Molecular Bonding Element for Automotive Fuel Sensors
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Solution Overview
Problem
Existing sensors for automotive systems fail to accurately and reliably measure properties of caustic working fluids due to inadequate construction, particularly the degradation of mechanical bonds between materials with different coefficients of thermal expansion, leading to cyclic shear fatigue and incompatibility with space and cost constraints.
Innovation Solution
A sensing device with a substrate and sensing element bonded using a molecular bonding element with a coefficient of thermal expansion less than 10 ppm/°C, forming shear and tensile bonding areas to reduce thermal expansion differences and enhance durability, allowing for compact and reliable measurement of fluid properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If epoxy is used to bond glass and plastic together, then the bonding material is easy to apply, but the bond degrades over time due to cyclic shear fatigue from thermal expansion mismatch
Solution Approach 1:
The patent changes the fundamental parameter of the bonding mechanism from mechanical interlocking (epoxy) to molecular bonding. The bonding element is configured to form molecular bonds with both the glass portion of the sensing package and the plastic substrate, creating a chemically bonded interface that eliminates cyclic shear fatigue caused by thermal expansion mismatch.
Solution Approach 2:
The bonding element serves as an intermediary component between the glass sensing package and the plastic substrate. It provides molecular bonding interfaces with both materials while having a coefficient of thermal expansion less than 10 ppm/°C, which reduces thermal stress and prevents bond degradation over time.
2Reliability
If ceramic capacitive circuits on stainless steel foil are used, then chemical resistance is improved, but the fitting size becomes large and bulky
Solution Approach 1:
The patent employs composite material construction where a plastic substrate (providing chemical resistance) is molecularly bonded to a glass sensing package (providing sensing functionality). This composite approach eliminates the need for large stainless steel housings while maintaining compatibility with caustic working fluids.
Solution Approach 2:
The patent extracts the essential functional requirements from the traditional stainless steel housing design and implements them separately: chemical resistance is provided by the plastic substrate, while sensing functionality is provided by the glass sensing package. This separation allows for a much more compact overall design.
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 provides a robust and accurate sensing device that maintains performance under varying temperatures and pressures, reducing the risk of leaks and catastrophic failures, while being compatible with automotive system design constraints.
Implementation Method 1
The bonding element forms a first bonding area that comprises a molecular bond between the bonding element and a side of the sensing element. The first bonding area further comprises a molecular bond between the bonding element and the side portion.
Implementation Method 2
The bonding element has a coefficient of thermal expansion that is less than about 10 ppm/°C
Data Source
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AI summary
There are provided embodiments of a sensing device that comprise a sensing element, a substrate, and a bonding element, each being selected for environments that utilize caustic working fluids such as automotive fuel. Material for use as the bonding element can form molecular bonds with ceramics and glass. In one embodiment, the sensing device comprises a receptacle or cavity, in which are located the sensing element and the bonding element. This configuration facilitates the formation of bonds between the bonding element and each of the sensing element and a peripheral wall of the cavity. Such bonds are configured in a tensile bonding area and a shear bonding area, the combination of which is useful to secure the sensing element in the cavity. The sensing device can further comprise a seal such as an o- ring disposed in annular relation to the substrate to seal the sensing device to a peripheral device such as a fluid fitting, which may be found in a fuel system of an automobile.