Case Molded Capacitor Buffer Layer Vibration Damping
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Solution Overview
Problem
Metallized film capacitors used in hybrid electric vehicle motor inverter circuits generate audible noise due to vibration from alternating voltage, which is not effectively reduced by existing methods, particularly at high frequencies, and this noise propagates through the joining parts of metal and resin cases into vehicle cabins.
Innovation Solution
A case molded capacitor design incorporating a metallized film capacitor, bus bars, a resin-made internal case, molding resin, a metal external case, and a buffer material layer, where the buffer material layer is placed between the internal and external cases to moderate vibration and reduce noise propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metallized film capacitor is used in an inverter circuit of HEV, then the capacitor can operate at high voltage and provide smoothing function, but the capacitor generates audible noise due to vibration from alternating voltage
Solution Approach 1:
A buffer material layer is introduced as an intermediary substance between the internal case and external case. This buffer layer absorbs and dampens the vibration generated by the capacitor during operation, preventing the vibration from propagating through the case structure to generate audible noise, while the capacitor continues to perform its smoothing function in the inverter circuit
2Object-generated harmful factors
If sound proofing material is disposed between the capacitor element and resin case, then noise emission is reduced, but vibration still propagates through the joining part between metal case and resin case
Solution Approach 1:
The case structure is divided into two separate cases: an internal case that directly contains the capacitor element, and an external case that provides additional protection. The buffer material layer is placed at the joining interface between these two segmented cases, creating a vibration isolation zone that prevents vibration propagation while maintaining the structural integrity of the overall housing
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 buffer material layer significantly reduces vibration acceleration and noise emission by 1/20 compared to a comparison sample, achieving enhanced quietness suitable for hybrid electric vehicle applications.
Implementation Method 1
The buffer material layer is put in a gap made at least at a part between the internal case and the external case... the buffer material layer significantly reduces vibration acceleration and noise emission
Data Source
AI summary
A case molded capacitor has a metallized film capacitor, a pair of bus bars, a resin-made internal case, molding resin, a metal external case, and a buffer material layer. The bus bars are each connected to respective one of electrodes of the metallized film capacitor. The internal case contains the metallized film capacitor. The metallized film capacitor is submerged with molding resin in the internal case so as to expose parts of the bus bars. The external case contains the internal case and both cases are connected at a connecting part. A buffer material layer is put in a gap made at least at a part between the internal case and the external case.