Claims:We Claim

1. A fuel injector (10), said fuel injector (10) comprising:
a housing (12);
a solenoid (14) circumferentially defined within said housing (12);
a spring member (20) positioned within an opening defined in said solenoid (14), a first end of said spring member (20) positioned against said housing (12);
an armature plate (22) positioned against a second end of said spring member (20), said armature plate (22) adapted to reciprocate within said housing (12);
a first fuel flow passage (24) in flow communication between said armature plate (22) and a second fuel flow passage (26), said first fuel flow passage (24) in flow communication with said second fuel flow passage (26) and defined within said housing (12);
an injector needle (30) having a first end portion (32) and a second end portion (34) positioned within said housing (12), wherein the first end portion (32) of said injector needle (30) is positioned within the second fuel flow passage (26); characterized in that
a taper (38) circumferentially defined around the first end portion (32) of the injector needle (30) such that a gap (40) is defined between the first end portion (32) of the injector needle (30) and a fuel inlet supply path (42).

2. The fuel injector (10) in accordance with Claim 1 wherein fuel that is supplied through the fuel inlet supply path (42) is channeled to the second fluid flow passage (26) via the gap (40) that is defined between the first end portion (32) of the injector needle (30) and a fuel inlet supply path (42), thereby damping the movement of the injector needle (30) within the second fuel flow passage (26) when the injector needle (30) lifts upwardly to deliver fuel from said fuel injector (10).

3. The fuel injector (10) in accordance with Claim 1 wherein an angle of the taper (38) is equal to thirty degrees with respect to a vertical axis.
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a fuel injector, and more specifically to a fuel injector for a fuel injection system.

Background of the invention
[0002] DE 4332837 C1 describes an IC engine fuel injection system. Each nozzle has a throttling pintle between the needle valve and the injection hole, which widens towards the outlet. Thus the free cross-section increases with increasing needle stroke, giving an injection characteristic curve which is generally triangular, with a flat rising flank and a steep falling one. The pintle can be arranged to taper, while the outlet is cylindrical. The opening of the nozzle valve is controlled by the low pressure side of a pressure regulator.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a fuel injector in one embodiment of the invention.

Detailed description of the embodiments
[0004] Figure 1 illustrates a fuel injector 10. The fuel injector 10 comprises a housing 12, a solenoid 14 circumferentially defined within the housing 12. A spring member 20 is positioned within an opening defined in the solenoid 14, a first end of the spring member 20 positioned against the housing 12. An armature plate 22 is positioned against a second end of the spring member 20, the armature plate 22 adapted to reciprocate within the housing 12. A first fuel flow passage 24 is in flow communication between the armature plate 22 and a second fuel flow passage 26, the first fuel flow passage 24 in flow communication with the second fuel flow passage 26 and defined within the housing 12. An injector needle 30 having a first end portion 32 and a second end portion 34 positioned within the housing 12, wherein the first end portion 32 of the injector needle 30 is positioned within the second fuel flow passage 26. A taper 38 is circumferentially defined around the first end portion 32 of the injector needle 30 such that a gap 40 is defined between the first end portion 32 of the injector needle 30 and a fuel inlet supply path 42.

[0005] The fuel injector 10 comprises a housing 12. The housing 12 comprises a solenoid 14 circumferentially defined within a cavity defined within the housing 12. In the exemplary embodiment, the solenoid 14 is circumferentially defined within the housing 12 with a bore defined therethrough. A spring member 20 is positioned within the bore defined in the solenoid 14 such that the first end of the spring member 20 is positioned against the housing 12. The opposite second end of the spring member 20 is secured to an armature plate 22 by means of a fastener. The armature plate 22 is adapted to reciprocate within the housing 12. When the armature plate 22 is energized by supplying it with electric power, the armature plate 22 translates along the direction of the spring member 20. Thereby, the armature plate compresses the spring member 20 against the resistive force of the spring member 20. A first fuel flow passage 24 is in flow communication between the armature plate 22 and a second fuel flow passage 26. The first fuel flow passage 24 is adapted to channel the fuel that is present in the second fuel flow passage 26 when the armature plate 22 translates upwardly. More specifically, when the armature plate 22 translates upwardly against the resistive force of the spring member 20, the first fuel flow passage 24 is opened thereby allowing the fuel to flow there through.

[0006] An injector needle 30 having a first end portion 32 and an opposite second end portion 34 is positioned within the housing 12. The first end portion 32 of the injector needle 30 is positioned within the second fuel flow passage 26. The opposite second end portion 34 of the injector needle 30 is positioned within the housing 12 such that the opposite second end portion 34 of the injector needle 30 is proximate to the spray holes of the fuel injector 10. A taper 38 is circumferentially defined around the first end portion 32 of the injector needle 30. In an exemplary embodiment, the angle of the taper 38 is 30 degrees with respect to the vertical axis. In an alternate exemplary embodiment, the angle of the taper 38 is dependent on the diameter of the fuel inlet supply path 42 to ensure that the fuel from the fuel inlet supply path 42 is properly channeled to the second fuel flow passage 26 via the gap 40 that is defined between the first end portion 32 of the injector needle 30 and the fluid inlet supply path 42. Due to the taper 38 that is circumferentially defined around the first end portion 32 of the injector needle 30, a gap 40 is defined between the first end portion 32 of the injector needle 30 and a fuel inlet supply path 42 that delivers fuel to the second fuel flow passage 26. Fuel that flows through the fuel inlet supply path 42 is channeled to the second fuel flow passage 26 via the gap 40 that is defined between the first end portion 32 of the injector needle 30 and the fluid inlet supply path 42.

[0007] A working of the fuel injector 10 is described as an example. Fuel is supplied to the fuel inlet supply path 42 from a high pressure fuel pump. From the fuel inlet supply path 42, the fuel is channeled to the second fuel flow passage 26. More specifically, the fuel is channeled to the second fuel flow passage 26 via the gap 40 that is defined between the first end portion 32 of the injector needle 30 and the housing 12. When the solenoid 14 is energized by supplying electric power from a battery, the armature plate 22 is translated towards the solenoid 14 by compressing the spring member 20. More specifically, the armature plate 22 is translated upwardly against the resistive force of the spring member 20. Therein, the fuel that is present in the second fuel flow passage 26 flows to the first fuel flow passage 24 due to the higher pressure of fuel that is present in the second fuel flow passage 26 relative to the fuel that is present in the first fuel flow passage 24. The fuel that is channeled to the injector needle from the fuel inlet supply path 42 causes the injector needle 30 to lift upwardly, thereby causing the first end portion 32 of the injector needle 30 to compress against the fuel that is present in the second fuel flow passage 26. This leads to a damped translation of the injector needle 30 in the upward direction. The damping caused to the injector needle 30 by the fuel that is present in the second fuel flow passage 26 causes a deceased quantity of fuel to be injected from the spray holes of the fuel injector 10. Therefore, the fuel that is injected from the spray holes of the fuel injector 10 increases gradually with a reduced slope to finally result in a maximum quantity of fuel that is to be injected from the spray holes of the fuel injector 10. At the end of fuel injection, the solenoid 14 is de-energized by cutting the supply of electric power from the battery. Therein, the armature plate 22 is translated away from the solenoid 14, thereby closing the first fuel flow passage 24. At the same time, the fuel flow to the fluid inlet supply path 42 is terminated, thereby causing the injector needle 30 to return to its original position thereby closing the outlet opening of the spray holes of the fuel injector 10.

[0008] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.