JP2014097777A - Transmission ratio variable device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission ratio variable device capable of reducing a variation in a preload applied to a bearing gear, with a simple constitution.SOLUTION: A preload adjustment plug 78 is fastened by a screw to an input shaft 22, and a coil spring 80 is installed between the input shaft 22 and the preload adjustment plug 78. One end part of the coil spring 80 is inserted into a fixing through-hole 81 of the input shaft 22, and the other end part is inserted into one place of a plurality of fixing through-holes 82 provided in the circumferential direction of the preload adjustment plug 78 and penetrating in the axial direction. At this time, even if a clearance is formed in a meshing part of center bearing both end parts, the coil spring 80 receives torsional torque around the axis, and the preload adjustment plug 78 rotates in the direction for filling up the clearance of the meshing part of a center bearing by fastening torque of operating on the coil spring 80, and prevents reduction in preload force.

Description

  The present invention relates to a transmission ratio variable device.

  Conventionally, various transmission mechanisms using gears are known, and there is a demand for a transmission mechanism that can obtain a large reduction ratio with a small number of parts and a large transmission capacity. As such a transmission mechanism, by using a differential mechanism, the rotation of the input shaft based on the steering operation is added to the rotation based on the motor drive and transmitted to the output shaft, so that the rotation transmission ratio between the input and output shafts (the steering gear) A transmission ratio variable device that changes the ratio) and a vehicle steering device including the same have been proposed (see, for example, Patent Document 1).

  Such a reduction mechanism of the transmission ratio variable device includes a first gear that rotates integrally with the input shaft, a fourth gear that rotates integrally with the output shaft, a second gear that meshes with the first gear, and a third gear that meshes with the fourth gear. An oscillating gear mechanism having a gear and having an oscillating gear rotating around an axis inclined with respect to the axis of the first and fourth gears is provided as a differential mechanism. The oscillating gear rotates due to the difference in the number of teeth of the first gear and the second gear, and the fourth gear and the third gear, which are engaged with each other while oscillating in the axial direction of the input shaft via the bearing. The input is decelerated and transmitted to the output shaft, and the rotation transmission ratio between the input shaft and the output shaft is changed by rotating the oscillating gear using the driving means.

JP 2006-82718 A

  In such a transmission ratio variable device, there is a case in which an oscillating gear mechanism (reduction gear), that is, a so-called bearing gear meshing portion is displaced and abnormal noise is generated. Therefore, a structure is used in which axial preload (load) is applied to the meshing portion of the bearing gear in order to mesh at a stable position and suppress abnormal noise. For example, by applying a preload in the axial direction to the bearing gear with an elastic member such as a spring, or by using a method of providing a preload plug on the input shaft side and tightening and fixing while adjusting the tightening torque, Maintains good meshing condition. However, when the axial force of the preload plug is applied as a preload of the meshing portion of the bearing gear, the meshing occurs when the tooth surface is worn when the bearing gear is fixed by tightening the preload plug fixed to the input shaft. A gap occurs in the part. In addition, for example, when the aluminum material forming the housing and the iron material forming other members coexist in the path for applying the preload, the preload amount may change due to a temperature change. Therefore, it is necessary to manage the preload amount by the tightening torque of the preload plug, but there is a possibility that the preload amount is unstable due to large variations in preload due to wear or the like.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a transmission ratio variable device capable of reducing variations in preload applied to the bearing gear with a simple configuration. .

  In order to solve the above-mentioned problem, a transmission ratio variable device according to claim 1 includes an input shaft coupled to a steering wheel, a housing that supports the input shaft so as to be relatively rotatable, and a motor output with respect to the housing. A motor provided with a shaft capable of relative rotation, a speed reducer connected to the motor output shaft to output a turning angle with a reduced motor rotation angle, and the turning angle output from the speed reducer on the steered wheel side An output shaft that transmits to the first shaft, and the speed reducer is provided on the input shaft so as to be integrally rotatable and has first teeth formed on an end surface thereof, and is provided on the output shaft so as to be integrally rotatable. A fourth gear having fourth teeth formed on an end surface thereof facing the end surface of the first gear, an inclined shaft provided obliquely with respect to the input shaft, and supported by the inclined shaft so as to be relatively rotatable. The first and fourth gears; A second gear and a third gear having second and third teeth formed on different end faces so as to mesh with each other, and the rotation of the inclined shaft between the first and fourth gears An oscillating gear that rotates according to the difference in the number of teeth of either the first or fourth gear and the second and third gears while oscillating in the axial direction, and is movable in the axial direction on the input shaft And a preload adjusting plug that urges the input shaft in a direction to approach the output shaft, and the axial position of the input shaft of the preload adjusting plug moves to the speed reducer side. The gist of the invention is that a preload applying mechanism is provided for applying the axial preload to the speed reducer.

  According to the above configuration, when a tightening torque is applied to the preload adjusting plug that is rotatably screwed to the input shaft, the input shaft is pressed in the axial direction by the preload adjusting plug, and the gears of the reduction gears mesh with each other. Since the preload is applied to the portion, it is possible to adjust the axial preload applied to the reduction gear by changing the position of the preload adjusting plug. Thereby, since the preload in the axial direction of the input shaft is kept constant, it is possible to reduce variations in the size of the preload applied to the speed reducer.

  According to a second aspect of the present invention, in the transmission ratio variable device according to the first aspect, the preload applying mechanism is constructed between the input shaft and the preload adjusting plug and presses the preload adjusting plug. The gist of the present invention is to provide a coil spring that is movably rotated in the axial direction of the input shaft. According to the above configuration, the preload adjusting plug acts so that the axial gap of the meshing portion of each gear of the reduction gear is narrowed by the coil spring spanned between the input shaft and the preload adjusting plug. Further, it is possible to further reduce the axial backlash and prevent the preload from being reduced. Therefore, generation | occurrence | production of the noise and vibration in a reduction gear can be suppressed more.

  According to a third aspect of the present invention, in the transmission ratio variable device according to the second aspect, the preload adjusting plug has a plurality of fixing through-holes provided at one end side of the coil spring in the circumferential direction and inserted in the axial direction. The main point is that According to the above configuration, a plurality of through holes for fixing are provided in the circumferential direction in which one end side of the coil spring is inserted in the axial direction in the preload adjusting plug, and the torsion angle when the coil spring is attached can be changed. By setting the angle according to the spring constant and adjusting the torsional torque of the coil spring, the tightening torque of the preload adjusting plug can be adjusted with high accuracy.

  ADVANTAGE OF THE INVENTION According to this invention, the transmission ratio variable apparatus which can reduce the dispersion | variation in the preload provided to a bearing gear by simple structure can be provided.

The schematic diagram which shows schematic structure of the steering apparatus for vehicles provided with the transmission ratio variable apparatus which concerns on one Embodiment of this invention. The longitudinal section of the transmission ratio variable device concerning one embodiment of the present invention. FIG. 3 is a schematic view of a preload application mechanism in FIG. 2.

Next, a transmission ratio variable device mounted on a vehicle according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a vehicle steering apparatus 1 including a transmission ratio variable device 15 according to an embodiment of the present invention, and FIG. 2 is a transmission ratio variable device 15 according to an embodiment of the present invention. FIG. As shown in FIG. 1, in the vehicle steering apparatus 1, a steering shaft 3 to which a steering wheel 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. Thereby, the rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 is configured by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. Then, the reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, whereby the steering angle of the steered wheels 12, That is, the traveling direction of the vehicle is changed. The vehicle steering apparatus 1 according to the present embodiment converts the rotation of the assist motor 13 into the reciprocating motion of the rack shaft 5 by the ball screw mechanism 14 and transmits the converted torque to the steering system as an assist force. A so-called rack assist type electric power steering device is provided.

  The vehicle steering apparatus 1 includes a transmission ratio variable device 15 that varies the ratio of the steering angle (tire angle) of the steered wheels 12 to the steering angle (steering angle) of the steering wheel 2, that is, the transmission ratio (steering gear ratio). It is provided in the middle of the shaft 8. As shown in FIG. 2, the transmission ratio variable device 15 includes a substantially cylindrical housing 21 that is fixed to a vehicle body (not shown) of an automobile, and an input shaft 22 that serves as an input shaft to which rotation associated with a steering operation is input. And an output shaft 23 as an output shaft connected to the intermediate shaft 9 (see FIG. 1). The input shaft 22 and the output shaft 23 are rotatably supported with respect to the housing 21 and constitute the column shaft 8 (see FIG. 1). That is, the housing 21 is a non-rotating member that does not rotate due to the rotation of the input shaft 22. The transmission ratio variable device 15 includes a motor 24 housed in the housing 21 and a bearing gear (reduction gear) 25 as a differential mechanism. The transmission ratio variable device 15 uses a bearing gear 25 to add rotation based on motor drive to the rotation of the input shaft 22 and transmit it to the output shaft 23. Furthermore, the transmission ratio variable device 15 includes a lock mechanism 26 that can lock (restrict) the rotation of the motor 24 as necessary to mechanically fix the transmission ratio.

  Specifically, the housing 21 includes a cylindrical housing body 31 in which the motor 24 is accommodated, an annular upper cover 32 that covers one axial end side of the housing body 31 (right side in FIG. 2: arrow a1 side), a bearing An annular lower cover 33 that accommodates the gear 25 and covers the other axial end of the housing body 31 (left side in FIG. 2: arrow a2 side) is provided. The housing body 31 is formed with an annular partition wall 34 extending radially inward at substantially the center thereof, and the arrow a1 side of the partition wall 34 is a motor housing section 35 in which the motor 24 is housed. The arrow a2 side of the partition wall portion 34 is a gear housing portion 36 in which the bearing gear 25 is housed. The housing 21 includes a bottomed cylindrical lock case 37 that is fixed to the arrow a1 side of the upper cover 32. A lock mechanism 26 is accommodated in the lock case 37. The input shaft 22 is rotatably supported by a ball bearing 38 provided at the bottom of the lock case 37, and the output shaft 23 is rotatably supported by a ball bearing 39 provided on the lower cover 33. The input shaft 22 and the output shaft 23 are arranged coaxially with each other.

  The motor 24 is configured as a brushless motor including a stator 41 that is fixed in the motor housing 35 and a rotor 42 that is rotatably provided inside the stator 41. The motor rotation shaft (output shaft) 45 is formed in a hollow shape, and the input shaft 22 is coaxially inserted into the motor rotation shaft 45. Further, the axial length of the motor rotating shaft 45 is set to be longer than the axial length of the motor housing portion 35, and the shaft end on the arrow a1 side is disposed in the lock case 37, and the arrow The shaft end portion on the a2 side is disposed in the gear housing portion 36. The motor rotation shaft 45 is rotatably supported by a ball bearing 48 provided on the upper cover 32 and a ball bearing 49 provided on the partition wall 34. A housing recess recessed toward the motor housing 35 is formed in the center of the upper cover 32, and a rotation angle sensor 52 (for example, a resolver or the like) that detects the rotation angle of the rotor 42 is formed in the housing recess. ) Is housed.

  As shown in FIG. 2, an inclined shaft 53 is coupled to the shaft end portion on the arrow a2 side of the motor rotation shaft 45 so as to be integrally rotatable. The inclined shaft 53 has an axis L2 that is inclined with respect to the axis L1 of the motor rotation shaft 45 (the axis of the input shaft 22 and the output shaft 23). The outer peripheral surface of the inclined shaft 53 has a cylindrical shape inclined with respect to the axis L1. A radial needle bearing 56 that functions as a bearing is interposed between the inclined shaft 53 and the input shaft 22.

  The bearing gear 25 includes a Z1 gear (first gear) 61 coupled to the input shaft 22 so as to be integrally rotatable, a Z4 gear (fourth gear) 62 coupled to the output shaft 23 so as to be integrally rotatable, and a Z1 gear 61. And a Z4 gear 62, and a center bearing (oscillating gear) 63 connected to the motor rotation shaft 45 via an inclined shaft 53.

  Specifically, the Z1 gear 61 is formed in a disk shape, and a plurality of first teeth protruding toward the arrow a1 side are provided along the circumferential direction on the outer peripheral edge of the Z1 gear 61. In the present embodiment, each first tooth is constituted by a cylindrical roller that is arranged radially with respect to the Z1 gear 61 and is arranged so as to be rotatable about its axis. The Z1 gear 61 is formed with a through-hole penetrating in the axial direction at the center thereof. The Z1 gear 61 is connected to the input shaft 22 so as to be integrally rotatable with the input shaft 22 by serration fitting the shaft end portion of the input shaft 22 into the through hole. That is, the axis of the Z1 gear 61 coincides with the axis L1 of the motor rotation shaft 45.

  The Z4 gear 62 is formed in an annular shape, and the Z4 gear 62 is provided with a plurality of fourth teeth that protrude toward the arrow a2 side in the circumferential direction. In addition, in this embodiment, each 4th tooth | gear is comprised by the cylindrical roller arrange | positioned so that it can rotate to the surroundings of the axis line similarly to the Z1 gear 64, and is arrange | positioned radially with respect to the Z4 gear 62. Yes. The Z4 gear 62 is fixed to the inner periphery of a connecting cylinder 67 formed in a cylindrical shape, and is connected to the output shaft 23 via the connecting cylinder 67. The connecting cylinder 67 is rotatably supported by a ball bearing 68 provided adjacent to the partition wall 34 on the arrow a2 side, and is connected to the output shaft 23 so as to be integrally rotatable. That is, the Z4 gear 62 is connected to the output shaft 23 via the connecting cylinder 67 so as to be rotatable integrally therewith, and the axis of the Z4 gear 62 coincides with the axis L1 of the motor rotating shaft 45. . Ball bearings 69 and 70 are interposed between the connecting cylinder 67 and the Z1 gear 61 and between the inclined shaft 53 and the Z4 gear 62, respectively.

  The center bearing 63 includes a cylindrical inner ring, a cylindrical outer ring gear, and rolling elements (balls) interposed between the inner ring and the outer ring gear. A plurality of second teeth that can mesh with the first teeth are provided side by side in the circumferential direction on the end surface of the outer ring gear on the arrow a2 side (Z1 gear 61 side). On the other hand, on the end surface of the outer ring gear on the arrow a1 side (Z4 gear 62 side), a plurality of third teeth that can mesh with the fourth teeth are provided side by side in the circumferential direction. That is, the Z2 gear (second gear 76) and the Z3 gear (third gear) 77 are configured by the outer ring gear. In the present embodiment, the number N1 of the first teeth is set to be one less than the number N2 of the second teeth, and the number N3 of the third teeth is equal to the number N4 of the fourth teeth. It is set to the same number. For example, when the number of teeth N1 = 19, the number of teeth N2 = 20, the number of teeth N3 = 20, and the number of teeth N4 = 20, the reduction ratio between the motor rotation shaft 45 and the output shaft 23 at this stage is set to 20. Yes.

  The inner ring is connected to the outer periphery of the inclined shaft 53 so as to be integrally rotatable with the motor rotating shaft 45 by a fixing member fixed to the end of the inclined shaft 53 on the arrow a2 side. That is, the center axis of the center bearing 63 coincides with the axis L2 of the inclined shaft 53, and the center bearing 63 rotates around the axis inclined with respect to the axes of the Z1 and Z4 gears 61 and 62. In the outer ring gear, only a part of the Z2 gear 76 meshes with the Z1 gear 61 and only a part of the Z3 gear 77 meshes with the Z4 gear 62. Note that the meshing portion between the Z1 gear 61 and the Z2 gear 76 and the meshing portion between the Z4 gear 62 and the Z3 gear 77 are separated from each other by about 180 ° with the axes of the Z1 and Z4 gears 61 and 62 as the center. Further, axial preload is applied to the bearing gear 25 by the preload applying mechanism 79 so that the Z1 gear 61 and the Z4 gear 62 are close to each other. The preload applying mechanism 79 includes a preload adjusting plug 78 and a coil spring 80 that is stretched between the input shaft 22 and the preload adjusting plug 78 and generates a stress by a torsion torque when the preload adjusting plug 78 rotates. Yes. According to the above configuration, the preload force applied to the bearing gear 25 by the preload adjusting plug 78 is transmitted via the input shaft 22 to the two meshing portions (the Z2 gear 76 and the Z2 gear 76 and the center bearing 63 at both ends). A transmission path from the Z3 gear 77), the Z4 gear 62, the housing 21, and the bearing 38 to the preload adjusting plug 78 is formed.

  In the bearing gear 25 in which the input shaft 22, the output shaft 23, and the motor rotation shaft 45 are respectively connected in this way, the rotation of the input shaft 22 is transmitted from the Z1 gear 61 to the Z4 gear 62 via the center bearing 63, and connected. It is transmitted to the cylinder 67 and the output shaft 23. Further, when the motor 24 is driven and the motor rotating shaft 45 rotates, the inclined shaft 53 connected to the motor rotating shaft 45 performs an eccentric motion (swing motion). As a result, the outer ring gear eccentrically moves together with the inner ring fixed to the inclined shaft 53, and the meshing portion between the Z1 gear 61 and the Z2 gear 76 and the meshing portion between the Z4 gear 62 and the Z3 gear 77 rotate in the same direction. As a result, the rotation difference based on the number of teeth difference between the Z1 gear 61 and the Z2 gear 76 and the Z4 gear 62 and the Z3 gear 77 is added to the input shaft 22 as a rotation based on the motor drive and transmitted to the output shaft 23. (For example, when the reduction ratio is 20, the output shaft 23 is added by one rotation per 20 rotations of the motor rotation shaft 45). That is, the rotation transmission ratio between the input shaft 22 and the output shaft 23 according to the rotation based on the motor drive, that is, the transmission ratio between the steering wheel 2 (see FIG. 1) and the steered wheels 12 (see FIG. 1) ( Steering gear ratio) is changed.

  Next, FIG. 3 is a schematic view of the preload applying mechanism 79 in FIG. As shown in FIG. 3, a preload adjustment plug 78 is rotatably screwed to the input shaft 22, and a coil spring 80 is installed between the input shaft 22 and the preload adjustment plug 78. One end portion of the coil spring 80 is inserted into the fixing through hole 81 of the input shaft 22, and the other end portion is provided in the circumferential direction of the preload adjusting plug 78 and plural (in this embodiment, four) penetrating in the axial direction. The fixing through hole 82 is inserted through one place. By providing a plurality of fixing through holes 82, the torsion angle when the coil spring 80 is attached can be adjusted, and the torsion angle of the coil spring 80 can be set according to the spring constant. At this time, even if there is a gap (gap) between the meshing portions at both ends of the center bearing 63 (see FIG. 2), the coil spring 80 receives the torsional torque around the axis, and the tightening torque that acts on the coil spring 80 meshes. The preload adjusting plug 78 is rotated in a direction to fill the gap between the portions, thereby preventing a decrease in the preload.

  Next, the operation and effect of the transmission ratio variable device 15 according to the present embodiment configured as described above will be described.

  According to the above configuration, the tightening torque is applied to the preload adjusting plug 78 that is rotatably screwed to the input shaft 22 due to the torsion of the coil spring 80 spanned between the input shaft 22 and the preload adjusting plug 78. The preload adjusting plug 78 is provided such that its axial position is movable in the axial direction. The input shaft 22 is pressed in the axial direction by the preload adjusting plug 78, and the axial position of the preload adjusting plug 78 increases as the axial position of the preload adjusting plug 78 approaches the center bearing 63 at the meshing portion of each gear of the center bearing 63. Preload is applied. The preload adjusting plug 78 acts so that the axial gap (gap) of the meshing portion of each gear of the center bearing 63 is narrowed. Further, in order to change the torsion angle when the coil spring 80 is attached, a plurality of (four in this embodiment) fixing in the circumferential direction in which one end side of the coil spring 80 is inserted into the preload adjusting plug 78 in the axial direction. A through-hole 82 is provided. For this reason, by setting the torsion angle of the coil spring 80 according to the spring constant and adjusting the torsion torque of the coil spring 80, the tightening torque of the preload adjusting plug 78 can be accurately adjusted.

  As a result, the preload in the axial direction of the input shaft 22 is kept constant, and variations in the magnitude of the preload applied to the meshing portions of the gears of the center bearing 63 can be reduced. Further, the axial play can be further reduced to prevent the preload from being reduced. As a result, the generation of abnormal noise and vibration at the center bearing 63 can be further suppressed. Further, since the preload adjustment can be automatically performed even after the assembly, it is not necessary to provide a lock for the preload adjustment plug 78, and the working time for the torque adjustment and the lock prevention of the preload adjustment plug 78 can be shortened. Can do.

  As described above, according to the embodiment of the present invention, it is possible to provide a transmission ratio variable device that can reduce variation in preload applied to the bearing gear with a simple configuration.

  As mentioned above, although embodiment which concerns on this invention was described, this invention can also be implemented with another form.

  In the above embodiment, the preload adjusting plug 78 urges the input shaft 22 in the direction of decreasing the gap between the meshing portions of the center bearing 63 as the preload applying mechanism 79. It may be provided so as to be energized.

  In the above embodiment, a plurality of (four) through holes 82 for fixing the coil spring 80 are provided in the axial direction of the preload adjusting plug 78. However, the use range of the spring constant of the coil spring 80 is limited and the through hole is limited. May be reduced.

  In the above-described embodiment, the steering shaft 2 may be connected using the input shaft 22 as an output shaft, and the intermediate shaft 9 may be connected using the output shaft 23 as an input shaft. Further, the present invention is applied to the transmission ratio variable device 15 in which the housing 21 does not rotate due to the rotation of the input shaft 22, but is not limited to this, for example, the transmission ratio variable device in which the housing rotates integrally with the input shaft. You may apply to.

  In the above embodiment, the present invention is applied to the transmission ratio variable device 15 of the vehicle steering apparatus 1, but may be applied to a transmission ratio variable device used for other purposes.

1: vehicle steering device, 2: steering wheel, 3: steering shaft, 4: rack and pinion mechanism, 5: rack shaft, 8: column shaft, 9: intermediate shaft, 10: pinion shaft, 11: tie rod, 12: Steered wheel, 13: assist motor, 14: ball screw mechanism,
15: Transmission ratio variable device, 21, 31, 32, 33, 37: Housing, 17: Steering shaft, 22: Input shaft, 23: Output shaft, 24: Motor, 25: Bearing gear (reduction gear), 26: Lock Mechanism, 34: partition part, 35: motor housing part, 36: gear housing part, 38, 39, 48, 49, 56, 68, 69, 70: bearing, 41: stator, 42: rotor,
44: motor, 45: motor rotation axis (output shaft), 52: rotation angle sensor, 53: tilt axis,
61: Z1 gear (first gear), 62: Z4 gear (fourth gear), 63: center bearing (oscillating gear), 67: connecting cylinder, 76: Z2 gear (second gear), 77: Z3 gear ( Third gear), 78: Preload adjusting plug, 79: Preload applying mechanism, 80: Coil spring, 81, 82: Coil spring fixing through holes N1 to N4: Number of teeth, L1, L2: Shaft center

Claims (3)

An input shaft coupled to the steering wheel;
A housing that supports the input shaft in a relatively rotatable manner;
A motor provided with a motor output shaft that can rotate relative to the housing;
A reduction gear connected to the motor output shaft and outputting a turning angle with a reduced motor rotation angle;
An output shaft that transmits the steered angle output from the reducer to the steered wheel side, and
The speed reducer is
A first gear provided on the input shaft so as to be integrally rotatable and having first teeth formed on an end surface;
A fourth gear provided on the output shaft so as to be integrally rotatable, and having a fourth tooth formed on an end surface facing the end surface of the first gear;
An inclined axis provided obliquely to the input axis;
A second gear and a third gear, which are supported by the inclined shaft so as to be relatively rotatable, and have second and third teeth formed on different end faces so as to mesh with the first and fourth gears, respectively, The difference in the number of teeth between either the first or fourth gear and the second and third gears while swinging the input shaft in the axial direction with the rotation of the inclined shaft between the first and fourth gears. A rocking gear that is rotated by
The preload adjustment plug is screwed to the input shaft so as to be movable in the axial direction and urges the input shaft in a direction to approach the output shaft, and the axial position of the input shaft of the preload adjustment plug is A transmission ratio variable device comprising a preload applying mechanism that applies to the reducer the preload in the axial direction that increases as it moves toward the reducer. The transmission ratio variable device according to claim 1,
The preload applying mechanism includes a coil spring that is installed between the input shaft and the preload adjusting plug, and that presses the preload adjusting plug and rotates the input shaft so as to be movable in the axial direction of the input shaft. A transmission ratio variable device. The transmission ratio variable device according to claim 2,
The transmission ratio variable device according to claim 1, wherein the preload adjusting plug includes a plurality of fixing through holes provided at one end side of the coil spring in the circumferential direction and inserted in the axial direction.

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