Electric Steering Lock Malfunction Detection

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Solution Overview

Problem

Existing electric steering lock devices cannot detect failures in locking or unlocking limit switches when they remain persistently off, leading to undetected malfunctions.

Innovation Solution

An electric steering lock device comprising a control unit, locking and unlocking limit switches, a state detection component, and a malfunction diagnostic component that determines switch malfunctions by monitoring the state of the steering column lock and counting instances of both switches being off.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If limit switches are used to detect steering lock position, then steering lock state detection is enabled, but malfunction detection capability is insufficient when switches remain persistently off

Engineering Contradiction:

Improvesteering lock state detection reliabilityVSAvoidlimit switch malfunction detection difficulty

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The system performs preliminary actions by issuing commanded states (locking or unlocking) before detecting the actual state. The control unit commands a locking state, then checks if the locking limit switch is on; or commands an unlocking state, then checks if the unlocking limit switch is on. This preliminary commanded state allows the system to proactively test switch functionality rather than passively detecting failures.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by comparing the commanded steering lock state with the actual detected state from limit switches. The control unit issues a command (lock or unlock), monitors the corresponding limit switch response, and determines malfunction when there is no appropriate feedback (switch remains off when it should be on). This closed-loop feedback mechanism enables reliable malfunction detection.

Inventive Principle:

Principle #23Feedback

2Device complexity

If simple limit switch monitoring is used, then device complexity is reduced, but malfunction detection precision is insufficient

Engineering Contradiction:

Improvemonitoring system complexityVSAvoidswitch malfunction detection precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system applies dynamics by changing the operational state (locking or unlocking) and observing the dynamic response of the limit switches. Rather than using a static monitoring approach, the control unit dynamically transitions the steering lock between states and monitors switch behavior during these transitions. This dynamic approach enables precise malfunction detection while maintaining relatively simple device architecture.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS7327050B2Electric steering lock device and method thereof

Publication Date: 2008.02.05 NISSAN MOTOR CO LTD

AI summary

An electric steering lock device is configured with a control unit to operate a steering column lock between a steering locked state and a steering unlocked state. The electric steering lock device has a locking limit switch that turns on when a locking member reaches the locking stop position, and turns off when an unlocking command for the locking member is outputted. An unlocking limit switch of the electric steering lock device turns on when the locking member reaches the unlocking stop position, and turns off when a locking command for the locking member is outputted. The electric steering lock control unit determines that the locking limit switch or the unlocking limit switch has malfunctioned based on the state of the locking member.