PTC heating element and electric heater for a motor vehicle comprising such a PTC heating element
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Solution Overview
Problem
Existing PTC heating elements face challenges in achieving reliable electrical insulation on the outside while maintaining adequate heat transfer to heat-emitting surfaces, particularly in high-voltage applications like electric vehicles, where conventional insulating films can lead to short circuits due to unevenness and electrostatic effects.
Innovation Solution
A method involving a hybrid insulating layer composed of a film and an electrically insulating compound with good thermal conductivity, applied as a prefabricated unit to conductor tracks, which compensates for unevenness and provides reliable insulation, using a crosslinked silicone mass with filler particles for enhanced thermal conductivity and electrical safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional insulating film is used to cover the conductor tracks, then electrical insulation is provided, but heat transfer from the PTC element to the heat-emitting surface is reduced due to the film's poor thermal conductivity
Solution Approach 1:
The patent applies a composite insulating layer consisting of a film (such as polyimide) combined with an electrically insulating compound containing thermally conductive filler particles (such as aluminum oxide, aluminum nitride, or boron nitride). This composite structure provides both electrical insulation through the film and polymer matrix, while simultaneously improving heat transfer through the thermally conductive filler particles embedded in the compound.
Solution Approach 2:
The patent changes the thermal conductivity parameter of the insulating layer by incorporating filler particles with high thermal conductivity into the insulating compound. The filler content is optimized to achieve a balance between electrical insulation and thermal conductivity, with the compound containing 30-90 wt% of thermally conductive filler particles.
2Reliability
If a thick insulating layer is applied to ensure electrical insulation, then electrical safety is improved, but the layer thickness increases and heat transfer path is lengthened
Solution Approach 1:
The composite insulating layer allows achieving adequate electrical insulation with a thinner overall layer thickness by combining the film's insulating properties with the compound's fillers. The thermally conductive filler particles provide efficient heat transfer pathways through the insulating layer, reducing the effective thermal resistance despite the presence of the insulating matrix.
Solution Approach 2:
The insulating compound acts as an intermediary material between the conductor track and the heat-emitting surface, providing both electrical insulation and thermal conduction. The compound fills the gaps and unevenness between the film and the mating surface, ensuring continuous thermal contact while maintaining electrical insulation.
3Reliability
If the insulating layer surface is made uneven to compensate for surface irregularities, then contact uniformity is improved, but electrostatic discharge risk increases due to charge accumulation
Solution Approach 1:
The patent changes the surface electrical properties of the insulating layer by incorporating conductive or dissipative filler particles into the insulating compound. These filler particles (such as carbon-black filled polymers or metal oxide coatings) provide pathways for electrostatic charge dissipation, reducing charge accumulation on the uneven surface while maintaining the compensatory unevenness for better contact.
Solution Approach 2:
The insulating compound is formulated as a composite material combining electrically insulating polymers with charge-dissipative filler particles. This composite structure maintains the electrical insulation function while providing electrostatic discharge pathways through the filler network, mitigating the harmful effects of charge accumulation on uneven surfaces.
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 solution ensures reliable electrical insulation with improved thermal conductivity, preventing short circuits and ensuring safe operation under high voltage conditions, with specific dielectric strength, volume resistance, and tracking resistance values that meet safety standards.
Implementation Method 1
an electrically insulating compound with good thermal conductivity applied thereto
Implementation Method 2
electrical insulating layer has a layered structure with a film that usually runs through it and an electrically insulating compound
Implementation Method 3
specific dielectric strength, volume resistance, and tracking resistance values that meet safety standards
Implementation Method 4
using a crosslinked silicone mass with filler particles for enhanced thermal conductivity and electrical safety
Implementation Method 5
the insulating layer according to the invention offers the possibility, in particular due to the elastic and electrically insulating mass, of unevenness
Data Source
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AI summary
The present invention relates to a PTC heating element (2) for an electric heater for a motor vehicle and intends to provide a PTC heating element (2) which is electrically insulated in an improved manner on the outside, while also taking into account the need for adequate heat transfer from the PTC -Element (4) is to be taken into account on the heat-emitting surface through the electrical insulating layer (10). To solve the above problem, the present invention proposes an electrical insulating layer (10) that rests on the outside of at least one of the conductor tracks through which the PTC element (4) is energized and a film (14) and one applied thereto having electrically insulating mass (12) with good thermal conductivity. The electrical heating device according to the invention, in particular for a motor vehicle, is provided with at least one such PTC heating element (2).