ELECTRIC PROPULSION DEVICE

Abstract

An electric propulsion device includes a motor configured to rotate a propeller, a propeller shaft disposed below the motor and provided with the propeller in a rear part, a lower case accommodating a front part of the propeller shaft, and a cooling device configured to cool the motor. The cooling device includes a heat exchanger configured to cool refrigerant by using water outside the electric propulsion device as cooling water, a motor cooling jacket provided in the motor and configured to cool the motor by using the refrigerant, and a circulation passage configured to circulate the refrigerant between the heat exchanger and the motor cooling jacket. The heat exchanger is provided in the lower case.

Claims

1. An electric propulsion device comprising: a motor configured to rotate a propeller; a propeller shaft disposed below the motor and provided with the propeller in a rear part; a lower case accommodating a front part of the propeller shaft; and a cooling device configured to cool the motor, wherein the cooling device includes a heat exchanger configured to cool refrigerant by using water outside the electric propulsion device as cooling water, a motor cooling jacket provided in the motor and configured to cool the motor by using the refrigerant, and a circulation passage configured to circulate the refrigerant between the heat exchanger and the motor cooling jacket, and the heat exchanger is provided in the lower case.

2. The electric propulsion device according to claim 1, wherein the heat exchanger is provided on an outer circumferential side of the propeller shaft in the lower case.

3. The electric propulsion device according to claim 2, wherein the heat exchanger includes a cooling water passage in which the cooling water flows in an axial direction of the propeller shaft, and a refrigerant passage in which the refrigerant flows in a circumferential direction of the propeller shaft.

4. The electric propulsion device according to claim 3, wherein the cooling water passage includes a plurality of cooling tubes in which the cooling water flows, and each of the cooling tubes is disposed to pass in the refrigerant flowing in the refrigerant passage.

5. The electric propulsion device according to claim 3, wherein a propeller shaft accommodating hole extending in a front-rear direction is provided in a lower part of the lower case, a shaft housing having a cylindrical shape and supporting the propeller shaft to be rotatable is provided in the propeller shaft accommodating hole, and the cooling water passage and the refrigerant passage are provided between the propeller shaft accommodating hole and the shaft housing.

6. The electric propulsion device according to claim 5, wherein a space between the propeller shaft accommodating hole and the propeller shaft is divided by the shaft housing into a cooling water inlet chamber positioned in a front part of the space, a refrigerant flow chamber positioned in a front-rear middle part of the space, and a cooling water outlet chamber positioned in a rear part of the space, the refrigerant passage is formed in the refrigerant flow chamber, an inlet side end of the cooling water passage communicates with the cooling water inlet chamber, an outlet side end of the cooling water passage communicates with the cooling water outlet chamber, and the cooling water passage passes through the refrigerant flow chamber without communicating with inside of the refrigerant flow chamber.

7. The electric propulsion device according to claim 6, wherein the cooling device includes an intake port configured to take water outside the electric propulsion device into the electric propulsion device, and an intake passage connecting the intake port to the cooling water inlet chamber, the intake port is provided in a front part of a portion where the lower case and a skeg are coupled to each other, and the intake passage extends in the front-rear direction between the lower case and the skeg.

8. The electric propulsion device according to claim 6, wherein the cooling device includes an axial flow impeller configured to rotate integrally with the propeller shaft, the cooling water outlet chamber communicates with inside of a hub of the propeller, and the axial flow impeller is disposed in the cooling water outlet chamber, between the cooling water outlet chamber and the hub of the propeller, or in the hub of the propeller.

9. The electric propulsion device according to claim 6, wherein a baffle plate is provided in the refrigerant flow chamber so that the refrigerant flows in a zigzag shape in the refrigerant flow chamber.

10. The electric propulsion device according to claim 1, wherein the cooling device includes two heat exchangers, and one of the two heat exchangers is provided on an outer circumferential side of the propeller shaft in the lower case, and the other one of the two heat exchangers is provided above the propeller shaft in the lower case.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0005] FIG. 1 is an explanatory diagram illustrating an electric propulsion device according to a first example of the present invention as viewed from the left.

[0006] FIG. 2 is an explanatory diagram illustrating the electric propulsion device according to the first example of the present invention as viewed from behind.

[0007] FIG. 3 is a cross-sectional view illustrating the electric propulsion device cut along a line A-A in FIG. 2.

[0008] FIG. 4 is a block diagram illustrating a configuration of a cooling device in the electric propulsion device according to the first example of the present invention.

[0009] FIG. 5 is an explanatory diagram illustrating a lower part of a lower case of the electric propulsion device according to the first example of the present invention as viewed from the front.

[0010] FIG. 6 is a cross-sectional view illustrating a longitudinal cross section of a heat exchanger in the cooling device of the electric propulsion device according to the first example of the present invention.

[0011] FIG. 7A is an external view of the heat exchanger in FIG. 6 as viewed from the front, FIG. 7B is a cross-sectional view of the heat exchanger cut along a line B-B in FIG. 6 as viewed from the front, FIG. 7C is a cross-sectional view of the heat exchanger cut along a line C-C in FIG. 6 as viewed from the front, FIG. 7D is a cross-sectional view of the heat exchanger cut along a line D-D in FIG. 6 as viewed from the front, and FIG. 7E is an external view of the heat exchanger in FIG. 6 as viewed from behind.

[0012] FIG. 8 is an enlarged cross-sectional view of a portion of the electric propulsion device in FIG. 3 including the heat exchanger.

[0013] FIG. 9 is a block diagram illustrating a configuration of a cooling device in an electric propulsion device according to a second example of the present invention.

[0014] FIG. 10 is an explanatory diagram illustrating arrangement and the like of two heat exchangers in the electric propulsion device according to the second example of the present invention.

DETAILED DESCRIPTION OF EXEMPLIFIED EMBODIMENTS

[0015] When seawater flows in a metallic cooling jacket to cool the motor, the cooling jacket is corroded by the seawater. Flow paths of the cooling jacket have a smaller diameter and a more complex route than, for example, pipes connected to a pump that draws up seawater, and walls surrounding the flow paths are thin, so there is a risk that the cooling jacket is damaged faster due to corrosion, resulting in leakage of cooling water or the like.

[0016] The present invention is considering, for example, the problem described above, and an object of the present invention is to provide an electric propulsion device that can prevent corrosion of a cooling jacket.

[0017] An electric propulsion device according to an embodiment of the present invention includes a motor for rotating a propeller, a propeller shaft disposed below the motor and provided with the propeller in a rear part, a lower case that accommodates a front part of the propeller shaft, and a cooling device that cools the motor. In the electric propulsion device of the embodiment, the cooling device includes a heat exchanger that uses water outside the electric propulsion device as cooling water to cool refrigerant, a motor cooling jacket that is provided on the motor and uses the refrigerant to cool the motor, and a circulation passage that causes the refrigerant to circulate between the heat exchanger and the motor cooling jacket. In the electric propulsion device of the embodiment, the heat exchanger is provided in the lower case.

[0018] In the cooling device provided in the electric propulsion device of the embodiment, the heat exchanger uses water (for example, seawater) outside the electric propulsion device to cool the refrigerant. The motor cooling jacket uses the refrigerant cooled by the heat exchanger and circulating in the circulation passage to cool the motor. The motor cooling jacket uses the refrigerant circulating in the circulation passage to cool the motor, so water outside the electric propulsion device does not flow in the motor cooling jacket. That is, seawater does not flow in the motor cooling jacket. Therefore, according to the electric propulsion device of the embodiment, it is possible to prevent the motor cooling jacket from being corroded by seawater, and therefore it is possible to prevent corrosion of the motor cooling jacket.

[0019] In the electric propulsion device of the embodiment, the heat exchanger is provided in the lower case. Generally, a heat exchanger is heavy so that when the heat exchanger is mounted on an upper part of the electric propulsion device, a center of gravity of the electric propulsion device becomes high, resulting in deterioration in stability of mounting the electric propulsion device when the electric propulsion device is mounted on a boat. According to the electric propulsion device of the embodiment, since the heat exchanger is provided in the lower case, the heat exchanger can be positioned at a lower part of the electric propulsion device. Therefore, the center of gravity of the electric propulsion device can be lowered, and stability of mounting the electric propulsion device on the boat can be improved.

First Example

[0020] Some examples of the present invention will be described with reference to the drawings. In the description of each example, directions of up (Ud), down (Dd), front (Fd), back (Bd), left (Ld), and right (Rd) follow arrows drawn at the lower left in FIGS. 1 to 3, 5, 6, 8, and 10.

Electric Propulsion Device

[0021] FIG. 1 illustrates an electric propulsion device 1 according to a first example of the present invention as viewed from the left. FIG. 2 illustrates the electric propulsion device 1 as viewed from behind. FIG. 3 illustrates a cross section of the electric propulsion device 1 cut along a line A-A in FIG. 2 as viewed from the left.

[0022] The electric propulsion device 1 is a device for propelling a boat. As illustrated in FIG. 1, the electric propulsion device 1 of the example is an outboard motor, and is mounted on a transom of the boat. As illustrated in FIG. 3, the electric propulsion device 1 includes a motor 3, an inverter 6, a speed reducer 11, a drive shaft 14, a rotation transmission mechanism 15, a propeller shaft 18, and a propeller 21.

[0023] The motor 3 is a power source for rotating the propeller 21 and is, for example, an AC motor. The motor 3 includes an output shaft 4, a rotor, and a stator. The motor 3 includes a motor case 5. The output shaft 4 excluding an end that outputs power, the rotor, and the stator are accommodated in the motor case 5. The motor 3 is disposed in an upper part of the electric propulsion device 1. When the electric propulsion device 1 is mounted on the boat, the motor 3 is positioned above the water surface. The motor 3 is disposed so that an extension direction of the output shaft 4 is a vertical direction.

[0024] The inverter 6 is a device that controls driving of the motor 3. The inverter 6 includes an inverter body 7 in which a circuit that controls driving of the motor 3 and the like are provided, and an inverter case 8 in which the inverter body 7 is accommodated. The inverter 6 is disposed above the motor 3. The inverter 6 is mounted on the motor 3 via an inverter mounting member 10.

[0025] The speed reducer 11 is a device that reduces rotation of the output shaft 4 of the motor 3 and transmits the rotation to the drive shaft 14. The speed reducer 11 is disposed below the motor 3. The speed reducer 11 includes a drive gear 12 and a driven gear 13. The drive gear 12 is coupled to a lower end of the output shaft 4 of the motor 3 and rotates integrally with the output shaft 4. The driven gear 13 is disposed in front of the drive gear 12. The driven gear 13 is coupled to an upper end of the drive shaft 14. The driven gear 13 meshes with the drive gear 12. A gear ratio between the drive gear 12 and the driven gear 13 (the number of teeth of the driven gear 13 / the number of teeth of the drive gear 12) is greater than 1.

[0026] The drive shaft 14 is a shaft that transmits the rotation of the motor 3 after being reduced by the speed reducer 11 to the propeller shaft 18. The drive shaft 14 extends in the vertical direction from the speed reducer 11 to the rotation transmission mechanism 15. As described above, the driven gear 13 of the speed reducer 11 is coupled to the upper end of the drive shaft 14 and the drive shaft 14 rotates integrally with the driven gear 13.

[0027] The rotation transmission mechanism 15 is a mechanism that transmits rotation of the drive shaft 14 to the propeller shaft 18. The rotation transmission mechanism 15 includes two bevel gears 16 and 17 that mesh with each other. One bevel gear 16 is coupled to a lower end of the drive shaft 14 and rotates integrally with the drive shaft 14. The other bevel gear 17 is coupled to a front end of the propeller shaft 18.

[0028] The propeller shaft 18 extends in a front-rear direction and is disposed below the motor 3. As described above, the bevel gear 17 of the rotation transmission mechanism 15 is coupled to the front end of the propeller shaft 18 and the propeller shaft 18 rotates integrally with the bevel gear 17. The propeller 21 is coupled to a rear part of the propeller shaft 18 and rotates integrally with the propeller shaft 18. The propeller shaft 18 and the propeller 21 are disposed in a lower part of the electric propulsion device 1 and are positioned below the water surface when the electric propulsion device 1 is mounted on the boat.

[0029] By controlling the inverter 6, the motor 3 is driven and the output shaft 4 rotates. Rotation of the output shaft 4 is transmitted to the drive shaft 14 while being reduced by the speed reducer 11, thereby rotating the drive shaft 14. Rotation of the drive shaft 14 is transmitted to the propeller shaft 18 by the rotation transmission mechanism 15, thereby rotating the propeller shaft 18 and the propeller 21. Rotation of the propeller 21 generates thrust for the boat.

[0030] In the electric propulsion device 1, a middle case 25 is provided below the motor 3. The middle case 25 is coupled to the motor case 5 using a fastening member such as a bolt. The middle case 25 accommodates the speed reducer 11, an upper part of the drive shaft 14, and the like.

[0031] In the electric propulsion device 1, a lower case 27 is provided below the middle case 25. The lower case 27 is coupled to the middle case 25 using a fastening member such as a bolt. The lower case 27 accommodates a lower part of the drive shaft 14, the rotation transmission mechanism 15, a front part of the propeller shaft 18, and the like.

[0032] Specifically, a drive shaft insertion hole 28 extending in the vertical direction is provided in a front part of the lower case 27, and the lower part of the drive shaft 14 is inserted into the drive shaft insertion hole 28. A transmission mechanism accommodating chamber 29 is provided in a lower part of the front part of the lower case 27, and the rotation transmission mechanism 15 is accommodated in the transmission mechanism accommodating chamber 29. A propeller shaft accommodating hole 30 is provided in a lower part of the lower case 27 and behind the transmission mechanism accommodating chamber 29. The propeller shaft accommodating hole 30 extends in the front-rear direction. A front end side of the propeller shaft accommodating hole 30 communicates with inside of the transmission mechanism accommodating chamber 29, and a rear end side of the propeller shaft accommodating hole 30 communicates with inside of a hub 22 of the propeller 21.

[0033] A shaft housing 31 is fixedly provided in the propeller shaft accommodating hole 30. The shaft housing 31 is a member that supports the propeller shaft 18 via a bearing 20 to be rotatable relative to the lower case 27, and is formed in a cylindrical shape. The front part of the propeller shaft 18 is disposed in the shaft housing 31 and is supported in the shaft housing 31 via the bearing 20 to be rotatable.

[0034] An anti-cavitation plate 35 is provided above the propeller 21 in the lower case 27. A skeg 36 is provided in a lowermost part of the lower case 27.

[0035] As illustrated in FIG. 1, the electric propulsion device 1 includes a mounting mechanism 40 for mounting the electric propulsion device 1 on the boat. The mounting mechanism 40 includes a clamp bracket 41 that fixes the electric propulsion device 1 to the transom of the boat, a swivel bracket 43 connected to the clamp bracket 41 via a tilt shaft 42, a pilot shaft 44 that extends in the vertical direction and is supported by the swivel bracket 43 to be rotatable, and mounts 45 and 46 that connect both upper and lower ends of the pilot shaft 44 to the electric propulsion device 1.

Cooling Device

[0036] FIG. 4 illustrates a configuration of a cooling device 51 in the electric propulsion device 1. The cooling device 51 is a liquid-cooling cooling device that is provided in the electric propulsion device 1 and cools equipment that requires cooling, that is, equipment requiring cooling. The equipment requiring cooling provided in the electric propulsion device 1 is the motor 3, the inverter 6, and the speed reducer 11.

[0037] As illustrated in FIG. 4, the cooling device 51 includes a direct cooling system 52 and an indirect cooling system 71. The direct cooling system 52 is a system that cools refrigerant used in the indirect cooling system 71 by performing heat exchange between water (for example, seawater) outside the electric propulsion device 1 and the refrigerant used in the indirect cooling system 71. The indirect cooling system 71 is a system that cools the equipment requiring cooling by performing heat exchange between the refrigerant cooled in the direct cooling system and the equipment requiring cooling. The refrigerant is, for example, a coolant such as LLC.

Direct Cooling System

[0038] As illustrated in FIG. 4, the direct cooling system 52 includes an intake port 53, an intake passage 54, a heat exchanger 55, and a drain port 70.

[0039] The intake port 53 is a port that takes water outside the electric propulsion device 1 into the electric propulsion device 1 as cooling water. Here, FIG. 5 illustrates the lower part of the lower case 27 of the electric propulsion device 1 as viewed from the front. As illustrated in FIGS. 3 and 5, the intake port 53 is provided in a front part of a portion where the lower case 27 and the skeg 36 are coupled to each other, that is, at a base end of a front part of the skeg 36. The intake port 53 opens forward.

[0040] The intake passage 54 is a passage that connects the intake port 53 to a cooling water inlet chamber 61 of the heat exchanger 55, and is a passage that sends water outside the electric propulsion device 1 flowed into the intake port 53, that is, the cooling water, to the cooling water inlet chamber 61 of the heat exchanger 55. As illustrated in FIG. 3, the intake passage 54 extends in the front-rear direction between the lower case 27 and the skeg 36.

[0041] The heat exchanger 55 is a device that uses water outside the electric propulsion device 1 as cooling water to cool the refrigerant in the indirect cooling system 71. As illustrated in FIG. 3, the heat exchanger 55 is provided in the lower case 27. The heat exchanger 55 is provided in an outer circumferential side of the propeller shaft 18 in the lower case 27. Specifically, the heat exchanger 55 is formed on an outer periphery of the shaft housing 31 provided in the propeller shaft accommodating hole 30. When the electric propulsion device 1 is viewed from above, the heat exchanger 55 is disposed to overlap with the motor 3.

[0042] Here, FIG. 6 illustrates a longitudinal cross section of the heat exchanger 55. FIG. 7A illustrates the heat exchanger 55 in FIG. 6 as viewed from the front. FIG. 7B illustrates a cross section of the heat exchanger 55 cut along a line B-B in FIG. 6 as viewed from the front (left in FIG. 6). FIG. 7C illustrates a cross section of the heat exchanger 55 cut along a line C-C in FIG. 6 as viewed from the front. FIG. 7D illustrates a cross section of the heat exchanger 55 cut along a line D-D in FIG. 6 as viewed from the front. FIG. 7E illustrates the heat exchanger 55 in FIG. 6 as viewed from behind. FIG. 8 illustrates an enlarged view of a portion of the electric propulsion device 1 in FIG. 3 including the heat exchanger 55.

[0043] As illustrated in FIG. 6, the heat exchanger 55 includes a frontmost end partition wall portion 56, a front partition wall portion 57, a rear partition wall portion 58, the cooling water inlet chamber 61, a refrigerant flow chamber 62, a cooling water outlet chamber 63, a cooling water passage 64 (a plurality of cooling tubes 65), a refrigerant passage 67, and a baffle plate 68. The heat exchanger 55 includes an axial flow impeller 69 as illustrated in FIG. 8.

[0044] As illustrated in FIG. 6, the shaft housing 31 basically includes a cylindrical shaft housing body 32 and an annular fixing portion 33 that protrudes radially outward from a rear end of the shaft housing body 32. As illustrated in FIG. 8, the shaft housing 31 is attached to the lower case 27 by inserting the shaft housing body 32 into the propeller shaft accommodating hole 30 from behind and fixing the fixing portion 33 to a portion of the lower case 27 (a peripheral edge of an opening portion of the propeller shaft accommodating hole 30) using a fastening member such as a bolt.

[0045] As illustrated in FIG. 6, the frontmost end partition wall portion 56, the front partition wall portion 57, and the rear partition wall portion 58 of the heat exchanger 55 are formed in the shaft housing 31. The frontmost end partition wall portion 56, the front partition wall portion 57, and the rear partition wall portion 58 have a function of forming the cooling water inlet chamber 61, the refrigerant flow chamber 62, and the cooling water outlet chamber 63 on the outer circumferential side of the propeller shaft 18 in the propeller shaft accommodating hole 30. As illustrated in FIG. 8, a space between the propeller shaft accommodating hole 30 and the propeller shaft 18, specifically, the space between the propeller shaft accommodating hole 30 and the shaft housing body 32, is divided by the three partition wall portions 56, 57, and 58 into the cooling water inlet chamber 61, the refrigerant flow chamber 62, and the cooling water outlet chamber 63.

[0046] As illustrated in FIGS. 6 and 7A, the frontmost end partition wall portion 56 protrudes radially outward from a front end of the shaft housing body 32 and is formed around an entire circumference of the shaft housing body 32.

[0047] As illustrated in FIGS. 6 and 7B, the front partition wall portion 57 is positioned behind the frontmost end partition wall portion 56. The front partition wall portion 57 protrudes radially outward from a front part of the shaft housing body 32 and is formed around the entire circumference of the shaft housing body 32.

[0048] As illustrated in FIGS. 6 and 7E, the rear partition wall portion 58 is positioned behind the front partition wall portion 57. The rear partition wall portion 58 protrudes radially outward from a rear part of the shaft housing body 32 and is formed around the entire circumference of the shaft housing body 32.

[0049] As illustrated in FIG. 8, when the shaft housing 31 is disposed in the propeller shaft accommodating hole 30, the space between the propeller shaft accommodating hole 30 and the shaft housing body 32 is divided into the cooling water inlet chamber 61 positioned at a front part of the space, the refrigerant flow chamber 62 positioned in a front-rear middle part of the space, and the cooling water outlet chamber 63 positioned in a rear part of the space. Each of the cooling water inlet chamber 61, the refrigerant flow chamber 62, and the cooling water outlet chamber 63 is an annular space that completely surrounds an outer periphery of the shaft housing body 32.

[0050] The cooling water passage 64 is a passage in the heat exchanger 55 in which the cooling water flows. As illustrated in FIGS. 6, 7B to 7E, and 8, the cooling water passage 64 is formed by the plurality of cooling tubes 65 provided between the propeller shaft accommodating hole 30 and the shaft housing body 32. Each cooling tube 65 is a pipe made of metal having high thermal conductivity, such as copper. Each cooling tube 65 extends in an axial direction of the propeller shaft 18. A front end of each cooling tube 65 is supported by the front partition wall portion 57, and a rear end of each cooling tube 65 is supported by the rear partition wall portion 58. An inlet side end (the front end) of each cooling tube 65 opens to inside of the cooling water inlet chamber 61, and inside of each cooling tube 65 communicates with the inside of the cooling water inlet chamber 61. An outlet side end (the rear end) of each cooling tube 65 opens to inside of the cooling water outlet chamber 63, and inside of each cooling tube 65 communicates with the inside of the cooling water outlet chamber 63. As such, the cooling water inlet chamber 61 and the cooling water outlet chamber 63 communicate with each other via the cooling tubes 65. Each cooling tube 65 passes through the refrigerant flow chamber 62. As described below, each cooling tube 65 is disposed to pass in the refrigerant while the refrigerant flows in the refrigerant flow chamber 62. Although each cooling tube 65 passes through the refrigerant flow chamber 62, the inside of each cooling tube 65 does not communicate with inside of the refrigerant flow chamber 62. In the example, twelve cooling tubes 65 are arranged around the entire outer periphery of the shaft housing 31 at intervals of 30 degrees.

[0051] As illustrated in FIG. 8, a lower part of the cooling water inlet chamber 61 communicates with the intake passage 54. A rear part of the cooling water outlet chamber 63 widely opens rearward and communicates with the inside of the hub 22 of the propeller 21.

[0052] The refrigerant passage 67 is a passage in the heat exchanger 55 in which the refrigerant used in the indirect cooling system 71 flows. The refrigerant passage 67 is formed in the refrigerant flow chamber 62. As illustrated in FIG. 3, a circulation passage that causes the refrigerant to circulate in the indirect cooling system 71 is connected to the refrigerant flow chamber 62. Specifically, a lower end side of a hole portion 86B of a connection passage 86 configuring a portion of the circulation passage opens to an inner surface of an upper part of the propeller shaft accommodating hole 30. An opening portion on the lower end side of the hole portion 86B of the connection passage 86 is positioned above a front part of the refrigerant flow chamber 62. Therefore, the hole portion 86B of the connection passage 86 communicates with the front part of the refrigerant flow chamber 62. A lower end side of a hole portion 81A of a connection passage 81 configuring a portion of the circulation passage opens to the inner surface of the upper part of the propeller shaft accommodating hole 30. An opening portion on the lower end side of the hole portion 81A of the connection passage 81 is positioned above a rear part of the refrigerant flow chamber 62. Therefore, the hole portion 81A of the connection passage 81 communicates with the rear part of the refrigerant flow chamber 62. As illustrated in FIG. 8, an inlet end side of the refrigerant passage 67 is connected to the opening portion at the lower end side of the hole portion 86B of the connection passage 86, and an outlet end side of the refrigerant passage 67 is connected to the opening portion at the lower end side of the hole portion 81A of the connection passage 81.

[0053] As illustrated in FIG. 6, a plurality of baffle plates 68 are provided on an outer periphery side of the shaft housing body 32. Each baffle plate 68 is a circular plate having a hole at the center as illustrated in FIGS. 7C or 7D. The shaft housing body 32 is inserted into the central hole of each baffle plate 68. A cutout portion 68A is provided on a portion on an outer periphery side of each baffle plate 68 by cutting out a portion of the baffle plate 68. As illustrated in FIG. 6, the plurality of baffle plates 68 are arranged on the outer circumferential side of the shaft housing body 32 in a portion corresponding to the refrigerant flow chamber 62 at intervals in the front-rear direction. The plurality of baffle plates 68 are arranged such that a position of each cutout portion 68A is staggered in the vertical direction. In FIG. 6, the baffle plate 68 on a front side and the baffle plate 68 on a rear side among the three baffle plates 68 are arranged so that each cutout portion 68A is positioned below, and the baffle plate 68 in the middle is arranged so that the cutout portion 68A thereof is positioned above. The baffle plates 68 divide the inside of the refrigerant flow chamber 62 into a plurality of annular spaces having a ring shape. However, since the cutout portion 68A is formed in each baffle plate 68, portions of two adjacent annular spaces communicate with each other via the cutout portion 68A. As such, in the refrigerant flow chamber 62, the refrigerant passage 67 extending in a circumferential direction of the propeller shaft 18 is formed of the plurality of baffle plates 68. Since the plurality of baffle plates 68 are arranged so that the position of each cutout portion 68A is staggered in the vertical direction, when the electric propulsion device 1 is viewed from the side, a shape of the refrigerant passage 67 is a zigzag shape in the vertical direction (a folded-back shape in the vertical direction).

[0054] As illustrated in FIG. 8, the axial flow impeller 69 is disposed in the cooling water outlet chamber 63. The axial flow impeller 69 is positioned in front of the hub 22 of the propeller 21. The axial flow impeller 69 is coupled to the propeller shaft 18 and rotates integrally with the propeller shaft 18. The axial flow impeller 69 has a function of sending the cooling water flowed out of the cooling water passage 64 (each cooling tube 65) into the cooling water outlet chamber 63 to the inside of the hub 22 of the propeller 21.

[0055] The drain port 70 is a port that discharges the cooling water after flowing in the cooling water passage 64 of the heat exchanger 55 to outside of the electric propulsion device 1. The drain port 70 is formed in the hub 22 of the propeller 21 as illustrated in FIGS. 2 and 3.

[0056] A cooling operation of the refrigerant in the direct cooling system 52 will be described with reference to FIG. 8. In FIG. 8, white arrows indicate the flow of cooling water, and black arrows indicate the flow of refrigerant.

[0057] In FIG. 8, by driving the motor 3 of the electric propulsion device 1, the propeller 21 is rotated and the boat moves forward. When the boat is moving forward, water in front of the electric propulsion device 1 hits a front part of the lower part of the lower case 27. As a result, water outside the electric propulsion device 1 flows from the intake port 53 into the intake passage 54 as cooling water. The cooling water flowed into the intake passage 54 flows rearward in the intake passage 54 and flows into the cooling water inlet chamber 61 of the heat exchanger 55. In the heat exchanger 55, the cooling water flowed into the cooling water inlet chamber 61 flows into the cooling water passage 64, that is, into the plurality of cooling tubes 65. Next, the cooling water flows in each cooling tube 65 in the axial direction of the propeller shaft 18 and flows out into the cooling water outlet chamber 63. The cooling water flowed out into the cooling water outlet chamber 63 is sent to the inside of the hub 22 of the propeller 21 by the axial flow impeller 69 and is discharged to outside of the electric propulsion device 1 from the drain port 70.

[0058] In the indirect cooling system 71, by driving a refrigerant pump 75, the coolant flows in the circulation passage. The refrigerant flowing in the circulation passage flows in the hole portion 86B of the connection passage 86 that configures a portion of the circulation passage, and flows into the front side of the refrigerant flow chamber 62 in the heat exchanger 55, that is, into the inlet side end of the refrigerant passage 67. The refrigerant flowed into the inlet side end of the refrigerant passage 67 flows in the refrigerant passage 67 in the circumferential direction of the propeller shaft 18 and also in a zigzag shape in the vertical direction. After flowing in the refrigerant passage 67, the refrigerant flows out of the rear part of the refrigerant flow chamber 62, that is, of an outlet side end of the refrigerant passage 67, into the hole portion 81A of the connection passage 81 that configures a portion of the circulation passage.

[0059] As such, in the heat exchanger 55, the cooling water flows in the cooling water passage 64 (in each cooling tube 65), and further, the refrigerant flows in the refrigerant passage 67, thereby performing heat exchange between the cooling water and the refrigerant, and cooling the refrigerant by the cooling water.

Indirect Cooling System

[0060] As illustrated in FIG. 4, the indirect cooling system 71 includes a motor cooling jacket 72, an inverter cooling jacket 73, a speed reducer cooling jacket 74, the refrigerant pump 75, a degassing tank 76, and the circulation passage. The circulation passage also includes connection passages 81 to 87.

[0061] The motor cooling jacket 72 is a mechanism that uses the refrigerant to cool the motor 3. The motor cooling jacket 72 is provided in the motor 3 as illustrated in FIG. 3. For example, the motor cooling jacket 72 is configured of a flow path formed in the motor case 5 of the motor 3. The flow path configuring the motor cooling jacket 72 is formed over a wide area of the motor case 5. For example, the flow path is formed around the entire circumference of the motor case 5 and from one end to another end of the motor case 5 in the axial direction.

[0062] The inverter cooling jacket 73 is a mechanism that uses the refrigerant to cool the inverter 6. The inverter cooling jacket 73 is provided in the inverter 6 as illustrated in FIG. 3. For example, the inverter cooling jacket 73 is disposed at a lower part of a rear part of the inverter 6 and is positioned below a rear part of the inverter body 7. Specifically, the inverter cooling jacket 73 is configured of a flow path formed in a lower part of a rear part of the inverter case 8. The flow path extends from a left end to a right end of the inverter case 8.

[0063] The speed reducer cooling jacket 74 is a mechanism that uses the refrigerant to cool the speed reducer 11. The speed reducer cooling jacket 74 is configured of a flow path for the refrigerant passing a location adjacent to the speed reducer 11. The speed reducer cooling jacket 74 is disposed below the speed reducer 11 in the middle case 25.

[0064] The refrigerant pump 75 is a pump that causes the refrigerant to circulate in the circulation passage. The refrigerant pump 75 is an electric pump, and is driven by, for example, a dedicated motor for the refrigerant pump 75 different from the motor 3. As illustrated in FIG. 1, the refrigerant pump 75 is disposed above the heat exchanger 55. The refrigerant pump 75 is disposed behind the inverter 6. The refrigerant pump 75 is mounted on the rear part of the inverter 6. The refrigerant pump 75 can change a rotation speed of the dedicated motor for the refrigerant pump 75, for example, to adjust a flow rate of the refrigerant in the circulation passage. Accordingly, it is possible to control a temperature of the refrigerant.

[0065] The degassing tank 76 is a tank that has a function of separating gas from the refrigerant. Specifically, the degassing tank 76 has a function of releasing air bubbles generated in the refrigerant due to heat or the like, and a function as a reserve tank to absorb any increase or decrease in the amount of the refrigerant due to thermal expansion or aging of the refrigerant. The degassing tank 76 is disposed above the inverter 6 and mounted on the inverter 6.

[0066] The circulation passage is a passage that causes the refrigerant to circulate between the heat exchanger 55, the motor cooling jacket 72, the inverter cooling jacket 73, and the speed reducer cooling jacket 74. As illustrated in FIG. 4, in the indirect cooling system 71 of the example, the heat exchanger 55, the motor cooling jacket 72, the inverter cooling jacket 73, the refrigerant pump 75, and the speed reducer cooling jacket 74 are sequentially connected in series via the circulation passage. The circulation passage includes the connection passage 81 connecting the heat exchanger 55 to the motor cooling jacket 72, the connection passage 82 connecting the motor cooling jacket 72 to the inverter cooling jacket 73, the connection passage 83 connecting the inverter cooling jacket 73 to a passage joint portion 88, the connection passage 84 connecting the passage joint portion 88 to the refrigerant pump 75, the connection passage 85 connecting the refrigerant pump 75 to the speed reducer cooling jacket 74, the connection passage 86 connecting the speed reducer cooling jacket 74 to the heat exchanger 55, and the connection passage 87 connecting the passage joint portion 88 to the degassing tank 76.

[0067] As illustrated in FIGS. 3 and 8, an inlet side end of the connection passage 81 is connected to the outlet side end of the refrigerant passage 67 in the heat exchanger 55, and an outlet side end of the connection passage 81 is connected to an inlet port 72A of the motor cooling jacket 72. The connection passage 81 is formed by, for example, sequentially connecting the hole portion 81A, an inner tube portion 81B, and an outer tube portion 81C from the inlet side end toward the outlet side end. The hole portion 81A is formed in the lower case 27. The inner tube portion 81B is formed of, for example, a pipe or a hose, and extends roughly in the vertical direction from inside of the lower case 27 to inside of the middle case 25. The outer tube portion 81C is formed of, for example, a pipe or a hose, is positioned outside of the middle case 25 as illustrated in FIG. 2, and extends roughly in the vertical direction to the left of the middle case 25. As illustrated in FIGS. 1 and 3, a connection port 89 is formed on a left wall of the middle case 25 to communicate between inside and outside of the middle case 25, and an outlet side end of the inner tube portion 81B is connected to an inlet side end of the outer tube portion 81C via the connection port 89.

[0068] The connection passage 82 is provided in a portion extending from an upper rear left part of the motor case 5 to a lower rear left part of the inverter case 8. The connection passage 82 is formed by a hole provided in the above-mentioned portion and extending in the vertical direction. An inlet side end of the connection passage 82 is connected to an outlet port of the motor cooling jacket 72 provided in the upper rear left part of the motor case 5, and an outlet side end of the connection passage 82 is connected to an inlet port of the inverter cooling jacket 73 provided in the lower rear left part of the inverter case 8.

[0069] As illustrated in FIG. 2, the connection passage 83 is disposed on the right rear of the inverter 6. The connection passage 83 is formed of, for example, a hose or a pipe. An inlet side end of the connection passage 83 is connected to an outlet port of the inverter cooling jacket 73 that opens on a right surface of the lower part of the rear part of the inverter case 8. An outlet side end of the connection passage 83 is connected to the passage joint portion 88. The passage joint portion 88 is a portion that connects between the outlet side end of the connection passage 83, an inlet side end of the connection passage 84, and a lower end of the connection passage 87, and is formed of, for example, a T-shaped joint.

[0070] The connection passage 84 is disposed on the right of the refrigerant pump 75. The connection passage 84 is formed of, for example, a pipe. The inlet side end of the connection passage 84 is connected to the passage joint portion 88. An outlet side end of the connection passage 84 is connected to a suction port of the refrigerant pump 75 provided on a right surface of the refrigerant pump 75.

[0071] The connection passage 85 is disposed in a portion outside of the motor 3 and the middle case 25 and extending from behind the motor 3 to behind the middle case 25, and extends in the vertical direction. The connection passage 85 is formed of, for example, a pipe or a hose. An inlet side end of the connection passage 85 is connected to a discharge port of the refrigerant pump 75 provided in a lower right part of the refrigerant pump 75. As illustrated in FIG. 3, an inlet port 74A of the speed reducer cooling jacket 74 that communicates with inside of the speed reducer cooling jacket 74 and opens to a rear surface of the middle case 25 is provided in a rear part of the middle case 25. An outlet side end of the connection passage 85 is connected to the inlet port 74A.

[0072] As illustrated in FIGS. 3 and 8, an inlet side end of the connection passage 86 is connected to an outlet port 74B of the speed reducer cooling jacket 74, and an outlet side end of the connection passage 86 is connected to the inlet side end of the refrigerant passage 67 in the heat exchanger 55. The connection passage 86 is formed by, for example, sequentially connecting the inner tube portion 86A and the hole portion 86B from the inlet side end toward the outlet side end. The inner tube portion 86A is formed of, for example, a pipe or a hose, and extends roughly in the vertical direction from the inside of the middle case 25 to the inside of the lower case 27. The hole portion 86B is formed in the lower case 27.

[0073] The connection passage 87 is disposed above a rear right part of the inverter 6 and behind a right part of the degassing tank 76. The connection passage 87 is formed of, for example, a hose or a pipe. The lower end of the connection passage 87 is connected to the passage joint portion 88. An upper end of the connection passage 87 is connected to a rear right part of the degassing tank 76.

[0074] When the refrigerant pump 75 is driven, the refrigerant cooled by the heat exchanger 55 flows out of the outlet side end of the refrigerant passage 67 of the heat exchanger 55, flows in the connection passage 81, and then flows in the motor cooling jacket 72. The motor 3 is cooled by the refrigerant flowing in the motor cooling jacket 72. The refrigerant after flowing in the motor cooling jacket 72 flows in the connection passage 82 and then in the inverter cooling jacket 73. The inverter body 7 is cooled by the refrigerant flowing in the inverter cooling jacket 73. The refrigerant after flowing in the inverter cooling jacket 73 sequentially flows in the connection passage 83, the passage joint portion 88, the connection passage 84, the refrigerant pump 75, and the connection passage 85, then flows into the speed reducer cooling jacket 74, and flows in the speed reducer cooling jacket 74. The speed reducer 11 is cooled by the refrigerant flowing in the speed reducer cooling jacket 74. The refrigerant after flowing in the speed reducer cooling jacket 74 flows in the connection passage 86 and flows into the refrigerant passage 67 of the heat exchanger 55 from the inlet side end of the refrigerant passage 67. The refrigerant of which the temperature rose due to heat of the motor 3, the inverter 6, and the speed reducer 11 is cooled in the heat exchanger 55 by the cooling water taken in from outside of the electric propulsion device 1.

[0075] Refrigerant is stored in the degassing tank 76. The air bubbles in the refrigerant move into the degassing tank 76 via the connection passage 87 and are released to the atmosphere, for example, via a gas vent passage formed in the degassing tank 76. When the amount of refrigerant flowing in the circulation passage is small, a cap of the degassing tank 76 is removed and the refrigerant is injected into the degassing tank 76 so that the refrigerant can be replenished.

[0076] As described above, in the cooling device 51 provided in the electric propulsion device 1 of the example, the heat exchanger 55 uses water (for example, seawater) outside the electric propulsion device 1 to cool the refrigerant. The motor cooling jacket 72, the inverter cooling jacket 73, and the speed reducer cooling jacket 74 uses the refrigerant cooled by the heat exchanger and circulating in the circulation passage to cool the motor 3, the inverter 6, and the speed reducer 11, respectively. The motor cooling jacket 72 uses the refrigerant circulating the circulation passage to cool the motor 3, so water outside the electric propulsion device 1 does not flow in the motor cooling jacket 72. That is, seawater does not flow in the motor cooling jacket 72. Therefore, according to the electric propulsion device 1 of the example, it is possible to prevent the motor cooling jacket 72 from being corroded by seawater. Similarly, since seawater does not flow in the inverter cooling jacket 73, the inverter cooling jacket 73 can be prevented from being corroded by seawater. Similarly, since seawater does not flow in the speed reducer cooling jacket 74, the speed reducer cooling jacket 74 can be prevented from being corroded by seawater. Therefore, according to the electric propulsion device 1 of the example, corrosion of the motor cooling jacket 72, the inverter cooling jacket 73, and the speed reducer cooling jacket 74 can be prevented.

[0077] In the electric propulsion device 1 of the example, the heat exchanger 55 is provided in the lower case 27. Generally, a heat exchanger is heavy so that when the heat exchanger is mounted on an upper part of the electric propulsion device, a center of gravity of the electric propulsion device becomes high, resulting in deterioration in stability of mounting the electric propulsion device when the electric propulsion device is mounted on a boat. According to the electric propulsion device 1 of the example, since the heat exchanger 55 is provided in the lower case 27, the heat exchanger 55 can be positioned at the lower part of the electric propulsion device 1. Therefore, the center of gravity of the electric propulsion device 1 can be lowered, and stability of mounting the electric propulsion device 1 on the boat can be improved.

[0078] In the electric propulsion device 1 of the example, the heat exchanger 55 is provided in the lower case 27 on the outer circumferential side of the propeller shaft 18. By such configuration, the heat exchanger 55 is positioned at the lower part of the lower case 27 so that the center of gravity of the electric propulsion device 1 is lowered. Since the lower part of the lower case 27 is completely submerged in water, the water surrounding the lower case 27 can lower the temperature of the heat exchanger 55, thereby increasing cooling capacity for refrigerant by the heat exchanger 55.

[0079] In the electric propulsion device 1 of the example, the heat exchanger 55 includes the cooling water passage 64 in which cooling water flows in the axial direction of the propeller shaft 18, and the refrigerant passage 67 in which the refrigerant flows in the circumferential direction of the propeller shaft 18. By such configuration, the cooling water passage 64 can be made shorter than the refrigerant passage 67. Therefore, the cooling water can be exchanged quickly. The refrigerant passage 67 can be made longer than the cooling water passage 64. Therefore, a time from when the refrigerant flows into the heat exchanger 55 until when the refrigerant flows out of the heat exchanger 55 can be extended, and a time of cooling the refrigerant by the heat exchanger 55 can be extended. In general, cooling capacity for refrigerant by the heat exchanger 55 can be increased.

[0080] In the heat exchanger 55 according to the example, the cooling water passage 64 includes the plurality of cooling tubes 65 in which the cooling water flows, and each of the cooling tubes 65 is disposed to pass in the refrigerant flowing in the refrigerant passage 67. In such configuration, the refrigerant comes into contact with an outer circumferential surface of each cooling tube 65, thereby performing heat exchange between the cooling water and the refrigerant. By providing the plurality of cooling tubes 65, when the plurality of cooling tubes 65 are viewed as a whole, a contact area between the refrigerant and the cooling tubes 65 can be increased. Therefore, cooling capacity for refrigerant by the heat exchanger 55 can be increased.

[0081] In the electric propulsion device 1 of the example, the propeller shaft accommodating hole 30 is provided in the lower part of the lower case 27, the shaft housing 31 is provided in the propeller shaft accommodating hole 30, and the cooling water passage 64 and the refrigerant passage 67 of the heat exchanger 55 are provided between the propeller shaft accommodating hole 30 and the shaft housing body 32. By such configuration, a space in the propeller shaft accommodating hole 30 can be divided into an inner circumferential space in which oil for lubricating the bearing 20 and the like flows and an outer circumferential space in which the cooling water passage 64 and the refrigerant passage 67 of the heat exchanger 55 are provided, and the cooling water passage 64 and the refrigerant passage 67 can be easily provided on the outer periphery of the propeller shaft 18.

[0082] In the electric propulsion device 1 of the example, the space between the propeller shaft accommodating hole 30 and the propeller shaft 18 is divided by the shaft housing 31 into the cooling water inlet chamber 61, the refrigerant flow chamber 62, and the cooling water outlet chamber 63, the refrigerant passage 67 is formed in the refrigerant flow chamber 62, the inlet side end of the cooling water passage 64 communicates with inside of the cooling water inlet chamber 61, the outlet side end of the cooling water passage 64 communicates with inside of the cooling water outlet chamber 63, and the cooling water passage 64 passes through the refrigerant flow chamber 62 without communicating with inside of the refrigerant flow chamber 62. By such configuration, it is possible to realize arrangement of the cooling water passage 64 and the refrigerant passage 67 that can efficiently exchange heat between the cooling water and the refrigerant with a simple structure.

[0083] In the electric propulsion device 1 of the example, the intake port 53 that takes water outside the electric propulsion device 1 into the electric propulsion device 1 is provided in the front part of the portion where the lower case 27 and the skeg 36 are coupled to each other. By such configuration, it is possible to increase the amount of cooling water taken in while reducing resistance during movement of the boat. In the electric propulsion device 1 of the example, the intake passage 54 that connects the intake port 53 to the cooling water inlet chamber 61 extends in the front-rear direction between the lower case 27 and the skeg 36. By such configuration, the intake passage 54 can be shortened and the cooling water can be smoothly sent from the intake port 53 to the cooling water inlet chamber 61.

[0084] In the electric propulsion device 1 of the example, the cooling device 51 includes the axial flow impeller 69 that rotates integrally with the propeller shaft 18, in which the cooling water outlet chamber 63 is connected to the inside of the hub of the propeller 21, and the axial flow impeller 69 is disposed in the cooling water outlet chamber 63. By such configuration, rotation of the propeller shaft 18 can be used to smoothly discharge the cooling water after flowing in the cooling water passage 64 to outside of the electric propulsion device 1. Since the axial flow impeller 69 rotates due to the rotation of the propeller shaft 18, there is no need to provide a separate electric motor or the like for rotating the axial flow impeller 69, thereby making it possible to simplify the structure of the electric propulsion device 1 and reduce manufacturing costs of the electric propulsion device 1.

[0085] In the heat exchanger 55 according to the example, the baffle plate 68 is provided in the refrigerant flow chamber 62 so that the refrigerant flows in a zigzag shape in the refrigerant flow chamber 62. By such configuration, the refrigerant passage 67 formed in the refrigerant flow chamber 62 can be made longer, thus the cooling time for the refrigerant can be made longer, thereby increasing cooling capacity for refrigerant by the heat exchanger 55.

[0086] In the example, the heat exchanger 55 is disposed to overlap the motor 3 when the electric propulsion device 1 is viewed from above. By such configuration, the connection passages 81 and 86 can be shortened, and the refrigerant can smoothly flow in the circulation passage.

Second Example

[0087] FIG. 9 illustrates a configuration of a cooling device 91 in an electric propulsion device 90 according to a second example of the present invention. FIG. 10 illustrates arrangement of two heat exchangers 95 and 98 provided in the cooling device 91 in the electric propulsion device 90 according to the second example of the present invention.

[0088] The electric propulsion device 90 according to the second example of the present invention is characterized in that a direct cooling system 92 of the cooling device 91 provided in the electric propulsion device 90 includes two heat exchangers 95 and 98.

[0089] Specifically, as illustrated in FIG. 9, the direct cooling system 92 of the cooling device 91 includes a first intake port 93, a first intake passage 94, a first heat exchanger 95, a second intake port 96, a second intake passage 97, a second heat exchanger 98, a discharge passage 99 for the second heat exchanger 98, and a drain port 100.

[0090] The first intake port 93 is a port that takes water outside the electric propulsion device 90 into the electric propulsion device 90 as cooling water for the first heat exchanger 95. The first intake passage 94 is a passage that sends the cooling water to the first heat exchanger 95. The first heat exchanger 95 is a device that uses the cooling water to cool the refrigerant in the indirect cooling system 71. The first intake port 93, the first intake passage 94, and the first heat exchanger 95 are the same as the intake port 53, the intake passage 54, and the heat exchanger 55 in the cooling device 51 according to the first example of the present invention. That is, as illustrated in FIG. 10, the first intake port 93 opens in the front part of the portion where the lower case 27 and the skeg 36 are coupled to each other. The first intake passage 94 extends in the front-rear direction between the lower case 27 and the skeg 36. The first heat exchanger 95 is provided on the outer circumferential side of the propeller shaft 18 in the lower case 27.

[0091] The second intake port 96 is a port that takes water outside the electric propulsion device 90 into the electric propulsion device 90 as cooling water for the second heat exchanger 98. The second intake port 96 opens at a front part of a side surface of the lower case 27 below the anti-cavitation plate 35 and above the propeller shaft 18. The second intake port 96 is disposed in a position submerged in water. The second intake passage 97 is a passage that sends the cooling water taken into the electric propulsion device 90 from the second intake port 96 to the second heat exchanger 98. The second intake passage 97 is provided in the lower case 27.

[0092] The second heat exchanger 98 is a device that uses the cooling water supplied via the second intake passage 97 to cool the refrigerant in the indirect cooling system 71. The second heat exchanger 98 is provided above the propeller shaft 18 in the lower case 27. The second heat exchanger 98 is preferably disposed to overlap the anti-cavitation plate 35 when the electric propulsion device 90 is viewed from behind. As illustrated in FIG. 9, the second heat exchanger 98 is connected to midway of the connection passage 86 configuring a portion of the circulation passage of the indirect cooling system 71, and to midway of the connection passage 81 configuring a portion of the circulation passage of the indirect cooling system 71. The second heat exchanger 98 uses the cooling water supplied via the second intake passage 97 to cool the refrigerant flowing in the connection passage 86 and the refrigerant flowing in the connection passage 81.

[0093] The discharge passage 99 is a passage that transports the cooling water after flowing in the second heat exchanger 98 to the drain port 100. The discharge passage 99 is provided in the lower case 27.

[0094] The drain port 100 is a port that discharges the cooling water after flowing in the first heat exchanger 95 and the cooling water after flowing in the second heat exchanger 98 to outside of the electric propulsion device 90. The drain port 100 is formed in the hub of the propeller 21 similarly to the drain port 70 according to the first example.

[0095] When the boat is moving forward, water in front of the electric propulsion device 90 hits the front part of the lower part of the lower case 27. As a result, water outside the electric propulsion device 90 is sent to the first heat exchanger 95 via the first intake port 93 and the first intake passage 94 as cooling water, and the refrigerant in the indirect cooling system 71 is cooled by the first heat exchanger 95. When the boat is moving forward, water in front of the electric propulsion device 90 hits the lower part of the lower case 27, and water outside the electric propulsion device 90 is sent to the second heat exchanger 98 via the second intake port 96 and the second intake passage 97 as cooling water. The second intake passage 97 extends upward from the second intake port 96, and when the boat is moving at a high speed, water forcefully flows into the second intake port 96 and ascends in the second intake passage 97 to reach the second heat exchanger 98. Then, the refrigerant in the indirect cooling system 71 is cooled by the second heat exchanger 98.

[0096] According to the electric propulsion device 90 of the second example of the present invention, by providing two heat exchangers 95 and 98 in the direct cooling system 92 of the cooling device 91, cooling capacity for refrigerant by the cooling device 91 can be increased.

[0097] In each of the above-described examples, an example is given in which the refrigerant in the indirect cooling system 71 sequentially flows in the motor cooling jacket 72, the inverter cooling jacket 73, and the speed reducer cooling jacket 74, but the order of flow of the refrigerant between the plurality of cooling jackets is not limited.

[0098] In each of the above-described examples, an example is given in which the motor 3, the inverter 6, and the speed reducer 11 are cooled in the indirect cooling system 71, but the present invention is not limited thereto. For example, only the motor 3 or only the inverter 6 may be cooled in the indirect cooling system 71, and equipment other than the motor 3, the inverter 6, and the speed reducer 11 may be added as equipment to be cooled in the indirect cooling system 71.

[0099] In each of the above-described examples, an example is given in which the axial flow impeller 69 is provided in the cooling water outlet chamber 63 of the heat exchanger 55 (95), but the present invention is not limited thereto, and the axial flow impeller 69 may be provided between the cooling water outlet chamber 63 and the hub 22 of the propeller 21, or in the hub 22 of the propeller 21. The number of cooling tubes 65 forming the cooling water passage 64 of the heat exchanger 55 is not limited.

[0100] The electric propulsion device 1 (90) in each of the above-described examples is an outboard motor, but the present invention can also be applied to other types of electric marine propulsion devices such as inboard/outboard motors.

[0101] The present invention can be modified as appropriate without departing from the spirit or the concept of the invention as can be read from the claims and the entire specification, and electric propulsion devices incorporating such modifications are also included in the technical concept of the present invention.

[0102] According to the present invention, corrosion of the cooling jacket can be prevented.