Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2002-06-20
2004-12-14
Tran, Binh Q. (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S295000, C060S304000, C060S305000, C060S311000
Reexamination Certificate
active
06829891
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a technique of regulating and reducing particulates included in exhaust gases from an internal combustion engine.
BACKGROUND ART
The exhaust gas from internal combustion engines, especially Diesel engines, includes carbon-containing particulates like black smoke (soot), and there is a high demand of reducing the total emission of the carbon-containing particulates, in order to prevent further air pollution. There is a similar demand in direct injection gasoline engines where gasoline is directly injected into a combustion chamber, since the carbon-containing particulates may be discharged with the exhaust gas under some driving conditions.
One proposed method of remarkably reducing the carbon-containing particulates in the emission from an internal combustion engine has disposes a heat-resistant filter in an exhaust conduit of the internal combustion engine and uses the filter to trap the carbon-containing particulates included in the exhaust gas. This method significantly reduces the total quantity of the carbon-containing particulates released to the air, while requiring treatment of the trapped carbon-containing particulates to avoid potential troubles like the clogging of the filter and the lowered performance of the engine.
Several methods have been proposed to treat the trapped carbon-containing particulates. One proposed technique makes a noble metal catalyst, such as platinum, carried on the filter and utilizes the catalytic action of the noble metal for combustion (see JAPANESE PATENT PUBLICATION GAZETTE No. 7-106290). Another proposed technique intentionally raises the temperature of the exhaust gas for combustion of the trapped carbon-containing particulates on the filter (see PATENT APPLICATION No. 2000-161044). Combustion of the carbon-containing particulates by application of any of these techniques ensures treatment of the particulates prior to clogging of the filter. The filter having the higher trapping rate lowers the total quantity of the carbon-containing particulates released to the air.
The catalyst naturally deteriorates its performance in use. The catalyst used for a long time period can not completely treat the trapped carbon-containing particulates. This eventually leads to clogging of the filter. The technique of intentionally raising the temperature of the exhaust gas takes out the chemical energy of the fuel not in the form of the output of the engine but in the form of heat. This technique thus disadvantageously lowers the output of the engine or the fuel consumption efficiency.
By taking into account these problems, the inventors of the present invention have completed a technique of readily treating the trapped carbon-containing particulates and have filed for a patent application (PATENT APPLICATION No. 2000-300167). The technique disclosed in the application uses a heat-resistant filter to trap the carbon-containing particulates and the hydrocarbon compounds included in the flow of exhaust gas in a dispersive manner to bring the respective particulates and hydrocarbon compounds in contact with oxygen included in the exhaust gas. The dispersive trapping causes the hydrocarbon compounds to be gradually oxidized with oxygen in the exhaust gas, even when a filter inflow temperature of the exhaust gas is lower than a combustible temperature of the carbon-containing particulates. Highly active intermediate products and reaction heat produced through the oxidation are accumulated and eventually cause combustion of the carbon-containing particulates. Application of this technique enables the carbon-containing particulates to be effectively treated by simply making the carbon-containing particulates and the hydrocarbon compounds in the exhaust gas trapped on the filter in the dispersive manner. This is free from the problems like the clogging of the filter due to deterioration of the catalyst and the lowered performance of the engine.
It is, however, practically not easy for the filter to trap all the carbon-containing particulates and the hydrocarbon compounds included in the flow of exhaust gas in the dispersive manner to bring the respective particulates and hydrocarbon compounds in contact with oxygen included in the exhaust gas. It is thus highly probable that a trace amount of the carbon-containing particulates passes through the filter and is released to the air. The higher trapping rate of the filter to prevent the release makes it difficult to trap the carbon-containing particulates and the hydrocarbon compounds in a dispersive manner. This leads to failure of combustion of the trapped carbon-containing particulates with the exhaust gas of relatively low temperature.
The present invention has been completed to solve the drawbacks of the prior art techniques discussed above and to improve the technique of the pending patent application mentioned above. The object of the present invention is thus to stably control carbon-containing particulates included in the flow of exhaust gas from an internal combustion engine over a long time period without deteriorating the performances of the internal combustion engine and to reduce the total quantity of particulates released to the air.
DISCLOSURE OF THE INVENTION
At least part of the above and the other related objects is attained by a first emission control device that reduces carbon-containing particulates included in a flow of exhaust gas from an internal combustion engine. The first emission control device includes: a first heat-resistant filter medium that traps hydrocarbon compounds and the carbon-containing particulates included in the flow of exhaust gas in a dispersive manner to bring the respective particulates and hydrocarbon compounds in contact with oxygen included in the exhaust gas, and thereby makes the trapped hydrocarbon compounds and the trapped carbon-containing particulates subjected to combustion with the exhaust gas having a filter inflow temperature lower than a combustible temperature of the carbon-containing particulates; and a second heat-resistant filter medium that traps the remaining carbon-containing particulates, which have not been trapped by the first heat-resistant filter medium but have passed through the first heat-resistant filter medium.
There is an emission control method corresponding to the above emission control device.
The present invention is accordingly directed to a first emission control method that reduces carbon-containing particulates included in a flow of exhaust gas from an internal combustion engine. The first emission control method includes the steps of: using a first heat-resistant filter medium to trap hydrocarbon compounds and the carbon-containing particulates included in the flow of exhaust gas in a dispersive manner to bring the respective particulates and hydrocarbon compounds in contact with oxygen included in the exhaust gas; making the trapped hydrocarbon compounds and the trapped carbon-containing particulates subjected to combustion with the exhaust gas having an inflow temperature into the first heat-resistant filter medium lower than a combustible temperature of the carbon-containing particulates; and using a second heat-resistant filter medium to trap the remaining carbon-containing particulates, which have not been trapped by the first heat-resistant filter medium but have passed through the first heat-resistant filter medium.
In the first emission control device and the corresponding first emission control method, the first heat-resistant filter medium disposed upstream traps the carbon-containing particulates included in the flow of exhaust gas, and the second heat-resistant filter medium disposed downstream of the first heat-resistant filter medium traps the remaining carbon-containing particulates, which have not been trapped by the first heat-resistant filter medium but have passed through the first heat-resistant filter medium.
The arrangement of the present invention uses the second heat-resistant filter medium to trap and treat the remaining carbon-containing particulates pas
Henda Yoshimitsu
Kato Zenichiro
Kuroki Rentaro
Shiratani Kazuhiko
Sugiyama Toshihisa
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
Tran Binh Q.
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