Compact Worm Reducer Axial Force Support
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Solution Overview
Problem
Conventional worm reducers in electric power steering devices are bulky due to the need for a wheel-side support portion to counteract axial forces, which increases the length and size of the reducer.
Innovation Solution
The worm reducer design incorporates a rolling bearing with a flange portion on the outer ring, which is sandwiched between the housing and a retaining plate, eliminating the need for a stepped surface to support axial counterforces, thereby reducing the length of the housing and the overall size of the reducer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a wheel-side support portion is provided to counteract axial forces, then the axial force support capability is improved, but the axial length and overall size of the worm reducer increases
Solution Approach 1:
The invention merges the axial force support function into the existing bearing structure by adding a flange portion to the outer ring. This eliminates the need for a separate wheel-side support portion, as the flange itself provides the axial reaction force support while being integrated with the bearing assembly.
Solution Approach 2:
Instead of providing support from the wheel side (traditional approach), the invention inverts the support mechanism by using the bearing outer ring's flange portion to provide axial support from the opposite direction, thereby eliminating the need for the conventional wheel-side support portion.
2Length of moving object
If the housing length is reduced for compactness, then the overall size is improved, but the capability to support axial counterforces deteriorates
Solution Approach 1:
The invention combines the axial force support function with the bearing outer ring structure. The flange portion on the outer ring serves dual purposes: maintaining bearing functionality and providing axial counterforce support, thereby eliminating the need for extended housing length.
Solution Approach 2:
The bearing outer ring is given multiple functions: it supports radial loads (original bearing function), provides axial force support (new function via flange), and serves as a mounting reference for the retaining plate. This multi-functionality allows housing length reduction without compromising axial support capability.
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 configuration allows for a reduction in the axial length of the worm reducer, achieving a more compact size and weight, while maintaining torque transmission efficiency and reducing the risk of backlash and noise.
Implementation Method 1
the worm 14 is rotatably supported inside the worm accommodation portion 16 at two axial positions which interpose the worm teeth 17 by a pair of rolling bearings 18a, 18b of a deep groove ball bearing and the like
Data Source
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AI summary
A worm reducer which can be easily reduced in size is provided. A flange portion (30) which radially protrude outward is formed on an outer circumferential surface of an axial one end portion of an outer ring (19a) configuring a rolling bearing (18c) on an axial one side at an entire circumference. A holding portion (20a) is formed on an axial one end side portion of a worm accommodation portion (15a). The flange portion (30) is sandwiched in an axial direction between an axial one side face of a housing (12a) and a retaining plate (33) fixed and supported on the housing.