JP2013220665A - Steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small steering device having excellent durability.SOLUTION: A housing 9 is supported on a vehicle body by a mounting bracket 25 extending from the end 9a to the radial direction outside Y1. A boot 14 includes: a first fixed part 14a fixed to an edge 23a of an opening 23 of the housing 9; a second fixed part 14b fixed to a tie rod 11; and an intermediate fixed part 14c fixed to a socket 10a of a ball joint 10. An expansion/contraction absorbing part 30 provided between the first fixed part 14a and the intermediate fixed part 14c includes a looseness part 32 rising and falling in an axis direction X1. Looseness amount of the looseness part 32 is varied to absorb only an expansion/contraction motion of a rack shaft 8. An oscillation absorbing part 31 is provided between the intermediate fixed part 14c and the second fixed part 14b.

Description

  The present invention relates to a steering device.

In the steering device, the end of the rack shaft protruding from the rack housing is connected to the end of the tie rod via a ball joint, and generally a boot having a bellows structure that seals between the rack housing and the tie rod ( Rack boots).
On the other hand, in the steering device of Patent Document 1, the boot includes a cylindrical portion that does not expand and contract and a flexible portion that can be bent. The cylindrical portion is in sliding contact with the outer periphery of the end portion of the rack housing in the axial direction to absorb expansion and contraction of the rack shaft. The flexible portion is bent while sealing between the tube portion and the tie rod to absorb the bending of the tie rod with respect to the rack shaft.

JP 2009-90922 A

In the conventional general bellows-structure boot, since it is responsible for expansion and contraction and bending, the boot may bite into the ball joint socket. Moreover, since the conventional bellows structure is folded in the axial direction when the boot is contracted, the contraction amount may be limited.
By the way, depending on the design requirements on the vehicle side, the mount position for fixing the rack housing to the vehicle body may be arranged apart from the end of the rack housing in the axial direction. In that case, a long mounting arm is extended from the end of the rack housing, and the tip of the mounting arm is fixed to the vehicle body with screws. However, when a long mounting arm is used, the mounting structure is increased in size to secure the mounting strength to the vehicle body, and the steering device may be increased in size.

  Patent Document 1 does not describe an attachment mode to the vehicle body. If the mounting bracket is disposed in the rack housing in the steering device of Patent Document 1, it is disposed away from the end of the rack housing so as not to interfere with the cylindrical portion that is in sliding contact with the outer periphery of the end of the rack housing. become. Therefore, the mounting bracket becomes longer and the steering device including the mounting structure becomes larger.

  An object of the present invention is to provide a steering device that is small in size and excellent in durability.

  In order to achieve the above object, the invention of claim 1 is characterized in that a housing (9) having an opening (23) through which a rack shaft (8) is inserted into an end (9a), and a radially outward from the end of the housing. A mounting bracket (25) extending in the direction (Y1) and fixed to the vehicle body, a tie rod (11) connected to the end of the rack shaft via a ball joint (10), and an edge of the opening of the housing (23a) and a boot (14) covering between the tie rods, the boot being fixed to the tie rod, and a first fixing portion (14a) fixed to an edge of the opening of the housing Expansion and contraction of the rack shaft interposed between the second fixing portion (14b), the intermediate fixing portion (14c) fixed to the socket (10a) of the ball joint, and the first fixing portion and the intermediate fixing portion. Absorbs only exercise An expansion / contraction absorption part (30), and a swing absorption part (31) interposed between the intermediate fixing part and the second fixing part and absorbing only the swinging motion of the tie rod. The absorber has a slack portion (32) that undulates in the axial direction (X1), and is configured to absorb the expansion and contraction motion of the rack shaft by changing the slack amount of the slack portion. I will provide a.

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, at the center position of the expansion / contraction stroke of the rack shaft, the slack portion is connected to the first fixed portion and the large diameter cylindrical portion (33) and the intermediate fixed portion is connected to the large diameter. You may comprise the shape containing the small diameter cylinder part (34) arrange | positioned inside a cylinder part, and the folding | returning part (35) which connects the said large diameter cylinder part and the said small diameter cylinder part.

According to a third aspect of the present invention, the end portion of the housing has an enlarged diameter portion (24), and the slack portion is arranged in the enlarged diameter portion at the center position of the expansion / contraction stroke of the rack shaft. May be.
Moreover, at least one part of the said mounting bracket may be connected with the said enlarged diameter part like Claim 4.

According to the first aspect of the present invention, since the intermediate portion of the boot is used as the intermediate fixing portion and fixed to the socket of the ball joint, it is possible to prevent the boot from biting into the socket and to improve the durability of the boot.
Moreover, the expansion / contraction absorption part arrange | positioned at the housing side from the intermediate | middle fixing | fixed part absorbs only expansion / contraction by changing the amount of slack of the slack part which undulates in an axial direction. Therefore, the sealing performance of the protruding portion of the rack shaft from the rack housing can be secured without using the conventional bellows structure that undulates in the radial direction and is superimposed in the axial direction, and the degree of freedom in design can be expanded.

  Further, since the first fixing portion of the boot is fixed to the edge portion of the opening of the housing, the mounting bracket can be extended from a position close to the edge portion of the opening at the end portion of the housing. Therefore, the mounting bracket can connect the mounting position to the vehicle body and the housing at a short distance, and the mounting bracket itself can be reduced in size. As a result, the steering device including the mounting structure can be reduced in size.

  According to the invention of claim 2, at the center position of the expansion / contraction stroke of the rack shaft, the slack portion of the expansion / contraction absorption portion that absorbs only expansion / contraction is obtained by connecting the large-diameter cylindrical portion and the small-diameter cylindrical portion connected via the folded portion. Form. Since the boot is raised and lowered in the axial direction to absorb the axial stroke, it is necessary to use the overlap of the large diameter cylinder part and the small diameter cylinder part without overlapping in multiple stages like the conventional undulating bellows. The amount of expansion and contraction can be absorbed.

  According to the invention of claim 3, on the contraction side from the center position of the expansion / contraction stroke of the rack shaft, the folded back slack portion of the expansion / contraction absorption portion can be accommodated in the inner back side of the enlarged diameter portion of the housing, and the expansion / contraction stroke On the extension side from the center position, the expansion / contraction absorbing portion can be extended out of the housing so as to unwind the slack portion. Therefore, the required amount of expansion / contraction can be absorbed without overloading the expansion / contraction absorption part of the boot.

  According to the invention of claim 4, since at least a part of the mounting bracket is connected to the enlarged diameter portion, it is possible to extend from a position close to the edge of the opening at the end of the housing. Therefore, the mounting bracket can connect the mounting position to the vehicle body and the housing at a short distance, and the steering device can be substantially downsized through downsizing of the mounting bracket itself.

It is a typical schematic block diagram of the steering device of one Embodiment of this invention. FIG. 3 is an enlarged partial cross-sectional view of a main part of the steering device, showing a state where the rack shaft is arranged at the center position of the expansion / contraction stroke. FIG. 4 is a partial cross-sectional enlarged view of a main part of the steering device, showing a state in which the rack shaft is arranged on the contraction side from the center position of the expansion / contraction stroke. FIG. 4 is a partial cross-sectional enlarged view of a main part of the steering device, showing a state in which the rack shaft is arranged on the extending side from the center position of the expansion / contraction stroke.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a steering apparatus 1 according to an embodiment of the present invention. As shown in FIG. 1, the steering device 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, an intermediate shaft 5 connected to the steering shaft 3 via a universal joint 4, and an intermediate shaft 5. A rack shaft 8 as a steered shaft extending in the left-right direction of the automobile having a pinion shaft 7 connected to the vehicle through a universal joint 6 and a rack 81 meshing with a pinion 71 provided in the vicinity of the end of the pinion shaft 7 And have. The pinion shaft 7 and the rack shaft 8 constitute a steering mechanism A composed of a rack and pinion mechanism.

In the present embodiment, the steering device 1 is described as an electric power steering device. However, the present invention can be applied to all rack and pinion type steering devices.
The rack shaft 8 is supported in a housing 9 fixed to the vehicle body through a plurality of bearings (not shown) so as to be capable of linear reciprocation in the axial direction X1.

  Each end 8 a of the rack shaft 8 protrudes from a corresponding end 9 a of the housing 9. Each end portion 8 a of the rack shaft 8 is connected to one end portion 11 a of the corresponding tie rod 11 via the corresponding ball joint 10. The other end portion 11b of each tie rod 11 is connected to a corresponding steered wheel 13 via a corresponding knuckle arm 12, respectively.

The steering device 1 includes a pair of cylindrical boots 14. The boot 14 covers the end 9 a of the housing 9, the end 8 a of the rack shaft 8, the ball joint 10, and a part of the tie rod 11. The boot 14 is formed of, for example, a synthetic resin such as a polyolefin-based elastomer and has flexibility.
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 71 and the rack 81. Thereby, the turning of the steered wheel 13 is achieved. Further, with the movement of the rack shaft 8 in the axial direction X1, one of the boots 14 is extended, and the other boot 14 is shortened.

The steering shaft 3 is divided into a steering input shaft 3 a that is continuous with the steering member 2 and a steering output shaft 3 b that is continuous with the pinion shaft 7. The steering input shaft 3 a and the steering output shaft 3 b are the same via a torsion bar 15. Are connected to each other so as to be rotatable relative to each other.
A torque sensor 16 is provided for detecting a steering torque based on a relative rotational displacement amount between the steering input shaft 3a and the steering output shaft 3b via the torsion bar 15, and the torque detection result of the torque sensor 16 is obtained from an ECU (Electronic Control Unit). : Electronic control unit) 17.

  The ECU 17 drives and controls the steering assist electric motor 19 via a drive circuit (not shown) based on a torque detection result given from the torque sensor 16, a vehicle speed detection result given from the vehicle speed sensor 18, and the like. Specifically, the ECU 17 determines a target assist amount using a map in which the relationship between the torque and the target assist amount is stored for each vehicle speed, and controls the assist force generated by the electric motor 19 to approach the target assist amount. To do.

The output rotation of the electric motor 19 is decelerated through a speed reduction mechanism 20 as a transmission device and transmitted to the pinion shaft 7 and converted into a linear motion of the rack shaft 8 to assist steering.
The speed reduction mechanism 20 includes a worm 21 as a drive gear that is rotationally driven by the electric motor 19, and a worm wheel 22 as a driven gear that meshes with the worm 21 and is connected to the steering output shaft 3b so as to be integrally rotatable. .

  As shown in FIG. 1, the end 9 a of the housing 9 is provided with an opening 23 through which the rack shaft 8 is inserted. Further, the end 9a of the housing 9 has an enlarged diameter portion 24 whose diameter gradually increases toward the outer side. The opening 23 is disposed at the enlarged diameter end of the enlarged diameter portion 24. The enlarged diameter portion 24 may have a conical taper shape in which the diameter gradually increases, or the diameter may gradually increase.

  FIG. 2 shows a state in which the rack shaft 8 is disposed at the center position of the expansion / contraction stroke along the axial direction X1. As shown in FIG. 2, a mounting bracket 25 extending from the end 9a of the housing 9 in the radially outward direction Y1 is fixed to the outer periphery of the end 9a of the housing 9 by, for example, welding. A bolt (not shown) that passes through a screw insertion hole 26 provided in the mounting bracket 25 is screwed and fixed to a vehicle body side member (not shown).

At least a part of the mounting bracket 25 (in the example of FIG. 1, most of the base end portion of the mounting bracket 25) extends from the enlarged diameter portion 24. That is, the mounting bracket 25 is disposed in the vicinity of the edge 23 a of the opening 23.
The ball joint 10 has a socket 10 a that holds a ball head 10 b provided at an end 11 a of the tie rod 11.

  The boot 14 is disposed so as to cover between the edge 23 a of the opening 23 of the housing 9 and the tie rod 11. Specifically, the boot 14 includes a first fixing portion 14 a fixed to the edge portion 23 a of the opening 23 of the housing 9 using a first clamp 27, and a first fixing portion 14 fixed to the tie rod 11 using a second clamp 28. 2 fixing portions and an intermediate fixing portion 14c fixed to the socket 10a of the ball joint 10 using a third clamp 29.

The boot 14 is interposed between the first fixing portion 14a and the intermediate fixing portion 14c, and includes an expansion / contraction absorbing portion 30 that absorbs only the expansion / contraction motion of the rack shaft 8, an intermediate fixing portion 14c, and a second fixing portion 14b. And a swing absorbing portion 31 that absorbs only the swing motion of the tie rod 11.
The expansion / contraction absorption part 30 has the slack part 32 which undulates in the axial direction X1, and absorbs the expansion / contraction movement of the rack shaft 8 by changing the slack amount of the slack part 32.

  2, the slack portion 32 is disposed inside the large-diameter cylindrical portion 33 connected to the first fixed portion 14a and the large-diameter cylindrical portion 33 connected to the intermediate fixed portion 14c. The small-diameter cylindrical portion 34, the large-diameter cylindrical portion 33, and the folded portion 35 that connects the small-diameter cylindrical portion 34 are formed. The slack portion 32 is disposed in the enlarged diameter portion 24 at the center position of the expansion / contraction stroke of the rack shaft 8.

  Further, on the contraction side from the center position of the expansion / contraction stroke of the rack shaft 8, as shown in FIG. 3, the folded-back slack portion 32 of the expansion / contraction absorbing portion 30 is accommodated in the deeper side in the enlarged diameter portion 24 of the housing 9. To do. Further, on the extension side from the center position of the expansion / contraction stroke of the rack shaft 8, as shown in FIG. 4, the expansion / contraction absorbing portion 30 is extended out of the housing 9 so as to unwind the slack portion 32.

  According to the present embodiment, since the intermediate portion of the boot 14 is fixed to the socket 10a of the ball joint 10 as the intermediate fixing portion 14c, the boot 14 can be prevented from biting into the socket 10a and the durability of the boot 14 is improved. can do. That is, as shown in FIGS. 2 to 4, the intermediate fixing portion 14c of the boot 14 moves along with the socket 10a, so that the boot 14 is prevented from biting into the socket 10a.

Moreover, the expansion / contraction absorption part 30 arrange | positioned at the housing 9 side from the intermediate | middle fixing | fixed part 14c absorbs only expansion / contraction by changing the loosening amount of the loosening part 32 which undulates in the axial direction X1. That is, the sealing performance of the protruding portion of the rack shaft 8 from the housing 9 can be secured without using the conventional bellows structure that undulates in the radial direction and overlaps in the axial direction, and the degree of freedom in design can be expanded.
Further, since the first fixing portion 14 a of the boot 14 is fixed to the edge portion 23 a of the opening 23 of the housing 9, the mounting bracket 25 for attaching to the vehicle body is attached to the edge portion 23 a of the opening 23 at the end portion 9 a of the housing 9. It is possible to extend from a position close to. Therefore, the mounting bracket 25 can connect the mount center C1 to the vehicle body (corresponding to the center of the screw insertion hole 26) and the housing 9 at a short distance, so that the mounting bracket 25 itself can be miniaturized as much as possible. can do. As a result, the steering device 1 including the mounting structure can be reduced in size.

  Further, the slack portion 32 of the expansion / contraction absorbing portion 30 that absorbs only expansion / contraction at the center position of the expansion / contraction stroke of the rack shaft 8 forms a large-diameter cylindrical portion 33 and a small-diameter cylindrical portion 34 connected via a turn-back portion 35. To do. Since the boot 14 is raised and lowered in the axial direction X1 to absorb the stroke in the axial direction, the overlap amount of the large diameter cylindrical portion 33 and the small diameter cylindrical portion 34 can be obtained without overlapping in multiple stages like a conventional bellows that undulates in the radial direction. The required amount of expansion and contraction can be absorbed by changing.

  Further, on the side contracted from the center position of the expansion / contraction stroke of the rack shaft 8, as shown in FIG. 3, the folded-back slack portion 32 of the expansion / contraction absorption portion 30 is accommodated inside the diameter expansion portion 24 of the housing 9. be able to. On the extension side from the center position of the expansion / contraction stroke, as shown in FIG. 4, the expansion / contraction absorption part 30 can be extended out of the housing 9 so as to unwind the slack part 32. Therefore, the required amount of expansion / contraction can be absorbed without overloading the expansion / contraction absorber 30 of the boot 14.

  Further, since at least a part of the mounting bracket 25 is connected to the enlarged diameter portion 24, the mounting bracket 25 can be extended from a position near the edge portion 23a of the opening 23 at the end portion 9a of the housing 9. Become. Therefore, the mounting bracket 25 can connect the mount center C1 to the vehicle body (corresponding to the center of the screw insertion hole 26 of the mounting bracket 25) and the housing 9 at a short distance, and the steering device 1 can be reduced by downsizing the mounting bracket 25 itself. Miniaturization is substantially possible.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 2 ... Steering member, 7 ... Pinion shaft, 8 ... Rack shaft, 8a ... End of (rack shaft), 9 ... Housing, 9a ... End of (housing), 10 ... Ball joint, 10a ... Socket 11 tie rod 14 boot 14a first fixing portion 14b second fixing portion 14c intermediate fixing portion 23 opening 23a edge (opening) 24 diameter expanding portion 25 DESCRIPTION OF SYMBOLS ... Mounting bracket, 26 ... Screw insertion hole, 27 ... 1st clamp, 28 ... 2nd clamp, 29 ... 3rd clamp, 30 ... Expansion / contraction absorption part, 31 ... Swing absorption part, 32 ... Slack part, 33 ... Large diameter Cylindrical part, 34 ... Small diameter cylindrical part, 35 ... Folded part, C1 ... Mount center, X1 ... Axial direction, Y1 ... Radially outward

Claims (4)

A housing having an opening through which the rack shaft is inserted;
A mounting bracket extending radially outward from the end of the housing and secured to the vehicle body;
A tie rod connected to the end of the rack shaft via a ball joint;
A boot covering between the edge of the opening of the housing and the tie rod,
The boot includes a first fixing part fixed to an edge of the opening of the housing, a second fixing part fixed to the tie rod, an intermediate fixing part fixed to a socket of the ball joint, and the first fixing part. An expansion / contraction absorbing portion that is interposed between the fixing portion and the intermediate fixing portion and absorbs only the expansion / contraction movement of the rack shaft, and is interposed between the intermediate fixing portion and the second fixing portion to swing the tie rod. A swing absorbing part that absorbs only motion,
The expansion and contraction absorbing portion has a slack portion that undulates in the axial direction, and is configured to absorb the expansion and contraction motion of the rack shaft by changing a slack amount of the slack portion.   2. The slack portion according to claim 1, wherein the slack portion is disposed at a center position of the expansion / contraction stroke of the rack shaft, and is disposed on the inner side of the large diameter cylindrical portion that is continuous with the first fixing portion and the intermediate fixing portion. A steering device having a shape including a small-diameter cylindrical portion, and a folded portion connecting the large-diameter cylindrical portion and the small-diameter cylindrical portion. In Claim 1 or 2, the end of the housing has an enlarged diameter part,
The steering device, wherein the slack portion is disposed in the enlarged diameter portion at a center position of the expansion / contraction stroke of the rack shaft.   The steering device according to claim 3, wherein at least a part of the mounting bracket is connected to the enlarged diameter portion.

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