Steering Apparatus Dynamic Rear Wheel Control
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Solution Overview
Problem
Existing vehicle steering apparatuses can lead to oversteering of rear wheels relative to front wheels, resulting in increased tire scrub, poor traction, and tire damage due to inadequate control of steering angles during turning.
Innovation Solution
A steering apparatus that includes a torque sensor connected to the steering wheel and a controller, which operates the rear steering gear in response to torque changes, maintaining a predetermined kinematic relationship between front and rear wheels throughout a range of turning movements, and adjusting this relationship as needed to prevent oversteering and reduce tire scrub.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rear steering gear is operated to decrease the turning radius, then the vehicle's turning capability is improved, but the rear wheels may oversteer relative to the front wheels causing tire scrub and tire damage
Solution Approach 1:
The patent applies dynamics by making the rear wheel steering angle dynamically adjustable based on the front wheel steering angle. The rear steering gear is controlled to provide a variable steering ratio where the rear wheels steer more aggressively at small front wheel angles (to reduce turning radius) but less aggressively at large front wheel angles (to prevent oversteer and tire scrub). This dynamic adjustment resolves the contradiction between improving turning capability and preventing tire damage.
Solution Approach 2:
The patent changes the steering parameter (rear wheel steering angle) as a function of the front wheel steering angle. By establishing a non-linear relationship where the rear steering angle is proportional to the front steering angle raised to a power greater than one (θrear = k·θfront^n, where n>1), the system achieves aggressive steering at small angles while limiting oversteer at large angles, thereby resolving the contradiction between turning performance and tire protection.
2Manufacturing precision
If the rear steering gear is operated to maintain a fixed kinematic relationship, then the steering precision is improved, but the ability to adapt to different turning conditions is reduced
Solution Approach 1:
The patent resolves this contradiction by making the kinematic relationship dynamic rather than fixed. The rear steering gear is controlled to maintain a precise kinematic relationship at each instant, where the rear steering angle is continuously adjusted based on the current front steering angle. This dynamic precision allows the system to adapt to different turning conditions while maintaining accurate steering control throughout the entire range of motion.
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 effectively manages steering angles to minimize tire scrub, maintain traction, and prevent tire damage by dynamically controlling the rear wheels' turning in relation to the front wheels, thereby improving vehicle handling and extending tire life.
Implementation Method 1
A torque sensor is connected with the steering wheel. A controller is connected with the torque sensor and rear steering gear. The controller is operable to effect operation of the rear steering gear in response to an output from the torque sensor upon manual application of at least a predetermined torque to the steering wheel.
Data Source
AI summary
An apparatus for use in turning steerable vehicle wheels upon manual rotation of a hand wheel includes a torque sensor connected with a torque sensor and a rear steering gear. The controller selectively controls the rear steering gear in response to an output from the torque sensor upon manual application of at least a predetermined torque to the hand wheel. The controller selectively controls the rear steering gear in response to the output from the torque sensor through a first range of turning movement of the front wheels so that the steering angle of the rear wheels has a first relationship to the steering angle of the front wheels and through a second range of turning movement of the front wheels so that the steering angle of the rear wheels has a second relationship different from the first relationship.