Exhaust discharge control device for internal combustion engine

• US 6,233,925 B1
• Filed: 08/05/1999
• Issued: 05/22/2001
• Est. Priority Date: 08/28/1998
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Iguchi, Satoshi, Hirota, Shinya, Tanaka, Toshiaki
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): TRAN, BINH Q
• Application Number:
  US09/368,689
• Time in Patent Office: 656 Days
• Field of Search: 602/85, 602/95, 602/97, 602/87, 602/88, 602/89, 603/24, 602/91, 602/92, 602/86, 603/00, 603/01, 123/443
• US Class Current: 60/285
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 13/011 having two or more purifying devices arranged in parallel
• CPC Class Codes: F01N 2570/04 Sulfur or sulfur oxides
• CPC Class Codes: F01N 2610/03 the substance being hydrocarbons, e.g. engine fuel
• CPC Class Codes: F01N 3/0233 periodically cleaning filter by blowing a gas through the filter in a direction opposite to exhaust flow, e.g. exposing filter to engine air intake
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0821 combined with particulate filters catalysed diesel particulate filters F01N3/035
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/085 Sulfur or sulfur oxides
• CPC Class Codes: F01N 3/0864 Oxygen
• CPC Class Codes: F01N 3/0871 Regulation of absorbents or adsorbents, e.g. purging by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235
• CPC Class Codes: F01N 3/0878 Bypassing absorbents or adsorbents
• CPC Class Codes: F01N 3/0885 Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
• CPC Class Codes: F01N 3/2093 Periodically blowing a gas through the converter, e.g. in a direction opposite to exhaust gas flow or by reversing exhaust gas flow direction
• CPC Class Codes: F01N 3/22 Control of additional air supply only, e.g. using by-passes or variable air pump drives
• CPC Class Codes: F02D 2200/0804 Estimation of the temperature of the exhaust gas treatment apparatus
• CPC Class Codes: F02D 41/0275 the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/028 Desulfurisation of NOx traps or adsorbent
• CPC Class Codes: F02D 41/0295 : Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
• CPC Class Codes: F02D 41/1446 : the characteristics being exhaust temperatures

Abstract

An NO_x absorbent is arranged in an engine exhaust passage absorbs NO_x when the air-fuel ratio of inflowing exhaust gas is lean and discharges absorbed NO_x or SO_x when the oxygen concentration of inflowing exhaust gas decreases. When the air-fuel ratio of the exhaust gas flowing into the NO_x absorbent is rich, previously absorbed NO_x or SO_x is discharged from the NO_x absorbent. When NO_x or SO_x is to be discharged from the NO_x absorbent, oxygen is left in the exhaust gas flowing into the NO_x absorbent and the oxygen concentration of this exhaust gas is maintained within a predetermined range.

Claims

1. An exhaust discharge control device for an internal combustion engine comprising:

an NO_x absorbent located in an exhaust gas passage of the engine, wherein exhaust gas flows through the exhaust gas passage from upstream to downstream, the NO_x absorbent absorbing NO_x when an air-fuel ratio of exhaust gas flowing into the NO_x absorbent is lean and discharging absorbed NO_x when an oxygen concentration of the inflowing exhaust gas decreases;

oxygen concentration control means for allowing oxygen to remain in inflowing exhaust gas when one of NO_x and SO_x is to be discharged from the NO_x absorbent and for maintaining the oxygen concentration of the exhaust gas within a predetermined range; and

means for determining an amount of hydrocarbons adhered to the NO_x absorbent, wherein the oxygen concentration control means increases the oxygen concentration of inflowing exhaust gas to increase an amount of one of NO_x and SO_x discharged from the NO_x absorbent as the hydrocarbon amount increases.

2. An exhaust discharge control device for an internal combustion engine according to claim 1, further comprising means for detecting a temperature of the NO_x absorbent, wherein the oxygen concentration control means increases the oxygen concentration of the exhaust gas flowing into the NO_x absorbent to increase an amount of one of NO_x and SO_x discharged from the NO_x absorbent as the temperature increases.

3. An exhaust discharge control device for an internal combustion engine according to claim 2, wherein the means for detecting the temperature of the NO_x absorbent detects a temperature of the exhaust gas downstream of the NO_x absorbent to obtain the temperature of the NO_x absorbent.

4. An exhaust discharge control device for an internal combustion engine according to claim 1, wherein the NO_x absorbent includes a hydrocarbon absorbent, the hydrocarbon absorbent absorbing hydrocarbon when a temperature of the hydrocarbon absorbent is below a predetermined temperature and releasing absorbed hydrocarbon when the temperature of the hydrocarbon absorbent is at least the predetermined temperature.

5. An exhaust discharge control device for an internal combustion engine according to claim 1, wherein the NO_x absorbent includes an oxygen occluding material, the oxygen occluding material storing oxygen when the oxygen concentration of inflowing exhaust gas increases and discharging stored oxygen when the oxygen concentration of inflowing exhaust gas decreases.

6. An exhaust discharge control device for an internal combustion engine according to claim 5, wherein the NO_x absorbent includes a hydrocarbon absorbent, the hydrocarbon absorbent absorbing hydrocarbons when a temperature of the hydrocarbon absorbent is below a predetermined temperature and releasing absorbed hydrocarbons when the temperature of the hydrocarbon absorbent is at least the predetermined temperature.

7. An exhaust discharge control device for an internal combustion engine according to claim 1, further comprising:

air-fuel ratio control means for temporarily lowering an air-fuel ratio of the exhaust gas flowing into the NO_x absorbent and to discharge from the NO_x absorbent the one of NO_x and SO_x absorbed therein.

8. An exhaust discharge control device for an internal combustion engine according to claim 7, wherein the engine includes a plurality of cylinders and wherein the air-fuel ratio control means increases a fuel injection quantity for a part of the plurality of cylinders.

9. An exhaust discharge control device for an internal combustion engine according to claim 7, wherein

the air-fuel ratio control means conducts a fuel injection near a compression top dead center of the engine and a secondary injection in one of an engine expansion stroke and an engine exhaust stroke.

10. An exhaust discharge control device for an internal combustion engine comprising:

an occluding and reducing type NO_x catalyst disposed in an exhaust gas passage of the engine, wherein exhaust gas travels through the exhaust passage from upstream to downstream, the occluding and reducing type NO_x catalyst absorbing NO_x in the exhaust gas flowing therein when an air-fuel ratio of inflowing exhaust gas is lean and discharging absorbed NO_x therefrom when the air-fuel ratio of inflowing exhaust gas is one of stoichiometric and rich;

regeneration means for making the air-fuel ratio of in flowing exhaust gas one of stoichiometric and rich when SO_x absorbed by the occluding and reducing type NO_x catalyst during NO_x absorption is discharged from the occluding and reducing type NO_x catalyst;

rich atmosphere providing means for supplying and maintaining a predetermined amount of oxygen in an SO_x absorption region of the occluding and reducing NO_x catalyst when the regeneration means executes SO_x discharge; and

means for determining an amount of hydrocarbons adhered to the NO_x catalyst, wherein the rich atmosphere providing means increases the oxygen concentration of inflowing exhaust gas to increase an amount of one of NO_x and SO_x discharged from the NO_x catalyst as the hydrocarbon amount increases.

11. An exhaust discharge control device for an internal combustion engine according to claim 10, wherein

a timing of SO_x discharge execution by the regeneration means and the rich atmosphere providing means is controlled at a time at which a catalysis temperature of a downward region of the occluding and reducing type NO_x catalyst in an exhaust gas flow direction during SO_x discharge is higher than a catalysis temperature of an upward region of the occluding and reducing type NO_x catalyst.

12. An exhaust discharge control device for an internal combustion engine according to claim 10, wherein said rich atmosphere providing means includes means for supplying oxygen to a catalyst downstream of the occluding and reducing type NO_x catalyst during SO_x discharge.

13. An exhaust discharge control device for an internal combustion engine according to claim 10, wherein said internal combustion engine is a multiple-cylinder internal combustion engine and said rich atmosphere providing means comprises means for burning fuel in a first portion of the cylinders at a rich air-fuel ratio and for burning fuel at a lean air-fuel ratio in a second portion of the cylinders.

14. An exhaust discharge control device for an internal combustion engine comprising:

an occluding and reducing type NO_x catalyst disposed in an exhaust gas passage of the engine, wherein exhaust gas travels through the exhaust passage from upstream to downstream, the occluding and reducing type NO_x catalyst absorbing NO_x in the exhaust gas when an air-fuel ratio of inflowing exhaust gas is lean, and discharging absorbed NO_x when the air-fuel ratio of inflowing exhaust gas is one of stoichiometric and rich;

an SO_x absorbent arranged in said exhaust passage upstream of the occluding and reducing type NO_x catalyst, the SO_x absorbent absorbing SO_x when the air-fuel ratio of inflowing exhaust gas is lean and discharging the absorbed SO_x when the air-fuel ratio of inflowing exhaust gas is one of stoichiometric and rich;

regeneration means for making the air-fuel ratio of the exhaust gas one of stoichiometric and rich when the SO_x previously absorbed by the SO_x absorbent is to be discharged from the SO_x absorbent;

rich atmosphere providing means for controlling an oxygen content of inflowing exhaust gas so that a predetermined amount of oxygen enters an SO_x absorption region of said SO_x absorbent when the regeneration means executes SO_x discharge; and

means for determining an amount of hydrocarbons adhered to the NO_x catalyst, wherein the rich atmosphere providing means increases the oxygen concentration of inflowing exhaust gas to increase an amount of one of NO_x and SO_x discharged from the NO_x catalyst as the hydrocarbon amount increases.

15. An exhaust gas discharge control device for an internal combustion engine according to claim 14, wherein said rich atmosphere providing means includes means for supplying oxygen to said SO_x absorbent.