JP2002274397A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of easily and rapidly performing the adjustment of backlash, preventing the backlash from being produced over a long period, and preventing meshed points thereof with a first bevel gear and a second bevel gear from being largely displaced from each other following the adjustment of the backlash. SOLUTION: A holding member 8 for holding an electric motor M and a pivot shaft 1 is installed inside a pivot shaft housing H1 so as to be eccentrically rotated. The holding member 8 is energized in the specified rotational direction by a spring 24 to elastically press the first bevel gear 2 against a second bevel gear 4.

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 shaft is transmitted to a rotating body surrounding the rack shaft via a second bevel gear meshed with the shaft line intersecting at an acute angle, for example, and the rotational motion of the rotating body is transmitted between the rotating body and the rack shaft. It is possible to convert to a linear motion of a rack shaft by a ball screw as a rotary motion converting mechanism provided therebetween, and the electric motor is rotationally driven in response to rotation of a steering wheel (handle) to be connected to the rack shaft. One that assists a manual steering force to steer a steered wheel that has been set is provided (for example, Japanese Patent Application Laid-Open No. H8-20779).
No. 6).

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, when assembling the apparatus, a shim is arranged on a mating surface between a cylindrical holding member for holding the spindle and a spindle housing fitted with the holding member, and the spindle and the first bevel gear are arranged. By moving the bevel gear 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 in the axial direction becomes unnecessarily large due to the shim adjustment, the meshing point of the two bevel gears is greatly shifted from the preset meshing point, and the distance between the two bevel gears is reduced. There is also a problem that the power transmission efficiency of the vehicle decreases. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can easily and quickly adjust the backlash, and can prevent backlash from occurring for a long period of time. It is an object of the present invention to provide an electric power steering device capable of preventing a meshing point of each bevel gear from being largely displaced with a lash adjustment.

[0007]

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 support shaft housing for accommodating the support shaft, a rack shaft for turning steered wheels by linear movement, a rack housing for supporting the rack shaft so as to be linearly movable, A second bevel gear meshed with the bevel gears with their axes crossing each other and rotatably supported by a rack housing in a state of surrounding the rack shaft, wherein the second bevel gear is mounted. Rotator, and a rotary motion converting mechanism for converting the rotary motion of the rotary body into a linear motion of a rack shaft. The rotation of the electric motor is controlled by the support shaft, the first bevel gear, and the second bevel gear. To the rotating body via An electric power steering device that assists a manual steering force for steering a steered wheel by linearly moving the rack, and is provided eccentrically rotatable inside the spindle housing, and the electric power steering device is provided at one end. A motor is mounted, a cylindrical holding member for holding the support shaft concentrically with the inner peripheral surface, and a biasing force for the holding member in a predetermined rotation direction to move the first bevel gear to the second bevel gear. A spring for elastically pressing the gear is provided (claim 1).

According to the electric power steering apparatus having the above-described configuration, the first bevel gear can be moved in the radial direction by rotating and eccentrically holding the holding member, whereby the first bevel gear can be moved. The bevel gear can be moved toward and away from the second bevel gear. For this reason, it is possible to adjust the backlash of the meshing portion of both bevel gears only by adjusting the position of the holding member in the rotation direction. Also,
When each bevel gear wears out due to long-term use, the holding member is gradually rotated by the urging force of the spring, and the first bevel gear follows the wear and moves to the second bevel gear side. it can. For this reason, it is possible to prevent backlash from occurring at the meshing portion of both bevel gears due to the wear. Further, since the backlash is adjusted by moving the first bevel gear in the radial direction, there is no possibility that the predetermined meshing point is shifted in the axial direction.

In the electric power steering apparatus, a first spring receiving portion having a flange shape is protruded from the holding member.
A ring-shaped second spring receiving portion is rotatably arranged so as to face the spring receiving portion, and the first spring receiving portion and the second spring receiving portion are formed by forming the spring into a C-shape. With the spring interposed therebetween, one end of the spring is locked to the first spring receiving portion, and the other end is locked to the second spring receiving portion. Preferably, the rotation is regulated (claim 2). In this case, the spring can be easily arranged in a small space, and the holding member can be rotationally biased with a simple configuration. In addition, the biasing force of the spring can be adjusted by rotating the second spring receiving portion with the backlash adjusted by rotating the holding member.

In the electric power steering apparatus, the rotation preventing ring is screwed into the spindle housing, the rotation of the rotation preventing ring is restricted by a lock nut, and the rotation preventing ring is connected to the second spring receiving portion. It is preferable that the rear surface is rotatable integrally with the rear surface via a friction member (claim 3). In this case, the rotation of the second spring receiving portion can be adjusted via the friction member by loosening the lock nut and rotating the detent ring. Further, since the relative rotation between the second spring receiving portion and the rotation preventing ring is allowed, the rotational position of the second spring receiving portion with respect to the holding member can be easily and appropriately set.

[0011]

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 apparatus 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 a 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 as a rotating motion converting mechanism formed between the rotating body 5 and the rack shaft 3, A cylindrical holding member 8 for holding the electric motor M and the support shaft 1;
The main part is constituted by.

Referring also to FIG. 2, the housing H is composed of a spindle housing H1 that houses the spindle 1 and the first bevel gear 2, and a rack housing H2 that houses the rack shaft 3 and the rotating body 5. Become. This rack housing H2
It is divided into a first housing H2a that supports the right end in the drawing of the rotating body 5 and a second housing H2b that supports the left end in the drawing of the rotating body 5. In addition,
The first housing H2a is formed integrally with the spindle housing H1. Further, the first housing H2a
And the second housing H2b are connected to each other by a screw 10.

The electric motor M is fixed to the holding member 8 with the front outer periphery M1 of the casing fitted to the opening edge 8a at the upper end of the holding member 8. The axis of the output shaft m of the electric motor M forms an acute angle with the axis of the rack shaft 3. The support shaft 1 has a base end 1a attached to the output shaft m of the electric motor M so as to be integrally rotatable. The axis of the support shaft 1 is arranged on an extension of the axis of the output shaft m of the electric motor M. An intermediate portion of the support shaft 1 is rotatably held by the holding member 8 via a pair of rolling bearings 12. Therefore, the support shaft 1 is provided concentrically with the inner periphery of the holding member 8.

The lower end of the holding member 8 is rotatably fitted in a fitting hole H1a formed in the support shaft housing H1. The axis X of the outer periphery of the holding member 8
Are eccentric with respect to the axis Y of the inner circumference. Therefore,
By rotating the holding member 8, the first bevel gear 2 can be moved in the radial direction together with the electric motor M and the support shaft 1. Further, the holding member 8 is assembled to the support shaft housing H1 so that the first bevel gear 2 can be further deviated in the direction of the second bevel gear 4 from the state shown in FIG. 1 in which the first bevel gear 2 is meshed with the second bevel gear 4. Have been. A flange-shaped first spring receiving portion 8b is protruded from an intermediate portion in the axial direction of the holding member 8, and an enlarged diameter portion 8c for attaching the electric motor M is provided at an upper end portion. . The enlarged diameter portion 8c is integrated with the main body by a screw or the like.

A second spring receiving portion 21, a friction member 22, and a detent ring 23 are arranged between the first spring receiving portion 8b and the enlarged diameter portion 8c. The second
The spring receiving portion 21 has a ring shape, and is rotatably fitted to the spindle housing H1 in a state where one side surface thereof is opposed to the first spring receiving portion 8b with a gap provided. The friction member 22 has a flat ring shape, and is held between the second spring receiving portion 21 and the detent ring 23. The friction member 22 is formed of a metal, resin, ceramic, or a composite material thereof having a large friction coefficient in order to regulate the relative rotation between the second spring receiving portion 21 and the rotation preventing ring 23.

The detent ring 23 is attached to the spindle housing H1 by screwing an external thread on the outer periphery thereof into a female thread of the spindle housing H1. The rotation of the rotation preventing ring 23 is restricted by a lock nut 25 screwed into a male screw on the outer periphery thereof.
The rotation of the spring receiving portion 21 is restricted. Further, a plurality of engagement holes 23a for engaging a tool such as a ring turning tool are formed on the back surface of the rotation preventing ring 23. A gap for inserting the tool is provided between the back surface of the rotation preventing ring 23 and the enlarged diameter portion 8c of the holding member 8. Therefore, with the lock nut 25 being loosened, the first spring receiving portion 8b is rotated via the friction member 22 by rotating the detent ring 23 by engaging a tool in the engagement hole 23a through the gap. Can be done.

A spring 24 for urging the holding member 8 to rotate is interposed between the first spring receiving portion 8b and the second spring receiving portion 21. As shown in FIG. 3, the spring 24 has a C-shape, and one end 24b thereof is locked by a locking pin 8d protruding from the first spring receiving portion 8b.
The other end 24a is locked by a locking pin 21a protruding from the second spring receiving portion 21. In this state, the holding member 8 is urged to rotate, so that the second bevel gear 2 A preload is applied in the direction of the bevel gear 4. Since the spring 24 has a C-shape and is interposed between the spring receiving portions 8b and 21 as described above, the spring 24 can be easily arranged in a small space, and the holding member 8 can be formed easily. The configuration can be rotationally biased. Further, since the second spring receiving portion 21 can be rotated with respect to the detent ring 23 in a state where the lock nut 25 is loosened, the biasing force of the spring 24 can be easily set to an appropriate value. . In addition,
Between the tip of the locking pin 8d of the spring receiving portion 8b and the second spring receiving portion 21, and between the pin 2 of the second spring receiving portion 21
1a and the first spring receiving portion 8b, when the detent ring 23 is further screwed to rotate the second spring receiving portion 21, the second spring receiving portion 21 becomes the first spring receiving portion 8b.
A gap is provided to allow access to the spring receiving portion 8b.

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 is aligned with the axis of the rack shaft 3, and the teeth of the first bevel gear 2 mesh with the teeth of the outer periphery of the second bevel gear 4. is there. 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 ball screw 6 is configured 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 driven to rotate by a steering wheel (not shown).
And a pinion gear connected to the steering shaft 9a, and a rack gear meshed with the pinion gear and formed on the rack shaft 3. The rack shaft 3 is caused to linearly move as the steered wheels rotate. Can be. 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.

When assembling the electric power steering apparatus having the above structure, the holding member 8 is eccentrically rotated in a predetermined direction, and the first bevel gear 2 is moved together with the support shaft 1 in the direction of the second bevel gear 4. By doing so, it is possible to adjust the backlash of the meshing portion between the two bevel gears 2 and 4. Accordingly, the backlash can be easily and quickly adjusted, in combination with the fact that the electric motor M does not need to be repeatedly attached to and detached from the spindle housing H1.

Further, by rotating the rotation preventing ring 23 in a predetermined direction with the backlash adjusted, a biasing force is generated in the spring 24, and the holding member 8 can be rotationally biased. Thereby, the first bevel gear 2 can be constantly pressed in the direction of the second bevel gear 4. Therefore, even if the bevel gears 2 and 4 are worn out due to long-term use, the first bevel gear 2 can be moved toward the second bevel gear 4 by following the wear. As a result,
It is possible to prevent a backlash from occurring at a meshing portion between the two bevel gears 2 and 4 for a long period of time. In addition, the urging force of the spring 24 can be adjusted only by rotating the detent ring 23, so that the adjustment is easy and the first bevel gear 2 is moved in the radial direction. Therefore, due to the fact that the meshing point between the first bevel gear 2 and the second bevel gear 4 is largely shifted in the axial direction from the meshing point set in advance,
Power transmission efficiency can be prevented from lowering.

Further, when the bevel gears 2 and 4 are worn to some extent and the urging force of the spring 24 is reduced, the lock nut 25 is loosened and the detent ring 23 is tightened to increase the second rotation. The spring 2 is rotated by rotating the spring receiving portion 21.
4 can be adjusted to an appropriate value. For this reason, it is possible to prevent backlash from occurring for a longer period of time.

The electric power steering apparatus according to the present invention is not limited to the above-described embodiment. For example, the spring 24 is constituted by a torsion coil spring, and the rotation of the rotating body 5 is changed to the linear movement of the rack shaft 3. Various design changes can be made, such as using a bearing screw instead of the ball screw 6 as the rotating motion conversion mechanism for conversion. Further, the electric power steering device of the present invention
The present invention can also be applied to an electric power steering apparatus of a type in which the axes of the first bevel gear 2 and the second bevel gear 4 intersect at right angles rather than at acute angles.

[0026]

As described above, according to the electric power steering apparatus of the first aspect, it is possible to adjust the backlash of the meshing portion of the two bevel gears only by adjusting the position of the holding member in the rotational direction. Therefore, the conventional shim adjustment is unnecessary, and the backlash can be easily and quickly adjusted. Also, the first bevel gear can be moved to the second bevel gear side by following the wear of each bevel gear, so that the backlash occurs at the meshing portion of both bevel gears due to the wear. Can be prevented. For this reason, generation of rattling noise can be prevented without requiring maintenance for a long period of time. In addition, since the backlash is adjusted by moving the first bevel gear in the radial direction, there is no possibility that a preset mesh point shifts. For this reason, it is possible to prevent the power transmission efficiency of both bevel gears from decreasing.

According to the electric power steering apparatus of the second aspect, the spring can be easily arranged in a small space, and the holding member can be rotationally biased with a simple structure. In addition, when the bevel gears wear to some extent and the biasing force of the springs decreases, the biasing force of the springs can be adjusted to an appropriate value by rotating the second spring receiving portion. Rush can be prevented from occurring for a longer period of time.

According to the electric power steering apparatus of the third aspect, by rotating the detent ring,
Since the rotation of the second spring receiving portion can be adjusted via the friction member, the adjustment is easy. Further, since the relative rotation between the second spring receiving portion and the rotation preventing ring can be allowed, the rotational position of the second spring receiving portion with respect to the holding member can be easily and appropriately set.

[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 of a main part of the preceding figure.

FIG. 3 is an exploded perspective view of a spring portion.

[Explanation of symbols]

 Reference Signs List 1 support shaft 2 first bevel gear 3 rack shaft 4 second bevel gear 5 rotator 6 ball screw (rotational motion conversion mechanism) 8 holding member 8b first spring receiving part 9 rack and pinion mechanism 21 second spring receiver Part 22 Friction member 23 Detent ring 24 Spring M Electric motor m Output shaft H1 Support shaft housing H2 Rack housing

Claims (3)

[Claims] A support shaft connected to an output shaft of the electric motor so as to be integrally rotatable; a first bevel gear provided at a tip of the support shaft; a support shaft housing for accommodating the support shaft; A rack shaft that steers the steered wheels by moving, a rack housing that supports the rack shaft so as to be able to move linearly, and a second gear that is meshed with the first bevel gear in a state where the axes cross each other. A bevel gear, a rotating body rotatably supported by the rack housing in a state of surrounding the rack shaft, and having the second bevel gear attached thereto, and converting the rotational movement of the rotating body into a linear movement of the rack shaft. A rotating motion converting mechanism, and transmitting the rotation of the electric motor to the rotating body via the support shaft, the first bevel gear and the second bevel gear, thereby linearly moving the rack, and Assists manual steering force to steer That in the electric power steering apparatus, eccentric rotatably provided inside the support shaft housing,
A cylindrical holding member for holding the spindle coaxially with an inner peripheral surface while attaching the electric motor to one end, and urging the holding member in a predetermined rotation direction to rotate the first bevel gear. An electric power steering apparatus, comprising: a spring that elastically presses the second bevel gear. 2. A flange-shaped first spring receiving portion is protrudingly provided on the holding member, and a ring-shaped second spring receiving portion is rotatably arranged opposite to the first spring receiving portion. Along with
The first spring receiving portion and the second spring having a C-shape;
And the other end of the spring is fixed to the first spring receiving portion and the other end of the spring is fixed to the second spring receiving portion. 2. The electric power steering apparatus according to claim 1, wherein the rotation of the second spring receiving portion is restricted by a detent ring. 3. The rotation preventing ring is screwed into a spindle housing, and its rotation is regulated by a lock nut. The rotation preventing ring is integrally rotated on the back surface of the second spring receiving portion via a friction member. 3. The electric power steering device according to claim 2, wherein the electric power steering device is adapted to be as possible.