Worm Support Assembly for Zero-Clearance Electric Power Steering
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Solution Overview
Problem
Existing electric power steering systems face issues such as excessive friction torque, knocking noise, and reduced bearing load capacity due to manufacturing tolerances and installation errors, which are not effectively addressed by current solutions that increase costs and complexity.
Innovation Solution
A worm compression and support mechanism using a combination of compression assemblies and support assemblies, including blade springs and pre-tightening rubbers, to eliminate radial clearance and provide damping, thereby reducing noise and improving steering hand feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If bracket bearing or separate spring plunger is used to eliminate clearance, then zero clearance is achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines the bearing support function and the clearance elimination function into a single integrated bearing assembly. The bearing is designed with built-in preloading mechanisms that eliminate the need for separate bracket bearings or spring plungers, thereby reducing part count while achieving zero clearance between worm and worm wheel.
Solution Approach 2:
The bearing assembly is designed to perform multiple functions simultaneously: supporting the worm, eliminating radial clearance, providing preloading, and absorbing axial forces. This multi-functional design replaces multiple separate components with a single universal bearing unit, reducing overall system complexity.
2Reliability
If two ball bearings are used to support the worm, then support is provided, but cumulative error in coaxiality causes improper load and reduced bearing load capacity
Solution Approach 1:
The patent divides the bearing support system into functionally independent segments with self-aligning features. Each bearing is designed with spherical seats or adjustable mounting positions that allow independent alignment, preventing cumulative coaxiality errors from affecting the entire system. This segmentation breaks the error propagation chain.
3Manufacturing precision
If worm and worm wheel are made to fit tightly to eliminate clearance, then zero clearance is achieved, but rotational friction torque increases
Solution Approach 1:
The patent employs precise control of geometric parameters including contact pressure, surface finish quality, and micro-gaps between worm and worm wheel. By optimizing these parameters, the system achieves zero clearance without excessive tightness, maintaining low friction torque through controlled contact conditions rather than simply reducing gap size.
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 mechanism effectively eliminates clearance in the worm wheel and worm deceleration mechanism, reduces noise, and enhances steering hand feel while minimizing installation complexity and costs, occupying a smaller space.
Implementation Method 1
a compression assembly is arranged on the outer edge side of the small-end bearing, the compression assembly is in tight contact with the outer ring of the small-end bearing
Implementation Method 2
a support assembly is arranged above the compression assembly, and the lower surface of the support assembly is in tight contact with the compression assembly
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
A worm compression and support mechanism for an electric power steering system, comprising a housing (1), wherein a worm (5) and a worm wheel (6) are provided inside the housing (1); an upper end of the worm wheel (6) is in fit connection with the worm (5); one end of the worm (5) is sleeved with a big-end bearing (3), and the other end thereof is sleeved with a small-end bearing (7); a compression assembly is provided on an outer edge side of the small-end bearing (7); the compression assembly closely abuts against an outer ring of the small-end bearing (7); a support assembly is provided on an upper side of the small-end bearing (7); the support assembly is located above the compression assembly; and a lower surface of the support assembly closely abuts against the compression assembly. A pre-compression force is supplied by the compression assembly, a support assembly is arranged above the compression assembly, and the lower surface of the support assembly presses against the compression assembly to provide a limiting effect on the compression assembly in a vertical direction, and the compression assembly provides damping and hard limiting at the top and a side of the worm (5) to support and limit the oscillation of the worm (5) and to absorb the impact of the worm (5).