IT202000013588A1 - PUMPING UNIT 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 ? relating to a pump unit for supplying fuel, preferably gas oil, to an internal combustion engine.

In particular, the present invention ? relating to a pump assembly of the type comprising a piston pump for supplying fuel to an internal combustion engine; a gear pump for supplying fuel from a holding tank to the piston pump; and a hydraulic circuit for interconnecting the holding tank, the gear pump, the piston pump, and the internal combustion engine.

The gear pump comprises a pump body, which has a cup shape, ? limited by a substantially flat back wall and a shaped side wall, and is closed by a cover mounted in contact with the pump body parallel to the back wall itself.

The pump body and the cover define a containment chamber, which has a fuel inlet in the gear pump and a fuel outlet in the gear pump, and houses inside itself two gears coupled together to rotate around respective rotation axes substantially parallel to each other and perpendicular to the bottom wall and to the lid.

The gears are one angularly fixed to a drive shaft extending through the bottom wall and the other rotatably to a bearing pin projecting from the bottom wall.

Each gear? subjected to a thrust obtained as a result of a hydraulic force generated by the difference in pressure existing between the outlet and the inlet of the containment chamber and a mechanical force generated by the interaction between the two gears.

Known pumping units of the type described above, although supertested, have some drawbacks mainly due to the fact that the thrust exerted on each gear is transversal to the relative axis of rotation, and generates a bending moment on the gear itself.

Due to the clearances existing between the pump casing, the cover and the gears, the bending moment acting on each gear causes the displacement of the gear in contact with the bottom wall and/or the side wall and/or the cover of the chamber containment, the sliding of the gear on the bottom wall and/or on the side wall and/or on the lid of the containment chamber, and the asymmetric wear of the pump body and the lid, and compromise the correct functioning of the pumping group.

Purpose of the present invention? to provide a pump unit for feeding fuel, preferably gas 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 there is provided a pumping group for feeding fuel, preferably gas oil, to an internal combustion engine as claimed in the attached claims.

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

figure 1 ? a hydraulic diagram of a preferred embodiment of the pump unit of the present invention;

figure 2 ? a schematic front view, with parts removed for clarity, of a detail of the pump unit of figure 1; And

figure 3 ? a schematic section, with parts removed for clarity, of the detail of figure 2.

With reference to figure 1, with 1 ? indicated, as a whole, a pumping group for feeding fuel, preferably gas 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 suitable for nebulizing the fuel inside the relative combustion chambers (not shown) of the engine 3 itself.

The pump unit 1 comprises a high pressure pump 6 for feeding fuel to the engine 3; and a low pressure or pre-feed pump 7 for feeding the fuel from the tank 2 to the pump 6.

Pump 6? a piston pump comprising 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 illustrated, the number of cylinders 9 ? other than two, in particular equal to one, and the axes 10 are not parallel to each other.

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

The device 12 comprises a cam drive shaft 13, which ? housed in a 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) able to move the piston 11 itself with its suction stroke.

About the above? should it be specified that the shaft 13 ? configured so 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; a second branch 17 for connecting the pump 7 and the pump 6 together; and a third branch 18 to connect the pump 6 and the manifold 4 to each other.

Branch 17? provided with a filtering device 19 for filtering the fuel supplied to the cylinders 9, and also has a metering solenoid valve 20 mounted downstream of the device 19 in a fuel feed direction 21 along the branch 17 to selectively control the instantaneous flow of fuel fed to the pump 6 according to the values of a plurality? of engine operating parameters 3.

The branch 17 and the branch 18 are connected to each cylinder 9 through 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 fuel flow rate exceeding that required by 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 ? connected to the branch 17 downstream of the solenoid valve 20 in the direction 21 to feed the fuel flowing through the solenoid valve 20 to the inlet of the pump 7 when the solenoid valve 20 itself? closed.

The circuit 15 also has a sixth branch 26, which extends between the branch 17 and the pump body 8, ? connected to the branch 17 upstream of the solenoid valve 20 in the direction 21, and ? provided with a valve device 27.

Device 27 ? configured to control the feeding into the pump body 8 and into the chamber 14 of the fuel flow rate used to lubricate the cam transmission shaft 13 and of the fuel flow rate exceeding 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 24 and, therefore, into the branch 16.

According to what is illustrated in figures 2 and 3, the pump 7 ? a gear pump comprising a pump body 29, which ? fixed to the pump body 8, and has a cup shape.

The pump body 29 ? limited by a bottom wall 30 that is substantially flat and perpendicular to an axis 31 of rotation of the shaft 13, and is also limited by a shaped lateral wall 32.

The pump body 29 ? closed by a lid 33, which ? mounted in contact with the pump body 29 parallel to the wall 30, and defines, together with the pump body 29 itself, a containment chamber 34 having a fuel inlet 35 in the pump 7 and a fuel outlet 36 from the pump 7 itself.

The chamber 34 houses inside itself a pair of cylindrical gears 37, 38 coupled together.

The gear 37 ? coupled in an angularly fixed at one end? free of the shaft 13 protruding inside the chamber 34, and is moved by the shaft 13 around the axis 31.

The 38 gear? rotatably fitted onto a support pin 39, which has a longitudinal axis 40 parallel to axis 31, and protrudes axially from wall 30.

Each gear 37, 38 ? subject to a thrust F1 obtained as a result of a hydraulic force generated by the pressure difference existing between the outlet 36 and the inlet 35 of the chamber 34 and of a mechanical force generated by the interaction between the two gears 37, 38.

The thrust F1 acting on each gear 37, 38 ? transversal to the relative axis 31, 40 of rotation, in particular radial, lies in a plane P parallel to the relative axis 31, 40 of rotation itself, and ? arranged at an angle other than 0? compared to the thrust F1 acting on the other gear 37, 38.

Due to existing tolerances and clearances, each gear 37, 38 ? subjected to a bending moment M1 generated by the relative thrust F1.

The circuit 15 also comprises an eighth branch 41, which extends between one of the cylinders 9 and the chamber 34, and ? provided with a section reduction, in this case a calibrated hole 42, able to control the fuel supply along the branch 41 itself.

According to a variant not shown, branch 41 extends between branch 18 and chamber 34.

In this case, therefore, the branch 41 receives fuel at the delivery pressure of the high pressure pump 6 as an inlet.

Branch 41 communicates with chamber 34 via two feed holes 43, each of which ? obtained through the lid 33, and ? eccentric with respect to the relative axis 31, 40.

Each hole 43 ? facing a major face 44 of the relative gear 37, 38 substantially perpendicular to the relative axis 31, 40, and ? set out, in this case, in the corresponding plan P.

The fuel fed into the chamber 34 through each hole 43 exerts on the face 44 of the relative gear 37, 38 a hydraulic thrust F2 oriented, preferably but not necessarily, parallel to the relative axis 31, 40.

Each thrust F2 generates on the relative gear 37, 38 a bending moment M2 opposite to the corresponding bending moment M1.

AND? should it be specified that the pressure of the fuel fed into the chamber 34 through the holes 43 ? greater than the delivery pressure of pump 7 at outlet 36.

The pump 7 has some advantages mainly deriving from the fact that the thrust F2 and the bending moment M2 guarantee relatively reduced wear and correct lubrication of the pump body 29, of the cover 33, and of the gears 37, 38.

Claims (10)

1.- Pumping group for feeding fuel, preferably gas oil, to an internal combustion engine (3), the pumping group comprising a piston pump (6) for feeding fuel to the internal combustion engine (3); a gear pump (7) for feeding fuel from a holding tank (2) to the piston pump (6); and a hydraulic circuit (15) comprising a first branch (16) to connect the holding tank (2) and the gear pump (7) together, a second branch (17) to connect the gear pump (7 ) and the piston pump (6), and a third branch (18) for connecting the piston pump (6) and the internal combustion engine (3) to each other; the piston pump (6) comprising at least one cylinder (9) and a piston (11) slidably engaged in the cylinder (9) itself; and the gear pump (7) comprising a containment chamber (34) provided with an inlet (35) suitable for receiving the fuel from the first branch (16) and with an outlet (36) for feeding the fuel into the second branch (17 ), and a pair of gears (37, 38) mounted in the containment chamber (34) and coupled together to rotate about respective rotation axes (31, 40); and being characterized in that the hydraulic circuit (15) also comprises a fourth branch (41), which ? connected with the cylinder (9) or with the third branch (18), and communicates with the containment chamber (34) to generate a thrust (F2) on a major face (44) of each gear (37, 38). 2.- Pumping group according to Claim 1, wherein the fourth branch (41) comprises, for each gear (37, 38), a respective feed hole (43) oriented in such a way that the thrust (F2) acting on the ?gear (37, 38) is substantially parallel to the relative axis of rotation (31, 40). 3.- Pumping unit according to claim 2, wherein each feed hole (43) is facing the major face (44) of the relative gear (37, 38). 4.- Pumping unit according to claim 2 or 3, wherein each feed hole (43) is? eccentric with respect to the axis of rotation (31, 40) of the relative gear (37, 38). 5.- Pumping group according to any one of claims from 2 to 4, in which the gear pump (7) comprises a pump body (29), which has the shape of a cup-shaped body, ? limited by a back wall (30) and a side wall (32), and ? closed by a cover (33) mounted in contact with the side wall (32) itself; the feed holes (43) being formed through the cover (33). 6.- Pumping unit according to any one of claims from 2 to 5, wherein each gear (37, 38) ? subjected to a further thrust (F1) transversal to the relative axis of rotation (31, 40) and lying in a containment plane (P) parallel to the axis of rotation (31, 40) itself; each feed hole (43) being arranged in the relative containment plane (P). 7.- Pumping unit according to any one of the preceding claims, wherein the fourth branch (41) is? provided with a section reduction (42) to control the fuel supplied to the containment chamber (34). 8.- Pumping unit according to any one of the preceding claims and further comprising a transmission shaft (13), which protrudes inside the containment chamber (34), and ? engaged in an angularly fixed manner by a first said gear (37). 9.- Pumping unit according to any one of the preceding claims and further comprising a support pin (39), which protrudes inside the containment chamber (34), and ? rotatably engaged by a second said gear (38). 10.- Pumping unit according to any one of the preceding claims, wherein the major face (44) of each gear (37, 38) is? substantially perpendicular to the relative axis of rotation (31, 40).