A converter containing a NOx absorbing and reducing catalyst is disposed in the exhaust passage of an internal combustion engine. The upstream half portion (portion of the inlet side) of the substrate of the NOx absorbing and reducing catalyst in the converter carries the oxygen storage component that absorbs oxygen in the exhaust gas when the air-fuel ratio of the exhaust gas is lean and releases the absorbed oxygen when the air-fuel ratio of the exhaust gas flowing in is rich in addition to carrying the NOx absorbing and reducing catalyst. After NOx is absorbed by the NOx absorbing and reducing catalyst as a result of operating the engine at a lean air-fuel ratio, the engine is operated at a rich air-fuel ratio, so that NOx is released from the NOx absorbing and reducing catalyst and is purified by reduction. Here, oxygen is released from the oxygen storage component carried by the upstream half portion of the substrate and is reacted with the H 2 and CO components in the exhaust gas, so that the temperature of the NOx absorbing and reducing catalyst is raised within short periods of time due to the heat of reaction. Therefore, the catalyst exhibits increased activity and the NOx absorbing and reducing catalyst exhibits improved NOx purification capability.

Exhaust gas purification device for an internal combustion engine

An air-fuel ratio control system for an internal combustion engine includes a LAF sensor and an O2 sensor arranged in an exhaust pipe at respective locations upstream and downstream of a catalytic converter. A desired air-fuel ratio coefficient used in calculating an amount of fuel supplied to the engine is calculated based on operating conditions of the engine, and corrected based on output from the O2 sensor. The air-fuel ratio of a mixture supplied to the engine is feedback-controlled to a stoichiometric air-fuel ratio based on the corrected desired air-fuel ratio coefficient. When the output from the O2 sensor falls within a predetermined range, the desired air-fuel ratio coefficient is not corrected, but held at an immediately preceding value thereof.

Air-fuel ratio control system for internal combustion engines

An internal combustion engine wherein an HC treatment catalyst (12) having the function of adsorbing the HC in the exhaust gas is arranged upstream of the NOx selective reducing catalyst (14), an urea aqueous solution fed from the reducing agent feed valve (15) is arranged upstream of the HC treatment catalyst (12), urea, and NOx contained in the exhaust gas, and HC adsorbed on the HC treatment catalyst 12 are reacted with each other to form intermediate products having cyano groups, oximes, and amino groups, and these intermediate products are sent to the NOx selective reducing catalyst (14).

Exhaust purification device of internal combustion engine

An NOx absorbent (6, 6A) is installed in an exhaust conduit (4) of an internal combustion engine (2) capable of fuel combustion at lean air-fuel ratios. An oxygen concentration is repeatedly or continuously decreased by, for example, switching the air-fuel from the lean air-fuel ratio to a stoichiometric or rich air fuel ratio when the exhaust gas temperature is higher than 550°C or when NOx absorbent temperature is higher than 500°C. As a result, the SOx absorbed in the NOx absorbent (6, 6A) during lean air-fuel ratio, low temperature operation is released from the NOx absorbent (6, 6A), and the SOx-poisoned NOx absorbent is recovered.

Exhaust gas purification apparatus for an internal combustion engine

Provided is a catalyst article for simultaneously remediating the nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons present in diesel engine exhaust streams. The catalyst article has a soot filter coated with a material effective in the Selective Catalytic Reduction (SCR) of NOx by a reductant, e.g., ammonia.

Catalyzed scr filter and emission treatment system

NOx absorbent (18) is disposed in the exhaust gas path in the internal combustion engine and exhaust gas is adapted to flow constantly through said absorbent (18) during the operation of said engine. NOx absorbent (18) absorbs NOx when an air-fuel ratio of exhaust gas flowing into said absorbent (18) is lean and, when an air-fuel ratio of exhaust gas becomes equal to the theoretical air-fuel ratio or rich, it discharges NOx having been absorbed therein. Over almost the entire range of operation of the engine, lean mixed gas is burnt in the combustion chamber (3) and NOx generated at this time is absorbed by said absorbent (18). An air-fuel ratio of exhaust gas flowing into the NOx absorbent (18) is periodically made equal to the theoretical one or rich and NOx having been absorbed by the absorbent (18) is discharged and reduced at the same time.

Device for purifying exhaust of internal combustion engine

A device for purifying the exhaust gas of a diesel engine comprises a filter for collecting particulates which is arranged in the exhaust system of the engine, an oxidation catalyst arranged in the exhaust system upstream of the filter, diesel fuel supply unit for supplying diesel fuel to the oxidation catalyst when the filter must be regenerated, and a heater. The heater heats the diesel fuel supplied from the diesel fuel supply unit to the oxidation catalyst only in the initial step of supplying the diesel fuel when the temperature of the oxidation catalyst is lower than a predetermined temperature and the filter must be regenerated.

Device for purifying the exhaust gas of a diesel engine

PROBLEM TO BE SOLVED: To heighten exhaust purifying performance in a diesel engine so as to prevent air pollution by performing intake throttle and fuel supply at the time of detecting engine stop operation or engine speed reduction unnecessary to supply fuel to the engine and also detecting catalyst temperature being the specified temperature or higher. SOLUTION: An ECU 20 inputs output signals of a temperature sensor 15, an accelerator circuit sensor 16, an engine speed sensor 17, and the like, and controls an intake throttle valve 5 and a fuel injection pump 11 on the basis of specific arithmetic processing. That is, in case a catalyst held to particulate filters 7A-7D has reached the activated temperature when an ignition switch 18 is switched off, the intake throttle valve 5 is totally closed, and fuel supply is stopped in order to perform ash reducing treatment. When the engine speed is lowered to the specified fuel supply start rotating speed, fuel supply is resumed, and further when the engine speed is lowered to the specified fuel supply completion rotating state, fuel supply is stopped.

Exhaust emission control device for diesel engine

A wall-flow type filter for purifying exhaust gases having a number of cells formed in a direction of flow of exhaust gases, wherein every other cell is plugged on the exhaust gas inlet side but is opened on the exhaust gas outlet side, and the cells that are opened on the exhaust gas inlet side are plugged on the exhaust gas outlet side, and wherein a catalyst is carried in the pores formed in the porous walls among the cells.

Filter for purifying exhaust gases

An NOx absorbing agent (17) is disposed inside an exhaust gas passage of a combustion engine. This NOx absorbing agent (17) absorbs NOx when the air/fuel ratio of exhaust gas flowing thereinto is lean, and discharges NOx which it has absorbed when the air/fuel ratio of exhaust gas flowing thereinto becomes rich. The amount of NOx absorbed in the NOx absorbing agent (17) is estimated from the engine load and the number of revolutions of the engine, and when this estimated NOx amount becomes the maximum NOx absorbing capacity of the NOx absorbing agent (17), the air/fuel ratio of exhaust gas flowing into the NOx absorbing agent (17) is made rich.

Yasushi Araki

Papers

Device for purifying exhaust of internal combustion engine

Device for purifying the exhaust gas of a diesel engine

Exhaust emission control device for diesel engine

Filter for purifying exhaust gases

Exhaust emission control system for internal combustion engine