JP2008025687A - Bearing for wave gear device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and lightweight bearing for a wave gear device having high rigidity, low torque and high durability. <P>SOLUTION: The wave gear device 20 consists of a rigid internal gear 21, a flexible external gear 22 provided inside of the rigid internal gear 21 and a wave generator 23, provided inside of the external gear 22, for radially deflecting the flexible external gear 22, partially meshing it to the rigid internal gear 21 and moving a meshing position of both the gears 21, 22 in a circumference direction. The bearing 30 for the wave gear device for supporting the rigid internal gear 21 and the flexible external gear 22 in a relatively rotatable manner is a back face combination-type angular ball bearing having outer rings 31, 31 which can be internally fitted to a housing 27 to which the flexible external gear 22 is fixed, inner rings 32, 32 which can be externally fitted to the rigid internal gear 21 and a plurality of balls 33 provided with a contact angle α between a pair of outer ring raceway faces 31a, 31a of the outer rings 31, 31 and a pair of inner ring raceway faces 32a, 32a of the inner rings 32, 32. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wave gear device bearing that supports a rigid internal gear and a flexible external gear of a wave gear device in a relatively rotatable manner.

  2. Description of the Related Art Conventionally, a wave gear device with a small backlash and a low reduction ratio has been used as a speed reducer in a drive mechanism such as a robot. As the wave gear device, a cup type, a top hat type, a flat type, and the like have been devised depending on the shape of the flexible external gear to be incorporated, and all operations are the same (for example, see Patent Documents 1 and 2). .

  As shown in FIG. 7, the top hat type wave gear device 1 includes an annular rigid internal gear 2, a silk hat type flexible external gear 3 having a smaller number of teeth than the rigid internal gear 2, and an elliptical shape. It is mainly composed of a wave generator 4 having a shape outline. The flexible external gear 3 is arranged inside the rigid internal gear 2, and the flexible external gear 3 is deflected in the radial direction by the wave generator 4 to be partially with respect to the rigid internal gear 2. Engage. When the wave generator 4 is rotated by the rotation of the motor or the like, the meshing position of the two gears 2 and 3 is moved in the circumferential direction, and the two gears 2 and 3 are relatively rotated at a rotation speed corresponding to the difference in the number of teeth.

  The wave gear device 1 is connected to a motor and is provided around a hollow input shaft 5 having a cam plate portion 5a having an elliptical outline of the wave generator 4 on the outer peripheral surface. Around the hollow input shaft 5, first and second end plates 8, 9 supported via ball bearings 6, 7 are arranged so as to sandwich the wave gear device 1 between the axial directions, One end plate 8 is fastened and fixed to the flexible external gear 3, and the second end plate 9 is fastened and fixed to the rigid internal gear 2. Since one of the first end plate 8 and the second end plate 9 is connected to the load side and the other is fixed so as not to rotate, the decelerated rotation is output from the end plate side connected to the load side. Transmitted to the load side.

Further, in such a wave gear device 1, a cross roller bearing 10 (see FIG. 7) that can receive a moment load as a bearing that supports the rigid internal gear 2 and the flexible external gear 3 so as to be relatively rotatable. And 4-point contact ball bearings are used.
JP-A-9-217798 JP 2005-308131 A

  By the way, the above-mentioned cross roller bearing is a cylindrical roller that is alternately inclined by 45 degrees with respect to the center of the bearing, and can be loaded with radial load, axial load, and moment load. The capacity is determined, and the moment load that can be applied is limited by the bearing dimensions.

  Further, since the cylindrical rollers are rotated at an angle of 90 degrees with each other, the rotational friction is large, resulting in a large rotational torque. Furthermore, due to its structure, there is a short space (bearing space volume) in which the lubricant can be enclosed, and there is a problem in durability.

  In addition, since the cylindrical roller is inclined at 45 degrees with respect to the center of the bearing, the outer diameter of the inner ring and the outer ring is increased due to the restriction of the bearing cross-section height and the outer diameter becomes larger than the inner diameter. Therefore, there is a problem that the weight of the bearing is increased.

  Also, when a four-point contact ball bearing is applied, the moment load that can be applied cannot be increased as in the case of the cross roller bearing.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a bearing for a wave gear device that has high rigidity, low torque, and high durability, and is compact and lightweight. There is to do.

The above object of the present invention is achieved by the following configurations.
(1) A rigid internal gear, a flexible external gear arranged inside the rigid internal gear, and a radius inside the flexible external gear arranged inside the flexible external gear A wave generator comprising: a wave generator that is bent in a direction and partially meshed with the rigid internal gear and moves the meshing position of both gears in the circumferential direction; A wave gear device bearing that supports a flexible external gear so as to be relatively rotatable,
The bearing is
One of the rigid internal gear and the flexible external gear, or an outer ring that can be fitted in a housing to which the one is fixed,
The other of the rigid internal gear and the flexible external gear, or an inner ring that can be fitted onto a shaft portion to which the other is fixed,
A plurality of balls arranged with a contact angle between a pair of outer ring raceway surfaces of the outer ring and a pair of inner ring raceway surfaces of the inner ring;
It is a back combination type angular contact ball bearing provided with a wave gear device bearing.
(2) In the back combination type angular contact ball bearing, the other of the rigid internal gear and the flexible external gear, or a pressing member is bolted to the shaft portion to which the other is fixed, The wave gear device bearing according to (1), wherein a preload is applied by pressing an end face of the inner ring.
(3) The wave gear device bearing according to (1) or (2), wherein the outer end surface of the inner ring protrudes outward in the axial direction from the outer end surface of the outer ring.
(4) The back combination type angular contact ball bearing includes a crown type cage having pockets for holding the double row balls,
The bearing for a wave gear device according to any one of (1) to (3), wherein the pillar portion of the crown-shaped cage is inclined radially outward from the base portion toward the tip portion.
(5) A flange is formed axially outward from the inner ring raceway surface of the inner ring, and the flange has a height extending to the vicinity of the pitch circle of the ball. (4) The bearing for wave gear devices in any one of.

  According to the bearing for the wave gear device of the present invention, one of the rigid internal gear and the flexible external gear, or the outer ring that can be fitted in the housing to which the one is fixed, the rigid internal gear and the flexible gear. A plurality of external gears, or an inner ring that can be fitted onto a shaft portion to which the other is fixed, a pair of outer ring raceway surfaces of the outer ring and a pair of inner ring raceways of the inner ring with a contact angle. Since it is a back combination type angular contact ball bearing provided with a row of balls, it has high rigidity, low torque and high durability, and can be compact and lightweight.

  Hereinafter, the bearing for wave gear devices concerning each embodiment of the present invention is explained in detail with reference to drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a top hat type wave gear device to which the wave gear device bearing of the first embodiment is applied. The wave gear device 20 includes an annular rigid internal gear 21 in which internal teeth 21 a are formed on the inner peripheral surface, a silk hat type flexible external gear 22 disposed on the inner side, and an inner side of the gear 22. And a wave generator 23 to be fitted.

  The flexible external gear 22 includes a cylindrical body 22a, an annular diaphragm 22b extending continuously from one end of the body 22a at right angles to the outside in the radial direction, and an annular formed integrally with the diaphragm 22b. Boss 22c and cylindrical outer teeth 22d formed on the outer peripheral surface of the body 22a. The number of teeth of the outer teeth 22d is set to be smaller than the number of teeth of the inner teeth 21a (in this embodiment, two fewer than the inner teeth 21a).

  The wave generator 23 includes, for example, an annular rigid cam plate 24 having an elliptical contour, and an outer peripheral surface of the rigid cam plate 24 and a portion where the external teeth 22d of the flexible external gear are formed. A ball bearing 25 fitted between them. A hollow input shaft 26 to which a motor output shaft (not shown) and the like are connected is formed at the center of the rigid cam plate 24.

  In the wave gear device 20, when the rigid cam plate 24 connected to the motor output shaft rotates, the flexible external gear 22 is bent into an elliptical shape by the elliptical rigid cam plate 24 via the ball bearing 25. The meshing position of the inner teeth 21a and the outer teeth 22d meshed at two locations in the circumferential direction moves in the circumferential direction. Since the number of teeth of the internal teeth 21a and the external teeth 22d is different, a relative rotation corresponding to the difference in the number of teeth occurs between the internal teeth 21a and the external teeth 22d, and is greatly decelerated compared to the input rotational speed. The Then, by fixing one of the rigid internal gear 21 and the flexible external gear 22, a reduced rotation output can be obtained from the other gear.

  Here, between the outer peripheral surface of the rigid internal gear 21 and the inner peripheral surface of the housing 27 to which the flexible external gear 22 and the bolt are fixed, the rigid internal gear 21 and the flexible external gear 22 are provided. The wave gear device bearing 30 is disposed so as to rotatably support the shaft.

  As shown in FIG. 2, the bearing 30 includes a pair of outer rings 31 and 31 that can be fitted in the housing 27, a pair of inner rings 32 and 32 that can be fitted on the rigid internal gear 21, and the outer rings 31 and 31. A plurality of balls 33, 33 arranged in a double row with a contact angle α between the pair of inner ring raceway surfaces 32a, 32a of the pair of outer ring raceway surfaces 31a, 31a and the inner rings 32, 32; And a retainer 34, 34 having pockets for holding 33 respectively. The contact angle α of the balls 33, 33 in each row is opposite to each other.

  The pair of outer rings 31, 31 are fixed in the axial direction by an inwardly stepped portion 27 a formed in the housing 27 and a cover member 41 fixed to the axial end surface of the housing 27 with a bolt 40. On the other hand, the pair of inner rings 32, 32 is axially formed by an outward stepped portion 21 b formed on the rigid internal gear 21 and a pressing member 43 fixed to the axial end surface of the rigid internal gear 21 with a bolt 42. In addition to being fixed, the dimensions of the rigid internal gear 21 and the pressing member 43 are managed, and the end surface of the inner ring 32 is pressed by fastening the bolt of the pressing member 43, so that an appropriate preload is applied to the bearing.

  Further, the contact angle α of the back combination type angular ball bearing 30 is appropriately set in the range of 25 to 40 degrees, and the extension line L of the contact angle α is axially inward from the axial end surfaces of the inner rings 32 and 32. Thus, it is set so as to intersect with the inner peripheral surfaces of the inner rings 32, 32.

  Thus, by using the back combination type angular ball bearing 30 for the wave gear device 20, the operating point distance is increased by the back combination, the moment load is improved, and the rigid internal gear 21 ensures the moment. It is comprised so that a load can be loaded.

  Further, the rear combination angular ball bearing 30 has a small rotational torque because both the raceway surfaces 31a and 32a and the ball 33 are in point contact. On the other hand, the balls 33 are appropriately arranged by the cage 34, the bearing space volume can be sufficiently secured, and the grease life can be extended. For this reason, conventionally, maintenance for replenishing grease has been performed in a wave gear device to which a cross roller bearing is applied. However, in a wave gear device using a back combination type angular ball bearing 30, grease replenishment is not performed. It can be used until the endurance time of the wave gear device is reached.

  Furthermore, the back combination type angular contact ball bearing 30 can reduce the bearing cross-sectional height, reduce the wall thickness, and reduce the weight as compared with the cross roller bearing.

(Second Embodiment)
Next, a wave gear device bearing according to a second embodiment of the present invention will be described in detail with reference to FIGS. In addition, the same code | symbol is attached | subjected about a part equivalent to 1st Embodiment, and description is abbreviate | omitted or simplified.

  Similar to the first embodiment, the wave gear device bearing 50 of the present embodiment is a back combination angular ball bearing incorporated into the top hat type wave gear device 20, and a pair of outer rings that can be fitted in the housing 27. 51, 51, a pair of inner rings 52, 52 that can be externally fitted to the rigid internal gear 21, a pair of outer ring raceway surfaces 51a, 51a of the outer rings 51, 51 and a pair of inner ring raceway surfaces 52a, 52a of the inner rings 52, 52. There are provided a plurality of balls 53, 53 arranged in a double row with a contact angle α therebetween, and cages 54, 54 having pockets for holding the balls 53, 53 in each row, respectively. Further, as in the first embodiment, the pair of inner rings 52, 52 are pressed in the axial direction by the bolts 42 via the pressing members 43, thereby applying an appropriate preload to the bearings.

Here, in the back combination type angular contact ball bearing 50 of the present embodiment, the outer end surfaces 52b, 52b of the pair of inner rings 52, 52 are axially outward from the outer end surfaces 51b, 51b of the pair of outer rings 51, 51. It protrudes. Further, flanges 52c and 52c are formed axially outward from the inner ring raceway surfaces 52a and 52a of the pair of inner rings 52 and 52, and the flanges 52c and 52c are in the vicinity of the pitch circle PCD of the balls 53 and 53, specifically. In addition, the height extends to a position slightly lower than the pitch circle PCD. Thereby, a load point can be expanded and moment rigidity can be improved more and the restriction | limiting in the dimension of the housing 27 or the press member 43 can be eased.
Also in this embodiment, the contact angle α of the back combination type angular contact ball bearing 50 is appropriately set in the range of 25 to 40 degrees, and the extension line L of the contact angle α is the axis of the inner rings 52 and 52. It is set so as to cross the inner peripheral surfaces of the inner rings 52, 52 on the inner side in the axial direction from the direction outer end surfaces 52b, 52b.

In addition, the cages 54 and 54 of the present embodiment are synthetic resin crown-type cages, and the column portions 54a and 54a are provided so as to prevent interference with the flange portions 52c and 52c of the inner rings 52 and 52. It is formed to incline radially outward from the base toward the tip.
The cages 54 and 54 may be constituted by metal machined cages 54 'and 54' as shown in FIG. 5 instead of the synthetic resin crown cage.
Other configurations and operations are the same as those in the first embodiment.

  In addition, this invention is not limited to the thing of said embodiment, A change, improvement, etc. are possible suitably.

  In the top hat type wave gear device of the present embodiment, the outer ring of the back combination type angular ball bearing is fitted in the housing to which the flexible external gear is fixed, and the inner ring is fitted in the rigid internal gear. However, the outer ring may be fitted into the flexible external gear, and the inner ring may be fitted to the shaft portion to which the rigid internal gear is fixed. The back combination type angular contact ball bearing of the present invention can also be applied to the top hat type wave gear device shown in FIG.

In the present embodiment, the wave gear device has been described only for the top hat type, but the bearing for the wave gear device of the present invention can also be applied to a cup type or a flat type.
For example, in a cup-type wave gear device bearing, the outer ring of the back combination type angular ball bearing is fitted into a rigid internal gear or a housing to which the rigid internal gear is fixed, and the inner ring is flexible. The external gear or the flexible external gear is fitted on the shaft portion to which the external gear is fixed.

  In the present embodiment, the pair of outer rings and the pair of inner rings are arranged adjacent to each other. However, when there is a space, a spacer is arranged between the pair of outer rings and between the pair of inner rings. As a result, the bearing span can be increased and the rigidity can be further improved.

  Furthermore, the configuration of the back combination type angular ball bearing can be improved as appropriate, and the pair of outer rings may be formed integrally or may include a seal member.

  Here, using the back combination type angular contact ball bearing of the present invention shown in FIG. 3 and a conventional cross roller bearing, the outer diameter dimensions were made equal and the moment stiffness was compared. Table 1 shows the main dimensions, basic rated load and moment stiffness of each bearing, and FIG. 6 is a graph showing the moment stiffness with respect to the preload of the back combination angular ball bearing of the present invention.

  As shown in Table 1 and FIG. 6, in the conventional cross roller bearing, it is difficult to increase / decrease the moment load because the preload cannot be easily increased / decreased, but it is difficult to improve the moment rigidity. Then, it can be seen that the preload can be easily adjusted, and that the moment stiffness can be improved by increasing the preload.

It is sectional drawing of the wave gear apparatus with which the bearing for wave gear apparatuses which concerns on 1st Embodiment of this invention is applied. It is an expanded sectional view of the bearing for wave gear apparatuses of FIG. It is sectional drawing of the wave gear apparatus with which the bearing for wave gear apparatuses which concerns on 2nd Embodiment of this invention is applied. It is an expanded sectional view of the bearing for wave gear apparatuses of FIG. It is an expanded sectional view of the bearing for wave gear devices concerning the modification of a 2nd embodiment. It is the graph which showed the moment rigidity with respect to the preload load of the back combination type angular contact ball bearing of this invention. It is sectional drawing of the wave gear apparatus using the conventional cross roller bearing.

Explanation of symbols

20 Wave gear device 21 Rigid internal gear 22 Flexible external gear 23 Wave generator 27 Housing 30 Rear combined angular ball bearing 31 Outer ring 31a Outer ring raceway surface 32 Inner ring 32a Inner ring raceway surface 33 Ball α Contact angle

Claims (5)

A rigid internal gear, a flexible external gear disposed inside the rigid internal gear, and a flexible external gear disposed inside the flexible external gear, bending the flexible external gear in the radial direction. A wave generator that partially meshes with the rigid internal gear and moves the meshing position of both gears in the circumferential direction. A wave gear bearing that supports an external gear so as to be relatively rotatable,
The bearing is
One of the rigid internal gear and the flexible external gear, or an outer ring that can be fitted in a housing to which the one is fixed,
The other of the rigid internal gear and the flexible external gear, or an inner ring that can be fitted onto a shaft portion to which the other is fixed,
A plurality of balls arranged with a contact angle between a pair of outer ring raceway surfaces of the outer ring and a pair of inner ring raceway surfaces of the inner ring;
It is a back combination type angular contact ball bearing provided with a wave gear device bearing.   The back combination angular contact ball bearing has a pressing member bolted to the other of the rigid internal gear and the flexible external gear, or to the shaft portion to which the other is fixed, The wave gear device bearing according to claim 1, wherein a preload is applied by pressing the end face.   3. The wave gear device bearing according to claim 1, wherein an outer end surface of the inner ring projects axially outward from an outer end surface of the outer ring. 4. The back combination type angular contact ball bearing includes a crown type cage having pockets for holding the double row balls,
The bearing for a wave gear device according to any one of claims 1 to 3, wherein the pillar portion of the crown-shaped cage is inclined radially outward from the base portion toward the tip portion.   5. A flange portion is formed axially outward from the inner ring raceway surface of the inner ring, and the flange portion has a height extending to the vicinity of the pitch circle of the ball. A bearing for a wave gear device according to claim 1.

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