Electric Machine Safety Circuit with Breakable Joints
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Solution Overview
Problem
Electric machines, particularly in the automotive sector, face a growing need to prevent electrical short circuits that can lead to fires during accidents, as existing solutions are inadequate in ensuring safety against such incidents.
Innovation Solution
The design incorporates a sealed electric machine with a telescopic cap and weakening features that allow the cap to slide over the casing upon compression, along with a heat-dissipative wall and mechanically breakable joints in the conductive tracks, which disconnect the power circuit during an accident, preventing short circuits and fires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the electric machine uses a sealed enclosure with rigid casing and cap, then the structural strength and sealing are improved, but the risk of short circuits during accident increases
Solution Approach 1:
The power circuit is segmented into modular components (conductive tracks, electrically conductive element, joints) that can be independently disconnected. The weakening features create predetermined break points that allow controlled segmentation during accident, separating the conductive element from the conductive tracks to prevent short circuits while maintaining structural integrity during normal operation.
Solution Approach 2:
The weakening features are pre-configured in the conductive tracks and joints before the accident occurs. These predetermined weak points are designed to fail at specific locations under impact force, enabling automatic disconnection of the power circuit without requiring active sensing or control systems. The elastic element is also pre-loaded to push the conductive element away from the conductive tracks upon disconnection.
2Ease of manufacture
If the cap is made rigid and fixed to the casing, then the manufacturing simplicity is improved, but the ability to reduce short circuit risk during accident deteriorates
Solution Approach 1:
The cap is designed with telescopic capability relative to the casing, allowing it to move axially under impact force. This dynamic movement enables the cap to compress the elastic element and facilitate disconnection of the power circuit during accident, while maintaining a fixed rigid structure during normal operation. The telescopic feature is achieved through axial play between the cap and casing, allowing controlled movement only under extreme conditions.
3Reliability
If the conductive tracks are made mechanically strong and rigid, then the electrical connection reliability is improved, but the ability to disconnect during accident deteriorates
Solution Approach 1:
The conductive tracks are designed with non-uniform cross-sectional thickness, creating localized weak points (weakening features) at specific locations while maintaining adequate thickness in other areas for reliable electrical connection. The joints connecting the electrically conductive element to the conductive tracks are also designed with controlled weakness. This local quality differentiation allows the tracks to be strong where needed for electrical reliability but vulnerable at predetermined points for accident disconnection.
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 solution effectively reduces the risk of fires caused by short circuits by ensuring the electric machine's power circuit is disconnected during an accident, enhancing safety and compliance with stringent safety regulations.
Implementation Method 1
an elastic element (31) pushing the electrically conductive element (25) away from the first and second conductive tracks (21, 22)
Implementation Method 2
a heat-conductive filler (8), comprising, for example, a heat-conductive paste, is interposed between the conductive tracks (20) and the wall (4a) to fill in gaps between the two parts and facilitate heat conduction between them
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electric machine comprises a conductive element (25) disposed in such a way as to connect a first track (21) and a second track (22) of an electric power circuit to close the circuit; the conductive element (25) being held in position by at least one mechanically breakable joint (26) which, if subjected to a predetermined force, mechanically yields or breaks and thereby opens the electric power circuit; the machine comprises a system (50) for releasing the conductive element (50) from the first and/or the second track if the casing (2) of the electric machine is moved near the cap (3) which covers the machine.