DE112013001833B4 - Control device and control method for an internal combustion engine - Google Patents

Abstract

A control device (19) for an internal combustion engine for judging a cetane number of fuel by using a plurality of different judgment logics which correspond one-to-one to the judgments, characterized in that the control device makes judgments of the cetane number of fuel based on: a circumstance, that a misfire occurs, executes a fueled amount, and an amount of engine torque generated by the combustion of the fuel, and executes control of the internal combustion engine based on a lowest cetane number of the cetane numbers of fuel determined based on the various judgment logics.

Description

BACKGROUND OF THE INVENTION

Field of the invention

The invention relates to a control device for an internal combustion engine (also referred to as an engine control device) and a control method for an internal combustion engine (also referred to as an engine control method), which assess or determine the ignition quality or ignitability of fuel and a control of the internal combustion engine (also referred to as engine control) execute based on a result of the judgment.

Description of the prior art

A diesel engine burns injected fuel by igniting it through compression. Commercially available light oils, which are used as fuel by diesel engines, differ in their components or their composition and vary in ignition quality. The ignition quality of fuel has a great influence on the fact that a misfire occurs, the output power of the engine or the internal combustion engine, etc. In order to improve the output power, fuel consumption and pollutant emissions (emissions) of a diesel engine, it is therefore necessary to improve the ignition quality of the fuel that is currently being used and to set the manner in which the engine control is carried out with regard to the timing and amount of fuel injection, etc. according to the result of checking the ignition quality of the fuel.

The ignition quality or ignitability of light oil, which is used as a fuel in diesel engines, is determined using the cetane number of the light oil. The cetane number of a type of light oil is determined by the volume fraction or volume percentage of the amount of cetane in a mixture of cetane and α-methylnaphthalene, which shows the same ignition quality or readiness as the type of light oil.

Various logics for determining the cetane number of fuel have been proposed. For example, Japanese laid-open publication discloses JP 2011 - 256 840 A logic in which the cetane number of the fuel of a diesel engine is determined based on a relationship between the change in the speed of the diesel engine following fuel injection, the fuel injection timing, and the engine speed at the time of fuel injection. From US 2008/0 051 978 A1 it is known to determine the cetane number by a calculation method based on the amount of heat or the ignition delay, which is suitable for each driving condition, in order to increase the probability of an estimate of the cetane number, using the calculated estimated values the cetane number, the one with the highest reliability is used for the engine control.

It is conceivable to assess the ignition quality of fuel using different assessment logics. In this case, due to the differences in the assessment principles, the different assessment logics sometimes individually output different assessment results. This can then lead to the engine control unit tracking or hunting.

For example, it is assumed that the judgment based on a judgment logic A gives a judgment result that the cetane number of the currently used fuel is low, while the judgment based on a judgment logic B gives a judgment result that the cetane number of the currently used fuel is high. In this case, after making the judgment based on the judgment logic A, engine control is implemented based on the assumption that a fuel whose cetane number is low is used; on the other hand, after the judgment based on the judgment logic B has been carried out, engine control based on the assumption that a fuel whose cetane number is high is used is implemented. Therefore, every time the judgment is made based on one of the judgment logics, the manner in which the engine control is performed is changed, so that the control becomes unstable. Further prior art can be found in US 2007/0 044 759 A1 and in Wolfgang A. Halang: “Course 21661: safety-guided real-time systems I”; Hagen University; October 2004.

SUMMARY OF THE INVENTION

Proceeding from the prior art, the invention has the object of creating a control device and a control method for an internal combustion engine which are suitable for limiting the occurrence of control lag and can therefore carry out the engine control in a suitable manner, even if a plurality of different assessment logics are used, to assess the ignition quality or willingness of fuel. This object is achieved with the control device according to claim 1 and the control method according to claim 3; advantageous developments are the subject of the subclaims.

A control device for an internal combustion engine for judging a cetane number of fuel by using a plurality of different judgment logics that correspond one-to-one with the judgments, according to a first aspect of the invention, a control device has judgments of the cetane number of fuel based on a circumstance that a misfire occurs, a fueled amount , and an amount of the engine torque generated by the combustion of the fuel, and controls the internal combustion engine based on a lowest cetane number of the cetane numbers of fuel determined based on the various judgment logics.

In the above construction, when the judgments output various judgment results, the judgment result showing the lowest cetane number among the results of the judgments is used as the basis for controlling the engine. Thus, even if different judgment results are output, control lag can be suppressed. In addition, since the judgment result indicating the lowest cetane number is used to execute the engine control from the results of the judgments, robustness against misfire can be properly ensured. Therefore, with the above construction, even if a plurality of judgment methods are used to judge the ignition quality or cetane number of the fuel being used, it is possible to restrict the control lag and properly execute the engine control.

According to the first aspect of the invention, the control device for the internal combustion engine can stop execution of the judgment of the cetane number of the fuel based on the magnitude of the engine torque generated by the combustion of the fuel when the cetane number of the fuel is a predetermined number of times or more has the same value.

If the ignitability or quality (cetane number) of the fuel is low, misfire is likely to occur. Therefore, the ignition quality of the fuel being used can be judged based on the fact that a misfire occurs. Furthermore, when refueling, the composition of the fuel in the fuel tank usually changes, as a result of which the ignition quality of the fuel changes. The maximum amount of change in the ignition quality of the fuel can be determined from the amount refilled. In addition, when the ignition quality of the fuel decreases, the engine torque (torque of the internal combustion engine) generated by the combustion of a unit of mass of fuel changes. The ignition quality or cetane number of the fuel currently being used can thus also be determined on the basis of the magnitude of the engine torque that is generated by the combustion of the fuel. Therefore, with the above construction, the cetane number of the fuel being used is judged based on the fact that a misfire occurs, the amount of fuel being refueled, and the amount of engine torque generated by the combustion of the fuel.

When the judgments give different results, the engine control is carried out based on the judgment result, which of the various judgment results shows the lowest cetane number. Therefore, even if different judgment results are output, control lag is avoided. Since the engine control is carried out on the basis of the judgment result which shows the lowest ignition quality or cetane number, robustness against misfires can also be ensured. Therefore, with the above construction, even if a plurality of judgment methods are used to judge the cetane number of the fuel being used, it is possible to restrict the control lag and properly execute the engine control.

A control method for an internal combustion engine for judging a cetane number of fuel by using a plurality of different judgment logics corresponding one-to-one with the judgments according to a second aspect of the invention, comprising: making judgments of the cetane number of fuel based on: a circumstance, that a misfire occurs, an amount of fuel being refueled, and an amount of engine torque generated by the combustion of the fuel; and executing a control of the internal combustion engine based on a lowest cetane number of the cetane numbers of fuel determined based on the various assessment logics.

Figure list

• 1 eine allgemeine Ansicht, die schematisch den Gesamtaufbau einer Steuervorrichtung für eine Verbrennungskraftmaschine (nachfolgend vereinfacht auch als Motorsteuervorrichtung bezeichnet) gemäß einer Ausführungsform der Erfindung zeigt;
• 2 eine Schnittansicht, die den Aufbau eines Seitenabschnitts eines Injektors zeigt, der in einem Dieselmotor angeordnet ist, bei welchem die Ausführungsform Anwendung findet;
• 3 einen Graph, der ein Beispiel eines zeitabhängigen Schwingungsverlaufs der Kraftstoffeinspritzrate zeigt;
• 4 ein Flußschaubild, das einen Prozessablauf einer Drehmomentbasiert bestimmten Cetanzahlberechnungsroutine zeigt, die bei der vorstehenden Ausführungsform zur Anwendung kommt;
• 5A einen Graph, der die Änderung der Verbrennungskraftmaschinen- bzw. Motordrehzahl vor und nach der Ausführung der Kraftstoffeinspritzung zum Erfassen der Cetanzahl des Kraftstoffs zeigt; und 5B einen Graph, der die Verschiebung bzw. Änderung der Drehzahldifferenz vor und nach der Ausführung der Kraftstoffeinspritzung zum Erfassen der Cetanzahl des Kraftstoffs zeigt;
• 6 ein Flußschaubild, das einen Prozessablauf einer Steuerungscetanzahleinstellroutine zeigt, die bei der Ausführungsform zur Anwendung kommt; und
• 7 ein Zeitschaubild, das ein Beispiel der Arten der Änderung bzw. Verschiebung einer Fehlzündungbasiert bestimmten Cetanzahl, einer Nachtankbasiert bestimmten Cetanzahl, einer Drehmomentbasiert bestimmten Cetanzahl und einer Steuerungscetanzahl bei der Steuervorrichtung für eine Verbrennungskraftmaschine gemäß der Ausführungsform zeigt.

The features and advantages as well as the technical and economic significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, the same reference symbols denoting the same elements; here shows:

• 1 Fig. 13 is a general view schematically showing the overall structure of a control device for an internal combustion engine (hereinafter also referred to simply as a motor control device according to an embodiment of the invention;
• 2 Fig. 13 is a sectional view showing the structure of a side portion of an injector installed in a diesel engine to which the embodiment is applied;
• 3 Fig. 13 is a graph showing an example of a time-dependent waveform of the fuel injection rate;
• 4th Fig. 13 is a flowchart showing a process flow of a torque-based determined cetane number calculation routine used in the above embodiment;
• 5A a graph showing the change in engine speed before and after the execution of fuel injection for detecting the cetane number of the fuel; and 5B a graph showing the shift or change in the speed difference before and after the execution of the fuel injection for detecting the cetane number of the fuel;
• 6th Fig. 13 is a flowchart showing a process flow of a control count number setting routine used in the embodiment; and
• 7th FIG. 12 is a time chart showing an example of the ways of changing a misfire-based determined cetane number, a refueling-based determined cetane number, a torque-based determined cetane number, and a control cetane number in the control device for an internal combustion engine according to the embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment in which a control device for an internal combustion engine or a motor control device according to the invention is used will be described in detail with reference to FIG 1 to 7th described. The engine control apparatus of this embodiment is applied to a diesel engine mounted on a vehicle.

As in 1 shown is a fuel tank 10 of a diesel engine to which the control device of this embodiment is applied, with a fuel meter 11 equipped with the amount of fuel in the fuel tank 10 remaining fuel. There is also a fuel supply line 12th for supplying fuel to be supplied to the diesel engine with the fuel tank 10 connected. An intermediate section of the fuel supply line 12th is with a high pressure fuel pump 13th designed what fuel from the tank 10 pumps up and then pressurizes, and dispenses this pressurized fuel. A downstream end of the fuel supply line 12th is with a common rail 14th connected that holds the pressurized fuel. Injectors 16 for the cylinders of the diesel engine are with the common rail 14th connected. Each injector 16 has a fuel pressure sensor 17th showing the fuel pressure in the injector 16 detected. In addition, the injectors are 16 with a return line 18th connected to return excess fuel to the fuel tank.

The diesel engine designed in this way is controlled by an electronic control unit 19th controlled. The electronic control unit 19th includes a microcomputer that performs various calculation processes related to engine control. It also has the electronic control unit 19th an input circuit which receives signals from various sensors that detect the operating conditions of the diesel engine. The fuel meter 11 and the fuel pressure sensors 17th are connected to the input circuit. The other sensors connected to the input circuit include a suction pressure sensor 20th that detects intake air pressure, a speed sensor 21 that detects the speed of the diesel engine, a coolant temperature sensor 22nd that detects the temperature of a coolant of the diesel engine, an accelerator pedal sensor 23 that detects the amount of depression of an accelerator pedal, a vehicle speed sensor 24 that detects the vehicle speed, etc .. In addition, the electronic control unit 19th designed with control circuits for actuators to control different sections of the diesel engine. The control circuits include circuits that control the injectors 16 actuate the cylinder.

Further details of the structure of each of the injectors 16 provided for the respective cylinders of the diesel engine will be described. The diesel engine uses electrically controlled injectors as injectors 16 .

As in 2 each includes an injector 16 a housing 30th which has a hollow cylindrical shape. In the case 30th is a valve needle 31 in direction up and down in 2 mounted movable to and fro. There is also a feather 32 showing the valve needle 31 permanently down in 2 pushes, in a section of the case 30th arranged with respect to the valve needle 31 above in 2 lies.

Next are in the housing 30th two fuel chambers formed, separated from each other by the valve needle 31 are separated, more precisely a nozzle chamber 33 that are relatively below with respect to the valve needle 31 in 2 is arranged, as well as a pressure chamber 34 relating to the valve needle 31 above in 2 is arranged.

The nozzle chamber 33 is with injection ports 35 configured that a connection between the interior of the nozzle chamber 33 and the exterior of the case 30th produce. The nozzle chamber 33 is with a delivery line 36 connected that in the housing 30th is trained. The delivery line 36 is with the common rail 14th connected ( 1 ). Fuel comes from the common rail 14th via the delivery line 36 into the nozzle chamber 33 brought in.

On the other side is the pressure chamber 34 with the nozzle chamber 33 through a connecting line 37 connected, as well as with the aforementioned return line 18th through an outlet pipe 38 . It is also in the pressure chamber 34 a valve body 40 arranged, which is controlled by a pressure-electric actuator, which is formed by laminating pressure-electric elements, for example piezoelectric elements. The pressure chamber 34 thus becomes selective with the connecting line 37 and the outlet pipe 38 by controlling the valve body 40 connected.

A fuel pressure sensor configured as described above 17th is integral with an upper portion of the injector 16 in 2 intended. The fuel pressure sensor 17th is designed in such a way as to reduce the pressure of the fuel in the injection line 36 capture.

Each of the injectors designed in this way 16 works as follows. The pressure-electric actuator 39 assumes, when no control voltage is applied to it, a contracted state in which the entire length of the pressure-electric actuator 39 is reduced, thereby reducing the valve body 40 to arrange in one place that the pressure chamber 34 with the connecting line 37 communicated and from the outlet line 38 is separated. At this point the nozzle chambers communicate 33 and the pressure chamber 34 with each other so that the pressures in these two chambers are essentially the same. Because of this, the valve needle 31 at this point by the spring force of the spring 32 down in 2 pressed so that the injection ports 35 are locked. Therefore, there is no fuel from the injector at this point 16 injected.

If, on the other hand, a control voltage is applied to the pressure-electric actuator 39 is applied, its total length increases to the valve body 40 to arrange in one place that the pressure chamber 34 from the connection line 37 is separated and with the outlet pipe 38 communicates. At this point, fuel will come out of the pressure chamber 34 output and the pressure in the pressure chamber 34 decreases. The pressure in the nozzle chamber 33 therefore becomes greater than the pressure in the pressure chamber 34 . Due to the pressure difference at this point in time, the valve needle will 31 in 2 by the spring force of the spring 32 displaced upwards, that is, displaced in such a way that it moves away from the position at which the valve needle 31 the injection ports 35 locks. The injector 16 therefore injects fuel at this point in time.

In the embodiment configured as described above, the electronic control unit leads 19th performs fuel injection control of the diesel engine. More precisely, the electronic control unit calculates 19th a target value of the amount of fuel injection (target fuel injection amount) based on the engine speed, the low pressure amount of the accelerator pedal, and an estimated value of the cetane number (control cetane number) of the fuel used. The electronic control unit also calculates 19th Setpoint values of the fuel injection timing and the fuel injection duration from the setpoint fuel injection quantity and the engine speed. The electronic control unit sets according to these calculated target values 19th then a control voltage to the pressure-electric actuator 39 of each injector 16 to control fuel injection.

Further, in this embodiment, in conjunction with the above-described fuel injection control, a controller for forming a timing waveform of the fuel injection rate (the amount of fuel injected per unit time) of each injector based on the fuel pressure sensors 17th in every injector 16 detected fuel pressure by the electronic control unit 19th executed. This control is carried out in the following manner.

After the valve needle 31 an injector 16 from the injection ports 35 corresponding to the pressure-electric actuator 39 applied control voltage begins to increase, the pressure in the nozzle chamber decreases 33 gradually as the stroke of the valve needle increases 31 from. Then the application of the control voltage and the stroke of the valve needle ends 31 decreases. As the needle stroke decreases, the fuel pressure in the nozzle chamber increases 33 gradually on. Hence it is based on the information provided by the fuel pressure sensor 17th of the injector 16 detected fuel pressure possible to determine the point in time at which the valve needle 31 begins to lift (valve opening start time Tos), the time at which the The fuel injection rate becomes maximum (maximum fuel injection rate timing Toe), the timing at which the fuel injection rate starts to decrease (fuel injection rate decrease start timing Tcs), and the timing at which the valve needle lifts 31 ends (minimum stroke time tee). On the basis of the points in time determined in this way, an oscillation curve of the fuel injection rate as in FIG 3 shown determined. From this waveform it is possible to determine the current state of the fuel injection with a very high degree of accuracy. Incidentally, the electronic control unit takes place in this embodiment 19th the rate of change of fuel pressure (the hold time of fuel pressure) in each injector 16 and finds the above times based on the rate of change.

The electronic control unit 19th in this embodiment also assesses the cetane number of the fuel currently used, that is, it assesses the ignition quality or ignitability of the fuel. According to the results of this judgment, the electronic control unit 19th the manner of controlling the fuel injection timing, the fuel injection amount, the EGR amount, the charge rate, etc. This improves the output line, fuel consumption and pollutant exchange of the diesel engine. For example, when it is judged that the cetane number of the fuel currently in use is low, the electronic control unit changes 19th the type of control and, for example, increases the number of pilot injections carried out or the amount of pilot injection, adapts the timing of the pilot injection and the timing of the main injection early, decreases the EGR amount, increases the boost pressure, etc., to avoid the occurrence of a misfire, which off the low ignition quality or ignitability of the fuel originates to suppress.

In the engine control apparatus according to this embodiment, the cetane number of the fuel is judged using three judgment logics. The three judgment logics include judging the cetane number of the fuel based on a misfire, judging the cetane number of the fuel based on refueling, and judging the cetane number of the fuel based on the engine torque. These three assessment logics are described in detail below.

[EVALUATING THE CETANE NUMBER BASED ON A

MISFIRING] If a fuel with a low cetane number, the ignition quality of which is poor, is used, misfiring will increase. Therefore, from the occurrence of misfire, it is possible to determine the cetane number of the fuel currently in use.

More precisely, the electronic control unit detects 19th the occurrence of misfires based on changes in engine speed. When the number of times the misfire is detected reaches a predetermined value, the electronic control unit lowers 19th the judgment value of the cetane number of the fuel based on the circumstance of occurrence of the misfire, that is, the value of the misfire based on determined cetane number. Incidentally, the value of the misfire-based detected cetane number is reset to the initial value when refueling takes place. The number of times the misfire has been detected is cleared to "0" each time the fuel is refueled.

[ASSESSING THE CETANE NUMBER BASED ON THE

NIGHT REFUELING] When the fuel tank 10 refilled, the composition of the fuel in the fuel tank changes 10 and the cetane number of the fuel changes. The maximum value of the magnitude of the change in the cetane number can also be determined on the basis of the cetane number of the fuel before refueling, the amount of refueling, etc.

More specifically, judged if due to the increase in the amount of fuel in the fuel tank 10 remains, it is determined that refueling has taken place, the electronic control unit 19th the cetane number of the fuel after refueling based on the assumption that the fuel supplied is a fuel whose cetane number is the lowest of all usable fuels. The cetane number assessed or determined at this point in time, that is to say the refueling-based cetane number Cr, is calculated on the basis of the following equation (1). In the following equation (1), Fb represents the amount of in the fuel tank 10 before refueling (amount of fuel remaining before refueling), Fr represents the amount of fuel in the tank 10 charged fuel (amount of refueled fuel or amount of fuel charged into the tank) and Fa represents the amount of the fuel in the fuel tank 10 represents remaining fuel after refueling (after refueling amount of remaining fuel). In addition, Cb represents the determination value of the cetane number of the fuel in the fuel tank 10 before refueling represents (before refueling number) and Cm represents the minimum value of the cetane number (minimum cetane number) of the fuels that can be used. $$\text{Cr}=\left(\text{Cb}\times \text{Fb}+\text{Cm}\times \text{Fr.}\right)\text{/Fa}$$

The calculation of the refueling-based cetane number is carried out if refueling is noticed. The value of the refueling-based determined cetane number is reset to the initial value at the time of obtaining a result of the judgment of the cetane number based on the magnitude of the engine torque generated after the fuel injection.

[ASSESSING THE CETANE NUMBER BASED ON THE

ENGINE TORQUE] As the ignition quality of the fuel is higher, the amount of unburned fuel after combustion is smaller and the engine torque generated subsequent to fuel injection is larger. Hence, the electronic control unit performs 19th If an execution condition described below is met, a small amount of fuel is injected, finds or determines the size of the engine torque produced by the combustion of the small amount of injected fuel (produced torque or produced torque) and assesses the cetane number of the fuel based on the magnitude of the torque generated.

More specifically, the judgment of the cetane number based on the magnitude of the torque generated subsequently to the fuel injection (torque-based determined cetane number) is carried out by executing a torque-based determined cetane number calculation routine shown in FIG 4th is shown. The process of this routine is done by the electronic control unit 19th carried out repeatedly in a predetermined control cycle during the operation of the diesel engine.

When the process of this routine starts, go to step S100 determines whether the condition for performing the torque-based cetane number calculation is met. The execution condition is that all conditions (A) to (C) mentioned below are met. (A) The delay timing fuel cut of the diesel engine to be carried out in accordance with the interruption of the accelerator operation (ie, the depression of the accelerator pedal) is carried out. (B) The total amount of fuel injection resulting from the previous refill of the tank 10 follows is greater than or equal to a predetermined value α. The predetermined value α is set to a value that is greater than a total amount of fuel that is in the fuel lines that extend from the fuel tank 10 to the injectors 16 extend, can be introduced. That is, the fulfillment of condition (B) denotes the state that after the previous refueling, the fuel in the above-mentioned fuel lines is replaced by the newly supplied fuel from the fuel tank 10 was replaced. (C) It is not the case that the torque-based determined cetane number has been calculated by the routine a predetermined number of times or more consecutively than the previously calculated value. If the torque-based determined cetane number has been calculated by the routine a predetermined number of times or more often in succession than equal to the previously calculated value, it can be assumed that the calculated value of the torque-based determined cetane number remains unchanged in the next calculation. In such a case, therefore, the embodiment stops the calculation of the torque-based determined cetane number. Incidentally, the count of the number of times the torque-based cetane number has been calculated to be equal is reset at the point in time when refueling is detected.

If the execution condition is not met (NO), the execution of the routine ends immediately. If the execution condition is met (YES), the process goes to step S101 away. In step S101 Then, the fuel injection timing for detecting the cetane number of the fuel is adjusted based on the engine speed, the engine coolant temperature, and the intake air pressure. In addition, the engine speed, the engine coolant temperature, and the intake air pressure are used to calculate the fuel injection timing for the following reason.

The amount of fuel remaining unburned after combustion changes depending on the fuel injection time and the fuel's ability to ignite. If the fuel injection timing is relatively early, the time from the injection of the fuel to the in-cylinder pressure and / or the in-cylinder temperature decreases so that ignition is no longer possible is comparatively long. Therefore, if the fuel injection timing is earlier, the combustion continues for a longer period of time, and the amount of unburned fuel after combustion becomes smaller. On the other hand, when the fuel injection timing is later, the above-mentioned time from when the fuel is injected until no combustion is possible is shorter and the duration of the combustion is shorter, so that the amount of unburned fuel in the cylinder becomes larger. The time span from the injection of the fuel until the internal cylinder pressure and / or the internal cylinder temperature begin to decrease is shorter, the higher the engine speed. In order to standardize the combustion conditions, the point in time of the fuel injection for detecting the cetane number of the fuel must therefore be advanced further as the engine speed increases.

Further, when the cylinder wall temperature is relatively low, the maximum value of the in-cylinder temperature (peak value of the in-cylinder temperature) in the engine compression stroke is relatively low. When the intake air pressure is relatively low, the maximum value of the in-cylinder pressure (peak value of the in-cylinder pressure) in the engine compression stroke is relatively low. The lower the peak value of the inner cylinder temperature or the peak value of the inner cylinder pressure, the shorter the duration of a high temperature and high pressure phase in the cylinder, and the shorter the combustion duration. In order to make the combustion condition uniform, the fuel injection timing for detecting the cetane number must therefore be further advanced when the cylinder wall temperature is lower or the intake air pressure is lower.

Therefore, in this embodiment, in order to unify the combustion condition for detecting the cetane number of the injected fuel, the injection timing is set according to the engine speed, the cylinder wall temperature and the intake air pressure. More specifically, in this embodiment, the fuel injection timing for detecting the cetane number of the fuel is advanced as the engine speed is higher. Similarly, in this embodiment, the fuel injection timing for detecting the cetane number of the fuel is further advanced as the engine coolant temperature, which is an index value of the cylinder wall temperature, is lower. Also, in this embodiment, the timing of fuel injection for detecting the cetane number is advanced further when the intake air pressure is lower.

After the fuel injection timing has been set in the manner described above, a predetermined amount of fuel is injected at the set timing in the subsequent step S 102. Then, in step S 103, the magnitude of the (rotational) torque generated by this fuel injection is determined.

The calculation of the generated moment in step S103 is performed in the following manner. The electronic control unit 19th determines the engine speed at each specified cycle time and determines a difference between the detected engine speed and the engine speed in the previous cycle (finds a speed difference ΔNE).

5A shows the change or shift in the engine speed before and after the execution of the fuel injection for detecting the cetane number of the fuel and 5B shows the change or shift in the speed difference ΔNE at this point in time. Since the engine torque is generated due to the execution of the fuel injection for detecting the cetane number of the fuel, the engine speed increases or the rate of decrease of the engine speed decreases, so that the speed difference ΔNE increases. This time difference value of the increase in the speed difference ΔNE (which corresponds to the area of the hatched portion in 5B corresponds to) becomes larger, the larger the generated torque is. Therefore, in this embodiment, the time difference value of the increase in the speed difference ΔNE is calculated as an amount of change in the speed ΣΔNE, and the value of the amount is used as an index value of the generated torque.

In step S104 Then, the current fuel injection time and the current fuel injection amount are based on the time-dependent waveform of the fuel injection rate at in step S102 performed fuel injection is determined, and errors between the target values of the fuel injection timing and the fuel injection amount and the actual values of the fuel injection timing and the fuel injection amount (injection timing error and injection amount error) are calculated. Then, on the basis of the injection timing error and the injection quantity error, the amount of change in the rotational speed ΣΔNE is corrected. This correction is a correction of an amount corresponding to the amount of change in engine torque caused by the injection timing error and / or the injection amount error, and is performed to reduce the influence of the injection timing error and the injection amount error on the judgment result of the cetane number of the fuel. More specifically, the larger the injection timing error becomes toward the advance side (the side to which the injection timing is further advanced), the greater the generated torque, so that the amount of change in the rotational speed ΣΔNE for correction is further reduced. Furthermore, the larger the injection quantity error becomes on the side of an increase in quantity, the larger the generated torque, so that the amount of change in the rotational speed ΣΔNE for correction is further reduced.

Then in step S105 calculates a judged cetane number of the fuel based on a post-correction change amount of the rotational speed ΣΔNE and the engine rotational speed occurring at the time of execution of the fuel injection. The microcomputer of the electronic control unit 19th stores empirically predetermined relationships between the cetane number of the fuel and the amount of change in the speed ΣΔNE and the engine speed. The calculation from step S105 is executed based on these previously saved relationships. After the torque-based cetane number has been calculated, the execution of the routine ends.

[SETTING THE NUMBER OF CONTROLS]

As described above, the cetane number of the fuel currently in use is determined using three different assessment logics. These assessment logics differ from one another in the assessment principle and therefore sometimes output different assessment results with regard to the cetane number. In this embodiment, in order to avoid control lag in such a case, a judgment value of the cetane number of the fuel currently being used in the engine control, that is, a control cetane number, is set in the following manner.

The setting of the control cet number in this embodiment is carried out through the process of a control cet number setting routine shown in FIG 6th is shown. The process of this routine is repeated at predetermined control cycle times by the electronic control unit 19th carried out during operation of the diesel engine.

When the process starts the routine will first go to step S200 determines whether one of the three assessed values of the cetane number, that is to say the misfire-based certain cetane number, the refueling-based certain cetane number or the torque-based certain cetane number has been updated. If none of these three judgment values has been updated (NO), the process ends immediately. In this case, the control cetane number is kept at the current value.

On the other hand, if each of the three judgment values of the cetane number of the fuel has been updated (YES in step S200 ), the control cetane number is set to the lowest value of the misfire-based determined cetane number, the refueling-based determined cetane number and the torque-based determined cetane number, that is, the judgment result which outputs the lowest cetane number from the judgment results of the cetane number output by the three judgment logics. After that, the routine ends.

The operation of the above embodiment will now be described with reference to FIG 7th described. 7th Fig. 13 shows an example of the manner of changing the misfire-based detected cetane number, the refueling-based detected cetane number, the torque-based detected cetane number, and the control cetane number in the engine control apparatus of the embodiment.

Up to the point in time t1, the cetane number determined on the basis of torque is the smallest value of the cetane number determined on the basis of misfire, the cetane number determined on the basis of refueling and the cetane number determined on the basis of the torque. During the period up to time t1, therefore, the value of the torque-based cetane number is set as the value of the control cetane number.

If refueling takes place at time t1, the value of the refueling-based cetane number is updated, so that the value of the refueling-based cetane number is lower than the torque-based cetane number, which was the lowest assessment value of the cetane number of the fuel up to this point in time. From the point in time t1, the value of the refueling-based cetane number is therefore set as the value for the control cetane number.

Then, at time t2, the aforementioned execution condition is satisfied, and the judgment of the cetane number of the fuel based on the engine torque generated by the combustion of the fuel (the calculation of the torque-based determined cetane number) is carried out. In this judgment, the torque-based determined cetane number is calculated to be equal to the previous calculation result, so that the value of the torque-based determined cetane number does not change. Depending on the value of the torque-based determined cetane number, which is calculated at this point in time, the value of the refueling-based determined cetane number, which was updated due to the refueling at time t1, is reset to the initial value. As a result, the value of the refueling-based determined cetane number becomes larger than the value of the torque-based determined cetane number, so that the torque-based determined cetane number is the lowest value of the three evaluation values of the cetane number. Therefore, from time point t2, the value of the torque-based determined cetane number is set as the value of the control cetane number.

Then, if a misfire is detected at time t3, the value of the misfire is reduced based on the determined cetane number. As a result, the value of the misfire-based determined cetane number becomes lower than the value of the torque-based determined cetane number, which was the smallest value of the three judgment values of the cetane number of the fuel up to that point in time. Therefore, from time t3, the value of the misfire based determined cetane number is set as the value of the control cetane number.

If the tank is then refueled at time t4, the value of the refueling-based cetane number is updated. On the other hand, the value of the misfire-based detected cetane number is reset to the initial value in response to the refueling. As a result, the value of the refueling-based determined cetane number becomes lower than the value of the misfire-based determined cetane number and the value of the torque-based determined cetane number, so that, from time point t4, the currently updated value of the refueling-based determined cetane number is set as the value of the control cetane number.

Then, at time t5, the aforementioned execution condition is satisfied, and the process for calculating the torque-based determined cetane number is executed. In this calculation process, the torque-based cetane number is calculated to be equal to the value of the above calculation. Depending on the value of the torque-based determined cetane number that is calculated at this point in time, the value of the refueling-based determined cetane number, which was updated due to the refueling at time t4, is reset to the initial value. As a result, the value of the refueling-based determined cetane number becomes larger than the value of the torque-based determined cetane number, so that the value of the torque-based determined cetane number becomes the lowest value of the three judgment values of the cetane number. From the point in time t5, the value of the torque-based cetane number is therefore set as the value of the control cetane number.

Then, at time t6, the execution condition is met again and the process for calculating the torque-based cetane number is executed again. As a result, the value of the torque-based determined cetane number is increased. Then, from time t6, the increased value of the torque-based cetane number is set as the value of the control cetane number.

According to the control device for the internal combustion engine of the above-described embodiments, the following effects are obtained. In the embodiment, the control cetane number for use in engine control is set to the evaluation value of the cetane number which is the lowest of the three evaluation values of the cetane number (misfire-based determined cetane number, refueling-based determined cetane number and torque-based determined cetane number), which were determined using the individually different evaluation logics . Thus, even if the judgment values of the cetane number of the fuel are different from each other, control lag is prevented. Furthermore, since the judgment value of the cetane number, which indicates the lowest of the judgment values of the cetane number, is used, it is possible to avoid a certain robustness against the occurrence of misfires resulting from a low ignition quality of the fuel. According to this embodiment, even if a plurality of judgment methods are used to determine the ignition quality of the fuel currently being used, it is possible to prevent control lag and thus to properly execute engine control.

In the embodiment, the detection of the torque-based determined cetane number is no longer carried out if the torque-based determined cetane number has been calculated several times in succession with the same value. The detection of the torque-based determined cetane number is carried out by injecting fuel during a delay time point of fuel cut, during which no fuel injection normally takes place, and thus leads to fuel consumption which is usually unnecessary and to the generation of white smoke. In the embodiment, at the time point when it is determined that the value of the torque-based determined cetane number is substantially fixed, the detection of the torque-based determined cetane number is stopped. The fuel consumption for detection and the generation of white smoke associated with this condition can thus be suppressed.

In the embodiment, the value of the misfire-based determined cetane number is decreased in accordance with the detection of the misfire, and the value of the control cetane number is set to a value less than or equal to the value of the misfire-based determined cetane number. The reduced value of the misfire based determined cetane number is then maintained until refueling. In the embodiment, therefore, even if the value of the refueling-based determined cetane number and / or the value of the torque-based determined cetane number is large, the control cetane number is set low when a misfire occurs. Thus, even if unstable combustion that has led to misfire occurs, which is not the result of the poor ignition quality of the fuel, engine control can be carried out so that misfire can be avoided as much as possible. On the other hand, when refueling, the value of the misfire based determined cetane number is reset in response to the refueling, since it is believed that refueling can eliminate a factor for misfire. Because of this, it is possible to carry out an appropriate engine control which is accompanied by current circumstances in terms of combustion stability.

In this embodiment, the control device finds or determines on the basis of the time-dependent waveform of the fuel injection rate, which is based on the detection results of the fuel pressure in the injectors 16 was determined, the ACTUAL fuel injection time and the ACTUAL Fuel injection amount and corrects the generated torque (the amount of change in rotational speed ΣΔNE). Since the fuel injection amount for detecting the cetane number of the fuel is small, even a small change in the fuel injection timing and / or the fuel injection amount considerably affects the judgment results of the cetane number. In the embodiment, however, the actual fuel injection timing and the actual fuel injection amount are appropriately determined, and the calculation results of the generated torque are corrected. Therefore, the judgment of the cetane number based on the magnitude of the engine torque generated by the combustion of fuel can be carried out more accurately.

In the embodiment, the fuel injection timing for detecting the cetane number of the fuel is set according to the engine speed. More specifically, the timing of fuel injection for detecting the cetane number is advanced as the engine speed is higher. It is therefore possible to appropriately reduce the influence that a change in the generated torque depending on the engine speed has on the judgment results of the cetane number of the fuel.

In the embodiment, the fuel injection timing for detecting the cetane number of the fuel is set in accordance with the cylinder wall temperature. More specifically, the fuel injection timing for detecting the cetane number is advanced further when the engine coolant temperature, which is an index value of the cylinder wall temperature, is lower. It is therefore possible to appropriately suppress the influence that the change in the generated torque depending on the cylinder wall temperature has on the judgment result of the cetane number of the fuel.

In the embodiment, the fuel injection timing for detecting the cetane number of the fuel is set in accordance with the intake air pressure. More specifically, the fuel injection timing for detecting the cetane number is advanced the lower the intake air pressure. Therefore, it is possible to appropriately suppress the influence that the change in the generated torque depending on the intake air pressure has on the result of judging the cetane number of the fuel.

Besides, the above embodiment can also be carried out in the following modifications. Although in the above embodiment, it is detected that refueling has taken place by increasing the amount in the tank 10 remaining amount of fuel is determined by the fuel meter 11 is detected, the execution of the refueling can also be detected in other ways, for example by monitoring the opening / closing of the tank lid.

Although, in the embodiment, the amount of engine torque generated by the combustion of fuel is detected based on the change in the engine speed, the amount of engine torque generated by the combustion of fuel can also be determined based on other parameters, such as the amount of increase in the Internal cylinder pressure associated with combustion, or the like.

In the embodiment, although the fuel injection timing for detecting the cetane number of the fuel is set in accordance with the intake air pressure, the setting of the fuel injection timing can be omitted if the intake air pressure can be assumed to be substantially constant at the time the cetane number is detected, or if the changes in the torque generated by differences in intake air pressure are sufficiently low.

Although in the embodiment, the timing of fuel injection for detecting the cetane number of the fuel is set according to the cylinder wall temperature, the setting of the fuel injection timing can be omitted if it can be assumed that the cylinder wall temperature is substantially constant at the time of detecting the cetane number or the changes in the generated moments, which are caused by the differences in the cylinder wall temperature, are sufficiently small.

Although the fuel injection timing for detecting the cetane number is set in accordance with the engine speed in the above embodiment, the adjustment of the fuel injection timing can be omitted if it can be assumed that the engine speed is substantially constant at the time the cetane number is detected, or the changes of the generated torque, which are caused by differences in the engine speed, are sufficiently small.

In the above embodiment, there is a change in fuel pressure in each injector 16 is detected at the time of fuel injection to detect the cetane number, and the ACTUAL fuel injection time and the ACTUAL fuel injection quantity are determined on the basis of the result of the detection. Then, the amount of engine torque generated by the combustion of the fuel (the amount of change in the rotational speed ΣΔNE) is corrected in accordance with the ACTUAL fuel injection timing and the ACTUAL fuel injection amount obtained in the above-mentioned manner before it is used to judge the cetane number. However, if the fuel injection amount or the fuel injection timing can be controlled with sufficiently high accuracy, or if the change in the generated torque due to a change in the amount and / or the timing of the fuel injection is sufficiently small, it is possible to make the judgment of the cetane number of the fuel based on the magnitude of the torque generated by the combustion of the fuel can be determined more precisely without the need to carry out the correction.

In the above embodiment, when the value of the misfire-based determined cetane number of the fuel is temporarily decreased in response to the detection of the misfire, the decreased value of the misfire-based determined cetane number is maintained until refueling, so that a certain robustness to a Misfire can be ensured. In the case where other engine performances, for example fuel efficiency or output (power) are prioritized instead of robustness against misfire, it is possible to increase the value of the misfire based determined cetane number when the detection of the misfire ceases.

In the embodiment described above, when the torque-based determined cetane number of the fuel has been successively calculated with the same value several times, the detection of the torque-based determined cetane number is no longer performed. However, if the fuel consumption by the fuel injection for detecting the cetane number of the fuel and the generation of white smoke that accompanies this fuel injection can be sufficiently ignored, the torque-based determination of the cetane number can be continued even if the torque-based determination of the cetane number is carried out several times in a row was calculated with the same value.

Although in the embodiment the torque-based determined cetane number was detected during a fuel cutoff delay time, the torque-based determined cetane number can also be determined during a different time span than the fuel cutoff delay time.

Although the embodiment uses injectors 16 each of which uses the fuel pressure sensor 17th contains and using the pressure-electric actuator 39 works, it is also possible to use injectors that use other actuation (or control) methods, or injectors that do not have fuel pressure sensors 17th to have.

In the following, technical ideas that can be found from the above embodiment and its modifications will be described together with the effects of these technical ideas. The assessment of the ignition quality of the fuel based on the amount that has been refueled can also be based on the assumption that the fuel supplied during refueling can have the lowest ignition quality of all usable fuels.

The judgment of the ignition quality of the fuel based on the magnitude of the engine torque can also be made by calculating a judgment value of an index value of the ignition quality based on a relationship between the engine speed at the time of fuel injection, which is carried out for judgment, the magnitude of the engine torque, which is caused by the combustion of the is generated in accordance with the aforementioned fuel injection injected fuel, and take place at the time of fuel injection.

The judgment of the ignition quality of the fuel based on the magnitude of the engine torque can also be carried out using an amount of the change in the engine speed caused by the combustion of the fuel as an index value of the magnitude of the engine torque.

Claims (3)

A control device (19) for an internal combustion engine for judging a cetane number of fuel by using a plurality of different judgment logics which correspond one-to-one to the judgments, characterized in that the control device makes judgments of the cetane number of fuel based on: a circumstance, that a misfire occurs, a fueled amount, and a magnitude of the engine torque generated by the combustion of the fuel, and controls the internal combustion engine based on a lowest cetane number of the cetane numbers of fuel determined based on the various judgment logics. Control device for an internal combustion engine according to Claim 1 wherein the control device for an internal combustion engine stops executing the judgment of the cetane number of the fuel based on the magnitude of the engine torque generated by the combustion of the fuel when the cetane number of the fuel has the same value a predetermined number of times or more. An internal combustion engine control method for judging a cetane number of fuel by using a plurality of different judgment logics corresponding one-to-one with the judgments, characterized in that it comprises: performing judgments of the cetane number of fuel based on; a fact that a misfire occurs, a fueled amount, and an amount of engine torque generated by the combustion of the fuel, and executing control of the internal combustion engine based on a lowest cetane number of the cetane numbers of fuel determined based on the various judgment logics.

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