NOx purification apparatus for an internal combustion engine
AssigneeToyota Jidosha Kabushiki Kaisha
InventorShinichi Takeshima
Life of this patent
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Abstract
A plurality of lean NOx catalysts are installed in passages of a dual passage portion of an exhaust conduit of an internal combustion engine. A space velocity changing means including a valve is provided at a connecting portion of the passages so that the amount of exhaust gas flowing through the lean NOx catalysts is altered periodically. When a space velocity of exhaust gas at the lean NOx catalyst changes from a low velocity to a high velocity, an NOx purification rate of the lean NOx catalyst increases momentarily. By repeatedly generating the NOx purification rate increased conditions, the NOx purification rate of the NOx purification apparatus including the plurality of lean NOx catalysts is greatly increased.
Claims12
An NO.sup.x purification apparatus for an internal combustion engine comprising:
- an internal combustion engine having an exhaust conduit;
- a plurality of lean NO.sub.x catalysts including a first lean NO.sub.x catalyst and a second lean NO.sub.x catalyst arranged in parallel with each other in the exhaust conduit of the internal combustion engine;
- space velocity changing means for periodically changing a first velocity of exhaust gas at the first lean NO.sub.x catalyst and a second velocity of exhaust gas at the second lean NO.sub.x catalyst so that when the first velocity is high, the second velocity is low, and when the first velocity is changed so that it is low, the second velocity is changed so that it is high, wherein the space velocity changing means operates so that, at all times while the engine is running, a first portion of the exhaust gas flows through the first lean NO.sub.x catalyst and a second portion of the exhaust gas flows through the second NO.sub.x catalyst.
Dependencies are inferred from the claim text.