GB2437089A

GB2437089A - Wet sump assembly for an internal combustion engine

Info

Publication number: GB2437089A
Application number: GB0607445A
Authority: GB
Inventors: Ian Graham Pegg
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-04-13
Filing date: 2006-04-13
Publication date: 2007-10-17
Anticipated expiration: 2026-04-13
Also published as: GB0607445D0; GB2437089B

Abstract

The wet sump assembly 10 has a funnel shaped baffle plate 12 to return oil from the engine to an oil pan 11 and oil pick-up chamber 15. The baffle plate 12 has an imperforate central portion 14 and a border having a number of perforations 16 of a size such that it is difficult for cold oil to flow through them but hot oil can flow freely through them to the oil pan 11. Therefore upon engine start-up from cold most of the oil returning from the engine flows back via the imperforate central portion 14 of the baffle plate 12 directly to the oil pick-up chamber 15 where it is picked up by a pick-up pipe 20 for recirculation through the engine. This speeds up oil warm-up after a cold engine start and reduces both fuel usage and emissions. The baffle plate 12 may have four walls 17. The walls 17 of the pick-up chamber may have upper and lower bands of perforations 18, 19 respectively, the upper perforations being larger, separated by an imperforate region in order to partition the warm and cold oil during engine warm-up.

Description

205-1891GB A Wet Sulup Asseth1y for an Engine This invention relates to

internal combustion engines and in particular to a wet sump assembly for such an engine.

It is known that upon start up from cold it is desirable to heat the oil used to lubricate an engine as quickly as possible in order to reduce friction within the engine and hence fuel consumption.

For the fastest warm up of the oil, which leads to minimum fuel consumption, the smallest possible volume of oil is required. This smallest volume is given by the amount that is retained in the engine or is in the process a5 of draining down to the sump when the engine is running and any oil stored in the sump. In an effort to reduce the volume of oil that is initially circulating it is known from, for example, DE-37295545 to provide a partitioned sump in which an oil pick-up used to return oil from the sump to the engine is located in a separate chamber to which oil returning from the engine to the sump is returned. It is a requirement of such an oil pick-up chamber that the oil must at all times cover the oil pickup pipe because, if the pipe becomes uncovered the engine will be starved of oil and is then likely to suffer damage. Therefore the design of any such oil pick-up chamber provided to speed up the warm-up process, during engine warm-up, is always a compromise between potential oil starvation and the use of the minimum oil volume.

It is a problem with the design shown in DE-3729545 that if the oil level in the oil pick-up chamber falls then additional oil will enter the oil pick-up chamber from the bottom of the oil pick-up chamber which is the coldest oil in the system and this will tend to slow up the oil heating process.

2O5-1891GB It is an object of this invention to provide a wet sump assembly for an engine that provides rapid oil warm-up with reduced risk of oil starvation.

According to a first aspect of the invention there is provided a wet sump assembly for an engine comprising an oil pan to store oil for use in lubricating the engine, an oil pick-up chamber located within the oil pan, an oil pick-up pipe located within the oil pick-up chamber and a baffle plate to return oil from the engine to the oil pan and the oil pick up chamber wherein the oil pick-up chamber is separated from the oil pan by one or more walls each of which has a number of perforations therein of a predetermined size to control the flow of oil to the oil pick-up chamber from the oil pan and the baffle plate comprises a central imperforate portion bounded by a perforated border having a number of perforations formed therein of a predetermined size.

The size of the perforations in the perforated border may be such that, when the oil is cold, substantially all of the oil returning to the sump assembly from the engine flows directly to the oil pick-up chamber along the central imperforate portion.

The baffle plate may be funnel shaped so as to direct any oil returning from the engine towards the oil pick-up chamber.

The size of the perforations in the perforated border may be such that, when the oil is at a normal running temperature, oil can flow freely through the perforations into the oil pan.

At least one of the at least one walls may have larger perforations at an upper end thereof than at a lower end thereof.

205-1891GB At least one of the at least one walls forming the oil pick-up chamber may have a first band of perforations at an upper end thereof, a second band of perforations at a lower end thereof and an imperforate region disposed between the first and second bands of perforations.

According to a second aspect of the invention there is provided an internal combustion engine having a wet sump assembly in accordance with said first aspect of the invention.

The invention will now be described by way of example with reference to the accompanying drawing of which:-Fig.1 is a pictorial representation of a wet sump assembly for an engine according to the invention; Fig.2 is a cross-section along the line X-X on Fig.1; Fig.3 is a schematic diagram of a lubrication circuit for an internal combustion engine; and Fig.4 is a pictorial representation of an alternative embodiment of a wet sump assembly for an engine according to the invention.

With reference to Fig.3 there is shown an engine 1 having a number of internal lubrication passages 2 formed therein to deliver oil to components requiring lubrication and to return the oil to a sump assembly 10.

The wet sump assembly 10 comprises an oil pan 11 in which is located a small oil pick-up chamber 15. A pick-up pipe 20 is located within the oil pick-up chamber 15 to 205-1891GB transport oil from the sump assembly 10 to an oil circulation pump 4.

The oil pump 4 draws up oil from the oil pick-up chamber 15 and pumps it into the engine 1 via an oil feed pipe 5. The oil then flows through the passages 2 in the engine 1 and is returned to the oil pan 11 by means of an oil return pipe 3.

With reference to Figs.1 and 2 there is shown in greater detail the wet sump assembly 10 according to the invention.

The wet sump assembly 10 comprises of the oil pan 11 to store oil for use in lubricating the engine 1, the oil pick-up chamber 15 located within the oil pan 11, the oil pick-up pipe 20 located within the oil pick-up chamber 15 and a baffle plate 12 to return oil from the engine 1 to the oil pan 11 and the oil pick up chamber 15. The oil pick-up pipe 20 has a filter 21 to prevent debris from being transferred from the sump assembly 10 to the engine 1.

The oil pick-up chamber 15 is separated from the general volume of the oil pan 11 by four walls 17 each of which has a number of perforations 18, 19 therein of a predetermined size to control the flow of oil from the oil pan 11 to the oil pick-up chamber 15.

It will be appreciated that if the oil pick-up chamber is of a cylindrical form then only one wall would be required and that the shape of the oil pick-up chamber can be of any desired shape and is not limited to shapes using four walls.

Each of the walls forming the oil pick-up chamber 15 has a first band of perforations 18 at an upper end thereof and a second band of perforations 19 at a lower end thereof.

205-1891GB The region between these two bands has no perforations and so forms an imperforate region separating the first and second bands of perforations 18, 19.

The perforations 18 at the upper end of each wall 17 are larger than the perforations 19 at the lower end of each wall 17. Therefore, when the oil is warming up from cold it will be easier for oil to flow from the oil pan 11 into the oil pick-up chamber 15 through the upper perforations 18 than through the lower perforations 19. By correctly sizing the upper and lower perforations 18, 19 it is possible to prevent virtually any oil from flowing through the lower perforations 19 when the oil is in the cold start-up condition, while at the same time permitting oil to flow through the upper perforations 18 if the oil level in the oil pick-up chamber 15 falls below the level in the oil pan 11. This is important because, due to variations in density of the oil as it is heated from cold, warmer oil will always tend to sit upon cooler oil. In addition, because the warmest oil will have a lower viscosity than the cooler oil it will flow more freely through the upper perforations 18 than through the lower perforations 19. Therefore, by using larger perforations 18 at the upper end of each wall 17 it can be virtually guaranteed that any oil flowing from the oil pan 11 into the oil pick-up chamber 15 during initial warmup will be the warmest possible thereby speeding up the heating of the oil. The use of an imperforate region between the upper and lower bands of perforations 18 and 19 helps to partition the warm and cold oil during warm-up by preventing any oil flow in this region.

As shown on Fig.2, the level of the cold oil COL' in the oil pan 11 just after start-up from cold is higher than the level of the warmer oil HOL' in the oil pick-up chamber 15.

205-1891GB It will be appreciated that instead of the preferred embodiment described for the walls 17 they could alternatively have uniform perforations or perforations of varying size.

It will be appreciated that the size of the upper and lower perforations 18 and 19 will depend upon the temperature/viscosity characteristics of the oil used in the engine 1 and the need to ensure that the engine 1 is never starved of oil.

The baffle plate 12 comprises a central imperforate portion 14 bounded by a perforated border having a number of perforations 16 formed therein of a predetermined size. The size of the perforations 16 in the perforated border is such that, when the oil is cold, substantially all of the oil returning to the sump assembly 10 from the engine 1 will flow directly to the oil pick-up chamber 15 along the central imperforate portion 14. This is because, due to the high viscosity of the oil when it is cold, it is difficult for the oil to pass through the perforations 16.

As the oil returning to the sump assembly 10 is warmed its viscosity will reduce and some of the oil will then begin to pass through the perforations 16 in the perforated border and fall upon the oil in the oil pan 11. However, as this oil will be warmer than the oil in the oil pan 11 it will, as previously discussed, be of a lower density and sit upon the generally cooler oil in the oil pan 11.

The size of the perforations 16 in the perforated border is such that, when the oil is at a normal running temperature, any oil returning from the engine 1 will flow freely through the perforations 16 into the oil pan 16 thereby ensuring that at higher oil temperatures a considerable proportion of the oil returning from the engine 1 enters the oil pan 11 before flowing into the oil pick-up 205-1891GB chamber 15. This is to ensure that virtually the entire volume of oil stored in the oil pan 11 is used at higher temperatures rather than just a small volume which is continually recirculated. If only some of the oil is recirculated then this would artificially age the oil being recirculated and would also result in oil at a higher temperature being passed back to the pump 4 because the hot returning oil would not be mixed with the generally cooler oil stored in the oil pan 11.

It will be appreciated that the size of the perforations 16 will depend upon the temperature /viscosity characteristics of the oil used in the engine 1 and the need to ensure that the engine 1 is never starved of oil.

In order to ensure that, upon initial start-up when the oil is cool, as much of the oil returning from the engine 1 is circulated directly back to the oil pick-up chamber 15, the baffle plate 12 is funnel shaped and directs the oil returning from the engine 1 towards the oil pick-up chamber 15.

If the baffle plate 12 was flat rather than of an inclined funnel form then some of the oil returning from the engine 1 would stagnate upon the perforated border. This would provide an increased opportunity for the oil to then flow back to the oil pan 11 rather than the oil pick-up chamber 15 thereby slightly reducing the warm-up performance of the sump assembly.

With reference to Fig.4 there is shown an alternative wet sump assembly 110 to that previously described. The wet sump assembly comprises of an oil pan 111 and an oil pick up chamber 115 that extends across the whole width of the oil pan 111. Two baffle plates 44 are provided to channel returning oil to the oil pick-up chamber 115. Each of the baffle plates 44 has a perforated border 46. The sides of 205-1891GB the pick-up chamber 115 are defined by the walls of the oil pan 111 and two spaced apart plates 47 of which only one is visible on Fig.4. Each of the plates 47 has two sets of perforations 48, 49. The perforations 48 at the upper end of each plate are larger than the perforations 49 at the lower end of each plate. Therefore, as before, when the oil is warming up from cold it will be easier for oil to flow from the oil pan 111 into the oil pick-up chamber 115 through the upper perforations 48 than through the lower perforations 49.

Therefore in summary it is known that the cost of

vehicle ownership and CO2 emissions from vehicles are of increasing concern and measures to reduce fuel consumption and CO2 are required. NOx, HO and CO emissions also need to be reduced and these are particularly high at engine start up which is compounded by the catalyst temperature being below its light-off temperature.

A partial solution to these problems is to improve the rate of temperature rise of the oil being used for engine lubrication. This has been achieved in accordance with this invention by ensuring that any oil that has been heated in the engine due to friction or heat input from combustion is returned directly to the oil pickup, until the oil reaches a desired operating temperature.

The main benefits of this invention are: Start-up CO2 emissions are lowered, due to lower friction losses in the engine during warm up Piston temperatures are higher during warm up which reduces CO and HC emissions. This is due to hotter oil which cools the pistons via splash or jet cooling and results in more complete and stabile combustion.

205-1891GB Friction reduction within the engine effectively reduces the load/ fuel required for a given engine output.

This will reduce the NOx emissions on D.I. diesel powered engines, especially as NOx emissions are second or third order polynomial functions with respect to engine load for a given speed.

It will be appreciated by those skilled in the art that although the invention has been described by way of example with reference to one or more embodiments it is not limited to the disclosed embodiments and that one or more modifications to the disclosed embodiments or alternative embodiments could be constructed without departing from the scope of the invention.

Claims

205-1891GB -10 -Claims 1. A wet sump assembly for an engine comprising

an oil pan to store oil for use in lubricating the engine, an oil pick-up chamber located within the oil pan, an oil pick-up pipe located within the oil pick-up chamber and a baffle plate to return oil from the engine to the oil pan and the oil pick up chamber wherein the oil pick-up chamber is separated from the oil pan by one or more walls each of which has a number of perforations therein of a predetermined size to control the flow of oil to the oil pick-up chamber from the oil pan and the baffle plate comprises a central imperforate portion bounded by a perforated border having a number of perforations formed therein of a predetermined size.

2. An assembly as claimed in claim 1 wherein the size of the perforations in the perforated border is such that, when the oil is cold, substantially all of the oil returning to the sump assembly from the engine flows directly to the oil pick-up chamber along the central imperforate portion.

3. An assembly as claimed in claim 4 wherein the baffle plate is funnel shaped so as to direct any oil returning from the engine towards the oil pick-up chamber.

4. An assembly as claimed in any of claims 1 to 3 wherein the size of the perforations in the perforated border is such that, when the oil is at a normal running temperature, oil can flow freely through the perforations into the oil pan.

5. An assembly as claimed in any of claims 1 to 4 wherein at least one of the at least one walls has larger perforations at an upper end thereof than at a lower end thereof.

205-1891GB -11 - 6. An assembly as claimed in any of claims 1 to 5 wherein at least one of the at least one walls forming the oil pick-up chamber has a first band of perforations at an upper end thereof, a second band of perforations at a lower end thereof and an imperforate region disposed between the first and second bands of perforations.

7. An internal combustion engine having a wet sump assembly as claimed in any of claims 1 to 6.

8. A wet sump assembly for an engine substantially as described herein with reference to the accompanying drawing.

9. An internal combustion engine substantially as described herein with reference to the accompanying drawing.

Amendments to the claims have been filed as follows 2O5-1891GB Claims 1. A wet sump assembly for an engine comprising an oil pan to store oil for use in lubricating the engine, an oil pick-up chamber located within the oil pan, an oil pick-up pipe located within the oil pick-up chamber and a baffle plate to return oil from the engine to the oil pan and the oil pick up chamber wherein the oil pick-up chamber is separated from the oil pan by one or more walls each of io which has a number of perforations therein of a predetermined size to control the flow of oil to the oil Pick-up chamber from the oil pan and the baffle plate comprises a central imperforate portion bounded by a perforated border having a number of perforations formed therein of a predetermined Size, the size of the perforations in the perforated border being such that, when the oil is at a normal running temperature, the oil can flow freely through the perforations into the oil pan.

2. An assembly as claimed in claim 1 wherein the size of the perforations in the perforated border is such that, when the oil is cold, substantially all of the oil returning to the surnp assembly from the engine flows directly to the oil pick-up chamber along the central imperforate portion.

3. An assembly as claimed in claim 1 or in claim 2 wherein the baffle plate is funnel shaped so as to direct any oil returning from the engine towards the oil pick-up chamber.

4. An assembly as claimed in any of claims 1 to 3 wherein at least one of the at least one walls has larger perforations at an upper end thereof than at a lower end thereof.

5. An assembly as claimed in any of claims 1 to 4 wherein at least one of the at least one walls forming the 2O5-1891GB oil Pick-up chamber has a first band of perforations at an Upper end thereof, a second band of perforations at a lower end thereof and an imperforate region disposed between the first and second bands of perforations 6. An internal combustion engine having a wet sump assembly as Claimed in any of Claims 1 to 5.

7. A wet sump assembly for an engine substantially as described herein with reference to the accompanying drawing.

8. An internal combustion engine substantially as described herein with reference to the accompanying drawing.