Pumps – With condition responsive pumped fluid control – Expansible chamber pump distributor operation modified
Reexamination Certificate
1999-03-18
2001-05-29
Walberg, Teresa (Department: 3742)
Pumps
With condition responsive pumped fluid control
Expansible chamber pump distributor operation modified
C123S510000
Reexamination Certificate
active
06238190
ABSTRACT:
TECHNICAL FIELD
The invention relates to fuel injection pumps for internal combustion engines, particularly direct-injection diesel engines.
BACKGROUND OF THE INVENTION
Fuel delivery systems for internal combustion engines, such as spark ignition engines, require a fuel injector pump and a direct-injecting fuel nozzle for delivering fuel directly into the combustion chamber for each of the working cylinders of the engine. The pump includes a pump plunger that reciprocates in a pump pressure cavity. The plunger is driven mechanically by a crankshaft-driven camshaft so that the pumping stroke frequency is directly proportional to engine speed. Such systems further require a precision fuel control valve for establishing and interrupting fuel delivery from the pump to the nozzle, the valve being controlled by a solenoid actuator that in turn is responsive to controlled current pulses in a driver circuit for an electronic engine control system. As the injector pump creates the necessary pressure pulses, the metering of fuel delivery from the injector pump through the nozzles is under the control of the fuel control valve.
The injector pump is supplied with fuel by a fuel supply pump that communicates with the fuel supply side of the injector pump. It operates with a relatively low inlet fuel supply pressure. Fuel circulates continuously through the solenoid-operated fuel control valve as the fuel supply pump distributes fuel to the injector pump.
In a fuel supply system of this kind, it is possible for liquid fuel cavitation to occur, especially at high engine speeds when the injector pump supplies the nozzle with fuel at a relatively rapid rate. Since delivery of a fuel charge to the nozzle occurs with a pulse frequency that is related to engine speed, the inertia created by the mass of the fuel flow may be sufficient to create cavitation in the fuel delivery passage on the upstream side of the nozzle and on the downstream side of the solenoid-operated fuel control valve. Further, a tendency exists for pressure pulses to be fed back to the injector pump, particularly at high engine speeds. The solenoid-operated valve cannot effectively isolate the injector pump from pressure peaks that occur in the fuel delivery passages. If the pressure peaks enter the pump pressure cavity, damage to the pump and premature pump failure may occur because of the pressure forces caused by the pressure peaks.
BRIEF DESCRIPTION OF THE INVENTION
The fuel injector pump assembly of the present invention includes a snubber valve assembly located in a fuel delivery passage on the fuel delivery side of the solenoid-operated fuel control valve and on the upstream side of the injector nozzle. It provides relatively unrestricted fluid flow from an injector pump pressure cavity to the nozzle, but it includes a flow control orifice that provides a controlled restriction in reverse flow of fuel toward the control valve following each fuel pressure pulse in the injector pump pressure cavity. A pressure pulse occurs as the injector pump plunger is stroked, and the injector pump cavity pressure decreases as the control valve is opened during the injector pump refill cycle following delivery of a controlled fuel charged to the nozzle.
The snubber valve assembly includes a movable valve element situated in a fuel delivery passage formed in the pump body. It is subjected to fuel pressure on the outlet side of the pump. A valve seat formed in the pump body is engaged by a valve surface of the movable valve element. The valve surface preferably is of conical shape. A calibrated flow metering orifice is formed in the snubber valve element to provide continuous flow of fluid from the injector pump to the nozzle.
The movable valve element is displaceable from a fuel delivery passage closed position to a fuel delivery passage open position in response to development of a pressure pulse by the pump. This establishes a substantially unrestricted fuel flow passage that is parallel to the flow metering orifice.
The pressure developed by the injector pump is sufficient to cause the movable valve element to shift to an open position and to provide relatively unrestricted fluid flow to the nozzle through relatively large flow control orifices. When the pressure of the fuel charge is decreased due to the opening of the control valve, the valve closes the unrestricted fluid flow passage, although the calibrated fuel flow metering orifice continues to allow restricted back flow of fuel from the nozzle to the intake side of the pump plunger cavity.
The snubber valve assembly thus provides a controlled fluid flow restriction at the end of the fuel delivery pressure pulse cycle and a relatively unrestricted flow during the beginning of the fuel delivery pressure pulse cycle. This decreases the normal tendency of the fuel on the upstream side of the nozzle to cavitate. It also eliminates or substantially reduces the severity of the pressure pulses that normally could be fed back to the injector pump.
REFERENCES:
patent: 4246876 (1981-01-01), Bouwkamp et al.
patent: 4572433 (1986-02-01), Deckard
patent: 5012785 (1991-05-01), Long et al.
patent: 5390692 (1995-02-01), Jones et al.
patent: 5749717 (1998-05-01), Straub et al.
patent: 6006782 (1999-12-01), Felton
Czarnecki Philip James
Ogren Daniel Brian
Weliver Scott
Brooks & Kushman P.C.
Campbell Thor
Diesel Technology Company
Walberg Teresa
LandOfFree
Fuel injection pump and snubber valve assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuel injection pump and snubber valve assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel injection pump and snubber valve assembly will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2436718