JP2016064737A - Rack guide, and rack-pinion type steering device provided with rack guide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rack guide which supports a rack bar that is engaged with a pinion pivoted on a gear case through a rack tooth so as to be movable in an axial direction and achieves a reduction in manufacturing cost, and a rack-pinion type steering device provided with the rack guide.SOLUTION: A rack guide 6 has a sliding supporting surface 6a which contacts slidably with a projecting surface 3b in an opposite side to a side on which a rack tooth 3a in a rack bar 3 is formed and has a recessed shape. A part or all of the sliding supporting surface 6a is covered with a resin coating film 10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technology of a rack guide and a rack and pinion type steering apparatus including the rack guide.

Generally, a rack and pinion type steering device includes a gear case, a pinion that is pivotally supported by the gear case, a rack bar that is formed with rack teeth that mesh with the pinion, and the rack bar that can slide within the gear case. And a coil spring that urges the rack guide to be pressed against the rack bar.
Conventionally, the rack guide is formed of an Fe-based sintered metal or a synthetic resin.
Here, the rack guide made of Fe-based sintered metal has sufficient mechanical strength against the impact load received from the rack bar, but because the sliding friction resistance is large, the efficiency of the entire steering device is reduced, There was a possibility that it became a factor of operability deterioration.
On the other hand, since the rack guide made of synthetic resin has low sliding friction resistance, the overall efficiency of the steering device can be improved, but the mechanical strength against the impact load received from the rack bar is inferior. In addition, the durability of the steering device as a whole may be affected.

Therefore, as means for solving these problems, for example, a rack guide body formed of a metal member such as an Fe-based sintered metal or an aluminum alloy, and the surface is covered with a synthetic resin layer, the rack guide body There is known a technique related to a rack guide constituted by a sliding plate piece fixed to a rack.
More specifically, the conventional rack guide is composed of a rack guide body having a hole in the center and a sliding plate piece having a protrusion in the center. The sliding plate piece is fixedly attached to the rack guide body by press-fitting the protruding portion of the sliding plate piece (see, for example, “Patent Document 1”).

JP2013-28285A

  In the manufacturing process of the rack guide having such a configuration, a process for drawing the protrusion of the sliding plate piece and a process for drilling a hole corresponding to the protrusion on the rack guide body In addition, a process for press-fitting the protruding portion of the sliding plate piece into the hole of the rack guide body is required, which increases the manufacturing cost of the rack guide.

  The present invention has been made in view of the present problems described above, and supports a rack bar meshed with a pinion pivotally supported by a gear case via rack teeth so as to be movable in the axial direction. It is an object of the present invention to provide a rack guide and a rack and pinion steering apparatus including the rack guide, which can reduce the manufacturing cost, and a rack and pinion steering apparatus including the rack guide.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  In other words, the rack guide according to claim 1 of the present invention is a rack guide that supports a rack bar that meshes with a pinion that is pivotally supported by a gear case via rack teeth so as to be movable in the axial direction. The bar has a convex surface opposite to the side on which the rack teeth are formed, and a concave sliding support surface that is slidably in contact. The sliding support surface is partially or entirely covered with a resin coating film. It is characterized by being coated.

  As described above, in the rack guide of the present invention, since the resin support coating is directly coated on the sliding support surface, the sliding plate is fixed to the sliding support surface of the rack guide body like the conventional rack guide. There is no need to provide a separate piece, and not only can the number of parts be reduced, but also, for example, a process for forming a protrusion of the sliding plate piece and a hole of the rack guide body corresponding to the protrusion, Because there is no need to provide a process for press-fitting the protrusion of the sliding plate piece into the hole of the rack guide body, it is sufficient to cover the sliding support surface of the rack guide with a resin coating film. Thus, the manufacturing cost can be reduced.

  The rack guide according to claim 2 of the present invention is characterized in that the resin coating film has a solid lubricant and / or a hard material.

  As described above, in the rack guide of the present invention, the resin coating film includes a solid lubricant having an effect of reducing frictional resistance and a hard material having an effect of improving wear resistance. The effect of reducing the friction of the coating film and the effect of improving the wear resistance can be further enhanced.

  On the other hand, a rack and pinion steering device according to claim 3 of the present invention is characterized by including the rack guide according to claim 1 or claim 2.

  Thus, the rack and pinion type steering apparatus of the present invention includes the above-described rack guide of the present invention, so that the manufacturing cost of the entire apparatus can be reduced.

  As effects of the present invention, the following effects can be obtained.

  That is, according to the rack guide and the rack and pinion type steering apparatus including the rack guide according to the present invention, it is possible to reduce the manufacturing cost.

The cross-sectional side view which showed the whole structure of the rack and pinion type steering apparatus provided with the rack guide which concerns on one Embodiment of this invention. The perspective view which showed the structure of the rack guide. It is the figure which showed the structure (texture) on the surface of the coating film coat | covered on the sliding support surface of a rack guide, Comprising: (a) consists of the texture which enclosed the hard thing in the countless dot-shaped hole part. It is the figure which showed the coating film, (b) is the figure which showed the coating film which consists of a texture which enclosed the hard thing in the countless groove part. In the rack guide which concerns on one Embodiment of this invention, the enlarged side view which showed the structure of the sliding support surface. The cross-sectional side view which showed the whole structure of the rack and pinion type steering device provided with the conventional rack guide.

  Next, embodiments of the invention will be described.

[Rack and pinion steering device 1]
First, an overall configuration of a rack and pinion steering device 1 (hereinafter simply referred to as “steering device 1”) including a rack guide 6 embodying the present invention will be described with reference to FIG.
In the following description, for convenience, the vertical direction in FIG. 1 is described as the vertical direction of the steering device 1.
In FIG. 1, the direction of the arrow A is defined as the front of the steering device 1.

The steering device 1 in the present embodiment is a device for converting, for example, a rotation operation of a pinion 2 rotated by a steering wheel (not shown) into a straight movement operation of the rack bar 3.
The steering device 1 is provided with a gear case 4, and one end of the pinion 2 is inserted into the gear case 4, for example, toward the front (in the direction of arrow A in FIG. 1).

Here, a pinion tooth 2 a is formed at one end of the pinion 2.
In the gear case 4, one end of the pinion 2 is pivotally supported via a pair of bearings 5 and 5 arranged with the pinion teeth 2 a interposed therebetween.

  The other end of the pinion 2 extends in the axial direction outside the gear case 4 and is connected to a steering wheel (not shown).

A rack bar 3 that meshes with the pinion 2 is disposed inside the gear case 4.
Rack teeth 3a are formed on the outer peripheral surface of the central portion in the axial direction of the rack bar 3, and the back surface (the surface opposite to the side on which the rack teeth 3a are formed) with respect to the rack teeth 3a has a predetermined curvature. It is a convex surface 3b having a circular arc shape in a sectional view having a radius.

  The rack bar 3 is disposed below the pinion teeth 2a so as to extend in a direction orthogonal to the pinion 2 (for example, in the left-right direction in the present embodiment), and the pinion teeth 2a are connected to the rack bars 3a via the rack teeth 3a. Meshed.

  Both end portions of the rack bar 3 protrude from the inside of the gear case 4 to the outside, and the rack bar 3 slides in the axial direction (left and right direction) via a bearing member (not shown). Supported as possible.

A cylindrical projecting portion 4 a is integrally formed on the lower surface of the gear case 4.
The protruding portion 4a is formed at a position where the rack bar 3 is sandwiched between the pinion 2 and the rack bar 3 is slid on the inner peripheral portion (space portion surrounded by the inner peripheral surface). The rack guide 6 that is supported is slidably disposed in the extending direction of the projecting portion 4a (in the present embodiment, the vertical direction).

  And the rack guide 6 is urged | biased by the rack bar 3 side by the compression coil spring 8 arrange | positioned between the cover member 7 which obstruct | occludes the lower end of the protrusion part 4a.

  In the steering apparatus 1 having the above-described configuration, when the pinion 2 is rotated around the axis via a steering wheel (not shown), the rotational driving force applied to the pinion 2 is the pinion teeth. 2a and rack teeth 3a are transmitted in this order, and converted into a propulsive force in the axial direction of the rack bar 3.

[Rack guide 6]
Next, the configuration of the rack guide 6 will be described in detail with reference to FIGS.
In the following description, for the sake of convenience, the vertical direction in FIGS. 2 and 4 is defined as the vertical direction of the rack guide 6, and the vertical direction in FIG. 5 is defined as the vertical direction of the conventional rack and pinion steering device 101. Describe.
2, 4, and 5, the direction of the arrow A is described as being defined as the front of the rack guide 6 or the conventional rack and pinion type steering device 101.

As shown in FIG. 1, the rack guide 6 supports the rack bar 3 engaged with the pinion 2 so as to be slidable in the axial direction of the rack bar 3 while pressing the rack bar 3 toward the pinion 2 side. It is a member.
The rack guide 6 is made of, for example, a cylindrical metal member made of Fe-based sintered metal, aluminum alloy, or the like, and has a concave surface having an arc shape substantially the same as the convex surface 3b of the rack bar 3 at one end thereof. A sliding support surface 6a is formed, and a cylindrical hollow portion 6b capable of holding the compression coil spring 8 is formed at the other end.

The sliding support surface 6a is not necessarily formed with a constant radius of curvature, and may be formed with a different curvature.
For example, as shown in FIG. 4, the sliding support surface 6 a of the rack guide 6 in this embodiment is on one side (for example, the present embodiment) with respect to a vertical center line C passing through the axis O of the rack bar 3. The first sliding support surface 6a1 located in the region on the front side in the embodiment and the second sliding support surface 6a2 located in the region on the other side (for example, the rear side in the present embodiment). .

The first sliding support surface 6a1 passes through the axis O, and the first center line C1 that is inclined α1 ° forward with respect to the center line C is behind the axis O and the first center line C1. It is formed in a circular arc shape with the upper point O1 as the center of curvature.
Here, α1 ° is an angle that does not exceed αf ° (0 ° <α1 ° <αf °), and αf ° passes through the center line C, the front end of the sliding support surface 6a, and the axis O. It is an angle between the first virtual line L1.

On the other hand, the second sliding support surface 6a2 passes through the axis O, and the second center line C2 is inclined α2 ° rearward with respect to the center line C. It is formed in an arc shape with the center of curvature at the point O2 on the line C2.
Here, α2 ° is an angle that does not exceed αb ° (0 ° <α2 ° <αb °), and αb ° passes through the center line C, the rear end of the sliding support surface 6a, and the axis O. The angle between the second virtual line L2 and the second virtual line L2.

The first sliding support surface 6a1 circumscribes the arcuate convex surface 3b that is the outer peripheral surface of the rack bar 3 on the intersection D1 between the first center line C1 and the first sliding support surface 6a1. Is done.
Further, the second sliding support surface 6a2 circumscribes the arcuate convex surface 3b, which is the outer peripheral surface of the rack bar 3, on the intersection D2 between the second center line C2 and the second sliding support surface 6a2. Is done.

As described above, in the rack guide 6 according to the present embodiment, the first sliding support surface 6a1 and the first sliding support surface 6a1 having the curvature center O1 and the curvature center O2 at positions eccentric to the axis O and having different curvature radii from each other. The rack bar 3 is configured to be supported at two points at the intersection point D1 and the intersection point D2 by the sliding support surface 6a including the two sliding support surfaces 6a2.
As a result, the sliding contact area of the sliding support surface 6a with the arc-shaped convex surface 3b of the rack bar 3 becomes a line or a narrow strip shape, so that the sliding frictional resistance with the rack bar 3 can be further reduced. it can.

The rack guide 6 is disposed coaxially with the projecting portion 4a inside the gear case 4 with the sliding support surface 6a facing the rack bar 3 side. Further, the other end portion of the compression coil spring 8 whose one end portion is fixed by the lid member 7 is held via the cylindrical hollow portion 6b.
Thus, the rack guide 6 is in contact with the convex surface 3b of the rack bar 3 via the sliding support surface 6a, while the inner peripheral portion of the protruding portion 4a is axially oriented (in this embodiment, via the outer peripheral surface 6c). It is arranged to be slidable in the vertical direction. At this time, the rack guide 6 is always urged toward the rack bar 3 by the compression coil spring 8.

  By the way, as shown in FIG. 2, in this embodiment, the entire surface of the sliding support surface 6a of the rack guide 6 that can come into contact with the convex surface 3b of the rack bar 3, for example, by pad printing or roll coating, The resin coating film 10 is applied.

Here, the resin coating film 10 is a film coated for the purpose of reducing friction and improving wear resistance, and is formed to have a film thickness of several μm to several tens of μm.
The resin coating film 10 is made of, for example, a binder resin and a solid lubricant, a binder resin and a hard material, or a binder resin, a solid lubricant and a hard material.

  The binder resin is mainly used as a binder. For example, a polyamide-imide resin, a polyimide resin, an epoxy resin, a phenol resin, a polyacetal resin, a polyether ether kent resin, a polyphenylene sulfide resin polyamide, and an elastomer are used. At least one kind selected from among them can be used.

The solid lubricant is mainly used to reduce the frictional resistance, has excellent conformability and non-seizure property, and is contained in the binder resin as a fine powder.
Solid lubricants are, for example, graphite, carbon, molybdenum disulfide (MoS ₂ ), polytetrafluoroethylene (PTFE), tungsten disulfide (WS ₂ ), boron nitride (h-BN), and SB203. At least one selected one can be used.

The hard material is mainly used to improve wear resistance, and is made of a material having a larger Vickers hardness than the Vickers hardness of the rack guide 6. For example, when the rack guide 6 is made of an aluminum alloy (Vickers hardness HV50 to 100), it is desirable that the hard material is made of a material such as alumina (Vickers hardness HV150).
The hard material is, for example, silicon carbide (SiC), alumina (AlO ₃ ), titanium nitride (TiN), aluminum nitride (AlN), chromium dioxide (CrO ₂ ), silicon nitride (Si ₃ N ₄ ), zirconium dioxide. At least one kind selected from (ZrO ₂ ) and iron phosphide (Fe ₃ P) can be used.

Thus, as shown in FIG. 3, the resin coating film 10 includes a binder resin 10a, and a solid lubricant (not shown) and / or a hard material 10b contained in the binder resin 10a. The
At this time, as a structure (texture) on the surface of the resin coating film 10, for example, as shown in FIG. 3A, a plurality of dot-like hard objects 10b, 10b... Are formed on the binder resin 10a. It is good also as a structure distributed at random, or as shown in FIG.3 (b), several strip | belt-shaped hard objects 10b * 10b ... cross | intersects each other on the binder resin 10a at a grid | lattice form. May be configured to be distributed, or other configurations may be used.
Further, the groove portion may be formed by the resin coating film 10 applied to the surface of the sliding support surface 6a, or the groove processing is performed on the sliding support surface 6a itself, and the resin coating film is formed according to the groove shape. Ten coatings may be applied.

As described above, in the present embodiment, the resin coating film 10 is directly applied to the sliding support surface 6 a of the rack guide 6.
Therefore, it is also necessary to separately provide a sliding plate piece 106B that is fixed to the sliding support surface of the rack guide main body 106A, like the rack guide 106 provided in the conventional rack and pinion type steering apparatus 101 as shown in FIG. Therefore, the number of parts can be reduced.
Further, in the conventional manufacturing process of the rack guide 106, a process for drawing the protrusion 106b of the sliding plate piece 106B, or a hole 106a corresponding to the protrusion 106b is formed in the rack guide body 106A. A process for pressing and fitting the protrusion 106b of the sliding plate piece 106B into the hole 106a of the rack guide main body 106A is necessary. However, the manufacturing process of the rack guide 6 in this embodiment is necessary. In this case, it is not necessary to perform these steps, and only the step of covering the sliding support surface 6a of the rack guide 6 with the resin coating film 10 is sufficient.
Therefore, according to the rack guide 6 in the present embodiment, it is possible to reduce the manufacturing cost.

  The arrangement position of the rack guide 6 is not limited to the present embodiment, and as long as the rack bar 3 can be supported while being pressed to the pinion 2 side via the sliding support surface 6a, the rack guide 6 is arranged. It may be provided anywhere along the axial direction of the bar 3.

DESCRIPTION OF SYMBOLS 1 Rack and pinion type steering device 2 Pinion 2a Pinion tooth 3 Rack bar 3a Rack tooth 3b Convex surface 4 Gear case 6 Rack guide 6a Sliding support surface 10 Resin coating film 10b Hard object

Claims (3)

A rack guide that supports a rack bar that meshes with a pinion pivotally supported by a gear case via rack teeth, and is movable in the axial direction.
A convex surface on the opposite side of the rack bar on which the rack teeth are formed, and a concave sliding support surface that is slidably in contact with the rack bar;
The sliding support surface is partially or entirely covered with a resin coating film.
A rack guide characterized by that. The resin coating film has a solid lubricant and / or a hard material,
The rack guide according to claim 1, wherein: The rack guide according to claim 1 or claim 2 is provided.
A rack-and-pinion type steering device characterized by that.

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