Motor unit for electric bicycle and electric bicycle

Abstract

To provide a motor unit of an electric bicycle, which is reduced in weight and easily radiates heat generated in a motor, and an electric bicycle including the same.SOLUTION: The motor unit 2 includes a case 3, a motor 4 that is accommodated in the case 3 and has a rotor 41 and a stator 42, a rotary shaft unit 5 that penetrates the case 3, is disposed so as to be rotatable around an axis, and is connected to a pedal via a crank arm, and a transmission mechanism 6 that is accommodated in the case 3 and transmits a force from the motor 4 to the rotary shaft unit 5. The case 3 has a first case section side 3a that constitutes a part of the case 3 and inside which the rotor 41 and the stator 42 are disposed, and a second case section side 3b that constitutes the other part of the case 3. The first case portion side 3a is formed of a material having a higher heat transfer coefficient than the second case portion side 3b, and the second case portion side 3b is formed of a material having a lower specific weight than the first case portion side 3a.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Patent Document 1 describes a motor unit for an electric bicycle. The case of this motor unit is made of metal for the parts that require sufficient strength, such as the part that receives the bearing of the crankshaft, and other parts are made of resin for weight reduction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-219603 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the motor unit of the electric bicycle described in Patent Document 1, the case that covers the electric motor is made of resin. Therefore, although this motor unit can be made lighter, it has the problem of making it difficult to dissipate heat generated by the electric motor.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a motor unit for an electric bicycle and an electric bicycle that are lightweight and that easily dissipate heat generated by the motor. [Means for solving the problem]

[0006] A motor unit for an electric bicycle according to one aspect of the present disclosure includes a case, a motor housed within the case and having a rotor and a stator, and a rotating shaft unit that passes through the case and is rotatable about an axis and to which pedals are connected via crank arms. The motor unit further includes a transmission mechanism housed within the case and that transmits power from the motor to the rotating shaft unit. The case includes a first case portion that forms part of the case and has the rotor and stator disposed inside, and a second case portion that forms the other part of the case. The first case portion is made of a material with a higher thermal conductivity than the second case portion. The second case portion is made of a material with a lower specific gravity than the first case portion.

[0007] An electric bicycle according to one aspect of the present disclosure includes the motor unit described above and a frame to which the motor unit is attached at a lower portion and which supports a rider. [Effects of the Invention]

[0008] The motor unit of an electric bicycle and the electric bicycle according to one aspect of the present disclosure are lightweight and also facilitate the dissipation of heat generated by the motor. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic side view showing an electric bicycle according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a side view showing the bracket, motor unit, and cover provided on the electric bicycle. [Figure 3] FIG. 3 is a perspective view showing the motor unit of the same. [Figure 4] 4 is a cross-sectional view showing a cross section of the motor unit taken along the line AA in FIG. [Figure 5] FIG. 5 is an enlarged cross-sectional view of part B in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line CC in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] (One embodiment) 1. Overview The motor unit 2 (hereinafter simply referred to as the "motor unit 2") of an electric bicycle 1 according to one embodiment shown in FIGS. 1 to 4 includes a case 3 and a motor 4 housed within the case 3 and having a rotor 41 and a stator 42. The motor unit 2 further includes a rotary shaft unit 5 that passes through the case 3 and is rotatable about an axis, and to which pedals 180 are connected via crank arms 18, and a transmission mechanism 6 housed within the case 3 and that transmits power from the motor 4 to the rotary shaft unit 5. The case 3 includes a first case portion 3a that constitutes a part of the case 3 and in which the rotor 41 and stator 42 are disposed, and a second case portion 3b that constitutes the other part of the case 3. The first case portion 3a is formed of a material with a higher thermal conductivity than the second case portion 3b, and the second case portion 3b is formed of a material with a lower specific gravity than the first case portion 3a.

[0011] The electric bicycle 1 of one embodiment also includes a motor unit 2, and a frame 10 to which the motor unit 2 is attached at the bottom and which supports the rider.

[0012] In the electric bicycle 1 and motor unit 2 of one embodiment having the above configuration, the first case portion 3a of the case 3, on the inside of which the heat-generating parts of the motor 4 (i.e., the rotor 41 and stator 42) are arranged, is formed of a material with a higher thermal conductivity than the second case portion 3b. Therefore, in the electric bicycle 1 and motor unit 2 of one embodiment, it is easy to dissipate the heat generated by the motor 4. Also, in the electric bicycle 1 and motor unit 2 of one embodiment, the second case portion 3b, which constitutes the other part of the case 3, is formed of a material with a lower specific gravity than the first case portion 3a, making it easy to reduce the weight of the case 3. Therefore, in the electric bicycle 1 and motor unit 2 of one embodiment, it is easy to dissipate the heat generated by the motor 4 while achieving a lighter weight.

[0013] 2.Details Next, an electric bicycle 1 and a motor unit 2 according to one embodiment shown in Figures 1 to 6 will be described in more detail with reference to the drawings. In this embodiment, the electric bicycle 1 is an electrically assisted bicycle that adds auxiliary driving force from a motor 4 to the driving force of the rider. Note that the electric bicycle 1 may also be an electric motorcycle that runs solely on the driving force of the motor 4.

[0014] (Electric bicycle) As shown in Figure 1, the electric bicycle 1 includes a frame 10, a wheel 11, a motor unit 2, and a cover 12. In the following description, the direction of travel of the electric bicycle 1 is defined as the forward direction, the opposite direction as the rearward direction, and the left and right directions are defined based on the direction as seen by a rider riding the electric bicycle 1.

[0015] The frame 10 supports a rider who drives the electric bicycle 1. The weight of the frame 10 and the rider is supported on the ground via a front wheel 110 and a rear wheel 111 that constitute the wheels 11.

[0016] The frame 10 has a head pipe 101, an upper pipe 102, a lower pipe 103, a vertical pipe 104, a seat stay 105, a chain stay 106, and a bracket 107. The frame 10 is made of a metal such as aluminum or stainless steel, but may contain a non-metallic material in part. Furthermore, the entire frame 10 may be made of a non-metallic material, and the material of the frame 10 is not particularly limited.

[0017] The head pipe 101 is a cylindrical member. A handle post 13 is inserted through the head pipe 101. The handle post 13 is inserted into the head pipe 101 so as to be rotatable around its axis. A front fork 14 is formed at the lower end of the handle post 13. A front wheel 110 is rotatably attached to the front fork 14. A handle bar 15 is fixed to the upper end of the handle post 13. The handle bar 15 is provided with a hand operation unit for turning the electric power on and off, and a gear change operation unit for changing the speed using a gear change mechanism provided in the rear wheel 111.

[0018] The upper pipe 102 is a cylindrical member that extends diagonally downward and rearward from the head pipe 101. The front end of the upper pipe 102 is fixed to the rear side wall of the head pipe 101 by welding or the like. The rear end of the upper pipe 102 is fixed to the stand pipe 104.

[0019] The stand pipe 104 is a cylindrical member extending 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 stand pipe 104 by welding or the like. A shaft 160 extending downward from the saddle 16 is inserted into an opening at the upper end of the stand pipe 104. The shaft 160 is fixed to the stand pipe 104, thereby fixing the saddle 16 to the stand pipe 104. A bracket 107 is fixed to the lower end of the stand pipe 104.

[0020] The lower pipe 103 is a cylindrical member that extends diagonally downward and rearward from the head pipe 101. The front end of the lower pipe 103 is fixed by welding or the like to a portion of the rear side wall of the head pipe 101 that is lower than the portion to which the upper pipe 102 is fixed. A bracket 107 is fixed to the rear end of the lower pipe 103.

[0021] The bracket 107 is a part of the frame 10, and has the motor unit 2 attached thereto. The bracket 107 has insertion holes 1070 (see FIG. 2) through which screws 20 are inserted to fix the bracket 107 to the motor unit 2. In this embodiment, the bracket 107 is formed by combining a first bracket 107a and a second bracket 107b (see FIG. 6) that are aligned in the left-right direction.

[0022] The first bracket 107a located on the left side has three insertion holes 1070. Similarly, the second bracket 107b located on the right side has three insertion holes 1070. The three insertion holes 1070 of the first bracket 107a and the three insertion holes 1070 of the second bracket 107b are aligned one-to-one in the left-right direction.

[0023] The motor unit 2 is attached to the underside of the bracket 107. A space is formed between the inner surface of the bracket 107 and the outer surface of the motor unit 2 to allow wiring to pass through.

[0024] The front ends of the seat stays 105 are fixed by welding or the like to the rear end of the upper pipe 102. The seat stays 105 are two hollow members that extend diagonally downward and rearward from near the upper end of the vertical pipe 104. The rear ends of the seat stays 105 are fixed to the rear ends of the chain stays 106, and a rear wheel 111 is rotatably attached to this part.

[0025] A battery 17 for supplying power to the motor unit 2 is detachably attached to the bracket 107 and the lower pipe 103 .

[0026] A gear shift wire and a brake wire that connect a gear shift operation unit provided on the handlebar 15 to a gear shift mechanism of the rear wheel 111 are passed through the internal space of the lower pipe 103 and the bracket 107.

[0027] As shown in FIG. 2, the cover 12 includes a lower cover 120 that covers the motor unit 2 from below, and a first side cover 121 and a second side cover 122 that cover the motor unit 2 from the left side. Each of the covers 120, 121, and 122 is formed from a flame-retardant and weather-resistant resin. The lower cover 120 is fixed to the bracket 107 with screws. The first side cover 121 is disk-shaped and is engaged with the motor unit 2. The second side cover 122 has an opening 1220 inside which the first side cover 121 is disposed. The second side cover 122 is fixed to the motor unit 2 with screws, and supports the first side cover 121 by the periphery of the opening 1220. Note that the covers 120, 121, and 122 may all be formed from a material with high thermal conductivity, such as aluminum.

[0028] As shown in Figure 1, the electric bicycle 1 further includes a crank arm 18, one end of which is fixed to the rotating shaft unit 5 of the motor unit 2, and a pedal 180, which is rotatably attached to the other end of the crank arm 18. By pedaling the pedal 180, the rider of the electric bicycle 1 can transmit human-powered rotational force to the rotating shaft unit 5.

[0029] The electric bicycle 1 further includes a front sprocket (not shown) fixed to the rotating shaft unit 5 (more specifically, the output body 8), a rear sprocket 19 fixed to the hub of the rear wheel 111, and a chain 190 looped around the front sprocket and the rear sprocket 19.

[0030] (Motor unit) As shown in FIGS. 3 and 4, the motor unit 2 includes a case 3, a motor 4, a rotary shaft unit 5, and a transmission mechanism 6.

[0031] The case 3 forms the outer shell of the motor unit 2. The case 3 houses devices such as the motor 4, the rotary shaft unit 5, and the transmission mechanism 6 in an accommodation space formed inside. The case 3 has a first case portion 3a that forms part of the case 3 and has the rotor 41 and stator 42 of the motor 4 disposed inside, and a second case portion 3b that forms the other part of the case 3. The first case portion 3a is formed of a material with a higher thermal conductivity than the second case portion 3b, and the second case portion 3b is formed of a material with a lower specific gravity than the first case portion 3a.

[0032] In this embodiment, the case 3 has a first division body 30 and a second division body 31 that are aligned in the axial direction (i.e., the left-right direction) of the rotating shaft unit 5 and combined with each other. The first division body 30 and the second division body 31 each include axial holes 300, 310 through which the rotating shaft unit 5 is inserted. The first division body 30 located on the left side is the first case portion 3a, and the second division body 31 located on the right side is the second case portion 3b. The first division body 30 and the second division body 31 are combined to form the case 3.

[0033] The first divided body 30 is made of a material having a higher thermal conductivity than the second divided body 31, such as aluminum. The second divided body 31 is made of a material having a lower specific gravity than the first divided body 30, such as magnesium.

[0034] As shown in Figure 4, the internal storage space of the first division 30 on the left side is open to the right. The internal storage space of the second division 31 on the right side is open to the left. The first division 30 and the second division 31 are fitted together from the left and right so that their storage spaces are continuous, and are fixed to each other with fastening members made of bolts.

[0035] The first divided body 30 has a first mounting portion 301 that is fixed to the bracket 107 with a screw 20 (see FIG. 1). The second divided body 31 has a second mounting portion 311 that is fixed to the bracket 107 with a screw 20 (not shown).

[0036] In this embodiment, the first divisional body 30 has three first mounting portions 301. One first mounting portion 301 protrudes forward from the first divisional body 30, one first mounting portion 301 protrudes upward from the first divisional body 30, and one first mounting portion 301 protrudes rearward from the first divisional body 30.

[0037] The second divisional body 31 has three second mounting portions 311. Like the three first mounting portions 301, the three second mounting portions 311 protrude forward, upward, and rearward from the second divisional body 31. The three first mounting portions 301 and the three second mounting portions 311 are arranged one-to-one at intervals in the left-right direction.

[0038] A cylindrical member 21 is attached to the first attachment portion 301. The cylindrical member 21 can be advanced and retreated toward the bracket 107 and can have a screw 20 screwed into the inside thereof. In this embodiment, a cylindrical member 21 is attached to each of the three first attachment portions 301.

[0039] 6, the first mounting portion 301 is provided with a mounting hole 302 to which the cylindrical member 21 is attached so as to be able to move forward and backward. The second mounting portion 311 is provided with a fixing hole 312 to which the screw 20 is fixed. The mounting hole 302 has a larger diameter than the fixing hole 312.

[0040] A tubular member 21 forming a left-handed thread is screwed into the mounting hole 302. The tubular member 21 has a cylindrical main body 210 and a flange 211 protruding from one axial end (the left end in this embodiment) of the main body 210. A thread for forming a left-handed thread is provided on the outer peripheral surface of the main body 210. An inner peripheral surface of the main body 210 forms a threaded hole 212 provided with a thread groove for threading in a screw 20 forming a right-handed thread. The threaded hole 212 has the same diameter as the fixing hole 312 of the second mounting portion 311.

[0041] In this embodiment, the motor unit 2 is attached to the bracket 107 as follows.

[0042] First, the second mounting portion 311 of the second divided body 31 is placed against the inner surface of the right-side second bracket 107b, and in this state, the screw 20 is inserted from the outside (i.e., the right side) into the insertion hole 1070 of the right-side second bracket 107b. At this time, the screw 20 is screwed into the fixing hole 312 of the second mounting portion 311, and the second bracket 107b and the second mounting portion 311 are fixed together by the screw 20.

[0043] Next, the tip of a tool is inserted into the insertion hole 1070 of the left-side first bracket 107a from the outside (i.e., the left side), and the tip of the tool is inserted into the inside of the main body 210 of the tubular member 21 of the first mounting part 301, and the tubular member 21 is rotated clockwise with the tool. This allows the tubular member 21 to be pulled out from the first mounting part 301 (i.e., moved to the left), and the flange part 211 to come into contact with the inner surface of the first bracket 107a.

[0044] Next, the tool is withdrawn, and the screw 20 is inserted from the outside into the insertion hole 1070 of the first bracket 107a and screwed into the threaded hole 212 on the inner circumferential surface of the main body 210 of the tubular member 21, thereby fixing the first bracket 107a and the first mounting portion 301 via the tubular member 21. At this time, because the tubular member 21 is left-handed, even if the right-handed screw 20 is screwed into the tubular member 21, the tubular member 21 does not move relative to the first mounting portion 301, and the gap between the first mounting portion 301 and the first bracket 107a can be maintained filled with the tubular member 21. Therefore, when the screw 20 is screwed in, a force is unlikely to act on the first mounting portion 301 in a direction away from the second mounting portion 311, which prevents a gap from occurring at the joint between the first segment 30 and the second segment 31 and a decrease in the airtightness of the case 3.

[0045] In the electric bicycle 1 of this embodiment, the mating surfaces of the first bracket 107a and the second bracket 107b and the mating surfaces of the first divided body 30 and the second divided body 31 are aligned in the axial direction of the rotating shaft unit 5.

[0046] As shown in Fig. 4, the motor 4 is attached to the case 3. The motor 4 has a rotating shaft 40, a rotor 41 that rotates integrally with the rotating shaft 40, and a stator 42. A portion of the rotating shaft 40, the rotor 41, and the stator 42 are disposed inside the first divided body 30.

[0047] The first divided body 30 has a motor housing portion 303 that houses the rotor 41 and stator 42 of the motor 4. The motor housing portion 303 is cylindrical and has a bottom. A heat insulating film 304 is provided on the outer surface of the motor housing portion 303 (specifically, on the left surface and outer peripheral surface of the motor housing portion 303). The heat insulating film 304 is made of a material that has lower thermal conductivity than the first divided body 30, such as resin or rubber. The heat insulating film 304 may be formed by painting or coating, or may be attached to the outer surface of the motor housing portion 303.

[0048] The rotating shaft 40 is rotatably housed with its axis oriented in the left-right direction. The rotating shaft 40 protrudes from the stator 42 to one side (specifically, to the right), and teeth 400 that mesh with the transmission mechanism 6 are formed on the outer surface of the protruding portion. The right end of the rotating shaft 40 is supported by a rotating shaft support bearing 32 disposed in the second division body 31. The left end of the rotating shaft 40 does not protrude leftward from the stator 42, and is supported by a rotating shaft support bearing 33 disposed in the first division body 30.

[0049] The rotary shaft unit 5 has an input shaft 7 , an output body 8 , and an input body 9 .

[0050] The input shaft 7 passes through the case 3 in the left-right direction and is arranged to be rotatable about its axis. In this embodiment, the input shaft 7 is cylindrical, but it may be a solid round bar. One end of a crank arm 18 (see FIG. 1) is fixed to both ends of the input shaft 7 in the axial direction.

[0051] The first split body 30 of the case 3 has a first bearing 34, which rotatably supports the input shaft 7, at one end side in the axial direction (more specifically, the left end side). A shaft hole 300 through which the input shaft 7 passes is formed in the first split body 30, and the first bearing 34 is disposed inside this shaft hole 300. In this embodiment, the first bearing 34 is configured by a ball bearing. Note that the first bearing 34 is not limited to a ball bearing and may be various other bearings such as a roller bearing. An O-ring (not shown) is provided between the outer circumferential surface of the first bearing 34 and the first split body 30.

[0052] The case 3 has a second bearing 35, which rotatably supports the input shaft 7, at the other end side in the axial direction (more specifically, the right end side). A shaft hole 310 through which the input shaft 7 passes is formed in the second divided body 31, and the second bearing 35 is disposed inside this shaft hole 310. In this embodiment, the input shaft 7 is indirectly supported by the second bearing 35 via the output body 8. The second bearing 35 is formed by a ball bearing. Note that the second bearing 35 is not limited to a ball bearing and may be various other bearings such as a roller bearing. A cover member 23 is attached to the shaft hole 310.

[0053] An input body 9 is disposed on the outer peripheral surface of the input shaft 7. The input body 9 rotates integrally with the input shaft 7. The input body 9 is a cylindrical member whose axis faces the left-right direction and is disposed concentrically with the input shaft 7. The left-right length of the input body 9 is shorter than the left-right length of the input shaft 7. The input body 9 and the input shaft 7 have mating portions 900, 70 in part of their axial directions that fit together so as to prevent relative rotation around the axis. In this embodiment, the mating portions 900, 70, which are formed of a spline portion, serration portion, or the like, are formed on the left end of the input body 9 and on a part of the input shaft 7 corresponding to this portion. The mating portions 900, 70 may be configured to fit together using male and female threads.

[0054] The input body 9 is divided into a first input body 90 and a second input body 91. The first input body 90 is connected to the input shaft 7. The first input body 90 is disposed on the outer peripheral surface of the left portion of the input shaft 7 and is housed in the first divided body 30. A fitting portion 900 that fits with the input shaft 7 is formed at the left end of the first input body 90. A gap S1 is formed between the first input body 90 and the input shaft 7 in a portion to the right of the fitting portion 900 at the left end of the first input body 90. This makes it easier to insert the input shaft 7 into the cylindrical first input body 90.

[0055] The second input body 91 is located at a different position from the first input body 90 in the axial direction (specifically, to the right of the first input body 90) and is connected to the first input body 90 to transmit rotational force to the output body 8. The left end of the second input body 91 is located radially outward of the right end of the first input body 90, and the input bodies 90, 91 partially overlap in the radial direction. The first input body 90 and the second input body 91 have mating portions 901, 910 that fit together so as to prevent relative rotation around the axis. In this embodiment, the mating portions 901, 910, which are formed of spline portions, serration portions, or the like, are formed at the right end of the first input body 90 and the left end of the second input body 91. Note that in this disclosure, "radially overlapping" refers to a state in which at least a portion of each object overlaps when viewed in the radial direction.

[0056] The output body 8 is disposed rotatably about its axis along the outer peripheral surface of the input shaft 7, and receives a rotational force from the input body 9. The output body 8 is cylindrical, with its axis oriented in the left-right direction, and disposed concentrically with the input shaft 7. The left-right length of the output body 8 is shorter than the left-right length of the input shaft 7. The right end of the output body 8 passes through an axial hole 310 formed in the second divided body 31 and protrudes outside the case 3. The output body 8 is supported by a second bearing 35 disposed in the second divided body 31. The rotating shaft unit 5 is supported by the case 3 via the first bearing 34 and the second bearing 35.

[0057] A front sprocket (not shown) is fixed to a portion of the output body 8 that protrudes outside the case 3. The front sprocket rotates integrally with the output body 8.

[0058] A one-way clutch (not shown) is disposed between the input body 9 and the output body 8. When a rotational force is applied to the input body 9 in a direction that accelerates the electric bicycle 1 in the traveling direction (hereinafter referred to as the acceleration direction), the one-way clutch transmits this rotational force to the output body 8, and when a rotational force is applied in the opposite direction to the acceleration direction, the one-way clutch does not transmit this rotational force to the output body 8. When a rotational force in the acceleration direction is applied to the output body 8 via the transmission mechanism 6, the one-way clutch does not transmit this rotational force to the input body 9. In this embodiment, the one-way clutch has a ratchet and is supplied with grease. Note that various one-way clutches can be used as appropriate, and for example, a roller-type one-way clutch or a sprag-type one-way clutch may be used.

[0059] The output body 8 has a web 80 and a rim 81 on the outer peripheral surface side in the portion overlapping with the input body 9 in the axial direction. The web 80 protrudes radially outward. The rim 81 is continuous with the outer radial end of the web 80. The axial length of the rim 81 is longer than the axial length of the web 80. The rim 81 has teeth 810 on its outer peripheral surface that mesh with the transmission mechanism 6.

[0060] The transmission mechanism 6 is housed in the case 3 and transmits the rotation of the motor 4 to the rotary shaft unit 5 (more specifically, the output body 8). The transmission mechanism 6 has a first transmission gear 60 and a second transmission gear 61. The first transmission gear 60 rotates by the rotational force of the rotary shaft 40 of the motor 4. In this embodiment, the first transmission gear 60 is made of a cylindrical member and has teeth 600 formed on its outer circumferential surface that mesh with teeth 400 formed on the rotary shaft 40 of the motor 4. The first transmission gear 60 is arranged along the outer circumferential surface of a rotary transmission shaft 62 of the transmission mechanism 6.

[0061] The transmission rotation shaft 62 is rotatably housed in the case 3 with its axis oriented in the left-right direction. The transmission rotation shaft 62 is located rearward of the rotation shaft 40 of the motor 4, and is arranged in approximately the same position in the left-right direction as the portion of the rotation shaft 40 that protrudes rightward from the stator 42. The right end of the transmission rotation shaft 62 is supported by a transmission rotation shaft support bearing (not shown) arranged in the second division body 31.

[0062] The first transmission gear 60 is connected to the transmission rotation shaft 62 via a one-way clutch (not shown). When a rotational force in the acceleration direction is applied to the first transmission gear 60, the one-way clutch transmits this rotational force to the transmission rotation shaft 62, and when a rotational force in the direction opposite to the acceleration direction is applied, the one-way clutch does not transmit this rotational force to the transmission rotation shaft 62. Furthermore, when a rotational force in the acceleration direction is applied to the transmission rotation shaft 62, the one-way clutch does not transmit this rotational force to the first transmission gear 60.

[0063] A second transmission gear 61 is fixed to the right of the portion of the transmission rotation shaft 62 to which the one-way clutch is fixed so as to rotate integrally with the transmission rotation shaft 62. The second transmission gear 61 transmits the rotational force received from the first transmission gear 60 via the transmission rotation shaft 62 to a toothed portion 810 of the output body 8. The second transmission gear 61 has teeth on its outer circumferential surface that mesh with the toothed portion 810 of the rim 81 of the output body 8. The transmission mechanism 6 transmits the rotation of the motor 4 to the output body 8 at a reduced speed by the first transmission gear 60 and the second transmission gear 61. That is, the transmission mechanism 6 in this embodiment is a reduction mechanism.

[0064] When the rider pedals 180 (see Figure 1) of the electric bicycle 1, a rotational force in the acceleration direction is applied to the input shaft 7. When the input shaft 7 rotates, the first input body 90 and the second input body 91 rotate integrally with the input shaft 7. The rotational force in the acceleration direction of the second input body 91 is applied to the output body 8 via the one-way clutch, causing the output body 8 and the front sprocket to rotate in the acceleration direction. When the front sprocket rotates in the acceleration direction, a rotational force in the acceleration direction is applied to the rear sprocket 19 via the chain 190, causing the rear sprocket 19 and rear wheel 111 to rotate in the acceleration direction. This causes the electric bicycle 1 to move forward in the forward direction.

[0065] While the electric bicycle 1 is moving forward under human power, the rotational force from the motor 4 can be applied to the output body 8 as an auxiliary force. When the rotating shaft 40 of the motor 4 rotates in the acceleration direction, the first transmission gear 60 meshing with the rotating shaft 40 of the motor 4 rotates in the acceleration direction. The rotational force of the first transmission gear 60 in the acceleration direction is transmitted to the transmission rotating shaft 62 and the second transmission gear 61 via the one-way clutch, causing the second transmission gear 61 to rotate in the acceleration direction. The rotational force of the second transmission gear 61 in the acceleration direction is transmitted to the output body 8 meshing with the second transmission gear 61. In other words, the output body 8 functions as a force combiner that combines the rotational force of human power from the input body 9 and the rotational force from the motor 4. The motor unit 2 in this embodiment is a so-called single-shaft motor unit 2.

[0066] When the motor 4 is not driven while the electric bicycle 1 is moving forward under human power, it operates as follows. In this case, the output body 8 is rotating in the acceleration direction, so the second transmission gear 61 and the transmission rotation shaft 62 that mesh with the output body 8 rotate in the acceleration direction, but the rotational force of the transmission rotation shaft 62 in the acceleration direction is not transmitted to the first transmission gear 60 by the one-way clutch. As a result, when the motor 4 is not driven, the rotation shaft 40 and rotor 41 are prevented from rotating.

[0067] In the electric bicycle 1, the rotational force from the motor 4 is controlled according to the torque applied to the input shaft 7 and the number of rotations per unit time of the input shaft 7. The torque applied to the input shaft 7 is detected by a torque detection unit 36. The number of rotations per unit time of the input shaft 7 is detected by a rotation detection unit (not shown). The rotation detection unit is arranged within a partial range in the axial direction so as to follow the outer peripheral surface of the rotating shaft unit 5.

[0068] A control board 22 having a control unit that controls the motor 4 is disposed within the case 3. The control unit has, for example, a microcomputer, and controls the operation of each element by executing a program stored in a storage unit such as a ROM (Read Only Memory). Various types of control units can be used as appropriate, and detailed description thereof will be omitted. The control unit controls the rotational force from the motor 4 based on the torque detected by the torque detection unit and the rotation speed detected by the rotation detection unit.

[0069] The motor unit 2 has a third bearing 37 located between the first bearing 34 and the second bearing 35 in the axial direction. The third bearing 37 rotatably supports the input body 9. In this embodiment, the third bearing 37 is configured by a ball bearing. Note that the third bearing 37 is not limited to a ball bearing and may be various other bearings such as a roller bearing.

[0070] The cover member 23 is provided so as to cover the gap between the axial hole 310 of the second divided body 31 of the case 3 and the output body 8. In this embodiment, the cover member 23 is made of rubber. The cover member 23 has an annular (more specifically, circular) shape when viewed in the axial direction.

[0071] 5, the cover member 23 has an attachment portion 230 that is attached to the shaft hole 310 of the second divided body 31, and a first contact portion 231 that protrudes from the attachment portion 230 toward the rotating shaft unit 5 and comes into contact with the rotating shaft unit 5. The cover member 23 further has a second contact portion 232 that protrudes toward the rotating shaft unit 5 from a portion of the attachment portion 230 that is deeper than the first contact portion 231.

[0072] The mounting portion 230 has a U-shaped cross section perpendicular to the circumferential direction so as to sandwich the inner peripheral edge of the axial hole 310 of the second section 31. A first contact portion 231 protrudes from the inner peripheral edge of the inner surface (left side in this embodiment) of the mounting portion 230, and a second contact portion 232 protrudes from the outer periphery of the inner surface of the mounting portion 230. Each of the first contact portion 231 and the second contact portion 232 is annular (more specifically, circular) when viewed in the left-right direction, and protrudes toward the center of the mounting portion 230. In this embodiment, the first contact portion 231 and the second contact portion 232 are fin-shaped and are formed so as to become thinner as they approach the tip in the protruding direction.

[0073] The contact portions 231, 232 are configured so that, in a state in which the mounting portion 230 is attached to the axial hole 310 of the second segment 31, the first contact portion 231 abuts against the output body 8, and the second contact portion 232 abuts against an inner peripheral side raceway ring 350 of the second bearing 35 that supports the output body 8. Note that the second contact portion 232 may be configured to abut against a portion of the output body 8 that is closer to the second bearing 35 than the contact portion of the first contact portion 231.

[0074] In this way, the first contact portion 231 abuts against the output body 8, and the second contact portion 232 abuts against the inner raceway 350 of the second bearing 35, thereby doubly preventing foreign matter such as mud and sand from penetrating through the shaft hole 310 to the rolling body (i.e., ball 351) of the second bearing 35.

[0075] 3. Effects In the motor unit 2 of this embodiment described above, the portion of the case 3 where the rotor 41 and stator 42 of the motor 4 are arranged inside (motor accommodating portion 303) is formed from a material with high thermal conductivity, so that heat generated by the motor 4 can be easily dissipated through the case 3.

[0076] Here, in the motor unit 2 of this embodiment, the first partition 30 of the case 3, which constitutes approximately half of the axial direction of the rotating shaft unit 5, is formed from a material with high thermal conductivity, so that the surface area of ​​the first partition 30 is large and it is easy to dissipate the heat generated by the motor 4.

[0077] Furthermore, in the motor unit 2 of this embodiment, the second divided body 31 of the case 3, which constitutes approximately half of the axial direction of the rotating shaft unit 5, is made of a material with a low specific gravity, which makes it easy to reduce the overall weight of the case 3. Therefore, in the motor unit 2 of this embodiment, it is easy to reduce the weight of the case 3, and therefore the motor unit 2 as a whole.

[0078] Furthermore, in the motor unit 2 of this embodiment, the outer surface of the portion of the case 3 where the rotor 41 and stator 42 of the motor 4 are disposed is covered with a heat insulating film 304, thereby preventing the driver from coming into contact with the portion of the case 3 that is particularly susceptible to becoming hot. Furthermore, in the motor unit 2 of this embodiment, covering a portion of the case 3 with the heat insulating film 304 can also improve the design.

[0079] Furthermore, in the motor unit 2 of this embodiment, the first divided body 30 is covered with the cover 12, so that the driver can be prevented from coming into contact with the first divided body 30.

[0080] In addition, in the motor unit 2 of this embodiment, the tubular member 21 protrudes from the first mounting portion 301 of the first divided body 30, and since the first mounting portion 301 and the bracket 107 are not in direct contact with each other, heat from the first divided body 30 is less likely to be transmitted to the bracket 107.

[0081] Furthermore, in the motor unit 2 of this embodiment, the bracket 107 is fixed with the screw 20 to the tubular member 21 protruding from the first mounting portion 301, so that a gap is unlikely to occur between the first divided body 30 and the second divided body 31 that are fitted together. Therefore, in the motor unit 2 of this embodiment, it is easy to ensure the airtightness of the case 3.

[0082] Furthermore, in the motor unit 2 of this embodiment, the cover member 23 that fills the gap between the shaft hole 310 of the second divided body 31 of the case 3 and the output body 8 of the rotary shaft unit 5 can provide a double seal with the first contact portion 231 and the second contact portion 232. Therefore, in the motor unit 2 of this embodiment, foreign matter such as mud and sand is less likely to enter the case 3 through the shaft hole 310.

[0083] 4. Variations Next, a description will be given of modified examples of the above-described motor unit 2 and electric bicycle 1. The modified examples shown below can be combined as appropriate.

[0084] The case 3 is not limited to being formed by combining the first divided body 30 and the second divided body 31. The case 3 may also be formed by combining three or more divided bodies. Furthermore, only a portion of the first divided body 30 may be the first case portion 3a. In other words, only the motor accommodating portion 303 of the first divided body 30 may have a higher thermal conductivity than the second case portion 3b, and the other portions of the first divided body 30 may have the same thermal conductivity as the second case portion 3b.

[0085] The outer surface of the portion of the first divided body 30 where the rotor 41 and the stator 42 are disposed (that is, the motor accommodating portion 303 ) does not need to be covered with the heat insulating film 304 .

[0086] The first mounting portion 301 does not have to be fitted with a tubular member 21 that can be advanced and retreated toward the bracket 107 and into which the screw 20 can be screwed, and the gap between the first mounting portion 301 and the bracket 107 may be filled by other means.

[0087] The cover member 23 may have only one of the first contact portion 231 and the second contact portion 232, or may have another structure that can fill the gap between the shaft hole 310 and the rotating shaft unit 5.

[0088] The transmission mechanism 6 is not limited to a reduction mechanism.

[0089] The arrangement and structure of the motor 4, the transmission mechanism 6, and the rotary shaft unit 5 within the case 3 are not limited to the arrangement and structure shown in FIG.

[0090] The first divisional body 30 and the second divisional body 31 are not limited to a combination of aluminum and magnesium, and may be formed of other combinations of materials that satisfy certain conditions. For example, the second divisional body 31 may be formed of a non-metal such as resin. Furthermore, the first divisional body 30 may be formed by metal insert molding so that only the motor housing portion 303 is made of a material with high thermal conductivity such as aluminum.

[0091] (summary) As in the above-described embodiment and its modified example, the motor unit (2) of the first aspect has the following configuration.

[0092] The motor unit (2) of the first aspect includes a case (3), a motor (4) housed in the case (3) and having a rotor (41) and a stator (42), and a rotary shaft unit (5) that penetrates the case (3) and is rotatable about an axis, and to which a pedal (180) is connected via a crank arm (18). The motor unit (2) further includes a transmission mechanism (6) housed in the case (3) and that transmits power from the motor (4) to the rotary shaft unit (5). The case (3) includes a first case portion (3a) that constitutes a part of the case (3) and in which the rotor (41) and the stator (42) are disposed, and a second case portion (3b) that constitutes the other part of the case (3). The first case portion (3a) is made of a material with a higher thermal conductivity than the second case portion (3b), and the second case portion (3b) is made of a material with a lower specific gravity than the first case portion (3a).

[0093] In the motor unit (2) of the first aspect having the above configuration, the first case portion (3a) of the case (3), on the inside of which the heat-generating parts of the motor (4) (i.e., the rotor 41 and the stator 42) are arranged, is made of a material with high thermal conductivity, and therefore heat generated by the motor (4) is easily dissipated. Also, in the motor unit (2) of the first aspect, the second case portion (3b) constituting the other part of the case (3) is made of a material with a low specific gravity, and therefore the weight of the case (3) is easily reduced. Therefore, the motor unit (2) of the first aspect is lightweight and easily dissipates heat generated by the motor (4).

[0094] As in the above-described embodiment and its modified example, the motor unit (2) of the second aspect additionally includes the following configuration in addition to the configuration of the first aspect.

[0095] In the motor unit (2) of the second embodiment, the case (3) has a first divided body (30) and a second divided body (31) that are aligned in the axial direction of the rotating shaft unit (5) and combined with each other. The first divided body (30) and the second divided body (31) each include an axial hole (300, 310) through which the rotating shaft unit (5) is inserted. The first divided body (30) is the first case portion (3a), and the second divided body (31) is the second case portion (3b).

[0096] In the second embodiment of the motor unit (2) having the above configuration, the first case portion (3a) and the second case portion (3b) can each be made relatively large, which makes it easier to improve the heat dissipation performance of the first case portion (3a) and to reduce the weight of the case (3).

[0097] As in the embodiment and its modification described above, the motor unit (2) of the third aspect additionally includes the following configuration in addition to the configuration of the second aspect.

[0098] In the motor unit (2) of the third embodiment, the outer surface of the first split body (30) in which the rotor (41) and the stator (42) are disposed is covered with a heat insulating film (304).

[0099] In the third embodiment of the motor unit (2) having the above-described configuration, the outer surface of the part of the first divided body (30) where the rotor (41) and the stator (42) are located, which is prone to become hot, can be covered with an insulating film (304), thereby preventing contact with this hot part.

[0100] As in the above-described embodiment and its modified example, the motor unit (2) of the fourth aspect additionally includes the following configuration in addition to the configuration of the second or third aspect.

[0101] In the motor unit (2) of the fourth aspect, the first divided body (30) has a first mounting portion (301) that is fixed with a screw (20) to a bracket (107) at the bottom of the frame (10) of the electric bicycle (1). The second divided body (31) has a second mounting portion (311) that is fixed with a screw (20) to the bracket (107). A tubular member (21) is attached to the first mounting portion (301) that is movable toward and away from the bracket (107) and into which the screw (20) can be threaded.

[0102] In the motor unit (2) of the fourth aspect having the above configuration, the second mounting portion (311) of the second division (31) can be fixed to the bracket (107) with the screw (20), and the tubular member (21) pulled out from the first mounting portion (301) of the first division (30) toward the bracket (107) can be fixed to the bracket (107) with the screw (20). Therefore, in the motor unit (2) of the fourth aspect, when the screw (20) is tightened, force is not easily applied to the first mounting portion (301) in a direction approaching the bracket (107), which makes it easier to prevent a gap from occurring between the first division (30) and the second division (31) and thereby reduce the airtightness of the case (3).

[0103] As in the above-described embodiment and its modified example, the motor unit (2) of the fifth aspect additionally includes the following configuration in addition to the configuration of any one of the first to fourth aspects.

[0104] In a motor unit (2) of a fifth aspect, the case (3) has a shaft hole (310) through which the rotating shaft unit (5) is inserted. A cover member (23) is attached to the shaft hole (310) to fill the gap between the shaft hole (310) and the rotating shaft unit (5). The cover member (23) has an attachment portion (230) attached to the shaft hole (310) and a first contact portion (231) that protrudes from the attachment portion (230) toward the rotating shaft unit (5) and comes into contact with the rotating shaft unit (5). The cover member (23) further has a second contact portion (232) that protrudes toward the rotating shaft unit (5) from a portion of the attachment portion (230) that is deeper than the first contact portion (231).

[0105] In the fifth aspect of the motor unit (2) having the above-described configuration, the contact portions (231, 232) of the cover member (23) can doubly prevent foreign matter such as mud and sand from entering the case (3) through the gap between the shaft hole (310) of the case (3) and the rotating shaft unit (5).

[0106] As in the above-described embodiment and its variant, the electric bicycle (1) of the sixth aspect comprises a motor unit (2) of any one of the first to fifth aspects, and a frame (10) to which the motor unit (2) is attached at the bottom and which is supported by the rider.

[0107] In the sixth aspect of the electric bicycle (1) having the above configuration, the weight of the motor unit (2) can be reduced, making it easier to reduce the weight of the electric bicycle (1), and the heat generated by the motor (4) can be easily dissipated through the case (3), making it easier to improve the safety of the electric bicycle (1).

[0108] The present disclosure has been described above based on the embodiments shown in the accompanying drawings, but the present disclosure is not limited to the above embodiments, and appropriate design changes are possible within the intended scope of the present disclosure. [Explanation of symbols]

[0109] 1. Electric bicycle 2 motor units 3 Cases 3a First case part 3b Second case part 30 First split body 300 shaft hole 304 Heat insulating film 31 Second split body 310 Shaft hole 4 motors 41 Rotor 42 Stator 5 Rotation axis unit 6 Transmission mechanism 21 Cylindrical member 23 Cover member 230 Mounting part 231 First contact part 232 Second contact part 10 frames 107 Bracket

Claims

1. Case and a motor housed in the case and having a rotor and a stator; a rotating shaft unit that passes through the case and is rotatable about an axis, and to which a pedal is connected via a crank arm; a transmission mechanism housed in the case and transmitting power from the motor to the rotary shaft unit, The case is a first case portion that constitutes a part of the case and has the rotor and the stator disposed therein; a second case portion that constitutes another portion of the case, the first case portion is formed of a material having a higher thermal conductivity than the second case portion; The second case portion is formed of a material having a lower specific gravity than the first case portion. Electric bicycle motor unit.

2. the case has a first divided body and a second divided body that are aligned in the axial direction of the rotary shaft unit and combined with each other, each of the first divided body and the second divided body includes a shaft hole through which the rotary shaft unit is inserted; the first divided body is the first case portion, The second divided body is the second case portion. The motor unit of an electric bicycle according to claim 1.

3. an outer surface of the first divided body, in which the rotor and the stator are disposed, covered with a heat insulating film; The motor unit of an electric bicycle according to claim 2.

4. the first segment has a first mounting portion that is fixed to a bracket at the bottom of a frame of the electric bicycle with a screw; the second division body has a second mounting portion fixed to the bracket with a screw, a cylindrical member is attached to the first mounting portion, the cylindrical member being capable of advancing and retreating toward the bracket and into which the screw can be screwed; The motor unit of an electric bicycle according to claim 2.

5. the case has a shaft hole through which the rotary shaft unit is inserted, a cover member is attached to the shaft hole to fill a gap between the shaft hole and the rotary shaft unit; The cover member is a mounting portion that is attached to the shaft hole; a first contact portion that protrudes from the mounting portion toward the rotary shaft unit and comes into contact with the rotary shaft unit; a second contact portion protruding from a portion of the mounting portion that is deeper than the first contact portion toward the rotating shaft unit, The motor unit of an electric bicycle according to claim 1.

6. A motor unit according to any one of claims 1 to 5; a frame to which the motor unit is attached at a lower portion and which supports a driver; Electric bicycle.

Images