JP2014101071A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silent and inexpensive electric power steering device.SOLUTION: A first end part 18a and a second end part 18b of a worm 18 are supported by a first bearing 25 and a second bearing 26, respectively. A pair of first energization members 32, 33 placed on both sides of a pair of inner rings of a pair of angular contact ball bearings 27, 28 of the first bearing 25 (face-to-face duplex angular contact ball bearing) elastically energizes the worm 18 to a neutral position in an axial direction X1. A plate spring 50 (a second energization member) supported by a housing 17a energizes the second end part 18b toward a worm wheel 19 via the second bearing 26. A pre-pressure imparting member 31 fixes a pair of outer rings of the pair of angular contact ball bearings 27, 28 to the housing while pressing them in the axial direction X1, and imparts the pre-pressure in the axial direction to the first bearing 25.

Description

  The present invention relates to an electric power steering apparatus.

  In the electric power steering apparatus, the steering operation is torque-assisted by decelerating the output of the electric motor via the worm and the worm wheel and transmitting it to the steering mechanism. In order to suppress the rattling noise (rattle noise) caused by the backlash between the worm and the worm wheel, for example, an electric power steering device of Patent Document 1 has been proposed.

  In FIG. 6 of Patent Document 1, the outer ring of the first bearing that supports the first end of the worm (the end close to the electric motor) is fixed to the housing and adjacent to both sides of the inner ring of the first bearing. The pair of elastic members supports the worm so as to be slightly movable in the axial direction. On the other hand, the outer ring of the second bearing that supports the second end of the worm (the end far from the electric motor) is fixed to the housing, and between the inner ring of the second bearing and the second end of the worm shaft. The interposed elastic member urges the worm toward the worm wheel, and gives an elastic preload to the meshing portion between the worm and the worm wheel.

  On the other hand, in a joint structure in which the worm whose axial movement is restricted and the rotating shaft of the electric motor are fitted and connected so as to be able to rotate together, the worm and the rotating shaft are allowed to tilt. A structure in which one of the drum-shaped shaft portions is fitted to the other cylindrical portion has been proposed (for example, Patent Documents 2 and 3).

Japanese Patent No. 4196831 JP 2001-10512 A JP 2002-323059 A

In Patent Document 1, the first bearing is a single-row radial ball bearing and has a predetermined internal gap. When the internal clearance is large, the first bearing may generate noise when receiving an excitation force due to reverse input from the road surface side.
Conversely, when the internal gap is small, the tilt of the worm is restrained by the first bearing, and the worm may not be able to tilt smoothly. For this reason, the precision control of the internal clearance of the first bearing and the peripheral parts becomes strict, and the manufacturing cost increases.

In Patent Documents 2 and 3, for example, a polygonal cross section or a spline portion as a shaft portion of a joint structure is formed in a drum shape, so that the shape becomes complicated and the manufacturing cost increases.
Accordingly, an object of the present invention is to provide a quiet and inexpensive electric power steering apparatus.

  In order to achieve the above object, the first aspect of the invention of claim 1 is a first end portion connected to a rotating shaft (20) of an electric motor (16) through a joint (21) so as to be able to swing and transmit torque. 18a) and a worm (18) having a second end (18b) opposite the first end, a worm wheel (19) meshing with the worm, and a housing (17a) housing the worm and the worm wheel And a pair of angular ball bearings (27, 28; 127, 128; 227, 228), which are supported by the housing and support the first end of the worm so as to be rotatable and movable in the axial direction (X1). ) Arranged in a front combination, a first bearing (25; 125; 225) which is a front combination angular ball bearing, and a second bearing (2) which rotatably supports the second end of the worm. ) And the pair of inner rings (27b, 28b; 127b, 128b; 227b, 228b) of the pair of angular ball bearings with respect to the axial direction of the worm, and the worm is pivoted with respect to the pair of inner rings. A pair of first urging members (32, 33) elastically urging to a neutral position in the direction and the housing, and the second end of the worm is connected to the worm through the second bearing. A second urging member (50) that urges elastically in a direction (Y2) in which the center distance (D1) from the worm wheel decreases, and a pair of outer rings (27a, 28a; 127a) of the pair of angular ball bearings , 128a; 227a, 228a), and a preload applying member (31) for applying an axial preload to the first bearing by fixing it to the housing while pressing it in the axial direction, The bulging part which bulges toward the other in the axial center part of one of the inner circumferences (27c, 28c) of the pair of inner rings and the outer circumference of the first end part of the worm opposed thereto A steering device (1) provided with (40a; 140a; 260c) is provided.

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
Further, as in claim 2, the pair of inner rings may form an inner ring unit (160; 260) integrally formed of a single member.

  According to a third aspect of the present invention, the first end connected to the rotating shaft of the electric motor via a joint so as to be swingable and capable of transmitting torque, and the second end opposite to the first end are provided. A worm wheel that meshes with the worm, a housing that accommodates the worm and the worm wheel, and is supported by the housing so as to be movable in an axial direction, and a first end portion of the worm is rotatably supported. A first bearing (325; 525; 625), which is a rear combination angular ball bearing in which a pair of angular ball bearings (327, 328; 527, 528; 627, 628) are arranged in a rear combination, and a second of the worm. A second bearing that rotatably supports the end portion, and a pair of outer rings (327a, 328a; 527) of the pair of angular ball bearings with respect to the axial direction of the worm. , 528a; 627a, 628a) and a pair of first urging members (332, 333) for elastically urging the pair of outer rings toward an axial neutral position with respect to the housing; A second biasing member supported by the housing and elastically biasing the second end of the worm via the second bearing in a direction in which a distance between the centers of the worm and the worm wheel decreases; A preload that applies an axial preload to the first bearing by fixing a pair of inner rings (327b, 328b; 527b, 528b; 627b, 628b) of the pair of angular ball bearings to the worm while pressing them in the axial direction. An imparting member (331), and the axially central portion of one of the outer periphery of the pair of outer rings and the inner periphery of the bearing holding hole (329) of the housing facing the outer ring, Bulging portion that bulges toward towards (377a; 477a; 660c) to provide an electric power steering apparatus is provided.

  According to a fourth aspect of the present invention, the pair of outer rings may form an outer ring unit (560; 660) integrally formed of a single member.

  According to the first aspect of the present invention, the preload applying member is fixed to the housing while pressing the pair of outer rings of the pair of angular contact ball bearings in the front combination in the axial direction, thereby the first bearing (front combination angular contact ball bearing). An axial preload is applied to the. Therefore, even if the pair of inner rings of the first bearing elastically supports the worm in the axial direction via the pair of first biasing members, the axial preload only on the pair of outer rings of the first bearing causes the first The internal clearance of one bearing can be removed. Therefore, it is not necessary to strictly control the accuracy of peripheral parts and the like, and the manufacturing cost can be reduced. Also, when receiving an excitation force due to reverse input from the road surface side, abnormal noise in the first bearing Can be suppressed.

  The axial preload by the preload applying member is applied only to the first bearing and not applied to the worm, and in addition, the axial direction of either the inner periphery of the pair of inner rings or the outer periphery of the first end of the worm Since the bulging portion that bulges toward the other side is provided at the center of the second bearing member, the second urging member is used for adjusting the backlash despite the removal of the internal clearance of the first bearing. When tilting the worm, the worm can be tilted smoothly. And since it is not the structure which provides a drum-shaped part in a joint structure part like patent document 2, 3, a bulging part can be made into a simple shape and manufacturing cost can be made cheap.

According to the invention of claim 2, the structure can be simplified by integrally forming the pair of inner rings with a single material.
According to the third aspect of the present invention, the preload applying member is a first bearing which is a rear combination angular ball bearing by fixing the pair of inner rings of the pair of angular ball bearings of the rear combination to the worm while pressing the pair of inner rings in the axial direction. An axial preload is applied to the. Therefore, even when the housing elastically supports the pair of outer rings of the first bearing via the pair of first urging members, the internal clearance of the first bearing can be removed. As a result, it is possible to suppress the occurrence of abnormal noise in the first bearing when receiving an excitation force due to reverse input from the road surface side.

  In addition to the preload applied by the preload applying member being applied only to the first bearing and not being applied to the worm, in addition to the outer periphery of the pair of outer rings and the inner periphery of the housing, Since the bulging portion that bulges toward the other side is provided, the worm can be smoothly tilted when the second biasing member tilts the worm for backlash adjustment. And since it is not the structure which provides a drum-shaped part in a joint structure part like patent document 2, 3, a bulging part can be made into a simple shape and manufacturing cost can be made cheap.

  According to the invention of claim 4, the structure can be simplified by integrally forming the pair of outer rings with a single material.

1 is a schematic diagram of an electric power steering apparatus according to a first embodiment of the present invention, and shows a schematic configuration of the electric power steering apparatus. It is sectional drawing of the principal part of the electric power steering apparatus of FIG. FIG. 3 is an enlarged cross-sectional view of a main part of the electric power steering apparatus of FIG. 2, showing a periphery of a first end portion of a worm. It is sectional drawing which follows the VV line | wire of FIG. 2, and has shown the cross section of the 1st edge part of a worm | warm. It is a perspective view of the leaf | plate spring as an urging | biasing member. It is an expanded sectional view of the principal part of the electric power steering device of 2nd Embodiment of this invention, and has shown the periphery of the 1st edge part of a worm | warm. It is an expanded sectional view of the principal part of the electric power steering device of 3rd Embodiment of this invention, and has shown the periphery of the 1st edge part of a worm | warm. It is an expanded sectional view of the principal part of the electric power steering device of 4th Embodiment of this invention, and has shown the periphery of the 1st edge part of a worm | warm. It is sectional drawing of the principal part of the electric power steering apparatus of 5th Embodiment of this invention. FIG. 10 is an enlarged cross-sectional view of a part of the electric power steering apparatus of FIG. 9, showing a cross section of the first end of the worm. It is an expanded sectional view of the principal part of the electric power steering device of 6th Embodiment of this invention, and has shown the periphery of the 1st edge part of a worm | warm. It is an expanded sectional view of the principal part of the electric power steering device of 7th Embodiment of this invention, and has shown the periphery of the 1st edge part of a worm | warm. It is an expanded sectional view of the principal part of the electric power steering device of 8th Embodiment of this invention, and has shown the periphery of the 1st edge part of a worm | warm.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is a schematic configuration diagram of an electric power steering apparatus according to a first embodiment of the present invention. Referring to FIG. 1, an electric power steering device 1 includes a steering shaft 3 connected to a steering member 2 such as a steering wheel, an intermediate shaft 5 connected to the steering shaft 3 via a universal joint 4, A rack as a steered shaft extending in the left-right direction of an automobile, having a pinion shaft 7 connected to the shaft 5 via a universal joint 6 and a rack 8a meshing with the pinion 7a provided in the vicinity of the end of the pinion shaft 7 Bar 8. The pinion shaft 7 and the rack bar 8 constitute a turning mechanism A composed of a rack and pinion mechanism.

The rack bar 8 is supported in a housing 9 fixed to the vehicle body so as to be capable of linear reciprocation through a plurality of bearings (not shown). Both end portions of the rack bar 8 protrude to both sides of the housing 9, and tie rods 10 are coupled to the respective end portions. Each tie rod 10 is connected to a corresponding steered wheel 11 via a corresponding knuckle arm (not shown).
When the steering member 2 is operated and the steering shaft 3 is rotated, this rotation is converted into a linear motion of the rack bar 8 along the left-right direction of the automobile by the pinion 7a and the rack 8a. Thereby, the turning of the steered wheel 11 is achieved.

The steering shaft 3 includes an input-side first steering shaft 3a having a steering member 2 connected to one end thereof, an output-side second steering shaft 3b connected to the pinion shaft 7, a first steering shaft 3a, and a second steering shaft 3b. And a torsion bar 12 connected to be rotatable relative to each other on the same axis.
A torque sensor 13 is provided for detecting a steering torque based on a relative rotational displacement amount between the first steering shaft 3a and the second steering shaft 3b via the torsion bar 12. The torque detection result of the torque sensor 13 is given to an ECU (Electronic Control Unit) 14. The ECU 14 drives and controls the steering assisting electric motor 16 via the drive circuit 15 based on a torque detection result or a vehicle speed detection result given from a vehicle speed sensor (not shown).

  The output rotation of the electric motor 16 is decelerated via a speed reducer 17 as a transmission device and transmitted to the pinion shaft 7 and converted into a linear motion of the rack bar 8 to assist steering. The speed reducer 17 includes a worm 18 as a drive gear that is rotationally driven by the electric motor 16, and a worm wheel as a driven gear that meshes with the worm 18 and is connected to the second steering shaft 3 b of the steering shaft 3 so as to be integrally rotatable. 19.

As shown in FIG. 2, the worm 18 is disposed coaxially with the rotating shaft 20 of the electric motor 16. The worm 18 has a first end 18a and a second end 18b that are separated in the axial direction thereof, and a tooth portion 18c at an intermediate portion between the first end 18a and the second end 18b.
The worm wheel 19 is coupled to an intermediate portion in the axial direction of the second steering shaft 3b of the steering shaft 3 so as to be integrally rotatable and immovable in the axial direction. The worm wheel 19 includes an annular cored bar 19a coupled to the second steering shaft 3b so as to be integrally rotatable, and a synthetic resin member 19b surrounding the cored bar 19a and having teeth 19c formed on the outer periphery. The core metal 19a is inserted into the mold when the synthetic resin member 19b is molded with resin, for example.

  The first end portion 18a of the worm 18 and the end portion of the rotary shaft 20 (output shaft) of the electric motor 16 opposed to the first end portion 18a are connected via a joint 21 so as to be able to transmit torque and to swing with each other. Specifically, the joint 21 can rotate integrally with the first engagement member 22 connected to the rotating shaft 20 of the electric motor 16 so as to be integrally rotatable and not movable in the axial direction, and the first end 18 a of the worm 18. And the second engagement member 23 that is connected so as not to move in the axial direction, and is interposed between the first engagement member 22 and the second engagement member 23, and transmits torque between the engagement members 22, 23. The elastic member 24 is provided.

  The first engaging member 22 and the second engaging member 23 have the engaging protrusions 221 and 231 arranged alternately in the circumferential direction. Although not shown, the elastic member 24 has a plurality of engaging arms extending radially from the annular main body. A corresponding engagement arm of the elastic member 24 is sandwiched between engagement protrusions 221 and 231 adjacent to each other in the circumferential direction of both engagement members 22 and 23. The elastic member 24 of the joint 21 is elastically deformed, so that the worm 18 is allowed to swing with respect to the rotating shaft 20.

As shown in FIG. 3 in which a part of FIG. 2 is enlarged, the second engagement member 23 includes a boss 23a fitted to the first end 18a of the worm 18 so as to be integrally rotatable and non-movable in the axial direction, And an annular flange 23b extending radially outward from the boss 23a. The engaging protrusion 231 extends in the axial direction from the annular flange 23b.
Referring to FIG. 2 again, the first end portion 18a of the worm 18 is supported by the first bearing 25 fixed to the housing 17a of the speed reducer 17 so as to be rotatable and movable in the axial direction X1. The second end 18b of the worm 18 is rotatably supported by a second bearing 26 held by the housing 17a. The second bearing 26 is constituted by a radial ball bearing.

  Referring to FIG. 3, the first bearing 25 is constituted by a front combination angular ball bearing in which a pair of angular ball bearings 27 and 28 are arranged in a front combination. A pair of outer rings 27a and 28a of the pair of angular ball bearings 27 and 28 are fixed to a bearing holding hole 29 of the housing 17a. That is, the positioning step portion 30 provided in the bearing holding hole 29 of the housing 17a and the preload applying member 31 that also functions as a fixing screw that is screwed to the screw portion 29a of the inlet enlarged diameter portion of the bearing holding hole 29. The pair of outer rings 27a and 28a are fixed to the housing 17a with the pair of outer rings 27a and 28a being pressed in the axial direction X1. Thereby, the preload application member 31 applies a preload to the first bearing 25 (front combination angular contact ball bearing) in the axial direction X1 and removes an internal gap of the first bearing 25.

  The pair of inner rings 27 b and 28 b of the pair of angular ball bearings 27 and 28 are fitted to the outer periphery of the first end 18 a of the worm 18 so as to be integrally rotatable. A central portion in the axial direction X1 of the outer periphery of the first end portion 18a (a central portion in the axial direction X1 of the second portion 40 to be described later) is directed to inner peripheries 27c and 28c formed of cylindrical surfaces of the pair of inner rings 27b and 28b. A bulging portion 40a bulging in a drum shape is provided. The bulging portion 40a is in contact with inner peripheries 27c and 28c formed of cylindrical surfaces of the pair of inner rings 27b and 28b. Thereby, the worm 18 is easily tilted with respect to the first bearing 25. The bulging portion 40a may be formed by axially crowning the second portion 40 of the first end portion 18a.

A pair of first urging members 32 and 33 for urging the worm 18 toward the neutral position in the axial direction X1 with respect to the first bearing 25 are disposed on both sides of the pair of inner rings 27b and 28b. Yes. The first urging members 32 and 33 are made of an elastic member such as a bush made of an elastic material such as rubber or thermoplastic elastomer.
One first biasing member 32 is between an annular receiving plate 35 that is in contact with the positioning step 34 on the outer periphery of the worm 18 and an annular receiving plate 36 that is in contact with one end surface of one inner ring 27b. Is intervening. The other first urging member 33 includes an annular receiving plate 37 that contacts the other end surface of the other inner ring 28 b and an annular receiving plate that contacts the annular flange 23 b of the second engaging member 23 of the joint 21. 38. Each receiving plate 35, 36, 37, 38 is made of metal, for example.

On the outer periphery of the first end portion 18a, a first portion 39 in which the receiving plate 35 and one of the first urging members 32 are fitted, and a pair of inner rings 27b and 28b and the receiving plates 36 and 37 are fitted. The second portion 40 and the third portion 41 into which the boss 23a of the second engagement member 23 is fitted are provided in this order toward the shaft end side.
As shown in FIG. 2, the inner ring 42 of the second bearing 26 is fitted in an annular recess 43 provided on the outer periphery of the second end 18 b of the worm 18 so as to be integrally rotatable. One end surface of the inner ring 42 is in contact with a positioning step portion 44 provided on the outer periphery of the second end portion 18b, whereby the axial movement of the inner ring 42 with respect to the worm 18 is restricted.

  The housing 17 a is provided with a bearing holding hole 45 for holding the second bearing 26. The bearing holding hole 45 causes the second bearing 26 to move in the direction Y1, in which the distance D1 between the centers of the worm 18 and the worm wheel 19 (corresponding to the distance between the rotation center C1 of the worm 18 and the rotation center C2 of the worm wheel 19) increases or decreases. It is formed in a biasing hole that can be held so as to be biasable in Y2 (increasing direction Y1 and decreasing direction Y2).

An annular leaf spring 50 as a second urging member is interposed between the inner periphery of the bearing holding hole 45 and the outer periphery 46 a of the outer ring 46 of the second bearing 26. The leaf spring 50 biases the second bearing 26 in the direction Y2 in which the center distance D1 decreases.
The leaf spring 50 (second biasing member) is a thin plate-like member formed of, for example, a sheet metal. Referring to FIG. 4 which is a cross-sectional view taken along the line IV-IV in FIG. 2 and FIG. 5 which is a perspective view, the leaf spring 50 forms an end ring that surrounds the outer periphery 46a of the outer ring 46 of the second bearing 26. From the main body 51, a pair of rotation restricting portions 52 extending in a bent shape from the first end 51a and the second end 51b, which are circumferential ends of the main portion 51, and the rotation restricting portions 52, respectively. And a pair of cantilevered elastic tongues 53 each extending in a bent shape. The width of each rotation restricting portion 52 is narrower than the width of the main portion 51. The main body 51 is held on the inner periphery of the bearing holding hole 45 of the housing 17a by friction engagement.

As shown in FIG. 5, one of the pair of elastic tongues 53 is disposed on the first side edge 51c side, and the other elastic tongue piece 53 is disposed on the second side edge 51d side, and is staggered. Yes.
Referring again to FIG. 4, the bearing holding hole 45 of the housing 17 a is opposite to the second bearing 26 on the worm wheel 19 side (direction Y <b> 2 in which the center-to-center distance decreases) at a part of its inner periphery. A receiving recess 54 that is recessed in the direction (direction Y1 in which the distance between the centers increases) is formed. The tip of each elastic tongue 53 of the leaf spring 50 is received by the bottom 54c of the receiving recess 54 of the bearing holding hole 45, and the urging force of each elastic tongue 53 is the second of the worm 18 via the second bearing 26. The end 18b is biased in the direction Y2 in which the center distance D1 decreases.

Each of the receiving recesses 54 has a pair of inner walls 54a and 54b facing the circumferential direction Z1 of the bearing holding hole 45, and each rotation restricting portion 52 of the leaf spring 50 comes into contact with the corresponding inner walls 54a and 54b. The rotation of the leaf spring 50 in the circumferential direction Z1 of the bearing holding hole 45 is restricted.
The second end 18b of the worm 18 is urged by the leaf spring 50 (second urging member) in the direction Y2 that reduces the center distance D1 between the worm 18 and the worm wheel 19, whereby the worm 18 The backlash with the worm wheel 19 is suppressed to substantially zero. Thus, when the backlash is substantially zero, the start of the gear is delayed at the start of steering or the like, and there is a possibility that the responsiveness is deteriorated.

On the other hand, at the start of steering or the like, the worm 18 compresses one of the pair of first urging members 32 and 33 corresponding to the steering direction, and one of the axial directions X1 corresponding to the steering direction. By moving slightly to the side, it is possible to speed up the gear start at the start of steering and improve the responsiveness.
However, when the pair of first urging members 32 and 33 are arranged and used on both sides of the inner ring of the first bearing constituted by the conventional radial ball bearing, the preload is applied to the conventional radial ball bearing. Therefore, the internal clearance of the conventional radial bearing cannot be removed. For this reason, when receiving an excitation force by reverse input from the road surface, the conventional radial ball bearing may generate noise due to the internal gap.

  Therefore, according to the first embodiment, the preload imparting member 31 is fixed to the housing 17a while pressing the pair of outer rings 27a, 28a of the pair of angular ball bearings 27, 28 in the front combination in the axial direction X1, A preload in the axial direction X1 is applied to the front combination angular contact ball bearing as the first bearing 25. Therefore, even if the pair of inner rings 27b and 28b of the first bearing 25 elastically supports the worm 18 in the axial direction X1 via the pair of first biasing members 32 and 33, The internal clearance of the first bearing 25 can be removed by the axial preload only on the pair of outer rings 27 a and 28 a of the one bearing 25. Therefore, it is not necessary to strictly manage the accuracy of peripheral parts and the like, the manufacturing cost can be reduced, and the difference in the first bearing 25 can be obtained when receiving an excitation force due to reverse input from the road surface side. Generation of sound can be suppressed.

Further, the axial preload by the preload applying member 31 is applied only to the first bearing 25 and is not exerted on the worm 18, and in addition, the first worm 18 facing the inner circumference of the pair of inner rings 27b and 28b. A bulging portion 40a that bulges toward the inner peripheries 27c and 28c of the pair of inner rings 27b and 28b is provided in the central portion in the axial direction of the outer periphery (specifically, the second portion 40) of the end portion 18a. Therefore, even when the internal clearance of the first bearing 25 is removed, when the second biasing member (leaf spring 50) tilts the worm 18 for backlash adjustment, the worm 18 is smoothly tilted. be able to. And since it is not the structure which provides a drum-shaped part in a joint structure part like patent document 2, 3, the bulging part 40a can be made into a simple shape, and manufacturing cost can be made cheap.
(Second Embodiment)
Next, FIG. 6 shows a second embodiment of the present invention. The second embodiment of FIG. 6 is different from the first embodiment of FIG. 3 as follows. That is, in the first embodiment of FIG. 3, a bulging portion 40 a formed by axial crowning is provided on the second portion 40 on the outer periphery of the first end portion 18 a of the worm 18. On the other hand, in the second embodiment of FIG. 6, the second portion 140 of the first end portion 18a of the worm 18 has a bulging portion 140a formed by a cylindrical surface portion at the center in the axial direction X1, and an axial direction. A pair of conical tapered surface portions 140b and 140c opposite to each other are provided on both sides of the bulging portion 140a with respect to X1.

In the constituent elements of the second embodiment, the same constituent elements as those of the first embodiment are denoted by the same reference numerals as those of the constituent elements of the first embodiment. Also in the second embodiment, the same operational effects as in the first embodiment can be achieved, and a quiet and inexpensive electric power steering apparatus can be realized.
(Third embodiment)
Next, FIG. 7 shows a third embodiment of the present invention. The third embodiment of FIG. 7 is different from the first embodiment of FIG. That is, in the first embodiment of FIG. 3, a front combination angular ball bearing in which a pair of angular ball bearings 27 and 28 are arranged in a front combination is used as the first bearing 25. On the other hand, in the front combination angular contact ball bearing as the first bearing 125 of the third embodiment in FIG. 7, the inner rings 127b and 128b of the pair of angular contact ball bearings 127 and 128 are integrally formed of a single material. The inner ring unit 160 is configured, and double row raceway grooves 161 and 162 are provided on the outer periphery 160 a of the inner ring unit 160.

  An inner periphery 160b of the inner ring unit 160 is formed as a cylindrical surface, and a bulging portion 40a on the outer periphery of the first end 18a of the worm 18 is in contact therewith. The pair of outer rings 127a, 128a of the first bearing 125 (front combination angular contact ball bearing) is a separate type as in the second embodiment. Since the inner ring unit 160 is a double row, the front combination angular contact ball bearing as the first bearing 125 may be referred to as a double row angular contact ball bearing.

In the constituent elements of the third embodiment, the same constituent elements as those of the first embodiment are denoted by the same reference numerals as those of the constituent elements of the first embodiment. Also in the third embodiment, the same operational effects as in the first embodiment can be achieved, and a quiet and inexpensive electric power steering device can be realized.
(Fourth embodiment)
Next, FIG. 8 shows a fourth embodiment of the present invention. The fourth embodiment shown in FIG. 8 is different from the first embodiment shown in FIG. That is, in the first embodiment of FIG. 7, the inner periphery 160b of the inner ring unit 160 is formed in a cylindrical surface, and the bulging portion 40a is provided in the second portion 40 on the outer periphery of the first end 18a of the worm 18. Yes. On the other hand, in the fourth embodiment of FIG. 8, the second portion 240 on the outer periphery of the first end 18 a of the worm 18 is formed with a cylindrical surface, and the inner ring unit of the front combination angular ball bearing as the first bearing 225. A bulging portion 260c is provided in the axially central portion of the inner periphery 260b of 260.

  In the first bearing 225 (front combination angular contact ball bearing), the inner rings 227b and 228b of the pair of angular ball bearings 227 and 228 constitute an inner ring unit 260 integrally formed of a single material. Double-row track grooves 261 and 262 are provided on the outer periphery 260a. Since the inner ring unit 260 is a double row, the front combination angular contact ball bearing as the first bearing 225 may be referred to as a double row angular contact ball bearing.

In the constituent elements of the fourth embodiment, the same constituent elements as those of the third embodiment are denoted by the same reference numerals as those of the constituent elements of the third embodiment. Also in the fourth embodiment, the same operational effects as in the third embodiment can be obtained, and a quiet and inexpensive electric power steering apparatus can be realized.
(Fifth embodiment)
Next, FIG. 9 shows a fifth embodiment of the present invention. The fifth embodiment of FIG. 9 is different from the first embodiment of FIG. That is, in the embodiment of FIG. 2, the worm 18 is elastically supported in the axial direction X1 with respect to the first bearing 25 (front combination angular), and the bulging portion 40a is provided at the first end portion 18a of the worm 18. It has been.

  On the other hand, in the fifth embodiment, the first bearing 325 (back combined angular ball bearing) is elastically supported in the axial direction with respect to the housing 17a, and the first bearing 325 (front combined angular ball bearing), the worm 18, Can move integrally in the axial direction X1. Further, a bulging portion 377a formed by axial crowning is provided on the inner periphery of the bearing holding hole 329 of the housing 17a.

  With respect to the axial direction X1, a pair of outer rings 327a and 328a are placed on both sides of the pair of outer rings 327a and 328a of the pair of angular ball bearings 327 and 328 of the first bearing 325 (front combined angular contact ball bearing), and the neutral positions in the axial direction X1. A pair of first urging members 332 and 333 for urging is disposed. The pair of first biasing members 332 and 333 bias the worm 18 to the neutral position in the axial direction X1 via the first bearing 325 (front combination angular ball bearing). The first urging members 332 and 333 are made of an elastic member such as a bush made of an elastic material such as rubber or thermoplastic elastomer.

  As shown in FIG. 10 in which a part of FIG. 9 is enlarged, one first urging member 332 includes an annular receiving plate 371 in contact with the positioning step 370 on the inner periphery of the housing 17a and one outer ring 327a. Is interposed between an annular receiving plate 372 that is in contact with the end surface of one side (the side opposite to the joint 21 side). The other first urging member 333 is screwed into an annular receiving plate 373 that is in contact with the other end face (the joint 21 side) of the other outer ring 328a and a threaded portion 329a of the bearing holding hole 329 of the housing 17a. It is interposed between the receiving plate 375 in contact with the annular flange 374 a of the screw member 374. Each of the receiving plates 371, 372, 373, and 375 is made of metal, for example.

A first portion 376 into which a receiving plate 371 and one first biasing member 332 are fitted, a receiving plate 372 and a pair of outer rings 327a and 328a are fitted into the inner periphery of the bearing holding hole 329 of the housing 17a. A second portion 377 and a third portion 378 into which the receiving plate 373 and the cylindrical protrusion 374b of the screw member 374 are fitted are provided.
The bulging portion 377a is provided at the central portion in the axial direction X1 of the second portion 377 on the inner circumference of the bearing holding hole 329, and bulges toward the outer circumferences 327d and 328d of the pair of outer rings 327a and 328a. .

  The inner circumferences 327c and 328c of the pair of inner rings 327b and 328b are fitted to a bearing holding portion 380 formed of a cylindrical surface on the outer circumference of the first end portion 18a of the worm 18 so as to be integrally rotatable. In addition, one end surface of one inner ring 327b (opposite to the joint 21 side) abuts on the positioning step 381 at one end of the bearing holding portion 380, and the other end surface of the other inner ring 328b (joint 21 side) is , A preload applying member 331 made of, for example, a screw member that is screwed into the screw portion 382 of the first end portion 18a.

The preload applying member 331 is fixed to the first bearing 325 (front combined angular contact ball bearing) in the axial direction X1 by fixing the pair of inner rings 327b and 328b to the worm 18 while pressing the pair of inner rings 327b and 328b in the axial direction X1 (positioning step portion 381 side). The preload is given.
In the constituent elements of the fifth embodiment, the same constituent elements as those of the first embodiment of FIG. 3 are denoted by the same reference numerals as those of the constituent elements of the first embodiment.

  According to the fifth embodiment, the preload imparting member 331 fixes the pair of inner rings 327b and 328b of the pair of angular ball bearings 327 and 328 in the rear combination to the worm 18 while pressing the pair of inner rings 327b and 328b in the axial direction X1. A preload in the axial direction X1 is applied to the first bearing 325 which is an angular ball bearing. Therefore, even when the housing 17a is configured to elastically support the pair of outer rings 327a and 328a of the first bearing 325 via the pair of first biasing members 332 and 333, the internal gap of the first bearing 325 can be removed. As a result, the occurrence of abnormal noise in the first bearing 325 can be suppressed when receiving an excitation force due to reverse input from the road surface side.

Further, the preload by the preload applying member 331 is loaded only on the first bearing 325 and not on the worm 18, and in addition, the shaft of the inner periphery (second portion 377) of the bearing holding hole 329 of the housing 17 a. Since a bulging portion 377a that bulges toward the outer periphery of the pair of outer rings 327a and 328a is provided at the center in the direction X1, the disc spring 50 (second urging member) is used as a worm 18 for backlash adjustment. When tilting, the worm 18 can be tilted smoothly. And since it is not the structure which provides a drum-shaped part in a joint structure part like patent document 2, 3, the bulging part 377a can be made into a simple shape, and manufacturing cost can be made cheap.
(Sixth embodiment)
Next, FIG. 11 shows a sixth embodiment of the present invention. The sixth embodiment of FIG. 11 is different from the fifth embodiment of FIG. 10 as follows. That is, in the fifth embodiment of FIG. 10, a bulging portion 377a formed by axial crowning is provided on the inner periphery of the second portion 377 of the bearing holding hole 329 of the housing 17a. On the other hand, in the sixth embodiment of FIG. 11, the bulging portion 477a formed by the cylindrical surface portion of the central portion in the axial direction X1 on the inner periphery of the second portion 477 of the bearing holding hole 329, and the axial direction X1. A pair of conical tapered surface portions 477b and 477c opposite to each other are provided on both sides of the bulging portion 477a.

In the constituent elements of the sixth embodiment, the same constituent elements as those of the fifth embodiment are denoted by the same reference numerals as those of the constituent elements of the fifth embodiment. Also in the sixth embodiment, the same operational effects as in the fifth embodiment can be obtained, and a quiet and inexpensive electric power steering device can be realized.
(Seventh embodiment)
Next, FIG. 12 shows a seventh embodiment of the present invention. The seventh embodiment of FIG. 12 is different from the fifth embodiment of FIG. 10 as follows. That is, in the fifth embodiment of FIG. 10, a back combination angular ball bearing in which a pair of angular ball bearings 327 and 328 are arranged in a back surface combination is used as the first bearing 325. On the other hand, in the first bearing 525 (back combination angular ball bearing) of the third embodiment in FIG. 12, the outer rings 527a and 528a of the pair of angular ball bearings 527 and 528 are integrally formed of a single material. The outer ring unit 560 is configured, and double row raceway grooves 561 and 562 are provided on the inner periphery 560 b of the outer ring unit 560.

  The outer periphery 560a of the outer ring unit 560 is formed in a cylindrical surface, and the bulging portion 377a of the second portion 377 on the inner periphery of the bearing holding hole 329 of the housing 17a is in contact therewith. The pair of inner rings 527b and 528b of the first bearing 525 (back combination angular contact ball bearing) is the same as the fifth embodiment, and the inner circumferences 527c and 528c of the pair of inner rings 527b and 528b are the first of the worm 18. The end 18a is fitted to the bearing holding portion 380 so as to be integrally rotatable. Since the outer ring unit 560 is a double row, the back combination angular ball bearing as the first bearing 525 may be referred to as a double row angular ball bearing.

In the constituent elements of the seventh embodiment, the same constituent elements as those of the fifth embodiment are denoted by the same reference numerals as those of the constituent elements of the fifth embodiment. Also in the seventh embodiment, the same operational effects as in the fifth embodiment can be obtained, and a quiet and inexpensive electric power steering apparatus can be realized.
(Eighth embodiment)
Next, FIG. 13 shows an eighth embodiment of the present invention. The eighth embodiment shown in FIG. 13 is different from the seventh embodiment shown in FIG. That is, in the seventh embodiment of FIG. 12, the outer periphery 560a of the outer ring unit 560 is formed as a cylindrical surface, and the bulging portion 377a is provided in the second portion 377 of the inner periphery of the bearing holding hole 329 of the housing 17a. .

On the other hand, in the eighth embodiment shown in FIG. 13, the second portion 677 on the inner periphery of the bearing holding hole 329 of the housing 17a is formed of a cylindrical surface, and the outer ring unit of the first bearing 625 (back combination angular ball bearing). A bulging portion 660c is provided at the axially central portion of the outer periphery 660a of 660.
In the first bearing 625 (back combination angular ball bearing), the outer rings 627a and 628a of the pair of angular ball bearings 627 and 628 constitute an outer ring unit 660 integrally formed of a single material. Double row raceway grooves 661 and 662 are provided on the inner periphery 660b. Since the outer ring unit 660 is a double row, the back combination angular ball bearing as the first bearing 625 may be referred to as a double row angular ball bearing.

In the constituent elements of the eighth embodiment, the same constituent elements as those of the seventh embodiment are denoted by the same reference numerals as those of the constituent elements of the seventh embodiment. Also in the eighth embodiment, the same operational effects as in the seventh embodiment can be achieved, and a quiet and inexpensive electric power steering device can be realized.
The present invention is not limited to the above-described embodiments. For example, instead of the bulging portion 377a of FIG. 12 and the bulging portion 660c of FIG. 13, the present invention is provided between a pair of conical tapered portions as shown in FIG. A cylindrical bulged portion formed may be used.

  Further, as the preload applying members 31 and 331, a retaining ring fitted in the circumferential groove of the housing 17 a or the worm 18 may be used instead of the screw member. In addition, various modifications can be made within the scope of the claims of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 2 ... Steering member, 3 ... Steering shaft, 16 ... Electric motor, 17 ... Reduction gear, 17a ... Housing, 18 ... Worm, 18a ... 1st end part, 18b ... 2nd end part, 19 ... Worm wheel, 20 ... Rotary shaft of (electric motor), 21 ... Joint, 25 ... First bearing (front combination angular contact ball bearing), 26 ... Second bearing, 27,28 ... Angular contact ball bearing, 29 ... Bearing holding hole , 30 ... Positioning step part, 31 ... Preload applying member, 32, 33 ... First urging member, 50 ... Leaf spring (second urging member), 125 ... First bearing (front combination angular contact ball bearing), 127, 128 ... Angular contact ball bearing, 127a, 128a ... Outer ring, 127b, 128b ... Inner ring, 140a ... Swelling part, 140b, 140c ... Conical taper part, 160 ... Inner ring unit, 225 ... 1 bearing (front combination angular contact ball bearing), 227, 228 ... angular contact ball bearing, 227a, 228a ... outer ring, 227b, 228b ... inner ring, 260 ... inner ring unit, 260b ... inner circumference, 260c ... bulge, 325 ... first Bearings (back combination angular contact ball bearings), 327, 328 ... angular contact ball bearings, 327a, 328a ... outer ring, 327b, 328b ... inner ring, 331 ... preload application member, 332, 333 ... first biasing member, 377a ... bulge Part, 477a ... bulge part, 477b, 477c ... conical tapered surface part, 525 ... first bearing (back combination angular contact ball bearing), 527, 528 ... angular contact ball bearing, 527a, 528a ... outer ring, 527b, 527b ... inner ring 560 ... Outer ring unit, 625 ... First bearing (back combination angular contact ball bearing), 627, 628 Angular contact ball bearings, 627a, 628a ... outer ring, 627b, 628b ... inner ring, 660 ... outer ring unit, 660a ... outer periphery, 660c ... bulge, C1 ... (worm) rotation center, C2 ... (worm wheel) rotation center, D1 ... Center distance, Y1 ... Center direction distance increases, Y2 ... Center center distance decreases

Claims (4)

A worm having a first end coupled to a rotating shaft of an electric motor via a joint so as to be able to swing and capable of transmitting torque, and a second end opposite to the first end;
A worm wheel meshing with the worm;
A housing containing the worm and the worm wheel;
A first bearing that is a front combination angular ball bearing that is held by the housing, supports the first end of the worm so as to be rotatable and axially movable, and includes a pair of angular ball bearings arranged in a front combination. When,
A second bearing rotatably supporting the second end of the worm;
A pair of first attachments disposed on both sides of a pair of inner rings of the pair of angular ball bearings with respect to the axial direction of the worm, and elastically biasing the worm to an axial neutral position with respect to the pair of inner rings. A force member;
A second biasing member supported by the housing and elastically biasing the second end of the worm via the second bearing in a direction in which a distance between the centers of the worm and the worm wheel decreases;
A preload applying member that applies an axial preload to the first bearing by pressing the pair of outer rings of the pair of angular ball bearings in the housing while pressing the pair of outer rings in the axial direction;
A bulging portion that bulges toward the other is provided at the axial central portion of one of the inner circumference of the pair of inner rings and the outer circumference of the first end portion of the worm that faces the inner circumference. Electric power steering device.   2. The electric power steering apparatus according to claim 1, wherein the pair of inner rings forms an inner ring unit formed integrally with a single member. A worm having a first end coupled to a rotating shaft of an electric motor via a joint so as to be able to swing and capable of transmitting torque, and a second end opposite to the first end;
A worm wheel meshing with the worm;
A housing containing the worm and the worm wheel;
A first bearing which is a rear combination angular ball bearing supported by the housing so as to be movable in the axial direction, rotatably supporting a first end of the worm, and a pair of angular ball bearings arranged in a rear combination; ,
A second bearing rotatably supporting the second end of the worm;
A pair of first attachments disposed on both sides of a pair of outer rings of the pair of angular ball bearings with respect to the axial direction of the worm, and elastically biasing the pair of outer rings toward an axial neutral position relative to the housing. A force member;
A second biasing member supported by the housing and elastically biasing the second end of the worm via the second bearing in a direction in which a distance between the centers of the worm and the worm wheel decreases;
A preload applying member that applies an axial preload to the first bearing by pressing the pair of inner rings of the pair of angular ball bearings in the axial direction while fixing them to the worm,
Electric power provided with a bulging portion that bulges toward the other at the central portion in the axial direction of one of the outer circumference of the pair of outer rings and the inner circumference of the bearing holding hole of the housing facing the outer ring. Steering device.   4. The electric power steering apparatus according to claim 3, wherein the pair of outer rings forms an outer ring unit formed integrally with a single member.

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