Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-12-27
2001-06-19
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S496000
Reexamination Certificate
active
06247450
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a new fuel injector and fuel injection system for internal combustion engines and particularly for heavy-duty diesel cycle internal combustion engines. The present invention further relates to a fuel injector and fuel injection system which takes advantage of both electronic unit injectors and common rail fuel systems to improve power consumption for the fuel system in reference to drive of a camshaft train.
The present invention further relates to a fuel injection system and a fuel injector which provides high injection pressure characteristic of electronic unit injectors and flexibility of adjusting injection pressure in a common rail system.
The present invention further relates to a new, heavy duty diesel fuel injection system which take advantage of Electronic Unit Injectors (EUI) system, while improving EUI's flexibility to define injection timing and the ability to adjust injection pressure independent of the engine speed or load. In addition, the present invention improves power consumption for the fuel system and improves the roughness of the drive camshaft train.
2. Description of the Related Art
The present invention is related to a electronically controlled fuel injection system and a fuel injector which is capable of being driven from a camshaft train.
Deckard et al., U.S. Pat. No. 4,572,433 discloses an electromagnetic unit fuel injector for use in a multi-cylinder, diesel engine having an externally actuated pump for intensifying the pressure of fuel delivered to the pressure actuated injection valve controlling a flow discharge out through a spray outlet which is normally biased to a closed position by a spring. Pressurized fuel from the pump is supplied via a throttling orifice to a modulated pressure servo-controlled chamber having a servo piston means operatively associated with the injection valve. A drain passage extends from the servo control chamber with flow therethrough controlled by a solenoid actuated control valve in the form of a pop-it valve, which is normally biased to a closed position by a valve return spring of a predetermined force whereby the control valve is also operative as a pressure relief valve and preferably, a secondary pressure relief valve means is also incorporated into the unit injector so that all of the unit injectors for the engine will operate at a uniform maximum peak pressure.
Although Deckard '433 substantially achieves this goal, it has been observed that there are still variations in maximum peak pressure achievable in a fuel system and particularly between individual fuel injection units on an internal combustion engine. This variability in pressure can affect the performance of the engine and reduce the efficiency of the engine during operation.
Gibson et al., U.S. Pat. No. 5,535,723 discloses an electronically controlled fluid injector having pre-injection pressurizable fluid storage chamber in an outwardly opening direct operated check. The Gibson concept is directed to an improved electronically-controlled fuel injection system which comprises a fluid storage chamber in a direct operated check. Pressurization of the fluid in the storage chamber begins before the start of the fluid injection. Fluid injection begins by hydraulically unbalancing the check. Fluid injection sharply ends by hydraulically balancing the check to allow a biasing device to close the check. Fluids such as fuel can be injected as a purely vapor phase to improve mixing and combustion air. The system of Gibson et al controls several fluid injection parameters including higher peak fluid injection capability and less fluid injection pressure drop at the end of injection, thereby resulting in improved engine performance and lower noise, emissions, and wear.
Gibson et al achieves these purposes in part by use of a solenoid means which activates two valves for pressurizing the fuel prior to the injection. The first valve is movable between a first position, which opens fluid communication between the storage chamber and control passage and the second position to close fuel communication. The second valve is a three-way valve such as a pop-it valve or a spool valve which at its first position blocks fluid communication between a pressure control chamber and the control passage and opens fluid communication between the pressure control chamber and the injection chamber.
It has been determined that a simpler and more advanced system is necessary in order to address all the concerns in the fuel injection art. To this end, it's necessary to control the pressure of the fuel from the fuel source all the way through to the injection event. All of these things can be achieved by use of a simple injection mechanism such as disclosed in this application whereby the fuel system is controlled directly from the Engine Control Module (“ECM”) to ensure uniform pressure throughout and maximum results at all engine speeds.
The present invention is directed to overcoming one or more of the shortcomings as set forth above.
SUMMARY OF THE INVENTION
The present invention is a new, electronic controlled fuel injection system as well as an Electronic Unit Injector (EUI) for use in the same. The fuel injection system of the instant invention is designed for use in internal combustion engines and particularly heavy-duty diesel fuel injection systems and takes advantage of both Electronic Unit Injection (“EUI”) and common rail fuel systems. To this end, the high injection pressure of EUI's is combined with the flexibility of adjusting injection pressure in common rail systems. The design of the instant invention improves power consumption for the fuel system, as well as provides the roughness of the system to be driven by a camshaft train.
The system components are comprised of a fuel delivery pump which is preferably a low pressure pump so that output pressure is kept at a constant 10 bar through the relatively low pressure fuel line. The relatively low pressure fuel line is connected to an electronic controlled pressure regulator and pressure sensor. Fuel pressure is feedback adjusted by an electronic control module (ECM) to monitor fuel pressure in the common fuel delivery line and to adjust the pressure regulator to achieve a desired specific fuel delivery pressure accurately. The common fuel delivery line feeds diesel fuel to all injectors at a feed-back controlled pressure. A slow response solenoid with a Pulse Width Modulated (PMW) drive is used to operate the regulator, since the pressure in the common fuel delivery line may not vary rapidly.
Each cylinder in an internal combustion engine is equipped with an electronic unit injector. This electronic unit injector consists of an injector body with a metering orifice in accumulative chamber, a plunger with a returning spring, a solenoid control valve with a spring, and nozzle needle with spring. The fuel injection timing is controlled by the ECM through activation and deactivation of a solenoid control valve.
A metering orifice is precisely machined to provide a flow passage at the plunger bushing wall or in the plunger of the EUI. The amount of fuel being fed in the a cumulative chamber through the metering orifice will be determined by the fuel pressure on the common delivery line and the size of the metering orifice. The volume of the a cumulative chamber is 20 to 60 times the maximum fuel volume/cycle, and is optimized based upon a tradeoff between injector compactness, maximum injection pressure and maximum injector pressure drop.
The system further includes a camshaft with a plurality of specially designed cam lobe to drive the injector plungers. The cam has four sections. The first is a base circle section for fuel metering process. The second is a rising section for pressurizing fuel captured in the accumulative chamber. The third is a zero velocity section when a plunger reaches its maximum lift. The third section should be long enough to cover all possible injection timing sequences. The fourth section is a f
Detroit Diesel Corporation
Moulis Thomas N.
Panagos Bill C.
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