Motor unit and electric bicycle

Abstract

The purpose of the present invention is to provide: a motor unit with which it is possible to shorten the length of a case in a motor axial direction; and an electric bicycle. A motor unit (3) is provided with a case (4), a motor (5), an output body (8), a transmission mechanism (31), and a bearing (rotary shaft support bearing (552)). The motor (5) includes: a rotor (52) and a rotary shaft (51) that can rotate about a motor axis (50); and a stator (53). The motor (5) is accommodated in a motor accommodation space inside the case (4). The output body (8) is disposed so as to be rotatable about an output axis (axis (60)). The transmission mechanism (31) is accommodated inside the case (4) and transmits the force from the motor (5) to the output body (8). The bearing is disposed in the case (4) and supports the rotary shaft (51). Some or all of the bearing is located at the same position as the rotor (52) in the direction of the motor axis (50).

Description

Motor unit and electric bicycle

[0001] The present disclosure relates to a motor unit and an electric bicycle.

[0002] Patent Document 1 describes a drive unit used in a conventional electrically assisted bicycle. The drive unit described in Patent Document 1 includes a crankshaft, a motor, a transmission shaft extending parallel to the central axis of the crankshaft, and a bearing that supports the output shaft of the motor.

[0003] Japanese Patent Application Laid-Open No. 2014-196036

[0004] In the above-described conventional drive unit, the rotor and the bearing are arranged side by side in the axial direction of the output shaft, which results in a long length in the axial direction.

[0005] In view of the above-mentioned problems with the conventional technology, the present disclosure aims to provide a motor unit and an electric bicycle that can shorten the length of the case in the motor axial direction.

[0006] In order to solve the above problem, one form of motor unit includes a case, a motor, an output body, a transmission mechanism, and a bearing. The motor has a rotor and a rotating shaft rotatable about the motor axis, and a stator. The motor is accommodated in a motor accommodating space within the case. The output body is arranged to be rotatable about the output axis. The transmission mechanism is accommodated within the case and transmits force from the motor to the output body. The bearing is arranged in the case and supports the rotating shaft. Some or all of the bearing is in the same position as the rotor in the motor axial direction.

[0007] In order to solve the above problem, one form of electric bicycle includes the motor unit and a frame.

[0008] Fig. 1 is a side view of an electric bicycle according to a first embodiment. Fig. 2 is a cross-sectional view of the frame and motor unit of the electric bicycle. Fig. 3 is a cross-sectional view taken along a plane passing through the central axis of the rotation shaft of the motor of the motor unit and the central axis of the transmission rotation shaft of the transmission mechanism. Fig. 4 is a cross-sectional view taken along a plane passing through the central axis of the output shaft of the motor unit and the central axis of the transmission rotation shaft of the transmission mechanism. Fig. 5 is a front view of the motor unit as viewed from the second divided body side with the second divided body removed. Fig. 6 is a front view of the motor unit as viewed from the second divided body side with the second divided body and control board removed.

[0009] The present disclosure relates to a motor unit and an electric bicycle, and more specifically to a motor unit including a case, a motor, an output body, and a transmission mechanism, and to an electric bicycle such as an electrically assisted bicycle or an electric motorcycle that includes this motor unit.

[0010] A first embodiment of a motor unit and an electric bicycle according to the present disclosure will be described below with reference to FIGS. 1 to 5. FIG.

[0011] (Electric Bicycle) As shown in Figure 1, the electric bicycle 1 includes a frame 10, wheels 11, and a motor unit 3. The electric bicycle 1 has a designed traveling direction, and the traveling direction is fixed. In the following description, the traveling direction is referred to as the forward direction, and the opposite direction is referred to as the rearward direction. Furthermore, left and right refer to the left and right when facing forward.

[0012] The frame 10 supports a person (hereinafter referred to as the rider) who rides the electric bicycle 1. The weight of the frame 10 and the rider is supported on the ground via a front wheel 111 and a rear wheel 112 that make up the wheels 11.

[0013] The frame 10 has a head pipe 101, an upper pipe 102, a lower pipe 103, a vertical pipe 104, a seat stay 105, a chain stay 106, and a bracket 107. The frame 10 is made of a metal such as aluminum or stainless steel, but may contain a non-metallic material in part. Furthermore, the entire frame 10 may be made of a non-metallic material, and the material of the frame 10 is not particularly limited.

[0014] As shown in FIG. 2, the head pipe 101 is a cylindrical member that opens generally in the vertical direction. Note that "generally vertical direction" here means a direction that forms an angle of approximately 30 degrees or less with the vertical direction. As shown in FIG. 1, the handle post 12 is inserted into the head pipe 101 so as to penetrate vertically. The handle post 12 is inserted into the head pipe 101 so as to be rotatable about its axis. A front fork 121 is formed at the lower end of the handle post 12. A front wheel 111 is rotatably attached to the front fork 121. A handle bar 122 is fixed to the upper end of the handle post 12. The handle bar 122 is provided with a hand operation unit for turning the electric power on and off, and a gear change operation unit for changing the speed using the gear change mechanism of the rear wheel 112.

[0015] As shown in FIG. 2 , the upper pipe 102 is a tubular member that extends generally rearward from the head pipe 101. The upper pipe 102 does not necessarily have to be linear. Note that generally rearward here means a direction that forms an angle of approximately 40 degrees or less with the rear. The front end of the upper pipe 102 is fixed to the rear side wall of the head pipe 101 by welding or the like. The rear end of the upper pipe 102 is fixed to the stand pipe 104.

[0016] The stand pipe 104 is a cylindrical member that opens generally in the vertical direction. The rear end of the upper pipe 102 is fixed to the front side wall of the stand pipe 104 near its upper end by welding or the like. As shown in FIG. 1 , a shaft extending downward from the saddle 13 is inserted into the opening at the upper end of the stand pipe 104. By fixing this shaft to the stand pipe 104, the saddle 13 is fixed to the stand pipe 104. A bracket 107 is fixed to the lower end of the stand pipe 104.

[0017] As shown in FIG. 2 , the lower pipe 103 is a tubular member that extends obliquely downward and generally rearward from the head pipe 101. The upper pipe 102 does not necessarily have to be straight. Note that "diagonally downward and generally rearward" here means a direction that is lower than the rear and that is inclined downward from the direction in which the head pipe 101 extends. The front end of the lower pipe 103 is fixed, by welding or the like, to a portion of the rear side wall of the head pipe 101 that is lower than the portion to which the upper pipe 102 is fixed. A bracket 107 is fixed to the rear end of the lower pipe 103. The bracket 107 is part of the frame 10 and supports the motor unit 3.

[0018] The motor unit 3 is fixed to the underside of the bracket 107 and is supported by the bracket 107. A wiring space 108 is formed between the inner surface of the bracket 107 and the outer surface of the motor unit 3.

[0019] As shown in FIG. 1 , the front ends of the seat stays 105 are fixed to the rear end of the upper pipe 102 by fitting (including shrink fitting), fastening, welding, or the like. The seat stays 105 are two hollow or solid members that extend roughly rearward from near the upper end of the stand pipe 104. In the first embodiment, the front ends of the cylindrical seat stays 105 are fixed by welding or the like. The rear ends of the seat stays 105 are fixed to the rear ends of the chain stays 106, and a rear wheel 112 is rotatably attached to this part.

[0020] 2, the bracket 107 and the lower pipe 103 have a battery mounting portion 16 to which a battery 15 (see FIG. 1) for supplying power to the motor unit 3 is attached. The battery mounting portion 16 has a lower support portion 161 formed on the bracket 107 and an upper support portion 162 formed on the lower pipe 103. The lower support portion 161 is attached to support the battery 15 so that the lower end of the battery 15 does not easily fall off. The lower support portion 161 also has a plurality of terminals that are electrically connected to a plurality of battery terminals for power supply or signals formed on the lower end of the battery 15. One end of each of the plurality of terminals is electrically connected to one end of a wiring 163.

[0021] The upper support portion 162 has a locking device to which the upper end of the battery 15 is attached, and which locks the battery 15 to prevent it from falling off.

[0022] Furthermore, the shift wires 17 connecting the shift operation unit and the shift mechanism and the brake wires are passed through the lower pipe 103 and the wiring space 108 .

[0023] (Motor Unit) The motor unit 3 will be described below with reference to Figures 3 and 4. The motor unit 3 includes a case 4, a motor 5, an output body 8, and a transmission mechanism 31. The motor unit 3 further includes an input shaft 6 and an input body 7.

[0024] (Case) The case 4 forms the outer shell of the motor unit 3. The case 4 houses devices such as the transmission mechanism 31 in an accommodation space formed inside. The case 4 is mainly made of a metal such as aluminum or stainless steel, but a non-metal may also be used, and the material of the case 4 is not particularly limited.

[0025] The case 4 is divided into a first divided body 41 located on the left side and a second divided body 42 located on the right side. The first divided body 41 and the second divided body 42 are combined to form the case 4. The case 4 will be described in more detail later.

[0026] The first divided body 41 has an internal storage space that opens to the right. The first divided body 41 also has a motor storage section 43. The motor storage section 43 has a motor storage space 430 that protrudes to the left and stores the motor 5 therein. The motor storage section 43 is formed integrally with the first divided body 41. In other words, the motor storage section 43 constitutes a part of the case 4. The inner surface of the motor storage section 43 has an inner surface 431 positioned to surround the motor axis 50, and a rear wall surface 432 positioned at the end of the inner surface 431 in the direction of the motor axis 50.

[0027] In the first embodiment, the stator 53 is thermally connected to the case 4 in the direction of the motor axis 50. Specifically, the stator 53 is in thermal contact with the inner surface of the motor accommodating portion 43, the rear wall surface 432. The stator 53 and the rear wall surface 432 are in contact with each other via grease, which has high thermal conductivity. This allows heat from the motor 5 to be transferred to the case 4 via the grease and the rear wall surface 432, improving heat dissipation from the motor 5.

[0028] The stator 53 is also in thermal contact with the inner surface 431 of the inner surface of the motor accommodating portion 43. The stator 53 and the inner surface 431 are in contact with each other via grease, which has high thermal conductivity. This allows heat from the motor 5 to be transferred to the case 4 via the grease and the inner surface 431, improving heat dissipation from the motor 5.

[0029] The second divided body 42 has an internal storage space that is open to the left. The first divided body 41 and the second divided body 42 are aligned from the left and right so that their respective storage spaces are continuous, and are fixed to each other with fastening members (not shown) made of bolts. The case 4 is formed by fixing the first divided body 41 and the second divided body 42 to each other. The size, shape, thickness, etc. of the case 4 are not particularly limited. The storage space formed inside the case 4 may or may not be sealed.

[0030] (Motor) As shown in FIG. 3 , the motor 5 is attached to the case 4. More specifically, the motor 5 is housed mainly in the motor housing portion 43 attached to the first divided body 41. The motor 5 includes a rotor 52 and a rotating shaft 51 that are rotatable around the motor axis 50, and a stator 53. The rotating shaft 51 and the rotor 52 rotate integrally. In the first embodiment, the inner surface of the middle portion of the rotor 52 is fixed to the outer surface of the rotating shaft 51 in the direction of the motor axis 50 by an appropriate method such as shrink fitting. The rotor 52, the stator 53, and a portion of the rotating shaft 51 are located within the motor housing portion 43. The rotating shaft 51 is rotatably housed with its axis oriented in the left-right direction. The rotating shaft 51 protrudes from the stator 53 to one side (to the right in the first embodiment), and teeth 54 that mesh with the transmission mechanism 31 are formed on the outer surface of the protruding portion. The right end of the rotating shaft 51 is supported by a rotating shaft support bearing 551 arranged in the case 4 (second divided body 42). The left end of the rotating shaft 51 does not particularly protrude beyond the stator 53, and is supported by a rotating shaft support bearing 552 arranged in the motor accommodating portion 43 of the case 4. Part or all of the rotating shaft support bearing 552 is in the same position as the rotor 52 in the direction of the motor axis 50. In the first embodiment, a part of the right side of the rotating shaft support bearing 552 is recessed inside the rotor 52 in the direction of the motor axis 50. A recess is formed on the inner surface of the rotor 52 to avoid the rotating shaft support bearing 552, and the rotor 52 and the rotating shaft support bearing 552 do not come into contact with each other.

[0031] 5 and 6, the stator 53 has a heat-generating portion 531 in a portion of the circumferential direction around the motor axis 50. The heat-generating portion 531 is a portion that mainly constitutes a power circuit including the input terminals of the three-phase power supply in the stator 53, and generates heat due to the large current that flows through it. The input terminals that constitute the heat-generating portion 531 pass through holes formed in the control board 35 (described later) (see FIG. 3).

[0032] The case 4 is provided with a roll pin 48. The roll pin 48 prevents the stator 53 from rotating around the motor axis 50. The roll pin 48 is disposed at a facing portion of the stator 53 facing the heat generating portion 531 across the motor axis 50, and presses the facing portion of the stator 53 toward the motor axis 50.

[0033] The motor unit 3 also has a heat-generating part. The heat-generating part is located at the front of the case 4 in the direction of travel. Examples of the heat-generating part include a heat-generating part 531 and a heat-generating part 351 made up of elements mounted on the control board 35. When the electric bicycle 1 is traveling, air is blown onto the case 4 from the front, so by locating the heat-generating part at the front of the case 4, the heat-generating part of the case 4 can be cooled efficiently.

[0034] The stator 53 is prevented from rotating around the motor axis 50 by a roll pin 48, and is also adhesively bonded to the inner surface (inner surface 431, rear wall surface 432) of the motor housing portion 43. An adhesive reservoir 433 consisting of a recess is formed in part of the circumferential direction of the inner surface 431.

[0035] 4, the input shaft 6 penetrates the case 4 in the direction of an axis 60 (the left-right direction in the first embodiment) and is arranged to be rotatable about the axis 60 of the input shaft 6. In the first embodiment, the input shaft 6 is a cylindrical shaft made of a hollow member, but may be made of a solid member.

[0036] (First Bearing) The case 4 has a first bearing 45, which rotatably supports the input shaft 6, at one end side in the direction of the axis 60 (the left end side in the first embodiment). A shaft hole 411 through which the input shaft 6 passes is formed in the first divided body 41, and the first bearing 45 is disposed inside this shaft hole 411. In the first embodiment, the first bearing 45 is configured by a ball bearing. Note that the first bearing 45 is not limited to a ball bearing and various other bearings, such as a roller bearing, can also be used.

[0037] A seal member 371 made of an O-ring is disposed between the first bearing 45 and the first divided body 41. By disposing the seal member 371, it becomes difficult for the grease supplied to the first bearing 45 to leak. In this embodiment, the seal member 371 made of an O-ring is disposed between the first bearing 45 and the first divided body 41, but the first bearing 45 may be press-fitted into the first divided body 41 without using the seal member 371.

[0038] (Second Bearing) The case 4 also has a second bearing 46 rotatably supporting the input shaft 6 at the other end side in the direction of the axis 60 (the right end side in the first embodiment). A shaft hole 421 through which the input shaft 6 passes is formed in the second divided body 42, and the second bearing 46 is disposed inside this shaft hole 421. In the first embodiment, the input shaft 6 is indirectly supported by the second bearing 46 via the output body 8, which is disposed rotatably about the output axis (axis 60). In the first embodiment, the second bearing 46 is configured by a ball bearing. Note that the second bearing 46 is not limited to a ball bearing and various other bearings, such as a roller bearing, can also be used.

[0039] A seal member 373 made of an O-ring is disposed between the second bearing 46 and the second divided body 42. By disposing the seal member 373, the grease supplied to the second bearing 46 is less likely to leak.

[0040] The seal members 371 and 373 may be D-rings or the like instead of O-rings, and are not particularly limited.

[0041] (Crank Arm) One end of a crank arm 18 (see FIG. 1) is fixed to the end of the input shaft 6. A pedal 181 (see FIG. 1) is rotatably attached to the other end of the crank arm 18. The rider of the electric bicycle 1 can transmit human power and rotational force to the input shaft 6 by pedaling the pedal 181.

[0042] (Input Body) The input body 7 is disposed along the outer peripheral surface of the input shaft 6 and rotates integrally with the input shaft 6. The input body 7 is a cylindrical member with its axis 60 oriented in the left-right direction and disposed concentrically with the input shaft 6. The left-right length of the input body 7 is shorter than the left-right length of the input shaft 6. The input body 7 and the input shaft 6 have mating portions 711, 61 at a portion along the axis 60 that matingly engage with each other so as to be unable to rotate relatively around the axis 60. In the first embodiment, mating portions 711, 61 formed of spline portions, serration portions, or the like are formed on the left end portion of the input body 7 (more specifically, the first input body 71 described later) and the input shaft 6 corresponding to this portion. The mating portions 711, 61 may be configured to be mated by male and female threads.

[0043] Furthermore, in the first embodiment, the input body 7 is divided into a first input body 71 and a second input body 72. The first input body 71 is connected to the input shaft 6. The first input body 71 is located at a part of the input shaft 6 in the left-right direction and is housed within the first divided body 41. A fitting portion 711 that fits with the input shaft 6 is formed at the left end of the first input body 71. A gap 70 is formed between the first input body 71 and the input shaft 6 in a portion to the right of the fitting portion 711 at the left end of the first input body 71. This makes it easier to insert the input shaft 6 into the cylindrical first input body 71.

[0044] The second input body 72 is connected to the first input body 71 at a position different from that of the first input body 71 in the direction of the axis 60 (to the right of the first input body 71 in the first embodiment), and transmits a rotational force to the output body 8. However, a portion of the second input body 72 may be located at the same position in the left-right direction as that of the first input body 71. In the first embodiment, the left end of the second input body 72 is located radially outward of the right end of the first input body 71, and they overlap in the radial direction. The first input body 71 and the second input body 72 have mating portions 712, 721 that fit together so as to be unable to rotate relatively around the axis 60. In the first embodiment, the mating portions 712, 721, which are formed by spline portions, serration portions, or the like, are formed at the right end of the first input body 71 and the left end of the second input body 72. Note that, in the present invention, "overlapping in the radial direction" refers to a state in which at least a portion of each object overlaps when viewed in the radial direction.

[0045] (Output Body) The output body 8 is disposed rotatably around the output axis (axis 60) along the outer peripheral surface of the input shaft 6 and receives rotational force from the input body 7. The output axis, which is the rotation center of the output body 8, coincides with the axis 60, which is the rotation center of the input shaft 6. The output body 8 is a generally cylindrical member, and its axis 60 faces the left-right direction, and is disposed concentrically with the input shaft 6. The left-right length of the output body 8 is shorter than the left-right length of the input shaft 6. The right end of the output body 8 protrudes outside the case 4 through an axial hole 421 formed in the second divided body 42. The output body 8 is supported by a second bearing 46 disposed in the second divided body 42. The output body 8, together with the input shaft 6 and the input body 7, constitutes the rotating shaft unit 30. The rotating shaft unit 30 is supported by the case 4 via a first bearing 45 and a second bearing 46.

[0046] 1 and 2, a front sprocket 191 is fixed to a portion of the output body 8 that protrudes outside the case 4. The front sprocket 191 rotates integrally with the output body 8. A rear sprocket 192 is fixed to the hub of the rear wheel 112. A chain 193 is wound between the front sprocket 191 and the rear sprocket 192.

[0047] As shown in FIG. 4 , in the first embodiment, a one-way clutch 32 is disposed between the input body 7 and the output body 8. When a rotational force is applied to the input body 7 in a direction that accelerates the electric bicycle 1 in the traveling direction (hereinafter referred to as the acceleration direction), the one-way clutch 32 transmits the rotational force to the output body 8, and when a rotational force is applied in the direction opposite to the acceleration direction, the one-way clutch 32 does not transmit the rotational force to the output body 8. Furthermore, when a rotational force in the acceleration direction is applied to the output body 8 via a transmission mechanism 31 (described later), the one-way clutch 32 does not transmit the rotational force to the input body 7. In the first embodiment, the one-way clutch 32 has a ratchet and is supplied with grease. Note that various types of one-way clutches can be used as appropriate, and the type is not limited thereto. For example, a roller-type one-way clutch or a sprag-type one-way clutch may be used.

[0048] The output body 8 has a web 81 and a rim 82 on the outer peripheral surface side at a portion overlapping with the input body 7 in the direction of the axis 60. The web 81 protrudes radially outward. The rim 82 is continuous with the outer radial end of the web 81. The length of the rim 82 in the direction of the axis 60 is longer than the length of the web 81 in the direction of the axis 60. The rim 82 has teeth 83 on its outer peripheral surface that mesh with the transmission mechanism 31.

[0049] 3 and 4 , the transmission mechanism 31 is housed in the case 4 and transmits the force from the motor 5 to the output body 8. The transmission mechanism 31 has a first transmission gear 311 and a second transmission gear 312. The first transmission gear 311 rotates by the rotational force of the rotation shaft 51 of the motor 5. In the first embodiment, the first transmission gear 311 is formed of a cylindrical member, and has teeth 313 formed on its outer circumferential surface that mesh with teeth 54 formed on the rotation shaft 51 of the motor 5. The first transmission gear 311 is arranged along the outer circumferential surface of the transmission rotation shaft 310 of the transmission mechanism 31.

[0050] The transmission rotation shaft 310 is rotatably housed in the case 4 with its axis oriented in the left-right direction. The transmission rotation shaft 310 is located rearward of the rotation shaft 51 of the motor 5 and is disposed in approximately the same position in the left-right direction as the portion of the rotation shaft 51 that protrudes rightward from the stator 53. The left end of the transmission rotation shaft 310 is supported by a transmission rotation shaft support bearing 3141 disposed in the retainer 44. The right end of the transmission rotation shaft 310 is supported by a transmission rotation shaft support bearing 3142 disposed in the second division body 42.

[0051] The motor unit 3 includes a retainer 44. The retainer 44 is housed in the case 4. The retainer 44 has a holding portion that holds a transmission rotation shaft support bearing 3141 that receives the transmission rotation shaft 310. The retainer 44 is made of aluminum or an aluminum alloy. The retainer 44 may also be made of a magnesium alloy, an iron-based metal, or a resin. The retainer 44 is attached to the first divided body 41. The retainer 44 is attached to the first divided body 41 with a screw 441. When viewed in the direction of the motor axis 50, the retainer 44 is included inside the first transmission gear 311. Because the screw 441 is positioned so that it abuts against the first transmission gear 311 when moved in the removal direction, the screw 441 does not completely come off the first divided body 41, and the positional relationship between the retainer 44 and the first transmission gear 311 prevents the retainer 44 from falling off.

[0052] The first transmission gear 311 is connected to the transmission rotation shaft 310 via a one-way clutch 315. When a rotational force in the acceleration direction is applied to the first transmission gear 311, the one-way clutch 315 transmits the rotational force to the transmission rotation shaft 310, and when a rotational force in the direction opposite to the acceleration direction is applied, the one-way clutch 315 does not transmit the rotational force to the transmission rotation shaft 310. Furthermore, when a rotational force in the acceleration direction is applied to the transmission rotation shaft 310, the one-way clutch 315 does not transmit the rotational force to the first transmission gear 311.

[0053] A second transmission gear 312 is fixed to the right of the portion of the transmission rotation shaft 310 to which the one-way clutch 315 is fixed so as to rotate integrally with the transmission rotation shaft 310. The second transmission gear 312 transmits the rotational force received from the first transmission gear 311 via the transmission rotation shaft 310 to the toothed portion 83 of the output body 8. The second transmission gear 312 has, on its outer circumferential surface, toothed portions 316 that mesh with the toothed portion 83 formed on the rim 82 of the output body 8. The transmission mechanism 31 transmits the rotation of the motor 5 to the output body 8 at a reduced speed by the first transmission gear 311 and the second transmission gear 312. That is, the transmission mechanism 31 in the first embodiment is a reduction mechanism.

[0054] When the rider pedals 181 of the electric bicycle 1, a rotational force in the acceleration direction is applied to the input shaft 6. When the input shaft 6 rotates, the first input body 71 and the second input body 72 rotate integrally with the input shaft 6. The rotational force in the acceleration direction of the second input body 72 is applied to the output body 8 via the one-way clutch 32, causing the output body 8 and the front sprocket 191 to rotate in the acceleration direction. When the front sprocket 191 rotates in the acceleration direction, a rotational force in the acceleration direction is applied to the rear sprocket 192 via the chain 193, causing the rear sprocket 192 and the rear wheel 112 to rotate in the acceleration direction. This causes the electric bicycle 1 to move forward in the forward direction.

[0055] Furthermore, while the electric bicycle 1 is moving forward under human power, the rotational force from the motor 5 can be applied to the output body 8 as an auxiliary force. This will be explained in detail below. When the rotation shaft 51 of the motor 5 rotates in the acceleration direction, the first transmission gear 311 meshing with the rotation shaft 51 of the motor 5 rotates in the acceleration direction. The rotational force of the first transmission gear 311 in the acceleration direction is transmitted via the one-way clutch 315 to the transmission rotation shaft 310 and the second transmission gear 312 fixed to the transmission rotation shaft 310, causing the second transmission gear 312 to rotate in the acceleration direction. The rotational force of the second transmission gear 312 in the acceleration direction is transmitted to the output body 8 meshing with the second transmission gear 312. In other words, the output body 8 functions as a force combiner that combines the rotational force of the human power from the input body 7 and the rotational force from the motor 5. The motor unit 3 in the first embodiment is a so-called single-shaft motor unit 3.

[0056] Next, we will explain the case where the motor 5 is not driven while the electric bicycle 1 is moving forward under human power. In this case, the output body 8 is rotating in the acceleration direction, so the second transmission gear 312 and the transmission rotation shaft 310 that mesh with the output body 8 rotate in the acceleration direction, but the rotational force of the transmission rotation shaft 310 in the acceleration direction is not transmitted to the first transmission gear 311 by the one-way clutch 315. This prevents the rotation shaft 51 and rotor 52 from rotating when the motor 5 is not driven.

[0057] 3, in the electric bicycle 1, the rotational force from the motor 5 is controlled in accordance with the torque applied to the input shaft 6 and the number of rotations per unit time of the input shaft 6. The torque applied to the input shaft 6 is detected by a torque detection unit 33.

[0058] In the first embodiment, a magnetostrictive generating portion 331, to which magnetic anisotropy is imparted, is formed on the outer peripheral surface of the first input body 71. In addition, a coil 332 is disposed at a slight distance from the portion of the outer peripheral surface of the first input body 71 where the magnetostrictive generating portion 331 is provided. The magnetostrictive generating portion 331 and the coil 332 constitute a magnetostrictive torque sensor serving as the torque detection unit 33. Various types of magnetostrictive torque sensors can be appropriately used as such. In addition, the torque detection unit 33 is not limited to a magnetostrictive torque sensor.

[0059] (Input Shaft Rotation Detector) The number of rotations per unit time of the input shaft 6 is detected by a rotation detector (not shown). The rotation detector is disposed in a partial range in the direction of the axis 60 along the outer circumferential surface of the rotary shaft unit 30.

[0060] In the first embodiment, a rotating body (not shown) having teeth and light-transmitting portions formed between the teeth at regular intervals in the circumferential direction is fixed to a position on the outer peripheral surface of the input body 7, avoiding the coil 332 of the torque detection unit 33, so as to rotate integrally with the input body 7. Furthermore, optical sensors are arranged to sandwich the teeth of the rotating body from the left and right. The optical sensor has a light-emitting portion (not shown) arranged on the left side of the teeth and a light-receiving portion (not shown) arranged on the right side of the teeth, but the positional relationship between the light-emitting portion and the light-receiving portion is not limited. Various rotation detection units having such a rotating body and optical sensor can be used as appropriate. Furthermore, the rotation detection unit is not limited to one having a rotating body and an optical sensor.

[0061] (Control Board) A control board 35 having a control unit that controls the motor 5 is disposed within the case 4. The control unit has, for example, a microcomputer, and controls the operation of each element by executing a program stored in a storage unit such as a ROM (Read Only Memory). Various types of control units can be used as appropriate, and detailed description thereof will be omitted. The control unit controls the rotational force from the motor 5 based on the torque detected by the torque detection unit 33 and the rotation speed detected by the motor rotation detection unit 36.

[0062] (Rotor Rotation Detector) The motor unit 3 further includes a motor rotation detector 36 that detects the rotation speed of the rotor 52. The motor rotation detector 36 includes a rotation detection rotor 361 that is attached to the rotary shaft 51 and rotates together with the rotary shaft 51, and a detector 362 that detects the rotation of the rotation detection rotor 361. The rotation detection rotor 361 is magnetic. The rotation detection rotor 361 is attached to the rotary shaft 51 by a metal bush 56. The metal bush 56 is fixed to the outer surface of the rotary shaft 51 by an appropriate method such as shrink fitting. A flange is formed on the end (right end) of the metal bush 56 on the motor axis 50, extending radially and perpendicular to the motor axis 50, and the rotation detection rotor 361 is attached to this flange. The metal bush 56 is made of copper or a copper alloy, which is a non-magnetic material.

[0063] The detection unit 362 is a Hall IC that detects the magnetic force of the rotation detection rotor 361, and is arranged at a position corresponding to the rotational orbit of the rotation detection rotor 361 of the motor 5. The detection unit 362 is attached to the control board 35. By directly attaching the detection unit 362 to the control board 35, connectors and wiring that connect the detection unit 362 to the control board 35 are not required, making it easier to reduce the size of the motor unit 3.

[0064] It should be noted that various types of motor rotation detectors 36 having such a magnet and a Hall IC can be appropriately used, and the motor rotation detector 36 is not limited to those having a magnet and a Hall IC.

[0065] (Third Bearing) As shown in Fig. 4, the motor unit 3 has a third bearing 47 located between the first bearing 45 and the second bearing 46 in the direction of the axis 60. The third bearing 47 rotatably supports the input body 7. In the first embodiment, the third bearing 47 is configured by a ball bearing. Note that the third bearing 47 is not limited to a ball bearing and various other bearings such as a roller bearing can also be used.

[0066] (Summary of the first embodiment) A portion of the right side of the rotating shaft support bearing 552 is recessed inside the rotor 52 in the direction of the motor axis 50. This reduces the length of the motor 5 in the direction of the motor axis 50, and therefore reduces the length of the case 4 in the direction of the motor axis 50.

[0067] The stator 53 is in thermal contact with the inner wall surface 432 of the motor accommodating portion 43. This allows heat from the motor 5 to be transferred to the case 4 via the grease and the inner wall surface 432, improving heat dissipation from the motor 5.

[0068] The metal bushing 56 is attached to the rotary shaft 51, and a rotation detection rotor 361 is attached to the metal bushing 56, which rotates together with the rotary shaft 51. This improves heat dissipation from the rotor 52 (motor 5). Furthermore, by forming the metal bushing 56 from copper or a copper alloy, which is a non-magnetic material, it is possible to reduce or eliminate any influence on the motor rotation detection unit 36.

[0069] The roll pin 48 is disposed at a portion of the stator 53 facing the heat generating portion 531 across the motor axis 50, and presses the opposing portion of the stator 53 toward the motor axis 50. This causes the portion of the stator 53 facing the heat generating portion 531 to be pressed against the inner wall surface 432 of the motor accommodating portion 43, allowing heat from the heat generating portion 531 to be transferred to the case 4, improving heat dissipation from the motor 5.

[0070] By locating the heat generating part at the front of the case 4 in the direction of travel, air is blown onto the case 4 from the front while the electric bicycle 1 is traveling, allowing the heat generating part of the case 4 to be cooled efficiently.

[0071] (Modification) Next, a modification will be described.

[0072] The transmission mechanism 31 is not limited to a reduction mechanism.

[0073] The entire rotating shaft support bearing 552 may be located at the same position as the rotor 52 in the direction of the motor axis 50. In other words, the entire rotating shaft support bearing 552 may be recessed inside the rotor 52 in the direction of the motor axis 50.

[0074] The stator 53 and the rear wall surface 432 may be in contact with each other via a highly thermally conductive sheet. Alternatively, no member may be interposed between the stator 53 and the rear wall surface 432. Alternatively, the stator 53 and the rear wall surface 432 may be thermally isolated from each other.

[0075] The stator 53 and the inner surface 431 may be in contact with each other via a highly thermally conductive sheet or some other member having high thermal conductivity. Alternatively, no member may be interposed between the stator 53 and the inner surface 431. Alternatively, the stator 53 and the inner surface 431 may be thermally isolated from each other.

[0076] The center of the rotor 52 and the center of the stator 53 may be configured to be misaligned in the direction of the motor axis 50. In FIG. 3 , when the center of the rotor 52 is misaligned to the left of the center of the stator 53, the rotor 52 receives a force that moves it to the right of the stator 53. This reduces the force applied to the left-side rotating shaft support bearing 552, and also makes it possible to eliminate or reduce the size of a washer (e.g., a wave washer) between the rotating shaft support bearing 552 and the rear wall surface 432. Furthermore, when the center of the rotor 52 is misaligned to the right of the center of the stator 53, the rotor 52 receives a force that moves it to the left of the stator 53. This reduces the force applied to the right-side rotating shaft support bearing 551, and also makes it possible to eliminate or reduce the size of a washer (e.g., a wave washer) between the rotating shaft support bearing 551 and the second divided body 42.

[0077] The stator 53 may be bonded only to the inner surface 431 of the inner surface of the motor accommodating portion 43, without being bonded to the back wall surface 432. Note that the stator 53 does not necessarily have to be bonded to the inner surface of the motor accommodating portion 43.

[0078] The roll pin 48 is an optional configuration, and the case 4 does not necessarily have to include the roll pin 48. If the roll pin 48 is not provided, the stator 53 does not need to be prevented from rotating about the motor axis 50, but the stator 53 may be prevented from rotating about the motor axis 50 by other means instead of the roll pin 48, for example, by appropriate means such as a protrusion formed on the case 4.

[0079] Furthermore, if the roll pin 48 is not provided, the opposing portion of the stator 53 does not need to be pressed toward the motor axis 50, but the opposing portion of the stator 53 may be pressed toward the motor axis 50 by other means instead of the roll pin 48, for example, by an appropriate means such as a protrusion formed on the case 4.

[0080] (Summary) As is clear from the above-described embodiments and modifications, the motor unit (3) of the first aspect includes a case (4), a motor (5), an output body (8), a transmission mechanism (31), and a bearing (rotary shaft support bearing 552). The motor (5) has a rotor (52) and a rotating shaft (51) rotatable about a motor axis (50), and a stator (53). The motor (5) is accommodated in a motor accommodation space (430) in the case (4). The output body (8) is arranged to be rotatable about an output axis (axis 60). The transmission mechanism (31) is accommodated in the case (4) and transmits force from the motor (5) to the output body (8). The bearing is arranged in the case (4) and supports the rotating shaft (51). Part or all of the bearing is in the same position as the rotor (52) in the direction of the motor axis (50).

[0081] According to the first aspect, the length of the motor (5) in the direction of the motor axis (50) can be shortened, and therefore the length of the case (4) in the direction of the motor axis (50) can be shortened.

[0082] The motor unit (3) of the second aspect includes a case (4), a motor (5), an output body (8), and a transmission mechanism (31). The motor (5) has a rotor (52) and a rotating shaft (51) rotatable about a motor axis (50), and a stator (53). The motor (5) is housed in a motor housing space (430) within the case (4). The output body (8) is arranged to be rotatable about an output axis (axis 60). The transmission mechanism (31) is housed within the case (4) and transmits force from the motor (5) to the output body (8). The stator (53) is thermally connected to the case (4) in the direction of the motor axis (50).

[0083] According to the second aspect, heat from the motor (5) can be transferred to the case (4) through the grease and the inner wall surface (432), improving heat dissipation from the motor (5).

[0084] The second aspect can also be realized in combination with the first aspect.

[0085] The motor unit (3) of the third aspect includes a case (4), a motor (5), an output body (8), a transmission mechanism (31), and a roll pin (48). The motor (5) has a rotor (52) and a rotating shaft (51) rotatable around a motor axis (50), and a stator (53). The motor (5) is housed in a motor housing space (430) within the case (4). The output body (8) is arranged to be rotatable around the output axis (axis (60)). The transmission mechanism (31) is housed within the case (4) and transmits force from the motor (5) to the output body (8). The roll pin (48) prevents the stator (53) from rotating around the motor axis (50). The stator (53) has a heat-generating portion (531) in a portion of the circumference around the motor axis (50). The roll pin (48) is arranged at a facing portion of the stator (53) facing the heat generating portion (531) across the motor axis (50) of the stator (53), and presses the facing portion of the stator (53) toward the motor axis (50).

[0086] According to the third aspect, heat from the heat generating portion (531) can be transferred to the case (4), improving heat dissipation from the motor (5).

[0087] The third aspect can also be realized in combination with the first or second aspect.

[0088] The motor unit (3) of the fourth aspect includes a case (4), a motor (5), an output body (8), a transmission mechanism (31), and a metal bush. The motor (5) has a rotor (52) and a rotating shaft (51) rotatable about a motor axis (50), and a stator (53). The motor (5) is housed in a motor housing space (430) in the case (4). The output body (8) is arranged to be rotatable about an output axis (axis (60)). The transmission mechanism (31) is housed in the case (4) and transmits force from the motor (5) to the output body (8). The metal bush is attached to the rotating shaft (51), and a rotation detection rotor (361) that rotates together with the rotating shaft (51) is attached to the metal bush.

[0089] According to the fourth aspect, heat dissipation from the rotor (52) (motor (5)) is improved.

[0090] The fourth aspect can also be realized by combining it with any one or more of the first to third aspects.

[0091] The motor unit (3) of the fifth aspect includes a case (4), a motor (5), an output body (8), and a transmission mechanism (31). The motor (5) has a rotor (52) and a rotating shaft (51) rotatable about a motor axis (50), and a stator (53). The motor (5) is housed in a motor housing space (430) in the case (4). The output body (8) is arranged to be rotatable about an output axis (axis 60). The transmission mechanism (31) is housed in the case (4) and transmits force from the motor (5) to the output body (8). The center of the rotor (52) and the center of the stator (53) are misaligned in the direction of the motor axis (50).

[0092] According to the fifth aspect, the force applied to the bearings (rotating shaft support bearing (551), rotating shaft support bearing (552)) that support the rotating shaft (51) can be reduced.

[0093] The fifth aspect can also be realized by combining it with any one or more of the first to fourth aspects.

[0094] The electric bicycle (1) of the sixth aspect comprises the motor unit (3) of any one or more of the first to fifth aspects and a frame (10).

[0095] The seventh aspect can be realized in combination with the sixth aspect. In the seventh aspect, the electric bicycle (1) has a design direction of travel. The motor unit (3) has a heat generating portion (heat generating portion 531, heat generating portion 351). The heat generating portion is disposed at the front of the case (4) in the direction of travel.

[0096] According to the seventh aspect, air is blown onto the case (4) from the front while the electric bicycle (1) is in motion, thereby efficiently cooling the heat-generating parts of the case (4).

[0097] REFERENCE SIGNS LIST 1 Electric bicycle 10 Frame 3 Motor unit 31 Transmission mechanism 351 Heat generating part 4 Case 430 Motor accommodating space 5 Motor 50 Motor axis 51 Rotating shaft 52 Rotor 53 Stator 531 Heat generating part 552 Bearing (rotating shaft support bearing) 60 Axis (output axis) 8 Output body

Claims

1. A motor unit comprising: a case; a motor having a rotor and a rotating shaft rotatable around the motor axis, and a stator, and housed in a motor housing space within the case; an output body arranged to be rotatable around the output axis; a transmission mechanism housed within the case and transmitting force from the motor to the output body; and a bearing arranged in the case and supporting the rotating shaft, wherein some or all of the bearings are in the same position as the rotor in the motor axial direction.

2. A motor unit comprising: a case; a motor having a rotor and a rotating shaft rotatable around the motor axis, and a stator, and housed in a motor housing space within the case; an output body arranged rotatably around the output axis; and a transmission mechanism housed within the case and transmitting force from the motor to the output body, wherein the stator is thermally connected to the case in the direction of the motor axis.

3. A motor unit comprising: a case; a motor having a rotor and a rotating shaft rotatable about the motor axis, and a stator, and housed in a motor housing space within the case; an output body arranged to be rotatable about the output axis; a transmission mechanism housed within the case and transmitting force from the motor to the output body; and a roll pin that prevents the stator from rotating about the motor axis, wherein the stator has a heat generating portion in a portion of its circumference about the motor axis, and the roll pin is located at an opposing portion of the stator facing the heat generating portion across the motor axis, and presses the opposing portion of the stator towards the motor axis.

4. A motor unit comprising: a case; a motor having a rotor and a rotating shaft rotatable around the motor axis, and a stator, and housed in a motor housing space within the case; an output body arranged rotatably around the output axis; a transmission mechanism housed within the case and transmitting force from the motor to the output body; and a metal bush attached to the rotating shaft and having attached thereto a rotation detection rotating body that rotates together with the rotating shaft.

5. A motor unit comprising: a case; a motor having a rotor and a rotating shaft rotatable around the motor axis, and a stator, and housed in a motor housing space within the case; an output body arranged rotatably around the output axis; and a transmission mechanism housed within the case for transmitting force from the motor to the output body, wherein the center of the rotor and the center of the stator are offset in the direction of the motor axis.

6. An electric bicycle comprising the motor unit according to any one of claims 1 to 5 and a frame.

7. An electric bicycle according to claim 6, wherein the electric bicycle has a design direction of travel, the motor unit has a heat-generating part, and the heat-generating part is positioned at the front of the case in the direction of travel.

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