JP2013014251A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device capable of preventing the generation of rattling noise between a slide bearing held at a lower shaft and one end of an input shaft of the electric power steering device.SOLUTION: In this power steering device coaxially connecting an input shaft cylindrical part 35 connected to a steering wheel and a lower shaft cylindrical part 36 connected to a steering mechanism, at least one of one end 35a of the input shaft cylindrical part 35 and a holding part 36a of the lower shaft cylindrical part 36 rotatably holding the one end 35 is resin coated 26.

Description

  The present invention relates to a power steering device for a vehicle.

A power steering device for a vehicle includes an input shaft connected to a steering wheel, a lower shaft connected to a steering mechanism, a torsion bar that coaxially connects the input shaft and the lower shaft, and twisting of the torsion bar to detect steering torque. And a torque sensor for detection.
In order to improve the detection accuracy of the torque sensor, it is necessary for the input shaft to rotate smoothly while the input shaft and the lower shaft are arranged coaxially. For this reason, one end (lower shaft side) of the input shaft is rotatably supported by a slide bearing provided on the lower shaft. (Patent Document 1)

JP 2002-372469 A

According to this structure, the tolerance of the machining dimension of one end supported by the slide bearing of the input shaft, the tolerance of the machining dimension of the hole holding the sliding bearing of the lower shaft, the tolerance of the sliding bearing held by the lower shaft, etc. There are various tolerances. For this reason, in order to allow the input shaft to rotate smoothly, it is necessary to design a large gap dimension between the slide bearing and the input shaft.
However, when the gap size is increased in this way, a hitting sound may be generated between the slide bearing and one end of the input shaft.
SUMMARY OF THE INVENTION An object of the present invention is to provide a power steering device that can suppress the occurrence of hitting noise between one end of an input shaft and a sliding bearing held by a lower shaft.

  In order to solve the above-mentioned problem, an invention described in claim 1 includes an input shaft connected to the steering wheel, a lower shaft connected to the steering mechanism, a torsion bar that coaxially connects the input shaft and the lower shaft, In a power steering apparatus including an electric motor that generates a steering assist force according to torsion of a torsion bar, at least one end of the input shaft and a holding portion provided on the lower shaft that rotatably holds the one end The gist is that one is resin-coated.

  In the power steering device according to the present invention, one end of the input shaft is structured such that one end of the input shaft is directly inserted into the holding portion provided on the lower shaft via a resin coating to rotatably support the input shaft. Alternatively, the gap dimension between the holding portion provided on the lower shaft and the resin coating can be designed to be small, and as a result, abnormal noise (sounding between the lower shaft and the input shaft) can be suppressed.

  The gist of the invention described in claim 2 is that a lubricant is interposed between the one end and the holding portion. That is, the presence of the lubricant in the engaging portion allows the engaging portion to smoothly move the rotating portion, reacts quickly to impact, prevents the engaging portion from being worn, and prevents the engaging portion from being used for a long time. Wear can be prevented, and the generation of abnormal noise can be suppressed.

  It is possible to provide a power steering device that can suppress the generation of hitting sound between one end of the input shaft and the sliding bearing held by the lower shaft.

Sectional drawing which shows the structure provided with an electric motor in the steering mechanism side of this invention apparatus. Main part enlarged view of the first embodiment Main part enlarged view of the second embodiment

  Hereinafter, an electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view of a steering apparatus according to a first embodiment of the present invention. The steering device 1 transmits the movement of the steering wheel 2 to the steering mechanism 6 through the steering shaft 4 inserted inside the steering column 3 and the intermediate shaft 5 connected thereto, and this steering mechanism 6 To steer the wheel 7.

  The steering mechanism 6 is of a rack and pinion type. The steering mechanism 6 includes a pinion 8 that rotates by a steering operation, and a rack shaft 9 that meshes with the pinion 8. The rack shaft 9 is housed in a rack housing and is supported so as to be movable along the width direction of the vehicle body that is the axial length direction of the rack shaft 9. Both ends of the rack shaft 9 are connected to the steering wheel 7 via tie rods. The pinion 8 is rotatably supported and is connected to the intermediate shaft 5 and the steering shaft 4 so as to be integrally rotatable.

  Further, the steering column 3 is provided with a steering assist unit 14 for obtaining a steering assist force according to a steering operation. The steering assist unit 14 is disposed at the end of the steering column 3 on the wheel 7 side. The steering column 3 and the steering shaft 4 are normally disposed so that the steering wheel 2 side is inclined upward and toward the rear of the vehicle body. In the following description, the direction along the axial direction of the steering shaft 4 will be referred to as the vertical direction, and the steering wheel 2 side will be described as the upper side.

  The steering assist unit 14 includes a steering shaft 4, an electric motor 16 driven according to torque detected by the torque sensor 15, and a speed reduction mechanism 17 that transmits a steering assist force generated by the electric motor 16 to the steering shaft 4. And housings 18 and 19 that support these portions 15, 16, and 17 and constitute the lower portion of the steering column 3. The housings 18 and 19 are fixed to each other along the axial direction of the steering shaft 4 and constitute the lower part of the steering column 3. A cylindrical jacket 20 constituting the upper part of the steering column 3 is fixed to the end of the housing 18 side by side. The steering shaft 4 is inserted into the steering column 3 and is rotatably supported by a plurality of bearings 21, 22, 23 and the like.

  In the steering assist unit 14, the electric motor 16 generates a steering assist force in response to a signal from the torque sensor 15 for detecting a steering operation. The steering assist force is transmitted to the steering shaft 4 via the speed reduction mechanism 17. The steering shaft 4 includes a housing 30 accommodated in the jacket 20 and a lower portion 31 connected to the upper portion 30 and accommodated in the housings 18 and 19. The lower portion 31 includes an input shaft 32 disposed on the steering wheel 2 side, a lower shaft 33 and a torsion bar 34 on the steering mechanism 6 side.

  The input shaft 32 includes a cylindrical portion 35 (hereinafter referred to as an input shaft cylindrical portion), and the upper end portion of the input shaft 32 is connected to the steering wheel 2 via the upper portion 30 of the steering shaft 4. The lower shaft 33 includes a cylindrical portion 36 (hereinafter referred to as a lower shaft cylindrical portion), and a lower end portion of the lower shaft 33 is connected to the steering mechanism 6 via the intermediate shaft 5. The torsion bar 34 is inserted through the input shaft cylinder portion 35 and the lower shaft cylinder portion 36 to connect the input shaft 32 and the lower shaft 33 coaxially. Further, the torsion bar 34, the one end 35a of the input shaft cylinder part 35, and the holding part 36a of the lower shaft cylinder part 36 are concentrically disposed, and one end 35a of the input shaft cylinder part 35 and the lower shaft are arranged. A resin coating 26 is interposed between the cylindrical portion 36 and the holding portion 36a. In the example of FIG. 2, one end 35 a of the input shaft cylinder portion 35 is formed by the resin coating 26, but the holding portion 36 a of the lower shaft cylinder portion 36 may be formed by the resin coating 26.

  The resin coating 26 has good heat resistance, and a low friction material having excellent slidability is formed by spray coating or electrostatic coating using, for example, fluororesin, nylon, or polyacetal. Further, the gap between the outer periphery of the input shaft and the inner periphery of the lower shaft is formed to be small enough to be incorporated. Since the press-fitting engagement affects the detection of torsional torque of the torsion bar 34, it is strictly controlled.

  Further, the torsion bar 34 receives the torque and is torsionally deformed to relatively rotate and displace the input shaft 32 and the lower shaft 33. The input shaft 32 is provided with a plurality of, for example, two rings 46 and 47, and the lower shaft 33 is provided with a ring 48. A torque sensor 15 is disposed around the rings 46 to 48. The torque sensor 15 detects a twist angle generated in the torsion bar 34 according to the steering force as a change in magnetic characteristics. The torque sensor 15 has a pair of coils. The plurality of rings 46 to 48 made of a magnetic material disposed in the vicinity of the inner peripheral surface of the coil and the coil holder form a pair of magnetic circuits. The magnetic characteristics of the pair of magnetic circuits change according to the twist angle. Based on such changes, torque is detected, for example, with temperature compensation.

  The torque from the steering assisting electric motor 16 is transmitted to the lower shaft 33 via the speed reduction mechanism 17. The speed reduction mechanism 17 has a worm shaft 24 that rotates integrally with the rotation shaft of the electric motor 16, and a worm wheel 25 that meshes with the worm shaft 24. The worm wheel 25 is attached to the lower shaft 33 so as to be integrally rotatable. The torsion bar 34 has an upper end portion 37 and a lower end portion 38 that form a relatively large-diameter columnar shape, and a torsion region 39 having a relatively small diameter between the upper end portion 37 and the lower end portion 38. .

  The upper end portion 37 is fitted to the inner periphery of the input shaft 32 and is connected to the input shaft 32 and the upper portion 30 of the steering shaft 4 so as to be integrally rotatable. The lower end portion 38 has a cylindrical shape, is fitted to the inner periphery of the lower shaft 33, and is connected to the lower shaft 33 by a pin 41 so as to be integrally rotatable. The torsional region 39 is a part where relative movement with respect to the input shaft 32 is not restricted, and is a part where relative movement with respect to the lower shaft 33 is not restricted. The shape of the torsional region 39 is not particularly limited. For example, the middle part of the torsional region has a cylindrical shape with a small diameter, and the diameter is smoothly expanded in the vicinity of the upper end 37 and the lower end 38.

  With these configurations, in the power steering according to the present invention, one end 35a of the input shaft cylinder portion 35 and the holding portion 36a of the lower shaft cylinder portion 36 are connected to one end 35a of the input shaft cylinder portion 35 via the resin coating 26. The tube portion 36 is directly inserted into the holding portion 36a. Therefore, the gap dimension can be designed to be small, and as a result, abnormal noise (sounding sound between the holding portion 36a of the lower shaft cylinder portion 36 and the one end 35a of the input shaft cylinder portion 35) can be suppressed.

Since the resin coating 26 on the outer periphery of the embodiment shown in FIG. 2 can be applied to the outer peripheral surface of the one end 35a of the input shaft cylinder portion 35, the accuracy can be greatly improved because it is easy to make and easy to obtain. Therefore, the gap dimension can be designed to be small, and as a result, abnormal noise (sounding sound between the holding portion 36a of the lower shaft cylinder portion 36 and the one end 35a of the input shaft cylinder portion 35) can be suppressed.
Further, since the gap can be reduced, the detection sensitivity of the torque sensor 15 for detecting torque can be reduced, so that the detection sensitivity can be improved, the steering force can be appropriately assisted, and the steering performance can be improved.

Next, another embodiment will be described with reference to FIG. In addition, the thing of the same mechanism as the rack shaft support apparatus shown in FIG.
As shown in the second embodiment in FIG. 3, a lubricant is sealed in an engaging portion that rotatably engages one end 35a of the input shaft cylinder portion 35 and the holding portion 36a of the cylinder portion 36 of the lower shaft. A seal member 50 provided between at least one resin coating 26 on the outer periphery of one end 35 a of the shaft tube portion 35 or the inner periphery of one end 35 a of the lower shaft tube portion 35 is provided.

Further, the seal member 50 is interposed between the one end 35a of the input shaft cylinder portion 35 and the holding portion 36a of the lower shaft cylinder portion 36 in a pre-compressed state. This allows the seal member 50 to allow a predetermined amount of movement in the rotational direction of the one end 35a of the input shaft cylinder portion 35 and the holding portion 36a of the lower shaft cylinder portion 36, and to prevent the control from affecting the control beyond the predetermined amount. Has been. The predetermined amount can be set by adjusting the precompression load and the deformation amount of the seal member 50 by adjusting the engagement portion clearance, the diameter of the seal member 50, and the elastic coefficient of the seal member material.
As the material of the seal member 50, generally, various resin materials having elasticity in addition to acrylonitrile, butadiene rubber (NBR), various synthetic rubbers, polyamide resin having oil resistance can be used.

  Further, a lubricant 51 is sealed in a space 52 formed by one end 35 a of the input shaft cylinder portion 35, the holding portion 36 a of the lower shaft cylinder portion 36, and the seal member 50. Furthermore, a sufficient amount of lubricant that does not cause direct contact between the one end 35a of the input shaft cylinder portion 35 and the holding portion 36a of the lower shaft cylinder portion 36 is enclosed in the space portion 52. A synthetic oil polyα-olefin having a viscosity coefficient can also be used, and a grease using a synthetic oil polyαolefin as a base oil and Li soap as a thickener can also be used.

  Furthermore, according to the above configuration, since the lubricant 51 exists in the engaging portion, the engaging portion can smoothly move the rotating portion, can react quickly to an impact, and can prevent wear of the engaging portion. Since the seal member 50 is provided in the engaging portion, the lubricant 51 can be prevented from leaking, so that wear of the engaging portion can be prevented for a long period of time, and the generation of abnormal noise can be suppressed.

  Further, since the seal member 50 is an elastic body and can absorb the vibration of the one end 35a of the input shaft cylinder part 35, the impact at the time of a collision between the holding part 36a of the lower shaft cylinder part 36 and the one end 35a of the input shaft cylinder part 35 is prevented. Since it can absorb, generation | occurrence | production of abnormal noise can be suppressed.

  As described above, the input shaft 32 and the lower shaft 33 can be greatly improved in accuracy because the output side end portion of the input shaft cylindrical portion 35 is directly inserted into the lower shaft cylindrical portion 36 via the resin coating. Therefore, the gap size can be reduced, and in addition, the configuration of the lubricant 51 and the seal member 51 can be added to absorb the impact, so that abnormal noise (the holding portion 36a of the lower shaft cylinder portion 36 and the one end 35a of the input shaft cylinder portion 35) can be absorbed. It is possible to provide a power steering device capable of suppressing (sounding sound).

DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 2 ... Steering wheel, 6 ... Steering mechanism, 16 ... Electric motor, 17 ... Deceleration mechanism, 26 ... Resin coating, 32 ... Input shaft, 33 ... Lower shaft, 34 ... Torsion bar, 35 ... Input Tube portion of shaft, 36 ... Tube portion of lower shaft, 50 ... Seal member, 51 ... Lubricant

Claims (2)

  An input shaft that is connected to the steering wheel, a lower shaft that is connected to the steering mechanism, a torsion bar that coaxially connects the input shaft and the lower shaft, and an electric motor that generates a steering assist force according to the torsion of the torsion bar In the power steering apparatus provided, one end of the input shaft, a holding portion provided on the lower shaft that rotatably holds the one end, and at least one of the one end or the holding portion are resin-coated. Power steering device.   The power steering apparatus according to claim 1, wherein a lubricant is interposed between the one end and the holding portion.

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