JP2008089038A - Harmonic drive and transmission ratio adjusting device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a harmonic drive and a transmission ratio adjusting device using it, in which high-viscosity grease applied to an engaging portion of a stator gear and a driven gear with a flexible gear can be maintained in the engaging portion for the long term. <P>SOLUTION: A grease fluidity auxiliary plate 63 is installed in both end surfaces of a wave generator 54. A grease fluidity space 64 is demarcated between the grease fluidity auxiliary plate and the wave generator. A cross sectional area when the grease fluidity space is cut in a plane including an axis line O is formed to be the greatest in the major axis side of the wave generator, and gradually smaller toward the minor axis side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wave gear device having a configuration in which a stator gear and a driven gear are arranged on the outer periphery of a ring-shaped flexible gear, and a transmission ratio variable device using the wave gear device.

  A stator gear, a driven gear that is juxtaposed on the same axis as the stator gear and has a different number of teeth from the stator gear, and a ring-shaped flexible gear that is arranged on the same axis inside the stator gear and the driven gear so as to mesh with the stator gear and the driven gear. A well-known wave gear device comprising a gear and a wave generator that flexes the flexible gear into a non-circular shape and partially meshes with the stator gear and the driven gear and rotates the non-circular shape of the deflected flexible gear. It has been. Such a wave gear device is widely used as a reduction mechanism of a transmission ratio variable system that changes a ratio of a turning angle of a steered wheel to a steering angle of a steering wheel, as described in Patent Document 1, for example. In general, the speed reduction mechanism is mounted outside the passenger compartment and has an advantageous layout for sound and vibration. Therefore, vibration reduction is supported by a mass damper or the like.

However, when the mounting position of the speed reduction mechanism is from the outside of the conventional passenger compartment to the passenger compartment, high silence is required, so the conventional mass damper or the like cannot sufficiently cope with it, and the wave gear device itself It is necessary to reduce the generated vibration.
JP 2006-44534 A

  By the way, it has been confirmed that applying a high-viscosity grease to the meshing part of the stator gear and the driven gear and the flexible gear can reduce the vibration due to the damping effect of the grease. As the device rotates, the stator gear, driven gear and flexible gear partially mesh with each other, so excess high-viscosity grease escapes to both sides in the axial direction from the meshing part, and the grease that has escaped once again Since it does not return to the meshing portion, there is a possibility that the damping effect may be lowered in the long-time operation.

  The present invention has been made to solve the above-described conventional problems, and a wave gear capable of holding high-viscosity grease applied to a meshing portion of a stator gear and a driven gear and a flexible gear in the meshing portion for a long period of time. It is an object of the present invention to provide a device and a transmission ratio variable device using the same.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a stator gear, a driven gear arranged on the same axis as the stator gear and having a different number of teeth from the stator gear, and the same inside the stator gear and the driven gear. A ring-shaped flexible gear arranged on the axis and meshing with the stator gear and the driven gear, and flexibly flexing the flexible gear while flexing the flexible gear into a non-circular shape and partially meshing with the stator gear and the driven gear. A wave generator that rotates a non-circular shape, and a high-viscosity grease is applied to meshing portions of the stator gear, the driven gear, and the flexible gear, both ends of the wave generator Attach a grease flow assist plate to at least one of the surfaces, A grease flow space is defined between the grease flow auxiliary plate and the wave generator, and the cross-sectional area when the grease flow space is cut along a plane including the axis is the largest on the longer diameter side of the wave generator. In other words, it is formed so as to gradually become smaller toward the minor axis side.

  The invention according to claim 2 is characterized in that, in claim 1, the grease flow auxiliary plate is spaced apart from the end face of the wave generator radially outward on the longer diameter side of the wave generator. An inclined surface is formed, and the inclined surface is formed so that the inclination angle gradually decreases from the major axis side to the minor axis side of the wave generator.

  A feature of the invention according to claim 3 is that, in claim 1 or claim 2, the grease flow auxiliary plate is formed in a substantially elliptical shape.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the grease flow auxiliary plate is respectively attached to outer surfaces of plates provided at both ends of the wave generator. That is.

  According to a fifth aspect of the present invention, there is provided an input shaft through which rotation of a steering wheel is transmitted, and an output shaft that is rotatably supported by the input shaft and transmits rotation to a steering gear that gives a steered angle to a steered wheel. And a motor fixed coaxially to the input shaft, and a speed reduction mechanism provided between the motor shaft of the motor and the output shaft to transmit rotation to the output shaft by decelerating the rotation of the motor shaft. 5. A transmission ratio variable device for changing a ratio of a steered wheel turning angle to a wheel steering angle, wherein the wave gear device according to any one of claims 1 to 4 is used as the speed reduction mechanism. That is.

  According to the first aspect of the present invention, the grease flow auxiliary plate is mounted on both end faces of the wave generator, the grease flow space is defined between the grease flow auxiliary plate and the wave generator, Since the cross-sectional area is the largest on the long diameter side of the wave generator and gradually decreases toward the short diameter side, excess grease pushed out at the meshing part on the long diameter side is removed by the grease flow auxiliary plate. By the action of the shearing force, it is possible to circulate from the meshing portion on the long diameter side to the non-meshing portion on the short diameter side. As a result, when the short diameter side of the flexible gear is deformed to the long diameter side, the circulated grease can be interposed in the meshing portion of the stator gear, the driven gear and the flexible gear.

  This makes it possible to always retain high-viscosity grease at the meshing part of the stator gear, driven gear, and flexible gear, maintain the damping effect of the grease for a long time, and effectively reduce the vibration of the wave gear device. can do. In addition, the durability of the wave gear device can be improved by preventing the grease from running out.

  According to the invention of claim 2, the grease flow auxiliary plate is formed with an inclined surface that is inclined so as to be separated from the end face of the wave generator toward the radially outer side on the longer diameter side of the wave generator, The inclined surface is formed so that the inclination angle gradually decreases from the major axis side to the minor axis side of the wave generator, so that excess grease pushed out at the meshing part on the major axis side can be used to assist grease flow. By the retraction action by the inclined surface formed on the plate, it is possible to accurately circulate from the meshing portion on the long diameter side to the non-meshing portion on the short diameter side.

  According to the invention of claim 3, since the grease flow auxiliary plate is formed in a substantially elliptical shape, the excess grease pushed out in the meshing portion on the long diameter side is subjected to the action of shearing force by the grease flow auxiliary plate. By this, it is possible to circulate from the engaging portion on the long diameter side to the tooth portion on the short diameter side along the peripheral edge portion of the grease flow auxiliary plate.

  According to the invention of claim 4, since the grease flow auxiliary plates are respectively attached to the outer surfaces of the plates provided at both ends of the wave generator, they are applied to the meshing portions of the stator gear, the driven gear and the flexible gear. The highly viscous grease can be reliably separated from the lubricant that lubricates the ball bearings and the like in the wave generator.

  According to the fifth aspect of the present invention, the wave gear device according to any one of the first to fourth aspects is used as the speed reduction mechanism of the transmission ratio variable device that changes the ratio of the turning angle of the steered wheels to the steering angle of the steering wheel. Because it is used, high-viscosity grease can always be held in the meshing part of the stator gear and driven gear and flexible gear that constitute the speed reduction mechanism of the variable transmission ratio device, so that the damping effect by the grease can be maintained over a long period of time. Become. Therefore, the quietness of the speed reduction mechanism of the variable transmission ratio device can be improved without increasing costs due to a significant change in the structure of the speed reduction mechanism of the transmission ratio variable device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2, the upper steering shaft 11 to which the steering wheel 10 is attached is connected to the steering shaft 13 of the transmission ratio variable mechanism 12 via a rubber coupling 14. An output shaft 15 of the transmission ratio variable mechanism 12 is connected to a pinion shaft of a rack and pinion mechanism 17 that is a steering gear via a lower steering shaft 16 to transmit rotation. One end of a tie rod 19 is connected to each end of the rack shaft 18 of the rack and pinion mechanism 17, and the other end of each tie rod 19 is connected to the steered wheel 20 via a knuckle arm.

  The upper steering shaft 11 is provided with a steering angle sensor 21 that detects the steering angle of the steering wheel 10, and the lower steering shaft 16 is provided with a turning angle sensor 22 that detects the turning angle of the steered wheels 20. The steering angle of the steering wheel 10 and the turning angle of the steered wheels 19 are input to the electronic control unit 23. The vehicle speed output from the vehicle speed sensor 24 that detects the vehicle speed is also input to the electronic control unit 23. The electronic control unit 23 outputs a control signal for controlling the transmission ratio variable mechanism 12 based on the steering angle, the turning angle, the vehicle speed, and the like.

  The transmission ratio variable mechanism 12 includes an input shaft 25 that is configured by integrally connecting a stepped cylindrical portion 25a, an intermediate cylindrical portion 25b, and a bottom plate portion 25c, and is a small-diameter cylinder that protrudes above the stepped cylindrical portion 25a. The steering shaft 13 is spline-fitted on the common axis C to the portion 25d. The output shaft 15 is supported on the bottom plate portion 25c of the input shaft 25 so that the flange portion 15a can be rotated by a thrust bearing 26. The flange portion 15a, the speed reduction mechanism 30 and the motor 31 (DC brushless motor) are provided in the intermediate cylindrical portion 25b. ) Are sequentially accommodated on the common axis C. The shaft portion 15 b of the output shaft 15 penetrates the dust seal 32 and protrudes outside the input shaft 25.

  A case 34 of the motor 31 is fitted to the intermediate cylindrical portion 25b. The motor 31 has a motor shaft 35, and the motor shaft 35 is rotatably supported by bearings 37 and 38 at one end on the case 34 and at the center on the intermediate plate 36. The stepped cylindrical portion 25 a and the intermediate cylindrical portion 25 b are coupled by caulking in a state where the flange of the case 34 and the outer edge of the intermediate plate 36 are sandwiched. The bottom plate portion 25c that supports the output shaft 15 is screwed to the intermediate cylindrical portion 25b that houses the speed reduction mechanism 30 and the like, and is fixed by caulking.

  An engagement member 39 is integrally attached to the tip of the motor shaft 35, and the engagement member 39 is rotationally connected to the speed reduction mechanism 30 via a buffer member 40 formed of an elastic body such as rubber.

  Reference numeral 43 denotes a locking mechanism disposed in the large diameter portion of the stepped cylindrical portion 25a, which fixes (locks) the motor shaft 35 to the input shaft 25 when the power is turned off or when the system fails, and the steering wheel 10 rotates. Is transmitted to the steered wheel 20. The lock gear 44 fitted to the rear end of the motor shaft 35 is engaged with and disengaged from the engagement claw of the lock bar supported so as to be able to swing on the stepped cylindrical portion 25a. Since 43 is a known technique, detailed description thereof is omitted.

  Reference numeral 45 denotes a spiral cable device, in which an outer cylindrical body 46 is held by a vehicle body (not shown), and an inner storage body 47 is fitted on the outer periphery of the small diameter cylindrical portion 25d of the stepped cylindrical portion 25a. A flexible flat cable 48 wound between the outer cylinder 46 and the inner storage body 47 has one end fixed to the inner storage body 47 and wound around the inner storage body 47, and the other end is wound on the outer cylinder 46. It is fixed to. The lead wire connected to the flexible flat cable 48 on the inner housing 47 side and introduced into the input shaft 25 is connected to the stator coil of the motor 31 and the lead wire connected to the flexible flat cable 48 on the outer cylinder 46 side. Are connected to the electronic control unit 23, a battery and the like.

  The above-described reduction mechanism 30 is constituted by a wave gear mechanism, and the wave gear mechanism (deceleration mechanism) 30 includes a stator gear 51, a driven gear 52, a flexible gear 53, and a wave generator 54. The stator gear 51 is press-fitted and coupled to the intermediate cylindrical portion 25b, and the driven gear 52 is juxtaposed on the same axis O as the stator gear 51, is rotatably accommodated in the intermediate cylindrical portion 25b, and is rotationally connected to the flange portion 15a. On the inner peripheral surfaces of the stator gear 51 and the driven gear 52, gears having different numbers of teeth are formed. That is, the driven gear 52 is set to have a slightly smaller number of teeth than the stator gear 51. The wave generator 54 includes an elliptical cam 55 that is rotationally connected to the engagement member 39 via the buffer member 40, and the flexible gear 53 is disposed on the outer periphery of the cam 55 via the ball bearing 56. .

  As shown in detail in FIGS. 3 and 4, the flexible gear 53 is disposed on the same axis O inside the stator gear 51 and the driven gear 52, and the driven gear 52 is partially meshed with the stator gear 51 and the driven gear 52 on the outer periphery. Gears with the same number of teeth are formed. The flexible gear 53 is bent into an elliptical shape by an elliptical cam 55 of the wave generator 54, and the meshing point between the stator gear 51 and the driven gear 52 changes in the circumferential direction. At this time, since the driven gear 52 has the same number of teeth as the flexible gear 53, even if the flexible gear 53 is deformed, there is no relative rotation between the driven gear 52, but the number of teeth of the stator gear 51 and the flexible gear 53 is Because of the difference, the driven gear 52 rotates relative to the stator gear 51.

  An inner ring of an elliptical ball bearing 56 is fitted on the outer periphery of an elliptical cam 55 that is an input member of the wave gear mechanism 30, and a flexible outer ring that is rotatably supported by the inner ring via a plurality of balls. The inner periphery of the flexible gear 53 is fitted to the outer periphery of the outer periphery.

  Side plates 61 and 61 are disposed on both end faces of the cam 55 of the wave generator 54, and the side plates 61 and 61 sandwich the ball bearing 56 from both sides in the axial direction as shown in FIG. The cam 55 is integrally coupled to the cam 55 by a plurality of circumferential fasteners, for example, rivets 62. The side plates 61 and 61 have an oval shape that substantially matches the outer shape of the outer ring of the ball bearing 56, and grease for ball bearing lubrication is enclosed between the side plates 61 and 61 and the inner and outer rings of the ball bearing 56. Yes.

  As shown in FIG. 6, elliptical grease flow auxiliary plates 63 and 63 that are approximately similar to the shape of the flexible gear 53 are integrally attached to the outer surfaces of the side plates 61 and 61. The outer periphery of each is close to the respective internal teeth of the stator gear 51 and the driven gear 52. The grease flow auxiliary plates 63 and 63 may be fixed to the outer surfaces of the side plates 61 and 61 by appropriate coupling means such as adhesion or screwing, or the side plates 61 and 61 are attached to the cam 55 of the wave generator 54. You may make it attach to the wave generator 54 integrally with the side plates 61 and 61 using the rivet 62. FIG.

  The grease flow assist plates 63 and 63 define a grease flow space 64 between the wave generator 54 and the wave generator 54. The grease flow auxiliary plates 63, 63 are formed with an inclined surface 65 inclined on the major axis side X1 of the wave generator 54 so as to be gradually separated from the end surface of the wave generator 54 outward in the radial direction. The inclined surface 65 is formed so that the inclination angle gradually decreases from the major axis side X1 of the wave generator 54 toward the minor axis side X2, and the minor axis side X2 of the wave generator 54 is as shown in FIG. In addition, a straight line portion 66 that is close to the end face of the wave generator 54 is formed.

  As a result, the grease flow space 64 has the largest cross-sectional area when the grease flow space 64 is cut along a plane including the axis O on the long diameter side X1 of the wave generator 54, and gradually decreases toward the short diameter side X2. Formed to be. Further, the grease flow space 64 has an outer edge portion of the grease flow assisting plate 63 when the distance between the inner surface of the grease flow assisting plate 63 and the side plate 31 facing the grease flow assisting plate 63 is on the long diameter side X1 of the wave generator 54. And is gradually decreased toward the center of the wave generator 54 and gradually decreased from the major axis side X1 to the minor axis side X2 of the wave generator 54.

  Next, the operation of the steering apparatus provided with the transmission ratio variable mechanism having the above-described configuration will be described. When the driver steers the steering wheel 10 with the lock mechanism 43 unlocked, the steering angle of the steering wheel 10 is detected by the steering angle sensor 21. The electronic control device 23 inputs the steering angle and the turning angle from the steering angle sensor 21 and the turning angle sensor 22, and inputs the vehicle speed from the vehicle speed sensor 24. Then, the electronic control unit 23 calculates the target turning angle based on the vehicle speed, the steering angle, and the like. Based on the difference between the target turning angle and the turning angle of the steered wheels 20 detected by the turning angle sensor 22, a control signal for controlling the motor 31 is output from the electronic control unit 23.

  The control signal output from the electronic control unit 23 is sent to the motor 31 of the transmission ratio variable mechanism 12, and the motor 31 is operated based on this control signal, and the motor shaft 35 is rotated. When the motor shaft 35 rotates, the cam 55 of the wave generator 54 is rotated. At this time, as shown in FIG. 4A, the flexible gear 53 is deformed in an elliptical shape and meshes with the stator gear 51 and the driven gear 52 at both ends of the long diameter side X1 of the cam 55, and the short diameter side X2 Both end portions are in a non-engagement state separated from the stator gear 51 and the driven gear 52. When the cam 55 of the wave generator 54 is rotated in this state, the number of teeth of the driven gear 52 is less than the number of teeth of the stator gear 51, so that when the wave generator 54 makes one rotation, the driven gear 52 is moved relative to the input shaft 25. Thus, the wave generator 54 is rotated while being decelerated by the reduction ratio of the wave gear mechanism (deceleration mechanism) 30 in the same direction as the rotation direction of the wave generator 54. The reduction ratio is a value obtained by dividing the difference in the number of teeth between the stator gear 51 and the driven gear 52 by the number of teeth in the driven gear 52.

  The output shaft 15 is rotated by the rotation of the driven gear 52, and the rotation of the output shaft 15 is transmitted to the pinion shaft of the rack and pinion mechanism 17 via the lower steering shaft 16, and the rack shaft 18 is moved to rotate via the tie rod 19. The steered wheel 20 is steered. Thereby, the transmission ratio between the steering angle of the steering wheel 10 and the turning angle of the steered wheels 19 can be changed according to the rotation of the motor shaft 35.

  By the way, the high-viscosity grease applied between the stator gear 51 and the driven gear 52 of the wave gear mechanism 30 and the flexible gear 53 is partially engaged with the stator gear 51, the driven gear 52, and the flexible gear 53 on the long diameter side X1. In the meshing portion, excess grease escapes to both sides in the axial direction and flows into the grease flow space 64 defined by the inclined surfaces 65 formed in the grease flow auxiliary plates 63 and 63. The high-viscosity grease that has flowed into the grease flow space 64 is disengaged from the meshing portion on the long-diameter side X1 to the non-meshing on the short-diameter side X2 due to the action of shearing force by the grease flow auxiliary plates 63 and 63 that rotate with the wave generator 54 The part is flowed in the circumferential direction.

  The inclined surfaces 65 of the grease flow auxiliary plates 63, 63 are formed so that the inclination angle gradually decreases from the long diameter side X1 to the short diameter side X2 of the wave generator 54, so that the grease flow space 64 has the long diameter. Since it is gradually narrowed in the circumferential direction from the meshing portion on the side X1 toward the tooth portion on the short-diameter side X2, the high viscosity grease is absorbed in the grease flow space 64 by the shearing action of the grease flow auxiliary plates 63 and 63. It is sent to the back side which became narrow. That is, the high-viscosity grease is drawn from the major axis side X1 of the flexible gear 53 to the minor axis side X2 along the peripheral edge portions of the elliptical grease flow assist plates 63, 63. Thus, the grease pushed out from the meshing portion flows from the major axis side X1 to the minor axis side X2 as the wave generator 54 rotates. Note that when the grease is drawn, the drawn portion has a negative pressure, so that the grease is further drawn into the negative pressure portion, and the grease circulation action is promoted.

  As a result, as shown in FIG. 4B, when the wave generator 54 is rotated 90 degrees and the short diameter side X2 of the flexible gear 53 is deformed to the long diameter side X1, the wave motion is performed as described above. The highly viscous grease supplied to the short diameter side X2 of the generator 54 is interposed in the meshing portion between the stator gear 51 and the driven gear 52, and such an operation is repeated by the rotation of the wave generator 54. The grease pushed out from the meshing portion is circulated to the next meshing portion, and the grease is always interposed in the meshing portion of the stator gear 51 and the driven gear 52 and the flexible gear 53 due to the circulating action of the grease. It becomes like this.

  As a result, the highly viscous grease applied between the stator gear 51 and the driven gear 52 and the flexible gear 53 can be held in the meshing portion of the stator gear 51 and the driven gear 52 and the flexible gear 53 for a long period of time, and the damping effect by the grease can be achieved. It will be sustainable for a long time. As a result, vibration noise generated from the wave gear mechanism 30 can be effectively suppressed, and even if the reduction gear of the variable reduction ratio system is mounted in the vehicle interior, it is transmitted from the wave gear mechanism 30 to the vehicle interior. Noise can be reduced, and high silence can be obtained.

  FIG. 8 shows another embodiment of the present invention. In order to further promote the circulating action of the highly viscous grease by the grease flow auxiliary plates 63, 63, the inclined surface 65 of the grease flow auxiliary plates 63, 63 is shown. A mountain shape 65a is formed inside. By forming such a chevron shape 65a, a shearing force generated by the rotation of the grease flow auxiliary plates 63, 63 can generate a component force that draws the highly viscous grease to the back side as indicated by an arrow. The circulation property of grease can be further enhanced. The same parts as those of the previous embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the above-described embodiment, the grease flow assisting plates 63 and 63 are mounted on both end faces of the cam 55 of the wave generator 54. However, the grease flow assisting plate 63 is mounted only on either one of the both end faces. You can also. This is possible when used in such a posture that the axis O of the wave gear mechanism 30 is generally oriented in the vertical direction, and the grease flow auxiliary plate 63 is mounted only on the lower end surface of the wave generator 54. It becomes. By doing so, the number of parts can be reduced as compared with the above-described embodiment while the grease circulation assisting plate 63 exerts the grease circulation action.

  In the above-described embodiment, the grease flow auxiliary plates 63 and 63 are attached to the outer surfaces of the side plates 61 and 61 provided on both end surfaces of the cam 55 of the wave generator 54. If a shield bearing having lubricity is used, the side plates 61 and 61 can be eliminated. In such a wave gear mechanism, the grease flow auxiliary plates 63 and 63 are directly attached to both end faces of the wave generator 54. You can also

  In the above-described embodiment, the grease flow assisting plates 63 and 63 are described as having an elliptical shape that approximates the outer shape of the flexible gear 53. However, the grease flow assisting plates 63 and 63 include the stator gear 51 and It can also be made into the perfect circle shape loosely fitted in the inner periphery of the driven gear 52 with a slight clearance, and is not limited to an elliptical shape.

  As described above, the present invention is not limited to the above-described embodiments, and various forms can be adopted without departing from the gist of the present invention described in the claims.

1 is an overall configuration diagram of a steering apparatus provided with a transmission ratio variable mechanism showing an embodiment of the present invention. It is sectional drawing of the transmission ratio variable mechanism which concerns on embodiment of this invention. It is an expanded sectional view of the deceleration mechanism provided in the transmission ratio variable mechanism. It is sectional drawing cut | disconnected along 4-4 line | wire of FIG. 3, (A) and (B) show a mutually different operating state. It is the figure seen from the arrow along the 5-5 line of FIG. It is the figure seen from the arrow 6 direction of FIG. It is sectional drawing cut | disconnected along the 7-7 line | wire of FIG. It is a figure which shows other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Steering wheel, 12 ... Transmission ratio variable mechanism, 13 ... Steering shaft, 15 ... Output shaft, 17 ... Rack and pinion mechanism, 20 ... Steering wheel, 21 ... Steering angle sensor, 22 ... steering angle sensor, 23 ... electronic control device, 24 ... vehicle speed sensor, 25 ... input shaft, 30 ... wave gear mechanism (deceleration mechanism), 31 ... -Motor, 35 ... Motor shaft, 51 ... Stator gear, 52 ... Driven gear, 53 ... Flexible gear, 54 ... Wave generator, 55 ... Cam, 56 ... Ball bearing, 61 ... side plate, 63 ... grease flow auxiliary plate, 64 ... grease flow space, 65 ... inclined surface, X1 ... major axis side, X2 ... minor axis side.

Claims (5)

A stator gear, a driven gear arranged on the same axis as the stator gear and having a different number of teeth from the stator gear, and a ring shape disposed on the same axis inside the stator gear and the driven gear so as to mesh with the stator gear and the driven gear A flexible gear, and a wave generator that flexes the flexible gear into a non-circular shape and partially meshes with the stator gear and the driven gear, and rotates the non-circular shape of the deflected flexible gear, A wave gear device formed by applying high-viscosity grease to a meshing portion between a driven gear and the flexible gear,
A grease flow auxiliary plate is attached to at least one of both end faces of the wave generator, and a grease flow space is defined between the grease flow auxiliary plate and the wave generator. A wave gear device characterized in that a cross-sectional area when cut along a plane including the largest is formed to be the largest on the long diameter side of the wave generator and gradually decrease toward the short diameter side.   2. The grease flow assist plate according to claim 1, wherein an inclined surface is formed on the longer diameter side of the wave generator so as to be inclined outwardly in the radial direction from the end face of the wave generator. The wave gear device is characterized in that the surface is formed so that the inclination angle gradually decreases from the major axis side to the minor axis side of the wave generator.   3. The wave gear device according to claim 1, wherein the grease flow auxiliary plate is formed in a substantially elliptical shape.   4. The wave gear device according to claim 1, wherein the grease flow auxiliary plates are respectively attached to outer surfaces of plates provided at both ends of the wave generator. 5. An input shaft to which rotation of the steering wheel is transmitted, an output shaft that is rotatably supported by the input shaft and transmits a steering angle to the steered wheels, and that transmits rotation to the steering gear, and is coaxially fixed to the input shaft A motor, and a speed reduction mechanism provided between the motor shaft of the motor and the output shaft for reducing the rotation of the motor shaft and transmitting it to the output shaft, and turning the steered wheels with respect to the steering angle of the steering wheel A transmission ratio variable device that changes a ratio of angles,
5. A transmission ratio variable device using the wave gear device according to any one of claims 1 to 4 as the speed reduction mechanism.

Images