JP2001219855A - Electrically-powered steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the harsh grating striking noise by a stopper of an electrically-powered steering device located in a cabin when the relative rotation of an input shaft and an output shaft is regulated in a predetermined range by the stopper interposed between both shafts. SOLUTION: When a steering wheel is turned in a relatively early manner such as in the stationary steering, an elastic member 47 fitted to a moving end of a rack shaft 13 abuts on a rack stopper 39 of a rack housing 14 before a first stopper mechanism interposed between the input shaft and the output shaft works, and the shock in the stationary steering is absorbed. The first stopper mechanism works with in a substantially elastic stroke range of the elastic member 47. The striking speed when abutting portions of the first stopper mechanism are abut on each other is weakened. No disagreeable noise by the striking noise is felt by a driver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for assisting a steering force by a rotating force of an electric motor.

[0002]

2. Description of the Related Art In a conventional hydraulic power steering apparatus, a valve mechanism is formed between an input shaft and an output shaft, but the relative rotation between the input shaft and the output shaft is controlled. A so-called valve stopper that regulates the angle to a predetermined angle is provided. Since the valve stopper is located in the oil in the engine room, the collision sound of the valve stopper is hardly heard by the driver in the vehicle compartment.

On the other hand, in the case of an electric power steering apparatus that generates a steering assisting force by an electric motor provided on a column, a stopper that regulates the relative rotation between an input shaft and an output shaft is disposed in a vehicle interior. Therefore, when the steering wheel is turned to the maximum, for example, at the time of stationary installation, the tapping sound of the stopper is transmitted as harsh sound to the driver.
Therefore, it is conceivable to interpose a cushioning material such as rubber in a stopper portion between the input shaft and the output shaft, but the space is narrow and the layout is practically difficult. Further, even if a cushioning material is provided, only a cushioning material having a small shock absorption capacity can be provided, and the durability deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric power steering apparatus capable of greatly reducing the generation of an impact sound when stationary. .

[0005]

Means for Solving the Problems and Effects of the Invention To achieve the above object, the present invention provides a steering mechanism for driving a motor in accordance with the relative displacement between an input shaft and an output shaft connected via a torsion bar. In the electric power steering apparatus for generating a steering assist force for driving the motor, a pair of abutting portions interposed between the input shaft and the output shaft and abutting each other to regulate the relative rotation of both shafts within a predetermined range. A second stopper mechanism that has a pair of contact members that contact each other when the sliding shaft included in the steering mechanism is at the moving end and that regulates the moving range of the sliding shaft. Wherein at least one of the contact members includes an elastic member, and the second stopper mechanism acts before the first stopper mechanism when the sliding shaft moves to the moving end. Is what you do.

According to the present invention, when the steering wheel is turned to the maximum during stationary steering or the like, the second stopper including the elastic member outside the vehicle compartment is provided before the first stopper mechanism disposed in the vehicle compartment operates. The mechanism works first, and the abutting members including the elastic members abut each other to sufficiently reduce the impact. This makes it possible to reduce the impact speed when the contact portions of the first stopper mechanism make contact with each other, or to avoid contact in some cases. Therefore, it is possible to prevent the generation of unpleasant noise in the vehicle cabin due to the impact sound of the first stopper mechanism.

It is preferable that the first stopper mechanism operates within a substantial elastic stroke range of the elastic member included in the second stopper mechanism. This is because this allows both stopper mechanisms to perform their essential functions in a state where the above-mentioned impact sound is prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of an electric power steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, in the present electric power steering device (hereinafter simply referred to as a power steering device), an input shaft 2 on which a steering wheel 1 is mounted, and an output shaft 4 on which a steering mechanism 3 is mounted. Are connected coaxially through a torsion bar 5. The input shaft 2 and the output shaft 4 are rotatably supported via bearings 7 and 8 in a cylindrical housing 6 made of an aluminum alloy mounted on a vehicle body (not shown). The housing 6 is formed by combining an upper housing 6a and a lower housing 6b. Bearing 9 is output shaft 2
Is rotatably supported by the lower housing 6b.

The lower end of the output shaft 4 is connected via a universal joint 10 to a steering mechanism 3 comprising, for example, a rack and pinion mechanism. The steering mechanism 3 includes the output shaft 4 and the universal joint 1
0 and a pinion shaft 12 connected so as to be integrally rotatable
And a rack shaft 13 as a sliding shaft that meshes with the pinion shaft 12. Rack shaft 13 as sliding shaft
Is supported slidably in the axial direction inside a rack housing 14 extending in the left-right direction of the vehicle body. Both ends of the rack shaft 13 project from both sides of the rack housing 14,
The operating wheels 15,
15. A gear housing 17 that rotatably supports the pinion shaft 12 is fixed to an intermediate portion in the longitudinal direction of the rack housing 14 so as to intersect with the rack housing 14.

A first cylinder 19 made of a magnetic material is fixed to the outer periphery of the input shaft 2 via a sleeve 18 made of a nonmagnetic material. Further, a second cylinder 20 made of a magnetic material is fixed to the upper outer periphery of the output shaft 4. Both cylinders 1
A large number of rectangular teeth 21 and 22 are formed on the opposite end faces 9 and 20 at a constant pitch in the circumferential direction.
A predetermined space is maintained between the teeth 21 and 22. On the other hand, inside the housing, coil cylinders 23 and 24 having a U-shaped cross section made of a sintered metal as a magnetic material are fixed. The cylinder 24 is disposed so as to straddle the opposing portion between the first cylinder 19 and the second cylinder 20. A temperature compensation coil 25 and a torque detection coil 26 serving as a torque sensor are housed in the cylinders 23 and 24.
3 is the first cylinder 19 and the cylinder 24 is the first cylinder 19
And the second cylinder 20 and a magnetic circuit.

Signals from the torque detecting coil 26 and the temperature compensating coil 25 are given to a control unit 28 via a sensor circuit 27. The control unit 28 uses the signals to control the direction and magnitude of the steering torque applied to the steering wheel 1. Then, the steering assist motor 30 connected to the output side of the control unit 28 via the drive circuit 29 is rotated in the direction corresponding to the operation direction of the steering wheel 1.
A lower housing 6 is provided on a rotating shaft (not shown) of the motor 30.
A worm shaft 31 that is rotatably supported through b is connected to the worm shaft 31, and a worm wheel 32 driven by the worm shaft 31 is attached to an intermediate portion of the output shaft 4 in the axial length direction so as to be integrally rotatable. Have been.

Further, a reduced diameter portion 33 is provided at an end of the input shaft 2, and the reduced diameter portion 33 is accommodated in a hole 34 provided in the output shaft 4. Outer peripheral surface of reduced diameter portion 33 and hole 34
Abutment portions which are substantially in contact with the inner circumferential surface of the first stopper mechanism, and these constitute a first stopper mechanism 35.
In the first stopper mechanism 35, for example, as shown in FIG. 2, the relative rotation between the input shaft 2 and the output shaft 4 is controlled to a predetermined value by forming the reduced diameter portion 33 and the hole 34 into a cross-sectional shape having a two-sided width. Regulate to a range.

On the other hand, reference numeral 36 denotes a rack bush inserted into the end 38 of the cylinder tube 37 of the rack housing 14. Reference numeral 39 denotes a rack stopper which covers the end 38 of the cylinder tube 37 while allowing the rack shaft 13 to enter and exit. It is. The tie rod 16 is attached to the end 40 of the rack shaft 13.
Are connected by screws 42. Further, a holder 44 made of an annular synthetic resin is fixed to the end portion 40 of the rack shaft 13 so as to be received on the end surface 43 of the joint 41. The holder 44 has a reduced diameter portion 45 on the rack stopper 39 side and a large diameter portion 46 on the joint 41 side, and an annular elastic member 47 such as rubber is externally fitted and fixed to the reduced diameter portion 45. Holder 4
As the synthetic resin used for No. 4, for example, a polyamide resin such as nylon 6 or nylon 6.6 can be used.
Further, examples of the rubber used for the elastic member 47 include NBR (acrylonitrile butadiene rubber) and CR (chloroprene rubber).

One end of the elastic member 47 abuts on an annular step portion 48 between the large diameter portion 46 and the reduced diameter portion 45, and the other end is connected to the reduced diameter portion 4.
5 protrudes from the end surface 49 toward the rack stopper 39 by a predetermined length d. Rack stopper 39 and elastic member 47
Constitute contact members that contact each other, and these constitute a second stopper mechanism 50.
In the second stopper mechanism 50, when the rack shaft 13 slides to the stroke end, the elastic member 47 comes into contact with the rack stopper 39, and a substantial elastic stroke of the elastic member 47 corresponding to the predetermined length d described above. It only shrinks and absorbs shock during this deformation. Since the elastic member 47 is received by the holder 44 made of synthetic resin, the cushioning property is high. Further, the reduced diameter portion 33 of the first stopper mechanism 35 is set so as to contact the inner peripheral surface of the hole 34 within the range of the substantial elastic stroke of the elastic member 47.

The positional relationship between the components of each of the stopper mechanisms 35 and 50 is set so that the first stopper mechanism 35 operates after the second stopper mechanism 50 buffers. In the present embodiment, when the steering wheel 1 is turned to the maximum during a stationary operation or the like, before the reduced diameter portion 33 of the first stopper mechanism 35 disposed in the vehicle interior and the inner peripheral surface of the hole 34 come into contact with each other. Then, the elastic member 47 of the second stopper mechanism 50, which is outside the vehicle compartment and has a high cushioning force, comes into contact with the rack stopper 39 first, and the impact at the time of contact is reduced. Thereby, for example, it is possible to reduce the impact speed when the reduced diameter portion 33 of the first stopper mechanism 35 and the inner peripheral surface of the hole 34 come into contact with each other, or to avoid the contact in some cases. Therefore, it is possible to prevent unpleasant noise due to the impact sound of the first stopper mechanism 35 from being generated in the vehicle interior.

FIG. 4 is a sectional view of a main part of a steering mechanism according to another embodiment of the present invention, and FIG. 5 is a sectional view taken along line VV of FIG. Referring to FIG. 4, the present embodiment is different from the embodiment of FIG. 3 in that second elastic member 47 is externally fitted and fixed to holder 44 in second stopper mechanism 50 of the embodiment of FIG. However, in the second stopper mechanism 50A of the present embodiment, the elastic member 53 is integrally formed with the holder 51. The holder 51 includes an annular groove 56 located on the rack stopper 39 side and the joint 4.
It has a plurality (for example, four) of D-shaped holes 52 located on one side and arranged at equal intervals in the circumferential direction. The plurality of D-shaped holes 52 communicate with the annular groove 56. That is, the D-shaped hole 52 is opened at the bottom of the annular groove 56.

The holder 51 is made of a polyamide resin (nylon 6
After being formed of a synthetic resin such as nylon or nylon 66) or a similar relatively hard material, the elastic member 53 is made of NBR (acrylonitrile butadiene rubber), CR (chloroprene rubber), or a similar comparative material having high shock absorption characteristics. Molded on the holder 51 with a soft material rubber. A part of the elastic member 53 is disposed in the annular groove 56 and projects from an end surface of the holder 51 having a predetermined length d (the length d is set to about 2 mm in the present embodiment). The rest fills the plurality of D-shaped holes 52. In this embodiment, a step 55 is formed in the D-shaped hole 52, and the step 54 of the elastic member 53 abuts, whereby the elastic member 53 is positively held by the holder 51.

According to the present embodiment, the elastic member 53 is formed integrally with the holder 51. However, the elastic member 53 may be formed separately from the holder 51 and vulcanized and bonded to the holder 51. In the embodiment of FIG. 4, the same components as those of FIG. 3 are denoted by the same reference numerals, and description thereof is omitted. According to the present embodiment, as in the embodiment of FIG.
Unpleasant noise due to the impact sound of the stopper mechanism 35 can be prevented from being generated in the passenger compartment.

Further, by integrally forming the elastic member 53 with the holder 51, the fixing of the elastic member 53 to the holder 51 is ensured. As a result, even if the elastic member 53 collides with the rack stopper 39, it is possible to reliably prevent the elastic member 53 from dropping from the holder 51 or being damaged. The present invention is not limited to the above embodiments. For example, in each of the above embodiments, the elastic member moves integrally with the rack shaft 13. However, the present invention is not limited to this. It may be fixed to the rack stopper 39. Further, the elastic member may be arranged on both the rack stopper 39 and the holder 44 (51). Further, the holder 44 (51) may be omitted, and the elastic member may be held by the joint 41. In addition, various changes can be made within the scope of the present invention.

[0020]

Embodiment and Comparative Example An embodiment corresponding to the electric power steering apparatus shown in FIGS.
A stationary test was performed on the comparative example in which the rotation angle (d) of the steering wheel 1 was removed.
eg) and the torsion angle (deg) of the torsion bar 5 were actually measured using a sensor, and the results shown in FIG. 6 were obtained.
Referring to FIG. 6, in the embodiment shown by the solid line, the gradient of the torsion bar torsion angle between the point A at which the second stopper mechanism works and the point B at which the first stopper mechanism works is indicated by a dashed line. Is significantly smaller than the comparative example shown by. From this, it was proved in the example that the impact energy at the time of the contact of the first stopper mechanism was small, and the generation of a loud tapping sound could be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electric power steering apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of FIG. 1 cut across a reduced diameter portion of an input shaft.

FIG. 3 is a sectional view of a main part of the steering mechanism.

FIG. 4 is a sectional view of a main part of an electric power steering apparatus according to another embodiment of the present invention.

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIG. 6 is a graph showing the relationship between the rotation angle of the steering wheel and the torsion angle of the torsion bar.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 input shaft 3 steering mechanism 4 output shaft 5 torsion bar (torsion member) 12 pinion shaft 13 rack shaft (sliding shaft) 30 motor 35 first stopper mechanism 33 reduced diameter portion 34 hole 39 rack stopper ( Contact member) 44 Holder 47 Elastic member (Contact member) 50, 50A Second stopper mechanism 51 Holder 53 Elastic member (Contact member)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Deyama 3-5-8 Minamisenba, Chuo-ku, Osaka-shi Inside Koyo Seiko Co., Ltd. (72) Inventor Etsuro Kitami 3-58-8 Minamisenba, Chuo-ku, Osaka-shi Koyo Seiko Inside (72) Inventor Hiroaki Murakami 3-5-8 Minamisenba, Chuo-ku, Osaka-shi Inside Koyo Seiko Co., Ltd. (72) Inventor Teruo Tsutsui 3-58-8 Minamisenba, Chuo-ku, Osaka-shi Koyo Seiko Co., Ltd. 72) Inventor Takashi Tsutsui 3-5-8 Minamisenba, Chuo-ku, Osaka-shi F-term in Koyo Seiko Co., Ltd. 2F051 AA01 AB05 BA03 3D033 CA04 CA16 CA28 JB01

Claims (2)

[Claims] An electric power steering apparatus for driving a motor in accordance with a relative displacement between an input shaft and an output shaft connected via a torsion bar to generate a steering assist force for driving a steering mechanism. A first stopper mechanism including a pair of abutting portions interposed between the input shaft and the output shaft and abutting on each other to regulate the relative rotation of the two shafts within a predetermined range; and a sliding shaft included in the steering mechanism moves. A second stopper mechanism that has a pair of abutting members that abut on each other in a state at the end, and that regulates a moving range of the sliding shaft, wherein at least one abutting member includes an elastic member, and the sliding shaft is An electric power steering apparatus, wherein the second stopper mechanism works before the first stopper mechanism when moving to the moving end. 2. The electric power steering system according to claim 1, wherein the first stopper mechanism operates within a substantial elastic stroke range of an elastic member included in the second stopper mechanism. Taking device.