JP2002187561A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of backlash by means of a cylinder, and facilitate the machining of a stationary member for housing a driving gear and the assembly of a biasing means. SOLUTION: A biasing means for biasing a worm 71 rotated by a steering assisting motor 6 toward a worm wheel 72 comprises the cylinder 20 having an arc recess 21 defined between an inner circumference fitted with a bearing 10 for supporting the worm 71 and an outer circumference fitted in a housing 8, and an arc deflective plate portion 22 deflectable radially inside the recess 21. An elasticity restoring force of the deflective plate portion 22 biases the worm 71 toward the worm wheel 72.

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 using a motor as a source of a steering assist force.

[0002]

2. Description of the Related Art In the steering of a motor vehicle, the steering operation of a steering wheel disposed inside a vehicle compartment is performed by turning the steering wheel (generally, a front wheel) outside the vehicle compartment for steering. This is done by telling the steering mechanism.

FIG. 6 is a sectional view of a conventional electric power steering apparatus, and FIG. 7 is a sectional view of a speed reduction mechanism.
As an electric power steering device for an automobile, FIG.
As shown in FIG. 1, for example, a first steering shaft 101 connected to a steered wheel 100 for steering, an upper end thereof is coaxially connected to a lower end of the steering shaft 101 via a torsion bar 102, and the lower end thereof is a wheel. A second steering shaft 103 connected to a steering mechanism connected to the first steering shaft 101, a torque sensor 104 that detects a torque applied to the first steering shaft 101 by rotating the steered wheels 100 by a torsion generated in the torsion bar 102, A steering assist motor 105 driven based on the detection result of the torque sensor 104;
A speed reduction mechanism having a worm 106 and a worm wheel 107 connected to the output shaft 05 and reducing the rotation of the output shaft and transmitting the rotation to the second steering shaft 103. The operation of the mechanism is
It is configured to assist by the rotation of 5, and to reduce the labor burden on the driver for steering.

The worm 106 constituting the speed reduction mechanism is supported by a fitting hole of a housing 110 via a pair of rolling bearings 108, 108 as shown in FIG. The shaft 103 is shown in FIG.
As shown in (1), it is supported by a fitting hole of the housing 110 via a pair of rolling bearings 109, 109, and is prevented from moving in the radial direction and the axial direction.

When the speed reduction mechanism is used as described above, the distance between the rotation centers of the worm 106 and the worm wheel 107 and the distance between the rotation bearings 108 and 109 are reduced in order to reduce the amount of backlash at the meshing portion between the worm 106 and the worm wheel 107. Worm 1 processed so that the center-to-center distance of the fitting hole into which the hole is fitted matches within an allowable range.
06, worm wheel 107, rolling bearing 108, 1
09, the second steering shaft 103, and the housing 110 are selected and assembled, but this assembly requires a lot of time, and the wear of the teeth of the worm 106 and the worm wheel 107 increases. The amount of rush has increased, and improvements have been requested.

Accordingly, as described in Japanese Patent Application Laid-Open No. 2000-43939, a motor-side shaft is rotatably supported by a housing via a rolling bearing, and a shaft opposite to the worm motor is movable in a radial direction. A spring body for urging the bearing through a pressing body abutting on a peripheral surface of the bearing fitted to the shaft portion and applying a preload to a meshing portion of the worm with the worm wheel; There has been proposed an electric power steering apparatus in which the distance between the rotation centers is adjusted by adjusting the amount, and the amount of backlash can be adjusted.

[0007]

However, in the transmission power steering apparatus in which the distance between the rotation centers is adjusted by using the pressing body and the spring body as described above,
Since it is necessary to form a mounting hole perpendicular to the axis of the worm in the housing in which the worm is housed, the workability of the housing is deteriorated, and the number of parts of the biasing means is increased. The workability of assembling the biasing means is deteriorated, and improvement has been demanded.

The present invention has been made in view of such circumstances, and is provided between an inner peripheral surface on which a bearing for supporting a driving gear is fitted and an outer peripheral surface fitted on a stationary member. By using a cylindrical body having an arc-shaped concave portion and an arc-shaped flexible plate portion that can be bent radially inward of the concave portion, the drive gear is biased in the direction of the driven gear,
The amount of backlash can be reduced,
It is an object of the present invention to provide an electric power steering device capable of improving workability of a stationary member for accommodating a drive gear and assembling work of a biasing means.

The recess is opened to one end of the cylindrical portion,
An object of the present invention is to provide an electric power steering device in which a tubular body can be easily formed by molding by forming an annular shape closed at the other end, and the cost of the biasing means can be reduced.

Further, by forming the cylindrical body having an arc-shaped flexible plate portion which can be bent radially outside the concave portion, the amount of bending of the flexible plate portion can be reduced without reducing the thickness of the flexible plate portion. It is an object of the present invention to provide an electric power steering device capable of reducing the elastic restoring force against the power steering.

Further, the fitting portion into which the cylindrical body is fitted is formed as a through-hole penetrating in the axial direction of the worm, and the cylindrical body is closed at one end with respect to the recess. It is an object of the present invention to provide an electric power steering device that can be easily assembled into a fitting portion and can close one end of the fitting portion with a cylindrical body.

[0012]

An electric power steering apparatus according to a first aspect of the present invention is supported by bearings, and has a driving gear rotated by a steering assisting motor, and meshes with the driving gear to form a steering mechanism. And a biasing means for biasing the drive gear in the direction of the driven gear, wherein the biasing means is fitted with the bearing. An arc-shaped recess provided between the inner peripheral surface and the outer peripheral surface fitted to the stationary-side member, and an arc-shaped flexible plate portion that can bend radially inward from the concave portion. It is characterized by being a cylindrical body.

In the first aspect, the drive gear can be biased in the direction of the driven gear by the flexible plate portion of the cylindrical body, so that the amount of backlash can be reduced. In addition, since the biasing means is a cylindrical body formed concentrically with the drive gear, the fitting portion into which the cylindrical body is fitted can be machined together with the accommodating portion in which the drive gear is accommodated. The body can be inserted and incorporated in the axial direction of the drive gear. Further, when the driving gear separates in the radial direction from the driven gear due to a meshing reaction force applied to the meshing portion meshed with the driven gear, the bending plate portion abuts on the outer plate portion while bending in the recess, and Since the amount of deflection of the plate portion can be limited, the drive gear can be prevented from moving beyond the allowable deviation amount, and the mesh between the worm and the worm wheel can be improved.

An electric power steering apparatus according to a second aspect of the present invention is characterized in that the recess is formed in an annular shape which is opened at one end of the cylindrical body and closed at the other end.

According to the second aspect of the present invention, the cylindrical body can be easily formed by molding, the number of components of the biasing means can be reduced to one, and the cost of the biasing means can be reduced. Can be.

An electric power steering apparatus according to a third aspect of the present invention is characterized in that the cylindrical body has an arc-shaped bending plate portion that can be bent radially outside the recess.

According to the third aspect of the present invention, since the inner flexible plate can be bent while the outer flexible plate than the recess is bent, the flexible plate can be bent without reducing the thickness of the flexible plate. The elastic restoring force with respect to the bending amount of the portion can be reduced.

According to a fourth aspect of the present invention, in the electric power steering apparatus, the stationary member has a through-hole penetrating a fitting portion with the outer peripheral surface fitted in the axial direction of the drive gear. Is characterized in that the inside of the recess is closed at one end.

According to a fourth aspect of the present invention, one end of the fitting portion is closed by the cylindrical body by fitting the outer peripheral surface of the cylindrical body into a fitting portion penetrating in the axial direction of the drive gear. In other words, since the cylindrical body also serves as the lid member of the storage section, the number of parts and the cost can be reduced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. Embodiment 1 FIG. 1 is a sectional view of an electric power steering apparatus according to the present invention. The electric power steering device has a first end connected to the steered wheel 1 for steering and a first end having a cylindrical portion at the other end.
And a torsion bar 3 inserted into the cylindrical portion, one end of which is coaxially connected to the other end of the steering shaft 2 and twisted by the action of steering torque applied to the steered wheels 1.
A second steering shaft 4 whose other end is coaxially connected to the other end of the torsion bar 3, and a relative rotation of the first and second steering shafts 2 and 4 according to the torsion of the torsion bar 3. A torque sensor 5 for detecting a steering torque applied to the steered wheels 1 based on the amount of displacement, a steering assist motor 6 (see FIG. 2) driven based on the torque detected by the torque sensor 5, A drive gear (hereinafter, referred to as a worm) 71 and a driven gear (hereinafter, referred to as a worm wheel), which are linked to the rotation, reduce the rotation, and transmit the reduced rotation to the second steering shaft 4.
There is provided a speed reduction mechanism 7 having a motor 72 and a housing 8 in which the torque sensor 5 and the speed reduction mechanism 7 are accommodated. The motor 6 is mounted on the housing 8.

The housing 8 includes a first housing portion 8a for housing the torque sensor 5 and a second housing portion 8b continuous with the housing portion 8a and housing the worm wheel 72.
And a third accommodating portion 8c which is continuous with the accommodating portion 8b and accommodates the worm 71.

FIG. 2 is an enlarged sectional view of the speed reduction mechanism.
The third housing portion 8c is elongated in the axial direction of the worm 71, and has a first fitting hole 81 and an annular retaining groove 82 at one end in the longitudinal direction. Also, the third storage unit 8
At the other end of c, a second fitting hole 83, an abutting portion 84 continuous with one end of the fitting hole 83, and a screw hole 85 continuous with the other end of the fitting hole 83 are provided. The screw ring 9 is screwed into the screw hole 85. The motor 6 having a case communicating with the third housing portion 8c is attached to the housing 8.

The reduction mechanism 7 has shaft portions 71a, 71b at both ends.
The shaft 71b at the other end is connected to the output shaft 60 of the motor 6.
And a worm wheel 72 fitted and fixed in the middle of the second steering shaft 4. The engagement of the worm 71 and the worm wheel 72 reduces the rotation of the output shaft 60 to reduce , And from the second steering shaft 4 via a universal joint to, for example, a rack and pinion type steering mechanism (not shown).

The worm 71 is disposed so as to intersect with the axis of the second steering shaft 4. The inner race of the first rolling bearing 10 is fitted to the shaft 71 a at one end of the worm 71. By fitting the synthetic resin tubular body 20 fixed to the outer ring into the first fitting hole 81, the shaft portion 71a at one end is rotatably supported by the first fitting hole 81, and the other. The shaft 71b at the end is connected to the second rolling bearing 11 via the second rolling bearing 11.
The screw ring 9 screwed into the screw hole 85 abuts on the outer ring of the second rolling bearing 11, and the outer ring of the rolling bearing 11 contacts the outer ring of the rolling bearing 11.
, And restricts the movement of the second rolling bearing 11 and the worm 71 in the axial direction. Also, the shaft 71 at the other end
b is spline-fitted to the inner surface of the connecting cylinder 12 and connected to the output shaft 60.

FIG. 3 is an enlarged sectional view of the worm supporting portion, and FIG. 4 is a sectional view taken along line IV-IV of FIG. The cylindrical body 20 is formed by molding a thermoplastic synthetic resin such as a relatively flexible nylon resin, polyacetal, or Teflon (registered trademark), and an inner peripheral surface on which the rolling bearing 10 is fitted and the first peripheral surface. An annular concave portion 21 provided between the outer peripheral surfaces fitted in the fitting holes 81, an annular flexible plate portion 22 that can bend radially inward from the concave portion 21, and a concave portion. It has an annular flexible plate portion 23 that can be bent more radially outward than 21 and a lid portion 24 in which one end of the flexible plate portion 22 is closed.

In the single state, the center of the inner flexible plate portion 22 is biased toward the side of biasing the worm 71 toward the point of engagement with the worm wheel 72 with respect to the center of the outer flexible plate portion 23, and The elastic restoring force is applied to the worm 71 via the rolling bearing 10, and biases the worm 71 to the point of engagement with the worm wheel 72.

The recess 21 is an annular shape which is opened at one end of the cylindrical body 20 and closed at the other end, and has a width dimension of, for example, 0.1.
mm to about 0.5 mm, preferably about 0.3 mm, and furthermore, the flexible plate portions 22, 2 formed by the recesses 21.
3 is about 0.5 mm to 2.0 mm each,
The inner flexible plate portion 22 can be bent with the bottom portion of the concave portion 21 as a fulcrum within the width dimension of 1, so that the worm 71 is biased toward the worm wheel 72 via the rolling bearing 10 by this bending. .

The thickness of the outer flexible plate 23 is made different at one end and the other end, and the thickness at the other end is made smaller than the thickness at the one end. It is bendable with respect to one end, one end is fitted in the fitting hole 81, and the other end is not fitted.

Further, a contact portion 25 for contacting the outer ring of the rolling bearing 10 is provided inside one end of the inner flexible plate portion 22, and the flange portion 7 projecting from the contact portion 25 and the shaft portion 71a is provided.
The movement of the rolling bearing 10 is prevented by 1c. The retaining ring 13 fitted in the retaining groove 82 prevents the cylindrical body 20 from being pulled out of the fitting hole 81.

When the worm 71 is incorporated in the electric power steering apparatus configured as described above, the worm 71 in which the second rolling bearing 11 is fitted is inserted from the second fitting hole 83 into the third accommodating portion 8c. Then, the second rolling bearing 11 is fitted into the second fitting hole 83, and the screw ring 9 is screwed into the screw hole 85 to support the motor-side shaft portion 71b of the worm 71 in the housing 8. And the movement of the worm 71 in the axial direction can be restricted.

Next, the inner peripheral surface of the cylindrical body 20 is fitted to the rolling bearing 10 such that the center of the inner flexible plate portion 22 is on the side of the meshing point with respect to the center of the outer flexible plate portion 22. By fitting one end of the outer flexible plate portion 23 into the fitting hole 81, the inner flexible plate portion 22 of the cylindrical body 20 bends toward the opposite side of the worm wheel 72 about the bottom of the recess 21 as a fulcrum. The worm 71 is connected to the worm wheel 7 via a rolling bearing by the elastic restoring force of the inner flexible plate portion 22.
2 can be shifted to the meshing point.

The bias of the worm 71 causes the worm 7 to move.
1 and the amount of backlash at the meshing portion of the worm wheel 72 can be reduced, and even when the meshing state changes over time due to an increase in the amount of wear of the teeth of the worm 71 and the worm wheel 72, the backlash can be reduced. The amount can be reduced. In addition, the worm 71 is moved by the worm wheel 7 due to the meshing reaction force applied to the meshing portion where the worm 71 meshes with the worm wheel 72.
When the inner flexible plate 22 is pressed so as to be spaced apart in the radial direction, the inner flexible plate 22 abuts against the outer flexible plate 23 while bending in the recess 21, and the amount of bending of the inner flexible plate 22 is reduced. Can be restricted. Therefore, it is possible to prevent the worm from moving beyond the allowable deviation amount, and it is possible to improve the engagement between the worm 71 and the worm wheel 72.

Further, since the cylindrical body 20 is formed concentrically with the worm 71, the fitting hole 8 into which the cylindrical body 20 is fitted is formed.
1 can be processed together with the third housing portion 8c in which the worm 71 is housed, and the cylindrical body 20 can be inserted in the same direction as the worm 71 to be easily assembled. Since the built-in cylinder 20 closes the first fitting hole 81, in other words, the cylinder 20 also serves as the lid member of the housing portion 8c, so that the number of parts and the cost are reduced. be able to.

After the cylindrical body has been assembled as described above, the retaining ring 13 is fitted into the retaining groove 82 so that the one end shaft of the worm 71 can be supported by the housing 8 and the rolling bearings 10 and The movement of the cylindrical body 20 in the axial direction can be restricted.

Embodiment 2 FIGS. 5A and 5B show the structure of a cylinder according to Embodiment 2; FIG. 5A is an enlarged sectional view, and FIG. 5B is a sectional view taken along line V-V in FIG. In the electric power steering apparatus according to the second embodiment, instead of using the cylindrical body 20 having the annular recess 21 as in the first embodiment, a force for biasing the worm 71 to the meshing point with the worm wheel 72 is generated. An arc-shaped concave portion 21a at a first position and a second position opposite to the first position, and arc-shaped flexible plate portions 22a and 23a that can bend radially inward and outward of the concave portion 21a. Cylindrical body 20 having
a.

In the second embodiment, the non-recessed portion of the cylindrical body 20a changes the moving direction of the rolling bearing 10 to the worm 71.
Of the worm 71 is adjusted so as to be deviated toward the meshing point with the worm wheel 72.
2 can maintain an appropriate meshing position in the axial direction.

That is, the worm 71 of the speed reduction mechanism 7 has its tooth trace twisted in the rotation direction with respect to the rotation center line,
When a rotational torque is applied from the worm 71 to the worm wheel 72, in other words, when steering is assisted by the rotation of the motor 6, a component force (engaging reaction force) is generated so that the worm 71 moves in the radial direction along the tooth trace of the worm wheel 72. ) Occurs, and the worm 71 is pressed in the radial direction by the component force. In the second embodiment, the movement direction of the rolling bearing 10 is restricted to the direction in which the recess 21a is provided, and Since the movement in the concave direction is prevented, the meshing position of the worm 71 is
Can be properly held in the axial direction of the shaft.

Since other structures and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals.
The detailed description and the description of the operation will be omitted.

In the embodiment described above, the cylinders 20 and 20a may be made of synthetic resin, or may be made of rubber or metal. Further, the cylindrical bodies 20, 20a
The recesses 21 and 21a included in the first embodiment are formed in an annular shape as in the first embodiment, or the first position where a force to bias the worm 71 toward the worm wheel 72 is generated as in the second embodiment and opposite to the first position. Besides the second position on the side,
For example, a configuration provided only at the first position may be adopted.

Further, in the above-described embodiment, the inner flexible plate portion 22 of the cylindrical body 20 is offset from the center of the outer flexible plate portion 22. However, the inner and outer flexible plate portions 22, 23, the first fitting hole 81 is deviated from the center of the second fitting hole 83, and the worm 71 is connected to the worm wheel 72 via the rolling bearing 10 by the flexible plate portion 22 of the cylindrical body 20. It may be biased in the direction.

In the embodiment described above, the rolling bearing 10 is used as a bearing for supporting the shaft portion 71a at one end of the worm 71 to the housing 8, but the bearing may be a sliding bearing.

The speed reduction mechanism 7 of the embodiment described above is a worm gear having a drive gear 71 as a worm and a driven gear 72 as a worm wheel.
A hypoid gear including a drive gear that is a hypoid pinion and a driven gear that is a hypoid wheel may be used. Further, the reduction mechanism may be a bevel gear.

[0043]

According to the first aspect of the present invention, the amount of backlash can be reduced by the cylindrical body, and the workability of the stationary member accommodating the drive gear and the workability of assembling the biasing means can be improved. Further, it is possible to prevent the drive gear from moving beyond the allowable deviation amount, and it is possible to improve the engagement between the worm and the worm wheel.

According to the second aspect, the cylindrical body can be easily formed by molding, and the cost of the biasing means can be reduced.

According to the third aspect of the present invention, since the inner flexible plate can be bent while bending the outer flexible plate than the recess, the flexible plate can be bent without reducing the thickness of the flexible plate. The elastic restoring force with respect to the amount of deflection can be reduced.

According to the fourth aspect, since one end of the fitting portion can be closed by the cylindrical body, the number of parts and the cost can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a speed reduction mechanism of the electric power steering device according to the present invention.

FIG. 3 is an enlarged sectional view of a worm support portion of the electric power steering device according to the present invention.

FIG. 4 is a sectional view taken along line IV-IV of FIG.

5A and 5B show a configuration of a cylindrical body of an electric power steering apparatus according to a second embodiment of the present invention, wherein FIG. 5A is an enlarged cross-sectional view, and FIG. 5B is a cross-sectional view taken along line VV in FIG. It is.

FIG. 6 is a sectional view of a conventional electric power steering device.

FIG. 7 is a sectional view of a speed reduction mechanism portion of a conventional electric power steering device.

[Explanation of symbols]

 Reference Signs List 6 Motor 8 Housing (stationary member) 10 Rolling bearing (bearing) 20 Cylindrical body 21 Recess 22 Inner flexure plate 23 Outer flexure plate 71 Worm (drive gear) 72 Worm wheel (driven gear) 81 Fitting part (Mating hole)

Claims (4)

[Claims] 1. A driving gear supported by bearings and rotated by a steering assist motor, a driven gear meshing with the driving gear and connected to a steering mechanism, and the driving gear moving in the direction of the driven gear. And a biasing means for biasing, the steering assisting by rotation of the motor, wherein the biasing means comprises an inner peripheral surface fitted with the bearing and an outer peripheral surface fitted to the stationary member. An electric power steering device, comprising: a cylindrical body having an arc-shaped recess provided between surfaces and an arc-shaped flexure plate portion capable of flexing radially inward of the recess. 2. The electric power steering apparatus according to claim 1, wherein the recess is formed in an annular shape that is opened at one end of the cylindrical body and closed at the other end. 3. The electric power steering apparatus according to claim 1, wherein the cylindrical body has an arc-shaped flexible plate portion that can be bent radially outside the recess. 4. The stationary-side member is a through-hole that penetrates a fitting portion to which the outer peripheral surface is fitted in the axial direction of the drive gear, and the cylindrical body is inside the concave portion at one end. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is closed.