An exhaust emission control system of an internal combustion engine capable of post injection is disclosed which provides control such that the injection timing in sub injection is set to a point earlier than the target injection timing when the sub injection is started, and the injection timing in the sub injection is then delayed to the target injection timing. This realizes the post injection under the optimum conditions and enables an efficient rise in the exhaust temperature while inhibiting deterioration of the drivability due to a rapid change in torque.

Exhaust emission control system of internal combustion engine

An engine has a plurality of the cylinders. The cylinders are divided into a first cylinder group and a second cylinder group, and each cylinder group is connected, via a corresponding branch exhaust passage, to a common interconnecting exhaust passage. In the interconnecting exhaust passage, an exhaust gas purifying catalyst is arranged. The air-fuel ratio of the exhaust gas of the first cylinder group is made lean to feed oxygen to the exhaust gas purifying catalyst, and the air-fuel ratio of the second cylinder group is made rich to feed fuel for heating to the exhaust gas purifying catalyst, so that the oxygen and the fuel for heating react with each other to heat the exhaust gas purifying catalyst to reactivate the exhaust gas purifying catalyst when the reactivation of the exhaust gas purifying catalyst is must be performed. In each branch exhaust passage, a start catalyst is arranged.

Device for purifying exhaust gas of engine

An engine control computer estimates the cumulative NOx storage in a NOx trap based on engine operating conditions and enters a NOx purge mode of operation when a maximum storage capacity limit, based on trap temperature, is exceeded. The purge mode is terminated when NOx storage level decreases below a minimum storage capacity limit. The rate of NOx dissipation is also based on trap temperature.

Method and apparatus for maintaining catalyst efficiency of a NOx trap

According to the present invention, there is provided an exhaust gas purification device for an engine having an exhaust passage, the device comprising a catalyst arranged in the exhaust passage and having an upstream end and a downstream end, a purification ratio of exhaust gas by the catalyst becoming more than a predetermined ratio when a temperature of the catalyst is within a predetermined temperature range, cooling means for cooling the upstream end of the catalyst, heating means for heating the downstream end of the catalyst, and control means for controlling the cooling means and the heating means to maintain the temperature of a portion of the catalyst, which portion is positioned between the upstream end and the downstream end, in the predetermined temperature range.

An exhaust gas purification device for an internal combustion engine

An exhaust gas-purifying catalyst includes a substrate, and a catalytic layer facing the substrate and including a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope. Another exhaust gas-purifying catalyst includes a substrate, and a catalytic layer formed on the substrate using slurry containing a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope.

Exhaust gas purifying catalyst

In the present invention, the exhaust gas from the engine (1) is divided into a first (4a) and a second branch (4b) exhaust passages after it passes through a three-way reducing and oxidizing catalyst (11), and the two branch exhaust passages merge into an exhaust gas outlet passage (5). In the first branch exhaust passage (4a), an oxidizing catalyst (13) is disposed, and in the exhaust gas outlet passage (5), a denitrating and oxidizing catalyst (15) is disposed. NOX in the exhaust gas from the engine is all converted to N₂ and NH₃ by the three-way reducing and oxidizing catalyst (11) and a part of the NH₃ generated by the three-way catalyst flows into the first branch exhaust passage (4a) and is converted to NOX again by the oxidizing catalyst (13). The amount of NOX produced by the oxidizing catalyst (13) and the amount of NOX flowing through the second branch exhaust passage (4b) is determined by the flow distribution ratio of the first and the second branch exhaust passages. In this invention, the flow ratio is determined in such a manner that the amount of the NOX produced by the oxidizing catalyst (13) and the amount of the NH₃ passing through the second branch exhaust passage (4b) are stoichiometric to produce N₂ and H₂O. Therefore, when these exhaust gases flow into the denitrating and oxidizing catalyst (15) after they mix with each other in the exhaust gas outlet passage (5), all the NOX and the NH₃ are converted to N₂ and H₂O by the denitrating and oxidizing catalyst (15) without producing any surplus NOX or NH₃.

An exhaust gas purification device for an engine

A NOx absorbing agent, characterized in that it comprises a crystalline ZrO2 composite oxide containing at least one element of trivalent rare earth metals and divalent alkaline earth metals added thereto and, carried thereon, at least one element of alkali metals and alkaline earth metals; and an absorption reduction type catalyst for removing NOx, characterized in that it comprises the NOx absorbing agent and a noble metal. Preferably, the NOx absorbing agent further comprises aluminum carried on the ZrO2 composite oxide. The NOx absorbing agent is supposed to absorb NOx through a mechanism wherein an electron released from an alkali metal or the like is incorporated into an oxygen defect portion of the crystalline ZrO2 composite oxide and the resultant oxygen defect portion acts as a strong basic point donating an electron to an electrophilic component such as NOx. The absorption reduction type catalyst for removing NOx exhibits high performance capability of removing NOx even under a condition wherein an exhaust gas has a temperature of 500°C or higher.

Nox absorbing agent and absorption reduction type catalyst for removing nox

An automotive exhaust catalyst includes an alumina support having pores, an NO x storage member loaded in the pores having a pore diameter of from 10 to 30A at least, and a noble metal element loaded on the alumina support. The automotive exhaust catalyst can store NO x in a large amount in fuel-lean or oxygen-rich atmosphere, and inhibit the alumina support from sintering, because the NO x storage member is loaded in a highly dispersed manner.

O Toyota Jidosha K K Tanaka

Papers

An exhaust gas purification device for an engine

Nox absorbing agent and absorption reduction type catalyst for removing nox

Catalyst for treating automotive exhaust