Internal-combustion engines – Charge forming device – Crankcase vapor used with combustible mixture
Reexamination Certificate
2000-01-28
2001-03-06
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Charge forming device
Crankcase vapor used with combustible mixture
C123S573000
Reexamination Certificate
active
06196206
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for cleaning internal combustion engine crankcase breather (blow-by) gas and an internal combustion engine including said apparatus.
During the compression and power strokes in an internal combustion engine, the difference in gas pressures above and below a piston is sufficient to cause leakage (blow-by) of gas past the piston into the engine crankcase. The resulting increase in pressure within the crankcase can force oil past by the engine oil seals and this pressure may also damage the seals and hence lead to further leakage of oil.
To diminish the damaging effects of blow-by it is normal to relieve the crankcase pressure either by venting the breather gas to atmosphere via an open breather or by connecting the crankcase to the engine air intake system whereby breather gas is conveyed to the engine combustion chamber via the engine air inlet system and under the control of a pressure regulating means. This latter system constitutes a closed-circuit breather system.
It is desirable to include, in breather systems, means to retrieve oil contained in breather gas and return this to the engine lubricating oil system for re-use. Otherwise the carry-over of oil will lead to pollution and, in a closed-circuit system, to fouling of turbocharger compressor vanes, engine poppet valves and other components in contact with inlet air.
As well as leading to contamination and emission problems, the carry-over of oil in breather gas will reduce the volume of oil available for the lubricating and cooling requirements of the engine. It is desirable to minimised oil carry-over, and an oil/air separator is therefore included in most closed-circuit breather systems.
A further problem with oil carry-over in the closed-circuit breather system of an engine, especially of the diesel type, is that the oil can fuel the engine and lead to an unintentional and possibly severe increase in engine speed known as ‘run-away’.
The run-away problem may be exacerbated where, the engine is operated at high gradients (angles of inclination), especially where conditions of abuse prevail, and in particular where the designed maximum oil level in the sump has been exceeded, where the intake air filter is dirty and/or where blow-by levels are high due to engine wear. Under these abuse conditions, even where a conventional separator is provided the breather system may take up more oil than the separator can handle and oil can be drawn into the engine air intake system and hence to the combustion chamber where it can fuel the engine and lead to run-away.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for separating oil from breather gas in an internal combustion engine, in particular an engine operating at high gradients.
It is a further object of the present invention to provide a method of separating oil from breather gas in an internal combustion engine, in particular an engine operating at high gradients.
According to a first aspect of the present invention an internal combustion engine breather system comprises:
a lower engine volume defined by an engine crankcase and an upper engine volume defined by a top cover;
an upper forward part of the crankcase including a housing defining a volume to accept a fuel injectior pump;
breather gas inlet means disposed to receive breather gas from one or more locations within the volume defined by the fuel injector pump housing;
breather gas conduit means fluidly connecting said breather gas inlet means to a separator capable of separating oil from suspension within the breather gas;
breather balancing conduit means to fluidly connect the separator to the upper volume defined by the top cover of the casing;
oil drain means to remove separated oil from the separator;
gas outlet conduit means to remove the cleaned gaseous product from the separator.
Conventional breather devices generally have the breather inlet means positioned to accept breather gas from the volume within the engine casing defined by the top cover. In accordance with the present invention, at least some of the breather gas is taken from the vicinity of fuel injector pump housing in the forward part of the engine crankcase. It has been found that, particularly where engines are operating at severe inclinations, gas taken from this part of the engine casing is likely to have a lower oil content in suspension within the breather gas than is the case for gas taken from more active locations in the engine, such as the upper volume defined by the top cover.
Thus, in a breather system in accordance with the invention, the breather gas which reaches the separator is likely to have a lower oil content, and the problems detailed above associated with more severe operational situations are likely to be mitigated, and the likelihood that oil content rises to a point where a given separator is unable to cope is diminished.
The invention takes advantage of the lower oil content generally found in breather gases within the lower crankcase volume of the engine casing. However, greater oscillation of gas pressure is frequently encountered within this volume during operation of the engine, which can oppose free draining of the oil through the oil drain means. This problem is mitigated in the apparatus of the invention by the provision of a further conduit fluidly connecting the separator with the volume in the top cover. It is found in practice that the gas pressure within the volume in the top cover is likely to be lower during the compression and power strokes than that within the crankcase volume. The arrangement exploits this pressure differential, and in effect provides damping of the excessive fluctuation of pressure at the primary breather inlet located within the injector pump volume.
The balancing conduit may effect a fluid connection of the top cover and the separator by comprising a fluid connection between the volume defined by the top cover and the breather gas conduit means. Alternatively, the balancing conduit means may provide a fluid connection between the volume defined by the top cover and the separator through an inlet into the separator which is distinct from an inlet therein for the breather gas conduit means.
The engine air intake means may be in the form of a turbocharger intake, or in the form of a conventional air inlet manifold.
Passageways may be provided within an engine cylinder head to provide a fluid connection between the upper and lower volumes within the engine casing, although given constraints of available space these are likely to be too constricted in size to produce complete equalisation of conditions within the two volumes. The present invention exploits in particular the difference in conditions within the breather gas in the two volumes which is encountered in practice.
Preferably, the lower portion of the crankcase defines a lubricating oil sump, and the forward part of the engine casing comprises a timing case for enclosing drive means, the volume defined by the timing case being fluidly connected to the volume defined by the fuel injection pump housing and substantially open to the sump at a lower end. In this arrangement, the volume defined by the timing case is fluidly connected via suitable conduits within an engine cylinder head to the upper volume defined by the top cover of the engine casing.
The oil drain means conveniently returns oil to the sump.
The invention is particularly suited to a closed breather system, in which the gas outlet conduit means fluidly connect with, and convey the cleaned gaseous product of the separator to the engine air intake system.
To assist free draining of separated oil at high operating inclinations, the separator may be located in a position as high on the engine as practicable, and the oil drain means may include non-return valve means to prevent draining oil being forced back up the oil drain means by gas pressure variation.
The invention exploits the relatively lower content of oil in fine suspension wit
Hickman Alan J.
McMahon Marguerite
Perkins Engines Company Limited
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