US007886588B2 (12) United States Patent (10) Patent No.: US 7,886,588 B2 PÖhmerer et al. (45) Date of Patent: Feb. 15, 2011 (54) METHOD FOR DETERMINING CURRENT (56) References Cited OXYGEN LOADING OF A 3-WAY CATALYTIC CONVERTER OF A LAMBDA-CONTROLLED U.S. PATENT DOCUMENTS INTERNAL COMBUSTON ENGINE 5,842,339 A 12/1998 Bush et al. 6,694,243 B2 * 2/2004 Shi et al. .................... TO1,114 (75) Inventors: Wolf-Dieter Pöhmerer, Colomiers (FR): 2002fOO69864 A1 6/2002 Takahashi et al. Volker Renz, Würzburg (DE); Gerd 2002fO116919 A1 8, 2002 Rosel et al. Rösel, Regensburg (DE); Milos Tichy, 2002/O120386 A1* 8, 2002 Shi et al. .................... TO1,114 Regensburg (DE) 2005, 0166578 A1 8, 2005 Pohmerer et al. (73) Assignee: Continental Automotive GmbH, 2008/O163608 A1* 7/2008 Yacoub ....................... 60,276 Hannover (DE) 2009/0126344 A1* 5/2009 Arlt et al. ..................... 60,276 (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 FOREIGN PATENT DOCUMENTS U.S.C. 154(b) by 520 days. DE 19851843 A1 5, 2000 DE 19953. 601 C2 5, 2001 (21) Appl. No.: 10/590,788 DE 19953691 A1 5, 2001 (22) PCT Filed: Dec. 6, 2004 DE 100 39 709 A1 3, 2002 (86). PCT No.: PCT/EP2004/053283 (Continued) S371 (c)(1), (2), (4) Date: Sep. 11, 2008 OTHER PUBLICATIONS Japanese Office Action, JP Application No. 2006-553462. 23 pages, (87) PCT Pub. No.: WO2005/083250 Apr. 28, 2009. PCT Pub. Date: Sep. 9, 2005 Primary Examiner Eric S McCall (74) Attorney, Agent, or Firm—King & Spalding L.L.P. (65) Prior Publication Data (57) ABSTRACT US 2008/0314O23 A1 Dec. 25, 2008 (30) Foreign Application Priority Data The invention relates to a method for determining the actual Feb. 27, 2004 (DE) ....................... 10 2004 O09 615 oxygen load of a 3-path catalyst of a lambda-controlled inter nal combustion engine, whereby a value for the actual oxygen (51) Int. Cl. load is calculated from the signal of a pre-catalyst lambda GOIM 5/10 (2006.01) probe and the measured air mass flow rate by integration over (52) U.S. Cl. ................................................... 73/114.75 time, whereby the post-catalyst lambda probe is initialized (58) Field of Classification Search .............. 73/114.69, when the signal is interrupted. 73/114.71, 114.73, 114.75 See application file for complete search history. 14 Claims, 5 Drawing Sheets US 7,886,588 B2 Page 2 FOREIGN PATENT DOCUMENTS JP 2003O49639 A 2, 2003 WO WO994.7795 A2 9, 1999 DE 102 O1989 A1 T 2003 WO WOO 109490 A1 2, 2001 DE 102 20 337 A1 11, 2003 WO WO2005/083250 9, 2005 EP 1718853 A1 11, 2006 * cited by examiner U.S. Patent Feb. 15, 2011 Sheet 1 of 5 US 7,886,588 B2 FIG 3 U.S. Patent Feb. 15, 2011 Sheet 2 of 5 US 7,886,588 B2 FIG 3 Post-Converter signal breakthrough down/up? mO2 is set too mg or, as 18 the case may be, to mO2max 20 Integration over time Post-Converter signal breakthrough down/up? ls the air-mass integral since the last breakthrough too large? 26 Adaptation and storage of mC2 max 28 integration over time, calculation of current qO2 U.S. Patent Feb. 15, 2011 Sheet 3 of 5 US 7,886,588 B2 FIG 4 U.S. Patent Feb. 15, 2011 Sheet 4 of 5 US 7,886,588 B2 100 -S ---------------------------------------------------- s na cNO 50------------------N---------------------------------- t O t tpUC end OO --S-------------------------rear a as a ball a try - Ysis is brax a srate CN 50 w er sys r aw t PUC end \ t U.S. Patent Feb. 15, 2011 Sheet 5 of 5 US 7,886,588 B2 US 7,886,588 B2 1. 2 METHOD FOR DETERMINING CURRENT The post-converter lambda probe's signal is therefore usu OXYGEN LOADING OF A 3-WAY CATALYTIC ally constant in the case of a catalytic converter having suffi CONVERTER OF A LAMBDA-CONTROLLED cient oxygen storage capacity and a properly functioning INTERNAL COMBUSTON ENGINE lambda controller. If the signal rises or falls, the catalytic converter has been either sated with oxygen or completely CROSS REFERENCE TO RELATED emptied of oxygen so that it will no longer be able to com APPLICATIONS pensate a fluctuation in the fuel/air ratio. This is referred to also as “breaking through' of the post-converter lambda This application is the US National Stage of International probe's signal to a rich or, as the case may be, lean mixture. Application No. PCT/EP2004/053283, filed Dec. 6, 2004 and 10 Breaking through of the post-converter lambda-probe Sig claims the benefit thereof. The International Application nal hence indicates that the catalytic converters oxygen Stor claims the benefits of German Patent application No. 10 2004 age capacity is exhausted or that no more oxygen is stored. 009 615.5 filed Feb. 27, 2004. All of the applications are However, no information is available between said two lim incorporated by reference herein in their entirety. iting values about the catalytic converter's actual, current oxygen loading. Said information would, though, be very FIELD OF THE INVENTION 15 helpful for maintaining the oxygen loading at around half the The invention relates to a method for determining current storage capacity and hence for providing the same buffering oxygen loading of a 3-way catalytic converter of a lambda on the rich and lean side, as a result of which breaking through controlled internal combustion engine having a linear pre of the post-converter lambda-probe signal will be preven converter lambda probe connected upstream of the catalytic tively avoided and the most favorable conditions for catalytic converter, a post-converter lambda probe connected down converter diagnosing furthermore created. stream of the catalytic converter, and a device for measuring SUMMARY OF THE INVENTION the air-mass flow rate. The invention is furthermore directed toward a number of methods for regulating, controlling, and/ or monitoring the exhaust treatment of a lambda-controlled 25 The object of the invention is therefore to provide a method internal combustion engine that use the values determined by for determining current oxygen loading of a lambda-con means of the inventive method for the catalytic converters trolled internal combustion engine's 3-way catalytic con current oxygen loading. Verter. Said object is achieved by means of the invention defined in BACKGROUND OF THE INVENTION 30 the claims. Advantageous developments of the invention are the Sub A 3-way catalytic converter can only convert pollutants in ject of the subclaims. an optimal manner if the fuel/air ratio is within a narrow range The method for determining current oxygen loading around lambdas 1. Said range is referred to also as the cata employs the signals of a linear pre-converter lambda probe, of lytic-converter window. Only with fuel/air ratios of said kind 35 a post-converter lambda probe, and of a device for measuring will the exhaust composition be such that the oxygen released the air-mass flow rate, with a value for current oxygen loading when the nitrogen oxides are reduced will suffice to almost being calculated from the pre-converter lambda probe's sig completely oxidize the exhaust gas’s HC and CO components nal and from the measured air-mass flow rate by integration into CO and H2O. Mixing is therefore controlled in an inter over time and said value being set to 0 if the post-converter nal combustion engine having a 3-way catalytic converter by 40 lambda probe's signal breaks through to rich mixtures, what is termed a lambda controller to a target value of because breaking through indicates that no more oxygen is lambdas 1. To compensate brief fluctuations in the fuel/air stored in the catalytic converter. Integrated faults, for example ratio the catalytic converter also contains a coating (wash measuring faults in the air-mass flow rate or in the pre-con coat) made of a material, for example CeO (di-cerium tri verter lambda probe's signal, will be reset through said cali oxide), that can briefly store oxygen and will bind or release 45 brating. it as and when required. The value for current oxygen loading is preferably calcu A linear pre-converter lambda probe is arranged upstream lated using the formula of the catalytic converter so that mixing can be controlled. Said probe measures the residual oxygen component con tained in the exhaust gas. A post-converter lambda probe 50 1 downstream of the catalytic converter serves to monitor the inO2 = (O2). o (I rihL dt, catalytic converter function. The catalytic converter's oxygen storage capacity is therein checked using what is termed OSC-based catalytic-converter diagnosing (OSC-oxygen where mo2 is the current oxygen loading, w is the pre storage capacity). Rich/lean oscillating of the mixture is pro- 55 converter lambda probe's signal, rinL is the air-mass flow rate, duced for this purpose through pre-controlling by the lambda and 02 is the mass component of oxygen in air. The latter controller. An intact catalytic converter will compensate is about 23%. The values for w and mL are time-dependent. oscillating using its oxygen storage capacity so that the post If current oxygen loading is determined continuously in converter lambda probe's probe voltage will oscillate with this manner it will also be possible to calculate a value for the only a small amplitude. If though, the catalytic converter has 60 catalytic converter's oxygen storage capacity.