GB2328887A

GB2328887A - Minimising water re-entrainment in fuel filters

Info

Publication number: GB2328887A
Application number: GB9817294A
Authority: GB
Inventors: Eduardo Aller Blanco; Eduardo Ramirez Hernandez; Diego Alegre Jos Maria De; Enrique Alcalde Serrano
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-08-27
Filing date: 1998-08-07
Publication date: 1999-03-10
Anticipated expiration: 2018-08-07
Also published as: DE19737264A1; DE19737264B4; GB2328887B; ES2153750B1; GB9817294D0; ES2153750A1

Abstract

A fuel filter, comprising a wound filter element 12 arranged in a housing 11 above a space 25 for storing water separated from the fuel, is provided with means (porous sieve, deep bed filter or felt disc 32) to reduce the force of the filtered fuel as it exits from the filter element 12 by dividing it up into many small streams. This ensures that the fuel streams do not impinge as strongly as they otherwise would on the surface of the water in the water storage space, and so re-entrainment of water in the fuel is minimised. The fuel, preferably diesel fuel, enters through inlet 15, flows axially through filter element 12, through the felt disc 32, through a filter supporting ring 23, into the water storage space 25 and up through a central tube 22 to the outlet 17. The filter element is wound from a V-shaped web of filter material, with the folded edge at the bottom end, or (not shown) from two or more webs. The fuel filter may be a throw-away cartridge.

Description

2328887 1 Lig.uid filter for fuels

Background art

The invention proceeds from a liquid filter for fuels, in particular for diesel fuel, according to the type indicated in detail in the preamble of the main claim Such a liquid filter for fuels is already known from DE 15 36 766 A I, in which the liquid filter with its housing is composed of three parts, namely a cover co i i g the connections, a filter box and a shell-shaped base part which are held together by a central threaded joint. Said filter box accommodates an axially swept wound-type filter element the bottom end of which is adjoined by a water storage space in the base part. Disposed in the bottom of the filter box are D- shaped mouldings arranged at uniform intervals in a circle, on the flat surfaces of which the wound-type filter element is supported, while their longitudinal edges are -designed as throughfiow openings. Although the flows directly through said throow openings extend approximately tangentially in a radial plane, said partial streams are redirected axially downwards into the water storage space by the semicircular portions of the D-shaped mouldings. In said base part, said partial streams strike the separated water, are deflected and may, as they subsequently flow off through the centmi middle tube, still entrain water droplets. The water separation is therefore impaired, above all when the liquid filter cleans extensive streams of fuel. This applies also when the water storage space is small and there is little space available for deflecting the fuel stream, with the restdt that water droplets may easily be entrained at the clean side.

2 From DE 23 05 128 C3, moreover, a liquid filter having a wound-type filter element is known which is manufactured by winding a V-shaped web spirally around a central middle tube while adding suitable sealants. Here, 'm order during operation to prevent dirt particles from working through in the region of the folded edge of the V-shaped web, a woollen thread is inserted into the pocket base of the V-shaped web, said woollen thread acting like a deep-bed filter and thereby improving the separation efficiency of the liquid filter. Here too, if said woundtype filter element is used to clean diesel fuels, there is a risk, especially at high fuel flow rates and particularly given a compact construction of the liquid filter, of development of a localized, stronger flow at the clean side, which flow strikes the water separated in the water storage space and may in the process entrain water droplets in the fuel stream. There is no reference to an improvement of the water separation here.

From GB 1402 586, moreover, a liquid filter having a wound-type filter element in a box-like style of construction is known, a disc-shaped felt filter being disposed as a roughing filter upstream of the wound-type filter element made of filter paper. Said felt filter acting as a deepbed filter is situated at the dirty side and is intended to increase the cleaning action and, in addition, also the life of the filter. The problem of water separation in the water storage space situated below the wound-type filter element is not mentioned here.

Advantages of the invention In contrast, the liquid filter for fuels according to the invention having the characterizmg features of the main claim has the advantage that it improves the water separation especially in the case of large fuel streams and hence promotes a compact design of such liquid filters having a water storage space. By virtue of 3 the means according to the invention, the throughfiow directly downstream of the bottom end of the wound-type filter element is now distributed better and more uniformly into a plurality of small pressure medium streams. As a whole, the flow rate in said region is reduced because now the entire available annular surface is utilized as uniformly as possible for the througliflow. The force of the througliflow streams in the region of the deflection zone in the water storage space is then much lower so that the water separation is less disturbed and so at the clean side f th ewer water droplets are entrained. The water separation is erefore improved precisely in the case of large throughfiow streams. It is also therefore possible to make the height of the water storage space smaller in an axial direction without jeopardizing the water separation function so that altogether, a more compact design of the liquid filter is possible. The design of the liquid filter is moreover space-saving and inexpensive and does not require any major modifications to existing structural parts.

is Advantageous developments and improvements of the liquid filter indicated in the main claim are possible by virtue of the measures outlined in the sub-claims. For a simple and inexpensive solution, a construction of the liquid filter according to claim 2 is particularly advantageous. For reliable and efficient operation combined with a space-saving design, it is advantageous when the liquid filter is constructed according to claim 3. Further advantageous refinements are evident from the remaining claims, the description and the drawing.

Drawing An embodiment of the invention is illustrated in the drawing and described in detail below. The single figure shows in a simplified manner a longitudinal section through an embodiment of the liquid filter according to the invention.

4 Description of the embodiment

The figure shows in a simplified manner a longitudinal section through a liquid filter 10 for diesel fuel, which in the present case is designed as a throw-away box. The liquid filter 10 has a housing 11, which inside accommodates an axially swept wound-type filter element 12.

The housing 11 comprises a pot-shaped housing part 13, which is closed at its open end by a cover 14. Formed in the cover 14 is an inlet 15 for unfiltered fuel, which comprises a plurality of inlet bores 16 uniformly distributed along a diameter. The cover 14 further has an outlet 17 for filtered fuel, which is formed by a central opening 18 in the cover. For sealing between inlet 15 and outlet 17 as well as in an outward direction when the liquid filter 10 is fastened to a 15 machine component (not shown in detail), two scaling rings 19, 21 are disposed on the outside of the cover 14.

Inside the housing 11, a centrally disposed middle tube 22 extends downwards from the outlet 17 and rests with its other end on a perforated supporting ring 23.

The supporting ring 23 is situated in the bottom half of the pot-shaped housing part 13 on a shoulder 24 of the housing part 13 and separates the wound- type filter element 12 from a water storage space 25 situated underneath. The water storage space 25 may be emptied out through a drain plug 26 and is connected by a central pipe socket 27 of the supporting ring 23 to the interior of the middle tube 22 and hence to the outlet 17.

The middle tube 22 is a part of the wound-type filter element 12 and carries on its outer periphery the actual winding 28 comprising a filter paper web, which is V- shaped in cross section and is wound, while adding sealant, spirally around the middle tube 22 in the manner known as such from the initially described background art. The winding 28, which is swept axially from top to bottom therefore fills the annular space between the wall of the pot- shaped housing part 13 and the middle tube 22. The spirally extending folded edge 29 of the V-shaped filter paper web in said case forms a bottom end 31 of the wound-type filter element 12. Said bottom end 31 lies a slight distance apart from the perforated supporting ring 23, said annular space formed between end 3 1, supporting ring 23, middle tube 22 and housing part 13 being filled by an annular disc 32 made of felt.

Thus, by means of said relatively thin annular disc 32 the winding 28 too is supported by its bottom end 31 on the supporting ring 23.

The relatively flat annular disc 32 is thin in an axial direction, so that little installation space is lost for the winding 28 itself, but on the other hand is so thick that, dependent on the used material, felt a particularly effective division and homogenization of the flow occurs in said region. Its thickness may advantageously be, say, the thickness of one to two turns of the V-shaped web winding.

The mode of operation of the liquid filter 10 is described below, with it being taken for granted that its basic function is known as such.

The fuel to be filtered, above all diesel oil, flows through the inlet 15 into the interior of the housing 11 and streams axially from top to bottom through the actual winding 28, during which process it is cleaned. The filtered fuel stream leaving the wound-type filter element 12 at the bottom end 3 1 then flows through the a disc 32 made of felt and through the perforated supporting ring 23 into the water storage space 25, where the liquid stream is deflected and flows in a 1 6 clean state through the pipe socket 27 and the middle tube 22 to the outlet 17. The annular disc 32 made of felt in said case forms a means 33 of homogenizing the throughfiow of the fuel stream and ensuring that the througliflow in said flow region is uniformly distributed into a plurality of small throughfiow streams. By virtue of the action of the annular disc 32 and utilizing the entire cross section of flow between the wall of the housing part 13 and the middle tube 22, the flow rate becomes as uniform as possible and also, above all, lower so that the force of the fuel stream entering the water storage space 25 is much lower. The flow deflected in the water storage space 25 and conveyed towards the outlet 17 is therefore no longer powerful enough to entrain the water collected in the water storage space 25 at the bottom, or water droplets still in suspension, towards the outlet 17. Thus, the water separation flinction is substantially improved, particularly when the liquid filter 10 is required to process and clean large streams of fuel. Fuel streams of an increased flow rate which arise in a locally limited manner as a result of contamination of the winding 28 are damped by the felt annular disc 32 in such a way that their potential disturbing influence upon the water separation in the water storage space 25 may no longer arise. Said means 33 according to the invention have the further advantage that the safety clearance between the supporting ring 23 and the predicted height of the water level in the water storage space 25 given a set flow rate may be reduced without separated water be g entrained; for identical througliflow streams, the liquid filter 10 may therefore be designed more compactly.

Although felt as the material for the annular disc 32 is a particularly simple, easy to-use and inexpensive means 33 owing to its insensitivity to water and its effect of assisting water separation, other materials may also be used for said means; for example, it is also possible to use a corresponding deep-bed filter made of suitable materials such as plastic. material, metal, paper or the like. Furthermore, instead 7 of the felt separating disc 32, a suitable porous sieve may also be used for the same purpose. Instead of the illustrated wound-type filter element 12 with a Vshaped web winding, it is also possible in a known manner to use a winding manufactured from two or more webs of filter material. Instead of the throw-away box illustrated by way of example, the liquid filter 10 may also be designed in a different manner, e.g. as a multi-part housing filter. It is further possible, where necessary, also to combine the functions of the means 33 and the supporting ring 23 in a common structural part. Additional modifications are also possible without departing from the idea of the invention.

8

Claims

Liquid filter for fuels, in particular for diesel fuel, having a woundtype filter element, which is disposed Mi a housing and inserted between an inlet for unfiltered fuel and an outlet for filtered fuel, the wound-type filter element being swept axially in a longitudinal direction of the liquid filter and there being disposed mi the housing below the wound-type filter element a water storage space, in which the fuel having flowed through the wound-type filter element is deflected and water ent- ained by the fuel may be separated, while the filtered fuel is conveyed through a central middle tube to the outlet, and having a supporting ring, which is associated with the wound-type filter element at the latter's bottom end and has openings for passage of the fuel, characterized in that installed downstream of the wound-type filter element (12) at its clean side and upstream of the water storage space (25) is a means (33) of homogenizing the througliflow of the fuel stream.
2. Liquid filter according to claim 1, characterized in that the means (
3 3) is disposed between the bottom end (3 1) of the wound-" filter element ( 12) and the supporting ring (23).

Liquid filter according to claim 1 or 2, characterized in that the means (33) takes the form of a flat annular disc (32), which extends radially between the wall of the housing (11) and the middle tube (22).
4. Liquid filter according to one of claims 1 to 3, characterized in that a flat layer of a deep-bed filter (32) is used as a means.

9
5. Liquid filter according to one of claims 1 to 4, characterized in that a felt material (32) is used as a means.
6. Liquid filter according to one of claims 1 to 3, characterized in that 5 a porous sieve is used as a means.
7. Liquid filter according to one or more of claims 1 to 6, characterized in that the wound-type filter element (12) comprises a winding (28), in which a V shaped web of filter material is wound spirally around a middle tube (22) and the folded edge (29) of the V-shaped web lies at the bottom end (3 1) of the wound type filter element (12).
8. Liquid filter according to one of claims 1 to 7, characterized in that the liquid filter (10) takes the form of a throw-away box.
9.

Liquid filter according to one of claims 1 to 8, characterized in that the inlet (15) and the outlet (17) are disposed in a cover (14) of the housing (11).
10. Liquid filter according to one of claims 1 to 9, characterized in that the winding (28) in the wound-type filter element (12) is swept from top to bottom.
11. Liquid filter according to one of claims 3 to 10, characterized in that the axial thickness of the annular disc (32) in relation to its axial extension is relatively small, being in particular the thickness of one to two turns of the Vshaped web winding (28).
12. A liquid filter for fuels substantially as herein described with reference to the accompanymig drawings.