Process for checking the operability of an exhaust gas purification catalyst

• US 6,739,176 B2
• Filed: 03/16/2001
• Issued: 05/25/2004
• Est. Priority Date: 03/21/2000
• Status: Expired due to Term

• Current Assignee: Umicore AG & Company KG (Umicore S.A.)
• Original Assignee: dmc2 Degussa Metals Catalysts Cerdec AG (Vectra Corp.)
• Inventors: Lox, Egbert, Klein, Harald, Kreuzer, Thomas, Gieshoff, Jürgen, Neuhausen, Ulrich
• Primary Examiner(s): Pert, Evan
• Assistant Examiner(s): Harrison, Monica D.
• Application Number:
  US09/809,355
• Publication Number:
  US 20010033815A1
• Time in Patent Office: 1,166 Days
• Field of Search: 73/233.1, 73/233.2, 731/181, 731/182, 73/250.1, 731/16, 73/310.6, 602/74, 602/75, 602/76, 602/77, 602/85, 602/70, 701/109, 701/103, 701/101
• US Class Current: 73/23.31
• 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 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 11/005 the temperature or pressure being estimated, e.g. by means of a theoretical model
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A process for checking the operability of an exhaust gas purification catalyst for diesel engines, which has a light-off temperature and a degree of conversion r_CO for carbon monoxide (CO), by direct measurement of the carbon monoxide concentration in combination with a temperature measurement. To evaluate the remaining catalytic activity of the catalyst the difference ΔT between the current catalyst exit temperature T_E of the exhaust gas and the light-off temperature T_CO,50%,fresh of the fresh catalyst for carbon monoxide stored as a function of the speed and load

ΔT=T_E−T_CO,50%,fresh

is determined and the degree of conversion r_CO for carbon monoxide is ascertained.

Claims

1. A process for checking the operability of a catalyst for purification of the exhaust gases of a combustion engine during operation of the engine, wherein the catalyst comprises a light-off temperature T_CO,50% and a conversion ratio r_CO for carbon monoxide and the combustion engine is equipped with an electronic control system comprising engine electronics and OBD electronics and wherein a malfunction of the catalyst exists at an operation point of the engine if the conversion ratio r_CO for carbon monoxide is below a limit value r_{CO, L} while simultaneously the exhaust gas temperature T_E is by an amount Δ

T_L larger than the light-off temperature T_{CO,50%, new} of the new catalyst.

2. A process according to claim 1, wherein the conversion ratio r_CO for carbon monoxide is determined as:

$r_{\mathrm{CO}}=1-\frac{c_{\mathrm{CO},2}}{c_{\mathrm{CO},1}},$

wherein c_CO,2 is the measured concentration of carbon monoxide in the exhaust gas after the catalyst and c_CO,1 is the measured concentration of carbon monoxide before the catalyst.

3. A process according to claim 1, wherein the conversion ratio r_CO for carbon monoxide is determined as:

$r_{\mathrm{CO}}=1-\frac{c_{\mathrm{CO},2}}{c_{\mathrm{CO},\mathrm{engine}}},$

wherein c_CO,2 is the concentration of carbon monoxide in the exhaust gas after the catalyst and c_CO,engine is the concentration of carbon monoxide stored as performance characteristic of the corresponding engine operation point in the electronic OBD system.

4. A process according to claim 1, wherein a malfunction of the catalyst is registered in the OBD-electronics.

5. A process according to claim 4, wherein determination of malfunction of the catalyst is done at a selection of operation points.

6. A process according to claim 5, wherein the catalyst is rated severely damaged if a number of operation points for which a malfunction was found exceeds a preset permissible number n_M of operation points with catalyst malfunction.

7. A process according to claim 5, wherein the catalyst is rated severely damaged if the number of operation points for which a malfunction was found exceeds a preset permissible number n_M of operation points with catalyst malfunction during a preset time interval Δ

t_M.

8. A process according to claim 6, wherein when the catalyst is rated severely damaged, a signal for replacing the catalyst is given.