JP4239810B2 - Steering gear device - Google Patents

Description

  The present invention relates to a steering gear device constituting a steering system of a vehicle, and more particularly to a steering gear device incorporating a rack and pinion mechanism.

  2. Description of the Related Art Conventionally, as a steering gear device constituting a vehicle steering system, a device incorporating a rack and pinion mechanism is generally known. This type of steering gear device usually incorporates a rack guide for applying a preload to the rack and pinion mechanism. The rack guide is formed in a generally cup shape in which a curved concave surface capable of pressing the peripheral surface of the rack shaft is formed at the distal end, and an accommodation hole for accommodating a coil spring or the like is opened at the proximal end. The rack guide is slidably fitted into the guide hole of the rack housing in a spring-biased state, and the peripheral surface of the rack shaft is pressed toward the pinion shaft by the curved concave surface at the tip. The rack and pinion mechanism is configured to apply a preload (see, for example, Patent Documents 1 and 2).

  Here, Patent Document 1 discloses a rack shaft as technical means for preventing the rack guide from vibrating with the guide hole and generating noise when external force from the road surface is input to the rack shaft. Technical means for maintaining the clearance between the rack guide and the guide hole in a direction orthogonal to the stroke direction of the cylinder in a zero state is disclosed. In this technical means, a rack guide formed of a resin material having a low coefficient of friction is formed in an elliptical cross-sectional shape having a major axis in a direction orthogonal to the stroke direction of the rack shaft. The cylindrical base end portion of the rack guide is divided into an outer cylindrical portion and an inner cylindrical portion by a slit, and the outer cylindrical portion is configured to be easily elastically deformed in the major axis direction so that the diameter can be reduced. The outer cylinder portion is set to have a longer diameter than the inner diameter of the guide hole, so that the clearance between the longer diameter of the rack guide and the guide hole is maintained in a zero state.

Further, in Patent Document 2, as a technical means for preventing the rack guide from vibrating in the radial direction inside the guide hole and generating a hitting sound, the rack guide is loaded on the base end side with a load from the rack shaft. Technical means for pressing the peripheral surface of the base end portion of the rack guide against the inner surface of the guide hole when pushed back to the back is disclosed. In this technical means, the cup-shaped rack guide is formed with a slit capable of expanding the diameter of the peripheral surface of the cylindrical base end, and on the base end side of the rack guide, A cam is provided for expanding and expanding the cylindrical base end portion of the rack guide when the rack guide is pushed back to the base end portion side.
JP 59-216764 A JP 2002-87290 A

  By the way, the original function of the rack guide is to apply a preload to the rack and pinion mechanism so that the rack shaft moves smoothly and smoothly in the stroke direction according to the rotation of the pinion shaft. At the same time, if it can move slightly in the stroke direction, the rack shaft starts moving smoothly and the steering performance is improved. On the other hand, if the front end of the rack guide that presses the rack shaft rattles in a direction perpendicular to the stroke direction of the rack shaft, the steering torque rises slowly at the start of steering or at the time of turnback steering, resulting in poor steering performance. There's a problem.

  In this respect, the steering gear devices described in Patent Documents 1 and 2 both prevent the generation of noise due to the vibration of the rack guide, and the front end of the rack guide is orthogonal to the stroke direction of the rack shaft. Since it is not possible to positively suppress the rattling in the direction of turning, there is a problem that the steering performance at the time of starting steering or turning back is deteriorated.

  Therefore, an object of the present invention is to provide a steering gear device that can improve the steering performance at the start of steering or at the time of turnback steering.

In the steering gear device according to the present invention, a rack guide that applies a preload to the rack and pinion mechanism by pressing the peripheral surface of the rack shaft meshing with the pinion shaft toward the pinion shaft side is slidably fitted into the guide hole of the rack housing. In the steering gear device, the clearance between the inner peripheral surface of the guide hole of the rack housing and the outer peripheral surface of the rack guide is set such that the clearance in the stroke direction of the rack shaft is set to be large over the entire length of the rack guide, and The clearance in the direction orthogonal to the rack shaft is set to be small at the end of the rack guide located on the rack shaft side, and a convex portion that reduces the clearance in the direction orthogonal to the stroke direction is formed on the outer peripheral surface of the end of the rack guide. It is formed .

  In the steering gear device according to the present invention, when the rack shaft moves in the stroke direction according to the rotation of the pinion shaft at the time of starting steering or turning back, the rack guide is moved together with the rack shaft by a large clearance in the stroke direction of the rack shaft. Since it can move in the stroke direction, the rack shaft starts moving smoothly and the steering performance is improved. At that time, the front end of the rack guide that presses the rack shaft is restrained from rattling in the direction perpendicular to the stroke direction by a small clearance in the direction perpendicular to the stroke direction of the rack shaft. It becomes quick and improves the steering.

  In the steering gear device of the present invention, the cross-sectional shape of the inner peripheral surface of the guide hole can be formed in an oval shape that is long in the stroke direction of the rack shaft. In this case, the guide hole can be easily processed by moving a rotary tool such as a milling cutter in the stroke direction.

  According to the steering gear device of the present invention, when the rack shaft moves in the stroke direction according to the rotation of the pinion shaft at the time of starting steering or turning back, the rack guide can move in the stroke direction together with the rack shaft by a large clearance. Therefore, the rack shaft starts moving smoothly. Further, at that time, since the backlash in the direction perpendicular to the stroke direction is suppressed by the small clearance, the rising of the steering torque becomes rapid. Therefore, according to the present invention, it is possible to improve the steering performance at the time of starting steering or turning back.

  Embodiments of a steering gear device according to the present invention will be described below with reference to the drawings. In the drawings to be referred to, FIG. 1 is a longitudinal sectional view showing a structure of a steering gear device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II-II shown in FIG.

  A steering gear device according to an embodiment is a rack and pinion type steering gear device that constitutes a part of a power steering system between a steering wheel and wheels of a vehicle (not shown). As shown in FIG. 1, the steering gear device includes a pinion shaft 3 that is supported by a rack housing 1 through bearings 2 </ b> A, 2 </ b> B, and 2 </ b> C so as to be rotatable about its axis, and an axial stroke with respect to the rack housing 1. The rack shaft 4 is slidably supported in the direction, and a rack 4A formed on one side of the peripheral surface of the rack shaft 4 meshes with a pinion 3A formed on the lower end portion of the pinion shaft 3.

  At a position facing the pinion 3A of the pinion shaft 3 across the rack shaft 4, a rack guide 5 is provided that presses the rack shaft 4 toward the pinion 3A and applies a preload to the rack and pinion mechanism. The rack guide 5 has a curved concave surface 5A capable of pressing the peripheral surface of the rack shaft 4 on the opposite side of the rack 4A, formed at the distal end portion, and a housing hole 5B for accommodating the coil spring 6 is opened at the proximal end portion. It is formed in a cup shape.

  Such a rack guide 5 is fitted in a guide hole 1B formed in the boss portion 1A of the rack housing 1 and is slidable in the axial direction. A plug 7 for receiving the coil spring 6 is screwed and fixed to the opening of the guide hole 1B of the boss 1A so that the rack guide 5 is pressed toward the rack shaft 4 by the urging force of the coil spring 6. A retaining nut 8 is attached to the outer periphery of the plug 7 so as to function as a double nut.

  Here, as shown in FIG. 2, the cross-sectional shape of the inner peripheral surface of the guide hole 1B formed in the boss 1A is an oval long in the stroke direction XX along which the rack shaft 4 slides, that is, the length It is formed in an oval shape of L and width W. The guide hole 1B is formed in the same oval cross-sectional shape over the entire length in the depth direction by slightly moving an appropriate rotary tool such as a milling cutter in the stroke direction XX.

  On the other hand, the cross-sectional shape of the outer peripheral surface of the rack guide 5 is formed in a circular shape having a diameter d slightly smaller than the width W of the guide hole 1B. The outer peripheral surface of the rack guide 5 is formed in a similar circular cross-sectional shape over the entire length of the rack guide 5.

  As a result, the clearance between the inner peripheral surface of the guide hole 1B and the outer peripheral surface of the rack guide 5 is set such that the clearance in the stroke direction XX of the rack shaft 4 is set to be large over the entire length of the rack guide 5, and the stroke direction X- The clearance in the direction YY perpendicular to X is set to be small at least at the tip of the rack guide 5.

  Here, the clearance in the stroke direction XX of the rack shaft 4 is set as a dimensional difference between the length L of the guide hole 1B and the diameter d of the rack guide 5. The clearance in the direction YY perpendicular to the stroke direction XX is set as a dimensional difference between the width W of the guide hole 1B and the diameter d of the rack guide 5.

  In the steering gear device of the embodiment configured as described above, the rack shaft 4 moves in the stroke direction XX in accordance with the rotation of the pinion shaft 3 at the start of steering by turning a steering wheel (not shown) or at the time of turnback steering. When moving, the rack guide 5 can move in the stroke direction XX together with the rack shaft 4 by a clearance that is largely set with respect to the stroke direction XX of the rack shaft 4. For this reason, the rack shaft 4 starts to move smoothly and the steering performance is improved.

  Further, when the rack shaft 4 moves in the stroke direction XX according to the rotation of the pinion shaft 3 at the time of starting steering or turning back, the tip of the rack guide 5 that presses the peripheral surface of the rack shaft 4 toward the pinion 3A side. Due to the clearance set small with respect to the direction YY perpendicular to the stroke direction XX of the rack shaft 4, rattling of the direction YY perpendicular to the stroke direction XX is suppressed. For this reason, the rising characteristic of the steering torque becomes a quick characteristic as shown by a broken line as compared with the slow characteristic of the conventional example shown by a solid line in FIG. 3, and the steering performance is improved.

  Therefore, according to the steering gear device of one embodiment, it is possible to improve the steering performance at the time of starting steering or turning back. Further, since the cross-sectional shape of the inner peripheral surface of the guide hole 1B into which the rack guide 5 is fitted is an ellipse that is long in the stroke direction XX of the rack shaft 4, a rotary tool such as a milling cutter is moved in the stroke direction X. The guide hole 1B can be easily processed by moving along -X.

  The steering gear device according to the present invention is not limited to one embodiment. For example, as shown in FIG. 4, the cross-sectional shape of the inner peripheral surface of the guide hole 1B formed in the boss portion 1A may be formed in a circular shape having an inner diameter D over the entire length in the depth direction of the guide hole 1B. In this case, the cross-sectional shape of the outer peripheral surface of the rack guide 5 is basically a circle having a diameter d1 smaller than the inner diameter D of the guide hole 1B. A pair of convex portions 5C and 5C that reduce the clearance in the direction YY perpendicular to X are formed. That is, the pair of convex portions 5C, 5C, whose outer peripheral surface forms an arc surface, are formed on the diameter line of the rack guide 5 corresponding to the direction YY perpendicular to the stroke direction XX.

  Here, the clearance between the guide hole 1B and the rack guide 5 in the stroke direction XX of the rack shaft 4 is set as a dimensional difference between the inner diameter D of the guide hole 1B and the diameter d1 of the rack guide 5. The clearance in the direction YY perpendicular to the stroke direction XX is set as a dimensional difference between the inner diameter D of the guide hole 1B and the diameter d2 between the pair of convex portions 5C, 5C of the rack guide 5.

  As described above, also in the steering gear device in which the clearance between the inner peripheral surface of the guide hole 1B and the outer peripheral surface of the rack guide 5 is set as described above, it is possible to improve the steering performance at the time of starting steering or turning back. it can.

It is a longitudinal cross-sectional view which shows the structure of the steering gear apparatus which concerns on one Embodiment of this invention. It is sectional drawing which follows the II-II line | wire shown in FIG. It is a graph which shows the relationship between the steering angle and steering torque of the steering gear apparatus which concerns on one Embodiment. It is sectional drawing corresponding to FIG. 2 of the steering gear apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

1 rack housing 1A boss 1B guide hole 2A bearing 2B bearing 2C bearing 3 pinion shaft 3A pinion 4 rack shaft 4A rack 5 rack guide 5A curved concave surface 5B receiving hole 5C convex portion 6 coil spring 7 plug 8 nut

Claims (1)

In a steering gear device in which a rack guide that presses a peripheral surface of a rack shaft that meshes with a pinion shaft toward the pinion shaft side and applies a preload to the rack and pinion mechanism is slidably fitted in a guide hole of the rack housing.
The clearance between the inner peripheral surface of the guide hole of the rack housing and the outer peripheral surface of the rack guide is set so that the clearance in the stroke direction of the rack shaft is set to be large over the entire length of the rack guide and is orthogonal to the stroke direction. The clearance is set small at the tip of the rack guide located on the rack shaft side ,
A steering gear device is characterized in that a convex portion for reducing a clearance in a direction orthogonal to the stroke direction is formed on an outer peripheral surface of a tip portion of the rack guide .

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