JP2012236489A - Rack shaft support device and steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rack shaft support device which can suppress the generation of noise for a long period of time.SOLUTION: The rack shaft support device 13 has an eccentric cam 27 which is rotatably supported around the first support center C1 of an internal periphery support face 26 by the internal periphery support face 26 of the internal periphery 10a of a rack housing 10. The eccentric cam 27 includes an external periphery supported face 32 concentric with the first support center C1, and an internal face cam face 33 having a second support center C2 which is concentric with the external periphery 8b of a rack shaft 8 and eccentric with the first support center C1. An elastic energization member 28 elastically energizes the eccentric cam 27 to a prescribed rotation direction Y1 around the first support center C1. The rack shaft 8 is pressed against the side of a pinion shaft 7 via the eccentric cam 27 by an energization force of the elastic energization member 28, and backlash is eliminated.

Description

  The present invention relates to a rack shaft support device and a vehicle steering device.

2. Description of the Related Art Conventionally, in a rack-and-pinion type steering device, a rack shaft having a structure that supports a rack shaft so as to be movable in the axial direction by using a direct-acting rack guide (also referred to as a support yoke) that moves forward and backward in the radial direction of the rack shaft. Support devices are commonly used.
The rack shaft support device includes a rack guide that is slidable in a depth direction of the holding hole (corresponding to a radial direction of the rack shaft) in a holding hole provided in a housing that protrudes orthogonally from the rack housing; A compression coil spring that urges the rack guide in the depth direction of the holding hole is accommodated. The rack guide biased by the compression coil spring supports the rack shaft so as to be slidable in the axial direction while pressing the rack shaft toward the pinion shaft.

However, when traveling on a rough road or the like, if the rack shaft vibrates in the forward / backward direction of the rack guide due to input from the wheels, the rack shaft and the rack guide are moved away from each other for a moment. For this reason, rattling noise is generated at the meshing portion of the rack and the pinion, or the rack guide that has rattled collides with each portion in the holding hole, and generates rattling noise and the like.
Further, during the stationary steering, the rack guide tilted in the holding hole is in a state of being hooked on the inner periphery of the holding hole, and then the hook guide is released and the rack guide suddenly starts to slide (so-called “so-called”). (Stick-slip phenomenon), the rack guide collides with each part in the holding hole, and a hitting sound (a so-called rich sound, stick-slip sound) is generated.

  On the other hand, Patent Document 1 proposes a rack shaft support device that supports a rack shaft by a rack adapter that is supported by a housing and through which the rack shaft is inserted. The rack adapter includes an outer periphery supported portion supported by a housing and an inner periphery support portion that supports a rack shaft, and a support center of the inner periphery support portion is a support center of the outer periphery supported portion, It is arranged eccentrically.

JP 2000-264234 A

In Patent Document 1, by adjusting the rotational position of the rack adapter, the backlash between the rack and the pinion is set to an appropriate amount, and then a fixing screw inserted through the long hole of the flange of the rack adapter is attached to the end surface of the housing. By screwing into the screw hole, the rotational position of the rack adapter after the backlash adjustment is fixed.
Since the position of the rack adapter is fixed in this way, if the sliding portion between the inner peripheral support portion of the rack adapter and the rack shaft is worn due to long-term use, the amount of backlash increases, and the rack and pinion There is a problem that noise due to the hitting sound is generated in the meshing portion.

  The present invention has been made in view of the above problems, and an object thereof is to provide a rack shaft support device capable of suppressing the generation of noise over a long period of time and a vehicle steering device including the same.

  In order to achieve the above object, the invention according to claim 1 is directed to a rack shaft support device (13) that supports a rack shaft (8) that meshes with a pinion shaft (7) that rotates in accordance with steering and performs linear motion. A cylindrical housing (10) through which the rack shaft is inserted, an inner peripheral support surface (26; 26A) provided on the inner periphery (10a) of the housing and having a first support center (C1), and an inner periphery thereof An eccentric cam (27; 27A) as a rack guide that is rotatably supported by the support surface around the first support center and guides the linear movement of the rack shaft, and the eccentric cam around the first support center. An elastic biasing member (28; 28A) that presses the rack shaft toward the pinion shaft via the eccentric cam by elastically biasing in the rotational direction (Y1). With support center An inner peripheral cam surface (33) having a second outer support center (C2) concentric with the outer peripheral supported surface (32; 32A) of the core and the outer periphery (8b) of the rack shaft and eccentric with respect to the first support center. And 33A).

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
According to a second aspect of the present invention, the eccentric cam includes a predetermined region (273) in the circumferential direction, and the predetermined region of the eccentric cam is disposed on a side opposite to the pinion shaft with respect to the rack shaft. The thickness (t) in the radial direction may be increased from the predetermined region toward the direction (Y2) opposite to the predetermined rotation direction.

Moreover, a friction reduction part (36; 36A) may be provided in the said inner peripheral cam surface of the said eccentric cam like Claim 3.
According to a fourth aspect of the present invention, the housing includes a first end portion (11) relatively close to the pinion shaft and a second end portion (12) relatively far from the pinion shaft, and the eccentricity. The cam may be disposed at a predetermined position between a center position (PC) between the second end portion and the pinion shaft and the first end portion.

According to a fifth aspect of the present invention, the eccentric cam may be disposed at the first end portion.
According to a sixth aspect of the present invention, a positioning member (10, 30) including a positioning surface (29, 31) for positioning the eccentric cam in the axial direction of the housing is provided, and the eccentric cam is positioned by the positioning surface. In addition, a friction reducing portion (371, 372) may be provided on one of the positioning surface and the positioned surface.

  The invention of claim 7 provides a vehicle steering device (1) that supports the rack shaft by the rack shaft support device described above.

  According to the first aspect of the present invention, the eccentric cam as a rack guide rotatably supported by the inner peripheral support surface of the housing is provided with a predetermined around the first support center of the inner peripheral support surface by the elastic biasing member. It is elastically biased in the direction of rotation. Because the elastic biasing force of the elastic biasing member can always keep the rack shaft pressed against the pinion shaft via the eccentric cam, the backlash between the pinion and the rack can be maintained at zero for a long period of time. it can. In addition, since a linear motion rack guide (support yoke) that linearly moves in the radial direction of the rack shaft is not used, there is a risk of occurrence of stick-slip noise due to the tilt of the linear motion rack guide (support yoke). Absent. Therefore, silence can be maintained over a long period of time.

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
According to the second aspect of the present invention, when the sliding portion between the inner peripheral support surface of the eccentric cam and the rack shaft is worn over a long period of use, the eccentric biasing member is operated by the elastic biasing member. It is rotationally displaced in the predetermined rotation direction. Thereby, it arrange | positions on the opposite side to a pinion axis | shaft with respect to a rack axis | shaft, and can maintain the radial thickness constant in the predetermined area | region of an eccentric cam. Therefore, the backlash can be maintained at zero for a long time regardless of the occurrence of wear.

According to the invention of claim 3, since the friction reducing portion is provided on the inner peripheral cam surface of the eccentric cam, the rotational friction resistance of the eccentric cam is reduced, and as a result, the backlash is maintained at zero. The eccentric cam can be smoothly rotated. In addition, even when used for a long period of time, wear hardly occurs at the sliding portion between the inner peripheral cam surface and the rack shaft.
According to the invention of claim 4, the rack shaft is supported by a rack bush typically disposed at the second end of the housing, a pinion shaft that supports the rack shaft in the first radial direction, and the rack shaft. Three-point support is performed using the eccentric cam that is supported in the second radial direction, which is the opposite direction of the first radial direction. Here, since the eccentric cam is disposed between the center position between the second end portion and the pinion shaft to the first end portion of the housing, the pinion shaft is relative to the first end portion of the housing. The rack shaft can be favorably pressed toward the pinion shaft by the eccentric cam elastically biased in a predetermined rotational direction.

According to the fifth aspect of the present invention, the rack bush that has been conventionally disposed at the first end of the housing can be eliminated, and the function of the rack bush can be shared by the eccentric cam, thus simplifying the structure. be able to.
According to the invention of claim 6, the eccentric cam can be positioned in the axial direction of the housing by the positioning surface of the positioning member. In addition, since the friction reducing portion is provided on either one of the positioning surface and the positioned surface of the eccentric cam, the rotational motion of the eccentric cam for maintaining the backlash to zero can be smoothly performed.

  According to the seventh aspect of the invention, it is possible to realize a vehicle steering apparatus that can suppress the generation of noise over a long period of time.

1 is a schematic diagram showing a schematic configuration of an electric power steering device as a rack and pinion type vehicle steering device including a rack shaft support device according to an embodiment of the present invention. It is sectional drawing of a rack shaft support apparatus. It is sectional drawing which follows the III-III line of FIG. It is a schematic diagram which shows the support structure of a rack shaft. It is sectional drawing of the rack shaft support apparatus of another embodiment of this invention. It is sectional drawing of the principal part of the rack shaft support apparatus of another embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus to which a rack shaft support device according to an embodiment of the present invention is applied. Referring to FIG. 1, an electric power steering device 1 as a vehicle steering device includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, and an intermediate connected to the steering shaft 3 via a universal joint 4. A shaft 5, a pinion shaft 7 connected to the intermediate shaft 5 via a universal joint 6, and a rack 8 a that meshes with a pinion 7 a provided on the pinion shaft 7 are formed to have an appropriate length in the axial direction X 1, and the axial direction X 1 ( And a rack shaft 8 as a steered shaft extending in the left-right direction of the automobile. The pinion shaft 7 and the rack shaft 8 constitute a steering mechanism A composed of a rack and pinion mechanism.

  The rack shaft 8 is inserted into a cylindrical rack housing 10 fixed to the vehicle body 9. The rack housing 10 has a first end portion 11 and a second end portion 12. The rack shaft 8 is supported by a rack shaft support device 13 held at the first end 11 of the rack housing 10 and a rack bush 14 held at the second end 12 so as to be movable in the axial direction X1. Yes. The rack shaft support device 13 has a function of a rack bush for supporting the rack shaft 8 and a function of removing backlash of the pinion 7a and the rack 8a.

  The pinion shaft 7 extends into the pinion housing 50 that intersects the vicinity of the first end portion 11 of the rack housing 10, and the pinion 7 a is integrally formed in the pinion housing 50. The pinion shaft 7 is rotatably supported by a pinion housing 50 via a bearing (not shown). At the intersection of the pinion housing 50 and the rack housing 10, the pinion 7a and the rack 8a are engaged with each other.

Both ends of the rack shaft 8 protrude to both sides of the rack housing 10, and tie rods 15 are coupled to the respective ends. Each tie rod 15 is connected to a corresponding steered wheel 16 via a corresponding knuckle arm (not shown).
The steering shaft 3 is rotatably supported by a cylindrical column housing 18 fixed to the vehicle body 9 via a bracket 17 via a bearing (not shown). The steering shaft 3 includes a steering input shaft 3 a connected to the steering member 2 and a steering output shaft 3 b connected to the intermediate shaft 5. The steering input shaft 3a and the steering output shaft 3b are connected via a torsion bar 19 so as to be relatively rotatable on the same axis. The torque sensor 20 disposed around the steering shaft 3 detects the steering torque input to the steering member 2 based on the relative rotational displacement amounts of the steering input shaft 3a and the steering output shaft 3b.

  The electric power steering apparatus 1 includes an electric motor 21 for assisting steering and a speed reduction mechanism 22 as a transmission mechanism for transmitting the output torque of the electric motor 21 to the steering mechanism A. The speed reduction mechanism 22 includes a worm 23 as a drive gear that is rotationally driven by the electric motor 21, and a worm wheel 24 that meshes with the worm 23 and is connected to the steering output shaft 3b so as to be integrally rotatable. ing.

  When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion in the axial direction X1 of the rack shaft 8 by the pinion 7a and the rack 8a. Thereby, the turning of the steered wheels 16 is achieved. A torque detection result by the torque sensor 20 and a vehicle speed detection result from a vehicle speed sensor (not shown) are given to an ECU (Electronic Control Unit) 25, and the ECU 25 controls the drive of the electric motor 21 based on these detection results. As a result, the steering output shaft 3b is rotationally driven via the speed reduction mechanism 22 to assist steering.

  FIG. 2 is an enlarged cross-sectional view of the rack shaft support device, and FIG. 3 is a cross-sectional view taken along line III-III in FIG. As shown in FIG. 2, the rack shaft support device 13 is provided on the inner periphery 10 a of the housing 10, and has an inner periphery support surface 26 having a first support center C <b> 1 and a first support center C <b> 1 around the inner periphery support surface 26. And a cylindrical eccentric cam 27 supported rotatably. The eccentric cam 27 functions as a rack guide that guides linear movement of the rack shaft 8 in the axial direction X1.

  As shown in FIG. 3, the rack shaft support device 13 includes an elastic biasing member 28 that elastically biases the eccentric cam 27 in a predetermined rotational direction Y1. The elastic biasing member 28 functions to press the rack shaft 8 toward the pinion shaft 7 via the eccentric cam 27 by elastically biasing the eccentric cam 27 in a predetermined rotational direction Y1 around the support center C1. . The urging direction of the elastic urging member 28 corresponds to a predetermined rotation direction Y1.

  As shown in FIG. 2, the eccentric cam 27 includes a first positioning surface 29 formed of an annular step formed on the inner periphery 10 a of the rack housing 10 and a screw on the inner periphery 10 a of the first end 11 of the rack housing 10. It arrange | positions between the 2nd positioning surface 31 which consists of an end surface of the cyclic | annular stopper 30 which consists of a screw screwed by the part 10b. The axial movement of the eccentric cam 27 is restricted by the positioning surfaces 29 and 31.

The eccentric cam 27 includes a first positioned surface 271 having one end surface facing the first positioning surface 29 of the rack housing 10 and a second positioned surface 272 having the other end surface facing the second positioning surface 31 of the stopper 30. And have.
The respective positioned surfaces 271 and 272 of the eccentric cam 27 are in gentle contact with the corresponding positioning surfaces 29 and 31 or opposed with a minute gap. Therefore, the resistance given to the rotation of the eccentric cam 27 by the first positioning surface 29 and the stopper 30 is kept small.

As shown in FIG. 3, the eccentric cam 27 includes an outer peripheral supported surface 32 composed of a cylindrical surface concentric with the first support center C <b> 1 and an inner peripheral cam surface 33. The inner peripheral cam surface 33 is a cylindrical surface having a second support center C2 that is concentric with the outer periphery 8b of the rack shaft 8 and is eccentric with respect to the first support center C1.
The eccentric cam 27 includes a protrusion 34 that protrudes radially outward from the outer peripheral supported surface 32. The protrusion 34 extends into a recess 35 provided on the inner peripheral support surface 26 of the rack housing 10. As the eccentric cam 27 rotates, the projection 34 can be displaced in the recess 35. The elastic biasing member 28 is interposed between the seat 351 formed by the inner surface of the recess 35 and the projection 34. The elastic biasing member 28 is made of, for example, a compression coil spring, and elastically biases the eccentric cam 27 in a predetermined rotational direction Y1 through the protrusion 34.

The eccentric cam 27 includes a predetermined region 273 in the circumferential direction. The predetermined region 273 of the eccentric cam 27 is disposed on the opposite side of the rack shaft 8 from the pinion shaft 7. That is, the rack shaft 8 is arranged between the predetermined region 273 of the eccentric cam 27 and the pinion shaft 7.
The thickness t of the eccentric cam 27 in the radial direction (the radial direction centered on the first support center C1) is opposite to the predetermined rotation direction Y1 (corresponding to the biasing direction of the elastic biasing member 28) from the predetermined region 273. The thickness is increased toward Y2. That is, the thickness t2 in the region 274 separated by a predetermined distance, for example, in the opposite direction Y2 is larger than the thickness t1 in the predetermined region 273 (t1 <t2). Thereby, the rack shaft 8 can be substantially pressed against the pinion shaft 7 via the eccentric cam 27 by the elastic biasing of the elastic biasing member 28.

  The offset amount e1 of the first support center C1 and the second support center C2 in the direction Z1 orthogonal to both the first support center C1 and the center axis C3 of the pinion shaft 7 presses the rack shaft 8 toward the pinion shaft 7 side. It corresponds to the amount. The maximum value of the offset amount e1 is the eccentric amount e of the second support center C2 with respect to the first support center C1, but the offset amount e1 does not reach the eccentric amount e even if wear or the like occurs during long-term use. The initial value of the offset amount e1 is set. Specifically, an initial value of the rotational angle position of the eccentric cam 27 is set.

Further, a friction reducing portion 36 is provided on the inner peripheral cam surface 33 of the eccentric cam 27. The friction reduction part 34 may be a low friction sheet such as a fluororesin attached to the inner peripheral cam surface 33, or may be a low friction layer such as a fluororesin layer coated on the inner peripheral cam surface 33. There may be.
According to the present embodiment, the eccentric cam 27 as a rack guide that is rotatably supported by the inner peripheral support surface 26 of the rack housing 10 is moved by the elastic biasing member 28 to the first support center of the inner peripheral support surface 26. It is elastically biased in a predetermined rotation direction Y1 around C1.

  Since the rack shaft 8 can always be pressed against the pinion shaft 7 via the eccentric cam 27 by the elastic biasing force of the elastic biasing member 28, the backlash between the pinion 7a and the rack 8a can be maintained over a long period of time. Can be maintained at zero. In addition, since a linear motion rack guide (support yoke) that linearly moves in the radial direction of the rack shaft is not used, there is a risk of occurrence of stick-slip noise or the like due to the tilt of the linear motion rack guide (support yoke). Nor. Therefore, it is possible to realize the rack shaft support device 13 and the electric power steering device 1 that can maintain silence over a long period of time.

  A predetermined region 273 of the eccentric cam 27 is arranged on the opposite side of the rack shaft 8 from the pinion shaft 7. That is, the rack shaft 8 is arranged between the predetermined region 273 of the eccentric cam 27 and the pinion shaft 7. The thickness t of the eccentric cam 27 in the radial direction is increased from the predetermined region 273 toward the direction Y2 opposite to the predetermined rotation direction Y1. This has the following advantages.

  That is, wear occurs at the sliding portion between the inner peripheral cam surface 33 of the eccentric cam 27 (the friction reducing portion 36 provided on the inner peripheral cam surface 33 in this embodiment) and the rack shaft 8 after long-term use. In this case, the eccentric cam 27 is rotationally displaced in the predetermined rotational direction Y1 by the action of the elastic biasing member 28. Thereby, the radial thickness t1 can be kept constant in the predetermined region 273 of the eccentric cam 27 disposed on the opposite side of the rack shaft 8 from the pinion shaft 7. Therefore, the backlash can be maintained at zero for a long time regardless of the occurrence of wear.

  Further, since the friction reducing portion 36 is provided on the inner circumferential cam surface 33 of the eccentric cam 27, the rotational friction resistance of the eccentric cam 27 is reduced. Therefore, the rotational motion of the eccentric cam 27 for maintaining the backlash at zero can be smoothly performed. Further, even when used for a long period of time, the sliding portion between the inner peripheral cam surface 33 (the friction reducing portion 36 in the present embodiment) and the rack shaft 8 is less likely to be worn. Further, the elastic urging member 28 that elastically urges the eccentric cam 27 can be reduced in size, and as a result, the rack shaft support device 13 can be reduced in size.

  In addition, since the eccentric cam 27 is disposed at the first end 11 of the rack housing 10 and supports the rack shaft 8, the rack bush conventionally disposed at the first end 11 of the rack housing 10 is eliminated. Can do. That is, the eccentric cam 27 can serve both as a rack bushing function and a function of removing the backlash between the pinion 7a and the rack 8a, so that the structure can be simplified.

As shown in FIG. 4, which is a schematic diagram, the rack shaft 8 is supported at the second end 12 of the rack housing 10 and the rack bush 14 supports the rack shaft 8 in all radial directions, and the rack. Three-point support using a pinion shaft 7 that supports the shaft 8 in the first radial direction R1 and an eccentric cam 27 that supports the rack shaft 8 in the second radial direction R2 that is opposite to the first radial direction R1. .
The eccentric cam 27 of the rack shaft support device 13 is moved from the central position PC between the position P1 of the pinion shaft 7 and the position P2 of the rack bush 14 (corresponding to the position of the second end 12) of the rack housing 10. What is necessary is just to be arrange | positioned in the predetermined position in the arrangement | positioning area | region Q between the position P3 of the 1st edge part 11. FIG.

  As a result, the eccentric cam 27 is disposed at a position relatively close to the pinion shaft 7, so that the rack shaft 8 is moved toward the pinion shaft 7 by the eccentric cam 27 elastically biased in a predetermined rotational direction Y1. It is because it can press well. The present embodiment has been described based on an example in which the rack shaft support device 13 is disposed at the position P3 of the first end portion 11 of the rack housing 10.

FIG. 5 shows another embodiment of the present invention. In the embodiment described above, the eccentric cam 27 surrounds the entire circumference of the rack shaft 8. However, in the rack shaft support device 13 </ b> A of the present embodiment, the eccentric cam 27 </ b> A disposed in approximately half of the rack shaft 8 in the circumferential direction. Is used.
The eccentric cam 27A includes an outer peripheral supported surface 32A formed of a part of a cylindrical surface concentric with the first support center C1, and an inner peripheral cam surface 33A. The inner peripheral cam surface 33A is formed of a part of a cylindrical surface having a second support center C2 that is concentric with the outer periphery 8b of the rack shaft 8 and is eccentric with respect to the first support center C1. The inner circumferential cam surface 33A is provided with a friction reducing portion 36A made of a low friction sheet such as a fluororesin.

26 A of inner peripheral support surfaces of the housing 10 are arrange | positioned in the area | region wider than the arrangement | positioning area | region of the eccentric cam 27A regarding the circumferential direction. This is because the inner peripheral support surface 26A needs to cover the movement range of the eccentric cam 27A in the rotational direction.
The elastic biasing member 28A is provided between a seat portion 10c provided by projecting a part of the inner periphery 10a of the housing 10 and one end surface 275 in the circumferential direction of the eccentric cam 27A facing the seat portion 10c. Intervene. In the configuration of the present embodiment, the same reference numerals as those of the embodiment of FIG. 3 are assigned to the same configurations as those of the embodiment of FIG.

Also in the present embodiment, as in the embodiment of FIG. 3, the rack shaft that can maintain the backlash between the pinion 7a and the rack 8a at zero over a long period of time and can maintain quietness over a long period of time. The support device 13A and the electric power steering device can be realized.
Further, since the eccentric cam 27A does not surround the entire circumference of the rack shaft 8, it is easy to assemble the eccentric cam 27A with respect to the rack shaft 8, and the assemblability is improved. Therefore, the manufacturing cost can be reduced.

  The present invention is not limited to the above-described embodiments. For example, as shown in FIG. 6, one of the first positioned surface 271 of the eccentric cam 27 and the first positioning surface 29 of the rack housing 10 ( In FIG. 6, the first positioning surface 271) may be provided with a friction reducing portion 371 configured by a low friction sheet such as a fluororesin or a low friction layer. Further, a low friction sheet such as a fluororesin or a low friction sheet is provided on either one of the end surfaces of the second positioning surface 272 of the eccentric cam 27 and the second positioning surface 31 of the stopper 30 (second positioning surface 272 in FIG. 6). A friction reduction unit 372 configured by a friction layer may be provided. In this case, the rotational resistance of the eccentric cam 27 can be further reduced. Further, wear of the positioning surface and the positioned surface can be reduced, and the eccentric cam 27 can be prevented from rattling in the axial direction after long-term use.

Although not shown, the stopper 30 is abolished, the rack housing 10 is caulked from the outer periphery, the protrusion is bulged on the inner periphery 10a, and the first positioning surface 29 including the bulged protrusion and the positioning step portion is used. The axial movement of the eccentric cam 27 may be restricted.
Further, the vehicle steering device is not limited to the electric power steering device 1, and may be manual steering or a hydraulic power steering device. In addition, various modifications can be made within the scope of the claims of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (vehicle steering device), 2 ... Steering member, 7 ... Pinion shaft, 7a ... Pinion, 8 ... Rack shaft, 8a ... Rack, 8b ... Outer periphery, 10 ... Rack housing, 10a ... Inner periphery, DESCRIPTION OF SYMBOLS 11 ... 1st edge part, 12 ... 2nd edge part, 13; 13A ... Rack axis | shaft support apparatus, 14 ... Rack bush, 26; 26A ... Inner peripheral support surface, 27; 27A ... Eccentric cam, 271 ... 1st to-be-positioned Surface, 272, second positioned surface, 273, predetermined region, 28; 28A, elastic biasing member, 29, first positioning surface, 30, stopper, 31, second positioning surface, 32, 32A, outer peripheral supported surface 33; 33A ... inner circumferential cam surface, 34 ... protrusion, 35 ... concave, 36,36A ... friction reduction part, 371,372 ... friction reduction part, P1, P2, P3 ... position, PC ... center position, Q ... arrangement Region, R1 ... 1st diameter Countercurrent, R2 ... second radial, X1 ... axial direction, Y1 ... predetermined rotational direction, Y2 ... opposite directions, Z1 ... orthogonal direction

Claims (7)

In a rack shaft support device that supports a rack shaft that meshes with a pinion shaft that rotates with steering and moves linearly,
A cylindrical housing through which the rack shaft is inserted;
An inner peripheral support surface provided on an inner periphery of the housing and having a first support center;
An eccentric cam as a rack guide that is rotatably supported about the first support center by the inner peripheral support surface and guides the linear movement of the rack shaft;
An elastic biasing member that presses the rack shaft toward the pinion shaft via the eccentric cam by elastically biasing the eccentric cam in a predetermined rotation direction around the first support center;
The eccentric cam has an outer peripheral supported surface concentric with the first support center, an inner peripheral cam surface having a second support center concentric with the outer periphery of a rack shaft and eccentric with respect to the first support center; Rack shaft support device including In Claim 1, the eccentric cam includes a predetermined region in the circumferential direction,
The predetermined region of the eccentric cam is disposed on the opposite side of the pinion shaft with respect to the rack shaft,
A rack shaft support device in which the thickness of the eccentric cam in the radial direction increases from the predetermined region toward the direction opposite to the predetermined rotation direction.   The rack shaft support device according to claim 1 or 2, wherein a friction reduction portion is provided on the inner peripheral cam surface of the eccentric cam. The housing according to any one of claims 1 to 3, wherein the housing includes a first end portion that is relatively close to the pinion shaft, and a second end portion that is relatively far from the pinion shaft,
The eccentric cam is a rack shaft support device disposed at a predetermined position between a center position between the second end portion and the pinion shaft and the first end portion.   The rack shaft support device according to claim 4, wherein the eccentric cam is disposed at the first end portion. The positioning member according to any one of claims 1 to 5, comprising a positioning surface for positioning the eccentric cam in an axial direction of the housing,
The eccentric cam includes a positioned surface positioned by the positioning surface;
A rack shaft support device in which a friction reducing portion is provided on one of the positioning surface and the positioned surface.   A vehicle steering apparatus in which a rack shaft is supported by the rack shaft support device according to any one of claims 1 to 6.

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