Viscoelastic Fluid Reducer for Electric Power Steering Noise
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Solution Overview
Problem
Electric power steering device reducers experience noise due to clearance from wear and moisture absorption in the worm and worm wheel, as well as from impact sounds transferred from the road surface, leading to inaccurate steering assist.
Innovation Solution
A reducer design incorporating a worm shaft with bearings and a gear housing filled with viscoelastic fluid to support the worm wheel, which prevents clearance from wear and moisture absorption, reduces rattle noise from road surface impacts, and minimizes clearance changes due to rotational torque variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional reducer structure with worm and worm wheel is used, then the steering assist function is provided, but clearance occurs due to wear and moisture absorption leading to noise
Solution Approach 1:
The patent changes the physical state and properties of the supporting medium from solid (traditional bearings) to viscoelastic fluid. This fluid allows the worm shaft bearing to dynamically adjust its support characteristics, maintaining optimal contact and preventing clearance while dampening vibrations and noise from road impacts and operational wear.
Solution Approach 2:
The viscoelastic fluid acts as an intermediary substance between the worm shaft bearing and the support structure. This mediator absorbs moisture that would otherwise cause clearance, provides continuous support to prevent wear-induced gaps, and dampens impact noises from being transmitted through the reducer structure.
2Ease of operation
If the reducer operates under varying rotational torque conditions, then steering assist is provided, but clearance changes occur leading to inaccurate steering assist
Solution Approach 1:
The viscoelastic fluid provides dynamic support characteristics that adapt to varying torque conditions. Unlike rigid bearings that maintain fixed clearance, the viscoelastic material dynamically adjusts its stiffness and damping properties based on the applied load, maintaining optimal worm-worm wheel engagement across different steering conditions and eliminating clearance variations.
3Reliability
If road surface impacts are transferred through the steering system, then vehicle response is maintained, but rattle noise is generated
Solution Approach 1:
The viscoelastic fluid provides beforehand cushioning by continuously damping vibrations and impacts before they can propagate through the reducer structure as rattle noise. The fluid's inherent damping properties absorb road surface impacts at their source, preventing them from causing harmful vibrations and noise while still allowing the steering system to respond to driver input.
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 reduces noise and maintains accurate steering assist by preventing clearance and minimizing torque-induced changes, enhancing the precision of driver-assisted steering.
Implementation Method 1
a support member coupled to the gear housing so as to support the second worm shaft bearing toward a worm wheel and filled with a viscoelastic fluid
Data Source
AI summary
The present embodiments relates to a reducer of an electric power steering device. An embodiment of the present embodiments provides a reducer of an electric power steering device, including: a worm shaft having a first worm shaft bearing and a second worm shaft bearing coupled to one end portion, which is connected to a motor shaft, and to the other end portion, which is opposite thereto, respectively; a gear housing that contains the first worm shaft bearing, the second worm shaft bearing, and the worm shaft; and a support member coupled to the inner peripheral surface of the hear housing so as to support the outer race of the second worm shaft toward the worm wheel and filled with a viscoelastic fluid.