Field of the invention
[001] This invention relates to the field of fuel injection systems for an internal
combustion engine. The invention relates in specific to a high pressure fuel pump.
Background of the invention
[002] High pressure fuel pumps are used in fuel injection pumps. The pumps receive fuel through inlet, pressurize them using a plunger and deliver the pressurized fuel to the engine. Typically at the inlet of the pumps a ball valve is disposed. The ball valve allow the fuel to flow in one direction, normally from the inlet to the compression chamber. The ball valve has a spring and the compression and expansion of the spring enables opening and closing of the ball valve.
[003] The prior art US 6,209,527 Bl discloses such valve. The prior art discloses pressure regulating valve, which has a valve chamber having an inlet for connecting to a pressure Source, a discharge chamber communicating through a valve opening with the valve chamber, a valve member, a valve Seat Surrounding the valve opening, a valve closing Spring which presses the valve member against the valve Seat with an adjustable Spring force.
Brief description of the accompanying drawing
[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 fuel pump according to one embodiment of the
invention
Fig. 2 illustrates a blown up view of a ball valve

Detailed description of the embodiments
[006] FIG. 1 illustrates atypical high pressure fuel pump 100 according to the prior art. The high pressure fuel pump is just referred as pump in this document. The pump 100 comprises a housing 102, a plunger 104 which moves reciprocally in a bore in the housingl02, an inlet connector 106 and a ball valve 108 to receive fuel, an outlet bore 109 through which the pressurized fuel is delivered to the engine and a return path 110 which returns excess fuel to the fuel reservoir which is not shown. The outlet bore 109 is in perpendicular plane to the view of the fig. 1.
[007] The plunger is driven by a roller tappet which is driven in turn by a cam shaft of the engine which is not shown. The roller tappet pushes the plunger 104 in the direction of the compression chamber 111 and the spring 113 pulls the plunger in the direction of the roller tappet thereby causing the compression stroke and the suction stroke respectively.
[008] During the suction stroke, the ball valve 108 opens and the plunger 104 moves in the direction of roller tappet because of the spring tension. The fuel is sucked into the compression chamber 111. When the plunger 104 starts moving in the direction of the compression chamber 111, the ball valve 108 closes, the fuel is pressurized in the compression chamber 111. Once the pressure increases in the compression chamber 111, the pressurized fuel is delivered through the outlet bore 109 to the engine. This cycle repeats as long as the engine is running.
[009] The fuel to the high pressure pump is delivered by a feed pup. The fuel enters into the pump through the inlet. There is a ball valve at the inlet which on opening connects the inlet to the compression chamber. The ball valve comprises a ball and a spring. The spring has a pretension. During the suction stroke, once the pressure of the

incoming fuel into the inlet overcomes the tension of the spring, the ball lifts and the fuel flows from the inlet to the compression chamber through the ball valve. In the prior art, the spring is a linear spring with the coils of the spring having equal spacing. With this the ball lifts gradually in a linear rate. After the suction stroke, the compression stroke begins and the ball closes the ball valve. This enables the compression of the fuel in the compression chamber. The rate at which the ball valve opens is referred as lift rate.
[010] When the ball is lifting gradually with a linear rate, the velocity of the fuel passing through the ball valve, develops gradually and it is initially slow. If there is a particle stuck in between the sealing of the ball valve and the ball, the ball will not be able to move to close the ball valve, resulting in permanent open position of the ball valve. With the ball valve remaining open permanently, the pump will not be able to pressurize the fuel. This results in engine not starting.
[Oil] To overcome this disadvantage, the invention proposes a progressive spring 114a, 114b instead of a linear spring at the ball valve 108. The progressive spring 114 which comprises the parts 114a and 114b has different spacings between the coils of the spring. At the opening side of the progressive spring, the coils 114a are widely placed. At the closing side of the progressive spring, the coils 114b are closely placed.
[012] With the progressive spring 114 at the inlet as part of the ball valve 108, the ball lifts initially at a faster rate. This causes higher velocity of the fuel from inlet into the compression chamber 111. Because of the higher velocity, even if any particle is stuck between the valve sealing and the ball, the particle is flushed out. During the later part of the lift, the coils with lesser spacing act and the lift of the ball happens at a relatively slower rate. This combination of widely spaced and closely spaced coils of the

progressive spring 114 will result in overall required delivery of the fuel into the compression chamber 111.
[013] By using a simple progressive spring 114, the starting of the engine is achieved at faster rate. Also the problem of ball valve remaining open because of some particle getting stuck between the ball and the valve sealing is eliminated.

CLAIMS
We Claim:
1. A pump (100) comprising :
a housing (102);
a plunger (104) moving in a bore in said housing (102);
an inlet connector (106) and a ball valve (108) in said housing (102), to
receive fuel for pressurizing;
an outlet bore (109) to deliver pressurized fuel;
a return path (110) in said housing (102) to return excess fuel;
a sealing ring (112) to prevent mixing of fuel with lubricating oil; said pump (100) characterized by a progressive spring (114) as part of said ball valve (108).
2. A pump (100) according to claim 1 wherein said progressive spring 114 has at least two different coil spacings (114a, 114b) for the coils
3. A pump (100) according to claim 1 wherein said progressive spring (114a, 114b) has different tensions for different spacings of the spring
4. A pump (100) according to claim 1 wherein said progressive spring (114a, 114b) opens said ball valve (108) at least with two different lift rates.