JP3941203B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus that applies a steering assist torque to a steering system by using the rotational force of an electric motor, and in particular, noise generated due to driving of the electric motor or the like is reduced. Is.
[0002]
[Prior art]
In an electric power steering device, the rotational force generated on the output shaft of the electric motor is often too small as a steering assist torque, and is usually transmitted to the steering system via a speed reduction mechanism that serves as a booster. It is supposed to be. As such a speed reduction mechanism, for example, a gear train composed of a worm to which the rotational force of the electric motor is input and a worm wheel fixed to the rotating shaft of the steering system so as to mesh with the worm can be applied.
[0003]
Since the rotational force of the output shaft of the electric motor needs to be transmitted to the speed reduction mechanism, the electric motor is fixed to the housing of the speed reduction mechanism with a bolt or the like so as to be disposed in the vicinity of the speed reduction mechanism. Was common.
[0004]
Further, the output shaft of the electric motor and the speed reduction mechanism are generally spline-coupled to allow some relative displacement in the axial direction.
[0005]
[Problems to be solved by the invention]
Here, in the electric power steering apparatus as described above, in order to obtain an appropriate steering force when the driver performs the steering operation, the rotational force according to the steering speed and the tire-side load at that time. However, during normal steering, the output shaft of the electric motor that inputs rotational force to the speed reduction mechanism rotates at a high speed, so that a rotating sound such as a brush sound is generated. In some cases, the driver may feel uncomfortable.
[0006]
In addition, vibration generated by the rotation of the output shaft of the electric motor is transmitted from the output shaft to the speed reduction mechanism side, and resonance occurs in components such as the speed reduction mechanism, which may cause a large noise.
[0007]
The present invention has been made paying attention to such an unsolved problem of the conventional technology, and is an electric power steering device capable of reducing noise generated due to operation of an electric motor or the like. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is directed to an electric motor that generates a rotational force on an output shaft according to a steering torque of a steering system, and the rotational force generated on the output shaft of the electric motor. An electric power steering apparatus comprising: a speed reduction mechanism for transmitting to a system; a cylindrical portion is provided coaxially with the output shaft of the electric motor, and both between the output shaft of the electric motor and the cylindrical portion. An elastic body that allows relative rotation between them is interposed, and a shaft that constitutes the speed reduction mechanism is separated from an elastic body that allows relative rotation, via an elastic body that allows sliding in the axial direction. The shaft is rotatably supported by the housing of the speed reduction mechanism, and one end of the shaft is splined to the cylindrical portion coaxially therewith .
[0011]
In the first aspect of the invention, the maximum torsion angle of the elastic body that allows relative rotation between the motor output shaft and the cylindrical portion provided on the motor output shaft is further within a predetermined angle range. It is desirable to provide a stopper for regulating the inside (claim 2).
[0012]
In the invention according to claim 1, the elastic body that allows relative rotation between the motor output shaft and the cylindrical portion provided on the motor output shaft is provided between the motor output shaft and the cylindrical portion. It is desirable to arrange them so as to allow the inclination between the axes.
[0013]
Furthermore, in the invention according to claim 1, the elastic body that allows relative rotation between the motor output shaft and the cylindrical portion provided on the motor output shaft is provided between the motor output shaft and the cylindrical portion. It is desirable to provide a stopper that restricts the maximum torsional angle of the elastic body within a predetermined angle range, while being arranged so as to allow the inclination of the axes.
[0015]
Here, in the invention according to claim 1, the vibration generated in the output shaft of the electric motor is caused by the elastic body interposed between the cylindrical portion provided in the output shaft of the electric motor and the output shaft of the electric motor. The possibility that a large amount of noise is generated due to resonance transmitted to the speed reduction mechanism side is reduced. At this time, the shaft constituting the speed reduction mechanism is rotatably supported by the housing of the speed reduction mechanism via an elastic body that allows sliding in the axial direction, and one end of the shaft is output from the electric motor. since spline-coupled coaxially with this cylindrical portion provided on the shaft, possibly noise due to the vibration generated in the output shaft direction of the electric motor occurs can be reduced.
[0016]
Furthermore, in the invention according to claim 2 , by providing the stopper, the rigidity in the rotational direction between the output shaft of the electric motor and the cylindrical portion, that is, between the output shaft of the electric motor and the speed reduction mechanism is increased. Can be secured.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partially broken front view showing an overall configuration of an electric power steering apparatus 1 to which the present invention is applied, and FIG. 2 is a cross-sectional view taken along line AA of FIG.
[0018]
First, the configuration will be described. In the steering column 2, an input shaft 3 and an output shaft 4 connected via a torsion bar (not shown) are rotatably supported by bearings, and the input shaft 3 is not shown in FIG. A steering wheel is integrally attached to the upper end side in the rotation direction, and a pinion shaft constituting a known rack and pinion type steering device is connected to the lower end side of the output shaft 4 (not shown) in FIG. ing. Accordingly, the steering torque generated when the driver steers the steering wheel is transmitted to the steered wheels (not shown) via the input shaft 3, the torsion bar, the output shaft 4, and the rack and pinion type steering device. ing.
[0019]
The steering column 2 has a built-in torque sensor that detects the steering torque generated in the steering system by detecting the relative rotation between the input shaft 3 and the output shaft 4 caused by torsion of the torsion bar. Thus, the detection result of the torque sensor is supplied to a controller (not shown). The controller executes predetermined calculation processing based on the steering torque, and appropriately supplies a drive signal to the electric motor 10 described later so that a steering assist torque that reduces the burden on the driver is applied to the steering system. It is supposed to be.
[0020]
A worm wheel 5 is coaxially fixed to the output shaft 4 so as to be integrated with the output shaft 4 in the rotational direction, and the worm 6 meshing with the worm wheel 5 is rotatably supported in the housing 7 by bearings 7a and 7b. It is supported.
[0021]
That is, the shaft 6A passes through the worm 6 so as to be integrated in the rotational direction and the axial direction, and one end of the shaft 6A is rotatably supported in the housing 7 via the bearing 7a. A position slightly inside the end is rotatably supported in the housing 7 via a bearing 7b. Note that the shaft 6A, slightly enters the part to the worm 6 side than the bearing 7a, a member 6a _1, 6a ₂ of the thin ring-shaped, between the two members 6a ₁ and 6a _2, both members 6a _1, 6a ₂ is provided with a ring-shaped rubber-like elastic body 8a vulcanized and bonded to the worm 6 side slightly from the bearing 7b, and the thin ring-shaped members 6b ₁ and 6b ₂ Between the members 6b ₁ and 6b ₂ is interposed a ring-shaped rubber-like elastic body 8b vulcanized and bonded to both members 6b ₁ and 6b ₂ . For this reason, the shaft 6A can be displaced relative to the housing 7 in the axial direction with the elastic deformation of the elastic bodies 8a and 8b.
[0022]
On the other hand, the electric motor 10 is fixed to the side of the housing 7 that is pointed to by the other end of the shaft 6A.
Here, in the electric motor 10, a flange portion 10B is formed on the outer periphery of the end portion on the side from which the output shaft 10A protrudes, and a bolt 11 penetrating the flange portion 10B is formed on the female screw portion 7c formed in the housing 7. It is fixed by screwing.
[0023]
Specifically, as shown in FIG. 3 which is a view in the direction of arrow B in FIG. 2 (a cross-sectional view with respect to the line CC in FIG. 2), the electric motor 10 is separated by 120 degrees at regular intervals in the circumferential direction. A flange portion 10B is formed at each of the three positions so as to protrude outward in the radial direction, and a through hole 10C penetrating between the front and back surfaces is formed at a substantially central portion of each flange portion 10B.
[0024]
In each through hole 10C, a mount bush 12 is provided in which a rubber-like elastic body 12B is attached to the outer peripheral surface of a metal cylindrical member 12A. The cylindrical member 12A of each mount bush 12 is formed such that its axial length is slightly longer than the thickness of the flange portion 10B. Further, the elastic body 12B of each mount bush 12 is formed to have a slightly longer dimension than the metal cylindrical member 12A, as shown in FIG. 4 which is a cross-sectional view of the state before mounting in the through hole 10C. A flange portion 12C is formed so as to sandwich the inner peripheral surface of 10C from the front and back sides, and has a U-shaped cross section.
[0025]
For this reason, the mount bush 12 is disposed in the through-hole 10C, and the elastic body 12B sandwiches the inner peripheral surface of the through-hole 10C from the front and back sides. When the screw is inserted into the female screw portion 7 c, first, the elastic body 12 B is sandwiched between the seat hook 11 A and the housing 7. When the bolt 11 is further screwed in, the elastic body 12B is compressed in the axial direction, and finally, the cylindrical member 12A is sandwiched between the seat glasses 11A and the housing 7. Then, both flange portions 12C of the elastic body 12B are sandwiched between the seat hook 11A and the flange portion 10B and between the flange portion 10B and the housing 7 in a compressed state.
[0026]
At this time, the other parts of the housing 7 and the electric motor 10 are not in contact with each other, as shown in FIG. 5 which is an enlarged view of a portion D in FIG. That is, when the bolt 11 is screwed to the end as described above and the cylindrical member 12A is sandwiched between the seat collar 11A and the housing 7, there is a gap G ₁ between the flange portion 10B and the end surface of the housing 7. Further, the outer diameter of the portion of the front end side of the output shaft 10A with respect to the flange portion 10B of the electric motor 10 is the same as that of the opening portion 7A of the housing 7 on the side where the electric motor 10 is fixed. it becomes slightly shorter than the inner diameter, thereby, between the inside opening 7A peripheral surface and the electric motor 10 the outer peripheral surface, so that the gap G ₂ is formed. In order to reliably prevent contact between the inner peripheral surface of the opening 7A and the outer peripheral surface of the electric motor 10, a circumferential groove 10D that is continuous in the circumferential direction at a portion on the distal end side of the output shaft 10A with respect to the flange portion 10B of the electric motor 10. And an O-ring 13 made of a rubber-like elastic body is accommodated in the circumferential groove 10D. That is, since the O-ring 13 is interposed between the inner surface of the opening 7A and the outer surface of the electric motor 10, the centering action of matching the axial centers of the opening 7A and the electric motor 10 by the elastic restoring force of the O-ring 13 is achieved. I try to get it.
[0027]
The output shaft 10A of the electric motor 10 located in the housing 7 and the other end portion of the shaft 6A are arranged coaxially, and both end faces are opposed to each other. When torque is applied, they are connected via a torque limiter 15 that causes slipping.
[0028]
That is, the torque limiter 15 has two disk members 15A and 15B that are capable of transmitting torque through friction when the surfaces come into contact with each other and slip when an extremely large torque is applied. have. One disk member 15A is spline-coupled to the output shaft 10A, and is thereby integrated with the output shaft 10A in the rotational direction. Further, the other disc member 15B has a cylindrical portion 15C integrally formed on its inner diameter side, and the end portion of the cylindrical portion 15C is also shown in FIG. A small-diameter cylindrical portion 15D is coaxially inserted inside, and a rubber-like elastic body 16 is vulcanized and bonded between the inner peripheral surface of the cylindrical portion 15C and the outer peripheral surface of the cylindrical portion 15D. It is fixed by. For this reason, between the cylindrical portions 15C and 15D, relative rotation is possible with elastic deformation of the elastic body 16, and the axes can be inclined.
[0029]
Further, as shown in FIG. 6 (b) which is a right side view of FIG. 6 (a), the end of the inner cylindrical portion 15D facing the inside of the housing 7 has two positions separated by 180 degrees in the circumferential direction. with notches 15a are formed in the respective, in the end portion of the same side of the outer cylindrical portion 15 C, the convex portion 15b is formed similarly directed radially inward on each of the 180 degree spaced second position in the circumferential direction And the front-end | tip part of the convex part 15b has entered into the notch 15a. The width of the convex portion 15b is slightly smaller than the width of the notch 15a, so that the relative rotation between the cylindrical portions 15C and 15D due to the elastic deformation of the elastic body 16 is within a predetermined angle range. A restricting stopper is formed. 6A corresponds to a cross-sectional view taken along line EE in FIG.
[0030]
Further, a spline is formed on the inner peripheral surface of the cylindrical portion 15D, and a spline is also formed on the outer peripheral surface of the other end portion of the shaft 6A. By connecting both the splines, the cylindrical portion 15D, the shaft 6A, etc. The end portions are coaxially integrated in the rotational direction.
[0031]
Accordingly, the rotational force generated on the output shaft 10A of the electric motor 10 is first input to the disk member 15A of the torque limiter 15, and is transmitted from there to the disk member 15B via friction, and is elastic from the cylindrical portion 15C. It is input to the cylindrical portion 15D through the body 16 and reaches the other end of the shaft 6A.
[0032]
Next, the operation of the present embodiment will be described.
Now, assuming that the steering system is in a straight traveling state and the steering torque is zero, no relative rotation occurs between the input shaft 3 and the output shaft 4, so the torque sensor does not detect the steering torque, and the steering system No steering assist torque is generated.
[0033]
On the other hand, when the steering wheel is steered and a rotational force is generated on the input shaft 3, the rotational force is transmitted to the output shaft 4 via the torsion bar. At this time, the output shaft 4 has a resistance force according to a frictional force such as a frictional force between the steered wheels and the road surface or a meshing of a gear of a rack and pinion type steering device configured on the lower end side (not shown) of the output shaft 4. Therefore, a relative rotation is generated between the input shaft 3 and the output shaft 4 and the output shaft 4 is delayed by twisting the torsion bar, and the relative rotation is detected by the torque sensor as a steering torque.
[0034]
Then, since a controller (not shown) supplies a drive current to the electric motor 10 according to the direction and magnitude of the steering torque detected by the torque sensor, the steering generated in the steering system is applied to the output shaft 10A of the electric motor 10. A rotational force is generated according to the direction and magnitude of the torque, and the rotational force is transmitted to the output shaft 4 via the torque limiter 15, the shaft 6A, the worm 6 and the worm wheel 5, and the steering assist torque is applied to the output shaft 4. Is applied, the steering torque is reduced, and the burden on the driver is reduced.
[0035]
Here, when the electric motor 10 is in a driving state, noise such as a brush sound is generated in the electric motor 10, and this is transmitted to the case of the electric motor 10. In other words, the electric motor 10 in the driving state can be considered as a noise source / vibration source, but in the present embodiment, the electric motor 10 and the housing 7 are interposed only through the elastic body 12B of the mount bush 12. Therefore, the vibration transmitted from the electric motor 10 to the housing 7 can be attenuated, and the deterioration of noise can be reduced.
[0036]
Moreover, since the mount bush 12 is provided at three positions spaced apart at equal intervals in the circumferential direction, it is possible to prevent the static posture of the electric motor 10 from becoming unstable.
In addition, since the torque limiter 15 and the shaft 6A are coupled via the elastic body 16, relative rotation between the two is permitted with the elastic deformation of the elastic body 16. Vibrations such as rotational fluctuations generated in the output shaft 10A as a result of the drive can be attenuated by the elastic body 16, and can be prevented from being transmitted to the shaft 6A side as it is. As a result, the possibility that the worm 6 and the worm wheel 5 are resonated by the vibration of the output shaft 10A and the noise and vibration level is deteriorated is reduced.
[0037]
The torque limiter 15 is provided with a notch 15a and a convex portion 15b as limiters capable of allowing relative rotation between the cylindrical portions 15D and 15C within a predetermined angle range. When the generated rotational torque exceeds a certain value, the notch portion 15a and the convex portion 15b come into contact with each other, and further relative rotation between the cylindrical portions 15D and 15C becomes impossible. Strength.
[0038]
Further, as described above, when the electric motor 10 and the housing 7 are coupled only via the elastic body 12B, the mounting angle of the electric motor 10 with respect to the housing 7 may fluctuate. Since the elastic body 16 in 15 is bent, the inclination of the shaft centers between the output shaft 10A and the shaft 6A is allowed, so that an excessive load is prevented from being applied to other members.
[0039]
Furthermore, since the shaft 6A is splined to the cylindrical portion 15D and supported by the bearings 7a and 7b via the elastic bodies 8a and 8b, the axial position thereof is variable. Then, for example, when the steering wheel is turned in one direction, for example, when the vehicle is aligned, the rotation direction of the output shaft 10A is suddenly reversed and only the backlash is generated. Although there is a concern that the tooth surfaces of the worm 6 and the worm wheel 5 that are separated from each other collide with each other, in the present embodiment, the impact force generated between the tooth surfaces between the worm 6 and the worm wheel 5 is an elastic body. 8a and 8b can be absorbed to some extent by elastic deformation, impact noise can be reduced, and noise reduction is also achieved.
[0040]
Here, in this embodiment, a steering system is constituted by the input shaft 3, the output shaft 4, the torsion bar, the rack and pinion type steering device, and the like, and the speed reduction mechanism is constituted by the worm wheel 5 and the worm 6, and the housing 7 is Corresponds to the housing of the speed reduction mechanism.
[0041]
【The invention's effect】
As described above, according to the present invention, a cylindrical portion is provided on the output shaft of the electric motor, and an elastic body that allows relative rotation between the output shaft and the cylindrical portion of the electric motor is interposed. There is an effect that noise generated due to driving of the electric motor or the like can be reduced. Further, the shaft constituting the speed reduction mechanism is rotatably supported on the housing of the speed reduction mechanism via an elastic body that allows sliding in the axial direction, and one end of the shaft is provided on the output shaft of the electric motor. By spline coupling to the cylindrical portion coaxially therewith, there is an effect that it is possible to reduce the possibility of noise being generated due to vibrations generated in the output shaft direction of the electric motor.
[Brief description of the drawings]
FIG. 1 is a partially broken front view showing an overall configuration of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
3 is a view in the direction of arrow B in FIG.
FIG. 4 is a cross-sectional view of a mount bush.
FIG. 5 is an enlarged view of a portion D in FIG. 2;
FIG. 6 is an enlarged cross-sectional view of a coupling portion between a torque limiter and a shaft.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric power steering device 3 Input shaft 4 Output shaft 5 Worm wheel 6 Worm 7 Housing (housing for reduction mechanism)
DESCRIPTION OF SYMBOLS 10 Electric motor 10A Output shaft 12 Mount bush 12B Elastic body 15 Torque limiter 16 Elastic body

Claims (2)

An electric power steering apparatus comprising: an electric motor that generates a rotational force according to a steering torque of a steering system on an output shaft; and a speed reduction mechanism that transmits the rotational force generated on the output shaft of the electric motor to the steering system. ,
A cylindrical portion is provided coaxially with the output shaft of the electric motor, and an elastic body that allows relative rotation between the output shaft and the cylindrical portion of the electric motor is interposed therebetween.
The shaft constituting the speed reduction mechanism is rotatably supported on the housing of the speed reduction mechanism via an elastic body that allows sliding in the axial direction different from the elastic body that allows the relative rotation, and An electric power steering apparatus , wherein one end of the shaft is splined to the cylindrical portion coaxially therewith. 2. The electric motor according to claim 1, further comprising a stopper for restricting a maximum torsion angle of an elastic body that allows relative rotation between an output shaft of the electric motor and the cylindrical portion within a predetermined angle range. Power steering device.

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