Arc-Shaped Gear Engagement for High-Ratio Compact Deceleration

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Solution Overview

Problem

Existing deceleration mechanisms face limitations in increasing the deceleration ratio without increasing the size, as the number of teeth on the helical gear is already minimal, leading to interference and deterioration in engagement state.

Innovation Solution

The deceleration mechanism employs a first gear with a spiral tooth and a second gear with inclined teeth, featuring an arc-shaped engagement structure with a curvature center eccentric from the rotation center, allowing for increased tooth count on the second gear while maintaining a single tooth on the first gear, thus enhancing the deceleration ratio without size increase.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the number of teeth on the driven side helical gear is increased to increase the deceleration ratio, then the deceleration ratio increases, but the adjacent teeth are arranged close to each other causing interference and deterioration in engagement state

Engineering Contradiction:
Improvedeceleration ratioVSAvoidengagement state
Core Design Contradiction:
PowerVSReliability

Solution Approach 1:

The invention applies curved surface geometry to the gear tooth engagement. Specifically, the engagement projected part has a curvature center at a position eccentric from the rotation center, creating an arc-shaped engagement path. This curvature allows the teeth to engage along a rounded path rather than a straight line, preventing interference even when teeth are closely spaced, thereby enabling high deceleration ratios without compromising engagement reliability

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention introduces asymmetry in the gear tooth configuration. The first gear has a single tooth with an engagement projected part whose curvature center is eccentric from the rotation center, while the second gear has multiple teeth with engagement recessed parts. This asymmetric design allows the single tooth of the first gear to sequentially engage with multiple teeth of the second gear along an arc path, achieving high deceleration ratio while maintaining proper engagement

Inventive Principle:
Principle #4Asymmetry

2Volume of moving object

If the number of teeth on the helical gear is minimized to reduce size, then the deceleration mechanism becomes compact, but the ability to increase deceleration ratio is limited

Engineering Contradiction:
Improvedeceleration mechanism sizeVSAvoiddeceleration ratio
Core Design Contradiction:
Volume of moving objectVSPower

Solution Approach 1:

The invention transitions from conventional linear gear engagement to arc-shaped engagement in a different geometric dimension. By positioning the curvature center of the engagement projected part eccentric from the rotation center, the teeth engage along a curved path that utilizes the radial dimension more effectively. This allows a single tooth on the first gear to engage with multiple teeth on the second gear sequentially, achieving high deceleration ratio without increasing the overall size of the deceleration mechanism

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration maintains a stable engagement state and increases the deceleration ratio effectively, allowing for compact design and efficient operation.

Implementation Method 1

a first gear (31) rotated by the rotary shaft (23), and a second gear (32) rotated by the first gear (31). The first gear (31) has an engagement projected part (31c) formed in an arc shape, and the second gear (32) has an engagement recessed part (32d) engaged with the engagement projected part (31c)

Methodology Applied
Scientific EffectMechanical Advantage: Mechanical Advantage

Data Source

PatentEP3779240B1Deceleration mechanism and motor having deceleration mechanism installed therein
Publication Date: 2023.12.20 MITSUBA CORP
  • EP3779240B1 patent drawingFigure 1~2
  • EP3779240B1 patent drawingFigure 3
  • EP3779240B1 patent drawingFigure 4~5

AI summary

According to the present invention, one engagement protrusion part 31c having a spiral shape is provided in a pinion gear 31, a plurality of engagement recess parts 32d engaged with the engagement protrusion part 31c are provided in a helical gear 32, and the engagement protrusion part 31c and the engagement recess parts 32d are each formed to have an arc shape in a direction perpendicular to the axial direction of the pinion gear 31. As a result, the pinion gear 31 and the helical gear 32 can be configured in an arc-shaped protrusion/recess engagement structure that does not deteriorate the state of engagement therebetween. Also, by increasing the number of teeth on the helical gear 32 while keeping the number of teeth on the pinion gear 31 at one tooth, the difference in the number of teeth can be easily increased. Therefore, the deceleration ratio of a deceleration mechanism 30 can be increased without increasing the volume thereof.