Rear wheel steering gear and vehicle

Abstract

The invention provides a rear wheel steering gear and a vehicle. The rear wheel steering gear comprises a lead screw and a nut which are meshed with each other, a shell of the rear wheel steering gear is used for being fixedly connected with a frame and fixing one of the lead screw and the nut, the other one of the lead screw and the nut is used for being in transmission connection with a rear wheel on one side of the vehicle through a pull rod, and the axial direction of the lead screw is parallel to the center connecting line of the rear wheels on the two sides of the vehicle. Wherein the wheel speed difference of the rear wheels on the two sides of the vehicle is larger than a first preset wheel speed difference, the lead screw is used for rotating relative to the nut, and the other one of the lead screw and the nut generates axial displacement and drives the rear wheel on one side of the vehicle to deflect through a pull rod. The rear wheel steering gear responds to the wheel speed difference of the rear wheels on the two sides of the vehicle to drive the rear wheels on one side of the vehicle to steer, structures such as a steering motor and a speed reducer are omitted, self miniaturization is facilitated, and cost is reduced.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and in particular to a rear wheel steering gear and a vehicle. Background Art

[0002] The rear-wheel steering gear is used to control the steering of the rear wheels of the vehicle. Through the steering coordination of the rear wheels and the front wheels, the turning radius of the vehicle can be reduced, the sideslip angle of the vehicle's center of mass can be reduced, the steady-state overshoot of the vehicle's yaw rate can be reduced, and a smooth change of direction can be achieved. However, the structural design of the rear-wheel steering gear will affect the interior space of the vehicle, and the relatively complex internal structure of the rear-wheel steering gear will also increase the cost of the vehicle. Summary of the invention

[0003] The present application provides a rear wheel steering device and a vehicle. The rear wheel steering device drives one rear wheel of the vehicle to steer in response to the wheel speed difference between the rear wheels on both sides of the vehicle, omitting structures such as a steering motor and a reducer, which is conducive to miniaturization and cost reduction.

[0004] In a first aspect, the present application provides a rear-wheel steering gear, which includes a screw and a nut that mesh with each other, a housing of the rear-wheel steering gear used to fix a vehicle frame and to fix one of the screw and the nut, the other of the screw and the nut used to connect one side of the rear wheel of the vehicle through a pull rod transmission, the axial direction of the screw is parallel to the center line of the rear wheels on both sides of the vehicle, wherein the wheel speed difference between the rear wheels on both sides of the vehicle is greater than a first preset wheel speed difference, the screw is used to rotate relative to the nut, and the other of the screw and the nut generates an axial displacement and drives the rear wheel on one side of the vehicle to deflect through a pull rod.

[0005] The rear wheel steering device provided by the present application drives the rear wheel to deflect through a screw and a nut that mesh with each other. The axial force of the relative rotation of the screw and the nut is provided by the wheel speed difference of the rear wheels on both sides of the vehicle. That is, the screw and the nut in the rear wheel steering device of the present application drive the rear wheel on one side of the vehicle to steer in response to the wheel speed difference of the rear wheels on both sides of the vehicle. Compared with the structure in which the rear wheel steering device is driven by a steering motor and a reducer to drive the rear wheel to deflect, the rear wheel steering device provided by the present application has a simpler structure, a smaller volume and a lower cost.

[0006] In one implementation, the nut includes a plurality of planetary rollers, which surround the lead screw at intervals along the circumference of the lead screw and are respectively meshed with the lead screw, and the nut is meshed with the lead screw through the plurality of planetary rollers.

[0007] In this implementation, the screw and the nut cooperate to form a planetary roller screw structure. The planetary roller screw has a certain axial self-locking ability, which can keep the rear wheel relatively stable during the vehicle's driving and prevent the rear wheel from deflecting due to lateral impact from the road surface.

[0008] In one implementation, the rear-wheel steering gear includes a locking mechanism, which is used to lock the relative rotation of the lead screw and the nut to limit the deflection of one of the rear wheels on one side of the vehicle.

[0009] In this implementation, the locking mechanism is used to provide an axial locking force to ensure the stable attitude of the rear wheels during vehicle driving and improve the ability of the rear wheels to resist lateral impact.

[0010] In one implementation, the locking mechanism includes an electromagnetic switch and a movable member. The electromagnetic switch is fixed to the housing and is used to drive the movable member to move towards one of the rotating parts between the lead screw and the nut. The movable member is used to lock or unlock one of the rotating parts between the lead screw and the nut.

[0011] In this implementation, by controlling the electromagnetic switch, it is possible to control the movable member to lock or release one of the rotating parts between the lead screw and the nut, thereby realizing the active control of the rear-wheel steering gear. When the rear wheels of the vehicle need to deflect, the relative rotation of the lead screw and the nut is released through the electromagnetic switch, thereby driving the rear wheels to deflect by a preset angle.

[0012] In one implementation, the rear-wheel steering gear includes a displacement sensor, which is fixed to the housing and faces one of the rotating parts between the lead screw and the nut. The displacement sensor is used to detect the displacement of one of the rotating parts between the lead screw and the nut.

[0013] In this implementation, the displacement sensor is used to monitor the axial displacement formed after the relative rotation of the lead screw and the nut, thereby indirectly detecting the deflection angle of the rear wheels of the vehicle and realizing the closed-loop control of the rear-wheel deflection of the vehicle.

[0014] In a second aspect, the present application provides a vehicle, which includes two drive motors and two rear-wheel steering gears provided in any of the above implementations. Along the central connection line direction of the rear wheels on both sides of the vehicle, the two drive motors and the two rear-wheel steering gears are respectively arranged between the rear wheels on both sides of the vehicle. The two drive motors are arranged adjacent to each other, and the two rear-wheel steering gears are arranged at intervals. The two drive motors are used to respectively drive the rear wheels on both sides of the vehicle to rotate, and the two rear-wheel steering gears are used to respectively drive the rear wheels on both sides of the vehicle to deflect. Among them, in response to the front-wheel steering angle of the vehicle being less than the first preset rotation angle, the two drive motors are used to drive the rear wheels on both sides of the vehicle to generate a wheel speed difference less than or equal to the first preset wheel speed difference.

[0015] The vehicle provided by the present application drives the rear wheels on both sides of the vehicle to rotate respectively through two drive motors, and drives the rear wheels on both sides of the vehicle to deflect respectively through two rear-wheel steering gears. In the scenario where the vehicle is going straight or turning at a small angle, the wheel speed difference between the rear wheels on both sides of the vehicle is controlled to be small through the two drive motors, which can limit the deflection of the rear wheels on both sides of the vehicle and maintain the normal driving of the vehicle. Since the vehicle provided by the present application adopts the above-mentioned rear-wheel steering gear, the internal space of the vehicle is relatively large and the cost is reduced.

[0016] In an implementation manner, in response to the angle of the front wheels of the vehicle turning left being greater than a first preset turning angle, two drive motors are used to drive the rear wheels on both sides of the vehicle to generate a wheel speed difference greater than a first preset wheel speed difference, and the lead screws and nuts of two rear wheel steering gears respectively rotate relative to each other, and the two rear wheel steering gears drive the rear wheels on both sides of the corresponding connected vehicle to deflect leftward respectively.

[0017] In this implementation manner, when the angle of the front wheels of the vehicle turns left greatly, the vehicle provided by the present application can drive the rear wheels on both sides of the vehicle through two drive motors to form a large wheel speed difference, so that the two rear wheel steering gears drive the rear wheels on both sides of the vehicle to deflect leftward respectively to achieve smooth direction change.

[0018] In an implementation manner, in response to the angle of the front wheels of the vehicle turning left increasing, two drive motors are used to drive the rear wheels on both sides of the vehicle to generate an increasing wheel speed difference, and two rear wheel steering gears are used to drive the rear wheels on both sides of the vehicle to deflect leftward by increasing angles respectively.

[0019] In this implementation manner, the wheel speed difference formed by the two drive motors driving the rear wheels on both sides of the vehicle increases as the steering angle of the vehicle increases, that is, the deflection angles of the rear wheels on both sides of the vehicle provided by the present application change linearly with the steering angle of the vehicle. During the steering process of the vehicle, the deflection angles of the rear wheels and the front wheels match each other, which is beneficial to the smooth direction change of the vehicle.

[0020] In an implementation manner, during the process of the front wheels of the vehicle turning left, in response to the steering angle of the front wheels of the vehicle being greater than a second preset turning angle, two drive motors are used to drive the rear wheels on both sides of the vehicle to generate a wheel speed difference greater than a second preset wheel speed difference, and two rear wheel steering gears are used to drive the rear wheels on both sides of the vehicle to deflect leftward by increasing angles respectively, where the second preset turning angle is greater than the first preset turning angle, and the second preset wheel speed difference is greater than the first preset wheel speed difference. During the process of the front wheels of the vehicle turning from the first preset turning angle to the second preset turning angle, the wheel speed difference between the rear wheels on both sides of the vehicle is equal to the first preset wheel speed difference.

[0021] In this implementation manner, the wheel speed difference formed by the two drive motors driving the rear wheels on both sides of the vehicle increases stepwise as the steering angle of the vehicle increases, that is, the deflection angles of the rear wheels on both sides of the vehicle provided by the present application change stepwise with the steering angle of the vehicle. This is beneficial to simplifying the control logic of the two drive motors in the vehicle and reducing the control precision.

[0022] In an implementation manner, in response to the steering angle of the front wheels of the vehicle being greater than the first preset turning angle and lasting for a first preset duration, the two rear wheel steering gears lock the corresponding lead screws and nuts respectively, the lead screws and nuts of the two rear wheel steering gears do not rotate relative to each other respectively, and the deflection angles of the rear wheels on both sides of the vehicle remain unchanged.

[0023] In this implementation, during the continuous steering of the vehicle provided by the present application, the rear-wheel steering gear can lock the deflection angles of the two rear wheels of the vehicle, eliminating the need for two drive motors to continuously drive the two rear wheels of the vehicle to form a wheel speed difference, thereby reducing the power consumption of the vehicle and saving the computing resources of the vehicle.

[0024] In one implementation, during the process of the front wheels of the vehicle turning left and then returning to the straight position, in response to the angle of the front wheels of the vehicle returning to the straight position being greater than the third preset turning angle, the two rear-wheel steering gears respectively unlock the corresponding lead screws and nuts, and the lead screws and nuts of the two rear-wheel steering gears respectively rotate relative to each other. The two drive motors are used to drive the wheel speed difference generated by the two rear wheels of the vehicle to decrease, and the deflection angles of the two rear wheels of the vehicle decrease.

[0025] In this implementation, during the process of the vehicle provided by the present application returning to the straight position after steering, the two drive motors are used to reduce the wheel speed difference between the two rear wheels of the vehicle, thereby driving the two rear wheels on both sides of the vehicle to reduce the deflection angle and return to the straight position with the vehicle.

[0026] In one implementation, in response to the angular velocity of the front wheels of the vehicle turning left being greater than the first preset steering angular velocity, the two rear-wheel steering gears respectively unlock the corresponding lead screws and nuts, and the lead screws and nuts of the two rear-wheel steering gears respectively rotate relative to each other. The two drive motors are used to drive the wheel speed difference generated by the two rear wheels of the vehicle, and the two rear wheels of the vehicle respectively deflect to the left.

[0027] In this implementation, during the rapid steering of the vehicle provided by the present application, the rear-wheel steering gear drives the rear wheels to deflect in response to the wheel speed difference between the two rear wheels, avoiding restricting the deflection of the two rear wheels of the vehicle due to the rear-wheel steering gear being in the locked state.

[0028] In one implementation, in response to the slip ratio of any one of the two rear wheels of the vehicle being greater than the first preset slip ratio, the two rear-wheel steering gears respectively lock the corresponding lead screws and nuts, and the lead screws and nuts of the two rear-wheel steering gears respectively do not rotate relative to each other, and the deflection angles of the two rear wheels of the vehicle remain unchanged.

[0029] In this implementation, when any one of the rear wheels of the vehicle provided by the present application slips during steering, the rear-wheel steering gear locks the deflection of the two rear wheels of the vehicle to maintain the stability of the vehicle body posture and prevent the vehicle from yawing.

[0030] In one implementation, the steering wheel of the vehicle controls the steering of the vehicle wheels through electronic signals. During the reverse process of the vehicle, in response to the steering angle of the steering wheel of the vehicle turning left being greater than the fourth preset turning angle, the two drive motors are used to drive the wheel speed difference generated by the two rear wheels of the vehicle, the lead screws and nuts of the two rear-wheel steering gears respectively rotate relative to each other, and the two rear-wheel steering gears drive the two rear wheels of the vehicle connected correspondingly to deflect to the left respectively.

[0031] In this implementation, during the reverse process of the vehicle provided by the present application, the wheel speed difference between the two rear wheels is controlled by two drive motors, and two rear wheel steering gears can be used to drive the two rear wheels to deflect respectively, so as to realize reverse by rear wheel steering. The reverse process of the vehicle is smoother and simplifies the direction control logic of the vehicle.

[0032] In one implementation, during the reverse process of the vehicle, in response to the left steering angle of the vehicle's steering wheel being greater than the fourth preset rotation angle, the two front wheels on both sides of the vehicle deflect to the right.

[0033] In this implementation, during the reverse process of the vehicle provided by the present application, the front wheels can also be controlled to turn synchronously, so that the front wheels and rear wheels of the vehicle cooperate with each other to improve the reverse flexibility of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the present application, the drawings required for the implementation will be briefly introduced below. Obviously, the drawings in the following description are only some implementations of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 Schematic diagram of the external structure of the vehicle provided by an embodiment of the present application;

[0036] Figure 2 Schematic diagram of the structure of the rear wheel steering gear and the rear wheel provided by an embodiment of the present application;

[0037] Figure 3 Schematic diagram of the structure of the rear wheel steering gear and the rear wheel provided by an embodiment of the present application;

[0038] Figure 4 Schematic diagram of the partial structure of the vehicle provided by an embodiment of the present application;

[0039] Figure 5 Schematic diagram of the rear wheel deflection in the vehicle provided by an embodiment of the present application;

[0040] Figure 6 Schematic diagram of the internal structure of the rear wheel steering gear provided by an embodiment of the present application;

[0041] Figure 7 Control logic diagram of the vehicle provided by an embodiment of the present application in a driving state;

[0042] Figure 8 Control logic diagram of the vehicle provided by an embodiment of the present application in another driving state. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0044] The present application provides a rear-wheel steering gear. The rear-wheel steering gear includes a lead screw and a nut that mesh with each other. The housing of the rear-wheel steering gear is used to fixedly connect to the vehicle frame and fix one of the lead screw and the nut. The other of the lead screw and the nut is used to drive and connect one side rear wheel of the vehicle through a pull rod. The axial direction of the lead screw is parallel to the center connection line of the two side rear wheels of the vehicle. When the wheel speed difference between the two side rear wheels of the vehicle is greater than a first preset wheel speed difference, the lead screw is used to rotate relative to the nut to generate an axial displacement and drive one side rear wheel of the vehicle to deflect. The rear-wheel steering gear provided by the present application has a simpler structure, a smaller volume and a lower cost.

[0045] The present application provides a vehicle. The vehicle includes two drive motors and two rear-wheel steering gears provided in any of the above implementation manners. Along the center connection line direction of the two side rear wheels of the vehicle, the two drive motors and the two rear-wheel steering gears are respectively arranged between the two side rear wheels of the vehicle. The two drive motors are arranged adjacent to each other, and the two rear-wheel steering gears are arranged adjacent to each other. The two drive motors are used to respectively drive the two side rear wheels of the vehicle to rotate, and the two rear-wheel steering gears are used to respectively drive the two side rear wheels of the vehicle to deflect. When the front-wheel steering angle of the vehicle is less than a first preset steering angle, the two drive motors are used to drive the two side rear wheels of the vehicle to generate a wheel speed difference less than or equal to the first preset wheel speed difference. Because the vehicle provided by the present application adopts the above rear-wheel steering gear, the internal space of the vehicle is relatively large and the cost is reduced.

[0046] Please refer to Figure 1 the schematic diagram of the external structure of a vehicle 200 provided by an embodiment of the present application as shown.

[0047] As Figure 1 shown, the vehicle 200 provided by the present application includes a vehicle frame 201, at least two rear wheels 202 and at least one front wheel 203. The vehicle frame 201 is used to rotatably connect the rear wheels 202 and the front wheels 203. Each side of the vehicle 200 includes at least one rear wheel 202. The vehicle 200 also includes two drive motors 210 and two rear-wheel steering gears 100 provided by the present application. Along the center connection line direction of the two side rear wheels 202 of the vehicle 200, the two drive motors 210 and the two rear-wheel steering gears 100 are respectively arranged between the two side rear wheels 202 of the vehicle 200. Along the arrangement direction of the rear wheels 202 and the front wheels 203, the two drive motors 210 and the two rear-wheel steering gears 100 are arranged at intervals.

[0048] Among them, two drive motors 210 are arranged adjacent to each other between the two rear wheels 202 on both sides of the vehicle 200. The two drive motors 210 are used to drive the rotation of the two rear wheels 202 on both sides of the vehicle 200 respectively, and each drive motor 210 is used to drive the rotation of one rear wheel 202 on one side of the vehicle 200 to which it is correspondingly connected. Two rear-wheel steering gears 100 are arranged adjacent to each other between the two rear wheels 202 on both sides of the vehicle 200. The two rear-wheel steering gears 100 are used to drive the deflection of the two rear wheels 202 on both sides of the vehicle 200 respectively, and each rear-wheel steering gear 100 is used to drive the deflection of one rear wheel 202 on one side of the vehicle 200 to which it is correspondingly connected.

[0049] In one embodiment, the vehicle 200 further includes two front wheels 203, and the two front wheels 203 are arranged on both sides of the vehicle 200. When the vehicle 200 drives the rear wheels 202 to rotate through the two drive motors 210, the vehicle 200 is a dual-drive rear-mounted power system. In one embodiment, the vehicle 200 further includes two other drive motors 210, and each drive motor 210 is used to drive one front wheel 203 on one side of the vehicle 200. That is, in this embodiment, the vehicle 200 drives the two rear wheels 202 and the two front wheels 203 respectively through four drive motors, and the vehicle 200 is a four-wheel drive power system.

[0050] The vehicle 200 steers through the front wheels 203 during driving. In one embodiment, the steering system of the vehicle 200 drives the front wheels 203 to steer mechanically or hydraulically, and the corresponding vehicle 200 adopts a traditional automotive chassis. In another embodiment, the steering system of the vehicle 200 drives the front wheels 203 to steer by sending a steering command to a steering motor, and the corresponding vehicle 200 adopts a steer-by-wire chassis. The vehicle 200 provided in this application is applicable to any of the above-mentioned chassis architectures.

[0051] Please refer to Figure 2 and Figure 3 , where Figure 2 is a schematic structural diagram of the rear-wheel steering gear 100 and the rear wheel 202 provided in one embodiment of this application; Figure 3 is a schematic structural diagram of the rear-wheel steering gear 100 and the rear wheel 202 provided in one embodiment of this application.

[0052] The rear-wheel steering gear 100 provided in this application includes a housing 10, and the housing 10 is used to accommodate a lead screw 20 and a nut 30. The axial direction of the lead screw 20 is substantially parallel to the center connection line of the two rear wheels 202 on both sides of the vehicle 200. The nut 30 is sleeved outside the lead screw 20 and meshes with the lead screw 20. When the lead screw 20 and the nut 30 rotate relative to each other, a displacement along the axial direction of the lead screw 20 will be formed between the lead screw 20 and the nut 30. That is, the displacement between the lead screw 20 and the nut 30 is along the direction of the center connection line of the two rear wheels 202 on both sides of the vehicle 200. Either the lead screw 20 or the nut 30 of this application can be fixed for implementation.

[0053] The housing 10 of the rear-wheel steering gear 100 is used for fixedly connecting to the vehicle frame 201, and the housing 10 is also used for fixedly connecting to the lead screw 20 or fixedly connecting to the nut 30. Thus, the lead screw 20 or the nut 30 is fixedly connected to the vehicle frame 201. When the lead screw 20 and the nut 30 rotate relative to each other, one of the lead screw 20 and the nut 30 that is not relatively fixed to the vehicle frame 201 will rotate relative to the vehicle frame 201 and displace along the center connection line direction of the two rear wheels 202 on both sides of the vehicle 200 relative to the vehicle frame 201. One of the lead screw 20 and the nut 30 that is not relatively fixed to the vehicle frame 201 is also used for drivingly connecting to one rear wheel 202 on one side of the vehicle 200 through a pull rod 204, so as to drive the rear wheel 202 to deflect relative to the vehicle frame 201 to change the steering.

[0054] That is to say, one of the lead screw 20 and the nut 30 of the rear-wheel steering gear 100 of the present application is fixedly connected to the vehicle frame 201 through the housing 10, and the other of the lead screw 20 and the nut 30 is rotatable relative to the vehicle frame 201. The rotatable one of the lead screw 20 and the nut 30 is drivingly connected to one rear wheel 202 on one side of the vehicle 200 through a pull rod 204. When the lead screw 20 and the nut 30 rotate relative to each other, the rotatable one of the lead screw 20 and the nut 30 displaces relative to the vehicle frame 201 along the center connection line of the two rear wheels 202 on both sides of the vehicle 200, so as to drive one rear wheel 202 on one side of the vehicle 200 to deflect.

[0055] As Figure 2 shown, the housing 10 is used for fixedly connecting to the vehicle frame 201 and the nut 30, and the lead screw 20 is used for drivingly connecting to the pull rod 204. When the nut 30 rotates relative to the lead screw 20, the lead screw 20 drives the pull rod 204 to move along the center connection line direction of the two rear wheels 202 on both sides of the vehicle 200, and the rear-wheel steering gear 100 provided by the present application can drive the rear wheels 202 of the vehicle 200 to deflect.

[0056] As Figure 3 shown, the housing 10 is used for fixedly connecting to the vehicle frame 201 and the lead screw 20, and the nut 30 is used for drivingly connecting to the pull rod 204. When the nut 30 rotates relative to the lead screw 20, the nut 30 drives the pull rod 204 to move along the center connection line direction of the two rear wheels 202 on both sides of the vehicle 200, and the rear-wheel steering gear 100 provided by the present application can drive the rear wheels 202 of the vehicle 200 to deflect.

[0057] In Figure 2 the embodiment shown, the lead screw 20 is received in the housing 10, and the lead screw 20 axially expands and contracts in the inner cavity of the housing 10 to drive the pull rod 204. In Figure 3In the described embodiments, a shield may also be fixed to the outside of the nut 30. The nut 30 is accommodated in the shield to form protection and is drivingly connected to the pull rod 204 through the shield. The rear-wheel steering gear 100 of the present application does not limit the specific structures and connection manners of the housing 10, the lead screw 20, the nut 30, and the pull rod 204. Any combination form in the prior art that realizes transmission through the mutually meshing lead screw 20 and nut 30 and drives one rear wheel 202 of the vehicle 200 to deflect relative to the vehicle frame 201 through the housing 10 and the pull rod 204 is applicable to the rear-wheel steering gear 100 provided by the present application.

[0058] Thus, two rear-wheel steering gears 100 are arranged between the rear wheels 202 on both sides of the vehicle 200. Each rear-wheel steering gear 100 is used for drivingly connecting the vehicle frame 201 and one rear wheel 202 on one side, and is used for driving the corresponding connected rear wheel 202 to deflect relative to the vehicle frame 201.

[0059] In one embodiment, the housing 10 is used for rotatably connecting to the vehicle frame 201, so as to allow the rear-wheel steering gear 100 to rotate a certain angle relative to the vehicle frame 201. The rear-wheel steering gear 100 forms an included angle with the center connection line of the rear wheels 202 on both sides. The rear-wheel steering gear 100 also cooperates with the pull rod 204 to rotate to drive one rear wheel 202 to deflect. After the rear-wheel steering gear 100 rotates relative to the vehicle frame 201, it can drive the connected rear wheel 202 to form a larger-angle deflection, so as to improve the flexibility of the vehicle 200.

[0060] Please refer to Figure 4 , in which Figure 4 is a schematic diagram of a partial structure of the vehicle 200 provided by an embodiment of the present application.

[0061] For the convenience of description, in the embodiments of the present application, the rear wheels 202 on both sides of the vehicle 200 are respectively defined as the first rear wheel 2021 and the second rear wheel 2022. One of the two rear-wheel steering gears 100 close to the first rear wheel 2021 is the first rear-wheel steering gear 101, and one of the two rear-wheel steering gears 100 close to the second rear wheel 2022 is the second rear-wheel steering gear 102. Along the center connection line direction of the first rear wheel 2021 and the second rear wheel 2022, the first rear wheel 2021, the first rear-wheel steering gear 101, the second rear-wheel steering gear 102, and the second rear wheel 2022 are arranged in sequence.

[0062] Correspondingly, two drive motors 210 are also defined as the first drive motor 211 and the second drive motor 212 respectively. The first drive motor 211 is used for driving the first rear wheel 2021 to rotate, and the second drive motor 212 is used for driving the second rear wheel 2022 to rotate. Along the center connection line direction of the first rear wheel 2021 and the second rear wheel 2022, the first rear wheel 2021, the first drive motor 211, the second drive motor 212, and the second rear wheel 2022 are arranged in sequence. As Figure 4As shown, the first rear wheel 2021, the first rear-wheel steering gear 101, and the first drive motor 211 are arranged on the same side of the vehicle 200, and the second rear wheel 2022, the second rear-wheel steering gear 102, and the second drive motor 212 are arranged on the other side of the vehicle 200.

[0063] The first drive motor 211 is used to drive the first rear wheel 2021 to rotate independently, and the second drive motor 212 is used to drive the second rear wheel 2022 to rotate independently. The vehicle 200 of the present application can drive a speed difference to form between the first rear wheel 2021 and the second rear wheel 2022 through the cooperation of the first drive motor 211 and the second drive motor 212. Lateral forces are formed under the action of the speed difference between the first rear wheel 2021 and the second rear wheel 2022, and the lateral forces are respectively transmitted to the first rear-wheel steering gear 101 and the second rear-wheel steering gear 102 through two tie rods 204, thereby driving the respective lead screws 20 and nuts 30 of the first rear-wheel steering gear 101 and the second rear-wheel steering gear 102 to rotate relative to each other and respectively form axial displacements. The first rear-wheel steering gear 101 and the second rear-wheel steering gear 102 respectively drive the first rear wheel 2021 and the second rear wheel 2022 to deflect under the action of the speed difference, and the rear wheels 202 on both sides of the vehicle 200 are deflected.

[0064] Please refer to Figure 5 , in which Figure 5 is a schematic diagram of the deflection of the rear wheels 202 in the vehicle 200 provided by an embodiment of the present application.

[0065] As Figure 5 shown, assuming that the wheelbase of the vehicle 200 is L and the distance between the rear wheels 202 on both sides of the vehicle 200 is W, then the distance between the front wheels 203 on both sides of the vehicle 200 is also W. When the vehicle 200 turns left, the turning radius of the center of mass of the vehicle 200 is R, and the center of the curve is point O. The steering angle φ FL of the left front wheel 203 and the steering angle φ FR of the right front wheel 203 are fitted to obtain the steering angle φ 0 of the front wheels 203 of the vehicle 200.

[0066] At this time, the speed ratio of the rear wheels 202 on both sides of the vehicle 200 satisfies formula (1):

[0067]

[0068] wherein, V RL is the wheel speed of the first rear wheel 2021, and V RR is the wheel speed of the second rear wheel 2022.

[0069] Correspondingly, the speed ratio of the front wheels 203 on both sides of the vehicle 200 satisfies formula (2):

[0070]

[0071] Among them, V FL is the wheel speed of the left front wheel 203, and V FR is the wheel speed of the right front wheel 203.

[0072] It can be derived from formula (1) and formula (2) to obtain formula (3):

[0073]

[0074] Because the distance W between the two rear wheels 202 on both sides of the vehicle 200 is a fixed value, the rotational speed difference between the first rear wheel 2021 and the second rear wheel 2022 of the vehicle 200 is related to the turning radius R of the vehicle 200 and is also related to the wheel speeds of the two rear wheels 202 on both sides of the vehicle 200. During the left turn of the vehicle 200, the first rear wheel 2021 is located between the center O of the curve and the second rear wheel 2022, and the first rear wheel 2021 and the second rear wheel 2022 respectively form the inner and outer rear wheels 202 of the vehicle 200. After calculating the required wheel speed difference between the inner and outer rear wheels 202 of the vehicle 200 in a curve with a radius of R, the wheel speed difference between the two rear wheels 202 on both sides of the vehicle 200 can be controlled to control the lateral forces received by the first rear wheel 2021 and the second rear wheel 2022, so that the first rear wheel steering gear 101 and the second rear wheel steering gear 102 respectively form an axial displacement under the action of the lateral force, and then drive the first rear wheel 2021 and the second rear wheel 2022 to deflect to the left, improving the problem of understeering or oversteering of the vehicle 200.

[0075] That is to say, because the rear wheel steering gear 100 provided in this application can generate an axial displacement in response to the lateral force received by the connected rear wheel 202, and then drive the connected rear wheel 202 to deflect. The vehicle 200 provided in this application can form a rotational speed difference by driving the two rear wheels 202 on both sides through two drive motors 210 respectively, and then control the magnitude of the lateral forces received by the two rear wheel steering gears 100, so as to control the deflection angles of the two rear wheels 202 respectively through the two rear wheel steering gears 100.

[0076] The rotational speed difference between the two rear wheels 202 on both sides of the vehicle 200 is related to the turning radius R of the vehicle 200, and the turning radius R of the vehicle 200 can refer to the steering angle φ of the front wheels 203 of the vehicle 200 0 . It can be understood that the larger the turning radius R of the vehicle 200, the 0 smaller the steering angle φ of the front wheels 203 of the vehicle 200. On the contrary, the smaller the turning radius R of the vehicle 200, the 0 larger the steering angle φ of the front wheels 203 of the vehicle 200. For the vehicle 200 of this application, in response to the steering angle of the front wheels 203 of the vehicle 200 being less than the first preset turning angle φ 1Two drive motors 210 are used to drive the rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference less than or equal to the first preset wheel speed difference V 1 , the first preset wheel speed difference V 1 can generally be set to 5 - 15 r / min.

[0077] Among them, the first preset wheel speed difference V 1 can be understood as the wheel speed difference at which the lead screw 20 and the nut 30 in the rear wheel steering gear 100 provided in the present application start to rotate relative to each other. That is, when the wheel speed difference between the rear wheels 202 on both sides of the vehicle 200 in the present application is greater than the first preset wheel speed difference V 1 , the lead screws 20 of the two rear wheel steering gears 100 are used to rotate relative to the nuts 30 to generate an axial displacement and drive the rear wheels 202 on both sides of the vehicle 200 to deflect. The lead screw 20 and the nut 30 in the rear wheel steering gear 100 provided in the present application drive one rear wheel 202 of the vehicle 200 to turn in response to the wheel speed difference between the rear wheels 202 on both sides of the vehicle 200. Compared with the structure that drives the rear wheel steering gear 100 to drive the rear wheels 202 to deflect through a steering motor and a speed reducer, the structure of the rear wheel steering gear 100 provided in the present application is simpler, smaller in volume and lower in cost.

[0078] When the vehicle 200 provided in the present application is driving straight or passing through a curve with a large turning radius R, the two drive motors 210 are used to control the rear wheels 202 on both sides of the vehicle 200 to have a smaller rotational speed difference, so as to limit the deflection of the rear wheels 202 on both sides of the vehicle 200 and maintain the normal driving of the vehicle 200. Because the vehicle 200 provided in the present application adopts the rear wheel steering gear 100, the internal space of the vehicle 200 is relatively large and the cost is reduced.

[0079] In one embodiment, the nut 30 includes a plurality of planetary rollers. Along the circumferential direction of the lead screw 20, the plurality of planetary rollers are spaced around the lead screw 20 and respectively mesh with the lead screw 20. The nut 30 meshes with the lead screw 20 through the plurality of planetary rollers. Thus, the lead screw 20 and the nut 30 cooperate to form the structure of a planetary roller screw 20. The planetary roller screw 20 has a certain axial self-locking ability, which can keep the rear wheels 202 relatively stable during the driving of the vehicle 200 and avoid the rear wheels 202 from deflecting due to the lateral impact of the road surface.

[0080] Exemplarily, the nut 30 forms a self-locking force with the lead screw 20 through a plurality of planetary rollers. The magnitude of the self-locking force matches the lateral force formed when the wheel speed difference between the rear wheels 202 on both sides of the vehicle 200 is equal to the first preset wheel speed difference V 1 so that a self-locking force can be formed between the two rear wheel steering gears 100 when the wheel speed difference between the rear wheels 202 on both sides of the vehicle 200 is less than the first preset wheel speed difference V 1When the axial displacement of itself is restricted by the self-locking of the planetary roller screw, a wheel speed difference greater than the first preset wheel speed difference V is generated between the rear wheels 202 on both sides of the vehicle 200. 1 When driving, the planetary roller screw is driven to generate a rotational motion to form an axial displacement and drive the rear wheel 202 to deflect.

[0081] In one embodiment, the two drive motors 210 include a motor controller, and the motor controller is used to send control signals to the two drive motors 210 respectively to control the two drive motors 210 to cooperate to form a desired wheel speed difference.

[0082] In one embodiment, the two drive motors 210 each include a motor controller, and the two motor controllers are used to send control signals to one drive motor 210 connected thereto respectively, and the two motor controllers cooperate to control the two drive motors 210 to form a desired wheel speed difference.

[0083] In one embodiment, the rear wheel steering gear 100 includes a locking mechanism 40, and the locking mechanism 40 is used to lock the relative rotation of the lead screw 20 and the nut 30 to limit the deflection of the rear wheel 202 on one side of the vehicle 200. In this embodiment, the locking mechanism 40 is also used to provide an axial locking force to ensure the attitude stability of the rear wheel 202 during the driving of the vehicle 200 and improve the ability of the rear wheel 202 to resist lateral impact.

[0084] Please refer to Figure 6 where Figure 6 is a schematic internal structure diagram of the rear wheel steering gear 100 provided by an embodiment of the present application.

[0085] In one embodiment, the locking mechanism 40 and the nut 30 are arranged at intervals along the axial direction of the lead screw 20. The locking mechanism 40 can be used to lock the rotation of one of the nut 30 or the lead screw 20 that is not fixedly connected to the housing 10, that is, the locking mechanism 40 is used to lock the rotation of one of the nut 30 and the lead screw 20, thereby restricting the relative rotation between the nut 30 and the lead screw 20.

[0086] In one embodiment, the locking mechanism 40 includes an electromagnetic switch 41 and a movable member 42. The electromagnetic switch 41 is fixed to the housing 10, and the electromagnetic switch 41 is used to drive the movable member 42 to move towards one of the lead screw 20 and the nut 30 that rotates, and the movable member 42 is used to lock or release the rotation of one of the lead screw 20 and the nut 30.

[0087] In this embodiment, the electromagnetic switch 41 can be used to control the movement of the movable member 42 within the housing 10. The movement direction of the movable member 42 is towards or away from the rotating one of the lead screw 20 and the nut 30. When the movable member 42 moves towards the rotating one, the relative rotation of the lead screw 20 and the nut 30 can be locked. When the movable member 42 moves away from the rotating one, the relative rotation of the lead screw 20 and the nut 30 can be released. Thus, the active control of the rear-wheel steering gear 100 is achieved. When it is necessary to deflect the rear wheels 202 of the vehicle 200, the electromagnetic switch 41 is used to drive the movable member 42 to release the relative rotation of the lead screw 20 and the nut 30, thereby driving the rear wheels 202 to deflect by a preset angle.

[0088] The locking mechanism 40 can provide a relatively large locking force and relatively high reliability. The locking mechanism 40 can achieve the active control of the rear-wheel steering gear 100, ensure the attitude stability of the rear wheels 202 during the driving of the vehicle 200, and improve the ability of the rear wheels 202 to resist lateral impact.

[0089] In one embodiment, the motor controller is used to issue a control signal to control the electromagnetic switch 41 to open or close, thereby driving the movable member 42 to move towards or away from the rotating one of the nut 30 and the lead screw 20.

[0090] In one embodiment, the nut 30 of the rear-wheel steering gear 100 includes a plurality of planetary rollers, and the rear-wheel steering gear 100 further includes a locking mechanism 40. Through the cooperation of the locking mechanism 40 and the planetary roller lead screw, the axial locking ability of the rear-wheel steering gear 100 can be further improved, and the effect of active control of the rear-wheel steering gear 100 can be achieved, ensuring the smooth driving of the vehicle 200.

[0091] In one embodiment, the rear-wheel steering gear 100 includes a displacement sensor 50. The displacement sensor 50 is fixed to the housing 10 and faces the rotating one of the lead screw 20 and the nut 30. The displacement sensor 50 is used to detect the displacement of the rotating one of the lead screw 20 and the nut 30.

[0092] In this embodiment, the displacement sensor 50 is used to monitor the axial displacement formed after the relative rotation of the lead screw and the nut 30, thereby indirectly detecting the deflection angle of the rear wheels 202 of the vehicle 200 and realizing the closed-loop control of the deflection of the rear wheels 202 of the vehicle 200. When the axial displacement of the lead screw 20 or the nut 30 in any rear-wheel steering gear 100 deviates from the expected displacement, the deflection angle of the rear wheels 202 on the side of the vehicle 200 connected to the rear-wheel steering gear 100 deviates from the expected angle. At this time, the deflection angle of the rear wheels 202 on this side can be adjusted by controlling the wheel speed difference between the rear wheels 202 on both sides of the vehicle 200, so that the rear wheels 202 on this side deflect towards the expected angle, ensuring the vehicle 200 passes through the curve smoothly.

[0093] An embodiment, the motor controller is used to receive the monitoring data of the displacement sensor 50.

[0094] An embodiment, in response to the steering angle of the front wheels 203 of the vehicle 200 turning left being greater than the first preset turning angle φ 1 Two drive motors 210 are used to drive the rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference greater than the first preset wheel speed difference V 1 , the lead screws 20 and nuts 30 of the two rear wheel steering gears 100 rotate relatively respectively, and the two rear wheel steering gears 100 drive the rear wheels 202 on both sides of the corresponding connected vehicle 200 to deflect leftward respectively. The first preset turning angle φ 1 Is usually a relatively small turning angle, such as 3 degrees, etc.

[0095] Please refer to Figure 7 And Figure 8 , where Figure 7 Is the control logic diagram of the vehicle 200 provided by an embodiment of the present application in a driving state; Figure 8 Is the control logic diagram of the vehicle 200 provided by an embodiment of the present application in another driving state.

[0096] Such as Figure 7 As shown, when the steering angle of the front wheels 203 of the vehicle 200 is less than the first preset turning angle φ 1 When, the motor controller controls to issue a control signal to control the locking mechanism 40 to lock the relative rotation of the lead screw 20 and the nut 30. The rear wheel steering gear 100 restricts the displacement of the tie rod 204, and the rear wheels 202 on both sides of the vehicle 200 drive the vehicle 200 to travel in a non-deflected form. The displacement sensor 50 is used to monitor the axial displacement of the lead screw 20 or the nut 30, and transmits the monitoring data to the motor controller, so as to form a closed-loop control of the rear wheel steering gear 100.

[0097] The motor controller also issues a control signal to control the first drive motor 211 and the second drive motor 212 to drive the first rear wheel 2021 and the second rear wheel 2022 to rotate at a desired speed respectively.

[0098] Such as Figure 8 As shown, when the front wheels 203 of the vehicle 200 deflect leftward and the steering angle is greater than the first preset turning angle φ 1 When, the body of the vehicle 200 yaws leftward. The motor controller controls to issue a control signal to make the two drive motors 210 form a wheel speed difference. At this time, the rotational speed of the left first rear wheel 2021 is less than that of the second rear wheel 2022, and the rotational speed difference between the first rear wheel 2021 and the second rear wheel 2022 is greater than the first preset wheel speed difference V 1。The first rear wheel 2021 and the second rear wheel 2022 respectively generate lateral forces and transmit the lateral forces to the first rear wheel steering gear 101 and the second rear wheel steering gear 102 through the tie rods 204.

[0099] The motor controller also issues a control signal to unlock the locking mechanism 40. Under the action of the lateral force, the lead screws 20 and the nuts 30 of the two rear wheel steering gears 100 rotate relative to each other. The two rear wheel steering gears 100 respectively drive the two tie rods 204 to move leftward, and the rear wheels 202 on both sides of the vehicle 200 are respectively deflected leftward. Among them, the rotational speed of the first rear wheel 2021 is relatively small, and the lateral force generated by it is relatively small. The deflection angle of the first rear wheel 2021 is smaller than the deflection angle of the second rear wheel 2022. The vehicle 200 can change its direction smoothly through the deflection of the rear wheels 202 on both sides.

[0100] In one embodiment, in response to the angle of the front wheels 203 of the vehicle 200 turning right being greater than the first preset turning angle φ 1 The two drive motors 210 are used to drive the rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference greater than the first preset wheel speed difference V 1 , the lead screws 20 and the nuts 30 of the two rear wheel steering gears 100 respectively generate relative rotations, and the two rear wheel steering gears 100 drive the rear wheels 202 on both sides of the corresponding connected vehicle 200 to be respectively deflected rightward.

[0101] Similar to the scenario of the above embodiment, when the vehicle 200 turns right, the two drive motors 210 are used to drive the rotational speed of the first rear wheel 2021 to be greater than the rotational speed of the second rear wheel 2022, and the wheel speed difference between the two rear wheels 202 is made greater than the first preset wheel speed difference V 1 , the rear wheels 202 on both sides of the vehicle 200 are respectively deflected rightward, and the vehicle 200 can change its direction smoothly. Among them, the rotational speed of the second rear wheel 2022 is relatively small, and the deflection angle of the first rear wheel 2021 is greater than the deflection angle of the second rear wheel 2022.

[0102] Thus, when the vehicle 200 turns towards one side and the turning angle is relatively large, the two drive motors 210 drive the rear wheels 202 on both sides of the vehicle 200 to form a wheel speed difference greater than the first preset wheel speed difference V 1 , so that the two rear wheel steering gears 100 respectively drive the two tie rods 204 to displace towards the same side where the vehicle 200 turns, and drive the rear wheels 202 on both sides of the vehicle 200 to deflect towards the same side where the vehicle 200 turns. The vehicle 200 can change its direction smoothly through the deflection of the rear wheels 202 on both sides.

[0103] In one embodiment, in response to the angle of the front wheels 203 of the vehicle 200 turning left increasing, the two drive motors 210 are used to drive the wheel speed difference generated by the rear wheels 202 on both sides of the vehicle 200 to increase, and the two rear wheel steering gears 100 are used to drive the angles of the rear wheels 202 on both sides of the vehicle 200 to deflect leftward to increase respectively.

[0104] In this embodiment, when the turning angle of the front wheels 203 of the vehicle 200 to the left is greater than the first preset turning angle φ 1 and continues to increase, it is necessary to further increase the turning angles of the two rear wheels 202 on both sides of the vehicle 200 to the left to adapt to the turning angle of the front wheels 203 of the vehicle 200. At this time, the two drive motors 210 drive the two rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference relative to the first preset wheel speed difference V 1 to further increase, that is, the wheel speed of the second rear wheel 2022 is further increased relative to the wheel speed of the first rear wheel 2021, so as to increase the turning angles of the two rear wheels 202 on both sides of the vehicle 200 to the left.

[0105] An embodiment, in response to the increase in the turning angle of the front wheels 203 of the vehicle 200 to the right, the two drive motors 210 are used to drive the two rear wheels 202 on both sides of the vehicle 200 to generate an increased wheel speed difference. At this time, the two drive motors 210 drive the two rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference relative to the first preset wheel speed difference V 1 to further increase, that is, the wheel speed of the first rear wheel 2021 is further increased relative to the wheel speed of the second rear wheel 2022, and the two rear wheel steering gears 100 are used to drive the two rear wheels 202 on both sides of the vehicle 200 to turn to the right by increased angles respectively.

[0106] In the above two embodiments, the wheel speed difference formed by the two drive motors 210 driving the two rear wheels 202 on both sides of the vehicle 200 increases as the turning angle of the vehicle 200 increases. That is, the turning angles of the two rear wheels 202 on both sides of the vehicle 200 provided in this application change linearly with the turning angle of the front wheels 203 of the vehicle 200. The turning angles of the rear wheels 202 and the front wheels 203 of the vehicle 200 match each other during the turning process, which is beneficial to the vehicle 200 to change direction smoothly.

[0107] An embodiment, during the process of the front wheels 203 of the vehicle 200 turning to the left, in response to the turning angle of the front wheels 203 of the vehicle 200 being greater than the second preset turning angle φ 2 the two drive motors 210 are used to drive the two rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference greater than the second preset wheel speed difference V 2 , and the two rear wheel steering gears 100 are used to drive the two rear wheels 202 on both sides of the vehicle 200 to turn to the left by increased angles respectively, where the second preset turning angle φ 2 is greater than the first preset turning angle φ 1 , and the second preset wheel speed difference V 2 is greater than the first preset wheel speed difference V 1 . During the process of the front wheels 203 of the vehicle 200 turning from the first preset turning angle φ 1 to the second preset turning angle φ 2 , the wheel speed difference between the two rear wheels 202 of the vehicle 200 is equal to the first preset wheel speed difference V1 .

[0108] An embodiment, during the process of the front wheels 203 of the vehicle 200 turning right, in response to the steering angle of the front wheels 203 of the vehicle 200 being greater than the second preset turning angle φ 2 The wheel speed difference generated by the two drive motors 210 for driving the rear wheels 202 on both sides of the vehicle 200 is greater than the second preset wheel speed difference V 2 , and the two rear wheel steering gears 100 are used to drive the rear wheels 202 on both sides of the vehicle 200 to deflect to the right by increasing angles respectively, where the second preset turning angle φ 2 is greater than the first preset turning angle φ 1 , and the second preset wheel speed difference V 2 is greater than the first preset wheel speed difference V 1 . During the process of the front wheels 203 of the vehicle 200 turning from the first preset turning angle φ 1 to the second preset turning angle φ 2 , the wheel speed difference between the rear wheels 202 on both sides of the vehicle 200 is equal to the first preset wheel speed difference V 1 .

[0109] In the above two embodiments, when the steering angle of the front wheels 203 of the vehicle 200 is greater than the first preset turning angle φ 1 and continues to increase, if the steering angle of the front wheels 203 does not exceed the second preset turning angle φ 2 , then the wheel speed difference formed by the two drive motors 210 driving the rear wheels 202 on both sides of the vehicle 200 is maintained at the first preset wheel speed difference V 1 . The relative locking between the lead screw 20 and the nut 30 in the two rear wheel steering gears 100 makes the deflection angles of the rear wheels 202 on both sides of the vehicle 200 relatively fixed, which is beneficial to the vehicle 200 to maintain the stability of the body.

[0110] When the steering angle of the front wheels 203 of the vehicle 200 is greater than the second preset turning angle φ 2 , the wheel speed difference formed by the two drive motors 210 driving the rear wheels 202 on both sides of the vehicle 200 is increased to the second preset wheel speed difference V 2 . The relative rotation between the lead screw 20 and the nut 30 in the two rear wheel steering gears 100 makes the deflection angles of the rear wheels 202 on both sides of the vehicle 200 increase further to match the steering angle of the front wheels 203.

[0111] Thus, the wheel speed difference formed by the two drive motors 210 driving the rear wheels 202 on both sides of the vehicle 200 increases step by step as the steering angle of the vehicle 200 increases, that is, the deflection angles of the rear wheels 202 on both sides of the vehicle 200 provided in this application change step by step with the steering angle of the vehicle 200. Such a control method can simplify the control logic of the two drive motors 210 in the vehicle 200 and reduce the control precision requirements for the two drive motors 210.

[0112] An embodiment, in response to the steering angle of the front wheels 203 of the vehicle 200 being greater than the first preset steering angle φ 1 and lasting for the first preset duration t1, the two rear-wheel steering gears 100 lock the corresponding lead screws 20 and nuts 30 respectively to prevent relative rotation, and the deflection angles of the two rear wheels 202 on both sides of the vehicle 200 remain unchanged. Exemplarily, the rear-wheel steering gear 100 locks the relative rotation of the lead screw 20 and the nut 30 through a locking mechanism 40 or through the self-locking force of the lead screw 20 and the nut 30.

[0113] In this embodiment, when the steering angle of the front wheels 203 of the vehicle 200 is greater than the first preset steering angle φ 1 and the two drive motors 210 drive the two rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference greater than the first preset wheel speed difference V 1 After that, if the duration of the two drive motors 210 driving the two rear wheels 202 on both sides of the vehicle 200 exceeds the first preset duration t1, it can be understood that the vehicle 200 is in the process of continuous steering.

[0114] In such a scenario, when the two rear wheels 202 on both sides of the vehicle 200 are deflected to the preset angle, the requirement for the vehicle 200 to continuously steer can be met. By locking the deflection angles of the two rear wheels 202 of the vehicle 200 through the rear-wheel steering gear 100, the two drive motors 210 are saved from continuously driving the two rear wheels 202 on both sides of the vehicle 200 to form a wheel speed difference, thereby reducing the power consumption of the vehicle 200 and saving the computing resources of the vehicle 200.

[0115] An embodiment, during the process of the front wheels 203 of the vehicle 200 turning to the left and then returning to the straight position, in response to the return angle of the front wheels 203 of the vehicle 200 being greater than the third preset steering angle φ 3 , the two rear-wheel steering gears 100 release the corresponding lead screws 20 and nuts 30 respectively to generate relative rotation, and the two drive motors 210 are used to drive the wheel speed difference generated by the two rear wheels 202 on both sides of the vehicle 200 to decrease, and the deflection angles of the two rear wheels 202 on both sides of the vehicle 200 decrease.

[0116] An embodiment, during the process of the front wheels 203 of the vehicle 200 turning to the right and then returning to the straight position, in response to the return angle of the front wheels 203 of the vehicle 200 being greater than the third preset steering angle φ 3 , the two rear-wheel steering gears 100 release the corresponding lead screws 20 and nuts 30 respectively to generate relative rotation, and the two drive motors 210 are used to drive the wheel speed difference generated by the two rear wheels 202 on both sides of the vehicle 200 to decrease, and the deflection angles of the two rear wheels 202 on both sides of the vehicle 200 decrease.

[0117] In the above two embodiments, when the steering angle of the front wheels 203 of the vehicle 200 is greater than the first preset steering angle φ 1, the two drive motors 210 drive the rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference greater than the first preset wheel speed difference V 1 After that, during the process of the vehicle 200 returning to the straight position after steering, the present application controls the front wheels 203 to deflect in the reverse direction. At this time, the rear wheels 202 on both sides of the vehicle 200 are in a deflected state, and the rear wheels 202 will form a reverse lateral force during the process of the vehicle 200 returning to the straight position and drive the two rear wheel steering gears 100 to return to the straight position respectively.

[0118] Thus, when the steering angle of the front wheels 203 of the vehicle 200 provided by the present application is greater than the third preset steering angle φ 3 The vehicle 200 provided by the present application reduces the wheel speed difference between the rear wheels 202 on both sides of the vehicle 200 through the two drive motors 210, and keeps the lead screw 20 and the nut 30 in the rear wheel steering gear 100 relatively rotatable. The rear wheels 202 on both sides of the vehicle 200 reduce the deflection angle and return to the straight position along with the vehicle 200.

[0119] In one embodiment, the third preset steering angle φ 3 is less than or equal to the first preset steering angle φ 1 , and the timing of the two drive motors 210 reducing the wheel speed difference during the process of the vehicle 200 returning to the straight position after steering can be appropriately advanced, and the relative rotation of the lead screw 20 and the nut 30 is released in advance, which is beneficial to ensuring that the rear wheels 202 on both sides of the vehicle 200 are fully returned to the straight position.

[0120] In one embodiment, in response to the angular velocity of the front wheels 203 of the vehicle 200 turning to the left being greater than the first preset steering angular velocity ω 1 The two rear wheel steering gears 100 respectively release the corresponding lead screw 20 and nut 30 to generate relative rotation, the two drive motors 210 are used to drive the rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference, and the rear wheels 202 on both sides of the vehicle 200 deflect to the left respectively.

[0121] In one embodiment, in response to the angular velocity of the front wheels 203 of the vehicle 200 turning to the right being greater than the first preset steering angular velocity ω 1 The two rear wheel steering gears 100 respectively release the corresponding lead screw 20 and nut 30 to generate relative rotation, the two drive motors 210 are used to drive the rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference, and the rear wheels 202 on both sides of the vehicle 200 deflect to the right respectively.

[0122] In the above two embodiments, when the angular velocity of the front wheels 203 of the vehicle 200 provided by the present application turning to one side exceeds the first preset steering angular velocity ω 1When the vehicle 200 is in the process of rapid steering. Before this process, the vehicle 200 may be in a straight - driving state or in a state of uniform cornering. That is, before the vehicle 200 enters rapid steering, the lead screw 20 and the nut 30 of the rear - wheel steering gear 100 may be in a relatively locked state. During the rapid - steering process of the vehicle 200, the body stability decreases. It is advisable to release the relative rotation of the lead screw 20 and the nut 30 and drive the two rear wheels 202 on both sides of the vehicle 200 to deflect, so as to cooperate with the rapid steering of the vehicle 200.

[0123] Accordingly, in response to the angular velocity of the front wheels 203 of the vehicle 200 turning to either side being greater than the first preset steering angular velocity ω 1 , the two drive motors 210 are used to control the wheel - speed difference between the two rear wheels 202 of the vehicle 200 to drive the two rear wheels 202 on both sides to deflect, which can improve the body stability of the vehicle 200 and ensure the vehicle 200 steers smoothly and quickly.

[0124] In one embodiment, in response to the slip ratio of any one of the two rear wheels 202 of the vehicle 200 being greater than the first preset slip ratio k 1 , the two rear - wheel steering gears 100 respectively lock the corresponding lead screws 20 and nuts 30 so that no relative rotation occurs, and the deflection angles of the two rear wheels 202 on both sides of the vehicle 200 remain unchanged.

[0125] In this embodiment, when the slip ratio of any one of the rear wheels 202 of the vehicle 200 provided in this application is greater than the first preset slip ratio k during the steering process 1 , it indicates that the grip of the rear wheel 202 on this side is insufficient and slipping occurs. At this time, even if the two drive motors 210 drive the two rear wheels 202 on both sides of the vehicle 200 to form a wheel - speed difference, it is impossible to provide the desired lateral force for the two rear wheels 202 on both sides, and thus it is impossible to drive the two rear wheels 202 on both sides to deflect to the desired angle.

[0126] On the other hand, when one side of the rear wheels 202 of the vehicle 200 slips, the rear - wheel steering gear 100 locking the deflection of the two rear wheels 202 of the vehicle 200 can maintain the body attitude stability, prevent the vehicle 200 from yawing, and ensure user safety.

[0127] In one embodiment, the steering wheel of the vehicle 200 controls the wheel steering of the vehicle 200 through an electronic signal. During the reverse process of the vehicle 200, in response to the left - turning angle of the steering wheel of the vehicle 200 being greater than the fourth preset turning angle φ 4 , the two drive motors 210 are used to drive the two rear wheels 202 of the vehicle 200 to generate a wheel - speed difference, the lead screws 20 and nuts 30 of the two rear - wheel steering gears 100 respectively generate relative rotation, and the two rear - wheel steering gears 100 drive the two rear wheels 202 on both sides of the corresponding connected vehicle 200 to deflect to the left respectively.

[0128] An embodiment, during the reverse driving of the vehicle 200, in response to the right steering angle of the steering wheel of the vehicle 200 being greater than the fourth preset rotation angle φ 4 , the two drive motors 210 are used to drive the rear wheels 202 on both sides of the vehicle 200 to generate a wheel speed difference. The lead screws 20 and nuts 30 of the two rear-wheel steering gears 100 rotate relatively respectively, and the two rear-wheel steering gears 100 drive the rear wheels 202 on both sides of the corresponding connected vehicle 200 to deflect to the right respectively.

[0129] In the above two embodiments, the vehicle 200 adopts a steer-by-wire chassis. The steering wheel of the vehicle 200 controls the wheel steering of the vehicle 200 through an electronic signal. During the reverse driving of the vehicle 200 provided in this application, by controlling the two drive motors 210 to generate a wheel speed difference between the rear wheels 202 on both sides, the two rear-wheel steering gears 100 can be used to drive the two rear wheels 202 to deflect respectively, so as to realize reverse driving through the steering of the rear wheels 202.

[0130] Among them, the rear wheels 202 on both sides of the vehicle 200 serve as the steering guide wheels of the vehicle 200 during reverse driving, and their steering actions are similar to the steering actions of the vehicle 200 when the front wheels 203 are used as the steering guide wheels during forward driving. The vehicle 200 provided in this application can use the rear wheels 202 to guide the vehicle 200 to complete reverse driving through the cooperation of the drive motor 210 and the rear-wheel steering gear 100, and the direction control logic of the vehicle 200 during reverse driving is relatively simple.

[0131] On the other hand, the rear wheels 202 can also be used to provide power for the vehicle 200 to reverse, that is, the rear wheels 202 can also serve as the traction wheels of the vehicle 200 during reverse driving, and their traction actions are similar to the traction actions of the vehicle 200 when the front wheels 203 are used as the traction wheels during forward driving, which can further simplify the control logic of the vehicle 200 during reverse driving and ensure that the vehicle 200 completes reverse driving smoothly.

[0132] An embodiment, the fourth preset rotation angle φ 4 is less than or equal to the first preset rotation angle φ 1 , and the vehicle 200 can also complete reverse driving in a posture with a small steering angle, which is convenient for the vehicle 200 to adapt to more driving scenarios.

[0133] An embodiment, during the reverse driving of the vehicle 200, in response to the left steering angle of the steering wheel of the vehicle 200 being greater than the fourth preset rotation angle φ 4 The front wheels 203 on both sides of the vehicle 200 deflect to the right.

[0134] An embodiment, during the reverse driving of the vehicle 200, in response to the right steering angle of the steering wheel of the vehicle 200 being greater than the fourth preset rotation angle φ 4 The front wheels 203 on both sides of the vehicle 200 deflect to the left.

[0135] In the above two embodiments, the vehicle 200 provided by the present application can also control the front wheels 203 to steer synchronously during the reverse process, so that the front wheels 203 and the rear wheels 202 of the vehicle 200 cooperate with each other to improve the reverse flexibility of the vehicle 200. Since the vehicle speed of the vehicle 200 is relatively low during the reverse process, when the two drive motors 210 drive the rear wheels 202 on both sides of the vehicle 200 to form a wheel speed difference, the vehicle 200 can also control the front wheels 203 to deflect in the direction opposite to that of the rear wheels 202, thereby forming a posture in which the front wheels 203 on both sides of the vehicle 200 deflect towards one side of the vehicle 200 and the rear wheels 202 on both sides of the vehicle 200 deflect towards the other side of the vehicle 200. When the vehicle 200 is in a posture where the deflection directions of the front wheels 203 and the rear wheels 202 are opposite, the turning radius becomes smaller and the flexibility is improved, which is beneficial for the vehicle 200 to complete the reverse more smoothly.

[0136] Finally, it should be noted that the rear wheel steering gear provided by the present application can also be used for the front wheel steering of the vehicle where the front wheels have independent drive, to help the front wheels use the speed difference to achieve steering.

[0137] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the protection scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these changes and modifications.

Claims

1. A rear wheel steering gear, characterized in that: The rear wheel steering gear comprises a screw and a nut meshing with each other, the housing of the rear wheel steering gear is used to fix the vehicle frame and to fix one of the screw and the nut, the other of the screw and the nut is used to connect one side of the rear wheel of the vehicle through a pull rod transmission, the axial direction of the screw is parallel to the center line of the rear wheels on both sides of the vehicle, wherein: The wheel speed difference between the rear wheels on both sides of the vehicle is greater than the first preset wheel speed difference. The screw is used to rotate relative to the nut, and the other of the screw and the nut generates axial displacement and drives the rear wheel on one side of the vehicle to deflect through a pull rod.

2. The rear wheel steering gear according to claim 1, characterized in that: The nut includes a plurality of planetary rollers, which surround the lead screw at intervals along the circumference of the lead screw and are respectively engaged with the lead screw, and the nut is engaged with the lead screw through the plurality of planetary rollers.

3. The rear wheel steering gear according to claim 1 or 2, characterized in that: The rear wheel steering gear comprises a locking mechanism, and the locking mechanism is used to lock the relative rotation of the lead screw and the nut to limit the deflection of the rear wheel on one side of the vehicle.

4. The rear wheel steering gear according to claim 3, characterized in that: The locking mechanism includes an electromagnetic switch and a movable part. The electromagnetic switch is fixed to the housing and is used to drive the movable part to move toward a rotating one of the lead screw and the nut. The movable part is used to lock or unlock the rotating one of the lead screw and the nut.

5. The rear wheel steering gear according to any one of claims 4, characterized in that: The rear wheel steering gear includes a displacement sensor fixed to the housing and facing the rotating one of the lead screw and the nut, the displacement sensor being used to detect a displacement amount of the rotating one of the lead screw and the nut.

6. A vehicle, characterized in that: The vehicle comprises two drive motors and two rear wheel steering devices according to any one of claims 1 to 5. Along the center line direction of the rear wheels on both sides of the vehicle, the two drive motors and the two rear wheel steering devices are respectively arranged between the rear wheels on both sides of the vehicle, the two drive motors are arranged adjacent to each other, and the two rear wheel steering devices are arranged at intervals. The two drive motors are used to drive the rear wheels on both sides of the vehicle to rotate respectively, and the two rear wheel steering devices are used to drive the rear wheels on both sides of the vehicle to deflect respectively, wherein: In response to a front wheel steering angle of the vehicle being less than a first preset steering angle, the two drive motors are used to drive the rear wheels on both sides of the vehicle to generate a wheel speed difference that is less than or equal to the first preset wheel speed difference.

7. The vehicle according to claim 6, characterized in that In response to the front wheels of the vehicle turning left at an angle greater than the first preset turning angle, the two drive motors are used to drive the rear wheels on both sides of the vehicle to produce a wheel speed difference greater than the first preset wheel speed difference, the lead screws and the nuts of the two rear wheel steering gears respectively rotate relative to each other, and the two rear wheel steering gears drive the correspondingly connected rear wheels on both sides of the vehicle to deflect to the left respectively.

8. The vehicle according to claim 7, characterized in that In response to the increase in the left turning angle of the vehicle's front wheels, the wheel speed difference generated by the two drive motors driving the rear wheels on both sides of the vehicle increases, and the two rear wheel steering gears are used to increase the left deflection angle of the rear wheels on both sides of the vehicle.

9. The vehicle according to claim 8, characterized in that During the process of the front wheels of the vehicle turning to the left, in response to the steering angle of the front wheels of the vehicle being greater than the second preset angle, the two drive motors are used to drive the rear wheels on both sides of the vehicle to generate a wheel speed difference greater than the second preset wheel speed difference, and the two rear wheel steering gears are used to respectively drive the rear wheels on both sides of the vehicle to increase their left deflection angle, wherein the second preset turning angle is greater than the first preset turning angle, and the second preset wheel speed difference is greater than the first preset wheel speed difference, and during the process of the front wheels of the vehicle turning from the first preset turning angle to the second preset turning angle, the wheel speed difference of the rear wheels on both sides of the vehicle is equal to the first preset wheel speed difference.

10. The vehicle according to any one of claims 7 to 9, characterized in that: In response to the front wheel steering angle of the vehicle being greater than the first preset angle and lasting for a first preset time, the two rear wheel steering gears respectively lock the corresponding lead screws and nuts, the lead screws and nuts of the two rear wheel steering gears respectively do not produce relative rotation, and the deflection angles of the rear wheels on both sides of the vehicle remain unchanged.

11. The vehicle according to any one of claims 7 to 10, characterized in that: During the process of the front wheels of the vehicle returning to the center after turning left, in response to the angle of the front wheels of the vehicle returning to the center being greater than the third preset turning angle, the two rear wheel steering gears respectively unlock the corresponding lead screws and nuts, the lead screws and nuts of the two rear wheel steering gears respectively rotate relative to each other, the wheel speed difference generated by the two drive motors driving the rear wheels on both sides of the vehicle is reduced, and the deflection angle of the rear wheels on both sides of the vehicle is reduced.

12. The vehicle according to any one of claims 7 to 11, characterized in that: In response to the angular velocity of the vehicle's front wheels turning left being greater than a first preset steering angular velocity, the two rear wheel steering gears respectively contact and lock the corresponding lead screws and nuts, the lead screws and nuts of the two rear wheel steering gears respectively produce relative rotation, the two drive motors are used to drive the rear wheels on both sides of the vehicle to produce a wheel speed difference, and the rear wheels on both sides of the vehicle respectively deflect to the left.

13. The vehicle according to any one of claims 7 to 12, characterized in that: In response to the slip rate of any one of the rear wheels on both sides of the vehicle being greater than the first preset slip rate, the two rear wheel steering gears respectively lock the corresponding lead screws and nuts, the lead screws and nuts of the two rear wheel steering gears respectively do not produce relative rotation, and the deflection angles of the rear wheels on both sides of the vehicle remain unchanged.

14. The vehicle according to any one of claims 7 to 13, characterized in that: The steering wheel of the vehicle controls the steering of the vehicle's wheels through electronic signals. During the reversing process of the vehicle, in response to the left steering angle of the vehicle's steering wheel being greater than a fourth preset angle, the two drive motors are used to drive the rear wheels on both sides of the vehicle to produce a wheel speed difference, and the lead screws and the nuts of the two rear wheel steering gears respectively rotate relative to each other, and the two rear wheel steering gears drive the correspondingly connected rear wheels on both sides of the vehicle to deflect to the left respectively.

15. The vehicle according to claim 14, characterized in that During the reversing process of the vehicle, in response to the steering wheel of the vehicle turning left at an angle greater than the fourth preset turning angle, the front wheels on both sides of the vehicle turn right.

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