GB2500889A

GB2500889A - Method of operating a fuel injection system which corrects for pump efficiency and injector performance

Info

Publication number: GB2500889A
Application number: GB1205924.2A
Authority: GB
Inventors: Antonio Arpaia; Massimiliano Melis; Vincenzo Rampino
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-04-02
Filing date: 2012-04-02
Publication date: 2013-10-09
Also published as: GB201205924D0

Abstract

Disclosed is a method of operating a fuel injection system of an internal combustion engine, the injection system comprising a low pressure pump for supplying fuel to a high pressure pump via a fuel rail, such as a common rail, and a fuel injector for injecting fuel into a cylinder of the engine. The method comprises determining a nominal fuel quantity to be injected into the cylinder as a function of an engine operating point and determining a correction fuel quantity as a function of an index indicative of a high pressure pump efficiency and of an injector performance. The target quantity of fuel to be injected is determined by adding the values of the nominal fuel quantity and the correction quantity and the low pressure pump is controlled to supply the target fuel quantity to the high pressure pump. The high pressure pump efficiency may take in to account leakage in the system and the injector performance correction factor allows for corrections arising from the age of the injector and resulting deterioration and wear. An engine system, computer program for calculating the corrected fuel quantities and engine control unit using the program are also disclosed.

Description

METHOD OF OPERATING A FUEL INJECTION SYSTEM OFAN INTERNAL

COMBUSTION ENGINE

TECHNICAL FIELD

The present disclosure relates to a method of operating a fuel injection system of an internal combustion engine.

BACKGROUND

It is known that modem Diesel engines are provided with a fuel injection system for directly injecting fuel into the cylinders of the engine.

The fuel injection system generally comprises a fuel common rail and a plurality of electrically controlled fuel injectors, which are individually located in a respective cylinder of the engine and which are hydraulically connected to the fuel common rail through dedicated feeding conduits.

The fuel in the common rail is maintained at a high pressure by an high pressure pump and enters the injector through a fluid inlet and is directed towards a control chamber in the upper portion of the injector and to a lower portion of the injector where a nozzle and a movable needle are provided.

The fuel is supplied to the high pressure pump by a low pressure pump located in the fuel tank, a fuel filter being provided between an outlet of the low pressure pump and an inlet of the high pressure pump.

The low pressure pump of the known fuel injection systems is a pump having a fixed delivery fuel capacity which is calculated for supplying a sufficient quantity of fuel in the worse operating engine condition, i.e. when the requested fuel quantity to be injected is at the maximum value.

A drawback of the above disclosed injection systems is that the pump is operated always in the worse operating condition, i.e. independently from the actual fuel quantity requested for operating the engine; this fact is the cause of an unnecessary fuel consumption, due to the mechanical and electrical power absorption for operating the low pressure pump.

A different approach is to use, instead of a low pressure pump having a fixed delivery fuel capacity, a variable displacement pump, namely a pump whose rotation speed and thus the fuel flow rate can be controlled by means of its characteristics curve, determining a driving current suitable to vary accordingly the fuel flow in order to deliver the fuel quantity requested by the engine operating point.

However, to perform these operations in a correct way depending on the engine operating point it is necessary to take into account a series of variables that are due to the performance of the components downstream of the low pressure pump, in particular the high pressure pump and the fuel injector(s).

An object of an embodiment of the invention is to provide a method of operating a fuel injection system of an intemal combustion engine which allows the delivering of a correct fuel quantity requested for operating the engine for each operating point.

Another object of an embodiment of the invention is to provide a method of operating a fuel injection system of an intemal combustion engine which allows a substantial reduction of C02, of fuel consumption and of electrical load.

Another object of an embodiment of the invention is to provide a fuel injection system of an internal combustion engine that can be controlled in closed loop for supplying the actual fuel requested for operating the engine for each operating point These and other objects are achieved by a method of operating a fuel injection system having the features recited in the independent claim.

These objects are achieved by a method, by an engine, by a computer program and computer program product, and by an electromagnetic signal having the features recited in the independent claims.

The dependent claims delineate preferred and/or especially advantageous aspects.

SUMMARY

An embodiment of the disclosure provides a method of operating a fuel injection system of an intemal combustion engine, wherein the injection system comprises a low pressure pump for supplying fuel to an high pressure pump, and a fuel injector for injecting fuel into a cylinder of the engine, said fuel injector being hydraulically connected to the high pressure pump through a fuel rail, the method comprising the following steps: -determining a nominal fuel quantity to be injected into the cylinder, as a function of an engine operating point, -determining a correction fuel quantity as a function of an index indicative of a high pressure pump efficiency r and of an injector performance, -determining a target quantity of fuel to be injected by adding the values of the nominal and the correction quantity, -regulating a low pressure pump operating parameter for supplying the target fuel quantity to the high pressure pump.

An advantage of this embodiment is that a target fuel quantity is supplied from the low pressure pump to the high pressure pump, such a value depending on the engine operating point. This allows a reduction of fuel consumption, electrical load and CO2 emission.

According to another embodiment of the invention, the efficiency of the high pressure pump is calculated according to the following equation: fl (Xv_LF)*AF*A where A is a pump discharge coefficient, LF is a factor that takes into account pump losses, AF is a pump ageing factor and A is a pump inlet valve opening area.

An advantage of this embodiment is that allows to take into account the effect of the high pressure pump efficiency in order to determine the correction fuel quantity.

According to a further embodiment of the invention, the parameter X is calculated according to the following equation: I 7 = -a, (n)p;01, + a1 ii ± a0 (n) where P,au is a rail pressure and a0(n), a1(n) and a2(n) are functions of an engine speed.

An advantage of this embodiment is that it corielates the pump discharge coefficient with the rail pressure.

According to another embodiment of the invention, the parameter LF is calculated according to the following equation: LF = K,Ap vnp,,, V1., where KIeak is a factor that depends on the geometrical features of the clearances between piston and sleeve and that linearly varies with the rail pressure, Ap is the difference between a maximum and a minimum pump pressure, v is the viscosity of the fuel, n is an engine speed, p is the fuel density and VdISPI a volumetric displacement of the pump.

An advantage of this embodiment is that t correlates the pump losses with the relevant factors that determine losses phenomena.

According to a further embodiment of the invention injector performance is determined as a function of an injector's fuel leakage value Vleakage and as a function of a differential fuel quantity AQ indicative of an ageing of the injector.

An advantage of this embodiment is that it takes into account the two main effects influencing the injection performance.

According to an embodiment of the invention, the injector's fuel leakage value Vieaicage is determined according to the following equation: = f,(p1T, )ET2 ÷f'1(p,.,T)*ET+fJp,,,T1,) where ET is an energizing time of the injector (160) and f3,11 and f2 are functions of a rail pressure Prau and of a fuel temperature T1.

An advantage of this embodiment is that it gives a formula to calculate the effect of an injector's leakage.

According to an embodiment of the invention, the fuel quantity AQageng indicative of an ageing of the injector is determined according to the following equation: = ± + where P81, is a rail pressure and c0,c1 and c2 are functions of the distance traveled.

An advantage of this embodiment is that allows it gives a formula to calculate the effect of an injector's ageing in terms of a fuel quantity.

According to an embodiment of the invention, an injector energizing time is chosen as the parameter indicative of the nominal fuel quantity.

An advantage of this embodiment is that the use of the energizing time, as parameter indicative of the nominal fuel quantity, is useful for controlling the injectors.

According to another embodiment of the invention, a rotation speed of the low pressure pump is chosen as low pressure pump operating parameter.

An advantage of this embodiment is that the control of rotation speed of the pump allows to deliver the target fuel quantity.

Another embodiment of the invention provides an apparatus for operating an internal combustion engine equipped with an injection system, wherein the injection system comprises a low pressure pump for supplying fuel to an high pressure pump, and a fuel injector for injecting the fuel into a cylinder of the engine, the fuel injector being hydraulically connected to the high pressure pump through a fuel rail, the apparatus comprising: -means for determining a nominal fuel quantity to be injected into the cylinder, as a function of an engine operating point, -means for determining a correction fuel quantity as a function of an index indicative of a high pressure pump efficiency 1 and of an injector performance, -means for determining a target quantity of fuel to be injected by adding the values of the nominal and the correction quantity, -means for regulating a low pressure pump operating parameter for supplying the target fuel quantity to the high pressure pump.

This embodiment of the invention has the same advantages of the method disclosed above, namely the apparatus determines a target fuel quantity to be supplied from the low pressure pump to the high pressure pump, such a value depending on the engine operating point. This allows a reduction of fuel consumption, electrical load and CO2 emission.

According to an aspect of this embodiment, the apparatus calculates the efficiency 1 of the high pressure pump according to the following equation: 11 (Xv_LF)*AF*A

S

where X is a pump discharge coefficient, LF is a factor that takes into account pump losses, AF is a pump ageing factor and A is a pump inlet valve opening area.

According to a further aspect of this embodiment, the apparatus calculates the parameter Xaccording to the following equation: = (n)p + )praji ± a0o) where Praji is a rail pressure and a0(n), a1(n) and a2(n) are functions of an engine speed.

An advantage of this embodiment is that it correlates the pump discharge coefficient with the rail pressure.

According to a further aspect of this embodiment, the apparatus calculates the parameter LF according to the following equation: LF= K1Ap 1 5 unp, VdV,,, where k,k is a factor that depends on the geometrical features of the clearances between piston and sleeve and that linearly varies with the rail pressure, ap is the difference between a maximum and a minimum pump pressure, v is the viscosity of the fuel, n is an engine speed, Pip Is the fuel density and Vdjspi a volumetric displacement of the pump.

An advantage of this embodiment is that it correlates the pump losses with the relevant factors that determine losses phenomena.

According to a further embodiment of the invention, the apparatus determines injector performance as a function of an injectors fuel leakage value Vieaige and as a function of a differential fuel quantity AQ indicative of an ageing of the injector.

According to an embodiment of the invention, the apparatus determines the injector's fuel leakage value Vieage according to the following equation: = f,( ,31T,).ET2 where ET is an energizing time of the injector (160) and f0f1 and f2 are functions of a rail pressure Praü and of a fuel temperature lip.

According to an embodiment of the invention, the apparatus determines the fuel quantity aQageing indicative of an ageing of the injector according to the following equation: = C2 + Pratt + C0 where P,ajr is a rail pressure and c0,c1 and c2 are functions of the distance traveled.

According to an embodiment of the invention, the apparatus employs an injector energizing time as the parameter indicative of the nominal fuel quantity.

According to another embodiment of the invention, the apparatus employs a rotation speed of the low pressure pump as the low pressure pump operating parameter.

Still another embodiment of the invention provides an automotive system comprising an internal combustion engine equipped with an injection system, wherein the injection system comprises a low pressure pump for supplying fuel to an high pressure pump, and a fuel injector for injecting the fuel into a cylinder of the engine, the fuel injector being hydraulically connected to the high pressure pump through a fuel rail, an Electronic Control Unit, wherein the Electronic Control Unit is configured to: -determine a nominal fuel quantity to be injected into the cylinder, as a function of an engine operating point, -determine a correction fuel quantity as a function of an index indicative of a high pressure pump efficiency 1 and of an injector performance, -determine a target quantity of fuel to be injected by adding the nominal and the correction quantity, -regulate a low pressure pump operating parameter for supplying the target fuel quantity to the high pressure pump.

Also, this embodiment of the invention has the same advantages of the method disclosed above.

The method according to one of its aspects can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described above, and in the form of computer program product comprising the computer program.

The computer program product can be embodied as a control apparatus for an internal combustion engine, comprising an Electronic Control Unit (ECU), a data carrier associated to the ECU, and the computer program stored in a data carrier, so that the control apparatus defines the embodiments described in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method described above are carried out.

The method according to a further aspect can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represents a computer program to carry out all steps of the method.

A still further aspect of the disclosure provides an internal combustion engine specially arranged for carrying out the method claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals denote like elements, and in which: Figure 1 shows an automotive system; Figure 2 is a cross-section of an internal combustion engine belonging to the automotive system of figure 1; Figure 3 represents a cross-sectional view, with parts removed for reasons of clarity, of a fuel injection system suitable to perform the various embodiments of the invention; Figure 4 is a schematic representation of a control logic that can be employed to control the fuel injection system of Figure 3 according to an embodiment of the invention; Figure 5 is a schematic representation of a model of a fuel injector performance used in the control logic of Figure 4; and Figure 6 is a schematic representation of a model of an high pressure pump efficiency used in the control logic of Figure 4.

DETAILED DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will now be described with reference to the enclosed drawings without intent to limit application and uses.

Some embodiments may include an automotive system 100, as shown in Figures 1 and 2, that includes an internal combustion engine (ICE) 110 having an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145.

A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150.

A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140.

The fuel is provided by a fuel injection system 600, equipped with an injector 160, that will be described in more detail hereinafter.

Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from an intake port 210 and alternately allow exhaust gases to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200.

In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NO traps, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and particulate fitters.

Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200.

Another EGR system (not represented for simplicity) could be coupled between the pipes after turbine and the pipe before compressor (low pressure EGR or long-route E G R).

The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

The automotive system 100 may further include an electronic control unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110.

The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445.

According to some embodiments of the invention, the ECU 450 may receive signals from the fuel injection system 600, as will be explained hereinafter.

Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, and the cam phaser 155. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with a memory system, or data carrier 460, and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system, and send and receive signals to/from the interface bus. The memory system may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.

In Figure 3 the fuel injection system 600, according to an embodiment of the invention is illustrated, the fuel injection system 600 comprises a low pressure (LP) pump 601, positioned within a fuel tank 602 containing fuel. The low pressure pump is a variable displacement pump operable for sending fuel to an high pressure (HP) pump 603 through a fuel line 604 equipped with a fuel filter 605. The high pressure pump 603 has the function to pressurize the fuel at a predetermined pressure value (as a function of a desired engine operating point) and to supply the pressurized fuel to a fuel rail 606 through an high pressure line 607. The high pressure (HP) pump is equipped with a pressure sensor 620 for measuring the fuel pressure at an inlet port of the high pressure (HP) pump 603, the pressure sensor 620 being electrically connected to the ECU 450.

The low pressure pump 601, being a variable displacement pump, is able to deliver a target fuel quantity, which is correlated to the engine operating point, by varying its speed of rotation.

The fuel rail 606 is hydraulicallyconnected, through fuel lines 610, to the injectors for injecting the fuel into the cylinders 125 (Figure 1).

The fuel injectors 160 are also connected back to the fuel tank 602 by means of a re-circulating fuel line 608 for discharging of static and dynamic fuel leakages which occur during the operation of the injectors 160.

The low and the high pressure pumps are electrically connected to the ECU 450 which manages their operating mode according to the engine operating points.

Figure 4 is a schematic representation of a control logic that can be employed to control the fuel injection system of Figure 3, according to an embodiment of the invention.

In a first step an engine map 500 evaluates a rail pressure Frau and a nominal engine fuel quantity Q,, requests as a function of an engine 110 operating point, expressed in terms of an engine load and an engine speed.

A map, stored in the data carrier 460, correlates each nominal fuel quantity Q to a predetermined energizing time El value (block 521) of the injectors 160, i.e. the time of activation of the injectors 160 for injecting the nominal fuel quantity Q, into the cylinders 125.

However, due to the effects of the high pressure pump 606 and of the injector 160, a quantity of fuel different from the nominal fuel quantity Q, would be injected into the cylinder.

Therefore a correction fuel quantity Q must be calculated taking into account the high pressure pump efficiency (block 502) and the fuel injector performance (block 504) and added to the nominal fuel quantity an in order to inject the target fuel quantity Q into the cylinder 125.

More specifically, the correction fuel quantity Q0 is the sum of a pump fuel correction quantity QqHP and of an injector fuel correction quantity Qi.

The pump fuel correction quantity QqHP is an additional fuel quantity requested to the low pressure pump 601 that is due to the fact that the high pressure pump 603 has an efficiency q that may be determined according to the model of block 502 explained hereinafter (Figure 5).

Also, the injector fuel correction quantity Q is a further additional quantity that is due to factors influencing the performance of the injector 160, such as leakage and ageing, and that may be determined according to the model of block 504 explained hereinafter (Figure 6).

The pump fuel correction quantity QHP is then added (adder 503) to the injector fuel correction quantity Q1 to determine the fuel correction quantity Q. Then the correction fuel quantity Q is added (adder 505) to the nominal fuel quantity an to obtain the target fuel quantity Q that is injected for the engine operating point.

Finally, the target fuel quantity required Q1 by engine 110 is input into the low pressure pump characteristic curve (block 508) in order to determine the driving current l of the low pressure pump 601 (block 512) to vary the pump rotation speed in such a way to deliver the target fuel quantity Q requested by the specific engine operating point.

According to a further embodiment of the invention, a pressure sensor 620 can be provided at the high pressure pump 603 inlet to give a pressure value feedback in such a way that the driving current of the low pressure pump may be adjusted in closed loop (block 510), using a correction value I that is added (adder 507) to the driving current l determined in open loop, in order to obtain a corrected driving current It (block 512).

Figure 5 is a schematic representation of the model of block 504 for a fuel injector performance used in the control logic of Figure 4.

The fuel injector performance model is divided in two portions. The first portion is a fuel injector leakage model (block 522) in which a fuel leakage value Vleakage is evaluated as a function of injector energizing time (ET), using the following equation: Td'aklgc = f2(PraijTp)T2 ÷f1('p,T,iET + where ET is the energizing time of the injector 160 and f0,f1 and f2 are functions of a rail pressure Praf) and of a fuel temperature at the inlet of the filter 605.

The second portion of the injector performance model is an injector ageing model (block 524) in which the ageing of the injector is expressed as a differential fuel quantity value AQageng lost as a function of rail pressure Praj;, using the following equation: Qageg = ± + where c0,c1 and c2 are functions of the distance traveled by the vehicle.

Figure 6 shows a schematic representation of the main features of the model of block 502 for an high pressure pump 603 efficiency i used in the control logic of Figure 4.

According to this model, the efficiency r of the high pressure pump 603 is calculated by means of the following equation: where ?is a pump discharge coefficient, LF is a factor that takes into account pump losses, AF is a pump ageing factor and A is the pump inlet valve opening area.

The parameters X,LF and AF are modeled through physical/empirical laws and validated through experimental tests.

More specifically, the parameter X, is modeled by means of the following equation: = -a, (n)p,? + a1 (n)praji ± a0n) where Praji is a rail pressure and a0(n), a1(n) and a2(n) are functions of engine speed.

The parameter LF is modeled by means of the following equation: LF = iSp Ut? PIP Vd(SP, where K(eak is a factor that depends on the geometrical features of the clearances between piston and sleeve and that linearly varies with the rail pressure PraY, Ap is the difference between a maximum and a minimum pump pressure, v is the viscosity of the fuel, ii is the engine speed, PIP is the fuel density and VdjspI is the displacement of the pump.

Therefore the efficiency 1 of the high pressure pump 603 is given by the multiplication (multiplier 515) of the term (A, -LF) (block 514) with the pump ageing factor AF which in turn is multiplied (multiplier 517) with the pump inlet valve opening area A (Figure 5).

To determine the fuel flow requested to the low pressure pump due to the efficiency of the high pressure pump, the efficiency rj of the high pressure pump 603 is multiplied (multiplier 519) with the fuel flow requested by the high pressure pump 603.

Therefore, in order to deliver the target quantity Q, and thus to determine the fuel correction quantity Q to be added to the nominal fuel quantity Q, the injector fuel correction quantity Q1 is determined, using the model of Figure 5.

Then, using the model of figure 6, the high pressure pump fuel correction quantity QHP is determined. Finally the fuel correction quantity Q is determined adding the fuel correction quantity Q to the high pressure pump fuel correction quantity QHP.

The fuel correction quantity Q0 is added to the nominal fuel quantity Q to obtain the target fuel quantity value Q. The target fuel quantity value Q is input into the low pressure pump characteristic curve (block 508) in order to determine the driving current l of the low pressure pump 601 (block 512) to vary the pump rotation speed accordingly.

A supplemental benefit of the various embodiments of the invention is a decreased calibration effort necessary to develop the control strategy.

Moreover, the same model can be applied to different pump families.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCE NUMBERS

automotive system internal combustion engine (ICE) engine block 125 cylinder cylinder head camshaft piston crankshaft 150 combustion chamber cam phaser fuel injector intake manifold 205 air intake duct 210 intake airport 215 valves of the cylinder 220 exhaust gas port 225 exhaust manifold 230 turbocharger 240 compressor 244 exhaust line portion 250 turbine 260 intercooler 270 exhaust system 275exhaustline 280 exhaust aftertreatment device 285 LNT trap 290 VGT actuator 300 EGR system 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 combustion pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure sensor 445 accelerator pedal position sensor 450 electronic control unit (ECU) 460 data carrier 500 block 502 block 503 adder 504 block 505 adder 506 block 508 block 510 block 512 block 514 block 515 multiplier 516 block 517 multiplier 518 block 519 multiplier 520 block 521 block 522 block 524 block 600 fuel injection system 601 low pressure pump 602 fuel tank 603 high pressure pump 604 fuel line 605 fuel filter 606 fuel rail 607 high pressure line 608 re-circulating fuel line 610 fuel lines 620 HP pressure sensor

Claims

CLAIMS1. Method of operating a fuel injection system (600) for an internal combustion engine (110), wherein the injection system (600) comprises a low pressure pump (601) for supplying fuel to an high pressure pump (603), and a fuel injector (160) for injecting fuel into a cylinder (125) of the engine (110), said fuel injector (160) being hydraulically connected to the high pressure pump (603) through a fuel rail (606), the method comprising the following steps: -determining a nominal fuel quantity to be injected into the cylinder (125), as a function of an engine (110) operating point, -determining a correction fuel quantity as a function of an index indicative of a high pressure pump efficiency and of an injector performance, -determining a target quantity of fuel to be injected by adding the values of the nominal and the correction quantity, -regulating a low pressure pump (601) operating parameter for supplying the target fuel quantity to the high pressure pump (603).
2. A method according to claim 1, wherein the efficiency ii of the high pressure pump (603) is calculated according to the following equation: ii (Xv_LF)*AF*A where X, is a pump discharge coefficient, LF is a factor that takes into account pump losses, AF is a pump ageing factor and A is a pump inlet valve opening area
3. A method according to claim 2, wherein the parameter Xis calculated according to the following equation: A1, -a2 + a1(n)p1,1 ± where Praa is a rail pressure and a0(n), a1(n) and a2(n) are functions of an engine speed.
4. A method according to claim 2, wherein the parameter LF is calculated according to the following equation: LF = KIGk tiP unp1 J/411 where k,9Sk is a factor that depends on the geometrical features of the clearances between piston and sleeve and that linearly varies with the rail pressure, ap is the difference between a maximum and a minimum pump pressure, v is the viscosity of the fuel, ii is an engine speed, Pip is the fuel density and V4 a volumetric displacement of the pump.
5. A method according to claim 1, wherein the injector (160) performance is calculated as a function of an injector's fuel leakage value Vieage and a function of a differential fuel quantity AQ indicative of an ageing of the injector (110).
6. A method according to claim 5, wherein the injector's fuel leakage value Vieakage is determined according to the following equation: = f2(p,117J FT2 where ET is an energizing time of the injector (160) and f0,f1 and f2 are functions of a rail pressure Pran and of a fuel temperature
7. A method according to claim 5, wherein the differential fuel quantity aQageing indicative of an ageing of the injector (110) is determined according to the following equation: = C2 p ± Prnii + where Pr is a rail pressure and c0,c1 and c2 are functions of the distance traveled.
8. A method according to claim 1, wherein the nominal fuel quantity is determined as a function of an injector energizing time.
9. A method according to claim 1, wherein a rotation speed of the low pressure pump is chosen as a low pressure pump operating parameter.
10. Internal combustion engine (110), the combustion engine (110) comprising sensors for the measurement of combustion parameters, the engine (110) being equipped with a fuel injection system (600) and an Electronic Control Unit (ECU) (450) configured for carrying out the method according to any of the preceding claims.
11. An apparatus for operating an internal combustion engine (110) equipped with an injection system (600), wherein the injection system (600) comprises a low pressure pump (601) for supplying fuel to an high pressure pump (603), and a fuel injector (160) for injecting the fuel into a cylinder (125) of the engine (110), the fuel injector (160) being hydraulically connected to the high pressure pump (603) through a fuel rail (606), the apparatus comprising: -means for determining a nominal fuel quantity to be injected into the cyhnder (125), as a function of an engine (110) operating point, -means for determining a correction fuel quantity as a function of an index indicative of a high pressure pump efficiency and of an injector performance, -means for determining a target quantity of fuel to be injected by adding the values of the nominal and the correction quantity, -means for regulating a low pressure pump (601) operating parameter for supplying the target fuel quantity to the high pressure pump (603).
12. An automotive system (100) comprising an internal combustion engine (110) equipped with an injection system (600), wherein the injection system (600) comprises a low pressure pump (601) for supplying fuel to an high pressure pump (603), and a fuel injector (160) for injecting the fuel into a cylinder (125) of the engine (110), the fuel injector (160) being hydraulically connected to the high pressure pump (603) through a fuel rail (606), an Electronic Control Unit (450), wherein the Electronic Control Unit (450) is configured to: -determine a nominal fuel quantity to be injected into the cylinder (125), as a function of an engine (110) operating point, -determine a correction fuel quantity as a function of an index indicative of a high pressure pump efficiency and of an injector performance, -determine a target quantity of fuel to be injected by adding the nominal and the correction quantity, -regulate a low pressure pump (601) operating parameter for supplying the target fuel quantity to the high pressure pump (603).
13. A computer program comprising a computer-code suitable for performing the method according to any of the claims 1-9.
14. Computer program product on which the computer program according to claim 13 is stored.
15. Control apparatus for an internal combustion engine (10), comprising an Electronic Control Unit (20), a data carrier (22) associated to the Electronic Control Unit (20) and a computer program according to claim 13 stored in the data carrier (22),