GB2172652A

GB2172652A - A fuel injector for compression ignition engines

Info

Publication number: GB2172652A
Application number: GB08507131A
Authority: GB
Inventors: Henry Edwin Woodward
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-03-19
Filing date: 1985-03-19
Publication date: 1986-09-24
Also published as: GB8507131D0; GB2172652B

Abstract

A valve member 8 is movable outwardly by fuel pressure in an annulus 4 against the bias of a spring 7 and combustion chamber pressure on the end face 11. Outlets 17 or a central outlet (17A, Fig. 3) are opened as the member 8 moves beyond the end 18 of the injector body 18 or over the bevelled face (33) of a central fixed pintle (32) within the central outlet. A check valve 15 (15A, Fig. 3) opens to permit fuel flow to the outlets 17(17A) and during injector provides for pressure increase in the chamber 16 between the check valve and the outlets to prevent injector dribble. Different forms of outlet and spray direction and described. <IMAGE>

Description

SPECIFICATION A fuel injector for compression ignition engines The invention provides for improved injection features in all types of compression ignition engines but particularly for direct injection engines.

In conventional injectors the nozzle starts to close when fuel pressure falls to a pre-determined level after the fuel pump has ceased to deliver fuel, the fuel pressure then continues to fall during the period taken for the nozzle to close. During this period of falling fuel pressure the gas pressure in the combustion chamber rises due to continued compression and/or combustion. Consequently the positive pressure difference between fuel and gas, required to generate sufficient fuel velocity in the spray to cause adequate atomisation, falls and the degree of atomisation suffers with the result that the relatively large droplets of fuel at the end of injection do not have sufficient time to burn completely. This impairs the efficiency of the combustion cycle and produces smoke in the exhaust.In extreme cases fuel pressure drops below the level of the gas pressure before the nozzle closes, then 'blow back' occurs in which case hot gas enters the nozzle causing carbonisation of fuel therein and fouling of the internal parts of the nozzle, this fouling causing deterioration of operation of the injection process.

A second feature of conventional injectors is that they have a fixed orifice area with the result that low fuel flow rate at low load causes inadequate atomisation, and high fuel flow rate at high load causes high pressure which imposes excessive mechanical loads on the engine. This feature has been overcome in Indirect Injection Engines by the use of the known Pintle nozzle in which an extension of the nozzle valve forms a shaped movable plug in a single orifice on the axis of the nozzle, the shape being arranged to vary the effective orifice area as the nozzle opens. The Indirect Injection Engine suffers from excessive pumping losses which makes it less efficient than the Direct Injection Engine. Also the I.D. Engine has higher heat loss than the D.l. engine, which makes it more difficult to start when cold.

Attempts to simultaneously control the area of the multiple orifices required by the more efficient D.I. engine, by a Pintle inside the sac partially blocking the inner ends of the orifices, have been unsuccessful because the major resistance to fuel flow, hence the highest fluid velocity, was inside the nozzle and not at the point where the fuel entered the combustion chamber.

The present invention provides an improved injector by control of orifice area to match engine load, the control being at the orifice outlets so that there are no significant pressure losses within the injector, and by providing increased injection pressure at the orifices during the closing action of the nozzle.

A further feature of the invention is that the effective orifice cross section can be made a shape other than circular with a major and minor axis and, either axis can be in line with, transvers to, or at some selected angle to the direction of air swirl.

The invention provides for a liquid fuel injector for an internal combustion engine, constructed and arranged so as to match orifice area to the rate of fuel supply, the point of area control being at the orifice outlet so as to avoid significant pressure losse within the injector, the mechanism being particularly suitable for multi-orifice injectors but being adaptable also for single orifice injectors.

The invention also provides for a liquid fuel injector for an internal combustion engine, including a nozzle section which starts to close after fuel supply to the nozzle ceases and the pressure of said fuel supply drops to a level controlled jointly by a main spring and the prevailing gas pressure in the combustion chamber, and in which the closing action of the nozzle generates an enhanced pressure at the end of injection causing finer atomisation of the last stage of injection with consequent reduction of the time required for evaporation and combustion.

The invention further provides for a liquid fuel injector for an internal combustion engine which may be integral with, or separate from, a pump which supplies a timed and metered supply of fuel, said injector containing a nozzle barrel component which is urged outwardly by both a main spring and by gas pressure in the combustion chamber, said nozzle barrel being of cylindrical form but closed at the outer end adjacent to the combustion chamber but having one or more orifices in its end face or in the periphery adjacent to the end face, there geing valving means within said nozzle barrel to prevent the passage of fuel or gas either way when the nozzle barrel is in the closed position, and to allow free passage of fuel towards the combustion chamber when high pressure in the fuel supply causes the nozzle barrel to move away from its seated position.

The cylindrical outer surface of the nozzle barrel is a close sliding fit in a bore in the injector body and a high pressure seal is provided to prevent the escape of fuel from within the injector body to the combustion chamber.

Said nozzle orifices in the periphery of the nozzle barrel are completely or partially covered at their outer ends when the barrel is in its seated position, by the end of said bore in the injector body or by a separate nozzle sleeve, and gradually uncovered as the barrel moves away from its seated position. For an orifice in the end face of the nozzle sleeve, a probe, integral with or attached to the station ary central part of the injector, projects through the orifice and both probe and orifice are shaped so that the effective flow area is completely or partially restricted when the valving means within the nozzle barrel is seated, and the effective flow area is increased as the barrel moves away from its seated position.The complete or partial sealing of the orifices, at their outer ends, between injections, prevents exudation of fuel into the combustion chamber from the space between said valving means and the orifices, so reducing the accumulation of carbon on the nozzle surface. Said sealing of the orifices also prevents combustion gases entering the space between the valving means and the orifices so preventing fuel degradation within said space and orifices and accummulation of carbon therein. Reduction of carbon accumulation on the surface and in the orifices, or any other parts of the nozzle, prolongs the useful service life of the injector and extends the intervals required between maintenance of the injector.

The invention still further provides for valving means within the injector which cause the injector to start to open when fuel pressure, acting on a defined area of a movable component, overcomes the combined forces of the main spring and of gas pressure in the combustion chamber acting on a defined external area of a component of the injector, and when the injector has started to open, the fuel pressure acts on an additional defined area within the injector to ensure adequate opening, and when fuel supply pressure falls to allow said spring and gas forces to close the injector, the closing action is resisted solely by pressure of fuel, in a cavity between said valve means and said orifice(s), which acts on an area which is smaller than the area on which fuel pressure acts to open the injector, also smaller than the area acted upon by gas pressure to urge the injector closed, with the result that fuel pressure generated in said cavity is substantially higher than the fuel pressure required to open the injector, also substantially higher than gas pressure. The fuel trapped in said cavity is injected into the combustion chamber through the said variable area orifice(s) at said substantially higher pressure as the injector closes to terminate injection, This substantially higher pressure ensures that the final phase of injection is finely atomised to provide for rapid atomisation and combustion of the fuel.

With the above described injector an increase of gas pressure in the combustion chamber causes an increase of fuel pressure required to open the injector, which is opposite to the feature of known injectors in which a rise of gas pressure reduces the fuel pressure required to open the injector. These differing characteristics make injectors covered by this invention less liable than known injectors to re-open as a result of secondary pressure pulses which occur in the fuel supply passages.

The injector is particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a section through one form of the injector according to the invention and having multiple orifices in the periphery of the nozzle barrel, and in which leak-off arrangements are unnecessary because the main spring chamber is pressurised.

Figure 2 shows variations to improve the form and direction of multiple fuel sprays, and an alternative seal housing.

Figure 3 is a section through another form of the injector having an orifice in the end face of the nozzle barrel.

Figure 4 shows variations of orifice and groove configurations which provide for adjustment of spray form to improve fuel-air mixing.

Figure 5 is a variation of the injector in which the main spring chamber is vented to low pressure by leak-off via known methods.

Fuel oil from an injection pump enters at the inlet 1, and passes down the central passage 2. and angled passages 3. to the annulus 4.

from which it can pass through passages 5.

to the space 6. housing the main spring 7.

The fuel pressure then exerts a downward force on the nozzle barrel 8. acting over the annular area between the lower guide diam. 9.

and the seat 10. This force is resisted by cylinder gas pressure acting upward on the end face 11 of the nozzle barrel 8. and by the main spring 7. which also acts upward on the barrel. When the hydraulic force due to the fuel exceeds the combined gas and spring forces, the barrel moves downward to allow fuel to flow to the annular space 12. and through passages 13. and 14. then past the check valve 15. to the space 16. Fuel pressure then acts downward on the whole of the area within the guide diam. 9. to increase the downward force on the barrel to cause a definite opening at the seat 10. also uncovering the outer ends of the orifices 17. by the lip 18. If the injection quantity is small as at low load, or the injection rate is low as at low speed, then the orifices will open only sufficiently to suit the prevailing conditions. As injection rate is increased the orifice area is also increased to maintain a pressure differential, between fuel and gas, which is always adequate for good atomisation whilst avoiding the necessity for excessive pressure at high load and speed.

An increase of gas pressure on the face 11.

increases the upward load on the nozzle barrel 8. so requires an increase of fuel pressure to open the injector. This is in contrast to a conventional injector in which gas pressure assists in nozzle opening so that an increase in gas pressure reduces the fuel pressure re quired to open the nozzle, so reducing the initial and subsequent pressure differential between the fuel and gas. Since the fuel pressure required to re-open the new nozzle increases when gas pressure is increased, the nozzle is highly resistant to secondary injection.

At the end of injection when pressure falls, at the inlet 1. of the injector, pressure also falls in annulii 4. and 12. the spring chamber 6. and passage 14. The check valve 5. is quickly closed by the pressure in the space 16. assisted by the valve spring 19. The nozzle barrel 8. is then urged upward by the main spring 7. and by gas pressure acting on the end face 11. These combined forces are resisted only by pressure of trapped fuel, in the space 16. which has an area equal to that of the guide diam. 20. This area is much smaller than that between the guide 9. and the seat 10. which was pressurised to open the nozzle, so the trapped pressure in the space 16.

is raised to a much higher pressure than the nozzle opening pressure. Fuel at this high pressure is discharged through the orifices 17.

as the nozzle closes, to cause fine atomisation of the last of the fuel to be injected.

The lip 18. is radially short and terminates in a sharp edge 21. which avoids fuel spreading over the end face 22. of the injector body 23. When it is required that the fuel sprays be directed into specific parts of the combustion chamber, the nozzle barrel 8. may be located in relation to the upper body portion 24. by the dowel 25. The upper body portion is in turn located in relation to the engine cylinder head by the means used to clamp the injector in position. Typically this may be by means of flats 26. which engage with a matching clamp plate (not shown) which bears on the surface 27. to urge the injector downwards against the sealing washer 28. A high pressure seal 32. prevents oil at pressure in the spring chamber from leaking to the combustion chamber. The close fit of the guide 9.

and the buffer cavity 33. in association with the very short time period for which the spring chamber is pressurised, prevent the seal 32. being subjected to the extremes of pressure which occur in the spring chamber.

To facilitate the machining, of the cavities for the high pressure seal 32. and buffer space 33A Fig. 2., and the fitting of the seal, the body part 23. may be shortened and a separate nozzle sleeve 38. be fitted around the lower end of the nozzle barrel 8. This sleeve may be retained in position by the normal clamping means used to hold the injector in the engine, or an additional cap nut may be used.

A refinement consisting of grooves 29. Fig.

2. may be included to provide additional guidance to the sprays. In this case the body part 23. and the nozzle sleeve 38. must also be located in relation to the barrel 8. This may be achieved by moving the dowel 25. Fig. 1 radially outward to the position 25A. where it engages simultaneously with parts 8. 23. and 24. and using a second dowel 39. Fig. 2 between said body and said nozzle sleeve. A washer 40 may be used to keep the seal 32.

in its correct position.

Adjustment of opening pressure is possible by adjustment of the shims 30. Fig. 1. which may be located at either end of the main spring 7.

Adjustment of the relationship between the orifices 17. and the lip 18. or grooves 29.

can be made by adjustment of the shims 31.

This setting enables control of movement of the barrel 8. before the orifices start to open, or a small residual opening of the orifices between injections. These facilities are useful in matching an injector to an engine, however, the dimensions of the components are such that reasonable production tolerances make adjustment of either feature unnecessary at the original assembly or in service. The space 37 between the body 23 and the nozzle barrel 8. controls the maximum displacement, of the nozzle barrrel, which may be limited to prevent complete uncovering of the orifices.

As part of the closing force applied to the nozzle barrel is provided by gas pressure acting on the end face 11. the force required of the main spring 7. is less than is required of the main spring of a conventional injector, so the spring wire diameter may be reduced. This reduces the possible minimum diameter of the whole injector.

Because of the small injector size made possible by this design it should no longer be necessary to locate the injector at an angle to the axis of the engine cylinder as is currently common in two valve engines. However, for existing engines, and the new designs where an angled injector is preferred, the tip may be arranged as at Fig. 2 where the included angle of the orifices 17. can be offset to the axis of the injector. Similarly the lip 18. and grooves 29. may be positioned to match the positions of the outer ends of the orifices.

For I.D. engines and opposed piston engines, or any other type which requires a central orifice in the end of the nozzle, the arrangement shown in Fig. 3. is suitable. The drilling 14A. in the centre piece 24A. is shortened and this centre piece given a conical tip with seat 35. and a probe 32. Fig. 3. which may be an insert as shown or made integral with the centre piece 24A. This probe projects through an orifice 17A. in the end of the barrel 8A. The end of the probe 32. may be tapered or given an inverted conical end as in conventional pintle nozzles. Alternatively, means to deflect the spray may be used such as forming an angled flat 33. which matches with an angled groove 34., at the side of the main orifice 17A.This arrangement gives the required increase of flow area through the ori fice as the nozzle barrel 8A. moves downward, and also deflects the spray a controlled angle from the axis of the nozzle.

To suit this central orifice arrangement the check valve 1 5A is made cylindrical and the conical tip of the centre piece 24A. seats in a conical recess at the top of the check valve to form a sealing seat 35. The lower end of the check valve is conical and forms a sealing seat with the nozzle barrel at 36. This replaces seat 10. in the arrangement of Fig. 1.

In operation the nozzle starts to open when oil pressure, in the spaces 4 and 12A., acting on the annular area between the guide diameter 9. and the seat diameter 35., overcomes the forces of the main spring 7. and of the gas pressure acting on the end face 11 A.

As the barrel moves downward the positive pressure difference between the spaces 12A.

and 16. keeps the check valve on its lower seat 36. so oil flows past the opening seat 35. to raise pressure in the space 16. so increases the opening force to ensure a substantial opening, the degree of opening being matched to the pumping rate, hence to engine power.

At the end of injection, when pump spill causes a reduction of pressure in the spaces 4. and 12A. the reversal of the pressure difference across the check valve 15A. causes the valve to move upward to seat at 35. so trapping fuel in the space 16. which is pressurised by the combined forces of the main spring 7. and gas pressure acting on the end face 11 A. Because of the small cross sectional area of the space 16. a very high pressure is generated therein as the barrel moves upward to terminate injection when stopped by the seat at 36. This very high pressure gives the required fine atomisation for the last phase of injection.

It is the prime function of a fuel spray to create rapid mixing of fuel and air. With the circular orifice common to conventional injectors the ratio of spray surface area to core volume is at the minimum. With an injector constructed to the present invention the orifice cross sectional area is shaped according to the overlapping of a circular orifice by either a shaped lip or a shaped plug, and the resulting non-circular aperture produces a non-circular spray section which increases the surface to volume ratio of the spray, and the major and minor axes of the spray may be positioned in relation to the direction of air swirl to have the optimum effect on combustion.Three possible variations are shown in Fig. 4. in which 29.1, 29.2 and 29.3 show alternative forms of the grooves in the lip of the nozzle sleeve 38, and C1, C2 and C3, show relative locations of the orifice 17. in the nozzle closed position, and 01, 02 and 03, show relative locations of the orifice 17 in the Nozzle fuliy open position. Arrangement 4.1 provides a dense circular spray for maximum penetration.

Arrangement 4.2 places the major axis of the orifice in line with air motion and arrangement 4.3 places the minor axis of the spray in line with air motion. Variations between these relative locations vary the angles between the spray axes and the direction of air motion, also different forms of grooves 29. are possible.

When the orifice 17. is not completely uncovered at the maximum opening of the nozzle the machined orifice in the nozzle barrel may be made a much larger diameter than the required effective diameter of the orifice in service. This feature greatly facilitates machining, reduces the effect of any carbon formation which might occur, and reduces internal flow losses before the effective orifice.

The forms of injector described in Fig. 1-4 possess the advantage that no leak-off arrangements are required in the injector or the associated hydraulic system. In Fig. 5. the main spring chamber 6A is vented via passage 40. to the leak pipe 41. which passes through the injector cap 42. Although this adds slightly to the complexity of the system it enables a reduction of diameter of the injector and improves the ability of the designer to adjust the relationship of spring force/nozzle opening, hence the relationship of injection pressure/nozzle opening. Also the amount of fuel trapped between the seat of the check valve 15B and the orifices, between injections, is reduced.

Fuel entering the injector at the inlet union 1A passes through the passage 2A. to space 42. housing the check valve return spring 19A., then to the annular passage 45. between the bore of the inner guide 43. and the check valve extension rod 44. from where it can pass through thesradial passages 46. to pressurise the annular space 47. between said inner guide 43. and the bore of the nozzle barrel 8B. Fuel in the annular space 45. also pressurises part of check valve 48. within the seat circle 52. causing a downward load which is transmitted to the nozzle barrel 8B via the nozzle seat 49. The annular space 47.

separates a lower guide diam. 50. and an upper guide diam. 51, 51A. As shown on the right hand side of Fig. 5. guide diam. 51A. is larger than guide diam. 50. so the pressurised oil in the space 47. adds to the downward load on the nozzle barrel 8B. As shown on the left hand side of Fig. 5. the upper guide diam. 51. is the same as the lower guide diam. 50. so the oil pressurised in space 47.

applies no downward or upward load on the nozzle barrel 8B. Adjustment of the guide diam. 51A. and seat circle diam. 52. controls the area of the nozzle sleeve 8B. which is subjected to fuel oil entering the injector via inlet 1A.

The guide diam. 51A. can be made smaller or larger than the diam. 9A. of the guide between the nozzle sleeve 8B. and the injector body 23A. When made smaller as shown in Fig. 5. the downward force, exerted on the nozzle barrel 8B. by fuel oil entering the injector at inlet 1. on the nozzle barrel 8. of Fig.

1. This reduced force due to fuel pressure in the arrangement of Fig. 5. reduces the loading required of the main spring 7A. with two advantages. Firstly reduced wire diam. reduces the spring O.D. hence the l.D. of the spring housing 6A. Furthermore, as this spring housing is vented to low pressure its wall thickness may be reduced giving a twofold reduction of the O.D. of the injector body 23A.

which facilitates accommodation in an engine cylinder head. Secondly the designer has greater latitude in selection of spring rate in order to control the relationship of injection pressure/nozzle opening.

Two methods of accommodating leak-off fuel are illustrated in Fig. 5. Firstly a leak-off pipe 53. passes through the injector cap 54.

with the O.D. of the pipe sealed to the cap by any known means. A vertical drilling 52. connects the main spring chamber 6A. with said leak-off pipe. Alternatively a seal (not shown) may be fitted between the injector and the housing into which it is fitted in the engine, then leak-off fuel may drain out of port 55. to the space surrounding the injector then away through passages in the engine structure.

The injector as described in Figs. 1-5. is suitable for use with a fuel pump which supplies an injector, or a multiplicity of injectors, through high pressure pipes. For engines having separate, combined pump and injector units for each cylinder, all components below the level of line X---X, Fig. 1. may be directly attached to the pumping section in the same manner as conventional nozzles are attached to known pump injector pumping sections.

Claims

CLAIMS 1. A liquid fuel injector for compression ignition engines, having one or more orifices, the area of which are automatically controlled to suit both the fuel flow rate, and the pressure differential between the fuel and the combustion chamber gas. 2. A liquid fuel injector as claimed in claim 1. in which the location of control of orifice area is at the outer end(s) of the orifice(s) and this area is always the smallest flow area throughout the injection system, so that parasitic flow losses within the system are minimised, and the energy dissipated in atomising the fuel is maximised. 3. A liquid fuel injector as claimed in claim 1. in which opening of the injector is resisted both by a spring force, and by the force of pressure of gas within the combustion chamber acting on a defined outer area of a component of the injector, and opening of the injector is caused by pressure of fuel acting on a defined area of a component within the injector, said area within the injector being smaller than said outer area so that the injector can only be open when fuel pressure is substantially greater than gas pressure. 4. A liquid fuel injector as claimed in claims 1.-3. in which the closing action of the injector generates a fuel pressure within a space between a nozzle valve and the orifice(s), said fuel pressure being substantially higher than the prevailing pressure of gas in the combustion chamber. 5. A liquid fuel injector as claimed in claims 1.-4. in which the effective cross section of the orifice(s) may be non circular, and of variable shape as the orifice(s) open in order to adjust the relationship between orifice area and penetration of the fuel spray into the combustion chamber 6. A liquid fuel injector as claimed in claim 5. in which the major and minor axes of the area of cross section of the fuel spray may be located at any desired angle to the direction of movement of gas within the combustion chamber. 7. A liquid fuel injector as claimed in claims 1.-6. which may be constructed with a pressurised main spring chamber, then leak-off arrangements are not required. Alternatively the main spring chamber may be vented then leak-off arrangements by known methods are required. 8. A multi-orifice version of the injector as claimed in claims 5.-6. in which control of orifice area and shape is achieved by means of relative motion between a sliding component containing drilled orifices, and a surrounding sleeve with a lip or cut-outs which gradually uncover the orifices as the sliding component moves. 9. A single orifice version of the injector as claimed in claims 5.-6. in which control of orifice area and shape is achieved by means of relative motion between a sliding component containing a drilled or shaped orifice in its end face, and a matching contoured probe extending through said orifice. 10. A liquid fuel injector substantially as described herein with reference to Figs. 1.-5. of the accompanying drawings. CLAIMS Amendments to the claims have been filed, and have the following effect: New or textually amended claims have been filed as follows:

1. A fuel injector for l.C. engines of the type in which a piston component containing orifices is moved by fuel pressure into the combustion chamber during injection against the restraining forces of a return spring and of gas pressure acting on the end face of the piston component, said fuel injector having specific means to control the fuel-air mixing in the combustion chamber by controlling the direction and cross sectional area, shape and alignment of the sprays, and by eliminating fuel leakage from, and gas blow-back into, the injector between injections.

2. A fuel injector as in claim 1. in which prevention of leakage along the clearance between the piston component and its guide is achieved by means of a sealing component located at some point along the guide.

3. A fuel injector as in claim 1. in which the prevention of leakage along the clearance between the piston component and its guide is achieved by arranging that the inboard end of the guide is always connected to a space which is maintained at a low pressure by venting.

4. A fuel injector as in claim 1. which incorporates the known device that movement of the piston component causes orifices in its periphery to be progressively uncovered by the end of the guide means, in which cut-outs in the end face of the guide are shaped and located in relationship to said orifices so as to control the direction of the sprays and the alignment of the major axes of the sprays in relationship to the air motion in the combustion chamber.

5. A fuel injector as in claim 1. which incorporates an orifice in the end face of the piston component said orifice being normally plugged by a fixed spigot, the internal and external shapes of the orifice and plug respectively being arranged so that outward movement of the piston component opens a channei between the orifice and the plug to form an effective spray orifice, said channel may be deflected at an angle to the axis of the injector.

6. A fuel injector as in claims 1.-5. which contains sealing valve means which is opened by the initial movement of the piston component to allow fuel at high pressure to flow to a space within the piston component to act on an additional area so substantially increasing the force tending to move the piston component thus ensuring swift opening of the orifices.

7. A fuel injector as in claims 1.-5. in which a non return valve in the piston component closes when the supply of pressurised fuel to the injector ceases, said valve closure causing the trapping of a discrete quantity of fuel between the valve and the injection orifices, said fuel being discharged through the injection orifices into the combustion chamber by the return movement of the piston component under the influence of the return spring within the injector and of gas pressure acting on the end face of the piston component.The cross section of the cavity containing the trapped fuel being smaller than the relevent areas of the piston component subjected to fuel pressure either before or during the preceding stages of the injection process, the return motion of the piston component generates a higher injection pressure for the last stage of injection than occurred during the preceding stages, so providing finest atomisation for rapid evaporation and combustion of the last of the fuel charge.

8. A fuel injector as in claims 1.-5. in which a valve makes sealing contact with a part of the piston component immediately inboard of the injection orifices to terminate injection and to prevent any seepage of fuel from the injector into the combustion chamber between injections. Said sealing contact also serves prevent gas blow-back into the injector between injections.

9. A fuel injector as in claims 7. and 8. in which a single valve with two sealing edges performs the functions described separately in claims 7. and 8.

10. A fuel injector for l.C. engines containing any combination of the features described in claims 1.-9.

11. A fuel injector for l.C. engines constructed substantially as described herein with reference to the accompanying drawings 1.-5.