JP4654532B2 - Joint structure, reduction mechanism and steering assist device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a joint structure for connecting an output shaft and a rotating shaft of an electric motor.And a speed reduction mechanism using the sameThe present invention relates to a steering assist device.
[0002]
[Prior art]
Conventionally, as a steering assist device for an automobile, as shown in FIG. 5, a first steering shaft 102 to which a steering wheel (handle) 101 is attached, and a second steering provided in series below the first steering shaft 102. The shaft 104 is connected to each other via the torsion bar 103, and the steering torque is detected by the torque sensor 105 based on the relative rotational displacement between the first steering shaft 102 and the second steering shaft 104. The steering assist electric motor 106 is driven based on the detection result of the torque sensor 105, and the rotation of the electric motor 106 is decelerated by the speed reduction mechanism 109 and transmitted to the second steering shaft 104, so that the manual operation by the steering wheel 101 is performed. An assisting steering force is provided.
[0003]
The speed reduction mechanism 109 includes a worm shaft 107 provided with a worm, and a synthetic resin worm wheel 108 attached to the second steering shaft 104 so as to rotate integrally with the worm. The worm shaft 107 is connected to the output shaft of the electric motor 106 through a joint so as to be integrally rotatable. Further, the worm shaft 107 and the second steering shaft 104 are respectively supported by bearings at both axial end portions thereof, and are prevented from moving in the radial direction and the axial length direction.
[0004]
In the above-described conventional steering assist device, when backlash occurs at the portion where the worm of the worm shaft 107 is engaged with the worm wheel 108, a so-called rattling noise is generated, which leaks into the vehicle and is inconvenient to the driver and passengers. May give a pleasant feeling. For this reason, the dimensions of the worm shaft 107 and the worm wheel 108 are selected at the time of manufacturing the apparatus, and the two are combined so that the backlash does not occur. However, even if the backlash is adjusted during the manufacture of the device in this way, the worm of the worm shaft 107 and the teeth of the worm wheel 108 are worn with the use of the steering assist device, so that the occurrence of backlash is avoided. It is difficult. Further, the worm wheel 108 made of synthetic resin may expand due to water absorption, heat, or the like, and the rotational torque (rotational resistance) may increase.
Therefore, by supporting the worm shaft 107 toward the worm wheel 108 so that the worm shaft 107 can be biased, the worm shaft 107 is biased toward the worm wheel 108 by a spring, thereby causing backlash and increasing rotational torque. There has been proposed a steering assist device that prevents such a situation.
[0005]
Specifically, in FIG. 6, in this conventional steering assist device, the worm shaft 107 is rotatably supported by the gear housing 110 via the first and second bearings 111 and 112. Further, at one end of the worm shaft 107, a serration 113 is press-fitted into a serration hole 114a formed in a cylindrical joint member 114. An output shaft 106a of the electric motor 106 is press-fitted into the joint member 114 so as to be integrally rotatable, and the worm shaft 107 and the output shaft 106a are connected to be able to rotate integrally through the serration 113 and the joint member 114. ing.
[0006]
The first bearing 111 is constituted by a ball bearing. One end of the worm shaft 107 is press-fitted into the inner ring of the first bearing 111 and is inserted into the first bearing hole 110 a of the gear housing 110. A cylindrical screw body 115 is screwed into the first bearing hole 110a to contact the outer ring of the first bearing 111 and prevent the worm shaft 107 from rattling in the axial direction. .
The second bearing 112 is constituted by a ball bearing, and is attached to the second bearing hole 110b of the gear housing 110 so as to be biased toward the worm wheel 108. That is, an arc-shaped gap 110c is provided between the inner back portion of the second bearing hole 110b and the second bearing 112, and the second bearing 112 is moved toward the worm wheel 108 by the gap 110c. It can be done. In addition, when the second bearing 112 is biased toward the worm wheel 108, the bias on the one end side of the worm shaft 107 is loose due to the radial clearance of the first bearing 111 or between the output shaft 106 a and the joint member 114. The worm shaft 107 is allowed to be eccentric and tilted with respect to the output shaft 106a.
[0007]
A biasing means 116 that biases the second bearing 112 toward the worm wheel 108 is attached to the opening side of the second bearing hole 110b. The urging means 116 is movably disposed in the second bearing hole 110b, and is supported by the support yoke 116a that abuts against the outer ring of the second bearing 112, and the support yoke 116a. A spring 116b that is biased toward the side 108, a screw body 116c that is screwed to the end of the second bearing hole 110b and adjusts the amount of deflection of the spring 116b, and a lock nut 116d that is screwed into the screw body 116c. I have.
With the above configuration, in this conventional steering assist device, when the worm 107a of the worm shaft 107 and the teeth of the worm wheel 108 are worn, the worm shaft 107 is biased toward the worm wheel 108 by the spring 116b, thereby backlash. Was prevented from occurring. Further, when the worm wheel 108 expands due to water absorption or heat, the worm shaft 107 is prevented from being released to the opposite side of the worm wheel 108 to increase the rotational torque.
[0008]
[Problems to be solved by the invention]
However, in the conventional steering assist device as described above, the worm shaft 107 and the output shaft 106a are connected using the serration 113 and the joint member 114, so that one end of the worm shaft 107 is connected to the first bearing. Therefore, there is a problem that the length of the worm shaft 107 in the axial direction becomes longer and the apparatus becomes larger.
[0009]
Further, since one end portion of the worm shaft 107 protrudes from the first bearing 111 toward the electric motor 106 and is connected to the output shaft 106a, the one end portion is restrained by the output shaft 106a, and the radial direction of the first bearing 111 is increased. Since the rattling due to the gap cannot be used effectively, the adjustment amount of the deviation amount by the urging means 116 at the other end of the worm shaft 107, that is, the eccentricity between the output shaft 106a and the worm shaft 107, and Tilt adjustment range was limited to a small value. In addition, since the adjustment range of the eccentricity and tilting of the output shaft 106a and the worm shaft 107 is limited to a small value in this way, when the worm shaft 107 and the electric motor 106 are assembled to the gear housing 110, the output shaft 106a Therefore, it is necessary to align the worm shaft 107 with the worm shaft 107 with high accuracy, and it is difficult to connect the output shaft 106a and the worm shaft 107.
[0010]
  In view of the conventional problems as described above, the present invention can connect an output shaft of an electric motor and a rotary shaft rotated by the output shaft in a small space, and the output shaft and the rotary shaft. Joint structure that makes it possible to increase the adjustment range of eccentricity and tilting with respect to the output shaft and thereby facilitate the connection work between the output shaft and the rotating shaftAnd a speed reduction mechanism using the sameAn object is to provide a steering assist device.
[0011]
  The joint structure of the present invention enables a rotary shaft supported rotatably by a bearing to rotate integrally with an output shaft of an electric motor.directlyA connecting joint structure,
  With the center position of the bearing in the axial direction of the rotating shaft, with the center position of the connecting portion between one end of the rotating shaft and the output shaft substantially matched, the rotating shaft and the output shaft Connected to each other in a swingable manner, and
  The center of oscillation is the bearingcenterIt is a position (Claim 1).
[0012]
According to the joint structure configured as described above, in the state where the center position of the connecting portion between the one end portion of the rotating shaft and the output shaft of the electric motor is substantially matched with the above-described center position of the bearing, the bearing By supporting the rotating shaft in a freely rotatable manner, the other end portion of the rotating shaft can be largely deviated from the output shaft by utilizing the shakiness caused by the radial gap of the bearing very effectively. Therefore, the adjustment range of the eccentricity and tilting of the output shaft and the rotation shaft can be increased, and thus the connection work between the output shaft and the rotation shaft can be easily performed. Moreover, the joint structure is simple and the axial length can be shortened.
[0013]
  In the joint structure (Claim 1), the rotating shaft and the output shaft are slidably connected to each other.BecauseThus, the adjustment range of the eccentricity and tilting between the output shaft and the rotating shaft can be further increased, so that the connecting operation between the output shaft and the rotating shaft can be performed more easily.
[0014]
  The speed reduction mechanism of the present invention is a speed reduction mechanism for transmitting the rotation of the electric motor at a reduced speed,
  A worm shaft connected to the output shaft of the electric motor using the joint structure according to claim 1;
  A worm wheel that can be meshed with a worm integrally formed in an intermediate portion of the worm shaft;
  With
  The worm shaft is supported so as to be deflectable toward the worm wheel, and the worm shaft is urged toward the worm wheel by urging means (claim 2).
  Further, the steering assist device of the present invention steers by transmitting the rotation of the electric motor to the steering shaft via the worm shaft as the rotating shaft provided with the worm and the worm wheel meshed with the worm of the worm shaft. In the steering assist device for assisting,
  A bearing attached to one end of the worm shaft and rotatably supporting the worm shaft;
  A joint structure having a concave portion provided on one end portion side of the worm shaft and a convex portion provided on the output shaft side of the electric motor and engaged with the concave portion is provided at a connecting portion between the worm shaft and the output shaft. And
  With the center position of the bearing in the axial direction of the worm shaft substantially aligned with the center position of the connecting portion, the worm shaft and the output shaft aredirectlyConsolidated
  The worm shaft is supported to be deflectable toward the worm wheel, the worm shaft is urged toward the worm wheel by the urging means, and
  The center of oscillation of the worm shaft is the bearingcenterIt is a position (Claim 3).
[0015]
  Configured as aboveDeceleration mechanism andAccording to the steering assist device, the rotation of the output shaft of the electric motor can be transmitted to the worm shaft through the joint structure. In addition, the other end of the worm shaft can be greatly deviated from the output shaft by making effective use of rattling due to the radial clearance of the bearing, so that the eccentricity and tilting of the output shaft and the worm shaft can be prevented. The adjustment width can be increased, and the connecting operation between the output shaft and the worm shaft can be easily performed. In addition, since the joint structure is simple and the length in the axial direction can be shortened, the output shaft and the worm shaft can be connected in a small space.
[0016]
  Also, aboveDeceleration mechanism andSteering aidIn placeLeaveIsThe worm shaft is supported to be deflectable toward the worm wheel, and the worm shaft is biased toward the worm wheel by the biasing means.The
  In this case, since the worm shaft can be biased toward the worm wheel, coupled with the fact that the adjustment range of the eccentricity and tilting of the output shaft and the worm shaft is increased, the worm shaft is directed toward the worm wheel without difficulty. Can be moved. For this reason, the worm shaft can be reliably moved by following the wear of the worm wheel by the biasing means.
  In the steering assist device described above, the connection between the concave portion and the convex portion can be a spline connection including a spline hole and a spline shaft.
[0017]
  Further, the steering assist device (claim)3), The convex portion is constituted by a tip portion of the output shaft formed in a drum shape with a regular polygonal cross section and a bulging central portion in the axial direction, and the concave portion is one end portion of the worm shaft. It is preferable that the tip end portion is pivotably connected so as to be formed by cutting out the shape into a regular polygonal cross section in the axial direction.
  In this case, the output shaft and the worm shaft can be directly connected without providing dedicated joint members that respectively constitute the convex portion and the concave portion, and the configuration of the apparatus can be simplified. In addition, since the tip is pivotably connected to the recess, the adjustment range of the eccentricity and tilting of the output shaft and the worm shaft can be increased, so that the connection work between the output shaft and the worm shaft is possible. Can be performed more easily.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the joint structure of the present inventionSpeed reduction mechanism and operation using the sameA preferred embodiment showing a rudder auxiliary device will be described with reference to the drawings.
  FIG. 3 is a cross-sectional view showing the overall structure of the steering assist device of the present invention. The steering assist device includes a first steering shaft 2 that attaches a steering wheel 1 to the upper end, a cylindrical second steering shaft 4 that is connected to the lower end of the first steering shaft 2 via a torsion bar 3, and the first A torque sensor 5 that detects a steering torque based on a relative rotational displacement between the first steering shaft 2 and the second steering shaft 4; and a steering assisting electric motor 6 that is driven based on the detection result of the torque sensor 5. A reduction mechanism 7 that reduces the rotation of the electric motor 6 and transmits it to the second steering shaft 4 is provided.
  The first steering shaft 2 is supported by being surrounded by a first steering column 9 and a second steering column 10, and the first steering column 9 is attached to the vehicle body A via a bracket 12. The torque sensor 5 is housed in a sensor housing H1, the speed reduction mechanism 7 is housed in a gear housing H2, and the electric motor 6 is attached to the gear housing H2.
[0019]
The first steering shaft 2 has a cylindrical first shaft body 2a with the steering wheel 1 attached to an upper end portion thereof, and a state where the lower end portion of the first shaft body 2a is allowed to move in the axial direction. A rod-shaped second shaft body 2b fitted to be integrally rotatable is provided, and a cylindrical third shaft body 2d connected to the second shaft body 2b by a pin 2c. The intermediate portion of the first shaft body 2 a is rotatably supported by a cylindrical first steering column 9 via a bearing 13. In addition, a buffer member 2e made of synthetic resin is provided between the first and second shaft bodies 2a and 2b for absorbing impact energy acting on the steered wheels 1 from the driver at the time of a car collision or the like. Yes. Further, the torque sensor 5 is disposed between the third shaft body 2 d and the second steering shaft 4.
[0020]
The upper end of the second steering column 10 is slidably fitted to the first steering column 9, and the lower end is fitted to the sensor housing H1. When the impact energy is absorbed, the first steering column 10 is The steering column 9 can be moved in the axial direction with respect to the second steering column 10.
A torsion bar 3 is introduced into the second steering shaft 4, and a lower end portion of the second steering shaft 4 is connected to the torsion bar 3 by a pin 4a so as to be integrally rotatable. An intermediate portion in the axial direction of the second steering shaft 4 is rotatably supported by the gear housing H2 via a pair of bearings 14 and 15, and a worm wheel is interposed between the bearings 14 and 15 between 4b. The inner periphery of 72 is fitted so as to be integrally rotatable.
[0021]
As shown in FIG. 1, the speed reduction mechanism 7 is fitted to a worm shaft 70 connected to the output shaft 60 of the electric motor 6 using the joint structure 8 of the present invention, and the second steering shaft 4 so as to be integrally rotatable. And the combined worm wheel 72. A worm 71 is integrally formed at an intermediate portion in the axial direction of the worm shaft 70, and the worm 71 is engaged with a worm wheel 72. Therefore, the rotation of the output shaft 60 of the electric motor 6 can be decelerated by the worm shaft 70 and the worm wheel 72 and transmitted to the second steering shaft 4. The rotation of the second steering shaft 4 is transmitted via a universal joint J (see FIG. 3) to, for example, a rack and pinion type steering mechanism connected to a wheel.
[0022]
The worm shaft 70 is disposed so as to be orthogonal to the axis of the second steering shaft 4, and one end portion 70 a and the other end portion 70 b are respectively connected to the gear housing via the first and second bearings 16 and 17. It is rotatably supported by the first and second bearing holes 91 and 92 of H2 (see FIG. 1).
The first bearing 16 is constituted by a ball bearing. One end portion 70a of the worm shaft 70 is press-fitted into the inner ring 16a, and the outer ring 16b is inserted into the first bearing hole 91. A cylindrical screw body 18 is screwed into the first bearing hole 91 to contact the outer ring 16b of the first bearing 16 and prevent the worm shaft 70 from rattling in the axial length direction. ing.
The second bearing 17 is constituted by a metal bearing, and is attached to the second bearing hole 92 so as to be biased toward the worm wheel 72. That is, as shown in FIG. 4, a gap 92a is provided between the inner back portion of the second bearing hole 92 and the second bearing 17, and the second bearing 17 is warmed by the gap 92a. It can move to the wheel 72 side.
[0023]
A plug 34 is screwed into the opening side of the second bearing hole 92. Between the plug 34 and the second bearing 17, the second bearing 17 is constantly urged toward the worm wheel 72. A compression coil spring 32 as an urging means is interposed in an elastically contracted state. In the case of the figure, the compression coil spring 32 is accommodated inside a bottomed cylindrical projection 17b that projects from the outer periphery of the outer ring 17a of the second bearing 17. The biasing force of the compression coil spring 32 is adjusted to an optimum value by adjusting the screwing amount of the plug 34 into the second bearing hole 92. The plug 34 is fixed by a lock nut 35.
In addition to the above configuration, for example, as in the case shown in FIG. 6, the second bearing 17 is configured by a ball bearing, and the support yoke movably disposed in the second bearing hole 92 is biased by a spring. Thus, the second bearing 17 may be urged toward the worm wheel 72.
[0024]
As shown in FIG. 1, the joint structure 8 includes a concave portion 8a provided on the one end portion 70a side of the worm shaft 70 and a convex portion 8b provided on the output shaft 60 side and engaged with the concave portion 8a. In the state where the central position of the connecting portion constituted by the concave portion 8a and the convex portion 8b is substantially matched with the central position of the first bearing 16 in the axial direction of the worm shaft 70, the worm The shaft 70 and the output shaft 60 are connected.
[0025]
As shown in FIGS. 2A and 2B, the convex portion 8b is formed by processing the tip end portion of the output shaft 60 into a drum shape in which the central portion in the axial direction bulges, for example, with a regular hexagonal cross section. It is a thing. The concave portion 8a is formed by cutting out one end portion 70a of the worm shaft 70 in the axial direction, and the convex portion (tip portion) 8b is connected to be swingable. Thus, by processing the one end portion 70a of the worm shaft 70 to be connected and the tip portion of the output shaft 60 into the concave portion 8a and the convex portion 8b, respectively, the output shaft 60 and the worm shaft can be provided without providing a dedicated joint member. 70 can be directly connected. Furthermore, since the convex portion 8b is swingably connected to the concave portion 8a, the other end portion 70b of the worm shaft 70 can be biased more greatly with respect to the output shaft 60.
The concave portion 8a and the convex portion 8b are not limited to a regular hexagonal cross section as long as the rotation of the output shaft 60 can be transmitted to the worm shaft 70, but the torque from the output shaft 60 to the worm shaft 70 is not limited. Those having a regular tetragonal to octagonal cross section with little transmission loss are preferred.
[0026]
As described above, in the steering assist device of the present embodiment, the worm shaft 70 and the output shaft 60 are connected by the joint structure 8, and the center position of the connecting portion is set in the axial direction of the worm shaft 70 of the first bearing 16. Therefore, the other end portion 70b of the worm shaft 70 can be biased with respect to the output shaft 60 around the first bearing 16, and the radial direction of the first bearing 16 can be made. The other end portion 70b of the worm shaft 70 can be largely biased with respect to the output shaft 60 by making effective use of the rattling due to the gap and the rattling due to the gap at the connecting portion. Therefore, the adjustment range of the eccentricity and tilting of the output shaft 60 and the worm shaft 70 can be increased, so that the connection accuracy between the worm shaft 70 and the output shaft 60 does not need to be particularly increased, and the connection work is facilitated. Yes. In addition, the joint structure 8 is simple, and unlike the above-described conventional example using serrations and joint members, the axial length can be extremely shortened, and the reduction mechanism 7 can be downsized accordingly. .
[0027]
In the present embodiment, the worm shaft 70 is supported to be deflectable toward the worm wheel 72, and the worm shaft 70 is biased toward the worm wheel 72 by the compression coil spring 32. 71 can be elastically pressed against the worm wheel 72. Furthermore, coupled with the fact that the adjustment range of eccentricity and tilting of the output shaft 60 and the worm shaft 70 is increased, the worm shaft 70 can be moved toward the worm wheel 72 without difficulty. Therefore, even when the tooth surfaces of the worm 71 and the worm wheel 72 are worn due to long-term use, it is possible to prevent the backlash from occurring due to the worm 71 following the wear. Further, when the synthetic resin worm wheel 72 expands due to water absorption or heat, it is possible to prevent the worm shaft 70 from escaping to the opposite side of the worm wheel 72 to increase the rotational torque. In addition, since the worm 71 of the worm shaft 70 can be elastically pressed against the worm wheel 72 as described above, the backlash is adjusted without being affected by the dimensional error of the parts including the two when assembled. be able to.
[0028]
Further, the concave portion 8a and the convex portion 8b of the joint structure 8 are formed by processing the one end portion 70a of the worm shaft 70 to be connected and the tip end portion of the output shaft 60, respectively. The output shaft 60 and the worm shaft 70 can be directly connected without providing a dedicated joint member constituting each of the portions 8b, and the configuration of the device can be simplified. Further, since the convex portion 8b is slidably connected to the concave portion 8a, the adjustment range of the eccentricity and tilting of the output shaft 60 and the worm shaft 70 can be further increased. The connecting operation with the shaft 70 can be performed more easily.
[0029]
In the above description, the configuration for connecting the output shaft 60 of the electric motor 6 and the worm shaft 70 has been described. However, the joint structure of the present invention is not limited to this, and the bearing in the axial direction of the rotating shaft is not limited thereto. If the rotation shaft and the output shaft are connected in a state where the center position of the connecting portion between the one end portion of the rotation shaft and the output shaft is substantially matched to the center position of the output shaft 60, It can also be suitably used as a joint structure that connects various rotating shafts that are rotationally driven by the output shaft 60. For example, a spline hole and a spline shaft are provided at one end portion 70a of the worm shaft 70 and the tip end portion of the output shaft 60, respectively, and the center position of the spline coupling substantially matches the above-described center position of the first bearing 16. But you can.
[0030]
【The invention's effect】
As described above, according to the joint structure of the first aspect, the other end portion of the rotating shaft is largely biased with respect to the output shaft of the electric motor by extremely effectively using the rattling caused by the radial clearance of the bearing. Therefore, the adjustment range of eccentricity and tilting of the output shaft and the rotation shaft can be increased. As a result, it is not necessary to align the output shaft and the rotating shaft with high accuracy, and the connecting operation of the two can be performed easily. In addition, since the joint structure is simple and small, the output shaft and the rotating shaft can be connected in a small space. For this reason, size reduction of various apparatuses provided with an electric motor and a rotating shaft can be achieved.
[0031]
  AlsoSince the rotary shaft and the output shaft are pivotably connected to each other, the adjustment range of the eccentricity and tilting of the output shaft and the rotary shaft can be increased, and thus the connecting operation of the output shaft and the rotary shaft is possible. Can be performed more easily.
[0032]
  The speed reduction mechanism according to claim 2 andAccording to the steering assist device of the third aspect, the output shaft of the electric motor and the worm shaft are connected using a joint structure having a simple structure and a short length in the axial direction. Can be planned. In addition, the other end of the worm shaft can be greatly deviated from the output shaft by making effective use of rattling due to the radial clearance of the bearing, so that the eccentricity and tilting of the output shaft and the worm shaft can be prevented. The adjustment range can be increased. As a result, it is not necessary to align the output shaft and the worm shaft with high accuracy, and the connecting operation of the two can be performed easily.
[0033]
  AlsoSince the worm shaft can be biased toward the worm wheel, the worm shaft can be moved toward the worm wheel without difficulty, coupled with the fact that the adjustment range of eccentricity and tilt between the output shaft and the worm shaft is increased. be able to. For this reason, the urging means can easily move the worm following the wear of the worm wheel, thereby preventing the backlash from occurring easily and reliably.
[0034]
According to the steering assist device of the fifth aspect, the output shaft and the worm shaft can be directly connected without providing dedicated joint members respectively constituting the convex portion and the concave portion. The configuration can be simplified. In addition, since the convex portion is connected to the concave portion so as to be able to swing, the adjustment range of the eccentricity and tilting of the output shaft and the worm shaft can be further increased, and thus the connecting operation of the output shaft and the worm shaft is possible. Can be performed more easily.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an electric motor and a speed reduction mechanism portion of a steering assist device according to an embodiment of the present invention.
2A is a perspective view showing a convex portion provided at the tip of the output shaft of the electric motor shown in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line IIb-IIb in FIG.
FIG. 3 is a cross-sectional view showing the overall structure of the steering assist device of the present invention.
4 is a cross-sectional view taken along line IV-IV in FIG.
FIG. 5 is a cross-sectional view showing the entire structure of a conventional steering assist device.
FIG. 6 is a cross-sectional view showing an electric motor and a speed reduction mechanism in another conventional steering assist device.
[Explanation of symbols]
1 Steering wheel
32 Compression coil spring (biasing means)
6 Electric motor
60 output shaft
7 Deceleration mechanism
70 Worm shaft (rotary shaft)
70a one end
71 Warm
72 Worm Wheel
8 Joint structure
8a recess
8b Convex part
16 First bearing (bearing)
17 Second bearing

Claims (5)

A joint structure for directly connecting a rotating shaft rotatably supported by a bearing to an output shaft of an electric motor so as to be integrally rotatable;
With the center position of the bearing in the axial direction of the rotating shaft substantially aligned with the center position of the connecting portion between one end of the rotating shaft and the output shaft, the rotating shaft and the output shaft are Connected to each other in a swingable manner, and
A joint structure characterized in that a center of the swing is a center position of the bearing. A speed reduction mechanism for decelerating and transmitting the rotation of the electric motor,
A worm shaft connected to the output shaft of the electric motor using the joint structure according to claim 1;
It has a worm wheel that can be meshed with the worm that is integrally formed in the middle part of this worm shaft,
A speed reduction mechanism characterized by supporting the worm shaft toward the worm wheel so that it can be biased, and urging the worm shaft toward the worm wheel by an urging means. In a steering assist device for assisting steering by transmitting rotation of an electric motor to a steering shaft via a worm shaft as a rotating shaft provided with a worm and a worm wheel meshed with the worm of the worm shaft,
A bearing attached to one end of the worm shaft and rotatably supporting the worm shaft;
A joint structure having a concave portion provided on one end portion side of the worm shaft and a convex portion provided on the output shaft side of the electric motor and engaged with the concave portion is provided at a connecting portion between the worm shaft and the output shaft. And
The worm shaft and the output shaft are directly connected to a center position of the bearing in the axial direction of the worm shaft in a state where the center position of the connecting portion is substantially matched.
The worm shaft is supported to be deflectable toward the worm wheel, the worm shaft is urged toward the worm wheel by the urging means, and
A steering assist device, wherein the center of oscillation of the worm shaft is a center position of the bearing.   The steering assist device according to claim 3, wherein the connection between the concave portion and the convex portion is a spline coupling including a spline hole and a spline shaft. The convex portion is constituted by a tip portion of the output shaft formed in a drum shape with a regular polygonal cross section and a bulging center portion in the axial direction,
4. The steering assist according to claim 3, wherein the recess is formed by cutting one end portion of the worm shaft into a regular polygonal cross section in the axial direction, and the tip end portion is swingably connected. apparatus.

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