Exhaust gas purification device for internal combustion engine

Abstract

An auxiliary agent supply means ( 32, 58 ) is provided to supply, upstream of an exhaust gas purification means ( 24, 56, 78 ), an auxiliary agent for maintaining the exhaust gas purifying function of the exhaust gas purification means ( 24, 56, 78 ). A control means ( 38 ) for controlling the auxiliary agent supply means ( 32, 58 ), thereby regulating the amount of the auxiliary agent supplied includes a standard supply quantity determination section ( 40, 50, 68, 86 ) for determining standard supply quantity of the auxiliary agent required to maintain the exhaust gas purifying function, a target supply quantity determination section ( 42, 52, 70, 88 ) for determining target supply quantity of the auxiliary agent, by correcting the standard supply quantity on the basis of exhaust pressure, and a supply control section ( 44, 54, 72, 90 ) for controlling the auxiliary agent supply means to supply the auxiliary agent in the target supply quantity.

1 . An exhaust gas purification device for an internal combustion engine, comprising:
 an exhaust gas purification means provided in an exhaust passage of the internal combustion engine for purifying exhaust gas exhausted from the internal combustion engine,   an auxiliary agent supply means for supplying an auxiliary agent for maintaining the exhaust gas purifying function of the exhaust gas purification means, into the exhaust passage, upstream of the exhaust gas purification means,   a variation factor parameter detection means for detecting the value of a variation factor parameter which causes variations in the amount of the auxiliary agent supplied, and   a control means for controlling the auxiliary agent supply means, thereby regulating the amount of the auxiliary agent supplied into the exhaust passage, wherein   the control means includes   a standard supply quantity determination section for determining standard supply quantity of the auxiliary agent required to maintain the exhaust gas purifying function of the exhaust gas purification means;   a target supply quantity determination section for determining target supply quantity of the auxiliary agent, by correcting the standard supply quantity determined by the standard supply quantity determination section, on the basis of the value of the parameter detected by the variation factor parameter detection means; and   a supply control section for controlling the auxiliary agent supply means to supply the auxiliary agent in the target supply quantity determined by the target supply quantity determination section.   
   
   
       2 . The exhaust gas purification device for the internal combustion engine according to  claim 1 , wherein the variation factor parameter detection means includes an exhaust pressure detection means for detecting exhaust pressure in the exhaust passage, upstream of the exhaust gas purification means, and the variation factor parameter is the exhaust pressure. 
   
   
       3 . The exhaust gas purification device for the internal combustion engine according to  claim 2 , wherein
 the auxiliary agent supply means is designed to supply and stop supplying the auxiliary agent by opening and closing a solenoid valve, and   the supply control section performs duty cycle control of opening and closing of the solenoid valve so as to supply the auxiliary agent into the exhaust passage in the target supply quantity.   
   
   
       4 . The exhaust gas purification device for the internal combustion engine according to  claim 3 , wherein the supply control section performs the duty cycle control of opening and closing of the solenoid valve such that the duty cycle becomes greater as the exhaust pressure increases. 
   
   
       5 . The exhaust gas purification device for the internal combustion engine according to  claim 1 , wherein the variation factor parameter detection means includes an auxiliary agent temperature detection means for detecting the temperature of the auxiliary agent, and the variation factor parameter is the auxiliary agent temperature. 
   
   
       6 . The exhaust gas purification device for the internal combustion engine according to  claim 5 , wherein the variation factor parameter detection means further includes an exhaust pressure detection means for detecting exhaust pressure in the exhaust passage, upstream of the exhaust gas purification means, and the target supply quantity determination section determines the target supply quantity by correcting the standard supply quantity on the basis of the exhaust pressure detected by the exhaust pressure detection means and the auxiliary agent temperature detected by the auxiliary agent temperature detection means. 
   
   
       7 . The exhaust gas purification device for the internal combustion engine according to  claim 6 , wherein
 the auxiliary agent supply means is designed to supply and stop supplying the auxiliary agent by opening and closing a solenoid valve, and   the supply control section performs duty cycle control of opening and closing of the solenoid valve so as to supply the auxiliary agent into the exhaust passage in the target supply quantity.   
   
   
       8 . The exhaust gas purification device for the internal combustion engine according to  claim 7 , wherein the supply control section performs the duty cycle control of opening and closing of the solenoid valve such that a duty cycle for the duty cycle control becomes smaller as the auxiliary agent temperature increases. 
   
   
       9 . The exhaust gas purification device for the internal combustion engine according to  claim 1 , wherein the exhaust gas purification means is an NOx adsorption catalyst designed to adsorb NOx in exhaust gas that enters into the NOx adsorption catalyst when the air-fuel ratio of the exhaust gas is lean, and release and reduce the adsorbed NOx when the air-fuel ratio of the exhaust gas is rich,
 the auxiliary agent supply means supplies fuel as the auxiliary agent into the exhaust passage, upstream of the NOx adsorption catalyst, and   the standard supply quantity determination means determines standard supply quantity of the fuel required to cause the NOx adsorption catalyst to release and reduce the NOx adsorbed by the NOx adsorption catalyst.   
   
   
       10 . The exhaust gas purification device for the internal combustion engine according to  claim 1 , wherein
 the exhaust gas purification means is an NOx adsorption catalyst designed to adsorb NOx in exhaust gas that enters into the NOx adsorption catalyst when the air-fuel ratio of the exhaust gas is lean, and release and reduce the adsorbed NOx when the air-fuel ratio of the exhaust gas is rich,   the auxiliary agent supply means supplies fuel as the auxiliary agent into the exhaust passage, upstream of the NOx adsorption catalyst, and   the standard supply quantity determination means determines standard supply quantity of the fuel required to restore the NOx adsorption capacity of the NOx adsorption catalyst that has lowered due to sulfur component adsorbed from the exhaust gas by the NOx adsorption catalyst, by causing the NOx adsorption catalyst to release the adsorbed sulfur component.   
   
   
       11 . The exhaust gas purification device for the internal combustion engine according to  claim 1 , wherein
 the exhaust gas purification means is a NOx catalyst designed to selectively reduce NOx in the exhaust gas,   the auxiliary agent supply means supplies urea water as the auxiliary agent into the exhaust passage, upstream of the NOx catalyst, and   the standard supply quantity determination means determines standard supply quantity of the urea water required for the NOx catalyst to selectively reduce the NOx in the exhaust gas.   
   
   
       12 . The exhaust gas purification device for the internal combustion engine according to  claim 1 , wherein
 the exhaust gas purification means is a particulate filter designed to trap particulate matter in the exhaust gas,   the auxiliary agent supply means supplies fuel as the auxiliary agent into the exhaust passage, upstream of the particulate filter, and   the standard supply quantity determination means determines standard supply quantity of the fuel required to regenerate the particulate filter by burning off particulate matter trapped by the particulate filter.   
   
   
       13 . The exhaust gas purification device for the internal combustion engine according to  claim 2 , further comprising an exhaust throttle disposed in the exhaust passage to regulate exhaust gas flow rate in the exhaust passage, wherein
 the exhaust pressure detection means detects the exhaust pressure in the exhaust passage, upstream of the exhaust throttle, and   the auxiliary agent supply means is disposed upstream of the exhaust throttle.   
   
   
       14 . The exhaust gas purification device for the internal combustion engine according to  claim 6 , further comprising an exhaust throttle disposed in the exhaust passage to regulate exhaust gas flow rate in the exhaust passage, wherein
 the exhaust pressure detection means detects the exhaust pressure in the exhaust passage, upstream of the exhaust throttle, and   the auxiliary agent supply means is disposed upstream of the exhaust throttle.