Measuring and testing – Simulating operating condition – Marine
Reexamination Certificate
1998-06-24
2003-06-10
Oen, William (Department: 2855)
Measuring and testing
Simulating operating condition
Marine
Reexamination Certificate
active
06575022
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to engine crankcase gas blow-by sensors and, more particularly, to an engine crankcase gas blow-by sensor using a venturi and a differential pressure transducer to measure volumetric flow of blow-by gases.
BACKGROUND OF THE INVENTION
Ideally, the pressure within an internal combustion engine crankcase should be maintained at a level equal to or slightly less than atmospheric pressure to prevent external oil leakage through the various gasketed joints, such as that between the valve cover and the cylinder head. As is well known, in an internal combustion engine, a so-called blow-by gas is emitted in the crankcase as a result of leaks of intake air-fuel mixture and combustion gases through the clearances around piston rings, during the compression, combustion and/or exhaust cycles. Because of these blow-by gases, the crankcase pressure will inherently rise, promoting leakage of oil from the crankcase. Originally, the crankcase pressure was vented to the atmosphere through a breather in order to solve this problem.
More recently, environmental considerations have dictated that the blow-by gases in the crankcase be vented back to the combustion chamber rather than being released to the atmosphere. Such closed crankcase ventilation (CCV) systems recycle the blow-by gas by burning these gases together with the intake air-fuel mixture.
Heavy duty and high horsepower internal combustion engines run under severe and sometimes adverse conditions, where engine downtime is expensive and service is not always available. A good method of checking an engine's “health” is to periodically, or preferably continuously, monitor the flow of crankcase blow-by gases. The greater the quantity of blow-by gases escaping around the pistons, the poorer the condition of the engine. Therefore, sensing of the amount of blow-by gas in an engine can detect catastrophic failures (i.e. an instantaneous increase in the amount of blow-by gas) or monitor engine wear over time in order to predict when the engine will require an overhaul (i.e. a slowly increasing amount of blow-by gas).
A good way to measure the volume of blow-by gas entering the crankcase is to measure the pressure of such gases in the crankcase. However, closed crankcase ventilation systems do not allow any of the crankcase gases to be vented through an orifice, which would be required in order to measure the crankcase pressure. There is therefore a need for an alternative way to measure the amount of blow-by gas entering the engine crankcase and to collect this data for making determinations of engine health. The present invention is directed toward meeting this need.
SUMMARY OF THE INVENTION
The present invention relates to an engine crankcase gas blow-by sensor. In a closed crankcase ventilation system, crankcase gases are caused to flow through a venturi which includes high pressure and low pressure taps. The high and low pressure taps are coupled to a differential pressure transducer which produces an output that is proportional to the volumetric flow of crankcase gases through the venturi. The use of a venturi in conjunction with a differential pressure sensor offers a low resistance path for the flow of crankcase gases and allows continuous monitoring of blow-by without exceeding the operating pressure limitations of various oil seals. Such a sensor is particularly suited for closed crankcase ventilation (ccv) systems, as it doesn't require venting of crankcase gases to the atmosphere (but will also work well on open systems).
In one form of the invention, an internal combustion engine is disclosed, comprising at least one cylinder; at least one piston slidingly disposed within the at least one cylinder in order to define a combustion chamber above the piston; an air intake system operable to supply air to the combustion chamber; a crankcase coupled to the at least one cylinder, wherein an interior of the crankcase is in fluid communication with an interior of the at least one cylinder below the at least one piston, wherein combustion gases which blow-by the at least one piston may enter the crankcase; a venturi having an inlet port and an outlet port, wherein the inlet port is coupled to the crankcase interior and the outlet port is coupled to the air intake system such that gas within the crankcase may flow through the venturi; a high pressure tap extending from an exterior of the venturi to an interior of the venturi; a low pressure tap extending from the venturi exterior to the venturi interior; and a sensor coupled to the venturi and operative to measure a differential pressure between the high pressure tap and the low pressure tap.
In another form of the invention, an engine crankcase gas blow-by sensor is disclosed, comprising an engine crankcase operative to contain blow-by gases; an air intake system; a venturi having an inlet port and an outlet port, wherein the inlet port is coupled to an interior of the engine crankcase and the outlet port is coupled to the air intake system such that gas within the crankcase may flow through the venturi; a high pressure tap extending from an exterior of the venturi to an interior of the venturi; a low pressure tap extending from the venturi exterior to the venturi interior; and a sensor coupled to the venturi and operative to measure a differential pressure between the high pressure tap and the low pressure tap.
In another form of the invention a method of evaluating performance of an internal combustion engine is disclosed, comprising the steps of: (a) routing at least a portion of blow-by gases within a crankcase of the engine through a venturi having a high pressure tap and a low pressure tap; (b) measuring a pressure differential between the high pressure tap and the low pressure tap; and (c) outputting a signal that is proportional to the measured pressure differential.
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Bhagwat Abhay P.
Kuhns George M.
Schneider Matthew L.
Schuppe Alfred
Cummins Engine Company, Inc.
Oen William
Woodard, Emhardt, Naughton Moriarty & McNett LLP
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