JP3580506B2 - Silk hat type flexible meshing gear device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a silk hat type flexible meshing gear device incorporating a silk hat shaped flexible external gear. More specifically, the present invention relates to a silk hat type flexible meshing gear device capable of reducing stress concentration of a silk hat shaped external gear having a reduced outer diameter.
[0002]
[Prior art]
As a flexible meshing gear device, a type in which a flexible external gear has a silk hat shape is known. In this specification, this type of device will be referred to as a silk hat type flexible meshing gear. FIG. 6 is a longitudinal sectional view of the flexible external gear of the silk hat type flexible meshing gear device cut along a plane including the device axis. As shown in this figure, a flexible external gear 1 has a cylindrical body 2, an annular diaphragm 3 having an inner peripheral end continuous with the base side open end, and a diaphragm 3. 3 is provided with an annular thick boss portion 5 which is continuous with the outer peripheral end portion. External teeth 4 are integrally formed in the outer peripheral portion of the opening end on the distal end side of the body portion 4 in the circumferential direction.
[0003]
This type of device is convenient when the rotary member or the like is arranged to penetrate along the device axis 1a. That is, since the diaphragm portion 3 of the flexible external gear extends radially outward from the end of the body portion 2, a rotating member or the like can be disposed so as to penetrate the space inside the body portion 3. However, since the diaphragm portion 3 extends outward in the radial direction, the outer diameter of the device becomes larger than that of a cup-shaped flexible meshing gear device incorporating a cup-shaped flexible external gear. . In order to reduce the outer diameter of the apparatus, the outer diameter of the diaphragm 3 may be reduced. However, as indicated by arrows in FIG. 6, large bending stress is repeatedly applied to the diaphragm portion 3 by the deformation of the body portion 2 bent in the radial direction by a wave generator (not shown). Therefore, when the diameter of the diaphragm portion 3 is reduced, the stress generated at the inner peripheral end portion 3a and the outer peripheral end portion 3b of the diaphragm portion 3 increases in inverse proportion thereto. As a result, stress concentration occurs at these inner and outer peripheral ends, which is not preferable.
[0004]
Therefore, in Japanese Utility Model Laid-Open Publication No. 3-118346, the present applicant reduces the thickness of the diaphragm portion at the center portion and increases the thickness at both end portions, whereby the diaphragm portion at the inner peripheral end portion and the outer peripheral end portion thereof is formed. A configuration that alleviates stress concentration is proposed.
[0005]
[Problems to be solved by the invention]
The present invention relates to an improvement of the device disclosed in the above publication. The above publication discloses that the thickness of the diaphragm is reduced at the center.
[0006]
In order to clarify the other points, the present inventors examined the stress generation state of the silk hat type flexible external gear in the silk hat type flexible meshing gear device and performed a number of experiments. .
[0007]
The present invention is based on the results of such studies, and it is an object of the present invention to propose a shape of a diaphragm portion that can more efficiently reduce the stress concentration in the diaphragm portion and can make the stress state generated in this portion uniform. And
[0008]
[Means for Solving the Problems]
The present invention provides an annular rigid internal gear, a flexible external gear inside thereof, and a radial internal bending of the external gear arranged inside the rigid internal gear so as to partially form the rigid internal gear. And a wave generator for rotating these meshing positions in the circumferential direction while meshing with each other. The external gear has a cylindrical body having external teeth formed on an outer peripheral surface on one opening end side. And an annular diaphragm part whose inner peripheral end is continuous with the other open end of the body part, and an annular boss part formed continuously with the outer peripheral end of the diaphragm part. In a silk hat type flexible meshing gear device having a silk hat shape, the cross-sectional shape of a flexible external gear is set as follows.
[0009]
That is, when the diaphragm portion of the external gear is cut along a plane including the device axis, the thickness of the inner peripheral end is t (A), and the thickness of the outer peripheral end is t (C). Assuming that the thickness of the substantially central portion between the inner peripheral end and the outer peripheral end is t (B), t (A) is set to the maximum thickness, t (B) is set to the minimum thickness, and t (A) is set. )> T (C)> t (B).
[0010]
Here, in order to smooth the change in the stress distribution from the inner peripheral end to the outer peripheral end of the diaphragm portion, the cross-sectional shape of the diaphragm portion of the external gear is defined by at least one surface contour shape by a plurality of curves. It is preferable that the thickness is changed smoothly in a prescribed manner.
[0011]
According to the study by the present inventors, the relationship between the thickness t (A) of the inner peripheral end portion and the thickness t (B) of the central portion is such that t (A) / t (B) is about 1. It is preferred that the value be in the range of 5 to about 2.2. The relationship between the thickness t (C) of the outer peripheral end and the thickness t (B) of the central portion is such that t (C) / t (B) is in the range of about 1.4 to about 2.0. It is preferable to set so that
[0012]
[Action]
In the diaphragm portion of the silk hat type flexible external gear, the stress distribution from the inner peripheral end to the outer peripheral end becomes gentle. Further, stress concentration at the inner peripheral end and the outer peripheral end is also avoided. As a result, the outer diameter of the diaphragm can be reduced.
[0013]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIGS. 1 and 2 show the overall configuration of a silk hat type flexible meshing gear device of this embodiment. In this figure, the device 11 comprises a ring-shaped rigid internal gear 12, a silk hat-shaped flexible external gear 13 arranged inside this, and an elliptical wave generator 14 fitted inside this. It is configured. The flexible external gear 13 has a cylindrical body portion 22, an annular diaphragm portion 23 having an inner peripheral end portion 23 a continuous with a base end opening thereof, and an outer peripheral end portion 23 b of the diaphragm portion 23. And a thick annular boss 25 integrally formed. External teeth 24 are integrally formed in the outer peripheral portion of the opening end on the distal end side of the body 22 in the circumferential direction. The annular boss portion 25 is for attachment to another member (not shown), and the body portion 22 and the diaphragm portion 23 are supported by the boss portion 25 in a cantilever state.
[0015]
On the other hand, the wave generator 14 includes a hollow hub 14a, an elliptical rigid cam plate 14b fitted on the outer periphery thereof, and a ball bearing 14c fitted on the outer periphery. The wave generator 14 deflects the portion of the body 22 where the external teeth 24 of the flexible external gear are formed into an elliptical shape, and the two external tooth portions located at both ends of the long axis of the elliptical shape are removed. The internal gear 12 meshes with the internal teeth 12 a of the rigid internal gear 12. When the wave generator 14 rotates about the device axis 11a in this state, these meshing positions rotate in the circumferential direction. By this rotation, relative rotation occurs between the flexible external gear 13 and the rigid internal gear 12 according to the difference in the number of teeth between the external teeth and the internal teeth. Therefore, for example, if the rigid internal gear 12 is fixed and the wave generator 14 is used as a high-speed rotation input element, the external gear 13 becomes a reduced rotation output element, from which a reduced rotation output is obtained. .
[0016]
FIG. 3 is a view showing a vertical cross section of the top hat-shaped flexible external gear 13 cut along a plane including the device axis 11a. FIG. 4 is an enlarged view of the diaphragm uneven portion of the flexible external gear 13. The cross-sectional shape of each part is as follows when cut along a plane including the apparatus axis 11a. First, the inner peripheral surface of the body portion 22 of the external gear 13 is defined by a straight line 22b that is parallel to the apparatus axis 11a from a front end opening end 22a. A point 22c on the base end side of the straight line 22b is connected to an arc 22d smoothly continuing to the straight line 22b. At the point A, the other end of the arc 22d smoothly continues to a straight line 231 perpendicular to the device axis 11a, which defines the back surface of the diaphragm portion 23. The other end of the straight line 231 on the outer peripheral side is smoothly continued at a point C to an arc 25a continuous with the back surface of the boss 25. The other end of the arc 25a is connected to a straight line 25b orthogonal to the device axis 11a.
[0017]
On the other hand, the outer peripheral surface of the body 22 of the external gear 13 is basically defined by a straight line 22e parallel to the straight line 22b on the inner peripheral surface side. External teeth 24 are integrally formed on the outer peripheral portion on the tip side of the body portion 22 as described above. The center of the end of the straight line 22e smoothly continues to the convex arc 22f at the point O1. The center of the arc 22f smoothly continues to the concave arc 22g of O2. Further, the concave arc 22g smoothly continues to the concave arc 22h whose center has a smaller curvature than the concave arc 22h. The concave arc 22h smoothly continues to the concave arc 22i whose center of curvature is O4. As described above, the base portion of the body 22 is formed by the arc 22g with a thin portion thinner than the thickness t (22) of the body 22 defined by the straight lines 22b and 22e.
[0018]
The center defining the surface side of the diaphragm portion 23 of the circular arc 22i is smoothly continued to the circular arc 233 of O5. This arc 233 has a center slightly larger in curvature than the center at the center position of the diaphragm portion 23, that is, the point B which is the center position between the points A and C, smoothly continues to the arc 234 of O6. . The other end of the arc 234 smoothly continues to a straight line 25c orthogonal to the device axis 11a that defines the surface of the boss 25. As described above, the rear surface side of the diaphragm portion 23 is defined by the straight line 231, and the front surface side is defined by the two arcs 233 and 234.
[0019]
The two arcs 233 and 234 are continuous at a point B which is the center of the diaphragm 23. Accordingly, the minimum thickness of the diaphragm portion 23 defined by these straight lines and arcs is the thickness t (B) at point B, which is the center position. The thickness t (A) at point A, which is the inner peripheral end of the diaphragm 23, is the maximum thickness. Further, the thickness t (C) at point C, which is the outer peripheral end of the diaphragm portion 23, is slightly smaller than the thickness t (A).
[0020]
As described above, in the flexible meshing gear device 11 in which the cross-sectional shape of the flexible external gear 13 is defined, the distribution of the stress generated in the diaphragm portion 23 during its operation is smoother and more uniform than before. In addition, the stress concentration at the inner peripheral end and the outer peripheral end is sufficiently reduced. Therefore, the outer diameter of the diaphragm portion 23 can be made smaller than in the related art. That is, the apparatus outer diameter dimension D in FIG. 3 can be reduced. Further, since the stress generated in the diaphragm portion 23 can be reduced, the length L (22) of the body portion 22 can be shortened.
[0021]
On the other hand, in the present example, a thin portion is formed in a portion of the body 22 that is continuous with the inner peripheral end of the diaphragm 23. According to experiments by the present inventors, this portion is a portion where the generated stress is small. Therefore, by making this portion thinner than the thickness of the adjacent body portion 22, the stress distribution from the body portion 22 to the diaphragm portion 23 can be made uniform.
[0022]
Here, according to experiments by the present inventors, when the thickness at the points A and C is set within the following range with respect to the minimum thickness t (B), the thickness from the inner peripheral end of the diaphragm portion 23 is changed. It was confirmed that the stress portion toward the outer peripheral end became gentle, and the stress concentration at the inner peripheral end and the outer peripheral end was reduced.
[0023]
1.5 <t (A) / t (B) <2.2
1.4 <t (C) / t (B) <2.0
In this example, two arcs 233 and 234 are used to regulate the thickness of the diaphragm 23. However, the thickness of the diaphragm portion 23 may be defined using three or more arcs. Further, although the back surface of the diaphragm portion 23 is defined by a straight line 231, the front surface side may be defined by a straight line using a curve instead. Further, both surfaces of the diaphragm portion 23 may be defined by a curve, and may be set to have a cross-sectional shape satisfying the above-described conditions.
[0024]
Further, in this example, the thin portion is formed on the outer peripheral surface side of the body portion 22. However, such a thin portion may be formed on the inner peripheral surface side of the body portion 22 instead. Alternatively, this portion may be defined by a concave curve on both the outer peripheral surface and the inner peripheral surface to be a thin portion.
[0025]
Here, according to experiments by the present inventors, it is desirable that the thickness t (221) of the thin portion 221 of the body 22 be set to about 80% of the thickness t (22) of the body 22. It was confirmed that.
[0026]
Next, the coning of the flexible external gear 13 in the silk hat type flexible meshing gear device 11 will be considered. The flexible external gear 13 is repeatedly bent into an elliptical shape by a wave generator 14 fitted therein. In order to reduce the coning force acting on the bearing 14c of the wave generator 14 due to this deformation phenomenon, that is, the coning, it is necessary to shorten the length (teeth length) L (24) of the external teeth 24 in the tooth trace direction. preferable. If the tooth length L (24) is shortened, the axial length L (22) of the body 22 can be shortened accordingly. That is, it is possible to realize a flexible meshing gear device having a short shaft length. However, when the shaft length is reduced, as shown in FIG. 5, the coning angle θ of the flexible external gear 13 increases. As a result, the stress generated in the diaphragm 23 also increases.
[0027]
However, by setting the thickness of each portion of the flexible external gear 13 as in the device 11 of the present embodiment described above, excessive stress concentration occurs even if the shaft length is shortened. It was also confirmed that the distribution of the generated stress could be made gentle.
[0028]
Here, according to experiments by the present inventors, etc., the length L (22) of the body 22 of the flexible external gear 13 is determined by changing the opening diameter of the external teeth, that is, the pitch circle diameter D (p) of the external teeth. It has been determined that it is desirable to set the size within a range of about 20 to about 70% of the above. In addition, it was confirmed that it is desirable that the length L (24) of the external teeth in the tooth trace direction is practically set to a length in the range of about 10 to about 30% of the pitch circle diameter D (p).
[0029]
【The invention's effect】
As described above, in the silk hat-type flexible meshing gear device of the present invention, the thickness of the diaphragm portion of the flexible external gear having the silk hat shape is set to the minimum thickness at the center portion and the inner peripheral end portion. In the maximum thickness, the thickness of the outer peripheral end is set to be thinner than the thickness of the inner peripheral end and larger than the thickness of the central part, and such a thickness is set along the outer peripheral end from the inner peripheral end. The thickness is smoothly changed so that the thickness is formed. Therefore, according to the present invention, stress concentration at the inner peripheral end and the outer peripheral end of the diaphragm can be reduced, and the generated stress distribution of the diaphragm can be made uniform. Therefore, the outer diameter of the diaphragm can be made smaller than before. Further, even if the length of the body portion is shortened, excessive stress concentration can be prevented from being generated at the inner and outer peripheral ends of the diaphragm portion, so that a flexible external gear having a short shaft length can be realized.
[0030]
As described above, according to the present invention, it is possible to realize a small and compact silk hat type flexible meshing gear device having a short shaft length as well as an outer diameter.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a silk hat type flexible meshing gear device according to an embodiment of the present invention.
FIG. 2 is a schematic front view of the apparatus of FIG. 1 as viewed from a direction of an arrow.
FIG. 3 is a longitudinal sectional view showing a silk hat-shaped flexible external gear of the apparatus shown in FIG. 1;
FIG. 4 is a partially enlarged sectional view showing a diaphragm portion of the external gear shown in FIG. 3 in an enlarged manner.
FIG. 5 is an explanatory view showing an increase in a coning angle by shortening the axial length of a flexible external gear.
FIG. 6 is an explanatory view for explaining a problem of a conventional silk hat type flexible meshing gear device.
[Explanation of symbols]
Reference numeral 11: Silk-hat type flexible meshing gear device 11a: Device axis 12: Rigid internal gear 13: Flexible external gear having a silk hat shape 14: Wave generator 22 ... Body 23 ... Diaphragm part 24 ... External teeth 25 ... Boss 221 ... Thick part A of the body part ... Inner peripheral end part B of the diaphragm part ... Central part C of the diaphragm part ... Outer peripheral end t (A) of the diaphragm part ... Thickness of the inner peripheral end t (B) ... Thickness of the central part t (C) ... Thickness of the outer peripheral end t ( 22) Thickness of torso t (221) Thickness of thin portion

Claims (4)

An annular rigid internal gear, an internal flexible external gear, and a radial internal flexure of the external gear that is disposed on the inner side and partially meshes with the rigid internal gear; A wave generator configured to rotate these meshing positions in a circumferential direction, wherein the external gear has a cylindrical body having external teeth formed on an outer peripheral surface on one opening end side; An annular diaphragm portion whose inner peripheral end is continuous with the other open end of the portion, and a silk hat shape having an annular boss portion formed continuously at the outer peripheral end of the diaphragm portion. And
The sectional shape of the diaphragm portion of the external gear when cut along a plane including the device axis is as follows: the thickness of the inner peripheral end is t (A), and the thickness of the outer peripheral end is t (C). Assuming that the thickness of the substantially central portion between the peripheral end and the outer peripheral end is t (B), t (A) is set to the maximum thickness, t (B) is set to the minimum thickness, and t (A)> A silk-hat-type flexible meshing gear device, wherein t (C)> t (B) is set. 2. The cross-sectional shape of the diaphragm portion of the external gear according to claim 1, wherein at least one surface contour is defined by a plurality of curves, and the thickness is from the central portion to the inner peripheral end and the outer peripheral end. A silk hat-type flexible meshing gear device characterized by being set so as to increase smoothly toward a portion. 3. The relation between the thickness t (A) of the inner peripheral end and the thickness t (B) of the central portion according to claim 1 or 2, wherein t (A) / t (B) is about 1.5. A silk hat type flexible mesh gear device, wherein the gear ratio is set to be within a range of about 2.2. 4. The relationship between the thickness t (C) of the outer peripheral edge and the thickness t (B) of the central portion according to claim 1, 2 or 3, wherein t (C) / t (B) is about 1.4. , Which is set to be in the range of about 2.0 to about 2.0.

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