PTC Heater Contact Plate Coating for Moisture Insulation

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Solution Overview

Problem

High-voltage PTC heating devices in motor vehicles face electrical safety issues due to moisture and impurities in the fluid being heated, which can lead to short circuits between contact plates of different polarities, compromising insulation and device reliability.

Innovation Solution

The implementation of a non-conductive coating around the contact plates, with only the contact surface exposed, and an electrically insulating frame to seal the PTC element from the environment, preventing moisture and dirt ingress, and optionally using a contact projection to enhance sealing and reduce metallization on the edge regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If contact plates are exposed to the environment for electrical connection, then ease of operation is improved, but electrical insulation deteriorates due to moisture and contaminants causing short circuits

Engineering Contradiction:

Improveelectrical connectionVSAvoidelectrical insulation

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A non-conductive coating is applied to the contact plates, forming a thin film barrier that prevents moisture and contaminants from causing short circuits while allowing the contact plates to perform their electrical connection function. The coating covers the entire surface of the contact plates except for the contact surfaces that need to remain exposed for electrical connection.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The contact plates are designed with differentiated surface properties: the contact surfaces remain exposed and conductive for electrical connection, while the remaining surfaces are covered with a non-conductive coating for insulation. This local differentiation allows each part of the contact plate to serve its specific function optimally.

Inventive Principle:

Principle #3Local quality

2Reliability

If contact plates are completely covered with non-conductive coating, then electrical insulation is improved, but electrical connection capability deteriorates

Engineering Contradiction:

Improveelectrical insulationVSAvoidelectrical connection

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If PTC element is directly exposed to the fluid being heated, then heat transfer efficiency is improved, but electrical safety deteriorates due to moisture ingress causing short circuits

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidelectrical safety

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A non-conductive coating is applied to the PTC element that is permeable to heat but impermeable to moisture and contaminants. This coating allows heat to be transferred efficiently to the fluid while preventing moisture ingress that would cause short circuits and electrical safety issues.

Inventive Principle:

Principle #30Flexible shells and thin films

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 configuration significantly enhances electrical safety by preventing short circuits and ensuring reliable operation even when coatings deteriorate, maintaining effective insulation and heat transfer while reducing the risk of electrical failures.

Implementation Method 1

PTC heating device with at least one PTC element and contact plates which are assigned to different polarities for energizing the PTC element

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The contact plates are surrounded by a non-conductive coating, with the exception of the contact surfaces and free ends

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentEP4255110A1PTC heating device and electric heating device comprising same

Publication Date: 2023.10.04 EBERSPACHER CATEM GMBH & CO KG

Figure 1
Figure 2~5

AI summary

The present invention relates to a PTC heating device (12) with at least one PTC element (24) and contact plates (18; 34) which are assigned to different polarities for supplying current to the PTC element (24) and which are electrically conductive towards the PTC element (24), which is characterized with regard to safe electrical operation in that at least one of the contact plates (18) is provided with an electrically non-conductive coating (28) which surrounds the PTC element (24) in such a way that only a contact surface (20) formed by the contact plate (18) for the PTC element (24) is recessed within the coating (28).The present invention further relates to an electric heating device (12) with a frame (4) which forms inlet and outlet openings (6; 8) for a fluid to be heated and includes at least one PTC heating device (12) according to the present invention, on the opposite side surfaces of which a heat-emitting layer (14) is located.