Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2002-05-17
2004-01-13
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S457000
Reexamination Certificate
active
06675774
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a fuel injection system of the type employing a common rail and a pressure limiting valve for lowering system pressure
2. Description of the Prior Art
Fuel reservoir injection systems (so-called common rail systems) are known in principle. A distinction is made between common rail systems with a quantity-regulated high-pressure pump (known as CP3 systems), in which a pressure reduction in the fuel pressure reservoir (rail) is possible only via the injection and control quantity and leakage, and common rail systems in which a pressure limiting valve on the high-pressure side is used to lower the system pressure. The subject of the present invention is the latter type of system, that is, one with a pressure limiting valve for lowering the system pressure.
With respect to the prior art for such pressure limiting valves, reference may be made for instance to European Patent Disclosure EP 0 267 162 B1 and German Patent Disclosure DE 198 22 671 A1. The known pressure limiting valves are intended exclusively for mounting not only outside the fuel injection pump (the high-pressure pump) but also outside the fuel reservoir (rail) per se. Typically, the pressure limiting valve is secured to the end of the fuel reservoir remote from the high-pressure pump. Because of the high pressure prevailing in the fuel reservoir, until now a valve housing with a threaded stub for screwing the pressure limiting valve to the fuel reservoir was practically indispensable. Because of the high pressure, problems arise in particular in sealing off the pressure limiting valve from the fuel reservoir. Other inadequacies of the known system result from the requirement that on account of the high pressure, the valve housing must be very massive (high costs!) and because of the comparatively large installation space required.
OBJECT AND SUMMARY OF THE INVENTION
The object of the invention is to make suitable provisions for eliminating or at least significantly reducing the problems of sealing, components and installation space, at reasonable engineering effort and expense.
By means of the integration, according to the invention, of the valve seat and the valve body and thus of the essential functional elements of the pressure limiting valve with the fuel reservoir, the region where the pressure limiting valve is sealed off is shifted from the (former) high-pressure region to the low-pressure region, which makes the sealing task considerably easier to perform. At the same time, this provision of the invention advantageously provides a corresponding reduction in the installation space required and also affords the possibility of designing the pressure limiting valve housing, and its fastening to the fuel reservoir, in a less complicated way than before.
REFERENCES:
patent: 4205637 (1980-06-01), Ito et al.
patent: 4653528 (1987-03-01), Field et al.
patent: 4732131 (1988-03-01), Hensel
patent: 6135092 (2000-10-01), Schaenzer
patent: 6148798 (2000-11-01), Braun et al.
patent: 6311673 (2001-11-01), Hotta et al.
patent: 6336442 (2002-01-01), Kilgore
Boecking Friedrich
Frank Kurt
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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