Electric propulsion machine

Abstract

To miniaturize an electric propulsion machine in the electric propulsion machine having a pump for cooling a motor, and to solve a problem wherein durability of the pump for cooling the motor is reduced in the electric propulsion machine having a constitution for reversing the rotational direction of the motor.SOLUTION: The outboard motor 1 includes a motor provided in an upper portion of the outboard motor 1, a propeller shaft 5 provided in a lower portion of the outboard motor 1, a propeller 4 provided on the propeller shaft 5, a drive shaft 6 that extends in the up-down direction and transmits rotation of the motor to the propeller shaft 5, and a non-positive displacement water pump 22 that is provided on the propeller shaft 5 and supplies cooling water for cooling the motor to the motor.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electric propulsion device for propelling a vessel. [Background technology]

[0002] An electric propulsion unit is a type of marine propulsion unit that uses a motor (electric motor) as a power source to generate thrust. Some electric propulsion units are equipped with a water-cooling mechanism to cool the motor. Such electric propulsion units are equipped with a pump to supply cooling water to a water jacket attached to the motor.

[0003] Japanese Patent Application Laid-Open Publication No. 2005-162055 (Patent Document 1) describes an electric outboard motor equipped with a pump that supplies cooling water to a motor's water jacket. The outboard motor includes a drive shaft that transmits rotation of a motor mounted on the upper part of the outboard motor to a propeller shaft mounted on the lower part of the outboard motor, and the drive shaft extends vertically from the motor side to the propeller shaft side. A pump is mounted on the drive shaft, and the pump's impeller rotates integrally with the drive shaft. The outboard motor also includes a lower case mounted on the lower part, and a water intake port that draws water surrounding the outboard motor into the outboard motor. The water intake port is located below the anti-cavitation plate of the outboard motor. The pump, on the other hand, is located above the anti-cavitation plate. The outboard motor also includes a water intake passage that connects the water intake port to the pump's suction port and sends the water taken in through the water intake port to the pump as cooling water. When the motor is driven, the drive shaft rotates, causing the pump impeller to rotate. As the impeller rotates, cooling water taken in from the water intake port is drawn up into the pump through the water intake passage. The water drawn up into the pump is then discharged from the pump into the motor's water jacket. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-162055 Summary of the Invention [Problem to be solved by the invention]

[0005] In a marine propulsion device, such as the electric outboard motor described in JP 2005-162055 A, in which the water intake is located below the anti-cavitation plate and the pump is located above the anti-cavitation plate, and the cooling water taken in through the water intake is pumped up by the pump, the area around the pump impeller may not be filled with water when the marine propulsion device starts operating, i.e., when the pump begins to operate. Therefore, such a marine propulsion device uses a pump that does not require priming to operate, specifically a positive displacement pump with high suction capacity. Many conventional marine propulsion devices use a rotary variable displacement pump with a rubber impeller as a positive displacement pump with high suction capacity.

[0006] This rotary variable displacement pump has the ability to suck up water taken in through the water intake port after sucking out the air around the impeller and the air in the water intake passage when the pump starts to operate, but because it has such a high suction capacity, it is large and difficult to miniaturize. In conventional marine propulsion devices in which a rotary variable displacement pump is mounted on a drive shaft, the difficulty of miniaturizing the pump is thought to be one of the factors preventing the miniaturization of marine propulsion devices.

[0007] Furthermore, in a rotary volumetric pump with a rubber impeller, if the rotation direction of the impeller changes, the impeller is more susceptible to damage than if the rotation direction of the impeller is always constant, thereby reducing the durability of the pump. If the electric propulsion unit is configured to reverse the rotation direction of the motor when moving the boat forward and when moving the boat backward, the rotation direction of the drive shaft is reversed when moving the boat forward and when moving the boat backward, and therefore the rotation direction of the impeller is also reversed. Therefore, if a rotary volumetric pump with a rubber impeller is attached to the drive shaft of an electric propulsion unit configured to reverse the rotation direction of the motor when moving the boat forward and when moving the boat backward, the durability of the pump will be reduced.

[0008] The present invention has been made in consideration of the problems described above, and a first object of the present invention is to reduce the size of an electric propulsion unit equipped with a pump for cooling a motor. A second object of the present invention is to solve the problem of reduced durability of the pump for cooling a motor in an electric propulsion unit configured to reverse the rotation direction of the motor. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides an electric propulsion unit for propelling a vessel, comprising: a motor provided on an upper portion of the electric propulsion unit; a propeller shaft provided on a lower portion of the electric propulsion unit; a propeller provided on the propeller shaft; a drive shaft extending in the vertical direction and transmitting rotation of the motor to the propeller shaft; and a non-positive displacement pump provided on the propeller shaft and supplying cooling water to the motor to cool it. [Effects of the Invention]

[0010] According to the present invention, it is possible to reduce the size of an electric propulsion unit equipped with a pump for cooling a motor, and it is also possible to solve the problem of reduced durability of the pump for cooling a motor in an electric propulsion unit configured to reverse the rotation direction of the motor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an overall view showing an outboard motor that is a first embodiment of an electric propulsion unit of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a lower part of the outboard motor in FIG. [Figure 3] 3 is an enlarged cross-sectional view showing a portion of the lower part of the outboard motor in FIG. 2 where a water pump is provided. [Figure 4] FIG. 4 is a cross-sectional view showing the lower part of an outboard motor that is a second embodiment of an electric propulsion unit according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] An electric propulsion unit according to an embodiment of the present invention is an electric propulsion unit for propelling a vessel, and includes a motor provided on the upper part of the electric propulsion unit, a propeller shaft provided on the lower part of the electric propulsion unit, a propeller provided on the propeller shaft, a drive shaft extending in the vertical direction and transmitting the rotation of the motor to the propeller shaft, and a non-positive displacement pump provided on the propeller shaft for supplying cooling water to the motor to cool it.

[0013] In the electric propulsion unit of this embodiment, the pump is mounted on the propeller shaft. When the electric propulsion unit is installed on a vessel, the propeller shaft is located below the water surface, and the pump mounted on the propeller shaft is also located below the water surface. This makes it easy to ensure that the pump is primed, that is, it is easy to create a state in which the area around the impeller is filled with water when the pump starts operating. This makes it possible to use a non-positive displacement pump that requires priming. Non-positive displacement pumps are easier to miniaturize than rotary variable displacement pumps with rubber impellers. Therefore, with the electric propulsion unit of this embodiment, the use of a non-positive displacement pump allows for the electric propulsion unit to be miniaturized.

[0014] Furthermore, in the electric propulsion device of this embodiment, the rotation of the motor is transmitted to the propeller shaft via the drive shaft. When the rotation direction of the motor is reversed, the rotation direction of the propeller shaft is also reversed. The pump is mounted on the propeller shaft and rotates integrally with the propeller shaft. Therefore, when the rotation direction of the motor is reversed, the rotation direction of the pump impeller is also reversed. When using a pump in a configuration in which the rotation direction of the impeller is reversed, the durability of a rotary variable displacement pump having a rubber impeller is compared with the durability of a non-positive displacement pump, and the durability of the non-positive displacement pump is significantly higher. Therefore, the electric propulsion device of this embodiment using a non-positive displacement pump can solve the above-mentioned problem of low durability of the motor cooling pump in an electric propulsion device configured to reverse the rotation direction of the motor. [Example]

[0015] Two embodiments of the electric propulsion device of the present invention will be described with reference to Figures 1 to 4. In the description, when referring to the directions of up (Ud), down (Dd), front (Fd), and rear (Bd), please refer to the arrows drawn at the bottom right of each figure.

[0016] Fig. 1 shows an outboard motor 1 that is a first embodiment of an electric propulsion unit of the present invention. Fig. 2 shows a cross section of the lower part of the outboard motor 1, divided into left and right halves along a plane passing through the center of the outboard motor 1 in the lateral direction. Fig. 3 shows an enlarged view of the portion of the lower part of the outboard motor 1 in Fig. 2 where a water pump 22 is provided.

[0017] An outboard motor 1 is a device that is attached to a boat and propels the boat. As shown in Fig. 1, the outboard motor 1 includes a motor 2, which is a power source that generates propulsive force for the boat, a motor control device 3 that controls the drive of the motor 2, a propeller 4 that generates propulsive force for the boat from the rotation of the motor 2, a propeller shaft 5 to which the propeller 4 is fixed, a drive shaft 6 that transmits the rotation of the motor 2 to the propeller shaft 5, and a gear mechanism 7 that, together with the drive shaft 6, transmits the rotation of the motor 2 to the propeller shaft 5.

[0018] The motor 2 and motor control device 3 are provided on the top of the outboard motor 1 and are located above the water surface when the outboard motor 1 is attached to a boat. The outboard motor 1 also has an upper case 10, within which the motor 2 and motor control device 3 are housed.

[0019] The propeller 4, propeller shaft 5, and gear mechanism 7 are mounted on the bottom of the outboard motor 1 and are located below the water surface when the outboard motor 1 is attached to a boat. The propeller shaft 5 extends in the fore-and-aft direction, and the propeller 4 is fixed to the rear portion of the propeller shaft 5. The outboard motor 1 also has a lower case 11, in which the front portion of the propeller shaft 5 and the gear mechanism 7 are housed. The lower case 11 is also provided with an anti-cavitation plate 12.

[0020] The drive shaft 6 extends vertically from the motor 2 toward the propeller shaft 5. An upper portion of the drive shaft 6 is located within an upper case 10, and an upper end portion of the drive shaft 6 is connected to an output shaft of the motor 2. A lower portion of the drive shaft 6 is located within a lower case 11. A lower end portion of the drive shaft 6 is connected to the propeller shaft 5 via a gear mechanism 7. Specifically, the gear mechanism 7 includes a drive gear 8 and a driven gear 9, and the drive gear 8 is fixed to the lower end portion of the drive shaft 6, and the driven gear 9 is fixed to the front portion of the propeller shaft 5. The drive gear 8 and the driven gear 9 are each bevel gears that mesh with each other.

[0021] The motor control device 3 includes, for example, an inverter that generates a drive current for driving the motor 2, and a host control unit that controls the inverter in response to an operation input from outside the outboard motor 1. When driving the motor 2, the motor control device 3 selects the rotation direction of the motor 2 in response to an operation input from outside the outboard motor 1. Specifically, the motor control device 3 rotates the motor 2 in one direction when moving the boat forward, and rotates the motor 2 in the other direction when moving the boat backward. When the motor 2 rotates in one direction under the control of the motor control device 3, the rotation of the motor 2 is transmitted from its output shaft to the drive shaft 6, which then rotates. The rotation of the drive shaft 6 is then transmitted to the propeller shaft 5 via a gear mechanism 7, causing the propeller shaft 5 and the propeller 4 to rotate in the forward direction. The forward rotation of the propeller 4 generates a thrust force that moves the boat forward. When the motor 2 is rotated in the other direction under the control of the motor control device 3, the rotation is transmitted to the propeller shaft 5 via the drive shaft 6 and the gear mechanism 7, causing the propeller shaft 5 and the propeller 4 to rotate in the reverse direction. The reverse rotation of the propeller 4 generates a propulsive force that moves the vessel backward.

[0022] Furthermore, the outboard motor 1 is equipped with a clamp bracket 13 for attaching the outboard motor 1 to the transom of the boat, and a swivel bracket 14 for connecting the outboard motor 1 to the boat so that the horizontal orientation of the propeller 4 relative to the boat can be changed.

[0023] The outboard motor 1 also includes a water-cooled cooling mechanism 20 that cools the motor 2. The cooling mechanism 20 includes a water intake 21 that draws water from around the outboard motor 1 into the outboard motor 1 as cooling water, a water pump 22 that supplies the cooling water drawn in from the water intake 21 to the motor 2, and a water jacket 30 that cools the motor 2 by circulating the cooling water around, for example, the outer periphery of the motor 2.

[0024] The water pump 22 is a non-positive displacement pump, such as a centrifugal pump. The water pump 22 is provided on the front end side of the propeller shaft 5. Specifically, as shown in FIG. 3 , the water pump 22 includes a pump shaft 23 and an impeller 24. The pump shaft 23 extends in the front-to-rear direction. The rear end of the pump shaft 23 is connected to the front end of the propeller shaft 5. The impeller 24 is fixed to the front end of the pump shaft 23. The pump shaft 23 and the impeller 24 rotate integrally with the propeller shaft 5. A support member 25 that supports the front end of the propeller shaft 5 and the pump shaft 23 is provided in the front part of the lower part of the lower case 11. The front end of the propeller shaft 5 and the pump shaft 23 are rotatably supported by the support member 25 via bearings. A pump chamber 26 is formed in the front part of the lower part of the lower case 11 and in front of the support member 25, and the impeller 24 is disposed in the pump chamber 26. In addition, a suction port 27 is formed in the front part of the pump chamber 26, and a discharge port 28 is formed in the upper part of the pump chamber 26.

[0025] The water intake 21 is provided at the front of the lower part of the lower case 11. The water intake 21 is located forward of the propeller shaft 5. The water intake 21 is located forward of the water pump 22, specifically, immediately in front of the pump chamber 26 and the impeller 24. The suction port 27 and the impeller 24 face the water intake 21. The water intake 21 is provided with a strainer to prevent underwater dust and the like from entering the outboard motor 1. In addition, a water intake passage 29 is provided between the water intake 21 and the suction port 27, connecting them. The water intake passage 29 extends in the fore-and-aft direction. The water intake passage 29 is extremely short, and the water intake 21 and the suction port 27 are located very close to each other.

[0026] As shown in FIG. 1 , the water jacket 30 is provided on the motor 2. The water jacket 30 is configured, for example, by a cooling water passage formed to cover the entire outer periphery of the motor 2. A transfer passage 33 is provided between the discharge port 28 of the pump chamber 26 and the water jacket 30, transferring cooling water from the water pump 22 to the water jacket 30. The transfer passage 33 is provided forward of the drive shaft 6 within the outboard motor 1. A lower portion of the transfer passage 33 is disposed within the lower case 11, as shown in FIG. 2 , and a lower end portion of the transfer passage 33 is connected to the discharge port 28 of the pump chamber 26, as shown in FIG. 3 . An upper portion of the transfer passage 33 is disposed within the upper case 10, as shown in FIG. 1 , and an upper end portion of the transfer passage 33 is connected to a cooling water inlet 31 of the water jacket 30. A drain passage 34 is connected to a cooling water outlet 32 ​​of the water jacket 30, and discharges the cooling water to the outside of the outboard motor 1 after flowing through the water jacket 30.

[0027] In the outboard motor 1, the pump chamber 26 is located immediately behind the water intake 21, and the pump chamber 26 and the water intake 21 are located at the same position in the vertical direction. Therefore, when the outboard motor 1 is mounted on a boat and the water intake 21 is completely submerged in water, water around the outboard motor 1 naturally flows from the water intake 21 into the pump chamber 26. As a result, the pump chamber 26 is filled with water, and the area around the impeller 24 is filled with water. In this way, in the outboard motor 1, the water intake 21 being completely submerged in water ensures that the water pump 22 is primed.

[0028] Thereafter, when the motor 2 is driven and the propeller shaft 5 rotates, the impeller 24 of the water pump 22 rotates together with the propeller shaft 5. The rotation of the impeller 24 causes water that has flowed into the pump chamber 26 from the water intake 21 to be sent as cooling water to the water jacket 30 via the transfer passage 33. The cooling water sent to the water jacket 30 circulates within the water jacket 30, thereby cooling the motor 2. After circulating within the water jacket 30, the cooling water is discharged to the outside of the outboard motor 1 via the drain passage 34, for example, from an outlet provided in the boss of the propeller 4.

[0029] Furthermore, the rotation direction of the impeller 24 of the water pump 22 is determined by the rotation direction of the propeller shaft 5, so the rotation direction of the impeller 24 is opposite when the propeller shaft 5 rotates forward and when the propeller shaft 5 rotates reverse. However, the water pump 22 provided on the outboard motor 1 can exert its suction capacity and discharge capacity regardless of the rotation direction of the impeller 24.

[0030] Furthermore, because the water intake 21 is located immediately before the suction port 27 of the pump chamber 26, when the boat moves forward, the water around the outboard motor 1 flows forcefully into the pump chamber 26 through the water intake 21. The water pressure at this time assists in promoting the rotation of the impeller 24, resulting in smoother flow of cooling water from the water intake 21 to the water jacket 30.

[0031] As described above, in the outboard motor 1 according to the first embodiment of the present invention, the water pump 22 is mounted on the propeller shaft 5. Because the water pump 22 is mounted on the propeller shaft 5, the water pump 22 is located below the anti-cavitation plate 12. When the outboard motor 1 is installed on a boat, the entire water pump 22 is located below the water surface. This facilitates priming the water pump 22. Therefore, the outboard motor 1 can employ a non-positive displacement pump, which requires priming, as the water pump 22. Non-positive displacement pumps are easier to downsize than the rotary variable displacement pumps with rubber impellers used in many conventional marine propulsion units. Therefore, the outboard motor 1 according to this embodiment employs a non-positive displacement pump, thereby enabling the outboard motor to be downsized. Furthermore, among non-positive displacement pumps, centrifugal pumps are small and lightweight due to their simple structure. Using a centrifugal pump as the water pump 22 facilitates the downsizing and weight reduction of the outboard motor 1.

[0032] Furthermore, in the outboard motor 1 of this embodiment, the rotation direction of the impeller 24 reverses in response to the change in the rotation direction of the propeller 4. Generally, when using a pump with a reversible impeller rotation direction, the durability of a non-positive displacement pump is significantly higher than that of a rotary variable displacement pump with a rubber impeller. Therefore, the outboard motor 1 of this embodiment, which uses a non-positive displacement pump as the water pump 22, can solve the problem of reduced durability of motor cooling pumps in electric propulsion units with a reversible motor rotation direction.

[0033] Furthermore, in the outboard motor 1 of this embodiment, the water pump 22 is provided at the front end of the propeller shaft 5. By providing the water pump 22 at the front end of the propeller shaft 5, the lower case 11 of the outboard motor 1 of this embodiment can be prevented from becoming larger than the lower case of an outboard motor using an engine (internal combustion engine), even though the water pump 22 is provided on the propeller shaft 5. That is, many outboard motors that use an engine as a power source to generate propulsion force for a boat are equipped with a shift device that changes the rotation direction of the propeller (see, for example, Japanese Patent Application Laid-Open No. 2012-144186). Because it is difficult to reverse the rotation direction of the crankshaft of an engine, many outboard motors using engines are equipped with a shift device that changes the rotation direction of the propeller. More specifically, in outboard motors that use an engine as a power source, a gear mechanism is provided between the lower end of the drive shaft extending downward from the engine and the front of the propeller shaft. The gear mechanism includes a drive gear fixed to the lower end of the drive shaft, a forward gear meshing with the drive gear and rotating in the forward direction as the drive shaft rotates, a reverse gear meshing with the drive gear and rotating in the reverse direction as the drive shaft rotates, and a dog clutch that switches between connecting the forward gear to the propeller shaft to rotate the propeller shaft forward and connecting the reverse gear to the propeller shaft to rotate the propeller shaft reversely. The shift device controls the dog clutch in accordance with an input for switching the propeller rotation direction, thereby switching the rotation direction of the propeller shaft and the propeller. Typically, in an outboard motor using an engine, the input for switching the propeller rotation direction is made at the front of the upper part of the outboard motor, while the dog clutch, which is controlled by the shift device, is located at the lower part of the outboard motor. Therefore, the shift device includes a shift rod for transmitting the input for switching the propeller rotation direction to the dog clutch, and the shift rod extends vertically from a portion of the outboard motor forward of the drive shaft.The shift device further includes a shift slider that connects the lower end of the shift rod to the dog clutch, and the shift slider is provided on the front end side of the propeller shaft. In the outboard motor 1 of this embodiment, the motor 2 is the power source that generates propulsion for the boat, and the rotation direction of the motor 2 is controlled by the motor control device 3 to switch the rotation direction of the propeller 4. Therefore, the outboard motor 1 of this embodiment does not require a shift device, and is therefore not provided with a shift device. Therefore, a shift slider is not provided on the front end side of the propeller shaft 5. According to the outboard motor 1 of this embodiment, by locating the water pump 22 on the front end side of the propeller shaft 5, the location of the water pump 22 can be utilized, which would otherwise be the location of the shift slider of the shift device in an outboard motor using an engine. Furthermore, by using a small non-positive displacement pump as the water pump 22, the water pump 22 can be located in the same location without increasing the space where the shift slider of the shift device would be located in an outboard motor using an engine. Therefore, according to the outboard motor 1 of this embodiment, even though the propeller shaft 5 is provided with the water pump 22, the lower case 11 can be prevented from becoming larger than the lower case of an outboard motor using an engine.

[0034] The outboard motor 1 of this embodiment also includes a transfer passage 33 that transfers cooling water from the water pump 22 to the water jacket 30 of the motor 2, and the transfer passage 33 is located forward of the drive shaft 6 within the outboard motor 1. By locating the transfer passage 33 forward of the drive shaft 6 within the outboard motor 1, the location of the transfer passage 33 can be utilized where the shift rod of the shift device is located in an outboard motor using an engine. This prevents the lower case 11 of the outboard motor 1 of this embodiment from being larger than the lower case of an outboard motor using an engine.

[0035] In the outboard motor 1 of this embodiment, the water intake 21 is located forward of the propeller shaft 5, and the water pump 22 faces the water intake 21. The suction port 27 of the pump chamber 26, in which the impeller 24 of the water pump 22 is located, is located immediately behind the water intake 21. This configuration significantly shortens the distance between the water intake 21 and the water pump 22, allowing the water pump 22 to easily draw water from around the outboard motor 1 into the outboard motor 1 via the water intake 21. Even if the suction capacity of the water pump 22 is low, the water from around the outboard motor 1 can be sufficiently drawn into the outboard motor 1 via the water intake 21. Furthermore, because the water intake 21 and the pump chamber 26 are located very close to each other, water from around the outboard motor 1 flows smoothly into the pump chamber 26 when the water pump 22 is stopped. This allows the pump chamber 26 to be filled with water quickly, ensuring rapid and reliable priming of the water pump 22. Furthermore, since the water intake 21 and the water pump 22 are located very close to each other and the water intake 21 is positioned in front of the water pump 22, when the boat is moving forward, the water around the outboard motor 1 can be forcefully flowed from the water intake 21 toward the water pump 22, and the pressure of this water can be used to promote the rotation of the impeller 24, thereby improving the smooth flow of cooling water from the water intake 21 to the water jacket 30.

[0036] In the outboard motor 1 of this embodiment, the rear end of the pump shaft 23 of the water pump 22 is connected to the front end of the propeller shaft 5. This configuration allows the rotation of the propeller shaft 5 to be transmitted to the impeller 24 of the water pump 22, which is provided on the front end side of the propeller shaft 5, with a simple structure. [Example]

[0037] FIG. 4 shows a cross section of the lower part of an outboard motor 51 that is a second embodiment of an electric propulsion unit of the present invention. In the outboard motor 51 of the second embodiment shown in FIG. 4, the same components as those in the outboard motor 1 of the first embodiment are designated by the same reference numerals, and their description will be omitted or simplified. A feature of the outboard motor 51 of the second embodiment is that another water pump 52 is provided between the water pump 22 and the motor 2, and the water pump 52 transfers the cooling water discharged from the water pump 22 to the water jacket 30 of the motor 2. In the following description of the second embodiment, the water pump 22 located immediately after the water intake 21 will be referred to as the "first water pump 22," and the water pump 52 located between the first water pump 22 and the motor 2 will be referred to as the "second water pump 52."

[0038] In FIG. 4 , second water pump 52 is a non-positive displacement pump, such as a mixed flow pump. Second water pump 52 is disposed downstream of first water pump 22 in the direction of coolant flow, and is located between first water pump 22 and water jacket 30 of motor 2. Specifically, second water pump 52 is disposed at the boundary between upper case 10 and lower case 11. An impeller 53 of second water pump 52 is fixed to drive shaft 6. A pump chamber 54 accommodating impeller 53 of second water pump 52 is provided on the outer circumferential side of drive shaft 6 at the boundary between upper case 10 and lower case 11. An inlet port 55 is provided at the bottom of pump chamber 54, and an outlet port 56 is provided at the top of pump chamber 54.

[0039] Furthermore, while the outboard motor 1 of the first embodiment is provided with a transfer passage 33 that transfers cooling water from the water pump 22 to the water jacket 30 of the motor 2, in the outboard motor 51 of the second embodiment, the transfer passage is divided into a lower transfer passage 57 that connects the first water pump 22 and the second water pump 52, and an upper transfer passage 58 that connects the second water pump 52 and the water jacket 30 of the motor 2. Furthermore, an introduction passage 59 is provided between the upper end of the lower transfer passage 57 and the suction port 55 of the pump chamber 54, for guiding the cooling water that has flowed through the lower transfer passage 57 to the suction port 55.

[0040] When the motor 2 is driven, the drive shaft 6 and the propeller shaft 5 each rotate. The impeller 53 of the second water pump 52 rotates together with the drive shaft 6, and the impeller 24 of the first water pump 22 rotates together with the propeller shaft 5. The rotation of the impeller 24 of the first water pump 22 and the impeller 53 of the second water pump 52 causes water taken in through the water intake 21 to flow as cooling water through the pump chamber 26, the lower transfer passage 57, the introduction passage 59, the pump chamber 54, and the upper transfer passage 58, in that order, and then be supplied to the water jacket 30. The cooling water supplied to the water jacket 30 flows through the water jacket 30, thereby cooling the motor 2. After flowing through the water jacket 30, the cooling water is discharged from the outboard motor 1 via the drain passage 34, for example, from an outlet provided in the boss of the propeller 4.

[0041] The outboard motor 51 of the second embodiment of the present invention, having this configuration, achieves the same effects as the outboard motor 1 of the first embodiment of the present invention. Specifically, the second water pump 52 is a non-positive displacement pump, which is easier to reduce in size than a rotary variable displacement pump with a rubber impeller. Therefore, the outboard motor 51 of the second embodiment can achieve a smaller size of the outboard motor 1 compared to conventional outboard motors, even while including the first water pump 22 and the second water pump 52. Furthermore, by using non-positive displacement pumps for both the first water pump 22 and the second water pump 52, the problem of reduced durability of the motor cooling pump in an electric propulsion unit configured to reverse the rotation direction of the motor 2 can be resolved.

[0042] Furthermore, because the outboard motor 51 of the second embodiment is equipped with the second water pump 52, even if the discharge capacity of the first water pump 22 is low, the first water pump 22 and the second water pump 52 work together to smoothly send cooling water to the water jacket 30 of the motor 2. This allows a small pump with low discharge capacity to be used as the first water pump 22, thereby contributing to the miniaturization of the outboard motor 51. Furthermore, by having the first water pump 22 and the second water pump 52 work together, the second water pump 52 can also be made smaller, which also contributes to the miniaturization of the outboard motor 51.

[0043] Although the first embodiment uses a centrifugal pump as the water pump 22 and the second embodiment uses a mixed flow pump as the water pump 52, the present invention is not limited to this. Other types or models of non-positive displacement pumps may also be used as the water pump 22 or the water pump 52.

[0044] In the first embodiment, the motor 2 is cooled by supplying cooling water to the water jacket 30 of the motor 2 by the water pump 22, but the present invention is not limited to this. For example, a water jacket may be provided for the inverter of the motor control device 3, and cooling water may be supplied to both the water jacket 30 of the motor 2 and the water jacket of the inverter by the water pump 22, thereby cooling the motor 2 and the inverter, respectively. This configuration may also be applied to the second embodiment.

[0045] Furthermore, as described above, an outboard motor is used as an example in each of the first and second embodiments of the present invention, but the present invention is not limited to this and can also be applied to other types of electric propulsion units, such as an outboard inboard motor.

[0046] Furthermore, the present invention may be modified as appropriate within the scope of the claims and the spirit or concept of the invention as can be read from the entire specification, and electric propulsion devices with such modifications are also included in the technical concept of the present invention. [Explanation of symbols]

[0047] 1.51 Outboard motor (electric propulsion unit) 2 motors 4 propellers 5 propeller shaft 6 drive shaft 21 Water Intake 22 Water pump (pump) 33 Transfer passage 52 Water pump (other pump) 57 Lower transfer passage (transfer passage) 58 Upper transfer passage (transfer passage)

Claims

1. An electric propulsion device for propelling a vessel, a motor provided on an upper portion of the electric propulsion device; a propeller shaft provided at a lower portion of the electric propulsion unit; a propeller provided on the propeller shaft; a drive shaft extending in the vertical direction and transmitting rotation of the motor to the propeller shaft; a non-positive displacement pump provided on the propeller shaft for supplying cooling water to the motor.

2. 2. The electric propulsion device according to claim 1, wherein the pump is provided on the front end side of the propeller shaft.

3. 3. The electric propulsion device according to claim 2, further comprising a transfer passage for transferring cooling water from the pump to the motor, the transfer passage being located forward of the drive shaft within the electric propulsion device.

4. 3. The electric propulsion device according to claim 2, further comprising a water intake that takes in water around the electric propulsion device into the electric propulsion device, the water intake being provided forward of the propeller shaft, and the pump facing the water intake.

5. 3. The electric propulsion device according to claim 2, wherein the pump comprises a pump shaft and an impeller, the impeller being provided at a front end of the pump shaft, and the rear end of the pump shaft being connected to a front end of the propeller shaft.

6. 2. The electric propulsion device according to claim 1, further comprising: another non-positive displacement pump provided between the pump and the motor for transferring the cooling water discharged from the pump to the motor.

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