JP5768460B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device that assists a driver's steering by driving an electric motor in response to an operation of a steering member such as a steering wheel (steering wheel) performed by the driver, and in particular, rotation of the electric motor. The present invention relates to an electric power steering apparatus provided with a speed reducing device that decelerates and transmits the speed to a steering shaft.

2. Description of the Related Art Conventionally, there is known an electric power steering device that includes a reduction gear that decelerates the rotation of an electric motor and transmits it to a steering shaft (see, for example, Patent Document 1).
Patent Document 1 describes an electric power steering device including a reduction gear that prevents rattling between both shafts by interposing an elastic member between a motor rotation shaft and a worm shaft of an electric motor. Yes.

There is also known an electric power steering device including a reduction gear that allows the worm shaft to swing (see, for example, Patent Document 2).
In Patent Document 2, the worm shaft is swung around the convex portion by the moving body provided on the shaft portion side at one end of the worm shaft and by the convex portion provided on the shaft portion at the other end of the worm shaft. An electric power steering device with a reduction gear capable of being described is described.

JP 2002-145083 A JP 2002-211943 A

The electric power steering apparatus provided with the reduction gear described in Patent Document 1 or Patent Document 2 copes with two-way vibration, rattling, eccentricity, and the like between the motor rotation shaft and the worm shaft of the electric motor. Is.
However, if there is a misalignment between the motor shaft and the worm shaft, the rear bearing portion of the electric motor receives a radial load, and a noise is generated between the inner side surface of the motor case and the bearing outer ring, or the rotor of the electric motor There may be an imbalance in the magnetic attractive force between the magnet and the stator, which may generate operating noise.

FIG. 4 is a diagram for explaining the influence on the rear bearing portion of the electric motor when the motor shaft and the worm shaft are poorly aligned.
The motor rotating shaft 21 of the electric motor 11 is connected to the worm shaft 13 via the motor side joint portion 61 and the worm side joint portion 32.
The motor rotating shaft 21 of the electric motor 11 has a motor case 40 at one end (21) via a front bearing 35, and the rear side, that is, the other end 34, via a rear bearing 36 and a wave washer 43. Is rotatably supported.

When there is poor alignment between the motor rotating shaft 21 and the worm shaft 13 of the electric motor 11, that is, when there is a shaft misalignment (coaxiality misalignment), tilt, or whirling, the shaft misalignment, etc. Although absorbed by the joint unit 15, a constant load is generated at the position indicated by the joint unit 15 of the motor rotating shaft 21 and the worm shaft 13 of the electric motor 11, that is, the load acting portion 29 of FIG. 4. The load is a moment (lengths L1 and L2) centered on the center point 30 of the front bearing 35 and acts on the rear side of the electric motor 11, and the rear bearing 36 moves in the radial (radius) direction. Will receive a load. Therefore, when the alignment failure between the motor rotating shaft 21 and the worm shaft 13 of the electric motor 11 is large, the outer ring of the rear bearing 36 and the inner side surface of the motor case 40 at the contact point 70 shown in FIG. As a result, a hitting sound is generated, or the operating sound is deteriorated due to an imbalance of the magnetic attractive force between the magnet of the rotor 42 of the electric motor 11 and the stator 41.

The present invention has been made in order to solve the above-described problems. The object of the present invention is to provide a motor case inner side surface and a bearing outer side when there is poor alignment between the motor rotating shaft and the worm shaft of the electric motor. It is an object of the present invention to provide an electric power steering apparatus including an electric motor that prevents generation of hitting sound from a wheel and deterioration of operation sound due to imbalance of magnetic attraction force between a rotor magnet and a stator.

In order to solve the above problems, the invention according to claim 1 is directed to an electric motor for assisting steering driven according to a torque applied to a steering shaft, a worm wheel connected to the steering shaft, a worm shaft which engages with the worm wheel, a worm gear consisting of, said a case for accommodating the electric motor and the worm gear, within the case, a pair of motors for supporting both ends of the motors rotating shaft of the electric motor and side bearing, in front Symbol case, fitted to mate with the pair of worm side bearing for supporting both ends of the worm shaft, the one end portion of the one end and the front Kiu Omu axis of said motors rotating shaft the electric power steering apparatus equipped with a coupling portion, wherein the motor-side rear bearing supporting the other end portion of the motor rotation shaft of the motor-side bearing casing Disposed between the wave washer for pressing the motor shaft into the fitting portion through the motor-side rear bearing, in the case, provided the motors rotating shaft on the same axis A protrusion provided on the outer ring of the motor-side rear bearing, and the wave washer has an inner peripheral edge abutting on an outer periphery of the protrusion and an outer peripheral edge engaging the groove. Is the gist.

According to the above configuration, even when there is a misalignment between the motor rotating shaft and the worm shaft of the electric motor, the protrusion provided on the rear side in the motor case and the outer ring of the rear bearing are provided. When the wave washer on the other end of the motor rotating shaft of the electric motor is in contact with the groove, the rear bearing is pressed against movement in the radial (radial) direction within the motor case. It is possible to prevent the generation of a hitting sound due to contact with the motor and the deterioration of the operating sound due to the unbalance of the magnetic attractive force between the rotor magnet and stator of the electric motor.

If there is a misalignment between the motor rotating shaft and the worm shaft of the electric motor, operation is caused by the generation of striking sound between the inner side of the motor case and the bearing outer ring, or by the magnetic attraction force between the rotor magnet and the stator. An electric power steering apparatus including an electric motor that prevents deterioration of sound can be provided.

The schematic diagram which shows schematic structure of the electric power steering apparatus which concerns on one Embodiment of this invention. FIG. 2 is a detailed view of the electric power steering apparatus shown in FIG. 1. FIG. 3 is a detailed view showing a specific configuration of the electric motor shown in FIG. 2. The figure explaining the influence on the motor bearing part on the rear side when there is poor alignment between the motor rotation shaft and the worm shaft.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus of the present invention. The steering mechanism 2 of the power steering apparatus 1 is, for example, a rack and pinion type. The steering mechanism 2 includes a steering shaft 6 that is rotatably supported by a vehicle body having a steering wheel 4 provided at one end via a steering column, a pinion 7 provided at the other end of the steering shaft 6, and the pinion 7 and a rack shaft 8 that reciprocates to steer the wheel 5 by the movement of the steering wheel 4. The rack shaft 8 extends in the width direction of the vehicle, which is to the left and right with respect to the traveling direction of the vehicle, and wheels 5 are connected to end portions of the rack shaft 8 via tie rods 10 and the like.

An electric power steering device 3 as a power drive mechanism includes an electric motor 11 as a driving source of steering assist force, and a worm gear 12 including a worm shaft 13 and a worm wheel 14 that transmit torque from the electric motor 11 to the steering shaft 6. A joint unit 15 as a fitting portion that is interposed between the worm shaft 13 and the motor rotating shaft 21 of the electric motor 11 and transmits torque; a torque sensor 16 that detects torque applied to the steering shaft 6; A control unit (ECU) 17 including a microcomputer that drives the electric motor 11 while controlling the electric motor 11 in accordance with an output signal from the torque sensor 16 is provided.

  In the electric power steering device 3, the steering assisting electric motor 11 driven according to the torque loaded on the steering shaft 6 is rotated by the steering mechanism 2 via the worm shaft 13 and the worm wheel 14. Tell the shaft 6.

FIG. 2 is a detailed view of the electric power steering apparatus 3 shown in FIG. The electric power steering device 3 has worm side bearings 18 and 19 that rotatably support the worm shaft 13, and a case 20 that accommodates the worm side bearings 18 and 19, the worm gear 12, the worm shaft 13, the worm wheel 14, and the like. doing. The case 20 is fixed to a steering column (not shown). In the case 20, the worm wheel 14 is attached to be integrally rotatable with the steering shaft 6. The case 20 supports the one end portion 24 and the other end portion 25 of the worm shaft 13 through the worm side bearings 18 and 19, respectively, so as to be rotatable. The position of the worm side bearing 19 is supported by a screw mechanism 49, an adjustment member 48, and the like provided in the case 20 so that the position thereof can be adjusted.

Further, a motor case 40 is fixed to the case 20, and the motor case 40 accommodates a stator 41, a rotor 42, a front bearing 35, a rear bearing 36, a wave washer 43 and the like that constitute the electric motor 11. Motor shaft 21 of the electric motor 11, the end portion (21) is supported by the front bearing 35, Li Ya side, i.e., the other end portion 34 via the rear bearing 36 and the wave washer 43, the motor case 40 And is supported in a pressed state by a wave washer 43. At this time, when an excessive load is applied from the joint unit 15, the wave washer 43 is supported so as not to move in the radial direction with respect to a predetermined amount of radial load.

  FIG. 3 is a detailed view showing a specific configuration of the electric motor 11 in the electric power steering apparatus 3 shown in FIG.

As shown in FIG. 3, the motor case 40 houses a stator 41, a rotor 42, a rear bearing 36, a wave washer 43 and the like that constitute the electric motor 11. A rear hole 51 for assembling the rotor 42 is provided on the rear side of the motor case 40, and a metal protrusion 50 is attached around the rear hole 51 as a spacer, for example, by adhesion. Further, the outer ring of the rear bearing 36 is provided with a groove 52 having a concave shape over the entire circumference, and the rear bearing 36 is pressed toward the joint unit 15 with the wave washer 43 in contact with the groove 52 and the protrusion 50. Yes. The other end 34 of the motor rotating shaft 21 can be rotated in the motor case 40 via the rear bearing 36 and the wave washer 43, and is supported in a pressed state by the wave washer 43. Therefore, when an excessive load is applied from the joint unit 15, the joint unit 15 is supported so as to suppress movement in the radial direction.

Thus, the present invention prevents the load caused by the alignment failure from acting on the rear side of the electric motor 11, that is, the other end 34 of the motor rotating shaft 21 and the rear bearing 36.
As described above, when there is a poor alignment between the motor rotating shaft 21 and the worm shaft 13 of the electric motor 11, the wave washer 43 is prevented from slipping due to the misalignment or the like, and the rear bearing 36 is loaded in the radial direction. The wave washer 43 suppresses the movement in the radial direction even when receiving.

Next, the operation and effect of the electric power steering apparatus 3 of the present embodiment configured as described above will be described.
Between the motor rotating shaft 21 and the worm shaft 13 of the electric motor 11, there is a worm for misalignment during assembly and for adjusting the backlash between the worm shaft 13 and the worm wheel 14 (see FIG. 2). An alignment defect exists due to adjustment of the shaft 13 or the like.
At this time, a radial load of the rear bearing 36 of the electric motor 11 is generated due to this alignment failure, but the inner peripheral edge of the wave washer 43 is brought into contact with the outer periphery of the protrusion 50 provided on the rear side in the motor case 40. By engaging the outer peripheral edge portion with the groove portion 52 provided in the outer ring of the rear bearing 36, the wave washer 43 is prevented from slipping and the rear bearing 36 is prevented from moving in the radial direction.

Thus, the axial load of the wave washer 43 is intact, against the load in the radial direction to support the other end portion 34 of the motor shaft 21, the outer ring of the motor case 40 inner side surface and the rear bearing 36 It is possible to prevent the deterioration of the operation sound due to the generation of the hitting sound and the unbalance of the magnetic attractive force between the magnet of the rotor 42 of the electric motor 11 and the stator 41.
Furthermore, by reducing the load in the axial direction of the wave washer 43 and suppressing the increase in motor loss torque caused by mechanical friction such as bearing loss, the delay in returning the steering wheel (worm wheel) after steering, etc. The steering feeling can be prevented from being lowered, the wear of the bearing can be suppressed, and the operation and durability of the bearing can be improved.
Moreover, since the wave washer 43 can be easily positioned by the above configuration, the assembly accuracy of the rotating shaft 21 of the electric motor 11 is improved.

In addition, you may change this embodiment as follows.
The present invention is not limited to the above-described embodiment. For example, the protrusion 50 shown in FIG. 3 is a ring-shaped metal material. However, a wave washer 43 using a resin molded product such as a resin coupler is used. It is also possible to abut. At this time, the side surface in the motor case 40 facing the rear bearing 36 is also covered with the resin coupler, and even if the rear bearing 36 moves in the radial direction, it comes into contact with the resin, so that the hitting sound is suppressed.
In the present embodiment, an example in which the present invention is applied to a steering wheel of a vehicle has been described. However, the embodiment may be embodied in a machine tool or the like.

1: power steering device, 2: steering mechanism, 3: electric power steering device,
4: Steering wheel, 5: Wheel, 6: Steering shaft, 7: Pinion,
8: rack shaft, 9: rack, 10: tie rod, 11: electric motor,
12: Worm gear, 13: Worm shaft (24: one end, 25: other end) ,
14: Worm wheel, 15: Joint unit (fitting part) , 16: Torque sensor,
17: ECU (control part), 18, 19: Worm side bearing, 20: Case,
21: motor rotating shaft (21: one end, 34: other end) , 29: load acting portion, 30: middle point, 32: worm side joint, 33: elastic member,
35 , 36 : motor side bearing (35: front bearing, 36: rear bearing ) ,
40: motor case, 41: stator, 42: rotor, 43: wave washer,
48: adjustment member, 49: screw mechanism, 50: motor case protrusion,
51: Motor case rear hole, 52: Rear bearing outer ring groove

Claims (1)

An electric motor for assisting steering driven in accordance with torque applied to the steering shaft;
A worm gear comprising: a worm wheel connected to the steering shaft; and a worm shaft engaged with the worm wheel ;
A case for housing the electric motor and the worm gear ;
In the case, and a pair of motor-side bearing for supporting both ends of motors rotating shaft of the electric motor,
In front Symbol case, a pair of worm side bearing for supporting both ends of the worm shaft,
The electric power steering apparatus provided with a fitting portion fitted to one end portion of the one end and the front Kiu Omu axis of said motors rotating shaft,
The motor-side bearing is provided between the case and a motor-side rear bearing that supports the other end of the motor rotation shaft, and the motor rotation shaft is moved to the fitting portion side via the motor-side rear bearing. A wave washer to press,
In the case, and a protrusion provided on the motors rotating shaft on the same axis,
A groove provided on the outer ring of the motor-side rear bearing,
The wave washer is
An electric power steering device characterized in that an inner peripheral edge abuts on an outer periphery of the protrusion and an outer peripheral edge engages with the groove.

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