Exhaust Emission Control System
First Claim
1. An exhaust emission control system, comprising:
- a NOx storage catalyst provided in an exhaust passage of an engine and configured to store NOx;
a urea selective catalytic reduction (SCR) catalyst provided in the exhaust passage downstream of the NOx storage catalyst; and
a processor configured to execute a NOx reduction controlling module to set a NOx reduction condition and, when the NOx reduction condition is satisfied, perform NOx reduction processing in which an air-fuel ratio of exhaust gas is set to be one of near a stoichiometric air-fuel ratio and rich, and the NOx stored in the NOx storage catalyst is reduced, the NOx reduction condition being set looser for the NOx reduction processing performed a first time after the engine is started than the NOx reduction processing performed a second and subsequent times after the engine is started.
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Accused Products
Abstract
An exhaust emission control system is provided, which includes a NOx storage catalyst provided in an exhaust passage of an engine and configured to store NOx, a urea SCR catalyst provided in the exhaust passage, downstream of the NOx storage catalyst, and a NOx reduction controlling module configured to set a NOx reduction condition and, when the NOx reduction condition is satisfied, performs NOx reduction processing in which an air-fuel ratio of exhaust gas is set to be one of near a stoichiometric air-fuel ratio and rich, and the NOx stored in the NOx storage catalyst is reduced, the NOx reduction condition being set looser for the NOx reduction processing performed the first time after the engine is started than the NOx reduction processing performed the second and subsequent times after the engine is started.
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Citations
8 Claims
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1. An exhaust emission control system, comprising:
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a NOx storage catalyst provided in an exhaust passage of an engine and configured to store NOx; a urea selective catalytic reduction (SCR) catalyst provided in the exhaust passage downstream of the NOx storage catalyst; and a processor configured to execute a NOx reduction controlling module to set a NOx reduction condition and, when the NOx reduction condition is satisfied, perform NOx reduction processing in which an air-fuel ratio of exhaust gas is set to be one of near a stoichiometric air-fuel ratio and rich, and the NOx stored in the NOx storage catalyst is reduced, the NOx reduction condition being set looser for the NOx reduction processing performed a first time after the engine is started than the NOx reduction processing performed a second and subsequent times after the engine is started. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification