JPH0451234Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a strain wave gear device, and more particularly, to an improvement of its thin-walled cylindrical external gear.

[Prior art and its problems]

Conventionally, a flexible motor has an elliptical wave generator connected to an input shaft, and a bottom wall closed at one end, the wave generator being radially deflected by the wave generator and connected to an output shaft. Wave gear devices are known that include a thin-walled cylindrical external gear and a circular internal gear that is arranged around the external gear and cooperates with the external gear. For example, the second
In the wave gear structure shown in the figure, the reference numeral 10 is the input shaft 1.
2, the reference numeral 14 indicates a flexible thin-walled cylindrical external gear, and the reference numeral 16 indicates a circular internal gear. As shown in FIG. 3, the conventional thin-walled cylindrical external gear 14 has a bottom wall 18 at the closed end and a tooth row 20 provided circumferentially on the outer circumferential surface at the open end.

A portion of this tooth row 20 is bent into, for example, an ellipse, and the oval is rotated, and this rotation causes the bottom wall 18 to bend to the left and right in the figure. A boss 22 projects from the outer surface of the bottom wall 18 in the axial direction, and a bolt hole 24 passing through the boss in the axial direction and spaced apart in the radial direction is provided. 14 can be connected to an output shaft (not shown in FIGS. 2 and 3). The joint portion between the outer boss 22 and the bottom wall 18 of the thin cylindrical external gear 14 has a radius of curvature centered on the outer side.
This prevents stress concentration due to bending. On the other hand, bottom wall 1
The inner surface of the boss 8 including the joint with the inner end of the boss 22 is flat. When the head of the mounting bolt or the washer comes into contact with this flat portion 26, the inward deflection of the bottom wall 18 is inhibited. In particular, the bending force is concentrated at the boundary portion, and the stress due to the bending is concentrated. Therefore, when a wave gear device having this structure is used for a long period of time, fatigue failure is likely to occur at the boundary portion.

[Purpose of invention]

An object of the present invention is to provide a strain wave gear device having a thin cylindrical external gear having a structure in which such fatigue failure is unlikely to occur.

[Structure of the idea]

To achieve this objective, the present invention comprises an oval wave generator connected to the input shaft, radially deflected by the wave generator and connected to the output shaft, with one end connected to the output shaft. a flexible thin-walled cylindrical external gear having a closing bottom wall;
In a wave gear device that is arranged surrounding this external gear and includes a circular internal gear that cooperates with the external gear, a boss for attaching the thin-walled cylindrical external gear to the output shaft is located on the bottom wall of the thin-walled cylindrical external gear. The boss is provided with a protrusion that protrudes axially from the bottom wall inwardly and outwardly, and the inner protrusion has a diameter that is the same as or smaller than the diameter of the outer protrusion, and these inner and outer protrusions and the bottom wall, each of which has a radius of curvature centered on the outside.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, particularly FIG.

In FIG. 1, a flexible thin-walled cylindrical external gear 30 shown here has a circumferential tooth row 32 on its outer peripheral surface,
As shown in FIG. 2, the system operates in the same way as a wave gear, but according to the invention, the boss 36 connected to its bottom wall 34 not only has a projection 40 projecting axially outward from the bottom wall 34; Projection part 38 projecting inward
The diameter of the inner protrusion 38 is equal to or smaller than the diameter of the outer protrusion 40. Therefore, the head of the mounting bolt 44 floats from the flat bottom wall 34, and stress concentration due to bending deformation is avoided.

As can be seen from FIG. 1, the inner and outer protrusions 38,
The joint 35 with the bottom wall 34 of each of 40 has an externally centered radius of curvature. As mentioned above, the boss 36 has a plurality of bolt holes 42 passing through it in the axial direction and spaced apart in the circumferential direction, and the bolts 44 are passed through these bolt holes 42 to attach the thin cylindrical external gear 30. is connected to the output shaft 46.

[Effect of idea]

According to the structure of the present invention, since the protruding part is formed inside the boss, the head of the mounting bolt and the washer are lifted from the flat bottom wall, and therefore, the head of the mounting bolt and the washer are lifted from the flat bottom wall, and therefore, the protrusion is formed on the inside of the boss. Even if deflection occurs in the bottom wall, there is no stress concentration and fatigue failure is reduced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a flexible thin-walled cylindrical external gear according to the present invention, FIG. 2 is a cross-sectional view of a wave gear device that can use this thin-walled cylindrical external gear, and FIG. 3 is a FIG. 2 is a vertical cross-sectional view of a conventional flexible thin-walled cylindrical external gear. Explanation of symbols, 10...Wave generator,
12...Input shaft, 14...Thin cylindrical external gear, 16
... Internal gear, 18 ... Bottom wall, 20 ... Teeth row, 22
... Boss, 24 ... Bolt hole, 30 ... Thin cylindrical external gear, 32 ... Teeth row, 34 ... Bottom wall, 35 ...
joint portion, 36... boss, 38, 40... protrusion,
42... Bolt hole, 44... Bolt, 46... Output shaft.

Claims (1)

[Scope of utility model registration request] an elliptical wave generator connected to the input shaft; a flexible flexible structure having a bottom wall closed at one end, adapted to be radially deflected by the wave generator and connected to the output shaft; In a wave gear device that includes a thin-walled cylindrical external gear and a circular internal gear that is arranged around the external gear and cooperates with the external gear, the boss for attaching the thin-walled cylindrical external gear to the output shaft is thin-walled. The boss is provided on the bottom wall of the cylindrical external gear, and the boss consists of a protrusion that protrudes inward and outward from the bottom wall in the axial direction, and the inner protrusion has a diameter that is the same as or smaller than the diameter of the outer protrusion. . A strain wave gear device, wherein each of the connecting portions between the inner and outer protrusions and the bottom wall has a radius of curvature centered on the outside.