Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Patent
1991-09-05
1993-08-03
Koczo, Michael
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
123425, F02B 3712, F02P 514
Patent
active
052318303
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for the closed-loop knock control of an internal combustion engine. A method for closed loop knock control is known in which--when one cylinder knocks an ignition angle retardation of at least this cylinder and then a resetting of the ignition angle is effected.
In the operation of an internal combustion engine, so-called "knocking" represents a critical operating condition which has an extremely unfavorable effect on the life of the internal combustion engine. A so-called closed-loop knock control which shifts the ignition angle in the "retarded" direction when a cylinder of the internal combustion engine knocks is known. This shift of the ignition angle allows knocking to be eliminated. After a certain time, controlled resetting to the original ignition angle, which is, for example, stored in a map, is effected. The controlled resetting is preferably carried out in steps until the controlled map angle is reached. If the cylinder knocks again, the process is repeated. The resetting is not carried out as far as the controlled map angle if knocking has already occurred previously. A retardation is then performed again starting from the current ignition angle.
A so-called adaptive closed-loop knock control is also known, in which the ignition angle at which the associated cylinder knocks with a permissible knocking intensity is stored. This ignition angle is used in subsequent control operations instead of an ignition angle stored in a map.
In turbocharged engines, ignition angle retardation is problematic because this leads to an increase in the exhaust gas temperature and thus to a possibly impermissible thermal loading of the turbine of the turbocharger.
SUMMARY OF THE INVENTION
In contrast, the method according to the invention for the closed-loop knock control of an internal combustion engine has the advantage that it can be employed in internal combustion engines with a turbocharger. According to the invention, when an ignition-angle limiting value dependent on the exhaust gas temperature of the internal combustion engine is reached, a reduction of the boost pressure of the turbocharger is effected. For as long as the ignition-angle limiting value is exceeded, the boost pressure, preferably in each case after a delay, is reduced by a defined amount. The boost pressure is increased again as soon as the ignition-angle limiting value is reassumed due to the resetting or controlled resetting of the ignition angle, the boost pressure values established being stored as a function of the respective operating condition of the internal combustion engine for the purpose of adaptive process control and adopted as starting values when the same operating conditions are driven to again. This is thus an adaptive closed-loop knock control with regard to the boost pressure, i.e. a closed-loop knock control which adapts itself. The exhaust gas temperature problems to be expected due to the ignition retardation are counteracted due to the reduction of the boost pressure. The associated data of the operating conditions driven to in each case are stored, enabling the already stored, i.e. "learned" values to be used again when a particular operating condition is reached once more. With regard to the ignition angle, it is also possible for the required retardations of the cylinders to be stored for adaptive process control, i.e. the "learned" ignition angle retardations come into effect very rapidly at, for example, a transition from idling to full load. In order to avoid an excessively high temperature of the outlet valves of the internal combustion engine and--as already mentioned--of the turbocharger, the boost pressure is immediately reduced by the adapted amount. This spontaneous boost pressure reduction does not even allow the exhaust gas temperature problems mentioned to occur in the first place.
According to a further development of the invention, it is envisaged that the ignition angle retardation and the resetting or controlled resetting of the ignit
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Entenmann Robert
Philipp Matthias
Rohde Siegfried
Rothhaar Ulrich
Stengel Bernhard
Koczo Michael
Robert & Bosch GmbH
Striker Michael J.
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