Steering-by-wire angle limiting mechanism and steering-by-wire system
By combining the design of a sliding cam and a guide nut, the problems of large axial force and excessive length in the steer-by-wire angle limiting mechanism are solved, achieving a compact structure and high torque load, thus improving driving comfort and angle adjustment accuracy.
Patent Information
- Application Number
- CN202423078489.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-11-11
- Estimated Expiration
- 2034-12-13
AI Technical Summary
Existing steer-by-wire angle limiting mechanisms suffer from problems such as high axial force, bearing damage, and excessive axial length. They cannot effectively withstand the rotational torque at the end of the steering wheel, and their structure is not conducive to the axial arrangement of the steer-by-wire column.
The design employs a combination of a sliding cam and a guide nut, utilizing a variable pitch thread and multiple stop surfaces to achieve rotational locking. Combining the rotation and axial translation of the sliding cam, the design is compact and can withstand a rotational torque of 200 N*m. The rotation angle is adjusted through the variable pitch thread and multiple limit switches.
It achieves multi-turn limiting within a small envelope space, reduces friction torque fluctuations, avoids knocking sounds, improves driving comfort, and can precisely adjust the steering wheel rotation angle to adapt to different needs.
Smart Images
Figure CN223533542U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of automotive steering system technology, specifically to a steer-by-wire angle limiting mechanism and a steer-by-wire system. Background Technology
[0002] With the increasing maturity of intelligent driving technology, the application of fully autonomous driving technology is just around the corner. At that time, the steering operation of the car will be completely controlled by the onboard computer, so the steering wheel will be unnecessary when not driven manually. However, situations requiring human intervention will still exist, so the emergence of a retractable steer-by-wire column is an inevitable trend. This provides steering operation and can be retracted when not needed, providing more spacious space for the driver's seat.
[0003] The steer-by-wire column is a subsystem of the automotive steer-by-wire system. Its main functions include providing power assist feedback to simulate road feel, offering mechanical rotational hard limits, collapsible energy absorption, adjusting the steering wheel position, connecting to the vehicle's crossbeam, and connecting to the guard's combination switch. Currently, because the steer-by-wire column lacks a central shaft, there is no rigid mechanical link between the steering wheel and the tires; therefore, it relies on axial limits on the steering gear to control the steering wheel's rotational limits.
[0004] Currently, there are two main types of threaded solutions used in existing wire-controlled angle limit mechanisms:
[0005] One type is the equal thread mechanism, which achieves multi-turn limiting, but the end of the angle is locked by axial limiting. The disadvantage of axial limiting is that the axial force is too large. The normal 100Nm of rotational torque is converted into an axial force of 15000N, which is a great damage to the bearing of the rotating shaft. Therefore, the axial limiting cannot withstand the excessive end rotational torque.
[0006] Another type is the equal thread mechanism, which achieves multi-turn limiting and uses circumferential limiting and locking at the end. Because of the equal thread mechanism, the circumferential limiting at the end requires a large pitch. With the addition of a 3mm overlap and 45° locking at the end, and a total of 3 turns, the entire angle limiting mechanism requires an axial length of 72mm, which is a very large envelope and not conducive to the axial arrangement requirements of the wire control column. Utility Model Content
[0007] To solve the above-mentioned technical problems, this utility model provides a steer-by-wire angle limiting mechanism, including a housing, a rotating shaft, a sliding cam, a locking cam, and a guide nut;
[0008] The locking cam has an upper stop surface, which is adapted to the lower stop surface of the sliding cam; the locking cam is fixed to the bottom of the housing.
[0009] The guide nut is fixed inside the housing and located above the locking cam; the guide nut has a variable pitch internal thread, the pitch of the middle part of the thread is smaller than the pitch of the upper and lower threads; the housing has a lower stop surface near the upper part of the guide nut, the lower stop surface is adapted to the upper stop surface of the sliding cam.
[0010] The sliding cam has an internal spline, a guide pin, an upper stop surface, and a lower stop surface; the sliding cam is installed in the guide nut, and through the cooperation of the guide pin and the internal thread of the guide nut, the sliding cam can rotate and move up and down within the guide nut;
[0011] The rotating shaft is mounted in the housing via bearings, with its upper part connected to the input shaft of the steer-by-wire system and its lower part having splines; the rotating shaft drives the sliding cam to rotate through the cooperation of the splines in the sliding cam.
[0012] When the sliding cam moves to the position near the upper end of the guide nut, the rotation of the rotating shaft is locked by the contact between the upper stop surface of the sliding cam and the lower stop surface of the housing; when the sliding cam moves to the position near the lower end of the guide nut, the rotation of the rotating shaft is locked by the contact between the lower stop surface of the sliding cam and the upper stop surface of the locking cam.
[0013] Preferably, the outer ring of the locking cam has a mounting boss, which is used to fix it to the bottom of the housing.
[0014] Preferably, there are three guide pins.
[0015] Preferably, the guide nut is made of plastic.
[0016] This utility model also provides a steer-by-wire system, including a steering shaft, a steering column, a road feel simulation control unit, a connecting harness, a reduction mechanism, a steering gear, a steering gear motor, a power assist control unit, and a tie rod;
[0017] The input shaft is connected to the steering wheel via a spline, and the input shaft is also connected to the steering column via a spline. The road feel simulation control unit includes a controller, a motor, and a steering angle limiting mechanism. The steering column is connected to the input shaft of the road feel simulation control unit via a spline, and the input shaft is connected to the rotation shaft of the steering angle limiting mechanism.
[0018] Preferably, the motor of the road feel simulation control unit and the steering angle limiting mechanism share a housing.
[0019] This utility model's steer-by-wire angle limiting mechanism adopts a design with a fixed guide nut and sliding cam, resulting in a smaller footprint, more compact structure, and superior NVH and friction torque performance. Because the steer-by-wire column lacks an intermediate shaft connection, a rotation angle limiting device is added to the column to synchronize with the steering gear. The sliding cam rotates along the helical guide rail of the fixed nut and translates axially up and down, achieving multi-turn locking after multiple rotations, i.e., multi-angle limiting. The rotation angle is easily adjustable; the total rotation angle can be adjusted by setting the total length of the threaded guide groove. Simultaneously, when the sliding cam reaches its final position, two bosses block and lock, achieving end-of-pipe locking. The relatively small pitch of the threaded guide groove in the middle section saves axial space and creates axial overlap with the two bosses on the rotating shaft and the limiting boss on the fixed cam, effectively achieving the purpose of stopping the steering wheel. Two end-of-pipe stops can be designed, with each pair of bosses featuring a ramp design to enhance strength and withstand the rotational torque at the end of the steering wheel, up to a maximum of 200 N*m. Attached Figure Description
[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:
[0021] Figure 1 This is an exploded view of the steer-by-wire angle limiting mechanism structure of Example 1;
[0022] Figure 2 and Figure 3 This is a schematic diagram of the sliding cam in Example 1;
[0023] Figure 4 This is a schematic diagram of the shell in Example 1;
[0024] Figure 5 This is a schematic diagram of the guide nut in Example 1;
[0025] Figure 6 This is a schematic diagram of the locking cam in Example 1;
[0026] Figure 7 and Figure 8 This is a schematic diagram illustrating the rotation locking position achieved by the steer-by-wire angle limiting mechanism in Example 1.
[0027] Figure 9 This is a schematic diagram of the steer-by-wire system in Example 2;
[0028] Figure 10 This is a schematic diagram showing the arrangement of the steering angle limiting mechanism in the road feel simulation control unit in Example 2. Detailed Implementation
[0029] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can fully understand other advantages and technical effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through different specific embodiments, and the details in this specification can also be applied based on different viewpoints, with various modifications or changes made without departing from the overall design concept of the utility model. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. The following exemplary embodiments of this utility model can be implemented in many different forms and should not be construed as being limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of this utility model thorough and complete, and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art.
[0030] Example 1
[0031] like Figure 1 As shown, this embodiment provides a steer-by-wire angle limiting mechanism, including a housing 31, a rotating shaft 32, a sliding cam 33, a locking cam 34, and a guide nut 35;
[0032] like Figure 6 As shown, the locking cam 34 has an upper stop surface, which is adapted to the lower stop surface of the sliding cam 33; the locking cam 34 is fixed to the bottom of the housing 31. Preferably, the outer ring of the locking cam 34 has a mounting boss, which fixes it to the bottom of the housing.
[0033] The guide nut 35 is fixed inside the housing and located above the locking cam 34; as Figure 5 As shown, the guide nut has a variable pitch internal thread, with the pitch of the middle portion of the thread being smaller than the pitch of the upper and lower threads; as Figure 4 As shown, the housing has a lower stop surface near the upper part of the guide nut, and the lower stop surface is adapted to the upper stop surface of the sliding cam;
[0034] like Figure 2 and Figure 3 As shown, the sliding cam has an internal spline, a guide pin, an upper stop surface, and a lower stop surface. The sliding cam is installed inside a guide nut, and through the engagement of the guide pin with the internal thread of the guide nut, the sliding cam can rotate and move up and down within the guide nut. In this embodiment, there are three guide pins.
[0035] The rotating shaft is mounted in the housing via bearings, with its upper part connected to the input shaft of the steer-by-wire system and its lower part having splines; the rotating shaft drives the sliding cam to rotate through the cooperation of the splines in the sliding cam.
[0036] like Figure 8 As shown, when the sliding cam 33 moves to the position near the upper end of the guide nut 35, the rotation of the rotating shaft 32 is locked by the contact between the upper stop surface of the sliding cam 33 and the lower stop surface of the housing 31; Figure 7 As shown, when the sliding cam 33 moves to the lower end near the guide nut 35, the rotation of the rotating shaft 32 is locked by the contact between the lower stop surface of the sliding cam 33 and the upper stop surface of the locking cam 34. The rotational torque of the steering wheel is transmitted to the sliding cam 33 through a spline connection, and then transmitted to the housing 31 through the sliding cam 33, thus achieving torque blocking.
[0037] Because it uses a variable pitch thread, it achieves both circumferential locking and the advantage of small envelope. With a 3-turn stroke, the end locking load is 150Nm, and the overall envelope is only 30mm. The middle section has a small pitch and the end has a large pitch, which effectively ensures the overlap of the end locking boss.
[0038] Meanwhile, due to the design of 8-protrusion locking, the range of materials that can be selected for the cam is wider and the material stress is lower. Plastic or metal can be selected, and if plastic parts are selected, the knocking sound of the end locking can be avoided.
[0039] When the sliding cam rotates along the guide nut, there will be very stable friction and no excessive frictional torque fluctuations. At the same time, there is no knocking sound throughout the process, which improves driving comfort.
[0040] The guide nut thread groove can be designed with different numbers of turns to achieve the required total number of steering wheel rotations. Moreover, it can be easily adjusted to a precise rotation angle value. For example, any angle such as ±575° or ±538° can be easily achieved.
[0041] Example 2
[0042] like Figure 9 and Figure 10As shown, this embodiment provides a steer-by-wire system, including a steering shaft 1, a steering column 2, a road feel simulation control unit 3 (including a controller, a motor, and a steering angle limiting mechanism), a connecting harness 4, a reduction mechanism 5, a steering gear 6, a steering gear motor 7, a steering gear assist control unit 8, and a tie rod 9. The steering wheel is splined to the input shaft 1. When the driver applies torque (hereinafter referred to as hand force) to turn the steering wheel, it drives the steering shaft 1 to rotate. The steering shaft 1 is connected to the steering column 2 via a spline. The controller on the road feel simulation control unit 3 transmits angle signals to the steering gear assist control unit 8 through the connecting harness 4. The steering column 2 and the steering gear 6 are connected only by wire 4. The steering gear assist control unit 8 drives the motor 7 to provide assistance based on the road load, pushing the rack to move left and right, which in turn drives the tires to rotate via the tie rod 9 to achieve steering. At the same time, the power steering control unit 8 will feed back the road resistance to the road feel simulation control unit 3. The control unit will calculate the matching feel torque according to the built-in software algorithm and drive the motor in the road feel simulation control unit 3 to provide resistance torque. After the reduction mechanism 5 reduces the speed and increases the torque, the torque will be fed back to the steering wheel, so that the entire steering column can provide the driver with virtual road feedback.
[0043] The road feel simulation control unit 3 includes a controller, a motor, and a steering angle limiting mechanism. The steering column is connected to the input shaft of the road feel simulation control unit via a spline, and the input shaft is connected to the rotation shaft of the steering angle limiting mechanism. The steering angle limiting mechanism is the steering angle limiting mechanism described in Embodiment 1.
[0044] Preferably, the motor of the road feel simulation control unit and the steering angle limiting mechanism share a housing.
[0045] The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the present invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the present invention, and these should also be considered within the scope of protection of the present invention.
Claims
1. A steer-by-wire angle limiting mechanism, characterized in that, Includes housing, rotating shaft, sliding cam, locking cam, and guide nut; The locking cam has an upper stop surface, which is adapted to the lower stop surface of the sliding cam; the locking cam is fixed to the bottom of the housing. The guide nut is fixed inside the housing and located above the locking cam; the guide nut has a variable pitch internal thread, the pitch of the middle part of the thread is smaller than the pitch of the upper and lower threads; the housing has a lower stop surface near the upper part of the guide nut, the lower stop surface is adapted to the upper stop surface of the sliding cam. The sliding cam has an internal spline, a guide pin, an upper stop surface, and a lower stop surface; the sliding cam is installed in the guide nut, and through the cooperation of the guide pin and the internal thread of the guide nut, the sliding cam can rotate and move up and down within the guide nut; The rotating shaft is mounted in the housing via bearings, with its upper part connected to the input shaft of the steer-by-wire system and its lower part having splines; the rotating shaft drives the sliding cam to rotate through the cooperation of the splines in the sliding cam. When the sliding cam moves to the position near the upper end of the guide nut, the rotation of the rotating shaft is locked by the contact between the upper stop surface of the sliding cam and the lower stop surface of the housing; when the sliding cam moves to the position near the lower end of the guide nut, the rotation of the rotating shaft is locked by the contact between the lower stop surface of the sliding cam and the upper stop surface of the locking cam.
2. The steer-by-wire angle limiting mechanism according to claim 1, characterized in that, The outer ring of the locking cam has a mounting boss, which is used to fix it to the bottom of the housing.
3. The steer-by-wire angle limiting mechanism according to claim 1, characterized in that, There are three guide pins.
4. The steer-by-wire angle limiting mechanism according to claim 1, characterized in that, The guide nut is made of plastic.
5. A steer-by-wire system, characterized in that, This includes the steering shaft, steering column, road feel simulation control unit, wiring harness, reduction gear, steering gear motor, power steering control unit, and tie rod; The input shaft is connected to the steering wheel via a spline and to the steering column via a spline; the road feel simulation control unit includes a controller, a motor, and a steering angle limiting mechanism; the steering column is connected to the input shaft of the road feel simulation control unit via a spline, and the input shaft is connected to the rotation shaft of the steering angle limiting mechanism; the steering angle limiting mechanism is the steering angle limiting mechanism as described in any one of claims 1 to 4.
6. The steer-by-wire system according to claim 5, characterized in that, The motor and steering angle limiting mechanism of the road feel simulation control unit share a housing.