Machine element or mechanism – Gearing
Patent
1996-02-15
1997-11-18
Marmor, Charles A.
Machine element or mechanism
Gearing
74462, F16H 3704, F16H 5508
Patent
active
056876203
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a flexible meshing type gear device. More particularly, this invention relates to the tooth profiles of a rigid internal gear and a flexible external gear used in a flexible meshing type gear device.
BACKGROUND ART
A flexible meshing type gear device typically consists of a rigid circular internal gear, a flexible external gear which has, for example, 2 n (n being a positive integer) fewer teeth than the internal gear and which is disposed inside the internal gear and flexed into an elliptical shape so as to mesh with the internal gear at two places, and a wave generator fitted inside the external gear for flexing it into an elliptical shape.
Although the basic tooth profile for the gears of a flexible meshing type gear device is linear (see U.S. Pat. No. 2,906,143), flexible meshing type gear devices using involute gears have also been developed (see JP-B 45-41171). In addition, for increasing device load capacity the present inventor proposed a system using as the tooth face profile of both gears the curve obtained by similarity transforming the moving path, at a reduction ratio of 1/2, over a prescribed range from the meshing limit point on the path based on the rack approximation of the tooth of the external gear relative to the internal gear (JP-A 63-115943). This is a system for obtaining continuous contact between the tooth profiles of the tooth faces of both gears.
There is known a flexible meshing type gear device of a type fitted with a cup-shaped flexible external gear. In this type of device, a three-dimensional phenomenon called coning occurs in which the insertion of the elliptical wave generator causes the amount of flexing (difference between the major and minor axes of the ellipse) to gradually increase from the diaphragm side toward the opening portion of the cup-shaped flexible external gear approximately in proportion to the distance from the diaphragm. The tooth profiles described in the aforementioned publications do not take this coning into consideration, however. Therefore, while continuous meshing of the tooth profiles of the two gears can be realized for tooth traces with specific sections (e.g., a non-deviated section corresponding to the normal amount of flexing), tooth interference and other problems arise for other sections of the tooth trace.
The inventor later proposed a flexible meshing type gear device enabling a wider mesh range, without interference, over the entire tooth trace of the cup-shaped flexible external gear. This device is proposed, for example, in Japanese Patent Applications Hei 3-357036 and Hei 3-357037.
The performance being demanded of flexible meshing type gear devices is becoming increasingly sophisticated. To respond to this demand, it is necessary to further improve device strength and wear resistance. There is a particular need to improve the wear resistance of the tooth surface to the maximum possible.
All of the aforementioned inventions enable continuous meshing along the tooth trace. However, the meshing is so-called countermovement meshing. Since it is therefore impossible to avoid disadvantages from the point of maintaining a lubricating oil film between the tooth surfaces, a certain limit on the permissible delivered torque is present owing to tooth surface wear caused by oil film rupture. Because of this, a strong need is felt for an improvement in this respect.
DISCLOSURE OF THE INVENTION
For achieving the aforesaid improvement, this invention undertakes to change the both convex tooth profiles performing countermovement meshing to convex and concave tooth profiles performing pass meshing, proposes a tooth-number reversal method described later, and derives the tooth profile from a moving path with reverse phase.
More specifically, this invention is characterized in that the following configuration is adopted in a flexible meshing type gear device having a rigid internal gear, a flexible external gear inside the internal gear and a wave generator for flexing the external gear into an elliptic
REFERENCES:
patent: 2906143 (1959-09-01), Musser
patent: 4601216 (1986-07-01), Inoue et al.
patent: 4823638 (1989-04-01), Ishikawa
patent: 4974470 (1990-12-01), Ishikawa et al.
patent: 5269202 (1993-12-01), Kiyosawa et al.
patent: 5388483 (1995-02-01), Ishida et al.
patent: 5485766 (1996-01-01), Ishikawa
Estremsky Sherry Lynn
Harmonic Drive Systems Inc.
Marmor Charles A.
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