FR3045733A1 - FILTER FOR INJECTOR - Google Patents

Abstract

A filter (14) for a fuel injector, the filter (14) comprising an outer member (26) and an inner member (24), the inner member (24) being coaxially inserted into the outer member (26) and defining between them an annular space (E).

Description

Injector filter

TECHNICAL AREA

The present invention relates to a fuel injector and more particularly to a filter arranged in the inlet mouth of an injector.

BACKGROUND OF THE INVENTION

Fuel injection devices, in particular diesel, must remove the particles present in the fuel to protect their operation. For this there are filters that are arranged in the inlet channel of the injector. The filters have cylindrical shapes provided with calibrated holes to retain fine particles, the holes having diameters of the order of 50 to 100 micrometers made by laser drilling. The filter manufacturing techniques do not make it possible to stop long and fine particles as well as compact particles whose size is less than 35 micrometers. The object of the present invention is to provide a filter which overcomes these disadvantages.

SUMMARY OF THE INVENTION

The present invention aims to overcome the disadvantages mentioned above by providing a filter designed to be arranged in an inlet channel of a pressurized fuel injector for an internal combustion engine. The filter has an elongate shape extending along a major axis. The filter comprises a filtering outer member whose peripheral wall is provided with a first external series of through holes and an inner filter member whose peripheral wall is provided with a second inner series of through holes, the inner member being inserted concentric in the outer limb.

In particular, the two filtering members define between them an annular space.

In addition, the directory space can be of constant radial thickness. In another embodiment, the annular space is of non-constant radial thickness. In addition, the outer filter member and the inner filter member are angularly oriented about the main axis relative to each other so that the holes of the first outer series and the holes of the second inner series are off-axis.

In one embodiment of laser drilling the offset of the inner holes and the outer holes is obtained according to the formula:

L = (D2e + Dls) / 2 + G where L is the misalignment between the axes,

Dis is the diameter of the inner hole of the second inner series, and D2e is the outer hole diameter of the first outer series, and G is an inter-hole overlap distance greater than or equal to zero.

In addition, the inter-hole overlap distance can be strictly greater than zero. In addition, each hole of the second inner series of the inner member opens into the annular space in the vicinity of a plurality of holes of the first outer series of the outer member, the axis of said hole of the inner member being equidistant from the axes of said holes of the outer limb. In another embodiment of the filter, the axis of the hole of the inner member may also not be equidistant from the axes of the hole of the outer member.

In another embodiment, the holes have a variable section and the diameter of the inner hole corresponds to the smaller diameter of the hole of the inner member. In addition, the radial thickness of the annular space is less than or equal to the smallest diameter of the holes of the inner member. In another embodiment, the radial thickness of the annular space may be strictly smaller than the diameter of the smallest section of the holes of the lower limb.

In addition, a fuel injector is provided with a filter described above. In addition, the filter is arranged in the input channel. The method for producing the filter comprises the following steps: a) providing a raw part of inner member devoid of holes, b) making in the raw part of the inner member the second series of holes by means of a laser drilling, the holes being arranged according to a network c) providing a blank piece of outer member without holes, d) producing in the rough part of the outer member the first "series of holes by means of laser drilling, the holes being arranged according to a regular network e) co-axially inserting the part made in step b) in the part made in step d), f) angularly orienting the inner member relative to the outer member so that the inner holes are offset relative to the holes exteriors.

BRIEF DESCRIPTION OF THE DRAWINGS Other features, objects and advantages of the invention will appear on reading the detailed description which follows, and with reference to the appended drawings, given by way of non-limiting example and in which: FIG. 1 is a longitudinal section of an injector using a filter according to the invention. FIG. 2 is an enlarged longitudinal section of the filter of the injector of FIG. 1.

Figure 3 is an enlarged longitudinal section of the inner filter inserted into an outer filter according to the preferred embodiment of the invention. - Figure 4 is a sectional view of the inner holes of the inner member of the filter according to the preferred embodiment of the invention. - Figure 5 is a sectional view of the outer holes of the outer member of the filter. FIG. 6 is a radial diagram of the top of FIG. 3. FIGS. 7, 8, 9 schematize the overlap of the holes of the filter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described with reference to the figures and for the sake of clarity and conciseness of the description a top-down orientation in the sense of FIG. 1 will be used without any limiting intention as to the extent of protection, particularly with regard to the different installations of an injector in a vehicle. Words such as "up, down, below, above, vertical, up, down ..." will be used without limiting intent.

In a known fuel injector 10, such as that shown in FIG. 1, fuel under high pressure enters an inlet channel 12, circulates in a high pressure circuit and is then sprayed via injection holes located in the nozzle of the injector 10. The invention is here described in the context of a diesel injector but could easily be used in a gas injector. The fuel under high pressure passes through a filter 14 arranged to retain impurities and other particles that can damage the precision mechanics of the injector 10. The particles can be of various shapes such as compact or thin and elongated .

The filter 14 shown in FIG. 2 has an elongate and cylindrical shape extending along an axis X of the inlet channel 12. The axis X corresponds to the longitudinal axis of the filter 14. The filter 14 comprises a first fastening portion 16 tightly mounted with interference in the inlet channel 12, this portion defining a fuel inlet section and a second filter portion 18 longer than the first portion 16 and of smaller diameter, the second portion 18 being provided at its periphery numerous filtration holes. In operation, the fuel enters through the inlet channel 12 and then filtered spring in an annular passage 22 defines between the wall of the inlet channel 12 and the outer wall of the second filtering portion 18.

More particularly, according to the longitudinal section of the filter 14 shown in FIG. 3, the filter 14 comprises a filtering inner member 24 and an outer filtering member 26, the inner member 24 being inserted into the outer member 26.

Referring to Figures 3 and 4, the filter 14 has a gap E between the inner member 24 and the outer member 26. The space E is annular. The space E is constant radially and along its length along the axis X in the filtering portion 18 of the filter. In another alternative space E may not be constant and have deviations from one point to another along the circumference or over the length, the deviations may go beyond the usual tolerance of the order of +/- 10 micrometers. The outer member 26 is composed of two parts, a first fixing portion 17 and a second filtering portion 19. The second filtering portion 19 is elongate and cylindrical in shape and has an inner wall 28 and an outer wall 30. The filtering portion 19 comprises a cylindrical tube with a first external series of holes opening 21 and having at one end a spherical tip 32 which closes the outer member. The tip 32 of the filtering part 19 may alternatively be flat, ovoid or have any other shape. The inner member 24 is inserted into the outer member 26 of the filter. The inner member 24 is composed of two parts, a first full tubular portion 34, a second tubular filter portion 36 with a second inner series of through holes 38 of smaller diameter than the first portion 34 and a spherical tip 40 which closes the filtering portion of the inner member 24 located opposite the first portion 34. The tip 40 of the filter portion 36 may alternately be flat, ovoid or have any other shape. The second filtering portion 36 is of elongate and cylindrical shape and has an inner wall 37 and an outer wall 39.

The holes 20 of the filter 14 comprise the filter holes 38 of the inner member 24, of smaller diameter DI and, the filter holes 21 of the outer member 26, of smaller diameter D2. The through holes 21, 38 are made via laser technology which gives them a conical shape.

With reference to FIG. 5, the holes 21 of the outer limb made by laser technology have two different diameters D2e and D2s at their two ends on the inner wall 28 and on the outer wall 30. D2e is the input diameter and D2s is the outlet diameter in the direction of flow of fuel inside the outer member 26. The holes 21 have a divergent shape, that is to say that in the direction of fuel flow the holes have a diameter of D2e input smaller than the output diameter D2s. The inlet diameter D2e is proximal to the annular space E corresponding to the opening diameter of the hole 21 in the inner wall of the outer member. The holes 38 of the inner member also made by laser technology have two different diameters DleetDls at both ends on the inner wall 37 and on the outer wall 39. Die is the input diameter and Dis is the output diameter corresponding to the direction of circulation the holes 38 also have a divergent shape, that is, in the direction of fuel flow the holes have an input diameter Die smaller than the diameter of the fuel. Dis. output The outlet diameter Dis is proximal to the annular space E corresponding to the opening diameter of the hole 38 in the outer wall of the inner member. According to the section of Figure 4, the holes 21 of the outer member 26 extend along an axis Y1 and the holes 38 of the inner member 24 extend along an axis Y2. The holes being made all around the filtering part, the corresponding axes Y1, Y2, are perpendicular and radial, or transverse, to the longitudinal axis X of the filter. Given the spatial distribution of the holes, each hole corresponds to its own axis YI, Y2, the axes forming part of a radiating network. Other forms of holes 21, 38 can be obtained, for example cylindrical holes of constant diameter DI, or converging holes, in contrast to diverging, input diameter larger than the output diameters.

With reference to FIG. 5, the shape of the holes 21 is generally conical because of the peak power of the laser beam used for drilling, which explains the difference in the diameters at the two ends of the hole, the inlet diameter of the hole being larger than the exit diameter. According to alternatives not shown, the holes of the outer member 26 and the inner member 24 may also be square holes see other forms. The assembly of the inner member 24 of the filter in the outer member 26 will now be described in a preferred embodiment: a) providing an inner member blank 24 without holes. The inner member 24 is first made from a circular flat sheet, for example of constant radial thickness of 0.3 to 0.5 mm. The sheet is then deep drawn to an elongated tube shape. b) making in the raw part of the inner member 24 the second series of holes 38 by means of a laser drilling, the holes being arranged in a regular pattern. The regular network may be a network of holes distributed over a set of coaxial circles arranged at regular intervals along the cylinder represented by the filtering portion 36 of the inner member. The inner member 24 is pierced by rotating the inner member about its longitudinal axis. The inner member 24 may be stainless steel. c) provide a raw piece of outer member 26 without holes. The outer member 26 is also made from a circular flat sheet, for example of constant radial thickness of 0.3 to 0.5 mm, which is then deep drawn to an elongate tube shape. d) producing in the raw part of the outer member 26 the first set of holes 21 by means of a laser piercing, the holes 21 being arranged in a regular pattern. The regular network may for example be an array of holes distributed over a set of coaxial circles arranged at regular intervals along the cylinder represented by the filtering portion 19 of the outer member. The outer member 26 is pierced using laser technology by rotating the outer member 26 about its longitudinal axis X. Due to the laser beam the bottom of the hole has a smaller diameter than the inlet diameter of the piercing. filtration hole. In other cases during laser drilling, one may not have the smallest diameter of the hole at one end. The outer member 26 may be stainless steel. e) coaxially inserting the part made in step b) in the part made in step d). The inner member 24 is inserted coaxially into the open end of the outer member 26. The inner member 24 is inserted until its spherical tip 40 comes into contact with the spherical tip 32 of the outer member 26. Another embodiment of Alternative realization is that the spherical tips do not touch each other. f) angularly orient the inner member relative to the outer member so that the inner holes 38 are always offset from the outer holes 21 of the outer member. g) The inner member 24 and the outer member 26 thus assembled are fixed together, preferably by laser welding.

Referring to Figure 4, the through holes 38 of the inner member have two diameters Die and Dis. Those skilled in the art are well aware that the holes shown are perfectly shaped, especially the cones, but that in fact the laser drilling induces variations in geometry and dimensional tolerances making the largest diameters, or the smallest, may not be exactly at the openings of the holes.

With reference to FIG. 5, the through-holes 21 of the outer member 26 have two diameters D2e and D2s, D2e corresponding to the inlet diameter, which in the case of a conical hole diverge from the smallest section and D2s corresponding to the diameter. output, which in the case of a conical hole diverge perfect, is the largest diameter.

As shown in FIG. 4, the space E has a value always positive and smaller than the smallest diameter DI of the hole 38 of the inner member 24. The space E can thus block the particles that would have passed through the internal holes 38. For example if the space E has a value of 20 micrometers, the particles which are 30 micrometers will be able to pass through the internal holes 38 and will not be able to pass the space E to reach the hole 21 of the outer member 26.

As shown in FIG. 6, the holes 21 of the outer member 26 and the holes 38 of the inner member 24 have an offset L. FIG. 6 is an enlarged view projected on a plane tangential to the surface of the filtering part, the offset L being defined as follows: L = (D2e + Dls) / 2 + G where G is an inter-hole overlap distance greater than zero, opening of the hole 38 of the inner member in the outer face 39 has a diameter Dis and the opening of the hole 21 of the outer member in the inner face 28 has a diameter D2e.

In one embodiment of the filter 14 with laser drilling, the holes are tapered tapering at one end. Each hole 38 of the inner member opens into the annular space E in the vicinity of a plurality of holes of the outer member. The axis Y1 of the hole 38 of the inner member is equidistant from the axes Y2 of the holes 21 of the outer member. In another embodiment of the filter 14, the axis Y1 of the hole 38 of the inner member may not be equidistant from the axes Y2 of the holes 21 of the outer member, while having no overlap between the inner holes and the external holes.

In one embodiment where the inner holes 38 and the outer holes 21 are cylindrical, Dis is equal to Die and D2s is equal to D2e.

As shown in FIG. 7, the inter-hole overlap distance G is the distance between the two diameter circumferences Dis of the conical holes 38 and of the diameter D2e of the conical holes 21, the inter-hole overlap distance G being the distance which separates two straight lines T21 and T38 parallel to each other and tangent to the two circumferences. The two lines are transverse to the line passing through the two centers of the holes 21, 38. In FIG. 7, the inter-hole overlap distance G is positive.

With reference to FIG. 8, in another embodiment, the inter-hole overlap distance G will be equal to zero, which means that the holes 21, 38 are tangent relative to one another without coming into contact with each other. overlap. In fact the two circumferences of the holes 21, 38 are tangent to each other. In this figure the conical holes 38 have the diameter Dis and the conical holes 21 have a diameter D2e.

When mounting the filter 14 in the inlet channel 12 of the injector 10, the fixing portion 16 whose outer diameter D16 is greater than the diameter DI8 of the filtration portion 18 interferes with the diameter D22 of the inlet channel 12. The filter 14 is mounted tightly in the inlet channel 12. To ensure that the filter 14 will be force-fitted simply, quickly and economically, one skilled in the art will be able to verify the permissible interference between a diameter D16 of the attachment portion 16 and an inner diameter D12 of the inlet channel 12. It is also known that it is necessary to ensure the choice of materials and the operating temperature range to ensure reliable interference over time.

With reference to FIG. 8, the holes 21, 38 are represented in a configuration where G is the inter-hole distance between the conical holes 38 of the lower limb 24 and the conical holes 21 of the outer limb 26. In this case the distance inter-hole recovery G is zero. This indicates that the diameters Dis and D2e of the holes 21, 38 are tangent to one another.

With reference to FIG. 9, the inter-hole overlap distance G is negative. This configuration in FIG. 9, which does not form part of the invention, can let the long and thin particles and the compact particles pass through the two filtering members 24, 26 of the filter 14. The particles would then disturb the operation of the device. injection.

In operation, the fuel enters the injector 10 through the inlet channel 12 where the filter 14 is mounted. The fuel passes through the filter 14 by the diameter Die of the holes 38 of the inner member 24, then leaves the inner member 24 by the diameter Dis of the inner holes 38. Then the fuel flows in the space E and enters the outer member 26 by the diameter D2e and through the holes 21 to exit by the diameter D2s. The fuel then flows in the annular passage 22 to go towards the nozzle of the injector 10 located at the distal end of the inlet channel 12.

LIST OF REFERENCES USED 10 Injector 12 input channel 14 Filter 16 first part attachment of the filter 17 first filtering part of the outer member 18 second filtering part of the filter 19 second filtering part of the outer member 20 filtering holes of the filter 21 holes of the outer member 22 annular passage 24 inner filtering member 26 outer filtering member 28 inner wall of the second portion 30 outer wall of the second portion 32 spherical tip of the outer member 34 first solid portion of the inner member 36 second filtering portion of the inner member 37 inner wall of the second part 38 holes of the inner member 39 outer wall of the second part 40 spherical end of the inner member 44 misalignment between the axes DI smaller diameter of the inner hole Die inlet diameter of the inner hole Dis outlet diameter of the inner hole D2 diameter the smaller of the outer hole D2e outer hole entry diameter D2 s external hole exit diameter D16 outer diameter of the filter attachment portion DI8 inner diameter of the inlet channel D22 outer diameter of the filter portion E outer and inner member spacing X main axis of the filter and the air channel input Y1 axis of the outer hole of the outer member Y2 axis of the inner hole of the inner member T21 right tangent to the outer hole T38 right tangent to the inner hole

Claims (8)

A filter (14) arranged to be arranged in an inlet channel (12) of a pressurized fuel injector for an internal combustion engine, the filter (14) having an elongate shape extending along an main axis (X) and comprising: - an outer filter member (26) whose peripheral wall is provided with a first external series of through holes (21) and - an inner filter member (24) whose peripheral wall is provided a second inner series of through holes (38), - the inner member (24) being coaxially inserted into the outer member (26); characterized in that the two filtering members define between them an annular space E. 2. Filter (14) according to the preceding claim, wherein the outer filter member (26) and the inner filter member (24) are angularly oriented around the main axis (X) relative to each other. so that the holes (21) of the first outer series and the holes (38) of the second inner series are off-axis. 3. Filter (14) according to claim 2, wherein the offset of the inner holes (38) and the outer holes (21) is obtained according to the formula: L = (D2e + Dls) / 2 + G wherein L is the Offset between the axes, Dis is the exit diameter of the inner hole (38) of the second inner series, and D2e is the inlet diameter of the outer hole (21) of the first outer series, and G is a lap distance. inter-hole greater than or equal to zero. The filter (14) of claim 3, wherein the inter-hole overlap distance (G) is strictly greater than zero. A filter (14) according to any one of the preceding claims, wherein the radial thickness of the annular space (E) is smaller than or equal to the smallest diameter (D1) of the holes (38) of the inner limb (24). ). 6. Filter (14) according to any one of claims 1 to 5 wherein, each hole (38) of the second inner series of the inner member (24) opens into the annular space (E) in the vicinity of a plurality of holes (21) of the first outer series of the outer member (26), the axis of said hole of the inner member (24) being equidistant from the axes of said holes of the outer member (26). 7. A fuel injector (10) provided with a filter (14) made according to any one of the preceding claims, the filter (14) being arranged in the inlet channel (12). A method of making a filter (14) according to claim 7, comprising the steps of: a) providing an inner member blank (24) without holes, b) forming in the gross part of the inner member (24) the second series of holes (38) by means of laser drilling, the holes (38) being arranged in a regular pattern; c) providing a blank piece of outer member (26) without holes, d) forming in the blank piece of the outer member (26) the first series of holes (21) by means of a laser drilling, the holes (21) being arranged according to a regular network, e) coaxially inserting the part made in step b) in the part made in step d), f) angularly orienting the inner member (24) relative to the outer member (26) so that the inner holes (38) are offset relative to the outer holes (21).