JP2023139768A - Circumferential division cam wave generator - Google Patents

Abstract

To provide an improved wave generator capable of preventing a phenomenon that backlash occurs or that friction torque decreases.SOLUTION: In a wave generator for a harmonic speed reducer, a plurality of long-diameter side split cams and the same number of short-diameter side split cams are alternately abutted along a circumferential direction to form one cam, an outer peripheral surface of the long-diameter side split cam has a constant circumferential surface with a small radius, an outer peripheral surface of the short-diameter side split cam has a constant circumferential surface with a large radius, and a common tangent line is formed at a point where the circumferential surface of the long-diameter side split cam and the circumferential surface of the short-diameter side split cam are in contact with each other. This makes it easy to shape a cam surface of a wave generator.SELECTED DRAWING: Figure 3

Description

The present invention relates to a wave generator, which is a component of a harmonic reducer mainly applied to the joints of industrial robots, and more specifically, to prevent phenomena such as backlash and reduction of friction torque. Regarding the improved wave generator.

Generally, the harmonic reducer 10 applied to industrial robots transmits the high-speed rotation of a servo motor to the output shaft at a high reduction ratio of 1:30 to 1:320, but the core of the reduction is as shown in Figure 1. As the elliptical wave generator 11 rotates, the point where the surrounding flex spline 12 meshes with the outer circular spline 13 moves along the circumferential direction and rotates in the opposite direction by the difference in the number of teeth. It is to make it.

However, the harmonic reducer based on this principle has a problem in that backlash occurs due to space between teeth due to design and machining errors in tooth profiles and wear of parts such as bearings.

In particular, since the wave generator 11 has an elliptical cam shape, it is quite difficult to precisely process its outer shape, making it difficult to mass produce and resulting in high production costs. Furthermore, there is a problem in that very expensive equipment is required for precise measurement of the cam shape of the wave generator 11. Furthermore, since the flex spline 12 must be assembled to the wave generator 11 in an elastically deformed state, a skilled technique is required and productivity is low.

On the other hand, in order to solve such problems, the applicant has published Patent Document 1: Korean Patent No. 10-2303050 (publication date: September 16, 2021), Patent Document 2: Korean Patent No. 10-2345641 ( Publication date: December 31, 2021) and Patent Document 3: Korean Patent Publication No. 10-2021-0155587 (Publication date: December 23, 2021).

The core of this is to solve the tooth profile design and the resulting backlash problem by converting the coupling between the flex spline 22 and the circular spline 23 into a face-to-face friction structure, as shown in FIG.

However, even in this case, there were still difficulties in processing the cam-type wave generator 21. In particular, if the vertical surface pressure V from the wave generator 21 is not sufficiently transmitted to the flex spline 22 side due to machining errors, friction surface wear, bearing wear, etc., the friction force f with the circular spline 23 decreases and enough friction is achieved. It has been pointed out that since no torque is generated, the performance as a speed reducer cannot be guaranteed.

Korean Patent No. 10-2303050 (Publication date: September 16, 2021) Korean Patent No. 10-2345641 (Publication date: December 31, 2021) Korean Patent Publication No. 10-2021-0155587 (Publication date: December 23, 2021)

A first object of the present invention is to provide an improved wave generator that can be easily shaped.

A second object of the present invention is to create a wave generator that can prevent backlash from occurring in the case of a toothed type reducer and prevent the transmitted vertical surface pressure from decreasing in the case of a toothless type reducer. Our goal is to provide the following.

In order to achieve the above object, the present invention provides a wave generator for a harmonic reduction gear in which a plurality of long-diameter divided cams and an equal number of short-diameter divided cams are alternately butted against each other along the circumferential direction. forming one cam, the outer circumferential surface of the longer diameter side split cam has a constant circumferential surface with a small radius, and the outer circumferential surface of the short diameter side split cam has a constant circumferential surface with a large radius; A wave generator is provided, wherein the circumferential surface of the long-diameter side divided cam and the circumferential surface of the short-diameter side divided cam have a common tangent at a point where they touch each other.

Here, V grooves are formed on the circumferential surface of the long diameter side split cam and the circumferential surface of the short diameter side split cam so as to be connected to each other in the circumferential direction, thereby forming one track. , a number of balls may be mounted along the trajectory.
Alternatively, a large number of rollers may be rolled into contact with the circumferential surface of the long-diameter side divided cam and the circumferential surface of the short-diameter side divided cam.

At this time, partition walls are connected to each other in the circumferential direction on both sides of the circumferential surface of the long-diameter side split cam and the circumferential surface of the short-diameter side split cam to prevent the roller from leaving the track. The rollers may be formed to form one track, and the plurality of rollers may be mounted along the track.

Alternatively, one flexible bearing inner ring is coupled to the circumferential surface of the plurality of long-diameter side split cams and the circumferential surface of the plurality of short-diameter side split cams, and a plurality of balls are connected on the flexible bearing inner ring. Alternatively, a roller may be installed.
At this time, one flexible bearing outer ring may be coupled to the plurality of balls or rollers.

On the other hand, a central shaft is installed inside the plurality of long-diameter side divided cams and short-diameter side divided cams, and the inner peripheral surface of the plurality of long-diameter side divided cams and the short-diameter side divided cam and the outer peripheral surface of the central shaft A tapered groove inclined in the axial direction extends in the circumferential direction, and a large number of balls are inserted into the tapered groove, and the large number of balls are inserted through a lock nut coupled to the outer circumferential surface of the central shaft. By pressurizing the ball in the axial direction, it is also possible to finely adjust the positions of the plurality of long diameter side divided cams and short diameter side divided cams outward.

At this time, the long-diameter side divided cam has a long hole extending in the circumferential direction adjacent to the circumferential surface of the long-diameter side divided cam, and the long-diameter side divided cam has a long hole extending in the circumferential direction, and Pressure force can also be exerted in the radial direction through elastic deformation in which the width of the elongated hole becomes narrower.

Alternatively, a central shaft is installed inside the plurality of long-diameter side divided cams and the short-diameter side divided cams, and a center shaft is installed on the inner peripheral surface of the plurality of long-diameter side divided cams and the short-diameter side divided cams in the axial direction, respectively. An inclined tapered groove is provided, a ball is inserted into the tapered groove, and the ball is pressurized in the axial direction via a lock nut coupled to the outer circumferential surface of the central shaft. It is also possible to finely adjust the position of the short diameter side split cam outward.

At this time, a flange that supports the plurality of long-diameter side divided cams and short-diameter side divided cams in the axial direction extends in the radial direction from one end of the central shaft, and the flange is pressurized by the ball. By elastically deforming in the axial direction by the plurality of long diameter side divided cams and short diameter side divided cams, excessive force is transmitted in the radial direction via the plurality of long diameter side divided cams and short diameter side divided cams. It can also be prevented.

As described above, according to the wave generator of the present invention, each of the outer circumferential surfaces of the long-diameter side split cam and the short-diameter side split cam has a circumferential surface with a constant radius, so that lathe processing or grinding by simple rotation is possible. There is an advantage that the outer circumferential surface of the split cam can be precision-machined easily, quickly, and accurately.

In addition, from the configuration in which a ball is inserted into a tapered groove between the split cam and the center shaft and pressurized with a lock nut, by finely adjusting the split cam outward, the flex spline and circular spline connected to the outside can be adjusted. Since the space can be brought into close contact with each other, it is possible to prevent backlash from occurring in the case of a toothed type connection, and it is possible to prevent a decrease in the transmitted vertical surface pressure in the case of a toothless type connection.

1 is a front view and a detailed view of a toothed harmonic reducer according to the prior art; FIG. 1 is a front view and a detailed view of a toothless harmonic reducer according to the prior art; FIG. FIG. 1 is a front view of a wave generator according to an embodiment of the invention. 4 is a front view showing a modification of the wave generator of FIG. 3. FIG. 4 is a left side view of the wave generator of FIG. 3. FIG. 6 is a left side view showing a modification of the wave generator of FIG. 5. FIG. 6 is a left side view showing a modification of the wave generator of FIG. 5. FIG. 6 is a left side view showing a modification of the wave generator of FIG. 5. FIG. 6 is a sectional view of FIG. 5. FIG. 10 is a sectional view showing a modification of FIG. 9. FIG. 11 is a partially exploded perspective view showing another modification of FIG. 10. FIG. FIG. 3 is a front view of a wave generator according to another embodiment of the invention. FIG. 13 is a front view for explaining the elastic portion of the long-diameter side split cam of FIG. 12; FIG. 13 is a perspective view showing the wave generator of FIG. 12 cut away. 4 is a front view and a sectional view of a toothless harmonic reduction gear to which the wave generator of FIG. 3 is applied. FIG. 13 is a front view and a sectional view of a tooth-type harmonic reducer to which the wave generator of FIG. 12 is applied. FIG.

As shown in FIG. 3, in the wave generator 100 according to the embodiment of the present invention, two long-diameter divided cams 111 and two short-diameter divided cams 112 are alternately abutted against each other in the circumferential direction to form one cam 110. Form.

The long diameter side divided cam 111 and the short diameter side divided cam 112 each have circumferential surfaces 111a and 112a with a constant radius, that is, a perfect circular circumferential surface, so the long diameter side divided cam 111 has a circumferential surface 111a with a small radius r1. The short diameter side split cam 112 has a circumferential surface 112a with a large radius r2.

At this time, the longer diameter side divided cam 111 and the shorter diameter side divided cam 112 have different centers O1 and O2, and have a common tangent L to each other at the point P where each circumferential surface 111a and the circumferential surface 112a touch. Thus, the circumferential surfaces 111a and 112a are smoothly connected. By doing so, it is possible to realize the outer peripheral surface of one cam consisting of the four divided cams 111 and 112.

A cam using a combination of split cams in this way can also be realized by a combination of six split cams, that is, three long-diameter split cams 111' and three short-diameter split cams 112', as shown in FIG. The same principle can also be applied to eight split cams.

Further, in all the combinations of split cams, the circumferential surfaces 111a and 111a' of the longer diameter side split cams 111 and 111' serve as working surfaces for the outer flex spline (see 12 in FIG. 1) or the circular spline 13.

A large number of balls 120 roll along the circumferential surfaces 111a and 112a of the long-diameter side divided cam 111 and the short-diameter side divided cam 112 and come into contact with each other. For this purpose, V grooves 111b and 112b are formed in the circumferential surfaces 111a and 112a so as to be connected in the circumferential direction, as shown in FIG. It can be made to be attached.

Alternatively, as shown in FIG. 6, a flexible bearing inner ring 130 may be coupled to the circumferential surfaces 111a and 112a, and the balls 120 may be mounted thereon. A configuration may be adopted in which the outer ring 140 is further coupled. Meanwhile, in FIGS. 6 and 7, the balls 120 and the flexible bearing inner and outer rings 130 and 140 can be replaced with rollers (not shown) and flexible bearing inner and outer rings (not shown) that match the rollers.

As another modification, as shown in FIG. 8, a configuration may be adopted in which a large number of rollers 150 roll on and contact the circumferential surfaces 111a and 112a of the long-diameter side divided cam 111 and the short-diameter side divided cam 112. To this end, partition walls 111c having a constant width are formed on the circumferential surfaces 111a and 112a so as to be connected in the circumferential direction for smooth orbital circulation of the roller 150. It is also possible to attach it without leaving the orbits on 111a and 112a.

On the other hand, in consideration of processing errors of the wave generator 100, installation errors in the reducer, and occurrence of wear due to use, a ball 170 is installed between the split cams 111 and 112 and their central axis 160 as shown in FIG. By interposing the split cams 111 and 112, the radial positions of the split cams 111 and 112 can be finely adjusted.

Specifically, by forming an inclined tapered surface 161 on the outer circumferential surface of the central shaft 160, a tapered groove H is provided between the inner circumferential surfaces 111d of the split cams 111 and 112, and the ball 170 is Allow it to be inserted. A lock nut 180 is screwed onto the outer peripheral surface of the central shaft 160 to press the ball 170 into the tapered groove H via the washer 181. As a result, the positions of the split cams 111 and 112 can be adjusted outwardly, that is, in the radial direction, by the ball 170 that is about to be inserted inside the tapered groove H.

As shown in FIG. 10, the above-mentioned tapered groove H is formed by forming the outer circumferential surface of the central shaft 160' into a circumferential surface having a constant radius, and by forming the inner circumferential surface 111e of the split cams 111 and 112 into a tapered surface. It can also be formed by

Alternatively, as shown in FIG. 11, tapered grooves 111f and 112f inclined in the axial direction are formed on the inner circumferential surfaces of the split cams 111 and 112, and the ball 170' is inserted into each tapered groove 111f and 112f. Alternatively, a configuration may be adopted in which pressure is applied using a lock nut (see 180' in FIG. 10).

On the other hand, in FIG. 3, due to wear of the balls 120 or rollers that circulate and rotate on the circumferential surfaces 111a and 112a of the split cams 111 and 112 and their bearings, and/or the flex spline coupled to the outside of the wave generator 100 (FIG. When the vertical surface pressure decreases or backlash occurs due to wear of the circular spline (see 12) or the circular spline (see 13), the structure that can automatically compensate for this is shown in Figs. As shown in FIG. 14, an elongated hole 111g extending in the circumferential direction can be provided at an inner point adjacent to the circumferential surface 111a of the long-diameter side split cam 111.

In FIG. 14, the split cam 111, which receives an outward force from the ball 170 that is pressurized by the lock nut 180, applies a pressing force to the ball 120 on the circumferential surface 111a through elastic deformation that narrows the width of the elongated hole 111g. Demonstrate. As a result, the ball 120 comes into closer contact with the outer flex spline (see 12 in FIG. 1) and the circular spline 13, thereby making it possible to prevent a reduction in the transmitted vertical surface pressure and the occurrence of backlash.

At this time, a flange 162 extending radially from one end of the central shaft 160 to support the split cams 111 and 112 is provided with a notch 162a at its base end, so that the lock nut 180 can be attached to the flange 162. When the force with which the ball 170 is pressurized is excessive, the flange 162 is elastically deformed in the axial direction (in the left direction in FIG. 14) to prevent the excessive force from being directly transmitted to the split cams 111 and 112. It can be prevented.

In this embodiment, the notch 162a is formed for elastic deformation of the flange 162 in the axial direction. However, the present invention is not limited to such a structure, and the thickness of the flange 162 is reduced to improve Various other measures can be applied to replace the configuration, such as ways to make deformation easier.
The configuration in which the flange 160 is elastically deformed in this way can also be applied to a structure as shown in FIG. 10 in which the split cam 111 is not provided with the elongated hole 111g.

FIG. 15 shows a toothless harmonic reducer 200 to which the wave generator 100 of FIGS. 3 and 10 is applied, in which a flex spline 210 is transformed into a circular spline 220 by vertical surface pressure from balls 120 on the outside of split cams 111 and 112. The driven shaft 230 is rotated at a larger reduction ratio than the drive shaft (i.e., the center shaft 160) by performing reverse rotation due to the difference in diameter while rolling on the inner peripheral surface of the driven shaft 230.

FIG. 16 shows a toothed harmonic reducer 300 to which the wave generator of FIGS. 12 and 14 is applied, in which the flex spline 310 is brought into close contact with the circular spline 320 by pressurization of the outer balls 120 of the split cams 111 and 112. In this state of engagement, the engagement point moves in the circumferential direction and rotates in the opposite direction by the difference in the number of teeth, thereby rotating the driven shaft 330 at a large reduction ratio.

On the other hand, since the above-mentioned wave generator is only one embodiment to aid understanding of the present invention, the scope of rights and technical scope of the present invention defined by the following claims is not limited to what has been described above. .

100 Wave generator 110 Cam 111 Long diameter side split cam 111a Circumferential surface 111b V-groove 111c Partition wall 111d Inner circumferential surface 111e Inner circumferential surface (tapered surface)
111f Tapered groove 111g Long hole 112 Short diameter side split cam 112a Circumferential surface 112b V groove 112f Tapered groove 120 Ball 130 Flexible bearing inner ring 140 Flexible bearing outer ring 150 Roller 160 Center shaft 161 Tapered surface 162 Flange 162a Notch 17 0 ball 180 lock nut

Claims (10)

In the wave generator for harmonic reducer,
A plurality of long-diameter side split cams and the same number of short-diameter side split cams are alternately abutted along the circumferential direction to form one cam,
The outer circumferential surface of the long diameter side split cam has a constant circumferential surface with a small radius,
The outer peripheral surface of the short diameter side split cam has a constant circumferential surface with a large radius,
A wave generator characterized in that a circumferential surface of the long-diameter side divided cam and a circumferential surface of the short-diameter side divided cam have a common tangent at a point where they touch each other. V-grooves are formed on the circumferential surface of the long-diameter side split cam and the circumferential surface of the short-diameter side split cam so as to be connected to each other in the circumferential direction, thereby forming one orbit,
The wave generator according to claim 1, wherein a large number of balls are mounted along the trajectory. The wave generator according to claim 1, wherein a large number of rollers roll on and contact the circumferential surface of the long-diameter side divided cam and the circumferential surface of the short-diameter side divided cam. Partition walls are formed on both sides of the circumferential surface of the long-diameter side split cam and the circumferential surface of the short-diameter side split cam so as to be connected to each other in the circumferential direction for guiding the roller to prevent it from leaving the track. By doing so, one orbit is formed,
The wave generator according to claim 3, wherein the plurality of rollers are mounted along the track. One flexible bearing inner ring is coupled to the circumferential surface of the plurality of long-diameter side split cams and the circumferential surface of the plurality of short-diameter side split cams,
The wave generator according to claim 1, wherein a large number of balls or rollers are mounted on the flexible bearing inner ring. The wave generator according to claim 5, wherein one flexible bearing outer ring is coupled on the plurality of balls or rollers. A central shaft is installed inside the plurality of long diameter side divided cams and short diameter side divided cams,
A tapered groove inclined in the axial direction extends in the circumferential direction between the inner circumferential surfaces of the plurality of long-diameter side split cams and the short-diameter side split cams and the outer circumferential surface of the central shaft,
A large number of balls are inserted into the tapered groove,
The positions of the plurality of long-diameter side split cams and short-diameter side split cams are finely adjusted outward by pressurizing the plurality of balls in the axial direction via a lock nut coupled to an outer peripheral surface of the central shaft. The wave generator according to item 1. The long diameter side split cam is
The long diameter side split cam has a long hole extending in the circumferential direction adjacent to the circumferential surface thereof, and the long hole is elastically deformed so that the width of the long hole is narrowed by a large number of balls pressurized in the axial direction. 8. The wave generator according to claim 7, which exerts a pressing force in the radial direction through the wave generator. A central shaft is installed inside the plurality of long diameter side divided cams and short diameter side divided cams,
A tapered groove inclined in the axial direction is provided on the inner peripheral surface of each of the plurality of long-diameter side divided cams and short-diameter side divided cams,
A ball is inserted into the tapered groove,
Claim 1: The positions of the plurality of long-diameter side split cams and short-diameter side split cams are finely adjusted outward by pressurizing the ball in the axial direction via a lock nut coupled to an outer circumferential surface of the central shaft. The wave generator described in. A flange that axially supports the plurality of long-diameter side divided cams and short-diameter side divided cams extends in the radial direction from one end of the central shaft,
The flange is elastically deformed in the axial direction by the plurality of long-diameter divided cams and short-diameter divided cams that are pressurized by the balls, so that excessive force is applied to the plurality of long-diameter divided cams and the short-diameter divided cams. 8. A wave generator according to claim 7, which prevents radial transmission through the cam.

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