Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-04-11
2002-06-18
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S447000
Reexamination Certificate
active
06405709
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to cyclic pressurization systems, such as fuel systems, including cam actuated unit injectors for storage and recovery of fuel pressurization energy.
BACKGROUND OF THE INVENTION
Designers of fuel systems for diesel engines have come under increasing pressure to achieve ever higher standards of emission abatement while also achieving improved fuel efficiency. It is commonly accepted among such designers that the capability of flexibly adjust injection pressure in the 35 to 200 MP a range is desirable to achieve satisfactory reduction of emissions and increased fuel efficiency. In addition, more precise and predictable control on a cycle by cycle basis (i.e., rapid adjustment) will need to be exercised over various aspects of each fuel injection event such as the metering, timing, pressure, and rate of fuel injection including provision for a pilot injection just prior to the main injection event immediately following the main injection event. At the same time, designers are required to consider the costs associated with the development, manufacture and reliability of any new fuel system since such costs can be staggering not just for design and testing but also for the ancillary costs associated with changing existing engine architecture to accept new types of fuel systems.
Within this context, advanced diesel fuel injection systems are evolving to provide greater flexibility and efficiency in both their application and operation. In recent years, the fuel systems industry has focused attention on the development of energy accumulating, nozzle controlled, fuel system concepts that provide engine speed and load independent control over fuel injection timing, pressure, quantity and multiple injection rate shape. This focused attention has lead to the commercialization of several concepts packaged in the general form of a fluid pressurizing pump connected to a hydraulic energy storage device or high pressure common rail (HPCR) connected to one or more electrically operable injector nozzles. An example of this type of system is disclosed in the commonly assigned International PCT Application WO 94/27041. Other examples include Stumpp et. al. “Common Rail—An Attractive Fuel Injection System for Passenger Car DI Diesel Engines,” SAE Technical Paper Series, No. 960870; Guerrassi et. al., “A Common Rail Injection System for High Speed Direct Injection Diesel Engines,” SAE Technical Paper Series, No. 980803; and Osenga et al. “CAT GEARS Up Next Generation Fuel Systems,” Diesel Progress, August 1998, pp. 82-90.
While these prior art approaches are suitable in many ways, they generally require changes in the architecture of the engine. In particular, the adoption of a high pressure common rail system as a substitute for a fuel system including unit injectors can necessitate a complete redesign of the engine head since the space reserved for the unit injectors is now occupied by an electronically controlled nozzle. At the same time, a high pressure pump is required to be located on the engine in a position permitting a drive connection with the engine crankshaft. This arrangement may require redesign of the gear train at one end of the engine and/or a redesigned camshaft. If the camshaft is changed, various cam driven linkages will likely also require modification.
Numerous examples exist of energy accumulating, nozzle controlled, fuel system concepts employing mechanically actuated unit injectors. For example, see U.S. Pat. Nos. 5,094,215 to Gustafson; 5,535,723 to Gibson et al.; 5,551,398 to Gibson et al.; and 5,676,114 to Tarr et al. (see FIG.
17
). In each of these systems, however, the fuel that is pressurized is fluidically isolated within a single pressurization chamber located within each injector. Still other patents, e.g. U.S. Pat. Nos. 5,676,114 to Tarr et al. and 5,819,704 to Tarr et al., describe a flexible and efficient fuel system that is compatible with known types of high pressure common rail (HPCR), unit pump, and unit injector physical forms. None of these references, however, suggests joining injectors or synchronizing pumping. In fact, no known fuel system, commercially available, combines the energy storage and pumping capacities of two or more mechanically actuated unit injectors to form a high pressure, high volume fuel system for supplying fuel under the precise control necessary to achieve reduced emissions and improved fuel efficiency.
SUMMARY OF THE INVENTION
A general object of this invention is to provide a fluid pressurizing system that overcomes the deficiencies of the prior art by providing a mechanism including plural mechanically actuated pressurizing units for storing and recovering the energy of pressurization.
Another object of this invention is to provide a fuel system that overcomes the deficiencies of the prior art by providing a mechanism for storing and recovering the energy of fuel pressurization while employing cam actuated unit fuel injectors having dimensional and operating characteristics that permit adoption on existing engines with only minimal changes to the basic architecture of the engine such as the head, cam and injector drive trains.
Another object of this invention is to provide a fuel system that significantly increases the hydraulic energy storage and pumping capacities of mechanically actuated unit injectors that fit within the space provided for more conventional unit injectors.
Still another object of this invention is to provide a fuel system that operates to cyclically impart pressurization energy to and recover pressurization energy from fuel trapped within one or more sets of fluidically linked, synchronously operated unit injectors wherein multiple sets may be operated out of phase of each other by a predetermined angular amount.
Another object of this invention is to provide a fuel system including a plurality of unit injectors wherein each injector has a pressurizing plunger mounted for reciprocation within said bore to form a fuel pressurizing chamber from which fuel may be withdrawn at relatively high pressure for injection into a corresponding combustion chamber of the engine through said injection orifice and wherein a camshaft linkage is provided to synchronously reciprocate the pressurizing plungers of one or more sets of two or more unit injectors as the engine camshaft rotates to impart, pressurization energy to fuel trapped within said fuel pressurizing chambers when said pressurizing plungers advance and to recover pressurization energy from fuel trapped within the fuel pressurizing chambers when the pressurizing plungers retract.
Yet another objective is to provide a fuel system of the type described above including a first interconnecting line for allowing selective fluidic interconnection of the fuel pressurizing chambers formed within a first set of unit injectors to allow fluidic linkage of the volume of fuel being simultaneously pressurized and depressurized within the interconnected fuel pressurizing chambers of a first set of unit injectors, wherein the total volume of fuel that is fluidically linked together within a first set of synchronized unit injectors may be made to substantially exceed the volume of fuel injected during each injection event to avoid substantial loss of injection pressure from the beginning to end of each injection event.
Still another object is to provide a fuel system of the type disclosed above including in association with each set of synchronized unit injectors a first pressure control valve moveable between an open condition in which fuel is allowed to flow in either direction between the source of fuel and the interconnected fuel pressurizing chambers of the set of unit injectors and a closed condition in which energy may be imparted to the fuel within the fuel pressurizing chambers of the set of unit injectors as the corresponding pressurizing plungers are advanced and in which energy may be recovered from the fuel within the fuel pressurizing chambers of a first set a unit injectors as the corresponding pressurizing plungers
Benson Donald J.
Carroll, III John T.
Tarr Yul J.
Tikk Laszlo D.
Tuken Taner
Cummins Inc.
Gimie Mahmoud
Leedom Jr. Charles M.
Nixon & Peabody LLP
Yuen Henry C.
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