Independent wheel steering device

Abstract

The application discloses an independent wheel steering device, when the wheel needs to be locked at any position, the first motor stops rotating, the second motor drives the driving gear to rotate, the driving gear drives the driven gear to rotate, the driven gear drives the screw rod to rotate synchronously, since the screw rod is connected with the pressing assembly through threads, the screw rod only rotates, the pressing assembly moves along the axial direction of the screw rod, the second motor drives the pressing assembly to move along the axial direction of the screw rod through the driving gear and the driven gear, until the pressing assembly presses the worm, the worm and the worm wheel are tightly abutted, the meshing gap between the worm wheel and the worm is eliminated, and the wheel has the ability to be locked at any position. The locking torque calculation formula (T=F f ·d1 / 2) of the second motor clearly shows the relationship between the locking force and the worm diameter and the friction factor, when the system is powered off or fails, the pressing assembly instantaneously fixes the worm through static friction (F f >F t ), and the safety is improved since the steering shaft connected with the worm is prevented from being accidentally deflected.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile steering technology, in particular to an independent wheel steering device. BACKGROUND

[0002] In the vehicle steering system, especially in the field of electric power steering (EPS) or steer-by-wire (SBW) technology, how to realize reliable locking of the wheel at any position is one of the key technical problems. The current mainstream scheme relies on the self-locking characteristics of the servo motor combined with the worm and gear reduction mechanism, and uses the design principle that the helix angle of the worm is smaller than the friction angle to realize reverse self-locking. However, in actual working conditions, the meshing surface of the worm and gear can be increased to 0.1-0.3mm after long-term wear, and under the inertia impact generated by frequent starting and stopping of the vehicle or the continuous vibration caused by road bumps, the output shaft end will produce cumulative angular deviation, resulting in serious deterioration of the positioning accuracy of the steering wheel, which can cause vehicle trajectory deviation and even loss of control risk. SUMMARY

[0003] In view of the above technical problems, the present application provides an independent wheel steering device, which overcomes at least one of the above deficiencies.

[0004] The technical scheme adopted by the present application is as follows: an independent wheel steering device, comprising 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 with the worm, and the worm is engaged with the transmission assembly;

[0005] The locking assembly comprises 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 with the driving gear, the driving gear is engaged with the driven gear, one end of the screw rod is rotatably connected with the locking housing, the other end of the screw rod passes through the driven gear and is threadedly connected with the pressing assembly, the screw rod is coaxially fixedly connected with the driven gear, and the other end of the pressing assembly is provided with a groove which is in movable abutment with the worm;

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

[0007] The static friction force generated by the contact between the pressing assembly and the worm is F f , the tangential force of the contact point between the worm and the pressing assembly when the worm has a tendency to rotate is F t , and 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, wherein:

[0008]

[0009]

[0010] T1 is the worm required self-locking torque, d1 is the worm diameter, μ1 is the friction factor between the compression assembly and the worm, F N is the positive pressure of the compression assembly.

[0011] Optionally, the second motor drives the driving gear to rotate through the output torque, the compression assembly moves along the axial direction under the rotation of the screw rod, the force value generated by the rotation of the screw rod to push the compression assembly is the positive pressure value of the compression assembly, and the positive pressure F N of the compression assembly is calculated according to the following formula:

[0012]

[0013]

[0014]

[0015] Wherein, F a is the thrust generated by the rotation of the screw rod, T2 is the torque of the second motor acting on the screw rod, T3 is the torque provided by the second motor, η1 is the transmission efficiency of the screw rod, η2 is the transmission efficiency of the driving gear and the driving gear, μ2 is the friction coefficient between the screw rod and the compression assembly, and α is the lead angle of the screw rod.

[0016] Optionally, the ratio of the number of teeth of the driving gear to the number of teeth of the driving gear is m, and the moving speed of the compression assembly is:

[0017]

[0018] The response time of the second motor is:

[0019] Wherein, n is the second motor speed, P is the pitch between the screw threads, and S is the movement stroke of the compression assembly.

[0020] Optionally, the locking housing is provided with a first containing groove, the driving gear and the driven gear are rotatably installed in the first containing groove, the locking housing is provided with an annular hole in which a bearing is installed, the screw rod abuts against the inner ring of the bearing, the groove is an arc-shaped groove, and one side of the arc-shaped groove towards the worm is provided with a flexible pad.

[0021] Optionally, the screw rod is fixedly connected with a limiting block at one end close to the driven gear, the compression assembly abuts against the limiting block, and the top surface of the limiting block is higher than the groove opening of the first containing groove.

[0022] Optionally, the compression assembly comprises a transmission plate and a pressing block, the transmission plate comprises an extension and an extension plate integrally connected with the extension, an inner wall of the extension is provided with an internal thread connected with a screw rod, one end of the pressing block is fixedly connected with the extension plate, and the other end of the pressing block is provided with the groove.

[0023] Optionally, the locking shell is provided with a second containing groove, the pressing block is fixedly connected with the transmission plate through a screw, the screw comprises a screw cap and a nail part integrally connected with the screw cap, the screw cap is in sliding fit with the second containing groove, and the nail part is fixedly connected with the pressing block through the transmission plate.

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

[0025] Optionally, the compression assembly comprises a top block, an internal thread in the top block is rotationally connected with a screw rod, and an outer wall of the top block is provided with a plane in sliding fit with the transmission shell.

[0026] Optionally, the transmission assembly comprises 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 an outer wall of the first transmission shaft, the worm is in mesh with the first worm gear, and the second worm gear is coaxially arranged on an outer wall of the second transmission shaft and in mesh with the transmission wheel.

[0027] The beneficial effects of the present application are as follows: the first motor drives the transmission assembly to rotate through the worm, so that the transmission assembly drives the wheels to steer, when the wheels need to be locked at any position, the first motor stops rotating, the second motor drives the driving gear to rotate, the driving gear drives the driven gear to rotate, the driven gear drives the screw rod to synchronously rotate, since the screw rod is connected with the compression assembly through threads, the screw rod only rotates, and the compression assembly moves along the axial direction of the screw rod, the second motor drives the compression assembly to move along the axial direction of the screw rod through the driving gear and the driven gear, until the compression assembly compresses the worm, so that the worm and the worm gear are tightly abutted, the meshing gap between the worm gear and the worm is eliminated, and the wheels have the ability to be locked at any position. When the system is powered off or fails, the compression assembly instantaneously fixes the worm through static friction (F f >F t ) to prevent the steering shaft connected with the worm from being accidentally deflected, and the safety is improved. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 The structure schematic diagram of the independent wheel steering device is provided for the present application;

[0029] Fig. 2 The schematic diagram of the locking assembly of the independent wheel steering device is provided for the embodiment 1 of the present application;

[0030] Fig. 3The schematic view of the locking assembly of the independent wheel steering device according to the embodiment 2 of the present application;

[0031] Fig. 4 The schematic view of the locking assembly of the independent wheel steering device according to the embodiment 2 of the present application.

[0032] The marks in the drawings are as follows: 1, second motor; 2, driving gear; 3, driven gear; 4, screw rod; 5, pressing block; 6, extension; 7, extension plate; 8, locking housing; 9, first accommodating groove; 10, second accommodating 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

[0033] The present application will be further described in detail below in conjunction with the drawings and embodiments.

[0034] As shown in the drawings, Figs. 1 to 4 An independent wheel steering device, characterized in that it comprises 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 with the worm 15, and the worm 15 is engaged with the transmission assembly; the locking assembly comprises a second motor 1, a driving gear 2, a driven gear 3, a screw rod 4, a pressing assembly, and a locking housing 8, the output end of the second motor 1 is coaxially connected with the driving gear 2, the driving gear 2 is engaged with the driven gear 3, one end of the screw rod 4 is rotatably connected with the locking housing 8, the other end of the screw rod 4 is threadedly connected with the pressing assembly through the driven gear 3, the screw rod 4 is coaxially fixedly connected with the driven gear 3, and the other end of the pressing assembly is provided with a groove 26 which movably abuts against the worm 15; 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 with 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 of the contact point between the worm 15 and the pressing assembly when the worm 15 has a rotating tendency is F t , and when the wheel needs to be locked, F f >F t The calculation formula of the locking torque of the second motor 1 is T = F f ·d1 / 2, wherein:

[0035]

[0036]

[0037] T1 is the worm required self-locking torque, d1 is the worm diameter, μ1 is the friction factor between the compression assembly and the worm, F N is the positive pressure of the compression assembly.

[0038] The first motor 18 drives the transmission assembly to rotate through the worm 15, so that the transmission assembly drives the wheels to steer. When the wheels need to be locked at 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 rod 4 to rotate synchronously. Since the screw rod 4 is connected with the compression assembly through threads, the screw rod 4 only rotates, and the compression assembly moves along the axial direction of the screw rod 4. The second motor 1 drives the compression assembly to move along the axial direction of the screw rod 4 through the driving gear 2 and the driven gear 3, until the compression assembly compresses the worm 15, so that the worm 15 is tightly abutted against the worm wheel, the meshing gap between the worm wheel and the worm 15 is eliminated, and the wheels have the ability to be locked at any position. The locking torque calculation formula of the second motor 1 (T=Ff•d1 / 2) clearly shows the relationship between the locking torque, the diameter of the worm 15 and the friction factor. In the case of power failure or fault of the system, the compression assembly can instantaneously fix the worm 15 through static friction (Ff>Ft), so as to prevent the steering shaft connected with the worm wheel from being accidentally deflected, and improve the safety.

[0039] The second motor 1 drives the driving gear 2 to drive the transmission to operate, the screw rod 4 rotates to drive the compression assembly to move along the axial direction, the force value generated by the rotation of the screw rod 4 to push the compression assembly is the positive pressure value of the compression assembly, and the positive pressure F N of the compression assembly is calculated by the following formula:

[0040]

[0041]

[0042]

[0043] Wherein, F a is the thrust generated by the rotation of the screw rod, T2 is the torque of the second motor acting on the screw rod, T3 is the torque provided by the second motor, η1 is the transmission efficiency of the screw rod, η2 is the transmission efficiency of the driven gear and the driving gear, μ2 is the friction coefficient between the screw rod and the compression assembly, and α is the lead angle of the screw rod. Here, η1≈40%, η2≈95%, when the compression assembly is the compression block 5 and the transmission plate, μ2 is the friction coefficient between the screw rod 4 and the extended part 6 of the transmission plate; when the compression assembly is the top block 11, μ2 is the friction coefficient between the screw rod 4 and the top block 11.

[0044] The ratio of the number of teeth of the driven gear 3 to the number of teeth of the driving gear 2 is m, so the ratio of the rotational speed of the second motor 1 to the rotational speed of the screw rod 4 is m, and the moving speed of the compression assembly is:

[0045]

[0046] Second motor response time:

[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 travel of the clamping assembly.

[0048] By matching the tooth ratio of the driving and driven gears with the screw pitch, and combining this with the formula for the moving speed of the clamping assembly, a rapid response to the locking action is achieved, meeting the requirements for high-frequency locking. In this embodiment, the tooth ratio of the driven gear to the driving gear is 2, increasing the torque. The second motor uses a 14HS20-1504S hybrid stepper motor, which combines the structural characteristics of permanent magnet and reactive stepper motors. Its electromagnetic torque mainly comes from two parts: hysteresis torque (generated by the permanent magnet) and reactive torque (caused by changes in inductance). The total electromagnetic torque can be expressed as:

[0049]

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

[0051] The formula for calculating hysteresis torque is:

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

[0053] The formula for calculating the reaction torque is: , where L(θ) is the inductance as a function of the rotor angle (H).

[0054] Let be the derivative of the inductance with respect to the angle, and represent the rate of change of inductance.

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

[0056] like Fig. 4As 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 is engaged 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, and the second worm gear 25 is engaged with the transmission wheel 23. The second transmission shaft 24 can be connected with the wheel connecting shaft, and the two-stage worm gear transmission design (first worm gear 21→transmission wheel 23→second worm gear 25) realizes large reduction ratio, amplifies the output torque of the second motor 1, and is suitable for the steering demand of heavy vehicles. The first worm gear 21, the transmission wheel 23 and the second worm gear 25 are helical gears respectively, and the tooth surface contact line is progressive when the helical gears are engaged, which significantly reduces impact and noise compared with spur gears.

[0057] As shown in Figs. 1-4 , the locking housing 8 is provided with a first container groove 9, the driving gear 2 and the driven gear 3 are rotatably installed in the first container groove 9, the locking housing 8 is provided with an annular hole 20 provided with a bearing 13, the screw rod 4 abuts against the inner ring of the bearing 13, the recess 26 is an arc-shaped groove, and one side of the arc-shaped groove facing the worm 15 is provided with a flexible pad 27. μ1 is the friction factor between the flexible pad 27 and the worm 15, the screw rod 4 is rotatably connected with the locking housing 8 through the bearing 13, the hole wall of the annular hole 20 protrudes from the locking housing 8, and the outer peripheral wall of the hole wall of the annular hole 20 is connected with an end cover 14 through threads. Such design facilitates the installation of the bearing 13 and the screw rod 4. The arc-shaped recess 26 is self-adaptively attached to the outer circular surface of the worm 15, which increases the contact area, disperses the locking force and avoids stress concentration. The flexible pad 27 (such as rubber or polyurethane) provides a shock-absorbing function, reduces locking noise, and protects the surface plating of the worm 15 from being scratched.

[0058] As shown in Fig. 1 and 3 , the screw rod 4 is fixedly connected with a limiting block 17 at one end close to the driven gear 3, the pressing assembly is movably abutted against the limiting block 17, and the top surface of the limiting block 17 is higher than the groove of the first container groove 9. The abutment of the limiting block 17 and the pressing assembly forms a mechanical hard limit, which prevents the gear from disengaging due to excessive back-off of the screw rod 4.

[0059] Embodiment 1

[0060] As shown in Fig. 1 , the pressing assembly includes a transmission plate and a pressing block 5, the transmission plate includes an extension part 6 and an extension plate 7 integrally connected with the extension part 6, the inner peripheral wall of the extension part 6 is provided with an internal thread connected with the screw rod 4, one end of the pressing block 5 is fixedly connected with the extension plate 7, and the other end of the pressing block 5 is provided with the recess 26. The screw rod 4 is connected with the transmission plate through threads, the transmission plate moves along the axial direction of the screw rod 4, the transmission plate drives the pressing block 5 to move along the axial direction of the screw rod 4, and the pressing block 5 moves close to or away from the worm 15.

[0061] The locking housing 8 is provided with a second accommodating groove 10, the pressing block 5 is fixedly connected with the transmission plate through a screw, the screw comprises a screw cap 16 and a nail part integrally connected with the screw cap 16, the screw cap 16 is in sliding fit with the second accommodating groove 10, and the nail part is fixedly connected with the pressing block 5 through the transmission plate. The pressing block 5 has a screw hole matched with the screw, and the transmission plate can also be provided with the screw hole. The groove depth of the second accommodating groove 10 is greater than the movement stroke of the screw cap 16, and the screw cap 16 is in clearance fit with the second accommodating groove 10. Since the transmission plate has a tendency to rotate with the screw rod 4 when the screw rod 4 rotates, the screw cap 16 is in clearance fit with the second accommodating groove 10, the screw cap 16 of the screw is in sliding fit with the second accommodating groove 10, a guide structure is formed, the straight line movement track of the pressing assembly is ensured to be stable, and deviation and jamming are prevented. The shape of the outer peripheral wall of the pressing block 5 is not required here.

[0062] Embodiment 2

[0063] The pressing assembly comprises a top block 11, the inside of the top block 11 is provided with an internal thread rotationally connected with the screw rod 4, and the outer peripheral wall of the top block 11 is provided with a plane 12 in sliding fit with the transmission housing 19. Since the top block 11 has a tendency to rotate with the screw rod 4 when the screw rod 4 rotates, the transmission housing 19 is provided with a through hole matched with the shape of the top block 11, the top block 11 can be an arc plane structure, or the cross section of the top block 11 is quadrangular or triangular, the plane 12 avoids the circumferential rotation of the top block 11 in the transmission housing 19, the edge is in axial sliding fit with the transmission housing 19, a guide structure is formed, the straight line movement track of the top block 11 is ensured to be stable, and deviation and jamming are prevented.

[0064] It can be understood that the specific embodiments described above are only used to explain the related application, and are not limited to the application. In addition, it should be noted that only the parts related to the application are shown in the drawings for convenience of description. The technical solutions in the same embodiment and the technical solutions in different embodiments can be arranged and combined to form new technical solutions without contradiction or conflict. Any equivalent structural transformation using the contents of the application specification and drawings, direct or indirect application in other related technical fields, are also included in the protection scope of the application.

Claims

1. An independent wheel steering device, characterized in that, It includes a first motor, a worm gear, a transmission assembly, a transmission housing, and a locking assembly. The output end of the first motor is fixedly connected to the worm gear, and the worm gear meshes with the transmission assembly. The locking assembly includes a second motor, a drive gear, a driven gear, a screw, a clamping assembly, and a locking housing. The output end of the second motor is coaxially connected to the drive gear, and the drive gear meshes with the driven gear. One end of the screw is rotatably connected to the locking housing, and the other end of the screw passes through the driven gear and is threadedly connected to the clamping assembly. The screw and the driven gear are coaxially fixedly connected, and the other end of the clamping assembly is provided with a groove that moves against the worm gear. The worm gear, transmission assembly, and second motor are respectively located 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 gear is F. f When the worm gear has a tendency to rotate, the tangential force F at the contact point with the clamping assembly t When the wheels need to be locked, F f >F t The formula for calculating 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 worm diameter, μ1 is the friction factor between the clamping assembly and the worm, and F... N This refers to the positive pressure applied to the clamping component.

2. The independent wheel steering device according to claim 1, characterized in that, The second motor drives the drive gear transmission to operate through output torque. The rotation of the screw causes the clamping assembly to move axially. The force generated by the rotation of the screw pushing 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 T1 is the thrust generated by the rotation of the screw, T2 is the torque of the second motor acting 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 between the driven gear and the driving gear, μ2 is the coefficient of friction 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 on the driven gear to the number of teeth on the driving gear is m, and the moving speed of the clamping assembly is: ； Second motor response time: ; Where n is the speed of the second motor, P is the pitch between the screw threads, and S is the 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, and the driving gear and the driven gear are rotatably installed inside the first receiving groove. The locking housing is provided with an annular hole for installing 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 gear.

5. The independent wheel steering device according to claim 4, characterized in that, The end of the screw near the driven gear is fixedly connected to a limiting block, and the clamping assembly moves against the limiting block. The top surface of the limiting block is higher than the opening of the first receiving 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 and an extension plate integrally connected to the extension. The inner peripheral wall of the extension is provided with an internal thread that connects to a screw. 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. The pressure block is fixedly connected to the transmission plate by screws. The screw includes a nut and a nail portion integrally connected to the nut. The nut is slidably engaged with the second receiving groove. 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 groove is greater than the travel of the nut, and the nut is in clearance fit with the second groove.

9. The independent wheel steering device according to claim 1, characterized in that, The clamping assembly includes a top block, the top block having an internal thread that is rotatably connected to the screw, and the outer peripheral wall of the top block having a plane that slides with the transmission housing.

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 disposed on the outer peripheral wall of the first transmission shaft. The worm meshes with the first worm gear. The second worm gear is coaxially disposed on the outer peripheral wall of the second transmission shaft and meshes with the transmission wheel.

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