Internal-combustion engines – Charge forming device – With fuel pump
Patent
1993-08-19
1996-07-30
Miller, Carl S.
Internal-combustion engines
Charge forming device
With fuel pump
123506, F02M 3704
Patent
active
055402062
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a fuel injection device for internal combustion engines.
Fuel injection devices for internal combustion engines are very common and have gained acceptance in practical applications in many different variations, all of which have different deficiencies.
Pumps with plungers or pistons that are activated by cams are customary for the direct injection of diesel fuel as well as the injection in the so-called precombustion chamber process, whereby the cams are arranged on a cam shaft that is directly driven by the crank shaft. The quantitative adjustment is facilitated by control edges machined into the pistons or plungers. Pumps of this type require a high operating power over the entire crank path of the internal combustion engine or the diesel engine, and may thus not be controlled electronically.
An injection device of the initially mentioned type may in comparison be regulated by an electronic control. The construction of such a known injection device is in the following described with reference to FIG. 1 in conjunction with FIGS. 2 and 3, which illustrate typical pressure profiles of the pressure impulse device by means of which fuel is supplied to the injection nozzle.
Fuel is fed from the fuel tank (1) into a fuel line (5) at a pressure between approximately 3 and 10 bar by means of a fuel pump (2), whereby a pressure regulator (3) and a damping device (4) are arranged in said line. A shut-off valve (6) which is, for example, activated electromagnetically is arranged at the end of the line (5), and the fuel accelerated by the pump (2) is returned to the fuel tank (1) via the shut-off valve if said valve is opened. The abrupt closing of the shut-off valve (6) transforms the kinetic energy of the fuel flowing through the line (5) as well as the line (7) into pressure energy. The intensity of the thus created pressure impulse is approximately between 20 and 80 bar, which in other words means approximately 10 times the flow pressure produced by the pump (2) in the line (5), which is also called the oscillation line. The pressure impulse created at the shut-off valve (6) is used for the ejection of the thus accelerated fuel via an injection nozzle (10), which is, via a pressure line (9), connected to the valve (6) and thus the line (5).
This known fuel injection device may be controlled electronically, i.e., by means of an electronic control unit (8) that is connected to the valve (6), due to the utilization of a shut-off valve that may be controlled electromagnetically,
The pressure impulse produced in the pressure line (5) during the abrupt closing of the shut-off valve (6) travels through the lines (5,7 and 9) in the form of a pressure wave at the speed of sound, whereby the energy of the pressure wave in the lines (5 and 9) is available for the ejection of fuel via the nozzle (10). The pressure wave propagating in the oscillation line (5) is reflected at the outlet of the pump (2), and travels back to the shut-off valve (6). The duration of this direct pressure impulse phase corresponds with the duration in which the pressure wave travels through the oscillation line (5), and causes the pressure duration at the injection nozzle (10). After this direct pressure impulse phase, a residual pressure energy which travels back and forth in the oscillation line remains in the oscillation line (5). FIG. 2 illustrates a typical temporal profile of the pressure impulses in the oscillation line if no damping device (4) is arranged in the line (5). This pressure profile is characterized by a primary pressure wave with maximum energy and a subsequent secondary pressure wave with increasingly decreasing energy. Any of these pressure waves may basically cause an injection. However, the sequence of these pressure waves limits the obtainable operating frequency of the system, which is the reason why the secondary pressure waves are suppressed for the benefit of defined operating conditions. The damping device (4) which suppresses all secondary pressure waves and is arranged in the oscillation line
REFERENCES:
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patent: 3709639 (1973-01-01), Suda
patent: 3961612 (1976-06-01), Okamoto
patent: 4345565 (1982-08-01), Bottoms
patent: 4599983 (1986-07-01), Omachi
patent: 4699103 (1987-10-01), Tsukahara
patent: 4712528 (1987-12-01), Schaffitz
Ficht GmbH
Miller Carl S.
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