JP2001334946A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily absorb the fluctuation of a reverse input load inputted from a steering wheel to a steering shaft as kickback and surely transmit the output of a motor from the tooth of an annular tooth body to the tooth of a fitting body even when an elastic body for absorbing the fluctuation of the reverse input load is broken. SOLUTION: A driven gear 9 to which the output of a steering auxiliary motor is transmitted from a drive gear 8 comprises the annular tooth body 91 and the fitting body 92 fitted to the inside of the annular tooth body 91. The annular tooth body 91 and the fitting body 92 are provided with mutually meshing teeth 91a and 92b, respectively, and the elastic body 19 is provided between both the teeth 91a and 92b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric 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 schematic diagram showing a layout configuration of a conventional electric steering device. As an electric steering device for a vehicle, for example, as shown in FIG. 6, a first steering shaft 101 connected to a steered wheel 100 for steering, and the steering shaft 1
01 and a second steering shaft 103 connected via a torsion bar 102, and a torque sensor 1 for detecting a torque applied to the first steering shaft 101 by rotating the steered wheels 100 by a torsion generated in the torsion bar 102.
04 and a control unit 1 that drives and controls a steering assist motor 105 based on the torque detected by the torque sensor 104.
06, a reduction mechanism having a worm 107 and a worm wheel 108 connected to the output shaft of the motor 105 and reducing the rotation of the output shaft and transmitting the rotation to the second steering shaft 103; 10
9, a pinion shaft 110 connected to the second steering shaft 103 and rack teeth meshing with the pinion are provided, and steering mechanisms 112, 1 are provided on left and right steering wheels 111, 111.
And a rack shaft 113 that is connected to the rack shaft 113 through the rack shaft 113.

Then, a steering operation force due to the rotation of the steered wheels 100 is transmitted to the rack shaft 113 via the first steering shaft 101, the torsion bar 102, and the pinion shaft 110,
The rack shaft 113 is moved in the axial direction, and the steering mechanism 11 is moved.
2, 112, and the steering mechanism 112,
The operation of 112 is assisted by the rotation of the motor 105,
It is configured to reduce the burden on the driver for steering.

The worm 107 constituting the speed reduction mechanism is disposed so as to intersect with the axis of the second steering shaft 103, and the worm wheel 108 is formed in an annular disk shape, or It is formed in a structure including an annular tooth body having teeth meshing with the worm 107 and a fitting body fitted on the inner peripheral surface of the annular tooth body, and is attached to the second steering shaft 103. The output shaft, the speed reduction mechanism, and the steering shaft 103 are directly connected.

FIG. 7 is a sectional view of a worm wheel portion of another electric steering device, and FIG. 8 is a side view of the worm wheel. The worm wheel 120 of the speed reduction mechanism has an annular tooth body 123 having teeth 121 meshing with the worm, as described in Japanese Patent Application Laid-Open No. 9-2297, and a sleeve 122 fitted and fixed on the inner periphery thereof. The sleeve 122
A diameter-reduced ring 124 having a split groove and fitted to the inner periphery of the shaft so as to allow relative rotation, an outer periphery of an inner ring 126 fitted and fixed to an outer periphery of the steering shaft 125, and an inner periphery of the reduced-diameter ring 124. An elastic ring 128 having a plurality of through holes 127 spaced apart in the circumferential direction and having a plurality of through holes 127, and configured to transmit rotational torque between the annular tooth body 123 and the steering shaft 125;

When the rotational torque becomes excessive, the elastic ring 128 is torsionally deformed by the rotational torque, and the diameter of the elastic ring 128 is reduced together with the diameter of the elastic ring 128 due to the torsion. Reducing ring 124 and sleeve 1
The frictional resistance between the outer ring 22 and the outer ring 22 is reduced, and the reduced diameter ring 124 and the annular tooth body 123 rotate relative to each other, causing the output shaft of the motor to idle.

[0008]

However, in the former electric steering apparatus constructed as described above, the motor 1
Since the output shaft 05, the deceleration mechanism, and the steering shaft 103 are directly connected, when the steered wheel 111 runs over the uneven portion on an unmaintained road or the like, a general steering operation force regardless of the rotation of the steered wheel 100 is applied. As a kickback, a reverse input load is input from the steered wheels 111 to the steering shaft 103, giving an unpleasant feeling to the driver.

That is, when the steering wheel 111 rides on the uneven portion, the rack shaft 113 moves in the axial direction, and the torsion bar 102 moves through the pinion shaft 110 and the steering shaft 103.
The torque sensor 104 detects the torsion of the torsion bar 102, the motor 105 is driven by a command from the control unit 106, and the rotation transmitted from the motor 105 to the steering shaft 103 via the speed reduction mechanism. The torque fluctuates instantaneously, and the fluctuation of the rotation torque
03, 101 to the steered wheels 100, giving the driver an unpleasant feeling.

Further, when assisting the operation of the steering mechanism 112 which operates by the rotation of the steering wheel 100, the motor 105
Therefore, a sudden rise in torque when a large steering assist force is suddenly applied to the worm 107 cannot be alleviated, which gives an unpleasant feeling to the driver.

In the latter electric steering device,
Since the elastic ring 128 is provided between the annular teeth 123 meshing with the worm and the steering shaft 125, the rotational torque transmitted from the motor to the steering shaft 125 via the speed reduction mechanism fluctuates instantaneously as described above. In this case, the fluctuation of the rotation torque can be absorbed by the elastic ring 128, but the elastic ring
28, the frictional resistance between the diameter reducing ring 124 and the sleeve 122 is reduced, so that the rotation torque cannot be transmitted from the motor to the steering shaft 125, and the annular tooth body 123 has a total length in the axial direction. , The elastic ring 128 bends when the gear body of the annular tooth body 123 is subjected to gear cutting or when the worm and the worm wheel 120 are assembled. There is a problem that the center of the teeth 123 is likely to be misaligned.

An object of the present invention is to provide an electric steering device which can solve the above problems.

[0013]

Means for Solving the Problems and Effects of the Invention An electric steering apparatus according to a first aspect of the present invention is a motor-driven steering apparatus comprising: a driving gear for outputting the output of a motor for assisting steering; and an annular tooth having teeth on the outside for meshing with the driving gear. In the electric steering apparatus configured to transmit the steering to a steering mechanism via a body and a driven gear having a fitting body fitted inside the annular tooth body to assist the steering, the annular tooth body and the fitting body are Are provided with teeth that can mesh with each other, and an elastic body is provided between the two teeth.

According to the first aspect of the present invention, since the output of the motor can be transmitted from the teeth of the annular teeth meshing with the driving gear to the teeth of the fitting body via the elastic body, the output from the steered wheels to the steering shaft can be obtained. Variations in the reverse input load input as kickback can be favorably absorbed by the elastic body, and the steering feeling can be stabilized. Moreover, since the teeth of the annular tooth and the teeth of the fitting body can be meshed with each other, even when the elastic body is damaged by use, the output of the motor is reliably transmitted from the teeth of the annular tooth body to the teeth of the fitting body. can do.

The electric steering apparatus according to the second invention is characterized in that the elastic body is a ring having a concave portion fitted to both teeth.

According to the second aspect of the present invention, the elastic body can be easily mounted by coating the teeth of the annular tooth body or the fitting body with an elastic material such as synthetic rubber.

An electric steering apparatus according to a third aspect of the present invention is characterized in that the tooth portion has a taper in a direction in which the fitting body is fitted to the annular tooth body.

According to the third aspect of the present invention, rattling of the annular tooth body in the axial direction can be effectively prevented by engagement of both teeth.

According to a fourth aspect of the present invention, there is provided an electric steering device, wherein one of the annular tooth body and the fitting body has a movement restricting portion for limiting movement in a direction in which the fitting body is fitted to the annular tooth body. And
It is characterized by comprising a pressing body for pressing the other of the fitting body and the annular tooth body toward the movement restricting portion.

According to the fourth aspect of the present invention, the annular tooth body and the fitting body can be easily integrated with each other by the movement restricting portion and the pressing body, so that the driven gear can be easily assembled.

According to a fifth aspect of the present invention, in the electric steering device, the movement restricting portion is circular, and the other of the fitting body and the annular tooth body is fitted on the peripheral surface of the movement restricting portion to form the elastic body. It is characterized in that it has a bending prevention portion for preventing bending in the radial direction.

According to the fifth aspect, the radial load applied to the annular tooth body can be transmitted from the deflection preventing portion and the movement restricting portion to the fitting body, so that the elastic body is not bent in the radial direction. Gear cutting can be performed on an annular tooth body without teeth, and the elastic body can be assembled without bending in the radial direction. Can be eliminated.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a schematic diagram showing a layout configuration of an electric steering device according to the present invention, and FIG. 2 is a sectional view of the electric steering device.

The electric steering apparatus has a first steering shaft 2 having an upper end connected to a steered wheel 1 for steering and a lower end having a tubular portion.
A torsion bar 3 which is inserted into the cylindrical portion and whose upper end is coaxially connected to the lower end of the steering shaft 2 and which is twisted by the action of steering torque applied to the steered wheels 1; And a second steering shaft 4 whose lower end is coaxially connected to the lower end of the torsion bar 3, and first and second steering shafts 2, 4 corresponding 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 a relative rotational displacement of the motor, a control unit 7 for driving and controlling a steering assist motor 6 based on the torque detected by the torque sensor 5, 6, a drive gear (hereinafter referred to as a worm) 8 that reduces the rotation and transmits the same to the second steering shaft 4 and a driven gear (hereinafter referred to as a worm wheel) that meshes with the worm 8.
And a housing 11 in which the torque sensor 5 and the speed reduction mechanism 10 are accommodated.
The motor 6 is mounted on the housing 11.

Further, the lower end of the second steering shaft 4 is connected to a pinion shaft 13 via a universal joint 12,
The pinion provided on the pinion shaft 13 meshes with rack teeth provided on a rack shaft 16 connected to left and right steering wheels 14, 14 via steering mechanisms 15, 15, so that the steering wheel 1
The steering operation force due to the rotation of the shaft is transmitted to the rack shaft 16, the rack shaft 16 is moved in the axial direction, and the steering mechanisms 15, 1
5, the operation of the steering mechanisms 15, 15 is assisted by the rotation of the motor 6, so that the driver's labor for steering is reduced.

FIG. 3 is an enlarged sectional view of the speed reduction mechanism, FIG. 4 is an enlarged sectional view of the worm wheel, and FIG. 5 is an exploded enlarged sectional view of the worm wheel. The worm 8 is disposed so as to intersect with the axis of the steering shaft 4, and the worm wheel 9 is disposed between first and second bearings 17 and 18 that support the steering shaft 4 in the housing 11. And
It is fitted and fixed at the middle of the steering shaft 4.

The worm wheel 9 is mounted on the worm 8
An annular tooth body 91 having a plurality of teeth 9a meshing with the annular tooth body 91, and an annular fitting body 92 fitted inside the annular tooth body 91 via an elastic body 19 are provided at the center of the fitting body 92. The drilled through hole 92a is fitted to the steering shaft 4.

The teeth 91a and 92b which can be engaged with each other are provided inside the annular tooth body 91 and outside the fitting body 92. Further, the fitting body 92 is fitted to both teeth 91a and 92b. In the direction (axial direction). At the large diameter end of the teeth 92b of the fitting body 92, a circular movement limiting portion 92c for limiting the movement of the annular tooth body 91 in the fitting direction (axial length direction) is provided over the entire circumference. Further, a flexure preventing portion 9 fitted on the peripheral surface of the movement restricting portion 92c to prevent the elastic body 19 from flexing in the radial direction.
1b is provided at the axial end of the teeth 91a of the annular tooth body 91.

The elastic body 19 is formed in a ring having a concave portion 19a fitted to each of the teeth 91a and 92b.
The elastic body 19 is formed integrally with the teeth 92b by coating the teeth 92b with an elastic material such as synthetic rubber.

The worm wheel 9 and the bearing 18
An annular pressing body 20 that presses the annular tooth body 91 toward the movement restricting portion 92c is disposed between the two, and the pressing body 20 is press-fitted and fixed to the steering shaft 4.

In the electric steering apparatus constructed as described above, the fitting body 92 having the elastic body 19 provided on the teeth 92b is fitted and fixed to the steering shaft 4 to which the first bearing 17 is press-fitted and fixed. An annular tooth body 91 having no teeth 9a is fitted to the teeth 92b of the united body 92 via the elastic body 19. At this time, tooth 9
Since the portions 1a and 92b have a taper in the fitting direction (axial direction), it is possible to favorably prevent the annular tooth body 91 from rattling in the axial direction.

When the teeth 91a and 92b are fitted, the deflection preventing portion 91b is fitted on the peripheral surface of the movement restricting portion 92c, and the radial load applied to the annular tooth body 91 moves from the bending preventing portion 91b. The elastic member 19 is transmitted to the restricting portion 92c and can be prevented from bending in the radial direction.

Then, the pressing body 20 is fitted and fixed to the steering shaft 4, and the annular tooth body 91 is moved by the pressing body 20 to the movement limiting section 9.
2c so that the annular tooth body 91 and the fitting body 92 are integrated.

As described above, the outer peripheral surface of the annular tooth body 91 is subjected to gear cutting in a state where the annular tooth body 91 and the fitting body 92 are integrated, and the teeth 9a are formed. Since the load in the radial direction at the time of the gear cutting is transmitted from the deflection preventing portion 91b to the movement restricting portion 92c as described above, the teeth 9a can be formed without causing misalignment.

After the gear teeth 91 have been subjected to gear cutting,
The steering shaft 4 into which the second bearing 18 is press-fitted and fixed is inserted into the housing 11, the steering shaft 4 is supported on the housing 11 via bearings 17, 18, and the worm 8 meshes with the worm wheel 9.

When the steering wheels 14, 14 of the motor vehicle equipped with the electric steering device are mounted on uneven roads or the like on uneven roads, the rack shaft 16 moves in the axial direction, and the pinion shaft 13 and the steering shaft are moved. 4, the torsion bar 3 is twisted. The torque sensor 5 detects the torsion of the torsion bar 3, and when the motor 6 is momentarily driven by a command from the control unit 7, in other words, kickback. When the reverse input load is input to the steering shaft 4 from the steered wheels 14 and 14 and the motor 6 performs the steering assist momentarily, the fluctuation of the rotational torque transmitted from the worm 8 to the worm wheel 9 is changed by the elastic body 19. It can absorb and stabilize the steering feeling.

In addition, since the teeth 91a and 92b of the annular tooth body 91 and the fitting body 92 can mesh with each other without providing the elastic body 19, even if the elastic body 19 is damaged by use, the motor 6 can be used. Output of the annular tooth body 91
From the teeth 91a of the fitting body 92 to the teeth 92b of the fitting body 92.

When assisting the operation of the steering mechanisms 15, 15 which are operated by the rotation of the steered wheels 1, the sudden rise of torque when a large steering assist force is suddenly applied to the worm 8 from the motor 6 is worm. Elastic body 19 of wheel 9
Therefore, the steering feeling can be stabilized and the steering feeling can be stabilized.

In the above-described embodiment, the annular elastic body 19 is provided between the teeth 91a and 92b of the annular tooth body 91 and the fitting body 92.
a, 92b may be provided only between the circumferential side surfaces. The elastic body 19 is formed by coating,
The ring-shaped member may be fitted to the teeth 91a and 92b, or may be vulcanized and bonded to the teeth 91a or 92b.

The speed reduction mechanism 10 of the embodiment described above is a worm gear provided with a drive gear 8 as a worm and a driven gear 9 as a worm wheel, and a drive gear and a hypoid wheel as a hypoid pinion. It may be a hypoid gear provided with a certain driven gear. Further, the reduction mechanism may be a bevel gear.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a layout configuration of an electric steering device according to the present invention.

FIG. 2 is a sectional view of an electric steering device according to the present invention.

FIG. 3 is an enlarged sectional view of a speed reduction mechanism portion of the electric steering device according to the present invention.

FIG. 4 is an enlarged sectional view of a worm wheel of the electric steering device according to the present invention.

FIG. 5 is an exploded enlarged sectional view of a worm wheel of the electric steering device according to the present invention.

FIG. 6 is a schematic diagram showing a layout configuration of a conventional electric steering device.

FIG. 7 is a sectional view of a worm wheel portion of another conventional electric steering device.

FIG. 8 is a side view of a worm wheel of another conventional electric steering device.

[Explanation of symbols]

 Reference Signs List 6 motor 8 drive gear (worm) 9 driven gear (worm wheel) 9a tooth 91 annular tooth body 91a tooth 91b deflection preventing section 92 fitting body 92b tooth 92c movement restricting section 19 elastic body 20 pressing body

Continued on the front page F term (reference) 3D033 CA02 CA04 3J009 DA11 DA16 EA05 EA19 EA23 EA37 EB14 FA04 FA08 3J030 AA03 AA11 BA03 BB02 BC02 BD04 5H607 AA12 BB01 CC03 EE32

Claims (5)

[Claims] 1. A driven gear comprising: a drive gear for outputting the output of a steering assist motor; an annular tooth body having teeth on the outside that mesh with the drive gear; and a fitting body fitted inside the annular tooth body. In the electric steering device, which is transmitted to the steering mechanism through and to assist the steering, the annular tooth body and the fitting body are:
An electric steering device comprising: teeth that can mesh with each other; and an elastic body provided between the two teeth. 2. The electric steering apparatus according to claim 1, wherein the elastic body is a ring having a concave portion fitted to both teeth. 3. The electric steering apparatus according to claim 1, wherein the tooth portion has a taper in a direction in which the fitting body is fitted to the annular tooth body. 4. One of the annular tooth body and the fitting body has a movement restricting portion for limiting movement in a direction in which the fitting body is fitted to the annular tooth body. The electric steering device according to any one of claims 1 to 3, further comprising a pressing body that presses the other toward the movement restriction unit. 5. The movement restricting portion is circular, and the other of the fitting body and the annular tooth body is fitted on a peripheral surface of the movement restricting portion to prevent bending of the elastic body in a radial direction. The electric steering device according to claim 4, further comprising a portion.