Application of the sensor technology in the diesel engine

Sensor carbon dioxide emissions from fuel efficiency to reduce carbon dioxide emissions is the hottest topic in today's automotive sector. The European Commission recently announced a safer, more environmentally friendly cars roadmap to 2012. Significant change in the automotive consumer buying patterns also confirmed that consumers want to be able to meet their own personal and professional needs of the highest fuel efficiency car. Progress through the mixed-fuel technology, automotive manufacturers are introduced to reduce the carbon dioxide emissions of new cars. There are also some technical committed to this goal, such as Blue Motion, Econetic and Efficient Dynamics.

Diesel engine pollution than gasoline-powered car, which is a fact. In particular, the diesel particulate body injury, will cause lung irritation, cancer and heart disease. Older diesel engines will emit a larger visible particles, like black smoke, new engine particulate emissions are generally small, and can not be seen with the naked eye.

These emissions cleaner, car manufacturers to build a diesel particulate filter (diesel particulate filters DPF). Since 1980, these filters have been used for off-road vehicles, since 1996 for some ordinary car. DPF can now capture diesel soot particles down to 2.5 microns, therefore particulate emissions reduced from 60% to 7%. DPF using a porous ceramic material, and will eventually be saturated, and need to be cleaned and regenerated. For such maintenance requires heating the DPF to the exhaust gas temperature above +600 ℃. In order to achieve this a higher than normal temperature, the ECU (electronic control unit) will temporarily delaying the fuel injection, and restricting suction. In this case, the sensor become a key control element: by using a pressure sensor to measure the voltage drop on the filter, it can determine the most efficient point in time starts the regeneration process.

Interface Implementation

To the diesel filter module, for example, a traditional varistor element differential pressure sensor installed in the DPF. The pressure range of the sensor to check for a smaller, generally 0 to 15psi. A sensor interface IC (such as the Melexis MLC90320 CMOS analog sensor interface) connected to the sensor output terminal, and constitute a resistive Wheatstone bridge circuit. This interface can be a small change in voltage of the resistor (typically a few millivolts) is converted to the relatively large changes in the output voltage of. With this structure, the circuit to be able to compare the filter before and after the pressure signal. The interface chip for the sensor's signal for amplification and correction, it is converted into the value of the ECU to be able to identify. When the saturation of the DPF, the interface will be detected before the filter, there is a greater pressure differential between the signal after the. Interface IC for amplification and compensate for this difference, passed to the ECU. This process allows the sensor interface to control the communication between the detection element and the ECU, to ensure the filter for normal work.

Sensor interface

In the above example, the detection element of the varistor is connected to the input terminal of the sensor interface, and its signal for the compensation of the gain and offset, to determine the output signal of a well calibrated. In addition, using three different coarse stage and 10-bit digital-to-analog converter (DAC), the output of this particular interface architecture uses a 10 DAC, the output variation range for accurate calibration.

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