Concentric coaxial centrally-mounted electric motor for electric-power-assisted bicycle

Abstract

Provided in the present invention is a concentric coaxial centrally-mounted electric motor for an electric-power-assisted bicycle. The electric motor comprises a housing, a left end cover, a right end cover, a central shaft, a torque sensor, an electric motor stator, an electric motor rotor, a first inner end cover, a guide ring, a wave generator, an inner flexspline, an outer flexspline, an inner one-way clutch, and an outer one-way clutch, wherein the axes of the central shaft and the electric motor rotor are located on the same axis as the rotation centers of the inner flexspline and an output shaft; the torque sensor is arranged centrally or in an offset manner in an electric motor housing, and is configured to acquire pedaling force variations during riding and convert same into an electrical signal for output; the electric motor rotor and the electric motor stator are arranged in a space enclosed by the first inner end cover and a second inner end cover; and the wave generator, the inner flexspline, the outer flexspline and the guide ring are mounted on the right side of the first inner end cover in sequence from inside to outside. The inner one-way clutch is connected to the inner wall of the output shaft in a meshing manner, the outer one-way clutch is arranged on the outer wall of the output shaft, and when rotating, the central shaft drives the inner one-way clutch to rotate, thereby driving the output shaft to rotate.

Description

A concentric and coaxial mid-drive motor for electric-assist bicycles Technical Field

[0001] This invention relates to the field of motors for electric bicycles, and in particular to a concentric and coaxial mid-drive motor for electric bicycles. Background Technology

[0002] When using an electric-assist bicycle, the rider still rides like a traditional bicycle, with the motor providing assistance. The amount of assistance can be automatically adjusted by the controller based on the rider's riding habits. Mid-motor electric-assist bicycles, in particular, mount the motor at the bicycle's bottom bracket, near the pedals, and transmit power to the rear wheel via a transmission system. This design offers advantages such as a more balanced weight distribution and greater stability during cornering.

[0003] Currently, the commercially available mid-drive motors are generally dual-shaft motors, meaning the motor shaft and pedal shaft are separate and connected by multi-stage gears. Some are coaxial motors using multi-stage planetary gears for speed reduction. This design suffers from low transmission efficiency, large size, and heavy weight, increasing the overall weight of the bicycle and occupying a large space, hindering miniaturization and lightweight design. Furthermore, existing mid-drive motors increase the torque required for pedaling in situations such as low battery or battery failure, negatively impacting the riding experience. CN119051346A discloses a coaxial mid-drive motor for electric bicycles, including a motor housing, an assist device installed within the motor housing, a hollow power output shaft, and a manual drive shaft with an integrated torque sensor. The manual drive shaft is connected to the hollow power output shaft via a manual drive clutch. The assist device includes a control system, a reduction mechanism, a motor stator, and a motor rotor. The motor rotor outputs torque to the hollow power output shaft via the reduction mechanism and an electric drive clutch.

[0004] To address the aforementioned issues, a mid-drive motor design with a compact structure, rational component layout, and strong adaptability is urgently needed. This design should ensure sufficient operating power while achieving miniaturization, weight reduction, and ease of mass production, thereby improving the overall riding performance and user experience of the vehicle. In particular, further optimization is required in the placement and control of the torque sensor to achieve precise torque detection and control, thereby improving the motor's operating efficiency and stability. Technical solutions

[0005] The present invention aims to solve the problems of miniaturization, lightweighting and easy mass production that are difficult to solve with current technology, and provides a concentric and coaxial mid-drive motor for electric-assist bicycles.

[0006] A concentric and coaxial mid-drive motor for electric-assist bicycles includes a housing, a left end cover, a right end cover, a bottom bracket, a torque sensor, a motor stator, a motor rotor, a guide ring, a wave generator, an inner flexible wheel, an outer flexible wheel, an inner one-way clutch, an outer one-way clutch, an output shaft, a first bearing, a second bearing, a third bearing, a fifth bearing, a sixth bearing, and a seventh bearing.

[0007] The central shaft, the axis of the motor rotor, and the rotation center of the inner flexible wheel and the output shaft are located on the same axis; the housing, left end cover, and right end cover together constitute the motor housing; a first inner end cover and a second inner end cover are provided from the inner wall of the housing inward, wherein one end of the first inner end cover is located on the right side of the motor rotor and stator, and the second inner end cover is located on the left side of the motor rotor and stator; and at least one of the first and second inner end covers is detachably connected to the housing; the two ends of the central shaft are respectively located on the inner rings of the first and seventh bearings, the outer ring of the first bearing is located inside the left end cover, the outer ring of the seventh bearing is located on the inner wall of the output shaft, the outer ring of the sixth bearing is located on the inner wall of the right end cover, the inner ring of the sixth bearing is located on the outer wall of the output shaft, and the output end of the inner flexible wheel is connected to the inner ring of the fifth bearing. The outer ring of the fifth bearing is located within the inner ring of the right end cover; the inner ring of the torque sensor is fixedly located within the outer ring of the central shaft, and the outer ring of the torque sensor is located within the inner one-way clutch, which is installed on the inner wall of the output shaft; the motor rotor and stator are located within the space formed by the first and second inner end covers; the outer ring of the third bearing is located within the inner ring of the first inner end cover, which is fixed to the inner ring of the housing; the wave generator is coaxially connected to the motor rotor, and is installed within the inner flexible wheel, which is installed within the outer flexible wheel, which is fixed to the right end cover. One end of the outer ring of the outer flexible wheel is located inside the guide ring, and an outer one-way clutch is installed on the inner wall of the inner ring of the inner flexible wheel away from the guide ring, which is installed on the outer wall of the output shaft. The torque sensor is centrally located within or offset within the motor housing, and is used to obtain the force change during pedaling and convert it into an electrical signal output.

[0008] In one embodiment, the torque sensor is a torque-sensing strain gauge sensor. The inner ring of the torque sensor is disposed around the outer ring of the central shaft. As the torque sensor rotates with the central shaft, it acquires the voltage value during pedaling. The strain gauge undergoes slight bending, causing a change in its resistance, generating an induced voltage. The circuit board within the torque sensor calculates the voltage value based on the resistance change and converts it into an electrical signal. Furthermore, the mid-drive motor includes a controller, which is electrically connected to both the torque sensor and the motor stator. The controller outputs a corresponding voltage to the motor stator based on the electrical signal value transmitted by the torque sensor, thereby providing the rider with appropriate torque. The controller can be located inside the motor housing or externally.

[0009] In one embodiment, the torque sensor is a pressure-sensitive strain gauge sensor, and the torque sensor is disposed between the outer ring of the first bearing and the left end cover; the strain gauge of the torque sensor obtains the voltage value when pedaling while riding, and the slight bending of the strain gauge causes a change in its resistance value, generating an induced voltage. The circuit board inside the torque sensor calculates the voltage value based on the change in resistance value and converts it into an electrical signal; moreover, the mid-mounted motor also includes a controller, which is electrically connected to the torque sensor and the motor stator respectively, and is used to output a voltage of a corresponding magnitude to the motor stator according to the electrical signal value transmitted by the torque sensor.

[0010] In one embodiment, the motor stator is fixed to the inner ring of the housing; one end of the outer ring of the motor rotor is located in the inner ring of the second bearing, the outer ring of the second bearing is located in the inner ring of the second inner end cover, the other end of the outer ring of the motor rotor is located in the inner ring of the third bearing, and the permanent magnet of the motor rotor is located in the inner ring of the stator.

[0011] In another possible embodiment, the motor stator is fixed to the end face of the housing; one end of the outer ring of the motor rotor is located in the inner ring of the second bearing, the outer ring of the second bearing is located in the inner ring of the second inner end cover, the other end of the outer ring of the motor rotor is located in the inner ring of the third bearing, and the permanent magnet of the motor rotor is located in the outer ring of the stator.

[0012] In another possible embodiment, the motor stator is fixed to the end face of the housing; one end of the outer ring of the motor rotor is located in the inner ring of the second bearing, the outer ring of the second bearing is located in the inner ring of the second inner end cover, the other end of the outer ring of the motor rotor is located in the inner ring of the third bearing, and the permanent magnet of the rotor is located on one side of the stator.

[0013] In another possible embodiment, when the torque sensor is biased within the motor housing, the motor stator is fixed to the inner ring of the housing; one end of the inner ring of the motor rotor is located on the outer ring of the second bearing (not shown in the figure; in practice, it can be limited by a groove / protrusion / circlip), and the other end of the inner ring of the motor rotor is located on the outer ring of the third bearing. The inner rings of the first, second, and third bearings are all located on the outer ring of the central shaft; the permanent magnet of the rotor is located on the inner ring of the stator. Furthermore, the central shaft has a boss along its outer wall, with its two sides used to limit the first and second bearings respectively; and the central shaft also has an annular groove along its outer wall, the contour of which matches the protruding flange of the inner ring of the third bearing, thereby limiting the third bearing. In a more preferred embodiment, the inner rings of the first, second, and third bearings are connected to the outer ring of the central shaft by an interference fit, and the outer rings of the first, second, and third bearings are connected to the corresponding components by a clearance fit.

[0014] In one embodiment, a guide ring, a wave generator, an inner flexible wheel, and an outer flexible wheel form a reduction mechanism, and the axes of the central shaft, the rotor shaft, and the rotation center of the reduction mechanism are located on the same axis. The central shaft is a hollow shaft and is arranged along the axial direction of the motor housing. A torque sensor, an inner one-way clutch, and an output shaft are sequentially arranged on the outer wall of the central shaft towards the motor housing. The inner ring of the torque sensor is fixedly connected to the central shaft, and the outer ring of the torque sensor is slidably connected to the inner one-way clutch. The inner one-way clutch is engaged with the inner wall of the output shaft. The outer wall of the output shaft is engaged with the outer one-way clutch.

[0015] In one embodiment, the outer diameter of the motor stator has an annular boss, and the interior of the housing has a groove recessed inward from its inner surface. The position of the groove is adapted to the position of the boss on the motor stator to accommodate the boss of the motor stator and thus restrict the position of the motor stator.

[0016] In one embodiment, the wave generator is coaxially arranged with the inner flexible wheel and the outer flexible wheel; the inner wall of the wave generator is threadedly connected to the outer wall of the rotating shaft for rotating with the rotating shaft of the motor rotor; the outer wall of the wave generator is connected to the inner flexible wheel, and the outer flexible wheel is sleeved on the outer wall of the inner flexible wheel; an L-shaped guide ring is provided at one end of the outer flexible wheel and at the outer wall connected thereto for limiting the deformation of the outer flexible wheel and limiting the axial displacement of the outer flexible wheel and the inner flexible wheel;

[0017] Furthermore, the inner sidewall of the end of the inner flexible wheel away from the guide ring is in contact with the outer one-way clutch.

[0018] In another embodiment, the inner and outer flexible wheels do not have teeth on their inner walls. The wave generator uses an elliptical cam with external ball bearings, commonly used in existing harmonic reducers. The cam allows the two ends of the major axis of the inner flexible wheel to contact and press against the inner wall of the outer flexible wheel. When the wave generator is actuated, the wall of the wave generator abuts against the wall of the inner flexible wheel, causing the inner flexible wheel to undergo elliptical elastic deformation and become elliptical. At the two ends of the minor axis of the ellipse, the opposing inner walls of the inner and outer flexible wheels completely separate. Due to the circumference difference between the outer diameter of the inner flexible wheel and the inner diameter of the outer flexible wheel, the outer wall at the two ends of the major axis of the inner flexible wheel contacts and presses against part of the inner wall of the outer flexible wheel, thus transmitting torque through friction. The inner and outer flexible wheels of this speed reduction mechanism do not have meshing teeth. The inner flexible wheel rolls smoothly inside the outer flexible wheel, which greatly improves stability. Moreover, the radii of the inner and outer flexible wheels are not affected by the size of the meshing teeth, which allows for a very wide range of transmission ratios. Furthermore, compared to the preparation of meshing teeth, it greatly reduces the manufacturing difficulty.

[0019] In another embodiment, the present invention discloses a concentric and coaxial mid-drive motor for electric-assist bicycles, including a housing, a left end cover, a right end cover, a bottom bracket, a torque sensor, a motor stator, a motor rotor, a guide ring, a wave generator, an inner flexible wheel, an outer flexible wheel, an inner one-way clutch, an outer one-way clutch, an output shaft, a first bearing, a second bearing, a third bearing, a fifth bearing, a sixth bearing, and a seventh bearing.

[0020] The rotation centers of the central shaft, the motor rotor, the inner flexible wheel, and the output shaft are located on the same axis; the housing, the left end cover, and the right end cover together constitute the motor housing; a first inner end cover is provided from the inner wall of the housing inward;

[0021] The motor stator is fixed to the inner ring of the housing; one end of the inner ring of the motor rotor is located on the outer ring of the second bearing, and the other end of the inner ring of the motor rotor is located on the outer ring of the third bearing. The inner rings of the first, second, and third bearings are all set on the outer ring of the central shaft; the outer ring of the first bearing is fixed to the inner ring of the torque sensor, the outer ring of the seventh bearing is fixed to the inner wall of the output shaft, the outer ring of the sixth bearing is fixed to the inner wall of the right end cover, and the inner ring of the sixth bearing is fixed to the outer wall of the output shaft. The output end of the inner flexible wheel is connected to the inner ring of the fifth bearing, and the outer ring of the fifth bearing is fixed to the inner ring of the right end cover. The inner one-way clutch is installed on the inner wall of the output shaft. The wave generator is coaxially connected to the motor rotor and is installed inside the inner flexible wheel. The inner flexible wheel is installed inside the outer flexible wheel, which is fixed to the right end cover. One end of the outer ring of the outer flexible wheel is located inside the guide ring. An outer one-way clutch is installed on the inner wall of the inner ring of the inner flexible wheel away from the guide ring, and the outer one-way clutch is installed on the outer wall of the output shaft.

[0022] In one embodiment, the operation of the controller includes:

[0023] Receive the electrical signal value of the voltage transmitted by the torque sensor;

[0024] If the received voltage signal value is greater than the preset voltage value, the motor is started, and 100% of the rated voltage is output to the motor stator, generating a rotating magnetic field. The rotating magnetic field interacts with the magnetic field of the magnetic ring, causing the shaft to rotate, which in turn causes the input end of the reduction mechanism to rotate, reducing the rotation speed of the shaft and increasing the torque output to the external one-way clutch connected to the output end of the reduction mechanism. The external one-way clutch transmits the torque to the output shaft, which, together with the pedaling torque, drives the bicycle.

[0025] If the received voltage signal value is within 20-90% of the preset voltage value, start the motor and output 60-80% of the rated voltage to the motor stator.

[0026] If the received electrical signal value is less than 20% of the preset voltage value, the motor will be turned off and no voltage will be output to the motor stator. Beneficial effects

[0027] The concentric and coaxial mid-drive motor for electric-assisted bicycles described in this invention has the following beneficial effects:

[0028] The present invention adopts a concentric and coaxial structural design, with the first and seventh bearings serving as rotational supports for the central shaft, and the third and fifth bearings serving as rotational supports for the reduction mechanism formed by the guide ring, wave generator, inner flexible wheel, and outer flexible wheel; the second and third bearings serve as rotational supports for the rotor's shaft, and the axes of the three rotational supports are located on the same axis.

[0029] By using a torque sensor to detect the pedaling torque during cycling in real time, two types of signals are transmitted: a voltage signal and a frequency signal. The controller outputs the corresponding voltage to the motor stator according to the signal value, thereby providing the rider with suitable torque. This achieves precise torque detection and control, improves the cycling experience, and significantly enhances safety. Attached Figure Description

[0030] Figure 1 is a cross-sectional view of the concentric and coaxial mid-mounted motor for electric-assisted bicycles according to Embodiment 1 of the present invention;

[0031] Figure 2 is an external view of the concentric and coaxial mid-mounted motor for the electric-assist bicycle described in Embodiment 1 of the present invention;

[0032] Figure 3 is a partial schematic diagram of the first partition in Embodiment 1 of the present invention;

[0033] Figure 4 is a partial schematic diagram of the first partition in Embodiment 2 of the present invention;

[0034] Figure 5 is a cross-sectional view of the concentric and coaxial mid-drive motor for electric-assisted bicycles according to Embodiment 3 of the present invention;

[0035] Figure 6 is a cross-sectional view of the concentric and coaxial mid-drive motor for electric-assisted bicycles according to Embodiment 4 of the present invention;

[0036] Figure 7 is a cross-sectional view of the concentric and coaxial mid-mounted motor for electric-assisted bicycles according to Embodiment 5 of the present invention;

[0037] Figure 8 is a cross-sectional view of the concentric and coaxial mid-drive motor for electric-assisted bicycles according to Embodiment 6 of the present invention;

[0038] Figure 9 is a cross-sectional view of the concentric coaxial mid-drive motor for electric-assisted bicycles according to Embodiment 7 of the present invention.

[0039] Among them, 1: central shaft; 2: first bearing; 3: snap ring; 4: torque sensor; 5: left end cover; 6: second bearing; 7: rotating shaft; 8: magnetic ring; 9: housing; 10: motor stator; 11: third bearing; 12: cam; 13: first inner end cover; 14: fourth bearing; 15: outer support ring; 16: inner flexible wheel; 17: outer flexible wheel; 18: bearing retaining ring; 19: right end cover; 20: fifth bearing; 21: inner one-way clutch; 22: outer one-way clutch; 23: sixth bearing; 24: seventh bearing; 25: output shaft; 26: O-ring; 27: magnetic tile; 28: rotor core; 29: circuit board; 30: second inner end cover. Embodiments of the present invention

[0040] To make the objectives, technical solutions, beneficial effects, and significant advancements of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings provided in the examples of the present invention. Obviously, all the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort and in accordance with the content, implementation methods, and drawings of the present invention are within the scope of protection of the present invention.

[0041] It should be noted that the terms "first," "second," "third," etc., in the specification and claims of this invention are only used to distinguish different objects, and not to describe a specific order.

[0042] It should also be noted that the following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. Example 1

[0043] As shown in Figure 1, a concentric coaxial mid-drive motor for electric-assist bicycles includes a motor housing, a motor stator 10, a motor rotor, a bottom shaft 1, a torque sensor 4, a controller, an inner one-way clutch 21, an outer one-way clutch 22, and a reduction mechanism. The controller is electrically connected to the motor stator 10 and the torque sensor 4, respectively.

[0044] As shown in Figure 2, the motor housing, from left to right, includes a left end cover 5, a housing 9, and a right end cover 19, which are fixedly connected by bolts. The housing 9 includes an annular shell, with two annular components extending from the inner wall of the annular shell towards the interior space: a first inner end cover 13 and a second inner end cover 30. The first inner end cover 13 is detachably connected to the housing 9 via a sliding fit and is located in the middle of the housing 9. The second inner end cover 30 is integrally formed with the annular shell of the housing 9 and extends inward from the inner wall of the housing 9 near the left end cover 5. Furthermore, the left end cover 5, housing 9, first inner end cover 13, second inner end cover 30, and right end cover 19 are all made of aluminum alloy, thus achieving lightweight construction. The controller is installed inside the motor housing, but can also be installed outside the motor housing depending on the actual situation.

[0045] The central shaft 1 is a hollow shaft and is arranged along the axial direction of the motor housing. The two sides of the central shaft 1 are connected to the foot pedals via cranks. From one end to the other end (Figure 1 shows from left to right), the outer wall of the central shaft 1 consists of the first bearing 2, the torque sensor 4, the inner one-way clutch 21, and the seventh bearing 24. Part of the inner ring of the output shaft 25 is supported by the central shaft through the seventh bearing.

[0046] The left end cover 5 and the right end cover 19 each have an opening for the central shaft 1 to pass through. The inner wall of the left end cover 5 is connected to the central shaft 1 via a first bearing 2, and a retaining spring 3 is disposed at the bottom of the first bearing 2 to limit the first bearing 2. The inner wall of the right end cover 19 is connected to the output shaft 25 via a sixth bearing 23.

[0047] The seventh bearing 24 is disposed between the inner wall of the output shaft 25 and the outer wall of the central shaft 1, and the seventh bearing 24 and the sixth bearing 23 are coaxially disposed and corresponding in position; moreover, an O-ring 26 is provided at the end where the output shaft 25 is connected to the central shaft, which is used as an oil seal and for waterproofing.

[0048] The motor rotor includes a magnetic ring 8 and a rotating shaft 7. The rotating shaft 7 is the motor shaft, and has a protruding ring on its outer wall near the left end cover. A third bearing 11 and a second bearing 6 are respectively provided at both ends of the ring. The bearing on each side of the protruding ring ensures more stable rotation of the rotating shaft 7. One end of the first inner end cover 13 is fixedly installed to the housing. The end of the first inner end cover 13 away from the housing has a flange protruding along its inner wall to limit the third bearing. The third bearing 11 is located in the middle of the central shaft 1. The outer ring of the third bearing is located in the area formed by the inner wall of the inner ring of the first inner end cover and the flange, and the outer wall of the third bearing 11 is slidably installed with the first inner end cover 13. Inside the motor housing, the first inner end cover 13 divides the internal space formed by the left end cover 5, the housing 9, and the right end cover 19 into a first partition and a second partition arranged coaxially.

[0049] The first partition contains a motor stator 10, a motor rotor, and a second bearing 6. Furthermore, within the first partition, in the axial direction from the left end cover to the first inner end cover 13, the outer wall of the rotating shaft 7 is sequentially provided with a second bearing 6, a magnetic ring 8, and a third bearing 11. The inner wall of the second bearing 6 is interference-fitted with the outer wall of one end of the rotating shaft 7, and the outer wall of the second bearing is slidably fitted with the second inner end cover 30. The inner wall of the magnetic ring 8 is fixedly connected to the outer wall of the ring portion of the rotating shaft, and the outer wall of the magnetic ring 8 has a certain gap with the motor stator 10. The motor stator 10 is used to drive the magnetic ring 8 to rotate the rotating shaft 7 based on the principle of electromagnetic induction. The magnetic ring 8 and the rotating shaft 7 form the motor rotor of the mid-mounted motor.

[0050] As shown in Figure 3, the outer ring of the motor stator 10 has an annular boss, which corresponds to the groove position of the housing 9, thereby restricting the position of the motor stator and making the motor stator more stable during operation.

[0051] A speed reduction mechanism is provided within the second partition. The speed reduction mechanism includes an inner flexible wheel 16, an outer flexible wheel 17, and a wave generator, with the wave generator coaxially arranged with both the inner and outer flexible wheels. The wave generator includes an elliptical cam 12 and a fourth bearing 14; the inner wall of the cam 12 is threadedly connected to the outer wall of the rotating shaft 7 for rotation with the shaft 7; the outer wall of the fourth bearing 14 is connected to the inner flexible wheel 16, and the fourth bearing 14 is a flexible bearing; the outer flexible wheel 17 is sleeved on the outer wall of the inner flexible wheel 16. Furthermore, the inner flexible wheel 16 is a thin-walled cup shape, and the outer flexible wheel 17 has a cap-shaped structure. The flange of the outer flexible wheel 17 has holes for axially fixing it to the right end cover 19 via bolts.

[0052] The inner flexible wheel 16 and the outer flexible wheel 17 are both manufactured using existing harmonic reducer flexible wheel processing technology and commonly used flexible wheel steel. The inner walls of the outer flexible wheel 16 and the inner flexible wheel 17 can contact each other, and there are no meshing teeth on the opposite walls of the outer flexible wheel 16 and the inner flexible wheel 17.

[0053] An L-shaped guide ring 15 is provided at one end of the outer flexible wheel 17 and at its connected outer wall. A wave-shaped spring pad (not shown in the figure) is provided between the guide ring 15 and the first inner end cover. The guide ring 15 has an L-shaped cross-section, with a vertically arranged ring portion and an inner flange. The ring portion of the guide ring 15 is in coaxial contact with the outer flexible wheel, and the inner flange of the guide ring 15 is perpendicular to and in contact with the end faces of the outer and inner flexible wheels to limit their axial displacement. The guide ring 15 is made of high-hardness steel and machined to limit the deformation of the outer flexible wheel. When the inner flexible wheel 16, outer flexible wheel 17 and wave generator are assembled, the outer flexible wheel undergoes elliptical deformation. Its deformation is limited by the guide ring 15. The inner flexible wheel 16 always maintains a portion of its wall surface continuously contacting and pressing the wall surface of the outer flexible wheel in the direction of the wave generator's rotation. Due to the circumference difference between the outer diameter of the inner flexible wheel and the inner diameter of the outer flexible wheel, the wave generator rotates and drives the long shaft of the inner flexible wheel to roll locally inside the outer flexible wheel, resulting in relative rotation with the outer flexible wheel, thus achieving the speed reducer effect of deceleration and torque increase.

[0054] The side wall of the end of the inner flexible wheel 16 away from the guide ring 15 is the output area. The inner side wall of the output area is in contact with the outer one-way clutch 22, and the outer side wall of the output area is connected to the inner wall of the fifth bearing 20. The outer wall of the fifth bearing is connected to the right end cover 19.

[0055] A bearing retaining ring 18 is coaxially disposed between the inner flexible gear and the fifth bearing 20 to limit the fifth bearing 20.

[0056] The torque sensor 4 is a torque-sensing strain gauge sensor, comprising a strain gauge and a circuit board. Since the torque sensor is located on the outer wall of the central shaft, the circuit board is not shown in the figure. The strain gauge is electrically connected to the circuit board, and the circuit board is electrically connected to the controller. The strain gauge sensor obtains the voltage value during pedaling as the central shaft rotates. A slight bending of the strain gauge causes a change in its resistance. The circuit board inside the strain gauge sensor calculates the voltage value based on the resistance change and converts it into an electrical signal, which is used to provide the controller with a voltage value (for the torque) and the corresponding frequency value (for the pedaling frequency). When the torque sensor provides a frequency value to the controller, an additional multi-pole magnetic ring is installed on the torque sensor.

[0057] The inner ring of the torque sensor is interference-fitted to the central shaft 1, and the outer ring of the torque sensor 4 is slidably connected to the inner one-way clutch 21. The inner one-way clutch 21 is engaged with the inner wall of the output shaft 25, and the outer wall of the output shaft 25 is engaged with the outer one-way clutch 22. Moreover, both the inner one-way clutch 21 and the outer one-way clutch 22 are disc-shaped structures. The purpose of setting two clutches to connect the output shaft 25 together is that when the motor is not working, that is, when only pedaling force is used, the resistance of the reduction mechanism will not be transmitted to the output shaft 25 because the outer one-way clutch 22 is disengaged from the inner wall of the inner flexible wheel 16. Similarly, when the motor is working, the outer one-way clutch 22 contacts the inner flexible wheel 16, and the reduction mechanism transmits the torque of the motor shaft 7 to the outer one-way clutch 22, which then transmits the torque to the output shaft 25.

[0058] Furthermore, multiple circumferentially arranged Hall sensors are fixedly installed on the outer wall of the motor stator 10, and these Hall sensors, together with the magnetic ring 8, form an encoder. The Hall sensors are electrically connected to the controller.

[0059] The controller uses a DSP chip and adjusts the output voltage of the motor stator 10 according to the voltage signal output by the torque sensor based on the set algorithm logic, thereby controlling the motor to output a suitable torque to improve riding comfort. The controller can also automatically adjust control parameters according to the motor's operating status, including reducing the target torque when the battery is too low or damaged.

[0060] In use, the operation of the concentric and coaxial mid-drive motor for the electric-assist bicycle includes:

[0061] During the start-up and riding of the electric vehicle, when powered by pedaling, the crank and bottom shaft connected to the pedal rotate, causing the torque sensor 4 fixed to its outer wall to rotate. The bottom shaft 1 transmits torque to the torque sensor 4. As the torque sensor 4 rotates with the bottom shaft, it obtains the pressure during pedaling. The strain gauge undergoes a slight bending, causing a change in its resistance value. The circuit board inside the strain gauge sensor calculates the voltage value based on the change in resistance. During rotation, the internal one-way clutch 21 rotates together, which in turn drives the output shaft 25 to rotate. When the output shaft 25 is subjected to the resistance of the electric bicycle, the torque sensor converts the voltage value into an electrical signal and outputs it to the controller.

[0062] The controller receives the electrical signal transmitted by the torque sensor 4; if the received voltage signal is greater than the preset voltage value, i.e. when encountering a large slope or during the initial ride, it outputs 100% of the rated voltage to the motor stator 10 to generate a rotating magnetic field; the rotating magnetic field interacts with the magnetic field of the magnetic ring 8, causing the rotating shaft 7 to rotate, and the cam 12 of the wave generator rotates with the rotating shaft 7, thereby driving the fourth bearing 14 to rotate. Under the combined action of the fourth bearing 14, the outer flexible wheel 17 and the guide ring 15, the inner flexible wheel 16 reduces the rotational speed of the rotating shaft 7 and increases the torque output to the outer one-way clutch 22. The outer one-way clutch 22 transmits the torque to the output shaft 25, which, together with the pedaling torque, drives the bicycle.

[0063] When the electrical signal of the voltage transmitted by the torque sensor 4 is within 20-90% of the preset voltage value, the controller outputs 10-100% of the rated voltage to the motor stator 10, providing the rider with more comfortable torque.

[0064] When the electrical signal of the voltage transmitted by the torque sensor 4 is less than 20% of the preset voltage value, that is, when riding downhill at a high speed, the controller will no longer output voltage to the motor stator 10. Example 2

[0065] An electric-assist bicycle includes a concentric coaxial mid-drive motor, comprising a motor housing, a motor stator 10, a rotor core 28, a bottom bracket 1, a torque sensor 4, a controller, an inner one-way clutch 21, an outer one-way clutch 22, and a reduction mechanism. The bottom bracket 1 is connected to pedals on both sides via cranks. It is then connected to the rear wheel of the bicycle via a chain.

[0066] The structure of the concentric and coaxial mid-drive motor for the electric-assist bicycle in Example 2 is basically the same as that in Example 1. The same parts will not be repeated. Only the differences will be described below.

[0067] In Embodiment 1, the magnetic ring 8 and the rotating shaft 7 form the motor rotor of the mid-mounted motor, and the outer wall of the rotating shaft is provided with a protruding ring portion. The motor stator and rotor are disposed between the first inner end cover and the second inner end cover. Unlike Embodiment 1, the motor rotor in Embodiment 2 is a rotor core 28 as shown in Figure 4. The outer wall of the rotating shaft 7 does not have a protruding ring portion. The rotor core 28 is fitted to the outer diameter of the rotating shaft 7 by an interference fit, and the magnetic tiles 27 are attached to the outer ring of the rotor core 28.

[0068] The reduction mechanism includes a flexible wheel, a rigid wheel, and a wave generator, with the wave generator coaxially arranged with the flexible wheel and the rigid wheel. Both the flexible wheel and the rigid wheel are manufactured using existing harmonic reducer flexure processing technology and commonly used steel materials. The outer wall of the flexible wheel and the inner wall of the rigid wheel have meshing teeth, and there is a difference in the number of teeth between the two wheels. The wave generator causes the flexible wheel to undergo non-circular elastic deformation and partially mesh with the rigid wheel.

[0069] The side wall of the end of the flexible wheel away from the first inner end cover 13 is the output area. The inner side wall of the output area can contact the outer one-way clutch 22, and the outer side wall of the output area is connected to the inner wall of the fifth bearing 20. The outer wall of the fifth bearing is connected to the right end cover 19. In use, when the output end speed is greater than the output shaft speed 25, the inner side wall of the output area contacts the outer one-way clutch 22. When the output shaft speed 25 is greater than the output end of the flexible wheel, the inner side wall of the output area disengages from the outer one-way clutch 22.

[0070] The torque sensor 4 is further provided with a multi-pole magnetic ring at one end of its inner ring, and a coil is provided on the outer ring of the multi-pole magnetic ring. The coil is fixed and the multi-pole magnetic ring rotates with the central shaft 1.

[0071] In use, the operation of the concentric and coaxial mid-drive motor for the electric-assist bicycle includes:

[0072] When riding, the crank connected to the pedal drives the bottom bracket to rotate, which in turn drives the torque sensor 4 fixed on its outer wall to rotate; when rotating, it drives the inner one-way clutch 21 to rotate together, which in turn drives the output shaft 25 to rotate; when the output shaft 25 is subjected to the resistance of the electric bicycle, the multi-pole magnetic ring rotates with the bottom bracket 1, and it generates a periodic signal with the coil induction.

[0073] The controller receives the electrical signal transmitted by the torque sensor 4 and calculates the current pedal frequency (i.e., the rotational speed of the central axis) based on the period frequency.

[0074] The controller presets a cadence value of speed / second. It compares the received current speed cadence value with the preset speed cadence value. If the current speed cadence value monitored by the torque sensor 4 is greater than or equal to the preset speed cadence value of the controller, the motor is turned off and no voltage is output to the motor stator 10. At this time, the shaft 7 does not rotate, that is, it does not provide input to the reduction mechanism, and the rider does not need to use electric assist at this time.

[0075] When the current speed cadence monitored by torque sensor 4 is less than the preset speed cadence value, the motor is started to provide input to the reduction mechanism and drive the bicycle together with the pedaling torque. Example 3

[0076] As shown in Figure 5, an electric-assist bicycle includes a concentric coaxial mid-drive motor, comprising a motor housing, a motor stator 10, a motor rotor, a bottom shaft 1, a torque sensor 4, a controller, an inner one-way clutch 21, an outer one-way clutch 22, and a reduction mechanism. The bottom shaft 1 is connected to pedals on both sides via cranks. It is then connected to the rear wheel of the bicycle via a chain.

[0077] The structure of the concentric coaxial mid-drive motor for the electric-assist bicycle in Embodiment 3 is basically the same as that in Embodiment 1, and the identical parts will not be described again. The difference from Embodiment 1 is that the motor housing, from left to right, includes a left end cover 5, a housing 9, and a right end cover 19. The housing 9 includes an annular shell, with two annular components arranged from the inner wall of the annular shell towards the interior space: a first inner end cover 13 and a second inner end cover 30. The first inner end cover 13 is integrally formed with the housing 9 and is located in the middle of the housing 9. The second inner end cover is detachably connected to the annular shell of the housing 9 by a sliding fit, and one end of the second inner end cover 30 is located on the inner wall of the housing 9 near the left end cover 5. Example 4

[0078] As shown in Figure 6, an electric-assist bicycle includes a concentric coaxial mid-drive motor, comprising a motor housing, a motor stator 10, a motor rotor, a bottom shaft 1, a torque sensor 4, a controller, an inner one-way clutch 21, an outer one-way clutch 22, and a reduction mechanism. The bottom shaft 1 is connected to pedals on both sides via cranks. It is then connected to the rear wheel of the bicycle via a chain.

[0079] The structure of the concentric and coaxial mid-drive motor for the electric-assist bicycle in Example 4 is basically the same as that in Example 1, and the same parts will not be described again. The difference from Example 1 is that the motor is an external rotor type motor. The motor stator is fixed on the inner end face of the housing. The magnet 8 and the rotating shaft 7 form the motor rotor of the mid-drive motor. One end of the outer ring of the rotating shaft 7 of the motor rotor is interference-fitted to the inner ring of the second bearing 6. The outer ring of the second bearing 6 is located in the inner ring of the second inner end cover 30. The other end of the outer ring of the rotating shaft 7 is interference-fitted to the inner ring of the third bearing 11. The magnet 8 of the rotor is located in the outer ring of the stator 10. Example 5

[0080] As shown in Figure 7, an electric-assist bicycle includes a concentric coaxial mid-drive motor, comprising a motor housing, a motor stator 10, a motor rotor, a bottom shaft 1, a torque sensor 4, a controller, an inner one-way clutch 21, an outer one-way clutch 22, and a reduction mechanism. The bottom shaft 1 is connected to pedals on both sides via cranks. It is then connected to the rear wheel of the bicycle via a chain.

[0081] The structure of the concentric coaxial mid-drive motor for the electric-assist bicycle in Example 5 is basically the same as that in Example 1, and the same parts will not be described again. The difference from Example 1 is that the motor is an axial flux motor. The magnet 8 and the shaft 7 form the motor rotor of the mid-drive motor. The motor stator 10 is fixed on the inner end face of the housing 9. One end of the outer ring of the motor rotor shaft 7 is interference-fitted to the inner ring of the second bearing 6. The outer ring of the second bearing 6 is located in the inner ring of the second inner end cover 30. The other end of the outer ring of the shaft 7 is interference-fitted to the inner ring of the third bearing 11. The magnet 8 of the rotor is located on one side of the stator 10. Example 6

[0082] As shown in Figure 8, an electric-assist bicycle includes a concentric coaxial mid-drive motor, comprising a motor housing, a motor stator 10, a motor rotor, a bottom shaft 1, a torque sensor 4, a controller, an inner one-way clutch 21, an outer one-way clutch 22, and a reduction mechanism. The bottom shaft 1 is connected to pedals on both sides via cranks. It is then connected to the rear wheel of the bicycle via a chain.

[0083] The torque sensor 4 is a pressure-sensitive strain gauge sensor, including a strain gauge and a circuit board 28. The strain gauge and the circuit board 29 are electrically connected. The controller is electrically connected to the motor stator 10 and the circuit board 29 respectively.

[0084] The structure of the concentric and coaxial mid-drive motor for the electric-assist bicycle in Example 6 is basically the same as that in Example 1. The same parts will not be repeated. Only the differences will be described below.

[0085] The outer wall of the central shaft 1, from one end to the other (from left to right in Figure 1), consists of a first bearing 2, an inner one-way clutch 21, and a seventh bearing, respectively. Part of the inner ring of the output shaft 25 is supported by the central shaft through the seventh bearing. An annular boss is provided along the outer wall of the central shaft, and one side of the boss is used to limit the first bearing 2.

[0086] The torque sensor 4 is disposed on the outer ring of the first bearing 2, and the circuit board 28 is fixedly disposed inside the left end cover 5. The torque sensor 4 obtains the voltage when pedaling by means of a strain gauge. The strain gauge undergoes a slight bending, which causes a change in its resistance value. The circuit board 4 calculates the voltage value based on the change in resistance value and provides the voltage change value to the controller. Example 7

[0087] As shown in Figure 9, an electric-assist bicycle includes a concentric coaxial mid-drive motor, comprising a motor housing, a motor stator 10, a motor rotor, a bottom shaft 1, a torque sensor 4, a controller, an inner one-way clutch 21, an outer one-way clutch 22, and a reduction mechanism. The bottom shaft 1 is connected to pedals on both sides via cranks. It is then connected to the rear wheel of the bicycle via a chain.

[0088] The structure of the mid-drive motor for the electric-assisted bicycle in Example 7 is basically the same as that in Example 5. The same parts will not be described again. Only the differences will be described below.

[0089] The central shaft has an annular boss along its outer wall, and the two sides of the boss are used to limit the first bearing 2 and the second bearing 6 respectively; and the central shaft also has a groove along its outer wall, the outline of which is adapted to the flange protruding from the inner ring of the third bearing 11, so that the groove limits the third bearing 11.

[0090] One end of the inner ring of the motor rotor is located on the outer ring of the second bearing, and the other end of the inner ring of the motor rotor is located on the outer ring of the third bearing. The inner rings of the first bearing 2, the second bearing 6 and the third bearing 11 are all interference-fitted on the outer ring of the central shaft.

[0091] Furthermore, the inner flexible wheel has meshing teeth on its outer wall and the outer flexible wheel's inner wall, and there is a difference in the number of teeth between the inner and outer flexible wheels. The wave generator causes the inner flexible wheel to undergo non-circular elastic deformation and partially mesh with the outer flexible wheel.

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. Non-essential improvements, adjustments or substitutions made by those skilled in the art based on the content of this specification are all within the scope of protection claimed by the present invention.

Claims

1. A concentric and coaxial mid-drive motor for an electric-assist bicycle, characterized in that, Includes housing (9), left end cover (5), right end cover (19), central shaft (1), torque sensor (4), motor stator (10), motor rotor, guide ring (15), wave generator, inner flexible wheel (16), outer flexible wheel (17), inner one-way clutch (21), outer one-way clutch (22), output shaft (25), first bearing (2), second bearing (6), third bearing (11), fifth bearing (20), sixth bearing (23), and seventh bearing (24); The axis of the central shaft (1), the axis of the rotor, and the rotation center of the inner flexible wheel (16) and the output shaft (25) are located on the same axis; the housing (9), the left end cover (5), and the right end cover (19) together constitute the motor housing; a first inner end cover (13) and a second inner end cover (30) are provided from the inner wall of the housing (9), wherein one end of the first inner end cover (13) is located on the right side of the motor rotor and stator, and one end of the second inner end cover (30) is located on the left side of the motor rotor and stator; and at least one of the first inner end cover (13) and the second inner end cover (30) is detachably connected to the housing (9); the two ends of the central shaft (1) are respectively provided in the inner ring of the first bearing (2) and the inner ring of the seventh bearing (24), the outer ring of the first bearing (2) is provided in the left end cover (5), the outer ring of the seventh bearing (24) is provided in the inner wall of the output shaft (25), the outer ring of the sixth bearing (23) is provided in the inner wall of the right end cover, and the sixth bearing (23) The inner ring is set on the outer wall of the output shaft. The output end of the inner flexible wheel (16) is connected to the inner ring of the fifth bearing (20). The outer ring of the fifth bearing (20) is set on the inner ring of the right end cover (19). The inner one-way clutch (21) is set on the inner wall of the output shaft (25). The motor rotor and stator are set in the space formed by the first inner end cover and the second inner end cover. The outer ring of the first inner end cover (13) is fixed on the inner ring of the housing (9). The wave generator is coaxially connected to the motor rotor. The wave generator is installed in the inner flexible wheel (16). The inner flexible wheel (16) is installed in the outer flexible wheel (17). The outer flexible wheel (17) is fixed on the right end cover (19). One end of the outer ring of the outer flexible wheel (17) is located inside the guide ring (15). The inner wall of the inner ring of the inner flexible wheel (16) away from the guide ring (15) is provided with an outer one-way clutch (22). The outer one-way clutch (22) is set on the outer wall of the output shaft (25). The torque sensor is centrally located inside or offset inside the motor housing to obtain changes in force during pedaling and convert them into electrical signals for output.

2. The concentric coaxial mid-drive motor for electric-assisted bicycles according to claim 1, characterized in that, The torque sensor (4) is a torque-sensing strain gauge sensor. The inner ring of the torque sensor (4) is set on the outer ring of the central shaft (1). When the torque sensor (4) rotates with the central shaft, it obtains the voltage value when pedaling and converts it into an electrical signal. The central motor also includes a controller. The controller is electrically connected to the torque sensor (4) and the motor stator (10) respectively, and is used to output a voltage of a corresponding magnitude to the motor stator according to the electrical signal value transmitted by the torque sensor (4).

3. The concentric coaxial mid-drive motor for electric-assisted bicycles according to claim 1, characterized in that, The torque sensor (4) is a pressure-sensitive strain gauge sensor. The torque sensor (4) is disposed between the outer ring of the first bearing (2) and the left end cover (5). The torque sensor (4) obtains the voltage value when pedaling through the strain gauge and converts it into an electrical signal. The mid-mounted motor also includes a controller. The controller is electrically connected to the torque sensor (4) and the motor stator (10) respectively, and is used to output a voltage of a corresponding magnitude to the motor stator according to the electrical signal value transmitted by the torque sensor (4).

4. The concentric coaxial mid-drive motor for electric-assisted bicycles according to claim 2 or 3, characterized in that, The working process of the controller includes: Receive the electrical signal value of the voltage transmitted by the torque sensor (4); If the received voltage signal value is greater than the preset voltage value, the motor is started and outputs 100% of the rated voltage to the motor stator (10) to generate a rotating magnetic field. The rotating magnetic field interacts with the magnetic field of the rotor, causing the rotor to rotate, which in turn causes the wave generator to rotate, reducing the speed of the rotor and increasing the torque output to the external one-way clutch (22) connected to the inner flexible wheel (16). The external one-way clutch (22) transmits the torque to the output shaft (25), which, together with the pedaling torque, drives the bicycle.

5. The concentric coaxial mid-drive motor for electric-assisted bicycles according to claim 1, characterized in that, The motor is an internal rotor type motor. One end of the outer ring of the motor rotor is located in the inner ring of the second bearing (6), the outer ring of the second bearing (6) is located in the inner ring of the second inner end cover (30), and the other end of the outer ring of the motor rotor is located in the inner ring of the third bearing (11).

6. The concentric coaxial mid-drive motor for electric-assisted bicycles according to claim 1, characterized in that, The motor is an external rotor type motor, and the motor stator is fixed on the housing; one end of the outer ring of the motor rotor is located in the inner ring of the second bearing (6), the outer ring of the second bearing (6) is located in the inner ring of the second inner end cover (30), the other end of the outer ring of the motor rotor is located in the inner ring of the third bearing (11), and the permanent magnet of the rotor is located in the outer ring of the stator.

7. The concentric coaxial mid-drive motor for electric-assisted bicycles according to claim 1, characterized in that, The motor is an axial flux motor, and the motor stator is fixed on the housing. One end of the outer ring of the motor rotor is located in the inner ring of the second bearing (6), the outer ring of the second bearing (6) is located in the inner ring of the second inner end cover (30), the other end of the outer ring of the motor rotor is located in the inner ring of the third bearing (11), and the permanent magnet of the rotor is located on the axial side of the stator.

8. The concentric coaxial mid-drive motor for electric-assisted bicycles according to any one of claims 5 to 7, characterized in that, The inner flexible wheel (16) and the outer flexible wheel (17) have no teeth on their inner walls, and the circumference of the outer wall of the inner flexible wheel is smaller than the circumference of the inner wall of the outer flexible wheel.

9. The concentric coaxial mid-drive motor for electric-assisted bicycles according to any one of claims 5 to 7, characterized in that, The inner flexible wheel (16) and / or the outer flexible wheel (17) are made of PEEK material, and teeth are provided on the outer wall of the inner flexible wheel or the inner wall of the outer flexible wheel. The number of teeth on the outer flexible wheel is at least two more than that on the inner flexible wheel.

10. The concentric coaxial mid-drive motor for electric-assisted bicycles according to any one of claims 5 to 7, characterized in that, The outer wall of the inner flexible wheel (16) and the inner wall of the outer flexible wheel (17) are provided with teeth, and the outer flexible wheel has at least two more teeth than the inner flexible wheel.

11. A concentric and coaxial mid-drive motor for an electric-assist bicycle, characterized in that, Housing (9), left end cover (5), right end cover (19), central shaft (1), torque sensor (4), motor stator (10), motor rotor, guide ring (15), wave generator, inner flexible wheel (16), outer flexible wheel (17), inner one-way clutch (21), outer one-way clutch (22), output shaft (25), first bearing (2), second bearing (6), third bearing (11), fifth bearing (20), sixth bearing (23), seventh bearing (24); The central shaft (1), the axis of the motor rotor, the rotation center of the inner flexible wheel (16), and the output shaft (25) are located on the same axis; the housing (9), the left end cover (5), and the right end cover (19) together constitute the motor housing; a first inner end cover (13) is provided from the inner wall of the housing inward. The motor stator is fixed to the inner ring of the housing (9); one end of the inner ring of the motor rotor is located on the outer ring of the second bearing (6), and the other end of the inner ring of the motor rotor is located on the outer ring of the third bearing (11). The inner rings of the first bearing (2), the second bearing (6), and the third bearing (11) are all set on the outer ring of the central shaft (1); the outer ring of the first bearing (2) is fixed to the inner ring of the torque sensor, the outer ring of the seventh bearing (24) is fixed to the inner wall of the output shaft (25), the outer ring of the sixth bearing (23) is fixed to the inner wall of the right end cover (19), and the inner ring of the sixth bearing (23) is fixed to the outer wall of the output shaft (25). The output end of the inner flexible wheel (16) is connected to the inner ring of the fifth bearing (20), and the outer ring of the fifth bearing (20) is fixed to the inner ring of the right end cover (19); the inner one-way clutch (21) is installed on the inner wall of the output shaft; the wave generator is coaxially connected to the motor rotor, the wave generator is installed in the inner flexible wheel, the inner flexible wheel is installed in the outer flexible wheel, the outer flexible wheel is fixed on the right end cover, one end of the outer ring of the outer flexible wheel is located inside the guide ring, and an outer one-way clutch (22) is installed on the inner wall of the inner ring of the inner flexible wheel away from the guide ring, and the outer one-way clutch (22) is installed on the outer wall of the output shaft.

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