Electric outboard motor

Abstract

An electric outboard motor for propelling a boat. The electric outboard motor includes an outer case that forms at least a part of an outer shell of the electric outboard motor and that is to be disposed underwater, a propeller rotatably supported by the outer case, a motor provided inside the outer case and configured to rotate the propeller, and a liquid or semi-solid cooling medium interposed between an outer peripheral surface of the motor and an inner surface of the outer case.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2025-015014 filed on January 31, 2025, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to an electric outboard motor.BACKGROUND ART

[0003] An electric outboard motor is known that is equipped with a motor (electric motor) as a power source for rotating a propeller. In some electric outboard motors, the motor is located on a lower portion of the electric outboard motor, that is, a portion of the electric outboard motor that is submerged in the water. JPH10-16886A describes a boat propulsion device equivalent to such an electric outboard motor.

[0004] The boat propulsion device described in the above publication is provided with an electric drive unit at its lower portion. The electric drive unit has a metal casing that forms its outer shell, and an electric motor is accommodated inside the casing. The electric motor includes a metal motor case that forms part of a stator, a rotor accommodated in the motor case, a commutator, and brushes.

[0005] The boat propulsion device described in the above publication uses a DC commutator motor as the motor, but currently, various motors such as brushless motors and AC motors are used as motors for electric outboard motors in addition to DC commutator motors. All of these motors generate heat during operation, so cooling of the motors must be considered.

[0006] When the motor is disposed within an outer case that forms an outer shell of the electric outboard motor and is located in a submerged portion of the electric outboard motor, heat generated by the motor can be dissipated into the water via the outer case, thereby cooling the motor.

[0007] In this regard, in the boat propulsion device described in the above publication, a rear or front end of the motor case where the brushes are arranged is brought into contact with the outer case (the casing that forms the outer shell of the electric drive unit), and heat generated between the commutator and the brushes is transferred to the outer case via this contact portion, and the heat is then dissipated from the outer case into the water. However, considering that the heat generated by a DC commutator motor is not limited to the heat generated between the commutator and the brushes, simply bringing a part of the motor where the brushes are located into contact with the outer case may reduce a cooling effect on the motor.

[0008] Furthermore, when a brushless motor, an AC motor, or the like is used as the motor for an electric outboard motor, simply contacting a front or rear end of the motor with the outer case results in a small area of the contact portion, which means that an amount of heat transferred from the motor to the outer case is small, and this could result in a reduced cooling effect for the motor.

[0009] Some electric outboard motors of the related art have a structure in which a motor is fitted, for example by shrink fitting, into an outer case that forms an outer shell of the electric outboard motor and is located in a submerged portion of the electric outboard motor, so that an outer peripheral surface of the motor is in full contact with an inner surface of the outer case. In such electric outboard motors, a contact area between the motor and the outer case is large, so a large amount of heat is transferred from the motor to the outer case, which is thought to increase a cooling effect on the motor. However, in the case of a structure in which the motor is fitted inside the outer case, it is difficult to remove the motor fitted inside the outer case from the outer case. Therefore, when the motor needs to be replaced due to a malfunction of the motor or the like, the motor must be replaced along with the outer case, which increases a cost of maintaining the electric outboard motor.SUMMARY OF INVENTION

[0010] Aspect of non-limiting embodiments of the present disclosure relates to provide an electric outboard motor that can increase an amount of heat dissipated from a motor into the water through an outer case, and that allows the motor to be easily attached to and detached from the outer case.

[0011] Aspects of certain non-limiting embodiments of the present disclosure address the features discussed above and / or other features not described above. However, aspects of the non-limiting embodiments are not required to address the above features, and aspects of the non-limiting embodiments of the present disclosure may not address features described above.

[0012] According to an aspect of the present disclosure, there is provided an electric outboard motor for propelling a boat, the electric outboard motor including:

[0013] an outer case that forms at least a part of an outer shell of the electric outboard motor and that is to be disposed underwater;

[0014] a propeller rotatably supported by the outer case;

[0015] a motor provided inside the outer case and configured to rotate the propeller; and

[0016] a liquid or semi-solid cooling medium interposed between an outer peripheral surface of the motor and an inner surface of the outer case.BRIEF DESCRIPTION OF DRAWINGS

[0017] Exemplary embodiment(s) of the present invention will be described in detail based on the following figures, wherein:

[0018] FIG. 1 is an explanatory diagram illustrating an electric outboard motor according to an example of the present disclosure;

[0019] FIG. 2 is a cross-sectional view of a lower unit of the electric outboard motor according to the example of the present disclosure;

[0020] FIG. 3 is an enlarged cross-sectional view illustrating a main part of the lower unit of the electric outboard motor according to the example of the present disclosure;

[0021] FIG. 4 is an explanatory diagram illustrating portions through which lubricating oil can flow within the lower unit of the electric outboard motor according to the example of the present disclosure;

[0022] FIG. 5 is an explanatory diagram illustrating a motor and a motor support member of the electric outboard motor according to the example of the present disclosure;

[0023] FIG. 6A is a cross-sectional view illustrating the motor support member of the electric outboard motor according to the example of the present disclosure taken along a line VIa-VIa in FIG. 5; and

[0024] FIG. 6B is a cross-sectional view illustrating the motor support member taken along a line VIb-VIb in FIG. 6A.DESCRIPTION OF EMBODIMENTS

[0025] An electric outboard motor according to an embodiment of the present disclosure includes an outer case that forms at least a part of an outer shell of the electric outboard motor and that is disposed underwater, a propeller that is rotatably supported by the outer case, a motor that is provided within the outer case and configured to rotate the propeller, and a liquid or semi-solid cooling medium that is interposed between an outer peripheral surface of the motor and an inner surface of the outer case.

[0026] In the electric outboard motor of this embodiment, a liquid or semi-solid cooling medium is interposed between the outer peripheral surface of the motor and the inner surface of the outer case. For example, when the motor is mounted inside the outer case, a space is formed between the outer peripheral surface of the motor and the inner surface of the outer case, and the cooling medium is placed in this space. This allows the cooling medium to be interposed between the outer peripheral surface of the motor and the inner surface of the outer case. Since the cooling medium is interposed between the outer peripheral surface of the motor and the inner surface of the outer case, heat generated by the motor when the motor is operating is transferred from the motor to the cooling medium, then from the cooling medium to the outer case, and then dissipated from the outer case into the water. The space between the outer peripheral surface of the motor and the inner surface of the outer case is formed so as to cover a wide area of the outer peripheral surface of the motor, and the cooling medium is, for example, circulated or filled within that space, thereby increasing a contact area between the outer peripheral surface of the motor and the cooling medium, and a contact area between the cooling medium and the inner surface of the outer case. Therefore, an amount of heat transferred from the motor to the outer case via the cooling medium can be increased. As described above, according to this embodiment, an amount of heat dissipated from the motor into the water via the outer case can be increased, thereby improving the cooling effect on the motor.

[0027] Furthermore, a structure in which the motor is detachable from the outer case and a liquid or semi-solid cooling medium is interposed between the outer peripheral surface of the motor and the inner surface of the outer case can be easily constructed. For example, a structure in which the motor can be detachably attached to the outer case can be easily constructed by attaching the motor to the outer case using a detachable fixing member such as a bolt, or by forming threads on a part of the outer peripheral surface of the motor and a part of the inner peripheral surface of the outer case and screwing the motor to the outer case. When the motor is detachably attached to the outer case in this manner, a space is formed between the outer peripheral surface of the motor and the inner surface of the outer case, and a liquid or semi-solid cooling medium is placed in this space, making it easy to create a structure in which a liquid or semi-solid cooling medium is interposed between the outer peripheral surface of the motor and the inner surface of the outer case.

[0028] Furthermore, since the cooling medium in this embodiment is liquid or semi-solid, a degree to which the cooling medium interferes with the attachment and detachment of the motor to and from the outer case is small compared to when the cooling medium is solid. That is, the cooling medium interposed between the outer peripheral surface of the motor and the inner surface of the outer case is in contact with the outer peripheral surface of the motor and the inner surface of the outer case. When a solid cooling medium comes into contact with the outer peripheral surface of the motor and the inner surface of the outer case, friction between the cooling medium and the outer peripheral surface of the motor and between the cooling medium and the inner surface of the outer case will make it difficult to attach or detach the motor from the outer case. In contrast, the cooling medium in this embodiment is liquid or semi-solid, making it easy to attach and detach the motor from the outer case of the motor. Furthermore, when the cooling medium is liquid, when removing the motor from the outer case, the cooling medium can be discharged from between the outer peripheral surface of the motor and the inner surface of the outer case to the outside of the outer case before removing the motor from the outer case, and when attaching the motor to the outer case, the cooling medium can be injected between the outer peripheral surface of the motor and the inner surface of the outer case after attaching the motor to the outer case. In this way, the cooling medium does not interfere with the attachment and detachment of the motor to and from the outer case. When the cooling medium is a gas, the cooling medium does not hinder the attachment and detachment of the motor to the outer case. However, since gaseous substances have a lower thermal conductivity than liquid or semi-solid substances, it becomes difficult to improve the cooling effect on the motor when the cooling medium is a gas.

[0029] As described above, the electric outboard motor of this embodiment can increase the amount of heat dissipated from the motor into the water via the outer case, and can also make the motor easily detachable from the outer case.Embodiment

[0030] An example of the present disclosure will be described with reference to the drawings. For ease of description, when describing directions of up (Ud), down (Dd), front (Fd), back (Bd), left (Ld), and right (Rd) in the example, the arrows drawn at the bottom left of each figure will be used.Electric Outboard Motor

[0031] FIG. 1 illustrates an electric outboard motor 1 according to the example of the present disclosure. The electric outboard motor 1 is a device configured to propel a boat and is attached to the boat. As illustrated in FIG. 1, the electric outboard motor 1 includes a lower unit 2, an operating handle 71, a connecting portion 73, a clamp bracket 74, and a swivel bracket 75.

[0032] The lower unit 2 is a unit disposed on a lower portion of the electric outboard motor 1, and is provided with a propeller 21, a motor 31, and the like. The operating handle 71 is a handle for operating the electric outboard motor 1 and is disposed on an upper portion of the electric outboard motor 1. The connecting portion 73 is a member that connects the lower unit 2 and the operating handle 71, and is formed in a columnar or cylindrical shape that extends in an up-down direction. The clamp bracket 74 is a mechanism for attaching and fixing the electric outboard motor 1 to a transom of the boat. The swivel bracket 75 is a mechanism that supports the connecting portion 73 so that the connecting portion 73 can pivot about its axis A. The swivel bracket 75 is connected to the clamp bracket 74.

[0033] When the electric outboard motor 1 is attached to the transom of the boat and the boat is stopped, the lower unit 2 is located below the water surface, and the operating handle 71, the clamp bracket 74, and the swivel bracket 75 are located above the water surface. An operator can change rotation speed and rotation direction of the motor 31 provided in the lower unit 2 by grasping a grip 72 provided at a tip of the operating handle 71 and pivoting the grip 72 around its axis B. By changing the rotation speed of the motor 31, the rotation speed of the propeller 21 can be changed, and the speed of the boat can be changed. Furthermore, by changing the rotation direction of the motor 31, the rotation direction of the propeller 21 can be changed, and the boat can be switched between forward and reverse motion. In addition, the operator can grasp the grip 72 and pivot the operating handle 71 around the axis A of the connecting portion 73 to pivot the lower unit 2 horizontally and change the direction of the propeller 21 provided on the lower unit 2. By changing the direction of the propeller 21, the boat can be turned.Lower Unit

[0034] FIG. 2 illustrates a cross section of the lower unit 2 as viewed from the left, taken along a plane that passes through a center of the lower unit 2 in a left-right direction and extends in up-down and front-rear directions.

[0035] As illustrated in FIG. 2, the lower unit 2 includes an outer case 3, the propeller 21, a propeller shaft 25, a plurality of (for example, two) bearings 28 that support the propeller shaft 25, the motor 31, a reduction gear 45, and an inverter 46.

[0036] The outer case 3 forms an outer shell of the lower unit 2. When the electric outboard motor 1 is mounted on the transom of the boat and the boat is stationary, the outer case 3 is placed in water. The outer case 3 is made of a metal material such as aluminum. As illustrated in FIG. 1, the outer case 3 includes an outer case body 4, a lid portion 9, and a reduction gear case portion 12.

[0037] The outer case body 4 has a cylindrical portion 5 formed in a cylindrical shape with an axis extending in the front-rear direction, and a columnar portion 6 formed in a columnar shape extending upward from the cylindrical portion 5. A skeg 7 is integrally formed or attached to a lower end of the cylindrical portion 5. An anti-cavitation plate 8 is integrally formed or attached to an upper portion of the columnar portion 6.

[0038] The lid portion 9 is formed in a cup shape and is attached to a front end of the cylindrical portion 5 of the outer case body 4 using a connecting member 10 such as a bolt. A front opening of the cylindrical portion 5 is closed by the lid portion 9. As illustrated in FIG. 2, a seal 11 (for example, a sealing member such as an O-ring) is provided between the cylindrical portion 5 and the lid portion 9 to prevent water from entering the outer case 3.

[0039] As illustrated in FIG. 1, the reduction gear case portion 12 has an axis extending in the front-rear direction and is formed in a cylindrical shape of which a diameter decreases toward the rear. The reduction gear case portion 12 is attached to a rear end of the cylindrical portion 5 of the outer case body 4 using a connecting member 13 such as a bolt. As illustrated in FIG. 2, a seal 14 (for example, a sealing member such as an O-ring) is provided between the cylindrical portion 5 and the reduction gear case portion 12 to prevent water from entering the outer case 3. The seal 14 also has a function of preventing lubricating oil P, which will be described below, from leaking out of the outer case 3.

[0040] Further, an inverter accommodating portion 15, a motor accommodating portion 16, a reduction gear accommodating portion 17, and a bearing accommodating portion 18 are provided inside the outer case 3. Specifically, the inverter accommodating portion 15 and the motor accommodating portion 16 are provided inside the cylindrical portion 5 of the outer case body 4. The reduction gear accommodating portion 17 and the bearing accommodating portion 18 are provided inside the reduction gear case portion 12. The inverter accommodating portion 15 is disposed in front of the motor accommodating portion 16, and the inverter accommodating portion 15 and the motor accommodating portion 16 are adjacent to each other. The reduction gear accommodating portion 17 is disposed behind the motor accommodating portion 16, and the reduction gear accommodating portion 17 and the motor accommodating portion 16 are adjacent to each other. The bearing accommodating portion 18 is disposed behind the reduction gear accommodating portion 17, and the bearing accommodating portion 18 and the reduction gear accommodating portion 17 are adjacent to each other. The reduction gear accommodating portion 17 is a specific example of a "power transmission mechanism accommodating portion".

[0041] The propeller 21 is configured to generates propulsive force for the boat by rotating. The propeller 21 is disposed at the rear of the outer case 3 and is rotatably supported by the outer case 3 via the propeller shaft 25 and the bearing 28. The propeller 21 includes a hub 22 and a plurality of blades 23. The propeller shaft 25 extends in the front-rear direction. A front portion of the propeller shaft 25 is disposed inside the outer case 3, specifically, in a portion from the reduction gear accommodating portion 17 to the bearing accommodating portion 18 within the outer case 3. The plurality of bearings 28 are disposed inside the bearing accommodating portion 18 of the outer case 3. The front portion of the propeller shaft 25 is rotatably supported by the plurality of bearings 28 on the reduction gear case portion 12 of the outer case 3. In addition, the propeller 21 is attached and fixed to a rear end side of the propeller shaft 25. The propeller 21 is secured to the propeller shaft 25 by a cotter pin 26 and a propeller nut 27. In addition, a seal 29 (sealing member, sealing mechanism, or the like) is provided between a rear end of the reduction gear case portion 12 and the propeller shaft 25 to prevent water from entering the reduction gear case portion 12. The seal 29 also has a function of preventing the lubricating oil P, which will be described below, from leaking out of the outer case 3.

[0042] The motor 31 is a power source that rotates the propeller 21. The motor 31 is disposed inside the motor accommodating portion 16 of the outer case 3. The motor 31 is, for example, an AC motor. The motor 31 has a motor shaft 32, a rotor 33, a stator 34, and a motor case 35. The motor shaft 32 extends in the front-rear direction. The motor shaft 32 is rotatably supported by the motor case 35 via a bearing 40 and a bearing 41. The motor shaft 32 and the propeller shaft 25 are arranged coaxially with each other, that is, an axis of the motor shaft 32 and an axis of the propeller shaft 25 are both axis C. The rotor 33 is located on an outer periphery of the motor shaft 32 and configured to rotate integrally with the motor shaft 32. The stator 34 is located on an outer periphery of the rotor 33 and is fixed to the motor case 35.

[0043] The motor case 35 is a case that accommodates the motor shaft 32, the bearings 40 and 41, the rotor 33, and the stator 34. The motor case 35 has a motor case body 36 and a closing member 38. The motor case body 36 is formed into a cylindrical shape with a bottom from a metal material such as steel or aluminum and is positioned so that the bottom on one axial side faces forward and an opening on the other axial side faces rearward. In addition, a hole is provided in a center of the bottom of the motor case body 36. The closing member 38 is a disk-shaped member with a hole in the center and is attached to a rear end of the motor case body 36. A seal 39 (for example, a sealing member such as an O-ring) is provided between the motor case body 36 and the closing member 38 to prevent the lubricating oil P, which will be described below, from entering the motor 31. The motor shaft 32 passes through a hole provided in the center of the closing member 38 and protrudes rearward from inside the motor case 35 to outside the motor case 35. In addition, a seal 42 (sealing member or sealing mechanism, or the like) is provided between the closing member 38 and the motor shaft 32 to prevent the lubricating oil P, which will be described below, from entering the motor 31.

[0044] Further, a fixing portion 37 for fixing the motor 31 to the outer case body 4 is provided on an outer peripheral portion of a front end of the motor case body 36. Although one fixing portion 37 is illustrated in FIG. 2, a plurality of fixing portions 37 (for example, three fixing portions 37 spaced approximately 120 degrees apart in a circumferential direction) are provided on the outer peripheral portion of the front end of the motor case body 36. Each fixing portion 37 of the motor case body 36 is attached and fixed to the outer case body 4 using a fixing member 43 such as a bolt. As a result, the motor 31 is fixed to the outer case body 4.

[0045] The reduction gear 45 is a device configured to transmit the rotation of the motor shaft 32 to the propeller shaft 25 while reducing the rotation speed, and has, for example, a planetary reduction mechanism. The reduction gear 45 is disposed inside the reduction gear accommodating portion 17 of the outer case 3. The reduction gear 45 is a specific example of a "power transmission mechanism".

[0046] The inverter 46 is a device configured to control the driving of the motor 31. The inverter 46 is configured to output, to the motor 31, a driving current to drive the motor 31. The inverter 46 is disposed inside the inverter accommodating portion 15 of the outer case 3. In this example, the inverter 46 is attached to a front surface of the motor case 35. Furthermore, a signal cable 47 for transmitting a control signal to the inverter 46 and a power cable 48 for supplying power to the inverter 46 are connected to the inverter 46.Lubrication and Cooling Structures

[0047] A structure of the lower unit 2 of the electric outboard motor 1 for lubricating and cooling the reduction gear 45 and the bearing 28, as well as for cooling the motor 31, will be described with reference to FIGS. 3, 4, 5, 6A, and 6B. FIG. 3 illustrates an enlarged view of the motor accommodating portion 16, the reduction gear accommodating portion 17, and the bearing accommodating portion 18 in FIG. 2. FIG. 4 illustrates portions of the outer case 3 through which the lubricating oil P can flow. FIG. 5 illustrates the motor 31 and a motor support member 53 separated from each other as viewed from the left. FIG. 6A illustrates a cross section of the motor support member 53 taken along a line VIa-VIa in FIG. 5, as viewed from the front (left in FIG. 5). FIG. 6B illustrates a cross section of the motor support member 53 taken along a line VIb-VIb in FIG. 6A, viewed from the left (right in FIG. 6A).

[0048] As illustrated in FIG. 3, an outer peripheral space 61 is formed on an outer peripheral side of the motor 31, inside the outer case body 4. The outer peripheral space 61 is provided between an outer peripheral surface of the motor 31 and an inner surface of the outer case body 4. Specifically, the outer peripheral space 61 is provided between an outer peripheral surface of the motor case 35 and an inner peripheral surface of the cylindrical portion 5 of the outer case body 4, in other words, between the outer peripheral surface of the motor case 35 and an inner peripheral surface of the motor accommodating portion 16. The outer peripheral space 61 is a specific example of a "space".

[0049] The outer peripheral space 61 will be described in detail. As illustrated in FIG. 5, a motor support portion 51 is provided at a front end portion of the motor case 35. The motor support portion 51 protrudes radially outward from an outer peripheral surface of the front end portion of the motor case 35 and extends around the entire periphery of the motor case 35. The motor support portion 51 is integrally formed with the motor case 35. Further, for example, two grooves are formed around the entire periphery of an outer peripheral surface of the motor support portion 51, and a seal 52 (for example, a sealing member such as an O-ring) is provided in each groove.

[0050] The motor support member 53 is provided at a rear end portion of the motor case 35. As illustrated in FIGS. 5, 6A, and 6B, the motor support member 53 is formed in a cylindrical shape with a bottom and is positioned so that the opening on one axial side faces forward and the bottom on the other axial side faces backward. A shaft insertion hole 54 is formed in a center of the bottom of the motor support member 53. In addition, a plurality of communication holes 55 are formed in an outer peripheral portion of the bottom of the motor support member 53. In addition, a plurality of notches 56 are formed on an outer peripheral surface of the motor support member 53. Furthermore, an axial length L1 of the motor support member 53 is shorter than an axial length L2 of the motor case 35. An inner diameter D1 of the motor support member 53 is set to a value substantially equal to an outer diameter D3 of the rear end portion of the motor case 35 so that the rear end portion of the motor case 35 fits inside the motor support member 53. The outer diameter D2 of the motor support member 53 is set to a value larger than the outer diameter D3 of the rear end portion of the motor case 35. The rear end portion of the motor case 35 fits inside the motor support member 53. In this manner, the motor support member 53 is attached to the rear end portion of the motor case 35. As illustrated in FIG. 3, when the motor support member 53 is attached to the rear end portion of the motor case 35, the motor support member 53 protrudes radially outward from the outer peripheral surface of the rear end portion of the motor case 35. The motor shaft 32 passes through the shaft insertion hole 54 in the motor support member 53.

[0051] As illustrated in FIG. 3, in a state where the motor 31 to which the motor support member 53 is attached is placed inside the motor accommodating portion 16 of the outer case body 4, the outer peripheral surface of the motor support portion 51 and each seal 52 are in contact with the inner peripheral surface of the motor accommodating portion 16. In addition, the outer peripheral surface of the motor support member 53 is in contact with the inner peripheral surface of the motor accommodating portion 16. On the other hand, the outer peripheral surface (the portion of the outer peripheral surface of the motor case 35 excluding the motor support portion 51) of the motor case 35 is spaced apart from the inner peripheral surface of the motor accommodating portion 16. As a result, an outer peripheral space 61 is formed between the outer peripheral surface of the motor case 35 and the inner peripheral surface of the motor accommodating portion 16. The outer peripheral space 61 is formed around the entire periphery of the motor case 35.

[0052] The seal 52 is in liquid-tight contact with the inner peripheral surface of the motor accommodating portion 16 over the entire periphery. The seal 52 has a function of preventing the lubricating oil P, which will be described below, from leaking from the outer peripheral space 61 into the inverter accommodating portion 15. The outer peripheral space 61 is separated from the inside of the inverter accommodating portion 15 by the seal 52. On the other hand, the outer peripheral space 61 and the inside of the reduction gear accommodating portion 17 are in communication with each other via the shaft insertion hole 54, the communication holes 55, and the notches 56 provided in the motor support member 53. The inside of the reduction gear accommodating portion 17 and the inside of the bearing accommodating portion 18 are in communication with each other.

[0053] The lubricating oil P is sealed in the reduction gear accommodating portion 17, the bearing accommodating portion 18, and the outer peripheral space 61. The lubricating oil P is stirred by the operation of the reduction gear 45. As a result, the lubricating oil P flows through the reduction gear accommodating portion 17, the bearing accommodating portion 18, and the outer peripheral space 61. In FIG. 4, the hatched portions are portions through which the lubricating oil P can flow. Although not illustrated in FIG. 4, the lubricating oil P also flows inside the reduction gear 45 and inside each bearing 28. The lubricating oil P is a specific example of a "cooling medium".

[0054] The lubricating oil P lubricates the reduction gear 45 and each bearing 28. Furthermore, the lubricating oil P cools the reduction gear 45, the bearings 28, and the motor 31. That is, heat generated from the reduction gear 45 when the reduction gear 45 is operating is transferred from the reduction gear 45 to the lubricating oil P, transferred from the lubricating oil P to the reduction gear case portion 12, and dissipated into the water from the reduction gear case portion 12. Similarly, heat generated from each bearing 28 due to the rotation of the propeller shaft 25 is transferred to the reduction gear case portion 12 via the lubricating oil P, and is dissipated from the reduction gear case portion 12 into the water. In addition, heat generated by the motor 31 when the motor 31 is operating is transferred from the motor case 35 to the lubricating oil P in the outer peripheral space 61, transferred from the lubricating oil P to the outer case body 4, and dissipated into the water from the outer case body 4.

[0055] The outer peripheral space 61 is formed between the outer peripheral surface of the motor case 35 and the inner peripheral surface of the motor accommodating portion 16. The outer peripheral space 61 is formed around the entire outer periphery of the motor case 35 and is also formed around the entire inner periphery of the motor accommodating portion 16. Therefore, the lubricating oil P in the outer peripheral space 61 can be in contact with the outer peripheral surface of the motor case 35 over the entire periphery, and can be in contact with the inner peripheral surface of the motor accommodating portion 16 over the entire periphery. Therefore, a contact area between the outer peripheral surface of the motor case 35 and the lubricating oil P, and a contact area between the lubricating oil P and the inner peripheral surface of the motor accommodating portion 16 can be increased. Therefore, an amount of heat transferred from the motor 31 to the outer case body 4 via the lubricating oil P can be increased.

[0056] Furthermore, the lubricating oil P is stirred by the operation of the reduction gear 45, and flows and moves within the reduction gear accommodating portion 17, the bearing accommodating portion 18, and the outer peripheral space 61. This increases the cooling effect of the lubricating oil P on the motor 31.Lubricating Oil Drainage and Filling

[0057] As illustrated in FIG. 3 or 4, the reduction gear case portion 12 is provided with a drain bolt hole 57. The drain bolt hole 57 communicates with the inside of the reduction gear accommodating portion 17. A drain bolt 58 is fastened to the drain bolt hole 57. By removing the drain bolt 58, the lubricating oil P inside the reduction gear accommodating portion 17, the bearing accommodating portion 18, and the outer peripheral space 61 can be discharged to the outside of the outer case 3 through the drain bolt hole 57, and the lubricating oil P can be injected into the reduction gear accommodating portion 17, the bearing accommodating portion 18, and the outer peripheral space 61 from the outside of the outer case 3. Also, although not illustrated, a check bolt is provided in the reduction gear case portion 12 to check an amount of lubricating oil injected, and the check bolt is fastened to a check bolt hole that communicates with the reduction gear accommodating portion 17.Motor Installation / Removal

[0058] The motor 31 is detachable from the outer case 3. The motor 31 can be removed from the outer case 3, for example, in the following manner. In FIG. 2, first, the cotter pin 26 and the propeller nut 27 are removed, and the propeller 21 is removed from the propeller shaft 25. Next, the drain bolt 58 is removed, and the lubricating oil P is drained out of the outer case 3 through the drain bolt hole 57. Next, the connecting member 13 is removed, and the reduction gear case portion 12 is removed from the outer case body 4. By removing the reduction gear case portion 12 from the outer case body 4, the reduction gear 45 and the propeller shaft 25 are separated from the motor shaft 32. Next, the connecting member 10 (see FIG. 1) is removed, and the lid portion 9 is removed from the outer case body 4. Next, the fixing member 43 that fixes the motor 31 to the outer case body 4 is removed. Next, the motor 31 is pulled out from the opening at the rear side of the outer case body 4.

[0059] The motor 31 can be attached to the outer case 3, for example, by the following method. First, the motor 31 is inserted into the outer case body 4 through the opening at the rear side of the outer case body 4. Next, the fixing member 43 is fastened to fix the motor 31 to the outer case body 4. Next, the lid portion 9 is attached to the outer case body 4 and the connecting member 10 is fastened to fix the lid portion 9 to the outer case body 4. Next, the reduction gear 45 and the propeller shaft 25 are connected to the motor shaft 32, and the reduction gear case portion 12 is attached to the outer case body 4. Then, the connecting member 13 is fastened to fix the reduction gear case portion 12 to the outer case body 4. Next, lubricating oil is poured in through the drain bolt hole 57, and after the pouring is completed, the drain bolt 58 is tightened in the drain bolt hole 57. Next, the propeller 21 is attached to the propeller shaft 25, the propeller nut 27 is fastened to the propeller shaft 25, and the cotter pin 26 is attached.

[0060] As described above, in the electric outboard motor 1 of this example, the outer peripheral space 61 is formed between the outer peripheral surface of the motor case 35 and the inner peripheral surface of the outer case body 4, and the lubricating oil P flows within the outer peripheral space 61. The lubricating oil P functions as a cooling medium that transfers the heat of the motor 31 to the outer case 3. That is, in the electric outboard motor 1 of this example, a liquid cooling medium is interposed between the outer peripheral surface of the motor 31 and the inner surface of the outer case 3. This increases an amount of heat dissipated from the motor 31 into the water via the outer case 3, thereby improving the cooling effect on the motor 31. Furthermore, the motor 31 is detachably fixed to the outer case body 4 using the fixing member 43, and the motor 31 can be easily attached to and detached from the outer case 3 as described above. In this way, with the electric outboard motor 1 of this example, the amount of heat dissipated from the motor 31 into the water via the outer case 3 can be increased, and the motor 31 can be easily attached and detached to and from the outer case 3.

[0061] Furthermore, the outer peripheral space 61 is formed around the entire outer periphery of the motor case 35, and the lubricating oil P in the outer peripheral space 61 can flow around the entire outer periphery of the motor 31. This increases the contact area between the motor 31 and the lubricating oil P, and the contact area between the lubricating oil P and the outer case 3, thereby increasing the amount of heat transferred from the motor 31 to the outer case 3 via the lubricating oil P and improving the cooling effect on the motor 31.

[0062] In addition, the outer peripheral space 61 communicates with the inside of the reduction gear accommodating portion 17, and when the reduction gear 45 is operating, the lubricating oil P can move between the outer peripheral space 61 and the inside of the reduction gear accommodating portion 17. This allows the cooling effect of the lubricating oil P on the motor 31 to be enhanced.

[0063] Furthermore, the inside of the reduction gear accommodating portion 17 communicates with the inside of the bearing accommodating portion 18, and as a result, the lubricating oil P can move not only between the outer peripheral space 61 and the inside of the reduction gear accommodating portion 17, but also between the inside of the reduction gear accommodating portion 17 and the inside of the bearing accommodating portion 18. This further enhances the cooling effect of the lubricating oil P on the motor 31.

[0064] In the above-described example, the lubricating oil P is interposed between the outer peripheral surface of the motor 31 and the inner surface of the outer case 3. The lubricating oil P is an example of a liquid cooling medium. The cooling medium in the present disclosure is not limited to lubricating oil, but may be grease. Grease is an example of a semi-solid cooling medium.

[0065] Furthermore, an area in which the liquid or semi-solid cooling medium is interposed between the outer peripheral surface of the motor 31 and the inner surface of the outer case 3 does not have to be the entire outer periphery of the motor 31. However, it is preferable to have a liquid or semi-solid cooling medium widely interposed between the outer peripheral surface of the motor 31 and the inner surface of the outer case 3.

[0066] In addition, in the above-described example, an example is given in which the motor support portion 51 and the motor support member 53 form the outer peripheral space 61 between the outer peripheral surface of the motor 31 and the inner surface of the outer case 3, but the method of forming a space between the outer peripheral surface of the motor 31 and the inner surface of the outer case 3 is not limited to this. For example, a space may be formed between the outer peripheral surface of the motor 31 and the inner surface of the outer case 3 by forming a recess or a protrusion on the inner surface of the outer case 3.

[0067] In addition, in the above-described example, the reduction gear 45 is provided between the motor shaft 32 and the propeller shaft 25, which are arranged coaxially, to reduce the rotation of the motor shaft 32 before transmitting it to the propeller shaft 25, but the present invention is not limited to this. The motor shaft 32 and the propeller shaft 25 do not have to be arranged coaxially with each other. Moreover, instead of the reduction gear 45, a power transmission mechanism may be provided that transmits the rotation of the motor shaft 32 to the propeller shaft 25 without reducing the rotation speed. Furthermore, for example, when the electric outboard motor is small, the motor shaft and the propeller shaft may be integrated, and no reduction gear (or power transmission mechanism) may be provided.

[0068] Furthermore, in the above-described example, the motor 31 is detachably fixed to the outer case body 4 using the fixing member 43, thereby making the motor 31 detachable from the outer case 3, but the method for making the motor 31 detachable from the outer case 3 is not limited to this. For example, threads may be formed on a part of the outer peripheral surface of the motor and a part of the inner peripheral surface of the outer case, and the motor may be screwed to the outer case. The motor 31 may also be detachably attached to the outer case 3 using a locking mechanism.

[0069] 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 outboard motors with such modifications are also included within the technical concept of the present invention.

Claims

1. An electric outboard motor for propelling a boat, the electric outboard motor comprising:an outer case that forms at least a part of an outer shell of the electric outboard motor and that is to be disposed underwater;a propeller rotatably supported by the outer case;a motor provided inside the outer case and configured to rotate the propeller; anda liquid or semi-solid cooling medium interposed between an outer peripheral surface of the motor and an inner surface of the outer case.

2. The electric outboard motor according to claim 1, wherein a space is formed between the outer peripheral surface of the motor and the inner surface of the outer case over an entire periphery of the motor, and the cooling medium is disposed inside the space.

3. The electric outboard motor according to claim 1, further comprising:a power transmission mechanism provided inside the outer case and configured to transmit power of the motor to the propeller, wherein the cooling medium is lubricating oil for lubricating the power transmission mechanism.

4. The electric outboard motor according to claim 3, wherein a motor accommodating portion and a power transmission mechanism accommodating portion are provided inside the outer case,the motor is disposed inside the motor accommodating portion,the power transmission mechanism is disposed inside the power transmission mechanism accommodating portion,a space is provided between the outer peripheral surface of the motor and the inner surface of the motor accommodating portion,the space communicates with an inside of the power transmission mechanism accommodating portion, andthe lubricating oil flows through the power transmission mechanism accommodating portion and inside the space.

5. The electric outboard motor according to claim 1, further comprising:a propeller shaft having one end disposed inside the outer case and an other end to which the propeller is attached; anda bearing provided inside the outer case and supporting the propeller shaft rotatably relative to the outer case, wherein the cooling medium is lubricating oil for lubricating the bearing.

6. The electric outboard motor according to claim 5, wherein a motor accommodating portion and a bearing accommodating portion are provided inside the outer case,the motor is disposed inside the motor accommodating portion,the bearing is disposed inside the bearing accommodating portion,a space is provided between the outer peripheral surface of the motor and the inner surface of the motor accommodating portion,the space communicates with an inside of the bearing accommodating portion, andthe lubricating oil flows through the bearing accommodating portion and the space.

7. The electric outboard motor according to claim 1, further comprising:a propeller shaft having one end disposed inside the outer case and an other end to which the propeller is attached;a bearing provided inside the outer case and supporting the propeller shaft rotatably relative to the outer case; anda power transmission mechanism provided inside the outer case and configured to transmit power of the motor to the propeller shaft, wherein the cooling medium is lubricating oil for lubricating the bearing and the power transmission mechanism.

8. The electric outboard motor according to claim 7, wherein a motor accommodating portion, a power transmission mechanism accommodating portion, and a bearing accommodating portion are provided inside the outer case,the motor is disposed inside the motor accommodating portion,the power transmission mechanism is disposed inside the power transmission mechanism accommodating portion,the bearing is disposed inside the bearing accommodating portion,a space is provided between the outer peripheral surface of the motor and the inner surface of the motor accommodating portion,the space communicates with an inside of the power transmission mechanism accommodating portion,the power transmission mechanism accommodating portion communicates with an inside of the bearing accommodating portion, andthe lubricating oil flows through the power transmission mechanism accommodating portion, the bearing accommodating portion, and the space.

Images