ITMI20091138A1 - FUEL SUPPLY SYSTEM TO AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

"FUEL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE"

The present invention relates to a fuel supply system for an internal combustion engine, in particular a Diesel internal combustion engine installed on a motor vehicle.

A system of the type described above generally comprises, in a known way, a fuel supply tank (at low pressure) and a fuel distribution manifold (at high pressure) connected to each other by means of a pumping unit, a hydraulic circuit of which comprises a pump pre-feed and a high pressure pump arranged in series.

It is also known to use part of the fuel for the lubrication of the pumping unit and, in particular, of the high pressure pump, which normally has an internal compartment housing an actuation mechanism for the high pressure pump itself and provided a pipe for returning the excess fuel to the supply tank.

A system of the type described above has the drawback that, with the engine off, the internal compartment of the high pressure pump tends to gradually empty; and this entails a high risk that the actuation mechanism of the high pressure pump seizes during the starting of the engine following a prolonged stop.

The purpose of the present invention is to provide a fuel supply system to an internal combustion engine, which system allows to eliminate the drawback described above.

According to the present invention, a plant is provided 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 implementation, in which:

- Figure 1 is a schematic view, with parts removed for clarity, of a preferred embodiment of the plant of the present invention; And

Figures 2 to 4 show, in section, a detail of Figure 1 in respective operating configurations.

In Figure 1, 1 indicates as a whole a plant for supplying fuel, substantially diesel oil, from a tank 2 to an internal combustion engine 3, in particular to an engine 3 of the Diesel cycle type.

The engine 3 comprises fuel supply injectors 4 arranged downstream of a manifold 5, defined by a container generally known as COMMON RAIL, for distributing the fuel. The manifold 5 is adapted to contain the fuel inside it at a pressure preferably, but not necessarily, higher than 2000 bar.

The system 1 comprises a group 6 for pumping the fuel from the tank 2 to the manifold 5, and a control device 7 adapted to regulate the flow of fuel through the system 1 on the basis of the demand, moment by moment, for fuel by engine 3.

The pumping unit 6 in turn comprises a pre-feed pump 8, preferably of the gear type, and a high pressure pump 9, preferably of the volumetric piston type 10, arranged in series along a hydraulic circuit 11, which connects the tank 2 and the manifold 5 together through the pumping unit 6 itself.

The high-pressure pump 9 comprises a pump body 12, in which a compartment 13 is obtained, preferably with a circular section, for the partial housing of a mechanism 14 for actuating the pistons 10, which, as will be better explained below, are linked to the implementation mechanism 14; inside the compartment 13 there are cavities 15, in each of which the free end of a respective piston 10 is engaged, in an axially sliding and fluid-tight manner. In general, both the pistons 10 and the cavities 15 they have a circular section.

The actuation mechanism 14 comprises a shaft 16, which is rotatably mounted around an axis 17 and comprises an eccentric portion 18, on which a polygonal ring 19 is fitted in a freely rotatable manner.

The shaft 16 is rotatably mounted inside the pump body 12 through the interposition of special bearings or support bushings (not shown), of a known type, arranged on opposite bands of the compartment 13; the assembly of the shaft 16 inside the pump body 12 is of a known type and also includes gaskets of a known type (not shown) to prevent the leakage of the fuel outside the pump body 12 itself. Furthermore, the shaft 16 is connected, in a known way and not shown, to a transmission shaft at the output of the motor 3 and, according to a preferred embodiment (not shown), also to the pre-feeding pump 8, which is driven by shaft 16 together with high pressure pump 9.

Each piston 10 is coupled in a sliding manner, by means of a respective intermediate element or slide 20, to a respective peripheral flat surface of the polygonal ring 19, which roto-translates, in use, around the shaft 16; thanks to the sliding of the relative slide 20 along the relative peripheral flat surface, the rotation of the shaft 16 around its own axis 17 corresponds to an alternative axial movement of each piston 10 in a relative radial direction with respect to the axis 17 itself and along the respective cavity 15.

Generally, the pistons 10, which in the example shown are three, but could be in different numbers, are evenly distributed around the axis 17.

Each cavity 15 communicates with the hydraulic circuit 11 through a supply valve 21 and a delivery valve 22, which are recessed inside the pump body 12 and are of a known type.

The hydraulic circuit 11 comprises a delivery portion P1 of the fuel from the tank 2 to the engine 3, and a return portion P2, to the tank 2, of the excess fuel not absorbed by the engine 3.

More in detail, the delivery portion P1 comprises: - a connecting branch 23 between the tank 2 to an inlet of the pre-feeding pump 8; along the connecting branch 23 a pre-filter 231, a priming pump 232 of the manual type and a calibrated hole 233 are arranged in series;

- an assembly 24 of by-pass branches, in particular a pair of by-pass branches indicated with 24a and, respectively, 24b, connected to the connection branch 23 upstream of the pre-supply pump 8 and able to bypass the pre-feed pump 8 in different flow directions according to the conditions of use; the by-pass branches 24a and 24b comprise respective non-return valves 241 and 242 respectively;

- a filtering branch 25 connected to an outlet of the pre-feeding pump 8 and to the by-pass branches 24a and 24b; the filter branch 25 extends through a filter 251;

- a distribution branch 26 adapted to receive the fuel from the filtering branch 25 and comprising a metering valve 261 and a plurality of branches 26 ', each of which is arranged downstream of the metering valve 261 and is connected to a respective valve feed 21 of the high pressure pump 9;

- a delivery branch 27, which is connected to the filtering branch 25 in parallel with the distribution branch 26, extends through a calibrated hole 271 and flows into the internal compartment 13 of the high pressure pump 9;

- a regulation branch 28, which is connected to the filtering branch 25 in parallel to the distribution branch 26 and to the delivery branch 27 and flows into the overflow valve 29; And

- a plurality of high pressure branches 30 ', each of which is arranged downstream of a respective said delivery valve 22 of the high pressure pump 9; the high pressure branches 30 'converge in a single high pressure branch 30 feeding the manifold 5.

The return portion P2 includes:

- a branch 31 for collecting the recirculating fuel extending between the engine 3 and the tank 2;

- an outlet branch 32 from manifold 5, flowing into branch 31 and controlled by a non-return valve 321 designed to keep the pressure inside the manifold 5 below a predetermined maximum value;

- a return branch 33, which is arranged at the outlet from the internal compartment 13 of the high pressure pump 9 and flows into the overflow valve 29;

- a recirculation branch 35 coming out of the overflow valve 29 and flowing into the connecting branch 23; And

- a recirculation branch 34 coming out of the overflow valve 29 and flowing into the collection branch 31.

According to a preferred embodiment, not shown, the pre-feeding pump 8 and the high pressure pump 9 are inserted inside a common pump body, in which the branches of the hydraulic circuit 11 are made by removing material.

The overflow valve 29 has the function:

- both to convey, in the connecting branch 23 and upstream of the pre-supply pump 8, the excess fuel placed upstream of the calibrated hole 271 and inside the branch 28;

- is to convey, in the recirculation branch 34 and, consequently, in the collection branch 31 upstream of the tank 2, the excess fuel which is contained in the internal compartment 13 and which flows from the internal compartment 13 through the return branch 33;

- is to prevent fuel from escaping from the interior compartment 13 during a stop phase.

According to what is illustrated in Figures 2 to 4, the overflow valve 29 comprises a tubular body 36 having a longitudinal axis 37 and a plurality of openings which define the openings through which the overflow valve 29 communicates with the branches 28, 33, 34 and 35. In particular, the overflow valve 29 has an axial opening 38 communicating with the regulation branch 28, at least one radial opening 39 communicating with the recirculation and pressure limiting branch 35 (in the example shown in Figures 2 to 4 two radial openings 39 are provided, but the number of radial openings 39 could be different), a radial opening 40 communicating with the return branch 33, and a radial return opening 41 communicating with the recirculation branch 34.

The overflow valve 29 has an internal cavity with a circular section, which faces the openings 38, 39, 40 and 41 and is limited by an internal surface 42 of the tubular body 36; precisely, the axial opening 38 is coaxial to the longitudinal axis 37 and is placed at a free end of the body 36; while, the radial openings 40 and 41 form a pair of openings aligned with each other in a direction transverse to the axis 37 and are arranged on opposite bands of the body 36 with respect to the axis 37 itself. Similarly to the above, if there are two radial openings 39 (fig. 2 to 4), the latter are arranged aligned with each other in a direction transversal to the axis 37 and from opposite bands of the body 36 with respect to the axis 37 itself.

Inside the tubular body 36 there are a shutter 43 and a locking element 44 interconnected with each other by means of an adjustment spring 45.

The shutter 43 is inserted inside the tubular body 36 and has an end facing the axial opening 38 and an end in contact with the spring 45, which is arranged in contact with the locking element 44.

In the illustrated example (fig. 2 to 4), the locking element 44 has a spherical shape, is wedged on one end of the body 36 opposite the axial opening 38 and is arranged against the internal surface 42 of the body 36 same.

The shutter 43 is rotatable and axially movable with respect to the axis 37 and, according to what is illustrated in Figures 2 to 4, has a U-shaped cavity 46 facing the axial opening 38 and communicating with the adjustment branch 28, and a pair of longitudinal sections 47 and 49 arranged in contact with the internal surface 42 and separated from each other by an internal section 48 separated from the internal surface 42. At the section 48 the shutter 43 limits, together with the internal surface 42 of the tubular body 36, a return chamber 50, which is adapted to put the return branch 33 and the recirculation branch 34 in communication with each other.

The following will describe the operation of the fuel supply system 1 to an internal combustion engine 3 and the operation of the overflow valve 29.

The lubrication of the system 1 is carried out by means of the same fuel which is channeled, by means of the priming pump 232, into the delivery portion P1 during a filling phase, which is carried out before carrying out the first activation of the system 1 to avoid possible seizures.

By thrusting the priming pump 232, the fuel passes through the complex 24 along the branch 24b by-passing the parked pre-feeding pump 8 and flowing, among other things, into the internal compartment 13 of the high pressure pump 9.

During the regular operation of the system 1, the fuel leaving the tank 2 passes through the connecting branch 23 and the assembly 24 of by-pass branches 24a and 24b, passing along the branch 24b and then passing through the filter 251 of the filtering 25. Downstream of the filter 251, part of the fuel is fed to the delivery valves 21 through the distribution branch 26 and its branches 26 ', while another part of the fuel flows along the delivery branch 27 to the compartment 13 of the high pressure pump 9. In this regard, it should be pointed out that the quantity of fuel supplied to the delivery valves 21 is regulated by the metering valve 261 along the distribution branch 26.

In the event of an excess of fuel upstream of the metering valve 261 and of the calibration hole 271, the fuel is sent via the regulation branch 28 to the overflow valve 29, which conveys the excess fuel, inside the regulation 28 itself, in the connection branch 23 upstream of the pre-feed pump 8.

Based on the foregoing, the use of the overflow valve 29 avoids the occurrence of peak pressures upstream of the high pressure pump 9.

The excess fuel in the internal compartment 13 is conveyed, through the return branch 33, to the overflow valve 29, which communicates in the return branch 33 itself with the recirculation branch 34 allowing the return of the fuel to the tank 2.

Figure 2 illustrates the overflow valve 29 in a configuration assumed with the engine 3 off or during the filling phase of the circuit 11. In this configuration, the shutter 43 is arranged in such a way as to completely stop the flow of fuel through the overflow valve 29 itself; in particular, the section 47 closes the radial openings 39 and the section 49 closes the radial openings 40 and 41. Ultimately, in this configuration, the fuel is conveyed completely to the supply valves 21 and to the internal compartment 13.

Figure 3 illustrates the overflow valve 29 in its configuration for recirculating the excess fuel inside the internal compartment 13. In this configuration, the section 47 closes the radial opening 39, while the chamber 50 faces both at the radial opening 40, and at the radial opening 41 allowing the passage of the fuel from the return branch 33 to the recirculation branch 34.

Figure 4 illustrates the overflow valve 29 in one of its configurations, in which the excess fuel is made to drain from the regulation branch 28, to avoid peak pressures upstream of the high-pressure pump 9, and from the return branch. 33 to discharge the excess fuel contained in the internal compartment 13. In this configuration the shutter 43 is arranged so as to make the regulation branch 28 communicate with the recirculation branch 35 and the return branch 33 with the recirculation branch 34 .

The position of the shutter 43 inside the tubular body 36 is determined by the pressure that the fuel coming from the regulation branch 28 exerts on the shutter 43; in particular, the shutter 43 slides towards the locking element 44 when the pressure exerted by the fuel on the shutter 43 itself exceeds the resistant force of the spring 45; similarly, the shutter 43 slides towards the axial opening 38 when the resistant force of the spring 45 exceeds the value of the pressure exerted by the fuel on the shutter 43.

In relation to the foregoing, the direction and extent of the sliding of the shutter 43 inside the tubular body 36 are a function of the dimensions of the cross section of the shutter 43, of the resistant force of the spring 45 and of the value of the pressure of the fuel in the regulation branch 28.

It follows from the foregoing that the overflow valve 29 remains, with the engine 3 off, in the configuration illustrated in Figure 2, and the portion 49 closes the radial openings 40 and 41 preventing the fuel from returning to the tank 2.

Claims (12)

CLAIMS 1. Fuel supply system to an internal combustion engine (3), the system (1) comprising a tank (2) for the fuel, a fuel distribution manifold (5) and a pumping unit (6) connecting the tank (2) and the manifold (5) to each other; the pumping unit (6) comprising a first pre-feed pump (8), a second high pressure pump (9) which has an internal compartment (13) and an actuation mechanism (14) housed inside the compartment internal (13) itself, and a delivery branch (27) and a return branch (33) communicating with the internal compartment (13) to feed the fuel to, and respectively to drain the fuel from the internal compartment (13); the system (1) being characterized by the fact that it includes an overflow valve (29) communicating with the return branch (33). 2. System according to claim 1, and comprising a hydraulic circuit (11), which comprises a delivery portion (P1) of the fuel from the tank (2); the delivery portion (P1) comprising: - a connection branch (23) for feeding the fuel from the tank (2) to an inlet of the pre-feeding pump (8); - a set (24) of by-pass branches (24a, 24b) connected to the connection branch (23) upstream of the pre-supply pump (8) and able to by-pass the pre-supply pump (8) in directions of different flow according to the conditions of use; - a filtering branch (25) connected to an output of the pre-supply pump (8) and to the by-pass branches (24a, 24b); - a distribution branch (26) adapted to receive the fuel from the filtering branch (25) and comprising a metering valve (261) and a plurality of branches (26 '), each of which is arranged downstream of the metering valve (261) and is connected to a respective supply valve (21) of the high pressure pump (9); - the delivery branch (27), which is connected to the filtering branch (25) in parallel to the distribution branch (26), extends through a calibrated hole (271) and flows into the internal compartment (13) of the high pressure pump pressure (9); - a regulation branch (28), which is connected to the filtering branch (25) in parallel to the distribution branch (26) and to the delivery branch (27) and flows into the overflow valve (29); And - a plurality of high pressure branches (30 '), each of which is arranged downstream of a respective delivery valve (22) of the high pressure pump (9); the high pressure branches (30 ') converging into a single high pressure branch (30) supplying the manifold (5). System according to claim 1 or 2, and comprising a hydraulic circuit (11), which comprises a portion (P2) for returning the fuel to the tank (2); the return portion (P2) comprising: - a collection branch (31) of the recirculating fuel extending between the engine (3) and the tank (2); - an outlet branch (32) from the manifold (5), flowing into the collection branch (31) and controlled by a non-return valve (321) designed to keep the pressure inside the manifold (5) below a predetermined maximum value; - the return branch (33), which is arranged at the outlet from the internal compartment (13) of the high pressure pump (9) and flows into the overflow valve (29); - a first recirculation branch (35) coming out of the overflow valve (29) and flowing into the connecting branch (23); And - a second recirculation branch (34) coming out of the overflow valve (29) and flowing into the collection branch (31). 4. System according to claims 2 and 3, wherein the overflow valve (29) comprises a tubular body (36) having a longitudinal axis (37) and a plurality of openings (38, 39, 40, 41) which define the openings through which the overflow valve (29) communicates with the regulating (28), return (33) and recirculation (34, 35) branches. 5. Plant according to claim 4, wherein the overflow valve (29) has an axial opening (38) communicating with the regulation branch (28), at least a first radial opening (39) communicating with the first recirculation (35), a second radial opening (40) communicating with the return branch (33), and a third radial opening (41) communicating with the second recirculation branch (34). 6. Implant according to claim 5, and comprising two said first radial openings (39) aligned to each other in a direction transverse to the longitudinal axis (37) and arranged on opposite bands of the tubular body (36) with respect to the longitudinal axis (37 ) same. 7. Implant according to claim 5 or 6, wherein the second and third radial opening (40, 41) are arranged aligned with each other in a direction transverse to the longitudinal axis (37) and are arranged on opposite bands of the tubular body ( 36) with respect to the longitudinal axis (37) itself. System according to one of claims 5 to 7, wherein the overflow valve (29) comprises a shutter (43), which is mounted axially sliding along an inner seat (42) of the tubular body (36) from and towards axial opening (38) and against the action of elastic means (45). 9. System according to claim 8, wherein the overflow valve (29) comprises a locking element (44) arranged inside said internal seat (42) and at one end of the tubular body (36) opposite to that carrying the axial opening (38); the elastic means (45) being interposed between the locking element (44) and the shutter (43). 10. Implant according to claim 9, in which the locking element (44) is spherical in shape and is wedged inside the said internal seat (42). 11. System according to one of claims 8 to 10, in which the shutter (43) is rotatable about the longitudinal axis (37) and has an axial cavity (46) facing the axial opening (38) and communicating with the adjustment branch (28), and an intermediate annular groove (50) adapted to arrange the second and third radial opening (40, 41) in communication with each other. Overflow valve for a fuel supply system (1) to an internal combustion engine (3) according to one of the preceding claims.