Patent ID: 8706385
Filing Date: 2014-04-22
Classification: F02D,F02M,Y02T

Abstract:
1. An exhaust gas recirculation device of an internal combustion engine, comprising: a low-pressure EGR passage that connects an exhaust passage and an intake passage; a high-pressure EGR passage that connects the exhaust passage upstream of a position of connection of the exhaust passage with the low-pressure EGR passage and the intake passage downstream of a position of connection of the intake passage with the low-pressure EGR passage; a low-pressure EGR valve that adjusts flow amount of exhaust gas that flows in the low-pressure EGR passage; a high-pressure EGR valve that adjusts the flow amount of exhaust gas that flows in the high-pressure EGR passage; an oxygen concentration acquisition device that is disposed in the intake passage downstream of a position of connection of the intake passage with the high-pressure EGR passage or in the exhaust passage upstream of the position of the connection of the exhaust passage with the low-pressure EGR passage, the oxygen concentration acquisition device acquires oxygen concentration of the gas flowing in the passage in which the oxygen concentration acquisition device is disposed; an EGR gas amount estimation device that, if a predetermined EGR gas amount estimation condition is satisfied, estimates the flow amount of exhaust gas flowing in at least one of the low-pressure EGR passage and the high-pressure EGR passage that is set as at least one estimation-object EGR passage, based on the oxygen concentration acquired by the oxygen concentration acquisition device at a timing at which the exhaust gas recirculated into the intake passage via the at least one estimation-object EGR passage reaches the oxygen concentration acquisition device; a storage device that stores a correspondence relation between the flow amount of the exhaust gas recirculated into the intake passage via the estimation-object EGR passage and opening degree of an EGR valve that is provided in the estimation-object EGR passage; and a learning device that amends the correspondence relation stored in the storage device based on a difference between the flow amount of exhaust gas estimated by the EGR gas amount estimation device and a target flow amount of exhaust gas that is to be recirculated via the estimation-object EGR passage when the predetermined EGR gas amount estimation condition is satisfied; wherein the internal combustion engine further includes a first throttle valve that is provided in the intake passage upstream of the position of the connection with the low-pressure EGR passage and that is capable of adjusting an intake amount, and a second throttle valve that is provided in the intake passage downstream of the position of the connection with the low-pressure EGR passage and upstream of the position of the connection with the high-pressure EGR passage and that is capable of adjusting the intake amount; the internal combustion engine is an object of application of a fuel-cut control in which supply of fuel to the internal combustion engine is stopped if a predetermined fuel-cut condition is satisfied; the predetermined EGR gas amount estimation condition is the predetermined fuel-cut condition; the low-pressure EGR passage and the high-pressure EGR passage are set as the estimation-object EGR passage; the oxygen concentration acquisition device is disposed in the exhaust passage upstream of the position of the connection with the low-pressure EGR passage; the EGR as amount estimation device, if the predetermined EGR gas amount estimation condition is satisfied, firstly fully closes the low-pressure EGR valve and the high-pressure EGR valve, and fully opens the first throttle valve and the second throttle valve, and then retains, as a first oxygen concentration, the oxygen concentration that is acquired by the oxygen concentration acquisition device at a time point at which a gas existing in the intake passage downstream of the position of the connection with the high-pressure EGR passage when the predetermined EGR gas amount estimation condition is satisfied reaches the oxygen concentration acquisition device, and retains, as a second oxygen concentration, the oxygen concentration that is acquired by the oxygen concentration acquisition device at a time point at which a gas existing in the intake passage upstream of the position of the connection with the high-pressure EGR passage and downstream of the position of the connection with the low-pressure EGR passage when the predetermined EGR gas amount estimation condition is satisfied reaches the oxygen concentration acquisition device, and estimates the flow amount of exhaust gas recirculated via the low-pressure EGR passage and the flow amount of exhaust gas recirculated via the high-pressure EGR passage when the predetermined EGR gas amount estimation condition is satisfied, based on the first oxygen concentration and the second oxygen concentration.