EP0263808B1 - Pump element of a fuel pump for an injection combustion engine - Google Patents

Pump element of a fuel pump for an injection combustion engine Download PDF

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Publication number
EP0263808B1
EP0263808B1 EP19870890210 EP87890210A EP0263808B1 EP 0263808 B1 EP0263808 B1 EP 0263808B1 EP 19870890210 EP19870890210 EP 19870890210 EP 87890210 A EP87890210 A EP 87890210A EP 0263808 B1 EP0263808 B1 EP 0263808B1
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EP
European Patent Office
Prior art keywords
plunger
bore
delivery
pump element
control edge
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Expired - Lifetime
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EP19870890210
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German (de)
French (fr)
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EP0263808A1 (en
Inventor
Theodor Dipl.-Ing. Dr. Stipek
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Robert Bosch AG
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Robert Bosch AG
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/20—Varying fuel delivery in quantity or timing
    • F02M59/24—Varying fuel delivery in quantity or timing with constant-length-stroke pistons having variable effective portion of stroke
    • F02M59/26—Varying fuel delivery in quantity or timing with constant-length-stroke pistons having variable effective portion of stroke caused by movements of pistons relative to their cylinders
    • F02M59/265—Varying fuel delivery in quantity or timing with constant-length-stroke pistons having variable effective portion of stroke caused by movements of pistons relative to their cylinders characterised by the arrangement or form of spill port of spill contour on the piston
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M55/00—Fuel-injection apparatus characterised by their fuel conduits or their venting means; Arrangements of conduits between fuel tank and pump F02M37/00
    • F02M55/001—Pumps with means for preventing erosion on fuel discharge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00—Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/44—Details, components parts, or accessories not provided for in, or of interest apart from, the apparatus of groups F02M59/02 - F02M59/42; Pumps having transducers, e.g. to measure displacement of pump rack or piston

Definitions

  • the invention relates to a pump element of a fuel injection pump for injection internal combustion engines, in which the pump piston liner has at least one suction and overflow bore, which is ground over by control edges of the pump piston and the delivery end is determined by opening the suction and overflow bore, one in the area of the piston face arranged control edge determines the start of delivery and an arranged, in particular oblique, control edge on the piston skirt determines the delivery end, the pump piston having an axial bore, from which in the area of its end facing the piston face at least one radial bore extends, which on the piston skirt in which the suction and overflow bore overlapping area between the control edge determining the end of conveyance and the control edge determining the start of conveyance opens.
  • a device of the type mentioned at the outset has become known, for example, from DE-A 1 954 123, the axial bore in the piston originating from the working chamber thereof and via a radial bore in the region of the oblique control groove to end the injection process by connection to a suction and overflow hole opens.
  • the axial bore also opens into a throttle bore arranged between the two control edges, in order to allow part of the fuel delivered under pressure to flow away throttled in a rotational position of the pump piston corresponding to an idling operation, in order to reduce the noise load when the engine is idling.
  • the object of the invention is to counteract such cavitations and erosions.
  • the invention essentially consists in that the axial bore against the working space of the pump piston is designed to be closed, and that at least one radial bore opening at the piston skirt extends from the axial bore in the region of its end facing away from the piston face, which at least during one Part of the piston stroke is connected to a flushing oil supply bore provided in the pump piston bushing, through which fuel is supplied to the axial bore independently of the delivery of the pump element under a pressure exceeding the pressure in the suction chamber. From this flushing oil supply bore in the pump piston liner, fuel reaches the axial bore of the pump piston and from there through the radial bore into the suction and overflow bore of the pump piston liner.
  • the fuel Since the pressure of this fuel used for purging is above the pressure in the suction chamber, the fuel enters the suction and overflow bore and displaces the vapor bubbles away from the pump piston in the direction of the suction chamber. Since the radial bore emanating from the axial bore lies between the control edge that determines the delivery end and the control edge that determines the start of delivery, the steam bubbles are flushed away from the suction and overflow bore just before the control edge that determines the delivery end releases the suction and overflow bore. When the diverter jet, which has a large amount of energy, enters the suction and overflow bore, the vapor bubbles are already largely displaced from the critical point, namely from the pump piston.
  • the pressure of the flushing fuel jet is substantially lower than the pressure of the fuel jet that is turned off at the end of delivery, the vapor bubbles cannot be imploded hard by the flushing fuel jet.
  • the flushing fuel jet enters the suction and overflow bore of the pump piston liner as soon as the mouth of the radial bore begins to grind over the suction and overflow bore, and this flushing fuel jet therefore preferentially pushes the gas bubbles off the top of the suction and overflow bore, and this is the top side the critical point at which the pilot jet hits. Cavitation and erosion by hard imploding of the vapor bubbles is therefore largely avoided in this way.
  • the openings of the radial bores on the piston skirt preferably lie at equal distances from the control edge which determines the end of the delivery, so that the conditions for supplying the fuel used for purging are not changed.
  • the arrangement of several radial bores has the advantage that the flushing fuel enters the suction and overflow bore axially at all rotational positions of the piston, thereby promoting the removal of the gas or vapor bubbles.
  • the radial bore provided in the region of the end of the axial bore facing the piston end face can also open into a groove on the piston skirt that runs parallel to the control edge that determines the delivery end.
  • the arrangement can be such that the radial bore provided in the region of the end of the axial bore facing away from the piston end surface opens into a groove running parallel to the control edge which determines the conveying end, the axial distance from this control edge approximately equal to the axial distance of the flushing oil supply bore from the Suction and overflow drilling corresponds.
  • the flushing fuel is supplied intermittently whenever the mouth of the radial bore slides over the suction and overflow bore.
  • the radial bore provided in the region of the end of the axial bore facing away from the piston end face may open into an annular groove, the axial extent of which is at least equal to a substantial part of the piston stroke. In this case, the flushing fuel is supplied to the axial bore continuously, the flushing fuel only emerging from the radial bore when it drags over the suction and overflow bore of the pump piston liner.
  • Fig. 1 shows a partial axial section through a pump element
  • Fig. 2 shows the flow conditions in the S aug / overflow bore shortly before the static delivery begins
  • Fig. 3 shows a variant for flushing oil supply
  • Fig. 4 shows a development of the pump piston with modified radial Holes.
  • the pump piston with 1 and the pump piston sleeve with 2 is designated. 3 is the working area of the pump piston.
  • diametrically opposite two suction and overflow openings 4 are provided, which open into the suction chamber 5, and are ground through oblique control edges 6, which determine the end of the delivery.
  • An axial bore 7 is provided in the piston 1, which is closed off from the working space 3 by a plug 8.
  • a radial bore 10 emerges, which opens into a helical groove 11 on the jacket of the pump piston 1, which runs parallel to the oblique control edge 6.
  • the pump piston bushing 2 there is a flushing fuel supply bore 12, through which fuel is supplied via a connection 13 at a higher pressure than the pressure in the suction chamber 5.
  • radial bores 14 extend from this axial bore, the orifices 15 of which lie on the circumference of the piston in a row running parallel to the control edge 6.
  • the groove 11 is arranged so that it sweeps over the flushing fuel supply hole 12 when the mouths 15 of the holes 14 grind over the suction and overflow holes 4.
  • the condition for this is that the axial distance between the orifices 15 of the bores 14 and the bore 10 in the piston is approximately equal to the axial distance of the bore 12 from the suction and overflow bore 4.
  • Fig. 2 shows the position of the piston 1 at the start of delivery.
  • the control edge formed by the end face 9 closes off the suction and overflow opening 4 of the pump piston liner 2 and a jet of fuel enters the suction and overflow bore 4 when it is closed in the direction of arrow 18.
  • the suction and overflow opening through the end face 9 of the piston 1 is terminated, the fuel flow into the bores is suddenly interrupted, which creates a vacuum which is decisive for the formation of vapor bubbles. This illustration explains why 4 vapor bubbles occur in the suction and overflow bore.
  • Fig. 3 shows in a partial section a modified embodiment.
  • the radial bore 10 starting from the axial bore 7 of the pump piston 1 opens into an annular groove 19 of the piston 1, into which the flushing fuel feed bore 12 opens.
  • the axial extent of this annular groove is at least equal to a substantial part of the stroke of the pump piston 1, so that the flushing fuel continuously enters the axial bore 7.
  • the flushing fuel can be supplied separately under pressure via a connection 13
  • the supply can be carried out in a simple manner at a low speed low or low flow rates to save drive energy for a pump.
  • a separate pump is arranged and a valve which can be controlled via a control unit as a function of the speed or delivery rate of the pump is provided.
  • the pump can be switched by the control unit.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)

Description

Die Erfindung bezieht sich auf ein Pumpenelement einer Brennstoffeinspritzpumpe für Einspritzbrennkraftmschinen, bei welchem die Pumpenkolbenbüchse wenigstens eine Saug- und Überströmbohrung aufweist, die durch Steuerkanten des Pumpenkolbens überschliffen wird und das Förderende durch Aufsteuern der Saug- und Überströmbohrung bestimmt wird, wobei eine im Bereich der Kolbenstirnfläche angeordnete Steuerkante den Förderbeginn und eine am Kolbenmantel angeordnete, insbesondere schräge, Steuerkante das Förderende bestimmt, wobei der Pumpenkolben eine axiale Bohrung aufweist, von welcher im Bereich ihres der Kolbenstirnfläche zugewendeten Endes wenigstens eine Radialbohrung ausgeht, welche am Kolbenmantel in dem die Saug- und Überströmbohrung überschleifenden Bereich zwischen der das Förderende bestimmenden Steuerkante und der den Förderbeginn bestimmenden Steuerkante mündet.The invention relates to a pump element of a fuel injection pump for injection internal combustion engines, in which the pump piston liner has at least one suction and overflow bore, which is ground over by control edges of the pump piston and the delivery end is determined by opening the suction and overflow bore, one in the area of the piston face arranged control edge determines the start of delivery and an arranged, in particular oblique, control edge on the piston skirt determines the delivery end, the pump piston having an axial bore, from which in the area of its end facing the piston face at least one radial bore extends, which on the piston skirt in which the suction and overflow bore overlapping area between the control edge determining the end of conveyance and the control edge determining the start of conveyance opens.

Eine Einrichtung der eingangs genannten Art ist beispielsweise aus der DE-A 1 954 123 bekanntgeworden, wobei die axiale Bohrung im Kolben vom Arbeitsraum desselben ausgeht und über eine radiale Bohrung in den Bereich der schräg verlaufenden Absteuernut zur Beendigung des Einspritzvorganges durch Verbindung mit einer Saug- und Überströmbohrung mündet. Die axiale Bohrung mündet weiters in eine zwischen den zwei Steuerkanten angeordnete Drosselbohrung, um in einer einem Leerlauf entsprechenden Drehlage des Pumpenkolbens bereits einen Teil des unter Druck geförderten Kraftstoffes gedrosselt abströmen zu lassen, um die Geräuschbelastung im Leerlaufbetrieb des Motors zu senken.A device of the type mentioned at the outset has become known, for example, from DE-A 1 954 123, the axial bore in the piston originating from the working chamber thereof and via a radial bore in the region of the oblique control groove to end the injection process by connection to a suction and overflow hole opens. The axial bore also opens into a throttle bore arranged between the two control edges, in order to allow part of the fuel delivered under pressure to flow away throttled in a rotational position of the pump piston corresponding to an idling operation, in order to reduce the noise load when the engine is idling.

Bei Pumpenelementen ist es darüberhinaus bekannt, daß sich durch den plötzlichen Abschluß der Saug- und Überströmbohrung bei Förderbeginn Dampfblasen in der Saug- und Überströmbohrung bilden. Durch den Pumpenkolben wird der Kraftstoff im Arbeitsraum der Pumpe auf sehr hohe Drücke von beispielsweise 1000 bar und auch mehr gebracht und bei Förderende strömt dieser hochkomprimierte Kraftstoff in die Saug- und Überströmbohrung. Durch die Drucksteigerung in der Saug- und Überströmbohrung implodieren diese Dampfblasen und es werden dadurch Kavitationen und Erosionen an der Wandung der Saug- und Überströmbohrung und auch am Kolbenmantel und an der Steuerkante verursacht. Aus der DE-A 2 807 808 ist es bekannt geworden, Kraftstoff, der im Pumpenarbeitsraum unter Druck gesetzt wurde, über eine Drosselbohrung abzuzweigen und vor dem Aufsteuern der Überströmbohrung in die Überströmbohrung einzuführen, um Dampfblasen aus dieser Uberströmbohrung wegzufördern. Die abgezweigte Kraftstoffmenge ist von der Toleranz der Drosselbohrung und von dem im Arbeitsraum des Pumpenkolbens auftretenden Druck abhängig. Diese nicht genau bestimmte abgezweigte Kraftstoffmenge verringert die Fördermenge des Pumpenkolbens und es ergeben sich daher Unterschiede in der Fördermenge der verschiedenen Pumpenelemente, was zu Ungleichmäßigkeiten im Motorlauf führt.In the case of pump elements, it is also known that the sudden termination of the suction and overflow bore forms steam bubbles in the suction and overflow bore at the start of delivery. The pump piston brings the fuel in the working area of the pump to very high pressures of, for example, 1000 bar and more, and at the end of delivery this highly compressed fuel flows into the suction and overflow bore. Due to the pressure increase in the suction and overflow bore, these vapor bubbles implode and cavitation and erosion are caused on the wall of the suction and overflow bore and also on the piston skirt and on the control edge. From DE-A 2 807 808 it has become known to branch off fuel that has been pressurized in the pump work space via a throttle bore and to introduce it into the overflow bore before opening the overflow bore in order to convey vapor bubbles away from this overflow bore. The amount of fuel diverted depends on the tolerance of the throttle bore and on the pressure occurring in the working area of the pump piston. This not exactly determined branched fuel quantity reduces the delivery quantity of the pump piston and there are therefore differences in the delivery quantity of the different pump elements, which leads to irregularities in the running of the engine.

Die Erfindung stellt sich zur Aufgabe, solchen Kavitationen und Erosionen entgegenzuwirken. Zur Erfüllung dieser Aufgabe besteht die Erfindung im wesentlichen darin, daß die axiale Bohrung gegen den Arbeitsraum des Pumpenkolbens abgeschlossen ausgebildet ist, und daß von der axialen Bohrung im Bereich ihres von der Kolbenstirnfläche abgewendeten Endes wenigstens eine am Kolbenmantel mündende Radialbohrung ausgeht, welche zumindest während eines Teiles des Kolbenhubes mit einer in der Pumpenkolbenbüchse vorgesehenen Spülölzuführungsbohrung in Verbindung steht, durch welche Kraftstoff unabhängig von der Förderung des Pumpenelementes unter einem den Druck im Saugraum übersteigenden Druck der axialen Bohrung zugeführt wird. Von dieser Spülölzuführungsbohrung in der Pumpenkolbenbüchse gelangt Kraftstoff in die axiale Bohrung des Pumpenkolbens und von dieser wieder durch die radiale Bohrung in die Saug- und Überströmbohrung der Pumpenkolbenbüchse. Da der Druck dieses zum Spülen verwendeten Kraftstoffes über dem Druck im Saugraum liegt, tritt der Kraftstoff in die Saug- und Überströmbohrung ein und verdrängt die Dampfblasen vom Pumpenkolben weg in Richtung zum Saugraum. Da die von der axialen Bohrung ausgehende radiale Bohrung zwischen der das Förderende bestimmenden Steuerkante und der den Förderbeginn bestimmenden Steuerkante liegt, erfolgt somit die Wegspülung der Dampfblasen aus der Saug- und Uberströmbohrung knapp bevor die das Förderende bestimmende Steuerkante die Saug- und Überströmbohrung freigibt. Wenn nun der eine große Energie aufweisende Absteuerstrahl in die Saug- und Überströmbohrung eintritt, sind die Dampfblasen bereits weitgehend von der kritischen Stelle, nämlich vom Pumpenkolben, abgedrängt. Da der Druck des Spülkraftstoffstrahles wesentlich geringer ist als der Druck des bei Förderende abgesteuerten Brennstoffstrahles, kann auch kein hartes Implodieren der Dampfblasen durch den Spülkraftstoffstrahl erfolgen. Der Spülkraftstoffstrahl tritt in die Saug-und Überströmbohrung der Pumpenkolbenbüchse ein, sobald die Mündung der radialen Bohrung die Saug- und Überströmbohrung zu überschleifen beginnt, und dieser Spülkraftstoffstrahl drängt daher bevorzugt an der Oberseite der Saug- und Überströmbohrung die Gasblasen ab und gerade diese Oberseite ist die kritische Stelle, an welcher der Absteuerstrahl auftrifft. Es wird daher auf diese Weise Kavitation und Erosion durch ein hartes Implodieren der Dampfblasen weitgehend vermieden. Da die zum Spülen dienende Kraftstoffmenge gesondert zugeführt wird und nicht von der zu fördernden Kraftstoffmenge abgezweigt wird, sind Unregelmä- βigkeiten in der Kraftstofförderung vermieden. Es ist auch möglich, den Spülkraftstoff erst ab einer bestimmten Fördermenge und/oder Motordrehzahl zuzuführen, bei welcher die Kavitation unangenehm zu werden beginnt und die Spülkraftstoffzufuhr im Teillast- oder Teildrehzahlbereich zu unterlassen.The object of the invention is to counteract such cavitations and erosions. To achieve this object, the invention essentially consists in that the axial bore against the working space of the pump piston is designed to be closed, and that at least one radial bore opening at the piston skirt extends from the axial bore in the region of its end facing away from the piston face, which at least during one Part of the piston stroke is connected to a flushing oil supply bore provided in the pump piston bushing, through which fuel is supplied to the axial bore independently of the delivery of the pump element under a pressure exceeding the pressure in the suction chamber. From this flushing oil supply bore in the pump piston liner, fuel reaches the axial bore of the pump piston and from there through the radial bore into the suction and overflow bore of the pump piston liner. Since the pressure of this fuel used for purging is above the pressure in the suction chamber, the fuel enters the suction and overflow bore and displaces the vapor bubbles away from the pump piston in the direction of the suction chamber. Since the radial bore emanating from the axial bore lies between the control edge that determines the delivery end and the control edge that determines the start of delivery, the steam bubbles are flushed away from the suction and overflow bore just before the control edge that determines the delivery end releases the suction and overflow bore. When the diverter jet, which has a large amount of energy, enters the suction and overflow bore, the vapor bubbles are already largely displaced from the critical point, namely from the pump piston. Since the pressure of the flushing fuel jet is substantially lower than the pressure of the fuel jet that is turned off at the end of delivery, the vapor bubbles cannot be imploded hard by the flushing fuel jet. The flushing fuel jet enters the suction and overflow bore of the pump piston liner as soon as the mouth of the radial bore begins to grind over the suction and overflow bore, and this flushing fuel jet therefore preferentially pushes the gas bubbles off the top of the suction and overflow bore, and this is the top side the critical point at which the pilot jet hits. Cavitation and erosion by hard imploding of the vapor bubbles is therefore largely avoided in this way. Since the amount of fuel used for purging is supplied separately and is not branched off from the amount of fuel to be delivered, irregularities in fuel delivery are avoided. It is also possible to supply the flushing fuel only from a certain delivery rate and / or engine speed at which the cavitation begins to become uncomfortable and to refrain from supplying the flushing fuel in the part-load or part-speed range.

Gemäß der Erfindung sind vorzugsweise im Bereich des der Kolbenstirnfläche zugewendeten Endes der axialen Bohrung mehrere radiale Bohrungen vorgesehen, deren Mündungen am Kolbenmantel in einem Abstand voneinander liegen, der kleiner ist als der Durchmesser der Saug- und Überströmbohrung. Dadurch wird bei einem Pumpenelement, dessen Fördermenge durch Verdrehen des Kolbens geregelt wird, die Gewähr geboten, daß bei allen Drehstellungen des Pumpenkolbens der zum Spülen verwendete Kraftstoff in die Saug- und Überströmöffnung gelangt. Vorzugsweise liegen gemäß der Erfindung die Mündungen der Radialbohrungen am Kolbenmantel in gleichen Abständen von der das Förderende bestimmenden Steuerkante, so daß die Bedingungen für die Zuführung des zum Spülen verwendeten Kraftstoffes nicht verändert werden. Die Anordnung mehrerer Radialbohrungen hat den Vorteil, daß der Spülkraftstoff bei allen Drehstellungen des Kolbens axial in die Saug und Uberströmbohrung eintritt, wodurch die Wegförderung der Gas- oder Dampfblasen begünstigt wird. Gemäß der Erfindung kann aber auch die im Bereich des der Kolbenstirnfläche zugewendeten Endes der axialen Bohrung vorgesehene Radialbohrung in eine parallel zu der das Förderende bestimmenden Steuerkante verlaufende Nut am Kolbenmantel münden.According to the invention are preferably in the area of the En facing the piston face of the axial bore several radial bores are provided, the orifices of which lie on the piston skirt at a distance from one another which is smaller than the diameter of the suction and overflow bore. As a result, in the case of a pump element, the delivery rate of which is regulated by rotating the piston, the guarantee is provided that the fuel used for purging will reach the suction and overflow opening at all rotational positions of the pump piston. According to the invention, the openings of the radial bores on the piston skirt preferably lie at equal distances from the control edge which determines the end of the delivery, so that the conditions for supplying the fuel used for purging are not changed. The arrangement of several radial bores has the advantage that the flushing fuel enters the suction and overflow bore axially at all rotational positions of the piston, thereby promoting the removal of the gas or vapor bubbles. According to the invention, however, the radial bore provided in the region of the end of the axial bore facing the piston end face can also open into a groove on the piston skirt that runs parallel to the control edge that determines the delivery end.

Gemäß der Erfindung kann die Anordnung so getroffen sein, daß die im Bereich des von der Kolbenstirnfläche abgewendeten Endes der axialen Bohrung vorgesehene Radialbohrung in eine parallel zu der das Förderende bestimmenden Steuerkante verlaufende Nut mündet, deren Axialabstand von dieser Steuerkante ungefähr dem Axialabstand der Spülölzuführungsbohrung von der Saug- und Überströmbohrung entspricht. In diesem Falle wird der Spülkraftstoff stoßweise immer dann zugeführt, wenn die Mündung der Radialbohrung die Saug- und Uberströmbohrung überschleift. Es kann aber gemäß der Erfindung auch die im Bereich des von der Kolbenstirnfläche abgewendeten Endes der axialen Bohrung vorgesehene Radialbohrung in eine Ringnut münden, deren axiale Erstreckung zumindest gleich einem wesentlichen Teil des Kolbenhubes ist. In diesem Fall erfolgt die Zuführung des Spülkraftstoffes zu der axialen Bohrung kontinuierlich, wobei der Spülkraftstoff nur dann aus der Radialbohrung austritt, wenn diese die Saug- und Uberströmbohrung der Pumpenkolbenbüchse überschleift.According to the invention, the arrangement can be such that the radial bore provided in the region of the end of the axial bore facing away from the piston end surface opens into a groove running parallel to the control edge which determines the conveying end, the axial distance from this control edge approximately equal to the axial distance of the flushing oil supply bore from the Suction and overflow drilling corresponds. In this case, the flushing fuel is supplied intermittently whenever the mouth of the radial bore slides over the suction and overflow bore. However, according to the invention, the radial bore provided in the region of the end of the axial bore facing away from the piston end face may open into an annular groove, the axial extent of which is at least equal to a substantial part of the piston stroke. In this case, the flushing fuel is supplied to the axial bore continuously, the flushing fuel only emerging from the radial bore when it drags over the suction and overflow bore of the pump piston liner.

Weiters ist es gemäß der Erfindung möglich, die Bohrungsdurchmesser der radialen Bohrungen, welche im Bereich des Kolbenkopfes münden, unterschiedlich auszuführen, so daß beispielsweise bei größeren Kraftstoffördermengen des Pumpenelementes auch größere Spülmengen vorhanden sind.Furthermore, according to the invention it is possible to design the bore diameters of the radial bores, which open out in the region of the piston head, differently, so that, for example, larger flushing quantities are also available with larger fuel delivery quantities of the pump element.

In der Zeichnung ist die Erfindung an Hand eines Ausführungsbeispieles schematisch erläutert.In the drawing, the invention is explained schematically using an exemplary embodiment.

Fig. 1 zeigt einen Teil-Axialschnitt durch ein Pumpenelement, Fig. 2 zeigt die Strömungsverhältnisse in der S aug-/Überströmbohrung kurz vor dem statischen Förderbeginn, Fig. 3 zeigt eine Variante zur Spülölzuführung und Fig. 4 eine Abwicklung des Pumpenkolbens mit abgewandelten radialen Bohrungen.Fig. 1 shows a partial axial section through a pump element, Fig. 2 shows the flow conditions in the S aug / overflow bore shortly before the static delivery begins, Fig. 3 shows a variant for flushing oil supply and Fig. 4 shows a development of the pump piston with modified radial Holes.

In Fig. 1 ist der Pumpenkolben mit 1 und die Pumpenkolbenbüchse mit 2 bezeichnet. 3 ist der Arbeitsraum des Pumpenkolbens. In der Pumpenkolbenbüchse sind diametral gegenüberliegend zwei Saug- und Überströmöffnungen 4 vorgesehen, welche in den Saugraum 5 münden, und durch schräge Absteuerkanten 6, welche das Förderende bestimmen, überschliffen werden.In Fig. 1, the pump piston with 1 and the pump piston sleeve with 2 is designated. 3 is the working area of the pump piston. In the pump piston liner, diametrically opposite two suction and overflow openings 4 are provided, which open into the suction chamber 5, and are ground through oblique control edges 6, which determine the end of the delivery.

Im Kolben 1 ist eine axiale Bohrung 7 vorgesehen, welche gegen den Arbeitsraum 3 durch einen Stopfen 8 abgeschlossen ist. Im Bereich des von der Kolbenstirnfläche 9 abgewendeten Endes der axialen Bohrung 7 geht eine radiale Bohrung 10 aus, die in eine schraubenlinienförmige Nut 11 am Mantel des Pumpenkolbens 1, welche parallel zu der schrägen Steuerkante 6 verläuft, mündet. In der Pumpenkolbenbüchse 2 ist eine Spülkraftstoffzuführungsbohrung 12 vorgesehen, durch welche über einen Anschluß 13 Kraftstoff unter einem höheren Druck als der Druck im Saugraum 5 zugeführt wird. Im Bereich des der Kolbenstirnfläche 9 zugewendeten Endes der axialen Bohrung 7 gehen von dieser axialen Bohrung radiale Bohrungen 14 aus, deren Mündungen 15 am Kolbenumfang in einer parallel zur Steuerkante 6 verlaufenden Reihe liegen. Die Nut 11 ist so angeordnet, daß sie die Spülkraftstoffzuführungsbohrung 12 dann überschleift, wenn die Mündungen 15 der Bohrungen 14 die Saug- und Überströmbohrungen 4 überschleifen. Hiefür ist Bedingung, daß der axiale Abstand zwischen den Mündungen 15 der Bohrungen 14 und der Bohrung 10 im Kolben ungefähr gleich ist dem Axialabstand der Bohrung 12 von der Saug- und Überströmbohrung 4.An axial bore 7 is provided in the piston 1, which is closed off from the working space 3 by a plug 8. In the area of the end of the axial bore 7 facing away from the piston face 9, a radial bore 10 emerges, which opens into a helical groove 11 on the jacket of the pump piston 1, which runs parallel to the oblique control edge 6. In the pump piston bushing 2 there is a flushing fuel supply bore 12, through which fuel is supplied via a connection 13 at a higher pressure than the pressure in the suction chamber 5. In the area of the end of the axial bore 7 facing the piston face 9, radial bores 14 extend from this axial bore, the orifices 15 of which lie on the circumference of the piston in a row running parallel to the control edge 6. The groove 11 is arranged so that it sweeps over the flushing fuel supply hole 12 when the mouths 15 of the holes 14 grind over the suction and overflow holes 4. The condition for this is that the axial distance between the orifices 15 of the bores 14 and the bore 10 in the piston is approximately equal to the axial distance of the bore 12 from the suction and overflow bore 4.

Sobald die Mündung 15 einer solchen Bohrung 14 die Saug- und Überströmöffnung 4 überschleift, wird der Spülkraftstoff in die axiale Nut gefördert und tritt nun in Richtung des Pfeiles 16 über die Bohrungen 14 in die Saug- und Überströmbohrungen 4 der Pumpenkolbenbüchse 2 ein. Knapp nachher tritt der bei Förderende durch die schräge Steuerkante 6 abgesteuerte Brennstoffstrahl in Richtung des Pfeiles 17 in die Saug- und Überströmbohrung 4 ein.As soon as the mouth 15 of such a bore 14 slides over the suction and overflow opening 4, the flushing fuel is conveyed into the axial groove and now enters the suction and overflow bores 4 of the pump piston liner 2 in the direction of arrow 16 via the bores 14. Shortly afterwards, the fuel jet which is deflected by the oblique control edge 6 at the end of delivery enters the suction and overflow bore 4 in the direction of arrow 17.

Fig. 2 zeigt die Stellung des Kolbens 1 bei Förderbeginn. Die durch die Stirnfläche 9 gebildete Steuerkante schließt die Saug- und Überströmöffnung 4 der Pumpenkolbenbüchse 2 ab und ein Strahl des Brennstoffes tritt beim Abschließen in Richtung des Pfeiles 18 in die Saug- und Überströmbohrung 4 ein. Bei Abschluß der Saug- und Überströmöffnung durch die Stirnfläche 9 des Kolbens 1 wird der Kraftstoffstrom in die Bohrungen plötzlich unterbrochen, wodurch ein Unterdruck entsteht, der für die Dampfblasenbildung maßgeblich ist. Diese Darstellung erklärt, warum in der Saug- und Überströmbohrung 4 Dampfblasen auftreten.Fig. 2 shows the position of the piston 1 at the start of delivery. The control edge formed by the end face 9 closes off the suction and overflow opening 4 of the pump piston liner 2 and a jet of fuel enters the suction and overflow bore 4 when it is closed in the direction of arrow 18. When the suction and overflow opening through the end face 9 of the piston 1 is terminated, the fuel flow into the bores is suddenly interrupted, which creates a vacuum which is decisive for the formation of vapor bubbles. This illustration explains why 4 vapor bubbles occur in the suction and overflow bore.

Fig. 3 zeigt in einem Teilschnitt eine abgewandelte Ausführungsform. Hier mündet die von der axialen Bohrung 7 des Pumpenkolbens 1 ausgehende radiale Bohrung 10 in eine Ringnut 19 des Kolbens 1, in welche die Spülkraftstoffzuführungsbohrung 12 mündet. Die axiale Erstreckung dieser Ringnut ist zumindest gleich einem wesentlichen Teil des Hubes des Pumpenkolbens 1, so daß der Spülkraftstoff kontinuierlich in die axiale Bohrung 7 eintritt.Fig. 3 shows in a partial section a modified embodiment. Here, the radial bore 10 starting from the axial bore 7 of the pump piston 1 opens into an annular groove 19 of the piston 1, into which the flushing fuel feed bore 12 opens. The axial extent of this annular groove is at least equal to a substantial part of the stroke of the pump piston 1, so that the flushing fuel continuously enters the axial bore 7.

Da der Spülkraftstoff über einen Anschluß 13 gesondert unter Druck zuführbar ist, läßt sich in einfacher Weise die Zuführung bei geringen Drehzahlen oder geringen Fördermengen unterbinden, um Antriebsenergie für eine Pumpe zu sparen. Zu diesem Zweck ist eine gesonderte Pumpe angeordnet und ein über eine Steuereinheit in Abhängigkeit von Drehzahl oder Fördermenge der Pumpe steuerbares Ventil vorgesehen. Alternativ oder zusätzlich kann die Pumpe durch die Steuereinheit geschaltet werden.Since the flushing fuel can be supplied separately under pressure via a connection 13, the supply can be carried out in a simple manner at a low speed low or low flow rates to save drive energy for a pump. For this purpose, a separate pump is arranged and a valve which can be controlled via a control unit as a function of the speed or delivery rate of the pump is provided. Alternatively or additionally, the pump can be switched by the control unit.

Claims (9)

1. A pump element of a fuel injection pump for injection-type internal combustion engines, in which the pumping plunger barrel (2) has at least one intake and overflow port (4) over which control edges (6, 9) of the pumping plunger (1) slide and the end of delivery is determined by opening of the intake and overflow port (4), the start of delivery being determined by a control edge disposed in the vicinity of the end face (9) of the plunger and the end of delivery being determined by a control edge (6), especially an oblique one, disposed on the plunger skirt, wherein the pumping plunger (1) has an axial bore, from which, in the vicinity of its end nearest the end face (9) of the plunger, there extends at least one radial bore (14) which opens on to the plunger skirt in the area which slides over the intake and overflow port (4) between the control edge (6), which determines the end of delivery, and the control edge (9), which determines the start of delivery, characterised in that the axial bore (7) is formed closed off from the working chamber of the pumping plunger (1), and in that from the axial bore (7) in the vicinity of its end remote from the end face (9) of the plunger, there extends at least one radial bore (10) opening on to the plunger skirt which, at least during part of the plunger stroke, is in communication with a scavenge-oil feed bore (12) provided in the pumping plunger barrel, through which fuel is fed to the axial bore (10) independently of the delivery of the pump element at a pressure which exceeds the pressure in the intake chamber.
2. A pump element according to Claim 1, characterised in that, in the vicinity of the end of the axial bore (7) nearest the end face (9) of the plunger, there are provided several radial bores (14), the mouths (15) of which are situated on the plunger skirt at a distance from each other which is smaller than the diameter of the intake and overflow port (4).
3. A pump element according to Claim 2, characterised in that the mouths (15) of the radial bores (14) on the plunger skirt are situated at equal distances from the control edge (6) determining the end of delivery.
4. A pump element according to Claim 1, 2 or 3, characterised in that the radial bores (14) are of differing diameters, larger diameters being provided in the areas where there is a larger delivery stroke.
5. A pump element according to Claim 1, characterised in that the radial bore (14), which is provided in the vicinity of the end of the axial bore (7) nearest the end face (9) of the plunger, opens in to a groove in the plunger skirt extending parallel to the control edge (6) determining the end of delivery.
6. A pump element according to any one of Claims 1 to 5, characterised in that the radial bore (10), which is provided in the vicinity of the end of the axial bore (7) remote from the end face (9) of the plunger, opens into a groove (11) extending parallel to the control edge (6) determining the end of delivery, the axial distance of said groove from this control edge corresponding approximately to the axial distance of the scavenge-oil feed bore (12) from the intake and overflow port (4).
7. A pump element according to any one of Claims 1 to 5, characterised in that the radial bore (10), which is provided in the vicinity of the end of the axial bore (7) remote from the end face (9) of the plunger, opens into an annular groove (11) whose axial extent is at least equal to a substantial part of the plunger stroke.
8. A pump element according to any of Claims 1 to 7, characterised in that the scavenging fuel can be admitted only after a certain speed of rotation has been reached.
9. A pump element according to any one of Claims 1 to 8, characterised in that the scavenging fuel can be admitted only after a certain delivery rate has been reached.
EP19870890210 1986-09-10 1987-09-10 Pump element of a fuel pump for an injection combustion engine Expired - Lifetime EP0263808B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT0243886A AT404058B (en) 1986-09-10 1986-09-10 PUMP ELEMENT OF A FUEL INJECTION PUMP FOR INJECTION COMBUSTION ENGINES
AT2438/86 1986-09-10

Publications (2)

Publication Number Publication Date
EP0263808A1 EP0263808A1 (en) 1988-04-13
EP0263808B1 true EP0263808B1 (en) 1990-04-25

Family

ID=3534355

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870890210 Expired - Lifetime EP0263808B1 (en) 1986-09-10 1987-09-10 Pump element of a fuel pump for an injection combustion engine

Country Status (3)

Country Link
EP (1) EP0263808B1 (en)
AT (1) AT404058B (en)
DE (1) DE3762446D1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3839753A1 (en) * 1988-11-25 1990-05-31 Bosch Gmbh Robert PUMP ELEMENT OF A FUEL INJECTION PUMP FOR INJECTION COMBUSTION ENGINES
DE4006409A1 (en) * 1990-03-01 1991-09-19 Bosch Gmbh Robert FUEL INJECTION DEVICE FOR INJECTION COMBUSTION ENGINES

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR788642A (en) * 1935-04-11 1935-10-14 Fuel injection pumps
FR843031A (en) * 1938-02-25 1939-06-23 Prec Mecanique S A Improvements to piston pumps, especially fuel injection pumps
US2513883A (en) * 1947-01-15 1950-07-04 Ingersoll Rand Co Fuel pump for engines
DE1954123A1 (en) * 1968-11-04 1970-05-27 Nippon Denso Co Fuel injection pump for diesel engines
GB1594124A (en) * 1977-04-30 1981-07-30 Lucas Industries Ltd Liquid fuel injection pumps
GB1594472A (en) * 1977-04-30 1981-07-30 Lucas Industries Ltd Fuel injection pumps
DE3347430A1 (en) * 1983-12-29 1985-07-11 Robert Bosch Gmbh, 7000 Stuttgart FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES

Also Published As

Publication number Publication date
AT404058B (en) 1998-08-25
ATA243886A (en) 1997-12-15
EP0263808A1 (en) 1988-04-13
DE3762446D1 (en) 1990-05-31

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