Flat strain wave gearing

Patent metadata

Field	Value
Publication number	US-10352426-B2
Application number	US-201515033815-A
Country	US
Kind code	B2
Filing date	May 29, 2015
Priority date	May 29, 2015
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

A flat strain wave gearing (1) has a mechanism for preventing a flexible externally toothed gear (4) from moving in the direction of the device center axis (1a) with respect to a rigid internally toothed gears (2, 3). The mechanism has an inner-peripheral groove (11) formed on inner teeth (3a) of the internally toothed gear (3), an outer-peripheral groove (12) formed on outer teeth (4a) of the externally toothed gear (4), and a flexible ring (13) mounted between the inner-peripheral groove (11) and the outer-peripheral groove (12). The ring (13) is engageable with groove inner-peripheral surfaces (11a, 11b, 12a, 12b), from the direction of the device center axis (1a), at meshing positions of the both gears (2, 4).

First claim

The invention claimed is:

1. A flat strain wave gearing, comprising:
a first rigid gear;
a second rigid gear arranged coaxially with and adjacent to the first rigid gear;
a cylindrical flexible gear arranged coaxially inside of or outside of the first and second rigid gears;
a wave generator for causing the flexible gear to flex into a non-circular shape and partially mesh with the first and second rigid gears, and causing meshing positions to move in a circumferential direction;
a first groove formed on teeth of the first rigid gear throughout a periphery thereof;
a second groove formed on teeth of the flexible gear throughout a periphery thereof so as to face the first groove; and
a radially flexible first ring arranged between the first and second grooves,
the first ring being configured to engage with first and second groove inner-peripheral surfaces of the first and second grooves, from a direction along a device center axis, at the meshing positions between the first rigid gear and the flexible gear,
wherein the first groove inner-peripheral surface of the first groove has a first groove side surface and a second groove side surface facing each other,
the second groove inner-peripheral surface of the second groove has a third groove side surface and a fourth groove side surface facing each other,
the first ring is positioned between the first groove side surface and the fourth groove side surface to restrict movement of the first rigid gear relative to the flexible gear in one direction along the device center axis, and
the first ring is positioned between the second groove side surface and the third groove side surface so as to restrict the movement of the first rigid gear relative to the flexible gear in an opposite direction along the device center axis,
the first rigid gear is a first internally toothed gear;
the second rigid gear is a second internally toothed gear;
the flexible gear is an externally toothed gear;
the wave generator causes the externally toothed gear to flex into an ellipsoidal shape and mesh with the first and second internally toothed gears at both major-axis ends of the ellipsoidal shape;
a number of teeth of the first internally toothed gear is the same as a number of teeth of the externally toothed gear;
a number of teeth of the second internally toothed gear is 2n greater than the number of teeth of the first internally toothed gear, where n is a positive integer;
the second internally toothed gear is secured so as not to rotate; and
for each rotation of the wave generator, the externally toothed gear undergoes relative rotation in accordance with the difference in the number of teeth with respect to the second internally toothed gear, and the first internally toothed gear rotates integrally with the externally toothed gear,
an inside diameter of the first ring is equal to a core diameter of the second groove formed in the externally toothed gear;
the core diameter of the second groove is greater than a root circle diameter of the externally toothed gear before flexed into the ellipsoidal shape; and
a core diameter of the first groove formed in the first internally toothed gear is greater than a major axis of the first ring when flexed into the ellipsoidal shape.

2. The flat strain wave gearing according to claim 1 , wherein
the first groove is formed at a position that is set apart, by at least half a tooth width of the first rigid gear, from an end of the first rigid gear on a second-rigid-gear side along the direction of the device center axis.

3. The flat strain wave gearing according to claim 1 , wherein
half a difference between an outside diameter and an inside diameter of the first ring is set to a value equal to or less than a tooth depth of the flexible gear.

4. The flat strain wave gearing according to claim 1 , further comprising:
a third groove formed on the teeth of the second rigid gear throughout the periphery thereof;
a fourth groove formed on the teeth of the flexible gear throughout the periphery thereof so as to face the third groove; and
a flexible second ring arranged between the third and fourth grooves,
the second ring being configured to engage with a groove inner-peripheral surface of each of the third and fourth grooves, from the direction along the device center axis, at meshing positions between the second rigid gear and the flexible gear.

5. The flat strain wave gearing according to claim 4 , wherein
the third groove is formed at a position that is set apart, by at least half a tooth width of the second rigid gear, from an end of the second rigid gear on a first-rigid-gear side along the direction of the device center axis.

6. The flat strain wave gearing according to claim 4 , wherein
half a difference between an outside diameter and an inside diameter of the second ring is set to a value equal to or less than a tooth depth of the flexible gear.

7. The flat strain wave gearing according to claim 1 , wherein
the first ring is:
a ring configured by winding a plate spring into a spiral;
a ring comprising a garter spring;
a bellows-shaped ring configured by curving a plate spring into a bellows shape; or
a ring comprising a diagonal-winding coil spring.

Assignees

• Harmonic Drive Systems

Inventors

• Kobayashi Masaru
• Hoshina Tatsuro

Classifications

• F16H55/18

  Special devices for taking up backlash {(for gears having orbital motion F16H1/2863)} · CPC title

• F16H55/0833

  Flexible toothed member, e.g. harmonic drive · CPC title

• F16H2049/003

  Features of the flexsplines therefor · CPC title

• F16H55/16

  relating to teeth only · CPC title

• F16H1/32

  in which the central axis of the gearing lies inside the periphery of an orbital gear · CPC title