Cooking Appliance Door Latch Detection Using Motor Current Analysis

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Solution Overview

Problem

Existing door lock assemblies in cooking appliances require additional cam and switch components to verify the position of the door latch, increasing part count, cost, and potential for latch failure, especially during pyrolytic cycles where precise door closure is crucial.

Innovation Solution

A controller monitors the motor current to determine the torque applied to the door latch, eliminating the need for physical switches by sensing when the current reaches a threshold indicative of a latched state, and uses predefined current draw curves to differentiate between normal and obstructed closure or error conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If cam and switch components are added to verify door latch position, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvedoor latch position detection accuracyVSAvoidpart count

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces mechanical cam and switch components with an electrical sensing system. The motor controller monitors motor current draw to detect door latch position, substituting mechanical verification with electrical measurement. This eliminates the need for physical switches while maintaining detection accuracy through current threshold analysis.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The motor itself serves dual purposes: it both actuates the door latch and provides sensing information through its current draw characteristics. The system uses the motor's own electrical characteristics to detect latch position, eliminating the need for separate sensing components. The motor current naturally indicates latch engagement state without requiring additional sensors.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If cam and switch components are added to verify door latch position, then measurement precision is improved, but reliability worsens

Engineering Contradiction:

Improvedoor latch position detection accuracyVSAvoidlatch failure potential

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts and removes the cam and switch components from the door latch assembly. By eliminating these mechanical verification components, the system reduces potential failure points while maintaining detection capability through motor current monitoring. The harmful elements (additional mechanical parts that can fail) are removed while preserving the essential function.

Inventive Principle:

Principle #2Taking out (Extraction)

3Device complexity

If motor current monitoring is used to detect door latch position, then device complexity is reduced, but measurement precision may worsen

Engineering Contradiction:

Improvepart countVSAvoiddoor latch position detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system continuously monitors motor current draw and uses this feedback to determine door latch position. The controller adjusts motor operation based on current feedback, deactivating the motor when current reaches a threshold indicating latch engagement. This closed-loop feedback ensures accurate position detection through electrical parameters.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent detects door latch position by monitoring changes in motor current parameters. The system identifies latch engagement through specific current draw characteristics and thresholds, translating mechanical position into electrical parameter changes. This parameter-based detection maintains precision while simplifying the physical component structure.

Inventive Principle:

Principle #35Parameter changes

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 approach reduces part count and cost while ensuring accurate door closure detection without additional components, enhancing reliability and safety during pyrolytic cycles by monitoring motor current patterns.

Implementation Method 1

A current sensor is configured to measure a current draw of the motor

Methodology Applied

Scientific EffectElectrical current measurement: Ohmmeter

Implementation Method 2

A controller monitors motor current to determine the torque applied to the door latch, eliminating the need for physical switches by sensing when the current reaches a threshold indicative of a latched state

Methodology Applied

Scientific EffectTorque sensing through current monitoring: Torque

Data Source

PatentUS12021463B2Door latch detection with motor current analysis

Publication Date: 2024.06.25 WHIRLPOOL CORP

AI summary

Controlling a door latch of a cooking appliance is provided. A controller monitors motor current of a motor driving a door latch during a locking operation of a door of the cooking appliance. The controller deactivates the motor responsive to the motor current reaching a closed door threshold amount of current. The controller indicates the door being in a closed state responsive to the current draw over time matching a predefined current draw curve.