Starter Relay Failure Detection via Dual-Relay State Machine

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Solution Overview

Problem

Micro-hybrid vehicles face a safety risk due to starter relay failures, where a welded-closed contact can continuously power the starter motor, potentially causing damage, and there is a need for a diagnostic mechanism to detect such failures to prevent harm and allow safe operation.

Innovation Solution

A method and apparatus that utilize two relays in the starter circuit, with a diagnostic routine to determine if either relay is in a closed position when it should be open, and disable the starter operation to prevent damage, using a state machine to monitor and control the relays' states and simulate failures for calibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single relay is used to control the starter motor in micro-hybrid vehicles, then the device complexity is reduced, but the reliability deteriorates due to the risk of welded-closed contacts causing continuous starter motor operation

Engineering Contradiction:

Improverelay control structureVSAvoidstarter relay failure detection

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single relay control function is segmented into two separate relays (first relay and second relay) in series configuration. This segmentation allows independent monitoring of each relay's state, enabling detection of welded-closed contacts while maintaining a relatively simple overall structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A diagnostic routine acts as an intermediary mechanism that monitors the states of both relays and detects failures. The routine determines whether either relay is in a closed position when it should be open, providing reliability enhancement without requiring complex hardware modifications.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If diagnostic monitoring is added to detect relay failures, then the reliability is improved, but the device complexity increases due to additional monitoring systems

Engineering Contradiction:

Improverelay failure detectionVSAvoiddiagnostic system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The existing control module that normally controls relay operation is made to perform self-diagnosis by monitoring its own relay states. The control module executes a diagnostic routine that determines relay positions using the same computational resources already allocated for normal operation, eliminating the need for separate dedicated monitoring hardware.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The control module is designed with multi-functionality, serving both as the normal operational controller and as the diagnostic monitoring system. This universal design allows one component to perform multiple functions, reducing overall system complexity while maintaining reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If the starter relay fails in a welded-closed position, then the starter motor becomes continuously powered, but this causes harmful effects such as damage to the starter motor, flywheel, or flex plate ring gear

Engineering Contradiction:

Improvestarter motor operationVSAvoiddamage to starter components

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The diagnostic routine performs preliminary detection of relay failure states before continuous operation can cause damage. By monitoring relay positions and detecting welded-closed conditions in advance, the system can take preventive action to disable the starter motor, avoiding damage to the starter motor, flywheel, or flex plate ring gear.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control module continuously monitors the states of both relays and receives feedback about their positions. When the diagnostic routine detects that either relay is in a closed position when it should be open, the system provides feedback to disable the starter motor operation, preventing harmful effects from occurring.

Inventive Principle:

Principle #23Feedback

4Reliability

If two relays are used instead of one, then the reliability is improved through failure detection, but the device complexity increases due to additional relays and control logic

Engineering Contradiction:

Improvestarter circuit reliabilityVSAvoidrelay control circuit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control logic for both relays and the diagnostic monitoring function are merged into a single control module. This integration allows the system to manage two relays and perform failure detection using unified control circuitry, reducing the complexity that would otherwise arise from having separate control systems for each relay.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8831815B2Method of diagnosing a starter relay failure using synchronized state machine

Publication Date: 2014.09.09 FCA US LLC

AI summary

A method and electrical system for detecting and compensating for a failure in a starter circuit that comprises first and second relays in a circuit path to a starter motor of a vehicle. The method and system determine if at least one of the first or second relays is in a closed position when it should be in an open position and disables a vehicle starter operation if it is determined that at least one of the first or second relays is in the closed position when it should be in the open position. The vehicle starter operation could be a stop-start operation of the engine.