Leaf Spring Asymmetry and Bumper Engagement
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Solution Overview
Problem
Traditional leaf spring configurations in vehicle suspension systems are heavy, resulting in harsh ride quality due to high mass and stiffness, which is exacerbated by increased stresses from stringent braking requirements, leading to issues with ride comfort and potential fractures.
Innovation Solution
A suspension system using a lighter weight leaf spring with tapered surfaces and a bumper that engages during compression to adjust roll stiffness, allowing for customized vertical spring rates and reduced mass, while avoiding a center hole to minimize stress and fracture risk, and utilizing a closer clamping fastener pattern to increase active spring material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional leaf spring configurations are used with equal length front and rear limbs to meet braking requirements, then braking capability and roll stiffness are improved, but vehicle mass and spring weight increase significantly
Solution Approach 1:
The patent applies asymmetry by configuring the leaf spring with unequal front and rear limb lengths. The front limb has a first length while the rear limb has a second length that is different from the first length. This asymmetric configuration allows the spring to meet braking force requirements and roll stiffness requirements without requiring a massive, symmetric design, thereby reducing overall spring weight while maintaining the necessary mechanical performance.
2Force
If leaf spring thickness and vertical spring rate are increased to handle axle windup and braking forces, then braking capability and roll stiffness are improved, but ride quality becomes harsh
Solution Approach 1:
The patent applies local quality by varying the thickness of the leaf spring along its length rather than using a uniform thickness. The spring has a first thickness in a first portion and a second thickness in a second portion, with the second thickness being greater than the first thickness. This allows the spring to have sufficient local stiffness in critical areas to handle braking forces and axle windup, while maintaining thinner sections in other areas to provide a softer, more comfortable ride quality.
3Ease of manufacture
If a center hole is included in the leaf spring for axle coupling, then axle coupling is simplified, but stress concentration and fracture risk increase
Solution Approach 1:
The patent applies the extraction principle by removing the center hole from the leaf spring design. Instead of having a hole through the center of the spring for axle coupling, the design uses a solid continuous structure. This eliminates the stress concentration that would occur at the hole boundaries, thereby reducing the risk of fracture while still allowing for axle coupling through alternative means such as eye loops at the spring ends or other coupling mechanisms that do not require compromising the spring's structural integrity.
4Speed
If faster braking is implemented to meet new laws, then braking performance is improved, but stresses on suspension components increase
Solution Approach 1:
The patent applies dynamics by configuring the leaf spring with asymmetric limb lengths that allow it to dynamically adapt to different loading conditions. The unequal front and rear limb lengths enable the spring to optimize its stress distribution during high-speed braking events, allowing faster braking to be implemented while managing the resulting stresses on suspension components more effectively than a symmetric design would allow.
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 solution provides improved ride comfort, reduced unsprung mass, and increased roll stiffness during dynamic maneuvers, while maintaining effective jounce and rear limb windup management, thus enhancing overall suspension performance.
Implementation Method 1
a bumper disposed between the leaf spring and the vehicle frame member, and wherein a center of the bumper is located forward and inward of a center of the axle coupling assembly, such that when the suspension is in a roll condition and the bumper is engaged and compressed, roll stiffness of the leaf spring is increased
Implementation Method 2
The leaf spring also includes tapered upper and lower surfaces in an axle seat portion
Data Source
AI summary
Suspension systems, leaf springs and methods of providing a leaf spring in a suspension system are disclosed. The suspension systems, leaf springs and methods of providing a leaf spring in a suspension system allow use of a lighter weight leaf spring while providing customized roll stiffness and vertical spring rate that are complemented by a bumper that engages the leaf spring assembly when compressed to at least a preselected position.