Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Patent
1993-08-12
1995-04-11
Dolinar, Andrew M.
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
123690, 731181, F02D 4122
Patent
active
054048613
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and a device for assessing the operating capacity of a lambda control of an internal-combustion engine, which outputs regulated values FR which are to fluctuate about a desired regulated value FR.sub.- DES.
In order to generate as little harmful gas as possible when internal-combustion engines are running, these are operated by means of a lambda control with pilot control. This makes it possible to determine fuel quantities which are to be fed respectively to the engine in accordance with the air intake, in such a way that a predetermined lambda value is maintained as accurately as possible. When values of operating quantities change, a value for the fuel metering matched to the changed operating values is determined immediately by the pilot control, and this value is then finely adjusted by means of the lambda control.
The pilot-control values for a particular internal-combustion engine are determined for in each case exactly fixed operating values and operating parameters. However, when an internal-combustion engine is operating under practical conditions, the current operating parameters often deviate from those which were used to determine the pilot-control values, for example a different fuel is used. The predetermined pilot-control values then do not exactly match the current operating situation. To remedy this deficiency, there are so-called learning or adaptive lambda-control systems. These output at least one adaptation value, by means of which the pilot-control values are corrected. The adaptation value is determined by means of the deviation between the regulated value output by a lambda controller and a desired regulated value.
Faults increasing the emission of harmful gas can occur when an internal-combustion engine is in operation. The Californian Environmental Authority CARB demands that a fault is to be indicated when the permissible limit value for a harmful gas is exceeded by 50% during the so-called FTP cycle. It has proposed, in this respect, that at least one adaptation value be monitored and a fault signal output when the latter exceeds a predetermined threshold value.
It was shown that methods and devices according to this proposal are not capable of indicating all the faults which cause the limit value for a harmful gas to be exceeded by 50% in the FTP cycle.
SUMMARY OF THE INVENTION
The object therefore was to provide a method and a device for assessing the operating capacity of a lambda control, which are capable of indicating difficulties in the control which lead to an undesirable increase in the emission of harmful gas.
The method according to the invention for assessing the operating capacity of a lambda control, which outputs regulated values FR which are to fluctuate about a desired regulated value FR.sub.- DES, which lambda control is assisted by an adaptation outputting adaptation values, is characterised in that absolute value of deviation of the regulated values from the desired regulated value, is calculated continuously; and SW.sub.- EW; and decision-quantity threshold value.
Preferably, not only the decision values are used to assess whether the fault signal is to be output, but the values of the at least one adaptation quantity are also included. In this case, the fault signal is output either when the current decision value exceeds the associated threshold value or when an adaptation value exceeds its associated threshold value. In this case, where the decision value is used in addition to the adaptation values for assessing the operating capacity, it is a further advantage to determine the decision value with a higher time constant than the at least one adaptation value. Faults are then usually indicated in terms of the adaptation values, whereas an indication in terms of the decision value takes place only in special cases.
The finding, on which the method mentioned is based, is now to be illustrated by means of an example. Let it be assumed that, under high loads, the fuel pump on the lambda-controlled internal-combust
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patent: 4947818 (1990-08-01), Kamohara et al.
patent: 5065726 (1991-11-01), Klenk
patent: 5070847 (1991-12-01), Akiyama et al.
Dolinar Andrew M.
Robert & Bosch GmbH
Striker Michael J.
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