IT201800004282A1 - PUMPING GROUP TO FEED FUEL, PREFERABLY DIESEL, TO AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

"PUMPING GROUP TO FEED FUEL, PREFERABLY DIESEL, TO AN INTERNAL COMBUSTION ENGINE"

The present invention relates to a pumping unit for feeding fuel, preferably diesel fuel, to an internal combustion engine.

In particular, the present invention relates to a pumping unit of the type comprising a high pressure pump, for example a piston pump, suitable for supplying fuel to an internal combustion engine; a pre-feed pump, for example a gear pump, adapted to feed fuel from a containment tank to the piston pump; and a hydraulic circuit to connect together the containment tank, the pre-feed pump, the high pressure pump, and the internal combustion engine.

In this case, the piston pump comprises a pump body; at least two cylinders formed in the pump body and slidingly engaged by respective pistons; and an actuation device for moving the pistons along the relative cylinders with a reciprocating rectilinear motion comprising a stroke of intake of the fuel in the cylinders and a stroke of delivery of the fuel to the internal combustion engine.

The two cylinders have respective longitudinal axes parallel to each other and are each associated with a respective valve for the intake of the fuel in the cylinder and with a respective valve for delivering fuel to the internal combustion engine.

The actuation device is configured in such a way as to simultaneously move a piston with its suction stroke and the other piston with its delivery stroke.

The hydraulic circuit comprises a first branch for connecting the containment tank and the gear pump to each other; a second branch for connecting the gear pump and the piston pump together; and a third branch for connecting the piston pump and the internal combustion engine together.

The second branch comprises a feed manifold and, for each cylinder, a respective intake duct for connecting the feed manifold with the cylinder itself.

Generally, the hydraulic circuit also comprises a metering solenoid valve mounted along the supply manifold of the second branch to selectively control 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 combustion engine. internal.

The dosing solenoid valve includes a valve body mounted in the supply manifold, and a shutter engaged in a sliding manner in the valve body to move between an open position and a closed position of the dosing solenoid valve itself.

In use, the delivery stroke of each piston commands the closing of the relative intake valve. During the closing of each intake valve, a part of the fuel compressed by the relative piston exits from the relative cylinder firstly along the relative intake duct and, then, both along the intake duct of the other intake valve, and along the power supply manifold.

Known pumping units of the type described above have some drawbacks mainly deriving from the fact that:

the pressure waves generated along the intake duct of each cylinder by the fuel leaking from the other cylinder favor the opening, and therefore further delay the closure, of the relative intake valve, amplifying the phenomenon just described; And

the pressure waves generated along the supply manifold by the fuel leaking from the two cylinders favor the opening of the shutter of the metering solenoid valve, compromising the supply of the correct fuel flow to the piston pump and, therefore, to the internal combustion engine .

The object of the present invention is to provide a pumping unit for supplying fuel, preferably diesel oil, to an internal combustion engine which is free from the drawbacks described above and which is simple and economical to implement.

According to the present invention, a pumping unit is provided for feeding fuel, preferably diesel oil, to an internal combustion engine as claimed in the attached claims.

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

Figure 1 is a hydraulic diagram of a preferred embodiment of the pumping unit of the present invention; And

Figure 2 is a schematic sectional view, with parts removed for clarity, of a detail of the pumping unit of Figure 1.

With reference to Figure 1, the number 1 indicates, as a whole, a pumping unit for feeding fuel, preferably diesel oil, from a containment tank 2 to an internal combustion engine 3, in this case a Diesel internal combustion engine.

The engine 3 comprises a fuel distribution manifold 4, commonly indicated with the term "common rail", and a plurality of injectors 5 connected to the manifold 4 and adapted to atomize the fuel inside the relative combustion chambers (not illustrated) of the motor 3 itself.

The pumping unit 1 comprises a high pressure pump 6, ie a piston pump, for supplying fuel to the engine 3; and a low pressure or pre-feed pump 7, i.e. a gear pump, for example electrically operated, to feed the fuel from the tank 2 to the pump 6.

The pump 6 comprises a pump body 8 and, in this case, two cylinders 9, which are formed in the pump body 8, and have respective longitudinal axes 10 substantially parallel to each other.

According to a variant not shown, the number of cylinders 9 is different from two and the axes 10 are not parallel to each other.

The cylinders 9 are engaged in a sliding manner by respective movable pistons 11, under the thrust of an actuation device 12, with a reciprocating rectilinear motion comprising an intake stroke of the fuel in the relative cylinders 9 and a stroke of delivery of the fuel to the engine 3 .

The device 12 comprises a cam transmission shaft 13, which is housed in a first containment chamber 14 obtained in the pump body 8, and is adapted to move the pistons 11 with their delivery stroke.

The device 12 also comprises, for each piston 11, a respective spring (not shown), which is housed in a second containment chamber (not shown) obtained in the pump body 8, and is adapted to move the piston 11 itself with its suction stroke.

Regarding the above, it should be noted that the shaft 13 is configured in such a way as to simultaneously move a piston 11 with its suction stroke and the other piston 11 with its delivery stroke.

The pumping unit 1 also comprises a hydraulic circuit 15 comprising, in turn, a first branch 16 for connecting the tank 2 and the pump 7 together; a second branch 17 for connecting pump 7 and pump 6 together; and a third branch 18 to connect the pump 6 and the manifold 4 together.

The branch 17 is provided with a filtering device 19 for filtering the fuel fed to the cylinders 9, and also has a metering solenoid valve 20 mounted downstream of the device 19 in a direction 21 for the advancement of the fuel along the branch 17 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.

The branch 17 and the branch 18 are connected to each cylinder 9 by means of an intake valve 22 and, respectively, a delivery valve 23.

The circuit 15 also comprises a fourth branch 24, which extends between the manifold 4 and the branch 16, and allows the flow of fuel in excess of that necessary for the injectors 5 to be discharged into the branch 16; and a fifth branch 25, which extends between the branch 17 and the branch 16, and is connected to the branch 17 downstream of the solenoid valve 20 in the direction 21 to feed the fuel leaking through the solenoid valve 20 to the inlet of the pump 7 when the solenoid valve 20 itself is closed.

The circuit 15 also has a sixth branch 26, which extends between the branch 17 and the branch 24, is connected to the branch 17 upstream of the solenoid valve 20 in the direction 21, and is provided with a valve device 27.

The device 27 is configured to control the supply in the pump body 8 and in the chamber 14 of the fuel flow used to lubricate the cam transmission shaft 13 and the fuel flow in excess of that fed through the solenoid valve 20.

Finally, the circuit 15 comprises a seventh branch 28 to feed the fuel flowing through the pump body 8 into the branch 26 and, therefore, into the tank 2.

As illustrated in Figure 2, the branch 17 comprises a supply manifold 29 and, for each cylinder 9, a respective intake duct 30 for connecting the manifold 29 with the cylinder 9 itself.

The metering solenoid valve 20 comprises a tubular-shaped valve body 31, which is mounted in the manifold 29 coaxially to a longitudinal axis 32 of the manifold 29 itself, and has an annular-shaped inlet channel 33, which extends around the axis 32, and communicates with the branch 17 to feed the fuel through the valve body 31.

The valve body 31 is slidably engaged by a shutter 34, which has a cup shape, is limited axially by a bottom wall 35 arranged perpendicular to the axis 32, and is provided with a plurality of distributed connection holes 36 around axis 32 itself.

The shutter 34 is movable between an opening position, in which the holes 36 are aligned radially with the channel 33, and a closing position, in which the holes 36 are axially offset with respect to the channel 33 itself.

The shutter 34 is moved, and normally maintained, in its open position by a spring 37, and is moved from its open position to its closed position against the action of the spring 37 by an electromagnetic actuator 38 of a known type engaged on wall 35.

The manifold 29 comprises a first section 29a, which extends downstream of the solenoid valve 20 in the direction 21, and communicates with the two ducts 30, and a second section 29b extending downstream of the ducts 30 and of the section 29a itself.

The section 29b communicates with a pneumatic tank 39 comprising an elongated chamber 40, which has, in this case, a longitudinal axis 41 transversal to the axis 32 of the manifold 29 and, therefore, to the direction 21 of advancement of the fuel along the manifold 29.

The chamber 40 also has a first open end and directly connected to the section 29b and a second end closed in fluid-tight by a plug 42.

The chamber 40 contains within it a compressible gaseous fluid, for example air, trapped between the plug 42 and the fuel which completely fills the manifold 29.

According to a variant not shown, the chamber 40 is formed coaxially to the axis 32 and is aligned with the section 29b of the manifold 29 in the direction 21.

According to a further variant not shown, the section 29b of the manifold 29 and the chamber 40 are separated from each other by an elastically deformable membrane.

In use, the pressure waves generated in the manifold 29 by the fuel coming from the ducts 30 during the closing of the relative intake valves 22 are compensated by the compressible gaseous fluid contained in the chamber 40 of the tank 39. In other words, the compressible gaseous fluid contained in the chamber 40 is adapted to vary its own volume under the thrust of the pressure waves generated in the ducts 30 and, therefore, in the manifold 29 by the closure of the valves 22.

The compensation of the pressure waves generated in the manifold 29 by the closure of the valves 22 has some advantages mainly deriving from the fact that: the pressure waves in the manifold 29 are relatively small;

the manifold 29 has relatively low wear;

the intake valves 22 have a relatively low opening and closing speed; And

the pumping unit 1 has a relatively high flow rate, stability and duration.

Claims (1)

CLAIMS 1.- Pumping unit for feeding fuel, preferably diesel oil, to an internal combustion engine (3), the pumping unit comprising a high pressure pump (6) for feeding fuel to the internal combustion engine (3), the high pressure pump (6) comprising at least two cylinders (9) and, for each cylinder (9), a respective piston (11) slidingly engaged in the cylinder (9) and a respective intake valve (22) movable between a closed position and an open position of the cylinder (9) itself; a pre-feed pump (7) for feeding fuel from a containment tank (2) to the high pressure pump (6); and a hydraulic circuit (15) to connect together the containment tank (2), the pre-supply pump (7), the high pressure pump (6), and the internal combustion engine (3), the circuit hydraulic (15) comprising a fuel feed manifold (29) to the high pressure pump (6) and, for each cylinder (9), a respective intake duct (30) to connect the feed manifold (29) with the cylinder (9) itself; and being characterized by the fact that the hydraulic circuit (15) also comprises a pneumatic compensation tank (39) containing a compressible gaseous fluid capable of varying its volume under the thrust of the pressure waves generated in the suction ducts (30) and, therefore, in the supply manifold (29) by closing the intake valves (22). 2.- Pumping unit according to Claim 1, in which the pneumatic compensation tank (39) is directly connected to the supply manifold (29). 3.- Pumping unit according to Claim 1, in which the supply manifold (29) and the pneumatic compensation tank (39) are separated from each other by an elastically deformable membrane. 4.- Pumping unit according to any one of the preceding claims, in which the supply manifold (29) and the pneumatic compensation tank (39) have respective longitudinal axes (32, 41) which are substantially transverse to each other. 5.- Pumping unit according to any one of claims 1 to 3, in which the supply manifold (29) and the pneumatic compensation tank (39) have respective longitudinal axes (32, 41) substantially parallel, in particular coinciding, Between them. 6.- Pumping unit according to any one of the preceding claims, in which the supply manifold (29) has a closed axial end; the intake ducts (30) being distributed along the supply manifold (29). 7.- Pumping unit according to Claim 6, in which the pneumatic compensation tank (39) is connected with the supply manifold (29) downstream of the two suction ducts (30) in a direction of advance (21) of the fuel along the feed manifold (29) itself. 8.- Pumping unit according to any of the preceding claims, in which the pneumatic compensation tank (39) has an opening and is provided with a cap (42) for closing the opening itself. 9.- Pumping unit according to any one of the preceding claims, wherein the hydraulic circuit (15) further comprises a metering valve device (20) mounted along the supply manifold (29); the two intake ducts (30) being connected with the feed manifold (29) downstream of the metering valve device (20) in a direction of advance (21) of the fuel along the feed manifold (29) itself.