JP2006044571A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive electric power steering device not requiring labor for assembling. <P>SOLUTION: The electric power steering device is provided with a decelerator 17 as a transmission for transmitting power of an electric motor for steering assistance to a steering mechanism. The decelerator 17 includes a worm shaft 18 connected to an output shaft 20 of the electric motor; and a worm wheel 19 engaged with the worm shaft 18. The worm shaft 18 is elastically supported by a first support member 51 movably in an axial direction X. The first support member 51 includes first and second annular plates 61, 62 and an elastic member 63 interposed between the annular plates 61, 62. The annular plates 62, 61 corresponding to restriction parts 71, 72 extending from the respective annular plates 61, 62 are abutted on each other, thereby, a restriction mechanism R for restricting an axial direction of the worm shaft 18 is constituted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus that obtains a steering assist force by an electric motor.

A reduction gear is used in an electric power steering device for an automobile. For example, in the column type EPS, the rotation of the output shaft of the motor is decelerated through the worm shaft and the worm wheel, so that the output of the motor is amplified and transmitted to the steering mechanism, and the steering operation is torque-assisted.
The end portion of the worm shaft of the speed reducer is rotatably supported via a bearing.

2. Description of the Related Art Conventionally, there has been provided an electric power steering device that elastically supports a worm shaft in the axial direction using a support member in which a pair of annular washers are connected to each other with rubber interposed therebetween (see, for example, Patent Document 1).
JP 2002-284020 A

In the electric power steering device described above, the stepped portion of the worm shaft abuts against the end face of the bearing inner ring, thereby restricting the amount of axial movement (corresponding to the allowable amount of axial movement) of the worm shaft.
Therefore, the movable amount of the worm shaft cannot be measured unless the worm shaft, the support member, the bearing and the like are combined. Therefore, it is necessary to measure in the production line, which takes time and increases the production cost.

  The present invention has been made in view of the above problems, and an object thereof is to provide an inexpensive electric power steering apparatus that does not require time and effort for assembly.

  In order to solve the above-described problems, the present invention provides an electric motor for assisting steering, a worm shaft connected to an output shaft of the electric motor, a worm wheel meshing with the worm shaft, and an axial direction of the worm shaft. And a support member that elastically supports the worm shaft, and the support member incorporates a restriction mechanism for restricting the amount of movement of the worm shaft in the axial direction.

In the present invention, since the support member incorporates the regulation mechanism, the movable amount of the worm shaft can be measured only by the support member. Therefore, it is not necessary to measure the movable amount on the production line, and the production cost can be reduced.
According to the present invention, the support member includes a first annular plate that is received by an end face of an inner ring of a bearing that rotatably supports the worm shaft, and a second annular plate that receives a positioning step portion formed on the worm shaft. And an elastic member interposed between the first and second annular plates, and the restricting mechanism includes a restricting portion extending from at least one of the first and second annular plates and capable of contacting the other. In some cases, the restricting portion is embedded in the elastic member. In this case, since the restricting portion is embedded in the elastic member, it is possible to suppress the occurrence of abnormal noise and wear caused by the restricting portion.

  In the present invention, the restricting portion includes first and second restricting portions integrally extending from the first and second annular plates, respectively, and the first annular plate, the first restricting portion, The first unit constituted by the second unit and the second unit constituted by the second annular plate and the second restricting portion are arranged in a mutually opposite direction and are arranged in a phase shifted in the circumferential direction. It may consist of units. In this case, the manufacturing cost can be further reduced through the common use of the components in the support member.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, an electric power steering apparatus 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, an intermediate shaft 5 connected to the steering shaft 3 via a universal joint 4, and an intermediate As a steered shaft extending in the left-right direction of an automobile, having a pinion shaft 7 connected to the shaft 5 via a universal joint 6 and rack teeth 8a meshing with pinion teeth 7a provided in the vicinity of the end of the pinion shaft 7 Rack bar 8. The pinion shaft 7 and the rack bar 8 constitute a steering mechanism A including a rack and pinion mechanism.

The rack bar 8 is supported in a housing 9 fixed to the vehicle body so as to be capable of linear reciprocation through a plurality of bearings (not shown). Both end portions of the rack bar 8 protrude to both sides of the housing 9, and tie rods 10 are coupled to the respective end portions. Each tie rod 10 is connected to a corresponding wheel 11 via a corresponding knuckle arm (not shown).
When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion of the rack bar 8 along the left-right direction of the automobile by the pinion teeth 7a and the rack teeth 8a. Thereby, steering of the wheel 11 is achieved.

The steering shaft 3 is divided into an input shaft 3a connected to the steering member 2 and an output shaft 3b connected to the pinion shaft 7. These input and output shafts 3a and 3b are on the same axis line via a torsion bar 12. They are connected to each other so as to be relatively rotatable.
A torque sensor 13 is provided for detecting a steering torque based on a relative rotational displacement amount between the input and output shafts 3a and 3b via the torsion bar 12, and the torque detection result of the torque sensor 13 is an ECU (Electronic Control Unit: electronic). Control unit) 14. The ECU 14 drives and controls the steering assisting electric motor 16 via the drive circuit 15 based on a torque detection result or a vehicle speed detection result given from a vehicle speed sensor (not shown). The output rotation of the electric motor 16 is decelerated through a speed reducer 17 as a transmission device, transmitted to the output shaft 3b of the steering shaft 3, and further converted into a linear motion of the rack bar 8 through the pinion shaft 7 for steering. Is assisted.

The speed reducer 17 is a worm shaft 18 as a drive gear that is rotationally driven by the electric motor 16, and a worm wheel as a driven gear that meshes with the worm shaft 18 and is connected to the output shaft 3b of the steering shaft 3 so as to be integrally rotatable. 19 is provided.
Referring to FIG. 2, worm shaft 18 is arranged coaxially with output shaft 20 of electric motor 16. The worm shaft 18 has first and second end portions 18a and 18b that are separated from each other in the axial length direction, and has a tooth portion at an intermediate portion 18c between the first and second end portions 18a and 18b.

  The worm wheel 19 is connected to an intermediate portion in the axial direction of the output shaft 3b of the steering shaft 3 so as to be integrally rotatable and immovable in the axial direction. The worm wheel 19 includes an annular cored bar 19a coupled to the output shaft 3b so as to be integrally rotatable, and a synthetic resin member 19b surrounding the cored bar 19a and having teeth 19c formed on the outer periphery. The core metal 19a is inserted into the mold when the synthetic resin member 19b is molded with resin, for example.

A region including the tooth meshing portion B of the worm shaft 18 and the worm wheel 19 is filled with a lubricant such as grease. The first end 18a of the worm shaft 18 and the output shaft 20 of the electric motor 16 are connected to each other coaxially via a cylindrical joint 21 so that power can be transmitted.
The first and second end portions 18a and 18b of the worm shaft 18 are rotatably supported by the housing 40 of the speed reducer 17 through corresponding first and second bearings 22 and 23, respectively. The first and second bearings 22 and 23 are ball bearings, for example.

Inner rings 24 and 25 of the first and second bearings 22 and 23 are fitted to corresponding first and second end portions 18a and 18b of the worm shaft 18 so as to be integrally rotatable. First and second support members 51 and 52 for elastically supporting the worm shaft 18 in the axial direction X are disposed at the first and second end portions 18a and 18b of the worm shaft 18, respectively.
The outer ring 26 of the first bearing 22 is non-rotatably held in the bearing holding hole 27 of the housing 40 of the speed reducer 17. The outer ring 28 of the second bearing 23 is non-rotatably held in the bearing holding hole 29 of the housing 40 of the speed reducer 17.

  Further, the first bearing 22 is positioned in the axial direction of the worm shaft 18 by screwing the screw member 30 into the screw hole 31 formed continuously with the bearing holding hole 27. On the other hand, the outer ring 28 of the second bearing 23 abuts on the annular positioning portion 32 of the end wall 41 of the housing 40, whereby the worm shaft 18 is positioned in the axial direction. Thereby, as a result of setting the distance between the first and second bearings 22 and 23, the biasing force of the first and second support members 51 and 52 is adjusted. The screw member 30 after adjustment is fixed by the lock member 33.

  The first end 18 a of the worm shaft 18 and the output shaft 20 of the electric motor 16 are respectively fitted from the corresponding ends of the joint 21 and coupled to the joint 21. Specifically, the spline portion 18d provided at the first end portion 18a of the worm shaft 18 is splined to the joint 21 so as to be movable in the axial direction, while the output shaft 20 of the electric motor 16 is jointed by, for example, press fitting. Combined with

Referring to FIGS. 3 and 4 which are enlarged views, the inner rings 24 and 25 of the first and second bearings 22 and 23 are respectively connected to the corresponding first and second step portions 18e and 18f of the worm shaft 18. , Facing each other with a predetermined interval. The first and second step portions 18e and 18f are opposite to each other.
The first support member 51 is interposed between the end surface 24 a of the inner ring 24 of the first bearing 22 and the first positioning step portion 18 e of the worm shaft 18. The second support member 52 is interposed between the end face 25 a of the inner ring 25 of the second bearing 23 and the second positioning step portion 18 f of the worm shaft 18.

Referring to FIG. 3, the first support member 51 includes a first annular plate 61 made of metal received by the end face 24 a of the inner ring 24 of the first bearing 22, and a first positioning step of the worm shaft 18. A second annular plate 62 that receives the portion 18e, and an elastic member 63 including, for example, rubber, interposed between the first and second annular plates 61 and 62 are included.
Similarly, with reference to FIG. 4, the second support member 52 includes a first annular plate 61, a second annular plate 62, and an elastic member 63. The first annular plate 61 of the second support member 52 is received by the end face 25 a of the inner ring 25 of the second bearing 23, and the second annular plate 62 of the second support member 52 is the second annular plate 62 of the worm shaft 18. 2 positioning step portions 18f are received.

Referring to FIG. 3, the first annular plate 61 extends a first restricting portion 71 extending toward the second annular plate 62, and the second annular plate 62 is located on the first annular plate 61 side. A second restricting portion 72 extending in the direction is extended. The first and second restricting portions 71 and 72 are embedded in the elastic member 63.
The heights of the first and second restricting portions 71 and 72 are equal to each other, and as a result, the distance between the tip of the first restricting portion 71 and the corresponding second annular plate 62 and the second restricting portion 72. The distance between the first tip and the corresponding first annular plate 61 is equal to the distance d.

  When the worm shaft 18 moves in any one of the axial directions X, the elastic member 63 is compressed in the support member 51 or 52 corresponding to the moving direction, and the first and second annular plates 61 and 62 approach each other, When the restricting portions 71 and 72 come into contact with the corresponding annular plates 62 and 61, the movement of the worm shaft 18 in the moving direction is restricted. Therefore, the distance d corresponds to the amount of movement (allowable movement amount) of the worm shaft 18 in one and the other in the axial direction X.

A restriction mechanism R for restricting the movable amount of the worm shaft 18 in the axial direction is provided by the restricting portions 71 and 72 and the second and first annular plates 62 and 61 that are in contact with the restricting portions 71 and 72, respectively. It is configured. The restriction mechanism R is built in each support member 51 and 52.
As shown in FIG. 5, the first restricting portion 71 includes arc-shaped protrusions arranged at equal intervals in the circumferential direction C on the circumference concentric with the first annular plate 61. Similarly, the second restricting portion 72 includes arc-shaped protrusions arranged at equal intervals in the circumferential direction C on the circumference concentric with the second annular plate 62.

  As shown in FIGS. 3 and 4, in each of the support members 51 and 52, the first unit U <b> 1 including the first annular plate 61 and the first restricting portion 71, and the second annular plate 62, The second unit U2 configured with the second restricting portion 72 is disposed in the opposite direction, and uses a common unit disposed with a phase shifted in the circumferential direction C as shown in FIG. Therefore, the manufacturing cost is reduced through the common use of parts.

According to the present embodiment, since the first and second support members 51 and 52 each incorporate the restriction mechanism R, the movable amount of the worm shaft 18 is measured only by the first and second support members 51 and 52. can do. Therefore, it is not necessary to measure the movable amount on the production line, and the production cost can be reduced.
Moreover, since the 1st and 2nd control parts 71 and 72 are embed | buried in the elastic member 63, it can suppress generation | occurrence | production of the noise and wear which the 1st and 2nd control parts 71 and 72 cause. it can.

  The present invention is not limited to the above-described embodiment. For example, the first and second units U1 and U2 may have different specifications. In that case, for example, the first and second restricting portions 71 and 72 may be annular protrusions having different diameters.

It is a mimetic diagram showing a schematic structure of an electric power steering device of one embodiment of the present invention. It is sectional drawing of the principal part of an electric power steering device. It is an expanded sectional view of the important section of an electric power steering device. It is an expanded sectional view of another principal part of an electric power steering device. It is sectional drawing of a 1st supporting member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering device 2 Steering member 3 Steering shaft 5 Intermediate shaft 7 Pinion shaft 8 Rack bar 10 Tie rod 11 Wheel A Steering mechanism 16 Electric motor 17 Reduction gear (transmission device)
18 Worm shaft 18a First end portion 18b Second end portion 18c Intermediate portion 18d Spline portion 18e First positioning step portion 18f Second positioning step portion 19 Worm wheel 22 First bearing 23 Second bearing 24, 25 inner rings 24a, 25a end face 51 first support member 52 second support member 61 first annular plate 62 second annular plate 63 elastic member 71 first restricting portion 72 second restricting portion R restricting mechanism X shaft Direction C Circumferential direction U1 First unit U2 Second unit

Claims (3)

An electric motor for assisting steering;
A worm shaft connected to the output shaft of the electric motor;
A worm wheel meshing with the worm shaft and connected to the steering mechanism;
A support member that elastically supports the worm shaft so as to be movable in the axial direction;
The electric power steering apparatus according to claim 1, wherein the support member includes a restriction mechanism for restricting a movable amount of the worm shaft in the axial direction. 2. The support member according to claim 1, wherein the support member includes a first annular plate that is received by an end face of an inner ring of a bearing that rotatably supports the worm shaft, and a second annular plate that receives a positioning step portion formed on the worm shaft. An elastic member interposed between the first and second annular plates,
The regulation mechanism includes a regulation part that extends from at least one of the first and second annular plates and can abut against the other, and the regulation part is embedded in an elastic member.   In Claim 2, the said restriction | limiting part contains the 1st and 2nd restriction | limiting part integrally extended from the 1st and 2nd annular plate, respectively, and the 1st annular plate and the 1st restriction | limiting part are The first unit constituted and the second unit constituted by the second annular plate and the second restricting portion are arranged in opposite directions and are arranged in a phase-shifted manner in the circumferential direction. Electric power steering device using

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