Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1992-02-28
1993-05-04
Cross, E. Rollins
Internal-combustion engines
Charge forming device
Fuel injection system
417372, 123449, F02M 3900
Patent
active
052072010
DESCRIPTION:
BRIEF SUMMARY
STATE OF TECHNOLOGY
The invention is based on a fuel distribution injection pump for internal combustion engines as defined hereinafter.
In a known fuel injection pump of this distributor type (DE 36 05 452 A1), a magnetically operated valve is so designed that it closes when energizing current is applied, and it opens when the energizing current is removed. During the intake stroke of the pump plunger, the magnetically operated valve remains unenergized so that fuel can be drawn into the pump chamber from the fuel feed, by the pump plunger. As soon as the magnetically operated valve is energized, it closes, and the intake process is completed. This is followed by the start of the compression or pressure stroke of the pump plunger, in which the fuel present in the pump chamber is pressurized. The pressurized fuel passes through an axial hole and a distribution hole into one of the distribution channels in the pump cylinder, from where the fuel to be injected into one of the cylinders is delivered into the connected injection valve. The fuel injection is completed as soon as the energization of the magnetically operated valve is removed. The magnetically operated valve opens, and any fuel still present in the pump chamber is pushed out via the magnetically operated valve into the fuel infeed. The process of opening and closing the magnetically operated valve thus controls the amount of fuel supplied for injection. The problem involved is that of dimensioning the cross-section of flow for the fuel in the magnetically operated valve. To ensure good filling of the pump chamber, the cross-section should be as large as possible, albeit that a large cross-section of flow necessitates longer switching times and a higher current consumption of the magnetically operated valve.
ADVANTAGES OF THE INVENTION
In contrast, the fuel distribution injection pump of the present invention has the advantage that with good filling of the pump chamber, the cross-section of flow of the magnetically operated valve can be kept small, thus allowing for short duration switching and low current consumption of the magnetically operated valve. According to the invention, this is achieved by virtue of the fact that during the intake stroke of the pump plunger, an additional filling of the pump chamber takes place via the filling and relief holes, by-passing the magnetically operated valve. The relief hole has thus a dual function, first--as already described in the DE 24 49 332 C2--to compensate the lateral forces during the pressure stroke of the pump plunger, which act on the pump plunger via the distribution hole, and further, as an additional filling aid during the intake stroke of the pump plunger. In addition, the use of the relief hole for filling the pump chamber has the advantage that no additional dead volume arises in the filling region, which is particularly important when petrol is used as the fuel, because of its low compression module. The diaphragm reservoir then prevents temporary pressure drops during the intake stroke of the pump plunger, so that an exactly reproducible filling of the pump chamber is ensured with every intake stroke.
The measures listed herein enable advantageous developments and improvements of the fuel distribution injection pump set forth herein.
According to an advantageous embodiment of the invention, the filling holes in the pump cylinder are arranged obliquely, i.e. angled acutely, relative to the cylinder axis. This results in an elliptical terminating area of the filling holes, at the transition from the pump cylinder to the pump plunger, which is of advantage for reasons of the cross-section, since the pump plunger during its revolution also performs an axial movement. If in accordance with another embodiment of the invention, the membrane reservoir is connected via a restrictor to a pressureless fuel return, then a certain amount of fuel will be constantly flowing off. The membranae reservoir is thus constantly flushed, and additionally, heat is dissipated, which promotes the accuracy and
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Haag Gottlob
Rembold Helmut
Schlagmuller Walter
Cross E. Rollins
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas
Robert & Bosch GmbH
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