GB2500926A

GB2500926A - Determining fuel injection faults in an automotive i.c. engine

Info

Publication number: GB2500926A
Application number: GB1206163.6A
Authority: GB
Inventors: Massimiliano Melis; Antonio Arpaia
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-04-05
Filing date: 2012-04-05
Publication date: 2013-10-09
Anticipated expiration: 2032-04-05
Also published as: GB201206163D0; GB2500926B

Abstract

A method of determining fuel injection faults in an automotive i.c. engine is disclosed, the injector(s) comprising a solenoid actuator controlled by an electronic control unit which operates each fuel injection by generating an electric opening command and a subsequent electric closing command. The method comprises: measuring (step 20) an actuator closing time 9; comparing (step 21) the actuator closing time 9 with an expected actuator closing time 8 as a function of the electric command current and the dynamic of the actuator, and determining a difference ET thereof; comparing (step 22) the difference ET with a predetermined threshold and, if such difference is greater than said threshold, and evaluating (23) a potential injection fault and confirming it (step 26), based on the value of such difference. The predetermined threshold may be the sum of a calibrated tolerance Ref and a safety factor SF.

Description

METHOD OF DETERMINING INJECTION FAULTS IN AN INTERNAL COMBUSTION

ENGINE

TECHNICAL FIELD

The present disclosure relates to a method of determining injection faults in an internal combustion engine.

BACKGROUND

It is known that modern engines are provided with a fuel injection system for directly injecting the 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 rail through dedicated injection lines.

Each fuel injector generally comprises a nozzle and a movable needle which repeatedly opens and closes this nozzle; fuel can thus be injected into the cylinder giving rise to single or multi-injection pattems at each engine cycle.

The needle is moved with the aid of a dedicated actuator, typically a solenoid actuator, which is controlled by an electronic control unit (ECU). The ECU operates each fuel injection by generating an electric opening command, causing the actuator to open the fuel injector nozzle for a predetermined amount of time, and a subsequent electric closing command, causing the actuator to close the fuel injector nozzle, The time between the electric opening command and the electric closing command is generally referred as energizing time of the fuel injector, and it is determined by the ECU as a function of a desired quantity of fuel to be injected.

The actuator closing time (see Fig. 4, ref. 8, 9) is an important parameter to detect potential failure of the injector. According to its conventional definition, is the time duration from the start of the electric closing command till the end of the actuator opening. Being known the dynamic of the actuator, is possible to estimate the actuator expected closing time 8. On the other side, by using the Lenz law, is possible to monitor the actuator closing time 9 when the same is not anymore energized. Intact, the actuator movement induces in its solenoid a current that can be read by the ECU and indicates the movement of the valve.

Documents disclosing similar technical content are known. For example, DE 10 2004 021 356 Al describes the operation of a magnetically actuated fuel injection valve which has closely controlled opening and closing times to provide accurate fuel metering. The magnetic flux cycle is measured and is compared with a reference to control the cycle [Abstract] (0005]. The methods provides means to access the reliability of the opening and closing behavior of the injection valves [0004]. A computer program for carrying out the method is claimed [claim 81. Although the reference values and measured values for the magnetic flux are provided as a function of time, the patent application does not provide an explicit method for determining and accessing the closing time of the valve, DE 10 2010 018 20 Al describes a method for determining a time duration for an electric actuation of a direct-injection valve for an internal combustion engine. The effect of the induced electric force by eddy currents is considered by applying a calculated reference model to the measured voltage [0076). Also described is a corresponding device and a computer program for carrying out the described method. The patent application does not provide a method for fault detection.

Therefore a need exists for a method that allows to accurately measure the actuator closing time and to compare it with an expected actuator closing time, in order to detect TO an injection fault; more particularly, which injector is working badly, thus decreasing the number of "no trouble found" cases coming back from the field.

An object of an embodiment of the invention is to provide a method that comparing the expected actuator closing time with the measured actuator closing time, can detect whether an injection is properly performed or if an injection fault is arising.

Another object is to provide an apparatus which allows to perform the above method.

These objects are achieved by a method, by an apparatus, 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 determining an injection faults in an internal combustion engine of an automotive system, the engine being provided with at least one injector, the injector comprising a solenoid actuator, the automotive system comprising an electronic control unit (ECU) operating each fuel injection by generating an electric opening command, causing the actuator to open the fuel injector nozzle for a predetermined amount of time, and a subsequent electric closing command, causing the actuator to close the fuel injector nozzle, the method comprising: -measuring an actuator closing time, -comparing the actuator closing time with an expected actuator closing time as a function of the electric command and the dynamic of the actuator, and determining a difference thereof, -comparing such difference with a predetermined threshold and, in case such difference is greater than said threshold, -evaluating a potential injection fault and confirming it, based on the value of such difference.

Consequently, an apparatus is disclosed for determining an injection faults in an internal combustion engine, comprising: -means for measuring an actuator closing time, -means for comparing the actuator closing time with an expected actuator closing time as a function of the electric command and the dynamic of the actuator, and determining a difference thereof, -means for comparing such difference with a predetermined threshold and, in case such difference is greater than said threshold, -means for evaluating a potential injection fault and confirming it, based on the value of such difference.

An advantage of this embodiment is that it allows to detect an injection fault and more particularly, which injector is working badly, thus decreasing the number of "no trouble

found" cases coming back from the field.

According to a further embodiment of the invention, the phase of measuring an actuator closing time is performed according to the Lenz law and determining the closing time as the time when the inducted current in the solenoid actuator reaches its maximum.

An advantage of this embodiment is that it provides a method to determine the actuator closing time without using any additional sensor.

According to an embodiment of the invention, the predetermined threshold is the sum of a calibrated tolerance and a safety factor.

An advantage of this embodiment is that it allows the method to avoid failure misdetections.

According to another embodiment of the invention, the step of comparing the difference between the actuator closing time and the expected closing time with a predetermined threshold is repeated at least three times.

An advantage of this embodiment is that it further allows the method to avoid failure misdetections.

According to still another embodiment of the invention, the potential injection fault, based on the value of such difference, is an actuator sliding resistance or mechanical fault or an blocked open fault.

An advantage of this embodiment is that it allows technicians to easily find failure root causes.

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. 6

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, in which: Figure 1 shows an automotive system.

Figure 2 is a section of an internal combustion engine belonging to the automotive system of figure 1.

Figure 3 is a section of the upper part of an injector, showing its solenoid actuator Figure 4 is a graph depicting the actuator expected closing time and a generic actuator closing time.

Figure 5 is a flowchart of a method for determining injection faults in an internal combustion engine, according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Some embodiments may include an automotive system 100, as shown in Figures land 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 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 NOx traps, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and 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 and equipped with a data carrier 40. 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. 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 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.

Turning back to the fuel injection, in Fig. 3 the fuel injector 160 comprises a solenoid actuator 1, which further comprises a fixed core 2, a coil 3 and a shutter 4. The ECU 450 operates each fuel injection by generating an electric opening command 5', causing the actuator to open the fuel injector nozzle for a predetermined amount of time, and a subsequent electric closing command 5", causing the actuator to close the fuel injector nozzle. Due to response delay and mechanical inertia, the actuator closes the fuel injector with a certain delay with respect to electric closing command. This delay can be easily predict, knowing the electromagnetic characteristic of the solenoid actuator (core 2 and coil 3) and the inertial characteristics of its shutter 4. If this delay becomes greater than the expected one, then there is the possibility of an injector fault.

The proposed method consists of a diagnostic algorithm, which uses a known technology to read the actuator closing time without using any additional movement sensor. Infact, see Fig. 4, a graph of current vs. time, 5 is a typical electric command of the injector; after the end of the electric command, the residual movement of the shutter 4 induces a current 6, 7 in the coil 3, according to the known Lenz's law, The maximum value of such current is reached when the shutter 4 closes. With 6 is indicated the current profile due to an expected actuator closing time 8, while 7 shows the current profile for a generic actuator closing time 9. Comparing the expected actuator closing time with the generic actuator closing time, the method can detect whether the injector is working properly or not. To measure the generic closing time g a specific switch is implemented in the ECU.

This switch closes the injector driving circuit to let the ECU measure the inducted current by the Lenz effect.

According to a preferred embodiment, the method of determining an injection faults in an internal combustion engine comprises the steps of (see Fig. 5): -measuring 20 the actuator closing time 9, for example in a nonlimitative way, by determining it as the time when the solenoid inducted current 7 reaches its maximum; -comparing 21 the actuator closing time 9 with an expected actuator closing time 8 as a function of the electric command 5 and the dynamic of the actuator, and determining a difference AET thereof, -comparing 22 such difference AET with a predetermined threshold and, in case such difference is greater than said threshold, -evaluating 23 a potential injection fault and confirming it, based on the value of such difference.

According to a preferred embodiment of the invention, the predetermined threshold is the sum of a calibrated tolerance Ref and a safety factor SF. Both the calibrated tolerance Ref and the safety factor SF are used to avoid failure misdetection. In other words, if the generic value 9 is greater than the expected value 8 of about few microseconds, this condition could not imply a failure but simply an acceptable lifetime drift. To avoid misdetection, a typical value of Ref is 20 ss, while SF could be equal to 1,5 x Ref.

Also, to avoid failure misdetections, according to another embodiment of the invention, the step of comparing 22 the difference between the actuator closing time and the expected closing time with a predetermined threshold is repeated at least three times, In particular, once the condition 22 (AET > Ref+SF) is satisfied, the method evaluates 23 a potential fault condition and initializes 23 a counter at the value of 1. The control loop is restarted 25 until the condition 24 Counter> 2 is satisfied.

Once this condition is satisfied, the evaluation of the potential failure is confirmed 26.

According to still another embodiment of the invention, the potential injection fault, based on the value of such difference, is an actuator sliding resistance or mechanical fault or an blocked open fault. In particular: * if AET c A, there is a potential actuator sliding resistance * if A < ,SET c B, there is a potential mechanical fault * if aET > B, there is a potential blocked open fault where A and B are a reference value which depend on the injector and engine characteristics. A typical value for A is 100 ts 1for B 200 is.

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 S 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

1 solenoid actuator 2 fixed core 3 coil 4 shutter electric command current 5', 5" electric command current (opening, closing) 6 inducted current for an expected actuator closing time 7 inducted current for a generic actuator closing time 8 expected actuator closing time 9 generic actuator closing time block 21 block 22 block 23 block 24 block block 26 block data carrier 100 automotive system internal combustion engine engine block cylinder cylinder head 135 camshaft piston crankshaft combustion chamber cam phaser 160 fuel injector fuel rail fuel pump fuel source intake manifold 205 air intake pipe 210 intake port 215 valves 220 port 225 exhaust manifold 230 turbocharger 240 compressor 245 turbocharger shaft 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 aftertreatment devices 290 VGT actuator 300 exhaust gas recirculation 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 temperature and level sensors 385 lubricating oil temperature and level sensor 390 metal temperature sensor 400 fuel rail pressure sensor 410 cam position sensor 420 crank position sensor 430 exhaust pressure and temperature sensors 440 EGS temperature sensor 445 accelerator position sensor 446 accelerator pedal 450 ECU

Claims

CLAIMS1. Method of determining an injection faults in an internal combustion engine (110) of an automotive system (100), the engine being provided with at least one injector (160), the injector comprising a solenoid actuator (1), the automotive system comprising an electronic control unit (450), operating each fuel injection by generating an electric opening command (5'), causing the actuator to open the fuel injector nozzle for a predetermined amount of time, and a subsequent electric closing command(5"), causing the actuator to close the fuel injector nozzle, the method comprising: -measuring (20) an actuator closing time (9), -comparing (21) the actuator closing time (9) with an expected actuator closing time (8) as a function of the electric command current (5) and the dynamic of the actuator, and determining a difference (SET) thereof, -comparing (22) such difference (zET) with a predetermined threshold and, in case such difference is greater than said threshold, -evaluating (23) a potential injection fault and confirming it (26), based on the value of such difference.
2. Method according to claim 1, wherein the phase of measuring (20) an actuator closing time is performed according to the Lenz law and determining the closing time as the time when the inducted current in the solenoid actuator (1) reaches its maximum.
3. Method according to claim 1, wherein said predetermined threshold is the sum of a calibrated tolerance (Ref) and a safety factor (SF).
4. Method according to claim 1, wherein the step of comparing (22) the difference (zXET) between the actuator closing time (9) and the expected closing time (8) with a predetermined threshold is repeated at least three times.
5. Method according to claim 1, wherein the potential injection fault, based on the value of said difference (AET), is an actuator sliding resistance or a mechanical fault or a blocked open fault.
6. Internal combustion engine (110) of an automotive system (100) equipped with fuel injectors (160), receiving fuel from injection lines (14), the automotive system (100) comprising an electronic control unit (450) configured for carrying out the method according to claims 1-5.
7. A computer program comprising a computer-code suitable for performing the method according to any of the claims 1-5.
8. Computer program product on which the computer program according to claim 7 is stored.
9. Control apparatus for an internal combustion engine, comprising an Electronic Control Unit (450), a data carrier (40) associated to the Electronic Control Unit (450) and a computer program according to claim 7 stored in the data carrier (40).
10. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 7.