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Research paper−171−Synthesiology - English edition Vol.5 No.3 pp.171-180 (Dec. 2012) for the high-precision control of combustion in the combustion chamber, it is necessary to develop a new inter-cylindrical combustion pressure sensor with heat resistance of 400 °C or more that allows direct, high-speed measurement of the pressure in combustion chambers.[1]1.2 Situation of the combustion pressure sensorThe piezoresistant semiconductor pressure sensor, which is the most prevalent type of pressure sensor, is small, highly sensitive, highly befitting for mass production, and dominates 83.2 % (quantity base) of the market.[2] However, its service temperature limit is about 120 °C. To increase the heat resistance, researches are being done to insert heat-insulating barrier (alumina) in the lower part of the gage, to use sapphire diaphragm, or to use chromic oxide and silicon carbide (SiC) that are highly heat resistant as the material for the gage. However, sufficient heat resistance has not been achieved.In 1992, Toyota Motor Corporation installed a semiconductor pressure sensor for the first time in the world as the combustion pressure sensor in its mass-produced car, by maintaining the maximum temperature of the sensor element to 120 °C or lower by devising the sensor structure and layout, but this system is currently not used. From 2009, BorgWarner BERU Systems GmbH of Germany provides a glow plug with a function of the semiconductor pressure sensor incorporated into the combustion pressure sensor. Although this has been installed in some of the green diesel cars of Audi AG and Volkswagen AG, it is not yet used widely.1 Introduction1.1 Necessity of the combustion pressure sensor in mass-produced carsThe improvement of fuel efficiency and measures for low pollution in automobile engines are urgent issues that must be tackled to counter the global warming caused by carbon dioxides and the elevated price of crude oil that started around 2008. Various regulations pertaining to the emissions from engines will gradually become effective around the world, such as the “Fuel Economy Standard for Heavy Duty Vehicles” from 2015 in Japan, the “Euro VI” from 2014 in Europe, and the enforcement of new gas emission standards in the United States. As measures to such regulations, the automobile companies are engaging in R&Ds for various new cars, including those with direct-injection engine, green diesel, biofuel, hybrid, electric, hydrogen, fuel cell, and others. However, at least for the next 10 to 20 years, automobiles with engines that use oil as fuel will remain the mainstream. Along with the increased performance of tires and reduced body weight, active researches are done for increased combustion efficiency, filtering technology for gas emissions, and the technologies for electronic combustion control. Various measurement technologies for pressure, temperature, flow rate, vibration, and others are necessary to develop such technology. Particularly, there are great expectations both in volume and quality of the information that can be obtained from pressure measurement, judging from the necessity, installability, precision, responsiveness, and economic feasibility of sensor development. Especially - Application to a combustion pressure sensor for mass-produced cars-In this paper, we show the process of research and development of a combustion pressure sensor using an aluminum nitride (AlN) thin film, which we developed for the first time in the world. At the time we envisaged the R&D in 2003, most sensors used a piezoelectric single crystal. The research of a combustion pressure sensor using an AlN thin film was an unexplored field, and the usefulness of an AlN thin film was not yet well recognized. However, since we started the R&D, domestic and foreign auto parts companies and universities showed interest, and we carried out joint research with a domestic company and a university toward practical use of the sensor. Consequently, we have succeeded in developing a sensor of small size, high sensitivity, and without the need of cooling. We now conduct research to resolve the problems such as stabilization of sensor signals and simplification of the sensor structure for practical use.Development of a pressure sensor using a piezoelectric material thin filmKeywords : Combustion pressure sensors, mass-produced cars, aluminum nitride thin films, piezoelectric type, laminate structure [Translation from Synthesiology, Vol.5, No.3, p.162-170 (2012)]Morito Akiyama*, Tatsuo Tabaru and Kazushi KishiMeasurement Solution Research Center, AIST 807-1 Shuku-machi, Tosu 841-0052, Japan *E-mail : Original manuscript received January 27, 2012, Revisions received March 21, 2012, Accepted March 23, 2012

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