Leaf Spring Trailing Arm Suspension for Heavy Trucks
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Solution Overview
Problem
Modern heavy-duty trucks face challenges in designing leaf springs that balance load capacity with low spring rates for optimal ride comfort and adequate roll stiffness, often requiring supplementary roll stiffening mechanisms, while air springs on rear axles lack axle locating functionality, necessitating additional linkages that can introduce wear and lash.
Innovation Solution
A leaf spring assembly with a trailing arm and air springs that provides low vertical spring rate and high roll stiffness without supplementary roll stabilization mechanisms, using a tapered trailing arm for efficient load distribution and a restraint mechanism to limit lateral motion, allowing for longitudinal movement of the leaf spring relative to the trailing arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If leaf springs are designed with high load capacity, then the spring rate becomes too high for optimal ride comfort, but if the spring rate is reduced for comfort, then roll stiffness becomes inadequate
Solution Approach 1:
The patent combines the functions of the trailing arm and leaf spring into a single integrated assembly. The trailing arm provides the primary load-bearing structure with optimized stiffness characteristics, while the leaf spring acts as a supplementary element that absorbs vertical loads without compromising roll stiffness. This merging allows the system to achieve both high load capacity and low spring rate for ride comfort.
Solution Approach 2:
The suspension system is segmented into distinct functional components: the trailing arm handles lateral positioning and roll stiffness, while the leaf spring handles vertical load support. This segmentation allows each component to be optimized for its specific function, enabling the leaf spring to have a low spring rate without sacrificing overall roll stability.
2Object-generated harmful factors
If air springs are used to achieve low spring rates, then ride comfort improves, but axle locating functionality is lost requiring additional linkages
Solution Approach 1:
The trailing arm serves multiple functions simultaneously: it provides lateral axle positioning, resists lateral loads, contributes to roll stiffness, and allows vertical suspension movement. This multi-functionality eliminates the need for separate linkages that would be required if air springs alone were used, thereby reducing device complexity while maintaining ride comfort.
3Reliability
If additional linkages and pivots are introduced to the rear of each beam, then axle locating capability is improved, but wear and lash in the linkage increase
Solution Approach 1:
The patent extracts the axle locating function from the leaf spring assembly and assigns it to the trailing arm. By removing the need for additional linkages and pivots at the rear of the beam, the design eliminates the sources of wear and lash while maintaining adequate axle locating capability through the trailing arm's inherent structural properties.
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 achieves a balance of low sprung mass natural frequency, low vertical spring rate, and high roll stiffness without additional linkages, reducing wear and lash, and enhancing ride comfort by distributing loads efficiently and providing redundant fore-aft restraint.
Implementation Method 1
Two air springs are interposed between each beam and the vehicle frame and support the sprung mass
Implementation Method 2
Supplemental roll stiffness is generated from the flexural stiffness of the forward ends of the beams and the torsional stiffness of the axle which together act as an anti-roll bar under roll deflection
Implementation Method 3
Supplemental roll stiffness is generated from the flexural stiffness of the forward ends of the beams and the torsional stiffness of the axle which together act as an anti-roll bar under roll deflection
Data Source
AI summary
A leaf spring assembly for a vehicle having a frame and an axle. The leaf spring assembly includes a first leaf spring and a trailing arm having first and second ends. The first end of the trailing arm adapted to be coupled to the frame to form a trailing arm attachment point. The first leaf spring is disposed beneath the trailing arm and includes a width defining a lateral direction and first and second ends defining a longitudinal direction. The first end of the first leaf spring being concentrically wound with the first end of the trailing arm and adapted to be attached to the frame.