Cross Leaf Spring Dimensioning for Anti-Roll Stiffness
Solution Overview
Problem
Quadrilateral suspensions with cross leaf spring in vehicles face challenges in achieving optimal dynamic behavior without the weight and size increase of anti-roll bars, which are necessary for effective anti-roll performance, and removing these bars deteriorates vehicle performance, especially on bends.
Innovation Solution
A method for dimensioning a quadrilateral or McPherson suspension with a cross leaf spring that allows for the removal of the anti-roll bar by optimizing the leaf spring's thickness and positioning to achieve the desired vertical stiffness ratios, enabling the same performance as a suspension with an anti-roll bar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an anti-roll bar is added to the suspension system, then the anti-roll performance is improved, but the weight and size of the suspension system increase
Solution Approach 1:
The patent combines the anti-roll function with the existing cross leaf spring by positioning the leaf spring to act as an anti-roll bar. The leaf spring is configured to connect opposite sides of the vehicle body and is designed to resist rolling motion through its geometric arrangement and elastic properties, thereby eliminating the need for a separate anti-roll bar component.
Solution Approach 2:
The cross leaf spring is designed to perform multiple functions: it serves as both a suspension element for vertical load support and as an anti-roll bar for resisting rolling motion. This multi-functional design allows the same component to provide both suspension and anti-roll performance, reducing overall system complexity and weight.
2Reliability
If an anti-roll bar is added to the suspension system, then the anti-roll performance is improved, but the size of the suspension system increases
Solution Approach 1:
The patent combines the anti-roll function with the existing cross leaf spring by positioning the leaf spring to act as an anti-roll bar. The leaf spring is configured to connect opposite sides of the vehicle body and is designed to resist rolling motion through its geometric arrangement and elastic properties, thereby eliminating the need for a separate anti-roll bar component.
3Weight of moving object
If the anti-roll bar is removed from the suspension system, then the weight and size are reduced, but the vehicle performance on bends deteriorates
Solution Approach 1:
The cross leaf spring is designed to perform multiple functions: it serves as both a suspension element for vertical load support and as an anti-roll bar for resisting rolling motion. This multi-functional design allows the same component to provide both suspension and anti-roll performance, reducing overall system complexity and weight.
4Reliability
If the leaf spring is designed to provide anti-roll function, then the anti-roll performance is improved, but the complexity of dimensioning and design increases
Solution Approach 1:
The patent provides specific dimensioning criteria and formulas for designing the leaf spring as an anti-roll bar. Key parameters include the leaf spring thickness, width, and length, which are calculated based on the desired anti-roll stiffness and vertical load requirements. The design methodology establishes relationships between these parameters to achieve the target stiffness ratio, simplifying the design process through systematic parameter optimization.
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 method allows for the removal of the anti-roll bar while maintaining optimal vehicle dynamics, specifically achieving a vertical stiffness ratio that opposes rolling motion, thus enhancing performance without the added weight and size of the anti-roll bar.
Implementation Method 1
the 'vertical stiffness upon symmetrical loads' of the leaf spring is defined as the ratio between the vertical load per unit applied to one end of the leaf spring for the vertical displacement of the same end
Data Source
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AI summary
Method for dimensioning a quadrilateral or McPherson suspension (S) with cross leaf spring (LS) defining a longitudinal development (Y), arranged parallel to a symmetrical vehicle axle defined by the suspension (S), having an intermediate point of reference (M), an end point (L/2) connected to a lower arm (AL) of the suspension and a constraint point (1/2), intermediate between the first two, constrained to a fixed part (C), said method comprising a step of defining the following distances measured along said longitudinal development (Y) starting from said intermediate point of reference (M) : - P = distance of the connection (X2) between lower arm (AL) and wheel hub (SP), - L/2 = distance from said end point (L/2) of the leaf spring (LS), - H = distance of the hinging between said first part of the lower arm and said fixed part (C), - 1/2 = distance of said intermediate constraint point (1/2); - a step of defining with d a difference/distance between H and L/2 and with b a difference/distance between H and P, - a step of defining R = b/ (b-d), - a step of defining ks = ksosp * R2 [eq.l], where ks is the stiffness of the leaf spring upon symmetrical vertical loads and ksosp is the stiffness of the suspension upon symmetrical vertical loads, - a step of defining a thickness h of said leaf spring (LS) according to the following equations: - h = hO between said reference intermediate point (M) and 1/2, - h(Y) = 2* ( (Y- (costi) ) / (cost2) )0-5 between 1/2 and L/2 [eq. 2 ], where Y is an independent variable, costi = 1015.00942 and cost2 = -8.51224 and wherein the material of said leaf spring has a Young module comprised between 195 GPa and 210 GPa.