WO2017194625A1

WO2017194625A1 - Fuel injector for an internal combustion engine

Info

Publication number: WO2017194625A1
Application number: PCT/EP2017/061220
Authority: WO
Inventors: Ludovic Sauvetre
Original assignee: Delphi International Operations Luxembourg S.À R.L.
Priority date: 2016-05-13
Filing date: 2017-05-10
Publication date: 2017-11-16
Also published as: FR3051229B1; FR3051229A1

Abstract

A fuel injector for an internal combustion engine, comprising an injection nozzle (12) having a nozzle body (16), a seat (34) with an injection port (36) passing therethrough, and a needle (14); a control chamber (52); and a control valve assembly (18). A micro-drilled filter element is positioned between the inlet of the inlet passage (70) and the outlet of the outlet passage (72). The control chamber is connected to the control valve, which includes, at one end, a control valve seat (82) defining a seat surface (88) through which a plurality of microchannels (90) are provided, forming both the micro-drilled filter element and a calibrated cross-section of the outlet passage (74).

Description

Fuel Injector for Internal Combustion Engine Technical Area

The present invention generally relates to the field of fuel injection in internal combustion engines, and more specifically to a fuel injector for such an engine.

State of the art

In an internal combustion engine such as those generally used in motor vehicles, an injector is a device that allows the supply of high pressure fuel into a combustion chamber.

The injector conventionally comprises a nozzle body, cylindrical, in which the fuel is introduced at high pressure. The nozzle body has a seat traversed by a plurality of injection holes that communicate with the combustion chamber.

A needle is arranged in the nozzle body, sliding axially between two extreme positions: an open position in which a first end of the needle is spaced from the seat, allowing the injection of fuel into the combustion chamber; and a closed position in which the first end of the needle rests on the seat so as to prohibit fuel injection.

In a known manner, the movements of the needle are controlled by a control valve associated with an actuator, which makes it possible to adjust the pressure in a chamber of

control located above the needle. Typically, the second end of the needle is received in the control chamber and undergoes the pressure prevailing in the chamber of command, which generates a pressing force in the closing direction. In addition, a needle spring forced

also the needle in closing direction.

The control chamber is supplied with high pressure fuel via an inlet passage comprising a calibrated section, called INO, defining a feed rate. The fuel escapes from the control chamber through an outlet passage connected to the control valve, the opening of which allows the control chamber to communicate with the low pressure fuel return circuit. The outlet passage includes a calibrated section, called SPO, fixing the flow of fuel escaping from the control chamber.

The control valve typically includes a body with a bore terminating at one end by a sealing seat. The closure member has an axially movable stem shape in the bore; it is connected at its first end, seat side, to the actuator frame, the first end further comprising an annular sealing surface cooperating with the seat of the body for closing the control valve. The second end of the closure member serves as a guide in the bore. The outlet passage from the control chamber opens laterally into the bore at an annular chamber, upstream of the seat, formed by a radial groove in the member

shutter. The closure member is prestressed in

closing direction by a spring.

The opening of the injector is done by feeding

the solenoid actuator, whose movable armature is able to lift the closure member of the control valve of the sealing seat, putting the control chamber into position.

communication with the low pressure circuit. it

causes a leakage flow controlled by the orifice SPO, which causes a pressure drop in the chamber of

ordered. The injection takes place when the pressure acting on the front part of the needle exceeds the force exerted by the needle spring and the fuel pressure in the control chamber, causing the lifting of the needle.

Such an injector is for example described in the

WO2016 / 005180 or EP 2647826. The construction of the control valve presented therein, said "balanced", facilitates its actuation by the solenoid; it has been used with satisfaction in many models of injectors.

It should be noted, however, that in modern motor vehicles, the tendency is for fuel pressure in the injector to become higher and higher, with

above 2000 bars. With such pressure, the problem of sealing the closure of the control valve becomes important.

A poor closing of the control valve causes a loss of efficiency of the injection and thus a loss of power of the engine which goes to a total malfunction of the injection and a stop of the engine.

A cause of leakage at the control valve is related to the presence in the fuel of

particles / impurities, which settle and / or accumulate at the sealing seat of the control valve and cause damage.

The appearance of leaks at the valve of

command is a critical problem because in a cycle

injection time, the closing time of the control valve is large in proportion to the opening time. Object of the invention

The object of the present invention is to provide a fuel injector designed to limit the wear of the seat of the control valve by particles carried by the

fuel.

General description of the invention

To pursue this objective, the present invention proposes a fuel injector for a combustion engine.

internal combustion, comprising a high pressure fuel delivery channel; an injection nozzle which comprises a substantially cylindrical nozzle body in communication with the high pressure fuel delivery channel; a seat associated with at least one injection port; and a needle arranged in the nozzle body, which controls by displacement, at a first end cooperating with the seat, the opening and closing of the injection orifices. It also comprises a control chamber filled, in operation, with fuel so as to exert pressure on a

second end of the needle, the control chamber being in permanent fluid connection with the high pressure fuel channel via an inlet passage. A control valve assembly is connected to the control chamber via an outlet passage having a section calibrated to define a leakage flow, which allows the flow to be varied.

selectively the fuel pressure in the control chamber to move the needle, the control valve assembly actuating a closure member movable with respect to a sealing seat so as to open / close the outlet passage between the control chamber and a low pressure fuel channel; and a high guide member for guiding the second end of the needle. According to the invention, the injector comprises a microperforated filter element placed between the entrance of the inlet passage and the exit of the outlet passage.

This filter element allows the filtration of particles contained in the fuel in the direct vicinity of the control valve, before the fuel passes through it.

Such an injector makes it possible to retain the particles entrained by the fuel upstream of the valve of

command and therefore significantly reduce

Damage to the valve seat, which is responsible for the valve closing incorrectly in the injectors

conventional.

Advantageously, the outlet passage comprises, at its end opposite the control chamber, the control valve seat through which it opens into a valve chamber; and the control valve seat defines a seat surface traversed by a plurality of microchannels, forming both the micro-pierced filter element and the calibrated section.

The valve seat is therefore combined with a micro-pierced end section of the outlet passage, thereby simplifying the diversity of the elements of the injector. The micro-channels thus positioned have the dual function of filtering and regulating the fuel flow (replacing the traditional calibrated orifice named SPO). The sizing of the micro-channels, during their design, is defined to provide a predetermined rate, in particular similar to a traditional SPO.

In the closed position of the control valve, the closure member rests on the seat and covers the seat surface, thus blocking the micro-channels of the seat. Preferably, the seat surface is substantially flat and the sealing surface of the closure member co-operating with the seat surface is substantially flat; organ

shutter preferably moving substantially perpendicular to the seat.

As will be understood by those skilled in the art, the use of micro-channels in the valve seat reduces control forces in such an unbalanced valve structure, compared to a conventionally designed valve seat.

According to the variants, the shutter member may take the form of a sphere truncated by a plane, the flat face forming the sealing surface; the truncated sphere being partially received in a housing at the end of an actuating rod.

According to the variants, the high guide element comprises a sleeve portion defining a guide bore and a head portion comprising the control chamber in which the guide bore opens, the high guide element being positioned in a passageway. inlet of the nozzle body; and the inlet passage and the outlet passage with the valve seat are integrated in the top guide.

According to the variants, the filter element comprises at least 40 micropilled holes; the filter element comprises microbeads with a diameter of less than 40 microns; the micro-holes may also be in the form of grooves.

For implementation in a diesel engine, considering the pressures involved and the desired flow rates, the filter element advantageously comprises at least 40 micro-channels, preferably between 40 and 1000, for a lower microchannel diameter or equal to 40 μιτι. In particular, for a diameter of micro-channels between 10 and

40 μιτι, we can have between 40 and 500 holes. For example, for a diameter of microholes between 20 and 30 μιτι can be between 80 and 250 holes. According to the variants, the inlet passage is arranged in the high guide element and the filter element is associated with the inlet passage. The filter element may take the form of a micropilled filter cylinder fitted on the portion of the top guide comprising the inlet passage, so as to cover the inlet. All the fuel entering the high guide is forced through this filter cylinder.

Alternatively, the inlet passage of the top guide may be formed by a plurality of micro-channels integrated in the wall of the top guide, the number and the diameter of these microchannels being chosen to obtain the combined effect of filter element micropilled and calibrated section of the inlet passage.

It remains to be noted that although the present invention was developed in the context of a diesel injector, it is entirely transferable to an injector of gasoline or any other fuel.

Detailed description using the figures

Other features and characteristics of the invention will emerge from the detailed description of at least one advantageous embodiment presented below, in

illustrative, with reference to the accompanying drawings. These show:

Figure 1: a perspective view of a section

longitudinal of an embodiment of the present injector;

Figure 2 is a perspective view of a detail of Figure 1;

Figure 3: A view of a close-up detail of the Figure

2;

Figure 4: a curve illustrating, for a constant fuel flow, the relationship between the number of

micro-holes and their diameter; Figure 5 is a perspective view, in section, of another embodiment of the present injector; and

Figures 6 to 8: sectional views of various embodiments of the present injector, in which the filter element is associated with the inlet passage.

In the remainder of the description, elements having an identical structure or similar functions will be designated by the same reference sign. We will adopt by convention, without limitation, a local coordinate system having an axial orientation A along the main axis of an injector according to the invention.

In the rest of the description, the terms "up" and "down" are used not only with reference to the orientation of the figure, but also with reference to the usual name given to these elements by professionals.

FIG. 1 shows an embodiment of the present fuel injector 10 of an internal combustion engine of a motor vehicle, in this case a diesel engine (although the invention is fully transferable to a fuel injector). gasoline or any other fuel), the injector 10 being generally part of an injection system comprising several injectors. The description will detail the elements of the invention and will remain more succinct and general as to the surrounding elements.

The injector 10 extends along the main axis A and

comprises, from bottom to top: a nozzle 12 comprising a needle 14 arranged in a nozzle body 16; a control valve assembly 18; and an actuator 20 comprising an actuator body 22 accommodating a fixed coil 24 and a movable magnetic armature 26. These different elements are held together with each other by any appropriate means. Conventionally, it is possible to use an injector body (not shown) in the form of a nut on a shoulder of the nozzle body 16 and screwing

directly on the actuator body 22 or on an upper portion of the injector body, said injector door body, accommodating the actuator 20 and in part the valve assembly 18.

The nozzle body 16, of substantially cylindrical shape of revolution about the axis A, comprises a stepped inner axial bore 28, extending from a high end 30, where it has a large diameter, to a low end 32 closing in a point so as to form a conical nozzle body seat 34 for controlling access of the fuel to at least one injection port 36 extending through the conical wall of the nozzle body 16, to communicate with a combustion chamber not shown.

The needle 14 comprises two projecting annular sections 38 improving the guidance of the needle 14 in the bore. The passage of fuel at this level is for example one or more orifices (or throats) no

represented, straight or helical, in the annular protrusion 38.

The guidance of the needle 14 in the upper part (also called the second end) is obtained by an independent piece, called high guide element 42, arranged in the inlet section 44 of the nozzle 12, against a shoulder 46 allowing its centering and axial locking.

The high guide member 42 guides in the axial direction to the upper portion of the needle 14, referred to as the needle head 48, through a central guide bore 50.

The reference numeral 52 designates a control chamber containing pressurized fuel, which makes it possible to exert a hydraulic force on the needle head 48 to control the opening and closing of the needle 14.

The needle 14 is generally cylindrical and extends axially along the axis A between the needle head 48, at the top of the needle. the figure, and a pointed end (also referred to as the first end), at the bottom of the figure, forming a needle seat 54 cooperating with the nozzle body seat 34.

When the needle 14 rests with its seat 54 on the seat of the nozzle body 34, it is in the closed position PF, fuel injection via the orifices 36 is prevented. The lifting of the needle 14 is obtained by adjusting the pressure in the control chamber 52, which allows the needle 14 to be brought into a fully open position PO

(Typically in the upper stop - not shown), in which the fuel is allowed to pass to the injection ports 36, downstream of the seat 34.

As can be seen, the needle 14 is provided with an annular protuberance 56 whose upper face 58, directed towards the needle head 48, provides a bearing surface for a spring 60 urging the needle 14 towards its position closed PF in which the tip of the needle 14 rests on its seat 34 and closes the injection ports 36. The spring is arranged under the high guide 42 and is pressed against a lower annular surface 62 of the top guide 42.

The injector 10 is conventionally provided with a fuel circulation circuit which, on the one hand, allows the supply of high pressure fuel via a high pressure circuit, from an inlet mouth to the injection ports 36 ; and on the other hand, the recirculation of fuel to a low pressure tank via a low pressure internal circuit. In Fig. 1, the high pressure fuel supply channel is indicated 66, and a low pressure fuel return channel is indicated 68.

The high-pressure circuit comprises in particular a bypass channel, called the inlet passage 70, leading to the control chamber 52, from which a discharge channel, said outlet passage, starts in the direction of the low pressure. 72, controlled in opening and closing by the control valve assembly 18. It will be noted that the outlet passage 72, and preferably the inlet passage 70, each comprise a calibrated section:

the calibrated section of the outlet passage 72 is indicated 74;

the calibrated section of the inlet passage 70 is indicated 76.

Indeed, it is conventionally played on the ratio of the effective passage diameters of the calibrated sections of the inlet passages 70 and outlet 72 to define, under normal operating conditions, a predetermined leakage rate of the fuel out of the control chamber 52 to the low pressure, when the control valve 18 is open.

When the coil 24 of the actuator, typically an electromagnet, is electrically powered, it attracts a magnetic armature 26 connected to the shutter member 78 of the control valve 18, which opens the outlet passage 72 and allows the fuel trapped in the control chamber 52 to evacuate to the low pressure circuit 68. The pressure in the control chamber 52 then drops, and the needle 14 moves in the bore of the nozzle body 16 to its open position PO in which the needle seat 54 is remote from the nozzle body seat 34, so as to allow the injection of fuel via the injection ports 36. The top of the needle head 48 being in higher abutment in the control chamber 52.

When the actuator is not energized, the magnetic armature assembly 26 and shutter member 78 of the control valve is pushed by a valve spring (no

represented) to a position in which the channel

evacuation system is closed, which holds in the chamber of command 52 the high pressure fuel that gets there. The pressure in the control chamber 52 then rises and the needle 14, pushed back by the spring and the pressure in the control chamber 52, moves towards the closed position PF, in which the needle seat 54 is in contact sealing against the nozzle body seat 34, so as to prohibit the injection of fuel.

It will be appreciated that in the present injector 10, the calibrated section 74 of the outlet passage 72 takes the form of a micropilled filter element, in order to retain the

particles / impurities carried by the fuel. It will further be appreciated that this filter element is integrated with a sealing seat 82 of the control valve assembly 18.

Referring more particularly to FIGS. 2 and 3, it should be noted that the outlet passage 72, made in a head block 84 (of the top guide) overlying the control chamber 52, comprises, at its end opposite to (remote from) the control chamber 52, the sealing seat 82 of the control valve assembly 18, through which it opens into a valve chamber 86.

The control valve seat 82 defines a seat surface 88 into which a plurality of microchannels 90 forming the filter element open. In the closed position of the control valve 18, the closure member 78 rests on the seat 82 and covers the seat surface 88, thus closing the end of the microchannels 90 and preventing communication to the valve chamber 86.

Thus, the outlet passage 72 terminates in a calibrated filtering section 74, which is a solid section traversed by a plurality of micro-channels 90 in communication with the upstream part of the inlet passage 70 and therefore with the chamber of control 52, and opening into the valve chamber 86 at the seat 82. This calibrated section micropercée 74 integrated seat 82 performs the functions:

filter element: retaining the particles carried by the fuel thanks to the small diameter of the channels 90; and - of calibrated section: the number and the diameter of the microchannels are chosen to obtain a flow

predetermined fuel, equivalent to a conventional calibrated orifice SPO.

For a better seal, the seat surface 88 is substantially flat, and the sealing surface 100 of the closure member 78 cooperating with the seat surface 88 is also substantially flat. The closure member 78 moves substantially perpendicular to the seat surface 88. In the valve chamber 86, the seat surface 88 is optionally placed in a bowl recess 92, projecting from the bottom of the bowl 92. .

The shutter member 78 is associated with a control rod 94 guided axially, parallel to the axis A, by a bore 96 made in a guide body 98.

For better alignment, the closure member 78 takes the form of a sphere truncated by a plane, the flat face forming the sealing surface 100. The truncated sphere is received in a ball joint in a housing 102 to the end of the control rod 94. This ball joint connection allows self-alignment of the closure member 78 on the seat 82, for a better sealing on closing.

It should be noted that in the present variant, the top guide 42 comprises a sleeve portion 104 defining the guide bore, as well as the head block 84 comprising the outlet passage 72. As can be seen in FIG. head block 84 defines the upper wall of the control chamber 52, and the guide bore 104 opens into the control chamber 52. The needle 14 thus closes the control chamber 52, and includes, for example, a narrowed end section 106 in the control chamber 52.

The top guide 42 is a one-piece piece that guides and surrounds the second end of the needle 14. The top guide 42 incorporates the control chamber 52, the inlet passage 70, the outlet passage 72 and the valve seat 82. control.

The top guide 42 has a general T shape, the

sleeve 104 being inserted into the inlet of the nozzle body 16, and the head block 84 closing the inlet thereof.

The upper portion of the head block 84 cooperates with the guide bore 104 to define the valve chamber 86. The reference sign 108 designates a portion of

positioning 108 axial groove which is housed in a cavity provided in the lower portion of the guide body 98. The positioning portion 108 has a peripheral wall bearing against the cylindrical wall 109 of the cavity. The sealing seat 82 is arranged in the positioning part 108.

As presented above, the calibrated section

micropercée 74 combined with the seat 82 of the control valve assembly 18 performs both functions of (a) flow control and (b) filtering. In practice, this microperced section 74 can be calibrated so that it delivers a passage rate equivalent to the flow rate of a passage of a conventional calibrated orifice SPO, whereas the filtering function rather requires a sizing of the microchannels 90. in relation to the diameter of the particles to be filtered.

The number of microchannels 90 required to allow the flow of a given flow rate increases as the diameter of the microchannels 90 decreases. This relationship is illustrated in Figure 4, in which the curve fixes the relationship diameter / number of holes for a flow rate of 300 ml / min. Note that the relationship is not linear and that from a certain diameter, here 55 μιτι, the curve flattens substantially. From 40 μιτι, the number of holes increases rapidly compared to the decrease in diameter.

It follows from this observation that from a certain diameter of the micro-channels 90, the obstruction of a micro-channel by a particle has a negligible influence on the resulting flow rate at the seat 82 of the set of control valve 18, and thus on the operation of the injector 10.

For the design of the present injector 10, a pair (number of holes, diameter) which is in the flattened section of the curve of FIG. For example, a micro-channel diameter 90 less than

40 μιτι. More particularly, the calibrated filter section 74 comprises at least 40 holes of diameter less than 40 μιτι, more particularly between 40 and 500 holes, having a diameter of less than 40μηη, in particular between 40 and 10 μιτι.

The injector 10 according to the invention, by its advantageous design of the region of the control valve seat combined with the calibrated filtering section, thus makes it possible to reduce the wear caused by the accumulation of particles at the closure of the valve. control valve and

improve the performance and durability of the injector 10.

Embodiments will be described below, without limitation, by comparison with the first embodiment, and with reference to Figures 5 to 8.

In a variant, as shown in FIG. 5, the head block 841 is an independent piece of the top guide 421, compared to the high one-piece guide 42 of the Fig.1. For example, the head block 841 may have a plate shape fastened by compression between the faces facing the high guide 421 and the guide body 98 of the control valve assembly.

As in the previous variant, the head block 841 defines the upper wall of the control chamber 52. The head block 841 also comprises the valve seat 82 traversed by a plurality of micro-channels 90 sized to ensure the times the functions of fuel flow regulation and filtering.

This variant allows the separation of the walls of the control chamber 52 between several parts, and thus the use of parts whose manufacture can be simpler and more economical.

While FIGS. 1, 2, 3 and 5 relate to embodiments in which the microperforated filter element is present in the outlet passage 72 of the control chamber 52, it is also possible to associate a micropilled filter element with the inlet passage 70, whether alternately or in addition to the micropilled filter element of the outlet passage 72.

In the variant of FIG. 6, a filter element 110 is positioned at the inlet of the inlet passage 70, around the sleeve of the top guide 422 422, the inlet passage 70 comprising a conventional calibrated section 76 is that is to say a single orifice of diameter determined so as to ensure the flow control function. The inlet passage 70 comprises an annular annular groove 111 section, which continues with the calibrated section 76. It will be noted that the inlet groove 111 is centered on the calibrated section 76. The inlet passage 70 is located at the bottom of the sleeve 1042 of the top guide 422, an intermediate chamber 112 is provided inside the sleeve 1042, into which the calibrated section 76 opens. annular allows the passage of fuel upwards, that is to say towards the control chamber 52

The filter element 110 is constituted by a cylindrical part which defines a filter cylinder, which is

forcibly fitted around the top guide 422 at the inlet passage 70. The filter cylinder 110 is traversed by a plurality of micro-channels 90 extending radially and able to filter the fuel.

Once the filter cylinder 110 has been pushed onto the top guide 422, microstrokes 90 are opposite the inlet groove 111 over the entire circumference of the top guide 422.

In this way, the fuel filtering function is provided at the entrance of the inlet passage 70 of the top guide 422.

This variant allows a larger fuel filtering area, and greater flexibility in the sizing of micro-channels 90. The flow rate at the inlet of the inlet passage 70 can be defined larger than that at the level of the calibrated section 76. Thus, with a large number of microchannels 90, when a portion of these microchannels 90 is plugged, the flow control function remains stable.

In another variant, represented in FIG. 7, as in the preceding variant, the filtering is ensured at the level of the inlet passage 70.

As can be seen, the top guide 423 is circumferentially traversed at the sleeve 1043 by a plurality of microchannels 90 which allow entry of the high pressure fuel into the interior of the sleeve 1043, to the control chamber 52.

The number and the diameter of these micro-channels 90 are chosen to ensure both the flow control function at the inlet passage 70 of the top guide 423, and the fuel filtering function.

In another variant, as shown in FIG. 8, the top guide 424 has at the sleeve portion 1044 a plurality of axial through slots 114 distributed at its circumference so as to allow fuel to enter the guide. up to 424 the control room 52.

Slots 114 are sized to provide an inlet passage 70 which provides both flow control and fuel filtering functions.

Claims

claims

A fuel injector for an internal combustion engine, comprising:

a high pressure fuel delivery channel (66);

an injection nozzle (12) which comprises:

a substantially cylindrical nozzle body (16) in communication with the high pressure fuel delivery channel (66);

a seat (34) associated with at least one injection port

(36); and

a needle (14) arranged in the nozzle body (16) which displaces, at a first end (32) cooperating with the seat (34), opening and closing of the injection ports ( 36);

a control chamber (52) filled with

operating, fueling so as to exert pressure on a second end (30) of the needle (14), the control chamber (52) being in permanent fluid connection with the fuel delivery channel via a passage of entrance (70);

a control valve assembly (18) connected to the control chamber (52) via an outlet passage (72) including a calibrated section (74) for defining a leakage rate, which selectively varies the fuel pressure in the control chamber (52) to move the needle (14), the control valve assembly (18) actuating a closure member (78) movable relative to a sealing seat (82) for opening, respectively closing, the outlet passage (72) between the control chamber (52) and a low pressure fuel channel (68); a high guide member (42) for guiding the second end of the needle (14);

characterized in that

a micropilled filter element is placed between the entrance of the inlet passage (70) and the outlet of the outlet passage (72);

and wherein the outlet passage (72) comprises, at its end remote from the control chamber (52), the control valve seat (82) through which it opens into a valve chamber (86); and the valve seat (82) of

control defines a seat surface (88) traversed by a plurality of microchannels (90), forming both the micropilled filter element and the calibrated section of the outlet passage (74).

2. Injector according to claim 1, wherein in the closed position of the control valve, the closure member (78) rests on the seat (82) and covers the seat surface (88), thus closing the microchannels (90) of the seat (82).

3. Injector according to claim 2, wherein the seat surface (88) is substantially flat and the sealing surface (100) of the closure member (78) cooperating with the seat surface (88) is substantially plane ; the closure member (78) preferably moving substantially perpendicular to the seat surface (88).

Injector according to claim 3, wherein the organ

shutter (78) takes the form of a sphere truncated by a plane, the planar face forming the sealing surface (100); and the truncated sphere is partially received in a housing (102) at the end of an actuating rod (94).

Injector according to any of the preceding claims, wherein the top guide member (42) comprises a sleeve portion (104) defining a guide bore (50) and a head block (84) comprising the control (52) into which the guide bore (50) opens, the upper guide member (42) being arranged in an inlet section (44) of the nozzle (12); and the inlet passage (70) and the outlet passage (72) with the valve seat (82) are integrated with the top guide (42).

6. Injector according to any one of the preceding claims, wherein the filter element comprises at least 40 micro-channels (90), preferably between 40 and 500, having a diameter of less than or equal to 40 μιτι, in particular between 40 and 10 μιτι in diameter.