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GB2491110A - Method of operating an internal combustion engine having crankshaft position sensor correction means - Google Patents

Method of operating an internal combustion engine having crankshaft position sensor correction means Download PDF

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Publication number
GB2491110A
GB2491110A GB1108386.2A GB201108386A GB2491110A GB 2491110 A GB2491110 A GB 2491110A GB 201108386 A GB201108386 A GB 201108386A GB 2491110 A GB2491110 A GB 2491110A
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GB
United Kingdom
Prior art keywords
value
angular position
top dead
crankshaft angular
crankshaft
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB1108386.2A
Other versions
GB201108386D0 (en
Inventor
Claudio Monferrato
Alberto Vassallo
Luca Scavone
Manuel Tugnolo
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GM Global Technology Operations LLC
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GM Global Technology Operations LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by GM Global Technology Operations LLC filed Critical GM Global Technology Operations LLC
Priority to GB1108386.2A priority Critical patent/GB2491110A/en
Publication of GB201108386D0 publication Critical patent/GB201108386D0/en
Publication of GB2491110A publication Critical patent/GB2491110A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/009—Electrical control of supply of combustible mixture or its constituents using means for generating position or synchronisation signals
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
    • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
    • F02D35/023—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining the cylinder pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2441—Methods of calibrating or learning characterised by the learning conditions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F02D41/2474—Characteristics of sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/32—Controlling fuel injection of the low pressure type
    • F02D41/34—Controlling fuel injection of the low pressure type with means for controlling injection timing or duration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/32—Controlling fuel injection of the low pressure type
    • F02D41/34—Controlling fuel injection of the low pressure type with means for controlling injection timing or duration
    • F02D41/345—Controlling injection timing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
    • F02D2041/1413—Controller structures or design
    • F02D2041/1432—Controller structures or design the system including a filter, e.g. a low pass or high pass filter
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/12—Introducing corrections for particular operating conditions for deceleration
    • F02D41/123—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

Disclosed is a method of operating an internal combustion engine having crankshaft position sensor correction means. The invention provides a method for operating an in­ternal combustion engine equipped with a crankshaft angular po­sition sensor, comprising the steps of determining a definitive value of a top dead center position error and then of using this de­finitive value to correct measurements made by the crankshaft angular position sensor thereafter. The corrected sensor can be used until a replacement of the crankshaft angular position sensor is fitted.

Description

METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE
TEG1NIL FIflD The present invention relates to a method *for operating an internal combustion engine, in particular an internal combustion engine of a motor vehicle, such as for example a Diesel engine or a gasoline en-gine. aan
As known, an internal combustion engine comprises an engine block in- cluding at least a cylinder, which accorrmodates a reciprocating pis-ton and is closed by a cylinder head that cooperates with the piston to define a combustion chamber.
The piston is mechanically coupled to a crankshaft, so that a reci-procating movement of the piston is transformed in a rotation of the crankshaft and vice versa.
In particular, each rotation of the crankshaft causes two strokes of the piston in the cylinder, namely a stroke in which the piston moves towards the cylinder head, thereby reducing the inner volume of the combustion chamber, and a stroke in which the piston moves away from the cylinder head, thereby increasing the inner volume of the combus-tion chamber.
The position of the piston that is nearer to the cylinder head, name-ly the position of the piston that causes the inner volume of the combustion chamber to reach the lowest value, is conventionally re-ferred as top dead center (TDC) position and corresponds to a precise angular position of the crankshaft.
Nowadays, the angular position of the crankshaft is a key parameter which is involved in many control strategy of the internal combustion engine operation.
By way of example, the angular position of the crankshaft is used for phasing the fuel injections during the engine cycles, and it is also used for calculating combustion parameters indicative of the torque released during the engine cycles, such as the Indicated Mean Effec-tive Pressure (IMEP), which can in turn be used for torque control and estimation.
For this reason, the internal combustion engine is conventionally equipped with a crankshaft angular position sensor, which schemati-cally comprises a crankshaft wheel coaxially fixed to the crankshaft and a stationary electric component cooperating with the crankshaft wheel, wherein the crankshaft wheel and the stationary electric com-ponent are desigued so that each possible angular position of the crankshaft wheel causes the electric component to generate a corres-ponding electric signal.
These signals are sent to an Engine Control Unit (ECU), which assigns a default value to the sensed crankshaft angular position that is ex-pected to correspond to the TOO position (typically 0 degrees), and then evaluates any other crankshaft angular position with reference to that default value.
However, unavoidable mounting errors of the crankshaft wheel on the crankshaft, or even of the stationary electric component on the en- gine block, normally cause that the TOO position sensed by the crank-shaft angular position sensor does not perfectly match with the real TOO position.
This drawback introduces a TOO position error between the sensed TOO position and the real one, which affects all the measurements of crankshaft angular position, so that it has a very bad impact on the efficiency of all the controlling strategies in which these measure-ments are implied.
In order to solve this drawback, it is known a strategy that provides for the ECU to determine a crankshaft angular position value TOO real corresponding to the real TOO position, according to the following equation: TDC -real = F max_ angle -AG -thermo wherein Pmax angle is the crankshaft angular position value sensed by the crankshaft angular position sensor at the instant in which the pressure within the corrbustion chamber during an engine cycle reaches its higher value, and Lie thermo is a value of a thermodynamic loss angle.
Pmax angle is determined with the aid of an in-cylinder pressure sen-sor, during an engine cycle performed without injection of fuel in the combustion charrber, so that the pressure depends exclusively on the position of the piston.
Aethermo is a correction factor that takes into account the heat transfer and the air mass leakage occurring during this engine cycle, and it is selected, on the basis of the engine speed, among a group of preset values of the thermodynamic loss angle, which are ernpiri-cally determined during a calibration activity performed on a test internal combustion engine and which are stored in a memory system in corrimunication with the ECU.
The calculated TDC real is then subtracted from the default value TDC crank of crankshaft angular position that the ECU assigns to the TOC position, in order to calculate the TDC position error TDC ac-cording to the following equation: ATDC = TDC _crank -TDC_real.
Thereafter, the value ATDC is used for correcting all the crankshaft angular position measurements operated by the crankshaft angular po-sition sensor.
According to this known strategy, the ECU performs the calculation of TDC real repeatedly during the overall life of the internal combus- tion engine, so as to update each time the value £TDC of the TEE po-sition error to be used in the correction.
However, while the thermodynamic loss angle values £ethenno used for calculating TDC real remains always unchanged, the heat transfer and the air mass leakage occurring during the engine cycles are influ-enced by the aging of the engine components.
As a consequence, the calculation of TDC real and therefore of LITDC become progressively more and more unreliable, thereby worsening the efficacy of the correction applied to the crankshaft angular position measurements and then every control strategy in which these measure-ments are involved.
An object of an embodiment of the present invention is that of solv-ing the above mentioned drawback.
Another object is that of improving the operation of an internal com-bustion engine by providing a more robust value of the TDC position error between the sensed TDC position and the real one.
Still another object of the invention is to reach the mentioned goals with a simple, rational and rather inexpensive solution.
DISCLOSURE
These and other objects are attained through the features of the em-bodiments of the invention as reported in the independent claims. The dependent claims refers to preferred or particularly advantageous features of the various erftodiments of the invention.
In particular, an embodiment of the invention provides a method for operating an internal combustion engine equipped with a crankshaft angular position sensor, comprising the steps of determining a defin-itive value of a top dead center (TDC) position error, and then of using this definitive value to correct measurements made by the crankshaft angular position sensor until a replacement of the crank-shaft angular position sensor is identified.
In this contest, the replacement of the crankshaft angular position sensor is intended as the replacement of at least a component of the crankshaft angular position sensor that can affect the TDC position error, such as the crankshaft wheel or the stationary electric compo-nent.
As a matter of fact, this solution is based on the observation that, since the TX position error is essentially due to an imperfect posi-tioning of the components of the crankshaft angular position sensor, typically of the crankshaft wheel on the engine crankshaft, the TX position error should not be affected by the aging of the internal combustion engine but to remain constant during the overall life of the internal combustion engine, unless a replacement of the crank-shaft angular position sensor occurs.
As a consequence, provided that the definitive value of the TX posi-tion error is determined in a reliable way, the solution of using this definitive value to correct measurements made by the crankshaft angular position sensor is more reliable than the known solution of repeatedly updating it.
In this regard, an aspect of the embodiment of the invention provides for monitoring a value of an aging parameter of the internal combus-tion engine, and for performing the above mentioned determination of the definitive value of the top dead center position error as soon as the monitored value of the aging parameter exceeds a predetermined threshold value thereof.
This aspect is based on the observation that during a first part of the internal combustion engine life, typically until the so called break-in of the internal combustion engine is over, the TDC position error can slightly change due to normal adjustments of the components involved.
S In order to provide a robust TDC position error, which is not too af-fected neither by this phenomenon nor by an excessive aging of the internal combustion engine, it is therefore advisable to determine its definitive value soon after the above mentioned first part of the engine life.
The aging parameter involved can be an overall distance covered by a vehicle equipped with the internal combustion engine since it was brand new, which can be expressed for exanple in term of a number of kilometers.
In fact, the overall distance covered by the vehicle is a reliable parameter of the internal combustion engine aging.
According to an aspect of the embodiment of the invention, the defin-itive value of the top dead center position error is determined on the basis of one or more provisional values of the top dead position error, each of which has been evaluated while the monitored value of the aging parameter was below or equal to the predetermined threshold value thereof and with the steps of: -monitoring pressure within a combustion chamber of the internal combustion engine during an engine cycle, and -calculating the provisional value LTDC of the top dead center position error according to the following equation: TDC = TDC _crank -Prnax cingle + A9hermo wherein TOC crank is a default value of the crankshaft angular posi-tion at which the top dead center position is expected, Ernax angle is a value of the crankshaft angular position sensed by the crankshaft angular position sensor at the instant in which the monitored pres-sure reaches its maximum value, and aethermo is a preset value of a thermodynamic loss angle.
This provisional values of the TX position error have the advantage of being particularly reliable, because they are calculated while the aging of the internal combustion engine is approximately the same un- der which the thermodynamic loss angle value aethermo are conven-tionally calibrated.
Using these provisional values is therefore advantageously possible to establish a very reliable definitive value of the TDC position er-ror.
Before being used to establish the definitive value of the top dead center position error, the provisional values of the top dead center position error can be filtered, in order to disregard provisional values affected by measuring errors or other noises, thereby further increasing the robustness of the definitive value of the TX position error.
In this regard, the definitive value of the top dead center position error can be reliably determined as an average of the provisional values thereof.
According to another aspect of the embodiment of the invention, once the definitive value of the top dead center position error has been determined, the method further provides for repeatedly updating a current value of a thermodynamic loss angle, wherein this current value is updated each time with the steps of: -monitoring pressure within a combustion charter of the internal combustion engine during an engine cycle, -calculating the current value Aethermo* of the thermodynamic loss angle according to the following equation: ts9_thermo* = A_TDC_def -TDC _crcznk + Prnax_angle wherein L\TECdef is the definitive value of the top dead center po-sition error, TDC crank is default value of the crankshaft angular position at which the top dead center position is expected, Pmax angle is a value of the crankshaft angular position sensed by the crankshaft angular position sensor at the instant in which the monitored pressure reaches its maximum value.
Since the definitive value of the TDC position error does not change, this aspect of the invention allows to progressively correcting the current values of the thermodynamic loss angle in order to take into consideration the current aging condition of the internal combustion engine.
The progressively corrected values can be memorized and then advanta- geously used for other tasks, in particular for calculating an up-dated definitive value of the top dead center position error, if it beoomes necessary.
In this regard, an aspect of the embodiment of the invention provides for updating the definitive value of the top dead center position er-ror, if a replacement of the crankshaft angular position sensor is identified.
As a matter of fact, the replacement of the crankshaft angular posi-S tion sensor, namely the replacement of at least of one its components such as for example the crankshaft wheel, is one of the few causes for which the TDC position error can really change during the overall engine life.
The definitive value of the top dead center position error can be up-dated on the basis of one or more additional values of the top dead center position error, each of which is evaluated after the identifi-cation of the replacement of the crankshaft angular position sensor and with the steps of: -monitoring pressure within a combustion chamber of the internal combustion engine during an engine cycle, -calculating the additional value ATDC* of the top dead center position error according to the following equation: A_TDC = TDC_crank_Pmax_angle+Mjhermo* wherein TDC crank is a default value of the crankshaft angular posi-tion at which the top dead center position is expected, Pmax angle is a value of the crankshaft angular position sensed by the crankshaft angular position sensor at the instant in which the monitored pres-sure reaches its maximum value, and LiO thermo* is the current value of the thermodynamic loss angle.
This solution allows to establish an updated definitive value of the TDC position error which advantageously takes into account the effect that the aging of the internal combustion engine had had on the ther-modynamic loss angles.
The methods according to the invention can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the methods described above, and in the form of a computer program product comprising the computer program.
The computer program product can be embodied as an internal cornbus-tion engine comprising an engine control unit (ECU), a memory system associated to the ECU, and the computer program stored in the memory system, so that, when the ECU executes the computer program, all the steps of the method described above are carried out.
The method can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.
Another embodiment of the invention provides an apparatus for operat- ing an internal combustion engine comprising a crankshaft angular po-sition sensor and control means in communication with the crankshaft angular position sensor, wherein the control means are configured for determining a definitive value of a top dead center position error, and then for using this definitive value to correct measurements made by the crankshaft angular position sensor until a replacement of the crankshaft angular position sensor is identified.
Still another embodiment of the invention provides an automotive sys-tam comprising: an internal combustion engine comprising an engine block defining a set of cylinders, each of which is provided with a reciprocating pis-ton coupled to rotate a crankshaft, and with a cylinder head that cooperates with the piston to define a combustion chamber, a crank-shaft angular position sensor, an in-cylinder pressure sensor for monitoring pressure within a combustion chamber, and an electronic control unit in communication with the crankshaft angular position sensor and with the in-cylinder pressure sensor, wherein the engine control unit is configured for determining a definitive value of a top dead center position error, and then for using this definitive value to correct measurements made by the crankshaft angular position sensor until a replacement of a crankshaft angular position sensor is identified.
Also this embodiment of the invention achieves the advantages of the method described above.
BRIEF DESGRIPTICtI OF THE DRAWINGS The present invention will now be described, by way of exarple, with reference to the accompanying drawings.
Figure 1 shows an automotive system of a motor vehicle.
Figure 2 is the section lI-Il of an internal combustion engine be-longing to the automotive system of figure 1.
Figure 3 is a flowchart illustrating a method according to an errbodi-ment of the invention.
DETAILED DESC9IPTIQ 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 chant- ber 150. A fuel and air mixture (not shown) is disposed in the com-bustion 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 increases the pressure of the fuel received from 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 S and manifold 200. An intercooler 260 disposed in the duct 205 may re-duce 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 ex-pansion 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 aftertreatrrtent 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 (SOR) systems, and particulate filters. Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled be-tween 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 de- vices associated with the ICE 110. The ECU 450 may receive input sig- nals from various sensors configured to generate the signals in pro-portion to various physical parameters associated with the ICE 110.
The sensors include, but are not limited to, a mass airflow and tem-perature sensor 340, a manifold pressure and temperature sensor 350, an in-cylinder pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crankshaft angular position sensor 420, exhaust pres-sure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445.
In particular, the crankshaft angular position sensor 420 schemati- cally comprises a crankshaft wheel 421 coaxially fixed to the crank-shaft 145 and a stationary electric component 422 cooperating with the crankshaft wheel 421, wherein the crankshaft wheel 421 and the stationary electric component 422 are designed so that each possible angular position of the crankshaft wheel 421 causes the stationary electric component 422 to generate a corresponding electric signal, which is sent to the ECU 450. The crankshaft wheel 421 is coupled to the crankshaft 145 so that a given electric signal generated by the stationary electric component 422 is expected to correspond to the TDC position of a piston 140 in the respective cylinder 125. The ECU 450 is then configured to relate this given electric signal with a default value of the crankshaft angular position, typically 0 de-grees, and then evaluates any other crankshaft angular position with reference to that default value.
Furthermore, the ECU 450 may generate output signals to various con-trol 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 corrununication 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 cen-tral processing unit (CPU) in corrrunication with a memory system 460 and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system 460, and send and receive signals to/from the interface bus. The memory system 460 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 digi- tal signals to/from the various sensors and control devices. The pro-gram may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.
In particular, many ICE control strategies generally requires the ECU 450 to constantly measure the actual angular position of the crank-shaft 145, through the above mentioned crankshaft angular position sensor 420.
In this regard, all the crankshaft angular position measurements are affected by a chronic error, conventionally referred as top dead cen-ter (TOO) position error, which is generally due to the unavoidable slight mounting errors of the crankshaft wheel 421 on the crankshaft 145, or even of the stationary electric component 422 on the engine block 120.
In fact, these slight mounting errors cause the TOO position sensed by the crankshaft angular position sensor 420 to not perfectly coin- cide with the real TOO position of the piston 140 in the correspond-ing cylinder 125, thereby generating a measurement error that will also affects the other measurements of the crankshaft angular posi-tion.
For this reason, the ECU 450 is generally configured for evaluating the TOO position error and then for using it to correct the crank-shaft angular position measurements.
The TOO position error is evaluated by the ECU 450 during an engine cycle in which no fuel is injected into the related combustion cham- ber 150, so that the pressure therein depends exclusively on the po-sition of piston 140.
The evaluation provides for the ECU 450 to monitor the pressure with-in the combustion chamber 150 during the mentioned engine cycle through the in-cylinder pressure sensor 360, to monitor the angular position of the crankshaft 145 during the same engine cycle through the crankshaft angular position sensor 420, and then to calculate a value ATOC of the TOO position error according to the following equ-ation: A_TDC TDC _crank -Pmax_angle + AOhermo wherein TDC crank is the default value (typically 0 degrees) of the crankshaft angular position at which the TDC position is expected, Pmax angle is the value of the crankshaft angular position sensed by the crankshaft angular position sensor 420 at the instant in which the monitored pressure reaches its maximum value during the above mentioned engine cycle, and £iB thento is a preset value of a thermo-dynamic loss angle.
As a matter of fact, Pmax angle is the crankshaft angular position that would correspond to the real TDC position of the piston 140, if no heat transfer nor air mass leakage occurred during the engine cycle.
A9thermo is a correction factor that takes into account these heat transfer and the air mass leakage, and it is selected, on the basis of a current value of the engine speed, among a group of preset val-ues of the thermodynamic loss angle, which are stored in the memory system 460.
These preset values of the thermodynamic loss angle are empirically determined during a calibration activity performed on a test internal combustion engine.
In particular, the preset values are conventionally determined on a test internal combustion engine whose aging condition is that of an internal combustion engine soon after the break-in stage.
Turning now to the ICE 110, an embodiment of the invention provides for the ECU 450 to consider the TDC position error during the overall engine life, according to the strategy shown in the flowchart of fig-ure 3.
First of all, the strategy provides for the ECU 450 to monitor a val-ue AV of an aging parameter of the ICE 110 (block 10).
In this case, the ICE aging parameter is the overall distance, for example in term of number of kilometers, which has been covered by the motor vehicle equipped with ICE 110, since this motor vehicle was brand new.
The monitored value AV is then corrpared with a predetermined thre-shold value AVth of the aging parameter (block 11), wherein this threshold value defines a predetermined aging condition of the ICE 110.
Preferably, the threshold value AVth defines the ICE aging condition at the end of the break-in stage, which can be quantified by way of example in 5000 Km covered by the motor vehicle since it was brand new.
As long as the monitored value AV is below or equal to the predeter-mined threshold value AVth, the strategy provides for the ECU 450 to repeatedly updating the value iTDC of TDC position error (block 12) to be used in the correction of the crankshaft angular position mea-surements.
The TDC position error value TDC is updated each time using the evaluation strategy described above, so as to calculate a new (cur- rent) value LiTDC of the TDC position error that replaces the pre-viou one.
The scheduling of each updating is established by the ECU 450 accord-ing to a conventional strategy.
As soon as the monitored value AV exceeds the threshold value AVth, namely as soon as the ICE break-in stage is over, the strategy pro- vides for determining a definitive value TECdef of the TIC Posi-tion error (block 13).
This definitive value ATDCdef can be determined on the basis of one or more of the provisional TIC position error values that had been evaluated till then, for example on the basis of the last ten TIC po-sition error values (or any other preset number of TIC position error values) that had been evaluated before the monitored values AV has exceeded the threshold value AVth.
By way of example, the definitive value ATICdef can be calculated as an average of these selected and previously evaluated TIC position error values.
According to an aspect of the strategy, before being used to estab- lish the definitive value aTEC* of the top dead center position er- ror, these selected and previously evaluated TIC position error val-ues can be filtered, in order to disregard the values affected by measuring errors or other noises.
Once the definitive value ATDCdef of the top dead center position error has been determined, it is kept unchanged and used to correct every crankshaft angular position measurement made by the crankshaft angular position sensor 420 until the ECU 450 identifies (block 14) that a replacement of the crankshaft angular position sensor 420 has occurred.
In this contest, the replacement of the crankshaft angular position sensor 420 is to be intended broadly as the replacement of at least a component of the crankshaft angular position sensor 420 that can af-fect the T position error, such as the crankshaft wheel 421 or the stationary electric component 422.
The replacement of the crankshaft position sensor 420 is generally performed in case of fault or breakdown, and it can be identified by the ECU 450 through an automatic procedure or simply through an input provided manually by an operator.
As long as no replacement of the crankshaft position sensor 420 is identified, the definitive value e2TDCdef is kept unchanged and the strategy further provides for repeatedly updating a current value Aethemo* of the thermodynamic loss angle (block 15) which is stored in the memory module 460.
Each updating is performed by evaluating the thermodynamic loss an-gle, so as to obtain a new current value LiD thermo* that replaces the previous one.
The thermodynamic loss angle is evaluated by the ECU 450 during an engine cycle in which no fuel is injected into the combustion chamber 150, so that the pressure therein depends exclusively on the position of piston 140.
The evaluation provides for the ECU 450 to monitor the pressure with-in the combustion chamber 150 during the mentioned engine cycle through the in-cylinder pressure sensor 360, to monitor the angular position of the crankshaft 145 during the same engine cycle through the crankshaft angular position sensor 420, and then to calculate the current value Aethermo* of the thermodynamic loss angle according to the following equation: AU -thermo* = A -TDC -clef -TDC -crank + P max_angle wherein ôTDCdef is the definitive value of the TOO position error, TDC crank is the default value (typically 0 degrees) of the crank-shaft angular position at which the TOO position is expected, Pmax angle is the value of the crankshaft angular position sensed by the crankshaft angular position sensor 420 at the instant in which the monitored pressure reaches its maximum value during the above mentioned engine cycle.
Since the definitive value aToCdef is always the same, the last up-dated value Aethenno* memorized in the memory system 460 reliably takes into account the heat transfer and the air mass leakage that occurs in the combustion chamber 150, due to the current aging condi-tion of the ICE 110.
The scheduling of each thennodynamic loss angle updating is estab-lished by the ECU 450 according to a strategy similar to that used for updating the TOO position error before the engine brake-in was over.
As soon as a replacement of the crankshaft angular position sensor 420 is identified, the strategy provides for the ECU 450 to update the definitive value ATDCdef of the TOO position error (block 16), which will be thereafter used for correcting the crankshaft angular position measurements, as well as for updating the current value tie thermo* of the thermodynamic loss angle (at least until a further replacement of the crankshaft angular position sensor 420 is identi-fied).
In particular, the definitive value ATLCdef is updated with the steps of evaluating one or more additional values of the TDC position error and of using this additional values for determining a new de-finitive value ATDCdef that replaces the previous one, by way of example as an average of these additional values, possibly after their filtration.
As before, each additional values is evaluated by the ECU 450 during an engine cycle in which no fuel is injected into the combustion chamber 150, so that the pressure therein depends exclusively on the position of piston 140.
The evaluation provides for the ECU 450 to monitor the pressure with-in the combustion chamber 150 during the mentioned engine cycle through the in-cylinder pressure sensor 360, to monitor the angular position of the crankshaft 145 during the same engine cycle through the crankshaft angular position sensor 420, and then to calculate the additional value ATDC* of the TDC position error according to the following equation: A_TDC* = TDC _crank -APmax_angle + AG _therrno * wherein TDC crank is the default value (typically 0 degrees) of the crankshaft angular position at which the TDC position is expected, Prnax angle is the value of the crankshaft angular position sensed by the crankshaft angular position sensor 420 at the instant in which the monitored pressure reaches its maximum value during the above mentioned engine cycle, and Lie thermo* is the last updated value of the thermodynamic loss angle.
In this way, the updated definitive value tTDCdef of the TDC posi- tion error is advantageously determined taking into account the cur-rent aging condition of the ICE 110.
According to an aspect of the invention, the strategy described above is performed by the ECU 450, with the aid of a computer program stored in the memory system 460 connected to the ECU 450, so that when the ECU 450 runs the program all the steps of the strategy are carried out.
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 exam- ples, and are not intended to limit the scope, applicability, or con- figuration in any way. Rather, the foregoing summary and detailed de-scription 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 ar-rangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.
REFEPEMES block
11 block 12 block 13 block 14 block block 16 block 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 duct 210 intake port 215 valves 220 port 225 exhaust manifold 230 turbocharger 240 compressor 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 in-cylinder pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 cam position sensor 420 crankshaft angular position sensor 421 crankshaft wheel 422 stationary electric component 430 exhaust pressure and temperature sensors 440 EGR temperature sensor 445 accelerator pedal position sensor 450 ECU 460 memory system cians

Claims (15)

1. A method for operating an internal combustion engine (110) equipped with a crankshaft angular position sensor (420), com-prising the steps of determining a definitive value of a top dead center position error and then of using this definitive value to correct measurements made by the crankshaft angular position sen-sor (420) until a replacement of the crankshaft angular position sensor (420) is identified.
2. A method according to claim 1, comprising the further steps of monitoring a value of an aging parameter of the internal combus- tion engine (110), and of performing the determination of the de-finitive value of the top dead center position error as soon as the monitored value of the aging parameter exceeds a predeter-mined threshold value thereof.
3. A method according to claim 2, wherein the aging parameter is an overall distance covered by a vehicle equipped with the internal combustion engine (110).
4. A method according to claim 2 or 3, wherein the definitive value of the top dead center position error is determined on the basis of one or more provisional values of the top dead position error, each of which has been evaluated while the monitored value of the aging parameter was below or equal the predetermined threshold value thereof and with the steps of: -monitoring pressure within a combustion chamber (150) of the internal combustion engine (110) during an engine cycle, and -calculating the provisional value ATDO cf the top dead cen-ter position error according to the following equation: A _TDC TDC _crank -P max cingle + AO_thermo wherein TOO crank is a default value of the crankshaft angular position at which the top dead center position is expected, Pmax angle is a value of the crankshaft angular position sensed by the crankshaft angular position sensor (420) at the instant in which the monitored pressure reaches its maximum value, and Aethermo is a preset value of a thermodynamic loss angle.
5. A method according to claim 4, wherein the provisional values of the top dead center position error are filtered, before being used to determine the definitive value of the top dead center po-sition error.
6. A method according to claim 4 or 5, wherein the definitive value of the top dead center position error is determined as an average of the provisional values thereof.
7. A method according to any of the preceding claims, which provides for repeatedly updating a current value of a thermodynamic loss angle, wherein this current value is updated with the steps of: -monitoring pressure within a combustion chamber (150) of the internal combustion engine (110) during an engine cycle, -calculating the current value Aethermo* of the thermodynarn-ic loss angle according to the following formula: M_thermo* = ATDC_def -TDC crank + P max_angle wherein ATDCdef is the definitive value of the top dead center position error, TOO crank is a default value of the crankshaft angular position provided by the crankshaft angular position sen-sor at which the top dead center position is expected, Prnax angle is a value of the crankshaft angular position provided by the crankshaft angular position sensor (420) at which the monitored pressure reaches its maximum value.
8. A method according to claim 7, comprising the step of updating the definitive value of the top dead center position error, if a replacement of the crankshaft wheel position sensor (420) is identified.
9. A method according to claim 8, wherein the definitive value of the top dead center position error is updated on the basis of one or more additional values of the top dead center position error, each of which is evaluated after the identification of the re-placement of the crankshaft angular position sensor (420) and with the steps of:: -monitoring pressure within a combustion chamber (150) of the internal combustion engine (110) during an engine cycle, -calculating the additional value ATDC* of the top dead cen-ter position error according to the following equation: a_TDC* = TDC _crank -Prnax angle + AO_thermo * wherein TOO_crank is a default value of the crankshaft angular position at which the top dead center position is expected, Pmax angle is a value of the crankshaft angular position sensed by the crankshaft angular position sensor at which the monitored pressure reaches its maximum value, and rethermo* is the current value of the thermodynamic loss angle.
10. A computer program comprising a computer code suitable for per-forming the method according to any of the preceding claims.
11. A computer program product on which the computer program of claim is stored.
12. An internal combustion engine (110) comprising an engine control unit (450), a memory system (460) associated to the engine con-trol unit (450), and a computer program according to claim 10 stored in the memory system (460).
13. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 10.
14. An apparatus for operating an internal combustion engine (110) comprising a crankshaft angular position sensor and control means (450) in communication with the crankshaft angular position sen- sor (420), wherein the control means (450) are configured for de- termining a definitive value of the top dead center position er- ror, and then for using this definitive value to correct measure-ments made by the crankshaft angular position sensor (420) until a replacement of the crankshaft angular position sensor (420) is identified.
15. An automotive system (100) comprising: an internal combustion engine (110) comprising an engine block (120) defining a set of cylinders (125), each of which is provided with a reciprocating piston (140) coupled to rotate a crankshaft (145), and with a cylinder head (130) that cooperates with the piston (140) to define a combustion chamber (150), a crankshaft angular po- sition sensor (420), an in-cylinder pressure sensor (360) for moni-toring pressure within a combustion chamber (150), and an electronic control unit (450) in corrinunication with the crankshaft angular posi-tion sensor (420) and with the in-cylinder pressure sensor (360), wherein the engine control unit (450) is configured for using a value of a top dead center position error, and wherein the engine control unit (450) is further configured for determining a definitive value of a top dead center position error, and then for using this defini- tive value to correct measurements made by the crankshaft angular po- sition sensor (420) unchanged until a replacement of a crankshaft an-gular position sensor (420) is identified.
GB1108386.2A 2011-05-19 2011-05-19 Method of operating an internal combustion engine having crankshaft position sensor correction means Withdrawn GB2491110A (en)

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