D5.4 - Mirco-Sensors for Automotive Liquid Properties Monitoring

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
D5 - Media Properties Sensors
H. Dobrinski, T. Eggers, J. Stürmann, M. Lindemann - Hella Fahrzeugkomponenten GmbH, Bremen (Germany)
612 - 617


Because of upcoming new emission regulations like Euro 6 or EPA10 the fuel efficiency, emissions and lifetime of modern combustion engines need to be increased by a sophisticated motor management. Additionally, an increased fuel admixtures of bioethanol or bio-diesel together with new technologies as for instance particle filters in the exhaust gas after treatment components of diesel engines become more and more important.
To cover all of these new requirements a lot of parameters have to be considered. Sensor systems currently available on the market are not sufficient because either they are too big, too slow and/or too expensive for an automotive integration.
Using examples of an oil level & quality sensor and an ethanol content & pressure sensor it will be demonstrated how the integration of different functionalities in small micro-sensors for automotive applications can be realized.

The first example is an innovative combination-sensor for modern oil management systems in vehicles. The sensor component is capable to measure six independent oil parameters (viscosity, density, permittivity, conductance, level, temperature) continuously during normal engine operation. It comprises an ultrasonic transducer for the oil level detection as well as a Tuning Fork mechanical resonator for the oil condition measurement. Both elements have been realized as small tiny multi-chip modules which are combined on a mechanical flange. Besides the specific sensor elements (piezo-ceramic disc for generation and detection of ultrasonic waves, Tuning Fork as mechanical resonator) each multi-chip module contents of an ASIC for the measurement and signal preconditioning as well as passive components (diodes, capacitors) to fulfill the automotive EMC requirements. All data are transmitted to the external ECU by a 1-wire digital interface protocol. In addition to the measurement and signal preconditioning software already implemented on the integrated microcontroller an AUTOSAR-conform software module will be provided to the customer. This software evaluates the incoming signals from the sensor and calculates the current oil quality considering additional information from the engine. The intelligent Oil Condition Algorithm (OCA) detects contaminants and extreme oil conditions at an early stage. Oil change intervals can be adapted to the specific car and the individual driving behavior in a more precise way than it is possible with existing oil condition monitoring concepts and algorithms. Because the oil level can be measured even when the engine is stopped, the sensor ensures an overfill detection comparable to a regular dipstick, which will be redundant hereby.

The combination-sensor for simultaneous measurement of absolute fuel pressure and ethanol content of fuel is the second example. It will be screwed in the fuel line of direct injection engines or mounted directly to the conveyor module inside the tank. The fuel pressure is needed as a control parameter for fuel pumps in fuel lines without return path in order to ensure a bubble-free filling of the high pressure fuel rail. The ethanol content data is used for the engine control to burn the fuel efficiently and fulfill future emission regulations in flex fuel vehicles. The sensor outputs the actual fuel temperature reading as an option, too. It features a SENT-interface for safe digital outputting the multiple data.