Augmented Rack-and-Pinion Steering for Negligible Bumpsteer
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Solution Overview
Problem
Current steering systems for front solid axle four-wheel drive vehicles, particularly those with triangulated 4-link suspension, suffer from bumpsteer issues due to the interaction between the draglink and suspension links during articulation, and existing rack and pinion systems are not robust enough to handle the heavy-duty conditions of these vehicles.
Innovation Solution
A steering system incorporating a rack and pinion gearset with a slow steering ratio, an augmented chain and sprocket assembly, and either electric or hydraulic power assist, where the control valve is remotely located to isolate it from the front axle, ensuring precise steering response and minimizing bumpsteer through coordinated forces and reduced unintended displacement during articulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a rack and pinion gearset with quick steering ratio is used, then steering response speed is improved, but bumpsteer increases during articulation
Solution Approach 1:
The patent changes the steering ratio parameter from quick to slow (18:1 or 20:1), which reduces bumpsteer during articulation. This parameter change trades off some steering response speed for significantly reduced bumpsteer, and the power assist system compensates for the slower mechanical ratio to maintain acceptable overall response characteristics.
2Device complexity
If the control valve is integrated with the rack and pinion gearset on the front axle, then system compactness is improved, but the control valve is exposed to adverse off-road conditions
Solution Approach 1:
The control valve is extracted from the rack and pinion gearset assembly and relocated to a separate mounting location away from the front axle. This separation protects the control valve from adverse off-road conditions such as vibrations, shocks, and contamination, while maintaining system functionality through separate hydraulic line connections.
3Measurement precision
If hydraulic pressure force and pinion shaft force are coordinated, then steering precision is improved, but system complexity increases
Solution Approach 1:
The system employs feedback through the hydraulic circuit where the control valve responds to steering input and coordinates hydraulic pressure force with the pinion shaft force. The hydraulic system provides force feedback that assists the driver while maintaining precise steering control, with the slow steering ratio providing mechanical feedback that reduces bumpsteer effects.
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 system achieves negligible bumpsteer during suspension travel and articulation, providing a quick and precise steering response suitable for heavy-duty applications, while withstanding the rigors of off-road conditions.
Implementation Method 1
The basic operation of the rack and pinion gearset involves a toothed pinion shaft meshing with a toothed rack. During the meshing process, the pinion shaft interacts with the rack such that the rotation of the pinion shaft causes a linear displacement of the rack.
Implementation Method 2
The internal components include a large sprocket, small sprocket, chain, input shaft, and output shaft. The chain is positioned around the large and small sprockets such that the links on the chain are able to contact the teeth on the large and small sprockets.
Implementation Method 3
The internal components are able to include an electric motor. The electric motor is located next to the input shaft or output shaft such that the electric motor can exert a torque force on the input shaft or output shaft, respectively. The torque force multiplies the rotational torque from the steering input.
Implementation Method 4
Hydraulic fluid passes from the control valve to the ram such that the hydraulic pressure is generated in the ram. The hydraulic pressure in the ram defines the hydraulic pressure force that is exerted on the rack, which displaces the rack.
Implementation Method 5
The control valve regulates the flow of hydraulic fluid to the ram. The hydraulic fluid generates hydraulic pressure in the ram which defines a hydraulic pressure force of the ram.
Data Source
AI summary
The present invention is a steering system for a beam-type solid axle arrangement. The steering system is designed to operate in conjunction with the triangulated link-style suspension system with zero bumpsteer during suspension travel and negligible bumpsteer during articulation. Accurate steering throughout suspension operations is satisfied with mechanical linkages that include a slow ratio rack and pinion gearset and unique augmented chain and sprocket assembly. The slow ratio of the rack and pinion gearset ensures negligible bumpsteer during articulation, thereby leading to negligible if any bumpsteer throughout operation of the suspension system. Meanwhile, augmentation of the chain and sprocket assembly defines a steering quickener effect thereby speeding up the rack and pinion gearset and restoring quick steering response. Effortless steering is ensured by appropriate use of electric or hydraulic assist devices.