Dry sump lubrication system for an internal combustion engine

A dry sump lubrication system for an internal combustion engine which includes a cam housing, a crankcase and an oil sump therein. The lubrication system includes an oil tank, a conduit connecting the oil tank to the engine and an oil pump for pumping oil from the sump. The pump may include a plurality of pumping stages. An air separator is directly connected to the pump to remove air from the oil. Oil is conducted from the air separator to the oil tank. Separated air is conducted from the air separator to a canister which is vented to the atmosphere. Oil particles will be condensed out of the air in the canister and will be conducted back to the engine through a conduit which is connected to the engine housing, which conduit includes a restrictor whereby engine pressure will not be equalized with the atmospheric pressure in the canister. A pressure relief is also provided for the oil tank by means of a one way check valve which connects the oil tank to the canister.

BACKGROUND OF THE INVENTION 
This invention relates to a lubrication system for an internal combustion 
engine and more particularly to a dry sump lubrication system including a 
non-vented oil tank which is located externally of the engine crankcase. 
Dry sump lubrication systems are commonly used with high performance 
engines such as engines used in race cars or aircraft. In such dry sump 
lubrication systems a supply of lubricating oil is kept in a reservoir or 
tank which is separate from the sump portion of the crankcase of the 
engine and which is generally located externally of the engine. During 
operation of the engine oil is pumped from this tank and is fed directly 
to the bearings and other parts of the engine which are to be lubricated. 
The oil which is thrown from the crankshaft and bearings during the 
operation of the engine is received in a sump located in a lower part of 
the crankcase from whence the oil is pumped back to the tank by means of a 
separate pump. However, the lubricating oil which is pumped from the sump 
contains a large quantity of air, which has been absorbed into the oil due 
to splashing of the oil during the lubricating process. Furthermore, air 
is also absorbed into the oil as the oil is pumped from the sump by the 
scavenger pump. This absorbed air in the lubricating oil results in 
lowered lubricating efficiency of the oil, thereby causing undesirable 
heating of the engine and loss of engine efficiency. Furthermore, the 
lower lubricating efficiency of the oil increases the wear of the engine 
and therefore lowers the life of the various engine parts. 
Various solutions to this problem have been offered by the prior art dry 
sump lubricating systems. Thus, for instance, in some engines castor oil 
has been used as a lubricant, since the foaming property of castor oil is 
superior to that of mineral oil. 
Another solution which has been offered is disclosed in U.S. Pat. No. 
2,538,983. In this patent a separate deaerator is provided for deaerating 
the oil after it is pumped from the engine sump by the scavenger pump and 
before the oil is returned to the engine. The deaerater consists of a 
cylindrical tank in which the oil is sprayed tangentially against the 
inside surface of the tank wall. Some of the entrained air is thereby 
separated from the oil by centrifugal force due to the rotating movement 
of the oil during passage of the oil along the inside surface of the 
cylindrical wall from the inlet to the outlet of the deaerator. This type 
of air separator is relatively inefficient and does not remove sufficient 
quantities of air. Another problem with this type of air separator is its 
complexity. It is therefore desired to provide a dry sump lubrication 
system wherein an effective and simple air separator is provided. 
In prior art dry sump lubrication systems the engine and oil tank are 
generally vented to the atmosphere whereby the engine operates at 
substantially atmospheric pressure. By operating the engine at atmospheric 
pressure, increased friction will result in the engine thereby causing 
lower efficiency of the engine. It is therefore desired to provide a dry 
sump lubrication system including a non-vented oil tank which communicates 
with the engine whereby the engine and oil tank are operated at below 
atmospheric pressure. 
U.S. Pat. No. 2,888,097, discloses a dry sump lubrication system for 
aircraft engine wherein a separate deaerating pump is provided for 
deaerating the oil as it leaves the scavenger pump. This patent also 
discloses two stages of scavenger pumps and furthermore discloses a 
lubricant pump for returning deaerated lubricant to the engine. In this 
system oil is removed and directly returned to engine 10, while a separate 
oil tank is used only as an overflow tank. Furthermore, in this 
lubrication system the air which is separated from the oil is fed to a 
gear casing which houses the gears for driving the lubricant pump, the 
deaerating pump, and the scavenger pump. The gear casing is vented to the 
atmosphere. Since this engine does not appear to be provided with a 
pressure relief, pressures may build up in the engine which can cause 
failure of gaskets and burning up of the engine. An additional problem 
with this structure is that any oil which is entrained in the air entering 
the gear casing, and which condenses out in the gear casing, will tend to 
fill up the gear casing and will overflow through the vent out of the 
engine. This is of course unsatisfactory, particularly in race cars. 
It is therefore desired to provide a dry sump lubrication system wherein 
any oil which condenses out of the separated oil may be returned to the 
engine, wherein the engine and oil tank are operated at sub-atmospheric 
pressure and wherein the nonvented oil tank is provided with a pressure 
relief valve. 
SUMMARY OF THE INVENTION 
The present invention overcomes the disadvantages of the above described 
prior art lubrication systems by providing an improved dry sump 
lubrication system therefor. 
The present invention provides a method for lubricating an internal 
combustion engine having a crankcase, an oil sump in the crankcase, an oil 
tank in communication with the crankcase, and a vented container. The 
method comprises pumping oil from the crankcase sump, separating entrained 
air from the pumped oil and feeding the separated oil to the oil tank from 
which it is pumped back to the engine. The method furthermore comprises 
feeding the separated air to the vented container and condensing oil 
particles out of the separated air. The condensed oil is then returned 
from the vented container to the engine. Furthermore, the method comprises 
providing a pressure relief for the oil tank. 
One advantage of the method and apparatus of the present invention is that 
the lubricating oil which is returned to the engine for lubrication 
thereof is substantially free of entrained air and therefore has greater 
film strength and better lubricating properties than oil having a quantity 
of air entrained therein. This removal of air from the lubrication oil and 
the resultant improvement in the lubrication properties of the oil results 
in lower frictional losses in the engine and the attendant improved 
efficiency of the engine. Furthermore, improvement in the lubrication 
properties of the oil will cause the engine to operate at a lower 
temperature, thereby also increasing the engine efficiency. Lastly, the 
improvement in the lubrication properties of the oil will reduce engine 
wear and therefore will increase the life of the engine. 
A further advantage of the invention is that the engine and oil tank will 
operate at sub-atmospheric pressures since the engine oil tank is 
non-vented, thereby lowering friction in the engine and improving the 
operating efficiency of the engine. 
A still further advantage of the invention is that, in case a piston burns 
up in the engine, the possibility of pressure build up in the crankcase 
and engine blow-up is eliminated by providing a pressure relief valve for 
the non-vented oil tank. 
Still another advantage of the invention is that oil particles entrained in 
the separated air will be condensed out and returned to the engine. 
Yet another advantage of the present invention is the provision of a 
combined pump and air separator which are driven from a common shaft and 
which are relatively simple and inexpensive to repair. 
The present invention, in one form thereof, comprises a dry sump 
lubrication system for an internal combustion engine which includes a 
crankcase. An oil tank is connected to the engine by means of a conduit 
and an oil pump is connected to the crankcase to pump oil therefrom. An 
air separator, connected to the pump, separates entrained air from the 
oil. Oil is conducted from the separator to the oil tank and separated air 
is conducted from the separator to a container. The container also 
includes a vent. A one way valve is connected to the oil tank for 
relieving pressure in the tank while preventing air flow from the 
atmosphere into the tank. 
The present invention, in one form thereof, further provides a dry sump 
lubrication system for an internal combustion engine which includes a 
crankcase having an oil sump therein. The lubrication system comprises an 
oil tank and a first conduit connecting the oil tank to the engine for air 
flow communication therewith. The oil tank is also connected to the engine 
by an oil flow conduit. An oil pump which includes a plurality of pumping 
stages pumps oil from the sump. An air separator is connected to the pump 
to receive oil therefrom and to separate entrained air from the oil. A 
second conduit connects the oil outlet of the air separator to the oil 
tank. A third conduit connects the air outlet of the separator to a 
container which is vented to the atmosphere. A fourth conduit which 
includes a restrictor connects the container to the engine. A fifth 
conduit connects the oil tank to the container. A check valve is connected 
in the fifth conduit for preventing fluid flow from the container to the 
oil tank and for enabling fluid flow from the oil tank to the container. 
The present invention, in one form thereof, still further provides a method 
for lubricating an internal combustion engine including a crankcase having 
an oil sump, an oil tank in communication with the crankcase, a container 
and a one way valve. The method comprises pumping oil from the crankcase 
sump, separating entrained air from the pumped oil, conducting the 
separated oil to the oil tank, conducting the separated air to a container 
which is vented to the atmosphere, and preventing pressure build-up in the 
oil tank by providing a one way valve to relieve pressure in the engine 
and oil tank. 
It is an object of the present invention to provide an improved method and 
apparatus for a dry sump lubrication system for an internal combustion 
engine. 
It is another object of the present invention to provide an improved dry 
sump lubrication system which utilizes a non-vented oil tank. 
Still another object of the present invention is to provide a dry sump 
lubrication system including a vented container for condensing oil 
particles out of the air which has been separated from the lubricant oil. 
A further object of the present invention is to provide a dry sump 
lubrication system wherein oil which is condensed out in the separated air 
container is returned to the engine. 
A yet further object of the present invention is to provide a dry sump 
lubrication system wherein a non-vented oil tank is provided with a 
pressure relief valve and wherein the engine and oil tank are operated at 
subatmospheric pressures. 
Still a further object of the present invention is to provide a dry sump 
lubrication system including a combined pump and air separator.

Corresponding reference characters indicate corresponding parts throughout 
the several views of the drawings. 
The exemplifications set out herein illustrate a preferred embodiment of 
the invention, in one form thereof, and such exemplifications are not to 
be construed as limiting the scope of the disclosure or the scope of the 
invention in any manner. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, what is disclosed is an engine 10 including a 
crankcase 12. Crankcase 12 includes a sump 20 in a lower portion thereof. 
Engine 12 is a high performance engine such as a race engine or an 
aircraft engine which operates at relatively high RPMs. Engine 10 also 
includes a cam housing 14 and an oil tank 16 located externally of 
crankcase 12. Oil tank 16 is relatively small and only needs to have 
sufficient capacity to contain a quantity of oil to be supplied to 
crankcase 12 for continuous lubrication of the engine. 
Oil tank 16 is connected to crankcase 12 by means of a breather conduit 18 
whereby tank 16 and engine 10 operate at the same operating pressure. Tank 
16 is connected by a conduit 22 to a pressure pump section 26 of a pump 
and and air separator assembly 24. Assembly 24 comprises a pressure pump 
section 26, scavenger pump section 27, and an air separator section 28. 
Oil is returned to sump 20 from pressure pump 26 by way of conduit 29. 
Oil, including entrained air, is fed to scavenger pump section 27 by means 
of conduit 30. Scavenger pump section 27 supplies oil to air separator 28. 
Air separator 28 is provided with two outlets 31 and 32 for separated oil 
and air respectively. Outlet 31 receives separated oil from separator 28. 
Oil flows from outlet 31 through conduit 34 back to oil tank 16. 
Separated air flows from separator 28 through outlet 32 and a conduit 36 to 
an inlet 40 of a canister or container 38. Container 38 is provided with a 
vent 42 for venting container 38 to the atmosphere. Container 38 is also 
provided with an oil outlet 44 located near the bottom of container 38 
whereby oil, which is condensed out of the separated air in container 38, 
may be returned to the engine by means of an inlet 46 and a conduit 47. 
Conduit 47 is also provided with a restriction 48 whereby no appreciable 
equalization of pressures will occur between engine 10 and vented 
container 38. Restriction 48 is sufficiently large to cause a small 
quantity of condensed oil to be continuously drawn out of container 38 
into cam housing 14 because of the pressure differential which exists 
across restriction 48. As further explained hereinafter, engine 10 
operates at subatmospheric pressure, whereas container 38 operates at 
atmospheric pressure, whereby a pressure differential is generated across 
restriction 48. It should be understood that the connection between 
container 38 and engine 10 may be made at any convenient location on 
engine 10. In the illustrated preferred embodiment, the connection is made 
on cam housing 14. Pressure relief is provided for oil tank 16 by means of 
a one way check valve 52 which is connected to an inlet 54 of container 38 
by a conduit 50. 
Referring now to FIG. 2, the pump and air separator assembly 24 is shown in 
an exploded perspective view. While the housing sections for pressure pump 
26, scavenger pump 27, and air separator assembly 28 have been shown, the 
rotors for the respective sections of the device have not been shown in 
FIG. 2. The pump and air separator assembly is the subject of a copending 
patent application Ser. No. 804,671 filed on Dec. 4, 1985 herewith by the 
applicant of the instant invention and that disclosure is incorporated 
herein by reference. 
Referring further to FIG. 1 and 2, pressure pump section 26 includes an end 
plate 60 provided with a drive shaft 62. Drive shaft 62 drives all 
rotating parts for all segments of pressure pump 26, scavenger pump 27, 
and air separator 28, whereby the rotors of the assembly are driven in 
unison. A gerotor pump housing 64 is shown including an oil inlet 66 which 
is connected to conduit 22 to supply oil containing entrained air from oil 
tank 16 to pressure pump 26. Oil outlet 67 of pump 26 is connected by 
conduit 29 to engine oil sump 20. Housing 64 is also provided with a 
cavity 68 within which a gerotor (not shown) revolves. While in the 
disclosed embodiment a gerotor pump 26 including housing 64 is provided, 
it should be understood that alternative positive displacement pumps could 
be substituted therefor. Housing 64 includes four apertures 69 for 
receiving four suitable fasteners 71 to secure housing 64 to the pump 
housing sections of scavenger pump 27 and air separator 28. A divider 
plate 70 is secured to pump housing 64 and includes four apertures 72 
through which fasteners 71 project to secure housing 64 and plate 70 to 
the first scavenger pump section housing 74. Plate 70 also includes 
twoapertures 73 for receiving the ends of the scavenger rotor shafts (not 
shown). 
Housing 74 includes cavity 76 therein within which the scavenger rotors 
(not shown) revolve. Housing 74 in turn is secured to divider plate 78 by 
means of the fasteners 71 which extend through four apertures 77 in 
housing 74 and four apertures 79 in plate 78. Housing 74 includes aperture 
80 through which oil enters scavenger pump housing 74 from oil sump 20 by 
way of conduit 30. Oil flows from scavenger housing 74 through an aperture 
81 in divider plate 78 to the second scavenger stage which includes a 
housing 84. Divider plate 78 includes two apertures 82 for receiving the 
shafts of the scavenger rotors (not shown). Second scavenger stage housing 
84 includes a cavity 86 therein within which the rotors of the second 
scavenger stage revolve. Housing 84 also includes four apertures 85 for 
receiving fasteners 71 for securing housing 84 in assembly 24. Housing 84 
also includes oil inlet aperture 88 for receiving oil from oil sump 20 via 
oil conduit 30. 
Divider plate 90 includes two apertures 92 for receiving the rotor shafts 
(not shown) of the scavenger rotors (not shown). Plate 90 is connected to 
the air separator section 28 and housing 84 by fasteners 71 which extend 
through four apertures 93. Oil exits scavenger housing 84 through aperture 
96 in plate 90. Air separator 28 includes a separator plate 94 secured to 
divider plate 86 and to a separator housing 98. Housing 98 includes a 
cavity 100 within which the separator rotor (not shown) revolves. 
Separator housing 98 is secured to divider plate 90 and a separator end 
plate 102 by means of fasteners 71 which extend through apertures 93, 99, 
and 103. Separator end plate 102 includes an oil outlet 31 and air outlet 
32. All of the sections of the pump and separator assembly 24 are thus 
secured together by means of the four bolts 71 which are received in 
apertures 61, 69, 72, 77, 79, 85, 93, 99, and 103 located in each of the 
respective aligned housing sections, divider plates, and end plates. 
Accordingly it is relatively simple to repair the pump and separator 
assembly 24 by merely loosening bolts 71 and repairing the particular 
section which is malfunctioning. Bolts 71 may either be threaded into 
apertures 103 of plate 102 or may receive nuts (not shown) on the threaded 
ends thereof. 
In operation, and by referring to FIGS. 1 and 2, the lubrication system 
functions as follows. Oil containing entrained air is continuously pumped 
from sump 20 through conduit 30 by means of scavenger pump 27 including 
two scavenger stages having housings 74 and 84. While, in the preferred 
embodiment, two scavenger pump stages have been shown, it should be 
understood that additional scavenger stages could be added. For purposes 
of the preferred embodiment it has been found that two stages are 
sufficient. Typically the scavenger stages can pull approximately 10 
inches of vacuum, thereby providing a relatively constant sub- atmospheric 
pressure in the engine. However, if more vacuum were desired, additional 
scavenger stages could be added. Conversely, if less vacuum were desired, 
one scavenger stage could be provided. 
The oil, after being pumped from the last scavenger stage housing 84, will 
enter air separator housing 98 through aperture 96 in divider plate 90. 
Separator 28 operates on the centrifugal principle. The heavier oil is 
spun to the outside of housing 98 whereas the lighter air will remain at 
the center of housing 98. The oil will be returned back to oil tank 16 
through oil outlet 31 and conduit 34 after which the oil be will 
circulated through engine 10 by means of pressure pump 26 and conduits 22 
and 29. The separated air will be fed to container 38 by way of separator 
air outlet 32 and conduit 36 so that any oil particles which are entrained 
in this separated air may be condensed out in container 38 and returned to 
engine 10 by means of conduit 47. The remaining air entering container 38 
is vented to the atmosphere by means of vent 42. Since engine 10 normally 
operates at subatmospheric pressures, oil will flow from container 38 to 
cam housing 14 due to the pressure differential across restriction 48. 
Restriction 48, which may comprise any suitable restrictor such as a valve 
or a capillary tube, insures that the vacuum generated in engine 10 by 
pump assembly 24 will be maintained and will not be lost by way of the 
connection of conduit 47 with cam housing 14 to vented container 38. 
The one way pressure relief check valve 52 for oil tank 16 provides a 
further safety feature for the engine lubrication system. If a piston 
should burn in engine 10 or if some other occasion should arise whereby 
the pressure in engine 10 rises, this pressure will be relieved by way of 
the connection of conduit 18 to oil tank 16 which is at substantially the 
same pressure as engine 10. This high pressure will be relieved from tank 
16 by way of conduit 50 and one way check valve 52 to container 38. Check 
valve 52 will not permit pressure equalization between oil tank 16 and the 
atmosphere but permits only one way fluid flow from oil tank 16 to 
container 38 to relieve fluid pressure in tank 16 in excess of atmospheric 
pressure. Tank 16 may also be vented directly to the atmosphere by way of 
check valve 52 rather than returning line 50 to container 38. 
Subatmospheric pressures will be maintained in engine 10 and tank 16 as 
valve 52 will be closed to reverse fluid flow. 
While this invention has been described as having a preferred design it 
will be understood that it is capable of further modification. This 
application is therefore intended to cover any variations, uses, or 
adaptations, of the invention following the general principles thereof and 
including such departures from the present disclosure as come within known 
or customary practice in the art to which this invention pertains and fall 
within the limits of the appended claims.