JP2013018296A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device that simplifies assembly and reducing an impact input to a steering gear housing in the maximum steering.SOLUTION: The electric power steering device includes: a pinion shaft coupled with a steering wheel; a rack shaft 28 which is coupled with the pinion shaft and is reciprocally movable in the steering gear housing 29 within a regulated range; a ball joint 31 provided on the rack shaft 28; a tie rod 33 connected to the ball joint 31; and a steering rack boot 10 which covers the ball joint 31. The steering rack boot 10 includes a first impact absorbing part 12 provided at one end side and a second impact absorbing part 16 provided at the other end side. The first impact absorbing part 12 and the second impact absorbing part 16 are brought into contact with each other in the vicinity of the stroke end of the rack shaft 28.

Description

  The present invention relates to an electric power steering apparatus.

  A power steering device for steering an automobile includes a hydraulic type (hydraulic PS) that assists a steering force required for a driver's steering operation by a driving force of a hydraulic cylinder and an electric motor that assists by a driving force of an electric motor. There is a formula (EPS). In recent years, in power steering devices, the number of devices employing the EPS has been increasing.

JP 2009-274692 A (see, for example, paragraphs [0014]-[0017], [FIG. 1], [FIG. 2], etc. of the specification)

  However, in the apparatus adopting the above-described EPS, so-called electric power steering apparatus, at the time of maximum steering (at the time of locking), that is, at the end (stroke end) of the reciprocation of the rack shaft that reciprocates by steering the steering wheel, The ball joint at the end of the shaft and the steering gear housing that rotatably holds the rack shaft are in strong contact with each other, and the impact input at that time is larger than that in the device employing the hydraulic PS described above. Since such an impact input acts on each member of the steering force transmission system between the steering wheel and the rack shaft (for example, an intermediate shaft, a serration portion (hook-type joint), a fastening bolt, etc.), Therefore, it is necessary to take measures such as increasing the strength and changing the material of each member to a high-strength material.

  In the above-mentioned Patent Document 1, when the rack shaft reaches the steering limit, the electric shock absorber provided on the inner end surface of the ball joint and the stopper member provided on the inner peripheral surface of the gear housing are brought into contact with each other. A power steering device is disclosed. In the electric power steering apparatus described in Patent Document 1, the assembly position of the buffer member is an inner end surface of a ball joint covered with a steering rack boot, and the assembly position of the stopper member is an inner peripheral surface of the gear housing. Therefore, the work of assembling the buffer member and the stopper member is complicated.

  From the above, the present invention has been made to solve the above-described problems, and can simplify the assembly work while reducing the impact input to the steering gear housing during maximum steering. An object of the present invention is to provide a simple electric power steering device.

  An electric power steering apparatus according to the present invention that solves the above-described problems includes a pinion shaft connected to a steering wheel, and a rack that is connected to the pinion shaft and can reciprocate within a steering gear housing within a restricted range. An electric power steering apparatus comprising a shaft, a ball joint provided on the rack shaft, a tie rod connected to the ball joint, and a boot covering the ball joint, wherein the boot is on one end side And a second shock absorbing portion provided on the other end side, in the vicinity of the stroke end of the rack shaft, the first shock absorbing portion and the second shock absorbing portion. It is characterized by being in contact with the absorption part.

  An electric power steering apparatus according to the present invention that solves the above-described problems is the electric power steering apparatus according to the above-described invention, wherein the boot is a cylindrical shape formed in an accordion shape, and the first shock absorbing portion is The second shock absorbing member includes a small diameter portion and a large diameter portion connected to the small diameter portion and having a larger diameter than the small diameter portion. The portion has a cylindrical shape with a hole portion through which the ball joint can be inserted at the center, and includes a step portion attached to an end portion of the steering gear housing.

  The electric power steering apparatus according to the present invention that solves the above-described problems is the electric power steering apparatus according to the above-described invention, wherein the second shock absorbing portion is disposed on an end side facing the first shock absorbing portion. It is provided with the provided taper part.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power steering apparatus which can simplify an assembly | attachment operation | work can be implement | achieved, relieving the impact input to the steering gear housing at the time of the maximum steering.

It is sectional drawing of one edge part vicinity of the steering gear housing with which the electric power steering apparatus which concerns on 1st Example of this invention is provided. It is sectional drawing of the other edge part vicinity of the steering gear housing with which the electric power steering apparatus which concerns on 1st Example of this invention is provided. It is the perspective view which showed the outline | summary of the electric power steering apparatus which concerns on 1st Example of this invention. FIGS. 4A and 4B are explanatory diagrams of the electric power steering apparatus according to the first embodiment of the present invention, in which FIG. 4A shows a state at the time of steering wheel right steering, and FIG. 4B at the time of steering wheel right maximum steering. Indicates the state.

  Hereinafter, an embodiment for carrying out an electric power steering apparatus according to the present invention will be described in detail with reference to FIGS.

  As shown in FIG. 3, the electric power steering apparatus according to this embodiment includes a steering wheel 21 operated by a driver, and a steering shaft 22 that is connected to the steering wheel 21 and transmits a steering force by the operation. . The steering shaft 22 is rotatably held by the steering column 23. The steering shaft 22 is connected to the intermediate shaft 24 by a hook-type joint (hereinafter referred to as a first joint) 3. The intermediate shaft 24 is connected to the pinion shaft 25 by a hook-type joint (hereinafter referred to as a second joint) 4. The pinion shaft 25 is rotatably held by the pinion 26. A rack shaft 28 that is rotatably held by a steering gear housing (steering rack housing) 29 is engaged with the lower end portion of the pinion shaft 25. That is, the rack shaft 28 can reciprocate within the steering gear housing 29 within a restricted range. Thereby, the rotational motion transmitted to the pinion shaft 25 is converted into a straight motion by the rack shaft 28.

  Ball joints 31 and 32 are respectively provided at both ends of the rack shaft 28. The ball joints 31 and 32 are provided with spherical end portions 33a and 34a of tie rods 33 and 34 so as to be pivotable. Therefore, the rotation of the steering wheel 21 is transmitted to the steering shaft 22, the intermediate shaft 24, the pinion shaft 25, the rack shaft 28, the tie rods 33 and 34, the tie rod end (not shown), and the knuckle arm (not shown). Steering wheels (not shown) are steered.

  The electric power steering device is fixed to a vehicle body skeleton (not shown) by bolting with a support portion 1 provided near the center of the steering column 23 and a support portion 2 provided near the lower end of the steering column 23. It is supported by being. An electric motor 20 for assisting the driver's steering by inputting torque to the steering shaft 22 is installed on the support portion 2 in the vicinity of the lower end portion of the steering column 23.

  Steering rack boots 10 are respectively attached around the ball joints 31 and 32 described above. The steering rack boot 10 is fixed to the tie rods 33 and 34 by a clip 42 and is fixed to the rack shaft 28 by a clamp 41.

  The steering rack boot 10 includes a cylindrical portion 11, a first impact absorbing portion 12 provided on one end portion 11 a side of the cylindrical portion 11, and a second impact provided on the other end portion 11 b side of the cylindrical portion 11. An absorber 16. The cylinder part 11 is formed in a bellows shape in the axial direction.

  The first impact absorbing portion 12 has a cylindrical shape in which a hole portion 13 having the same diameter as the tie rods 33 and 34 is formed at the center. The first shock absorber 12 is connected to the small-diameter portion 14 provided on one end side and the small-diameter portion 14 and is provided on the other end-side and has a larger diameter than the small-diameter portion 14. 15. The large diameter portion 15 is formed in such a size that it can come into contact with an end portion 16a of the second shock absorbing portion 16 described later at the end of the reciprocation of the rack shaft 28. The end portion 12a of the first shock absorbing portion 12 facing the second shock absorbing portion 16 is formed flat.

  The second shock absorber 16 has a cylindrical shape with a hole 19 through which the ball joints 31 and 32 can be inserted. On one end side of the second shock absorbing portion 16, a step portion 17 that can be fitted into the end portions 29 a and 29 b of the steering gear housing 29 is provided. On the outer peripheral side of the second end portion 16a of the second shock absorbing portion 16, a tapered portion 18 is formed that increases in diameter toward the center side. An end portion 16a facing the first shock absorbing portion 12 in the second shock absorbing portion 16 is formed flat.

  Examples of the first shock absorbing portion 12 and the second shock absorbing portion 16 include materials that are elastically deformable and made of the same material as the steering rack boot 10.

  Here, a case where the steering wheel 21 is steered to the right in the electric power steering apparatus having the above-described configuration will be described with reference to FIGS. 4 (a) and 4 (b).

  First, when the driver steers the steering wheel to the right, the steering force is transmitted to the rack shaft 28 via the steering shaft 22, the first joint 3, the intermediate shaft 24, the second joint 4, and the pinion shaft 25. At this time, the rack shaft 28 moves from the neutral position (see FIG. 1) to the left side (right side in FIG. 1), and on the right end side of the steering gear housing 29, the ball joint 31 is moved to the steering gear housing 29. Will move into the hole 29c provided at one end 29a.

  In the vicinity of the right steering limit, as shown in FIG. 4A, one end 12 a of the first shock absorber 12 and one end 16 a of the second shock absorber 16 are in contact with each other.

  Further, when the vehicle is steered to the right and reaches the maximum right steering limit, one end 12a of the first shock absorber 12 contacts one end 16a of the second shock absorber 16 as shown in FIG. In addition, pressure acts on the second shock absorber 16. Since the second shock absorbing portion 16 includes a tapered portion 18 whose diameter increases toward the center portion side, when receiving a force from the one end portion 16a side of the second shock absorbing portion 16, it is easily elastically deformed at first. Gradually becomes difficult to elastically deform. That is, the shock absorbing force by the second shock absorbing portion 16 is the greatest in the vicinity of the location where the inner end 31 a of the ball joint 31 contacts the hole 29 c of the steering gear housing 29. Thereby, at the right maximum steering limit, the impact input to the steering gear housing 29 by the ball joint 31 is most mitigated.

  Even during left steering, the second shock absorbing portion 16 includes the tapered portion 18 as in right steering. Therefore, when the force is received from the one end portion 16a side of the second shock absorbing portion 16, Is easily elastically deformed but gradually becomes difficult to elastically deform. Thereby, even at the left maximum steering limit, the impact input to the steering gear housing 29 by the ball joint 32 is most mitigated.

  Therefore, according to the electric power steering apparatus according to the present embodiment, the first shock absorbing portion 12 and the second shock absorbing portion are provided in the vicinity of the end (stroke end) of the reciprocating operation of the rack shaft 28 by providing the above-described configuration. 16, the impact input to the steering gear housing 29 at the time of maximum steering can be reduced. As a result, compared with a conventional electric power steering apparatus without the first shock absorbing portion and the second shock absorbing portion, the shock input at the end of the reciprocating operation of the rack shaft 28, that is, the shock input at the time of steering lock is alleviated. As a result, the operational feeling when the steering is locked is also improved. Since the steering rack boot 10 integrally includes the cylindrical portion 11 covering the ball joints 31 and 32, the first impact absorbing portion 12 and the second impact absorbing portion 16, the number of parts can be reduced. In addition, an increase in manufacturing cost can be suppressed. Furthermore, it is not necessary to separately assemble the first shock absorbing portion 12 and the second shock absorbing portion 16, and assembling workability is improved.

  The steering rack boot 10 has a cylindrical shape formed in an accordion shape, the first shock absorbing portion 12 has a cylindrical shape in which a hole portion 13 through which the tie rods 33 and 34 are inserted is formed at the center, and the small diameter portion 14 and the small diameter portion. A cylinder having a large diameter portion 15 connected to the portion 14 and having a larger diameter than the small diameter portion 14, and the second shock absorbing portion 16 having a hole portion 19 through which the ball joints 31 and 32 can be inserted. By providing the stepped portion 17 attached to the end portions 29a and 29b of the steering gear housing 29, the first shock absorbing portion 12 and the second shock absorbing portion 16 are reliably in contact with each other at the time of maximum steering. The impact input can be reduced by elastic deformation. Further, the steering rack boot 10 can be easily attached to the steering gear housing 29 and the tie rods 33 and 34.

  The second shock absorbing portion 16 includes the tapered portion 18 provided on the end 16a facing the first shock absorbing portion 12 so that the ball joints 31 and 32 can be attached to the steering gear housing 29 during maximum steering. Impact input can be mitigated most. Further, the force for reducing the impact input can be adjusted according to the proximity distance between the ball joints 31 and 32 and the holes 29c and 29d of the steering gear housing 29.

  In the present embodiment, the electric power steering device in which both the first shock absorbing portion 12 and the second shock absorbing portion 16 are cylindrical has been described. However, the hole portion through which the rack shaft can be inserted is formed at the center. It is also possible to provide an electric power steering device that includes a first shock absorbing portion and a second shock absorbing portion formed in a shape that can be in surface contact with each other. Even such an electric power steering device has the same effects as the electric power steering device described above.

  In addition, although the present Example demonstrated the electric power steering apparatus provided with the electric motor 20 provided in the support part 2 of the lower end part vicinity of the steering column 23, it is an electric power steering apparatus provided with the electric motor provided in the pinion. It is also possible to apply.

  The present invention relates to an electric power steering apparatus, which can reduce impact input at the end of the reciprocating operation of the rack shaft, reduce the number of parts, and suppress an increase in manufacturing cost. Furthermore, since the assemblability can be improved, it can be used extremely beneficially in the automobile industry and the like.

DESCRIPTION OF SYMBOLS 1, 2 Support part 3, 4 Joint 10 Steering rack boot 11 Cylinder part 12 First shock absorption part 13 Hole part 14 Small diameter part 15 Large diameter part 16 Second shock absorption part 17 Step part 18 Taper part 19 Hole part 20 Electric motor 21 Steering wheel 22 Steering shaft 23 Steering column 24 Intermediate shaft 25 Pinion shaft 26 Pinion 28 Rack shaft 29 Steering gear housing 31, 32 Ball joint 33, 34 Tie rod 41 Clamp 42 Clip

Claims (3)

A pinion shaft coupled to a steering wheel; a rack shaft coupled to the pinion shaft and capable of reciprocating within a steering gear housing within a restricted range; a ball joint provided on the rack shaft; and the ball An electric power steering device comprising a tie rod connected to a joint and a boot covering the ball joint,
The boot has a first shock absorber provided on one end side;
A second shock absorbing portion provided on the other end side,
An electric power steering apparatus characterized in that the first shock absorbing portion and the second shock absorbing portion are in contact with each other in the vicinity of a stroke end of the rack shaft. An electric power steering apparatus according to claim 1,
The boot is in the shape of a bellows,
The first impact absorbing portion is formed in a cylindrical shape having a hole portion through which the tie rod is inserted at the center, a small diameter portion, and a large diameter portion connected to the small diameter portion and having a larger diameter than the small diameter portion. Prepared,
The electric power steering device, wherein the second shock absorbing portion is formed in a cylindrical shape with a hole portion through which the ball joint can be inserted at the center, and includes a step portion attached to an end portion of the steering gear housing. . An electric power steering apparatus according to claim 2,
The electric power steering apparatus, wherein the second shock absorbing portion includes a tapered portion provided on an end side facing the first shock absorbing portion.

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