Coil Spring Asymmetric Cross Section Stress Dispersion
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Solution Overview
Problem
Conventional coil springs with flat faces on a circular or rectangular section suffer from uneven stress distribution in the circumferential direction, leading to stress discontinuity and reduced evenness, despite effectively dispersing stress in the diametral direction.
Innovation Solution
The coil spring design features flat faces on one side in a semi-circular shape and the other side in a non-circular shape with varying diameters, with the inclination of flat faces forming a wedge shape to achieve continuous stress dispersion in the circumferential direction, reducing oblateness and shortening the close contact length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If flat faces are provided on a spring wire with a circular section to receive load stably, then stress dispersion in the diametral direction is improved, but stress dispersion in the circumferential direction deteriorates due to stress bias
Solution Approach 1:
The patent applies asymmetry by changing the cross-sectional shape from a symmetric circular section to an asymmetric shape where one side has a flat face and the other side has a curved surface. This asymmetric configuration allows the flat face to contact adjacent coils for stable load reception while the curved surface distributes stress more evenly in the circumferential direction, resolving the contradiction between load stability and stress dispersion.
2Length of moving object
If oblateness T/W is reduced to achieve longer stroke and lower stiffness, then close contact length is shortened, but stress evenness deteriorates
Solution Approach 1:
The patent applies local quality by creating different surface characteristics at different locations of the spring wire cross-section. The flat face portion provides localized contact for load reception, while the curved surface portion provides localized stress distribution. This local differentiation allows the spring to achieve longer stroke through reduced oblateness while maintaining stress evenness through the complementary curved surface geometry.
Data Source
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AI summary
A coil spring has a spring wire wound in a coil shape having an outer diameter side portion and an inner diameter side portion on a peripheral shape in a cross section thereof, one of the outer diameter side portion and inner diameter side portion formed in a semi-circular shape expressed by x2+y2=b2, the other thereof formed in a non-circular shape with a long diameter "a" and a short diameter "b" expressed by (x/a)α+(y/b)α=1, and value of the "α" set in a range of 1.85 to 2.45, and contact faces provided between the inner diameter side portion and the outer diameter side portion on the peripheral shape in the cross section such that each contact face comes into contact with a contact face of an adjacent coil in an axial direction along an axis line of the coil spring.