JP2002240728A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device dispensing with the adjustment of backlash, as a principle, between bevel gears geared with each other. SOLUTION: A support shaft 1 having a first bevel gear 2 in its tip is axially movably formed relative to an output shaft m of an electric motor M. The support shaft 1 is energized in the direction of the second bevel gear 4 by an energizing member 8.

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 obtaining a steering assist force for a vehicle by an electric motor.

[0002]

2. Description of the Related Art Conventionally, as the electric power steering apparatus, the rotation of an electric motor is controlled by a first bevel gear connected to an output shaft via a support shaft, and a first bevel gear with respect to the first bevel gear. The rack shaft is transmitted to a rotating body surrounding the rack shaft via a second bevel gear meshed with the axes crossing each other, and the rotating motion of the rotating body is provided between the rotating body and the rack shaft. To be able to convert the linear motion of the rack shaft by the provided ball screw, and to turn the steered wheels connected to the rack shaft by rotating the electric motor in response to the rotation of the steering wheel (handle). (See, for example, Japanese Patent Application Laid-Open No. 8-207796).

However, in the above-described conventional electric power steering apparatus, backlash may occur at a portion where the first and second bevel gears mesh with each other due to processing accuracy and assembly accuracy of the first and second bevel gears. When this backlash occurs, a so-called rattling sound is generated when the steering wheel is steered, and this leaks into the vehicle and may cause discomfort to the driver or the passenger. Therefore, at the time of assembling the apparatus, a shim is arranged on the mating surface between the spindle and the spindle housing accommodating the first bevel gear and the electric motor, and the spindle and the first bevel are arranged together with the output shaft of the electric motor. By integrally moving the gears in the axial direction, the engagement of the first bevel gear with the second bevel gear is adjusted so that the backlash does not occur.

[0004]

However, in the above-mentioned backlash adjustment work, it is usually impossible to properly engage both bevel gears with one shim adjustment, and it is necessary to repeat the shim adjustment many times. is there. Moreover, it is necessary to attach and detach the electric motor to and from the spindle housing every time the shim is adjusted. For this reason, there is a problem that the adjustment of the backlash is complicated and takes much time.

[0005] Even if the apparatus is adjusted so as not to cause backlash at the time of assembling the apparatus as described above, backlash occurs because the tooth surface of each bevel gear is worn due to long-term use of the apparatus. It is difficult to avoid. For this reason, there has been a problem that complicated maintenance is required, for example, it is necessary to disassemble the electric power steering apparatus periodically to perform backlash adjustment.

Further, if the amount of movement of the first bevel gear with respect to the second bevel gear becomes unnecessarily large due to the shim adjustment, the mesh point of the two bevel gears greatly deviates from a preset mesh point, and There is also a problem that the power transmission efficiency between the gears is reduced. In addition, there is a problem that vibrations caused by the rotation of the support shaft are transmitted to the support shaft housing via the bearing, and noise is generated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an electric power steering apparatus which does not basically require backlash adjustment. Another object of the present invention is to provide an electric power steering device capable of preventing backlash from occurring for a long period of time. Further, the present invention provides the first bevel gear and the second bevel gear with the adjustment of the backlash.
It is an object of the present invention to provide an electric power steering device capable of preventing a point of engagement with a bevel gear from being largely displaced. A further object of the present invention is to provide an electric power steering device capable of suppressing generation of noise due to vibration of a support shaft.

[0008]

An electric power steering apparatus according to the present invention for achieving the above object is provided with a support shaft connected to an output shaft of an electric motor so as to be integrally rotatable, and a tip end of the support shaft. A first bevel gear, a rack shaft that steers steered wheels by linear movement, a second bevel gear meshed with the first bevel gear so that their axes cross each other, A rotating body rotatably supported by the housing in a state of surrounding the rack shaft and rotatable integrally with the second bevel gear, and a ball screw configured between the rotating body and the rack shaft; An electric power for assisting a manual steering force for steering the steered wheels by transmitting the rotation of the electric motor to the rotating body via the first bevel gear and the second bevel gear to linearly move the rack. In the steering device, front And movable support shaft to the second bevel gear direction, is characterized in that biases the support shaft by the urging member to the second bevel gear direction (claim 1).

According to the electric power steering apparatus having the above-described structure, the support shaft is movable in the second bevel gear direction, and the support shaft is biased in the second bevel gear direction by the biasing member. Therefore, the first bevel gear can be pressed against the second bevel gear. For this reason, when assembling the apparatus, it is basically unnecessary to adjust the backlash of both bevel gears. Further, even if each bevel gear is worn due to long-term use, the biasing member can move the first bevel gear to the second bevel gear by following the wear. For this reason, it is possible to prevent backlash from occurring at the meshing portion of both bevel gears.

[0010] In the electric power steering apparatus, it is preferable that the urging member is interposed between the support shaft and an output shaft of the electric motor (claim 2).
The urging member can be easily arranged. In the electric power steering device, it is preferable that an elastically deformable buffer member is disposed between the support shaft and a housing supporting the support shaft (claim 3).
The vibration accompanying the rotation of the support shaft can be absorbed by the buffer member.

In the electric power steering apparatus, the first housing supports the one end of the rotating body in a state where relative movement in the axial direction is allowed,
A second housing that supports the other end of the rotating body in a state where relative movement in the axial direction is regulated,
It is preferable that the relative position of the first housing and the second housing in the rack axis direction can be adjusted by a housing position adjusting mechanism. In this case,
By adjusting the relative position of the first housing and the second housing in the rack axis direction by the housing position adjusting mechanism, the rotating body is moved in the rack axis direction together with the second bevel gear, and The mesh point of the bevel gear can be adjusted.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electric power steering apparatus according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing one embodiment of the electric power steering apparatus of the present invention. The electric power steering device includes a housing H, an electric motor M attached to the housing H, a spindle 1 driven to rotate by the electric motor M, and a first shaft provided at the tip of the spindle 1. A bevel gear 2, a rack shaft 3 that passes through the inside of the housing H and steers steered wheels (not shown) by linear movement, a second bevel gear 4 meshed with the first bevel gear 2, A rotating body 5 rotatably supported by the housing H in a state surrounding the rack shaft 3, a ball screw 6 formed between the rotating body 5 and the rack shaft 3, and a second support shaft 1. The main part is constituted by an urging member 8 for urging in the direction of the bevel gear 4 and a rack and pinion mechanism 9 for converting the rotation of the steered wheels into a linear motion of the rack shaft 3.

Referring to FIG. 2 as well, the housing H includes a spindle housing H1 on which the electric motor M is mounted and which accommodates the spindle 1 and the first bevel gear 2, and a rack shaft 3
And a rack housing H2 for accommodating the rotating body 5. The rack housing H2 supports a first housing H2a that supports a right end in the drawing of the rotating body 5 and a left end in the drawing of the rotating body 5. And a second housing H2b. The electric motor M is fixed to the spindle housing H1 in a state where a lower outer periphery M1 of the casing is fitted to an opening edge H1a of the spindle housing H1. The axis of the output shaft m of the electric motor M is orthogonal to the axis of the rack shaft 3.

The first housing H2a and the second housing H2b are connected to each other so that a relative position in the axial direction can be adjusted by a housing position adjusting mechanism 10. The housing position adjusting mechanism 10 is provided with the first
Female screw 10 formed on the inner periphery of the left end of the housing H2a
a formed on the outer periphery of the right end of the second housing H2b;
The first housing H2a includes a male screw 10b screwed into the female screw 10a and a lock nut 10c screwed into the male screw 10b, and by adjusting the screwing depth of the male screw 10b into the female screw 10a. The relative position in the axial direction with respect to the second housing H2b can be adjusted. By tightening the lock nut 10c after this adjustment, it is possible to restrict the displacement of the relative position in the axial direction between the two.

The support shaft 1 has a base end 1a attached to an output shaft m of the electric motor M via a joint 1b so as to be integrally rotatable. The axis of this spindle 1 is
It is arranged on an extension of the axis of the output shaft m of the electric motor M. A part of the support shaft 1 is provided with a pair of rolling bearings 1.
2 and rotatably held by the spindle housing H1. The pair of rolling bearings 12 allow the support shaft 1 to move in the axial direction.

A soft metal 20 as a cushioning member is provided between the pair of rolling bearings 12 and the spindle housing H1.
(See FIG. 4). This soft metal 20
Is a cylindrical cored bar 20a whose inner and outer circumferences are covered with rubber 20b (see FIG. 5), and is elastically deformable in the radial direction. The soft metal 20 can absorb the vibration caused by the rotation of the support shaft 1 and suppress the generation of noise. Further, since the support shaft 1 can be tilted and eccentric with respect to the axis of the output shaft m of the electric motor M, the support shaft 1 can be smoothly rotated.

The joint 1b is cylindrical, and its upper inner periphery is press-fitted into the output shaft m of the electric motor M, and its lower inner periphery is provided with a serration through the proximal end 1a of the support shaft 1. Are fitted in such a manner that movement in the axial direction is allowed. A predetermined gap S is provided inside the joint 1b and between the end face of the output shaft m of the electric motor M and the end face of the base end 1a of the support shaft 1.
The urging member 8 is disposed at the position (see FIG. 3). The biasing member 8 is formed of a compression coil spring, and is interposed between the end face of the output shaft m of the electric motor M and the end face of the base end 1a of the support shaft 1 in a state of being elastically contracted. Therefore, the support shaft 1 is always urged by the urging member 8 in the direction of the second bevel gear 4 together with the first bevel gear 2. Since the urging member 8 is interposed between the support shaft 1 and the output shaft m as described above, the arrangement of the urging member 8 is simplified. That is, when the one end of the urging member 8 is received on the fixed side such as the spindle housing H1, a thrust bearing for allowing relative rotation between the one end and the fixed side is required. Although the structure of the device becomes complicated, if the urging member 8 is interposed between the support shaft 1 and the output shaft m, both of which are on the rotating side, as described above, the thrust bearing is unnecessary, and accordingly, The structure of the device can be simplified.

The rack shaft 3 is held by the first housing H2a and the second housing H2b so as to be linearly movable in the axial direction. Both ends of the rack shaft 3 are connected to steered wheels (not shown) via ball joints 16, and the steered wheels can be steered by the linear movement. On the right end side of the rack shaft 3 in the drawing, a rack gear constituting a part of the rack and pinion mechanism 9 is formed.

The second bevel gear 4 is fitted and attached to the outer periphery of the rotating body 5, and in this state, rotation with respect to the rotating body 5 and movement in the axial direction are restricted. The axis of the second bevel gear 4 coincides with the axis of the rack shaft 3, and the first bevel gear 2 is moved along the axial direction with respect to the teeth of the second bevel gear 4. Freely meshed. The first bevel gear 2 is formed integrally with the tip of the support shaft 1.

The rotating body 5 is fitted on the outer periphery of the rack shaft 3 with a gap, and the right end thereof is a first rolling bearing 13.
And the left end is rotatably supported by the second housing H2b via the second rolling bearing 14. The first rolling bearing 13 is constituted by a ball bearing,
The rotating body 5 is held while the rotating body 5 is allowed to move in the axial direction. In addition, the second rolling bearing 14
Is also constituted by a ball bearing, and the inner ring is also used by the rotating body 5. The relative movement in the axial direction between the outer ring 14a of the second rolling bearing 14 and the second housing H2b is restricted. Therefore, when the second housing H2b is moved in the axial direction of the rack shaft 3, the rotating body 5 can be moved in the axial direction, and the second bevel gear 4 is moved in the axial direction along with this movement. be able to.

The ball screw 6 is provided between the rotating body 5 and the rack shaft 3, and converts the rotation of the rotating body 5 into a linear motion of the rack shaft 3. The rack and pinion mechanism 9 includes a steering shaft 9a that is rotationally driven by a steering wheel (not shown), a pinion gear connected to the steering shaft 9a, and a rack gear that is meshed with the pinion gear and formed on the rack shaft 3. Yes,
The rack shaft 3 can be linearly moved with the rotation of the steered wheels. The rotation torque of the steering shaft 9a is detected by a torque sensor, and the electric motor M is driven by a power corresponding to the detected rotation torque to apply a steering assist force to the rack shaft 3.

In the electric power steering apparatus having the above configuration, the support shaft 1 is urged by the urging member 8 and is movable in the direction of the second bevel gear 4, so that the first bevel gear 2 is It can always be pressed against the second bevel gear 4. Therefore, at the time of assembling the device, the backlash of the meshing portion between the two bevel gears 2 and 4 can be automatically adjusted. Therefore, the adjustment of the backlash is basically unnecessary. However, depending on the assembly accuracy, the backlash adjustment allowance may be excessive and it may be necessary to use shim adjustment together, but even in this case, the backlash can be adjusted with approximate shim adjustment, making it easier to adjust It can be performed quickly.

When the first bevel gear 2 largely moves in the direction of the second bevel gear 4 to eliminate the backlash, the housing position adjusting mechanism 10
By moving and adjusting the second bevel gear 4 in the axial direction together with the second housing H2b and the rotating body 5, the amount of movement of the first bevel gear 2 can be reduced. For this reason, it is possible to prevent the power transmission efficiency from being reduced due to the fact that the meshing point between the first bevel gear 2 and the second bevel gear 4 is largely displaced from the preset meshing point. .

The electric power steering apparatus according to the present invention is not limited to the above-described embodiment. For example, a rubber sleeve portion may be used in place of the soft metal 20 as a cushioning member. Various design changes can be made, such as being interposed between the rolling bearing 1 and the rolling bearing 12. The present invention can also be applied to an electric power steering device of a type in which the axes of the first bevel gear 2 and the second bevel gear 4 intersect at an acute angle instead of a right angle.

[0025]

As described above, according to the electric power steering apparatus of the first aspect, the support shaft is urged by the urging member to press the first bevel gear against the second bevel gear. So, when assembling the device,
Adjustment of the backlash of both bevel gears is basically unnecessary. Further, even if each bevel gear is worn due to long-term use, the first bevel gear can be moved to the second bevel gear side by the biasing member by following the wear. Backlash can be prevented from occurring at the meshing portion of the. Therefore, occurrence of rattling noise can be prevented without requiring maintenance, and it is possible to prevent discomfort to a driver or a passenger due to the rattling noise for a long period of time. it can.

According to the second aspect of the present invention, since the urging member is interposed between the support shaft and the output shaft of the electric motor, the urging member can be easily arranged. According to the electric power steering apparatus of the third aspect, the vibration accompanying the rotation of the support shaft can be absorbed by the buffer member interposed between the support shaft and the housing supporting the support shaft. It is possible to suppress the generation of noise due to the above.

According to the electric power steering apparatus of the fourth aspect, the second bevel gear and the rotating body can be moved in the axial direction of the rack by the housing position adjusting mechanism. The point of engagement with the second bevel gear can be adjusted. For this reason, it is possible to prevent the power transmission efficiency of both bevel gears from decreasing.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing an urging member.

FIG. 3 is an enlarged sectional view of a main part of the preceding figure.

FIG. 4 is an enlarged sectional view showing a mounting structure of a spindle.

FIG. 5 is an enlarged sectional view showing a soft metal.

[Explanation of symbols]

 Reference Signs List 1 support shaft 2 first bevel gear 3 rack shaft 4 second bevel gear 5 rotor 6 ball screw 8 biasing member 9 rack and pinion mechanism 10 housing position adjusting mechanism 20 soft metal (buffer member) M electric motor m output shaft H housing H1 spindle housing H2 rack housing H2a first housing H2b second housing

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D033 CA04 CA05 CA22 CA23 JB03 JB17 3J009 DA03 DA11 EA06 EA16 EA23 EA32 FA08

Claims (4)

[Claims] 1. A support shaft connected to an output shaft of an electric motor so as to be integrally rotatable, a first bevel gear provided at a tip of the support shaft, and a rack shaft for turning steered wheels by linear movement. A second bevel gear meshed with the first bevel gear with their axes crossing each other, and a second bevel gear rotatably supported by a housing surrounding the rack shaft;
And a ball screw formed between the rotating body and the rack shaft, and the rotation of the electric motor is performed via the first bevel gear and the second bevel gear. An electric power steering device that assists a manual steering force for steering the steered wheels by transmitting the rack linearly by transmitting the rack to the rotating body, wherein the support shaft is movable in a second bevel gear direction. An electric power steering device, wherein the support shaft is urged in a second bevel gear direction by an urging member. 2. The electric power steering apparatus according to claim 1, wherein said urging member is interposed between said support shaft and an output shaft of said electric motor. 3. The electric power steering apparatus according to claim 1, wherein an elastically deformable cushioning member is disposed between said support shaft and a housing supporting said support shaft. 4. A first housing for supporting one end of the rotating body in a state in which relative movement in the axial direction is allowed.
And a second housing that supports the other end of the rotating body in a state where relative movement in the axial direction is restricted, and a rack axial direction of the first housing and the second housing. 2. The electric power steering apparatus according to claim 1, wherein a relative position of the power steering apparatus is adjustable by a housing position adjusting mechanism.