JP5882065B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an improved technique for an electric power steering apparatus.

  An electric power steering device mounted on a vehicle is a mechanism in which drive torque generated by an electric motor is added to steering torque via a worm gear mechanism.

  The worm gear mechanism includes a worm formed integrally with a worm shaft connected to a motor shaft of an electric motor, and a worm wheel that meshes with and follows the worm. When connecting a worm shaft to a motor shaft, it is known to use a shaft coupling (see, for example, Patent Document 1 (FIGS. 1 and 4)).

  In a worm gear mechanism of an electric power steering apparatus as disclosed in Patent Document 1, a worm shaft is connected to a motor shaft via a star rubber shaft joint. The shaft coupling includes a first member attached to the tip of the motor shaft, a second member attached to the tip of the worm shaft, and a rubber elastic member into which these first and second members are fitted. The elastic member has a substantially cross shape.

  By the way, depending on the worm gear mechanism, the worm shaft may be biased toward the worm wheel. This is because the backlash provided between the worm and the worm wheel of the worm gear mechanism can be removed by urging. More specifically, the bearing supporting the worm shaft is biased toward the worm wheel by a spring at the end of the worm shaft opposite to the worm shaft connected to the motor shaft.

  On the other hand, the end of the worm shaft on the motor shaft side tends to be displaced in a direction away from the worm wheel with a motor-side bearing (for example, a self-aligning bearing) as a fulcrum. At this time, if the elastic force of the elastic member of the shaft coupling is excessively high, the end of the motor shaft cannot be displaced sufficiently. If the end on the motor shaft side cannot be displaced sufficiently, the worm shaft cannot be sufficiently pressed against the worm wheel. Due to the inability to press, backlash cannot be removed sufficiently.

Japanese Patent No. 4007159

  An object of the present invention is to provide an electric power steering apparatus equipped with a shaft coupling having appropriate elasticity.

According to the first aspect of the present invention, a worm shaft of a worm gear mechanism including a worm and a worm wheel provided on a worm shaft is connected to a motor shaft of an electric motor via a shaft coupling, and a drive torque generated by the electric motor is generated. In the electric power steering device that is added to the steering torque via the worm gear mechanism, the shaft coupling is provided on the motor shaft of the electric motor, the first member having a plurality of convex portions extending in the axial direction, and the tip of the worm shaft. A second member having a plurality of protrusions extending in the axial direction, and an elastic member for transmitting torque provided between the protrusions of the first member and the protrusions of the second member in the circumferential direction. The protrusion of the first member is formed with a protrusion protruding toward the elastic member at the end on the worm shaft side from the facing surface facing the elastic member. , In contact with the elastic member, the projecting portion of the first member, to the surface facing the elastic member exhibits a stepped shape, or, among the convex portions of the second member, the surface facing the elastic member A protrusion that protrudes toward the elastic member is formed at the end on the worm shaft side, the protrusion contacts the elastic member, and the protrusion of the second member faces the opposing surface that faces the elastic member. , characterized by coloration a step shape.

According to a second aspect of the present invention, the worm shaft of a worm gear mechanism comprising a worm and a worm wheel provided on the worm shaft is connected to the motor shaft of the electric motor via a shaft coupling, and the drive torque generated by the electric motor In the electric power steering apparatus in which is added to the steering torque via the worm gear mechanism, the shaft coupling is provided on the motor shaft of the electric motor, the first member having a plurality of convex portions extending in the axial direction, and the tip of the worm shaft A second member having a plurality of convex portions extending in the axial direction, and an elastic member that is provided between the convex portions of the first member and the second member in the circumferential direction and transmits torque. And a protrusion that protrudes toward the elastic member at the end on the worm shaft side is formed from the opposing surface that faces the elastic member among the protrusions of the first member. Part is in contact with the elastic member, the projecting portion of the first member is constituted by an inclined surface inclined toward the elastic member from the opposite surface facing the elastic member, or, among the convex portions of the second member, resilient A projecting portion projecting toward the elastic member is formed at the end on the worm shaft side from the facing surface facing the member, the projecting portion contacts the elastic member, and the projecting portion of the second member is formed on the elastic member. It is comprised by the inclined surface inclined toward the elastic member from the opposing surface which opposes, It is characterized by the above-mentioned.

According to a third aspect of the present invention, a concave portion that absorbs deformation when the elastic member is deformed is formed at the end on the worm shaft side of the convex portion of the second member.

In the invention which concerns on Claim 1 and 2 , the protrusion part which protrudes toward an elastic member is formed in the edge part by the side of a worm shaft from the opposing surface which opposes an elastic member among the convex parts of a 1st or 2nd member. The protruding portion comes into contact with the elastic member. That is, the motor shaft side of the convex portion where the protruding portion is formed among the opposing surfaces of the convex portion of the first or second member is not brought into contact with the elastic member. By not contacting the motor shaft side, the end of the worm shaft on the motor shaft side can be easily displaced. Since the end of the motor shaft can be easily displaced, the backlash between the worm and the worm wheel is effectively achieved by urging the end opposite to the motor shaft toward the worm wheel. Can be removed.

  On the other hand, when a large torque is applied from the motor shaft, the first member is pressed toward the elastic member with a strong force. When the first member is pressed by a large force, the elastic member is elastically deformed. When the elastic member is elastically deformed, a portion other than the protruding portion of the opposing surface of the convex portion of the first or second member also contacts the elastic member. Since the part other than the projecting part comes into contact with the elastic member and the contact area increases, the torque of the motor shaft can be transmitted to the second member and the worm shaft more reliably, so that the torque can be transmitted with high torsional rigidity. it can.

In particular, in the invention according to claim 1 , the protrusion has a step shape. By adjusting the height of the step, it is possible to adjust the magnitude of torque required to bend the elastic member. A simple means of adjusting the height of the step can advantageously adjust the amount of torque required to bend the elastic member.

In particular, in the invention according to claim 2 , the projecting portion has a shape inclined toward the elastic member. Due to the inclined shape, the magnitude of torque required to bend the elastic member can be set in stages. A simple means of adjusting the tilt angle allows the required torque magnitude to be set, and the necessary torque magnitude to be set in stages, thereby providing the torque required for a more appropriate value. Can be set.

In the invention which concerns on Claim 3 , a part of elastic member escapes to a recessed part by elastically deforming. By setting it as the structure which escapes to a recessed part, an elastic member can be made easier to deform | transform. The elastic member is easily deformed when the second member is displaced. In the present invention in which the second member is desired to be easily displaced, it is effective to form the recess.

1 is a schematic diagram of an electric power steering apparatus according to the present invention. It is a whole block diagram of the electric power steering apparatus shown by FIG. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is a disassembled perspective view of the shaft coupling which concerns on Example 1 shown by FIG. FIG. 6 is an enlarged view of 6 parts in FIG. 5. It is a perspective view of the shaft coupling which concerns on Example 1 shown by FIG. FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 7. FIG. 8 is an enlarged view of 9 parts in FIG. 7. It is a figure explaining the effect | action of the shaft coupling which concerns on Example 1. FIG. It is the 11-11 line sectional view of Drawing 4. It is a figure explaining the shaft coupling which concerns on Example 2. FIG. It is a figure explaining the shaft coupling which concerns on Example 3. FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  An electric power steering apparatus according to a first embodiment will be described with reference to the drawings.

  As shown in FIG. 1, the electric power steering apparatus 10 includes a steering system 20 that extends from a steering wheel 21 of a vehicle to steering wheels 29 and 29 (for example, front wheels) of the vehicle, and an auxiliary torque that applies an auxiliary torque to the steering system 20. Mechanism 40.

  The steering system 20 is connected to a steering wheel 21 via a steering shaft 22 and universal shaft joints 23, 23, and a pinion shaft 24 is connected to the pinion shaft 24 via a rack and pinion mechanism 25. The left and right steering wheels 29, 29 are connected to both ends of 26 through left and right tie rods 27, 27 and knuckle 28, 28.

  The rack and pinion mechanism 25 includes a pinion 31 formed on the pinion shaft 24 and a rack 32 formed on the rack shaft 26.

  According to the steering system 20, when the driver steers the steering wheel 21, the left and right steering wheels 29 and 29 are steered by the steering torque via the rack and pinion mechanism 25 and the left and right tie rods 27 and 27. Can do.

  The auxiliary torque mechanism 40 detects the steering torque of the steering system 20 applied to the steering wheel 21 with the steering torque sensor 41, and generates a control signal with the control unit 42 based on the torque detection signal of the steering torque sensor 41. An auxiliary torque corresponding to the steering torque is generated by the electric motor (electric motor) 43 based on the signal, and this auxiliary torque is transmitted to the pinion shaft 24 via the worm gear mechanism 44, and the auxiliary torque is further transmitted from the pinion shaft 24 to the steering system 20. This is a mechanism for transmitting to the rack and pinion mechanism 25.

  The steering torque sensor 41 detects the torque applied to the pinion shaft 24 and outputs it as a torque detection signal, and is constituted by, for example, a magnetostrictive torque sensor or a torsion bar torque sensor.

  According to the electric power steering apparatus 10, the steering wheels 29 and 29 can be steered by the rack shaft 26 by a combined torque obtained by adding the auxiliary torque of the electric motor 43 to the steering torque of the driver.

  As shown in FIG. 2, the housing 51 extends in the vehicle width direction (left-right direction in the figure), and accommodates the rack shaft 26 so as to be slidable in the axial direction. The rack shaft 26 is connected to tie rods 27, 27 via ball joints 52, 52 at both longitudinal ends protruding from the housing 51.

  As shown in FIG. 3, the electric power steering apparatus 10 houses the pinion shaft 24, the rack and pinion mechanism 25, the steering torque sensor 41, and the worm gear mechanism 44 in the housing 51, and the upper opening of the housing 51 is formed in the upper cover portion 53. It was closed with. The steering torque sensor 41 is attached to the upper cover portion 53.

  The housing 51 has an upper portion 24u, a longitudinal center portion 24m, and a lower end portion 24d of the pinion shaft 24 extending vertically through three bearings (a first bearing 55, a second bearing 56, and a third bearing 57 in order from top to bottom). Further, the electric motor 43 is attached and a rack guide 60 is provided. Roller bearings are used for the three bearings 55 to 57.

  The rack guide 60 is rack pressing means that includes a guide portion 61 that contacts the rack shaft 26 from the side opposite to the rack 32 and an adjustment bolt 63 that presses the guide portion 61 via a compression spring 62.

  As shown in FIG. 4, the electric motor 43 is attached to the side surface of the housing 51 and includes a lateral motor shaft (output shaft) 43 a. The motor shaft 43 a extends into the housing 51 and is connected to the worm shaft 46 by a shaft coupling 45. The housing 51 supports both end portions 46a and 46b of the worm shaft 46 via bearings 47 and 48 so as to be rotatable and to restrict movement in the axial direction. The two bearings 47 and 48 are both rolling bearings.

  A female screw hole 51 a is formed in the housing 51 toward the bearing 48. The female screw hole 51a is a hole whose surface is cut into a female screw shape. The female screw hole 51a is closed when the male screw cover 66 is screwed together. The male screw lid 66 is a hollow lid-like member having a male screw cut on the outer periphery. A spring 67 is accommodated in the male screw cover 66. One end of the spring 67 is in contact with the male screw lid 67 and the other end is in contact with the bearing 48.

  The bearing 48 is biased toward the worm wheel 80 by a spring 67. By urging the bearing 48, the worm shaft 46 is also urged toward the worm wheel 80. That is, a spring (biasing means) 67 for urging the worm shaft 46 toward the worm wheel 80 is provided at the end 46b of the worm shaft 46 on the opposite side to the motor shaft 43a.

  In addition, the bearing 48 is accommodated in a bearing accommodating portion 51b formed in the housing 51 (see FIG. 11). The bearing housing 51b has an elliptical shape having a long diameter in the direction of the worm wheel 80.

  The worm shaft 46 is biased toward the worm wheel 80 by a spring 67 via a bearing 48. By pressing the worm shaft 46 toward the worm wheel 80, the backlash generated between the worm 70 and the wheel 80 is removed. By removing the backlash, the rattling noise can be reduced and the steering feeling of the occupant can be improved.

  The worm gear mechanism 44 is an auxiliary torque transmission mechanism that transmits auxiliary torque generated by the electric motor 43 to the pinion shaft 24, that is, a booster mechanism. More specifically, the worm gear mechanism 44 includes a worm 70 and a worm wheel 80 that meshes with the worm 70. The worm wheel 80 is hereinafter abbreviated as “wheel 80”. The center line CL of the wheel 80 is disposed substantially perpendicular to the center line WL of the worm 70. The center line CL of the wheel 80 is also the center line CL of the pinion shaft 24.

The worm 70 is a metal product integrally formed with the worm shaft 46, for example, a steel product such as a carbon steel material for machine structure (JIS-G-4051). The wheel 80 is a resin product such as a nylon resin as a whole or at least a portion of the teeth 81. Since the resin product wheel 80 is meshed with the metal product worm 70, meshing can be made relatively smooth and noise can be further reduced.
Details of the shaft coupling 45 will be described in the following figures.

  As shown in FIG. 5, the shaft coupling 45 includes a first steel member 90 fitted to the motor shaft 43a, a second steel member 100 fitted to the worm shaft 46, and the first of these. It consists of the elastic member 110 with which the 1 member 90 and the 2nd member 100 are fitted. The elastic member 110 can be made of an elastic material such as rubber or soft resin.

  The first member 90 includes a columnar fitting portion 91 that is fitted to the motor shaft 43 a, a disk-like base portion 92 that is integrally formed at the tip of the fitting portion 91, and an elastic member that is elastic from the base portion 92. It is composed of a convex portion 93 having a triangular shape in cross section extending toward the member 110. Four protrusions 93 extend from the base 92.

  The second member 100 includes a cylindrical fitting portion 101 into which the worm shaft 46 is fitted, a donut-shaped support plate 102 that is widened in the circumferential direction from the tip of the fitting portion 101, and elastic from the support plate 102. It consists of four convex portions 103 extending toward the member 110.

  The elastic member 110 has a round hole 111 passing through the center thereof, and eight leg portions 112 having a substantially rectangular shape in cross section extend from the center of the round hole 111 toward the outer periphery. A substantially V-shaped gap 113 is opened between the leg 112 and the leg 112. These gaps 113 are also formed at eight places.

The convex portion 93 of the first member 90 can be inserted into the gap 113 of the elastic member 110 as indicated by the arrow (1). A side surface of the convex portion 93 of the first member 90 is a facing surface 93 a that faces the gap 113 of the elastic member 110. The same applies to the convex portion 103 of the second member 100. That is, the convex portion 103 of the second member 100 can be inserted into the gap 113 of the elastic member 110 as indicated by the arrow (2). The side surface of the convex portion 103 of the second member 100 is a facing surface 103 a that faces the gap 113 of the elastic member 110.
Details of the convex portion 103 of the second member 100 will be described with reference to the following drawings.

As shown in FIG. 6, in the second member 100, a substantially arc-shaped concave portion 105 is formed at a corner where the convex portion 103 is raised from the support plate 102. Further, the protruding portion 106 protrudes from the facing surface 103 a of the second member 100 toward the circumferential direction of the second member 100. The protrusion 106 is formed continuously with respect to the recess 105 and is formed over the entire width direction of the facing surface 103a.
Details of the assembled shaft coupling will be described in the following figures.

  As shown in FIG. 7, the first member 90 is fitted into the elastic member 110. The second member 100 is fitted into the elastic member 110 so as to sandwich the elastic member 110 in the axial direction with the first member 90. When the shaft coupling 45 is viewed from the circumferential direction, the leg portion 112 of the elastic member 110, the convex portion 93 of the first member 90, the leg portion 112 of the elastic member 110, and the convex portion 103 of the second member 100 are repeatedly arranged in this order. Has been.

  As shown in FIG. 8, the elastic member 110 has eight leg portions 112 formed at equal intervals in the circumferential direction. As for the 1st member 90 inserted by this elastic member 110, the four convex parts 93 are formed in the circumferential direction at equal intervals. Similarly, in the second member 100, four convex portions 103 are formed at equal intervals in the circumferential direction.

  Of the convex portion 93 of the first member 90, the entire opposing surface 93 a that opposes the leg portion 112 of the elastic member 110 is in contact with the elastic member 110. On the other hand, only the protruding portion 106 is in contact with the leg portion 112 on the facing surface 103 a of the second member 100.

  As shown in FIG. 9, the base 92 of the first member 90 and the support plate 102 of the second member 100 are in contact with the end surface of the elastic member 110 in the axial direction. The tip surface 103b of the convex portion 103 faces the base portion 92 with a distance δ1. Similarly, the front end surface of the convex portion of the first member 90 faces the support plate 102 of the second member 100 at a predetermined distance. That is, the first member 90 and the second member 100 do not contact each other.

  The protruding portion 106 includes a first tapered portion 106a extending in an inclined manner from the general surface 103aa of the facing surface 103a, a contact surface 106b extending from the first tapered portion 106a and always contacting the elastic member 110, and the contact surface 106b. The second taper portion 106c is formed to be inclined from the surface 106b and integrally connected to the concave portion 105. The protrusion 106 protrudes from the general surface 103aa of the facing surface 103a by a height h.

  Of the convex portion 103 of the second member 100, a protruding portion that protrudes toward the elastic member 110 at the end (left side in the drawing) on the worm shaft (FIG. 7, reference numeral 46) side from the facing surface 103a facing the elastic member 110. 106 is formed, and the protruding portion 106 contacts the elastic member 110. That is, the end portion (right side in the drawing) on the motor shaft (see FIG. 7, 43 a) side of the facing surface 103 a of the convex portion 103 of the second member 100 is not brought into contact with the elastic member 110. By not contacting the end of the motor shaft, the end of the worm shaft 46 on the motor shaft can be easily displaced. Since the end on the motor shaft 43a side can be easily displaced, the end on the opposite side of the motor shaft is urged toward the wheel (FIG. 4, reference numeral 80), so that the worm (FIG. 4, reference numeral 70) and the wheel between the wheels can be effectively removed.

  In addition, the front end surface 103 b of the convex portion 103 is provided away from the first member 90 by a predetermined distance. By separating the first member 90 from the first member 90 by a predetermined distance, contact between the first member 90 and the second member 100 can be prevented, and displacement of the second member 100 can be allowed more. In the present invention in which the second member 100 is easily displaced and the backlash between the worm and the wheel is effectively removed, the tip surface 103b of the convex portion 103 is provided away from the first member 90 by a predetermined distance. Very important.

  As shown in FIG. 10A, in a state before the torque is transmitted from the first member, the general surface 103aa of the facing surface 103a and the elastic member 110 are kept in a state separated by a distance h. From this state, the elastic member 110 is pressed toward the second member 100 by applying torque generated by the motor (FIG. 4, reference numeral 43).

  As shown in FIG. 10B, when the elastic member 110 is pressed against the second member 100, the elastic member 110 is slightly elastically deformed. By elastically deforming, the elastic member 110 comes into contact with the first tapered portion 106 a of the protruding portion 106. The step-shaped protruding portion 106 is connected to the general surface 103aa via the first tapered portion 106a. By forming the inclined first tapered portion 106a, the contact area between the elastic member 110 and the second member 100 can be increased. Torque generated by the motor can be transmitted to the second member 100 more reliably.

Further, a part of the elastic member 110 is elastically deformed so that a part thereof escapes to the recess 105. By setting it as the structure which escapes to a recessed part, the elastic member 110 can be made easier to deform | transform. The elastic member 110 is easily deformed when the second member 100 is displaced. In the present invention in which the second member 100 is desired to be easily displaced, it is effective to form the recess 105.
Although it is difficult to elastically deform, the concave portion 105 may not be provided.

  As shown in FIG. 10C, the elastic member 110 is further deformed by applying more torque. Further, the deformed elastic member 110 is in contact with the entire facing surface 103 a of the second member 100.

  When a large torque is applied from the motor shaft (FIG. 4, reference numeral 43a), the first member (FIG. 7, reference numeral 90) is pressed toward the elastic member 110 with a strong force. When the first member is pressed by a large force, the elastic member 110 is elastically deformed. When the elastic member 110 is elastically deformed, portions of the opposing surface 103 a of the convex portion 103 of the second member 100 other than the projecting portion 106 also contact the elastic member 110. A portion other than the protruding portion 106 comes into contact with the elastic member 110, and the contact area increases, whereby the torque of the motor shaft can be more reliably transmitted to the second member 100 and the worm shaft (FIG. 4, reference numeral 46).

In addition, the protrusion 106 exhibits a step shape. By adjusting the height of the step (see FIGS. 10A and 10H), the magnitude of the torque required to bend the elastic member 110 can be adjusted. A simple means of adjusting the height of the step can advantageously adjust the magnitude of torque required to bend the elastic member 110.
Another embodiment of the present invention will be described in the following figures.

Next, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 12 shows a shaft coupling according to the second embodiment, corresponding to FIG.
As shown in FIG. 12, the shaft coupling 120 extends from the facing surface 133 a facing the elastic member 110 to the elastic member 110 at the end on the worm shaft side (left side in the drawing) of the convex portion 133 of the first member 130. A protruding portion 136 that protrudes toward the surface is formed, and the protruding portion 136 is in contact with the elastic member 110. The tip surface 133 b of the convex portion 133 is separated from the second member 100 by δ2.

  The effect of the present invention can also be obtained in the shaft coupling 120 according to the second embodiment formed as described above.

Next, Embodiment 3 of the present invention will be described with reference to the drawings.
FIG. 13 shows a shaft coupling according to the third embodiment, corresponding to FIG.
As shown in FIG. 13, the shaft coupling 140 has a shape in which the protruding portion 156 of the second member 150 is inclined toward the elastic member 110.

  The effect of the present invention can also be obtained in the shaft coupling 140 according to the third embodiment formed as described above.

  In addition, since the protruding portion 156 has an inclined shape, the magnitude of torque required to bend the elastic member 110 can be set in a stepwise manner. A simple means of adjusting the tilt angle allows the required torque magnitude to be set, and the necessary torque magnitude to be set in stages, thereby providing the torque required for a more appropriate value. Can be set.

In addition, although the shaft coupling according to the present invention has been described as an example in which the protruding portion is formed on either the first member or the second member, the protruding portion is provided on both the first member and the second member. It may be formed. That is, the present invention is not limited to the case where the protruding portion is formed on either the first member or the second member.
Moreover, when forming a protrusion part in both the 1st member and the 2nd member, the shape which made the protrusion part of the 1st member into a step shape, for example, and inclined the protrusion part of the 2nd member toward the elastic member It is also possible. That is, the step shape and the shape inclined toward the elastic member can be applied in combination.

  The electric power steering device of the present invention is suitable for use in passenger cars.

  DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 43 ... Electric motor, 43a ... Motor shaft, 44 ... Worm gear mechanism, 45, 120, 140 ... Shaft coupling, 46 ... Worm shaft, 70 ... Worm, 80 ... Worm wheel, 90, 130th 1 member, 93, 133 ... convex portion of the first member, 100, 150 ... second member, 103 ... convex portion of the second member, 106, 136, 156 ... projecting portion, 110 ... elastic member.

Claims (3)

The worm shaft of the worm gear mechanism composed of a worm and a worm wheel provided on the worm shaft is connected to the motor shaft of the electric motor via a shaft coupling,
In the electric power steering device in which the drive torque generated by the electric motor is added to the steering torque via the worm gear mechanism,
The shaft coupling is
A first member provided on the motor shaft of the electric motor and having a plurality of convex portions extending in the axial direction;
A second member provided at the tip of the worm shaft and having a plurality of protrusions extending in the axial direction;
An elastic member that is provided between the convex portion of the first member and the convex portion of the second member in the circumferential direction and transmits torque;
Of the convex portions of the first member, a projecting portion that projects toward the elastic member is formed at an end portion on the worm shaft side from a facing surface facing the elastic member, and the projecting portion is formed by the elastic member. In contact with
The protrusion of the first member exhibits a step shape with respect to the facing surface facing the elastic member,
Alternatively, a protruding portion that protrudes toward the elastic member at the end on the worm shaft side is formed from a facing surface that faces the elastic member among the convex portions of the second member. In contact with the elastic member ,
The protrusion of the second member, to the facing surface that faces the elastic member, the electric power steering apparatus characterized by which develops a stepped shape. The worm shaft of the worm gear mechanism composed of a worm and a worm wheel provided on the worm shaft is connected to the motor shaft of the electric motor via a shaft coupling,
In the electric power steering device in which the drive torque generated by the electric motor is added to the steering torque via the worm gear mechanism,
The shaft coupling is
A first member provided on the motor shaft of the electric motor and having a plurality of convex portions extending in the axial direction;
A second member provided at the tip of the worm shaft and having a plurality of protrusions extending in the axial direction;
An elastic member that is provided between the convex portion of the first member and the convex portion of the second member in the circumferential direction and transmits torque;
Of the convex portions of the first member, a projecting portion that projects toward the elastic member is formed at an end portion on the worm shaft side from a facing surface facing the elastic member, and the projecting portion is formed by the elastic member. In contact with
The protruding portion of the first member is configured by an inclined surface that is inclined toward the elastic member from a facing surface that faces the elastic member.
Alternatively, a protruding portion that protrudes toward the elastic member at the end on the worm shaft side is formed from a facing surface that faces the elastic member among the convex portions of the second member. In contact with the elastic member,
The protrusion of the second member, the resilient member the resilient member electrostatic power steering apparatus you characterized in that it is constituted by inclined inclined plane toward the a facing surface that faces toward. The recessed part which absorbs the deformation | transformation part when the said elastic member deform | transforms is formed in the edge part by the side of the said worm shaft among the convex parts of the said 2nd member, The Claim 1 or Claim characterized by the above-mentioned. 2. The electric power steering apparatus according to claim 1.

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