Compact Ceramic Sensor Element via Length-to-Width Ratio Optimization
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Solution Overview
Problem
Existing gas sensor elements, such as lambda probes, face challenges in maintaining temperature resistance and mechanical stability due to the ion conductivity of solid electrolytes like YSZ at high temperatures, particularly in shorter designs where vias become hotter and require complex insulation, increasing production costs and vulnerability to mechanical loads.
Innovation Solution
A sensor element with a ceramic layer structure having a length-to-width ratio of 6.0 to 8.5 and via diameters of at least 0.5 mm, featuring a thick insulating layer of at least 30 μm to prevent short circuits and ensure mechanical stability, allowing for high contact resistances even above 500°C, and a design that withstands bending and shaking loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the sensor element is made short (length < 65 mm) to reduce size and cost, then the installation space and material cost are reduced, but the via holes become hotter and require complex insulation layers to prevent short circuits
Solution Approach 1:
The patent changes the geometric parameters of the sensor element, specifically the length-to-width ratio (L/W) is set between 6.0 and 8.5, and via diameters are set to at least 0.5 mm. These parameter changes allow the sensor to be short while maintaining sufficient temperature gradient and reducing via temperature, eliminating the need for complex insulation layers.
Solution Approach 2:
The patent uses a simplified via design that copies the successful temperature gradient approach from longer sensors, applying it to short sensors through optimized dimensional ratios rather than complex insulation structures.
2Reliability
If complex insulating layers are added to via holes to prevent short circuits at high temperatures, then electrical insulation is improved, but production costs and manufacturing effort increase considerably
Solution Approach 1:
By changing the geometric parameters (L/W ratio of 6.0-8.5, via diameters ≥0.5 mm), the patent reduces via temperature sufficiently to eliminate the need for complex insulation layers, thereby improving ease of manufacture while maintaining electrical insulation reliability through the optimized temperature gradient.
3Adaptability or versatility
If the sensor element is made short to extend application freedom in motor design, then adaptability is improved, but the via area temperature increases and approaches the critical temperature of the solid electrolyte
Solution Approach 1:
The patent applies parameter changes by setting specific L/W ratios (6.0-8.5) and via diameter minimums (0.5 mm) that maintain sufficient temperature gradient even in short sensors, keeping via temperatures below the critical 350°C threshold of YSZ while enabling compact designs for extended application freedom.
4Ease of manufacture
If via holes are made larger (diameter ≥ 0.5 mm) to reduce temperature and eliminate insulation needs, then manufacturing is simplified, but the mechanical strength of the layer structure may be reduced
Solution Approach 1:
The patent optimizes the via diameter to be at least 0.5 mm, which is sufficiently large to reduce via temperature and eliminate complex insulation needs, while the specific L/W ratio range (6.0-8.5) is chosen to maintain adequate mechanical strength by balancing the structural integrity requirements with the thermal management needs.
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 enables the production of robust, temperature-resistant, and cost-effective gas sensors with reduced production effort, suitable for installation in small spaces, maintaining performance under high loads and temperatures.
Implementation Method 1
allowing for high contact resistances even above 500°C
Implementation Method 2
at least one ceramic solid electrolyte connecting the electrodes... known solid electrolytes are, for example, yttrium-stabilized zirconium dioxide (YSZ)... which become ionically conductive at higher temperatures
Implementation Method 3
the same requirements regarding robustness and temperature resistance apply... a sufficiently large temperature gradient over the length of the sensor element, which means that the temperature of the ceramic in the area of the via holes during sensor operation is always below a critical temperature
Data Source
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AI summary
The invention relates to a sensor element (112) for detecting at least one property of a gas in a measuring gas space (164), in particular for determining a proportion of a gas component. The sensor element (112) comprises at least one layer structure (110) having at least two electrodes (114, 116) and at least one ceramic solid electrolyte (118) connecting the electrodes (114, 116). The layer structure (110) has a longitudinal extension of a length L parallel to one or more layer planes of the layer structure (110) and a transverse extension of a width B, the ratio L/B being smaller than 10.