Control unit and control method for reductant supply device

Abstract

There are provided a reductant supply device and a control method for the reductant supply device, which can prevent heat damage of a reductant injection valve, and also prevent crystallization of urea solution due to excessive cooling of the solution reductant. The reductant supply device which is used in an exhaust gas purification device that injects and supplies, as a reductant, a urea solution to an exhaust gas upstream side of a reduction catalyst disposed in an exhaust gas passage of an internal combustion engine, and that reduces and purifies nitrogen oxides contained in exhaust gas using the reduction catalyst, the reductant supply device having a reductant injection valve that is fixed to an exhaust pipe on the exhaust gas upstream side of the reduction catalyst, includes: a cooling water circulation passage that circulates at least part of cooling water of the internal combustion engine to cool the reductant injection valve; flow rate control means for adjusting a flow rate of cooling water flowing through the cooling water circulation passage; temperature detection means for detecting a temperature of the reductant injection valve; and control means for controlling the flow rate control means based on the temperature of the reductant injection valve.

1 - 6 . (canceled) 
     
     
         7 . A reductant supply device which is used in an exhaust gas purification device that injects and supplies, as a reductant, a urea solution to an exhaust gas upstream side of a reduction catalyst disposed in an exhaust gas passage of an internal combustion engine, and that reduces and purifies nitrogen oxides contained in exhaust gas using the reduction catalyst, the reductant supply device having a reductant injection valve that is fixed to an exhaust pipe on the exhaust gas upstream side of the reduction catalyst, the reductant supply device comprising:
 a cooling water circulation passage that circulates at least part of cooling water of the internal combustion engine to cool the reductant injection valve;   flow rate control means for adjusting a flow rate of cooling water flowing through the cooling water circulation passage;   temperature detection means for detecting a temperature of the reductant injection valve; and   control means for controlling the flow rate control means based on the temperature of the reductant injection valve.   
     
     
         8 . The reductant supply device according to  claim 7 , wherein the control means controls the flow rate control means such that the temperature of the reductant injection valve is maintained at a temperature lower than a heat resistance temperature of the reductant injection valve. 
     
     
         9 . The reductant supply device according to  claim 7 , wherein the control means controls the flow rate control means such that the temperature of the reductant injection valve is maintained at a temperature equal to or higher than a boiling point of the urea solution. 
     
     
         10 . The reductant supply device according to  claim 8 , wherein the control means controls the flow rate control means such that the temperature of the reductant injection valve is maintained at a temperature equal to or higher than a boiling point of the urea solution. 
     
     
         11 . The reductant supply device according to  claim 7 , wherein the temperature detection means calculates a temperature at a tip of the reductant injection valve based on at least one of a temperature of the exhaust gas, a flow rate of the exhaust gas, a temperature of the liquid reductant, a temperature of the cooling water, an outside air temperature, and an injection supply amount from the reductant injection valve. 
     
     
         12 . The reductant supply device according to  claim 8 , wherein the temperature detection means calculates a temperature at a tip of the reductant injection valve based on at least one of a temperature of the exhaust gas, a flow rate of the exhaust gas, a temperature of the liquid reductant, a temperature of the cooling water, an outside air temperature, and an injection supply amount from the reductant injection valve. 
     
     
         13 . The reductant supply device according to  claim 9 , wherein the temperature detection means calculates a temperature at a tip of the reductant injection valve based on at least one of a temperature of the exhaust gas, a flow rate of the exhaust gas, a temperature of the liquid reductant, a temperature of the cooling water, an outside air temperature, and an injection supply amount from the reductant injection valve. 
     
     
         14 . The reductant supply device according to  claim 10 , wherein the temperature detection means calculates a temperature at a tip of the reductant injection valve based on at least one of a temperature of the exhaust gas, a flow rate of the exhaust gas, a temperature of the liquid reductant, a temperature of the cooling water, an outside air temperature, and an injection supply amount from the reductant injection valve. 
     
     
         15 . The reductant supply device according to  claim 7 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         16 . The reductant supply device according to  claim 8 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         17 . The reductant supply device according to  claim 9 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         18 . The reductant supply device according to  claim 10 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         19 . The reductant supply device according to  claim 11 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         20 . The reductant supply device according to  claim 12 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         21 . The reductant supply device according to  claim 13 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         22 . The reductant supply device according to  claim 14 , wherein if the cooling water circulation passage, the flow rate control means and the control means are respectively referred to as a first cooling water circulation passage, first flow rate control means and first control means, the reductant supply device further comprising:
 a second cooling water circulation passage that circulates at least part of the cooling water of the internal combustion engine in order to adjust a temperature of the urea solution in a storage tank that stores the urea solution;   second flow rate control means for adjusting a flow rate of the cooling water that flows through the second cooling water circulation passage; and   second control means for controlling the second flow rate control means based on the temperature of the urea solution in the storage tank.   
     
     
         23 . A control method for a reductant supply device which is used in an exhaust gas purification device that injects and supplies a liquid reductant to an exhaust gas upstream side of a reduction catalyst disposed in an exhaust gas passage of an internal combustion engine, and that reduces and purifies nitrogen oxides contained in exhaust gas using the reduction catalyst, the reductant supply device having a reductant injection valve that is fixed to an exhaust pipe on the exhaust gas upstream side of the reduction catalyst, the control method comprising:
 cooling the reductant injection valve by circulating at least part of cooling water of the internal combustion engine;   detecting a temperature of the reductant injection valve; and   controlling a flow rate of the cooling water such that a temperature of a fuel control valve is maintained in a predetermined range.