Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-07-16
2001-03-20
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C123S692000, C123S691000, C701S110000, C701S111000, C701S109000, C073S117020
Reexamination Certificate
active
06202415
ABSTRACT:
BACKGROUND INFORMATION
German Patent No. 1 95 13 156 describes an internal combustion engine, composed of two cylinder banks, in which each cylinder bank has its own exhaust-gas turbocharger. By controlling the exhaust-gas turbines arranged in the exhaust trains of the two cylinder banks, the boost pressure in the shared intake train of the two cylinder banks is controlled to a setpoint value. If at this point, a fault occurs in one of the two exhaust trains, for example, the catalytic converter becomes clogged, or there is a defect in the boost pressure controller, or a malfunction of the exhaust-gas turbine, etc., this becomes noticeable by different rotational frequencies of the two exhaust-gas turbochargers. Namely, the control circuit will compensate for the system deviation of the boost-pressure actual value compared to the boost-pressure setpoint value, caused by the fault occurring on one side, by an upward adjustment of the turbocharger on the fault-free side. In so doing, the rotational frequency of the turbocharger can reach a critical value which results in its destruction.
To rule out the destruction of a turbocharger in the event of a fault, according to German Patent No. 195 13 156, provision is made for a fault-detection device which, when it detects a fault on one side in one of the two exhaust trains, interrupts the closed-loop charging control and switches over to an open-loop control. The open-loop control is designed in such a way that the turbocharger does not enter into its critical rotational-frequency range. For example, the fault-detection circuit detects engine misfirings in the two cylinder banks. In so doing, it determines the rate of occurrence of engine misfirings for the individual cylinder banks and, if the rate of occurrence exceeds a predefined limiting value, it signals that a fault exists on one side in one of the two exhaust trains.
A longer time can pass until a defect in one of the two exhaust trains leads to engine misfirings in one of the cylinder banks, during which time the control circuit will already have adjusted one of the two exhaust-gas turbochargers into a critical rotational-frequency range. Therefore, an object of the present invention is to provide a method and a device for monitoring the functioning of two exhaust-gas turbochargers that belong to two separate cylinder banks of an internal combustion engine, which makes it possible to detect a defect in one of the exhaust trains as quickly as possible, so that appropriate protective measures can be initiated for the turbochargers.
SUMMARY OF THE INVENTION
In the method and device according to the present invention, a determination of irregular running is carried out for each cylinder bank, the irregular-running values ascertained in each case are compared to a lower and an upper threshold value, and the upper threshold value is regulated in such a way that all irregular-running values below it are not caused by combustion misses. A defect in the exhaust train is signaled when an irregular-running value lying between the lower and the upper threshold value is determined for at least one of the two cylinder banks, and the difference between the irregular-running values of the two cylinder banks exceeds a threshold. Using this method or a device implementing this method, a defect is already detected in a timely manner, long before engine misfirings occur.
Instead of subjecting the absolute irregular-running values to a threshold-value decision, irregular-running values averaged over several ignition cycles can also be supplied to the threshold-value decision element.
The method of the present invention also makes it possible to decide which of the two turbochargers is defective. Namely, according to the method, that turbocharger is classified as defective which belongs to a cylinder bank for which an irregular-running value has been determined that lies between the lower and the upper threshold value and is greater than an irregular-running value ascertained for the other cylinder bank.
A plausibility check for a detected defect in an exhaust train can be carried out by comparing the signals from lambda probes, arranged in the exhaust channels of the two cylinder banks, to one another, and drawing upon an amount of deviation between the two lambda probe signals exceeding a predefined limiting value as the plausibility criterion.
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Baeuerle Michael
Lohmann Andrea
Ries-Mueller Klaus
Denion Thomas
Kenyon & Kenyon
Robert & Bosch GmbH
Trieu Thai-Ba
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