Rack Bush Groove Geometry for Steering Response Rigidity
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Solution Overview
Problem
The existing rack bush in rack-and-pinion steering mechanisms experiences time lag in steering operation due to compressive deformation of elastic rings under reaction forces from tires, affecting the feeling of steering.
Innovation Solution
A bearing design with a mounting groove having a large-diameter part and a small-diameter part, where the elastic ring is positioned to face the reaction force, reducing the gap between the bush body and the housing, thereby improving rigidity and reducing time lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If elastic rings are mounted on the bearing body to tighten the rack bar, then the clearance between the bearing body and rack bar is eliminated, but the elastic rings are compressively deformed under reaction force causing time lag in steering operation
Solution Approach 1:
The mounting groove is designed with different radial positions for different functions: one portion is positioned to eliminate clearance between the bearing body and rack bar, while another portion is positioned to reduce deformation under reaction force. This local differentiation of groove geometry resolves the contradiction by optimizing each region for its specific function.
2Reliability
If the mounting groove is positioned to eliminate clearance, then the rack bar is tightly secured, but the bearing body moves within the housing under reaction force
Solution Approach 1:
The mounting groove has different radial positions at different locations: one location optimized for eliminating clearance to secure the rack bar, and another location optimized for minimizing movement within the housing under reaction force. This local quality differentiation allows simultaneous achievement of both securing reliability and positional stability.
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 improved design enhances the rigidity against reaction forces, reduces movement of the rack bar within the housing, and minimizes the effect on steering operation feel without compromising sliding characteristics.
Implementation Method 1
an elastic ring mounted on the bush body; the mounting groove has a large-diameter part where a groove bottom in a circumferential direction of the mounting groove has a first radius and a small-diameter part where the groove bottom in the circumferential direction has a second radius smaller than the first radius
Data Source
AI summary
To reduce the effect of a steering operation on feeling. A rack bush comprises: a bush body that is accommodated in a cylindrical housing, supports a load exerted on a rack bar while allowing the rack bar to move in the direction of an axial center O, and can be extended and retracted in a radial direction; and an elastic ring mounted on the bush body. The bush body has a mounting groove for mounting the elastic ring, the mounting groove being formed peripherally in an outer peripheral surface, and the mounting groove having a large-diameter part where the circumferential radius of a groove bottom is a first radius r1, and a small-diameter part where said radius is a second radius r2 that is less than the first radius r1. This configuration allows the formation of an elastic ring protruding part, in which the elastic ring protrudes greatly from the outer peripheral surface of the bush body, and an elastic ring embedded part, in which the elastic ring is embedded in the outer peripheral surface of the bush body.