Rear wheel steering actuator and vehicle

Abstract

The present application provides a rear wheel steering actuator and a vehicle. The rear wheel steering actuator comprises a steering motor, a transmission mechanism, and a screw. The steering motor is used for driving, after a rotation speed change by means of the transmission mechanism, the screw to steer a rear wheel of the vehicle. In the radial direction of a screw shaft of the screw, the distance between the central axis of a motor shaft of the steering motor and the central axis of the screw shaft is less than the radius of a housing of the steering motor. In the rear wheel steering actuator provided by the present application, the volume of the rear wheel steering actuator is reduced by limiting the radial spacing between the steering motor and the screw, so as to increase the interior space of the vehicle.

Description

A rear-wheel steering system and a vehicle

[0001] This application claims priority to Chinese Patent Application No. 202510244724.9, filed on February 28, 2025, entitled "A Rear Wheel Steering System and a Vehicle", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of vehicle steering technology, specifically to a rear-wheel steering system and a vehicle. Background Technology

[0003] The rear-wheel steering system is used to control the steering of the vehicle's rear wheels, thereby reducing the vehicle's turning radius and improving vehicle stability and comfort. An excessively large rear-wheel steering system would occupy too much interior space, therefore its size needs to be reduced to save interior space. Summary of the Invention

[0004] This application provides a rear-wheel steering system and a vehicle. The rear-wheel steering system reduces its volume to increase the vehicle's interior space by limiting the radial distance between the steering motor and the lead screw.

[0005] In a first aspect, this application provides a rear wheel steering system, which includes a steering motor, a transmission mechanism, and a lead screw. The steering motor drives the lead screw to steer the rear wheels of the vehicle after the transmission mechanism changes the rotational speed. The distance between the center axis of the motor shaft of the steering motor and the center axis of the lead screw along the radial direction of the lead screw is less than the radius of the housing of the steering motor.

[0006] The rear-wheel steering system provided in this application uses a steering motor that drives the screw of a lead screw to rotate via a transmission mechanism, thereby steering the rear wheels of the vehicle. The transmission mechanism reduces the output speed of the steering motor to increase torque, ensuring that the lead screw reliably drives the rear wheels to steer. Since the steering motor is relatively large in the radial direction of the lead screw, this application's rear-wheel steering system utilizes the cooperation between the transmission mechanism and the lead screw to ensure that the lead screw at least partially overlaps the steering motor housing in the radial direction. This compresses the radial dimension of the rear-wheel steering system, thereby reducing its volume and increasing the vehicle's interior space.

[0007] In one implementation, the transmission mechanism includes a planetary gear transmission mechanism, wherein the sun gear of the planetary gear transmission mechanism is used to receive the drive rotation of the steering motor, the planet gears of the planetary gear transmission mechanism are used to mesh with the sun gear and output the drive rotation through the planet gear carrier of the planetary gear transmission mechanism, and the outer gear ring of the planetary gear transmission mechanism is used to be fixed to the housing of the rear wheel steering gear and mesh with the planet gears.

[0008] In this implementation, the sun gear and planetary gear carrier of the planetary gear transmission mechanism rotate around the same central axis. This can reduce the radial distance between the central axis of the steering motor shaft and the central axis of the screw while ensuring the reduction ratio of the transmission mechanism, thereby compressing the overall size of the rear wheel steering gear of this application along the radial direction of the screw.

[0009] In one implementation, along the axial direction of the screw, the central axis of the steering motor shaft, the central axis of the sun gear, and the central axis of the lead screw are sequentially aligned.

[0010] In this implementation, the steering motor, planetary gear transmission mechanism and lead screw of the rear wheel steering gear are arranged coaxially, the central axis of the lead screw coincides with the central axis of the steering motor, and the size of the rear wheel steering gear along the radial direction of the lead screw is approximately equal to the size of the steering motor housing, which can effectively limit the overall size of the rear wheel steering gear.

[0011] In one implementation, along the axial direction of the screw, the central axis of the sun gear coincides with the central axis of the lead screw; along the radial direction of the screw, the distance between the central axis of the sun gear and the central axis of the steering motor shaft is greater than the radius of the motor shaft.

[0012] In this implementation, the planetary gear transmission mechanism is arranged coaxially with the lead screw. Along the radial direction of the lead screw, the distance between the central axis of the lead screw and the central axis of the steering motor is relatively small. The size of the rear wheel steering gear is approximately equal to the size of the steering motor housing, which can also effectively limit the overall size of the rear wheel steering gear.

[0013] In one implementation, the transmission mechanism includes a parallel shaft gear transmission mechanism. The input wheel of the parallel shaft gear transmission mechanism is used to receive the drive rotation of the steering motor, and the output wheel of the parallel shaft gear transmission mechanism is used to mesh with the input wheel and drive the sun wheel to rotate by being fixed coaxially with the sun wheel. The diameter of the input wheel is smaller than the diameter of the output wheel.

[0014] In this implementation, the transmission mechanism increases the reduction ratio through a parallel shaft gear transmission mechanism, which reduces the volume of the planetary gear transmission mechanism, thereby controlling the overall volume of the transmission mechanism. This ensures that the radial dimension of the transmission mechanism along the screw is smaller than the size of the steering motor housing, while also considering the distance between the central axis of the lead screw and the central axis of the motor shaft. This controls the overall radial dimension of the rear wheel steering gear while meeting the torque output requirements of the rear wheel steering gear. The parallel shaft gear transmission mechanism also has high transmission efficiency, which can improve the overall transmission efficiency of the rear wheel steering gear.

[0015] In one implementation, the transmission mechanism includes a drive pulley and a belt. The motor shaft drives the drive pulley to rotate, and the drive pulley drives the belt to drive the sun gear. The structure of the drive pulley and belt is relatively simple, which is beneficial for the internal structure arrangement of the rear wheel steering gear.

[0016] In one implementation, the planetary gear carrier is fixedly connected to the lead screw, the nut of the lead screw meshes with the periphery of the lead screw, and the nut along the axial direction of the lead screw is used to fix the steering tie rod of the rear wheel steering gear. The lead screw is used to receive the drive rotation of the planetary gear transmission mechanism and to drive the rear wheels of the vehicle to steer through the steering tie rod.

[0017] In this implementation, the nut and screw of the lead screw are fixedly connected to the vehicle's steering tie rod and the transmission mechanism of the rear wheel steering gear, respectively. The steering motor of the rear wheel steering gear drives the screw to rotate through the transmission mechanism, thereby driving the nut to displace the steering tie rod along the central axis of the screw. The rear wheel steering gear can then steer the vehicle's rear wheels through the steering tie rod.

[0018] In one implementation, the planetary gear carrier is fixedly connected to the nut of the lead screw, the nut of the lead screw meshes with the periphery of the screw rod, the screw rod along the axial direction is used to fixally connect the steering tie rod of the rear wheel steering gear, the lead screw is used to receive the drive rotation of the planetary gear transmission mechanism and to drive the rear wheels of the vehicle to steer through the steering tie rod.

[0019] In this implementation, the nut and screw of the lead screw are fixedly connected to the transmission mechanism of the rear wheel steering system and the steering tie rod of the vehicle, respectively. The steering motor of the rear wheel steering system drives the nut to rotate through the transmission mechanism, thereby driving the screw to move the steering tie rod axially, so that the rear wheel steering system can turn the rear wheels of the vehicle through the steering tie rod.

[0020] In one implementation, the axial steering tie rod along the screw includes two opposing ends, one end of which is used to embed into the housing of the transmission mechanism and for driving the lead screw, and the other end of which is used to drive one of the rear wheels of the vehicle.

[0021] In one implementation, the steering tie rod includes a receiving groove with the opening of the groove facing the sun gear along the axial direction of the lead screw, the receiving groove being used to receive a section of the lead screw.

[0022] In one implementation, a nut is fixed to the wall of a receiving groove, the nut being used to receive the drive of the screw and for displacement along the axial direction of the screw to drive the steering tie rod.

[0023] In one implementation, a nut is fixed to the motor shaft, and the nut is used to rotate with the motor shaft to drive the screw to move axially and drive the steering tie rod.

[0024] In one implementation, the planetary gear transmission mechanism includes three planetary gears. It can also be configured with four or five planetary gears as needed.

[0025] In this implementation, when the planetary gear transmission mechanism includes three planetary gears, the transmission mechanism can balance the reduction ratio, torque carrying capacity, NVH noise, and ease of installation, thus improving the overall performance of the rear wheel steering system. When the planetary gear transmission mechanism includes five planetary gears, the transmission mechanism has a larger torque carrying capacity, which can improve the reliability of the rear wheel steering system. When the planetary gear transmission mechanism includes four planetary gears, the rear wheel steering system can balance the reduction ratio, torque carrying capacity, NVH noise, and ease of installation.

[0026] In one implementation, the lead screw is a planetary roller lead screw, which includes multiple planetary rollers. The multiple planetary rollers are spaced around the screw along the circumference of the screw and mesh with the screw respectively. The nut of the lead screw is connected to the screw through the multiple planetary rollers.

[0027] In this implementation, the planetary roller screw has high transmission efficiency and good self-locking capability. It can drive the screw to rotate and ensure transmission efficiency when driven by the steering motor, and can limit the rotation of the screw when the steering motor stops driving, thereby preventing the rear wheels of the vehicle from being impacted and causing undesirable steering.

[0028] In one implementation, the planetary roller screw includes 10 planetary rollers.

[0029] In this implementation, when the planetary roller screw includes 10 planetary rollers, the locking capability and ease of installation of the screw can be balanced, avoiding undesirable steering of the rear wheel due to a small number of planetary rollers, and avoiding inconvenience in installation of the planetary roller screw due to a large number of planetary rollers.

[0030] In one implementation, the nut is fixed to the wall of the receiving groove, and the screw is used to rotate with the transmission mechanism and drive multiple planetary rollers to move axially along the screw. The multiple planetary rollers are used to drive the nut to move synchronously.

[0031] In one implementation, a nut is fixed to a transmission mechanism. The nut rotates with the transmission mechanism to drive multiple planetary rollers to rotate around a screw. The multiple planetary rollers drive the screw to move along its own axial direction.

[0032] In one implementation, the outer peripheral surface of the screw includes radial protrusions, which are spaced apart along the axial direction of the screw on the side of the nut away from the sun gear, and the diameter of the radial protrusions is larger than the inner diameter of the nut; or, the radial protrusions are used to be embedded in the groove wall of the receiving groove.

[0033] In one implementation, in response to a first control signal, a steering motor continuously outputs a first preset torque toward a planetary roller screw, and the first control signal instructs the rear wheel steering system to turn the rear wheels of the vehicle to a preset angle.

[0034] In this implementation, after the rear wheels of the vehicle driven by the rear wheel steering system provided in this application are turned to a preset angle, the steering motor is also used to continuously output a first preset torque to hold the planetary roller screw through the transmission mechanism, thereby increasing the support torque on the rear wheels to limit the rear wheels from producing undesirable steering.

[0035] In one implementation, the first preset torque is equal to the stall torque of the steering motor, or the difference between the first preset torque and the stall torque of the steering motor is less than the first preset difference.

[0036] In one implementation, the lead screw is a ball screw, and the rear wheel steering system includes a locking mechanism. The locking mechanism is used to drive the motor shaft and the ball screw. When the steering motor is working, the locking mechanism is used to receive the drive of the motor shaft to drive the ball screw to move. The locking mechanism is also used to restrict the movement of the ball screw when the steering motor stops working.

[0037] In this implementation, the ball screw has high transmission efficiency, enabling it to rotate when driven by the steering motor and improving the overall transmission efficiency of the rear wheel steering system. The locking mechanism is used to achieve self-locking of the rear wheel steering system, preventing undesirable steering of the vehicle's rear wheels after impact.

[0038] In one implementation, the locking mechanism includes a driving member, a one-way clutch, and a driven member. The driving member is fixedly connected to a motor shaft, the driven member is connected to a ball screw drive, and the one-way clutch is used to restrict the movement of the driven member and to receive the drive from the driving member and drive the driven member.

[0039] In this implementation, the locking mechanism is fixedly connected to the motor shaft and the ball screw through the driving component and the driven component, respectively. The driving component drives the driven component to rotate, and the driven component is restricted from rotating relative to the driving component by the one-way clutch, thereby realizing the self-locking function of the rear wheel steering system.

[0040] In one implementation, in response to a second control signal, a steering motor continuously outputs a second preset torque toward a ball screw, and the second control signal instructs the rear wheel steering system to turn the rear wheels of the vehicle to a preset angle.

[0041] In this implementation, after the rear wheels of the vehicle driven by the rear wheel steering system provided in this application are turned to a preset angle, the steering motor is also used to continuously output a second preset torque to hold the transmission mechanism and the ball screw through the locking mechanism, thereby increasing the support torque on the rear wheels to limit the rear wheels from producing undesirable steering.

[0042] In one implementation, the second preset torque is less than the first preset torque. Because the locking mechanism has a stronger locking capability than the planetary roller screw, the steering motor can reduce its output torque to limit undesirable steering of the rear wheels and save energy consumption of the rear wheel steering system.

[0043] In one implementation, the rear wheel steering system includes a displacement sensor for detecting the amount of displacement of the lead screw.

[0044] In this implementation, the rear wheel steering system indirectly detects the steering angle of the rear wheels by detecting the displacement of the lead screw, thereby ensuring reliable steering of the rear wheels.

[0045] In one implementation, the displacement sensor includes a detection component fixed to the housing of the rear wheel steering gear, and a moving component of the displacement sensor fixed to the steering tie rod of the rear wheel and moving along the axial direction of the steering tie rod.

[0046] In one implementation, the rear-wheel steering system includes two steering motors, two transmission mechanisms, and two lead screws, with each steering motor driving a lead screw via a transmission mechanism to actuate the rear wheels on one side of the vehicle.

[0047] In one implementation, the rear wheel steering system includes two transmission mechanisms and two lead screws. The steering motor includes two motor shafts, which are located on both sides of the motor stator of the steering motor. Each motor shaft is used to drive a lead screw through a transmission mechanism to drive the rear wheel on one side of the vehicle.

[0048] In one implementation, the rear wheel steering system includes two transmission mechanisms and two lead screws, with the motor shaft of the steering motor passing through the inner hole of the motor rotor and used to drive the two transmission mechanisms respectively.

[0049] In one implementation, the rear wheel steering system includes two locking mechanisms.

[0050] One implementation involves the two lead screws having the same thread direction and the two rear wheels rotating in the same direction.

[0051] One implementation involves the two lead screws having opposite thread directions and the two rear wheels rotating in opposite directions.

[0052] Secondly, this application provides a vehicle including one or more rear wheels and a rear-wheel steering system provided in any of the above implementations, the rear-wheel steering system being used to drive the one or more rear wheels to turn. The vehicle of this application, while possessing rear-wheel steering functionality, has a larger interior space, which facilitates the arrangement of the remaining vehicle components. Attached Figure Description

[0053] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0054] Figure 1 is a schematic diagram of the vehicle architecture provided in one embodiment of this application;

[0055] Figure 2 is a partial structural schematic diagram of a vehicle provided in one embodiment of this application;

[0056] Figure 3 is a schematic diagram of the structure of the rear wheel steering system provided in one embodiment of this application;

[0057] Figure 4 is an exploded structural diagram of the rear wheel steering system provided in one embodiment of this application;

[0058] Figure 5 is a cross-sectional structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0059] Figure 6 is a partial structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0060] Figure 7 is a partially exploded structural diagram of the rear wheel steering system provided in one embodiment of this application;

[0061] Figure 8 is a partially exploded structural diagram of the rear wheel steering system provided in one embodiment of this application;

[0062] Figure 9 is a partial cross-sectional structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0063] Figure 10 is a simplified diagram of the transmission structure of the rear wheel steering system provided in one embodiment of this application;

[0064] Figure 11 is a simplified diagram of the transmission structure of the rear wheel steering system provided in one embodiment of this application;

[0065] Figure 12 is a partial structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0066] Figure 13 is a partially exploded structural diagram of the rear wheel steering system provided in one embodiment of this application;

[0067] Figure 14 is a partial cross-sectional structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0068] Figure 15 is a partial structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0069] Figure 16 is a partially exploded structural diagram of the rear wheel steering system provided in one embodiment of this application;

[0070] Figure 17 is a partially exploded structural diagram of the rear wheel steering system provided in one embodiment of this application;

[0071] Figure 18 is a partial cross-sectional structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0072] Figure 19 is a partially exploded structural diagram of the rear wheel steering system provided in one embodiment of this application;

[0073] Figure 20 is a cross-sectional structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0074] Figure 21 is a partial structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0075] Figure 22 is a partial cross-sectional structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0076] Figure 23 is a partial cross-sectional structural schematic diagram of the rear wheel steering system provided in one embodiment of this application;

[0077] Figure 24 is a schematic diagram of the vehicle architecture provided in one embodiment of this application.

[0078] Reference numerals: 1000-Vehicle; 1001-Frame; 1002-Rear wheel; 1003-Front wheel; 100-Rear wheel steering gear; 10-Steering motor; 11-Motor shaft; 12-Motor stator; 13-Motor rotor; 20-Transmission mechanism; 21-Planetary gear transmission mechanism; 211-Sun gear; 212-Planet gears; 213-Planet gear carrier; 2131-Shaft hole; 2132-Receiving groove; 214-External gear ring; 22-Parallel shaft gear transmission mechanism; 221-Input gear; 222-Output gear; 30-Lead screw; 30a-Planetary roller screw 30b-Ball screw; 31-Screw; 311-Radial protrusion; 32-Nut; 33-Planetary roller; 331-First threaded section; 332-Second threaded section; 34-Ball; 40-Housing; 41-First housing; 42-Second housing; 43-First receiving groove; 50-Steering tie rod; 51-First end; 52-Second end; 53-Second receiving groove; 60-Sensor; 61-Displacement sensor; 611-Detection component; 612-Moving component; 70-Locking mechanism; 71-Driver; 72-One-way clutch; 73-Driven component. Detailed Implementation

[0079] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0080] This application provides a rear-wheel steering system, which includes a steering motor, a transmission mechanism, and a lead screw. The steering motor drives the lead screw to steer the rear wheels of the vehicle after the transmission mechanism changes its speed. The distance between the center axis of the steering motor shaft and the center axis of the lead screw along the radial direction of the lead screw is less than the radius of the steering motor housing. This rear-wheel steering system compresses the radial dimension of the rear-wheel steering system, thereby reducing its volume and increasing the interior space of the vehicle.

[0081] This application provides a vehicle including one or more rear wheels and a rear-wheel steering system provided in this application, the rear-wheel steering system being used to drive the one or more rear wheels to turn. The vehicle of this application, while possessing rear-wheel steering functionality, has a larger interior space, which facilitates the arrangement of the remaining vehicle components.

[0082] Please refer to Figure 1, which is a schematic diagram of the architecture of a vehicle 1000 provided in one embodiment of this application.

[0083] As shown in Figure 1, the vehicle 1000 provided in this application includes a rear-wheel steering unit 100, which is fixed to the frame 1001 and is throttle-connected to one or more rear wheels 1002 of the vehicle 1000. The rear-wheel steering unit 100 is used to drive one or more rear wheels 1002 of the vehicle 1000 to turn, thereby increasing the range of steering angle control of the vehicle 1000 and reducing the occurrence of understeer or oversteer of the vehicle 1000.

[0084] For example, in some scenarios where vehicle 1000 needs to turn or make a U-turn with a small turning radius, the turning radius can be reduced and the vehicle's agility improved by controlling the front wheels 1003 and rear wheels 1002 to rotate in opposite directions. In other scenarios where vehicle 1000 needs to corner at a certain speed, the front wheels 1003 and rear wheels 1002 can be controlled to rotate in the same direction, thereby reducing the vehicle's sideslip angle and the steady-state overshoot of its yaw rate, thus enhancing the vehicle's handling stability.

[0085] In one embodiment, the vehicle 1000 provided in this application has two front wheels 1003 and two rear wheels 1002. The two front wheels 1003 are arranged on both sides of the vehicle 1000, and the two rear wheels 1002 are arranged on both sides of the vehicle 1000. The rear wheel steering unit 100 of this application is used to drive the two rear wheels 1002 of the vehicle 1000 to change the steering. It should be noted that the number of front wheels 1003 and rear wheels 1002 of the vehicle 1000 provided in this application includes, but is not limited to, two. For example, in another embodiment, the vehicle 1000 provided in this application may have multiple front wheels 1003 and multiple rear wheels 1002. The rear wheel steering unit 100 is driven to a plurality of the multiple rear wheels 1002 and is used to drive the plurality of rear wheels 1002 to change the steering.

[0086] Please refer to Figures 2 to 5, where Figure 2 is a partial structural schematic diagram of the vehicle 1000 provided in one embodiment of this application; Figure 3 is a structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application; Figure 4 is an exploded structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application; and Figure 5 is a cross-sectional structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0087] As shown in Figures 2 to 5, the rear-wheel steering system 100 provided in this application includes a steering motor 10, a transmission mechanism 20, and a lead screw 30. The steering motor 10, after its rotational speed is changed via the transmission mechanism 20, drives the lead screw 30 to steer one or more rear wheels 1002 of the vehicle 1000. That is, the steering motor 10 provides driving force to change the steering of one or more rear wheels 1002. The transmission mechanism 20 connects the motor shaft 11 of the steering motor 10 and the lead screw 30. The transmission mechanism 20 also adjusts the rotational speed and torque of the driving force output by the steering motor 10 and transmits the adjusted driving force to the lead screw 30. The lead screw 30 converts the rotational motion of the motor shaft 11 of the steering motor 10 into linear displacement along the axial direction of the lead screw 30 and outputs it to one or more rear wheels 1002, thereby causing one or more rear wheels 1002 to deflect relative to the vehicle frame 1001, thus achieving steering of the rear wheels 1002.

[0088] In one embodiment, the rear wheel steering system 100 provided in this application includes a housing 40 for fixing to a vehicle frame 1001. The housing 40 is also used to house a steering motor 10, a transmission mechanism 20, and at least partially houses a lead screw 30.

[0089] In one embodiment, the housing 40 includes a first housing 41, which is fixed relative to the vehicle frame 1001. The steering motor 10 also includes a motor stator 12 and a motor rotor 13. Both the motor stator 12 and the motor rotor 13 are housed within the first housing 41, and a portion of the motor shaft 11 extends out of the first housing 41. That is, the first housing 41 serves as the housing for the steering motor 10. The motor rotor 13 is coaxially fixed to the motor shaft 11. Along the circumference of the motor shaft 11, the motor stator 12 is sleeved around the periphery of the motor rotor 13. When the motor stator 12 is energized, it drives the motor rotor 13 to rotate, thereby causing the motor shaft 11 to rotate and output driving force.

[0090] In one embodiment, the motor shaft 11 of the steering motor 10 is parallel to the axial direction of the rear wheel 1002.

[0091] In one embodiment, a lead screw 30 extends axially parallel to the rear wheel 1002. The lead screw 30 includes an input end and an output end. A transmission mechanism 20 is used to drive the motor shaft 11 of the steering motor 10 and the input end of the lead screw 30. The input end of the lead screw 30 receives drive from the steering motor 10 via the transmission mechanism 20, and the output end of the lead screw 30 is used to drive the rear wheel 1002 of the vehicle 1000. The lead screw 30 converts the rotational motion of the motor shaft 11 of the steering motor 10 into linear displacement along the axial direction of the lead screw 30 and outputs it to the rear wheel 1002 via the output end to drive the rear wheel 1002 to steer.

[0092] In one embodiment, the transmission mechanism 20 is used to reduce the speed output by the steering motor 10 to increase the torque, thereby ensuring the displacement of the lead screw 30 along its own axial direction, and thus ensuring that the lead screw 30 reliably drives the rear wheel 1002 to achieve steering.

[0093] The lead screw 30 includes a screw 31 and a nut 32. The screw 31 extends axially parallel to the rear wheel 1002, and the nut 32 is sleeved on the outer circumferential surface of the screw 31. The thread on the inner circumferential surface of the nut 32 engages with the outer circumferential surface of the screw 31. In one embodiment, the screw 31 serves as the input end of the lead screw 30, and the nut 32 serves as the output end of the lead screw 30. That is, the screw 31 is driven by the steering motor 10 through the transmission mechanism 20, and the nut 32 is drively connected to the rear wheel 1002 of the vehicle 1000. During the steering of the rear wheel 1002, the screw 31 rotates with the rotation of the motor shaft 11, thereby causing the nut 32 to be displaced axially along the screw 31, thus steering the rear wheel 1002 of the vehicle 1000.

[0094] In another embodiment, nut 32 serves as the input end of lead screw 30, and screw 31 serves as the output end of lead screw 30. That is, nut 32 receives drive from steering motor 10 via transmission mechanism 20, and screw 31 is drively connected to the rear wheel 1002 of vehicle 1000. During the steering process of the rear wheel 1002, nut 32 rotates with the rotation of motor shaft 11, thereby causing screw 31 to displace along its own axial direction, thus steering the rear wheel 1002.

[0095] In one embodiment, the rear-wheel steering system 100 provided in this application includes a steering tie rod 50, which is used to drive the lead screw 30 and the rear wheel 1002. That is, the output end of the lead screw 30 is driven to the rear wheel 1002 of the vehicle 1000 through the steering tie rod 50. When the rear wheel 1002 of the vehicle 1000 provided in this application needs to turn, the motor shaft 11 of the steering motor 10 rotates, and the rear-wheel steering system 100 of this application transmits the driving force of the motor shaft 11 toward the lead screw 30 through the transmission mechanism 20, so that the lead screw 30 is displaced along its own axial direction and pulls the steering tie rod 50 to move, thereby causing the rear wheel 1002 to deflect relative to the frame 1001, thus realizing the steering of the rear wheel 1002.

[0096] In one embodiment, the steering tie rod 50 and the screw 31 of the lead screw 30 are arranged coaxially. Thus, the rear wheel steering system 100 of this application drives the lead screw 30 to move axially along its own axis, thereby causing the steering tie rod 50 to move axially along the lead screw 30, thereby driving the rear wheels 1002 to steer.

[0097] Along the radial direction of the lead screw 31 of the lead screw 30, the distance between the central axis of the motor shaft 11 of the steering motor 10 and the central axis of the lead screw 31 of the lead screw 30 is less than the radius of the first housing 41 of the steering motor 10. The first housing 41 of the steering motor 10 is a rotating structure, and its radius can be understood as the distance between the central axis of the motor shaft 11 of the steering motor 10 and the outer wall of the first housing 41. For ease of understanding, the distance between the central axis of the motor shaft 11 of the steering motor 10 and the central axis of the lead screw 31 of the lead screw 30 is defined as d, and the radius of the first housing 41 of the steering motor 10 is defined as r, where 0 ≤ d < r. Therefore, the lead screw 31 of the lead screw 30 at least partially overlaps with the first housing 41 of the steering motor 10 along its own radial direction.

[0098] The rear-wheel steering system 100 provided in this application uses a steering motor 10 to drive a lead screw 30 to rotate via a transmission mechanism 20, thereby steering the rear wheels 1002 of the vehicle 1000. The transmission mechanism 20 is used to reduce the output speed of the steering motor 10 to increase the torque, thereby ensuring that the lead screw 30 reliably drives the rear wheels 1002 to achieve steering. In order to ensure that the driving force provided by the steering motor 10 can reliably drive the rear wheels 1002 to turn, the radial dimension of the steering motor 10 along the lead screw 30 is relatively large. In the prior art, the steering motor 10 and the screw 31 of the lead screw 30 are spaced apart along the radial direction of the lead screw 30, resulting in a larger radial dimension of the rear-wheel steering system 100. The rear wheel steering system 100 provided in this application utilizes the cooperation between the transmission mechanism 20 and the lead screw 30 to ensure that the rear wheel steering system 100 can realize the function of driving the rear wheel 1002 to turn, while also ensuring that the screw 31 of the lead screw 30 at least partially overlaps with the first housing 41 of the steering motor 10 in the radial direction, thereby compressing the spatial dimension of the rear wheel steering system 100 in the radial direction of the lead screw 30, thereby reducing the volume of the rear wheel steering system 100 and increasing the internal space of the vehicle 1000.

[0099] Please refer to Figure 6 for details. Figure 6 is a partial structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0100] In one embodiment, the housing 40 includes a second housing 42, and the transmission mechanism 20 includes a planetary gear transmission mechanism 21. The second housing 42 is fixed relative to the frame 1001 and is used to house the planetary gear transmission mechanism 21. That is, the second housing 42 is the housing of the transmission mechanism 20.

[0101] Please refer to Figures 7 to 9. Figure 7 is a partially exploded structural diagram of the rear wheel steering system 100 provided in one embodiment of this application; Figure 8 is a partially exploded structural diagram of the rear wheel steering system provided in one embodiment of this application; and Figure 9 is a partially cross-sectional structural diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0102] In one embodiment, the planetary gear transmission mechanism 21 includes a sun gear 211, planet gears 212, a planet gear carrier 213, and an external gear ring 214. Multiple planet gears 212 are arranged circumferentially around the sun gear 211 and are used for meshing and transmission with it. The sun gear 211 receives the drive rotation from the steering motor 10, i.e., it is connected to the motor shaft 11 of the steering motor 10. The sun gear 211 also drives the planet gears 212 to rotate. The planet gears 212 are fixed to the planet gear carrier 213 so that they drive the planet gear carrier 213 to rotate synchronously under the drive of the sun gear 211. The planet gear carrier 213 is connected to the lead screw 30 to output driving force to the lead screw 30 and drive it to rotate. The rear wheel steering system 100 provided in this application achieves the transmission effect between the steering motor 10 and the lead screw 30 through the planetary gear transmission mechanism 21.

[0103] In one embodiment, the planetary gear carrier 213 includes a shaft hole 2131 and a plurality of receiving slots 2132, which are spaced circumferentially around the periphery of the shaft hole 2131. The shaft hole 2131 is used to receive a sun gear 211, and each receiving slot 2132 is used to receive a planet gear 212. The planetary gear carrier 213 is used to fix the plurality of planet gears 212 so as to rotate with the planet gears 212.

[0104] The external gear ring 214 is used to fix itself inside the second housing 42 of the rear wheel steering gear 100 of this application. The external gear ring 214 is used to be sleeved around the periphery of the multiple planetary gears 212 and the planetary gear support 213, and is used to mesh with the multiple planetary gears 212 so as to provide support for the multiple planetary gears 212.

[0105] During the rotation of the motor shaft 11 of the steering motor 10 in this application, the rotation of the motor shaft 11 drives the sun gear 211 to rotate, which in turn drives the multiple planetary gears 212 to rotate. The rotation of the multiple planetary gears 212 synchronously drives the planetary gear carrier 213 to rotate, thereby driving the lead screw 30 to rotate. In the embodiment where the screw 31 of the lead screw 30 is used as the input end of the lead screw 30, the planetary gear carrier 213 is driven to the screw 31 of the lead screw 30. The rotation of the planetary gear carrier 213 drives the screw 31 to rotate, so that the nut 32 is displaced relative to the screw 31 along the axial direction of the screw 31, thereby driving the rear wheel 1002 to rotate. In the embodiment where the nut 32 of the lead screw 30 is used as the input end, the planetary gear carrier 213 is driven to the nut 32 of the lead screw 30. The rotation of the planetary gear carrier 213 drives the nut 32 to rotate, so that the screw 31 is displaced relative to the nut 32 along its own axial direction, thereby driving the rear wheel 1002 to rotate.

[0106] In this embodiment, the planetary gear transmission mechanism 21 receives drive from the motor shaft 11 via the smaller-radius sun gear 211 and outputs driving force to the lead screw 30 via the planetary gear carrier 213 located around the sun gear 211. This enables the planetary gear transmission mechanism 21 to achieve a speed reduction and torque increase effect while maintaining its reduction ratio. Furthermore, since the sun gear 211 and planetary gear carrier 213 of the planetary gear transmission mechanism 21 rotate around the same central axis (i.e., both rotate around the central axis of the sun gear 211), the input and output axes of the planetary gear transmission mechanism 21 coincide, reducing the radial distance between the central axis of the motor shaft 11 of the steering motor 10 and the central axis of the lead screw 31. In other words, the rear wheel steering gear 100 provided in this application can reduce the radial distance between the central axis of the motor shaft 11 of the steering motor 10 and the central axis of the lead screw 31 while maintaining the reduction ratio of the planetary gear transmission mechanism 21, thereby compressing the overall size of the rear wheel steering gear 100 along the radial direction of the lead screw 31.

[0107] In one embodiment, the planetary gear transmission mechanism 21 includes three planetary gears 212, which are evenly arranged around the periphery of the sun gear 211 along its circumference and are used for meshing and transmission with the sun gear 211. By setting the number of planetary gears 212 to three, this application enables the transmission mechanism 20 to balance the reduction ratio, torque carrying capacity, NVH noise, and ease of installation, thereby improving the overall performance of the rear wheel steering system 100 of this application.

[0108] It should be noted that the number of planetary gears 212 in the above embodiments is merely an illustrative example and does not represent the specific number of planetary gears 212 in other embodiments of this application. That is, the number of planetary gears 212 in this application can be adaptively adjusted according to actual application scenarios. For example, in another embodiment, the number of planetary gears 212 is four or five. When the planetary gear transmission mechanism 21 includes four planetary gears 212, the rear wheel steering system 100 of this application can balance reduction ratio, torque carrying capacity, NVH noise, and installation convenience. When the planetary gear transmission mechanism 21 includes five planetary gears 212, the torque carrying capacity of the transmission mechanism 20 is greater, which can improve the reliability of the rear wheel steering system 100 of this application.

[0109] Please refer to Figure 10 for details. Figure 10 is a simplified diagram of the transmission structure of the rear wheel steering system 100 provided in one embodiment of this application.

[0110] In one embodiment, along the axial direction of the screw 31, the central axis of the motor shaft 11 of the steering motor 10, the central axis of the sun gear 211, and the central axis of the screw 31 of the lead screw 30 sequentially coincide. That is, the steering motor 10, the planetary gear transmission mechanism 21, and the lead screw 30 are arranged coaxially, thereby coinciding with the central axis of the lead screw 30 and the central axis of the steering motor 10. Along the radial direction of the screw 31, the maximum size of the rear wheel steering gear 100 of this application is approximately equal to the size of the first housing 41 of the steering motor 10, which can effectively limit the overall size of the rear wheel steering gear 100 provided in this application.

[0111] In one embodiment, the motor shaft 11 of the steering motor 10 and the gear shaft of the sun gear 211 are integrally formed. That is, the motor shaft 11 of the steering motor 10 and the gear shaft of the sun gear 211 are coaxially arranged.

[0112] In one embodiment, the motor shaft 11 of the steering motor 10 is connected to the gear shaft of the sun gear 211 by interference fit.

[0113] Please refer to Figure 11 for details. Figure 11 is a simplified diagram of the transmission structure of the rear wheel steering system 100 provided in one embodiment of this application.

[0114] In one embodiment, along the axial direction of the screw 31, the central axis of the sun gear 211 coincides with the central axis of the screw 31 of the lead screw 30, meaning the planetary gear transmission mechanism 21 and the lead screw 30 are coaxially arranged. Along the radial direction of the screw 31, the distance between the central axis of the sun gear 211 and the central axis of the motor shaft 11 of the steering motor 10 is greater than the radius of the motor shaft 11. That is, along the radial direction of the screw 31, the gear shaft of the sun gear 211 and the motor shaft 11 of the steering motor 10 are spaced apart. This results in a relatively small distance between the central axis of the screw 31 and the central axis of the steering motor 10 along the radial direction of the screw 31. The maximum size of the rear wheel steering gear 100 provided in this application is approximately equal to the size of the first housing 41 of the steering motor 10, which also effectively limits the overall size of the rear wheel steering gear 100 provided in this application.

[0115] In one embodiment, the transmission mechanism 20 includes a parallel shaft gear transmission mechanism 22, which includes an input gear 221 and an output gear 222. The input gear 221 receives the drive rotation from the steering motor 10 and meshes with the output gear 222, which outputs driving force to the sun gear 211 of the planetary gear transmission mechanism 21. In another embodiment, the input gear 221 is fitted and fixed to the motor shaft 11 so that it rotates with the motor shaft 11 when the motor shaft 11 rotates. The output gear 222 is coaxially fixed with the sun gear 211. When the steering motor 10 is working, the input gear 221 rotates with the rotation of the motor shaft 11 and drives the output gear 222 to rotate, thereby driving the sun gear 211 to rotate, achieving the effect of outputting the driving force of the steering motor 10 to the sun gear 211 of the planetary gear transmission mechanism 21.

[0116] In one embodiment, the diameter of the input wheel 221 is smaller than the diameter of the output wheel 222. The parallel shaft gear transmission mechanism 22 can create a deceleration effect from the input wheel 221 to the output wheel 222. Thus, a first-stage transmission can be formed between the motor shaft 11 of the steering motor 10 and the sun gear 211 of the planetary gear transmission mechanism 21 via the parallel shaft gear transmission mechanism 22, achieving first-stage deceleration and torque increase. A second-stage transmission can be formed between the planetary gear carrier 213 of the planetary gear transmission mechanism 21 and the lead screw 30, achieving second-stage deceleration and torque increase.

[0117] The rear-wheel steering system 100 provided in this application can achieve two-stage reduction, thereby significantly reducing the rotational speed of the driving force output by the steering motor 10 and significantly increasing the torque of the driving force output by the steering motor 10. Alternatively, it can be understood that the transmission mechanism 20 can increase the reduction ratio through the parallel shaft gear transmission mechanism 22. Thus, while ensuring a reliable reduction ratio for the transmission mechanism 20, the volume of the planetary gear transmission mechanism 21 can be reduced, thereby controlling the overall volume of the transmission mechanism 20 so that the radial dimension of the transmission mechanism 20 along the screw 31 is smaller than the dimension of the first housing 41 of the steering motor 10. The rear-wheel steering system 100 provided in this application can reduce the overall radial dimension of the rear-wheel steering system 100 along the screw 31 while meeting the required output torque. Furthermore, the parallel shaft gear transmission mechanism 22 also has high transmission efficiency, which can improve the overall transmission efficiency of the rear-wheel steering system 100 of this application.

[0118] It should be noted that the transmission method between the motor shaft 11 of the steering motor 10 and the sun gear 211 in the planetary gear transmission mechanism 21 in the above embodiments is only an example. That is, the transmission method between the motor shaft 11 of the steering motor 10 and the sun gear 211 in the planetary gear transmission mechanism 21 includes, but is not limited to, parallel shaft gear transmission. For example, in another embodiment, the transmission mechanism 20 includes a transmission wheel and a belt (not shown in the figure). The transmission wheel is used to receive the drive rotation of the steering motor 10, that is, the transmission wheel is sleeved and fixed to the motor shaft 11. The belt is used to drive the transmission wheel and the sun gear 211 to transmit the driving force of the steering motor 10 to the sun gear 211. When the steering motor 10 is working, the motor shaft 11 drives the transmission wheel to rotate and drives the belt to drive the sun gear 211 to rotate, which can also achieve the effect of outputting the driving force of the steering motor 10 towards the sun gear 211 of the planetary gear transmission mechanism 21. It can be understood that the structure of the transmission wheel and the belt is relatively simple, which is beneficial to the internal structure arrangement of the rear wheel steering gear 100 of this application.

[0119] In one embodiment, the diameter of the drive wheel is smaller than the diameter of the sun wheel 211.

[0120] Please refer to Figures 12 to 14, where Figure 12 is a partial structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application; Figure 13 is a partial exploded structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application; and Figure 14 is a partial cross-sectional structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0121] In one embodiment, the planetary gear carrier 213 is fixedly connected to the screw 31 of the lead screw 30. The nut 32 of the lead screw 30 engages with the periphery of the screw 31. Along the axial direction of the screw 31, the nut 32 is used to fixably connect the steering tie rod 50 of the rear wheel steering gear 100. The lead screw 30 is used to receive the drive rotation of the planetary gear transmission mechanism 21 and to drive the rear wheels 1002 of the vehicle 1000 to steer via the steering tie rod 50. That is, the screw 31 serves as the input end of the lead screw 30, and the nut 32 serves as the output end of the lead screw 30. In this embodiment, the nut 32 and the screw 31 of the lead screw 30 are fixedly connected to the steering tie rod 50 of the vehicle 1000 and the transmission mechanism 20 of the rear wheel steering gear 100, respectively. In this application, the steering motor 10 of the rear wheel steering gear 100 drives the screw 31 to rotate through the transmission mechanism 20, thereby driving the nut 32 to move the steering tie rod 50 along the central axis of the screw 31. The rear wheel steering gear 100 can then turn the rear wheels 1002 of the vehicle 1000 through the steering tie rod 50.

[0122] In one embodiment, the planetary gear carrier 213 includes a bushing located on the side of the planetary gear carrier 213 away from the steering motor 10, along the axial direction of the screw 31. Along the axial direction of the screw 31, one end of the screw 31 away from the rear wheel 1002 is embedded in the bushing, thereby achieving a fixed connection between the planetary gear carrier 213 and the screw 31.

[0123] In one embodiment, the planetary gear carrier 213 is fixedly connected to the nut 32 of the lead screw 30. The nut 32 of the lead screw 30 meshes with the periphery of the screw rod 31. Along the axial direction of the screw rod 31, the screw rod 31 is used to fixably connect to the steering tie rod 50 of the rear wheel steering gear 100. The lead screw 30 is used to receive the drive rotation of the planetary gear transmission mechanism 21 and to drive the rear wheels 1002 of the vehicle 1000 to steer via the steering tie rod 50. That is, the nut 32 serves as the input end of the lead screw 30, and the screw rod 31 serves as the output end of the lead screw 30. In this embodiment, the nut 32 and the screw rod 31 of the lead screw 30 are fixedly connected to the transmission mechanism 20 of the rear wheel steering gear 100 and the steering tie rod 50 of the vehicle 1000, respectively. In this application, the steering motor 10 of the rear wheel steering gear 100 drives the nut 32 to rotate through the transmission mechanism 20, thereby driving the screw 31 to drive the steering tie rod 50 to move axially along the screw 31. The rear wheel steering gear 100 can then drive the rear wheels 1002 of the vehicle 1000 to turn through the steering tie rod 50.

[0124] In one embodiment, the second housing 42 is used to house the planetary gear transmission mechanism 21 and to at least partially house the lead screw 30.

[0125] In one embodiment, the steering tie rod 50 includes two opposing ends along the axial direction of the screw 31. For ease of description, the two ends of the steering tie rod 50 are defined as a first end 51 and a second end 52, respectively. Along the axial direction of the screw 31, the first end 51 is located between the transmission mechanism 20 and the second end 52. The first end 51 is used to embed into the second housing 42 of the transmission mechanism 20 and to drive the lead screw 30. The second end 52 is used to drive a rear wheel 1002 of the vehicle 1000 and to steer the rear wheel 1002 of the vehicle 1000.

[0126] The second housing 42 of the transmission mechanism 20 includes a receiving groove, which, for ease of explanation, is defined as the first receiving groove 43. The planetary gear transmission mechanism 21 and part of the lead screw 30 are accommodated in the first receiving groove 43. Along the axial direction of the screw 31, the opening of the first receiving groove 43 faces away from the sun gear 211. The first end 51 of the steering tie rod 50 extends into the first receiving groove 43 through the opening portion of the first receiving groove 43 and is connected to the lead screw 30 in a transmission manner. In this embodiment, by partially accommodating the steering tie rod 50 in the second housing 42 of the transmission mechanism 20, the overall size of the rear wheel steering gear 100 along the axial direction of the screw 31 can be reduced, which is beneficial for the miniaturization design of the rear wheel steering gear 100.

[0127] In one embodiment, the first end 51 of the steering tie rod 50 is slidably connected to the groove wall of the first receiving groove 43 along the axial direction of the screw 31. That is, the second housing 42 of the transmission mechanism 20 can be used to limit the radial displacement of the steering tie rod 50 along the screw 31, so as to improve the steering accuracy of the rear wheel steering gear 100 of this application.

[0128] In one embodiment, the steering tie rod 50 includes a receiving groove, which, for ease of description, is defined as a second receiving groove 53. Along the axial direction of the screw 31, the opening of the second receiving groove 53 faces the sun gear 211, and the second receiving groove 53 is used to receive a portion of the lead screw 30. That is, the first end 51 of the steering tie rod 50 includes the second receiving groove 53, and along the axial direction of the screw 31, the end of the lead screw 30 facing away from the sun gear 211 extends into the second receiving groove 53 through the opening portion of the second receiving groove 53. In this embodiment, by utilizing the second receiving groove 53 of the steering tie rod 50 to partially accommodate the lead screw 30, the overall size of the rear wheel steering gear 100 along the axial direction of the screw 31 can be reduced, facilitating the miniaturization design of the rear wheel steering gear 100.

[0129] In one embodiment, the nut 32 of the lead screw 30 is fixed to the groove wall of the second receiving groove 53. The nut 32 is used to receive the drive from the screw 31 and to move along the axial direction of the screw 31 to drive the steering tie rod 50. That is, the screw 31 serves as the input end of the lead screw 30 and is used to drive the planetary gear transmission mechanism 21 to receive the drive rotation from the steering motor 10. The nut 32 serves as the output end of the lead screw 30 and is fixedly connected to the steering tie rod 50. It receives the drive from the screw 31 and moves along the axial direction of the screw 31 as the screw 31 rotates to drive the steering tie rod 50 to move, thereby turning the rear wheel 1002.

[0130] In another embodiment, the nut 32 of the lead screw 30 is fixed to the motor shaft 11. The nut 32 is used to drive the screw 31 to move axially along its own axis and drive the steering tie rod 50 as the motor shaft 11 rotates. That is, the nut 32 serves as the input end of the lead screw 30, which is fixedly connected to the motor shaft 11 to receive the drive rotation of the steering motor 10. The screw 31 serves as the output end of the lead screw 30, which is fixedly connected to the steering tie rod 50 to receive the drive from the nut 32. It moves axially along its own axis as the nut 32 rotates to drive the steering tie rod 50 to move, thereby turning the rear wheel 1002.

[0131] Please refer to Figures 15 and 16 for details. Figure 15 is a partial structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application; Figure 16 is a partially exploded structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0132] In one embodiment, the lead screw 30 is a planetary roller screw 30a, which includes a plurality of planetary rollers 33. Along the circumference of the screw 31, the plurality of planetary roller screws 30a are spaced apart around the periphery of the screw 31 and respectively mesh with the screw 31. The nut 32 of the lead screw 30 is connected to the screw 31 via the plurality of planetary rollers 33.

[0133] Each planetary roller 33 includes a first threaded section 331 along the axial direction of the screw 31. The first threaded section 331 engages with the thread on the outer circumferential surface of the screw 31, allowing the screw 31 to rotate under the drive of the steering motor 10, thus rotating each planetary roller 33 and simultaneously displacing each planetary roller 33 along the axial direction of the screw 31. A nut 32 is sleeved around the periphery of the multiple planetary rollers 33, with its inner wall spaced from the first threaded section 331 along the radial direction of the lead screw 30. The multiple planetary rollers 33 are respectively used for rotatable connection with the nut 32. That is, each planetary roller 33 can roll within the nut 32 around the central axis of the screw 31, causing the nut 32 to displace along the axial direction of the screw 31.

[0134] In this embodiment, the first threaded section 331 of the planetary roller 33 engages with the thread on the outer circumferential surface of the screw 31, generating line contact rolling friction between the planetary roller 33 and the screw 31. This increases the contact surface and force-bearing surface during the transmission process. On one hand, this design improves transmission efficiency when the steering motor 10 is operating. On the other hand, when the steering motor 10 is not operating, the greater friction between the planetary roller 33 and the screw 31 enhances the self-locking capability of the lead screw 30. When the rear wheel 1002 experiences an unexpected steering reaction due to ground impact, it may reverse-drive the steering tie rod 50, causing the lead screw 30 to displace axially along the screw 31. The rear wheel steering system 100 of this application can limit the rotation angle of the lead screw 30 through the self-locking function of the planetary roller lead screw 30a, thereby limiting the axial displacement of the steering tie rod 50 and thus limiting the angle at which the rear wheel 1002 undergoes an unexpected steering reaction.

[0135] The rear wheel steering system 100 provided in this application has high transmission efficiency and good self-locking capability of planetary roller screw 30a. When it is driven by steering motor 10, it can drive screw 30 to rotate and ensure transmission efficiency. When steering motor 10 stops driving, it can limit the rotation of screw 30, thereby preventing the rear wheel 1002 of vehicle 1000 from being subjected to impact and causing undesirable steering.

[0136] In one embodiment, each planetary roller 33 includes two second threaded segments 332, arranged on either side of the first threaded segment 331 along the axial direction of the screw 31. Each second threaded segment 332 is used for threaded engagement with the nut 32. Thus, the threaded engagement between the second threaded segments 332 of each planetary roller 33 and the nut 32 restricts the radial displacement of the planetary roller 33 and the nut 32 along the screw 31, preventing radial offset of the planetary roller 33 during axial movement along the screw 31, thereby improving steering accuracy.

[0137] In one embodiment, the planetary roller screw 30a includes six planetary rollers 33.

[0138] In one embodiment, the planetary roller screw 30a includes 10 planetary rollers 33. In this embodiment, when the planetary roller screw 30a includes 10 planetary rollers 33, the locking capability and ease of installation of the screw 30 can be balanced, avoiding undesirable steering of the rear wheel 1002 due to a small number of planetary rollers 33, and avoiding inconvenience in installation of the planetary roller screw 30a due to a large number of planetary rollers 33.

[0139] It should be noted that the number of planetary rollers 33 in the above embodiments is only an example. The number of planetary rollers 33 in the rear wheel steering gear 100 of this application can be adjusted adaptively according to the actual application scenario.

[0140] In one embodiment, the nut 32 is fixed to the wall of the second receiving groove 53. The screw 31 rotates with the transmission mechanism 20 and drives multiple planetary rollers 33 to move axially along the screw 31. The multiple planetary rollers 33 drive the nut 32 to move synchronously. That is, the screw 31 serves as the input end of the lead screw 30 and is used for transmission connection with the transmission mechanism 20. The nut 32 serves as the output end of the lead screw 30, and the input end and output end are connected by multiple planetary rollers 33. The motor shaft 11 of the steering motor 10 outputs a drive to rotate through the transmission mechanism 20, thereby driving the screw 31 to rotate around its own axis, thereby driving the multiple planetary rollers 33 to move axially along the screw 31, and thus driving the nut 32 to move synchronously.

[0141] In another embodiment, the nut 32 is fixed to the transmission mechanism 20. The nut 32 rotates with the transmission mechanism 20 to drive multiple planetary rollers 33 to rotate around the screw 31. The multiple planetary rollers 33 drive the screw 31 to move axially. That is, the nut 32 serves as the input end of the lead screw 30 and is used for transmission connection with the transmission mechanism 20. The screw 31 serves as the output end of the lead screw 30, and the input end and output end are connected by multiple planetary rollers 33. The motor shaft 11 of the steering motor 10 outputs a drive rotation through the transmission mechanism 20 to drive the nut 32 to rotate around the axis of the screw 31, thereby driving the multiple planetary rollers 33 to rotate around the axis of the screw 31, and further driving the screw 31 to move axially.

[0142] In one embodiment, the outer peripheral surface of the screw 31 includes radial protrusions 311, that is, along the radial direction of the screw 31, the radial protrusions 311 extend from the outer peripheral surface of the screw 31 in a direction away from the screw 31. Along the axial direction of the screw 31, the radial protrusions 311 are spaced apart on the side of the nut 32 opposite to the sun gear 211. It is understood that when the steering motor 10 is operating, the lead screw 30 receives the driving force of the steering motor 10 output through the transmission mechanism 20, causing a relative displacement between the nut 32 and the screw 31 along the axial direction of the screw 31, thereby driving the steering tie rod 50 to move and steer the rear wheel 1002. This application uses the radial protrusions 311 along the radial direction of the screw 31 at the end of the nut 32 opposite to the sun gear 211. The radial protrusions 311 can be used to limit the amount of relative displacement between the nut 32 and the screw 31 along the axial direction of the screw 31, preventing excessive relative displacement between the nut 32 and the screw 31 from causing it to fall off.

[0143] In one embodiment, the diameter of the radial protrusion 311 is larger than the inner diameter of the nut 32, that is, along the radial direction of the screw 31, the distance from the outer wall of the radial protrusion 311 to the central axis of the screw 31 is greater than the radius of the nut 32. By setting the diameter of the radial protrusion 311 to be larger than the inner diameter of the nut 32, this application allows the radial protrusion 311 to limit the relative displacement between the planetary rollers 33 and the nut 32, preventing excessive relative displacement between the planetary rollers 33 and the nut 32 from causing the planetary rollers 33 to detach from the nut 32.

[0144] In one embodiment, the radial protrusion 311 is embedded in the wall of the second receiving groove 53. That is, the radial protrusion 311 is received within the second receiving groove 53 and embedded in its wall to be fixedly connected to the steering tie rod 50. Thus, the screw 31 can serve as the output end of the lead screw 30. When the screw 31 moves axially relative to the nut 32, it can drive the steering tie rod 50 to move, thereby steering the rear wheel 1002. Furthermore, the wall of the second receiving groove 53, through the radial protrusion 311, can restrict the displacement of the screw 31 in the radial direction, preventing the screw 31 from deviating and thus improving steering accuracy.

[0145] In one embodiment, the rear wheel steering system 100 provided in this application includes a controller (not shown in the figure), which is used to communicate with the steering motor 10. When the rear wheels 1002 of the vehicle 1000 need to turn, the controller is used to control the rotation of the motor shaft 11 of the steering motor 10 to drive the transmission mechanism 20 to rotate the lead screw 30 by a certain angle, thereby controlling the rear wheels 1002 to rotate by a preset angle.

[0146] In one embodiment, after the rear wheels 1002 of the vehicle 1000 have finished turning, the controller is also used to drive the motor shaft 11 of the steering motor 10 to continue rotating, so as to drive the transmission mechanism 20 to hold the lead screw 30, thereby increasing the support torque on the rear wheels 1002 and limiting the rear wheels 1002 from producing unintended steering.

[0147] In one embodiment, the rear wheel steering system 100 provided in this application includes a sensor 60, which is fixed to the second housing 42 of the rear wheel steering system 100 and is used to detect the axial displacement of the lead screw 30. It should be noted that the axial displacement of the lead screw 30 can be the axial displacement of the screw 31 or the axial displacement of the nut 32 along the screw 31. The steering motor 10 rotates its shaft 11 by a certain angle based on the detection signal from the sensor 60 to control the steering angle of the rear wheel 1002. In this embodiment, detecting the displacement of the lead screw 30 through the sensor 60 can indirectly detect the steering angle of the rear wheel 1002, which is beneficial for controlling the rotation angle of the motor shaft 11 of the steering motor 10, thereby ensuring reliable steering of the rear wheel 1002.

[0148] In one embodiment, sensor 60 is used to transmit a detection signal to a controller, which is used to receive the detection signal output by sensor 60 and indirectly calculate the steering angle of rear wheel 1002.

[0149] In one embodiment, sensor 60 includes a displacement sensor fixed to the second housing 42 and used to directly detect the axial displacement of lead screw 30.

[0150] In one embodiment, in response to a first control signal, the steering motor 10 continuously outputs a first preset torque toward the planetary roller screw 30a. The first control signal instructs the rear wheel steering unit 100 to drive the rear wheels 1002 of the vehicle 1000 to turn to a preset angle. Specifically, the sensor 60 detects the axial displacement of the planetary roller screw 30a and outputs a detection signal to the controller. The controller determines whether to generate the first control signal based on the detection signal from the sensor 60. The first control signal instructs the rear wheel steering unit 100 to drive the rear wheels 1002 of the vehicle 1000 to turn to the preset angle. The controller also, in response to the first control signal, drives the steering motor 10 to continuously output driving force, enabling the transmission mechanism 20 to hold the planetary roller screw 30a, thereby increasing the support torque on the rear wheels 1002 and limiting unintended steering of the rear wheels 1002. That is, after the rear wheel steering system 100 drives the rear wheel 1002 to rotate to a preset angle, the steering motor 10 continuously outputs torque to assist the planetary roller screw 30a in locking the steering tie rod 50 and prevent the rear wheel 1002 from turning unexpectedly.

[0151] In one embodiment, the first preset torque is equal to the stall torque of the steering motor 10.

[0152] In one embodiment, the difference between the first preset torque and the stall torque of the steering motor 10 is less than the first preset difference.

[0153] Please refer to Figures 17 and 18. Figure 17 is a partially exploded structural diagram of the rear wheel steering system 100 provided in one embodiment of this application; Figure 18 is a partially cross-sectional structural diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0154] In one embodiment, the lead screw 30 is a ball screw 30b. That is, the ball screw 30b includes a plurality of balls 34. Along the circumference of the screw 31, the plurality of balls 34 are spaced around the periphery of the screw 31, and are located between the inner circumferential surface of the nut 32 and the outer circumferential surface of the screw 31, abutting against both surfaces. In this embodiment, the plurality of balls 34 can reduce the friction between the nut 32 and the screw 31, thereby improving the transmission efficiency of the rear wheel steering system 100.

[0155] Please refer to Figures 19 and 20 for reference. Figure 19 is a partially exploded structural diagram of the rear wheel steering system 100 provided in one embodiment of this application; Figure 20 is a cross-sectional structural diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0156] In one embodiment, the rear wheel steering system 100 provided in this application includes a locking mechanism 70. The locking mechanism 70 is used to drive the motor shaft 11 and the ball screw 30b. When the steering motor 10 is operating, the locking mechanism 70 receives the drive from the motor shaft 11 to move the ball screw 30b, thereby driving the rear wheel 1002 to turn. The locking mechanism 70 is also used to restrict the movement of the ball screw 30b when the steering motor 10 is not operating. That is, when the motor shaft 11 of the steering motor 10 rotates, the locking mechanism 70 receives the drive from the motor shaft 11 and drives the ball screw 30b to rotate to generate axial displacement, thereby driving the rear wheel 1002 to turn. When the motor shaft 11 of the steering motor 10 is not rotating, the locking mechanism 70 is used to limit the rotation angle of the ball screw 30b, thereby limiting the axial displacement of the ball screw 30b and limiting the angle at which the rear wheel 1002 will turn unexpectedly due to ground impact.

[0157] In this embodiment, the ball screw 30b has high transmission efficiency, can rotate and generate axial displacement when driven by the steering motor 10, and improves the overall transmission efficiency of the rear wheel steering system 100. The locking mechanism 70 is used to achieve self-locking of the rear wheel steering system 100 to prevent the rear wheels 1002 of the vehicle 1000 from turning undesirably after being impacted by the ground.

[0158] In one embodiment, the locking mechanism 70 is used to drive the sun gear 211 of the motor shaft 11 and the planetary gear transmission mechanism 21. When the steering motor 10 is working, the locking mechanism 70 is used to receive the drive of the motor shaft 11 and drive the sun gear 211 to rotate, thereby driving the ball screw 30b to rotate and generate axial displacement, thereby turning the rear wheel 1002. When the steering motor 10 is not working, the locking mechanism 70 is also used to limit the rotation of the sun gear 211 to limit the rotation of the ball screw 30b, thereby limiting the amount of axial displacement of the ball screw 30b, and thus limiting the rear wheel 1002 from generating an unintended steering angle.

[0159] Please refer to Figures 21 and 22 for reference. Figure 21 is a partial structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application; Figure 22 is a partial cross-sectional structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0160] In one embodiment, the locking mechanism 70 includes a driving member 71, a one-way clutch 72, and a driven member 73. The driving member 71 is fixedly connected to the motor shaft 11 and receives the drive rotation of the steering motor 10. The one-way clutch 72 is used to drive the driving member 71 and the driven member 73, and can be used to engage or disengage the drive member 71 and the driven member 73, and to limit the rotation of the driven member 73 relative to the driving member 71. The driven member 73 is drivenly connected to the ball screw 30b and outputs the driving force of the steering motor 10 to the ball screw 30b.

[0161] When the rear wheels 1002 of vehicle 1000 need to turn, the motor shaft 11 of steering motor 10 rotates, causing drive component 71 to rotate synchronously. One-way clutch 72 links drive component 71 and driven component 73, transmitting the drive force of drive component 71 to driven component 73, causing driven component 73 to rotate, which in turn causes ball screw 30b to rotate, generating axial displacement, thereby driving rear wheel 1002 to turn. When vehicle 1000 travels on uneven road surfaces, causing rear wheel 1002 to undergo unintended steering due to ground impact, rear wheel 1002 will reverse, causing ball screw 30b to displace axially, thereby causing driven component 73 to rotate. One-way clutch 72 can disengage the linkage between drive component 71 and driven component 73 and limit the rotation angle of driven component 73 to apply locking force to screw 30, achieving the self-locking function of rear wheel steering gear 100, thereby limiting the axial displacement of screw 30 and thus limiting the unintended steering angle of rear wheel 1002.

[0162] In one embodiment, the driven member 73 is used to drively connect with the ball screw 30b via the transmission mechanism 20. That is, the driven member 73 is used to drively connect with the sun gear 211 in order to achieve the transmission connection effect between the locking mechanism 70 and the ball screw 30b.

[0163] In one embodiment, in response to a second control signal, the steering motor 10 continuously outputs a second preset torque toward the ball screw 30b. The second control signal instructs the rear wheel steering unit 100 to drive the rear wheels 1002 of the vehicle 1000 to turn to a preset angle. Specifically, the sensor 60 detects the axial displacement of the ball screw 30b and outputs a detection signal to the controller. The controller determines whether to generate a first control signal based on the detection signal from the sensor 60. The first control signal instructs the rear wheel steering unit 100 to drive the rear wheels 1002 of the vehicle 1000 to turn to the preset angle. The controller also, in response to the first control signal, drives the steering motor 10 to continuously output driving force, enabling the locking mechanism 70 to hold the transmission mechanism 20 and the ball screw 30b, thereby increasing the support torque on the rear wheels 1002 and limiting unintended steering of the rear wheels 1002. That is, after the rear wheel steering system 100 drives the rear wheel 1002 to rotate to a preset angle, the steering motor 10 continuously outputs torque to assist the planetary roller screw 30a in locking the steering tie rod 50 and prevent the rear wheel 1002 from turning unexpectedly.

[0164] In one embodiment, the second preset torque is less than the first preset torque. Because the locking capability of the locking mechanism 70 is stronger than that of the planetary roller screw 30a, in this embodiment, by locking the transmission mechanism 20 and the ball screw 30b through the locking mechanism 70, the frequency of unintended steering of the rear wheel 1002 can be reduced. That is, the steering motor 10 can limit the unintended steering of the rear wheel 1002 with a smaller output torque. This avoids the phenomenon of limiting the unintended steering of the rear wheel 1002 by driving the steering motor 10 to work in a stalled state for a long time. This extends the service life of the steering motor 10 and saves energy consumption of the rear wheel steering system 100 provided in this application.

[0165] Please refer to Figure 23 for reference. Figure 23 is a partial cross-sectional structural schematic diagram of the rear wheel steering system 100 provided in one embodiment of this application.

[0166] In one embodiment, the rear wheel steering gear 100 provided in this application includes a displacement sensor 61, which is used to detect the displacement of the lead screw 30. The displacement sensor 61 includes a detection component 611 and a moving component 612. The detection component 611 is fixed to the second housing 42 of the rear wheel steering gear 100, and the moving component 612 is fixed to the steering tie rod 50 of the rear wheel 1002 and moves along the axial direction of the steering tie rod 50.

[0167] As shown in Figure 23, the detection component 611 of the displacement sensor 61 is fixed on the second housing 42 of the rear wheel steering gear 100 near the end of the steering tie rod 50, and the moving component 612 of the displacement sensor 61 is fixed on the end of the steering tie rod 50 of the rear wheel 1002. The displacement sensor 61 can be a magnetoelectric induction type or a voltage-current type sensor. This application takes a magnetoelectric induction type displacement sensor as an example. When the moving component 612 and the steering tie rod 50 of the rear wheel 1002 move along the axial direction of the steering tie rod 50, the detection component 611 can measure the displacement of the moving component 612 through electromagnetic induction, that is, measure the displacement of the steering tie rod 50, and transmit it to the rear wheel controller for controlling the steering of the rear wheel 1002.

[0168] In this embodiment, the displacement sensor 61 is installed on the second housing 42 and the end of the steering tie rod 50, which can effectively reduce the influence of the rotation of the screw 31 and nut 32 of the lead screw 30 on the displacement measurement of the steering tie rod 50, ensuring the accuracy of the measurement, and at the same time making the installation and maintenance of the sensor 60 more convenient.

[0169] In one embodiment, the detection component 611 of the displacement sensor 61 and the moving component 612 are spaced apart from each other along the radial direction of the screw 31. This prevents friction between the moving component 612 and the detection component 611 during the movement of the steering tie rod 50, ensuring the detection accuracy of the displacement sensor 61 and extending its service life.

[0170] In one embodiment, the rear wheel steering system 100 provided in this application includes two transmission mechanisms 20 and two lead screws 30. The central axes of the two lead screws 30 coincide, and the two lead screws are arranged on both sides of the steering motor 10 along their own axial direction. The two transmission mechanisms 20 are arranged on both sides of the steering motor 10 along the axial direction of the lead screws 30. The steering motor 10 includes two motor shafts 11, which are arranged on both sides of the motor stator 12 of the steering motor 10. Each motor shaft 11 is used to drive a lead screw 30 through a transmission mechanism 20 to steer the rear wheel 1002 on one side of the vehicle 1000.

[0171] It should be noted that the number of motor shafts 11 of the steering motor 10 in the above embodiments is only for illustrative purposes. For example, in another embodiment, the steering motor 10 of this application includes one motor shaft 11, and the rear wheel steering device 100 of this application includes two transmission mechanisms 20 and two lead screws 30. The motor shaft 11 of the steering motor 10 is used to pass through the inner hole of the motor rotor 13 and to drive the two transmission mechanisms 20 respectively. The two transmission mechanisms 20 respectively transmit the driving force to a corresponding lead screw 30, thereby driving the rear wheel 1002 on the corresponding side to turn.

[0172] Please refer to Figure 24 for details. Figure 24 is a schematic diagram of the architecture of a vehicle 1000 provided in one embodiment of this application.

[0173] In one embodiment, the rear wheel steering system 100 provided in this application includes two steering motors 10, two transmission mechanisms 20, and two lead screws 30. The two steering motors 10 are arranged at intervals along the axial direction of the lead screws 30, and each steering motor 10 drives one lead screw 30 through a transmission mechanism 20 to steer the rear wheel 1002 on one side of the vehicle 1000.

[0174] In one implementation, the rear-wheel steering system 100 provided in this application includes two locking mechanisms 70. Along the axial direction of the lead screw 30, the two locking mechanisms 70 are positioned on either side of the steering motor 10. Each locking mechanism 70 is used to drive the steering motor 10 and a lead screw 30. When the steering motor 10 is operating, each locking mechanism 70 is driven by the motor shaft 11 to move one of the lead screws 30 on the corresponding side, thereby driving the rear wheel 1002 on the corresponding side to steer. Each locking mechanism 70 is also used to restrict the movement of one of the lead screws 30 on the corresponding side when the steering motor 10 is not operating.

[0175] In one implementation, the screws 31 of the two lead screws 30 have the same thread direction, and the two rear wheels 1002 rotate in the same direction.

[0176] In one implementation, the screws 31 of the two lead screws 30 have opposite thread directions, and the two rear wheels 1002 rotate in opposite directions. That is, along the axial direction of the rear wheels 1002, the screws 31 of the two lead screws 30 have opposite thread directions. Thus, when the steering motor 10 is working, the steering motor 10 can drive the lead screws 30 on both sides of the steering motor 10 to rotate in opposite directions, so that the two rear wheels 1002 on both sides of the vehicle 1000 rotate in opposite directions, thereby adjusting the relative shape of the two rear wheels 1002 and making the vehicle 1000 suitable for different application scenarios.

[0177] In one embodiment, the steering motor 10 drives the lead screws 30 on both sides of the steering motor 10 to rotate in opposite directions, causing the two rear wheels 1002 on both sides of the vehicle 1000 to deflect relative to each other, forming an "outward" shape. This shape can reduce the turning radius of the vehicle 1000 and improve the agility of the vehicle 1000.

[0178] In one embodiment, the steering motor 10 drives the lead screws 30 on both sides of the steering motor 10 to rotate in opposite directions, causing the two rear wheels 1002 on both sides of the vehicle 1000 to deflect relative to each other, forming an "inward" shape. This shape can improve the vehicle 1000's resistance to lateral disturbances, increase the vehicle 1000's stability, and reduce braking distance.

[0179] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the scope of protection of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A rear-wheel steering system, characterized in that, The rear wheel steering system includes a steering motor, a transmission mechanism, and a lead screw. The steering motor drives the lead screw to steer the rear wheels of the vehicle after the transmission mechanism changes the rotational speed. The distance between the center axis of the motor shaft of the steering motor and the center axis of the lead screw along the radial direction of the lead screw is less than the radius of the housing of the steering motor.

2. The rear wheel steering system according to claim 1, characterized in that, The transmission mechanism includes a planetary gear transmission mechanism, wherein the sun gear of the planetary gear transmission mechanism is used to receive the drive rotation of the steering motor, the planet gears of the planetary gear transmission mechanism are used to mesh with the sun gear and output drive rotation through the planet gear bracket of the planetary gear transmission mechanism, and the outer gear ring of the planetary gear transmission mechanism is used to be fixed to the housing of the rear wheel steering gear and mesh with the planet gears.

3. The rear wheel steering system according to claim 2, characterized in that, Along the axial direction of the screw, the central axis of the motor shaft of the steering motor, the central axis of the sun gear, and the central axis of the lead screw coincide in sequence.

4. The rear wheel steering system according to claim 2, characterized in that, Along the axial direction of the screw, the central axis of the sun gear coincides with the central axis of the lead screw; along the radial direction of the screw, the distance between the central axis of the sun gear and the central axis of the motor shaft of the steering motor is greater than the radius of the motor shaft.

5. The rear wheel steering system according to claim 4, characterized in that, The transmission mechanism includes a parallel shaft gear transmission mechanism. The input wheel of the parallel shaft gear transmission mechanism is used to receive the drive rotation of the steering motor. The output wheel of the parallel shaft gear transmission mechanism is used to mesh with the input wheel and drive the sun gear to rotate by being coaxially fixed with the sun gear. The diameter of the input wheel is smaller than the diameter of the output wheel.

6. The rear wheel steering system according to any one of claims 2-5, characterized in that, The planetary gear carrier is fixedly connected to the lead screw, and the nut of the lead screw meshes with the periphery of the lead screw. Along the axial direction of the lead screw, the nut is used to fix the steering tie rod of the rear wheel steering gear. The lead screw is used to receive the drive rotation of the planetary gear transmission mechanism and to drive the rear wheels of the vehicle to steer through the steering tie rod.

7. The rear wheel steering system according to any one of claims 2-5, characterized in that, The planetary gear carrier is fixedly connected to the nut of the lead screw, the nut of the lead screw meshes with the periphery of the screw rod, and the screw rod is used to fixally connect the steering tie rod of the rear wheel steering gear along the axial direction of the screw rod. The lead screw is used to receive the drive rotation of the planetary gear transmission mechanism and to drive the rear wheels of the vehicle to steer through the steering tie rod.

8. The rear wheel steering system according to any one of claims 2-7, characterized in that, The planetary gear transmission mechanism includes three planetary gears.

9. The rear wheel steering system according to any one of claims 1-8, characterized in that, The lead screw is a planetary roller lead screw, which includes multiple planetary rollers. These planetary rollers are spaced apart around the screw along its circumference and mesh with it. The nut of the lead screw is connected to the screw via the multiple planetary rollers. The planetary roller screw comprises 10 planetary rollers.

10. The rear wheel steering system according to claim 9, characterized in that, In response to a first control signal, the steering motor continuously outputs a first preset torque toward the planetary roller screw, the first control signal being used to instruct the rear wheel steering system to turn the rear wheels of the vehicle to a preset angle.

11. The rear wheel steering system according to any one of claims 1-8, characterized in that, The lead screw is a ball screw, and the rear wheel steering gear includes a locking mechanism. The locking mechanism is used to drive the motor shaft and the ball screw. When the steering motor is working, the locking mechanism is used to receive the drive of the motor shaft to drive the ball screw to move. The locking mechanism is also used to restrict the movement of the ball screw when the steering motor stops working.

12. The rear wheel steering system according to claim 11, characterized in that, The locking mechanism includes a driving member, a one-way clutch, and a driven member. The driving member is fixedly connected to the motor shaft, the driven member is connected to the ball screw drive, and the one-way clutch is used to restrict the movement of the driven member and to receive the drive from the driving member and drive the driven member.

13. The rear wheel steering system according to claim 11 or 12, characterized in that, In response to a second control signal, the steering motor continuously outputs a second preset torque toward the ball screw, the second control signal instructing the rear wheel steering unit to turn the rear wheels of the vehicle to a preset angle.

14. The rear wheel steering system according to any one of claims 1-13, characterized in that, The rear wheel steering system includes a displacement sensor for detecting the displacement of the lead screw, wherein: The detection component of the displacement sensor is fixed to the housing of the rear wheel steering gear, and the moving component of the displacement sensor is fixed to the steering tie rod of the rear wheel and moves along the axial direction of the steering tie rod.

15. A vehicle, characterized in that, The vehicles include: One or more rear wheels; The rear wheel steering system as described in any one of claims 1-14, wherein the rear wheel steering system is used to drive the one or more rear wheels to steer.

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