Wishbone Linkage and Modular Bushings for Steering Axle Roll Stiffness
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Solution Overview
Problem
Existing vehicle suspension systems face challenges in incorporating a torque box configuration in steering axles due to packaging constraints and undesirable steering kinematics, leading to issues like over-steer and increased weight and cost.
Innovation Solution
A wishbone-shaped linkage with a modular bushing assembly is used, featuring a base with laterally and longitudinally oriented limbs, partially wrapped plates, and adjustable bushing lobes, which enhances lateral and roll stiffness while minimizing weight and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a torque box configuration is used in steering axle suspension systems, then roll stability is improved, but packaging constraints and steering kinematics issues arise causing over-steer
Solution Approach 1:
The torque box is divided into separate components: a wishbone-shaped linkage with individual arms that can be positioned independently, and separate bushing assemblies at each mounting point. This segmentation allows optimization of each component's position and orientation to achieve proper steering kinematics while maintaining roll stability.
Solution Approach 2:
The bushing assemblies incorporate compliant elements that allow dynamic adjustment of the linkage's effective position and orientation during steering operations. This dynamic compliance compensates for the rigid geometry constraints, enabling proper steering kinematics while maintaining the structural integrity needed for roll stability.
2Force
If leaf springs are used to control axle motions, then vertical spring rate is achieved, but weight and cost increase significantly
Solution Approach 1:
The leaf spring component is extracted and replaced with a combination of a compact torque box linkage and separate bushing assemblies. The bushings provide the necessary compliance and spring characteristics, while the linkage provides the structural support, eliminating the need for heavy leaf springs while maintaining vertical spring rate control.
Solution Approach 2:
The bushing assemblies use elastomeric materials with specific durometer ratings and geometric configurations to achieve the required vertical spring rate characteristics. By adjusting bushing material properties, dimensions, and pre-loads, the desired force-deflection characteristics are obtained without the weight of traditional leaf springs.
3Stability of the object's composition
If a stabilizer bar is added to achieve desired vertical spring rate for ride comfort, then roll stability is improved, but cost and weight increase
Solution Approach 1:
The roll stability function is merged into the torque box linkage structure itself. The wishbone-shaped linkage with its specific geometry and bushing configuration provides inherent roll resistance as part of its primary suspension function, eliminating the need for a separate stabilizer bar while maintaining roll stability.
Solution Approach 2:
The torque box linkage serves multiple functions simultaneously: it provides vertical spring support, controls axle motions, provides roll stability, and maintains proper steering kinematics. This multi-functionality eliminates the need for separate components like stabilizer bars, reducing overall system weight and complexity.
Data Source
AI summary
A vehicle suspension system includes a wishbone-shaped linkage having a base, with two limbs extending from the base. Each limb is configured to support a laterally and longitudinally oriented bushing assembly, which may include a bushing assembly received by a laterally and longitudinally oriented mounting tube associated with a free end of the limb. The base includes upper and lower plates wrapping only partially around a laterally extending cross tube. A modular bushing assembly including a pair of bushing lobes and a bar pin is partially received within the cross tube, with the bushing lobes being adjustably positioned on the bar pin to allow for adjustment of the conical rate of the bushing assembly. A mounting assembly includes a pair of mount blocks secured to a vehicle axle, with the bar pin being secured with respect to the axle via the mount blocks, thereby associating the linkage to the axle.