Worm Reducer Step-Surface Labyrinth for Long-Life Lubrication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional worm reducers in electric power steering devices face challenges in maintaining lubricity at the meshing portion between wheel teeth and worm teeth over a long period, as grease used for lubrication can be pushed out and escape into rolling bearings, reducing its effectiveness.
Innovation Solution
The implementation of a worm reducer design featuring housing side step surfaces and worm side step surfaces that create a labyrinth effect, preventing grease from escaping and maintaining lubricity by ensuring it remains within the meshing portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grease is used for lubrication at the meshing portion, then lubrication effectiveness is improved, but grease escapes into rolling bearings over time reducing lubrication duration
Solution Approach 1:
The worm accommodating portion is segmented into a first accommodating portion and a second accommodating portion separated by a partition wall. The first portion contains the meshing portion with grease lubrication, while the second portion contains the rolling bearings. This segmentation prevents grease from the meshing portion from escaping into the rolling bearing portion, maintaining lubrication effectiveness at the meshing portion while preventing grease migration that would reduce lubrication duration.
Solution Approach 2:
A partition wall acts as an intermediary barrier between the meshing portion and the rolling bearings. This partition wall prevents direct communication between the grease-filled meshing portion and the rolling bearing portion, thereby stopping grease from escaping into the bearings while still allowing the worm to rotate between the two portions.
2Ease of operation
If the worm accommodating portion is open to allow worm rotation, then ease of operation is improved, but grease escapes from the meshing portion reducing reliability
Solution Approach 1:
The open worm accommodating portion is segmented by a partition wall into two separate chambers. This allows the worm to rotate freely within the first accommodating portion (maintaining ease of operation) while the partition wall prevents grease from escaping into the second accommodating portion (maintaining grease retention and reliability).
Solution Approach 2:
The first accommodating portion is designed with grease-filled lubrication properties specifically at the meshing portion, while the second accommodating portion is designed to house rolling bearings without grease. This local differentiation of quality ensures that grease remains where it is needed for lubrication while preventing its migration to areas where it would cause harm.
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 effectively maintains lubricity at the meshing portion for a longer duration, preventing grease from escaping and ensuring reliable operation of the worm reducer, even under impact loads, while preventing interference and damage to tooth surfaces.
Implementation Method 1
a coil spring 21 is provided between the pressing piece 20 and the worm accommodating portion 16. The distal end portion of the worm 14 is elastically pressed toward the worm wheel 13
Implementation Method 2
the housing side step surface 24 provided on the inner circumferential surface of the worm accommodating portion 16 and the worm side step surface 27 provided on the outer circumferential surface of the worm 14 closely face each other. Therefore, due to a labyrinth effect occurring between the housing side step surface 24 and the worm side step surface 27, grease pushed out from the meshing portion can be prevented from moving in the axial direction
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A worm reducer includes: a housing including a wheel accommodating portion, and a worm accommodating portion; a worm wheel including wheel teeth disposed on an outer circumferential surface and rotatably supported inside the wheel accommodating portion; and a worm including worm teeth disposed on an outer circumferential surface to mesh with the wheel teeth and rotatably supported inside the worm accommodating portion, wherein a proximal end portion of the worm is connected to a drive shaft such that torque can be transmitted. An inner circumferential surface of the worm accommodating portion includes a housing side step surface which faces a proximal end side in an axial direction of the worm. An outer circumferential surface of the worm includes a worm side step surface which closely faces the housing side step surface in the axial direction at a portion axially deviated from a portion where the worm teeth are disposed.