WO2005031148A1

WO2005031148A1 - Diesel fuel filter

Info

Publication number: WO2005031148A1
Application number: PCT/EP2004/010651
Authority: WO
Inventors: Giorgio Girondi
Original assignee: Ufi Filters S.P.A.
Priority date: 2003-09-29
Filing date: 2004-09-21
Publication date: 2005-04-07
Also published as: ITRE20030090A1

Abstract

Diesel fuel filter comprising a casing (4), the interior volume of which is separated by a filtering baffle into two separate chambers to which a fuel inlet conduit (11) and a fuel outlet conduit (12) are connected respectively, with the chamber to which the fuel inlet conduit (11) is connected there being associated a container (101) of elongate shape which extends into the chamber interior and contains a regenerable chemical compound, said container (101) being provided with first means for triggering an exothermic transformation within the compound, and with second means for returning the compound to its starting condition.

Description

DESCRIPTION DIESEL FUEL FILTER

TECHNICAL FIELD The present invention relates, in a totally general sense, to diesel engines and more particularly to a diesel fuel filter.

PRIOR ART

Diesel fuel for automotive use is known to normally contain impurities, because of which the diesel engine feed system must be provided with a suitable fuel filter.

Modern diesel fuel filters generally consist of a cup-shaped casing closed by a cover and containing a coaxial filter cartridge of toroidal form.

Between the casing and cup two chambers are defined for passage of the diesel fuel to be filtered and of the filtered diesel fuel respectively, the first connected to the pump unit and the second to the injection unit.

The chamber for passage of the diesel fuel to be filtered is normally provided by the inner region of the filter cartridge.

In addition to said impurities, diesel fuel also generally contains waxy materials, such as paraffin, which are fluid even at relatively low temperatures, of the order of -10°C, and which tend to thicken until they solidify at lower temperatures, of the order of -20/25°C.

Hence, if the engine remains inactive for a certain time at very low temperatures (less than about -20°C), said waxy materials such as paraffin separate from the diesel fuel and solidify, with consequent clogging of the filter, making it impossible to operate the engine. During the winter season said filter clogging problem is generally overcome by mixing suitable additives with the diesel fuel to conveniently lower the temperature at which the paraffin separates from the diesel fuel and solidifies. However it can happen that a vehicle fed with diesel fuel not containing additive finds itself in a particularly cold place where it remains at rest for a long time, with obvious consequences.

DISCLOSURE OF THE INVENTION The main object of the present invention is to remedy the aforesaid problem.

Another object of the invention is to achieve said objective within the framework of a simple, rational, reliable and low-cost construction. Said objects are attained by a filter having the characteristics indicated in the claims.

In a totally general sense, it is of the type stated in the introduction, i.e. comprising a casing, the interior volume of which is separated into two separate chambers by a filtering baffle and to which a fuel inlet conduit and a fuel outlet conduit are connected respectively. With the chamber to which the fuel inlet conduit is connected there is associated a container containing a regenerable chemical compound, and presenting first means for triggering an exothermic transformation of said compound, and second means for triggering an inverse transformation of said compound which returns it to its starting condition. In a preferred embodiment of the invention, said casing is shaped as a cup closed by a cover, the filtering baffle being a toroidal filter cartridge coaxial with the cup-shaped casing. Said container, which is of elongate shape, is associated with the cover and is inserted into the interior of the filter cartridge which is coaxial with it. For the objects of the invention, a convenient regenerable chemical compound has proved to be a metastable supersaturated solution which is in the liquid state prior to said exothermic transformation, and which is able to remain such even under conditions of strong supercooling, and of substantial calm. The same supercooled liquid solution is able, following a disturbance to the state of the system, to solidify to generate heat, and to again liquefy following heating.

Said solution can consist of a solution of sodium acetate trihydrate (CH₃COONa.3H₂O) and distilled water in weight proportions of 85-95% and 15-5% respectively. The supersaturated conditions of said solution of sodium acetate trihydrate and distilled water become critical when it reaches a temperature of the order of -20/25°C, which corresponds to the temperature at which the waxy materials (such as paraffin) present in the diesel fuel (not containing additive) separate from it and solidify, to hence clog the filter.

When this supersaturated solution, supercooled as stated, is disturbed it rapidly solidifies to emit a quantity of heat sufficient to heat the diesel fuel contained in the filter to a temperature at which the paraffin liquefies, of the order of -5/10°C. The solution is disturbed by virtue of said first means, which according to an advantageous characteristic of the invention are sensitive to the operating conditions of the filter, in particular its pressure regime.

More precisely, said first means are inactive in the presence of relatively low pressures, such as those pertaining during normal filtration with the engine running, and are activated in the presence of relatively high pressures, such as the sudden pressure increase which occurs when the engine is started with the filter clogged by paraffin solidified due to the cold.

Preferably said first means are a portion of said container, said portion being positioned in contact with the compound present therein and being arranged to deform elastically towards it, into a stable triggering position, following said sudden pressure peak.

By this means an exothermic reaction is triggered, as stated, within the solution, on termination of which the solution is in the solid state.

To regenerate the solution, i.e. to return it to its liquid starting state under metastable supersaturated conditions, said second means are activated, these comprising a heater element sealedly inserted into the container and immersed in the solution present therein.

Said heater element preferably consists of an electrical resistance element connected to the vehicle battery.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and the constructional merits of the invention will be more apparent from the ensuing description given with reference to the figures of the accompanying drawings which illustrate a particular preferred embodiment by way of non-limiting example. Figure 1 is a partial axial section through a diesel fuel filter according to the invention.

Figure 2 is an enlarged-scale section through the heater device positioned at the centre of the filter.

BEST MODE FOR CARRYING OUT THE INVENTION From said figures, and in particular Figure 1 , it can be seen that the filter comprises a cup-shaped casing 1 closed by a cover 2 and containing a coaxial toroidal filter cartridge 3. The cartridge 3 divides the interior volume of the casing 1 into two separate chambers to which an inlet conduit 11 and an outlet conduit 12 for the diesel fuel are connected respectively.

In particular, the cartridge 3 comprises a perforated inner cylindrical wall 4; a perforated outer cylindrical wall 5; a blind end 6 supported by profiled lugs 7 associated with the base of the cup 2; and a circular headpiece 8 against which an overlying hollow profiled element 9 rests, urged by the cover 2.

Between said cover 2 and said element 9 there is a compartment 10 which at the top communicates with the conduit 11 through which the diesel fuel to be filtered enters, and at the bottom is sealedly connected to the central hole of said headpiece 8.

Said inlet conduit 11 is fixed in a non-aligned position to the cover 2, which also carries the filtered diesel fuel outlet conduit 12, passing through a region of the cover 2 which is situated outside the compartment 10 (see Figure 1 ).

According to the invention, the cover 2 is centrally holed to provide the seat for mounting a heater device indicated by 100 in the figure.

Said device 100 is shown schematically in Figure 1 , its component elements being shown in Figure 2.

It comprises a relatively thin rigid cylindrical enclosure 101 , which can be of metal or plastic.

The outer diameter of said enclosure 101 is less than the inner diameter of the port which connects the compartment 10 to the inner region of the cartridge 3, its length being of the same order of magnitude as that of the cartridge 3. The enclosure 101 is sealedly closed at both ends, specifically at the bottom by an elastically deformable diaphragm 102, and at the top by a projecting rigid plug 103 (see Figure 3).

The upper end of the enclosure 101 is sealedly connected to the central hole of the cover 2, against which it rests via a suitable shoulder visible in Figure 2.

Said sealed connection can be obtained in any suitable manner, such as by screwing, welding, or gluing.

As can be seen in Figure 2, from the plug 102 there branches a coaxial rod 104 having an outer diameter much less than the inner diameter of the enclosure 101 , and a length of the same order of magnitude as this latter.

Said rod 104 consists of, or incorporates, an electrical resistance element intended to be connected to the battery of a diesel engine vehicle by the cable 105.

Said rod 104 is immersed in a regenerable chemical compound 106 which almost completely fills the enclosure 101.

In the present case said regenerable chemical compound consists of a metastable supersaturated solution.

According to the teachings of the invention, and as also stated in the introduction, it is preferably liquid at the moment of installation of the filter, and is able to remain such even under very cold conditions, provided it is left in a substantially calm state, i.e. not disturbed by external means.

If this is not the case it undergoes a liquid/solid phase transformation, with simultaneous considerable sudden heat emission.

When the solution is subsequently heated it undergoes a solid/liquid state change, with restoration of the starting conditions, so that it is again able to generate heat when necessary.

In the present case said metastable supersaturated liquid solution consists of a solution of sodium acetate trihydrate (CH₃COONa.3H₂0) and distilled water in weight proportions of 85-95% and 15-5% respectively.

The supersaturated conditions of this solution become critical substantially at the temperature (about -20 to -25°C) at which waxy materials (such as paraffin) separate from the diesel fuel and solidify.

Under these conditions the supercooled solution can as stated solidify in the presence of a disturbing action, produced by the elastically deformable diaphragm 102 (see Figure 2). This latter consists of a thin generally metal plate covered by a cap 107 of elastomeric material, such as rubber, sealedly fixed to the base of the enclosure 101.

Said cap 107 and said lamina 102 are connected together by a generally rigid central push pin. Finally, the cap 107 is shaped and dimensioned such as to elastically deform only when the filter interior is subjected to a comparatively very much higher pressure than that during the normal filtering process with the engine running.

The described filter operates as follows, assuming that the engine with which it is associated is fed with diesel fuel not containing additive. When the engine rotates, filtration takes place in normal manner, with the cap 107 undeformed and the diaphragm or lamina 102 in a stable rest position.

This is also the case even when the engine operates in a very cold place, i.e. an environment in which the temperature can reach values below the paraffin separation and solidification temperature, because the diesel fuel is automatically heated by the effect of the pumping action.

However, if under such situations the engine is stopped and remains at rest for a period sufficient to separate and solidify the paraffin, the filter becomes clogged. On restarting the engine with the filter clogged, the diesel fuel, which is forcibly fed into the filter by the pumping unit, causes the system pressure to suddenly increase, to cause the virtually instantaneous deformation of the cap 107 and a simultaneous sudden deformation of the lamina 102.

The deformation of the lamina 102 triggers the strongly exothermic reaction of the compound 106, which is completed in a few moments to transform the compound from liquid to solid and release a determined quantity of heat.

The quantity of the compound 106 is suitably proportioned to the characteristics of the filter, such as to generate a quantity of heat sufficient to heat the diesel fuel contained in the filter within a very short time to a temperature such as to dissolve the paraffin and return it to solution, for example of the order of -5 to -10°C.

By this means the engine can be started and operate normally, with consequent restoration of normal pressure conditions within the filter and automatic return of the lamina 102 and cap 108 to their rest or starting conditions.

With a certain delay relative to said liquid-to-solid change of state of the compound 106, this latter is returned to its starting conditions, i.e. to the liquid state.

This is achieved by energizing the resistance element associated with the rod 104, which heats up to liquefy the previously solidified compound 106.

The natural cooling which follows returns the system to metastable conditions.

From specific tests carried out with normal automobile filters containing said solution of sodium acetate trihydrate and distilled water, it has been found that said liquefaction is completed within fairly short times, of the order of one minute or slightly more, with the resistance element heating the solution to a temperature of about 65-70°C.

Finally, it should be noted that the resistance element feed cable 106 is intercepted by a change-over device, i.e. a switch, provided to maintain said resistance element normally excluded, and to activate it for a period at least equal to that required for complete liquefaction.

Claims

1. A diesel fuel filter comprising a casing, the interior volume of which is separated by a filtering baffle into two separate chambers to which a fuel inlet conduit and a fuel outlet conduit are connected respectively, characterised in that with the chamber to which the fuel inlet conduit is connected there is associated a container (101 ) of elongate shape which extends into the chamber interior and contains a regenerable chemical compound (106), said container being provided with first means for triggering an exothermic transformation within the compound, and with second means for returning the compound to its starting condition.

2. A filter as claimed in claim 1 , characterised in that said regenerable chemical compound consists of a metastable supersaturated solution which is in the liquid state prior to said exothermic transformation and is able to remain such even under conditions of strong supercooling if in a calm condition, but which in the presence of a disturbance solidifies with an exothermic reaction, said solution being able to return to the liquid state following heating.

3. A filter as claimed in claim 2, characterised in that said metastable supersaturated liquid solution is a solution of sodium acetate trihydrate and distilled water in weight proportions of 85-95% and 15-5% respectively.

4. A filter as claimed in claim 1 , characterised in that said first means comprise at least one portion of said container positioned in contact with the compound present therein, and arranged to deform elastically towards the container interior when the external pressure present is greater than the pressure in the cup during normal diesel fuel filtration.

5. A filter as claimed in claim 4, characterised in that said deformation of said at least one portion is under the control of a push pin which branches from a cap of elastomeric material positioned to surround said portion, said cap being shaped and dimensioned such as to resist without deformation the pressure due to said normal diesel fuel filtration.

6. A filter as claimed in claim 1 , characterised in that said second means comprise a heater element which is sealedly inserted into said container and embedded in the compound present therein, and is connected to an external energy source.

7. A filter as claimed in claim 6, characterised in that said heater element comprises an electrical resistance element to be connected to a vehicle battery.

8. A filter as claimed in claim 7, characterised in that a switch device is positioned along the power cable to said electrical resistance element to maintain said resistance element normally excluded, but to energize it for a predetermined period after exothermic transformation of the compound.

9. A filter as claimed in claim 1 , characterised in that the filter casing is cup-shaped and is upperly closed by a cover.

10. A filter as claimed in claims 1 and 9, characterised in that said filtering baffle is a filter cartridge coaxial with said cup-shaped casing and arranged to separate the interior volume of said casing into two coaxial chambers, namely an inner chamber to which the fuel inlet conduit is connected and an outer chamber to which the fuel outlet conduit is connected.