Exhaust gas reflux amount adjusting device

Abstract

There is provided an exhaust gas reflux amount adjusting device capable of reducing the possibility of deterioration of a catalyst causing an operation failure of an EGR valve. An EGR gas reflux amount restricting device 30 includes a catalyst deterioration degree calculating unit 31 for calculating a catalyst deterioration degree actual measurement Ddm based on detection results from an air fuel ratio sensor 21 and an oxygen sensor 22, a catalyst deterioration degree determining unit 32 for determining whether the catalyst deterioration degree actual measurement Ddm is equal to or greater than a first predetermined value, and an EGR gas reflux amount restriction instructing unit 33 for controlling an EGR valve 17 to restrict an EGR gas reflux amount when the catalyst deterioration degree determining unit 32 determines that the catalyst deterioration degree actual measurement Ddm is equal to or greater than the first predetermined value.

1 . An exhaust gas reflux amount adjusting device for an exhaust gas reflux apparatus for channeling back to an inlet pipe a part of exhaust gas from an internal combustion engine; said exhaust gas reflux amount adjusting device comprising:
 a catalyst that is deployed in an exhaust pipe and purifies the exhaust gas;   an EGR gas passage for connecting the downstream side of the catalyst deployed in the exhaust pipe to the inlet pipe,   an EGR valve that is deployed in the EGR gas passage and adjusts the EGR gas reflux amount to be channeled back to the inlet pipe;   an upstream oxygen sensor that is deployed on the upstream side of the catalyst deployed in the exhaust pipe and detects an amount of oxygen in the exhaust gas;   a downstream oxygen sensor that is deployed on the downstream side of the catalyst deployed in the exhaust pipe and detects the amount of oxygen in the exhaust gas; and   an EGR gas reflux amount restricting device for controlling the EGR valve, and   wherein the EGR gas reflux amount restricting device comprises:   a catalyst deterioration degree calculating unit for calculating a catalyst deterioration degree based on detection results from the upstream oxygen sensor and the downstream oxygen sensor; and   an EGR gas reflux amount restriction instructing unit for instructing the EGR valve to restrict the EGR gas reflux amount, and   wherein when the catalyst deterioration degree is equal to or greater than a first predetermined value, the EGR gas reflux amount restriction instructing unit controls the EGR valve to restrict the EGR gas reflux amount.   
     
     
         2 . An exhaust gas reflux amount adjusting device for an exhaust gas reflux apparatus for channeling back to an inlet pipe a part of exhaust gas from an internal combustion engine; said exhaust gas reflux amount adjusting device comprising:
 a catalyst that is deployed in an exhaust pipe and purifies the exhaust gas;   an EGR gas passage for connecting the downstream side of the catalyst deployed in the exhaust pipe to the inlet pipe;   an EGR valve that is deployed in the EGR gas passage and adjusts the EGR gas reflux amount to be channeled back to the inlet pipe;   an upstream oxygen sensor that is deployed on the upstream side of the catalyst deployed in the exhaust pipe and detects an amount of oxygen in the exhaust gas;   a downstream oxygen sensor that is deployed on the downstream side of the catalyst deployed in the exhaust pipe and detects an amount of oxygen in the exhaust gas; and   an EGR gas reflux amount restricting device for controlling the EGR valve, and   wherein the EGR gas reflux amount restricting device comprises:   a catalyst deterioration degree calculating unit for calculating a catalyst deterioration degree based on detection results from the upstream oxygen sensor and the downstream oxygen sensor; and   an EGR gas reflux amount restriction instructing unit for instructing the EGR valve to restrict the EGR gas reflux amount, and   wherein when the catalyst deterioration degree is equal to or greater than a second predetermined value, the EGR gas reflux amount restriction instructing unit controls the EGR valve to restrict the EGR gas reflux amount so that the higher the catalyst deterioration degree is, the smaller is the set reflux rate.   
     
     
         3 . An exhaust gas reflux amount adjusting device for an exhaust gas reflux apparatus for channeling back to an inlet pipe a part of exhaust gas from an internal combustion engine; said exhaust gas reflux amount adjusting device comprising:
 a catalyst that is deployed in an exhaust pipe and purifies the exhaust gas;   an EGR gas passage for connecting the downstream side of the catalyst deployed in the exhaust pipe to the inlet pipe;   an EGR valve that is deployed in the EGR gas passage and adjusts the EGR gas reflux amount to be channeled back to the inlet pipe;   an upstream oxygen sensor that is deployed on the upstream side of the catalyst deployed in the exhaust pipe and detects an amount of oxygen in the exhaust gas;   a downstream oxygen sensor that is deployed on the downstream side of the catalyst deployed in the exhaust pipe and detects an amount of oxygen in the exhaust gas;   an EGR gas reflux amount restricting device for controlling the EGR valve, and,   wherein the EGR gas reflux amount restricting device comprises:   a catalyst deterioration degree calculating/recording unit for calculating and recording a catalyst deterioration degree actual measurement value based on detection results from the upstream oxygen sensor and the downstream oxygen sensor; and   an EGR gas reflux amount restriction instructing unit for instructing the EGR valve to restrict the EGR gas reflux amount, and   wherein the EGR gas reflux amount restricting device records the catalyst deterioration degree actual measurement value for every driving cycle and calculates an average of the catalyst deterioration degree actual measurement in every previous driving cycle and catalyst deterioration degree measurement in the present driving cycle, and starts restriction of the EGR gas reflux amount if the average is equal to or greater than a first predetermined value, and cancels the restriction of the EGR gas reflux amount if the average is less than a second predetermined value.   
     
     
         4 . The exhaust as reflux amount adjusting device according to  claim 3 , wherein the restriction of the EGR gas reflux amount is performed by closing the EGR valve. 
     
     
         5 . The exhaust as reflux amount adjusting device according to  claim 3 , wherein the restriction of the EGR gas reflux amount is performed so that the higher the average or the catalyst deterioration degree actual measurement in the present driving cycle is, the smaller is the set reflux rate.