Independent wheel steering device

Abstract

According to the independent wheel steering device, when a wheel needs to be locked at any position, a first motor stops rotating, a second motor drives a driving gear to rotate, the driving gear drives a driven gear to rotate, and the driven gear drives a screw to rotate synchronously; the pressing assembly moves in the axial direction of the threaded rod, the second motor drives the pressing assembly to move in the axial direction of the threaded rod through the driving gear and the driven gear till the pressing assembly presses the worm, the worm and the worm gear abut against each other tightly, the meshing gap between the worm gear and the worm is eliminated, and the wheel has the capacity of being locked at any position. The relationship among the locking force, the diameter of the worm and the friction factor is defined through the locking torque calculation formula (T = Ff.d1 / 2) of the second motor, when the system is powered off or breaks down, the pressing assembly instantly fixes the worm through the static friction force (Ffgt, Ft), the steering shaft connected with the worm gear is prevented from accidentally deflecting, and safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle steering, and particularly to an independent wheel steering device. Background Art

[0002] In a vehicle steering system, especially in the technical fields of electric power steering (EPS) or steer-by-wire (SBW), how to achieve reliable locking of wheels at any position is one of the key technical problems. The current mainstream solution relies on the self-locking characteristic of a servo motor cooperating with a worm and worm gear reduction mechanism, and utilizes the design principle that the worm helix angle is less than the friction angle to achieve reverse self-locking. However, in actual working conditions, after long-term wear of the meshing surface of the worm and worm gear, the tooth side clearance can increase to 0.1 - 0.3 mm. Under the inertial impact generated by frequent start and stop of the vehicle or the continuous vibration caused by road surface bumps, a cumulative angular deviation will occur at the output shaft end, resulting in serious deterioration of the steering wheel positioning accuracy, and may lead to risks such as vehicle trajectory deviation and even out of control. Summary of the Invention

[0003] In view of the above technical problems, the present invention proposes an independent wheel steering device, which overcomes at least one deficiency.

[0004] The technical solution adopted by the present invention is as follows: An independent wheel steering device includes a first motor, a worm, a transmission assembly, a transmission housing, and a locking assembly. The output end of the first motor is fixedly connected to the worm, and the worm meshes with the transmission assembly;

[0005] The locking assembly includes a second motor, a driving gear, a driven gear, a screw rod, a pressing assembly, and a locking housing. The output end of the second motor is coaxially connected to the driving gear. The driving gear meshes with the driven gear. One end of the screw rod is rotatably connected to the locking housing, and the other end of the screw rod passes through the driven gear and is threadedly connected to the pressing assembly. The screw rod is coaxially and fixedly connected to the driven gear. The other end of the pressing assembly is provided with a groove that abuts against the worm movably;

[0006] The worm, the transmission assembly, and the second motor are respectively arranged inside the transmission housing, and the locking housing is connected to the transmission housing;

[0007] The static friction force generated by the contact between the pressing assembly and the worm is F f , and the tangential force F t at the contact point between the worm and the pressing assembly when the worm has a tendency to rotate. When the wheel needs to be locked, F f > F t , and the calculation formula for the locking torque of the second motor is: T = F f · d 1 / 2, where:

[0008]

[0009]

[0010] T 1 For the worm, the self-locking torque is required, and d 1 is the worm diameter, and μ 1 is the friction factor between the pressing component and the worm, and F N is the normal pressure of the pressing component.

[0011] Optionally, the second motor drives the driving gear to rotate by outputting torque. The rotation of the screw drives the pressing component to move axially. The force value generated by the rotation of the screw to push the pressing component is the normal pressure value of the pressing component. The normal pressure F N of the pressing component is calculated by the formula:

[0012]

[0013]

[0014]

[0015] wherein, F a is the thrust generated by the rotation of the screw, T 2 is the torque of the second motor acting on the screw, T 3 is the torque provided by the second motor, η 1 is the transmission efficiency of the screw, η 2 is the transmission efficiency between the driven gear and the driving gear, μ 2 is the friction coefficient between the screw and the pressing component, and α is the lead angle of the screw.

[0016] Optionally, the ratio of the number of teeth of the driven gear to the number of teeth of the driving gear is m, and the moving speed of the pressing component is:

[0017]

[0018] Response time of the second motor:

[0019] wherein, n is the rotational speed of the second motor, P is the pitch between the screw threads, and S is the moving stroke of the pressing component.

[0020] Optionally, the locking housing is provided with a first accommodation groove, the driving gear and the driven gear are rotatably installed inside the first accommodation groove, the locking housing is provided with an annular hole installed with a bearing, the screw abuts against the inner ring of the bearing, the groove is an arc-shaped groove, and a flexible pad is provided on the side of the arc-shaped groove facing the worm.

[0021] Optionally, a limiting block is fixedly connected to one end of the screw rod close to the passive gear. The pressing component is in movable abutment with the limiting block, and the top surface of the limiting block is higher than the notch of the first accommodating groove.

[0022] Optionally, the pressing component includes a transmission plate and a pressing block. The transmission plate includes an extending portion and an extending plate integrally connected to the extending portion. An internal thread connected to the screw rod is provided on the inner peripheral wall of the extending portion. One end of the pressing block is fixedly connected to the extending plate, and the other end of the pressing block is provided with the groove.

[0023] Optionally, the locking housing is provided with a second accommodating groove. The pressing block is fixedly connected to the transmission plate by a screw. The screw includes a nut and a nail portion integrally connected to the nut. The nut is in sliding fit with the second accommodating groove, and the nail portion passes through the transmission plate and is fixedly connected to the pressing block.

[0024] Optionally, the groove depth of the second accommodating groove is greater than the movement stroke of the nut, and the nut is in clearance fit with the second accommodating groove.

[0025] Optionally, the pressing component includes a top block. An internal thread rotatably connected to the screw rod is provided inside the top block, and a plane in sliding fit with the transmission housing is provided on the outer peripheral wall of the top block.

[0026] Optionally, the transmission component includes a first worm gear, a first transmission shaft, a transmission wheel, a second transmission shaft, and a second worm gear. The first worm gear and the transmission wheel are coaxially arranged on the outer peripheral wall of the first transmission shaft. The worm is meshed with the first worm gear. The second worm gear is coaxially arranged on the outer peripheral wall of the second transmission shaft. The second worm gear is meshed with the transmission wheel.

[0027] The beneficial effects of the present invention are as follows: The first motor drives the transmission component to rotate through the worm, so that the transmission component drives the wheel to turn. When the wheel needs to be locked at any position, the first motor stops rotating, and the second motor drives the active gear to rotate. The active gear drives the passive gear to rotate, and the passive gear drives the screw rod to rotate synchronously. Since the screw rod is threadedly connected to the pressing component, the screw rod only makes a rotational motion, and the pressing component moves along the axial direction of the screw rod. The second motor drives the pressing component to move along the axial direction of the screw rod through the active gear and the passive gear until the pressing component presses the worm, so that the worm is in close abutment with the worm gear, eliminating the meshing clearance between the worm gear and the worm, enabling the wheel to have the ability to be locked at any position. When the system is powered off or fails, the pressing component instantaneously fixes the worm through static friction (F f >F t ) to prevent the steering shaft connected to the worm gear from deflecting accidentally, improving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of the independent wheel steering device proposed by the present invention;

[0029] Figure 2 Schematic diagram of the locking assembly of the independent wheel steering device proposed in Embodiment 1 of the present invention;

[0030] Figure 3 Schematic diagram of the locking assembly of the independent wheel steering device proposed in Embodiment 2 of the present invention;

[0031] Figure 4 Schematic diagram of the locking assembly of the independent wheel steering device proposed in Embodiment 2 of the present invention.

[0032] The reference numerals in each drawing are: 1, second motor; 2, driving gear; 3, driven gear; 4, screw; 5, pressing block; 6, extension part; 7, extension plate; 8, locking housing; 9, first accommodation groove; 10, second accommodation groove; 11, top block; 12, plane; 13, bearing; 14, end cover; 15, worm; 16, nut; 17, limiting block; 18, first motor; 19, transmission housing; 20, annular hole; 21, first worm gear; 22, first transmission shaft; 23, transmission wheel; 24, second transmission shaft; 25, second worm gear; 26, groove; 27, flexible pad. Detailed Description of the Invention

[0033] The following further elaborates the present application in conjunction with the drawings and embodiments.

[0034] As Figures 1 to 4 shown, an independent wheel steering device, characterized in that it includes a first motor 18, a worm 15, a transmission assembly, a transmission housing 19, and a locking assembly. The output end of the first motor 18 is fixedly connected to the worm 15, and the worm 15 meshes with the transmission assembly; the locking assembly includes a second motor 1, a driving gear 2, a driven gear 3, a screw 4, a pressing assembly, and a locking housing 8. The output end of the second motor 1 is coaxially connected to the driving gear 2, the driving gear 2 meshes with the driven gear 3, one end of the screw 4 is rotatably connected to the locking housing 8, the other end of the screw 4 passes through the driven gear 3 and is threadedly connected to the pressing assembly, the screw 4 is coaxially and fixedly connected to the driven gear 3, and the other end of the pressing assembly is provided with a groove 26 that abuts against the worm 15 movably; the worm 15, the transmission assembly, and the second motor 1 are respectively arranged inside the transmission housing 19, and the locking housing 8 is connected to the transmission housing 19; the static friction force generated by the contact between the pressing assembly and the worm 15 is F f , the tangential force F t at the contact point between the worm 15 and the pressing assembly when the worm 15 has a tendency to rotate. When the wheel needs to be locked, F f >F t , the calculation formula for the locking torque of the second motor 1 is: T = F f ·d 1 / 2, where:

[0035]

[0036]

[0037] T 1 The self-locking torque requirement for the worm is d 1 is the worm diameter, μ 1 is the friction factor between the pressing component and the worm, F N is the normal pressure of the pressing component.

[0038] The first motor 18 drives the transmission component to rotate through the worm 15, causing the transmission component to drive the wheels to turn. When the wheels need to be locked in any position, the first motor 18 stops rotating, and the second motor 1 drives the driving gear 2 to rotate. The driving gear 2 drives the driven gear 3 to rotate, and the driven gear 3 drives the screw 4 to rotate synchronously. Since the screw 4 is threadedly connected to the pressing component, the screw 4 only makes a rotational movement, and the pressing component moves along the axial direction of the screw 4. The second motor 1 drives the pressing component to move along the axial direction of the screw 4 through the driving gear 2 and the driven gear 3 until the pressing component presses the worm 15, causing the worm 15 to closely abut against the worm wheel, eliminating the meshing clearance between the worm wheel and the worm 15, and enabling the wheels to have the ability to be locked in any position. The calculation formula for the locking torque of the second motor 1 (T = Ff • d1 / 2) clarifies the relationship between the locking force and the diameter of the worm 15 and the friction factor. When the system is powered off or fails, the pressing component instantaneously fixes the worm 15 through static friction (Ff > Ft), preventing the steering shaft connected to the worm wheel from deflecting accidentally and enhancing safety.

[0039] The second motor 1 drives the driving gear 2 to drive and operate through the output torque. The rotation of the screw 4 drives the pressing component to move axially. The force value generated by the rotation of the screw 4 to push the pressing component is the normal pressure value of the pressing component. The normal pressure F of the pressing component N The calculation formula is:

[0040]

[0041]

[0042]

[0043] Among them, F a is the thrust generated by the rotation of the screw, T 2 is the torque applied by the second motor on the screw, T 3 is the torque provided by the second motor, η 1 is the transmission efficiency of the screw, η 2 is the transmission efficiency between the driven gear and the driving gear, μ 2 is the friction coefficient between the screw and the pressing component, and α is the lead angle of the screw. Here η1 ≈40%, η 2 ≈95%, when the pressing component is the pressing block 5 and the transmission plate, μ 2 is the friction coefficient between the screw 4 and the extension part 6 of the transmission plate; when the pressing component is the top block 11, μ 2 is the friction coefficient between the screw 4 and the top block 11.

[0044] If the ratio of the number of teeth of the passive gear 3 to the number of teeth of the active gear 2 is m, then the ratio of the rotational speed of the second motor 1 to the rotational speed of the screw 4 is m, and the moving speed of the pressing component is:

[0045]

[0046] Response time of the second motor:

[0047] where n is the rotational speed of the second motor 1, P is the pitch between the threads of the screw 4, and S is the moving stroke of the pressing component.

[0048] By matching the tooth number ratio of the driving gear and the driven gear with the screw pitch, and combining with the moving speed formula of the pressing component, a rapid response of the locking action is achieved to meet the high-frequency locking requirement. In this embodiment, the ratio of the number of teeth of the passive gear to the number of teeth of the active gear is 2, increasing the torque. The second motor used is a 14HS20-1504S type hybrid stepping motor, which combines the structural characteristics of the permanent magnet type and the reaction type stepping motors. Its electromagnetic torque mainly comes from two parts: the hysteresis torque (generated by the permanent magnet) and the reaction torque (caused by the change of inductance). The total electromagnetic torque can be expressed as:

[0049]

[0050] where: T e is the total electromagnetic torque, T m is the hysteresis torque, generated by the interaction between the permanent magnet and the exciting current, T r is the reaction torque, caused by the change of inductance with the rotor position.

[0051] The calculation formula of the hysteresis torque is:

[0052] where, K m is the hysteresis torque coefficient, related to the magnetic potential of the permanent magnet, the motor structure, etc., I is the phase current (A), N r is the number of rotor teeth, and θ is the current position angle of the rotor (electrical angle, rad).

[0053] The calculation formula of the reaction torque is: , where L(θ) is the function of inductance with respect to the rotor angle (H),

[0054] is the derivative of the inductance with respect to the rotation angle, representing the rate of change of inductance.

[0055] The expression for the total electromagnetic torque is: .

[0056] As Figure 4 shown, the transmission assembly includes a first worm gear 21, a first transmission shaft 22, a transmission wheel 23, a second transmission shaft 24, and a second worm gear 25. The first worm gear 21 and the transmission wheel 23 are coaxially arranged on the outer peripheral wall of the first transmission shaft 22. The worm 15 meshes with the first worm gear 21. The second worm gear 25 is coaxially arranged on the outer peripheral wall of the second transmission shaft 24. The second worm gear 25 meshes with the transmission wheel 23. The second transmission shaft 24 can be connected to the wheel connecting shaft. The two-stage worm gear transmission design (first worm gear 21 → transmission wheel 23 → second worm gear 25) realizes a large reduction ratio, amplifies the output torque of the second motor 1, and is suitable for the steering requirements of heavy vehicles. The first worm gear 21, the transmission wheel 23, and the second worm gear 25 are respectively helical gears. When helical gears mesh, the tooth surface contact line is progressive, significantly reducing impact and noise compared with spur gears.

[0057] As Figures 1 - 4 shown, the locking housing 8 is provided with a first accommodation groove 9. The driving gear 2 and the driven gear 3 are rotatably installed inside the first accommodation groove 9. The locking housing 8 is provided with an annular hole 20 installed with a bearing 13. The screw rod 4 abuts against the inner ring of the bearing 13. The groove 26 is an arc-shaped groove. A flexible pad 27 is provided on the surface of the arc-shaped groove facing the worm 15. μ 1 is the friction factor between the flexible pad 27 and the worm 15. The screw rod 4 is rotatably connected to the locking housing 8 through the bearing 13. The hole wall of the annular hole 20 of the locking housing 8 protrudes from the locking housing 8. The outer peripheral wall of the hole wall of the annular hole 20 is threadedly connected with an end cover 14. Such a design facilitates the installation of the bearing 13 and the screw rod 4. The arc-shaped groove 26 adaptively fits the outer circular surface of the worm 15, increasing the contact area, dispersing the locking force, and avoiding stress concentration. The flexible pad 27 (such as rubber or polyurethane) provides a buffer and vibration absorption function, reducing the locking noise and protecting the surface coating of the worm 15 from being scratched.

[0058] As Figure 1 and 3 shown, a limiting block 17 is fixedly connected to one end of the screw rod 4 close to the driven gear 3. The pressing assembly is movably abutted against the limiting block 17. The top surface of the limiting block 17 is higher than the notch of the first accommodation groove 9. The limiting block 17 abuts against the pressing assembly to form a mechanical hard limit, preventing the screw rod 4 from retreating excessively and causing the gears to disengage.

[0059] Embodiment 1

[0060] As Figure 1As shown in the figure, the pressing assembly includes a transmission plate and a pressing block 5. The transmission plate includes an extension portion 6 and an extension plate 7 integrally connected to the extension portion 6. The inner peripheral wall of the extension portion 6 is provided with an internal thread connected to the screw 4. One end of the pressing block 5 is fixedly connected to the extension plate 7, and the other end of the pressing block 5 is provided with the groove 26. The screw 4 is threadedly connected to the transmission plate, and the transmission plate moves along the axial direction of the screw 4. The transmission plate drives the pressing block 5 to move along the axial direction of the screw 4, approaching or departing from the worm 15.

[0061] The locking housing 8 is provided with a second accommodation groove 10. The pressing block 5 is fixedly connected to the transmission plate by screws. The screws include a nut 16 and a nail portion integrally connected to the nut 16. The nut 16 is slidably engaged with the second accommodation groove 10, and the nail portion passes through the transmission plate and is fixedly connected to the pressing block 5. The pressing block 5 has a screw hole for cooperating with the screw, and the transmission plate may also be provided with this screw hole. The groove depth of the second accommodation groove 10 is greater than the movement stroke of the nut 16, and the nut 16 is in clearance fit with the second accommodation groove 10. Since the screw 4 has a tendency to rotate together with the transmission plate when rotating, the nut 16 of the screw is in clearance fit with the second accommodation groove 10, and the nut 16 of the screw is slidably engaged with the second accommodation groove 10, forming a guiding structure to ensure the stable linear movement trajectory of the pressing assembly, prevent skew jamming, and no requirements are made for the shape of the outer peripheral wall of the pressing block 5 here.

[0062] Embodiment 2

[0063] The pressing assembly includes a top block 11. The inner part of the top block 11 is provided with an internal thread rotatably connected to the screw 4. The outer peripheral wall of the top block 11 is provided with a plane 12 slidably engaged with the transmission housing 19. Since the screw 4 has a tendency to rotate together with the top block 11 when rotating, the transmission housing 19 is provided with a through hole matching the shape of the top block 11. The top block 11 can be an arc surface + plane structure, or the cross section of the top block 11 is quadrilateral or triangular. The plane 12 prevents the top block 11 from rotating circumferentially within the transmission housing 19, and the edge is slidably engaged with the transmission housing 19 along the axial direction, forming a guiding structure to ensure the stable linear movement trajectory of the top block 11 and prevent skew jamming.

[0064] It can be understood that the specific embodiments described above are only used to explain the relevant invention, rather than limiting the invention. In addition, it should be noted that for the convenience of description, only the parts related to the invention are shown in the drawings. Multiple technical solutions in the same embodiment, as well as multiple technical solutions in different embodiments, can be arranged and combined to form new technical solutions without contradiction or conflict. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention, directly or indirectly applied in other related technical fields, is similarly included in the protection scope of the present invention.

Claims

1. An independent wheel steering device, characterized in that: It includes a first motor, a worm, a transmission assembly, a transmission housing, and a locking assembly, wherein the output end of the first motor is fixedly connected to the worm, and the worm is meshed with the transmission assembly; The locking assembly includes a second motor, a driving gear, a passive gear, a screw, a clamping assembly, and a locking housing, wherein the output end of the second motor is coaxially connected to the driving gear, the driving gear is meshed with the passive gear, one end of the screw is rotatably connected to the locking housing, the other end of the screw passes through the passive gear and is threadedly connected to the clamping assembly, the screw is coaxially fixedly connected to the passive gear, and the other end of the clamping assembly is provided with a groove that movably abuts against the worm; The worm, the transmission assembly, and the second motor are respectively arranged inside the transmission housing, and the locking housing is connected to the transmission housing; The static friction force generated by the contact between the clamping assembly and the worm is F f , when the worm has a tendency to rotate, the tangential force F at the contact point with the clamping assembly t When the wheel needs to be locked, F f >F t , the calculation formula of the locking torque of the second motor is: T=F f d1 / 2, where: ； ； T1 is the required self-locking torque of the worm, d1 is the diameter of the worm, μ1 is the friction factor between the clamping assembly and the worm, F N is the positive pressure of the clamping assembly.

2. The independent wheel steering device according to claim 1, characterized in that: The second motor drives the driving gear to operate by outputting torque, and the screw rotates to drive the clamping assembly to move axially. The force generated by the screw rotating to push the clamping assembly is the positive pressure value of the clamping assembly. The positive pressure F of the clamping assembly is N The calculation formula is: ； ； ； Among them, F a is the thrust generated by the rotation of the screw, T2 is the torque applied by the second motor on the screw, T3 is the torque provided by the second motor, η1 is the transmission efficiency of the screw, η2 is the transmission efficiency of the passive gear and the active gear, μ2 is the friction coefficient between the screw and the clamping assembly, and α is the lead angle of the screw.

3. The independent wheel steering device according to claim 1, characterized in that: The ratio of the number of teeth of the passive gear to the number of teeth of the active gear is m, and the moving speed of the clamping assembly is: ； Second motor response time: ; Wherein, n is the rotation speed of the second motor, P is the pitch between the screw threads, and S is the movement stroke of the clamping assembly.

4. The independent wheel steering device according to claim 1, characterized in that: The locking housing is provided with a first receiving groove, the driving gear and the driven gear are rotatably installed inside the first receiving groove, the locking housing is provided with an annular hole with a bearing installed, the screw is abutted against the inner ring of the bearing, the groove is an arc groove, and a flexible pad is provided on the side of the arc groove facing the worm.

5. The independent wheel steering device according to claim 4, characterized in that: One end of the screw rod close to the passive gear is fixedly connected to a limiting block, the pressing assembly movably abuts against the limiting block, and the top surface of the limiting block is higher than the notch of the first containing groove.

6. The independent wheel steering device according to claim 1, characterized in that: The clamping assembly includes a transmission plate and a pressure block. The transmission plate includes an extension portion and an extension plate integrally connected to the extension portion. The inner peripheral wall of the extension portion is provided with an internal thread connected to a screw rod. One end of the pressure block is fixedly connected to the extension plate, and the other end of the pressure block is provided with the groove.

7. The independent wheel steering device according to claim 6, characterized in that: The locking housing is provided with a second receiving groove, and the pressure block is fixedly connected to the transmission plate by a screw. The screw includes a nut and a nail portion integrally connected to the nut. The nut is slidably matched with the second receiving groove, and the nail portion passes through the transmission plate and is fixedly connected to the pressure block.

8. The independent wheel steering device according to claim 7, characterized in that: The depth of the second receiving groove is greater than the movement stroke of the nut, and the nut is loosely matched with the second receiving groove.

9. The independent wheel steering device according to claim 1, characterized in that: The clamping assembly comprises a top block, an internal thread rotatably connected to the screw rod is arranged inside the top block, and a plane slidably matched with the transmission housing is arranged on the outer peripheral wall of the top block.

10. The independent wheel steering device according to claim 1, characterized in that: The transmission assembly includes a first worm gear, a first transmission shaft, a transmission wheel, a second transmission shaft and a second worm gear. The first worm gear and the transmission wheel are coaxially arranged on the outer peripheral wall of the first transmission shaft, the worm is meshed with the first worm gear, the second worm gear is coaxially arranged on the outer peripheral wall of the second transmission shaft, and the second worm gear is meshed with the transmission wheel.

Images