Device for internal combustion engine

Abstract

In the case of an internal combustion engine equipped with a turbocharger having a low-pressure EGR flow passage, an EGR rate inside a combustion chamber temporarily drops when accelerating from a high-EGR operation, resulting in the occurrence of knocking and poor emission due to a deviation in air-fuel ratio. A control device for an internal combustion engine according to the present invention is provided with: a turbocharger; a low-pressure EGR flow passage which connects an exhaust pipe disposed on the downstream side of a turbine of the turbocharger with an intake pipe disposed on the upstream side of a compressor of the turbocharger; a throttle valve for controlling the amount of gas flowing into cylinders; and an EGR valve which is disposed in the EGR flow passage in order to control an EGR flow rate. When acceleration is requested while operating at an EGR rate equal to or higher than a predetermined value, a control amount of the opening degree of the throttle valve with respect to the opening degree of an accelerator is set smaller than when acceleration is requested while operating at an EGR rate equal to or lower than the predetermined value.

Description

technical field [0001] The present invention relates to a control device for controlling a supercharged engine provided with a low-pressure EGR flow path. Background technique [0002] In recent years, attempts have been made to improve the efficiency of engines in order to reduce the fuel consumption of automobiles. One of the improvement techniques is high compression ratio. By increasing the compression ratio, the theoretical thermal efficiency of the internal combustion engine increases. On the other hand, developments regarding downsizing of engines are also being carried out as a measure to reduce fuel consumption. By reducing the size, pumping losses can be reduced and mechanical losses can be reduced. However, in order to maintain torque (output) in a downsized engine, it is necessary to increase the supercharging pressure. [0003] In highly boosted engine systems, in order to avoid abnormal combustion, an EGR system that returns a part of the exhaust gas to the...

AI Technical Summary

Problems solved by technology

Generally speaking, in the low-pressure EGR system, due to the long path from the confluence of exhaust gas and fresh air to the cylinder, the confluence is located upstream of the throttle valve, etc., there is such a transition during deceleration or acceleration operation. When the exhaust gas volume temporarily increases or decreases, the EGR rate cannot stably reach the target value.

Therefore, due to the transient mismatch of the EGR rate, there are problems of exhaust deterioration due to fluctuations in the air-fuel ratio, noise due to knocking, torque fluctuations, and worst case, misfires.

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