Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2001-11-08
2002-08-27
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S446000, C123S300000
Reexamination Certificate
active
06439202
ABSTRACT:
TECHNICAL FIELD
This invention relates to a fuel system for an internal combustion engine and more particularly to a unit injector fuel system including a common rail capable of offering a variety of injection pressure and rate-shaping characteristics.
BACKGROUND
A fuel system is the component of an internal combustion engine which often has the greatest impact on performance and cost. Accordingly, fuel systems for internal combustion engines have received a significant portion of the total engineering effort expended to date on the development of the internal combustion engine. For this reason, today's engine designer has an extraordinary array of choices and possible permutations of known fuel system concepts and features. Design effort typically involves extremely complex and subtle compromises among considerations such as cost, size, reliability, performance, ease of manufacture, and retrofit capability on existing engine designs.
The challenge to contemporary designers has been significantly increased by the need to respond to governmentally mandated emissions abatement standards while maintaining or improving fuel efficiency. In view of the mature nature of fuel system designs, it is extremely difficult to extract both improved engine performance and emissions abatement from further innovations in the fuel system art. Commercially competitive fuel injection systems of the future will almost certainly need to not only incorporate new design features for better achieving various objectives including improved engine performance and emissions abatement but, combine the appropriate features in the most effective manner to form a system capable of most efficiently, effectively and reliably achieving the greatest number of objectives.
Some of the most important features for achieving objectives such as improved engine performance and emissions abatement include high injection pressure capability, improved hydraulic and mechanical efficiency, quick pressure response and effective and reliable injection rate shaping capability. Other important features include drive train noise control and packaging flexibility for enabling installation on various engine configurations including retrofitting existing engines. In recent years, in an effort to provide greater operating flexibility and performance, the fuel systems industry has focused considerable attention on developing energy accumulating, nozzle controlled concepts that provide engine speed and load independent control over fuel injection timing, pressure, quantity and multiple injection rate shaping. This attention has lead to the commercialization of fuel systems packaged in the general form of a fluid pressurizing pump connected to a hydraulic energy storage device, i.e. an high pressure accumulator or common rail, connected to one or more electrically operable injector nozzles. SAE Technical Papers 960870 and 980803 both disclose common rail fuel injection systems having a high pressure common rail containing high pressure fuel for delivery to multiple injectors. Each injector includes a servo-controlled needle valve element assembly. The assembly includes a control volume in communication with an outer end of the needle valve element, a drain circuit for draining fuel from the control volume to a low pressure drain, and an injection control valve positioned along the drain circuit for controlling the flow of fuel through the drain circuit so as to cause the movement of the needle valve element between open and closed positions. Opening of the injection control valve causes a reduction in the fuel pressure in the control volume resulting in a pressure differential which forces the needle valve open, and closing of the injection control valve causes an increase in the control volume pressure and closing of the needle valve. U.S. Pat. No. 5,133,645 to Crowley et al. discloses a similar system. These systems all permit speed and load independent pressure control, a broad fuel injection timing range, and fast injection timing, quantity, and multiple pulse rate shaping transient response. However, in these systems, fuel injection pressure is varied by changing the pressure in the entire common rail making fuel pressure responsiveness difficult to achieve. Moreover, the large volume of fuel at high pressure requires more expensive seals along with greater risk of leakage and repair costs.
Another conventional approach is disclosed in U.S. Pat. Nos. 5,535,723 and 5,551,398 and SAE Technical Paper 961285 which disclose a unit fuel injector system including a mechanically actuated plunger in each injector and a servo-controlled needle valve element assembly. Fuel is supplied to each injector at a low supply pressure and pressurized by the plunger to a very high injection pressure. Each of these systems also includes a pump control valve for controlling the flow out of a pumping chamber to control the pressurization of the fuel to a high pressure level. These systems advantageously permit very high injection pressures. U.S. Pat. No. 5,463,996 issued to Maley et al. discloses a similar system wherein the high pressure fuel for injection is generated by a hydraulically driven intensifier plunger.
Consequently, there is a need for a high pressure fuel system for an internal combustion engine which is capable of providing enhanced operating flexibility and performance with respect to at least injection pressure and rate shaping while protecting investments in existing engine architectures.
SUMMARY OF THE INVENTION
It is an object of the present invention, therefore, to overcome the disadvantages of the prior art and to provide a fuel injection system capable of effectively and predictably controlling fuel injection timing and metering.
It is another object of the present invention to provide a fuel injection system capable of controlling fuel injection pressure independent from engine speed.
It is yet another object of the present invention to provide a fuel injection system capable of providing greater operating flexibility and performance.
It is a further object of the present invention to provide a fuel injection system capable of providing a wide range of selectable injection pressure levels for creating multiple injections including pilot and/or post injections in combination with a main injection event.
It is a still further object of the present invention to provide a highly efficient high pressure fuel injection system capable of recuperating the pressure energy stored in the pressurized fuel in the common rail following an injection event.
Yet another object of the present invention is to provide a fuel injection system which protects investments in existing engine architectures by being easy to retrofit on existing mechanically operated unit injector-equipped engines.
Still another object of the present invention is to provide a fuel injection system capable of providing extremely high pressures main injections while permitting lower pressure pilot injections.
A still further object of the present invention is to provide a fuel injection system capable of combining the desirable features of mechanically operated unit injectors and contemporary common rail concepts in packaging that is cost effective.
Yet another object of the present invention is to provide a fuel injection system which provides rapid pressure response, improved small injection metering repeatability and accuracy, improved limp home and fail safe functionality and energy recovery for improved operating efficiency.
Another object of the present invention is to provide a fuel system capable of high pressure injections, triangular rising rate shape and high modularity and redundancy.
It is yet another object of the present invention to provide a high pressure fuel injection system capable of a broad fuel injection timing range supporting pilot, main, post and after treatment needs; speed and load independent pressure control; low noise, vibration and harshness (NVH); and high operating efficiency.
It is still another object of the present invention to provide
Benson Donald J
Carroll, III John T.
Peters Lester L
Brackett, Jr. Tim L.
Cummins Inc.
Leedom Jr. Charles M.
Miller Carl S.
Nixon & Peabody LLP
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