JP3815962B2 - 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]
Automobile steering is performed by turning a steering wheel arranged inside the passenger compartment to a steering mechanism arranged outside the passenger compartment for steering the steering wheel (generally the front wheels). Done.
[0003]
FIG. 7 is a cross-sectional view of a conventional electric power steering apparatus, and FIG. 8 is a cross-sectional view of a speed reduction mechanism portion.
As an electric power steering apparatus for an automobile, as shown in FIG. 7, for example, a first steering shaft 101 connected to a steering wheel 100 for steering, and the steering shaft 101 are coaxially connected via a torsion bar 102. The second steering shaft 103 connected to the steering mechanism connected to the wheel and the torque detected by the twist generated in the torsion bar 102 by rotating the steering wheel 100 to the first steering shaft 101 A sensor 104, a steering assist motor 105 driven based on the detection result of the torque sensor 104, and an output shaft of the motor 105, and the rotation of the output shaft is decelerated to reduce the second steering shaft 103. And a speed reduction mechanism having a worm wheel 107, and the operation of the steering mechanism in accordance with the rotation of the steering wheel 100. Assisted by the rotation of the motor 105, it is configured to reduce the driver effort burden for steering.
[0004]
As shown in FIG. 8, the worm 106 constituting the speed reduction mechanism is supported by a fitting hole of the housing 110 via a pair of rolling bearings 108, 108, and a second steering shaft 103 provided with a worm wheel 107 is provided. It is supported by the fitting hole of the housing 110 via a pair of rolling bearings 109, 109, and is prevented from moving in the radial direction and the axial direction.
[0005]
When the speed reduction mechanism is used in this way, the rotation of the worm 106 and the worm wheel 107 is performed in order to reduce the backlash amount at the meshing portion of the worm 106 and the worm wheel 107 and eliminate the rattling noise caused by the backlash at the time of turning. The worm 106, the worm wheel 107, the rolling bearings 108, 109, the first one processed so that the center distance and the center distance of the fitting hole into which the rolling bearings 108, 109 are fitted are matched within an allowable range. The two steering shafts 103 and the housing 110 are selected and assembled. However, this assembly takes a lot of time, this assembly takes a lot of time, and the worm 106 and the worm wheel 107 are assembled. Increasing tooth wear will increase the amount of backlash. It had been Nozomu.
[0006]
Therefore, as described in Japanese Patent Application Laid-Open No. 2000-43739, the motor side shaft portion is attached to the side of the meshing portion with the worm wheel by attaching the shaft portion on the opposite side to the motor of the worm that is rotatably supported by the housing via the rolling bearing. And a pressing body having a spring body for applying preload to the meshing portion and an adjusting screw for adjusting the amount of deflection of the spring body, and applying preload to the meshing portion of the worm with the worm wheel by the pressing body. There has been proposed an electric power steering apparatus configured to reduce the amount of backlash.
[0007]
[Problems to be solved by the invention]
However, since the preload is applied to the mesh portion of the worm that is pressed by the pressing body with the worm wheel as described above, there is a problem that the mesh resistance of the mesh portion increases.
[0008]
The present invention has been made in view of such circumstances, and is provided with a configuration in which a restraining means for suppressing the pressing force is provided by applying a drag force against the pressing force by the pressing body to the drive gear. Provided is an electric power steering device capable of reducing the amount of backlash and reducing the meshing resistance of the meshing portion without applying a preload to the drive gear due to the balance between the pressing force by the restraint and the restraining force by the restraining means. For the purpose.
[0009]
It is another object of the present invention to provide an electric power steering apparatus that can simplify the structure of the restraining means by using the restraining means as an elastic body disposed on the opposite side of the pressing body with respect to the drive gear. And
[0010]
Another object of the present invention is to provide an electric power steering device that can eliminate an increase in the number of assembly steps due to the provision of an elastic body by supporting the drive gear with a bearing provided with an elastic body. To do.
[0011]
Furthermore, by providing the drive gear with a resistance against the pressing force by the male screw and providing an elastic body that suppresses the pressing force, the balance between the pressing force by the male screw and the suppression force by the elastic body It is an object of the present invention to provide an electric power steering device that can reduce the amount of backlash without applying preload to the drive gear and can reduce the meshing resistance of the meshing portion.
[0012]
[Means for Solving the Problems]
An electric power steering apparatus according to a first aspect of the present invention includes a drive gear rotated by a steering assist motor, a driven gear meshing with the drive gear and connected to a steering mechanism, and a meshing portion of the drive gear with the driven gear. In the electric power steering apparatus provided with a pressing body that is pressed to the side, and assisting steering by rotation of the motor, the driving gear gives the driving gear a resistance force against the pressing force of the pressing body, and the pressing gear An elastic body that suppresses the force is supported by a holding cylinder provided on the peripheral surface of the elastic body and a bearing fitted in the holding cylinder .
[0013]
In the first invention, the pressing body presses the drive gear toward the meshing portion side with the driven gear. Since this pressing force is suppressed by the suppression means, the pressing force and the suppression force by the suppression means The driving gear can be stopped at a balanced position, the backlash amount can be reduced without applying preload to the driving gear, and the meshing resistance of the meshing portion can be reduced.
[0018]
An electric power steering apparatus according to a second aspect of the present invention includes a drive gear rotated by a steering assist motor, a driven gear meshed with the drive gear and connected to a steering mechanism, and a meshing portion of the drive gear with the driven gear. In the electric power steering apparatus provided with a pressing body that is pressed to the side and assisting the steering by the rotation of the motor, the pressing body uses a male screw to which a lock nut is screwed so that the relative rotation is possible. The drive gear gives a resistance force against the pressing force by the male screw to the drive gear, and an elastic body for suppressing the pressing force is provided on the peripheral surface of the holding cylinder, and the bearing is fitted in the holding cylinder. It is characterized by being supported by.
[0019]
In the second invention, the male screw presses the drive gear to the meshing portion side with the driven gear via the bearing, but since this pressing force is suppressed by the elastic body, the pressing force and the elastic body The driving gear can be stopped at a position balanced with the suppression force, and the backlash amount can be reduced without applying preload to the driving gear.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
Embodiment 1
FIG. 1 is a sectional view of an electric power steering apparatus according to the present invention.
The electric power steering apparatus has one end connected to a steering wheel 1 for steering and a first steering shaft 2 having a cylindrical portion at the other end, and is inserted into the cylindrical portion, and one end thereof is the other end of the steering shaft 2. A torsion bar 3 that is coaxially coupled to the steering wheel 1 and twisted by the action of a steering torque applied to the steering wheel 1, and a second steering shaft 4 that is coaxially coupled to the other end of the torsion bar 3; A torque sensor 5 for detecting a steering torque applied to the steered wheel 1 by a relative rotational displacement amount of the first and second steering shafts 2 and 4 according to the twist of the torsion bar 3, and a torque detected by the torque sensor 5 A steering assist motor 6 driven on the basis of the motor, a drive gear (hereinafter referred to as a worm) 71 and a driven gear which are linked to the rotation of the motor 6 and decelerate the rotation and transmit it to the second steering shaft 4. (Hereinafter referred to as warm hoi A speed reduction mechanism 7 having called Le) 72, and a housing 8 in which the torque sensor 5 and the reduction mechanism 7 is housed, the motor 6 is attached to the housing 8.
[0021]
The housing 8 is continuous with the first accommodating portion 8a for accommodating the torque sensor 5, the accommodating portion 8a, the second accommodating portion 8b for accommodating the worm wheel 72, and the accommodating portion 8b. And a third accommodating portion 8c that accommodates the worm 71.
[0022]
2 is a cross-sectional view of the speed reduction mechanism, and FIG. 3 is an enlarged cross-sectional view taken along line III-III in FIG.
The accommodating portion 8c is elongated in the axial direction of the worm 71, and a first fitting hole 81 and a holding hole 82 drilled to face the inner surface of the fitting hole 81 are provided at one end in the longitudinal direction. A pressing body 10 for moving the first rolling bearing 9 supporting the shaft portion 71a at one end of the worm 71 in the holding hole 82 in the radial direction so as to preload the meshing portion of the worm 71 with the worm wheel 72 is movable. It is held in.
[0023]
The pressing body 10 uses a male screw 10a screwed into the holding hole 82, one end of which is in contact with the outer peripheral surface of the rolling bearing 9, and the other end is a lock nut that prevents the screw 10a from loosening. 11 is screwed so as to be relatively rotatable.
[0024]
A second fitting hole 83 and a screw hole 84 continuing to the fitting hole 83 are provided at the other end of the accommodating portion 8c, and a screw ring 12 for adjusting the axial position of the worm 71 is screwed into the screw hole 84. A lock nut 13 is screwed onto the screw ring 12. Further, the motor 6 having a case communicating with the third accommodating portion 8c is attached to the housing 8.
[0025]
The speed reduction mechanism 7 includes a shaft portion 71b connected to the output shaft 60 of the motor 6 and a worm 71 having the shaft portion 71a, and a worm wheel 72 fitted and fixed in the middle of the second steering shaft 4. The rotation of the output shaft 60 is decelerated and transmitted to the second steering shaft 4 by the meshing of the worm 71 and the worm wheel 72, and a steering mechanism of, for example, a rack and pinion type is passed from the second steering shaft 4 via a universal joint. (Not shown).
[0026]
The worm 71 is arranged so as to cross the axis of the second steering shaft 4, and the first and second rolling bearings 9, 14 are fitted to shaft portions 71 a, 71 b provided integrally at both ends thereof. It is.
[0027]
Around the first rolling bearing 9, the first fitting hole 81 is fitted into the first fitting hole 81 to suppress the pressing force by giving the worm 71 a resistance against the pressing force by the male screw 10a. And a holding cylinder 16 joined to the inside of the elastic body 15, and the first rolling bearing 9 is fitted in the holding cylinder 16.
[0028]
FIG. 4 is a perspective view of the holding cylinder and the elastic body.
The elastic body 15 is made of synthetic rubber and is bent in the fitting hole 81 by the pressing force of the male screw 10a. Further, a through hole 15a penetrating in the radial direction is provided at a position facing the holding hole 82, and one end of the male screw 10a is inserted into the through hole 15a. It is made to contact | abut to the outer peripheral surface.
[0029]
At one end of the holding cylinder 16 in the axial direction, a disk-shaped flange 16a bent in the radial direction is provided.
[0030]
In the electric power steering apparatus configured as described above, when the worm 71 is incorporated, the holding cylinder 16 having the elastic body 15 bonded to the outer peripheral surface thereof is inserted into the third housing portion 8c, and the elastic body 15 is inserted into the first housing. After fitting and fixing in the fitting hole 82, the worm 71 fitted with the first and second rolling bearings 9 and 14 is inserted from the second fitting hole 83 into the third accommodating portion 8c, and the first The rolling bearing 9 is fitted into the holding cylinder 16 and the second rolling bearing 14 is fitted into the second fitting hole 83, and the screw ring 12 is screwed into the screw hole 84.
[0031]
The rotational operating force of the screw ring 12 is transmitted to the worm 71 via the outer ring, the rolling element, and the inner ring of the second rolling bearing 14, and there is no gap in the axial direction of the second rolling bearing 14 and the worm 71 Further, the rotational operating force of the screw ring 12 is transmitted from the worm 71 to the flange portion 16a of the holding cylinder 16 via the inner ring, rolling elements and outer ring of the first rolling bearing 9. In addition, there is no gap in the axial direction of the rolling bearing 9, and the play of the worm 71 in the axial direction can be prevented.
[0032]
Next, by turning the male screw 10a screwed into the holding hole 82, one end of the male screw 10a is inserted into the through hole 15a of the elastic body 15, and abuts on the outer peripheral surface of the holding cylinder 16, thereby holding the holding screw. The worm 71 is pressed against the meshing portion side with the worm wheel 72 through the cylinder 16 and the rolling bearing 9. By this pressing, the elastic body 15 is bent, and a preload is applied to the meshing portion of the worm 71 with the worm wheel 72. In this case, since the pressing force by the external screw 10a is suppressed by the elastic restoring force of the elastic body 15, the worm 71 can be stopped at a position where the pressing force and the suppressing force (elastic restoring force) by the elastic body 15 are balanced. In addition, the backlash amount can be reduced without applying preload to the worm 71, and the meshing resistance of the meshing portion can be reduced.
[0033]
Further, since the lock nut 11 is screwed to the male screw 10a, the lock nut 11 can be attached even when the meshing state changes with time due to an increase in the wear amount of the teeth of the worm 71 and the worm wheel 72. The position of the worm 71 relative to the worm wheel 72 can be corrected by turning the male screw 10a, and the backlash amount can be reduced.
[0034]
Embodiment 2 (Reference Example)
FIG. 5 is a cross-sectional view showing a configuration of an electric power steering apparatus according to a reference example . In the electric power steering apparatus shown as a reference example in the second embodiment, the holding cylinder 16 is eliminated, and the first rolling bearing 9a in which the elastic body 15 is joined to the outer peripheral surface thereof by joining means such as vulcanization adhesion is provided. In use, the rolling bearing 9 a supports the shaft portion 71 a of the worm 71.
[0035]
In the second embodiment, one end of the pressing body 10 using the male screw 10a comes into contact with the outer peripheral surface of the first rolling bearing 9a through the through hole 15a of the elastic body 15, and the first rolling bearing 9a. The worm 71 is pressed to the side of the meshing portion with the worm wheel 72 through the. By this pressing, the elastic body 15 is bent, and a preload is applied to the meshing portion of the worm 71 with the worm wheel 72. The worm 71 can be stopped at a position where the pressing force and the restraining force (elastic restoring force) by the elastic body are balanced, the backlash amount can be reduced without applying preload to the worm 71, and the meshing portion The meshing resistance can be reduced.
[0036]
In the second embodiment, since the other configurations and operations are the same as those of the first embodiment, common parts are denoted by the same reference numerals, and detailed description of the configuration and description of the operation are omitted.
[0037]
Embodiment 3 (reference example)
FIG. 6 is a cross-sectional view showing a configuration of an electric power steering apparatus according to a reference example . The electric power steering apparatus shown as a reference example in the third embodiment is arranged only on the side opposite to the pressing body 10 with respect to the worm 71 without forming the elastic body 15 as a restraining means in a cylindrical shape. The elastic body 15b is used.
[0038]
In the third embodiment, one end of the pressing body 10 using the male screw 10 a comes into contact with the outer peripheral surface of the holding cylinder 16, and the worm 71 is moved to the side of the meshing portion with the worm wheel 72 through the holding cylinder 16. Will be pressed. The elastic body 15b is bent by this pressing and preload is applied to the meshing portion of the worm 71 with the worm wheel 72, but the worm 71 is in a position where the pressing force and the restraining force (elastic restoring force) by the elastic body 15b are balanced. The amount of backlash can be reduced without applying preload to the worm 71, and the meshing resistance of the meshing portion can be reduced.
[0039]
In the third embodiment, since other configurations and operations are the same as those in the first embodiment, common parts are denoted by the same reference numerals, and detailed description of the configuration and description of the operation are omitted.
[0040]
In the embodiment described above, the male screw 10a to which the lock nut 11 is screwed is used as the pressing body 10, and the loosening of the male screw 10a is prevented by the lock nut 11. 11, the backlash amount may be reduced as described above, and then the other end of the male screw 10a may be caulked to prevent loosening of the male screw 10a.
[0041]
In the embodiment described above, the rolling bearings 9 and 9a are used as bearings for supporting one end of the worm 71. However, a sliding bearing may be used.
[0042]
The speed reduction mechanism 7 according to the embodiment described above is a worm gear provided with a drive gear 71 that is a worm 71 and a driven gear 72 that is a worm wheel, and is also a driven gear that is a hypoid pinion and a driven wheel that is a hypoid wheel. It may be a hypoid gear provided with a gear. Further, the reduction mechanism may be a bevel gear.
[0043]
【The invention's effect】
According to the first invention, since the pressing force of the pressing body that presses the drive gear toward the meshing portion with the driven gear is suppressed by the suppression means, the drive gear is at a position where the pressing force and the suppression force by the suppression means are balanced. The backlash amount can be reduced without applying preload to the drive gear, and the meshing resistance of the meshing portion can be reduced.
[0046]
According to the second aspect of the invention, the pressing force of the male screw that presses the drive gear toward the meshing portion with the driven gear is suppressed by the elastic body, so that the driving force is driven at a position where the pressing force and the elastic restoring force of the elastic body are balanced. The gear can be stopped, and the amount of backlash can be reduced without applying preload to the drive gear.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an electric power steering apparatus according to the present invention.
FIG. 2 is a cross-sectional view of a speed reduction mechanism portion of the electric power steering apparatus according to the present invention.
FIG. 3 is an enlarged cross-sectional view taken along line III-III in FIG.
FIG. 4 is a perspective view of a holding cylinder and an elastic body of the electric power steering apparatus according to the present invention.
FIG. 5 is a cross-sectional view showing a configuration of an electric power steering apparatus according to a reference example .
FIG. 6 is a cross-sectional view showing a configuration of an electric power steering apparatus according to a reference example .
FIG. 7 is a cross-sectional view of a conventional electric power steering device.
FIG. 8 is a cross-sectional view of a speed reduction mechanism portion of a conventional electric power steering apparatus.
[Explanation of symbols]
6 Motor 9, 9a First rolling bearing (bearing)
DESCRIPTION OF SYMBOLS 10 Pushing body 10a Male screw 11 Lock nut 15, 15b Elastic body (suppression means)
16 Holding cylinder 71 Worm (drive gear)
72 Worm wheel (driven gear)

Claims (2)

A drive gear that is rotated by a steering assist motor, a driven gear that meshes with the drive gear and is connected to a steering mechanism, and a pressing body that presses the drive gear toward the meshing portion with the driven gear, In the electric power steering apparatus configured to assist steering by rotation of a motor, an elastic body that suppresses the pressing force by applying a resistance to the driving gear to the driving gear against the pressing force by the pressing body is provided on a peripheral surface thereof. An electric power steering apparatus characterized by being supported by a provided holding cylinder and a bearing fitted inside the holding cylinder .   A drive gear that is rotated by a steering assist motor, a driven gear that meshes with the drive gear and is connected to a steering mechanism, and a pressing body that presses the drive gear toward the meshing portion with the driven gear, In the electric power steering apparatus configured to assist steering by rotation of a motor, the pressing body uses a male screw to which a lock nut is screwed so that the relative rotation is possible, and the driving gear is a pressing force by the male screw. An elastic body that applies a drag force to the drive gear to suppress the pressing force is supported by a holding cylinder provided on a peripheral surface thereof and a bearing fitted in the holding cylinder. Power steering device.

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