Cantilevered Worm Gear Assembly With Controlled Shaft Deflection
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Solution Overview
Problem
Power steering mechanisms with cantilevered worm arrangements are prone to either over-constraint or excessive bending, which can lead to structural failure.
Innovation Solution
A power steering assembly featuring an electric motor with a single, integrally formed shaft extending axially from a first end to a second end, where the second end is cantilevered to deflect, and a limiter bushing surrounding the shaft provides a controlled clearance to prevent over-constraint and allow for deflection without breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the worm shaft is rigidly constrained, then structural stability is improved, but the shaft cannot deflect and may break under extreme loads
Solution Approach 1:
The patent changes the constraint parameter from rigid (zero clearance) to controlled clearance (small gap), allowing the shaft to deflect within limits while maintaining stability during normal operation. This parameter change resolves the contradiction by enabling both stability and flexibility.
Solution Approach 2:
The patent transitions from a static rigid constraint to a dynamic controlled clearance system that adapts to operating conditions. During normal operation, the clearance is sufficient to maintain stability, while during extreme loads, the shaft can deflect to prevent breaking.
2Reliability
If the worm shaft is allowed to deflect freely, then flexibility and damage prevention are improved, but the shaft becomes over-constrained and may bend excessively
Solution Approach 1:
The patent applies parameter change by setting a specific controlled clearance value that limits deflection while allowing sufficient movement. This prevents both excessive bending and breaking, resolving the contradiction between flexibility and stability.
Solution Approach 2:
The patent introduces an intermediary element (the controlled clearance space) between the shaft and housing that mediates between rigid constraint and free deflection. This intermediary allows controlled movement while preventing excessive deflection.
3Strength
If multiple bearings are used to support the worm shaft, then structural support is improved, but the complexity of the assembly increases
Solution Approach 1:
The patent extracts the second bearing from the assembly, relying instead on the controlled clearance between the shaft and housing to provide the necessary support and deflection control. This reduces complexity while maintaining adequate structural support.
Solution Approach 2:
The housing structure serves multiple functions: it provides structural support, defines the controlled clearance, and acts as a constraint mechanism. This multi-functionality replaces the need for additional specialized components like the second bearing.
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 solution effectively balances structural support and flexibility, preventing damage from extreme operational conditions while maintaining normal operation functionality.
Implementation Method 1
the single, integrally formed shaft extending axially from a first end to a second end and being cantilevered to allow the second end to deflect
Implementation Method 2
a bushing surrounding a portion of the shaft proximate the second end of the shaft, the bushing and the portion of the shaft defining a clearance therebetween
Data Source
AI summary
A power steering assembly includes an electric motor having an output shaft extending therefrom. The assembly also includes a housing containing a worm gear operatively coupled to a steering shaft, the worm gear rotatable about a worm gear axis. The assembly further includes an electric motor and a worm arranged to engage the worm gear, the worm extending from the output shaft of the electric motor as a single, integrally formed shaft, the single, integrally formed shaft extending axially from a first end to a second end and being cantilevered to allow the second end to deflect. The assembly yet further includes a bushing surrounding a portion of the shaft proximate the second end of the shaft, the bushing and the portion of the shaft defining a clearance therebetween.