Variable Steering Gear Ratio Rack for Vehicle Stability
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Solution Overview
Problem
Conventional steering systems for vehicles face challenges in maintaining high-speed stability, direct feel, and response linearity, especially during low-speed and middle-speed travel, while also requiring reduced steering frequency and force in parking, which existing MDPS systems fail to address effectively.
Innovation Solution
A steering apparatus with a variable steering gear ratio that includes a linear increase, upper limit-maintained, and linear decrease section, where the gear ratio changes based on the rotation angle of the steering wheel, incorporating an electric motor for sub-steering assistance, allowing for improved direct feel and response while minimizing motor capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixed steering gear ratio is used in conventional steering systems, then the structure is simple, but high-speed stability and direct feel cannot be simultaneously ensured across different speed conditions
Solution Approach 1:
The patent applies the dynamics principle by making the steering gear ratio variable rather than fixed. The tooth gap of the rack gear is designed to change according to the position of the steering pinion, creating different steering gear ratios in different steering sections. This allows the steering system to adapt dynamically to different driving conditions (high-speed, low-speed, parking), resolving the contradiction between maintaining stability and avoiding excessive complexity.
2Ease of operation
If a variable steering gear ratio is implemented to improve direct feel and response linearity, then steering performance improves, but the structure becomes more complex
Solution Approach 1:
The patent applies the local quality principle by designing different tooth gap characteristics in different sections of the rack gear. Specifically, the tooth gap varies in the neutral section, left turn section, and right turn section to provide optimal direct feel and response linearity for each steering condition. This localized optimization improves ease of operation without requiring a complete redesign of the entire steering system.
3Ease of operation
If steering frequency and force are reduced for parking operations, then parking maneuverability improves, but response linearity may deteriorate
Solution Approach 1:
The patent applies dynamics by implementing a variable steering gear ratio that automatically adjusts according to the steering position. In parking sections (large steering angles), the gear ratio is designed to reduce steering frequency and force requirements, improving maneuverability. Meanwhile, in neutral and small-angle sections, the gear ratio maintains response linearity. This dynamic adaptation resolves the contradiction between parking ease and response precision.
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 ensures high-speed stability, direct feel, and response linearity during low-speed and middle-speed travel, reduces steering frequency and force in parking, and enhances the performance of MDPS systems with improved direct feel and response while reducing the electric motor's capacity.
Implementation Method 1
An electric motor providing sub-steering force in accordance with operation of the steering wheel may be connected to the steering pinion
Implementation Method 2
a steering pinion rotated by operation of a steering wheel, and a steering rack bar having a rack engaged with the steering pinion to move straight in a longitudinal direction thereof
Data Source
AI summary
A steering apparatus for a vehicle may include a steering pinion rotated by operation of a steering wheel, and a steering rack bar having a rack engaged with the steering pinion to move straight in a longitudinal direction thereof, wherein a tooth gap in a gear of the rack changes such that a steering gear ratio corresponding to a linear displacement of the steering rack bar according to rotation of the steering pinion increases and then decreases in both sections from the center of the rack to both ends thereof.