Fuel pumping device for two-stroke engines with an additional dr

Details Fuel pumping device for two-stroke engines with an additional dr Fuel pumping device for two-stroke engines with an additional dr

1999-01-28

2000-12-19

Walberg, Teresa

Pumps

Motor driven

Electric or magnetic motor

417380, 417395, 123 73C, 123 73AD, F04B 1700, F04B 4306

Patent

active

061620289

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention is based on a fuel pumping device for an internal combustion engine operating in accordance with the two-cycle principle.
Such a fuel pumping device is known from DE 37 27 266 A1. This document describes a diaphragm piston pump, which delivers and compresses fuel for operating an injection device. To this end, the fuel is supplied to the diaphragm piston pump from a fuel tank via a pre-delivery pump. The fuel which is compressed there is delivered to the injection valve. The diaphragm piston pump is provided with motive force by the pulse air diverted out of the crankcase of the internal combustion engine. To this end a diaphragm is seated on the piston compressing the fuel, on which the pulse air acts on the side facing away from the piston. The overpressure being created in the crankcase during a combustion cycle actuates the compression piston. A mechanical spring, together with the underpressure in the crankcase during the compression cycle of the two-cycle engine, performs the return stroke of the compression piston.
A comparable diaphragm piston pump for a fuel injection device is described in DE 41 25 593 A1, wherein the return stroke of the compression-piston takes place by means of a leaf spring package. The spring rate of the leaf spring package can be mechanically changed by means of an adjustment screw.


SUMMARY OF THE INVENTION

The fuel pumping device in accordance with the invention contains at least one diaphragm piston pump, wherein the pulse air connection terminates in a housing chamber located between the diaphragm and the pump piston. At least one spring element acts on each side of the diaphragm, wherein the spring element arranged in the housing chamber is supported on the diaphragm via the separate pump piston. The pulse air is in direct connection with the pump piston in this structural variant. For one, this has the advantage that the oil-containing pulse air flowing in from the crankshaft lubricates the moving parts in this housing section, so that the spring supports and the seal between the pump piston and the housing element guiding it undergo less wear. For another thing, in case of a leak between the pump piston and the housing element guiding it, the fuel coming out there is aspirated during the compression stroke of the two-cycle engine. Therefore the fuel does not get to the outside as in the known diaphragm piston pumps.
In addition, the fuel pumping device is equipped with a drive unit which supports it at least in the starting and/or the idle phase. The drive unit acts on the pump piston via the diaphragm by means of a pressurizing tappet, which oscillates synchronously with the pressure pulsation of the amount of gas enclosed in the crankcase. By means of this a minimum injection pressure required for the operation of the two-cycle engine is generated at least during the starting and/or idling rpm, i.e. during low pressure pulsation.
The drive unit can be a permanent magnet generator, for example, which supplies the magnet with the required energy at respectively the correct time. The dynamic tuning of the electro-magnetic actuator preferably takes place in respect to the optimal function during starting, or respectively idling. The electrical support is no longer needed at higher engine rpm. The pressure pulsation is sufficient for generating the minimum injection pressure.
The pressurizing tappet of the drive unit can of course also be supported on the single spring element which, inter alia, causes the compression stroke of the pump piston.
Furthermore, with the diaphragm piston pump introduced here, there is no rigid mechanical connection between the pump piston and the diaphragm on which the pulse air acts, or respectively its diaphragm disk. The stroke of the diaphragm is transferred, free of lateral forces, to the pump piston. This also reduces the wear on the pump.
The diaphragm piston pump can be equipped with a manual key. To this end, the pressurizing tappet of the electrical drive unit is extended out of the hous

REFERENCES:
patent: 4022174 (1977-05-01), Brinkman
patent: 4086036 (1978-04-01), Hagen et al.
patent: 4813391 (1989-03-01), Geyer et al.
patent: 5197417 (1993-03-01), Tuckermann et al.
patent: 5315968 (1994-05-01), Niebrzydoski
patent: 5735250 (1998-04-01), Rembold et al.

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