Title

PUMP ASSEMBLY FOR SUPPLYING FU EL, PREFERABLY DI ESEL, TO AN INTERNAL COMBUSTION ENGINE

The present invention relates to a pump assembly for supplying fuel, preferably diesel, to an internal combustion engine.

More specifically, the present invention relates to a pump assembly comprising a high-pressure pump for supplying fuel to an internal combustion engine; and a pre-supply pump for supplying the fuel from a container tank to the high-pressure pump.

The high-pressure pump is a pump with pistons comprising a pump body; at least one cylinder made in the pump body; and a piston engaged slidingly in said cylinder.

The piston can move along the cylinder with an alternating rectilinear movement comprising an intake stroke for taking fuel into the cylinder and a compression stroke for compressing the fuel contained in said cylinder. The supply of fuel by the pre-supply pump to the cylinder is controlled by an intake valve, and the supply of fuel from the cylinder to the internal combustion engine is controlled by a delivery valve.

The intake valve comprises a valve body mounted inside the pump body; a shut- off member engaged slidingly through the valve body to move between an open position and a closed position of the cylinder; a disc fitted on the shut-off member; and a spring interposed between the valve body and the disc so as to move the shut-off member into its closed position, and normally keep it there.

The disc and the shut-off member have respective coupling portions of cylindrical shape coupled together by interference.

Known pump assemblies of the type described above have a number of drawbacks, mainly due to the fact that the movement of the shut-off member into its open position causes the disc to impact against the valve body and the movement of the shut-off member into its closed position causes the shut-off member to impact against said valve body.

The impacts of the disc and the shut-off member against the valve body cause flexion of the shut-off member, a relative movement between the shut-off member and the disc and, therefore, a relatively high contact pressure at the ends of the coupling portions. Consequently, the shut-off member is subject to friction wear and its fatigue strength and lifetime are thus relatively poor. The aim of the present invention is to provide a pump assembly for supplying fuel, preferably diesel, to an internal combustion engine that does not have the above drawbacks and that may be implemented simply and economically.

According to the present invention, a pump assembly for supplying fuel, preferably diesel, to an internal combustion engine is provided as claimed in the attached claims.

The present invention will now be described with reference to the attached drawings, which illustrate a non-limiting embodiment thereof, in which:

Figures 1 and 2 are two schematic views in section, with parts cut away for clarity, of a preferred embodiment of the pump assembly of the present invention; and

Figure 3 is a schematic view in section, on an enlarged scale and with parts cut away for clarity, of a detail of Figures 1 and 2.

With reference to Figures 1 and 2, reference sign 1 indicates, as a whole, a pump assembly for supplying fuel, preferably diesel, from a container tank (not shown) to an internal combustion engine (not shown), in this case a diesel internal combustion engine. The pump assembly 1 comprises a high-pressure pump 2 for supplying the fuel to the internal combustion engine (not shown), and a low-pressure or pre-supply pump 3 for supplying the fuel from the container tank (not shown) to the pump 2. The high-pressure pump 2 is a pump with pistons having a pump body 4 comprising a container housing 5, which has a central bore 6 with a longitudinal axis 7, and which further has at least one lateral bore 8 (usually a plurality of bores 8 distributed uniformly about the axis 7) with a longitudinal axis 9 that is transverse to the axis 7 and extends radially towards the outside of the housing 5 from said bore 6.

Each bore 8 is closed off by a cylinder head 10, which is in contact with the housing 5 and has a protuberance 11 projecting into the bore 8 coaxially to the axis 9.

The cylinder head 10 has a central bore 12, made through the cylinder head 10 coaxially to the axis 9, and comprising a wider portion 13 and a narrower portion 14 aligned with one another along said axis 9. The portion 14 is on the side towards the bore 6, and defines a cylinder 15 of the pump 2 engaged slidingly by a piston 16 that can move, pushed by an actuator device 17, with an alternating rectilinear movement comprising an intake stroke for taking in the fuel into the cylinder 15 and a compression stroke for compressing the fuel contained inside said cylinder 15. The device 17 comprises a tubular sleeve 18, which is engaged slidingly inside the bore 8 coaxially to the axis 9, extends around the cylinder 15, and has an internal annular flange 19 that projects radially from an internal surface of the sleeve 18 and splits said sleeve 18 into two cylindrical portions 20, 21, of which the portion 20 is on the side towards the bore 6.

The device 17 further comprises a cam follower 22 comprising a coupling block 23 of substantially cylindrical shape, which is blocked by interference inside the portion 20, and is in contact with the flange 19, and bears a cam follower roll 24.

The roll 24 projects from the block 23 towards the bore 6, and is coupled rotationally to the block 23 so as to rotate, with respect to said block 23, about its own longitudinal axis 25 which is substantially perpendicular to the axis 9.

The flange 19 bears an annular disc 26, which extends around the piston 16, is inserted inside the portion 21 of the sleeve 18 coaxially to the axis 9, and has an outer peripheral edge axially on the side towards the flange 19 and an inner peripheral edge axially on the side towards a head of said piston 16.

The device 17 further comprises a compression spring 27, which is mounted between the protuberance 11 and the sleeve 18 coaxially to the axis 9, and is interposed between the cylinder head 10 and the disc 26 so as to move, and normally keep, the disc 26 in contact with the flange 19 and the roll 24 in contact with a cam 28 formed on an external surface of an intermediate portion of a transmission shaft 29 mounted through the bore 6 so as to rotate, with respect to the housing 5, about the axis 7.

The supply of fuel into each cylinder 15 is selectively controlled by an associated intake valve 30 of known type, while the supply of fuel from each cylinder 15 to the internal combustion engine (not shown) is selectively controlled by an associated delivery valve 31 of known type.

The intake valve 30 comprises a valve body 32 blocked axially inside the portion 13 by a cover 33 screwed into the cylinder head 10, and a shut-off member 34 of elongate shape, which is mounted coaxially to the axis 9, and is engaged slidingly through the valve body 32 so as to move parallel to the axis 9 between a closed position and an open position of the cylinder 15.

The shut-off member 34 is moved into its closed position, and normally kept there, by a spring 35 interposed between the valve body 32 and a disc 36, which is fitted on the shut-off member 34 transversely to the axis 9, and is coupled by interference with said shut-off member 34.

As shown in Figure 3, the shut-off member 34 comprises a coupling portion 37 of cylindrical shape extending inside the disc 36.

The disc 36 has a central bore 38, which is delimited axially by two end planes E that are perpendicular to the axis 9, and is further delimited by an internal wall 39 extending around said axis 9. The bore 38 has, in an initial configuration thereof (not shown), prior to coupling with the shut-off member 34, a variable diameter with the largest diameter at the planes E and the smallest diameter at an intermediate plane I that is parallel to said planes E.

Consequently, the wall 39 has a shape domed towards the axis 9.

With reference to what is described above, it should be specified that the portion 37 of the shut-off member 34 has a diameter smaller than the diameter of the bore 38 at the planes E and a diameter larger than the diameter of the bore 38 at the plane I.

In this case: the bore 38 has the same diameter at the planes E; the plane I is a median plane of the disc 36 equidistant from the planes E; and the diameter of the bore 38 varies continuously from each plane E to the plane I.

Moreover, the bore 38 has, in a final configuration thereof (Figure 3), following the coupling with the shut-off member 34, a central section 40 of cylindrical shape, and two end sections 41 arranged on either side of the section 40 along the axis 9. Each section 41 has a diameter that increases from the section 40 to the relative plane E in such a way that, at the planes E, the wall 39 is not in contact with the shut-off member 34.

In other words, in the final configuration thereof (Figure 3), the bore 38 is coupled by interference with the shut-off member 34 only at the section 40, and has a diameter larger than the diameter of the portion 37 along the sections 41. Since, at the planes E, the shut-off member 34 and the disc 36 are not in contact with one another, the contact pressures at the planes E are relatively low and the shut-off member 34 has a relatively good lifetime and resistance to wear.