JP2020131920A - Rack guide and gear mechanism - Google Patents

Abstract

To provide a rack guide which can support a rack bar more stably over a longer period, and a gear mechanism with use of the rack guide.SOLUTION: A rack guide 30 comprises: a first rack guide part 31 having a recessed first slide surface 300a which supports a back face 22 of a rack bar 20; and a second rack guide part 32 which is accommodated in the first rack guide part 31, and has a recessed second slide surface 300b which supports the back face 22 of the rack bar 20. The second rack guide part 32 is energized by a first energization member 33 in a direction extruded from the first rack guide part 31 to the rack bar 20 side. The first slide surface 300a is divided into two slide surface holding pieces 319a, 319b along an axis O2 direction of the rack bar 20, and is energized by a second energization member 34 in a direction in which two slide surface holding pieces 319a, 319b approach each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to a rack guide that presses a rack bar against a pinion in a rack and pinion used for an automobile steering device or the like, and in particular, a rack guide having an excellent sliding surface in terms of both wear resistance and slidability. (Support yoke) and the gear mechanism using this.

In a rack and pinion used for a steering device of an automobile, the rack and pinion is arranged on the back surface (the surface opposite to the rack gear) of the rack bar housed in the housing, and the rack bar is pressed against the pinion while being guided in the axial direction thereof. As a rack guide, for example, the rack guide described in Patent Document 1 is known.

The rack guides are a first rack guide having a concave first tip surface that supports the back surface of the rack bar, and a concave second rack guide that is arranged in the first rack guide and supports the back surface of the rack bar. It includes a second rack guide having a tip surface. Here, the first tip surface is made of a material having excellent wear resistance, and the second tip surface is made of a material having excellent slidability. Further, the second rack guide is urged by an elastic member in a direction of being pushed out from the first rack guide toward the rack bar, whereby the second tip surface is pressed against the back surface of the rack bar. .. Then, when the load applied from the rack bar to the rack guide is equal to or less than the urging force applied to the second rack guide by the elastic member, the rack guide moves the second rack guide from the first rack guide to the rack bar side. The extruded rack bar is supported only by the second tip surface, which has excellent slidability. Therefore, the operability can be improved. On the other hand, when the load applied from the rack bar to the rack guide is larger than the urging force applied to the second rack guide by the elastic member, the second rack guide is pushed back and the rack bar is subjected to the first excellent wear resistance. It is supported by both the tip surface of the surface and the second tip surface having excellent slidability. Therefore, the second tip surface can be protected and durability can be ensured. Therefore, according to this rug guide, it is possible to improve the operability and secure the durability at the same time.

Japanese Patent No. 5125568

By the way, in the rack guide described in Patent Document 1, when the load applied from the rack bar to the rack guide is larger than the urging force applied to the second rack guide by the elastic member, the rack bar is attached to the first tip surface and the rack guide. In order to support both of the second tip surfaces, high dimensional accuracy is required for the first tip surface. For example, if the diameter of the first tip surface is larger than the diameter of the back surface of the rack bar, even if the second rack guide is pushed back, the rack bar does not come into contact with the first tip surface and the second tip surface May continue to be supported only by. In this case, it is not possible to protect the second tip surface and ensure durability. On the other hand, if the diameter of the first tip surface is smaller than the diameter of the back surface of the rack bar, the second rack guide is pushed back and the back surface of the rack bar hits both the first tip surface and the second tip surface. Even if they come into contact with each other, the load applied from the rack bar to the rack guide may be concentrated on the first tip surface. In this case, the operability deteriorates sharply.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rack guide capable of supporting a rack bar more stably for a longer period of time, and a gear mechanism using the same.

In order to solve the above problems, the rack guide according to the present invention is housed in a first rack guide portion having a concave first sliding surface that supports the back surface of the rack bar, and a first rack guide portion. A second rack guide portion having a concave second sliding surface that supports the back surface of the rack bar is provided. Here, the second rack guide portion is urged in the direction of being pushed out from the first rack guide portion toward the rack bar by the first urging means. Further, the first sliding surface piece is divided into two sliding surface pieces along the axial direction of the rack bar, and the two sliding surface pieces are attached in a direction approaching each other by the second urging means. It is being pushed. The first sliding surface is made of a material having better abrasion resistance than the second sliding surface (a material having a smaller specific abrasion amount than the second sliding surface), and the second sliding surface. The surface is preferably made of a material having better slidability than the first sliding surface (a material having a friction coefficient smaller than that of the first sliding surface).

For example, the rack guide of the present invention
A rack bar having a rack gear that meshes with the pinion gear is slidably supported from the opposite side of the rack gear, and the rack bar that moves according to the rotation of the pinion gear is guided in the axial direction of the rack bar. It ’s a rack guide,
A first rack guide portion having a concave first sliding surface that supports the back surface of the rack bar located on the opposite side of the rack gear.
A second rack guide portion housed in the first rack guide portion and having a concave second sliding surface that supports the back surface of the rack bar, and a second rack guide portion.
A first urging means for urging the second rack guide portion in a direction of pushing the second rack guide portion from the first rack guide portion toward the rack bar side.
With a second urging means,
The first sliding surface is
It is divided into two sliding surface pieces along the axial direction of the rack bar.
The second urging means is
The two sliding surface pieces are urged in a direction close to each other.

Further, the gear mechanism of the present invention is
A gear mechanism that changes the direction of travel of a moving body according to the rotation of the steering wheel.
A pinion gear that rotates according to the rotation of the steering wheel,
A rack gear that meshes with the pinion gear is formed, and the rack bar that reciprocates according to the rotation of the pinion gear and changes the direction of the wheel of the moving body by meshing with the pinion gear and the rack gear.
The rack guide is provided with the rack guide that slidably supports the rack bar in the axial direction of the rack bar.

In the present invention, the load applied from the rack bar to the rack guide is larger than the urging force applied to the second rack guide portion by the first urging means, whereby the second rack guide portion is pushed back and the rack is pushed back. When the back surface of the bar abuts on both the first sliding surface and the second sliding surface, the radial component of the load applied to the first sliding surface is first by the second urging means. When it is larger than the urging force (contraction force) applied to the sliding surface of the above, the two sliding surface pieces constituting the first sliding surface are pulled apart from each other. As a result, when a large load is applied from the rack bar to the rack guide, the contact range with the back surface of the rack bar gradually increases, so that a sudden increase in friction can be prevented, and the load applied from the rack bar to the rack guide can be prevented. It can be prevented from concentrating on any of the sliding surfaces and dispersed on the first sliding surface and the second sliding surface. Therefore, according to the present invention, it is possible to reduce the influence of the decrease in operability due to the first sliding surface while preventing the wear of the second sliding surface, so that the rack bar can be made more stable for a longer period of time. Can be supported.

FIG. 1 is a schematic cross-sectional view of a gear mechanism 1 of a steering device according to an embodiment of the present invention. 2 (A), 2 (B), and 2 (C) are a plan view, a front view, and a bottom view of the rack guide 30 shown in FIG. 3A and 3B are a cross-sectional view taken along the line AA and a cross-sectional view taken along the line BB of the rack guide shown in FIG. 2A. FIG. 4 is a diagram for explaining the shapes of the first and second sliding surfaces 300a and 300b. 5 (A) and 5 (B) are a front view and a plan view of the rack guide 30 for explaining the rack bar support mode in the low load region. 6 (A) and 6 (B) are a front view and a plan view of the rack guide 30 for explaining the rack bar support mode in a high load region. FIG. 7 is a schematic cross-sectional view of a modified example 1A of the gear mechanism 1 according to the embodiment of the present invention.

Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings. For convenience of the following description, the axis O2 direction of the rack bar 20 (the direction of reciprocating movement of the rack bar 20) is the X direction, and the pressing direction of the rack gear 21 against the pinion gear 11 is the Z direction, which is perpendicular to the X and Z directions. Direction is defined as Y direction, and these directions are appropriately displayed in each figure.

FIG. 1 is a cross-sectional view of the gear mechanism 1 of the steering device according to the present embodiment.

The steering device according to the present embodiment has a rack and pinion type gear mechanism 1 that converts the rotational motion of the steering shaft into a linear motion and transmits this linear motion to a link mechanism that changes the direction of the wheels. .. The steering device may or may not be equipped with a power steering mechanism that assists the movement of the pinion gear 11 or the rack bar 20 with a motor.

As shown in the figure, the gear mechanism 1 includes a pinion shaft 10 on which a pinion gear 11 is formed, a rack bar 20 on which a rack gear 21 that meshes with the pinion gear 11 is formed, and a pair of rotatably supporting the pinion shaft 10. A rolling bearing 40, a rack guide 30 that guides a rack bar 20 that reciprocates in the X direction as the pinion gear 11 rotates, a housing 70 in which these parts 10 to 40 are incorporated, and a cap 60 that closes the housing 70. ,have.

The pinion shaft 10 is a columnar member arranged so that the axis O1 is inclined with respect to the Y direction, and a helical gear, for example, is formed as a pinion gear 11 on the outer peripheral surface 12 thereof. The pinion gear 11 is housed in a pinion gear accommodating chamber 73 provided in the housing 70, and the pinion shaft 10 rotates around an axial center O1 via a pair of rolling bearings 40 at positions on both sides of the pinion gear 11. It is possible to be supported by the housing 70. One end 13 of the pinion shaft 10 projects from the opening 74 formed in the housing 70 to the outside of the pinion gear accommodating chamber 73 and is connected to a steering shaft (not shown). As a result, the pinion gear 11 rotates in conjunction with the steering shaft that rotates in response to the operation of the steering wheel.

The rack bar 20 is a columnar member arranged along the X direction, and although not shown, both ends thereof are connected to a link mechanism for changing the direction of the wheels via a ball joint. The plurality of teeth constituting the rack gear 21 are formed side by side in the X direction on the outer peripheral surface of the rack bar 20, and mesh with the teeth of the pinion gear 11 at a predetermined meshing position in the pinion gear accommodating chamber 73 of the housing 70. The back surface of the rack bar 20 (the outer peripheral surface having an arc-shaped YZ cross section located on the opposite side of the rack gear 21) 22 is provided by the rack guide 30 according to the magnitude of the load applied to the rack guide 30 by the rack bar 20. It is slidably supported. When the pinion shaft 10 rotates together with the steering shaft, the rack bar 20 is guided by the rack guide 30 and reciprocates in the X direction to swing the link mechanism due to the engagement between the pinion gear 11 and the rack gear 21. As a result, the direction of the wheel changes according to the operation of the steering wheel.

The housing 70 has a tubular rack case portion 71 arranged along the X direction, and a tubular cylinder case portion 72 protruding in the Z direction from the outer circumference of the rack case portion 71.

Inside the rack case portion 71, the rack bar 20 is housed so as to be reciprocally movable in the X direction. Further, a pinion gear accommodating chamber 73 is provided inside the rack case portion 71. As described above, the pinion gear accommodating chamber 73 includes a pinion gear 11 and a pair of rolling bearings 40 that rotatably hold the pinion shaft 10 so that the pinion gear 11 meshes with the rack gear 21 at a predetermined meshing position. , Is housed. Further, in the rack case portion 71, an opening 74 connecting the inside and the outside of the pinion gear accommodating chamber 73 is formed toward the steering shaft side (not shown), and the pinion connected to the steering shaft (not shown) is connected. One end 13 of the shaft 10 projects from the opening 74 to the outside of the pinion gear accommodating chamber 73.

On the other hand, the cylinder case portion 72 is integrally formed with the rack case portion 71 so as to be located on the opposite side of the pinion gear 11 with respect to the rack bar 20, and is integrally formed with the inside of the cylinder case portion 72 and the rack case portion 71. It is connected to the inside via an opening 75 facing the pinion gear 11 in the pinion gear accommodating chamber 73. Further, a screw portion 77 for fixing the cap 60 is formed on the inner wall surface 78 of the open end portion 76 of the cylinder case portion 72.

The rack guide 30 faces the two sliding surfaces (first sliding surface 300a and second sliding surface 300b) that slidably support the back surface 22 of the rack bar 20 toward the back surface 22 side of the rack bar 20. It is housed inside the cylinder case portion 72 in the Z direction, and is positioned on the opposite side of the pinion gear 11 with respect to the rack bar 20 (the back surface 22 side of the rack bar 20 at the meshing position between the pinion gear 11 and the rack gear 21). ing. The detailed structure of the rack guide 30 will be described later.

The cap 60 has a disk shape that can be fitted into the open end portion 76 of the cylinder case portion 72, and a screw portion 62 is formed on the outer periphery of the cap 60. By inserting the rack guide 30 into the cylinder case portion 72 of the housing 70 and screwing the screw portion 62 of the cap 60 into the screw portion 77 of the open end portion 76 of the cylinder case portion 72, the open end of the cylinder case portion 72 is screwed. The cap 60 is fixed to the portion 76 to close the cylinder case portion 72.

Next, the detailed structure of the rack guide 30 will be described.

2 (A), 2 (B), and 2 (C) are a plan view, a front view, and a bottom view of the rack guide 30 shown in FIG. 3 (A) and 3 (B) are a cross-sectional view taken along the line AA and a cross-sectional view taken along the line BB of the rack guide shown in FIG. 2 (A).

As shown in the figure, the rack guide 30 is attached to a columnar first rack guide portion 31 having a concave first sliding surface 300a that supports the back surface 22 of the rack bar 20 and a first rack guide portion 31. A first unit composed of a cylindrical second rack guide portion 32 having a concave second sliding surface 300b that is housed and supports the back surface 22 of the rack bar 20, and a spring member such as a coil spring or a leaf spring. It has an urging member 33 of the above and a second urging member 34 composed of an O-ring or the like.

The first rack guide portion 31 is provided on the base portion 311 in which the accommodating portion 310 for accommodating the second rack guide portion 32 in the Z direction is formed, and the end surface 312 on the opening side of the base portion 311. It has a sliding surface holding portion 314, which is arranged and has an insertion hole 313 through which the second rack guide portion 32 is movably inserted in the Z direction.

The base portion 311 is arranged on the cap 60 side, and its back surface (the surface opposite to the end surface 312 on the opening side) 3110 comes into contact with the back surface 61 of the cap 60. Further, the bottom surface 3100 of the accommodating portion 310 of the base portion 311 functions as a spring seat of the first urging member 33 composed of spring members such as coil springs and leaf springs.

The sliding surface holding portion 314 has a recess 316 formed on the end surface 315 facing the back surface 22 of the rack bar 20 so as to follow the shape of the back surface 22 of the rack bar 20, and the recess 316 has a first sliding surface. The first rack guide sheet 317 forming the 300a is fixed. Further, an annular groove 3180 in the circumferential direction is formed on the outer peripheral surface 318 of the sliding surface holding portion 314, and inside the annular groove 3180, an O having a wire diameter larger than the depth dimension of the annular groove 3180 is formed. A second urging member 34 such as a ring is attached. Further, the sliding surface holding portion 314 is divided into two sliding surface holding pieces 319a and 319b from the center along the axial center O2 direction of the rack bar 20, and is mounted on the annular groove 3180 on the outer peripheral surface 318. The second urging member 34 urges the two sliding surface holding pieces 319a and 319b in the direction of bringing them closer to each other.

The second rack guide portion 32 has a recess 321 formed on the end surface 320 facing the back surface 22 of the rack bar 20 so as to follow the shape of the back surface 22 of the rack bar 20, and the second sliding is formed in the recess 321. A second rack guide sheet 322 forming the surface 300b is fixed.

Further, on the back surface (the surface opposite to the end surface 320) 323 of the second rack guide portion 32, a spring which is a recess for accommodating the first urging member 33 composed of a coil spring, a leaf spring, or the like. A guide 324 is formed. Here, the natural length of the first urging member 33 is longer than the depth of the spring guide 324. Therefore, one end of the first urging member 33 projects from the spring guide 324 and comes into contact with the bottom surface 3100 of the accommodating portion 310 provided in the base portion 311 of the first rack guide portion 31. As a result, the first urging member 33 urges the second rack guide portion 32 in the direction of pushing the second rack guide portion 32 from the first rack guide portion 31 toward the rack bar 20, and the rack gear 21 is pressed against the pinion gear 11. Therefore, the separation of the teeth at the meshing position between the rack gear 21 and the pinion gear 11 is prevented.

Further, the space formed between the back surface 323 of the second rack guide portion 32 and the bottom surface 3100 of the accommodating portion 310 provided on the base portion 311 of the first rack guide portion 31 and the space formed by the spring guide 324 is lubricated. It functions as a grease storage chamber 329 for storing grease (not shown). Further, the second rack guide portion 32 is formed with a grease supply path 326 penetrating the end surface 320 and the bottom surface 325 of the spring guide 324. When the load applied from the rack bar 20 to the rack guide 30 is larger than the urging force applied to the second rack guide portion 32 by the first urging member 33, and this pushes back the second rack guide portion 32, The grease storage chamber 329 is compressed, and the lubricating grease stored in the grease storage chamber 329 is supplied to the second sliding surface 300b through the grease supply path 326. In the no-load state in which the load of the rack bar 20 is not applied to the rack guide 30, the height H1 of the grease storage chamber 329 is from the protrusion length H2 from the first rack guide portion 31 of the second rack guide portion 32. Is also set to be large (see FIG. 3 (A)).

Further, an annular groove 3270 in the circumferential direction is formed on the outer peripheral surface 327 of the second rack guide portion 32, and the wire diameter inside the annular groove 3270 is larger than the depth dimension of the annular groove 3270. An elastic member 328 such as an O-ring is embedded. As a result, the gap between the outer peripheral surface 327 of the second rack guide portion 32 and the inner wall 3111 of the accommodating portion 310 provided in the base portion 311 of the first rack guide portion 31 is sealed and stored in the grease storage chamber 329. It is possible to prevent the lubricating grease from leaking from this gap.

In the present embodiment, the second rack guide portion 32, the accommodating portion 310 of the base portion 311 of the first rack guide portion 31 accommodating the second rack guide portion 32, and the sliding surface holding portion 314 are used. The planar shape of the insertion hole 313 (XY cross-sectional shape perpendicular to the axis O3 of the rack guide 30) is an elliptical shape (see FIG. 2A). This is to prevent the second rack guide portion 32 from rotating about the axial center O3 of the rack guide 30 with respect to the first rack guide portion 31. However, the planar shape is not limited to the elliptical shape as long as this rotation can be prevented.

Next, details of the first sliding surface 300a and the second sliding surface 300b will be described.

The first rack guide sheet 317 forming the first sliding surface 300a is a material having better abrasion resistance than the second rack guide sheet 322 forming the second sliding surface 300b (second rack). The second rack guide sheet 322, which is made of a material having a smaller specific abrasion amount than the guide sheet 322 and forms the second sliding surface 300b, has better slidability than the first rack guide sheet 317. It is made of a material (a material having a coefficient of friction smaller than that of the first rack guide sheet 317).

The materials of the first rack guide sheet 317 and the second rack guide sheet 322 are a combination of sliding materials suitable for use as a slide bearing, which satisfies the above relationship, in the usage environment of the rack guide 30. It may be appropriately selected and used according to the manufacturing cost and the like.

For example, sliding materials suitable for use as sliding bearings include polytetrafluoroethylene (PTFE), polyacetal (POM), polyethylene (PE), polyolefin (PO), polyamide (PA), and aromatic polyamide (aromatic). PA), polybutylene terephthalate (PBT), polyphenylene terephthalate (PPS), polyurethane (PU), phenol resin (PF), polyether ether ketone (PEEK), ultra high molecular weight polyethylene (UHMWPE), liquid crystal polymer (LCP), Examples thereof include polyketone, compounds in which additives (lubricants, fiber strengthening agents, etc.) are added using these materials as base resins, copper-based sintered materials, and iron-based sintered materials.

The superiority or inferiority of the slidability between the sliding materials is determined by bringing the test piece of each sliding material into surface contact with the mating surface of the same material as the rack bar 20 under the conditions determined based on the usage environment of the rack guide 30. It is determined by comparing the dynamic friction coefficients obtained by performing the reciprocating friction and wear test, and the superiority or inferiority of the wear resistance between the sliding materials is the specific wear obtained from the weight change of the test piece before and after this friction and wear test. Determined by comparing quantities. For example, according to the rule that a sliding material with a smaller coefficient of kinetic friction has better slidability and a sliding material with a smaller specific wear amount has better wear resistance, the slidability and friction resistance between the sliding materials are superior or inferior. To determine.

For example, when PTFE is used as the material for the second rack guide sheet 322, PA having better wear resistance than PTFE can be used as the material for the first rack guide sheet 317. When POM is used as the material of the second rack guide sheet 322, fiber reinforced PA having better wear resistance than POM can be used as the material of the first rack guide sheet 317. When an oil-impregnated POM is used as the material for the second rack guide sheet 322, a fiber-reinforced POM having better wear resistance than the oil-impregnated POM can be used as the material for the first rack guide sheet 317.

FIG. 4 is a diagram for explaining the shapes of the first and second sliding surfaces 300a and 300b (hereinafter, also simply referred to as sliding surfaces 300).

As shown in the figure, the sliding surface 300 has a cross section perpendicular to the axis O2 direction of the rack bar 20 in a YZ cross section, and the axis O3 of the rack guide 30 (the axis O2 of the rack bar 20 and the sliding surface 300). The two contact positions TA and TB that are line-symmetric with respect to the straight line connecting the bottom center C) are set as the contact positions with the back surface 22 of the rack bar 20. In this way, the back surface 22 of the rack bar 20 is brought into contact with the sliding surface 300 at the two contact positions TA and TB that are line-symmetrical with respect to the axial center O3 of the rack guide 30, so that the rack guide 30 can be seen in the YZ cross section. It is possible to prevent rattling of the rack bar 20 in a direction perpendicular to the axis O3 of the rack bar 20, whereby the back surface 22 of the rack bar 20 can be stably and slidably supported.

Here, the contact positions TA and TB are set within a range in which the angle θ formed by the straight line connecting the axis O2 of the rack bar 20 and the contact positions TA and TB and the axis O3 of the rack guide 30 is 50 degrees or less. It is preferable to be done. When the angle θ formed is larger than 50 degrees, the frictional force between the back surface 22 of the rack bar 20 and the sliding surface 300 becomes large (wedge effect), and the sliding performance of the rack guide deteriorates. However, if the angle θ formed is too small, the two contact positions TA and TB become too close to each other, and the rack bar 20 is prevented from rattling in the direction perpendicular to the axis O3 of the rack guide 30 in the YZ cross section. Can't. Therefore, the angle θ formed is more preferably in the range of 5 degrees to 45 degrees.

Further, the sliding surface 300 includes a pair of arcuate surfaces 301a and 301b that pass through the contact positions TA and TB, respectively, in the YZ cross section and are line-symmetric with respect to the axial center O3 of the rack guide 30. The curvature centers OA and OB of these arcuate surfaces 301a and 301b are located on the rack gear 11 side of the curvature center O2 of the back surface 22 of the rack bar 20, and are line-symmetrical with respect to the axis O3 of the rack guide 30. It is in. Further, the radius of curvature R2 of these arcuate surfaces 301a and 301b is larger than the radius of curvature R1 of the back surface 22 of the rack bar 20.

The load applied from the rack bar 20 to the rack guide 30 is larger than the urging force applied to the second rack guide portion 32 by the first urging member 33, whereby the second rack guide portion 32 is pushed back. In this case, in order to ensure that the back surface 22 of the rack bar 20 is in contact with the first sliding surface 300a, the radius of curvature R2 of the arcuate surfaces 301a and 301b of the first sliding surface 300a is the second sliding. It is preferable that the arc surfaces 301a and 301b of the surface 300b are set to be slightly smaller than the radius of curvature R2.

Next, the rack bar support mode by the rack guide 30 having the above configuration will be described.

[Rack bar support mode in low load range]
5 (A) and 5 (B) are a front view and a plan view of the rack guide 30 for explaining the rack bar support mode in the low load region.

As shown in the figure, a load applied from the tire to the rack guide 30 via the rack bar 20 is applied to the second rack guide portion 32 by the first urging member 33, such as when traveling on a road surface in good condition. In the low load range below the force, the second rack guide portion 32 is pushed out from the first rack guide portion 31 toward the rack bar 20, and only the second sliding surface 300b is the rack bar at the contact positions TA and TB. Contact the back surface 22 of 20. Since the rack bar 20 is not in contact with the first sliding surface 300a and is supported only by the second sliding surface 300b, which has better slidability than the first sliding surface 300a, the steering is steered. The rack bar 20 smoothly reciprocates in conjunction with the operation, and a smooth steering feeling can be obtained.

[Rack bar support mode in high load range]
6 (A) and 6 (B) are a front view and a plan view of the rack guide 30 for explaining the rack bar support mode in a high load region.

As shown in the figure, when the tire is impacted from the road surface or the like, a load applied from the tire to the rack guide 30 via the rack bar 20 is applied to the second rack guide portion 32 by the first urging member 33. In a high load region larger than the urging force to be applied, the second rack guide portion 32 is pushed back into the accommodating portion 310 of the base portion 311 of the first rack guide portion 31 in addition to the second sliding surface 300b. The first sliding surface 300a, which has better wear resistance than the second sliding surface 300b, comes into contact with the back surface 22 of the rack bar 20 at the contact positions TA and TB. Here, the radius of curvature R2 of the arcuate surfaces 301a and 301b of the first sliding surface 300a is set to the second sliding surface so that the back surface 22 of the rack bar 20 is surely in contact with the first sliding surface 300a. If the arc surfaces 301a and 301b of 300b are set to be slightly smaller than the radius of curvature R2, the load applied from the rack bar 20 to the rack guide 30 is inferior in slidability to the second sliding surface 300b. It may concentrate on the sliding surface 300a and affect the steering feeling. However, the radial component of the load applied to the first sliding surface 300a is larger than the urging force (contraction force) applied to the sliding surface holding portion 314 of the first rack guide portion 31 by the second urging member 34. The two sliding surface holding pieces 319a and 319b constituting the sliding surface holding portion 314 are separated from each other, and the load applied from the rack bar 20 to the rack guide 30 is not concentrated on the first sliding surface 300a. It is dispersed on the first sliding surface 300a and the second sliding surface 300b. Therefore, in a high load region, it is possible to prevent the second sliding surface 300b from being worn and to reduce the influence of the deterioration of the steering feeling due to the first sliding surface 300a.

Further, in the high load region, the grease storage chamber 329 is compressed, and the lubricating grease stored in the grease storage chamber 329 is supplied to the second sliding surface 300b through the grease supply path 326. As a result, the slidability of the second sliding surface 300b is improved, and a smooth steering feeling can be obtained.

In the high load region where a larger load is applied from the tire to the rack guide 30 via the rack bar 20, the first sliding surface 300a and the second sliding surface 300b are elastically deformed to form the rack bar 20. It comes into surface contact with the back surface 22 and supports the rack bar 20.

The embodiment of the present invention has been described above.

In the present embodiment, the load applied from the rack bar 20 to the rack guide 30 is larger than the urging force applied to the second rack guide portion 32 by the first urging member 33 such as the coil spring and the leaf spring. When the second rack guide portion 32 is pushed back and the back surface 22 of the rack bar 20 comes into contact with both the first sliding surface 300a and the second sliding surface 300b, the first sliding surface When the radial component of the load applied to the 300a is larger than the urging force (contraction force) applied to the sliding surface holding portion 314 of the first rack guide portion 31 by the second urging member 34 such as the O-ring, sliding The two sliding surface holding pieces 319a and 319b constituting the surface holding portion 314 are separated from each other. As a result, when a large load is applied from the rack bar 20 to the rack guide 30, the contact range of the rack bar 20 with the back surface 22 gradually increases, so that a sudden increase in friction can be prevented, and the rack bar 20 to the rack It is possible to prevent the load applied to the guide 30 from concentrating on one of the sliding surfaces 300 and disperse it on the first sliding surface 300a and the second sliding surface 300b. Therefore, according to the present embodiment, the second sliding surface 300b, which is inferior in wear resistance to the first sliding surface 300a, is prevented from being worn, and the second sliding surface 300b is slid as compared to the second sliding surface 300b. Since the influence of the decrease in operability due to the first sliding surface 300a, which is inferior in mobility, can be reduced, the rack bar 20 can be supported more stably for a longer period of time.

Further, in the present embodiment, the first and second sliding surfaces 300a and 300b have an axial center O3 (rack bar) of the rack guide 30 in a YZ cross section which is a cross section perpendicular to the axial center O2 direction of the rack bar 20. Two contact positions TA and TB that are line-symmetrical with respect to (a straight line connecting the axial center O2 of 20 and the center C of the bottom of the sliding surface 300) are set as contact positions with the back surface 22 of the rack bar 20. Therefore, according to the present embodiment, it is possible to prevent the rack bar 20 from rattling in the direction perpendicular to the axial center O3 of the rack guide 30 in the YZ cross section, whereby the back surface 22 of the rack bar 20 can be prevented from rattling. Can be stably and slidably supported.

Further, in the present embodiment, it is formed between the back surface 323 of the second rack guide portion 32 and the bottom surface 3100 of the accommodating portion 310 provided on the base portion 311 of the first rack guide portion 31 and by the spring guide 324. The space to be used functions as a grease storage chamber 329 for storing lubricating grease, and a grease supply path 326 that penetrates the end surface 320 of the second rack guide portion 32 and the bottom surface 325 of the spring guide 324 is provided. Then, the load applied from the rack bar 20 to the rack guide 30 is larger than the urging force applied to the second rack guide portion 32 by the first urging member 33, whereby the second rack guide portion 32 is pushed back. In this case, the grease storage chamber 329 is compressed, and the lubricating grease stored in the grease storage chamber 329 is supplied to the second sliding surface 300b through the grease supply path 326. Thereby, the steering feeling at the time of high load can be improved.

The present invention is not limited to the above embodiment, and many modifications can be made within the scope of the gist thereof.

For example, in the above embodiment, the first rack guide portion 31 is composed of a base portion 311 and a sliding surface holding portion 314, but the present invention is not limited thereto. Like the rack guide 30A of the gear mechanism 1A shown in FIG. 7, the first rack guide portion 31 is provided only by the sliding surface holding portion 314 (sliding surface holding pieces 319a and 319b) extending to the back surface 61 of the cap 60. It may be configured. In this case, the space formed between the back surface 323 of the second rack guide portion 32 and the back surface 61 of the cap 60 and the spring guide 324 functions as a grease storage chamber 329 for storing lubricating grease. Further, the back surface 61 of the cap 60 functions as a spring seat of the first urging member 33.

Further, in the above embodiment, as the first urging member 33 that urges the second rack guide portion 32 in the direction of pushing out from the first rack guide portion 31 toward the rack bar 20, a coil spring, a leaf spring, or the like is used. However, the present invention is not limited to this. A rubber member may be used for the first urging member 33. Alternatively, the elastic force of the lubricating grease stored in the grease storage chamber 329 may be used as the first urging member 33.

Further, in the above embodiment, the first rack guide sheet 317 forming the first sliding surface 300a is more wear resistant than the second rack guide sheet 322 forming the second sliding surface 300b. The second rack guide sheet 322, which is formed of an excellent material and forms the second sliding surface 300b, is formed of a material having better slidability than the first rack guide sheet 317. However, the present invention is not limited to this. The same sliding material may be used for the first rack guide sheet 317 and the second rack guide sheet 322. Even in this case, when a large load is applied from the rack bar 20 to the rack guide 30, the load applied from the rack bar 20 to the rack guide 30 is distributed to the first sliding surface 300a and the second sliding surface 300b. Since the wear of the second sliding surface 300b can be prevented, the rack bar 20 can be supported more stably for a longer period of time.

Further, in the above embodiment, the second sliding surface 300b is an arc surface (see FIG. 4), but the present invention is not limited to this. The second sliding surface 300b has two inclined surfaces that are line-symmetric with respect to the axis O3 of the rack guide 30 in a YZ cross section that is a cross section perpendicular to the axis O2 direction of the rack bar 20 (for example, V). (Character shape) may be used.

Further, in the above embodiment, an example of application to a vehicle steering device is given, but the present invention is not limited to the vehicle steering device, and the present invention is not limited to the vehicle steering device, for example, a rack and pinion type gear mechanism such as a focusing mechanism of an optical device. It can be widely applied to the equipment that uses.

1, 1A: Gear mechanism 10: Pinion shaft 11: Pinion gear 12: Outer surface of pinion shaft 10 13: End of pinion shaft 10 20: Rack bar 21: Rack gear 22: Rear surface of rack bar 20, 30, 30A: Rack guide 31: 1st rack guide part 32: 2nd rack guide part 33: 1st urging member 34: 2nd urging member 40: Rolling bearing 60: Cap 61: Back surface of cap 60 62: Cap 60 Screw part 70: Housing 71: Rack case part 72: Cylinder case part 73: Pinion gear accommodation chamber 74, 75: Opening 76: Open end part of cylinder case part 72 77: Thread part of cylinder case part 72: Cylinder case Inner wall surface of portion 72: Sliding surface 300a: First sliding surface 300b: Second sliding surface 310: Accommodating portion 311: Base portion 312: End surface on the opening side of base portion 311 313: First rack Insertion hole of guide portion 31 314: Sliding surface holding portion 315: End surface of sliding surface holding portion 314 316: Recessed portion of sliding surface holding portion 314 317: First rack guide sheet 318: Sliding surface holding portion 314 Outer peripheral surface 319a, 319b: Sliding surface holding piece 320: End surface of the second rack guide portion 32 321: Recessed portion of the second rack guide portion 32 322: Second rack guide sheet 323: Second rack guide portion 32 324: Spring guide 325: Bottom surface of spring guide 324 326: Grease supply path 327: Outer peripheral surface of second rack guide portion 32 328: Elastic member 329: Grease storage chamber 3100: Bottom surface of accommodating portion 310 3110: Base portion Back surface of 311 3111: Inner wall of accommodating portion 310 3180: Circular groove of sliding surface holding portion 314 3270: Circular groove of second rack guide portion 32

Claims (9)

A rack bar having a rack gear that meshes with the pinion gear is slidably supported from the opposite side of the rack gear, and the rack bar that moves according to the rotation of the pinion gear is guided in the axial direction of the rack bar. It ’s a rack guide,
A first rack guide portion having a concave first sliding surface that supports the back surface of the rack bar located on the opposite side of the rack gear.
A second rack guide portion housed in the first rack guide portion and having a concave second sliding surface that supports the back surface of the rack bar, and a second rack guide portion.
A first urging means for urging the second rack guide portion in a direction of pushing the second rack guide portion from the first rack guide portion toward the rack bar side.
With a second urging means,
The first sliding surface is
It is divided into two sliding surface pieces along the axial direction of the rack bar.
The second urging means is
A rack guide characterized in that the two sliding surface pieces are urged in a direction in which they are brought closer to each other. The rack guide according to claim 1.
The second sliding surface of the second rack guide portion is attached in a direction in which the second rack guide portion is pushed out from the first rack guide portion toward the rack bar by the first urging means. By being pushed, it comes into contact with the back surface of the rack bar and
The first sliding surface of the first rack guide portion has the second rack guide portion pushed back toward the first rack guide portion by a load applied to the rack bar. A rack guide characterized in that it comes into contact with the back surface of the rack bar together with the second sliding surface of the rack guide portion. The rack guide according to claim 1 or 2.
The first sliding surface is formed of a material having a smaller specific wear amount than the second sliding surface.
The rack guide is characterized in that the second sliding surface is made of a material having a friction coefficient smaller than that of the first sliding surface. The rack guide according to any one of claims 1 to 3.
The second sliding surface is
A rack guide characterized in that, in a cross section perpendicular to the axial direction of the rack bar, two positions line-symmetrical with respect to the axial center of the rack guide are set as contact positions with the back surface of the rack bar. The rack guide according to any one of claims 1 to 4.
The first sliding surface is
A rack guide characterized in that, in a cross section perpendicular to the axial direction of the rack bar, two positions line-symmetrical with respect to the axial center of the rack guide are set as contact positions with the back surface of the rack bar. The rack guide according to claim 5.
A rack guide characterized in that the first sliding surface is an arc surface. The rack guide according to claim 5.
The first sliding surface is
A rack guide characterized by having two inclined surfaces line-symmetrical with respect to the axis of the rack guide in a cross section perpendicular to the axis direction of the rack bar. The rack guide according to any one of claims 1 to 7.
A storage chamber for storing lubricating grease whose capacity changes depending on the positional relationship of the second rack guide portion with respect to the first rack guide portion, which is urged by the first urging means.
It is characterized by further including a supply path for supplying the lubricating grease stored in the storage chamber onto the second sliding surface, which connects the second sliding surface and the storage chamber. Rack guide to. A gear mechanism that changes the direction of travel of a moving body according to the rotation of the steering wheel.
A pinion gear that rotates according to the rotation of the steering wheel,
A rack gear that meshes with the pinion gear is formed, and the rack bar that reciprocates according to the rotation of the pinion gear and changes the direction of the wheel of the moving body by meshing with the pinion gear and the rack gear.
The gear mechanism according to any one of claims 1 to 8, further comprising a rack guide that slidably supports the rack bar in the axial direction of the rack bar.

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