ITUB20155666A1 - PUMP FOR POWERING HIGH-PRESSURE FUEL TO AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

"PUMP TO FEED HIGH PRESSURE FUEL TO AN INTERNAL COMBUSTION ENGINE"

The present invention relates to a pump for feeding high pressure fuel to an internal combustion engine.

More in detail, the present invention relates to a high-pressure pump for fuel supply systems to a Common Rail internal combustion engine, to which the following discussion will make explicit reference without thereby losing generality.

As is known, the high pressure pumps of the currently most widespread Common Rail systems comprise: a pump body structured to be fixed on the cylinder block of the internal combustion engine; an actuation shaft inserted axially rotatably inside the pump body, and adapted to be connected to the drive shaft of the internal combustion engine to be rotated by the latter, and a head positioned to close the upper end of a large cylindrical cavity, which extends in the pump body coaxial to a reference axis locally perpendicular to the axis of rotation of the drive shaft, and has its lower end facing the periphery of a lobe cam integral with the drive shaft.

In addition, the high pressure pumps of the Common Rail systems also include: an oblong pumping piston, which is inserted in an axially sliding manner inside a cylindrical cavity which extends inside the body of the head coaxially to the cylindrical cavity of the body pump, in such a way as to form a variable volume chamber inside the head, and moreover protrudes from the lower end of the head until it reaches and abuts against the peripheral surface of the lobe cam; and a helical spring which is positioned inside the cylindrical cavity of the pump body, with a first end abutting the head and a second end abutting the lower end of the pumping piston, and is structured in such a way as to prevent the piston from rising inside the cylindrical cavity of the head with consequent reduction of the volume of the variable volume chamber, and at the same time keeping the lower end of the piston always abutting the peripheral surface of the lobe cam.

Finally, the high pressure pumps of Common Rail systems are equipped with an intake valve and a delivery valve which are positioned on the upper part of the head, near the variable volume chamber, in such a way as to communicate with the latter. The intake valve controls the entry of fuel from the low pressure pump into the variable volume chamber of the cylinder head, while the delivery valve controls the exit of high pressure fuel from the variable volume chamber of the cylinder head to the internal combustion engine.

More in detail, the intake valve essentially comprises: a movable obturator with a mushroom-like structure, which is positioned on the upper end of the variable volume chamber substantially coaxial to the pumping piston, with the discoidal head inside the variable volume chamber and with the stem inserted through and axially sliding in the body of the head; and a helical contrast spring, which is adapted to keep the mobile obturator in an elastic way in a closed position in which the disc-shaped head of the obturator abuts against the body of the cylinder head, closing a series of supply ducts which bring the fuel at low pressure into the variable volume chamber of the cylinder head.

Furthermore, in the most modern high-pressure pumps, the suction valve also includes an electromagnetic actuator which is fixed on the head, immediately above the stem of the mobile shutter, and is able to axially move the mobile shutter in such a way as to being able to directly control the opening and / or closing of the mobile shutter regardless of the action of the contrast spring.

Experimental tests have shown that, during normal operation of the intake valve, the multiple mechanical forces involved and the high movement speeds of the mobile shutter can cause very violent impacts between the top of the stem and the mobile core of the electromagnetic actuator. with all the drawbacks that this entails.

In the event of particularly violent impacts, in fact, the stem and the movable core can bounce repeatedly before settling stably against each other, and this makes the opening and / or closing of the intake valve imprecise.

In addition, very violent impacts in the long term can lead to excessive wear of the contact area between the two components, with the problems that this entails.

The object of the present invention is to obviate the drawbacks described above.

In accordance with these objectives, according to the present invention a pump is provided for supplying high pressure fuel to an internal combustion engine as defined in claim 1 and preferably, but not necessarily, in any of the claims dependent on it.

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 side view, with parts in section and parts removed for clarity, of a pump for feeding high-pressure fuel to an internal combustion engine, made according to the dictates of the present invention;

Figure 2 is an enlarged view of the upper part of the pump head illustrated in Figure 1, with the suction valve open; while

Figure 3 is an enlarged view of the upper part of the pump head illustrated in Figure 1, with the suction valve closed.

With reference to Figure 1, the number 1 indicates as a whole a pump for feeding fuel at high pressure to an internal combustion engine (not shown), which can be advantageously used in systems for feeding fuel to an engine. to burst.

More in detail, the pump 1 can be advantageously used in Common Rail type fuel supply systems, which are used to feed high-pressure diesel oil to a Diesel internal combustion engine.

The pump 1 comprises: an external pump body 2 which is preferably structured in such a way as to be fixed on the housing of the internal combustion engine (not shown); an actuation shaft 3 which is inserted in an axially rotatable way inside the pump body 2, preferably with the interposition of suitable bearings and / or bushings, so as to be able to rotate freely around its longitudinal axis A; and a head 4 which is positioned to close the upper end / opening of a large cylindrical cavity 5 which extends in the pump body 2 transversely to the rotation axis A of the drive shaft 3, and has the lower end / opening directly facing the periphery of a lobe cam 6 present on the drive shaft 3.

More in detail, in the example illustrated, the pump body 2 is preferably structured to be rigidly fixed to the engine block of a generic internal combustion engine (not shown). The cylindrical cavity 5 instead extends into the pump body 2 coaxial to a reference axis B preferably locally perpendicular to the rotation axis A of the drive shaft 3.

In addition, the drive shaft 3 is preferably structured in such a way as to project with a cantilevered end from the pump body 2, and to be mechanically connected therein to the drive shaft of the internal combustion engine (not shown), so that the drive shaft 3 can be rotated by the internal combustion engine. Preferably, the lobe cam 6 is also made in a single piece with the drive shaft 3.

With reference to Figure 1, the pump 1 also comprises a pumping piston 7 preferably of substantially cylindrical shape, which axially slidingly engages a corresponding oblong cavity 8 which extends inside the head 4 coaxial to a locally substantially parallel reference axis. and optionally also coinciding with the longitudinal axis B of the cylindrical cavity 5. The oblong cavity 8 also has a cross section complementary to that of the piston 7 and is blind at the top, so that the piston 7 can form, inside the head 4, a small closed chamber with variable volume 9 intended to receive the fuel to be pumped to the internal combustion engine (not shown).

Preferably, the piston 7 also has an oblong shape so as to protrude from the head 4 and project in a cantilever way inside the cylindrical cavity 5, towards the drive shaft 3.

The actuation shaft 3 is adapted to move the pumping piston 7 with reciprocating rectilinear motion inside the oblong cavity 8, in such a way as to cyclically vary the volume of the closed chamber with variable volume 9.

In the example illustrated, in particular, the pumping piston 7 preferably protrudes from the lower end of the head 4 and extends inside the cylindrical cavity 5 coaxial to the axis B, until it reaches the lobe cam 6, so that the actuation shaft 3, rotating around the axis A, can impart an alternating rectilinear motion to the piston 7 inside the cylindrical cavity 8, with consequent cyclical variation of the volume of the variable volume chamber 9 present in the head 4.

More in detail, in the example illustrated, the lower end of the piston 7 preferably rests on the peripheral surface of the cam 6 preferably, but not necessarily, by means of the interposition of a rolling tappet 10 which is preferably integral with the lower end of the piston. 7, and axially slidingly engages the lower portion of the cylindrical cavity 5.

With reference to Figure 1, the pump 1 is also preferably also equipped with an elastic member 11 which is adapted to counteract the rising of the piston 7 inside the oblong cavity 8, with a consequent reduction in the volume of the variable volume chamber 9, and at the same time as keeping the lower end of the pumping piston 7, or if present the tappet 10, always resting on the peripheral surface of the lobe cam 6.

More in detail, in the example illustrated, the pump 1 is preferably equipped with a helical spring 11, which extends inside the cylindrical cavity 5 remaining locally coaxial with the piston 7, so as to have a first end abutting the head 4 and a second end abutting the tappet 10 which, in turn, is preferably rigidly fixed to the lower end of the pumping piston 7. The helical spring 11 is structured in such a way as to oppose the piston 7 rising inside the cavity oblong 8, and at the same time keep the tappet 10 always resting on the peripheral surface of the cam 6.

With reference to Figure 1, the pump 1 is also equipped with an intake valve 12 and a delivery valve 13, which are located on the upper part of the head 4, near the variable volume chamber 9. The delivery valve 13 is structured in such a way as to allow the automatic discharge of the high pressure fuel from the variable volume chamber 9 when the piston 7 rises inside the oblong cavity 8 causing a reduction in the volume of the variable volume chamber 9, and is interposed between the variable volume chamber 9 and a fuel discharge duct 14 which preferably in turn communicates with the high pressure fuel distribution manifold (not shown) of the Common Rail type fuel supply system.

The delivery valve 13 is a component already widely known in the sector of high pressure fuel pumps for Common Rail systems, and will therefore not be further described, except to specify that it is preferably housed in the head 4, inside the exhaust duct. fuel 14.

The intake valve 12, on the other hand, is structured in such a way as to allow the selective entry of low pressure fuel into the variable volume chamber 9 when the piston 7 descends into the oblong cavity 8 causing an increase in the volume of the chamber. variable volume 9, and is interposed between the same variable volume chamber 9 and a generic low pressure fuel source.

More in detail, the intake valve 12 is preferably interposed between the variable volume chamber 9 and the delivery of an auxiliary pump, which is capable of sucking the fuel from a generic fuel tank (not shown) and then sending it to the inlet. to pump 1 with a pressure of a few bars.

In the example illustrated, in particular, the intake valve 12 is preferably interposed between the variable volume chamber 9 and the delivery of an electric or gear pump (not shown) which is capable of sucking fuel from a generic tank of the fuel (not shown) and then send it to the inlet to the variable volume chamber 9 with a pressure preferably between 2 and 3 bar.

With reference to Figures 1, 2 and 3, in particular, the variable volume chamber 9 preferably communicates with the low pressure fuel source, or better with the delivery of the auxiliary pump, through one or more fuel supply ducts 15 which they extend inside the head body 4 up to the variable volume chamber 9.

The intake valve 12 is selectively adapted to fluid-tightly obstruct the fuel supply duct (s) 15 so as to control the flow of fuel entering the variable volume chamber 9.

More in detail, with particular reference to Figures 2 and 3, the intake valve 12 is at least partially housed inside the head 4, and comprises: an oblong-shaped mobile obturator 16, which is inserted in an axially sliding manner in the body of the cylinder head 4, in such a way as to be able to move between a closed position (see figure 3) in which the body of the movable shutter 16 blocks the fuel supply duct (s) 15 in a fluid-tight manner, and an open position (see figure 2) in which the body of the movable shutter 16 does not obstruct the fuel supply ducts 15 in a fluid-tight manner, thus allowing the free passage of fuel towards the variable volume chamber 9; and preferably also an elastic member 17 which is adapted to bring and retain the movable shutter 15 in an elastic way in the closed position.

In other words, the movable shutter 16 is inserted in an axially sliding manner into the body of the cylinder head 4 in such a way as to be able to move to and from a closed position in which the movable shutter 16 prevents the flow of fuel to the volume chamber. variable 9.

In addition, the intake valve 12 also comprises: an electromagnetic actuator 18 which is positioned next to the mobile shutter 16, and is equipped with a movable core 19 which faces and aligned with the mobile shutter 16, and is capable of moving axially from and towards the mobile shutter 16 in a direction parallel to the longitudinal axis of the mobile shutter 16 in order to be able selectively to abut on an axial end 20 of the mobile shutter 16 and then axially push the mobile shutter 16; and at least one fluid-dynamic damper 21 which is interposed between the movable core 19 and the axial end 20 of the movable shutter 16.

More in detail, the movable core 19 of the electromagnetic actuator 18 is selectively adapted to abut against the axial end 20 of the movable obturator 16 to exert on the mobile obturator 16 an axial thrust f opposite / opposite to the axial thrust exerted by the member. elastic 17.

The fluid-dynamic damper 21, on the other hand, is adapted to dampen the axial movements of the movable core 19 with respect to the movable shutter 16 and vice versa.

Preferably, the movable core 19 of the electromagnetic actuator 18 and the axial end 20 of the movable shutter 16 are also structured in such a way as to be able to selectively engage / insert axially into each other, and are suitable for forming the fluid-dynamic damper 21 when they mate with each other.

In other words, the fluid dynamic damper 21 is divided into two parts which are preferably incorporated one in the movable shutter 16, and the other in the movable core 19 of the electromagnetic actuator 18.

More in detail, with reference to Figures 2 and 3, the fluid dynamic damper 21 preferably comprises; a protruding rectilinear stem 22 which protrudes from the movable shutter 16 towards the movable core 19 parallel to the direction of displacement of the movable core 19; and a blind seat 23 which is made on the body of the movable core 19 of the electromagnetic actuator 18 in such a way as to be facing and aligned with the stem 22, and has a shape substantially complementary to that of the distal end of the protruding stem 22 in such a way as to be engageable in an axially sliding / telescope manner by the stem 22 of the movable shutter 16.

In the example illustrated, in particular, the axial end 20 of the movable obturator 16 preferably coincides with the distal end of the protruding stem 22 of the fluid dynamic damper 21, so that the movable core 19 of the electromagnetic actuator 18 is able to be arranged abuts directly on the protruding stem 22.

With reference to Figures 2 and 3, in the example illustrated, in particular, the mobile obturator 16 extends inside the head 4 remaining locally coaxial to a reference axis which is preferably locally substantially parallel and optionally also coincident with the longitudinal axis of the oblong cavity 8, i.e. with axis B.

Preferably, the mobile obturator 16 additionally protrudes from the head 4, inside a blind hollow seat 24 and preferably also of a substantially cylindrical shape, which is made on the surface of the head 4 next to the variable volume chamber 9. More in detail, the hollow seat 24 extends inside the body of the head 4 towards the oblong cavity 8, or better towards the variable volume chamber 9, remaining locally coaxial to the longitudinal axis B of the oblong cavity 8.

Preferably, the fuel supply ducts 15 also extend from the variable volume chamber 9 to the bottom of the hollow seat 24, and are preferably angularly distributed all around the movable shutter 16.

In the example illustrated, moreover, the mobile shutter 16 preferably has a mushroom-like structure, and extends inside the head 4 coaxial to the axis B, so that the head 16a of the mobile shutter 16 is housed in the inside the variable volume chamber 9, close to the bottom of the oblong cavity 8, and that the rectilinear stem 16b protrudes from the bottom of the hollow seat 24 and extends inside the hollow seat 24 always remaining coaxial to the axis B.

The head 16a of the movable obturator 16 is preferably sized to be able to selectively shut / obstruct the fuel supply ducts 15 in a fluid-tight manner when the movable obturator 16 is in the closed position.

The distal end of the rectilinear stem 16b is instead adapted to abut the movable core 19 of the electromagnetic actuator 18, and therefore coincides with the axial end 20 of the movable shutter 16.

Preferably, the rectilinear stem 16b also performs the function of the protruding stem 22 of the fluid-dynamic damper 21.

With reference to Figures 2 and 3, preferably the elastic member 17 of the intake valve 12 is instead constituted by a helical spring, which is fitted on the straight stem 16b of the mobile obturator 16 in such a way as to have a first end abutting on the bottom of the hollow seat 24, and a second end abutting on a plate or cup 26 which in turn is rigidly fixed on the straight stem 16b, at a predetermined distance from the distal end 20 of the stem 16b.

The helical spring 17 is structured in such a way as to resiliently retain the head 16a of the movable shutter 16 abutting against the bottom of the oblong cavity 8, so as to obstruct the mouths of the fuel supply ducts 15 in a fluid-tight manner.

With reference to figures 1, 2 and 3, preferably the electromagnetic actuator 18 is instead arranged above the movable actuator 16, with the movable core 19 coaxial to the movable actuator 16, and the blind seat 23 is made on the body of the core movable 19 in such a way as to be aligned and facing the distal end of the straight stem 16b,

More in detail, the electromagnetic actuator 18 is preferably at least partially housed inside the hollow seat 24 on the surface of the head 4, above the axial end 20 of the movable shutter 16. Preferably, the electromagnetic actuator 18 is also structured in a manner such as to fluid-tightly obstruct the upper part of the hollow seat 24, forming a fuel transit chamber 27 on the bottom of the hollow seat 24, which communicates with the low-pressure fuel source, and houses the fluid-dynamic damper inside 21 and optionally also the axial end 20 of the movable shutter 16.

In the example illustrated, in particular, the fuel transit chamber 27 preferably has a substantially discoidal shape, houses the end portion of the stem 16b of the mobile actuator 16 and the elastic member 17, and is finally connected to the delivery of the auxiliary pump, preferably through at least one fuel supply duct 28, which extends inside the body of the head 4 preferably up to the bottom of the hollow seat 24.

Preferably, the fuel supply line or ducts 15 further extend from the fuel transit chamber 27 to the variable volume chamber 9.

With reference to Figures 2 and 3, in the example illustrated, in particular, the electromagnetic actuator 18 preferably comprises: a support bushing 29 which is housed inside the hollow seat 24 in such a way as to face the movable shutter 16 , and is centrally provided with a long tubular through portion 30 inside which the movable core 19 is housed in an axially sliding manner; an elastic member 31 which is preferably housed inside the through tubular portion 30, and is adapted to push the movable core 19 in an elastic manner towards the bottom of the hollow seat 24, against the axial end 20 of the movable shutter 16; and a toroidal coil 32 which is fitted on the through tubular portion 30 of the bushing 29, and is adapted to produce an axial electromagnetic field which is capable of moving the movable core 19 away from the axial end 20 of the movable shutter 16, overcoming the elastic thrust of the elastic member 31.

In other words, the electromagnetic actuator 18 additionally comprises; an elastic member 31 which is able to push the movable core 19 in an elastic way towards the axial end 20 of the movable shutter 16; and a coil 32 which is adapted to produce an axial electromagnetic field which is capable of moving the movable core 19 away from the axial end 20 of the movable shutter 16, overcoming the elastic thrust of the elastic member 31.

In the example illustrated, in particular, the movable core 19 preferably has a substantially cylindrical shape, and is equipped with a series of longitudinal through ducts which are angularly distributed around the longitudinal axis of the movable core 19.

The support bushing 29, on the other hand, is preferably fitted inside the hollow seat 24 in a fluid-tight manner, preferably by means of the interposition of at least one annular sealing gasket.

Finally, the elastic member 31 is preferably adapted to push and hold the movable core 19 in an elastic way against an annular shoulder which is positioned in correspondence with the lower mouth of the through tubular portion 30, i.e. at the directly facing mouth. at the bottom of the hollow seat 24, and the rectilinear stem 16b of the mobile obturator 16 is dimensioned in such a way as to project into the through tubular portion 30 of the bushing 29, preferably until it reaches and goes beyond the annular shoulder mentioned above.

More in detail, with reference to Figures 2 and 3, in the illustrated example, the electromagnetic actuator 18 is preferably equipped with an obturator plug 33 which closes the upper end of the through tubular portion 30 of the bushing 29 in a fluid-tight manner. predetermined distance from the movable shutter 19; and the elastic member 33 is preferably constituted by a helical spring which extends inside the tubular through portion 30 substantially coaxial to the longitudinal axis B, so as to have a first end abutting the mobile core 19, and a second end abuts on a threaded dowel 34 which is screwed in an adjustable position inside a blind hole which extends into the body of the shutter 33 coaxial to the longitudinal axis B.

With reference to Figures 2 and 3, preferably the electromagnetic actuator 18 finally also comprises an external casing 35 with a cup-shaped structure, preferably of a substantially cylindrical shape, which surrounds and protects the toroidal coil 32, and is stably fixed to the support bushing 29 of the plunger 19.

Preferably, the outer casing 35 is also dimensioned in such a way as to be at least partially inserted in the hollow seat 24.

The operation of the pump 1 can be easily deduced from what has been described above and does not require further explanations.

On the other hand, as regards the fluid-dynamic damper 21, the space between the axial end 20 of the movable shutter 16 and the movable core 19 is always full of fuel so that when the distal end 20 of the stem 26 of the movable shutter 16 begins to penetrate inside the blind seat 23 present on the movable core 19, the fuel contained inside the blind seat 23 must necessarily come out of the blind seat 23. However, the escape of the fuel is hindered by the restriction that forms between the end distal 20 of the stem 26 and the movable core 19, whereby the movable core 19 undergoes a significant deceleration before hitting the distal end 20 of the stem 26 of the movable shutter 16.

The advantages associated with the presence of the fluid-dynamic damper 21 between the movable shutter 16 and the movable core 19 are considerable.

In the first place, the fluid dynamic damper 21 minimizes the rebounds of the movable core 19 of the electromagnetic actuator 18 following the impact with the axial end 20 of the movable obturator 16, allowing better control of the instant of opening of the intake valve. 12.

In addition, the fluid dynamic damper 21 reduces the speed with which the movable core 19 impacts on the axial end 20 of the movable obturator 16, avoiding wear and / or plastic deformation of the material in correspondence with the contact area between the movable obturator 16 and the mobile core 19.

Finally, it is clear that modifications and variations can be made to the pump 1 without departing from the scope of the present invention.

For example, in a different embodiment, the protruding stem 22 of the fluid dynamic damper 21 can project from the movable core 19 towards the axial end 20 of the movable shutter 16, parallel to the direction of movement of the movable core 19; and the blind seat 23 can be made directly on the axial end 20 of the movable shutter 16 in such a way as to be engageable in an axially sliding / telescopic way by the stem 22 of the movable core 19.

Claims (10)

R IV EN D IC A T IO N I 1. Pump (1) for supplying high pressure fuel to an internal combustion engine, of the type comprising: a head (4); a piston (7) which axially slidingly engages a first oblong cavity (8) present in the head (4) forming, inside said head (4), a variable volume chamber (9) intended to receive the fuel to be pump to the internal combustion engine; and an intake valve (12) which controls the entry of fuel into the variable volume chamber (9); the intake valve (12) comprising in turn: an oblong-shaped movable obturator (16), which is inserted in an axially sliding manner in the body of the head (4) in such a way as to be able to move to and from a closed position in wherein the movable shutter (18) prevents the flow of fuel to the variable volume chamber (9); and an electromagnetic actuator (18) which is positioned next to the mobile shutter (16), and is equipped with a movable core (19) which is aligned with the mobile shutter (16), and is able to move axially from and to towards the mobile shutter (16) to position itself against an axial end (20) of the mobile shutter (16) and then axially push said mobile shutter (16); said pump (1) being characterized in that the intake valve (12) comprises fluid-dynamic shock-absorbing means (21) interposed between the movable core (19) of the electromagnetic actuator (18) and the axial end (20) of the shutter mobile (16). 2. Pump according to claim 1, characterized in that the movable core (19) of the electromagnetic actuator (18) and the axial end (20) of the movable shutter (16) are adapted to compose said fluid-dynamic shock-absorbing means (21 ) when they mate to each other. 3. Pump according to claim 2, characterized in that said fluid-dynamic shock-absorbing means (21) comprise: a protruding stem (22) which protrudes from the movable shutter (16) towards the movable core (19) or vice versa, parallel to the direction of displacement of the mobile core (19); and a blind seat (23) which is made on the movable core (19) or on the movable shutter (16) aligned in front of said protruding stem (22), and has a shape substantially complementary to that of the distal end of the protruding stem ( 22) in such a way as to be axially slidable engageable by the protruding stem (22). 4. Pump according to claim 3, characterized by the fact that the protruding stem (22) protrudes from the movable shutter (16) and the movable core (19) of the electromagnetic actuator (18) is able to be arranged directly in abutment on the distal end (20) of said protruding stem (22). 5. Pump according to any one of the preceding claims, characterized in that the suction valve (12) also comprises a first elastic member (17) adapted to bring and retain the movable shutter (16) in an elastic manner in said closing position ; the movable core of the electromagnetic actuator (19) being able to exert on said movable shutter (16) an axial thrust (f) contrary to that exerted by said first elastic member (18). Pump according to any one of the preceding claims, characterized in that the electromagnetic actuator (18) additionally comprises; a second elastic member (31) adapted to push the movable core (19) in an elastic manner towards the axial end (20) of the movable shutter (16); and a coil (32) which is able to produce an axial electromagnetic field which is able to move the movable core (19) away from the axial end (20) of the movable shutter (16), overcoming the elastic thrust of said second member elastic (31). 7. Pump according to any one of the preceding claims, characterized in that the movable shutter (16) protrudes from the bottom of a second hollow seat (24) which is made on the surface of the head (4) next to the volume chamber variable (9) and the electromagnetic actuator (18) is at least partially housed inside said second hollow seat (24), above the movable shutter (16). 8. Pump according to claim 7, characterized in that the electromagnetic actuator (18) hermetically obstructs said second hollow seat (24), forming a fuel transit chamber (27) on the bottom of the second hollow seat (24) ), which houses the fluid-dynamic shock-absorbing means (21) and preferably also the axial end (20) of the movable shutter (16). 9. Pump according to claim 8, characterized in that said fuel transit chamber (27) is in communication with a fuel source, and also communicates with the variable volume chamber (9) through one or more supply ducts of the fuel. fuel (15); when it is in the closed position, the movable shutter (16) being able to seal said or said fuel supply ducts (15) in a fluid-tight manner. Pump according to any one of the preceding claims, wherein said pump (1) also comprises a pump body (2) and a drive shaft (3) inserted in an axially rotatable way inside the pump body (2); the head (4) being placed on the mouth of a second oblong cavity (5) which extends into the pump body (2) transversely to the drive shaft (3), and faces a cam (6) present on said shaft actuation (3); said piston (7) being structured in such a way as to protrude from the head (4) and extend inside the second oblong cavity (5), until it reaches said cam (6), so that said drive shaft ( 3), by rotating around its longitudinal axis (A), can give the piston (7) an alternating rectilinear motion inside the first oblong cavity (8).