JP2012062940A - Harmonic drive gearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a harmonic drive gearing capable of reducing vibration and rotational error with a simple structure without causing addition of new parts and increase in size.SOLUTION: A bolt 18 penetrates a motor flange 16, a circular spline 14 and the first and second outer ring members 45 and 46 of a cross roller bearing 17, and is then screwed into the bottom portion 21 of a housing 11. Even if the deformation of the bottom portion 21 is produced due to the screwing of the bolt 18, a slight gap is created between the first and second outer ring members 45 and 46 of the cross roller bearing 17 for a roller member 43 to be interposed therebetween. The deformation of the bottom portion 21 therefore is absorbed by the gap between the first and second outer ring members 45 and 46 and consequently is not transmitted to the circular spline 14. As a result, the deformation of the circular spline 14 and the following deformation in the engagement portion between the inner tooth 31 of the circular spline 14 and the outer tooth 36 of a flexible spline 15 are suppressed.

Description

  The present invention relates to a wave gear device.

  2. Description of the Related Art Conventionally, there has been known a wave gear device that includes a cylindrical circular spline having internal teeth and an elliptical cylindrical flexspline having external teeth meshing with the internal teeth, and the flexspline is rotationally driven by a wave generator. Such a wave gear device is called, for example, a harmonic drive ("Harmonic Drive" is a registered trademark), and the rotational speed of the motor input to the wave generator is reduced by the relative rotation of the circular spline and the flex spline. And output from the flexspline (see Patent Document 1). The relative rotation of the circular spline and the flex spline is supported by a cross roller bearing having an outer ring portion fixed to the housing.

  In the case of the wave gear device having such an arrangement, the circular spline is fixed to the housing by the first bolt together with the motor flange integrated with the motor. Specifically, the first bolt passes through the motor flange and the circular spline and is screwed to the housing. At this time, the first bolt that fixes the circular spline and the motor to the housing is screwed into the housing from one end side of the housing, that is, from the motor side. On the other hand, the cross roller bearing is fixed to the housing by another second bolt different from the first bolt. Specifically, the second bolt passes through the outer ring portion of the cross roller bearing and is screwed to the housing. At this time, the second bolt for fixing the cross roller bearing is screwed into the housing from the other end side of the housing, that is, the side opposite to the first bolt. This is an apparatus used for a robot including a wave gear device, which is configured by combining a plurality of parts obtained through different distribution channels. That is, in the case of a wave gear device, a housing, a motor including a motor flange, a wave generator, a flex spline, a circular spline, a cross roller bearing, and the like are individually manufactured by a plurality of manufacturers. Therefore, in the case of a conventional wave gear device, the motor and the circular spline are assembled from one end side of the housing and the cross roller bearing is assembled from the other end side of the housing in order to increase the assembling efficiency.

  In such a conventional wave gear device, the vicinity of the tap portion of the housing, that is, the vicinity of the screw hole of the housing, is slightly deformed by screwing the first bolt into the housing. The circular spline is sandwiched between the motor flange and the housing. Therefore, the circular spline is in contact with the housing, and the inner teeth are also deformed due to the slight deformation of the housing.

  By the way, in the case of an industrial robot or the like, high dynamic and static accuracy is required for the position and angle of the hand. In such industrial robots, precision is not ensured only by control processing, but precision of the components that make up each part, that is, precision of the mechanical structure and dimensions, is also used to ensure precision. ing. For this reason, high accuracy is required for various components constituting the wave gear device. In particular, the smoothness of the surface in the drive portion with rotation affects the reduction of vibration, and this vibration has a great influence on the dynamic accuracy at the tip of the robot hand. However, no matter how high the surface accuracy is, slight deformation occurs in the vicinity of the screw hole of the housing due to the screwing of the first bolt as described above. This deformation deforms the circular spline and consequently affects the internal teeth of the circular spline. As a result, there is a problem that deformation occurs at the meshing portion between the inner teeth of the circular spline and the outer teeth of the flexspline, causing vibration and rotation errors.

  In addition, downsizing and simplification of facilities in factories are always required. Therefore, it is necessary to avoid the enlargement of equipment using robots. Therefore, it is difficult to add a new vibration suppressing member for reducing vibration generated from the wave gear device.

Japanese Patent No. 4052490

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a wave gear device that reduces vibration and rotation errors with a simple structure without adding new parts and increasing the size.

  In the first aspect of the present invention, the cross roller bearing is disposed between the bottom of the housing and the circular spline. Here, the cross roller bearing has an outer ring portion, an inner ring portion, and a roller member in order to support relative rotation of the flexspline and the circular spline. The outer ring portion is fixed to the housing together with the circular spline. On the other hand, the inner ring portion is fixed to the flexspline on the inner peripheral side of the outer ring portion and rotates together with the flexspline. Between the outer ring portion and the inner ring portion, a roller member for smoothing the relative rotation is sandwiched. This roller member is provided in the middle of the cross roller bearing in the axial direction. As described above, in order to provide the roller member in the middle of the cross roller bearing in the axial direction, the outer ring portion needs to be divided into two members in the axial direction. That is, the roller member is disposed between the boundary between the outer ring portions divided into two and the inner ring portion facing the boundary. According to the first aspect of the present invention, when the cross roller bearing having such a configuration is arranged between the bottom portion and the circular spline, when the fixing member is screwed to the bottom portion, the deformation generated in the bottom portion of the housing is It is transmitted to the roller bearing. The cross roller bearing is divided into an outer ring portion and an inner ring portion, and the outer ring portion is further divided into two in the axial direction in order to dispose the roller member in the axial direction. Here, no matter how high the processing accuracy is, the size of the gap formed between the two outer ring portions is sufficiently larger than the deformation that occurs at the bottom of the housing due to screwing of the fixing member. Therefore, even if the bottom of the housing is deformed by screwing the fixing member and the deformation is transmitted to the outer ring portion on the bottom side and the outer ring portion on the bottom side is inclined, this inclination is formed between the two outer ring portions. Absorbed by the gap. As a result, deformation caused by screwing of the fixing member is absorbed by the outer ring portion of the cross roller bearing and is not transmitted to the circular spline in contact with the cross roller bearing. Thereby, the deformation | transformation of a circular spline and the deformation | transformation of the internal tooth accompanying this are also suppressed. Furthermore, since the deformation is absorbed by utilizing the gap formed between the two outer ring portions of the cross roller bearing, no additional parts are required and the size is not increased. Therefore, vibration and rotation errors between the circular spline and the flexspline can be reduced with a simple structure without causing the addition of new parts and an increase in size.

Sectional drawing which shows the outline of the wave gear apparatus by one Embodiment Sectional drawing which shows the outline of the conventional wave gear apparatus as a comparative example The schematic diagram which expanded the principal part of the wave gear apparatus shown in FIG. Schematic diagram for explaining the inclination of the outer ring portion in the main portion shown in FIG.

Hereinafter, a wave gear device according to an embodiment will be described with reference to the drawings.
As shown in FIG. 1, a wave gear device 10 according to an embodiment is used as a mechanism for transmitting a driving force of an articulated robot, for example. The wave gear device 10 includes a housing 11, a motor 12, a wave generator 13, a circular spline 14, a flex spline 15, a motor flange 16, a cross roller bearing 17, and a bolt 18 as a fixing member. The housing 11 is formed in a cylindrical shape and has a bottom portion 21. The bottom 21 projects radially inward from one end in the axial direction of the housing 11. In the case of FIG. 1, the bottom 21 is provided on the lower end side of the housing 11. The motor 12 is provided at the end opposite to the bottom 21 in the axial direction of the housing 11. The motor 12 is a servo motor, for example, and generates driving force when energized. The motor 12 has a rotating shaft member 22 at the end on the bottom 21 side.

  The wave generator 13 is accommodated coaxially with the housing 11 inside the housing 11. The wave generator 13 is fixed to the rotating shaft member 22 of the motor 12 and rotates integrally with the rotating shaft member 22. The bolt 23 fixes the wave generator 13 to the rotating shaft member 22 of the motor 12. The wave generator 13 is formed in an elliptical cam shape having a major axis and a minor axis. The wave generator 13 has a thin bearing 24 at an outer peripheral edge thereof. The bearing 24 includes an inner ring member 25, an outer ring member 26, and a ball member 27. The inner ring member 25 is fixed to the outer wall of the wave generator 13. The outer ring member 26 is formed in a thin shape and presses the flex spline 15 radially outward via the ball member 27.

  The circular spline 14 is provided on the outer peripheral side of the wave generator 13 and is fixed on the inner peripheral side of the housing 11. The circular spline 14 is formed in a cylindrical shape and has internal teeth 31 on the inner peripheral side. Unlike the wave generator 13, the circular spline 14 is formed in a perfect circular cylinder. The circular spline 14 has a hole 32 penetrating in the axial direction, that is, the plate thickness direction.

  The flex spline 15 is sandwiched between the wave generator 13 and the circular spline 14. That is, the circular spline 14 is positioned on the outer peripheral side of the flexspline 15, and the wave generator 13 is positioned on the inner peripheral side of the flexspline 15. The flex spline 15 is formed in a cup shape having a diaphragm 34 and a cylindrical portion 35. The flexspline 15 is formed of a thin metal so as to be elastically deformable. The cylindrical portion 35 is formed in a cylindrical shape, and a diaphragm 34 is integrally connected to one end in the axial direction, that is, the end opposite to the motor 12. The cylindrical portion 35 has external teeth 36 on the outer peripheral side at the end opposite to the diaphragm 34. The outer teeth 36 mesh with the inner teeth 31 of the circular spline 14. The diaphragm 34 is integrally connected to the output shaft portion 37. The output shaft portion 37 is formed in a cylindrical shape to which an output shaft (not shown) is attached on the inner peripheral side.

  A wave generator 13 is provided on the inner peripheral side of the flex spline 15. The elliptical wave generator 13 presses the flex spline 15 toward the circular spline 14 at both ends on the long diameter side. As a result, the flexspline 15 is deformed into an elliptical ring shape, and both end portions in the major axis direction are in contact with the inner peripheral side of the circular spline 14. As a result, the outer teeth 36 of the flex spline 15 are in mesh with the inner teeth 31 of the circular spline 14 at both ends in the major axis direction. On the other hand, the flexspline 15 deformed into an elliptical annular shape is separated from the wave generator 13 at both ends in the minor axis direction. Therefore, the outer teeth 36 of the flexspline 15 are in a state of being separated from the inner teeth 31 of the circular spline 14 in the minor axis direction.

  The rotation input from the rotating shaft member 22 of the motor 12 is transmitted to the wave generator 13. Thereby, the wave generator 13 rotates together with the rotating shaft member 22 of the motor 12. The flex spline 15 is bent in an elliptical shape by the wave generator 13 as described above. Therefore, in the flexspline 15, the outer teeth 36 mesh with the inner teeth 31 of the circular spline 14 at both ends in the major axis direction, and the outer teeth 36 are separated from the inner teeth 31 of the circular spline 14 in the minor axis direction. Here, the circular spline 14 is fixed to the housing 11. Therefore, when the wave generator 13 on the input side rotates, the flex spline 15 is elastically deformed, and the meshing position with the circular spline 14 is sequentially moved. As a result, when the wave generator 13 rotates once, the flex spline 15 rotates relatively to the side opposite to the rotation direction of the wave generator 13 by the difference in the number of teeth between the external teeth 36 and the internal teeth 31. Thereby, the rotation input from the rotating shaft member 22 of the motor 12 is decelerated and transmitted to the output shaft portion 37 integrated with the flex spline 15.

  The motor flange 16 is provided integrally with the motor 12 at the end of the motor 12 on the wave generator 13 side. The motor flange 16 extends radially outward from the motor 12. Thereby, the motor flange 16 covers the inner peripheral side on the side opposite to the bottom 21 of the housing 11, that is, on the wave generator 13 side of the housing 11. The motor flange 16 may be formed in a disc shape so as to cover the entire side opposite to the bottom portion 21 of the housing 11, or may be formed in a fan shape or a wing shape and a part on the opposite side to the bottom portion 21 of the housing 11. It is good also as a structure covered. The motor flange 16 has a hole 39 penetrating in the axial direction, that is, the plate thickness direction.

  The cross roller bearing 17 includes an inner ring portion 41, an outer ring portion 42, and a roller member 43. The inner ring portion 41 covers the outside of the flexspline 15 and rotates integrally with the flexspline 15. Specifically, the inner ring portion 41 is fixed integrally with the diaphragm 34 and the output shaft portion 37 of the flexspline 15. The bolt 44 fixes the output shaft portion 37, the diaphragm 34, and the inner ring portion 41 with the diaphragm 34 sandwiched between the output shaft portion 37 and the inner ring portion 41. As a result, the inner ring portion 41 rotates integrally with the flex spline 15 and the output shaft portion 37.

  The outer ring portion 42 is fixed to the inner peripheral side of the housing 11 on the outer peripheral side of the inner ring portion 41. Thereby, the inner ring | wheel part 41 and the outer ring | wheel part 42 rotate relatively. The outer ring portion 42 is divided into two parts in the axial direction, and includes a first outer ring portion 45 and a second outer ring portion 46. An outer ring portion 42 composed of the first outer ring portion 45 and the second outer ring portion 46 is sandwiched between the circular spline 14 and the bottom portion 21 of the housing 11. The roller member 43 is rotatably provided between the inner ring portion 41 and the outer ring portion 42 and assists relative rotation between the inner ring portion 41 and the outer ring portion 42. That is, by providing the roller member 43 between the inner ring portion 41 and the outer ring portion 42, the relative rotation between the inner ring portion 41 and the outer ring portion 42 becomes smooth. The roller member 43 is provided at a boundary portion between the first outer ring portion 45 and the second outer ring portion 46 in the axial direction of the cross roller bearing 17. As described above, the roller member 43 is provided between the inner ring portion 41 and the outer ring portion 42. Therefore, by dividing the outer ring portion 42 into the first outer ring portion 45 and the second outer ring portion 46 in the axial direction, the roller member 43 is formed between the inner ring portion 41 and the outer ring portion 42 in the intermediate portion in the axial direction of the cross roller bearing 17. It can be provided in between. The first outer ring portion 45 has a hole 47 penetrating in the axial direction, that is, the plate thickness direction, and the second outer ring portion 46 has a hole 48 penetrating in the plate thickness direction.

  The bolt 18 as a fixing member has a male screw portion 51 at the tip, that is, the lower end in FIG. The bolt 18 is screwed to a female screw portion 52 in which a male screw portion 51 at the tip is formed on the bottom portion 21 of the housing 11. The hole 39 of the motor flange 16, the hole 32 of the circular spline 14, the hole 47 of the first outer ring portion 45, and the hole 48 of the second outer ring portion 46 are arranged coaxially with the female screw portion 52 of the housing 11. Thereby, the bolt 18 passes through the hole 39 of the motor flange 16, the hole 32 of the circular spline 14, the hole 47 of the first outer ring portion 45, and the hole 48 of the second outer ring portion 46 from above in FIG. Is screwed to the female screw portion 52. By screwing the bolt 18 to the bottom 21 of the housing 11, the motor 12 integrated with the motor flange 16, the circular spline 14, and the outer ring portion 42 of the cross roller bearing 17 are fixed to the housing 11. The female flange 52 is not formed in the hole 39 of the motor flange 16, the hole 32 of the circular spline 14, the hole 47 of the first outer ring portion 45, and the hole 48 of the second outer ring portion 46. Therefore, the bolt 18 is not screwed to the motor flange 16, the circular spline 14, the first outer ring portion 45, and the second outer ring portion 46.

Next, characteristics of the wave gear device 10 of the present embodiment having the above-described configuration will be described in comparison with a conventional example.
In the wave gear device 10 of the present embodiment, the circular spline 14 and the outer ring portion 42 of the cross roller bearing 17 are sandwiched between the motor flange 16 and the bottom portion 21. The bolt 18 that fixes the motor flange 16 integral with the motor 12, the circular spline 14, and the outer ring portion 42 of the cross roller bearing 17 to the housing 11 is screwed only to the bottom portion 21 of the housing 11.

  Incidentally, a conventional wave gear device 110 as shown in FIG. 2 includes a housing 111, a motor 112, a wave generator 113, a circular spline 114, a flex spline 115, a motor flange 116, a cross roller bearing 117, and a bolt 118 as a fixing member. And a bolt 119. The cross roller bearing 117 includes an inner ring portion 141, an outer ring portion 142 divided into two, and a roller member 143. The motor 112 and the circular spline 114 integrated with the motor flange 116 are fixed to the bottom 121 of the housing 111 from one side in the axial direction, that is, from the upper side in FIG. On the other hand, the outer ring portion 142 of the cross roller bearing 117 is fixed to the bottom 121 of the housing 111 by a bolt 119 from the lower side of FIG. The motor 112, the wave generator 113, the circular spline 114, the flex spline 115, and the cross roller bearing 117 which constitute the wave gear device 110 are individually manufactured by a plurality of manufacturers as described above. Therefore, in the case of the conventional wave gear device 110, the motor 112 and the circular spline 114 are assembled from the upper side which is one end portion of the housing 111, and the cross roller bearing 117 is assembled from the lower side which is the other end portion of the housing 111. This increases the efficiency of assembly.

  In the case of such a conventional wave gear device 110, slight deformation generated in the bottom 121 of the housing 111 due to tightening of the bolt 118 directly acts on the circular spline 114. Therefore, the circular spline 114 is slightly inclined with respect to the central axis. As a result, a slight shift occurs between the inner teeth 131 of the circular spline 114 and the outer teeth 136 of the flex spline 115, and this slight shift causes noise and vibration. The inclination of the circular spline 114 and the accompanying noise and vibration are generated when the bolt 118 is fastened to the bottom 121 of the housing 111. Therefore, it is difficult to avoid any improvement in the smoothness of the end surface of the bottom 121 of the housing 111 on the circular spline 114 side and the end surface of the circular spline 114 on the bottom 121 side.

  On the other hand, as shown in FIG. 1, in this embodiment, the bolt 18 passes through the motor flange 16, the circular spline 14, and the outer ring portion 42 of the cross roller bearing 17 and is screwed to the bottom portion 21 of the housing 11. Therefore, when the bolt 18 is screwed to the bottom portion 21 of the housing 11, the bottom portion 21 is slightly deformed 60 on the end surface on the outer ring portion 42 side around the female screw portion 52 as shown in FIG. 3. FIG. 3 is a diagram schematically showing the contact portion between the bottom portion 21 and the cross roller bearing 17 in order to simplify the description of the present embodiment, and does not show actual dimensions.

  A slight deformation 60 of the bottom portion 21 of the housing 11 is transmitted to the outer ring portion 42 of the cross roller bearing 17 in contact with the bottom portion 21. Specifically, the slight deformation 60 of the bottom portion 21 is transmitted to the second outer ring portion 46 in contact with the bottom portion 21. The second outer ring portion 46 is in contact with the first outer ring portion 45 on the side opposite to the bottom portion 21. On the other hand, the outer ring portion 42 of the cross roller bearing 17 holds the roller member 43 between the inner ring portion 41 and an intermediate portion in the axial direction. Therefore, a minute gap 61 is formed microscopically between the first outer ring portion 45 and the second outer ring portion 46. The minute gap 61 between the first outer ring portion 45 and the second outer ring portion 46 is sufficiently larger than the deformation 60 generated in the bottom portion 21 of the housing 11 by screwing of the bolt 18 no matter how high the processing accuracy is increased. growing. That is, the amount of deformation caused by the deformation 60 of the bottom portion 21 of the housing 11 is about 1/10 μm, whereas the minute gap 61 generated between the first outer ring portion 45 and the second outer ring portion 46 is about several μm. Become. Accordingly, even if the bottom portion 21 of the housing 11 is deformed by screwing the bolt 18 and the second outer ring portion 46 contacting the bottom portion 21 is slightly inclined due to the deformation 60 of the bottom portion 21, the inclination of the second outer ring portion 46 is 4, it is absorbed by the minute gap 61 between the first outer ring portion 45 and the second outer ring portion 46. In FIG. 4, the initial state of the second outer ring portion 46 before the bolt 18 is screwed is indicated by a solid line, and the inclined state of the second outer ring portion 46 after the bolt 18 is screwed is indicated by a broken line. . As described above, the inclination of the second outer ring portion 46 is absorbed by the minute gap 61 so that the inclination of the second outer ring portion 46 due to the deformation 60 of the bottom portion 21 is not transmitted to the first outer ring portion 45. Accordingly, the circular spline 14 in contact with the first outer ring portion 45 is not affected by the deformation 60 of the bottom portion 21 due to the screwing of the bolt 18. Therefore, there is no slight shift caused by the screwing of the bolt 18 in the meshing between the inner teeth 31 of the circular spline 14 and the outer teeth 36 of the flex spline 15. FIG. 4 is also a schematic diagram for explaining the present embodiment similarly to FIG. 3 and does not show actual dimensions.

  As described above, in one embodiment, even when the bolt 18 is screwed to the bottom 21 of the housing 11, the deformation of the circular spline 14, and the internal teeth 31 of the circular spline 14 and the external teeth of the flex spline 15. The deformation at the meshing portion with 36 is suppressed. Further, the deformation of the housing 11 caused by the screwing of the bolt 18 and the inclination of the second outer ring portion 46 due to the deformation are avoided in processing formed between the first outer ring portion 45 and the second outer ring portion 46. It absorbs using the minute gap 61 that cannot be absorbed. Therefore, it is not necessary to add new parts, and the size of various parts such as the housing 11 is not increased. Therefore, it is possible to reduce vibration and rotation errors between the circular spline 14 and the flex spline 15 with a simple structure without causing the addition and enlargement of new parts.

  The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

  In the drawings, 10 is a wave gear device, 11 is a housing, 12 is a motor, 13 is a wave generator, 14 is a circular spline, 15 is a flex spline, 16 is a motor flange, 17 is a cross roller bearing, and 18 is a bolt (fixing member). , 21 is a bottom portion, 31 is an internal tooth, 36 is an external tooth, 37 is an output shaft portion, 41 is an inner ring portion, 42 is an outer ring portion, and 43 is a roller member.

Claims (1)

A cylindrical housing having an annular bottom projecting radially inward at one end;
A motor that is provided at an end opposite to the bottom in the axial direction of the housing and generates a driving force by energization;
A wave generator accommodated coaxially with the housing inside the housing and rotated by a driving force from the motor;
A circular spline provided on the outer peripheral side of the wave generator, formed in a cylindrical shape having internal teeth on the inner peripheral side, and fixed to the housing;
The wave generator is sandwiched between the wave generator and the circular spline and has outer teeth meshing with the inner teeth on the outer peripheral side, and is rotated by the wave generator while meshing with the circular spline. A flex spline that decelerates and transmits to the output shaft provided at the end opposite to the motor;
A motor flange provided integrally with the motor at the end of the motor on the wave generator side, extending radially outward, and covering the wave generator side of the housing;
An inner ring portion that rotates integrally with the flexspline, and is sandwiched between the circular spline and the bottom portion on the outer peripheral side of the inner ring portion, is fixed to the inner peripheral side of the housing, and rotates relative to the inner ring portion. An outer ring portion that is divided into two in the axial direction, and a roller member that is provided between a boundary between the two outer ring portions and the inner ring portion and supports relative rotation between the inner ring portion and the outer ring portion. A cross roller bearing having,
The motor flange, the circular spline, and the outer ring portion that are integrated with the motor flange are fixed to the housing by screwing the end portion through the motor flange, the circular spline, and the outer ring portion to the bottom portion. Members,
A wave gear device comprising:

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