JP5176548B2 - Electric power steering device - Google Patents

Description

  The electric power steering apparatus according to the present invention is used as a steering apparatus for an automobile, and reduces the force required for the driver to operate the steering wheel by using an electric motor as an auxiliary power source. It is. The present invention suppresses the generation of unpleasant noise called rattling noise at the spline engaging portion between the output shaft of the electric motor and the worm shaft of the speed reducer constituting such an electric power steering apparatus. It was invented with the intention of realizing such a structure.

  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 the worm speed reducer, if no measures are taken, the backlash existing in the meshing portion of the worm and the worm wheel, the distal end portion of the output shaft of the electric motor, and the proximal end portion of the worm shaft When the rotation direction of the rotating shaft is changed based on the backlash existing in the coupling portion, an unpleasant noise called a rattling noise may occur.

  As a structure that can suppress the generation of such rattling noise, conventionally, as described in Patent Document 1, it has been considered to elastically press the worm toward the worm wheel by an elastic member such as a spring. . 10 to 11 show an example of the electric power steering apparatus described in Patent Document 1 among them. A front end portion of a steering shaft 2 that is a rotating shaft that is rotated in a predetermined direction by the steering wheel 1 is rotatably supported inside the housing 3, and the worm wheel 4 is fixed to this portion. The worm teeth 5 that mesh with the worm wheel 4 are provided in the axial intermediate portion of the worm shaft 6, and both ends of the worm 8 that is rotationally driven by the electric motor 7 are paired with a pair of rolling bearings such as a single row deep groove ball bearing. 9a and 9b are rotatably supported in the housing 3. Further, a pressing piece 10 is externally fitted to a portion protruding from the rolling bearing 9 a at the tip of the worm shaft 6, and an elastic member such as a coil spring 11 is provided between the pressing piece 10 and the housing 3. Yes. The coil spring 11 presses the worm teeth 6 toward the worm wheel 4 through the pressing piece 10. That is, backlash between the worm teeth 6 and the worm wheel 4 is suppressed by swinging and moving the worm 8 with the rolling bearing 9b supporting the base end portion of the worm 8 as a fulcrum. ing. With such a configuration, generation of rattling noise based on backlash between the worm teeth 6 and the worm wheel 4 is suppressed.

  In the case of the conventional structure as described above, it is possible to suppress the occurrence of the rattling noise at the meshing portion between the worm tooth 5 and the worm wheel 4, but the tip of the output shaft 12 of the electric motor 7 and the worm The rattling noise generated at the joint with the base end of the shaft 6 cannot be suppressed. This point will be described below. A spline hole 13 is formed at the base end of the worm shaft 6 so that the tip end of the output shaft 12 of the electric motor 7 and the base end of the worm shaft 6 can be freely transmitted. 6 is formed in an open state on the base end face. A spline shaft portion 14 is formed at the tip of the output shaft 12. The spline shaft portion 14 and the spline hole 13 are spline-engaged so that the output shaft 12 and the worm shaft 6 are freely coupled to transmit torque. The “spline” in the present specification and claims includes what is called “serration” with a fine pitch.

  If the spline shaft portion 14 and the spline hole 13 are in spline engagement with no circumferential clearance (without backlash), the distal end portion of the output shaft 12 and the proximal end portion of the worm shaft 6 No rattling noise is generated at the coupling part (spline engaging part). However, in the actual case, a backlash exists in the spline engaging portion. The backlash of the spline engaging portion is necessary so that the work of spline engaging the spline shaft portion 14 and the spline hole 13 can be easily performed. Further, as the back end of the worm shaft 6 is pressed against the worm wheel 4 in order to eliminate the backlash of the meshed portion between the worm teeth 5 and the worm wheel 4, the central axis of the output shaft 12 is pushed. In order to prevent the torque required for rotating the output shaft 12 from increasing, the spline engaging portion is not distorted to the extent that the worm shaft 6 is slightly deviated from the central axis. In addition, the backlash is necessary.

  However, if there is backlash in the spline engaging portion, the male spline teeth provided on the outer peripheral surface of the spline shaft portion 14 when the electric motor 7 is started and stopped or when the rotation direction is changed. And the circumferential side surface of the female spline teeth provided on the inner circumferential surface of the spline hole 13 collide vigorously, and the rattling noise is generated. Further, such a rattling noise is also generated when the male and female spline teeth collide with each other vigorously due to an impact accompanying traveling. Regardless of the cause, the rattling noise as described above becomes more significant as the backlash of the spline engaging portion becomes larger. However, I tried to keep it as small as possible. However, if this backlash is reduced, it becomes difficult to insert the spline shaft portion 14 into the spline hole 13 accordingly, the assembling workability is lowered, and the manufacturing cost of the electric power steering apparatus is increased. Further, unless the assembly accuracy between the output shaft 12 and the worm shaft 6 is increased, the problem of the torque increase due to the galling is likely to occur, which also increases the manufacturing cost of the electric power steering apparatus. Further, in the case of the structure that eliminates the backlash of the meshing portion between the worm tooth 5 and the worm wheel 4 as described above, the backlash of the meshing portion between the two spline teeth is required to eliminate the backlash. It cannot be lost.

In view of such circumstances, hitting noise is conventionally generated at the meshing portion between the two spline teeth by sandwiching an elastic ring between the outer peripheral surface of the spline shaft portion and the inner peripheral surface of the spline hole. It is considered to prevent this. As shown in FIGS. 12 to 14, this conventional structure is caused by backlash existing in a spline engaging portion 19 between the base end portion of the worm shaft 6 and the output shaft 12 of the electric motor 7 (see FIGS. 10 to 11). An elastic ring 23 is provided between the outer peripheral surface of the spline shaft portion 14 and the inner peripheral surface of the spline hole 13 in order to suppress the rattling noise. The inner and outer peripheral edges of the elastic ring 23 are frictionally engaged with the outer peripheral surface of the spline shaft portion 14 and the inner peripheral surface of the spline hole 13, so that the torque transmission direction between the spline shaft portion 14 and the spline hole 13 is increased. The relative displacement speed is suppressed and the rattling noise is suppressed.
However, in the case of the conventional structure, with respect to the circumferential direction (torque transmission direction) of the spline engaging portion 19, the outer peripheral surface of the spline shaft portion 14 and the inner peripheral surface of the spline hole 13 and the inner and outer surfaces of the elastic ring 23. Both peripheral edges are engaged only by a simple frictional force. Moreover, since the lubricant such as grease exists in the spline engaging portion 19, the frictional force cannot be increased so much. Therefore, slip torque at the spline engaging portion 19 (torque required for sliding the friction engaging portion of the friction ring 23 to relatively displace the spline shaft portion 14 and the spline hole 13 in the rotational direction. ) Is small. Therefore, it is possible to prevent the tooth tips of the male and female spline teeth 18 and 17 from colliding with each other, but the circumferential side surfaces of these male and female spline teeth 18 and 17 collide with each other. Things cannot be prevented sufficiently. That is, it is not possible to prevent the occurrence of rattling noise based on the collision between the circumferential side surfaces.

  Further, in Patent Document 2, a rattling sound based on backlash existing in the spline engaging portion 19 between the base end portion of the worm shaft 6a and the output shaft 12a of the electric motor 7 as shown in FIGS. In order to suppress, a structure is described in which a pair of elastic rings 23c and 23d are provided between the outer peripheral surface of the spline shaft portion 14a and the inner peripheral surface of the spline hole 13a. In such a structure described in Patent Document 2, the inner peripheral edge of both elastic rings 23c and 23d and the outer peripheral surface (bottom surface of the locking groove) of the spline shaft portion 14a are not particularly accompanied by uneven engagement. Because of the simple frictional engagement, it is impossible to prevent the male spline teeth 18 and the female spline teeth 17 from colliding with each other in the circumferential direction as in the first example of the conventional structure described above. The rattling noise cannot be suppressed sufficiently.

JP 2004-306898 A JP 2004-122852 A

  In view of the above-described circumstances, the present invention has a structure that ensures a certain amount of backlash of the spline engaging portion between the spline shaft portion and the spline hole, so that rattling noise is generated in the spline engaging portion. The present invention was invented to realize an electric power steering device that can be suppressed sufficiently effectively.

The electric power steering apparatus of the present invention, like the conventionally known electric power steering apparatus, includes a housing, a rotating shaft, a worm wheel, a worm, an electric motor, a torque joint portion, And an elastic ring.
Of these, the housing is supported by a fixed part such as a vehicle body and does not rotate during steering.
The rotating shaft is rotatably provided with respect to the housing, and is rotated by an operation of a steering wheel, and gives a steering angle to the steered wheels in accordance with the rotation. As such a rotation shaft, any shaft that moves in synchronization with the steering wheel and the steering wheel can be used. For example, the input shaft (pinion shaft) of the steering shaft 2 or the intermediate shaft 15 and further the steering gear unit 16 in the structure shown in FIG.

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.
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 axial end of the worm shaft is rotatably supported by the housing by a bearing.
In the electric motor, the base end portion of the worm shaft and the front end portion of the output shaft are engaged with each other so that torque can be freely transmitted, and the worm shaft can be driven to rotate in both directions.
For this purpose, a spline hole is formed in one of the proximal end of the worm shaft and the distal end of the output shaft so as to open to the proximal end surface of the worm shaft or the distal end surface of the output shaft. doing. Further, a spline shaft portion is formed at the other end portion of the base end portion of the worm shaft and the distal end portion of the output shaft.
In addition, the torque joint portion includes a spline shaft portion provided with one end of the distal end portion of the output shaft and a proximal end portion of the worm shaft, the male spline teeth being formed on the outer peripheral surface, A spline provided with female spline teeth on the inner peripheral surface provided at the other end portion of the distal end portion of the output shaft and the base end portion of the worm shaft so as to open to the end surface of the other end portion. The hole is spline-engaged. And the said torque coupling part can freely transmit the torque from the output shaft of the said electric motor to the said worm | warm.
Further, the elastic ring is provided in an elastically compressed state in the radial direction between the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion.

In particular, in the electric power steering apparatus of the present invention, the elastic ring is installed in a portion that is axially disengaged from the spline engaging portion between the male spline teeth and the female spline teeth. In addition, the outer peripheral surface of the elastic ring on the inner peripheral surface of the spline hole and the portion of the outer peripheral surface of the spline shaft portion on which the inner peripheral edge of the elastic ring opposes respectively. forming a concave-convex portion with respect to the direction. Then, the inner and outer periphery of the elastic ring, respectively by recess-projection engaging with the both concave-convex portion.
Furthermore, an uneven portion related to the circumferential direction formed on a portion of the inner peripheral surface of the spline hole facing the outer peripheral edge of the elastic ring, and an uneven portion of the female spline teeth formed on the inner peripheral surface of the spline hole, The phase in the circumferential direction is the same. Further, an uneven portion related to the circumferential direction formed on a portion of the outer peripheral surface of the spline shaft portion facing the inner peripheral edge of the elastic ring, and an uneven portion of the male spline teeth formed on the outer peripheral surface of the spline shaft portion. The phase in the circumferential direction is the same.

  When the electric power steering apparatus of the present invention as described above is implemented, for example, as described in claim 2, the elastic ring is any of the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion. It latches in the latching ditch | groove formed over the perimeter on one peripheral surface. And the uneven | corrugated | grooved part regarding the said circumferential direction is formed in the bottom face of this latching ditch | groove.

  Further, when the electric power steering apparatus of the present invention is implemented, for example, as described in claim 3, the concave and convex portions are not formed on the inner and outer peripheral edge portions of the elastic ring in a free state. The elastic ring is elastically compressed between the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion, and the inner and outer peripheral edges of the elastic ring are elastically deformed. Both the inner and outer peripheral edge portions are engaged with the concave and convex portions formed on the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion, respectively.

  Alternatively, as described in claim 4, an elastic ring having uneven portions on both the inner and outer peripheral portions is used in a free state. Then, in a state where the elastic ring is mounted between the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion, the uneven portions formed on both the inner and outer peripheral portions of the elastic ring are respectively connected to the inner peripheral surface of the spline hole, And it engages with the uneven part formed in the outer peripheral surface of the spline shaft part.

  Further, when the electric power steering apparatus of the present invention is implemented, for example, as described in claim 5, a portion of the inner peripheral surface of the spline hole facing the outer peripheral edge of the elastic ring, and the spline shaft A protruding edge that protrudes toward the elastic ring is provided on a part of the outer peripheral surface of the portion, which is opposed to the inner peripheral edge of the elastic ring.

According to the electric power steering apparatus of the present invention having the above-described configuration, the rotation direction of the electric motor is rapidly increased with a structure that ensures a certain amount of backlash of the spline engaging portion between the spline shaft portion and the spline hole. It is possible to sufficiently suppress the rattling noise that is generated when converted into a sound.
That is, both the inner and outer peripheral edges of the elastic member and the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion are mechanically engaged not only by frictional engagement but also by both concave and convex portions. The resistance against the relative displacement between the output shaft of the electric motor and the worm shaft in the rotational direction is great. Specifically, for this relative displacement, it is necessary to elastically deform the elastic member in a direction in which the outer diameter portion and the inner diameter portion of the elastic member are shifted in the circumferential direction. For this reason, the resistance is increased to sufficiently suppress the rattling noise.
Further, by making the phase in the circumferential direction of the both concavo-convex portions and the concavo-convex portions of the female spline teeth and the male spline teeth the same, the work efficiency can be improved by simultaneously forming the both concavo-convex portions and both the spline teeth. The cost can be increased and the manufacturing cost can be reduced.

[First example of embodiment]
FIGS. 1-7 has shown the 1st example of embodiment of this invention corresponding to Claims 1-3 . The electric power steering device of this example is characterized by a spline shaft portion 14 provided at the distal end portion (right end portion in FIG. 1) of the output shaft 12 of the electric motor 7 and a proximal end portion (FIG. 1). The left end portion of ˜2) is in the joint portion with the spline hole 13 and its peripheral structure. In addition, since the structure and operation of the entire electric power steering apparatus are the same as those conventionally known, including the structures described in Patent Documents 1 and 2, the same as the conventional structure. The illustrations and explanations of the parts are omitted or simplified, and the characteristic parts of this example will be mainly described below.

The spline hole 13 is formed concentrically with the worm shaft 6 in a state where the spline hole 13 is opened at the base end surface of the worm shaft 6. Further, the spline shaft portion 14 is formed concentrically with the output shaft 12 at the distal end portion of the output shaft 12. The spline shaft portion 14 and the spline hole 13 are spline-engaged so that the output shaft 12 and the worm shaft 6 are freely coupled to transmit torque. The pitch circle diameter of each female spline tooth 17, 17 formed on the inner peripheral surface of the spline hole 13 is slightly larger than the pitch circle diameter of each male spline tooth 18, 18 formed on the outer peripheral surface of the spline shaft portion 14. Thus, the spline shaft portion 14 can be loosely inserted into the spline hole 13. Accordingly, the spline engaging portion 19 between the spline shaft portion 14 and the spline hole 13 has a tip portion of the worm shaft 6 (FIG. 1) in order to eliminate backlash of the meshing portion between the worm tooth 5 and the worm wheel 4. There is sufficient backlash to displace the right end of the worm wheel 4 toward the worm wheel 4. In other words, in accordance with the elimination of the backlash at the meshing portion between the worm tooth 5 and the worm wheel 4, inconveniences such as galling are less likely to occur in the spline engagement portion 19.

As described above, a portion that is loosely spline-engaged between the inner peripheral surface of the spline hole 13 and the outer peripheral surface of the spline shaft portion 14 is axially disengaged from the spline engagement portion, such as an O-ring. An annular elastic ring 23 is provided. The elastic ring 23 is formed of an elastic material such as an elastomer such as rubber. Further, in order to make it possible to assemble such an elastic ring 23, the outer peripheral surface of the spline shaft portion 14 is positioned at a position (in the left side in FIGS. The inner diameter side locking groove 20 is formed over the entire circumference. A plurality of concave portions 21 and 21 are formed on the bottom surface of the inner diameter side engaging concave groove 20, and concave and convex portions in the circumferential direction are provided on the bottom surface. The groove bottom diameter of the inner diameter side engaging concave groove 20 is slightly larger than the inner diameter of the elastic ring 23 in the free state. The spline hole 13 is located on the inner peripheral surface of the spline hole 17 and 17 so as to be axially disengaged from the female spline teeth 17, 17. A locking groove 22 is formed. A plurality of recesses 25 are formed on the bottom surface of the outer diameter side locking recess groove 22, and uneven portions in the circumferential direction are provided on the bottom surface. Further, the groove bottom diameter of the outer diameter side locking concave groove 22 is slightly smaller than the outer diameter of the elastic ring 23 in the free state. The elastic ring 23 is locked so as to span the outer diameter side locking groove 22 and the inner diameter side locking groove 20.

  In this state, the elastic ring 23 is elastically compressed in the radial direction between the bottom surfaces of both the inner diameter side and outer diameter side locking grooves 20 and 22. And a part of elastic material which comprises the said elastic ring 23 enters in said each recessed part 21 and 25, as shown to FIGS. In this state, the inner and outer peripheral edges of the elastic ring 23 and the bottom surfaces of the locking grooves 20 and 22 are mechanically unevenly engaged as well as frictionally engaged. Therefore, both the inner and outer peripheral edges of the elastic ring 23 are engaged with the bottom surfaces of the locking grooves 20 and 22 in a state in which they are difficult to move in the circumferential direction. For this reason, when the circumferential direction side surfaces of the male and female spline teeth 18 and 17 tend to collide with each other with the rotation direction change of the electric motor 7, the elastic ring 23 is in contact with the collision. This is a large resistance against the force to be attempted (the force with which the output shaft 12 and the worm shaft 6 are relatively displaced in the torque transmission direction) (provides a buffering effect). That is, even if the circumferential side surfaces of the male and female spline teeth 17 and 18 tend to collide with each other with vigor, the elastic ring 23 attenuates the momentum and can suppress the collision. In short, the circumferential direction of each male spline tooth 18, 18 formed on the outer peripheral surface of the spline shaft portion 14 as the electric motor 7 is started, stopped, rotational direction changed, oscillating displacement of the worm shaft 6, etc. Even when the side surface and the circumferential side surface of each female spline tooth 17, 17 formed on the inner peripheral surface of the spline hole 13 tend to collide vigorously, the elastic ring 23 attenuates this momentum, Reduce collisions. As a result, the spline engagement portion 19 can sufficiently suppress the occurrence of rattling noise.

  Further, as described above, in this example, the inner and outer diameter side locking grooves 20 and 22 are provided with concave and convex portions made of concave portions 21 and 25, respectively. The concavo-convex portion composed of the concave portions 21 and 25 is concentric with the male and female spline teeth 18 and 17 and is positioned axially away from the male and female spline teeth 18 and 17 (FIGS. 2 on the left). Therefore, when forming the recesses 21 and 25, the male and female spline teeth 18 and 17 can be processed simultaneously with rolling, forging, broaching, and the like. In that case, the recessed parts 21 and 21 provided in the bottom face of the said inner diameter side latching ditch | groove 20 and the tooth bottom part of the said male spline shaft part 14 become the same shape and the same phase (FIGS. 3-5). Moreover, the recessed parts 25 and 25 provided in the bottom face of the said outer diameter side latching ditch | groove 22, and the tooth bottom part of the said spline hole 13 become the same shape and the same phase (FIGS. 3-5). In this way, by simultaneously molding the concave portions 21 and 25 and the male and female spline teeth 18 and 17, the working efficiency is increased and the manufacturing cost can be reduced.

  Further, as shown in FIG. 7, the elastic ring 23 a may be provided with gear-shaped uneven portions 26 a and 26 a having a fine pitch on the inner and outer peripheral surfaces of the elastic ring 23. If such an elastic ring 23a is used, the resistance against the force that is relatively displaced in the rotational direction of the engaging portion between the inner and outer peripheral edges of the elastic ring 23a and the bottom surfaces of the locking grooves 20 and 22 is used. Can be made larger. When the male and female spline teeth 18 and 17 tend to collide with each other in the circumferential direction, the effect of preventing rattling noise can be further improved.

[Second Example of Embodiment]
FIG. 8 shows a second example of an embodiment of the present invention corresponding to claims 1 to 2 and 4. In the case of this example, as the elastic ring 23b, the concave portions 21 and 25 for forming the concave and convex portions respectively formed on the inner and outer peripheral surfaces of the inner diameter side and outer diameter side locking concave grooves 20 and 22 respectively. A thing provided with the convex parts 28 and 28 of the shape which can be engaged with each of these concave parts 21 and 25 at the phase which corresponds (refer FIGS. 3-4) is used. That is, the cross-sectional shape regarding the virtual plane orthogonal to the central axis of the intermediate portion in the axial direction of the elastic ring 23b is the bottom surface of both the inner diameter side and outer diameter side locking grooves 20, 22, and both the locking grooves 20 , 22 is substantially the same as the cross-sectional shape in the same direction of the space formed between the recesses 21, 25 formed on the bottom surface of. However, the groove bottom diameter of the inner diameter side locking concave groove 20 is slightly larger than the inner diameter of the elastic ring 23b in the free state, and the groove bottom diameter of the outer diameter side locking concave groove 22 is larger. Is slightly smaller than the outer diameter of the elastic ring 23b in the free state. For this reason, the elastic ring 23b is elastically compressed in the radial direction between the bottom surfaces of the inner diameter side and outer diameter side locking grooves 20 and 22 in which the recesses 21 and 25 are formed. . Further, in this state, the convex portion 28 provided in the elastic ring 23b and the concave portions 21 and 25 formed in the inner diameter side and outer diameter side engaging concave grooves 20 and 22 are engaged with each other in a concave and convex manner. For this reason, when the male and female spline teeth 18 and 17 tend to collide with each other in the circumferential direction, the resistance of the elastic ring 23b to the circumferential direction is increased. Become. The structure and operation of the other parts are the same as the structure shown in the first example.

[Third example of embodiment]
FIG. 9 shows a third example of an embodiment of the present invention corresponding to claims 1, 2, 4, and 5. In the case of this example, it protrudes toward the elastic ring 23b at the opening edge of each recess 21 and 25 provided to form an uneven portion in both the inner diameter side and outer diameter side locking grooves 20 and 22. Projecting edges 27 are formed. These protruding edges 27 and 27 are elastically cut into both the inner and outer peripheral edges of the elastic ring 23b. In this way, since each of the projecting edges 27 and 27 is elastically bited into the inner and outer peripheral edges of the elastic ring 23b, the worm shaft 6 and the output shaft 12 The resistance against relative displacement in the torque transmission direction can be increased and ensured appropriately. The structure and operation of the other parts are the same as the structure shown in the second example.
In addition, although illustration is abbreviate | omitted, it replaces with a recessed part and forms a convex part in the bottom face of both inner diameter side and the outer diameter side latching ditch | grooves 20 and 22, and this convex part bites into both the inner and outer peripheral edge parts of an elastic ring. You can also do things. In this case, it is preferable to match the phase in the circumferential direction with the crests of both male and female spline teeth.
Contrary to the illustrated example, a spline hole can be provided on the output shaft side, and a spline shaft portion can be provided on the worm shaft side.

The figure equivalent to the expanded EE cross section of FIG. 10 which shows the 1st example of embodiment of this invention. The A section enlarged view of FIG. The expanded BB sectional drawing of FIG. The C section enlarged view of FIG. The expanded DD sectional view of FIG. The elastic ring assembled | attached to the structure of the 1st example of embodiment of this invention is shown, (a) is the figure seen from the axial direction, (b) was seen from the side of (a) in the state cut | disconnected partially. Figure. The figure similar to FIG. 6 which shows the other example of the elastic ring similarly assembled | attached to the structure of a 1st example. The figure similar to FIG. 6 which shows the elastic ring similarly assembled | attached to the structure of a 2nd example. The figure similar to FIG. 4 which shows the 3rd example of embodiment of this invention. The partial cutting side view which shows the 1st example of a prior art structure. The expanded EE sectional view of FIG. The fragmentary sectional view equivalent to the center part of FIG. 11 which shows the 2nd example of a prior art structure. The expanded FF sectional view of FIG. The G section enlarged view of FIG. The figure equivalent to the right half part of FIG. 11 which shows the 3rd example of a prior art structure. The figure which took out and expanded the spline shaft part and elastic ring which exist in the left part of FIG. FIG. 16 is an enlarged HH sectional view of FIG. 15.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Housing 4 Worm wheel 5 Worm tooth | gear 6, 6a Worm shaft 7 Electric motor 8 Worm 9a, 9b Rolling bearing 10 Pressing piece 11 Coil spring 12, 12a Output shaft 13, 13a Spline hole 14, 14a Spline shaft Part 15 Intermediate shaft 16 Steering gear unit 17 Female spline teeth 18 Male spline teeth 19 Spline engaging part 20 Inner diameter side engaging groove 21 Recess 22 Outer diameter side engaging groove 23, 23a, 23b, 23c, 23d Elastic ring 24 Torque joint 25 Recess
26a Concavity and convexity 27 Projection edge 28 Convex

Claims (5)

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. In a state where the worm teeth are engaged with the worm wheel, the worm shaft is rotatably supported with respect to the housing by a bearing at the axial end of the worm shaft, and the output shaft is rotated to drive the worm. An electric motor arranged concentrically with the worm, and provided between the tip end of these output shafts and the base end of the worm, from this output shaft to this worm A torque coupling portion that allows torque transmission freely, and the torque coupling portion is provided on an outer peripheral surface provided at one end of the distal end portion of the output shaft and the proximal end portion of the worm shaft. Provided at the other end of the spline shaft portion forming the male spline teeth, the distal end portion of the output shaft, and the proximal end portion of the worm shaft so as to open to the end surface of the other end portion. A spline hole in which female spline teeth are formed on the inner peripheral surface is spline-engaged, and an elastic ring is provided between the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion. In the electric power steering apparatus provided in an elastically compressed state between the surfaces, the elastic ring is disengaged in the axial direction from the spline engaging portion between the male spline teeth and the female spline teeth. Installed in the part Portion outer periphery of the elastic ring faces among the inner peripheral surface of the spline hole and the portion where the inner periphery of the elastic ring of the outer circumferential surface of the spline shaft portion is opposed, for each circumferential uneven portion is formed, the inner and outer periphery of the elastic ring, which is engaged both these uneven portions and uneven engagement respectively, in a portion outer periphery of the elastic ring of the inner peripheral surface of the spline hole faces The inner circumferential edge of the elastic ring is the phase in the circumferential direction between the formed uneven portion and the uneven portion of the female spline teeth formed on the inner peripheral surface of the spline hole, and the outer peripheral surface of the spline shaft portion. The electric power steering apparatus characterized in that the uneven portions formed on the opposing portions and the uneven portions of the male spline teeth formed on the outer peripheral surface of the spline shaft portion are in phase with each other. .   The elastic ring is locked in a locking groove formed over the entire circumference on one of the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion. The electric power steering apparatus according to claim 1, wherein an uneven portion in the circumferential direction is formed on a bottom surface of the concave groove.   The elastic ring is elastically compressed between the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion without forming irregularities on the inner and outer peripheral edges of the elastic ring in a free state. With the inner and outer peripheral edges elastically deformed, the inner and outer peripheral edges of the elastic ring are engaged with the concave and convex portions formed on the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion, respectively. Item 3. The electric power steering apparatus according to any one of Items 1 and 2.   Using an elastic ring with irregularities on the inner and outer peripheral edges in a free state, and mounting this elastic ring between the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft, The concavo-convex portions formed on both peripheral portions are concavo-convexly engaged with the concavo-convex portions formed on the inner peripheral surface of the spline hole and the outer peripheral surface of the spline shaft portion, respectively. The described electric power steering device.   A portion of the inner peripheral surface of the spline hole facing the outer peripheral edge of the elastic ring and a portion of the outer peripheral surface of the spline shaft portion facing the inner peripheral edge of the elastic ring are directed toward the elastic ring. The electric power steering device according to any one of claims 1 to 4, wherein a protruding edge is provided.

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