Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
1999-12-28
2001-03-06
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S446000, C239S090000
Reexamination Certificate
active
06196199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, generally, to fuel injector assemblies for internal combustion engines. More specifically, the present invention relates to such a fuel injector having an improved solenoid operated check valve located below the pump chamber and above the nozzle assembly within the injector body.
2. Description of the Related Art
Fuel injector assemblies are employed in internal combustion engines for delivering a predetermined, metered mixture of fuel and air to the combustion chamber at preselected intervals. Fuel injectors commonly employed in the related art typically include a cylindrical bore formed in the main injector body. A plunger is reciprocated within the cylindrical bore to increase the pressure of the fuel. A solenoid actuated control valve is mounted in an injector side body and communicates with a source of fuel. A high pressure fuel passage extends between the solenoid actuated control valve and the cylinder bore. Fuel at relatively low pressure is supplied to the control valve which then meters the delivery of the fuel at predetermined intervals through a fuel passage to the cylindrical bore. Fuel at very high pressures is delivered to a fuel nozzle assembly and ultimately dispersed from the injector.
In the case of compression ignition or diesel engines, the fuel/air mixture is delivered at relatively high pressures. Presently, conventional injectors are delivering this mixture at pressures as high as 32,000 psi. These are fairly high pressures and have required considerable engineering attention to ensure the structural integrity of the injector, good sealing properties and the effective atomization of the fuel within the combustion chamber. In essence, the modern diesel engine must provide substantial fuel economy advantages while meeting ever more stringent emission regulations. However, increasing demands for greater fuel economy, cleaner burning, fewer emissions and NO
x
control have placed, and will continue to place, even higher demands on the engine's fuel delivery system, including increasing the fuel pressure within the injector.
In part to meet the challenges discussed above, electronic engine control modules have been employed to control the beginning and end of the fuel injection event, injection timing and fuel quantity, to improve fuel economy and meet emission requirements.
However, problems still remain. For example, fuel injectors of the type commonly known in the art and briefly described above often include relatively long, internal fuel flow passages. These passages include those extending from the control valve to the pump chamber, passages extending from the pump chamber to the nozzle assembly and passages extending between the high pressure fuel passage and any low pressure fuel return passages. During an injection event, it is not uncommon for pressure waves to develop within these passages. The dynamics of such pressure waves can have a negative effect on fuel injection. In addition, injectors which include shared passages for both fuel feed in and spilling are particularly susceptible to this problem.
Furthermore, it is not uncommon for the solenoid actuated control valve used in the injectors of the related art to experience mechanical bouncing as the valve member is cycled between its open and closed positions. This causes imprecise injection control at the beginning and end of the injection event and is undesirable. Thus, there is an ongoing need in the art for better control over these injection parameters during the span of the injection event in a cost effective manner.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages in the related art in a fuel injector assembly for an internal combustion engine having an injector body in fluid communication with a source of fuel. The injector assembly further includes a nozzle assembly through which fuel is dispersed from the fuel injector assembly during an injection event. A high pressure fuel delivery system provides high pressure fuel to the nozzle assembly. The injector body also defines a low pressure fuel spill gallery in which unused fuel is collected from the fuel delivery system. The high pressure fuel delivery system includes a cylindrical bore and a plunger supported for reciprocation within the cylindrical bore. A pump chamber is defined by the plunger and the cylindrical bore. A high pressure fuel passage extends through the injector body from the pump chamber to the nozzle assembly for dispersing fuel at high pressures from the injector assembly.
In addition, the injector assembly includes a solenoid operated check valve which is located between the pump chamber and the nozzle assembly and between the low pressure fuel spill gallery and the high pressure fuel passage. The check valve is operable to control the pressure in the high pressure fuel delivery system. More specifically, the check valve is movable between an open position wherein fluid communication is established between the high pressure fuel passage and the low pressure spill gallery thereby reducing the pressure in the fuel delivery system, to a closed position which interrupts fluid communication between the high pressure fuel passage and the low pressure spill gallery thereby increasing the pressure in the fuel delivery system and facilitating the delivery of fuel at high pressure from the pump chamber to the nozzle assembly.
The fuel injector assembly is therefore compact having the control valve located very close to the nozzle assembly. The injector assembly employs very short flow passages extending from the high pressure fuel passage to the control valve as well as from the control valve to the low pressure fuel spill gallery. The pump chamber is also formed at a relatively low place along the vertical length of the injector assembly. Furthermore, the fuel injector assembly requires no changes to mount it to a cylinder head.
Thus, one advantage of the fuel injector of the present invention is that it minimizes the effects of pressure wave dynamics on the control valve and nozzle assemblies by using very short flow passages and locating the control valve between the pumping chamber and the nozzle assembly at a position low on the injector assembly.
Another advantage of the present invention is that it minimizes the effects of fuel feeding and spilling pressures on the injector performance by employing separate fuel feed in and fuel return passages.
Another advantage of the present invention is that it provides for more accurate control of the solenoid actuated check valve. This feature results in better control of the injection event and provides for better pilot injection capability.
Other objects, features and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in connection with the accompanying drawings.
REFERENCES:
patent: 4402456 (1983-09-01), Schneider
patent: 5443047 (1995-08-01), Ishiwata et al.
patent: 5463996 (1995-11-01), Maley
patent: 5535723 (1996-07-01), Gibson et al.
patent: 5628293 (1997-05-01), Gibson
patent: 5743228 (1998-04-01), Shorey et al.
patent: 5819704 (1998-10-01), Tarr et al.
patent: 5915361 (1999-06-01), Heinz et al.
patent: 5941215 (1999-08-01), Augustin
Detroit Diesel Corporation
Moulis Thomas N.
Panagos Bill C
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