Design And Analysis Of High Temperature Pressure Sensor For Vehicle

The measurement of engine exhaust pressure is of great significance to the study of engine performance. Because of the high temperature of the exhaust valve, the normal pressure sensor can not work normally, so the study of the high temperature pressure sensor in the engine exhaust valve is worth further study.Through investigation and research, this paper designs and analyzes the piezoresistive silicon carbide(Si C) high temperature pressure sensor. The design, selection and analysis of the sensing diaphragm are conducted, and the packaging scheme is also selected, then proposed a thermal-structure coupling analysis method to simulate the working conditions of the engine exhaust valve. The basic performance of the sensor was simulated, and the performance of the sensor was studied and verified by experiments, Specific tasks of this paper are as follows:(1)Based on the theory of small deflection theory, the size of the sensing diaphragm is designed. The performance of the sensing diaphragm is studied by using ANSYS. The comparison, selection and analysis are conducted between different kinds of diaphragms, the output of the sensor is estimated. Based on the finite element method, the influence of length and thickness of the sensing diaphragm on the output and the sensitivity of the sensor is studied, which proves the rationality of the design.(2)A suitable packaging scheme is selected, the steady thermal-structure coupling analysis and transient thermal-structure coupling analysis are carried out combined with the working condition of the engine exhaust valve, to study the effect of the temperature and the thermal shock on the performance of the sensor. The influence of the thermal stress on the surface of the sensing diaphragm caused by packaging is analyzed. The results show that the selected package scheme can ensure the sensor in the engine exhaust valve of high temperature environment can still have a good working performance.(3)The distribution of the stress in the diaphragm is analyzed with different temperatures, the location of the piezoresistors are also determined, the stress field and the output voltage of the diaphragm are simulated under different temperatures and pressures.(4)For a type of high temperature pressure sensor, the static performance test and the temperature influence test are carried out. The performances of the high temperature pressure sensor in high temperature are discussed, the output of high temperature pressure sensor is analyzed, and the simulation result is verified through the experiment.The results of the above study and experiment provide a basis for the design of high temperature pressure sensor.