Steering force actuator

Abstract

A steering force actuator includes: a housing; a motor mounted in the housing and configured to provide a rotational force; a sun gear configured to be rotated by the motor; a ring gear mounted in the housing and disposed to surround the sun gear; a carrier configured to be rotated by meshing between the sun gear and the ring gear, in which a steering shaft interlocked with a steering wheel is mounted on the carrier; and an elastic relaxation member mounted on the carrier to reduce backlash. In the steering force actuator according to the present disclosure, an elastic relaxation member applied to a carrier is pre-loaded to elastically support a carrier pin provided in the carrier, thereby suppressing the occurrence of backlash and enabling a load to be uniformly transmitted to a planetary gear. Therefore, noise and vibration can be reduced. The steering force actuator may improve steering feel and reduce gear transmission errors and operation noise by minimizing backlash in planetary gears.

Description

TECHNICAL FIELD

[0001] An exemplary embodiment of the present disclosure relates to a steering force actuator, and more particularly, to a steering force actuator that can improve steering feeling and reduce gear transmission error and operating noise by minimizing backlash in a planetary gear. BACKGROUND

[0002] As autonomous vehicle technology advances, steering systems are expected to transition from EPS systems to steer-by-wire (SBW) systems. SBW systems can easily change steering gear ratios depending on the driving situation of a vehicle, which can improve driving convenience and vehicle stability.

[0003] SBW systems are composed of a steering force actuator (SFA) and a roadwheel actuator (RWA). The SFA provides a reaction force to a steering wheel to ensure that a driver experiences steering feeling when turning the steering wheel. The SFA includes a steering reaction force motor and a reduction machine. By disposing the steering reaction force motor and the reduction machine coaxially with a steering column, the SFA can reduce its installation space, and the steering wheel can be easily stored on an instrument panel.

[0004] In a conventional planetary gear type reduction machine applied to a conventional SFA, the distance between the shafts is fixed, and it is challenging to apply a backlash compensation device. In addition, it is challenging to achieve steering feeling due to backlash between the gears compared to a conventional worm reduction machine or a belt reduction machine. Therefore, improvement is needed.

[0005] Related technology of the present disclosure is disclosed in Korean Patent No. 10-0530034 (registered on November 14, 2005, and entitled "Steering repulsion power control device of steer-by-wire system, which controls repulsion power torque by width acceleration"). SUMMARY

[0006] An object of the present disclosure is to provide a steering force actuator that can improve steering feeling and reduce gear transmission error and operating noise by minimizing backlash in a planetary gear.

[0007] A steering force actuator according to the present disclosure includes a housing, a motor installed in the housing and configured to provide a rotational force, a sun gear configured to rotate by the motor, a ring gear installed in the housing and disposed to surround the sun gear, a gear carrier configured to rotate by meshing between the sun gear and the ring gear, in which a steering shaft interlocked with a steering wheel is installed on the gear carrier, and an elastic relaxation part installed on the gear carrier to reduce backlash.

[0008] The sun gear can include a sun shaft connected to the motor and configured to rotate by being disposed coaxially with the steering shaft, and sun teeth formed on the sun shaft and configured to engage with the gear carrier.

[0009] The gear carrier includes a gear carrier body connected to the steering shaft, a plurality of gear carrier pins configured to pass through the gear carrier body and be supported on the elastic relaxation member, a planetary gear installed on the gear carrier pin and configured to cause rotation of the gear carrier body by engaging with the sun gear and the ring gear, and a gear carrier fixer configured to fix the planetary gear to the gear carrier body.

[0010] The gear carrier hole can be formed on the gear carrier body such that the gear carrier pin passes through the gear carrier body, and the elastic relaxation member inserted into the gear carrier hole can be configured to elastically support the gear carrier pin.

[0011] At least one of the gear carrier hole and the gear carrier pin can be provided with a rotation restriction portion configured to restrict the rotation of the elastic relaxation member about an axis.

[0012] The elastic relaxation member can include a first elastic portion configured to be in close contact with an inner circumferential surface of the gear carrier hole, a second elastic portion configured to be in close contact with an outer circumferential surface of the gear carrier pin, and a third elastic portion configured to connect the first elastic portion and the second elastic portion, wherein the first elastic portion and the second elastic portion are alternately disposed in a circumferential direction.

[0013] Both ends of the elastic relaxation member can be spaced apart from each other.

[0014] Both ends of the elastic relaxation member can be disposed to be in close contact with the inner circumferential surface of the gear carrier hole or the outer circumferential surface of the gear carrier pin and face each other.

[0015] The elastic relaxation member can further include a fourth elastic portion configured to connect both ends of the elastic relaxation member and contract under an external force and recover when the external force is removed.

[0016] Both ends of the elastic relaxation member can correspond to a direction of a load applied to the gear carrier pin.

[0017] In a steering force actuator according to the present disclosure, an elastic relaxation member applied to a gear carrier is preloaded to elastically support a gear carrier pin provided in the gear carrier, thereby suppressing the occurrence of backlash and enabling a load to be uniformly transmitted to a planetary gear. Accordingly, the occurrence of noise and vibration can be mitigated. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a view schematically showing a steering force actuator according to an embodiment of the present disclosure.

[0019] Figure 2 is a view schematically illustrating a sun gear according to an embodiment of the disclosure.

[0020] Figure 3 is an assembled perspective view schematically illustrating a gear carrier according to an embodiment of the disclosure.

[0021] Figure 4 is an exploded perspective view schematically illustrating a gear carrier according to an embodiment of the disclosure.

[0022] Figure 5 is a cross-sectional view schematically illustrating a gear carrier according to an embodiment of the disclosure.

[0023] Figure 6 is a view schematically illustrating an elastic relaxation member according to an embodiment of the disclosure.

[0024] Figure 7 is a view schematically illustrating an elastic relaxation member mounted on a gear carrier hole according to an embodiment of the disclosure.

[0025] Figure 8 is a view schematically illustrating arrangement of an elastic relaxation member based on a load applied to a gear carrier according to an embodiment of the disclosure.

[0026] Figure 9A and 9B is a view schematically illustrating both ends of an elastic relaxation member and movement of the elastic relaxation member based on a load direction according to an embodiment of the disclosure. DETAILED DESCRIPTION

[0027] Hereinafter, a steering force actuator will be described by various exemplary embodiments with reference to the accompanying drawings. It should be considered that the thickness of each line or the size of each component in the drawings can be exaggerated for clarity and convenience of description. Also, the terms as used herein are defined in consideration of their functions in the disclosure, and the terms can be changed according to the intention or practice of a user or an operator. Therefore, the terms should be defined based on the overall disclosure set forth herein.

[0028] Figure 1 is a view schematically illustrating a steering force actuator according to an embodiment of the disclosure. Referring to Figure 1 , a steering force actuator 1 according to an embodiment of the disclosure can include a housing 10, a motor 20, a sun gear 30, a ring gear 40, a gear carrier 50, and an elastic relaxation member 60.

[0029] The housing 10 can be mounted on the vehicle body. For example, the housing 10 can be positioned below the steering wheel 100 and can be fixedly mounted on the vehicle body. A pair of housings 10 can be assembled to cover internal components.

[0030] The motor 20 can be mounted in the housing 10 and can provide rotational force. For example, the motor 20 can be driven in response to a signal from a sensor configured to detect rotation of the steering wheel 100 and provide a reaction force to the steering wheel 100. The motor 20, configured to provide rotational force when electricity is applied, can be implemented in various embodiments.

[0031] The sun gear 30 can be rotated by the motor 20. For example, the sun gear 30 can be rotated by being directly connected to the motor 20.

[0032] The ring gear 40 can be mounted in the housing 10 and arranged to surround the sun gear 30. For example, the ring gear 40 can be integrally formed on the inner wall of the housing 10, or it can be fixedly mounted in the housing 10. The ring gear 40 can be annular, and the teeth can be formed along its inner circumferential surface.

[0033] The gear carrier 50 can rotate via the meshing between the sun gear 30 and the ring gear 40, and the steering shaft 200, interlocked with the steering wheel 100, can be mounted on the gear carrier 50. For example, the steering shaft 200 can be connected to the steering wheel 100 operated by the driver, and the steering shaft 200 can pass through the housing 10 and be press-fitted into the gear carrier 50. The steering shaft 200 can be arranged in a straight line with the central axis of the sun gear 30.

[0034] A resilient relaxation member 60 can be mounted on the gear carrier 50 to reduce backlash. For example, the resilient relaxation member 60 can be made of a metallic material and can have an elastically deformable and resilient shape. The resilient relaxation member 60 can contract and recover depending on whether a load is applied to the gear carrier 50, thereby suppressing backlash. The resilient relaxation member 60 can provide a preload to the gear carrier 50.

[0035] Figure 2 This is a schematic view illustrating a sun gear according to an embodiment of this disclosure. (Refer to...) Figure 2 According to embodiments of the present disclosure, the sun gear 30 may include a sun shaft 31 and sun gear teeth 32.

[0036] The sun shaft 31 can be connected to the rotating shaft of the motor 20 and can be rotated by being coaxially arranged with the steering shaft 200. For example, the sun shaft 31 can be inserted into the gear carrier 50.

[0037] The sun gear teeth 32 can be formed on the sun shaft 31 and can be engaged with the gear carrier 50. For example, the sun gear teeth 32 can be a gear formed around the sun shaft 31. The sun gear teeth 32 can be press-fitted into the sun shaft 31, or can be integrally formed with the sun shaft 31.

[0038] Figure 3 FIG. 1 is a perspective view schematically illustrating a gear carrier according to an embodiment of the present disclosure. Figure 4 FIG. 2 is an exploded perspective view schematically illustrating a gear carrier according to an embodiment of the present disclosure. Figure 5 FIG. 3 is a cross-sectional view schematically illustrating a gear carrier according to an embodiment of the present disclosure. Figure 6 FIG. 4 is a view schematically illustrating an elastic relaxation member according to an embodiment of the present disclosure. Figure 7 FIG. 5 is a view schematically illustrating an elastic relaxation member mounted on a gear carrier hole according to an embodiment of the present disclosure. Figure 8 FIG. 6 is a view schematically illustrating an arrangement of an elastic relaxation member based on a load applied to a gear carrier according to an embodiment of the present disclosure. Referring to Figures 3 to 8 The gear carrier 50 according to an embodiment of the present disclosure can include a gear carrier body 51, a gear carrier pin 52, a planetary gear 53, and a gear carrier holder 54.

[0039] The gear carrier body 51 can be connected to the steering shaft 200. For example, the gear carrier body 51 can include a body plate 511 having a disc shape, and a body connector 512 protruding from a central portion of the body plate 511 toward the steering shaft 200 and transmitting a rotational reaction force to the steering shaft 200. The body connector 512 can be exposed to the outside by passing through the housing 10.

[0040] A plurality of gear carrier pins 52 can pass through the gear carrier body 51 and be supported on the elastic relaxation member 60. For example, the gear carrier pin 52 can include a pin engagement portion 521 located on the body plate 511, and a pin shaft 522 extending from the pin engagement portion 521 and passing through the body plate 511.

[0041] The planetary gear 53 can be mounted on the gear carrier pin 52 and can cause rotation of the gear carrier body 51 by being engaged with the sun gear 30 and the ring gear 40. For example, the planetary gear 53 can be formed in two stages, with teeth of different diameters. The planetary gear 53 can include a first gear 531 engaged with the sun gear teeth 32, and a second gear 532 having a larger diameter than the first gear 531 and engaged with the ring gear 40. The planetary gear 53 can be engaged with the sun gear 30 and the ring gear 40 fixed in place, and rotate around the gear carrier pin 52 as a central axis, thereby causing the gear carrier body 51 itself to rotate.

[0042] The gear carrier fixer 54 can fix the planetary gear 53 to the gear carrier body 51. For example, the gear carrier fixer 54 can be mounted on the gear carrier pin 52 such that the gear carrier pin 52 is maintained to be installed on the gear carrier body 51.

[0043] The gear carrier fixer 54 can include a fixing flat washer 541, a fixing elastic washer 542, and a fixing snap ring 543. The fixing flat washer 541 can be penetrated by the pin stem 522 and can have a shape of a flat cross-section. The fixing elastic washer 542 can be penetrated by the pin stem 522 and can have a shape of a wavy curved cross-section. The fixing elastic washer 542 can be made of a high elastic material such as spring steel. The fixing snap ring 543 can be installed on the pin stem 522 to prevent the fixing flat washer 541 and the fixing elastic washer 542 from being displaced.

[0044] The fixing elastic washer 542 can elastically press the planetary gear 53 toward the gear carrier body 51. Accordingly, the planetary gear 53 can be maximally in contact with the gear carrier body 51, thereby minimizing a gap.

[0045] Further, the pin engagement portion 521 can be maximally in contact with the body plate 511 by the elastic force of the fixing elastic washer 542. Accordingly, even if the planetary gear 53 is a so-called two-stage gear having the first gear 531 and the second gear 532 with different diameters, tilting can be prevented.

[0046] The gear carrier hole 55 can be formed on the gear carrier body 51 such that the gear carrier pin 52 can penetrate the gear carrier body 51. For example, a plurality of gear carrier holes 55 can be disposed to be spaced apart from each other in a circumferential direction of the gear carrier body 51. The plurality of gear carrier holes 55 can be formed by penetrating the gear carrier body 51 in a thickness direction of the gear carrier body 51. The plurality of gear carrier holes 55 can be formed at equal angles with respect to a central axis of the steering shaft 200 and can be formed to be spaced apart from each other by an equal distance. Three gear carrier holes 55 can be formed in the circumferential direction of the gear carrier body 51, and the planetary gears 53 can be respectively installed on the gear carrier pins 52 penetrating the gear carrier holes 55.

[0047] The elastic relaxation member 60 can be inserted into the gear carrier hole 55 to elastically support the gear carrier pin 52. For example, the pin engagement portion 521 can be designed to have a cross-sectional diameter greater than a hole diameter of the gear carrier hole 55. The pin stem 522 can be designed to have a cross-sectional diameter smaller than the hole diameter of the gear carrier hole 55. Accordingly, a space can be formed between the pin stem 522 and the gear carrier hole 55, and the elastic relaxation member 60 can be inserted into the space to provide a preload to the pin stem 522.

[0048] At least one of the gear hole 55 and the gear pin 52 can be provided with a rotation limiting portion 70 configured to limit the rotation of the elastic relaxation member 60 about the axis. For example, the rotation limiting portion 70 can protrude from the inner circumferential surface of the gear hole 55 to limit the rotation of the gear pin 52. Also, the rotation limiting portion 70 can extend from the gear pin 52 and be inserted into a recessed area of the inner circumferential surface of the gear hole 55. Also, the elastic relaxation member 60 can be designed such that an appropriate preload is formed on the elastic relaxation member 60 itself during initial assembly.

[0049] The elastic relaxation member 60 according to the embodiments of the disclosure can include a first elastic portion 61, a second elastic portion 62, and a third elastic portion 63. The first elastic portion 61 to the third elastic portion 63 can be integrally formed in a circumferential direction. The elastic relaxation member 60 can be made of an elastic material such as a spring.

[0050] The first elastic portion 61 is in close contact with the inner circumferential surface of the gear hole 55, the second elastic portion 62 is in close contact with the outer circumferential surface of the gear pin 52, and the third elastic portion 63 can connect the first elastic portion 61 and the second elastic portion 62. The first elastic portion 61 and the second elastic portion 62 can be alternately disposed in the circumferential direction. For example, the first elastic portion 61 can have a curved shape to form point contact or surface contact with the inner circumferential surface of the gear hole 55. The second elastic portion 62 can have a curved shape to form point contact or surface contact with the outer circumferential surface of the gear pin 52. At least two first elastic portions 61 and at least two second elastic portions 62 can be formed at equal intervals in the circumferential direction, respectively.

[0051] Both ends of the elastic relaxation member 60 can be spaced apart from each other. For example, the elastic relaxation member 60 can be formed to have a closed cross-section to form a partially cut surface, or can be molded in a mold such that both ends are spaced apart from each other.

[0052] Both ends of the elastic relaxation member 60 can be disposed to be in close contact with the inner circumferential surface of the gear hole 55 or the outer circumferential surface of the gear pin 52 and face each other. For example, the first end 81 and the second end 82 can each be disposed to be in close contact with the outer circumferential surface of the gear pin 52 and face each other.

[0053] The elastic relaxation member 60 can further include a fourth elastic portion 64. The fourth elastic portion 64 can connect both ends of the elastic relaxation member 60. The fourth elastic portion 64 can be contracted by an external force and restored when the external force is removed. For example, the fourth elastic portion 64 can further connect the first end 81 and the second end 82, and can be deformed when the first end 81 and the second end 82 are brought close to each other by an external force. In addition, when the external force is removed, additional resilience can be provided to return the first end 81 and the second end 82 to their initial positions.

[0054] Both ends of the elastic relaxation member 60 can correspond to the direction of the load applied to the gear carrier pins 52. For example, the three gear carrier pins 52 can be disposed at intervals of 120 degrees on the gear carrier body 51, and an imaginary line x extending from the gear carrier body 51 to the gear carrier pins 52 can be disposed to pass through between the first end 81 and the second end 82.

[0055] Figure 9A And 9B are views schematically showing both ends of an elastic relaxation member according to an embodiment of the disclosure and movement of the elastic relaxation member based on the direction of a load. Referring to Figure 9A And 9B When both ends of the elastic relaxation member 60 are disposed in the 6 o'clock direction and the load on the gear carrier pins 52 is in the 12 o'clock direction, the elastic relaxation member 60 can be deformed so that the first end 81 and the second end 82 can be brought close to each other. When both ends of the elastic relaxation member 60 are disposed in the 6 o'clock direction and the load on the gear carrier pins 52 is also in the 6 o'clock direction, the elastic relaxation member 60 can be deformed so that the first end 81 and the second end 82 can be deformed in the 6 o'clock direction.

[0056] The following is a description of the operation of a steering force actuator according to an embodiment of the disclosure having the above-described configuration.

[0057] The gear carrier pins 52 pass through a plurality of gear carrier holes 55 formed on the gear carrier body 51, respectively, and the elastic relaxation member 60 is inserted between the gear carrier holes 55 and the gear carrier pins 52 to provide a preload. The sun gear 30 is disposed between the gear carrier pins 52, and the planetary gears 53 are mounted on the passing gear carrier pins 52 and then fixed by using the gear carrier retainer 54.

[0058] When the motor 20 is mounted in the housing 10 and then the motor 20 and the sun gear 30 are connected, the planetary gears 53 are engaged with the sun gear 30 and the ring gear 40.

[0059] Further, the both ends of the elastic relaxation member 60 are spaced apart from each other such that the first end 81 and the second end 82 move based on the direction of the load to disperse the load. Accordingly, the elastic portion becomes longer than a case where the both ends are not spaced apart from each other and form a closed curve, thereby suppressing the occurrence of plastic deformation.

[0060] Since the elastic modulus varies depending on the positions of the both ends of the elastic relaxation member 60 that are spaced apart from each other, a proper assembly position is required. Since the radial gear force is smaller than the tangential gear force, the assembly position of the elastic relaxation member 60 should be at a portion where the elastic modulus of the elastic relaxation member 60 is low.

[0061] In the planetary gear, meshing occurs at two points: a point between the planetary gear 53 and the sun gear 30, and a point between the planetary gear 53 and the ring gear 40. For example, if the initial assembly condition of the elastic relaxation member 60 results in a (-) backlash at either of the two points, a force corresponding to the size of the (-) backlash acts on the elastic relaxation member 60. In this case, a (+) backlash is formed at the other of the two points. The elastic relaxation member 60 serves to move the planetary gear 53 from the point where the (-) backlash is formed to the other point where the (+) backlash is formed, thereby preventing gear jamming caused by the (-) backlash while maintaining a minimum backlash. Further, in a conventional planetary gear, the sum of the radial forces is zero under an operating condition, so the backlash under the initial assembly condition is maintained. Further, for a compound planetary gear in which the sum of the radial forces is not zero, the radial forces act in the direction of the sun gear, so the minimum backlash condition can always be satisfied.

[0062] In a conventional planetary gear, manufacturing errors, such as tooth thickness variation, gear accuracy error, deviation of the distance between the shafts, and continuous meshing between the sun gear and the plurality of planetary gears, prevent the load transmitted from the input shaft from being uniformly transmitted to the plurality of planetary gears. Accordingly, gear transmission error increases, making the conventional planetary gear susceptible to noise and vibration. However, in the present disclosure, when the elastic relaxation member 60 inserted into the carrier hole 55 elastically supports the carrier pin 52, self-positioning adjustment of the carrier pin 52 enables the load to be uniformly transmitted to the plurality of planetary gears 53, thereby reducing gear transmission error.

[0063] In the steering force actuator 1 according to the embodiment of the present disclosure, the elastic relaxation member 60 applied to the carrier 50 is preloaded to elastically support the carrier pin 52 disposed in the carrier 50, thereby maintaining a minimum backlash, suppressing the occurrence of gear jamming, and enabling the load to be uniformly transmitted to the planetary gear 53. Accordingly, the occurrence of noise and vibration can be mitigated.

[0064] While the present disclosure has been described with reference to the implementations illustrated in the drawings, the implementations are merely for the purpose of illustration and are not intended to limit the disclosure to the implementations described herein.

Claims

1. A steering force actuator comprising: a housing; a motor installed in the housing and configured to provide a rotational force; a sun gear configured to be rotated by the motor; a ring gear installed in the housing and disposed to surround the sun gear; a carrier configured to be rotated by meshing between the sun gear and the ring gear, wherein a steering shaft interlocked with a steering wheel is installed on the carrier; and an elastic relaxation member installed on the carrier to reduce backlash.

2. The steering force actuator according to claim 1, wherein The sun gear comprises: a sun shaft connected to the motor and configured to be rotated by being disposed coaxially with the steering shaft; and sun teeth formed on the sun shaft and configured to mesh with the carrier.

3. The steering force actuator of claim 1, wherein, The carrier comprises: a carrier body connected to the steering shaft; a plurality of carrier pins configured to pass through the carrier body and be supported on the elastic relaxation member; a planetary gear installed on the carrier pin and configured to cause rotation of the carrier body by meshing with the sun gear and the ring gear; and a carrier fixer configured to fix the planetary gear to the carrier body. 4.The steering force actuator of claim 3, wherein: a carrier hole is formed on the carrier body such that the carrier pin passes through the carrier body, and the elastic relaxation member inserted into the carrier hole is configured to elastically support the carrier pin.

5. The steering force actuator of claim 4, wherein, At least one of the carrier hole and the carrier pin is provided with a rotation restriction portion configured to restrict the axis rotation of the elastic relaxation member.

6. The steering force actuator of claim 4, wherein, The elastic relaxation member comprises: a first elastic portion configured to be in close contact with an inner circumferential surface of the carrier hole; a second elastic portion configured to be in close contact with an outer circumferential surface of the carrier pin; and a third elastic portion configured to connect the first elastic portion and the second elastic portion, wherein the first elastic portion and the second elastic portion are alternately disposed in a circumferential direction.

7. The steering force actuator of claim 6, wherein, Both ends of the elastic relaxation member are spaced apart from each other.

8. The steering force actuator of claim 7, wherein, Both ends of the elastic relaxation member are disposed in close contact with the inner circumferential surface of the carrier hole or the outer circumferential surface of the carrier pin and face each other.

9. The steering force actuator of claim 7, wherein, The elastic relaxation member further comprises a fourth elastic portion configured to: connect both ends of the elastic relaxation member; and contract under an external force and recover when the external force is removed.

10. The steering force actuator of claim 7, wherein, Both ends of the elastic relaxation member correspond to a direction of a load applied to the carrier pin.

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