DE112022000672T5 - COMBUSTION ENGINE CONTROL DEVICE - Google Patents

Abstract

An internal combustion engine control device includes a combustion state estimating unit that estimates the combustion state of an engine based on a first in-cylinder pressure detected near an ignition timing and a second in-cylinder pressure detected near a combustion end timing. The combustion state estimation unit calculates the difference between the first in-cylinder pressure and the second in-cylinder pressure in multiple cycles and estimates the amount of torque variation of the internal combustion engine based on the variation rate of the difference in the multiple cycles.

Description

Technical area

The present invention relates to an internal combustion engine control device.

Technical background

In recent years, regulations on fuel consumption and harmful components in exhaust gases for automobile-type vehicles have been tightened, and there is a tendency that these regulations will be further tightened in the future. In this regard, a technology for estimating the state in a combustion chamber of an engine and controlling the engine based on the estimation result is known. By appropriately controlling the air-fuel ratio, ignition timing, and the like according to the current combustion state, the thermal efficiency of the engine can be increased and emissions of harmful gases can be reduced.

A method of obtaining a heat generation distribution and a combustion torque from a result of detection of an in-cylinder pressure by a pressure sensor is widely applied to the estimation of the combustion state of the engine. Such technology for estimating the state of combustion is disclosed, for example, in PTL 1 and PTL 2.

PTL 1 describes that providing an in-cylinder pressure sensor that detects the pressure within a cylinder, calculating a specified torque and a pumping loss torque based on the in-cylinder pressure detected by the in-cylinder pressure sensor, and calculating a torque of an internal combustion engine using the specified torque and the pumping loss Torque is calculated.

PTL 2 describes a technology in which the in-cylinder pressure is sampled at a crankshaft angle position of 60° before top dead center and at a crankshaft angle position of 60° after top dead center, and the detected pressure ratio is used as a combustion state parameter.

Quote list

Patent literature

• PTL 1: JP 2017-57803 A
• PTL 2: JP 2002-97996 A

Summary of the invention

Technical problem

The method described in PTL 1 for estimating the combustion state based on a measurement result (in-cylinder pressure) of the in-cylinder pressure sensor requires a time series pressure value in a predetermined portion of an engine cycle, for example, a portion with a crankshaft angle of 360° centered at the compression top dead center. Further, in order to estimate the combustion state with sufficient accuracy, it is necessary to sample the pressure at an interval of about 1° or less of the crankshaft angle. Therefore, a control device that estimates the combustion state must have a large storage capacity and a high computing power. In addition, a pressure sensor that supports fast scanning is also required. This results in the problem that the cost of the engine system increases.

Further, PTL 2 describes that the in-cylinder pressure is detected at the crankshaft angle position of 60° before top dead center and the crankshaft angle position of 60° after top dead center, but it was found that the combustion state of the internal combustion engine (engine) is not accurately determined based on the Inner cylinder pressure recorded at the positions can be estimated.

The present invention has been made in view of this situation, and an object of the present invention is to provide an internal combustion engine control apparatus capable of estimating the combustion state of an internal combustion engine at low cost.

the solution of the problem

An internal combustion engine control device according to the present invention includes a combustion state estimating unit that estimates the combustion state of an internal combustion engine based on a first in-cylinder pressure detected near an ignition timing and a second in-cylinder pressure detected near a combustion end timing.

Advantageous effects of the invention

According to the present invention, an internal combustion engine control apparatus capable of estimating the combustion state of an internal combustion engine at low cost can be provided.

Problems, configurations and effects different from those described above will be understood from the following description of embodiments.

Brief description of the drawings

• 1 eine Schnittansicht eines Gesamtkonfigurationsbeispiels eines Motors gemäß einer ersten Ausführungsform der vorliegenden Erfindung,
• 2 ein Blockdiagramm eines Konfigurationsbeispiels einer Steuereinrichtung gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 3 ein Flussdiagramm eines Beispiels der Verarbeitung zum Schätzen des Betrags der Motordrehmomentvariation, wobei die Verarbeitung durch eine Drehmomentvariation-Schätzeinheit der Steuereinrichtung gemäß der ersten Ausführungsform der vorliegenden Erfindung ausgeführt wird,
• 4 ein Kennfeld einer Korrelation zwischen der Zyklusvariationsrate eines Differenzdrucks und dem Betrag der Motordrehmomentvariation gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 5 einen Graph eines Beispiels eines Zeitablaufs für die Erfassung des Zylinderinnendrucks gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 6 ein Kennfeld eines Beispiels eines Schätzfehlers der Drehmomentvariation in Abhängigkeit von der Differenz zwischen dem Erfassungszeitpunkt des ersten Zylinderinnendrucks und dem Zündzeitpunkt gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 7 ein Diagramm eines wünschenswerten Modus einer Änderung des Erfassungszeitpunkts des ersten Zylinderinnendrucks in Abhängigkeit von einer Änderung des Zündzeitpunkts gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 8 ein Kennfeld eines Beispiels eines Schätzfehlers der Motordrehmomentvariation in Abhängigkeit von der Differenz zwischen der Erfassungszeit des zweiten Zylinderinnendrucks und CA90 + 20° gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 9 ein Kennfeld einer Beziehung zwischen dem Verbrennungszeitpunkt und dem Integralwert der Wärmeerzeugungsrate gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 10 ein Diagramm eines wünschenswerten Modus einer Änderung der Erfassungszeit für den zweiten Zylinderinnendruck in Abhängigkeit von einer Änderung von CA90 + 20° gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 11 ein Diagramm eines Beispiels eines Steuerblocks der Steuereinrichtung, welche die Abgasrezirkulations(EGR)-Steuerung ausführt, gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 12 ein Diagramm eines Beispiels der Steuerung eines Aktuators auf der Grundlage der Abweichung δCoV in einem EGR-System gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 13 ein Diagramm eines Beispiels, bei dem die Steuereinrichtung gemäß der ersten Ausführungsform der vorliegenden Erfindung die Zündenergiemenge, die Gasströmungsintensität, das Kompressionsverhältnis und die Ansauglufttemperatur auf der Grundlage der Abweichung δCoV steuert,
• 14 ein Diagramm eines Beispiels der Steuerung des Aktuators auf der Grundlage der Abweichung δCoV in einem Magerverbrennungssystem gemäß der ersten Ausführungsform der vorliegenden Erfindung,
• 15 ein Blockdiagramm eines Konfigurationsbeispiels einer Steuereinrichtung gemäß einer zweiten Ausführungsform der vorliegenden Erfindung,
• 16 ein Kennfeld einer Korrelation zwischen dem Referenz-Verbrennungsschwerpunkt und dem Verhältnis zwischen dem ersten Zylinderinnendruck und dem zweiten Zylinderinnendruck gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 17 ein Diagramm eines Beispiels eines Korrekturbetrags für den Referenz-Verbrennungsschwerpunkt in Abhängigkeit von einer Änderung des volumetrischen Wirkungsgrads gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 18 ein Diagramm eines Beispiels eines Korrekturbetrags für den Referenz-Verbrennungsschwerpunkt in Abhängigkeit von einer Änderung der Motordrehzahl gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 19 ein Flussdiagramm eines Beispiels einer Prozedur zum Schätzen des Verbrennungsschwerpunkts, wobei die Prozedur von einer Verbrennungsschwerpunkt-Schätzeinheit der Steuereinrichtung gemäß der zweiten Ausführungsform der vorliegenden Erfindung ausgeführt wird,
• 20 ein Diagramm einer allgemeinen Beziehung zwischen einem optimalen Verbrennungsschwerpunkt und der Kraftstoffverbrauchsrate eines Motors gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 21 ein Diagramm eines Beispiels eines Steuerblocks der Steuereinrichtung, die eine EGR-Steuerung ausführt, gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 22 ein Kennfeld einer Korrelation zwischen der Differenz zwischen dem ersten Zylinderinnendruck und dem zweiten Zylinderinnendruck und dem Referenz-Verbrennungsschwerpunkt gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 23 ein Diagramm eines Beispiels eines zeitlichen Verlaufs des Zündsignals, der Primärspannung und der Sekundärspannung einer Zündspule und des Sekundärstroms gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 24 ein Kennfeld einer Korrelation zwischen dem Maximalwert der Primärspannung und dem Maximalwert der Sekundärspannung unmittelbar nach Beginn der Entladung und dem Zylinderinnendruck während der Entladung gemäß der zweiten Ausführungsform der vorliegenden Erfindung,
• 25 ein Blockdiagramm eines Konfigurationsbeispiels von der Zündspule bis zur Steuereinrichtung, falls die Steuereinrichtung gemäß der zweiten Ausführungsform der vorliegenden Erfindung den Zylinderinnendruck auf der Grundlage der Sekundärspannung der Zündspule erhält,
• 26 ein Kennfeld einer Korrelation zwischen der Entladungsperiode und dem Zylinderinnendruck während der Entladung gemäß der zweiten Ausführungsform der vorliegenden Erfindung und
• 27 ein Blockdiagramm eines Konfigurationsbeispiels von einem Kurbelwellenwinkelsensor bis zur Steuereinrichtung, falls die Steuereinrichtung gemäß der zweiten Ausführungsform der vorliegenden Erfindung den Zylinderinnendruck auf der Grundlage der Winkelbeschleunigung einer Kurbelwelle erhält.

Show it:

• 1 1 is a sectional view of an overall configuration example of an engine according to a first embodiment of the present invention,
• 2 a block diagram of a configuration example of a control device according to the first embodiment of the present invention,
• 3 is a flowchart of an example of processing for estimating the amount of engine torque variation, the processing being carried out by a torque variation estimating unit of the controller according to the first embodiment of the present invention,
• 4 a map of a correlation between the cycle variation rate of a differential pressure and the amount of engine torque variation according to the first embodiment of the present invention,
• 5 12 is a graph showing an example of timing for detecting the in-cylinder pressure according to the first embodiment of the present invention,
• 6 1 is a map of an example of an estimation error of the torque variation depending on the difference between the detection timing of the first in-cylinder pressure and the ignition timing according to the first embodiment of the present invention,
• 7 a diagram of a desirable mode of change in detection timing of the first in-cylinder pressure depending on a change in ignition timing according to the first embodiment of the present invention,
• 8th 1 is a map of an example of an estimation error of the engine torque variation depending on the difference between the detection time of the second in-cylinder pressure and CA90 + 20° according to the first embodiment of the present invention,
• 9 a map of a relationship between the combustion timing and the integral value of the heat generation rate according to the first embodiment of the present invention,
• 10 12 is a diagram of a desirable mode of change in detection time for the second in-cylinder pressure depending on a change of CA90 + 20° according to the first embodiment of the present invention,
• 11 12 is a diagram of an example of a control block of the control device that executes the exhaust gas recirculation (EGR) control according to the first embodiment of the present invention,
• 12 a diagram of an example of controlling an actuator based on the deviation δCoV in an EGR system according to the first embodiment of the present invention,
• 13 a diagram of an example in which the control device according to the first embodiment of the present invention controls the ignition energy amount, the gas flow intensity, the compression ratio and the intake air temperature based on the deviation δCoV,
• 14 a diagram of an example of control of the actuator based on the deviation δCoV in a lean-burn system according to the first embodiment of the present invention,
• 15 a block diagram of a configuration example of a control device according to a second embodiment of the present invention,
• 16 a map of a correlation between the reference center of combustion and the ratio between the first in-cylinder pressure and the second in-cylinder pressure according to the second embodiment of the present invention,
• 17 is a diagram showing an example of a correction amount for the reference center of combustion depending on a change in volumetric efficiency according to the second embodiment of the present invention,
• 18 is a diagram showing an example of a reference combustion center correction amount depending on a change in engine speed according to the second embodiment of the present invention,
• 19 a flowchart of an example of a procedure for estimating the center of combustion, the procedure being carried out by a center of combustion estimating unit of the control device according to the second embodiment of the present invention,
• 20 12 is a diagram of a general relationship between an optimal center of combustion and the fuel consumption rate of an engine according to the second embodiment of the present invention,
• 21 12 is a diagram of an example of a control block of the controller executing EGR control according to the second embodiment of the present invention,
• 22 a map of a correlation between the difference between the first in-cylinder pressure and the second in-cylinder pressure and the reference center of combustion according to the second embodiment of the present invention,
• 23 a diagram of an example of a time profile of the ignition signal, the primary voltage and the secondary voltage of an ignition coil and the secondary current according to the second embodiment of the present invention,
• 24 a map of a correlation between the maximum value of the primary voltage and the maximum value of the secondary voltage immediately after the start of the discharge and the in-cylinder pressure during the discharge according to the second embodiment of the present invention,
• 25 a block diagram of a configuration example from the ignition coil to the controller if the controller according to the second embodiment of the present invention obtains the in-cylinder pressure based on the secondary voltage of the ignition coil,
• 26 a map of a correlation between the discharge period and the in-cylinder pressure during discharge according to the second embodiment of the present invention and
• 27 1 is a block diagram of a configuration example from a crankshaft angle sensor to the controller if the controller according to the second embodiment of the present invention obtains the in-cylinder pressure based on the angular acceleration of a crankshaft.

Description of embodiments

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the present description and drawings, components having substantially the same function or configuration are referred to by the same reference numeral and overlapping description is omitted.

<First Embodiment>

[Configuration example of a motor]

First, with reference to 1 describes an example of an engine to which the present invention is applied.

1 is a sectional view showing an example of the overall configuration of an engine 1 according to a first embodiment of the present invention.

Engine 1 is an example of a four-stroke gasoline engine with spark ignition. A combustion chamber of the engine 1 is formed by an engine head, a cylinder 13, a piston 14, an intake valve 15 and an exhaust valve 16. In the engine 1, a fuel injection valve 18 is provided at an intake passage 21, and an injector of the fuel injection valve 18 penetrates into the intake passage 21, so that a so-called port injection internal combustion engine is formed.

A spark plug 17b is mounted on the engine head, and an ignition coil 17a is mounted on the spark plug 17b. A pressure sensor 10 is provided on the motor head. For example, the pressure sensor 10 detects the in-cylinder pressure in a cylinder 13 by detecting the deformation of a metal diaphragm due to a differential pressure through a piezoresistive element.

Air for combustion is sucked into the combustion chamber via an air cleaner 19, a throttle valve 20 and the intake duct 21. The combustion gas (exhaust gas) emerging from the combustion chamber is discharged into the atmosphere via an exhaust gas duct 24 and a catalytic converter 25.

The amount of air drawn into the combustion chamber is measured by an air flow sensor 22 provided in front of the throttle valve 20. The air-fuel ratio of the gas (exhaust gas) exhausted from the combustion chamber is detected by an air-fuel ratio sensor 27 provided in front of the catalyst 25.

The exhaust duct 24 and the intake duct 21 are connected to one another via an exhaust gas recirculation line 28, and a so-called exhaust gas recirculation system (EGR system) is formed, in which part of the exhaust gas flowing through the exhaust duct 24 enters the interior of the intake duct 21 is returned. The amount of exhaust gas flowing through the EGR line 28 is adjusted by an EGR valve 29.

Furthermore, a control rotor 26 (signal rotor) is provided in a shaft section of a crankshaft. A crank angle sensor 11 (detection unit) disposed near the control rotor 26 (detection target unit) detects the rotation of the control rotor 26 to detect the rotation and phase of the crankshaft, i.e. H. the engine speed. Detection signals of the pressure sensor 10, the crank angle sensor 11, the air flow sensor 22 and the air-fuel ratio sensor 27 are input to the controller 12.

The controller 12 is an example of a control device of the engine 1, and an engine control unit (ECU), for example, is used. The controller 12 gives commands such as the opening degree of the throttle valve 20, the opening degree of the EGR valve 29, the timing of fuel injection by the fuel injection valve 18 and the amount of fuel injected thereby, and the timing of ignition by the spark plug 17b based on the detection values of various Sensors and controls the motor 1 so that it is in a predetermined operating state.

Although in 1 Although only a single cylinder is shown to illustrate the configuration of the combustion chamber of the engine 1, the engine according to the present embodiment may be a multi-cylinder engine having a plurality of cylinders.

[Configuration Example of Control Device]

2 is a block diagram showing a configuration example of the controller 12 according to the first embodiment of the present invention.

The control device 12 has an input/output unit 121, a control unit 122 and a memory unit 123, which are electrically connected to one another via a system bus (not shown).

The input/output unit 121 has an input port and an output port (not shown), and performs input and output processing of various signals to each device and sensor in the vehicle on which the engine 1 is mounted. For example, the input/output unit 121 reads a signal from the pressure sensor 10 and sends the signal to the control unit 122. In addition, the input/output unit 121 outputs a control signal to each device according to a command from the control unit 122.

The control unit 122 controls the operation of the engine 1. For example, the control unit 122 controls the throttle opening degree, the EGR opening degree, the fuel injection amount and the ignition timing depending on a combustion stability state of the engine 1. The control unit 122 according to the first embodiment has a torque variation estimation unit 122a and an engine control unit 122b. The torque variation estimation unit 122a is used as an example of a combustion state estimation unit.

The torque variation estimation unit 122a estimates the amount of engine torque variation based on the in-cylinder pressure detected by the pressure sensor 10. The combustion state of the engine 1 estimated according to the present embodiment is the amount from the torque variation estimation unit of the engine. The combustion state estimation unit (torque variation estimation unit 122a) estimates the combustion state of the internal combustion engine (engine 1) based on a first in-cylinder pressure P1 detected near an ignition timing and a second in-cylinder pressure P2 detected near a combustion end timing . Therefore, the combustion state estimation unit (torque variation estimation unit 122a) calculates the difference between the first in-cylinder pressure P1 and the second in-cylinder pressure P2 in a number of cycles and estimates the amount of torque variation of the internal combustion engine (engine 1) based on the variation rate of the difference in the Number of cycles.

The engine control unit (engine control unit 122b) controls the EGR rate or the air-fuel ratio based on the amount of engine torque variation. For example, the engine control unit 122b may control the EGR rate or the air-fuel ratio by estimating the EGR opening degree, the throttle opening degree, and the fuel injection amount of the engine 1 based on the amount of engine torque variation estimated by the torque variation estimating unit 122a is received, changes. The engine control unit (engine control unit 122b) may also control ignition energy, in-cylinder flow intensity, compression ratio, or intake air temperature based on the amount of engine torque variation.

The memory unit 123 may or may not be a volatile memory such as a random access memory (RAM). volatile memory such as read-only memory (ROM). Recorded in the control unit 123 is a control program that is executed by an arithmetic processing device (not shown) included in the control device 12. The arithmetic processing device reads the control program from the storage unit 123 and executes the control program, thereby implementing the function of each block of the control unit 122. As the calculation processing device, for example, a central processing unit (CPU) or a microprocessor unit (MPU) is used. The controller 12 may include a non-volatile auxiliary storage device including a semiconductor memory or the like, and the control program described above may be stored in the auxiliary storage device.

[Processing of Estimation of Engine Torque Variation Amount]

Next, an example of processing the estimation of the amount of engine torque variation performed by the controller 12 will be described with reference to 3 described.

3 is a flowchart illustrating an example of processing the estimation of the amount of engine torque variation performed by the torque variation estimating unit 122a of the controller 12.

First, the torque variation estimation unit 122a initializes a variable S and a variable Q to 0 (S1). Then, the torque variation estimation unit 122a detects the first in-cylinder pressure P1 (referred to as “in-cylinder pressure P1” in the drawing) near the ignition timing (S2) detected by the pressure sensor 10. Subsequently, the torque variation estimating unit 122a detects the second in-cylinder pressure P2 (referred to as “in-cylinder pressure P2” in the drawing) near the combustion end timing (S3) detected by the pressure sensor 10.

Subsequently, the torque variation estimating unit 122a calculates the differential pressure dP = P2 - P1 between the second in-cylinder pressure P2 and the first in-cylinder pressure P1 (S4) and adds dP to the variable S (S5). Further, the squared value of dP is added to the variable Q (S6). The torque variation estimating unit 122a repeats the processing from step S2 to step S6 N times (e.g., N = 100), which is set as a predetermined number of cycles, to assign an integrated value of the pressure differences dP for N cycles as the variable S receive. In addition, the torque variation estimation unit 122a obtains an integrated value of the squares of the pressure differences dP for N cycles as the variable Q.

Next, the torque variation estimation unit 122a divides the integrated value S of the pressure differences dP by the predetermined number N of cycles to obtain a cycle average value dPmean of the pressure differences dP (S7).

Next, the torque variation estimation unit 122a obtains the cycle variation rate Cov from dP of the differential pressure dP (S8). The cycle variation rate Cov of dP of the differential pressure dP is obtained by the following formula (1) by normalizing the cycle standard deviation of the differential pressure dP with the cycle mean dPmean of the pressure differences dP and expressed as a percentage. A coefficient of variation is represented by Cov.

[Math. 1] $$\text{CoV from dP}=\left[{\left\{Q\text{/}N-dPmea{n}^2\right\}}^{1\text{/}2}\text{/}dPmean\right]\times 100$$

Next, the torque variation estimation unit 122a calculates the amount Cov of IMEP of the engine torque variation from the cycle variation rate Cov of dP of the differential pressure dP (S9). Here, a method of calculating the amount of engine torque variation in step S9 is described with reference to 4 described.

4 is a map showing a correlation between the cycle variation rate Cov of dP [%] of the differential pressure dP and the amount (Cov of IMEP [%]) of the engine torque variation. This map illustrates the results of actually measuring the cycle variation rate Cov of dP, the differential pressure dP and the amount (Cov of IMEP) of engine torque variation using a spark ignition engine.

The amount of engine torque variation is defined as Cov of IMEP [%], which is an amount obtained by normalizing the standard deviation of the specified mean effective pressure (IMEP) in N cycles with the mean of the IMEPs in N cycles.

According to the new finding of the inventor of the present application, it was found that a strong correlation is obtained between the indicator Cov of IMEP, which indicates the amount (degree) of engine torque variation, and the cycle variation rate Cov of dP of the differential pressure dP, as in 4 shown. Therefore, the inventor of the present application has found that the amount of engine torque variation can be estimated from the cycle variation rate Cov of dP of the differential pressure dP.

In the memory unit 123 of the control device 12, the correlation between Cov of IMEP and Cov of dP obtained in advance by calibration is stored as a correlation formula or table data. The torque variation estimation unit 122a refers to the correlation formula or the table data from the storage unit 123 and obtains the amount Cov of IMEP of the engine torque variation from Cov of dP.

Then, the torque variation estimating unit 122a sends the obtained amount Cov of IMEP of the engine torque variation to the engine control unit 122b (S10). After a predetermined time, the processing of this flowchart is executed again from step S1.

Here is with reference to 5 a time sequence for recording the internal cylinder pressure is described.
5 is a graph showing an example of the timing of in-cylinder pressure detection. In the in 5 In the diagram shown, the horizontal axis represents a crank angle [degrees] and the vertical axis represents the cylinder internal pressure [bar].

The graph (1) of 5 shows an example of the timing of the detection of the internal cylinder pressure according to the prior art. From the state of change in in-cylinder pressure shown in graph (1), it can be seen that the in-cylinder pressure becomes maximum when the crank angle is about 360°.

A prior art control device disclosed in PTL 1 detects the in-cylinder pressure measured by an in-cylinder pressure sensor at a high sampling rate (e.g., an interval in which the crank angle is 1 degree or less) to determine the combustion state of a combustion chamber. The circles drawn in the graph show the times when the internal cylinder pressure was recorded. However, in the method according to the prior art, in which the control device detects the in-cylinder pressure at a high sampling rate, not only is a computing load imposed on the control device, but the storage capacity for storing the in-cylinder pressure detected by the control device must also be increased. For this reason, when using the prior art method, the cost of the engine system increases.

A prior art control device disclosed in PTL 2 also detects the combustion state of an engine using in-cylinder pressures at two points of a crank angle position of 60° before a top dead center and a crank angle position of 60° after top dead center can be detected, which, however, is different from the detection time for the in-cylinder pressure according to the present embodiment. Therefore, to detect the combustion state with the technology disclosed in PTL 2, complicated calculations are required and the combustion state cannot be accurately estimated at low cost.

[Print Capture Timing]

The graph (2) in 5 shows an example of the timing of detecting the in-cylinder pressure according to the present embodiment. The change in in-cylinder pressure shown in graph (2) is similar to the change in in-cylinder pressure shown in graph (1). An ignition point represented by an ignition mark and a combustion duration represented by a thick bar line have been newly added to the drawing.

In the combustion state estimation processing executed by the controller 12 according to the first embodiment, the in-cylinder pressure is detected at two times in one cycle. The two times include a time at which the first in-cylinder pressure P1 is detected in a compression stroke (“Detection of P1 pressure” in the drawing), and a time at which the second in-cylinder pressure P2 is detected in an expansion stroke (“Detection of P2 pressure” in the drawing). The time at which the control device 12 detects the first cylinder internal pressure P1 is close to the ignition point. The time at which the control device 12 detects the second cylinder internal pressure P2 is close to the end of combustion time. The reason why the detection timing of the in-cylinder pressure is defined in this way is that the amount of combustion energy generated by combustion is represented as the difference between the in-cylinder pressures before and after combustion.

For example, if the detection timing of the first in-cylinder pressure P1 is before the ignition timing, the energy of compression of the gas in the cylinder from the pressure detection time to the ignition timing, which is the start timing of combustion, is determined by the difference between the first in-cylinder pressure P1 and the second Inner cylinder pressure P2 is shown. For example, if the detection time of the second cylinder internal pressure P2 is after the end time of combustion, the energy of expansion of the gas in the cylinder from the end time of combustion to the printer detection time is represented by the difference between the first internal cylinder pressure P1 and the second internal cylinder pressure P2.

The compression energy and the expansion energy influence the energy generated by combustion too much and cause an estimation error in the combustion state estimation processing according to the first embodiment. Therefore, for accurate estimation of the combustion state by the control device 12, the detection timing of the first in-cylinder pressure P1 is preferably as close as possible to the ignition timing, and the detection timing of the second in-cylinder pressure P2 is preferably as close as possible to the combustion end timing. Then, the controller 12 determines the combustion state (the ignition timing or the like) of the engine 1 based on the first in-cylinder pressure P1 and the second in-cylinder pressure P2 detected at two times. As a result, the computing load of the control device 12 is reduced and the storage capacity for storing the in-cylinder pressure can be reduced.

6 is a map showing an example of an estimation error of the engine torque variation with respect to the difference (ms) between the detection timing of the first in-cylinder pressure P1 and the ignition timing. The ignition timing is the time at which the discharge for ignition is initiated in the spark plug 17b. This map shows how an error [%] between an estimated value and a measured value of the amount of engine torque variation according to the first embodiment depends on the difference between the detection time of the first in-cylinder pressure P1 and the ignition timing.

As in 6 As shown, the estimation error of the amount of engine torque variation increases with the difference between the detection time of the first in-cylinder pressure P1 and the ignition timing. Therefore, an allowable error is set for estimating the amount of engine torque variation. In order to make the estimation error of the amount of engine torque variation smaller than an error required in engine control, the difference between the detection timing of the first in-cylinder pressure P1 and the ignition timing is desirably at most 1 ms. Therefore, the combustion state estimation unit (torque variation estimation unit 122a) sets the difference between the detection timing of the first in-cylinder pressure P1 and the ignition timing of the cylinder to at most 1 ms.

7 is a diagram showing a desirable mode of changing the detection timing for the first in-cylinder pressure P1 depending on a change in the ignition timing. In 7 the dotted line indicates that the ignition timing and the detection timing of the first in-cylinder pressure P1 are the same. The solid line indicates that the difference between the ignition timing and the detection timing of the first in-cylinder pressure P1 is 1 ms. That is, a range located between the two solid lines is a desired detection time for the first in-cylinder pressure P1. Therefore, the combustion state estimating unit (torque variation estimating unit 122a) changes the detection timing of the first in-cylinder pressure P1 according to the ignition timing of the cylinder.

8th is a map showing an example of an estimation error of the engine torque variation with respect to the difference (°) between the detection timing of the second in-cylinder pressure P2 and a timing delayed by 20° from a 90% combustion timing CA90 (hereinafter abbreviated as “CA90 + 20°”) timing shows. This map shows how an error [%] between an estimated value and a measured value of the amount of engine torque variation depends on the difference between the detection time of the second in-cylinder pressure P2 and CA90 + 20°. Therefore, the combustion state estimation unit (torque variation estimation unit 122a) changes the detection timing of the second in-cylinder pressure P2 according to the 90% combustion timing CA90 of the cylinder.

As in 8th As shown, the estimation error of the amount of engine torque variation increases as the difference between the detection time of the second in-cylinder pressure P2 and CA90 + 20° increases. Therefore, an allowable error is set for estimating the amount of engine torque variation. In order to make the estimation error of the amount of engine torque variation smaller than the error required in engine control, the difference between the detection time of the second in-cylinder pressure P2 and CA90 + 20° is desirably at most 10°.

9 is a map showing a relationship between the combustion timing and an integral value of the heat generation rate.

The 90% combustion timing CA90 shown in the drawing is defined as the crankshaft angle (°) at which the integral value of the heat generation rate is 90% when the integral value of the heat generation rate at the end of combustion is 100%. Similar is a 50% burn time Point CA50 is defined as the crank angle at which the integral value of the heat generation rate is 50%. The combustion time CA50 is also referred to as the reference combustion center CA50ref.

Because the combustion rate changes for each cycle, the 90% combustion timing also changes for each cycle. Therefore the in 9 90% combustion time CA90 shown according to the first embodiment indicates the 90% combustion time averaged over a predetermined number of cycles (for example 100 cycles).

10 is a diagram showing a desirable mode of changing the detection timing of the second in-cylinder pressure P2 depending on a change of CA90 + 20°. In 10 the dotted line indicates that CA90 + 20° and the detection time of the second in-cylinder pressure P2 are the same. The solid line indicates that the difference between CA90 + 20° and the detection time of the second in-cylinder pressure P2 is 10°. That is, a range located between the two solid lines is a desired detection time for the second in-cylinder pressure P2. Therefore, the combustion state estimation unit (torque variation estimation unit 122a) sets the difference between the detection timing of the second in-cylinder pressure P2 and the timing delayed by 20° from the 90% combustion timing CA90 (90% combustion timing CA90 + 20°) of the cylinder to at most 10 °.

In general, the 90% combustion timing CA90 depends on engine operating condition parameters such as engine speed, load, air-fuel ratio, EGR rate, ignition timing and cooling water temperature. In the memory unit 123 of the control device 12, the 90% combustion time CA90 for the engine operating state parameter, obtained in advance through calibration, is stored as map data. The torque variation estimation unit 122a may obtain the 90% combustion timing CA90 by referring to the map data based on the current engine operating state parameter.

[EGR system]

Next, an example of engine control by the engine control unit 122b will be described.

For example, in the EGR system included in the engine 1, the controller 12 must appropriately control the EGR rate in order to increase the thermal efficiency of the engine 1. In general, when the EGR rate is increased at part load, the pumping loss is reduced and the thermal efficiency is increased. In addition, it is also possible to reduce cooling loss and NOx emissions because the combustion temperature is reduced by increasing the EGR rate. Further, it is also possible to suppress knocking and reduce exhaust loss by increasing the EGR rate at a high load.

On the other hand, if the EGR rate is too high, the ignition quality of the air-fuel mixture or a flame propagation property is reduced, thereby increasing the possibility of misfire occurring. Therefore, it is important that the controller 12 increases the EGR rate as much as possible within a misfire-free range or a misfire-permissible range in order to increase the thermal efficiency of the engine 1.

If a misfire cycle occurs during operation of the engine 1, the engine torque variation increases. Therefore, the controller 12 can increase the thermal efficiency of the engine while suppressing misfires by estimating the amount of engine torque variation and changing the EGR rate based on the amount of engine torque variation.

11 is a diagram showing an example of a control block of the controller 12 whereby the EGR control is executed. The torque variation estimation unit 122a estimates the current amount CoV of IMEP of the engine torque variation based on the output of the pressure sensor 10 of the engine 1.

A deviation calculation unit 122c included in the engine control unit 122b calculates a deviation δCoV by subtracting a target amount (target CoV) of the engine torque variation from the current amount CoV of IMEP of the engine torque variation. The target CoV is read out from the ROM of the storage unit 123 by the engine control unit 122b.

An operation amount calculation unit 122d included in the engine control unit 122b calculates an operation amount for an actuator of the engine 1 based on the deviation δCoV. The actuator is, for example, a device provided in the engine 1 for adjusting the opening degrees of the throttle valve 20 and the EGR valve 29 and for adjusting the ignition timing of the spark plug 17b. The actuation strength calculation Power unit 122d has, for example, a PID controller. The operation amount calculation unit 122d obtains the operation amount of the actuator of the engine 1 so that the current amount CoV of IMEP of the engine torque variation approaches the target amount (target CoV) of the engine torque variation. Then, the engine control unit 122b sends the operation strength of the actuator of the engine 1 to the engine 1 to control the operating state of the engine 1.

(Example of controlling the actuator in the EGR system)

12 is a diagram showing an example of controlling the actuator based on the deviation δCoV in the EGR system. The horizontal axis represents the deviation δCoV [%], and the vertical axis represents a state of the actuator or the like.

For example, when the actuator is controlled based on the deviation δCoV, the controller 12 of the EGR system suppresses the amount of engine torque variation as the deviation δCoV increases. Therefore, the controller 12 controls so that the opening degree (dotted line) of the EGR valve 29 and the opening degree (solid line) of the throttle valve 20 become small. Because the EGR rate is reduced by this control, the ignition delay time is shortened and the combustion rate is increased. Therefore, the controller 12 controls an ignition advance angle (the line with alternating long and short dashes) so that its magnitude is small to properly set the combustion timing (at a timing for optimal fuel consumption).

If the amount of engine torque variation is greater than or equal to a predetermined value, the EGR rate is controlled to a low value by the controller 12 to suppress a cycle variation of the torque. This controls the combustion of the engine 1 to be stable. If the amount of engine torque variation is less than the predetermined value, the controller 12 may increase the thermal efficiency of the engine 1 by setting the EGR rate to a high value.

It is also conceivable that the amount of ignition energy supplied to the spark plug 17b, the gas flow intensity in the cylinder, the compression ratio and the intake air temperature are adjustable, and the controller 12 controls the amounts of this adjustment based on the deviation δCoV.

13 is a diagram showing an example in which the controller 12 controls the ignition energy amount, the gas flow intensity, the compression ratio and the intake air temperature based on the deviation δCoV. In 13 the horizontal axis represents the deviation δCoV [%] and the vertical axis represents the ignition energy or the like.

In general, ignition or flame propagation is promoted and torque variation is suppressed when the ignition energy amount, in-cylinder gas flow intensity, compression ratio and intake air temperature are higher. Therefore it is as in 13 shown, it is desirable that the control device 12 carries out a control in which the values of these conditions increase as the deviation δCoV increases.

For example, the amount of ignition energy can be adjusted by the control device 12 by controlling the amount of current supplied to the spark plug 17b. The gas flow intensity in the cylinder can be adjusted by the control device 12 by controlling the flow speed of the air in the intake duct 21. The compression ratio can be adjusted by the control device 12 by controlling the position of the top dead center of the piston 14. The intake air temperature can be adjusted by the control device 12 by controlling the switching on/off of a heater provided in the intake duct 21.

In controlling these, the controller 12 may control the gas flow intensity, the compression ratio, or the intake air temperature alone or control some of them in combination. In addition to controlling them, the controller 12 may combine the above-described control of the EGR valve opening degree, the throttle valve opening degree, or the ignition advance angle.

[lean burn system]

Further, in the lean combustion system included in the internal combustion engine 1, it is also necessary to appropriately control the air-fuel ratio in order to increase the thermal efficiency of the engine 1. In general, when the air-fuel ratio is increased at part load, pumping loss is reduced and thermal efficiency is increased. In addition, because the combustion temperature is reduced by increasing the air-fuel ratio, it is also possible to reduce the cooling loss and NOx emission. On the other hand, if the air-fuel ratio is too high, the ignition quality of the air-fuel Fuel mixture or flame propagation characteristics are reduced, thereby increasing the possibility of misfires occurring. Therefore, it is important that the controller 12 performs control to increase the air-fuel ratio as much as possible within a range in which misfire does not occur or a range in which misfire is permitted in order to achieve the thermal To increase the efficiency of motor 1.

(Example of controlling the actuator in the lean combustion system)

14 is a diagram showing an example of controlling the actuator based on the deviation δCoV in the lean-burn system. In 14 the horizontal axis represents the deviation δCoV [%] and the vertical axis represents the state of the actuator or the like.

The control device 12 in the lean-burn system controls the actuator based on the deviation δCoV. For example, to suppress the cycle variation of torque, the controller 12 controls the actuator such that the opening degree (solid line) of the throttle valve 20 decreases as the deviation δCoV increases. Because the air-fuel ratio is reduced by this control, the ignition delay time is shortened and the combustion rate is increased. Therefore, the controller 12 controls the actuator such that the ignition advance angle (the line with alternating long and short dashes) decreases to appropriately set the combustion timing (at a timing for optimal fuel consumption).

By this control, in a case where the amount of engine torque variation is equal to or greater than a predetermined value, the air-fuel ratio is set to a low value to suppress the cycle variation of torque. By setting the air-fuel ratio to a low value, the combustion of the engine 1 is controlled to be stable. In a case where the amount of engine torque variation is smaller than the predetermined value, the air-fuel ratio is set to a high value so that the thermal efficiency can be increased.

The control of the ignition energy amount, the gas flow intensity in the cylinder, the compression ratio and the intake air temperature, as in 13 shown can also be applied to the lean combustion system as with the EGR system described above.

<Second Embodiment>

[Estimation of Center of Combustion]

Next, a control device according to a second embodiment of the present invention, which estimates the combustion center CA50 based on a first in-cylinder pressure P1 detected near an ignition timing and a second in-cylinder pressure P2 detected near a combustion end timing, will be described.

As in 9 As shown, the center of combustion CA50 is defined as a crankshaft angle at which the integral value of a heat generation rate is 100% when the integral value of the heat generation rate at the end of combustion is 50%. Further, the center of combustion changes for each cycle depending on a cycle variation of the combustion rate, and the center of combustion CA50 according to the second embodiment indicates the center of combustion averaged over a predetermined number of cycles (for example, 100 cycles).

15 is a block diagram showing a configuration example of a controller 12A according to the second embodiment.

The control device 12A has an input/output unit 121, a control unit 124 and a memory unit 123, which are electrically connected to one another via a system bus (not shown).

The input/output unit 121 and the storage unit 123 are similar to the input/output unit 121 and the storage unit 123 of the controller 12 according to the first embodiment, so a detailed description thereof is omitted.

The control unit 124 controls the operation of an engine 1. For example, the control unit 124 controls the throttle opening degree, the EGR opening degree, the fuel injection amount and the ignition timing depending on a combustion stability state of the engine 1. The control unit 124 according to the second embodiment has a combustion center estimation unit 124a and an engine control unit 124b.

The combustion center estimation unit 124a estimates the combustion center CA50 based on an in-cylinder pressure detected by a pressure sensor 10. The combustion state of the engine 1 estimated according to the present embodiment is the combustion center CA50.

An engine control unit (engine control unit 122b) controls ignition timing based on the ratio between a first in-cylinder pressure P1 and a second in-cylinder pressure P2. For example, the engine control unit 124b controls the ignition timing and the like of the engine 1 based on the combustion center CA50 obtained from the combustion center estimating unit 124a.

[Principle of center of combustion estimation]

Next, a principle of estimating the center of combustion with respect to the 16 until 18 described.

16 is a map showing a correlation between a reference combustion center CA50ref (°) and the ratio between the first in-cylinder pressure P1 and the second in-cylinder pressure P2. This map represents results of an actual measurement of the pressure ratio P2/P1 and the reference combustion center CA50ref when using a spark ignition engine. The combustion center estimation unit 124a detects the first in-cylinder pressure P1 near the ignition timing through the pressure sensor 10 and the second in-cylinder pressure P2 near the combustion end timing. 16 shows the result of measuring the pressure ratio P2/P1 and the reference combustion center CA50ref while keeping the volumetric efficiency and speed of the engine 1 constant. Here the volumetric efficiency is defined as the volumetric reference efficiency ηref and the speed is defined as the reference speed Nref.

According to new findings by the inventor of the present application, it was found that one in 16 shown strong correlation between the reference center of combustion CA50ref and the ratio P2/P1 between the first internal cylinder pressure P1 detected near the ignition point and the second internal cylinder pressure P2 recorded near the end of combustion time. Therefore, the inventor of the present application has found that the reference combustion center CA50ref can be estimated from the pressure ratio P2/P1.

In addition, according to new findings of the inventor of the present application, it has been found that the combustion center of gravity estimating unit 124a can estimate the combustion center of gravity CA50 at the current rotational speed and the current volumetric efficiency by correcting the reference combustion center of gravity CA50ref estimated with the reference volumetric efficiency ηref and the reference rotational speed Nref, if the volumetric efficiency is different from the reference volumetric efficiency ηref and the engine speed is different from the reference speed Nref.

17 is a diagram showing an example of a correction amount ΔCA50_1 (°) for the reference combustion center CA50ref depending on a change in volumetric efficiency (%).

18 is a diagram showing an example of a correction amount ΔCA50_2 (°) for the reference combustion center CA50ref depending on a change in engine speed (rpm).

Based on these correction amounts ΔCA50_1 and ΔCA50_2, the combustion center CA50 at the current speed and volumetric efficiency is obtained by the following formula (2).

[Math. 2] $$\text{APPROX}50=\text{APPROX}50\text{ref}+\mathrm{<figure-callout\; id="50"\; label="\Delta \; APPROX"\; filenames="DE112022000672T5\_0011.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\text{APPROX}50\_1+\mathrm{<figure-callout\; id="50"\; label="\Delta \; APPROX"\; filenames="DE112022000672T5\_0011.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\text{APPROX}50\_2$$

In addition, the combustion center estimation unit 124a can calculate the combustion center CA50 by obtaining the correction amount for the reference combustion center CA50ref for each reference value of not only the volumetric efficiency and the rotational speed but also, for example, the EGR rate, the air-fuel ratio, etc Estimate the ignition timing, the cooling water temperature and the like and make the correction to the reference combustion center CA50ref with higher accuracy.

Next, the processing for estimating the combustion center CA50 executed by the controller 12A is performed with reference to 19 described.
19 is a flowchart showing an example of a procedure for estimating the center of combustion by the center of combustion estimating unit 124a of the controller 12A.

First, the combustion center estimation unit 124a initializes a variable R to 0 (S21). Next, the combustion center estimation unit 124a receives the first in-cylinder pressure P1 near the ignition timing detected by the pressure sensor 10 (S22). The combustion center estimation unit 124a then receives the second in-cylinder pressure P2 detected by the pressure sensor 10 in the vicinity of the combustion end time (S23).

Next, the combustion center estimating unit 124a obtains the ratio PR=P2/P1 between the second in-cylinder pressure P2 and the first in-cylinder pressure P1 (S24), and adds the ratio PR to the variable R (S25). The combustion center estimating unit 124a repeats steps S22 to S25 a predetermined number N times (for example, N = 100), thereby obtaining the integrated value of the pressure ratios PR for N cycles as R.

After N cycles have elapsed, the combustion center estimation unit 124a obtains a cycle average PRmean of the pressure ratios PR by dividing the integrated value R of PR by the predetermined number N of cycles (S26).

Next, the combustion center estimation unit 124a calculates the reference combustion center CA50ref based on the average value PRmean of the pressure ratio PR (S27). In the storage unit 123 of the control device 12A, a correlation between the pressure ratio PR obtained in advance by calibration and the reference combustion center CA50ref is stored as a correlation formula or table data. The combustion center estimating unit 124a calculates the reference combustion center CA50ref based on the average value PRmean of the pressure ratio PR by referring to the correlation formula or the table data.

Then, the combustion center estimation unit 124a calculates the combustion center CA50 based on the reference combustion center CA50ref and the combustion center correction value ΔCA50. In the storage unit 123 of the controller 12A, a correlation between the volumetric efficiency and the center of combustion correction value, a correlation between the rotation speed and the center of combustion correction value, and the like obtained in advance by calibration are maintained as correlation formulas or table data. The combustion center estimation unit 124a obtains the sum of the combustion center correction values ΔCA50 by referring to the correlation formula or the table data, and adds the sum to the reference combustion center CA50ref to obtain the combustion center CA50 (S28).

Finally, the combustion center estimation unit 124a sends the obtained combustion center CA50 to the engine control unit 124b (S29).

[Motor control]

Next, an example of engine control by the engine control unit 124b will be described.

In order to increase the thermal efficiency of the engine, the center of combustion must be set appropriately.

20 is a graph showing a general relationship between an optimal center of combustion CA50 and the engine's fuel consumption rate.

In general, the work of compression of the piston increases and thermal efficiency decreases as the center of combustion is advanced from an appropriate point in time. Additionally, exhaust energy increases and thermal efficiency decreases as the center of combustion is delayed from the appropriate point in time (target).

Normally, the ignition timing in the engine is set in advance for each load and speed so that the center of combustion is at an optimal time. However, it is also conceivable that the center of combustion is shifted from the optimal point in time due to a change in an environmental condition, a change in properties of engine components over time, and the like. Therefore, by controlling the ignition timing and setting the combustion center at a predetermined optimal timing, the engine control unit 124b can maintain a high thermal efficiency of the engine even if the environmental condition or the characteristic of the engine component changes over time.

21 shows an example of a control block of the controller 12A, whereby the EGR control is carried out.

The combustion center estimation unit 124a estimates the current combustion center CA50 based on the output (in-cylinder pressure) of the pressure sensor 10 provided in the engine 1.

A deviation calculation unit 124c included in the engine control unit 124b obtains a deviation δCA50 between the current combustion center CA50 and a target combustion center CA50 (referred to as “target CA50” in the drawing).

An ignition timing calculation unit 124d included in the engine control unit 124b calculates the ignition timing of engine 1 based on the deviation δCA50. The ignition timing calculation unit 124d is implemented, for example, by a PID controller and obtains the ignition timing of the engine 1 such that the current combustion center of gravity approaches the target combustion center of gravity. Then, the engine control unit 124b sends the ignition timing obtained from the ignition timing calculation unit 124d to the engine 1, and the operation of the engine 1 is carried out at a new ignition timing.

Although the method for estimating the combustion center CA50 has been described in the present embodiment, the present invention is not limited to the combustion center CA50. The combustion state estimation unit may estimate a combustion phase based on the ratio between the first in-cylinder pressure P1 and the second in-cylinder pressure P2. For example, the combustion phase may be estimated to have a 10% combustion timing CA10 and the 90% combustion timing CA90 by the combustion state estimating unit using the ratio P2/P1 between the first in-cylinder pressure P1 detected near the ignition timing and that nearby second internal cylinder pressure P2 detected at the end of combustion can be estimated.

Furthermore, the pressure ratio is not limited to P2/P1 and may also be P1/P2. In addition, if the pressure difference ΔP = P2 - P1 or ΔP = P1 - P2 is used instead of the pressure ratio, the combustion phase can be estimated by a similar method. An example using the pressure difference ΔP = P2 - P1 is given with reference to 22 described.

22 is a map showing a correlation between the difference between the first in-cylinder pressure P1 and the second in-cylinder pressure P2 and the reference combustion center CA50ref (°). This map represents results of an actual measurement of the pressure difference P2 - P1 and the reference combustion center CA50ref when using a spark ignition engine. Here, similarly, the first cylinder internal pressure P1 is detected near the ignition timing by the pressure sensor 10 and the second cylinder internal pressure P2 is detected near the combustion end timing. 22 shows a result of a measurement of the pressure difference P2 - P1 and the reference combustion center CA50ref while keeping the volumetric efficiency and the speed of the engine 1 constant. Here the volumetric efficiency is defined as the volumetric reference efficiency ηref and the speed is defined as the reference speed Nref.

According to new findings by the inventor of the present application, it was found that one in 22 shown strong correlation between the reference combustion center CA50ref and the pressure difference P2 - P1 between the first cylinder internal pressure P1 detected near the ignition point and the second cylinder internal pressure P2 recorded near the end of combustion time. Therefore, the inventor of the present application has found that the reference combustion center CA50ref can be estimated from the pressure difference P2 - P1.

In addition, according to new findings of the inventor of the present application, it has been found that the combustion center of gravity estimating unit 124a can estimate the combustion center of gravity CA50 at the current rotational speed and the current volumetric efficiency by correcting the reference combustion center of gravity CA50ref estimated with the reference volumetric efficiency ηref and the reference rotational speed Nref, if the volumetric efficiency is different from the reference volumetric efficiency ηref and the engine speed is different from the reference speed Nref.

<Example of Obtaining In-Cylinder Pressure Using Discharge Voltage>

Although the example has been described in which the controllers 12 and 12A according to the above-described embodiments detect the in-cylinder pressure using the pressure sensor 10, the in-cylinder pressure can also be obtained using a method in which the pressure sensor 10 is not used.

For example, the control device 12 can obtain the in-cylinder pressure based on the discharge voltage of the ignition coil 17a. Therefore, the combustion state estimation unit (pressure calculation unit 31a) can obtain the first in-cylinder pressure P1 and the second in-cylinder pressure P2 based on a voltage value of the ignition coil (ignition coil 17a), a current value of the ignition coil (ignition coil 17a), or a discharge time of the ignition coil (ignition coil 17a).

23 is a diagram showing an example of the timing of an ignition signal, a primary voltage and a secondary voltage of the ignition coil 17a, and a secondary current. The ignition signal for the ignition coil 17a is generated by the control device 12. Then they change Voltage (primary voltage) on the primary side of the ignition coil 17a, the voltage (secondary voltage) on the secondary side and the current (secondary current) on the secondary side over time. The discharge period is defined as the period in which the secondary current begins to change when the ignition signal goes from a high level to a low level and returns to the original value.

24 is a map showing a correlation between a maximum value V1max of the primary voltage immediately after the start of the discharge, a maximum value V2max of the secondary voltage and an in-cylinder pressure during the discharge. 24 shows a state in which changes occur in the ignition signal, the primary voltage and the secondary voltage of the ignition coil 17a and the secondary current.

When the ignition signal goes from high to low level, a large potential difference is generated on the secondary side of the ignition coil 17a and a discharge is initiated in the spark plug 17b. The maximum value V2max (kV) of the secondary voltage immediately after the start of the discharge has a high correlation with the in-cylinder pressure during the discharge, as in 24 is shown. Therefore, the in-cylinder pressure during discharge can be obtained by measuring the maximum value V2max of the secondary voltage.

In addition, a counter electromotive force is generated on the primary side of the ignition coil 17a immediately after the discharge of the spark plug 17b, and the maximum value V1max (V) of the primary voltage immediately after the start of the discharge also has a high correlation with the in-cylinder pressure during the discharge, as shown in 24 is shown. Therefore, the controller 12 can also obtain the in-cylinder pressure during discharge by measuring the maximum value V1max of the primary voltage of the ignition coil 17a.

25 is a block diagram showing a configuration example from the ignition coil 17a to the controller 12 in a case where the controller 12 obtains the in-cylinder pressure based on the secondary voltage of the ignition coil 17a.

The internal combustion engine (engine 1) has the ignition coil (ignition coil 17a) and a voltage peak holding unit (peak holding circuit 30), which detects the voltage of the ignition coil (ignition coil 17a) and holds the peak value of the voltage of the ignition coil (ignition coil 17a). Then, the combustion state estimation unit (pressure calculation unit 31a) calculates the first in-cylinder pressure P1 and the second in-cylinder pressure P2 based on the peak value.

The secondary voltage of the ignition coil 17a is sent to the peak holding circuit 30, the peak value of the secondary voltage measured within a predetermined time is held by the peak holding circuit 30, and the peak value of the secondary voltage is detected as the maximum value V2max of the secondary voltage. The peak hold circuit 30 may be provided in a circuit that supplies the ignition signal to the ignition coil 17a.

The peak holding circuit 30 sends the maximum value V2max of the secondary voltage to the controller 12. The pressure calculation unit 31a in the controller 12 obtains the in-cylinder pressure during discharge using a correlation formula between the maximum secondary voltage V2max and the in-cylinder pressure obtained in advance by calibration or from table data.

In addition, the pressure calculation unit 31a performs processing for obtaining the in-cylinder pressure based on the primary voltage of the ignition coil 17a in the same manner as the processing for obtaining the in-cylinder pressure based on the secondary voltage. That is, the maximum value V1max of the primary voltage of the ignition coil 17a is detected by the peak holding circuit 30 and sent to the controller 12. The pressure calculation unit 31a provided in the controller 12 obtains the in-cylinder pressure during discharge using a correlation formula between the primary voltage maximum value V1max and the in-cylinder pressure obtained in advance by calibration or table data.

When the detection of the in-cylinder pressure by the ignition coil 17a is applied to a combustion state estimation method according to the present embodiment, the pressure calculation unit 31a first obtains the in-cylinder pressure P1 based on the secondary voltage maximum value V2max or the primary voltage maximum value V1max associated with the discharge at the ignition timing comes along. In addition, in the vicinity of the combustion end timing, the controller 12 sends the ignition signal to the ignition coil 17a, and the discharge is carried out from the ignition coil 17a. The second discharge occurs upon obtaining the second in-cylinder pressure P2, but ignition does not occur at this time. The pressure calculation unit 31a obtains the second in-cylinder pressure P2 based on the secondary voltage maximum value V2max or the primary voltage maximum value V1max of the ignition coil 17a during discharge.

If the pressure calculation unit 31a obtains the in-cylinder pressure based on the voltage of the ignition coil 17a, the ignition coil 17a must be charged and discharged, so the detection of the in-cylinder pressure must be carried out at regular intervals (for example, 4 ms or more). However, in the combustion state detection method according to the present embodiment, the pressure calculation unit 31a can detect the in-cylinder pressure near the ignition timing and near the combustion end timing. Usually, the interval between the ignition timing and the combustion end timing is longer than the time for charging/discharging the ignition coil 17a. Therefore, in the combustion state estimation method according to the present embodiment, it is preferable to adopt a method in which the in-cylinder pressure is detected based on the voltage of the ignition coil 17a.

When the pressure calculation unit 31a detects the in-cylinder pressure based on the voltage of the ignition coil 17a as described above, the pressure sensor 10 becomes unnecessary and the cost of the engine system can be reduced. In addition, no space needs to be provided for mounting the pressure sensor 10, resulting in the advantage that the degree of freedom for designing the engine with respect to, for example, a cooling water passage and the shape of the combustion chamber is increased.

(Example of Obtaining In-Cylinder Pressure Using Discharge Period)

The in-cylinder pressure can be obtained not only using the maximum voltage of the ignition coil 17a but also using the discharge period. In general, the discharge period of the ignition coil 17a decreases as the in-cylinder pressure increases. 26 shows as a discharge period the period from the start of discharge to the time when the secondary current of the ignition coil 17a becomes equal to or smaller than a predetermined value.

26 is a map showing a correlation between the discharge period and the in-cylinder pressure during discharge. This map shows results of an actual measurement of the discharge period [ms] and the in-cylinder pressure during discharge when using a spark ignition engine.

It has been found, according to new findings of the inventor of the present application, that a strong correlation can be obtained between the discharge period and the in-cylinder pressure at discharge, as shown in 26 is shown. The pressure calculation unit 31a can obtain the in-cylinder pressure using the correlation between the in-cylinder pressure and the discharge period of the ignition coil 17a. Therefore, the combustion center CA50 can be estimated based on the first in-cylinder pressure P1 detected near the ignition timing and the second in-cylinder pressure P2 detected near the combustion end timing based on the discharge period.

(Example of Obtaining In-Cylinder Pressure Using Crankshaft Angular Acceleration)

Further, the combustion state estimation unit (pressure calculation unit 31b) may obtain the first in-cylinder pressure P1 and the second in-cylinder pressure P2 based on the angular acceleration of the crankshaft.

The angular acceleration of the crankshaft is expressed by the following formula (3). ω represents the crankshaft speed, J represents the moment of inertia, T _e represents the combustion torque, and T _L represents the load torque. The load torque T _L is estimated based on the speed of the engine 1.

[Math. 3] $$J\frac{d\omega }{dt}=T_e-T_L$$

The combustion torque T _e is expressed by the following formula (4), which is a function of the in-cylinder pressure Pc and the crankshaft angle θ.

[Math. 4] $$T_e=func.\left(P_c,\theta \right)$$

The controller 12 can obtain the in-cylinder pressure Pc at the crankshaft angle θ by substituting the angular acceleration dω/dt of the crankshaft at the crankshaft angle θ into formula (3) and simultaneously solving the equation using formula (4).

27 is a block diagram showing a configuration example from the crank angle sensor 11 to the controller 12 in a case where the controller 12 obtains the in-cylinder pressure based on the angular acceleration of the crankshaft.

The internal combustion engine (engine 1) has an angular acceleration calculation unit (angular acceleration calculation unit 32) which calculates the angular acceleration of the crankshaft.

The combustion state estimation unit (pressure calculation unit 31b) calculates the first in-cylinder pressure P1 and the second in-cylinder pressure P2 based on the angular acceleration of the crankshaft.

The crankshaft angle θ detected by the crankshaft angle sensor 11 is sent to the angular acceleration calculation unit 32. The angular acceleration calculation unit 32 calculates the angular acceleration dω/dt of the crankshaft using the crankshaft angle θ. Then, the angular acceleration calculation unit 32 sends the angular acceleration dω/dt of the crankshaft and the crankshaft angle θ to the controller 12. The pressure calculation unit 31b in the controller 12 obtains the in-cylinder pressure by simultaneously solving the equations from the formulas (3) and (4).

If the detection of the in-cylinder pressure based on the angular acceleration of the crankshaft is applied to the combustion state estimation method according to the present embodiment, the angular acceleration calculation unit 32 detects the angular acceleration dω/dt of the crankshaft using the crankshaft angle sensor 11 in the vicinity of the ignition timing and in the Proximity to the end of combustion time. The pressure calculation unit 31b solves the equations of formulas (3) and (4) simultaneously using the angular acceleration dω/dt to obtain the first in-cylinder pressure P1 near the ignition timing and the second in-cylinder pressure P2 near the combustion end timing.

When the in-cylinder pressure Pc is detected based on the angular acceleration of the crankshaft in this way, the pressure sensor 10 becomes unnecessary and the cost of the engine system can be reduced.

The above-described controller 12 according to the first and second embodiments can accurately estimate the combustion state (the torque variation and the combustion phase) using the in-cylinder pressure. According to the first and second embodiments, the combustion state can be accurately estimated using two in-cylinder pressures detected near the ignition timing and near the combustion end timing per cycle for estimating the combustion state. Additionally, because the calculation is performed using two internal cylinder pressures, the required memory and computational load can be reduced.

In addition, because the rapid pressure sensing is unnecessary, the controller 12 may detect the in-cylinder pressure using existing engine devices such as the ignition coil 17a and the crank angle sensor 11 without using an in-cylinder pressure sensor. This can reduce the system cost required for estimating the combustion state.

<Other>

The present invention is not limited to the respective embodiments described above, and various other application examples and modified examples are of course possible as long as the spirit of the present invention as described in the claims is not impaired.

For example, the configuration of the controller 12 in each embodiment described above has been described in detail in order to describe the present invention in an easy-to-understand manner, but the present invention is not necessarily limited to having all of the components described. Further, some of the components of a particular embodiment may be replaced with the components of another embodiment. Additionally, the components of a particular embodiment may be added to configure another embodiment. Additionally, a portion of the configuration of each embodiment may be added to, removed from, or replaced with another embodiment.

In addition, some or all of the above-described configurations, functions, processing units, and the like of the controller 12 may be implemented by hardware, for example, by integrated circuit design. A field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like can be used as hardware.

In addition, the control lines and information lines indicate those considered necessary for the explanation, and they do not necessarily indicate all the control lines and information lines in the product. In practice it can be assumed that almost all configurations are connected.

Furthermore, in the 3 and 19 In the flowchart shown, several processing processes can be carried out in parallel or the processing sequence can be changed within an area that does not influence the processing result.

Reference symbol list

1

engine

10

Pressure sensor

12

Control device

17a

ignition coil

17b

spark plug

30

Peak hold circuit

31a

Pressure calculation unit

31b

Pressure calculation unit

32

Angular acceleration calculation unit

121

Input/output unit

122

Control unit

122a

Torque variation estimation unit

122b

Engine control unit

122c

Deviation calculation unit

122d

Actuation strength calculation unit

123

Storage unit

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2017057803 A [0005]
• JP 2002097996 A [0005]

Claims (14)

Internal combustion engine control device, comprising: a combustion state estimation unit that estimates the combustion state of an internal combustion engine based on a first in-cylinder pressure detected near an ignition timing and a second in-cylinder pressure detected near a combustion end timing. Internal combustion engine control device Claim 1 , wherein the combustion state estimating unit calculates the difference between the first in-cylinder pressure and the second in-cylinder pressure in multiple cycles and estimates the amount of torque variation of the internal combustion engine based on the variation rate of the difference in the multiple cycles. Internal combustion engine control device Claim 2 , further comprising: an engine control unit that controls the exhaust gas recirculation (EGR) rate or the air-fuel ratio based on the amount of torque variation. Internal combustion engine control device Claim 2 , further comprising: an engine control unit that controls the ignition energy, the intensity of the flow in the cylinder, the compression ratio and / or the intake air temperature based on the amount of torque variation. Internal combustion engine control device Claim 1 , wherein the combustion state estimation unit changes the detection timing of the first in-cylinder pressure according to the ignition timing of the cylinder. Internal combustion engine control device Claim 5 , wherein the combustion state estimation unit sets the difference between the detection timing of the first cylinder internal pressure and the ignition timing of the cylinder to at most 1 ms. Internal combustion engine control device Claim 1 , wherein the combustion state estimating unit changes the detection timing of the second in-cylinder pressure according to a 90% combustion timing of the cylinder. Internal combustion engine control device Claim 7 , wherein the combustion state estimation unit sets the difference between the detection timing of the second cylinder internal pressure and a timing delayed by 20° compared to the 90% combustion timing of the cylinder to at most 10°. Internal combustion engine control device Claim 1 , wherein the combustion state estimating unit estimates the combustion phase based on the ratio between the first in-cylinder pressure and the second in-cylinder pressure. Internal combustion engine control device Claim 9 , further comprising: an engine control unit that controls the ignition timing based on the ratio between the first in-cylinder pressure and the second in-cylinder pressure. Internal combustion engine control device Claim 1 , wherein the combustion state estimating unit obtains the first in-cylinder pressure and the second in-cylinder pressure based on the voltage value of an ignition coil, the current value of the ignition coil, or the discharge time of the ignition coil. Internal combustion engine control device Claim 1 , wherein the internal combustion engine includes an ignition coil and a voltage peak holding unit that detects the voltage of the ignition coil and holds the peak value of the voltage of the ignition coil, and the combustion state estimation unit calculates the first in-cylinder pressure and the second in-cylinder pressure based on the peak value. Internal combustion engine control device Claim 1 , wherein the combustion state estimation unit obtains the first in-cylinder pressure and the second in-cylinder pressure based on the angular acceleration of a crankshaft. Internal combustion engine control device Claim 1 , wherein the internal combustion engine includes an angular acceleration calculation unit that calculates the angular acceleration of a crankshaft, and the combustion state estimation unit calculates the first in-cylinder pressure and the second in-cylinder pressure based on the angular acceleration of the crankshaft.

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