Exhaust gas purifying facility with nitrogen oxides absorption-reduction catalyst

• US 6,460,329 B2
• Filed: 06/08/2001
• Issued: 10/08/2002
• Est. Priority Date: 06/16/2000
• Status: Expired due to Fees

• Current Assignee: Isuzu Motors Limited
• Original Assignee: Isuzu Motors Limited
• Inventors: Shimotani, Keiji, Tsunoda, Hiroshi, Yamada, Hiroyuki
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): TRAN, BINH Q
• Application Number:
  US09/875,918
• Publication Number:
  US 20020026790A1
• Time in Patent Office: 487 Days
• Field of Search: 602/85, 602/86, 602/95, 602/97, 602/76, 603/01
• US Class Current: 60/285
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2550/03 of sorbing activity of adsorbents or absorbents
• CPC Class Codes: F01N 2570/04 Sulfur or sulfur oxides
• CPC Class Codes: F01N 3/0842 Nitrogen 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 2200/0806 NOx storage amount, i.e. amount of NOx stored on NOx trap
• CPC Class Codes: F02D 2200/0808 NOx storage capacity, i.e. maximum amount of NOx that can be stored on NOx trap
• 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 41/146 the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/1463 of the exhaust gases downstream of exhaust gas treatment apparatus
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

In an exhaust gas purifying apparatus 1 provided with a nitrogen oxides absorption-reduction catalyst 2 for executing rich spike when the integrated value NOx mass of the NOx computed from the operating state of the engine E exceeds the predetermined first reference value NOxSL, a NOx sensor 13 is provided downstream from the nitrogen oxides absorption-reduction catalyst 2 so that the predetermined first reference value NOXSL is corrected when the value RSNOX detected by the NOx sensor 13 immediately after the rich spike is executed exceeds the predetermined second reference value RSSL. In this arrangement, since the variations in the NOx absorbing amount caused by the deterioration of the catalyst is monitored using the value detected by the NOx sensor for introducing a rich spike at appropriate moments, the purifying performance with respect to NOx in exhaust gas can be improved outstanding as a hole.

Claims

1. An exhaust gas purifying apparatus 1 having a nitrogen oxides absorption-reduction catalyst comprising:

a nitrogen oxides absorption-reduction catalyst 2 having a nitrogen oxides absorbing substance 4 provided in the exhaust passage 11 of the internal combustion engine E for absorbing nitrogen oxides when the air/fuel ratio is lean and discharging nitrogen oxides when the air/fuel ratio is theoretical air/fuel ratio or rich, and a precious metal catalyst 3; and

a control apparatus 10 for computing the integrated value of NOx (NOxmass) from the engine load, the number of revolutions of the engine, and the intake air mass, so that a rich spike is executed when the integrated value of NOx (NOxmass) exceeds the predetermined first reference value (NOxSL);

characterized in that a NOx sensor 13 is provided downstream from the nitrogen oxides absorption-reduction catalyst 2, and in that the control apparatus 10 corrects the predetermined first reference value (NOxSL) when the value detected by the NOx sensor 13 (RSNOx) immediately after the rich spike is executed exceeds the predetermined second reference value (RSSL).

2. An exhaust gas purifying apparatus having a nitrogen oxides absorption-reduction catalyst as set forth in claim 1, characterized in that the control apparatus 10 performs the operation in regeneration mode in the rich air/fuel ratio when the predetermined first reference value (NOXSL) is smaller than the predetermined third reference value (RGSL).

3. An exhaust gas purifying apparatus having a nitrogen oxides absorption-reduction catalyst as set forth in claim 2, characterized in that the control apparatus 10 determines that the nitrogen. oxides absorption-reduction catalyst 2 is in the abnormal state when the value detected by the NOx sensor 13 (RSNOx) immediately after executing the operation in regeneration mode exceeds the predetermined fourth reference value (RSSL2).