Patent ID: 6868329
Filing Date: 2005-03-15
Classification: F02B,F02D,F02M,Y02T

Abstract:
1. A control method of an EGR system for recirculating part of an exhaust gas into an air supply circuit via an EGR valve provided at an EGR passage for connecting said air supply circuit and an exhaust circuit of an engine, comprising the steps of: (a) obtaining, at each predetermined time interval, a flow rate of air, which is taken into the engine in an operational state at the time; (b) detecting an engine speed, a fuel flow rate, and a difference in pressure in front of and behind the EGR valve, in said operational state; (c) obtaining a target EGR valve opening degree in said operational state from relationship of the target EGR valve opening degree, which is previously set, corresponding to the detected engine speed and the detected fuel flow rate; (d) obtaining a virtual EGR gas flow rate from the detected pressure difference and the target EGR valve opening degree in said operational state; (e) obtaining a virtual EGR rate from the obtained air flow rate, the detected fuel flow rate, and the virtual EGR gas flow rate; (f) obtaining a target EGR rate in said operational state from relationship of the target EGR rate, which is previously set, corresponding to the detected engine speed and the detected fuel flow rate; (g) obtaining an EGR valve opening degree correction coefficient in said operational state from relationship of the EGR valve opening degree correction coefficient, which is previously set, corresponding to a difference or a ratio of the virtual EGR rate and the target EGR rate; (h) obtaining a command EGR valve opening degree to be used for an actual control from the EGR valve opening degree correction coefficient in said operational state, and the target EGR valve opening degree in said operational state; and (i) operating an actuator for driving said EGR valve to attain the command EGR valve opening degree.