PTC Electric Heater Spring Pressure Element to Reduce Stress Peaks
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Solution Overview
Problem
Existing electric heating devices with PTC elements face issues due to manufacturing tolerances, leading to dimensional fluctuations and stress peaks, which can result in inefficient heat transfer and potential mechanical damage, as the wedge-shaped pressure elements may not fit properly or provide adequate coverage of the heat extraction surfaces.
Innovation Solution
A pressure element with spring segments formed from a sheet metal strip is used, which adapts to the conical shape of the receiving pocket, distributing pressure evenly over the heat extraction surface of the PTC element, eliminating the need for insulating layers for voltages up to 25 VAC or 60 VDC, and allowing for direct conductive connection, thereby enhancing heat transfer and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a wedge-shaped pressure element is used to clamp layers in a receiving pocket tapering towards its lower closed end, then good heat transfer between PTC element and receiving pocket surfaces is achieved, but stress peaks occur that can break the PTC element or ceramic insulating layer
Solution Approach 1:
The pressure element changes from a rigid wedge shape to a flexible spring structure that can deform elastically. This parameter change in structural rigidity allows the pressure element to adapt to manufacturing tolerances while distributing clamping force uniformly, preventing stress peaks that would damage the PTC element or insulating layer.
Solution Approach 2:
The pressure element is made from a simple sheet metal strip with spring segments formed by punching and bending, creating a robust, replaceable component that can withstand repeated thermal and mechanical cycles without degrading, eliminating the need for expensive ceramic insulating layers.
2Ease of manufacture
If the receiving pocket has a tapering cross-sectional shape for production reasons, then manufacturing is simplified, but manufacturing tolerances cause dimensional fluctuations that prevent proper fit of the pressure element
Solution Approach 1:
The pressure element transitions from a static rigid wedge to a dynamic spring structure that can adjust its position and applied force. This dynamic capability allows the element to compensate for dimensional variations in the receiving pocket caused by manufacturing tolerances, maintaining proper fit and function across production variations.
Solution Approach 2:
The spring segments provide variable compression force based on the actual dimensions of the receiving pocket, adapting the clamping pressure to match the specific instance of the component. This parameter adaptation ensures reliable electrical contact and heat transfer despite manufacturing tolerances in the tapering receiving pocket.
3Volume of stationary object
If the free space before the wedge element is introduced is too small, then the receiving pocket structure is compact, but insufficient coverage of the heat extraction surface results in overheating and poor efficiency
Solution Approach 1:
The pressure element is divided into multiple spring segments formed by punching the sheet metal strip. These segments distribute the clamping force across multiple contact points along the heat extraction surface, ensuring complete coverage and efficient heat transfer even in compact receiving pockets with limited free space.
Solution Approach 2:
The spring segments are positioned to provide localized pressure at specific contact points along the heat extraction surface. This localized pressure distribution ensures that the entire surface area between the lower end and insertion opening is effectively engaged for heat transfer, maximizing efficiency within the available space.
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 efficient heat transfer and reduced risk of mechanical damage by adapting to manufacturing tolerances, maintaining efficient power uptake and thermal conductivity, while avoiding stress peaks and ensuring reliable electrical connectivity.
Implementation Method 1
The pressure element comprises a sheet metal strip and may be formed solely by the sheet metal strip. The sheet metal strip has spring segments formed by punching and bending from the plane of the sheet metal strip.
Implementation Method 2
PTC heating element (10) with at least one PTC element (18) and conductor tracks (20, 22) for energizing the PTC element (18) with different polarities
Implementation Method 3
a pressure element holds heat extraction surfaces of the PTC element abutted against oppositely disposed inner surfaces of the receiving pocket (24)
Data Source
AI summary
An electric heating device includes a housing having a partition wall which separates a connection chamber from a heating chamber for dissipating heat and from which at least one receiving pocket, protruding into the heating chamber as a heating rib tapering towards its lower, closed end protrudes. A PTC heating element includes at least one PTC element and conductor tracks for energizing the PTC element with different polarities. The conductor tracks are electrically conductively connected to the PTC element and are electrically connected in the connection chamber. A pressure element is received which holds heat extraction surfaces of the PTC element abutted against oppositely disposed inner surfaces of the receiving pocket. The pressure element includes a sheet metal strip which, by punching and bending, forms spring segments protruding from the plane of the sheet metal strip. The spring elements are provided in a planar manner distributed over a heat extraction surface of the PTC element provided adjoining the respective pressure element.