Power Steering Worm Drive Coupling for Backlash-Free Meshing
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Solution Overview
Problem
Worm drives in power-assisted steering systems experience drive backlash due to component tolerances and thermal expansion, leading to unwanted noises during alternate steering, which existing solutions attempt to address with complex and costly designs.
Innovation Solution
A coupling comprising a hub and an elastic spring bush is used to transmit torque and provide spring-loading for the worm, eliminating the need for additional fixed bearings and damping torque peaks, while an oval floating bearing bush compensates for backlash without allowing lateral drifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spring-loading and pivotable mounting of the worm is implemented using special spring plates, holders, or sleeves with adjusting screws, then drive backlash is eliminated, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the spring-loading function and the fixed support function into a single elastic spring bush component. This bush is pressed onto the worm and provides both the elastic preloading force needed to eliminate backlash and the fixed support for the worm, eliminating the need for separate spring plates, holders, or adjusting screws.
Solution Approach 2:
The elastic spring bush serves multiple functions simultaneously: it provides spring-loading to eliminate backlash, acts as a fixed bearing for the worm, and compensates for thermal expansion and manufacturing tolerances. This multi-functional design simplifies the overall structure while maintaining reliability.
2Manufacturing precision
If additional fixed bearings and spring-loading mechanisms are added to eliminate backlash, then steering precision improves, but weight increases
Solution Approach 1:
The patent merges the functions of fixed bearings and spring-loading mechanisms into the elastic spring bush, which is pressed onto the worm. This single component provides both support and preloading, eliminating the need for additional separate parts and reducing overall weight.
Solution Approach 2:
The patent uses the elastic properties of the spring bush material to provide the necessary preloading force. By selecting appropriate material parameters (elastic modulus, Shore hardness), the system achieves backlash-free steering with a lightweight elastic component rather than heavy metallic spring mechanisms.
3Ease of manufacture
If rigid mounting of the worm is used to maintain position, then manufacturing simplicity is maintained, but noise from vibrations and direction changes increases
Solution Approach 1:
The patent changes the mounting parameter from rigid to elastic by using the spring bush. This elastic mounting allows the worm to accommodate vibrations and thermal expansion while maintaining preloading contact with the gear, thereby reducing noise from alternate steering without complicating the manufacturing process.
Solution Approach 2:
The elastic spring bush acts as an intermediary between the worm and the housing. It mediates the interaction by providing a compliant connection that absorbs vibrations and noise while maintaining the necessary preloading force, simplifying the mounting process compared to rigid alternatives.
4Manufacturing precision
If preloading force is increased to eliminate backlash completely, then steering precision improves, but idle starting torque increases
Solution Approach 1:
The patent optimizes the preloading force by selecting appropriate Shore hardness for the spring bush material. This allows achieving backlash elimination with minimal preloading force, reducing idle starting torque while maintaining steering precision through the elastic compliance of the bush.
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 costs and weight, ensures backlash-free steering, and effectively dampens noise from vehicle vibrations and direction changes, protecting drive components and minimizing idle starting torque.
Implementation Method 1
the coupling comprises a hub and an elastic spring bush
Implementation Method 2
the worm is connected to the elastic spring bush by an interference fit
Implementation Method 3
The elastic spring bush also provides the spring-loading of the worm in order to ensure meshing without backlash
Implementation Method 4
The rubber-elastic spring mounting additionally ensures that torque peaks which arise as a result of the driving dynamics are damped or cushioned
Implementation Method 5
The rubber-elastic spring mounting additionally ensures that torque peaks which arise as a result of the driving dynamics are damped or cushioned
Implementation Method 6
The other side of the worm is connected to an oval floating bearing bush
Data Source
AI summary
A worm drive for a power steering system of a motor vehicle is disclosed. The worm drive includes a worm gear, a worm which meshes with the worm gear, and an electric motor which drives the worm. One side of the worm is connected by a coupling to the electric motor and the other side of the worm is mounted in a floating bearing. The coupling consists of a hub and an elastic spring bush. The floating bearing is oval-shaped in order to allow vertical movements of the worm, and the worm is spring-loaded on the worm gear by the coupling.