Engine exhaust gas control system having NOx catalyst
US6148612A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 6, 1998 |
| Grant date | Nov 21, 2000 |
| Priority date | — |
| Expiry date | Oct 6, 2018 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF02D41/1456
- WIPO fieldEngines, pumps, turbines
- WIPO sectorMechanical engineering
Abstract
In an engine exhaust system, an NOx catalyst for occluding NOx in a state of the lean air-fuel ratio and reducing the occluded NOx in the state of the rich air-fuel ratio. A CPU sets a target air-fuel ratio of a mixture supplied to an engine to the lean side with respect to the stoichiometric air-fuel ratio for the lean mixture combustion. The CPU sets a rich time for a rich mixture combustion in accordance with the engine operating state and the NOx purification rate in the NOx catalyst. In this moment, the shortest rich time is set within a range in which a desired NOx purification rate by the NOx catalyst is obtained. A three-way catalyst may be arranged upstream of the NOx catalyst. The three-way catalyst carries only a noble metal such as platinum having no oxygen storing capability.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.