This invention relates to an oil reservoir system for an engine comprising an oil container
which includes an oil reservoir, which is in fluidic communication with an oil circulation system
of an engine, and a ventilated headspace; the system also comprising an oil filter located at the
interior of said oil container. The invention also relates to a method for deaeration of an oil of an
oil reservoir which is in fluidic communication with an oil circulation system of an engine.
Furthermore, the invention relates to a vehicle comprising the oil reservoir system.
Many engines make use of one or more fluids for their operation. Such fluids are often oil
compositions and include, for instance, engine oil, lubricating oil and hydraulic oil. For example,
internal combustion engines use lubricating oil compositions. Also, electric engines use heat
exchange oils for example to cool the engine, to heat the engine or to cool and heat the engine
during different operating conditions. Such oils are generally held in reservoirs associated with
the engine and may require periodic replacement, for instance when the quality of the oil is no
longer acceptable.
The quality of the oil is commonly assessed based on its level of contamination. For
example, lubricating oil compositions used in internal combustion engines may contain soot
particles, solid precipitants, dirt and sludge contaminants which compromise the lubricating
properties of the oil, leading to excessive engine wear. In order to extend the life of oils used in
engines, oil filters are typically relied upon to prevent, reduce, manage or ameliorate oil
contamination by trapping contaminants in a suitable filter medium, which is routinely replaced or
cleaned. The oil filter is typically located upstream of sensitive components of the engine and
typically downstream of the pump.
n addition to contamination with solid particulate, another issue affecting the
performance of oil compositions used for engines is the level of aeration of the oil. As a result of
exposure of oil compositions to air during use, air may become dissolved or otherwise entrained
in the oil compositions to a varying degree. For instance, in the lubrication system of an internal
combustion engine, oil is pumped from a reservoir to supply bearings and other components of the
engine which are susceptible to wear. As the oil is distributed over the moving components of the
engine, the likelihood of dissolution and/or entrainment of air is increased significantly.
In the case of a dry sump engine system, oil drains into a shallow sump at the bottom of
the crankcase, from where it is pumped by a scavenger pump to an external oil reservoir. This
stage of the circulation involves pumping of a mixture of oil and air from the crankshaft, which
exacerbates oil aeration. At least one further pump is also used in the dry sump system for
redistributing the lubricating oil to the engine. Significant oil aeration lowers the lubricating
efficiency of the oil, which can lead to excessive engine wear, undesirable heating of the engine
and a general reduction in engine efficiency. More generally, entrained air in oil can also lead to
undesirable oil oxidation.
A common means for reducing oil aeration is the integration of an oil deaerator into the
system, A typical oil deaerator is, for instance, described in US 2,538,983, which is used in
connection with an internal combustion engine. The oil deaerator disclosed therein comprises a
cylindrical tank and relies on centrifugal forces that are developed when the oil is sprayed
tangentially against the cylindrical inside surface of the tank in order to help separate air which is
entrained in the oil.
Similarly, US 2,705,053 relates to oil degasification and a lubricating system. That
system includes an oil reservoir, and a source of mist of lubricating oil and gas; an oil degasifying
device connected to said oil reservoir. Said degasifying device comprises: a helically arranged
conduit provided with an inlet for gas and oil at its upper end and an oi outlet at its lower end in
communication with said oil reservoir; a helically arranged, similarly inclined conduit of smaller
external radius of generation than said first-named conduit and telescoping and co-axially
arranged with respect to said first-named conduit, said smaller conduit having a closed lower end,
a gas outlet at the upper end and a series of radially outwardly extending ports in communication
with the first-named conduit. Means are also provided for supplying mixed oil and gas at high
velocity from a source to the inlet of said first named conduit.
The form of deaeration described in both US 2,538,983 and US 2,705,053, i.e. that which
relies on developing centrifugal forces, is known to be insufficient for removing significant
quantities of entrained gas from oil. There remains a need for a simplified solution to the
problems of oil contamination and aeration of oil used in oil circulation systems of engines.
It has been found by the present inventors that the location and arrangement of an oil
filter, forming part of an oil reservoir system which is in fluidic communication with an oil
circulation system of an engine, can be utilised for deaeration of an oil, in addition to the
removal of solid contaminants therefrom.
According to an aspect of the present invention, there is provided an oil reservoir system
for an engine, which engine comprises an oil circulation system, the reservoir system comprising:
an oil container comprising an oil reservoir which is in fluidic communication with an oil
circulation system of an engine, and a headspace which is in fluidic communication with a
ventilation means;
an oil filter located at the interior of the oil container and in fluidic communication with
the oil reservoir; and
wherein the oil filter is constrained such that when oil is circulated by the oil circulation
system of the engine, oil is forced through the oil filter and out into the body of oil in the
reservoir.
The term "oil" used herein is intended to include all oils, mixtures of different oils and oil
compositions which may be used in oil circulation systems of engines. Thus, for example,
lubricating oil compositions comprising one or more oil base stocks and at least one lubricating
oil additive are intended to be covered by the term "oil" herein. Similarly, a single oil for use as a
hydraulic oil in an oil circulating system of an electric engine is intended to be covered by use of
the term "oil" herein.
Mixtures of oil and gas, including aerated oils, may take several different forms. The term
"unbound gas/air" used herein is intended to refer to gas which is essentially free of any
entrainment in oil (not suspended therein). In a container comprising a mixture of oil and gas,
large bubbles of gas (those of more than 1 mm diameter) maybe free to move through the liquid
oil phase, for instance, as a result of the different densities of the two fluids, such that the oil and
gas occupy two distinct layers within the container. In such an arrangement, the gas layer sitting
above the oil layer corresponds to unbound gas/air.
Alternatively, gas may be entirely dissolved in oil to the extent that the particles of the gas
are fully integrated into the liquid phase. This form of gas is referred to herein as "dissolved
gas/air". Typically, petroleum oils comprise up to 9 vol.% of dissolved air per bar absolute
pressure. The solubility of gases in a liquid oil phase is typically proportional to the pressure of
the oil. Consequently, as the pressure of an oil decreases, for example during its passage through
crankshaft oil drillings, the solubility of dissolved gas therein also decreases. Gas particles thus
may come out of solution and form small bubbles in the liquid, which may become entrained in
the oil.
Thus, a further form of oil-gas mixture is where gas is suspended in the liquid oil phase
without being dissolved in the oil. For instance, it is possible for small bubbles (for example,
those of less than 1 mm diameter) to remain substantially suspended in a liquid oil phase,
particularly in high viscosity oils. This form of gas is referred to as "entrained gas" herein.
Larger bubbles of gas that have mobility in an oil may also be considered to be entrained gas,
when these bubbles do not have an escape path to a free surface (i.e. to an interface with unbound
gas/air), such that they remain entrained in the oil.
The pressure of an oil can also have an indirect effect on the level of entrained gas therein.
As described above, when dissolved gas comes out of solution, entrained gas is formed. As a
result, decreasing the pressure of an oil can lead to increased levels of entrained gas therein.
When the pressure of an oil is decreased, solubility of dissolved gas decreases so that gas
dissolved in the oil comes out of solution, and is thereby effectively converted to entrained gas.
This has a particularly negative impact for oil circulating in an oil circulation system of an engine.
Lower pressures are observed in the vicinity of the moving parts of the engine, where substantial
lubrication is required, yet the amount of entrained gas in the oil, which is far more detrimental to
lubrication properties than dissolved gas, is likely to be higher at this stage of the cycle.
A yet further form of an oil-gas mixture is a foam, which is generally formed when there
is a major proportion of gas phase dispersed within the liquid oi phase. Oil based foams typically
comprise closely packed bubbles of gas surrounded by a thin film of liquid oil phase. Foam only
occurs where oil is in fluidic contact with an unbound gas/air surface.
It has been found that when oil having entrained gas as described above flows through an
oil filter in accordance with the present invention, entrained gas may be separated from its
suspension in oil and vented to a ventilated headspace within the oil container of the fluid
reservoir system.
The invention will now be described by way of example only and with reference to the
following drawings in which Figures 1 and 2 represent in schematic cross-section, oil
reservoir systems according to embodiments of the present invention. Figure 3 represents in
schematic cross-section, an oil filter suitable for use in the oil reservoir system of the present
invention. In the drawings, like reference numerals are used to indicate like elements.
Figure 1 is a schematic of an oil reservoir system for an engine according to an
embodiment of the present invention. Referring to Figure 1, an oil reservoir system comprises an
oil container 1 comprising: a ventilated headspace 2 above an oil fluid reservoir 3. An oil outlet 4
is arranged to couple the oil reservoir 3 in fluidic communication with an oil circulation system of
an engine 15, so as to supply oil from reservoir 3 to the engine 15, via return line 12 and by means
of return pump 16. A ventilation means in the form of breather 5 is arranged so as to couple the
headspace 2 with a crankcase ventilation system of the engine, thereby allowing gas to be passed
into and out from the container 1. An oil inlet 6 is arranged to couple the oil reservoir 3 in fluidic
communication with the oil circulation system of the engine 15, so as to provide oil reservoir 3
with oil from the engine 15, via scavenger line 10 and by means of scavenger pump 17. In Figure
1, oil is circulated by means of return and scavenger pumps 16 and 17, respectively. However,
the present invention is not so limited. The oil circulation system may be either of an open or
closed loop oil circulation system.
An oil filter 8 is located at the interior of the oil container 1 and is preferably at least
partially submerged in the oil of reservoir 3, as shown in Figure 1.
In some embodiments, oil filter 8 is arranged such that oil entering the container is
conveyed directly to the oil filter 8. As shown in Figure 1, the oil filter 8 is arranged in the
container 1 such that, when oil is circulated by the oil circulation system of the engine, oil is
conveyed from scavenger line 10 through inlet 6 of the container 1 directly to the oil filter 8.
When oil enters oil filter 8, entrained gas in the oil collects at the surface of the filter medium
(not shown) and forms larger bubbles, before being forced through the filter medium. Filtered
oil emerges from oil filter 8 and enters the body of oil in the reservoir 3. Large bubbles also
exit the oil filter 8 and enter the body of oil in the reservoir 3, from where they travel upwards
to the headspace 2 of the container 1, which is ventilated by means of breather 5.
In some embodiments, the oil reservoir system may comprise an oi container 1 which
includes an outlet 4 and an inlet 6 which independently comprise ports comprising self-sealing
valves and/or non-return valves.
In general, self-sealing ports have the characteristic that when corresponding ports are
being connected, a seal is made between the connecting ports before valve or valves open to allow
fluid to flow. On disconnection, the valve or valves close to seal off each of the ports before the
seal between the ports is broken. Suitable valves include spring loaded poppet valves and biased
non-return valves. Each self-sealing port may provide a "dry break" in which no fluid flows on
connection or disconnection of the ports. Alternatively, each self-sealing port of the system
may provide a "damp break" in which there is flow of only a non-essential amount of fluid,
for example a few drips of liquid, on disconnection or connection of the port.
In some embodiments, the oil container 1 may be a self-contained replaceable unit fixable
for fluidic communication with the oil circulation system of the engine. Thus, a replaceable oil
container 1 may be provided as a self-contained system containing fresh, refreshed or unused
engine lubricating oil composition which may conveniently replace an existing external oil
container for an engine, which container comprises a reservoir containing used or spent
engine lubricating oil composition. If the existing oil container to be replaced also contains
an oil filter, that may also be replaced together with the spent oil composition. Such a
replaceable oil container 1 may be manufactured from metal and/or plastics material. Suitable
materials include reinforced thermoplastics material which for example, may be suitable for
operation at temperatures of up to 150 °C for extended periods of time. Such an oil container 1
may suitably comprise one or more latches to fix the container in fluidic communication with the
oil circulation system of the engine.
Still referring to Figure , the headspace 2 above the oil reservoir in the container 1 is in
fluidic communication with a ventilation means 5. In some embodiments, the ventilation means 5
may suitably comprise a vent port arranged on the container. In some embodiments, a vent port is
connected in fluidic communication with the engine (for example to the air inlet manifold of an
internal combustion engine), gas may flow into the headspace or out of the headspace of the
container. This facilitates modification of the oil pressure in the reservoir, for instance such that it
is higher or lower than the pressure of the engine crankcase. In some embodiments, the vent port
is connected to a breather or a vent tube extending into the headspace. The vent tube may suitably
be located at a location distant from the oi reservoir 3 and the oil filter 8 so as to reduce or
mitigate ingress of oil into the vent tube. n at least some examples, the oil reservoir comprises a
perforate deflector adapted to inhibit fluid flow into the vent tube whilst allowing flow of gas into
and out from the vent tube. These and any other examples of the disclosure may reduce or
mitigate the risk of fluid entering a vent tube in the headspace.
Figure 2 is a schematic cross-section of oil reservoir system for an engine according to
another embodiment of the present invention. Referring to Figure 2, an oil reservoir system
comprises an oil container in the form of an oil pan 20 located at the bottom of the crankcase
of an engine 30 comprising: a ventilated headspace 22 above an oil reservoir 23; a ventilation
means in the form of a breather 24 arranged so as to couple the headspace 22 with a crankcase
ventilation system of the engine (not shown). A primary oil pump 26 is arranged so as to
pump oil from the reservoir 23 to the moving components of the engine. An oil filter 25 is
submerged in the oil of oil reservoir 23 of the oil pan 20. Oil filter 25 is arranged so that
when oil is circulated by pump 26 oil flows into the filter 25. In some embodiments, as
shown in Figure 2, oil which has been pressurised by pump 26 is conveyed directly to the oil
filter 25 by means of an outlet, such as bleed line 27 from the pump 26.
When oil enters oil filter 25, entrained gas in the oil collects at the surface of the filter
medium (not shown) and forms larger bubbles, before being forced through the filter medium.
Filtered oil emerges from oil filter 25 and enters the body of oil in the reservoir 23. Large
bubbles also exit the oil filter 25 and enter the body of oil in the reservoir 23, from where they
travel to the headspace 22, which is ventilated by means of breather 24.
As shown in Figure 2, in some embodiments, the oil container may suitably comprise an
oil pan 20 located within the sump space of an engine crankcase, for example, as in the case of a
wet sump system for an internal combustion engine. During circulation of oil by the oil
circulation system of the engine, which in Figure 2 comprises pump 26, oil may drain from the
moving components of the engine 30 and collect in the oil pan 20. The oil pan 20 may be integral
with or secured to the crankcase of the engine. The oil reservoir 23 is therefore formed in the oil
pan 20 at the bottom of the crankcase where oil which has drained from the engine components
has collected.
The headspace 22 above the oil reservoir 23 is in fluidic communication with a ventilation
means 24. The ventilation means 24 may suitably comprise the crankcase ventilation system of
the engine. Gas in the crankcase may be supplied to the air intake manifold of the engine. For
example, the crankcase may comprise a positive crankcase ventilation (PCV) system comprising a
PCV valve, which may feed gas in the crankcase back into the air intake manifold. In another
example, the crankcase may comprise a closed crankcase ventilation system.
Figure 3 is an exposed view of an example oil filter 40 for use with the oil reservoir
system of the present invention. Oil filter 40 comprises a filter medium 44 with an inner surface
45 defining an inner region 47 and an outer surface 46. In Figure 3, during operation, oil flows
through the inlet 42 and into the inner region 47 of the oil filter 40 before passing through the
filter medium 44, after which it is expelled from the filter 40 to the body of oil in the oil reservoir
of the container.
It has been found that when oil having entrained gas as described hereinbefore flows
through an oil filter 40, entrained gas which is suspended in the oil does not readily penetrate the
filter medium, which helps remove entrained gas from the oil. Without being bound by any
particularly theory, it is believed that small bubbles of entrained gas are brought into contact with
each other at the surface 45 of the filter medium 44, where the small bubbles combine to form
larger bubbles which are less capable of being held in suspension by the oil. The larger bubbles of
gas which collect on the surface 45 of the filter medium 44 may subsequently be forced through
the filter medium 44 upon the build-up of pressure in the filter from pumping the circulating oil.
Larger bubbles of gas which exit the filter 40 enter the body of oil in the reservoir of the
oil container, where they are not readily held in suspension, having mobility in the oil phase.
Thus, when the oil filter 40 is located at the interior of an oil container comprising an oil reservoir
and a ventilated headspace, as illustrated in Figures 1 and 2, the gas which exits the oil filter 40
may travel to the headspace of the container (i.e. following an escape path), where it may be
ventilated with the other unbound gas occupying the headspace.
The flow direction of oil, which is through the filter 40 and out to the body of oil of the
reservoir of the container, and the presence of the ventilated headspace are considered to be
critical to the process of removing entrained gas and thereby deaerating the oil. Again, without
being bound by any particular theory, it is believed that without the ventilated head space, gas
which might be removed from suspension in the oil upon passage through the filter medium may
subsequently be re-entrained in the oil upon exiting the oil filter. Re-entrainment of gas maybe as
a result of, for instance, the pressures the oil-gas mixture is exposed to in the absence of
ventilation. Moreover, without an escape path for entrained gas to follow to an area
accommodating unbound gas, bubbles remain entrained in the oil, and thus contribute to a higher
level of oil aeration.
There are several advantages to the oil reservoir system described herein. One such
advantage is that it may obviate the use of a separate deaerator device for deaeration of oil
used in an oil circulation system of an engine. Another advantage is that the oil flow
configuration in the oil reservoir system of the present invention affords greater control in terms
of handling and distribution. A further advantage of locating the oil filter at the interior of the oil
container is that this may allow a finer oil filter to be used than in alternative setups, for instance,
where the oil filter is integrated on a suction line (connected to a return pump inlet port), a
pressure line, or a return line of an oil circulation system for an engine. This may have one or
more of the following benefits: (a) increased filtration efficiency; and (b) finer filtration. A yet
further advantage of locating the oil filter at the interior of the oil container is that this may allow
a larger oil filter to be used than in alternative setups. This may have the benefit that i)
entrainment by the oil of particulate held in the filter medium as a result of a blockage or in the
case of excess back pressure through the filter can be substantially avoided; and ii) lifetime of the
filter may be increased.
In some embodiments, as shown in Figure 3, the oil filter 40 comprises a filter medium 44
which has an inner surface 45 defining an inner region 47 of the filter medium 44 and an outer
surface 46, wherein the inner surface 45 is of smaller surface area than the outer surface 46, and,
when oil is circulated by the oil circulation system of the engine, oil is directed to the inner region
47 of the filter medium from where it is forced outward through, and out of, the filter medium 44.
In alternative embodiments, the oil filter 40 comprises a filter medium 44 which has an
inner surface 45 defining an inner region 47 of the filter medium 44 and an outer surface 46,
wherein the inner surface 45 is of smaller surface area than the outer surface 46, and, when oil is
circulated by the oil circulation system of the engine, oil is directed to the outer surface 46 of the
filter medium from where it is forced inward through, and out of, the filter medium 44 into the
inner region 47 (i.e. the opposite flow direction to that depicted in Figure 3).
n all embodiments, filtered oi emerges from the oil filter 40 and into the body of oil of
the oil reservoir of the container. In this arrangement, bubbles of gas emerge from the filter and
also enter the oil reservoir from where they can travel, by virtue of the difference in density, to the
ventilated headspace which sits above the oil reservoir.
The oil filter described hereinbefore comprises a filter medium. Suitable oil filters include
a filter medium typically comprising cellulose, fiberglass and/or metal filter elements. Preferably,
the filter elements of the filter medium are pleated. The filter may be suitable for filtering
particles in the range 1 to 100 microns, suitably in the range 2 to 50 microns, for example i the
range 3 to 20 microns. The oil filter may operate at elevated pressure. Such filters are well known
in the art and can be readily adapted for different oil flow directions through the filter medium, as
well as through the filter.
In some embodiments, as shown in Figure 3, the oil filter 40 comprises a tubular filter
medium 44 defining a central channel 47 and oil is forced radially through the filter medium.
Examples of such filters include spin-on filters which may be mounted in-line with oil filter inlet
piping, as well as cartridge- or canister-type filters, which may be adapted for different directions
of flow of oil through the filter medium.
In some embodiments, as illustrated in Figure 3, the oil filter 40 comprises a filter housing
4 1 comprising an inlet 42 for oil and an outlet (not shown). In some examples, the inlet 42 and
outlet of the filter housing 4 1 each comprise a conduit which includes a non-return valve. In other
examples, the housing 4 may comprise at least one perforated, or otherwise permeable, surface
so as to allow the passage of oil and gas out of the oil filter 40 and into the body of oil of the
reservoir.
In some embodiments, the oil filter 40 may further comprise an overflow relief means
(now shown) configured such that oil entering the oi filter 40 is diverted so that it does not pass
through the filter medium 44 of the filter and does not entrain particulate material which is held
by the filter medium 44, when the filter medium 44 is blocked or there is excessive back pressure.
In some examples, said overflow relief means comprises a bypass valve.
The oil filter may be located at the interior of the oil container by mounting inside the oil
container by any suitable means of which the skilled person is aware, for instance by securing to
an interior wall of the oil container. The oil filter may thus be mounted inside the container such
that it is fully, or at least partially, submerged by oil in the oi reservoir of the container, when oil
is being circulated by the oil circulation system of the engine.
Other variations and modifications of the system will be apparent to persons of skill in
the art in the context of the present disclosure.
The engine may be any form of engine suitable for use with a motor. Suitable engines
include internal combustion engines, which may be characterised by spark ignition or
compression ignition, turbine engines and electric engines.
During operation, the oil reservoir of the oil container contains an oil. The oil may, for
instance, be a lubricating engine oil composition or a heat exchange oil composition for an electric
engine. The engine lubricating oil composition may have heat exchange properties.
The engine lubricating oil composition may comprise at least one base stock and at least
one engine lubricating oil additive. Suitable base stocks include bio-derived base stocks, mineral
oil derived base stocks, synthetic base stocks and semi-synthetic base stocks. Suitable engine
lubricating oil additives are known in the art. Examples of additives include organic and/or
inorganic compounds. Typically, according to at least some examples, the engine lubricating oil
composition comprises about 60 to 90 % by weight in total of base stocks and about 40 to 0 %
by weight additives. Suitable engine lubricating oil compositions include lubricating oil
compositions for internal combustion engines.
The engine lubricating oil composition may be a mono-viscosity grade or a multi-viscosity
grade engine lubricating oil composition. Examples of suitable engine lubricating oil
compositions include single purpose lubricating oil compositions and multi-purpose lubricating
oil compositions.
According to at least some examples, the engine lubricating oil composition is a
lubricating oil composition for an internal combustion engine, for example a spark ignition
internal combustion engine and/or a compression ignition internal combustion engine.
The oil composition may be a heat exchange oil composition for an electric engine. Thus,
an external oil container may be provided as a self-contained system containing fresh, refreshed or
unused heat exchange oil composition for an electric engine which may conveniently replace an
existing external oil container for an electric engine, which container comprises a reservoir
containing used or spent heat exchange oil composition. If the existing oil container to be
replaced also contains an oil filter, that may also be replaced together with the spent or oil
composition.
Suitable heat exchange oil compositions for electric engines include those which comprise
organic and/or non-organic performance boosting additives. Suitable heat exchange fluids include
be man-made or bio-derived oil compositions. According to at least some embodiments, the heat
exchange oil compositions have hydraulic characteristics.
The oil for circulation by the circulation system of the engine may thus comprise entrained
gas. For example, the oil may comprise over 5 vol.% entrained gas, over 0 vol.% entrained gas,
over 20 vol.% entrained gas, over 30 vol.% entrained gas, or over 40 vol.% entrained. In some
embodiments, the oi may comprise between 5 vol.% and 15 vol.% entrained gas. In other
embodiments, the oil composition may comprise over 50 vol.% entrained gas.
According to another aspect, the present invention also provides a method of reducing the
amount of entrained gas in an oil of an oil reservoir system for an engine, which engine comprises
an oil circulation system, said method comprising the steps of i) locating an oil filter in an oil
reservoir within an oil container of the oil reservoir system; and ii) constraining the oil filter such
that, when oil is circulated by the oil circulation system of the engine, oil is forced through the oil
filter and out into the body of oil in the reservoir. The oil reservoir system may be as described
hereinbefore and be in fluidic communication with an oil circulation system of an engine by any
suitable means as described hereinbefore
In some embodiments, the oil container comprises an oil inlet and the method comprises
arranging the oil filter such that oil entering the oil inlet of the container is conveyed directly to
the oil filter.
In other embodiments, the oil container comprises an oil pan located within the sump of
the engine; the oil circulation system of the engine comprises a pump located in the reservoir of
the oil pan; and the method comprises arranging the oil filter so that it is in fluidic communication
with an outlet of the pump which supplies oil which has been pressurised by the pump.
The oil filter used in the method aspect of the invention may be any oil filter as described
hereinbefore.
In yet another aspect, the present invention provides a vehicle comprising the oil reservoir
system described hereinbefore. Suitable vehicles include motorcycles, earthmoving vehicles,
mining vehicles, heavy duty vehicles and passenger cars.

Claims:
An oil reservoir system for an engine, which engine comprises an oil circulation system,
the reservoir system comprising:
an oil container comprising an oil reservoir which is in fluidic communication with
an oil circulation system of an engine, and a headspace which is in fluidic communication
with a ventilation means;
an oil filter located at the interior of the oil container and in fluidic communication
with the oil reservoir; and
wherein the oil filter is constrained such that when oil is circulated by the oil
circulation system of the engine, oil is forced through the oil filter and out into the body of
oil in the reservoir.
An oil reservoir system according to Claim 1, wherein, when oil is circulated by the oil
circulation system of the engine, the oil filter is at least partially, or fully, submerged by
oil in the reservoir.
An oil reservoir system according to Claim 1 or Claim 2, wherein the oil filter comprises a
filter medium which has an inner surface defining an inner region of the filter medium and
an outer surface, wherein the inner surface is of smaller surface area than the outer
surface, and, when oil is circulated by the oil circulation system of the engine, oil is
directed to the inner region of the filter medium from where it is forced outward through,
and out of, the filter medium.
An oil reservoir system according to Claim 1 or Claim 2, wherein the oil filter comprises a
filter medium which has an inner surface defining an inner region of the filter medium and
an outer surface, wherein the inner surface is of smaller surface area than the outer
surface, and, when oil is circulated by the oil circulation system of the engine, oil is
directed to the outer surface of the filter medium from where it is forced inward through,
and out of, the filter medium into the inner region, before entering the body of oil of the
oil reservoir.
An oil reservoir system according to any of Claims 1 to 4, wherein the oil filter comprises
a tubular filter medium defining a central channel and oil is forced radially through the
filter medium.
6. reservoir system according to any of the preceding claims, wherein the oil filter
comprises a filter housing comprising an inlet for oil and an outlet, preferably wherein the
inlet and outlet of the filter housing each comprise a conduit which includes a non-return
valve.
7 An oil reservoir system according to any of Claims 1 to 6, wherein the oil filter further
comprises an overflow relief means configured such that oil entering the oil filter is
diverted so that it does not pass through the filter medium of the filter and does not entrain
particulate material which is held by the filter medium, when the filter medium is blocked
or there is excessive back pressure.
8. An oil reservoir system according to Claim 7, wherein the overflow relief means
comprises a bypass valve.
9. An oil reservoir system according to any of the preceding claims, wherein the oil
container comprises an inlet which is in fluidic communication with the oil circulation
system of the engine and the oil filter is arranged such that oil entering the inlet of the
container is conveyed directly to the oil filter.
10. An oil reservoir system according to any of the preceding claims, wherein the container is
a self-contained replaceable unit fixable for fluidic communication with the oil circulation
system of the engine.
11. An oil reservoir system according to Claim 10, wherein the means for ventilation of the
headspace comprises a vent port in the container.
12. An oil reservoir system according to any of Claims 1 to 8, wherein the container
comprises an oil pan located within the sump of the engine.
13. An oil reservoir system according to Claim 12, wherein the oil circulation system of the
engine comprises a pump located in the reservoir of the oil pan and the oil filter is
arranged so that the oil filter is in fluidic communication with an outlet of the pump which
supplies oil which has been pressurised by the pump.
14. An oil reservoir system according to any of Claims 1 to 13, wherein the means for
ventilation of the headspace comprises a positive crankcase ventilation (PCV) system.
15. An oil reservoir system according to any of Claims 1 to 13, wherein the means for
ventilation of the headspace comprises a closed crankcase ventilation system.
16. An oil reservoir system according to any of the preceding claims wherein, when oil is
circulated by the oil circulation system of the engine, entrained gas is separated from
suspension in the oil upon passage through the filter medium of the filter and gas exiting
the oil filter passes through the body of oil in the reservoir to the ventilated headspace.
17. A method of reducing the amount of entrained gas in an oil of an oil reservoir system for
an engine, which engine comprises an oil circulation system, said method comprising the
steps of i) locating an oil filter i an oil reservoir within an oil container of the oi
reservoir system; and ii) constraining the oil filter such that, when oil is circulated by the
oil circulation system of the engine, oil is forced through the oil filter and out into the
body of oil in the reservoir.
18. A method according to Claim 17, wherein the oil container comprises an oil inlet and the
method comprises arranging the oil filter such that oil entering the oil inlet of the
container is conveyed directly to the oil filter.
19. A method according to Claim 17, wherein the oil container comprises an oil pan located
within the sump of the engine and the oil circulation system of the engine comprises a
pump located in the reservoir of the oil pan and the method comprises arranging the oil
filter so that it is in fluidic communication with an outlet of the pump which supplies oil
which has been pressurised by the pump.
20. A method according to any of Claims 17 to 19, wherein the oil filter is as defined in any of
Claims 1 to 7.
21. A vehicle comprising an oil circulation system as defined in any of Claims 1 to 16.