Exhaust gas purification device for an engine

• US 5,472,673 A
• Filed: 11/14/1994
• Issued: 12/05/1995
• Est. Priority Date: 08/04/1992
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Iguchi, Satoshi, Katoh, Kenji, Goto, Masato, Kihara, Tetsuro
• Primary Examiner(s): Warden, Robert J.
• Assistant Examiner(s): TRAN, HIEN THI
• Application Number:
  US08/340,438
• Time in Patent Office: 386 Days
• Field of Search: 422/169-171, 60/277, 60/274, 60/276, 60/297, 60/285, 60/301, 423/239.1, 423/213.5, 423/244.01, 423/244.02, 423/244.07, 502/303, 55/385.3, 95/129, 95/137, 96/131, 96/132, 96/116
• US Class Current: 422/169
• CPC Class Codes: B01D 2255/1021 Platinum
• CPC Class Codes: B01D 2255/2042 Barium
• CPC Class Codes: B01D 2255/2045 Calcium
• CPC Class Codes: B01D 2255/2061 Yttrium
• CPC Class Codes: B01D 2255/2063 Lanthanum
• 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 53/9422 for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
• 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 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 3/0807 by using absorbents or adsorbents
• 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: 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

Abstract

An engine comprising an exhaust passage having therein a NO_x absorbent which absorbs the NO_x when the air-fuel ratio of the exhaust gas flowing into the NO_x absorbent is lean and releases the absorbed NO_x when the air-fuel ratio of the exhaust gas flowing into the NO_x absorbent becomes the stoichiometric air-fuel ratio or rich. A sulphur trapping device for trapping SO_x contained in the exhaust gas is arranged in the exhaust passage upstream of the NO_x absorbent.

Claims

1. An exhaust gas purification device for an engine comprising:

an engine;

an exhaust passage which extends from an upstream end which receives exhaust gas from the engine, to a downstream end from which exhaust gas is released;

an NO_x absorbent arranged in the exhaust passage, wherein the NO_x absorbent absorbs NO_x contained in the exhaust gas when a concentration of oxygen in the exhaust gas flowing into the NO_x absorbent is above a predetermined oxygen concentration, and wherein said NO_x absorbent releases the absorbed NO_x when the concentration of oxygen in the exhaust gas flowing into said NO_x absorbent is lower than the predetermined oxygen concentration; and

sulphur trapping means arranged in the exhaust passage upstream of said NO_x absorbent for trapping SO_x contained in the exhaust gas, wherein the trapped SO_x is not released from the sulphur trapping means when the concentration of oxygen in the exhaust gas flowing into said sulphur trapping means is lower than the predetermined oxygen concentration so that SO_x is prevented from reaching and being absorbed into the NO_x absorbent.

2. An exhaust gas purification device according to claim 1, wherein said sulphur trapping means comprises a SO_x absorbent which absorbs SO_x therein.

3. An exhaust gas purification device according to claim 2, wherein said SO_x absorbent contains at least one substance selected from alkali metals comprising potassium, sodium, lithium, cesium;

alkali-earth metals comprising barium, calcium; and

rare-earth metals comprising lanthanum, yttrium and contains platinum.

4. An exhaust gas purification device according to claim 3, wherein said NO_x absorbent includes platinum and contains at least one substance selected from the group consisting of potassium, sodium, lithium, cesium, barium, calcium, lanthanum and yttrium, and wherein an amount of said metals contained in said SO_x absorbent is larger than an amount of said metals contained in said NO_x absorbent.

5. An exhaust gas purification device according to claim 1, further comprising means for controlling the concentration of oxygen in the exhaust gas so that the concentration of oxygen in the exhaust gas is above the predetermined oxygen concentration when NO_x is to be absorbed in said NO_x absorbent and so that the concentration of oxygen in the exhaust gas is below the predetermined oxygen concentration when NO_x is to be released from said NO_x absorbent, wherein the means for controlling the concentration of oxygen in the exhaust gas is coupled to the engine.

6. An exhaust gas purification device according to claim 5, wherein said means for controlling the concentration of oxygen in the exhaust gas includes means for controlling an air-fuel ratio of an air-fuel mixture fed into the engine.

7. An exhaust purification device according to claim 1, wherein said NO_x absorbent includes platinum and contains at least one substance selected from the group consisting of potassium, sodium, lithium, cesium, barium, calcium, lanthanum and yttrium.

8. An exhaust gas purification device according to claim 2, wherein the NO_x absorbent is arranged in a first casing and wherein the SO_x absorbent is arranged in a second casing separate from the first casing.