Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1991-03-25
1993-09-21
Miller, Carl S.
Internal-combustion engines
Charge forming device
Fuel injection system
123506, 123387, F02M 4100
Patent
active
052459713
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a fuel-injection pump.
A fuel-injection pump of this type is to be taken, for example, from the older German Application P 3,804,025, now U.S. Pat. No. 4,879,984. In this older version of a fuel-injection pump, the fuel flow was distributed by a plurality of pumps to the injection ports of injection valves by means of a rotary slide valve which was synchronously driven in rotational movement at a predetermined transmission ratio relative to the engine shaft. The injection quantity and injection time were controlled by opening or closing an overflow channel to a relief volume by means of a solenoid valve. When it is necessary to distribute the fuel flow to a plurality of cylinders of an internal-combustion engine, with the increasing number of cylinders of the internal-combustion engine there is a reduction of the particular angular sector of the rotary slide valve which is available for geometrical reasons and over which the injection quantity and the injection time for an individual cylinder can be influenced by means of the solenoid valve. After operating for a relatively long period of time, a rotary slide valve driven simply in rotational movement tends to exhibit signs of wear which in turn cause the rotary slide to seize in its guide.
The fuel-injection pump according to the invention affords the possibility, by means of an axial displacement of the rotary slide valve, of counteracting a seizure of the rotary slide valve in its guide. At the same time, an axial displacement of the rotary slide valve, with an appropriate design of the circumferentially extending recesses for distributing the fuel flow to individual cylinders, and/or a relative rotation of the rotary slide valve in relation to the rotary drive allows the possibility of adjusting the injection time over a larger angular sector than would be possible otherwise in view of the geometrical limits placed on the configuration of the circumferentially measured length of the grooves of the rotary slide valve which serve for distribution. Particularly in internal-combustion engines with more than four cylinders, without an additional possibility of influencing the shift of the injection time, the geometrical limits of the rotary slide valve itself are already clearly detectable.
To shift the effective angular sector for distributing the fuel flow to an injection port of a particular cylinder of the internal-combustion engine, advantageously the design is such that the rotary slide valve can be fixed in its rotary position or displacement position in dependence on an operating parameter of the internal-combustion engine. Considered as an operating parameter of the internal-combustion engine here is primarily the speed of the internal-combustion engine or else a control variable related to the speed of the internal-combustion engine, such as, for example, the fuel pressure of a fuel pump driven in synchronism with the engine shaft, an oil pressure or the like. The corresponding control variable can also be derived from a centrifugal governor.
To influence the particular desired displacement position of the rotary slide valve dependent on an operating parameter in the direction of its axis of rotation, the rotary slide valve can advantageously be displaceable in the direction of this axis of rotation against a stop adjustable in dependence on an operating parameter. The measure of providing a separate stop of this type makes it possible in a simple way to utilise a pressure dependent on an operating parameter for adjusting the stop, advantageously the design being such that the adjustable stop is formed by a stop piston which can be subjected hydraulically to speed-dependent pressure. Instead of a separate stop piston of this type, the rotary slide valve itself can also be designed in a simple way as a piston, in which case subjecting such a rotary slide valve designed as a piston to a pressure medium on the piston end face can be utilised directly for displacing the rotary slide valve, and advantageously the working space
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Haag Gottlob
Linder Ernst
Rembold Helmut
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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