ITBO980561A1 - GROUP OF FUEL SUPPLY TO AN ENDOTHERMAL ENGINE. - Google Patents

Description

DESCRIPTION

of the patent for industrial invention

The present invention relates to a fuel supply unit for an internal combustion engine.

The present invention finds advantageous application in petrol engines, and relates, in particular, to a power supply unit of the type commonly referred to as "direct injection", that is, suitable for supplying petrol directly into the combustion chambers of the engine by means of injectors.

Figure 1 in the annex schematically illustrates a known type of "direct injection" power supply unit currently used in motor vehicles on the market.

With reference to Figure 1, 1 'indicates a group for feeding petrol to the combustion chambers 2' of an endothermic engine 3 '. The unit 1 'comprises a fuel manifold 4', inside which the high pressure petrol (about 120 bar) is stored and must be fed to the combustion chambers 3 '; a plurality of injectors 5 'connected to the manifold 4', and adapted to supply on command a determined quantity of petrol to each combustion chamber 3 '; and a 6 'petrol storage tank.

There are also provided a suction pump 7 'adapted to take the petrol from the tank 6' to feed it at low pressure (about 4 bar) towards the manifold 4 ', and a high pressure pump 8', which has its own suction 8a 'connected to the delivery 7m' of the draft pump 7 'and its own delivery 8m' connected to the fuel manifold 4 'to feed the high pressure petrol.

The suction pump 7 'is arranged in correspondence with the tank 6', for example submerged, and consists of an electric pump which is operated by the battery of the motor 3 'when the motor is started. Furthermore, a low pressure regulator 9 'is provided between the suction pump 7' and the high-pressure pump 8 'to stabilize the pressure of the petrol entering the high-pressure pump 8' through the return to the tank 6 ' of the petrol pumped in excess by the suction pump 7 '.

The high-pressure pump 8 'is a volumetric mechanical pump (for example a piston pump), and is coupled to the camshaft 10' of the motor 3 'which defines its drive unit. In this way, the high pressure pump 8 'has a flow rate which is a function solely of the rotation speed of the camshaft 10' (and therefore of the number of revolutions per minute of the crankshaft of the engine), and, in use , cyclically sends to the manifold 4 'a quantity of fuel greater than the quantity which must be fed to the injectors 5' to satisfy the requirements of the engine 3 '. In fact, when, for example, the engine has a high number of revolutions per minute and the accelerator pedal is lifted, the high-pressure pump 8 'continues to pump fuel into the manifold 4' despite the fact that the injectors 5 'do not supply fuel to the chambers. combustion 2 '.

Consequently, the supply unit 1 'is provided with a pressure regulator 11' arranged on the manifold 4 'to prevent the gasoline pressure inside the manifold itself from exceeding a determined threshold value, and has a recirculation duct 12 'connecting the regulator 11' with the intake 8a 'of the pump 8' to convey towards the pump itself the excess petrol which the regulator 11 'taps from the manifold 4'.

The known and above described feeding unit 1 'has many drawbacks.

In the first place, since the manifold 4 'is located at a considerable distance from the high-pressure pump 8', the recirculation duct 12 'has a long length and consequently is difficult to locate inside the engine compartment. In fact, being traversed by highly flammable fuel, the recirculation duct 12 'must be arranged in a protected position, away from sources of heat or sharp parts that could compromise its structural integrity.

Secondly, the high pressure pump 8 'must supply the delivery 8m' with a pressure such as to ensure both the flow of petrol to the manifold 4 'and the return of excess fuel through the recirculation duct 12', causing dissipation consistent energy.

Finally, the unit 1 'has a non-negligible structural complexity and involves high production costs due to the simultaneous presence of the suction pump 7', the low pressure regulator 9 'and the pressure regulator 11' applied to the manifold 4 '.

The purpose of the present invention is to provide a fuel supply unit to an internal combustion engine which solves the aforementioned drawbacks, i.e. which is structurally simple and economical, which allows to minimize energy consumption, and which makes the presence of the recirculation duct superfluous. .

According to the present invention, a fuel supply unit is provided to at least one combustion chamber of an internal combustion engine, the supply unit comprising a fuel manifold; at least one injector connected to the manifold to supply on command a determined quantity of fuel to the combustion chamber; a fuel storage tank; and a pumping device for sending the fuel at high pressure into said manifold; the unit being characterized in that the pumping device comprises a volumetric pump for drawing the fuel directly from the tank and for feeding it at high pressure directly to the manifold; and an electric motor coupled to said volumetric pump to define the driving unit thereof, and adapted to be piloted by means of a control signal; the unit further comprising a control unit adapted to control said electric motor by means of said control signal to supply to the manifold only the quantity of fuel which corresponds to the requirement of the internal combustion engine, regulating the pressure inside the manifold itself.

For a better understanding of the present invention, a preferred embodiment is now described, purely by way of non-limiting example, with reference to the attached drawings, in which:

Figure 1 schematically illustrates a unit for feeding fuel to an internal combustion engine, of the "direct injection" type and of known type;

Figure 2 illustrates a unit for feeding fuel to an internal combustion engine made according to the dictates of the present invention;

Figure 3 represents the characteristic which expresses the trend of the transmitted torque as a function of the driving current in an electric motor forming part of the power supply unit of Figure 2;

Figure 4 represents the characteristic which expresses the delivery pressure trend as a function of the torque received in a pump belonging to the unit of Figure 2; And

- figure 5 represents the characteristic which expresses the trend of the pump delivery pressure as a function of the driving current of the electric motor.

With reference to Figure 2, 1 indicates as a whole a group for feeding petrol to the combustion chambers 2 of an endothermic engine 3. In particular, the feeding unit 1 is of the so-called "direct injection" type, that is, it is able to supply on command a certain quantity of petrol inside each combustion chamber 2 by nebulizing the fuel directly inside the chamber 2 itself. .

The supply unit 1 comprises a fuel manifold 4 adapted to receive and accumulate the fuel before it is fed to the combustion chambers 2; a fuel storage tank 5, inside which the fuel necessary for the operation of the engine 3 is stored; and a pumping device 6, detailed below, adapted to take the petrol directly from the tank 5 to feed it at high pressure (for example 120 bar) directly to the fuel manifold 4.

Connected to the manifold 4 are a plurality of injectors 7 of known type, which, under the control action of a driving unit 8, are able to supply a determined quantity of gasoline contained in the manifold 4 itself inside the chambers 2 combustion. In the example illustrated, the number of injectors 7 is equal to the number of combustion chambers 2 present in the engine 3, and the driving unit 8 is integrated in the engine control unit 9 to which the overall management of the engine 3 itself is delegated.

According to the present invention, the pumping device 6 comprises a high-pressure pump 11, of the volumetric type, suitable for directly withdrawing the fuel from the tank 5 to feed it at high pressure into the manifold 4, and an electric motor 12, which is coupled to the pump 11, defines the driving unit of the pump itself, and is piloted by a control unit 13 which is part of the group 1 and also integrated in the control unit 9.

The control unit 13 is adapted to control the electric motor 12 to regulate the flow rate and the pressure of the fuel which is supplied to the manifold 4. In particular, the control unit 13 is adapted to control the electric motor 13 in such a way that, instant by instant, the quantity of fuel that is pumped to the manifold 4 is equal to the quantity of fuel that is supplied to the combustion chambers, i.e. the requirement of the endothermic engine 3, while maintaining, at the same time, a determined pressure inside the collector itself.

In the example illustrated in Figure 2, the pump 11 is arranged in correspondence with the tank 5, and in particular it is immersed in the tank itself, and has its own delivery 11m connected to the manifold 4 by means of a duct 14 along which a filter 15 is arranged fuel suitable for eliminating any impurities in the fuel before the latter is introduced into the manifold 4. In this example, the pump 11 is defined by a piston pump of a known type, ie it has at least one variable volume pumping chamber (not shown) , which is defined by at least one seat (cylinder) obtained in the main body of the pump 11 and by a respective piston mounted axially sliding in the seat itself. The piston is coupled in a known way to the output shaft (not shown) of the electric motor 12 in such a way that the stroke of the piston, and therefore the suction and fuel pumping phases, are determined by the movement of the output shaft of the electric motor 12.

The volumetric pump 11 has a flow rate which is a function of the speed of the electric motor 12; in particular, this flow rate is proportional to the number of revolutions per minute of the output shaft of the electric motor 12 itself.

In the illustrated embodiment, the volumetric pump 11 has a characteristic C-P, which expresses the relationship between the input torque C (i.e. the torque delivered by the motor 12) and the delivery pressure P, of the type illustrated in Figure 4. As shown in Figure 4. can note the C-P characteristic is linear until the pressure P assumes a threshold value Pth which is higher than the pressure value that is to be maintained inside the manifold 4 to ensure a correct supply of petrol to the combustion chambers 2. In the example shown, the pressure value to be maintained in manifold 4 is equal to 120 bar.

The electric motor 12 coupled to the pump 11 is arranged in correspondence with the tank 5, and in particular can be positioned directly inside the tank itself (as shown in Figure 2), or, alternatively, outside it. Furthermore, the electric motor 12 is powered by a source of electrical energy (for example the battery of the internal combustion engine 3), and is driven by the control unit 13 through a control signal I.

In the example illustrated, the electric motor 12 is a direct current electric motor of a known type (schematically represented in Figure 2) which is driven in current by the control unit 13 through the control signal I in current. The electric motor 12 has a characteristic C-I, which expresses the relationship between the driving current I and the torque C delivered, of the type illustrated in Figure 3. As can be seen, the characteristic C-I is linear at least until the torque C assumes a torque value (in the figure equal to 1.2 Nm) at which, in the C-P characteristic of the pump 11, the pressure P reaches the aforementioned desired pressure value, ie 120 bar.

In this way, by combining the characteristic of the electric motor 12 with the characteristic of the pump 11, a pumping device 6 is produced which has the input-output characteristic shown in figure 5. In particular, the relationship between the driving current I and the delivery pressure P is linear for the entire section of interest, that is, at least until the pressure P reaches the desired pressure value for the manifold 4 (in our case 120 bar).

The pumping device 6 is therefore a sort of electric pump piloted by the control unit 13 to supply to the manifold 4 only the quantity of gasoline which corresponds to the requirement of the endothermic engine 3, and to regulate the pressure P of the fuel introduced into the manifold 4 itself.

According to the present invention, moreover, the supply unit 1 is provided with a pressure sensor 16 (of a known type and schematically illustrated in Figure 2) arranged in correspondence with the manifold 4 to generate a signal S indicative of the pressure of the fuel inside of the manifold 4 itself. The sensor 16 is connected to the control unit 13 to feed it the signal S and thus communicate to it the pressure actually present inside the manifold 4.

In this way the sensor 16, the control unit 13, the electric motor 12 and the volumetric pump 11 realize a feedback system through which it is possible to regulate the fuel pressure inside the manifold 4 to the desired pressure value.

In use, when the pressure of the fuel inside the manifold 4 is lowered, for example following the supply of fuel to the combustion chambers 2, the control unit 13 notices this lowering by means of the pressure signal S coming from the sensor 16, and controls the electric motor 12 through the control signal I. Under this control action, the electric motor 12 delivers the torque C which allows the pump 11 to pump fuel directly to the manifold 4 so as to restore the desired pressure inside the manifold 4 itself. The intensity of the control action is determined by the control unit 13 on the basis of both the deviation of the measured pressure from the desired pressure and the P-I characteristic (figure 5) of the pumping device 6. In this way the pressure is restored desired inside the manifold 4 by feeding into the manifold itself only the quantity of petrol which corresponds to the requirements of the endothermic engine 3.

From the above it emerges therefore that a single pump 11 is sufficient to take the fuel from the tank 5 and introduce it at high pressure into the manifold 4, and that, at the same time, the regulation of the pressure inside the manifold 4 is carried out by piloting the electric motor 12.

It should be emphasized that for the purposes of the present invention it is not necessary that the electric motor 12 be a direct current motor, nor that it be controlled in current. In fact, the electric motor 12 could be, for example, of the brushless type, or of alternating current type and so on, while the control signal I could be of a different type. Similarly, it remains clear that the pump 11 could be a volumetric pump different from the piston pump previously described. In fact, the volumetric pump 11 could be, for example, a known type rotary lobe pump.

The choice of the type of pump 11 and of the electric motor 12 is made with a view to realizing a pumping device 6 having a linear relationship between the motor control signal and the pump outlet pressure at least until the outlet pressure assumes the pressure value to be maintained in manifold 4 (see figure 5).

The power supply unit 1 object of the present invention has considerable advantages over known type power units (see Figure 1).

First of all, the power supply unit according to the invention is much simpler from a structural point of view and, at the same time, much cheaper, as it makes the presence of the electric suction pump, the low pressure regulator, the high regulator unnecessary. pressure and, finally, of the recirculation duct.

Furthermore, the pumping device according to the invention allows the direct regulation of the pressure inside the manifold by means of the control unit, allowing to significantly reduce the energy dissipation since it is no longer necessary to supply the fuel to the manifold with such a pressure. to ensure the return of excess fuel to the tank through the recirculation duct. In this regard, it is evident that having released the fuel pumping from the camshaft of the internal combustion engine, i.e. from the number of revolutions per minute of the crankshaft, it is possible to feed the manifold only the quantity of petrol which corresponds to the actual requirement. of the internal combustion engine, thus minimizing energy consumption.

In this way, when, for example, the internal combustion engine has a high number of revolutions per minute and the fuel supply to the combustion chambers is interrupted, fuel is not continued to be pumped to the manifold, contrary to what happens in the fuel units. known type power supply.

Finally, the elimination of the low pressure suction pump avoids having to carry out the starting at low pressure.

Claims (9)

R IV EN D ICA TION I 1. Fuel supply unit (1) to at least one combustion chamber (2) of an internal combustion engine (3), the power supply unit comprising a fuel manifold (4); at least one injector (7) connected to the manifold (4) to supply on command a determined quantity of fuel to the combustion chamber (2); a fuel storage tank (5); and a pumping device (6) for sending the fuel at high pressure into said manifold (4); the unit (1) being characterized in that the pumping device (6) comprises a volumetric pump (11) for withdrawing the fuel directly from the tank (5) and for feeding it at high pressure directly to the manifold (4); and an electric motor (12) coupled to said volumetric pump (11) to define the driving unit thereof, and able to be piloted by means of a control signal (I); the unit (1) further comprising a control unit (13) adapted to drive said electric motor (12) by means of said control signal (I) to supply to the manifold (4) only the quantity of fuel which corresponds to the requirements of the endothermic engine (3), by adjusting the pressure inside the manifold (4) itself. 2. Feeding unit according to claim 1, characterized in that it comprises sensor means (16) for generating a feedback signal (S) correlated to the pressure inside the manifold (4); the said control unit (13) receiving the said feedback signal (S) and being able to control the electric motor (12), according to the feedback signal (S) itself, to regulate the flow rate and the pressure of the fuel to be feed to the manifold (4). 3. Supply unit according to claim 2, characterized in that said sensor means (16) comprise a pressure sensor (16) arranged in correspondence with the manifold (4) to detect the pressure inside the manifold (4) itself; the said pressure sensor (16), the said control unit (13), the said electric motor (12) and the said volumetric pump (11) defining a feedback system adapted to regulate the pressure inside the manifold (4) in in such a way as to guarantee a pressure determined inside the manifold (4) itself. 4. Feeding unit according to claim 3, characterized in that the pumping device (6) has an input-output characteristic (P-I), expressing the relationship between said control signal (I) and the delivery pressure (P ) of the said pump (11), having a substantially linear course at least until the pressure (P) exceeds the said determined pressure. 5. Feeding unit according to claim 3 or 4, characterized in that said volumetric pump (11) has a characteristic (P-C) expressing the relationship between the input torque (C) and the delivery pressure (P), having a substantially linear trend at least until the pressure assumes a threshold value (Pth) in any case higher than the said determined pressure. 6. Power supply unit according to claim 5, characterized in that the electric motor (12) has a characteristic (C-I) expressing the relationship between said control signal (I) and the torque delivered (C) to said pump (11 ), having a substantially linear trend at least until the torque itself assumes a value at which the delivery pressure of the said pump (11) assumes the said desired pressure. 7. Power supply unit according to any one of the preceding claims, characterized in that said electric motor (12) is a direct current electric motor, which is powered by an electric power source, and is driven in current by the unit control signal (13) by means of the current control signal (I). 8. Feeding unit according to any one of the preceding claims characterized in that the said volumetric pump (11) is a piston pump arranged inside the said tank (5). 9. Feeding unit according to any one of the preceding claims, characterized in that the said electric motor (12) is arranged inside the said tank (5) or, alternatively, outside the tank (5) itself.