JP2008137473A - Rack for steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rack for a steering device and a steering device with small increase of the number of parts and small rising of manufacturing cost in which stress is not concentrated to a base of a rack tooth engaged with a pinion at a stroke end of the rack. <P>SOLUTION: When a steering wheel 101 is operated and the rack 31 reaches a stroke end at a left side, a rack end 34 on a right side of the rack 31 is abutted on a stopper 26 fixed to a right end of a housing 21 to stop the rack 31. At the stroke end on the left side of the rack 31, large thrust in a direction of arrow F1 in Fig. 5 (2) is applied to the rack teeth 322, 323 engaged with the pinion 221. However, since rounds 36, 36 with large radius of curvature are formed on the bases of the right tooth surfaces 35A, 35A in the rack teeth 322, 323, stress concentration is relaxed and durability of the rack teeth 322, 323 is enhanced. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a steering device rack and a steering device having a steering device rack, and more particularly to a steering device rack having improved rack tooth strength at a stroke end of the rack and a steering device having a steering device rack. It is.

  There is a steering device that operates a steering wheel to rotate a pinion, reciprocally moves a rack that meshes with the pinion, and steers a steered wheel via a tie rod. In such a rack and pinion type steering device, when the rack reaches the stroke end, the rack end fixed to the rack end comes into contact with a stopper fixed to the end of the rack housing, and the rack stops.

  Therefore, when the rack stops at the stroke end, a large thrust acts on the rack teeth that mesh with the pinion, and stress concentrates on the rack teeth, resulting in insufficient rack teeth strength. .

  There is a steering device disclosed in Patent Document 1 as a steering device that alleviates the action of a large thrust on the rack teeth of a portion engaged with the pinion at the stroke end of such a rack.

  In the steering device disclosed in Patent Document 1, when the rack reaches the stroke end, the rack end fixed to the rack end abuts against a buffer member fixed to the end of the rack housing, thereby mitigating shock when the rack stops. In addition, noise and thrust acting on the rack teeth are reduced.

  In such a steering device of Patent Document 1, since it is necessary to mount a buffer member between the rack end and the rack housing, the number of parts increases, the manufacturing cost increases, and the axial space of the rack also increases. There is a problem of growing.

JP-A-8-133102

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a steering device rack and a steering device in which stress is not concentrated on the base of a rack tooth meshing with a pinion at the stroke end of the rack, and the increase in the number of parts and the increase in manufacturing cost are small. .

  The above problem is solved by the following means. That is, the first invention relates to a rack for a steering device that meshes with a pinion that rotates by operation of a steering wheel and reciprocates to apply a steering force to a steering gear. The radius of curvature of the root of the tooth surface on the side where the thrust from the pinion acts is larger than the radius of curvature of the root of the tooth surface on the side where the thrust from the pinion does not act This is a rack for a steering device.

  According to a second aspect of the present invention, there is provided a steering apparatus having a rack that meshes with a pinion that rotates by operation of a steering wheel and reciprocates and applies a steering force to a steering gear. The radius of curvature of the root of the tooth surface on the side where the thrust from the pinion acts is larger than the radius of curvature of the roundness of the tooth surface on the side of the tooth surface where the thrust from the pinion does not act, Steering apparatus.

  In the steering device rack and the steering device of the present invention, the curvature radius of the roundness of the tooth root of the tooth surface on the side on which the thrust from the pinion acts on the rack tooth that meshes with the pinion at the stroke end of the rack is the thrust from the pinion. The radius of curvature of the root of the tooth surface on the non-acting side is larger than the radius of curvature. Accordingly, stress is not concentrated on the base of the rack teeth meshing with the pinion at the stroke end of the rack, so that the durability of the rack is improved, the number of parts is not increased, and the increase in manufacturing cost is small.

  In addition, since the steering device rack of the present invention has a simple shape, it can be easily manufactured not only by non-cutting processing such as cold forging but also by cutting processing such as hobbing or slotter processing. Surface grinding and polishing are also facilitated.

  FIG. 1 shows a steering apparatus according to an embodiment of the present invention, wherein (1) is an overall perspective view of a column assist type rack and pinion type steering apparatus, and (2) is an overall perspective view of the pinion assist type rack and pinion type steering apparatus.

  The column assist type rack and pinion type power steering apparatus shown in FIG. 1A applies a steering assist force of a motor 102 attached to an intermediate portion of a column 105 to a steering shaft in order to reduce the operation force of the steering wheel 101. ing. Then, the rotation of the steering shaft is transmitted to the intermediate shaft 106, the rack of the rack and pinion type steering gear 103 is reciprocated, and the steering wheel is steered via the tie rod 104.

  The pinion assist type rack and pinion type power steering apparatus shown in FIG. 1 (2) applies the steering assist force of the motor 107 to the pinion shaft that meshes with the rack of the steering gear 103 in order to reduce the operating force of the steering wheel 101. ing. The rack of the steering gear 103 that meshes with the pinion of the pinion shaft is reciprocated to steer the steered wheel via the tie rod 104.

  In such column assist type and pinion assist type rack and pinion type power steering devices, the steering assist force acts on the meshing surface between the rack and the pinion. Therefore, when the rack end comes into contact with the end surface of the rack housing at the stroke end of the rack, a large thrust acts on the rack, and a large stress acts on the tooth base of the rack tooth that meshes with the pinion at the rack stroke end.

  2 is a longitudinal sectional view showing a meshing portion between a rack and a pinion of the column assist type rack and pinion type steering device of FIG. 3 is a cross-sectional view taken along line AA of FIG. 2 showing a state where the rack is at the center position of the rack stroke. 4 is a cross-sectional view taken along line AA of FIG. 2 showing a state where the rack is at the end of the rack stroke.

  As shown in FIG. 2, the lower end portion of the pinion shaft 22 is pivotally supported by a ball bearing 23 and a needle bearing 24 on the housing 21 of the steering gear 103. The upper end of the pinion shaft 22 is connected to the intermediate shaft 106 in FIG. 1 (1) via a cardan joint (not shown).

  The rotation of the pinion shaft 22 is transmitted to the rack 31 via the pinion 221, and is connected to the rack 31 via FIG. 1 (1) and the tie rods (steering devices) 104 and 104 of FIGS. Change the direction of the helm.

  In the rolling rack guide, a roller 41 is pressed against an outer periphery 33 on the back side of the rack teeth 32 of the rack 31 by an adjustment cover 42. The roller 41 is rotatably supported on a cylindrical shaft body 43 by a plurality of needle rollers 44. The shaft body 43 is accommodated in the groove 451 of the cylindrical holder 45. The rack guide is not limited to the rolling rack guide of the embodiment of the present invention, and may be a sliding rack guide.

  A guide hole 25 having a circular cross section is formed in the housing 21, and a holder 45 is fitted into the guide hole 25 so as to be slidable in the left-right direction in FIG. The adjustment cover 42 is rotated to appropriately adjust the screwing distance, and the adjustment cover 42 is prevented from loosening with the lock nut 46, so that the holder 45 is pressed against the rack 31 side via the disc spring 47, and the outer periphery 33 of the rack 31. The roller 41 is pressed against the surface. Thereby, the backlash of the meshing part between the pinion 221 and the rack 31 is eliminated, and the rack 31 moves smoothly.

  As shown in FIGS. 3 and 4, a rack end 34 is fixed to the left end of the rack 31, and this rack end 34 is coupled to a tie rod 104 via a ball joint (not shown), and the steering force of the steering wheel 101 is applied to the wheel. To communicate. Although not shown, a rack end 34 shown in FIGS. 3 and 4 is also fixed to the right end of the rack 31 and coupled to the right tie rod 104 via a ball joint.

  As shown in FIG. 4, the rack 31 moves to the right side, and at the stroke end on the right side of the rack 31, the rack end 34 comes into contact with the stopper 26 fixed to the left end of the housing 21. Is restricted from being removed from the pinion 221.

  5 (1) is a front view showing a single rack according to an embodiment of the present invention, FIG. 5 (2) is an enlarged cross-sectional view of a portion P in FIG. 5 (1), and FIG. 5 (3) is Q in FIG. FIG.

  As shown in FIGS. 5 (1) and (2), the two adjacent rack teeth (teeth) 322 and 323 on the right end side of the rack 31 have a radius of curvature at the roots of the right tooth surfaces 35A and 35A. Large rounds 36, 36 are formed. The rounds 36 and 36 having a large curvature radius are smoothly connected to the right tooth surfaces 35A and 35A.

  Further, rounds 37 and 37 having a small radius of curvature are formed at the root of the left tooth surface 35B of the rack tooth 322 and the tooth base of the left tooth surface 35B of the rack tooth 321 adjacent to the right of the rack tooth 322. . The rounds 37 and 37 having a small curvature radius are smoothly connected to the rounds 36 and 36 having a large curvature radius.

  The three adjacent rack teeth 326, 327, and 328 on the left end side of the rack 31 have a radius of curvature at the tooth base of the left tooth surface, contrary to the roundness of the tooth base of the rack teeth 322 and 323 on the right end side. A large roundness is formed. In addition, roundness having a small curvature radius is formed at the root of the right tooth surface of the rack teeth 327 and 328 and the root of the right tooth surface of the rack tooth 329 adjacent to the left of the rack tooth 328.

  The rack teeth obtained by removing the rack teeth 323 from the rack teeth 321 and the rack teeth 326 from the rack teeth 329 are, for example, two rack teeth 324 and 325 adjacent to each other as shown in FIG. Rounds 38, 38 having the same radius of curvature are formed at the roots of the right tooth surface 35A of 325 and the left tooth surface 35B of the rack tooth 324.

  Accordingly, when the steering wheel 101 is operated to rotate the pinion 221 in FIG. 2, the rack 31 moves to the left in FIG. 5 (1). When the rack 31 reaches the left stroke end, the rack end 34 on the right side of the rack 31 comes into contact with the stopper 26 fixed to the right end of the housing 21 and the rack 31 stops.

  Therefore, at the stroke end on the left side of the rack 31, the teeth of the right tooth surfaces 35 </ b> A and 35 </ b> A of the rack teeth 322 and 323 meshing with the pinion 221 are large in the direction of the arrow F <b> 1 in FIGS. Thrust acts. However, since the rack teeth 322 and 323 are formed with rounds 36 and 36 having a large radius of curvature at the bases of the right tooth surfaces 35A and 35A, the stress concentration is alleviated and the rack teeth 322 and 323 are durable. Improves. Moreover, since the number of parts does not increase, the number of assembling steps is reduced, and the increase in manufacturing cost is small.

  In the embodiment of the present invention, the radius of curvature of the round 38 having the same radius of curvature is 1.2 mm. Moreover, the curvature radius of the round 36 with a large curvature radius is 3.0 mm. As a result of analyzing the stress acting on the tooth root, the stress acting on the tooth surface of the tooth surface having a radius of curvature of 3.0 mm acts on the tooth root of the tooth surface having a radius of curvature of 1.2 mm. Is suppressed to about 80% of the stress.

  Further, when the steering wheel 101 is operated in the reverse direction and the rack 31 moves to the right side in FIG. 5A and the rack 31 reaches the right stroke end, the rack end 34 on the left side of the rack 31 is moved to the housing. The rack 31 stops in contact with the stopper 26 fixed to the left end of 21.

  Therefore, at the stroke end on the right side of the rack 31, a large thrust in the direction of arrow F2 in FIG. 5 (1) acts on the teeth of the left tooth surface of the rack teeth 326, 327, and 328 engaged with the pinion 221. However, since the rack teeth 326, 327, and 328 are formed with rounds having a large radius of curvature at the base of the left tooth surface, the stress concentration is reduced, and the durability of the rack teeth 326, 327, and 328 is improved. improves.

  Since the rack 31 of the embodiment of the present invention has a simple shape, it can be easily manufactured not only by non-cutting processing such as cold forging but also by cutting processing such as hobbing and slotter processing. Grinding and polishing are easy.

  In the above embodiment, the round 36 having a large radius of curvature is formed by an arc, but is not limited to an arc, and may be a curve having a shape that smoothly connects to a tooth surface, such as a compound arc or an ellipse.

  In the above-described embodiment, an example in which the present invention is applied to a steering apparatus having an electric power steering apparatus has been described. However, the present invention may be applied to a steering apparatus without an electric power steering apparatus.

1 shows a steering apparatus according to an embodiment of the present invention, wherein (1) is an overall perspective view of a column assist type rack and pinion type steering apparatus, and (2) is an overall perspective view of the pinion assist type rack and pinion type steering apparatus. It is a longitudinal cross-sectional view which shows the meshing part of the rack and pinion of the column assist type | mold rack and pinion type steering device of FIG. It is AA sectional drawing of FIG. 2 which shows the state which has a rack in the center position of a stroke. It is AA sectional drawing of FIG. 2 which shows the state which has a rack in the edge part of a rack stroke. (1) is the front view which shows the rack single-piece | unit of the Example of this invention, (2) is the P section expanded sectional view of (1), (3) is the Q section expanded sectional view of (1).

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Steering wheel 102 Motor 103 Steering gear 104 Tie rod 105 Column 106 Intermediate shaft 107 Motor 21 Housing 22 Pinion shaft 221 Pinion 23 Ball bearing 24 Needle bearing 25 Guide hole 26 Stopper 31 Rack 32 Rack teeth 321, 322, 323 Rack teeth 324, 325 Rack teeth 326, 327, 328, 329 Rack teeth 33 Outer periphery 34 Rack end 35A Right tooth surface 35B Left tooth surface 36 Round with large radius of curvature 37 Round with small radius of curvature 38 Round with same radius of curvature 41 Roller 42 Adjust cover 43 Shaft 44 Needle roller 45 Holder 451 Groove 46 Lock nut 47 Disc spring

Claims (2)

In a steering device rack that meshes with a pinion that rotates by the operation of a steering wheel, reciprocates, and applies steering force to a steering gear.
The radius of curvature of the tooth root of the tooth surface on the side where the thrust from the pinion acts on the rack tooth that meshes with the pinion at the stroke end of the rack is the tooth radius of the tooth surface on the side where the thrust from the pinion does not act A rack for a steering device, wherein the rack is formed to be larger than a rounded radius of curvature. In a steering apparatus having a rack that meshes with a pinion that rotates by operation of a steering wheel and reciprocates and applies a steering force to a steering gear.
The radius of curvature of the tooth root of the tooth surface on the side where the thrust from the pinion acts on the rack tooth that meshes with the pinion at the stroke end of the rack is the tooth radius of the tooth surface on the side where the thrust from the pinion does not act A steering device characterized by being formed to be larger than a rounded radius of curvature.

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