Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-05-19
2001-05-08
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S501000
Reexamination Certificate
active
06227166
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to hydraulically-actuated fuel injection systems, and more particularly to a hydraulically-actuated electronically-controlled fuel injector whose actuation is mechanically enabled.
BACKGROUND ART
In most fuel injectors, fuel is pressurized within the injector body by a reciprocating plunger. In one class of fuel injection systems, this plunger is driven downward during its pumping stroke by utilizing a relatively high pressure hydraulic actuation fluid. While virtually any available fluid, including fuel fluid, could conceivably be used as the hydraulic medium in such a fuel injector, Caterpillar, Inc. of Peoria, Ill. has encountered considerable success in utilizing engine lubricating oil as the hydraulic medium in hydraulically-actuated fuel injectors. An example of such a hydraulically-actuated electronically-controlled (HEUI) fuel injector is shown for example in U.S. Pat. No. 5,213,083 to Glassey.
In, a typical HEUI fuel injector, the flow of high pressure actuation fluid to an individual injector is controlled by a solenoid actuated control valve attached to each individual injector. Each injection event is initiated when an engine electronic control module commands energization of the solenoid actuated control valve to move it to open an injector's high pressure actuation fluid inlet. As high pressure actuation fluid (oil) flows into the injector, the internal plunger is driven downward to pressurize fuel. When the fuel reaches a valve opening pressure, a needle valve member opens and fuel commences to spray out of the nozzle outlet of the individual injector. Each fuel injection event is ended by de-energizing the solenoid actuated control valve to close the high pressure actuation fluid inlet. This in turn ends the downward pumping stroke of the internal plunger and causes fuel pressure to drop. When the fuel pressure drops below a certain pressure, the needle valve member closes the nozzle outlet, and the injection event is ended. Between injection events, some biasing means, such as a return spring, retracts the plunger for a subsequent injection event.
While these basic HEUI fuel injectors have performed magnificently for many years, engineers are continuously looking for ways to improve the same. It has become well known that particulate and NOx emissions from a diesel engine can be significantly reduced if one has the ability to control an injection rate profile independent of engine operating conditions. For instance, one injection profile will optimize emissions at idle conditions, whereas a completely different injection rate profile will optimize emissions at a high rpm fully loaded condition for a particular diesel engine. Injection rate profiles have generally been divided into four different groups including pilot injection, boot shaped injection, ramp-square injection and square injection. In almost all cases, engineers have discovered that emissions can be significantly improved if each injection event can be ended as abruptly as possible.
In order to improve control over injection rate shaping and hence the ability to reduce undesirable emissions in a diesel engine utilizing a HEUI type fuel injection system, Caterpillar, Inc. introduced the concept of a directly operated needle valve in HEUI type fuel injectors. This concept is disclosed, for example, in U.S. Pat. No. 5,463,996 to Maley et al. In this type of fuel injector, a first solenoid control valve controls the opening and closing of the high pressure actuation fluid inlet and a second solenoid control valve controls the opening and closing of the needle valve member. In this fuel injector, the needle valve member is modified to include a closing hydraulic surface on one end that is exposed to fluid pressure in a needle control chamber. The needle control valve opens the needle control chamber to one of either a source of high pressure fluid or a low pressure passage. The injector is designed such that the needle valve member will not open or will abruptly close whenever the needle control chamber is opened to the source of high pressure fluid. When the needle control chamber is open to the low pressure passage, the needle valve member behaves as a conventional needle check valve. While the innovation of direct control over the needle valve permits a significant improvement in injection rate shaping, the inclusion of two separate solenoid actuated control valves is less than desirable from both a cost and reliability or robustness standpoint.
The present invention is directed to improving upon the hydraulically-actuated electronically-controlled fuel injection systems of the prior art.
DISCLOSURE OF THE INVENTION
In one embodiment of the present invention, a fuel injection system includes a fuel injector that defines an actuation fluid cavity, a fuel inlet and a nozzle outlet. An actuation fluid supply passage connects the actuation fluid cavity to a source of relatively high pressure actuation fluid. A fuel fluid supply passage connects the fuel inlet to a source of relatively low pressure fuel fluid. A mechanically actuated valve is attached to the actuation fluid supply passage and is moveable between an open position in which the actuation fluid supply passage is open, and a closed position in which the actuation fluid supply passage is closed.
In another embodiment, a fuel injector includes an injector body that defines an actuation fluid inlet, an actuation fluid cavity, a needle control chamber, a fuel inlet and a nozzle outlet. A mechanically actuated valve is attached to the injector body and moveable between a first position in which the actuation fluid inlet is open to the actuation fluid cavity and a second position in which the actuation fluid cavity is closed to the actuation fluid inlet. A needle valve member is positioned in the injector body and has a closing hydraulic surface exposed to fluid pressure in the needle control chamber. The needle valve member is moveable between an open position in which the nozzle outlet is open and a closed position in which the nozzle outlet is blocked. A needle control valve is attached to the injector body and moveable between an off position in which the needle control chamber is open to a source of high pressure fluid and an on position in which the needle control chamber is open to a source of low pressure fluid.
In still another embodiment of the present invention, a fuel injector includes an injector body that defines an actuation fluid inlet, an actuation fluid drain, an actuation fluid cavity, a needle control chamber, a fuel inlet and a nozzle outlet. A mechanically actuated valve is attached to the injector body and includes a cam actuated tappet member exposed outside of the injector body and a spool valve member positioned in the injector body. The spool valve member is moveable between a first position in which the actuation fluid cavity is open to the actuation fluid inlet but closed to the actuation fluid drain, and a second position in which the actuation fluid cavity is closed to the actuation fluid inlet but open to the actuation fluid drain. A needle valve member is positioned in the injector body and has a closing hydraulic surface exposed to fluid pressure in the needle control chamber. The needle valve member is moveable between an open position in which the nozzle outlet is open and a closed position in which the nozzle outlet is blocked. A needle control valve is attached to the injector body and moveable between an open position in which the needle control chamber is open to a source of high pressure fluid and an on position in which the needle control chamber is open to a source of low pressure fluid.
REFERENCES:
patent: 3955547 (1976-05-01), Aoki et al.
patent: 4425893 (1984-01-01), McJones et al.
patent: 4440132 (1984-04-01), Terada et al.
patent: 4674448 (1987-06-01), Steiger
patent: 4784101 (1988-11-01), Iwanaga et al.
patent: 5176120 (1993-01-01), Takahashi
patent: 5213083 (1993-05-01), Glassey
patent: 5245970 (1993-09-01), Iwaszkiewicz et al.
patent:
Caterpillar Inc.
Liell & McNeil
Miller Carl S.
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