Claims:We Claim:
1 A valve pin (20) of an inlet valve (100) for a high pressure pump (300), said valve pin (20) comprising:
a valve pin head (22);
a valve pin neck (24); and
a hollow valve pin body (26);
characterized in that:
said valve pin head (22) comprising a conical portion adapted to be seated on said valve seat (18);
said valve pin neck (24) extending from said conical portion and comprising at least two holes (24a) and (24b) for allowing fuel to flow from an inlet side (14) of said inlet valve (100) to said valve pin head (22); and
said hollow valve pin body (26) extending from said valve pin neck (24) and having diameter larger than diameter of said valve pin neck (24).

2 The valve pin (20) as claimed in claim 1, wherein said valve pin head (22) is adapted to be seated on a valve seat (18) of said inlet valve (100).

3 An inlet valve (100) for a high pressure pump (300) in a fuel injection system, said inlet valve (100) comprising:
a housing (12) defining an inlet port (14) and an outlet port (16);
a valve seat (18) defined by said housing (12);
a valve pin (20) seated on said valve seat (18), said valve pin (20) comprising a valve pin head (22), a valve pin neck (24) and a hollow valve pin body (26);
characterized in that:
said valve pin head (22) comprising a conical portion adapted to be seated on said valve seat (18);
said valve pin neck (24) extending from said conical portion and comprising at least two holes (24a) and (24b) for allowing fuel to flow from said inlet side (14) to said valve pin head (22); and
said hollow valve pin body (26) extending from said valve pin neck (24) and having diameter larger than diameter of said valve pin neck (24).

4 The inlet valve (100) as claimed in claim 3, wherein said valve pin (20) is operable to move between an open position and said closed position.

5 The inlet valve (100) as claimed in claim 3, wherein in said conical portion of said valve pin (20) is away from said valve seat (18) when said valve pin (20) is in an open position.

6 The inlet valve (100) as claimed in claim 3, wherein in said conical portion of said valve pin (20) is seated on said valve seat (18) when said valve pin (20) is in a closed position.

7 A high pressure pump (300) for a fuel injection system, said high pressure pump (300) comprising:
a pumping chamber (32);
a delivery valve (34) adapted to deliver pressurized fuel to a high pressure rail;
a delivery valve holder (40)
characterized in that
an inlet valve (100) in flow communication with said pumping chamber (32), said inlet valve (100) comprising a valve pin (20), said valve pin (20) comprising a valve pin head (22) having a conical portion, a valve pin neck (24) extending from said conical portion and comprising at least two holes (24a) and (24b), and a hollow valve pin body (26) extending from said valve pin neck (24) and having diameter larger than diameter of said valve pin neck (24).

8 The high pressure pump (300) as claimed in claim 7, wherein said valve pin (20) is movable between an open position and a closed position.
, Description:Field of the invention
[0001] This invention relates to an inlet valve for a high pressure pump in a fuel injection system.

Background of the invention
[0002] In a high pressure pump, the plunger reciprocates between a TDC and BDC of a pumping chamber for pressurizing fuel. Such high pressure pump comprises a unidirectional inlet valve located upstream from the pumping chamber. Fuel from the fuel tank enters into an inlet chamber of the inlet valve. As the fuel is accumulated in the inlet chamber, the pressure of the fuel in the inlet chamber rises. When the pressure of the fuel in the inlet chamber is above a threshold, a valve pin of the inlet valve is lifted away from a valve seat thereby allowing fuel to flow into the pumping chamber located downstream from the inlet valve. The valve pin comprises a conical section that is adapted to be seated on the valve seat.

[0003] The fuel is pressurized in the pumping chamber and the pressurized fuel accumulates in a delivery chamber that is located downstream from the inlet valve. As the pressurized fuel accumulates in a delivery chamber, a pressure difference is created between the fuel in the inlet chamber and the delivery chamber. Due to this pressure difference, the valve pin of the inlet valve is pushed downwards and the conical section of the valve pin is seated on the valve seat. Such an arrangement provides an effective sealing between the inlet chamber and the delivery chamber.

[0004] When the inlet valve is about to close, some high pressure fuel leaks into the inlet chamber. The high pressure fuel then tends to move towards the low pressure fuel area downstream of the inlet chamber due to its momentum. Such movement of the fuel creates a void near the valve seat causing vapour bubbles. Further, pressure waves due to movement of the high pressure fuel towards the low pressure, hit walls of the inlet valve and bounce back and strike the vapour bubbles. As a result, the vapour bubbles implode releasing energy. Such implosion of the vapour bubble causes scooping of the material in the valve seat. This phenomenon is also referred to as cavitation erosion effect. Such cavitation erosion effect at the valve seat fails to form an effective sealing between the delivery chamber and the inlet chamber. As a result, pressurized fuel in the delivery chamber tends to leak into the inlet chamber.

[0005] In the light of the foregoing discussion there is a need for designing an inlet valve such that cavitation erosion effect is minimized and hence no fuel leakage occurs.

Brief description of the accompanying drawings

[0006] Figure 1 illustrates a high pressure pump for a fuel injection system, in accordance with an embodiment of the present disclosure;

[0007] Figure 2 illustrates an inlet valve for a high pressure pump in a fuel injection system, in accordance with an embodiment of the present disclosure;

[0008] Figure 3 illustrates a valve pin of an inlet valve for a high pressure pump, in accordance with an embodiment of the present disclosure.

Detailed description

[0009] The present disclosure discloses a valve pin 20 and an inlet valve 100 for a high pressure pump. The disclosure also discloses a high pressure pump 300 of a fuel injection system.

[00010] The valve pin 20 comprises a valve pin head 22, a valve pin neck 24 and a hollow valve pin body 26. The valve pin 20 is further characterized by the valve pin head 22 that comprises a conical portion adapted to be seated on the valve seat 18 and the valve pin neck 24 that extends from the conical portion and comprises at least two holes 24a and 24b for allowing fuel to flow from an inlet port 14 of the inlet valve 100 to the valve pin head 22 and the hollow valve pin body 26 that extends from the valve pin neck 24 and has diameter larger than diameter of the valve pin neck 24.

[00011] The inlet valve 100 for a high pressure pump comprises a housing 12 that defines an inlet port 14, an outlet port 16 and a valve seat 18. The inlet valve 100 also comprises a valve pin 20 seated on the valve seat 18. The valve pin 20 comprises a valve pin head 22, a valve pin neck 24 and a hollow valve pin body 26. The valve pin 20 is characterized such as to comprise a valve pin head 22 comprising a conical portion adapted to be seated on the valve seat 18, the valve pin neck 24 extending from the conical portion and comprising at least two holes 24a and 24b for allowing fuel to flow from the inlet port 14 to the valve pin head 22 and the hollow valve pin body 26 extending from the valve pin neck 24 and having diameter larger than diameter of the valve pin neck 24.

[00012] The high pressure pump 300 for a fuel injection system comprising a pumping chamber 32 and a delivery valve 34 adapted to deliver pressurized fuel to a high pressure rail. The high pressure pump 300 is characterized such as to comprise an inlet valve 100 in flow communication with the pumping chamber 32 and is located upstream of the pumping chamber 32. The inlet valve 100 comprises a valve pin 20 having a conical portion, a valve pin neck extending from the conical portion and comprising at least two holes 24a and 24b, and a hollow valve pin body extending from the valve pin neck 24 and having diameter larger than diameter of the valve pin neck 24.

[00013] Figure 1 illustrates a high pressure pump for a fuel injection system, in accordance with an embodiment of the present disclosure. The high pressure pump 300 comprises the pumping chamber 32 and a recess. The recess holds an inlet valve 100, a delivery valve 34 and a delivery valve holder 40. The inlet valve 100 and the delivery valve 34 are held together in a particular position through a pin 42.

[00014] The inlet valve 100 is located within the recess of the fuel pump 300 and is positioned upstream of the pumping chamber 32. The inlet valve 100 is explained in conjunction with Figure 2. The inlet valve 100 has a housing 12 and the housing 12 holds elements of the inlet valve 100. The housing 12 defines the inlet port 14, the outlet port 16, an inlet channel 44 and an outlet channel 46. The inlet channel 44 is in fluid communication with an outlet of a fuel tank. Fuel from the fuel tank flows along the inlet channel 44 and reaches the inlet port 14. The outlet channel 46 is in flow communication with the pumping chamber 32. The housing 12 also defines a valve seat 18 at the outlet port 16 upon which a valve pin 20 can be seated. The valve seat 18 is conical in shape.

[00015] The valve pin 20, as shown in Figure 3, is characterized to comprise a valve pin head 22, a valve pin neck 24 and a hollow valve pin body 26. The valve pin head 22 comprises a conical portion adapted to be seated on the valve seat. The valve pin neck 24 is a short hollow section that extends from the conical portion and comprises at least two holes 24a and 24b for allowing fuel to flow from the inlet port 14 of the inlet valve 100 to the valve pin head 22. In some embodiments, the valve pin neck 24 comprises at least four holes. The hollow valve pin body 26 extends from the valve pin neck 24 has diameter larger than diameter of the valve pin neck 24.

[00016] The valve pin 20 is adapted to move between an open position and a closed position. When the valve pin 20 is seated on a valve seat 18 then it is considered that the inlet valve 100 is in closed position. When the valve pin 20 is lifted from the valve seat then the inlet valve 100 is considered to be in open position. When the valve pin 20 is seated on the valve seat 18 an effective sealing is provided at the outlet port 16 of the inlet valve 100.

[00017] Working of the fuel pump with the inlet valve in accordance with an embodiment of the present disclosure is explained in the below paragraphs.

[00018] The fuel from the fuel tank flows along the inlet channel 44 and reaches the inlet port 14 of the inlet valve 100. The fuel from the inlet port 14 then flows into an inlet chamber 14a of the inlet valve 100. The inlet chamber 14a is clearly shown in Figure 2. Fuel accumulated in the inlet chamber 14a flows through the hollow valve pin body 26 and comes out through the holes 24a and 24b that are located in the valve pin neck 24.

[00019] As the inlet chamber 14a is filled with the fuel, pressure of the fuel in the inlet chamber 14a continuously increases and the fuel flows through the holes 24a and 24b. When the pressure of the fuel is above a threshold value, the valve pin 20 is lifted from the valve seat 18. When the valve pin 20 is lifted from the valve seat 18, the fuel filled in the inlet chamber 14a flows towards the outlet port 16. Fuel from the outlet port 16 flows into the pumping chamber 32 through the outlet channel 46.

[00020] The fuel flowing into the pumping chamber 32 is pressurized by a plunger adapted to reciprocate within the pumping chamber 32. Pressurized fuel then flows into a delivery chamber 36 in the delivery valve 34 through the outlet channel 46. As the pressurized fuel gets accumulated in the delivery chamber 36, the pressure of the fuel in the delivery chamber 36 pushes the valve pin 20 to be seated on the valve seat 18 of the inlet valve 100. Hence, the inlet valve 100 is now said to be in closed position and high pressure fuel accumulated in the delivery chamber 36 is thus delivered to a fuel rail through the delivery valve 34.

[00021] As the inlet valve 100 closes, the high pressure fuel present in the delivery chamber 36 leaks into the inlet chamber 14a. Pressure waves in the high pressure fuel hits the hollow valve pin body 26 since the diameter of the hollow valve pin body 26 is greater than the diameter of the valve pin neck 24. Further, after striking the hollow valve pin body 26, the pressure waves reflect back immediately leading to lesser void formation and hence lesser vapour bubbles are formed. Therefore the energy released by the vapour bubbles when they implode is less. Since the valve pin neck 24 is short and the valve pin head 22 has a larger diameter, the pressure waves arriving from the valve pin head 22 oscillates at high frequency thereby preventing the vapour bubbles from growing into large size. As a result of such a valve pin construction, cavitation erosion effect occurring at the valve seat 18 or the valve pin head 22 is minimized thereby enabling efficient sealing. Hence leakage of the high pressure fuel towards the inlet chamber 14a of the inlet valve 100 is minimized.

[00022] According to this disclosure, by designing the valve pin having a valve pin neck with at least two holes and a hollow valve pin body having diameter larger than the diameter of the valve pin neck, the cavitation erosion effect at the conical portion of the valve pin head and at the valve seat is minimized. Hence, leakage of pressurized fuel from high pressure side to a low pressure side is minimized.

[00023] 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 the material of the valve pin, material of the housing are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.