Exhaust-gas cleaning device for engine

• US 20020119080A1
• Filed: 02/25/2002
• Published: 08/29/2002
• Est. Priority Date: 02/27/2001
• Status: Active Grant

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Shigetsu, Masahiko, Imada, Michihiro, Kuroki, Masayuki
• Granted Patent: US 6,976,355 B2
• Time in Patent Office: Days
• US Class Current: 422/168
• CPC Class Codes: B01D 53/944 Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts three-way-catalysts [TWC] B01D53/9445
• CPC Class Codes: F01N 2570/12 Hydrocarbons
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0835 Hydrocarbons
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 2200/0804 Estimation of the temperature of the exhaust gas treatment apparatus
• CPC Class Codes: F02D 2200/602 Pedal position
• CPC Class Codes: F02D 2200/703 Atmospheric pressure
• CPC Class Codes: F02D 41/024 to increase temperature of the exhaust gas treating apparatus
• CPC Class Codes: F02D 41/064 at cold start F02D41/067 takes precedence
• CPC Class Codes: F02D 41/1444 characterised by the characteristics of the combustion gases
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02M 26/21 with EGR valves located at or near the connection to the intake system
• CPC Class Codes: F02M 26/48 EGR valve position sensors details of the sensor installation in the valve housing F02M26/72
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

An exhaust-gas cleaning device for an engine comprises an HC-adsorbing catalytic converter disposed in an exhaust passage, the HC-adsorbing catalytic converter including an HC-adsorbing material which adsorbs HC contained in exhaust gas at low temperatures and releases adsorbed HC as the temperature increases, an oxygen storage material which occludes oxygen when the concentration of oxygen in the exhaust gas is high and releases occluded oxygen as the oxygen concentration drops, and a three-way catalys metal layer which oxidizes HC released from the HC-adsorbing material, and an oxygen concentration controller which controls the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter in such a manner that oxygen is released from the oxygen storage material when the engine is in an operating condition in which HC is released from the HC-adsorbing material.

Claims

1. An exhaust-gas cleaning device for an engine, said exhaust-gas cleaning device comprising:

an HC-adsorbing catalytic converter disposed in an exhaust passage, the HC-adsorbing catalytic converter including;

an HC-adsorbing material which adsorbs HC contained in exhaust gas and releases adsorbed HC as temperature increases;

an oxygen storage material which occludes oxygen when the concentration of oxygen in the exhaust gas is high and releases occluded oxygen as the oxygen concentration drops; and

an oxidizing catalytic metal which oxidizes HC released from the HC-adsorbing material; and

an oxygen concentration controller which controls the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter in such a manner that oxygen is released from the oxygen storage material when the engine is in an operating condition in which HC is released from the HC-adsorbing material.

2. The exhaust-gas cleaning device according to claim 1, wherein the oxygen concentration controller controls the engine in such a manner that the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter becomes equal to or less than 0.3% when the engine is in the operating condition in which HC is released from the HC-adsorbing material.

3. The exhaust-gas cleaning device according to claim 1, the oxygen concentration controller including an air-fuel ratio controller for controlling average air-fuel ratio in a combustion chamber of the engine, wherein the air-fuel ratio controller controls the engine in such a manner that a value corresponding to the ratio between the oxygen concentration and the concentration of a reducing agent contained in the exhaust gas flowing into the HC-adsorbing catalytic converter becomes appropriate for creating an exhaust gas atmosphere which is obtained by burning a mixture at an average air-fuel ratio of 14.7 or less in the combustion chamber so that oxygen is released from the oxygen storage material when the engine is in the operating condition in which HC is released from the HC-adsorbing material.

4. The exhaust-gas cleaning device according to claim 1, the oxygen concentration controller including an air-fuel ratio controller for controlling average air-fuel ratio in a combustion chamber of the engine, wherein the air-fuel ratio controller controls the engine in such a manner that a value corresponding to the ratio between the oxygen concentration and the concentration of a reducing agent contained in the exhaust gas flowing into the HC-adsorbing catalytic converter becomes appropriate for creating an exhaust gas atmosphere which is obtained by burning a mixture at an average air-fuel ratio between 13.5 and 14.5 in the combustion chamber so that oxygen is released from the oxygen storage material when the engine is in the operating condition in which HC is released from the HC-adsorbing material.

5. The exhaust-gas cleaning device according to any one of claims 1 through 4, wherein the oxygen concentration controller controls the engine in such a manner that the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter matches a set value without becoming alternately higher and lower than the set value.

6. The exhaust-gas cleaning device according to claim 3 or claim 4, wherein the air-fuel ratio controller performs feedback control operation for making the average air-fuel ratio in the combustion chamber alternately higher and lower than a set air-fuel ratio based on the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter, and wherein feedback control gain for air-fuel ratio control operation performed by the air-fuel ratio controller is set to a small value when the engine is in the operating condition in which HC is released from the HC-adsorbing material than when the engine is in an operating condition in which releasing of HC from the HC-adsorbing material has finished.

7. The exhaust-gas cleaning device according to any one of claims 1 through 4, wherein the HC-adsorbing material is disposed on a carrier of the HC-adsorbing catalytic converter and an oxidizing catalyst layer is formed on the outside of the HC-adsorbing material.

8. The exhaust-gas cleaning device according to claim 7, wherein the oxygen storage material is contained in the oxidizing catalyst layer.

9. An exhaust-gas cleaning device for an engine, said exhaust-gas cleaning device comprising:

an HC-adsorbing catalytic converter disposed in an exhaust passage, the HC-adsorbing catalytic converter including;

an HC-adsorbing material which adsorbs HC contained in exhaust gas and releases adsorbed HC as temperature increases;

an oxygen storage material which occludes oxygen when the concentration of oxygen in the exhaust gas is high and releases occluded oxygen as the oxygen concentration drops; and

an oxidizing catalytic metal which oxidizes HC released from the HC-adsorbing material; and

an oxygen concentration controller which controls the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter in such a manner that oxygen is released from the oxygen storage material when the engine is in an operating condition in which HC is released from the HC-adsorbing material, and the oxygen concentration controller including;

an air-fuel ratio controller for controlling average air-fuel ratio in a combustion chamber of the engine, wherein the air-fuel ratio controller controls the engine in such a manner that a value corresponding to the ratio between the oxygen concentration and the concentration of a reducing agent contained in the exhaust gas flowing into the HC-adsorbing catalytic converter becomes appropriate for creating an exhaust gas atmosphere which is obtained by burning a mixture at an average air-fuel ratio of 14.7 or less in the combustion chamber so that oxygen is released from the oxygen storage material when the engine is in the operating condition in which HC is released from the HC-adsorbing material and

the air-fuel ratio controller performs feedback control operation for making the average air-fuel ratio in the combustion chamber alternately higher and lower than a set air-fuel ratio based on the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter, and wherein feedback control gain for air-fuel ratio control operation performed by the air-fuel ratio controller is set to a small value when the engine is in the operating condition in which HC is released from the HC-adsorbing material than when the engine is in an operating condition in which releasing of HC from the HC-adsorbing material has finished.

10. An exhaust-gas cleaning device for an engine, said exhaust-gas cleaning device comprising:

HC-adsorbing catalytic converting means disposed in an exhaust passage, the HC-adsorbing catalytic converting means including;

an HC-adsorbing material which adsorbs HC contained in exhaust gas and releases adsorbed HC as temperature increases;

an oxygen storage material which occludes oxygen when the concentration of oxygen in the exhaust gas is high and releases occluded oxygen as the oxygen concentration drops; and

an oxidizing catalytic metal which oxidizes HC released from the HC-adsorbing material; and

an oxygen concentration controlling means for controlling the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converter in such a manner that oxygen is released from the oxygen storage material when the engine is in an operating condition in which HC is released from the HC-adsorbing material and the oxygen concentration controlling means controls the engine in such a manner that the oxygen concentration in the exhaust gas on the upstream side of the HC-adsorbing catalytic converting means becomes equal to or less than 0.3% when the engine is in the operating condition in which HC is released from the HC-adsorbing material.