WO2010149617A1

WO2010149617A1 - A fuel filter

Info

Publication number: WO2010149617A1
Application number: PCT/EP2010/058727
Authority: WO
Inventors: Giorgio Girondi
Original assignee: Ufi Innovation Center S.R.L.
Priority date: 2009-06-23
Filing date: 2010-06-21
Publication date: 2010-12-29
Also published as: ITRE20090064A1

Abstract

A fuel filter comprising an external casing (2) provided with at least an inlet mouth (22) and an outlet mouth (23), and a filter cartridge (3) contained internally of the casing (2), such as to filter the fuel which flows from the inlet mouth (22) towards the outlet mouth (23), the filter cartridge (3) comprising two support elements (32, 33) between which at least two distinct cylindrical filter walls (30, 31) are interposed and retrained, which two filter walls (30, 31) are destined to be crossed in series by the fuel flowing from the inlet mouth (22) towards the outlet mouth (23) of the external casing (2), the filter wall (30) located more upstream with respect to the flow direction of the fuel having a lower filtration efficiency than the other filter wall (31).

Description

A FUEL FILTER

Technical Field

The invention relates to fuel filters associated to internal combustion engines supplied with combustible fossil fuels, mainly though not exclusively filters for diesel or biodiesel associated to diesel engines.

In particular, the present invention relates to fuel filters associated to internal combustion engines of vehicles such as motor cars, lorries or buses.

As is known, a fuel filter generally comprises an external casing provided with an inlet mouth for the fuel to be filtered and an outlet mouth for the filtered fuel.

A filter cartridge is housed internally of the casing, which filter cartridge is destined to be crossed by the fuel flowing from the inlet mouth towards the outlet mouth, such as to retain the impurities which may be present in the fuel.

Background Art

A typical filter cartridge comprises a single tubular filter wall which is interposed and constrained between two support plates fastened to opposite ends of the filter wall.

One of these support plates is fastened to the casing of the filter, such that the filter wall sub-divides the internal volume into two distinct chambers, of which a first chamber set in communication with the inlet mouth of the fuel to be filtered, and a second chamber set in communication with the outlet mouth of the filtered fuel.

From a functional point of view, each filter wall has a filtering efficiency and an accumulation capacity.

The filtering efficiency is a parameter representing the particle-retaining capacity (particles of given dimensions) of a filter wall; a greater filtering efficiency corresponds to a greater retaining of small-dimension particles.

The accumulation capacity is a parameter representing the maximum quantity of particles which can be retained by the filter wall before it clogs up.

From a constructional point of view, various types of filter walls exist. In particular, the prior art comprises flat filter walls built of cellulose- or polymer-based non-woven textile (polyamide, polypropylene, etc.) which are generally pleated in star-fashion in order to increase the filtering surface thereof. Also known are deep-filter walls, consisting of a filter medium of a certain thickness which is generally made using polymer fibres. Given a same size and filtering efficiency, deep-filter walls can accumulate a greater quantity of impurities in comparison to flat walls, and therefore normally have a longer working life. On the other hand, deep-filter walls generally produce greater load losses, caused by the rather large thickness of the filtering medium. In order to improve the filtering efficiency and the overall accumulation capacity of fuel filters, multi-wall filter cartridges have been developed, which comprise two filtering walls destined to be crossed in series by the fuel flowing from the inlet mouth to the outlet mouth.

The filter wall located further upstream with respect to the flow has a lower filtering efficiency with respect to the downstream filter wall. In this way, the upstream filter wall is destined to perform a rough first filtration of the fuel, while the downstream filter wall deals with the final filtration.

Thanks to the pre-filtering stage, the downstream filter can have a greater efficiency than is the case when a single filter is used. A single filter wall would quickly become clogged by the largest particles transported with the fuel, while the presence of a pre-filtering wall enables the largest particles to be retained upstream, thus stopping the downstream wall from becoming clogged too quickly.

In known multi-wall cartridges, both the filter walls have a tubular shape and are coaxially inserted one internally of another, and separated by a narrow annular space which is closed off between the support plates. The above constructional solution however has numerous drawbacks.

One of the drawbacks consists in the fact that in order to be inserted one into another, the filter walls must have different dimensions, such that during a manufacturing stage it is necessary to make two differently-dimensioned filter walls, with a consequent increase in costs.

A further drawback relates mainly to the filtration of diesel and biodiesel. These types of fuel normally contain small quantities of water which have to be separated from the fuel before the fuel reaches the engine.

The separation of the water can be obtained by passing the fuel through a special deep-filter wall, which is made of a material which facilitates coalescing of the water. In multi-wall filters the deep filter has to used as a pre-filtering wall, such as to be crossed first by the fuel.

It follows that the water which separates during the passage through the pre- filtering wall is collected in the annular space that separates the prefiltration filtering wall from the filter wall located further downstream with respect to the flow direction. As the space is closed by the support plates, the cartridge has to be provided with a drainage system for the accumulated water, for example a plurality of holes afforded in the lower support plate in a position corresponding to the space, which complicates the construction of the filter cartridge, leading to an increase in costs. Disclosure of Invention

An aim of the present invention is to make available a fuel filter provided with a multi-wall filter cartridge which obviates the above-mentioned drawbacks of known cartridges. A further aim of the invention is to attain the above-mentioned aim in the ambit of a simple, rational and relatively inexpensive solution.

The aims are attained by the characteristics of the invention as set out in independent claim 1. The dependent claims delineate preferred and/or especially advantageous aspects of the invention. In particular, a fuel filter is provided which comprises an external casing provided with at least an inlet mouth and an outlet mouth, and a filter cartridge contained internally of the casing for filtering the fuel which flows from the inlet mouth towards the outlet mouth. The filter cartridge comprises two support elements between which at least two distinct cylindrical filter walls are interposed and constrained, which filter walls are destined to be crossed in series by the fuel which flows from the inlet mouth towards the outlet mouth of the external casing. The filter wall located further upstream with respect to the flow direction of the fuel has a lower filtering efficiency with respect to the other. According to the invention, the filter walls are arranged flanked and externally of one another. Thanks to this solution, a compact filter cartridge is obtained which can perform both the pre-filtration stage and the final filtration stage of the fuel, attaining, with a single component, high characteristics of filter efficiency and accumulation capacity.

Filter walls located arranged one externally of another in this way guarantee greater constructional flexibility and liberty, from which there derives the possibility of easily obviating the drawbacks of known-type multi-wall cartridges.

This arrangement does not involve stringent constraints of the dimensions of the filter walls, which can for example be equal, such as to obtain a saving in terms of manufacturing costs. Further, this arrangement does not afford an annular space between the filter walls.

In a case in which the filter is used for filtering diesel and biodiesel, the water which separates from the fuel during the crossing of the upstream filter wall can run freely and collect on the bottom of the external casing, without there being any need to predispose a drainage system.

In a preferred aspect of the invention, at least three cylindrical filter walls are interposed and retained between the support elements of the filter cartridge, which support elements are arranged one externally of another. At least two of the filter walls are destined to be crossed in parallel by the fuel flowing from the inlet mouth towards the outlet mouth of the external casing, while at least a third filter wall is destined to be crossed in series with respect to the preceding walls. Thanks to this solution, the filter walls arranged in parallel perform a same stage of the fuel filter process, while the other stage is performed by the third filter wall arranged in series.

In other words, the filter walls arranged in parallel can be located upstream of the third filter wall, such as to perform the prefiltration stage, or can be located downstream of the third filter wall, such as to perform the final filtration stage.

In both cases, the use of filter walls arranged in parallel leads to many advantages. At a same given filtering efficiency and dimensions, the filter walls arranged in parallel obtain overall a greater accumulation capacity with respect to a single filter wall, increasing the useful working life of the cartridge.

Given a same filtering efficiency and overall accumulation capacity, the filter walls arranged in parallel can be realised with a smaller thickness with respect to a single filter wall, thus reducing load losses.

The filtering walls, being arranged in parallel, provide advantages in terms of safety too, as if a filter wall is completely clogged, the others can continue to perform their function.

Brief Description of Drawings Further characteristics and advantages of the invention will emerge from a reading of the following description, which is provided by way of non-limiting example with the aid of the figures of the accompanying drawings.

Figure 1 is a filter of the invention, sectioned along plane l-l of figure 2.

Figure 2 is section M-Il of figure 1. Figure 3 is a variant of the filter of the invention, sectioned along plane Ill-Ill of figure 4.

Figure 4 is section IV-IV of figure 3.

Figure 5 is a further variant of the filter of the invention, sectioned along plane

V-V of figure 6. Figure 6 is section Vl-Vl of figure 5. In the accompanying figures of the drawings, three embodiments are illustrated of a fuel filter 1 destined to be associated to an internal combustion engine supplied with fossil fuel, such as petrol, diesel, biodiesel or others. More particularly, the fuel filter 1 is destined to be associated to the internal combustion engine of a vehicle, such as a motor car, a lorry, a bus or others. The filter 1 comprises an external casing 2, which is defined by a beaker- shaped lower recipient 20, and by an upper lid 21 , which is fixed to the lower recipient 20 in order to close the lower recipient 20 hermetically. The upper lid 21 is provided with two passage mouths which open internally of the casing 2, of which an inlet mouth 22 for the fuel to be filtered and an outlet mouth 23 for the filtered fuel.

The filter 1 further comprises a filter cartridge 3, which is fixed to the upper lid 21 and is contained internally of the lower recipient 20 such as to filter the fuel flowing from the inlet mouth 22 towards the outlet mouth 23 of the external casing 2.

The filter cartridge 3 is removable so that it can be replaced. According to the invention, the filter cartridge 3 comprises a plurality of cylindrical filter walls, of which at least a filter wall 30 and at least a filter wall 31 destined to be crossed in series by the fuel flowing from the inlet mouth 22 to the outlet mouth 23.

The filter wall 30 is destined to be crossed first by the fuel flow, and has a lower filtering efficiency with respect to the efficiency per second through the filter wall. In this way, the filter wall 30 performs a fuel pre-filtration stage, with the aim of retaining the larger impurities, while the filter wall 31 performs the stage of final filtration of the fuel, with the aim of retaining the smallest impurities. The overall filtering efficiency of the fuel filter 1 is thus determined by the filtering efficiency of the second filter wall 31. The filter wall 31 can have a very high filtering efficiency, as the prefiltration filter wall 30 retains the larger particles upstream, whereas they otherwise may have rapidly clogged the second filter wall 31. In this way a fuel filter 1 is obtained which is generally more efficient than the usual filters, i.e. filters without a prefiltration stage.

In the illustrated embodiments, all the filter walls 30 and 31 are deep-filter walls made of polymer fibres, which are preferably realised usingf a melt- blown process.

The different filtering efficiency between the prefiltration filter walls 30 and the second filter walls 31 can be determined depending on the type of material they are made of, or by regulating the production process such that the density of the fibres is different. However, the filter walls 30 and/or 31 can be made in other ways, for example flat non-woven textile walls made of a cellulose or polymer base, star-pleated in order to increase the filtering surface.

The invention thus provides, in a same cartridge 3, the possibility of having filters made of different materials with respect to the filter walls 31. In an important aspect of the invention, the filter walls 30 and 31 are interposed with parallel and vertical axes between a single lower support element 32 and a single upper support element 33, such that the filter cartridge 3 constitutes overall a single compact component. In a further important aspect of the invention, the filter walls 30 and 31 are each beside and external of the others, such as to make the construction of the filter cartridge 3 simple and flexible.

In the embodiment illustrated in figures 1 and 2, the filter cartridge 3 comprises three distinct filter walls, of which two prefiltration filter walls 30 and a second filter wall 31. The filter walls 30 and 31 are all of the same size, i.e. the same height, the same external diameter and the same wall thickness. The filter walls 30 and 31 are equidistant from an axis of symmetry A passing through the centre of the filter cartridge 3, with respect to which they are also angularly equidistant from one another. The prefiltration filter walls 30 can be made of different materials, for example one of the two filter walls 30 can be made of PP (polypropylene) and the other of PA (polyamide). The lower support element 32 comprises a continuous plate, which is fixed to and hermetically closes the bottom end of all the filter walls 30 and 31.

The upper support element 33 comprises a perforated plate 34 which is fixed to the upper end of all the filter walls 30 and 31 , and comprises three distinct through-openings, each of which is located at the internal cavity of a respective filter wall 30 or 31.

The upper support element 33 further comprises an inlet conduit 35 and a first internal chamber 36, which is in communication with the inlet conduit 35 and with the internal cavity of both the filter walls 30, through the respective through-openings in the plate 34.

The upper support element 33 finally comprises an outflow conduit 37 and a second internal chamber 38, which is in communication with the outflow conduit 37 and with the internal cavity of the filter wall 31 , via the respective through-opening in the plate 34. The upper support element 33 is fixed to the upper lid 21 , with the inlet conduit 35 sealedly entering the inlet mouth 22 and with the outflow conduit

37 sealedly entering the outlet mouth 23.

In this way, the fuel entering the inlet mouth 22 is guided to run along the inlet conduit 35 towards the internal chamber 36. The internal chamber 36 functions as a manifold which subdivides the fuel flow into the internal cavities of the filter walls 30 that are in communication there-with.

The fuel crosses the filter walls 30 radially from the outside towards the inside. The filter walls 30 are thus crossed in parallel by the fuel flow, and together perform the prefiltration stage.

The fact that the prefiltration stage is performed by two filter walls 30 arranged in parallel provides many advantages with respect to a case in which it is performed by one filter wall alone. Given a same filtering efficiency and dimensions, two filter walls 30 arranged in parallel overall obtain a greater accumulation capacity with respect to a single filter wall, thus increasing the working life of the filter cartridge 3. Given a same filtering efficiency and overall accumulation capacity, two filter walls 30 arranged in parallel can be made with a smaller thickness than with a single filter, thus reducing load loss.

If one of the two filter walls 30 arranged in parallel becomes completely clogged, the other can continue to perform its function without requiring the immediate replacement of the filter cartridge 3.

After having crossed the prefiltration filter walls 30, the fuel is forced to pass through the second filter wall 31 , flowing radially from the outside towards the inside thereof. The second filter wall 31 is thus arranged in series with respect to the filter walls 30, such as to perform the final fuel filtration stage.

The fuel passes from the internal cavity of the second filter wall 31 to the internal chamber 38 and finally flows into the outflow conduit 37 towards the outlet mouth 23. In the embodiment illustrated in figures 3 and 4, the filter cartridge 3 comprises four distinct filter walls, of which a pair of prefiltration filter walls 30 and a pair of second filter walls 31.

In this case too, the filter walls 30 and 31 all have the same dimensions, and are equidistant from an axis of symmetry A passing through the centre of the filter cartridge 3, with respect to which they are also angularly equidistant from one another.

The filter walls 30 can be realised in a differentiated material, and the filter walls 31 can be made of different materials.

The internal chamber 36 of the upper support element 33 is in communication with the inlet conduit 35 and with the internal chamber of both the filter walls 30, through two respective through-openings in the plate 34. Similarly the internal chamber 38 is in communication with the outflow conduit 37 and with the internal cavity of both the filter walls 31 , via two respective through-openings in the plate 34. In this case too, the upper support element 33 is fixed to the upper lid 21 , with the inlet conduit 35 sealedly entering the inlet mouth 22, and with the outflow conduit 37 sealedly entering the inside of the outlet mouth 23. In this way, the fuel to be filtered is initially forced to pass the filter walls 30 in parallel, the filter walls 30 being destined to perform the prefiltration stage.

The filter walls 30 are radially crossed from the inside towards the outside.

After having crossed the filter walls 30, the fuel is forced to cross the filter walls 31 too in parallel, which filter walls 31 are destined to perform the final filtration stage.

The filter walls 31 are radially crossed from the outside towards the inside.

The filtered fuel finally passes into the internal chamber 38 and exits from the outflow conduit 37. In the illustrated embodiment of figures 5 and 6, the filter cartridge 3 comprises five distinct filter walls, namely a group of four prefiltration filter walls 30 and one second filter wall 31 only.

The filter wall 31 has a diameter and a wall thickness which is greater than that of the filter walls 30, and is coaxial to an axis of symmetry A passing through the centre of the filter cartridge 3.

All the filter walls 30 the same dimensions, and are equidistant from the axis of symmetry A passing through the centre of the filter cartridge 3, with respect to which they are further angularly equidistant from one another.

In this case too, the filter walls 30 can be made of different materials from one another.

The internal chamber 36 of the upper support element 33 is in communication with the inlet conduit 35 and with the internal cavity of the four prefiltration filter walls 30, via four respective through-openings in the plate 34. The outflow conduit 37 is in direct communication with the internal cavity of the filter wall 31.

The upper support element 33 is fixed to the upper lid 21 of the filter, with the inlet conduit 35 sealedly entering the inlet mouth 22 and with the outflow conduit 37 sealedly entering the outlet mouth 23. In this way, the fuel to be filtered crosses the four prefiltration filter walls 30 in parallel, which filter walls 30 perform the filtration stage, passing internally of each of them towards the outside, thus through the only second filter wall 31 which performs the final filtration stage, flowing from the outside towards the inside, before exiting from the outflow conduit 37 in the filtered state. Naturally the above-described examples are only three of the innumerable embodiments the cartridge 3 of the invention could take. In particular, it is stressed that the maximum number of prefiltration filter walls

30 is not limited to the four units shown in the example of figure 6, but might also be a greater number.

By maintaining the structure of figure 6, a filter cartridge 3 can be made having a single central filtering wall 31 and six or eight prefiltration filter walls 30 located externally and about the filter wall 31.

In the same way, the cartridge 3 can be provided with two or more filter walls

31 destined to be crossed in parallel by the fuel in order to perform the final stage of filtration together.

In a particular case in which the filter 1 is destined to filter diesel or biodiesel, the filter cartridge 3 is preferably destined also to perform separation of any water contained in the fuel.

Best Mode for Carrying Out The Invention

To attain this object various alternative solutions can be implemented.

A first solution is to use filter walls 30 that are destined to perform not only the prefiltration of the solid particles but also the separation of any water contained in the fuel.

The filter walls 30 can be deep-filter walls which are realised by a melt-blown process using a polymer material having the property required for facilitating the coalescence of the water. The polymer material can be different from the material used for realising the filter wall 31.

In this way, the water separates during the passage of the fuel through the filter walls 30, and forms drops on the external lateral surface thereof, then running downwards towards the lower support platform 32. The water is free to flow on the lower platform 32 towards the perimeter margins and to fall onto the bottom of the lower recipient 20, where drainage means of the accumulated water can be located. A further solution is to use filter walls 30 destined to perform only the prefiltration of the fuel, and to associate a water-repellent wall to each of the filter walls 30, for example a coalescence net.

Each filter wall 30 and relative water-repellent wall must be crossed by the fuel in series, with the water-repellent wall downstream of the filter wall 30 with respect to the flow direction of the fuel.

In the example illustrated herein, in which each filter wall 30 is radially crossed from the inside towards the outside, the water-repellent walls would be placed such as to externally surround the filter wall 30 itself, leaving between them only a narrow intermediate space.

Should the filter wall 30 be crossed from the outside to the inside, the water- repellent wall would have to be located internally.

Obviously a technical expert in the sector might make numerous modifications of a technical-applicational nature to the filter 1 as described herein, without forsaking the ambit of the invention as claimed herein below.

Claims

1) A fuel filter comprising: a. an external casing (2) provided with a cover comprising at least an inlet mouth (22) and an outlet mouth (23), and b. a filter cartridge (3) contained internally of the casing (2) and connected to the cover, such as to filter the fuel which flows from the inlet mouth (22) towards the outlet mouth (23), c. the filter cartridge (3) comprising two first and second support elements (32, 33) between which at least two distinct cylindrical filter walls (30, 31 ) are interposed and retrained, d. which two filter walls (30, 31 ) are destined to be crossed in series by the fuel flowing from the inlet mouth (22) towards the outlet mouth (23) of the external casing (2), the filter wall (30) located more upstream with respect to the flow direction of the fuel having a different filtration efficiency than the other filter wall (31 ), characterised in that the second support element (33) comprise a flat wall having at least one first aperture communicating with the inlet mouth of the cover and with the axial cavity of each filter walls (30) located upstream with respect to the flow direction of the fuel, and at least one second aperture communicating with the outlet mouth of the cover and with the axial cavity of each filter wall (31 ) located downstream with respect to the flow direction of the fuel, the filter walls (30, 31 ) being arranged externally of one another. 2) A fuel filter according to claim 1 characterised in that the second support element (33) comprises a first internal chamber (36) which is in communication with a conduit (35) intended to be connected to the inlet mouth (22) of the cover and with the internal volume of at least one filter wall (30), and a second internal chamber 38, which is in communication with a conduits (37) intended to be connected to the oulet mouth (23) of the cover, and with the internal volume of at least one filter walls (31 ), 3) The fuel filter of claim 1 , characterised in that at least three cylindrical filter walls (32, 33) are interposed between the support elements (32, 33) of the filter cartridge (3), each of which is arranged externally of all the others, at least two of the filter walls (30) being destined to be crossed in parallel by the fuel flowing from the inlet mouth (22) towards the outlet mouth (23) of the external casing (2), and at least a third filter wall (31 ) being destined to be crossed in series with respect to the preceding filter walls.

4) The fuel filter of claim 3, characterised in that the at least two filter walls (30) destined to be crossed in parallel are arranged upstream of the at least a third filter wall (31 ) with respect to the fuel flow direction, and have a lower filter efficiency with respect to the at least a third filter wall (31 ).

5) The fuel filter of claim 3, characterised in that the at least two filter walls (30) destined to be crossed in parallel are arranged downstream of the at least a third filter wall (31 ) with respect to the fuel flow direction, and have a filtration efficiency which is greater than the at least a third filter wall (31 ).

6) The fuel filter of claim 1 , characterised in that at least four cylindrical filter walls (30, 31 ) are interposed and retained between the support elements (32, 33) of the filter cartridge (3), each of which four filter cylindrical filter walls (30, 31 ) is arranged externally of another thereof, at least a group of the filter walls (30) being destined to be crossed in parallel by the fuel which flows from the inlet mouth (22) towards the outlet mouth (23) of the external casing (2), at least a further group of the filter walls (31 ) being destined to be crossed in parallel by the fuel flowing from the inlet mouth (22) towards the outlet mouth (23) of the external casing (2), the groups of filter walls being destined to be crossed in series by the fuel flowing from the inlet mouth (22) towards the outlet mouth (23) of the external casing (2), the filter walls (30) of the group located further upstream of the fuel flow direction having a filtration efficiency which is lower than a filtration efficiency of the filter walls (31 ) of the other group. 7) The fuel filter of claim 2, characterised in that a support element (33) of the support elements of the filter cartridge (3) comprises a first conduit (35), which is communication with an internal volume of the filter wall (30) or filter walls (30) which are located further upstream with respect to the fuel flow direction, and a second conduit (37), which is in communication with the internal volume of the other filter wall or walls (31 ) of the cartridge (3), the conduits (35, 37) being destined to be directed connected respectively with the inlet mouth (22) and the outlet mouth (23) of the external casing (2).

8) The fuel filter of claim 7, characterised in that the support element (33) comprises at least an internal chamber (36) which is in communication with one of the conduits (35) and with the internal volume of a group of filter walls (30). 9) The fuel filter of any one of the preceding claims, characterised in that the filter wall or walls (30) which are located more upstream of the fuel flow direction are associated to a wall destined to obtain separation of any water which may be present in the fuel. 10). The fuel filter of any one of the preceding claims, characterised in that the filter wall or walls (30) which are located more upstream with respect to the fuel flow direction are deep-filter walls configured also for obtaining separation of any water present in the fuel.

11). The fuel filter of any one of the preceding claims, characterised in that all the filter walls (30, 31 ) of the filter cartridge (3) are deep-filter walls. 12). The fuel filter of claim 10, characterised in that the filter walls (30, 31 ) are of a same size.

13). The fuel filter of claim 11 , characterised in that the filter walls (30, 31 ) are made by a melt-blown process. 14). The filter of any one of the preceding claims, characterised in that at least two of the filter walls (30, 31 ) are made of different materials.