초록 ▼

A control method of an EGR system of an engine capable of effectively performing an EGR control at a time of rapid acceleration. For this purpose, an intake air flow rate of the engine is obtained, and from a target EGR valve opening degree and a difference in pressure in front of and behind the EGR

A control method of an EGR system of an engine capable of effectively performing an EGR control at a time of rapid acceleration. For this purpose, an intake air flow rate of the engine is obtained, and from a target EGR valve opening degree and a difference in pressure in front of and behind the EGR valve, a virtual EGR gas flow rate is arithmetically operated. A virtual EGR rate is obtained from the intake air flow rate, the fuel flow rate and the virtual EGR gas flow rate, and a difference from or a ratio to a target EGR rate obtained from the engine speed and the fuel flow rate is obtained. A command EGR valve opening degree is obtained from an EGR valve opening degree correction coefficient obtained from the difference or the ratio, and the target EGR valve opening degree, whereby the EGR vale is driven.

대표청구항 ▼

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,

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. 2. A control method of an EGR system which has an EGR valve provided at an EGR passage for connecting an air supply circuit and an exhaust circuit of an engine, a bypass circuit for connecting said air supply circuit and said exhaust circuit to equalize air supply pressure and exhaust pressure, and a bypass valve provided at said bypass circuit, and recirculates part of an exhaust gas into said air supply circuit via said EGR valve, 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 a bypass valve opening degree correction coefficient in said operational state from relationship of the bypass 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 target bypass valve opening degree in said operational state from relationship of the target bypass valve opening degree, which is previously set, corresponding to the detected engine speed and the detected fuel flow rate; (i) obtaining a command bypass valve opening degree to be used for an actual control from the bypass valve opening degree correction coefficient in said operational state, and the target bypass valve opening degree in said operational state; and (j) operating an actuator for driving said bypass valve to attain the command bypass valve opening degree.