JP2005035346A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of accurately adjusting backlash without reducing power transmission efficiency of a motor. <P>SOLUTION: The electric power steering device is provided with: a worm wheel connected to a steering shaft; and a worm shaft fixed to a rotation shaft of the motor and engaged with the worm wheel. In the electric power steering device, steering operation force of a driver is assisted by driving force of the motor. There are provided: a worm shaft side housing supporting the worm shaft and the motor; first and second housings for clamping the worm shaft side housing in an axial direction of the worm wheel and supporting the worm wheel by at least one housing; and a backlash adjustment mechanism for relatively moving the worm shaft side housing against the first and second housings and adjusting the inter-axis distance of the worm shaft and the worm wheel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of an electric power steering apparatus having a backlash adjusting mechanism for adjusting the meshing between the worm shaft and the worm gear.
[0002]
[Prior art]
As this type of prior art, there is known an electric power steering device including an adjustment mechanism 8 that moves a tip side of a worm shaft 1 supported by a ball bearing 3 by a small amount (for example, see Patent Document 1). .
[0003]
[Patent Document 1]
JP 2002-266987 A.
[0004]
[Problems to be solved by the invention]
However, in the above prior art, since the worm shaft 1 is configured to rotate around the motor 4 side, there is a difference in the distance from the worm wheel 2 at both ends of the worm shaft 1. Therefore, there is a problem that the backlash on the motor 4 side of the worm shaft 1 cannot be adjusted with high accuracy.
[0005]
Further, since it is necessary to provide a power transmission joint structure (cylindrical inner diameter spline 45 and outer diameter spline 15) that allows the movement of the worm shaft 1 between the motor 4 and the worm shaft 1, there is a loss of power transmission. There was a problem that occurred.
[0006]
The present invention has been made paying attention to the above-mentioned problems, and an object of the present invention is to provide an electric power steering device capable of accurately adjusting backlash without accompanying reduction in power transmission efficiency of the motor. It is in.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention includes a worm wheel coupled to a steering shaft and a worm shaft fixed to a rotating shaft of a motor and meshing with the worm wheel. In the electric power steering device for assisting an operating force, a worm shaft side housing that supports the worm shaft and the motor, a worm shaft side housing sandwiched in the axial direction of the worm wheel, and at least one of the first and the worm wheel supporting the worm wheel A second housing and a backlash adjusting mechanism for adjusting a distance between the worm shaft and the worm wheel by moving the worm shaft side housing relative to the first and second housings are provided. And
[0008]
Therefore, in the electric power steering device of the present invention, the backlash can be adjusted without changing the axial direction of the worm shaft and the rotating shaft of the motor because the worm shaft and the motor always move together during the backlash adjustment. , It is possible to avoid a decrease in power transmission efficiency. In addition, the worm shaft side housing can be moved in any direction orthogonal to the axis of the worm wheel, so the worm shaft can be moved in the inter-axis distance direction with the worm wheel, and the backlash can be adjusted with high accuracy. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment for realizing an electric power steering apparatus of the present invention will be described based on a first example.
[0010]
(First embodiment)
FIG. 1 is a longitudinal sectional view showing an electric power steering apparatus according to a first embodiment, and FIG. 2 is a plan view of the electric power steering apparatus.
The electric power steering apparatus includes three housings: an input shaft side housing (first housing) 1, an output shaft side housing (second housing) 2, and a worm shaft side housing 3.
[0011]
The input shaft side housing 1 accommodates an input shaft 4 connected to a steering shaft (not shown), a torque sensor 5 and a sensor substrate 6. The input shaft 4 is fitted into a through hole 1 a formed in the center of the input shaft side housing 1 via a bush 7. A gap between the input shaft 4 and the through hole 1a is sealed with a dust seal 8. A torsion bar 9 is provided inside the input shaft 4.
[0012]
The output shaft side housing 2 accommodates an output shaft 10 and a steering gear 11. The output shaft 10 is supported by the output shaft side housing 2 via a bearing 10b, and the torsion bar 9 is serrated. As a result, the output shaft 10 is elastically rotated relative to the input shaft 4 according to the steering torque. Further, the output shaft 10 is formed with a pinion 10 a that meshes with a rack 11 a formed on the steering gear 11.
[0013]
The worm shaft side housing 3 accommodates a worm shaft 12 and an electric motor 13. Further, an opening 3 a for arranging the worm wheel 14 is formed in the central portion of the worm shaft side housing 3. The free end side of the worm shaft 12 is rotatably supported by a bearing 12 a provided in the worm shaft side housing 3.
[0014]
Bolt holes 15 a to 15 c for bolting the three housings 1 to 3 are formed in the input shaft side housing 1 and the output shaft side housing 2. The worm shaft side housing 3 is also formed with bolt insertion holes 16a and 16b and eccentric cam insertion holes 16c at positions corresponding to the bolt holes 15a to 15c, respectively, but these bolt insertion holes 16a and 16b and eccentricity are formed. The cam insertion hole 16c is set to have a larger diameter than the bolt holes 15a to 15c.
[0015]
That is, when the housing is assembled, the position of the worm shaft side housing 3 in the direction perpendicular to the axis can be slightly adjusted with respect to the other two housings 1 and 2. At this time, the opening 3 a formed in the worm shaft side housing 3 is set to a size that does not interfere with the worm wheel 14.
[0016]
The bolt hole 15c and the eccentric cam insertion hole 16c are formed at positions facing the worm shaft 12 with the worm wheel 14 interposed therebetween. A cam shaft 17 as shown in FIG. 3 is inserted through the bolt hole 15c and the eccentric cam insertion hole 16c.
[0017]
The cam shaft 17 has two circular eccentric cams 18 that are eccentric by Δx with respect to the axis of the cam shaft 17. Further, male screw portions 17a and 17a are formed at both ends of the cam shaft 17, and a rack portion 17b is formed at the center in the vertical direction.
[0018]
An adjustment bolt (adjustment portion) 19 that meshes with the rack portion 17 b of the cam shaft 17 passes through the worm shaft side housing 3. The adjusting bolt 19 is provided with a bolt head 19a that can be turned by hand. The adjustment shaft 19 and the cam shaft 17 having the eccentric cam 18 constitute a backlash adjustment mechanism. The adjustment bolt 19 is fixed by the nut 20 after the backlash adjustment.
[0019]
Next, the operation will be described.
[Adjustment of backlash during housing assembly]
When assembling the three housings, first, the positions of the bolt holes 15a and 15b of the input shaft side housing 1 are temporarily fixed with bolts and nuts, and the cam shaft 17 is inserted into the bolt hole 15c (eccentric cam insertion hole 16c). Temporarily secure the top and bottom with nuts. At this time, the input shaft side housing 1 and the output shaft side housing 2 are aligned by the two bolts and the cam shaft 17. Incidentally, as shown in FIG. 2, center distance L between the axis _{O 2} of the axis _{O 1} and the worm shaft 12 of the worm wheel 14 is _{L 0.}
[0020]
Subsequently, when the bolt head 19a of the adjustment bolt 19 is manually turned, the cam shaft 17 is rotated by the rotation of the bolt head 19a, whereby the worm shaft side housing 3 is moved relative to the input shaft side housing 1 and the output shaft side housing 2. It rotates around the cam shaft 17 while keeping the direction constant, that is, keeping the direction of the inter-axis distance L constant.
[0021]
FIG. 4 shows a state where the camshaft 17 is rotated 90 ° clockwise from FIG. 2 from the state shown in FIG. At this time, the distance L between the worm wheel 14 and the worm shaft 12 is:
L = L ₀ + Δx
It has become. Further, the worm shaft 12 is moved to the free end side by Δx from the state of FIG.
[0022]
When the camshaft 17 is rotated 90 degrees clockwise in FIG. 4 from the state of FIG. 4, the state of FIG. 5 is obtained. At this time, the distance L between the worm wheel 14 and the worm shaft 12 is:
L = L ₀ + 2 × Δx
It has become. Further, the worm shaft 12 has moved by Δx toward the electric motor 13 from the state shown in FIG.
[0023]
That is, the backlash between the worm wheel 14 and the worm shaft 12 can be adjusted within a range of 2 × Δx while the adjustment bolt 19 is turned manually to rotate the cam shaft 17 by 180 °.
[0024]
After the adjustment of the backlash, the rotation of the adjusting bolt 19 is locked by the nut 20 and the three temporarily fixed housings are fastened by bolts and nuts. Since the threaded portion of the adjustment bolt 19 and the cam shaft 17 are engaged with each other by the rack portion 17b, it is impossible to rotate the adjustment bolt 19 from the rack portion 17b side. Therefore, by fixing the rotation of the adjusting bolt 19, even when an external force is input to the worm shaft 12 from the input shaft 4 or the output shaft 10 side, the worm shaft side housing 3 is connected to the input shaft side housing 1 and the output shaft side. There is no relative movement with respect to the housing 2.
[0025]
Next, the effect will be described.
In the electric power steering apparatus according to the first embodiment, the following effects can be obtained.
[0026]
(1) At the time of backlash adjustment, since the direction of the inter-axis distance L between the worm shaft 12 and the worm wheel 14 is always constant, the backlash can be adjusted with high accuracy and no meshing abnormality occurs. Further, since the worm shaft 12 and the electric motor 13 are both supported by the worm shaft side housing 3 and move integrally, the rotating shaft of the electric motor 13 and the axis O ₂ of the worm shaft 12 always coincide with each other. The power transmission efficiency of the electric motor 13 does not decrease with the backlash adjustment (corresponding to claim 1).
[0027]
(2) The input shaft side housing 1, the output shaft side housing 2, and the worm shaft side housing 3 are connected by a cam shaft 17 (eccentric cam mechanism) having an eccentric cam 18, and the adjustment bolt 19 is used to connect the worm shaft side housing. Since the adjustment is always possible from the outside of 3, the backlash can be accurately adjusted with a simple configuration (corresponding to claim 2).
[0028]
(3) Since the backlash adjustment mechanism can absorb the dimensional error and assembly error of each part, the machining accuracy of the worm wheel 14 and the worm shaft 12 and the assembly accuracy of the three housings can be roughened, and the cost can be reduced.
[0029]
(4) The rack portion 17b is formed on the cam shaft 17 and the operator manually rotates the adjusting bolt 19 that meshes with the rack portion 17b, whereby the eccentric cam 18 is rotated and the space between the worm wheel 14 and the worm shaft 12 is increased. Since the distance L is adjusted, the backlash can be adjusted more finely.
[0030]
(5) Since the adjustment bolt 19 cannot be rotated from the cam shaft 17 side, when an external force is input to the worm shaft 12 from the input shaft 4 or the output shaft 10 side, the cam shaft 17 rotates and the worm shaft 12 And the relative position of the worm gear 14 can be reliably prevented from shifting.
[0031]
(6) Since the input shaft side housing 1, the output shaft side housing 2, and the worm shaft side housing 3 are separately provided and fastened with bolts, the respective housings are integrated after the parts are assembled to each housing. be able to. Therefore, it is easy to assemble parts to each housing (for example, assembling the torque sensor 5 to the input shaft side housing 1).
[0032]
(7) Since the camshaft 17 has the three functions of fixing the three housings, aligning the input shaft side housing 1 and the output shaft side housing 2, and adjusting the backlash, the fixing member of the three housings Compared with the case where the backlash adjusting member is provided separately, the number of parts is small, which is advantageous in terms of cost.
[0033]
Further, technical ideas other than the claims that can be grasped from the first embodiment will be described together with the effects thereof.
[0034]
(A) In the electric power steering apparatus according to claim 1 or 2,
An electric power steering apparatus, wherein the backlash adjusting mechanism is disposed at a position facing a worm shaft with a worm wheel interposed therebetween.
[0035]
With this configuration, the motor does not get in the way during backlash adjustment, which is advantageous in terms of workability.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an electric power steering apparatus according to a first embodiment.
FIG. 2 is a plan view of the electric power steering apparatus.
FIG. 3 is a side view showing an eccentric cam.
FIG. 4 is a plan view of an essential part of the electric power steering apparatus showing the operation of the first embodiment.
FIG. 5 is a plan view of an essential part of the electric power steering apparatus showing the operation of the first embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Input shaft side housing 1a Through-hole 2 Output shaft side housing 3 Worm shaft side housing 3a Opening part 4 Input shaft 5 Torque sensor 6 Sensor board 7 Bush 8 Dust seal 9 Torsion bar 10 Output shaft 10a Pinion 10b Bearing 11 Steering gear 11a Rack 12 Worm shaft 12a Bearing 13 Electric motor 14 Worm wheel 15a-15c Bolt hole 16a, 16b Bolt insertion hole 16c Eccentric cam insertion hole 17 Cam shaft 17a Male thread portion 17b Rack portion 18 Eccentric cam 19 Adjustment bolt 19a Bolt head 20 Nut

Claims (2)

In an electric power steering apparatus comprising a worm wheel coupled to a steering shaft and a worm shaft fixed to a rotating shaft of a motor and meshing with the worm wheel, and assisting a steering operation force of a driver by a driving force of the motor,
A worm shaft side housing for supporting the worm shaft and the motor;
First and second housings sandwiching the worm shaft side housing in the axial direction of the worm wheel and supporting the worm wheel at least on one side;
A backlash adjusting mechanism that moves the worm shaft side housing relative to the first and second housings to adjust a distance between the worm shaft and the worm wheel;
An electric power steering device characterized by comprising: The electric power steering apparatus according to claim 1, wherein
The backlash adjusting mechanism is
An eccentric cam connecting the first and second housings and the worm shaft side housing;
An adjustment unit for adjusting the rotation angle of the eccentric cam;
An electric power steering apparatus comprising:

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