Claims:1. A radial piston pump (102), comprising
a housing (302) having at least one pumping chamber (126), said at least one pumping chamber (126) in flow communication with an inlet (120) to receive fuel and an outlet (122) to discharge pressurized fuel;
a piston (125) located in said at least one pumping chamber (126), said piston (125) is adapted to reciprocate for pressurizing said fuel,
a drive shaft (124) located in a drive chamber (304) of said housing (302), for imparting reciprocal movement to said piston (125) of said at least one pumping chamber (126), said drive chamber (304) supplied with fuel for lubrication of said drive shaft (124), characterized in that:
a bore (208) forming a channel between said inlet (120) and said drive chamber (304).
2. The radial piston pump (102) as claimed in claim 1, wherein said drive shaft (124) comprises a cam fit to one end, said cam imparts reciprocal movement to said piston (125).
3. The radial piston pump (102) as claimed in claim 1, wherein said cam is eccentrically fit to said drive shaft (124).
4. The radial piston pump (102) as claimed in claim 1, wherein said cam is centrally fit to said drive shaft (124) but comprises varying profile.
5. The radial piston pump (102) as claimed in claim 1, wherein said inlet (120) is a ring canal providing a common intake for at least two pumping chambers (126).
6. The radial piston pump (102) as claimed in claim 1, wherein said bore (208) is formed in a flange between said inlet (120) and said drive chamber (304).
7. The radial piston pump (102) as claimed in claim 1 is a high pressure pump.
, Description:Field of the invention:
[0001] The present invention relates to a high pressure pump and particularly relates to Zero Delivery Circuit (ZDC) for a radial piston pump.

Background of the invention:
[0002] According to a patent literature 2474/CHE/2014, a high pressure radial piston pump is disclosed. The high pressure radial piston pump comprises at least a pump housing, a plunger and a drive chamber. The high pressure radial piston pump is characterized by a lubrication supply line fitted to the pump housing. The lubrication supply line is in fluid communication with an overflow line of a fuel metering unit for supplying fuel to lubricate said drive chamber.
Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0004] Fig. 1 illustrates a hydraulic circuit diagram of a fuel delivery system as known in the art;
[0005] Fig. 2 illustrates the hydraulic circuit diagram of the fuel delivery system, according to an embodiment of the present invention, and
[0006] Fig. 3 illustrates a side cross section view of a radial piston pump, according to an embodiment of the present invention.

Detailed description of the embodiments:
[0007] Fig. 1 illustrates a hydraulic circuit diagram of a fuel delivery system as known in the art. The fuel delivery system 100 delivers diesel to a common rail 132. The system 100 comprises a fuel tank 112 fit with a low pressure pump 110. The low pressure pump 110 supplies fuel to a high pressure pump through a filter 114. The high pressure pump is a radial piston pump 102. A housing 302 (shown in Fig. 3) comprises a network of a low pressure circuit along with high pressure circuit. The network comprises interconnected bores drilled inside the housing 302.
[0008] The fuel from the filter 114 reaches to a metering valve 116 comprising but not limited to a solenoid valve or a Magnetic Proportional valve (MProp). An overflow valve 118 is provided which is in flow communication with the metering valve 116. The overflow valve 118 maintains or regulates the required pressure of the fuel for the operation of the metering valve 116. Only the required quantity of fuel is metered by the metering valve 116. The extra/ additional fuel from the overflow valve 118 is sent back to the fuel tank 112 through a backflow channel 104, either directly or through a backflow connector 106.
[0009] The radial piston pump 102 comprises at least one pumping chamber 126 and a piston 125. In the present invention the radial piston pump 102 comprises three pumping chambers 126 and corresponding three pistons 125, and the same must not be understood in limiting sense, as the present invention is applicable for the radial piston pump 102 comprising one, or two, four or more pumping chambers 126. Further, in the Fig. 1, only one pumping chamber 126 and one piston 125 is numbered for the sake of simplicity of explanation, and is applicable for others.
[0010] When the metering valve 116 is open, the fuel passes to the inlet 120 and enters the pumping chamber 126 through a Low Pressure Valve (LPV) 128. The piston 125 pressurizes the fuel when actuated by a drive shaft 124. Due to high pressure of the fuel, a High Pressure Valve (HPV) 130 opens, and the pressurized fuel is supplied to the common rail 132. The inlet 120 and the outlet 122, along with the LPV 128 and the HPV 130 are shown for different pumping chambers 126, in order to maintain simplicity of illustrations and explanation. The fuel simultaneously flows through each of the pumping chambers 126 comprising the respective inlet 120, outlet 122 and the LPV 128, the HPV 130. The pressurized fuel from the outlets 122 of all the three pumping chambers 126 are combined and then supplied to the input of common rail 132.
[0011] An input of metering valve 116 is connected to supply line from the low pressure pump 110 through a connector. When the metering valve 116 is in closed, some amount of fuel with low pressure leaks through. The leaked fuel fills up in the inlet 120 of all the three pumping chambers 126. Since the pressure of the leaked fuel is too less (for example less than 1.2 bar), the LPV 128 does not open. The leaked fuel passes out through a path called as Zero Delivery Circuit (ZDC) 108. The ZDC 108 is fit with a throttle Zero Delivery Throttle (ZDT) (of for example 0.4mm diameter) and connects to backflow channel 104.
[0012] Fig. 2 illustrates the hydraulic circuit diagram of the fuel delivery system, according to an embodiment of the present invention. The radial piston pump 102 comprises a housing 302 having at least one pumping chamber 126. The at least one pumping chamber 126 is in flow communication with the inlet 120 to receive fuel and the outlet 122 to discharge pressurized fuel. The piston 125 is located in each of the at least one pumping chamber 126. The piston 125 is adapted to reciprocate for pressurizing the fuel. The drive shaft 124 is located in the drive chamber 304 of the housing 302, for imparting reciprocal movement to the piston 125 of the at least one pumping chamber 126. The drive chamber 304 is supplied with fuel for lubrication of the drive shaft 124 and other mechanical components. The radial piston pump 102 is characterized by a bore 208 forming a channel between the inlet 120 and the drive chamber 304. The overall function as explained in Fig. 1 remains same.
[0013] The pressure of the leaked fuel is too less and cannot open the LPV 128 of the pumping chamber 126. The bore 208 (example: a step bore of 0.4 mm to 1.5 mm diameter), is made on a wall/flange of housing 302 between the inlet 120 and the drive chamber 304. The bore 208 allows the fuel to flow from the inlet 120 to the drive chamber 304 and connects to backflow channel 104 along with lubrication fuel. Thus, hole/ bore 208 in the flange acts as ZDT. The arrows in the Fig. 1 and Fig. 2 corresponds to direction of fuel flow.
[0014] Fig. 3 illustrates a side cross section view of a radial piston pump, according to an embodiment of the present invention. The drive shaft 124 comprises a cam fit to one end. The drive shaft 124 imparts reciprocal movement to the piston 125 through the cam. The cam is eccentrically fit to the drive shaft 124. Alternatively, the cam is centrally fit to the drive shaft 124 but comprises varying profile. The fuel to the inlet 120 of all the three pumping chambers 126 is either supplied independently or through a common supply chamber called as ring canal. The ring canal provides a common intake for at least two pumping chambers 126. The bore 208 is formed in a flange between the inlet 120 and the drive chamber 304. The radial piston pump 102 is a high pressure pump for a common rail fuel injection.
[0015] Introduction of the bore 208 in the flange/ housing 302 enables to eliminate the ZDC 108 in the housing 302. Elimination of materials like ZDT and a ball to close the ZDC, in turn reduces the corresponding material cost. The elimination of ZDT pressing and ball pressing in turn reduces manufacturing cost, assembly cost and also reduces the complexity of machining in the housing 302. The ZDC 108 is removed and replaced by the bore 208.
[0016] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. 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.