JP2013036576A - Rack shaft support unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rack shaft support unit capable of improving a steering feeling by eliminating hooked feeling at the start of steering in a structure for supporting a rack shaft by a bushing.SOLUTION: This rack shaft support unit 10 includes: a rack bushing 18 for slidably supporting the rack shaft 8 in an axial direction X; a case 17 for housing the rack bushing 18 so that it can move from a neutral position to both sides of in the axial direction X; and an elastic ring 19. A centering groove 27 is formed at an inner circumferential surface 17A of the case 17, and a fitting groove 30 is formed at an outer circumferential surface 18A of the rack bushing 18. The elastic ring 19 elastically supports the rack bushing 18 in a fitted state relative to the fitting groove 30 and the centering groove 27, and is elastically deformed as the rack bushing 18 moves in the case 17 from the neutral position in the axial direction X.

Description

  The present invention relates to a rack shaft support unit for supporting a rack shaft in a vehicle steering device.

A rack and pinion type vehicle steering device is known. The steering device of Patent Document 1 has a pinion shaft connected to a steering hole and rack teeth meshing with the pinion of the pinion shaft, and the wheels are steered while sliding in the vehicle width direction according to steering of the steering wheel. Including the turning axis.
The steering device includes a cylindrical housing that houses a steered shaft, and a cylindrical bush that is housed in the housing in a state of being externally fitted to the steered shaft, and is movable in the axial direction in this state. And further.

On the inner peripheral surface of the housing, there is a fitting portion that forms a circumferential surface extending in the axial direction of the steered shaft, and an annular first step portion that extends perpendicularly outward from the axial end of the fitting portion in the radial direction. An annular recess having a circumferential surface extending outward in the axial direction from the outer peripheral edge of the first step portion and an annular second step portion extending orthogonally outward from the axial outer edge of the annular recess in the radial direction are formed. ing.
An annular flange projects from one end in the axial direction of the bush, and two annular grooves are provided on the outer peripheral surface of the bush other than the flange. A flexible ring such as an O-ring is fitted in each annular groove. A part of the flexible ring of each annular groove protrudes radially outward from the annular groove.

  In the bush accommodated in the housing, a portion other than the flange is disposed in the fitting portion, and the flange is disposed in the annular recess. In this state, each flexible ring of the bush is in contact with the fitting portion of the housing. In addition, since the limit ring is externally fitted to the steered shaft and is in contact with the second step portion from the outside in the axial direction, the flange in the annular recess has an Located between. The entire bush can move in the axial direction as long as the flange does not contact the restriction ring or the first stepped portion. The bush is in the neutral position when the flange is located exactly in the middle of the restriction ring and the first step.

  The housing elastically supports the bush and the steered shaft in the radial direction through a flexible ring at the fitting portion. This suppresses rattling of the steered shaft during normal travel and prevents the generation of noise due to rattling. On the other hand, when the radial load (radial load) from the steered shaft to the bush increases due to reverse input from the wheel side, the bush is displaced radially outward, and the outer peripheral surface thereof is the inner peripheral surface (fitting) of the housing. Contact). Thereby, since the bending of the steered shaft in the radial direction is prevented, the support rigidity of the steered shaft can be maintained.

  In the configuration described in Patent Document 1, since the bush can move in the axial direction as described above, at the initial time point when the steering shaft starts to slide and the steered shaft starts to slide, the steered shaft is It slides with a bush without rubbing against the inner peripheral surface. Thus, when the steering wheel starts to steer the steering wheel, the steering person is less likely to be caught due to the friction between the steered shaft and the inner peripheral surface of the bush. Therefore, it is possible to improve the steering feeling at the beginning of steering.

JP 2007-50762 A

  In the configuration described in Patent Document 1, rubbing between the steered shaft and the bush can be prevented in the initial stage of steering, but when the steered shaft slides with the bush, it is fitted into each annular groove on the outer peripheral surface of the bush. There is a possibility that the bent flexible ring may rub against the fitting portion. For this reason, when the steering wheel starts to steer the steering wheel, there is a risk that the steering wheel will be caught due to the friction between the flexible ring and the fitting portion. There is a limit.

  Moreover, in the structure of patent document 1, when a turning shaft slides with a bush, a bush will shift | deviate to an axial direction from the original neutral position. Even if the bush is shifted to one side in the axial direction and an attempt is made to further slide the steered shaft in either direction, the bush cannot be slid along with the steered shaft. Therefore, since rubbing occurs between the steered shaft and the inner peripheral surface of the bush, there is a possibility that the steering wheel must start steering the steering wheel while feeling a catch when resuming the steering.

  The present invention has been made in view of such a background, and provides a rack shaft support unit that can improve the steering feeling by eliminating the feeling of being caught at the start of steering in a configuration in which the rack shaft is supported by a bush. The purpose is to do.

  The invention according to claim 1 is a rack shaft support unit (10) for supporting a rack shaft (8) movable in the axial direction (X), and is an annular body that is externally fitted to the rack shaft. A rack bush (18) that supports the rack shaft so as to be slidable in the axial direction, and an annular body that is externally fitted to the rack bush, the position of which is fixed, and the rack bush In a case (17) for accommodating the rack bush in a state in which a movement allowance (Q) is secured so as to be movable from a predetermined neutral position in the axial direction to both sides in the axial direction, and an inner peripheral surface (17A) of the case A centering groove (27) formed at a position facing the outer peripheral surface (18A) of the rack bush in the neutral position, and formed on the outer peripheral surface of the rack bush so as to face the centering groove. The ring is fitted into the fitting groove (30) for fitting the ring and the fitting groove of the rack bush, and is fitted into the centering groove from the inside in the radial direction, and the rack bush is axially and radially (R And an elastic ring (19) that elastically deforms as the rack bush moves in the axial direction from the neutral position in the case. Is a unit.

  According to a second aspect of the present invention, the fitting groove of the rack bush is a single annular groove formed in the center in the axial direction of the outer peripheral surface of the rack bush and extending in the circumferential direction. The elastic ring is fitted, and one centering groove is provided at a position facing the fitting groove from the outside in the radial direction when the rack bush is in the neutral position. The rack shaft support unit according to claim 1.

  According to a third aspect of the present invention, the fitting groove of the rack bush is formed one by one at both end portions in the axial direction of the outer peripheral surface of the rack bush, and the end portion is cut out along the entire circumference in the axial direction. And an open end shape that is open to both outer sides in the radial direction, and the elastic ring is fitted one by one in each fitting groove, and the centering groove is formed when the rack bush is in the neutral position. The rack shaft support unit according to claim 1, wherein one rack shaft support unit is provided at a position facing each fitting groove from the outside in the radial direction.

The invention according to claim 4 is the rack shaft support unit according to any one of claims 1 to 3, wherein the elastic ring includes an O-ring.
According to a fifth aspect of the present invention, at both ends in the axial direction of the case, an annular shape protruding radially inward is provided, and flanges (25) for restricting movement of the rack bush in the axial direction are provided. The rack shaft support unit according to any one of claims 1 to 4, wherein the rack shaft support unit is provided.

According to a sixth aspect of the present invention, a plurality of slits (31) for reducing the diameter of the rack bush than the flange when the rack bush is accommodated in the case are formed at intervals in the circumferential direction. The rack shaft support unit according to claim 5, wherein the rack shaft support unit is provided.
The invention according to claim 7 is characterized in that the case also serves as a stopper for restricting movement of the rack shaft over a predetermined amount by contacting the rack shaft or a member (11) moving together with the rack shaft. A rack shaft support unit according to any one of claims 1 to 6.

  In addition, in the above, the numbers in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

  According to the first aspect of the present invention, the rack bush is elastically supported by the elastic ring and is pressed against the rack shaft, and in this state, the movement allowance is shifted from the neutral position to both sides in the axial direction in the case. Can only move. Therefore, at the initial time when the rack shaft starts to move in the axial direction with the start of steering, the rack bush moves in the axial direction from the neutral position together with the rack shaft. Thus, the steering person is less likely to be caught due to the friction between the rack shaft and the inner peripheral surface of the rack bush at the start of steering.

  Further, when the rack bush moves in the axial direction from the neutral position at the start of steering, the elastic ring is elastically deformed in a state of being fitted into both the fitting groove of the rack bush and the centering groove on the inner peripheral surface of the case. That is, when the rack bush moves, the elastic ring does not rub against the inner peripheral surface of the case, so that the steering wheel can also feel a feeling of catching due to the friction between the elastic ring and the inner peripheral surface of the case at the start of steering. It becomes difficult to receive.

If the rack bush moves for a while at the start of steering, the shear resistance generated by the elastic deformation of the elastic ring exceeds the static frictional force between the rack bush and the rack shaft. Accordingly, the rack shaft cannot move, and the rack shaft moves in the axial direction while sliding with respect to the rack bush.
The elastic ring that is elastically deformed while being fitted in both the fitting groove and the centering groove generates a restoring force (shearing resistance described above) to return to the original shape. Therefore, when the steering (that is, the movement of the rack shaft) is stopped, the restoring force causes the rack bush to return to the neutral position in the case while sliding with respect to the rack shaft. Therefore, even at the initial time point when the steering is started again thereafter, the rack bush moves integrally with the rack shaft in the axial direction from the neutral position, and the elastic ring elastically deforms. You don't have to feel it.

As a result, in the configuration in which the rack shaft is supported by the bush, the feeling of being caught at the start of steering can be eliminated and the steering feeling can be improved.
Further, since the rack bush, the case and the elastic ring are unitized as a rack shaft support unit, as long as the unit itself is attached to a steering device or the like, the above-mentioned can be easily performed without troublesome adjustment. It is possible to improve the steering feeling by eliminating the feeling of being caught.

  According to the second aspect of the present invention, since only one elastic ring is provided, the elastic ring is elastically deformed when the rack bush moves integrally with the rack shaft in the axial direction from the neutral position. It is easy. Thereby, when the rack bush is moved integrally with the rack shaft in the axial direction at the start of steering, the shear resistance due to the elastic deformation of the elastic ring is reduced. Therefore, the steering person is not required to feel the above-mentioned catching feeling, and the steering feeling can be further improved.

  According to the third aspect of the present invention, since two elastic rings are provided in total, the rack bush has a radially inner periphery of the case as compared with the case where only one elastic ring is provided. It becomes difficult to displace to the surface side. As a result, even if the radial load (radial load) from the rack shaft to the rack bush increases due to reverse input from the wheel side, the rack bush becomes difficult to contact the inner peripheral surface of the case. Occurrence of abnormal noise associated with contact with the inner peripheral surface of the case can be suppressed. Thereby, the steering feeling can be further improved.

  Furthermore, since the fitting grooves into which the elastic rings are fitted one by one at both ends in the axial direction of the outer peripheral surface of the rack bush are open-ended, the rack bush moves integrally with the rack shaft in the axial direction from the neutral position. In doing so, only the elastic ring on the downstream side in the moving direction of the rack bush among the two elastic rings is elastically deformed. Therefore, the point that the rack bush moves in the axial direction is not substantially different from the case where only one elastic ring is provided. Therefore, similarly to the second aspect of the invention, when the steering is started, the shearing resistance due to the elastic deformation of the elastic ring accompanying the movement of the rack bush is reduced, so that the steering feeling can be further improved. .

According to invention of Claim 4, an elastic ring can be easily comprised with an O-ring.
According to the fifth aspect of the present invention, the axial movement of the rack bush within the range of movement allowance can be realized by the flange. In addition, when the input from the wheels (tires, etc.) becomes an excessive input that causes the rack shaft to bend, the flange supports the rack shaft, so that the load that can be withstood until the rack shaft bends or breaks. Can be improved.

According to the invention of claim 6, by reducing the diameter of the rack bush, the rack bush can be easily passed through the hollow portion of the flange and accommodated in the case.
According to the seventh aspect of the present invention, it is not necessary to separately provide a stopper for restricting the movement of the rack shaft beyond a predetermined level, so that the number of parts can be reduced.

FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus 1 to which a rack shaft support unit 10 according to an embodiment of the present invention is applied. FIG. 2 is a schematic cross-sectional view of the backlash removal mechanism 14 that applies preload to the meshing portions of the rack 8A and the pinion 7A. 3 is an enlarged cross-sectional view of a portion around the rack shaft support unit 10 in FIG. FIG. 4 is a schematic cross-sectional view of the rack shaft support unit 10. FIG. 5 is a front view of the rack bush 18. 6 is a cross-sectional view taken along the line VI-VI in FIG. FIG. 7 shows a state in which the rack bush 18 has moved to one side in the axial direction X in FIG. FIG. 8 is a graph showing the relationship between the operation torque of the steering member 2 and the stroke amount of the rack shaft 8. The solid line shows the case of this embodiment, and the broken line shows the conventional case. FIG. 9 is a diagram showing hysteresis based on the relationship between the operation torque of the steering member 2 and the stroke amount of the rack shaft 8. FIG. 10 is a diagram in which a modification example in FIG. 3 is applied. FIG. 11 is a diagram in which a modified example is applied in FIG. FIG. 12 is a diagram in which a modified example is applied in FIG.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus 1 to which a rack shaft support unit 10 according to an embodiment of the present invention is applied.
Referring to FIG. 1, a vehicle steering apparatus 1 includes a steering member 2 such as a steering wheel, a steering shaft 3, a first universal joint 4, an intermediate shaft 5, a second universal joint 6, and a pinion shaft 7. And a rack shaft 8. The steering shaft 3 is connected to the steering member 2. The steering shaft 3 and the intermediate shaft 5 are connected via the first universal joint 4. The intermediate shaft 5 and the pinion shaft 7 are connected via a second universal joint 6.

A pinion 7A is provided near the end of the pinion shaft 7, and a rack 8A that meshes with the pinion 7A is provided on the rack shaft 8. The rack shaft 8 extends in the vehicle width direction (left-right direction). The pinion shaft 7 and the rack shaft 8 constitute a turning mechanism 100 including a rack and pinion mechanism.
The rack shaft 8 is supported in a housing 9 fixed to a vehicle body (not shown) so as to be capable of linear reciprocation along an axial direction X (corresponding to the vehicle width direction). The housing 9 is made of a metal such as aluminum. Of both ends of the housing 9 in the axial direction X, the first end 91 is relatively far from the pinion 7A, and the second end 92 is relatively close to the pinion 7A. The rack shaft support unit 10 according to the embodiment of the present invention is disposed at the first end 91 of the housing 9 and supports the rack shaft 8 so as to be movable in the axial direction X.

In the present embodiment, the rack shaft support unit 10 will be described based on an example in which only the first end portion 91 of the housing 9 is disposed. However, the rack shaft support unit 10 includes only the second end portion 92 of the housing 9. It may be arranged in both, and may be arranged in both the 1st end 91 and the 2nd end 92.
Both end portions of the rack shaft 8 protrude to both outer sides of the housing 9, and tie rods 12 are coupled to the respective end portions via joints 11. Each tie rod 12 is connected to a wheel 13 via a corresponding knuckle arm (not shown).

When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion (slide) of the rack shaft 8 along the axial direction X by the pinion 7A and the rack 8A. Thereby, the steering of each wheel 13 is achieved.
Although not shown in FIG. 1, the rack shaft 8 is elastically attached to the pinion shaft 7 side at an intermediate portion in the axial direction X of the housing 9 in order to remove backlash of the meshing portion of the rack 8A and the pinion 7A. A backlash removing mechanism 14 is provided.

FIG. 2 is a schematic cross-sectional view of the backlash removal mechanism 14 that applies preload to the meshing portions of the rack 8A and the pinion 7A.
As shown in FIG. 2, the backlash removal mechanism 14 includes, as an example, a support yoke 15 that supports the rack shaft 8 so as to be slidable in the axial direction X, and the rack shaft 8 via the support yoke 15 as a pinion shaft. And an elastic member 16 biasing toward the 7 side.

3 is an enlarged cross-sectional view of a portion around the rack shaft support unit 10 in FIG.
In FIG. 3, the periphery of the first end 91 of the housing 9 is illustrated. In the first end portion 91, the hollow portion of the housing 9 is exposed as the opening 9 </ b> A on the outer end surface in the axial direction X. An inner peripheral surface 9B that defines a hollow portion in the housing 9 is a circumferential surface that extends along the axial direction X continuously from the opening 9A. The inner peripheral surface 9B is tapered in two steps toward the direction away from the opening 9A (right side in FIG. 3), then reduced in one step, and thereafter extends with the same diameter. The portion of the inner peripheral surface 9B that is reduced in diameter by one step is an annular surface that is flat in the radial direction R, and serves as a positioning surface 9C.

The rack shaft support unit 10 is press-fitted from the opening 9A side to the inner peripheral surface 9B of the housing 9, and is positioned in the axial direction X by coming into contact with the positioning surface 9C from the opening 9A side.
FIG. 4 is a schematic cross-sectional view of the rack shaft support unit 10.
As shown in FIG. 4, the rack shaft support unit 10 includes a case 17, a rack bush 18, and an elastic ring 19.

Case 17 is an annular body made of metal such as aluminum. The axial direction of the case 17 and the axial direction X of the rack shaft 8 are the same. The radial direction R of the case 17 and the radial direction of the inner peripheral surface 9B (see FIG. 3) of the housing 9 are the same.
At both ends in the axial direction X of the case 17, flanges 25 projecting inward in the radial direction R are integrally provided. Each flange 25 has an annular shape when viewed in the axial direction X. The cross-sectional shape when the case 17 provided with the flanges 25 at both ends in the axial direction X is cut by a flat surface orthogonal to the circumferential direction is substantially U-shaped as shown in FIG. Therefore, an annular inner circumferential recess 28 defined by the flanges 25 and the case 17 on both sides is provided on the inner circumference of the case 17.

  In the case 17, a fitting groove 26 that is recessed outward in the radial direction R is formed in the center in the axial direction X on the inner peripheral surface 17 </ b> A in a portion other than the flange 25. The fitting groove 26 is an annular shape extending in the circumferential direction. The groove wall 26A of the fitting groove 26 is flat in the radial direction R, and the bottom surface 26B of the fitting groove 26 is flat in the axial direction X. A centering groove 27 that is recessed outward in the radial direction R is formed at the center in the axial direction X of the bottom surface 26B. The section of the centering groove 27 when cut by a flat surface orthogonal to the circumferential direction is substantially triangular, and becomes narrower and sharper toward the outside in the radial direction R.

FIG. 5 is a front view of the rack bush 18. 6 is a cross-sectional view taken along the line VI-VI in FIG.
Still referring to FIG. 4, the rack bush 18 is an annular body made of synthetic resin. Examples of the material of the rack bush 18 include POM (polyoxymethylene). The axial direction X of the rack bush 18 and the axial direction X of the case 17 are the same, and the radial direction R of the rack bush 18 and the radial direction R of the case 17 are the same.

One insertion groove 30 is formed at the center in the axial direction X of the outer peripheral surface 18A of the rack bush 18. The fitting groove 30 is an annular groove extending in the circumferential direction of the rack bush 18. One elastic ring 19 is fitted into the fitting groove 30 as described later. The cross section of the fitting groove 30 when cut by a flat surface orthogonal to the circumferential direction is rectangular.
A plurality of slits 31 are formed in the rack bush 18 at intervals in the circumferential direction. Each slit 31 extends in the axial direction X while penetrating the peripheral wall of the rack bush 18 in the radial direction R (see FIGS. 5 and 6). The slit 31 includes a slit 31A extending from one end (left end in FIG. 4) to the middle of the other end side (right end side) in the axial direction X, and one end from the other end (right end in FIG. 4) of the rack bush 18 There is a slit 31B extending to the middle of the side (left end side). The slits 31A and the slits 31B are alternately arranged in the circumferential direction.

  When the rack bush 18 is tightened from the outside in the radial direction R, the circumferential distance between the slits 31 is narrowed, so that the rack bush 18 can be reduced in diameter. The rack bush 18 having a reduced diameter has an elastic repulsive force that tends to return to its original state. Therefore, if the tightening to the rack bush 18 is eliminated, the circumferential interval between the slits 31 is widened by the elastic repulsive force of the rack bush 18 itself, so that the rack bush 18 is expanded to the original size. Thus, the rack bush 18 can be elastically deformed in the radial direction R and the circumferential direction within the range of the circumferential interval between the slits 31.

Such a rack bush 18 is accommodated in the case 17. In other words, the case 17 is externally fitted to the rack bush 18.
The elastic ring 19 is formed in an annular shape by an elastic body such as rubber. The axial direction X of the elastic ring 19 and the axial direction X of the case 17 and the rack bush 18 are the same. The radial direction R of the elastic ring 19 and the radial direction R of the case 17 and the rack bush 18 are the same. Is the same.

The cross-sectional shape when the elastic ring 19 is cut by a flat surface orthogonal to the circumferential direction is circular. An O-ring can be used as the elastic ring 19. Thereby, the elastic ring 19 can be configured easily.
In FIG. 4, one elastic ring 19 is externally fitted to the rack bush 18 and is fitted into the fitting groove 30 of the outer peripheral surface 18 </ b> A of the rack bush 18. At this time, in the elastic ring 19, a portion of substantially the outer half or more in the radial direction R protrudes from the fitting groove 30.

Next, assembly of the rack shaft support unit 10 will be described.
First, the rack bush 18 in a state where one elastic ring 19 is fitted in the fitting groove 30 is disposed outside the axial direction X with respect to the flange 25 of the case 17. The rack bush 18 is once reduced in diameter with respect to the flange 25 of the case 17 by picking it with a hand or a tool. Next, the rack bush 18 having a reduced diameter is passed from the axial direction X through the hollow portion of the flange 25. Thereafter, when a hand, a tool, or the like is separated from the rack bush 18, the rack bush 18 expands its diameter by its own elastic repulsive force and fits in the inner peripheral recess 28 of the case 17, as shown in FIG. Thus, since the rack bush 18 can be reduced in diameter by forming the slits 31, it can be easily accommodated in the case 17 through the hollow portion of the flange 25.

The rack bush 18 accommodated in the case 17 is located in the inner peripheral recess 28, that is, between the flanges 25 on both sides of the case 17. Since the flanges 25 are positioned on both outer sides of the rack bush 18 in the axial direction X, the rack bush 18 is prevented from being pulled out from the case 17 in the axial direction X.
Further, the inner peripheral surface 18B of the rack bush 18 in the state accommodated in the case 17 protrudes inward in the radial direction R from the inner peripheral edge of each flange 25.

  Here, the position in the middle of the flanges 25 on both sides in the axial direction X is the neutral position in the axial direction X of the rack bush 18, and FIG. 4 shows a state in which the rack bush 18 is in the neutral position. At this time, a movement allowance Q in the axial direction X is ensured between the rack bush 18 and the flanges 25 at the neutral position. The movement allowances Q on both sides of the rack bush 18 when the rack bush 18 is in the neutral position are substantially the same. Therefore, the rack bush 18 can move by the same movement allowance Q from the neutral position to both sides in the axial direction X while being accommodated in the case 17. Then, when the rack bush 18 moves from the neutral position in any direction in the axial direction X by the movement allowance Q, since either flange 25 is positioned beyond the rack bush 18, no further movement is possible. That is, each flange 25 restricts the movement of the rack bush 18 in the axial direction X by a predetermined amount or more. Such a flange 25 can realize the movement of the rack bush 18 in the axial direction X within the range of the movement allowance Q.

When the rack bush 18 accommodated in the case 17 is in the neutral position, the fitting groove 26 and the centering groove 27 of the inner peripheral surface 17A of the case 17 are from the outer side in the radial direction R with respect to the outer peripheral surface 18A of the rack bush 18. It faces the fitting groove 30 of the outer peripheral surface 18A at the same position in the axial direction X and faces the fitting groove 30 from the outside in the radial direction R.
As described above, when the rack bush 18 is accommodated in the case 17 and disposed in the neutral position, the single elastic ring 19 fitted in the fitting groove 30 of the outer peripheral surface 18A of the rack bush 18 is fitted into the case 17. The groove 26 and the centering groove 27 are fitted from the inside in the radial direction R. Thereby, the assembly of the rack shaft support unit 10 is completed.

  In this state, the case 17 and the rack bush 18 are connected via only one elastic ring 19, and the elastic ring 19 is sandwiched between the case 17 and the rack bush 18, so that the radial direction X is The rack bush 18 is elastically supported in the axial direction X and the radial direction R while being compressed to some extent. The inner part in the radial direction R of the elastic ring 19 in a compressed state is fitted into the fitting groove 30 of the rack bush 18 so that there is no gap in the axial direction X. Further, the outer portion of the elastic ring 19 in the radial direction R is fitted in the fitting groove 26 of the case 17 with play so that a certain amount of gap is generated in the axial direction X. However, the outer end portion in the radial direction R of the elastic ring 19 is fitted into the centering groove 27 so as to bite from the inner side in the radial direction R. Therefore, the elastic ring 19 fits tightly (tightly) into the fitting groove 30 of the rack bush 18 and the centering groove 27 of the case 17 so as not to be detached.

  The rack shaft support unit 10 assembled in this way is assembled to the housing 9 by being press-fitted into the inner peripheral surface 9B of the housing 9 and brought into contact with the positioning surface 9C as described above with reference to FIG. At this time, in the rack shaft support unit 10, the case 17 is press-fitted into the inner peripheral surface 9 </ b> B of the housing 9 and abuts against the positioning surface 9 </ b> C, thereby fixing the position of the case 17 in each of the axial direction X and the radial direction R. Has been. As a result, the rack shaft support unit 10 is held by the housing 9. Note that only a part of the outer periphery of the case 17 in the axial direction X is press-fitted into the inner peripheral surface 9B of the housing 9. As a result, the fitting length between the case 17 and the housing 9 is minimized, the load from the case 17 to the housing 9 is reduced, and the durability of the housing 9 is improved.

In this state, referring to FIG. 4, rack bush 18 is externally fitted to rack shaft 8, and inner peripheral surface 18 </ b> B of rack bush 18 is in surface contact with outer peripheral surface 8 </ b> B of rack shaft 8. doing. As a result, the rack bush 18 supports the rack shaft 8 so as to be slidable in the axial direction X.
Thus, the rack shaft 8 supported by the rack bush 18 slides in the axial direction X while rubbing against the inner peripheral surface 18B of the rack bush 18 in accordance with the steering of the steering member 2 (see FIG. 1). . Here, when the rack shaft 8 is fully slid in the direction (right side in FIG. 3) entering the housing 9 from the opening 9A (see FIG. 3), a member that moves together with the rack shaft 8 (for example, the joint 11 described above). 1 (see FIG. 1) also enters the housing 9 through the opening 9A and contacts the left side surface (the left flange 25) of the case 17. As a result, further sliding of the rack shaft 8 is restricted. That is, the case 17 (the left flange 25) also serves as a stopper that restricts the rack shaft 8 from moving more than a predetermined amount. A portion that contacts the case 17 may be provided on the rack shaft 8 itself, and the portion of the rack shaft 8 that contacts the case 17 may further restrict the sliding of the rack shaft 8. In any case, since it is not necessary to provide a separate stopper for restricting the movement of the rack shaft 8 beyond a predetermined amount, the number of parts can be reduced.

  As described above, the elastic ring 19 elastically supports the rack bush 18 in the axial direction X and the radial direction R. Therefore, the rack bush 18 having the slits 31 is elastically reduced in diameter by the elastic contraction force acting inward in the radial direction R in the elastic ring 19. Thereby, the inner peripheral surface 18B of the rack bush 18 is in surface contact with the outer peripheral surface 8B of the rack shaft 8 without a gap.

  Here, when the radial load (radial load) applied to the rack bush 18 from the rack shaft 8 is small during traveling of the vehicle, the inner diameter of the outer peripheral surface 18A of the rack bush 18 and the inner peripheral recess 28 of the case 17 is reduced. A gap S in the radial direction R is secured across the entire circumferential direction between the circumferential surface 17A. Therefore, when the radial load is small, the rack bush 18 is elastically supported by the elastic ring 19 so as to float inward from the inner peripheral surface 17A of the case 17 in the radial direction R. Therefore, since the rack shaft 8 supported by the rack bush 18 is also elastically supported, it is possible to prevent the rack shaft 8 from rattling.

  On the other hand, the reverse input from the wheel 13 may act on the rack shaft 8 due to the wheel 13 (see FIG. 1) hitting the curb during traveling. When the radial load from the rack shaft 8 to the rack bush 18 increases due to this reverse input, the rack bush 18 is displaced outward in the radial direction R while compressing the elastic ring 19, and finally the outer periphery of the rack bush 18 is The surface 18A contacts the inner peripheral surface 17A of the case 17. As a result, the rack bush 18 can no longer be displaced outward in the radial direction R, so that the rack shaft 8 is prevented from being bent in the radial direction R, so that the support rigidity of the rack shaft 8 during the reverse input action is maintained. it can. Further, when the input from the wheel 13 becomes an excessive input such that the rack shaft 8 bends, the flange 25 supports the rack shaft 8, so that the load that can be withstanded until the rack shaft 8 bends or breaks. Can be improved.

And the magnitude relationship of the dimension of the principal part in the rack shaft support unit 10 which concerns on this embodiment is as follows. Here, “width” refers to a dimension in the axial direction X.
(1) Inner width of case 17 (interval between one pair of flanges 25) B-full width AS of rack bush 18> groove width GB of fitting groove 26 of case 17-groove width GA of fitting groove 30
(2) GB ≧ GA
(3) Outer diameter A of rack bush 18> center diameter of elastic ring 19 (diameter at the center of circular cross section) RC
(4) A> Inner diameter RB of flange 25> Inner diameter a of rack bush 18
Under the condition (1), the above-described movement allowance Q is secured on both sides of the rack bush 18. Under the conditions (2) and (3), the elastic ring 19 is maintained in both the fitting groove 26 and the fitting groove 30 in accordance with the movement of the rack bush 18 in the axial direction X. It can be elastically deformed in the axial direction X. In order to prevent the elastic ring 19 from shifting in the axial direction X in a state in which the elastic ring 19 is fitted in the fitting groove 26 and the fitting groove 30, GB and GA cut the elastic ring 19 on a flat surface orthogonal to the circumferential direction. It is preferable that the diameter is the same as or smaller than the diameter of the cross section. Under the condition (4), the rack bush 18 does not come out of the case 17 to the outside in the axial direction X, and the inner peripheral surface 18B of the rack bush 18 contacts the outer peripheral surface 8B of the rack shaft 8 to Can support reliably. Note that RB is preferably a value as close as possible to a. If so, the flange 25 can reliably come into contact with the rack shaft 8 or a member that moves together with the rack shaft 8 (the above-described joint 11 or the like, see FIG. 1). Can be fulfilled reliably.

FIG. 7 shows a state in which the rack bush 18 has moved to one side in the axial direction X in FIG.
In this rack shaft support unit 10, as shown in FIG. 7, the rack bush 18 is moved from the neutral position (see FIG. 4) to one side in the axial direction X (right side in FIG. 4) in the case 17. . Since the elastic ring 19 is firmly fitted into the fitting groove 30 of the rack bush 18 and the centering groove 27 of the case 17 so as not to be detached, the elastic ring 19 is elastically deformed in accordance with the movement of the rack bush 18. The cross section (see FIG. 4) of the elastic ring 19 that was a perfect circle before the deformation is elliptical with the elastic deformation of the elastic ring 19.

  As described above, the rack bush 18 is elastically supported by the elastic ring 19 and pressed against the rack shaft 8. When the elastic ring 19 starts elastic deformation in this state, immediately after the start, the static friction force between the inner peripheral surface 18B of the rack bush 18 and the outer peripheral surface 8B of the rack shaft 8 is more elastic. It exceeds the shear resistance generated by deformation. The rack bush 18 can move from the neutral position to both sides in the axial direction X by the movement allowance Q while being accommodated in the case 17.

  Therefore, at the initial time point when the rack shaft 8 starts to move in the axial direction X with the start of steering of the steering member 2 (see FIG. 1), the rack shaft 8 slides. The rack bush 18 that is supported is moved integrally with the rack shaft 8 in the axial direction X from the neutral position. That is, since the rack shaft 8 and the rack bush 18 are accompanied in the axial direction X, the steering person can move the rack shaft 8 and the inner peripheral surface 18B of the rack bush 18 at the start of steering (at the beginning of movement of the rack shaft 8). It becomes difficult to receive a feeling of being caught due to rubbing.

  Specifically, when the rack shaft 8 moves in the axial direction X with steering, first, the elastic ring 19 is sheared and the rack bush 18 is connected to the rack shaft 8 while the elastic ring 19 is sheared. During the minute stroke, it is accompanied (moved integrally) in the axial direction X. Therefore, since the rack shaft 8 can be started with a force smaller than the static friction force between the rack shaft 8 and the rack bush 18, the operation torque at the start of steering of the steering member 2 can be made extremely small. it can. Therefore, it is possible to lose the feeling of being caught as a steering feeling.

  Further, when the rack bush 18 moves in the axial direction X from the neutral position at the start of steering, the elastic ring 19 is elastic in a state of being fitted into both the fitting groove 30 of the rack bush 18 and the centering groove 27 of the case 17. Deform. That is, when the rack bush 18 moves, the elastic ring 19 does not slide on the inner peripheral surface 17A of the case 17, so that the steering wheel can slide between the elastic ring 19 and the inner peripheral surface 17A of the case 17 at the start of steering. It also becomes difficult to receive a feeling of catching due to rubbing.

FIG. 8 is a graph showing the relationship between the operation torque of the steering member 2 and the stroke amount of the rack shaft 8. The solid line shows the case of this embodiment, and the broken line shows the conventional case.
In this embodiment, as shown by the solid line in FIG. 8, the rack shaft 8 can be stroked when the operation torque of the steering member 2 is small. In FIG. 8, a broken line indicates a case where a conventional rack bush is used. In the conventional case, the rack shaft 8 does not make a stroke unless the operation torque of the steering member 2 exceeds the torque corresponding to the static friction force between the rack bush 18 and the rack shaft 8.

  In this embodiment, referring to FIG. 7, when the rack bush 18 moves for a while at the stage immediately after the start of steering, the shear resistance generated by elastic deformation (shear deformation) of the elastic ring 19 causes the rack bush 18 and the rack shaft to move. 8 is exceeded (see point P in FIG. 8). Note that the shear resistance exceeds the static friction force before the rack bush 18 is moved by the movement allowance Q, and accordingly, the elastic modulus of the elastic ring 19 and the like are appropriately set.

When the shear resistance exceeds the static friction force in this way, the rack bush 18 cannot move any more with the rack shaft 8, and the rack shaft 8 moves against the rack bush 18 according to the steering amount of the steering member 2. It moves further in the axial direction X while sliding.
The elastic ring 19 that is elastically deformed in a state of being fitted into both the fitting groove 30 and the centering groove 27 generates a restoring force (shear resistance described above) to return to the original shape. Therefore, when the steering (that is, the movement of the rack shaft 8) is stopped, the restoring force causes the rack bush 18 to slide in the axial direction X with respect to the rack shaft 8 and return to the neutral position in the case 17 (see FIG. 4). At this time, the centering groove 27 urges (centers) the elastic ring 19 fitted in the fitting groove 30 to the neutral position side. Therefore, even at the initial time when the steering is started again thereafter, the rack bush 18 moves integrally with the rack shaft 8 in the axial direction X from the neutral position, and the elastic ring 19 is elastically deformed. This avoids the above-mentioned feeling of catching.

FIG. 9 is a diagram showing hysteresis based on the relationship between the operation torque of the steering member 2 and the stroke amount of the rack shaft 8.
Since the rack bush 18 is thus easily returned to the neutral position, referring to FIG. 9, the hysteresis generated when the steering member 2 is steered in the opposite direction can be reduced, and the locus of the hysteresis can be reduced. It is also possible to increase the rectangularity of the image (making the locus closer to a rectangle). Thereby, the responsiveness of the rack bush 18 can be improved.

As a result, in the configuration in which the rack shaft 8 is supported by the rack bush 18 as shown in FIG. 4, it is possible to improve the steering feeling by eliminating the feeling of being caught when the steering member 2 (see FIG. 1) starts steering. it can.
In particular, since only one elastic ring 19 is provided, the elastic ring 19 is easily elastically deformed when the rack bush 18 moves integrally with the rack shaft 8 in the axial direction X from the neutral position. (See FIG. 7). Thereby, when the rack bush 18 moves integrally with the rack shaft 8 in the axial direction X at the start of steering, the shear resistance due to the elastic deformation of the elastic ring 19 is reduced. Therefore, the steering person is not required to feel the above-mentioned catching feeling, and the steering feeling can be further improved.

  Furthermore, since the rack bush 18, the case 17, and the elastic ring 19 are unitized as the rack shaft support unit 10, the assembling property to the vehicle is remarkably improved. Then, as long as this unit itself is attached to a vehicle steering device or the like, it is possible to easily improve the steering feeling without the above-mentioned feeling of catching without any troublesome adjustment.

Next, a modified example will be described.
FIG. 10 is a diagram in which a modification example in FIG. 3 is applied. FIG. 11 is a diagram in which a modified example is applied in FIG. FIG. 12 is a diagram in which a modified example is applied in FIG.
10 to 12, members similar to those described so far are denoted by the same reference numerals, and description thereof is omitted.

10 to 12, the number of elastic rings 19 is two, and accordingly, the centering groove 27 of the case 17 and the fitting grooves 30 of the rack bush 18 are also formed two by two. Yes. In the modification, the fitting groove 26 (see FIG. 4) on the case 17 side is omitted. Other configurations are the same as those of the embodiments described so far (see FIGS. 3 to 7).
Referring to FIG. 11, the fitting grooves 30 of the rack bush 18 are formed one by one at both ends in the axial direction X of the outer peripheral surface 18 </ b> A of the rack bush 18. Each fitting groove 30 has a notch extending along the entire circumference in the axial direction X of the outer circumferential surface 18A of the rack bush 18. Each fitting groove 30 is L-shaped when viewed from the circumferential direction, in other words, has an open end shape opened to both outer sides in the axial direction X and the radial direction R. In FIG. 11, the left fitting groove 30A is open to the outside (left side) in the axial direction X and the outside in the radial direction R, and the right fitting groove 30B is arranged outside (right side) and the diameter in the axial direction X. Open to the outside in the direction R. As shown in FIG. 12, one elastic ring 19 is fitted in each fitting groove 30. Each elastic ring 19 is compressed between the case 17 and the rack bush 18.

As shown in FIG. 12, one centering groove 27 of the case 17 is provided at a position facing each fitting groove 30 from the outside in the radial direction R when the rack bush 18 is in the neutral position.
The size relationship of the dimensions of the main part of the rack shaft support unit 10 according to such a modification is as follows.
(1) Inner width of case 17 (space between one pair of flanges 25) B> full width AS of rack bush 18
(2) Condition (A> RC) of (3) in the above-described embodiment
(3) Condition (4) of the above-described embodiment (A>RB> a)
Under the condition (1), the above-described movement allowance Q is secured on both sides of the rack bush 18. The effects of the conditions (2) and (3) are as described in the above-described embodiment.

  The fitting grooves 30 into which the elastic rings 19 are fitted one by one at both ends in the axial direction X of the outer peripheral surface 18A of the rack bush 18 are open-ended as described above. Therefore, when the rack bush 18 moves integrally with the rack shaft 8 in the axial direction X from the neutral position, only the elastic ring 19 on the downstream side in the moving direction of the rack bush 18 is elastic among the two elastic rings 19. Deform.

  Specifically, for example, when the rack bush 18 moves to the right in FIG. 12, the elastic ring 19B fitted in the right fitting groove 30B, which is the downstream side in the movement direction, is moved from the upstream side in the movement direction by the rack bush 18. While being pressed, it is fitted into the right centering groove 27B. Therefore, the elastic ring 19B fitted in the fitting groove 30B is fitted so as not to be disengaged from the right fitting groove 30B and the centering groove 27B while the rack bush 18 moves to the right. On the other hand, when the rack bush 18 moves to the right side, the elastic ring 19A on the upstream side (left side in FIG. 12) in the moving direction of the rack bush 18 cannot accompany the rack bush 18 and goes upstream from the fitting groove 30A. It is in a state of playing with partly protruding. Therefore, when the rack bush 18 moves to the right side, only the right elastic ring 19B is elastically deformed, and the left elastic ring 19A is not elastically deformed.

On the other hand, when the rack bush 18 moves to the left in FIG. 12, only the left elastic ring 19A is elastically deformed, and the right elastic ring 19B is not elastically deformed.
Therefore, at the point where the rack bush 18 moves in the axial direction X, only one of the two elastic rings 19 is elastically deformed, which is substantially different from the case where only one elastic ring 19 is provided. Will not change. Therefore, as in the case of the above-described embodiment (see FIGS. 3 to 7), the shearing resistance due to the elastic deformation of the elastic ring 19 accompanying the movement of the rack bush 18 is reduced at the start of steering, thereby reducing the steering fee. The ring can be further improved. Further, the elastic ring 19 on the downstream side in the moving direction, which is elastically deformed in a state of being fitted in both the fitting groove 30 and the centering groove 27, generates a restoring force (shear resistance) for returning to the original shape. Therefore, even in the modified example, when the steering (movement of the rack shaft 8) is stopped, the rack bush 18 slides in the axial direction X with respect to the rack shaft 8 by this restoring force, and the neutral position in the case 17 is reached. (See FIG. 12). Note that when the rack bush 18 returns to the neutral position, the elastic ring 19 that has been idle until now (that was on the upstream side in the movement direction at the start of steering) fits into the fitting groove 30 again.

  However, in this modified example, since the two elastic rings 19 are provided in total, the rack bush 18 is provided in the radial direction R of the case 17 as compared with the case where only one elastic ring 19 is provided. It becomes difficult to displace to the inner peripheral surface 17A side. That is, the radial rigidity of the rack bush 18 is improved. Thereby, even if the radial load R (radial load) from the rack shaft 8 to the rack bush 18 increases due to reverse input from the wheel 13 (see FIG. 1) side, The rack bush 18 is less likely to contact the inner peripheral surface 17A of the case 17. Therefore, it is possible to further suppress the generation of noise due to the contact between the rack bush 18 and the inner peripheral surface 17A of the case 17 due to reverse input. Thereby, the steering feeling can be further improved.

That is, in this modified example, in addition to being able to reduce the feeling of catching immediately after the start of steering as in the above-described embodiment, the generation of noise due to the rack bush 18 coming into contact with the inner peripheral surface 17A of the case 17 is further suppressed. it can.
The present invention is not limited to the embodiment described above, and various modifications can be made within the scope of the claims.

For example, referring to FIG. 3, the case 17 may be a member on the housing 9 side instead of a member on the rack shaft support unit 10 side. In this case, the case 17 may be formed integrally with the housing 9. Then, in the rack shaft support unit 10, the structure can be simplified by eliminating the case 17.
Further, each of the centering groove 27 and the fitting groove 30 may have an arc shape along the outer peripheral surface of the elastic ring 19 when cut by a flat surface orthogonal to the circumferential direction. Then, the elastic ring 19 is fitted into the centering groove 27 and the fitting groove 30 so as not to be further detached.

  DESCRIPTION OF SYMBOLS 8 ... Rack shaft, 10 ... Rack shaft support unit, 11 ... Joint, 17 ... Case, 17A ... Inner peripheral surface, 18 ... Rack bush, 18A ... Outer peripheral surface, 19 ... Elastic ring, 25 ... Flange, 27 ... Centering groove, 30 ... Insertion groove, 31 ... Slit, Q ... Movement allowance, R ... Radial direction, X ... Axial direction

Claims (7)

A rack shaft support unit for supporting a rack shaft movable in an axial direction,
A rack bush that is externally fitted to the rack shaft, and supports the rack shaft so as to be slidable in the axial direction;
An annular body externally fitted to the rack bush, the position is fixed, and a movement allowance is secured so that the rack bush can move from a predetermined neutral position to both sides in the axial direction in the axial direction. A case for accommodating the rack bush in a state;
A centering groove formed at a position facing the outer peripheral surface of the rack bush at the neutral position on the inner peripheral surface of the case;
An insertion groove for fitting a ring formed on the outer peripheral surface of the rack bush so as to face the centering groove;
The rack bushing is fitted in the fitting groove of the rack bushing, and is fitted from the radially inner side to the centering groove, and elastically supports the rack bushing in the axial direction and the radial direction. An elastic ring that elastically deforms as it moves in the axial direction from the neutral position;
A rack shaft support unit comprising: The fitting groove of the rack bush is a single annular groove formed in the axial center of the outer peripheral surface of the rack bush and extending in the circumferential direction, and the one elastic ring is fitted into the fitting groove. And
The rack shaft support according to claim 1, wherein the centering groove is provided at a position facing the fitting groove from a radially outer side when the rack bush is in the neutral position. unit. The rack bushing groove is formed one by one at both axial end portions of the outer peripheral surface of the rack bush, and is open to both the axial and radial outer sides while notching the entire end portion. Open end shape, one elastic ring is fitted into each fitting groove,
2. The rack according to claim 1, wherein one centering groove is provided at a position facing each of the fitting grooves from the outside in the radial direction when the rack bush is in the neutral position. Shaft support unit.   The rack shaft support unit according to claim 1, wherein the elastic ring includes an O-ring.   The flanges that restrict the movement of the rack bush in the axial direction are provided at both ends in the axial direction of the case. The rack shaft support unit according to any one of the above.   6. The rack bush is formed with a plurality of slits spaced apart in the circumferential direction for reducing the diameter of the rack bush than the flange when the rack bush is housed in the case. The rack shaft support unit described.   The said case serves as a stopper which controls the movement more than the predetermined of the said rack axis | shaft by contact | abutting to the member which moves with the said rack axis | shaft or the said rack axis | shaft, The any one of Claims 1-6 characterized by the above-mentioned. Rack shaft support unit.

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