IT201600114608A1 - FUEL SUPPLY PUMP - Google Patents

Description

"FUEL PUMP"

TECHNIQUE SECTOR

The present invention relates to a fuel feed pump.

ANTERIOR ART

The present invention finds advantageous application in internal combustion engines. In particular, the present invention finds advantageous, but not exclusive application in small displacement internal combustion engines for motor vehicles to which the following discussion will make explicit reference without thereby losing generality.

In the sector of small displacement motor vehicles, it is known to produce an internal combustion engine comprising a cylinder connected to an intake manifold by means of at least one intake valve and to an exhaust manifold by means of at least one exhaust valve.

The intake manifold feeds air from the external environment into the cylinder, while the exhaust manifold discharges the gases produced by combustion outside the cylinder to feed them to a muffler and, therefore, into the atmosphere.

The fuel (normally petrol) is fed to the cylinder by means of an electronic fuel injection system comprising an injector located near the intake valve to inject the fuel into the intake manifold or arranged so as to inject the fuel directly into the intake manifold. inside the cylinder.

The fuel system also includes a fuel pump, which takes the fuel from a containment tank at atmospheric pressure, and feeds it to the injector under the control of an electronic control unit, which drives the injector in order to inject cyclically the fuel during the aspiration phases of the cylinder, and also drives the fuel pump to supply the fuel to the injector with a constant pressure.

The fuel system also includes a fuel pump, which takes the fuel from a containment tank at atmospheric pressure, and feeds it to the injector under the control of an electronic control unit, which drives the injector in order to inject cyclically the fuel during the aspiration phases of the cylinder, and also drives the fuel pump to supply the fuel to the injector with a constant pressure.

Generally, the fuel pump comprises a tubular pump body defining a supply channel connected on one side to the fuel tank and on the opposite side to the injector.

The supply channel is engaged in a sliding manner by a piston defining, inside the pump body, a variable volume pumping chamber, which is connected to the injector through the interposition of a non-return valve, and is connected moreover, with the supply channel through a plurality of openings obtained through the piston and closed, normally, by a reed valve fixed to the piston itself.

The piston is movable along the feed channel with a reciprocating rectilinear motion under the thrust of an actuation device comprising an electromagnetic actuator able to move the piston with a stroke of suction of the fuel in the pump body and a spring able to move the piston with a fuel delivery stroke to the injector.

The fuel pump also comprises a first end-of-stroke member for stopping the piston at the end of the intake stroke, and a second end-stroke member for stopping the piston at the end of the delivery stroke.

The known fuel supply pumps of the type described above have some drawbacks mainly deriving from the fact that, when the motor vehicle is started and the internal combustion engine idling, these pumps have a noise deriving from the impact of the piston both against the first limit stop member is against the second relatively high limit stop member.

DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a fuel feed pump which is free from the drawbacks described above and which is simple and economical to manufacture.

According to the present invention, a fuel feed pump is realized according to what is claimed in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

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 schematic view of an internal combustion engine provided with a preferred embodiment of the fuel feed pump of the present invention;

Figure 2 is a sectional view of the fuel feed pump of Figure 1;

Figure 3 is a plan view of a first detail of Figure 2;

Figure 4 is a sectional view along the line IV-IV of Figure 3;

figure 5 represents two perspective views of a second detail of figure 2;

Figure 7 is a plan view of the detail of Figure 5;

- figure 7 is a sectional view along the line VII-VII of the detail of figure 6;

Figure 8 is a sectional view of a second embodiment of the fuel feed pump of the present invention;

Figure 9 illustrates the filling of a pumping chamber of a fuel feed pump made in accordance with the present invention; And

Figure 10 is a schematic view of a fuel tank of the internal combustion engine of Figure 1.

PREFERRED FORMS OF IMPLEMENTATION OF THE INVENTION

Number 1 in Figure 1 indicates, as a whole, an internal combustion engine comprising a cylinder 2, which is connected to an intake manifold 3 via at least one intake valve 4 and to an exhaust manifold 5 via at least an exhaust valve 6.

The intake manifold 3 is supplied with air coming from the external environment from a supply duct 7 controlled by a butterfly or shutter valve 8, and is connected to the cylinder 2 by means of an intake duct 9 controlled by the valve 4. Similarly , the exhaust manifold 5 is connected to the cylinder 2 by means of an exhaust duct 10 controlled by the valve 6, and is also connected to an emission duct 11, the free end of which is connected, in turn, to a muffler (known and not illustrated) to release combustion gases into the atmosphere.

The fuel, in this case petrol, is fed to the cylinder 2 by means of an electronic injection power system 12 comprising an injector 13 located near the valve 4 to inject the fuel itself into the duct 9.

According to a variant not shown, the injector 13 is arranged so as to inject the fuel directly into the cylinder 2.

The system 12 also includes a fuel supply pump 14, which communicates hydraulically with a containment tank 15 at atmospheric pressure through a first supply duct 16 and with the injector 13 through a second supply duct 17.

The operation of the system 12 is selectively controlled by an electronic control unit 18, which drives the injector 13 to cyclically feed the fuel to the cylinder 2 during the intake phases of the internal combustion engine, and also drives the pump 14 to supply the fuel to the injector 13 with a constant and predetermined pressure.

According to what is illustrated in Figure 2, the pump 14 comprises a pump body 19 shaped so as to define a cylinder 20, which has a substantially vertical longitudinal axis 21, and comprises an enlarged upper portion 22 and a narrow lower portion 23.

The portion 23 is connected with the duct 17 and, therefore, the injector 13 through a fuel outlet fitting 24 protruding from the pump body 19 along the axis 21.

The portion 22 of the cylinder 20 is slidably engaged by a piston 25 comprising a plate 26, which is mounted perpendicular to the axis 21, and defines, inside the portion 22, an upper chamber 27 and a lower chamber 28 aligned along axis 21 itself.

The piston 25 also includes a tubular anchor 29, which is mounted inside the chamber 27 coaxially to the axis 21, and is coupled in an axially fixed manner to the plate 26.

Chamber 28 is a variable volume pumping chamber connected to the injector 13 through the interposition of a non-return valve 30 housed in the portion 23 of the cylinder 20.

With reference to Figures 3 and 4, the fuel is fed into the chamber 28 by means of an intake valve 31 comprising a plurality of supply holes 32 obtained through the plate 26 parallel to the axis 21 and a deformable lamina 33 suitable for controlling selectively feeding the fuel into the chamber 28 itself.

The lamina 33 comprises an external annular crown 34 fixed along a perimeter edge of the plate 26 by welding, and a plurality of central circular petals 35, which are equal in number to the number of holes 32, each associated with a respective hole 32, and are connected to the crown 34 by means of respective elastically deformable arms 36, each of which is able to move, and normally maintain, the relative petal 35 in a closing position of the relative hole 32.

As shown in Figure 2, the piston 25 is movable along the axis 21 inside the portion 22 under the thrust of an actuation device 37 comprising an electromagnetic actuator 38 comprising, in turn, an annular coil 39 housed in the body pump 19 outside the cylinder 20 and a tubular magnetic pole 40 fixed inside the portion 22 coaxially to the axis 21.

The pole 40 is mounted in a position facing the anchor 29, and defines, together with the anchor 29 and the cylinder 20, a cylindrical space 41 with variable volume suitable for being occupied by the fuel.

According to what is better illustrated in Figure 4, the pump 14 also includes a tubular funnel 42, which is mounted inside the portion 22 coaxially to the axis 21, and is arranged with its concavity facing the plate 26.

The funnel 42 comprises a cylindrical portion 43 having a diameter smaller than the minimum internal diameter of the pole 40, and a conical shaped cup portion 44 resting on the plate 26.

The funnel 42 is kept in contact with the plate 26 by a spring 45, which defines part of the device 37, extends around the funnel 42, and is mounted between the pole 40 and the portion 44 coaxially to the axis 21.

In use, the piston 25 is moved by the actuation device 37 with a reciprocating rectilinear motion along the axis 21 comprising an intake stroke for drawing fuel through the intake valve 31 and inside the pumping chamber 28 and a stroke to discharge the fuel through the valve 30 and outside the chamber 28 itself.

At the end of the delivery stroke, the coil 39 of the electromagnetic actuator 38 is energized; the piston 25 is moved against the action of the spring 45 in contact with the pole 40 in order to increase the volume of the chamber 28; and the petals 35 of the intake valve 31 are displaced by the pressure of the fuel present inside the portion 44 from their closed positions of the holes 32 into respective open positions of the holes 32 themselves so as to allow the fuel to enter the chamber 28.

At the end of the suction stroke, the coil 39 of the actuator 38 is de-energized; the petals 35 of the intake valve 31 are moved back into their closed positions by the relative arms 36; and the piston 25 is moved by the spring 45 so as to reduce the volume of the chamber 28 and open the valve 30.

The piston 25 is stopped at the end of the suction stroke from pole 40 and at the end of the delivery stroke by a stroke end ring 46 mounted in the portion 22 coaxially to the axis 21.

To reduce the noise resulting from the impact of the anchor 29 against the pole 40, the pump 14 is provided with a damper device 47, substantially annular in shape and coaxial to the axis 21. The damper device 47 is interposed between the anchor 29 and the pole 40 and is preferably made of an elastomeric or plastic material. The damper device 47 is at least partially housed within the space 41.

According to what is better illustrated in figures 5 to 7, the damper device 47 comprises an annular portion 48, which is arranged, in use within an annular groove 49 obtained in the pole 40 and facing the anchor 29.

The damper device 47 then comprises appendages 50 which protrude from the annular portion 48 and are turned towards the anchor 29; the appendices 50 are preferably distributed uniformly around the axis 21. According to a preferred variant, the appendages 50 have a rounded shape; the appendages 50 have a semicircular shape in section.

Between two successive appendages 50 a passage P is defined to allow the fuel to seep from the space 41 during the intake stroke of the piston 25. The appendages 50 are arranged inside the space 41 creating an alternation of solids (defined by the appendices 50 same) and voids which allows the fuel to escape from the space 41 even when the piston 25 reaches the top dead center at the end of the intake stroke.

The damper device 47 is shaped so as not to prevent the escape of the fuel from the space 41 during the intake stroke of the piston 25; in other words, the damper device 47 is made in such a way as to cushion the noise generated by the impact of the anchor 29 against the pole 40 and, at the same time, allow fuel to leak through the interstices defined between two adjoining appendages 50.

According to a variant not shown, the damper device 47 can be made as a ring coaxial to the axis 21 and provided with a portion 48, which is arranged, in use, inside the annular groove 49 obtained in the pole 40 and facing the anchor 29 and a portion that extends into the space 41 and is provided with through openings suitable for allowing the fuel to exit the space 41 during the intake stroke of the piston 25.

The variant illustrated in figure 8 differs from what is illustrated in figure 2 only in that, in order to further reduce the noise produced by the pump 14 and, in particular, to reduce the noise deriving from the impact of the plate 26 against the ring 46 at the end of the delivery stroke, the pump 14 is provided with a further damper device 51, substantially annular in shape and coaxial to the axis 21. The damper device 51 is interposed between the plate 26 and the ring 46 and is preferably made of a material elastomeric or plastic.

The damper device 51 is quite similar to the damper device 47 and comprises an annular portion 52, which is arranged, in use inside an annular groove 53 obtained in the ring 46 and facing the plate 26.

The damper device 51 then comprises appendages 54 which protrude from the annular portion 52 and are turned towards the plate 26; the appendices 54 are preferably distributed uniformly around the axis 21. According to a preferred variant, the appendages 54 have a rounded shape; the appendages 54 have a semicircular shape in section. The appendages 54 are arranged inside the lower chamber 28, creating an alternation of solids (defined by the appendices 54 themselves) and voids which allows all the fuel to be discharged through the valve 30 and outside the lower chamber 28 itself at the end of the stroke delivery.

In other words, the damper device 51 is at least partially housed inside the lower pumping chamber 28; and in the damper device 51 there is defined at least one passage P realized to allow to empty all the fuel of the pumping chamber 28 during the fuel delivery stroke.

According to a variant not illustrated, the damper device 51 can be made as a ring coaxial to the axis 21 and provided with a portion 52, which is arranged, in use, inside the annular groove 53 obtained in the ring 46 and facing the plate 26 and a portion that extends inside the chamber 28 and is provided with through openings suitable for allowing the fuel to escape from the chamber 28 during the delivery stroke of the piston 25.

During the normal operation of the pump 14, the noise resulting from the impact of the plate 26 against the ring 46 at the end of the delivery stroke is muffled by a fuel reserve contained within the lower chamber 28. When the internal combustion engine 1 is switched on, the fuel reserve necessary to muffle the noise generated by the impact of the plate 26 against the ring 46 at the end of the delivery stroke is not present inside the lower chamber 28.

The control strategy implemented for the pump 14 is then described to reduce the noise generated at start-up by the impact of the plate 26 against the ring 46 at the end of the delivery stroke and illustrated in Figure 9:

- the so-called Key-on phase preceding the ignition of the internal combustion engine 1 is initially recognized (typically, the electronic control unit 18 receives a signal that allows it to recognize the imminent ignition phase of the internal combustion engine 1 and to start the piloting phase of the pump 14 prior to the ignition of the internal combustion engine 1);

- a phase of filling of the lower chamber 28 is started prior to the ignition of the internal combustion engine 1 in which the pump 14 is piloted at a reduced power W, i.e. a power W lower than the nominal operating power of the pump 14 to allow creating a fuel reserve inside the lower chamber 28;

- a pressurization phase following the filling phase is started, in which the fuel reaches a nominal operating pressure P value.

In this way, when the fuel system 12 is started, there is already a reserve of fuel inside the lower chamber 28 which makes it possible to considerably reduce the noise resulting from the impact of the plate 26 against the ring 46 at the end of the delivery stroke.

During the filling phase, the pressure of the fuel present inside the portion 44 is such as to move the petals 35 of the intake valve 31 from their closed positions of the holes 32 into the respective open positions of the holes 32 themselves so as to allow the fuel entering the chamber 28 during the intake stroke. The fuel pressure inside the lower chamber 28 reaches a value such as to allow the fuel to be discharged through the valve 30 outside the lower chamber 28 itself during the delivery stroke and thus also to fill the connection pipe of the pump 14 with injector 13. Since the filling phase precedes an ignition phase of the internal combustion engine 1, the injector 13 is closed and no fuel is introduced into the respective cylinder 2. During the fuel delivery stroke , the excess fuel is then drawn from the lower chamber 28 to the variable volume cylindrical space 41.

The number of pumping cycles during the filling phase are defined experimentally by trying to optimize the compromise between the need to reach the pressurization phase in the shortest possible time, ensuring the lowest possible noise.

According to what is illustrated in Figure 10, the fuel supply pump 14 is not drowned inside the tank 15 at atmospheric pressure but is disposed externally to said tank 15 with which it communicates hydraulically through the supply duct 16. In particular, the pump body 19 defines the supply channel 16 connected to the fuel containment tank 15.

The pump 14 is connected to a bottom wall 55 of the tank 15 and draws in the tank 15 through the supply duct 16 which communicates with the inside of the tank 15 itself through a through opening made in the bottom wall 55.

The bottom opening that connects the supply duct 16 with the inside of the tank 15 is surrounded by a cartridge filter 56 made to purify the fuel that is fed to the pump 14 and avoid damaging the pump 14 itself. The cartridge filter 56 has a substantially tubular shape and is arranged in such a way as to completely surround the bottom opening that connects the supply duct 16 with the inside of the tank 15.

The cartridge filter 56 is made so as to have a first end 57 in contact with the bottom wall 55 of the tank 15 or directly in communication with the supply duct 16; while the second end 58 has always emerged, ie beyond the free surface of the fuel contained in the tank 15. The end 58 is never submerged and extends beyond the free surface of the fuel contained in the tank 15, in any condition.

Even when the tank 15 is filled, a dead volume V of air is contained inside the tank 15 in which, through the emerged end 58 of the cartridge filter 56, the fuel bubbles generated when the fuel contained inside the tank 15 changes state from liquid to gaseous due to the heat generated by the atmospheric conditions in which the fuel system 12 operates and / or by the operation of the internal combustion engine 1 (phenomenon known as vapor locking).

The electronic injection feeding system 12 and the fuel feeding pump 14 have up to now described some advantages mainly deriving from the fact that the presence of the damper device 47 and of the damper device 51 allows to considerably reduce, respectively, the noise produced. by the impact of the anchor 29 against the pole 40 at the end of the suction stroke and the noise produced by the impact of the plate 26 against the ring 46 at the end of the delivery stroke.

Furthermore, the construction of the cartridge filter 56 provided with the end 58 emerging inside the tank 15 allows, in any operating condition, to vent the fuel bubbles that are generated when the fuel contained inside the tank 15 changes state. from liquid to gaseous due to the heat generated by the atmospheric conditions in which the fuel system 12 operates and / or by the operation of the internal combustion engine 1 avoiding damage to the other components of the fuel system 12.

Furthermore, both the electronic injection power supply system 12 and the fuel feed pump 14 are easy and economical to manufacture.

Claims (1)

CLAIMS 1.- Fuel feed pump (14) comprising: - a pump body (19) defining a cylinder (20) having a longitudinal axis (21); - a piston (25) slidably engaged in the cylinder (20) along the longitudinal axis (21) and defining, inside the cylinder (20), a variable volume pumping chamber (28) provided with at least one valve Delivery (30) connectable to an injector (13) and a supply chamber (27), which communicates with a fuel containment tank (15), and is connected to the pumping chamber (28) through at least one intake valve (31); the piston then comprises a tubular anchor (29) arranged inside the supply chamber (27) coaxially to the longitudinal axis (21); and - an actuation device (37) for moving the piston (25) along the longitudinal axis (21) inside the cylinder (20) with a reciprocating rectilinear motion comprising an intake stroke of the fuel in the pumping chamber (28 ) and a fuel delivery stroke to the injector (13); the actuation device (37) comprises a first end-of-stroke member (40) for stopping the piston (25) at the end of the suction stroke; the pump is characterized by the fact that the anchor (29) and the first stop member (40) define between them a cylindrical space (41) with variable volume for the fuel in which a first device (47) annular shape, coaxial to the longitudinal axis (21) in which at least one passage (P) is defined to allow the fuel to leak from the pumping chamber (28) to the cylindrical space (41) during the fuel pressurization stroke. 2.- Pump according to Claim 1 and comprising a second end-of-stroke member (46) for stopping the piston (25) at the end of the delivery stroke (30); wherein, the piston (25) comprises a plate (26), which separates the pumping chamber (28) from the supply chamber (27) inside the cylinder (20) and is coupled in an axially fixed manner to the anchor ( 29); and in which, the pump (14) comprises a second annular-shaped damper device (51), coaxial to the longitudinal axis (21) interposed between the second end-stroke member (46) and the plate (26). 3.- Pump according to claim 2, wherein the second damper device (51) is at least partially housed inside the pumping chamber (28); and in which, in the second damper device (51) there is defined at least one passage (P) made to allow to empty all the fuel of the pumping chamber (28) during the fuel delivery stroke. 4.- Pump according to one of the preceding claims, in which the damper device (47, 51) is made of an elastomeric or plastic material. 5.- Pump according to one of the preceding claims, wherein the damper device (47, 51) comprises an annular portion (48, 52) arranged inside a respective annular groove (49, 53) obtained, respectively, in the first and / or in the second end-of-stroke organ (40, 46). 6.- Pump according to one of the preceding claims, wherein the damper device (47, 51) comprises a plurality of appendages (50, 54); each passage (P) for the fuel is defined between two adjoining appendages (50, 54). 7.- Pump according to claim 6, in which the appendages (50, 54) are distributed uniformly around the longitudinal axis (21). 8. A pump according to Claim 7 or 7, wherein the appendages (50, 54) have a rounded shape.