WO2008046707A1

WO2008046707A1 - A filter for diesel fuel

Info

Publication number: WO2008046707A1
Application number: PCT/EP2007/059917
Authority: WO
Inventors: Giorgio Girondi
Original assignee: Ufi Filters S.P.A.
Priority date: 2006-10-17
Filing date: 2007-09-19
Publication date: 2008-04-24
Also published as: ITRE20060123A1

Abstract

A filter for diesel fuel comprising a container casing (2) which is provided with an inlet mouth (22) for diesel to be treated and an outlet mouth (23) for treated diesel, and internally of which at least a filtering wall (30) for filtering the diesel and a retaining wall (4) for holding back water contained in the diesel through coalescence are housed in series. The retaining wall (4) is located downstream of the filtering wall (30) with respect to a flow of the diesel fuel, and the container casing (2) is provided with a bottom (27) for collecting the water which is held back by the retaining wall (4); the retaining wall (4) is positioned above the filtering wall (30) with respect to the bottom of the container casing (2).

Description

A FILTER FOR DIESEL FUEL

Technical Field

The invention relates to a diesel filter destined to be associated to diesel motors for traction, such as for example automobile or truck engines.

Background Art

As is known, diesel traction engines are supplied by sophisticated injection systems which inject diesel oil at high pressure directly into cylinders.

To prevent the injection devices from being damaged during operation, the diesel fuel must first be filtered so as to remove the impurities contained therein.

The filters used to perform this function generally comprise a container casing provided with an inlet mouth for the diesel to be filtered and an outlet mouth of the filtered diesel. A filter cartridge is housed internally of the container casing, which cartridge sub-divides the internal volume of the casing into two distinct chambers, of which a first chamber communicates with the inlet mouth and a second chamber communicates with the outlet mouth.

The filter cartridges can be made in various shapes and of various materials.

A typical filter cartridge is one which comprises a substantially tubular filtering wall which is radially crossed by the fuel to be filtered.

The tubular filtering wall is generally constituted by a sheet of cellulose material, which is pleated longitudinally such as to take on a characteristic star-shaped conformation that increases the filtering surface thereof while not increasing the mass thereof.

A problem of diesel fuel injection systems for engines is that the diesel generally contains a certain quantity of water, which causes oxidation phenomena that in a short time can seriously damage the mechanical organs of the injection system.

To solve this problem, retaining walls are used which if crossed by the diesel are able to hold back the water contained in it. The retaining walls are usually constituted by a slim hydrophobic net, which is specially designed to let the diesel pass through while holding back the water particles and favouring their aggregation via coalescence.

The hydrophobic net is installed internally of the container casing of the diesel filter and positioned downstream of the filtering wall, such as not to be damaged by the solid particles which might be present in the diesel.

In particular, the hydrophobic net is generally positioned in the low part of the container casing, below the filtering wall.

In this way, the water held back by the hydrophobic net can drip without wetting the filtering wall and accumulate on the bottom of the container casing, from which it is expelled via a special discharge tap valve.

A drawback of this solution is that if the level of the water accumulated on the bottom of the casing reaches the hydrophobic net, the net is no longer able to perform its function. As the hydrophobic net is located below the filtering wall, it is evident that the quantity of water that can be accumulated on the bottom of the filter is generally very small, especially taking into account that diesel filter must be very contained in size in order to occupy a small space inside the vehicle engine compartment. This leads to the need to remove the water accumulated internally of the filter very often, generating problems relating to the correct functioning of the system.

Disclosure of Invention

The aim of the present invention is to obviate the above-described drawback by providing a simple, rational and inexpensive solution.

The aim is attained by a diesel filter comprising a container casing which is provided with an inlet mouth for the diesel to be treated and an outlet mouth for the treated diesel, internally of which at least a filtering wall for filtering the diesel and a retaining wall for holding back the water contained in the diesel fuel are housed in series, the retaining wall being located downstream of the filtering wall. In the invention, the retaining wall is positioned above the filtering wall with respect to the bottom of the container casing.

In this way, a more compact and rational arrangement of the components internally of the container casing is obtained, enabling the space available for the accumulation of water retained by the retaining wall to be increased, without increasing overall size.

In order to prevent the retained water from wetting the filtering wall, the invention preferably includes interposing, between the retaining wall and the underlying filtering wall, a solid gabled surface covering and protecting the filtering wall.

In a preferred embodiment of the invention, the filtering wall is tubular and is radially crossed by the diesel to be treated, and is arranged vertically internally of the container casing such as to have the lower end thereof facing towards the bottom of the casing. It has been found that this type of filtering wall is in itself able to hold back a small part of the water contained in the diesel passing through it, by coalescence.

The diesel which is held back internally of the filter is advantageously subjected to two successive stages of retaining and coalescence of the water.

The first stage takes place in the passage through the tubular filter wall, where a first part of the water is removed from the diesel, while the second stage is performed in the passage through the retaining wall which effectively completes the removal of the water. This solution in particular leads to a high degree of treatment of the water, even when the flow rates of the diesel to be treated are very high. In a further preferred embodiment of the invention, the container casing of the filter comprises a tumbler-shaped lower body which makes the bottom suitable for collecting water, and an upper closing cover which is provided with the above-mentioned inlet mouth and outlet mouth of the diesel. The filtering wall is vertically inserted internally of the tumbler body and is fixed to the closing cover by means of a tubular support element which places it in communication with the overlying inlet mouth of the diesel fuel to be filtered. The retaining wall exhibits a substantially flat shape and is directly coupled to the support element.

In particular, the retaining wall exhibits an annular conformation provided with an external shape which inserts snugly internally of the tumbler body such as to close it completely, and is also provided with a central opening in which the tubular support element snugly fits.

Thanks to this solution, the assembly of the diesel filter is very simple and rational, and enables a rapid substitution of the filtering wall and the retaining wall to be made whenever necessary. Brief description of the Drawings Further characteristics and advantage 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, in which:

- figure 1 is a longitudinal section of a diesel filter according to the invention;

- figure 2 is section N-Il of figure 1 ; - figure 3 is section Ill-Ill of figure 1.

Best Mode for Carrying Out the Invention.

The diesel filter 1 illustrated in figure 1 comprises a container casing, denoted in its entirety by 2, which comprises a tumbler-shaped lower body 20 sealedly closed by an upper cover 21. The upper cover 21 affords a central inlet mouth 22 of the diesel to be treated, and a lateral outlet mouth 23 for the treated diesel. A filtering cartridge 3 subdivides the internal volume of the casing 2 into two separate chambers, namely a first chamber 24 communicating with the inlet mouth 22 and a second chamber 25 communicating with the outlet mouth 23. The filtering cartridge 3 comprises a substantially tubular filtering wall 30 which is positioned internally of the casing 2 such as to be positioned vertically during normal use of the diesel filter 1. In the illustrated embodiment, the filtering wall 30 is made of a cellulose- based material, and is pleated longitudinally such as to exhibit, in transversal section, a characteristic star-shaped conformation which offers the diesel a greater active filtering surface while not increasing the volume thereof (see figure 3). The ends of the filtering wall 30 are sealedly closed respectively by a lower plate 31 and an upper plate 32.

The upper plate 32 is perforated at the centre thereof and is sealedly hooked to a tubular support element 33, which is in turn sealedly fixed to the upper cover 21 at the inlet mouth 22. The cavity of the support element 33 sets the inlet mouth 22 in direct communication with the internal volume of the tubular filtering wall 30, which thus defines the first chamber 24 of the diesel to be filtered. Further, the body of the support element 33 exhibits a conical lower tract 34 which tapers towards the inlet mouth 22, which conical lower tract 34 is coaxial to the filtering wall 30 and substantially surmounts the whole surface of the upper plate 32, such as to make available a gabled space 35 which superiorly covers the filtering cartridge 3.

A retaining wall, in the present embodiment a hydrophobic net 4, is housed internally of the container casing 2, and intercepts the whole passage section of the second chamber 25, so that it is crossed by all the diesel flowing from the filtering wall 30 towards the outlet mouth 23.

The hydrophobic net 4 is covered with a coating substance such as poly- tetra-fluoro-ethylene (PTFE - usually known as Teflon), or silicone, or the like, and exhibits a maximum net size which is not greater than 200 micron, such as to allow the diesel to pass freely and to intercept the water contained in the diesel. In a preferred embodiment, the hydrophobic net 4 is a textile made of a single wire having a diameter comprised between 20 and 200 micron, with a net size of between 25 and 200 micron. The hydrophobic net 4 is preferably made of stainless steel, nylon or polyamide.

The coating substance can be applied on both sides of the hydrophobic net or only on one side thereof, for example by spraying and subsequent drying in a kiln, such as to obtain a thickness of the coating which is preferably comprised between 2 and 8 micron. In the example illustrated in figure 1 , the hydrophobic net 4 is located in the upper zone of the filter, at a distance from the bottom 27 of the container casing 2 which is greater than the tubular filter wall 30. In particular, it is shaped as a flat circular crown and is coaxially snugly inserted on the support element, which supports it on an intermediate tract 36 located above the above-mentioned conical tract 34.

The intermediate tract 36 comprises a shoulder 37 from which four radial ribs 38 project, which ribs 38 are angularly equidistanced and extend up to the lateral wall of the tumbler body 20 of the casing 2, where they fit into corresponding recesses afforded in a narrow circumferential shelf 26 projecting from the lateral wall (see figure 2).

The hydrophobic net 4 has a smaller diameter than the shoulder 37 and an external diameter which is equal to the diameter of the lateral wall of the tumbler body. In this way, it rests on the shoulder 37, on the radial ribs 38 and on the circumferential shelf 26, and is solidly constrained to the ribs 38 and shelf 26 by known fastening means, thus intercepting the whole passage section of the second chamber 25.

During use, the diesel enters the inlet mouth 22 internally of the cavity of the support element 33, from where it freely flows downwards internally of the first chamber 24 delimited by the tubular filtering wall 30. Owing to the presence of the lower plate 31 , the diesel is forced radially to cross the filtering wall 30, then passing internally of the second chamber 25.

During the passage through the filtering wall 30, the diesel is purified by the suspended solid particles which might be present. Further, the filtering wall 30 enables a first part of the water containing in the diesel to be separated from it; the particles of the water tend to aggregate by effect of coalescence on contact with the external surface of the filtering wall

30 and to slide by force of gravity in a downwards direction, until it drips onto the bottom 27 of the container casing 2. This coalescence phenomenon is facilitated by the fact that the filtering wall

30 is crossed from the inside towards the outside, causing a sharp slowing- down of the diesel and water mixture.

In this circumstance, the diesel tends to slow down less with respect to the water dispersed therein, which water collects at the filtering wall 30, accentuating the coalescence phenomenon.

Internally of the second chamber 25, the diesel, previously purified and at least partially freed of the water, rises towards the outlet mouth 23, crossing the hydrophobic net 4.

As previously mentioned, the hydrophobic net 4 allows the diesel to pass but blocks the remaining water, which aggregates thereon by coalescence, giving rise to drops which fall by force of gravity onto the gabled surface 35 of the support element 33, sliding therefrom downwards, finally dripping onto the bottom 27 of the container casing 2.

From the bottom 27 of the container casing 2, the accumulated water is periodically expelled via a discharge tap valve which is not illustrated, as it is of known type.

Claims

1 ). A filter for diesel fuel comprising a container casing (2) which is provided with an inlet mouth (22) for diesel to be treated and an outlet mouth (23) for treated diesel, and internally of which at least a filtering wall (30) for filtering the diesel and a retaining wall (4) for holding back water contained in the diesel by effect of coalescence are housed in series, the retaining wall (4) being located downstream of the filtering wall (30) with respect to a flow of the diesel fuel, the container casing (2) being provided with a bottom (27) for collecting the water which is held back by the retaining wall (4), wherein the retaining wall (4) is positioned above the filtering wall (30) with respect to the bottom of the container casing (2).

2). The filter of claim 1 , wherein a conical body (34) is interposed between the filtering wall (30) and the retaining wall (4), which conical body (34) is tapered towards the retaining wall (4) and is located such as to cover the filtering wall (30).

3). The filter of claim 1 , wherein the retaining wall (4) is associated to a tubular support element (33) which fixes the filtering wall (30) to the container casing (2) and which places the filtering wall (30) in communication with the inlet mouth (22) of the diesel to be treated. 4). The filter of claim 3, wherein the retaining wall (4) exhibits a flat conformation, and is snugly inserted internally of the container casing (2), and is provided with a central opening in which the tubular support element (33) of the filtering wall (30) is snugly fitted. 5). The filter of claim 4, wherein the retaining wall (4) rests on an intermediate tract (36) of the tubular support element (33).

6). The filter of claim 4, wherein the retaining wall (4) rests on a shelf (26) which projects from the container casing (2) towards an inside thereof. 7). The filter of claim 1 , wherein the retaining wall comprises a hydrophobic net (4) which allows the diesel to pass and which holds back the water contained in the diesel by effect of coalescence.

8). The filter of claim 7, wherein the hydrophobic net (4) is coated with a substance comprised in a group constituted by poly-tetra-fluoro-ethylene and silicone.

9). The filter of claim 7, wherein a mean size of the hydrophobic net (4) does not exceed about 200 micron.

10). The filter of claim 1 , wherein the filtering wall (30) is tubular and is arranged internally of the container casing (2) such as to be radially crossed by the diesel fuel to be treated.

11 ). The filter of claim 10, wherein the tubular filtering wall (30) is positioned such as to be crossed by the diesel fuel in a direction going from internally of the filter towards outside the filter.