Fluid sprinkling – spraying – and diffusing – Unitary injection nozzle and pump or accumulator plunger
Patent
1990-11-26
1992-11-03
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Unitary injection nozzle and pump or accumulator plunger
123503, F02M 5920
Patent
active
051600889
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a fuel injection pump for diesel engines, in which at least one pump piston with a pump piston bushing creates a high pressure chamber and is surrounded by a control sleeve, whereby the angle position between pump piston and control sleeve is variable to adjust the quantity and whereby an axial bore hole in the pump piston connects the high pressure chamber with a control bore hole or a groove forming a shutoff edge and a startup edge to end the injection process, which works together with a control edge or control hole in the control sleeve.
In DE-OS 35 90 194, various versions of a series pump are described, whereby in one embodiment a radial bore hole in the piston works together with a startup edge and a shutoff edge of the control sleeve and in another embodiment a groove on the piston supplied by a radial bore hole works together with a control bore hole in the control sleeve.
In DE-OS 36 30 647, a pump nozzle is described in whose injection pump a groove on the piston fed by a radial bore hole works together with a control bore hole in the control sleeve. In other pump nozzles (e.g DE-OS 31 43 073) a radial bore hole of the pump piston works together with control edges of the control sleeve. In all of them, the control sleeve can also be moved axially to adjust the start of injection.
All these injection pumps, with an axial bore hole in the piston that leads from the high pressure to the control openings, are of the SIMMS construction type, which distinguishes itself with a symmetrical and thus light and easy to manufacture piston. However, at very high injection pressures and high pump piston speed, in current diesel engines with speeds up to 5000 rpm and high pressure injection, this construction type has disadvantages.
Starting at a certain engine speed and with late injection start, a quantity of fuel leaks out of the injector nozzle before the start of the injection and/or the pilot injection in nozzles with divided injection, the so-called pre-supply. This is undesirable, since its disrupts that exact control of the injection start, disrupts the form of the injection curve by an extended injection duration and interruption of the pressure increase and decreases the injection adjusting range.
This disadvantageous pre-supply is caused by the fact that starting at the pump piston position in which the feed holes are already closed, the axial and the connecting radial bore holes in the piston and/or in the control sleeve still have fuel flowing through them until the radial bore holes are completely closed. At certain pump piston speeds, this causes a pressure wave passing through the axial bore hole which is deflected into the high pressure chamber if the cross section of the radial bore holes is too small. These pressure peaks can exceed the opening pressure of the injection nozzle, whereby a little fuel passes into the engine combustion chamber.
A further cause of the pre-supply is the throttle effect of the various bore holes. With successive covering of the control bore hole, as well as with fast cross section decrease, the pressure in the high pressure chamber increases so strongly according to the throttle curve that the opening pressure of the valve needle is achieved prematurely.
Modern vehicle diesel engines have a deceleration fuel shut off that shuts off the fuel supply completely during braking and when driving over downhill stretches. In this zero-feed, as it is called, in the known injection pumps, there are sudden injections at higher engine speeds because of similar dynamic effects. This represents a heavy safety risk and also increases fuel consumption. In fact, during zero feed, the flow path between SIMMS bore hole and control sleeve chamber may never be completely closed. The free cross section must even remain so large that in spite of dynamic effects and throttle curve the opening pressure of the valve needle is not achieved.
Finally, a fine adjustment of the idle injection pump that is as exact as possible is desireable above all in modern diesel e
REFERENCES:
patent: 4571161 (1986-02-01), Leblanc et al.
patent: 4846114 (1989-07-01), List
Baumgartner Peter
Weiss Gerhard
Kashnikow Andres
Morris Lesley D.
Voest-Alpine Automotive Gesellschaft m.b.H.
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