JP2015107683A - Rack shaft support device and steering device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rack shaft support device which inhibits deterioration of steering feeling when steering is started, and to provide a steering device including the rack shaft support device.SOLUTION: A rack shaft support device 30 includes: a support yoke 40; a low friction sheet 50 pressed against a rack shaft 16; a plug 32 fixed to a rack housing 20; and a coil spring 31 which presses the support yoke 40 toward the rack shaft 16. A yoke projection surface 45 is formed on an outer peripheral surface of the support yoke 40. A surface of the low friction sheet 50, which is pressed to the rack shaft 16, has a sheet projection surface 51. A sheet top part 51A of the sheet projection surface 51 and a yoke top part 45A of the yoke projection surface 45 are formed into circular shapes in a cross section view viewed in a longitudinal direction of the rack shaft 16.

Description

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

  A conventional steering device is equipped with a rack shaft support device to reduce rattle noise of rack teeth and pinion teeth. This rack shaft support device supports the rack shaft by pressing the support yoke against the rack shaft by the biasing force of the coil spring. Further, when the steering member is steered, the rack shaft moves in the longitudinal direction of the rack shaft while sliding with the low friction sheet fixed to the support yoke. Patent Document 1 discloses an example of the configuration of a conventional steering device and rack shaft support device.

Japanese Utility Model Publication No. 61-23969

  In recent years, for the purpose of further reducing the rattle noise of rack teeth and pinion teeth, a rack shaft support device has been proposed in which the biasing force of the coil spring is set to be large so that the force with which the support yoke pushes the rack shaft is increased. .

  However, when the force with which the support yoke pushes the rack shaft increases, the frictional force between the low friction sheet and the rack shaft increases. Thereby, the steering torque for moving the rack shaft is increased. For this reason, since a steering torque required when the driver starts to steer increases, the steering feeling may be deteriorated.

  An object of the present invention is to provide a rack shaft support device capable of suppressing deterioration of a steering feeling when starting steering, and a steering device including the device.

  [1] An independent form of the rack shaft support device has the following matters. That is, a support yoke that is formed in a cylindrical shape, is accommodated in a rack housing, and is movable in a pressing direction that is a direction in which the rack shaft is pressed in the rack housing, and is disposed between the support yoke and the rack shaft. A low friction sheet pressed against the rack shaft; a plug disposed on the opposite side of the rack shaft from the support yoke; and fixed to the rack housing; and disposed between the support yoke and the plug A coil spring that pushes the support yoke toward the rack shaft, and the support yoke is disposed on the rack shaft side with respect to the yoke back surface portion that is a portion on the plug side and the yoke back surface portion. The low friction sheet is fixed and supports the rack shaft A yoke support surface that protrudes in the radial direction of the support yoke is formed on the outer peripheral surface of the support yoke, and a surface that is pressed against the rack shaft in the low friction sheet A sheet projecting surface projecting in a direction from the yoke back surface toward the yoke support portion is formed, and the top of the sheet projecting surface and the top of the yoke projecting surface are circular in a longitudinal sectional view of the rack shaft. It is formed in an arc shape.

  According to this rack shaft support device, since the yoke protruding surface is formed on the support yoke and the sheet protruding surface is formed on the low friction sheet, there is a gap between the outer peripheral surface of the support yoke and the inner peripheral surface of the rack housing. A gap is formed between the surface that is formed and pressed against the rack shaft in the low friction sheet and the rack shaft. Therefore, the support yoke tilts when the rack shaft begins to move by steering and the force of the rack shaft moving acts on the low friction sheet. Here, since the top portion of the seat protruding surface is formed in an arc shape, when the support yoke is tilted as the rack shaft moves, rolling resistance is generated between the rack shaft and the top portion of the seat protruding surface. Since this rolling resistance is smaller than the static frictional force and the dynamic frictional force between the low friction sheet and the rack shaft, the rack shaft moves even if the force to move the rack shaft by steering is small during the period in which the support yoke tilts. start. For this reason, since the force required when the driver starts to steer is reduced, deterioration of the steering feeling is suppressed.

  As the rack shaft moves in one direction and the amount of tilt of the support yoke increases, both sides of the outer peripheral surface of the support yoke contact the inner peripheral surface of the rack housing in the longitudinal direction of the rack shaft. Thereby, the inclination of the support yoke stops. At this time, the support yoke is supported by the rack shaft and the rack housing in an inclined state. Therefore, even if the rack shaft moves in one direction, the support yoke is kept in contact with the inner peripheral surface of the rack housing, so that rattling of the support yoke is suppressed.

  Further, assuming that the yoke protruding surface is omitted from the outer peripheral surface of the support yoke, it is necessary to increase the gap between the outer peripheral surface of the support yoke and the inner peripheral surface of the rack housing in order to tilt the support yoke. On the other hand, when the gap between the outer peripheral surface of the cylindrical support yoke and the inner peripheral surface of the rack housing is large, the support yoke is not stable due to external forces such as vehicle vibration.

  The outer peripheral surface of the support yoke of the rack shaft support device is formed on the outer peripheral surface of the support yoke other than the top of the yoke protruding surface and the rack housing even if the clearance between the top of the yoke protruding surface and the inner peripheral surface of the rack housing is small. A gap is formed between the inner peripheral surface and the support yoke so that the support yoke can tilt. For this reason, when an external force such as vehicle vibration is applied to the support yoke, the movement of the support yoke in the radial direction of the support yoke is restricted by the top portion of the yoke projecting surface coming into contact with the inner peripheral surface of the rack housing. For this reason, shakiness of the support yoke can be reduced.

  [2] An embodiment dependent on the rack shaft support device has the following matters. That is, it has a pressing member disposed coaxially with the support yoke between the support yoke and the coil spring, and pressed against the support yoke by the coil spring, and the support yoke is pressed against the pressing member. A pressing projection surface that protrudes in a direction from the yoke back surface portion toward the yoke support portion is formed on a surface of the pressing member that faces the back surface.

  According to this rack shaft support device, since a gap is formed between the surface of the pressing member that faces the back surface of the support yoke and the back surface of the support yoke, when the support yoke is inclined, the pressing member faces the back surface. The gap between the surface and the back surface is reduced. For this reason, it is suppressed that a pressing member inclines when a support yoke inclines. For this reason, it is suppressed that the amount of compression of a coil spring changes by bending of a coil spring resulting from tilting of a pressing member. For this reason, it is suppressed that the force with which a coil spring presses a support yoke changes.

[3] An embodiment dependent on the rack shaft support device has the following matters. That is, the sheet protruding surface and the yoke protruding surface have the same shape.
According to this rack shaft support device, when the support yoke is supported by the rack housing in an inclined state, compared to the case where the seat protrusion surface and the yoke protrusion surface are different from each other, The sum of the contact area with the inner peripheral surface and the contact area between the seat protruding surface and the rack shaft is increased. For this reason, the support yoke can be more stably supported by the rack shaft and the rack housing. Therefore, the effect of stabilizing the posture of the support yoke is enhanced.

  [4] An embodiment dependent on the rack shaft support device has the following matters. That is, a steering device provided with the rack shaft support device.

  The rack shaft support device and the steering device can suppress the deterioration of the steering feeling when starting to steer.

The block diagram of the steering device of embodiment. Sectional drawing of the rack shaft support apparatus of the Z2-Z2 line | wire of FIG. 1, and its periphery. (A) is a cross-sectional view of the rack shaft support device of Z3-Z3 line of FIG. 2 and its surroundings, (b) is an enlarged view of a part of the sheet protruding surface of the low friction sheet of (a), (c) The enlarged view of a part of pressing pressing surface of the pressing member of a). The typical sectional view of the state before showing the operation of the rack shaft support device of an embodiment, and the support yoke inclining. The typical sectional view in the state where the operation of the rack shaft support device of an embodiment was shown and the support yoke inclined. Sectional drawing of the support yoke of other embodiment, and its periphery.

The configuration of the steering device 1 will be described with reference to FIG.
The steering shaft 10 to which the steering member 2 is fixed is connected to the rack shaft 16 via a rack and pinion mechanism 15. The rack shaft 16 is inserted into a cylinder of a substantially cylindrical rack housing 20 and supported so as to be reciprocally movable in the axial direction via a rack shaft support device 30 and a rack bush (not shown). Thereby, the rotation of the steering shaft 10 accompanying the steering of the steering member 2 is converted into a reciprocating linear motion of the rack shaft 16 by the rack and pinion mechanism 15. The steering shaft 10 is configured by connecting a column shaft 11, an intermediate shaft 12, and a pinion shaft 13 via two universal joints 14. The reciprocating motion of the rack shaft 16 accompanying the rotation of the steering shaft 10 is transmitted to the knuckle (not shown) via the tie rods 17 connected to both ends of the rack shaft 16, thereby turning steered wheels (not shown). The steering angle, that is, the traveling direction of the vehicle is changed.

  The steering device 1 of this embodiment is configured as a column assist type electric power steering device. The steering device 1 includes a motor 18 and a speed reduction mechanism 19 including a worm and wheel as an assist device. The motor 18 is drivingly connected to the column shaft 11 via a speed reduction mechanism 19. The rotation of the motor 18 is decelerated by the deceleration mechanism 19 and transmitted to the column shaft 11, so that the motor torque is applied to the column shaft 11 as an assist force. The steering device 1 calculates a steering torque applied to the steering shaft 10 based on a torque sensor (not shown) that detects torsion of a torsion bar (not shown) provided on the steering shaft 10. Then, the steering device 1 calculates the assist force based on the steering torque.

A configuration of a part of the rack housing 20 will be described with reference to FIG.
The rack housing 20 has a support wall 21. The support wall 21 is formed in a cylindrical shape. A housing space 23 is formed in the support wall 21. The accommodation space 23 communicates with a space in the rack housing 20 in which the rack shaft 16 is accommodated. A female screw 22 </ b> A is formed in the opening 22 on the opposite side of the support wall 21 from the rack shaft 16.

A detailed configuration of the rack shaft support device 30 will be described with reference to FIG.
The rack shaft support device 30 is accommodated in the accommodation space 23 of the support wall 21. The rack shaft support device 30 supports the rack shaft 16 by pushing the rack shaft 16 toward the pinion shaft 13.

  The rack shaft support device 30 includes a support yoke 40, a low friction sheet 50, a pressing member 60, a coil spring 31, and a plug 32. The support yoke 40 supports the rack shaft 16. The low friction sheet 50 reduces the frictional force between the rack shaft 16 and the low friction sheet 50. The pressing member 60 presses the support yoke 40 toward the rack shaft 16 by the coil spring 31. The coil spring 31 applies a force to the support yoke 40 to push the support yoke 40 against the rack shaft 16. The plug 32 closes the accommodation space 23.

  The support yoke 40 is made of a metal material. The support yoke 40 is formed in a cylindrical shape. The support yoke 40 is disposed on the opposite side of the rack shaft 16 from the pinion shaft 13. The support yoke 40 is inserted into the support wall 21 via a gap with the support wall 21 in the radial direction of the support yoke 40. The support yoke 40 is movable in a direction in which the rack shaft 16 is pressed (hereinafter referred to as “pressing direction ZP”). The support yoke 40 includes a yoke main body 41, a yoke support portion 42, and a yoke back surface portion 43. The yoke main body 41, the yoke support part 42, and the yoke back part 43 are integrated.

  The yoke support portion 42 is formed in a curved shape that opens on the rack shaft 16 side in a cross-sectional view in a direction orthogonal to the longitudinal direction of the rack shaft 16 (hereinafter, “rack axis direction ZR”). The yoke support portion 42 is located on the rack shaft 16 side with respect to the yoke body 41. The yoke support portion 42 surrounds the back surface portion 16 </ b> A of the rack shaft 16. The yoke back surface portion 43 is located on the side opposite to the yoke support portion 42 with respect to the yoke body 41. A yoke hole 44 is formed in the yoke back surface portion 43. The yoke hole 44 opens on the opposite side to the yoke body 41 in the pressing direction ZP. A bottom surface 44A of the yoke hole 44 is parallel to the rack axial direction ZR. The bottom surface 44A corresponds to “a back surface pressed by a pressing member”.

  The low friction sheet 50 is formed of a resin material that has excellent wear resistance and a low friction coefficient. An example of the material of the low friction sheet 50 is carbon fiber reinforced polyacetal (POM). The low friction sheet 50 is formed in a curved shape. The low friction sheet 50 is fixed to the inner surface 42 </ b> A of the yoke support portion 42. The low friction sheet 50 is in contact with the back surface portion 16 </ b> A of the rack shaft 16.

The pressing member 60 is formed in a disk shape. The pressing member 60 is accommodated in the yoke hole 44. The pressing member 60 is disposed coaxially with the central axis CA of the support yoke 40.
The coil spring 31 is disposed on the side opposite to the yoke body 41 with respect to the pressing member 60. The coil spring 31 is disposed coaxially with the central axis CA of the support yoke 40. One end of the coil spring 31 is attached to the pressing member 60. The other end of the coil spring 31 is attached to the plug 32. The coil spring 31 is compressed by the pressing member 60 and the plug 32.

The plug 32 is disposed on the side opposite to the support yoke 40 with respect to the coil spring 31. The plug 32 is screwed into the female screw 22 </ b> A of the support wall 21.
With such a configuration of the rack shaft support device 30, the rack shaft support device 30 pushes the support yoke 40 toward the rack shaft 16 by the biasing force of the coil spring 31. For this reason, the low friction sheet 50 is pressed against the rack shaft 16. When the steering member 2 (see FIG. 1) is steered, the rack shaft 16 moves in the rack axial direction ZR while sliding with the low friction sheet 50 by the steering member 2 being steered.

  With reference to FIG. 3, the shape of the support yoke 40, the low friction sheet | seat 50, and the pressing member 60 which are the characteristic parts of this rack shaft support apparatus is demonstrated. FIG. 3 shows a cross-sectional structure of the rack shaft support device 30 along the rack axial direction ZR.

  As shown in FIG. 3A, in the support yoke 40, a yoke protruding surface 45 is formed on the outer peripheral surface corresponding to the yoke main body 41 and the yoke back surface portion 43. The yoke protruding surface 45 is crowned. As an example of the crowning shape of the yoke protruding surface 45, the yoke protruding surface 45 has a radius of curvature at both ends of the yoke protruding surface 45 smaller than the radius of curvature at the center between both ends of the yoke protruding surface 45 in the pressing direction ZP. It is formed into a shape. The yoke protruding surface 45 is closest to the inner peripheral surface 21A of the support wall 21 at the yoke top 45A, which is the central portion between both ends of the yoke protruding surface 45. The yoke top portion 45A includes a portion including a bottom surface 44A of the yoke hole 44 and a line along the central axis CA of the support yoke 40 (hereinafter, “imaginary line VL”) and the yoke protruding surface 45 intersect. The yoke protruding surface 45 is separated from the inner peripheral surface 21A of the support wall 21 as it goes from the yoke top 45A toward both ends in the pressing direction ZP. The shape of the yoke top 45 </ b> A is an arc shape that protrudes radially outward of the support yoke 40. The center of curvature of the yoke top 45 </ b> A is a contact point between the pressing member 60 and the bottom surface 44 </ b> A of the yoke hole 44 (hereinafter “tilt center TC”). The yoke top 45 </ b> A is the outermost diameter of the support yoke 40. The shape of the yoke protrusion 45 is symmetric with respect to the virtual line VL.

  A sheet protruding surface 51 is formed on a surface of the low friction sheet 50 that is pressed against the back surface portion 16 </ b> A of the rack shaft 16. The sheet protruding surface 51 protrudes from the yoke back surface portion 43 of the support yoke 40 toward the yoke support portion 42. The sheet projecting surface 51 is located coaxially with the central axis CA of the support yoke 40. The sheet protruding surface 51 is formed over the entire low friction sheet 50 in the rack axial direction ZR. The sheet projecting surface 51 is formed over the entire low friction sheet 50 in a direction perpendicular to the rack axial direction ZR and along the back surface portion 16A (see FIG. 2).

  As shown in FIG. 3B, the shape of the sheet protrusion 51 is symmetric with respect to the center axis CA of the support yoke 40. The sheet protruding surface 51 includes a curved surface portion (hereinafter, “sheet top portion 51A”) including a portion that is coaxial with the center axis CA of the support yoke 40, and a sheet taper portion formed on both sides of the sheet top portion 51A in the rack axial direction ZR. 51B. The sheet top 51A and the sheet taper 51B are continuous.

  The sheet top portion 51 </ b> A is in contact with the back surface portion 16 </ b> A of the rack shaft 16. The shape of the sheet top 51A is a circular arc that is convex toward the back surface 16A. The seat top portion 51A has a vertex that is coaxial with the central axis CA of the support yoke 40, and is separated from the back surface portion 16A as the distance from the central axis CA increases.

  The sheet taper part 51B is formed linearly. The sheet taper portion 51B is separated from the back surface portion 16A in the pressing direction ZP as it is separated from the sheet top portion 51A in the rack axial direction ZR.

  As shown in FIG. 3A, a pressing protrusion surface 61 is formed on the end surface of the pressing member 60 that faces the bottom surface 44 </ b> A of the yoke hole 44. The pressing projection surface 61 is located coaxially with the central axis CA of the support yoke 40.

  As shown in FIG. 3C, the pressing projection surface 61 includes a curved surface portion (hereinafter referred to as “pressing top portion 61A”) including a portion coaxial with the center axis CA of the support yoke 40, and pressing in the rack axial direction ZR. It has a pressing taper portion 61B formed on both sides of the top portion 61A. The pressing top portion 61A and the pressing taper portion 61B are continuous. The pressing projection surface 61 is symmetric with respect to the center axis CA of the support yoke 40.

  The pressing top portion 61 </ b> A is in contact with the bottom surface 44 </ b> A of the yoke hole 44. The shape of the pressing top portion 61A is an arc shape that is convex toward the bottom surface 44A. The pressing top portion 61A has a vertex that is coaxial with the central axis CA of the support yoke 40, and is separated from the bottom surface 44A as the distance from the central axis CA increases. The pressing top portion 61A is formed in the same shape as the sheet top portion 51A.

  The pressing taper portion 61B is formed in a linear shape. The pressing taper portion 61B is separated from the bottom surface 44A as it is separated from the pressing top portion 61A in the rack axial direction ZR. As shown in FIG. 3A, the pressing taper portion 61 </ b> B is parallel to the sheet taper portion 51 </ b> B of the low friction sheet 50. The dimension of the pressing taper part 61B is smaller than the dimension of the sheet taper part 51B.

  The operation of the rack shaft support device 30 will be described with reference to FIGS. 4 and 5. In FIGS. 4 and 5, for convenience of explanation, the inclination of the yoke projecting surface 45, the sheet projecting surface 51, and the pressing projecting surface 61 is shown greatly.

  When the driver starts to operate the steering member 2 (see FIG. 1), the rotational force of the pinion shaft 13 is a force that moves the rack shaft 16 in the axial direction of the rack shaft 16 via the rack and pinion mechanism 15. To be granted. 4 and 5, as an example, the rack shaft 16 moves in the direction indicated by the white arrow in the figure.

  As shown in FIG. 4, due to the force that moves the rack shaft 16, the force that moves the sheet protruding surface 51 in the moving direction of the rack shaft 16 acts on the sheet top 51 </ b> A of the sheet protruding surface 51. As a result, a force that causes the support yoke 40 to tilt the support yoke 40 counterclockwise in the drawing about the tilt center TC acts on the support yoke 40.

  As shown in FIG. 5, when the rack shaft 16 starts to move, the seat top 51 </ b> A moves in the moving direction of the rack shaft 16 along with the movement of the rack shaft 16. As a result, the support yoke 40 tilts counterclockwise in the figure. At this time, the low friction sheet 50 rolls against the back surface portion 16 </ b> A of the rack shaft 16. And the sheet taper part 51B on the opposite side to the moving direction of the rack shaft 16 on the sheet protruding surface 51 is in surface contact with the back surface part 16A.

  Further, when the support yoke 40 is inclined, a portion 45 </ b> B corresponding to the yoke body 41 contacts the support wall 21 on the yoke protrusion surface 45 on the moving direction side of the rack shaft 16. Further, a portion 45 </ b> C corresponding to the yoke back surface portion 43 contacts the support wall 21 on the yoke protrusion surface 45 on the opposite side to the movement direction of the rack shaft 16. Thereby, both sides of the support yoke 40 are supported by the support walls 21 in the rack axial direction ZR.

  When the driver further operates the steering member 2 with the support yoke 40 tilted, the seat taper portion 51B on the opposite side to the moving direction of the rack shaft 16 in the low friction sheet 50 is the back portion 16A of the rack shaft 16. The rack shaft 16 moves with respect to the low friction sheet 50 in a state of surface contact with the low friction sheet 50. For this reason, the back surface portion 16 </ b> A and the low friction sheet 50 become sliding friction, and a dynamic friction force is generated between the back surface portion 16 </ b> A and the low friction sheet 50.

  Further, when the support yoke 40 is inclined, the bottom surface 44 </ b> A of the yoke hole 44 approaches a portion of the pressing taper portion 61 </ b> B of the pressing member 60 opposite to the moving direction of the rack shaft 16. When the sheet taper portion 51B comes into surface contact with the back surface portion 16A, the bottom surface 44A comes into contact with the pressing taper portion 61B. In this manner, the pressing member 60 is prevented from being tilted with respect to the central axis CA of the support yoke 40 when the support yoke 40 is tilted.

  In addition, after the support yoke 40 is inclined once by the movement of the rack shaft 16, the state in which the support yoke 40 is inclined is maintained. That is, even when the steering yoke is steered to the neutral position, the support yoke 40 is tilted. Further, the direction in which the support yoke 40 tilts differs depending on the moving direction of the rack shaft 16.

  For example, it is assumed that the support yoke 40 is tilted due to the rack shaft 16 moving to the white arrow in the figure, and a force that moves the rack shaft 16 in the direction opposite to the white arrow is applied. At this time, a force that moves the rack shaft 16 acts on the low friction sheet 50, and thus a force that the support yoke 40 tilts clockwise in the drawing acts on the support yoke 40. When the rack shaft 16 starts to move, the low friction sheet 50 and the support yoke 40 roll with respect to the rack shaft 16 by the sheet top 51A of the sheet protrusion 51 and the yoke top 45A of the yoke protrusion 45.

  The rack shaft support device 30 has the following operations and effects. In the following description, the “assumed support yoke” indicates a configuration in which the yoke protrusion surface 45 is omitted from the outer peripheral surface of the support yoke 40.

  (1) Since the steering device 1 calculates the assist force based on the twist amount of the torsion bar detected by the torque sensor, the assist force is applied to the steering shaft 10 after the driver starts operating the steering member 2. Has a time lag. Before the assist force is applied to the steering shaft 10, the driver operates the steering member 2 as the static friction force generated between the rack shaft 16 and the low friction sheet 50 increases as the rack shaft 16 moves. Increases the power required to start. For this reason, a steering feeling may be deteriorated.

  In the rack shaft support device 30 of the present embodiment, the sheet top 51A of the sheet protrusion surface 51 of the low friction sheet 50 is formed in an arc shape. As a result, when the driver starts operating the steering member 2, that is, when the rack shaft 16 starts to move, the seat top 51A rolls with respect to the back surface 16A of the rack shaft 16, so the back surface portion 16A and the low friction sheet 50 In the meantime, rolling resistance is generated. This rolling resistance is smaller than the static friction force and the dynamic friction force between the low friction sheet 50 and the back surface portion 16A. For this reason, the rack shaft 16 starts to move smoothly. Therefore, since the force required when the driver starts operating the steering member 2 is reduced, the deterioration of the steering feeling is suppressed.

  Further, the conventional rack shaft support device moves the rack shaft by applying to the rack shaft a force that is greater than the static friction force between the low friction sheet and the rack back surface portion of the rack shaft. Then, when the rack shaft starts to move, since the static friction is changed to dynamic friction, the dynamic friction force between the low friction sheet and the rack back surface portion is sufficiently smaller than the static friction force. Thereby, the difference between the force applied to the rack shaft and the dynamic friction force becomes sufficiently large. For this reason, since the rack shaft starts to move based on the difference between the force applied to the rack shaft and the dynamic friction force, the movement at the beginning of the movement of the rack shaft becomes high speed. For this reason, the sound (stick-slip sound) resulting from the sliding of the low friction sheet and the back portion of the rack shaft increases.

  On the other hand, the rack shaft support device 30 of the present embodiment has a force necessary for the rack shaft 16 to start moving from a stationary state and a force necessary for the rack shaft 16 to move due to the rolling of the seat top 51A. The difference is small. For this reason, since the rack shaft 16 starts to move smoothly, an increase in stick-slip noise due to sliding of the low friction sheet and the back surface portion 16A of the rack shaft 16 is suppressed.

  (2) The yoke top 45A of the yoke protrusion 45 of the support yoke 40 is formed in an arc shape. For this reason, when the support yoke 40 tilts, even if the yoke top 45A contacts the inner peripheral surface 21A of the support wall 21, the yoke protruding surface 45 is in relation to the inner peripheral surface 21A of the support wall 21 as the support yoke 40 tilts. roll over. For this reason, it is suppressed that the yoke protrusion 45 obstructs the tilting operation of the support yoke 40.

  Further, as the amount of inclination of the support yoke 40 increases, the yoke protrusion surfaces 45 on both sides of the support yoke 40 come into contact with the support wall 21 in the rack axial direction ZR. For this reason, the support yoke 40 is supported by the support wall 21. For this reason, even if the rack shaft 16 moves, the inclined posture of the support yoke 40 is maintained. Therefore, rattling of the support yoke 40 due to the movement of the rack shaft 16 is suppressed.

  Further, in the case of the rack shaft support device using the assumed support yoke, it is necessary to increase the gap between the outer peripheral surface of the assumed support yoke and the inner peripheral surface 21A of the support wall 21 because the assumed support yoke is inclined. On the other hand, when the gap between the outer peripheral surface of the assumed support yoke and the inner peripheral surface 21A of the support wall 21 is large, the play of the assumed support yoke due to an external force such as vehicle vibration increases.

  In the support yoke 40 of the present embodiment, the yoke top 45A of the yoke protrusion 45 is closest to the inner peripheral surface 21A of the support wall 21, and is separated from the inner peripheral surface 21A of the support wall 21 as it is away from the yoke top 45A. For this reason, the support yoke 40 can be tilted even if the gap between the yoke top 45A and the inner peripheral surface 21A of the support wall 21 is small. Therefore, when an external force such as vehicle vibration is applied to the support yoke 40 in a state where the support yoke 40 is not supported by the support wall 21, the yoke top 45 </ b> A comes into contact with the inner peripheral surface 21 </ b> A of the support wall 21. The movement of the support yoke 40 in the radial direction of the support yoke 40 is restricted. For this reason, rattling of the support yoke 40 can be reduced.

  (3) A gap is formed between the pressing taper portion 61 </ b> B of the pressing protrusion surface 61 of the pressing member 60 and the bottom surface 44 </ b> A of the yoke hole 44. For this reason, when the support yoke 40 is inclined, the gap between the pressing taper portion 61B and the bottom surface 44A is reduced. For this reason, the bottom surface 44A is unlikely to contact the pressing taper portion 61B. For this reason, the pressing member 60 is not easily tilted. For this reason, it is suppressed that the coil spring 31 bends and the compression amount of the coil spring 31 changes due to the pressing member 60 being inclined. Therefore, a change in the force with which the coil spring 31 pushes the support yoke 40 is suppressed.

  (4) Since the sheet taper portion 51B is formed on the sheet protruding surface 51 of the low friction sheet 50, when the support yoke 40 is inclined, the sheet taper portion 51B and the back surface portion 16A of the rack shaft 16 are in surface contact. . For this reason, since the pressure which acts on the sheet | seat protrusion 51 from the back surface part 16A becomes small, the wear of the low friction sheet 50 in the thickness direction of the sheet protrusion 51 decreases.

  (5) The pressing taper portion 61B of the pressing member 60 and the sheet taper portion 51B of the low friction sheet 50 are parallel to each other. For this reason, when the support yoke 40 is inclined and the sheet taper portion 51B contacts the back surface portion 16A of the rack shaft 16, the pressing taper portion 61B contacts the bottom surface 44A of the yoke hole 44 of the support yoke 40. For this reason, the frictional force between the pressing taper portion 61B and the bottom surface 44A is larger than the frictional force between the pressing top portion 61A and the bottom surface 44A, so that the pressing member 60 is not easily displaced from the support yoke 40. For this reason, it is suppressed that the coil spring 31 bends and the compression amount of the coil spring 31 changes due to the pressing member 60 moving from the support yoke 40. Therefore, a change in the force with which the coil spring 31 pushes the support yoke 40 is suppressed.

  In addition, the specific form which this rack shaft support apparatus and this steering apparatus can take is not limited to the content shown by the said embodiment. The present rack shaft support device and the present steering device can take the form of a modification of the embodiment shown below, for example.

  In the modified support yoke 40, the yoke hole 44 is omitted. In this case, in the pressing direction ZP, the tip portion of the yoke back surface portion 43 of the support yoke 40 is formed in a planar shape. The pressing member 60 is pressed against the tip portion of the yoke back surface portion 43.

In the pressing member 60 of the modified example, the pressing protrusion surface 61 is omitted.
The pressing member 60 is omitted from the rack shaft support device 30 according to the modification. In this case, the coil spring 31 contacts the bottom surface 44 </ b> A of the support yoke 40.

  -The sheet taper part 51B of a modification is formed in the curved shape dented in the direction spaced apart from the rack shaft 16 in the pressing direction ZP. The pressing taper portion 61B of the pressing member 60 can be similarly changed.

-At least one of the sheet projecting surface 51 of the modified low friction sheet 50 and the pressing projecting surface 61 of the modified pressing member 60 is crowned.
As shown in FIG. 6, the yoke protrusion surface 45 of the support yoke 40 according to the modified example includes a yoke top portion 45D and a yoke taper portion 45E instead of the crowning shape. The yoke top 45D has the same shape as the yoke top 45A. The yoke taper portion 45E is separated from the inner peripheral surface 21A of the support wall 21 as it is separated from the yoke top portion 45D.

The modified yoke protruding surface 45 is formed only on the yoke body 41 or the yoke back surface portion 43.
-The sheet | seat protrusion surface 51 of a modification is formed in a part of rack axial direction ZR of the surface which opposes the back surface part 16A of the rack shaft 16 in the low friction sheet | seat 50. FIG.

  In the modified rack shaft support device 30, the sheet protrusion surface 51 of the low friction sheet 50 and the yoke protrusion surface 45 of the support yoke 40 have the same shape. According to this configuration, when the support yoke 40 is supported by the support wall 21 in a tilted state, the yoke protruding surface 45 and the sheet protruding surface 51 and the yoke protruding surface 45 are compared with the configuration assumed to have different shapes. The sum of the contact area between the support wall 21 and the inner peripheral surface 21 </ b> A and the contact area between the seat protrusion 51 and the back surface portion 16 </ b> A of the rack shaft 16 is increased. Therefore, the support yoke 40 is stably supported by the rack shaft 16 and the support wall 21.

  As shown in FIG. 6, the rack shaft support device 30 according to the modification has elastic members 70 attached to both sides of the yoke top 45 </ b> A of the yoke protrusion 45 of the support yoke 40. An example of the elastic member 70 is an O-ring. According to this configuration, when the support yoke 40 is tilted, the contact sound between the support yoke 40 and the support wall 21 is reduced.

  In the rack shaft support device 30 according to the modified example, an elastic member (not shown) may be attached to the inner peripheral portion of the support wall 21 of the rack housing 20 instead of the elastic member 70 of the yoke protruding surface 45. Further, in the rack shaft support device 30 of the modified example, the elastic member 70 may be attached to the yoke protrusion 45 and the elastic member may be attached to the inner peripheral portion of the support wall 21.

  The modified steering device 1 has a configuration of a pinion assist type or rack assist type electric power steering device instead of the configuration of the column assist type electric power steering device.

  The steering device 1 according to the modification has an electrohydraulic assist device including an electric pump or a hydraulic assist device instead of the electric assist device having the motor 18 and the speed reduction mechanism 19. Further, the assist device is omitted from the steering device 1 according to the modification.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 16 ... Rack shaft, 20 ... Rack housing, 21A ... Inner peripheral surface, 30 ... Rack shaft support device, 31 ... Coil spring, 32 ... Plug, 40 ... Support yoke, 42 ... Yoke support part, 43 ... Yoke back surface, 44A ... bottom surface (back surface), 45 ... yoke protruding surface, 45A ... yoke top (top of yoke protruding surface), 50 ... low friction sheet, 51 ... sheet protruding surface, 51A ... sheet top (sheet protruding surface) Top part), 60 ... Pressing member, 61 ... Pressing projection surface, CA ... Center axis, ZR ... Rack axis direction (longitudinal direction of the rack shaft), ZP ... Pushing direction.

Claims (4)

A support yoke that is formed in a cylindrical shape, is accommodated in a rack housing, and is movable in a pressing direction that is a direction in which the rack shaft is pressed in the rack housing;
A low friction sheet disposed between the support yoke and the rack shaft and pressed against the rack shaft;
A plug disposed on the opposite side of the rack shaft with respect to the support yoke, and fixed to the rack housing;
A coil spring disposed between the support yoke and the plug and pressing the support yoke toward the rack shaft;
The support yoke is disposed on the rack shaft side with respect to the yoke back surface portion that is a portion on the plug side, and the yoke that is the portion that supports the rack shaft, to which the low friction sheet is fixed. Having a support,
On the outer peripheral surface of the support yoke, a yoke protruding surface protruding in the radial direction of the support yoke is formed,
In the low friction sheet, a surface that is pressed against the rack shaft is formed with a sheet protruding surface that protrudes in a direction from the yoke back surface toward the yoke support portion,
The top part of the said sheet | seat protrusion surface and the top part of the said yoke protrusion surface are formed in circular arc shape in the cross sectional view of the longitudinal direction of the said rack shaft. A pressing member disposed coaxially with the support yoke between the support yoke and the coil spring, and pressed against the support yoke by the coil spring;
The support yoke has a back surface pressed by the pressing member;
The rack shaft support device according to claim 1, wherein a pressing projecting surface that projects in a direction from the yoke back surface toward the yoke support portion is formed on a surface of the pressing member that faces the back surface. The rack shaft support device according to claim 1, wherein the seat projecting surface and the yoke projecting surface have the same shape.   A steering apparatus provided with the rack shaft support apparatus as described in any one of Claims 1-3.