CLIAMS:I Claim:

1. A fuel injection system, comprising;
a high pressure pump 100 having an inlet port 102 and an outlet valve 104; and
a metering unit 106 having an inlet 107 and an outlet 108, characterized in that
said outlet 108 of said metering unit 106 is coupled with said inlet port 102.
2. The fuel injection system of claim 1, wherein said inlet port 102 is configured as a throttle valve.
3. The fuel injection system of claim 1, wherein outlet 108 of said metering unit 106 is in communication with said inlet port 102 of said high pressure pump 100.
4. The fuel injection system of claim 1, wherein said metering unit 106 is coupled to said inlet port 102 through removable fastening members.
5. The fuel injection system of claim 1, wherein said metering unit 106 is enclosed in a housing, an outlet of said housing is coupled to said inlet port 102 of said high pressure pump 100.
,TagSPECI:FIELD OF THE INVENTION
[001] This invention relates to the field of inlet metering in a high pressure pump of a fuel injection system.

BACKGROUND OF THE INVENTION
[002] A metering unit is used to deliver fuel received from the fuel tank to a high pressure pump. Usually, an inlet valve is used in conjunction with the metering unit before the fuel reaches the intake of the high pressure pump. The use of inlet valve along with the metering unit adds up to the overall cost. Hence there is a need for a system that is cost effective and performs effective inlet metering to the high pressure pump.

[003] Prior art US patent number 6446606 discloses a fuel injection system for internal combustion engines, having a distributor tube and a high-pressure pump that is driven as a function of engine rpm and that serves to generate the fuel pressure and throughput required in the distributor tube in the applicable operating state of the engine. The system also includes a fuel metering unit, which is associated with the high-pressure pump and includes a regulating valve which is actuated electromagnetically. The fuel metering unit is disposed in the high-pressure pump, and the outlet of the regulating valve discharges into the low-pressure region of the high-pressure pump. The above design features make a fuel metering unit possible that is capable of metering the exact quantity of fuel desired in the applicable engine operating state to the high-pressure pump of the CR system.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[005] FIG. 1 illustrates a high pressure pump in a fuel injection system in accordance with one of the embodiments.

[006] FIG. 2 illustrates a metering unit enclosed in a housing.

DETAILED DESCRIPTION OF THE EMBODIMENTS
[007] FIG. 1 illustrates a high pressure pump 100 in a fuel injection system in accordance with one of the embodiments. The fuel injection system comprises a high pressure pump 100 having an inlet port 102 and an outlet valve 104 and a metering unit 106 having an inlet 107 and an outlet 108. The inlet 107 of the metering unit 106 receives fuel from a fuel tank. The fuel injection system is characterized in that the outlet 108 of the metering unit 106 is coupled with the inlet port 102. The inlet port 102 is configured as a throttle valve. Varying the rate of flow of fuel through the metering unit 106 varies the pressure at the inlet port 102, which behaves like a throttle and therefore varies the pressure at which fuel is delivered to the high pressure pump 100. As the outlet 108 of the metering unit 106 is directly in communication with the inlet port 102, the need for an inlet valve to the high pressure pump 100 is eliminated.

[008] The pressure at which fuel is received by the high pressure pump 100 happens based on the difference between the set point pressure that is calculated by the engine control unit (ECU) and actual pressure that is determined from the rail pressure sensor. The ECU increases and/ or decreases the rate of flow of fuel from the metering unit 106 based on the quantiy of fuel that is required for pressurization in the high pressure pump 100.The metering unit 106 is coupled to the inlet port 102 through removable fastening members.

[009] FIG. 2 illustrates a metering unit 106 enclosed in a housing. In an embodiment the metering unit 106 is enclosed in housing, an outlet of the housing is coupled to the inlet port 102 of the high pressure pump 100. The fuel from the fuel tank is delivered to the metering unit 106 through the housing. The housing is placed proximal to inlet port 102 of the high pressure pump 100 thereby eliminating the need for an inlet valve.

[0010] 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.