Claims:We Claim:
1. A fuel injection pump 100 comprising at least:
an inlet port 102, said inlet port 102 opening 109 into a first flow path 104 and a second flow path 106, said first flow path 104 delivering fuel to a pressurizing chamber 108 and said second flow path 106 in flow communication with a sealing ring chamber 110, characterized in that:
a valve 112 located along said second flow path 106, said valve proximal to said sealing ring chamber 110, and adapted to open in dependence of the difference in pressure of fuel in said second flow path 106 and said sealing ring chamber 110.

2. The fuel injection pump of claim 1, wherein said second flow path further comprises a stopper.

3. The fuel injection pump of claim 1, wherein said valve is one of a spool type valve and a cone type valve.

4. The fuel injection pump 100 of claim 1, wherein said valve 112 is a ball valve.

5. The fuel injection pump 100 of claim 1 and 4, wherein said ball valve 112 is located at the interface of inlet port 102 and second flow path 106.
, Description:Field of the invention
[0001]This invention relates to the field of a fuel injection pump.

Background of the invention
[0002]The function of a fuel injection pump is to deliver pressurized fuel to the common rail and in turn to the fuel injector. The fuel injection pump comprises a pressurizing chamber with a reciprocating plunger. The plunger derives motion from a cam, the cam being driven by engine crankshaft. Since the cam is lubricated by engine oil, in order to prevent oil from mixing with fuel, a plunger sealing ring is provided. A flow path in the fuel injection pump connects the sealing ring chamber to the inlet of the fuel injection pump. The function of the flow path is to flush out any fuel remaining in the sealing ring chamber and to deliver the fuel to the inlet port. In case of any damage to the sealing ring, the fuel in the sealing ring chamber flows beyond sealing ring and mixes with the oil that lubricates the cam will mix with the fuel leading fuel in oil dilution. Hence, there is a need to avoid the above mentioned problem of mixing of oil and fuel.

Brief description of the accompanying drawing
[0003] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0004] FIG. 1 illustrates a fuel injection pump; and

[0005] FIG. 2 illustrates an embodiment of the fuel injection pump comprising a valve located in the sealing ring chamber.

Detailed description of the embodiments
[0006] FIG. 1 illustrates a fuel injection pump. The fuel injection pump 100, comprises an inlet port 102, the inlet port 102 opens into a first flow path 104 and a second flow path 106. The first flow path 104 delivers fuel to a pressurizing chamber 108 and the second flow path 106 is in flow communication with a sealing ring chamber 110. A valve 112 is located along the second flow path 106, the valve 112 being proximal to the sealing ring chamber 110, and adapted to open in dependence of the difference in pressure of fuel in the second flow path 106 and the sealing ring chamber 110.

[0007]The constructional features of the fuel injection pump 100 will be explained in further detail. The fuel injection pump 100 comprises an inlet port 102. The inlet port 102 receives fuel from a fuel tank (not shown) via a pipe. The inlet port 102 opens into a first flow path 104 that delivers fuel to a pressurizing chamber 108. The inlet port 102 also opens into a second flow path 106, the second flow path 106 is in flow communication with a sealing ring chamber 110. The sealing ring chamber 110 houses a sealing ring that is used to prevent mixing of oil and fuel during the reciprocating movement of plunger 105. A valve 112 is located along the second flow path 106, the valve 112 is proximal to the sealing ring chamber 110. In an embodiment the valve 112 may be a ball valve. In an embodiment the ball valve 112 is located at the interface of inlet port 102 and second flow path 106. The ball valve 112 may be a spring loaded valve. When the ball valve 112 is located at the above mentioned location, the fuel cannot flow from the inlet port 102 into the second flow path 106. This prevents mixing of fuel and oil in the pressurizing chamber.

[0008]The working of fuel injection pump 100 will be explained in further detail. The fuel injection pump 100 receives fuel from a fuel tank (not shown) via a pipe. The fuel reaches flows through the inlet port 102 and reaches the first flow path 104. The first flow path 104 delivers fuel to a pressurizing chamber 108. The fuel that is received is pressurized due to the movement of plunger 105. The plunger 105 is driven by the cam 107 (via a roller tappet) which is lubricated by the engine oil. The reciprocating movement of the plunger 105 may cause the oil that lubricates the cam to flow towards the pressurizing chamber 108 and mix with fuel. Also, a part of the fuel from the pressurizing chamber may flow towards the sealing ring chamber 110. The fuel that is accumulated in the sealing ring chamber 110 flows via the second flow path 106, to reach the inlet port 102 of the fuel injection pump 100. The pressure required for flow of fuel is generated due to the reciprocating movement of plunger 105. The fuel that is present in the sealing ring chamber 110 is thus flushed through second flow path 106.

[0009] In case of failure of the sealing ring, the pressure in the ring chamber falls below the pressure of fuel flowing through the inlet port 102, due to this there is tendency for a part of the fuel to flow from the inlet port 102 via the second flow path 106 and enter the sealing ring chamber 110. Upon entering the sealing ring chamber 110 the fuel may flow beyond the sealing ring chamber mix with the oil that lubricates the cam 107 and roller tappet (not shown) , in order to prevent the fuel from the entering the sealing ring chamber 110 and further mixing with oil, a valve 112 is provided. The valve 112 is located proximal to the sealing ring chamber 110, and adapted to open in dependence of the difference in pressure of fuel in the second flow path 106 and the sealing ring chamber 110. The fuel that flows through the second flow path 106 causes the valve 112 to block an opening 109 in the second flow path 106. By blocking the opening 109, the fuel no longer flows from the second flow path and into the sealing ring chamber. This prevents mixing of fuel with oil leading to dilution.

[0010] With the use of the above mentioned valve 112 it is possible to prevent mixing of fuel with oil in the sealing ring chamber in the case of breakage in the sealing ring. Also, during normal working of the pump, the difference in pressure of fuel present in the sealing ring chamber and the second flow path 106, will cause the valve 112 to allow the fuel to flow from sealing ring chamber 108 to the inlet port 102 thereby preventing accumulation of fuel in the sealing ring chamber 108.

[0011] FIG. 2 illustrates an embodiment of the fuel injection pump comprising a valve located in the sealing ring chamber. In an embodiment the valve 112 is located in the sealing ring chamber 110. The valve 112 prevents flow of fuel from the second flow path 106 into the sealing ring chamber 110 in case of failure in the sealing ring that is located in the sealing ring chamber 110. By having the valve 112 located in the sealing ring chamber 110, the mixing of fuel with oil is prevented as the valve closes the flow path of fuel.

[0012]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 the type of fuel injection pump used and the material used for sealing washer. 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.