実車テストにおける図示平均有効圧計測の検討

抄録

In the development of automobile engines aimed at low pollution and high mileage, the monitoring of the combustion state of each cylinder is important. With combustion monitors, the pressure diagram is measured each degree of the crank angle (360 pulses/rev.), and parameters such as the indicated mean effective pressure, which directly indicates the work in each cycle, are broadly calculated. Although pressure diagram measurement is mainly performed in engine bench tests, recently, testing on actual vehicles or in a state close to an actual vehicle is increasingly being performed. On-Board tests differ from bench tests in that it is difficult to attach a crank angle sensor, and the crank angle signal of the computer for engine control (ECU) is considered to be taken as the sampling pulse. However, the interval of the ECU’s crank angle signal is wide at 6 degrees (60 pulses/rev.), and so a missing tooth is provided to detect the TDC position. This missing tooth is considered to be the cause of error in IMEP calculation. In this paper, we calculated IMEP from the pressure diagram that was generated at a sampling interval equivalent to the crank angle signal of the ECU, and investigated the calculation error on IMEP obtained from the pressure diagram that was measured at every degree. As a result of this, the calculation error changed due to the untoothed crank angle, and error increased the most when the missing tooth was in the vicinity of 30 degrees from TDC. Accordingly, it was found that an error-reducing measure was possible by setting the untoothed crank angle to an appropriate value. Upon performing verification while taking the pressure diagram mean value at the crank pulse before and after the untoothed crank angle as the pressure diagram of the untoothed crank angle as the countermeasure for this, we confirmed that the calculation error almost completely disappeared, independent of the missing tooth position.