Claims:We Claim:
1. A fuel injection pump (200), comprising, at least:
a delivery valve holder (202), said delivery valve holder (202) comprising a central bore (203);
a filler piece (206) comprising at least a first flow path (208) and located within said central bore(203) of said delivery valve holder (202); characterized in that
said filler piece (206) comprising at least a second flow path (210); and

a valve located on a valve seat formed at one end of said first flow path of said filler piece in a manner so as to throttle flow of fuel through said first flow path (208) and said second flow path (210) during operation of said fuel injection pump.

2. The fuel injection pump (200) of claim 1, wherein said valve is at least one chosen from a group comprising a ball valve, a poppet valve or a pintle valve.

3. The fuel injection pump (200) of claim 1, wherein said first flow path and said second flow path are in flow communication with a high pressure pipe during fuel delivery to a high pressure pipe.

4. The fuel injection pump (200) of claim 1 and 3, wherein said high pressure pipe is in flow communication with said second flow path during closing of an injector. , Description:Field of the invention
[0001] This invention relates to the field of a fuel injection pump.

Background of the invention
[0002] A fuel injection pump comprises at least a plunger body with a barrel and a delivery valve holder. Fuel pressurized in the barrel, is delivered to the high pressure pipe through the delivery valve holder. The delivery valve holder houses at least the following components, namely, a delivery valve pin, a filler piece, a throttle holder and a throttle plate. During assembly, the throttle holder and throttle plate are pressed tight into the housing of the delivery valve holder. It is observed that as the high pressure fuel passes through the throttle plate to reach the high pressure pipe, the pressure of fuel may cause the throttle plate to tilt, and/ or move within the delivery valve holder causing wear and tear leading to breakage of throttle plate. Hence, there is need to mechanism and/ or a device that performs the function of throttling in the delivery valve holder, without the use of a throttle plate.
[0003] Prior art patent application US 4467767 discloses a fuel injection pump for internal combustion engines having an equal-pressure relief valve, which has a structure requiring little space when installed and is provided with a fastener element. The equal-pressure relief valve comprises a pressure valve body, onto which a beaker-shaped filler piece protruding into the interior of the pressure valve spring is placed. The structural unit comprising the pressure valve body and the filler piece containing the relief valve is held together, even when the pipe connector fitting or the pressure valve spring is removed, by means of the transit fastener element provided with a fastener ring. The invention is applicable both to single and series fuel injection pumps as well as to distributor injection pumps, particularly when space for installation is restricted.

Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0005] FIG. 1 illustrates a fuel injection pump with a delivery valve holder as per the state of art; and
[0006] FIG. 2 illustrates a fuel injection pump in accordance with at least one of the embodiments.

Detailed description of the embodiments
[0007] FIG. 1 illustrates a fuel injection pump 100 with a delivery valve holder 103 as per the state of art. Fuel is received in the fuel injection pump 100 through the inlet port 103 and reaches the element chamber 105. During the upward movement of the plunger, the fuel received in the element chamber 105 is displaced and the fuel tries to escape through the inlet ports. Upon closure of the inlet port by the plunger top surface, the fuel is entrapped inside the element chamber starts getting pressurized till the time it reaches the opening pressure of delivery valve (DV) spring. Due to pressure force DV pin 108 starts lifting against the spring force. As soon as the DV pin 108 opens, the fuel passes through DV spring chamber volume, filler piece 104 and is injected from the pump at outlet of delivery valve holder area after lifting the throttle plate 106. The fuel delivery from the injector happens until the pressure is generated in the system equal to nozzle opening pressure. Pressure is further built in the injector because of the smaller diameter spray holes and finally the fuel gets delivered in an atomized form into the combustion chamber of the engine.
[0008] At end of injection delivery at injector, a pressure wave is generated in the high pressure line due to closing of injector nozzle pin (not shown). The pressure peaks of this wave can lead to reopening of the nozzle pin and can lead to unwarranted secondary injection. The throttle plate in the delivery valve holder directs a portion of the high pressure fuel into the DV spring volume and dampens the pressure peaks thereby avoiding high pressure peaks leading to secondary injection. During delivery stroke, the fuel flows into and around the throttle plate 106 through spacer ring whereas during return stoke, throttle plate 106 is pushed back to its seat on the throttle plate holder 107 by the spring force and thereby allowing the fuel flow only through the throttle hole to dampen the pressure wave.
[0009] FIG. 2 illustrates a fuel injection pump 200 in accordance with at least one of the embodiments. The fuel injection pump 200 comprises at least a delivery valve holder 202, the delivery valve holder 202 comprises at least a central bore 203. A filler piece 206 comprising comprising at least a first flow path 208, is located within the central bore 203 of the delivery valve holder 202. The filler piece 206 comprises a second flow path 210. A valve 212 is located on a valve seat formed at one end of said first flow path 208 of said filler piece 206 in a manner so as to throttle flow of fuel through said first flow path 208 and said second flow path 210 during operation of the fuel injection pump 200. The valve 212 is at least one chosen from a group comprising a ball valve, a poppet valve or a pintle valve. The first flow path 208 and the second flow path 210 are in flow communication with a high pressure pipe during fuel delivery to a high pressure pipe. The high pressure pipe is in flow communication with the second flow path during closing of an injector signifying the end of injection to a particular engine cylinder.
[00010] The constructional features of the fuel injection pump 200 incorporation the filler piece 206 and valve 212 will now be described in further detail. The fuel injection pump 200 comprises at least a delivery valve holder 202. The delivery valve holder 202 is attached to the plunger body 207. The plunger body 207, comprises a plunger barrel. The delivery valve holder 202 helps in directing fuel received from the plunger barrel into the high pressure pipe. The delivery valve holder 202 comprises a central bore 203. A delivery valve pin 204 is located at one end of the central bore 203. The delivery valve holder 202 also comprises a filler piece 206. The filler piece 206 comprises a first flow path 208 and a second flow path 210. A valve seat formed at one end of the first flow path of the filler piece 206. A valve 212 is located on the valve seat.
[00011] The working of the proposed fuel injection pump 200 for injection high pressure fuel to the injector will now be explained in further detail with reference to FIG. 2. Initially it is assumed that the fuel reaches the element chamber 205 of the fuel injection pump through the inlet port. Also, it should understood that the pressurization of fuel happens due to the upward movement of plunger that is located in the plunger body.
[00012] The upward movement of the plunger, causes the inlet port to be closed and the fuel to be pressurized. The pressurized fuel causes the delivery valve pin 204 to lift, the fuel now enters the central bore 203 of the delivery valve holder 202. The fuel then passes through the first flow path 208 of the filler piece 206. The valve 212 that is seated on the valve seat of the filler piece 206 is lifted due to the flow of fuel. The fuel then flows out of the delivery valve holder 202 to reach high pressure pipe, in order to reach injector, for injection into the engine cylinders.
[00013] Upon completion of injection, when the injector closes, a pressure wave is generated. In order to dampen the pressure wave, the fuel remaining in the high pressure pipe is channeled back into the delivery valve holder 202. The high pressure fuel causes the valve 212 to be seated on the valve seat, blocking the first flow path 208 in the filler piece 206. The fuel then flows through the second flow path 210 that is provided on the filler piece 206. The diameter of the second flow path 210 of the filler piece 206 is such that the pressure wave is dampened.
[00014] By using the above mentioned fuel injection pump, with the modified filler piece 206, it is possible to avoid the throttle plate 106 (Fig. 1) that is used in state of art. Also, the problem of throttle plate edge break is not there anymore.
[00015] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of profile of the filler piece, the location of the second flow path in the filler piece, and also the type of valve used. 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.