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] The present disclosure relates to the field of a fuel injector and a nozzle retaining nut for a fuel injector.
Background of the invention
[0002] Engineers are often looking for ways to reduce or eliminate combustion gas leakage around fuel injectors mounted in an engine. Combustion gas leakage is particularly problematic in the case of diesel type engines since the injector bores in the head of the engine open directly to the combustion space.

[0003] In the past, adequate sealing around the injectors has been accomplished through the use of a combination of malleable metallic (copper, brass, etc.) sleeves, elastomeric sealing washers and substantially large clamping forces pushing the individual injector into its bore in the engine.

[0004] Because of the necessary dimensional tolerancing of the injector's outer surface, injector bore in the engine and the malleable metallic sleeve, combustion gas leakage can still sometimes occur despite the relatively high clamping forces used to attach fuel injectors to a given engine.

[0005] In other words, combustion gas leakage can occasionally occur around one or more fuel injectors of an engine despite the fact that all of the fuel injector clamps have been torqued down with the same relatively high magnitude. In addition, engine vibrations and/or thermal loads can sometimes cause one or more injector clamping bolts to slightly loosen over an extended period of time, resulting in combustion gas leakage.
[0006] Conventional washer materials can typically not withstand the relatively high temperatures and cyclic pressures encountered near the tip of a fuel injector. Conventional sealing washer usually can only withstand temperatures up to about 300° F., and at the higher end of this scale the useful life of a given O-ring is relatively short.

[0007] In the existing fuel injector assembly according to the state of the art, there is surface contact between nozzle retaining nut face and sealing washer. Depending on the surface roughness of this interface and the availability of space between them, there is possibility of combustion gas leakage onto injector outer body surface.

[0008] Efforts have been made in the related prior art to provide different solutions for preventing the leakage and escape of combustion gases in internal combustion engines. For example, a US patent no. US 8813727 B2 provides a sealing assembly for a pressurized fuel feed system for an internal combustion engine. The seal assembly comprises providing a fuel conduit having a fluid flow passage therethrough for conveyance of a pressurized fuel-containing gas in a general fluid-flow direction with a first sealing surface disposed on the fuel conduit. A second sealing surface engages with the first sealing surface, such as to provide a fluid-tight connection preventing pressurized gas from leaving the fluid flow passage. The said first and second sealing surfaces are substantially perpendicular to the general fluid-flow direction. An O-ring is disposed between the first sealing surface and second sealing surface, the O-ring being compressed by the first and second sealing surfaces to form said fluid-tight connection. Preferably the O-ring is subjected to a squeeze of at least 40%, more preferably 50%, when the first and second sealing surfaces are coupled together. However, the invention in the prior art will not be able to prevent the escape of the combustion gases through the imperfections in the contact surface between the sealing surfaces.

Brief description of the accompanying drawings
[0009] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0010] Figure 1 illustrates a fuel injector (200) according to an embodiment of the invention.

[0011] Figure 2 illustrates a magnified sectional view of the embodiment of the invention.

Detailed description of the drawings
[0011] There is provided an internal combustion engine in which the cylinders (not shown) are covered by a cylinder head (not shown) and each cylinder is provided with a fuel injector (200) and a combustion chamber (220), the combustion chamber (220) volume of each cylinder being formed predominantly in the associated piston (not shown). The fuel injector (200) is situated in the side wall of the cylinder adjacent to the cylinder head. The portion of combustion chamber (220) formed in the piston is concentrated in one part of the crown of the piston so as to form extensive "squish" areas between the cooperating surfaces of the piston and the cylinder head. The cylinder head is provided with a shield (not shown) projecting substantially in the axial direction within the cylinder on the side thereof opposite to the fuel injector (200) and the said shield having an impingement surface facing towards the fuel injector (200) and the fuel injector (200) is arranged to direct a single compact jet of fuel, at a substantially zero angle of divergence, substantially perpendicularly to the said impingement surface, so that the impingement of the fuel jet on the said impingement surface causes fine atomization of the fuel.

[0013] The fuel injector (200) comprises an injector body (not shown), and a nozzle body (215) that is positioned against the injector body such that a fuel inlet flow path (not shown) that is defined in the injector body is in alignment with a fuel inlet flow path (not shown) that is defined in the nozzle body (215). The alignment of the fuel inlet flow path that is defined in the injector body with the fuel inlet flow path that is defined in the nozzle body (215) facilitates a flow of fuel from the fuel inlet flow path of the injector body to the fuel inlet flow path of the nozzle body (215). In one embodiment, during an assembly of the fuel inlet flow path that is defined in the injector body with the fuel inlet flow path that is defined in the nozzle body, a small clearance exists between the fuel inlet flow path that is defined in the injector body and the fuel inlet flow path that is defined in the nozzle body (215). The clearance that is defined between the fuel inlet flow path that is defined in the injector body and the fuel inlet flow path that is defined in the nozzle body (215) facilitates for the flow of fuel that flows from the fuel inlet flow path that is defined in the injector body to the fuel inlet flow path that is defined in the nozzle body (215). From the clearance that is defined between the fuel inlet flow path that is defined in the injector body and the fuel inlet flow path that is defined in the nozzle body (215), the fuel flows to the outer periphery of the nozzle body (215).

[0012] Figure 1 illustrates a fuel injector (200) according to an embodiment of the invention. The fuel injector (200) assembly is configured to be mounted on a cylinder head of an engine and comprises at least a nozzle holder (225) adapted to be mechanically engaged to a nozzle body (215). The nozzle body (215) is adapted to be located within the cylinder head of the engine via a nozzle retaining nut (210). The fuel injector (200) is affixed in position in the cylinder head using a sealing washer (205). The nozzle retaining nut (210) has a tapering surface introduced in its bottom face (210a) when the fuel injector (200) is held in assembly position.

[0012] In the existing design, there is surface contact between nozzle retaining nut (210) bottom face (210a) & sealing washer (215) interface. Depending on the surface roughness of this interface there is possibility of combustion gas leakage onto injector outer body surface.

[0013] In order to arrest the combustion gas leakage, a tapering surface is provided on the nozzle retaining nut bottom surface (210a), which positively arrests the combustion gas leakage onto injector body. The combustion gas leakage is arrested as the provided tapering surface on the bottom surface (210a) of the nozzle retaining nut (210) acts as a leakage stopper. The tapering of the bottom surface (210a) of the nozzle retaining nut (210) is done by a phase grinding machine.

[0014] In the present embodiment, the tapering surface (210a) of the nozzle retaining nut (210) meeting the top end (205a) of the sealing washer (205) is tapered downwards such that the tapered surface (210a) of the nozzle retaining nut (210) meets the tip of the top surface (205a) of the sealing washer (205). Correspondingly, the tapering of the bottom surface (210a) of the nozzle retaining nut (210) is tapered at an upwards angle to meet the nozzle body (215) to provide a fuel path for the leaked combustion gas to flow. In one embodiment, the tapering bottom surface (201a) of the nozzle retaining nut (210) realizes the working of the invention even at an angle of 1 or 2 degrees less than 90 degrees on the nozzle body (215) approximately. This arrangement of the present embodiment creates a line contact between the tapering surface (210a) of the nozzle retaining nut (210) and the sealing washer (205). This tapering does not cause any issue with how the injector is seated in the cylinder head. The top surface of the sealing washer (205a) is flat enough to accommodate the nozzle retaining nut (210) and therefore the injector (200) seats properly. The sealing washer (205) creates enough resistance to not make the injector spring up from the seating. The sealing washer (205) deforms on the tapered surface (210a) thus comfortably holding the injector (200) in place.

[0015] When combustion gas pressure builds up in the combustion chamber (220), the gas flowing upwards through the space available between the nozzle body (215) and the cylinder head, onwards towards the space between the nozzle retaining nut bottom face (210a) and the sealing washer (205) is therefore successfully arrested at the meeting point of the bottom face (210a) of the nozzle retaining nut (210) and in line contact with the sealing washer (215). This, in turn, stops the leaked gas from flowing more upwards to the body of the fuel injector (200).

[0016] The arresting of the leaked combustion gas helps prolong the life of the fuel injector (200) which would otherwise be susceptible to blackening and consecutively corrosion of the body of the fuel injector (200) due to the extreme high temperature of the leaked combustion gas. The arrested combustion gas might cause corrosion of the sealing washer (205), however that is easily replaceable. There is almost no corrosion caused due to the arrested combustion gas on the tapered bottom surface (201a) of the nozzle retaining nut (210a) because the nozzle retaining nut (210) contains a zinc phosphate coating that prevents corrosion.

[0017] Thereby, the thermal load on the rest of the devices of the fuel injection system is also reduced. It also helps reduce power loss as well as avoid safety concerns, because in worst case combustion gas leakage can lead to safety issues like firing. With the life span of the fuel injector (100) and in turn of the fuel injection system prolonged, there will be chances of fewer field complaints.
[0018] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification to the fuel injector is envisaged and form a part of this invention. The scope of this invention is limited only by the claims.
, Claims:We Claim:
1. A fuel injector, for injecting fuel into a combustion chamber (220) of an internal combustion engine, with a nozzle body (215) which is designed to project into the combustion chamber (220) and is clamped to a holding body by a nozzle retaining nut (210) said nozzle retaining nut (210) having a top surface and a bottom surface (210a); and with a sealing washer (205), said sealing washer having a top surface and a bottom surface (205a), for sealing off the combustion chamber (220) from the nozzle body (215) region, characterized in that the bottom surface of the nozzle retaining nut (210) is a tapering surface (210a) that comes in contact with the sealing washer (205).

2. The fuel injector (200) as claimed in claim 1, wherein the tapering surface (210a) of the nozzle retaining nut (210) tapers upwards at an angle to meet the nozzle body (215).

3. The fuel injector (200) as claimed in claim 1, wherein the tapering surface (210a) of the nozzle retaining nut (210) tapers downwards to create a contact with the top surface (205a) of the sealing washer (205).

4. The fuel injector (200) as claimed in claim 1, wherein the contact with the tapering surface (210a) of the nozzle retaining nut (210) and the top surface (205a) of the sealing washer (205) is a line contact.