PUMP UNIT FOR SUPPLYING FUEL, PREFERABLY DIESEL OIL, FROM A CONTAINING TANK TO AN INTERNAL COMBUSTION ENGINE

Description

[0001] The present invention relates to a pump unit for supplying fuel, preferably diesel oil, from a containing tank to an internal combustion engine.

[0002] In particular, the present invention relates to a pump unit of the type comprising a pre-feed pump, for example an electric pump, adapted to draw the fuel from a containing tank; a high-pressure pump, for example a piston pump, adapted to feed the fuel to an internal combustion engine; and a fluid circuit comprising, in turn, a first branch for interconnecting the electric pump and the piston pump, and a second branch for interconnecting the piston pump and the internal combustion engine. Such a pump unit is known from the document WO 2009/065761 A1.

[0003] The fluid circuit of the known pump unit comprises, additionally, a metering solenoid valve positioned on the first branch for the selective control of the instantaneous flow rate of fuel supplied to the piston pump as a function of the values of a plurality of operating parameters of the internal combustion engine, and a third branch, which interconnects the first branch and the containing tank, is connected to the first branch upstream of the metering solenoid valve in a direction of advance of the fuel along the first branch, and enables at least some of the flow of fuel in excess of that which is supplied through the metering solenoid valve to be discharged into the containing tank.

[0004] The third branch is provided with an overflow valve, which is mounted in a first mounting aperture formed through a pump housing of the piston pump, and has an inlet for the inflow of the fuel into the overflow valve, at least one outlet for the outflow of the fuel from the overflow valve, and a slide valve which is movable between a position which closes the outlet and a position which opens the outlet.

[0005] The third branch is also at least partially formed by a connector which is mounted in a second mounting aperture formed through the pump housing of the piston pump transversely with respect to the aforesaid first mounting aperture, is in fluid communication with the outlet of the overflow valve, and projects from the pump housing for connection to a pipe for supplying the fuel to the containing tank.

[0006] From the document WO 2011/012402 A1 a pump unit is known which is provided with an overflow valve and a tubular connector which is mounted in a mounting aperture of the pump housing. The overflow valve and the tubular connector are located at different positions in the pump housing.

[0007] The known pump units of the type described above have a number of drawbacks, mainly due to the fact that the provision of two mounting apertures, namely one for the overflow valve and one for the connector, requires the execution of relatively complicated, lengthy and costly machining operations on the aforesaid pump housing.

[0008] The object of the present invention is to provide a pump unit for supplying fuel, preferably diesel oil, from a containing tank to an internal combustion engine which is free of the drawbacks described above and which is simple and economical to produce.

[0009] According to the present invention, a pump unit is provided for supplying fuel, preferably diesel oil, from a containing tank to an internal combustion engine, as claimed in the appended claims.

[0010] The present invention will now be described with reference to the attached drawings, which show a non-limiting example of its embodiment, in which:

Figure 1 is a fluid diagram of a preferred embodiment of the pump unit of the present invention and

Figure 2 is a schematic view, with parts in section and parts removed for clarity, of a detail of the pump unit of Figure 1.

[0011] With reference to Figure 1, the number 1 indicates the whole of a pump unit for supplying a liquid fuel, preferably diesel oil, from a containing tank 2 to an internal combustion engine 3, in the present case a diesel engine comprising a fuel distribution manifold 4, commonly known as a "common rail", and a plurality of injectors 5 connected to the manifold 4 and adapted to spray the fuel into corresponding combustion chambers (not shown) of the engine 3.

[0012] The pump unit 1 comprises a high-pressure pump 6, in the present case a piston pump, adapted to supply the fuel to the engine 3, and a low-pressure or pre-feed pump, in the present case an electric pump, adapted to supply the fuel from the tank 2 to the pump 6.

[0013] The pump 6 comprises a pump housing 8 having a specified longitudinal axis 9, and at least one cylinder 10, which is formed in the pump housing 8, has a longitudinal axis 11 substantially perpendicular to the axis 9, and is engaged slidably by a piston 12.

[0014] The piston 12 is moved along the cylinder 10 by an actuator 13 of a known type fitted in the pump housing 8 and having a reciprocating rectilinear motion comprising an outward stroke for drawing the fuel into the cylinder 10 and a return stroke for compressing the fuel contained in the cylinder 10.

[0015] The pump unit 1 also comprises a fluid circuit 14 for supplying the fuel, comprising, in turn, a first branch 15, which interconnects the pumps 6 and 7, extends through the pump housing 8 to lubricate the actuator 13, and is connected to the cylinder 10 through an intake valve 16, and a second branch 17, which extends between the pump 6 and the manifold 4, and is connected to the cylinder 10 through a delivery valve 18.

[0016] The branch 15 is provided with a metering solenoid valve 19, which is mounted upstream of the valve 16 in a direction 20 of advance of the fuel along the branches 15 and 17, is movable between a position which closes the branch 15 and a position which opens it, and is adapted to control selectively the instantaneous flow rate of fuel supplied to the pump 6 as a function of the values of a plurality of operating parameters of the engine 3.

[0017] The circuit 14 also comprises a third branch 21, which connects the branch 15 upstream of the solenoid valve 19 in the direction 20 to the tank 2, and enables at least some of the flow of fuel in excess of that which is supplied through the solenoid valve 19 to be discharged into the tank 2, and a fourth branch 22, which extends between the manifold 4 and the branch 21, and enables the flow of fuel in excess of that required by the injectors 5 to be discharged into the tank 2.

[0018] The circuit 14 also has a fifth branch 23 for discharging into the branch 21, and consequently into the tank 2, any fuel supplied through the pump housing 8 from the branch 15 and leaking through the support bearings (not shown) of the actuator 13, and a sixth branch 24, which is connected to the branch 15 downstream of the solenoid valve 19 in the direction 20, extends between the branch 15 and the branch 21, allows the absorption of the flow of fuel leaking through the solenoid valve 19 when the solenoid valve 19 is closed, and is provided with a calibrated aperture 25 designed so as to limit the quantity of fuel absorbed by the branch 24 to a value below a specified threshold when the solenoid valve 19 is open.

[0019] As shown in Figures 1 and 2, the branch 21 is provided with an overflow valve 26 mounted in a mounting aperture 27 which is formed through the pump housing 8, has a specified longitudinal axis 28, and comprises a constricted portion 27a and a wider portion 27b, interconnected by an annular shoulder 29 which is substantially transverse with respect to the axis 28.

[0020] The valve 26 comprises a substantially cylindrical valve housing 30, which extends coaxially with the axis 28, is mounted in the aperture 27 by means of an interposed ring seal 31, has an axial aperture 32 for the entry of fuel into the valve housing 30, and is provided with at least two radial apertures for the outflow of the fuel from the valve housing 30.

[0021] The valve 26 also comprises a slide valve 34, which is mounted in the valve housing 30 coaxially with the axis 28, is moved to, and normally kept in, a position which closes the apertures 33 (Fig. 2) by a spring 35 interposed between the valve housing 30 and the slide valve 34, and is moved by the fuel against the action of the spring 35 from the position which closes the apertures 33 to a position (not shown) which opens the apertures.

[0022] The fuel supplied through the apertures 33 as a result of the movement of the slide valve 34 to its open position is collected in a portion 36 of the aperture 27 which can also receive the fuel from the branch 23.

[0023] The branch 31 also comprises a tubular connector 37 made in one piece with the valve housing 30 so as to form a single sleeve 38, this sleeve being locked by interference in the portion 27b coaxially with the axis 28.

[0024] The tubular connector 37 is connected to a pipe (not shown) forming part of the branch 21, and communicates with the portion 36 through at least two connecting apertures 39, which are formed through the sleeve 38 and are inclined with respect to the axis 28.

Claims

1. Pump unit for supplying fuel, preferably diesel oil, from a containing tank (2) to an internal combustion engine (3), the pump unit comprising a pre-feed pump (7) adapted to draw the fuel from the containing tank (2); a high-pressure pump (6), having a pump housing (8) provided with a mounting aperture (27); and a fluid circuit (14) comprising, in turn, a first branch (15) for interconnecting the pre-feed pump (7) and the high-pressure pump (6), a second branch (17) for interconnecting the high-pressure pump (6) and the internal combustion engine (3), and a third branch for interconnecting the first branch (15) and the containing tank (2); the third branch (21) comprising an overflow valve (26) mounted in the mounting aperture (27), and a tubular connector (37), which is mounted downstream of the overflow valve (26) in a direction of advance (20) of the fuel along the third branch (21), and is connected to a pipe forming part of the third branch (21); the pump unit being characterized in that the overflow valve (26) and the tubular connector (37) are mounted coaxially with each other in the mounting aperture (27), that the overflow valve (26) comprises a valve housing (30) and a plug (34) engaged slidably in the valve housing (30) so as to be moved between a closed and an open position of the overflow valve (26) and that the valve housing (30) and the tubular connector (37) are made in one piece.

2. Pump unit according to Claim 1, wherein the valve housing (30) and the tubular connector (37) are locked by interference in the mounting aperture.

3. Pump unit according to Claim 1 or 2, wherein the mounting aperture (27) has a longitudinal axis (28) and an end-stop shoulder (29) formed transversely with respect to the longitudinal axis (28).

4. Pump unit according to Claim 3, wherein the mounting aperture (27) comprises a constricted portion (27a) and a wider portion (27b) interconnected by the end-stop shoulder (29).

5. Pump unit according to any one of Claims 2 to 4, wherein the overflow valve (26) comprises an inlet (32) for the inflow of fuel into the valve housing (30) and at least one outlet (33) for the outflow of the fuel from the valve housing (30); the mounting aperture (27) comprising a collecting portion (36) which is in fluid communication with the outlet (33), and is also in fluid communication with the tubular connector (37) through at least one passage (39) formed through the valve housing (30) and the tubular connector (37) itself.

6. Pump unit according to Claim 5, wherein the passage (39) comprises an aperture formed through the valve housing (30) and the tubular connector (37).

Ansprüche

1. Pumpeinheit zur Zufuhr von Kraftstoff, vorzugsweise Dieselöl, von einem Aufnahmetank (2) zu einem Verbrennungsmotor (3), wobei die Pumpeinheit eine Vorförderpumpe (7), die dazu ausgeführt ist, Kraftstoff aus dem Aufnahmetank (2) zu saugen; eine Hochdruckpumpe (6) mit einem Pumpengehäuse (8), das mit einer Montageöffnung (27) versehen ist; und einen Fluidkreislauf (14) umfasst, der wiederum einen ersten Zweig (15) zum Miteinanderverbinden der Vorförderpumpe (7) und der Hochdruckpumpe (6), einen zweiten Zweig (17) zum Miteinanderverbinden der Hochdruckpumpe (6) und des Verbrennungsmotors (3) und einen dritten Zweig zum Miteinanderverbinden des ersten Zweigs (15) und des Aufnahmetanks (2) umfasst; wobei der dritte Zweig (21) ein in der Montageöffnung (27) angebrachtes Überströmventil (26) und einen stromabwärts des Überströmventils (26) in einer Fortbewegungsrichtung (20) des Kraftstoffs entlang dem dritten Zweig (21) angebrachten röhrenförmigen Verbinder (37) umfasst, der mit einem Rohrbildungsteil des dritten Zweigs (21) verbunden ist; wobei die Pumpeinheit dadurch gekennzeichnet ist, dass das Überströmventil (26) und der röhrenförmige Verbinder (37) koaxial miteinander in der Montageöffnung (27) angebracht sind, das Überströmventil (26) ein Ventilgehäuse (30) und einen Stopfen (34) umfasst, der verschiebbar in dem Ventilgehäuse (30) zur Bewegung zwischen einer geschlossenen und einer geöffneten Stellung des Überströmventils (26) in Eingriff steht, und das Ventilgehäuse (30) und der röhrenförmige Verbinder (37) einstückig hergestellt sind.

2. Pumpeinheit nach Anspruch 1, wobei das Ventilgehäuse (30) und der röhrenförmige Verbinder (37) durch Presspassung in der Montageöffnung verriegelt sind.

3. Pumpeinheit nach Anspruch 1 oder 2, wobei die Montageöffnung (27) eine Längsachse (28) und eine Endanschlagschulter (29), die bezüglich der Längsachse (28) quer ausgebildet ist, aufweist.

4. Pumpeinheit nach Anspruch 3, wobei die Montageöffnung (27) einen verengten Teil (27a) und einen breiteren Teil (27b), die durch die Endanschlagschulter (29) miteinander verbunden sind, umfasst.

5. Pumpeinheit nach einem der Ansprüche 2 bis 4, wobei das Überströmventil (26) einen Einlass (32) zum Zufluss von Kraftstoff in das Ventilgehäuse (30) und mindestens einen Auslass (33) zum Abfluss des Kraftstoffs aus dem Ventilgehäuse (30) umfasst; wobei die Montageöffnung (27) einen Sammelteil (36) umfasst, der mit dem Auslass (33) in fluidischer Verbindung steht und auch durch mindestens einen durch das Ventilgehäuse (30) und den röhrenförmigen Verbinder (37) selbst ausgebildeten Durchgang (39) mit dem röhrenförmigen Verbinder (37) in fluidischer Verbindung steht.

6. Pumpeinheit nach Anspruch 5, wobei der Durchgang (39) eine durch das Ventilgehäuse (30) und den röhrenförmigen Verbinder (37) ausgebildete Öffnung umfasst.

Revendications

1. Unité de pompe pour l'apport de carburant, de préférence de carburant diesel, d'un réservoir de stockage (2) à un moteur à combustion interne (3), l'unité de pompe comprenant une pompe de pré-alimentation (7) conçue pour prélever le carburant du réservoir de stockage (2) ; une pompe à haute pression (6), comportant un carter de pompe (8) pourvu d'une ouverture de fixation (27) ; et un circuit de fluide (14) comprenant, successivement, une première branche (15) servant à raccorder mutuellement la pompe de pré-alimentation (7) et la pompe à haute pression (6), une deuxième branche (17) servant à raccorder mutuellement la pompe à haute pression (6) et le moteur à combustion interne (3), et une troisième branche servant à raccorder mutuellement la première branche (15) et le réservoir de stockage (2) ; la troisième branche (21) comprenant une valve de trop-plein (26) installée dans l'ouverture de fixation (27), et un raccord tubulaire (37), qui est installé en aval de la valve de trop-plein (26) dans une direction d'avance (20) du carburant le long de la troisième branche (21), et est raccordé à une partie formant conduit de la troisième branche (21) ; l'unité de pompe étant caractérisée en ce que la valve de trop-plein (26) et le raccord tubulaire (37) sont installés de manière coaxiale l'un vis-à-vis de l'autre dans l'ouverture de fixation (27), en ce que la valve de trop-plein (26) comprend un logement de valve (30) et un obturateur (34) logé à coulissement dans le logement de valve (30) de façon à être déplacé entre une position fermée et une position ouverte de la valve de trop-plein (26) et en ce que le logement de valve (30) et le raccord tubulaire (37) sont réalisés d'un seul tenant.

2. Unité de pompe selon la revendication 1, dans laquelle le logement de valve (30) et le raccord tubulaire (37) sont bloqués par serrage dans l'ouverture de fixation.

3. Unité de pompe selon la revendication 1 ou 2, dans laquelle l'ouverture de fixation (27) comporte un axe longitudinal (28) et un épaulement de fin de course (29) formé transversalement par rapport à l'axe longitudinal (28).

4. Unité de pompe selon la revendication 3, dans laquelle l'ouverture de fixation (27) comprend une partie étranglée (27a) et une partie plus large (27b) raccordées mutuellement par l'épaulement de fin de course (29).

5. Unité de pompe selon l'une quelconque des revendications 2 à 4, dans laquelle la valve de trop-plein (26) comprend une entrée (32) pour l'entrée de carburant dans le logement de valve (30) et au moins une sortie (33) pour la sortie du carburant du logement de valve (30), l'ouverture de fixation (27) comprenant une partie de collecte (36) qui est en communication fluidique avec la sortie (33), et qui est également en communication fluidique avec le raccord tubulaire (37) par le biais d'au moins un passage (39) formé à travers le logement de valve (30) et le raccord tubulaire (37) lui-même.

6. Unité de pompe selon la revendication 5, dans laquelle le passage (39) comprend une ouverture formée à travers le logement de valve (30) et le raccord tubulaire (37).

Drawing