Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
2001-05-23
2004-08-24
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
Reexamination Certificate
active
06779388
ABSTRACT:
BACKGROUND INFORMATION
In the operation of internal combustion engines, gaps in the piston ring cause leakage flows from the combustion chamber into the crankcase. These are the so-called blowby losses. As a result, the pressure in the crankcase is increased by the engine oil and oil gases. To prevent the pressure in the crankcase from becoming too great, the blowby gases must be removed from the crankcase. Present-day internal combustion engines use closed ventilation systems. The blowby gases are fed to the intake tract and return again to the combustion chamber. However, it is disadvantageous that the blowby gases lead to contamination of the combustion mixture, thereby negatively affecting combustion.
Ventilation is typically carried out in a closed system, by the vacuum in the intake pipe. Due to stricter exhaust emission regulations, attempts are also underway to produce a certain overpressure in the crankcase using a valve in the vent line, and to first purge the vapors in the presence of a stable (fixed) overpressure.
Legal reasons make it unacceptable to vent the crankcase into the environment. The resulting difficulty is that one must be able to reliably detect leaks, as can occur due to damaged vent lines, for example. To date, this diagnosis has been made indirectly by performing a threshold value comparison on the values of the mixture adaptation. However, in order for the mixture adaptation to respond, the hose diameter must be selected to be wide enough to draw in a corresponding amount of blowby. However, this kind of diagnosis, in turn, limits the design of the crankcase ventilation system.
SUMMARY OF THE INVENTION
The method according to the present invention has the advantage that an exact diagnosis of the crankcase ventilation system is possible, without having to accept structural restrictions. It is particularly advantageous that, on the one hand, the blowby gases and, as such, the engine emissions are reduced as a result of an optimized operating method. On the other hand, friction losses in the crankcase are also reduced, thereby potentially also resulting in advantages with respect to consumption.
It is considered particularly advantageous that the pulse valve is closed for a predefined time span during the pressure build-up phase. In this phase, the pressure change can be determined, and the system can be simultaneously checked for potential leaks.
Adjusting the closing time of the pulse valve as a function of important operating parameters of the internal combustion engine results in an advantageous possibility to optimally control the siphoning of the oil vapors. Thus, in response to a greater engine load, for example, the timing for the pulse valve can be extended, without the combustion process being significantly disrupted.
Ventilation can also be optimized in the case of different operating modes, in particular, stratified operation or homogenous operation.
Since cycle times for the pulse valve can become very short in the event of a high rotational frequency, it is advisable to first open the valve at a preselected pressure. As a result, the flow of the vapors into the intake tract can be controlled, and, thus, ventilation is adapted to the load condition of the engine.
If the engine loses a larger quantity of oil, this also has an effect on the pressure in the crankcase. Checking the pressure characteristic results in a simple method for monitoring the oil level in the crankcase. Advantageously it is, therefore, no longer necessary to use an oil-level sensor.
Furthermore, it is considered advantageous to use conventional pressure sensors for measuring the ambient pressure. Such a sensor is used for fuel tank ventilation, for example.
Advantageously, to comply with environmental demands and to detect potential leaks early, a statement regarding the seal tightness of the ventilation system is made possible by monitoring the pressure characteristic.
Using the pressure signal of the pressure sensor can also be advantageously applied for other control functions. For example, according to oil type, age, and temperature, oil sludge, which can block the line, can be deposited, especially in the vent line, To prevent these deposits or to remove them again, an electrically operated heater is used in some engine systems. This heater is advantageously switched on as needed when there is a pressure signal in the crankcase. If, for example, at cold temperatures, it is detected that there is an increase in pressure in the crankcase, the heater is switched on. However, if there is no increase in pressure, the heater does not need to be switched on, since there is no blockage in the vent line.
Furthermore, it is advantageous to consider the characteristic curve of the pressure signal in assessing engine wear. Particularly in the case of older engines, there is an increase in blowby losses due to the increased clearance between the piston rings and cylinder wall. This then leads to increased pressure in the crankcase with respect to an intact engine. By comparing the measured values to stored threshold values, the state of the engine can be deduced.
REFERENCES:
patent: 3673994 (1972-07-01), Aono
patent: 3754538 (1973-08-01), Ephraim, Jr. et al.
patent: 5697349 (1997-12-01), Blum
patent: 04 237811 (1992-08-01), None
patent: 2723402 (1996-02-01), None
Baeuerle Michael
Ries-Mueller Klaus
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