Square-Section Coil Spring for Nonlinear Stiffness and Lower Weight
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Solution Overview
Problem
Existing coil springs for vehicle suspension with nonlinear characteristics face challenges in reducing weight while maintaining desired stiffness, as the processing of tapered sections with significantly reduced wire diameters is costly and inefficient, and increasing the number of turns leads to increased vehicle weight due to dead turn parts.
Innovation Solution
A coil spring design featuring a round section portion, a square section portion with sides less than or equal to the square root of half the diameter of the round section, and a taper portion with 1.0 turns or more, allowing for easier formation of the square section using reduction rolls and reducing the sectional area, thereby achieving nonlinear characteristics with reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the wire diameter of the taper portion is significantly reduced to achieve nonlinear characteristics, then the spring constant in small load area is decreased, but the processing cost increases and processing time is extended
Solution Approach 1:
The patent changes the geometric parameters of the wire rod by forming a square section portion with side length less than or equal to 0.707 times the diameter of the round section portion. This parameter change allows the taper portion to achieve the required reduction in stiffness without requiring extreme wire diameter reduction, thus avoiding excessive processing costs and time while still achieving the desired nonlinear spring characteristics
Solution Approach 2:
The patent introduces asymmetry by changing the cross-sectional shape from circular to square in the taper portion. This asymmetric square section geometry provides different mechanical properties compared to a circular section, enabling the taper portion to achieve the required stiffness reduction for nonlinear characteristics without requiring as extreme a reduction in dimension, thereby reducing processing difficulty and cost
2Force
If the number of turns of the taper portion and small-section portion is increased to decrease the spring constant in small load area, then the nonlinear characteristics are improved, but the weight of the vehicle increases due to dead turn parts
Solution Approach 1:
The patent changes the cross-sectional shape parameter from circular to square with reduced side length in the taper portion. This geometric parameter change increases the efficiency of each turn, allowing the desired nonlinear spring characteristics to be achieved with fewer turns, thereby reducing the number of dead turn parts and minimizing the increase in vehicle weight
Solution Approach 2:
The patent applies local quality by creating a square section portion specifically in the taper region where different mechanical properties are needed. This localized geometric modification optimizes the stiffness characteristics in the taper portion without affecting the entire spring, enabling better control over the number of effective turns and reducing unnecessary weight from excess turns
3Ease of manufacture
If a flat portion with rectangular section is formed by rolling the wire rod to achieve nonlinear characteristics, then the ease of manufacture is improved, but the polar moment of inertia is very large making it difficult to reduce coil spring weight
Solution Approach 1:
The patent uses a square section instead of a flat rectangular section, creating an asymmetric geometry that provides better weight reduction than conventional flat portions. The square cross-section with side length less than or equal to 0.707 times the round section diameter achieves the desired reduction in polar moment of inertia while maintaining ease of manufacture through rolling processes
Solution Approach 2:
The patent optimizes the geometric parameters by forming a square section with specifically controlled side length (less than or equal to 0.707 times the round section diameter). This parameter optimization achieves the right balance between manufacturability through rolling and weight reduction, avoiding the excessive polar moment of inertia associated with conventional flat rectangular sections
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 results in a lightweight coil spring with nonlinear characteristics, where the square section portion can be formed easily and with a significantly reduced sectional area, maintaining spring functionality while minimizing weight, and the taper portion ensures adequate stress distribution without excessive weight increase.
Implementation Method 1
a particular reduction roll needs to be used to make the wire diameter sufficiently less by plastic working
Implementation Method 2
the coil spring is deflected with a first spring constant... the coil spring is deflected with a second spring constant
Data Source
AI summary
According to an embodiment, a coil spring includes a wire rod having an end and the other end. The wire rod of the coil spring includes, with regard to a section of the wire rod, a round section portion of an effective spring part, a square section portion in which the section is substantially square, and a taper portion. The square section portion includes an end turn part. A length of each side of the section of the square section portion is less than or equal to a square root of ½ multiplied by a diameter of the wire rod of the round section portion. In the taper portion, from the round section portion to the square section portion, the section changes from a round shape to substantially a square shape, and a sectional area is decreased.