Power-Assisted Steering Assembly With Belt-Failure Backup Drive
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Solution Overview
Problem
Power-assisted steering systems fail to maintain functionality after a failure of the drive belt, leading to a loss of power-assistance to the steering rack.
Innovation Solution
A power-assisted steering assembly with a primary and secondary transmission mechanism, where the secondary mechanism is designed to take over power transmission only after the primary mechanism fails, utilizing a motor coupling and rack coupling with a lost-motion mechanism and compressible elements to isolate and protect the secondary mechanism from excessive power until failure, and a housing to prevent drive belt interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a primary transmission mechanism with a drive belt is used to transmit power from the motor shaft to the steering rack, then power transmission efficiency is improved, but the system loses functionality after drive belt failure
Solution Approach 1:
The transmission system is divided into a primary transmission mechanism (drive belt) and a secondary transmission mechanism (directly connected gears), allowing the system to segment power transmission paths and switch between them based on operational status
Solution Approach 2:
The secondary transmission mechanism is pre-configured and protected by the lost-motion mechanism during normal operation, ready to take over immediately upon primary mechanism failure without requiring system reconfiguration
2Reliability
If a secondary transmission mechanism is added for fail-operational capability, then system reliability is improved, but the secondary mechanism may fail due to excessive loading during normal operation
Solution Approach 1:
The lost-motion mechanism acts as an intermediary between the motor coupling and rack coupling, selectively engaging the secondary transmission mechanism only when the primary mechanism fails, thereby protecting it from excessive loading during normal operation
Solution Approach 2:
The coupling system dynamically switches between primary and secondary transmission mechanisms based on operational conditions, with the lost-motion mechanism allowing relative rotation during normal operation and locking when failure occurs
3Reliability
If the motor coupling and rack coupling transmit equal power to both primary and secondary transmission mechanisms, then fail-operational capability is improved, but the secondary mechanism experiences unnecessary loading
Solution Approach 1:
The lost-motion mechanism creates different power transmission characteristics for different parts of the coupling system, allowing the primary transmission mechanism to receive full power during normal operation while the secondary mechanism remains protected
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
Ensures continuous operation of the power-assisted steering system by allowing the secondary transmission mechanism to take over power transmission after primary mechanism failure, minimizing motor backlash and preventing secondary mechanism failure, while maintaining consistent power assistance.
Implementation Method 1
a lost-motion mechanism connecting the first couple part to the second couple part, the lost-motion mechanism allowing relative rotation of the first couple part and second couple part
Implementation Method 2
a primary transmission mechanism configured to transmit power from the motor shaft to the steering rack, the primary transmission mechanism including a drive belt
Data Source
AI summary
A power-assisted steering assembly for a vehicle comprises: a motor shaft for transmitting torque from a motor; a steering rack; a primary transmission mechanism; a secondary transmission mechanism; a motor coupling; and a rack coupling. The primary transmission mechanism is configured to transmit power from the motor shaft to the steering rack and includes a drive belt. The secondary transmission mechanism is configured to transmit power from the motor shaft to the steering rack upon a failure of the primary transmission mechanism. The motor coupling is configured to transmit power from the motor shaft to the primary transmission mechanism and the secondary transmission mechanism. The rack coupling is configured to transmit power from the primary transmission mechanism and the secondary transmission mechanism to the steering rack. Prior to the failure of the primary transmission mechanism, the motor coupling and rack coupling are configured to transmit a greater amount of power to the primary transmission mechanism than to the secondary transmission mechanism.