PUMP UNIT FOR SUPPLYING FUEL, PREFERABLY DIESEL OIL, TO AN INTERNAL COMBUSTION ENGINE

Description

[0001] The present invention relates to a pump unit for supplying fuel, preferably diesel oil, to an internal combustion engine according to the preamble of claim 1.

[0002] Such a pump unit is known from the document EP 1 553 296 A1. This pump unit comprises a pump housing, a delivery passage formed in the pump housing for supplying fluid and a check valve positioned in the delivery passage. The check valve comprises a plug which is movable between a position in which it opens the delivery passage and a position in which it closes the passage. A first seat is formed in the delivery passage to receive the plug after its movement from the open to the closed position. The pump further comprises a stop element fitted in the delivery passage and provided with a second seat for receiving and retaining the plug after movement of the latter from the closed to the open position. The stop element comprises at least one tubular portion which has an axially open free end forming said second seat and which is hydraulically connected to the delivery passage when the plug is placed in its open position.

[0003] When the plug is in its open position and is in abutment with the second seat the flow of fluid is along the outside of the tubular portion. A hydraulic force is exerted on the plug by the fluid contained in the tubular portion and this hydraulic force is acting against the force exerted by the fluid contained in the delivery passage. Therefore it is difficult to keep the plug in its open position.

[0004] The object of the present invention is to provide a pump unit for supplying fuel, preferably diesel oil, to an internal combustion engine which is free of the drawbacks described above and which is simple and economical to produce.

[0005] According to the present invention, a pump unit is provided for supplying fuel, preferably diesel oil, to an internal combustion engine, as claimed in the appended claims. When the plug is in its open position the flow of fuel is through the tubular portion of the stop element which causes a pressure drop in the fuel, resulting in a lower pressure of the fuel contained in the tubular portion. As a consequence the plug is substantially held in the second seat throughout the delivery phase without the possibility of moving axially and/or radially.

[0006] The present invention will now be described with reference to the attached figure which shows, in longitudinal section and with parts removed for clarity, a nonlimiting exemplary embodiment of the invention.

[0007] With reference to the attached figure, the number 1 indicates, as a whole, a pump unit for supplying fuel, preferably diesel oil, to an internal combustion engine (not shown).

[0008] The pump unit 1 comprises, in the present case, a pump housing 2; a known piston pump, which is not shown, for supplying the fuel to the aforesaid internal combustion engine (not shown); and a known gear pump, which is not shown, for supplying the fuel to the piston pump (not shown).

[0009] The piston pump (not shown) comprises at least one cylinder which is engaged slidably by a piston which can move with a reciprocating rectilinear motion along the cylinder, and which is associated with a passage for the intake of fuel into the cylinder and with a passage 3 for delivering the fuel to the internal combustion engine (not shown).

[0010] The passage 3 has a specified longitudinal axis 4, and comprises a constricted portion 5 communicating with the cylinder of the piston pump (not shown), an enlarged portion 6 communicating with the internal combustion engine (not shown), and an intermediate portion 7, which extends between portions 5 and 6, and forms an annular conical seat 8 which is substantially coaxial with the axis 4.

[0011] The seat 8 forms part of a check valve 9, which is housed in the passage 3 to prevent the backflow of the fuel into the cylinder of the piston pump (not shown), this valve also comprising a substantially spherical plug 10, which is movable between a position in which the passage 3 is closed and a position in which it is open, and being provided with a stop member 11 mounted in the portion 6 to halt the movement of the plug 10 in its open position.

[0012] The member 11 is substantially screw-shaped and comprises a head 12 screwed into the pump housing 2 and a tubular shank 13, which extends into the portion 6 coaxially with the axis 4, and has an outside diameter which is smaller than the inside diameter of the portion 6. The free end of the shank 13 facing the plug 10 is axially open and forms an annular conical seat 14 for halting the movement of the plug 10 in its open position.

[0013] The shank 13 forms, in combination with the portion 6, an annular chamber 15 which is substantially coaxial with the axis 4, and also has an internal passage 16 which is coaxial with the axis 4, and comprises an enlarged portion 17 facing the plug 10 and a constricted portion 18 facing the head 12.

[0014] The portion 17 houses within it a spring 19, mounted coaxially with the axis 4, for moving the plug 10 into its closed position and normally keeping it there, and communicates with the chamber 15 through a plurality of holes 20 which are uniformly distributed about the axis 4 and which are formed through the shank 13 transversely with respect to the axis 4; and the portion 18 communicates with an annular manifold 21 formed in the pump housing 2 coaxially with the axis 4 through a plurality of holes 22, which are uniformly distributed about the axis 4, and which are formed through the shank 13 transversely with respect to the axis 4.

[0015] The portion 6 and the shank 13 are also coupled together in a fluid-tight way by the interposition of an annular seal 23, in the present case an O-ring, mounted coaxially with the axis 4 in an intermediate point of the shank 13 between the holes 20 and 22.

[0016] In use, the plug 10 is moved, by the fuel supplied by the piston pump (not shown) along the passage 3, to the position in which it opens the passage 3, thus enabling the fuel to flow, in succession, through the intermediate portion 7, along the chamber 15, through the holes 20, along the passage 16, through the holes 22, and into the manifold 21.

[0017] Since the diameter of the plug 10 and the inside diameter of the portion 17 are controlled selectively in such a way that the force exerted on the plug 10 by the fuel contained in the passage 3 is greater than the sum of the forces exerted on the plug 10 by the spring 19 and by the fuel contained in the passage 16, and since the supply of the fuel along the chamber 15 and through the holes 20 causes a pressure drop in the fuel, resulting in a lower pressure in the passage 16 than in the passage 3, the plug 10 is moved along a rectilinear path along the axis 4 in such a way that it engages the seat 14, and is substantially held in the seat 14 throughout the delivery phase of the piston pump (not shown) without the possibility of moving axially and/or radially.

[0018] At the end of the delivery phase and during the intake phase of the piston pump (not shown), the plug 10 is moved along a substantially rectilinear path along the axis 4 by the force of the spring 19 and the fuel contained in the passage 16, in such a way that it engages the seat 8 and closes the passage 3 relatively quickly.

[0019] Because of the presence and shape of the stop member 11, and of the shank 13 in particular, it is therefore possible to move the plug 10 into its open and closed positions along substantially rectilinear paths along the axis 4, to hold the plug 10 in the seat 14 throughout the delivery phase of the piston pump (not shown), to prevent radial and/or axial movements of the plug 10 in the seats 8 and 14 so as to reduce the wear on the plug 10, the seats 8 and 14, and the spring 19, and to reduce the closing time of the plug 10, thus improving the efficiency of the pump unit 1.

[0020] In a first variant which is not shown, the spring 19 is omitted, and the plug 10 is closed solely by the force of the fuel contained in the passage 16.

[0021] In another variant which is not shown, the annular seal 23 is omitted and the shank 13 is made in such a way that it comprises a constricted end portion, which is provided with the holes 20, and which has an outside diameter smaller than the diameter of the portion 6, and an enlarged intermediate portion, which extends between the holes 20 and 22, has an outside diameter substantially equal to the diameter of the portion 6, enables the fuel to be diverted through the holes 20 so as to provide the desired pressure drop in the fuel in the passage 16, and simultaneously prevents the fuel from flowing directly into the manifold 21 along the chamber 15.

Claims

1. Pump unit for supplying fuel, preferably diesel oil, to an internal combustion engine, the pump comprising a pump housing (2), a delivery passage (3) formed in the pump housing (2) for supplying the fuel to the internal combustion engine, and a check valve (9) positioned in the delivery passage (3), the check valve (9) comprising a plug (10), which is movable between a position in which it opens the delivery passage (3) and a position in which it closes the passage, and a first seat (8) formed in the delivery passage (3) to receive the plug (10) after its movement from the open to the closed position, the pump further comprising a stop element (11) fitted in the delivery passage (3) and provided with a second seat (14) for receiving and retaining the plug (10) after movement of the latter from the closed to the open position, wherein the stop element (11) comprises at least one tubular portion (13) which has an axially open free end forming said second seat (14) and which is hydraulically connected to the delivery passage (3) when the plug (10) is placed in its open position, characterized in that the stop element (11) comprises at least one aperture (20) for the entry of the fuel into the tubular portion (13) and at least one aperture (22) for the outflow of the fuel from the tubular portion (13), wherein the tubular portion (13) has a specified longitudinal axis (4), the entry aperture (20) being substantially transverse with respect to the axis (4), the force exerted on the plug (10) by the fuel contained in the tubular portion (13) being smaller than the force exerted on the plug (10) by the fuel supplied through said first seat (8), in such a way that the plug (10) is held in its open position.

2. Pump unit according to Claim 1 and additionally comprising a hydraulic circuit (6, 7, 15, 20) for supplying the fuel through the first seat (8) and into the tubular portion (13); the hydraulic circuit (6, 7, 15, 20) being shaped in such a way that the pressure exerted on the plug (10) by the fuel contained in the tubular portion (13) is lower than the pressure exerted on the plug (10) by the fuel supplied through said first seat (8).

3. Pump unit according to Claim 1, in which the tubular portion (13) comprises at least a first portion which has an outside diameter smaller than the diameter of the corresponding portion (6) of the delivery passage (3), and which is provided with said entry aperture (20).

4. Pump unit according to any one of Claims 1 to 3 and additionally comprising a sealing device (23) interposed between the delivery passage (3) and the stop element (11) to divert the fuel through said entry aperture (20).

5. Pump unit according to Claim 4, in which the sealing device (23) comprises an annular gasket (23) mounted between the delivery passage (3) and the stop element (11) and between the entry aperture (20) and the outflow aperture (22).

6. Pump unit according to Claim 4, in which the tubular portion (13) comprises a second portion which extends between the entry aperture (20) and the outflow aperture (22), and has an outside diameter substantially equal to the diameter of the corresponding portion (6) of the delivery passage (3).

7. Pump unit according to any one of Claims 1 to 6, in which the check valve (9) additionally comprises a spring (19) which pushes the plug (10) towards its closed position; the force exerted on the plug (10) by the fuel supplied through said first seat (8) being greater than the sum of the forces exerted on the plug (10) by the spring (19) and by the fuel contained in the tubular portion (13).

8. Pump unit according to any one of the preceding claims, in which the stop element (11) is fixed in the pump housing (2).

Ansprüche

1. Pumpeinheit für die Kraftstoffzufuhr, vorzugsweise Diesel, zu einem Verbrennungsmotor, wobei die Pumpe ein Pumpengehäuse (2), einen in dem Pumpengehäuse (2) ausgebildeten Zufuhrkanal (3) zum Zuführen des Kraftstoffs zu einem Verbrennungsmotor und ein in dem Zufuhrkanal (3) positioniertes Rückschlagventil (9) umfasst, wobei das Rückschlagventil (9) einen Stopfen (10), der zwischen einer Stellung, in der er den Zufuhrkanal (3) öffnet, und einer Stellung, in der er den Kanal schließt, bewegbar ist, und einen ersten Sitz (8), der in dem Zufuhrkanal (3) dahingehend ausgebildet ist, den Stopfen (10) nach seiner Bewegung aus der geöffneten in die geschlossene Stellung aufzunehmen, umfasst, wobei die Pumpe ferner ein Anschlagelement (11) umfasst, das in dem Zufuhrkanal (3) eingebaut und mit einem zweiten Sitz (14) zur Aufnahme und zum Halten des Stopfens (10) nach seiner Bewegung aus der geschlossenen in die geöffnete Stellung versehen ist, wobei das Anschlagelement (11) mindestens einen rohrförmigen Abschnitt (13) umfasst, der ein axial offenes freies Ende, das den zweiten Sitz (14) bildet, aufweist und der mit dem Zufuhrkanal (3) hydraulisch verbunden ist, wenn der Stopfen (10) in seiner geöffneten Stellung platziert ist, dadurch gekennzeichnet, dass das Anschlagelement (11) mindestens eine Öffnung (20) für das Einströmen des Kraftstoffs in den rohrförmigen Abschnitt (13) und mindestens eine Öffnung (22) für das Ausströmen des Kraftstoffs aus dem rohrförmigen Abschnitt (13) umfasst, wobei der rohrförmige Abschnitt (13) eine spezifizierte Längsachse (4) aufweist, wobei die Einströmöffnung (20) im Wesentlichen quer zur Achse (4) verläuft, wobei die durch den in dem rohrförmigen Abschnitt (13) enthaltenen Kraftstoff auf den Stopfen (10) ausgeübte Kraft weniger als die von dem durch den ersten Sitz (8) zugeführten Kraftstoff auf den Stopfen (10) ausgeübte Kraft beträgt, so dass der Stopfen (10) in seiner geöffneten Stellung gehalten wird.

2. Pumpeinheit nach Anspruch 1, die zusätzlich einen Hydraulikkreis (6, 7, 15, 20) zur Zufuhr des Kraftstoffs durch den ersten Sitz (8) und in den rohrförmigen Abschnitt (13) umfasst; wobei der Hydraulikkreis (6, 7, 15, 20) derart geformt ist, dass der durch den in dem rohrförmigen Abschnitt (13) enthaltenen Kraftstoff auf den Stopfen (10) ausgeübte Druck weniger als der durch den durch den ersten Sitz (8) zugeführten Kraftstoff auf den Stopfen (10) ausgeübte Druck beträgt.

3. Pumpeinheit nach Anspruch 1, wobei der rohrförmige Abschnitt (13) mindestens einen ersten Abschnitt umfasst, der einen Außendurchmesser, der weniger als der Durchmesser des entsprechenden Abschnitts (6) des Zufuhrkanals (3) beträgt, aufweist und der mit der Einströmöffnung (20) versehen ist.

4. Pumpeinheit nach einem der Ansprüche 1-3, die zusätzlich eine zwischen dem Zufuhrkanal (3) und dem Anschlagelement (11) zwischengelagerte Dichtungsvorrichtung (23) zum Umleiten des Kraftstoffs durch die Einströmöffnung (20) umfasst.

5. Pumpeinheit nach Anspruch 4, wobei die Dichtungsvorrichtung (23) eine ringförmige Dichtung (23) umfasst, die zwischen dem Zufuhrkanal (3) und dem Anschlagelement (11) und zwischen der Einströmöffnung (20) und der Ausströmöffnung (22) befestigt ist.

6. Pumpeinheit nach Anspruch 4, wobei der rohrförmige Abschnitt (13) einen zweiten Abschnitt umfasst, der sich zwischen der Einströmöffnung (20) und der Ausströmöffnung (22) erstreckt und einen Außendurchmesser aufweist, der dem Durchmesser des entsprechenden Abschnitts (6) des Zufuhrkanals (3) im Wesentlichen entspricht.

7. Pumpeinheit nach einem der Ansprüche 1-6, wobei das Rückschlagventil (9) zusätzlich eine Feder (19) umfasst, die den Stopfen (10) in seine geschlossene Stellung drückt; wobei die durch den durch den ersten Sitz (8) zugeführten Kraftstoff auf den Stopfen (10) ausgeübte Kraft mehr als die Summe der von der Feder (19) und dem in dem rohrförmigen Abschnitt (13) enthaltenen Kraftstoff auf den Stopfen (10) ausgeübten Kräfte beträgt.

8. Pumpeinheit nach einem der vorhergehenden Ansprüche, wobei das Anschlagelement (11) in dem Pumpengehäuse (2) fixiert ist.

Revendications

1. Unité de pompe servant à l'alimentation en carburant, de préférence en carburant diesel, d'un moteur à combustion interne, la pompe comprenant un logement de pompe (2), un passage de distribution (3) formé dans le logement de pompe (2) servant à amener le carburant au moteur à combustion interne, et une soupape anti-retour (9) placée dans le passage de distribution (3), la soupape anti-retour (9) comprenant un obturateur (10), qui est mobile entre une position dans laquelle il ouvre le passage de distribution (3) et une position dans laquelle il ferme le passage, et un premier siège (8) formé dans le passage de distribution (3) pour recevoir l'obturateur (10) après son déplacement de la position ouverte à la position fermée, la pompe comprenant en outre un élément d'arrêt (11) installé dans le passage de distribution (3) et pourvu d'un second siège (14) destiné à recevoir et retenir l'obturateur (10) après un déplacement de ce dernier de la position fermée à la position ouverte, l'élément d'arrêt (11) comprenant au moins une partie tubulaire (13) qui comporte une extrémité libre axialement ouverte formant ledit second siège (14) et qui est reliée par voie hydraulique au passage de distribution (3) lorsque l'obturateur (10) est placé dans sa position ouverte, caractérisée en ce que l'élément d'arrêt (11) comprend au moins une ouverture (20) pour l'entrée du carburant dans la partie tubulaire (13) et au moins une ouverture (22) pour la sortie du carburant de la partie tubulaire (13), la partie tubulaire (13) présentant un axe longitudinal spécifié (4), l'ouverture d'entrée (20) étant essentiellement transversale par rapport à l'axe (4), la force exercée sur l'obturateur (10) par le carburant présent dans la partie tubulaire (13) étant inférieure à la force exercée sur l'obturateur (10) par le carburant amené à travers ledit premier siège (8), de telle sorte que l'obturateur (10) soit maintenu dans sa position ouverte.

2. Unité de pompe selon la revendication 1 et comprenant en outre un circuit hydraulique (6, 7, 15, 20) servant à amener le carburant à travers le premier siège (8) et dans la partie tubulaire (13) ; le circuit hydraulique (6, 7, 15, 20) étant formé de telle sorte que la pression exercée sur l'obturateur (10) par le carburant présent dans la partie tubulaire (13) est inférieure à la pression exercée sur l'obturateur (10) par le carburant amené à travers ledit premier siège (8).

3. Unité de pompe selon la revendication 1, dans laquelle la partie tubulaire (13) comprend au moins une première partie qui présente un diamètre extérieur inférieur au diamètre de la partie correspondante (6) du passage de distribution (3), et qui est pourvue de ladite ouverture d'entrée (20) .

4. Unité de pompe selon l'une quelconque des revendications 1 à 3, et comprenant en outre un dispositif d'étanchéité (23) intercalé entre le passage de distribution (3) et l'élément d'arrêt (11) afin de dévier le carburant à travers ladite ouverture d'entrée (20).

5. Unité de pompe selon la revendication 4, dans laquelle le dispositif d'étanchéité (23) comprend un joint d'étanchéité annulaire (23) installé entre le passage de distribution (3) et l'élément d'arrêt (11) et entre l'ouverture d'entrée (20) et l'ouverture de sortie (22).

6. Unité de pompe selon la revendication 4, dans laquelle la partie tubulaire (13) comprend une seconde partie qui s'étend entre l'ouverture d'entrée (20) et l'ouverture de sortie (22), et présente un diamètre extérieur essentiellement égal au diamètre de la partie correspondante (6) du passage de distribution (3).

7. Unité de pompe selon l'une quelconque des revendications 1 à 6, dans laquelle la soupape anti-retour (9) comprend en outre un ressort (19) qui pousse l'obturateur (10) en direction de sa position fermée ; la force exercée sur l'obturateur (10) par le carburant amené à travers ledit premier siège (8) étant supérieure à la somme des forces exercées sur l'obturateur (10) par le ressort (19) et le carburant présent dans la partie tubulaire (13).

8. Unité de pompe selon l'une quelconque des revendications précédentes, dans laquelle l'élément d'arrêt (11) est fixé dans le logement de pompe (2).

Drawing