Worm Reducer Tip Support Assembly for Backlash Noise Suppression
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Solution Overview
Problem
The existing worm reducers in electric power steering devices suffer from unwanted tooth rattling noise due to backlash at the meshing portion between the worm wheel and worm teeth, which is exacerbated by dimensional and assembly errors, leading to displacement of the worm tip end portion during changes in rotation direction.
Innovation Solution
A worm reducer design incorporating a holder with protruding portions and a pad elastically biased by an elastic member, which applies a preload to the tip end portion of the worm, reducing displacement and suppressing backlash through grease supply to critical contact points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the tip end portion of the worm is elastically biased toward the worm wheel side to suppress tooth rattling noise, then the backlash at the meshing portion is reduced, but the worm tip end portion may be displaced vigorously in the third direction when the rotation direction changes
Solution Approach 1:
The patent introduces a holder as an intermediary component between the worm and the worm accommodating portion. The holder includes guide portions that constrain the worm tip end portion's movement in the third direction, allowing the elastic biasing to suppress backlash while preventing excessive displacement during rotation direction changes.
Solution Approach 2:
The patent applies local quality by providing guide portions only at specific locations where the worm tip end portion interacts with the holder. This localized constraint structure allows the worm to be elastically biased for noise suppression while maintaining stability in the third direction through the guide portions' geometric constraints.
2Object-generated harmful factors
If the holder and pad structure with multiple components is introduced to suppress abnormal noise, then the noise reduction effectiveness is improved, but the assembly complexity increases
Solution Approach 1:
The patent merges the holder and pad into a integrated assembly unit that is pre-assembled together before installation into the worm reducer. This combining approach maintains the noise suppression functionality while simplifying the overall assembly process by reducing the number of separate assembly steps.
Solution Approach 2:
The holder and pad are pre-assembled into a complete assembly unit before being installed into the worm reducer. This preliminary action allows the complex multi-component structure to be prepared in advance, making the final installation simpler and more manageable.
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 design effectively minimizes displacement of the worm tip end portion during rotation direction changes, thereby reducing abnormal noise and improving assembly workability.
Implementation Method 1
an elastic member installed to extend over the protruding portion and the pad base portion and elastically biases the tip end portion of the worm toward a worm wheel side via the pad
Implementation Method 2
supplying a part of the grease to the contact portion between the elastic member and the pad base portion through the first grease supply portion, and to the contact portion between the elastic member and the protruding portion through the second grease supply portion
Data Source
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AI summary
In the present invention, a holder (19) has, in the vicinity of a contact part (P1) between an elastic member (21) and a pad base (55), a first grease feed part (74) for feeding grease to the contact part (P1) between the elastic member (21) and the pad base (55), and has, in the vicinity of a contact part (P2) between the elastic member (21) and a protrusion (44), a second grease feed part (75) for feeding grease to the contact part (P2) between the elastic member (21) and the protrusion (44).