Hydraulic pump circuit

#The present disclosure is directed to a circuit for a hydraulic pump and, more particularly, to a drain prevention circuit for a hydraulic pump.

#Hydraulic pumps are commonly used for many purposes in many different applications. Vehicles, such as, for example, highway trucks and off-highway work machines, commonly include hydraulic pumps that are driven by an engine in the vehicle to generate a flow of pressurized fluid. The pressurized fluid may be used for any of a number of purposes during the operation of the vehicle. A highway truck, for example, may use pressurized fluid to operate a fuel injection system or a braking system. A work machine, for example, may use pressurized fluid to propel the machine around a work site or to move a work implement.

#A hydraulic pump typically draws fluid from a reservoir and applies work to the fluid to increase the pressure of the fluid. The hydraulic pump may direct the pressurized fluid into a fluid rail or another supply system. The hydraulic pump may be configured to vary the amount of pressurized fluid that is directed into the fluid rail. This may be accomplished with a variable displacement pump or with a fixed displacement pump that has a variable flow.

#FIG. 1 is a schematic and diagrammatic representation of a first exemplary hydraulic pump; and

#FIG. 2 is a schematic and diagrammatic representation of a fuel injection system having a hydraulic pump in accordance with an exemplary embodiment of the present invention.

#An exemplary embodiment of a pump 10 is diagrammatically and schematically illustrated in FIG. 1. In the illustrated embodiment, pump 10 is a fixed-displacement variable flow pump. It is contemplated, however, that the present disclosure may be applied to other types of pumps, such as, for example, variable displacement pumps.

#As illustrated in FIG. 1, pump 10 includes a housing 13 and an inlet 12. Inlet 12 may be connected to a tank 28 that stores a supply of low pressure operating fluid. Tank 28 may be part of an engine lubrication system, such as, for example, a lubricating oil sump and the operating fluid may be a lubricating oil.

#Inlet 12 directs the low pressure operating fluid to a pumping element 18. Pumping element 18 applies work to the low pressure fluid to increase the pressure of the fluid. Pumping element 18 may include, for example, a series of pistons (not shown) that are driven by a swashplate (not shown) to pressurize the operating fluid. The angle of the swashplate may be constant to provide a fixed displacement pump. Alternatively, the angle of the swashplate may be variable to change the displacement of the pump. One skilled in the art will recognize that another type of pumping element 18 may also be used, such as, for example, a gear, gearotor, or vane pump, to pressurize the operating fluid.