Claims:We Claim:
1. A housing (100) for a high pressure fuel injection pump, said housing comprising at least:
plurality of bores defining flow path of fuel, said at least one bore (102) in flow communication with a metering unit, characterized in that
an overflow valve (104) located within said at least one bore (102), said overflow valve (104) comprising a plate (106), a spring (108) and a reciprocating member 112;

a first end (110) of said spring (108) abutting said plate (106), a second end (111) of said spring (108) abutting said reciprocating member (112) and said reciprocating member (112) abutting a stopper (114);

said reciprocating member (112) compresses said spring (108) in dependence of pressure of fuel and stiffness of said spring (108) in order to allow fuel from said metering unit through said at least one bore (102).

2. The housing (100) of claim 1, wherein said at least one bore opens into a first flow path (116), said first flow path (116) in flow communication with a fuel tank.

3. The housing (100) of claim 1, wherein said at least one bore opens into a second flow path (118), said second flow path (118) in flow communication with a polygonal ring of said high pressure fuel injection pump.

4. The housing (100) of claim 1, wherein said plate (106) is press-fitted into said at least one bore.

5. The housing (100) of claim 1, wherein said overflow valve is integrated with said housing 100.

6. The housing (100) of claim 1, wherein said overflow valve is removably fitted within said bore.

7. The housing 100 of claim 1, wherein said plate is provided with a recess.

8. The housing (100) of claim 1, wherein said reciprocating member (112) has a recess.

9. The housing (100) of claim 1 and 7, wherein said first end (110) of said spring (108) abuts said plate (106) through said recess.

10. The housing (100) of claim 1 and 8, wherein said second end (111) of said spring abuts said reciprocating member (112) through said recess.
, Description:Field of the invention
[0001] This invention relates to the field of a high pressure fuel injection pump.

Background of the invention
[0002] A fuel injection pump is used to pressurize fuel received from a fuel tank and send the pressurized fuel to an injector. The fuel injection pump is generally housed in a pump housing. The housing comprises multiple bores, these bores establish flow communication of fuel, both to and from the fuel injection pump. An overflow valve is used for maintaining stable pressure in the fuel injection pump. Whenever the pressure of fuel in the fuel injection pump exceeds a set pressure, the overflow valve opens to relieve the fuel and in turn relieve excess pressure. In addition to relieving excess pressure, the overflow valve also performs the function of lubrication of the components of the fuel injection pump. In the present generation fuel injection pump, the overflow valve is separate sub-assembly to the pump housing. In order to accommodate the overflow valve, a separate bore is drilled in the housing of the fuel injection pump. The overflow valve is then accommodated and sealed into the housing with the help of an O-ring. It is observed that the life of O-ring is limited, due to factors like, vibration, property of material used in O-ring, temperature, etc. Any damage to O-ring, will lead to leakage of fuel from the overflow valve. Hence there is a need to replace the existing concept of using an overflow valve as a separate unit from the housing of the fuel injection pump.

[0003] Prior art patent application DE-102008042089 discloses an overflow valve for inlet pipe of dosing unit of high-pressure pump of fuel injecting device of internal combustion engine, having a spring area that is connected with inlet via pressure balance pipeline, where throttle is provided in pipeline. The valve has a valve housing comprising an inlet and an outlet, where the outlet is connected with an inlet pipe and a fuel tank. The outlet is closable by a control piston that is movably guided into the valve housing against the force of a compression spring. A spring area is connected with the inlet via a pressure balance pipeline, where a throttle is provided in the pressure balance pipeline. The control piston is rigidly connected with a guide rod.

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 housing for a high pressure fuel injection pump.

Detailed description of the embodiments
[0006] FIG. 1 illustrates a housing 100 for a high pressure fuel injection pump. A housing 100 for a fuel injection pump is used to enclose the fuel injection pump, drive component like the pump shaft, metering unit, overflow valve and the connectors. The housing 100 also serves to connect a network of bores through the connectors. The bores are generally drilled in the housing 100. These bores enable low pressure fuel to flow into the fuel injection pump, and also cause the high pressure fuel to be delivered to the high pressure pipe from the fuel injection pump in order to reach the injector. Located, in one of the bores is an overflow valve. The overflow valve is used to maintain the fuel pressure in the fuel injection pump within a specified limit, and is also used to lubricate the components of the fuel injection pump. The overflow valve in the proposed housing 100 will now be described in further detail.

[0007] The housing 100 for a high pressure fuel injection pump, comprises plurality of bores defining flow path of fuel, at least one bore (102) is in flow communication with a metering unit. An overflow valve (104) is located within the bore (102), the overflow valve (104) comprises a plate (106), a spring (108), and a reciprocating member 112. The overflow valve is removably fitted within the bore. The plate is press-fitted into the bore and is provided with a recess. A first end (110) of the spring (108) abuts the plate (106), and a second end of the spring (108) abuts the reciprocating member, the reciprocating member abutting a stopper (114). The reciprocating member has a recess. The second end of the spring abuts the reciprocating member through the recess. The reciprocating member (112) compresses the spring (108) in dependence of pressure of fuel and stiffness of the spring (108) in order to allow fuel from the metering unit through the bore (102). The bore opens into a first flow path, the first flow path is in flow communication with a fuel tank. The bore opens into a second flow path (118), the second flow path (118) is in flow communication with a polygonal ring of the high pressure fuel injection pump. The above mentioned overflow valve performs two main functions, firstly during working of the high pressure fuel injection pump, the overflow valve continuously supplies fuel through the second flow path (118) for lubrication of components of the high pressure fuel injection pump and secondly excess fuel if any, is sent back through the first flow path to relieve pressure in the fuel injection pump. The above two functions will now be explained in further detail.

(I) Lubrication function: In order to understand the lubrication function of overflow valve in further detail, the function of a metering unit that controls the flow of fuel in the housing 100 of the high pressure fuel injection pump is described. The metering unit is generally controlled by an electronic control unit or is actuated electromagnetically. The metering unit has at least one inlet connector that supplies fuel from the fuel tank. The metering unit delivers the fuel to the inlet of the high pressure fuel injection pump through one of the connectors leading from the metering unit to the inlet of the high pressure fuel injection pump. During working of the high pressure fuel injection pump, a certain quantity of fuel needs to be supplied to the components of the fuel injection pump for lubrication. The fuel that is needed for lubrication flows from the metering unit through the bore 102 that contains the overflow valve 104. The overflow valve 104 is integrated with the housing 100 of the fuel injection pump with the help of a plate 106. The fuel passes through the plate to reach the polygonal ring through the second flow path (118). The rotation of the polygonal ring causes the fuel to be splashed onto different components that require lubrication. Thus, lubrication of different components of the fuel injection pump is achieved.

(II) Overflow function: Generally, the fuel injection pump is designed to operate under certain pressure value, as decided by the maximum pressure of fuel that the fuel injection pump can withstand. Any excess pressure of fuel that is produced has to be relieved in order to prevent damage to the injector and components of the fuel injection pump. In order to relieve excess fuel and in turn relieve the pressure in the fuel injection pump, the fuel that is flowing through the bore (102) causes the reciprocating member (112) to compress the spring (108) in dependence of pressure of fuel and stiffness of the spring (108) in order to allow fuel from the metering unit through the bore (102). The compression of the spring causes the first flow path (116) to open. The high pressure fuel flows through the first flow path (116) and to reach the fuel tank. Once excess fuel has been relieved, the spring expands, causing the reciprocating member to abut the stopper (114). The function of the stopper (114) is to prevent any excess travel to the reciprocating member. Alternately, instead of the stopper (114), as step may be provided on the bore. The width of the step is such that it is less than the diameter of the reciprocating member.

[0008] Since the overflow valve (104) is now integrated with the housing 100 of the fuel injection pump, the leakage of the fuel that would happen if the overflow valve was made separate and then assembled onto the housing 100 of the fuel injection pump with the help of an O-ring is avoided. The use of an overflow valve (104) that is integrated with the housing 100 of the fuel injection pump eliminates the need for drilling complex bores in the housing 100 of the fuel injection pump.

[0009] 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 type of valve used and the configuration of the electric feed pump. 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.