Coaxial bicycle with mid-mounted power unit

Abstract

A coaxial mid-mounted power unit for bicycles comprises a hollow shaft motor and a reduction gear mechanism housed within a motor mount. The output end of the reduction gear mechanism is connected to a one-way bearing housing a chainring mount via a one-way bearing. A crankshaft, pivotally connected to the one-way bearing housing via another one-way bearing, is also present in this configuration. The two one-way bearings are installed in opposite directions and located on different sides of the one-way bearing housing. A strain gauge is mounted on the crankshaft. An annular conductive track assembly attached to the crankshaft engages with a spring assembly on the control circuit board within the motor mount to conduct electricity. This allows the strain gauge to directly measure the torque changes of the crankshaft. By positioning the one-way bearings on different sides of the one-way bearing housing, the power transmission paths for pedaling and electric assistance are divided into inner and outer sides, avoiding interference between transmission structures.

Description

Technical Field

[0001] This invention relates to a power unit for a bicycle; more particularly to a coaxial, mid-mounted power unit for a bicycle. Background Technology

[0002] Existing bicycle power devices, such as patent application No. I646016 "Electric-assisted bicycle drive device", patent application No. M437304 "Electric-assisted bicycle mid-mounted power output mechanism", and patent application No. M472666 "Electric-assisted bicycle pedaling force sensing mechanism", all have a motor that provides power assistance in the bicycle. The motor uses sensing elements such as strain gauges to sense the torque of the user's pedaling and thereby determines the amount of power assistance torque that the motor outputs to the crankshaft.

[0003] Although the power unit of the bicycle can sense the torque that drives the bicycle forward by the user's pedaling through the strain gauge, the strain gauge is located in the sleeve around the chainring or crankshaft. Therefore, it cannot reflect the user's pedaling action in real time during measurement and cannot obtain the torque change of the crankshaft caused by the pedaling force. This may cause the motor power output to have a problem of auxiliary power lag, which affects the smoothness of the bicycle user's riding experience. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a coaxial bicycle mid-mounted power unit, which involves placing a strain gauge on the surface of the crankshaft, and utilizing two control circuit boards facing each other, each with a spring group and an annular conductive track group between them, which conduct electricity during relative rotation, to transmit the torque data measured by the strain gauge to the control circuit board, thereby achieving the effect of controlling the motor output auxiliary power with real-time torque data.

[0005] To achieve the above objectives, the present invention provides a coaxial mid-mounted power unit for bicycles, comprising a motor mount, a hollow shaft motor, a reduction gear, a chain drive assembly, a crankshaft, and a signal transmission assembly, wherein a centerline is defined at the axis of the motor mount. The hollow shaft motor is disposed within the motor mount and a hollow shaft is disposed at a position corresponding to the centerline. The reduction gear is disposed within the motor mount and has an input end and an output end on each of its opposite sides. The input end is coupled to the hollow shaft, the output end has a sleeve, and the reduction gear has a shaft hole at a position corresponding to the centerline. The chain drive assembly is provided with a one-way bearing seat, having a first pipe section, a second pipe section, and a middle section connecting the first pipe section and the second pipe section. The outer diameter of the first pipe section is smaller than the inner diameter of the second pipe section. A first one-way bearing is sleeved on the outer circumferential surface of the first pipe section and embedded in the inner circumferential surface of the sleeve. A second one-way bearing with the opposite direction of rotation to the first one-way bearing is embedded in the inner circumferential surface of the second pipe section. A chain drive seat is connected to the second pipe section.

[0006] The crankshaft pivotally passes through the hollow shaft, the shaft hole, and the one-way bearing housing along the axis. Both ends of the crankshaft pivotally pass through the two sides of the motor housing. One side of the crankshaft has a wheel portion with a larger diameter, which is embedded in the inner circumferential surface of the second one-way bearing. The other side of the crankshaft has a groove, and a strain gauge is attached to the inner surface of the groove. The signal transmission assembly includes a rotary seat, which is fitted onto the portion of the crankshaft that has or is adjacent to the groove. The rotary seat has a ring portion, to which a circuit board electrically connected to the strain gauge is attached. A control circuit board electrically connected to the hollow shaft motor is fixed in the motor housing, facing the circuit board. A spring sheet assembly is provided on one of the circuit boards and the control circuit board, and an annular conductive track assembly is provided on the surface of the other. The spring sheet assembly elastically abuts against the annular conductive track assembly in a direction parallel to the axis, thereby electrically connecting the two.

[0007] This invention is installed on a bicycle. When the user pedals, the crankshaft rotates via the crank. In addition to the crankshaft driving the second one-way bearing from the inside of the second tube section to rotate the one-way bearing seat and the chainring seat, the swivel seat and the circuit board also rotate relative to the control circuit board, which is fixed to the crankshaft. A strain gauge on the crankshaft surface senses the torque under force in real time. This torque is transmitted through frictional contact between the spring assembly and the annular conductive track assembly on the circuit board surface, immediately transmitting the torque data to the control circuit board. The magnitude of the torque determines the output of electric assistance from the hollow shaft motor. Through the deceleration mechanism, the output end of the deceleration mechanism drives the first one-way bearing from the outside of the first tube section to rotate the one-way bearing seat and the chainring seat, achieving the effect of human power combined with electric assistance to propel the bicycle forward.

[0008] The advantage of this invention lies in the fact that the strain gauge, mounted on the surface of the crankshaft, can sense and obtain the torque generated when the crankshaft is subjected to force in real time, and transmit the torque data to the control circuit board. This allows the coaxial bicycle mid-drive unit to immediately control the hollow shaft motor to output power when needed, resulting in a smoother riding experience for the user. Furthermore, the spring assembly and the annular conductive track assembly can be radially arranged on the opposite surfaces of the control circuit board and the circuit board, respectively, minimizing the volume occupied by the control circuit board and the circuit board along the axis L, thereby reducing the axial length of the coaxial bicycle mid-drive unit. Attached Figure Description

[0009] Figure 1 This is a perspective view of a preferred embodiment of the present invention.

[0010] Figure 2 This is an exploded view of the preferred embodiment of the present invention described above.

[0011] Figure 3 This is an exploded view of another preferred embodiment of the present invention.

[0012] Figure 4 This is an exploded view of the deceleration structure of the preferred embodiment of the present invention.

[0013] Figure 5 This is an exploded view of the signal transmission component of the preferred embodiment of the present invention.

[0014] Figure 6 This is a front view of the preferred embodiment of the present invention described above.

[0015] Figure 7 for Figure 6 Sectional view in direction 7-7.

[0016] Figure 8 for Figure 7A cross-sectional view of the hollow shaft motor and its reduction gear structure.

[0017] Figure 9 This is a side view of the preferred embodiment of the present invention described above.

[0018] Figure 10 for Figure 9 A sectional view along the 10-10 direction.

[0019] Figure 11 This is an exploded view of the hollow shaft and transmission gear in another preferred embodiment of the present invention.

[0020] Figure 12 for Figure 11 A breakdown diagram from another angle. Detailed Implementation

[0021] To more clearly illustrate the present invention, preferred embodiments are described in detail below with reference to the accompanying drawings. Please refer to... Figures 1 to 5 As shown, a coaxial bicycle mid-mounted power unit 100 according to a preferred embodiment of the present invention includes a motor mount 10, a hollow shaft motor 20, a reduction gear 30, a chain drive assembly 40, a crankshaft 50, and a signal transmission assembly 60, wherein:

[0022] The motor base 10 is a horizontally arranged cylindrical body with a motor base tube 12. The motor base tube 12 has a right end edge and a left end edge. A ring-shaped front cover 14 is attached to the right end edge of the motor base tube 12. A right spacer ring 141 and a right bearing 142 are embedded on the left and right sides of the inner circumference of the front cover 14. A rear cover 16 is attached to the left end edge of the motor base tube 12. A left bearing seat 161 is located in the middle of the rear cover 16. A left bearing 162 is embedded in the left bearing seat 161. An axis line L is defined at the axis of the motor base 10. The axis line L passes through the center of the left bearing 162 and the center of the right bearing 142.

[0023] The hollow shaft motor 20 is disposed within the motor base 10. Specifically, the hollow shaft motor 20 is disposed on the left side within the motor base tube 12, and a transmission hollow shaft 22 is disposed on the hollow shaft motor 20 at a position corresponding to the axis L. The reduction structure 30 is disposed within the motor base 10. Specifically, the reduction structure 30 is disposed on the right side within the motor base tube 12. Each side of the reduction structure 30 in opposite directions has an input end 32 and an output end 34. The input end 32 is connected to the hollow shaft 22 of the hollow shaft motor 20, and the output end 34 has a sleeve 341. Please refer to [reference needed]. Figure 6 , Figure 7As shown, the deceleration structure 30 has a shaft hole H at a position corresponding to the axis L, and the shaft hole H communicates with the interior of the hollow shaft 22.

[0024] Please refer to Figures 1 to 3 and Figure 6 , Figure 7 As shown, the chain drive assembly 40 includes a one-way bearing seat 42, a first one-way bearing 44, a second one-way bearing 46, and a chain drive seat 48. The one-way bearing seat 42 is a tube surrounding the axis L, and has a first tube segment 421, a second tube segment 422, and a middle section 423 connecting the first tube segment 421 and the second tube segment 422; the outer diameter of the first tube segment 421 is smaller than the inner diameter of the second tube segment 422, and at least part of the outer peripheral surface of the second tube segment 422 is embedded in the inner peripheral surface of the right bearing 142.

[0025] The first one-way bearing 44 is sleeved and fixed on the outer peripheral surface of the first tube section 421. The first one-way bearing 44 is embedded in the inner peripheral surface of the sleeve 341 of the deceleration structure 30. The right spacer ring 141 is disposed between the outer peripheral surface of the sleeve 341 and the inner peripheral surface of the front cover 14. The deceleration structure 30 can drive the one-way bearing seat 42 to rotate through the first one-way bearing 44 via the sleeve 341 of the output end 34. The second one-way bearing 46 is embedded in the inner peripheral surface of the second tube section 422. The direction of rotation of the second one-way bearing 46 is opposite to that of the first one-way bearing 44. The chainring seat 48 is coupled to the second tube section 422 of the one-way bearing seat 42 to provide chainring engagement for the bicycle.

[0026] The crankshaft 50 is pivotally inserted along the axis L through the center of the hollow shaft 22, the shaft hole H, and the center of the one-way bearing seat 42, allowing the crankshaft 50 to rotate freely relative to the hollow shaft motor 20, the chain drive assembly 40, and the chain drive assembly 40. The right end of the crankshaft 50 is pivotally inserted through the center of the front cover 14, and the left end of the crankshaft 50 is pivotally inserted through the left bearing 162 embedded in the middle of the rear cover 16. The crankshaft 50 also forms a crank engagement portion 52 at each of its left and right ends that protrude from the motor seat 10, for providing a connection between the bicycle crank and the pedal.

[0027] On one side of the crankshaft 50, for example in this preferred embodiment, there is a wheel portion 54 with a larger diameter than other parts corresponding to the second one-way bearing 46 on the right side of the crankshaft 50. The wheel portion 54 is embedded in the inner circumferential surface of the second one-way bearing 46. This allows the crankshaft 50 to rotate via its wheel portion 54 through the second one-way bearing 46 when the user pedals, thus rotating the one-way bearing seat 42 and the chainring seat 48, enabling the chainring and chain mounted on the chainring seat 48 of the bicycle to operate normally. On the other side of the crankshaft 50, for example in this preferred embodiment, there is a groove 56 on the left side of the crankshaft 50. The groove 56 is located on the crankshaft 50 between the hollow shaft motor 20 and the rear cover 16, and a strain gauge 561 is attached to the inner surface of the groove 56.

[0028] Please refer to Figure 2 , Figure 3 , Figure 5 and Figure 7 As shown, the signal transmission assembly 60 includes a rotary seat 62, a circuit board 64, and a control circuit board 66. The rotary seat 62 is a disc body, and is secured to the crankshaft 50 by screws or fasteners, thus fixing the rotary seat 62 to the portion of the crankshaft 50 with the groove 56. The rotary seat 62 has a ring portion 621, the surface of which is perpendicular to the axis L. In other preferred embodiments, the rotary seat 62 may also be fixed to the portion of the crankshaft 50 adjacent to the groove 56. The circuit board 64 is attached to the surface of the ring portion 621 and is electrically connected to the strain gauge 561 via a wire. The control circuit board 66 is fixedly disposed in the motor housing 10 with the circuit board 64 facing each other. Specifically, in this preferred embodiment, the control circuit board 66 is fixedly disposed on the inner surface of the rear cover 16, and there is a fixed gap between the control circuit board 66 and the circuit board 64.

[0029] The control circuit board 66 is electrically connected to the hollow shaft motor 20 to receive the torque signal of the crankshaft 50 measured in real time by the strain gauge 561, and then intelligently judges to control the hollow shaft motor 20 to output electric assistance. A spring sheet group 661 is provided on the control circuit board 66, and an annular conductive track group 641 centered on the axis line L is provided on the surface of the circuit board 64. The spring sheet group 661 elastically abuts against the annular conductive track group 641 in a direction parallel to the axis line L, so that the circuit board 64 and the control circuit board 66 can maintain an electrical connection when they rotate face to face around the axis line L, so that the torque signal of the crankshaft 50 measured in real time by the strain gauge 561 can be transmitted and fed back to the control circuit board 66 via the circuit board 64, the annular conductive track group 641, and the spring sheet group 661. Furthermore, the control circuit board 66 and the circuit board 64 are constructed as annular plates, which allows the spring sheet group 661 and the annular conductive track group 641 to be radially arranged on the opposite surfaces of the control circuit board 66 and the circuit board 64, respectively. This results in a smaller volume occupied by the structure of the control circuit board 66 and the circuit board 64 along the axis L, thereby reducing the axial length of the coaxial bicycle mid-mounted power unit 100.

[0030] In addition to the preferred embodiment described above, the present invention may also involve placing the spring contact group 661 on the control circuit board 66 and the annular conductive track group 641 on the circuit board 64. Alternatively, the spring contact group 661 may be placed on the circuit board 64, and the annular conductive track group 641 centered on the axis L may be placed on the surface of the control circuit board 66. In this case, the spring contact group 661 still elastically abuts against the annular conductive track group 641 in a direction parallel to the axis L, so that the circuit board 64 and the control circuit board 66 can maintain an electrical connection when they rotate face-to-face around the axis L.

[0031] When the preferred embodiment of the present invention is used, the coaxial bicycle central power unit 100 is installed at the bottom bracket of the bicycle frame. The crank joints 52 at both ends of the crank shaft 50 connect the crank and the pedals. The bicycle chainring is fitted and fixed around the chainring seat 48, and the chain is positioned between the chainring and the freewheel of the bicycle's rear wheel. When the preferred embodiment of the present invention is used, the bicycle is propelled by either human power or electric assistance. In the human power scenario, when the user pedals to rotate the crank shaft 50, please refer to... Figures 6 to 7 As shown, the crankshaft 50 will rotate, and its wheel portion 54 will drive the second one-way bearing 46 to rotate. The second one-way bearing 46 will drive the second tube section 422 of the one-way bearing seat 42 from the inside, causing the one-way bearing seat 42 and the chain wheel seat 48 to rotate together, driving the chain and flywheel to rotate, thereby propelling the bicycle forward.

[0032] Please refer to Figures 2 to 3 and Figure 5 , Figure 7 As shown, in the case of electric assistance, during the user's pedaling that rotates the crankshaft 50, the rotary seat 62 and the circuit board 64 rotate together with the crankshaft 50. Therefore, the control circuit board 66, which is fixed to the motor mount 10, rotates relative to it. During this process, the strain gauge 561 also senses the torque generated by the force on the crankshaft 50 in real time and transmits the signal to the circuit board 64. Through the frictional contact between the spring assembly 661 and the annular conductive track assembly 641 on the surface of the circuit board 64, the circuit board 64 and the control circuit board 66 maintain an electrical connection despite relative rotation. This allows the torque signal measured by the strain gauge 561 to be continuously transmitted to the control circuit board 66, enabling the control circuit board 66 to continuously receive the torque signal of the crankshaft 50 measured in real time by the strain gauge 561. The magnitude of the torque is used to determine the amount of electric assistance output by the hollow shaft motor 20.

[0033] When the hollow shaft motor 20 outputs electric assistance, the hollow shaft 22 drives the input end 32 of the reduction mechanism 30. After being reduced in speed by the reduction mechanism 30, the output end 34 drives the first one-way bearing 44 to rotate. Through the first one-way bearing 44, the first tube section 421 of the one-way bearing seat 42 is driven from the outside, causing the one-way bearing seat 42 and the chain wheel seat 48 to rotate together, driving the chain and flywheel to rotate, thereby propelling the bicycle forward. This allows the hollow shaft motor 20 to quickly respond to the torque of the crankshaft 50 and output electric assistance power in real time, making the user feel a smoother ride. Furthermore, when the one-way bearing seat 42 and the chain plate seat 48 are driven to rotate by human or electric auxiliary power, the one-way bearing seat 42 is rotated by the second one-way bearing 46 disposed on the inner circumferential surface of the one-way bearing seat 42, or by the first one-way bearing 44 disposed on the outer circumferential surface of the one-way bearing seat 42. This divides the power transmission path of human and electric auxiliary power into the inner and outer sides of the one-way bearing seat 42, thus avoiding mutual interference between the transmission structures of different power sources.

[0034] Further details describe the construction of the preferred embodiments described above. Please refer to [link / reference needed]. Figure 7 , Figure 8As shown, a first bearing 51 is provided between the inner circumferential surface of the crankshaft 50 and the hollow shaft 22, a second bearing 53 is provided between the crankshaft 50 and the hole wall of the shaft hole H, and a third bearing 55 is provided between the crankshaft 50 and the inner circumferential surface of the first tube section 421 of the one-way bearing seat 42, so that the crankshaft 50 can pivot along the axis L through the center of the hollow shaft 22, the shaft hole H and the one-way bearing seat 42. In this preferred embodiment, the first bearing 51, the second bearing 53 and the third bearing 55 are sliding bearings.

[0035] Please refer to Figures 2 to 3 as well as Figure 5 , Figure 7 As shown, the rotary seat 62 has a cylindrical portion 622, which is sleeved on the portion of the crankshaft 50 where the groove 56 is located. The cylindrical portion 622 is fixed to the crankshaft 50 by a fastener passing through the cylindrical portion 622 and screwed onto it or by being pressed against the crankshaft 50. The ring portion 621 is wrapped around the cylindrical portion 622. The circuit board 64 is an annular circuit board; when the circuit board 64 is attached to the surface of the ring portion 621, it also wraps around the cylindrical portion 622. The groove 56 is... An annular groove surrounding the crankshaft 50 has a through-hole 623 penetrating the cylindrical portion 622 at a position corresponding to the groove 56, and an opening 624 penetrating the annular portion 621 and connecting to the through-hole 623. The wire connecting the circuit board 64 and the strain gauge 561 passes outward from the through-hole 623 to the opening 624 and is electrically connected to the circuit board 64. In other preferred embodiments, the opening 624 may be omitted, so that the wire is connected to the circuit board 64 immediately after passing through the through-hole 623.

[0036] The spring assembly 661 includes four springs 662 arranged linearly along the radial direction of the crankshaft 50. The annular conductive track assembly 641 has four concentric annular conductive tracks 642 with increasing diameters to match the number of springs 662. The springs 662 elastically abut against each conductive track 642. In other preferred embodiments, the spring assembly 661 may include other numbers of springs 662, in which case the number of conductive tracks 642 in the annular conductive track assembly 641 is set to have the same diameter as the number of springs 662.

[0037] Furthermore, in order to improve the conductivity between the circuit board 64 and the control circuit board 66, in this preferred embodiment, the control circuit board 66 is further configured as an annular circuit board with the same area as the first one-way bearing 44, and multiple spring groups 661 are arranged around the axis L. For example, in this preferred embodiment, two more spring groups 661 are added in addition to the original spring groups 661. The number of springs 662 included in each spring group 661 is the same as the arrangement of the multiple springs 662, so that each spring group 661 can elastically abut against the annular conductive track group 641 in the same way, and each conductive track 642 can simultaneously electrically connect the springs 662 arranged in the same order in the multiple spring groups 661. For example, in this preferred embodiment, the same conductive track 642 simultaneously contacts three springs 662 arranged in the same order.

[0038] The hollow shaft motor 20 is coaxial with the reduction gear 30, the one-way bearing housing 42, and the crankshaft 50. The hollow shaft motor 20 has a housing 24, which is fixedly installed inside the motor seat tube 12 of the motor housing 10. The hollow shaft 22 is pivotally inserted through the center of the housing 24. A stator 26 is fixedly installed around the periphery inside the housing 24. A rotor 28 is fixedly attached to the outer circumferential surface of the hollow shaft 22. The hollow shaft 22 has a large-diameter portion 221 at one end facing the reduction gear 30, which has a larger inner diameter than the inner diameter of other parts. The inner circumferential surface of the large-diameter portion 221 is circular, and multiple keyways 222 are formed around and spaced apart on the inner circumferential surface of the large-diameter portion 221.

[0039] Please refer to Figure 4 , Figure 7 and Figures 9 to 10As shown, the reduction structure 30 is a planetary gear reducer with an internal gear ring 36. The internal gear ring 36 is fixedly disposed inside the motor seat tube 12 of the motor seat 10, and the internal gear ring 36 is screwed to the right end face of the housing 24 of the hollow shaft motor 20. A first-order planetary carrier 361 and a second-order planetary gear carrier 362 are respectively disposed on the left and right sides inside the internal gear ring 36. On one side of the first-order planetary carrier 361 facing away from the second-order planetary gear carrier 362, as in this preferred embodiment, multiple first planetary gears 363 are combined on the left side in a manner surrounding the axis L. The outer side of gear 363 meshes with the internal gear ring 36. On the other side of the first-order planetary carrier 361, i.e. the right side, multiple second planetary gears 364 are connected to the second-order planetary carrier 362 in a manner surrounding the axis L. The outer sides of the multiple second planetary gears 364 mesh with the internal gear ring 36, and the inner sides of the multiple second planetary gears 364 mesh with a sun gear 365. The sleeve 341 is concentrically connected around the right side of the second-order planetary carrier 362, so that the sleeve 341 extends to the right from the area covered by the internal gear ring 36 into the area surrounded by the front cover 14.

[0040] The input end 32 of the reduction mechanism 30 has a transmission gear 32A that serves as a sun gear. The shaft hole H of the reduction mechanism 30 passes through the center of the transmission gear 32A, the first-order planetary carrier 361, and the second-order planetary carrier 362. The right half of the transmission gear 32A meshes with the inner side of the plurality of first planetary gears 363, and the left half of the transmission gear 32A extends into the large-diameter portion 221 of the hollow shaft 22. A key block 223 is embedded in each of the plurality of keyways 222. The inner side of the plurality of key blocks 223 is embedded around the transmission gear 32A and fixed, so that the hollow shaft 22 is connected to the input end 32 of the reduction mechanism 30.

[0041] In addition to the preferred embodiment described above, the transmission gear 32A of the input end 32 is connected to the large-diameter portion 221 of the hollow shaft 22 by embedding its left half with multiple key blocks 223. Please refer to... Figure 11 , Figure 12As shown, in another preferred embodiment of the present invention, the keyway 222 described above may be omitted, and the inner circumferential surface of the large-diameter portion 221 may be changed from a circle to a hexagonal groove 221B. The transmission gear 32A may be configured to have only the right half, and a nested ring 32B may be provided corresponding to the large-diameter portion 221. The nested ring 32B is a hexagonal ring whose outer circumferential surface mates with the wall of the groove 221B. The nested ring 32B is concentrically attached to the side wall of the transmission gear 32A, and the outer diameter of the nested ring 32B is smaller than the diameter of the transmission gear 32A. The transmission gear 32A is embedded in the groove 221B with the nested ring 32B, so that the hollow shaft 22 is connected to the input end 32.

[0042] In another preferred embodiment described above, in addition to being a hexagonal groove, the groove 221B can also be a non-circular groove such as a square, pentagon, or a circle with two opposite parallel surfaces on opposite sides. In this case, as long as the nested ring 32B that concentrically connects the side wall of the transmission gear 32A is set as a ring whose outer circumferential surface mates with the wall surface of the groove 221B, the transmission gear 32A can be connected to the hollow shaft 22 by embedding its nested ring 32B into the groove 221B.

[0043] In the preferred embodiment described above, the transmission gear 32A is connected to the hollow shaft 22 by inserting its left half into the large-diameter portion 221. In another preferred embodiment, the transmission gear 32A is connected to the hollow shaft 22 by inserting its sidewall-connected nested ring 32B into the large-diameter portion 221. Compared to the prior art of pressing gears around the motor shaft (hollow shaft 22), the transmission gear 32A axially coupled to the hollow shaft 22 in this invention can be designed with a smaller diameter. When the tooth size is comparable, the transmission gear 32A has fewer teeth. When the internal gear ring 36 is the same, the reduction ratio of the planetary reducer (reduction structure 30) is determined by the number of teeth on the sun gear (transmission gear 32A): the fewer the number of teeth on the sun gear, the higher the reduction ratio; the more the number of teeth on the sun gear, the lower the reduction ratio. Since the transmission gear 32A of the present invention has fewer teeth, the reduction ratio of the reduction structure 30 can be improved.

[0044] Please refer to Figures 2 to 3 and Figure 7As shown, the front cover 14 is an annular body with an inner diameter slightly smaller than that of the motor seat tube 12. The one-way bearing seat 42 passes through the inner side of the front cover 14, and a portion of the second tube section 422 extends to the right beyond the area encircled by the front cover 14. The portion of the second tube section 422 extending beyond the front cover 14 has a protruding ring portion 424. The aforementioned right bearing 142 is sleeved and fixed to the outer circumferential surface of the second tube section 422, located to the left of the protruding ring portion 424. The chain wheel seat 48 is a cap-shaped disc body and is screwed onto the protruding ring portion 424 of the second tube section 422 with its inner circumferential thread. The outer circumferential surface of the chain wheel seat 48 has a threaded portion 481, a retaining flange 482 is formed at the left end of the threaded portion 481, a chain wheel washer 483 is abutted against the right side of the retaining flange 482, and a clamping ring 484 is screwed into the threaded portion 481.

[0045] In this preferred embodiment, the shortest distance between the outer circumferential surface of the first pipe section 421 and the inner circumferential surface of the second pipe section 422 along the crankshaft 50 is equal to the shortest distance between the inner and outer circumferential surfaces of the first one-way bearing 44 along the crankshaft 50, and also equal to the shortest distance between the inner and outer circumferential surfaces of the second one-way bearing 46 along the crankshaft 50. The middle section 423 is a ring-shaped sheet extending from the inside out and perpendicular to the axis L. By using the same size parts for the first one-way bearing 44 and the second one-way bearing 46 and placing them side by side on the left and right sides of the middle section 423, the number of parts can be reduced and the diameter of the motor base 10 can be reduced, making the motor base 10 miniaturized.

[0046] The above description is only a preferred embodiment of the present invention. Any equivalent changes made by applying the present invention specification and the claims should be included within the patent scope of the present invention.

[0047] Explanation of reference numerals in the attached figures

[0048] [This invention]

[0049] 100: Coaxial bicycle with mid-mounted power unit

[0050] 10: Motor mount

[0051] 12: Motor seat tube

[0052] 14: Front Cover

[0053] 141: Right spacer ring

[0054] 142: Right bearing

[0055] 16: Back cover

[0056] 161: Left bearing housing

[0057] 162: Left bearing

[0058] 20: Hollow shaft motor

[0059] 22: Hollow Shaft

[0060] 221: Large diameter part

[0061] 221B: Socket

[0062] 222: Keyway

[0063] 223: Key Block

[0064] 24: Outer shell

[0065] 26: Stator

[0066] 28: Rotor

[0067] 30: Deceleration Structure

[0068] 32: Input terminal

[0069] 32A: Transmission gear

[0070] 32B: Nested ring

[0071] 34: Output terminal

[0072] 341: Sleeve

[0073] 36: Internal Gear Ring

[0074] 361: First-order planetary support

[0075] 362: Second-order planetary gear carrier

[0076] 363: First Planetary Gear

[0077] 364: Second Planetary Gear

[0078] 365: Sun Gear

[0079] 40: Chain drive component

[0080] 42: One-way bearing housing

[0081] 421: First Pipe Section

[0082] 422: Second Pipe Section

[0083] 423: Middle Section

[0084] 424: convex ring part

[0085] 44: First one-way bearing

[0086] 46: Second one-way bearing

[0087] 48: Chain plate base

[0088] 481: Threaded section

[0089] 482: Obstruction

[0090] 483: Chain wheel washer

[0091] 484: Tightening Ring

[0092] 50: Crankshaft

[0093] 51: First bearing

[0094] 52: Crank joint

[0095] 53: Second bearing

[0096] 54: Wheel section

[0097] 55: Third bearing

[0098] 56: Groove

[0099] 561: Strain Gauge

[0100] 60: Signal transmission component

[0101] 62: Rotary Seat

[0102] 621: Ring Section

[0103] 622: Cylinder section

[0104] 623: piercing

[0105] 624: Opening

[0106] 64: Circuit Board

[0107] 641: Circular Conductive Track Assembly

[0108] 642: Conductive track

[0109] 66: Control circuit board

[0110] 661: Shrapnel Set

[0111] 662: Shrapnel

[0112] H: Shaft hole

[0113] L: Centerline

Claims

1. A coaxial mid-mounted power unit for bicycles, comprising: A motor mount, with a centerline defined at its axis; A hollow shaft motor is disposed within the motor housing and a hollow shaft is disposed at a position corresponding to the axis centerline; A speed reduction structure is disposed inside the motor base and has an input end and an output end on each side in opposite directions. The input end is connected to the hollow shaft, and the output end has a sleeve. The speed reduction structure has a shaft hole at a position corresponding to the axis centerline. A chain drive assembly includes a one-way bearing seat and comprises a first pipe section, a second pipe section, and a middle section connecting the first and second pipe sections. The outer diameter of the first pipe section is smaller than the inner diameter of the second pipe section. A first one-way bearing is sleeved on the outer circumferential surface of the first pipe section and embedded in the inner circumferential surface of the sleeve. A second one-way bearing with the opposite rotation direction to the first one-way bearing is embedded on the inner circumferential surface of the second pipe section. A chain drive seat is connected to the second pipe section. A crankshaft pivotally passes through the hollow shaft, the shaft hole, and the one-way bearing housing along the axis. Both ends of the crankshaft pivotally pass through the two sides of the motor housing. One side of the crankshaft has a wheel portion with a larger diameter, which is embedded in the inner circumferential surface of the second one-way bearing. The other side of the crankshaft has a groove, and a strain gauge is attached to the inner surface of the groove. A signal transmission component includes a rotary seat, which is fitted onto the portion of the crankshaft having or adjacent to the groove. The rotary seat has a ring portion, to which a circuit board electrically connected to the strain gauge is attached. A control circuit board electrically connected to the hollow shaft motor is fixed in the motor housing in a face-to-face configuration with the circuit board. A spring sheet assembly is provided on one of the circuit boards and the control circuit board, and an annular conductive track assembly is provided on the surface of the other. The spring sheet assembly elastically abuts against the annular conductive track assembly in a direction parallel to the axis of rotation, thereby electrically connecting the two.

2. The coaxial bicycle mid-mounted power unit as described in claim 1, wherein, The spring assembly includes multiple springs arranged in a straight line along the radial direction of the crankshaft. The annular conductive track assembly is provided with several rings of conductive tracks with diameters ranging from small to large, in accordance with the number of the multiple springs. The multiple springs elastically abut against each conductive track.

3. The coaxial bicycle mid-mounted power unit as described in claim 2, wherein, Furthermore, on the circuit board or control circuit board where the spring sheet group is provided, two additional identical spring sheet groups are provided. The number of spring sheets included in the multiple spring sheet groups is the same as the arrangement of the multiple spring sheets. The multiple spring sheet groups are arranged in a manner surrounding the axis, so that each conductive track simultaneously contacts each spring sheet in the multiple spring sheet groups with the same arrangement order.

4. The coaxial bicycle mid-mounted power unit as described in claim 1, wherein, The rotary seat has a cylindrical portion that is sleeved and fixed to the crankshaft. The ring portion is wrapped around the cylindrical portion. The circuit board is an annular circuit board that is wrapped around the cylindrical portion. A through-hole passes through the cylindrical portion, and an opening connected to the through-hole passes through the ring portion. A wire is connected between the circuit board and the strain gauge. The wire passes out from the through-hole to the opening and is electrically connected to the circuit board.

5. The coaxial bicycle mid-mounted power unit as described in claim 1, wherein, The motor housing has a motor housing tube, the hollow shaft motor and the reduction structure are respectively embedded in the left and right sides of the motor housing tube, a front cover is attached to the right end edge of the motor housing tube, and a rear cover is attached to the left end edge of the motor housing tube. The rear cover has a left bearing seat in the middle, and a left bearing is embedded in the left bearing seat. The right and left ends of the crankshaft pivotally pass through the center of the front cover and the left bearing, respectively.

6. The coaxial bicycle mid-mounted power unit as described in claim 5, wherein, The front cover is a ring, with a right spacer ring and a right bearing embedded on the left and right sides of the inner circumferential surface of the front cover. The right spacer ring is located between the outer circumferential surface of the sleeve and the inner circumferential surface of the front cover. At least part of the outer circumferential surface of the second pipe section is embedded and connected to the inner circumferential surface of the right bearing, and the remaining part of the second pipe section extends to the right beyond the range of the front cover. The part of the second pipe section extending out of the front cover has a protruding ring portion. The chain plate seat is a cap-shaped disc and is screwed to the protruding ring portion on its inner circumferential edge.

7. The coaxial bicycle mid-mounted power unit as described in claim 6, wherein, The outer peripheral surface of the chain plate seat has a threaded portion, a retaining flange is formed at the left end of the threaded portion, a chain plate washer is abutted on the right side of the retaining flange, and a tightening ring is screwed into the threaded portion.

8. The coaxial bicycle mid-mounted power unit as described in claim 1, wherein, The shortest distance between the outer circumferential surface of the first pipe section and the inner circumferential surface of the second pipe section along the crankshaft radial direction is equal to the shortest distance between the inner and outer circumferential surfaces of the first one-way bearing along the crankshaft radial direction, and is also equal to the shortest distance between the inner and outer circumferential surfaces of the second one-way bearing along the crankshaft radial direction.

9. The coaxial bicycle mid-mounted power unit as described in claim 1, wherein, The hollow shaft has a large-diameter section at one end facing the reduction mechanism, which is larger than the inner diameter of other parts. Multiple keyways are formed on the inner circumferential surface of the large-diameter section. The reduction mechanism is a planetary gear reducer and the input end is a transmission gear. Part of the transmission gear extends into the large-diameter section of the hollow shaft. A key block is embedded in each of the multiple keyways. The inner side of the multiple key blocks is embedded and fixed around the transmission gear.

10. The coaxial bicycle mid-mounted power unit as described in claim 9, wherein, The reduction gear structure has an internal gear ring, which is fixedly installed inside the motor housing. A first-order planetary carrier and a second-order planetary gear carrier are arranged on each side of the internal gear ring. On one side of the first-order planetary carrier opposite to the second-order planetary gear carrier, multiple first planetary gears are coupled around the axis. The outer sides of the multiple first planetary gears mesh with the internal gear ring, and the inner sides mesh with another part of the transmission gear. On the other side of the first-order planetary carrier and between it and the second-order planetary gear carrier, multiple second planetary gears are coupled around the axis. The outer sides of the multiple second planetary gears mesh with the internal gear ring, and the inner sides of the multiple second planetary gears mesh with a sun gear. The sleeve is concentrically coupled to the second-order planetary gear carrier and protrudes beyond the area covered by the internal gear ring.

11. The coaxial bicycle mid-mounted power unit as described in claim 1, wherein, The hollow shaft has a large-diameter section at one end facing the reduction structure, which is larger than the inner diameter of other parts. A non-circular groove is formed on the inner circumferential surface of the large-diameter section. The reduction structure is a planetary gear reducer and the input end is a transmission gear. A nested ring is concentrically attached to the side wall of the transmission gear, and the nested ring is embedded in the groove for fixation.

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