Battery Pack Breaker Case Structure for Low-Temperature Contact Stability
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Solution Overview
Problem
Conventional breakers using thermally-actuated elements with different thermal expansion coefficients experience excessive curvature at low temperatures, leading to interference with the resin case and decreased contact pressure, which can cause separation of movable and fixed contacts, increasing contact resistance.
Innovation Solution
A breaker design with a fixed piece embedded in a resin case, featuring a recessed portion, a first penetrating portion, an island portion, and a connecting portion that prevents interference between the thermally-actuated element and the case, maintaining stable contact pressure even at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermally-actuated element with different thermal expansion coefficients is used, then the breaker can provide thermal protection functionality, but the curvature becomes excessively large at low temperatures causing interference with the resin case and contact separation
Solution Approach 1:
The patent introduces a resin case as an intermediary component between the thermally-actuated element and the external environment. This resin case absorbs and accommodates the excessive curvature deformation of the thermally-actuated element at low temperatures, preventing direct interference with the movable piece and maintaining stable electrical contact while preserving the thermal protection functionality.
2Device complexity
If the thermally-actuated element is accommodated in a simple resin case, then the device structure is simple, but the element interferes with the case at low temperatures causing contact pressure decrease
Solution Approach 1:
The resin case is segmented into multiple functional regions: a recessed portion that accommodates the thermally-actuated element, outer peripheral portions that provide structural support, and connecting portions that bridge the recessed portion and outer peripheral portions. This segmentation allows each region to perform its specific function - the recessed portion isolates the element, while the connecting portions maintain structural integrity, thereby preventing contact pressure decrease without significantly increasing overall device complexity.
3Stability of the object's composition
If the four corners of the thermally-actuated element contact with the resin case, then the element is constrained, but the central portion pushes up the movable piece causing contact separation
Solution Approach 1:
The resin case is designed with non-uniform local properties: the recessed portion provides a confined space that constrains the four corners of the thermally-actuated element for stable positioning, while the central region of the recessed portion maintains sufficient clearance to prevent the element's central portion from pushing up the movable piece. This local differentiation of constraints ensures both positioning stability and electrical contact 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 design avoids interference and maintains stable conduction by preventing the movable piece from being pushed up by the thermally-actuated element, ensuring low contact resistance and reliable electrical connection.
Implementation Method 1
a thermally-actuated element which is deformed in response to temperature changes so as to shift the movable piece from a conductive state in which the movable contact contacts with the fixed contact to a cut-off state in which the movable contact is separated from the fixed contact
Implementation Method 2
a movable piece which has an elastic portion being elastically deformable, and a movable contact in one end portion of the elastic portion, and which presses the movable contact so as to contact with the fixed contact
Data Source
Figure 1
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AI summary
The breaker 1 comprises a fixed piece 2, a movable piece 4, a thermally-actuated element 5 and a resin case 10. The fixed piece 2 has an embedded portion 25 embedded in the resin case 10 in a region which overlaps with the thermally-actuated element 5 in a plan view viewed in the thickness direction. The resin case 10 has an outer peripheral portion 74 formed on the outer perimeter of a recessed portion 73, a first penetrating portion 75 penetrating the recessed portion 73 to expose the embedded portion 25 to the thermally-actuated element 5 side, an island portion 76 interposed between the fixed piece 2 and the thermally-actuated element 5 in the inside of the first through portion 75, and a connecting portion 77 connecting between the outer peripheral portion 74 and the island portion 76.