# US 12,181,022 B1 · Speed reduction mechanism

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- Number: US 12,181,022 B1
- Document ID: US12181022B1
- Status: Granted
- Kind: B1
- Application number: 18/593,950
- Filed: 2024-03-03
- Granted: 2024-12-31
- Earliest claimed: 2023-07-24
- Assignees: Mitsuba Corporation
- Applicants: MITSUBA Corporation
- Inventors: Motoaki Kobayashi; Teppei Tokizaki
- Web page: https://patentgrep.com/patent/US12181022B1

## CPC

- F16H 1/28: with gears having orbital motion
- F16H: GEARING

## Abstract

A speed reduction mechanism has an increased reduction ratio while achieving downsizing. A speed reduction mechanism 30 includes a rotating shaft 10, a pinion gear 11 including a first tooth portion 11a extending spirally along a longitudinal direction Q1 of the rotating shaft 10, three planetary gears 12 including spiral second tooth portions 12e and arranged side by side in a circumferential direction Q2 of the rotating shaft 10, a housing portion 14 housing the three planetary gears 12, and an internal gear 13 including a spiral third tooth portion 13a meshing with the second tooth portions 12e. The first tooth portion 11a has at least a part of a tooth profile cross section formed in an arc shape. The second tooth portion 12e meshes with the first tooth portion 11a in a state of being in contact with a portion where the tooth profile cross section is arc-shaped.

## Claims

### Claim 1

A speed reduction mechanism, comprising:
a rotating shaft;
a first gear provided on an outer peripheral portion of the rotating shaft and comprising a first tooth portion that extends spirally along a longitudinal direction of the rotating shaft;
a plurality of second gears each comprising a spiral second tooth portion that meshes with the first tooth portion and arranged side by side in a circumferential direction of the rotating shaft;
a housing portion housing the plurality of second gears; and
a third gear provided on an inner peripheral portion of the housing portion and comprising a spiral third tooth portion that meshes with the second tooth portion,
wherein the first tooth portion has at least a part of a tooth profile cross section formed in an arc shape, and
the second tooth portion meshes with the first tooth portion in a state of being in contact with a portion where the tooth profile cross section is arc-shaped, wherein in a case where a pitch circle radius of the second gear is R1,
a center-to-center distance from a rotation center of the rotating shaft to a rotation center of the second gear is L1, and
an angle calculated by a formula of (180°(sum of interior angles of triangle)−90°)−(360°/number of the second gears/2) is θ,
the pitch circle radius R1<(the center-to-center distance L1×cos θ).

### Claim 2 (depends on 1)

The speed reduction mechanism according to claim 1, wherein at least three second gears are arranged side by side in the circumferential direction of the rotating shaft.