# US 6,336,320 B1 · Exhaust gas purification device for an internal combustion engine

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- Number: US 6,336,320 B1
- Document ID: US6336320B1
- Status: Granted
- Kind: B1
- Application number: 09/345,406
- Filed: 1999-07-01
- Granted: 2002-01-08
- Earliest claimed: 1999-07-01
- Web page: https://patentgrep.com/patent/US6336320B1

## CPC

- F01N 3/0842: {Nitrogen oxides}
- F01N 3/0814: {combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts}
- F01N 9/00: Electrical control of exhaust gas treating apparatus (monitoring or diagnostic devices for exhaust-gas treatment apparatus F01N11/00; conjoint electrical control of two or more combustion engine functions F02D43/00)
- F01N 13/009: {having two or more separate purifying devices arranged in series}
- F01N 13/011: {having two or more purifying devices arranged in parallel}
- F02D 41/0275: {the exhaust gas treating apparatus being a NOx trap or adsorbent}
- F02D 41/1462: {with determination means using an estimation}
- F02D 41/1465: {with determination means using an estimation}
- F02D 41/405: {with post injections}
- F01N 2250/12: absorption or adsorption, and catalytic conversion
- F01N 2570/16: Oxygen
- F02D 41/1446: {the characteristics being exhaust temperatures}
- F02D 41/3011: {according to or using specific or several modes of combustion}
- F02D 41/3029: {further comprising a homogeneous charge spark-ignited mode}
- F02D 41/402: {Multiple injections}
- F02D 2200/0614: Actual fuel mass or fuel injection amount
- F02D 2200/0802: Temperature of the exhaust gas treatment apparatus
- F02D 2200/0804: Estimation of the temperature of the exhaust gas treatment apparatus
- F02D 2200/0806: NOx storage amount, i.e. amount of NOx stored on NOx trap
- F02D 2200/0814: Oxygen storage amount
- F02D 2200/0818: SOx storage amount, e.g. for SOx trap or NOx trap
- F02D 2200/101: Engine speed
- Y02T 10/40: Engine management systems
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

Start catalysts (SCs) having an O2 storage function are disposed in an exhaust gas passage of an internal combustion engine, and an NOx occluding and reducing catalyst is disposed in the exhaust gas passages downstream of the SCs. NOx in the exhaust gas is absorbed by the NOx occluding and reducing catalyst when the engine is in operation at a lean air-fuel ratio. When NOx is to be released, the engine is operated at a rich air-fuel ratio so that exhaust gas having a rich air-fuel ratio flows into the SCs and into the NOx occluding and reducing catalyst. An electronic control unit (ECU) executes the secondary fuel injection that does not contribute to the combustion in the expansion stroke or in the exhaust stroke of each cylinder by using a direct cylinder fuel injection valve at the time when the engine operating air-fuel ratio is to be changed from a lean air-fuel ratio operation to a rich air-fuel ratio, so that exhaust gas having a rich air-fuel ratio flows into the SC and that oxygen stored in the SC is released. At the time of changing over the air-fuel ratio, therefore, the air-fuel ratio is changed from the lean side to the rich side without delay, eliminating such an occurrence that NOx is released from the NOx occluding and reducing catalyst without being purified at the time of changing the air-fuel ratio.