GB2516656A

GB2516656A - A control apparatus for controlling fuel injection into an internal combustion engine

Info

Publication number: GB2516656A
Application number: GB1313481.2A
Authority: GB
Inventors: Massimiliano Melis; Antonio Arpaia; Daniele Carboni
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2013-07-29
Filing date: 2013-07-29
Publication date: 2015-02-04
Also published as: GB201313481D0

Abstract

A control apparatus for controlling fuel injection into an internal combustion engine 110, the engine 110 having an injector 160 connected to a rail 170, a fuel pressure sensor 500, and is controlled by energizing a control valve 517. The control apparatus comprising an Electronic Control Unit (ECU) 450, connected to the fuel pressure sensor 500, and configured to : monitor a fuel pressure signal value in the injector 160; determine an actual quantity of fuel (Qinj, fig.4) injected into the cylinder 125 as a function of the signal value; determine a target value (Q T, fig.4) of a quantity of fuel to be injected; calculate a difference (Qcorr, fig.4) between the target value (QT) and the actual quantity of fuel (Qinj) and calculate a corrected value (ETcorr, fig.4) of an energising time of the injector 160 as a function of the difference (Qcorr). The method provides real time quality control of the injected fuel allowing for variations in the manufacturing and/or the effects of aging related wear and tear.

Description

A CONTROL APPARATUS FOR CONTROLLING FUEL INJECTION INTO AN

iNTERNAL COMBUSTiON ENGINE

TECHNICAL FIELD

The present disclosure relates to a control apparatus for controlling fuel injection into an internal combustion engine.

BACKGROUND

An internal combustion engine for a motor vehicle generally comprises an engine block which defines at least one cylinder accommodating a reciprocating piston coupled to rotate a crankshaft. The cylinder is closed by a cylinder head that cooperates with the reciprocating piston to define a combustion chamber. A fuel and air mixture is cyclically disposed in the combustion chamber and ignited, thereby generating hot expanding exhaust gasses that cause the reciprocating movements of the piston. The fuel is injected into each cylinder by a respective fuel injector. The fuel is provided at high pressure to each fuel injector from a fuel rail in fluid communication with a high pressure fuel pump that increase the pressure of the fuel received from a fuel source.

An Electronic Control Unit of the engine receives a torque request expressed by an accelerator pedal position read by an accelerator pedal position sensor and, according to internal programs stored in a memory unit or data carrier, calculates a Start of Injection (SQl) time for starting each injection and an Energizing Time (ED of each injection, namely the length of time during which a fuel injector is energized during an injection pulse. Appropriate electrical signals are therefore sent of the actuators of the injectors to perform the required injections.

Even if an electronic control of the injection allows to obtain an efficient management of the fuel injection, the injectors themselves may be affected by an aging drift that modifies their performance during time with respect to those obtainable according to the nominal characteristics of the injector causing, for example, a negative impact on engine-out emissions.

A second kind of drift is the production drift, namely the differences that may occur in the performance of one injector with respect of another injector of the same type due to the variability of the production process.

However, due to stringent emissions targets and higher power output requirements, it is needed to decrease as much as possible the effects of injector to injector and injection to injection drift.

In fact, it is known that a significant emission deterioration over engine life time is caused by the ageing drift of the injectors.

Moreover, large engineering margins have to be taken into account when calibrating emission and full load performance of the engine, in order to ensure emission compliance and engine structural safety, for example expressed by a maximum inlet turbo temperature allowed or by other parameters.

An object of an embodiment disclosed is to provide a closed loop strategy that is able to compute the injected fuel quantity and the injector leakages values, allowing a real time injection quantity control.

Another object of the present disclosure is to meet these goals by means of a simple, rational and inexpensive solution.

These objects are achieved by a method, by an engine, by an automotive system, 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 control apparatus controlling fuel injection into an internal combustion engine, the engine being equipped with an injector for injecting fuel into a cylinder, the injector being fluidically connected to a rail and equipped with a fuel pressure sensor and being controlled by energizing a control valve thereof, the control apparatus comprising an Electronic Control Unit, connected to the fuel pressure sensor, and configured to: -monitor a signal value representative of a fuel pressure in the injector; -determine an actual quantity of fuel injected into the cylinder as a function of the signal value; -determine a target value of a quantity of fuel to be injected into the cylinder; -calculate a difference between the target value and the actual quantity of fuel; and -calculate a corrected value of an Energizing Time of the injector as a function of the difference.

An advantage of this embodiment is that the use of a closed loop function helps decreasing the unavoidable production dispersion and compensating the ageing effect.

Moreover, the closed loop strategy makes possible to reduce engineering margins, while calibrating emission and power.

Furthermore, the strategy makes feasible a real time diagnosis of the injections that is beneficial on a number of ways, for example having the potential to avoid fire hazard due to continuous injection.

According to another embodiment of the invention, the Electronic Control Unit is configured to determine an instant in which an injectors nozzle opens and an instant in which the injectors valve closes, by monitoring the signal value representative of fuel pressure in the injector.

An advantage of this embodiment is that it allows to determine an interval of time that is relevant for the identification of an approximating function of the pressure over time useful to calculate the actual quantity injected.

According to still another embodiment of the invention, the Electronic Control Unit is configured to determine an approximating function representing a fuel pressure in the injector by interpolating the values of the monitored signal from the instant in which an injector's nozzle opens and an instant in which the injector's valve closes.

An advantage of this embodiment is that it provides an approximating function of the pressure over time useful to calculate the actual quantity injected.

In still another embodiment of the invention, the Electronic Control Unit is configured to determine an actual quantity of fuel injected into the cylinder by calculating the integral: It?2 QftJ=J K*p(t)dt tills where K is a factor that is a function of an Energizing Time of the injector, of a fuel temperature and of a pressure in the rail.

An advantage of this embodiment is that it allows to calculate an actual quantity of fuel injected into a cylinder.

According to another embodiment of the invention, the Electronic Control Unit is configured to determine an actual value of the factor K by means of an experimentally determined map stored in a data carrier associated with the Electronic Control Unit.

An advantage of this embodiment is that the various values of factor K depending on different values of Energizing Time of the injector, of fuel temperature and of pressure in the rail can be predetermined by an experimental activity and stored in a memory or data carrier associated with the ECU in the form of maps.

According to another embodiment of the invention, the Electronic Control Unit is configured to determine an instant in which the control valve of the injector opens and an instant in which an injector's nozzle closes, by monitoring the signal value representative of fuel pressure in the injector.

An advantage of this embodiment is that it allows to provide data useful to estimate a total leakage of the injector, as well as the timing of opening and closing of the nozzle of the injector.

According to another embodiment of the invention, the Electronic Control Unit is configured to estimate a total leakage of the injector using the relationship: VDp Qicak -Bulk where V is the total volume of the high pressure fuel circuit, Dp is a difference of pressure between a set point rail pressure and a pressure value estimated starting from a linear interpolation of the pressure drop from the instant of opening of a the control valve of the injector to the instant in which the injector's nozzle opens and calculating the pressure value at the instant of closure of the injector nozzle according to the linear interpolation, and Bulk is the fuel bulk modulus.

An advantage of this embodiment is that it allows to estimate the total leakage of the injector, an information that can be used, for example, for diagnostic purposes or to improve rail pressure control.

According to another embodiment of the invention, the Electronic Control Unit is configured to estimate a Nozzle Opening Delay between a target electrical Start Of Injection value and the instant in which an injectors nozzle opens.

An advantage of this embodiment is that it allows to diagnose the performance of the injector, in particular in the opening phase.

According to another embodiment of the invention, the Electronic Control Unit is configured to estimate a Nozzle Closing Delay (NCD) between a target electrical End Of Injection value and the instant in which an injector's nozzle closes.

An advantage of this embodiment is that it allows to diagnose the performance of the injector, in particular in the closing phase.

Another embodiment of the invention provides a method of controlling fuel injection into an internal combustion engine, the engine being equipped with an injector for injecting fuel into a cylinder, the injector being fluidically connected to a rail and equipped with a fuel pressure sensor and being controlled by energizing a control valve thereof, the method comprising the steps of: -monitoring a signal value representative of a fuel pressure in the injector; -determining an actual quantity of fuel injected into the cylinder as a function of the signal value; -determining a target value of a quantity of fuel to be injected into the cylinder; -calculating a difference between the target value and the actual quantity of fuel; and -calculating a corrected value of an Energizing Time of the injector as a function of the difference.

According to another embodiment of the invention, the method comprises a step of determining an instant in which an injector's nozzle opens and an instant in which the injectors valve closes, by monitoring the signal value representative of fuel pressure in the injector.

According to still another embodiment of the invention, the method comprises a step of determining an approximating function representing a fuel pressure in the injector by interpolating the values of the monitored signal from the instant in which an injector's nozzle opens and an instant in which the injector's valve closes.

In still another embodiment of the invention, the method comprises a step of determining an actual quantity of fuel injected into the cylinder by calculating the integral: tp2 Qznj=j K*p(t)dt tp4 where K is a factor that is a function of an Energizing Time of the injector, of a fuel temperature and of a pressure in the rail.

According to another embodiment of the invention, the method comprises a step of determining an actual value of the factor K by means of an experimentally determined map stored in a data carrier associated with the Electronic Control Unit.

An advantage of this embodiment is that the various values of factor K depending on different values of Energizing Time of the injector, of fuel temperature and of pressure in the rail can be predetermined by an experimental activity and stored in a mameory or data carrier associated with the ECU in the form of maps.

According to another embodiment of the invention, the method comprises a step of determining an instant in which the control valve of the injector opens and an instant in which an injector's nozzle closes, by monitoring the signal value representative of fuel pressure in the injector.

According to another embodiment of the invention, the method comprises a step of estimating a total leakage of the injector using the relationship: V Dp -Bulk where V is the total volume of an high pressure fUel circuit comprising the injector and the rail, Bulk is the fuel bulk modulus, Dp is a difference of pressure between a set point rail pressure Ps and a pressure value Pz at the instant in which the injector's nozzle closes, the pressure value pz being estimated by a linear interpolation of the pressure drop from the instant in which the control valve of the injector opens to the instant in which the injector's nozzle opens.

According to another embodiment of the invention, the method comprises a step of estimating a Nozzle Opening Delay between a target electrical Start Of Injection value and the instant in which an injector's nozzle opens.

According to another embodiment of the invention, the method comprises a step of estimating a Nozzle Closing Delay (NCD) between a target electrical End Of Injection value and the instant in which an injector's nozzle closes.

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.

Another embodiment of the invention provides an apparatus for controlling fuel injection into an internal combustion engine, the engine being equipped with an injector for injecting fuel into a cylinder, the injector being fluidically connected to a rail and equipped with a fuel pressure sensor and being controlled by energizing a control valve thereof, the apparatus comprising: -means for monitoring a signal value representative of a fuel pressure in the injector; -means for determining an actual quantity of fuel injected into the cylinder as a function of the signal value; -means for determining a target value of a quantity of fuel to be injected into the cylinder; -means for calculating a difference between the target value and the actual quantity of fuel; and -means for calculating a corrected value of an Energizing Time of the injector as a function of the difference.

According to another embodiment of the invention, the apparatus comprises means for determining an instant in which an injector's nozzle opens and an instant in which the injector's valve close, by monitoring the signal value representative of fuel pressure in the injector.

According to still another embodiment of the invention, the apparatus comprises means for determining an approximating function representing a fuel pressure in the injector by interpolating the values of the monitored signal from the instant in which an injector's nozzle opens and an instant in which the injector's valve closes.

In still another embodiment of the invention, the method comprises a step of determining an actual quantity of fuel injected into the cylinder by calculating the integral: 1tp2 K*p(t)dt ti,4 where K is a factor that is a function of an Energizing Time of the injector, of a fuel temperature and of a pressure in the rail.

According to another embodiment of the invention, the apparatus comprises means for determining an actual value of the factor K by means of an experimentally determined map stored in a data carrier associated with the Electronic Control Unit.

According to another embodiment of the invention, the apparatus comprises means for determining an instant of opening of the control valve of the injector and an instant of closure of the nozzle, by monitoring the signal value representative of fuel pressure in the injector.

According to another embodiment of the invention, the apparatus comprises means for estimating a total leakage of the injector using the relationship: VDp Qzeak = Bulk where V is the total volume of an high pressure fuel circuit comprising the injector and the rail, Bulk is the fuel bulk modulus, Dp is a difference of pressure between a set point rail pressure Pta and a pressure value Pz at the instant in which the injector's nozzle closes, the pressure value Pz being estimated by a linear interpolation of the pressure drop from the instant in which the control valve of the injector opens to the instant in which the injector's nozzle opens.

According to another embodiment of the invention, the apparatus comprises means for estimating a Nozzle Opening Delay between a target electrical Start Of Injection value and the instant in which an injectors nozzle opens.

According to another embodiment of the invention, the apparatus comprises means for estimating a Nozzle Closing Delay (NCD) between a target electrical End Of Injection value and the instant of closure of the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, 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 is a schematic representation of a control apparatus for the automotive system according to an embodiment of the invention; Figure 4 is a flowchart representing the main steps of an embodiment of the invention; Figure 5 is graph representing an injectors inlet pressure and fuel flow as a function of time during a fuel injection; Figure 6 represents a map used in an embodiment of the invention; Figure 7 is a flowchart representing the main steps of another embodiment of the invention; Figure 8 represents a flowchart for calculating injector's dynamic leakage, according to an embodiment of the invention; Figure 9 is a flowchart representing the main steps of another embodiment of the invention; and Figure 10 is graph representing an injector's current profile and fuel flow as a function of time during a fuel injection.

DETAILED DESCRIPTION OF THE DRAWINGS

Preferred embodiments will now be described with reference to the enclosed drawings.

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 at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received a fuel source 190. 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 the 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. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices include, but are not limited to, catalytic converters (two and three way), such as a Diesel Oxidation Catalyst (DOG) 285, lean NOx traps 287, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, SGRF (SCR on Filter) 280, and S particulate filters. Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. 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, an exhaust pressure sensor and an exhaust temperature sensor 470, an EGR temperature sensor 440, and an accelerator pedal position sensor 445. 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.

The program stored in the memory system is transmitted from outside via a cable or in a wireless fashion. Outside the automotive system 100 it is normally visible as a computer program product, which is also called computer readable medium or machine readable medium in the art, and which should be understood to be a computer program code residing on a carrier, said carrier being transitory or non-transitory in nature with the consequence that the computer program product can be regarded to be transitory or non-transitory in nature.

An example of a transitory computer program product is a signal, e.g. an electromagnetic signal such as an optical signal, which is a transitory carrier for the computer program code. Carrying such computer program code can be achieved by modulating the signal by a conventional modulation technique such as QPSK for digital data, such that binary data representing said computer program code is impressed on the transitory electromagnetic signal. Such signals are e.g. made use of when transmitting computer program code in a wireless fashion via a WiFi connection to a laptop.

In case of a non-transitory computer program product the computer program code is embodied in a tangible storage medium. The storage medium is then the non-transitory carrier mentioned above, such that the computer program code.is permanently or non-permanently stored in a retrievable way in or on this storage medium. The storage medium can be of conventional type known in computer technology such as a flash memory, an Asic, a CD or the like.

Instead of an ECU 450, the automotive system 100 may have a different type of processor to provide the electronic logic, e.g. an embedded controller, an onboard computer, or any processing module that might be deployed in the vehicle.

In Figure 3 a schematic representation of a control apparatus for the automotive system according to an embodiment of the invention is represented.

Each fuel injector 160 receives fuel from the common rail 170 at high pressure and supplies fuel to the respective cylinder 125 of the engine 110 by injecting the fuel into a combustion chamber of the cylinder under the control of the Electronic Control Unit 450.

Each injector 160 comprises a nozzle 509 normally held closed by a needle 507 which is movable in an axial seat for opening or closing the nozzle 509 under the control of an actuator device, such as a solenoidal valve 505, that is energized under command of the Electrical Control Unit 450 for a certain Energizing Time (El).

By electrically energizing the solenoid 505, an armature 511 is attracted towards the solenoid 505, and a control chamber 515 of the injector 160 is opened.

The opening of the control chamber 515 lifts the needle 507 and the nozzle 509 is opened and certain quantity of fuel in injected into the cylinder 125.

When the solenoid 505 is de-energized by the ECU 450, a spring (not represented for simplicity) pushes the armature 511 back into the original position, closing the control chamber 515 and a spring 513 pushes the needle 507 to close the nozzle 509.

Thus the operations of the solenoid 505, the armature 511 and the control chamber 515 act as a control valve 517 for the injector 160.

More specifically, the ECU 450 determines a, Start of Injection (SQl) and an Energizing Time (ET) of actuation of the fuel injector for each injection as a function of a torque request by the driver or, eventually, of other parameters.

Each fuel injector 160 is provided with a fluid inlet 502 for receiving fuel form the rail 170 and a fuel outlet 504 for recirculating a leaked portion of fuel into the tank 190.

Each fuel injector 160 is provided with an inlet fuel pressure sensor 500. In other embodiments of the invention only some injectors 160 or even only one injector 160 may be provided with an injector pressure sensor 500.

Each injector pressure sensor 500 is connected to the Electronic Control Unit 450 in order to communicate signals representative of the fuel pressure P(t) in the injector thereto.

Known injector pressure sensors are suitable to generate high frequency signals allowing the determination of a pressure curve such as curve A represented in Figure 5.

As explained in the following description, by means of the acquisition of a singal representative of the actual injector inlet pressure P(t) as a function of time by the injector pressure sensor 500, an actual injected fuel quantity Qi1 can be computed.

The injected quantity QInj is thus compared to a calibrated target quantity OT, enabling a closed loop correction of the fuel quantity injected.

Figure 4 is a flowchart representing the main steps of an embodiment of the invention.

In Figure 4, block 510 represents a step in which the injector inlet pressure P(t) is acquired by the ECU 450 by means of input signals from an injector pressure sensor 500 and, on the basis of these information, five key injection points (P1-PS in Figure 5) that are relevant for the calculation of an actual injected fuel quantity Q1 are determined.

These operations will be explained in belier detail hereinafter, with particular reference to Figures 5-6.

Furthermore, these points may be used for further calculations, such as an estimation of the total injector's leakage and of the injector's performance such as, for example, injection timing.

S In the flowchart of Figure 4, block 570 represents an engine operating point defined in terms of Energizing Time of the injector 160 and of pressure Pii in the common rail 170.

When an injection is performed according to a certain engine operating point, a fuel pressure P(t) as a function of time at the inlet of the injector 160 is monitored for the duration of the injection and the five key points P1 -P5 of the monitored pressure variation curve are determined in block 510.

The output of the five key points detection block 510 can then be used for several different operations.

A first operation (block 530) is to calculate a total injected quantity Q1,1 as a function of the pressure and of the fuel temperature FTemp measured by a fuel temperature sensor or estimated by a model.

Then the total injected quantity Q1, can be compared with a target fuel quantity QT and a corrected fuel quantity Q can be determined as difference between the total injected quantity Q and the target fuel quantity QT.

A corrected Energizing Time ETWff can then be determined as a function of the corrected fuel quantity Q. The corrected Energizing Time ETr can then be input into the engine operating point block 570 and used in order to correct the operation of the injector 160.

Figure 5 is graph representing an injector inlet pressure as a function of time measured by pressure sensor 500 (curve A) during a fuel injection. Furthermore, a fuel flow (curve B) as a function of time is represented.

In Figure 5 five relevant points P1-PS of the pressure curve A have also been represented.

In particular, for each injector 160, the injector inlet pressure P(t) can be acquired by the ECU 450 by reading the signal output of the respective injector pressure sensor 500 over time.

A computer program stored in the data carrier 460 associated with the ECU 450 is able to detect each of the five key injection points P1 -P5 of the pressure curve A relevant for the injection calculation.

In Figure 5, point P1 represents the instant of opening of the injector control valve 517, following a current impulse commanded by the ECU 450 in order to start an injection.

In fact, when the solenoid 505 is activated, the armature 511 is lifted against the resistance of a spring to open one or more orifices that allows fuel to exit from the control chamber 515 of the injector 160 and leak back into the fuel circuit via injector outlet 504, causing a phenomenon known as dynamic leakage and reducing the pressure in a control chamber 515 of the injector 160.

Since the control chamber 515 is in fluidic connection with the injectors inlet 502, the sensor 500 detects a first reduction in the fuel pressure P (t).

Therefore, the start of the dynamic leakage can be detected by detecting a first change of slope of curve A at point P1, or in other words by detecting a first decrease in the injector inlet pressure P(t) over time.

After a certain delay, depending on the injectors performance, the pressure drop in the control chamber 515 allows the needle 507 to be lifted against the resistance of spring 513 and the injector's nozzle 509 is opened.

Since in an actual injector performance there is a delay between the start of the current impulse that operates the injector and the actual nozzle opening, monitoring the injector inlet pressure P(t) allows to detect the instant in which the injector's nozzle 509 opens.

The nozzle 509 opening coincides with the start of the injection flow and is detected by virtue of a significant slope change in curve A, in which a significant decrease in the.

injector inlet pressure P(t) begins, namely at point P2.

Moreover, the pressure value Ptnj measured in point P2, at the start of the injection flow, is lower than the set point rail pressure p, due to injector's dynamic leakage that occurred in the time elapsed from point P1 and point P2.

Point P3 represents the instant in which there is a minimum value in the injector inlet pressure P(t). This value correspond with a maximum of the fuel flow in the cylinder 125 of the internal combustion engine 110, taking into account a small delay with respect to the minimum pressure value.

Curve B, that represents the injected fuel quantity as a function of time, is also represented in Figure 5 as a reference.

When the ECU 450 stops the current impulse that has been directed tothe valve 517, the solenoid 505 stops attracting the armature 511 and a spring pushes the armature back to close the control valve 517 of the injector 160.

This operation of the injector 160 can be detected by monitoring the injector inlet pressure P(t) and detecting a point P4 in which injector's inlet pressure value is equal to the value Pini measured at point P2, namely at the start of injection.

When the injector's control valve 517 closes completely, the pressure in the control chamber 515 increases until spring 513 pushes the needle 507 down until it closes completely the nozzle 509.

This final operation of the injector 160 can be detected by monitoring the injector inlet pressure P(t) and detecting a point P5 in which injector's inlet pressure value is equal to the set point rail pressure Praji.

In Figure 5, an inclined line C is also drawn, the line C passing through points P1 and P2.

Line C is also prolonged until it reaches the instant of time corresponding to point P5, namely the instant of closure of the nozzle 509, and a difference Dp from a pressure value Z calculated along the line C at that instant and the set point rail pressure Praii is calculated.

The use of this difference Dp will be explained thereinafter.

Considering the shape of the curve of the pressure between the points P2 and P4, it can be seen that this curve can be interpolated in order to find an approximating function p(t) of the form: (1) p(t)=at4 bt'+ct2+dt+ e where a,b,c,d, and e are coefficients found by interpolation and t is time.

Knowing the shape of the interpolated pressure curve p(t) in the interval between P2 and P4 it is possible to calculate the actual injected fuel quantity Qjq (block 530) as a function of the fuel temperature Fiemp.

To do so it is necessary to first consider that, from a theoretical standpoint, on a long pipe, the volumetric flow is proportional to pressure p by a proportionality factor which includes pipe section A, fuel density p and sound speed a, a relationship that can be expressed by the formula: dv A (2) However, in case of an actual engine system comprising a common rail 170 and one or more injectors 160, it is necessary to make some adjustments to the above theoretical model in order to take into account the difference between the theoretical fuel circuit layout (expressed with the long pipe equation) and the actual layout of the fuel circuit represented by the injector 160 and the common rail 170.

To do so, it is possible to define a series of factors K that take into account the parameters of formula (2), namely pipe section A, fuel density p and sound speed a, and additionally the injector energizing time ET and the rail pressure p(0).

Factors K, as above defined, are then employed in the formula: = K(ET, T,.p(O))p(t) where El is the Energizing Time of the injection, K are factors determined by virtue of an experimental activity on the actual engine system.

Taking into account different values of Energizing Time and of fuel temperature F7emp a series of maps 600 can be determined, each map 605,605" being determined for a different value of rail pressure p (0), such a P1, P1+1 and so on (Figure 6).

The relation between the approximating function p(t) representative of the injector's inlet pressure P(t) over time, as measured by the injector sensor 500, and the actual injected fuel quantity Q11, is therefore determined by virtue of an experimental activity on an hydraulic rig bench for the particular engine system studied and the values of the factors K are determined by performing several injection flow measurements during said experimental activity.

This theoretical background, combined with the experimental activity, allows for the actual injected fuel quantity Q1to be calculated by the following integral: (4) = dt = J'72K(ET, T,p(O))p(t)dt where the factors K determined by the experimental activity are stored in the maps map 605',605" and p(t) is the approximating function of the injector's inlet pressure P(t) overtime, as measured by the injector pressure sensor 500 between points P2 and P4 of pressure curve A. Generally speaking, the Electronic Control Unit 450 is configured to determine an actual quantity of fuel Q,, injected into the cylinder 125 by calculating the integral: I-ti,2 71 =3 K*p(t)cit tP4 where K is an appropriate factor read from the experimentally determined map 600,605605' stored in a data carrier 460 associated with the Electronic Control Unit 450.

As stated above, the total injected quantity Q is then used in a closed loop control of the injected quantity since it can be compared with a target fuel quantity OT to determine a corrected fuel quantity Q. A corrected Energizing Time ETff can then be determined as a function of the corrected fuel quantity Q and used in order to correct the operation of the injector 160.

According to a further embodiment of the invention, represented in the flowchart of Figure 7, it is also possible to estimate a total injector leakage QLeak, given by the sum of a static and of a dynamic leakage, knowing points P1,P2 and P5 of the injector inlet pressure curve of block 510.

As it is known, static leakage of a fuel injector is fuel leakage from the injector to the low-pressure side thereof that may occur despite no fuel injection is carried out, due to imperfect sealing of the various parts. Dynamic leakage occurs during operations of the injector, namely when the solenoid 505 is activated and an armature 511 is lifted against the resistance of a spring to open one or more orifices that allows fuel to exit from the control chamber 515 of the injector 160 and teak back into the fuel circuit.

This evaluation is performed by block 560 of Figure 7 that takes, as input, the output of the five key points detection block 510 and the fuel temperature Fiemp.

The calculations performed by block 560 will be better explained in connection with the description of Figure 8 which represents a flowchart for estimating an injector total leakage Q103k according to an embodiment of the invention.

To calculate the total leakage Qk, the following formula is used: VDp (5) -Bulk where V is the total volume of the high pressure fuel circuit, namely given by the volume of the common rail 170 to which is it is added the volume of the various pipes connecting to the injectors 160, Dp is an estimated difference of pressure by considering point P1 P2 and P5 of the injector inlet pressure P (t) overtime, and Bulk is the fuel bulk modulus.

The fuel bulk modulus Bulk is calculated as a function of the fuel temperature by means of a map stored in the data carrier 460 associated to the ECU 450 (block 610), while the difference of pressure Dp is calculated by linear interpolation of the points P1, P2 and PS of the pressure curve (block 620).

More specifically, Dp is a difference of pressure between the set paint rail pressure p,,, and a pressure value Pz estimated starting from a linear Interpolation of the pressure drop from the instant P1 of opening of a the control valve 517 of the injector 160 to the instant P2 in which the injectors nozzle 509 opens and calculating the pressure value pz at the instant P5 of closure of the injector nozzle 509 according to the linear interpolation, and Bulk is the fuel bulk modulus.

These values are then input in the formula (5) in order to estimate the injectors total leakage Qe8k (block 630).

The estimated injector's total leakage value Qleak is not used for correcting the injection quantity but, for example for a better control of the low pressure pump, since an estimation of the total leakage value may give a better representation of the fluidic phenomena in the fuel circuit.

Furthermore, the total leakage value QIk can be used for diagnostic purposes (block 540).

For example if a total leakage value Qleak is too high with respect to a predetermined threshold, it may signify that the injector 160 is blocked open.

On the contrary, if a total leakage value Oleak is too low with respect to a predetermined threshold, it may signify that the injector 160 is blocked closed.

In each case, appropriate Diagnostic Trouble Codes (DCT) may be issued by the ECU 450.

Block 540 may also receive the value of actual injected fuel quantity Q,1 for diagnostic purposes.

This may be helpful to determine any malfunction of the injector 160 due, for example, to excessive drift or other phenomena.

An actual injected fuel quantity too high with respect to a predetermined threshold may signify, for example, that particles or impurities are blocking the injector, an actual injected fuel quantity Q, too low with respect to a predetermined threshold, may signify coking issues.

Also in these cases, appropriate Diagnostic Trouble Codes (DCT) may be issued by the ECU 450.

The actual injected fuel quantity Q,1 may be considered to be not too high or not too low if it can be corrected by the closed loop in tunable number of loops.

The flowchart of Figure 9 represents a further embodiment of the invention where an actual Nozzle Opening Delay (NOD) from the start of the current impulse that operates the injector 160 to the actual nozzle opening and an actual Nozzle Closing Delay (NCD) from the end of the current impulse to the injector's nozzle 509 closure (block 520) can be estimated.

In Figure 9, a block 580 represents a target electrical Start Of Injection value SOfr, namely the instant of time, as represented by a crankshaft angle, that the ECU 450 considers for starting an electrical impulse for an injection.

This value is compared (in block 520) with the instant in which the injector nozzle 509 opens1 namely point P2, as determined knowing the shape of the injector inlet pressure curve of block 510.

Figure 10 is graph representing an injector current profile D and a fuel flow as a function of time during a fuel injection (curve B).

More specifically, the current profile D is a nominal current profile, characterized by a target electrical Start Of Injection value SOl and a target electrical End Of Injection value EOI1-.

Therefore in block 520 an estimation of the Nozzle Opening Delay (NOD) can be performed by calculating the time elapsed between the target electrical Start Of Injection value SOli and the instant of time represented by point P2, namely the instant in which the injector nozzle 509 opens.

The knowledge of the NOD can be used, for example, for diagnostic purposes to diagnose the injection timing and suitable Diagnostic trouble Codes (DTC) may. be issued if necessary.

If the estimated NOD value is between an acceptable range, a suitable correction of the Start Of Injection value SOkoIr can be calculated and input into the engine operating point block 570 for correcting the Start Of Injection target value 501T.

In the same fashion, the time elapsed between the target electrical End Of In. jection value EOIT and the instant of time represented by point P5. namely the instant in which the injector nozzle 509 is closed can be estimated, this time representing the Nozzle Closing Delay (NCD).

The knowledge of the NCD can be used, for example, for diagnostic purposes to diagnose the injection timing and suitable Diagnostic trouble Codes (DTC) may be issued if necessary.

If the estimated NCD value is between an acceptable range, a suitable correction of the End Of Injection value EOl0 can be calculated an input into the engine operating point block 570 for correcting the End Of Injection target value EOIT.

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 fuel rail fuel pump 190 fuel source intake manifold 205 air intake duct 210 intake air port 215 valves of the cylinder 220 exhaust gas port 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 SCRF (SCR on Filter) 285 DOC 287 LNT trap 290 VGT actuator 300 EGR system 305 EGR bypass valve 307 EGR bypass 310 EGR coaler 315 EGR circuit 317 branch of EGR circuit 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 445 accelerator pedal position sensor 450 electronic control unit (ECU) 460 data carrier 500 injector pressure sensor 502 injector inlet 502 injector outlet 505 solenoidal valve 507 needle 509 nozzle 510 block 511 armature 513 needle spring 515 control chamber 517 injector control valve 520 block 530 block 540 block 550 block 560 block 570 block 580 block 600 series of maps 605',605" maps 610 block 620 block 630 block

Claims

CLAIMS1. A control apparatus for controlling fuel injection into an internal combustion engine (110), the engine (110) being equipped with an injector (160) for injecting fuel into a cylinder (125), the injector (160) being fluidically connected to a rail (170) and equipped with a fuel pressure sensor (500) and being controlled by energizing a control valve (517) thereof, the control apparatus comprising an Electronic Control Unit (450), connected to the fuel pressure sensor (500), and configured to: -monitor a signal value representative of a fuel pressure in the injector (160); -determine an actual quantity of fuel (Q,1) injected into the cylinder (125) as a function of the signal value; -determine a target value (QT) of a quantity of fuel to be injected into the cylinder (125); -calculate a difference (Qcorr) between the target value (QT) and the actual quantity of fuel (Q,1); and -calculate a corrected value (ETc0) of an Energizing Time of the injector (160) as a function of the difference (QcQ1).
2. A control apparatus according to claim 1, wherein the Electronic Control Unit (450) is configured to determine an instant (P2) in which an injector's nozzle (509) opens and an instant (P4) in which the injector's valve (517) closes, by monitoring the signal value representative of the fuel pressure in the injector (160).
3. A control apparatus according to claim 2, wherein the Electronic Control Unit (450) is configured to determine an approximating function p(t) representing a fuel pressure in the injector (160) by interpolating values of the monitored signal from the instant (P2) in which an injector's nozzle (509) opens and the instant (P4) in which the injector's valve (517).
4. A control apparatus according to claim 3, wherein the Electronic Control Unit (450) is configured to determine an actual quantity of fuel (Q,01) injected into the cylinder (125) by calculating the integral: j-t Q,1 =3 K*p(t)dt tp4 where K is a factor that is a function of an Energizing Time of the injector (160), of a fuel temperature (Fiemp) and of a pressure in the rail (170).
5. A control apparatus according to claim 4, wherein the Electronic Control Unit (450) is configured to determine an actual value of the factor K by means of an experimentally determined map (600,605',605") stored in a data carrier (460) associated with the Electronic Control Unit (450).
6. A control apparatus according to claim 1, wherein the Electronic Control Unit (450) is configured to determine an instant (P1) in which the control valve (505) of the injector (160) opens and an instant (P5) in which an injector's nozzle (509) closes, by monitoring the signal value representative of the fuel pressure in the injector (160).
7. A control apparatus according to claim 2 and 6, wherein the Electronic Control Unit (450) is configured to estimate a total leakage (QLeak) of the injector (160) using the relationship: V Dp Qetuc Bulk where V is the total volume of an high pressure fuel circuit comprising the injector (160) and the rail (170), Bulk is the fuel bulk modulus, Dp is a difference of pressure between a set point rail pressure (Prail) and a pressure value (Pz) at the instant (P5) in which the injector's nozzle (509) closes, the pressure value (Pz) being estimated by a linear interpolation of the pressure drop from the instant (P1) in which the control valve (505) of the injector (160) opens to the instant (P2) in which the injector's nozzle (509) opens.
8. A control apparatus according to claim 2, wherein the Electronic Control Unit (450) is configured to estimate a Nozzle Opening Delay between a target electrical Start Of Injection value (SOIT) and the instant (P2) in which an injector's nozzle (509) opens.
9. A control apparatus according to claim 2, wherein the Electronic Control Unit (450) is configured to estimate a Nozzle Closing Delay (NCD) between a target electrical End Of Injection value (EOIT) and the instant (PS) in which the injectors nozzle (509) closes.
10. A method of controlling fuel injection into an internal combustion engine (110), the engine (110) being equipped with an injector (160) for injecting fuel into a cylinder (125), the injector (160) being fluidically connected to a rail (170) and equipped with a fuel pressure sensor (500) and being controlled by energizing a control valve (517) thereof, the method comprising the steps of: -monitoring a signal value representative of a fuel pressure in the injector (160); -determining an actual quantity of fuel (Q) injected into the cylinder (125) as a function of the signal value; -determining a target value (QT) of a quantity of fuel to be injected into the cylinder (125): -calculating a difference (Qcor,.) between the target value (Q-1-) and the actual quantity of fuel (Q,); and -calculating a corrected value (ETCOff) of an Energizing Time of the injector (160) as a function of the difference (Qcor).
11. An automotive system comprising an internal combustion engine (110) managed by an engine Electronic Control Unit (450), the engine (110) being equipped with an injector (160) for injecting fuel into a cylinder (125), the injector (160) being fluidically connected to a rail (170) and equipped with a fuel pressure sensor (500) and being controlled by energizing a control valve (517) thereof, the Electronic Control Unit (450) being connected to the fluid level sensor (510) and being configured to: -monitor a signal value representative of a fuel pressure in the injector (160); -determine an actual quantity of fuel (Q1) injected into the cylinder (125) as a function of the signal value; -determine a target value (Q-1-) of a quantity of fuel to be injected into the cylinder (125); -calculate a difference (Qeoff) between the target value (QT) and the actual quantity of fuel (Q,);and -calculate a corrected value (ETc) of an Energizing Time of the injector (160) as a function of the difference (Qcori.).
12. A computer program comprising a computer-code suitable for performing the method according to claim 10.
13. Computer program product on which the computer program according to claim 12 is stored.