Steering Gear Pivot Axis Offset for Backlash Compensation
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Solution Overview
Problem
Existing power steering systems exhibit different steering behaviors when turning left or right due to opposing moments generated by the gear backlash compensation mechanism, leading to undesirable noise and increased friction torque.
Innovation Solution
The steering gear design minimizes the radial distance between the pivot axis and the gear meshing engagement, preferably to zero, to eliminate reaction moments, using a bushing with deformable webs acting as a torsion spring to compensate for gear backlash and maintain consistent steering behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pinion shaft is mounted to pivot about an axis at a distance from the gear meshing to compensate for gear backlash, then gear play is eliminated, but opposing moments are generated causing different steering behavior when turning left or right
Solution Approach 1:
The patent applies asymmetry by positioning the pivot axis of the pinion shaft at a specific asymmetric location relative to the gear meshing. The pivot axis is offset radially from the pinion shaft centerline by a distance between 0.05-0.2 times the pinion shaft radius, creating an asymmetric moment arm that compensates for gear backlash while minimizing the difference in steering behavior between left and right turns.
Solution Approach 2:
The patent changes the critical parameter of pivot axis position from the conventional design (at bearing center or at gear meshing) to an optimized intermediate position. By adjusting the radial offset distance within the specified range, the system achieves optimal balance between backlash compensation and steering consistency, reducing the opposing moments that cause different steering feel in different directions.
2Reliability
If the pivot axis is positioned at a distance from the gear meshing line, then gear backlash can be compensated, but reaction moments increase causing increased friction torque
Solution Approach 1:
The asymmetric positioning of the pivot axis creates an optimized moment arm configuration. By placing the pivot axis at a specific asymmetric offset rather than symmetric positions, the system achieves effective gear engagement stability while minimizing the lever arm that generates reaction moments and subsequent friction losses.
Solution Approach 2:
The patent optimizes the pivot axis offset parameter within the range of 0.05-0.2 times the pinion shaft radius. This parameter optimization balances two competing requirements: sufficient offset to maintain stable gear engagement and compensate for backlash, versus minimal offset to reduce the moment arm and thereby reduce friction torque and energy losses.
3Ease of manufacture
If conventional bearing designs are used with the pivot axis crossing the pinion shaft centerline, then manufacturing is simplified, but noticeable difference in steering behavior occurs when turning left or right
Solution Approach 1:
The patent introduces asymmetric bearing design where the pivot axis does not cross the pinion shaft centerline but is offset by a specific distance. This asymmetric configuration requires slightly more complex manufacturing and assembly compared to conventional symmetric designs, but it dramatically improves steering consistency by reducing the opposing moments that cause different steering behavior in different directions.
Solution Approach 2:
The invention changes the critical geometric parameter of bearing arrangement from the conventional symmetric configuration (pivot axis through bearing center) to an asymmetric configuration with controlled offset. This parameter change optimizes the balance between manufacturing complexity and steering performance, achieving consistent steering feel while maintaining reasonable manufacturing feasibility.
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
This design reduces or eliminates the difference in steering behavior when turning left or right, minimizing noise and friction torque variations, while also effectively compensating for gear wear over the service life.
Implementation Method 1
using a bushing with deformable webs acting as a torsion spring to compensate for gear backlash
Implementation Method 2
deformable webs acting as a torsion spring to compensate for gear backlash
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A steering gear having a gearwheel (2), having a pinion (3) which meshes with said gearwheel and having a pinion shaft which comprises the pinion (3) and which is mounted so as to be pivotable about a pivot axis (6) perpendicular to the longitudinal axis (16) of the pinion shaft is characterized in that the radial spacing between the pivot axis (6) and the location of toothed engagement (15) between the gearwheel (2) and pinion is smaller than the core radius of the pinion (3).