Addition-amount controller for exhaust gas purifying agent and exhaust emission control system

Abstract

In an addition-amount controller for an exhaust gas purifying agent to be used for an exhaust emission control system of an engine, one mode is executed based on satisfaction of an execution condition for each mode, from among a plurality of control modes. The control modes includes a purification control mode in which an addition amount of NH 3 or an additive serving as a generating source of the NH 3 is determined according to a predetermined parameter associated with an amount of NO x in the exhaust gas, and a storage control mode in which the addition amount is set to be larger than that in the purification control mode. When a rotation speed of an output shaft of the engine is determined to be decelerated from a higher speed state than an allowable level, the execution condition of the storage control mode is satisfied after a predetermined dissatisfaction time period from start of the deceleration.

1 . An addition-amount controller for an exhaust gas purifying agent, the controller being applied to an exhaust emission control system for purifying exhaust gas emitted from an internal combustion engine, the exhaust emission control system including a catalyst for promoting a specific exhaust gas purification reaction in a temperature range having a critical reaction temperature as a lower limit, and an addition valve for adding an additive of NH 3  (ammonia) or an additive serving as a generating source of the NH 3  to the catalyst itself or the exhaust gas on an upstream side with respect to the catalyst, the additive being adapted to purify NO x  (nitrogen oxides) in the exhaust gas by the exhaust gas purification reaction on the catalyst, the addition-amount controller being adapted to control an amount of addition by the addition valve, the catalyst having properties of storing NH 3  and further decreasing the critical reaction temperature as the amount of NH 3  storage is increased, the addition-amount controller comprising:
 mode selection means for selecting one mode to be executed at that time based on satisfaction of an execution condition for each mode, from among a plurality of control modes, the control modes including a purification control mode in which the addition amount by the addition valve is determined according to a predetermined parameter associated with an amount of NO x  in the exhaust gas, and a storage control mode in which the addition amount by the addition valve is set to be larger than that in the purification control mode; and   condition determining means for determining whether a rotation speed of an output shaft of the internal combustion engine is decelerated from a higher speed state than an allowable level,   wherein the execution condition of the storage control mode is set to be satisfied after a predetermined dissatisfaction time period from start of the deceleration when the condition determining means determines that the rotation speed is decelerated from the higher speed state.   
   
   
       2 . An addition-amount controller for an exhaust gas purifying agent, the controller being applied to an exhaust emission control system for purifying exhaust gas emitted from an internal combustion engine, the exhaust emission control system including a catalyst for promoting a specific exhaust gas purification reaction in a temperature range having a critical reaction temperature as a lower limit, and an addition valve for adding an additive of NH 3  (ammonia) or an additive serving as a generating source of the NH 3  to the catalyst itself or the exhaust gas on an upstream side with respect to the catalyst, the additive being adapted to purify NO x  (nitrogen oxides) in the exhaust gas by the exhaust gas purification reaction on the catalyst, the addition-amount controller being adapted to control an amount of addition by the addition valve, the catalyst having properties of storing NH 3  and further decreasing the critical reaction temperature as the amount of NH 3  storage is increased, the addition-amount controller comprising:
 mode selection means for selecting one mode to be executed at that time based on satisfaction of an execution condition for each mode, from among a plurality of control modes, the control modes including a purification control mode in which the addition amount by the addition valve is determined according to a predetermined parameter associated with an amount of NO x  in the exhaust gas, and a storage control mode in which the addition amount by the addition valve is set to be larger than that in the purification control mode; and   condition determining means for determining whether an amount of fluctuation in a load on the output shaft of the internal combustion engine toward a negative side is larger than an allowable level,   wherein the execution condition of the storage control mode is set to be satisfied after a predetermined dissatisfaction time period from the fluctuation when the condition determining means determines that the amount of fluctuation in the load toward the negative side is larger than the allowable level.   
   
   
       3 . An addition-amount controller for an exhaust gas purifying agent, the controller being applied to an exhaust emission control system for purifying exhaust gas emitted from an internal combustion engine, the exhaust emission control system including a catalyst for promoting a specific exhaust gas purification reaction in a temperature range having a critical reaction temperature as a lower limit, and an addition valve for adding an additive of NH 3  (ammonia) or an additive serving as a generating source of the NH 3  to the catalyst itself or the exhaust gas on an upstream side with respect to the catalyst, the additive being adapted to purify NO x  (nitrogen oxides) in the exhaust gas by the exhaust gas purification reaction on the catalyst, the addition-amount controller being adapted to control an amount of addition by the addition valve, the catalyst having properties of storing NH 3  and further decreasing the critical reaction temperature as the amount of NH 3  storage is increased, the addition-amount controller comprising:
 mode selection means for selecting one mode to be executed at that time based on satisfaction of an execution condition for each mode, from among a plurality of control modes, the control modes including a purification control mode in which the addition amount by the addition valve is determined according to a predetermined parameter associated with an amount of NO x  in the exhaust gas, and a storage control mode in which the addition amount by the addition valve is set to be larger than that in the purification control mode; and   condition determining means for determining whether an amount of fluctuation in the rotation speed of the output shaft of the internal combustion engine toward the negative side is larger than an allowable level,   wherein the execution condition of the storage control mode is set to be satisfied after a predetermined dissatisfaction time period from the fluctuation when the condition determining means determines that the amount of fluctuation in the rotation speed toward the negative side is larger than the allowable level.   
   
   
       4 . An addition-amount controller for an exhaust gas purifying agent, the controller being applied to an exhaust emission control system for purifying exhaust gas emitted from an internal combustion engine, the exhaust emission control system including a catalyst for promoting a specific exhaust gas purification reaction in a temperature range having a critical reaction temperature as a lower limit, and an addition valve for adding an additive of NH 3  (ammonia) or an additive serving as a generating source of the NH 3  to the catalyst itself or the exhaust gas on an upstream side with respect to the catalyst, the additive being adapted to purify NO x  (nitrogen oxides) in the exhaust gas by the exhaust gas purification reaction on the catalyst, the addition-amount controller being adapted to control an amount of addition by the addition valve, the catalyst having properties of storing NH 3  and further decreasing the critical reaction temperature as the amount of NH 3  storage is increased, the addition-amount controller comprising:
 mode selection means for selecting one mode to be executed at that time based on satisfaction of an execution condition for each mode, from among a plurality of control modes, the control modes including a purification control mode in which the addition amount by the addition valve is determined according to a predetermined parameter associated with an amount of NO x  in the exhaust gas, and a storage control mode in which the addition amount by the addition valve is set to be larger than that in the purification control mode; and   condition determining means for determining whether fuel cut is performed in the internal combustion engine,   wherein the execution condition of the storage control mode is set to be satisfied after a predetermined dissatisfaction time period from start of the fuel cut when the condition determining means determines that the fuel cut is performed.   
   
   
       5 . The addition-amount controller for an exhaust gas purifying agent according to  claim 1 , further comprising catalyst temperature determination means for determining whether the temperature of the catalyst at that time is lower than an allowable level,
 wherein the predetermined dissatisfaction time period has end timing at which the catalyst temperature determination means determines that the temperature of the catalyst is lower than the allowable level.   
   
   
       6 . The addition-amount controller for an exhaust gas purifying agent according to  claim 5 , wherein, when the temperature of the catalyst at that time is in a predetermined temperature range having the critical reaction temperature or a predetermined temperature smaller than the critical reaction temperature as an upper limit boundary value, the catalyst temperature determination means determines that the temperature of the catalyst at that time is lower than the allowable level. 
   
   
       7 . The addition-amount controller for an exhaust gas purifying agent, according to  claim 1 , wherein the execution condition of the purification control mode is set to be satisfied when the execution condition of the storage control mode is not satisfied, and
 wherein the mode selection means switches between two types of the control modes of the purification control mode and the storage control mode according to satisfaction or dissatisfaction of the execution condition.   
   
   
       8 . The addition-amount controller for an exhaust gas purifying agent, according to  claim 1 , further comprising:
 operating mode determination means for determining whether the operating mode of the internal combustion engine is a preset operating mode in which a load on the output shaft of the internal combustion engine is controlled to be decreased when the catalyst is at a high temperature exceeding the critical reaction temperature; and   prohibition means for prohibiting addition of NH 3  or the additive serving as the generating source of NH 3  by the addition valve to the catalyst in the amount of storing NH 3 , during a predetermined time period, when the operating mode determination means determines that the operating mode at that time is the preset operating mode.   
   
   
       9 . An addition-amount controller for an exhaust gas purifying agent, the controller being applied to an exhaust emission control system for purifying exhaust gas emitted from an internal combustion engine, the exhaust emission control system including a catalyst for promoting a specific exhaust gas purification reaction in a temperature range having a critical reaction temperature as a lower limit, and an addition valve for adding an additive of NH 3  (ammonia) or an additive serving as a generating source of the NH 3  to the catalyst itself or the exhaust gas on an upstream side with respect to the catalyst, the additive being adapted to purify NO x  (nitrogen oxides) in the exhaust gas by the exhaust gas purification reaction on the catalyst, the addition-amount controller being adapted to control an amount of addition by the addition valve, the catalyst having properties of storing NH 3  and further decreasing the critical reaction temperature as the amount of NH 3  storage is increased, the addition-amount controller comprising:
 operating mode determination means for determining whether the operating mode of the internal combustion engine is a preset operating mode in which a load on the output shaft of the internal combustion engine is controlled to be decreased when the catalyst is at a high temperature exceeding the critical reaction temperature; and   prohibition means for prohibiting addition of NH 3  or the additive serving as the generating source of NH 3  by the addition valve to the catalyst in the amount of storing NH 3 , only during a predetermined time period, when the operating mode determination means determines that the operating mode at that time is the preset operating mode.   
   
   
       10 . The addition-amount controller for an exhaust gas purifying agent according to  claim 1 , wherein the addition valve is adapted to inject and add a urea aqueous solution as the additive to the exhaust gas on an upstream side with respect to the catalyst. 
   
   
       11 . An exhaust emission control system comprising:
 the addition-amount controller as in  claim 10 ;   the catalyst and the addition valve; and   a urea water supply device for supplying the urea aqueous solution to the addition valve.