JP4127074B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus using a motor as a generation source of steering assist force.
[0002]
[Prior art]
The electric power steering device using a motor as a source of steering assist force to reduce the burden on the driver for steering is compared with a hydraulic power steering device using a hydraulic actuator as a source of steering assist force. In recent years, the range of application tends to be expanded because it has the advantage of easily controlling the assisting force characteristics according to the running state such as the vehicle speed and the steering frequency.
[0003]
The electric power steering device is configured to drive the motor based on a detection result of a steering torque applied to the steered wheels for steering and transmit the rotational force of the motor to steering means to assist steering. Yes.
[0004]
In the electric power steering device and the hydraulic power steering device, a rotation angle detector for detecting the rotation angle of the steering means from the steering angle midpoint of the steered wheels is used.
The rotation angle detector is generally configured as a separate device, and is incorporated as a part of, for example, a combination switch unit in an assembly line of an automobile manufacturer.
[0005]
As described in Patent Documents 1 and 2, for example, the rotation angle detector includes an annular drive gear that is fitted and fixed to a peripheral surface of a rotation shaft connected to a steering wheel, and a driven rotation that meshes with the annular drive gear. And a detection unit for detecting the rotation angle of the annular drive gear that rotates together with the rotation shaft, and includes two driven gears having magnets and a circuit component that generates rotation angle information as the annular drive gear rotates. And a support housing that supports the detection unit.
[0006]
[Patent Document 1]
JP 2000-159037 A [Patent Document 2]
JP-T-2001-505667 Publication [0007]
[Problems to be solved by the invention]
When a rotation angle detector configured as a separate device from the electric power steering device is incorporated in the electric power steering device in this way, for example, the annular drive gear is fitted and fixed to a steering shaft as a rotation shaft, and the steering shaft is Since the support housing is attached to a housing that is rotatably supported, there are the following problems.
When the reverse input from the road surface is transmitted to the steering shaft and the steering shaft swings, the steering shaft and the housing are relatively displaced, so that the annular drive gear fitted to the steering shaft is greatly bent, and the detection unit This will cause deterioration in detection at the point of time, and will also cause damage to the rotation angle detector.
[0008]
The present invention has been made in view of such circumstances. The main object of the present invention is to accurately detect the detection unit even when the reverse input from the road surface is transmitted to the steering means. An object of the present invention is to provide an electric power steering device that can prevent damage.
[0009]
[Means for Solving the Problems]
An electric power steering apparatus according to a first aspect of the present invention has a rotating shaft that is rotatably supported by a support member, and rotates by detecting a rotation angle of the steering means that rotates by rotation of a steering assist motor. An electric power steering apparatus including an angle detector and assisting steering by rotation of the motor, further comprising an elastic fitting member that is fitted to an outer peripheral portion of the rotation shaft, and the rotation angle detector includes a rotating wheel and , Two idler wheels which are arranged apart from each other in the circumferential direction of the rotating wheel and mesh with the rotating wheel and rotate freely, and the rotation angle of each of the idler wheels is detected, and the rotation according to the detected result A detecting unit that detects a rotation angle of the wheel; and a holding unit that holds the detecting unit and is fixed to the support member, and the rotating wheel is fitted to the rotating shaft via the elastic fitting member. It is characterized by being.
[0010]
In the first invention, the rotating wheel of the rotation angle detector having the rotating wheel and the two idler wheels meshing with the rotating wheel is fitted to the rotating shaft of the steering means via the elastic fitting member. Therefore, when the reverse input from the road surface is transmitted to the rotating shaft of the steering means, the elastic fitting member is bent by the reverse input, and the reverse input can be absorbed. Therefore, adverse effects due to the reverse input can be reduced, the detection by the detection unit can be accurately performed, and the rotation angle detector can be prevented from being damaged.
[0011]
The electric power steering apparatus according to a second aspect of the invention is characterized in that the elastic fitting member comprises an elastic ring fitted on a peripheral surface of a rotating shaft.
In the second invention, since the elastic fitting member can be provided by inserting and fitting the elastic ring to the peripheral surface of the rotating shaft, the rotation angle detector can be easily incorporated after the steering means is assembled.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
1 is a cross-sectional view showing the overall configuration of an electric power steering apparatus according to the present invention, FIG. 2 is an enlarged cross-sectional view of a rotation angle detector portion, and FIG. 3 is a cross-sectional view taken along line III-III in FIG.
[0013]
The steering apparatus shown in FIG. 1 is an electric power steering apparatus that uses a motor as a generation source of steering assist force. The input shaft 1 is connected to the steered wheels A, and is coaxial with the input shaft 1 via a torsion bar 2. An output shaft 3 as a rotation shaft connected to the input shaft 1, a torque sensor 4 for detecting torque applied to the input shaft 1, a steering assist motor 5 driven based on the torque detected by the torque sensor 4, A reduction gear mechanism 6 that transmits the rotation of the motor 5 to the output shaft 3, a rotation angle detector 7 that detects the rotation angle of the output shaft 3, and a rack and pinion type steering mechanism (not shown). And a transmission shaft (not shown) such as a universal joint to be interlocked. The input shaft 1, the torsion bar 2, the output shaft 3, and the transmission shaft constitute steering means.
[0014]
The input shaft 1 has a sensor support cylinder 1a into which one end of a torsion bar 2 is inserted, and a target 8 fitted and fixed to the outer periphery of the sensor support cylinder 1a. One end of the sensor support cylinder 1a is a needle. It is supported in a housing 10 as a support member via a bearing 9.
[0015]
The output shaft 3 is formed in a cylindrical shape into which the other end of the sensor support cylinder 1a and the other end of the torsion bar 2 are inserted. The output shaft 3 has a target 11 adjacent to the target 8 at one end portion, and a threaded portion 3a and an uneven strip 3b (outer peripheral portion) composed of serrations connected to the threaded portion 3a on the outer peripheral portion of the other end portion. Is provided. An elastic ring 12 as an elastic fitting member is fitted to the concavo-convex portion 3b, and a nut 14 for applying a preload in the axial direction to a rolling bearing 13 described later is screwed to the screw portion 3a. A worm wheel 6a of the reduction gear mechanism 6 is fitted and fixed in the axial direction of the output shaft 3, and both sides of the worm wheel 6a are supported in the housing 10 via rolling bearings 13 and 15. Has been.
[0016]
The housing 10 includes a cylindrical first housing portion 10a in which the torque sensor 4 is housed, a substantially bowl-shaped second housing portion 10b which is connected to one end of the first housing portion 10a and houses a worm wheel 6a, And a third housing portion 10c in which a worm 6b connected to one side of the second housing portion 10b and connected to the output shaft of the motor 5 is housed. The 2nd accommodating part 10b and the 3rd accommodating part 10c are shape | molded integrally, the other end of the 1st accommodating part 10a is fitted by the 2nd accommodating part 10b, and it is connected by connection means, such as a volt | bolt. Further, fitting holes 10d and 10e are provided at the other end portion of the first housing portion 10a and the end portion of the second housing portion 10b opposite to the first housing portion 10a, and the fitting holes 10d and 10e are provided with the fitting holes 10d and 10e. The outer rings of the rolling bearings 13 and 15 are fitted and fixed, and the output shaft 3 is fitted and supported on the inner rings of the rolling bearings 13 and 15. In the rolling bearing 13 fitted in the fitting hole 10e, the inner ring is pressed in the axial direction by tightening of the nut 14 screwed into the threaded portion 3a, and the rolling bearing 13 of the rolling bearing 13 due to the gap between the inner ring and the outer ring is pressed. By eliminating rattling, the displacement of the output shaft 3 supported by the rolling bearing 13 in the axial length direction can be eliminated.
[0017]
A pedestal having a support surface 10f that is substantially orthogonal to the rotation center of the output shaft 3 is provided at the opposite end of the second storage portion 10b to the first storage portion 10a, and the rotation angle detector 7 is attached to the support surface 10f with a bolt or the like. It is detachably attached by means.
[0018]
The rotation angle detector 7 is elastically fitted to the outer peripheral portion of the elastic ring 12 and has a large-diameter rotating wheel 71 having teeth of n teeth on the outer peripheral portion, and is spaced apart in the circumferential direction of the rotating wheel 71. Two small rotating wheels 72, 73 that are arranged and mesh with the rotating wheel 71 to rotate, magnets 74, 74 fixed to the rotation center of each of the rotating wheels 72, 73, and rotation of the rotating wheel 71 And a detection unit 75 that detects a rotation angle of the rotating wheel 71 and a holding unit 76 that holds the detection unit 75 and is fixed to the support surface 10f. Have.
[0019]
A plurality of grooves 71 a are provided at positions separated in the circumferential direction at the inner peripheral portion of the rotating wheel 71. One idler wheel 72 has m teeth, and the other idler wheel 73 has m + 1 teeth.
[0020]
The detection unit 75 has two variable resistance characteristics such as an anisotropic magnetoresistive element (AMR element) and the like, which change in electrical characteristics (resistance) due to the action of a magnetic field, and face the magnet side ends of the idle wheels 72 and 73. Elements 75a and 75a and a circuit board 75b that supports the elements 75a and 75a are provided. The resistance values of the elements 75a and 75a are changed as a function of the direction in which the elements 75a and 75a are directed in the external magnetic field. Is configured to generate a voltage that is a function of the rotation angle. Each element 75a, 75a undergoes a voltage change that rises during an angle of about 180 ° when the idler wheels 72, 73 make one revolution, and then the voltage drops again during an angle of about 180 °. Then, after the idle wheels 72 and 73 have rotated 360 °, this voltage change is repeated. In this case, since the number of teeth of the idle wheels 72 and 73 is different, different voltage changes are given to the elements 75a and 75a. This voltage is equivalent to the rotation angle of the idle wheels 72 and 73. As a result, the detection unit 75 is outputted from the output unit of the detection signal detected in accordance with the rotation angle of the idle wheel 72 and 73 as rotation angle. This detection signal is given to a control unit (not shown) using a microprocessor. The control unit obtains the rotation angle of the rotating wheel 71 that rotates integrally with the output shaft 3 from the difference between the rotation angles of the idle wheels 72 and 73 (difference in detection signal).
[0021]
The holding portion 76 has a bowl-shaped case 76a having a through hole in which one end portion of the rotating wheel 71 is rotatably inserted, and an open portion of the case 76a is closed, and the other end portion of the rotating wheel 71 is rotatably inserted. A lid 76b having a through hole, and the case 76a and the lid 76b are attached to the support surface 10f of the housing 10 in a state where the case 76a and the lid 76b are coupled by a coupling means such as a small screw. The idler wheels 72 and 73 are rotatably supported on the lid body 76b. In addition, you may provide the convex part and recessed part for positioning which determine the attachment position of the rotation angle detector 7 between the cover body 76b and the support surface 10f.
[0022]
The elastic ring 12 is made of an elastic material such as flexible synthetic rubber or synthetic resin, and the inner peripheral portion fitted to the concavo-convex ridge 3b bends corresponding to the concavo-convex ridge 3b. 3 and rotate together. A convex portion 12b that engages with the groove 71a protrudes from the outer circumferential portion of the elastic ring 12 in the circumferential direction, and the rotating wheel 71 and the elastic ring 12 are engaged by the engagement between the convex portion 12b and the groove 71a. It is designed to rotate in conjunction. A recess 12 a having a size corresponding to the nut 14 is provided on one side of the elastic ring 12.
[0023]
The torque sensor 4 detects the torque applied to the input shaft 1 by the steering of the steered wheels A by the torsion generated in the torsion bar 2, and the steering assist motor 5 is based on the torque detected by the torque sensor 4. Are configured to be driven and controlled.
[0024]
The electric power steering apparatus configured as described above has an output shaft in which the worm wheel 6a and the target 11 are fitted and fixed to the inner ring of the rolling bearing 13 fitted and fixed in the fitting hole 10e of the second housing portion 10b. 3 is inserted, and a nut 14 is screwed onto the threaded portion 3 a of the output shaft 3 to apply a preload in the axial direction to the rolling bearing 13. Further, the first housing portion 10a in which the torque sensor 4 is housed and the rolling bearing 15 is fitted and fixed in the fitting hole 10d is connected to the second housing portion 10b, and the middle of the output shaft 3 is connected to the inner ring of the rolling bearing 15. The output shaft 3 is inserted into the housing 10 via the two rolling bearings 13 and 15. Then, the elastic ring 12 is fitted to the concave and convex strip 3 b of the output shaft 3, the elastic ring 12 is fixed to the output shaft 3, and the inner peripheral portion of the rotating wheel 71 of the rotation angle detector 7 is The rotation angle detector 7 can be mounted by elastically fitting the holding portion 76 to the support surface 10f of the second housing portion 10b.
[0025]
Thus, since the output shaft 3 elastically fits the rotating wheel 71 of the rotation angle detector 7 to the elastic ring 12 via the elastic ring 12, the reverse input from the road surface causes the steering mechanism and the transmission shaft to move. When the output shaft 3 is transmitted to the output shaft 3 and is shaken, the elastic ring 12 is bent by the reverse input, and the vibration of the output shaft 3 due to the reverse input can be absorbed by the elastic ring 12. Therefore, adverse effects due to reverse input can be reduced, detection by the detection unit 75 can be performed accurately, and damage to the rotation angle detector 7 can be prevented.
Further, when the output shaft 3 rotates through the input shaft 1 and the torsion bar 2 by steering the steering wheel A, the rotational force of the output shaft 3 is transmitted to the rotating wheel 71 through the elastic ring 12, and the rotating wheel Since 71 rotates in conjunction with the output shaft 3, the rotation angle of the rotating wheel 71, and hence the rotation angle of the output shaft 3, can be detected by the rotation angle detector 7.
[0026]
The output shaft 3 that supports the rotating wheel 71 of the rotation angle detector 7 is supported by a rolling bearing 13 so as not to be displaced in the axial direction. Since there is no backlash in the long direction, the displacement of the rotation angle detector 7 in the axial length direction can be reduced, the detection accuracy can be increased, and the durability of the rotation angle detector 7 can be increased. Can do.
Moreover, since the rotating wheel support part of the output shaft 3 is provided with the concave and convex ridges 3b made of serrations, the entire output shaft 3 including the concavo-convex ridges 3b can be formed by non-cutting processing such as rolling. The machining cost of the shaft 3 and thus the cost of the electric power steering device can be reduced.
[0027]
In the embodiment described above, the ridges 3b are provided on the outer periphery of the output shaft 3, and the elastic ring 12 having a circular peripheral surface on the inside is fitted to the ridges 3b. It is good also as a structure which provides an uneven | corrugated strip | belt in the inner peripheral part of the elastic ring 12, and meshes uneven | corrugated strips. Moreover, the output shaft 3 is made into a circular surrounding surface, and uneven | corrugated strips, such as a serration, are provided in the inner peripheral part of the elastic ring 12. It is possible to provide the concave and convex portions so as to be elastically fitted to the circular peripheral surface of the output shaft 3, and the elastic ring 12 may be coupled by an adhesive means such as vulcanization adhesion. Therefore, the coupling structure with the output shaft of the elastic ring 12 is not particularly limited.
[0028]
Moreover, although it was set as the elastic fitting member which consists of the elastic ring 12, this elastic fitting member is good also as a some protruding item | line which separated in the circumferential direction and was couple | bonded by adhesion means, such as vulcanization adhesion | attachment, The shape of the elastic fitting member is not particularly limited.
[0029]
【The invention's effect】
As described above in detail, according to the first invention, adverse effects due to reverse input from the road surface can be reduced, detection at the detection unit can be performed accurately, and damage to the rotation angle detector can be prevented.
[0030]
According to the second invention, the rotation angle detector can be easily incorporated after the steering means is assembled.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the overall configuration of an electric power steering apparatus according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a rotation angle detector portion of the electric power steering apparatus according to the present invention.
3 is a cross-sectional view taken along line III-III in FIG.
[Explanation of symbols]
1 Input shaft (steering means)
2 Torsion bar (steering means)
3 Output shaft (rotating shaft, steering means)
3b Concave and convex strip (outer periphery)
5 Motor 7 Rotation Angle Detector 71 Rotating Wheel 75 Detecting Unit 76 Holding Unit 10 Housing (Supporting Member)
12 Elastic ring (elastic fitting member)

Claims (2)

A rotating shaft is rotatably supported by the support member, and includes a steering unit that rotates by rotation of a steering assisting motor, and a rotation angle detector that detects a rotation angle of the steering unit. the electric power steering apparatus for steering assistance, an elastic engaging member which is fitted to the outer peripheral portion of the rotary shaft, the rotational angle detector includes a rotating wheel, spaced apart in the circumferential direction of the rotary wheel Two idler wheels arranged and meshed with the rotating wheels, and detecting a rotation angle of each of the idler wheels, and detecting a rotation angle of the rotating wheel according to the detected result , An electric power steering apparatus characterized by having a holding portion that holds the detection portion and is fixed to the support member, and the rotating wheel is fitted to the rotating shaft via the elastic fitting member. .   The electric power steering apparatus according to claim 1, wherein the elastic fitting member is formed of an elastic ring fitted to a peripheral surface of a rotating shaft.

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