Lead screw transmission and rack drive power steering system

Abstract

This application relates to the field of steering technology, providing a lead screw drive device and a rack-and-pinion power steering system. The lead screw drive device includes: a lead screw shaft; two sets of ball nut assemblies spaced apart on the lead screw shaft; a dual-output motor with two output shafts coaxially connected and synchronously driven by the rotor of the dual-output motor; and two sets of transmission mechanisms, with the two output shafts respectively connected to the nuts of the two sets of ball nut assemblies via the two sets of transmission mechanisms. The lead screw drive device of this application utilizes a redundant design where the dual-output motor drives the two sets of ball nut assemblies mounted on the lead screw shaft through two sets of transmission mechanisms. This simplified and stable structure achieves reliable and efficient driving of the lead screw shaft. The lead screw drive device of this application can be applied to rack-and-pinion power steering systems, effectively providing steering assistance through a simplified and stable redundant design, thereby improving the safety and reliability of the steering system.

Description

Technical Field

[0001] This application relates to the field of steering technology, and more specifically, to lead screw drives and rack and pinion power steering systems. Background Technology

[0002] Traditional rack-and-pinion power steering systems typically use only one transmission mechanism to convert and transmit the motor torque to the rack, thus achieving the goal of power steering.

[0003] Current steer-by-wire systems also rely on rack and pinion drives for power steering. Since there is no mechanical connection between the rack and the steering wheel in a steer-by-wire system, the issue of loss of steering function due to transmission mechanism failure needs to be considered.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Utility Model Content

[0005] This application provides a lead screw drive device and a rack and pinion power steering system. It utilizes a redundant design of dual-output motors driving two sets of ball nut assemblies mounted on the lead screw shaft through two sets of transmission mechanisms. Through a simplified and stable structure, it achieves reliable and efficient drive of the lead screw shaft. This application can be applied to rack and pinion power steering systems such as steer-by-wire systems to effectively provide steering assistance.

[0006] One aspect of this application provides a lead screw drive device, comprising: a lead screw shaft; two sets of ball nut assemblies spaced apart on the lead screw shaft; a dual-output motor having two output shafts coaxially connected and synchronously driven by the rotor of the dual-output motor; and two sets of transmission mechanisms, wherein the two output shafts are respectively connected to the nuts of the two sets of ball nut assemblies through the two sets of transmission mechanisms.

[0007] The lead screw, as a power output element, converts rotary motion into linear motion. Two sets of ball nut assemblies, a dual-output motor, and two sets of transmission mechanisms are designed for redundancy. Even if one set fails, the other can still drive the lead screw, ensuring basic steering functionality is not lost. Specifically, the two transmission mechanisms transmit the power from the dual-output motor to the two nuts via two independent power transmission paths, enabling the two sets of ball nut assemblies to drive the lead screw efficiently. The dual-output motor drives two coaxially connected output shafts through a single rotor, ensuring absolute synchronization of the output torque and speed of the two output shafts from the power source.

[0008] Therefore, the lead screw drive device of this application utilizes a redundant design of two sets of ball nut assemblies mounted on the lead screw shaft through two sets of transmission mechanisms driven by a dual-output motor. This simplified and stable structure enables reliable and efficient driving of the lead screw shaft. The lead screw drive device of this application can be applied to rack and pinion power steering systems such as electric power steering systems and steer-by-wire systems. Through its simplified and stable redundant design, it effectively provides steering assistance and improves the safety and reliability of the steering system.

[0009] In some embodiments, the two sets of transmission mechanisms are arranged symmetrically with respect to the dual-output motor, and / or the two sets of ball nut assemblies are arranged symmetrically on the lead screw shaft. The symmetrical arrangement of the two sets of transmission mechanisms / two sets of ball nut assemblies ensures the balance and synchronization of the transmission forces on both sides, further ensuring the smooth and reliable movement of the lead screw shaft.

[0010] In some embodiments, the transmission mechanism is a belt drive mechanism, wherein the diameter of the first pulley connected to the output shaft is smaller than the diameter of the second pulley connected to the nut. Belt drives have the characteristics of buffering vibration, smooth operation, and quiet operation. The smaller diameter of the first pulley compared to the second pulley enables speed reduction and torque amplification, allowing a larger screw shaft thrust to be generated using a dual-output motor with a smaller torque.

[0011] In some embodiments, the second pulley and the nut are connected by a spline connection, an interference fit, or a locking mechanism; both sets of belt drive mechanisms are respectively equipped with tensioners or tensioned during assembly using tooling equipment. The connection between the second pulley and the nut needs to transmit a large torque; a reliable rigid connection can be achieved through a spline connection, interference fit, or locking mechanism, ensuring effective torque transmission. Furthermore, by using independent tensioners (e.g., tensioning pulleys) or by directly tensioning and locking using special tooling equipment, both sets of belt drive mechanisms can maintain optimal tension.

[0012] In some embodiments, the transmission mechanism is a gear transmission mechanism, wherein the diameter of the first gear connected to the output shaft is smaller than the diameter of the second gear connected to the nut. Gear transmission has high efficiency and a compact structure. By designing the diameter of the first gear to be smaller than that of the second gear, the function of speed reduction and torque increase is also achieved.

[0013] In some embodiments, the nut is sleeved on the lead screw shaft, the transmission component of the transmission mechanism is sleeved on the nut, and a bearing is provided on the nut. The bearing is used to support the ball nut assembly, and the nut can be assembled to the housing via the bearing.

[0014] In some embodiments, the bearing is any of the following: angular contact ball bearing; tapered roller bearing; deep groove ball bearing; and thrust bearing. Angular contact ball bearings can withstand huge axial and radial forces, tapered roller bearings have high load-carrying capacity, deep groove ball bearings can withstand radial forces, and thrust bearings can withstand axial forces. The combination of the two can also achieve a stable support function.

[0015] In some embodiments, the end of the nut is provided with a shoulder, and a washer or direct contact is provided between the shoulder and the bearing. The washer serves to dampen vibration and can adjust the preload of the bearing.

[0016] According to another aspect of this application, a rack-and-pinion power steering system is provided, the rack-and-pinion power steering system being configured with a lead screw drive device as described in any of the above embodiments, wherein the lead screw shaft serves as a rack or is rigidly connected to a rack, and both ends of the rack are connected to wheel ends.

[0017] The rack-and-pinion power steering system is equipped with the aforementioned screw drive device. The rack is driven by two output shafts of a dual-output motor, two sets of transmission mechanisms, and two sets of ball nut assemblies. This not only increases the output force of the rack but also effectively improves safety redundancy and reliability.

[0018] In some embodiments, the rack-and-pinion power steering system is applied to a steer-by-wire system; or, the rack-and-pinion power steering system is applied to an electric power steering system, wherein the rack is connected to the steering column of the electric power steering system via a gear mechanism.

[0019] The electric power steering system / steer-by-wire system is equipped with the aforementioned screw drive device. The rack is driven by two output shafts of the dual-output motor, two sets of transmission mechanisms, and two sets of ball nut assemblies. This not only increases the output force of the rack and improves the steering assist capability, but also effectively enhances safety redundancy and reliability.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0022] Figure 1 This document shows a schematic diagram of the screw drive device in an embodiment of this application.

[0023] Figure 2 This application shows a schematic diagram of the specific application structure of the lead screw drive device in the embodiments of this application;

[0024] Figure 3 A schematic diagram of the rack and pinion power steering system in an embodiment of this application is shown. Detailed Implementation

[0025] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0026] The accompanying drawings are merely illustrative of this application and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar structures, and therefore, repeated descriptions of them will be omitted.

[0027] The use of terms such as "first," "second," and similar words in the specific description does not indicate any order, quantity, or importance, but is merely used to distinguish different components. The terms "left," "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, in the description of this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be a connection within two elements.

[0028] It should be noted that, unless otherwise specified, the embodiments of this application and the features in different embodiments can be combined with each other.

[0029] Figure 1 The structure of the lead screw drive device is illustrated, with reference to... Figure 1 As shown, the lead screw transmission device provided in this application embodiment includes: a lead screw shaft 110; two sets of ball nut assemblies 120, which are spaced apart on the lead screw shaft 110; a dual-output motor 200, which has two output shafts 210, which are coaxially connected and synchronously driven by the rotor of the dual-output motor 200; and two sets of transmission mechanisms 300, through which the two output shafts 210 are respectively connected to the nuts of the two sets of ball nut assemblies 120.

[0030] The lead screw shaft 110 serves as the power output element, converting rotary motion into linear motion. Two sets of ball nut assemblies 120, a dual-output motor 200, and two sets of transmission mechanisms 300 are designed for redundancy. Even if one set fails, the other can still drive the lead screw shaft 110, ensuring basic steering functionality is not lost. The two sets of transmission mechanisms 300 transmit the power of the dual-output motor 200 to the two nuts via two independent power transmission paths, enabling the two sets of ball nut assemblies 120 to drive the lead screw shaft 110 efficiently. The dual-output motor 200 drives two coaxially connected output shafts 210 through a single rotor, ensuring absolute synchronization of the output torque and speed of the two output shafts 210 from the power source. This avoids the control complexity, response delay, and torque interference problems associated with using two independent motors, reducing abnormal noise and wear, and improving the smoothness and reliability of the transmission.

[0031] Therefore, the lead screw drive device of this application utilizes a redundant design where two sets of ball nut assemblies 120 mounted on the lead screw shaft 110 are driven by two sets of transmission mechanisms 300 through a dual-output motor 200. This simplified and stable structure achieves reliable and efficient driving of the lead screw shaft 110. The lead screw drive device of this application can be applied to rack-and-pinion power steering systems such as electric power steering systems and steer-by-wire systems. Through its simplified and stable redundant design, it effectively provides steering assistance, improving the safety and reliability of the steering system. This application provides a higher safety and higher reliability redundant solution for rack-and-pinion power steering systems, especially steer-by-wire systems. It is suitable for vehicles with high rack force requirements, such as commercial vehicles requiring 15kN-35kN rack force, but is not limited thereto.

[0032] In practical applications, the two output shafts 210 of the dual-output motor 200 can be controlled by a dual-channel ECU (Electronic Control Unit) to further ensure the consistency, synchronization and safety of the two output shafts 210.

[0033] In some embodiments, the two sets of transmission mechanisms 300 are symmetrically arranged relative to the dual-output motor 200, and / or the two sets of ball nut assemblies 120 are symmetrically arranged on the lead screw shaft 110. The symmetrical arrangement of the two sets of transmission mechanisms 300 and the two sets of ball nut assemblies 120 ensures the balance and synchronization of the transmission forces on both sides, further ensuring the smooth and reliable movement of the lead screw shaft 110, thereby optimizing the performance of the lead screw transmission device and the applied rack and pinion power steering system.

[0034] It should be noted that although the embodiment with symmetrical arrangement of the two sets of transmission mechanisms 300 / two sets of ball nut assemblies 120 has been described exemplarily, the present invention is not limited thereto. For example, the ball nut assemblies 120 can also be arranged asymmetrically in the same direction according to actual needs, specifically, asymmetrical with respect to the midpoint line perpendicular to the axis of the dual output motor 200, and can be simultaneously offset to the right or simultaneously offset to the left with respect to the bearing 123.

[0035] In some embodiments, the transmission mechanism 300 is a belt drive mechanism, wherein the diameter of the first pulley 310 connected to the output shaft 210 is smaller than the diameter of the second pulley 320 connected to the nut. Belt drives have the characteristics of buffering vibration, smooth operation, and quiet operation. The smaller diameter of the first pulley 310 compared to the second pulley 320 enables speed reduction and torque amplification transmission, allowing a larger screw shaft thrust to be generated using a dual-output motor 200 with a smaller torque. In specific transmission, the first pulley 310, belt 330, and second pulley 320 reduce and amplify the torque output by the dual-output motor 200 before transmitting it to the ball nut assembly 120. The ball nut assembly 120, in cooperation with the screw shaft 110, converts the rotational motion and rotational torque of the second pulley 320 into the linear motion and linear driving force of the screw shaft 110, thereby providing steering assistance.

[0036] In some embodiments, the second pulley 320 is splined, interference-fitted, or locked to the nut using a locking mechanism; both sets of belt drive mechanisms are equipped with tensioners or tensioned during assembly using tooling equipment. The connection between the second pulley 320 and the nut needs to transmit a large torque. A reliable rigid connection can be achieved through splined connection, interference fit, or locking mechanism, ensuring effective torque transmission. Specifically, the splined connection can be achieved by machining external splines on the outer wall of the nut and internal splines on the inner wall of the second pulley 320, achieving extremely high load-bearing capacity through the connection of internal and external splines. An interference fit can be achieved by assembling the second pulley 320 onto the nut through thermoforming, achieving a high-strength connection. Furthermore, tensioning during assembly using independent tensioners (e.g., tensioning pulleys) or separately using tooling equipment allows both sets of belt drive mechanisms to maintain optimal tension. In practical applications, belts gradually wear and stretch with use, leading to a decrease in tension and affecting transmission efficiency and synchronization. The design of independent belt adjustment for two sets of belt drive mechanisms allows each set of belt drive mechanisms to adjust the tension autonomously according to needs, ensuring that each redundant path can work stably and efficiently, thus improving reliability.

[0037] In some embodiments, the transmission mechanism 300 is a gear transmission mechanism, wherein the diameter of the first gear connected to the output shaft 210 is smaller than the diameter of the second gear connected to the nut. Gear transmission has high efficiency and a compact structure. The design of the first gear having a smaller diameter than the second gear also achieves the function of speed reduction and torque amplification. Specifically, during transmission, the first and second gears reduce and amplify the torque output by the dual-output motor 200 and transmit it to the ball nut assembly 120. The ball nut assembly 120, in cooperation with the lead screw shaft 110, converts the rotational motion and rotational torque of the second gear into the linear motion and linear driving force of the lead screw shaft 110, thereby providing steering assistance.

[0038] In other embodiments, in addition to belt drive and gear drive, other suitable transmission methods can also be used to achieve the transmission between the dual-output motor 200 and the ball nut assembly 120.

[0039] Furthermore, Figure 2 The diagram illustrates the specific application structure of the lead screw drive device, combined with... Figure 1 and Figure 2 As shown, in some embodiments, the nut 122 is sleeved on the lead screw shaft 110, the transmission component 300' of the transmission mechanism 300 is sleeved on the nut 122, and a bearing 123 is provided on the nut 122. The bearing 123 is used to support the ball nut assembly 120, and the nut 122 can be assembled to the housing through the bearing 123.

[0040] In some embodiments, bearing 123 may be any of the following: angular contact ball bearing; tapered roller bearing; deep groove ball bearing; and thrust bearing. Angular contact ball bearings can withstand enormous axial and radial forces, making them suitable for applications in rack-and-pinion power steering systems; tapered roller bearings have high load-carrying capacity, making them particularly suitable for heavy-duty applications; deep groove ball bearings can withstand radial forces, and thrust bearings can withstand axial forces; the combination of the two can also achieve stable support.

[0041] In other embodiments, other bearing types may be used to support the ball nut assembly 120.

[0042] In some embodiments, the end of the nut 122 is provided with a shoulder 124, and a washer 125 is provided between the shoulder 124 and the bearing 123, or the shoulder 124 and the bearing 123 can directly contact and fit. The washer 125 plays a role in shock absorption and can adjust the preload of the bearing 123 to improve the support rigidity and reduce movement and abnormal noise during operation.

[0043] This application embodiment also provides a rack-and-pinion power steering system, which is configured with a lead screw drive device as described in any of the above embodiments, wherein the lead screw shaft 110 serves as a rack or is rigidly connected to the rack, and both ends of the rack are connected to the wheel ends.

[0044] Figure 3 The structure of a rack and pinion power steering system is illustrated, with reference to... Figure 3 and combined Figure 1 and Figure 2 As shown, during the operation of the rack-and-pinion power steering system, the vehicle battery drives the dual-output motor 200 to generate assist torque. This assist torque is evenly output through two output shafts 210 and drives two sets of ball bearing nut assemblies 120 to rotate via two sets of transmission mechanisms 300. This rotational motion is further converted into linear motion of the rack 110', pushing the wheels (specifically the front wheels, but this invention is not limited to this; when applied to a rear-wheel steering system, the rear wheels) connected to both ends of the rack 110' to deflect left and right, thus forming steering motion. The rack-and-pinion power steering system, equipped with the aforementioned screw drive device, uses the two output shafts 210 of the dual-output motor 200, two sets of transmission mechanisms 300, and two sets of ball bearing nut assemblies 120 to jointly drive the rack 110', which not only increases the output force of the rack 110' but also effectively improves safety redundancy and reliability.

[0045] Rack-and-pinion power steering systems can be applied to steer-by-wire systems; rack-and-pinion power steering systems can be applied to rear-wheel steering systems; or, rack-and-pinion power steering systems can be applied to electric power steering systems, wherein the rack 110' is connected to the steering column 400 of the electric power steering system via a gear mechanism. Figure 3 The diagram specifically illustrates an electric power steering system; for a steer-by-wire system, there may be no mechanical connection between the rack 110' and the steering column 400.

[0046] The electric power steering system / steer-by-wire system / rear wheel steering system is equipped with the aforementioned screw drive device. The rack 110' is driven by the two output shafts 210 of the dual output motor 200, two sets of transmission mechanisms 300 and two sets of ball nut assemblies 120. This not only increases the output force of the rack 110' and improves the steering assist capability, but also effectively enhances safety redundancy and reliability.

[0047] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of this application and should not be construed as limiting the specific implementation of this application to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of this application, and all such modifications or substitutions should be considered within the scope of protection of this application.

Claims

1. A lead screw transmission device, characterized in that, include: Lead screw shaft; Two sets of ball nut assemblies are spaced apart on the lead screw shaft; A dual-output motor having two output shafts, the two output shafts being coaxially connected and synchronously driven by the rotor of the dual-output motor; Two sets of transmission mechanisms are provided, and the two output shafts are respectively connected to the nuts of the two sets of ball nut assemblies through the two sets of transmission mechanisms.

2. The lead screw transmission device as described in claim 1, characterized in that, The two sets of transmission mechanisms are arranged symmetrically with respect to the dual-output motor, and / or the two sets of ball nut assemblies are arranged symmetrically on the lead screw shaft.

3. The lead screw transmission device as described in claim 1, characterized in that, The transmission mechanism is a belt drive mechanism, wherein: The diameter of the first pulley connected to the output shaft is smaller than the diameter of the second pulley connected to the nut.

4. The lead screw transmission device as described in claim 3, characterized in that, The second pulley is connected to the nut by a spline connection, an interference fit, or a locking mechanism. The two sets of belt drive mechanisms are respectively equipped with tensioners or tensioned during the assembly process by tooling equipment.

5. The lead screw transmission device as described in claim 1, characterized in that, The transmission mechanism is a gear transmission mechanism, wherein: The diameter of the first gear connected to the output shaft is smaller than the diameter of the second gear connected to the nut.

6. The lead screw drive device according to any one of claims 1 to 5, characterized in that, The nut is sleeved on the lead screw shaft, the transmission component of the transmission mechanism is sleeved on the nut, and a bearing is provided on the nut.

7. The lead screw transmission device as described in claim 6, characterized in that, The bearing is any of the following: Angular contact ball bearings; Tapered roller bearings; Deep groove ball bearings and thrust bearings.

8. The lead screw transmission device as described in claim 6, characterized in that, The nut has a shoulder at its end, and a washer or direct contact is provided between the shoulder and the bearing.

9. A rack-and-pinion power steering system, characterized in that, The device is equipped with a lead screw drive as described in any one of claims 1 to 8, wherein the lead screw shaft is a rack or rigidly connected to a rack, and both ends of the rack are connected to wheel ends.

10. The rack-and-pinion power steering system as described in claim 9, characterized in that, The rack and pinion power steering system is applied to the steer-by-wire system; Alternatively, the rack-and-pinion power steering system is applied to an electric power steering system, wherein the rack is connected to the steering column of the electric power steering system via a gear mechanism.

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