JP3624308B2 - Electric steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric 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. 6 is a cross-sectional view of an electric steering apparatus according to a conventional example, and FIG. 7 is a cross-sectional view of a speed reduction mechanism portion.
As shown in FIG. 6, for example, an electric steering apparatus for an automobile includes a first steering shaft 101 coupled to a steering wheel 100 for steering, and a lower end of the steering shaft 101 via a torsion bar 102. A torque applied to the first steering shaft 101 by rotating the steering wheel 100 and a second steering shaft 103 connected to a steering mechanism whose upper end is connected coaxially and whose lower end is connected to a wheel. Torque sensor 104 detected by twist generated in bar 102, steering assist motor 105 driven based on the detection result of torque sensor 104, and the output shaft of motor 105 are connected to decelerate the rotation of the output shaft. And a decelerating mechanism having a worm 106 and a worm wheel 107 that transmit to the second steering shaft 103, and a steering mechanism according to the rotation of the steering wheel 100 The operation was assisted by the rotation of the motor 105, it is configured to reduce the driver effort burden for steering.
[0004]
As shown in FIG. 7, 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 worm 106 and the worm wheel 107 are used in this way, the distance between the rotation centers of the worm 106 and the worm wheel 107 and the rolling bearings 108 and 109 are fitted to reduce the backlash amount of the meshing portion. The worm 106, the worm wheel 107, the rolling bearings 108 and 109, the second steering shaft 103, and the housing 110, which are processed so that the distance between the centers of the fitting holes is within an allowable range, are selected and assembled. As a result, much time is required for the assembly, and the amount of backlash increases due to increased wear of the teeth of the worm 106 and the worm wheel 107, so that an improvement measure has been demanded.
[0006]
Further, a rubber ring is provided between the outer peripheral surfaces of the rolling bearings 108 and 108 that support the worm 106 connected to the output shaft of the motor 105 and the fitting hole of the housing 110, and the worm 106 is moved by the elastic restoring force of the rubber ring. 2. Description of the Related Art There is known an electric steering device that is configured to be urged in a radial direction to reduce the amount of backlash at the meshing portion of the worm 106 and the worm wheel 107.
[0007]
[Problems to be solved by the invention]
However, in the conventional electric steering apparatus configured to reduce the backlash amount using the rubber ring as described above, the rubber ring provided around the outer periphery of the rolling bearing in the steering direction in the radial direction. Therefore, there is a problem that the rubber ring is liable to sag and the like, and the amount of backlash increases due to this deterioration, and the elastic restoring force of the rubber ring itself Because of the biasing, the degree of freedom of setting the preload by this biasing is relatively low, and when the rubber ring is assembled by expanding the diameter, the rubber ring is often damaged. Further, there is a risk of deterioration due to a lubricant such as grease.
[0008]
The present invention has been made in view of such circumstances, and the coil spring has a configuration in which the coil spring is wound around the outer periphery of the rolling bearing so that the axial center thereof is annular, thereby reducing the backlash amount by the coil spring. Another object of the present invention is to provide an electric steering device that can improve the durability of the coil spring and can relatively increase the degree of freedom in setting a preload.
[0009]
Further, by setting the winding angle of the coil spring to 30 ° to 75 ° with respect to the axial center, the amount of change in the elastic restoring force with respect to the amount of bending can be relatively reduced, and the meshing portion of the small diameter gear and the large diameter gear An object of the present invention is to provide an electric steering apparatus capable of reducing the resistance of the motor.
[0010]
[Means for Solving the Problems]
An electric steering device according to a first aspect of the invention is a small-diameter gear that is interlocked with the rotation of a steering assisting motor and is rotatably supported in a housing via a rolling bearing, and the small-diameter gear meshes with the small-diameter gear. In the electric steering apparatus having a large-diameter gear attached to a steering shaft that is arranged non-parallel to the rotation center of the motor and assisting the steering by the rotation of the motor, the rolling bearing is loosely fitted on the inner periphery thereof And the outer peripheral portion includes a holding cylinder fitted and fixed in the housing, and a plurality of annular grooves are provided in the inner peripheral portion of the holding cylinder or the outer peripheral portion of the rolling bearing. Each of the coil springs is wound so that its axis is annular.
[0011]
In the first invention, when the small-diameter gear is supported in the housing , the coil springs are fitted and held in the plurality of annular grooves, and the coil springs are slightly bent between the inner peripheral portion and the outer peripheral portion. Then, the coil spring and the rolling bearing are inserted and supported in the housing together with the holding body, and a preload in the radial direction is applied to the small diameter gear. By this preload, the small-diameter gear is biased toward the large-diameter gear, and the backlash amount of the meshing portion of these small-diameter gear and large-diameter gear can be reduced. In addition, since the coil spring is wound so that its axis is in an annular shape, the durability of the coil spring can be improved compared to the conventional one using a rubber ring, and the preload can be set freely. The degree can be made relatively large, and the coil spring can be prevented from being damaged during assembly.
[0012]
The electric steering apparatus according to a second aspect is characterized in that the winding angle of the coil spring is 30 ° to 75 ° with respect to the axis.
[0013]
In the second invention, since the coil spring is inclined between 30 ° and 75 ° between the inner peripheral portion and the outer peripheral portion, the amount of change in the elastic restoring force with respect to the deflection amount can be relatively reduced. The resistance of the meshing portion of the small diameter gear and the large diameter gear can be reduced. Therefore, the return resistance of the steered wheel after the motor assists in steering can be reduced, and the steered wheel can be returned smoothly.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a sectional view of an electric steering apparatus according to the present invention.
The electric 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 one end of the electric steering device inserted into the cylindrical portion. A torsion bar 3 that is coaxially connected to the end and is twisted by the action of a steering torque applied to the steered wheel 1, one end of which is inserted around the cylindrical part, and the other end is connected to the other end of the torsion bar 3. A steering torque applied to the steered wheel 1 is detected by a relative rotational displacement amount between the second steering shaft 4 connected coaxially and the first and second steering shafts 2 and 4 according to the twist of the torsion bar 3. A torque sensor 5 that rotates, a steering assisting motor 6 that is driven based on the torque detected by the torque sensor 5, and the second steering shaft 4 that decelerates the rotation in conjunction with the rotation of the motor 6. A small-diameter gear (hereinafter referred to as a worm) 71 for transmission and The diameter gear (hereinafter referred to as a worm wheel) speed reduction mechanism 7 with 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.
[0015]
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.
[0016]
FIG. 2 is a cross-sectional view of the speed reduction mechanism portion.
The accommodating portion 8c is elongated in the axial length direction of the worm 71, and a first fitting hole 81 is provided at one end in the longitudinal direction, and the holding cylinder 9 is fitted into the fitting hole 81 by press-fitting. A second fitting hole 82 and a screw hole 83 continuous to the fitting hole 82 are provided at the other end of the accommodating portion 8c, and the screw ring 10 is screwed into the screw hole 83. Further, an abutting portion 84 is provided in the middle in the longitudinal direction of the accommodating portion 8c so that one end of a second bearing, which will be described later, abuts via a substantially semicircular seat body 11.
[0017]
Further, the motor 6 having a case communicating with the third accommodating portion 8c is attached to the housing 8.
[0018]
The speed reduction mechanism 7 includes a worm 71 having a shaft portion 71 a connected to the output shaft 60 of the motor 6, 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 engagement of the wheel 72, and is transmitted from the second steering shaft 4 to, for example, a rack and pinion type steering mechanism (not shown) via a universal joint. I try to communicate.
[0019]
The worm 71 is arranged so as to cross the axis of the second steering shaft 4, and the inner ring of the first rolling bearing 12 is fitted to the shaft portion 71a at one end thereof, and the outer ring of the rolling bearing 12 is By loosely fitting into the holding cylinder 9, the shaft portion 71 a at one end is rotatably supported by the first fitting hole 81, and the shaft portion 71 a at the other end is supported via the second rolling bearing 13. The screw ring 10 rotatably supported by the two fitting holes 82 and screwed into the screw hole 83 abuts against the outer ring of the second rolling bearing 13, and the screw ring 10, the seat body 11, The contact portion 84 restricts the movement of the second rolling bearing 13 in the axial length direction. Further, the other end shaft portion 71 a is spline-fitted to the inner surface of the joint tube 14 and connected to the output shaft 60. Note that a retaining ring 15 is provided on the shaft 71 a at one end, and the retaining ring 15 restrains the worm 71 from moving in the direction opposite to the motor 6.
[0020]
FIG. 3 is an enlarged cross-sectional view taken along line III-III in FIG.
The first rolling bearing 12 can move in the radial direction with respect to the holding cylinder 9 by an amount of a clearance gap due to loose fitting in the holding cylinder 9, and the holding cylinder 9 has a plurality of annular grooves 16 on its inner peripheral surface. , 16 are spaced apart from each other, and coil springs 17, 17 that are in contact with the outer peripheral surface of the first rolling bearing 12 are fitted and held in the annular grooves 16, 16 so that the axial center thereof is annular. is there.
[0021]
FIG. 4 is a front view of the coil spring, and FIG. 5 is a diagram showing the relationship between the amount of deflection of the coil spring and the elastic restoring force.
The coil springs 17 and 17 are formed by winding a metal wire having a wire diameter of 0.1 to 0.2 mm in a coil shape. The coil springs 17 and 17 are wound so that the axial center thereof is annular, Both ends are connected. These coil springs 17, 17 have outer peripheral portions held in the annular grooves 16, 16, inner peripheral portions are in contact with the outer peripheral surface of the rolling bearing 12, and the rolling bearing 12 is bent by the bending between the inner peripheral portion and the outer peripheral portion. Is urged in the radial direction, and the worm 71 is urged toward the meshing portion with the worm wheel 72. In addition, the coil spring 17 is inclined so that the winding angle is 30 ° to 75 ° with respect to the axis, and the amount of change in the elastic restoring force relative to the amount of deflection is relatively large when preload is applied as shown in FIG. There are few.
[0022]
In the embodiment, when the worm 71 is incorporated, for example, the coil spring 17 is fitted and held in the annular grooves 16 and 16 so that the axial center thereof is annular, and the first rolling bearing 12 is idled on the inner peripheral surface thereof. With the holding cylinder 9 fitted into the first fitting hole 81 of the housing 8 being press-fitted and attached, the worm 71 is inserted from the second fitting hole 82 into the third accommodating portion 8c, and the worm The one end side shaft portion 71 a of 71 is fitted and supported to the inner ring of the first rolling bearing 12, and the second rolling bearing 13 is fitted to the second fitting hole 82 and the other end side shaft portion 71 a of the worm 71. Then, by screwing the screw ring 10 into the screw hole 83, the outer ring of the second rolling bearing 13 is sandwiched between the seat body 11 and the screw ring 10, and the movement of the worm 71 in the axial length direction is restricted.
[0023]
The coil spring 17 that urges the incorporated worm 71 has an inner peripheral portion that abuts against the first rolling bearing 12 and urges the rolling bearing 12 in the radial direction from the entire circumferential position, thereby causing the worm 71 to move toward the worm wheel. The backlash amount of the engaging portion of the worm 71 and the worm wheel 72 can be reduced, and the amount of wear of the teeth of the worm 71 and the worm wheel 72 is increased, or the composition is combined. The amount of backlash can be reduced even when the meshing state changes with time due to the resin worm wheel 72 contracting due to a low temperature in winter or the like. Furthermore, since the coil spring 17 is wound so that its axis is annular, the durability of the coil spring 17 can be enhanced as compared with the conventional one using a rubber ring. In addition, since the amount of change in the elastic restoring force relative to the amount of deflection of the coil spring 17 is relatively small in a state where preload is applied, the meshing resistance of the worm 71 and the worm wheel 72 can be reduced, and the motor 6 assists in steering. The return resistance of the rear steering wheel can be reduced.
[0024]
In the embodiment described above, the holding cylinder 9 that is fixed to the housing 8 is provided and the coil spring 17 is held in the holding cylinder 9. However, the annular groove of the holding cylinder 9 is eliminated, and the outer periphery of the rolling bearing 12 is removed. The coil groove 17 may be held on the rolling bearing 12 by providing the annular groove 16 on the surface . By providing the holding cylinder 9 as in the embodiment, the coil spring 17 and the first rolling bearing 12 can be easily incorporated into the housing 8.
[0025]
The coil spring 17 is formed into an annular shape by connecting both ends of the coil spring. However, the coil spring is wound in, for example, the annular groove 16 so that its axis is substantially C-shaped without connecting both ends of the coil spring. It is good also as a ring by turning .
[0026]
The speed reduction mechanism 7 of the embodiment described above is a worm gear including a small gear 71 that is a worm and a large gear 72 that is a worm wheel, and a large gear that is a small gear 71 and a hypoid wheel that are hypoid pinions. A hypoid gear provided with the gear 72 may be used.
[0027]
【The invention's effect】
According to the first aspect of the invention, the coil spring is wound so that its axis is annular, and the rolling bearing is urged in the radial direction. In addition, since the holding cylinder is provided, the coil spring and the rolling bearing can be easily assembled into the housing. In addition, since the coil spring is wound so that its axis is annular, the durability of the coil spring can be improved compared to the conventional one using a rubber ring, and it is caused by backlash over a long period of time. Sound noise can be prevented from leaking into the vehicle compartment, the degree of freedom in setting the preload can be relatively increased, and the coil spring can be prevented from being damaged during assembly.
[0028]
According to the second invention, the coil spring is inclined between 30 ° and 75 ° between the inner peripheral portion and the outer peripheral portion, and the amount of change in the elastic restoring force with respect to the deflection amount can be relatively reduced. The meshing resistance of the small-diameter gear and the large-diameter gear can be reduced, the return resistance of the steering wheel after the motor assists steering can be reduced, and the steering wheel can be returned smoothly.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an electric steering apparatus according to the present invention.
FIG. 2 is a sectional view of a speed reduction mechanism portion of the electric 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 front view of a coil spring of the electric steering apparatus according to the present invention.
FIG. 5 is a diagram showing the relationship between the amount of deflection of the coil spring and the elastic restoring force of the electric steering apparatus according to the present invention.
FIG. 6 is a cross-sectional view of a conventional electric steering apparatus.
FIG. 7 is a cross-sectional view of a speed reduction mechanism portion of a conventional electric steering apparatus.
[Explanation of symbols]
4 Steering shaft 6 Motor 7 Reduction mechanism 71 Small diameter gear (worm)
72 Large diameter gear (worm wheel)
8 Housing 12 First rolling bearing 17 Coil spring

Claims (2)

A small-diameter gear that is rotatably supported in the housing via a rolling bearing in conjunction with the rotation of the steering assist motor, and a steering shaft that meshes with the small-diameter gear and is arranged non-parallel to the rotation center of the small-diameter gear. In the electric steering apparatus provided with a large-diameter gear attached to the motor and assisting steering by the rotation of the motor, the rolling bearing is loosely fitted to the inner peripheral portion thereof, and the outer peripheral portion thereof is fitted to the housing. A holding cylinder to be fixed is provided, and a plurality of annular grooves are provided in an inner peripheral part of the holding cylinder or an outer peripheral part of the rolling bearing, and a coil spring is provided in each of the annular grooves, and an axial center thereof is annular. An electric steering apparatus that is wound as described above. The electric steering apparatus according to claim 1, wherein a winding angle of the coil spring is 30 to 75 degrees with respect to an axis.

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