Title of Invention

A POSITIVE CRANKCASE VENTILATION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

Abstract A positive crankcase ventilation system for an internal combustion engine is disclosed. The system includes an engine having a cylinder air intake system connected to associated cylinders and a filtered air inlet to a crankcase for admitting air to mix with crankcase vapors. A throttle is disposed in the cylinder air intake system for controlling airflow to the associated cylinders. The system further includes a venturi nozzle having an inlet and an outlet. The venturi nozzle inlet is connected to the crankcase for receiving the mixture of filtered air and crankcase vapors. The venturi nozzle outlet is connected to the cylinder air intake system at a location subject to variable intake vacuum pressure between the throttle and the cylinders to allow the mixture of filtered air and crankcase vapors to be drawn into the inlet air passing to the cylinders downstream of the throttle.
Full Text 1
GP-305707
ENGINE PCV SYSTEM WITH VENTURI NOZZLE
FOR FLOW REGULATION
TECHNICAL FIELD
[0001] This invention relates to positive crankcase ventilation (PCV)
systems, and more particularly to flow regulation ill PCY systems,
BACKGROUND OF THE INVENTION
[0002] It is known in the art relating to internal combustion engines
to use a positive crankcase ventilation (PCV) system to remove crankcase
vapors (including unburned fuel and combustion products that leak past the
piston rings, oil vapors, and other vapors present in the crankcase) from the
crankcase. PCV systems recirculate crankcase vapors in lieu of exhausting
the vapors to the atmosphere, thereby reducing engine emissions while also
advantageously improving engine efficiency and increasing engine life.
Generally, PCV systems utilize engine vacuum to draw fresh air from an
engine air intake system through the crankcase. The level of engine vacuum
varies with engine operating conditions (i.e., idle, acceleration, constant
speed, deceleration). During periods of engine idle or deceleration, engine
vacuum is high and therefore capable of producing flow rates through the
PCV system that are generally at or above a flow rate necessary for
sufficient crankcase ventilation. On the other hand, during periods of
constant speed or acceleration, engine vacuum is low and therefore it
produces lower flow rates than when the engine vacuum is high. The flow
rate through the PCV system is therefore typically regulated to provide
desirable flow rates at all or most of the various operating conditions.
[0003] Conventionally, there are two common methods in a PCV
system of regulating flow from the crankcase to the engine air intake system,
such as to the air intake manifold. One method is to use a spring-loaded

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PCV flow control valve while the other method is to employ a simple orifice
in place of a PCV valve. A spring-loaded PCV valve opens at a
predetermined pressure differential across the valve (e.g., between the
crankcase and the valve outlet). When the pressure differential across the
valve is greater than the pressure differential required to open the valve, the
flow rate through the valve is approximately constant. While a spring-loaded
PCV valve provides a generally constant flow rate above a certain pressure
differential, it has a relatively higher cost than a simple orifice and can
potentially generate noise at certain points of instability. On the other hand,
while a simple orifice design is relatively less complex and less expensive, it
provides less than ideal flow regulation for some of the range of pressure
differentials present in the PCV system during engine operation. Therefore,
a need exists for a PCV system that is both cost effective and able to provide
a flow rate through the PCV system that is generally constant over an
extended range of the pressure differentials between the crankcase and the
engine air intake.
SUMMARY OF THE INVENTION
[0004] The present invention provides a PCV system for an internal
combustion engine that utilizes a venturi nozzle to regulate flow in place of a
spring-loaded PCV valve or a simple orifice. The venturi nozzle is relatively
low in cost and simple in design while also capable of maintaining a
generally constant flow rate over most of the range of pressure differentials
present in the PCV system.
[0005] In an exemplary embodiment of the present invention, a
positive crankcase ventilation (PCV) system in an engine includes a cylinder
air intake system connected to associated cylinders and a filtered air inlet to a
crankcase for admitting air to mix with crankcase blow-by gases and other
crankcase vapors (all referred to herein as crankcase vapors). A throttle is
disposed in the cylinder air intake system for controlling airflow to the

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associated engine cylinders. The PCV system further includes a venturi
nozzle having an inlet and an outlet. The venturi nozzle inlet is connected to
the crankcase for receiving the mixture of filtered air and crankcase vapors.
The venturi nozzle outlet is connected to the cylinder air intake system at a
location subject to variable intake vacuum pressure between the throttle and
the cylinders to allow the mixture of filtered air and crankcase vapors to be
drawn into the inlet air passing to the cylinders downstream of the throttle.
[0006] In a further embodiment, the present invention provides an
internal combustion engine including a crankcase and at least one cylinder.
A piston is reciprocable in each cylinder and defines a variable volume
combustion chamber therein. A filtered cylinder air intake system is in fluid
communication with each combustion chamber. A crankcase air inlet is
connected between the cylinder air intake system and the crankcase for
admitting filtered air into the crankcase to mix with crankcase vapors. A
throttle is disposed in the cylinder air intake system downstream of the
crankcase air inlet. The engine further includes a venturi nozzle having an
inlet and an outlet. The venturi nozzle inlet is connected to the crankcase for
receiving the mixture of filtered air and crankcase vapors. The venturi
nozzle outlet is connected to the cylinder air intake system between the
throttle and the combustion chambers to allow the mixture of filtered air and
crankcase vapors to be drawn into the inlet air passing to the combustion
chambers by the vacuum developed downstream of the throttle. The venturi
nozzle is sized to reach sonic flow velocity during most of the vacuum
pressure range of engine operation, thereby controlling PCV vapor flow at a
constant value over most of the engine operating range.
[0007] These and other features and advantages of the invention will
be more fully understood from the following description of certain specific
embodiments of the invention taken together with the accompanying
drawings.

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DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of an internal combustion engine
illustrating a positive crankcase ventilation (PCV) system in accordance with
the present invention;
[0009] FIG. 2 is a cross-sectional view of a venturi nozzle included
in the PCV system of the present invention; and
[0010] FIG. 3 is a graph of relative flow rate through the venturi
nozzle versus relative pressure drop across the venturi nozzle for three sizes
of nozzles.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
[0011] Referring now to the drawings in detail, numeral 10 generally
indicates an internal combustion engine in accordance with the present
invention. The internal combustion engine 10 generally includes a crankcase
12 and at least one cylinder 14. A piston 16 is reciprocable in each cylinder
14 and defines a variable volume combustion chamber 18 therein. A filtered
cylinder air intake system 20 is in fluid communication with each combustion
chamber 18. The cylinder air intake system 20 generally extends from the
fresh air inlet 22 to the cylinder intake valves 24 located in the cylinder
intake ports 26. The cylinder air intake system 20 may include one or more
of an air filter 28, a supercharger assembly (not shown), and an air intake
manifold 30. A throttle 32 is also disposed in the cylinder air intake system
20 for controlling cylinder intake airflow to the associated cylinders 14. The
cylinder air intake system 20 may alternatively be referred to as an air
induction system.
[0012] During engine operation, fresh inlet air enters the combustion
chamber 18 via the cylinder air intake system 20 as the intake valves 24 open
and close. The fresh inlet air is mixed with fuel to form a combustible
mixture that is ignited to drive the piston 16. In a four cycle engine, during

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the power stroke in which combustion takes place, some of the combustion
products and unburned fuel escape into the crankcase 12 past piston rings of
the pistons 16 and adjacent walls of the cylinders 14. The gases that escape
past the piston rings are generally referred to as crankcase blow-by gases.
The crankcase blow-by gases and other vapors present in the crankcase (for
example, oil vapors) are hereinafter collectively referred to as crankcase
vapors 34 and are schematically illustrated by black arrows in FIG. 1.

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[0013] Positive internal ventilation of the crankcase is necessary to
extend the useful life of the engine oil and to prevent the escape of controlled
air polluting emissions from the engine. To manage the crankcase vapors
34, the engine 10 utilizes a positive crankcase ventilation (PCV) system 36.
The PCV system 36 includes a crankcase air inlet 38 connected between the
cylinder air intake system 20 and the crankcase 12 upstream of the throttle
32. The crankcase air inlet 38 admits filtered air 40, schematically
illustrated by light arrows in FIG. 1, from the cylinder air intake system 20
into the crankcase 12 to mix with crankcase vapors 34 present in the
crankcase 12.
[0014] The crankcase air inlet 38 may include a conduit 42 such as a
tube or hose running from the cylinder air intake system 20 to a fitting on the
engine 10, such as a fitting in a valve cover 44 of the engine 10 or other
similarly related part such as a cam cover. The PCV system 36 further
includes a venturi nozzle 46 having an inlet 48 and an outlet 50. The venturi
nozzle inlet 48 is connected to the crankcase 12 for receiving the mixture 52
of filtered ventilation air and crankcase vapors that is schematically
illustrated by dashed arrows in FIG. 1. The venturi nozzle outlet 50 is
connected to the cylinder air intake system 20 at a location subject to
variable intake vacuum pressure between the throttle 32 and the cylinders 14.
This allows the mixture of air and crankcase vapors 52 to be drawn into the
inlet air in the cylinder air intake system 20 that passes to the cylinders 14.
The PCV system 36 'thereby ventilates the crankcase and recirculates the
crankcase vapors 34 into the combustion chambers 18 to burn the crankcase
vapors and to exhaust them through the engine's exhaust system (not shown).
[0015] In a specific embodiment, the venturi nozzle outlet 50 may be
connected to an air inlet of a supercharger assembly that is connected in the
cylinder air intake system 20. Alternatively, as shown in FIG. 1, the venturi
nozzle outlet 50 may be connected to the air intake manifold 30 in the
cylinder air intake syltem 20. A conduit 54 such as a tube or hose may

7
connect the nozzle outlet 50 to the intake manifold 30. The venturi nozzle
46 may also be mounted in an engine cover, such as a valve cover 56 of the
engine 10, or other similarly related part such as a cam cover, through which
flow of the mixture of filtered air and crankcase vapors 52 passes to the
vacuum portion of the intake system. Generally, the venturi nozzle 46 may
replace a spring-loaded PCV flow control valve, orifice, or other flow
regulating device found in a conventional PCV system.
[0016] An exemplary venturi nozzle 46 design is illustrated in FIG.
2. The venturi nozzle 46 is sized to provide generally constant flow under
engine operating conditions wherein the throttle 32 is at least partially closed
and a substantial intake vacuum is present. The venturi nozzle 46 is
preferably sized to reach a sonic flow velocity adequate to maintain a
vacuum in the crankcase during most normal conditions of engine operation,
thereby controlling PCV vapor flow at a constant value over most of the
engine operating range.
[0017] As is graphically illustrated in FIG. 3, with an exemplary
venturi nozzle 46, the flow rate through the venturi nozzle (y-axis) is
generally constant when the ratio of pressure at the venturi nozzle outlet 50
to pressure at the venturi nozzle inlet 48 (x-axis) is equal to or less than
approximately 0.90 wherein the venturi controls the maximum flow. This is
a significant improvement over a simple orifice design that begins to limit
the flow rate when the pressure ratio is at or below approximately 0.528.
The venturi nozzle 46 is therefore capable of passing a much larger
maximum flow rate for crankcase ventilation for the same pressure ratio as
an orifice with less than two-thirds the maximum flow rate. Further, the
maximum flow rate is maintained over most of the engine operating range,
dropping off only when the Pom/Pin pressure ratio drops below 0.90, as may
occur during engine operation at or near wide open throttle. It is possible
that an ideally configured nozzle could reach an outlet over inlet pressure
ratio of up to 0.95 before reaching the maximum flow rate.

8
[0018] The point of minimum diameter of the venturi nozzle 46, also
referred to as the throat 46 of the nozzle, determines the maximum stabilized
flow rate through the venturi nozzle 46, i.e. the choked flow condition. For
example, in a venturi nozzle 46 generally shaped as shown in FIG. 2, a
throat radius of approximately 0.9206 mm produces a maximum flow rate of
around 30 liters per minute (1pm), a throat radius of approximately 1.1835
mm produces a maximum flow rate of about 50 1pm, and a throat radius of
approximately 1.3978 mm produces a maximum flow rate of approximately
70 1pm. Relative flow rates as a function of nozzle pressure drop for the
three nozzle sizes described are shown in FIG. 3, the relative flow rate being
the actual flow rate through the nozzle relative to maximum flow rate
through the nozzle. The nozzle with throat radius of 0.9206 mm is
represented by line 60, the nozzle with throat radius of 1.1835 mm is
represented by line 62, and the nozzle with throat radius of 1.3978 mm is
represented by line 64.
[0019] As is apparent from FIG. 3, the relative flow characteristics
of the different sizes of nozzles are nearly equivalent. The suitable size and
shape for the venturi nozzle 46 therefore depends on such factors as the size
of the engine 10 and the flow rate needed to sufficiently vent the engine
crankcase 12. The present invention is not limited to any specific size or
shape of venturi nozzle.
[0020] While the invention has been described by reference to certain
preferred embodiments, it should be understood that numerous changes could
be made within the spirit and scope of the inventive concepts described.
Accordingly, it is intended that the invention not be limited to the disclosed
embodiments, but that it have the full scope permitted by the language of the
following claims.
9
CLAIMS
1. A positive crankcase ventilation system for an internal
combustion engine, the system comprising:
an engine having a cylinder a*ir intake system connected to
associated cylinders and a filtered air inlet to a crankcase for admitting air to
mix with crankcase vapors;
a throttle disposed in the cylinder air intake system for controlling
cylinder intake airflow to the associated cylinders; and
a venturi nozzle having an inlet and an outlet;
the venturi nozzle inlet being connected to the crankcase for
receiving the mixture of filtered air and crankcase vapors, and the venturi
nozzle outlet being connected to the cylinder air intake system at a location
subject to variable intake vacuum pressures between the throttle and the
cylinders to allow the mixture of filtered air and crankcase vapors to be
drawn into the inlet air passing to the cylinders downstream of the throttle.
2. The system of claim 1 wherein the venturi nozzle is sized to
provide generally constant flow under engine operating conditions when the
throttle is at least partially closed and a substantial intake vacuum is present.
3. The system of claim 1 wherein a flow rate through the venturi
nozzle is generally constant when a ratio of pressure at the venturi nozzle
outlet to pressure at the venturi nozzle inlet is equal to or less than
approximately 0.90.
4. The system of claim 1 wherein the filtered air inlet connects
with the cylinder air intake system upstream of the throttle.

10
5. The system of claim 1 wherein the venturi nozzle outlet is
connected to an air inlet of an engine supercharger assembly connected in the
cylinder air intake system.
6. The system of claim 1 wherein the venturi nozzle outlet is
connected to an engine air intake manifold in the cylinder air intake system.
7. The system of claim 1 wherein the venturi nozzle is mounted
in an engine cover through which the flow of the mixture of filtered air and
crankcase vapors passes to the vacuum portion of the intake system.
8. An internal combustion engine comprising:
a crankcase and at least one cylinder;
a piston reciprocable in each cylinder and defining a variable
volume combustion chamber therein;
a filtered cylinder air intake system in fluid communication with
each combustion chamber;
a crankcase air inlet connected between the cylinder air intake
system and the crankcase for admitting filtered air into the crankcase to mix
with crankcase vapors;
a throttle disposed in the cylinder air intake system downstream of
the crankcase air inlet; and
a venturi nozzle having an inlet and an outlet, the venturi nozzle
inlet being connected to the crankcase for receiving the mixture of filtered
air and crankcase vapors, and the venturi nozzle outlet being connected to
the cylinder air intake system at a location subject to variable intake vacuum
pressures between the throttle and the combustion chambers to allow the
mixture of filtered air and crankcase vapors to be drawn into the inlet air
passing to the combustion chambers downstream of the throttle.

11
9. The engine of claim 8 wherein the venturi nozzle is sized to
provide generally constant flow under engine operating conditions when the
throttle is at least partially closed and a substantial vacuum is present.
10. The engine of claim 8 wherein a flow rate through the
venturi nozzle is generally constant when a ratio of pressure at the venturi
nozzle outlet to pressure at the venturi nozzle inlet is equal to or less than
approximately 0.90.
11. The engine of claim 8 wherein the cylinder air intake system
includes a supercharger assembly, and the venturi nozzle outlet is connected
to an air inlet of the supercharger assembly.
12. The engine of claim 8 wherein the cylinder air intake system
includes an engine air intake manifold, and the venturi nozzle outlet is
connected to the engine air intake manifold.
13. The engine of claim 8 wherein the venturi nozzle is mounted
in an engine cover through which the flow of the mixture of filtered air and
crankcase vapors passes to the vacuum portion of the intake system.

A positive crankcase ventilation system for an internal combustion
engine is disclosed. The system includes an engine having a cylinder air
intake system connected to associated cylinders and a filtered air inlet to a
crankcase for admitting air to mix with crankcase vapors. A throttle is
disposed in the cylinder air intake system for controlling airflow to the
associated cylinders. The system further includes a venturi nozzle having an
inlet and an outlet. The venturi nozzle inlet is connected to the crankcase for
receiving the mixture of filtered air and crankcase vapors. The venturi nozzle
outlet is connected to the cylinder air intake system at a location subject to
variable intake vacuum pressure between the throttle and the cylinders to allow
the mixture of filtered air and crankcase vapors to be drawn into the inlet air
passing to the cylinders downstream of the throttle.

Documents:

01573-kol-2007-abstract.pdf

01573-kol-2007-assignment.pdf

01573-kol-2007-claims.pdf

01573-kol-2007-correspondence others 1.1.pdf

01573-kol-2007-correspondence others.pdf

01573-kol-2007-description complete.pdf

01573-kol-2007-drawings.pdf

01573-kol-2007-form 1.pdf

01573-kol-2007-form 2.pdf

01573-kol-2007-form 3.pdf

01573-kol-2007-form 5.pdf

01573-kol-2007-priority document.pdf

1573-KOL-2007-ABSTRACT.pdf

1573-KOL-2007-AMANDED CLAIMS.pdf

1573-KOL-2007-ASSIGNMENT.1.3.pdf

1573-KOL-2007-CORRESPONDENCE 1.1.pdf

1573-KOL-2007-CORRESPONDENCE 1.5.pdf

1573-kol-2007-CORRESPONDENCE OTHERS 1.2.pdf

1573-KOL-2007-CORRESPONDENCE OTHERS 1.3.pdf

1573-KOL-2007-CORRESPONDENCE-1.4.pdf

1573-KOL-2007-CORRESPONDENCE.1.3.pdf

1573-KOL-2007-DESCRIPTION (COMPLETE).pdf

1573-KOL-2007-DRAWINGS.pdf

1573-KOL-2007-EXAMINATION REPORT.1.3.pdf

1573-KOL-2007-FORM 1-1.1.pdf

1573-KOL-2007-FORM 1.pdf

1573-KOL-2007-FORM 18.1.3.pdf

1573-kol-2007-FORM 18.pdf

1573-KOL-2007-FORM 2.pdf

1573-KOL-2007-FORM 3.1.3.pdf

1573-KOL-2007-FORM 3.pdf

1573-KOL-2007-FORM 5-1.1.pdf

1573-KOL-2007-FORM 5.1.3.pdf

1573-KOL-2007-FORM 5.pdf

1573-KOL-2007-GPA.1.3.pdf

1573-KOL-2007-GRANTED-ABSTRACT.pdf

1573-KOL-2007-GRANTED-CLAIMS.pdf

1573-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1573-KOL-2007-GRANTED-DRAWINGS.pdf

1573-KOL-2007-GRANTED-FORM 1.pdf

1573-KOL-2007-GRANTED-FORM 2.pdf

1573-KOL-2007-GRANTED-LETTER PATENT.pdf

1573-KOL-2007-GRANTED-SPECIFICATION.pdf

1573-KOL-2007-OTHERS 1.2.pdf

1573-KOL-2007-OTHERS-1.1.pdf

1573-KOL-2007-OTHERS.1.3.pdf

1573-KOL-2007-OTHERS.pdf

1573-KOL-2007-PA.pdf

1573-KOL-2007-PETITION UNDER RULE 137.pdf

1573-KOL-2007-REPLY TO EXAMINATION REPORT.1.3.pdf

1573-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-01573-kol-2007.jpg


Patent Number 248763
Indian Patent Application Number 1573/KOL/2007
PG Journal Number 34/2011
Publication Date 26-Aug-2011
Grant Date 22-Aug-2011
Date of Filing 21-Nov-2007
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS, INC.
Applicant Address 300 GM RENAISSANCE CENTER, DETROIT, MICHIGAN
Inventors:
# Inventor's Name Inventor's Address
1 SCOTT A. KAVANAGH 13421 LAKEVIEW, SHELBY TOWNSHIP, MICHIGAN 48315
2 THOMAS A. SPIX 1177 MILL VALLEY ROCHESTER HILLS, MICHIGAN 48306
3 DAVID K. STILES 1490 MILLER, LAKE ORION MICHIGAN 48362
PCT International Classification Number F01M13/00; F01M13/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/625832 2007-01-23 U.S.A.