JP4244642B2 - 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]
An electric power steering apparatus for a vehicle includes a motor for assisting steering and a reduction gear mechanism that transmits a rotational force of the motor to the steering means, and the operation of the steering means according to the rotation of the steering means. It is configured to assist with the rotation of the vehicle and reduce the labor burden on the driver for steering.
[0003]
The reduction gear mechanism includes a worm as a drive gear that is interlocked with the rotation of the motor and a worm wheel as a driven gear that meshes with the worm.
In the electric power steering device in which the reduction gear mechanism is used in this way, in order to reduce the backlash amount of the meshing portion of the worm and the worm wheel, and eliminate the rattling noise due to the backlash at the time of turning, Although the worm, the worm wheel, and the housing are selected and assembled so that the distance between the rotation centers of the worm and the worm wheel is within an allowable range (so-called layered assembly), this assembly takes a lot of time.
[0004]
Therefore, a cylindrical shape that can move the worm on the non-motor side of the worm, which is rotatably supported by the housing via the rolling bearing, on the motor-side shaft portion and the non-motor-side shaft portion in the direction in which the worm is pressed against the worm wheel. Bearing member, a coil spring for urging the bearing member, and an operating body for moving the bearing member via the coil spring, and by operating the operating body, a preload is applied to the meshing portion of the worm with the worm wheel. In addition, there is known an electric power steering apparatus configured to adjust the backlash amount of the meshing portion so as to eliminate rattling noise due to backlash during turning (for example, Patent Document 1). .
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-211943
[Problems to be solved by the invention]
However, in the electric power steering apparatus provided with the bearing member, the coil spring, and the operating body as in Patent Document 1, a relatively large number of parts are required to reduce the backlash amount of the meshing portion. There was a demand for improvement. Also, since the worm moves so as to tilt as a whole around one end connected to the drive shaft of the motor, when the preload is applied to the meshing portion, the meshing state may fluctuate greatly compared to when the preload is not applied. there were.
[0007]
The present invention has been made in view of such circumstances, and a main object is to reduce the number of parts for reducing the backlash amount of the meshing portion and to easily reduce the backlash amount. An object of the present invention is to provide an electric power steering device that can be used.
Another object of the present invention is to provide an electric power steering device that can reduce the change in the meshing state at the meshing portion when preload is applied to the meshing portion.
[0008]
[Means for Solving the Problems]
An electric power steering apparatus according to a first aspect of the present invention is a drive gear that is rotated by a steering assist motor and is rotatably supported in a housing via two bearings, and meshes with the drive gear and is used as a steering means. In the electric power steering apparatus provided with a connected driven gear and assisting steering by rotation of the motor, the housing has an opening at a position facing the outer peripheral surface of each bearing , and the housing is provided from the outside of the housing. Two pressing portions that are inserted into the openings and elastically press the respective bearings so as to press the driving gear toward the driven gear; a connecting portion that connects the pressing portions; and the connecting portion is located outside the housing. And a pressing body having a mounting portion attached to the housing.
[0009]
In the first invention, in a state where the drive gear is supported in the housing via the two bearings, the pressing member is inserted into the two openings of the housing which are set at positions facing the outer peripheral surfaces of the two bearings. By inserting the two pressing portions, the pressing portions can elastically press the two bearings and apply preload to the meshing portion, so that the backlash amount of the meshing portion can be easily adjusted. Moreover, since the backlash amount of the meshing portion can be adjusted by one pressing body, the structure is simple, and the cost can be reduced in combination with the simple adjustment of the backlash amount.
Moreover, since the drive gear can be moved as a whole by the pressing body, when a preload is applied to the meshing portion, the change in the contact state between the tooth surfaces at the meshing portion can be reduced.
[0010]
The electric power steering apparatus according to a second aspect is characterized in that the pressing body is made of an elastic plate.
In the second invention, the molded pressing body can be used, and the cost can be further reduced.
[0011]
An electric power steering apparatus according to a third aspect of the present invention is a drive gear that is rotated by a steering assist motor and is rotatably supported in a housing via two bearings, and meshes with the drive gear to serve as a steering means. In the electric power steering apparatus provided with a connected driven gear and assisting steering by rotation of the motor, the housing has an opening at a position facing the outer peripheral surface of each bearing , and the housing is provided from the outside of the housing. Two pressing portions that are inserted into the openings and press the respective bearings so as to press the drive gear toward the driven gear, a connecting portion that connects the pressing portions, and a housing in which the connecting portion is positioned outside the housing. And a pressing body having a mounting portion attached to the housing, and an elastic body is provided between the pressing body and the housing or each bearing. .
In the third invention, the cost of the pressing body, and hence the cost of the electric power steering device can be reduced as compared with the case where the entire pressing body is formed of an elastic material.
[0012]
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 an enlarged cross-sectional view showing a configuration of a reduction gear mechanism portion of an electric power steering device according to the present invention, FIG. 2 is a cross-sectional view showing an overall configuration of the electric power steering device, and FIG. FIG. 4 is a plan view showing a configuration of a reduction gear mechanism portion.
[0013]
The electric power steering apparatus is connected to a steering assist motor 1 and a drive shaft 1a of the motor 1 via a shaft coupling 2, and a worm 3 as a small gear and a worm as a large gear meshing with the worm 3. A reduction gear mechanism A having a wheel 4, a housing 5 as a support member that accommodates and supports the reduction gear mechanism A, and steering means 6 connected to the reduction gear mechanism A are provided.
[0014]
The steering means 6 has one end connected to the steering wheel B for steering and an input shaft 61 having a cylindrical portion 61 a at the other end, and is inserted into the cylindrical portion 61 a and one end thereof is connected to the input shaft 61. A torsion bar 62 connected to the cylinder portion 61a and twisted by the action of steering torque applied to the steered wheel B, and an output shaft 63 connected to the other end portion of the torsion bar 62 and connected to the reduction gear mechanism A. The output shaft 63 is connected to, for example, a rack and pinion type steering mechanism (not shown) via a universal joint.
[0015]
The housing 5 accommodates a worm 3 having shaft portions 3b and 3c at both ends of the tooth portion 3a, and has a substantially semi-cylindrical shape in which the shaft portions 3b and 3c of the worm 3 are rotatably supported via rolling bearings 7 and 8. The first housing portion 5a and the second housing portion 5b which is connected to the first housing portion 5a and houses the worm wheel 4 are provided. The second housing portion 5b has an output shaft 63 and an output shaft 63. The worm wheel 4 is supported via two fitted rolling bearings 10 and 11. Moreover, it has the motor attachment part 5c connected to the longitudinal direction one end part of the 1st accommodating part 5a, and the motor 1 is attached to this motor attachment part 5c.
[0016]
The first accommodating portion 5a has a substantially semi-cylindrical shape whose outer surface is curved in a substantially C shape, one end in the longitudinal direction thereof is opened as a worm insertion port 5d, and the other end is closed. Fitting holes 51 and 52 into which the outer rings 7a and 8a of the rolling bearings 7 and 8 are removably fitted at both longitudinal ends of the first accommodating part 5a, and the peripheral surfaces of the fitting holes 51 and 52 Openings 53 and 54 are provided so as to face a part. The fitting holes 51 and 52 are formed in an oval shape decentered in the direction in which the distance H between the rotation centers of the worm 3 and the worm wheel 4 is increased, and the rolling bearings 7 and 8 are rotated in the fitting holes 51 and 52. It can be moved in the direction in which the center-to-center distance H increases. In addition, two locking recesses 55, 55 are provided on the outer surface of the first housing portion 5a at positions beyond the semicircular position.
[0017]
The worm 3 includes a tooth portion 3a and shaft portions 3b and 3c connected to both ends of the tooth portion 3a. Inner rings 7b and 8b of rolling bearings 7 and 8 are fitted into the shaft portions 3b and 3c by press-fitting. The inner rings 7b, 8b are restricted from moving in the axial direction by abutting against the edge of the tooth portion 3a. Since the outer rings 7a and 8a of the rolling bearings 7 and 8 into which the inner rings 7b and 8b are press-fitted are detachably fitted into the fitting holes 51 and 52, the fitting between the fitting holes 51 and 52 and the outer rings 7a and 8a is performed. There is a slight gap. One shaft portion 3 b is connected to the drive shaft 1 a of the motor 1 through the shaft coupling 2.
[0018]
FIG. 5 is a perspective view showing the configuration of the pressing body.
In this way, a pressing body 9 that elastically presses the rolling bearings 7 and 8 supporting the shaft portions 3b and 3c of the worm 3 in a direction in which the distance H between the rotation centers becomes shorter is attached to the housing 5. The pressing body 9 is made of a formed spring steel plate, and includes two pressing portions 91 and 91 inserted into the openings 53 and 54 of the housing 5, a band-shaped connecting portion 92 that connects the pressing portions 91 and 91, There are two attachment portions 93, 93 that are attached to the housing 5 by positioning the connecting portion 92 outside the first housing portion 5 a.
[0019]
The pressing portions 91 and 91 are inclined outward in the axial length direction of the worm 3 so as to contact a part of the edges of the outer rings 7a and 8a of the rolling bearings 7 and 8, and the rolling bearings 7 and 8 have a radial direction. A pressing force and a component force in the axial direction are applied.
[0020]
The connecting portion 92 has a longitudinal direction parallel to the axis of the worm 3 and is disposed at the center of the first accommodating portion 5a in the bending direction.
[0021]
The attachment parts 93, 93 are curved in an arc shape from the longitudinal center part of the connecting part 92, and have locking projections 94, 94 at their tips. Then, by engaging the locking projections 94, 94 with the locking recesses 55, 55 of the housing 5, the pressing portions 91, 91 are bent via the connecting portion 92, and the pressing portions 91, 91 are elastically restored. The rolling bearings 7 and 8 are elastically pressed in a direction in which the distance H between the rotation centers is shortened by force.
[0022]
In the electric power steering apparatus configured as described above, when the worm 3 is incorporated, for example, the worm 3 in which the inner rings 7b and 8b of the rolling bearings 7 and 8 are press-fitted into the shaft portions 3b and 3c is accommodated in the housing 5 in the first housing. The outer ring 7a of the rolling bearing 7 is inserted into the fitting hole 51, and the outer ring 8a of the rolling bearing 8 is fitted into the fitting hole 52 from one end of the part 5a. It supports to the 1st accommodating part 5a.
[0023]
After the worm 3 is assembled, the pressing portions 91 and 91 of the pressing body 9 are inserted into the openings 53 and 54 from the outside of the first housing portion 5a, and the pressing portions 91 and 91 are the edges of the outer rings 7a and 8a in the rolling bearings 7 and 8. The mounting portions 93 and 93 are externally fitted to the outside of the first housing portion 5a, and the engaging convex portions 94 and 94 are engaged with the engaging concave portions 55 and 55, respectively. By attaching the pressing body 9, the pressing portions 91, 91 are bent through the connecting portion 92, and the elastic bearing force of the pressing portions 91, 91 causes the rolling bearings 7, 8 to move in a direction in which the distance H between the rotation centers becomes shorter. Can be elastically pressed. The pressing force of the pressing portions 91 and 91 is applied to the rolling bearings 7 and 8 as a pressing force in the radial direction and a component force in the axial length direction, and by the component force in the axial length direction, the rolling bearings 7 and 8 The outer rings 7a and 8a are pressed in the axial direction, the outer rings 7a and 8a move in the axial direction with respect to the inner rings 7b and 8b, the axial clearance of the rolling bearings 7 and 8 disappears, and the axial direction of the worm 3 moves. Can be prevented, and the backlash amount of the meshing portion can be adjusted.
[0024]
In this way, after the worm 3 is assembled, the rolling bearings 7 and 8 can be elastically pressed by attaching the pressing body 9 from the outside of the housing 5 and preload can be applied to the meshing portion. Adjustment can be simplified. Further, since the backlash amount of the meshing portion can be adjusted by one pressing body 9, the structure is simple, and the cost can be reduced in combination with the simple adjustment of the backlash amount.
[0025]
In addition, since the pressing body 9 presses the two rolling bearings 7 and 8 that support the worm 3 with both ends to move (bias) the worm 3 toward the worm wheel as a whole, a preload is applied to the meshing portion. When this occurs, the change in the contact state between the tooth surfaces at the meshing portion can be reduced.
[0026]
Embodiment 2
6 is an enlarged sectional view showing the configuration of the reduction gear mechanism portion of the second embodiment, FIG. 7 is a plan view showing the configuration of the reduction gear mechanism portion, and FIG. 8 is a perspective view showing the configuration of the pressing body.
In the electric power steering apparatus according to the second embodiment, instead of attaching the pressing body 9 to the outside of the first accommodating portion 5a as in the first embodiment, the pressing body 9a is provided in the vicinity of the openings 53 and 54. It was locked and attached. The pressing body 9a is made of a formed spring steel plate, is inserted into the openings 53 and 54 of the housing 5, and has two pressing portions 91 and 91 that are in contact with part of the edges of the outer rings 7a and 8a of the rolling bearings 7 and 8. Each of the pressing portions 91, 91 has a strip-shaped connecting portion 92 that connects one end of the pressing portions 91, 91, and mounting portions 96, 97 that are connected to the other ends of the pressing portions 91, 91 via bent portions 95, 95. The tip of one attachment part 96 is formed in a bowl shape.
In the vicinity of the opening 53 of the housing 5, a locking recess 56 for locking the flange portion of the mounting portion 96 is provided, and in the vicinity of the opening 54, a locking recess 57 for locking the mounting portion 97. Is provided.
[0027]
In Embodiment 2, after the worm 3 is assembled, the pressing portions 91 and 91 of the pressing body 9a are inserted into the openings 53 and 54 from the outside of the first housing portion 5a, and the pressing portions 91 and 91 are inserted into the rolling bearing 7. , 8 is brought into contact with a part of the edge of the outer ring 7a, 8a, one mounting portion 97 is locked to the locking recess 57, and the flange portion of the other mounting portion 96 is locked to the locking recess 56. The pressing portions 91 and 91 are bent by the attachment of the pressing body 9a, and the rolling bearings 7 and 8 can be elastically pressed in a direction in which the distance H between the rotation centers is shortened by the elastic restoring force of the pressing portions 91 and 91. it can.
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof and description of operations and effects are omitted.
[0028]
Embodiment 3
FIG. 9 is an enlarged cross-sectional view showing the configuration of the reduction gear mechanism portion of the third embodiment.
The electric power steering apparatus according to the third embodiment is configured by replacing the entire pressing bodies 9 and 9a with a flexible elastic plate such as a spring steel plate as in the first and second embodiments. Elastic bodies 12, 12 are provided between the pressing portions 91, 91 of the pressing body 9 b made of a flexible material and the rolling bearings 7, 8, and the rolling bearings 7, 8 are caused by the elastic restoring force of the elastic bodies 12, 12. Is configured to press.
The elastic bodies 12 and 12 in the first embodiment are made of an elastic plate such as synthetic rubber, and are coupled to the pressing bearings 91 and 91 on the side of the rolling bearings 7 and 8, and the elastic bodies 12 and 12 are outer rings in the rolling bearings 7 and 8. 7a and 8a are in contact with part of the edge.
[0029]
In the third embodiment, after the worm 3 is assembled, the pressing portions 91 and 91 of the pressing body 9b are inserted into the openings 53 and 54 from the outside of the first housing portion 5a, and the elastic bodies 12 and 12 are inserted into the rolling bearing 7. , 8 is brought into contact with a part of the edge of the outer ring 7a, 8a, the mounting portions 93, 93 are fitted outside the first housing portion 5a, and the engaging convex portions 94, 94 are engaged with the engaging concave portions 55, 55. By engaging, the elastic bodies 12 and 12 are bent, and the rolling bearings 7 and 8 can be elastically pressed in the direction in which the distance H between the rotation centers is shortened by the elastic restoring force of the elastic bodies 12 and 12.
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof and description of operations and effects are omitted.
[0030]
In the third embodiment, the elastic body 12 is provided between the pressing portions 91 and 91 and the rolling bearings 7 and 8, and between the pressing portions 91 and 91 and the openings 53 and 54 of the housing 5. You may provide between the connection part 92 or the attachment parts 93 and 93 and the housing 5. FIG. In this case, the elastic bodies 12 and 12 are configured to be coupled to, for example, the outer surfaces of the pressing portions 91 and 91, the connecting portions 92, or the inner surfaces of the mounting portions 93 and 93.
[0031]
In the embodiment described above, the reduction gear mechanism A is a worm gear including the worm 3 that is a driving gear and the worm wheel 4 that is a driven gear, and also a hypoid pinion that is a driving gear and a hypoid that is a driven gear. It may be a hypoid gear with a wheel. Further, the reduction gear mechanism may be a bevel gear.
[0032]
【The invention's effect】
According to the first invention, the backlash amount of the meshing portion can be adjusted by one pressing body, and the pressing body can be attached from the outside of the housing while the drive gear is supported in the housing. Therefore, the backlash amount can be easily adjusted, the structure is simple, and the cost can be reduced. Further , when preload is applied to the meshing portion, the change in the contact state between the tooth surfaces at the meshing portion can be reduced.
[0033]
According to the second invention, the molded pressing body can be used, and the cost can be further reduced.
[0034]
According to the third aspect of the present invention, the cost of the pressing body, and hence the cost of the electric power steering device can be reduced as compared with the case where the entire pressing body is formed of an elastic material.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view showing a configuration of a reduction gear mechanism portion of a first embodiment of an electric power steering apparatus according to the present invention.
FIG. 2 is a cross-sectional view showing the overall configuration of the electric power steering apparatus according to the present invention.
3 is a cross-sectional view taken along line III-III in FIG.
FIG. 4 is a plan view showing a configuration of a reduction gear mechanism portion of the electric power steering apparatus according to the present invention.
FIG. 5 is a perspective view showing a configuration of a pressing body of the electric power steering apparatus according to the present invention.
FIG. 6 is an enlarged cross-sectional view showing a configuration of a reduction gear mechanism portion of a second embodiment.
7 is a plan view showing a configuration of a reduction gear mechanism portion of a second embodiment. FIG.
FIG. 8 is a perspective view showing a configuration of a pressing body according to a second embodiment.
FIG. 9 is an enlarged cross-sectional view showing a configuration of a reduction gear mechanism portion according to a third embodiment.
[Explanation of symbols]
1 Motor 3 Worm (drive gear)
4 Worm wheel (driven gear)
5 Housing 53, 54 Opening 6 Steering means 7, 8 Rolling bearing (bearing)
9, 9a, 9b Pressing body 91 Pressing part 92 Connecting part 93, 96, 97 Mounting part 12 Elastic body

Claims (3)

A drive gear that is rotated by a steering assist motor and rotatably supported in the housing via two bearings, and a driven gear that meshes with the drive gear and is connected to the steering means; In the electric power steering apparatus configured to assist steering, the housing has an opening at a position facing the outer peripheral surface of each bearing , and is inserted into the opening from the outside of the housing, and the drive gear is used as a driven gear. A pressing body having two pressing portions that elastically press each bearing so as to be pressed, a connecting portion that connects the pressing portions, and a mounting portion that is attached to the housing by positioning the connecting portion outside the housing. An electric power steering apparatus comprising:   The electric power steering apparatus according to claim 1, wherein the pressing body is made of an elastic plate. A drive gear that is rotated by a steering assist motor and rotatably supported in the housing via two bearings, and a driven gear that meshes with the drive gear and is connected to the steering means; In the electric power steering apparatus configured to assist steering, the housing has an opening at a position facing the outer peripheral surface of each bearing , and is inserted into the opening from the outside of the housing, and the drive gear is used as a driven gear. A pressing body having two pressing portions that press the bearings so as to be pressed, a connecting portion that connects the pressing portions, and a mounting portion that is attached to the housing with the connecting portion positioned outside the housing. An electric power steering device, wherein an elastic body is provided between the pressing body and the housing or each bearing.

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