U.S. patent application number 16/117571 was filed with the patent office on 2019-03-07 for oil sump, an internal combustion engine, a vehicle and a method.
The applicant listed for this patent is JAGUAR LAND ROVER LIMITED. Invention is credited to William HUTCHINS.
Application Number | 20190072015 16/117571 |
Document ID | / |
Family ID | 60050678 |
Filed Date | 2019-03-07 |
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United States Patent
Application |
20190072015 |
Kind Code |
A1 |
HUTCHINS; William |
March 7, 2019 |
OIL SUMP, AN INTERNAL COMBUSTION ENGINE, A VEHICLE AND A METHOD
Abstract
An oil sump, an internal combustion engine, a vehicle and a
method are disclosed. The oil sump comprises a container defining a
volume for containing oil in which the volume comprises a primary
volume for containing an oil outlet, a secondary volume and an
intermediate volume. A first wall divides the primary volume from
the intermediate volume. The first wall comprises a first
restricted flow means configured to enable a restricted flow of oil
from the intermediate volume to the primary volume. A second wall
comprising a second restricted flow means is arranged to divide the
secondary volume from the intermediate volume. A top-up arrangement
is configured to direct returned oil to the secondary volume and
enable excess returned oil to overflow into the intermediate
volume. A first weir means is positioned to enable an overflow of
returned oil into the primary volume.
Inventors: |
HUTCHINS; William; (Whitley,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JAGUAR LAND ROVER LIMITED |
Warwickshire |
|
GB |
|
|
Family ID: |
60050678 |
Appl. No.: |
16/117571 |
Filed: |
August 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01M 2011/0045 20130101;
F01M 2011/0066 20130101; F01M 2011/007 20130101; F01M 11/0004
20130101 |
International
Class: |
F01M 11/00 20060101
F01M011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2017 |
GB |
1714119.3 |
Claims
1. An oil sump comprising: a container defining a volume for
containing oil, the volume comprising a primary volume, a secondary
volume and an intermediate volume; a first wall dividing the
primary volume from the intermediate volume, the first wall
comprising a first restricted flow means configured to enable a
restricted flow of oil from the intermediate volume to the primary
volume; a second wall dividing the secondary volume from the
intermediate volume comprising a second restricted flow means
configured to enable a restricted flow of oil from the secondary
volume to the intermediate volume; a first weir means positioned to
enable a first overflow of oil into the primary volume; a top-up
arrangement configured to direct returned oil to the secondary
volume and enable excess returned oil to overflow into the
intermediate volume; and an oil outlet for pumping oil from the
primary volume to an internal combustion engine.
2. The oil sump of claim 1, wherein the first weir means comprises
a first weir wall for allowing the first overflow of oil to flow
from the intermediate volume over the first weir wall into the
primary volume.
3. The oil sump of claim 1, wherein the first weir means is
configured to enable the first overflow of oil when oil within the
intermediate volume is above a first height; the top-up arrangement
is configured to enable the excess returned oil to overflow into
the intermediate volume when oil within the secondary volume is
above a second height; and the second height of oil is equal to or
higher than the first height of oil.
4. The oil sump of claim 1, wherein the first restricted flow means
comprises a trap door configured to move from a closed position to
an open position at, or above, a threshold temperature.
5. The oil sump of claim 1, wherein one or both of the first
restricted flow means and the second restricted flow means
comprises a mesh.
6. The oil sump of claim 1, wherein the second restricted flow
means comprises: a trap door configured to move from a closed
position to an open position at, or above, a threshold
temperature.
7. The oil sump of claim 1, further including a cover extending
over a first portion of the intermediate volume and positioned to
enable the excess returned oil from the top-up arrangement to fall
onto the cover; wherein the cover defines at least one hole to
enable oil to enter the first portion of the intermediate
volume.
8. The oil sump of claim 7, wherein the at least one hole of the
cover is dimensioned to provide a first resistance to flow of oil
at an operational temperature; the first restricted flow means of
the first wall is dimensioned to provide a second resistance to
flow of oil at the operational temperature; and the second
resistance is lower than the first resistance.
9. The oil sump of claim 1, wherein the secondary volume contains a
deflection means configured to deflect returned oil entering the
secondary volume away from the second restricted flow means of the
second wall.
10. The oil sump of claim 1, wherein the first wall surrounds the
primary volume and the second wall surrounds the intermediate
volume and the first wall.
11. The oil sump of claim 1, wherein: the container comprises an
outer wall and a plurality of baffles configured to direct flow of
oil within the container, the plurality of baffles defining a
pickup chamber for containing an oil outlet and a plurality of
outer chambers surrounding the pickup chamber.
12. The oil sump of claim 11, wherein at least a portion of each
one of the plurality of baffles extends from a respective first
position adjacent to the outer wall to a respective second position
adjacent to the pickup chamber.
13. The oil sump of claim 12, wherein the plurality of baffles
extend from the respective second positions around the pickup
chamber in the same rotational direction.
14. The oil sump of claim 1, wherein the top-up arrangement
comprises: a second weir means positioned to enable the excess
returned oil to overflow from the top-up arrangement into the
intermediate volume; and a first cover wall positioned to cover the
secondary volume, the first cover wall having an outer surface
configured to enable oil falling on the outer surface to flow
towards the intermediate volume via the second weir means.
15. The oil sump of claim 14, wherein the first cover wall defines
at least one opening to enable oil to flow from the outer surface
into the secondary volume.
16. The oil sump of claim 14, wherein the second weir means
comprises a second weir wall for allowing the excess returned oil
to flow over the second weir wall into the intermediate volume.
17. The oil sump of claim 14, wherein the oil sump comprises a
second cover wall positioned over the primary volume, the second
cover wall being arranged to direct oil falling on the second cover
wall onto the first cover wall.
18. The oil sump of claim 14, wherein the first cover wall
comprises a trough, and an opening extends through a tube extending
from the trough.
19. A vehicle comprising the oil sump of claim 1.
20. A method of circulating oil through a sump of an internal
combustion engine, the sump comprising a first wall dividing a
primary volume from an intermediate volume and a second wall
dividing a secondary volume from the intermediate volume, the
method comprising: pumping oil from the primary volume of the sump;
allowing oil returned from the internal combustion engine to flow
into the secondary volume of the sump; in dependence on the
secondary volume being full, allowing returned oil to overflow into
the intermediate volume of the sump to fill the intermediate
volume; allowing oil to overflow into the primary volume wherein a
first rate of oil leakage through the first wall depends on a
temperature of oil neighboring the first wall and a second rate of
oil leakage through the second wall depends on a difference in
fluid pressure across the second wall; and at temperatures of the
oil neighboring the first wall that are below a threshold
temperature, allowing oil to flow into the intermediate volume at a
rate that maintains a volume of oil in the intermediate volume
sufficient to resist leakage of oil through the second wall.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to United Kingdom Patent
Application No. GB 1714119.3, filed on 4 Sep. 2017.
TECHNICAL FIELD
[0002] The present disclosure relates to an oil sump, an internal
combustion engine, a vehicle and a method. In particular, but not
exclusively it relates to an oil sump, an internal combustion
engine, a vehicle and a method in a vehicle such as a road
vehicle.
[0003] Aspects of the invention relate to an oil sump, an internal
combustion engine, a vehicle and a method.
BACKGROUND
[0004] Oil of an internal combustion engine is repeatedly
circulated from a sump to parts of the engine to provide, amongst
other things, lubrication. A relatively small quantity of oil (for
example 1 litre) could be used to provide the required lubrication
but a larger quantity (for example 5 litres) is generally used to
enable de-aeration of the oil, to provide chemical durability and
to enable cooling when the engine is hot.
[0005] It takes a relatively long time (typically 30 minutes for 5
litres) to heat all of the oil, because of heat losses to the
engine block and to surrounding structures and air. A problem with
such a long period of time is that while the oil is cool, its
viscosity is relatively high, and therefore the efficiency of the
engine is reduced while the oil warms up.
[0006] It is an aim of the present invention to address this
problem.
SUMMARY OF THE INVENTION
[0007] Aspects and embodiments of the invention provide an oil
sump, an internal combustion engine, a vehicle and a method as
claimed in the appended claims.
[0008] According to an aspect of the invention there is provided an
oil sump comprising: a container defining a volume for containing
oil, the volume comprising a primary volume, a secondary volume and
an intermediate volume; a first wall dividing the primary volume
from the intermediate volume, the first wall comprising a first
restricted flow means configured to enable a restricted flow of oil
from the intermediate volume to the primary volume; a second wall
comprising a second restricted flow means arranged to divide the
secondary volume from the intermediate volume; a first weir means
positioned to enable a first overflow of oil into the primary
volume; and a top-up arrangement configured to direct returned oil
to the secondary volume and enable excess returned oil to overflow
into the intermediate volume.
[0009] For an internal combustion engine incorporating such an oil
sump, this provides the advantage that, during an initial period
after the engine is started, only a portion of the oil in the sump
is used to lubricate the engine and that oil is warmed up
relatively quickly. This results in the viscosity of the oil
reducing relatively quickly and increased efficiency of the
engine.
[0010] In some embodiments the first weir means comprises a first
weir wall for allowing the first overflow of oil to flow from the
intermediate volume over the first weir wall into the primary
volume.
[0011] In some embodiments the top-up arrangement comprises: a
second weir means positioned to enable the excess returned oil to
overflow into the intermediate volume; and a first cover wall
positioned over the secondary volume, the first cover wall having
an outer surface configured to enable oil falling on the outer
surface towards the intermediate volume via the second weir means.
This provides the advantage that oil falling towards the secondary
volume may be used to top-up the intermediate volume and, when the
intermediate volume is full, allow the oil to overspill into the
primary volume.
[0012] In some embodiments the first cover wall defines the top-up
port to enable oil to flow from the outer surface into the
secondary volume. This provides the advantage of a simple
arrangement to enable oil falling onto the first cover wall to be
used to fill the secondary volume.
[0013] In some embodiments the second weir means comprises a second
weir wall for allowing excess returned oil to flow over the second
weir wall into the intermediate volume.
[0014] In some embodiments: the first weir means is configured to
enable the first overflow of oil when oil within the intermediate
volume is above a first height; the top-up arrangement is
configured to enable the excess returned oil to overflow into the
intermediate volume when oil within the secondary volume is above a
second height; and the first height of oil is equal to the second
height of oil. This provides the advantage that the pressures of
oil on either side of the second restricted flow means are equal
when the oil overflows the first weir means and the second weir
means, and therefore there is no flow of oil through the second
restricted flow means.
[0015] In some embodiments the first restricted flow means
comprises: a trap door configured to move from a closed position to
an open position at, or above, a threshold temperature; and/or a
mesh.
[0016] The word "mesh" as used herein refers to a sheet of material
defining an array of holes. For example, a mesh may comprise a
network of wires or filaments, such as polymeric fibers, or it may
be a substantially continuous sheet of material in which an array
of holes has been formed, for example in a molding process.
[0017] In some embodiments the first restricted flow means
comprises a trap door configured to move from a closed position to
an open position at, or above, a threshold temperature. This
provides the advantage of increased flow through the first
restricted flow means at a temperature that is determined by the
trap door.
[0018] In some embodiments the first restricted flow means
comprises a mesh. This provides the advantage of a simple and
compact construction without need for a moving part, such as a
door.
[0019] In some embodiments the second restricted flow means
comprises: a trap door configured to move from a closed position to
an open position at, or above, a threshold temperature; and/or a
mesh.
[0020] In some embodiments the second restricted flow means
comprises a mesh. This provides the advantage of a simple and
compact construction without need for a moving part, such as a
door.
[0021] In some embodiments the oil sump comprises a cover extending
over a first portion of the intermediate volume and positioned to
enable the excess oil from the top-up arrangement to fall onto the
cover; and the cover defines at least one hole to enable oil to
enter the first portion of the intermediate volume. This provides
the advantage of reduced mixing of hot oil passing over the second
weir means into the intermediate volume with colder oil disposed
beneath the cover.
[0022] In some embodiments the at least one hole in the cover is
dimensioned to provide a first resistance to flow of oil at a first
threshold temperature; the first restricted flow means of the first
wall is dimensioned to provide a second resistance to flow of oil
at the first threshold temperature; and the second resistance is
lower than the first resistance. This provides the advantage that
at the first threshold temperature, the oil level in the
intermediate volume falls, resulting in oil flowing through the
second restricted flow means into the intermediate volume.
[0023] In some embodiments the oil sump comprises a second cover
wall positioned over the primary volume, the second cover wall
being arranged to direct oil falling on the second cover wall onto
the first cover wall. This provides the advantage that all oil
falling back down from an internal combustion engine into the sump
may be used to top-up the secondary volume. Therefore the secondary
volume is topped up sooner after the engine is started and oil that
overflows into the primary volume warms up more quickly.
[0024] In some embodiments the first cover wall comprises a trough,
and the top-up port extends through a tube extending from the
trough. This provides the advantage that, when the secondary volume
is full, hot oil flowing past the top-up port to the intermediate
volume, has less effect on the cold stagnant oil in the secondary
volume.
[0025] In some embodiments the secondary volume contains a
deflection means configured to deflect returned oil entering the
secondary volume away from the second restricted flow means of the
second wall. This provides the advantage that cold oil adjacent to
the second restricted flow means is less disturbed by oil entering
the secondary volume.
[0026] In some embodiments the first wall surrounds the primary
volume and the second wall surrounds the intermediate volume and
the first wall.
[0027] In some embodiments: the container comprises an outer wall
and a plurality of baffles configured to direct flow of oil within
the container, the plurality of baffles defining a pickup chamber
for containing an oil outlet and a plurality of outer chambers
surrounding the pickup chamber.
[0028] In some embodiments at least a portion of each one of the
plurality of baffles extends from a respective first position
adjacent to the outer wall to a respective second position adjacent
to the pickup chamber. This provides the advantage that the
plurality of baffles enables flow of oil to the pickup chamber and
prevents unwanted sloshing of oil within the sump. It also enables
bay-to-bay breathing within an engine to cause flows of air through
the pickup chamber, which may be used to separate oil droplets from
the air.
[0029] In some embodiments the plurality of baffles extend from the
second positions around the pickup chamber in the same rotational
direction. This provides the advantage that the baffles cause air
and oil entering the pickup chamber to circulate within the pickup
chamber to further prevent sloshing and assist separation of air
and oil.
[0030] In some embodiments the plurality of baffles comprises a
first plurality of baffles and a second plurality of baffles, and
at least a portion of each one of the second plurality of baffles
extend around the pickup chamber to provide walls of the pickup
chamber. This provides the advantage that oil circulating within
the pickup chamber may be retained within the pickup chamber to
further prevent sloshing and assist separation of air and oil. Also
the second plurality of baffles may be configured to cause air and
oil entering the pickup chamber to flow in the same rotational
direction within the pickup chamber. For example, each one of the
second plurality of baffles may be provided with the same
rotational direction to cause the rotational flow within the pickup
chamber.
[0031] In some embodiments each one of the second plurality of
baffles is different to each one of the first plurality of baffles;
and the second plurality of baffles form a ring of louvres
surrounding the pickup chamber.
[0032] In some embodiments in which the plurality of baffles
comprises a first plurality of baffles and a second plurality of
baffles, the first wall and the second wall intersect each one of
the first plurality of baffles.
[0033] According to another aspect of the invention there is
provided an internal combustion engine comprising the oil sump
according to any one of the previous paragraphs and engine oil.
[0034] In some embodiments, at temperatures of engine oil below a
threshold temperature, the first restricted flow means is
configured to enable a restricted flow of oil at a first rate of
flow and the at least one hole defined by the cover is configured
to allow a rate of flow of oil into the first portion of the
intermediate volume that is equal to the first rate of flow. This
provides the advantage that the level of oil in the intermediate
volume may be kept the same as the level in the secondary volume to
prevent oil leakage through the second restricted flow means.
[0035] In some embodiments, at temperatures of engine oil above the
threshold temperature, the at least one hole in the cover is
configured to limit a rate of flow of oil into the first portion of
the intermediate volume to a second rate of flow, and the first
restricted flow means is configured to allow a rate of flow of oil
that is higher than the second rate of flow. This provides the
advantage that when the oil has reached the threshold temperature
the oil in the intermediate volume is able to reduce and allow
leakage of oil from the secondary volume. In this way, all oil may
be used when the oil has reached a sufficiently high
temperature.
[0036] According to a further aspect of the invention there is
provided a vehicle comprising an internal combustion engine
according to any one of the previous paragraphs.
[0037] According to yet another aspect of the invention there is
provided a method of circulating oil through a sump of an internal
combustion engine, in which the sump comprises a first wall
dividing a primary volume from an intermediate volume and a second
wall dividing a secondary volume from the intermediate volume, the
method comprising: pumping oil from the primary volume of the sump;
allowing oil returned from the internal combustion engine to flow
into the secondary volume of the sump; in dependence on the
secondary volume being full, allowing returned oil to overflow into
an intermediate volume of the sump to fill the intermediate volume;
and allowing oil to overflow into the primary volume, wherein: a
rate of oil leakage through the first wall depends on the
temperature of oil neighboring the first wall; a rate of oil
leakage through the second wall depends on difference in fluid
pressure across the second wall; and the method comprises, at
temperatures of oil neighboring the first wall that are below a
threshold temperature, allowing oil to flow into the intermediate
volume at a rate that maintains a volume of oil in the intermediate
volume sufficient to resist leakage of oil through the second
wall.
[0038] This provides the advantage that the second wall may be
provided with a flow means to allow oil to flow through the wall,
so that oil within the secondary volume may be used to lubricate
the engine, but until the threshold temperature is reached, leakage
through that flow means is prevented by maintaining the volume of
oil in the intermediate volume.
[0039] In some embodiments the method comprises, at temperatures
above the threshold temperature, restricting a rate of flow of oil
into the intermediate volume to a limited rate of flow, which is
lower than the rate of leakage through the first wall, to cause the
volume of oil in the intermediate volume to fall, causing oil to
leak through the second wall into the intermediate volume. This
provides a method of enabling all oil in the sump to be used, when
the temperature returning to the sump from the engine has reached a
required value.
[0040] In some embodiments the first wall comprises a mesh and
viscosity of the oil below the threshold temperature maintains
leakage of oil through the mesh at a rate that is below the limited
rate of flow.
[0041] In some embodiments the first wall comprises a trap door and
the method comprises opening the trap door by causing temperature
of oil neighboring the trap door to rise above the threshold
temperature.
[0042] In some embodiments the second wall comprises a mesh to
enable leakage through the second wall in dependence of a pressure
difference across the second wall.
[0043] According to yet a further aspect of the invention there is
provided an oil sump comprising: a container defining a volume for
containing oil, the volume comprising a primary volume, a secondary
volume and an intermediate volume; an oil outlet located within the
primary volume; a first wall dividing the primary volume from the
intermediate volume, the first wall comprising a first restricted
flow means configured to enable a restricted flow of oil from the
intermediate volume to the primary volume, the first restricted
flow means comprising a first trap door configured to move from a
closed position to an open position at, or above, a threshold
temperature and/or a first mesh; a first weir wall positioned to
enable a first overflow of oil from the intermediate volume into
the primary volume; a second wall dividing the secondary volume
from the intermediate volume, the second wall comprising a second
restricted flow means configured to enable a restricted flow of oil
from the secondary volume to the intermediate volume, the second
restricted flow means comprising a second trap door configured to
move from a closed position to an open position at, or above, a
second threshold temperature and/or a second mesh; a top-up
arrangement configured to enable returned oil to keep the secondary
volume full of oil and enable excess returned oil to overflow into
the intermediate volume.
[0044] According to yet a further aspect of the invention there is
provided an oil sump comprising: a container defining a volume for
containing oil, the volume comprising a primary volume for
containing an oil outlet, a secondary volume and an intermediate
volume; a first wall dividing the primary volume from the
intermediate volume, the first wall comprising a first restricted
flow means configured to enable a restricted flow of oil from the
intermediate volume to the primary volume; a second wall dividing
the secondary volume from the intermediate volume, the second wall
comprising a second restricted flow means configured to enable a
restricted flow of oil from the secondary volume to the
intermediate volume; a top-up arrangement configured to keep the
secondary volume full of oil and enable excess returned oil to flow
into the intermediate volume; and a first weir means configured to
enable an overflow of returned oil into the primary volume.
[0045] The oil sump may be for an internal combustion engine of a
vehicle such as a road vehicle.
[0046] Within the scope of this application it is expressly
intended that the various aspects, embodiments, examples and
alternatives set out in the preceding paragraphs, in the claims
and/or in the following description and drawings, and in particular
the individual features thereof, may be taken independently or in
any combination. That is, all embodiments and/or features of any
embodiment can be combined in any way and/or combination, unless
such features are incompatible. The applicant reserves the right to
change any originally filed claim or file any new claim
accordingly, including the right to amend any originally filed
claim to depend from and/or incorporate any feature of any other
claim although not originally claimed in that manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] One or more embodiments of the invention will now be
described, by way of example only, with reference to the
accompanying drawings, in which:
[0048] FIG. 1 shows a vehicle comprising an internal combustion
engine that has an oil sump embodying the present invention;
[0049] FIG. 2 shows a plan view of the oil sump;
[0050] FIG. 3 shows a cross-sectional view of the sump;
[0051] FIG. 4 shows an equal level of oil in each of three volumes
of the sump;
[0052] FIG. 5 shows the sump shortly after starting the engine,
when secondary volume and an intermediate volume have filled with
oil;
[0053] FIG. 6 shows the sump when oil in the intermediate volume
has warmed up and the levels of oil in the intermediate volume and
secondary volume have started to fall;
[0054] FIG. 7 shows a perspective view of an alternative oil sump
that embodies the present invention;
[0055] FIG. 8 shows a cross-sectional view of the alternative oil
sump of FIG. 7;
[0056] FIG. 9 shows the sump of FIG. 8 with a trap door in a closed
position and the same level of oil in each of the three
volumes;
[0057] FIG. 10 shows the oil sump of FIG. 8 with the secondary
volume and the intermediate volume full of oil and excess oil
flowing over a second weir wall and a first weir wall into a
primary volume;
[0058] FIG. 11 shows the sump of FIG. 8 with a trap door open, the
level in the intermediate volume reduced approximately the same as
that in the primary volume and all returned oil flowing into the
secondary volume;
[0059] FIG. 12 shows the sump of FIG. 8 when the engine has been
turned off and oil in the three volumes is able to equalize;
[0060] FIG. 13 shows another alternative sump embodying the present
invention;
[0061] FIG. 14 shows an embodiment of the engine of FIG. 1
comprising an alternative oil sump 103A;
[0062] FIG. 15 shows a plan view of the sump of FIG. 14 with an
upper sump wall in place;
[0063] FIG. 16 shows a plan view of the sump of FIG. 14 with the
upper sump wall removed;
[0064] FIGS. 17 and 18 show flows, at different times, around the
baffles in the vicinity of a pickup chamber of the sump of FIG.
14;
[0065] FIG. 19 shows a cross-sectional view of the sump of FIG.
14;
[0066] FIG. 20 shows the same level of oil in each of three volumes
within the sump of FIG. 14;
[0067] FIG. 21 shows the sump of FIG. 14 shortly after starting the
engine, when a secondary volume and an intermediate volume are
filled with oil;
[0068] FIG. 22 shows the oil sump when the level of oil in the
intermediate volume has dropped and the level of oil in the
secondary volume has begun to drop; and
[0069] FIG. 23 shows a plan view of another alternative sump
embodying the present invention.
DETAILED DESCRIPTION
[0070] A vehicle 101 is shown in FIG. 1. The vehicle 101 comprises
an internal combustion engine 102, which has an oil sump 103. The
internal combustion engine 102 (referred to below simply as "the
engine 102") may have a construction that is generally known in the
art, except for the oil sump 103, which will be described in detail
below.
[0071] In the present embodiment the vehicle 101 is a car, but in
alternative embodiments, the vehicle 101 may be another type of
road vehicle or a vehicle other than a road vehicle that comprises
an internal combustion engine.
[0072] FIG. 2 shows a plan view of the oil sump 103, and FIG. 3
shows a cross-sectional view of the sump 103 through the plane 201
shown in FIG. 2. The oil sump 103 comprises a container 202 having
a lower wall 203 and an outer wall 204 extending upwards from the
lower wall 203. The lower wall 203 and the outer wall 204 of the
container 202 define a volume 205 for containing oil (not shown in
FIGS. 2 and 3). The volume 205 comprises three volumes: a primary
volume 206; a secondary volume 207; and an intermediate volume 208.
The primary volume 206 is suitable for containing an oil outlet 209
on a pickup tube 210, or an oil pump, to enable oil to be pumped
from the sump 103 during use.
[0073] A first wall 211 divides the primary volume 206 from the
intermediate volume 208, and a second wall 212 divides the
secondary volume 207 from the intermediate volume 208. A portion
213 of the first wall 211 may be impervious to oil, but the first
wall 211 comprises a first restricted flow means 214 configured to
enable a restricted flow of oil from the intermediate volume 208 to
the primary volume 206. The first restricted flow means 214 is
configured to provide a passageway for a flow of oil from the
intermediate volume 208 to the primary volume 206 when oil adjacent
to the first restricted flow means 214 is above a first threshold
temperature. The first restricted flow means 214 may be configured
to allow a slower flow of oil for temperatures below the first
threshold temperature.
[0074] Similarly a portion 215 of the second wall 212 may be
impervious to oil, but the second wall 212 comprises a second
restricted flow means 216 configured to enable a restricted flow of
oil from the secondary volume 207 to the intermediate volume 208.
The second restricted flow means 216 is configured to provide a
passageway for a flow of oil from the secondary volume 207 to the
intermediate volume 208 when oil adjacent to the second restricted
flow means 216 is above a second threshold temperature. The second
restricted flow means 216 may be configured to allow a slower flow
of oil for temperatures below the second threshold temperature. The
second threshold temperature may be equal to the first threshold
temperature.
[0075] In the present embodiment, the first restricted flow means
214 and second restricted flow means 216 each comprise a mesh 214A
and 216A respectively. Consequently, motor oil is able to leak
through the first and second restricted flow means 214 and 216 when
the oil is hot and has relatively low viscosity and also when it is
cold and has relatively high viscosity. However, it will be
understood that the hot oil is able to flow more easily through the
mesh 214A and 216A when the oil is hot.
[0076] In the present embodiment, the holes in the mesh 214A and
216A have dimensions of about 0.2 mm but in alternative embodiments
the holes may have dimensions of between 0.1 mm and 0.5 mm.
[0077] In alternative embodiments, the first and/or second
restricted flow means 214 and 216 may each comprise an opening in
the respective wall 211 and 212 and a trap door actuated by a
bimetallic strip configured to maintain the trap door in a closed
position for temperatures below a threshold temperature and to open
the trap door above the threshold temperature. The trap doors may
allow a relatively small flow of oil to leak through the respective
opening when they are in the closed positions. (An embodiment that
includes a trap door will be described later below with regard to
FIGS. 7 to 12.)
[0078] The oil sump 103 also comprises a first weir means 217 that
is positioned to enable a first overflow of oil from the
intermediate volume 208 into the primary volume 206 when oil within
the intermediate volume 208 is above a predefined height. The first
weir means 217 comprises a first weir wall 218 for allowing the
first overflow of oil to flow from the intermediate volume 208 over
the first weir wall 218 into the primary volume 206. The first weir
wall 218 may be provided by the first wall 211, which is configured
to allow an overflow of oil over the top of the first wall 211 or
through an aperture formed in the first wall 211. In an alternative
embodiment, the first weir wall 218 comprises a wall of a duct
extending between the intermediate volume 208 and the primary
volume 206. For example, the duct may be provided by an overflow
pipe. In the embodiment of FIGS. 2 and 3, the first weir wall 218
comprises an element attached to the first wall 211 that extends
upwards from the top of the first wall 211.
[0079] During operation of the engine 102, oil is pumped from the
sump 103 via the outlet 209 to various parts of the engine 102 as
is known. Returned oil falls back down into the sump 103 to be
reused, and at least a portion of the returned oil falls towards
the secondary volume, as indicated by arrows 221. However, the oil
sump 103 also comprises a top-up arrangement 219 configured to
direct returned oil to a top-up port 220 of the secondary volume
207 and also enable excess returned oil to overflow into the
intermediate volume 208. As used herein, the expression "excess
returned oil" means oil returned from the engine 102 and available
to fill the secondary volume but which cannot be accommodated by
the secondary volume 207 due to it being full.
[0080] The top-up arrangement 219 comprises a second weir means 222
positioned to enable the excess returned oil to overflow into the
intermediate volume 208. The top-up arrangement 219 also comprises
a first cover wall 223, which is positioned over the secondary
volume 207. The first cover wall 223 has an outer surface 224 that
is sloped to direct oil falling on the outer surface 224 towards
the top-up port 220 and towards the intermediate volume 208 via the
second weir means 222.
[0081] In the embodiment of FIGS. 2 and 3, the first cover wall 223
defines an aperture 220 which provides the top-up port 220, to
enable oil to flow from the outer surface 224 into the secondary
volume 207.
[0082] The second weir means 222 comprises a second weir wall 225
for allowing excess returned oil to flow over the second weir wall
225 into the intermediate volume 208. I.e., the second weir wall
225 is arranged to allow oil to overflow into the intermediate
volume 208 when the level of oil in the secondary volume 207 is at
or above a second height. In the present embodiment the second
height is substantially level with the first height of the first
weir wall 218 but in other embodiments the first height may be
higher than the second height, so that when the intermediate volume
is full of oil the levels of oil in the intermediate volume 208 and
the secondary volume 207 are equal.
[0083] In the embodiment of FIGS. 2 and 3, the second weir wall 225
is provided by an end portion of the first cover wall 223 that is
disposed above the second wall 212.
[0084] In an alternative embodiment the second wall 212 may provide
the second weir wall 225, which is configured to allow an overflow
of oil over the top of the second wall 212 or through an aperture
formed in the second wall 212. Alternatively, the second weir wall
225 may comprise a wall of a duct extending between the secondary
volume 207 and the intermediate volume 208. For example, the duct
may be provided by an overflow pipe.
[0085] The first cover wall 223 may be contoured to direct oil from
the whole of its width 226 towards the top-up port 220, and/or as
shown in FIGS. 2 and 3, a barrier wall 227, that is higher than the
second weir wall 225, may be provided to prevent oil from running
off the outer surface 224 at positions that are distant from the
top-up port 220. Consequently, all oil flowing down the outer
surface 224 must pass through the top-up port 220, or over or
adjacent to the top-up port 220 before flowing over the second weir
wall 225.
[0086] The sump 103 may comprise a second cover wall 228 that
slopes from an upper end, downwards over the primary volume 206,
the intermediate volume 208 and a part of the first cover wall 223,
to a lower end over the first cover wall 223. Thus, during use, oil
falling towards the primary volume 206 and the intermediate volume
208 falls onto the second cover wall 228 and runs down the second
cover wall 228 onto the first cover wall 223. In this way, all oil
that is returned to the sump 103 may be directed towards the top-up
port 220. In other embodiments, alternative means of directing all
returned all to the first cover wall 223 may be provided.
[0087] Various stages of the operation of the oil sump 103 during
operation of the engine 102 are illustrated in the cross-sectional
views of FIGS. 4, 5 and 6. In each of the FIGS. 4, 5 and 6 the sump
contains motor oil 401. In FIG. 4, the oil 401 has the same level
in each of the three volumes 206, 207 and 208. This situation
exists when the engine 102 has been switched off for a period of
time, so that the oil levels in each of the three volumes has been
able to equalize by flowing through the restricted flow means 214
and 216.
[0088] When the engine 102 is first started and oil 401 is pumped
out of the primary volume 206, the oil level in the primary volume
206 falls. At this stage, the oil 401 is cold and relatively
viscous, and the flow through the meshes 214A and 216A is limited
to a relatively low rate of flow compared to the rate at which oil
401 is pumped from the primary volume 206. Oil 401 pumped from the
primary volume 206 lubricates the engine 102 but eventually falls
back down towards the sump 103, where at least a portion of the
returning oil falls on the first cover wall 223.
[0089] The returned oil 401 runs down the outer surface 224 of the
first cover wall 223 towards the intermediate volume 208. However,
initially the returned oil drops through the top-up port 220 and
begins to fill the secondary volume 207. When the secondary volume
207 is full and the level of oil 401 has reached the top of the
second weir wall 225, the oil overflows the second weir wall 225
and begins to fill the intermediate volume 208. When the
intermediate volume is full and the level of oil 401 in the
intermediate volume 208 has reached the top of the first weir wall
218, the oil overflows the first weir wall 218 and returns to the
primary volume 206. This situation is shown in FIG. 5.
[0090] Thus, in FIG. 5 the secondary volume 207 and the
intermediate volume 208 are full of oil 401 and the level of oil in
the primary volume 206 has dropped in comparison to the initial
level shown in FIG. 4. A first portion 501 (shown in dotted
outline) of the oil 401 lost from the primary volume 206 represents
the oil that has been used to top up the secondary volume 207 and
the intermediate volume 208. A second portion 502 (shown in dotted
outline) of the oil 401 lost from the primary volume 206 represents
oil that is stuck around the wetted areas of the engine 102.
[0091] Typically, the state shown in FIG. 5 is achieved within 15
to 40 seconds of the engine 102 being started, while the oil 401 is
still relatively cool. From that time onwards, additional returned
oil falling on the first cover wall 223 generally flows over the
second weir wall 225 and the first weir wall 218 back to the
primary volume 206. As the engine 102 is run, the oil 401
circulated around the engine 102 and returned to the primary volume
206 is heated up by the engine 102, but the oil 401 in the
secondary volume 207 and the intermediate volume 208 remains
relatively stagnant and cool. Because only the relatively small
volume of oil 401 in the primary volume 206 is being repeatedly
circulated around the engine 103 at this stage, the oil 401 in the
primary volume 206 reaches higher temperatures more quickly than it
would do if all of the oil 401 were being circulated around the
engine 103. Consequently, the viscosity of the oil 401 used to
lubricate the engine 102 reduces more rapidly than it would if all
of the oil 401 were being circulated, and so the efficiency of the
engine 102 similarly increases more rapidly.
[0092] Because the first weir wall 218 and the second weir wall 225
extend up to about the same height, the levels of oil 401 in the
secondary volume 207 and the intermediate volume 208 are
substantially equal, and there is no difference in pressure of the
oil from one side of the second flow restriction means 216 to the
other side. Consequently, there is no leakage of oil 401 from the
secondary volume 207 to the intermediate volume 208 through the
second flow restriction means 216.
[0093] When the intermediate volume 208 is first filled with oil
401, the oil in the intermediate volume 208 is relatively cold and
has a high viscosity. Consequently, oil only leaks slowly through
the first mesh 214A, and so only a relatively small amount of cold
oil from the intermediate volume 208 is mixed into the relatively
hot oil in the primary volume 206. It may be noted that, while
almost all oil 401 that flows over the second weir wall 225 also
flows over the first weir wall 218 into the primary volume 206, a
portion of the oil flowing over the second weir wall 225 tops up
the intermediate volume 208 to maintain its oil at the same level
as that of the secondary volume 207.
[0094] The temperature of oil in the intermediate volume 208 rises
slowly due to conduction through the first wall 211 and the first
flow restricting means 214 and also due to the small quantities of
hot oil used to top up the intermediate volume 208. As its
temperature rises, the viscosity of oil 401 in the intermediate
volume 208 reduces and the rate of leakage of oil through the mesh
214A increases. Consequently, the portion of oil flowing over the
second weir wall 225 that is used to top up the intermediate volume
208 increases while the portion flowing over the first weir wall
218 decreases, until the rate of oil flowing through the first mesh
214A is greater than the rate of oil flowing over the second weir
wall 225. When this happens, the level of oil 401 in the
intermediate volume 208 begins to drop and oil no longer flows over
the first weir wall 218.
[0095] In an alternative embodiment, a baffle or cover 503 (shown
in dashed outline in FIG. 5) is provided that extends over a lower
first portion 504 of the intermediate volume 208. A hole 506
provides a passageway between a second portion 505 of the
intermediate volume 208, which is above the cover 503 of the first
portion 504. The hole 506 is provided to enable oil to run down
from the second portion 505 of the intermediate volume 208 past the
cover 503 to allow the initial filling of the intermediate volume
208. The hole 506 may be formed in the cover 503 or may be provided
between the cover 503 and the first wall 211, as shown in FIG. 5,
or may be provided between the cover 503 and the second wall
212.
[0096] When the intermediate volume 208 is full, as shown in FIG.
5, the cover 503 resists mixing of the hot oil 401 that flows over
the second weir wall 225 with the relatively cold oil 401 in the
first portion 504 of intermediate volume 208. Consequently, oil 401
in the relatively small second portion 505 of the intermediate
volume 208 may be warmed while oil in the first portion 504
adjacent to the mesh 214A, warms up more slowly. Consequently, the
presence of the baffle or cover 503 may increase the period of time
from the engine 102 being started until the level in the
intermediate volume 208 begins to fall.
[0097] When the level of oil 401 in the intermediate volume 208
drops to below the level in the secondary volume 207 a difference
in pressure is produced across the second mesh 216A that causes the
oil 401 to begin flowing from the secondary volume 207 through the
second mesh 216A into the intermediate volume 208. Oil in the
secondary volume 207 is topped-up with hot oil flowing down the
first cover wall 223 and through the top-up port 220.
[0098] When the rate of flow of oil 401 through the second mesh
216A becomes greater than the rate at which oil is topping up the
secondary volume 207, the level of oil 401 in the secondary volume
207 begins to drop. FIG. 6 shows the oil sump 103 at this stage, in
which the level of oil 401 in the intermediate volume 208 has
dropped and consequently the level of oil 401 in the secondary
volume 207 has begun to drop. From this time onwards substantially
all of the oil 401 returned to the first cover wall 223 falls
through the top-up port 220 into the secondary volume 207, and oil
401 flows through the second mesh 216A and the first mesh 214A to
the primary volume 206, where it is recirculated via the outlet
209. Thus, all of the oil 401 in the oil sump 103 is then used to
lubricate the engine 102.
[0099] When the engine 102 is stopped, oil 401 drains back down
into the sump 103 and the levels of oil in the three volumes 206,
207 and 208 equalize, so that the sump 103 is once again as shown
in FIG. 4.
[0100] It should be understood from the above description that: the
operation of the sump 103 enables a relatively small portion of the
oil 401 to lubricate the engine 102 when the engine 102 is first
switched on, so that the oil 401 used at this stage reaches higher
temperatures more quickly and the efficiency of the engine is
improved; all oil is eventually used and circulated around the
engine 102; and the portion of oil 401 present in the primary
volume 206 at the end of use is not the same portion of oil that
was present in the primary volume 206 at the start of use.
[0101] An alternative oil sump 103 for the engine 102 is shown in a
perspective view in FIG. 7 and a cross-sectional view in FIG. 8.
The oil sump 103 of FIGS. 7 and 8 has many of the same features as
the oil sump 103 of FIGS. 2 to 6, and features that are common to
both sumps 103 have been labelled in the same way. Thus, the oil
sump of FIGS. 7 and 8 comprises a container 202 that defines a
volume 205 for containing oil (not shown in FIGS. 2 and 3). The
volume 205 comprises three volumes: a primary volume 206; a
secondary volume 207; and an intermediate volume 208. The primary
volume 206 is suitable for containing an oil outlet 209 (shown in
FIG. 8) on a pickup tube 210, or an oil pump, to enable oil to be
pumped from the sump 103 during use.
[0102] A first wall 211 divides the primary volume 206 from the
intermediate volume 208, and a second wall 212 divides the
secondary volume 207 from the intermediate volume 208. The first
wall 211 comprises a first restricted flow means 214 configured to
enable a restricted flow of oil from the intermediate volume 208 to
the primary volume 206. The first restricted flow means 214 differs
from that of FIGS. 2 and 3 in that it comprises a trap door 214B
rather than a mesh. The trap door 214B comprises actuation means
configured to cause the door to remain closed for temperatures up
to a first threshold temperature and to open as the temperature
rises above the first threshold temperature. In the present
embodiment the trap door 214B is actuated by a bimetallic strip.
The bimetallic strip may be of a type that is typically produced
for electrical safety cut-outs or thermostats.
[0103] The trap door 214B may be configured to allow some leakage
of oil when it is closed but allow a much greater flow when it is
open.
[0104] The second wall 212 comprises a second restricted flow means
216 configured to enable a restricted flow of oil from the
secondary volume 207 to the intermediate volume 208. The second
restricted flow means 216 is configured to provide a passageway for
a flow of oil from the secondary volume 207 to the intermediate
volume 208 when oil adjacent to the second restricted flow means
216 is above a second threshold temperature. The second restricted
flow means 216 may be configured to allow a slower flow of oil for
temperatures below the second threshold temperature. The second
threshold temperature may be equal to the first threshold
temperature. In the present embodiment, the second restricted flow
means 216 comprises a mesh 216A, like that of FIGS. 2 and 3.
[0105] The oil sump 103 also comprises a first weir means 217 that
is positioned to enable a first overflow of oil from the
intermediate volume 208 into the primary volume 206 when oil within
the intermediate volume is above a predefined height. In the
present embodiment, the first wall 211 provides the function of the
first weir means 217. I.e. when the intermediate volume 208 is
full, oil is able to overflow the first wall 211 into the primary
volume 206.
[0106] The oil sump 103 of FIGS. 7 and 8 also comprises a top-up
arrangement 219 configured to direct returned oil to two top-up
ports 220 of the secondary volume 207 and also to enable excess
returned oil to overflow into the intermediate volume 208. The
top-up arrangement 219 comprises a second weir means 222 positioned
to enable excess returned oil to overflow into the intermediate
volume 208. The top-up arrangement 219 also comprises a first cover
wall 223, which is positioned over the secondary volume 207, and
which has an outer surface 224 that is sloped to direct oil falling
on the outer surface 224 towards the intermediate volume 208 via
the second weir means 222.
[0107] In the embodiment of FIGS. 7 and 8, a trough 802 is
positioned towards the lower end of the first cover wall 223 and
the top-up ports 220 each comprise a bore of a tube 803 that
extends downwards from the bottom of the trough 802. A deflection
means 804, comprising a baffle, is positioned below the ends of the
tubes 803 and is configured to deflect oil flowing from the tubes
803 away from the mesh 216A.
[0108] The second weir means 222 comprises a second weir wall 225
for allowing excess returned oil to flow over the second weir wall
225 into the intermediate volume 208. In the embodiment of FIGS. 7
and 8, the second weir wall 225 is provided by a side wall of the
trough 802.
[0109] The first cover wall 223 is provided with an upwardly
extending breather tube 805 that has a breather aperture 806 near
to its uppermost end. The breather tube 805 is provided to ensure
air can escape from the secondary volume 207 during filling with
oil.
[0110] The oil sump 103 of FIGS. 7 and 8 also comprises a cover 801
which covers a first portion 504 of the intermediate volume 208.
The cover 801 defines two holes 807 which extend from an second
portion 505 of the intermediate volume 208, which is above the
cover 801, to the first portion 504. The holes 807 are dimensioned
to limit the rate of flow of oil into the first portion 504 of the
intermediate volume 208 such that the holes 807 provide a higher
resistance to flow of oil than the first flow restriction means 214
for temperatures above the threshold temperature. I.e. when the
trap door 214B is open, it is configured to provide less resistance
to flow of oil into the primary volume 206 than the resistance to
flow provided by the holes 807.
[0111] The oil sump 103 of FIGS. 7 and 8 may be provided with a
second cover wall, like the second cover wall 228 described above
with regard to FIG. 3.
[0112] Various stages of the operation of the oil sump 103 of FIGS.
7 and 8 during operation of the engine 102 are illustrated in the
cross-sectional views of FIGS. 9, 10, 11 and 12. In each of the
FIGS. 9, 10, 11 and 12 the sump 103 contains motor oil 401. In FIG.
9, the trap door 214B is in the closed position and the oil 401 has
the same level in each of the three volumes 206, 207 and 208. This
situation exists when the engine 102 has been switched off for a
period of time, so that the oil levels in each of the three volumes
206, 207 and 208 have been able to equalize by flowing through the
trap door 214B and the mesh 216A. The equalization may occur while
the oil 401 is hot and the trap door 214B is open. Alternatively,
for example when the engine 102 was only previous used for a very
brief period of time and the trap door 214B did not open, the
equalization may occur by leakage of oil past the trap door 214B in
its closed position.
[0113] When the engine 102 is first started, oil 401 is pumped out
of the primary volume 206 via the pickup tube 210 to lubricate the
engine 102. Returned oil 401 falling on the first cover wall 223
flows down the first cover wall 223 and into the second volume 207,
via the trough 802 and the top-up ports 220, until the secondary
volume 207 is full. When the second volume 207 is full, the top-up
ports 220 (i.e., the bores of the tubes 803) and the trough 802
also contain oil 401. With the secondary volume 207 full, oil 401
begins to overflow the second weir wall 225 onto the cover 801
disposed in the intermediate volume 208 and begins filling the
intermediate volume 208. When the intermediate volume 208 is full,
the oil 401 then overflows the first weir wall 218 into the primary
volume 206.
[0114] From then onwards, most of the oil 401 that is pumped from
the primary volume 206 around the engine 102 and returned to the
first cover wall 223 returns to the primary volume 206 via the
first and second weir walls 218 and 225. Consequently the
relatively small volume of oil 401 that is pumped around the engine
102 heats up quickly while the oil 401 in the secondary volume 207
and intermediate volume 208 remains cold and stagnant.
[0115] The oil sump 103 is shown in FIG. 10 with the secondary
volume 207 and the intermediate volume 208 full of oil 401 and
excess oil flowing over the second weir wall 225 and the first weir
wall 218 into the primary volume 206. The level of oil 401 in the
secondary volume 207 is substantially equal to the level in the
intermediate volume 208. Therefore there is substantially no
pressure difference from one side of the mesh 216A to its other
side and no flow of oil through the mesh 216A.
[0116] Due to the closed trap door 214B not providing a perfect
seal, when the intermediate volume 208 is full, some oil 401 may
leak from the intermediate volume 208 past the trap door 214B into
the primary volume 206. However, the intermediate volume 208 is
topped-up by a portion of the oil 401 overflowing the second weir
wall 225. The holes 807 in the cover 801 are sufficiently large to
enable a rate of flow that is at least equal to the rate at which
oil leaks past the closed trap door 214B, and so the intermediate
volume 208 is kept topped up.
[0117] With the sump 103 in the state as shown in FIG. 10, hot oil
returning to the sump 103 may mix with the small quantities of oil
in the trough 802 and the second portion 505 of the intermediate
volume 208. The larger quantity of oil in the secondary volume 207
remains cold and relatively undisturbed by the returning oil. Also,
only a relatively small quantity of warmed oil passes through the
holes 807 in the cover 801 to the first portion 504 of the
intermediate volume 208 to compensate for the oil leaking past the
closed trap door 214B. In contrast, oil in the primary volume 206
of the sump 103 is repeatedly pumped through the pickup tube 210
and used to lubricate the engine 102 as the engine warms up.
Consequently the oil 401 in the primary volume 206, which is used
to lubricate the engine 102, warms up relatively quickly, and
similarly its viscosity falls relatively quickly.
[0118] When the engine 102 and the oil 401 in the primary volume
206 becomes sufficiently hot, the trap door 214B reaches a
threshold temperature at which it is moved into its open position.
This results in an increased rate of flow of oil from the
intermediate volume 208 through the trap door 214B into the primary
volume 206. The holes 807 in the cover 801 are dimensioned to
provide a greater resistance to the rate of flow of oil than the
open trap door 214B and so the quantity of oil in the intermediate
volume 208 begins to fall. As the quantity of oil in the
intermediate volume 208 reduces, a pressure difference appears
across the mesh 216A, which causes the cold oil in the secondary
volume 207 to flow through the mesh 216A into the intermediate
volume 208. The flow through the mesh 216A causes the level in the
secondary volume 207 to fall and so hot oil returning to the first
cover wall 223 flows into the secondary volume 207 rather than
flowing over the second weir wall 225.
[0119] In an alternative embodiment the cover 801 may be provided
with one or more breather tubes that extend upwards from the
general level of the cover 801 to height above the level that is
locally attained by the oil 401. The breather tubes enable air to
escape from the second volume 207 as oil 401 flows into the second
volume.
[0120] The sump 103 is shown in FIG. 11 with the trap door 214B
open, the level in the intermediate volume 208 reduced to be
approximately the same as that in the primary volume 206 and all
returned oil 401 flowing into the secondary volume 207. From then
onwards, returned oil flows through the secondary volume 207, the
mesh 216A to the intermediate volume 208 and the trap door 214B to
the primary volume 206, and therefore all of the oil 401 is used to
lubricate the engine 102.
[0121] When the engine 102 is turned off, oil in the three volumes
206, 207 and 208 is able to equalize as shown in FIG. 12. When the
oil 401 has cooled sufficiently, the trap door 214B closes and the
sump returns to the state shown in FIG. 9.
[0122] Another alternative sump 103 embodying the present invention
is shown in use in FIG. 13. The sump 103 of FIG. 13 is identical to
that described with reference to FIGS. 7 to 12, except the trap
door 214B is replaced by a mesh 214A, which provides a restricted
flow means 214 between the intermediate volume 208 and the primary
volume 206. In this embodiment, when the oil 401 is relatively
cold, the holes 807 in the cover 801 are sufficiently large to
enable oil 401 to flow through them at a rate that is equal to the
flow through the mesh 214A, and so the intermediate volume 208 may
be kept topped up, as shown in FIG. 13. However, when the oil 401
adjacent to the mesh 214A reaches a threshold temperature, the rate
of flow through the mesh 214A becomes greater than that allowed by
the holes 807 in the cover 801, and so the level of oil 401 in the
intermediate volume 208 drops
[0123] In the above described embodiments, the oil 401 returned to
the first cover wall 223 is directed to the intermediate volume 208
and oil overflows from the intermediate volume into the primary
volume 207. However, in an alternative embodiment, oil 401 is
permanently prevented from overflowing from the intermediate volume
208 into the primary volume 206 by a relatively high wall. A first
weir wall is provided between the first cover wall 223 and the
primary volume 206, and a second weir wall 225 is provided between
the first cover wall 223 and the intermediate volume 208. The first
weir wall is higher than the second weir wall 225, and so the
intermediate volume 208 and the secondary volume 207 are topped up
to the height of the first weir wall and then surplus oil overflows
into the primary volume 206.
[0124] An embodiment of the engine 102 comprising an alternative
oil sump 103A is shown in the somewhat schematic view of FIG. 14.
In the present embodiment, the engine 102 comprises four cylinders
1402, each containing a respective piston 1403. Thus, cylinder
1402A contains a piston 1403A, cylinder 1402B contains a piston
1403B, cylinder 1402C contains a piston 1403C, and cylinder 1402D
contains a piston 1403D. Each cylinder 1402 in combination with its
respective piston 1403 defines a combustion chamber.
[0125] Each of the pistons 1403 is connected to a crankshaft 1404
by a respective connecting rod 1405. The crankshaft 1404 is located
within a crankcase 1401 and it is supported by front and rear main
bearings and also by intermediate bearings located within internal
walls 1406, which divide space within the crankcase 1401 into four
separate bays 1407. During operation of the engine 102, the bays
1407 contain air that is contaminated with blow-by gases escaping
from the combustion chambers and droplets of oil used to lubricate
moving parts of the engine 102. For the purposes of the present
specification the mixture of air, blow-by gases and oil droplets
will simply be referred to as "air".
[0126] The interior of the sump 103A is separated from the bays
1407 by an upper sump wall 1420 of the sump 103A, which provides an
end wall of the bays 1407.
[0127] During operation of the engine 102, the reciprocating motion
of the pistons 1402 causes the volume of each of the bays 1407 to
repeatedly change. To avoid compression of the air within the bays
1407, passageways may be provided between neighboring bays 1407
through the internal walls 1406. However, in the present
embodiment, bay-to-bay breathing is provided via the oil sump 103A
by slots 1408 formed in the upper sump wall 1420 of the sump 103A.
One or more slots 1408 are provided in the upper sump wall 1420 at
the lower end of each one of the bays 1407. I.e., in the present
embodiment, in which the engine has four bays 1407, one or more
slots 1408A are positioned at the end of a first bay 1407A, one or
more slots 1408B are positioned at the end of a second bay 1407B,
one or more slots 1408C are positioned at the end of a third bay
1407C, and one or more slots 1408D are positioned at the end of a
fourth bay 1407D.
[0128] During operation, the pistons 1403A and 1403D are lowered,
decreasing the volume of the first bay 1407A and the fourth bay
1407D, and the pistons 1403B and 1403C are simultaneously raised,
increasing the volume of the second bay 1407B and the third bay
1407C. This causes air to be forced through the first slot(s) 1408A
and the fourth slot(s) 1408D allowing air to escape from the first
and fourth bays, 1407A and 1407D, into the sump 103A and out
through the second slot(s) 1408B and the third slot(s) 1408C into
the second and third bays, 1407B and 1407C. Subsequently, as the
pistons 1403B and 1403C are lowered, decreasing the volume of the
second bay 1407B and the third bay 1407C, and the pistons 1403A and
1403D are simultaneously raised, increasing the volume of the first
bay 1407A and the fourth bay 1407D, air is forced through the
second slot(s) 1408B and the third slot(s) 1408C allowing air to
escape from the second and third bays, 1407B and 1407C, into the
sump 103A and out through the first slot(s) 1408A and fourth
slot(s) 1408D into the first and fourth bays, 1407A and 1407D.
[0129] In this manner air is pumped between the bays 1407 backwards
and forwards through the sump 103A. The sump 103A comprises baffles
1421 and 1422 (illustrated schematically in FIG. 14) configured to
cause the air pumped through the sump 103A to take a circuitous
route that causes separation of the oil droplets from the air in
which they are supported.
[0130] A plan view of the sump 103A with the upper sump wall 1420
in place is shown in FIG. 15, and a plan view of the sump 103A with
the upper sump wall 1420 removed is shown in FIG. 16. For the sake
of clarity, some features within the sump 103A have been omitted
from the plan view of FIG. 15. The positions of the interior walls
1406 of the engine 102 are illustrated by dotted lines in FIG.
15.
[0131] In the embodiment of FIG. 15, one slot 1408 is provided in
the upper sump wall 1420 at the lower end of each of the four bays
1407. In alternative embodiments, several slots 1408 are provided
for each of the bays 1407.
[0132] The oil sump 103A comprises a first plurality of baffles
1421 which define a corresponding number of outer chambers 1501. A
first baffle 1421A separates a first outer chamber 1501A of the
sump 103A from a fourth outer chamber 1501D of the sump 103A; a
second baffle 1421B separates the first outer chamber 1501A from a
second outer chamber 1501B of the sump 103A; a third baffle 1421C
separates the second outer chamber 1501B from a third outer chamber
1501C of the sump 103A; and a fourth baffle 1421D separates the
third outer chamber 1501C from the fourth outer chamber 1501D.
[0133] Each of the baffles 1421 extend inwards from a respective
first position 1502 adjacent to the outer wall 204 of the sump 103A
to a second position 1503 adjacent to a pickup chamber 1504
containing an oil outlet 1505 of a pickup tube 1506. A gap 1507 is
provided between the second positions 1503 of neighboring ones of
the baffles 1421 enable flow of oil from the outer chambers 1501 to
the pickup chamber 1504 during use.
[0134] In the embodiment of FIG. 15, the oil sump 103A also
comprises a second plurality of baffles 1422 that are different to
the first plurality of baffles 1421. The second plurality of
baffles 1422 are in the form of a ring of louvres which reside on a
curve extending across the gaps 1507 between the second positions
1503 of the first baffles 1421 to provide walls of the pickup
chamber 1504. The second plurality of baffles 1422 divide up each
of the gaps 1507 into several (in this embodiment 6) slots. The
baffles 1422 are angled to the curve on which they reside so that
the width of the louvre extends from an outer edge to an inner edge
in the same rotational direction around the pickup chamber 1504.
Thus, in use, the baffles 1422 cause fluid flowing from each one of
the outer chambers 1501 into the pickup chamber 1504 to flow in the
same rotational direction around the pickup chamber 1504.
[0135] In the present embodiment, the second plurality of baffles
1422 comprises 24 baffles arranged to divide each of the four gaps
1507 into six slots. However, other quantities of baffles 1422 are
provided in alternative embodiments. For example, in alternative
embodiments, just one baffle 1422 is positioned within each of the
gaps between neighboring ones of the first plurality of baffles
1421. For example, in an embodiment the sump has four of the first
baffles 1421 and four of the second baffles 1422.
[0136] In the embodiment of FIG. 15, each outer chamber 1501 is
able to receive a flow of air (containing oil droplets) from the
bays 1407 of the engine 102 via a respective slot 1408. The slots
1408 are positioned within the upper sump wall 1420 so that each
outer chamber 1501 receives air from a respective one of the bays
1407. In the present embodiment, the second outer chamber 1501B
receives air via the first slots 1408A from the first bay 1407A;
the third outer chamber 1501C receives air via the second slots
1408B from the second bay 1407B; the first outer chamber 1501A
receives air via the third slots 1408C from the third bay 1407C;
and the fourth outer chamber 1501D receives air via the fourth
slots 1408D from the fourth bay 1407D.
[0137] During operation of the engine 102, oil is pumped out of the
sump 103A through the pickup tube 1506 via the outlet 1505 in the
pickup chamber 1504. Consequently, oil flows from the outer
chambers 1501 through the gaps 1507 into the pickup chamber 1504.
The second plurality of baffles 1422 cause oil entering the pickup
chamber 1504 to flow in a clockwise direction around the pickup
chamber 1504, which causes a continuous clockwise motion of oil
within the pickup chamber 1504.
[0138] A portion of the oil entering the pickup chamber 1504 may be
in the form of foam floating on the top of the bulk of the oil. The
clockwise flow of the oil within the pickup chamber 1504 has a
centrifugal-type effect, in that the denser component of the foam,
i.e. the oil, is forced towards the outside of the flow where it
coalesces with the bulk of the oil, and the lighter component, i.e.
air, is forced inwards towards the middle of the pickup chamber
1504. Thus, the circular flow of oil within the pickup chamber 1504
assists the removal of air from the oil before it is pumped around
the engine 102.
[0139] When the pistons 1403A and 1403D (shown in FIG. 14) are
lowered, air is forced out of the bays 1407A and 1407D through
slots 1408A and 1408D into the outer chambers 1501B and 205D of the
oil sump 103A. Simultaneously, air is drawn into the bays 1407B and
1407C from the outer chambers 1501C and 205A. Consequently, air is
pumped through the pickup chamber 1504 as illustrated in FIG. 17,
which shows flows around the baffles 1421 and 1422 in the vicinity
of the pickup chamber 1504. Specifically, air containing oil
droplets is forced into the pickup chamber 1504 from the outer
chamber 1501B through the slots between the baffles 1422 that are
between the baffles 1421B and 1421C and air is also forced into the
pickup chamber 1504 from the outer chamber 1501D between the
baffles 1421A and 1421D.
[0140] Simultaneously, air is drawn out of the pickup chamber 1504
into the outer chambers 1501A and 1501C. The flows of air entering
the pickup chamber 1504 from outer chambers 1501B and 1501D are
relatively focused and have a direction that is substantially in a
clockwise direction around the pickup chamber 1504. In contrast,
the air entering the outer chambers 1501A and 1501C is drawn from
the pickup chamber 1504 over a wider range of angles. Consequently,
the net flow of mass of air within the pickup chamber 1504 is
clockwise as in indicated by circular arrows 1701.
[0141] In addition, the relatively high inertia of oil droplets
suspended in the air in the pickup chamber 1504, tends to cause the
oil droplets to continue on a path past the slots between the
baffles 1422 and to remain within the pickup chamber 1504.
Consequently, the air drawn out of the pickup chamber 1504 into
outer chambers 1501 and 1501C is relatively free of oil when
compared to the air entering the pickup chamber 1504 from outer
chambers 1501B and 1501D.
[0142] Similarly, when the pistons 1403B and 1403C (shown in FIG.
14) are lowered, air is forced out of the bays 1407B and 1407C
through slots 1408B and 1408C into the outer chambers 1501C and
1501A (shown in FIG. 15) of the oil sump 103A. Simultaneously, air
is drawn into the bays 1407A and 1407D from the outer chambers
1501B and 1501D as the pistons 1403A and 1403D are raised.
Consequently, air is pumped through the pickup chamber 1504 as
shown in FIG. 18. Specifically, air containing oil droplets is
forced into the pickup chamber 1504 from the outer chamber 1501A
through the slots between baffles 1422 that are between the baffles
1421A and 1421B and air is also forced into the pickup chamber 1504
from the outer chamber 1501C between the baffles 1421C and
1421D.
[0143] Simultaneously, air is drawn out of the pickup chamber 1504
into the outer chambers 1501B and 1501D. The flows of air entering
the pickup chamber 1504 from outer chambers 1501A and 1501C are
relatively focused and have a direction that is substantially in a
clockwise direction around the pickup chamber 1504. In contrast,
the air entering the outer chambers 1501B and 1501D is drawn from
the pickup chamber 1504 over a wider range of angles. Consequently,
the net flow of mass of air within the pickup chamber 1504 is
clockwise as in indicated by circular arrows 1701.
[0144] Because the net airflow within the pickup chamber 1504 is
clockwise for both upward strokes and downward strokes of each
piston 1403, the oil droplets suspended in the air circulating
within the pickup chamber 1504 are able to attain high speeds and
their momentum tends to force them outwards towards the surrounding
wall of the pickup chamber 1504, which is provided by the baffles
1422. Oil droplets colliding with the baffles 1422, other oil
droplets or the bulk of the oil within the pickup chamber 1504 are
able to coalesce with other droplets or the bulk of the oil. Also,
because the oil droplets are forced outwards and removed from the
circulating air, the air towards the middle of the pickup chamber
1504 becomes relatively free of oil droplets.
[0145] Another feature of the oil sump 103A is illustrated in FIG.
16. Like the oil sumps 103 of FIGS. 2 to 13, the oil sump 103A of
FIGS. 15 and 16 comprises a first wall 211 dividing a primary
volume 206 from an intermediate volume 208, and a second wall 212
dividing a secondary volume 207 from the intermediate volume 208.
However, in the present embodiment, the first wall 211 extends
around the periphery of the primary volume 206, which contains the
baffles 1422 and the pickup chamber 1504. Similarly, the second
wall 212 extends around the outside of the intermediate volume 208,
which extends around the primary volume 206. The secondary volume
207 extends around the outside of the second wall 212.
[0146] The first wall 211 and the second wall 212 are divided into
four sections by the baffles 1421. The baffles 1421 also divide the
secondary volume 207 into four parts and divide the intermediate
volume 208 into four parts. Consequently, each of the outer
chambers 1501 is divided by the first wall 211 and the second wall
212 into a first part, which forms part of the primary chamber 206,
a second part which forms a part of the intermediate volume 208 and
a third part which forms a part of the secondary volume 207.
[0147] A somewhat schematic cross-sectional view of the sump 103A
is shown in FIG. 19, which shows the first wall 211 and the second
wall 212 within the outer regions 1501 and 1501C. In the present
embodiment, the whole of the first wall 211 and the second wall 212
are formed of a mesh material. The second wall 212 comprises two
layers 1901 and 1902 of mesh with a second intermediate volume 1903
between the two layers. The secondary volume 207 has a first cover
wall 1904 which is also formed of a mesh. The first cover wall 1904
has a concaved outer surface 1905 which extends up to a high
portion 1906 to form a second weir means 222. The first cover wall
1904 and the second weir means 222 provides a top-up arrangement
219 configured to enable returned oil to flow through the holes in
the mesh forming the first cover wall 1904 into the secondary
volume 207 and also enable excess returned oil to overflow into the
intermediate volume 208.
[0148] A cover 1907 is provided over a lower first portion 1908 of
the intermediate volume 208. The cover 1907 is also formed of a
mesh, and the cover has a concave outer surface 1909 which slopes
upwards to a high portion 1910 that forms a first weir means 217.
The concave outer surface 1909 of the cover 1907 defines an second
portion 1911 of the intermediate volume 208 which temporarily
contains oil during use, as will be described below.
[0149] In the embodiment of FIG. 19, the first wall 211, both
layers 1901 and 1902 of the second wall 212, the first cover wall
1904 and the cover 1907 in each of the outer chambers 1501 is
formed of a single sheet of mesh material that is pressed into a
shape to provide those features 211, 212, 1904 and 1907. During use
of the oil sump 103A, oil is able to flow between the secondary
volume 207 and the intermediate volume 208, and between the
intermediate volume 208 and the primary volume 206 through the
apertures formed in the mesh material. Thus, the mesh material
forming the first wall 211 and the mesh material forming the second
wall 212 provides a first restricted flow means 214 and a second
restricted flow means 216 respectively.
[0150] It should be understood that the first wall 211, the second
wall 212, the first cover wall 1904 and the cover 1907 in the outer
chamber 1501A extend from the first baffle 1421A to the second
baffle 1421B. Similarly the first wall 211, both layers 1901 and
1902 of the second wall 212, the first cover wall 1904 and the
cover 1907 in the other outer chambers 1501 extend between the two
baffles 1421 that define those outer chambers 1501.
[0151] The mesh material providing the features 211, 212, 1904 and
1907 may be formed of woven metal wires that are sufficiently stiff
to maintain the shape illustrated in FIGS. 16 and 19. Alternatively
the mesh material may be formed of polymer fibres. In some
embodiments, the mesh material may be supported by a polymer frame
that is molded onto the mesh material in the required shape, so
that the mesh material extends between sections of the frame. In
alternative embodiments, instead of the first cover wall 1904 and
the cover 1907 comprising mesh material, each of the outer chambers
1501 contains a structure similar to that illustrated and described
with reference to FIGS. 2 to 6 or 7 to 13.
[0152] The baffles 1421 may be formed as an integral part of the
container 202. For example, the container 202 and the baffles 1421
may be formed from a composite material or a metal alloy in a
single molding process.
[0153] As described above, air blown into, and drawn out of, the
sump 103A via the slots 1408 in the upper sump wall 1420, causes
air to be blown from the outer chambers 1501 into the pickup
chamber 1504 and to be drawn out of the pickup chamber 1504 into
the outer chambers 1501.
[0154] Due to the presence of the first cover wall 1904 and the
cover 1907, the air generally enters the pickup chamber 1504 from
an elevated position above the first weir means 217.
[0155] In the present embodiment, the sump 103A comprises an air
deflection means 1912 that extends downwards from the upper sump
wall 1420 adjacent to the second plurality of baffles 1422. The air
deflection means 1912 may form a part of the upper sump wall 1420
or a part of an element comprising the ring of louvres, i.e.
baffles 1422. The air deflection means 1912 comprises a curved
surface 1913 configured to deflect air downwards as it flows from
the outer chambers 1501 into the pickup chamber 1504. Consequently,
during operation of the engine 102, airborne oil droplets carried
into the pickup chamber 1504 are projected downwards towards the
bulk of the oil in the pickup chamber 1504. In contrast, when air
is drawn from the pickup chamber 1505 into an outer chamber 1501,
the air is drawn from a range of heights of the pickup chamber
1504, including the upper end of the pickup chamber 1504 where the
concentration of airborne oil droplets is relatively low. This
therefore provides another mechanism to cause air drawn from the
pickup chamber 1504 to be cleaner than the air blown into it.
[0156] The oil sump 103A is illustrated in use in FIGS. 20, 21 and
22. In each of the FIGS. 20 to 22 the sump contains engine oil 401.
In FIG. 20, the oil 401 has the same level in each of the three
volumes 206, 207 and 208. This situation exists when the engine 102
has been switched off for a period of time, so that the oil levels
in each of the three volumes has been able to equalize by flowing
through the first wall 211 and the second wall 212.
[0157] When the engine 102 is first started and oil 401 is pumped
out of the primary volume 206, via the outlet 1505 and the pickup
tube 1506, the oil level in the primary volume 206 falls. At this
stage, the oil 401 is cold and relatively viscous, and the flow
through the first wall 211 and second wall 212 is limited to a
relatively low rate of flow compared to the rate at which oil 401
is pumped from the primary volume 206. Oil 401 pumped from the
primary volume 206 lubricates the engine 102 but eventually falls
back down towards the sump 103A, where at least a portion of the
returning oil passes through the slots 1408 and lands on the first
cover wall 1904.
[0158] At this stage, the returned oil 401 passes through the
apertures of the mesh forming the first cover wall 1904 and begins
to fill the secondary volume 207. When the secondary volume 207 is
full and the level of oil 401 has reached the top of the high
portion 1906 of the first cover wall 1904, which provides the
second weir means 222, the oil overflows the second weir means 222
and falls onto the cover 1907. At this stage, the oil 401 falling
on the cover 1907 passes through the holes in the mesh forming the
cover 1907 and begins to fill the intermediate volume 208.
[0159] During filling of the secondary volume 207 and the
intermediate volume 208 the relatively small second intermediate
volume 1903 in the second wall 212 also fills with oil 401.
[0160] When the intermediate volume 208 is full and the level of
oil 401 in the intermediate volume 208 has reached the top of the
high portion 1910 of the cover 1907, which forms the first weir
means 217, the oil overflows the first weir means 217 and returns
to the primary volume 206. This situation is shown in FIG. 21.
[0161] In FIG. 21 the secondary volume 207 and the intermediate
volume 208 are full of oil 401 and the level of oil in the primary
volume 206 has dropped in comparison to the initial level shown in
FIG. 20. From the moment when the oil 401 begins to overflow the
first weir means 217, additional returned oil falling towards the
first cover wall 1904 lands on oil residing above the first cover
wall 1904 and overflows into the intermediate volume 208. The oil
residing above the first cover wall 1904 may therefore warm up but
the oil below the first cover wall 1904 is undisturbed and remains
cold. The oil overflowing into the intermediate volume 208 flows
over the cover 1907 and into the primary chamber 206, where it may
be recirculated around the engine 102 via the pickup tube 1506.
[0162] As the engine 102 is run, the oil 401 circulated around the
engine 102 and returned to the primary volume 206 is heated up by
the engine 102, but the oil 401 in the secondary volume 207 and the
intermediate volume 208 remains relatively stagnant and cool.
Because only the relatively small volume of oil 401 in the primary
volume 206 is being repeatedly circulated around the engine 103 at
this stage, the oil 401 in the primary volume 206 reaches higher
temperatures more quickly than it would do if all of the oil 401
were being circulated around the engine 103. Consequently, the
viscosity of the oil 401 used to lubricate the engine 102 reduces
more rapidly than it would if all of the oil 401 were being
circulated, and so the efficiency of the engine 102 increases more
rapidly.
[0163] Because the first weir means 217 and the second weir means
222 extend up to about the same height, the levels of oil 401 in
the secondary volume 207 and the intermediate volume 208 are
substantially equal, and there is no difference in pressure of the
oil from one side of the second wall 212 to the other side.
Consequently, there is no leakage of oil 401 from the secondary
volume 207 to the intermediate volume 208 through the layers of
mesh 1901 and 1902 forming the second wall 212.
[0164] When the intermediate volume 208 is first filled with oil
401, the oil in the intermediate volume 208 is relatively cold and
has a high viscosity. Consequently, oil may leak through the first
wall 211 but only slowly. Almost all oil 401 that flows over the
second weir means 222 also flows over the first weir means 217 into
the primary volume 206, but a smaller portion of the oil flowing
over the second weir means 222 tops up the intermediate volume 208
to maintain its oil at the same level as that of the secondary
volume 207.
[0165] While the oil sump 103A is in this state, if the engine 102
is temporarily stopped, for example for a minute at a traffic
junction, oil will continue to leak slowly through the first wall
211 and as a result the level of oil in the intermediate volume 208
may begin to fall. A pressure difference will therefore be produced
across the first layer 1901 of the second wall 212 and oil will
begin to leak though the first layer 1901 as a result. This in turn
will cause a pressure difference to appear across the second layer
1902 of the second wall 212 and oil will begin to leak from the
secondary volume 207 into the second intermediate volume 1903 in
the second wall 212. However, due to the high viscosity of the cold
oil in the secondary volume 207 only a relatively slow rate of
leakage results. It will also be appreciated that the pressure
differences across each layer 1901 and 1902 of the second wall will
be reduced when compared to a similar arrangement that has only one
layer of mesh.
[0166] During operation of the engine 102, the temperature of oil
in the intermediate volume 208 slowly rises due to conduction
through the first wall 211 and also due to the small quantities of
hot oil used to top up the intermediate volume 208. As its
temperature rises, the viscosity of oil 401 in the intermediate
volume 208 reduces and the rate of leakage of oil through the first
wall 211 increases. Consequently, the portion of oil flowing over
the second weir means 222 that is used to top up the intermediate
volume 208 increases while the portion flowing over the first weir
means 217 decreases.
[0167] The mesh forming the cover 1907 limits the rate at which oil
401 is able to flow into the first portion 1908 of the intermediate
volume 208. When the rate of oil flowing through the first wall 211
becomes greater than the rate of oil flowing through the cover
1907, the level of oil 401 in the first portion 1908 of the
intermediate volume 208 begins to drop. This causes a difference in
pressure across the second wall 212 that causes the oil 401 to
begin flowing from the secondary volume 207 through the second wall
212 into the intermediate volume 208. Oil in the secondary volume
207 is then topped-up with hot oil flowing through the mesh forming
the first cover wall 1904.
[0168] When the rate of flow of oil 401 through the second wall 212
becomes greater than the rate at which oil is topping up the
secondary volume 207, the level of oil 401 in the secondary volume
207 begins to drop. FIG. 22 shows the oil sump 103A at this stage,
in which the level of oil 401 in the intermediate volume 208 has
dropped and consequently the level of oil 401 in the secondary
volume 207 has begun to drop. From this time onwards most of the
oil 401 returned to the first cover wall 1904 falls through the
mesh forming the first cover wall 1904 into the secondary volume
207, and oil 401 flows through the second wall 212 and the first
wall 211 to the primary volume 206, where it is recirculated via
the outlet 209. Thus, all of the oil 401 in the oil sump 103A is
then used to lubricate the engine 102.
[0169] When the engine 102 is stopped for a prolonged period, oil
401 drains back down into the sump 103A and the levels of oil in
the three volumes 206, 207 and 208 equalize, so that the sump 103A
is once again in the state shown in FIG. 20.
[0170] In an alternative embodiment, the oil sump has a first wall
surrounding a primary volume and a second wall surrounding the
first wall, so that the intermediate volume surrounds the primary
volume and the secondary volume surrounds the intermediate volume,
in a similar manner to the oil sump 103 of FIGS. 15 to 22. However
in the alternative embodiment, the sump is not provided with
baffles 1421 and 1422 as described with reference to FIGS. 15 to
22.
[0171] Another alternative sump 103A, embodying the present
invention is shown in the plan view of FIG. 23. The sump 103A of
FIG. 23 is similar to that of FIGS. 15 to 22, except in the
configuration of its baffles 1421 and by the absence of the baffles
1422 in the form of louvres surrounding the pickup chamber 206.
[0172] The sump 103A of FIG. 23 has four baffles 1421 which extend
inwards from a respective first position 1502, next to the outer
wall 204 of the sump 103A, to a respective second position 1503,
next to a pickup chamber 206. A gap 2302 is provided between each
baffle 1421 and an end 2303 of a neighbouring baffle 1421. Each of
the gaps 2302 enable a flow of oil from a respective outer chamber
1501 to the pickup chamber 1504 alongside a baffle 1421 that
extends past the gap 2302. For example, oil is able to flow from
the outer chamber 1501D, through the gap 2302 between the baffle
1421D and the end 2303 of the baffle 1421A, and into the pickup
chamber 1504 alongside the baffle 1421D. Each of the baffles 1421
has an end portion 2301 that extends from its second position 1503
around the pickup chamber 206, which causes oil entering the pickup
chamber 206 to circulate within the pickup chamber 206 during use.
In the present embodiment the end portions 2301 extend along a
curve, but in an alternative embodiment the end portions are
straight.
[0173] The end portions 2301 of the baffles 1421 all extend in the
same rotational direction from the second positions 1503 around the
pickup chamber 1504. In the present example, the end portions 2301
all extend clockwise around the pickup chamber 1504 to an end 2303
of the baffle 1421. Consequently, the baffles 1421 cause oil
flowing into the pickup chamber 1504 from each of the outer
chambers 1501 to flow in the same rotational direction (i.e.
clockwise in this embodiment) around the pickup chamber 1504. In
addition, air pumped through the sump 103A by bay-to-bay breathing,
as described with reference to FIGS. 14 to 18, is caused to
circulate in the same rotational direction (i.e. clockwise in this
embodiment.)
[0174] The sump 103A of FIG. 23 has a first wall 211, a second wall
212, a first cover wall 1904 and a cover 1907 like those described
above in regard to the sump 103A of FIGS. 15 to 22.
[0175] In the above described embodiments of FIGS. 15 to 23, the
sump 103A comprises: four baffles 1421 that extend inwards from the
outer wall 204 to the pickup chamber 206; and a corresponding
number (i.e. four) outer chambers 1501. However, in some
alternative embodiments the sump 103A comprises just three such
baffles 1421, while in other embodiments the sump comprises more
than four of such baffles 1421. For example, in one embodiment, in
which the engine 102 has six cylinders, the sump has six baffles
1421 defining six outer regions.
[0176] Although embodiments of the present invention have been
described in the preceding paragraphs with reference to various
examples, it should be appreciated that modifications to the
examples given can be made without departing from the scope of the
invention as claimed.
[0177] Features described in the preceding description may be used
in combinations other than the combinations explicitly
described.
[0178] Although functions have been described with reference to
certain features, those functions may be performable by other
features whether described or not.
[0179] Although features have been described with reference to
certain embodiments, those features may also be present in other
embodiments whether described or not.
[0180] Whilst endeavoring in the foregoing specification to draw
attention to those features of the invention believed to be of
particular importance it should be understood that the Applicant
claims protection in respect of any patentable feature or
combination of features hereinbefore referred to and/or shown in
the drawings whether or not particular emphasis has been placed
thereon.
* * * * *