Hub motor, power-assisted bicycle and pedaling frequency detection method

Abstract

The invention relates to a hub motor, a power-assisted bicycle and a pedaling frequency detection method, the hub motor comprises a shell, a motor cover plate, a main shaft, a tower footing, a strain cover plate, a rotor, a stator and a torque sensor, the motor cover plate is installed at one end of the shell, and the motor cover plate and the shell jointly define a mounting inner cavity; one end of the main shaft is mounted in the mounting inner cavity, and the other end of the main shaft extends out of the mounting inner cavity; the tower footing is rotatably arranged on the main shaft in a sleeving manner; a strain cover plate is rotatably arranged at one end of the main shaft in a sleeving manner, is positioned in the mounting inner cavity, is positioned on one side of the tower footing and is in clutch connection with the tower footing through a one-way clutch structure; the strain cover plate comprises an outer ring fixed with the motor cover plate, a seat body structure rotatably sleeving the main shaft, and a disc body structure located between the outer ring and the seat body structure, and a plurality of through holes uniformly distributed at intervals in the circumferential direction are formed in the disc body structure in a penetrating manner.

Description

Technical Field

[0001] This invention relates to the field of electric bicycle technology, and more particularly to a hub motor, an electric bicycle, and a method for detecting pedal frequency. Background Technology

[0002] Electric-assisted bicycles are a popular and economical mode of transportation. They mainly consist of a hub motor that outputs power, sensors that collect riding status data, a controller that controls the system, and an instrument that provides human-machine interaction.

[0003] The hub motor is mounted on the rear wheel of the bicycle, replacing the traditional rear wheel hub. The rim and spokes are woven into the spoke holes of the hub motor to form the entire rear wheel. The bottom bracket of the hub motor is bolted to the bicycle frame, and the hub motor housing drives the rear wheel to rotate through the spokes.

[0004] Sensors can be divided into bottom bracket sensors and freehub sensors. Bottom bracket sensors are installed at the bottom bracket position of a bicycle, replacing the traditional bottom bracket. The pedals and cranks are bolted to both sides of the sensor's output shaft. Freehub sensors are installed at the freehub position of the bicycle, replacing the traditional mechanical freehub. The derailleur is mounted on the freehub. Sensors can collect information such as riding cadence and torque, and contain internal acquisition circuitry.

[0005] However, in the existing technology, the sensor and the hub motor are structurally separate, that is, neither the central axis sensor nor the tower base sensor is located inside the hub motor housing and the cover plate cavity.

[0006] Because the bottom bracket sensor is located at the bottom bracket position, it is difficult to install. If it is not tightened properly during installation, the sensor wire may be damaged, resulting in malfunction. Secondly, since it replaces the bottom bracket of a traditional bicycle, the style of the bottom bracket is not compatible with the traditional bottom bracket related parts and specifications. For example, the chainline value needs to be adjusted to the specifications of non-drive bicycles.

[0007] The tower-type sensor is installed on the outer part of the tower base of the hub motor, which is outside the hub motor housing cavity. First, the space outside the tower base is small and encroaches on the space of the clutch components, making it difficult to select and install the sensor components. Second, the size and strength of the relevant components of the tower base clutch function are reduced at the same time.

[0008] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0009] The main objective of this invention is to provide a hub motor, an electric bicycle, and a cadence detection method, aiming to solve the aforementioned technical problems in the prior art.

[0010] To achieve the above objectives, the present invention provides a hub motor, the hub motor comprising: case; A motor cover plate is installed at one end of the housing and together with the housing defines an installation cavity; The rotor and stator are located within the mounting cavity; The spindle has one end installed inside the mounting cavity and the other end extending out of the mounting cavity; The tower base is rotatably fitted onto the main shaft; A strain gauge cover plate is rotatably sleeved on one end of the main shaft and located in the mounting cavity. The strain gauge cover plate is located on one side of the tower base and is engaged and disengaged from the tower base via a one-way clutch structure. The strain gauge cover plate includes an outer ring fixed to the motor cover plate, a seat structure rotatably sleeved on the main shaft, and a disc structure located between the outer ring and the seat structure. The disc structure has a plurality of through holes evenly spaced along the circumference. A spoke structure is formed between two adjacent through holes. The plurality of spoke structures include strain spokes and support spokes. The thickness of the disc structure is less than the thickness of the outer ring, and the thickness of the strain spokes is less than the thickness of the support spokes. A torque sensor is located inside the mounting cavity and is attached to the side of the strain spoke; Wherein, the maximum stress borne by the strain spoke under the support load is less than the yield strength of the strain spoke material; the strain spokes and the support spokes are arranged alternately at intervals along the circumference of the disc structure, and the torque sensor is attached to the side of only the strain spokes in the multiple spoke structures.

[0011] Preferably, in the hub motor, there are two torque sensors, and the two torque sensors are arranged at a 90-degree angle. The strain gauges are of two types, with two torque sensors attached to each strain gauge in a one-to-one correspondence.

[0012] Preferably, in the hub motor, at least one support spoke is provided between the two strain spokes.

[0013] Preferably, in the hub motor, when the torque generated by the supporting load is K×35Nm, the strain generated by the strain spokes is greater than K×1.5×10. -4 mm, where K is a coefficient.

[0014] Preferably, in the hub motor, the hub motor further includes a rotor circuit board and a stator circuit board located in the mounting cavity, and the rotor circuit board and the stator circuit board are wirelessly connected via an electromagnetic field; The rotor circuit board is fixed to the motor cover and electrically connected to the two torque sensors. It is used to calculate the current torque based on the data detected by the two torque sensors and to wirelessly transmit the torque signal to the stator circuit board. The stator circuit board is arranged opposite to the rotor circuit board and is fixed to the planetary gear bracket of the hub motor. The stator circuit board is used to supply power to the rotor circuit board and to transmit the received torque signal via wire.

[0015] Preferably, in the hub motor, the rotor circuit board and the stator circuit board are connected by electromagnetic field coupling; The stator circuit board has a first mounting surface facing the rotor circuit board, and a first coil formed by a circuit diagram is arranged on the first mounting surface. The rotor circuit board has a second mounting surface facing the stator circuit board, and a second coil with a circuit diagram is arranged on the second mounting surface. The first coil and the second coil are arranged opposite to each other. When the first coil is energized, it generates an alternating electromagnetic field, and the second coil senses the electromagnetic field to obtain electrical energy for power supply. The rotor circuit board modulates the torque signal into the electromagnetic field formed by the first coil, and the stator circuit board senses the electromagnetic field carrying the torque signal through the first coil and demodulates and extracts the torque data.

[0016] Preferably, in the hub motor, a fixed magnetic ring is provided inside the tower base, and a first Hall sensor for detecting the rotation signal of the fixed magnetic ring is provided on the rotor circuit board; The housing is provided with a rotational magnet, and the stator of the hub motor is provided with a second Hall sensor for detecting the rotational signal of the rotational magnet.

[0017] To achieve the above objectives, the present invention also provides an electric bicycle, which includes the aforementioned hub motor.

[0018] To achieve the above objectives, the present invention also provides a method for detecting cadence in a power-assisted bicycle, comprising: When the hub motor is not assisting or the hub motor speed is lower than the pedaling speed, the speed of the assisted bicycle is used as the rider's cadence. When the hub motor starts to assist and the hub motor speed exceeds the pedaling speed, the relative speed between the motor cover plate and the strain cover plate and the freehub base is the cadence speed, which is used as the rider's cadence.

[0019] Preferably, in the above-described method for detecting cadence in an electric bicycle, the step of using the relative velocity between the motor cover plate and the strain cover plate and the freehub base as the cadence speed as the rider's cadence includes: The rotation signal of the fixed magnetic ring located in the tower base is detected by the first Hall sensor located on the rotor circuit board; The rider's current cadence is determined based on the rotation signal.

[0020] The present invention has at least the following beneficial effects: This invention optimizes the structure of the electric bicycle by setting a strain gauge inside the hub motor and installing a torque sensor on the strain gauge. This improves the overall reliability of the bicycle, avoids the problem of limited space outside the freehub base encroaching on the space of the clutch components, which would otherwise lead to difficulties in selecting and installing sensor components, and avoids a simultaneous reduction in the size and strength of the related components of the freehub base clutch function. Attached Figure Description

[0021] Figure 1 A schematic diagram of one embodiment of the hub motor provided by the present invention; Figure 2 for Figure 1 A schematic diagram of the middle section structure; Figure 3 This is a partial schematic diagram of the strain gauge plate in the figure; Figure 4 This is a schematic diagram of a cover plate in the prior art; Figure 5 and Figure 6 The results are the strain and stress simulation results for a conventional cover plate. Figure 7 and Figure 8 The figures show the strain-stress simulation results of the strain cover plate provided by this invention.

[0022] Figure 9 The flowchart is provided by the present invention for the cadence detection method for the above-mentioned power-assisted bicycle.

[0023] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0025] In this embodiment of the invention, the term "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0026] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0027] In this embodiment of the invention, the term "multiple" refers to two or more, and other quantifiers are similar.

[0028] In this invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this invention.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of the present invention to facilitate a better understanding of the invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0030] This invention provides a hub motor; please refer to [link / reference]. Figures 1 to 3 The hub motor 100 includes a housing 1, a motor cover 2, a main shaft 3, a tower base 4, a strain cover 5, a rotor and a stator, and a torque sensor 6.

[0031] A motor cover plate 2 is mounted on one end of the housing 1, and together with the housing 1, defines a mounting cavity 11. One end of the main shaft 3 is mounted within the mounting cavity 11, and the other end extends out of the mounting cavity 11. A tower base 4 is rotatably fitted onto the main shaft 3. The rotor and stator are located within the mounting cavity. The structure of components such as the housing 1, motor cover plate 2, main shaft 3, rotor, and stator is consistent with that of existing hub motors 100, and will not be described in detail here.

[0032] The strain gauge 5 is rotatably sleeved on one end of the main shaft 3 and located in the mounting cavity 11. The strain gauge 5 is located on one side of the tower base 4 and is engaged and disengaged from the tower base 4 via a one-way clutch structure. The strain gauge 5 includes an outer ring 51 fixed to the motor cover 2, a seat structure 52 rotatably sleeved on the main shaft 3, and a disc structure 53 located between the outer ring 51 and the seat structure 52. The disc structure 53 has multiple through holes evenly spaced along the circumference, and a spoke structure is formed between two adjacent through holes. The multiple spoke structures include strain spokes 531 and support spokes. 532, the thickness of the disc structure 53 is less than the thickness of the outer ring 51, and the thickness of the strain spoke 531 is less than the thickness of the support spoke 532; the torque sensor 6 is located inside the mounting cavity 11 and is attached to the side of the strain spoke 531; wherein, under the support load, the maximum stress borne by the strain spoke 531 is less than the yield strength of the strain spoke 531 material; the strain spoke 531 and the support spoke 532 are arranged alternately along the circumference of the disc structure 53, and the torque sensor 6 is attached to the side of only the strain spoke 531 among the multiple spoke structures.

[0033] More specifically, the disc structure 53 is provided with N spoke structures, including M strain spokes 531 and (NM) support spokes 532. The M strain spokes and (NM) support spokes are arranged alternately at intervals along the circumference, and the torque sensor 6 is only attached to the side of the strain spokes 531.

[0034] by Figure 3 For example, Figure 3 It includes two strain spokes 531a and 531b and six support spokes 532a, 532b, 532c, 532d, 532e, and 532f. Support spokes 532a are spaced between strain spokes 531a and 531b. Torque sensors 6 are attached to the sides of strain spokes 531a and 531b respectively.

[0035] It should be noted that the disc structure 53 of the strain gauge cover 5 provided by the present invention is thinner than that of a conventional flange, and naturally the strain spokes 531 are also thinner, thus increasing the sensitivity of the sensor. The thickness of the disc structure 53 is less than the thickness of the outer ring 51, and the thickness of the strain spokes 531 is less than the thickness of the support spokes 532, thus increasing the sensitivity of the sensor while ensuring the support strength.

[0036] Furthermore, when the torque generated by the supporting load is K×35Nm, the strain generated by the strain spokes 531 is greater than K×1.5×10. -4mm, where K is a coefficient. The material of the strain gauge 5 can be selected according to the specific torque required to bear, as long as the torque generated by the supporting load is K×35Nm, the strain generated by the strain spokes 531 is greater than K×1.5×10. - 4 mm is sufficient. For example, when the torque generated by the supporting load is 35 Nm, the strain generated by the strain spokes 531 needs to be greater than 1.5 × 10⁻⁶ mm. -4 mm. In some embodiments, the strain gauge 5 is made of 20CrMo, with a corresponding yield strength of 685MPa.

[0037] This invention utilizes a strain gauge cover 5 on one side of the freehub base 4, connected to the freehub base 4 via a one-way clutch mechanism. When the rider actively pedals, the freehub base 4 transmits a positive torque to the strain gauge cover 5. The one-way clutch mechanism is "locked" by the torque, connecting the freehub base 4 to the seat structure 52 of the strain gauge cover 5. Thus, the rotation of the freehub base 4 causes the strain gauge cover 5 to rotate synchronously. The outer ring 51 remains stationary due to its fixation to the motor cover 2, causing the strain gauge spokes 531 to undergo torsional deformation. During coasting or when the hub motor 100 provides individual assistance, the one-way clutch mechanism disengages. For example, during coasting, when the rider stops pedaling, the wheel's inertia causes the hub motor 100's housing 1 to rotate. At this point, the torque transmission direction reverses, and the seat structure 52 of the strain gauge cover 5 does not rotate with the motor cover 2. The pawl and ratchet of the one-way clutch mechanism separate, disengaging the freehub base 4 from the strain gauge cover 5 and preventing the wheel from causing the pedals to spin freely.

[0038] The strain gauge cover 5 connects the ratchet ring of the freehub base 4 and the motor cover 2, serving as a support for the wheel hub. By placing the strain gauge cover 5 inside the wheel hub motor 100, this invention optimizes the structure of the electric bicycle, improves the overall reliability of the vehicle, avoids the problem of limited space outside the freehub base 4 encroaching on the space of the clutch components, which would otherwise lead to difficulties in selecting and installing sensor components, and prevents a simultaneous reduction in the size and strength of the clutch-related components of the freehub base 4.

[0039] In some embodiments, there are two torque sensors 6 arranged at a 90-degree angle; there are also two strain gauges 531, with each torque sensor 6 corresponding to one of the two strain gauges 531. This allows a bridge circuit to be formed by the two torque sensors 6 arranged at a 90-degree angle, thus enabling the extraction of the deformation signal corresponding to the torque.

[0040] Preferably, at least one supporting spoke 532 is provided between the two strain spokes 531. Since the thickness of the strain spokes 531 is less than the thickness of the supporting spokes 532, the strain cover plate 5 has better strength by providing at least one supporting spoke 532 between the two strain spokes 531. In some embodiments, eight spokes are provided; of course, in other embodiments, four or other numbers of spokes can be provided, as long as the strength requirements are met.

[0041] Traditionally, the 4-type sensor is installed on the outer part of the hub motor 100's hub base 4, that is, outside the cavity of the hub motor 100 housing 1. This has two drawbacks: firstly, the space outside the hub base 4 is limited and encroaches on the space for clutch components, making sensor selection and installation difficult; secondly, the size and strength of the clutch-related components of the hub base 4 are simultaneously reduced. Furthermore, this placement on the outside of the hub motor 100 cavity (i.e., the previously mentioned mounting cavity 11) makes communication with the inside of the hub motor 100 cavity very difficult (limited space, requiring connecting cables from the outside to the inside, making installation very space-consuming). Moreover, the hub base 4 is a consumable component; once it wears out, the entire system needs to be replaced, meaning the 4-type sensor located outside the hub motor 100 housing 1 cavity also needs to be replaced.

[0042] The present invention uses a strain cover plate 5 located inside the mounting cavity 11 instead of the traditional tower base 4 type sensor, and attaches the torque sensor 6 to the strain cover plate 5, thus eliminating the need to consider the above-mentioned problems.

[0043] In some embodiments, the hub motor 100 further includes a rotor circuit board 72 and a stator circuit board 71 located in the mounting cavity 11, the rotor circuit board 72 and the stator circuit board 71 being wirelessly connected via an electromagnetic field. Since the main shaft 3, motor output cable, motor stator, rotor housing 1, and planetary gear bracket, which are fixed to the rear fork of the electric bicycle, do not rotate when the wheel rotates, while the motor housing 1, motor cover plate 2, strain gauge cover plate 5, and freehub base 4 all rotate relative to the rear fork when the wheel rotates, it is impossible to use a wiring harness to transmit the signal from the torque sensor 6 on the strain gauge cover plate 5 to the fixed structure. By setting the rotor circuit board 72 and the stator circuit board 71 to be wirelessly connected via an electromagnetic field, the signal from the torque sensor 6 on the rotating strain gauge cover plate 5 can be transmitted, processed, and output through the motor output cable.

[0044] Specifically, in some embodiments, the rotor circuit board 72 and the stator circuit board 71 are connected by electromagnetic field coupling; the stator circuit board 71 is fixed to the planetary gear support of the hub motor 100, the stator circuit board 71 has a first mounting surface facing the rotor circuit board 72, and a first coil with a circuit drawn on the first mounting surface is arranged thereon; the rotor circuit board 72 has a second mounting surface facing the stator circuit board 71, and a second coil with a circuit drawn on the second mounting surface is arranged thereon, the first coil and the second coil are arranged opposite to each other; wherein, when the first coil is energized, it generates an alternating electromagnetic field, and the second coil senses the electromagnetic field to obtain electrical energy for power supply; the rotor circuit board 72 modulates the torque signal into the electromagnetic field formed by the first coil, and the stator circuit board 71 senses the electromagnetic field carrying the torque signal through the first coil and demodulates and extracts the torque data.

[0045] The rotor circuit board 72 is fixed to the motor cover plate 2 and electrically connected to the two torque sensors 6. It calculates the current torque based on the data detected by the two torque sensors 6 and wirelessly transmits the torque signal to the stator circuit board 71. In some embodiments, the rotor circuit board 72 is bolted to the motor cover plate 2. A second coil with circuitry is drawn on the left side of the PCB, and electronic components are placed in the gap between the right side and the motor cover plate 2. When the wheel rotates, the rotor circuit board 72 rotates relative to the rear fork. It has no external power supply; instead, it generates electrical energy through the electromagnetic field induced by the first coil of the stator circuit board 71, which powers the electronic components on the rotor circuit board 72.

[0046] The stator circuit board 71 is disposed opposite to the rotor circuit board 72, and the stator circuit board 71 is fixed to the planetary gear support of the hub motor 100. The stator circuit board 71 supplies power to the rotor circuit board 72 and transmits the received torque signal via a wired connection. Specifically, the stator circuit board 71 converts electrical energy into an alternating electromagnetic field through a first coil to provide power to the rotor circuit board 72 on the rotating side. The stator circuit board 71 separates the torque data from the signal modulated into the electromagnetic field by the rotor circuit board 72, demodulates the torque data to obtain a torque signal, and transmits the demodulated torque signal via a wired connection through the CAN bus.

[0047] Because the hub motor 100 provided by this invention uses a strain gauge 5 located inside the mounting cavity 11 instead of the traditional freehub base 4 type sensor, and the torque sensor 6 is attached to the strain gauge 5, the torque detection device is located inside the hub motor 100. Traditionally, the torque sensor is located outside the hub motor 100, allowing direct monitoring of the rider's cadence. This invention, by placing the torque detection device inside the hub motor 100, cannot directly monitor the rider's cadence. Therefore, in this embodiment, a fixed magnetic ring 81 is provided inside the freehub base 4, and a first Hall sensor for detecting the rotation signal of the fixed magnetic ring 81 is provided on the rotor circuit board 72; a rotational magnet 82 is provided on the housing 1, and a second Hall sensor for detecting the rotation signal of the rotational magnet 82 is provided on the stator of the hub motor 100.

[0048] When the hub motor 100 is not assisting or its speed is lower than the pedaling speed, the wheel is driven by the chain, and the one-way clutch is engaged. The power transmission path is: sprocket → chain → freewheel → freehub base 4 → clutch structure → strain gauge plate 5 → motor cover plate 2 → housing 1 → wheel. At this time, the speeds of the motor cover plate 2, strain gauge plate 5, housing 1, and freehub base 4 are all the same, and the speed of the assisted bicycle is the rider's cadence. Therefore, in some embodiments, a rotational magnet 82 is provided on the housing 1, and a second Hall sensor is provided on the stator of the hub motor 100 to detect the rotation signal of the rotational magnet 82. The housing 1 drives the rotational magnet 82 to rotate, and the rotational magnet 82 periodically sweeps across the second Hall sensor on the stator. The second Hall sensor outputs high and low level pulse signals. By counting the number of pulses per unit time and combining it with the number of rotational magnets 82, the rotational speed of the housing 1 is calculated, which is the cadence.

[0049] When the hub motor 100 starts assist and its speed exceeds the pedaling speed, the torque transmission direction reverses, and the one-way clutch structure is disengaged. At this time, the speed (cadence) of the freehub base 4 is not equal to the speed (vehicle speed) of the housing 1. The relative speed between the motor cover plate 2 and the strain gauge cover plate 5 and the freehub base 4 is the cadence speed, which is used as the rider's cadence. Therefore, in some embodiments, a fixed magnetic ring 81 is provided inside the freehub base 4, and a first Hall sensor is provided on the rotor circuit board 72 for detecting the rotation signal of the fixed magnetic ring 81.

[0050] The following discussion focuses on the strain gauge 5 provided by this invention and conventional gauges (such as...). Figure 4 Stress-strain simulations were performed for comparison (as shown). Taking the base 4 and strain cover 5 fixed by 6 screws as an example, the corresponding simulation boundary conditions are: applying a fixing constraint to the 6 screw holes; the maximum torque at the crankshaft of the electric bicycle is 100 Nm, the torque transmitted to the base 4 is 35 Nm, and a radial load of 250 N is applied to the bearing hole.

[0051] Figure 5 and Figure 6 The figures show the strain and stress simulation results for a conventional cover plate. Figure 7 and Figure 8 The illustration shows the strain-stress simulation results of the strain cover plate 5 provided by this invention. The simulation results show that the strain at the conventional cover plate flange is <7.5×10⁻⁶. -5 mm, which does not meet the strain requirement. The strain at the flange of the strain cover plate 5 provided by this invention is >2.0×10 mm. -4 mm, meeting strain requirements; maximum stress is 170MPa, far below the material's yield strength.

[0052] The present invention also provides an electric bicycle including the aforementioned hub motor 100. Embodiments of this electric bicycle include embodiments of the aforementioned hub motor 100, and the beneficial effects of the aforementioned hub motor 100 can be applied to this electric bicycle.

[0053] The present invention also provides a method for detecting cadence in the above-mentioned power-assisted bicycle, such as... Figure 9 As shown, the cadence detection method for the above-mentioned power-assisted bicycle includes steps S210 and S220.

[0054] In step S210, when the hub motor 100 is not providing assistance or the speed of the hub motor 100 is lower than the pedaling speed, the speed of the assisted bicycle is taken as the rider's cadence. When the hub motor 100 is not providing assistance or the speed of the hub motor 100 is lower than the pedaling speed, the wheel is driven by the chain, the one-way clutch structure is engaged, and the power transmission path is: sprocket → chain → freewheel → freehub base 4 → clutch structure → strain gauge cover 5 → motor cover 2 → housing 1 → wheel. At this time, the speeds of motor cover 2, strain gauge cover 5, housing 1, and freehub base 4 are all the same, and the speed of the assisted bicycle at this time is the rider's cadence.

[0055] In step S220, when the hub motor 100 starts to assist and the speed of the hub motor 100 exceeds the pedaling speed, the relative speed between the motor cover plate 2 and the strain cover plate 5 and the freehub base 4 is the cadence speed, which is used as the rider's cadence.

[0056] When the hub motor 100 starts assisting and its speed exceeds the pedaling speed, the torque transmission direction reverses, and the one-way clutch structure is disengaged. At this time, the speed of the freehub base 4 (cadence) is not equal to the speed of the housing 1 (vehicle speed). The relative speed between the motor cover plate 2 and the strain gauge cover plate 5 and the freehub base 4 is the cadence speed, which is used as the rider's cadence.

[0057] It should be noted that steps S210 and S220 may not be in any order; or step S210 may come first and step S220 may come later; or step S220 may come first and step S210 may come later.

[0058] In specific implementation, step S220 includes acquiring the rotation signal of the fixed magnetic ring 81 located in the freehub base 4 detected by the first Hall sensor located on the rotor circuit board 72; and determining the rider's current cadence based on the rotation signal. Since the fixed magnetic ring 81 is fixed inside the freehub base 4, and the first Hall sensor is fixed on the rotor circuit board 72 that rotates with the rotation of the housing 1, the first Hall sensor detects the relative rotational speed between the freehub base 4 and the rotor circuit board 72, i.e., the cadence.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A hub motor, characterized in that, include: case; A motor cover plate is installed at one end of the housing and together with the housing defines an installation cavity; The rotor and stator are located within the mounting cavity; The spindle has one end installed inside the mounting cavity and the other end extending out of the mounting cavity; The tower base is rotatably fitted onto the main shaft; A strain gauge cover plate is rotatably sleeved on one end of the main shaft and located in the mounting cavity. The strain gauge cover plate is located on one side of the tower base and is engaged and disengaged from the tower base via a one-way clutch structure. The strain gauge cover plate includes an outer ring fixed to the motor cover plate, a seat structure rotatably sleeved on the main shaft, and a disc structure located between the outer ring and the seat structure. The disc structure has a plurality of through holes evenly spaced along the circumference. A spoke structure is formed between two adjacent through holes. The plurality of spoke structures include strain spokes and support spokes. The thickness of the disc structure is less than the thickness of the outer ring, and the thickness of the strain spokes is less than the thickness of the support spokes. A torque sensor is located inside the mounting cavity and is attached to the side of the strain spoke; Wherein, the maximum stress borne by the strain spoke under the support load is less than the yield strength of the strain spoke material; the strain spokes and the support spokes are arranged alternately at intervals along the circumference of the disc structure, and the torque sensor is attached to the side of only the strain spokes in the multiple spoke structures.

2. The hub motor as described in claim 1, characterized in that, The number of torque sensors is two, and the two torque sensors are arranged at a 90-degree angle. The strain gauges are of two types, with two torque sensors attached to each strain gauge in a one-to-one correspondence.

3. The hub motor as described in claim 2, characterized in that, At least one support spoke is provided between the two strain spokes.

4. The hub motor as described in claim 2, characterized in that, When the torque generated by the supporting load is K×35Nm, the strain generated by the strain spokes is greater than K×1.5×10. -4 mm, K is a coefficient.

5. The hub motor as described in claim 2, characterized in that, The hub motor also includes a rotor circuit board and a stator circuit board located in the mounting cavity, and the rotor circuit board and the stator circuit board are wirelessly connected via an electromagnetic field. The rotor circuit board is fixed to the motor cover and electrically connected to the two torque sensors. It is used to calculate the current torque based on the data detected by the two torque sensors and to wirelessly transmit the torque signal to the stator circuit board. The stator circuit board is arranged opposite to the rotor circuit board and is fixed to the planetary gear bracket of the hub motor. The stator circuit board is used to supply power to the rotor circuit board and to transmit the received torque signal via wire.

6. The hub motor as described in claim 5, characterized in that, The rotor circuit board and the stator circuit board are connected by electromagnetic field coupling; The stator circuit board has a first mounting surface facing the rotor circuit board, and a first coil formed by a circuit diagram is arranged on the first mounting surface. The rotor circuit board has a second mounting surface facing the stator circuit board, and a second coil with a circuit diagram is arranged on the second mounting surface. The first coil and the second coil are arranged opposite to each other. When the first coil is energized, it generates an alternating electromagnetic field, and the second coil senses the electromagnetic field to obtain electrical energy for power supply. The rotor circuit board modulates the torque signal into the electromagnetic field formed by the first coil, and the stator circuit board senses the electromagnetic field carrying the torque signal through the first coil and demodulates and extracts the torque data.

7. The hub motor as described in any one of claims 1 to 6, characterized in that, The tower base is equipped with a fixed magnetic ring, and the rotor circuit board is equipped with a first Hall sensor for detecting the rotation signal of the fixed magnetic ring. The housing is provided with a rotational magnet, and the stator of the hub motor is provided with a second Hall sensor for detecting the rotational signal of the rotational magnet.

8. A power-assisted bicycle, characterized in that, Including the hub motor as described in any one of claims 1 to 7.

9. A method for detecting cadence in a power-assisted bicycle as described in claim 8, characterized in that, include: When the hub motor is not assisting or the hub motor speed is lower than the pedaling speed, the speed of the assisted bicycle is used as the rider's cadence. When the hub motor starts to assist and the hub motor speed exceeds the pedaling speed, the relative speed between the motor cover plate and the strain cover plate and the freehub base is the cadence speed, which is used as the rider's cadence.

10. The method for detecting cadence in a power-assisted bicycle as described in claim 9, characterized in that, The method of using the relative speed between the motor cover plate and the strain cover plate and the base of the freehub as the cadence speed as the rider's cadence includes: The rotation signal of the fixed magnetic ring located in the tower base is detected by the first Hall sensor located on the rotor circuit board; The rider's current cadence is determined based on the rotation signal.

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