In order to measure the pollutant amounts according to emission standards such as EURO 6 and, in the future, EURO 7, an increasing number of sensors are being implemented in exhaust gas systems and near the engine in vehicles. Limited space necessitates small, robust sensors that are easy and affordable to integrate. These sensors must be highly temperature-resistant and reliable under extreme conditions in order to work properly on a constant basis. The monitoring of temperature as well as nitric oxide and soot particle concentrations takes place in an extremely hot and corrosive environment. In exhaust applications, sensors must withstand temperatures over 1000°C (1800°F) for several thousand cycles. At the same time, they must withstand chemical influences, such as petrol or diesel fuels and their respective exhaust emissions, including AdBlue solution.
Limited space challenges
In order to achieve robust resistance to harsh elements, conventional sensor designs use complex designs comprised of many different individual components. One central component is the sensor feedthrough, which enables continuous pass-through of electricity and/or measurement data. Typically, ceramic powder or sintered ceramic elements are used during the manufacturing process for electrical insulation and to protect against heat and corrosion. These are held in position by metal rings or springs. The individual components in these sensor feedthroughs require additional space, making the design relatively large and complex for integration into an exhaust gas system. Furthermore, producing this multi-component system requires many manufacturing steps.
Compact and simple: sensor designs with HEATAN™
In contrast, HEATAN™ sensor feedthroughs deliver robust performance in the form of a ready-to-install single component that is constructed with just three parts: metal housing, metal or ceramic conductor, and glass-ceramic sealing material. All that needs to be added are attachments and cabling. Thanks to the smaller quantity of individual parts and reduced production steps, HEATAN™ feedthroughs enable lower costs for purchasing and installation. Sensor manufacturers benefit from a simple and economical replacement solution with incredible longevity for a true “fit & forget” installation.
In comparison to conventional feedthroughs for high-temperature sensors, HEATAN™ allows for a very simple and compact sensor design. The feedthroughs are quick and easy to integrate and can be customized. Options include equipping an external thread in order to attach the component to other parts or devices, such as exhaust pipes from combustion engines. The thread diameters are less than 14 millimetres and typically between thread sizes M14 and M4. With these sizes in mind, the number of sensor components in an exhaust gas system can be increased or sensors can be positioned in narrow places.
Glass-ceramic withstands 1000°C and above
Innovative HEATAN™ sensor feedthroughs are created in an efficient production process based on a unique material combination: glass-ceramic and metal. It is based on proven hermetic glass-to-metal sealing technology, which has been used in countless automotive applications for decades – including airbag ignitor feedthroughs. During a special furnace process, the metal components and sealant form a completely gas-tight bond. Instead of using glass as a sealing material, a highly temperature-resistant glass-ceramic sealant is used. The result is similar to the material design principles of well-established CERAN® glass-ceramic cooktops.
The sealing material is heated and forms a direct hermetic connection to the metal components. This eliminates the need for rings or springs to fix the insulation material and allows glass-ceramic seals to deliver higher robustness and reliability compared to conventional feedthroughs.
In production, the melting and glass phase in a defined temperature process is followed by the ceramization phase. This establishes the required mechanical material stability at extreme temperatures. The glass-ceramic produced in this way offers reliable sealing at operating temperatures of more than 300°C and peak temperatures over 1,000°C (1800°F) in extreme conditions with aggressive chemicals and exhaust gases. It can also withstand temperature cycles over a total distance up to 300,000 kilometres (180,000 miles), depending on the design.