Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1999-04-07
2000-11-28
Miller, Carl S.
Internal-combustion engines
Charge forming device
Fuel injection system
123467, F02M 3704
Patent
active
061521094
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a liquid-fuel injection device for an internal combustion engine.
BACKGROUND OF THE INVENTION
Conventionally, liquid fuel is injected into an internal combustion engine, for example a compression-ignition engine, using a means that establishes fuel pressure, which is in the form of an injection pump capable cyclically of placing fuel under high pressure in a variable-volume chamber formed in a pump cylinder and delimited by a plunger actuated by a camshaft that is kinematically connected to the main shaft or crankshaft of the engine.
The compressed fuel is injected through an injection nozzle which communicates, via a number of injection holes with the working or combustion chamber of the engine, this nozzle including a chamber which communicates with the cylinder of the injection pump, generally through one-way passage means such as a non-return valve. The communication between this chamber and the working or combustion chamber is interrupted by a sliding needle resting, by virtue of the action of elastic return means, on a conical seat formed in the said nozzle upstream of the said injection holes.
This needle includes a cylindrical body sliding in a bore formed in the nozzle and of a diameter that exceeds that of the conical bearing surface of the needle on its seat, so that when the pressure of the fuel exceeds a certain value, known as the rated pressure of the injector, it lifts off its seat to allow injection to take place. When the plunger of the injection pump has travelled beyond a certain position, beyond which the pump cylinder will find itself in communication with low-pressure fuel-supply means, the pressure in the nozzle drops and the injection needle is returned onto its seat, to close the nozzle again, under the action of the aforementioned elastic return means.
In spite of its great simplicity, this conventional device presents serious drawbacks. Firstly, the injection pressure depends on the engine speed and varies with it. Next, because of the necessarily limited force of the return spring, the end of injection occurs at a low pressure which no longer allows the fuel to be finely atomized, this generating unburnt hydrocarbons and particles of soot.
Some of these drawbacks may be avoided using an injection device of the type proposed in Patent FR-A-1,351,593. In such a device, fuel from the pressure-establishing means, such as a pump or an accumulator, is sent to an injection chamber delimited by a plunger moving against a powerful spring, so as to fill the chamber with pressurized fuel during the non-injection phase. This chamber opens directly into the injector cavity in which the shut-off means, such as a needle whose lift can be controlled either by an independent hydraulic circuit or by a circuit using fuel, move. When the needle is made to open and therefore injection is made to take place, the needle moves, over a long travel, until it comes into abutment against the plunger of the injection chamber, this plunger, as it advances delivering fuel from the injection chamber to the injection nozzle, causing the needle to close again.
Such a device does, however, have drawbacks which make it unsuitable for use with very high injection pressures which are used in modern engines and which would result in a heightened risk of fuel leaks and in a loss of power because of some of the fuel spilling out of the injector volume into the supply circuit, not to mention the problem of over-specifying the return spring.
DOS 1,944,862 has also already described an injection device comprising an injection chamber in which a differential plunger moves and which is in direct communication with the injector, control means allowing the injection chamber to be filled, during the non-injection phase, against the action of the pressure of a fuel accumulator kept charged by a high-pressure pump. This device does, however, present appreciable drawbacks. In particular, the injection pressure is only a fraction of the pressure supplied by the pump and
REFERENCES:
patent: 4572136 (1986-02-01), Takeuchi et al.
patent: 4718384 (1988-01-01), Takahashi
patent: 4877187 (1989-10-01), Daly
patent: 5199402 (1993-04-01), Melchior
patent: 5381772 (1995-01-01), Melchior et al.
patent: 5469828 (1995-11-01), Heimberg et al.
patent: 5809771 (1998-09-01), Wernberg
patent: 5896843 (1999-04-01), Lorraine
patent: 6053712 (2000-04-01), Konishi et al.
LandOfFree
Liquid fuel injecting device for internal combustion engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid fuel injecting device for internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid fuel injecting device for internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1714605