Internal-combustion engines – Charge forming device – With fuel pump
Patent
1994-09-02
1995-11-28
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
With fuel pump
123499, 123447, F02M 5104, F02M 6306
Patent
active
054698286
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a fuel injection device for internal combustion engines according to the type disclosed in the preamble of claim 1.
Fuel injection devices whose electrically driven reciprocating pumps work according to the so-called solid-state energy storage principle, have a delivery plunger or cylinder which on a specific path is accelerated virtually without resistance, whereby usually fuel is moved before the build-up of the delivery pressure required for the ejection of the fuel through the injection nozzle. In this way, before the pressure build-up necessary for the actual injection, kinetic energy is absorbed or stored which is then abruptly converted into a pressure rise in the fuel.
With a so-called pump-nozzle element operating on the solid-state energy storage principle known from DD-PS 120 514, the fuel delivery space accommodating the delivery plunger of the injection pump has in a first section axially parallel arranged grooves in the inner wall through which the fuel can flow off to the rear of the delivery plunger when the delivery plunger begins to move without a significant pressure build-up in the fuel. The adjacent second section of the fuel delivery space is the actual pressure chamber which does not have grooves. When the accelerated delivery plunger enters this pressure chamber, it is abruptly slowed down by the incompressible fuel, so that the stored kinetic energy is converted into a pressure impulse which overcomes the resistance of the injection nozzle so that fuel is injected. An attendant disadvantage is that when the delivery plunger enters the second section of the delivery space, unfavorable gap conditions viz. a relatively large gap width and a relatively small gap length produce noticeably high pressure losses which particularly reduce the possible speed and pressure level of the pressure buildup and so exert an unfavorable influence on the ejection. The pressure losses are caused by flowing off of fuel from the pressure chamber into the pressure antechamber (first section of the fuel delivery space).
According to DD-PS 213 472 this advantage should be avoided if in the pressure chamber of the delivery plunger an impact body is arranged on which the plunger, accelerated almost without resistance, impacts, so that the pressure loss during the pressure build-up can be kept acceptably small by a relatively large gap length despite a relatively large gap width (large manufacturing tolerances) between the impact body and the inner wall of the pressure chamber. This has, however, the disadvantage that the impact leads to considerable wear of the impacting elements. Moreover, the impact sets up longitudinal oscillations in the impact body and these oscillations are transferred to the fuel and in the form of high-frequency pressure oscillations disturb the injection process.
A special disadvantage of these known solid-state energy storage injection devices is that the injection process can only be controlled to a very limited extent and can therefore only be adapted to the load conditions of the engine to DE-OS 23 07 435, where the reciprocating pump has for moving pump element a sleeve-like pump cylinder which slides endwise on a pump piston in fixed position in the pump housing and defines the pump pressure chamber which is connected to the injection device via a longitudinal bore in the pump piston. A cross bore in the pump cylinder allows the flowing off of fuel to the rear of the cylinder during energy storage. The passage of the piston front edge across the bore results in the pressure build-up and so to the ejection of fuel. Here too, clearance losses are high during pressure build-up.
The object of the invention is the creation of a cheap, simple to manufacture device for fuel injection of the type described above, which makes possible the injection of fuel without noticeable pressure losses during pressure build-up, free from wear, precisely metered according to load and especially suitable for high-speed combustion engines.
This object is achieved by the chara
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Heimberg Wolfgang
Hellmich Wolfram
Kogl Franz
Malatinszky Paul
Ficht GmbH
Moulis Thomas N.
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