Dual-motor assisting device of moped and control method thereof

Abstract

The application discloses a double-motor assisting device of a moped and a control method thereof. The assisting device comprises a middle shaft assembly, a first planetary mechanism, a second planetary mechanism, a driving motor, a transition shaft assembly and a variable-speed motor. The middle shaft assembly comprises a middle shaft, a first shaft sleeve, a first gear, a second gear and a first one-way clutch for establishing a one-way transmission relationship between the second gear and the first shaft sleeve. The transition shaft assembly comprises a transition shaft, a third gear, a fourth gear and a second clutch, which is bidirectional locking when engaged. The variable-speed motor is connected with a sun gear of the first planetary mechanism. In the first planetary mechanism, a first planetary carrier is in transmission connection with the fourth gear, and an outer gear ring is in transmission connection with an external transmission unit. The second planetary mechanism comprises the external transmission unit. The driving motor is connected with the second planetary mechanism, and the external transmission unit is in transmission connection with the first gear. The second gear is in meshing with the third gear.

Description

Technical Field

[0001] This invention relates to the field of electric bicycle accessories technology, and in particular to a dual-motor assist device for electric bicycles and its control method. Background Technology

[0002] With the popularization of green travel concepts, electric-assist bicycles have become a core product for short-distance urban travel and leisure cycling. The current mainstream single-motor solution with mechanical gears has problems such as limited gears, shifting jerks, and insufficient adaptability to various scenarios. The industry has gradually developed an electronic continuously variable transmission (CVT) solution with dual motors and planetary gear mechanisms to optimize the riding experience.

[0003] The invention patent application with publication number CN121180347A provides a dual-motor power assist scheme based on a single planetary gear set. By having two motors respectively input power to the sun gear and ring gear of the planetary gear system, and using multiple sets of one-way clutches to construct a dual-branch power architecture, five riding modes can be realized, which to some extent solves the smoothness and responsiveness problems of traditional solutions.

[0004] However, this solution still has inherent flaws that cannot be avoided in engineering applications: First, the energy recovery and human power generation functions heavily rely on the residual battery power, requiring the locking gear ring to be powered on to generate electricity. When the battery is depleted, the function is completely ineffective, and the reliability under extreme conditions is insufficient. Second, the two motors are still coupled within the same planetary gear system. When adjusting the speed, complex algorithms are needed to compensate the drive motor output in real time, which places high demands on the controller's computing power and accuracy. Power fluctuations are prone to occur when the load changes abruptly. Third, under pure electric and heavy-load conditions, the power of the two motors needs to be output after differential synthesis through the planetary gear system, resulting in additional transmission losses. There is still room for improvement in torque output efficiency and power responsiveness. Fourth, under non-assisted conditions, the motor and gear system still maintain meshing and linkage with the output end, and it is impossible to completely isolate mechanical drag and electromagnetic resistance, resulting in incomplete optimization of the pedal feel when riding without electricity. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the present invention provides a dual-motor assist device for electric bicycles and its control method, which aims to achieve complete decoupling of drive and speed regulation functions by reconstructing the power topology of dual motors and planetary mechanism, thereby improving the system's adaptability to all scenarios and riding reliability.

[0006] Technical solution: To achieve the above objectives, the present invention provides a dual-motor power assist device for a power-assisted bicycle, comprising a central shaft assembly, a first planetary mechanism, a second planetary mechanism, a drive motor, and a variable speed motor; the central shaft assembly includes a central shaft and a first bushing sleeved on the central shaft, the end of the first bushing being fixed on the central shaft; the second gear is connected to the wheel via a sprocket and a chain;

[0007] The central shaft assembly also includes a first gear and a second gear;

[0008] The central shaft assembly also includes a first one-way clutch that establishes a one-way transmission relationship between the second gear and the first bushing; human power is synchronously input to the first bushing via the central shaft and can be directly input to the second gear through the first one-way clutch; when the rotational speed of the second gear is higher than that of the first bushing, the first one-way clutch automatically disengages to cut off the reverse transmission between the output end and the central shaft;

[0009] The dual-motor assist device also includes a transition shaft assembly, which includes a transition shaft and a third gear and a fourth gear mounted on the transition shaft;

[0010] The first planetary mechanism includes a sun gear, a first planet carrier, an external gear ring, and planet gears; the variable speed motor is connected to the sun gear; the first planet carrier is driven by the fourth gear; and the external gear ring is driven by the external transmission unit.

[0011] The second planetary mechanism includes an external transmission unit, the drive motor is connected to the central sun gear in the second planetary mechanism, and the external transmission unit is connected to the first gear transmission.

[0012] The second gear meshes with the third gear. The second gear is used to output power to the wheels, and a second clutch is provided between the third gear or the fourth gear and the transition shaft. When the second clutch is engaged, it provides bidirectional locking.

[0013] In a preferred embodiment, a second bushing is also fitted on the central shaft, and the first gear and the second gear are coaxially mounted on the second bushing; the second gear and the second bushing are relatively fixed and can be integrally formed; the first gear is rotatably disposed relative to the second bushing; and the first one-way clutch is disposed between the second bushing and the first bushing.

[0014] Furthermore, the first planetary mechanism (2) and / or the second planetary mechanism are NGWN type planetary gear reduction mechanisms.

[0015] Furthermore, a torque sensor and a cadence sensor are also installed on the central axis assembly.

[0016] Furthermore, the central shaft of the drive motor, the central shaft of the variable speed motor, the axis of the transition shaft, and the axis of the central shaft are arranged in a quadrilateral shape. Specifically, the drive motor and the transition shaft are diagonally opposite each other, and the variable speed motor and the central shaft are diagonally opposite each other.

[0017] The first gear is equipped with a manual emergency locking mechanism, which is a manually insertable locking pin used to mechanically lock the first gear and the housing when the battery is depleted, and to lock the outer gear ring via the external transmission unit.

[0018] The control method for the dual-motor assist device of the electric bicycle described above is implemented by the control unit, which obtains control commands to get target mode information and switches to the corresponding operating mode based on the target mode information. The operating modes include manual transmission without gear shifting, manual power generation mode, hybrid continuously variable transmission mode, manual continuously variable transmission mode, kinetic energy recovery mode, and pure electric mode.

[0019] In automatic control mode, the control method includes:

[0020] Step S1: The rider's pedaling torque is obtained by a torque sensor installed on the first bushing, and the cadence signal is obtained by a cadence sensor installed on the bottom bracket. The target power assist and the target speed ratio are determined by combining the vehicle speed.

[0021] Step S2: Determine the current cycling scenario based on torque and cadence thresholds to identify the target operating mode;

[0022] Step S3: Switch to the corresponding operating mode according to the target operating mode.

[0023] Furthermore, when the pedaling torque detected by the torque sensor is lower than the first threshold and the pedal frequency detected by the cadence sensor is lower than the second threshold, the target operating mode is determined to be pure electric mode.

[0024] When the vehicle speed is higher than the third threshold and the cadence is lower than the fourth threshold, the target operating mode is determined to be the kinetic energy recovery mode.

[0025] When the pedaling torque detected by the torque sensor is higher than the first threshold and the pedaling frequency is lower than the second threshold, the target operating mode is determined to be either hybrid continuously variable transmission (CVT) mode or manual continuously variable transmission (CVT) mode.

[0026] Furthermore, when the operating mode is manual power generation mode, when the battery has power, the drive motor is controlled to receive a microampere-level weak current, and the external transmission unit is locked by electromagnetic holding force, so that the first gear and the external gear ring connected to the external transmission unit remain stationary; when the battery is completely depleted, the wheels and the external transmission unit are fixed by a mechanical parking lock mechanism, realizing passive locking of the external gear ring; the manual drive of the central shaft drives the second gear to rotate via the first bushing and the first one-way clutch, and the power is transmitted to the first planetary carrier via the transition shaft assembly, so that the rotor of the variable speed motor cuts the magnetic field to generate electricity.

[0027] Furthermore, the continuously variable transmission (CVT) mode is achieved by adjusting the rotational speed of the transmission motor. The control unit presets a speed ratio adjustment algorithm, calculates the target speed ratio between the outer gear ring and the bottom bracket based on the real-time cadence obtained from the cadence sensor and the current vehicle speed, and drives the transmission motor to adjust the rotational speed of the sun gear so that the output speed remains continuously adjustable relative to the cadence.

[0028] Furthermore, the operating mode also includes a multi-gear simulation mode. The control unit stores multiple preset fixed speed ratios, which are the ratios of wheel speed to human pedaling frequency. The control method includes: receiving a gear switching command, obtaining the current input pedaling frequency and real-time vehicle speed of the central axle, controlling the transmission motor to compensate for the speed difference of the sun gear, so that the ratio of wheel speed to human pedaling frequency is locked at the preset fixed speed ratio of the corresponding gear.

[0029] Beneficial Effects: The dual-motor power-assist device and its control method for the electric bicycle of the present invention have the following beneficial effects:

[0030] (1) In this invention, a manual mechanical direct drive branch and a motor speed regulation branch are constructed through the cooperation of the first one-way clutch and the second clutch. The first one-way clutch enables manual power to directly drive the second gear and automatically disengages when the speed of the second gear is higher than that of the first bushing; the second clutch, which is bidirectionally locked when engaged, is used to selectively connect or disconnect the power path between the second gear and the first planetary carrier. The power of the drive motor and the variable speed motor is synthesized by the first planetary mechanism and output by the first planetary carrier, and merges with the manual power at the second gear; by controlling the operation of the variable speed motor, the speed ratio of pedal frequency and vehicle speed can be electronically adjusted, and the power flow can be flexibly distributed according to the load conditions to achieve smooth switching of multiple modes. This solution physically separates the speed regulation function and the drive function, eliminates the strong synchronous interference caused by the direct meshing of the gear rings of the two motors in the prior art, reduces the control difficulty, and transforms the control logic under hybrid conditions from the dual-variable synchronous calculation of strong coupling of the two motors to the single-point speed ratio regulation with the variable speed motor as the core, thereby improving the real-time response speed and operation stability of the system.

[0031] (2) The use of a quadrilateral diagonal layout optimizes the spatial compactness of the dual motors and dual planetary gear sets, reducing the overall size of the system. This arrangement ensures reasonable avoidance of each gear set in the axial and radial directions, reducing the installation space requirements.

[0032] (3) Through the control method of the present invention, it is possible to switch between multiple working modes. In automatic mode, the control system can monitor the signals of torque sensor and cadence sensor in real time. By using electromagnetic force in conjunction with ratchet logic, it realizes integrated management from static power generation to dynamic assistance. While providing continuously variable transmission function, it ensures smooth switching between different modes and improves the intelligence level and energy efficiency of the whole vehicle.

[0033] (4) Speed ​​change can be achieved without setting up a separate speed change mechanism, and stepless speed change can be achieved. It can also simulate multi-gear speed change.

[0034] (5) The input of the central shaft in this invention is provided by a drive source, which is a human-powered crank or a fuel engine. Accordingly, this device can be used in electric bicycles or hybrid motorcycles. Attached Figure Description

[0035] Figure 1 A first-person view of the dual-motor assist device for a power-assisted bicycle;

[0036] Figure 2 This is a second-view structural diagram of the dual-motor assist device for a power-assisted bicycle.

[0037] In the diagram: 1-Central shaft assembly; 11-Central shaft; 12-First bushing; 13-Second bushing; 14-First gear; 15-First one-way clutch; 16-Second gear; 17-Torque sensor; 18-Pedal frequency sensor; 2-First planetary mechanism; 21-Planetary gear; 22-First planetary carrier; 23-External gear ring; 3-Second planetary mechanism; 31-External transmission unit; 4-Drive motor; 5-Variable speed motor; 6-Transition shaft assembly; 61-Transition shaft; 62-Third gear; 63-Fourth gear; 7-Second clutch. Detailed Implementation

[0038] like Figure 1 and Figure 2 The dual-motor assist device of the electric bicycle shown includes a central shaft assembly 1, a first planetary mechanism 2, a second planetary mechanism 3, a drive motor 4, and a variable speed motor 5; the central shaft assembly 1 includes a central shaft 11 and a first bushing 12 sleeved on the central shaft 11, the end of the first bushing 12 being fixed on the central shaft 11; the second gear 16 is connected to the wheel via a sprocket and a chain;

[0039] The central shaft assembly 1 also includes a first gear 14 and a second gear 16;

[0040] The central shaft assembly 1 further includes a first one-way clutch 15 that establishes a one-way transmission relationship between the second gear 16 and the first bushing 12; human power is synchronously input to the first bushing 12 via the central shaft 11, and can be directly input to the second gear 16 through the first one-way clutch 15; when the rotational speed of the second gear 16 is higher than that of the first bushing 12, the first one-way clutch 15 automatically disengages to cut off the reverse transmission between the output end and the central shaft 11;

[0041] The dual-motor assist device also includes a transition shaft assembly 6, which includes a transition shaft 61 and a third gear 62 and a fourth gear 63 mounted on the transition shaft 61.

[0042] The first planetary mechanism 2 includes a sun gear, a first planet carrier 22, an external gear ring 23, and planet gears 21; the variable speed motor 5 is connected to the sun gear; the first planet carrier 22 is driven by the fourth gear 63; the external gear ring 23 is driven by the external transmission unit 31; in this embodiment, the first planet carrier 22 has a gear portion that meshes with the fourth gear 63, and the outer side of the external gear ring 23 has a gear portion that meshes with the external transmission unit 31;

[0043] The second planetary mechanism 3 includes an external transmission unit 31. The drive motor 4 is connected to the central sun gear in the second planetary mechanism 3. The external transmission unit 31 is connected to the first gear 14 in a transmission connection. In this embodiment, the external transmission unit 31 is the second planet carrier of the second planetary mechanism 3. The outer side of the second planet carrier has gear portions that mesh with the first gear 14 and the external gear ring 23 respectively.

[0044] Preferably, the first planetary mechanism 2 and / or the second planetary mechanism 3 are NGWN type planetary gear reduction mechanisms, which are composed of two sets of meshing relationships: internal meshing gear pairs and external meshing gear pairs. Under coaxial arrangement, they achieve a large reduction ratio and high load capacity, so that the output of the drive motor 4 is sent to the external transmission unit 31 after reduction and torque amplification.

[0045] The second gear 16 meshes with the third gear 62. A second clutch 7 is provided between the fourth gear 63 and the transition shaft 61. This second clutch 7 is an electronically controlled clutch, such as an electromagnetic clutch, which has two states: engagement and disengagement. When engaged, it is bidirectionally locked to connect or disconnect the bidirectional power path between the second gear 16 and the first planetary carrier 22: disengaging in manual, non-shifting mode to decouple the first planetary carrier 22 from the second gear 16, preventing the motor and gear set from being dragged back by the output end and generating riding drag resistance; engaging in modes such as manual power generation, kinetic energy recovery, and electric drive to transmit power bidirectionally between the second gear 16 and the first planetary carrier 22. This completely cuts off the reverse transmission link in the non-working state, eliminates power internal circulation loss, and avoids transmission shock during mode switching.

[0046] In a preferred embodiment, a second bushing 13 is also fitted onto the central shaft 11. The first gear 14 and the second gear 16 are coaxially mounted on the second bushing 13. The second gear 16 and the second bushing 13 are fixed relative to each other and can be integrally formed. The first gear 14 is rotatably disposed relative to the second bushing 13. The first one-way clutch 15 is disposed between the second bushing 13 and the first bushing 12. A sprocket that has a transmission relationship with the wheel is fixed to the end of the second bushing 13.

[0047] The first gear 14 is equipped with a manual emergency locking mechanism, which is a manually pluggable locking pin used to mechanically lock the first gear 14 and the housing when the battery is depleted, and to lock the outer gear ring 23 via the external transmission unit 31.

[0048] In this invention, a direct-drive branch for manual operation and a speed-regulating branch for motors are constructed through the cooperation of a first one-way clutch 15 and a second clutch 7. The first one-way clutch 15 enables manual operation to directly drive the second gear 16 and automatically disengages when the speed of the second gear 16 exceeds that of the first bushing 12. The second clutch 7, which is bidirectionally locked during engagement, is used to selectively connect or disconnect the power path between the second gear 16 and the first planetary carrier 22. The power from the drive motor 4 and the variable-speed motor 5 is combined by the first planetary mechanism 2 and output by the first planetary carrier 22, where it merges with the manual power at the second gear 16. By controlling the operation of the variable-speed motor 5, the speed ratio between pedal frequency and vehicle speed can be electronically adjusted, and the power flow can be flexibly distributed according to the load conditions to achieve smooth switching between multiple modes. This solution physically separates the speed regulation function from the drive function, eliminating the strong synchronous interference caused by the direct meshing of the gear rings of the two motors in the existing technology. This reduces the difficulty of control and transforms the control logic under hybrid conditions from a dual-variable synchronous calculation with strong coupling between the two motors to a single-point speed ratio control with the variable speed motor as the core, thereby improving the real-time response speed and operational stability of the system.

[0049] Preferably, the first one-way clutch 15 is a roller ratchet mechanism or a wedge ratchet mechanism; the second clutch 7 is an electronically controlled two-way clutch, which is locked in both directions in the engaged state and releases the transmission connection between the third gear 62 or the fourth gear 63 and the transition shaft 61 in the disengaged state.

[0050] Preferably, a torque sensor 17 and a cadence sensor 18 are also installed on the central axis assembly 1.

[0051] Preferably, the central shaft of the drive motor 4, the central shaft of the variable speed motor 5, the axis of the transition shaft 61, and the axis of the central shaft 11 are arranged in a quadrilateral shape. Specifically, the drive motor 4 and the transition shaft 61 are diagonally opposite each other, and the variable speed motor 5 and the central shaft 11 are diagonally opposite each other.

[0052] The use of a quadrilateral diagonal layout optimizes the spatial compactness of the dual motors and dual planetary gear sets, reducing the overall system size. This arrangement ensures reasonable axial and radial clearance between the gear sets, reducing installation space requirements.

[0053] The aforementioned dual-motor assist device can operate in the following modes: manual transmission without gear shifting, manual power generation, hybrid continuously variable transmission (CVT) mode, manual CVT mode, kinetic energy recovery mode, and pure electric mode. The states of each component in these six modes are shown in the table below (clockwise and counterclockwise directions in the table are only used to distinguish the relative direction of the components):

[0054]

[0055] The following are the specific implementation logics for each operating mode:

[0056] (1) Manual transmission without speed change mode

[0057] In this mode, the system does not provide electric power assistance. Manual power is transmitted to the bottom bracket 11 via the crank, synchronously transferring power to the first bushing 12. This power then drives the second gear 16 to rotate synchronously via the first one-way clutch 15, ultimately driving the wheels through the chainring. Both the drive motor 4 and the transmission motor 5 are in a de-energized state; the first gear 14 and related motor transmission circuits do not participate in the output. When the first bushing 12 is manually driven to rotate clockwise, the first one-way clutch 15 drives the second gear 16 to rotate clockwise synchronously. The rotational speed of the second gear 16 is exactly the same as that of the first bushing 12, with no relative rotation. The first one-way clutch 15 remains engaged but without additional transmission loss. Simultaneously, the second clutch 7 between the fourth gear 63 and the transition shaft 61 disengages, decoupling the first planetary carrier 22 from the second gear 16. The rotation of the second gear 16 no longer drives the first planetary carrier 22 via the transition shaft assembly 6, and the transmission motor 5 is not driven. This completely cuts off the load resistance at the motor end, achieving a riding experience consistent with ordinary bicycles—no power assist and no drag.

[0058] (2) Human-powered power generation mode

[0059] When the vehicle is stationary, a weak current is applied to the drive motor 4, which uses electromagnetic holding force to lock the external transmission unit 31, thereby fixing the external gear ring 23 that meshes with the external transmission unit 31. When the rider pedals the bottom bracket 11, power is synchronously transmitted to the first bushing 12, which drives the second gear 16 to rotate clockwise via the first one-way clutch 15. The power is then transmitted to the first planetary carrier 22 via the third gear 62 meshing with the second gear 16, the transition shaft 61, the engaged and bidirectionally locked second clutch 7, and the fourth gear 63. Supported by the fixed external gear ring 23, all the power of the planetary carrier is concentrated on the sun gear, driving the rotor of the variable speed motor 5 to cut the magnetic field and generate electricity, thus achieving manual emergency charging in a stationary state.

[0060] (3) Hybrid continuously variable transmission mode

[0061] The control unit, based on the riding torque detected by the torque sensor 17, controls the drive motor 4 and the transmission motor 5 to work together, achieving power splitting and parallel connection with human power at the second gear 16. On one hand, human power directly drives the second gear 16 to rotate clockwise via the central shaft 11, the first bushing 12, and the first one-way clutch 15, forming a mechanical direct drive path; on the other hand, the drive motor 4 sends torque to the external gear ring 23 via the second planetary mechanism 3 and the external transmission unit 31, and the transmission motor 5 adjusts the speed of the sun gear. After being combined by the first planetary mechanism 2, the two are connected to the second gear 16 via the first planetary carrier 22, the engaged and bidirectionally locked second clutch 7, and the transition shaft assembly 6, forming a motor speed regulation path. The two power paths converge and are output at the second gear 16.

[0062] The system sets the output speed of the motor speed control circuit by electronically controlling the speed of the variable speed motor 5. When the output speed of the motor speed control circuit matches the direct drive speed of the central shaft 11, the first one-way clutch 15 is engaged, and the torques of the mechanical direct drive circuit and the motor speed control circuit are superimposed at the second gear 16, providing combined assistance. When the output speed of the motor speed control circuit is higher than the direct drive speed of the central shaft 11, the first one-way clutch 15 automatically disengages because the second gear 16 exceeds the first bushing 12, and the output speed is dominated by the motor speed control circuit. At this time, adjusting the variable speed motor 5 can make the output speed of the second gear 16 continuously change relative to the human pedal frequency, thereby achieving smooth stepless adjustment of the output speed ratio while providing hybrid power. In the above process, the variable speed motor 5 is only responsible for adjusting the speed of the sun gear according to the pedal frequency and vehicle speed to achieve the target speed ratio, and the drive motor 4 only outputs the matching assistance torque according to the torque sensor signal, without needing to perform complex speed compensation following the speed ratio change. The control logic of the two is independent, realizing smooth assistance output with single-point control.

[0063] (4) Manual continuously variable transmission mode

[0064] This mode uses human power as the main power source and achieves electronic stepless adjustment of the output speed ratio with the help of the first planetary mechanism 2. Human power drives the central shaft 11 through the crank, and the power is synchronously transmitted to the first bushing 12. The first bushing 12 drives the second gear 16 to rotate clockwise through the first one-way clutch 15, and the power is input to the first planetary carrier 22 through the engaged and bidirectionally locked second clutch 7 and the transition shaft assembly 6. The variable speed motor 5 adjusts the speed of the second gear 16 relative to the first bushing 12 to change the output speed of the second gear 16 relative to the central shaft 11.

[0065] The system continuously adjusts the speed of the first planetary carrier 22 by changing the compensation speed of the variable speed motor 5, based on the speed synthesis characteristics of the planetary gear mechanism, thereby changing the speed difference between the second gear 16 and the first bushing 12. When the speed of the second gear 16 is increased to exceed that of the first bushing 12, the first one-way clutch 15 disengages, and the output speed ratio is continuously set by the variable speed motor 5. During this process, the power required or excess by the first planetary mechanism 2 is balanced by the drive motor 4—when power is needed, the drive motor 4 inputs power through the external transmission unit 31 and the external gear ring 23; when there is excess power, the drive motor 4 absorbs power by generating electricity—thus, with human power as the main factor and the motor acting as a power buffer, the electronic continuously variable transmission function with continuously adjustable speed ratio between the output speed of the second gear 16 and the human pedal frequency is achieved.

[0066] (5) Kinetic energy recovery mode

[0067] During coasting or deceleration, the wheels drive the second gear 16 to rotate clockwise via the rear flywheel, and the power drives the first planetary carrier 22 via the transition shaft assembly 6. At this time, the system locks the sun gear rotor of the variable speed motor 5, so that all the power of the planetary carrier is transmitted to the external gear ring 23. The external gear ring 23 feeds back to the drive motor 4 through the external transmission unit 31 that meshes with it, realizing kinetic energy recovery and power generation.

[0068] During this process, the rotational speed of the second gear 16 is higher than that of the first bushing 12. The first one-way clutch 15 is automatically disengaged, cutting off the transmission link between the regenerative power and the central shaft 11, completely avoiding the dragging effect of the kinetic energy recovery process on the pedals. At the same time, the second clutch 7 remains engaged and locked in both directions, ensuring that the regenerative power is stably transmitted to the drive motor 4 through the transition shaft assembly 6 and the first planetary mechanism 2.

[0069] (6) Pure Electric Mode

[0070] With the central shaft 11 stationary, the drive motor 4 sends torque to the external transmission unit 31 via the second planetary mechanism 3, and then transmits it to the external gear ring 23 through meshing, serving as one input to the first planetary mechanism 2; the variable speed motor 5 adjusts the speed of the sun gear, serving as the other input. After the two inputs are combined by the first planetary mechanism 2, they are output from the first planetary carrier 22 via the fourth gear 63, the engaged and bidirectionally locked second clutch 7, the transition shaft 61, and the third gear 62 to the second gear 16, driving the wheels forward. The system can change the output speed ratio in real time by adjusting the speed of the variable speed motor 5 to adapt to different driving conditions such as flat roads and steep slopes. Since the speed of the second gear 16 is consistently higher than the speed of the first bushing 12 (with the central shaft 11 stationary), the first one-way clutch 15 automatically disengages, completely cutting off the transmission link between the second gear 16 and the central shaft 11, achieving pure electric drive without the pedals rotating.

[0071] The present invention also provides a control method for a dual-motor assist device for a power-assisted bicycle based on the above, which is implemented by a control unit, obtains control commands to obtain target mode information, and switches to the corresponding operating mode based on the target mode information;

[0072] In automatic control mode, the control method includes:

[0073] Step S1: The rider's pedaling torque is obtained by the torque sensor 17 installed on the first bushing 12, and the cadence signal is obtained by the cadence sensor 18 installed on the central axle 11. The target power assist and the target speed ratio are determined by combining the vehicle speed.

[0074] Step S2: Determine the current cycling scenario based on torque and cadence thresholds to identify the target operating mode;

[0075] Step S3: Switch to the corresponding operating mode according to the target operating mode.

[0076] Preferably, when the pedaling torque detected by the torque sensor 17 is lower than the first threshold and the pedal frequency detected by the cadence sensor 18 is lower than the second threshold, the target operating mode is determined to be pure electric mode.

[0077] When the vehicle speed is higher than the third threshold and the cadence is lower than the fourth threshold, the target operating mode is determined to be the kinetic energy recovery mode.

[0078] When the pedaling torque detected by the torque sensor 17 is higher than the first threshold and the pedaling frequency is lower than the second threshold, the target operating mode is determined to be either hybrid continuously variable transmission mode or manual continuously variable transmission mode.

[0079] Preferably, when the operating mode is the manual power generation mode, when the battery has power, the drive motor 4 is controlled to receive a microampere-level weak current, and the external transmission unit 31 is locked by electromagnetic holding force, so that the first gear 14 and the external gear ring 23 connected to the external transmission unit 31 remain stationary; when the battery is completely depleted, the wheels are fixed to the external transmission unit 31 by a mechanical parking lock mechanism, so as to achieve passive locking of the external gear ring 23; the central shaft 11 is manually driven to drive the second gear 16 to rotate via the first bushing 12 and the first one-way clutch 15, and the power is transmitted to the first planetary carrier 22 through the transition shaft assembly 6 and the engaged and bidirectionally locked second clutch 7, so that the rotor of the variable speed motor 5 cuts the magnetic field to generate electricity.

[0080] The control method of this invention can switch between multiple working modes. In automatic mode, the control system can monitor the signals of torque sensor 17 and cadence sensor 18 in real time. By using electromagnetic force in conjunction with ratchet logic, it realizes integrated management from static power generation to dynamic assistance. While providing continuously variable transmission function, it ensures smooth switching between different modes, thereby improving the intelligence level and energy efficiency of the whole vehicle.

[0081] Preferably, the continuously variable transmission (CVT) mode is achieved by adjusting the speed of the transmission motor 5 and balancing the power of the drive motor 4. The control unit presets a speed ratio adjustment algorithm, calculates the target speed ratio between the second gear 16 and the central axle 11 based on the real-time cadence obtained by the cadence sensor 18 and the current vehicle speed, and drives the transmission motor 5 to adjust the speed of the sun gear so that the output speed remains continuously adjustable relative to the cadence.

[0082] By utilizing the speed synthesis characteristics of the planetary gear mechanism, the system breaks free from the limitations of traditional mechanical gears and can automatically match the optimal speed ratio according to the riding load, keeping the rider within a comfortable cadence range and improving energy utilization efficiency.

[0083] Preferably, the operating mode further includes a multi-gear simulation mode. The control unit stores multiple preset fixed speed ratios, which are the ratios of wheel speed to human pedaling frequency. The control method includes: receiving a gear switching command, obtaining the current input pedaling frequency and real-time vehicle speed of the central axle 11, and controlling the transmission motor 5 to compensate for the speed difference of the sun gear, so that the ratio of wheel speed to human pedaling frequency is locked at the preset fixed speed ratio of the corresponding gear.

[0084] Through the above method, the present invention can simulate the feel of traditional mechanical gear shifting on the basis of electronic continuously variable transmission, provide riders with clear gear feedback, meet the riding habits of different users, and at the same time simplify the mechanical structure and reduce maintenance costs.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dual-motor assist device for a power-assisted bicycle, comprising a central shaft assembly (1), a first planetary mechanism (2), a second planetary mechanism (3), a drive motor (4), and a variable speed motor (5); the central shaft assembly (1) comprises a central shaft (11) and a first bushing (12) sleeved on the central shaft (11), the end of the first bushing (12) being fixed on the central shaft (11); characterized in that: The central shaft assembly (1) also includes a first gear (14) and a second gear (16). The central shaft assembly (1) further includes a first one-way clutch (15) that establishes a one-way transmission relationship between the second gear (16) and the first bushing (12). The dual-motor assist device also includes a transition shaft assembly (6), which includes a transition shaft (61) and a third gear (62) and a fourth gear (63) mounted on the transition shaft (61). The first planetary mechanism (2) includes a sun gear, a first planet carrier (22), an external gear ring (23), and planet gears (21); the variable speed motor (5) is connected to the sun gear; the first planet carrier (22) is connected to the fourth gear (63); the external gear ring (23) is connected to the external transmission unit (31). The second planetary mechanism (3) includes an external transmission unit (31), the drive motor (4) is connected to the second planetary mechanism (3), and the external transmission unit (31) is connected to the first gear (14) in a transmission connection; The second gear (16) meshes with the third gear (62), the second gear (16) is used to output power to the wheels, and a second clutch (7) is provided between the third gear (62) or the fourth gear (63) and the transition shaft (61).

2. The dual-motor assist device for the electric bicycle according to claim 1, characterized in that, A second bushing (13) is also fitted on the central shaft (11). The first gear (14) and the second gear (16) are coaxially mounted on the second bushing (13). The second gear (16) is fixed relative to the second bushing (13). The first gear (14) is rotatably mounted relative to the second bushing (13). The first one-way clutch (15) is located between the second bushing (13) and the first bushing (12).

3. The dual-motor assist device for the electric bicycle according to claim 1, characterized in that, The first planetary mechanism (2) and / or the second planetary mechanism (3) are NGWN type planetary gear reduction mechanisms.

4. The dual-motor assist device for the electric bicycle according to claim 1, characterized in that, A torque sensor (17) and a cadence sensor (18) are also installed on the central axis assembly (1).

5. The dual-motor assist device for the electric bicycle according to claim 1, characterized in that, The central shaft of the drive motor (4), the central shaft of the variable speed motor (5), the axis of the transition shaft (61), and the axis of the central shaft (11) are arranged in a quadrilateral shape.

6. The control method for the dual-motor assist device of the electric bicycle according to claim 1, implemented by a control unit, is characterized in that, The system obtains control commands to acquire target mode information and switches to the corresponding operating mode based on the target mode information. The operating modes include manual continuously variable transmission (CVT) mode, manual power generation mode, hybrid continuously variable transmission (CVT) mode, manual CVT mode, kinetic energy recovery mode, and pure electric mode. In automatic control mode, the control method includes: Step S1: The rider's pedaling torque is obtained by the torque sensor (17) installed on the first bushing (12), and the cadence signal is obtained by the cadence sensor (18) installed on the central axle (11). The target power assist and the target speed ratio are determined by combining the vehicle speed. Step S2: Determine the current cycling scenario based on torque and cadence thresholds to identify the target operating mode; Step S3: Switch to the corresponding operating mode according to the target operating mode.

7. The control method according to claim 6, characterized in that, When the pedaling torque detected by the torque sensor (17) is lower than the first threshold and the pedal frequency detected by the pedal frequency sensor (18) is lower than the second threshold, the target operating mode is determined to be pure electric mode. When the vehicle speed is higher than the third threshold and the cadence is lower than the fourth threshold, the target operating mode is determined to be the kinetic energy recovery mode. When the pedaling torque detected by the torque sensor (17) is higher than the first threshold and the pedaling frequency is lower than the second threshold, the target operating mode is determined to be either hybrid continuously variable transmission mode or manual continuously variable transmission mode.

8. The control method according to claim 6, characterized in that, When the operating mode is the manual power generation mode, when the battery is charged, the drive motor (4) is controlled to generate an electromagnetic holding force to lock the external transmission unit (31), thereby fixing the external gear ring (23) that meshes with the external transmission unit (31); when the battery is completely depleted, the wheels and the external transmission unit (31) are fixed by the mechanical parking locking mechanism to achieve passive locking of the external gear ring (23).

9. The control method according to claim 6, characterized in that, The manual continuously variable transmission mode is achieved by adjusting the speed of the variable speed motor (5).

10. The control method according to claim 6, characterized in that, The operating modes also include a multi-gear simulation mode.

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