Rack guide

Abstract

To provide a rack guide capable of stably replenishing a lubricant holding groove with a lubricant from a rack bar when the rack bar slides with respect to the rack guide.SOLUTION: A lubricant holding groove 122 extending in a short direction of a rack guide orthogonal to a longitudinal direction of the rack guide to hold a lubricant G present between a rack bar SD3 and a support surface 120A is disposed in a support surface 120A. The lubricant holding groove 122 has a water-intrusive lubricant introduction region 122a into which the lubricant G is introduced and a lubricant holding region 122b which is connected to the lubricant introduction region 122a and in which the lubricant G introduced from the lubricant introduction region 122a is held. The lubricant holding region 122b of the lubricant holding groove 122 is provided in a contact region 120A1 of the support surface 120A. The lubricant introduction region 122a of the lubricant holding groove 122 is provided in a separate opposite surface region 120A2o outside the support surface 120A, and formed symmetrical with respect to a center axis A in a groove longitudinal direction parallel to a sheet short direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a rack guide for a steering device that changes the steering angle of a tire, and particularly to a rack guide that guides a rack bar in the longitudinal direction of the bar.

Background Art

[0002] Conventionally, as a rack guide for guiding a rack bar in the longitudinal direction, there is known a rack guide provided with a pair of opposed inclined surfaces, a pair of flat surfaces continuous with each of the inclined surfaces, a bottom surface continuous with each of the flat surfaces, and a hollow protrusion extending toward the washer side at the center of the bottom surface, and having a multi-layer sliding piece that supports the rack bar (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the recess of the inclined surface of the multi-layer sliding piece of the above-described rack guide, a lubricant is filled, and when the rack bar moves in the longitudinal direction of the rack bar, the lubricant filled in the recess is supplied to the rack bar. However, since the replenishment of the lubricant to the recess is not sufficient, there is a risk that the lubricant will run out from the recess.

[0005] Therefore, the present invention solves the problems of the prior art as described above. That is, an object of the present invention is to provide a rack guide in which a lubricant is stably supplied from a rack bar to a lubricant holding groove when the rack bar slides with respect to the rack guide.

Means for Solving the Problems

[0006] The invention according to claim 1 is a rack guide for a steering device that changes the steering angle of a tire by guiding the rack bar in the longitudinal direction of the rack bar, the rack bar having a D-shaped cross section that meshes with a pinion formed on the steering shaft to convert the rotational motion of the steering shaft into linear motion, the support surface having a support surface that supports a sliding surface provided behind a meshing surface formed on the rack bar, the sliding surface of the rack bar being a curved surface formed with a single radius of curvature, the support surface having a contact region that slidably contacts the rack bar and a separated opposing region that is separated from the rack bar and the sliding direction of the rack bar, the contact region being an inner separated opposing region near the central axis in the longitudinal direction of the rack guide that extends in the longitudinal direction of the rack guide parallel to the sliding direction of the rack bar and the The aforementioned problems are solved by having a lubricant retaining groove on the support surface, which is sandwiched between the outer, spaced-apart opposing region far from the longitudinal central axis of the rack guide, extends in the short direction of the rack guide perpendicular to the longitudinal direction of the rack guide, and holds the lubricant present between the rack bar and the support surface, and having a prow-shaped lubricant introduction region for introducing the lubricant and a lubricant retaining region connected to the lubricant introduction region for holding the lubricant introduced from the lubricant introduction region, the lubricant retaining region of the lubricant retaining groove provided in the contact region of the support surface, and the lubricant introduction region of the lubricant retaining groove provided in the outer, spaced-apart opposing region on the support surface, and is formed symmetrically with respect to the longitudinal central axis of the groove parallel to the short direction of the rack guide.

[0007] The invention according to claim 2 further solves the aforementioned problems by having the lubricant holding region perpendicular to the contact region of the support surface that extends in the longitudinal direction of the rack guide, in addition to the configuration of the rack guide described in claim 1.

[0008] The invention according to claim 3 further solves the aforementioned problems by extending the lubricant holding region to the inner, spaced-apart opposing region on the support surface, in addition to the configuration of the rack guide described in claim 1 or claim 2.

[0009] The invention according to claim 4 further solves the aforementioned problems by having, in addition to the configuration of the rack guide described in claim 1 or claim 2, the opposing surface facing the sliding surface of the rack bar is positioned outside the support surface and further away from the rack bar than the support surface. [Effects of the Invention]

[0010] According to the rack guide of the invention of claim 1, a lubricant retaining groove is provided on the support surface, which extends in the short direction of the rack guide perpendicular to the longitudinal direction of the rack guide and holds the lubricant present between the rack bar and the support surface, and the lubricant retaining groove has a bow-shaped lubricant introduction region for introducing lubricant and a lubricant retaining region connected to this lubricant introduction region and holding the lubricant introduced from the lubricant introduction region, the lubricant retaining region of the lubricant retaining groove is provided in the contact region of the support surface, and the lubricant introduction region of the lubricant retaining groove is provided in the outer, spaced-apart opposing regions of the support surface. As a result, when the rack bar slides in the longitudinal direction of the bar, even if the lubricant held in the lubricant holding area of ​​the lubricant holding groove is dragged out of the lubricant holding groove by the lubricant adhering to the rack bar, the lubricant present in the lubricant introduction area is replenished to the lubricant holding area as a result of the lubricant flowing into the lubricant introduction area, which has become depleted of lubricant, as the rack bar slides, thus enabling a stable supply of lubricant to the lubricant holding groove via the rack bar. Furthermore, because the lubricant introduction region of the lubricant holding groove is formed symmetrically with respect to the central axis of the groove's longitudinal direction, which is parallel to the short direction of the rack guide, the amount of lubricant flowing into the lubricant introduction region no longer depends on the sliding direction of the rack bar which is perpendicular to the short direction of the rack guide. As a result, the total amount of lubricant on the support surface does not depend on the number or position of the lubricant holding grooves, thus increasing the degree of freedom in arranging the lubricant holding grooves on the support surface.

[0011] According to the rack guide of claim 2, in addition to the effects of the rack guide of claim 1, the lubricant holding region is perpendicular to the contact region of the support surface extending in the longitudinal direction of the rack guide. As a result, the lubricant held in the lubricant holding region adheres to the rack bar more easily than if it were to flow in the short direction of the rack guide as the rack bar slides in the longitudinal direction. Therefore, when the rack bar slides against the rack guide, lubricant is stably supplied from the lubricant holding groove to the rack bar, achieving both stable supply of lubricant from the rack bar to the lubricant holding groove and stable supply of lubricant from the lubricant holding groove to the rack bar.

[0012] According to the rack guide of claim 3, in addition to the effects of the rack guide of claim 1 or claim 2, the lubricant holding area is extended to the inner, spaced-apart opposing area on the support surface. As a result, the lubricant introduced from the lubricant introduction area into the lubricant holding groove spreads to the inner, spaced-apart opposing area on the support surface, and the lubricant that has spread to the inner, spaced-apart opposing area on the support surface is circulated to the outer, spaced-apart opposing area on the support surface by the sliding of the rack bar. Therefore, compared to a case where the lubricant holding area is not extended to the inner, spaced-apart opposing area on the support surface, a larger amount of lubricant contributing to the sliding of the rack bar can be held, thereby extending the life of the rack guide.

[0013] According to the rack guide of claim 4, in addition to the effects of the rack guide of claim 1 or claim 2, the opposing surface facing the sliding surface of the rack bar is positioned outside the support surface and further away from the rack bar than the support surface. Therefore, even if the lubricant interposed between the rack bar and the support surface overflows from between the rack bar and the support surface when the rack bar slides against the rack guide, it accumulates between the sliding surface of the rack bar and the opposing surface. This allows the lubricant to be easily stored on the rack guide, and the lubricant accumulated between the sliding surface of the rack bar and the opposing surface adheres to the rack bar and is supplied to the lubricant holding groove, thus allowing the lubricant to circulate between the entire support surface of the rack guide and the rack bar. [Brief explanation of the drawing]

[0014] [Figure 1] A cross-sectional view of a rack and pinion steering device incorporating a rack guide, which is one embodiment of the present invention. [Figure 2] A perspective view of the rack guide shown in Figure 1. [Figure 3] Figure 1 is a side view showing the arrangement relationship between the rack guide and rack bar. [Figure 4] A plan view of the rack guide as seen from direction IV in Figure 3. [Figure 5A] A plan view illustrating the flow of lubricant when the rack bar is moved to the right on the paper. [Figure 5B] A plan view illustrating the flow of lubricant when the rack bar is moved to the left of the paper. [Figure 6] Side view of the rack guide as seen from direction VI in Figures 5A and 5B. [Figure 7A] A plan view of a rack guide, which is a first modified example of the present invention. [Figure 7B] A plan view of a rack guide, which is a second modified example of the present invention. [Figure 7C] A plan view of a rack guide, which is a third modified example of the present invention. [Modes for carrying out the invention]

[0015] The present invention relates to a rack guide for a steering device that meshes with a pinion formed on a steering shaft to convert the rotational movement of the steering shaft into linear movement, and supports a sliding surface provided behind an engaging surface formed on a rack bar having a D-shaped cross section to guide the rack bar in the longitudinal direction of the bar to change the steering angle of a tire. The sliding surface of the rack bar is a curved surface formed with a single radius of curvature, and the support surface is a curved surface having a contact region that slidably contacts the rack bar and a spaced-apart opposing region that is spaced apart and opposed to the rack bar, and having the sliding direction of the rack bar. The contact region is sandwiched between an inner spaced-apart opposing region close to the longitudinal central axis of the rack guide extending in the longitudinal direction of the rack guide parallel to the sliding direction of the rack bar and an outer spaced-apart opposing region far from the longitudinal central axis of the rack guide. A lubricant holding groove that extends in the short direction of the rack guide orthogonal to the longitudinal direction of the rack guide and holds a lubricant present between the rack bar and the support surface is provided on the support surface. The lubricant holding groove has a bow-shaped lubricant introduction region for introducing the lubricant and a lubricant holding region that is connected to the lubricant introduction region and holds the lubricant introduced from the lubricant introduction region. The lubricant holding region of the lubricant holding groove is provided in the contact region of the support surface, and the lubricant introduction region of the lubricant holding groove is provided in the outer spaced-apart opposing region on the support surface and is symmetrically formed with respect to the longitudinal central axis of the groove parallel to the short direction of the rack guide. As long as the lubricant is stably supplied from the rack bar to the lubricant holding groove when the rack bar slides with respect to the rack guide, the specific implementation mode may be any one.

[0016] For example, the rack guide in the present invention is mounted on a rack-and-pinion type steering device of an automobile, and the automobile may be not only a gasoline vehicle or a diesel vehicle but also an electric vehicle or the like.

Example

[0017] Hereinafter, based on FIGS. 1 to 6, a rack guide 100 which is an embodiment of the present invention will be described.

[0018] <1. Installation environment of the rack guide> First, the environment in which the rack guide 100 is mounted will be described based on Figure 1, a cross-sectional view of a rack and pinion steering device incorporating a rack guide, which is one embodiment of the present invention.

[0019] As shown in Figure 1, the rack guide 100 of this embodiment is mounted on the rack and pinion steering system SD of a four-wheeled vehicle.

[0020] This rack and pinion steering device SD changes the steering angle of the tires (not shown) and comprises a device housing SD1, a steering shaft SD2 that rotates together with the steering wheel, a rack bar SD3 that meshes with the steering shaft SD2 and converts the rotational motion of the steering shaft SD2 into linear motion, a rack guide 100 that guides the rack bar SD3 in the longitudinal direction of the rack bar SD3, and a biasing spring SD4 that presses the rack guide 100 against the rack bar SD3.

[0021] A pinion SD2a is formed at the tip of the steering shaft SD2, which meshes with the rack bar SD3, and rotates together with the steering shaft SD2.

[0022] As shown in Figure 1, the rack bar SD3 has a sliding surface SD3a, which is a curved surface formed with a single radius of curvature Rb, and a meshing surface SD3b, which is located behind the sliding surface SD3a and forms a rack tooth that meshes with the steering shaft SD2, and has a D-shaped cross-section.

[0023] The biasing spring SD4 is interposed between the device housing SD1 and the rack guide 100.

[0024] <2. Structure of the rack guide> Next, the structure of the rack guide 100 will be described in detail based on Figures 1 to 4. Figure 2 is a perspective view of the rack guide shown in Figure 1, Figure 3 is a side view showing the arrangement of the rack guide and rack bar shown in Figure 1, and Figure 4 is a plan view of the rack guide as seen from direction IV in Figure 3.

[0025] As shown in Figure 2, the rack guide 100 comprises a rack guide body 110 and a sheet 120.

[0026] <2.1. Rack Guide Body> As shown in Figure 2, the rack guide body 110 is a cylindrical metal component. Furthermore, a sheet mounting groove 111 is formed at one end of the rack guide body 110, extending in the longitudinal direction of the sheet mounting groove (the x-direction in Figure 2) which is perpendicular to the direction in which the longitudinal central axis (rack guide central axis GA) of the rack guide body 110 extends (the z-direction in Figure 2). The cross-sectional shape of this sheet placement groove 111 is semicircular, as shown in Figures 1 and 3. Furthermore, as shown in Figure 1, a sheet engagement hole 111a1 is formed on the opposing surface 111a of the sheet mounting groove 111, which faces the sliding surface SD3a of the rack bar SD3, and engages with the protrusion 121 of the sheet 120.

[0027] <2.2. Sheet> Sheet 120 is a component made of a resin with excellent self-lubricating properties (for example, a fluororesin such as PTFE, a nylon resin, or a polyacetal resin such as POM), and as shown in Figure 3, its thickness is almost uniform. As shown in Figures 1 and 4, the sheet 120 has a protrusion 121 in the center in a plan view that projects toward the rack guide body 110. The sheet 120 is integrated with the rack guide body 110 by inserting the protrusion 121 into the sheet engagement hole 111a1 of the rack guide body 110 and engaging them. Therefore, when the sheet 120 is assembled to the rack guide body 110, the opposing surface 111a of the rack guide body 110 that faces the sliding surface SD3a of the rack bar SD3 is positioned further away from the rack bar SD3 than the support surface 120A of the sheet 120 that supports the sliding surface SD3a of the rack bar SD3, as shown in Figure 3. Furthermore, as shown in Figure 2, the outer dimensions of the sheet 120 are smaller than the outer dimensions of the opposing surface 111a of the rack guide body 110. Therefore, the opposing surface 111a of the rack guide body 110 is located outward from the support surface 120A of the sheet 120.

[0028] As shown in Figure 4, the support surface 120A of the sheet 120 is symmetric with respect to the longitudinal central axis LA of the sheet, which passes through the center of the protrusion 121 and extends in the longitudinal direction of the sheet (X direction in Figure 4), and also symmetric with respect to the short-direction central axis WA of the sheet, which passes through the center of the protrusion 121 and extends in the short direction of the sheet (Y direction in Figure 4). Here, the longitudinal center axis LA of the sheet and the transverse center axis WA of the sheet are orthogonal to the rack guide center axis GA.

[0029] The longitudinal direction of the sheet 120 is the same as the longitudinal direction of the sheet mounting groove of the rack guide body 110 and the longitudinal direction (sliding direction) of the rack bar SD3, and the longitudinal central axis LA of the sheet is coaxial with the longitudinal central axis of the rack guide. The short-side direction of sheet 120 is perpendicular to the long-side direction of sheet 120, and the short-side central axis WA is coaxial with the short-side central axis of the rack guide.

[0030] Furthermore, as shown in Figure 3, the support surface 120A has two curvature centers Os1 and Os2 when the sheet 120 is assembled to the rack guide body 110. As shown in Figure 3, these curvature centers Os1 and Os2 are positioned in the Y direction with the rack guide central axis GA in between, and their positions in the Z direction are approximately equal. Furthermore, the radius of curvature at the center of curvature Os1 and the radius of curvature at the center of curvature Os2 are the same radius of curvature Rs. In other words, the support surface 120A is not formed by a single curved surface like the sliding surface SD3a of the rack bar SD3, but rather by the combination of two curved surfaces. Furthermore, the center of curvature Ob of rack bar SD3 is located on the central axis GA of the rack guide.

[0031] As described above, when the sheet 120 is assembled to the rack guide body 110, the support surface 120A has a contact area 120A1 that slidably contacts the rack bar SD3 and a separated opposing area 120A2 that is separated from the rack bar SD3, as shown in Figures 3 and 4. As shown in Figures 3 and 4, there are two contact areas 120A1 on either side of the sheet's longitudinal central axis LA, and each is sandwiched in the short direction (Y direction) of the rack guide by an inner (closer to the sheet's longitudinal central axis LA) separated opposing area 120A2i and an outer (farther from the sheet's longitudinal central axis LA) separated opposing area 120A2o.

[0032] <2.2.1. Lubricant retention groove> As shown in Figures 2 and 4, the support surface 120A of the sheet 120 has multiple lubricant holding grooves 122 which are interposed between the sliding surface SD3a of the rack bar SD3 and the support surface 120A of the sheet 120 to hold a lubricant that allows the rack bar SD3 to slide smoothly against the sheet 120.

[0033] As shown in Figure 4, the lubricant retaining groove 122 is arranged on the support surface 120A so as to be symmetrical with respect to the longitudinal central axis LA of the sheet and the short central axis WA of the sheet.

[0034] The lubricant retaining groove 122 is a groove of constant depth and extends in the short direction of the sheet (short direction of the rack guide), as shown in Figure 4. Furthermore, as shown in Figure 4, the lubricant-retaining groove 122 is formed symmetrically with respect to the longitudinal axis A of the groove, which is parallel to the short direction of the rack guide.

[0035] Furthermore, as shown in Figure 4, the lubricant retaining groove 122 has a bow-shaped lubricant introduction region 122a for introducing lubricant, and a lubricant retaining region 122b connected to the lubricant introduction region 122a for retaining the lubricant introduced from the lubricant introduction region 122a.

[0036] As shown in Figure 4, the lubricant introduction region 122a is the end of the lubricant holding groove 122 that is farther from the longitudinal central axis LA of the sheet, and is bow-shaped. Furthermore, this lubricant introduction region 122a is provided in the outer, spaced-apart opposing region 120A2o of the support surface 120A.

[0037] As shown in Figure 4, the lubricant-holding region 122b is perpendicular to the contact region 120A1 of the support surface 120A and extends to the inner separated opposing region 120A2i of the support surface 120A.

[0038] <3. Flow of lubricant> Next, the flow of the lubricant G interposed between the rack bar SD3 and the rack guide 100 will be explained based on Figures 5A to 6. Figure 5A is a plan view illustrating the flow of lubricant when the rack bar is moved to the right of the paper, Figure 5B is a plan view illustrating the flow of lubricant when the rack bar is moved to the left of the paper, and Figure 6 is a side view of the rack guide as seen from direction VI in Figures 5A and 5B.

[0039] In the rack and pinion steering device SD described above, since the rack bar SD3 is coated with lubricant G, when the rack bar SD3 slides against the rack guide 100, lubricant G is interposed between the rack bar SD3 and the rack guide 100, as shown in Figures 5A to 6.

[0040] <3.1. Lubricant flow around the lubricant introduction area> First, based on Figures 5A and 5B, the flow of lubricant G around the lubricant introduction region 122a of the lubricant holding groove 122 will be explained.

[0041] The lubricant G adhering to the rack bar SD3 flows in the sliding direction of the rack bar SD3 on the support surface 120A of the sheet 120, as shown by the gray arrows in Figures 5A and 5B. As the lubricant G on the rack bar SD3 moves, the lubricant G in the outer separated opposing region 120A2o adhering to the sheet 120 also flows in the longitudinal direction of the sheet, as indicated by the white arrow, and flows into the lubricant retaining groove 122 from the lubricant introduction region 122a of the lubricant retaining groove 122. Here, because the lubricant introduction region 122a of the lubricant holding groove 122 is bow-shaped, the lubricant G that flows into the lubricant holding groove 122 flows toward the central axis LA in the longitudinal direction of the sheet.

[0042] <3.2. Flow of lubricant in the lubricant retention area> Next, the flow of lubricant G in the lubricant holding region 122b of the lubricant holding groove 122 will be described based on Figures 5A and 5B.

[0043] Of the lubricant G held in the lubricant holding area 122b, a portion of the lubricant G located in the contact area 120A1 of the support surface 120A adheres to the sliding surface SD3a of the rack bar SD3. Of the lubricant G held in the lubricant holding region 122b, a portion of the lubricant G located in the inner separated opposing region 120A2i on the support surface 120A flows out from the lubricant holding groove 122 in the direction of the sliding of the rack bar SD3 and toward the central axis LA in the longitudinal direction of the sheet as the rack bar SD3 moves. Therefore, in this embodiment, the lubricant G between the rack bar SD3 and the support surface 120A accumulates toward the longitudinal central axis LA of the sheet.

[0044] <3.3. Flow of lubricant around the end of the rack bar on the sliding direction side of the support surface> Next, the flow of lubricant G around the end of the support surface 120A on the side of the rack bar sliding direction will be described based on Figures 5A to 6.

[0045] In the inner separated opposing region 120A2i of the support surface 120A, as described above, there is an abundance of lubricant G, so as the rack bar SD3 slides, the lubricant G flows toward the opposing surface 111a. Then, as shown in Figure 6, the lubricant G fills the space between the rack bar SD3 and the opposing surface 111a, and the lubricant G flows toward the outer separated opposing region 120A2o on the support surface 120A, as indicated by the black arrow. When the lubricant G flows between the rack bar SD3 and the opposing surface 111a to the outer separated opposing region 120A2o on the support surface 120A, it adheres to the rack bar SD3 in the outer separated opposing region 120A2o. Then, as described above in <3.1.>, the lubricant adhering to the rack bar SD3 flows into the support surface 120A and is introduced into the lubricant introduction area 122a of the lubricant holding groove 122.

[0046] <3.4. Lubricant flow around the end of the support surface opposite to the side in the sliding direction of the rack bar> Next, based on Figures 5A and 5B, the flow of lubricant G around the end of the support surface 120A opposite to the rack bar sliding direction will be described.

[0047] When the lubricant G adhering to the rack bar SD3 reaches the upper part of the support surface 120A, the lubricant G located in the contact area 120A1 of the support surface 120A has difficulty flowing between the rack bar SD3 and the support surface 120A. Therefore, as shown in Figures 5A and 5B, most of it flows towards the outer separated opposing region 120A2o or the inner separated opposing region 120A2i, and flows from the outer separated opposing region 120A2o or the inner separated opposing region 120A2i between the rack bar SD3 and the support surface 120A.

[0048] <4. Effects> According to the rack guide 100 of this embodiment described above, a lubricant retaining groove 122 is provided on the support surface 120A to hold the lubricant G present between the rack bar SD3 and the support surface 120A, extending in the short direction of the sheet (short direction of the rack guide) perpendicular to the longitudinal direction of the sheet (long direction of the rack guide). The lubricant retaining groove 122 has a bow-shaped lubricant introduction region 122a for introducing the lubricant G, and a lubricant retaining region 122b connected to this lubricant introduction region 122a for holding the lubricant G introduced from the lubricant introduction region 122a. The lubricant retaining region 122b of the lubricant retaining groove 122 is provided in the contact region 120A1 of the support surface 120A, and the lubricant introduction region 122a of the lubricant retaining groove 122 is on the outer side of the support surface 120A. Because it is provided in the separated opposing region 120A2o, when the rack bar SD3 slides in the longitudinal direction of the bar, even if the lubricant G held in the lubricant holding region 122b of the lubricant holding groove 122 is dragged by the lubricant G adhering to the rack bar SD3 and flows out of the lubricant holding groove 122, the lubricant G present in the lubricant introduction region 122a is replenished to the lubricant holding region 122b as the lubricant G flows out of the lubricant holding region 122b of the lubricant holding groove 122. As a result, lubricant G flows into the lubricant introduction region 122a, which has become depleted of lubricant G, as the rack bar SD3 slides, thus enabling a stable supply of lubricant G to the lubricant holding groove 122 via the rack bar SD3. Therefore, the lubricant G adhering to the sliding surface SD3a of the rack bar SD3 will be used without bias, and the replacement timing of the lubricant G can be extended. Furthermore, since the lubricant introduction region 122a of the lubricant holding groove 122 is formed symmetrically with respect to the longitudinal axis A of the groove, which is parallel to the short direction of the sheet, the amount of lubricant G flowing into the lubricant introduction region 122a no longer depends on the sliding direction of the rack bar which is perpendicular to the short direction of the sheet. As a result, the total amount of lubricant G on the support surface 120A no longer depends on the number or position of the lubricant holding grooves 122, and the degree of freedom in arranging the lubricant holding grooves 122 on the support surface 120A can be increased.

[0049] Furthermore, because the lubricant holding region 122b is perpendicular to the contact region 120A1 of the support surface 120A extending in the longitudinal direction of the sheet, the lubricant G held in the lubricant holding region 122b is more likely to adhere to the rack bar SD3 than to flow in the short direction of the sheet as the rack bar SD3 slides in the longitudinal direction. As a result, when the rack bar SD3 slides against the rack guide 100, the lubricant G can be stably supplied from the lubricant holding groove 122 to the rack bar SD3. Consequently, when the rack bar SD3 slides against the rack guide 100, both a stable supply of lubricant G from the rack bar SD3 to the lubricant holding groove 122 and a stable supply of lubricant G from the lubricant holding groove 122 to the rack bar SD3 can be achieved simultaneously.

[0050] Furthermore, because the lubricant holding region 122b extends to the inner separated opposing region 120A2i on the support surface 120A, the lubricant G introduced from the lubricant introduction region 122a into the lubricant holding groove 122 spreads to the inner separated opposing region 120A2i on the support surface 120A. The lubricant G that has spread to the inner separated opposing region 120A2i on the support surface 120A is then circulated to the outer separated opposing region 120A2o on the support surface 120A by the sliding of the rack bar SD3. Therefore, compared to a case where the lubricant holding region does not extend to the inner separated opposing region on the support surface, more lubricant G contributing to the sliding of the rack bar SD3 can be held, thereby extending the life of the rack guide 100.

[0051] Furthermore, because the opposing surface 111a of the rack bar SD3, which faces the sliding surface SD3a of the rack bar SD3, is positioned outside the support surface 120A and further away from the rack bar SD3 than the support surface 120A, even if the lubricant G interposed between the rack bar SD3 and the support surface 120A overflows from between the rack bar SD3 and the support surface 120A when the rack bar SD3 slides against the rack guide 100, it accumulates between the sliding surface SD3a of the rack bar SD3 and the opposing surface 111a. This not only allows the lubricant G to be easily stored on the rack guide 100, but the lubricant G accumulated between the sliding surface SD3a of the rack bar SD3 and the opposing surface 111a adheres to the rack bar SD3 and is supplied to the lubricant holding groove 122, thus allowing the lubricant G to circulate between the entire support surface 120A of the rack guide 100 and the rack bar SD3.

[0052] <Variation> Although the rack guides described above are embodiments of the present invention, the rack guides of the present invention are not limited to those of the embodiments described above.

[0053] For example, in the embodiment described above, the rack guide body 110 was made of metal, but the material of the rack guide body is not limited to metal; for example, it may be made of resin.

[0054] For example, in the embodiment described above, the thickness of the sheet 120 was uniform, but the thickness of the sheet does not have to be uniform.

[0055] For example, in the embodiment described above, the number of lubricant retention grooves 122 in the sheet 120 was 14, but it is not limited to 14.

[0056] For example, in the embodiment described above, the rack guide 100 was composed of two components: a rack guide body 110 and a sheet 120. However, the rack guide body and the sheet may be formed as a single unit.

[0057] For example, in the above-described embodiment, the lubricant retaining groove 122 formed in the sheet 120 was formed from a bow-shaped lubricant introduction region 122a as shown in Figure 4 and a lubricant retaining region 122b connected to the lubricant introduction region 122a. However, the shape of the lubricant introduction region of the lubricant retaining groove is not limited to the above-described embodiment, as long as it is formed symmetrically with respect to the longitudinal central axis of the groove and is inclined with respect to this longitudinal central axis. For example, it may be a shape as shown in Figures 7A to 7C. In other words, the lubricant introduction region 222a may be formed in a trapezoidal shape, as in the rack guide 200 shown in Figure 7A, which is a plan view of the rack guide that is a first modification of the present invention; the lubricant introduction region 322a may be formed in a semicircular shape, as in the rack guide 300 shown in Figure 7B, which is a plan view of the rack guide that is a second modification of the present invention; or the lubricant introduction region 422a may be formed by combining two arcs, as in the rack guide 400 shown in Figure 7C, which is a plan view of the rack guide that is a third modification of the present invention. In other words, the "bow-like" shape is not limited to the shape of the embodiment described above (for example, Figure 4), but also includes trapezoidal shapes (Figure 7A), semicircular shapes (Figure 7B), and shapes that combine two arcs (Figure 7C). Furthermore, in the above-described embodiment, the side of the lubricant holding area of ​​the lubricant holding groove closest to the longitudinal axis of the sheet was a straight line substantially parallel to the longitudinal direction of the rack guide. However, the side of the lubricant holding area of ​​the lubricant holding groove closest to the longitudinal axis of the sheet does not have to be substantially parallel to the longitudinal direction of the rack guide, nor does it have to be a straight line.

[0058] For example, in the above-described embodiment, the lubricant retaining groove 122 was formed symmetrically with respect to the central axis in the longitudinal direction of the groove. However, if the lubricant introduction region of the lubricant retaining groove is formed symmetrically with respect to the central axis in the longitudinal direction of the groove, the lubricant retaining region does not need to be formed symmetrically with respect to the central axis in the longitudinal direction of the groove. [Explanation of symbols]

[0059] 100, 200, 300, 400... Rack Guide 110 ··· Rack guide body 111 ··· Sheet placement groove 111a... Opposite surface 111a1 ··· Sheet engagement hole 120... seats 120A... Support surface 120A1... Contact area 120A2...Separated opposing area 120A2i ··· Inner separated opposing region 120A2o ··· Outer separated opposing region 121 ··· Convex part 122, 222, 322, 422... Lubricant retention grooves 122a ··· Lubricant introduction area 122b ··· Lubricant retention area SD ··· Rack and pinion steering system SD1 ··· Device Housing SD2 ··· Steering shaft SD2a ··· pinion SD3 ··· Rack Bar SD3a ··· Sliding surface SD3b ··· Occlusal surface (rack teeth) SD4 ··· biasing spring GA ··· Rack guide central axis LA... Center axis in the longitudinal direction of the sheet (center axis in the longitudinal direction of the rack guide) WA ··· Sheet short-side central axis (rack guide short-side central axis) A... Groove longitudinal central axis Rb ··· Radius of curvature of rack bar Rs ··· Radius of curvature of the sheet Os1 ··· Center of curvature of the sheet Os2 ··· Center of curvature of the sheet Ob ··· Center of curvature of rack bar G ··· Lubricant

Claims

1. A rack guide for a steering device that changes the steering angle of a tire, comprising a support surface that supports a sliding surface provided behind the meshing surface formed on a rack bar with a D-shaped cross section that meshes with a pinion formed on the steering shaft to convert the rotational motion of the steering shaft into linear motion, and guiding the rack bar in the longitudinal direction of the rack bar, The sliding surface of the rack bar is a curved surface formed with a single radius of curvature. The support surface is a curved surface having a contact region that slidably contacts the rack bar and a separated opposing region that is spaced apart from the rack bar, and also having a sliding direction of the rack bar. The contact region is sandwiched between an inner, separated opposing region that extends in the longitudinal direction of the rack guide parallel to the sliding direction of the rack bar and is close to the central axis in the longitudinal direction of the rack guide, and an outer, separated opposing region that is far from the central axis in the longitudinal direction of the rack guide. A lubricant retaining groove is provided on the support surface, extending in the short direction of the rack guide perpendicular to the longitudinal direction of the rack guide, and holding the lubricant present between the rack bar and the support surface. The lubricant retaining groove has a bow-shaped lubricant introduction region for introducing the lubricant, and a lubricant retaining region connected to the lubricant introduction region for holding the lubricant introduced from the lubricant introduction region. The lubricant holding region of the lubricant holding groove is provided in the contact region of the support surface, A rack guide characterized in that the lubricant introduction region of the lubricant holding groove is provided in the outer, spaced-apart regions of the support surface and is formed symmetrically with respect to the central axis of the groove's longitudinal direction, which is parallel to the short direction of the rack guide.

2. The rack guide according to claim 1, characterized in that the lubricant holding region is perpendicular to the contact region of the support surface that extends in the longitudinal direction of the rack guide.

3. The rack guide according to claim 1 or 2, characterized in that the lubricant holding region extends to the inner, spaced-apart opposing region on the support surface.

4. The rack guide according to claim 1 or 2, characterized in that the opposing surface facing the sliding surface of the rack bar is positioned outside the support surface and further away from the rack bar than the support surface.

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