Method and arrangement for diagnosing the open-loop control of t

Details Method and arrangement for diagnosing the open-loop control of t Method and arrangement for diagnosing the open-loop control of t

1991-11-04

1993-09-14

Raevis, Robert

Measuring and testing

Vehicle chassis

Steering

731181, G01M 1500

Patent

active

052438538

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a diagnostic method for checking actuating elements of the closed-lop and/or open-loop control of operating parameters in combination with the idle control and the tank venting for internal combustion engines having an electronics control unit. During the operation of an internal combustion engine, it is known to trap gasoline vapors escaping from the tank primarily for reasons of environmental protection. This usually takes place with the aid of an activated-carbon filter which is flushed into the intake region of the engine via an assigned tank-venting valve (TEV) by means of a correspondingly clocked drive In this way, an additional air-quantity flow is supplied to the engine. The fuel component in the regenerating gas flow is adapted. The fuel quantity supplied to the engine is correspondingly reduced. For this reason, it is conventional to introduce a so-called mixture-adaptation inhibit during the tank-venting phases in order to prevent the occurrence of mis-adaptation and falsification in the characteristic fields of the learning systems because of tank-venting quantities which are difficult to detect.


BACKGROUND OF THE INVENTION

A diagnostic method for quantitatively checking actuating elements in internal combustion engines (U.S. Pat. No. 4,794,790) is known for which however a diagnosis is only then possible when the regenerating gas flow contains so little fuel that practically no additional fuel quantity results when a regenerating gas flow is supplied via the tank-venting valve.
Accordingly, it is an object of the invention to provide an appropriate diagnostic method which permits such actuators to be checked independently of the air/fuel ratio of the regenerating flow during operation.


SUMMARY OF THE INVENTION

The invention affords the advantage relative to what is known in that a check of the tank-venting valve can take place independently as to how much the activated carbon filter taking up the fuel vapors is saturated. For this reason, this check can be made any time during idle operation independently of how long the engine has already been in operation.
A check is also possible at any time in a service station. It is conceivable that this check can be carried out by a suitable test program or also by manual intervention from the outside. In addition, the diagnostic method presented here affords the advantage that no additional sensors are needed therefor. Precisely these sensors cause relatively high cost with the corresponding circuitry and present additional sources of error. This means that the suggested diagnostic method operates economically.
When the air/fuel ratio of the regenerating gas flow is equal to or greater than the air-fuel ratio at which the engine usually operates (.lambda..sub.0), then, for example, further test cycles can be carried out on the same basis in such a manner that a check of the idle actuator can be carried out in addition to the check of the tank-venting valve. The value of .lambda..sub.0 usually lies at 1. A .lambda..sub.0 >1 is as a rule required for lean engines.


BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are shown in the drawing and will be more carefully described in the following description.
FIG. 1 is a simplified schematic in the form of a block circuit diagram showing a possible realization of electronic, electrical and electro-mechanical closed-loop and open-loop elements as well as actuating elements for the operation of an engine with especially the regions of idle control as well as tank venting being presented;
FIG. 2 shows a flowchart of the diagnostic method for checking the tank-venting system; and,
FIG. 3 shows the flowchart of the diagnostic method for checking the tank-venting system and the idle open-loop control system.


DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The basic idea of the present invention is to carry out an actuator element diagnosis for the area of tank venting during operation of a motor vehicle and while the engine is ru

REFERENCES:
patent: 4402217 (1983-09-01), Higashiyama
patent: 4467769 (1984-08-01), Matsumura
patent: 4794790 (1989-01-01), Margarit-Metaxa et al.

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