CLIAMS:We Claim
1 A fuel injector (100) comprising:
a nozzle holder (105) comprising a bore (105a) to accommodate a spring (125);
a nozzle (110) fitted to one end of said nozzle holder (105), said nozzle (110) having a bore(112) accommodating a needle (114) in said bore (112) and said bore 112 being eccentric with respect to said bore (105a) when said nozzle (110) is fitted to said nozzle holder (105);
characterized in that
said bore (105a) of said nozzle holder (105) having two portions (105c) and (105d) of varying diameter; and
a pressure bolt (115) located in portion (105d) when said nozzle holder (105) and said nozzle (110) are fitted to each other and said pressure bolt (115) comprising a projection (115a) such that said pressure bolt (115) and said needle (114) are in contact through said projection (115a).

2 The fuel injector (100) as claimed in claim 1, wherein said pressure bolt (115) is within said bore (105a) and said pressure bolt (115) is eccentrically located with respect to an axis of said needle (114),

3 The method as claimed in claim 1, wherein a lock pin (120) is used to fit said nozzle holder (105) to said nozzle (110).

4 The method as claimed in claim 1, wherein said pressure bolt (115) having a guide element (115b) for holding a spring (125) in position

5 The fuel injector (100) as claimed in claim 1, wherein profile of said pressure bolt (115) is such that said pressure bolt (115) is adapted to move along the bore (105a) passing through portion (105c) and (105d) of said bore (105a) of said nozzle holder (105).
,TagSPECI:Complete specification: The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
[001] This invention relates to fuel injector.

Background of the invention
[002] A fuel injector is used for delivering high pressure fuel into a combustion chamber of an engine. Conventional fuel injectors comprise a nozzle holder that includes a bore, a nozzle and a distance piece. The bore of the nozzle holder houses a spring and a pressure bolt. The nozzle holder is in communication with the nozzle through the distance piece.

[003] The nozzle comprises a needle within. During fuel injection, the needle lifts against the direction of the spring force so that high pressure fuel is injected into the combustion chamber.

[004] The distance piece is located between the nozzle holder and the nozzle. The distance piece enables alignment of the nozzle holder and the nozzle so that during the needle lift, the force exerted by the needle acts on the spring and further, the spring force acts on the needle after fuel injection. However, there is still a need to improve design of the fuel injector to make it cost efficient.

[005] An US patent application, US5413281 describes a fuel injector with the distance piece being located between the nozzle holder and the nozzle.

Brief description of the accompanying drawings
[006] Figure 1 illustrates a fuel injector in accordance with an embodiment of the present disclosure; and
[007] Figure 2 illustrates a fuel injector according to prior arts.

Detailed description

[008] Figure 1 illustrates a fuel injector 100 in accordance with an embodiment of the present disclosure.

[009] In accordance with this disclosure, the fuel injector 100 comprises a nozzle holder 105 comprising a bore 105a. The fuel injector 100 also comprises a nozzle 110 fitted to one end of the nozzle holder 105. The nozzle 110 having a bore 112 accommodating a needle 114 in the bore 112 and the bore 112 being eccentric with respect to the bore 105a when the nozzle 110 is fitted to the nozzle holder 105. The fuel injector 100 is characterized by the bore 105a of the nozzle holder 105 having two portions 105c and 105d of varying diameter and a pressure bolt 115 located in portion 105d when the nozzle holder 105 and the nozzle 110 are fitted to each other and the pressure bolt 115 comprising a projection 115a such that the pressure bolt 115 and the needle 114 are in contact through the projection 115a.

[0010] The nozzle holder 105 and the nozzle 110 are fitted to each other through a lock pin 120. The bore 105a in the nozzle holder 105 houses the pressure bolt 115 and a spring 125. The bore 105a has two portions 105c and 105d of varying diameter. The pressure bolt 115 and the spring 125 are arranged inline with respect to the axis of the bore 105a. The axis of the bore 105a is eccentric with respect to the bore 112 of the nozzle 110. One end of the pressure bolt 115, is in contact with the spring 125 that is arranged inside the bore 105a. The bore 105a guides the spring 125 to move within. The working of the fuel injector 100 in accordance with an embodiment of this disclosure is explained in the below paragraphs.

[0011] The nozzle holder 105 has a fuel path 105b that is in fluid communication with a fuel path 110b of the nozzle 110. High pressure fuel passes from the fuel path 105b to the fuel path 110b in the nozzle 110. When the pressure of the fuel striking the needle 110a overcomes spring force of the spring 125, the needle 114 is lifted against direction of the spring force. When the needle 114 lifts, the high pressure fuel is injected through nozzle openings present in the nozzle 110. When the pressure of the fuel is lesser than the spring force, the needle 114 drops down thereby closing the nozzle openings.

[0012] The force exerted by the needle 114 against the spring 125 is through the pressure bolt 115. The pressure bolt 115 is located in portion (105d) when the nozzle holder 105 and said nozzle 110 are fitted to each other through the lock pin 120. . The profile of the pressure bolt 115 is such that it can move between the portion 105c and 105d of the bore 105a in the nozzle holder 105. Extent of movement of the pressure bolt 115 between the portion 105c and 105d of the bore 105a defines a needle lift length. Such profile of the pressure bolt 115 prevents the needle 114 from lifting beyond a maximum lift.

[0013] The pressure bolt 115 comprises a projection 115a at one end such that the pressure bolt 115 and the needle 114 are in contact through the projection 115a. The projection 115a creates a point contact with the needle 114 so that the spring force exerted by the spring 125 acts on the needle 114. The point contact enables spring force to be exerted on the needle 114 so that the needle 114 closes the nozzle openings when pressure of fuel is lesser than the spring force. The point contact between the pressure bolt 115 and the needle 114 also enables the force exerted by the needle 114 to act against the spring force during needle lift. A point contact is established against a surface contact because in case of surface contact most of the spring force is lost since the spring force should overcome the entire surface area before the force acts on the needle 114. Hence, the projection 115a provided in the pressure bolt 115 in this disclosure is such that it establishes a point contact with the needle 114.

[0014] In one example, the shape of the projection 115a may be semi circular. However, it should be noted that the shape of the projection 115a is not limited to semi circular and the projection 115a can be of various other shapes that provides point contact with the needle 114. The projection 115a may be machined along with the pressure bolt 115 or the projection 115a may be a separate element integrated to the pressure bolt 115 using various contact process, such as welding, soldering and the like.

[0015] Another end of the pressure bolt 115 is in contact with the spring 125 through a guide element 115b of the pressure bolt 115. The guide element 115b of the pressure bolt 115 guides the spring 125 to move along the bore 105a of the nozzle holder 105. The profile of the pressure bolt 115 is such that the pressure bolt 115 can move along the bore 105a passing through the portions 105c and 105d of the bore 105a. The portions 105c and 105d of the bore 105a enables the movement of the pressure bolt 115 to a particular extent. The extent upto which the pressure bolt 115 can move within the bore 105a defines the needle lift length. The profile of the pressure bolt 115 is such that it acts as a stopper thereby preventing lifting of the needle beyond maximum lift.

[0016] In the prior art, a distance piece 205 is present between the nozzle holder 210 and the nozzle 215. The fuel flows along the fuel path in the nozzle holder 210 and then through the fuel path in the distance piece 205 and then flows through the fuel path in the nozzle 215 as shown in Figure 2. Profile of the distance piece 205 is such that when the needle 220 moves in the direction against the spring force, the needle movement stops once maximum needle lift is attained as shown in Figure 2.

[0017] In the present disclosure, the distance piece is eliminated and the nozzle holder 105 is directly fitted to the nozzle 110 using a lock pin 120. Since the nozzle holder 105 is directly fitted to the nozzle 110, the axis of the nozzle holder 105 is made eccentric with respect to the axis of the nozzle 110 so that the fuel path 105b of the nozzle holder 105 is inline with the fuel path 110b of the nozzle 110. Such eccentric arrangement of the nozzle holder 105 with respect to the nozzle 110 allows fuel to flow continuously from the nozzle holder 105 to the nozzle 110 in the direction indicated by the arrow marks shown in Figure 1.

[0018] In the present disclosure, the distance piece is eliminated. Hence, the overall cost of the fuel injector 100 is reduced. Also, in the present disclosure, the needle 114 does not include a needle pin which in conventional fuel injectors is used for providing a point contact with a conventional pressure bolt. Therefore, the cost of machining the needle 114 is reduced thereby reducing overall cost of the fuel injector 100.

[0019] 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 process used in machining the pressure bolt, the nozzle holder, the nozzle and the needle are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.

[0020] CLAIMS
We Claim
1 A fuel injector (100) comprising:
a nozzle holder (105) comprising a bore (105a) to accommodate a spring (125);
a nozzle (110) fitted to one end of said nozzle holder (105), said nozzle (110) having a bore(112) accommodating a needle (114) in said bore (112) and said bore 112 being eccentric with respect to said bore (105a) when said nozzle (110) is fitted to said nozzle holder (105);
characterized in that
said bore (105a) of said nozzle holder (105) having two portions (105c) and (105d) of varying diameter; and
a pressure bolt (115) located in portion (105d) when said nozzle holder (105) and said nozzle (110) are fitted to each other and said pressure bolt (115) comprising a projection (115a) such that said pressure bolt (115) and said needle (114) are in contact through said projection (115a).

2 The fuel injector (100) as claimed in claim 1, wherein said pressure bolt (115) is within said bore (105a) and said pressure bolt (115) is eccentrically located with respect to an axis of said needle (114),

3 The method as claimed in claim 1, wherein a lock pin (120) is used to fit said nozzle holder (105) to said nozzle (110).

4 The method as claimed in claim 1, wherein said pressure bolt (115) having a guide element (115b) for holding a spring (125) in position

5 The fuel injector (100) as claimed in claim 1, wherein profile of said pressure bolt (115) is such that said pressure bolt (115) is adapted to move along the bore (105a) passing through portion (105c) and (105d) of said bore (105a) of said nozzle holder (105).
Dated this 31st day of March, 2015
(Digitally signed)
Kartik PUTTAIAH
Patent agent of the Applicants (IN/PA-1809)