Exhaust emission control device for internal combustion engine

Abstract

Provided is an exhaust emission control device for an internal combustion engine capable of high-efficiency DPF regeneration processing. The exhaust emission control device comprises a DPF for collecting PMs in exhaust emissions, which is provided in an exhaust pipe of an engine, a fuel reformer for reforming fuel to manufacture a reducing gas containing hydrogen and carbon monoxide and supplying the reducing gas from an introduction port provided on the upstream side of the DPF of the exhaust pipe into the exhaust pipe, which is provided separately from the exhaust pipe, a catalyst converter for continuously oxidizing the reducing gas, which is provided between the introduction port and the DPF of the exhaust pipe, and a regeneration means for performing regeneration processing for burning the PMs collected by the DPF while the reducing gas is supplied into the exhaust pipe by the fuel reformer.

1 . An exhaust emission control device for an internal combustion engine including a particulate filter that is provided in an exhaust channel of the internal combustion engine, and collects particulates in exhaust, the device comprising:
 a fuel reformer that is provided separately from the exhaust channel, produces a reducing gas containing hydrogen and carbon monoxide by reforming fuel, and supplies the reducing gas from an inlet provided in the exhaust channel upstream of the particulate filter into the exhaust channel;   a catalytic converter that is provided in the exhaust channel between the inlet and the particulate filter, and continuously oxidizes the reducing gas; and   a regeneration means for executing a regeneration process to cause particulates collected in the particulate filter to be combusted while supplying reducing gas from the fuel reformer into the exhaust channel.   
     
     
         2 . An exhaust emission control device for an internal combustion engine including a particulate filter that is provided in an exhaust channel of the internal combustion engine, and collects particulates in exhaust, the device comprising:
 a fuel reformer that is provided separately from the exhaust channel, produces a reducing gas containing hydrogen and carbon monoxide by reforming fuel, and supplies the reducing gas from an inlet provided in the exhaust channel upstream of the particulate filter into the exhaust channel; and   a regeneration means for executing a regeneration process to cause particulates collected in the particulate filter to be combusted while supplying reducing gas from the fuel reformer into the exhaust channel, wherein a catalyst having an oxidative function of continuously oxidizing reducing gas is supported on the particulate filter.   
     
     
         3 . An exhaust emission control device for an internal combustion engine according to  claim 1 , wherein the catalytic converter contains at least one selected from the group consisting of platinum, palladium, and rhodium. 
     
     
         4 . An exhaust emission control device for an internal combustion engine according to  claim 2 , wherein the catalyst having the oxidative function contains at least one selected from the group consisting of palladium, rhodium, platinum, silver, and gold. 
     
     
         5 . An exhaust emission control device for an internal combustion engine according to  claim 3 , further comprising an oxygen concentration detection means for detecting or estimating an oxygen concentration of exhaust in the exhaust channel flowing into the particulate filter. 
     
     
         6 . An exhaust emission control device for an internal combustion engine according to  claim 5 , wherein the reducing gas produced by the fuel reformer contains more carbon monoxide than hydrogen. 
     
     
         7 . An exhaust emission control device for an internal combustion engine according to  claim 6 , wherein a temperature of the reducing gas supplied by the fuel reformer is higher than a temperature of exhaust flowing through the exhaust channel at the inlet. 
     
     
         8 . An exhaust emission control device for an internal combustion engine according to  claim 1 , further comprising:
 a target concentration setting means for setting an oxygen concentration target value of exhaust flowing into the particulate filter while executing the regeneration process by way of the regeneration means; and   
       an oxygen concentration control means for controlling the oxygen concentration of exhaust so as to match the oxygen concentration target value thus set by the oxygen concentration setting means, by adjusting at least one amount an intake air amount of the internal combustion engine, an exhaust recirculation ratio of the internal combustion engine, a fuel injection amount of the internal combustion engine, and a supply amount of reducing gas from the fuel reformer. 
     
     
         9 . An exhaust emission control device for an internal combustion engine according to  claim 8 , wherein the target concentration setting means sets the oxygen concentration target value based on at least one among a flow rate of exhaust flowing through the exhaust channel, a temperature of the exhaust, and a deposition amount of particulates deposited on the particulate filter. 
     
     
         10 . An exhaust emission control device for an internal combustion engine according to  claim 9 , wherein the target concentration setting means, in a case of the internal combustion engine being in an idle operating state, sets the oxygen concentration target value to be low compared to a case of not being in an idle operating state. 
     
     
         11 . An exhaust emission control device for an internal combustion engine according to  claim 10 , wherein the target concentration setting means, in a case of the internal combustion engine being in a deceleration operating state, sets the oxygen concentration target value to be low compared to a case of not being in a deceleration operating state. 
     
     
         12 . An exhaust emission control device for an internal combustion engine according to  claim 11 , wherein the fuel reformer produces reducing gas with carbon monoxide as a main component by way of a partial oxidation reaction of hydrocarbon fuel and air. 
     
     
         13 . An exhaust emission control device for an internal combustion engine including a particulate filter that is provided in an exhaust channel of the internal combustion engine, and collects particulates in exhaust, the device comprising:
 a regeneration means for executing a regeneration process to cause particulates collected in the particulate filter to be combusted; and   a fuel reformer that is provided separately from the exhaust channel, produces a reducing gas containing hydrogen and carbon monoxide by reforming fuel, and supplies the reducing gas from an inlet provided in the exhaust channel upstream of the particulate filter into the exhaust channel,   wherein the regeneration means includes a normal regeneration means that executes a regeneration process without employing reducing gas produced by the fuel reformer, and a heated regeneration means that allows a regeneration process employing reducing gas produced by the fuel reformer to be executed, and switches between executing the regeneration process by way of the normal regeneration means and executing the regeneration process by way of the heated regeneration means according to a predetermined condition.   
     
     
         14 . An exhaust emission control device for an internal combustion engine according to  claim 13 , wherein the reducing gas produced by the fuel reformer contains more carbon monoxide than hydrogen. 
     
     
         15 . An exhaust emission control device for an internal combustion engine according to  claim 13 , wherein the catalytic converter that continuously oxidizes reducing gas is provided in the exhaust channel between the inlet and the particulate filter. 
     
     
         16 . An exhaust emission control device for an internal combustion engine according to  claim 13 , further comprising a combustion judgment means for judging whether particulates deposited on the particulate filter are in a combusted state,
 wherein the regeneration means executes the regeneration process by way of the normal regeneration means in a case of having been judged that the particulate are in a combusted state, and executes the regeneration process by way of the heated regeneration means in a case of having been judged that the particulates are not in a combusted state.   
     
     
         17 . An exhaust emission control device for an internal combustion engine according to  claim 16 , further comprising an oxygen concentration detection means for detecting or estimating an oxygen concentration of exhaust in the exhaust channel on a downstream side of the particulate filter,
 wherein the combustion judgment means judges whether the particulates are in a combusted state based on the oxygen concentration thus detected or estimated by the oxygen concentration detection means.   
     
     
         18 . An exhaust emission control device for an internal combustion engine according to  claim 16 , further comprising a downstream exhaust temperature detection means for detecting or estimating an exhaust temperature in the exhaust channel on a downstream side of the particulate filter,
 wherein the combustion judgment means judges whether the particulates are in a combusted state based on the exhaust temperature thus detected or estimated by the downstream exhaust temperature detection means.   
     
     
         19 . An exhaust emission control device for an internal combustion engine according to  claim 16 , wherein the heated regeneration means reduces the intake air amount of the internal combustion engine, increases the exhaust recirculation ratio of the internal combustion engine, or sets the charge efficiency of the internal combustion engine to be small, compared to a case of performing the regeneration process by way of the normal regeneration means. 
     
     
         20 . An exhaust emission control device for an internal combustion engine according to  claim 19 , wherein the heated regeneration means includes a first heated regeneration means for executing a regeneration process while supplying reducing gas from the fuel reformer into the exhaust channel, and a second heated regeneration means for executing a regeneration process without supplying reducing gas from the fuel reformer into the exhaust channel, and switches between executing the regeneration process by way of the first heated regeneration means and executing the regeneration process by way of the second heated regeneration means according to a predetermined condition. 
     
     
         21 . An exhaust emission control device for an internal combustion engine according to  claim 20 , further comprising an upstream exhaust temperature detection means for detecting or estimating a temperature of exhaust in the exhaust channel on an upstream side of the particulate filter,
 wherein the heated regeneration means executes the regeneration process by way of the first heated regeneration means in a case of the temperature thus detected by the upstream exhaust temperature detection means being lower than a predetermined judgment value.   
     
     
         22 . An exhaust emission control device for an internal combustion engine according to  claim 20 , further comprising a filter temperature estimation means for estimating or detecting a temperature of the particulate filter,
 wherein the heated regeneration means executes the regeneration process by way of the first heated regeneration means in a case of the temperature thus estimated or detected by the filter temperature estimation means being lower than a predetermined judgment value.   
     
     
         23 . An exhaust emission control device for an internal combustion engine according to  claim 20 , further comprising a torque estimation means for estimating a generated torque of the internal combustion engine,
 wherein the heated regeneration means executes the regeneration process by way of the first regeneration means in a case of the generated torque thus estimated or detected by the torque estimation means being less than a predetermined judgment value.   
     
     
         24 . An exhaust emission control device for an internal combustion engine according to  claim 23 , wherein the torque estimation means estimates the generated torque of the internal combustion engine based on at least one among a revolution speed of the internal combustion engine, a fuel injection amount, and a fuel injection timing. 
     
     
         25 . An exhaust emission control device for an internal combustion engine according to  claim 20  further comprising a timing means for measuring an elapsed time since starting up the internal combustion engine,
 wherein the heated regeneration means executes the regeneration process by way of the first heated regeneration means in a case of the elapsed time thus measured by the timing means being less than a predetermined judgment value.   
     
     
         26 . An exhaust emission control device for an internal combustion engine, including a NOx purification catalyst that is provided in an exhaust channel of the internal combustion engine and that, with an air/fuel ratio of exhaust flowing through the exhaust channel as an exhaust air/fuel ratio, adsorbs or occludes NOx in exhaust when the exhaust air/fuel ratio is made lean, and reduces the NOx adsorbed or occluded when the exhaust air fuel ratio is made rich, and
 a particulate filter that is provided in the exhaust channel further upstream than the NOx purification catalyst, and that collects particulates in exhaust, the device comprising:   a fuel reformer that is provided separately from the exhaust channel, produces a reducing gas containing hydrogen and carbon monoxide by reforming fuel, and supplies the reducing gas from an inlet provided in the exhaust channel between the particulate filter and the NOx purification catalyst into the exhaust channel.   
     
     
         27 . An exhaust emission control device for an internal combustion engine according to  claim 26 , wherein the reducing gas produced by the fuel reformer is at a pressure higher than atmospheric pressure, and contains more carbon monoxide than hydrogen by volume ratio. 
     
     
         28 . An exhaust emission control device for an internal combustion engine according to  claim 26 , wherein a temperature of the reducing gas supplied by the fuel reformer is higher than a temperature of exhaust flowing through the exhaust channel at the inlet. 
     
     
         29 . An exhaust emission control device for an internal combustion engine according to  claim 26 , wherein oxygen is contained in the exhaust flowing through the exhaust channel when reducing gas from the fuel reformer is introduced into the exhaust channel. 
     
     
         30 . An exhaust emission control device for an internal combustion engine according to  claim 26  further comprising:
 a regeneration means for selectively executing a normal regeneration operation that raises the particulate filter in temperature to cause particulates collected in the particulate filter to combust, and a simultaneous regeneration operation that supplies reducing gas from the fuel reformer into the exhaust channel while executing the normal regeneration operation to purify SOx adsorbed to the NOx purification catalyst according to a predetermined condition.   
     
     
         31 . An exhaust emission control device for an internal combustion engine according to  claim 30 , further comprising an exhaust temperature control means for controlling a temperature of exhaust when executing the normal regeneration operation by adjusting at least one among an intake air amount and boost pressure. 
     
     
         32 . An exhaust emission control device for an internal combustion engine according to  claim 30 , wherein a catalytic converter having an oxidative function is provided in the exhaust channel on an upstream side of the particulate filter, and
 wherein the regeneration means executes post injection when executing the normal regeneration operation.   
     
     
         33 . An exhaust emission control device for an internal combustion engine according to  claim 30 , wherein a catalyst having an oxidative function is supported on the particulate filter, and
 wherein the regeneration means executes post injection when executing the normal regeneration operation.   
     
     
         34 . An exhaust emission control device for an internal combustion engine according to  claim 30 , further comprising a particulate deposition amount estimation means for estimating or detecting a particulate deposition amount of the particulate filter,
 wherein the regeneration means executes the normal regeneration operation or the simultaneous regeneration operation in response to the particulate deposition amount thus estimated or detected by the particulate deposition amount estimation means having become at least a predetermined first estimation judgment value.   
     
     
         35 . An exhaust emission control device for an internal combustion engine according to  claim 30 , further comprising:
 a catalyst temperature estimation means for estimating or detecting a temperature of the NOx purification catalyst; and   a SOx poisoning amount estimation means for estimating or detecting a SOx poisoning amount of the NOx purification catalyst,   wherein the regeneration means executes the simultaneous regeneration operation in response to the temperature thus estimated or detected by the catalyst temperature estimation means being at least a predetermined temperature judgment value, and the SOx poisoning amount thus estimated or detected by the SOx poisoning amount estimation means having become at least a predetermined first poisoning judgment value.   
     
     
         36 . An exhaust emission control device for an internal combustion engine according to  claim 35 , wherein the regeneration means ends execution of the simultaneous regeneration operation and executes the normal regeneration operation, in response to the SOx poisoning amount estimated or detected by the SOx poisoning amount estimation means having become smaller than a predetermined second poisoning judgment value. 
     
     
         37 . An exhaust emission control device for an internal combustion engine according to  claim 26 , further comprising:
 an oxygen concentration detection means for detecting an oxygen concentration of exhaust in the exhaust channel in a vicinity of the NOx purification catalyst; and   a supply amount control means for controlling a supply amount of reducing gas supplied from the fuel reformer into the exhaust channel, according to the oxygen concentration thus detected by the oxygen concentration detection means.   
     
     
         38 . An exhaust emission control device for an internal combustion engine according to  claim 26 , wherein the fuel reformer produces reducing gas by way of a partial oxidation reaction of hydrocarbon fuel and air. 
     
     
         39 . An exhaust emission control device for an internal combustion engine according to  claim 26 , wherein the internal combustion engine uses light oil as fuel, and combusts the fuel by way of compression ignition.