Thermally Actuated Current Breaker with Vertical Contact Displacement
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Solution Overview
Problem
Current current cut-off devices face challenges in handling high currents due to increased contact resistance and require complex structures with positive temperature coefficient thermistors, which hinder miniaturization and increase manufacturing costs.
Innovation Solution
A current cut-off device with a plate-shaped terminal piece, a movable piece with an elastic portion, and a thermally actuated element that shifts the movable contact from a conductive to a cut-off state by moving it over the contact, using a resultant force of elastic force and thermal stress, without requiring a positive temperature coefficient thermistor, allowing for a compact and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the elastic force generated by the movable piece is increased to suppress contact resistance and handle large currents, then the current-carrying capacity is improved, but the thermally actuated element must generate larger stress which requires increasing its width, thereby preventing miniaturization of the device
Solution Approach 1:
The movable contact is designed to move from a first surface side to a second surface side opposite to the first surface of the terminal piece, utilizing vertical displacement across multiple dimensions. This dimensional approach allows the contact to clear the terminal contact effectively without requiring excessive elastic force or a wider thermally actuated element, thus resolving the contradiction between current-carrying capacity and device miniaturization
Solution Approach 2:
The elastic portion is configured to dynamically shift the movable contact from the conductive state to the cut-off state by moving it over the contact. This dynamic mechanism allows the system to achieve reliable current interruption with optimized elastic force, avoiding the need for oversized components while maintaining high current-carrying capacity
2Reliability
If a positive temperature coefficient thermistor is implemented to maintain the cut-off state, then the reliability of cut-off state maintenance is improved, but the structure becomes complex and manufacturing cost increases
Solution Approach 1:
The elastic portion serves a dual function: it provides the elastic force needed to move the movable contact during normal operation and automatically maintains the cut-off state after tripping. This self-service mechanism eliminates the need for additional components like positive temperature coefficient thermistors, achieving reliable cut-off state maintenance while keeping the structure simple and cost-effective
Solution Approach 2:
The thermally actuated element is designed to perform multiple functions: it detects temperature changes, generates stress to trigger the movable contact, and works with the elastic portion to maintain the cut-off state. This multi-functional design replaces what would traditionally require separate components, reducing structural complexity while maintaining reliability
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 device achieves high current-carrying capacity with reduced contact resistance and maintains the cut-off state through elastic force, enabling easy miniaturization and cost-effective production without complex thermistor structures.
Implementation Method 1
a thermally actuated element which presses the movable piece by deforming in accordance with a temperature change
Implementation Method 2
a movable piece including an elastic portion formed in a plate shape so as to be elastically deformed
Data Source
AI summary
A current cut-off device includes a plate-shaped terminal piece having a contact, a movable piece including an elastic portion formed in a plate shape so as to be elastically deformed and a movable contact arranged at one end portion of the elastic portion and having the movable contact so as to be pressed against and in contact with the contact, and a thermally actuated element which biases the movable piece by deforming in accordance with a temperature change and causes a state of the movable piece to be shifted from a conductive state in which the movable contact is in contact with the contact to a cut-off state in which the movable contact is separated from the contact. When the state of the movable piece is shifted from the conductive state to the cut-off state, as the movable contact moves, it gets over the contact.