Ceramic Pressure Sensor with Graded Adaptation Body
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Solution Overview
Problem
Pressure sensors with ceramic and metal joints face significant thermomechanical stresses due to differing thermal expansion coefficients, limiting their usable temperature range and potentially affecting measurement accuracy.
Innovation Solution
A pressure sensor design featuring a ceramic base body with a metal body connected via a pressure-tight mechanical connection, where the connection's thermal expansion coefficient gradually matches that of the ceramic to metal, using layered adaptation bodies with specific thermal expansion profiles and joints like sintering, active brazing, or welding to minimize stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ceramic base body is mechanically connected to metal body via pressure-tight connection, then pressure resistance and chemical resistance are improved, but thermomechanical stresses occur due to different coefficients of thermal expansion
Solution Approach 1:
The patent introduces an intermediate layer between the ceramic base body and the metal body. This intermediate layer has a coefficient of thermal expansion that is intermediate between ceramic and metal, serving as a stress buffer. The intermediate layer absorbs and distributes the thermomechanical stresses that arise during temperature changes, preventing direct stress transmission between the ceramic and metal components.
Solution Approach 2:
The patent employs composite material structures, specifically combining ceramic, intermediate layer materials, and metal in a layered configuration. This composite approach allows each material to contribute its advantageous properties: ceramic provides chemical resistance and pressure resistance, metal provides mechanical strength and ductility, while the intermediate layer provides thermal expansion compatibility. The composite structure effectively manages the inherent incompatibility between ceramic and metal thermal expansion coefficients.
2Reliability
If joining methods such as welding, soldering, or bonding are used to connect ceramic and metal, then pressure-tight connection is achieved, but thermomechanical stresses put strain on the joint and can lead to failure
Solution Approach 1:
The intermediate layer acts as a mediator between the ceramic base body and the metal body, enabling reliable joining while protecting the joint from thermomechanical stress. During welding, soldering, or bonding operations, the intermediate layer absorbs differential thermal expansion, preventing stress concentration at the ceramic-metal interface that would otherwise lead to joint failure or ceramic cracking.
Solution Approach 2:
The intermediate layer provides beforehand cushioning against thermomechanical stresses before they can damage the joint or ceramic components. By being positioned between the ceramic and metal, the intermediate layer preemptively absorbs and distributes thermal stresses during temperature changes, preventing strain on the joint and avoiding catastrophic failure modes such as ceramic cracking or joint delamination.
3Stress or pressure
If mechanical clamping systems using elastic elements like elastomer seals are used, then thermomechanical stresses are reduced, but this connection type is generally only suitable for clamping sensors into housing and unsuitable for connecting pressure supply lines to bores through ceramic base body
Solution Approach 1:
The patent uses a composite material approach where the intermediate layer combines properties of both rigid and elastic materials. This allows the connection system to achieve low thermomechanical stresses (similar to elastomeric connections) while maintaining the structural integrity and pressure-tightness required for connecting pressure supply lines to ceramic bores. The composite structure enables versatility across different connection applications.
Solution Approach 2:
The intermediate layer provides local quality differentiation within the connection system. Different regions of the intermediate layer can have different material properties optimized for specific functions: some regions provide stress buffering, while others provide sealing capability or structural support. This localized optimization enables the connection to function effectively in multiple applications, from sensor mounting to pressure line connection.
4Strength
If ceramic base body is used, then thermal resistance, chemical resistance, and pressure resistance are improved, but coefficient of thermal expansion differs significantly from metal bodies limiting temperature range
Solution Approach 1:
The intermediate layer serves as a thermal expansion mediator between the ceramic base body and metal components. During temperature changes, the intermediate layer's intermediate coefficient of thermal expansion allows it to expand and contract at a rate that bridges the gap between ceramic and metal, reducing differential thermal stress. This enables the assembly to withstand wider temperature ranges without joint failure or ceramic damage.
Solution Approach 2:
The patent creates a composite material system that combines ceramic, intermediate layer, and metal components. This composite structure leverages the high temperature stability and chemical resistance of ceramic while incorporating the ductility and thermal expansion compatibility of the intermediate layer and metal. The composite material approach effectively extends the usable temperature range of the overall assembly beyond what would be possible with direct ceramic-metal connections.
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 design reduces temperature-dependent stresses, allowing the pressure sensors to operate across a wide temperature range without elastomers, ensuring accurate measurements and extended lifespan.
Implementation Method 1
the adaptation body has a coefficient of thermal expansion which increases along the adaptation body in the direction extending from the base body to the metal body from a coefficient of thermal expansion corresponding to the coefficient of thermal expansion of the ceramic of the base body to a coefficient of thermal expansion corresponding to the coefficient of thermal expansion of the metal body
Implementation Method 2
the adaptation body is connected to the base body by a first joining and to the metal body by a second joining
Implementation Method 3
joints like sintering, active brazing, or welding
Implementation Method 4
joints like sintering, active brazing, or welding
Data Source
Figure 1
Figure 2~5
Figure 3
AI summary
Disclosed is a pressure sensor, with a base body (1) of ceramic, a measuring membrane (3, 41) arranged on the base body (1), a pressure measurement chamber (5) enclosed in the base body (1) under the measuring membrane (3, 41), and at least one metal body connected to the base body (1) using a pressure-tight, preferably elastomer-free, mechanical connection (7, 37, 49), wherein thermomechanical stresses caused by the connection (7, 37, 49) are reduced by the fact that the pressure-tight mechanical connection (7, 37, 49) is achieved using an adjustment body (9, 19, 39, 51) arranged between the base body (1) and the metal body, wherein the adjustment body has a thermal expansion coefficient (a(z)) that increases, in a direction (z) from the base body (1) to the metal body, from an expansion coefficient corresponding to a thermal expansion coefficient (a k ) of the ceramic of the base body (1) to an expansion coefficient corresponding to the thermal expansion coefficient (a M ) of the metal body, and the adjustment body (9, 19, 39, 51) is connected to the base body (1) by a first join (11) and to the metal body by a second join (13).