Electric assist units for bicycles and electric assist bicycles

Abstract

[Problem] To reduce the size of an electric power assist unit for a bicycle. [Solution] This electric assist unit comprises: a plurality of sun gears which have mutually differing numbers of teeth and to which a pedaling force from a rider is selectively input; a first planetary gear having a tooth surface respectively meshing with the plurality of sun gears; an electric motor that generates a driving force for assisting the pedaling force; a sun gear which differs from the plurality of sun gears, and to which the driving force from the electric motor is input; a second planetary gear that revolves and rotates together with the first planetary gear, and that meshes with the sun gear differing from the plurality of sun gears; a ring gear that is provided so as to be non-rotatable and meshes with the second planetary gear; a carrier that supports the first planetary gear and the second planetary gear; and a case that is connected with the carrier and transmits at least one among the pedaling force and the driving force to a drive wheel.

Description

Technical Field

[0001] The present invention relates to an electric assist unit for a bicycle and an electric assist bicycle.

Background Art

[0002] Patent Document 1 discloses a hub unit for a bicycle, which includes a drive motor that generates a driving force, a transmission mechanism unit that transmits the driving force of human power to a hub case (case), and a reduction mechanism unit that transmits the driving force of the drive motor to the hub case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an electric assist bicycle, since many parts such as a battery and an electric assist unit are required as compared with a normal bicycle, further miniaturization of the electric assist unit is demanded.

[0005] However, in the hub unit of Patent Document 1, the transmission mechanism unit includes a sun gear for a transmission, a planetary gear for a transmission, a planetary carrier for a transmission, and an outer ring gear for a transmission. The driving force of human power is input to the outer ring gear for a transmission, and the planetary carrier for a transmission outputs the driving force to the hub case. Further, the reduction mechanism unit includes a sun gear for a reduction gear, a planetary gear for a reduction gear, and an outer ring gear for a reduction gear. The planetary gear for a reduction gear meshes with the outer ring gear for a reduction gear, and the planetary carrier for a transmission that holds the planetary gear for a reduction gear outputs the driving force to the hub case. Thus, in the hub unit of Patent Document 1, since the sun gear, the planetary gear, and the outer ring gear are respectively provided in the transmission mechanism unit and the reduction mechanism unit, the structure is complicated and miniaturization is difficult.

[0006] This invention has been made in view of the above-mentioned problems, and aims to miniaturize the electric assist unit. [Means for solving the problem]

[0007] According to one aspect of the present invention, an electric assist unit for a bicycle includes: a plurality of sun gears having different numbers of teeth from each other to which pedaling force from the driver is selectively input; a first planetary gear having a tooth surface that meshes with each of the plurality of sun gears; an electric motor that generates a driving force to assist the pedaling force; a sun gear different from the plurality of sun gears to which the driving force from the electric motor is input; a second planetary gear that revolves and rotates integrally with the first planetary gear and meshes with a sun gear different from the plurality of sun gears; a ring gear that is provided so as not to rotate and meshes with the second planetary gear; a carrier that supports the first planetary gear and the second planetary gear; and a case connected to the carrier that transmits at least one of the pedaling force and the driving force to the drive wheel. [Effects of the Invention]

[0008] According to one aspect of the present invention, a single ring gear is provided that meshes with a second planetary gear, which is non-rotatable and revolves and rotates integrally with the first planetary gear. Therefore, it is not necessary to provide ring gears in the reduction mechanism that transmits the pedal force applied by the driver and in the transmission mechanism that transmits the driving force from the electric motor. Consequently, the electric assist unit can be miniaturized. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a side view illustrating an overview of an electric assist unit for a bicycle and an electric assist bicycle according to an embodiment of the present invention. [Figure 2A] Figure 2A is a diagram showing the configuration of the electric assist unit. [Figure 2B]Figure 2B is a diagram showing the configuration of an electric assist unit in a modified example. [Figure 3A] Figure 3A is a collinear diagram of the electric assist unit, showing the state when it is switched to the first stage. [Figure 3B] Figure 3B is a collinear diagram of the electric assist unit, showing the unit in the second stage. [Figure 3C] Figure 3C is a collinear diagram of the electric assist unit, showing the unit in the third stage. [Figure 4] Figure 4 is a cross-sectional view of the electric assist unit, showing the unit in the first stage. [Figure 5] Figure 5 is a cross-sectional view of the electric assist unit, showing the unit in the second stage. [Figure 6] Figure 6 is a cross-sectional view of the electric assist unit, showing the unit in the third stage. [Modes for carrying out the invention]

[0010] Hereinafter, with reference to the drawings, an electric assist unit for a bicycle (hereinafter simply referred to as "electric assist unit") 100 and an electric assist bicycle (hereinafter simply referred to as "bicycle") 1 equipped with the electric assist unit 100 according to an embodiment of the present invention will be described.

[0011] First, please refer to Figure 1 to explain the overall configuration of Bicycle 1.

[0012] Figure 1 is a side view illustrating the outline of a bicycle 1 equipped with an electric assist unit 100.

[0013] As shown in FIG. 1, the bicycle 1 includes a frame 2, a front wheel 3a, a rear wheel 3b as a driving wheel, a handlebar 4, a saddle 5, a driving sprocket 6a, a driven sprocket 6b, a chain 6c, a pair of pedals 7, a pair of crank arms 7b as crank portions, a crankshaft 7c, a support shaft 8, a controller 9a, a power storage unit 9b, and an electric assist unit 100.

[0014] The bicycle 1 is operated by a driver straddling and sitting on the saddle 5 and rowing the crank arms 7b via the pedals 7. The bicycle 1 drives the rear wheel 3b by the pedal pedaling force (driving torque) transmitted from the crank arms 7b to the crankshaft 7c and the driving force (assist torque) of the electric assist unit 100 having a magnitude corresponding to the pedal pedaling force.

[0015] The frame 2 is a so-called diamond-shaped frame having a substantially parallelogram shape in side view. The front wheel 3a and the rear wheel 3b are rotatably attached to the frame 2. The frame 2 has a front fork 2a that supports the front wheel 3a.

[0016] The front wheel 3a is steered left and right by the rotation of the front fork 2a by the operation of the driver's handlebar 4.

[0017] The rear wheel 3b rotates about the support shaft 8. The driven sprocket 6b and the electric assist unit 100 are attached to the rear wheel 3b.

[0018] The driving torque is transmitted to the driven sprocket 6b via a chain 6c wound around between the driving sprocket 6a to which the driving force from the crank arms 7b is input.

[0019] The electric assist unit 100 generates an assist torque that assists the pedal pedaling force by the driver. The electric assist unit 100 will be described in detail later while referring to FIGS. 2A and 2B.

[0020] Pedal 7 is used by the driver to input driving torque. Pedal 7 is connected to the crankshaft 7c via the crank arm 7b.

[0021] The support shaft 8 is attached to the frame 2. The support shaft 8 is mounted so as to be non-rotatable relative to the frame 2.

[0022] The controller 9a consists of a microcomputer equipped with a CPU, RAM, ROM, input / output interface, etc. The controller 9a can also be composed of multiple microcomputers. The controller 9a performs various processes by having the CPU read and execute a program stored in the ROM. Specifically, the controller 9a calculates the assist torque based on an electrical signal corresponding to the magnitude of the pedal force input from a torque sensor (not shown), which will be described later, and outputs a command signal to the electric motor 70 to generate the assist torque.

[0023] The energy storage unit 9b is a rechargeable secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. The energy storage unit 9b is detachably mounted from the frame 2.

[0024] Next, the configuration of the electric assist unit 100 will be described with reference to Figures 2A and 2B.

[0025] Figure 2A is a diagram showing the configuration of the electric assist unit 100. Figure 2B is a diagram showing the configuration of the electric assist unit 100 according to a modified example.

[0026] As shown in Figure 2A, the electric assist unit 100 comprises a case unit 10, a planetary gear mechanism 20, a torque sensor (not shown), an electric motor 70, a plurality (in this case, three) of one-way clutches 81, 82, and 83, and a power input member 90. The electric assist unit 100 has three selectable gears: a first stage (lowest stage), a second stage, and a third stage (highest stage).

[0027] The case unit 10 includes a fixed case 11, a rotating case 12 as a case, a support member 13, and a motor support part 14.

[0028] The fixed case 11 is fixed to the support shaft 8. The fixed case 11 does not rotate relative to the support shaft 8.

[0029] The rotating case 12 is provided separately from the fixed case 11. The rotating case 12 rotatably supports the rear wheel 3b with respect to the support shaft 8. The rotating case 12 is provided integrally with the carrier 50 of the planetary gear mechanism 20, which will be described later. The rotating case 12 rotates together with the carrier 50 with respect to the support shaft 8. The rotating case 12 is connected to the carrier 50 and transmits at least one of the pedal force and the driving force to the rear wheel 3b. The rotating case 12 rotates together with the rear wheel 3b with respect to the fixed case 11, with respect to the support shaft 8. The rear wheel 3b is attached to the outer circumference of the rotating case 12 via spokes (not shown).

[0030] The support member 13 rotates together with the rotating case 12 (carrier 50). The support member 13 supports the planetary gears 40 and 43 of the planetary gear mechanism 20, which will be described later, on the rotating case 12. The support member 13 supports the space between the planetary gears 40 and 43 of the planetary gear mechanism 20, which will be described later, on the rotating case 12.

[0031] In this way, the support member 13 supports the planetary gear 40 and planetary gear 43 from the rotating case 12, so the planetary gear 40 and planetary gear 43 are supported from both ends by the rotating case 12. Therefore, compared to the case where the planetary gear 40 and planetary gear 43 are supported from one end by the rotating case 12 in a cantilever manner, the planetary gear 40 and planetary gear 43 can be stably supported by the rotating case 12. Furthermore, since the support portion of the support member 13 on the carrier 50 side is positioned on the inner circumferential surface side of the rotating case 12 that supports the support member 13, rather than on the planetary gear 43 which is formed with a large diameter to reduce the rotation of the electric motor 70, the length of the support member 13 in the planetary gear radial direction can be shortened, and the support member 13 can be made smaller.

[0032] As shown in Figure 2B, the planetary gears 40 and 43 may be arranged sequentially in the axial direction, and the support member 13 may support the position furthest from the inner circumferential surface of the rotating case 12. In other words, the planetary gears 40 and 43 may be supported at both ends by the rotating case 12 and the support member 13.

[0033] The motor support portion 14 is formed as part of the fixed case 11. The motor support portion 14 supports the stator 71 of the electric motor 70 (described later) in a non-rotatable manner. The motor support portion 14 also supports the ring gear 60 of the planetary gear mechanism 20 (described later) in a non-rotatable manner.

[0034] The planetary gear mechanism 20 comprises sun gears 31 and 32 as a plurality of sun gears, sun gear 33 as a sun gear different from the plurality of sun gears, planetary gear 40 as a first planetary gear, planetary gear 43 as a second planetary gear, carrier 50, and ring gear 60.

[0035] The sun gears 31 and 32 have different numbers of teeth. The pedal force applied by the driver is selectively input to the sun gears 31 and 32.

[0036] The sun gear 31 is provided on the outer circumference of the power input member 90. The sun gear 31 is provided so as to sandwich the sun gear 32 between it and the inner circumferential surface of the rotating case 12. The sun gear 31 transmits power to the tooth surface 41 of the planetary gear 40, which will be described later, when the gear shift is switched to the first stage, which has the largest reduction ratio.

[0037] The sun gear 32 is provided on the outer circumference of the power input member 90. The sun gear 32 is provided so as to face the inner circumferential surface of the rotating case 12, aligned axially with the sun gear 31. The sun gear 32 has a larger outer diameter than the sun gear 31. The sun gear 32 transmits power to the tooth surface 42 of the planetary gear 40, which will be described later, when the gear shift is switched to the second gear, which has a smaller reduction ratio than the first gear.

[0038] The sun gear 33 is provided separately from the sun gears 31 and 32. The sun gear 33 is located on the outer circumference of the support shaft 8. The sun gear 33 receives driving force from the electric motor 70. The sun gear 33 transmits the assist torque of the electric motor 70 to the planetary gear 43.

[0039] The planetary gear 40 is supported by the carrier 50. The planetary gear 40 rotates on its own axis A and revolves around the outer circumference of the sun gear 31. The planetary gear 40 has multiple tooth surfaces 41 and 42 that mesh with the sun gears 31 and 32 respectively, are provided coaxially, and rotate as a single unit. That is, multiple tooth surfaces 41 and 42 are provided coaxially with each other to constitute the planetary gear 40.

[0040] The tooth surface 41 is provided so as to sandwich the tooth surface 42 between it and the inner circumferential surface of the rotating case 12. The tooth surface 41 meshes with the sun gear 31. Power from the sun gear 31 is transmitted to the tooth surface 41 when the gear shift is switched to the first gear.

[0041] The tooth surface 42 is positioned axially alongside the tooth surface 41 and faces the inner circumferential surface of the rotating case 12. The tooth surface 42 is coaxial with the tooth surface 41 and rotates together with it. The tooth surface 42 meshes with the sun gear 32. The tooth surface 42 is formed with a smaller outer diameter than the tooth surface 41. Power from the sun gear 32 is transmitted to the tooth surface 42 when the gear ratio is switched to the second gear.

[0042] The planetary gear 43 is provided separately from the planetary gear 40 and is supported by the carrier 50. The planetary gear 43 is provided so as to sandwich the support portion of the support member 13 between it and the planetary gear 40. The planetary gear 43 rotates on its own axis around the rotation axis A and revolves around the outer circumference of the sun gear 33. The planetary gear 43 is provided coaxially with the planetary gear 40 and revolves and rotates together with it. The planetary gear 43 has a tooth surface 44 that meshes with the sun gear 33 and a tooth surface 45 that meshes with the ring gear 60.

[0043] The tooth surface 44 has the largest outer diameter among the tooth surfaces 41, 42, 44, and 45. Regardless of the gear shift, the assist torque from the electric motor 70 is transmitted to the tooth surface 44 via the sun gear 33.

[0044] The tooth surface 45 is positioned axially alongside the tooth surface 44 and further away from the inner circumferential surface of the rotating case 12 on the planetary gear 40 side than the tooth surface 44. The tooth surface 45 is coaxial with the tooth surface 44 and rotates integrally with it. The tooth surface 45 is formed with a larger outer diameter than the planetary gear 40 and a smaller outer diameter than the tooth surface 44. The tooth surface 45 meshes with the inner circumference of the ring gear 60.

[0045] Thus, since the outer diameter of the tooth surface 45 that meshes with the inner circumference of the ring gear 60 is smaller than the outer diameter of the tooth surface 44, it is possible to suppress the radial increase in the rotating case 12 and increase the reduction ratio of the electric motor 70 to increase the assist torque. Alternatively, the ring gear 60 may be configured to mesh with the outer circumference of the tooth surface 44 without providing the tooth surface 45. In this case, since there is no need to provide the tooth surface 45, the axial length of the electric assist unit 100 can be reduced.

[0046] The carrier 50 is integrally mounted with the rotating case 12 and supports one axial end of the planetary gears 40 and 43. The parts of the planetary gears 40 and 43 that are away from the axial end are supported by the support member 13. In other words, the planetary gears 40 and 43 are supported at two points by the carrier 50 and the support member 13. The carrier 50 supports the planetary gears 40 and 43 so that they can rotate (spin) around the rotation axis A. As the planetary gears 40 and 43 revolve, the carrier 50 rotates together with the rotating case 12 around the support axis 8.

[0047] Thus, the pedal force applied by the driver is transmitted from the inner circumference to the outer circumference in the following order: sun gears 31, 32, planetary gear 40, carrier 50, rotating case 12, and rear wheel 3b. Therefore, compared to a case where the driving force is input from the ring gear on the outside of the carrier, which is a gear shifting mechanism, and output to the rotating case on the outside of the ring gear, the input and output paths of the driving force can be made simpler. Consequently, the electric assist unit 100 can be made smaller.

[0048] Furthermore, by using a sun gear 33 as the drive force input gear to which the drive force from the electric motor 70 is input, the drive force from the electric motor 70 is transmitted from the inner circumference to the outer circumference in the following order: sun gear 33, planetary gear 43, carrier 50, rotating case 12, and rear wheel 3b, similar to the input force input from the sun gear 33, planetary gear 43, carrier 50, rotating case 12, and rear wheel 3b. Therefore, compared to the case where the drive force is input from the ring gear on the outside of the carrier, which is a gear shifting mechanism, and output to the rotating case on the outside of the ring gear, the input and output paths of the drive force can be made simpler. Consequently, the electric assist unit 100 can be made smaller.

[0049] Furthermore, the electric assist unit 100 is provided with a single ring gear 60 that is non-rotatable and meshes with a planetary gear 43 that revolves and rotates integrally with the planetary gear 40. Therefore, it is not necessary to provide ring gears in the gear shifting mechanism that transmits the pedaling force from the driver and in the reduction mechanism that transmits the driving force from the electric motor 70. Consequently, the electric assist unit 100 can be made smaller.

[0050] The ring gear 60 is non-rotatably supported on the support shaft 8. The ring gear 60 meshes only with the tooth surface 45 of the planetary gear 43, but since the planetary gears 40 and 43 are mounted coaxially and revolve and rotate together, the ring gear 60 is a common ring gear for the planetary gears 40 and 43.

[0051] In this way, the ring gear 60 is shared between the input path for the driver's pedal force and the input path for the driving force from the electric motor 70, thus reducing the number of parts.

[0052] The electric motor 70 assists the driving force in accordance with the pedal pressure applied by the driver. The electric motor 70 is driven by a command from the controller 9a. The electric motor 70 generates assist torque using power supplied from the energy storage unit 9b.

[0053] The torque sensor detects the driving torque generated by the driver pedaling the crank arm 7b via the pedal 7 and transmitted to the crank shaft 7c. The torque sensor is a non-contact type torque sensor that detects torque based on the twist of the crank shaft 7c, for example, measured by magnetism.

[0054] The one-way clutch 81 is provided between the inner circumference of the sun gear 31 and the outer circumference of the power input member 90. The one-way clutch 81 switches between a state in which the pedal force applied by the driver is transmitted to the sun gear 31 via the power input member 90, and a state in which the rotation of the sun gear 31 is not transmitted to the pedal 7. As a result, the one-way clutch 81 transmits the pedal force applied by the driver to the sun gear 31 via the power input member 90. The one-way clutch 81 does not transmit the rotation of the sun gear 31 to the pedal 7.

[0055] The one-way clutch 82 is provided between the inner circumference of the sun gear 32 and the outer circumference of the power input member 90. The one-way clutch 82 switches between a state in which the pedal force applied by the driver is transmitted to the sun gear 32 via the power input member 90, and a state in which the rotation of the sun gear 32 is not transmitted to the pedal 7. As a result, the one-way clutch 82 transmits the pedal force applied by the driver to the sun gear 32 via the power input member 90. The one-way clutch 82 does not transmit the rotation of the sun gear 32 to the pedal 7.

[0056] The one-way clutch 83 is provided between the inner circumference of the rotating case 12 and the outer circumference of the power input member 90. The one-way clutch 83 switches between a state in which the pedal force applied by the driver is transmitted to the rotating case 12 via the power input member 90, and a state in which the rotation of the rotating case 12 is not transmitted to the pedal 7. The one-way clutch 83 transmits the pedal force applied by the driver to the rotating case 12 via the power input member 90.

[0057] As described above, multiple one-way clutches 81, 82, and 83 are provided. Therefore, even if pedal force is applied from two adjacent one-way clutches 81, 82, and 82 during gear shifting, the pedal force will not be transmitted to the sun gear 31, 32 or the rotating case 12 with the higher rotational speed. Thus, gear changes can be performed smoothly.

[0058] The power input member 90 is provided on the inner circumference of the driven sprocket 6b to which pedal force is input. The power input member 90 is a cylindrical member that is rotatably mounted on the outer circumference of the support shaft 8. The power input member 90 selectively transmits the drive torque input from the driven sprocket 6b to one of the sun gears 31, 32 and the rotating case 12 via one of the one-way clutches 81, 82, or 83.

[0059] Next, with reference to Figures 3A to 3C, each gear of the electric assist unit 100 will be described.

[0060] Figure 3A is a collinear diagram of the electric assist unit 100, showing the state when switched to the first stage. Figure 3B is a collinear diagram of the electric assist unit 100, showing the state when switched to the second stage. Figure 3C is a collinear diagram of the electric assist unit 100, showing the state when switched to the third stage.

[0061] As shown in Figure 3A, when the gear is switched to the lowest gear, the first gear, the drive torque input from the driven sprocket 6b via the power input member 90 is transmitted to the sun gear 31 via the one-way clutch 81. Since the sun gear 31 meshes with the tooth surface 41 of the planetary gear 40, the driving force is transmitted from the sun gear 31 to the planetary gear 40, and the revolution of the planetary gear 40 is transmitted from the carrier 50 to the rotating case 12. As a result, the driver's pedal force is reduced and transmitted to the rear wheels 3b.

[0062] In this case, the outer diameter of the sun gear 31 is smaller than that of the sun gear 32, and the outer diameter of the tooth surface 41 of the planetary gear 40 is larger than that of the tooth surface 42 (the number of teeth formed on tooth surface 41 is greater than the number of teeth formed on tooth surface 42), so the driver's pedal force is transmitted to the rear wheels 3b at the largest reduction ratio.

[0063] As shown in Figure 3B, when the gear is switched to the second gear, the drive torque input from the driven sprocket 6b via the power input member 90 is transmitted to the sun gear 32 via the one-way clutch 82. Since the sun gear 32 meshes with the tooth surface 42 of the planetary gear 40, the driving force is transmitted from the sun gear 32 to the planetary gear 40, and the revolution of the planetary gear 40 is transmitted from the carrier 50 to the rotating case 12. As a result, the driver's pedal force is reduced and transmitted to the rear wheels 3b.

[0064] In this case, the outer diameter of the sun gear 32 is larger than that of the sun gear 31, and the outer diameter of the tooth surface 42 of the planetary gear 40 is smaller than that of the tooth surface 41 (the number of teeth formed on the tooth surface 42 is less than the number of teeth formed on the tooth surface 41). Therefore, the driver's pedal force is transmitted to the rear wheels 3b with a smaller reduction ratio compared to when the gear is in the first gear.

[0065] As shown in Figure 3C, when the gear is switched to the highest gear, the third gear, the drive torque input from the driven sprocket 6b via the power input member 90 is transmitted directly to the rotating case 12 via the one-way clutch 83. At this time, the driven sprocket 6b, the power input member 90, and the rotating case 12 rotate as a single unit. As a result, the driver's pedal force is transmitted directly to the rear wheels 3b without deceleration.

[0066] Next, the specific configuration of the electric assist unit 100 will be described with reference to Figures 4 to 6. Note that the configuration of the electric assist unit 100 has already been explained with reference to Figures 2A and 2B, so redundant explanations will be omitted as appropriate.

[0067] Figure 4 is a cross-sectional view of the electric assist unit 100, showing the state when it is switched to the first stage. Figure 5 is a cross-sectional view of the electric assist unit 100, showing the state when it is switched to the second stage. Figure 6 is a cross-sectional view of the electric assist unit 100, showing the state when it is switched to the third stage.

[0068] The electric assist unit 100 comprises a case unit 10, a planetary gear mechanism 20, a torque sensor, an electric motor 70, a plurality of one-way clutches 81, 82, 83, a power input member 90, a speed shift shaft 92, and a sliding engagement member 94.

[0069] The case unit 10 includes a fixed case 11, a rotating case 12, a support member 13, and a motor support part 14.

[0070] The fixed case 11 is formed in a roughly cup shape with almost the entire surface of one axial side open. The fixed case 11 is attached to the support shaft 8 and rotates integrally with the support shaft 8. The fixed case 11 houses the electric motor 70, the sun gear 33, and the ring gear 60.

[0071] The rotating case 12 includes a first case 12a, a second case 12b, and a plurality of bolts 12c as fastening members.

[0072] The first case 12a is formed in a substantially cup shape with substantially the entire other surface in the axial direction being open. The first case 12a is rotatably supported on the outer circumference of the power input member 90 via a bearing 16. The first case 12a houses the sun gears 31, 32, the planetary gears 40, 43, and the one-way clutches 81, 82, 83. The first case 12a is provided so as to face the fixed case 11 with its opening opposite. One flange 17, to which spokes are connected, is provided on the outer circumference of the first case 12a so as to protrude outwards.

[0073] The second case 12b is formed in a substantially cup shape with substantially the entire surface of one axial side open. The second case 12b is provided with a gap between it and the outer surface of the fixed case 11 so as to cover the outside of the fixed case 11. The second case 12b is rotatably supported on the outer circumference of the fixed case 11 via a bearing 15. The second case 12b is provided so as to have its opening facing the first case 12a and is fastened to the first case 12a by bolts 12c. The opening of the second case 12b opens in the same direction as the opening of the fixed case 11. The other flange 17 to which the spokes are connected is provided on the outer circumference of the second case 12b so as to protrude outwards.

[0074] As a result, the electric assist unit 100 can be assembled simply by housing the sun gears 31, 32, planetary gears 40, 43, and one-way clutches 81, 82, 83 in the first case 12a, and the electric motor 70, sun gear 33, and ring gear 60 in the fixed case 11, then facing the openings of the first case 12a and the fixed case 11 toward each other, attaching the second case 12b, and fastening it to the first case 12a with bolts 12c.

[0075] The support member 13 is formed in a substantially cup shape, with substantially the entire surface of one axial side open and the rotation center and its vicinity on the other side open to allow insertion of the support shaft 8. The support member 13 is formed with a smaller outer diameter than the first case 12a. The support member 13 is attached to the radially extending inner wall surface of the first case 12a such that one of its opening surfaces faces the radially extending inner wall surface of the first case 12a. The support member 13 supports the planetary gears 40 and 43 via the bearing 13a so that they can rotate around the rotation axis A. As the planetary gears 40 and 43 revolve, the support member 13 rotates together with the planetary gears 40 and 43 around the support shaft 8.

[0076] The carrier 50 is provided integrally with the rotating case 12. In other words, the carrier 50 constitutes a part of the rotating case 12. The carrier 50 supports the planetary gears 40 and 43 via bearings 50a so that they can rotate around the rotation axis A. As the planetary gears 40 and 43 revolve, the carrier 50 rotates together with the planetary gears 40 and 43 around the support axis 8.

[0077] The electric motor 70 includes a stator 71 and a rotor 72. The stator 71 is supported so as not to rotate by a motor support 14. The rotor 72 is located on the inner circumference side of the stator 71 and rotates relative to the stator 71. A sun gear 33 is attached to the rotor 72. The rotor 72 rotates together with the sun gear 33.

[0078] The power input member 90 is rotatably supported on the outer circumference of the support shaft 8 via a bearing 91. The power input member 90 has a spline 90a as a first engaging portion and a spline 90b as a second engaging portion.

[0079] The spline 90a is formed on the outer circumference of the large-diameter portion and engages with the spline formed on the inner circumferential surface of the driven sprocket 6b.

[0080] The spline 90b is formed on the outer circumference of a smaller diameter portion that is smaller in diameter than the spline 90a and offset in the axial direction, and engages with the spline 94a of the sliding engagement member 94. The spline 90b always engages with the spline 94a regardless of the axial position of the sliding engagement member 94.

[0081] The speed change shaft 92 is axially slidable inside the support shaft 8, and the axial engagement position with the sliding engagement member 94 switches which inner races 81a, 82a, and 83a the sliding engagement member 94 rotates with.

[0082] This allows the gear ratio to be changed simply by altering the axial position of the gear shift shaft 92 based on the driver's operation. Therefore, for example, the gear ratio can be changed by the driver operating a lever or similar device, similar to the gear shifting on a regular bicycle.

[0083] The connecting member 93 is positioned perpendicular to the central axis of the transmission shaft 92 and engages with the transmission shaft 92 in the axial direction. The connecting member 93 connects the transmission shaft 92 and the sliding engagement member 94, allowing them to move together in the axial direction.

[0084] The sliding engagement member 94 is provided so as to be axially slidable with respect to the power input member 90 and engages with the power input member 90 so as to rotate together with the power input member 90. The sliding engagement member 94 engages with one of the inner races 81a, 82a, 83a of the plurality of one-way clutches 81, 82, 83 so as to rotate together with them.

[0085] Specifically, the sliding engagement member 94 is a member consisting of two coaxial cylindrical parts. The inner surface of the smaller diameter cylindrical part located on the inner circumference side of the sliding engagement member 94 engages with the connecting member 93. A spline 94a is formed on the inner surface of the larger diameter cylindrical part located on the outer circumference side of the sliding engagement member 94 as a third engagement part, and a spline 94b is formed on the outer surface as a fourth engagement part.

[0086] The spline 94a engages with the spline 90b of the power input member 90. The spline 94b selectively engages with one of the inner races 81a, 82a, or 83a of the one-way clutches 81, 82, or 83.

[0087] This allows the pedal force input from the power input member 90 to be transmitted to any of the one-way clutches 81, 82, or 83 simply by sliding the sliding engagement member 94 in the axial direction.

[0088] Next, we will explain each gear of the electric assist unit 100.

[0089] In the state shown in Figure 4, the gear ratio of the electric assist unit 100 is shifted to the first gear. At this time, the drive torque input from the driven sprocket 6b via the power input member 90 is transmitted to the sun gear 31 via the sliding engagement member 94 and the one-way clutch 81. Since the sun gear 31 meshes with the tooth surface 41 of the planetary gear 40, the driving force is transmitted from the sun gear 31 to the planetary gear 40, and the revolution of the planetary gear 40 is transmitted from the carrier 50 to the rotating case 12. As a result, the rotation of the driven sprocket 6b, which is rotated by the driver's pedal force, is reduced and transmitted to the rear wheel 3b. From this state, when the gear shift shaft 92 slides in the direction of retracting from the case unit 10 based on the driver's operation, the state shown in Figure 5 is switched.

[0090] In the state shown in Figure 5, the electric assist unit 100 is shifted to the second gear. At this time, the drive torque input from the driven sprocket 6b via the power input member 90 is transmitted to the sun gear 32 via the sliding engagement member 94 and the one-way clutch 82. Since the sun gear 32 meshes with the tooth surface 42 of the planetary gear 40, the driving force is transmitted from the sun gear 32 to the planetary gear 40, and the revolution of the planetary gear 40 is transmitted from the carrier 50 to the rotating case 12. As a result, the rotation of the driven sprocket 6b, which is rotated by the driver's pedal force, is reduced and transmitted to the rear wheel 3b. From this state, if the transmission shaft 92 slides further in the direction of retracting from the case unit 10 based on the driver's operation, it switches to the state shown in Figure 6.

[0091] In the state shown in Figure 6, the electric assist unit 100 is shifted to the third gear. At this time, the drive torque input from the driven sprocket 6b via the power input member 90 is directly transmitted to the rotating case 12 via the sliding engagement member 94 and the one-way clutch 83. At this time, the driven sprocket 6b, the power input member 90, and the rotating case 12 rotate as a single unit. As a result, the rotation of the driven sprocket 6b, which is rotated by the driver's pedal force, is directly transmitted to the rear wheel 3b without being decelerated.

[0092] Thus, in the electric assist unit 100, the input and output are equal in the third gear, and the first and second gears are configured to have a reduction gear ratio. As a result, when the assist torque is transmitted by the electric motor 70 to the rear wheel 3b, which is the drive wheel, and the unit is switched to the third gear, which is the highest gear and is used most frequently, the driver's pedal force is transmitted directly to the rotating case 12 without going through the various components of the planetary gear mechanism 20. Therefore, the load on the various components of the planetary gear mechanism 20 of the electric assist unit 100 is avoided, and the durability of the electric assist unit 100 can be improved.

[0093] The configuration and effects of this embodiment will now be explained in summary.

[0094] (1)(7) The electric assist unit 100 of the bicycle 1 comprises a plurality of sun gears 31, 32 having different numbers of teeth from each other to which pedaling force from the driver is selectively input; a planetary gear 40 having tooth surfaces 41, 42 that mesh with the plurality of sun gears 31, 32 respectively; an electric motor 70 that generates a driving force to assist pedaling force; a sun gear 33 different from the plurality of sun gears 31, 32 to which driving force from the electric motor 70 is input; a planetary gear 43 that revolves and rotates together with the planetary gear 40 and meshes with the sun gear 33 different from the plurality of sun gears 31, 32; a ring gear 60 that is not rotatable and meshes with the planetary gear 43; a carrier 50 that supports the planetary gear 40 and the planetary gear 43; and a rotating case 12 connected to the carrier 50 that transmits at least one of pedaling force and driving force to the rear wheel 3b.

[0095] In this configuration, the electric assist unit 100 is provided with a single ring gear 60 that meshes with a planetary gear 43, which is mounted so as not to rotate and revolves and rotates integrally with the planetary gear 40. Therefore, it is not necessary to provide ring gears in the gear shifting mechanism that transmits the pedaling force from the driver and in the reduction mechanism that transmits the driving force from the electric motor 70. Consequently, the electric assist unit 100 can be made smaller.

[0096] Furthermore, the pedal force applied by the driver is transmitted from the inner circumference to the outer circumference in the following order: sun gears 31, 32, planetary gear 40, carrier 50, rotating case 12, and rear wheel 3b. Therefore, compared to a case where the driving force is input from the ring gear on the outside of the carrier, which is the gear shifting mechanism, and output to the rotating case on the outside of the ring gear, the input and output paths of the driving force can be made simpler. Consequently, the electric assist unit 100 can be made smaller.

[0097] (2) The rotating case 12 also rotatably supports the rear wheel 3b with respect to the support shaft 8 and rotates together with the carrier 50 with respect to the support shaft 8.

[0098] In this configuration, the driver's pedal force is input to the sun gears 31, 32 or the rotating case 12 of the electric assist unit 100 via the drive sprocket 6a and the driven sprocket 6b. If the number of teeth on the driven sprocket 6b is less than the number of teeth on the drive sprocket 6a, the driving force transmitted from the drive sprocket 6a to the driven sprocket 6b is accelerated, and the torque input to the sun gears 31, 32 or the rotating case 12 is reduced accordingly. As a result, the load-bearing capacity of each component of the electric assist unit 100 can be reduced, and the size of the electric assist unit 100 can be suppressed.

[0099] (3) The electric assist unit 100 also includes multiple one-way clutches 81, 82 that switch between a state in which the pedal force applied by the driver is transmitted to multiple sun gears 31, 32, and a state in which the rotation of the multiple sun gears 31, 32 is not transmitted to the pedal 7.

[0100] With this configuration, since one-way clutches 81 and 82 are provided, even if pedal force is applied from both one-way clutches 81 and 82 during gear shifting, the pedal force is not transmitted to the sun gear 31 or 32 with the higher rotational speed. Therefore, gear changes can be made smoothly.

[0101] (4) The electric assist unit 100 further includes a power input member 90 provided on the inner circumference of the driven sprocket 6b to which pedal force is input, and a sliding engagement member 94 provided to slide axially with respect to the power input member 90, which engages with the power input member 90 so as to rotate together with the power input member 90 and engages with one of the inner races 81a, 82a, 83a of the plurality of one-way clutches 81, 82, 83 so as to rotate together.

[0102] With this configuration, the pedal force input from the power input member 90 can be transmitted to any of the one-way clutches 81, 82, or 83 simply by sliding the sliding engagement member 94 in the axial direction.

[0103] (5) The electric assist unit 100 is further equipped with a speed change shaft 92 that is axially slidable inside the support shaft 8 and switches which inner races 81a, 82a, and 83a the sliding engagement member 94 rotates with depending on the axial engagement position with the sliding engagement member 94.

[0104] With this configuration, the gear ratio can be changed simply by changing the axial position of the gear shift shaft 92 based on the driver's operation. Therefore, for example, the gear ratio can be changed by the driver operating a lever or the like, similar to the gear shifting of a normal bicycle.

[0105] (6) The electric assist unit 100 further includes a support member 13 that supports the rotating case 12 between the planetary gear 40 and the planetary gear 43.

[0106] In this configuration, the support member 13 supports the planetary gear 40 and planetary gear 43 from the rotating case 12, so the planetary gear 40 and planetary gear 43 are cantilevered to the rotating case 12. Therefore, the axial length of the planetary gear 40 and planetary gear 43 can be reduced compared to the case where the planetary gear 40 and planetary gear 43 are supported from both ends.

[0107] Although embodiments of the present invention have been described above, these embodiments are merely examples of how the present invention can be applied, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0108] For example, in the above embodiment, the electric assist unit 100 is attached to the rear wheel 3b together with the driven sprocket 6b. However, the electric assist unit 100 may also be attached to the crankshaft 7c together with the drive sprocket 6a. In this case, the pedaling force (driving torque) transmitted from the crank arm 7b to the crankshaft 7c when the driver pedals the crank arm 7b via the pedal 7 may be input to the sun gears 31, 32 or the rotating case 12. Alternatively, the output of the electric assist unit 100 may be transmitted to the drive sprocket 6a via the rotating case 12, and then to the driven sprocket 6b via a chain 6c wrapped between the drive sprocket 6a and the drive sprocket 6a, thereby rotating the rear wheel 3b.

[0109] Furthermore, in the above embodiment, the rotor 72 is a so-called inner rotor provided on the inner circumference of the stator 71. Alternatively, the stator may be provided on the inner circumference side, and the rotor may rotate around the outer circumference of the stator, making it a so-called outer rotor.

[0110] Furthermore, in the above embodiment, the system is configured to include multiple one-way clutches 81, 82 that switch between a state in which the pedal force applied by the driver is transmitted to each of the multiple sun gears 31, 32, and a state in which the rotation of the sun gears 31, 32 is not transmitted to the pedal 7. Alternatively, multiple clutches that simply switch between a state in which the pedal force applied by the driver is transmitted to each of the multiple sun gears 31, 32, and a state in which the rotation of the sun gears 31, 32 is not transmitted to the pedal 7 may be provided.

[0111] Furthermore, in the above embodiment, the system is configured to include a power input member 90 provided on the inner circumference of the driven sprocket 6b to which pedal force is input, and a sliding engagement member 94 provided to slide axially with respect to the power input member 90, engage with the power input member 90 so as to rotate together with the power input member 90, and engage to rotate together with one of the inner races 81a, 82a, 83a of the multiple one-way clutches 81, 82, 83. Alternatively, the system may be configured to include a rotational engagement member that rotates relative to an axis so as to rotate together with one of the inner races 81a, 82a, 83a of the multiple one-way clutches 81, 82, 83.

[0112] Furthermore, in the above embodiment, a support member 13 is provided to support the planetary gear 40 and planetary gear 43 between the rotating case 12, and the planetary gears 40 and 43 are arranged in order in the axial direction, with the support member 13 supporting the position furthest from the inner circumferential surface of the rotating case 12 on the planetary gear 40 side. Alternatively, a cantilever configuration may be used in which the carrier 50 is supported only by the wall portion of the rotating case 12, without the support member 13. [Explanation of Symbols]

[0113] 100 Electric Assist Unit 1 Bicycle 3b Rear wheels (drive wheels) 6b Driven sprocket 7 pedals 8 Support shaft 12-inch rotating case (case) 13 Support Member 31,32 Sanguia 33 Sangiya 40 Planetary Gear (First Planetary Gear) 41,42 Tooth surface 43 Planetary Gear (Second Planetary Gear) 44,45 Tooth surface 50 Carriers 60 Ring Gear 70 Electric motor 81, 82, 83 One-way clutch 81a, 82a, 83a Inner Lace 90 Power input member 92 Gear shift shaft 94 Sliding engagement member

Claims

1. It is an electric assist unit for bicycles. Multiple sun gears, each with a different number of teeth, to which the driver's pedal force is selectively input, A first planetary gear having tooth surfaces that mesh with each of the aforementioned multiple sun gears, An electric motor that generates a driving force to assist the pedal force, A sun gear different from the plurality of sun gears to which the driving force from the electric motor is input, A second planetary gear revolves and rotates integrally with the first planetary gear and meshes with a sun gear different from the plurality of sun gears, A ring gear is provided so as not to rotate and meshes with the second planetary gear, A carrier supporting the first planetary gear and the second planetary gear, A case connected to the carrier that transmits at least one of the pedal force and the driving force to the drive wheels, Equipped with, Electric assist unit for bicycles.

2. An electric assist unit for a bicycle according to claim 1, The case rotatably supports the drive wheel with respect to the support shaft and rotates together with the carrier with respect to the support shaft. Electric assist unit for bicycles.

3. An electric assist unit for a bicycle according to claim 2, The system further includes multiple one-way clutches that switch between a state in which the pedal force applied by the driver is transmitted to each of the multiple sun gears, and a state in which the rotation of the multiple sun gears is not transmitted to the pedal. Electric assist unit for bicycles.

4. The electric assist unit for a bicycle according to claim 3, A power input member is provided on the inner circumference of the driven sprocket to which the pedal force is applied, A sliding engagement member is provided to be slidably mounted in the axial direction with respect to the power input member, engages with the power input member so as to rotate together with the power input member, and engages with one of the inner races of the plurality of one-way clutches so as to rotate together with the power input member, It also has, Electric assist unit for bicycles.

5. The electric assist unit for a bicycle according to claim 4, The system further includes a variable speed shaft that is axially slidable inside the support shaft and switches which inner race the sliding engagement member rotates with depending on the axial engagement position with the sliding engagement member. Electric assist unit for bicycles.

6. An electric assist unit for a bicycle according to any one of claims 1 to 5, The case further includes a support member that supports the space between the first planetary gear and the second planetary gear. Electric assist unit for bicycles.

7. It is an electric assist bicycle, Multiple sun gears, each with a different number of teeth, to which the driver's pedal force is selectively input, A first planetary gear having tooth surfaces that mesh with each of the aforementioned multiple sun gears, An electric motor that generates a driving force to assist the pedal force, A sun gear different from the plurality of sun gears to which the driving force from the electric motor is input, A second planetary gear revolves and rotates integrally with the first planetary gear and meshes with a sun gear different from the plurality of sun gears, A ring gear is provided so as not to rotate and meshes with the second planetary gear, A carrier supporting the first planetary gear and the second planetary gear, A case connected to the carrier that transmits at least one of the pedal force and the driving force to the drive wheels, Equipped with, Electric-assist bicycle.

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