Fuel Injector Filter

Abstract

A filter for a control flow of a fuel injector, wherein a primary fuel flow enters the injector through an inlet aperture, and wherein part of the primary fuel flow forms a secondary fuel flow which enters a control valve through a control flow aperture, wherein the filter is located such that only the secondary flow of fuel passes through the filter, the filter includes filter orifices such as slots, holes or perforations, wherein at least one dimension of the filter orifices is less than the nozzle control valve lift value.

Claims

1-9. (canceled)

10. A fuel injector for use in delivering fuel in an internal combustion engine, the fuel injector comprising: a housing; an inlet aperture; a control flow aperture leading to a nozzle control valve having a known lift value; a needle piston; a nozzle cavity provided with at least one nozzle outlet opening, wherein a primary fuel flow enters the injector through the inlet aperture, and wherein part of the primary fuel flow forms a secondary fuel flow which enters the nozzle control valve through the control flow aperture, and wherein the nozzle control valve controls movement of the needle piston, thereby controlling flow of fuel out of the nozzle cavity through the at least one nozzle outlet opening; and a filter located such that only the secondary flow of fuel passes through the filter, the filter comprising at least one filter orifice, wherein at least one dimension of the at least one filter orifice is less than the known lift value of the nozzle control valve.

11. A fuel injector as claimed in claim 10 wherein the filter is located in a fuel flow path between the inlet aperture and the nozzle cavity such that the primary fuel flow passes over an upstream surface of the filter.

12. A fuel injector as claimed in claim 10 wherein the at least one dimension of the at least one filter orifice is between a half and a quarter of the known lift value of the nozzle control valve.

13. A fuel injector as claimed in claim 10 wherein the at least one filter orifice comprises a plurality of slots, wherein the at least one dimension of the slots is a width of each slot.

14. A fuel injector as claimed in claim 10 wherein the at least one filter orifice comprises a plurality of holes or perforations wherein the at least one dimension is a maximum diameter of each hole or perforation.

15. A fuel injector as claimed in claim 10 wherein the filter is mounted in the injector housing and comprises a tube, and wherein the at least one filter orifice is provided on a surface of the tube.

16. A fuel injector as claimed in claim 10 wherein the at least one filter orifice is provided on a surface of a component or part of the injector.

17. A fuel injector as claimed in claim 10 wherein the at least one filter orifice comprises a clearance between two components and wherein the at least one dimension of the at least one filter orifice is the clearance between the two components.

18. A fuel injector as claimed in claim 10 wherein the at least one filter orifice comprises a mesh comprising a plurality of mesh orifices and wherein the at least one dimension of the filter orifice is a minimum dimension of each mesh orifice.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a longitudinal cross-sectional view of an injector in accordance with the present invention;

[0026] FIG. 2 is a detailed cross-sectional partial view of the injector of FIG. 1 taken through a different longitudinal axis to FIG. 1;

[0027] FIG. 3 is a schematic cross-sectional partial view of an injector in accordance with the present invention;

[0028] FIG. 4 is an isometric view of one embodiment of a filter in accordance with the present invention;

[0029] FIG. 5 is a longitudinal cross-sectional view of the filter of FIG. 4;

[0030] FIG. 6 is an isometric view of the midsection of the filter of FIG. 4; and

[0031] FIG. 7 is a detailed partial front view of the midsection of FIG. 6; and

[0032] FIG. 8 is a partial cross-sectional view of an injector fitted with the filter of the FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Referring to the figures, the present invention comprises a fuel injector 2 suitable for delivering fuel to an engine cylinder or other combustion space of an internal combustion engine. The fuel injector 2 comprises an injector housing and an injector inlet aperture 12 (shown in FIGS. 2 and 3) through which a main, or primary fuel flow enters the injector 2, in direction A (FIG. 3). A nozzle cavity 56 is supplied with fuel from the primary flow.

[0034] The fuel injector 2 further comprises a nozzle control valve (located generally in region 52) including a valve seat (not shown in figures), the nozzle control valve having a known value of lift. Part of the primary fuel flow (typically 10%) forms a secondary, or control fuel flow, which is directed through a control flow aperture 14, in direction B (shown in FIG. 3) towards the control valve.

[0035] Fuel pressure within a valve control chamber controls the motion of a needle piston 58, thereby controlling the flow of fuel from the nozzle cavity 56, through nozzle outlet openings (not shown in the figures).

[0036] The injector 2 further comprises a filter 16 which, in the embodiment illustrated in the figures and most clearly illustrated in FIGS. 4 to 8, comprises a midsection 26 comprising an elongate tube of circular cross-section, a closed end cap 22 and a base section 24. The midsection 26 and the base section 24 are provided with through bores. The midsection 26 is provided with a plurality of filter orifices, which in the illustrated embodiment comprise elongate slots 20. The slots 20 have a width dimension W and a length dimension L (both shown in FIG. 7), the width dimension W being less than the known value of lift of the nozzle control valve.

[0037] In the embodiment shown in the figures, the base 24 of the filter 16 is mounted in a section of the piston guide 30, adjacent the control flow aperture 14, such that fuel flowing through the filter 16 subsequently flows through the control flow aperture 14 to the nozzle control valve.

[0038] Approximately spherical fuel contaminant particles having a diameter which is larger than the width W of the slots cannot pass through the filter 16. Contaminant particles having an irregular shape, wherein a smallest dimension of the particle is larger than the length L of the slots 20, will also be prevented from passing through the filter 16.

[0039] It is not necessary for a dimension of the filter orifices to be smaller than the smallest fuel contaminant particles. As one of the dimensions of the filter orifices is less than the nozzle control lift value, the only contaminant particles which are able to pass through the filter 16 and subsequently through the nozzle control valve, are smaller than the lift of the nozzle control valve. Damage to the seat of the nozzle control valve which would be caused by contaminant particles which are of a size similar to the lift of the nozzle control valve is thereby avoided.

[0040] The filter 16 is located in a main fuel path, i.e. in the path of the primary supply of fuel which flows between the inlet aperture 12 and the nozzle cavity 56. Any contaminant particles in the main fuel flow which are too large to pass through the filter 16, are flushed away from the upstream surface of the filter 16, i.e. the external surface of the tube forming the midsection 26 of the filter 16, by swirl of the primary fuel flow. Particles of such size are therefore carried by the fuel flowing into the nozzle cavity 56, and are subsequently flushed out of the nozzle outlet openings.

[0041] The diameter of the filter 16, and the length, width and number of the slots 20 may vary. In one particular embodiment, the midsection 26 has a diameter of 1.5 mm, and is provided with 2000 slots 20, each having a width of 5 microns and length of 200 microns. Accordingly, the width of the slots 20 is less than a typical value of lift of the nozzle control valve of, for example, 10 to 20 microns.

[0042] In particular examples of the present invention, one dimension of each filter orifice is between one half and one quarter of the size of the control valve lift.

[0043] In one particular embodiment, filter 16 is provided with 16 slots of 5 microns width by 6 mm length. This filter has four times the flow area of the control seat and results in a pressure drop across the filter of approximately 1/16th.

[0044] In further alternative embodiments, the filter 16 could be formed by a small clearance between two components, such that a singular filter orifice is formed between the components. In this embodiment, the dimension of the filter orifice which is smaller than the known lift of the nozzle control valve comprises the clearance between the two components.

[0045] Alternatively, the filter orifices could be formed as fine holes or other perforations, machined into a surface either of a filter 16 as illustrated in the figures, or into an alternative separate component located in the piston guide 30. In this embodiment, the at least one dimension which is smaller size of the known lift of the control valve is the maximum diameter of the holes or other perforations. Approximately spherical holes having a diameter larger than the maximum diameter of the holes or other perforations cannot pass through the filter 16. Furthermore, any fuel contaminant particles which are of an irregular shape, wherein the largest dimension of the particle is larger than the maximum diameter of the holes or perforations, are also prevented from passing through the filter 16.

[0046] Alternatively, the filter orifices could be formed as slots or holes, machined into a surface either of an existing component of the injector 2. In this embodiment, the at least one dimension which is smaller size of the known lift of the control valve is the width of the slots, or the diameter of the holes.

[0047] The filter 16 of the present invention may be used in an injector 2 wherein the control valve comprises a two-way control valve, or a three-way control valve wherein the flow requirement is minimized due to efficient use of control fuel.

REFERENCES

[0048] 2 injector [0049] 12 injector inlet aperture [0050] 14 control flow aperture [0051] 16 filter [0052] 20 slots [0053] 22 filter cap [0054] 24 filter base section [0055] 26 filter midsection [0056] 30 piston guide [0057] 50 control chamber [0058] 52 (region of) nozzle control valve [0059] 56 nozzle cavity [0060] 58 needle piston [0061] A direction of flow into injector [0062] B direction of flow into control valve [0063] L length of slots [0064] W width of slots