Claims:We claim:
1. A high pressure pump (100) for a fuel injection system (200), said high pressure pump (100) comprising :
- a housing (102)
- a fuel inlet (110) in said housing (102)
- a plunger (108) to pressurize fuel
- an outlet in said housing (102) to deliver pressurized fuel
Said high pressure pump (100) characterized by
-a channel (114) in said housing to receive a part of fuel for lubrication
of said pump (100)
- a throttle (115) in said channel (114) to regulate flow of fuel for lubrication of said pump (100)
2. A high pressure pump (100 according to claim 1 wherein said channel (114) guides said fuel to parts of said pump (100) for lubrication
3. A high pressure pump (100 according to claim 1 wherein said channel (114) is in fluid communication with said fuel inlet (110)
4. A fuel injection system (200) comprising:
- a high pressure pump (100);
- an electric feed pump (204) supplying fuel to high pressure pump (100),
said electric feed pump (204) controlled by an ECU (208);
said high pressure pump (100) comprising
- a housing (102);
- a fuel inlet (110) in said housing (102); a plunger (108) to pressurize fuel ;
- an outlet in said housing (102) to deliver pressurized fuel;
- a channel (114) in said housing (102) to receive a part of fuel for lubrication of said pump (100);
- a throttle (115) in said channel (114) to regulate flow of fuel for lubrication of said pump (100)
5. A fuel injection system (200) according to claim 4 wherein said ECU (208) controls the electric feed pump (204) depending upon engine operating conditions
, Description:Field of the invention:
[0001] This invention relates to the field of fuel injection systems. The invention relates in particular to high pressure pumps which supply fuel to the fuel injection systems.

Background of the invention:
[0002] The high pressure pump pressurizes fuel and delivers the fuel under high pressure to a common rail for injection into the internal combustion engines through a set of fuel injectors. The components of high pressure pump require lubrication. Hence a part of the fuel is used for lubricating the moving parts of the high pressure pump. This is typically achieved by means of an overflow valve. The high pressure pump typically comprises a gear pump, a high pressurizing part, a metering unit and an overflow valve.
[0003] Typically the gear pump is a low pressure pump, which sucks fuel from fuel tank, pressurizes the fuel and delivers at the inlet of the high pressurizing part. The metering unit ensures that the fuel is delivered at the inlet of the high pressure pump at required pressure. The overflow valve opens and lets the excess fuel to flow back to the fuel tank.
[0004] The high pressure pumps and the path for lubrication are known in prior arts. The US patent 6021761discloses a high pressure pump to divide fuel for pressurizing and for lubrication. The prior arte relates to a high-pressure pump for fuel delivery in fuel injection systems of internal combustion engines, which includes a tank, a pre-feed pump, and the high-pressure pump. The pre-feed pump aspirates a total fuel flow from the tank and this total fuel flow is divided into a lubricating flow, which is conveyed through the high pressure pump for the purpose of lubrication, and a delivery flow, which is acted on with high pressure by the high
[0005] pressure pump and is delivered to a common distributor rail.

Brief description of the accompanying drawings:
[0006] Shown in fig. 1 is a high pressure fuel pump according to one embodiment
[0007] Shown in fig 2 is a fuel injection system according to one embodiment of the invention
[0008] Shown in fig. 3

Detailed description of the embodiments:
[0009] Shown in fig. 1 is a high pressure pump 100. The high pressure pump 100 is a radial piston pump for high pressure fuel delivery to fuel injection system of internal combustion engine which is not shown in fig. 1. The pump includes a housing 102, in which a drive shaft 104, which has an eccentric shaft section 106, is rotatably supported by bearing components which are not shown in fig.1. A bush is provided which, which encompasses the eccentric shaft section 106, and the eccentric shaft section 106 rotates in this bush. On its circumference, the bush has 3 flattenings that are offset from one another by 120', against each of which a respective piston 108 rests. Each respective piston 108 is supported so that it can carry out a reciprocating motion in a cylinder chamber in the radial direction in relation to the drive shaft 104. The cylinder chamber is constituted by a bearing component which is not shown, that is inserted into housing in the radial direction in relation to the drive shaft 104.
[0010] The high pressure pump 100 is just referred as pump 100.
[0011] The fuel enters the pump through the fuel inlet 110 and flows into the compression chambers 112. The radial piston 108 pressurizes the fuel and supplies the pressurized fuel to common rail. The radial piston is also referred as plunger.
[0012] The bearings and other moving components need lubrication for smooth operations. Part of the fuel is used for this purpose.
[0013] The invention proposes a diversion path or a channel 114 from the inlet of the pump for the lubrication of the pump parts. The diversion path is used to guide a part of the fuel for the lubrication. The diversion path also comprises a throttle 115 to ensure fuel is at constant pressure in the diversion path. The fuel is guided toward the bearing and other moving parts of the pump for the lubrication.
[0014] The diversion path used for the lubrication eliminates the need of overflow valve used in the prior arts for the lubrication purpose. The disadvantage of using overflow valve is that the pressure at the inlet of the overflow valve has to be above a predefined threshold for the overflow valve to allow fuel to pass through. This disadvantage is eliminated in the pump according to the invention. Also need of overflow valve on the pump is eliminated making the pump manufacturing process much easier.
[0015] Also the pump 100 does not need the gear pump component to supply fuel to the high pressure pump. This is managed by controlling the electric feed pump available in the fuel injection system as explained with regard to fig. 2.
[0016] Shown in fig 2 is a fuel injection system 200 comprising the high pressure pump 100 explained in fig. 1. The fuel injection system comprises a fuel tank 201, an electric feed pump 204, a fuel filter 206, an electronic control unit 208, a common rail 210 and a set of injectors 212 to inject fuel into the cylinders of an engine which is not shown.
[0017] The electronic feed pump 204 sucks the fuel from the tank, pressurizes it. The pressurized fuel flows into the fuel filter 206.The fuel is filtered and the filtered fuel flows into the high pressure pump 100. The high pressure pump may comprise multiple plungers to pressurize the fuel further. The high pressure pump delivers the fuel at high pressure to the common rail 210. The fuel is stored in the common rail under high pressure and delivered to the injectors 212 for combustion in the engine. The common rail has a pressure control valve 214. Whenever the pressure in the common rail exceeds a pre-defined threshold, the pressure control valve 214 opens and the excess fuel returns to the fuel tank. Similarly the high pressure pump and the injectors are having return valves to return excess fuel to the tank whenever the pressure exceeds above a predefined threshold.
[0018] In the high pressure pumps used in prior arts had a metering unit built as integral part of the pump. The fuel injection system 200 shown in fig. 2 according to the invention eliminates the metering unit and uses the electric feed pump 204 to deliver required amount of fuel to the high pressure pump 100. The electric feed pump 204 is controlled by the electronic control unit ECU 208. The electronic control unit receives various parameters 216 through various sensors, to determine engine operating conditions. These parameters may comprise engine speed, engine load, torque demand, coolant temperature, common rail pressure etc. Based on these parameters the electronic control unit 208 determines engine operating conditions and determines the amount of fuel to be delivered by the electronic feed pump 204. The ECU 208 accordingly controls the electronic feed pump 204 by controlling the current or voltage supplied to the electric feed pump 204. The ECU 208 shown in fig. 2 may be a stand-alone ECU or it may be an existing ECU already available in the vehicle. The engine operating conditions here may refer to whether the engine is at no load, medium load or full load. There may be other criteria to determine engine operating conditions.
[0019] The invention proposes a simple high pressure pump and a simple fuel injection system using the high pressure pump. The invention has the below advantages:
[0020] The metering unit is eliminated. The electric feed pump performs the functionality of the metering unit.
[0021] The gear pump is eliminated. The electric feed pump is controlled based on the engine operating conditions to supply appropriate amount of fuel to the high pressure pump.
[0022] The overflow valve is eliminated. The lubrication which was performed by the overflow valve is provide by a diversion path in the pump.
[0023] All the above advantages result in simplifying the manufacturing process of the pump thereby reducing the cost of the high pressure pump as well as the fuel injection system.