Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-01-14
2001-04-10
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S506000
Reexamination Certificate
active
06213093
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a system and means for injecting fuel into internal combustion engines.
BACKGROUND ART
Some fuel injection systems have been designed as unit injectors which incorporate an hydraulically driven pressure intensifier with a stepped plunger for injecting fuel into an engine's cylinder where the fuel delivery and timing are controlled by an electronically controlled valve. The spray pattern of each injector is controlled by means of modulating the base oil pressure supplied to each unit injector.
It is known that in many diesel engines the optimum injection curve shapes vary depending on the engine's operating conditions. A pilot injection of a small amount of fuel separate from a main injection may be required at some operating conditions and a boot-shaped injection at other conditions, or a sharp leading front of an injection curve may be the best for another engine speed and load. The correlations between engine operating conditions and the optimum shapes of the injection curves are often complex. Therefore it is desirable for a diesel injection system to have the shape of an injection curve electronically controlled, so that an engine management system can set the optimum injection characteristics for a wider range of engine operating conditions.
Known unit injection system do not enable control of an injection curve shape independently from the actuating pressure due to the lack of a control channel which can be connected to a nozzle's locking chamber during certain stages of a plunger's metering and injection strokes.
The present invention concerns hydraulically actuated electronically controlled unit injection (HEUI) systems which are well known. The closest art known to the present invention is that of PCT/AU98/0073, the contents of which are incorporated herein by reference.
The difference between the injector and injection system of a first aspect of the present invention and that disclosed in PCT/AU98/0073 resides in the provision of an external groove on the plunger for connection of a plunger's compression chamber with a nozzle's locking chamber during an injection cut-off period.
A second aspect of the present invention resides in the inclusion of a control channel for stabilization and control of the pressure in the locking chamber during parts of the metering and injection strokes of a pressure intensifier, wherein this control channel and the locking chamber can be disconnected from each other by the plunger during an injection cut-off. The pressure in the control channel is typically controlled by an engine management system. When the control channel pressure is increased, the pressure in the compression chamber required to open the nozzle and begin the injection also increases, therefore the leading edge of the injection curve steepens. By means of varying the pressure in the control channel the shape of the leading edge of an injection curve can be controlled.
It is preferable to join the control channels of a set of unit injectors of an engine into a common control chamber with pressure in this chamber controlled by an engine management system. This ensures uniform injection timingmmon control chamber with pressure in this chamber controlled by an engine management system. This ensures uniform injection timing and shape of injection curves in the engine cylinders, simplifies the injection system design and helps keep the cost down as in this case only one pressure regulator is required and it can be mounted anywhere on an engine.
Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.
DISCLOSURE OF INVENTION
In accordance with a first aspect of the present invention there is provided a fuel injector of an injection system for an internal combustion engine, said injector comprising an inlet port; a spill port; a pressure intensifier comprised of a piston forming a working chamber and a spill chamber and a plunger forming a compression chamber, said spill chamber being connected to the spill port via a spill channel, said plunger having a control edge adapted to vary the flow area of said spill channel and close it off in dependence upon the plunger position; a nozzle with a needle, a locking chamber, means biasing the needle to close the nozzle and an outlet chamber connected to the compression chamber; a non-return valve, the inlet of the non-return valve being connected to the inlet port and the outlet of the non-return valve being connected to the compression chamber; an hydraulically controlled differential valve (HDV) comprising an HDV control chamber and having a valve located between the inlet port and the working chamber and opening into the working chamber upon opening, wherein said valve provides a throttling slot and a chamber connected to the HDV control chamber; resilient means biasing the HDV towards its closed position; a control valve installed between the HDV control chamber and the spill port; a cut-off channel connected to the locking chamber; a control channel connected to the spill port; said plunger having an external groove positioned so as to connect the cut-off channel to the compression chamber at an injection cut-off position of the plunger and adapted to connect the cut-off channel to the control channel at other positions.
In a preferred form of the first aspect, the valve located between the inlet port and the working chamber is a poppet with a seating face.
A fuel injection system for controlling an injector of the present invention comprises means for controlling the pressure in the control channel and means for detecting the start of injection comprising a pressure sensor installed in the control channel and an electronic conditioning unit.
In a second aspect the present invention consists in a fuel injector of a fuel injection system for an internal combustion engine, said injector comprising an inlet port; a spill port; a pressure intensifier comprised of a piston forming a working chamber and a spill chamber and a plunger forming a compression chamber, said spill chamber being connected to the spill port via a spill channel; said plunger having a control edge adapted to vary the flow area of said spill channel and close it off in dependence upon the position of the plunger; a nozzle with a needle, means biasing the needle to close the nozzle, an outlet chamber connected to the compression chamber and a locking chamber; a non-return valve, the inlet of the non-return valve being connected to the inlet port and the outlet of the non-return valve being connected to the compression chamber; an hydraulically controlled differential valve (HDV) comprising an HDV control chamber and having a valve located between the inlet port and the working chamber and opening into the working chamber upon opening; resilient means biasing the HDV towards its closed position; a control valve installed between the HDV control chamber and the spill port and adapted to connect said HDV control chamber with the spill port upon command from an engine management system; a cut-off channel connected to the nozzle locking chamber; a control channel connected to the cut-off channel; an additional control valve installed between the control channel and the spill port; said plunger having an external groove positioned so as to connect the compression chamber to the cut-off channel during an injection cut-off position of the plunger.
In a preferred embodiment of the second aspect of the invention, the valve located between the inlet port and the working chamber is a poppet with a seating face.
The present invention is related to unit injectors but includes features which enable electronic control to be applied to the shape of the injection curve of a unit injector independently of the base fluid pressure. I
Mitchell William Richard
Yudanov Sergi
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
Moulis Thomas N.
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