Rack guide

Abstract

To provide a rack guide capable of simultaneously achieving stable replenishment of a lubricant holding groove with a lubricant from a rack bar and stable supplying of the lubricant from the lubricant holding groove to the rack bar when the rack bar slides with respect to the rack guide.SOLUTION: At least a pair of lubricant holding grooves 122 holding a lubricant G present between a rack bar SD3 and a support surface 120A to face each other in a longitudinal direction of the rack bar is disposed in the support surface 120A in a form of extending in a short direction of the rack guide orthogonal to the longitudinal direction of the rack bar and swelling to be away from each other in the longitudinal direction of the rack bar. Apexes 122B1 of the lubricant holding grooves 122 in the longitudinal direction of the rack bar are arranged in a contact region 120A1.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 more 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 in the multi-layer sliding piece of the above-described rack guide, a lubricating oil agent is filled, and when the rack bar moves in the longitudinal direction of the rack bar, the lubricating oil agent filled in the recess is supplied to the rack bar. However, since the replenishment of the lubricating oil agent to the recess is not sufficient, there is a risk that the lubricating oil agent 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 that achieves 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 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 rack guide comprising a support surface that supports a sliding surface provided behind a meshing surface formed on the rack bar, wherein 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 separated from the rack bar, and the contact region is parallel to the sliding direction of the rack bar. The rack bar and the support surface are sandwiched between the inner, spaced-apart opposing region near the central axis in the longitudinal direction of the rack guide and the outer, spaced-apart opposing region far from the central axis in the longitudinal direction of the rack guide. At least one pair of lubricant-holding grooves, which hold the lubricant interposed between the rack bar and the support surface, are arranged on the support surface in a shape that bulges outwards from each other in the longitudinal direction of the rack guide, extending in the short direction of the rack guide perpendicular to the longitudinal direction of the rack guide, and the apex of the lubricant-holding groove in the longitudinal direction of the rack guide is positioned in the contact region, thereby solving the aforementioned problems.

[0007] The invention according to claim 2 further solves the aforementioned problems by having the lubricant retaining groove formed deeper in accordance with the bulging of the lubricant retaining groove, 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 having the lubricant retaining groove formed by a straight section perpendicular to the contact area of ​​the support surface extending in the longitudinal direction of the rack guide, and bulging sections passing through both ends of the straight section and the vertex, 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, in addition to the configuration of the rack guide described in claim 1 or claim 2, the pair of lubricant retaining grooves being formed symmetrically and having equal groove depths. [Effects of the Invention]

[0010] According to the rack guide of the invention of claim 1, at least one pair of lubricant-holding grooves, which hold the lubricant interposed between the rack bar and the support surface and are opposed to each other in the longitudinal direction of the rack guide, are arranged on the support surface in a shape that bulges outwards in the longitudinal direction of the rack guide, extending in the short direction of the rack guide perpendicular to the longitudinal direction of the rack guide, and the apex of the lubricant-holding groove in the longitudinal direction of the rack guide is positioned in the contact area, so that when the rack bar slides in the longitudinal direction of the bar, the lubricant held near the apex of the lubricant-holding groove is released into the rack Even if some lubricant adhering to the bar is dragged out of the lubricant retaining groove, the lubricant present in the inner and outer separated opposing regions is drawn towards the vicinity of the lubricant retaining groove as the lubricant near the apex of the lubricant retaining groove flows into the lubricant retaining groove from at least one of the support surface and the rack bar, thereby replenishing it. This ensures both a stable supply of lubricant from the rack bar to the lubricant retaining groove and a stable supply of lubricant from the lubricant retaining groove to the rack bar.

[0011] According to the rack guide of claim 2, in addition to the effects of the rack guide of claim 1, the lubricant retaining groove is formed to be deeper in accordance with the bulge of the lubricant retaining groove. As a result, lubricant tends to accumulate at the deeper outer end of the lubricant retaining groove, while it tends to flow out at the shallower inner end. When the rack bar slides toward the outer end of the lubricant retaining groove, the lubricant present in the inner and outer separated opposing regions flows into the lubricant retaining groove as the lubricant flows out from the outer end of the lubricant retaining groove due to the sliding of the rack bar, and is retained at the outer end of the lubricant retaining groove. Consequently, when the rack bar slides toward the inner end of the lubricant retaining groove, the lubricant held near the inner end of the lubricant retaining groove flows in accordance with the sliding of the rack bar and adheres to the rack bar. Therefore, it is possible to reliably achieve both a stable supply of lubricant from the rack bar to the lubricant retaining groove and a stable supply of lubricant from the lubricant retaining 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 retaining groove is formed by a straight section perpendicular to the contact area of ​​the support surface extending in the longitudinal direction of the rack guide, and bulging sections passing through both ends and the apex of this straight section. As a result, when the rack bar slides toward the straight section of the lubricant retaining groove, the lubricant held near the straight section of the lubricant retaining groove is more likely to adhere to the rack bar than if it were to flow in the short direction of the rack guide. Therefore, when the rack bar slides toward the rack guide, lubricant can be stably supplied from the lubricant retaining groove to the rack bar. Consequently, it is easier to achieve both stable supply of lubricant from the rack bar to the lubricant retaining groove and stable supply of lubricant from the lubricant retaining groove to the rack bar.

[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 pair of lubricant retaining grooves are formed symmetrically, and the groove depths of the pair of lubricant retaining grooves are equal to each other. As a result, the amount of lubricant flowing into the pair of lubricant retaining grooves balances the amount of lubricant flowing out of the pair of lubricant retaining grooves, making it easier to maintain a constant total amount of lubricant held by the rack guide. [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 5] Figure 4 shows the end view of the lubricant retention groove in the VV cross-section. [Figure 6A] Figure 1 is a plan view showing the arrangement of the rack guide, rack bar, and lubricant. [Figure 6B] Figure 6A shows the end view of the lubricant retention groove in the VIB-VIB section. [Figure 7A] A plan view illustrating the flow of lubricant when the rack bar is moved to the right on the paper. [Figure 7B] Figure 7A shows the end view of the lubricant retention groove in the VIIB-VIIB section. [Figure 8A] A plan view illustrating the flow of lubricant when the rack bar is moved to the left of the paper. [Figure 8B] Figure 8A shows the end view of the lubricant retention groove in the VIIIB-VIIIB section. [Figure 9A] A plan view of a rack guide, which is a first modified example of the present invention. [Figure 9B] A plan view of a rack guide, which is a second modified example of the present invention. [Figure 9C]Plan view of the rack guide which is the third modification of the present invention. [Figure 9D] Plan view of the rack guide which is the fourth modification of the present invention.

Mode for Carrying Out the Invention

[0015] The present invention includes a support surface that supports a sliding surface provided behind an engaging surface formed on a rack bar having a D-shaped cross section that meshes with a pinion formed on a steering shaft and converts the rotational movement of the steering shaft into linear movement, and guides the rack bar in the longitudinal direction of the bar to change the steering angle of the tire. The rack guide for a steering device is such that 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 spaced-apart opposing region that is spaced apart and opposed to 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, and at least a pair of lubricant holding grooves that hold a lubricant interposed between the rack bar and the support surface and face each other in the longitudinal direction of the rack guide extend in the short direction of the rack guide orthogonal to the longitudinal direction of the rack guide and are disposed on the support surface in a shape that bulges so as to move away from each other in the longitudinal direction of the rack guide. As long as it enables both stable replenishment of the lubricant from the rack bar to the lubricant holding grooves and stable supply of the lubricant from the lubricant holding grooves to the rack bar when the rack bar slides with respect to the rack guide, the specific embodiment thereof may be any.

[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.

Examples

[0017] Hereinafter, an embodiment of the present invention, a rack guide 100, will be described based on Figures 1 to 8B.

[0018] <1. Rack guide installation environment> 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 a 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 5. 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, Figure 4 is a plan view of the rack guide as seen from direction IV in Figure 3, and Figure 5 is an end view of the lubricant retaining groove in the VV section of Figure 4.

[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.

[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. In other words, the lubricant retaining grooves 122 are paired in the longitudinal direction of the sheet (with respect to the central axis WA in the short direction of the sheet), and the pair of lubricant retaining grooves 122 are formed symmetrically with respect to the central axis WA in the short direction of the sheet.

[0034] Furthermore, as shown in Figure 4, each lubricant-holding groove 122 extends in the short direction of the sheet (short direction of the rack guide) and bulges out in the long direction of the sheet (long direction of the rack guide) and away from the central axis WA in the short direction of the sheet. In other words, the pair of lubricant-retaining grooves 122, which are arranged symmetrically with respect to the central axis WA in the short direction of the sheet, bulge outwards from each other, and each lubricant-retaining groove 122 is formed by a straight portion 122A that extends in a direction perpendicular to the contact region 120A1 that extends in the longitudinal direction of the sheet (i.e., in the short direction of the sheet) and bulging portions 122B that bulge out from both ends of this straight portion 122A. Furthermore, the vertex 122B1 of this bulge 122B in the longitudinal direction of the sheet is positioned in the contact region 120A1, as shown in Figure 4.

[0035] The cross-sectional shape of the lubricant retaining groove 122 is as shown in Figure 5. The lubricant retaining groove 122 is formed from a vertical wall surface 122a that forms a bulge 122B and an inclined surface 122b that connects the vertical wall surface 122a and the support surface 120A. In other words, the straight section 122A is the boundary between the inclined surface 122b and the support surface 120A.

[0036] The vertical wall surface 122a extends in the thickness direction of the sheet 120, and as shown in Figure 2, the height is greatest near the vertex and least near both ends of the straight section 122A. In other words, the lubricant retaining groove 122 is formed deeper as it bulges out. To put it another way, in the longitudinal direction of the sheet, the outer end side of the lubricant retaining groove 122 (bulging portion 122B), which is farther from the central axis WA in the short direction of the sheet, is formed deeper than the inner end side of the lubricant retaining groove (straight portion 122A), which is closer to the central axis WA in the short direction of the sheet. Therefore, the groove depths of the pair of lubricant-retaining grooves 122, which are arranged symmetrically with respect to the central axis WA in the short direction of the sheet, are equal to each other.

[0037] <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 6A to 8B. Figure 6A is a plan view showing the arrangement of the rack guide, rack bar, and lubricant as shown in Figure 1; Figure 6B is an end view of the lubricant retaining groove in the VIB-VIB section of Figure 6A; Figure 7A is a plan view illustrating the flow of lubricant when the rack bar is moved to the right in the plane of the paper; Figure 7B is an end view of the lubricant retaining groove in the VIIB-VIIB section of Figure 7A; Figure 8A is a plan view illustrating the flow of lubricant when the rack bar is moved to the left in the plane of the paper; and Figure 8B is an end view of the lubricant retaining groove in the VIIIB-VIIIB section of Figure 8A.

[0038] 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 6A and 6B.

[0039] <3.1. When the rack bar moves to the right on the page> Then, as shown in Figures 7A and 7B, when the rack bar SD3 moves to the right on the plane of the paper, the lubricant G attached to the rack bar SD3 also moves to the right on the plane of the paper, as indicated by the gray arrows. As the lubricant G moves, the viscosity of the lubricant G causes the lubricant G on the sheet 120 to begin flowing as well.

[0040] <3.1.1. Lubricant flow on the right side of the paper relative to the center axis in the short direction of the sheet> First, we will explain the flow of lubricant G around the lubricant retaining groove 122, which is located to the right of the sheet's short-side central axis WA. In the area of ​​the sheet 120 where the lubricant retaining groove 122 is not formed, the lubricant G on the sheet 120 side flows toward the right side of the paper, i.e., toward the lubricant retaining groove 122, as the lubricant G on the rack bar SD3 side moves, as indicated by the white arrows in Figures 7A and 7B, and flows into the interior of the lubricant retaining groove 122 from the straight section 122A of the lubricant retaining groove 122. As the lubricant G flows into the lubricant retaining groove 122, the lubricant G adhering to the rack bar SD3 is also drawn towards the lubricant retaining groove 122.

[0041] As indicated by the white arrows, the lubricant G held in the separated opposing region 120A2 of the lubricant holding groove 122 is drawn towards the contact region 120A1 in the direction of least flow resistance, that is, rather than trying to overcome the vertical wall surface 122a. As a result, the most lubricant G is held in the lubricant holding groove 122 near the apex 122B1. Therefore, as the rack bar SD3 moves, the lubricant G held in the lubricant retaining groove 122 adheres most heavily to the rack bar SD3 in the contact area 120A1, that is, near the apex 122B1 of the lubricant retaining groove 122.

[0042] <3.1.2. Lubricant flow on the left side of the paper relative to the short-side central axis of the sheet> Next, we will describe the flow of lubricant G around the lubricant retaining groove 122, which is located to the left of the sheet's short-side central axis WA. As indicated by the white arrow, the lubricant G held in the lubricant retaining groove 122 flows out to the right side of the paper, that is, from the straight section 122A of the lubricant retaining groove 122 to the outside of the lubricant retaining groove 122, as the lubricant G on the rack bar SD3 side moves.

[0043] <3.2. If the Rack Bar SD3 moves to the left of the page> Then, as shown in Figures 8A and 8B, when the rack bar SD3 moves to the left of the paper, the lubricant G attached to the rack bar SD3 also moves to the left of the paper as the rack bar SD3 moves. As the lubricant G moves, the viscosity of the lubricant G causes the lubricant G on the sheet 120 to begin flowing as well. However, the behavior of the lubricant G on the rack bar SD3 and the lubricant G on the sheet 120 is exactly the same as when the rack bar SD3 moves to the right on the paper, as shown in Figures 7A and 7B, because the sheet 120 is symmetrical with respect to the central axis WA in the short direction of the sheet, except for the direction of movement of the rack bar SD3. In other words, if the amount of sliding movement of the rack bar SD3 is the same when the rack bar SD3 moves to the right on the plane of the paper and when the rack bar SD3 moves to the left on the plane of the paper, the amount of lubricant G flowing in and out of each lubricant holding groove 122 will be roughly balanced, so there will be almost no increase or decrease in the amount of lubricant G in the sheet 120.

[0044] <4. Effects> According to the rack guide 100 of this embodiment described above, a pair of lubricant retaining grooves 122, which hold the lubricant G interposed between the rack bar SD3 and the support surface 120A and are opposed to each other in the longitudinal direction of the sheet, are arranged on the support surface 120A in a shape that bulges outwards in the longitudinal direction of the sheet, 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), and the apex 122B1 of the lubricant retaining groove 122 in the longitudinal direction of the sheet is positioned in the contact area 120A1. As a result, when the sliding surface SD3a of the rack bar SD3 slides in the longitudinal direction of the bar, the lubricant G held near the apex 122B1 of the lubricant retaining groove 122 is released to the rack bar SD Even if the lubricant G adhering to 3 is dragged out of the lubricant retaining groove 122 and flows out to the outside of the lubricant retaining groove 122, the lubricant G present in the inner separated opposing region 120A2i and the outer separated opposing region 120A2o is drawn towards the vicinity of the apex 122B1 of the lubricant retaining groove 122, and the lubricant G flows into the lubricant retaining groove 122 from at least one of the support surface 120A and the rack bar SD3, replenishing it. This makes it possible to achieve both a stable supply of lubricant G from the rack bar SD3 to the lubricant retaining groove 122 and a stable supply of lubricant G from the lubricant retaining groove 122 to the rack bar SD3. Therefore, the lubricant G adhering to the sliding surface SD3a of the rack bar SD3 is used without bias, and the lifespan of the rack guide 100 can be extended.

[0045] Furthermore, since the lubricant retention grooves 122 are provided in all contact areas 120A1 on the support surface 120A, lubricant can be supplied to the rack bar SD3 without bias.

[0046] Furthermore, because the groove depth of each of the pair of lubricant retaining grooves 122 increases in the direction of bulging of each of the pair of lubricant retaining grooves 122, lubricant G tends to accumulate at the deeper outer end of the lubricant retaining groove 122, while lubricant G tends to flow out at the shallower inner end of the lubricant retaining groove 122. When the rack bar SD3 slides towards the outer end of the lubricant retaining groove 122, the lubricant G flows out from the outer end of the lubricant retaining groove 122 due to the sliding of the rack bar SD3, causing the inner separated opposing region 120A2i and the outer separated opposing region to move outwards. The lubricant G present in the adjacent region 120A2o flows into the lubricant holding groove 122 and is held at the outer end of the lubricant holding groove 122. As a result, when the rack bar SD3 slides toward the inner end of the lubricant holding groove 122, the lubricant G held near the inner end of the lubricant holding groove 122 flows in conjunction with the sliding of the rack bar SD3 to adhere to the rack bar SD3. This ensures 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.

[0047] Furthermore, since the lubricant retaining groove 122 is formed by a straight section 122A perpendicular to the contact area 120A1 of the support surface 120A extending in the longitudinal direction of the sheet, and a bulging section 122B passing through both ends and the vertex 122B1 of this straight section 122A, when the rack bar SD3 slides toward the straight section 122A side of the lubricant retaining groove 122, the lubricant G held near the straight section 122A of the lubricant retaining groove 122 is more likely to adhere to the rack bar SD3 than if it were to flow in the short direction of the sheet. As a result, when the rack bar SD3 slides toward the rack guide 100, the lubricant G can be stably supplied from the lubricant retaining groove 122 to the rack bar SD3, and as a result, it is easier to achieve both stable supply of lubricant G from the rack bar SD3 to the lubricant retaining groove 122 and stable supply of lubricant G from the lubricant retaining groove 122 to the rack bar SD3.

[0048] <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.

[0049] 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.

[0050] 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.

[0051] For example, in the embodiment described above, the number of lubricant retaining grooves 122 in the sheet 120 was 8, but the number of lubricant retaining grooves arranged in the sheet is not limited to 8, as long as they are arranged symmetrically with respect to the longitudinal central axis LA and the transverse central axis WA of the sheet.

[0052] 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.

[0053] For example, in the embodiment described above, the pair of lubricant retaining grooves 122 were aligned in the short direction of the sheet, but the pair of lubricant retaining grooves are not limited to being paired in the longitudinal direction of the rack guide, and may be offset in the short direction of the sheet, for example.

[0054] For example, in the above-described embodiment, the lubricant retaining groove 122 formed in the sheet 120 was formed from a straight portion 122A and an arc-shaped bulge 122B as shown in Figure 4. However, the shape of the lubricant retaining groove is not limited to the above-described embodiment, as long as it bulges in the longitudinal direction of the rack guide and its apex is located in the contact area. For example, it may have a shape as shown in Figures 9A to 9C. In other words, the lubricant retaining groove 222 may be formed from a straight portion 222A and a bent-line bulge portion 222B, as in the rack guide 200 shown in Figure 9A, which is a plan view of the rack guide that is a first modification of the present invention; the lubricant retaining groove 322 may be formed from two arc-shaped bulges, as in the rack guide 300 shown in Figure 9B, which is a plan view of the rack guide that is a second modification of the present invention; or the lubricant retaining groove 422 may be formed in a rhomboid shape, as in the rack guide 400 shown in Figure 9C, which is a plan view of the rack guide that is a third modification of the present invention.

[0055] For example, in the above-described embodiment, the pair of lubricant retaining grooves 122 formed in the sheet 120 were arranged around the sheet's short-direction central axis WA. However, the pair of lubricant retaining grooves in the present invention are not limited to this arrangement as long as they are paired in the longitudinal direction of the rack guide. For example, as shown in Figure 9D, a plan view of the rack guide which is a fifth modification of the present invention, the pair of lubricant retaining grooves 522 may be formed around an axis of symmetry A parallel to the sheet's short-direction central axis WA. [Explanation of symbols]

[0056] 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, 222A... Straight section 122B, 222B... bulge 122B1 ··· Vertex 122a... Standing wall surface 122b... Inclined surface 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... axis of symmetry 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 separated from 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 rack guide characterized in that at least one pair of lubricant-holding grooves, which hold the lubricant interposed between the rack bar and the support surface and are opposed to each other in the longitudinal direction of the rack guide, are arranged on the support surface in a shape that bulges outwards in the longitudinal direction of the rack guide, extending in the short direction of the rack guide perpendicular to the longitudinal direction of the rack guide, and the apex of the lubricant-holding groove in the longitudinal direction of the rack guide is positioned in the contact area.

2. The rack guide according to claim 1, characterized in that the lubricant retaining groove is formed to be deeper in accordance with the bulging of the lubricant retaining groove.

3. The rack guide according to claim 1 or 2, characterized in that the lubricant retaining groove is formed by a straight portion perpendicular to the contact area of ​​the support surface extending in the longitudinal direction of the rack guide, and a bulge portion passing through both ends of the straight portion and the vertex.

4. The pair of lubricant-retaining grooves are formed symmetrically, The rack guide according to claim 1 or 2, characterized in that the groove depths of the pair of lubricant-holding grooves are equal to each other.

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