Assist drive unit

Abstract

To provide an assist drive unit in which an assist motor is located coaxially with a pedal crank shaft and related components are compactly arranged.SOLUTION: An assist drive unit comprises: a first one-way clutch 26 which transmits a torque when a pedal crank shaft 3 normally rotates with respect to a unit output member 19, and does not transmit a load when the pedal crank shaft 3 reversely rotates with respect to the unit output member 19; and a second one-way clutch 28 which transmits an assist torque when an assist output member 47 normally rotates with respect to the unit output member 19. The first one-way clutch 26 and the second one-way clutch 28 are arranged coaxially with the pedal crank shaft 3 and are arranged side by side in an axial direction of the pedal crank shaft 3, and further, are arranged at a position where the clutches overlap with the assist motor 15 when viewed from a radian direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an assist drive unit.

Background Art

[0002] Conventionally, in a drive unit of an assist bicycle that applies assist torque by an electric motor to the pedal force of a rider, for example, in Patent Document 1, the human power driving force F1 is transmitted from the pedal crankshaft 15 to the input side rotating body 23, but the reverse force (the auxiliary driving force F2 from the motor 8 side) is not transmitted from the input side rotating body 23 to the pedal crankshaft 15. An input side one-way clutch 44 and an output side one-way clutch 45 provided in the rotational transmission path between the input side rotating body 23 and the rotational output portion 17 (between the outer periphery of the cylindrical portion 23b of the input side rotating body 23 and the inner periphery of the rotational output portion 17) are provided. A drive unit 9 is disclosed. The gear teeth on the outer periphery of the input side rotating body 23 are connected to the motor 8 side on a different axis from the pedal crankshaft 15. For example, in Patent Document 2, a drive unit 20 is disclosed in which a motor 31, a planetary roller reducer 40, and a one-way clutch 58 are arranged coaxially with the pedal crankshaft 39, and a one-way clutch 55 and a gear shaft 54 are arranged on a different axis from the pedal crankshaft 39. The human power driving force is transmitted to the drive sprocket 4 through the one-way clutch 58 coaxially with the pedal crankshaft 15, and the motor driving force is transmitted to the sprocket 4 through the one-way clutch 55 and the gear shaft 54 on a different axis from the pedal crankshaft 15.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the assist drive unit described above, if the assist motor is mounted on a separate axis from the pedal crank axis, the overall length of the unit increases, and the weight also tends to increase. On the other hand, in a configuration where the assist motor is mounted coaxially with the pedal crank axis, the single-axis structure necessitates a compact arrangement of each component.

[0005] Therefore, the present invention aims to provide an assist drive unit in which the assist motor is arranged coaxially with the pedal crank axis and related components are compactly arranged. [Means for solving the problem]

[0006] As a means of solving the above problems, the first aspect of the present invention is an assist drive unit (10) that applies assist torque to the pedal crank shaft (3) from an assist motor (15) arranged coaxially with the pedal crank shaft (3), comprising: a unit output member (19) arranged coaxially with the pedal crank shaft (3) and outputting driving force to the outside of the unit; and a first one that can transmit torque when the pedal crank shaft (3) rotates relative to the unit output member (19) in the direction of vehicle travel, and can slip and not transmit torque when the pedal crank shaft (3) rotates relative to the unit output member (19) in the opposite direction to the direction of vehicle travel. The system includes a one-way clutch (26), an assist output member (47) arranged coaxially with the unit output member (19) and outputting assist torque for the assist motor (15), and a second one-way clutch (28) that enables the transmission of assist torque when the assist output member (47) rotates relative to the unit output member (19) in the direction of vehicle travel. The first one-way clutch (26) and the second one-way clutch (28) are arranged coaxially with the pedal crank shaft (3), side by side in the axial direction of the pedal crank shaft (3), and are positioned to overlap with the assist motor (15) when viewed radially. With this configuration, the first one-way clutch that allows the pedal crank shaft to reverse and the second one-way clutch for transmitting assist torque are arranged coaxially with each other, and both one-way clutches are placed within the axial width of the assist motor, allowing the related components to be arranged compactly and the overall unit to be miniaturized.

[0007] A second aspect of the present invention, in the first aspect described above, comprises a sensor shaft (18) arranged coaxially with the pedal crank shaft (3) and adjacent to the unit output member (19) in the axial direction, wherein one end of the sensor shaft (18) is supported to rotate integrally with the pedal crank shaft (3), and the other end of the sensor shaft (18) is supported to rotate relative to the pedal crank shaft (3) via a needle bearing (27), and a first one-way clutch (26) is supported on the outer circumference of the other end of the sensor shaft (18). This configuration includes a sensor shaft in which one axial end is fixed to the pedal crank shaft and the other axial end is supported via a needle bearing. By supporting a first one-way clutch on the outer circumference of the other axial end of the sensor shaft, the first one-way clutch is supported with high rigidity, and the twisting between the axial ends of the sensor shaft is not hindered, allowing for good torque detection based on the twisting of the sensor shaft.

[0008] A third aspect of the present invention is the first or second aspect described above, which includes a reduction gear (40) located on the inner circumference of the assist motor (15) and positioned to overlap with the assist motor (15) when viewed radially. With this configuration, the reduction gear is positioned on the inner circumference of the assist motor and within the axial width of the assist motor, allowing for a compact arrangement of related components and thus reducing the overall size of the unit.

[0009] A fourth aspect of the present invention is that, in the third aspect described above, the assist motor (15) is of the inner rotor type, and an internal gear (41) of the reduction gear (40) is provided on the inner circumference of the rotor (15a) of the assist motor (15). With this configuration, the internal gear of the reduction gear is provided on the inner circumference of the inner rotor of the assist motor, allowing the input shaft for the reduction gear and the rotor shaft to which the magnets in the assist motor are attached to be used interchangeably. Furthermore, by using a common material such as S45C for the rotor material, it can be used as the back yoke for the magnetic path of the electromagnetic section.

[0010] A fifth aspect of the present invention is the fourth aspect described above, wherein the reduction gear (40) comprises a pair of axially adjacent internal planetary gear reduction gears (40a), and the internal gears (41) of each of the pair of internal planetary gear reduction gears (40a) are supported on the inner circumference of a single rotor (15a) via eccentric oscillation bearings (42), and thrust supports (40b) are attached to both axial sides of the inner circumference of the rotor (15a) to restrict the axial movement of the eccentric oscillation bearings (42). In this configuration, the operation of a pair of axially adjacent internal planetary gear reducers generates precessional motion, which acts as a thrust force on the output gear. Due to this effect, there is a risk that the eccentric oscillation bearing provided on the input gear (internal gear) may come loose from the input gear. As a means of suppressing this effect, for example, by providing general circlips as thrust supports on both axial sides of the eccentric oscillation bearing, the effect of the thrust force on the output gear can be reduced. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an assist drive unit in which the assist motor is arranged coaxially with the pedal crank shaft and related components are compactly arranged. [Brief explanation of the drawing]

[0012] [Figure 1] This is a left side view of a bicycle according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view of the assist drive unit of the above-mentioned bicycle, along the axial direction. [Figure 3] This is a perspective view of the rotor of the assist motor of the above-mentioned assist drive unit. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. Unless otherwise specified, directions such as front, rear, left, and right in the following description are the same as the directions of the vehicle described below. In addition, arrows FR indicating the front of the vehicle, LH indicating the left side of the vehicle, and UP indicating the top of the vehicle are shown in appropriate places in the drawings used in the following description. In this embodiment, "intermediate" means not only the center between the two ends of the object, but also the area inside between the two ends of the object. In the following description, it is assumed that the vehicle body is upright and not tilted to the left or right.

[0014] Figure 1 is a left side view of the bicycle 1 according to the embodiment. The bicycle 1 shown in Figure 1 is an electric assist bicycle equipped with an assist motor 15 that generates auxiliary power in accordance with the pedaling force applied to the pedals 2. The bicycle 1 has an assist drive unit 10 mounted around the pedal crank shaft 3 which is aligned in the left-right direction, and a battery 5 mounted, for example, along the frame 4. In the figure, reference numeral 6 indicates the front wheel, reference numeral 7 indicates the rear wheel, reference numeral 8 indicates the handlebars, reference numeral 9 indicates the seat, reference numeral 2a indicates the pedal crank arm, and line C1 indicates the rotational axis of the pedal crank shaft 3. Hereinafter, the direction along axis C1 will be referred to as the axial direction, the direction perpendicular to axis C1 will be referred to as the radial direction, and the direction of rotation around axis C1 will be referred to as the circumferential direction.

[0015] Figure 2 is a cross-sectional view of the assist drive unit 10 of bicycle 1 along the axial direction. Referring also to FIG. 2, the assist drive unit 10 includes an assist motor 15 configured coaxially with the pedal crankshaft 3, a speed reducer 40 also configured coaxially with the pedal crankshaft 3 and transmitting the driving force (torque) of the assist motor 15 to the pedal crankshaft 3, and a unit case 11 that houses the assist motor 15 and the speed reducer 40 and is supported by the vehicle body frame 4. The assist drive unit 10 is an electric drive unit with a compact single-axis structure in which the assist motor 15 and the speed reducer 40 are arranged coaxially with the pedal crankshaft 3, and is a drive unit that can be suitably used for an electric assist bicycle.

[0016] The unit case 11 is divided in the vehicle width direction into left and right case bodies 12 and 13. The left case body 12 is formed in a bottomed cylindrical shape that opens to the right, and the right case body 13 is formed in a bottomed cylindrical shape that opens to the left. The right case body 13 has a greater depth in the vehicle width direction than the left case body 12. The assist motor 15 and the speed reducer 40 are housed in a closed space formed by abutting the open portions of the left and right case bodies 12 and 13 against each other. In particular, the assist motor 15 and the speed reducer 40 are housed inside the right case body 13, and control system components such as a control board 36 and a sensor 37 are housed inside the left case body 12. The left and right case bodies 12 and 13 are integrally formed as cast parts made of, for example, an aluminum alloy.

[0017] The left case body 12 includes a left side wall 12a facing the left side of the vehicle and a left outer peripheral wall 12b extending rightward (toward the right case body 13) from the outer periphery of the left side wall 12a. At the central portion of the left side wall 12a, a left bearing portion 22 is provided for supporting the left side portion of the pedal crankshaft 3 and a sensor shaft 18 described later via a left bearing 22a. The right case body 13 includes a right side wall 13a facing the right side of the vehicle and a right outer peripheral wall 13b extending leftward (toward the left case body 12) from the outer periphery of the right side wall 13a. At the central portion of the right side wall 13a, a right bearing portion 23 is provided for supporting the right side portion of the pedal crankshaft 3 and an output shaft shaft (unit output member) 19 described later via a right bearing 23a. The left and right bearings 22a and 23a can be ball bearings with the same configuration as each other, and cost reduction can be achieved by sharing parts.

[0018] The assist motor 15 is an inner rotor type motor, and includes a cylindrical stator 15b fixed inside the right outer peripheral wall 13b of the right case body 13, and a similarly cylindrical rotor 15a disposed on the inner periphery of the stator 15b. The assist motor 15 of the embodiment is, for example, a DC motor, but the type of the motor is not particularly limited. FIG. 3 is a perspective view of the rotor 15a. Referring also to FIG. 3, a plurality of permanent magnets 15a1 arranged in the circumferential direction are fixed to the outer periphery of the rotor 15a. On the inner periphery of the rotor 15a, the input side gear 41 of the speed reducer 40 is supported via a bearing 42 for eccentric oscillation. The speed reducer 40 is composed of, for example, a pair of internal planetary gear mechanisms 40a adjacent in the axial direction. The pair of internal planetary gear mechanisms 40a are arranged so as to be within the entire width of the assist motor 15 in the axial direction, and are arranged so as to entirely overlap the assist motor 15 when viewed from the radial direction. Each internal planetary gear mechanism 40a is a mechanism including an input side gear (ring gear, internal gear) 41 and an output side gear (planetary gear, external gear) 45 that meshes with the gear teeth on the inner peripheral side of the input side gear 41. For example, the mechanism disclosed by the applicant in the publicity of Japanese Patent No. 6910197 can be preferably used.

[0019] Here, when a precession force is generated in the internal planetary gear mechanism 40a, a thrust force is generated in the output side gear 45. Due to the influence of this thrust force, the oscillation bearing 42 provided on the input side gear 41 may come out of the input side gear 41. In particular, in the output band with a large torque exceeding 50 Nm, the thrust force of the output side gear 45 is large, and the above-described influence also becomes large. In the embodiment, as a means for suppressing the influence of the thrust force of the output side gear 45, thrust receivers (for example, circlips) 40b that regulate the axial movement of the oscillation bearing 42 are attached to both axial sides of the inner periphery of the rotor 15a.

[0020] The rotor 15a is mounted to the right case body 13 via a pair of support rings 16 in the axial direction. The rotor 15a is supported by the left and right support rings 16 via rotor bearings 16a, each in the axial direction. Between the pair of rotor bearings 16a in the axial direction, a pair of oscillating bearings 42 are positioned. Rotor bearings 16a and oscillating bearings 42 adjacent to each other in the axial direction are in contact via thrust plates 16b. On the axially outer side of each rotor bearing 16a, a thrust support 40b is positioned, which is mounted on the inner circumference of the rotor 15a. Each thrust support 40b can receive the thrust force of the oscillating bearing 42 via the rotor bearings 16a and thrust plates 16b by contacting the adjacent rotor bearing 16a from the axially outer side.

[0021] The pedal crank shaft 3 has the base ends of the left and right pedal crank arms 2a fixed to each of its left and right ends so that they can rotate together. The shafts of the left and right pedals 2 are fixed to the tips of the left and right pedal crank arms 2a, respectively. A cylindrical transmission tube 17 is supported on the outer circumference of the pedal crank shaft 3. The transmission tube 17 is divided axially within the right case body 13. The left side of the transmission tube 17 is a sensor shaft 18 inserted into the left case body 12, and the right side of the transmission tube 17 is an output shaft (unit output member) 19 inserted into the right case body 13.

[0022] An enlarged diameter portion 19a is formed at the left end of the output shaft 19, surrounding the outer circumference of the right end of the sensor shaft 18 with a gap. Reference numeral 19b in the figure indicates a flange-shaped stepped wall formed radially at the base end (right end) of the enlarged diameter portion 19a. A first one-way clutch 26 is positioned between the inner circumferential surface of the enlarged diameter portion 19a and the outer circumferential surface of the right end of the sensor shaft 18. The right end of the output shaft 19 protrudes to the right (outside the case) of the right bearing portion 23, and a drive sprocket 31 is integrally rotatably mounted to this right end. The drive sprocket 31, together with the driven sprocket 32 ​​attached to the rear wheel 7 (drive wheel) and the endless drive chain 33 wrapped around both sprockets 31 and 32, is included in the chain-type transmission mechanism 34 that connects the pedal crankshaft 3 and the rear wheel 7.

[0023] The sensor shaft 18 is supported by fitting the inner circumference of its left end (one axial end) to the outer circumference of the left side of the pedal crank shaft 3 via splines or the like. The sensor shaft 18 can rotate integrally with the pedal crank shaft 3 in both forward and reverse directions. The right end (the other axial end) of the sensor shaft 18 is supported by a needle bearing 27 so that its inner circumference can rotate relative to the outer circumference of the left-right intermediate part (not limited to the center) of the pedal crank shaft 3. The needle bearing 27 is located in the intermediate part of the pedal crank shaft 3 in the axial direction (length direction) and between the outer peripheral protrusions of the pedal crank shaft 3, and is therefore attached to the pedal crank shaft 3 in a split structure. By positioning the needle bearing 27 between the end of the sensor shaft 18 and the pedal crank shaft 3, the runout of the end of the sensor shaft 18 is suppressed, improving the accuracy of torque detection described later, and also improving the accuracy of the operation of the first one-way clutch 26. The right end of the sensor shaft 18 is positioned inside the enlarged diameter portion 19a of the output shaft 19. The outer circumference of the right end of the sensor shaft 18 is supported by the inner circumference of the enlarged diameter portion 19a of the output shaft 19 via the first one-way clutch 26.

[0024] The first one-way clutch 26 enables torque transmission from the pedal crank shaft 3 to the output shaft 19 when the pedal crank shaft 3 attempts to rotate relative to the output shaft 19 in the forward direction (the direction that moves the bicycle 1 forward), allowing the bicycle 1 to be driven by the rider's pedaling force. On the other hand, when the output shaft 19 attempts to rotate relative to the pedal crank shaft 3 in the forward direction (i.e., when the pedal crank shaft 3 attempts to rotate relative to the output shaft 19 in the reverse direction), the first one-way clutch 26's built-in cam fails to engage and spins freely, rendering torque transmission impossible.

[0025] A cylindrical reducer output member 47 that supports the output gear 45 of the reducer 40 is positioned on the inner circumference side of the reducer 40. The reducer output member 47 is either integrally formed with the output gear 45 or has a separate output gear 45 fixed to it. The reducer output member 47 is positioned to surround the outer circumference of the output shaft 19 with a gap. A second one-way clutch 28 is positioned between the inner surface of the reducer output member 47 and the outer surface of the output shaft 19.

[0026] The second one-way clutch 28 enables the transmission of the assist torque of the assist motor 15 from the reduction gear output member 47 to the output shaft 19. When the reduction gear output member 47 attempts to rotate relative to the output shaft 19 in the forward direction (the direction that moves the bicycle 1 forward), the second one-way clutch 28 engages its built-in cam, enabling the transmission of torque to the output shaft 19. This allows the assist torque of the assist motor 15 to be applied to the output shaft 19. On the other hand, if the output shaft 19 attempts to rotate beyond the legal speed limit (for example, 24 km / h), the control board 36 outputs a command to the assist motor 15 to prevent it from generating torque. As a result, the rotor 15, the reduction gear 40, and the reduction gear output member 47 do not rotate, the cam inside the second one-way clutch 28 does not engage and it spins freely, and the pedal force assist from the assist motor 15 is lost.

[0027] In bicycle 1, when the rider pedals 2 to move, the driving force of the pedal crank shaft 3 is transmitted in the order of sensor shaft 18, first one-way clutch 26, and output shaft shaft 19, and then transmitted to the rear wheel 7 via chain-type transmission mechanism 34. At this time, when the assist motor 15 is driven in the forward direction, its driving force is transmitted to the reduction gear output member 47 via the reduction gear 40, and then to the output shaft shaft 19 via the second one-way clutch 28 to assist in reducing the pedaling force.

[0028] In the assist drive unit 10, it is possible to use one-way clutches 26 and 28 of the same type and shape but with different capacities, which not only reduces costs but also allows for the provision of a compact single-axis electric drive unit 10 by arranging a pair of one-way clutches 26 and 28 in double rows. The first one-way clutch 26 and the second one-way clutch 28 are arranged side by side in the axial direction (adjacent to each other, with the stepped wall 19b of the enlarged diameter portion 19a in between). The first one-way clutch 26 and the second one-way clutch 28 are arranged so that they fit within the entire width of the assist motor 15 in the axial direction. The first one-way clutch 26 and the second one-way clutch 28 are arranged so that their entirety overlaps the assist motor 15 when viewed from the radial direction.

[0029] In bicycle 1, when the bicycle is coasting with the pedals 2 stopped, the chain-type transmission mechanism 34 does not rotate due to the one-way clutch located on the axle of the rear wheel 7. In bicycle 1, when coasting stops, if an attempt is made to rotate the pedal crank axle 3 in the reverse direction via the pedals 2, the first one-way clutch 26 will slip because its built-in cam does not engage, making torque transmission impossible.

[0030] A thin strip 35a made of magnetic alloy is integrally wound around the outer circumferential surface of the axial middle portion of the sensor shaft 18. A torque detection coil 35b, supported by the left case body 12, is positioned on the outer circumferential side of the strip 35a. These strip 35a and torque detection coil 35b constitute a magnetostrictive torque sensor 35. In other words, the torque difference between the axial ends of the sensor shaft 18 causes shear strain in the strip 35a, and the torque acting on the sensor shaft 18 is detected by the torque detection coil 35b by detecting the change in the magnetic permeability of the strip 35a due to this strain.

[0031] Torque input from the pedal crankshaft 3 is received at the left end of the sensor shaft 18, and this torque is output from the right end of the sensor shaft 18 to the output shaft 19 via the first one-way clutch 26. At this time, if the magnetostrictive torque sensor 35 detects a torque exceeding a specified value, the assist motor 15 is driven to apply assist torque to the output shaft 19. This reduces the rotational torque of the pedal crankshaft 3 and, consequently, the pedaling force.

[0032] The drive control of the assist motor 15 is performed by a control device 36, which includes an MCU (Management Controller Unit) and a PDU (Power Drive Unit), housed within the left case body 12. Based on inputs from a magnetostrictive torque sensor 35 and a rotation sensor (not shown) that detects the rotation of the pedal crank shaft 3, the control device 36 outputs a control signal to the PDU to drive the assist motor 15. The control device 36 drives the assist motor 15 to assist the pedaling force when the speed of the bicycle 1 is below a specified value and a predetermined or greater forward rotation torque of the pedal crank shaft 3 is detected.

[0033] As described above, the assist drive unit 10 in the above embodiment is an assist drive unit 10 that applies assist torque to the pedal crankshaft 3 from an assist motor 15 arranged coaxially with the pedal crankshaft 3, and includes a unit output member 19 arranged coaxially with the pedal crankshaft 3 that outputs driving force to the outside of the unit, and is capable of transmitting torque when the pedal crankshaft 3 rotates relative to the unit output member 19 in the direction of vehicle travel (relative rotation in the forward direction), and when the pedal crankshaft 3 rotates relative to the unit output member 19 in the opposite direction to the direction of vehicle travel (relative rotation in the reverse direction), it slips and torque The system includes a first one-way clutch 26 that prevents torque transmission, an assist output member 47 which is coaxially arranged with the unit output member 19 and outputs assist torque for the assist motor 15, and a second one-way clutch 28 which enables the transmission of assist torque when the assist output member 47 rotates relative to the unit output member 19 in the direction of vehicle travel (relative rotation in the forward direction). The first one-way clutch 26 and the second one-way clutch 28 are coaxially arranged with the pedal crank shaft 3 and are positioned side by side in the axial direction of the pedal crank shaft 3, and are also positioned to overlap with the assist motor 15 when viewed radially. With this configuration, the first one-way clutch 26 that allows the pedal crank shaft 3 to reverse and the second one-way clutch 28 for transmitting assist torque are arranged coaxially with each other, and both one-way clutches are placed within the axial width of the assist motor 15, thereby enabling a compact arrangement of related components and a reduction in the overall size of the unit.

[0034] The assist drive unit 10 described above includes a sensor shaft 18 that is arranged coaxially with the pedal crankshaft 3 and adjacent to the unit output member 19 in the axial direction. The sensor shaft 18 has one axial end supported so as to be integrally rotatable with the pedal crankshaft 3, and the other axial end supported so as to be relative to the pedal crankshaft 3 via a needle bearing 27. A first one-way clutch 26 is supported on the outer circumference of the other axial end of the sensor shaft 18. This configuration includes a sensor shaft 18 with one axial end fixed to the pedal crank shaft 3 and the other axial end supported via a needle bearing 27. By supporting a first one-way clutch 26 on the outer circumference of the other axial end of the sensor shaft 18, the first one-way clutch 26 is supported with high rigidity, and the twisting between the axial ends of the sensor shaft 18 is not hindered, allowing for good torque detection based on the twisting of the sensor shaft 18.

[0035] The assist drive unit 10 described above includes a reduction gear 40 located on the inner circumference of the assist motor 15 and positioned to overlap with the assist motor 15 when viewed radially. With this configuration, the reduction gear 40 is positioned on the inner circumference of the assist motor 15 and within the axial width of the assist motor 15, allowing related components to be compactly arranged and the overall unit to be miniaturized.

[0036] In the assist drive unit 10 described above, the assist motor 15 is of the inner rotor type, and the internal gear 41 of the reduction gear 40 is provided on the inner circumference of the rotor 15a of the assist motor 15. With this configuration, the internal gear 41 of the reduction gear 40 is provided on the inner circumference of the inner rotor 15a of the assist motor 15, allowing the input shaft for the reduction gear 40 and the rotor shaft to which the magnets of the assist motor 15 are attached to be used interchangeably. Furthermore, by using a common material such as S45C for the rotor 15a, it can be used as the back yoke for the magnetic path of the electromagnetic section.

[0037] In the assist drive unit 10 described above, the reduction gear 40 comprises a pair of axially adjacent internal planetary gear reducers 40a, and the internal gears 41 of each of the pair of internal planetary gear reducers 40a are each supported on the inner circumference of a single rotor 15a via bearings 42 for eccentric oscillation, and thrust supports 40b are attached to both sides of the inner circumference of the rotor 15a in the axial direction to restrict the axial movement of the bearings 42 for eccentric oscillation. In this configuration, the operation of a pair of axially adjacent internal planetary gear reducers 40a generates precessional motion, which acts as a thrust force on the output gear 45. Due to this effect, there is a risk that the eccentric oscillation bearing 42 provided on the input gear 41 (internal gear 41) may come off the input gear 41. As a means of suppressing this effect, for example, by providing general circlips as thrust supports 40b on both axial sides of the eccentric oscillation bearing 42, the effect of the thrust force on the output gear 45 can be suppressed.

[0038] It should be noted that the present invention is not limited to the above-described embodiment. For example, the assist system of the embodiment may be mounted on a different type of bicycle (including three-wheeled and four-wheeled bicycles) than that shown in Figure 1. Furthermore, the configuration in the above embodiment is just one example of the present invention, and various modifications are possible without departing from the spirit of the invention, such as replacing the components of the embodiment with well-known components. [Explanation of Symbols]

[0039] 1 Bicycle 3. Pedal crank axle 10 Assist Drive Unit 15 Assist motor 15a Rotor 18 Sensor shaft 19. Output shaft (unit output component) 26 First One-Way Clutch 27 Needle bearings 28 Second one-way clutch 40 Reducer 40a Internal planetary gear reducer 41 Internal gear 42 bearings 47. Gear reducer output member (assist output member)

Claims

1. An assist drive unit (10) that applies assist torque to the pedal crank shaft (3) from an assist motor (15) arranged coaxially with the pedal crank shaft (3), A unit output member (19) is arranged coaxially with the pedal crank shaft (3) and outputs driving force to the outside of the unit, A first one-way clutch (26) is provided that allows torque to be transmitted when the pedal crank shaft (3) rotates relative to the unit output member (19) in the direction of vehicle travel, and when the pedal crank shaft (3) rotates relative to the unit output member (19) in the opposite direction to the direction of vehicle travel, it slips and is unable to transmit torque. An assist output member (47) is arranged coaxially with the unit output member (19) and outputs the assist torque of the assist motor (15), When the assist output member (47) rotates relative to the unit output member (19) in the direction of vehicle travel, a second one-way clutch (28) is provided to enable the transmission of the assist torque, The system includes a reduction gear (40) positioned to overlap with the assist motor (15) when viewed from the radial direction, The assist drive unit is configured such that the first one-way clutch (26) and the second one-way clutch (28) are arranged coaxially with the pedal crank shaft (3) and side by side in the axial direction of the pedal crank shaft (3), and are further positioned to overlap with the assist motor (15) and the reduction gear (40) when viewed from the radial direction.

2. An assist drive unit (10) that applies assist torque to the pedal crank shaft (3) from an assist motor (15) arranged coaxially with the pedal crank shaft (3), A unit output member (19) is arranged coaxially with the pedal crank shaft (3) and outputs driving force to the outside of the unit, A first one-way clutch (26) is provided that allows torque to be transmitted when the pedal crank shaft (3) rotates relative to the unit output member (19) in the direction of vehicle travel, and when the pedal crank shaft (3) rotates relative to the unit output member (19) in the opposite direction to the direction of vehicle travel, it slips and is unable to transmit torque. An assist output member (47) is arranged coaxially with the unit output member (19) and outputs the assist torque of the assist motor (15), When the assist output member (47) rotates relative to the unit output member (19) in the direction of vehicle travel, a second one-way clutch (28) is provided to enable the transmission of the assist torque, The unit comprises a sensor shaft (18) which is arranged coaxially with the pedal crank shaft (3) and adjacent to the unit output member (19) in the axial direction of the pedal crank shaft (3), The first one-way clutch (26) and the second one-way clutch (28) are arranged coaxially with the pedal crank shaft (3), and are positioned side by side in the axial direction of the pedal crank shaft (3), and are also positioned to overlap with the assist motor (15) when viewed radially. The assist drive unit comprises a sensor shaft (18) in which one axial end is supported so as to be integrally rotatable with the pedal crank shaft (3), and the other axial end is supported so as to be relative to the pedal crank shaft (3) via a needle bearing (27), and the first one-way clutch (26) is supported on the outer circumference of the other axial end of the sensor shaft (18).

3. An assist drive unit (10) that applies assist torque to the pedal crank shaft (3) from an assist motor (15) arranged coaxially with the pedal crank shaft (3), A unit output member (19) is arranged coaxially with the pedal crank shaft (3) and outputs driving force to the outside of the unit, A first one-way clutch (26) is provided that allows torque to be transmitted when the pedal crank shaft (3) rotates relative to the unit output member (19) in the direction of vehicle travel, and when the pedal crank shaft (3) rotates relative to the unit output member (19) in the opposite direction to the direction of vehicle travel, it slips and is unable to transmit torque. An assist output member (47) is arranged coaxially with the unit output member (19) and outputs the assist torque of the assist motor (15), When the assist output member (47) rotates relative to the unit output member (19) in the direction of vehicle travel, a second one-way clutch (28) is provided to enable the transmission of the assist torque, The system includes a reduction gear (40) located on the inner circumference of the assist motor (15) and positioned so as to overlap with the assist motor (15) when viewed radially, The first one-way clutch (26) and the second one-way clutch (28) are arranged coaxially with the pedal crank shaft (3), and are positioned side by side in the axial direction of the pedal crank shaft (3), and are also positioned to overlap with the assist motor (15) when viewed radially. The assist motor (15) is of the inner rotor type, An internal gear (41) of the reduction gear (40) is provided on the inner circumference of the rotor (15a) of the assist motor (15). The reduction gear (40) comprises a pair of internal planetary gear reducers (40a) adjacent to each other in the axial direction. Each of the pair of internal planetary gear reducers (40a) has an internal gear (41) which is supported on the inner circumference of the integrated rotor (15a) via an eccentric oscillation bearing (42). An assist drive unit in which thrust supports (40b) are attached to both axial sides of the inner circumference of the rotor (15a) to restrict the axial movement of the eccentric oscillation bearing (42).

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