JP2013155844A - Joint mechanism, worm speed reducer, and electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint mechanism configured to transmit rotation of one of first and second rotators to the others, to permit relative inclination of the first and second rotators, and to permit relative translation of the first and second rotators in a direction of the rotation center axis.SOLUTION: A joint mechanism 60 includes a first york 61, a second york 62, and a transmission member 63. The transmission member 63 can move in a direction of a first rotation center axis J relative to the first york 61, and can move in a direction of a second rotation center axis K relative to the second york 62. The transmission member 63 can rotate integrally with the first york 61 around the first rotation center axis J, and integrally with the second york 62 around the second rotation center axis K.

Description

  According to the present invention, a first rotating body that rotates around a first rotation center axis and a second rotating body that rotates around a second rotation center axis are connected to each other, and one of the first rotating body and the second rotating body is connected. The present invention relates to a joint mechanism that transmits rotation to the other side, a worm reducer, and an electric power steering device.

  The electric power steering device described in Patent Document 1 has a structure capable of tilting the worm shaft with respect to the output shaft of the electric motor and transmitting the rotation of the output shaft to the worm shaft. In this electric power steering apparatus, the end of the worm shaft opposite to the electric motor side is pressed against the worm wheel by the restoring force of the elastic member. This reduces backlash caused by dimensional errors and wear between the worm shaft and the worm wheel.

  The electric power steering device described in Patent Document 2 has a structure capable of translating the worm shaft in the axial direction and transmitting the rotation of the output shaft of the electric motor to the worm shaft. In this electric power steering device, the reaction force that the wheels receive from the road surface rotates the worm wheel via the wheel steering mechanism. The worm shaft receives a force that translates in the axial direction as the worm wheel rotates. The worm shaft translates to a position where the restoring force of the elastic member balances with the axial translational force. Thereby, generation | occurrence | production of the contact sound when a worm shaft contacts a bearing and the contact sound which a bearing contacts a housing is suppressed.

JP 2010-43744 A Special table 2003-511294 gazette

  From the viewpoint of enhancing the practicality of the electric power steering device, a structure in which the worm shaft can tilt with respect to the output shaft of the electric motor, a structure in which the worm shaft can translate in the axial direction, and rotation of the output shaft It is preferable that one mechanism has a structure capable of transmitting the pressure to the worm shaft. However, no such mechanism has been proposed at present.

  In order to solve the above problems, the present invention transmits one rotation of the first rotating body and the second rotating body to the other, and allows a relative inclination of the first rotating body and the second rotating body, Another object of the present invention is to provide a joint mechanism capable of allowing relative translation of the first rotating body and the second rotating body in the direction of the rotation center axis.

  (1) The first means connects the first rotating body rotating around the first rotation center axis and the second rotating body rotating around the second rotation center axis to each other. In the joint mechanism for transmitting rotation from one of the first rotating body and the second rotating body to the other, the joint mechanism extends in the first rotation center axis direction and is directed from the first rotating body toward the second rotating body. A plurality of first grooves projecting and positioned at predetermined intervals around the first rotation center axis and having first groove portions extending in the first rotation center axis direction formed on the surface on the first rotation center axis side. A first yoke having one arm portion, extending in the second rotation center axis direction, projecting from the second rotation body toward the first rotation body, and around the second rotation center axis; It is located alternately with arms A second yoke having a plurality of second arm portions in which a second groove portion extending in the second rotation center axis direction is formed on a surface on the second rotation center axis side; the plurality of first arm portions; A plurality of first projecting surfaces disposed in a space surrounded by the second arm portion, extending in a predetermined rotation center axis direction and having an arc shape projecting toward the first groove portion, and the predetermined rotation center axis direction And a plurality of second projecting surfaces having an arc shape projecting toward the second groove portion, and the first projecting surfaces are in contact with the corresponding first groove portions. The plurality of second projecting surfaces can be relatively translated in the rotation center axis direction, and can be relatively translated in the second rotation center axis direction in a state where the plurality of second projecting surfaces are in contact with the corresponding second groove portions. The first projecting surface of the corresponding first By rotating around the first rotation center axis in a state in contact with the groove portion, and by rotating around the second rotation center axis in a state in which the plurality of second projecting surfaces are in contact with the corresponding second groove portion, The gist of the present invention is a joint mechanism having a transmission member for transmitting rotational force from one of the first yoke and the second yoke to the other.

  The first yoke and the transmission member are allowed to translate integrally with respect to the second yoke in the second rotation center axis direction. The second yoke and the transmission member are allowed to translate integrally with respect to the first yoke in the first rotation center axis direction. Since the 1st protrusion surface of a transmission member has the circular arc shape which protrudes in a 1st groove part, it can rotate in the state which contacted the 1st groove part. Accordingly, the second yoke and the transmission member are allowed to be integrally inclined with respect to the first yoke. Since the 2nd protrusion surface of a transmission member has the circular arc shape which protrudes in a 2nd groove part, it can rotate in the state which contacted the 2nd groove part. Accordingly, the first yoke and the transmission member are allowed to be integrally inclined with respect to the second yoke. That is, the joint mechanism transmits one rotation of the first rotator and the second rotator to the other, allows a relative inclination of the first rotator and the second rotator, and in the direction of the rotation center axis. It is possible to allow relative translation of the first rotating body and the second rotating body.

  (2) The second means connects the first rotating body rotating around the first rotation center axis and the second rotating body rotating around the second rotation center axis to each other. In the joint mechanism for transmitting rotation from one of the first rotating body and the second rotating body to the other, the joint mechanism extends in the first rotation center axis direction and is directed from the first rotating body toward the second rotating body. A first projecting surface that protrudes and is located at a predetermined interval around the first rotation center axis and that extends in the first rotation center axis direction and projects from the surface on the first rotation center axis side is formed. A first yoke having a plurality of first arm portions, extending in the direction of the second rotation center axis, projecting from the second rotation body toward the first rotation body, and about the second rotation center axis Alternating with multiple first arms A second yoke having a plurality of second arm portions that are positioned and extend in the second rotation center axis direction and formed with second protrusion surfaces protruding from the second rotation center axis side surface; Arranged in a space surrounded by the plurality of first arm portions and the plurality of second arm portions, has an arc shape extending in a predetermined rotation center axis direction and projecting toward the first arm portion, and A plurality of first protrusions having a first groove portion having a shape corresponding to the first protrusion surface on a surface facing the first arm portion, and extending in the predetermined rotation center axis direction toward the second arm portion. A plurality of second projecting portions each having a projecting arc shape and having a second groove portion having a shape corresponding to the second projecting surface on a surface facing the second arm portion; In the state where one groove portion is in contact with the corresponding first projecting surface, the first time Relative movement is possible in the direction of the central axis, relative movement is possible in the direction of the second rotation central axis while the plurality of second groove portions are in contact with the corresponding second projecting surfaces, and the plurality of first groove portions are It rotates around the first rotation center axis in a state where it is in contact with the corresponding first protrusion surface, and the second rotation center axis is around the second rotation center axis in a state where the plurality of second groove portions are in contact with the corresponding second protrusion surface. The gist of the present invention is a joint mechanism having a transmission member that transmits a rotational force from one of the first yoke and the second yoke to the other by rotating to the other.

  The first yoke and the transmission member are allowed to translate integrally with respect to the second yoke in the second rotation center axis direction. The second yoke and the transmission member are allowed to translate integrally with respect to the first yoke in the first rotation center axis direction. Since the 1st protrusion part of a transmission member has the circular arc shape which protrudes toward a 1st arm part, it can rotate in the state which the 1st groove part and the 1st protrusion surface contacted. Accordingly, the second yoke and the transmission member are allowed to be integrally inclined with respect to the first yoke. Since the 2nd protrusion part of a transmission member has the circular arc shape which protrudes toward a 2nd arm part, it can rotate in the state which the 2nd groove part and the 2nd protrusion surface contacted. Accordingly, the first yoke and the transmission member are allowed to be integrally inclined with respect to the second yoke. That is, the joint mechanism transmits one rotation of the first rotator and the second rotator to the other, allows a relative inclination of the first rotator and the second rotator, and in the direction of the rotation center axis. It is possible to allow relative translation of the first rotating body and the second rotating body.

  (3) The third means is the invention according to claim 3, that is, the joint mechanism according to claim 1 or 2, wherein each of the first projecting surface and the second projecting surface forms an arc-shaped cross section. It is a summary.

  The first projecting surface and the second projecting surface have an arc shape. For this reason, when one of the first yoke and the transmission member rotates around the first rotation center axis in contact with the other, the surface pressure between the first projecting surface and the first groove portion is reduced. In addition, when one of the second yoke and the transmission member rotates around the second rotation center axis in a state of being in contact with the other, the surface pressure between the second projecting surface and the second groove portion is reduced.

  (4) The fourth means is the joint according to any one of claims 1 to 3, wherein the first groove portion and the second groove portion each have an arc-shaped cross section. The gist of the mechanism.

  The first groove portion and the second groove portion have an arc shape. For this reason, when one of the first yoke and the transmission member rotates around the first rotation center axis in contact with the other, the surface pressure between the first projecting surface and the first groove portion is reduced. In addition, when one of the second yoke and the transmission member rotates around the second rotation center axis in a state of being in contact with the other, the surface pressure between the second projecting surface and the second groove portion is reduced.

  (5) The fifth means is the invention according to claim 5, that is, the joint mechanism is at least between the first rotating body and the transmission member and between the second rotating body and the transmission member. The gist of the present invention is the joint mechanism according to any one of claims 1 to 4, which has a first elastic member on one side.

  When the joint mechanism has the first elastic member between the transmission member and the first rotating body, generation of contact noise due to relative translation of the first yoke and the transmission member is suppressed. Moreover, when it has a 1st elastic member between a transmission member and a 2nd rotary body, it is suppressed that a contact sound generate | occur | produces by relative translation of a 2nd yoke and a transmission member.

  (6) The sixth means is the invention according to claim 6, that is, the joint mechanism is configured such that the joint mechanism is between the tips of the plurality of second arm portions and the first rotating body, and the plurality of first arm portions. The gist of the present invention is the joint mechanism according to any one of claims 1 to 5, wherein a second elastic member is provided on at least one of the tip of the second rotating body and the second rotating body.

  When the joint mechanism has the second elastic member between the tip of the second arm portion and the first rotating body, the generation of contact sound due to the relative translation of the second yoke and the first yoke is suppressed. . Further, when the second elastic member is provided between the tip of the first arm portion and the second rotating body, the generation of contact sound due to the relative translation of the first yoke and the second yoke is suppressed.

  (7) The seventh means is the invention according to claim 7, that is, the joint mechanism according to any one of claims 1 to 6, the output shaft of the electric motor as the first rotating body, The gist of the present invention is a worm reduction mechanism having the worm shaft as the second rotating body.

  The worm speed reduction mechanism can have both a mechanism that allows the worm shaft to tilt with respect to the output shaft of the electric motor and a mechanism that allows translation of the worm shaft relative to the worm wheel.

  (8) The eighth means is the invention according to claim 8, that is, the joint mechanism according to any one of claims 1 to 6, the output shaft of the electric motor as the first rotating body, The gist of the invention is an electric power steering apparatus having the worm shaft as the second rotating body.

  The electric power steering device can have both a mechanism for pressing the worm shaft against the worm wheel by allowing the worm shaft to tilt with respect to the output shaft of the electric motor, and a mechanism for allowing the worm shaft to translate relative to the worm wheel. become.

  The present invention relates to transmitting the rotation of one of the first rotating body and the second rotating body to the other, allowing the relative inclination of the first rotating body and the second rotating body, and the first rotation body in the direction of the rotation center axis. Provided is a joint mechanism capable of allowing relative translation of a first rotating body and a second rotating body.

The block diagram which shows the whole structure about the vehicle steering device containing the coupling mechanism of one Embodiment of this invention. Sectional drawing which shows the cross-sectional structure of the plane parallel to the rotation center axis | shaft of a worm shaft, and orthogonal to the rotation center axis | shaft of a worm wheel about the deceleration mechanism of embodiment. Sectional drawing which shows the cross-sectional structure of the plane parallel to a rotation center axis | shaft about the joint mechanism of embodiment. Regarding the first and second yokes of the embodiment, (a) is a front view showing a front structure, (b) is a cross-sectional view showing a cross-sectional structure of the XC-XC plane of (a), and (c) is a cross-sectional view of (a). Sectional drawing which shows the cross-section of a XD-XD plane. About the motor side and worm side elastic member of an embodiment, (a) is a front view showing a front structure, and (b) is a side view showing a side structure. About the transmission member of embodiment, (a) is a side view which shows a side structure, (b) is sectional drawing which shows the cross-section of the XE-XE plane of (a). It is sectional drawing which shows the cross-section of the XB-XB plane of FIG. 3 in the coupling mechanism of embodiment, (a) is sectional drawing of the state in which the output shaft has stopped rotation, (b) is each 1st arm part. Sectional drawing when is in contact with the transmission member and sectional view showing an enlarged structure of the SB portion, (c) is a sectional view when the transmission member is in contact with each second arm, and SC Sectional drawing which shows the enlarged structure of a part. FIG. 3 is a cross-sectional view showing an enlarged structure of the SA portion of FIG. 2 for the speed reduction mechanism of the embodiment, where (a) is a cross-sectional view of the worm shaft inclined with respect to the output shaft, and (b) is an SD of (a). Sectional drawing which shows the enlarged structure of a part. FIG. 3 is a cross-sectional view showing an enlarged structure of the SA portion of FIG. 2 for the speed reduction mechanism of the embodiment, in which (a) is a cross-sectional view showing a state in which the worm shaft translates in the output shaft direction in the axial direction; Sectional drawing which shows the enlarged structure of SE part of). FIG. 3 is a cross-sectional view showing an enlarged structure of the SA portion of FIG. 2 for the speed reduction mechanism of the embodiment, wherein (a) is a cross-sectional view showing a state where the worm shaft is translated in the ball bearing direction in the axial direction, and (b) is (a Sectional drawing which shows the enlarged structure of SF part of FIG. Sectional drawing which shows the cross-sectional structure of the plane parallel to a rotation center axis | shaft about the coupling mechanism of a modification. It is sectional drawing which shows the cross-section of the XF-XF plane of FIG. 11 in the coupling mechanism of a modification, and sectional drawing in the state which the output shaft has stopped rotation. About the transmission member of a modification, (a) is a side view which shows a side structure, (b) is sectional drawing which shows the cross-section of the XG-XG plane of (a).

With reference to FIG. 1, the whole structure of the vehicle steering device 1 is demonstrated.
The vehicle steering apparatus 1 includes a steering wheel 10 that transmits torque to the column shaft 31, a steering apparatus 30 that changes the steering angle of the front wheels 20, an assist apparatus 40 that applies torque to the column shaft 31, and an assist motor 41. And a worm speed reduction mechanism 50 that transmits the rotation to the column shaft 31.

  In addition to the column shaft 31, the steering device 30 includes an intermediate shaft 32 that rotates together with the column shaft 31, and a pinion shaft 33 that rotates together with the intermediate shaft 32. In addition to this, a rack and pinion mechanism 34 connected to the pinion shaft 33 and a turning shaft 35 that changes the turning angle of the front wheels 20 are provided.

  The assist device 40 includes an assist motor 41 that applies torque to the column shaft 31, and a torque sensor 42 that detects steering torque input to the column shaft 31. In addition, a vehicle speed sensor 43 that detects the traveling speed of the vehicle and a control device 44 that controls the assist motor 41 in accordance with the steering torque and the traveling speed are provided. The assist motor 41 has an output shaft 41A.

The operation of the vehicle steering device 1 will be described.
The driver inputs a steering torque to the steering wheel 10 when changing the turning angle of the front wheels 20. The column shaft 31 rotates as the steering wheel 10 rotates. The control device 44 supplies current to the assist motor 41 according to the steering torque of the column shaft 31 and the traveling speed of the vehicle.

  The assist motor 41 rotates the output shaft 41A in response to the supply of current. The worm deceleration mechanism 50 decelerates the rotation of the output shaft 41 </ b> A and transmits it to the column shaft 31. The intermediate shaft 32 transmits the rotation of the column shaft 31 to the pinion shaft 33. The rack and pinion mechanism 34 converts the rotation of the pinion shaft 33 into an axial translational motion of the steered shaft 35. The steered shaft 35 moves a knuckle (not shown) via a tie rod by translational movement. And the turning angle of the front wheel 20 changes with operation | movement of a knuckle.

A detailed configuration of the worm reduction mechanism 50 will be described with reference to FIG.
(A) The rotation center axis of the output shaft 41A is the first rotation center axis J, and the rotation center axis of the worm shaft 54 is the second rotation center axis K.
(B) A direction along the first rotation center axis J is referred to as a “first axis direction A”.
(C) In the front view from the steering wheel 10 side of the column shaft 31 and in the first axial direction A, the direction from the left side to the right side is “first right direction A1”, and the direction from the right side to the left is “first” Left direction A2 ”.
(D) A direction along the second rotation center axis K is defined as a “second axis direction B”.
(E) In the front view of the column shaft 31 from the steering wheel 10 side and in the second axial direction B, the direction from the left side to the right side is “second right direction B1”, and the direction from the right side to the left side is “second” Left direction B2 ”.
(F) In the side view from the first left direction A2 and in the rotation direction Q around the first rotation center axis J, the clockwise direction is “forward direction Q1” and the counterclockwise direction is “reverse direction Q2”. To do.
(G) In a side view from the second left direction B2 and in the rotation direction P around the second rotation center axis K, the clockwise direction is “forward rotation direction P1” and the counterclockwise direction is “reverse rotation direction P2”. To do.
(H) The front direction from the steering wheel 10 side of the column shaft 31 and the counterclockwise direction in the rotation direction R around the rotation center U of the joint mechanism 60 is defined as a “forward rotation direction R1”.
(I) In the front view of the column shaft 31 from the steering wheel 10 side and in the rotation direction S around the rotation center axis V of the column shaft 31, the clockwise direction is defined as the “forward rotation direction S1” and the counterclockwise direction is defined as “ The reverse direction is S2.

  The worm speed reduction mechanism 50 includes a shaft accommodating portion 51 that accommodates the worm shaft 54, a bearing accommodating portion 52 that accommodates the ball bearing 57, and an end cover 53 that covers the bearing accommodating portion 52. In addition to this, it has a worm shaft 54 connected to the output shaft 41A, a worm wheel 55 meshing with the worm shaft 54, and a translational elastic member 56 into which one end of the worm shaft 54 is inserted. In addition, a ball bearing 57 that receives the rotation of the translational elastic member 56, a pressing elastic member 58 that applies a restoring force to the ball bearing 57, and a joint mechanism 60 that connects one end of the worm shaft 54 to the output shaft 41A. Have.

  The shaft accommodating portion 51 is formed in the worm reduction mechanism 50 as a cylindrical space extending in the first left direction A2. The bearing housing portion 52 is a columnar space in which the radius of the shaft housing portion 51 is enlarged from the opposite side of the shaft housing portion 51 to the output shaft 41A side, toward the first left direction A2. To penetrate. The end cover 53 is press-fitted into the opening end of the bearing housing portion 52.

  One end of the worm shaft 54 on the output shaft 41A side is supported by the joint mechanism 60 so as to be rotatable about the second rotation center axis K and to be translated in the second axial direction B. The worm wheel 55 is supported by the column shaft 31 so as to be rotatable integrally with the column shaft 31.

  The translational elastic member 56 has a cylindrical shape coaxial with the worm shaft 54. The translational elastic member 56 has an axial hole 56A into which the end of the worm shaft 54 opposite to the output shaft 41A side is inserted, and has an insertion part 56B that protrudes from the other end of the translational elastic member 56. The insertion portion 56B has a cylindrical shape in which the outer diameter of the translational elastic member 56 is reduced.

  In the ball bearing 57, the insertion portion 56B of the translational elastic member 56 is inserted so as to be rotatable around the second rotation center axis K. The pressing elastic member 58 is inserted in a compressed state between the ball bearing 57 and the bearing housing portion 52.

The detailed structure of the joint mechanism 60 will be described with reference to FIGS.
As shown in FIG. 3, the joint mechanism 60 includes a first yoke 61 that rotates integrally with the output shaft 41A, a second yoke 62 that rotates integrally with the worm shaft 54, and rotation of the first yoke 61. And a transmission member 63 for transmitting to the second yoke 62. In addition, a motor-side elastic member 64 that applies a restoring force to the transmission member 63 based on the first yoke 61, and a worm-side elastic member 65 that applies a restoring force to the transmission member 63 based on the second yoke 62; Have

The detailed structure of the first and second yokes 61 and 62 will be described with reference to FIG.
As shown in FIG. 4A, the first yoke 61 includes a first base portion 61A, a pair of first arm portions 61B, a first groove portion 61C formed in each first arm portion 61B, and an output shaft. A first press-fitting hole 61D into which 41A is press-fitted.

  As shown in FIGS. 4B and 4C, each first arm portion 61B protrudes from the first base portion 61A to the opposite side of the first press-fit hole 61D along the first rotation center axis J direction. To do. 61 A of 1st base parts have each 1st arm part 61B in the position which opposes on the 1st rotation central axis J as a center. Each first arm portion 61B has a first groove portion 61C extending in the first rotation center axis J direction on the surface on the first rotation center axis J side. Each first groove 61C has an arc-shaped cross section corresponding to a part of a circle having a curvature RA centered on the first rotation center axis J. The first base portion 61A has a first press-fit hole 61D on the surface opposite to the surface on which the first arm portion 61B is located. The first press-fitting hole 61D has a circular shape with a diameter centered on the first rotation center axis J and capable of press-fitting the output shaft 41A.

  As shown in FIG. 4A, the second yoke 62 includes a second base portion 62A, a pair of second arm portions 62B, a second groove portion 62C formed in each second arm portion 62B, and a worm shaft. 54 has a second press-fitting hole 62D into which one end of 54 is press-fitted.

  As shown in FIGS. 4B and 4C, each second arm portion 62B protrudes from the second base portion 62A to the opposite side of the second press-fit hole 62D along the second rotation center axis K direction. To do. The second base portion 62A has the second arm portions 62B at positions facing each other about the second rotation center axis K. Each second arm portion 62B has a second groove portion 62C extending in the second rotation center axis K direction on the surface on the second rotation center axis K side. Each of the second groove portions 62C has an arc-shaped cross section corresponding to a part of a circle having a curvature RA around the second rotation center axis K. The second base portion 62A has a second press-fit hole 62D on the surface opposite to the surface on which the second arm portion 62B is located. The second press-fitting hole 62D has a circular shape with a diameter about the second rotation center axis K and capable of press-fitting one end of the worm shaft 54.

With reference to FIG. 5, the detailed structures of the motor side elastic member 64 and the worm side elastic member 65 will be described.
As shown in FIGS. 5A and 5B, the motor-side elastic member 64 has a cylindrical shape with the first rotation center axis J as the center axis. The worm side elastic member 65 has a cylindrical shape with the second rotation center axis K as the center axis. The motor side elastic member 64 has a flange 64A at its end. The worm side elastic member 65 has a flange 65A at its end.

The detailed structure of the transmission member 63 will be described with reference to FIG.
As shown in FIG. 6 (b), the transmission member 63 rotates an ellipse M1 having the central axis N1 as a major axis among the central axes N1 and N2 orthogonal to each other around the minor axis (central axis N2). It is formed by aligning the center of the oblate ellipsoid O1 and the ellipsoid M2 formed by rotating the ellipse M2 having the central axis N2 as the major axis around the minor axis (center axis N1) with the rotation center U. It has an outer surface L.

  As shown in FIG. 6B, the transmission member 63 has a circular arc shape in which the surface corresponding to the outer surface of the oblate ellipsoid O1 in the outer surface L protrudes from the rotation center U toward both sides in the direction of the central axis N1. It has as a pair of 1st protrusion surface 63A. Further, the transmission member 63 has a surface corresponding to the outer surface of the oblong ellipsoid O2 in the outer surface L as a pair of arc-shaped second projecting surfaces 63B projecting from the rotation center U toward both sides in the direction of the central axis N2. .

  Each first projecting surface 63A has a curvature RB that is larger than the curvature RA of the first groove portion 61C in a cross section passing through the top of the transmission member 63 and the top of the pair of first projecting surfaces 63A and the rotation center U. . Each of the second projecting surfaces 63B is larger than the curvature RA of the second groove 62C in a front view of the transmitting member 63 and in a cross section of the transmitting member 63 passing through the apex of the pair of second projecting surfaces 63B and the rotation center U. It has a curvature RB.

With reference to FIG. 3, the relationship of each member of the joint mechanism 60 is demonstrated.
The motor-side elastic member 64 and the first yoke 61 have a relationship in which the first rotation center axis J is the central axis and are bonded to each other. Further, the worm side elastic member 65 and the second yoke 62 have a relationship in which the second rotation center axis K is a center axis and are bonded to each other.

  The first yoke 61 and the transmission member 63 have a relationship in which the first groove portions 61C and the first protruding surfaces 63A face each other. The 2nd yoke 62 and the transmission member 63 have the relationship where each 2nd groove part 62C and each 2nd protrusion surface 63B oppose.

The operation of the worm reduction mechanism 50 will be described with reference to FIG.
The control device 44 supplies current to the assist motor 41 according to the steering torque of the column shaft 31 and the traveling speed of the vehicle. The assist motor 41 rotates the output shaft 41A in response to the supply of current. The output shaft 41A rotates in the forward rotation direction Q1 when the assist motor 41 is supplied with a positive current. The output shaft 41A rotates in the reverse rotation direction Q2 when the assist motor 41 is supplied with a negative current.

  The joint mechanism 60 transmits the rotation of the output shaft 41A in the normal rotation direction Q1 to the worm shaft 54 as the rotation in the normal rotation direction P1. The worm wheel 55 rotates in the normal rotation direction S1 due to the meshing relationship with the worm shaft 54 as the worm shaft 54 rotates in the normal rotation direction P1. The column shaft 31 rotates integrally with the worm wheel 55 in the forward rotation direction S1.

  The joint mechanism 60 transmits the rotation of the output shaft 41A in the reverse rotation direction Q2 to the worm shaft 54 as the rotation in the reverse rotation direction P2. The worm wheel 55 rotates in the reverse rotation direction S2 due to the meshing relationship with the worm shaft 54 as the worm shaft 54 rotates in the reverse rotation direction P2. The column shaft 31 rotates integrally with the worm wheel 55 in the reverse rotation direction S2.

With reference to FIG. 7, the operation of the joint mechanism 60 when the output shaft 41A rotates in the normal rotation direction P1 will be described.
As shown in FIG. 7A, when the output shaft 41A stops rotating, the transmission member 63 contacts the first groove 61C located in the gravity direction among the pair of first grooves 61C by gravity. To do.

  As shown in FIG. 7B, when the output shaft 41A rotates in the normal rotation direction Q1, the first yoke 61 integrally rotates in the normal rotation direction Q1. Each first groove portion 61 </ b> C rotates in the forward rotation direction Q <b> 1 integrally with the first yoke 61. Each first projecting surface 63A comes into contact with each first groove 61C as each first groove 61C rotates in the normal rotation direction Q1. The transmission member 63 rotates in the normal rotation direction Q1 integrally with the first yoke 61 in accordance with the contact between each first groove 61C and each first projecting surface 63A.

  As shown in FIG. 7C, each second projecting surface 63B comes into contact with each second groove 62C when the transmission member 63 and the first yoke 61 integrally rotate in the normal rotation direction Q1. . The second yoke 62 rotates in the forward rotation direction P1 integrally with the transmission member 63 by the contact between each second projecting surface 63B and each second groove 62C. The worm shaft 54 rotates integrally with the second yoke 62 in the forward rotation direction P1.

  The operation of the joint mechanism 60 when the output shaft 41A rotates in the reverse rotation direction Q2 is the same as when the output shaft 41A rotates in the normal rotation direction Q1. That is, the rotation of the first yoke 61 and the transmission member 63 in the reverse rotation direction Q2 is transmitted to the second yoke 62 and the worm shaft 54 as the rotation in the reverse rotation direction P2.

The operation of the joint mechanism 60 when the worm shaft 54 is inclined with respect to the output shaft 41A will be described with reference to FIG.
When the worm shaft 54 and the worm wheel 55 are engaged with each other and worn, the diameter of the engagement portion is reduced. As a result, the worm shaft 54 is separated from the worm wheel 55.

  As shown in FIG. 8 (a), the ball bearing 57 becomes rotatable in the forward rotation direction R1 when the worm shaft 54 is separated from the worm wheel 55. The pressing elastic member 58 applies a restoring force that rotates in the forward rotation direction R <b> 1 to the ball bearing 57. The worm shaft 54 is given a restoring force that rotates in the forward rotation direction R <b> 1 from the pressing elastic member 58 via the ball bearing 57 and the translational elastic member 56.

  As shown in FIG. 8B, the second yoke 62 rotates integrally with the worm shaft 54 in the forward rotation direction R1 as the worm shaft 54 rotates in the forward rotation direction R1. Each second groove 62 </ b> C rotates integrally with the second yoke 62 in the normal rotation direction R <b> 1. Each 2nd protrusion surface 63B contacts each 2nd groove part 62C with rotation to the normal rotation direction R1 of each 2nd groove part 62C. The transmission member 63 is in a state in which each first projecting surface 63A is in contact with each first groove 61C as each second projecting surface 63B is rotated in the normal rotation direction R1 by contacting each second groove 62C. , Rotate around the rotation center U.

With reference to FIG. 9, the operation of the joint mechanism 60 when the worm shaft 54 translates by receiving the rotation of the worm wheel 55 in the forward rotation direction S1 will be described.
As shown in FIG. 9A, the worm shaft 54 receives a tangential force in the forward rotation direction S1 of the worm wheel 55 as the worm wheel 55 rotates in the forward rotation direction S1. The tangential force in the forward rotation direction S1 of the worm wheel 55 acts in the second right direction B1.

  As shown in FIG. 9B, the second yoke 62 receives a force in the second right direction B <b> 1 from the worm shaft 54. The force in the second right direction B1 is a ratio determined in accordance with the contact state between each second groove 62C and each second projecting surface 63B and each first groove 61C and each first projecting surface 63A. Dispersed in the forces of A1 and the second right direction B1.

  The second yoke 62 moves in the second right direction B1 with the second groove portions 62C and the second projecting surfaces 63B in contact with each other in accordance with the distributed force in the second right direction B1. The transmission member 63 translates in the first right direction A1 with the first groove portions 61C and the first projecting surfaces 63A in contact with each other in accordance with the distributed first right direction A1 force. Thereby, the worm shaft 54 translates with the translation of the second yoke 62 in the second right direction B1 and the translation of the transmission member 63 in the first right direction A1.

  The operation of the translational elastic member 56, the motor-side elastic member 64, and the worm-side elastic member 65 as the worm shaft 54 translates by receiving the rotation of the worm wheel 55 in the forward rotation direction S1 will be described.

  As shown in FIG. 9A, the translational elastic member 56 translates the worm shaft 54 in accordance with the translation of the second yoke 62 in the second right direction B1 and the translation member 63 in the first right direction A1. To restore to natural length. As shown in FIG. 9B, the motor-side elastic member 64 and the worm-side elastic member 65 translate the second yoke 62 in the second right direction B1 and translate the transmission member 63 in the first right direction A1. Compressed as it goes.

The operation of the joint mechanism 60 when the worm shaft 54 translates by receiving the rotation of the worm wheel 55 in the reverse rotation direction S2 will be described with reference to FIG.
As shown in FIG. 10A, the worm shaft 54 receives a tangential force in the reverse direction S2 of the worm wheel 55 as the worm wheel 55 rotates in the reverse direction S2. The tangential force in the reverse rotation direction S2 of the worm wheel 55 acts in the second left direction B2.

  As shown in FIG. 10B, the second yoke 62 receives a force in the second left direction B <b> 2 from the worm shaft 54. The force in the second left direction B2 depends on the ratio determined according to the contact state between each second groove 62C and each second projecting surface 63B and each first groove 61C and each first projecting surface 63A. Dispersed in the force between B2 and the first left direction A2.

  The second yoke 62 moves in the second left direction B2 in accordance with the distributed force in the second left direction B2, with the second groove portions 62C and the second projecting surfaces 63B in contact with each other. The transmission member 63 translates in the first left direction A2 in a state where each first groove 61C and each first projecting surface 63A are in contact with each other according to the distributed first left direction A2 force. Thereby, the worm shaft 54 translates with the translation of the second yoke 62 in the second left direction B2 and the translation of the transmission member 63 in the first left direction A2.

  The operation of the translational elastic member 56, the motor side elastic member 64, and the worm side elastic member 65 as the worm shaft 54 translates by receiving the rotation of the worm wheel 55 in the reverse rotation direction S2 will be described.

  As shown in FIG. 10A, the translational elastic member 56 translates the worm shaft 54 in accordance with the translation of the second yoke 62 in the second left direction B2 and the translation member 63 in the first left direction A2. Depending on, it is compressed. As shown in FIG. 10B, the motor-side elastic member 64 and the worm-side elastic member 65 translate the second yoke 62 in the second left direction B2 and the translation member 63 in the first left direction A2. Restore to natural length.

The joint mechanism 60 of this embodiment has the following effects.
(1) The joint mechanism 60 includes a first yoke 61 having a plurality of first arm portions 61B in which a first groove 61C extending in the first rotation center axis J direction has a first rotation center axis J side surface. The second groove 62C extending in the second rotation center axis K direction has a second yoke 62 having a plurality of second arm portions 62B formed on the surface on the second rotation center axis K side. Further, the joint mechanism 60 extends in a predetermined central axis direction and has a plurality of first protruding surfaces 63A having an arc shape protruding toward the first groove portion 61C, and extends in the central axis direction and toward the second groove portion 62C. And a transmission member 63 having a plurality of second projecting surfaces 63B having a circular arc shape projecting. The transmission member 63 can be relatively translated in the first rotation central axis J direction in a state where the plurality of first projecting surfaces 63A are in contact with the corresponding first groove portions 61C, and the plurality of second projecting surfaces 63B correspond. It can be relatively translated in the direction of the second rotation center axis K in a state where it is in contact with the second groove 62C. Further, the transmission member 63 rotates around the first rotation center axis J in a state in which the plurality of first projecting surfaces 63A are in contact with the corresponding first groove portions 61C, and the plurality of second projecting surfaces 63B correspond to the second ones. A rotational force is transmitted from one of the first yoke 61 and the second yoke 62 to the other by rotating around the second rotation center axis K in a state of contact with the groove 62C.

  According to the above configuration, the first yoke 61 and the transmission member 63 are allowed to translate integrally with respect to the second yoke 62 in the second rotation center axis K direction. The second yoke 62 and the transmission member 63 are allowed to translate integrally with respect to the first yoke 61 in the first rotation central axis J direction. Since the first projecting surface 63A of the transmission member 63 has an arc shape projecting into the first groove 61C, the first projecting surface 63A can rotate while being in contact with the first groove 61C. As a result, the second yoke 62 and the transmission member 63 are allowed to tilt integrally with the first yoke 61. Since the 2nd protrusion surface 63B of the transmission member 63 has the circular arc shape which protrudes in the 2nd groove part 62C, it can rotate in the state which contacted the 2nd groove part 62C. Thereby, the first yoke 61 and the transmission member 63 are allowed to be integrally inclined with respect to the second yoke 62. That is, the joint mechanism 60 can transmit the rotation of the output shaft 41A to the worm shaft 54, allow the worm shaft 54 to tilt with respect to the output shaft 41A, and allow the worm shaft 54 to translate with respect to the output shaft 41A. To.

(2) Each of the first projecting surface 63A and the second projecting surface 63B forms an arc-shaped cross section.
According to the above configuration, when one of the first yoke 61 and the transmission member 63 rotates around the first rotation center axis J in a state of contact with the other, the surface pressure between the first protruding surface 63A and the first groove portion 61C. Becomes smaller. In addition, when one of the second yoke 62 and the transmission member 63 rotates around the second rotation center axis K in a state of being in contact with the other, the surface pressure between the second projecting surface 63B and the second groove 62C is reduced.

(3) Each of the first groove portion 61C and the second groove portion 62C has an arc-shaped cross section.
According to the above configuration, when one of the first yoke 61 and the transmission member 63 rotates around the first rotation center axis J in a state of contact with the other, the surface pressure between the first protruding surface 63A and the first groove portion 61C. Becomes smaller. In addition, when one of the second yoke 62 and the transmission member 63 rotates around the second rotation center axis K in a state of being in contact with the other, the surface pressure between the second projecting surface 63B and the second groove 62C is reduced.

(4) The motor side elastic member 64 is provided between the first yoke 61 and the transmission member 63, and the worm side elastic member 65 is provided between the second yoke 62 and the transmission member 63.
Since the joint mechanism 60 includes the motor-side elastic member 64 between the transmission member 63 and the first yoke 61, the generation of contact noise due to relative translation between the first yoke 61 and the transmission member 63 is suppressed. The In addition, since the worm side elastic member 65 is provided between the transmission member 63 and the second yoke 62, the generation of contact sound due to the relative translation of the second yoke 62 and the transmission member 63 is suppressed.

(5) The assist device 40 includes a joint mechanism 60 that couples the output shaft 41 </ b> A and the worm shaft 54.
The assist device 40 includes a mechanism for pressing the worm shaft 54 against the worm wheel 55 by allowing the worm shaft 54 to tilt with respect to the output shaft 41 </ b> A of the assist motor 41, and a mechanism for allowing the worm shaft 54 to translate with respect to the worm wheel 55. It is possible to have both.

(6) The worm speed reduction mechanism 50 includes a joint mechanism 60 that connects the output shaft 41A and the worm shaft 54.
The worm speed reduction mechanism 50 can have both a mechanism that allows the worm shaft 54 to tilt with respect to the output shaft 41 </ b> A of the assist motor 41 and a mechanism that allows the worm shaft 54 to translate relative to the worm wheel 55. become.

  (7) The translational elastic member 56, the motor-side elastic member 64, and the worm-side elastic member 65 are compressed or restored as the worm shaft 54 is translated by receiving the rotation of the worm wheel 55.

  The assist device 40 stops driving the assist motor 41 when the steering angle is within a predetermined range with zero as a reference in order to suppress the application of torque associated with the correction steering during straight traveling. Therefore, the assist motor 41 stops momentarily when the vehicle traveling direction is switched to the left or right. At this time, as the worm wheel 55 is rotated by the steering torque input by the driver, the worm shaft 54 receives a tangential force in the rotational direction of the worm wheel 55 and translates. In the configuration without the translational elastic member 56, the motor-side elastic member 64, and the worm-side elastic member 65, the worm shaft 54 translates until it contacts the ball bearing 57 or the output shaft 41A. The worm wheel 55 stops rotating when the worm shaft 54 contacts the ball bearing 57 or the output shaft 41A. As the driver stops the rotation, the rotation of the column shaft 31 stops, and the driver feels uncomfortable. According to the above configuration, since the translation elastic member 56, the motor side elastic member 64, and the worm side elastic member 65 are provided, the contact when the translation of the worm shaft 54 is stopped can be eased, and the driver's uncomfortable feeling is suppressed. .

  The present invention includes embodiments other than the above-described embodiment. Hereinafter, the modification of the said embodiment as other embodiment of this invention is shown. The following modifications can be combined with each other.

  -With reference to FIGS. 11-13, the coupling mechanism of a modification is demonstrated. The first yoke 61 and the second yoke 62 of the embodiment have a first groove portion 61C and a second groove portion 62C, respectively. In addition, the transmission member 63 of the embodiment has a first projecting surface 63A and a second projecting surface 63B. On the other hand, the modified first yoke 71 and second yoke 72 have a first projecting surface 71C and a second projecting surface 72C, respectively. Further, the transmission member 73 of the modified example includes a first groove portion 73B and a second groove portion 73D.

  As shown in FIG. 11, the joint mechanism according to the modification includes a first yoke 71 having a first projecting surface 71C, a second yoke having a second projecting surface 72C, a first groove 73B, and a second groove 73D. And a transmission member 73.

  As shown in FIG. 12, the first arm portion 71 </ b> B of the first yoke 71 has a first projecting surface 71 </ b> C that projects toward the transmission member 73. The second arm portion 72 </ b> B of the second yoke 72 has a second projecting surface 72 </ b> C that projects toward the transmission member 73. The transmission member 73 includes a first groove 73B having a shape corresponding to the first projecting surface 71C and a second groove 73D having a shape corresponding to the second projecting surface 72C.

  As shown in FIG. 13A, the first groove 73B is formed on the first protrusion 73A so as to follow an arc shape protruding outward from the rotation center U. The second groove 73D is formed on the second protrusion 73C so as to follow an arc shape that protrudes outward from the rotation center U.

  As shown in FIGS. 11 to 13, the joint mechanism according to the modification includes a plurality of first protrusion surfaces 71 </ b> C that extend in the first rotation center axis J direction and protrude from the surface on the first rotation center axis J side. The first yoke 71 having the first arm portion 71B is provided. In addition, the joint mechanism according to the modified example includes a plurality of second arm portions 72B that extend in the second rotation center axis K direction and have second protrusion surfaces 72C that protrude from the surface on the second rotation center axis K side. Two yokes 72 are provided. Further, the joint mechanism of the modified example has an arc shape that extends in the predetermined central axis direction and projects toward the first arm portion 71B, and corresponds to the first projecting surface 71C on the surface facing the first arm portion 71B. The transmission member 73 includes a plurality of first projecting portions 73A having first groove portions 73B having a shape to be formed. In addition, the transmission member 73 has an arc shape that extends in the predetermined central axis direction and protrudes toward the second arm portion 72B, and a shape that corresponds to the second protrusion surface 72C on a surface facing the second arm portion 72B. A plurality of second projecting portions 73C having the second groove portions 73D.

According to the said structure, there exists an effect according to the effect which the joint mechanism 60 of embodiment has. That is, the effect according to the effects described in the embodiments (1) to (7) is achieved.
The first yoke 61 and the second yoke 62 of the embodiment each have two arm portions. On the other hand, in the joint mechanism of the modification, the first yoke and the second yoke have three or more arm portions.

  The joint mechanism 60 of the embodiment transmits the rotation of the first yoke 61 to the second yoke 62 via the transmission member 63. On the other hand, the joint mechanism of the modified example transmits the rotation of the second yoke 62 to the first yoke 61 via the transmission member 63.

  In the first arm portion 61B of the embodiment, the tip and the second base portion 62A are in direct contact. The tip of the second arm portion 62B is in direct contact with the first base portion 61A. On the other hand, in the joint mechanism of the modified example, an elastic member (second elastic member) is provided between at least one of the tip of the first arm and the second base and between the tip of the second arm and the first base. .

  The joint mechanism 60 of the embodiment has play with respect to the rotation around the first rotation center axis J and the second rotation center axis K. On the other hand, the joint mechanism of the modified example has no play with respect to the rotation around the first rotation center axis J and the rotation around the second rotation center axis K. That is, the curvature RA and the curvature RB are substantially equal.

  -Joint mechanism 60 of an embodiment inclines when worm shaft 54 rotates in forward direction R1. On the other hand, the joint mechanism of the modified example is allowed to tilt when the worm shaft 54 rotates in the direction opposite to the normal rotation direction R1.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 10 ... Steering wheel, 20 ... Front wheel, 30 ... Steering device, 31 ... Column shaft, 32 ... Intermediate shaft, 33 ... Pinion shaft, 34 ... Rack and pinion mechanism, 35 ... Steering shaft, DESCRIPTION OF SYMBOLS 40 ... Assist device (electric power steering device), 41 ... Assist motor, 41A ... Output shaft (first rotating body), 42 ... Torque sensor, 43 ... Vehicle speed sensor, 44 ... Control device, 50 ... Worm deceleration mechanism, 51 ... Shaft housing portion 52 ... Bearing housing portion 53 ... End cover 54 ... Worm shaft (second rotating body) 55 ... Worm wheel 56 ... Translational elastic member 56A ... Shaft hole 56B ... Insertion portion 57 ... Ball Bearing, 58 ... pressing elastic member, 60 ... joint mechanism, 61 ... first yoke (first rotating body), 61A ... first base, DESCRIPTION OF SYMBOLS 1B ... 1st arm part, 61C ... 1st groove part, 61D ... 1st press-fit hole, 62 ... 2nd yoke (2nd rotary body), 62A ... 2nd base part, 62B ... 2nd arm part, 62C ... 2nd groove part , 62D ... second press-fit hole, 63 ... transmission member, 63A ... first projecting surface, 63B ... second projecting surface, 64 ... motor side elastic member (first elastic member), 64A ... flange, 65 ... worm side elastic member (First elastic member), 65A ... flange, 70 ... joint mechanism, 71 ... first yoke (first rotating body), 71A ... first base, 71B ... first arm, 71C ... first projecting surface, 71D ... First press-fit hole, 72 ... second yoke (second rotating body), 72A ... second base, 72B ... second arm, 72C ... second projecting surface, 72D ... second press-fit hole, 73 ... transmission member, 73A ... 1st protrusion part, 73B ... 1st groove part, 73C ... 2nd protrusion part, 73D ... 2nd groove part.

Claims (8)

A first rotating body that rotates about the first rotation center axis and a second rotating body that rotates about the second rotation center axis are connected to each other, and one of the first rotating body and the second rotating body is changed from one to the other. In a joint mechanism that transmits rotation,
The first rotation center extends in the first rotation center axis direction, protrudes from the first rotation body toward the second rotation body, and is positioned at a predetermined interval around the first rotation center axis. A first yoke having a plurality of first arm portions in which a first groove portion extending in the axial direction is formed on a surface on the first rotation center axis side;
It extends in the second rotation center axis direction, protrudes from the second rotation body toward the first rotation body, and is alternately positioned with the plurality of first arm portions around the second rotation center axis. A second yoke having a plurality of second arm portions in which a second groove portion extending in the second rotation center axis direction is formed on a surface on the second rotation center axis side;
A plurality of first arcs disposed in a space surrounded by the plurality of first arm portions and the plurality of second arm portions and extending in a predetermined rotation center axis direction and projecting toward the first groove portion. A plurality of second projecting surfaces extending in the direction of the predetermined rotation center axis and projecting toward the second groove portion, and the plurality of first projecting surfaces correspond to the first projecting surfaces; The second rotation center axis direction can be relatively translated in the first rotation center axis direction in contact with the first groove portion, and the plurality of second projecting surfaces are in contact with the corresponding second groove portions. The plurality of first projecting surfaces rotate around the first rotation center axis in a state where the plurality of first projecting surfaces are in contact with the corresponding first groove portions, and the plurality of second projecting surfaces correspond to each other. Contact with the second groove Joint mechanism and a transmission member for transmitting a rotational force from one to the other of the first yoke and the second yoke by rotating around the second rotation center axis in the state. A first rotating body that rotates about the first rotation center axis and a second rotating body that rotates about the second rotation center axis are connected to each other, and one of the first rotating body and the second rotating body is changed from one to the other. In a joint mechanism that transmits rotation,
The first rotation center extends in the first rotation center axis direction, protrudes from the first rotation body toward the second rotation body, and is positioned at a predetermined interval around the first rotation center axis. A first yoke having a plurality of first arm portions extending in the axial direction and formed with a first projecting surface projecting from the surface on the first rotation center axis side;
It extends in the second rotation center axis direction, protrudes from the second rotation body toward the first rotation body, and is alternately positioned with the plurality of first arm portions around the second rotation center axis. A second yoke having a plurality of second arm portions extending in the second rotation center axis direction and formed with a second projecting surface projecting from the surface on the second rotation center axis side;
Having a circular arc shape disposed in a space surrounded by the plurality of first arm portions and the plurality of second arm portions, extending in a predetermined rotation center axis direction and projecting toward the first arm portion; and A plurality of first protrusions having a first groove part having a shape corresponding to the first protrusion surface on a surface facing the first arm part, and extending in the predetermined rotation center axis direction and toward the second arm part A plurality of second projecting portions having a second groove portion having a shape corresponding to the second projecting surface on a surface opposed to the second arm portion. The first groove portion is relatively movable in the first rotation center axis direction in contact with the corresponding first protruding surface, and the plurality of second groove portions are in contact with the corresponding second protruding surface. The plurality of first groove portions are relatively movable in the second rotation center axis direction. It rotates around the first rotation center axis in a state where it is in contact with the corresponding first protrusion surface, and the second rotation center axis is around the second rotation center axis in a state where the plurality of second grooves are in contact with the corresponding second protrusion surface A joint mechanism having a transmission member that transmits a rotational force from one of the first yoke and the second yoke to the other by rotating to the other.     3. The joint mechanism according to claim 1, wherein each of the first protruding surfaces and each of the second protruding surfaces forms an arc-shaped cross section.   The joint mechanism according to any one of claims 1 to 3, wherein each of the first groove portion and the second groove portion has an arc-shaped cross section.   The said joint mechanism has a 1st elastic member in at least one between the said 1st rotary body and the said transmission member, and between the said 2nd rotary body and the said transmission member. The joint mechanism described in 1.   The joint mechanism has a second elasticity between at least one of the ends of the plurality of second arm portions and the first rotating body and between at least one of the ends of the plurality of first arm portions and the second rotating body. The joint mechanism as described in any one of Claims 1-5 which has a member.   A worm reduction mechanism having the joint mechanism according to claim 1, an output shaft of an electric motor as the first rotating body, and a worm shaft as the second rotating body.   An electric power steering apparatus comprising the joint mechanism according to claim 1, an output shaft of an electric motor as the first rotating body, and a worm shaft as the second rotating body.