Claims:We claim:
1. A fuel pump (112), comprising:
a barrel (114) with an inlet port (116), and
a plunger (100) with a vertical groove (104) extending from a head (102) of said plunger (100) and in communication with a helix groove (106) in said plunger (100), said plunger (100) operable in a reciprocal manner, said plunger (100) comprising a first groove (108) and a second groove (110) provided at said head (102), characterized by,
said first groove (108) and said second groove (110) are made of equal width and positioned one below the other.

2. The fuel pump (112) as claimed in claim 1, wherein said second groove (110) is away from said head (102) of said plunger (100).

3. The fuel pump (112) as claimed in claim 1, wherein said first groove (108) and said second groove (110) are step grooves.

4. The fuel pump (112) as claimed in claim 1, wherein said first groove (108) is a load dependent groove.

5. The fuel pump (112) as claimed in claim 1, wherein said second groove (110) is a speed dependent groove.

6. The fuel pump (112) as claimed in claim 1, wherein said plunger (100) is in engagement with a control rack.

7. A plunger (100) of a fuel pump (112), said plunger (100) comprising:
a vertical groove (104) extending from a head (102) of said plunger (100) and in communication with a helix groove (106) in said plunger (100), said plunger (100) operable in a reciprocal manner, said plunger (100) comprising a first groove (108) and a second groove (110) provided at said head (102), characterized by,
said first groove (108) and said second groove (110) are made of equal width and positioned one below the other.

8. The plunger (100) as claimed in claim 7, wherein said second groove (110) is away from said head (102) of said plunger (100).

9. The plunger (100) as claimed in claim 7, wherein said first groove (108) and said second groove (110) are step grooves.

10. The plunger (100) as claimed in claim 7, wherein said plunger (100) is in engagement with a control rack.
, 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 invention relates to a fuel pump and a plunger of the same.

Background of the invention:
[0002] According to a prior art 3803/CHE/2013, a fuel pump is disclosed. The fuel pump comprises a plunger with a vertical groove extending from head of the plunger and in communication with a helix in the plunger. The fuel pump is also characterized by a circular groove provided along circumference, of the head, of the plunger. The circular groove is adapted to advance fuel injection timing at full load engine operating conditions. The fuel pump is further characterized by a step groove provided at the head, of the plunger, adjacent to the vertical groove. The step groove is adapted to retard fuel injection timing during part-load and no-load engine operating conditions.

Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0004] Fig. 1 illustrates a block diagram of a fuel pump with a plunger, according to an embodiment of the present invention;
[0005] Fig. 2 illustrates a head of an existing plunger;
[0006] Fig.3 illustrates the head of the plunger, according to an embodiment of present invention;
[0007] Fig. 4 illustrates a top view of the plunger, according to an embodiment of the present invention, and
[0008] Fig. 5 illustrates perspective views of the plunger, according to an embodiment of the present invention.

Detailed description of the embodiments:
[0009] Fig. 1 illustrates a block diagram of a fuel pump with a plunger, according to an embodiment of the present invention. The fuel pump 112, comprising a barrel 114 with an inlet port 116. A plunger 100 with a vertical groove 104 (shown in Fig. 4) extends from a head 102 of the plunger 100 and in communication with a helix groove 106 in the plunger 100. The plunger 100 operable in a reciprocal manner. The vertical groove 104 in combination with the head 102 is used to block the inlet port 116 at start of fuel injection and helix groove 106 to unblock the inlet port 116 at end of the fuel injection. The plunger 100 comprises a first groove 108 and a second groove 110 provided at the head 102, characterized by, the first groove 108 and the second groove 110 are made of equal width and positioned one below the other. The second groove 110 is away from the head 102 of the plunger 100. The first groove 108 and the second groove 110 are step grooves of same or different depth and width. Further, the first groove 108 is a load dependent groove, whereas the second groove 110 is a speed dependent groove.

[0010] A general construction and working of the plunger 100 is explained. The plunger 100 is housed within the barrel 114 of the fuel pump 112 and is driven by a CAM 118. The fuel is compressed within the barrel 114 by movement of the plunger 100 in vertical direction from the Bottom Dead Center (BDC) towards Top Dead Center (TDC). The movement of the plunger 100 from the BDC towards the TDC causes closure of the inlet port 116 of the barrel 114. The distance travelled by the plunger 100 from the BDC till the closure of the inlet port 116 is called as pre-stroke. Delivery of the fuel begins upon such closure of the inlet port 116. The delivery of the fuel into a high pressure line is called as effective stroke. An end of the effective stroke defines end of fuel injection. The end of fuel injection is achieved when the helix groove 106 unblocks the inlet port 116 in the barrel 114. The unblocking of the inlet port 116, by the helix groove 106, causes drop in pressure of the fuel. Further, the low pressure fuel flows from the vertical groove 104 along the helix groove 106 and thereby to the inlet port 116.

[0011] The end of fuel injection is controlled by a control rack (not shown). The control rack enables rotation of the plunger 100 such that the helix groove 106 unblocks the inlet port 116. The rotation of the plunger 100, by the control rack, is achieved using a rack and pinion mechanism based on the engine loading. Further, time instant at which the closure of the inlet port 116 occurs is referred to as fuel injection timing. The fuel injection timing can be advanced or retarded based on the engine operating conditions. The first groove 108 and the second groove 110 provided in the plunger 100 are used for obtaining such advanced or retarded fuel injection timing.

[0012] Fig. 2 illustrates a head of an existing plunger. A circular/annular groove 202 is provided along with a first groove 108. The circular groove 202 is across the entire circumference of the head 102. At full load region, and at high speed engine operating conditions, speed of the plunger 100 moving towards the TDC is also high. Due to high speed of the plunger 100, leakage of fuel through the circular groove 202 is negligible because the fuel acts as a solid layer/film around the circular groove 202 and also due to high speed of the plunger 100 the time available for the leakage is small, thereby also reducing pre-stroke. A speed dependent advance in injection is achieved because of the reducing pre-stoke. This is possible because of the fuel film formation that takes place in the circular groove 202. The film formation increases with increase in speed. Hence, with reference to the full load region, the timing is advance at light load region because of the circular groove 202 in addition to the first groove 108. However it has been noted that the extent of film formation is not complete in low load/Low speed operational region), indicated by hashed region 204 (which is also called as KA loss). However, the advance at lower load region are compromised due to leakage from the circular groove 202, which is unavoidable. The loss is shown by the hashed region 204.

[0013] In other words, the conventional plunger 100 comprises the circular groove 202 that covers the entire circumference of the plunger 100 and step groove that start from certain Control Rack Position (CRP) of the fuel pump 112 till the max CRP based on requirement. The circular groove 202 works on the principle of fuel film build up with increase in speed, in turn reducing the pre-stroke. A decrease in the pre-stroke causes the injection to be advanced. The radial depth of the circular groove 202 determines the speed at which advance starts while the length determines the extent of advance. However, the complete film build-up does not happen in practice due to improper film formation, because of which the advance at lower loads is compromised.

[0014] Fig.3 illustrates the head of the plunger, according to an embodiment of present invention. In the present invention, the second groove 110 is only limited to extent of the first groove 108. The circular groove 202 in the Fig. 2 is now reduced to the second groove 110 as shown in Fig. 3. The second groove 110 is provided only below the first groove 108, which results in elimination of the losses at lower loads due to the presence of circular groove 202 at lower loads region. With this change the extent of advance at lower loads is improved which was lower in the existing combination groove. The application of plunger 100 in Fig. 3 is different than the application of plunger 100 described in Fig. 2.

[0015] Fig. 4 illustrates a top view of the plunger, according to an embodiment of the present invention. The plunger 100 of the fuel pump 112 is provided. The plunger 100 comprising, the vertical groove 104 extending from the head 102 of the plunger 100 and in communication with the helix groove 106 in the plunger 100. The plunger 100 operable in the reciprocal manner. Further, the plunger 100 comprises the first groove 108 and the second groove 110 at the head 102 of the plunger 100, characterized by, the first groove 108 and the second groove 110 are made of equal width and positioned one below the other.

[0016] Fig. 5 illustrates perspective views of the plunger, according to an embodiment of the present invention. The second groove 110 is away from the head 102 of the plunger 100. The first groove 108 and the second groove 110 are step grooves. Also, the plunger 100 is in engagement with the control rack of the fuel pump 112.

[0017] According to an embodiment of the present invention, the plunger 100 is provided with the second groove 110 only on the functionally required region, i.e. the below the first groove 108 in the high load region. Thus improving the advance at lower loads which was being compromised by the losses due to the presence of circular groove 202. The short second groove 110 is provided for benefit in low load advance in the plunger 100 having the combination of the first groove 108 and the second groove 110.

[0018] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.