Claims:We Claim

1. A deflation flow path (12) of a fuel injection system (10), an upstream end of said deflation flow path (12) in flow communication with lubrication path of the high pressure fuel pump (14) and adapted to receive pressurized fuel from the high pressure fuel pump (14), a downstream end of said deflation flow path (12) in flow communication with a fuel discharge supply path (16) that is in flow communication with a fuel tank (18) and adapted to discharge fuel to the fuel tank (18), said deflation flow path (12) comprising:
a throttle (18) defined in said deflation flow path (12), said throttle (18) adapted to constrict a flow of fuel flowing through said deflation flow path (12); and
a deflation flow valve (20) in flow communication with said deflation flow path (12) and positioned downstream from said throttle (18), said deflation flow valve (20) adapted to control a flow of pressurized fuel and air bubbles from said throttle (18) to the fuel discharge supply path (16).

2. The deflation flow path (12) of a fuel injection system (10) in accordance with Claim 1 further comprising an overflow valve (22) positioned downstream from said deflation flow path (12) and in flow communication with the fuel discharge supply path (16), said overflow valve (22) adapted to channel the pressurized fuel and air bubbles that is supplied from the lubrication path of said high pressure fuel pump (14) to the fuel discharge supply path (16).

3. The deflation flow path (12) of a fuel injection system (10) in accordance with Claim 2 wherein said deflation flow valve (20) is adapted to open at a lower pressure than said overflow valve (22), thereby relieving the fuel and air bubbles that flows out of the high pressure fuel pump (14) at a lower pressure than said overflow valve (22).

4. The deflation flow path (12) of a fuel injection system (10) in accordance with Claim 2 wherein said throttle (18) is adapted to minimize the leakage of fuel through the deflation flow path (12) by throttling the flow of fuel through the deflation flow path (12), thereby allowing the pressurized fuel to flow to the fuel discharge supply path (16) via the overflow valve (22) during a normal discharge of fuel from the high pressure fuel pump (14).
, 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] This invention relates to a deflation flow path, and more specifically to a deflation flow path used in combination with an overflow valve in a fuel injection system.

Background of the invention
[0002] WO 18069020 A1 describes an overflow valve, in particular for a high pressure pump in a fuel injection system, comprising a valve element and a valve piston which is received in an axial bore of the valve element in an axially movable manner and to which the spring force of a spring is applied in the direction of an end-face inflow opening, wherein a filter device is mounted upstream of the inflow opening. According to the invention, the filter device comprises a plastic housing with at least one integrated filter fabric. The invention further relates to a high-pressure pump, in particular for a fuel injection system, comprising such an overflow valve and to a fuel injection system comprising a corresponding high pressure pump.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a schematic diagram of a deflation flow path of a fuel injection system in one embodiment of the invention.

Detailed description of the embodiments
[0004] Figure 1 illustrates a schematic diagram of a deflation flow path 12 of a fuel injection system 10 in one embodiment of the invention. An upstream end of the deflation flow path 12 is in flow communication with an lubrication path of the high pressure fuel pump 14 and adapted to receive pressurized fuel in addition with the pre-existing air from the high pressure fuel pump 14. A downstream end of the deflation flow path 12 is in flow communication with a fuel discharge supply path 16 that is in flow communication with a fuel tank 18 and adapted to discharge fuel with air bubbles to the fuel tank 18. The deflation flow path 12 comprises a throttle 18 defined in the deflation flow path 12, the throttle 18 adapted to constrict a flow of fuel flowing through the deflation flow path 12. A deflation flow valve 20 is in flow communication with the deflation flow path 12 and positioned downstream from the throttle 18, the deflation flow valve 20 adapted to control a flow of pressurized fuel along with air bubbles from the throttle 18 to the fuel discharge supply path 16.

[0005] Figure 1 illustrates a schematic diagram of a deflation flow path 12 of a fuel injection system 10 in one embodiment of the invention. The fuel injection system 10 comprises a high pressure fuel pump 14 that is adapted to supply pressurized fuel to a common rail 25. The excess pressurized fuel that is not required to be supplied to the common rail 25 is supplied to an overflow valve 22 of the fuel injection system 10 via an overflow fuel supply path 27. A fuel discharge supply path 16 is in flow communication with the overflow valve 22 and is adapted to channel the fuel that flows through the overflow valve 22 to the fuel tank 18 via the fuel discharge supply path 16. A deflation flow path 12 is in flow communication between the overflow fuel supply path 27 and the fuel discharge supply path 16 and is adapted to deliver pressurized fuel along with air bubbles from the overflow fuel supply path 27 to the fuel tank 18 via the fuel discharge supply path 16. More specifically, an upstream end of the deflation flow path 12 is in flow communication with an outlet of a high pressure fuel pump 14 and is adapted to receive fuel from the high pressure fuel pump 14. A downstream end of the deflation flow path 12 is in flow communication with the fuel discharge supply path 16 that is in flow communication with a fuel tank 18 and is adapted to discharge the channeled fuel along with air bubbles to the fuel tank 18, which in turns ensure that dry running of pump has not taken place.

[0006] In an exemplary embodiment, the deflation flow path 12 comprises a throttle 18 that is defined in the deflation flow path 12. The throttle 18 is adapted to constrict a flow of fuel through the deflation flow path 12. More specifically, the throttle 18 that is defined in the deflation flow path 12 is adapted to control a flow rate of fuel that flows through the deflation flow path 12, thereby reducing the leakage quantity of fuel that flows to the fuel discharge supply path 16 via the deflation flow path 12. A deflation flow valve 20 is in flow communication with the deflation flow path 12. More specifically, the deflation flow valve 20 is positioned downstream from the throttle 18 and is adapted to control a flow of pressurized fuel along with air bubbles from the capillary 18 to the fuel discharge supply path 18. In the exemplary embodiment, the fuel that is channeled from the outlet of the throttle 18 is supplied to the deflation flow valve 20. When the pressure of the fuel exiting the throttle 18 exceeds a minimum threshold pressure, the deflation flow valve 20 is opened, thereby channeling the fuel along with air bubbles past the deflation flow valve 20 and into the fuel tank 18 via the fuel discharge supply path 16.

[0007] The overflow valve 22 is positioned downstream from the deflation flow path 12 and is in flow communication with the fuel discharge supply path 16. More specifically, an upstream end of the overflow valve 22 is in flow communication with the overflow fuel supply path 27 and is adapted to receive the fuel that is supplied through the overflow fuel supply path 27. The excess pressurized fuel from the high pressure fuel pump 14 that is supplied to the overflow valve 22 via the overflow fuel supply path 27 flows through the overflow valve 22 and is discharged to the fuel discharge supply path 16. From the fuel discharge supply path 16, the excess pressurized fuel is channeled back to the fuel tank 18. In an exemplary embodiment, the deflation flow valve 20 is adapted to open at a lower pressure than that of the overflow valve 22. Therefore, during the initial starting up condition of the high pressure fuel pump 14, or when the pressure of the fuel that is delivered by the high pressure fuel pump 14 is lower than the pressure of the fuel that is required to open the overflow valve 22 to relieve the fuel there through, the lower pressure fuel along with air bubbles flows through the deflation flow path 12 via the throttle 18 and the deflation flow valve 20. From the deflation flow path 12, the lower pressure fuel along with air bubbles is delivered to the fuel tank 18 via the fuel discharge supply path 16. Therefore, the throttle 18 and the deflation flow valve 20 in the deflation flow path 12 relieves the fuel along with the air bubbles that flows out of the high pressure fuel pump 14 at a lower pressure than that which is required to open the overflow valve.

[0008] During the normal functioning of the high pressure fuel pump 14, the pressurized fuel is delivered at a normal delivery pressure. The pressurized fuel at the normal delivery pressure is allowed to flow to the fuel discharge supply path 16 via the overflow valve 22. As the overflow valve 22 is opened at a higher delivery pressure, a large portion of the fuel is channeled to the overflow valve 22. The throttle 18 is adapted to minimize the leakage of fuel through the deflation flow path 12 by throttling the flow of fuel through the deflation flow path 12. Due to the throttling effect 18, a lesser quantity to fuel is supplied to the fuel discharge supply path 16 via the deflation flow valve 20. Therefore, the throttle 18 minimizes the leakage of the fuel that flows through the deflation flow path 12 during the normal operation of the high pressure fuel pump 14.

[0009] A working of the deflation flow path 12 in a fuel injection system 10 is described as an example. Fuel along with air bubbles from the high pressure fuel pump 14 is supplied to an overflow fuel supply path 27. From the overflow fuel supply path 27, a portion of the fuel is channeled to the overflow valve 22, while the remaining portion of the fuel is channeled to the deflation flow path 12. During the normal functioning of the high pressure fuel pump 14, the pressurized fuel is supplied to the overflow valve 22. The overflow valve 22 is opened, thereby permitting the flow of pressurized fuel to the fuel discharge supply path 16 via the overflow valve 22. Owing to the flow of fuel through the overflow fuel supply path 27, a portion of the fuel is channeled to the deflation flow path 12. The throttle 18 that is present upstream from the deflation flow valve 20 produces a throttling effect on the fuel that flows through the deflation flow path 12. The reduced quantity of pressurized fuel therein flows through the deflation flow valve 20 from where it is delivered to the fuel discharge supply path 16. When the pressure of the fuel that is exiting the high pressure fuel pump 14 is below the threshold pressure that is required to open the overflow valve 22, the fuel in the overflow fuel supply path 27 remains stagnant. As the deflation flow valve 20 opens at a lower pressure than that of the overflow valve 22, the fuel along with air bubbles that is exiting the high pressure fuel pump 14 flows through the throttle 18 of the deflation flow path 12 and to the fuel discharge supply path 16 via the deflation flow valve 20. Therefore, the deflation flow path 12 serves to deliver pressurized fuel and air bubbles at a lower pressure than that of the overflow valve 22 to the fuel discharge supply path 16, thereby enabling lubrication of the high pressure fuel pump 14 during the starting up phase of the high pressure fuel pump 14.

[0010] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.