Internal Gear-Housing Separation Structure for Low-Noise Planetary Gears
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Solution Overview
Problem
The existing separation structure of internal gear and housing in planetary gear devices suffers from uneven contraction during resin molding, leading to dimensional accuracy issues and increased noise due to vibration transmission.
Innovation Solution
A separation structure featuring a tubular internal gear with a flange extending circumferentially and a recess on the flange, which forms a gap with the housing and restricts circumferential movement, thereby minimizing vibration transmission and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the internal gear is separated from the housing with a gap, then vibration transmission is reduced, but the internal gear may come into areal contact with the housing during operation causing noise
Solution Approach 1:
The patent applies local quality by creating a non-uniform gap structure between the internal gear and housing. The gap is maintained at most locations to prevent vibration transmission, but localized contact regions are permitted during operation to accommodate displacement without causing noise. This selective application of gap and contact zones resolves the contradiction between vibration reduction and noise prevention.
2Stability of the object's composition
If projections are formed on the internal gear for engagement, then circumferential movement is restricted, but uneven contraction occurs during resin molding deteriorating dimensional accuracy
Solution Approach 1:
The patent resolves the contradiction by changing the geometric parameters of the engagement structure. Instead of using projections that cause uneven contraction, the design uses a different configuration of engagement elements that maintain circumferential stability while being compatible with resin molding processes. The modified geometry allows uniform stress distribution during molding, preserving dimensional accuracy while still restricting unwanted movement.
3Ease of manufacture
If the internal gear and housing are separated, then manufacturing flexibility is improved, but assembly precision requirements increase
Solution Approach 1:
The patent introduces positioning elements as intermediaries between the internal gear and housing. These elements facilitate the separated structure by providing precise alignment and location during assembly. The positioning elements act as mediators that bridge the gap between manufacturing flexibility and assembly precision requirements, enabling easy manufacturing while ensuring accurate assembly through dedicated positioning features.
Data Source
AI summary
A separation structure of internal gear and housing includes an internal gear including a tubular body that has an inner circumferential surface and internal-gear teeth formed on the inner circumferential surface. The separation structure also includes a tubular housing configured to accommodate the internal gear. The tubular body includes a flange formed on an outer circumferential surface of the tubular body and projecting radially outward. The flange extends continuously and circumferentially along the tubular body, and the flange has a recess formed at an outer circumferential surface of the flange. A gap is formed between the outer circumferential surface of the tubular body of the internal gear and an inner circumferential surface of the housing. The housing has a projection. Contact between the recess of the flange and the projection of the housing restricts circumferential movement of the internal gear.