KR101615230B1 - Structure of worm shaft for electric power steering system - Google Patents

Abstract

The present invention relates to a structure of a worm shaft for an electric power steering system capable of minimizing a noise by absorbing a shock in case of axial displacement of the warm shaft, which is implemented by disposing a bearing holder having a ball and an elastic member at the end of the warm shaft as well as disposing a damper inside the bearing holder, to compensate for the vertical displacement of the warm shaft. According to the present invention, the structure of the warm shaft for an electric power steering system comprises: a warm shaft in which a gear unit is placed on the outer circumferential surface, wherein the gear unit has a tooth-engagement with a worm wheel; a ball bearing which is placed at the end of the worm shaft to be coupled; a bearing holder having a hollow to be coupled to surround the outer surface of the ball bearing, and having an accommodation hole perforated to accommodate the ball on the outer circumference surface; an elastic member which is combined to cover the outer circumferential surface of the bearing holder to intensify the coupling of the ball; and a damping means which interferes and buffers the movement of the ball bearing in case of axial displacement of the warm shaft.

Description

Technical Field [0001] The present invention relates to a worm shaft structure for an electric power steering device,

The present invention relates to a worm shaft structure of an electric power steering apparatus, and more particularly, to a worm shaft structure for an electric power steering apparatus that includes a ball member and an elastic member in a bearing holder for supporting a ball bearing coupled to an end of a worm shaft, The present invention relates to a worm shaft structure of an electric power steering apparatus having a damper member provided on an inner side of a bearing housing to reduce contact noise between a ball bearing and a bearing holder.

Generally, a power steering system is applied to a vehicle in order to ensure stability of a steering state. In such a power steering apparatus, a hydraulic power steering system (HPS) using hydraulic pressure has been widely used in vehicles Recently, unlike the conventional method using hydraulic pressure, the steering force of the driver is easily made by using the rotation force of the motor, and installation of an environmentally friendly electric power steering system (EPS) is increasing.

The electric power steering device drives the motor by the ECU in accordance with the driving conditions of the vehicle sensed by the vehicle speed sensor and the steering torque sensor to provide a light and comfortable steering feeling at low speed operation and at the same time, In the emergency situation, rapid steering is performed, and the optimum steering condition is provided to the driver.

The electric power steering device is divided into a column type (C-EPS), a pinion type (P-EPS), and a rack type (R-EPS) depending on the installed state.

The rack-type (R-EPS) steering device of the electric power steering device has an obtuse angle or an acute angle of inclination at one side of the rack housing, and a pinion gear of an installed electric motor supports the outer periphery of the rack bar. The ball nut is rotated by the driving force of the electric motor in the engaged state, and the rack bar is slid left and right by this rotational force, so that the assist force is generated according to the steering of the steering wheel.

Generally, in a worm gear speed reduction mechanism of an electric power steering apparatus, an axial distance between a gear accommodating side of a housing and an output shaft of a drive motor is set to a distance, with respect to an axial distance including a wedge radius of each worm and a worm gear.

For this reason, in addition to the setting backlash, additional backlash often arises due to unevenness in processing.

Such additional backlash serves as a main factor for impairing the reliability or technical level, such as giving the driver an unpleasant feeling due to the rattle sound when the vehicle runs on a road surface with a poor road surface condition.

As a countermeasure therefor, there has been employed a method of increasing the precision of gears and setting backlashes to be very small, or installing an elastic body or the like between the worm and its bearings for bearing to absorb vibration.

As described above, conventionally, when the distance between the center of the worm and the center of the worm gear varies due to abrasion of the gear, the preliminary pressure changes due to the minute displacement of the worm, which makes it difficult to secure a stable preliminary pressure .

As a prior art of a conventional electric power steering apparatus for improving this, there has been known a conventional electric power steering apparatus, which is mounted on a housing and has an auxiliary steering driving force as shown in Korean Registered Patent No. 10-1204306 entitled "Electric Power Steering Apparatus" A rotation shaft supported by a motor-side outer bearing mounted on the housing and splined to a shaft of the drive motor; an output shaft pivotally supported at a predetermined position of the housing and transmitting a steering force; And a worm gear integrally formed on the rotary shaft and the worm gear so as to be engaged with the worm, the worm gear being used to transmit the auxiliary steering force to the output shaft using the worm gear The bearing on the side facing the drive motor is supported by a bearing supporting member surrounding the outer peripheral surface of the bearing Wherein a resilient ring member is coupled to an annular groove formed on an outer circumferential surface of the bearing supporting member and a through hole formed on one side of the outer circumferential surface of the bearing supporting member is interposed between the resilient ring member and the outer peripheral surface of the bearing, So as to be brought into contact with each other.

Another prior art of the conventional electric power steering apparatus is disclosed in Korean Patent Laid-Open Publication No. 10-2013-0071257 entitled " Noise Reduction Type Electric Steering Device "(published on Mar. 31, 2013) A worm shaft rotatably engaged with the worm wheel; a bearing member coupled to the worm shaft to reduce friction generated during rotation; an inner member surrounding the outer periphery of the bearing member; an outer member disposed along the periphery of the inner member; And an elastic member provided between the inner member and the outer member to absorb the impact.

However, in the conventional warm shaft, the ball holder and the elastic member are provided in the bearing holder for supporting the end portion. However, when the worm shaft is displaced, the ball member comes into contact with the inner surface of the holder and generates contact noise.

Korean Patent Registration No. 10-1204306 entitled " Electric Power Steering Device "(Registered on November 19, 2012) Korean Patent Laid-Open No. 10-2013-0071257 entitled "Noise Reduction Type Electric-Powered Steering Device" (Published on 2013.06.28)

The object of the present invention is to provide a bearing holder having a ball member and an elastic member at the end of a worm shaft so as to compensate for a vertical displacement of the worm shaft, The present invention provides a worm shaft structure of an electric power steering apparatus having an improved structure for absorbing shocks and suppressing noise when an axial displacement of a worm shaft is generated by disposing a damper member inside a holder.

According to an aspect of the present invention, there is provided a worm gear device comprising: a worm shaft having a gear portion meshing with a worm wheel on an outer circumferential surface thereof; a ball bearing disposed at an end of the worm shaft; An elastic member coupled to surround the outer circumferential surface of the bearing holder to bind the ball member; and an elastic member coupled to the ball member, when the worm shaft is axially displaced, And damping means for interfering with movement and buffering.

The damping means includes a coupling groove formed concavely in the hollow inner peripheral surface of the bearing holder, and a damper member fitted into the coupling groove.

The coupling groove is formed in an elliptical shape in which a vertical inner diameter portion is larger than a horizontal inner diameter portion.

The damper member is made of a material which is elastically deformed as an external load is transmitted and can be restored by self-elastic force.

The damper member is formed in the shape of an elliptical ring in which a through hole is formed at the center and a vertical inner diameter portion of the through hole is formed larger than a horizontal inner diameter portion.

The present invention relates to a wormshaft structure which is capable of restricting movement distances with respect to vertical and axial displacements and reducing shock noise when a worm shaft is formed by engaging a bearing holder provided with damping means on the outside of a first ball bearing of a worm shaft structure Effect.

1 is a perspective view of an electric power steering apparatus to which a wormshaft structure of the present invention is applied.
2 is an exploded perspective view showing a configuration of a worm shaft structure of an electric power steering apparatus according to the present invention.
Figure 3 is an exploded perspective view of Figure 2 from another angle;
Fig. 4 is a view illustrating a state where the first ball bearing of the present invention is engaged with the bearing holder. Fig.
5 is a sectional view taken along the line AA in Fig.
6 is a view showing the state of use of the first ball bearing and the bearing holder when axial and vertical displacement occurs in the worm shaft of the present invention.
7 is a sectional view taken along line BB of Fig.

1 to 7, a worm shaft 200 having a gear portion 210 engaged with a worm wheel 100 is provided on an outer circumferential surface of the worm shaft 200, (310, 320) coupled to a left end and a right end of the worm shaft (200), and a ball (405) formed to surround the ball bearing (310) coupled to the left end, A bearing holder 400 in which a receiving hole 415 is perforated so as to be able to receive the member 510 and an elastic member 400 which is coupled to surround the outer circumferential surface of the bearing holder 400 and binds the ball member 510, And a damping means (600) for interfering with the movement of the ball bearing when the worm shaft (200) is displaced in the axial direction to buffer the worm shaft (200).

More specifically, the ball bearing includes a first ball bearing 310 coupled to the left end of the worm shaft 200 and a second ball bearing 320 coupled to the right end of the worm shaft 200 to support the rotation of the worm shaft 200 do.

The bearing holder 400 has a structure in which a hollow 405 having one side and the other side opened is formed and a concave circumferential groove 410 is formed on the outer circumferential surface.

In the bearing holder 400, the end of the worm shaft 200 coupled with the first ball bearing 310 is received inside the hollow 405.

In addition, the bearing holder 400 has a structure in which the receiving hole 415 is formed to bore the ball member 510 at the bottom of the peripheral groove 410.

The ball member 510 is received in the receiving hole 415 such that a part of the outer circumferential surface thereof protrudes outwardly of the peripheral groove 410 and the remaining part thereof protrudes into the hollow 405 of the bearing holder 400.

The bearing holder 400 has a function of restricting the outer circumference of the circumferential groove 410 so as to surround the elastic member 520 in the form of a ring to prevent the ball member 510 accommodated in the accommodation hole 415 from being separated from the outside .

The damping means 600 of the present invention includes a coupling groove 610 formed in a concave shape around the inner circumference of the hollow 405 of the bearing holder 400 and a damper member 620 fitted into the coupling groove 610, Respectively.

The engaging groove 610 is formed in a concave groove shape having an elliptical shape in which a vertical inner diameter portion is formed larger than a horizontal inner diameter portion.

The damper member 620 is formed in an elliptical O-ring shape in which a through hole is formed at the center and a vertical inner diameter portion of the through hole is larger than a horizontal inner diameter portion. The damper member 620 is elastically deformed as an external load is transmitted, As shown in FIG.

The damper member 620 may be made of a rubber material. The damper member 620 may be formed of rubber material. The outer circumferential edge of the damper member 620 is coupled to be received in the coupling groove 610 and the inner circumferential edge of the damper member 620 is coupled to the first ball bearing 310).

The present invention having such a configuration joins the first ball bearing 310 to the left end of the worm shaft 200 and the second ball bearing 320 to the right end of the worm shaft 200.

Thereafter, the first ball bearing 310 coupled to one end of the warm shaft 200 enters the hollow 405 of the bearing holder 400.

4 and 5, the left end of the worm shaft 200 to which the first ball bearing 310 is coupled is inserted into the hollow portion of the bearing holder 400. In the neutral state in which the worm shaft 200 is not displaced, The outer circumferential surface of the first ball bearing 310 is in contact with the ball member 510 and does not contact the damper member 620 coupled to the coupling groove 610. In this case,

The ball member 510 is accommodated in the receiving hole 415 and is in a state of being constrained to be prevented from being detached by the elastic member 520 in the form of an annular shape while being in contact with the outer peripheral surface of the first ball bearing 310, The resistance against the vertical height displacement generated in the rotating operation of the worm shaft 200 and the worm shaft 200 is compensated for and the vertical clearance of the worm shaft 200 is compensated.

That is, when the worm wheel 100 and the worm shaft 200 rotate in a direction perpendicular to the worm shaft 200, the first ball bearing 310 is lifted upward to move upward the ball member 510 The ball member 510 is resiliently supported by the elastic member 520 so that the ball member 510 is returned to the original position even if it vertically rises in the receiving hole 415 and the upward movement force of the first ball bearing 310 So that it can be compensated by the resistance against

When a vertical displacement occurs in the first ball bearing 310, the vertical movement amount can be limited due to the structure coupled in the hollow 405 of the bearing holder 400.

The damper member 620 is coupled to the coupling groove 610 formed in the inner circumferential surface of the hollow 405 of the bearing holder 400 when the worm shaft 200 is displaced in the axial direction The one end of the worm shaft 200 coupled with the first ball bearing 310 hits the damper member 620 so that the movement of the worm shaft 200 in the hollow 405 is restricted and the contact noise with the inner circumferential surface of the hollow 405 is reduced .

At this time, as shown in FIGS. 6 and 7, the worm shaft 200 moves in the vertical direction and the axial direction at the same time so that the first ball bearing 310 is moved upward to be in contact with the ball member 510, The end of the first ball bearing 310 is moved in the left direction of the drawing to contact the damper member 620. [

Accordingly, the present invention is applicable to a case in which the bearing holder 400 having the damping means 600 is coupled to the outside of the first ball bearing 310, so that the displacement of the worm shaft 200 in the vertical direction and the axial direction It has a useful advantage of being able to limit the travel distance and reduce the impact noise.

The present invention has the technical idea of compensating the vertical and axial displacements at the ends of the worm shaft, and can be modified in various ways without departing from the concept and scope of the present invention.

100: Worm wheel 200: Worm shaft
210: gear portion 310, 320: first and second ball bearings
400: Bearing holder 405: hollow
410: circumferential groove 415: receiving hole
510: ball member 520: elastic member
600: damping means 610: engaging groove
620: damper member

Claims (5)

A worm shaft 200 having a gear portion 210 engaged with a worm wheel 100 on an outer circumferential surface thereof,
A ball bearing disposed at an end of the warm shaft 200,
A bearing holder 400 formed with a hollow 405 and coupled to surround the outside of the ball bearing and having a receiving hole 415 formed therein to receive the ball member 510,
An elastic member 520 coupled to surround the outer periphery of the bearing holder 400 to bind the ball member 510,
A damping means 600 for providing a resistance against vertical displacement of the worm shaft 200 when the worm shaft 200 is displaced in the axial direction by interfering with the movement of the ball bearing in the axial direction displacement of the worm shaft 200, ),
The damping means 600 includes a coupling groove 610 formed concavely in the inner circumference of the hollow 405 of the bearing holder 400 and a damper member 620 fitted into the coupling groove 610,
The coupling groove 610 is formed in an elliptical shape in which a vertical inner diameter portion is formed larger than a horizontal inner diameter portion. The damper member 620 has a through hole at the center thereof. The vertical inner diameter portion of the through hole is longer than the horizontal inner diameter portion Formed in a largely formed elliptical ring shape,
The outer circumferential surface of the ball bearing which has entered the hollow interior of the bearing holder is in contact with the ball member and is not in contact with the damper member coupled to the coupling groove And the outer peripheral surface of the ball bearing is in contact with the damper member when axial displacement and vertical displacement of the worm shaft (200) occur. delete delete The method according to claim 1,
Wherein the damper member (620) is made of a material that is elastically deformed as the external load is transmitted and is restored by self-elastic force. delete

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