2 has been described as an example. For example, a water jacket may be provided for an inverter of the motor control device 3, and cooling water may be supplied from the water pump 22 to the water jacket 30 of the motor 2 and the water jacket of the inverter to cool the motor 2 and the inverter, respectively. This configuration may be applied to the above second embodiment.

[0054] Further, as described above, the outboard motor has been given as an example in each of the first and second embodiments of the present disclosure, but the present disclosure is not limited thereto. For example, the present disclosure can be applied to other types of electric propulsion machines such as a stern drive.

[0055] The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.