Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-05-01
2001-06-12
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S446000
Reexamination Certificate
active
06244250
ABSTRACT:
FIELD OF THE INVENTION
The invention is relates to a common rail injector having an injector housing that can be made to communicate via a high-pressure connection with a high-pressure reservoir. The nozzle needle is axially displaceable against a nozzle needle seat in order to adjust the injection onset and the injection quantity in a common rail injection system of an internal combustion engine as a function of the position of a magnet-controlled control piston that is prestressed counter to a spring.
BACKGROUND OF THE INVENTION
In conventional common rail injectors, it is true that the opening point and possibly the closing point of the magnet valve can be characterized by means of control current analysis, but the motion of the nozzle needle cannot. Functional monitoring of the injectors is possibly only at additional expense, for example with the needle stroke sensors.
OBJECT AND SUMMARY OF THE INVENTION
An object of the invention is to furnish a common rail injector of the type described at the outset in which the opening and/or closing operation of the nozzle needle is detectable in operation.
In a common rail injector having an injector housing that can be made to communicate via a high-pressure connection with a high-pressure reservoir and in which a nozzle needle is axially displaceable against a nozzle needle seat in order to adjust the injection onset and the injection quantity in a common rail injection system of an internal combustion engine. As a function of the position of a magnet-controlled control piston that is prestressed counter to a spring, this object is attained in that the nozzle needle is coupled via an intermediate piece to a servo piston that cooperates with the control piston. As a result, a direct communication between the nozzle needle and the servo piston is made possible. The injection onset for each injector can thus be associated with top dead center. A functional diagnosis of the injection event can be made at any time by means of control current analysis.
A particular embodiment of the invention is characterized in that between the high-pressure connection and a control chamber, a first throttle is provided, whose diameter is less than the diameter of a second throttle that is provided between the control chamber and a pressureless chamber in the interior of the servo piston. A first control piston seat and a second control piston seat, which are spaced apart from one another, are formed on the control piston between the control chamber and the pressureless chamber. The two seats on the control piston limit the stroke of the servo piston relative to the control piston. By means of the two throttles, it is attained that the pressure in the control chamber drops when there is flow through both throttles. This in turn means that the servo piston and the intermediate piece move into the control chamber, the effect of which is that the nozzle needle is lifted from its seat.
A further particular embodiment of the invention is characterized in that a stop for the servo piston is provided in the injector housing. By means of the stop, the motion of the servo piston in the opening direction of the nozzle needle is limited.
A further particular feature of the invention is characterized in that the end face, protruding into the control chamber, of the servo piston is larger than the face of the nozzle needle acted upon by pressure. This assures that the nozzle needle is pressed against the nozzle needle seat if the same pressure prevails in the control chamber and at the nozzle needle, and if there is no current through the magnet that actuates the control piston.
Further advantages, characteristics and details of the invention will become apparent from the ensuing description, in which an exemplary embodiment of the invention is described in detail in conjunction with the drawing. The characteristics recited in the claims and in the description can be essential to the invention individually or in arbitrary combination.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment taken in conjunction with the drawing.
REFERENCES:
patent: 4437443 (1984-03-01), Hofbauer
patent: 4545352 (1985-10-01), Jourde et al.
patent: 4784101 (1988-11-01), Iwanaga et al.
patent: 5176120 (1993-01-01), Takahashi
patent: 5341783 (1994-08-01), Beck et al.
patent: 5477834 (1995-12-01), Yoshizu
patent: 5915361 (1999-06-01), Heinz et al.
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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