Exhaust emission control device

Abstract

An exhaust emission control device includes an exhaust pipe, a catalyst in the pipe promoting reduction reaction of nitrogen oxide in exhaust air, a supply device for supplying an additive agent to an upstream side of the catalyst, a temperature detecting device for detecting exhaust air temperature, and a control device for controlling the supply device to regulate the additive agent amount supplied into the pipe. The control device stops supply of the additive agent when exhaust air temperature is lower than generation temperature needed to generate the reducing agent from the additive agent, and supplies the additive agent when exhaust air temperature is equal to or higher than generation temperature. When a predetermined time has elapsed after a start of supply of the additive agent, the control device reduces the additive agent amount supplied, compared to the additive agent amount supplied before the predetermined time has elapsed.

1 . An exhaust emission control device for generating a reducing agent from an additive agent by use of heat of exhaust air discharged from an internal combustion engine and for reducing nitrogen oxide included in the exhaust air by the reducing agent, the device comprising:
 an exhaust pipe defining a passage for the exhaust air;   a catalyst disposed in the exhaust pipe, the catalyst being capable of promoting reduction reaction of the nitrogen oxide in the exhaust air;   a supply means for supplying the additive agent to an upstream side of the catalyst in a flow direction of the exhaust air;   a temperature detecting means for detecting temperature of the exhaust air flowing through the exhaust pipe; and   a control means for controlling the supply means so as to regulate an amount of the additive agent supplied into the exhaust pipe, wherein:
 the control means stops the supply of the additive agent when the temperature of the exhaust air detected by the temperature detecting means is lower than a generation temperature that is needed to generate the reducing agent from the additive agent, and supplies the additive agent when the temperature of the exhaust air is equal to or higher than the generation temperature; and 
 when a predetermined time has elapsed after a start of the supply of the additive agent, the control means reduces the amount of the additive agent supplied, as compared to the amount of the additive agent supplied before the predetermined time has elapsed. 
   
   
   
       2 . An exhaust emission control device for generating a reducing agent from an additive agent by use of heat of exhaust air discharged from an internal combustion engine and for reducing nitrogen oxide included in the exhaust air by the reducing agent, the device comprising:
 an exhaust pipe defining a passage for the exhaust air;   a catalyst disposed in the exhaust pipe, the catalyst being capable of promoting reduction reaction of the nitrogen oxide in the exhaust air;   a supply means for supplying the additive agent to an upstream side of the catalyst in a flow direction of the exhaust air;   a temperature detecting means for detecting temperature of the exhaust air flowing through the exhaust pipe;   a reducing agent detecting means disposed on a downstream side of the catalyst in the flow direction of the exhaust air for detecting the reducing agent; and   a control means for controlling the supply means so as to regulate an amount of the additive agent supplied into the exhaust pipe, wherein:
 the control means stops the supply of the additive agent when the temperature of the exhaust air detected by the temperature detecting means is lower than a generation temperature that is needed to generate the reducing agent from the additive agent, and supplies the additive agent when the temperature of the exhaust air is equal to or higher than the generation temperature; and 
 when the reducing agent that is equal to or larger than a predetermined value is detected by the reducing agent detecting means after a start of the supply of the additive agent, the control means reduces the amount of the additive agent supplied, as compared to the amount of the additive agent supplied before the reducing agent that is equal to or larger than the predetermined value is detected. 
   
   
   
       3 . An exhaust emission control device for generating a reducing agent from an additive agent by use of heat of exhaust air discharged from an internal combustion engine and for reducing nitrogen oxide included in the exhaust air by the reducing agent, the device comprising:
 an exhaust pipe defining a passage for the exhaust air;   a catalyst disposed in the exhaust pipe, the catalyst being capable of promoting reduction reaction of the nitrogen oxide in the exhaust air;   a supply means for supplying the additive agent to an upstream side of the catalyst in a flow direction of the exhaust air;   a temperature detecting means for detecting temperature of the exhaust air flowing through the exhaust pipe; and   a control means for controlling the supply means so as to regulate an amount of the additive agent supplied into the exhaust pipe, wherein:
 the control means stops the supply of the additive agent when the temperature of the exhaust air detected by the temperature detecting means is lower than a generation temperature that is needed to generate the reducing agent from the additive agent, and supplies the additive agent when the temperature of the exhaust air is equal to or higher than the generation temperature; and 
 when the temperature of the exhaust air is equal to or higher than a predetermined temperature that is higher than the generation temperature, the control means reduces the amount of the additive agent supplied, as compared to the amount of the additive agent supplied when the temperature of the exhaust air is equal to or higher than the generation temperature and is lower than the predetermined temperature. 
   
   
   
       4 . An exhaust emission control device for generating a reducing agent from an additive agent by use of heat of exhaust air discharged from an internal combustion engine and for reducing nitrogen oxide included in the exhaust air by the reducing agent, the device comprising:
 an exhaust pipe defining a passage for the exhaust air;   a catalyst disposed in the exhaust pipe, the catalyst being capable of promoting reduction reaction of the nitrogen oxide in the exhaust air;   a supply means for supplying the additive agent to an upstream side of the catalyst in a flow direction of the exhaust air;   a temperature detecting means for detecting temperature of the exhaust air flowing through the exhaust pipe; and   a control means for controlling the supply means so as to regulate an amount of the additive agent supplied into the exhaust pipe, wherein:
 the control means stops the supply of the additive agent when the temperature of the exhaust air detected by the temperature detecting means is lower than a generation temperature that is needed to generate the reducing agent from the additive agent, and supplies the additive agent when the temperature of the exhaust air is equal to or higher than the generation temperature; and 
 when at least one of the following conditions is satisfied, the control means reduces the amount of the additive agent supplied, as compared to the amount of the additive agent supplied before the one of the following conditions is satisfied:
 the temperature of the exhaust air is equal to or higher than a predetermined temperature that is higher than the generation temperature; and 
 a predetermined time has elapsed after a start of the supply of the additive agent.