Steering Rack Thread Profile for Stable Steering Sensitivity
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Solution Overview
Problem
Current power-assisted steering systems, particularly motor-driven power steering (MDPS), experience fluctuations in steering sensitivity and stability, leading to degraded driver operation sense and vehicle instability, especially at high speeds.
Innovation Solution
A steering rack design with a threaded part featuring varying over ball diameters, thread groove curvature radii, and backlash along its length, engaged with a ball nut, to provide consistent steering sensitivity and improved driving stability by adjusting frictional forces and reaction forces based on the steering angle and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the over ball diameter is uniform along the threaded part, then the manufacturing process is simple, but the steering sensitivity fluctuates and driving stability deteriorates
Solution Approach 1:
The threaded part is designed with different over ball diameters in different regions: a first over ball diameter in the first region and a second over ball diameter in the second region. This local differentiation allows the patent to optimize steering sensitivity and driving stability in specific areas without complicating the entire threaded part structure, directly resolving the contradiction between reliability improvement and device complexity.
2Ease of operation
If the reaction force from the steering wheel is constant, then the driver operation sense is improved, but the steering rack structure becomes complex
Solution Approach 1:
The patent applies local quality by differentiating the threaded part structure into two regions with different over ball diameters. This regional differentiation enables the steering rack to provide a more constant reaction force to the driver during operation, improving ease of operation without requiring a completely complex redesign of the entire steering rack structure.
3Reliability
If the steering sensitivity is optimized for all steering angles, then the driving stability improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent divides the threaded part into two regions with different over ball diameters and corresponding thread groove curvature radii. This local differentiation allows for optimized steering sensitivity across different steering angles while maintaining manageable manufacturing precision requirements, as each region can be manufactured with specific tolerances rather than requiring uniform high precision throughout the entire threaded part.
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 design ensures a constant and stable steering sensitivity for the driver, enhancing vehicle stability and reducing operational fatigue, while maintaining a simple manufacturing process and cost-effectiveness.
Implementation Method 1
The screw gear teeth are engaged with a ball nut rotating by power of a motor through balls
Implementation Method 2
The over ball diameter variations create different frictional forces and reaction forces based on steering angle and speed
Data Source
AI summary
Disclosed herein are a steering rack and a method of manufacturing the same. The steering rack includes a body part having both ends, each of which is connectable to a respective wheel and extending in a width direction of a vehicle body, and a threaded part provided on one side of the body part and having screw gear teeth configured to be engageable with a ball nut configured to be rotatable by power of a motor by means of a ball. The screw gear teeth may be divided into a first area relatively adjacent to a center of the threaded part and a second area relatively adjacent to both ends of the threaded part, and an over ball diameter of the first area is different from an over ball diameter of the second area.