Marine propulsion

Abstract

To make it possible to reduce the size of a pump in a cooling device. [Solution] In the marine propulsion unit 1, the motor 3 is arranged so that the extension direction of the output shaft 4 is in the fore-and-aft direction, the reduction gear 9 is arranged in front of the motor 3, the drive shaft 8 extends downward from the reduction gear 9, and the cooling device includes a motor water jacket 63 that cools the motor 3, a water pump 54 that is arranged below the motor 3 and sends water taken in from a water intake 52 to the motor water jacket 63 as cooling water, and a supply passage 59 that connects the discharge outlet of the water pump 54 and the inlet of the motor water jacket 63.

Description

[Technical Field]

[0001] The present invention relates to a boat propulsion device equipped with a motor as a power source for rotating a propeller. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2005-162055 (Patent Document 1) describes an outboard motor equipped with a motor (electric motor) as a power source for rotating a propeller. In this outboard motor, the motor is located at the top of the outboard motor. When the outboard motor is mounted on a boat, the motor is located above the water surface. The motor is also positioned vertically so that its output shaft extends vertically. Meanwhile, the propeller is located at the bottom of the outboard motor. When the outboard motor is mounted on a boat, the propeller is located below the water surface. The propeller is mounted at the rear of a propeller shaft that extends in the fore-and-aft direction at the bottom of the outboard motor. A drive shaft is provided between the motor and the propeller shaft to transmit power from the motor to the propeller. The drive shaft extends vertically, and the upper end of the drive shaft is connected to the lower end of the motor's output shaft via a drive gear and a driven gear. The lower end of the drive shaft is connected to the propeller shaft via a bevel gear.

[0003] Furthermore, the outboard motor disclosed in JP 2005-162055 A is equipped with a water-cooled cooling system for cooling the motor. The cooling system includes a water jacket attached to the motor, a water intake port that draws water from outside the outboard motor into the outboard motor, and a pump that sends the water taken in through the water intake port to the water jacket. In this outboard motor, the water taken in through the water intake port is sent to the motor's water jacket as cooling water when the pump is driven. The cooling water flows through the water jacket to cool the motor.

[0004] In this outboard motor, the pump is mounted on the upper surface of the lower case, on which the propeller shaft is journaled. Meanwhile, the motor is located at a position significantly above the upper surface of the lower case. Therefore, the motor is located above the pump. Furthermore, between the pump and the motor, there is provided a passage (specifically, a cooling water pipe and a communication passage) that carries cooling water discharged from the pump to a water jacket provided on the motor. Furthermore, the pump is driven by the rotation of the drive shaft.

[0005] Generally, a motor's water jacket is made up of flow passages provided inside or around the motor, and coolant flows through the flow passages to cool the motor. The flow passages that make up the water jacket are generally formed over a wide area of ​​the motor. Specifically, the flow passages that make up the water jacket are formed around the entire circumference of the motor, extending from one axial end to the other axial end of the motor. By forming the flow passages that make up the water jacket over a wide area of ​​the motor in this way, the number of locations within or around the motor through which coolant flows can be increased, thereby improving the motor's cooling capacity provided by the water jacket. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-162055 Summary of the Invention [Problem to be solved by the invention]

[0007] To fully utilize the cooling capacity of the water jacket for the motor, the cooling water taken in through the water intake must be distributed throughout the entire flow path of the water jacket by the pump. Therefore, when determining the required head of a pump used in a cooling device for a marine propulsion motor, the difference in height between the water pump's discharge port and the uppermost end of the flow path of the water jacket provided on the motor must be taken into consideration so that the cooling water discharged from the pump can flow all the way to the uppermost end of the flow path of the water jacket. Specifically, the greater the difference in height between the water pump's discharge port and the uppermost end of the flow path of the water jacket provided on the motor, the higher the estimated required head of the pump must be.

[0008] Generally, most motors have a larger axial dimension (the direction in which the output shaft extends) than a radial dimension. Therefore, when a motor is vertically mounted with its output shaft extending vertically relative to the outboard motor, as in the outboard motor disclosed in Japanese Patent Application Laid-Open Publication No. 2005-162055, the uppermost end of the flow passages constituting the motor's water jacket is higher than when the motor is horizontally mounted with its output shaft extending horizontally relative to the outboard motor. As a result, the difference in height between the water pump discharge port and the uppermost end of the flow passages constituting the motor's water jacket becomes larger. This increases the required pump head, necessitating a larger pump to meet this required head when used in a cooling system for a marine propulsion unit. A larger pump size is undesirable because it increases the size of the marine propulsion unit and increases the manufacturing costs of the marine propulsion unit.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a marine propulsion device in which the pump in the cooling device can be made smaller. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a marine propulsion device including a motor, a drive shaft, a first transmission mechanism that transmits rotation of an output shaft of the motor to the drive shaft, a propeller shaft, a second transmission mechanism that transmits rotation of the drive shaft to the propeller shaft, a propeller, and a cooling device, wherein the motor is disposed so that the extension direction of the output shaft is in the fore-and-aft direction, the first transmission mechanism is disposed in front of the motor, the second transmission mechanism is disposed below the first transmission mechanism, and the drive shaft is disposed in the up-and-down direction between the first transmission mechanism and the second transmission mechanism. the cooling device includes a water intake port that takes water from outside the marine propulsion device into the marine propulsion device, a motor water jacket that is provided on the motor and cools the motor, a water pump that is positioned below the motor and sends the water taken into the marine propulsion device through the water intake port to the motor water jacket as cooling water, and a first cooling water passage that connects the discharge port of the water pump and the inlet of the motor water jacket. [Effects of the Invention]

[0011] According to the present invention, the pump in the cooling device can be made smaller. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an overall view showing the entire marine propulsion device according to an embodiment of the present invention as viewed from the left. [Figure 2] 1 is an explanatory diagram showing an upper part of a marine propulsion device according to an embodiment of the present invention as viewed from behind; [Figure 3] 3 is a cross-sectional view of the marine vessel propulsion device taken along the line AA in FIG. 2 as viewed from the left. [Figure 4] 1 is a perspective view showing an upper portion of a marine propulsion device according to an embodiment of the present invention, as viewed from the upper front left. FIG. [Figure 5]FIG. 2 is an explanatory diagram showing a motor, a reduction gear housing, a drive shaft housing, a mount housing, a lower case, and an inverter, each of which is separated, in a marine propulsion device according to an embodiment of the present invention. [Figure 6] 1 is a block diagram showing the configuration of a cooling device in a marine propulsion device according to an embodiment of the present invention; [Figure 7] 4 is an enlarged cross-sectional view of the portion of the marine propulsion device in FIG. 3 in which a water pump, a supply passage, a branch passage, and a reduction gear cooling chamber are provided. FIG. [Figure 8] 4A is an enlarged cross-sectional view of the motor in the marine propulsion device in FIG. 3, and FIG. 4B is an enlarged perspective view of the portion of the marine propulsion device in FIG. 4 where the outlet of the motor water jacket, the connecting passage, and the inlet of the inverter water jacket are provided. [Figure 9] 2A is a cross-sectional view showing the inverter, the inverter water jacket, and the connecting passage as seen from the left, taken along the cutting line BB in FIG. 2, and FIG. 2B is a cross-sectional view showing the inverter, the inverter water jacket, and part of the discharge passage as seen from the right, taken along the cutting line CC in FIG. 2. [Figure 10] 1 is a perspective view showing an upper portion of a marine propulsion device according to an embodiment of the present invention, as viewed from the rear right side. DETAILED DESCRIPTION OF THE INVENTION

[0013] A marine propulsion device according to an embodiment of the present invention includes a motor, a drive shaft, a first transmission mechanism that transmits rotation of an output shaft of the motor to the drive shaft, a propeller shaft, a second transmission mechanism that transmits rotation of the drive shaft to the propeller shaft, a propeller, and a cooling device.

[0014] In the marine propulsion device of this embodiment, the motor is disposed so that the extension direction of the output shaft is the fore-and-aft direction. The first transmission mechanism is disposed in front of the motor. The second transmission mechanism is disposed below the first transmission mechanism. The drive shaft extends in the up-and-down direction between the first transmission mechanism and the second transmission mechanism. The propeller shaft extends rearward from the second transmission mechanism. The propeller is provided at the rear of the propeller shaft.

[0015] In the marine propulsion device of this embodiment, when the motor is driven, the rotation of the output shaft is transmitted to the drive shaft by the first transmission mechanism, causing the drive shaft to rotate, and the rotation of the drive shaft is transmitted to the propeller shaft by the second transmission mechanism, causing the propeller shaft to rotate.

[0016] The cooling device for a marine propulsion unit of this embodiment includes a water intake port that draws water from outside the marine propulsion unit into the marine propulsion unit, a motor water jacket provided on the motor, a water pump that sends the water drawn into the marine propulsion unit through the water intake port to the motor water jacket as cooling water, and a first cooling water passage connecting the discharge port of the water pump to the inlet of the motor water jacket. The motor water jacket is formed by flow paths provided inside or around the motor. The flow paths that make up the motor water jacket are formed around the entire circumference of the motor, extending from one axial end to the other axial end of the motor. The water pump is located below the motor. In other words, the motor is located higher than the water pump. The motor water jacket provided on the motor is also located higher than the water pump.

[0017] In the marine propulsion device of this embodiment, water taken in through the water intake by driving the water pump flows through the first cooling water passage as cooling water and is sent to the motor water jacket. The cooling water sent to the motor water jacket flows through the flow path of the motor water jacket to cool the motor.

[0018] To fully utilize the motor cooling capacity of the motor water jacket, the cooling water taken in through the water intake must be distributed throughout the entire flow path that makes up the motor water jacket by the water pump. Therefore, when determining the required head of a water pump used in a cooling device for a marine propulsion unit, it is necessary to take into account the difference in height between the water pump discharge port and the uppermost end of the flow path that makes up the motor water jacket, so that the cooling water discharged from the water pump can flow all the way to the uppermost end of the flow path that makes up the motor water jacket.

[0019] Furthermore, motors generally have a cylindrical outer shape, and in most motors, the radial dimension of the motor is smaller than the axial dimension of the motor. Therefore, when two motors are placed on the same horizontal plane with their output shafts extending in the front-to-rear direction, the position of the top of the motor is lower when the output shaft extends in the front-to-rear direction than when the output shaft extends in the up-to-down direction. Furthermore, since the flow passages constituting the motor water jacket are formed around the entire circumference of the motor and extend from one axial end to the other axial end of the motor, when two motors with a motor water jacket are placed on the same horizontal plane with their output shafts extending in the front-to-rear direction, the position of the top of the flow passages constituting the motor water jacket is lower when the output shaft extends in the front-to-rear direction than when the output shaft extends in the up-to-down direction.

[0020] In the marine propulsion device of this embodiment, the motor is disposed transversely so that the extension direction of its output shaft is the longitudinal direction. Therefore, with the marine propulsion device of this embodiment, the position of the uppermost end of the flow passage constituting the motor water jacket can be lowered compared to a marine propulsion device in which the motor is disposed longitudinally so that the extension direction of its output shaft is the vertical direction of the marine propulsion device. This reduces the difference in height between the position of the water pump discharge port and the position of the uppermost end of the flow passage constituting the motor water jacket, thereby reducing the required head of the water pump used in the marine propulsion device. Because low-head water pumps are easier to downsize than high-head water pumps, reducing the required head of the water pump used in the marine propulsion device allows the water pump used in the marine propulsion device to be downsized. [Example]

[0021] A boat propulsion device according to an embodiment of the present invention will be described with reference to the drawings. In describing the embodiment, directions such as up (Ud), down (Dd), front (Fd), rear (Bd), left (Ld), and right (Rd) refer to the arrows drawn at the bottom left of Figures 1 to 4 and 7 to 10. These directions refer to directions in the boat propulsion device.

[0022] (Ship propulsion system) Fig. 1 shows the entire marine propulsion unit 1 according to an embodiment of the present invention as seen from the left. Fig. 2 shows the upper part of the marine propulsion unit 1 as seen from the rear. Fig. 3 shows a cross section of the marine propulsion unit 1 taken along section line AA in Fig. 2 as seen from the left. Fig. 4 shows the upper part of the marine propulsion unit 1 as seen from the upper left front. Fig. 5 shows the motor 3, reduction gear housing 25, drive shaft housing 26, mount housing 28, lower case 27, and inverter 35, each separated.

[0023] The marine propulsion unit 1 is a device for propelling a marine vessel. As shown in FIG. 1, the marine propulsion unit 1 of this embodiment is an outboard motor that is attached to a marine vessel. As shown in FIG. 3, the marine propulsion unit 1 includes a motor 3 that is a power source for rotating a propeller 20, a drive shaft 8 that transmits the power of the motor 3 to the propeller 20, a reduction gear 9 that reduces the rotation of an output shaft 4 of the motor 3 and transmits it to the drive shaft 8, a propeller shaft 13, a rotation transmission mechanism 14 that transmits the rotation of the drive shaft 8 to the propeller shaft 13, and the propeller 20 that converts the power of the motor 3 into propulsive force for the marine vessel. The reduction gear 9 is a specific example of a "first transmission mechanism," and the rotation transmission mechanism 14 is a specific example of a "second transmission mechanism."

[0024] The motor 3 and the reduction gear 9 are disposed in the upper part of the vessel propulsion unit 1. When the vessel propulsion unit 1 is attached to the vessel, the motor 3 and the reduction gear 9 are located above the water surface. Meanwhile, the rotation transmission mechanism 14, the propeller shaft 13, and the propeller 20 are disposed in the lower part of the vessel propulsion unit 1. When the vessel propulsion unit 1 is attached to the vessel, the rotation transmission mechanism 14, the propeller shaft 13, and the propeller 20 are located below the water surface.

[0025] As shown in Fig. 3, the motor 3 includes an output shaft 4 which is a power output shaft, a rotor 5 provided on the outer periphery of the output shaft 4, a stator 6 provided on the outer periphery of the rotor 5, and a substantially cylindrical motor case 7. The motor case 7 houses the output shaft 4 except for its tip, the rotor 5, and the stator 6. As shown in Fig. 3, the motor 3 is arranged so that the extension direction of the output shaft 4 is the front-rear direction.

[0026] As shown in FIG. 3, the reduction gear 9 is disposed in front of the motor 3. The reduction gear 9 includes a motor drive gear 10, a reduction gear 11, and a connecting shaft 12. Both the motor drive gear 10 and the reduction gear 11 are bevel gears. The rotation axis of the motor drive gear 10 extends in the front-to-rear direction. The rear portion of the motor drive gear 10 is connected to the front portion of the output shaft 4 of the motor 3, and the motor drive gear 10 rotates integrally with the output shaft 4. The rotation axis of the reduction gear 11 extends in the up-down direction. The reduction gear 11 is disposed in front of the motor drive gear 10 and meshes with the motor drive gear 10. The gear ratio between the motor drive gear 10 and the reduction gear 11 (number of teeth of the reduction gear 11 / number of teeth of the motor drive gear 10) is greater than 1. The connecting shaft 12 extends in the up-down direction. The upper end of the connecting shaft 12 is connected to the reduction gear 11, and the connecting shaft 12 rotates integrally with the reduction gear 11.

[0027] The drive shaft 8 extends in the vertical direction. The drive shaft 8 is disposed between the reduction gear device 9 and the rotation transmission mechanism 14. The upper end of the drive shaft 8 is connected to the lower end of the connecting shaft 12 of the reduction gear device 9, and the drive shaft 8 rotates integrally with the connecting shaft 12.

[0028] The rotation transmission mechanism 14 is disposed below the reduction gear 9. The rotation transmission mechanism 14 includes a transmission gear 15, a forward gear 16, a reverse gear 17, a dog clutch 18, and a shift plunger 19. The transmission gear 15, the forward gear 16, and the reverse gear 17 are all bevel gears. The rotation axis of the transmission gear 15 extends in the vertical direction. The transmission gear 15 is coupled to the lower end of the drive shaft 8 and rotates integrally with the drive shaft 8. The rotation axes of the forward gear 16 and the reverse gear 17 extend in the front-to-rear direction. The forward gear 16 is disposed in front of the transmission gear 15, and the reverse gear 17 is disposed behind the transmission gear 15. The forward gear 16 and the reverse gear 17 are each meshed with the transmission gear 15, and the forward gear 16 and the reverse gear 17 rotate in opposite directions upon receiving the rotation of the transmission gear 15. Furthermore, a through hole is formed in the center of the forward gear 16 and the center of the reverse gear 17, and the front portion of the propeller shaft 13 is inserted into these through holes. The forward gear 16 and the reverse gear 17 are not fixed to the propeller shaft 13 but are rotatable relative to the propeller shaft 13. A dog clutch 18 is disposed between the forward gear 16 and the reverse gear 17. The dog clutch 18 is attached to the front portion of the propeller shaft 13 so as to be unable to rotate relative to the propeller shaft 13 and to be movable in the front-rear direction relative to the propeller shaft 13. A shift plunger 19 is attached inside the front end of the propeller shaft 13 so as to be movable in the front-rear direction relative to the propeller shaft 13. The rear end of the shift plunger 19 is connected to the dog clutch 18. The front end of the shift plunger 19 is located near the lower end of a shift rod 23 (described below), and rotation of the shift rod 23 is transmitted to the shift plunger 19 via a cam mechanism. When the shift rod 23 rotates by driving the shift actuator 22 (described later), the rotation of the shift rod 23 is transmitted to the shift plunger 19 via the cam mechanism, causing the shift plunger 19 to move forward or backward, and in response, the dog clutch 18 moves forward or backward. When the dog clutch 18 moves forward, the dog clutch 18 and the forward gear 16 engage with each other, thereby transmitting the rotation of the forward gear 16 to the propeller shaft 13.On the other hand, when the dog clutch 18 moves rearward, the dog clutch 18 and the reverse gear 17 engage with each other, thereby transmitting the rotation of the reverse gear 17 to the propeller shaft 13 .

[0029] The propeller shaft 13 extends in the front-to-rear direction. The front portion of the propeller shaft 13 extends into the rotation transmission mechanism 14, and the rear portion of the propeller shaft 13 extends rearward from the rotation transmission mechanism 14. The propeller 20 is fixed to the rear portion of the propeller shaft 13 and rotates integrally with the propeller shaft 13.

[0030] The motor 3 is driven by the control of an inverter 35 (described later) so that the rotation direction of the output shaft 4 is always constant. When the motor 3 is driven, the rotation of the output shaft 4 of the motor 3 is transmitted to the forward gear 16 and the reverse gear 17 via the motor drive gear 10, the reduction gear 11, the connecting shaft 12, the drive shaft 8, and the transmission gear 15 in this order. When the dog clutch 18 is moved forward, the rotation of the forward gear 16 is transmitted to the propeller shaft 13, causing the propeller shaft 13 and the propeller 20 to rotate in the forward direction. The forward rotation of the propeller 20 generates a propulsive force that moves the vessel forward. On the other hand, when the dog clutch 18 is moved rearward, the rotation of the reverse gear 17 is transmitted to the propeller shaft 13, causing the propeller shaft 13 and the propeller 20 to rotate in the reverse direction. The reverse rotation of the propeller 20 generates a propulsive force that moves the vessel backward.

[0031] The marine propulsion unit 1 also includes a shift device 21 that controls switching of the rotation direction of the propeller 20. The shift device 21 has a shift actuator 22 and a shift rod 23. The shift actuator 22 is an actuator that controls movement of the dog clutch 18 and is provided in the upper front portion of the marine propulsion unit 1. The shift actuator 22 is, for example, a small motor. The shift rod 23 is a rod that transmits power from the shift actuator 22 to the shift plunger 19. The shift rod 23 extends in the vertical direction from the shift actuator 22 toward the front end of the shift plunger 19. The upper end of the shift rod 23 is connected to the shift actuator 22. The lower end of the shift rod 23 is located near the front end of the shift plunger 19. The shift rod 23 rotates when driven by the shift actuator 22. The rotational motion of the shift rod 23 is converted into linear motion in the front-to-rear direction of the shift plunger 19 by a cam mechanism provided between the lower end of the shift rod 23 and the front end of the shift plunger 19. As described above, the movement of the shift plunger 19 causes the dog clutch 18 to move.

[0032] The marine propulsion device 1 also includes a reduction gear housing 25 that covers the reduction gear 9, a drive shaft housing 26 that covers the upper part of the drive shaft 8, a lower case 27 that covers the lower part of the drive shaft 8, the rotation transmission mechanism 14, and the front part of the propeller shaft 13, and a mount housing 28 that covers the upper mount 44. The reduction gear housing 25 is a specific example of a "transmission mechanism housing."

[0033] 1, 3, and 5, the drive shaft housing 26 is disposed below the reduction gear housing 25 and is attached to the reduction gear housing 25 using fastening members such as bolts. The lower case 27 is disposed below the drive shaft housing 26 and is attached to the drive shaft housing 26 using fastening members such as bolts. The mount housing 28 is disposed above the reduction gear housing 25 and is attached to the reduction gear housing 25 using fastening members such as bolts.

[0034] The motor 3 is located behind the reduction gear housing 25 and the drive shaft housing 26. Specifically, the upper part of the motor 3 is located behind the reduction gear housing 25, and the lower part of the motor 3 is located behind the drive shaft housing 26. The motor 3 is attached to the reduction gear housing 25 and the drive shaft housing 26 using connecting members such as bolts.

[0035] The marine vessel propulsion device 1 also includes an inverter 35 that controls the drive of the motor 3. As shown in Fig. 1, the inverter 35 includes an inverter main body 36 that includes electric and electronic circuits that control the drive of the motor 3, and an inverter case 37 that houses the inverter main body 36. The inverter 35 has a generally rectangular parallelepiped outer shape. The inverter 35 is disposed above the motor 3 and attached to the motor 3 using fastening members such as bolts. The inverter 35 is also located below the upper surface 28A of the mount housing 28.

[0036] 1 and 4, the marine vessel propulsion unit 1 is provided with a pair of left and right clamp brackets 41 for attaching the marine vessel propulsion unit 1 to the marine vessel. A swivel bracket 42 is provided between the pair of clamp brackets 41. A pilot shaft 43 is rotatably supported on the swivel bracket 42. The pilot shaft 43 is connected to the marine vessel propulsion unit 1 by mounts 44 and 45. The front portion of the upper mount 44 is connected to the upper end of the pilot shaft 43, and the rear portion of the mount 44 is inserted into and attached to the mount housing 28. The front portion of the lower mount 45 is connected to the lower end of the pilot shaft 43, and the rear portion of the mount 45 is attached to the drive shaft housing 26. The marine vessel propulsion unit 1 can rotate horizontally relative to the marine vessel about the pilot shaft 43 as a rotation axis, thereby changing the direction of the propeller 20 in the left-right direction.

[0037] (cooling device) The marine vessel propulsion unit 1 also includes a cooling device 51 that cools the motor 3, the reduction gear 9, and the inverter 35. The cooling device 51 is a water-cooled cooling device that uses water (e.g., seawater) outside the marine vessel propulsion unit 1 to cool the motor 3, the reduction gear 9, and the inverter 35.

[0038] FIG. 6 shows the configuration of the cooling device 51. FIG. 7 shows an enlarged view of the portion of the marine propulsion unit 1 shown in FIG. 3 where the water pump 54, supply passage 59, branch passage 60, and reduction gear cooling chamber 61 are provided. FIG. 8(A) shows an enlarged view of the motor 3 in the marine propulsion unit 1 shown in FIG. 3. FIG. 8(B) shows an enlarged view of the portion of the marine propulsion unit 1 shown in FIG. 4 where the outlet 63F of the motor water jacket 63, the connecting passage 65, and the inlet 67A of the inverter water jacket 67 are provided. FIG. 9(A) shows a cross section of the inverter 35, inverter water jacket 67, and connecting passage 65 taken along section line BB in FIG. 2, as viewed from the left. FIG. 9(B) shows a cross section of the inverter 35, inverter water jacket 67, and part of the discharge passage 73 taken along section line CC in FIG. 2, as viewed from the right. FIG. 10 shows the upper part of the marine propulsion unit 1 as viewed from the rear right.

[0039] As shown in FIG. 6 , the cooling device 51 includes a water intake port 52, a water intake passage 53, a water pump 54, a supply passage 59, a branch passage 60, a reduction gear cooling chamber 61, a motor water jacket 63, a connecting passage 65, an inverter water jacket 67, a cooling water temperature control valve 71, a discharge passage 73, and a drain port 76. Note that the supply passage 59 is a specific example of a "first cooling water passage." The branch passage 60 is a specific example of a "second cooling water passage." The reduction gear cooling chamber 61 is a specific example of a "transmission mechanism cooling section." The connecting passage 65 is a specific example of a "third cooling water passage." The cooling water temperature control valve 71 is a specific example of a "valve." The discharge passage 73 is a specific example of a "fourth cooling water passage."

[0040] The water intake 52 is an opening through which water from outside the marine vessel propulsion device 1 is taken into the marine vessel propulsion device 1 as cooling water. The water intake 52 is provided in a submerged portion of the lower part of the marine vessel propulsion device 1. Specifically, as shown in FIG. 1 , the water intake 52 is provided in the front part of the lower case 27, below the anti-cavitation plate 29.

[0041] 3, water intake passage 53 is a passage that connects water intake port 52 and the suction port of water pump 54. Water intake passage 53 is formed, for example, by a hole formed in lower case 27. Cooling water taken in through water intake port 52 flows through water intake passage 53 toward the suction port of water pump 54.

[0042] The water pump 54 is a pump that sends cooling water taken into the marine propulsion device 1 from outside the marine propulsion device 1 through the water intake 52 to the motor water jacket 63 and the like. The water pump 54 is, for example, a rotary variable volume water pump. As shown in FIG. 7 , the water pump 54 is disposed below the reduction gear 9. The water pump 54 is also disposed below the motor 3. The water pump 54 is also disposed at a lower part within the drive shaft housing 26. An impeller 55 of the water pump 54 is attached to the drive shaft 8 and rotates integrally with the drive shaft 8. A pump case 56 of the water pump 54 is attached to the upper surface of the lower case 27.

[0043] Supply passage 59 is a passage that connects discharge port 56A of water pump 54 and inlet 63A of motor water jacket 63. Supply passage 59 is provided inside drive shaft housing 26. Supply passage 59 is composed of a tube 59A formed by, for example, a pipe or a hose, and a hole 59B formed in drive shaft housing 26. Cooling water discharged from discharge port 56A of water pump 54 flows through supply passage 59 toward inlet 63A of motor water jacket 63.

[0044] The branch passage 60 branches off from the supply passage 59 midway and connects the supply passage 59 with the reduction gear cooling chamber 61. The branch passage 60 is provided inside the drive shaft housing 26. The branch passage 60 is formed, for example, by a hole formed in the drive shaft housing 26.

[0045] The reduction gear cooling chamber 61 is a chamber that cools the oil in the reduction gear housing 25 with cooling water. Cooling the oil in the reduction gear housing 25 cools the motor drive gear 10, the reduction gear 11, and other components of the reduction gear 9. The reduction gear cooling chamber 61 is provided in an upper portion of the drive shaft housing 26. The reduction gear cooling chamber 61 is located below the reduction gear 9 and close to it. Cooling water flows from the supply passage 59 to the reduction gear cooling chamber 61 or from the reduction gear cooling chamber 61 to the supply passage 59 via the branch passage 60. For example, when the flow rate of cooling water in the supply passage 59 increases while the reduction gear cooling chamber 61 is not filled with cooling water, the cooling water flows from the supply passage 59 into the reduction gear cooling chamber 61 via the branch passage 60. On the other hand, when the flow rate of cooling water in the supply passage 59 decreases, the cooling water flows from the reduction gear cooling chamber 61 to the supply passage 59 via the branch passage 60.

[0046] As shown in FIG. 8A, the motor water jacket 63 is provided on the motor 3. The motor water jacket 63 is composed of flow passages arranged around the motor 3. The flow passages constituting the motor water jacket 63 are formed around the entire circumference of the motor 3, extending from one axial end to the other axial end of the motor 3. Specifically, the motor case 7 includes a cylindrical case body 7A that surrounds the outer periphery of the stator 6 along the entire circumference, a cover 7B that covers one axial end of the case body 7A so as to close it and has a central hole through which the output shaft 4 passes, and a cover 7C that closes the other axial end of the case body 7A. The motor water jacket 63 includes, for example, a flow passage 63B formed within the cover 7B, a flow passage 63C formed around the entire circumference in the peripheral wall of the case body 7A, a flow passage 63D formed within the cover 7C, and an outflow chamber 63E formed in the upper part of the case body 7A. The flow passages 63B, 63C, and 63D are holes through which cooling water can flow. The flow paths 63B and 63C communicate with each other, and the flow paths 63C and 63D communicate with each other. The motor 3 is cooled by the cooling water flowing through the motor water jacket 63, that is, the flow paths 63B, 63C, and 63D.

[0047] An inlet 63A of the motor water jacket 63 is provided at the lower front portion of the motor 3. The inlet 63A is formed at the front end portion of the lower portion of the cover 7B. The inlet 63A opens forward. The inlet 63A is connected to the supply passage 59 and also communicates with the flow passage 63B. Cooling water flows from the supply passage 59 through the inlet 63A and into the flow passage 63B.

[0048] An outlet 64 is provided above the horizontally-oriented motor 3. The outlet 64 is formed at the top of the case body 7A. An outlet chamber 63E is formed within the outlet 64. The outlet chamber 63E corresponds to the terminal end of the flow path that constitutes the motor water jacket 63. The outlet chamber 63E is also the uppermost end of the flow path that constitutes the motor water jacket 63 provided on the horizontally-oriented motor 3. The flow path 63C communicates with the inside of the outlet chamber 63E. As shown in FIG. 8(B), the outlet 64 is provided with an outlet 63F of the motor water jacket 63. The outlet 63F is formed on the left surface of the outlet 64 and opens to the left. The outlet 63F communicates with the inside of the outlet chamber 63E. The cooling water that flows through the flow paths 63B, 63C, and 63D passes through the outlet chamber 63E and flows out of the motor water jacket 63 from the outlet 63F.

[0049] The connecting passage 65 connects the outlet 63F of the motor water jacket 63 and the inlet 67A of the inverter water jacket 67. As shown in FIG. 8(B), the connecting passage 65 is formed, for example, by a hose 65A and a joint 65B. The inverter 35 is disposed above the motor 3, the outlet 63F of the motor water jacket 63 is disposed above the motor 3, and the inlet 67A of the inverter water jacket 67 is disposed below the inverter 35. Therefore, the outlet 63F of the motor water jacket 63 and the inlet 67A of the inverter water jacket 67 are very close to each other. Therefore, the length of the connecting passage 65 connecting them is very short. The cooling water flowing out from the outlet 63F of the motor water jacket 63 flows through the connecting passage 65 and into the inlet 67A of the inverter water jacket 67.

[0050] As shown in FIG. 9A, the inverter water jacket 67 is provided below the inverter 35. Specifically, a lower protrusion 68 that protrudes downward from the lower surface of the inverter case 37 is formed at the rear of the inverter case 37. The inverter water jacket 67 has a flow path 67B provided inside the lower protrusion 68. The flow path 67B is a hole through which cooling water can flow. The flow path 67B extends from the left end to the right end of the inverter 35 (lower protrusion 68). The inverter 35 is cooled by the cooling water flowing inside the inverter water jacket 67, i.e., inside the flow path 67B.

[0051] An inlet 67A of the inverter water jacket 67 is provided at the bottom of the left end of the lower protrusion 68. The inlet 67A opens downward. The inlet 67A is connected to the connecting passage 65 and also communicates with a flow path 67B. The cooling water flows from the connecting passage 65 through the inlet 67A and into the flow path 67B.

[0052] 9(B), an outlet 67C of the inverter water jacket 67 is provided at the bottom of the right end of the lower protrusion 68. The outlet 67C opens downward. The outlet 67C communicates with the inside of a flow path 67B via a water temperature control passage 69, which will be described later. The cooling water that flows through the inside of the flow path 67B passes through the water temperature control passage 69 and flows out of the inverter water jacket 67 from the outlet 67C.

[0053] A water temperature control passage 69 is provided at the right rear of the inverter 35. The water temperature control passage 69 is arranged so as to be wedged between a flow path 67B of the inverter water jacket 67 and an outlet 67C of the inverter water jacket 67. The water temperature control passage 69 is formed, for example, by holes formed in the right rear of the inverter case 37 and in an upper protrusion 70 that protrudes upward from the right rear of the top surface of the inverter case 37. One end of the water temperature control passage 69 communicates with the flow path 67B, and the other end of the water temperature control passage 69 communicates with the outlet 67C. The cooling water that flows through flow path 67B passes through the water temperature control passage 69 and reaches the outlet 67C.

[0054] A cooling water temperature control valve 71 is provided in the water temperature control passage 69. The cooling water temperature control valve 71 is a valve that changes the amount of cooling water flowing out of the inverter water jacket 67 in accordance with the temperature of the cooling water that has flowed through the inverter water jacket 67. Specifically, the cooling water temperature control valve 71 detects the temperature of the cooling water flowing through the water temperature control passage 69 and changes the valve opening based on the detected temperature to change the amount of cooling water flowing out from the outlet 67C of the inverter water jacket 67. A thermostat, for example, can be used as the cooling water temperature control valve 71. The cooling water temperature control valve 71 will be described in detail below.

[0055] The discharge passage 73 is a passage through which the cooling water flowing out from the outlet 67C of the inverter water jacket 67 flows toward the drain port 76. As shown in FIG. 10 , the discharge passage 73 is located on the right side of the upper part of the marine propulsion device 1, specifically, on the right front side of the motor 3. One end of the discharge passage 73 is connected to the outlet 67C of the inverter water jacket 67. The other end of the discharge passage 73 is connected to a communication hole 74 provided in the drive shaft housing 26. The communication hole 74 is provided in the right wall of the drive shaft housing 26 and communicates with the interior of the rear part of the drive shaft housing 26. The discharge passage 73 is composed of, for example, a drain pipe 73A, a joint 73B that connects one end of the drain pipe 73A to the outlet 67C of the inverter water jacket 67, and a joint 73C that connects the other end of the drain pipe 73A to the communication hole 74 of the drive shaft housing 26. The discharge passage 73 also passes outside the motor 3 at a position away from the motor 3. The cooling water flowing out from the outlet 67C of the inverter water jacket 67 flows through the discharge passage 73, then passes through the communication hole 74, and flows into the interior of the rear part of the drive shaft housing .

[0056] As shown in Figure 3, the water discharge port 76 is provided inside the hub of the propeller 20. In addition, in the marine vessel propulsion device 1, a space 75 is provided from the interior of the rear portion of the drive shaft housing 26 to the interior of the rear portion of the lower case 27. The cooling water that flows into the interior of the rear portion of the drive shaft housing 26 from the communication hole 74 flows through this space 75 and is then discharged from the marine vessel propulsion device 1 through the water discharge port 76.

[0057] The cooling device 51 operates as follows. When the drive shaft 8 is rotated by the drive of the motor 3, the water pump 54 is driven. As the water pump 54 is driven, water outside the marine propulsion unit 1 is taken in as cooling water through the water intake port 52, transported to the water pump 54 via the water intake passage 53, and discharged from the discharge port 56A of the water pump 54. The cooling water discharged from the discharge port 56A of the water pump 54 is supplied to the reduction gear cooling chamber 61 and the motor water jacket 63 via the supply passage 59 and the branch passage 60, respectively. The reduction gear 9 is cooled by the cooling water supplied to the motor water jacket 63. The cooling water supplied to the motor water jacket 63 flows within the motor water jacket 63, thereby cooling the motor 3. The cooling water flowing within the motor water jacket 63 is supplied to the inverter water jacket 67 via the connecting passage 65. The cooling water supplied to the inverter water jacket 67 flows inside the inverter water jacket 67, thereby cooling the inverter 35. The cooling water that flows inside the inverter water jacket 67 is carried through a discharge passage 73 into a space 75 provided inside the rear part of the drive shaft housing 26 and inside the rear part of the lower case 27, and then is discharged from a drain port 76 to the outside of the marine vessel propulsion device 1.

[0058] Furthermore, the cooling water that has flowed through flow path 67B of inverter water jacket 67 passes through water temperature control passage 69 and flows out from outlet 67C of inverter water jacket 67 into discharge passage 73. Cooling water temperature control valve 71 changes the amount of cooling water that flows out from outlet 67C of inverter water jacket 67 into discharge passage 73 according to the temperature of the cooling water flowing through water temperature control passage 69. Specifically, the cooling water temperature control valve 71 increases the amount of cooling water that flows out from outlet 67C of inverter water jacket 67 as the temperature of the cooling water flowing through water temperature control passage 69 increases.

[0059] The coolant temperature control valve 71 that operates in this manner can perform control to adjust the temperature of the coolant flowing mainly in the motor water jacket 63 and the inverter water jacket 67, mainly in accordance with the total amount of heat generated by the motor 3 and the inverter 35. Specifically, when the amount of heat generated mainly by the motor 3 and the inverter 35 increases and the temperature of the coolant flowing mainly in the motor water jacket 63 and the inverter water jacket 67 rises, the temperature of the coolant can be lowered.

[0060] Here, we will explain how by changing the amount of cooling water flowing out from the outlet 67C of the inverter water jacket 67 into the discharge passage 73 depending on the temperature of the cooling water flowing in the water temperature control passage 69, it is possible to perform control to adjust the temperature of the cooling water flowing mainly in the motor water jacket 63 and the inverter water jacket 67 depending mainly on the total heat generation of the motor 3 and the inverter 35.

[0061] The cooling water flowing through the water temperature control passage 69 is cooling water that has mainly flowed through the motor water jacket 63 and the flow path 67B of the inverter water jacket 67. Therefore, the temperature of the cooling water flowing through the water temperature control passage 69 rises mainly due to heat from the motor 3 and the inverter 35. Therefore, the temperature of the cooling water flowing through the water temperature control passage 69 can be considered to mainly represent the sum of the heat values ​​of the motor 3 and the inverter 35.

[0062] Furthermore, by changing the amount of cooling water flowing out from outlet 67C of inverter water jacket 67 into discharge passage 73, it is possible to change the amount of cooling water flowing mainly in motor water jacket 63 and inverter water jacket 67. Furthermore, by changing the amount of cooling water flowing in motor water jacket 63 and inverter water jacket 67, it is possible to change the temperature of the cooling water flowing in motor water jacket 63 and inverter water jacket 67. Specifically, by increasing the amount of cooling water flowing in motor water jacket 63 and inverter water jacket 67, it is possible to lower the temperature of the cooling water flowing in motor water jacket 63 and inverter water jacket 67.

[0063] Therefore, by changing the amount of cooling water flowing out from the outlet 67C of the inverter water jacket 67 into the discharge passage 73 in accordance with the temperature of the cooling water flowing in the water temperature control passage 69, it is possible to perform control to adjust the temperature of the cooling water flowing mainly in the motor water jacket 63 and the inverter water jacket 67 in accordance with the total heat generation mainly of the motor 3 and the inverter 35.

[0064] As described above, in the marine propulsion device 1 according to the embodiment of the present invention, the motor 3 is disposed so that the extension direction of its output shaft 4 is the longitudinal direction. Therefore, with the marine propulsion device 1 according to the embodiment, the position of the uppermost end portion of the flow passages constituting the motor water jacket 63 can be lowered compared to when the motor 3 is disposed vertically so that the extension direction of its output shaft 4 is the vertical direction of the marine propulsion device 1. This reduces the difference in height between the position of the discharge port 56A of the water pump 54 and the position of the uppermost end portion of the flow passages constituting the motor water jacket 63, thereby reducing the required head of the water pump 54 used in the marine propulsion device 1. Because low-head pumps are easier to miniaturize than high-head pumps, reducing the required head of the water pump used in the marine propulsion device 1 allows the water pump 54 used in the marine propulsion device 1 to be made smaller.

[0065] Furthermore, in the marine propulsion device 1 of this embodiment, the reduction gear 9 is disposed in front of the motor 3, the rotation transmission mechanism 14 is disposed below the reduction gear 9, the drive shaft 8 extends vertically between the reduction gear 9 and the rotation transmission mechanism 14, the impeller 55 of the water pump 54 is attached to the drive shaft 8, and the inlet 63A of the motor water jacket 63 is disposed in a lower part of the front of the motor 3. In this configuration, the reduction gear 9 is disposed in front of the motor 3, the rotation transmission mechanism 14 is disposed below the reduction gear 9, and the drive shaft 8 extends vertically between the reduction gear 9 and the rotation transmission mechanism 14, so that the drive shaft 8 is located below and in front of the motor 3. The water pump 54 is provided on the drive shaft 8 with the impeller 55 attached to the drive shaft 8, so that the water pump 54 is located below and in front of the motor 3. Therefore, the lower part of the front of the motor 3 is closer to the water pump 54 than any other part of the motor 3. Therefore, by locating the inlet 63A of the motor water jacket 63 in the lower front portion of the motor 3, the inlet 63A of the motor water jacket 63 can be brought closer to the water pump 54. This makes it possible to shorten the supply passage 59 connecting the discharge port 56A of the water pump 54 and the inlet 63A of the motor water jacket 63. By shortening the supply passage 59, it is possible to reduce the pressure loss caused by the coolant flowing through the supply passage 59.

[0066] Furthermore, in the marine vessel propulsion device 1 of this embodiment, the cooling device 51 includes a reduction gear cooling chamber 61 and a branch passage 60, and can cool the reduction gear 9 by supplying cooling water to the reduction gear cooling chamber 61 via the branch passage 60. This can improve the performance or durability of the reduction gear 9.

[0067] The marine propulsion device 1 of this embodiment also includes a drive shaft housing 26 that covers the upper part of the drive shaft 8. The motor 3 is attached to the drive shaft housing 26, and the water pump 54, reduction gear cooling chamber 61, supply passage 59, and branch passage 60 are provided within the drive shaft housing 26. In this configuration, the water pump 54, reduction gear cooling chamber 61, supply passage 59, branch passage 60, and motor 3 are all disposed inside or around the drive shaft housing 26. This allows the water pump 54, reduction gear cooling chamber 61, and motor 3 to be located close to one another, and the supply passage 59 and branch passage 60 to be shortened. This reduces pressure loss caused by the cooling water flowing through the supply passage 59 or the branch passage 60, enabling smooth supply of cooling water to the reduction gear cooling chamber 61 and the motor water jacket 63.

[0068] Furthermore, in the marine vessel propulsion device 1 of this embodiment, the cooling device 51 includes an inverter water jacket 67 and a connecting passage 65 that connects the outlet 63F of the motor water jacket 63 with the inlet 67A of the inverter water jacket 67, and can cool the inverter 35 by supplying cooling water to the inverter water jacket 67 via the connecting passage 65. This can improve the performance or durability of the inverter 35.

[0069] Furthermore, in the marine vessel propulsion device 1 of this embodiment, the inverter 35 is attached to the motor 3. Therefore, the inverter 35 and the motor 3 are close to each other. This allows the connecting passage 65 connecting the outlet 63F of the motor water jacket 63 and the inlet 67A of the inverter water jacket 67 to be shortened, thereby reducing pressure loss caused by the cooling water flowing through the connecting passage 65.

[0070] Furthermore, in the marine vessel propulsion device 1 of this embodiment, the inverter 35 is disposed above the motor 3, the outlet 63F of the motor water jacket 63 is disposed above the motor 3, and the inlet 67A of the inverter water jacket 67 is disposed below the inverter 35. With this configuration, the outlet 63F of the motor water jacket 63 and the inlet 67A of the inverter water jacket 67 can be positioned close to each other, and the connecting passage 65 connecting the outlet 63F of the motor water jacket 63 and the inlet 67A of the inverter water jacket 67 can be shortened. This reduces pressure loss caused by the cooling water flowing through the connecting passage 65.

[0071] Furthermore, in the marine vessel propulsion device 1 of this embodiment, the inverter 35 is disposed above the motor 3, and the inverter water jacket 67 is disposed below the inverter 35. This configuration allows the motor water jacket 63 and the inverter water jacket 67 to be closer to each other, thereby shortening the connecting passage 65.

[0072] Furthermore, in the marine vessel propulsion device 1 of this embodiment, the outlet 67C of the inverter water jacket 67 is disposed below the inverter 35. This makes it possible to shorten the discharge passage 73 that carries the cooling water flowing out from the outlet 67C of the inverter water jacket 67 to the drain port 76 disposed below the marine vessel propulsion device 1. It is also possible to prevent the discharge passage 73 from extending outward in the left-right direction of the marine vessel propulsion device 1.

[0073] Furthermore, in the cooling device 51 of the marine propulsion unit 1 of this embodiment, the discharge passage 73 passes through a position outside the motor 3, away from the motor 3. With this configuration, when high-temperature cooling water flows through the discharge passage 73, the heat of the cooling water is less likely to be transferred to the motor 3. This makes it possible to suppress a rise in temperature of the motor 3.

[0074] Furthermore, in the marine vessel propulsion device 1 of this embodiment, the cooling device 51 is provided with a cooling water temperature control valve 71 that changes the amount of cooling water flowing out of the inverter water jacket 67 in accordance with the temperature of the cooling water that has flowed through the inverter water jacket 67. This allows a single valve to perform control of the temperature of the cooling water flowing mainly through the motor water jacket 63 and the inverter water jacket 67 in accordance with the total amount of heat generated mainly by the motor 3 and the inverter 35, thereby simplifying the configuration for controlling the temperature of such cooling water.

[0075] Although the boat propulsion device 1 in the above embodiment is an outboard motor, the present invention can also be applied to other types of boat propulsion devices other than outboard motors, such as inboard-outboard motors.

[0076] Furthermore, the present invention can be modified as appropriate within the scope of the claims and the spirit or concept of the invention that can be read from the entire specification, and a marine propulsion device with such modifications is also included in the technical concept of the present invention. [Explanation of symbols]

[0077] 1 Ship propulsion system 3 motors 4 output shaft 8 Drive shaft 9. Reduction gear (first transmission mechanism) 13 Propeller shaft 14 Rotation transmission mechanism (second transmission mechanism) 20 propellers 25 Reduction gear housing (transmission mechanism housing) 26 Drive shaft housing 35 inverter 51 Cooling device 52 Water Intake 54 Water Pump 56A outlet 59 Supply passage (first cooling water passage) 60 Branch passage (second cooling water passage) 61 Reduction gear cooling chamber (transmission mechanism cooling section) 63 Motor water jacket 63A Inlet 63F Outlet 65 Connecting passage (third cooling water passage) 67 Inverter water jacket 67A Inlet 67C Outlet 71 Cooling water temperature control valve (valve) 73 Discharge passage (fourth cooling water passage) 76 Drain

Claims

1. A marine propulsion device including a motor, a drive shaft, a first transmission mechanism that transmits rotation of an output shaft of the motor to the drive shaft, a propeller shaft, a second transmission mechanism that transmits rotation of the drive shaft to the propeller shaft, a propeller, and a cooling device, the motor is disposed so that the extension direction of the output shaft is in the front-rear direction, the first transmission mechanism is disposed in front of the motor, the second transmission mechanism is disposed below the first transmission mechanism, the drive shaft extends in the up-down direction between the first transmission mechanism and the second transmission mechanism, the propeller shaft extends rearward from the second transmission mechanism, and the propeller is provided at the rear of the propeller shaft, The cooling device is a water intake that takes in water outside the marine vessel propulsion device into the marine vessel propulsion device; a motor water jacket provided on the motor to cool the motor; a water pump disposed below the motor and configured to send water taken into the marine propulsion device through the water intake port to the motor water jacket as cooling water; a first cooling water passage connecting a discharge port of the water pump and an inlet of the motor water jacket;

2. The water pump impeller is attached to the drive shaft, 2. The marine vessel propulsion device according to claim 1, wherein the inlet of the motor water jacket is disposed below the front portion of the motor.

3. a transmission mechanism housing that covers the first transmission mechanism; a drive shaft housing that is disposed below the transmission mechanism housing and covers an upper portion of the drive shaft, the motor is attached to the drive shaft housing; The cooling device is a transmission mechanism cooling unit that cools the first transmission mechanism using the cooling water; a second cooling water passage branching from the first cooling water passage and connecting the first cooling water passage and the transmission mechanism cooling portion, 2. The marine propulsion device according to claim 1, wherein the water pump, the transmission mechanism cooling section, the first cooling water passage, and the second cooling water passage are provided inside the drive shaft housing.

4. an inverter for controlling the driving of the motor; the inverter is attached to the motor; The cooling device is an inverter water jacket provided in the inverter and configured to cool the inverter; 2. A marine propulsion device according to claim 1, further comprising a third cooling water passage connecting the outlet of the motor water jacket and the inlet of the inverter water jacket.

5. 5. The marine propulsion device according to claim 4, wherein the inverter is disposed above the motor, the outlet of the motor water jacket is disposed above the motor, and the inlet of the inverter water jacket is disposed below the inverter.

6. 6. A marine propulsion device according to claim 5, wherein the inverter water jacket is disposed below the inverter.

7. 5. A marine vessel propulsion device according to claim 4, wherein the outlet of the inverter water jacket is disposed below the inverter.

8. The cooling device is a drain port for discharging cooling water from inside the marine propulsion device to outside the marine propulsion device; a fourth cooling water passage connected to the outlet of the inverter water jacket and allowing the cooling water flowing out from the outlet of the inverter water jacket to flow toward the drain outlet, 5. A marine propulsion device according to claim 4, wherein the fourth cooling water passage passes through a position outside the motor and away from the motor.

9. 5. The marine propulsion device according to claim 4, wherein the cooling device includes a valve that changes the amount of cooling water flowing out of the inverter water jacket in accordance with the temperature of the cooling water that has flowed through the inverter water jacket.

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