Catalyst temperature control device and method of internal combustion engine

(54) CATALYST TEMPERATURE CONTROL DEVICE AND METHOD OF INTERNAL COMBUSTION ENGINE

(75) Inventors: Hideaki Takahashi; Kimiyoshi

Nishizawa, both of Yokohama (JP)

(73) Assignee: Nissan Motor Co., Ltd., Yokohama (JP)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 09/537,515

(22) Filed: Mar. 29, 2000

(30) Foreign Application Priority Data

Mar. 30, 1999 (JP) 11-087895

(51) Int. C I. F01N 3/00

(52) U.S. CI 60/286; 60/285; 60/297;

60/300; 123/295; 123/300; 123/430; 123/431

(58) Field of Search 60/285, 300, 286,

60/297, 303, 277; 123/299, 295, 300, 430,

431

(56) References Cited

U.S. PATENT DOCUMENTS

5,479,775 A * 1/1996 Kraemer et al 60/274

5,974,791 A * 11/1999 Hirota et al 60/276

5,975,045 A * 11/1999 Mizuno 123/295

6,067,954 A * 5/2000 Kudou et al 123/299

6,141,960 A * 11/2000 Takami et al 60/286

6,173,571 Bl * 1/2001 Kaneko et al 60/286

* cited by examiner

Primary Examiner—-Thomas Denion

Assistant Examiner—Binh Tran

(74) Attorney, Agent, or Firm—Foley & Lardner

(57) ABSTRACT

A catalyst (9) is disposed in an exhaust passage (8) of an internal combustion engine (1) for trapping nitrogen oxides in the exhaust from a fuel mixture of a lean air-fuel ratio and reducing trapped nitrogen oxides in the exhaust from a fuel mixture of an air-fuel ratio other than the lean air-fuel ratio. The catalyst (9) also traps sulfur oxides in the exhaust when the catalyst temperature is less than a predetermined temperature, and discharges the trapped sulfur oxides when the catalyst temperature rises above the predetermined temperature. A microprocessor (10) calculates for example the sulfur oxide stored amount of the catalyst (9) based on engine running conditions, and determines that sulfur oxide discharge condition is satisfied when the sulfur oxide stored amount exceeds a predetermined amount. When the discharge condition is satisfied, the microprocessor (10) controls the fuel injection amount and fuel injection timing of the fuel injector (6) so as to generate a stratified air-fuel mixture in the combustion chamber (3). The stratified airfuel mixture comprises a first layer surrounding the spark plug (7) and a second layer situated outside the first layer. The first layer comprises an atomized air-fuel mixture of a rich air-fuel ratio within an ignitable range. The second layer is leaner than the first layer.

28 Claims, 17 Drawing Sheets