Controller of exhaust gas purifying agent and exhaust gas purifying system

Abstract

A quantity of a purifying agent that is added into an exhaust gas, reacts with a specific component in the exhaust gas, and purifies the exhaust gas is controlled. A controller is configured so as to be provided with a program to carry out either increment control for increasing the quantity of urea water sequentially or decrement control for decreasing the quantity of the urea water sequentially while monitoring, in NOx in the exhaust gas, the quantity not purified through the reaction with NH 3 (the discharged NOx quantity); and switch the quantity control from the currently adopted increment or decrement control to the other increment or decrement control in response to whether the feature of the change of the discharged NOx quantity comes to a predetermined feature.

1 . A controller of an exhaust gas purifying agent to control a quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a quantity control means for carrying out a first quantity control for increasing or decreasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring, in the specific component in the exhaust gas, a quantity of the unpurified specific component corresponding to a quantity not purified through a reaction with the purifying agent, and carrying out a second quantity control for decreasing or increasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring the quantity of the unpurified specific component, wherein   when a feature of the change of the unpurified specific component quantity comes to a predetermined feature by an implementation of the first quantity control, the first quantity control is stopped, and then, contrary to the first quantity control, the quantity control means carries out the second quantity control, and   when the feature of the change of the unpurified specific component quantity comes to a predetermined feature by an implementation of the second quantity control, the second quantity control is stopped.   
   
   
       2 . A controller of an exhaust gas purifying agent according to  claim 1 , wherein
 either the first quantity control or the second quantity control is a control to increase the quantity of the purifying agent sequentially at a predetermined rate and to stop when the quantity of the unpurified specific component exceeds an allowable range and does not change any more even when the quantity is increased; and   the other quantity control is the control to decrease the quantity of the purifying agent sequentially at a predetermined rate and to stop when the quantity of the unpurified specific component exceeds an allowable range and changes by decreasing the quantity.   
   
   
       3 . A controller of an exhaust gas purifying agent according to  claim 1 , wherein
 the quantity control means carries out the first quantity control and the second quantity control alternately repeatedly while predetermined conditions are satisfied by carrying out the first quantity control again after stopping the second quantity control.   
   
   
       4 . A controller of an exhaust gas purifying agent according to  claim 1 , wherein
 the quantity control means monitors the quantity of the unpurified specific component on the basis of an actually measured quantity of the unpurified specific component.   
   
   
       5 . A controller of an exhaust gas purifying agent according to  claim 1 , comprising
 an optimum quantity acquisition means for acquiring the quantity of the purifying agent when the second quantity control is stopped.   
   
   
       6 . A controller of an exhaust gas purifying agent according to  claim 5 , further comprising
 a means for storing the purifying agent quantity acquired by the optimum quantity acquisition means in a predetermined memory that can retain data in a nonvolatile manner.   
   
   
       7 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a quantity control means for carrying out a first quantity control for increasing or decreasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring, in the purifying agent, the quantity of the unreacted purifying agent corresponding to the quantity not consumed through the reaction with the specific component, and carrying out a second quantity control for decreasing or increasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring the quantity of the unreacted purifying agent, wherein   when a feature of the change of the unreacted purifying agent quantity comes to a predetermined feature by an implementation of the first quantity control, the first quantity control is stopped, and then, contrary to the first quantity control, the quantity control means carries out the second quantity control, and   when the feature of the change in the unreacted purifying agent quantity comes to a predetermined feature by an implementation of the second quantity control, the second quantity control is stopped.   
   
   
       8 . A controller of an exhaust gas purifying agent according to  claim 7 , wherein
 either the first quantity control or the second quantity control is a control to decrease the quantity of the purifying agent sequentially at a predetermined rate, and to stop when the quantity of an unreacted purifying agent exceeds an allowable range and does not change any more even when the quantity is decreased, and   the other quantity control is the control to increase the quantity of the purifying agent sequentially at a predetermined rate and to stop when the quantity of the unpurified specific component exceeds an allowable range and changes by the increase of the quantity.   
   
   
       9 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a quantity control means for carrying out a first quantity control for increasing or decreasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring, in the purifying agent, the quantity of the discharged purifying agent corresponding to the quantity discharged in air on the downstream where the purifying agent reacts with the specific component, and carrying out a second quantity control for decreasing or increasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring the quantity of the unreacted purifying agent, wherein   when a feature of the change of the unreacted purifying agent quantity comes to a predetermined feature by an implementation of the first quantity control, the first quantity control is stopped, and then, contrary to the first quantity control, the quantity control means carries out the second quantity control; and   when a feature of the change of the unreacted purifying agent quantity comes to a predetermined feature by an implementation of the second quantity control, the second quantity control is stopped.   
   
   
       10 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a practice control switching means for carrying out either a first quantity control for increasing the quantity of the purifying agent sequentially at a predetermined rate or a second quantity control for decreasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring, in the specific component in the exhaust gas, the quantity of the unpurified specific component corresponding to the quantity not purified through a reaction with the purifying agent; and switching the quantity control from the currently adopted first or second quantity control to the other first or second quantity control in response to whether a feature of the change in the unpurified specific component quantity comes to a predetermined feature.   
   
   
       11 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a practice control switching means for carrying out either a first quantity control for increasing the quantity of the purifying agent sequentially at a predetermined rate or a second quantity control for decreasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring, in the purifying agent, the quantity of the unreacted purifying agent corresponding to the quantity not consumed through a reaction with the specific component; and switching the quantity control from the currently adopted first or second quantity control to the other first or second quantity control in response to whether a feature of the change in the unreacted purifying agent quantity comes to a predetermined feature.   
   
   
       12 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a practice control switching means for carrying out either a first quantity control for increasing the quantity of the purifying agent sequentially at a predetermined rate or a second quantity control for decreasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring, in the purifying agent, the quantity of the discharged purifying agent corresponding to the quantity discharged in air on the downstream where the purifying agent reacts with the specific component; and switching the quantity control from the currently adopted first or second quantity control to the other first or second quantity control in response to whether a feature of the change in the discharged purifying agent quantity comes to a predetermined feature.   
   
   
       13 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a quantity control means for carrying out quantity control for increasing or decreasing the quantity of the purifying agent sequentially from a predetermined initial value at a predetermined rate while monitoring, in the specific component in the exhaust gas, the quantity of the unpurified specific component corresponding to the quantity not purified through the reaction with the purifying agent; and stopping the quantity control when a feature of the change in the unpurified specific component quantity comes to a predetermined feature by an implementation of the quantity control.   
   
   
       14 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a quantity control means for carrying out a quantity control for increasing or decreasing the quantity of the purifying agent sequentially from a predetermined initial value at a predetermined rate while monitoring, in the purifying agent, the quantity of the unreacted purifying agent corresponding to the quantity not consumed through the reaction with the specific component; and stopping the quantity control when the feature of the change of the unpurified specific component quantity comes to a predetermined feature by an implementation of the quantity control.   
   
   
       15 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a quantity control means for carrying out a quantity control for increasing or decreasing the quantity of the purifying agent sequentially from a predetermined initial value at a predetermined rate while monitoring, in the purifying agent, the quantity of the discharged purifying agent corresponding to the quantity discharged in air on the downstream where the purifying agent reacts with the specific component; and stopping the quantity control when the feature of the change of the unpurified specific component quantity comes to a predetermined feature by an implementation of the quantity control.   
   
   
       16 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a means for detecting the quantity of the purifying agent with which the quantity of the unpurified specific component is minimum and also the quantity of the unreacted purifying agent is minimum by monitoring at least one of, in the specific component in the exhaust gas, the quantity of the unpurified specific component corresponding to the quantity not purified through a reaction with the purifying agent and, in the purifying agent, the quantity of the unreacted purifying agent corresponding to the quantity not consumed through the reaction with the specific component.   
   
   
       17 . A controller of an exhaust gas purifying agent to control the quantity of a purifying agent added into an exhaust gas to purify the exhaust gas by reacting with a specific component in the exhaust gas, the controller comprising:
 a means for detecting the quantity of the purifying agent with which the quantity of the unpurified specific component is minimum and also the quantity of the discharged purifying agent is minimum by monitoring at least one of, in the specific component in the exhaust gas, the quantity of the unpurified specific component corresponding to the quantity not purified through the reaction with the purifying agent and, in the purifying agent, the quantity of the discharged purifying agent corresponding to the quantity discharged in air on the downstream where the purifying agent reacts with the specific component.   
   
   
       18 . A quantity controller of an exhaust gas purifying agent according to  claim 1 , wherein the specific component is nitrogen oxide (NOx) and the purifying agent is ammonia (NH 3 ) produced by being added in the form of a urea aqueous solution and decomposing in an exhaust gas. 
   
   
       19 . An exhaust gas purifying system comprising:
 a catalyst to accelerate specific exhaust gas purifying reaction;   a purifying agent feed valve to add a purifying agent to purify an exhaust gas by carrying out the exhaust gas purifying reaction with a specific component in the exhaust gas on the catalyst or an additive acting as the source of the purifying agent to the catalyst itself or the exhaust gas on the upstream side of the catalyst; and   a practice control switching means for carrying out either first quantity control for increasing the quantity of the purifying agent sequentially at a predetermined rate or second quantity control for decreasing the quantity of the purifying agent sequentially at a predetermined rate while monitoring, in the specific component in the exhaust gas, the quantity of the unpurified specific component corresponding to the quantity not purified through the exhaust gas purifying reaction, and switching the quantity control from the currently adopted first or second quantity control to the other first or second quantity control in response to whether a feature of the change of the unpurified specific component quantity comes to a predetermined feature.   
   
   
       20 . An exhaust gas purifying system according to  claim 19 , wherein
 the specific component is nitrogen oxide (NOx),   the additive is a urea aqueous solution, and   the catalyst accelerates NOx reduction reaction to reduce NOx through ammonia (NH 3 ) produced by decomposing the urea aqueous solution as the exhaust gas purifying reaction.