US 5,687,620 AGranted

Flexible meshing type gear device with a passing tooth profile

AssigneeHarmonic Drive Systems Inc.

InventorShoichi Ishikawa

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Abstract

In a meshing type gear device (1), spur gears are used for both a rigid internal gear (2) and a flexible external gear (3), and the number of teeth of the flexible gear (3) is made greater by two than that of the rigid internal gear (2). The tooth profile of the flexible external gear (3) is made convex and the shape thereof is that of a curve AC obtained by subjecting a gear tooth portion (curve portion between A and B), which, at the moving path L that the external gear describes relative to the internal gear, as determined by rack approximation, is convex relative to the internal gear, to similarity transformation at a reduction ratio .lambda. using the limiting point A of the contact between the two gears on the path as the origin, while the tooth profile of the rigid internal gear is made concave and the shape thereof is that of a curve AD obtained by subjecting the same portion convex relative to the internal gear at the moving path to similarity transformation at an enlargement ratio (1+.lambda.) using the limiting point A as the origin, whereby the meshing of the two gears maintains continuous contact and is of the passing type.

Claims3

Dependent claims

A flexible meshing type gear device with a pass meshing tooth profile having a rigid internal gear, a flexible external gear inside the internal gear and a wave generator for flexing the external gear into an elliptical cross-sectional shape, causing the external gear to mesh partially with the rigid internal gear and rotating the mesh position of the two gears in the circumferential direction, rotation of the wave generator producing relative rotation between the two gears, the flexible meshing type gear device with a pass meshing tooth profile being characterized in that

(a) the rigid internal gear and the flexible external gear are both spur gears,
(b) the number of teeth of the flexible external gear is two greater than that of the rigid internal gear,
(c) the tooth profile of the flexible external gear is convex and the shape thereof is that of a curve obtained by subjecting a moving part portion which, at a moving path that the external gear describes relative to the internal gear, as determined by rack approximation, is convex relative to the internal gear, to similarity transformation at a reduction ratio .lambda. using a limiting point of the contact between the two gears on the path as an origin, and
(d) the tooth profile of the rigid internal gear is concave and the shape thereof is that of a curve obtained by subjecting the same portion convex relative to the internal gear at the moving path to similarity transformation at an enlargement ratio (1+.lambda.) using the limiting point as the origin, whereby the meshing of the two gears maintains continuous contact and is of the passing type.

1 more element

Flexible meshing type gear device with a pass meshing tooth profile having a rigid internal gear, a cup-shaped flexible external gear inside the internal gear, and a wave generator for flexing the external gear into an elliptical cross-sectional shape such that an amount of deflection produced in a deflected portion of the external gear increases from a diaphragm side thereof toward an opening portion thereof approximately in proportion to a distance from the deflected portion to the diaphragm, causing the external gear to mesh partially with the rigid internal gear and rotating the mesh position of the two gears in the circumferential direction, rotation of the wave generator producing relative rotation between the two gears, the flexible meshing type gear device with a pass meshing tooth profile being characterized in that

(a) the rigid internal gear and the cup-shaped flexible external gear are both spur gears,
(b) the number of teeth of the cup-shaped flexible external gear is two greater than that of the rigid internal gear,
(c) the tooth profile of the cup-shaped flexible external gear is convex and the shape thereof is that of a curve obtained by subjecting a moving path portion which, at a moving path that the external gear describes relative to the internal gear in a basic section of the tooth trace, as determined by rack approximation, is convex relative to the internal gear, to similarity transformation at a reduction ratio .lambda. using a limiting point of the contact between the two gears on the path as an origin,
(d) the tooth profile of the rigid internal gear is concave and the shape thereof is that of a curve obtained by subjecting the same portion convex relative to the internal gear at the moving path to similarity transformation at an enlargement ratio (1+.lambda.) using the limiting point as the origin, whereby the meshing of the two gears maintain continuous contact and is of the passing type, and
(e) relieving is applied to teeth of the cup-shaped flexible external gear toward the opening side from the basic section of the tooth trace.

2 more elements

Dependencies are inferred from the claim text.