Self-Adjusting Rack Bearing for Steering Gear Rattle
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Solution Overview
Problem
Rack and pinion steering gear assemblies experience wear over time, leading to increased mesh clearance between the pinion shaft and rack, which can result in rattle noise and customer dissatisfaction, as existing biasing assemblies either lead to excessive force or resistance during initial assembly or fail to adjust effectively with wear.
Innovation Solution
A self-adjusting rack and pinion steering gear assembly featuring a biasing assembly with a gross adjustment member, a bearing assembly, and an accumulative adjustment assembly, which includes a compliance zone and a torsional spring to maintain optimal engagement between the pinion shaft and rack, allowing for continuous-variable axial movements to accommodate wear and dimensional variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional spring biasing assembly is used with a predefined compliance zone, then the rack bearing can be adjusted to provide initial mesh clearance, but the compliance zone enlarges over time due to wear leading to gear rattle
Solution Approach 1:
The biasing assembly is designed to dynamically adjust the compliance zone size in response to wear. As the pinion shaft and rack wear and move apart, the spring automatically compresses further, reducing the compliance zone size to maintain optimal mesh clearance and prevent rattle noise.
Solution Approach 2:
The system incorporates automatic feedback through the spring mechanism that senses the wear-induced separation between pinion shaft and rack, and responds by adjusting the rack bearing position to maintain proper mesh clearance without manual intervention.
2Reliability
If the adjustment plug is installed at too great a distance from the rack, then the compliance zone is too large causing rattle, but if installed too close, then excessive force increases steering resistance
Solution Approach 1:
Rather than using a fixed static position for the adjustment plug, the system employs a dynamic spring-based biasing assembly that automatically adjusts the compliance zone size based on actual wear conditions, eliminating the need to precisely predict the optimal initial position.
Solution Approach 2:
The biasing assembly performs self-adjustment through the spring mechanism that automatically responds to wear-induced changes in mesh clearance, eliminating the need for manual re-adjustment or complex initial positioning calculations.
3Manufacturing precision
If the rack bearing is biased into engagement with the rack using a spring, then mesh clearance is maintained, but the working range of the spring increases over time reducing biasing force
Solution Approach 1:
The spring biasing assembly is designed to dynamically adapt its compression state as wear occurs. The rack bearing is allowed to move axially within the housing, enabling the spring to compress further and maintain appropriate biasing force despite the increasing working range caused by wear.
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 self-adjusting mechanism ensures consistent engagement and reduced rattle noise by maintaining optimal biasing force, preventing excessive wear and resistance, thus enhancing the operational stability and customer satisfaction of the steering gear.
Implementation Method 1
A spring 26 exerts a biasing force on rack bearing 22 urging it into contact with rack 14
Implementation Method 2
Rack bearing 22 includes a slide lining 24 that is in direct contact with rack 14 and which can be used to reduce the frictional resistance to the relative sliding between rack 14 and rack bearing 22
Data Source
AI summary
A steering gear assembly with a pinion shaft, rack, housing and rack bearing. A biasing assembly biases the rack bearing against the rack and into engagement with the pinion. The biasing assembly includes a gross adjustment member secured to the housing, a bearing assembly with a bearing member coupled with the rack bearing and a first adjustment member. A first biasing member is coupled with the bearing member and first adjustment member which are relatively moveable to thereby define a compliance zone to allow for dimensional variations in the meshing of the rack and pinion. An adjustment biasing assembly is operably disposed between the gross adjustment member and the bearing assembly. The adjustment biasing assembly is disposed entirely within the housing, includes a second biasing member, and urges the first adjustment member toward the rack bearing in continuously-variable axial movements while preventing movement away from the rack bearing.