Suction controlled pump for HEUI systems
AssigneeBosch Rexroth AG
InventorsBrian William Smith, Eric D. Ramseyer, Mark Douglas Correll
Life of this patent
Estimating the term…
Abstract
A HEUI system uses a fixed displacement, radial piston pump to provide a generally constant pump flow of high pressure hydraulic fluid over the operating speed range of the radial piston pump to minimize parasitic power drains on the engine. The radial piston pump includes an orificing suction slot to vary the pump displacement over the operating speed of the pump. A throttling valve at the pump inlet may be provided to starve inlet fluid feed if reduced flow to the injectors is additionally required.
Claims38
A radial piston high pressure pump for an internal combustion engine, the engine having a hydraulically-actuated electronically-controlled fuel injection system including a fuel injector valving high pressure fluid in response to commands from an ECM to inject a quantity of fuel into an engine combustion chamber, the fuel injector in fluid communication with the outlet of the high pressure pump and the high pressure pump having an inlet in fluid communication with a low pressure pump and operable within a pump operating range, the high pressure pump comprising:
- a housing defining a centerline;
- a plurality of radially extending piston bores angularly spaced about the centerline, each piston bore having a discharge opening in fluid communication with the pump outlet, and each piston bore communicating with the pump inlet via an aperture having a set area;
- a check valve positioned in each discharge opening;
- a shaft rotatably received by the housing and substantially aligned with the central axis, the shaft defining a cam surface;
- and
- a plurality of pistons each having a first end engaging the cam surface and each reciprocatingly received within a respective piston bore, such that reciprocation of the pistons covers and uncovers the apertures, the pistons being reciprocable to pump fluid through the discharge openings to provide a substantially constant flow of fluid from the pump throughout the pump operating range.
In a diesel engine equipped with hydraulically actuated electronically controlled unit fuel injectors having a high pressure pump in fluid communication with a high pressure rail connected to the injectors in turn utilizing solenoids actuated by an ECM to control valving of high pressure pump fluid within the injectors to timely and variably actuate the injectors, the improvement comprising:
- a fixed displacement radial piston pump having a substantially constant flow over its operating range in unaltered fluid communication with said high pressure rail whereby an electronically controlled, pressure regulating valve controlling pump pressure in said high pressure rail is alleviated.
A constant flow, fixed displacement, radial piston pump comprising:
- a non-rotatable housing containing a plurality of radially extending piston bores angularly spaced about a centerline of the pump;
- a rotatable shaft having an eccentric cam surface;
- a piston movable within each bore having one end extending through a bore end and in sliding contact with the eccentric cam surface while the piston's opposite end is adjacent an outlet check valve at the opposite bore end;
- the pump having a discharge chamber in fluid communication with all piston check valves and with the pump outlet;
- and,
- each piston having a suction slot of set area communicable with the pump inlet, the suction slot transversely positioned at a set distance between the piston ends and sealed and opened by movement of each piston within its bore whereby fluid flow into the piston bore decreases in proportion to increases in shaft rotational speed after the operating speed of the pump has been reached.
A HEUI fuel injection system comprising
- a plurality of hydraulically-actuated fuel injectors,
- a low pressure pump, and
- a high pressure pump having an operating range, having an inlet communicating with the low pressure pump and having an outlet communicating with the fuel injectors for actuating the fuel injectors, the high pressure pump including a cam surface, a housing having a centerline and defining a plurality of piston bores extending radially away from the centerline, the piston bores having therein respective pistons biased against the cam surface such that relative rotation of the housing and the cam surface causes reciprocation of the pistons in the piston bores, each of the piston bores communicating with the pump outlet, and each of the piston bores being communicable with the pump inlet via an opening of set area so that the high pressure pump has a generally constant output flow over its operating range.
A HEUI fuel injection system comprising
- a plurality of hydraulically-actuated fuel injectors,
- a low pressure pump, and
- a high pressure pump having an operating range, having an inlet communicating with the low pressure pump and having an outlet communicating with the fuel injectors for actuating the fuel injectors, the high pressure pump including a stationary housing having a centerline and defining a central chamber in which a shaft is rotatable about the centerline, the shaft having thereon a cam surface that rotates with the shaft and that is eccentric relative to the shaft, and the housing defining a plurality of piston bores extending radially away from the centerline, each of the piston bores having a radially outer end communicating with the pump outlet via a check valve, the piston bores having therein respective pistons each having a radially inner end biased against the cam surface such that rotation of the cam surface causes reciprocation of the pistons in the piston bores, and each of the pistons having a hollow interior and having therein a respective opening of set area, the opening communicating with the pump inlet when the piston is in a suction position, the piston moving from the suction position toward the check valve to force fluid out of the piston bore through the check valve, so that the high pressure pump has a generally constant output flow over its operating range.
Dependencies are inferred from the claim text.