Power plants – Internal combustion engine with treatment or handling of... – Methods
Reexamination Certificate
1999-05-14
2001-08-07
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Methods
C060S277000, C060S285000, C123S479000, C123S481000, C123S090110
Reexamination Certificate
active
06269632
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 198 23 021.4 filed May 22, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to a method of operating an externally ignited, piston-type internal-combustion engine having electromagnetic valve drives for operating the cylinder valves which are fully variably controllable by an electronic engine control for adapting their timing to varying operational conditions. The engine further has a fuel injection device for the individual cylinders.
In internal-combustion engines of the above-outlined type an ignition failure may cause damage to an exhaust gas catalyst of the engine, because an uncombusted charge is admitted to the exhaust gas system. In case of an injection failure, unintended air is admitted to the exhaust gas system, causing the catalyst control to enrich the fuel supplied to the other cylinders. Such an occurrence may have an adverse effect on the emission and also on the catalyst.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved method of the above-outlined type which eliminates the discussed disadvantages.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of operating an externally-ignited internal-combustion engine which includes a plurality of engine cylinders each provided with cylinder valves, an ignition device, a fuel injection device and an electromagnetic valve drive for operating the cylinder valves, and which further includes an electronic engine control for controlling the cylinder valves, includes the following steps: monitoring the operation of the ignition device and/or the fuel injection device of each cylinder; and, during cold start and/or when a spark failure and/or an injection failure is detected in one of the cylinders during the monitoring step, adapting the control of the electromagnetic valve drives of that cylinder to the changed operational conditions.
Since both the fuel injection device and the occurrence of spark failures are monitored, the engine control may react to make suitable adaptations.
In case of a spark failure, the affected cylinder is filled with an air/fuel mixture which in the normal operational cycle would be driven uncombusted into the exhaust gas system. In an internal-combustion engine having an exhaust gas catalyst, particularly a regulated exhaust gas catalyst, such an occurrence may cause not only an overheating of the catalyst system but also an erroneous measurement by the regulating device of the exhaust catalyst takes place which, by means of a lambda-probe detects an erroneous value for a fuel excess in the exhaust gas, thus changing the fuel supply for the other, correctly operating cylinders.
In case of an injection failure, air instead of exhaust gas is driven into the exhaust system from the affected cylinder, so that the lambda-probe of the regulating device of the exhaust gas catalyst detects an excessive amount of oxygen in the exhaust gas and then, for the remaining, correctly operating cylinders the fuel supply is increased and thus the mixture is enriched which may be disadvantageous for the catalyst and may lead to increased pollutant emissions.
This method may find application in cold-starting conditions to increase the injected fuel quantities. As a result, a more favorable design of the fuel injection nozzle may be obtained. A fuel injection nozzle should normally be designed such that it is capable of delivering the required cold start fuel quantities. When using the method according to the invention, the nozzle, however, may be designed in a more advantageous manner since the quantity spread has to be designed only for a normal engine operation. In such a cold-starting strategy the ignition may remain switched off in the “first” second stroke or an ignition may be attempted, so that in case of success, an additional injection may be dispensed with.
According to a modification of the method for a cold start of the engine, the intake port may remain closed for a further one-half or entire work cycle, so that particularly in the first work cycle a sufficient excess starting quantity is made available. Since such a method is used for all the cylinders of the internal-combustion engine in the start phase, the insertion of a half stroke for synchronizing by empty strokes may also be dispensed with.
The method according to the invention thus advantageously utilizes the fact that in electromagnetic valve drives coupled with an electronic engine control the control of the cylinder valves is fully variable, that is, by means of the electronic engine control not only the valve operating times may be varied in the usual manner for adapting them to the different load conditions but, according to requirements, for the individual cylinders an individual control may be effected as well. If the engine control recognizes a combustion failure based on a spark failure, then by means of the engine control the exhaust valves of the affected cylinder may be maintained closed. Then, in the subsequent work cycle ignition is again attempted with the “old” mixture (charge). At the same time, the fuel injection device of the affected cylinder is shut off for the respective work cycle. Should the ignition be successful, the operation may continue in a normal manner. If the ignition does not succeed, a displacement of the mixture from the cylinder into the exhaust gas system must be considered. In case of a multiple failure the possibility is also provided to expel the mixture in doses in a switched-off state of the fuel injection system. Thus, particularly in case of a large charge introduced into the cylinder for full load or partial load conditions, the exhaust valves are controlled such that the doses of the charge are released by distributing them over several work cycles. In this manner a high stress on the catalyst is avoided.
In case a combustion does not occur because of an injection failure, then, during the upward motion of the piston, the intake valve is opened instead of the exhaust valve and the air contained in the cylinder is driven back into the intake port, so that a new dose of fuel may be injected into the returned air to obtain a combustion mixture. This measure prevents unintended air from gaining access to the exhaust gas system, and prevents the lambda-probe of the exhaust catalyst regulator from emitting a false signal concerning the exhaust gas composition which would lead to an increase of the fuel supply to the other cylinders for incorrectly enriching the air/fuel mixture. In case the injection to a cylinder misses several times consecutively, the engine control may immobilize the cylinder valves of the affected cylinder entirely or set only the gas outlet valves in a half-open position and, at the same time, shut off the fuel injection device of that cylinder, so that the internal-combustion engine only operates on the remaining cylinders. With a suitable design of the engine control, the idling state of one cylinder may be compensated for to a certain degree, so that the internal-combustion engine still operates with a sufficient power, for example, by changing the control times of the valves of the other cylinders to thus ensure a larger charge for each cylinder.
The method according to the invention is expediently so designed that the engine control applies, to the regulating device of the exhaust catalyst, a setting signal which serves for affecting the catalyst regulation and which is differentiated according to the respective failure event (spark failure or injection failure). In this manner, the lambda-probe regulation is “informed” about the respective control strategy of the engine control and is affected in such a manner that for the regulation of the catalyst, an introduction of uncombusted mixtures into the exhaust system in case of spark failure or an introduction of unintended air into the exhaust
Denion Thomas
FEV Motorentechnik GmbH
Kelemen Gabor J.
Tran Binh
Venable
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