Cushion Spring with Asymmetric Wire and Resin Member for Roll Rigidity
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Solution Overview
Problem
Existing cushion springs struggle to stably increase roll rigidity of the side portion of a seat cushion while maintaining even load distribution, leading to potential sinking and reduced support for occupants, especially when varying body sizes are considered.
Innovation Solution
A cushion spring design featuring a pair of formed wires bridged to a seat cushion frame with a resin member that includes deflection restricting portions and a rear connecting portion, which supports the seat cushion pad from the backside, connecting all crank-shaped portions in the side wires and providing additional support to the thighs and pelvis, thereby restricting deflection and enhancing roll rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the center wire and side wire are made symmetrical, then the manufacturing is simple, but the roll rigidity of the side portion cannot be sufficiently increased
Solution Approach 1:
The patent applies asymmetry by making the side wire extend further in the width direction than the center wire. Specifically, the side wire has a second extending portion that projects beyond the center wire's first extending portion, creating an asymmetric configuration that increases roll rigidity while maintaining manufacturing feasibility through systematic wire arrangement
Solution Approach 2:
The patent segments the wire structure into distinct functional portions: the center wire with its extending portion, the side wire with its additional second extending portion, and the connecting wire joining them. This segmentation allows each component to fulfill specific functions - the center wire provides central support, the side wire extends for roll rigidity, and the connecting wire integrates them
2Strength
If the hardness of the cushion pad is partially changed to increase roll rigidity, then the side portion rigidity improves, but elasticity weakening and hardness variation occur
Solution Approach 1:
The patent segments the support function between the spring structure and the cushion pad. The asymmetric wire configuration (center wire, side wire, connecting wire) provides the roll rigidity mechanically, while the cushion pad maintains its uniform hardness to provide elastic support, separating the rigidity function from the elasticity function
Solution Approach 2:
The patent creates a composite support system combining the metal spring structure (wires) with the cushion pad material. The metal structure provides rigid support for roll stability, while the cushion pad provides elastic comfort, achieving both roll rigidity and elasticity without modifying the pad's hardness distribution
3Strength
If the side wire is extended to increase roll rigidity, then the side support improves, but the load distribution becomes uneven
Solution Approach 1:
The patent applies local quality by having the side wire extend further only in the width direction (via the second extending portion) while maintaining appropriate load distribution through the connecting wire. The extended portion locally increases roll rigidity where needed, while the connecting wire ensures loads are properly distributed to the center wire and frame structure
Data Source
AI summary
There is provided a cushion spring including: a pair of formed wires bridged to a seat cushion frame in a seat front-rear direction and are arranged side by side in a seat width direction; and a resin member joined to the pair of formed wires. The resin member includes a rear connecting portion and a pair of deflection restricting portions, the rear connecting portion extending to connect between a side wire and a center wire and between the center wires in the seat width direction in a region on a seat rear side of an ischium supporting portion of the pair of formed wires that supports an ischium of the seated occupant via a seat cushion pad, the pair of deflection restricting portions extending from the rear connecting portion to connect all crank-shaped portions in the seat front-rear direction.