Motor units and electric bicycles

Abstract

To provide a motor unit that has enhanced quietness and durability, and to provide an electric bicycle including the same.SOLUTION: A motor unit 3 used for an electric bicycle includes: a crankshaft 6 driven by human power; a motor 5 with a motor shaft 51; an output body 8 for outputting rotation of the crankshaft 6; and a speed reduction mechanism 4 for transmitting rotation of the motor shaft 51 while reducing the speed thereof. The speed reduction mechanism 4 includes: a drive gear 413 rotating integrally with the motor shaft 51; and a driven gear 415 meshing with the drive gear 413. At least the driven gear 415 of the speed reduction mechanism 4 is made of a material that is polyacetal.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 describes an electric bicycle (electrically assisted bicycle) equipped with a motor unit. In this motor unit, a motor and a reduction mechanism are housed in a unit case that serves as an outer shell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 009995 Summary of the Invention [Problem to be solved by the invention]

[0004] The motor unit described above has room for improvement in terms of quietness and durability.

[0005] An object of the present disclosure is to provide a motor unit with improved quietness and durability, and an electric bicycle equipped with the same. [Means for solving the problem]

[0006] A motor unit according to one aspect of the present disclosure is a motor unit for use in an electric bicycle, and includes a crankshaft driven by human power, a motor having a motor shaft, an output body that outputs the rotation of the crankshaft, and a speed reduction mechanism that reduces the rotation of the motor shaft and transmits it to the output body. The speed reduction mechanism includes a drive gear that rotates integrally with the motor shaft, and a driven gear that meshes with the drive gear. At least the driven gear of the speed reduction mechanism is made of polyacetal.

[0007] An electric bicycle according to one aspect of the present disclosure comprises the motor unit according to the one or more aspects described above, and a wheel to which the rotational force of the motor of the motor unit is transmitted. Effect of the Invention

[0008] The present disclosure has an effect of providing a motor unit with improved quietness and durability, and an electric bicycle equipped with the same. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an electric bicycle according to one embodiment. [Diagram 2] FIG. 2 is a side view of a main part of a motor unit provided in the electric bicycle. [Diagram 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a cross-sectional view of a first modified example of the motor unit. [Diagram 5] FIG. 5 is a cross-sectional view of a second modified example of the motor unit. [Figure 6] FIG. 6 is a cross-sectional view of a third modified example of the motor unit. [Figure 7] FIG. 7 is a cross-sectional view of a fourth modified example of the motor unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [One embodiment] (Overall configuration of electric bicycle) The electric bicycle 1 of one embodiment is an electrically assisted bicycle. The electric bicycle 1 of one embodiment includes a frame 10, a motor unit 3 fixed to the frame 10, and two wheels 11 rotatably connected to the frame 10. The two wheels 11 are a front wheel 111 and a rear wheel 112. Of these, the rear wheel 112 is rotated by the driving force output from the motor unit 3.

[0011] The front, rear, left and right directions used in this document are defined based on the rider of the electric bicycle 1. In other words, the direction in which the rider rides the electric bicycle 1 is forward, the opposite side is rear, the left direction as seen from the rider is the left side, and the right direction as seen from the rider is the right side. Each configuration will be described in detail below.

[0012] (Frame) As shown in FIG. 1, 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 .

[0013] The frame 10 (i.e., each of the above-mentioned components constituting the frame 10) is made of a metal such as aluminum or stainless steel, but may contain a non-metallic material in part. The entire frame 10 may be made of a non-metallic material, and the material of the frame 10 is not particularly limited.

[0014] A handle post 12 is rotatably inserted through the head pipe 101. 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.

[0015] The front end of an upper pipe 102 is fixed to the head pipe 101. The rear end of the upper pipe 102 is fixed to a stand pipe 104. A pipe 132 extending downward from the saddle 13 is inserted into the upper end opening of the stand pipe 104. The saddle 13 is fixed by fixing this pipe 132 to the stand pipe 104. A bracket 107 is fixed to the lower end of the stand pipe 104.

[0016] A front end of a lower pipe 103 is further fixed to the head pipe 101. A bracket 107 is fixed to the rear end of the lower pipe 103.

[0017] The motor unit 3 is fixed to the underside of the bracket 107. The front end of the chain stay 106 is fixed to the rear end of the bracket 107.

[0018] The front end of a seat stay 105 is fixed to the rear end of the upper pipe 102. The rear end of the seat stay 105 is connected to the rear end of a chain stay 106, and a rear wheel 112 is rotatably attached to this connection. A battery 15 for supplying power to the motor unit 3 is detachably attached to the lower pipe 103.

[0019] (Motor unit) Next, the motor unit 3 will be described.

[0020] As shown in Fig. 2, the main part of the outer shell of the motor unit 3 is formed by a unit case 9. A motor 5, which is a drive source for driving and rotating the wheels 11, is attached to the unit case 9. As shown in Fig. 3, the unit case 9 accommodates the motor 5, a control board 35 for controlling the rotation of the motor 5, as well as a crankshaft 6, an input body 7, an output body 8, a reduction mechanism 4, etc.

[0021] (Unit case) The unit case 9 includes a first divided body 91 that forms one half of the unit case 9 in the left-right direction, a second divided body 92 that forms another half of the unit case 9 in the left-right direction, and an intermediate member 93 that is sandwiched between the first divided body 91 and the second divided body 92. The intermediate member 93 and the control board 35 are housed in a hollow portion that is formed by combining the first divided body 91 and the second divided body 92.

[0022] The intermediate member 93 is a separate member from the first divided body 91 and the second divided body 92, but may be formed integrally with the first divided body 91 or the second divided body 92.

[0023] A soft thermally conductive member 95 is disposed between the control board 35 and the second divided body 92. The second divided body 92 includes a heat dissipation portion 925 that protrudes inward, and a plate-shaped thermally conductive member 95 abuts against this heat dissipation portion 925. The heat dissipation portion 925 has a shape that is recessed inward from the surrounding portion of the second divided body 92, and the thermally conductive member 95 abuts against the bottom portion of the heat dissipation portion 925.

[0024] When viewed in the axial direction of the motor shaft 51, the heat dissipation portion 925 and the thermally conductive member 95 are within the range of an outer shape of the stator 53 described below. When viewed in the axial direction of the motor shaft 51, the thermally conductive member 95 is located at a position where at least a part of it overlaps with the stator 53.

[0025] In one embodiment of the motor unit 3, the heat dissipation section 925 and the thermally conductive member 95 are provided only on one thickness side of the control board 35 (the side facing the second division 92), but they may be provided on both thickness sides (i.e., both the side facing the second division 92 and the side facing the first division 91).

[0026] (motor) The motor 5 has a cylindrical motor shaft 51 , a rotor 52 coupled to the motor shaft 51 so as to rotate integrally with the motor shaft 51 , and a cylindrical stator 53 positioned to surround the rotor 52 .

[0027] A recess 912 for disposing a bearing 551 is formed on the inner surface of the first divided body 91. The bearing 551 is a bearing that rotatably supports the first axial end 511 of the motor shaft 51. The intermediate member 93 is formed with a through hole 931 through which the motor shaft 51 is inserted, and a recess 932 for disposing the bearing 551. The recess 932 is formed on the inner circumferential surface of the through hole 931. The bearing 552 rotatably supports an axial intermediate portion 515 of the motor shaft 51.

[0028] In the motor unit 3 of one embodiment, the second axial end 512 of the motor shaft 51 is not supported by a bearing. The first end 511 and the second end 512 of the motor shaft 51 are positioned opposite to each other in the axial direction.

[0029] For the sake of distinction, the bearing 551 and the bearing 552 will be referred to as a first bearing 551 and a second bearing 552 below. The first bearing 551 and the second bearing 552 are both ring-shaped deep groove ball bearings.

[0030] The inner diameter of the second bearing 552 is set to be larger than the inner diameter of the first bearing 551. The inner diameter of the first bearing 551 is preferably set within a range of 7 mm to 8 mm, for example, 7 mm or 8 mm. The inner diameter of the second bearing 552 is preferably set within a range of 10 mm to 12 mm, for example, 10 mm, 11 mm, or 12 mm. The inner diameter of the second bearing 552 is preferably smaller than the outer diameter of the first bearing 551.

[0031] The distance between the second bearing 552 and a first stage driving gear 413 described later is closer than the distance between the first bearing 551 and the first stage driving gear 413 .

[0032] In this way, of the first bearing 551 and the second bearing 552, the second bearing 552 which is closer to the driving gear 413 (and the driven gear 415 described below) is a relatively large bearing having a larger inner diameter than the first bearing 551, which has the advantage of increasing the rigidity of the entire structure supporting the motor shaft 51 and improving the accuracy of meshing between the first stage driving gear 413 and the driven gear 415.

[0033] In addition, since the inner diameter of the second bearing 552 is smaller than the outer diameter of the first bearing 551, the rigidity of the entire structure that supports the motor shaft 51 can be increased as described above, while making the motor unit 3 more compact.

[0034] (Crankshaft) The crankshaft 6 is rotatable about its own axis while being housed in the unit case 9. The first divided body 91 is formed with a through hole 911 through which the crankshaft 6 is inserted. The second divided body 92 is formed with a through hole 921 through which the crankshaft 6 is inserted.

[0035] Crank arms 18 (see FIG. 1) are fixed to both ends of the crankshaft 6. Pedals 181 are rotatably attached to the tips of the crank arms 18. The rider can apply manual rotational force to the crankshaft 6 by pedaling the pedals 181.

[0036] (Input body) The input body 7 is disposed along the outer circumferential surface of the crankshaft 6 inside the unit case 9. The input body 7 is a cylindrical member, and rotates integrally with the crankshaft 6.

[0037] The input body 7 is divided into a first input body 71 and a second input body 72. The second input body 72 is connected to the crankshaft 6 within the second divided body 92. The first input body 71 is connected to the output body 8 via a one-way clutch within the first divided body 91, and is configured to transmit rotational force to the output body 8. In the motor unit 3 of one embodiment, the first input body 71 and the second input body 72 are configured as separate bodies, but the first input body 71 and the second input body 72 may be configured as an integral body.

[0038] (Output body) The output body 8 is a cylindrical member, and is rotatably disposed along the outer circumferential surface of the crankshaft 6. One end of the output body 8 passes through a through hole 911 of the first divided body 91 and protrudes to the outside of the unit case 9.

[0039] A front sprocket 191 is fixed to a portion of the output body 8 that protrudes from the unit case 9. The front sprocket 191 rotates integrally with the output body 8. As shown in FIG. 1, 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.

[0040] 3, the output body 8 integrally has a web 81 and a rim 82. The web 81 protrudes radially outward from the output body 8. The rim 82 is continuous with the radially outer end of the web 81. The rim 82 is mechanically connected to the reduction mechanism 4, so that the rotational force of the reduction mechanism 4 is transmitted to the output body 8.

[0041] (Deceleration mechanism) The reduction mechanism 4 is configured to reduce the rotation of the motor 5 and transmit it to the output body 8. The reduction mechanism 4 is a three-stage parallel shaft gear type reduction mechanism including a first-stage reduction section 41, a first reduction shaft 45, a second-stage reduction section 42, a second reduction shaft 47, and a third-stage reduction section 43. Within the unit case 9, the motor shaft 51, the first reduction shaft 45, the second reduction shaft 47, and the crankshaft 6 are positioned parallel to one another.

[0042] Here, the number of reduction stages of the reduction mechanism 4 in the present application will be defined.

[0043] The number of reduction stages of the reduction mechanism 4 is the number of parts (i.e., reduction sections) in the power transmission path from the motor shaft 51 to the output body 8 where the rotation speed is reduced. The reduction section includes a plurality of rotating bodies connected to be capable of transmitting power, and the reduction in the rotation speed is realized when the rotation is transmitted through the plurality of rotating bodies. The rotating bodies may be, for example, gears, sprockets, etc. The plurality of rotating bodies may transmit the rotation by contacting each other, or may transmit the rotation via a power transmission body such as a chain or belt. Based on the above definition, the reduction mechanism 4 provided in the motor unit 3 in one embodiment is a three-stage reduction mechanism having three reduction sections (i.e., first-stage, second-stage, and third-stage reduction sections 41, 42, 43).

[0044] (First stage reduction section) The first-stage reduction gear portion 41 includes a first-stage driving gear 413 that rotates integrally with the motor shaft 51 , and a first-stage driven gear 415 that meshes with the first-stage driving gear 413 .

[0045] The first-stage drive gear 413 is configured with teeth formed by plastic processing a part of the metal motor shaft 51. The first-stage drive gear 413 is made of metal.

[0046] The motor shaft 51 includes a first end 511 supported by a first bearing 551, an intermediate portion 515 supported by a second bearing 552, and a portion 513 that is farther from the first end 511 than the intermediate portion 515, and a first stage drive gear 413 is formed on the outer peripheral surface of this portion 513 by plastic processing.

[0047] The plastic processing is, for example, forging or rolling. These plastic processing methods provide better surface roughness than the case where the driving gear 413 is formed by cutting the motor shaft 51. This reduces frictional resistance between the first-stage driving gear 413 and the driven gear 415, which reduces noise during driving and wear of the driven gear 415.

[0048] The first stage drive gear 413 is preferably shot peened, air blasted or coated.

[0049] Examples of shot peening include hard shot peening, semi-hard shot peening, WPC treatment, molybdenum disulfide shot peening, and Sirius processing. By subjecting the surface of the drive gear 413 to shot peening, the surface roughness of the drive gear 413 is improved and the surface slipperiness of the drive gear 413 is increased, so that the frictional resistance between the first-stage drive gear 413 and the driven gear 415 is reduced, and the effects of suppressing noise during driving and suppressing wear of the driven gear 415 are obtained. In addition, the wear resistance of the drive gear 413 is improved, and heat generation at the meshing portion between the drive gear 413 and the driven gear 415 is suppressed.

[0050] Air blasting includes, for example, air blasting using #100 media and air blasting using #400 media. By performing air blasting on the surface of the drive gear 413, the surface roughness of the drive gear 413 is improved and the slipperiness of the surface of the drive gear 413 is increased, so that the frictional resistance between the first-stage drive gear 413 and the driven gear 415 is reduced, and the effects of suppressing noise during driving and suppressing wear of the driven gear 415 are obtained.

[0051] Coatings include DLC (Diamond-Like Carbon) coating, Teflon (registered trademark) coating, dry lube treatment, alumite treatment, hard alumite treatment, molybdenum disulfide coating, and various plating treatments. Various plating treatments include, for example, hard chrome plating, electrolytic hard chrome carbide plating, trivalent chromate plating, nickel plating, electroless nickel plating, fluorine composite electroless nickel plating, fluorine composite electroless nickel plating, and Parker treatment.

[0052] By applying the above-mentioned coating to the surface of the drive gear 413, the surface roughness of the drive gear 413 is improved and the slipperiness of the surface of the drive gear 413 is increased, thereby reducing the frictional resistance between the first-stage drive gear 413 and the driven gear 415, thereby suppressing noise during driving and wear of the driven gear 415.

[0053] Next, the first stage driven gear 415 will be described.

[0054] The first-stage driven gear 415 is a member that meshes with the first-stage driving gear 413 and thereby rotates by receiving the rotational driving force of the motor shaft 51. The first-stage driven gear 415 has an outer circumferential surface formed with a plurality of teeth that mesh with the first-stage driving gear 413.

[0055] The first-stage driven gear 415 is a gear molded into a cylindrical shape using resin as a material. Specifically, the resin is polyacetal, but other resins such as nylon can also be used.

[0056] Polyacetal is a material having self-lubricating properties. By molding the first-stage driven gear 415 from polyacetal, wear of the driven gear 415 is suppressed, and the effects of suppressing noise during driving and increasing durability are obtained. In particular, in the first-stage reduction section 41 having a high rotation speed in the reduction mechanism 4, by making the driven gear 415 included therein from polyacetal, the effects of effectively suppressing the noise of the entire reduction mechanism 4 and effectively increasing the durability of the entire reduction mechanism 4 are obtained.

[0057] Generally, the driven gear included in a reduction mechanism tends to be large in diameter and heavy, but in the motor unit 3 of one embodiment, the driven gear 415 is molded from a resin such as polyacetal, thereby realizing a reduction in weight of the reduction mechanism 4 and, in turn, a reduction in weight of the entire electric bicycle 1. In addition, the reduction in weight of the driven gear 415 reduces the rotational moment of the driven gear 415, realizing agile operation when driving the electric bicycle 1 by the motor 5.

[0058] Here, assuming that driven gear 415 is made of nylon, in comparison, if driven gear 415 is made of polyacetal, there are advantages in that durability is further improved and that it can be provided at a relatively low cost.

[0059] Polyacetal is classified into two types, homopolymer and copolymer, based on its molecular structure. Either type of polyacetal, homopolymer or copolymer, can be used as the material for the driven gear 415.

[0060] A metallic first reduction shaft 45 is fixed to the inner peripheral surface of the first-stage driven gear 415. A first end 451 of the first reduction shaft 45 is rotatably supported by a bearing 461 arranged in the intermediate member 93. A second end 452 of the first reduction shaft 45 is rotatably supported by a bearing 462 arranged in the second divided body 92. Both the bearing 461 and the bearing 462 are ring-shaped deep groove ball bearings. The inner diameters of the bearing 461 and the bearing 462 are the same, and the outer diameters of the bearing 461 and the bearing 462 are the same.

[0061] When viewed in a direction perpendicular to the axial direction of the crankshaft 6 and the motor shaft 51, the bearing 461 is disposed so that at least a portion of it overlaps with the control board .

[0062] The metallic first reduction shaft 45 functions as a core inserted into the resin driven gear 415, which further increases the strength of the resin driven gear 415. The material of the driven gear 415 is polyacetal, which has lower heat resistance compared to nylon and the like, but the heat dissipation of the driven gear 415 is increased via the metallic first reduction shaft 45. The first reduction shaft 45 and the driven gear 415 may be provided by integral molding such as insert molding, or the first reduction shaft 45 may be provided by press-fitting into a through hole of the driven gear 415.

[0063] The above-described drive gear 413 and driven gear 415 constitute the first-stage reduction gear section 41. In the following, the structures of the first-stage drive gear 413 and driven gear 415 will be described in more detail.

[0064] The first-stage drive gear 413 and driven gear 415 are helical gears that mesh with each other. The drive gear 413 and driven gear 415 being helical gears has the advantage of increasing the meshing ratio of the first-stage reduction gear unit 41 (i.e., the meshing ratio between the drive gear 413 and the driven gear 415). In addition, the material of the driven gear 415 is polyacetal, which has a property of being less heat resistant than nylon and the like, but since the driven gear 415 is a helical gear, it is easier to stir up the surrounding air while the driven gear 415 is rotating, which has the advantage of increasing the heat dissipation of the driven gear 415.

[0065] The driving gear 413 and the driven gear 415 are preferably helical gears designed to have a helix angle in the range of 20° to 25°, but the helix angle can be set within other ranges. The helix angle of the helical gear is preferably set to 10° or more, but is also preferably set to 15° or more, 20° or more, or 25° or more. However, if the helix angle is too large, the driven gear 415 may tip over, so the helix angle is preferably set to 45° or less. In other words, the helix angle is preferably set in the range of 10° to 45°, and more preferably set in the range of 20° to 25°.

[0066] The width of the meshing portion of the first-stage reduction gear 41 (i.e., the meshing portion between the drive gear 413 and the driven gear 415) is set within a range of 15 mm to 20 mm. Here, the width means the width in the axial direction of the motor shaft 51. The width of the meshing portion of the first-stage reduction gear 41 is preferably set to 10 mm or more, but is also preferably set to 15 mm or more, or 20 mm or more. The width of the meshing portion of the first-stage reduction gear 41 is preferably set to 25 mm or less.

[0067] The module of the first stage driving gear 413 is set to 0.8 mm or more. The module is calculated by dividing the reference circle diameter of the gear by the number of teeth. The larger the module, the larger the dimension of each tooth is set under the same reference circle diameter of the driving gear 413, so that the teeth of the driving gear 413 and the driven gear 415 are less likely to break and their strength is increased.

[0068] The number of teeth of the first stage drive gear 413 is 6 or less and 2 or more. That is, the number of teeth of the first stage drive gear 413 can be 6, 5, 4, 3, or 2. It is also preferable to set the number of teeth of the drive gear 413 to 5 or less, or 4 or less. The smaller the number of teeth, the larger the dimension of each tooth is set under the condition that the reference circle diameter of the drive gear 413 is the same, so that the teeth of the drive gear 413 and the driven gear 415 are less likely to break and their strength is increased.

[0069] The reduction ratio of the first-stage reduction section 41 is set, for example, within a range from 6 to 7. The reduction ratio of the first-stage reduction section 41 is preferably set to 10 or less, and more preferably set to 9 or less, 8 or less, 7 or less, or 6 or less. The smaller the reduction ratio of the first-stage reduction section 41, the smaller the surface pressure per tooth of the drive gear 413 and the driven gear 415 becomes, making the teeth of the drive gear 413 and the driven gear 415 less likely to break and increasing their strength.

[0070] (Second stage reduction section) The second stage reduction portion 42 includes a second stage driving gear 423 that rotates integrally with the first reduction shaft 45 , and a second stage driven gear 425 that meshes with the second stage driving gear 423 .

[0071] The second-stage drive gear 423 is configured by teeth formed on the outer circumferential surface of the metallic first reduction shaft 45. The second-stage drive gear 423 can be formed by cutting or plastic processing of the first reduction shaft 45. The plastic processing is, for example, forging or rolling.

[0072] The second-stage driven gear 425 is a member that meshes with the second-stage driving gear 423 and rotates by receiving the rotational driving force of the first reduction shaft 45. The second-stage driven gear 425 has an outer circumferential surface formed with a plurality of teeth that mesh with the second-stage driving gear 423.

[0073] The second-stage driven gear 425 is a gear formed into a cylindrical shape using metal as a material. A metal second reduction shaft 47 is fixed to the inner peripheral surface of the second-stage driven gear 425. A first end 471 of the second reduction shaft 47 is rotatably supported by a bearing 481 arranged in the first division body 91. A second end 472 of the second reduction shaft 47 is rotatably supported by a bearing 482 arranged in the second division body 92. Both the bearing 481 and the bearing 482 are ring-shaped deep groove ball bearings. The inner diameter of the bearing 481 is set to be larger than the inner diameter of the bearing 482.

[0074] In the axial direction of the first reduction shaft 45, the control board 35 is located between the stator 53 of the motor 5 and the first-stage driven gear 415 and the second-stage reduction unit 42. More specifically, the control board 35 is located between the end of the stator 53 close to the second-stage reduction unit 42 (the driving gear 423 and the driven gear 425) and the end of the first-stage driven gear 415 close to the second-stage reduction unit 42 (the driving gear 423 and the driven gear 425). The end of the stator 53 here means the end of the outermost member among the members such as the teeth, windings, and laminated core that constitute the stator 53. With the above arrangement, the space in the motor unit 3 is effectively utilized, and the occurrence of dead space is suppressed. As a result, the motor unit 3 can be made smaller.

[0075] (Third stage reduction section) The third-stage reduction section 43 includes a third-stage driving gear 433 that rotates integrally with the second reduction shaft 47, and a third-stage driven gear 435 that meshes with the third-stage driving gear 433. The third-stage driving gear 433 is connected to the second reduction shaft 47 via a one-way clutch 44. The one-way clutch 44 is a clutch mechanism configured to transmit a rotational force only in one direction. The one-way clutch 44 is configured to transmit a rotational force in the direction in which it rotates in association with the rotational drive of the motor shaft 51, and to block the transmission of the rotational force in the opposite direction.

[0076] The third-stage driven gear 435 is integrally formed on the outer circumferential surface of the rim 82 of the output body 8. The third-stage driven gear 435 is configured to mesh with the third-stage driving gear 433, thereby receiving the rotational driving force of the second reduction shaft 47 and rotating. The third-stage driven gear 435 has a plurality of teeth formed thereon to mesh with the third-stage driving gear 433.

[0077] In the output body 8, the rotational force of the motor 5, which has been reduced in speed and transmitted via the reduction mechanism 4, and the rotational force of the crankshaft 6 due to human power are combined.

[0078] (Motor unit operation) Since the motor unit 3 in one embodiment has the above-mentioned configuration, when the crankshaft 6 rotates as a result of the rider pedaling the pedals 181 of the electric bicycle 1, the first input body 71 and the second input body 72 rotate integrally with the crankshaft 6. When the rotational force of the second input body 72 is transmitted to the output body 8, the output body 8 and the front sprocket 191 rotate. When the front sprocket 191 rotates, the rear sprocket 192 rotates via the chain 193, and the rear wheel 112 is driven to rotate.

[0079] Moreover, in the motor unit 3 of one embodiment, it is possible to apply the rotational force output from the motor 5 to the output body 8, as will be described below.

[0080] When the motor shaft 51 of the motor 5 rotates, the first-stage drive gear 413 and the driven gear 415 rotate while meshing with each other, and thus the first reduction shaft 45 rotates. When the first reduction shaft 45 rotates, the second-stage drive gear 423 and the driven gear 425 rotate while meshing with each other, and thus the second reduction shaft 47 rotates.

[0081] The rotational force of the second reduction shaft 47 is transmitted to the third-stage driving gear 433 and the driven gear 435 via the one-way clutch 44, and is then transmitted to the output body 8. The rotational force from the motor 5 and the rotational force generated by the driver pedaling the pedals 181 are transmitted to the output body 8 so as to be combined with each other.

[0082] In one embodiment of the motor unit 3, the reduction mechanism 4 is a three-stage parallel shaft gear type reduction mechanism including a first-stage reduction section 41, a first reduction shaft 45, a second-stage reduction section 42, a second reduction shaft 47, and a third-stage reduction section 43, of which a one-way clutch 44 is attached to the second reduction shaft 47. Therefore, when the electric bicycle 1 is traveling with the motor 5 stopped, many of the members included in the reduction mechanism 4 are prevented from rotating. The rider can feel a light ride when traveling with the motor 5 stopped.

[0083] In one embodiment of the electric bicycle 1, a control unit included in a control board 35 controls the rotation of the motor 5 in accordance with the torque applied to the crankshaft 6 and the number of rotations per unit time of the crankshaft 6. The torque applied to the crankshaft 6 is detected by a magnetostrictive torque detector 33 housed in the unit case 9.

[0084] The torque detector 33 is not limited to the magnetostrictive type, and other sensing types may be used, such as a type using a strain sensor or a pressure sensor, or a mechanical type using a torsion bar or a potentiometer.

[0085] The number of rotations per unit time of the crankshaft 6 is detected by the rotation detector 34. The rotation detector 34 is an optical rotation detector including a rotor 341 that rotates integrally with the input body 7, and an optical sensor 342 that is positioned at a small distance from the rotor 341.

[0086] The control unit of the control board 35 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). As this control unit, a known one can be appropriately used.

[0087] In one embodiment, the overall reduction ratio of the reduction mechanism 4 is set, for example, within a range from 30 to 35. The overall reduction ratio of the reduction mechanism 4 is preferably set to 40 or less, and more preferably set to 30 or less, 25 or less, or 20 or less. The smaller the overall reduction ratio of the reduction mechanism 4, the smaller the surface pressure per tooth of each gear included in the reduction mechanism 4, reducing wear and improving durability.

[0088] [Variations] Next, various modified examples of the motor unit 3 of one embodiment and the electric bicycle 1 equipped with the same will be described. Note that in the various modified examples described below, the same components as those already described will be denoted by the same reference numerals, and detailed description thereof will be omitted.

[0089] 4 is a cross-sectional view showing a first modified example of the motor unit 3 of the embodiment. In the first modified example, the position of the one-way clutch 49 incorporated in the reduction gear mechanism 4 differs from the position of the one-way clutch 44 shown in FIG.

[0090] That is, in the motor unit 3 of one embodiment, the one-way clutch 44 that functions to cut off the transmission of power in the reduction mechanism 4 when the motor 5 is stopped is interposed between the third-stage driving gear 433 and the second reduction shaft 47, whereas in the first modified example, the one-way clutch 49 that functions to cut off the transmission of power in the reduction mechanism 4 when the motor 5 is stopped is interposed between the second-stage driven gear 425 and the second reduction shaft 47. The one-way clutch 49 is configured to transmit a rotational force in the direction of rotation associated with the rotational drive of the motor shaft 51 and to cut off the transmission of the rotational force in the opposite direction.

[0091] In the first modified example, the reduction mechanism 4 is also a three-stage parallel shaft gear type reduction mechanism including a first-stage reduction section 41, a first reduction shaft 45, a second-stage reduction section 42, a second reduction shaft 47, and a third-stage reduction section 43, of which a one-way clutch 49 is attached to the second reduction shaft 47. Therefore, when the electric bicycle 1 is traveling with the motor 5 stopped, the rotation of many of the members included in the reduction mechanism 4 is suppressed. The rider can feel a lighter ride when traveling with the motor 5 stopped.

[0092] 5 is a cross-section showing a second modified example of the motor unit 3 of the embodiment. In the second modified example, a portion 94 of the unit case 9 that covers the stator 53 of the motor 5 is provided separately from the first divided body 91 and the second divided body 92. This portion 94 is formed into a cup shape using, for example, metal, and its opening edge portion is fixed to the first divided body 91. A second bearing 552 that rotatably supports an axial intermediate portion 515 of the motor shaft 51 and a bearing 461 that rotatably supports a first end portion 451 of the first reduction shaft 45 are disposed in the first divided body 91.

[0093] In addition, in the second modified example, when viewed in a direction perpendicular to the axial direction of the motor shaft 51, the bearing 552 supporting the middle portion of the motor shaft 51 and the bearing 461 supporting the end portion of the first reduction shaft 45 are arranged to at least partially overlap.

[0094] In the second modified example, the inner diameter of a bearing 481 arranged in the first split body 91 to support the first end 471 of the second reduction shaft 47 is set to be smaller than the inner diameter of a bearing 482 arranged in the second split body 92 to support the second end 472 of the second reduction shaft 47. The inner diameters of the bearings 481 and 482 may be set to be the same.

[0095] In the second modified example, in addition to disposing a thermally conductive member 95 between the control board 35 and the second divided body 92, a soft thermally conductive member 96 is disposed between the control board 35 and the first divided body 91. The first divided body 91 includes a heat dissipation portion 915 that protrudes inward, and a plate-shaped thermally conductive member 96 abuts against this heat dissipation portion 915. The heat dissipation portion 915 has a flat plate shape parallel to the control board 35, and the thermally conductive member 96 is sandwiched between the heat dissipation portion 915 and the control board 35.

[0096] When viewed in the axial direction of motor shaft 51, thermally conductive members 95, 96 and heat dissipation portions 925, 915 arranged on both sides of control board 35 in the thickness direction are within the outer shape of stator 53. When viewed in the axial direction of motor shaft 51, thermally conductive members 95, 96 are positioned so that at least a portion of them overlaps with stator 53.

[0097] 6 is a cross-sectional view showing a third modified example of the motor unit 3 of the embodiment. The basic configuration of the third modified example is the same as that of the second modified example, but in the third modified example, the position of the one-way clutch 495 incorporated in the reduction gear mechanism 4 differs from the position of the one-way clutch 44 in the second modified example.

[0098] Specifically, one-way clutch 495, which functions to cut off the transmission of power within reduction mechanism 4 when motor 5 is stopped, is mounted coaxially with crankshaft 6 so as to be interposed between output body 8 and third-stage driven gear 435. One-way clutch 495 is configured to transmit rotational force in the direction of rotation accompanying the rotational drive of motor shaft 51 and to cut off the transmission of rotational force in the opposite direction.

[0099] In the above embodiment and the first to third modified examples, the motor unit 3 includes a three-stage parallel shaft gear type reduction mechanism 4, but the reduction mechanism 4 is not limited to a three-stage reduction mechanism and may be a one-stage, two-stage, or four-stage reduction mechanism. In any case, the driven gear provided to mesh with the drive gear that rotates integrally with the motor shaft is made of polyacetal, which provides the effects of suppressing noise during driving and suppressing wear of the gears.

[0100] 7 is a schematic cross-sectional view showing a fourth modified example of the motor unit 3 of an embodiment. In the fourth modified example, the reduction mechanism 4 is a two-stage reduction mechanism including a first reduction shaft 45, a first-stage reduction section 41 that reduces the rotation of the motor shaft 51 and transmits it to the first reduction shaft 45, and a second-stage reduction section 42 that reduces the rotation of the first reduction shaft 45 and transmits it to the output body 8.

[0101] Additionally, in the fourth modified example, the motor unit 3 includes a speed change mechanism 31 in addition to the reduction gear mechanism 4. The speed change mechanism 31 is a mechanism interposed between the crankshaft 6 and the input body 7, and is configured to increase the rotation of the crankshaft 6 and transmit it to the input body 7 and, in turn, to the output body 8. The speed change mechanism 31 is not limited to a mechanism that increases the rotation of the crankshaft 6 and transmits it, and may be configured to reduce the rotation of the crankshaft 6 and transmit it to the input body 7 and the output body 8.

[0102] In addition, in one embodiment and various modified examples, only the first-stage driven gear 415 among various gears included in the reduction gear mechanism 4 is made of polyacetal, but it is possible to use polyacetal as the material for not only the first-stage driven gear 415 but also the other gears. For example, in addition to the first-stage driven gear 415, the second-stage driven gear 425 may be formed of polyacetal, in addition to the first-stage driven gear 415, the third-stage driven gear 435 may be formed of polyacetal, or in addition to the first-stage driven gear 415, the second-stage driven gear 425 and the third-stage driven gear 435 may be formed of polyacetal.

[0103] In other words, if the reduction mechanism 4 is a three-stage reduction as in one embodiment and the first to third modified examples, it is possible to form one or both of the second and third stage driven gears 425, 435 from polyacetal in addition to the first stage driven gear 415; if the reduction mechanism 4 is a four-stage reduction, it is possible to form at least one of the second to fourth stage driven gears from polyacetal in addition to the first stage driven gear; and if the reduction mechanism 4 is a two-stage reduction as in the fourth modified example, it is possible to form the second stage driven gear 425 from polyacetal in addition to the first stage driven gear 415.

[0104] In one embodiment and various modified examples, the motor unit 3 is a so-called single-shaft motor unit in which the rotational force transmitted through the reduction mechanism 4 and the rotational force of the crankshaft 6 are combined at the output body 8 arranged on the outer periphery of the crankshaft 6, but is not limited thereto and may be a conventionally known two-shaft motor unit. The two-shaft motor unit is a type of motor unit in which the output body 8 is composed of a first output body and a second output body. In this type of motor unit, the rotational force of the crankshaft 6 is output to the first output body arranged on the outer periphery of the crankshaft 6, and the rotational force transmitted through the reduction mechanism 4 is transmitted to the second output body located away from the crankshaft 6. The rotational forces of the first output body and the second output body are finally combined via a chain or the like. The configuration of the reduction mechanism 4 in one embodiment and various modified examples can be adopted in both single-shaft and two-shaft motor units.

[0105] Moreover, the electric bicycle 1 in one embodiment is a so-called power-assisted bicycle, but is not limited thereto, and may be an electric bicycle in which the wheels 11 can be rotated only by the rotational force of the motor 5. Moreover, the electric bicycle in one embodiment has two wheels 11, but the number of wheels 11 is not particularly limited, and may have, for example, three wheels 11.

[0106] [Aspects] As is clear from the above description of one embodiment and various modified examples thereof, the motor unit (3) of the first aspect is a motor unit (3) used in an electric bicycle (1), and includes a crankshaft (6) driven by human power, a motor (5) having a motor shaft (51), an output body (8) disposed on the outer periphery of the crankshaft (6) and outputting the rotation of the crankshaft (6), and a speed reduction mechanism (4) that reduces the rotation of the motor shaft (51) and transmits it to the output body (8). The speed reduction mechanism (4) includes a drive gear (413) that rotates integrally with the motor shaft (51), and a driven gear (415) that meshes with the drive gear (413). At least the driven gear (415) of the speed reduction mechanism (4) is made of polyacetal.

[0107] In the motor unit (3) of the first embodiment, attention is focused on the driven gear (415) which has a high rotation speed among the parts of the reduction gear mechanism (4), and this driven gear (415) is made of polyacetal. Since polyacetal has high self-lubricating properties among resins, it is possible to obtain the effects of suppressing wear of the driven gear (415) which has a high rotation speed, suppressing noise during driving, and increasing durability. As a result, according to the motor unit (3) of the first embodiment, the quietness and durability of the motor unit (3) are improved.

[0108] The motor unit (3) of the second embodiment is realized by combining with the motor unit (3) of the first embodiment. In the motor unit (3) of the second embodiment, the reduction mechanism (4) is a four-stage reduction mechanism of parallel shaft gear type.

[0109] In the motor unit (3) of the second embodiment, since the reduction gear mechanism (4) has four reduction stages, the reduction ratio of each stage can be reduced, and the surface pressure per tooth of the driving gear (413) and the driven gear (415) of the first stage, which have the highest rotation speed in the reduction gear mechanism (4), is reduced. As a result, the teeth of the driving gear (413) and the driven gear (415) are less likely to break, and their strength is increased.

[0110] The motor unit (3) of the third embodiment is realized by combining with the motor unit (3) of the first embodiment. In the motor unit (3) of the third embodiment, the reduction mechanism (4) is a three-stage reduction mechanism of parallel shaft gear type.

[0111] In the motor unit (3) of the third embodiment, the reduction gear mechanism (4) has three reduction stages, and therefore the reduction ratio of each stage can be reduced. As a result, the surface pressure per tooth of the driving gear (413) and the driven gear (415) of the first stage, which have the highest rotation speed in the reduction gear mechanism (4), is reduced. As a result, the teeth of the driving gear (413) and the driven gear (415) are less likely to break, and their strength is increased.

[0112] The motor unit (3) of the fourth embodiment is realized by combining with the motor unit (3) of the first embodiment. In the motor unit (3) of the fourth embodiment, the reduction mechanism (4) is a two-stage reduction mechanism of parallel shaft gear type.

[0113] In the motor unit (3) of the fourth embodiment, since the reduction gear mechanism (4) has two reduction stages, the reduction ratio of each stage can be reduced, and the surface pressure per tooth of the driving gear (413) and the driven gear (415) of the first stage, which have the higher rotation speed in the reduction gear mechanism (4), is reduced. As a result, the teeth of the driving gear (413) and the driven gear (415) are less likely to break, and their strength is increased.

[0114] The motor unit (3) of the fifth aspect is realized by combining with the motor unit (3) of the first aspect. In the motor unit (3) of the fifth aspect, the reduction mechanism (4) is a parallel shaft gear type reduction mechanism with one reduction stage.

[0115] In the motor unit (3) of the fifth embodiment, the reduction gear mechanism (4) is a single-stage reduction mechanism, and therefore the mechanism is made compact and lightweight. Furthermore, since the driven gear (415) is made of polyacetal, wear of the drive gear (413) and the driven gear (415) is suppressed, noise during driving is suppressed, and durability is improved.

[0116] The motor unit (3) of the sixth aspect is realized by combining with any one of the first to fourth aspects. The motor unit (3) of the sixth aspect further includes a control board (35). The reduction mechanism (4) further includes a first reduction shaft (45) that rotates integrally with the driven gear (415) and a second-stage drive gear (423) that rotates integrally with the first reduction shaft (45). The motor (5) further includes a stator (53). In the axial direction of the first reduction shaft (45), the control board (35) is located between an end of the stator (53) that is closer to the second-stage drive gear (423) and an end of the driven gear (415) that is closer to the second-stage drive gear (423).

[0117] In the motor unit (3) of the sixth aspect, the space within the unit is effectively utilized and the occurrence of dead space can be suppressed, so that the motor unit (3) can be made compact.

[0118] The motor unit (3) of the seventh aspect is realized by combining with any one of the aspects 1 to 4. In the motor unit (3) of the seventh aspect, the reduction mechanism (4) further includes a first reduction shaft (45) rotating integrally with the driven gear (415), a second-stage driving gear (423) rotating integrally with the first reduction shaft (45), a second-stage driven gear (425) meshing with the second-stage driving gear (423), a second reduction shaft (47) rotating integrally with the second-stage driven gear (425), and a one-way clutch (44, 49) attached to the second reduction shaft (47).

[0119] In the motor unit (3) of the seventh aspect, the one-way clutch (44, 49) is attached to the second reduction shaft (47) instead of the first reduction shaft (45), so that the driver can feel a lighter ride when driving with the motor (5) stopped.

[0120] The motor unit (3) of the eighth aspect is realized by combining with any one of the aspects from the first to the seventh. The motor unit (3) of the eighth aspect further includes a speed change mechanism (31) that reduces or increases the speed of the rotation of the crankshaft (6) and transmits it to the output body (8).

[0121] In the motor unit (3) of the eighth embodiment, the rotation of the crankshaft (6) caused by human power can be transmitted to the output body (8) with the speed changed.

[0122] The motor unit (3) of the ninth aspect is realized by combining with any one of the aspects from 1 to 8. In the motor unit (3) of the ninth aspect, the reduction ratio of the reduction mechanism (4) is 40 or less.

[0123] In the motor unit (3) of the ninth aspect, the motor unit (3) having a reduction ratio of 40 or less can be improved in quietness and durability.

[0124] The motor unit (3) of the tenth aspect is realized by combining with any one of the first to ninth aspects. The motor unit (3) of the tenth aspect further includes a first bearing (551) and a second bearing (552) that support the motor shaft (51). The distance between the second bearing (552) and the drive gear (413) is closer than the distance between the first bearing (551) and the drive gear (413). The inner diameter of the second bearing (552) is larger than the inner diameter of the first bearing (551).

[0125] In the motor unit (3) of the tenth embodiment, the rigidity of the entire structure supporting the motor shaft (51) having a high rotation speed is increased, so that the precision of meshing between the drive gear (413) and the driven gear (415) is improved.

[0126] The motor unit (3) of the eleventh aspect is realized by combining with any one of the first to tenth aspects. In the motor unit (3) of the eleventh aspect, the drive gear (413) is formed by plastic processing a part of the motor shaft (51).

[0127] In the motor unit (3) of the eleventh aspect, a good surface roughness is obtained in the driving gear (413), which reduces frictional resistance between the driving gear (413) and the driven gear (415), suppresses noise during driving, and suppresses wear of the driven gear (415).

[0128] The motor unit (3) of the twelfth aspect is realized by combining with any one of the first to eleventh aspects. In the motor unit (3) of the twelfth aspect, the drive gear (413) is subjected to shot peening, air blasting or coating.

[0129] In the motor unit (3) of the twelfth aspect, the surface roughness of the driving gear (413) is improved and the surface slipperiness of the driving gear (413) is increased, so that the frictional resistance between the driving gear (413) and the driven gear (415) is reduced, which has the effect of suppressing noise during driving and the effect of suppressing wear of the driven gear (415). Also, in the motor unit (3) of the twelfth aspect, the effect of improving the wear resistance of the driving gear (413) and the effect of improving heat dissipation are obtained.

[0130] The motor unit (3) of the thirteenth aspect is realized by combining with any one of the aspects from the first to the twelfth aspects. In the motor unit (3) of the thirteenth aspect, the drive gear (413) and the driven gear (415) are helical gears that mesh with each other.

[0131] In the motor unit (3) of the thirteenth aspect, the meshing ratio between the drive gear (413) and the driven gear (415) is increased. In addition, the driven gear (415) is made of polyacetal, which has a relatively low heat resistance, but the driven gear (415) tends to stir the surrounding air while rotating, thereby improving the heat dissipation performance of the driven gear (415).

[0132] The motor unit (3) of the 14th embodiment is realized by combining with the motor unit (3) of the 13th embodiment. In the motor unit (3) of the 14th embodiment, the driving gear (413) and the driven gear (415) are helical gears having a helix angle within a range of 10° to 45°.

[0133] In the motor unit (3) of the fourteenth embodiment, the meshing ratio between the drive gear (413) and the driven gear (415) is increased, and the driven gear (415) is prevented from falling over due to an excessively large helix angle.

[0134] The motor unit (3) of the 15th aspect is realized by combining with any one of the aspects 1 to 14. In the motor unit (3) of the 15th aspect, the width of the meshing portion between the drive gear (413) and the driven gear (415) is set to 10 mm or more.

[0135] In the motor unit (3) of the fifteenth aspect, the meshing of the drive gear (413) and the driven gear (415) is ensured, and noise reduction and durability can be improved.

[0136] The motor unit (3) of the 16th aspect is realized by combining with any one of the aspects 1 to 15. In the motor unit (3) of the 16th aspect, the module of the drive gear (413) is 0.8 mm or more.

[0137] In the motor unit (3) of the sixteenth aspect, the dimensions of each tooth of the drive gear (413) are ensured, so that the teeth of the drive gear (413) are less likely to break, and the strength is increased.

[0138] The motor unit (3) of the 17th aspect is realized by combining with any one of the aspects 1 to 16. In the motor unit (3) of the 17th aspect, the reduction ratio of the reduction gear part (41) constituted by the driving gear (413) and the driven gear (415) is 10 or less.

[0139] In the motor unit (3) of the seventeenth aspect, the surface pressure per tooth of the speed reducer portion (41) is reduced, so that the teeth are less likely to break and strength is increased.

[0140] The motor unit (3) of the 18th aspect is realized by combining with any one of the aspects 1 to 17. In the motor unit (3) of the 18th aspect, the number of teeth of the drive gear (413) is 2 or more and 6 or less.

[0141] In the motor unit (3) of the 18th embodiment, the number of teeth of the drive gear (413) and the number of teeth of the resin driven gear (415) that meshes with it can be reduced, making the teeth of the drive gear (413) and the driven gear (415), which have high rotation speeds, less likely to break, and further increasing durability.

[0142] The motor unit (3) of the 19th aspect is realized by combining with the motor unit (3) of the 18th aspect. In the motor unit (3) of the 19th aspect, the number of teeth of the drive gear (413) is 4 or less.

[0143] In the motor unit (3) of the nineteenth aspect, the number of teeth of the drive gear (413) and the number of teeth of the resin driven gear (415) meshing therewith can be further reduced, thereby improving durability.

[0144] The motor unit (3) of the 20th aspect is realized by combining with any one of the first to 19th aspects. In the motor unit (3) of the 20th aspect, the output body (8) is a member that combines the rotational force transmitted through the reduction gear mechanism (4) and the rotational force of the crankshaft (6).

[0145] In the motor unit (3) of the twentieth aspect, the quietness and durability are improved in the so-called single-shaft motor unit (3).

[0146] The electric bicycle (1) of the first aspect comprises a motor unit (3) of any one of the first to twentieth aspects and a wheel (11) to which the rotational force of the motor (5) of the motor unit (3) is transmitted.

[0147] In the electric bicycle (1) of the first aspect, the quietness and durability of the motor unit (3) are improved. [Explanation of symbols]

[0148] 1. Electric bicycle 3 Motor unit 4 Reduction mechanism 5 Motor 6 Crankshaft 8 Output Body 11 wheels 31 Transmission mechanism 35 Control Board 41 Reduction section 44 One-way clutch 45 1st reduction axis 47 2nd reduction axis 49 One-way clutch 51 Motor shaft 53 Stator 413 Drive Gear 415 Driven Gear 423 2nd stage drive gear 425 2nd stage driven gear 551 First bearing 552 Second bearing

Claims

1. A motor unit for use in an electric bicycle, The unit case and A crankshaft driven by human power; a motor having a motor shaft; an output body that outputs the rotation of the crankshaft; a reduction mechanism that reduces the rotation speed of the motor shaft and transmits the reduced rotation speed to the output body, The reduction mechanism includes: a drive gear for transmitting rotational force from the motor to a meshing gear; A driven gear that meshes with the drive gear; A reduction shaft that rotates integrally with the driven gear; A one-way clutch; and another drive gear connected to the outer diameter side of the reduction shaft via the one-way clutch, At least the driven gear of the reduction mechanism is made of polyacetal, The reduction shaft is made of metal and is fixed to the inner peripheral surface of the driven gear. Motor unit.

2. A motor unit for use in an electric bicycle, The unit case and A crankshaft driven by human power; a motor having a motor shaft; an output body that outputs the rotation of the crankshaft; a reduction mechanism that reduces the rotation speed of the motor shaft and transmits the reduced rotation speed to the output body, The reduction mechanism includes: a drive gear for transmitting rotational force from the motor to a meshing gear; A rotation shaft that rotates integrally with the drive gear; A driven gear that meshes with the drive gear; A one-way clutch; a reduction shaft connected to an inner diameter side of the driven gear via the one-way clutch; Including, At least the driven gear of the reduction mechanism is made of polyacetal. Motor unit.

3. The rotation axis of the reduction shaft and the rotation axis of the output body are different, The motor unit according to claim 1 or 2.

4. The reduction mechanism is a three-stage parallel shaft gear type reduction mechanism. A motor unit according to any one of claims 1 to 3.

5. The reduction mechanism is a two-stage parallel shaft gear type reduction mechanism. A motor unit according to any one of claims 1 to 3.

6. The unit case has a first divided body and a second divided body, an intermediate member is accommodated in a hollow portion formed by combining the first divided body and the second divided body; A first bearing that rotatably supports the motor shaft is disposed in the intermediate member. A motor unit according to any one of claims 1 to 5.

7. A second bearing is disposed in the intermediate member to rotatably support the first end of the reduction shaft, A third bearing that rotatably supports a second end of the reduction shaft is disposed in the second divided body. The motor unit of claim 6.

8. The present invention further includes a speed change mechanism that reduces or increases the speed of the rotation of the crankshaft and transmits the rotation to the output body. A motor unit according to any one of claims 1 to 7.

9. The reduction ratio of the reduction mechanism is 40 or less. A motor unit according to any one of claims 1 to 8.

10. A substrate is arranged so as to overlap at least a portion of the second bearing when viewed in a direction perpendicular to the axial direction of the motor shaft. The motor unit of claim 7.

11. The drive gear is formed by plastic processing a part of the motor shaft. A motor unit according to any one of claims 1 to 10.

12. The drive gear is shot peened, air blasted or coated A motor unit according to any one of claims 1 to 11.

13. A thermally conductive member is disposed between the substrate and the first divided body or the second divided body. The motor unit of claim 10.

14. The output body is a member in which the rotational force transmitted through the reduction mechanism and the rotational force of the crankshaft are combined. A motor unit according to any one of claims 1 to 13.

15. A motor unit according to any one of claims 1 to 14, and a wheel to which the rotational force of the motor of the motor unit is transmitted. Electric bicycle.

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