| 摘要 |
PURPOSE:To prevent deterioration in the performance of an internal combustion engine, by reducing error in the control of EGR (exhaust-gas recirculation) ratio by switching feedback control of the EGR ratio substantially to open-loop control in the operational range of engine where the amount of recirculated exhaust gas is small. CONSTITUTION:An EGR control circuit 12 controls the openings of a throttle valve 6 and an EGR valve 7 in response to the output signals of an engine load sensor 17 and a engine speed sensor 18, so as to obtain a prescribed EGR ratio suited for the operational conditions of engine. Further, in order to correct the EGR ratio, output signals of a sensor 21 for detecting the temperature of recirculated exhaust gas and a sensor 22 for detecting the temperature of mixture gas are also furnished to the control circuit 12. The control circuit 12 effects feedback control on the EGR ratio on the basis of these signals. Here, arrangement is such that control of the EGR ratio is switched from feedback control to open-loop control in the operational range of engine where the error in measurement of the EGR ratio tends to increase, i.e., where the opening of the EGR valve 7 is small, so as to reduce the error in control of the EGR ratio. |
