Rear Wheel Steering Converter With MR Fluid Self-Locking
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Solution Overview
Problem
Rear wheel steering systems face challenges in achieving high forward efficiency while ensuring reliable self-locking during reverse input, leading to increased motor size, cost, and energy loss, and reduced responsiveness due to intermittent locking mechanisms.
Innovation Solution
A rear wheel steering system utilizing a magnetorheological (MR) fluid controlled by an inverter and magnet switch, which softens or hardens based on the magnetic field applied, enabling efficient power transmission and reliable self-locking without additional controllers or sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lead screw mechanism is used for self-locking, then reverse input is blocked, but forward efficiency is significantly reduced
Solution Approach 1:
The patent applies magnetorheological fluid whose viscosity parameter can be dynamically changed by applying or removing magnetic fields. When magnetic field is applied, the fluid viscosity increases dramatically to provide self-locking; when magnetic field is removed, viscosity decreases to allow efficient power transmission. This resolves the contradiction by making the friction characteristic variable rather than fixed.
Solution Approach 2:
The patent makes the friction characteristic dynamic by using magnetorheological fluid that can switch between low-viscosity and high-viscosity states. The system transitions from a static friction mechanism (lead screw) to a dynamic one where the friction coefficient can be adjusted in real-time based on operational requirements, enabling both efficient power transmission and reliable self-locking.
2Loss of energy
If ball screw or planetary roller screw is used with solenoid valve for locking, then forward efficiency is improved, but responsiveness is reduced due to intermittent locking and additional control operations
Solution Approach 1:
The patent extracts the locking control function from the mechanical structure and places it in the magnetic field application system. Instead of using mechanical locks or solenoid valves that require intermittent engagement, the system continuously maintains readiness to lock by having the magnetorheological fluid already in place, requiring only magnetic field application for immediate locking action.
Solution Approach 2:
The patent replaces the mechanical locking system (solenoid valve and intermittent locking mechanism) with a magnetic field-based control system. The magnetorheological fluid responds immediately to magnetic field changes, eliminating the mechanical delays and intermittent operation of solenoid-based systems, thus improving responsiveness while maintaining high forward efficiency.
3Reliability
If lead screw mechanism is used for self-locking, then reverse input is blocked, but motor size and cost increase due to reduced forward efficiency
Solution Approach 1:
By changing the viscosity parameter of the lubricant from fixed to variable through magnetic field application, the system achieves both high forward efficiency (when magnetic field is off) and reliable self-locking (when magnetic field is on). This eliminates the need for oversized motors required by traditional lead screw mechanisms.
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 system achieves high forward efficiency with rapid locking and unlocking operations, reduces motor capacity, and provides a fail-safe function by maintaining self-locking in power-off conditions, thus improving operability and reducing costs and weight.
Implementation Method 1
a magnetorheological (MR) fluid being applied on the converting portion
Implementation Method 2
an electromagnet connected to the inverter and magnetizing to generate the magnetic field in a response to a current received from the inverter
Implementation Method 3
a permanent magnet connected to first and second end portions of a core of the electromagnet through conductive connectors
Data Source
AI summary
A rear wheel steering motor generates rotational force. A movement converter has a converting portion coupled to the wheel steering motor and configured to convert the rotational force transmitted from the rear wheel steering motor into a linear movement. An MR fluid is applied on the converting portion. An inverter controls driving of the rear wheel steering motor. A magnet switch works in concert with the inverter to change a magnetic field to selectively provide the magnetic field to the MR fluid of the movement converter.