Rear wheel steering system

Abstract

The invention relates to the technical field of automobile steering, in particular to a rear wheel steering system which comprises a parallel shaft steering assembly and a coaxial steering assembly which are used for controlling the rotation angle of a tire, the parallel shaft steering assembly and the coaxial steering assembly each comprise a shell, a movable end and a fixed end, and the movable ends and the fixed ends are arranged at the two ends of the shells correspondingly. The fixed end is fixedly connected with one end of the shell, the movable end is installed on a rear wheel steering knuckle, the parallel shaft steering assembly further comprises a first pushing assembly, the coaxial steering assembly further comprises a second pushing assembly, and the first pushing assembly and the second pushing assembly are both used for driving the movable end to do linear motion so as to adjust the steering angle of the rear wheel. The two steering motors can be controlled respectively to achieve independent operation of tires, the function of stabilizing a vehicle body under different road conditions is achieved, the risk of drifting or out-of-control of the vehicle is reduced, the vehicle can make accurate direction adjustment more easily during high-speed driving, and maneuverability and responsiveness of the vehicle are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle steering, and particularly to a rear-wheel steering system. Background Art

[0002] When a vehicle is turning, changes in the contact area of the wheels with the ground and the wheel alignment will cause changes in the steering characteristics. Rear-wheel steering technology can make up for the inherent defects of the vehicle steering mechanism caused by the use of pneumatic rubber tires. When the vehicle is moving at high speed, by braking one or several wheels, the driving attitude of the vehicle can be kept stable.

[0003] Currently, the main type is integral rear-wheel steering, which adopts a through structure, enabling the rear wheels to rotate synchronously, and it is impossible to achieve the effect of separately controlling the two rear wheels. At the same time, the intermediate transition part of the integral structure is too long, resulting in a relatively large overall weight and high space requirements, and there are disadvantages in the spatial layout of the vehicle parts. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a rear-wheel steering system, which solves the problem that the rear wheels rotate synchronously in the prior art and it is impossible to achieve the effect of separately controlling the two rear wheels.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] The rear-wheel steering system includes a parallel-axis steering component and a coaxial steering component for controlling the rotation angle of the tires. Both the parallel-axis steering component and the coaxial steering component include a housing, a movable end, and a fixed end. The movable end and the fixed end are respectively arranged at both ends of the housing. The fixed end is fixedly connected to one end of the housing, and the movable end is installed on the rear-wheel steering knuckle. The parallel-axis steering component further includes a first driving component, and the coaxial steering component further includes a second driving component. Both the first driving component and the second driving component are used to drive the movable end to move linearly to adjust the rear-wheel steering angle.

[0007] Further, the first driving component includes a first synchronous motor fixedly installed on the housing, a synchronous toothed belt transmission arranged on the output shaft of the first synchronous motor through a small synchronous pulley, and a ball screw transmission arranged at the bottom of the synchronous toothed belt through a large synchronous pulley. The large synchronous pulley is rotatably connected to the housing through a bearing.

[0008] Further, a first anti-backlash retaining ring fixed to the housing is rotatably arranged on the ball screw. One end of the ball screw is provided with a sliding screw that slides with the housing. The other end of the ball screw is fixedly connected to the movable end through a locking nut. A first position sensor matching one end of the sliding screw is fixed on one side of the housing.

[0009] Furthermore, the second driving component further includes a synchronous motor two fixedly arranged inside the housing. A locking clutch drivingly connected to the housing is installed on the output shaft of the synchronous motor two. A planetary reducer is drivingly connected to the locking clutch, and a threaded lead screw is fixed at the center of the planetary reducer.

[0010] Furthermore, a threaded sleeve is threadedly connected to the threaded lead screw. One end of the threaded sleeve is fixedly connected to the movable end. The threaded sleeve can only slide but not rotate relative to the housing. A second position sensor matching the threaded sleeve is provided on one side of the housing.

[0011] Furthermore, rubber bushings are provided on both the movable end and the fixed end.

[0012] By means of the above technical solution, the present invention provides a rear-wheel steering system. Compared with the prior art, it has at least the following beneficial effects:

[0013] 1. By setting the parallel-axis steering component and the coaxial steering component, the present invention can independently operate the tires by separately controlling the two steering motors, achieving the function of vehicle body stability under different road conditions, reducing the risk of vehicle fishtailing or losing control, making it easier for the vehicle to make precise direction adjustments when driving at high speed, and improving the mobility and responsiveness of the vehicle; moreover, the internal structure is compact, the requirement for installation space is low, and the weight is light.

[0014] 2. By actively adjusting the angle of the rear wheels, the present invention makes the vehicle attitude more stable when turning, reduces the roll and excessive tilting feeling of the vehicle body, improves the comfort of passengers. At the same time, the rear wheels cooperate with the front wheels to rotate, enabling the driver to feel more natural and smooth steering feedback, especially more significantly when driving at high speed or making emergency turns. Moreover, the active steering of the rear wheels helps the vehicle more accurately maintain the lane and the target driving trajectory, reducing the driver's operation burden.

[0015] 3. When changing lanes during high-speed driving, the present invention keeps the same direction as the front wheels through the angle change of the rear wheels, forming the effect of increased wheelbase, making the vehicle more agile and stable when driving at high speed. With the rear-wheel steering system, the turning radius is smaller than that of vehicles of the same level. And when the vehicle changes lanes, the same direction of the rear wheels and the front wheels can make the vehicle change lanes faster and more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0017] Figure 1 is a schematic structural diagram of the parallel-axis steering component of the present invention;

[0018] Figure 2 Front cross-sectional view of the parallel-axis steering assembly of the present invention;

[0019] Figure 3 Structural schematic diagram of the coaxial steering assembly of the present invention;

[0020] Figure 4 Front cross-sectional view of the coaxial steering assembly of the present invention.

[0021] In the figure:

[0022] 10. Parallel-axis steering assembly;

[0023] 20. Coaxial steering assembly;

[0024] 30. Housing; 40. Movable end; 50. Fixed end; 60. Rubber bushing;

[0025] 11. First pushing assembly; 111. First synchronous motor; 112. Synchronous toothed belt; 113. Ball screw; 114. First anti-backstop ring; 115. Sliding screw; 116. First position sensor;

[0026] 21. Second pushing assembly; 211. Second synchronous motor; 212. Locking clutch; 213. Planetary reducer; 214. Threaded screw; 215. Threaded sleeve. Detailed implementation manners

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] Embodiment 1

[0029] When the vehicle is traveling at a low speed, the reverse rotation of the rear wheels relative to the front wheels can be used to appropriately increase the oversteer. When a vehicle traveling at a high speed encounters an emergency lane change, there is a tendency to oversteer easily. By generating a very small but important steering of the rear wheels in the same direction as the front wheels, the tendency of oversteer can be compensated. Therefore, an auxiliary steering system is provided for the rear wheels to make the vehicle have better balance.

[0030] In order to control the two rear wheels separately and enhance the vehicle stability, as Figure 1 - Figure 2As shown, a rear-wheel steering system is provided, including a parallel-axis steering assembly 10 for controlling the rotation angle of the tire. The parallel-axis steering assembly 10 includes a housing 30, a movable end 40, a fixed end 50, and a first driving assembly 11. The movable end 40 and the fixed end 50 are respectively arranged at both ends of the housing 30. The fixed end 50 is fixedly connected to one end of the housing 30, and the movable end 40 is installed on the rear-wheel steering knuckle.

[0031] The first driving assembly 11 is used to drive the movable end 40 to move linearly to adjust the rear-wheel steering angle. The first driving assembly 11 includes a first synchronous motor 111 fixedly installed on the housing 30. The first synchronous motor 111 is set as a three-phase permanent magnet synchronous motor. The control part controls the input voltage of the first synchronous motor 111 by using PWM, thereby controlling the rotation speed of the first synchronous motor 111. Through a small synchronous pulley, a synchronous toothed belt 112 arranged on the output shaft of the first synchronous motor 111 is transmitted. The synchronous toothed belt 112 is used as a speed reduction and torque increase structure. The diameter ratio of the large pulley D and the small pulley d is used as the transmission ratio. I = D / d (I is the transmission ratio). At the same time, the synchronous toothed belt 112 has the characteristics of high transmission efficiency, convenient installation, and low noise. During operation, the synchronous toothed belt 112 is not easy to slip and will not cause output loss of the first synchronous motor 111;

[0032] A ball screw 113 is arranged at the bottom of the synchronous toothed belt 112 through a large synchronous pulley transmission. The fixed end 50 of the ball screw 113 uses a deep groove ball bearing as a structure for auxiliary rotation and friction reduction. Through the interference fit of the deep groove ball bearing and the sliding sleeve of the ball screw 113, and at the same time, a locking nut is used to fix the sliding sleeve of the screw. On the other side, it is the interference fit of the deep groove ball bearing and the end cover of the housing 30, so that the sliding sleeve of the ball screw 113 and the end cover maintain the freedom of rotation without the freedom of the sliding direction. The large synchronous pulley is rotationally connected to the housing 30 through a bearing. The bearing is set as a self-lubricating bearing. The self-lubricating bearing has the characteristics of small clearance, good wear resistance, and stable use function. Both ends are supported by self-lubricating bearings, which ensure the coaxiality of the core shaft during movement and avoid problems such as jamming and resistance generation during movement due to the offset force of the core shaft. The self-lubricating bearing is used as an auxiliary support for linear motion, and while realizing linear motion, it tries to reduce the friction and clearance of the motion as much as possible, making the overall operation smoother. The first synchronous motor 111 is parallel to the ball screw 113, and the power is transmitted to the rear wheel through the synchronous toothed belt 112 structure. A first anti-backstop ring 114 fixed to the housing 30 is rotationally arranged on the ball screw 113. One end of the ball screw 113 is provided with a sliding screw 115 sliding with the housing 30. The other end of the ball screw 113 is fixedly connected to the movable end 40 through a locking nut. A first position sensor 116 matching one end of the sliding screw 115 is fixed on one side of the housing 30. The first position sensor 116 is used as a position control feedback signal. After calibrating the initial position, the change in position during the movement process is used as the output of the signal.

[0033] By starting the synchronous motor 111, the output shaft of the synchronous motor 111 rotates, and the ball screw 113 is driven to rotate through the synchronous toothed belt 112, so that the rotational motion of the synchronous motor 111 is converted into linear motion, driving the sliding screw 115 to move in the housing 30, and then the movable end 40 is pushed to move through the extension and retraction of the ball screw 113, and the movable end 40 pushes the rear wheel to rotate, and the rear wheel is rotated by force, and the displacement signal is fed back by the position sensor 116 to control the rotation angle of the tire.

[0034] Embodiment 2

[0035] like Figure 3 - Figure 4 As shown, a coaxial steering assembly 20 for controlling the rotation angle of the tire is also provided. The coaxial steering assembly 20 includes a shell 30, a movable end 40, a fixed end 50 and a pushing assembly 21. The movable end 40 and the fixed end 50 are respectively arranged at both ends of the shell 30, the fixed end 50 is fixedly connected to one end of the shell 30, and the movable end 40 is installed on the rear wheel steering knuckle.

[0036] The propulsion component 21 is used to drive the movable end 40 to make a linear motion to adjust the steering angle of the rear wheel. The propulsion component 21 also includes a synchronous motor 211 fixedly arranged on the inner side of the shell 30. The synchronous motor 211 is set as a permanent magnet three-phase synchronous motor. The control part adjusts the input voltage of the synchronous motor 211 by using PWM to control the rotation speed of the synchronous motor 211. A locking nut is used as a structure to fix the synchronous motor 211 to the shell 30 to ensure that the synchronous motor 211 is rigidly connected to the shell 30. When the output shaft of the synchronous motor 211 rotates, it does not rotate relative to the shell 30. A locking clutch 212 that is transmission-connected to the shell 30 is installed on the output shaft of the synchronous motor 211. A planetary reducer 213 is transmission-connected to the locking clutch 212. The planetary reducer 213 is a speed reduction and torque increase structure. The planetary reducer 213 is small in size, light in weight, and has a high load-bearing capacity. The planetary reducer 213 has a long service life, stable operation and low noise. A threaded screw 214 is fixed at the axis of the planetary reducer 213, and a threaded sleeve 215 is threadedly connected to the threaded screw 214. One end of the threaded sleeve 215 is fixedly connected to the movable end 40. The synchronous motor 211 and the threaded screw 214 are on the same axis. The threaded screw 214 is used as the original element for force and displacement transmission. The locking clutch 212 is used as the stopping original element to prevent the threaded screw 214 from retreating. The planetary reducer 213 is used as a deceleration and torque increase structure. The threaded sleeve 215 and the housing 30 can only slide but not rotate. A position sensor 2 matching the threaded sleeve 215 is also provided on one side of the housing 30. The position sensor 2 can determine the displacement of the connection end of the rear wheel steering system, and convert it into the deflection angle of the tire through the ECU, accurately control different working conditions during the driving process of the whole vehicle, reduce the impact of the road surface and driving speed, and improve the stability of control.

[0037] When the synchronous motor two 211 is operating, the rotating shaft of the synchronous motor two 211 drives the locking clutch 212 to rotate. The synchronous motor two 211 drives the planetary reduction system to rotate. The planetary reduction system drives the threaded lead screw 214 to rotate. The threaded lead screw 214 drives the threaded sleeve 215 to move linearly inside the housing 30, pushing the movable end 40 to move, realizing the telescopic function. The movable end 40 pushes the rear wheel to rotate, and thus the rear wheel is forced to rotate. And in cooperation with the position sensor two to feedback the displacement signal to control the rotation angle of the tire.

[0038] Wherein, rubber bushings 60 are installed on both the movable end 40 and the fixed end 50. The rubber bushing 60 is used as a buffer structure at the connection position between the movable end 40 and the fixed end 50 to slow down the damage to the steering structure caused by the impact of the tire during driving, reduce the vibration caused by the rear wheel steering structure during the driving of the whole vehicle, and prevent the resonance situation. The rubber bushing 60 can also ensure that the deflection of the connecting shaft during the steering of the tire will not cause a large lateral force on the mandrel and the housing 30. At the same time, the rubber bushing 60 also has the function of reducing abnormal noise, reducing the noise during operation, and improving the overall NVH performance.

[0039] It should be noted that in this article, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0040] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Rear wheel steering system, characterized by: It comprises a parallel axis steering assembly (10) and a coaxial steering assembly (20) for controlling the rotation angle of a tire; The parallel axis steering assembly (10) and the coaxial steering assembly (20) both comprise a housing (30), a movable end (40) and a fixed end (50); the movable end (40) and the fixed end (50) are respectively arranged at two ends of the housing (30); the fixed end (50) is fixedly connected to one end of the housing (30); the movable end (40) is mounted on a rear wheel steering knuckle; the parallel axis steering assembly (10) further comprises a first pushing assembly (11); the coaxial steering assembly (20) further comprises a second pushing assembly (21); the first pushing assembly (11) and the second pushing assembly (21) are both used to drive the movable end (40) to perform linear motion to adjust the rear wheel steering angle.

2. The rear wheel steering system according to claim 1, characterized in that: The pushing assembly (11) comprises a synchronous motor (111) fixedly mounted on a housing (30), a synchronous toothed belt (112) arranged on an output shaft of the synchronous motor (111) and driven by a small synchronous wheel, and a ball screw (113) arranged at the bottom of the synchronous toothed belt (112) and driven by a large synchronous wheel, wherein the large synchronous wheel is rotatably connected to the housing (30) via a bearing.

3. The rear wheel steering system according to claim 2, characterized in that: A stop ring (114) fixed to the housing (30) is rotatably provided on the ball screw (113); a sliding screw (115) sliding with the housing (30) is provided at one end of the ball screw (113); the other end of the ball screw (113) is fixedly connected to the movable end (40) via a locking nut; and a position sensor (116) matching one end of the sliding screw (115) is fixed to one side of the housing (30).

4. The rear wheel steering system according to claim 1, characterized in that: The second pushing component (21) also includes a second synchronous motor (211) fixedly arranged on the inner side of the housing (30); a locking clutch (212) drivingly connected to the housing (30) is installed on the output shaft of the second synchronous motor (211); a planetary reducer (213) is drivingly connected to the locking clutch (212); and a threaded screw (214) is fixed at the axis of the planetary reducer (213).

5. The rear wheel steering system according to claim 4, characterized in that: A threaded sleeve (215) is threadedly connected to the threaded screw rod (214), one end of the threaded sleeve (215) is fixedly connected to the movable end (40), the threaded sleeve (215) and the housing (30) can only slide but not rotate, and a position sensor 2 matching the threaded sleeve (215) is also provided on one side of the housing (30).

6. The rear wheel steering system according to claim 1, characterized in that: The movable end (40) and the fixed end (50) are both provided with rubber bushings (60).

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