JP4100218B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus using an electric motor as a generation source of a steering assist force.
[0002]
[Prior art]
The electric power steering apparatus for a vehicle includes an electric motor for assisting steering and a reduction gear mechanism that transmits a rotational force of the electric motor to the steering means, and the operation of the steering means according to the rotation of the steering means is described above. It is configured to assist by the rotation of the electric motor and reduce the labor burden on the driver for steering.
[0003]
The reduction gear mechanism has a worm whose one end is interlocked with the output shaft of the electric motor, a worm wheel meshing with the worm and connected to the steering means, and the distance between the rotation center of the worm and the worm wheel becomes long and short. A pressing body that is capable of moving in a direction, and that presses the worm toward the worm wheel, and a coil spring that biases the pressing body to apply a preload to the meshing portion of the worm with the worm wheel, the meshing portion It is configured to reduce the amount of backlash by applying a preload to (for example, Patent Document 1).
[0004]
By the way, in the electric power steering device, when a reverse input load is applied to the worm from the steered wheel via the steering shaft when the vehicle travels on an uneven road, the worm has a long distance between the rotation centers. Since the pressing body moves and the coil spring bends while being pressed away from each other, a restricting body that restricts the amount of movement of the pressing body is provided. Further, since the pressing body and the regulating body are made of a metal material, an impact sound is generated when the moved pressing body abuts on the regulating body. Therefore, a buffer body such as a rubber plate or a synthetic resin plate is interposed between the pressing body and the regulating body to reduce the impact sound.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2003-2218
[Problems to be solved by the invention]
However, in the electric power steering apparatus provided with the shock absorber as described above, when the shock absorber has a high hardness, a sound is produced when the shock absorber comes into contact with the restrictor due to the reverse input load. In addition, when the hardness of the shock absorber is low, the durability is inferior to that of a shock absorber with high hardness, so when the shock absorber is deteriorated, the pressing body will be in direct contact with the restricting body, and it is expected that a noise will be produced. The
In addition, since a coil spring and a buffer body for adjusting the distance between the rotation centers are required separately from the pressing body and the limiting body, the number of parts is increased and the number of assembling steps is increased, and improvement measures are desired. It was.
[0007]
The present invention has been made in view of such circumstances, and provides an electric power steering device that can reduce noise in a pressing body portion due to a reverse input load and can reduce assembly man-hours. With the goal.
[0008]
[Means for Solving the Problems]
An electric power steering apparatus according to the present invention includes a drive gear rotated by an electric motor, a driven gear meshing with the drive gear and connected to the steering means, and a distance between the rotation centers of the drive gear and the driven gear is long and short. A pressing body that presses the drive gear toward the driven gear by this movement, a limiting body that restricts the amount of movement of the pressing body, and an interposition between the limiting body and the pressing body. An electric power steering apparatus comprising: a buffer body that urges the pressing body in a direction in which the distance between the rotation centers is shortened , and is configured to assist steering by rotation of the electric motor. has a recess on a side body and face, the cushion has a higher hardness than the soft portion and the soft quality portion having an elastic restoring force for applying a preload to meshing portions of the drive gear and the driven gear, 且A hard part having buffering properties is laminated in the moving direction of the pressing body, and the hard part has a thickness thicker than the depth of the recess, and the hard part is fitted into the recess. It is characterized by being held .
[0009]
In the present invention, when the drive gear is pressed so as to be separated in the direction in which the distance between the rotation centers becomes longer due to a reverse input load or the like, the soft portion of the buffer body comes into contact with, for example, the limiting body. It is possible to reduce the sound produced by the part. In addition, when the soft part deteriorates and breaks due to use over time, the hard part comes into contact with the restricting body instead of the soft part, so that the sounding at the buffer part can be reduced by the hard part. In addition, since the soft portion of the buffer body composed of the laminated soft portion and the hard portion applies a preload to the meshing portion, the number of parts can be reduced and the cost can be reduced as compared with the electric power steering device including the coil spring and the buffer body. Can be reduced.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof.
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, and FIG. 2 is a cross-sectional view showing an overall configuration of the electric power steering device.
[0013]
The electric power steering device is an electric motor 1 for assisting steering, and a drive gear connected to an output shaft 1a of the electric motor 1 via a shaft joint 2 having a male joint portion 2a and a female joint portion 2b. A reduction gear mechanism A having a worm 3 and a worm wheel 4 as a driven gear meshing with the worm 3, and a steering means 5 connected to the reduction gear mechanism A.
[0014]
The steering means 5 has one end connected to the steering wheel B for steering and a first steering shaft 51 having a cylindrical portion 51a at the other end, and is inserted into the cylindrical portion 51a, and one end thereof is the first. A torsion bar 52 that is connected to a cylindrical portion 51a of one steering shaft 51 and is twisted by the action of a steering torque applied to the steering wheel B, and the other end is connected to the other end of the torsion bar 52. The second steering shaft 53 is connected to, for example, a rack and pinion type steering mechanism (not shown) via a universal joint.
[0015]
The worm 3 of the reduction gear mechanism A has shaft portions 3 b and 3 c at both ends of the tooth portion 3 a, and the shaft portion 3 b as one end portion is rotatably supported by the housing 7 via the rolling bearing 6. In this state, the shaft is connected to the output shaft 1 a of the electric motor 1, and the shaft portion 3 c, which is the other end, is fitted and supported in the housing 7 via a cylindrical pressing body 8. The shaft portion 3 b is press-fitted into the inner ring 6 a of the rolling bearing 6. The worm wheel 4 is fitted and fixed in the middle of the second steering shaft 53.
[0016]
The housing 7 accommodates the worm 3, the first accommodating portion 7 a that rotatably supports the shaft portions 3 b and 3 c of the worm 3 via the rolling bearing 6 and the pressing body 8, and the worm wheel 4. It has the 2nd accommodating part 7b which supported the worm wheel 4 via the 2nd steering shaft 53 and the two rolling bearings 10 and 11 which were fitted by this 2nd steering shaft 53. As shown in FIG.
[0017]
The first accommodating portion 7a is elongated in the axial direction of the worm 3, and at one end in the longitudinal direction, a support hole 71 for loosely supporting the rolling bearing 6, a screw hole 72 connected to the support hole 71, and a motor attachment A portion 73 is provided, and a screw ring 12 for fixing the rolling bearing 6 to the screw hole 72 is screwed. Further, the electric motor 1 is attached to the motor attachment portion 73.
[0018]
At the other end of the first housing portion 7a, a concave hole 74 into which the shaft portion 3c of the worm 3 is inserted and the inner surface of the concave hole 74 are faced, and the distance H between the rotation centers of the worm 3 and the worm wheel 4 is long and short. A circular accommodation hole 75 drilled in the direction is provided. The shaft 3c is rotatably fitted in the accommodation hole 75, and the pressing body 8 that can move in the direction in which the distance H between the rotation centers becomes longer and shorter, and the restriction that limits the movement amount of the pressing body 8. A body 13 and a buffer body 14 that is interposed between the pressing body 8 and the limiting body 13 and biases the pressing body 8 in the direction in which the distance H between the rotation centers is shortened are accommodated. The restricting body 13 is screwed into the accommodation hole 75 so that the amount of deflection of the buffer body 14 can be adjusted by turning the restricting body 13.
[0019]
The pressing body 8 is formed of a metal material in a cylindrical shape, and is penetrated so as to be orthogonal to the moving direction at an intermediate position in the longitudinal direction, in other words, an intermediate position in the moving direction that moves along the receiving hole 75. A bearing hole 8a is provided, and a sliding bearing 81 in which the shaft portion 3c is rotatably fitted is provided in the bearing hole 8a, and the shaft portion 3c is pressed against the pressing body 8 via the sliding bearing 81. Is supported. In addition, a circular recess 8b is provided on a surface of the pressing body 8 facing the restricting body 13, and a buffer body 14 is fitted and held in the recess 8b.
[0020]
The buffer body 14 has a soft portion 14a made of a flexible soft material such as rubber, soft synthetic resin (for example, soft polyurethane home), and has a higher hardness than the soft portion 14a and has a buffer property of synthetic resin or the like. A hard portion 14b made of a hard material is laminated in the moving direction of the pressing body 8, the hard portion 14b is fitted into the concave portion 8b, and the soft portion 14a is in contact with the restricting body 13.
[0021]
The soft portion 14a urges the pressing body 8 by an elastic restoring force, and has an elastic force sufficient to apply a preload to the meshing portion of the worm 3 with the worm wheel 4, and is applied to the hard portion 14b by an adhesive or the like. Are combined. The hard part 14b is made of a synthetic resin plate and is thicker than the depth of the concave part 8b. When the soft part 14a is deteriorated and damaged, the hard part 14b comes into contact with the restricting body 13. It is.
[0022]
The output shaft 1a of the electric motor 1 and the shaft portion 3b of the worm 3 are interlocked and connected via a male joint portion 2a and a female joint portion 2b having serrations. The male joint portion 2a is configured by providing serrations on the peripheral surface of the shaft portion 3b, and the female joint portion 2b is configured by providing serrations inside the cylindrical member 2c fitted and fixed to the output shaft 1a. The male joint 2a and the female joint 2b are serrated.
[0023]
A torque sensor 15 for detecting the steering torque applied to the steered wheels B by the relative rotational displacement amount of the first steering shaft 51 and the second steering shaft 53 according to the twist of the torsion bar 52 is housed in the housing 7. The electric motor 1 is driven and controlled based on the torque detected by the torque sensor 15 and the like.
[0024]
In the electric power steering apparatus configured as described above, when the worm 3 is assembled, the pressing body 8 in which the buffer body 14 is fitted and held in the recess 8 b is inserted into the housing hole 75 of the housing 7. The shaft portion 3c of the worm 3 housed in the housing portion 7a is inserted into the bearing hole 8a of the pressing body 8 from the concave hole 74.
[0025]
After the worm 3 and the pressing body 8 are assembled in this way, the limiting body 13 is screwed into the receiving hole 75, and the pressing body 8 is moved via the buffer body 14 by rotating the limiting body 13, The worm 3 is swung with a support portion for the rolling bearing 6 as a fulcrum, the worm 3 is brought into contact with the tooth surface of the worm wheel 4, the distance H between the rotation centers of the worm 3 and the worm wheel 4 is adjusted, The amount of backlash at the meshing portion of the worm wheel 4 can be eliminated. Further, a buffer body 14 interposed between the pressing body 8 and the limiting body 13 urges the worm 3 toward the worm wheel 4 and applies a preload to the meshing portion of the worm 3 with the worm wheel 4. .
[0026]
A reverse input load is applied to the worm 3 from the steering wheel via the second steering shaft 53 and the worm wheel 4 when the vehicle travels on an uneven road, etc., so that the distance H between the rotation centers becomes longer. When the worm 3 is pressed and the pressing body 8 moves in the direction in which the distance H between the rotation centers becomes longer, the soft portion 14a of the buffer body 14 in which the soft portion 14a and the hard portion 14b are laminated is bent and pressed. Since the movement of the body 8 can be suppressed, it is possible to reduce the noise generated by the buffer body 14 and to reduce the increase in the amount of backlash. In addition, when the soft portion 14a is deteriorated due to use over time and the soft portion 14a is damaged by the reverse input load, the hard portion 14b comes into contact with the restricting body 13 and the movement of the pressing body 8 can be suppressed. Sound generated by the body 14 can be reduced.
[0027]
In the above in the embodiment described, slow衝体14 was a two-layer structure of the soft portion 14a and the hard layer, other, for example three layers soft portion 14a, 14a are stacked above and below the rigid portion 14b A structure may be sufficient, and it is good also as a structure laminated | stacked when the soft part 14a wraps the hard part 14b .
[0028]
FIG. 3 is an enlarged cross-sectional view showing another configuration of the reduction gear mechanism.
The reduction gear mechanism portion reduces the rotation of the electric motor 1 in two stages by a reduction mechanism C having a traction drive and a reduction gear mechanism A having a worm 3 and a worm wheel 4, so that the second steering shaft 53 is rotated. It is intended to be transmitted.
[0029]
The speed reduction mechanism C includes a sun roller portion 16 provided at an end portion of the output shaft 1 a of the electric motor 1, a plurality of rollers 17 that roll in contact with the sun roller portion 16, and a rotation center of the sun roller portion 16. And a support body 20 having a plurality of roller shafts 19 that support each roller 17 via a rolling bearing 18 and a cylindrical body 21 that contacts each roller 17 and surrounds each roller 17. The support 20 is formed integrally with the shaft portion 3 b of the worm 3, and the end of the output shaft 1 a is fitted to the center of the support 20 via a rolling bearing 22 so as to be relatively rotatable. The cylinder 21 is fixed to the inner side of the motor mounting portion 73 by a screw ring 23.
Further, the shaft portion 3 c on the counter-electric motor side of the worm 3 is supported by the other end portion of the first housing portion 7 a of the housing 7 via the rolling bearing 24.
[0030]
In the electric power steering apparatus configured as described above, the rotation of the electric motor 1 is transmitted to each roller 17 through the output shaft 1a and the sun roller portion 16, and the roller 17 revolves while rotating, whereby the roller shaft 19 and the support body are rotated. The rotation of the electric motor 1 can be decelerated through rotation of the worm 3 through the motor 20, and the rotation of the electric motor 1 can be further decelerated by the rotation of the worm wheel 4 meshing with the worm 3. As a result, a high speed reduction can be achieved, a high-speed rotation type electric motor can be used, and cost reduction, space saving, and high efficiency can be achieved.
In the embodiment of FIG. 3, other configurations and operations are the same as those of the embodiment of FIGS. 1 and 2. Therefore, the same components are denoted by the same reference numerals, and detailed descriptions and explanations of the functions and effects are given. Omitted.
[0031]
The reduction gear mechanism A according to the embodiment described above is a worm gear provided with a worm 3 as a driving gear and a worm wheel 4 as a driven gear, as well as a hypoid pinion and a hypoid as a driven gear. It may be a hypoid gear with a wheel. Further, a bevel gear and a helical gear may be used as the driving gear and the driven gear, or a gear obtained by combining a part of the helical gear and a part of the worm gear may be used.
[0032]
【The invention's effect】
As described above in detail, according to the present invention, when the drive gear is pressed by the reverse input load so as to be separated in the direction in which the distance between the rotation centers becomes longer, it is possible to reduce the noise generated in the buffer portion. In addition, even when the soft part is deteriorated due to use over time, it is possible to reduce the noise from the buffer part. In addition, the number of parts can be reduced and the cost can be reduced as compared with an electric power steering apparatus including a coil spring and a buffer.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view showing a configuration of a reduction gear mechanism portion 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.
FIG. 3 is an enlarged cross-sectional view showing another configuration of the reduction gear mechanism portion of the electric power steering apparatus according to the present invention.
[Explanation of symbols]
1 Electric motor 1a Output shaft 3 Worm (drive gear)
4 Worm wheel (driven gear)
8 Pressing body 13 Limiting body 14 Buffer body 14a Soft part 14b Hard part

Claims (1)

The drive gear rotated by the electric motor, the driven gear meshing with the drive gear and connected to the steering means, and the distance between the rotation centers of the drive gear and the driven gear can be moved in a longer and shorter direction. and pressing the pressing member toward the drive gear to the driven gear by a limiter for limiting the amount of movement of the pressing cylindrical body is interposed between said limiter and said pressing body, between the center of rotation pressing with body The electric power steering apparatus includes a shock absorber that biases the distance in a shorter direction, and assists steering by the rotation of the electric motor. The pusher has a recess on the side facing the limiter. and the cushion, the soft portion has an elastic restoring force for applying a preload to meshing portions of the drive gear and the driven gear and the higher hardness than soft quality portion, and a rigid portion said pressing member having a cushioning property How to move None of stacked laminated structure to said rigid portion has a thickness greater than the depth of said recess, an electric power steering apparatus, wherein a rigid portion are fitted held in said recess .

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