Control device for an internal combustion engine

Abstract

The present application provides a control device of an internal combustion engine, which enables operation of the internal combustion engine in a state where the dilution degree is close to a limit. A processor (CPU 23a) of the control device of the internal combustion engine calculates a variation amount of a parameter (for example, a combustion center position) indicating a combustion state of the internal combustion engine (combustion center variation amount calculation section 32). The processor (CPU 23a) corrects an operation amount of an actuator (for example, an EGR valve) that adjusts the dilution degree of the mixture gas based on a difference between the variation amount of the parameter indicating the combustion state and a target value of the variation amount, and causes the variation amount to approach the target value (actuator operation amount correction section 33).

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] There are many ways to improve the fuel economy of automobiles, but reducing the fuel consumption of internal combustion engines is crucial. To reduce fuel consumption, minimizing various losses generated during engine operation, such as pump losses, cooling losses, and exhaust losses, is effective. As a means of reducing pump and cooling losses, there are lean combustion methods, where the fuel-air ratio is leaner than the metered mixture ratio (stoichiometric ratio), and combustion methods that utilize EGR (Exhaust Gas Recirculation). EGR gases return a portion of the combustion gases to the intake side to dilute the fuel-air mixture. Hereinafter, lean combustion and combustion methods utilizing EGR gases will be collectively referred to as "diluted combustion."

[0003] When using dilution combustion, the intake manifold pressure is increased compared to when dilution combustion is not used, thus reducing pump losses in the internal combustion engine under low load conditions. Furthermore, compared to not using dilution combustion, the heat capacity for burning the same amount of fuel is increased, thus lowering the combustion temperature of the air-fuel mixture and reducing cooling losses. In addition, under high engine load conditions, the auto-ignition reaction caused by the introduction of EGR gas is suppressed, thereby preventing abnormal combustion. This allows for ignition timing to be advanced closer to optimal timing, thereby reducing exhaust losses.

[0004] To reduce fuel consumption, an appropriate air-fuel mixture dilution (the gas-fuel ratio shown below) needs to be set according to operating conditions. Air-fuel mixture dilution is typically evaluated using the mass ratio of the air-fuel mixture (comprising air and EGR gas) to the mass of fuel (G / F), the air-fuel ratio (A / F), and the proportion of EGR in the intake air (EGR rate). Generally, the air-fuel ratio and EGR rate are pre-fitted to each vehicle model. To achieve the same fit, various actuators are operated to obtain the appropriate air-fuel ratio and EGR rate values. During fitting, the air-fuel ratio and EGR rate are not set as limits, but rather with a certain margin (set margin), taking into account the performance changes caused by variations in engine performance and time over time. Therefore, compared to the limit value for each individual dilution, a smaller dilution setting may have the potential to improve efficiency.

[0005] In order to extract the remaining potential for efficiency improvement by setting a dilution limit, it is effective to detect the combustion state during driving and operate the dilution based on the detected state to set a dilution limit value for each individual.

[0006] For example, there is an internal combustion engine control device described in Japanese Patent Application Publication No. 2020-190234 (Patent Document 1). This Patent Document 1 proposes a combustion control scheme for an internal combustion engine, which estimates the combustion phase so that the combustion mass ratio estimated based on the output of a crank angle sensor becomes a set value, and operates the dilution ratio and ignition timing so that the estimated combustion phase becomes the set phase. Existing technical documents Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-190234 Summary of the Invention The technical problem that the invention aims to solve

[0008] In the patent literature, dilution is operated based on the combustion phase; therefore, for example, a dilution that achieves a combustion phase predetermined as a target value can be realized. On the other hand, the target value of this dilution is essentially set with a margin, rather than a limit value for the dilution. Furthermore, the achievable combustion phase is an average state, and it cannot be guaranteed that the deviation of the combustion state in each cycle is sufficiently small.

[0009] The purpose of this invention is to provide a control device for an internal combustion engine that can achieve the operation of the internal combustion engine under conditions where the dilution is close to the limit. Technical means for solving technical problems

[0010] To achieve the above objectives, the control device for the internal combustion engine of the present invention includes a processor that calculates the amount of change of a parameter representing the combustion state of the internal combustion engine, and corrects the operating amount of an actuator that adjusts the dilution of the air-fuel mixture based on the difference between the amount of change of the parameter representing the combustion state and a target value of the amount of change, and brings the amount of change close to the target value. Invention Effects

[0011] According to the present invention, the operation of an internal combustion engine can be achieved at a dilution level close to the limit. Other technical problems, structures, and effects beyond those described above will be further clarified through the following description of embodiments. Attached Figure Description

[0012] Figure 1 This is a structural diagram showing the system structure of an internal combustion engine. Figure 2 This is a structural diagram showing the structure of a control device for an internal combustion engine to which the present invention is applied. Figure 3 This is a control block diagram of an embodiment of the present invention. Figure 4A This is a control flowchart used to illustrate the control steps performed by the control block in an embodiment of the present invention. Figure 4B This is a graph showing the relationship between the EGR valve opening and the relative flow rate. Figure 5 This is a timing diagram showing the combustion state and the state of various actuators when implementing embodiments of the present invention. Figure 6 This is a control flowchart used to illustrate the control steps performed by the control block in an embodiment of the present invention. Figure 7 This is a timing diagram showing the combustion state and the state of various actuators when implementing embodiments of the present invention. Figure 8 This is a control flowchart used to illustrate the control steps performed by the control block in an embodiment of the present invention. Figure 9 This is a timing diagram showing the combustion state and the state of various actuators when implementing embodiments of the present invention. Figure 10 This is a control block diagram of an embodiment of the present invention. Figure 11 This is a control flowchart used to illustrate the control steps performed by the control block in an embodiment of the present invention. Figure 12 This is a control block diagram of Embodiment 2 of the present invention. Figure 13 This is a control block diagram of Embodiment 2 of the present invention. Figure 14 This is a control flowchart used to illustrate the control steps performed by the control block in Embodiment 2 of the present invention. Detailed Implementation

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and various modifications and applications of the technical concept of the present invention are also included within its scope.

[0014] This embodiment relates to a control device for an internal combustion engine, and particularly to the control of the dilution of a mixture corresponding to the combustion state in systems such as exhaust gas recirculation systems and lean combustion systems where a mixture of fuel and air is diluted for combustion, and the control of an ignition device. The object of this embodiment is to provide a control device for an internal combustion engine that, for example, can operate the dilution and ignition device based on the estimated change in the combustion state during driving, thereby achieving operation of the internal combustion engine in a state close to the limit of the dilution that can be set for each engine block.

[0015] [Implementation Method 1] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but will be used in a more detailed manner. Figures 1 to 3 The common structure in the following implementation methods will be explained.

[0016] Figure 1 The diagram shows the system structure of a spark-ignition internal combustion engine used in automobiles, which includes an in-cylinder combustion injection valve that directly injects gasoline fuel into the cylinder.

[0017] An internal combustion engine (ENG) is a spark-ignition type of internal combustion engine used in automobiles. It consists of an airflow sensor 1 that measures the intake air volume and temperature, a compressor 4a for boosting the intake air, an intercooler 7 for cooling the intake air, and an electronically controlled throttle valve 2 that adjusts the intake manifold pressure at appropriate locations on the intake manifold.

[0018] Here, the humidity sensor 3 is a sensor capable of detecting relative humidity and absolute humidity. In addition, in the internal combustion engine ENG, each cylinder includes a combustion injection device 13 (injector) for injecting fuel into the cylinder block 14 of each cylinder, and an ignition device (hereinafter referred to as ignition coil 16, spark plug 17) for providing ignition energy. In addition, the cylinder head is equipped with a variable valve 5 to adjust the air-fuel mixture flowing into the cylinder or the exhaust gas exiting the cylinder. The intake volume and internal EGR of all cylinders are adjusted by adjusting the variable valve 5.

[0019] Furthermore, although not shown, a high-pressure fuel pump for supplying high-pressure fuel to the combustion injection device 13 is connected to the combustion injection device 13 via a fuel line, which includes a fuel pressure sensor for measuring the combustion injection pressure. Additionally, a crank angle sensor 19 for detecting the piston position of the internal combustion engine is installed. The output information of the crank angle sensor 19 is sent to the ECU 20.

[0020] Furthermore, a turbine 4b for supplying rotational force to the compressor 4a of the turbocharger using exhaust energy, an electronically controlled wastegate valve 11 for adjusting the exhaust flow through the turbine 4b, a three-way catalytic converter 10 for purifying the exhaust, and an air-fuel ratio sensor 9, which acts as an air-fuel ratio detector and detects the air-fuel ratio of the exhaust gas upstream of the three-way catalytic converter 10, are provided at appropriate locations on the exhaust pipe 15. Additionally, a temperature sensor 18 is provided for measuring the temperature of the cooling water surrounding the internal combustion engine. Furthermore, although not shown, an EGR pipe is provided for returning exhaust gas from downstream of the three-way catalytic converter 10 in the exhaust pipe to upstream of the compressor 4a in the intake pipe. Moreover, an EGR valve (EGR mechanism) for controlling the EGR flow is installed at appropriate locations on the EGR pipe.

[0021] The output information obtained from the airflow sensor 1, temperature sensor 18, and air-fuel ratio sensor 9 is sent to the control unit (ECU 20) that controls the internal combustion engine. Additionally, the output signal from the throttle opening sensor 12 is sent to the ECU 20. The throttle opening sensor 12 detects the amount of throttle pedal depressed, i.e., the throttle opening.

[0022] The ECU 20 calculates the requested torque based on the output information of the throttle opening sensor 12. That is, the throttle opening sensor 12 is used as a requested torque detection sensor to detect the requested torque for the internal combustion engine. Furthermore, the ECU 20 calculates the engine speed based on the output information of the crank angle sensor. Based on the operating state of the internal combustion engine obtained from the output information of the aforementioned sensors, the ECU 20 optimally calculates the main operating parameters of the internal combustion engine, such as airflow, fuel injection quantity, ignition timing, and fuel pressure.

[0023] The fuel injection quantity calculated by ECU20 is converted into a valve opening pulse signal and sent to the fuel injection device 13. Furthermore, an ignition signal is sent to the ignition coil 16 to ensure ignition at the ignition timing calculated by ECU20. Additionally, the throttle opening calculated by ECU20 is sent as a throttle actuation signal to the electronically controlled throttle 2.

[0024] Fuel is injected into the air flowing into the cylinder 14 from the intake manifold through the intake valve to form a mixture. The mixture explodes at a predetermined ignition timing through a spark generated by the spark plug 17, using its combustion pressure to push the piston and provide the driving force for the internal combustion engine. In addition, the exhaust gas after the explosion is sent to the three-way catalytic converter 10 through the exhaust manifold 15, where the exhaust components are purified and discharged to the outside.

[0025] In such an internal combustion engine system, the details of this embodiment will now be described. Figure 2 A control block diagram showing the structure of the control device for an internal combustion engine to which the present invention is applied is provided. Input signals such as air volume information from the airflow sensor 1, throttle pedal input information from the throttle opening sensor 12, and angle information from the crank angle sensor 19 are input to the input circuit 21 of the ECU 20, which is a control unit. However, the input signals are not limited to these, so further explanation is provided as appropriate.

[0026] The input signals from each sensor are sent to the input port within input / output port 22. The input information sent to the input port is temporarily stored in RAM 23c and processed by CPU 23a according to a prescribed control program. The control program describing the processing is pre-written into ROM 23b.

[0027] The output information, calculated by the control program, representing the actuation quantities of the fuel injection valve and ignition coil controlling the internal combustion engine, is temporarily stored in RAM23c. It is then sent to the output port within input / output port 22 and, via their respective drive circuits, to the fuel injection valve and ignition coil. Additionally, the internal combustion engine uses other actuators besides these, but their description is omitted here.

[0028] In this embodiment, an ignition control unit 24 and an EGR rate control unit 25 are shown as the drive circuit. The ignition control unit 24 controls the energizing period and discharge energy of the ignition coil, while the EGR rate control unit controls the opening degree of the EGR valve. In this embodiment, the ignition control unit 24 for controlling the energizing time and discharge energy of the ignition coil is provided within the ECU 20, but it is not limited to this. A portion or all of the ignition control unit 24 can be installed in a device different from the ECU 20. The same applies to the EGR rate control unit 25.

[0029] Then, the EUC20 calculates the discharge energy of the spark plug based on the detected air volume, crank angle, coolant temperature, intake air temperature, etc., and energizes the ignition coil at the appropriate timing (energizing time, ignition timing) to ignite the gas mixture in the cylinder, and energizes the motor that operates the opening of the EGR valve to control the opening of the EGR valve.

[0030] Figure 3 This is a control block that shows an overview of the discharge energy control implemented by the ignition control unit 24 and the EGR rate control unit 25 within the control device of the internal combustion engine, namely the ECU 20, according to an embodiment of the present invention. In the stability determination unit 31, the engine's operating state is determined to be stable based on the detected actuator operation values ​​of the intake system, such as airflow, throttle opening, and EGR valve opening. The determination result is sent to the combustion center change calculation unit 32.

[0031] The combustion center change calculation unit 32 calculates the change in combustion center position based on crank angle sensor signals, particularly indicators of operating conditions (intake pressure, intake temperature, ignition timing, and variable valve timing) near ignition timing and before exhaust valve opening, and indicators of mixture dilution (EGR rate, air-fuel ratio, and humidity). The calculated change in combustion center position is input to the actuator operation amount correction unit 33. The actuator operation amount correction unit 33 sets the operating amounts of EGR valve opening, ignition timing, and primary coil current based on the estimated change in combustion center position and the combustion center position.

[0032] Figure 4AThe control flow for the calculation process of dilution control in Embodiment 1 is shown. Step S401 is the process performed by the combustion center change calculation unit 32, step S402 is the process performed by the stability determination unit 31, and steps S403 to S406 are the processes performed by the actuator operation amount correction unit.

[0033]

Step S401

[0034]

Step S402

[0035]

Step S403

[0036]

Step S404

[0037]

Step S405

[0038] Here, C is the adaptation coefficient, which can be determined experimentally. Therefore, the EGR flow rate increase / decrease target is determined based on the difference between the target change in combustion state and the actual change in combustion state. This allows the EGR flow rate increase / decrease rate to be adjusted according to the difference between the actual change in combustion state and the target change, thus shortening the time to reach optimal conditions. For example, the change in combustion state under the condition of achieving the allowable value of the engine's output change rate can be set as the target value for the change in combustion state.

[0039]

Step S406

[0040] The target value of the EGR flow rate increase / decrease calculated in step S405 is set as ΔRegr, and the EGR valve opening at the current moment is set as θ. In this case, the target value of the EGR flow rate is expressed by the following relationship. Target value of EGR flow = F(θ) C )×(1+ΔRegr)

[0041] First, as an example, we will illustrate the case where the operation of the EGR valve can be performed discretely. Here, Figure 4B The black dots in the diagram represent the relationship between the settable EGR valve opening and the flow rate. In this example, it is assumed that the settable opening and flow rate relationship is maintained as a mapping. That is, Figure 4BThe black dots in the diagram represent the settable EGR valve opening conditions and indicate the values ​​maintained on the mapping. When the EGR valve can be operated discretely, it is crucial to set the EGR valve opening within the target range when the opening varies.

[0042] For example, in Figure 4B In the case shown, the target value of the EGR flow is F(θ). C )×(1+ΔRegr) is the valve opening θ C+1 flow rate F(θ) C+1 The target value needs to be large; therefore, to prevent the EGR flow rate from exceeding the target value and causing combustion instability, the target value for the EGR valve opening needs to be set to θ. C+1 Therefore, in this case, the target value for the EGR valve opening can be set to θ. C+1 By setting the opening degree of the EGR valve in this way, the opening degree can be set within the range where the achieved EGR flow rate does not exceed the target value, thus suppressing the instability of the combustion state during EGR valve operation.

[0043] Next, we will explain the case where the operating amount of the EGR valve can be continuously set. In this case, the opening degree of the EGR valve can be set more precisely. In the following explanation, Figure 4B The black dots in the diagram represent values ​​retained on the map. The target value for EGR flow lies on the map F(θ). C+2 ) and F(θ) C+1 Therefore, using these values ​​with θ C+2 and θ C+1 The target value θ' of the EGR valve opening can be given by the following relationship. Target value θ' = A × (target value of EGR flow - F(θ)) C+1 ))+θ C+1 A=(θ C+2 -θ C+1 )÷(F(θ C+2 )-F(θ C+1 ))

[0044] By setting the target value for the EGR valve opening in this way, the achieved EGR flow rate can be made close to the target value assumed in step S405. As a result, the EGR flow rate can be increased within a range that suppresses combustion instability, further improving efficiency.

[0045] Furthermore, the above describes the handling of the case where the relationship between the EGR valve opening and the EGR flow rate is given by mapping, but the same idea can also be applied to the case where the relationship between the two is given by formula.

[0046] Through the above processing, dilution operations corresponding to changes in combustion state can be performed. Dilution settings can be configured according to individual dilution ranges, and optimal dilution settings can be achieved on the board. Furthermore, the flow rate increase / decrease target is determined based on the difference between the target change in combustion state and the actual change in combustion state. This allows for adjustments to the EGR flow rate based on the difference between the change in combustion state and the target change, thus shortening the time required to reach optimal conditions.

[0047] Figure 5 The following is an example of the results of the processing described above. From top to bottom, it shows the throttle opening, air volume (detected value), change in combustion center, stability assessment indicator, EGR valve opening, and EGR rate. Figure 5 During this process, various operations occur as time passes: at time t1, the throttle opening changes; at time t2, a stability determination is performed; at time t3, an EGR increase operation is initiated based on the change in the combustion center; at time t4, a stability determination is performed after the operation; and at time t5, an EGR decrease operation is initiated based on the change in the combustion center.

[0048] After the throttle opening changes at time t1, there are no changes in throttle opening, EGR valve, or air volume. Therefore, the system is considered stable at time t2, and the stability indicator becomes ON (=1). Here, since the EGR valve is open, it is determined that dilution combustion is being performed, and the change in the combustion center is smaller than the target value shown by the dashed line. Therefore, starting from time t3, the EGR valve is opened, and the operation of increasing the dilution begins.

[0049] If a stability check is performed again at time t4, it is determined that the absolute value of the difference between the change in the combustion center and the target value exceeds the specified range, and dilution reduction is initiated starting at time t5. The changes in EGR valve opening (ΔST3) at time t3 and at time t5 are based on the difference between the change in the combustion center and the target value; therefore, the changes in EGR valve opening (ΔST3) at time t3 and at time t5 may not be consistent.

[0050] Figure 6 The control flow for the calculation processing of dilution, ignition timing, and ignition energy control in Embodiment 1 is shown. Step S601 is the processing performed by the combustion center change calculation unit 32, step S602 is the processing performed by the stability determination unit 31, and steps S603 to S612 are the processing performed by the actuator operation amount correction unit 33.

[0051]

Step S601

[0052]

Step S602

[0053]

Step S603

[0054]

Step S604

[0055]

Step S605

[0056]

Step S606

[0057]

Step S607

Step S608

Step S609

[0058] The upper limit of the allowable coil charge under each operating condition is mapped, and a judgment is made based on this mapping, the current engine speed, and the throttle opening. Thus, based on the operating conditions and the upper limit of the coil charge, it can be determined whether the upper limit of the energy that the ignition coil can produce has been reached. Furthermore, if it is a system where an auxiliary current can be supplied during coil energization, this auxiliary current is also included in determining the set upper limit. If the upper limit has not been reached, the process proceeds to step S610 to increase ignition energy. If the upper limit has been reached, the process proceeds to step S611 to control the dilution effect.

[0059]

Step S611

Step S612

Step S613

[0060] Through the above processing, dilution control can be performed according to changes in combustion state. The dilution level can be set according to a range defined for each individual component, and the optimal dilution level can be set on the control panel. Furthermore, under conditions of significant changes in combustion state, ignition timing and ignition energy can be controlled, allowing for the use of fast-response actuators. Moreover, based on this control, appropriate dilution levels can be set, enabling efficiency improvements for each individual component based on its specific characteristics.

[0061] Figure 7The following is an example of the results of the processing described above. From top to bottom, it shows the throttle opening, air volume (detected value), change in one of the combustion states (i.e., the combustion center), stability assessment indicator, EGR valve opening, and EGR rate. Figure 7 During the process, as time progresses, ignition timing advance begins at time t1, and EGR is increased at time t2 based on the change in the combustion center. At time t4, it is determined that there is no ignition timing advance effect, so ignition timing correction and ignition energy (during primary coil energization) increase are performed, and EGR is decreased at time t5 based on the change in the combustion center.

[0062] Since the ignition timing adjustment starting from time t1 reduces the change in the combustion center position, it is determined that advancing the ignition timing is effective. The reduced change in combustion center position due to advanced ignition timing leads to a larger difference between the change in combustion center position and the target value shown by the dashed line. Therefore, starting at time t2, EGR is increased based on this difference. Thus, by performing operations based on changes in combustion state, it is possible to set a higher dilution state and achieve improved efficiency.

[0063] At time t4, it is determined that the change in combustion state caused by the advance of ignition timing is small. In order to increase the ignition energy, the energization period of the primary coil is increased. The change in combustion state decreases due to this increase in energization period, but it does not reach the target value shown by the dashed line. Therefore, dilution operation begins from time t5. At this time, the setting of the primary coil energization time is restored, but the ignition energy can be maintained without change.

[0064] By setting it up in this way, measures to reduce changes in combustion state can be implemented in a responsive order, thus more quickly avoiding situations with large changes in combustion state. Furthermore, in cases where the ignition system alone cannot resolve the issue, dilution adjustments can be made to optimize various operational parameters based on the performance of the ignition system.

[0065] Figure 8 This is a control flow used for the calculation processing of dilution, ignition timing, and ignition energy control in Embodiment 1, but the determination is based on the average value of the combustion state rather than the change in the combustion state. Step S801 is the process performed by the combustion center change calculation unit 32, step S802 is the process performed by the stability determination unit 31, and steps S803 to S810 are the processes performed by the actuator operation amount correction unit 33.

[0066]

Step S801

[0067]

Step S802

[0068]

Step S803

[0069]

Step S804

[0070]

Step S805

[0071]

Step S806

[0072]

Step S807

[0073]

Step S808

[0074]

Step S809

[0075]

Step S810

[0076]

Step S811

[0077] Ignition timing correction = Average combustion center position - Target combustion center position A positive value for the ignition timing correction indicates that the ignition timing should be delayed, while a negative value indicates that the ignition timing should be advanced. The target combustion center position can be set, for example, to 5 degrees. The target combustion center position does not have to be a constant value; it can be changed for each engine or for each operating condition. By setting it in this way, appropriate ignition timing can be easily performed according to the combustion state.

[0078] Through the above processing, dilution control corresponding to changes in combustion state can be performed. Dilution can be set according to a dilution range that can be defined for each individual unit, and the optimal dilution can be set on the control panel. Furthermore, under conditions of large changes in combustion state, ignition timing is controlled by averaging the combustion center position, allowing for quantitative setting of ignition timing. Additionally, by controlling ignition energy, a fast-response actuator can be used. Moreover, based on this control, an appropriate dilution can be set, enabling efficiency improvements for each individual unit based on its specific characteristics.

[0079] Figure 9 The following is an example of the results of the processing described above. From top to bottom, it shows the throttle opening, air volume (detected value), combustion center position in one combustion state, change in combustion center in one combustion state, stability judgment indicator, EGR valve opening, and EGR rate. Figure 9During the process, as time progresses, ignition advance operation begins at time t1, and EGR increase operation is performed at time t2 based on the change in combustion center. At time t4, the combustion center position is within the specified range enclosed by the dashed line, but the change in combustion center is greater than the target value, therefore, the increase in ignition energy (the energizing time of the primary coil increases) begins. Furthermore, at time t5, EGR decrease operation is performed based on the change in combustion center.

[0080] By adjusting the ignition timing starting from time t1, the combustion center position falls within a predetermined value. Furthermore, as the change in combustion center position decreases, the difference between the change in combustion center position and the target value shown by the dashed line increases. Therefore, starting at time t2, an EGR increase operation based on this difference is performed. Thus, by performing operations based on changes in combustion state, even after the ignition timing has been set to an appropriate state and the situation has stabilized, it is possible to set the dilution state to a higher state, thereby improving efficiency.

[0081] At time t4, the combustion center position is within the specified range, but the change in combustion state is greater than the specified value. Therefore, to increase the ignition energy, the energization period of the primary coil is increased. Due to this increased energization period, the change in combustion state caused by the energization of the ignition coil decreases, but it does not reach the target value shown by the dashed line. Therefore, dilution operation begins from time t5. At this time, the ignition energy is maintained without changing the setting of the primary coil energization time.

[0082] By setting it in this way, the ignition timing can be set to the appropriate state based on quantitative indicators, the ignition energy and dilution can be operated based on the changes in the combustion state, the appropriate means can be selected quickly, and the process can be quickly switched to a more efficient state.

[0083] Figure 10 Show execution Figure 3 The function block in the combustion center change calculation unit 32 processes the mixture. In the mixture state estimation unit 1001, the state of the mixture is estimated based on various inputs such as intake pressure, EGR rate, air-fuel ratio, humidity, intake temperature, and valve timing (variable valve timing mechanism (variable valve 5)). In the in-cylinder pressure history estimation unit 1002, the history of in-cylinder pressure or in-cylinder pressure at multiple crank angles is estimated based on the results estimated by the mixture state estimation unit and information on the angular velocity of the crank angle.

[0084] In the combustion center estimation unit 1003, the combustion center position is estimated based on the in-cylinder pressure information estimated by the in-cylinder pressure history estimation unit and the combustion model formula. Furthermore, in the combustion center position variation calculation unit 1004, the change in combustion center position is calculated based on the estimated values ​​of combustion center position over multiple cycles. The change in combustion state mentioned above represents the change in combustion center position.

[0085] Figure 11 It is shown Figure 10 The flowchart shows the processing performed by each functional block. Step S1101 is performed by the gas mixture state estimation unit, steps S1102 and S1103 are performed by the cylinder pressure history estimation unit 1002, step S1104 is performed by the combustion center estimation unit 1003, and step S1105 is performed by the combustion center position change calculation unit 1004.

[0086]

Step S1101

[0087] [Mathematical Expression 1]

[0088] Here, the energy input is Q. R、input[] [J], p int [Pa] is the intake pressure, V(θ) IVC )[m 3 [m³] represents the volume during the intake valve closing period. 3 ], V(θ TDC ) is the volume at the top endpoint [m 3 R is the gas constant [J / kg / K], T int Intake air temperature [K], AFR is air-fuel ratio [-], r EGR EGR rate [-], H L The lower heating value of the fuel [J].

[0089]

Step S1103

[0090] (i) The cylinder volume V(θ) reaches its maximum when the cylinder pressure reaches its maximum. pmax )

[0091] [Mathematical Expression 2]

[0092] Here, ω(θ) k ) is the angular velocity [rad / s], t(θ) k ) represents the crank angle θ k The time [s] under, p(θ) k ) represents the crank angle θ k The cylinder pressure [Pa] below, p atmp(θ) represents atmospheric pressure [Pa], γ represents the specific heat ratio of the unburned gas [-], and γb represents the specific heat ratio of the burned gas [-]. The specific heat ratios of the unburned and burned gases vary depending on the state of the gas, but can generally be set to values ​​of around 1.2 to 1.4. k A presumption can be used to presume a value. For example, the following presumption exists.

[0093] [Mathematical Expression 3]

[0094] [Mathematical Expression 4]

[0095] Here, Cint is a model constant, and ηE is the ratio of exhaust heat to input energy [-]. These values ​​can be determined in advance through engine testing and simulation.

[0096] (ii) The cylinder pressure is at its maximum crank angle.

[0097] [Mathematical Expression 5]

[0098] The cylinder volume V(θ) is maximized by increasing the cylinder pressure in (i). pmax Substitute V(θ) into the equation and calculate θ by solving the nonlinear equation. pmax .

[0099] (iii) Maximum cylinder pressure

[0100] [Mathematical Expression 6]

[0101] The cylinder volume V(θ) is maximized by increasing the cylinder pressure in (i). pmax Substitute V(θ) to calculate P max .

[0102]

Step S1104

[0103] (iv). Formula for the combustion ratio at maximum pressure

[0104] [Mathematical Expression 7]

[0105] Here, ηIE is the ratio of output and exhaust heat to input energy[-], and Cpmax is a model constant[-]. These values ​​can be determined in advance through engine testing and simulation.

[0106] Substitute the values ​​(i) to (iii) calculated in step S1103 into the calculation to determine the combustion ratio at maximum pressure.

[0107] (v). Formula for combustion period based on combustion ratio at maximum pressure

[0108] [Mathematical Expression 8]

[0109] Here, a and m are constants. These values ​​can be determined in advance through engine testing and simulation.

[0110] The combustion period is calculated by substituting the combustion ratio calculated in (iv) and the crank angle calculated in (ii).

[0111] (vi) Formula for the center position

[0112] [Mathematical Expression 9]

[0113] The combustion period calculated from (v) is substituted into the calculation to determine the location of the combustion center.

[0114]

Step S1105

[0115] By calculating the combustion center position as described above, the position and its changes can be calculated with high precision without using an in-cylinder pressure sensor or a corresponding detection device. The key point here is that the crankshaft angle sensor detects the angular velocity at two points: before and after ignition timing, and after top dead center. Since combustion occurs between these two conditions, the crankshaft angular velocity changes significantly, and this change is included as information; therefore, using the crankshaft angular velocity under these two conditions is appropriate.

[0116] The main features of this embodiment can also be summarized as follows.

[0117] The processor (CPU23a) of the internal combustion engine control unit Figure 2 ) Calculate the change in parameters representing the combustion state of the internal combustion engine (e.g., combustion center position) (combustion center change calculation unit 32, Figure 3 The processor (CPU23a) corrects the operating amount of the actuator (e.g., EGR valve) that adjusts the dilution of the gas-fuel mixture based on the difference between the change in the parameter representing the combustion state and the target value of the change, and brings the change close to the target value (actuator operating amount correction unit 33). Figure 3 ). As a result, the dilution ratio is adjusted so that the change in parameters representing the combustion state (e.g., the position of the combustion center) (the deviation of the combustion state) approaches the target value (the upper limit of the deviation of the combustion state). Therefore, it is possible to operate the internal combustion engine with the dilution ratio close to its limit. As a result, the fuel consumption of the internal combustion engine can be reduced.

[0118] The actuator is, for example, an EGR valve. When the change in a parameter representing the combustion state (e.g., combustion center position) is smaller than a target value, the processor (CPU23a) increases the opening of the EGR valve as the difference between the change and the target value increases (at time t3). Figure 5 On the other hand, when the change in the parameter representing the combustion state is larger than the target value, the opening of the EGR valve decreases as the difference between the change and the target value increases (at time t5). Figure 5 ).

[0119] This allows for adjustment of the EGR valve opening and brings the change in parameters representing combustion status closer to the target value.

[0120] Furthermore, the EGR in this embodiment is an external EGR, but it can also be an internal EGR. This internal EGR uses a variable valve timing mechanism (variable valve 5) to delay the timing of closing the exhaust valve, allowing exhaust gas to return to the combustion chamber. In this case, the actuator that adjusts the dilution of the air-fuel mixture is a variable valve timing structure, but it can also be said that the exhaust valve also functions as an EGR valve.

[0121] When the change in the parameter representing the combustion state is greater than the target value, the processor (CPU23a) advances the ignition timing (at time t1). Figure 7 This allows the changes in parameters representing the combustion state to decrease more quickly, thus approaching the target value.

[0122] Without reducing the change in ignition timing advance, the processor (CPU23a) increases the discharge energy generated by the ignition device (at time t4). Figure 7 This stabilizes the combustion state and reduces the variation in parameters representing the combustion state. Furthermore, it increases discharge energy only without any advance effect, thus suppressing wear on the spark plug electrodes.

[0123] Parameters indicating the combustion state include, for example, the average value of the combustion center position. When the average value of the combustion center position is outside a specified range, the processor (CPU23a) advances the ignition timing (at time t1). Figure 9 Therefore, the ignition timing can be advanced based on the average value of the combustion center position.

[0124] When the average value at the combustion center location is within the specified range, and the change in the parameter representing the combustion state is greater than the target value, the processor increases the discharge energy generated by the ignition device (at time t4). Figure 9 Therefore, the ignition timing can be advanced based on the average value of the combustion center position and the change in parameters representing the combustion state.

[0125] In this embodiment, the parameter representing the combustion state is the crank angle (combustion center position) at which the combustion ratio of the gas-fuel mixture is a predetermined value (0.5). However, it can also be an index related to the combustion ratio of the gas-fuel mixture, the maximum value of the cylinder pressure, or the crank angle at which the cylinder pressure is at its maximum. Thus, the internal combustion engine can be operated at a dilution ratio close to its limit.

[0126] Specifically, the parameter representing the combustion state is the combustion center position. The processor (CPU23a) estimates the in-cylinder pressure of the internal combustion engine based on the crankshaft angular velocity (ω1) at the first timing after ignition and the crankshaft angular velocity (ω2) at the second timing before the exhaust valve opens, and uses the estimated in-cylinder pressure to estimate the combustion center position. Figure 11 Therefore, the combustion center position can be estimated without using an in-cylinder sensor (pressure sensor). Furthermore, eliminating the need for an in-cylinder sensor reduces manufacturing costs.

[0127] Additionally, as explained in Embodiment 2, the location of the combustion center can be estimated using the in-cylinder pressure detected by the sensor. Figure 13 Therefore, for example, it can reduce the processor load.

[0128] In this embodiment, when the intake system is in a stable state, the processor (CPU23a) corrects the operating amount of the actuator. Figure 4A However, it can also be corrected when the driving state is at a constant speed or at a constant acceleration. Therefore, the actuator's operating amount (the object of correction) can be corrected while keeping the actuator's operating amount (the object of correction) as unchanged as possible.

[0129] Furthermore, in this embodiment, standard deviation is used as the variable, but the variable can simply be the deviation representing the difference from a reference value. The reference value does not have to be the average value, but rather a value representing a parameter (e.g., the combustion center position) indicating the combustion state in the previous combustion cycle. That is, the variable can be a cyclical change representing the change in each combustion cycle. Thus, for each combustion cycle, the dilution is adjusted, and the change in the parameter representing the combustion state (the deviation of the combustion state) approaches the target value (the upper limit of the deviation of the combustion state). Therefore, the operation of the internal combustion engine can be achieved with the dilution close to its limit.

[0130] [Implementation Method 2] Figure 12 This is a control block illustrating an outline of the discharge energy control implemented by the ignition control unit 24 and the EGR rate control unit 25 within the control device of the internal combustion engine, namely the ECU 20, according to an embodiment of the present invention. This is Embodiment 2. Figure 3 The difference in the implementation method is that the measured value of the cylinder pressure is used in the calculation of the change in the combustion center. Figure 3 and Figure 12 The stability determination unit and actuator operation correction unit are the same. The difference lies in the fact that a portion of the input to the combustion center change calculation unit is converted from the value of the crank angle sensor to the in-cylinder pressure.

[0131] Figure 13 The block structure of the combustion center change calculation unit 1202 in Embodiment 2 of the present invention is shown. The mixed gas state estimation unit 1301 and... Figure 10 The mixture state estimation unit 1001 is the same as that of the combustion center position variation calculation unit 1303. Figure 10 The combustion center position change calculation unit 1004 is the same. (Similar to) Figure 3 The difference lies in the fact that the cylinder pressure detection value is in an input state. Therefore, since there is no cylinder pressure history estimation unit and the combustion center estimation unit has different processing because the cylinder pressure detection value is input, the cylinder pressure history estimation value is not input.

[0132] use Figure 14 The processing of the combustion center estimation unit 1302 in Embodiment 2 will be explained.

[0133]

Step S1401

[0134] [Mathematical Expression 10]

[0135] Input the in-cylinder pressure before the exhaust valve opens and the in-cylinder pressure at ignition timing, and calculate the combustion ratio during the in-cylinder pressure detection period.

[0136]

Step S1402

[0137] [Mathematical Expression 11]

[0138] The combustion period is calculated by substituting the combustion ratio during the cylinder pressure detection period calculated in (vii).

[0139]

Step S1403

[0140] [Mathematical Expression 12]

[0141] The combustion period calculated in (viii) is substituted into the calculation to determine the location of the combustion center.

[0142] By calculating the combustion center position as described above, when using an in-cylinder pressure sensor or a corresponding detection device, the combustion center position and its changes can be calculated with high accuracy using less information. The key point above is to detect in-cylinder pressure at two points: before and after ignition timing, and after top dead center. The point after top dead center represents the state of combustion progression under a specified timing; it is more appropriate to select the state during combustion as much as possible. In addition, in-cylinder pressure can be detected using an in-cylinder pressure sensor, or indirectly from information related to in-cylinder pressure indicators (e.g., the secondary voltage of the ignition coil).

[0143] This invention is not limited to the embodiments described above, and includes various modifications. For example, the above embodiments are detailed descriptions provided for ease of understanding, and the invention is not necessarily limited to including all the structures described. Furthermore, a portion of the structure of one embodiment may be replaced with a structure of another embodiment; conversely, a structure of another embodiment may be added to the structure of one embodiment. Additionally, a portion of the structure in each embodiment may be added to, deleted from, or replaced with other structures.

[0144] Furthermore, the aforementioned structures and functions can be partially or entirely implemented in hardware, for example, by designing integrated circuits. Alternatively, they can be implemented in software by having a processor (microcomputer) interpret and execute programs that perform their respective functions. The programs, tables, files, and other information implementing these functions can be stored in recording devices such as memory, hard disks, SSDs (Solid State Drives), or recording media such as IC cards, SD cards, and DVDs.

[0145] Alternatively, the present invention can also be implemented in the following ways.

[0146] (1). A control device for an internal combustion engine, characterized in that it comprises a combustion state estimation unit for estimating the combustion state in the internal combustion engine, and an operation amount correction unit for adjusting the dilution based on the change in the combustion state.

[0147] (2).(1) The control device is characterized in that the combustion state is an index that is related to the combustion ratio of the gas mixture in the engine.

[0148] (3). The control device of (1) or (2) is characterized in that the combustion state is a crank angle with a specified combustion ratio of the gas mixture in the engine.

[0149] (4). The control device of (1) or (2) is characterized in that the combustion state is the maximum value of the cylinder pressure or the maximum crank angle of the cylinder pressure.

[0150] (5). (Estimation of combustion state based on input from two crank angle sensors) The control device of any one of (1) to (4) is characterized in that the combustion state estimation unit is a combustion state estimation unit that estimates the combustion state based on crank angle sensor information, and is configured to include: an in-cylinder pressure history estimation unit that estimates the in-cylinder history of the internal combustion engine based on the crank angle velocity at a predetermined time after ignition timing and the crank angle velocity at a predetermined time before the exhaust valve opens; and a combustion center estimation unit that estimates the combustion state based on the estimated in-cylinder pressure history.

[0151] (6). (Combustion state estimation based on two points of in-cylinder pressure detection or estimated value) The control device of any one of (1) to (4) is characterized in that the combustion state estimation unit is a combustion state estimation unit that estimates the combustion state based on the estimated or detected value of the in-cylinder pressure, and is configured to include: an in-cylinder pressure history estimation unit that estimates the in-cylinder history of the internal combustion engine based on the estimated or detected value of the in-cylinder pressure at a predetermined time after ignition timing and the estimated or detected value of the in-cylinder pressure at a predetermined time before the exhaust valve is opened; and a combustion center estimation unit that estimates the combustion state based on the estimated in-cylinder pressure history.

[0152] (7). (Specifically describe the situation where the dilution operation is proportional to the difference between the target and the amount of change) The control device of any one of (1) to (6) is characterized in that the operation amount correction unit makes the difference between the change in combustion state and the target value of the change in combustion state positively correlated with the operation amount of dilution.

[0153] (8). (Specifically describe the responses based on increased ignition energy when combustion is unstable) The control device of any one of (1) to (7) is characterized in that the operation amount correction unit includes a unit that, when the change in the combustion state is greater than the allowable upper limit of the change in the combustion state, performs an operation to increase the discharge energy generated by the ignition device of the internal combustion engine.

[0154] (9). The control device of any one of (1) to (8) is characterized in that, when the change in the combustion state is greater than the upper limit of the allowable change in the combustion state, the operation quantity correction unit performs an advance operation on the timing of the discharge energy generated by the ignition device of the internal combustion engine.

[0155] (10). The control device of any one of (1) to (8) is characterized in that, when the average value of the combustion state does not converge within a specified range, the operation quantity correction unit operates to time the discharge energy generated by the ignition device of the internal combustion engine.

[0156] (11). A control device for an internal combustion engine, characterized in that it is any one of (1) to (9) and has a stability determination unit for determining that the state of the intake system is in a stable state, and performs operation of various actuators when the stability determination unit determines that the system is stable.

[0157] (12). A control device for an internal combustion engine, characterized in that it is any one of (1) to (9) and has a driving state determination unit for determining that the driving state is in a constant speed state, and performs operation of various actuators when the driving state is determined to be in a constant speed state.

[0158] (13). A control device for an internal combustion engine, characterized in that it is any one of (1) to (9) and has a driving state determination unit for determining that the driving state is in a constant acceleration state, and performs operation of various actuators when the driving state is determined to be in a constant acceleration state.

[0159] According to (1)-(13), the dilution ratio can be operated based on the change in the combustion state of the internal combustion engine. Therefore, the change in the combustion state corresponding to the dilution ratio can be taken into account, and the dilution ratio can be set to the upper limit within the allowable range of combustion state changes. Since the dilution ratio can be set to the upper limit within the allowable range of combustion state changes, different dilution ratios can be set for each individual engine based on the deviation of each engine, thereby improving the efficiency during actual operation for each engine. Label Explanation

[0160] 1. Air Flow Sensor 2. Electronic throttle control 4. Supercharger 4a compressor 4b Turbo 5. Variable valve 6. Intake manifold 7. Intercooler 9. Air-fuel ratio sensor 10 Three-way catalyst 11 Electronically controlled exhaust valve 12 Throttle opening sensor 13 Fuel injection device 14 cylinders 15. Exhaust pipe 16 Ignition Coils 17 Spark plugs 18 Temperature Sensor 19 Crank Angle Sensor 20ECU 21 Input Circuit 22 Input / Output Ports 23a CPU 23b ROM 23c RAM 24 Ignition Control Unit 25 EGR rate control unit.

Claims

1. A control device for an internal combustion engine, characterized in that, The system includes a processor that calculates changes in parameters representing the combustion state of an internal combustion engine. Based on the difference between the change in these parameters and a target value, the processor adjusts the operation of an actuator that regulates the dilution of the air-fuel mixture, bringing the change closer to the target value. The actuator is an EGR valve. When the change in the parameter representing the combustion state is smaller than the target value, the processor increases the opening of the EGR valve as the difference increases. If the change in the parameter representing the combustion state is greater than the target value, the ignition timing is advanced, and the opening of the EGR valve decreases as the difference increases. Furthermore, without reducing the amount of change after advancing the ignition timing, the discharge energy generated by the ignition device is increased.

2. The control device for an internal combustion engine as described in claim 1, characterized in that, The parameter representing the combustion state is the position of the combustion center.

3. The control device for an internal combustion engine as described in claim 1, characterized in that, The parameters representing the combustion state are indicators related to the combustion ratio of the gas-fuel mixture, the crank angle at which the combustion ratio of the gas-fuel mixture reaches a specified value, the maximum value of the cylinder pressure, or the crank angle at which the cylinder pressure reaches its maximum.

4. The control device for an internal combustion engine as described in claim 1, characterized in that, The parameter representing the combustion state is the position of the combustion center. The processor estimates the in-cylinder pressure of the internal combustion engine based on the crank angular velocity at the first timing after ignition timing and the crank angular velocity at the second timing before the exhaust valve opens, and uses the estimated in-cylinder pressure to estimate the combustion center position, or uses the in-cylinder pressure detected by the sensor to estimate the combustion center position.

5. The control device for an internal combustion engine as described in claim 1, characterized in that, The processor corrects the operating amount of the actuator when the intake system is in a stable state, the driving state is in a constant speed state, or the driving state is in a constant acceleration state.

6. The control device for an internal combustion engine as described in claim 1, characterized in that, The change is a deviation representing the difference from the reference value. The reference value is the value of a parameter representing the combustion state in the previous combustion cycle.

7. A control device for an internal combustion engine, characterized in that, The system includes a processor that calculates changes in parameters representing the combustion state of an internal combustion engine. Based on the difference between the change in these parameters and a target value, the processor adjusts the operation of an actuator that regulates the dilution of the air-fuel mixture, bringing the change closer to the target value. The actuator is an EGR valve. When the change in the parameter representing the combustion state is smaller than the target value, the processor increases the opening of the EGR valve as the difference increases. When the change in the parameter representing the combustion state is greater than the target value, the opening degree of the EGR valve decreases as the difference increases. The parameter representing the combustion state is the average value of the combustion center position. When the average value at the combustion center position is outside a specified range, the processor advances the ignition timing. When the average value at the combustion center location is within a specified range and the change in the parameter representing the combustion state is greater than the target value, the discharge energy generated by the ignition device is increased.

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