Reclining device and seat
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Solution Overview
Problem
Conventional reclining devices for vehicle seats face strength weaknesses due to complex internal gear designs, leading to deformation under load and compromised smooth operation, particularly with the memory mechanism part, which affects the locking and reclining functions.
Innovation Solution
A reclining device with an internal gear featuring a thin and thick annular portion of equal outside diameters but different inside diameters, where the thick annular portion has a flat outer end surface, enhancing strength and allowing for a simpler L-shaped cross-section, reducing deformation risk and improving the flatness and smoothness of the stepped surface between locking and memory teeth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the internal gear is designed with a convex shape including small-diameter and large-diameter portions processed by fine blanking, then the memory internal teeth and locking internal teeth can be formed, but the strength is weakened and deformation is likely to occur under load
Solution Approach 1:
The internal gear is divided into two distinct portions: a small-diameter portion for memory internal teeth and a large-diameter portion for locking internal teeth. This segmentation allows each portion to be optimized independently - the small-diameter portion can be processed by fine blanking for precise tooth formation, while the large-diameter portion maintains greater strength and resistance to deformation under load.
Solution Approach 2:
Different regions of the internal gear are given different properties. The small-diameter portion has a geometry optimized for fine blanking processing and memory tooth engagement, while the large-diameter portion has a geometry optimized for strength and load-bearing capacity during locking operations.
2Ease of manufacture
If the small-diameter portion is fixed by welding, then the memory mechanism can be assembled, but the convex portion not subjected to heat treatment has small diameter and reduced coupling range affecting strength
Solution Approach 1:
The convex portion is designed with predetermined geometry and dimensions before assembly. The large-diameter portion is formed with sufficient diameter and coupling range in advance, ensuring that when the small-diameter portion is welded and assembled, the overall structure maintains adequate strength without requiring post-assembly modifications or heat treatment of the convex portion.
3Adaptability or versatility
If the internal gear has complex shapes with small-diameter and large-diameter portions, then both memory and locking functions can be achieved, but flatness on the stepped surface is difficult to secure and smooth operation is affected
Solution Approach 1:
The internal gear is segmented into two portions with a defined stepped surface between them. The small-diameter portion and large-diameter portion are designed as distinct segments that can be processed separately, allowing the stepped surface to be formed with controlled flatness. This segmentation enables independent optimization of each portion's geometry while maintaining the required flat transition zone for smooth operation.
Solution Approach 2:
The design transitions from a single-diameter geometry to a two-diameter stepped geometry, adding dimensional complexity to accommodate both memory and locking functions. The stepped surface created by this dimensional change provides a flat transition zone that facilitates smooth operation while enabling the dual-functionality of the internal gear.
Data Source
AI summary
An internal gear includes a thin annular portion and a thick annular portion whose outside diameters are the same and whose inside diameters are different are continuously provided integrally in an axial direction, and an outer peripheral surface of the thin annular portion and the thick annular portion is formed in a substantially L shape in a flush cross section. Therefore, a conventionally substantially convex section formed with the memory internal teeth does not become the weak point in terms of strength. An axial outer end surface of the thick annular portion of the internal gear is formed to be substantially flat, and the coupling cover member is fixed to the thick annular portion to be coupled to a frame of a seat cushion or a seat back.