阅读说明：本技术 齿条驱动电动动力辅助转向装置 (Rack-driven electric power-assisted steering device ) 是由 李宗栢 于 2020-02-25 设计创作，主要内容包括：本发明的实施例涉及一种齿条驱动电动动力辅助转向装置。本发明的实施例提供一种齿条驱动电动动力辅助转向装置,包括：齿条,该齿条在齿条壳体中沿轴向方向滑动并具有形成在其外周表面处的外周螺纹槽；滚珠螺母,该滚珠螺母具有形成在其内外周表面处并与齿条的外周螺纹槽相对应的内周螺纹槽,并具有形成在外周表面和内周表面之间的滚珠循环通道,该滚珠循环通道沿轴向方向穿过滚珠螺母；端盖,该端盖分别耦合到滚珠循环通道的一端和另一端,端盖中的每一个都具有滚珠返回孔,用于使滚珠循环通过滚珠循环通道、外周螺纹槽和内周螺纹槽；以及支撑构件,该支撑构件耦合到滚珠螺母的内周表面同时沿轴向方向支撑端盖。(Embodiments of the present invention relate to a rack-driven electric power-assisted steering apparatus. An embodiment of the present invention provides a rack-driven electric power-assisted steering apparatus including: a rack bar sliding in an axial direction in the rack housing and having an outer circumferential thread groove formed at an outer circumferential surface thereof; a ball nut having an inner circumferential thread groove formed at an inner and outer circumferential surface thereof and corresponding to the outer circumferential thread groove of the rack, and having a ball circulation passage formed between the outer and inner circumferential surfaces, the ball circulation passage passing through the ball nut in an axial direction; end caps coupled to one end and the other end of the ball circulation passage, respectively, each of the end caps having a ball return hole for circulating the balls through the ball circulation passage, the outer circumferential screw groove, and the inner circumferential screw groove; and a support member coupled to an inner circumferential surface of the ball nut while supporting the end cap in an axial direction.)

1. A rack drive power assisted steering apparatus comprising:

a rack axially sliding within a rack housing and having an outer peripheral helical groove formed in an outer peripheral surface;

a ball nut having an inner peripheral thread groove formed in an inner peripheral surface thereof, the inner peripheral thread groove corresponding to the outer peripheral thread groove of the rack;

a ball circulation path axially formed between the inner and outer peripheral surfaces through the ball nut;

an end cap having a ball return hole to circulate balls along the ball circulation path, the outer circumferential helical groove, and the inner circumferential helical groove, the end cap coupled to each of first and second ends of the ball circulation path; and

a support member coupled to the inner peripheral surface of the ball nut while axially supporting the end cap.

2. The rack drive power assisted steering apparatus according to claim 1, wherein the ball nut has a small diameter portion having an inner peripheral threaded groove and a large diameter portion having a larger diameter and provided on both opposite ends of the small diameter portion at the inner peripheral surface, and wherein the support member is coupled to the inner peripheral surface of the large diameter portion.

3. The rack drive power-assisted steering apparatus according to claim 2, wherein the support member is coupled to a stepped portion where the large diameter portion and the small diameter portion are connected together.

4. The rack drive power-assisted steering device according to claim 2, wherein insertion recesses are formed on two opposite sides of an inner peripheral surface of the large diameter portion to fit the support member.

5. The rack drive power-assisted steering device according to claim 4, wherein the support member is formed in an annular shape, and has a radially outer end fitted into the insertion recess and a radially inner end formed to an inner peripheral surface of the small diameter portion.

6. The rack drive power assisted steering apparatus according to claim 2 wherein the support member is formed of an annular resilient plastics material.

7. The rack drive power assisted steering apparatus according to claim 2 wherein the support member is formed of an annular resilient plastics material having a cut-out on one side.

8. The rack drive power-assisted steering apparatus according to claim 2, wherein the support member has a seat groove in an axially outer surface, and wherein an elastic member is fitted in the seat groove to elastically support the support member in a radial direction.

9. The rack-driven power-assisted steering apparatus according to claim 8, wherein the elastic member is formed in an annular shape having a cutout on a peripheral side.

10. The rack drive power-assisted steering apparatus according to claim 2, wherein the support member has a damper on a side surface that supports the end cover.

11. The rack drive power-assisted steering apparatus according to claim 2, wherein the support member has a seat groove in an inner peripheral surface, and wherein an elastic member is fitted into the seat groove to elastically support the support member in a radial direction.

12. The rack-driven power-assisted steering apparatus according to claim 11, wherein the elastic member is formed in an annular shape having a cutout on a peripheral side.

13. The rack drive power assisted steering apparatus according to claim 1 wherein a bearing support member is coupled to an axial end of the ball nut to axially support a bearing supporting rotation of the ball nut and prevent disengagement of the bearing.

14. The rack drive power assisted steering apparatus according to claim 13 wherein the bearing support member includes an out coupling portion coupled to an outer peripheral surface of the ball nut and an in coupling portion coupled to an inner peripheral surface of the ball nut to axially support the end cap.

15. The rack drive power-assisted steering apparatus according to claim 14, wherein the in-coupling portion has a damper on a side surface supporting the end cover.

16. The rack drive power assisted steering apparatus according to claim 15 wherein the bearing support member includes a side portion supporting one end of the ball nut, and wherein outer and inner ends of the side portion are connected to the out-coupling portion and the in-coupling portion, respectively.

17. The rack drive power assisted steering apparatus according to claim 16, wherein a threaded portion is formed in an inner peripheral surface of the outer coupling portion to be threadedly connected with a threaded portion formed in an outer peripheral surface of the ball nut.

18. The rack drive power assisted steering apparatus according to claim 17, wherein a threaded portion is formed in an outer peripheral surface of the inner coupling portion to be threadedly connected with a threaded portion formed in an inner peripheral surface of the ball nut.

19. The rack drive power-assisted steering apparatus according to claim 18, wherein an outer support end protruding radially outward is formed at one end of the out-coupling portion to support an inner race of the bearing.

20. The rack drive power-assisted steering apparatus according to claim 19, wherein an inner support end protruding radially inward is formed at one end of the inner coupling portion to support a side surface of the head cover.

Technical Field

Embodiments herein relate to a rack-driven power-assisted steering apparatus, and more particularly, to a rack-driven power-assisted steering apparatus with which driving stability and durability can be improved while reducing costs and assembly steps by simplifying a structure and reducing the number of parts assembled in a ball circulation structure of a ball nut and a rack.

Background

Generally, a conventional electric power assisted steering apparatus has: the ball nut is connected with the motor and the belt; and a rack bar sliding by rotation of the motor pulley, the nut pulley and the ball nut; as a component that transmits the driving force of the motor to the rack bar and generates a steering assist force to assist the steering force of the user.

However, since a ball circulation structure of the ball nut and the rack gear is provided with a complicated structure and many components, the cost and the assembly steps of such a conventional electric power assisted steering apparatus are increased.

Further, the assembled components are frequently broken down due to, for example, vibration caused by the operation of the ball nut and the rack or reverse impact load from the road surface when the ball nut is rotated to slide the rack, thereby affecting the driving stability and durability.

Disclosure of Invention

The present embodiment was conceived in the context of the above, and aims to improve the running stability and the durability while reducing the cost and the assembly steps by simplifying the structure and reducing the number of parts to be assembled in the ball circulation structure of the ball nut and the rack in the rack-driven power assist steering apparatus.

The object of the present embodiment is not limited to the above object, and other objects will be apparent to those skilled in the art from the following detailed description.

According to the present embodiment, there is provided a rack drive power-assisted steering apparatus including: a rack axially sliding within the rack housing and having an outer peripheral helical groove formed in an outer peripheral surface; a ball nut having an inner peripheral thread groove formed in an inner peripheral surface thereof, the inner peripheral thread groove corresponding to an outer peripheral thread groove of the rack; a ball circulation path axially formed between the inner and outer circumferential surfaces through the ball nut; an end cap having a ball return hole to circulate balls along the ball circulation path, the outer circumferential spiral groove and the inner circumferential spiral groove, the end cap being coupled to each of first and second ends of the ball circulation path; and a support member coupled to an inner circumferential surface of the ball nut while axially supporting the end cap.

According to the present embodiment, it is possible to reduce the cost and the assembly steps by simplifying the structure and reducing the number of parts provided in the ball circulation structure of the ball nut and the rack.

Further, according to the present embodiment, it is possible to improve the running stability and the durability by reducing the component failure due to the vibration caused by the operation of the ball nut and the rack or the reverse impact load from the road surface.

Drawings

Fig. 1 is a partial sectional view schematically showing a rack drive power-assisted steering apparatus according to the present embodiment;

fig. 2 is an exploded perspective view showing a part of the rack drive power-assisted steering apparatus according to the present embodiment; and is

Fig. 3 to 11 are sectional views showing a part of the rack drive power-assisted steering apparatus according to the present embodiment.

Detailed Description

In the following description of examples or embodiments of the disclosure, reference is made to the accompanying drawings in which is shown by way of illustration specific examples or embodiments in which the disclosure may be practiced, and in which the same reference numerals and symbols may be used to designate the same or similar components, even though they are shown in different drawings. Further, in the following description of examples or embodiments of the present disclosure, a detailed description of known functions and components incorporated herein will be omitted when it is determined that the description thereof may make the subject matter in some embodiments of the present disclosure unclear.

Terms such as "first," "second," "a," "B," "a," or "(B)" may be used herein to describe elements of the disclosure. Each of these terms is not intended to define the nature, order, sequence, or number of elements, etc., but rather is intended to distinguish the corresponding element from other elements. When it is referred to that a first element is "connected or coupled," "contacted or overlapped" with a second element, etc., it should be construed that not only the first element may be "directly connected or coupled to" or "directly contacted or overlapped to" the second element, but also a third element may be "interposed" between the first and second elements, or the first and second elements may be "connected or coupled," "contacted or overlapped" with each other by a fourth element, etc.

Fig. 1 is a partial sectional view schematically showing a rack drive power-assisted steering apparatus according to the present embodiment. Fig. 2 is an exploded perspective view showing a part of the rack drive power-assisted steering apparatus according to the present embodiment. Fig. 3 to 11 are sectional views showing a part of the rack drive power-assisted steering apparatus according to the present embodiment.

As shown in the drawing, according to the present embodiment, a rack drive power-assisted steering apparatus includes: a rack 155 axially sliding in the rack housing 201 and having an outer circumferential thread groove 155a formed in an outer circumferential surface thereof; a ball nut 220, the ball nut 220 having an inner circumferential screw groove 225 formed in an inner circumferential surface thereof, the inner circumferential screw groove 225 corresponding to the outer circumferential screw groove 155a of the rack 155; a ball circulation path 221, the ball circulation path 221 being axially formed between the inner peripheral surface and the outer peripheral surface through the ball nut 220; an end cap 229, the end cap 229 having ball return holes 229a to circulate balls along the ball circulation path 221, the outer circumferential spiral groove 155a, and the inner circumferential spiral groove 225, the end cap 229 being coupled to each of first and second ends of the ball circulation path 221; and a support member 213 coupled to an inner circumferential surface of the ball nut 220 while axially supporting the end cap 229.

First, referring to fig. 1, the rack drive power-assisted steering apparatus according to the present embodiment includes: a steering system 100 connected from a steering wheel 105 to two opposing wheels 150; and an auxiliary power mechanism 160 that provides steering auxiliary power to the steering system.

The steering system 100 includes a steering shaft 110, the steering shaft 110 having an upper end connected to the steering wheel 105 for rotation with the steering wheel 105 and a lower end connected to a pinion shaft 120 by a pair of universal joints 115.

Further, the pinion shaft 120 is connected to a rack bar 155 through a rack-and-pinion mechanism part 135, and both opposite ends of the rack bar 155 are connected to wheels 150 of the vehicle through a rod 140 and a knuckle arm 145.

The rack-and-pinion mechanism part 135 is formed of: a pinion 125 formed at a lower end of the pinion shaft 120 is engaged with a rack gear 130 formed on one side of an outer circumferential surface of the rack 155.

The auxiliary power mechanism 160 includes: a torque sensor 117 that detects a steering torque applied to the steering wheel 105 by the driver and outputs an electric signal proportional to the detected steering torque; an electronic control unit ECU that generates a control signal based on an electric signal supplied from the torque sensor 117; a motor 165 that generates steering assist power based on a control signal supplied from the electronic control unit; and a belt type transmission 170 which transmits the auxiliary power generated by the motor 165 to the rack gear 155 through a belt.

Such a rack-driven power-assisted steering apparatus includes a driving device and a driven device. The drive device includes: a motor 165 controlled by an electronic control unit ECU; a motor pulley coupled to a motor shaft; and a belt 210.

The driven device includes: a ball nut 220 supporting the rack gear 155 inside the rack housing 201 surrounding the rack gear 155; and a nut pulley 207 coupled to an outer circumferential surface of the ball nut 220.

A motor pulley connected to the motor and a nut pulley 207 connected to the rack gear 155 are arranged such that their rotation axes are parallel to each other. A belt 210 is wound around the motor pulley and nut pulley 207 to transmit the rotational force of the motor to the rack gear 155 through the ball nut 220. The rack moves left and right by the operation of the ball nut 220, and steering assist power is generated.

The ball nut 220 is coupled with the rack gear 155 by balls (not shown) and slides the rack gear 155 inside the rack housing 201 while rotating. The nut pulley 207 is coupled to one side of the outer circumferential surface of the ball nut 220 to rotate the ball nut 220, and the bearing 205 is mounted to the other side of the outer circumferential surface of the ball nut 220 to support the rotation.

A power transmission structure is provided on an outer circumferential surface of the rack bar 155 and an inner circumferential surface of the ball nut 220 to axially slide the rack bar 155 to generate steering auxiliary power. The power transmission structure includes an outer circumferential thread groove 155a spirally formed in an outer circumferential surface of the rack bar and having a semicircular or arc-shaped cross section, balls inserted therein, and an inner circumferential thread groove 225 spirally formed in an inner circumferential surface of the ball nut 220 to correspond to the outer circumferential thread groove 155a and having a semicircular or arc-shaped cross section.

The ball nut 220 is a hollow tube having an inner peripheral thread groove 225 formed in an inner peripheral surface thereof. The locking screw 227 is provided at an end of an outer ring of the bearing 205 coupled with an outer circumferential surface of the ball nut 220, and is screwed to an inner circumferential surface of the rack housing 201 to be fixed while supporting the bearing 205.

Further, a ball circulation path 221 is formed at one side of the ball nut 220 and the ball circulation path 221. End cover 229 has ball return holes 229a to allow balls to circulate along ball circulation path 221, outer circumferential screw groove 155a, and inner circumferential screw groove 225, and is coupled to two opposite sides of ball circulation path 221.

The ball nut 220 includes a small diameter portion 220a having an inner peripheral thread groove 225 and a large diameter portion 220b having an enlarged inner diameter at both opposite ends of the small diameter portion 220a, 220 a. The support member 213 is coupled to an inner circumferential surface of the large diameter portion 220b to axially support the end cap 229.

The support member 213 is coupled to a stepped portion where the large diameter portion 220b and the small diameter portion 220a are connected in a state of being elastically deformed inward in a radial direction.

The nut pulley 207 is coupled with a tolerance ring that radially generates an elastic force between the nut pulley 207 and an outer circumferential surface of the ball nut 220, thereby preventing the disengagement from the ball nut 220.

The locking screw 227 is screwed to the inner circumferential surface of the rack housing 201 on a first side of the outer race of the bearing 205, supporting the outer race of the bearing 205. The bearing support member 209 is screwed to the outer circumferential surface of the ball nut 220 at a second side of the inner race of the bearing 205, supporting the bearing 205.

The bearing 205 is slidably assembled to the outer circumferential surface of the ball nut 220, and a first side of the inner race of the bearing 205 is supported and fixed to a seat portion 223 having an enlarged diameter at a substantially middle portion of the ball nut 220.

An insertion recess 222 is formed in an inner peripheral surface of the large diameter portion 220b of the ball nut 220 to allow the support member 213 to be inserted therein, so that the support member 213 is supported in the insertion recess 222 while fastening the end cap 229.

The support member 213 is formed in an annular shape such that a radially outer end thereof is inserted into the insertion recess 222, and a radially inner end thereof is formed to reach an inner peripheral surface of the small diameter portion 220 a.

The support member 213 is formed of an elastic annular plastic material so as to be elastically deformable inward in a radial direction if fitted into the insertion recess 222, thereby facilitating assembly. Further, the support member 213 may be formed in a ring shape having a cutout at a side thereof.

Further, as shown in fig. 8, the support member 213 has a seating groove 213b formed in an axial outer surface, and an elastic member 213a for elastically supporting the support member 213 in a radial direction may be fitted into the seating groove 213 b.

The elastic member 213a is formed in an annular shape having a cutout at one circumferential side thereof, and is elastically deformable and fitted into the seating groove 213b of the support member 213 to radially generate an elastic restoring force.

Further, as shown in fig. 9, the support member 213 may have a seating groove 213b formed in an inner circumferential surface, and an elastic member 213a for elastically supporting the support member 213 in a radial direction may be fitted into the seating groove 213 b.

In this case, as described above, the elastic member 213a is formed in an annular shape having a cutout on the circumferential side thereof, and after being fitted to the seating groove 213b of the support member 213, the elastic member 213a elastically supports the elastic member 213 outward in the radial direction.

Further, the support member 213 is provided with a damper 212 at a side supporting the end cap 229 to absorb vibration and noise of the balls circulating along the end cap 229.

The bearing support member 209 is coupled to an axial end of the ball nut 220 to axially support the bearing 205 for supporting the rotation of the ball nut 220 and prevent its disengagement.

As shown in fig. 10 and 11, the bearing support member 209 includes an outer coupling portion 209a coupled to an outer circumferential surface of the ball nut 220, an inner coupling portion 209b coupled to an inner circumferential surface of the ball nut 220 to axially support the end cap 229, and a side portion 209c connecting them.

The inner coupling portion 209b is provided with a damper 208 at one side of the support end cap 229 to absorb vibration and noise of the balls circulating along the end cap 229.

The side portion 209c of the bearing support member 209 is coupled to support one end of the ball nut 220. The outer and inner ends of the side surface portion 209c are connected to the outer and inner coupling portions 209a and 209b, respectively, so as to be coupled to surround the outer and inner circumferential surfaces of the end of the ball nut 220.

A threaded portion is formed on an inner circumferential surface of the outer coupling portion 209a to be threadedly connected with a threaded portion formed on an outer circumferential surface of the ball nut 220, or a threaded portion is formed on an outer circumferential surface of the inner coupling portion 209b to be threadedly connected with a threaded portion formed on an inner circumferential surface of the ball nut 220.

Accordingly, the bearing support member 209 is screwed to the end of the ball nut 220, supporting and fixing the bearing 205 and the end cap 229.

At one end of the out-coupling portion 209a, an outer support end 209d may protrude radially outward to support the inner ring of the bearing 205, thereby increasing a support area for the inner ring of the bearing 205 and thus achieving stable support. Further, since the tool is supported by the stepped portion of the outer support end 209d when the bearing support member 209 is coupled, the assembly can be facilitated.

Further, as shown in fig. 11, at one end of the inner coupling portion 209b, the inner support end 209e may protrude radially inward to support a side surface of the end cap 229, thereby increasing a support area for the end cap 229 and allowing the side surface of the end cap 229 to be more stably supported.

According to the present embodiment, it is possible to reduce the cost and the assembly steps by simplifying the structure and reducing the number of parts to be assembled in the ball circulation structure of the ball nut and the rack.

Further, according to the present embodiment, it is possible to improve the running stability and the durability by reducing the component failure due to the vibration caused by the operation of the ball nut and the rack or the reverse impact load from the road surface.

Although it is described above that all components are combined to operate in one or in combination, embodiments of the present disclosure are not limited thereto. One or more components may be selectively combined and operated as long as they fall within the scope of the object of the embodiment.

When an element "comprises," "comprising," or "having" another element, the element can further include but not exclude the other element, and the terms "comprising," "including," and "having" are to be construed as not excluding the possibility of having or adding one or more features, numbers, steps, operations, elements, components, or combinations thereof. Unless defined otherwise, all scientific and technical terms used herein may have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The previous description is provided to enable any person skilled in the art to make and use the technical ideas of this disclosure, and is provided in the context of a particular application and its requirements. Various modifications, additions and substitutions to the described embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. The above description and the drawings provide examples of the technical idea of the present disclosure for illustrative purposes only. That is, the disclosed embodiments are intended to illustrate the scope of the technical idea of the present disclosure. Thus, the scope of the present disclosure is not limited to the illustrated embodiments, but is to be accorded the widest scope consistent with the claims. The scope of the disclosure is to be determined by the appended claims, and all technical equivalents thereof are intended to be embraced therein.

Cross Reference to Related Applications

This application claims the benefit of priority of korean patent application No. 10-2019-0026684, filed on 8.3.2019 from the korean intellectual property office, the entire contents of which are incorporated herein by reference.