ITMI20100350A1 - SYSTEM FOR FUEL SUPPLY TO AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

DESCRIPTION

â € œ SYSTEM FOR SUPPLYING FUEL TO AN INTERNAL COMBUSTION ENGINEâ €

The present invention relates to a system for supplying fuel to an internal combustion engine.

In particular, the present invention relates to a system for supplying fuel to an internal combustion engine, in which the system is of the type comprising a fuel tank, a fuel distribution manifold with high pressure, a pre-feed pump designed to suck the fuel from the tank, a high-pressure pump, and a dosing unit, which is designed to receive the fuel from the pre-feed pump to feed metered quantities of fuel to the high pressure pump; the dosing unit comprising a regulating valve, which in turn comprises a valve body having a cavity provided with an inlet communicating with a delivery of the pre-supply pump and a first outlet communicating with a side of suction of the high pressure pump; and a shutter mounted sliding along the cavity between a first position of communication of the inlet with the first outlet and a second position of separation between the inlet and the first outlet.

Normally, known and commonly used metering units consist of solenoid valves controlled by a control device which opens or closes the valve according to the fuel requirement of the engine. When, for example, no power is required from the engine, the metering unit is closed so that no more fuel is supplied to the manifold and the pressure inside the manifold does not increase excessively. However, it has been found that, for structural and functional reasons of the metering unit, it is essentially impossible to prevent a certain amount of fuel from leaking through the metering unit when the latter is closed. For this reason, a known system of the type specified above normally comprises a discharge branch which branches off from a point of the circuit arranged upstream of the high pressure pump and downstream of the aforementioned first outlet and is equipped with a hydraulic resistance , normally a bottleneck. In this way, by suitably adjusting the suction opening pressure of the high-pressure pump, it is possible to ensure that all the fuel that leaks from the closed metering unit through the first outlet flows, through the restriction, into the discharge branch without never reach the high pressure pump.

A solution of the type described above, while effectively solving the problem, nevertheless suffers from the drawback of weighing on the simplicity and cost-effectiveness of the system both because it requires the introduction of specific mechanical components, such as the throttling, and because © makes it necessary to perform, before setting up the system, a series of tests aimed at verifying, for example, the sealing capacity of the dosing unit and the resistance, especially in terms of life, of the pre-pump -supply, which is subject, when the metering unit is closed and the fuel flows through the choke, to a relatively high counter-pressure.

The object of the present invention is to provide a fuel supply system of the type specified above, which system is free from the drawbacks described above.

According to the present invention, a system is provided for supplying fuel to an internal combustion engine according to what is disclosed in claim 1 and, preferably, in any of the subsequent claims directly or indirectly dependent on claim 1.

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

Figure 1 schematically illustrates a preferred embodiment of the plant of the present invention;

- figure 2 shows, in axial section and with parts removed for clarity, a detail of the implant of figure 1;

Figures 3 and 4 show a detail of Figure 2 in respective operating configurations; And

Figure 5 illustrates a functional diagram of the detail of Figure 2.

In figure 1, 1 indicates, as a whole, a system for supplying fuel, substantially diesel, to an internal combustion engine (not shown), in particular an engine of the Diesel cycle type installed on a vehicle (not shown).

The system 1 comprises a fuel tank 2, a fuel distribution manifold 3, and a hydraulic circuit 4 connecting the tank 2 and the manifold 3 together.

The manifold 3 is defined by a container, generally known as COMMON RAIL, which is able to contain the fuel inside it at a pressure of the order of 1800-2000 bar and is connected to the engine (not shown) by means of a plurality of injectors 5 of known type.

The hydraulic circuit 4 comprises, in turn, a pre-feeding pump 6, which is suitable for sucking the fuel from the tank 2 through a connection branch 7, and a high-pressure pump 8, in this case of the volumetric type with one or more pumping elements, which is adapted to receive the low pressure fuel from the pre-feed pump 6 through a delivery branch 9 to feed the high pressure fuel to the manifold 3.

On the delivery branch 9 between the pre-supply pump 6 and the high pressure pump 8 there is a dosing unit 10, which defines, on the delivery branch 9, a first section 9a and a second section 9b and has the function , in use, to regulate the flow rate of fuel supplied to the high pressure pump 8 according to the fuel requirement of the internal combustion engine (not shown). For this purpose, the plant 1 comprises a control device 11 adapted to drive the dosing unit 10 according to the signals received from sensors (known and not illustrated) suitable to measure, in a known way, various related quantities engine operation (not shown).

As illustrated schematically in figure 1, the dosing unit 10 is essentially constituted by a three-way solenoid valve defined, as will be explained in detail below, by an inlet, which communicates, through the section 9a of the delivery branch 9, with the delivery of the pre-feeding pump 6; a first outlet, which communicates, through the section 9b of the delivery branch 9, with the suction side of the high-pressure pump 8; and a second outlet, which communicates, through a discharge branch 12, with the tank 2 or, according to a variant not shown, with the connection branch 7.

As illustrated in Figure 2, the dosing unit 10 is flanged on a support body 13, preferably constituted by the pump body of the high pressure pump 8, and comprises an electromagnetic head 14 and a regulating valve 15, which is integrated in the electromagnetic head 14 and is controlled by the electromagnetic head 14 itself to selectively put into communication, in the way that will be explained in detail below, the inlet of the regulating valve 15 with the aforementioned first and second outputs.

The electromagnetic head 14 comprises a coil 16, which is wound on a tubular body 17 made of non-magnetic material and coaxial to an axis 18, a sleeve 19 planted inside the tubular body 17, and a movable core 20, which is made of magnetizable material, is mounted in an axially sliding manner along the sleeve 19 and comprises a tubular stem 21 and a strut 22 integral with the tubular stem 21 and coaxial with the axis 18 and the sleeve 19.

The electromagnetic head 14 also comprises a closing cup 23, which is connected, at one end, to an electrical connector 24 and is provided, at the opposite end, with an external flange 25 for connecting the unit. metering 10 to the support body 13. Inside the closing cup 23, near the sleeve 19, a bearing 26 is inserted which has the function of axially guiding the movable core 20 along the sleeve 19.

The regulating valve 15 comprises a valve body 27 having a substantially cylindrical shape and provided with an intermediate flange 28, which extends radially inside the flange 25 in a coaxial position with the axis 18 and is arranged in contact with the body support 13 with the interposition of an O-ring 29.

The flange 28 defines, on the valve body 27, two portions 30 and 31 opposite each other and coaxial to the axis 18 and of which the portion 30 extends from the flange 25 towards the mobile core 20 and is sealedly engaged with the The interposition of an O-ring 32, inside the tubular body 17, in such a way as to define, together with the sleeve 19 and the closing cup 23, the housing and sliding seat of the mobile core 20.

The portion 31 is engaged, with the interposition of two O-rings 33, inside a substantially cylindrical seat 34, which is obtained in the support body 13 in a coaxial position to the axis 18 and communicates , through its own bottom surface 35, with a channel, which is obtained in the support body 13 coaxially to the axis 18 and defines the initial part of the section 9b of the delivery branch 9. The seat 34 also communicates through its own lateral surface 36, with two further channels, which are obtained in the support body 13 radially to the axis 18 and of which one is disposed in proximity to the flange 28 and defines the initial part of the discharge branch 12 and the The other is arranged in an intermediate position between the discharge branch 12 and the portion 9b and defines the end part of the portion 9a of the delivery branch 9.

Inside the portion 31 there is a cylindrical cavity 37 coaxial to the axis 18, presenting an axial hole 38 communicating with the section 9b, and engaged in an axially sliding manner by an obturator 39, which is defined by a tubular body comprising a cylindrical side wall 40 and, internally, an intermediate partition 41 perpendicular to axis 18 and adapted to divide the tubular body into two cups with opposing concavities. Immediately upstream of the hole 38, the cavity 37 is rigidly engaged by an annular bottom 42, which is coaxial to the axis 18 and defines a thrust support for a spring 43 wound by a helix around the axis 18 and compressed between the bottom 42 and the septum 41 to keep, in use, the septum 41 constantly in contact with a free end of the strut 22. This free end is engaged in an axially sliding manner in a hole 44 obtained in the portion 30 of the valve body 27.

The septum 41 divides the cavity 37 into two half-chambers 45 and 46, of which the half-chamber 45 contains the spring 43 and communicates with the section 9b through the hole 38, and the half-chamber 46 is crossed by the strut 22 and communicates through a hole 47 obtained in the portion 30, with an annular chamber 48 defined by the portion 30 inside an enlarged portion of the seat 34 and communicating with the delivery branch 12.

According to what is illustrated in Figure 2, in correspondence with the half-chamber 45 and the half-chamber 46, the side wall 40 of the shutter 39 has a plurality of slots 49 (of which only one is illustrated in Figures 2-4) and, respectively, of slots 50 (of which only one is illustrated in Figures 2-4), which, as will be explained better in the following, are suitable to selectively put into communication, according to the position of the shutter 39, the half-chamber 45 and , respectively, the semi-chamber 46 with an internal annular chamber 51, which is defined by the shutter 39 inside an enlarged portion of the cavity 37 and communicates, through a radial hole 52 obtained in the portion 31, with a chamber ring 53 defined by the portion 31 inside an enlarged portion of the seat 34 and communicating with the portion 9a.

In particular, according to what is illustrated in figures 2, 3 and 4, the obturator 39 is mounted to assume, in use, a normal first opening position (shown in the right half of figure 2 and in figure 3), in the which the spring 43 pushes the shutter 39 towards the electromagnetic head 14 and the section 9a is put in communication with the section 9b through the hole 52, the slots 49, the half chamber 45 and the hole 38, and a second position of opening (shown in the left half of figure 2 and in figure 4), in which the strut 22, following the energization of the coil 16, pushes the shutter 39, against the thrust of the spring 43, towards the bottom 42 in such a way as to put the section 9a in communication with the delivery branch 12 through the hole 52, the slits 50, the half-chamber 46 and the hole 47. According to the foregoing, therefore, the hole 52 defines the aforementioned inlet of the adjustment 15 and the holes 38 and 47 define, r inspectively, the aforementioned first and second outings.

In use, therefore, when power is required from the engine (not shown), energy is not supplied to the electromagnetic head 14 and the adjustment valve 15, located in the first open position, allows the fuel to pass from section 9a to section 9b and, from the latter, to the high pressure pump 8; when, on the other hand, no power is required from the engine (not shown), for example in over-revving conditions or when the vehicle proceeds downhill, the electromagnetic head 14 is energized following an activation signal emitted by the control device 11 and the regulating valve 15, moved to the second opening position, causes the fuel to flow from the section 9a to the discharge branch 12, thus preventing any fuel supply to the section 9b and, therefore, to the fuel pump. high pressure 8.

The advantages deriving from the present invention are easily recognizable in the simplification and, therefore, greater cost-effectiveness of the plant 1 as the presence of a separate mechanical component such as a hydraulic resistance is no longer necessary and it is no longer necessary to perform accurate tests for precisely establish the sealing capacity of the dosing unit in the closed position.

A further advantage is also obtained in terms of the life of the pre-feed pump 6 since, in the metering unit 10 of the plant 1, when the section 9b is isolated from the section 9a, the valve control valve 15 is not in a â € œcompletely closedâ € position, but is arranged in a further opening position, in which all the fuel supplied by the pre-supply pump 6 can flow from section 9a to section 12 with the consequence of subjecting the pre-feeding pump 6 to a considerably lower counter-pressure than that present, under the same conditions, in known systems of the same type.

Finally, according to what is clearly illustrated in Figure 3 or 4, the slits 49 each have a triangular shape with the vertex facing the septum 41, and the slots 50 each have a first square-shaped portion and a second protruding triangular portion from the first portion towards the septum 41.

In the graph of figure 5, the continuous curve, indicated by A, indicates, as a function of the energization current of the coil 16, the trend of the fuel flow supplied to the high-pressure pump 8, while the dashed curve, indicated by B , indicates, again as a function of the energization current, the flow rate of the fuel supplied to the delivery branch 12. The particular trend of curves A and B, guaranteed by the conformation and axial position of the slots 49 and 50, ensures a progressive reduction of the power supply to the high pressure pump 8 and, when the slots 49 are close to closing, the progressive opening of the slots 50, which open completely only when the shutter 39 has substantially reached the second opening position and the slots 49 have been completely closed. In this way it is ensured that the backflow of the fuel through the discharge branch 12 does not abruptly interrupt the delivery of the high-pressure pump 8.

Claims (9)

CLAIMS 1. System for supplying fuel to an internal combustion engine, the system (1) comprising a fuel tank (2), a high pressure fuel distribution manifold (3), a fuel pump pre-feed (6) designed to suck the fuel from the tank (2), a high pressure pump (8), and a metering unit (10), which is designed to receive the fuel from the pre-fuel pump - feeding (6) to feed metered quantities of fuel to the high pressure pump (8); the dosing unit (10) comprising a regulating valve (15), which in turn comprises a valve body (27) having a cavity (37) provided with an inlet (52) communicating with a delivery of the pre-feed pump (6) and a first outlet (38) communicating with a suction side of the high pressure pump (8); and a shutter (39) mounted sliding along the cavity (37) between a first communication position of the inlet (52) with the first outlet (38) and a second separation position between the inlet (52) and the first outlet (38); the system (1) being characterized by the fact that the regulating valve (15) is a three-way valve, in which the cavity (37) is provided with a second fuel discharge outlet (47); the second outlet (47) communicating with the inlet (52) when the shutter (39) is placed in the second position, and being separated from the inlet (52) when the shutter (39) is placed in the first position. 2. Plant according to claim 1, and comprising thrust means (43) for normally maintaining the shutter (39) in the first position. 3. Plant according to claim 2, wherein the metering unit (10) comprises an electro-actuator (22) for operating the shutter (39) against the action of the thrust means (43). 4. Plant according to one of the preceding claims, in which the cavity (37) has a longitudinal axis (18) and said inlet (52) is defined by a radial opening arranged in an intermediate position, along the axis ( 18), between the first and second exit (38, 47); the shutter (39) comprising a separation element (41) transversal to the axis (18) and able to divide the cavity (37) into a first and a second half chamber (45, 46) communicating, respectively, with the first and second exit (38, 47). 5. Plant according to claims 3 and 4, in which the electro-actuator (22) has a free end kept in contact with the separation element (41) by the thrust means (43). 6. System according to claim 4 or 5, in which the shutter (39) is tubular and further comprises a side wall (40), which is arranged around the said separation element (41), Ã It is coaxial to the axis (18) and has a plurality of first slots (49) and a plurality of second slots (50) arranged on opposite bands of the separation element (41); the first slots (49) connecting the inlet (52) with the first outlet (38) through the first half chamber (45) when the shutter (39) is in the first position, and the second slits (50 ) connecting the inlet (52) with the second outlet (47) through the second half chamber (46) when the shutter (39) is in the second position. 7. System according to claim 6, in which the distance and the relative axial position of the first and second slots (49, 50) are such that the second slots (50) are communicated with the inlet (52) only when the first slits (49) are substantially closed. 8. Plant according to claim 6 or 7, in which each first slot (49) has a triangular shape with the vertex facing the separation element (41), and each second slot (50) has a first square-shaped portion and a second triangular portion projecting from the first portion towards the separation element (41). 9. Plant according to claim 2 and one of claims 4 to 8, wherein the cavity (37) has an axial end opening defining said first outlet (38); the regulating valve (15) comprising an annular bottom (42) engaged inside the cavity (37) near the first outlet (38) and defining a contrast support for said thrust means (43), which they are elastic thrust means compressed between the bottom (42) and the separation element (41).