Steering Rack Pressure Angle Variation for Rattle Suppression
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Solution Overview
Problem
The existing rack-and-pinion steering systems experience gear rattle due to the separation of rack teeth from pinion teeth, which affects the steering feel, and there is a need to suppress gear rattle while maintaining good steering feel.
Innovation Solution
The steering system incorporates a pinion shaft with pinion teeth, a rack shaft with varying pressure angles in different regions, a support yoke, an urging member, and a restricting member to adjust the rotational resistance and steering feel by controlling the clearance between the support yoke and the restricting member, thereby minimizing gear rattle and enhancing steering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clearance between the support yoke and restricting member is reduced to suppress gear rattle, then the steering feel deteriorates due to increased rotational resistance
Solution Approach 1:
The pressure angle of rack teeth is varied locally according to position: larger pressure angles at center and end regions, smaller pressure angles at intermediate regions. This local differentiation allows the system to maintain good steering feel at the pinion shaft center while suppressing gear rattle at intermediate positions where separation occurs
Solution Approach 2:
The pressure angle parameter is changed across different regions of the rack teeth. By adjusting this geometric parameter, the patent achieves variable meshing characteristics that balance steering feel and gear rattle suppression without requiring physical modification of the clearance structure
2Ease of operation
If the pressure angle of rack teeth is increased to improve steering feel, then gear rattle increases due to greater separation force
Solution Approach 1:
Different pressure angles are assigned to different regions: larger pressure angles at center and end regions for good steering feel, smaller pressure angles at intermediate regions to reduce separation force and suppress gear rattle. This local quality differentiation resolves the contradiction between steering feel and gear rattle
Solution Approach 2:
The rack teeth are segmented into three regions (center, intermediate, end) with different pressure angle characteristics. This segmentation allows independent optimization of each region's meshing behavior to simultaneously achieve good steering feel and suppress gear rattle
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 effectively reduces gear rattle and improves steering feel by varying the pressure angles of the rack teeth, optimizing the force applied to the rack shaft, and adjusting the steering gear ratio based on the vehicle's driving situation.
Implementation Method 1
an urging member that applies force, which acts in an urging direction that is a direction in which the support yoke is pressed against the rack shaft, to the support yoke
Implementation Method 2
a pinion shaft that has a plurality of pinion teeth; a rack shaft that has a stroke region in which a plurality of rack teeth that mesh with the pinion teeth is formed
Data Source
AI summary
A pinion shaft of a steering system has a plurality of pinion teeth. A rack shaft has a stroke region in which a plurality of rack teeth that mesh with the pinion teeth is formed. The stroke region includes a center region that includes a center position of the stroke region, end regions, each of which includes an end position of the stroke region, and intermediate regions, each of which is located between the center region and one of the end regions. A pressure angle of each rack tooth included in each of the intermediate regions is smaller than a pressure angle of each rack tooth included in each of the center region and the end regions.