JP2009107392A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a structure attaining enhancement of durability of an elastic support member 23 for slightly displaceably supporting a worm in an axial direction. <P>SOLUTION: The elastic support member 23 includes a pair of flange plates 25, 25 of circular ring-like shape arranged with a space in an axial direction; and a displacement absorption material 24 of a circular ring-like shape made of an elastic material. Both axial end surfaces of the displacement absorption material 24 and mutually opposed surfaces of both flange plates 25, 25 are recession/projection-engagement in a direction suppressing relative displacement in a plane direction. For this, recession/projection parts 26, 27 engaged with each other are formed on both axial end surface of the displacement absorption material 24 and the mutually opposed surface of both flange plates 25, 25. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The electric power steering apparatus according to the present invention is used as a steering apparatus for an automobile, and uses an electric motor as auxiliary power to reduce the force required for the driver to operate the steering wheel. is there. The present invention was invented with the intention of improving the durability of the structure for suppressing the generation of unpleasant noise called rattling noise in the worm-type speed reducer constituting such an electric power steering device. It is.

  A power steering device is widely used as a device to reduce the force required for the driver to operate the steering wheel when giving a steering angle to the steered wheels (usually the front wheels except for special vehicles such as forklifts) Has been. In addition, an electric power steering apparatus that uses an electric motor as an auxiliary power source in such a power steering apparatus has begun to spread in recent years. The electric power steering device can be made smaller and lighter than the hydraulic power steering device, has advantages such as easy control of the magnitude (torque) of auxiliary power and less power loss of the engine.

  Various structures of the electric power steering apparatus are known. In any structure, the electric motor is attached to the rotating shaft that is rotated by the operation of the steering wheel and gives a steering angle to the steered wheel as the wheel rotates. Auxiliary power is applied through a speed reducer. In general, a worm reducer is used as the reducer. In the case of an electric power steering device using a worm speed reducer, a worm that is rotationally driven by the electric motor and a worm wheel that rotates together with the rotating shaft are engaged with each other, and auxiliary power of the electric motor is applied to the rotating shaft. Communicate freely. However, in the case of a worm reducer, if no measures are taken, it is called a rattling sound when changing the rotation direction of the rotating shaft based on the backlash existing in the meshing portion of the worm and the worm wheel. Unpleasant noise may occur.

Conventionally, the following structures (A) to (C) are known as structures for suppressing the occurrence of such rattling noise.
(A) The worm is elastically supported to allow a slight displacement in the axial direction, and the worm is elastically displaced in the axial direction at the start of power transmission between the worm and the worm wheel. Absorbs collision energy with the wheel.
(B) The worm is supported so as to be able to slightly swing around the base end portion, and the tip portion of the worm is elastically pressed toward the worm wheel, and the meshing portion between the worm and the worm wheel. Eliminate backlash.
(C) Combine the structures (A) and (B) above.

Of these structures (A) to (C), the structure (A) is described in Patent Documents 1 and 2, and the structure (B) is described in Patent Documents 3 to 5, respectively. Among these (A) to (C), an electric power steering apparatus having the structure of (A) and (C), which is an object of the present invention, will be described with reference to FIGS.
First, FIG. 9 shows an electric power steering apparatus having the structure (C) as a first example of a structure to be an object of the present invention. This electric power steering apparatus is configured to apply an auxiliary torque to a rotating shaft 2 that gives a steering angle to a steered wheel with rotation by an electric motor 1. The rotating shaft 2 is rotated in a predetermined direction by a steering wheel, and any of a steering shaft, an intermediate shaft, and an input shaft (pinion shaft) of the steering gear unit can be employed.

  The rotating shaft 2 is rotatably supported inside the housing 3, and a worm wheel 4 is fixed to this portion. The worm wheel 4 and the worm 5 constitute a worm-type speed reducer 6 so that the torque of the output shaft 7 of the electric motor 1 is transmitted to the rotary shaft 2. The base end portion (left end portion in FIG. 9) of the worm shaft 9 constituting the worm 5 and provided with the worm teeth 8 on the outer peripheral surface in the axial direction is formed at the tip end portion (right end portion in FIG. 9) of the output shaft 7. Torque transmission is possible by non-circular fitting such as serration engagement. Further, both end portions of the worm shaft 9 are respectively rotatable in the housing 3 by the base-end and tip-end radial rolling bearings 10 and 11 such as single row deep groove ball bearings, and the base end. It is supported so as to be able to slightly swing around the side. In order to make this oscillating displacement possible, the base end is provided with a positive internal clearance in the radial rolling bearing 10.

  Further, the base end portion of the worm shaft 9 is loosely fitted to an inner ring 12 a constituting the base end side radial rolling bearing 10. Further, there is elasticity between the axially opposite end surfaces of the inner ring 12a and the stepped surface 13 and the locking ring 14 provided at positions near the proximal end of the worm shaft 9 so as to sandwich the inner ring 12a from both axial sides. The support members 15a and 15b are sandwiched. Each of these elastic support members 15a and 15b includes a pair of flange plates 16 and 16 and a displacement absorbing member 17 as shown in FIGS. Of these, both flange plates 16 and 16 are each formed by forming a metal plate such as a steel plate into an annular shape, and are arranged concentrically with each other. The displacement absorbing member 17 is formed by forming an elastic material such as an elastomer such as rubber in a circular shape with a rectangular cross section. Such a displacement absorbing member 17 and the two flange plates 16 and 16 are bonded and fixed by baking or the like. Each of the elastic support members 15a and 15b, each configured as described above, has a small amount of the displacement absorbing material 17 between the axial end surfaces of the inner ring 12a and the stepped surface 13 and the locking ring 14. Installed in a compressed state in the axial direction. Accordingly, the base end portion of the worm shaft 9 is supported on the inner diameter side of the base end side radial rolling bearing 10 so as to be slightly displaceable in the axial direction.

  As described above, since the worm 5 is supported by the pair of elastic support members 15a and 15b so as to be able to be slightly displaced in the axial direction, torque is transmitted between the worm teeth 8 and the worm wheel 4. At the moment when the worm teeth 8 and the worm wheel 4 start to mesh, the worm 5 is displaced in the axial direction. At this time, the displacement absorbing member 17 constituting the elastic support member 15a (15b) existing on the front side in the displacement direction is elastically compressed in the axial direction. As a result, the impact applied to the meshing portion between the worm tooth 8 and the worm wheel 4 is alleviated, and the rattling noise generated at the meshing portion at the moment of starting the torque transmission is suppressed. In order to sufficiently secure the effect of suppressing the rattling noise, the worm wheel 4 is preferably made of a synthetic resin.

  In the case of the structure of the first example shown in FIG. 9, a pressing piece 18 is externally fitted to a portion of the tip portion of the worm shaft 9 that protrudes from the tip-side radial rolling bearing 11. An elastic member such as a coil spring 19 is provided between the housing 3 and the housing 3. The coil spring 19 presses the tip of the worm shaft 9 toward the worm wheel 4 through the pressing piece 18. Further, a bush 20 made of an elastic material such as rubber is installed between the inner peripheral surface of the inner ring 12 b constituting the tip side radial rolling bearing 11 and the outer peripheral surface of the worm shaft 9 near the tip. . The inner diameter of the bush 20 is slightly larger than the outer diameter of the portion near the tip of the worm shaft 9, and the portion near the tip of the worm shaft 9 is loosely inserted on the inner diameter side of the bush 20.

  In a neutral state where torque is not transmitted between the worm teeth 8 and the worm wheel 4, there is a gap between the inner peripheral surface of the bush 20 and the outer peripheral surface near the tip of the worm shaft 9. The tip portion of the worm shaft 9 is displaced toward the worm wheel 4 on the inner diameter side of the bush 20 based on the elasticity of the coil spring 19 due to the presence of the gap, and the worm teeth 8 are moved toward the worm wheel 4. Press toward. In the case of the structure of the first example, the backlash between the worm teeth 8 and the worm wheel 4 is suppressed by such a configuration, and the occurrence of the rattling noise is suppressed. The tip portion of the worm shaft 9 is rotatably supported by the pressing piece 18 immediately after the start of the torque transmission or when the torque to be transmitted is small. When the torque is large, the tip side radial rolling is performed. It is supported by the bearing 11. This point is described in Patent Document 4 and the like, and is not related to the gist of the present invention, and thus detailed description is omitted.

  FIG. 10 shows an electric power steering apparatus having the structure (A) as a second example of the structure to be the subject of the present invention. In this electric power steering device, the outer ring 21a, 21b constituting both the base end side, the tip end side, and the radial rolling bearings 10a, 11a for supporting both ends of the worm 5a are provided inside the housing 3a. It is fitted and fixed. Further, the base end portion and the tip end portion of the worm shaft 9a are fitted inside the inner rings 12a and 12b constituting the radial rolling bearings 10a and 11a so as to be axially displaceable. The elastic support members 15c and 15d are respectively provided between the stepped surfaces 13a and 13b formed at the base end portion and the tip end portion of the worm shaft 9a and the axial end surfaces of the inner rings 12a and 12b facing each other. Is provided.

  The basic configuration of these elastic support members 15c and 15d is the same as that of the elastic support members 15a and 15b incorporated in the structure of the first example described above. The inner diameters of the flange plates 16a, 16a on both the inner rings 12a, 12b side of the both elastic support members 15c, 15d incorporated in the structure of this example are reduced. And the inner diameter side step surfaces 22a and 22b formed on the inner diameter side portions of both the flange plates 16a and 16a on the end surfaces of the inner rings 12a and 12b and the intermediate portion proximal end portion and the distal end portion of the worm shaft 9a. Between them and loosely (allowing slight displacement in the axial direction). In the case of this example, the worm 5a is supported so as to be elastically displaceable with respect to the axial direction by the configuration as described above, and at the moment of starting torque transmission between the worm 5a and the worm wheel 4, these are supported. The rattling noise generated at the meshing portion between the worm 5a and the worm wheel 4 is suppressed.

  Whether the structure of the first example shown in FIG. 9 or the structure of the second example shown in FIG. 10 is used, the rattling noise suppression effect based on the axial displacement of the worms 5 and 5a. In order to sufficiently obtain the above, it is necessary to sufficiently secure the bonding strength between the flange plates 16 and 16a constituting the respective elastic support members 15a to 15d and the displacement absorbing member 17. For this reason, these flange plates 16 and 16a and the displacement absorbing member 17 are firmly joined together by bonding (including baking, which is bonded when the displacement absorbing member 17 is formed). However, the torque transmitted between the worm 5a and the worm wheel 4 is increased, and the amount of compression of the displacement absorbing material 17 is increased, or if the use conditions are severe, such as the ambient temperature is increased, it is extended for a long period of time. With use, the joint between the flange plates 16 and 16a and the displacement absorbing member 17 may be peeled off. And if this joint part peels, the rigidity between one pair of flange plates 16 and 16a which comprise each said elastic support members 15a-15d will fall, and the rattling by these each elastic support members 15a-15d Sound reduction effect is impaired. In recent years, the service life of automobiles tends to be long, and it is required to secure sufficient durability even for the durability of each of the elastic support members 15a to 15d, and countermeasures are desired.

Japanese Patent No. 3253578 International Publication WO2003 / 047948 JP 2000-43739 A JP 2004-306898 A JP-T-2006-513906

  In view of the circumstances as described above, the present invention has been invented to realize a structure capable of improving the durability of an elastic support member for supporting a worm so that it can be slightly displaced in the axial direction.

The electric power steering apparatus of the present invention includes a housing, a rotating shaft, a worm wheel, a worm, an electric motor, and an elastic support member, as in the above-described conventionally known electric power steering apparatus. Prepare.
Of these, the housing is supported by a fixed portion and does not rotate.
The rotating shaft is provided so as to be rotatable with respect to the housing, and is rotated by an operation of a steering wheel, and gives a steering angle to the steered wheels as it rotates. As such a rotating shaft, any of a steering shaft, an intermediate shaft, and an input shaft (pinion shaft) of the steering gear unit can be adopted.
Further, the worm wheel is concentric with a part of the rotating shaft inside the housing, concentric with the rotating shaft (a state in which relative rotation is prevented by an external fitting fixing by an interference fit, a key engagement, a spline engagement, etc. Supported) and rotate with this axis of rotation. Such a worm wheel may be made of a metal such as an iron-based alloy, but is preferably made of a synthetic resin in terms of suppressing rattling noise. As a kind of synthetic resin used in this case, it is a matter of course to use a high-strength resin having sufficient toughness, but a resin having a low friction coefficient and heat resistance is preferable. Further, if necessary, a reinforcing material such as carbon fiber or glass fiber (preferably carbon fiber having a low coefficient of friction and a low aggressiveness to the mating member) is contained.
The worm is provided with worm teeth at an intermediate portion in the axial direction of the worm shaft. Then, with the worm teeth meshed with the worm wheel, the base end of the worm shaft can be rotated with respect to the housing by the base end side radial rolling bearing, and the tip side can also be rotated by the front end side radial rolling bearing. To support.
In the electric motor, the base end portion of the worm shaft and the tip end portion of the output shaft are engaged with each other so as to freely transmit a rotational force, so that the worm shaft can be driven to rotate in both directions.

Further, the elastic support member is provided between a part of the worm and the housing, and supports the worm so as to be capable of displacement in the axial direction with respect to the housing. A member such as a radial rolling bearing is provided between the housing and the elastic member in a state where the axial displacement of the worm is suppressed with respect to the housing.
The elastic support member includes a pair of flange plates and a displacement absorbing material.
Each of the pair of flange plates is in the shape of a ring and is disposed with a gap in the axial direction.
The displacement absorbing material is made of an elastic material such as an elastomer such as rubber, and is provided between the flange plates with both axial end surfaces in contact with the surfaces of the flange plates facing each other. It has been.

In particular, in the electric power steering apparatus according to the present invention, the engagement between the axial ends of the displacement absorber and the opposing surfaces of the flange plates in a direction to prevent relative displacement in the plane direction. I am letting.
When implementing the present invention as described above, for example, as described in claim 2, uneven portions that engage with each other are formed on both end surfaces in the axial direction of the displacement absorbing material and on the surfaces of the flange plates facing each other. To do.
Alternatively, as described in claim 3, the protrusions provided on a part of the displacement absorbing material are made to enter the holes formed on the surfaces of the two flange plates facing each other so that the holes and the protrusions are uneven. Engage.
Alternatively, as described in claim 4, a hole and a convex portion adjacent to the opening of the hole are formed on the surfaces of the flange plates facing each other, and the protrusion provided on the displacement absorbing material is provided with the protrusion. While making it enter a hole, the said convex part is made to bite into the part adjacent to this projection part.

According to the present invention having the above-described configuration, the elastic support member incorporated in the mechanism for suppressing the backlash between the worm teeth and the worm wheel constituting the worm type reduction gear constituting the electric power steering apparatus. Can improve durability.
That is, in the case of the present invention, the concavo-convex portions formed on both end surfaces in the axial direction of the displacement absorber constituting the elastic support member and the concavo-convex portions formed on the mutually opposing surfaces of the pair of flange plates are mutually connected. Since they are engaged, a sufficient area of the joint surface can be secured. Further, even if a shearing force acts on the joint surface, it is difficult to apply a force in the direction of peeling the joint surface due to the mechanical engagement between the two uneven portions. For this reason, it is possible to secure sufficient bonding strength between the displacement absorbing material and the two flange plates, and to improve the durability of the elastic support member constituted by the displacement absorbing material and the two flange plates.

[First example of embodiment]
1 and 2 show a first example of an embodiment of the present invention corresponding to claims 1 and 2. The electric power steering apparatus according to this embodiment is characterized in that the bonding strength between the displacement absorbing member 24 and the pair of flange plates 25, 25 constituting the elastic support member 23 is improved, so that the elastic support member 23 This is to realize a structure capable of improving durability. In addition, regarding the structure and operation of the entire electric power steering apparatus, basically, including those described in Patent Documents 1 to 5 and those shown in FIGS. Similar to the known structure. Therefore, the illustration and description of the parts equivalent to those of the conventional structure are omitted or simplified, and the following description will focus on the characteristic parts of this example.

  The flange plates 25 and 25 are each formed in a washboard shape by a metal plate such as a steel plate, and concentric concave and convex portions 26 and 26 are provided on surfaces facing each other. The displacement absorbing member 24 is made of an elastic material such as an elastomer such as rubber as a whole, and has concentric concave and convex portions 27 and 27 on both end surfaces in the axial direction. Examples of the cross-sectional shape of the uneven portions 26 and 27 include a sawtooth shape as shown in FIG. 2A, a sine wave shape as shown in FIG. 2B, and a rack shape as shown in FIG. It can be adopted. In any of the shapes, the concave and convex portions 26 and 26 on the flange plate 25 and 25 side can be easily processed by pressing, turning, or the like. In any case, the pitch and height (amplitude) of the uneven portions 27 and 27 on the displacement absorbing material 24 side, and the pitch and height of the uneven portions 26 and 26 on the flange plates 25 and 25 side are used. The height (amplitude) is the same as each other. On the other hand, the phase in the radial direction of the concave and convex portions 27 and 27 on the side of the displacement absorber 24 and the phase in the same direction of the concave and convex portions 26 and 26 on the flange plates 25 and 25 are only a half pitch. It is off.

  Therefore, the concavo-convex portions 27, 27 on the displacement absorbing material 24 side and the concavo-convex portions 26, 26 on the both flange plates 25, 25 side are in close contact with each other in a concavo-convex engagement state. Further, in the case of this example, both end surfaces in the axial direction on the side of the displacement absorbing member 24 and the surfaces of the flange plates 25, 25 facing each other are bonded to each other. In order to manufacture such a structure of this example, the displacement absorbing material 24 is injection molded in a state where both the flange plates 25 and 25 are set in the cavity of the mold. Primers are applied in advance to the surfaces of the flanges 25, 25 facing each other. In this way, if the displacement absorbing member 24 is injection molded, the elastic support member 23 having a cross-sectional shape as shown in FIG. 2 can be easily manufactured.

  Such an elastic support member 23 includes concave and convex portions 27 and 27 formed on both end surfaces in the axial direction of the displacement absorbing member 24, and concave and convex portions 26 and 26 formed on opposite surfaces of the flange plates 25 and 25. Since the two are engaged with each other, a sufficient area (bonding area) of the joint surface can be secured. Further, based on the mechanical engagement between the concavo-convex portions 27 and 26, the displacement absorbing member 24 and the flange plates 25 and 25 are prevented from being relatively displaced in the radial direction. As a result, it is possible to sufficiently secure the bonding strength between the displacement absorbing member 24 and the two flange plates 25, 25, thereby improving the durability of the elastic support member 23.

[Second Example of Embodiment]
3 to 4 show a third example of an embodiment of the present invention corresponding to claims 1 and 3. In the case of this example, a plurality of through-holes 28 and 28 are respectively formed in a pair of flange plates 25a and 25a, and the flange plates 25a and 25a pass through both flange plates 25a and 25a in the axial direction. Formed at intervals. The inner diameter of each of the through holes 28, 28 is small on the surface side facing each other and large on the opposite surface side. For example, as shown in FIG. 4 (A), a mortar-shaped chamfered portion 29, 29 is formed on the opposite surface side, a large diameter portion 30 is formed as shown in (B), (C) Tilt the whole as shown in. Regardless of which shape is adopted, the protrusions 31, 31 projecting from the axially opposite end surfaces of the displacement absorbing material 24 a are allowed to enter the through holes 28, 28, respectively. And the above-mentioned through holes 28 and 28 are engaged with each other. Also in the case of manufacturing such a structure of this example, the displacement absorbing member 24a is injection-molded in a state where both the flange plates 25a and 25a are set in the cavity of the mold.

  In the case of the elastic support member 23a of this example having such a structure, the flange plates 25a and 25a and the flange plates 25a and 25a are connected to the flanges 25a and 25a based on the concavo-convex engagement between the projections 31 and 31 and the through holes 28 and 28. The displacement absorber 24a is prevented from being relatively displaced in the surface direction. Further, due to the anchor effect based on the engagement between the projections 31 and 31 and the through holes 28 and 28, the flange plates 25a and 25a and the displacement absorbing member 24a are prevented from separating in the axial direction. . As a result, in the case of the structure of this example, the bonding strength between the displacement absorbing member 24a and the flange plates 25a, 25a is more sufficiently ensured, and the durability of the elastic support member 23a is more sufficiently improved. I can plan.

[Third example of embodiment]
FIGS. 5-6 has shown the 3rd example of embodiment of this invention corresponding to Claim 1, 4. FIG. In the case of this example, by bending a plurality of circumferential positions of the pair of flange plates 25b, 25b, the through holes 28a, 28a penetrating both the flange plates 25b, 25b in the axial direction are mutually connected. Projection pieces 32 and 32 projecting in the approaching direction are formed. That is, a plurality of circumferentially equidistant portions of the flanges 25b and 25b are plastically deformed in a state where each of the flanges 25b and 25b bends the inside of a U-shaped cut having an opening in the radial direction. The protrusions 32 and 32 are formed. A part of the displacement absorbing member 24b is caused to enter the through holes 28a and 28a, and the protruding pieces 32 and 32 are bitten into the other part of the displacement absorbing member 24b. Also in the case of producing such a structure of this example, the displacement absorbing member 24b is injection-molded with both the flange plates 25b and 25b set in the cavity of the mold.

  In the case of the elastic support member 23b of this example having such a structure, the concave / convex engagement between a part of each of the displacement absorbing members 24b and the through holes 28a, 28a, and the protrusions 32, 32 are The flange plates 25b and 25b and the displacement absorbing material 24b are prevented from being relatively displaced in the surface direction based on the uneven engagement portion and the uneven engagement with the other portion of the displacement absorbing material 24b. Further, due to the anchor effect based on the engagement between the displacement absorbing member 24b and the projecting pieces 32, 32, the flange plates 25b, 25b and the displacement absorbing member 24b are prevented from separating in the axial direction. As a result, in the case of the structure of this example, the bonding strength between the displacement absorbing member 24b and the flange plates 25b and 25b is more sufficiently secured, and the durability of the elastic support member 23b is more sufficiently improved. I can plan.

[Fourth Example of Embodiment]
FIGS. 7 to 8 also show a fourth example of the embodiment of the invention corresponding to claims 1 and 4. In the case of this example, a plurality of circumferentially equidistant portions of the pair of flange plates 25c, 25c are plastically deformed in a state where each of the flange plates 25c, 25c is bent inside the H-shaped cut, and each of the through holes 28b, 28b Each protrusion 32a, 32a is formed. A part of the displacement absorbing material 24c is caused to enter the through holes 28b and 28b, and the protruding pieces 32a and 32a are bitten into the other part of the displacement absorbing material 24b. Also in the case of manufacturing such an elastic support member 23c of this example, the displacement absorbing material 24c is injection-molded with the flange plates 25c and 25c set in the cavity of the mold.

Sectional drawing and end elevation of an elastic support member showing the 1st example of an embodiment of the invention. FIG. 2B is an enlarged view of a portion of FIG. 1A showing three examples of cross-sectional shapes. Sectional drawing and end elevation of an elastic support member showing the 2nd example of an embodiment of the invention. The B part enlarged view of (A) of FIG. 3 which shows three examples of cross-sectional shape. Sectional drawing and end elevation of an elastic support member showing the 3rd example of an embodiment of the invention. FIG. 6 is an enlarged view of a section C in FIG. 5A showing a cross-sectional shape. Sectional drawing and the end elevation of an elastic support member which show the 4th example of an embodiment of the invention. FIG. 8 is an enlarged view of a portion D in FIG. 7A showing a cross-sectional shape. The partial cutaway view which shows the 1st example of the structure of the electric power steering device used as the object of this invention. The fragmentary sectional view which shows the 2nd example. Sectional drawing and end elevation of an elastic support member showing an example of a conventional structure. FIG. 12 is an enlarged view of a portion E in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Rotating shaft 3, 3a Housing 4 Worm wheel 5, 5a Worm 6 Reduction gear 7 Output shaft 8 Worm tooth 9, 9a Worm shaft 10, 10a Radial radial rolling bearing 11, 11a Radial rolling bearing 12a 12b Inner ring 13, 13a, 13b Stepped surface 14 Locking ring 15a, 15b, 15c, 15d Elastic support member 16, 16a Flange plate 17 Displacement absorber 18 Pressing piece 19 Coil spring 20 Bushing 21a, 21b Outer ring 22a, 22b Inner diameter side step Surface 23, 23a, 23b, 23c Elastic support member 24, 24a, 24b, 24c Displacement absorbing material 25, 25a, 25b, 25c Flange plate 26 Concavity and convexity 27 Concavity and convexity 28, 28a and 28b Through hole 29 Chamfered portion 30 Large diameter portion 31 Projection 32, 32a Projection

Claims (4)

  A housing that is supported by a fixed portion and does not rotate; a rotating shaft that is rotatably provided to the housing and is rotated by an operation of a steering wheel; A worm wheel that is supported concentrically with the rotary shaft inside the housing and rotates together with the rotary shaft, and a worm tooth is provided at an axially intermediate portion of the worm shaft. With the worm teeth meshed with the worm wheel, the worm supported rotatably with respect to the housing, the electric motor for rotationally driving the worm, and a portion of the worm between the housing and the housing And an elastic support member that supports the worm so that the worm can be displaced in the axial direction relative to the housing. Each is an annular shape, and a pair of flange plates arranged at intervals in the axial direction, and both axial end surfaces of the flange plates are opposed to each other. In an electric power steering apparatus provided with an annular displacement absorber made of an elastic material provided in contact with each other, both axial end surfaces of the displacement absorber and the two flange plates An electric power steering device characterized in that the surfaces facing each other are engaged in a concavo-convex manner in a direction that prevents relative displacement in the surface direction.   The electric power steering device according to claim 1, wherein concave and convex portions that engage with each other are formed on both end surfaces in the axial direction of the displacement absorbing material and surfaces of the two flange plates facing each other.   2. The electric motor according to claim 1, wherein the projections provided on a part of the displacement absorbing material are inserted into the holes formed on the surfaces of the two flange plates facing each other so that the projections and the projections are engaged with each other. Power steering device.   A hole and a convex part adjacent to the opening of the hole are formed on the surfaces of the two flange plates facing each other, and the protrusion provided on the displacement absorbing material enters the hole and is adjacent to the protrusion. The electric power steering apparatus according to claim 1, wherein the convex portion is bitten into the portion.

Images