In an internal combustion engine oil is usually drawn up from an oil sump positioned at the base of the internal combustion engine through an inlet pipe to a pump, forced through an oil filter unit, and then distributed to various components in the engine to lubricate and cool. The oil then returns to the oil sump, usually under gravity. Oil used to lubricate and cool must be filtered in order to keep the oil clean and thus working efficiently. Generally the oil filter unit is positioned upstream of the oil pump (i. e. on the pressure side) such that before oil is distributed to components in the engine, it passes through the filter so that it is cleaned. Usually the oil filter unit is attached to the outside of the engine and is required to be replaced every 10,000-20,000 miles or so because of its small size. There has recently been a drive to reduce the space which the oil filter unit takes up in the engine compartment.

A recent trend has been in the design of maintenance free engines where the engine is intended not to need servicing by the replacement of parts during the engine's lifetime. The design lifetime of an engine might typically be 100,000 miles or 150,000 miles. For large engines, the design lifetime might be 200,000 miles.

Larger pieces of debris can find their way into the oil sump. To prevent such debris from being sucked into the oil pump and damaging the oil pump, a coarse strainer is often positioned at the end of the inlet pipe in the oil sump.

An object of the present invention is to provide an improved filter arrangement. More particularly, it is an object of the present invention to provide a filter arrangement in which the filter of an internal combustion engine takes up no external space on the engine itself or in the engine compartment.

A first aspect of the present invention provides an internal combustion engine comprising: an engine block; an oil pan defining an oil sump, said engine block and said oil pan together defining a sealed unit; and an oil filter unit disposed at least partly within said oil sump within said sealed unit, wherein said oil filter unit

includes a planar filter element of a size chosen such that said oil filter unit will not need to be replaced during the engine lifetime.

The filter unit is chosen by providing one with an element with a surface area and/or volume to match the lifetime of the engine. This is a significant advantage because it means that the oil filter does not need to be replaced during routine maintenance allowing the internal combustion engine to be a sealed unit. In general, sumps are sufficiently large to accommodate large filter elements even if large enough to last the engine lifetime without a prohibative increase in size.

Also, in this way, the overall volume of an internal combustion engine with oil filter unit is decreased because the oil filter unit is disposed in the oil sump. This saves space in the engine compartment and there is no need for a separate oil filter unit, typically attached to the side of the engine. The space where the oil filter unit is housed in the present invention is otherwise wasted space which, if the filter is to last for the lifetime of the engine, is a large amount of space. The depth of the oil sump may need to be increased fractionally in order that the filter unit can be housed in the oil sump but this increase in volume is marginal and significantly, as a planar filter element is used, the height of the sump is not dramatically increased beyond that which is normal.

In the hereinafter described embodiments, the volume of space taken up by a filter unit can be as little as the solid volume of the oil filter unit because, if the oil filter unit is at least partly submerged in the oil in the oil sump, the amount of oil displaced is equal to only the solid volume of the individual components of the oil filter unit which is significantly less than the external volume of the oil filter unit due in part to the porous nature of the filter element.

Furthermore, fewer oil galleries are required in the engine block because the oil of the internal combustion engine does not need to leave the engine block to pass through an external filter unit. There are also advantages to disposing the filter unit in the oil sump relating to the construction of the filter unit. For example, any oil leaks from the oil filter unit are less of a problem when the oil filter unit is disposed in the oil sump than when it is disposed externally of the internal combustion engine

and so the construction requirements of the filter unit are less stringent.

Preferably the internal combustion engine of the hereinafter described embodiments is for a car and the oil filter unit comprises a filter element which has a surface area of 100, 000mm2 or greater and/or a volume of 15,000mm3 or more.

With a large area the pressure drop across the filter unit is kept low and a lower velocity of oil per unit area through the filter unit can be achieved than previously possible.

Preferably the planar filter element of the internal combustion engine of the present invention extends across the sump.

In this way the surface area of the filter element of the oil filter unit may be maximise for a given oil sump size because the filter element may extend across the entire upper surface of the oil in the oil sump.

According to a second aspect of the invention, there is provided an internal combustion engine comprising: an engine block; an oil pan defining an oil sump, said engine block and said oil pan together defining a sealed unit; and an oil filter unit disposed at least partly within said oil sump within said sealed unit, wherein oil filter unit includes a planar filter element and a planar housing with an inlet and an outlet enclosing said filter element.

In this way, before assembly into the sealed unit, the oil filter unit can be easily handled without fear of damaging the filter element. Furthermore, the number of critical oil seals which must not leak (i. e. those in which a leak would result in loss of oil from the engine) is reduced over prior art arrangements. This is because only the one conventional gasket between the engine and the oil pan is needed and the seal (s) between oil ducts of the engine and the filter unit are not critical as they may leak (because oil will leak harmlessly into the oil sump) which is not the case for equivalent duct/filter seals in conventional internal combustion engines.

Preferably the filter unit has a housing made of thermoplastic, thermosetting, or metal material. Thus, the cost of the filter unit can be further reduced.

Preferably in the internal combustion engine of the present invention the filter unit is on the suction side of the oil pump. In this way, oil entering the oil pump can

be filtered before entering the pump thereby protecting the pump. This is a particular advantage of having the filter unit being disposed in the oil sump According to a third aspect of the present invention, there is provided an internal combustion engine comprising: an engine block; an oil pan defining an oil sump, said engine block and said oil pan together defining a sealed unit; and a by- pass oil filter unit disposed at least partly within said oil sump within said sealed unit ; wherein said by-pass oil filter unit is arranged for filtering oil from said oil sump and returning filtered oil directly to said oil sump.

The by-pass filter unit may be used either on its own, or in conjunction with a filter unit as described in the first or second aspect of the invention or with a conventional filter arrangement. The by-pass filter unit may be used to clean the oil in the oil sump to a very high standard. This has advantages in that the oil may as a result have a longer lifetime than usual. Furthermore, the positioning of the by-pass filter unit in the sump is convenient as little energy is required to force oil through it as it is not vertically displaced from the sump thereby requiring lifting of oil as might be the case if it were located externally from the sump.

According to a fourth aspect of the present invention, there is provided an oil filter unit for disposition in a sealed unit defined by an engine block of an internal combustion engine and an oil pan.

According to a fifth aspect of the present invention there is provided an oil pan defining an oil sump for an internal combustion engine, in combination with an oil filter according to the fourth aspect of the present invention Other objects and advantages of the present invention will become apparent from the following description of various embodiments of the present invention with reference to the following drawings in which: Figure 1 is a cross section through an internal combustion engine in the longitudinal direction of the crank shaft of a first embodiment of the present invention; Figure 2 is a cross section through an internal combustion engine in the transverse direction of the crank shaft of a first embodiment of the present invention;

Figure 3 is a cross section through an internal combustion engine in the longitudinal direction of the crank shaft of an internal combustion engine according to a second embodiment of the present invention; Figure 4 is a cross section through an internal combustion engine in the transverse direction of the crank shaft of a second embodiment of the present invention; Figure 5 is a cross section through an internal combustion engine in the longitudinal direction of the crank shaft of an internal combustion engine according to a third embodiment of the present invention; Figure 6 is a perspective view of a fourth embodiment according to the present invention; and Figure 7 is a cross section through an oil pan for defining an oil sump of an internal combustion engine according to a fifth embodiment of the present invention.

In the figures like reference numerals are used to indicate like components.

Figures 1 and 2 illustrate an internal combustion engine 10 according to the present invention. The internal combustion engine 10 comprises an engine block 12, a crank shaft 14 and an oil pan 20. The oil pan 20 is attached to the bottom of the engine block 12 by conventional means to form a sealed unit.

The oil pan 20 defines an oil sump 26 and is comprised of side walls 22 and a base wall 24. An oil filter unit 30 is disposed within the oil pan 20 in spaced apart relationship to side and bottom walls of the oil pan such that oil surrounds the filter unit 30. The oil filter unit 30 is disposed between the engine block 12 and the oil pan 20 such that the filter unit 30 is at least partly disposed in the oil sump 26. By oil filter unit we mean a filter unit effective as a filter for the purpose of filtering engine oil for circulation through an internal combustion engine. This contrasts with a strainer which typically comprises a wire mesh with pores of about mm an is provided to strain large pieces of debris from the oil to prevent them from entering the oil pump.

The filter element 32 in the oil sump 26 is of a predetermined size. The size and media type of the filter element 32 is chosen according to the type of internal

combustion engine 10 the filter unit 30 is attached to and according to the expected lifetime of the engine 10. The size, for example, surface area, volume, pore size etc. is chosen such that the oil filter unit does not need to be replaced during the lifetime of the engine 10.

The filter unit 30 mounts a filter element 32 which is preferably comprised of a paper, felt or synthetic material or similar and is preferably a concertina fold filter element thereby maximising its surface area for the amount of space it occupies. The surface area of the filter element 32 is chosen such that, during the life time of the engine, the filter element 32 does not need to be replaced due to blockage.

The filter element 32 is a planar filter element as opposed to a conventional annular filter element. The term planar indicates that the two main outer surfaces of the element (once folded in the case of a concertina fold filter element) are generally or substantially parallel and generally or substantially flat but minor variations in parallelness and flatness are still intended to be covered by the term. In general, the filter element will be so positioned in the sump to extend across the sump 26 generally parallel to the level of oil in the sump 26.

The filter element 32 may have a range of thickness of from 0.5 mm for pleated or concertina fold media or up to 50.0 mm for a depth filter media. In the case of a depth filter element the surface area is preferably at least 10000mm2, more preferably 17500mm2, 60000mm2 or even 120000mm2 and in the case of a flat filter element the surface area is preferably at least 100000mm2, more preferably 150000mm2, 500000mm2 and still yet more preferably 1000000mm2 or even 1500000mm2.

Preferably the surface area is as large as the oil pan allows i. e. the element extends across the whole oil sump 26. Preferably the surface area is such that the ratio of the surface area of filter element 32 to the surface area of the upper surface of oil in the oil sump 26 is as near as possible, preferably at least 1: 1.

Furthermore, the filter element 32 preferably has pores which give filtration levels of 0. 05mm or less, more preferably a level of 0. 01mm or less and still yet more preferably a level 0. 005mm or less.

Preferably the filter element, whether or not it is a concertina filter element or a depth filter element, has a volume of at least 60000mm3, preferably 150000mm3.

More preferably the volume of the filter element is at least 200000mm3, and still yet more preferably is at least 350000mm3 for a car and at least 500000mm2 or even 750000mm3 for a truck. A filter element with such a size should last for about 100000 miles. If the filter element should last for about 150000 miles, which is the presently designed range of internal combustion engines, the filter element should preferably have a volume of at least 500000mm3 for a car or twice or even three times that for a truck.

A typical flow rate of oil through a filter element in a typical car internal combustion engine is about 20 litres/minute. The filter element of the present invention preferably has a volume of at least 10000mm3 per litre/minute of flow of oil designed, for a given engine, to flow through the filter element 32. More preferably, the filter element has a volume of at least 17500mm3 per litre/minute and still yet more preferably of at least 20000mm3 per litre/minute for a car and 30000mm3 or even 50000mm3 for a truck.

A further advantage of the filter unit 30 is that because of the large surface area of the filter element 32, the oil pressure drop over the filter element 32 is kept low. Also, the pores of the filter element 32 can be reduced in size in comparison to filter elements which are external to the engine block 12 because of the increase of surface area of the filter element 32 in comparison to those filters external of the engine block 12. Thus smaller contamination in the oil may be filtered out than previously and so the efficiency of the oil as a lubricant and/or coolant can be maximised as well as the useful lifetime of the oil being extended.

In the embodiment illustrated in Figure 1, the filter element 32 of the filter unit 30 is housed in a filter housing 34. The filter element 32 is a planar concertina fold filter element (as opposed to an annular concertina fold filter element) such that the filter element may extend across the oil sump and be housed in a planar housing 34. The housing surrounds the filter element 32 thereby to enclose it. The housing has an inlet 38 for filtered oil from the sump and an outlet 40 for filtered oil to pass

through. This arrangement is advantageous partly because of the ease of handling the filter units in which the filter element 32 is protected by the planar housing of a convenient shape and also because of the low materials cost associated with making such a housing. The housing is preferably made of a plastics material and is welded together using ultrasonic welding techniques. The housing may also be glued together or snap fitted together and may be made of a polymer or plastics material, thermoplastic, thermosetting or metal. Because the filter unit is disposed in the oil sump, it is not so critical that the housing does not leak as any leaking oil will pass directly into the oil sump. Thus, less care than previously needs to be taken in the manufacture of the housing. Furthermore, planar housings are easier to manufacture than cylindrical housings.

The housing 34 is provided with flanges 36 through which the filter unit 30 may be attached to the internal combustion engine 10. In the embodiment illustrated in Figure 1, this is achieved by bolting flanges 36 to attachment members 42 which are part of the engine block 12. In an alternative embodiment, illustrated in Figures 5,6 and 7, the filter unit 30 attached to the oil pan 20 by bolting the flanges 36 of the filter housing 34 to attachment members 42 extending upwards from the base wall 24 of the oil pan 20. It will be immediately apparent to those skilled in the art that there are other ways of attaching the filter unit 30 to the oil pan 20 or to the engine block 12.

The filter unit 30 is below the surface of the oil in the oil sump 26 or at least partly submerged. This ensures that the volume occupied by the filter element is only the total of the volumes of the solid individual components of the filter unit 30 rather than the external volume of the filter unit 30.

The oil in the oil sump 26 is distributed to various parts of the internal combustion engine to provide cooling and lubrication by a pump 50 which is optionally housed in the internal combustion engine 10. In the embodiment illustrated in Figure 1, the oil pump 50 is situated partly in the engine block 12 and partly in the oil sump 26. The pump 50 may be situated entirely within the engine block 12 or entirely within the oil sump 26 and may even be situated at least partly

submerged in the oil of the oil sump 26.

In the first embodiment of the present invention as illustrated in Figure 1, the filter unit 30 is attached to the suction side of the oil pump 50. Oil from the oil sump 26 travels through an oil inlet pipe 44 to the inlet 38 of the filter unit 30. Optionally a strainer 48 comprised of a plastic or wire mesh with a mesh size of greater than 0. lmm in diameter may be connected to an end of the oil inlet pipe 44 opposite the end of the oil inlet pipe which is connected to the inlet 38 of the filter unit 30. The end of the oil inlet pipe 44 or the strainer 48 is positioned in a recess 25 formed in the oil pan 20. The recess 25 provides a low point in the base wall 24 of the oil pan 20 in which oil collects. A first pipe 46 connects the outlet 40 of the filter unit 30 to the pump 50. The pump 50 then pumps the oil to the various components such as the rocker spindles, gudgeon pins and crank shaft bearings in the internal combustion engine 10. The oil returns to the oil sump 26 under gravity.

The positioning of the filter unit 30 before the oil pump 50 in the oil circuit is advantageous in that the pump 50 is protected from contaminants present in the oil such as swaths of metal etc.

A second embodiment according to the present invention is illustrated in Figures 3 and 4 which is the same as the first embodiment save as described below.

In this embodiment the filter unit 30 is attached to the pressure side of the oil pump 50 and an oil inlet pipe 144 provides for the passage of unfiltered oil from the oil sump 26 into an inlet of the oil pump 50. To protect the oil pump 50 a strainer 48 is attached to an end of the oil inlet pipe 144 opposite to the end which is attached to the oil pump 50. The oil pumped by oil pump 50 is routed via a second pipe 244 to the inlet 38 of the filter unit 30. That oil passes through the filter element 32 before being routed around the engine via a first pipe 46 which provides for the passage of oil from the outlet 40 of the filter unit 30.

The filter unit 30 of the present invention may include a non-return valve which prevents oil from draining out of the filter housing 34 through the inlet 38 which if allowed to happen, would introduce a delay in oil being supplied around the engine on start-up.

The filter unit 30 may also comprise a by-pass valve for the flow of oil by- passing the filter element 32 in the case when the pressure drop across the filter element 32 rises above a predetermined value. This allows oil to flow through the filter unit 30 around the engine even if the filter element 32 has become blocked with dirt. The filter unit 30 may also comprise a pressure relief valve.

Figure 5 illustrates a third embodiment of the present invention which is the same as the first and second embodiments save as described below.

In this embodiment the filter unit 30 is attached to the pressure side of the oil pump 50 in the same way as in the second embodiment. However, in this case, the filter unit housing 34 is attached to the oil pan 20. Also two filter elements 132,232 are housed in the housing 34. The filter element 132 is an in-line filter element which has the same properties as the filter element 32 of the second embodiment.

Oil which passes through in-line filter element 132 exits the filter housing 34 via a first pipe which provides for the passage of oil from a first outlet 140 associated with the full flow filter element 132 around the engine.

A fraction of the oil entering the filter unit housing 34 from second pipe 244 passes through a by-pass filter element 232. Typically the fraction of oil directed through the by-pass filter element 232 is about 10% of the total oil which passes through the second pipe 244 but may be any fraction depending on the relative resistance of the by-pass filter element 232 and in-line filter element 132. In this way, the by-pass filter element 232 may be provided with pores of a particularly small diameter, for example, to give filtration levels of less than 0. 001mm. In this way, the oil which is filtered by the by-pass filter element 232 is thoroughly clean.

This thoroughly clean oil is returned to the oil sump 26 directly via by-pass tube 146.

Although in the third embodiment the by-pass filter element 232 and the in- line filter element 132 are housed in the same housing, this is not necessarily the case. For example there may be a separate by-pass filter unit. Furthermore, it is possible that the in-line filter element 132 is connected to the suction side of the oil pump 50 rather than the pressure side as is illustrated. Then a fraction of oil leaving the oil pump 50 would enter the by-pass filter element 232 and return to the oil sump

26 whilst the remaining fraction of oil leaving the oil pump 50 would be directly routed around the engine in a similar way to that in the first embodiment.

In the third embodiment, the oil pump 50 is disposed within the oil sump 26 defined by the oil pan 20. The oil pump 50 is actually beneath the level of oil 126 in the oil sump 26. In this way noise-vibration-harshness (NVH) of the oil pump 50 may be reduced thus decreasing engine noise and increasing oil pump lifetime. The oil pump 50 may be attached to the oil pan 20 or to the engine block 12. Although the oil pump 50 is illustrated as being entirely below the level 126 of oil in the oil sump 26 this is not necessarily the case and the oil pump 50 may only be partially submerged whilst still maintaining the advantages described above.

A fourth embodiment of the present invention is illustrated in Figure 6 which is the same as the first and second embodiments save as described below. In this embodiment the filter unit 30 is disposed on the pressure side of the oil pump 50. Oil leaves the oil filter pump via a first portion of a second pipe 244A. The first portion of the second pipe 244A leads to a heat exchanger 300. A second portion of the second pipe 244B leads from the heat exchanger 300 to the oil filter unit 30. The heat exchanger 300 is attached to the housing 34 of the oil filter unit 30 via fasteners 320.

The heat exchange 300 contains at least one heat transfer element for the passage of cooling fluid therethrough. Cooling fluid enters the heat exchanger 300 through inlet 310 and leaves the heat exchanger 300 through outlet 312. Inlet 310 and outlet 312 extend through the oil side walls of the oil pan 20. The heat transfer elements inside the heat exchanger 300 may be of any size and shape. Oil which travels through the heat exchanger 300 will come into contact with the heat transfer elements and thereby be cooled by the heat transfer fluid flowing through those elements. Thus oil is routed by channels and forced by the oil pump 50 past the at least one heat transfer element.

In the embodiment illustrated in Figure 6 the heat transfer unit 300 and oil filter unit 30 are illustrated on the pressure side of the oil pump 50. This is not necessarily the case and either the oil filter unit or the heat transfer unit 30 or both

may be positioned on the suction side of the oil pump 50. In fact, oil need not necessarily be purposefully routed past the heat transfer elements; the heat transfer elements may simply be positioned in the oil sump and rely on natural mixing of oil in the oil sump for efficient cooling.

An oil pan according to a fifth embodiment is illustrated in Figure 7. The oil filter unit 30, the heat transfer unit 300 and the pump 50 are all disposed in the oil sump defined by the oil pan 20. Indeed those three components are all below the level of oil 126 in the oil sump 26 and all are attached to the oil pan 20. The oil pan of the fifth embodiment may be mounted to an engine block 12 as in the first to fourth embodiments.

Although five separate embodiments have been described above, it will be apparent to those skilled in the art, that features of each embodiment may be combined with features of other embodiments or may be used individually or even partly, as required.