JP2003261041A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a steering load at a steering area where a motor is not driven even in the case where the number of rolling bearing supporting a worm rotated by a steering assistance motor is one. <P>SOLUTION: The electric power steering device is provided with the rolling bearing 9 rotatably supporting the worm 6 rotated by the steering assistance motor 5; a first elastic part 21 arranged so as to contact with an inner periphery of an inner ring 9b of the rolling bearing 9 and retained to the worm 6 such that an expansion becomes possible by a force in an axial direction applied to the worm 6; two second elastic bodies 22, 23 retained to the worm so as to contact with both ends of the inner ring 9b and inhibiting a movement to an axial direction of the worm 6. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus using a motor as a source of steering assist force.

[0002]

2. Description of the Related Art As an electric power steering device for a vehicle, for example, an input shaft connected to steered wheels and an output shaft coaxially connected to the input shaft via a torsion bar are applied to the input shaft by relative angular displacement. The steering torque is detected, the motor for steering assist is driven based on the detected torque, and the rotational force of the motor is transmitted to the steering mechanism through the reduction gear mechanism to steer according to the rotation of the steered wheels. The operation of the mechanism is assisted by the rotation of the motor to reduce the labor load on the driver for steering.

The reduction gear mechanism includes a worm coupled to the drive shaft of the motor and a worm wheel meshing with the worm, and the worm wheel is provided in the middle of a transmission system path from the output shaft to the steering mechanism. Fitted and fixed.

Further, the worm is supported at its both ends by a pair of rolling bearings to enhance the rotatability of the worm.

By the way, since the worm of the electric power steering apparatus configured as described above is supported so as not to move in the axial direction with respect to the rolling bearings supporting both ends, the steering wheel is not supported. When the motor is rotated from the steering neutral position to the left or right to rotate the motor from the beginning of steering to assist the steering, the steering angle is small, for example, about 1 ° when the vehicle is traveling at high speed. At this time, steering assistance is also performed, which results in deterioration of steering feeling. Therefore, in general, the motor is not driven when the steering angle is as small as about 1 °, and is driven when the steering angle exceeds an appropriate steering angle.

[0006]

However, in the case where the motor is configured not to be driven until the steering angle exceeds the appropriate steering angle, the steering region where the motor is not driven,
That is, during steering in a region near the steering neutral position, the steering force of the steered wheels is transmitted to the drive shaft of the motor through the input shaft, the torsion bar, the output shaft, the worm wheel, and the worm, and the drive shaft is rotated. Will be. As a result, the load for rotating the drive shaft of the motor is applied to the steered wheels via the worm, the worm wheel, the output shaft, the torsion bar, and the input shaft, and the steering load increases.

The present invention has been made in view of the above circumstances, and a steering load in a steering region where the motor is not driven even when there is only one rolling bearing that supports the worm rotated by the steering assisting motor. It is an object of the present invention to provide an electric power steering device that can reduce power consumption.

[0008]

An electric power steering apparatus according to a first aspect of the present invention includes a worm rotated by a steering assisting motor, a rolling bearing rotatably supporting the worm, and a worm that meshes with the worm. A worm wheel connected to a steering mechanism, and an electric power steering device configured to assist steering by rotation of the motor, wherein an axial length that is arranged so as to contact an inner circumference of an inner ring of the rolling bearing and is added to the worm. A first elastic body that can be extended in the axial direction by a force in the axial direction, and two second elastic bodies that are held by the worm or the inner ring so as to contact both ends of the inner ring and that restrain the movement of the worm in the axial direction. And two elastic bodies.

According to the first aspect of the invention, the first elastic body is in contact with the inner circumference of the inner ring of one rolling bearing, and the second elastic body is in contact with both ends of the inner ring. When steering in either the left or right direction from the position, the axial elastic force applied to the worm causes the first elastic body to expand, and further causes one of the second elastic bodies to bend. As a result, the worm Even in a configuration in which the bearing means for supporting the motor has one rolling bearing, it is possible to reduce the steering load in the steering region where the motor is not driven. Moreover, since the load generated by the worm is shared by the first elastic body and the second elastic body, the durability of the first elastic body and the second elastic body can be improved, and the load can be used for a long period of time. it can.

The electric power steering apparatus according to the second aspect of the invention is characterized in that the first elastic body and the second elastic body are integrally formed.

According to the second aspect of the invention, since the positions of the first elastic body and the second elastic body can be maintained by holding the first elastic body on the worm, the first elastic body and the second elastic body can be maintained.
The process for holding the elastic body can be omitted, and further, the work of holding the first elastic body in the worm, in other words, the first elastic body and the two second elastic bodies can be incorporated by one work. Because it can, the first elastic body and the two second
Although the elastic body is provided, the assembling workability can be improved and the cost of the electric power steering device can be reduced.

The electric power steering apparatus according to the third aspect of the invention is characterized in that one of the second elastic bodies has a smaller force of suppressing movement of the worm in the axial direction than the other.

According to the third aspect of the invention, when the steering wheel is steered from the neutral steering position to either the left or right direction, the first elastic body is extended by the axial force applied to the worm, and the second elastic body is extended.
One of the elastic bodies will bend. Further, since one of the second elastic bodies has a small worm movement restraining force in the axial direction, the worm can be easily attached to the worm, and the steering load in the steering region where the motor is not driven can be reduced. . Moreover, if the first elastic body and the second elastic body are integrally formed, the second elastic body can prevent the first elastic body from slipping out of the inner ring, and the first elastic body and the second elastic body can be positioned at appropriate positions. It can be maintained for a long time.

When both ends of the worm are supported by rolling bearings, and the first elastic body and the second elastic body are provided between the inner ring of the two rolling bearings and the worm,
It is possible to equalize the worm movement suppressing force with respect to a constant steering angle in the left-right direction from the steering neutral position, and to improve the steering feeling. Further, in this case, since the first elastic body can be held by being fitted into the worm, the processing for holding the first elastic body can be omitted, and moreover, by the holding of the first elastic body, Since the second elastic body can be incorporated, in other words, the first elastic body and the second elastic body can be incorporated at the same time by one operation, and therefore, the assembling work is performed despite the provision of the first elastic body and the second elastic body. And the cost of the electric power steering device can be reduced.

In the electric power steering apparatus according to the fourth aspect of the present invention, the first elastic body has a cylindrical portion and an annular convex portion that is convex on the outer periphery of the cylindrical portion in the radial direction of the worm. .

According to the fourth aspect of the invention, the cylindrical portion is extended by the force applied to the worm in the axial direction and the annular convex portion on the outer periphery of the cylindrical portion is extended. The steering load on the vehicle can be gently reduced, and the steering feeling can be further improved.

The electric power steering apparatus according to the fifth aspect of the invention is characterized in that it has an annular body between the inner periphery of the first elastic body and the worm.

According to the fifth aspect of the invention, since the ring body can be fitted and held in the worm without contacting the first elastic body with the worm, the first elastic body and the second elastic body can be assembled more easily. Easier to do.

In the electric power steering apparatus according to the sixth aspect of the invention, the first elastic body and the second elastic body are O-rings.

In the sixth aspect of the invention, since the existing O-ring can be used, the cost of the first elastic body and the second elastic body, and thus the cost of the electric power steering device, can be reduced.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. First Embodiment FIG. 1 is a sectional view showing the configuration of a first embodiment of an electric power steering device according to the present invention. The electric power steering apparatus includes an input shaft 1 having an upper end connected to a steering wheel A for steering and a lower end having a tubular portion 1a, and the tubular portion 1.
and a lower end of the torsion bar 2 which is inserted into a and whose upper end is coaxially connected to the cylindrical portion 1a of the input shaft 1 and which is twisted by the action of the steering torque applied to the steered wheels A and whose lower end is the torsion bar 2. Shaft 3 coaxially connected to
And a torque sensor 4 for detecting a steering torque applied to the steered wheel A based on a relative rotational displacement amount of the input shaft 1 and the output shaft 3 according to the torsion of the torsion bar 2, and a torque detected by the torque sensor 4. Driven by a steering assist motor 5, a reduction gear mechanism B having a worm 6 and a worm wheel 7 that are interlocked with the rotation of the motor 5 to reduce the rotation and transmit the rotation to the output shaft 3, and the torque sensor. 4 and a housing 8 in which the reduction gear mechanism B is housed.

The housing 8 has the torque sensor 4
And a second accommodating portion 8 that is connected to the accommodating portion 8a and accommodates the worm wheel 7
b and a third accommodating portion 8c which is connected to the accommodating portion 8b and accommodates the worm 6.

FIG. 2 is a sectional view showing the structure of the reduction gear mechanism portion of the first embodiment. The third accommodating portion 8c is elongated in the axial direction of the worm 6, and one end in the longitudinal direction is open and the other end is closed. A fitting hole 81 into which the rolling bearing 9 is fitted, a screw hole 82 connected to one end of the fitting hole 81, and a motor mounting portion 83 connected to the screw hole 82 are provided at one end of the third housing portion 8c. It is provided. Then, the outer ring 9a of the rolling bearing 9 is fitted in the fitting hole 81, and the screw ring 10 abutting on one end of the outer ring 9a is screwed into the screw hole 82, so that the rolling bearing 9 extends in the axial direction. It regulates movement. The motor 5 is attached to the motor attachment portion 83.

Further, the other end of the third accommodating portion 8c faces a concave hole 84 into which the shaft portion 6c provided at the other end of the worm 6 is inserted and the inner surface of the concave hole 84, and the radial of the worm 6 is seen. A cylindrical guide hole 85 formed in the (radius) direction.
Is integrally provided with a guide member 86 having a slide bearing 11 in the guide hole 85 and is movable in the radial direction, and a biasing means for urging the push body 12 in one direction. The elastic body 13 is housed therein, and an operating body 14 for moving the pressing body 12 via the elastic body 13 is screwed to the opening edge side to the outside of the guide hole 85.

The reduction gear mechanism B is a worm 6 which is coupled to the drive shaft 50 of the motor 5 via a cylindrical shaft coupling 15.
And the worm wheel 7 that is fitted and fixed in the middle of the output shaft 3 and connected to the steering mechanism, the drive shaft 50.
Is transmitted to the output shaft 3 through a universal joint, and is transmitted to, for example, a rack and pinion type steering mechanism (not shown).

The worm 6 is arranged so as to intersect the axis of the output shaft 3 and has a tooth portion 6a having a plurality of teeth.
Shafts 6b and 6c are provided at both ends of the shaft. The shaft portion 6b at one end is rotatably supported in the fitting hole 81 via a movement suppressing body 20 (described later) and a rolling bearing 9. The shaft portion 6c at the other end is inserted into the slide bearing 11 through the recessed hole 84 so as to be movable in the axial direction, and is rotatably supported by the pressing body 12 via the slide bearing 11.

The rolling bearing 9 which supports the shaft portion 6b at one end includes an outer ring 9a, an inner ring 9b, and a plurality of rolling elements 9c interposed between the outer ring 9a and the inner ring 9b.

Thus, the rolling bearing 9 and the sliding bearing 11
A movement restraining body 20 made of rubber that restrains the movement of the worm 6 in the axial direction is fitted and held on a shaft portion 6b of the worm 6 which is rotatably supported by the shaft. This movement restraint body 2
Reference numeral 0 denotes a cylindrical first elastic portion 21 that contacts the inner circumference of the inner ring 9b, and two annular second elastic portions that are integrally formed at both ends of the first elastic portion 21 and that contact both ends of the inner ring 9b. Part 2
2 and 23, the first elastic portion 21 is fitted and held on the shaft portion 6b. In addition, the second elastic portion 23 has the tooth portion 6a.
Is arranged between the tooth portion 6a and the inner ring 9b so as to contact one end of the inner ring 9a. The first elastic portion 21 constitutes a first elastic body, and the second elastic portions 22 and 23 constitute two second elastic bodies.

The first elastic portion 21 is adapted to extend when the worm 6 is subjected to a force in the axial direction, with its outer circumference being in contact with the inner circumference of the inner ring 9b.
2 and 23 are adapted to bend to either one of the worm 6 in the axial direction when a force is applied to the worm 6 in one of the axial directions.
The flexure of the elastic portions 22 and 23 prevents the worm 6 from moving in the axial direction with respect to the inner ring 9b.

Further, the shaft portion 6 is provided through the slide bearing 11.
The pressing body 12 that supports c is formed in a cylindrical shape, and its intermediate position in the axial direction, in other words, the guide hole 8 is formed.
The slide bearing 11 is fitted and fixed in a fitting hole 12a that penetrates so as to be orthogonal to the moving direction in the middle of the moving direction along which the sliding bearing 11 moves.

Further, the elastic body 13 interposed between the pressing body 12 and the operating body 14 is formed of a coil spring, and the pressing body 12 is preloaded to the meshing portion of the worm 6 with the worm wheel 7. It is biased in the moving direction.
An annular elastic plate 16 made of synthetic rubber is interposed around the elastic body 13 between the pressing body 12 and the operating body 14, and the elastic body 13 is rotated by operating the operating body 14. After being bent by a predetermined dimension, the end surface of the operating body 14 comes into contact with the other surface of the elastic plate 16 so that the elastic plate 16 bends together with the elastic body 13.

In the electric power steering apparatus configured as described above, one end of the worm 6 whose one end is coupled to the drive shaft 50 of the motor 5 via the shaft coupling 15 is provided with the rolling bearing 9, and the other end is provided. The first of the movement restraining bodies 20 in which the second elastic portions 22 and 23 are integrally formed at both ends of the first elastic portion 21 is rotatably supported by the slide bearing 11, and the shaft portion 6b supported by the rolling bearing 9 is integrally formed. Since the elastic portion 21 is fitted and held and the first elastic portion 21 and the second elastic portions 22 and 23 suppress the movement of the worm 6 in the axial direction, the steering area where the motor 5 is not driven, that is, The steering force of the steered wheel A is steered in a steering range in which the steering angle of the vehicle at high speed is small, for example, about 1 °, so that the steering force of the steered wheel A passes through the input shaft 1, the torsion bar 2, the output shaft 3 and the worm wheel 7. Warm 6 When transmitted, the worm 6
By the component force in the axial direction applied to the worm 6, the worm 6 expands the first elastic portion 21 and moves the second elastic portion 23 in one axial direction while bending or the first elastic portion 21 expands. 2 While bending the elastic portion 22 and moving in the other axial direction, the rotation angle of the worm 6 becomes smaller, the transmission from the worm 6 to the drive shaft 50 of the motor 5 can be relaxed, and the steering in which the motor 5 is not driven The steering load in the area can be reduced.

Moreover, one second elastic portion 23 relaxes one axial force in the axial direction of the worm 6, and the other axial second elastic portion 22 relaxes the other axial force. The amount of bending of the second elastic portions 22 and 23 can be made equal to a constant steering angle in the left-right direction from the steering neutral position, and the steering feeling can be improved.

Further, since the first elastic portion 21 and the second elastic portions 22 and 23 share the axial force applied to the worm 6, the durability of the first elastic portion 21 and the second elastic portions 22 and 23 is improved. It can be increased and can be used for a long period of time.

Since the other end of the worm 6 is supported by the pressing body 12 urged by the elastic body 13 via the slide bearing 11, the elastic body 13 urges the worm 6 toward the worm wheel 7. However, the distance between the centers of rotation of the worm 6 and the worm wheel 7 can be adjusted, and the amount of backlash at the meshing portion of the worm 6 and the worm wheel 7 can be reduced.

Second Embodiment FIG. 3 is a sectional view showing the structure of a reduction gear mechanism portion according to a second embodiment. The electric power steering apparatus according to the second embodiment is different from the first embodiment in that the second elastic portions 22 and 23 having substantially the same size are integrally provided at both ends of the first elastic portion 21 instead of being integrally provided. Instead of the second elastic portion 22 on the outer side, a small portion 24a having a smaller movement restraining force in the axial direction of the worm 6 than the second elastic portion 23 is provided integrally with the second elastic portion 23 on the first elastic portion 21. It is a thing.

In the second embodiment, the second elastic portion 2
3 is thick and large so that the worm 6 bends in the axial direction when a force is applied to the worm 6 in the axial direction, and the worm 6 is restrained from moving in the axial direction. When the first elastic portion 21 is extended by the applied force in the axial direction, the first elastic portion 21 bends in the axial direction and is made thin and small so as to prevent the first elastic portion 21 from coming out of the inner ring 9b.

The movement restraining body 20 integrally formed from the first elastic portion 21, the second elastic portion 23 and the small-sized portion 24a having the above-described structure has, for example, two worms 6 at each end, as shown in FIG. It is used for a reduction gear mechanism B1 supported by bearings 9 and 17 so as to be movable in the axial direction. In this case, the movement suppressing body 20 fits the first elastic portion 21 to the shaft portions 6b and 6c so that the first elastic portion 21 contacts the inner circumferences of the inner rings 9b and 17b of the two rolling bearings 9 and 17. The second elastic portion 23 holds both ends of the tooth portion 6a and the inner rings 9b, 1
The tooth portion 6a is in contact with one end of 7b (the inner side in the axial direction).
And the inner rings 9b and 17b. Further, the thin small-sized portion 24a is in contact with the other ends (outside in the axial direction) of the inner rings 9b, 17b.

In the second embodiment, since the motor 5 is steered in the steering region where it is not driven, the steering force of the steered wheel A causes the input shaft 1, the torsion bar 2, the output shaft 3 and the worm wheel 7 to move. Is transmitted to the worm 6 via
When a force is applied to the worm 6 in one axial direction (to the right in FIG. 3), the first elastic portion 21 on the right side in FIG. 3 is extended and the second elastic portion 23 on the right side is bent, and The first elastic portion 21 on the left side of 3 can be moved in one axial direction while being extended. In addition, the first elastic portion 21 on the left side of FIG.
It can be surely prevented by a. Also, warm 6
When a force is applied to the other in the axial direction (left side in Fig. 3),
It is possible to extend the first elastic portion 21 on the left side of FIG. 3 and bend the second elastic portion 23 on the left side, and further move the first elastic portion 21 on the right side of FIG. 3 while moving in the other axial direction. . Moreover, the right small portion 24a can reliably prevent the first elastic portion 21 on the right side of FIG. 3 from coming off from the inner ring 9b. By thus moving the worm 6 to one side or the other side in the axial direction, the transmission from the worm 6 to the drive shaft 50 of the motor 5 can be mitigated, and the steering load in the steering region where the motor 5 is not driven is reduced. can do.

Since other configurations and operations are the same as those of the first embodiment, the same parts are designated by the same reference numerals,
The detailed explanation and the explanation of the action and effect are omitted.

Third Embodiment FIG. 4 is a sectional view showing the structure of the reduction gear mechanism portion of the third embodiment. The electric power steering apparatus according to the third embodiment has the second elastic portions 2 at both ends as in the second embodiment.
3, the metal ring body 18 is provided on the inner circumference of the first elastic portion 21 provided with the small portion 24a.

In the third embodiment, the ring body 18 is composed of a cylindrical portion 18a and a collar portion 18b which is continuous with one end of the cylindrical portion 18a and is in contact with the outer surface of the second elastic portion 23. The first elastic portion 21, the second elastic portion 23, and the small-sized portion 24a are vulcanized and molded on the outer side.

As in the second embodiment, the movement restraining member 20 having the ring member 18 provided on the inner circumference thereof is a reduction gear in which both ends of the worm 6 are rotatably supported by two rolling bearings 9 and 17. Used for mechanism B1. In this case, ring 1
The first elastic portion 21 is press-fitted and held in the shaft portions 6b and 6c so that the first elastic portion 21 is in contact with the inner circumferences of the inner rings 9b and 17b, and the collar portion 18b is in contact with one end and the other end of the tooth portion 6a. It is arranged between the tooth portion 6a and the inner rings 9b and 17b.

In the third embodiment, the metal shaft portion 6 is used.
Since the first elastic portion 21 can be held by the shaft portions 6b and 6c by press-fitting the metal ring bodies 18 and 18 into the shaft portions 6b and 6c, the first elastic portion 21 is directly fitted to the shaft portions 6b and 6c. The first elastic portion 21 and the second elastic portion 23, as compared with the case where they are held together.
Also, the small portion 24a can be easily incorporated.

Since other configurations and operations are the same as those of the first embodiment, the same parts are designated by the same reference numerals,
The detailed explanation and the explanation of the action and effect are omitted.

Fourth Embodiment FIG. 5 is a sectional view showing the structure of the reduction gear mechanism portion of the fourth embodiment. In the electric power steering apparatus according to the fourth embodiment, as in the third embodiment, the first elastic portion 21 of the movement suppressing body 20 provided with the metal ring body 18 on the inner circumference is
It is configured to have a cylindrical portion 21a provided with the ring body 18 on the inner side and an annular convex portion 21b which is uneven on the outer periphery of the cylindrical portion 21a in the radial direction of the worm 6.

In the fourth embodiment, the annular convex portion 21
b is formed integrally with the first elastic portion 21, the second elastic portion 23, and the small-sized portion 24a on the outside of the ring body 18 by vulcanization molding as in the second embodiment while being separated in the axial direction of the cylindrical portion 21a. The outer circumference of each annular convex portion 21b is the inner ring 9b, 17
It is in contact with the inner circumference of b.

In this way, the movement restraining member 20 having the annular convex portion 21b on the outer circumference is the same as in the second and third embodiments.
Is used for the reduction gear mechanism B1 whose both ends are rotatably supported by two rolling bearings 9 and 17. in this case,
The ring body 18 of the movement restraining body 20 is press-fitted and held in the shaft portions 6b and 6c so that the outer circumference of the annular convex portion 21b of the first elastic portion 21 contacts the inner circumferences of the inner rings 9b and 17b, and the collar portion 18b is formed. The tooth portion 6a is disposed between the tooth portion 6a and the inner rings 9b and 17b so as to come into contact with one end and the other end of the tooth portion 6a.

In the fourth embodiment, when the motor 5 is steered in the steering area where the motor 5 is not driven, a force is exerted on the worm 6 via the worm wheel 7 in one axial direction (rightward in FIG. 5). When added, the first elastic portion 2 on the right side of FIG.
The cylindrical portion 21a and the annular convex portion 21b of No. 1 are extended, the second elastic portion 23 on the right side is bent, and the cylindrical portion 21a and the annular convex portion 21b of the first elastic portion 21 on the left side of FIG. It can be moved in one direction in the long direction.
Further, when a force is applied to the worm 6 in the other axial direction (left side in FIG. 5), the cylindrical portion 21a and the annular convex portion 21b of the first elastic portion 21 on the left side in FIG. It is possible to bend the second elastic portion 23 and further move the cylindrical portion 21a and the annular convex portion 21b of the first elastic portion 21 on the right side of FIG. By thus moving the worm 6 to the other side in the axial direction, the transmission from the worm 6 to the drive shaft 50 of the motor 5 can be mitigated, and the steering load in the steering region where the motor 5 is not driven is reduced. be able to. Moreover, the first elastic portion 2
In No. 1, since the cylindrical portion 21a extends and the annular convex portion 21b on the outer periphery of the cylindrical portion 21a extends, the steering load in the steering region where the motor 5 is not driven can be gently reduced, and the steering feeling can be further improved. You can do better.

Since the other structure and operation are the same as those of the first to third embodiments, the same reference numerals are given to the same parts, and the detailed description and the operation and effect description thereof will be omitted.

Fifth Embodiment FIG. 6 is a sectional view showing the structure of the reduction gear mechanism portion of the fifth embodiment. The electric power steering apparatus according to the fifth embodiment is similar to the first to fourth embodiments in that the first elastic portion 2 is provided.
Instead of integrally molding the first and second elastic portions 22 and 23 or integrally molding the first elastic portion 21, the second elastic portion 23 and the small-sized portion 24a, a first elastic body made of a rubber O-ring. 30 and the second elastic bodies 31 and 32 are provided.

In the fifth embodiment, the shaft portion 6b is
3 annular grooves 61, 6 spaced apart in the axial direction on the outer periphery of
2, 63 are provided, and the depth of the central annular groove 62 is made deeper than the annular grooves 61, 63 on both sides.
In addition, the first elastic body 30 that is in contact with the inner circumference of the inner ring 9b and can be bent by the axial force applied to the worm 6
The inner ring 9 in the annular grooves 61 and 63 on both sides.
The second elastic bodies 31 and 32 contacting both ends of b are fitted and held. Further, between the inner circumference of the inner ring 9b and the outer circumference of the shaft portion 6b, a gap 33 that allows the first elastic body 30 to bend in the axial direction of the worm 6 by the axial force applied to the worm 6.
Is provided. The gap 33 is formed by the annular grooves 61 on both sides.
The outer diameter dimension between 63 is ensured by making it smaller than the outer diameter dimension on the outside in the axial direction of the annular grooves 61, 63 on both sides. In this way, the outer diameter of the shaft portion 6b is made different to secure the gap 33, so that the second elastic bodies 31 and 3 are formed.
The contact area with both ends of the second inner ring 9b can be made relatively large, and it is possible to increase the second area by the force in the axial direction applied to the worm 6.
It is easy to bend the entire elastic body 31, 32.

The first elastic body 30 and the second elastic bodies 31 and 32 configured as described above support the worm 6 movably in the axial direction by the rolling bearing 9 and the sliding bearing 11 as in the first embodiment. The reduction gear mechanism B described above or the reduction gear mechanism B1 in which the worm 6 is rotatably supported by the two rolling bearings 9 and 17 as in the second to fourth embodiments.

In the fifth embodiment, when the motor 5 is steered in the steering area where the motor 5 is not driven, the worm 6 receives a force in one axial direction (to the right in FIG. 6) in the axial direction. When added, the worm 6 can be moved in one axial direction while bending the first elastic body 30 and the second elastic body 32 in the axial direction of the worm 6. When a force is applied to the worm 6 in the other axial direction (the left side in FIG. 6), the first elastic body 30 and the second elastic body 31 are deflected in the axial direction of the worm 6 and the worm 6 is rotated. It can be moved in the other direction in the long direction. By thus moving the worm 6 to one side or the other side in the axial direction, the transmission from the worm 6 to the drive shaft 50 of the motor 5 can be mitigated, and the steering load in the steering region where the motor 5 is not driven is reduced. be able to. Moreover, since the existing O-ring is used,
The costs of the first elastic body 30 and the second elastic bodies 31 and 32, and consequently the cost of the electric power steering device, can be reduced.

In the fifth embodiment, the first elastic body 30 and the second elastic bodies 31, 32 are replaced by O-rings,
An annular elastic plate may be used. Further, the first elastic body 30 and / or the second elastic bodies 31, 32 may be held on the inner ring 9b by an adhesive or the like.

Since the other structure and operation are the same as those of the first to third embodiments, the same reference numerals are given to the same parts, and the detailed description and the operation and effect description thereof will be omitted.

Embodiment 6 An electric power steering apparatus according to Embodiment 6 is
In the configuration in which the second elastic portions 22 and 23, or the second elastic portion 23 and the small-sized portion 24a are integrally formed at both ends of the cylindrical first elastic portion 21 as in the first to fourth embodiments, the movement suppressing body is formed. Instead of fitting and holding the first elastic portion 21 of 20 on the shaft portion 6b or 6b, 6c, the first elastic portion 21 is fixed to the inner ring 9
It is fitted and held on the inner circumference of b or 9b, 17b.

FIG. 7 is a sectional view showing the structure of the reduction gear mechanism portion of the sixth embodiment. In the sixth embodiment, the first
When the elastic portion 21 is held on the inner circumference of the inner ring 9b, the structure shown in FIG. 7 is obtained. When the first elastic portion 21 is held on the inner circumference of the inner rings 9b, 17b, the structure is similar to that shown in FIGS. Become.

In FIG. 7, an annular convex portion 34 which is in contact with the outer surface of the second elastic portion 22 is provided on the shaft portion 6b. The annular convex portion 34 has an annular groove 64 formed in the middle of the shaft portion 6b.
It is configured by fitting a retaining ring to.

In FIG. 7, when a force is applied to the worm 6 in one axial direction (rightward in FIG. 7), the worm 6 is bent while bending the second elastic portion 23 on the left side in FIG. When the worm 6 is applied with a force in the other axial direction (left in FIG. 2), the worm 6 is bent while bending the second elastic portion 22 on the right side in FIG. It can be moved in the other direction in the long direction. By thus moving the worm 6 to one side or the other side in the axial direction, the transmission from the worm 6 to the drive shaft 50 of the motor 5 can be mitigated, and the steering load in the steering region where the motor 5 is not driven is reduced. be able to.

Since the other structure and operation are the same as those of the first to fourth embodiments, the same reference numerals are given to the same parts, and the detailed explanation and the explanation of the operation effects will be omitted.

In the first and fifth embodiments described above, one end of the worm 6 is supported by the rolling bearing 9 and the other end is supported by the slide bearing 11, but in addition, the slide bearing 11 of the first and fifth embodiments is supported. Instead of the above, the rolling bearing 17 may be used as in the second to fourth embodiments, and both ends of the worm 6 may be supported by the rolling bearings 9 and 17. In this case, the movement suppressing body 20 of FIG. 2 is arranged on the shaft portions 6b and 6c, and the first elastic body 30 and the second elastic bodies 31 and 32 of FIG. 6 are arranged on the shaft portions 6b and 6c side.

Further, in the first embodiment described above, the pressing body 12, the elastic body 13 and the operating body 14 for adjusting the distance between the rotation centers of the worm 6 and the worm wheel 7 are eliminated, and the accommodating portion 8c is eliminated. A sliding bearing (not shown) may be provided at the other end of the shaft, and the shaft portion may be supported by the sliding bearing so as to be movable in the axial direction.

[0064]

As described above in detail, according to the first invention,
Even in the configuration in which the bearing means that supports the worm has one rolling bearing, it is possible to reduce the steering load in the steering region where the motor is not driven. Moreover, the assembling workability can be improved despite the provision of the first elastic portion and the two second elastic portions. Furthermore, the durability of the first elastic body and the second elastic body can be enhanced, and the first elastic body and the second elastic body can be used for a long period of time.

According to the second aspect of the invention, the steering load in the steering region where the motor is not driven can be reduced and the first elastic body and the second elastic body can be used even if the bearing means for supporting the worm has a single rolling bearing. The process for holding the elastic body can be omitted, and the workability of assembling can be improved despite the provision of the first elastic body and the two second elastic bodies.

According to the third invention, it is possible to reduce the steering load in the steering region where the motor is not driven, and moreover,
One of the second elastic bodies can prevent the first elastic body and the second elastic body from slipping out from the inner ring, and can maintain the proper position for a long period of time. Also, the first elastic body,
Although the second elastic body is provided, the workability of assembling can be improved by one of the second elastic bodies, and the cost of the electric power steering device can be reduced.

According to the fourth invention, it is possible to gently reduce the steering load in the steering region where the motor is not driven,
The steering feeling can be further improved.

According to the fifth invention, the movement restraining body, the first elastic body and the second elastic body can be more easily incorporated.

According to the sixth aspect of the invention, the cost of the first elastic body and the second elastic body, and consequently the cost of the electric power steering device, can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a first embodiment of an electric power steering device according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a reduction gear mechanism portion according to the first embodiment.

FIG. 3 is a cross-sectional view showing a configuration of a reduction gear mechanism portion according to a second embodiment.

FIG. 4 is a sectional view showing a structure of a reduction gear mechanism portion according to a third embodiment.

FIG. 5 is a sectional view showing a structure of a reduction gear mechanism portion according to a fourth embodiment.

FIG. 6 is a sectional view showing a configuration of a reduction gear mechanism portion according to a fifth embodiment.

FIG. 7 is a sectional view showing a structure of a reduction gear mechanism portion according to a sixth embodiment.

[Explanation of symbols]

5 motor 6 warm 7 Worm wheel 9,17 Rolling bearing 9b, 17b inner ring 21 1st elastic part (1st elastic body) 22, 23, 24a Second elastic portion (second elastic body) 21a cylindrical part 21b annular protrusion 24a Small portion (second elastic body) 23 ring 30 First elastic body 31, 32 Second elastic body

Claims (6)

[Claims] 1. A worm that is rotated by a motor for steering assistance, a rolling bearing that rotatably supports the worm, and a worm wheel that meshes with the worm and is connected to a steering mechanism. In an electric power steering device for assisting steering, a first elastic member that is arranged so as to be in contact with an inner circumference of an inner ring of the rolling bearing and is expandable in the axial direction by a force applied to the worm in the axial direction. An electric power system comprising: a body; and two second elastic bodies held by the worm or the inner ring so as to be in contact with both ends of the inner ring and suppressing movement of the worm in the axial direction. Steering device. 2. The electric power steering apparatus according to claim 1, wherein the first elastic body and the second elastic body are integrally formed. 3. The electric power steering device according to claim 1, wherein one of the second elastic bodies has a smaller worm movement restraining force in the axial direction than the other. 4. The electric power steering system according to claim 1, wherein the first elastic body has a cylindrical portion and an annular convex portion that is convex on the outer periphery of the cylindrical portion in the radial direction of the worm. apparatus. 5. The electric power steering apparatus according to claim 1, further comprising an annular body between an inner circumference of the first elastic body and the worm. 6. The electric power steering device according to claim 1, wherein the first elastic body and the second elastic body are O-rings.