GB2305467A

GB2305467A - Engine oil sump

Info

Publication number: GB2305467A
Application number: GB9519524A
Authority: GB
Inventors: Roger Francis Gill
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1995-09-25
Filing date: 1995-09-25
Publication date: 1997-04-09
Also published as: GB9519524D0

Abstract

An oil pan 2 has a cylindrical enclosure 3 mounted within and spaced from the walls of the pan. An oil inlet 8 returns recirculating engine oil 9 to the enclosure 3 and an oil pickup tube 11 draws oil 4 from the enclosure 3 which has an aperture 13 at the bottom through which oil may flow into and out of the enclosure. The walls of the enclosure are formed by temperature deformable bi-metal or memory metal panels (120, Fig.3) adapted to deform once the temperature of the oil 4 is above a predetermined temperature to open gaps (26) between adjacent panel edges.

Description

Engine Oil Sump The invention relates to an oil sump for an internal combustion engine.

When an internal combustion engine is started from cold, oil recirculating within the engine will also be cold and will take some minutes to warm up. The time needed for the oil to reach normal operating temperature will be proportional to the amount of oil in the oil recirculation loop. Until the oil has reached its operating temperature, the engine fuel consumption and emissions will not be optimal, and wear within the engine will also be increased.

According to the present invention, there is provided an oil sump for an internal combustion engine comprising an oil pan with an enclosure therein, an oil inlet for returning oil to the enclosure, an oil pickup for drawing oil from the enclosure, the enclosure being spaced from the walls of the pan and having an aperture through which oil at the bottom of the enclosure may communicate with oil outside the enclosure and at least one temperature deformable panel adapted to deform above a predetermined temperature to open at least one passage in the enclosure through which oil inside the enclosure may mix with oil outside the enclosure.

The purpose of the aperture is to allow an ingress of oil into the enclosure when the passages are closed. This ingress will normally be necessary upon start up of the engine, before recirculated oil has had time to return to the sump, in order to prevent a loss of oil supply to the oil pickup. Preferably the aperture is in a base of the enclosure, so that heated oil does not escape through the aperture while the engine oil is reaching its operating temperature. Preferably the passage is in a side of the enclosure so that heated oil within the enclosure can mix more efficiently with oil outside the enclosure once the engine oil has reached its operating temperature.

The enclosure may have an open top which in use extends above the level of the oil in the oil pan.

The oil pickup should preferably draw oil from the lower half of the enclosure. The optimum level of the oil pickup within the enclosure will in general be determined by a compromise between the need to avoid loss of oil supply when the oil level within the enclosure is drawn down during start up, and the desire to draw hotter oil from nearer the top of the enclosure.

It is preferable if the enclosure is held within the oil pan by supporting means which extend downwards from above the container. These supporting means may be fixed directly to the underside of the engine and may, for example, be a set of parallel rods.

It is advantageous if each temperature deformable panel is fixed to the supporting means along one edge of each panel. The panels may then flex, as it were, about an axis defined by the fixed edge.

In a preferred embodiment of the invention, the passage is closed below the predetermined temperature when one temperature deformable panel flexes to seat against the fixed edge of another deformable panel. The outer surfaces of the enclosure may therefore all be formed from the temperature deformable panels.

If each panel is curved, then the enclosure may be essentially cylindrical when the enclosure is below the predetermined temperature. Since a cylindrical shape has a relatively low ratio of surface area to internal volume, particularly when compared with box-like enclosures, this shape will help minimise heat loss owing to conduction of heat through the enclosure during the phase when the engine oil is reaching its operating temperature.

In order to achieve a reasonable compromise between the speed with which the oil is heated, and the need to avoid losing oil supply to the oil pickup, either during start up or during cornering of a motor vehicle, the volume of oil in the enclosure should preferably be between 0.5 and 1.0 litre.

Also according to the invention, there is provided an internal combustion engine with an oil sump, the oil sump comprising an oil pan with an enclosure therein, an oil inlet for returning oil to the enclosure, an oil pickup for drawing oil from the enclosure, the enclosure being spaced from the pan and having an aperture through which oil at the bottom of the enclosure may communicate with oil outside the enclosure and at least one temperature deformable panel adapted to flex above a predetermined temperature to open at least one passage in the enclosure through which oil inside the enclosure may mix with oil outside the enclosure.

The invention will now be described in more detail by way of example with reference to the following drawings, in which: Figure 1 shows a side view in part cross section of an oil sump according to the invention; Figure 2 shows a perspective view of an enclosure of the oil sump of Figure 1; Figure 3 shows a bottom view of the enclosure of Figure 2; Figure 4 presents fuel economy test data for a 1.8 litre capacity gasoline engine, with and without the enclosure in the oil sump; and Figure 5 presents the test data of Figure 4 in terms of percentage improvements when the enclosure is in the sump.

Figure 1 shows a sump 1 for an internal combustion engine.

The engine (not shown) would be above the sump with a longitudinal axis in the plane of the page. The sump has an oil pan 2 with an enclosure 3 spaced from the walls of the oil pan. The oil pan 2 provides a reservoir for oil 4, the level of which outside and inside the enclosure is shown by the lines indicated with the numerals 5 and 6 respectively.

The oil inlet to the sump is a sump baffle 7, which has an aperture 8 to direct return oil 9 into an open top 10 of the container 3. Oil 4 is drawn from the sump by an oil pickup tube 11 which has at its mouth 12 a wire mesh filter.

The enclosure 3 has an open bottom 13 so that oil at the bottom of the enclosure can communicate with oil outside the enclosure. However, the top 14 of the enclosure 3 extends above the level of the oil 5 outside the enclosure so that oil inside the top of the enclosure is isolated from oil outside the enclosure.

Figure 1 depicts the operation of the oil sump when the engine is first started, but before oil has returned to the sump through an engine oil coolant circuit. The operation of the enclosure 3 will be described below, however, since the oil 4 will be cold, the only way for oil inside the enclosure to communicate with oil outside the enclosure is through the open bottom 13 of the enclosure.

Oil 4 is drawn into the pickup tube 11, as indicated by arrows. Because no oil has yet been returned through the aperture 8 in the sump baffle 7, the level of the oil 6 inside the enclosure 3 has been lowered with respect to the level of oil S outside the enclosure. Oil can only flow into the enclosure through a gap 15 between the open bottom 13 of the enclosure and the oil pan 2. The oil 4 will have a certain viscosity, which will depend inversely with temperature. The initial capacity of the oil in the enclosure, and the dimensions of the gap 15 must be selected so that oil can enter the enclosure through the gap at a sufficient rate so that the mouth 12 of the pickup tube 11 does not become exposed above the level of the oil 6. This must be so even for adverse conditions, that is, for very low oil temperatures, steep inclination of the engine, and for a minimum of oil within the sump.

Once oil has started returning through the sump baffle aperture 8, the level of oil within the enclosure 6 will rapidly equalise with the level outside 5. Hot returned oil will initially float near the top of the enclosure, and then work its way down to the mouth 12 of the oil pickup tube 11.

Figures 2 and 3 illustrate the operation of the enclosure 3, which is formed from four similar overlapping panels 20 which are straight in one direction and at right angles to this direction curved, so that the enclosure has a generally cylindrical shape. Along one straight edge 23, each panel 20 is fixed to a rod 21, which extends above the enclosure for mounting (not shown) to the underside of the engine. At the base of the enclosure 3, the four rods 21 are held together by a ring 22.

Each panel 20 is made from a bi-metallic or memory metal composition, so that as a panel is heated, the stresses within the panel will reduce the natural curvature.of the panel.

The panels 20 will be at a temperature at or between the oil temperatures either side of the enclosure. Below the normal operating oil temperature, the stresses within the panels will close any gap between the fixed edge 23 of one panel and a free edge 24 of the adjacent panel. As the oil temperature becomes cold the panels will therefore be sprung closed ever tighter. The ring 22 at the base of the enclosure needs to be robust enough to withstand the resulting compression from the panels 20.

As the temperatures of the oil 4 and panels 20 increases, the stresses within the panels will gradually release the spring effect closing the panels until at a predetermined temperature close to but under the nominal operating temperature of the oil, each panel will straighten out as indicated by the dashed outline panels 25 of Figure 3, to open a passage 26 between the fixed edge 23 of one panel, and the free edge 24 of an adjacent panel.

Oil from inside and outside the enclosure is then able to mix through the four passages 26 under the action of agitation due to the inlet and pickup flows, movement of a motor vehicle or vibration of the engine, and also from temperature difference driven flow throughout the oil pan.

The nominal volume of oil in the enclosure 3 is preferably no more than 1.0 litre, when the oil capacity of the sump is 3.5 litre. Typical dimensions of such a roughly cylindrical enclosure are a height of 100 mm, the top 20 mm of which will extend above the level of the oil, and an internal diameter of 100 mm, for a nominal capacity of just over 0.6 litres.

The thickness of the metal panels 20 will typically be in the range of 1 to 3 mm. When the passages 26 are closed, there will therefore be heat conduction through the thickness of the panels 20 from the oil within the enclosure to the cooler oil outside the enclosure. Up to a point, this conduction is desirable, because the panels need to heat through before they begin to straighten out.

However, until the temperature of the oil drawn into the pickup tube 11 approaches the normal engine operating temperature, unnecessary heat loss is minimised by the generally cylindrical shape of the enclosure, which will have a minimum of surface area to volume, the low position of the base aperture 13 and the separation of the enclosure 3 from any surfaces of the oil pan 2. Thermal conduction to the underside of the engine through the four rods 21 is negligible. The shape and arrangement of the enclosure 3 within the oil pan 2 therefore increase the rate at which oil within the enclosure reaches the operating temperature of the engine.

Fuel economy test data are presented in Figures 4 and 5, and follow the industry-standard European Drive Cycle.

The automobile in this test was a mid-size car with a 1.8 litre gasoline engine. An engine with an enclosure in the sump had improved fuel economy in all the standard test conditions, with a significant average improvement in fuel economy of 2.9%.

Emissions and engine wear will, of course, also be improved by the more rapid oil temperature increase.

The enclosure also provides a beneficial anti-surge effect when the panels are open. Each open panel 25 acts as a baffle surrounding the pickup tube 11, to resist the flow of oil from one end of the sump to another end which may occur, particularly upon cornering in a vehicle with a transversely mounted engine. Normally this movement of oil is not a problem, with the shape and capacity of the oil pan and the position of the pickup tube being designed so that the oil pickup tube does not become exposed above the level of the oil. However, this potential problem becomes more likely if the oil in the sump falls below the minimum design level. The panels may therefore provide a useful anti-surge effect in extreme conditions.

Although the anti-surge effect will not affect the oil level for a steady-state condition such as constant cornering, it may nevertheless permit the oil pickup tube to be mounted higher with respect to the nominal oil level than would otherwise be the case, and this higher position within the closed enclosure will result in a more rapid increase in temperature of the oil drawn from the enclosure by the oil pickup.

Other arrangements of thermally deformable panel may, of course, also be employed, for example flat panels hinged with bi-metallic compositions, or panels which are mounted along a horizontal fixed axis.

Claims

1. An oil sump for an internal combustion engine comprising an oil pan with an enclosure therein, an oil inlet for returning oil to the enclosure, an oil pickup for drawing oil from the enclosure, the enclosure being spaced from the walls of the pan and having an aperture through which oil at the bottom of the enclosure may communicate with oil outside the enclosure and at least one temperature deformable panel adapted to deform above a predetermined temperature to open at least one passage in the enclosure through which oil inside the enclosure may mix with oil outside the enclosure.

2. An oil sump according to Claim 1, in which the aperture is in a base of the enclosure.

3. An oil sump according to Claim 1 or Claim 2, in which the passage is in a side of the enclosure.

4. An oil sump according to any preceding claim, in which the enclosure has an open top, the top of the enclosure in use extending above the level of the oil in the oil pan.

5. An oil sump according to any preceding claim, in which the oil pickup is adapted to draw oil from the lower half of the enclosure.

6. An oil sump according to any preceding claim, in which the enclosure is held within the oil pan by supporting means which extend downwards from above the enclosure.

7. An oil sump according to Claim 6, in which the temperature deformable panel is fixed to the supporting means along one edge of the panel.

8. An oil sump according to Claim 7, in which the passage is closed below the predetermined temperature when one temperature deformable panel flexes to seat against the fixed edge of another deformable panel.

9. An oil sump according to any preceding claim, in which temperature deformable panels extend fully around the enclosure.

10. An oil sump according to any preceding claim, in which the enclosure is essentially cylindrical when below the predetermined temperature.

11. An oil sump according to any preceding claim, in which in use the volume of oil in the enclosure is between 0.5 and 1.0 litre.

12. An internal combustion engine with an oil sump, wherein the oil sump is as claimed in any one of Claims 1 to 11.

13. An oil sump substantially as herein described with reference to and as shown in the accompanying drawings.

14. An internal combustion engine with an oil sump, in which the oil sump is substantially as herein described with reference to and as shown in the accompanying drawings.