Worm Reducer Bearing Support for Backlash and Chatter Control
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Solution Overview
Problem
The existing worm reducer in steering devices experiences backlash and chattering due to dimensional and assembly errors, which increases friction and requires significant displacement of the worm tip end, leading to unwanted movement orthogonal to the elasticity direction, especially when the steering wheel's rotational direction is changed.
Innovation Solution
A worm reducer design incorporating a housing, worm wheel, worm, support bearing, elastic biasing means, and elastic holding means, where the elastic biasing means elastically biases the support bearing toward the worm wheel, and the elastic holding means holds the support bearing from both sides orthogonal to the biasing direction using leaf springs or a guide member, preventing displacement in the orthogonal direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the worm tip end is allowed to displace in the first direction to suppress backlash and chattering, then the engagement between worm teeth and wheel teeth is improved, but the worm tip end displaces in the second direction orthogonal to the biasing direction causing unwanted movement
Solution Approach 1:
The support bearing is segmented into two functional parts: the inner ring that is elastically biased in the first direction to allow worm tip displacement for backlash suppression, and the outer ring that is constrained in the second direction to prevent unwanted orthogonal movement. This segmentation allows independent control of movements in different directions.
Solution Approach 2:
The guide member acts as an intermediary between the support bearing and the housing. It receives the support bearing's outer ring and guides its movement, allowing elastic deformation in the first direction while constraining movement in the second direction. The guide member mediates between the need for elastic displacement and the need for orthogonal constraint.
2Reliability
If elastic biasing means is used to suppress backlash, then engagement quality is improved, but device complexity increases due to additional components
Solution Approach 1:
The guide member serves multiple functions: it guides the support bearing, provides the elastic biasing path, constrains orthogonal movement, and supports the outer ring. By making one component multi-functional, the patent reduces the need for separate dedicated components for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The guide member combines several functions that could otherwise require separate components: guidance, elastic biasing, and orthogonal constraint. By merging these functions into a single integrated component, the patent achieves backlash suppression while minimizing the increase in device complexity.
3Ease of operation
If the outer ring is constrained from both sides in the second direction, then orthogonal displacement is prevented, but the structure becomes more complex
Solution Approach 1:
The guide member is designed as a multi-functional component that simultaneously provides guidance, elastic biasing, and orthogonal constraint. By making the guide member universal, the patent achieves effective orthogonal constraint without adding numerous separate constraint components, thus limiting the increase in device complexity.
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 effectively suppresses backlash and chattering by ensuring the worm tip end does not displace orthogonally to the biasing direction, maintaining efficient torque transmission and reducing friction at the engagement between worm and wheel teeth.
Implementation Method 1
an elastic biasing means (81, 81a, 81b) which elastically biases the support bearing (17) toward the worm wheel (15)
Implementation Method 2
an elastic holding means (82, 82a) which elastically holds the outer ring (47) from both sides in a second direction
Data Source
AI summary
A worm reducer has: a housing having a wheel housing portion and a worm housing portion; a worm wheel; a worm, a support bearing having an inner ring externally fitted to the tip end portion of the worm and an outer ring; an elastic biasing means elastically biasing the outer ring toward the worm wheel side; and an elastic holding means elastically holding the outer ring from both sides in a direction orthogonal to a biasing direction by the elastic biasing means and to a center axis of the worm housing portion.