Motor unit for electric bicycle

Abstract

To provide a motor unit that can be easily assembled and an electric bicycle.SOLUTION: A motor unit 3 includes a case 4, a motor 5, an output body 8, a speed reduction mechanism 9 and a retainer 38. The motor 5 includes a rotor 52 and a stator 53. The stator 53 is housed in a motor housing space 430 inside the case 4. The output body 8 is disposed rotatably about an axis line 60. The speed reduction mechanism 9 is housed in the case 4 and reduces the speed of rotation of the motor 5 to transmit the same to the output body 8. The retainer 38 is housed in the case 4 and includes a holding part that holds a bearing 932 supporting a rotation shaft 90 of a gear included in the speed reduction mechanism 9. At least a part of the retainer 38 overlaps with at least a part of the motor 5 as viewed in the direction of the axis line 60. The bearing 932 is disposed at a radially inner side of the rotation shaft 90 from the gear and at a position overlapping at least a part of the gear as viewed in the radial direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a motor unit for an electric bicycle, and more particularly to a motor unit for an electric bicycle including a case, a motor, an output body, and a reduction mechanism.

Background Art

[0002] Conventionally, a power assist bicycle having a human power drive system and an electric power drive system has been known (see, for example, Patent Document 1). The power assist bicycle disclosed in Patent Document 1 includes a left and right two-piece case, a motor, and a reduction mechanism. The reduction mechanism includes a reduction shaft. A primary large gear that meshes with a small gear attached to the rotation shaft of the motor is formed at the left end of the reduction shaft, and a secondary small gear that meshes with a secondary large gear and transmits power to a crank sprocket and a rear wheel is formed at the right end of the reduction shaft. The reduction shaft is supported by bearings attached to each of the two-piece cases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the power assist bicycle as described above, the bearings that support the reduction shaft of the reduction mechanism are attached to the two-piece cases respectively. For this reason, the reduction shaft cannot be fixed until the two-piece case is closed, and there is a problem that the assembly is complicated.

[0005] The present invention has been invented in view of the above conventional problems, and an object thereof is to provide a motor unit for an electric bicycle that is easy to assemble.

Means for Solving the Problems

[0006] To solve the above problems, a motor unit for an electric bicycle according to one embodiment includes a case, a motor, an output body, a speed reduction mechanism, and a retainer. The motor has a rotor and a stator, and the stator is housed in a motor housing space within the case. The output body is disposed rotatably about an axis. The speed reduction mechanism is housed within the case and reduces the rotation of the motor and transmits it to the output body. The retainer is housed within the case and has a holding portion that holds a bearing that supports the rotation shaft of a gear included in the speed reduction mechanism. At least a part of the retainer overlaps at least a part of the motor when viewed in the axial direction. The bearing is disposed on the radially inner side of the rotation shaft with respect to the gear and at a position that overlaps at least a part of the gear when viewed in the radial direction.

Advantages of the Invention

[0007] In the motor unit for an electric bicycle according to one embodiment, the motor unit for an electric bicycle is easy to assemble.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a first embodiment of the motor unit and the electric bicycle of the present disclosure will be described with reference to FIGS. 1 and 2.

[0010] As shown in FIG. 1, the electric bicycle 1 includes a frame 10, wheels 11, and a motor unit 3. Note that the traveling direction of the electric bicycle 1 is determined by design. In the following description, the traveling direction is defined as the front, and the opposite direction is defined as the rear. Also, the left and right directions refer to the left and right directions when facing the front.

[0011] The frame 10 supports a person who operates the electric bicycle 1 (hereinafter referred to as the operator). The load of the frame 10 and the operator is supported by the ground via the front wheel 111 and the rear wheel 112 that constitute the wheels 11.

[0012] 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 2. The frame 10 is formed of a metal such as aluminum or stainless steel, but may partially include a non-metal. Also, the entire frame 10 may be formed of a non-metal, and the material of the frame 10 is not particularly limited.

[0013] The head pipe 101 is a cylindrical member that generally opens in the vertical direction. Here, the generally vertical direction means a direction forming an angle of 30 degrees or less with the vertical direction. A 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 rotatably about the axial direction. 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 handlebar 122 is fixed to the upper end of the handle post 12. The handlebar 122 is provided with a hand operation part for performing electric on / off and the like, and a shift operation part for changing the speed by a speed change mechanism of the rear wheel 112.

[0014] The upper pipe 102 is a cylindrical member that extends generally rearward from the head pipe 101. The upper pipe 102 does not necessarily have to be straight. Here, the generally rearward direction means a direction forming an angle of 40 degrees or less with the rearward direction. 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 vertical pipe 104.

[0015] The vertical pipe 104 is a cylindrical member that generally opens in the vertical direction. The rear end of the upper pipe 102 is fixed to the front side wall near the upper end of the vertical pipe 104 by welding or the like. A shaft extending downward from the saddle 13 is inserted into the opening at the upper end of the vertical pipe 104. By fixing this shaft to the vertical pipe 104, the saddle 13 is fixed to the vertical pipe 104. A bracket 2 is fixed to the lower end of the vertical pipe 104.

[0016] The lower pipe 103 is a cylindrical member that extends obliquely downward and generally rearward from the head pipe 101. The upper pipe 102 does not necessarily have to be straight. Here, the term "obliquely downward and generally rearward" means a direction that is below the rear side and also extends downward from the direction in which the head pipe 101 extends. The front end portion 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 below the portion to which the upper pipe 102 is fixed. A bracket 2 is fixed to the rear end portion of the lower pipe 103.

[0017] The bracket 2 is a part of the frame 10 and supports the motor unit 3. When viewed from the left - right direction, the intermediate portion in the front - rear direction of the bracket 2 is curved upward compared to both end portions, but it may be formed linearly in the front - rear direction, and the shape is not limited. The motor unit 3 is fixed below the bracket 2 and is supported by the bracket 2. The motor unit 3 is fixed to the bracket 2 by a fastening member 14 composed of bolts or bolt - nuts.

[0018] The front end portion of the seat stay 105 is fixed to the rear end portion of the upper pipe 102 by fitting (including shrink - fitting), fastening, welding, or the like. The seat stay 105 is two hollow or solid members that extend generally rearward from near the upper end portion of the upright pipe 104. In the first embodiment, the front end portion of the tubular seat stay 105 is fixed by welding or the like. The rear end portion of the seat stay 105 is fixed to the rear end portion of the chain stay 106, and the rear wheel 112 is rotatably attached to this portion.

[0019] Also, the bracket 2 and the lower pipe 103 have a battery mounting portion on which a battery 15 for supplying power to the motor unit 3 is mounted.

[0020] Also, in the lower pipe 103 and the wiring space, a shift wire and a brake wire that connect the shift operation portion and the transmission mechanism are passed through.

[0021] Hereinafter, the motor unit 3 will be described with reference to FIG. 2 and the like. The motor unit 3 includes a case 4, a motor 5, an input shaft 6, an input body 7, an output body 8, and a speed reduction mechanism 9.

[0022] The case 4 constitutes the outer shell of the motor unit 3. The case 4 houses devices such as the speed reduction mechanism 9 in the accommodation space formed inside. The case 4 is mainly formed of a metal such as aluminum or stainless steel, but a non-metal may be used, and the material of the case 4 is not particularly limited.

[0023] 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.

[0024] The internal accommodation space of the first divided body 41 is open to the right. Also, the first divided body 41 has a motor accommodation portion 43 that houses the motor 5 in part. The motor accommodation portion 43 protrudes leftward from the portion of the first divided body 41 other than the motor accommodation portion 43 and has a motor accommodation space 430 inside for housing the motor 5. The motor accommodation space 430 is a part of the accommodation space inside the case 4. In this embodiment, the motor accommodation space 430 is not straddled by the first divided body 41 and the second divided body 42 and is formed integrally with the first divided body 41, but may be formed integrally with the second divided body 42. The motor accommodation portion 43 is a part of the first divided body 41 and is formed integrally with the portion of the first divided body 41 other than the motor accommodation portion 43. The motor accommodation space 430 is located on the side opposite to the side where the sprocket 191 (the right side in FIG. 2) is located in the direction of the axis 60 inside the case 4 (the left side in FIG. 2). Note that the motor accommodation space 430 is preferably located on the side opposite to the sprocket 191 side (the left side in FIG. 2) of the sprocket 191 in the direction of the axis 60 inside the case 4.

[0025] On the inner surface 431 facing the motor accommodation space 430 of the motor accommodation portion 43, there is formed a stepped portion 433 that has a smaller diameter closer to the back wall surface 432 facing the motor accommodation space 430 of the motor accommodation portion 43 and a larger diameter farther from the back wall surface 432. By forming such a stepped portion 433, it becomes easier to position the stator 53. Also, when inserting the stator 53 into the motor accommodation space 430, since the front side of the inner diameter of the motor accommodation space 430 has a larger diameter, it is easy to insert the stator 53.

[0026] The second divided body 42 has an accommodation space inside that is open to the left. The first divided body 41 and the second divided body 42 are joined together from the left and right so that their respective accommodation spaces are continuous via a gasket 40, and are fixed to each other by a fastening member 44 made of a bolt. The first divided body 41 and the second divided body 42 are fixed to each other to form the case 4. Note that the size, shape, thickness, etc. of the case 4 are not particularly limited. Also, the accommodation space formed inside the case 4 may or may not be sealed.

[0027] The motor unit 3 includes a retainer 38. The retainer 38 is housed inside the case 4. The retainer 38 has a holding portion that holds a bearing 932 that supports the rotation shaft 90 of the gear included in the speed reduction mechanism 9. When viewed in the direction of the axis 60, at least a part of the retainer 38 overlaps at least a part of the motor 5. When viewed in the direction of the axis 60, the retainer 38 has a region that overlaps with the inner region surrounded by the outer circumference of the stator 53. When viewed in the direction of the axis 60, the area of the overlapping region is preferably 10% to 80% of the area of the inner region surrounded by the outer circumference of the stator 53. This ratio can be changed as appropriate, more preferably 10% to 60%, still more preferably 10% to 40%, and even more preferably 10% to 20%. By setting this ratio to 10% or more, the strength of the retainer 38 can be maintained. Also, the smaller the ratio, the more the weight of the retainer 38 can be reduced, and the weight of the motor unit 3 can be reduced. Note that overlapping when viewed in the direction of the axis 60 does not refer only to the region that overlaps with the axis 60 in the direction of the axis 60.

[0028] The retainer 38 is formed of aluminum or an aluminum alloy. This makes it easier to reduce the weight of the motor unit 3 compared to the case where the retainer 38 is formed of steel or an iron-based metal. Note that the retainer 38 may be formed of a magnesium alloy, an iron-based metal, or resin. When the retainer 38 is formed of an iron-based metal, it is possible to reduce the processing cost by forming the retainer 38 by pressing a sheet metal. When the retainer 38 is formed of resin, the strength can be improved by using a carbon-mixed resin (carbon fiber) or a resin containing reinforcing fibers. When the retainer 38 is formed of resin, it is easier to reduce the weight of the motor unit 3 and easier to reduce the manufacturing cost compared to the case where the retainer 38 is formed of metal.

[0029] The retainer 38 is attached to the case 4 on the side where the motor accommodation space 430 is located in the direction of the axis 60 within the case 4. The retainer 38 is attached to the first divided body 41. The retainer 38 is attached in contact with the first divided body 41 by a fixing tool such as a screw or fitting. Note that "contact" means that no other member is interposed between the members at the location where it is attached by a fixing tool or fitting. By attaching the retainer 38 to the case 4 on the side where the motor accommodation space 430 is located, at least a part of the retainer 38 is likely to overlap at least a part of the motor 5 when viewed in the direction of the axis 60. By at least a part of the retainer 38 overlapping at least a part of the motor 5, it is possible to prevent the oil adhering to the rotation shaft 51 (described later) of the motor 5 from scattering and adhering to the motor 5, and to prevent the motor 5 from shifting in the axial direction of the rotation shaft 51. Note that when the retainer 38 is formed of a material with good thermal conductivity such as metal and the retainer 38 is connected to the control board 35 and the motor 5, it is possible to easily dissipate the heat from the control board 35 and the motor 5. Note that the larger the ratio of the area within the outer diameter of the motor 5 when viewed in the direction of the axis 60 that overlaps with the retainer 38, the higher the effect of preventing the scattered oil from adhering to the motor 5 and the effect of heat dissipation.

[0030] The retainer 38 is formed with a through-hole 381 through which the rotation shaft 51 of the motor 5 passes. Further, the retainer 38 is formed with a through-hole 382 through which the stator 53 of the motor 5 passes. A bearing 932 is fitted into a part of this through-hole 382. The through-hole 382 functions as a holding portion for holding the bearing 932. Also, in the present embodiment, although the through-hole 382 is formed in the retainer 38 for fitting the bearing 932, a non-through hole may be formed in the retainer 38 and the bearing 932 may be fitted into this hole, or the bearing 932 may be brought into contact with the stator 53. In addition, a contactable portion where the retainer 38 and the stator 53 overlap may be provided when viewed in the radial direction of the input shaft 6. The retainer 38 and the stator 53 may always be in contact with each other, such as being fitted together, at the contactable portion, or they may come into contact when the stator 53 rotates. By the retainer 38 and the stator 53 coming into contact at the contactable portion, the stator 53 can be prevented from rotating. The contactable portion may be formed in the through-hole 382 or in another part of the retainer 38.

[0031] Further, the retainer 38 may have an opening or a notch separately from the through-holes 381 and 382. The retainer 38 may have a plurality of openings or notches. By having the opening or the notch, the weight of the motor unit 3 can be reduced. The opening or the notch of the retainer 38 may be formed radially from the rotation shaft 51 of the motor 5, or the retainer 38 may be formed in a porous mesh shape or a mesh shape.

[0032] Also, at least a part of the retainer 38 may be located between the speed reduction mechanism 9 and the control board 35. In the present embodiment, the retainer 38 has a partition wall 383 that separates the space where the speed reduction mechanism 9 is located and the space where the control board 35 is located. Thereby, it is possible to suppress the grease or lubricating oil used in the speed reduction mechanism 9 from scattering and adhering to the control board 35.

[0033] The motor 5 is attached to the case 4. The motor 5 has a rotating shaft 51, a rotor 52 that rotates integrally with the rotating shaft 51, and a stator 53. The motor 5 in the present embodiment is of an inner rotor type, but the motor 5 may be of an outer rotor type or a radial gap type or an axial gap type. A part of the rotor 52, the stator 53, and the rotating shaft 51 is located within the motor housing space 430. The rotating shaft 51 is rotatably accommodated such that the axial direction thereof faces the left-right direction. The rotating shaft 51 protrudes from the stator 53 to one side (the right side in the first embodiment), and a tooth portion 54 that meshes with the speed reduction mechanism 9 is formed on the outer surface of the protruding portion. The right end portion of the rotating shaft 51 is supported by a rotating shaft support bearing 551 disposed in the second divided body 42. The left end portion of the rotating shaft 51 does not protrude particularly from the stator 53 and is supported by a rotating shaft support bearing 552 disposed in the motor housing portion 43. Since the left and right end portions of the rotating shaft 51 are supported by the rotating shaft support bearing 551 and the rotating shaft support bearing 552, the meshing between the speed reduction mechanism 9 and the tooth portion 54 becomes good.

[0034] The input shaft 6 penetrates the case 4 in the direction of the axis 60, is rotatably arranged around the axis 60 of the input shaft 6, and can transmit a rotational force to the output body 8. The input shaft 6 is formed in a cylindrical shape by a hollow member in the first embodiment, but may be formed by a solid member.

[0035] The case 4 has a first bearing 45 that rotatably supports the input shaft 6 on one end side in the direction of the axis 60 (the left end side in the first embodiment). An input 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 in the input shaft hole 411. In the first embodiment, the first bearing 45 is constituted by a ball bearing. Note that various other bearings such as roller bearings can also be used as the first bearing 45, and it is not limited to a ball bearing.

[0036] 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, the grease supplied to the first bearing 45 is less likely to leak. In the present embodiment, the seal member 371 made of an O-ring is disposed between the first bearing 45 and the first divided body 41. However, the first bearing 45 may be press-fitted into the first divided body 41 without using the seal member 371.

[0037] Further, the case 4 has a second bearing 46 that rotatably supports the input shaft 6 on the other end side (the right end side in the first embodiment) in the axial direction of the axis 60. An input 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 in the input shaft hole 421. In the first embodiment, the input shaft 6 is indirectly supported by the second bearing 46 via the output body 8. In the first embodiment, the second bearing 46 is constituted by a ball bearing. Note that, as the second bearing 46, various other bearings such as roller bearings can be used and it is not limited to the ball bearing.

[0038] 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. Note that the seal member 373 may be a D-ring or the like instead of an O-ring and is not particularly limited.

[0039] As shown in FIG. 1, one end side of the crank arm 18 is fixed to the end of the input shaft 6. A pedal 181 is rotatably attached to the other end side of the crank arm 18. The driver of the electric bicycle 1 can transmit a manual rotational force to the input shaft 6 by rowing the pedal 181.

[0040] The input body 7 is arranged 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, the direction of its axis 60 is the left-right direction, and it is arranged concentrically with the input shaft 6. The length of the input body 7 in the left-right direction is shorter than the length of the input shaft 6 in the left-right direction. The input body 7 and the input shaft 6 have fitting portions 711 and 61 that fit together so as not to be relatively rotatable about the axis 60 in a part of the direction of the axis 60. In the first embodiment, fitting portions 711 and 61 made of a spline portion or a serration portion or the like are formed at 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 fitting portions 711 and 61 may be configured to fit by a male screw and a female screw.

[0041] 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 in a part of the input shaft 6 in the left-right direction and is housed in the first divided body 41. A fitting portion 711 that fits with the input shaft 6 is formed at the left end portion of the first input body 71. A gap 70 is formed between the input shaft 6 and a portion to the right of the fitting portion 711 at the left end portion of the first input body 71. This makes it easier to insert the input shaft 6 into the inside of the cylindrical first input body 71.

[0042] The second input body 72 is located 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 is connected to the first input body 71 to transmit a rotational force to the output body 8. However, the second input body 72 may be located at a position where a part thereof is the same as that of the first input body 71 in the left-right direction. In the first embodiment, the left end portion of the second input body 72 is located outside the radial direction of the right end portion of the first input body 71 and overlaps in the radial direction. The first input body 71 and the second input body 72 have fitting portions 712 and 721 that fit together so as not to be relatively rotatable about the axis 60. In the first embodiment, fitting portions 712 and 721 made of a spline portion or a serration portion or the like are formed at the right end portion of the first input body 71 and the left end portion of the second input body 72. In the present invention, "overlapping in the radial direction" means a state in which at least a part of each object overlaps when viewed in the radial direction.

[0043] The output body 8 is arranged to be rotatable about the axis 60 along the outer peripheral surface of the input shaft 6 and receives a rotational force from the input body 7. The output body 8 penetrates the case 4 in the direction of the axis 60, but it does not necessarily penetrate the case 4. The output body 8 is generally a cylindrical member, the direction of its axis 60 faces the left-right direction, and it is arranged concentrically with the input shaft 6. The length of the output body 8 in the left-right direction is shorter than the length of the input shaft 6 in the left-right direction. The right end portion of the output body 8 protrudes outside the case 4 through the input shaft hole 421 formed in the second divided body 42. The output body 8 is supported by the second bearing 46 arranged in the second divided body 42. The output body 8 constitutes a rotating shaft unit 30 together with the input shaft 6 and the input body 7. The rotating shaft unit 30 is supported by the case 4 via the first bearing 45 and the second bearing 46.

[0044] A front sprocket 191 is attached to the portion of the output body 8 protruding outside the case 4. The front sprocket 191 is attached to the output body 8 on one side in the direction of the axis 60 (the right side in the first embodiment). The front sprocket 191 rotates integrally with the output body 8. Also, as shown in FIG. 1, a rear sprocket 192 is fixed to the hub of the rear wheel 112. A chain 193 is looped around between the front sprocket 191 and the rear sprocket 192.

[0045] As shown in FIG. 2, in the first embodiment, a one-way clutch 32 is disposed between the input body 7 and the output body 8. The one-way clutch 32 transmits the rotational force applied to the input body 7 in the direction of accelerating the electric bicycle 1 in the traveling direction (hereinafter referred to as the acceleration direction) to the output body 8, and does not transmit the rotational force applied in the direction opposite to the acceleration direction to the output body 8. Further, the one-way clutch 32 does not transmit the rotational force in the acceleration direction to the input body 7 via a speed reduction mechanism 9 described later. In the first embodiment, the one-way clutch 32 has a ratchet and grease is supplied. Note that various types of one-way clutches 32 can be appropriately used and are not limited. For example, a roller type one-way clutch or a sprag type one-way clutch may be used, or a clutch that meshes in the direction of the axis 60 may also be used.

[0046] The output body 8 has a web 81 and a rim 82 on the outer peripheral surface side at a portion overlapping the input body 7 in the direction of the axis 60. The web 81 protrudes outward in the radial direction. The rim 82 is continuous with the radially outer end portion 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 a tooth portion 83 that meshes with the speed reduction mechanism 9 on the outer peripheral surface.

[0047] The speed reduction mechanism 9 is housed in the case 4 and reduces the rotation of the motor 5 and transmits it to the output body 8. The speed reduction mechanism 9 has two pairs of gears that mesh with each other. That is, the speed reduction mechanism 9 reduces the rotation of the motor 5 by so-called two-stage reduction and transmits it to the output body 8. Thereby, it becomes easier to obtain a large reduction ratio by the speed reduction mechanism 9.

[0048] The speed reduction mechanism 9 has a first transmission gear 91 and a second transmission gear 92. The outer diameter of the first transmission gear 91 is larger than the outer diameter of the second transmission gear 92. The number of teeth of the first transmission gear 91 is larger than the number of teeth of the second transmission gear 92.

[0049] The first transmission gear 91 rotates by the rotational force of the rotary shaft 51 of the motor 5. In the first embodiment, the first transmission gear 91 is constituted by a cylindrical member, and a tooth portion 911 that meshes with the tooth portion 54 formed on the rotary shaft 51 of the motor 5 is formed on the outer peripheral surface. The first transmission gear 91 is arranged along the outer peripheral surface of the transmission rotary shaft 90 of the speed reduction mechanism 9. In the first embodiment, the first transmission gear 91 is configured to directly receive the rotational force from the rotary shaft 51 of the motor 5, but a gear may be provided in between.

[0050] The transmission rotary shaft 90 is rotatably accommodated in the case 4 such that the axial direction faces the left - right direction. The right end portion of the transmission rotary shaft 90 is supported by a bearing 931 arranged in the second divided body 42. The left end portion of the transmission rotary shaft 90 is supported by a bearing 932 arranged in the retainer 38.

[0051] The first transmission gear 91 is connected to the transmission rotary shaft 90 via a one - way clutch 94. The one - way clutch 94 transmits the rotational force to the transmission rotary shaft 90 when a rotational force in the accelerating direction is applied to the first transmission gear 91, and does not transmit the rotational force to the transmission rotary shaft 90 when a rotational force in the direction opposite to the accelerating direction is applied. Also, when a rotational force in the accelerating direction is applied to the transmission rotary shaft 90, this rotational force is not transmitted to the first transmission gear 91.

[0052] On the right side of the portion of the transmission rotary shaft 90 where the one - way clutch 94 is fixed, a second transmission gear 92 is fixed so as to rotate integrally with the transmission rotary shaft 90. Note that, on the transmission rotary shaft 90, the second transmission gear 92 may be fixed to the left side of the portion where the one - way clutch 94 is fixed (the portion that directly or indirectly fixes the first transmission gear 91). The second transmission gear 92 transmits the rotational force received from the first transmission gear 91 via the transmission rotary shaft 90 to the tooth portion 83 of the output body 8. The second transmission gear 92 has a tooth portion 921 on the outer peripheral surface that meshes with the tooth portion 83 formed on the rim 82 of the output body 8.

[0053] When the driver pedals the pedal 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, and the output body 8 and the front sprocket 191 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, and the rear sprocket 192 and the rear wheel 112 rotate in the acceleration direction. Thereby, the electric bicycle 1 advances in the traveling direction.

[0054] Also, when the electric bicycle 1 is advancing in the traveling direction by human power, the rotational force from the motor 5 can be applied to the output body 8 as an auxiliary force. This will be described in detail below. When the rotating shaft 51 of the motor 5 rotates in the acceleration direction, the first transmission gear 91 meshing with the rotating shaft 51 of the motor 5 rotates in the acceleration direction. The rotational force in the acceleration direction of the first transmission gear 91 is transmitted to the transmission rotating shaft 90 and the second transmission gear 92 fixed to the transmission rotating shaft 90 via the one-way clutch 94, and the second transmission gear 92 rotates in the acceleration direction. The rotational force in the acceleration direction of the second transmission gear 92 is transmitted to the output body 8 meshing with the second transmission gear 92. That is, the output body 8 functions as a combined force body in which the rotational force of human power from the input body 7 and the rotational force from the motor 5 are combined. The motor unit 3 in the first embodiment is a so-called single-axis type motor unit 3. In the single-axis type motor unit 3, the rotational force of human power from the input body 7 and the rotational force from the motor 5 are combined within the case 4 of the motor unit 3 and output from the same output body 8.

[0055] Also, the case where the motor 5 is not driven when the electric bicycle 1 is advancing in the traveling direction by human power will be described. In this case, since the output body 8 is rotating in the acceleration direction, the second transmission gear 92 and the transmission rotating shaft 90 meshing with the output body 8 rotate in the acceleration direction, but the rotational force in the acceleration direction of the transmission rotating shaft 90 is not transmitted to the first transmission gear 91 by the one-way clutch 94. Thereby, when the motor 5 is not driven, the rotation of the rotating shaft 51 and the rotor 52 is prevented.

[0056] In the electric bicycle 1, the rotational force from the motor 5 is controlled according to the torque applied to the input shaft 6 and the number of revolutions of the input shaft 6 per unit time. The torque applied to the input shaft 6 is detected by the torque detection unit 33. The torque detection unit 33 is arranged in a partial range in the axial direction of the axis 60 along the outer peripheral surface of the rotary shaft unit 30.

[0057] In the first embodiment, a magnetostrictive generation portion 331 having magnetic anisotropy is formed on the outer peripheral surface of the first input body 71. Further, a coil 332 is arranged at a slight interval from the portion where the magnetostrictive generation portion 331 of the outer peripheral surface of the first input body 71 is provided. These magnetostrictive generation portion 331 and coil 332 constitute a magnetostrictive torque sensor as the torque detection unit 33. As such a magnetostrictive torque sensor, various types can be appropriately used. Further, the torque detection unit 33 is not limited to a magnetostrictive torque sensor.

[0058] The torque detection unit 33 is arranged on the left side of the first transmission gear 91, the second transmission gear 92, the one-way clutch 32, and the second bearing 46 in the axial direction of the axis 60.

[0059] The number of revolutions of the input shaft 6 per unit time is detected by the input shaft rotation detection unit 34. The input shaft rotation detection unit 34 is arranged in a partial range in the axial direction of the axis 60 along the outer peripheral surface of the rotary shaft unit 30.

[0060] In the first embodiment, on the outer peripheral surface side of the input body 7, to the right of the coil 332 of the torque detection unit 33, a first rotating body 341 having tooth portions formed at regular intervals in the circumferential direction and light-passing portions formed between the tooth portions is fixed so as to rotate integrally with the input body 7. Further, an optical sensor 342 is disposed so as to sandwich the tooth portions of the first rotating body 341 from the left and right. The optical sensor 342 has a light-emitting portion 343 disposed on the left side of the tooth portion and a light-receiving portion 344 disposed on the right side of the tooth portion, but the positional relationship between the light-emitting portion 343 and the light-receiving portion 344 is not limited. As the input shaft rotation detection unit 34 having such a first rotating body 341 and the optical sensor 342, various types can be appropriately used. Further, the input shaft rotation detection unit 34 is not limited to one having the first rotating body 341 and the optical sensor 342.

[0061] The motor unit 3 includes a control board 35 having a control unit for controlling the motor 5 in the case 4. The control unit has, for example, a microcomputer and controls the operations of the respective elements by executing a program stored in a storage unit such as a ROM (Read Only Memory). Various types of such control units can be appropriately used, and detailed description thereof is 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 rotational speed detected by the input shaft rotation detection unit 34.

[0062] The control board 35 and the rotor 52 overlap at least partially when viewed in the direction of the axis 60. Thereby, it is easy to reduce the size of the motor unit 3 (case 4).

[0063] 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 second rotating body 361 attached to the rotating shaft 51 and rotating integrally with the rotating shaft 51 and the rotor 52, and a detector 362. The second rotating body 361 has magnetism. As the detector 362, a Hall IC that detects the magnetic force of the second rotating body 361 is disposed at a position corresponding to the rotation orbit of the second rotating body 361 of the motor 5. The detector 362 is attached to the control board 35. Since the detector 362 is directly attached to the control board 35, a connector or wiring for connecting the detector 362 and the control board 35 becomes unnecessary, facilitating miniaturization of the motor unit 3.

[0064] Note that various types of motor rotation detectors 36 having such magnets and Hall ICs can be appropriately used. Further, the motor rotation detector 36 is not limited to those having magnets and Hall ICs.

[0065] The second divided body 42 of the case 4 integrally includes a heat radiating part 424. The heat radiating part 424 is connected to a member that generates heat on the inner surface of the case 4. The heat radiating part 424 may be provided at a location where the case 4 protrudes inward. Examples of the member that generates heat include the control board 35 and the motor 5. The heat radiating part 424 is connected to the control board 35 via a heat conductive member 425. That is, in the first embodiment, the control board 35 is connected to the case 4. Thereby, the heat generated on the control board 35 is efficiently radiated from the outer surface of the case 4 via the heat radiating part 424. Further, as described above, the retainer 38 is formed of a material having good heat conductivity such as metal, and further, the control board 35 may be provided on the retainer 38 so that the control board 35 and the retainer 38 are connected. Being connected means that the control board 35 and the retainer 38 are in direct contact or indirectly connected via another member. With this configuration, the heat generated on the control board 35 can be radiated from the first divided body 41 via the retainer 38.

[0066] Further, the retainer 38 may be connected to any of the heat radiating portions of the case 4. Thereby, the generated heat can be radiated from the case 4 through the retainer 38.

[0067] The motor unit 3 has a third bearing 47 positioned 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 constituted by a ball bearing. Note that, as the third bearing 47, various other bearings such as a roller bearing can be used, and it is not limited to a ball bearing.

[0068] By arranging the third bearing 47, the rotation of the rotary shaft unit 30 is stabilized. That is, if the third bearing 47 is not arranged, the rotary shaft unit 30 will be supported only by the two bearings of the first bearing 45 and the second bearing 46. In this case, the portion between the first bearing 45 and the second bearing 46 of the rotary shaft unit 30 is likely to vibrate in the radial direction of the shaft diameter. On the other hand, by arranging the third bearing 47, the portion between the first bearing 45 and the second bearing 46 is supported from the outside of the shaft diameter, and the rotary shaft unit 30 including the output body 8 and the output body 8 is less likely to vibrate in the radial direction of the shaft diameter. As a result, the rotation of the rotary shaft unit 30 is stabilized. When the rotation of the rotary shaft unit 30 is stabilized, the rotation of the front sprocket 191 is also stabilized, and the chain 193 wound around the front sprocket 191 is less likely to fall off from the front sprocket 191.

[0069] In the first embodiment, the third bearing 47 supports the second input body 72. By the third bearing 47 supporting the second input body 72 instead of the first input body 71, the portion close to the output body 8 to which force is applied by the speed reduction mechanism 9 can be supported, and the rotation of the rotary shaft unit 30 is further stabilized.

[0070] Also, in the first embodiment, the third bearing 47 is positioned between the input body 7 (the second input body 72) and the output body 8 that overlap in the radial direction of the input shaft 6. Thereby, the third bearing 47 is supported by the output body 8, and there is no need for the third bearing 47 to be attached to the case 4.

[0071] Furthermore, the third bearing 47 is positioned between the one-way clutch 32 and the torque detection unit 33 in the direction of the axis 60. As a result, in the direction of the axis 60, the torque detection unit 33 is positioned between the first bearing 45 and the third bearing 47, and the one-way clutch 32 is positioned between the third bearing 47 and the second bearing 46. The runout in the axial diameter direction of the portion where the torque detection unit 33 of the rotary shaft unit 30 is located and the portion where the one-way clutch 32 is located is suppressed.

[0072] Also, in the first embodiment, the second bearing 46 and the third bearing 47 support the output body 8. The second bearing 46 is disposed in the case 4 and supports the output body 8 from the radially outer side. The third bearing 47 is disposed in the second input body 72 and supports the output body 8 from the radially inner side. The output body 8 is supported from both the radially outer side and the radially inner side, and the output body 8 and the rotary shaft unit 30 including the output body 8 are less likely to vibrate in the axial diameter direction. As a result, the rotation of the rotary shaft unit 30 becomes more stable.

[0073] In the first embodiment, the motor unit 3 includes a retainer 38 that is separate from the case 4. The retainer 38 has a bearing 932 that supports the rotating shaft 90 of the gear included in the speed reduction mechanism 9. By providing the retainer 38 that is separate from the case 4, when inserting the motor 5 into the case 4 having the motor housing portion 43 integrally, the stator 53 can be inserted into the motor housing space 430 before attaching the retainer 38 to the case 4, so that it is easy to insert the stator 53 into the motor housing space 430.

[0074] Also, neither of the bearings 931 and 932 that support the transmission rotating shaft 90 of the speed reduction mechanism 9 is attached to the case 4, and one of the bearings 932 is attached to the retainer 38. If both of the bearings 931 and 932 were attached to the case 4, the transmission rotating shaft 90 would be positioned across the left and right ends of the case 4, occupying a large proportion of the accommodation space within the case 4, and the case 4 would tend to become larger. In the present embodiment, by attaching one of the bearings 932 to the retainer 38, it becomes unnecessary for the transmission rotating shaft 90 to be positioned across the left and right ends of the case 4, making it easier to miniaturize the transmission rotating shaft 90 and the case 4. Also, when assembling the motor unit 3, the rotating shaft of the speed reduction mechanism 9 can be held by the retainer 38 via the bearing 932, facilitating the assembly of the motor unit 3.

[0075] Next, the motor unit 3 of the second embodiment will be described with reference to FIGS. 3 to 6. Since the motor unit 3 of the second embodiment is mostly the same as the motor unit 3 of the first embodiment, components corresponding to those of the motor unit 3 of the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted, and mainly the components different from the first embodiment will be described.

[0076] The motor unit 3 in the first embodiment was a so-called single-axis type motor unit 3, whereas the motor unit 3 in the second embodiment is different in that it is a so-called two-axis type motor unit 3. In the two-axis type motor unit 3, the rotational force of the input from the input body 7 and the rotational force from the motor 5 are output from different output bodies 802 and the input driving force output body 801, which will be described later.

[0077] In the second embodiment, the motor unit 3 includes a human - power driving - force output body 801 and an output body 802. The human - power driving - force output body 801 constitutes the rotary - shaft unit 30. The rotational force applied to the input shaft 6 when the driver rows the pedal 181 is transmitted to the human - power driving - force output body 801, and then is finally transmitted to the rear wheel 112 via the sprocket 191, the chain 193, and the rear - side sprocket 192. Note that the input shaft 6 is formed in a cylindrical shape by a solid member in the second embodiment, but it may be formed by a hollow member.

[0078] The motor unit 3 includes an output body 802 different from the human - power driving - force output body 801. The rotational force from the motor 5 is transmitted to the output body 802 via the speed - reduction mechanism 9. In the second embodiment, the speed - reduction mechanism 9 reduces the rotation of the motor 5 by so - called single - stage reduction having only a pair of meshing gears and transmits it to the output body 802. The speed - reduction mechanism 9 has a first transmission gear 91, but does not have the second transmission gear 92 in the first embodiment. The transmission rotating shaft 90 constituting the speed - reduction mechanism 9 also serves as the output body 802. The first transmission gear 91 is connected to the output body 802 (transmission rotating shaft 90) via a one - way clutch 94, similar to the first embodiment.

[0079] A sprocket 194 different from the sprocket 191 is attached to a portion protruding outside the case 4 of the output body 802. The sprocket 194 is attached to the output body 802 on one side in the direction of the axis 60 (the right - hand side in the second embodiment). The sprocket 194 rotates integrally with the output body 802. The chain 193 is looped around the sprocket 191, the sprocket 192, and the sprocket 194. The rotational force of the output body 802 is finally transmitted to the rear wheel 112 via the sprocket 194, the chain 193, and the rear - side sprocket 192.

[0080] In the second embodiment, the input shaft rotation detection unit 34 rotates together with the rotation of the input shaft 6, and includes a third rotating body 345 that serves as a detected unit, and a rotation center shaft 346 that is fixed to a portion other than the rotation shaft unit 30. A fourth rotating body 347 is attached to the outer peripheral surface of the input shaft 6. The fourth rotating body 347 is attached by press-fitting, fitting, or screwing the outer peripheral surface of the input shaft 6 to its inner peripheral surface, and rotates integrally with the input shaft 6. The fourth rotating body 347 has a tooth portion at the tip of a portion extending in the radial direction of the input shaft 6. A fifth rotating body 348 having a tooth portion that meshes with this tooth portion is disposed on the rotation orbit of the tooth portion of the fourth rotating body 347. A magnetized third rotating body 345 is attached to the fifth rotating body 348. The third rotating body 345 rotates integrally with the fifth rotating body 348 and is interlocked with the rotation of the input shaft 6. The rotation of the third rotating body 345 is detected by a Hall IC described later.

[0081] The rotation center shaft 346 has a columnar shape with a uniform cross section. One end is fitted into the first divided body 41, and the other end is fitted into the second divided body 42, and does not rotate with respect to the case 4. The magnetic force of the third rotating body 345 is detected by a Hall IC included in the control board 35. The rotation center shaft 346 is inserted into the shaft hole of the fifth rotating body 348 and functions as the rotation shaft of the fifth rotating body 348.

[0082] The third rotating body 345 and the second rotating body 361 overlap when viewed in a direction orthogonal to the axis 60 direction. Thereby, the degree of freedom in the design of the motor unit 3 and the electric bicycle 1 is improved.

[0083] The retainer 38 and the stator 53 overlap at least partially when viewed in the axis 60 direction. Thereby, it is easy to reduce the size of the motor unit 3 (case 4).

[0084] Note that reference numeral 48 in FIGS. 3 and 4 is a metal bearing interposed between the input shaft 6 and the human power driving force output body 801, reference numeral 412 in FIG. 5 is a fastening member composed of a bolt for fixing the retainer 38 to the first divided body 41, and reference numeral 413 is a fastening member composed of a screw for fixing the control board 35 to the first divided body 41.

[0085] Next, a modified example will be described.

[0086] In the first embodiment, the speed reduction mechanism 9 reduces the rotation of the motor 5 by so-called two-stage speed reduction, and in the second embodiment, the speed reduction mechanism 9 reduces the rotation of the motor 5 by so-called single-stage speed reduction. However, the speed reduction by the speed reduction mechanism 9 is not limited to single-stage speed reduction or two-stage speed reduction. The speed reduction mechanism 9 may have three or more stages of speed reduction, that is, three or more pairs of meshing gears.

[0087] In the first and second embodiments, the retainer 38 was attached to the first divided body 41 by a fixing tool such as a screw or fitting, etc. However, the method of attaching the retainer 38 to the first divided body 41 is not limited. Further, the retainer 38 may be attached to the second divided body 42, and it is sufficient that it is attached to at least the case 4. At this time, the retainer 38 may be attached to the case 4 via a separate member. For example, as a separate member, the retainer 38 can be attached to the case 4 via a rubber sheet or urethane sheet that functions as a vibration-proof member. Further, the retainer 38 may contact both the first divided body 41 and the second divided body 42, and may be supported by both the first divided body 41 and the second divided body 42 via another member in between. In this case, the retainer 38 is surely fixed by the case 4. Further, the retainer 38 may be fitted to both the first divided body 41 and the second divided body 42. In this case, while improving the assembly rigidity of the retainer 38, the rigidity for receiving the bearing 932 provided in the retainer 38 is also improved, and the meshing accuracy between the first transmission gear 91 and the second transmission gear 92 is improved, which is effective for quieting the motor unit 3. Furthermore, the rigidity of the entire case 4 is improved, and the tooth striking sound and the electromagnetic sound of the motor 5 are less likely to leak to the outside of the case 4.

[0088] A hole or notch through which an electric wire connecting the motor 5 and the control board 35 passes may be formed in the retainer 38. Thereby, it becomes easier to route the electric wire connecting the motor 5 and the control board 35, and the degree of freedom in the design of the motor unit 3 and the electric bicycle 1 is improved. Note that this hole or notch may be used as the contactable part described above.

[0089] As is clear from the first embodiment, the second embodiment, and the modified examples thereof described above, the motor unit 3 of the first aspect includes a case 4, a motor 5, an output body 8, a speed reduction mechanism 9, and a retainer 38. The motor 5 has a rotor 52 and a stator 53, and the stator 53 is housed in a motor housing space 430 within the case 4. The output body 8 is disposed rotatably about an axis 60. The speed reduction mechanism 9 is housed within the case 4 and reduces the rotation of the motor 5 and transmits it to the output body 8. The retainer 38 is housed within the case 4 and has a holding portion that holds a bearing 932 that supports a rotating shaft (transmission rotating shaft 90) of a gear included in the speed reduction mechanism 9. At least a part of the retainer 38 overlaps at least a part of the motor 5 when viewed in the direction of the axis 60.

[0090] According to the first aspect, when assembling the motor unit 3, the rotating shaft of the speed reduction mechanism 9 can be held by the retainer 38 via the bearing 932, facilitating the assembly of the motor unit 3.

[0091] The second aspect can be realized in combination with the first aspect. In the second aspect, the retainer 38 is formed of aluminum, an aluminum alloy, or a magnesium alloy.

[0092] According to the second aspect, it is easier to reduce the weight of the motor unit 3 compared to the case where the retainer 38 is formed of steel or an iron-based metal.

[0093] The third aspect can be realized in combination with the first aspect. In the third aspect, the retainer 38 is formed of resin.

[0094] According to the third aspect, it is easier to reduce the weight of the motor unit 3 and easier to reduce the manufacturing cost compared to the case where the retainer 38 is formed of metal.

[0095] The fourth aspect can be realized by combination with any of the first to third aspects. In the fourth aspect, the speed reduction mechanism 9 has two pairs of gears meshing with each other.

[0096] According to the fourth aspect, it is easy to obtain a large speed reduction ratio by the speed reduction mechanism 9.

[0097] The fifth aspect can be realized by combination with any of the first to third aspects. In the fifth aspect, the speed reduction mechanism 9 has three pairs of gears meshing with each other.

[0098] According to the fifth aspect, it is easy to obtain a large speed reduction ratio by the speed reduction mechanism 9.

[0099] The sixth aspect can be realized by combination with any of the first to fifth aspects. In the sixth aspect, the case 4 is divided into a first divided body 41 and a second divided body 42 in the direction of the axis 60. The output body 8 is located on the second divided body side 42 in the direction of the axis 60. The motor accommodation space 430 is located in the first divided body 41.

[0100] According to the sixth aspect, it is easy to separate the motor accommodation space 430 from the output body 8.

[0101] The seventh aspect can be realized by combination with any of the first to fifth aspects. In the seventh aspect, the case 4 is divided into a first divided body 41 and a second divided body 42 in the direction of the axis 60. The output body 8 is located on the second divided body side 42 in the direction of the axis 60. The motor accommodation space 430 is located on the second divided body side 42.

[0102] According to the seventh aspect, it is easy to bring the motor accommodation space 430 close to the output body 8.

[0103] The eighth aspect can be realized by combination with any of the first to seventh aspects. In the eighth aspect, a motor housing portion 43 is formed in a part of the case 4, protruding outward from the other parts of the case 4, and a motor housing space 430 is formed inside. On the inner surface 431 facing the motor housing space 430 of the motor housing portion 43, a stepped portion 433 is formed such that the diameter is smaller closer to the back wall surface 432 facing the motor housing space 430 of the motor housing portion 43 and larger farther from the back wall surface 432.

[0104] According to the eighth aspect, it becomes easier to position the stator 53, and it is also easier to insert the stator 53 into the motor housing space 430.

[0105] The ninth aspect can be realized by combination with any of the first to eighth aspects. In the ninth aspect, the retainer 38 is attached to the case 4 on the side where the motor housing space 430 is located in the direction of the axis 60 inside the case 4.

[0106] According to the ninth aspect, it becomes easier for the retainer 38 to cover the motor 5 (especially the stator 53).

[0107] The tenth aspect can be realized by combination with the ninth aspect. In the tenth aspect, the retainer 38 is attached in contact with the case 4.

[0108] According to the tenth aspect, the bearing 932 can be held by the case 4 via the retainer 38.

[0109] The eleventh aspect can be realized by combination with the ninth aspect. In the eleventh aspect, the retainer 38 is attached to the case 4 via a vibration damping member.

[0110] According to the eleventh aspect, vibration from the rotating shaft of the speed reduction mechanism 9 is less likely to be transmitted to the case 4 via the bearing 932 and the retainer 38.

[0111] Aspect 12 can be realized by a combination with any of Aspects 1 to 11. In Aspect 12, the motor unit 3 further includes a control board 35 having a control unit that controls the motor 5. The control board 35 is provided on the retainer 38.

[0112] According to Aspect 12, the control board 35 is held by the retainer 38.

[0113] Aspect 13 can be realized by a combination with any of Aspects 1 to 12. In Aspect 13, the motor unit 3 further includes a control board 35 having a control unit that controls the motor 5. At least a part of the retainer 38 is located between the speed reduction mechanism 9 and the control board 35.

[0114] According to Aspect 13, it is possible to suppress the grease or lubricating oil used in the speed reduction mechanism 9 from scattering and adhering to the control board 35.

[0115] Aspect 14 can be realized by a combination with any of Aspects 1 to 13. In Aspect 14, the motor unit 3 further includes a control board 35 having a control unit that controls the motor 5. The control board 35 is connected to the case 4 via a heat conductive member.

[0116] According to Aspect 14, the heat generated in the control board 35 can be efficiently dissipated through the case 4.

[0117] Aspect 15 can be realized by a combination with any of Aspects 1 to 14. In Aspect 15, the motor unit 3 further includes a control board 35 having a control unit that controls the motor 5. A hole or notch through which an electric wire connecting the motor 5 and the control board 35 passes is formed in the retainer 38.

[0118] According to Aspect 15, it is easy to route the electric wire connecting the motor 5 and the control board 35, and the degree of freedom in the design of the motor unit 3 is improved.

[0119] Aspect 16 can be realized by combination with any one of Aspects 1 to 15. In Aspect 16, at least a part of the retainer 38 and the stator 53 overlap when viewed in the direction of the axis 60.

[0120] According to Aspect 16, it is easy to reduce the size of the motor unit 3.

[0121] Aspect 17 can be realized by combination with any one of Aspects 1 to 16. In Aspect 17, the motor unit 3 further includes a control board 35 having a control unit for controlling the motor 5. At least a part of the control board 35 and the rotor 52 overlap when viewed in the direction of the axis 60.

[0122] According to Aspect 17, it is easy to reduce the size of the motor unit 3.

[0123] Aspect 18 can be realized by combination with any one of Aspects 1 to 17. In Aspect 18, the case 4 has a first divided body 41 and a second divided body 42. The motor accommodation space 430 is formed integrally with the first divided body 41 or the second divided body 42.

[0124] According to Aspect 18, since the motor accommodation space 430 does not straddle the first divided body 41 and the second divided body 42, the shape and volume stability are high.

[0125] Aspect 19 can be realized by combination with any one of Aspects 1 to 18. In Aspect 19, the retainer 38 has a contactable part with which the stator 53 can come into contact.

[0126] According to Aspect 19, by the retainer 38 and the stator 53 coming into contact at the contactable part, the stator 53 can be prevented from rotating.

[0127] Aspect 20 can be realized by combination with any one of Aspects 1 to 19. In the 20th aspect, the case 4 has a heat radiating portion, and the retainer 38 is connected to the heat radiating portion.

[0128] According to the 20th aspect, the generated heat can be radiated from the case 4 via the retainer 38.

[0129] The 21st aspect can be realized by a combination with any of the 1st to 20th aspects. In the 21st aspect, the motor unit 3 further includes an input shaft 6 that penetrates the case 4 in the direction of the axis 60 and is rotatably arranged around the axis 60, and can transmit a rotational force to the output body 8.

[0130] According to the 21st aspect, in the motor unit 3 used in the so-called two-shaft type electric bicycle 1, it is not necessary for the transmission rotating shaft 90 to be located between the left and right ends of the case 4, and the transmission rotating shaft 90 and the case 4 can be easily miniaturized.

[0131] The 22nd aspect can be realized by a combination with any of the 1st to 21st aspects. In the 22nd aspect, the motor unit 3 further includes an input shaft 6 that penetrates the case 4 in the direction of the axis 60 and is rotatably arranged, and a human power driving force output body 801 that outputs the rotational force of the input shaft 6. The human power driving force output body 801 rotates around a second axis different from the axis 60.

[0132] According to the 22nd aspect, in the motor unit 3 used in the so-called two-shaft type electric bicycle 1, it is not necessary for the transmission rotating shaft 90 to be located between the left and right ends of the case 4, and the transmission rotating shaft 90 and the case 4 can be easily miniaturized.

[0133] Aspect 23 can be realized by combination with either of Aspects 21 or 22. In Aspect 23, the motor unit 3 further includes an input shaft rotation detector 34 and a motor rotation detector 36. The input shaft rotation detector 34 has a first rotating body 341 and detects the rotation speed of the input shaft 6. The motor rotation detector 36 has a second rotating body 361 and detects the rotation speed of the rotor 52. The first rotating body 341 and the second rotating body 361 overlap when viewed in a direction orthogonal to the axis 60 direction.

[0134] According to Aspect 23, the degree of freedom in the design of the motor unit 3 is improved.

[0135] Aspect 24 can be realized by combination with any of Aspects 1 to 23. In Aspect 24, the retainer 38 overlaps with 10% to 80% of the inner region surrounded by the outer periphery of the stator 53 when viewed from the axis 60 direction.

[0136] According to Aspect 24, it becomes easier to maintain the strength of the retainer 38 and to reduce the weight of the retainer 38.

[0137] Aspect 25 can be realized by combination with any of Aspects 1 to 24. In Aspect 25, the electric bicycle 1 includes the motor unit 3 of any of Aspects 1 to 24.

[0138] According to Aspect 25, it is no longer necessary for the transmission rotating shaft 90 to be located between the left and right ends of the case 4, and it becomes easier to miniaturize the transmission rotating shaft 90 and the case 4.

Explanation of Reference Numerals

[0139] 1 Electric bicycle 191 Sprocket 3 Motor unit 34 Input shaft rotation detector 341 First rotating body 35 Control board 36 Motor rotation detector 361 Second rotating body 38 Retainer 4 cases 41 First divided body 42 Second divided body 43 Motor housing part 430 Motor housing space 431 Inner surface 432 Rear wall surface 433 Step part 5 Motor 51 Rotation axis 52 Rotor 53 Stator 6 Input shaft 60 Axis line 8 Output body 801 Manpower driving force output body 802 Output body 9 Speed reducer 90 Rotation axis (transmission rotation axis) 932 Bearing

Claims

1. A case, a motor having a rotor and a stator, the stator being housed in a motor housing space within the case, an output body rotatably disposed about an axis, a speed reduction mechanism housed within the case for reducing the rotation of the motor and transmitting it to the output body, a retainer housed within the case and having a holding portion for holding bearings that support the rotation shafts of the gears of the speed reduction mechanism, at least a part of the retainer overlaps at least a part of the motor when viewed in the axial direction, the bearing is disposed radially inward of the rotation shaft relative to the gear and at a position overlapping at least a part of the gear when viewed in the radial direction, An electric bicycle motor unit.

2. The retainer is attached to a thick-walled portion of the case on the side where the motor housing space is located in the axial direction within the case. The electric bicycle motor unit according to Claim 1.

3. Further comprising a control board having a control portion for controlling the motor, at least a part of the retainer is located between the speed reduction mechanism and the control board The electric bicycle motor unit according to Claim 1 or 2.

4. At least a part of the retainer is the holding portion. The electric bicycle motor unit according to Claim 3.

5. Further comprising a motor rotation detection portion mounted on the control board for detecting the rotation state of the motor. The electric bicycle motor unit according to Claim 3.

6. The case is divided into a first divided body and a second divided body in the axial direction, The retainer is attached to the first divided body and the second divided body. The electric bicycle motor unit according to any one of Claims 1 to 5.

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