Gear train mechanism of timepiece

Patent metadata

Field	Value
Publication number	US-2019163136-A1
Application number	US-201716312950-A
Country	US
Kind code	A1
Filing date	Jun 19, 2017
Priority date	Jun 23, 2016
Publication date	May 30, 2019
Grant date	—

Abstract

A gear train mechanism of a timepiece is formed by a gear having an involute tooth profile, which is easily manufactured, and a pinion that meshes with the gear. In order to reduce a fluctuation in torque to be transmitted, a gear train mechanism of a timepiece includes a gear including a tooth having a tooth profile of an involute curve and a pinion including a tooth meshing with the tooth of the gear to transmit and receive a torque, wherein the torque to be transmitted from the gear to the pinion is substantially constant at least in a part of a first half of a meshing period of the gear and the pinion.

First claim

1 . A gear train mechanism of a timepiece, comprising:
a gear including a tooth having a tooth profile of an involute curve; and a pinion including a tooth meshing with the tooth of the gear to transmit and receive a torque, wherein the torque to be transmitted from one of the gear and the pinion to the other of the gear and the pinion is substantially constant at least in a part of a first half of a meshing period of the gear and the pinion.

2 . The gear train mechanism of the timepiece according to claim 1 , wherein a tooth profile of the pinion is set to a constant torque curve having a substantial constant torque to be transmitted from a virtual gear to the pinion when the tooth of the pinion meshes with a tooth of the virtual gear including an involute profile having a pressure angle larger than a pressure angle of the involute curve of the gear.

3 . The gear train mechanism of the timepiece according to claim 2 , wherein a number of teeth on the pinion is equal to 7 or more and equal to 15 or below.

4 . The gear train mechanism of the timepiece according to claim 1 , wherein a tooth profile of the pinion is set to a constant torque curve having a substantial constant torque to be transmitted from a virtual gear to the pinion when the tooth of the pinion meshes with a tooth of the virtual gear including an involute profile having a pressure angle smaller than a pressure angle of the involute curve of the gear.

5 . The gear train mechanism of the timepiece according to claim 4 , wherein a number of teeth on the pinion is equal to 11 or more and equal to 20 or below.

6 . The gear train mechanism of the timepiece according to claim 2 , wherein a difference Δα between the pressure angle α 2 of the gear and the pressure angle α 1 of the involute profile of the tooth of the virtual gear, i.e., Δα=α 1 −α 2 , satisfies a following condition,
− Z/ 2+5<Δα<− Z/ 2+8.

7 . The gear train mechanism of the timepiece according to claim 1 , wherein the torque to be transmitted from the pinion to the gear is substantially constant at least in a part of a second half of the meshing period.

8 . The gear train mechanism of the timepiece according to claim 7 , wherein a tooth profile of the pinion is set to a constant torque curve having a substantial constant torque to be transmitted from the pinion to a virtual gear when the tooth of the pinion meshes with a tooth of the virtual gear including an involute profile having a pressure angle smaller than a pressure angle of the involute curve of the gear.

9 . The gear train mechanism of the timepiece according to claim 7 , wherein a number of teeth on the pinion is equal to 7 or more and equal to 12 or below.

10 . The gear train mechanism of the timepiece according to claim 7 , wherein a difference Δα between the pressure angle α 2 of the gear and the pressure angle α 1 of the involute profile of the tooth of the virtual gear, i.e., Δα=α 1 −α 2 , satisfies a following condition,
Z/ 2−8<Δα< Z/ 2−5.

Assignees

• Citizen Watch Co Ltd

Inventors

• Fukuda Tadahiro
• Fukaya Shinpei

Classifications

• F16H55/0806 Primary

  Involute profile · CPC title

• G04B13/02

  Wheels; Pinions; Spindles; Pivots (bearings G04B31/00 {; chain wheels, spindles for chain wheels, also chains and driving weights G04B1/08}) · CPC title

• G04B13/027 Primary

  planar toothing: shape and design (adjusting the backlash of the arbors G04B35/00) · CPC title

• F16H55/08

  Profiling · CPC title