Exhaust purification device of internal combustion engine

• US 5,473,890 A
• Filed: 07/29/1994
• Issued: 12/12/1995
• Est. Priority Date: 12/03/1992
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Seto, Satomi, Iguchi, Satoshi, Tanaka, Toshiaki, Takeshima, Shinichi, Katoh, Kenji, Nakanishi, Kiyoshi
• Primary Examiner(s): Hart, Douglas
• Application Number:
  US08/256,922
• Time in Patent Office: 501 Days
• Field of Search: 60/285, 60/301, 60/311, 60/297, 60/286
• US Class Current: 60/285
• CPC Class Codes: B01D 53/0454 Controlling adsorption controlling temperature swing adsorption B01D53/0462, controlling pressure swing adsorption B01D53/047
• CPC Class Codes: B01D 53/8637 Simultaneously removing sulfur oxides and nitrogen oxides
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 2240/18 an adsorber or absorber
• CPC Class Codes: F01N 2570/04 Sulfur or sulfur oxides
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 2610/03 the substance being hydrocarbons, e.g. engine fuel
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/085 Sulfur or sulfur oxides
• 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 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
• CPC Class Codes: F02B 1/04 with fuel-air mixture admission into cylinder
• CPC Class Codes: F02D 41/0275 the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/0285 the exhaust gas treating apparatus being a SOx trap or adsorbent
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An NO_x absorbent (19) which absorbs NO_x when an air-fuel ratio of an inflowing exhaust gas is lean, while releases the absorbed NO_x when lowering an oxygen concentration in the inflowing exhaust gas, is arranged in an exhaust passage of an internal combustion engine. An SO_x absorbent (18) which absorbs SO_x when the air-fuel ratio of the inflowing exhaust gas is lean, while releases the absorbed SO_x when the air-fuel ratio of the inflowing exhaust gas is made rich is arranged in the exhaust passage on the upstream side of the NO_x absorbent (19). When the lean air-fuel mixture is burned, the SO_x is absorbed into the SO_x absorbent (18) and, at the same time, the NO_x is absorbed into the NO_x absorbent (19), and when the air-fuel ratio of the air-fuel mixture is switched from lean to rich, SO_x is released from the SO_x absorbent (18), and NO_x is released from the SO_x absorbent (19 ).

Claims

1. An exhaust purification device of an internal combustion engine provided with:

an exhaust passage;

an NO_x absorbent which is arranged in said exhaust passage, absorbs the NO_x when the air-fuel ratio of an inflowing exhaust gas is lean and, at the same time, releases the absorbed NO_x when an oxygen concentration in the inflowing exhaust gas is lowered;

an SO_x absorbent which is arranged in said exhaust passage on the upstream side of said NO_x absorbent, absorbs the SO_x when the air-fuel ratio of the inflowing exhaust gas is lean and, at the same time, releases the absorbed SO_x when the air-fuel ratio of the inflowing exhaust gas is made rich; and

an air-fuel ratio control means which controls the air-fuel ratio of the exhaust gas flowing into said SO_x absorbent, usually maintains the air-fuel ratio of the exhaust gas flowing into said SO_x absorbent lean, and makes the air-fuel ratio of the exhaust gas flowing into said SO_x absorbent rich when the SO_x should be released from said SO_x absorbent.

2. An exhaust purification device of an internal combustion engine according to claim 1, wherein the NO_x absorbent contains at least one member selected from alkali metals consisting of potassium, sodium, lithium, and cesium, alkali earths consisting of barium and calcium, and rare earths consisting of lanthanum and yttrium and platinum.

3. An exhaust purification device of an internal combustion engine according to claim 1, wherein the SO_x absorbent contains at least one member selected from copper, iron, manganese, nickel, sodium, tin, titanium, lithium, and titania.

4. An exhaust purification device of an internal combustion engine according to claim 1, wherein the SO_x absorbent contains the platinum.

5. An exhaust purification device of an internal combustion engine according to claim 1, wherein all the exhaust gas discharged from the engine flows into the SO_x absorbent and the NO_x absorbent.

6. An exhaust purification device of an internal combustion engine according to claim 5, wherein the SO_x absorbent and the NO_x absorbent are arranged in one casing.

7. An exhaust purification device of an internal combustion engine according to claim 1, wherein said air-fuel ratio control means controls the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent by controlling the air-fuel ratio of the air-fuel mixture burned in the engine;

the SO_x contained in the exhaust gas is absorbed into the SO_x absorbent when the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent is maintained lean by maintaining the air-fuel ratio of the air-fuel mixture burned in the engine lean, while the NO_x contained in the exhaust gas is absorbed into the NO_x absorbent.

8. An exhaust purification device of an internal combustion engine according to claim 7, wherein said air-fuel ratio control means releases the SO_x from the SO_x absorbent and, at the same time, makes the air-fuel ratio of the air-fuel mixture burned in the engine rich when the NO_x should be released from the NO_x absorbent.

9. An exhaust purification device of an internal combustion engine according to claim 8, wherein when said air-fuel ratio control means should release the SO_x from the SO_x absorbent and, at the same time, release the NO_x from the NO_x absorbent, it first makes the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent and the NO_x absorbent a first degree of richness determined in advance, and then maintains the same at a rich state by a second degree of richness smaller than this first degree of richness.

10. An exhaust purification device of an internal combustion engine according to claim 9, wherein said air-fuel ratio control means controls said first degree of richness and second degree of richness in accordance with a temperature representative of the temperature of the SO_x absorbent.

11. An exhaust purification device of an internal combustion engine according to claim 10, wherein the temperature representing the temperature of the SO_x absorbent is the temperature of the exhaust gas flowing into the SO_x absorbent.

12. An exhaust purification device of an internal combustion engine according to claim 10, wherein said air-fuel ratio control means makes said first degree of richness larger as the temperature representing the temperature of the SO_x absorbent becomes higher.

13. An exhaust purification device of an internal combustion engine according to claim 12, wherein said air-fuel ratio control means makes the time for which the air-fuel ratio of the exhaust gas is maintained at said first degree of richness shorter as the temperature representing the temperature of the SO_x absorbent becomes higher.

14. An exhaust purification device of an internal combustion engine according to claim 10, wherein said air-fuel ratio control means makes said second degree of richness larger as the temperature representing the temperature of the SO_x absorbent becomes higher.

15. An exhaust purification device of an internal combustion engine according to claim 10, wherein said air-fuel ratio control means makes the time for which the air-fuel ratio of the exhaust gas is maintained at said second degree of richness shorter as the temperature representing the temperature of the SO_x absorbent becomes higher.

16. An exhaust purification device of an internal combustion engine according to claim 8, wherein said air-fuel ratio control means makes the air-fuel ratio of the air-fuel mixture rich so as to release the NO_x from the NO_x absorbent with a time interval shorter than the time interval at which it makes the air-fuel ratio of the air-fuel mixture rich so as to release the SO_x from the SO_x absorbent and release the NO_x from the NO_x absorbent.

17. An exhaust purification device of an internal combustion engine according to claim 16, wherein said air-fuel ratio control means first of all makes the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent and the NO_x absorbent the predetermined degree of richness when the NO_x should be released from the NO_x absorbent, and then maintains the same at the stoichiometric air-fuel ratio.

18. An exhaust purification device of an internal combustion engine according to claim 17, wherein said air-fuel ratio control means controls said degree of richness in accordance with a temperature representative of the temperature of the NO_x absorbent.

19. An exhaust purification device of an internal combustion engine according to claim 18, wherein the temperature representing the temperature of the NO_x absorbent is the temperature of the exhaust gas flowing into the NO_x absorbent.

20. An exhaust purification device of an internal combustion engine according to claim 18, wherein said air-fuel ratio control means makes said degree of richness larger as the temperature representing the temperature of the NO_x absorbent becomes higher.

21. An exhaust purification device of an internal combustion engine according to claim 20, wherein said air-fuel ratio control means makes the time for which the air-fuel ratio of the exhaust gas is maintained at said degree of richness shorter as the temperature representing the temperature of the NO_x absorbent becomes higher.

22. An exhaust purification device of an internal combustion engine according to claim 17, wherein said air-fuel ratio control means makes the time for which the air-fuel ratio of the exhaust gas is maintained at the stoichiometric air-fuel ratio shorter as the temperature representing the temperature of the SO_x absorbent becomes higher.

23. An exhaust purification device of an internal combustion engine according to claim 1, wherein:

provision is made of a bypass passage which is branched from the exhaust passage positioned between the SO_x absorbent and the NO_x absorbent so as to bypass the NO_x absorbent, a switch valve arranged at the branch portion of the bypass passage from the exhaust passage, and a valve control means which performs the switching control of said switch valve so as to selectively introduce the exhaust gas to either of the NO_x absorbent or the bypass passage;

said valve control means holds the switch valve at a position at which the exhaust gas flows into the NO_x absorbent when the NO_x should be released from the NO_x absorbent and switches the switch valve to a position at which the exhaust gas flowing into the bypass passage when the SO_x should be released from the SO_x absorbent; and

said air-fuel ratio control means lowers the oxygen concentration in the exhaust gas flowing into the NO_x absorbent when the NO_x should be released from the NO_x absorbent and makes the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich when the SO_x should be released from the SO_x absorbent.

24. An exhaust purification device of an internal combustion engine according to claim 23, wherein said valve control means and said air-fuel ratio control means hold the switch valve at a position at which the exhaust gas flows into the NO_x absorbent when the SO_x should be released from the SO_x absorbent and, at the same time, make the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich, and thereafter switches the switch valve to a position at which the exhaust gas flows into the bypass passage and, at the same time, continuously maintains the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich.

25. An exhaust purification device of an internal combustion engine according to claim 23, wherein said valve control means and said air-fuel ratio control means hold the switch valve at a position at which the exhaust gas flows into the bypass passage when the SO_x should be released from the SO_x absorbent and, at the same time, make the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich, and thereafter switches the switch valve to the position at which the exhaust gas flows into the NO_x absorbent and, at the same time, continuously maintains the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich.

26. An exhaust purification device of an internal combustion engine according to claim 23, wherein said valve control means and said air-fuel ratio control means hold the switch valve at a position at which the exhaust gas flows into the NO_x absorbent if the temperature representing the temperature of the SO_x absorbent is lower than the predetermined set up temperature when the SO_x should be released from the SO_x and, at the same time, make the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich, and thereafter switch the switch valve to a position at which the exhaust gas flows into the bypass passage and, at the same time, continuously maintain the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich;

said valve control means and said air-fuel ratio control means switch the switch valve to a position at which the exhaust gas flows into the bypass passage if the temperature representing the temperature of the SO_x absorbent is higher than the predetermined set temperature when the SO_x should be released from the SO_x and, at the same time, make the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich, and thereafter hold the switch valve at a position at which the exhaust gas flows into the NO_x absorbent and, at the same time, continuously maintain the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich.

27. An exhaust purification device of an internal combustion engine according to claim 1, wherein provision is made of an NO_x releasing control means which lowers the oxygen concentration in the exhaust gas flowing into the NO_x absorbent exactly for a second set period determined in advance so as to release the NO_x from the NO_x absorbent when the period for which the air-fuel ratio of the exhaust gas flowing into the NO_x absorbent is made lean and the NO_x is absorbed into the NO_x absorbent exceeds the predetermined first set period.

28. An exhaust purification device of an internal combustion engine according to claim 27, wherein said NO_x releasing control means provides an NO_x amount estimation means which estimates the amount of NO_x absorbed in the NO_x absorbent;

and said NO_x releasing control means decides that said first set period has elapsed when the NO_x amount estimated by said NO_x amount estimation means exceeds a predetermined maximum value.

29. An exhaust purification device of an internal combustion engine according to claim 28, wherein said NO_x amount estimation means decides that the amount of NO_x absorbed in the NO_x absorbent exceeds said maximum value when the cumulative value of the engine rotational speed exceeds a predetermined set value.

30. An exhaust purification device of an internal combustion engine according to claim 28 , wherein said NO_x amount estimation means estimates the amount of NO_x absorbed into the NO_x absorbent from the amount of NO_x contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the NO_x absorbent is lean, estimates the amount of NO_x released from the NO_x absorbent based on the degree of richness of said exhaust gas when the air-fuel ratio of the exhaust gas flowing into the NO_x absorbent is rich and based on the temperature representing the temperature of the NO_x absorbent, and estimates the amount of NO_x continuously absorbed into the NO_x absorbent from this estimated NO_x release.

31. An exhaust purification device of an internal combustion engine according to claim 30, wherein said NO_x releasing control means decides that said second set period has elapsed when the NO_x amount estimated by said NO_x estimation means becomes smaller than a predetermined minimum value.

32. An exhaust purification device of an internal combustion engine according to claim 1, wherein provision is made of an SO_x releasing control means which makes the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich exactly for a second set period determined in advance so as to release the SO_x from the SO_x absorbent when the period for which the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent is made lean and the SO_x is absorbed into the SO_x absorbent exceeds the predetermined first set period.

33. An exhaust purification device of an internal combustion engine according to claim 32, wherein said SO_x releasing control means provides an SO_x amount estimation means which estimates the amount of NO_x absorbed in the SO_x absorbent;

and said SO_x releasing control means decides that said first set period has elapsed when the SO_x amount estimated by said SO_x amount estimation means exceeds a predetermined maximum value and decides that said second set period has elapsed when the SO_x amount estimated by said SO_x amount estimation means becomes smaller than a predetermined maximum value.

34. An exhaust purification device of an internal combustion engine according to claim 33, wherein said SO_x amount estimation means estimates the amount of SO_x absorbed into the SO_x absorbent from the amount of SO_x contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent is lean, estimates the amount of SO_x released from the SO_x absorbent based on the degree of richness of said exhaust gas when the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent is rich and based on the temperature representing the temperature of the SO_x absorbent, and estimates the amount of SO_x continuously absorbed into the SO_x absorbent from this released SO_x amount.

35. An exhaust purification device of an internal combustion engine according to claim 1, wherein said air-fuel ratio control means controls the air-fuel ratio of the exhaust gas in the exhaust passage and makes the air-fuel ratio of the exhaust gas flowing into the SO_x absorbent rich when the SO_x should be released from the SO_x absorbent.

36. An exhaust purification device of an internal combustion engine according to claim 35, wherein said air-fuel ratio control means feeds a reduction agent into the exhaust passage when the SO_x should be released from the SO_x absorbent.

37. An exhaust purification device of an internal combustion engine according to claim 36, wherein the above-described reduction agent is composed of at least one member selected from gasoline, isooctane, hexane, heptane, butane, propane, light oil, and lamp oil.