Wave gear device

Abstract

To provide wave gear device capable of increasing the strength of external teeth of a flexible external gear and making a rim thickness at the tooth bottom of the external teeth constant to prolong a service of a rim.SOLUTION: A wave gear device 1 comprises: an annular rigid internal gear 2; a flexible external gear 3 arranged coaxially inside the rigid internal gear 2, and provided with external teeth 31 having fewer teeth than internal teeth 21 of the rigid internal gear 2; a wave generator 4 fitted into the flexible external gear 3; and a connection part 5 that does not mesh with the internal teeth 21 and annularly connects the external teeth 31 to a front part 33 of a cylindrical part 32 of the flexible external gear 3, where a tooth bottom rim thickness t of the flexible external gear 3 is made constant.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a strain wave gear device. [Background technology]

[0002] A known conventional strain wave gearing is disclosed, for example, in Patent Document 1. The strain wave gearing disclosed in Patent Document 1 includes an annular rigid internal gear, a flexible external gear that is coaxially arranged inside the rigid internal gear and has external teeth with fewer teeth than the internal teeth of the rigid internal gear, and a wave generator fitted inside the flexible external gear, and the flexible external gear is configured as a tapered gear in which the product of the thickness of the flexible external gear and the amount of deflection in the major axis direction of a curve that passes through the center of the thickness direction of the root rim after the front end of the cylindrical portion of the flexible external gear is deflected into an ellipsoid is constant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-251588 Summary of the Invention [Problem to be solved by the invention]

[0004] The strain wave gear device disclosed in Patent Document 1 has a problem in that the rim thickness at the tooth bottom near the external teeth on the opposite side of the front end of the flexible external gear is thick, which increases the stress generated in the rim and shortens the lifespan of the rim.

[0005] In order to solve the above-mentioned problems, the object of the present invention is to provide a strain wave gear device that increases the strength of the external teeth of a flexible external gear and makes the rim thickness at the tooth roots of the external teeth of the flexible external gear thin and constant, thereby extending the life of the rim. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides a wave gear device as described in claim 1, which comprises an annular rigid internal gear, a flexible external gear arranged coaxially inside the rigid internal gear and provided with external teeth having fewer teeth than the internal teeth of the rigid internal gear, and a wave generator fitted inside the flexible external gear, wherein the flexible external gear is provided with a connecting portion that connects the external teeth in an annular shape to at least a portion of the front or rear of the external teeth that do not mesh with the internal teeth, and the root rim thickness of the external teeth is configured to be constant.

[0007] The inner diameter of the connecting portion described in claim 2 is configured to gradually increase with increasing distance from the external teeth. [Effects of the Invention]

[0008] According to the present invention, the strain wave gearing described in claim 1 has a connecting portion that connects the external teeth to an annular shape at the front or rear of the external teeth of the flexible external gear that do not mesh with the internal teeth of the rigid internal gear, thereby increasing the strength of the flexible external gear. Also, because the rim thickness at the roots of the external teeth of the flexible external gear is thin and constant, just like the cylindrical portion of the flexible external gear, stress generated in the rim is reduced, and the life of the rim can also be extended.

[0009] Furthermore, in the wave gear device described in claim 2, the change in the inner diameter of the connecting portion is small, so that excessive stress can be prevented from occurring in the rim. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a partial cross-sectional front view showing the configuration of a strain wave gear device according to a first embodiment of the present invention. FIG. [Figure 2] FIG. 2 is an enlarged cross-sectional front view of the external teeth of the flexible external gear of FIG. 1. [Figure 3] FIG. 3 is a partial cross-sectional side view of the arrow AA in FIG. 2. [Figure 4] FIG. 5 is a partial cross-sectional front view showing the configuration of a strain wave gear device according to a second embodiment of the present invention. [Figure 5] FIG. 5 is an enlarged cross-sectional front view of the external teeth of the flexible external gear of FIG. 4. [Figure 6] FIG. 10 is a partial cross-sectional front view showing the configuration of a strain wave gear device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.

[0012] (First embodiment) A first embodiment of the present invention will be described with reference to the drawings. As shown in Figures 1, 2, and 3, the strain wave gearing device 1 includes an annular rigid internal gear 2, a plurality of mounting holes 22, a flexible external gear 3 that is coaxially arranged inside the rigid internal gear 2 and has external teeth 31 with fewer teeth than the internal teeth 21 of the rigid internal gear 2, a non-circular wave generator 4 fitted inside the flexible external gear 3, and a connecting portion 5 (the black portion in Figures 1 and 2 and Figure 3) that connects to all of the external teeth 31 at a front portion 33 of a cylindrical portion 32 of the flexible external gear 3 that does not mesh with the internal teeth 21.

[0013] The flexible external gear 3 is composed of a plurality of external teeth 31 arranged circumferentially around the opening of the cylindrical portion 32, a diaphragm 34 connected to the cylindrical portion 32, a boss 35 provided on the diaphragm 34, and a plurality of mounting female threads 36 provided on the boss 35.

[0014] The wave generator 4 is composed of a non-circular cam 41, a hole 42 drilled in the center of the cam 41, a flexible inner ring 44 of a ball bearing 43 fixed to the cam 41, a flexible outer ring 45, and a plurality of balls 46 inserted into the flexible inner ring 44 and the flexible outer ring 45.

[0015] The connecting portion 5 is provided in a circular ring shape and connects to all of the external teeth 31 (from the tooth bottom to the tooth tip) at the front portion 33 of the cylindrical portion 32 where the external teeth 31 do not mesh with the internal teeth 21. The inner diameter of the connecting portion 5 gradually increases with increasing distance from the external teeth 31 to prevent excessive stress from being generated in the rim, and the tooth bottom rim thickness t of the external teeth 31 is configured to be constant and the same as that of the cylindrical portion 32.

[0016] With the above-described configuration, the external teeth 31 of the flexible external gear 3 are all connected to the connecting portion 5, which increases the strength of the external teeth 31 (increasing ratcheting torque in particular). Furthermore, the rim thickness t at the tooth base of the external teeth 31 is thin, the same as that of the cylindrical portion 32, and there is little change in the inner diameter of the connecting portion, so excessive stress does not occur in the rim, which also extends the life of the rim.

[0017] (Second embodiment) The same or equivalent components and members as those in the first embodiment are designated by the same part names and the same reference numerals, and redundant explanations will be omitted where appropriate. The following description will focus on the characteristic features of the second embodiment.

[0018] A second embodiment of the present invention will be described with reference to the drawings. As shown in Figures 4 and 5, the strain wave gearing 1 comprises an annular rigid internal gear 2, a flexible external gear 3 that is coaxially arranged inside the rigid internal gear 2 and has external teeth 31 with fewer teeth than the internal teeth 21 of the rigid internal gear 2, a wave generator 4 fitted inside the flexible external gear 3, and a connecting portion 5 (the black portion in Figures 4 and 5) that connects to all of the external teeth 31 at a rear portion 38 of the cylindrical portion 32 of the flexible external gear 3 that does not mesh with the internal teeth 21.

[0019] The flexible external gear 3 is composed of a plurality of external teeth 31 arranged circumferentially around the opening of the cylindrical portion 32, a diaphragm 34 connected to the cylindrical portion 32, a boss 35 provided on the diaphragm 34, and a plurality of mounting holes 37 provided on the boss 35.

[0020] The connecting portion 5 is provided at the rear portion 38 of the cylindrical portion 32 where the external teeth 31 do not mesh with the internal teeth 21, so as to connect to the entire portion (from the tooth bottom to the tooth tip) of the multiple external teeth 31 in an annular shape. The inner diameter of the connecting portion 5 gradually increases with increasing distance from the external teeth 31 to prevent excessive stress from being generated in the rim, and the tooth bottom rim thickness t of the external teeth 31 is configured to be constant and the same as that of the cylindrical portion 32.

[0021] With the above-described configuration, the external teeth 31 of the flexible external gear 3 are all connected to the connecting portion 5 at the rear portion 38, further increasing the strength of the external teeth 31. In addition, the rim thickness t at the tooth bottom of the external teeth 31 is thin, the same as that of the cylindrical portion 32, and there is little change in the inner diameter of the connecting portion, so excessive stress does not occur in the rim, which can also extend the life of the rim. Furthermore, unlike the strain wave gear device 1 of the first embodiment, the rigid internal gear 2 can be inserted from the right side of the flexible external gear 3.

[0022] (Third embodiment) The same or equivalent components and members as those in the first embodiment are designated by the same part names and the same reference numerals, and redundant explanations will be omitted where appropriate. The following description will focus on the characteristic features of the third embodiment.

[0023] A third embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 6, the strain wave gearing 1 includes an annular rigid internal gear 2, a flexible external gear 3 that is coaxially arranged inside the rigid internal gear 2 and has external teeth 31 with fewer teeth than the internal teeth 21 of the rigid internal gear 2, a wave generator 4 fitted inside the flexible external gear 3, and a connecting portion 5 (the black portion in Fig. 6) that connects to a portion of the external teeth 31 at a front portion 33 of a cylindrical portion 32 of the flexible external gear 3 that does not mesh with the internal teeth 21.

[0024] The connecting portion 5 is provided in a front portion 33 of the cylindrical portion 32 where the external teeth 31 do not mesh with the internal teeth 21, so as to be connected to a portion of the plurality of external teeth 31 (for example, from the tooth bottom to the pitch circle diameter) in an annular manner. The inner diameter of the connecting portion 5 gradually increases with increasing distance from the external teeth 31 to prevent excessive stress from being generated in the rim, and the tooth bottom rim thickness t of the external teeth 31 is configured to be constant and the same as that of the cylindrical portion 32.

[0025] The above-described configuration increases the strength of the external teeth 31 of the flexible external gear 3. Furthermore, the rim thickness t at the tooth bottom of the external teeth 31 is thin, being the same as that of the cylindrical portion 32, and there is little change in the inner diameter of the connecting portion, so excessive stress does not occur in the rim, and the life of the rim can be extended. Furthermore, because a portion of the external teeth 31 is connected to the connecting portion 5, the fracture strength of the teeth in the event of tooth skipping can be increased, unlike the wave gear devices 1 of the first and second embodiments.

[0026] Any modification or application is possible within the scope of the present invention. For example, the connecting portion 5 of the third embodiment may be provided at the rear portion 38 of the cylindrical portion 32. Furthermore, the tooth bottom rim thickness t of the external teeth 31 may be thicker and constant than the thickness of the cylindrical portion 32, provided that the tooth bottom and the cylindrical portion 32 are continuously connected. Furthermore, the inner diameter of the connecting portion 5 may be gradually increased with increasing distance from the external teeth 31 for reasons of processing, etc., regardless of the stress on the rim. Furthermore, in addition to the cup-shaped configurations of the first, second, and third embodiments, the present invention may also be applied to top hat-shaped and unit-shaped configurations. [Explanation of symbols]

[0027] 1... Harmonic gearing, 2... Rigid internal gear, 3... Flexible external gear, 4... Wave generator, 5... Connection portion, 21... Internal teeth, 22... Mounting hole, 31... External teeth, 32... Cylindrical portion, 33... Front portion, 34... Diaphragm, 35... Boss, 36... Female mounting thread, 37... Mounting hole, 38... Rear portion, 41... Cam, 42... Hole, 43... Ball bearing, 44... Flexible inner ring, 45... Flexible outer ring, 46... Ball

Claims

1. A wave gear device comprising: an annular rigid internal gear; a flexible external gear arranged coaxially inside the rigid internal gear and provided with external teeth having fewer teeth than the internal teeth of the rigid internal gear; and a wave generator fitted inside the flexible external gear, wherein the flexible external gear is provided with a connecting portion that connects the external teeth in an annular shape to at least a portion of the front or rear of the external teeth that do not mesh with the internal teeth, and the root rim thickness of the external teeth is configured to be constant.

2. The wave gear device according to claim 1, wherein the inner diameter of the connection portion gradually increases with increasing distance from the external teeth.

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