US 6,382,199 B1Granted

Method for diagnosing an exhaust-gas recirculation system of an internal combustion engine

AssigneeRobert Bosch GmbH

InventorsClaus-Dieter Nusser, Axel Stuber, Bernd Landes, Martin Haussmann, Peter Henkelmann, Joerg Kerner, Guido Ehlers

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Abstract

A method for diagnosing an exhaust-gas recirculation system of an internal combustion engine provides that the fuel quantity, which is needed for a desired mixture composition, is computed, at least approximately, in a control apparatus from at least stored data of the EGR system. The stored data can be in the form of a through-flow characteristic line. Thereafter, the fuel quantity is corrected by a control factor in dependence upon the mixture composition. The control factor is computed and stored when the EGR system is switched on and the control factor is computed and stored when the EGR system is switched off. The difference of these control factors is then formed and compared to pregiven values. A fault signal is outputted in the event of a deviation.

Claims6

Dependent claims

A method for diagnosing an exhaust-gas recirculation system of an internal combustion engine including a control apparatus for controlling said engine, the method comprising the steps of:

computing approximately a fuel quantity needed for a desired mixture composition in said control apparatus from stored data of said exhaust-gas recirculation system;
providing a lambda probe in said exhaust-gas recirculation system to generate a lambda control factor for operating on the time for injecting said fuel quantity;
checking whether following switch-on conditions for switching on said exhaust-gas recirculation system are satisfied:
(a) the engine is in a specific rpm/load window;
(b) the lambda control is active;
(c) the exhaust-gas recirculation is capable of activation;
and,
(d) the engine temperature exceeds a certain pregiven threshold;
when the switch-on conditions are satisfied, then:
computing and storing a first value of a lambda control factor for said desired mixture composition while said exhaust-gas recirculation system is switched on;
computing and storing a second value of said lambda control factor while said exhaust-gas recirculation system is switched off;
forming the difference between said first and second values of said lambda control factor;
comparing said difference to pregiven values;
and,
if said difference constitutes a departure from said pregiven values, then outputting a fault signal indicative of a fault in said exhaust-gas recirculation system.

12 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/759,458Filed 16 Jan 2001 · continuation
Priority: DE 197 19 2787 May 1997
Published: US 2001/0003919 A121 Jun 2001
Granted: 7 May 2002
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

F02D 41/0055
According to engine operating conditions: special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus
F02D 21/08
Peculiar to engines having other non-fuel gas added to combustion air: the other gas being the exhaust gas of engine
F02D 41/221
Safety or indicating devices for abnormal conditions: relating to the failure of actuators or electrically driven elements
F02M 26/46
Sensors specially adapted for EGR systems: for determining the characteristics of gases, e.g. composition