Coil Spring Cross-Section Transition for Nonlinear Load Reduction
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Solution Overview
Problem
Existing coil springs with nonlinear characteristics face challenges in reducing weight and processing complexity due to limitations in forming parts with extremely small diameters, leading to increased weight and processing costs.
Innovation Solution
A coil spring design featuring a round section portion, a square section portion, and a taper portion with specific geometric transitions, allowing for easier processing and reduced weight through the use of reduction rolls and plastic working.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the wire diameter is decreased to create a taper portion with smaller section, then the spring constant in small load area is reduced, but the processing difficulty and cost increase significantly
Solution Approach 1:
The patent changes the geometric parameters of the wire rod section by transitioning from a circular section to a square section with rounded corners. This parameter change allows the creation of a taper portion with reduced sectional area without requiring extreme wire diameter reduction, thereby achieving the desired spring constant while avoiding excessive processing difficulty
Solution Approach 2:
The patent applies local quality by creating a taper portion with a specific square-section geometry only in the region where reduced spring constant is needed, while maintaining the standard circular section in other parts of the coil spring. This localized geometric modification achieves the functional requirement without compromising the overall manufacturability of the spring
2Force
If the number of turns of the taper portion is increased to reduce spring constant, then the weight of the coil spring increases
Solution Approach 1:
The patent achieves reduction of spring constant by changing the cross-sectional geometry parameters (from circular to square with rounded corners) rather than increasing the number of turns. This parameter change allows achieving the desired force characteristics while minimizing the addition of dead turn parts and thus reducing weight increase
3Ease of manufacture
If a circular section wire rod is used, then the processing of small diameter parts is difficult, but a square section wire rod may have larger polar moment of inertia
Solution Approach 1:
The patent uses a square section with rounded corners instead of a circular section. This asymmetric geometry (compared to circular) provides easier processing for small diameter parts while the rounded corners help maintain adequate polar moment of inertia by distributing material away from the center, thus balancing manufacturability and structural strength
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
The design achieves a lightweight coil spring with nonlinear characteristics by reducing the sectional area and polar moment of inertia, resulting in a 20% weight reduction compared to conventional designs while maintaining equivalent spring characteristics.
Implementation Method 1
a square section portion (31) formed from an end (2a) of the wire rod (2), and a taper portion (32) formed between the round section portion (30) and the square section portion (31)
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
According to an embodiment, a coil spring includes a wire rod (2) having an end and the other end. The wire rod (2) of the coil spring includes, with regard to a section of the wire rod (2), a round section potion (30) of an effective spring part (13), a square section portion (31) in which the section is substantially square, and a taper portion (32). The square section portion (31) includes an end turn part (11)(12). A length of each side of the section of the square section portion (31) is less than or equal to a square root of 1/2 multiplied by a diameter of the wire rod (2) of the round section portion (30). In the taper portion (32), from the round section portion (30) to the square section portion (31), the section changes from a round shape to substantially a square shape, and a sectional area is decreased.