JP2001191934A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability in a buffer member having a gear shock absorption function in a torque transmission route of a motor in an electric power steering device. SOLUTION: This electric power steering device 10 has a bearing 50 rotatably supporting a worm wheel 44 as a steering assist gear independently of a pinion shaft 13, and the buffer member 60 is sandwiched between a lock part 65 of an arm 64 connected to the pinion shaft 13 and a lock part 66 provided in the worm wheel 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electric power steering apparatus.

[0002]

2. Description of the Related Art In an electric power steering apparatus, a pinion shaft connected to a steering shaft is meshed with a rack shaft, and a worm gear connected to an output shaft of a motor is meshed with a worm wheel. It is connected to a shaft and assists steering by transmitting the torque of the motor to the rack shaft.

In the prior art, as disclosed in Japanese Patent Application Laid-Open No. 61-33367, a worm gear is used to absorb tooth surface collision and vibration due to backlash of gears in a torque transmission path from a worm gear to a rack shaft. The wheel is connected to the pinion shaft in the rotational direction via a buffer member.

[0004]

However, in the prior art, the worm wheel is supported by the gear housing via the pinion shaft, and is not directly supported by the gear housing. On the other hand, when transmitting the torque of the motor, the worm gear exerts not only the torque but also the thrust load on the meshing portion with the worm wheel. The thrust load acts on one point in the circumferential direction, which is a meshing portion of the worm wheel with the worm gear, and acts as a force for tilting the worm wheel. At this time, since the worm wheel is only indirectly supported by the gear housing as described above, the worm wheel lacks stability and is forced to have a certain inclination due to a thrust load. The shock-absorbing member simultaneously generates elastic deformation for transmitting the torque transmitted from the worm wheel and torsional deformation due to its inclination, and the deterioration of durability is accelerated.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the durability and reliability of a shock-absorbing member having a function of absorbing a gear shock in a torque transmission path of a motor in an electric power steering apparatus.

[0006]

According to a first aspect of the present invention, a pinion shaft connected to a steering shaft is meshed with a rack shaft, and a steering assist gear driven by a motor is provided with a shock absorbing member in a rotational direction. An electric power steering device connected to the pinion shaft through a bearing that supports the steering assist gear so as to be rotatable independently of the pinion shaft, and an arm having the buffer member coupled to the pinion shaft. It is configured to be sandwiched between a locking portion and a locking portion provided on the steering assist gear.

According to a second aspect of the present invention, in the first aspect of the present invention, the steering assist gear is a worm wheel that meshes with a worm gear coupled to an output shaft of a motor, and the bearing is The worm wheel is provided at a position corresponding to an engagement position of the worm wheel with the worm gear in the axial direction of the worm wheel.

[0008]

According to the first aspect of the present invention, the following operations are provided. The steering assist gear is supported independently of the pinion shaft. Therefore, the steering assist gear is directly supported by the gear housing to be stabilized, and is also supported and stabilized at a portion where the rotation radius is larger than the pinion shaft. Therefore, the thrust load acting on the steering assist gear at the time of transmitting the torque of the motor is supported by the bearing of the steering assist gear, and the inclination of the steering assist gear due to the thrust load can be suppressed. The torsional deformation of the member can be prevented, and the durability reliability of the cushioning member can be improved.

According to the second aspect of the present invention, the following effects are obtained. The worm wheel is supported independently of the pinion shaft. Therefore, the worm wheel is directly supported and stabilized by the gear housing, and is supported and stabilized at a portion where the rotation radius is larger than the pinion shaft. Therefore, the thrust load acting on the worm wheel during torque transmission of the motor is supported by the bearing of the worm wheel, and the inclination of the worm wheel due to the thrust load can be suppressed. As a result, the torsion of the cushioning member caused by this inclination Deformation can be prevented, and the durability of the cushioning member can be improved.

The worm wheel bearing is provided at a position where the worm wheel and the worm gear mesh with each other. Therefore, the moment exerted on the worm wheel by the radial load acting on the worm wheel from the worm gear can be reduced, and the inclination of the worm wheel can be suppressed. Therefore, it is possible to secure the stability of the engagement between the worm wheel and the worm gear, and to further prevent torsional deformation of the cushioning member.

Since the worm wheel can be firmly supported directly on the gear housing, a worm reduction device having a large thrust load can be employed, and a high reduction ratio can be easily obtained.

[0012]

FIG. 1 is a schematic view showing an electric power steering apparatus, FIG. 2 is a longitudinal sectional view showing an electric power steering apparatus, FIG. 3 is a sectional view taken along line III-III of FIG.
FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, and FIG. 5 is an exploded perspective view showing a modification.

The electric power steering apparatus 10 is shown in FIG.
As shown in FIG. 3, a steering shaft 12 to which a steering wheel is connected is connected to a pinion shaft 13 inside the gear box 11, and the pinion shaft 13 is meshed with a rack shaft 14, so that The left and right tie rods 16 are connected to the parts via connecting bolts 15A and 15B.
A and 16B are connected, and the steering force of the steering wheel by the driver is assisted by a motor 17 fixed to the gear box 11.

As shown in FIG. 2, the gear box 11 includes first to third gear housings 11A to 11C. The gear box 11 includes a steering shaft 12, a pinion shaft 13, a bearing 21, and a bearing 2.
2 and 23, and the steering shaft 12 and the pinion shaft 13 are connected to each other by a torsion bar 24 inside them.

The gear box 11 has a cylindrical core 33 in which two detection coils 31 and 32 constituting a torque sensor 30 are engaged with the steering shaft 12 and the pinion shaft 13.
Is provided in the first housing 11A so as to surround the first housing 11A. The core 33 has a vertical groove 35 that engages with the guide pin 34 of the pinion shaft 13 so as to be movable only in the axial direction, and has a spiral groove 37 that engages with the slider pin 36 of the steering shaft 12. As a result, the steering torque applied to the steering wheel is applied to the steering shaft 12, and the elastic torsional deformation of the torsion bar 24 causes
When a relative displacement in the rotational direction occurs between the steering shaft 12 and the pinion shaft 13, the displacement in the rotational direction of the steering shaft 12 and the pinion shaft 13 causes the core 33 to be displaced in the axial direction. Coil 3
Detection coil 3 caused by magnetic change around 1, 32
The inductance of 1 and 32 changes. That is, the core 33
Moves toward the steering shaft 12, the inductance of the detection coil 31 closer to the core 33 increases, the inductance of the detection coil 32 closer to the core 33 decreases, and the steering torque can be detected by the change in the inductance.

In the gear box 11, the rack teeth 14A of the rack shaft 14 mesh with the pinion teeth 13A at the end of the pinion shaft 13 on the side opposite to the torque sensor 30. At this time, a cap 11D is fixed to the third gear housing 11C, and a rack guide 39 that is backed up by the cap 11D via a spring 38 supports the rack shaft 14 on the back.

As shown in FIG. 3, the gear box 11 supports the motor 17 in a third gear housing 11C, and has a worm gear 41 coupled to an output shaft of the motor 17 via a clutch 18 by bearings 42 and 43. Both ends are supported by the third gear housing 11C. The gear box 11 supports a worm wheel 44 as a steering assist gear meshing with the worm gear 41 in a third gear housing 11C by a bearing 50 as described later. The worm wheel 44 includes a boss 44A and a rim 44.
B, the rim 44B has teeth 44C, and the boss 44A
Is formed by insert metal fittings to secure the strength and the rim 4
4B is made of resin so as to reduce the noise of meshing with the worm gear 41.

The bearing 50 has an outer ring 50B mounted on the inner periphery of the boss 44A of the worm wheel 44 and is held by a retaining ring 51. The bearing 50 is also mounted on the annular support portion 52 of the third gear housing 11C by mounting the inner ring 50A. As a result, the worm wheel 44 is rotatably supported on the gear box 11 independently of the pinion shaft 13. The bearing 50 is provided at a position (the same position in the axial direction) corresponding to the meshing position of the worm wheel 44 with the worm gear 41 (the position of the tooth 44C) in the axial direction of the worm wheel 44. The worm wheel 44 has a boss 44A and the outer ring 5 of the bearing 50.
0B, the inner ring 50A of the bearing 50 is mounted on the annular support portion 52 of the third gear housing 11C, and the retaining ring 53 is engaged with the annular support portion 52 from the opening of the boss 44A, thereby making the gear box 11 Incorporated in.

The worm wheel 44 is connected to the pinion shaft 13 via a buffer member 60 in the direction of rotation. The buffer member 60 is made of an elastic body such as rubber, and includes buffer portions 62 at a plurality of positions in the circumferential direction of the annular portion 61 as shown in FIG. The buffer portion 62 has a U-shape, and both ends thereof are connected to the inner periphery of the annular portion 61. Thereby, the buffer member 6
No. 0 inserts a radial locking portion 65 provided on the outer periphery of an arm 64 connected to the pinion shaft 13 via a key 63 without a gap between adjacent buffer portions 62, 62, and a boss 44A of the worm wheel 44. Protrusion 6 provided on the upper surface of
6 is inserted into the hollow portion (the interior surrounded by the U-shape) of the buffer portion 62 without any gap, whereby the buffer member 60 is sandwiched between the locking portions 65 and 66 without any gap in the rotational direction.

That is, in the electric power steering apparatus 10, a control unit (not shown) that obtains the detection results of the vehicle speed sensor (not shown) and the torque sensor 30 described above.
Thus, the drive current of the motor 17 is determined from a predetermined assist force map, and the torque of the motor 17 that becomes an appropriate steering assist force according to the vehicle speed and the steering torque is determined by the pinion shaft 13.
To be given. The clutch 18 provided between the motor 17 and the worm gear 41 cuts off the steering assist force when assist is not required (at high speed).

According to this embodiment, the following operations are provided. The worm wheel 44 is supported independently of the pinion shaft 13. Therefore, the worm wheel 44 is directly supported and stabilized by the third gear housing 11 </ b> C, and is supported and stabilized at a portion where the rotation radius is larger than the pinion shaft 13. Therefore, the thrust load acting on the worm wheel 44 at the time of transmitting the torque of the motor 17 is supported by the bearing 50 of the worm wheel 44, and the inclination of the worm wheel 44 due to the thrust load can be suppressed. The torsional deformation of the cushioning member 60 can be prevented, and the durability reliability of the cushioning member 60 can be improved.

The bearing 50 of the worm wheel 44 is provided at a position where the worm wheel 44 and the worm gear 41 mesh with each other. Accordingly, the moment that the radial load acting on the worm wheel 44 from the worm gear 41 exerts on the worm wheel 44 can be reduced, and the inclination of the worm wheel 44 can be suppressed. Therefore, it is possible to secure the stable meshing of the worm wheel 44 with the worm gear 41,
In addition, the torsional deformation of the buffer member 60 can be further prevented.

Since the worm wheel 44 can be firmly supported directly on the third gear housing 11C, a worm reduction device having a large thrust load can be employed, and a high reduction ratio can be easily obtained.

The bearing 23 of the pinion shaft 13 and the bearing 50 of the worm wheel 44 are connected to the same third gear housing 11.
Since it is provided at C, the coaxial assembly accuracy of the pinion shaft 13 and the worm wheel 44 can be easily increased.

Since the bearings 42 and 43 of the worm gear 41 and the bearing 50 of the worm wheel 44 are provided in the same third gear housing 11C, the distance accuracy between the worm gear 41 and the worm wheel 44 can be easily increased.
The accuracy of engagement between the two can be easily increased.

FIG. 5 shows a cushioning member 70 according to a modification of the cushioning member 60 of FIG. The cushioning member 70 is made of an elastic body such as rubber, and has a rectangular rod-like cushioning portion 72 coupled to a plurality of positions in the circumferential direction of the annular portion 71 in a cantilevered lever shape. The buffer member 70 includes an arm 73 connected to the pinion shaft 13.
Of the outer circumference of the worm wheel 44 and the protruding locking portion 75 provided on the upper surface of the boss 44A of the worm wheel 44 are alternately formed in the recesses formed by the buffer portions 72, 72 adjacent to each other without any gap. , The cushioning member 70 is sandwiched between the locking portions 74 and 75 without any gap in the rotation direction.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design can be changed without departing from the scope of the present invention. The present invention is also included in the present invention.

[0028]

As described above, according to the present invention, in the electric power steering apparatus, the durability reliability of the buffer member having the function of absorbing the gear impact in the torque transmission path of the motor can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an electric power steering device.

FIG. 2 is a longitudinal sectional view showing the electric power steering device.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is an exploded perspective view showing a modification.

[Explanation of symbols]

 Reference Signs List 10 electric power steering device 12 steering shaft 13 pinion shaft 14 rack shaft 17 motor 41 worm gear 44 worm wheel (steering assist gear) 50 bearing 60, 70 cushioning member 64, 73 arm 65, 66, 74, 75 locking portion

Claims (2)

[Claims] An electric power steering system wherein a pinion shaft connected to a steering shaft is meshed with a rack shaft, and a steering assist gear driven by a motor is connected to the pinion shaft via a buffer member in a rotational direction. An apparatus, comprising: a bearing that rotatably supports the steering assist gear independently of a pinion shaft; a locking portion of an arm having the buffer member coupled to a pinion shaft; and a locking portion provided on the steering assist gear. An electric power steering device characterized by being sandwiched between the electric power steering device and the vehicle. 2. The steering assist gear is a worm wheel that meshes with a worm gear coupled to an output shaft of a motor, and the bearing corresponds to a meshing position of the worm wheel with the worm gear in the axial direction of the worm wheel. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is provided at a position where the electric power steering is performed.