Internal combustion engine control device and method of controlling internal combustion engine

Abstract

To provide an internal combustion engine control device and a method of controlling an internal combustion engine that can suppress degradation in estimation accuracy of piston temperature.SOLUTION: An internal combustion engine control device includes a piston temperature estimating unit 12, a temperature correction determining unit 15, a temperature correcting unit 14, and a target amount calculating unit 16. The piston temperature estimating unit 12 estimates a piston temperature in an internal combustion engine. The temperature correction determining unit 15 determines whether or not now is a correction timing for correcting an estimated piston temperature. The temperature correcting unit 14 corrects the estimated piston temperature estimated by the piston temperature estimating unit 12 to a prescribed temperature at the correction timing determined by the temperature correction determining unit 15. The target amount calculating unit 16 calculates a control target amount for an actuator of the internal combustion engine on the basis of the estimated piston temperature or the piston temperature corrected to the prescribed temperature by the temperature correcting unit.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine control device and a control method for an internal combustion engine. [Background technology]

[0002] Normally, an internal combustion engine mounted on a vehicle operates according to the operation amounts of various actuators adapted to specific environmental conditions such as temperature, humidity, and air pressure. For example, when driving on an actual road, the vehicle may be driven under conditions that are different from the environmental conditions and operating conditions of the internal combustion engine assumed at the time of adaptation. These environmental conditions are detected using various sensors, and the operation amounts are corrected according to the detected conditions.

[0003] Furthermore, when driving on real roads, not only environmental conditions but also the state of the internal combustion engine itself (for example, wall temperature, coolant temperature, parts) change and deviate from the state assumed at the time of adaptation. Therefore, in order to improve various vehicle performances (fuel economy, exhaust performance) when driving on real roads, it is important to understand the state during operation by estimating and detecting the state of the internal combustion engine and to operate the actuator according to the understood state of the internal combustion engine.

[0004] One condition that affects the performance of an internal combustion engine is the piston temperature of the engine. The piston temperature is a physical quantity related to the amount of operation of an actuator that affects fuel economy and exhaust performance. For example, when the piston temperature is high, the gas near the piston is heated, making abnormal combustion (knocking) more likely to occur. On the other hand, when the piston temperature is low, the fuel adhering to the piston is more likely to remain in liquid form, which can lead to the generation of unburned hydrocarbons and soot, which can worsen exhaust performance. Therefore, in order to operate various actuators installed in the internal combustion engine, it is necessary to improve the estimation accuracy of the piston temperature.

[0005] A technology for estimating piston temperature and controlling an actuator provided in an internal combustion engine is described, for example, in Patent Document 1. Patent Document 1 describes an internal combustion engine control device including an engine state estimation unit, a wall surface temperature estimation unit, and an operation amount calculation unit. The engine state estimation unit calculates an amount of energy transmitted from the gas to the wall surface based on a parameter related to an operating condition, a parameter related to a chemical condition of combustion, and a parameter related to an operating situation. The wall surface temperature estimation unit estimates the wall surface temperature based on the amount of energy transmitted from the gas to the wall surface. Then, the operation amount calculation unit calculates an operation amount of an actuator provided in the internal combustion engine based on the wall surface temperature estimated by the wall surface temperature estimation unit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2022-032184 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the technology described in Patent Document 1, the piston temperature is estimated by integrating the amount of energy transmitted from the gas in the internal combustion engine to the piston over time. Also, during the time integration process, errors contained in the amount of energy transmitted from the gas in the internal combustion engine to the piston accumulate. Therefore, the technology described in Patent Document 1 has a problem in that the estimation accuracy of the piston temperature decreases over time.

[0008] In consideration of the above problems, an object of the present invention is to provide an internal combustion engine control device and an internal combustion engine control method that can suppress a decrease in the estimation accuracy of the piston temperature. [Means for solving the problem]

[0009] In order to solve the above problems and achieve the object, an internal combustion engine control device includes a piston temperature estimation unit, a temperature correction determination unit, a temperature correction unit, and a target amount calculation unit. The piston temperature estimation unit estimates a piston temperature of the internal combustion engine based on a sensor output from a sensor provided in the internal combustion engine, an actuator operation amount, and an internal combustion engine state amount. The temperature correction determination unit determines whether or not it is a correction timing to correct the piston estimated temperature estimated by the piston temperature estimation unit, based on the sensor output, the actuator operation amount, and the internal combustion engine state amount. The temperature correction unit corrects the piston estimated temperature estimated by the piston temperature estimation unit to a predetermined temperature at the correction timing determined by the temperature correction determination unit. The target amount calculation unit calculates a control target amount of the actuator of the internal combustion engine, based on the piston estimated temperature estimated by the piston temperature estimation unit or the piston temperature corrected to the predetermined temperature by the temperature correction unit.

[0010] The control method for the internal combustion engine includes the following processes (1) to (4). (1) A process in which a piston temperature estimation unit estimates a piston temperature of an internal combustion engine based on a sensor output from a sensor provided in the internal combustion engine, an actuator operation amount, and an internal combustion engine state amount. (2) A process in which a temperature correction determination unit determines whether or not it is time to correct the estimated piston temperature estimated by the piston temperature estimation unit, based on the sensor output, the actuator operation amount, and the internal combustion engine state amount. (3) A process in which the temperature correction unit corrects the estimated piston temperature estimated by the piston temperature estimating unit at the correction timing determined by the temperature correction determination unit to a predetermined temperature. (4) A process in which a target amount calculation unit calculates a control target amount for an actuator of the internal combustion engine based on the piston estimated temperature estimated by the piston temperature estimation unit or the piston temperature corrected to a predetermined temperature by the temperature correction unit. Effect of the Invention

[0011] According to the internal combustion engine control device and the control method for an internal combustion engine configured as described above, it is possible to suppress a decrease in the estimation accuracy of the piston temperature. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing an internal combustion engine controlled by an internal combustion engine control device according to an embodiment; [Diagram 2] 1 is a block diagram showing a configuration of an internal combustion engine control device according to an embodiment; [Diagram 3] 4 is a flowchart showing a target ignition timing determination operation in the internal combustion engine control device according to the embodiment. [Figure 4] 4 is a flowchart showing an operation of determining a target oil jet flow rate in the internal combustion engine control device according to the embodiment. [Diagram 5] 2 is a block diagram showing a configuration of a piston temperature / target amount calculation unit in the internal combustion engine control device according to the embodiment. FIG. [Figure 6] 2 is a block diagram showing a configuration of a piston temperature estimation unit in the internal combustion engine control device according to the embodiment; FIG. [Figure 7] FIG. 11 is an explanatory diagram showing time histories of an estimated piston temperature and an actual piston temperature when a positive error occurs in the amount of energy transmitted to the piston. [Figure 8] FIG. 4 is an explanatory diagram showing the relationship between piston temperature and knock intensity. [Figure 9] 4 is a flowchart showing an operation of determining a correction timing for an estimated piston temperature in the internal combustion engine control device according to the embodiment; [Figure 10] FIG. 4 is an explanatory diagram showing the relationship between an oil jet flow rate and a knock intensity. [Figure 11] FIG. 4 is an explanatory diagram showing the relationship between the oil jet flow rate and the ignition timing. [Figure 12] FIG. 4 is an explanatory diagram showing the relationship between the temperature difference between the oil temperature and the water temperature and the cause of knocking. [Figure 13] 4 is a flowchart showing an operation of determining a temperature correction command and a temperature correction value in the internal combustion engine control device according to the embodiment. [Figure 14]4 is a flowchart showing an operation of calculating an estimated piston temperature in the internal combustion engine control device according to the embodiment. [Figure 15] 4 is an explanatory diagram showing an example of a time history of knock determination, temperature correction determination, estimated piston temperature, and piston temperature estimation error due to the correction operation of the estimated piston temperature in the internal combustion engine control device according to the embodiment. FIG. [Figure 16] FIG. 1 is an explanatory diagram showing an example of changes in piston temperature during knock with respect to changes in the octane number of fuel, the alcohol concentration in the fuel, the latent heat of vaporization of the fuel, the rotation speed of the internal combustion engine, the humidity of the intake air, and the EGR rate (the mass ratio of recirculated gas to the intake air). [Figure 17] 1 is an explanatory diagram showing an example of changes in piston temperature during knock with respect to changes in intake air amount, intake air pressure, intake air temperature, air-fuel ratio, compression ratio, and amount of deposits in the combustion chamber. FIG. [Figure 18] FIG. 4 is an explanatory diagram showing the relationship between the estimated piston temperature and the knock risk degree. [Figure 19] 1 is an explanatory diagram showing an example of a method for determining an oil jet flow rate based on a knock risk degree, which is implemented by a target amount calculation unit in an internal combustion engine control device according to an embodiment. FIG. [Figure 20] 11 is an explanatory diagram showing another example of a method for determining an oil jet flow rate based on a knock risk degree, which is implemented in a target amount calculation unit in an internal combustion engine control device according to an embodiment. FIG. [Figure 21] 21A and 21B are explanatory diagrams showing an example of a method for determining the ignition advance angular speed based on the knock risk degree in the internal combustion engine control device according to the embodiment. [Figure 22] 4 is an explanatory diagram showing an example of time history of knock determination, target ignition timing, piston temperature, and knock risk degree. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of an internal combustion engine control device will be described with reference to Figures 1 to 22. Note that the same reference numerals are used to designate common members in each figure.

[0014] 1. Example of embodiment First, an internal combustion engine control device according to an embodiment (hereinafter referred to as "this example") will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram showing an internal combustion engine.

[0015] 1-1. Example of internal combustion engine configuration First, a configuration example of an internal combustion engine will be described. The internal combustion engine 100 shown in FIG. 1 is a spark-ignition, four-stroke gasoline internal combustion engine that repeats four strokes: an intake stroke, a compression stroke, a combustion (expansion) stroke, and an exhaust stroke. Furthermore, the internal combustion engine 100 is a multi-cylinder engine having, for example, four cylinders. Note that the number of cylinders that the internal combustion engine 100 has is not limited to four, and the internal combustion engine 100 may have six or eight or more cylinders. Alternatively, the number of cylinders that the internal combustion engine 100 has may be three or less. Furthermore, the number of cycles of the internal combustion engine 100 is not limited to four,

[0016] 1, the internal combustion engine 100 includes a cylinder head 24, a cylinder block 23, a piston 25, an intake valve 26, and an exhaust valve 27. A combustion chamber is formed by the cylinder head 24, the cylinder block 23, the piston 25, the intake valve 26, and the exhaust valve 27. An ignition plug and an ignition coil 22 are installed in the cylinder head 24.

[0017] The internal combustion engine 100 also includes an electronically controlled throttle valve 31, an intake port 32, an exhaust port 33, a catalytic converter 34, and a fuel injector 35. The internal combustion engine 100 also includes an air flow sensor 36, an air-fuel ratio sensor 37, a knock sensor 38, an oil temperature sensor 39, an oil pan 40, and a water temperature sensor 41. The internal combustion engine 100 is controlled by an ECU (Engine Control Unit) 2.

[0018] Air for combustion is taken into the combustion chamber through an electronically controlled throttle valve 31 and an intake port 32. Then, the post-combustion gas (exhaust gas) discharged from the combustion chamber is discharged into the atmosphere through an exhaust port 33 and a catalytic converter 34. Also, fuel is supplied into the intake port 32 by a fuel injector 35.

[0019] The amount of air taken into the combustion chamber is measured by the ECU 2 reading the output of an airflow sensor 36 provided upstream of the electronically controlled throttle valve 31. A temperature sensor and a humidity sensor are also provided inside the airflow sensor 36. The ECU 2 reads the output of the airflow sensor 36 to detect the temperature and humidity of the intake air.

[0020] The air-fuel ratio of the gas (exhaust gas) discharged from the combustion chamber is detected by the ECU 2 reading the output of an air-fuel ratio sensor 37 provided upstream of the catalytic converter 34. In addition, a knock sensor 38 is provided in the cylinder block 23. The ECU 2 detects the knock state in the combustion chamber by reading the output of the knock sensor 38.

[0021] A water jacket 42 is provided within the cylinder block 23, and a cooling water pump (not shown) causes cooling water to flow through the water jacket 42, thereby cooling the cylinder block 23. Heat from the cooling water is released into the atmosphere by a radiator (not shown). A water temperature sensor 41 is provided in the water jacket 42. The ECU 2 reads the output of the water temperature sensor 41 to detect the temperature of the cooling water (water temperature).

[0022] An oil pan 40 that stores oil is provided below the cylinder block 23. An oil temperature sensor 39 is provided in the oil pan 40. The ECU 2 reads the output of the oil temperature sensor 39 to detect the temperature of the oil.

[0023] Furthermore, an oil jet 53 is attached to the cylinder block 23. The oil jet 53 has a function of cooling the piston 25 by injecting oil toward the back side of the piston 25.

[0024] The flow rate of oil injected by the oil jet 53 (oil jet flow rate) varies depending on the oil discharge pressure of an oil pump (not shown) connected to the oil jet 53. Alternatively, the flow rate of oil injected by the oil jet 53 varies depending on the opening of a valve mechanism (not shown) built into the oil jet 53. The discharge pressure of the oil pump or the opening of the valve mechanism built into the oil jet 53 is changed by an operation signal value sent from the ECU 2.

[0025] The cylinder block 23 is provided with an oil supply passage (main gallery) 56 that supplies oil to oil supply parts including the oil jet 53. The oil stored in the oil pan 40 provided at the bottom of the cylinder block 23 is pressurized by an oil pump (not shown). The oil pressurized by the oil pump is then supplied via the oil supply passage 56 to the oil jet 53 as well as to lubrication parts, hydraulically operated devices, etc.

[0026] Examples of the structure of the oil jet 53 include a die-cast type, a brazed two-piece type, and a brazed one-piece type. In the case of the die-cast type and the brazed two-piece type, the oil jet 53 is fastened to the cylinder block 23 by a fixing bolt incorporating a check ball. In the case of the brazed one-piece type that incorporates a valve mechanism, the oil jet 53 is fixed to the cylinder block side by a general fixing bolt that does not incorporate a check ball.

[0027] The check ball supplies oil to the oil jet 53 when the oil pressure in the oil supply passage 56 exceeds the set load of the spring due to the spring. In other words, the oil jet 53 is configured to spontaneously inject oil when the oil pressure of the oil supplied to the oil supply passage 56 of the internal combustion engine 100 exceeds a predetermined value.

[0028] On the other hand, if the oil jet 53 has a built-in valve mechanism, the valve is a solenoid type, and the oil jet can be stopped or the oil jet flow rate during injection can be adjusted by adjusting the opening degree of the valve.

[0029] The opening and closing timing of the intake valve 26 and the exhaust valve 27 is adjusted by a variable valve timing mechanism (not shown).

[0030] The ECU 2 calculates the required torque based on the output signal of the accelerator opening sensor 62. That is, the accelerator opening sensor 62 is used as a required torque detection sensor that detects the torque required for the internal combustion engine 100. The ECU 2 also calculates the rotation speed of the internal combustion engine 100 based on the output signal of the crank angle sensor 10. Then, the ECU 2 optimally calculates main operating quantities of the internal combustion engine 100, such as the air flow rate, fuel injection quantity, ignition timing, fuel pressure, oil pressure, and valve timing, based on the operating conditions of the internal combustion engine 100 obtained from the outputs of various sensors.

[0031] The fuel injection amount calculated by the ECU 2 is converted into a valve-opening pulse signal and output to the fuel injector 35. In addition, the ignition timing calculated by the ECU 2 is output as an ignition signal to the ignition coil 22. Furthermore, the throttle opening calculated by the ECU 2 is output to the electronically controlled throttle valve 31 as a throttle drive signal.

[0032] The internal combustion engine 100 may also be provided with an EGR (Exhaust Gas Recirculation) pipe (not shown) that connects the intake port (intake pipe) 32 and the exhaust port (exhaust pipe) 33. Then, a part of the exhaust gas passing through the exhaust port 33 may be returned to the intake port 32 through this EGR pipe. In this case, the ECU 2 adjusts the flow rate (EGR amount) of exhaust gas returned to the intake port 32 by manipulating the opening degree of a flow control valve provided in the EGR pipe based on the operating state of the internal combustion engine 100 obtained from the outputs of various sensors.

[0033] The internal combustion engine 100 may also be provided with a compression ratio variable mechanism (not shown). The compression ratio variable mechanism is a mechanism that changes the compression ratio by adjusting the stroke amount of the piston 25. In this case, the ECU 2 adjusts the compression ratio of the internal combustion engine 100 by operating the compression ratio variable mechanism (not shown) based on the operating state of the internal combustion engine 100 obtained from the outputs of various sensors.

[0034] The internal combustion engine 100 uses liquid fuels such as gasoline, alcohol (ethanol, methanol), and synthetic fuels (eFuel), gas fuels such as methane, propane, hydrogen, and ammonia, and mixed fuels made by mixing these.

[0035] 1-2. Example of ECU configuration Next, an example of the configuration of the ECU 2 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the ECU 2.

[0036] 2, the ECU 2 has an input circuit 3, an input / output port 4, a RAM (Random Access Memory) 5, a ROM (Read Only Memory) 6, and a CPU (Central Processing Unit) 7. The ECU 2 also has an oil jet control unit 8, an ignition control unit 9, and a piston temperature / target amount calculation unit 11.

[0037] Sensor output values ​​from various sensors, such as the water temperature from the water temperature sensor 41, the intake air volume from the airflow sensor 36, and the knock intensity from the knock sensor 38, are input to the input circuit 3. The input circuit 3 performs signal processing such as noise removal on the input signals and sends them to the input / output port 4. The values ​​input to the input ports of the input / output port 4 are stored in the RAM 5.

[0038] The ROM 6 stores a control program describing the contents of various arithmetic processes executed by the CPU 7, and maps, data tables, etc. used for each process. The RAM 5 is provided with a storage area for storing values ​​input to the input ports of the input / output port 4 and values ​​representing the manipulated variable of each actuator calculated according to the control program. The values ​​representing the manipulated variable of each actuator stored in the RAM 5 are sent to the output ports of the input / output port 4.

[0039] The piston temperature / target quantity calculation unit 11 receives the sensor output values, the operation amounts of each actuator, and the state quantities of the internal combustion engine from the input / output port 4, and estimates the piston temperature. Then, the piston temperature / target quantity calculation unit 11 calculates the control target quantities of each actuator based on the estimated piston temperature, and outputs them to the oil jet control unit 8 and the ignition control unit 9.

[0040] The oil jet control unit 8 calculates the existing target oil jet flow rate based on the sensor output values ​​and the operation amounts of each actuator received from the input / output port 4, and the state quantities of the internal combustion engine 100. The oil jet control unit 8 also receives the additional target oil jet flow rate from the piston temperature / target amount calculation unit 11. Then, the oil jet control unit 8 selects either the existing target oil jet flow rate or the additional target oil jet flow rate as the control target amount of the oil jet, and determines the operation amount of the oil jet 53.

[0041] The ignition control unit 9 obtains an existing target ignition timing based on the sensor output values ​​and the operation amounts of the actuators received from the input / output port 4, and the state amounts of the internal combustion engine 100. The ignition control unit 9 also receives an additional target ignition timing from the piston temperature / target amount calculation unit 11. Then, the ignition control unit 9 selects either the existing target ignition timing or the additional target ignition timing as a control target amount of the ignition timing, and determines the operation amount of the ignition coil 22.

[0042] That is, the oil jet control unit 8 and the ignition control unit 9 receive the actuator control target amount (hereinafter referred to as the additional target amount) determined by the piston temperature / target amount calculation unit 11. In addition, the oil jet control unit 8 and the ignition control unit 9 obtain the actuator control target amount (hereinafter referred to as the existing target amount) determined based on the sensor output value, the operation amount of each actuator, and the internal combustion engine state amount received from the input / output port 4 without going through the piston temperature / target amount calculation unit 11. Then, the oil jet control unit 8 and the ignition control unit 9 select the actuator control target amount optimal for the current internal combustion engine control from the two target amounts, the additional target amount and the existing target amount. In addition, the oil jet control unit 8 and the ignition control unit 9 obtain the actuator operation amount for achieving the selected control target amount and output it to the actuator.

[0043] In this way, the oil jet control unit 8 and the ignition control unit 9 select the additional target amount and the existing target amount because the optimal target amount may change depending on the internal combustion engine state, etc. For example, when a knock occurs, it is necessary to immediately retard the ignition timing in order to protect the internal combustion engine 100. Here, since the additional target amount is determined based on the estimated piston temperature, there is a possibility that a delay or error in response may occur. Therefore, when a knock occurs, it is desirable to control ignition using the ignition timing at the time of knock (existing target amount) determined based on the sensor output value, the operation amount of each actuator, and the internal combustion engine state amount received from the input / output port 4 without going through the piston temperature / target amount calculation unit 11 as the target ignition timing.

[0044] 1-3. Target ignition timing determination operation Next, the operation of determining the target ignition timing will be described with reference to FIG. FIG. 3 is a flowchart showing the operation of determining the target ignition timing.

[0045] 3, the ignition control unit 9 judges whether or not the knock judgment is ON (step S11). In the process of step S11, when it is judged that the knock judgment is OFF, that is, that a knock is not occurring (NO judgment in step S11), the ignition control unit 9 selects the target ignition timing (additional target amount) calculated by the piston temperature / target amount calculation unit 11 as the control target amount (step S12).

[0046] Furthermore, in the process of step S11, when it is determined that the knock determination is ON, that is, that a knock has occurred (YES determination in step S11), the ignition control unit 9 selects the knock ignition timing determined based on the sensor output values ​​received from the input / output port 4, the operation amounts of the actuators, and the internal combustion engine state amounts, as a control target amount (step S13). Specifically, the ignition control unit 9 selects the retarded ignition timing for transitioning the internal combustion engine 100 from a knock state to a non-knock state as a control target amount (step S13).

[0047] In this way, by selecting the control target amount of the ignition timing, it is possible to obtain the effect of controlling the ignition timing based on the estimated piston temperature. Furthermore, when a knock occurs, it is possible to prevent damage to the internal combustion engine 100 due to the knock.

[0048] 1-4. Operation for determining target oil jet flow rate Next, the operation of determining the target oil jet flow rate will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of determining the target oil jet flow rate.

[0049] Here, if friction on the piston sliding surface is large, it may be necessary to increase the oil jet flow rate to achieve lubrication. In this case, it is desirable to control the oil jet flow rate to the existing target amount determined based on the oil temperature or water temperature.

[0050] 4, the oil jet control unit 8 determines whether the oil temperature (or water temperature) is higher than a predetermined threshold value (e.g., 20°C) (step S21). In the process of step S21, if the oil temperature is higher than the threshold value (YES judgment in step S21), the oil jet control unit 8 selects the target oil jet flow rate (additional target amount) calculated by the piston temperature / target amount calculation unit 11 as the control target amount (step S22).

[0051] Also, in the processing of step S21, if the oil temperature is below the threshold value (NO judgment in step S21), the oil jet control unit 8 selects the oil jet flow rate (existing target amount) determined based on the oil temperature received from the input / output port 4 as the control target amount (step S23).

[0052] In this way, by selecting the control target amount of the oil jet flow rate, it is possible to obtain the effect of manipulating the oil jet flow rate based on the estimated piston temperature. Furthermore, when friction reduction on the piston sliding surface is required, it is possible to achieve an appropriate friction reduction based on the oil temperature (or water temperature).

[0053] In this embodiment, the oil jet control unit 8 and the ignition control unit 9 are used as an example of a control unit that determines the actuator operation amount, but the present invention is not limited to these. For example, the control unit that determines the actuator operation amount may be another actuator control unit such as a fuel injection control unit (outputting the operation amount of a fuel injection valve and a fuel pump), a valve timing control unit (outputting the operation amount of a valve timing mechanism), a variable compression ratio control unit (outputting the operation amount of a variable compression ratio mechanism), an air amount control unit (outputting the operation amount of an electronically controlled throttle valve), or a hydraulic control unit (outputting the operation amount of an oil pump).

[0054] 2. Example of piston temperature target calculation section Next, a configuration example of the piston temperature / target amount calculation unit 11 will be described with reference to FIG. FIG. 5 is a block diagram showing the configuration of a piston temperature / target amount calculation unit 11 which is a part of the internal configuration of the ECU 2. As shown in FIG.

[0055] As shown in Fig. 5, piston temperature / target quantity calculation unit 11 includes piston temperature estimation unit 12, temperature correction unit 14, temperature correction determination unit 15, and target quantity calculation unit 16. Piston temperature estimation unit 12 receives sensor output values, operation amounts of each actuator, and internal combustion engine state quantities from input / output port 4. Then, piston temperature estimation unit 12 estimates the piston temperature based on the sensor output values, operation amounts of each actuator, and internal combustion engine state quantities. Furthermore, piston temperature estimation unit 12 outputs the estimated piston temperature to target quantity calculation unit 16 and temperature correction determination unit 15.

[0056] Temperature correction determination unit 15 receives the sensor output value, the operation amount of each actuator, and the internal combustion engine state quantity from input / output port 4. Temperature correction determination unit 15 also receives the estimated piston temperature from piston temperature estimator 12. Then, temperature correction determination unit 15 determines the timing to correct the piston temperature based on the sensor output value, the operation amount of each actuator, the internal combustion engine state quantity, and the estimated piston temperature. Temperature correction determination unit 15 also outputs the determined temperature correction timing to temperature correction unit 14.

[0057] Temperature correction unit 14 outputs a correction command and a temperature correction value to piston temperature estimator 12 based on the timing of temperature correction determined by temperature correction determination unit 15. Temperature correction unit 14 also outputs a knocking piston temperature Tk, which will be described later, to target amount calculation unit 16. Then, target amount calculation unit 16 calculates a control target amount for each actuator based on the estimated piston temperature.

[0058] 2-1. Example of piston temperature estimation unit configuration Next, a configuration example of the piston temperature estimation unit 12 will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of the piston temperature estimation unit 12 which is a part of the internal configuration of the piston temperature / target amount calculation unit 11. As shown in FIG.

[0059] 6, piston temperature estimator 12 includes energy transmission amount estimator 17 and temperature calculator 18. Energy transmission amount estimator 17 receives the sensor output value, the operation amount of each actuator, and the internal combustion engine state quantity from input / output port 4. Then, energy transmission amount estimator 17 determines the amount of energy transmission to piston 25 based on the sensor output value, the operation amount of each actuator, and the internal combustion engine state quantity. Also, energy transmission amount estimator 17 outputs the determined amount of energy transmission to temperature calculator 18.

[0060] Temperature calculation unit 18 obtains the piston temperature from the amount of energy transmitted to piston 25. Here, temperature calculation unit 18 calculates the estimated piston temperature by the following formula 1 using the amount of energy transmitted to piston 25 input from energy transmission amount estimation unit 17. [Formula 1] TIFF2024176426000002.tif55157

[0061] Equation 1 is expressed in the form of a time integral of the amount of energy transmitted Q(t) to the piston 25. Therefore, if the amount of energy transmitted Q(t) to the piston 25 contains an error, the error may accumulate over time.

[0062] FIG. 7 is an explanatory diagram showing time histories of the estimated piston temperature and the actual piston temperature when a positive error occurs in the amount of energy transmitted to the piston. If a positive error occurs in the amount of energy transmitted to the piston 25, Q(t), the estimated piston temperature will be higher than the actual temperature, as shown in Fig. 7. Here, a case where a positive error occurs in the amount of energy transmitted to the piston Q(t) is a case where the amount of energy transmitted to the piston 25, Q, is overestimated. Then, as shown in Fig. 7, the difference between the estimated piston temperature and the actual temperature (estimation error of the piston temperature) increases over time.

[0063] FIG. 8 is a graph showing an example of the relationship between the piston temperature and the knock intensity. When an increase in the temperature of the piston 25 is the cause of the occurrence of knock, it is known that there is a strong linear correlation between the piston temperature and the knock intensity, as shown in Fig. 8. Here, when an increase in the temperature of the piston 25 is the cause of the occurrence of knock, it refers to the case where the self-ignition of gas on the piston surface that is heated by heat transfer from the piston is the cause of the occurrence of knock.

[0064] A typical internal combustion engine control device determines the knock intensity based on the output of knock sensor 38, and determines that a knock state exists (hereinafter, knock judgment is ON) when the knock intensity exceeds a predetermined knock judgment threshold. Also, as shown in Fig. 8, since there is a correlation between the piston temperature and the knock intensity, the piston temperature when knock judgment is ON (i.e., the knock intensity is the knock judgment threshold) is considered to be approximately constant. Hereinafter, the piston temperature when the knock intensity exceeds the knock judgment threshold is referred to as the knock-time piston temperature (predetermined temperature) Tk.

[0065] Therefore, in the piston temperature / target amount calculation unit 11 of this embodiment, when a predetermined condition is satisfied, the estimated piston temperature is corrected to the knocking piston temperature Tk, thereby preventing a decrease in the estimation accuracy of the piston temperature over time.

[0066] 3. Correction of estimated piston temperature Next, the correction operation of the estimated piston temperature will be described with reference to FIG. 9 to FIG. 3-1.Decision of the timing for correcting the estimated piston temperature First, the operation of determining the timing for correcting the estimated piston temperature will be described with reference to FIG. FIG. 9 is a flowchart showing an operation of determining the correction timing of the estimated piston temperature.

[0067] As shown in Fig. 9, the temperature correction determination unit 15 reads the knock state flag calculated by the ECU 2 and determines the current knock occurrence state (step S31). In the process of step S31, if the temperature correction determination unit 15 determines that the knock determination is ON (knock state), the process proceeds to step S32, and if the temperature correction determination unit 15 determines that the knock determination is OFF (not a knock state), the process proceeds to step S35. In the process of step S35, the temperature correction determination unit 15 sets the temperature correction determination flag to OFF (not the timing for correcting the estimated piston temperature). Then, the temperature correction determination unit 15 sends a message that the temperature correction determination flag is OFF to the temperature correction unit 14, and returns to the process of step S31.

[0068] In response to this, in the process of step S32, temperature correction determination unit 15 determines whether or not the deviation ΔT=|T(t)-Tk| between the current estimated piston temperature T(t) and the piston temperature Tk during knock is equal to or greater than a predetermined threshold value Tc (e.g., 10°C). If it is determined in the process of step S32 that the deviation ΔT is equal to or greater than the threshold value Tc (YES determination in step S32), the process proceeds to step S33. On the other hand, if it is determined in the process of step S32 that the deviation ΔT is not equal to or greater than the threshold value Tc (NO determination in step S32), the process proceeds to step S35.

[0069] Next, in the process of step S33, temperature correction determination unit 15 determines whether or not the knock is caused by the piston temperature. If it is determined in the process of step S33 that the knock is caused by the piston temperature (YES in step S33), the process proceeds to step S34. On the other hand, if it is determined in the process of step S33 that the knock is not caused by the piston temperature (NO in step S33), the process proceeds to step S35.

[0070] Next, in the process of step S34, the temperature correction determination unit 15 sets the temperature correction determination flag to ON (this is the timing for correcting the estimated piston temperature). Then, the temperature correction determination unit 15 notifies the temperature correction unit 14 that the temperature correction determination flag is ON, and the process returns to the process of step S31.

[0071] If it is determined by the above processing that knock caused by the piston temperature has occurred and that an error equal to or greater than threshold value Tc has occurred in the current estimated piston temperature, the temperature correction determination flag is ON and is sent from temperature correction determination unit 15 to temperature correction unit 14. In other cases, the temperature correction determination flag is OFF and is sent from temperature correction determination unit 15 to temperature correction unit 14.

[0072] Note that the process of determining whether an error of equal to or greater than threshold value Tc occurs in the current estimated piston temperature shown in the process of step S32 may be omitted. That is, regardless of the magnitude of the error in the current estimated piston temperature, when a knock caused by the piston temperature occurs, a temperature correction determination ON (temperature correction determination flag is ON) is sent from temperature correction determination unit 15 to temperature correction unit 14. When a knock caused by the piston temperature does not occur, a temperature correction determination OFF (temperature correction determination flag is OFF) may be sent from temperature correction determination unit 15 to temperature correction unit 14. However, by performing the process of determining whether an error of equal to or greater than threshold value Tc occurs in the current estimated piston temperature in the process of step S32, the calculation load on ECU 2 can be reduced.

[0073] 3-2.How to determine whether knock is caused by piston temperature Next, a method for determining whether or not the currently occurring knock is due to the piston temperature in the process of step S33 will be described with reference to FIGS.

[0074] Fig. 10 is an explanatory diagram showing the relationship between the oil jet flow rate and the knock intensity. Fig. 10 also shows an example of the change in knock intensity when the oil jet flow rate is changed with the ignition timing kept constant. As shown in Fig. 10, when knock is caused by piston temperature, increasing the oil jet flow rate to improve piston cooling reduces the knock intensity significantly. On the other hand, when knock is caused by factors other than piston temperature (for example, when knock is caused by an increase in the temperature of the cylinder head or cylinder liner), there is only a small change in knock intensity even if the oil jet flow rate is increased to improve piston cooling.

[0075] Therefore, as shown in Fig. 10, it is possible to determine whether or not a knock is caused by the piston temperature from the magnitude of the change in knock intensity relative to the change in oil jet flow rate. More specifically, if the magnitude of the change in knock intensity relative to the change in oil jet flow rate is equal to or greater than a predetermined threshold (for example, a 10% change in knock intensity relative to a 10% change in oil jet flow rate), it is determined that the knock is caused by the piston temperature. If the magnitude of the change in knock intensity relative to the change in oil jet flow rate is smaller than the predetermined threshold, it is possible to determine that the knock is caused by a factor other than the piston temperature.

[0076] Fig. 11 is an explanatory diagram showing the relationship between the oil jet flow rate and the ignition timing. Fig. 11 also shows the change in ignition timing (change in ignition timing of trace knock) when the oil jet flow rate is changed while keeping the knock intensity constant. As shown in Fig. 11, when the knock is caused by the piston temperature, increasing the oil jet flow rate to improve piston cooling increases the advance of the ignition timing. On the other hand, when the knock is caused by a factor other than the piston temperature, the change in ignition timing is small in response to a change in the oil jet flow rate.

[0077] Therefore, as shown in Fig. 11, it is possible to determine whether or not the knock is caused by the piston temperature from the magnitude of the change in ignition timing relative to the change in oil jet flow rate. More specifically, if the magnitude of the change in ignition timing relative to the change in oil jet flow rate is equal to or greater than a predetermined threshold (for example, a 0.1° change in ignition timing relative to a 10% change in oil jet flow rate), it is determined that the knock is caused by the piston temperature. If the magnitude of the change in ignition timing relative to the change in oil jet flow rate is smaller than the predetermined threshold, it is possible to determine that the knock is caused by a factor other than the piston temperature.

[0078] FIG. 12 is an explanatory diagram showing the relationship between the temperature difference between the oil temperature and the water temperature and the cause of knock. As shown in Fig. 12, piston temperature is highly correlated with oil temperature, while cylinder head temperature and cylinder liner temperature, which are causes of knock other than piston temperature, are highly correlated with water temperature. Therefore, if the temperature difference between the oil temperature and water temperature (oil temperature - water temperature) is greater than a preset threshold value ΔTc (e.g., 30°C), it is determined that the knock is caused by the piston temperature. If the temperature difference between the oil temperature and water temperature (oil temperature - water temperature) is equal to or less than the threshold value ΔTc, it is possible to determine that the knock is caused by a factor other than the piston temperature.

[0079] 3-3. Temperature correction command and temperature correction value determination operation Next, the operation of determining a temperature correction command and a temperature correction value in the temperature corrector 14 will be described with reference to FIG. FIG. 13 is a flowchart showing the operation of determining a temperature correction command and a temperature correction value.

[0080] 13, first, the temperature correction unit 14 receives a temperature correction judgment result from the temperature correction judgment unit 15. Then, the temperature correction unit 14 judges whether or not the temperature correction judgment flag is ON (step S41). In the process of step S41, if the temperature correction unit 14 judges that the temperature correction judgment flag is ON (it is the timing to correct the estimated piston temperature) (YES judgment in step S41), the temperature correction unit 14 proceeds to the process of step S42. In addition, in the process of step S41, if the temperature correction unit 14 judges that the temperature correction judgment flag is OFF (it is not the timing to correct the estimated piston temperature) (NO judgment in step S41), the temperature correction unit 14 proceeds to the process of step S44.

[0081] In the process of step S44, the temperature correction unit 14 sends a temperature correction command OFF (does not correct the estimated piston temperature) to the piston temperature estimating unit 12, and the process returns to the process of step S41.

[0082] Next, in the process of step S42, temperature correction unit 14 sets the knock piston temperature Tk as the temperature correction value of the estimated piston temperature. Then, temperature correction unit 14 sends a temperature correction command ON (to correct the estimated piston temperature) and the temperature correction value (knock piston temperature Tk) to piston temperature estimator 12 (step S43), and returns to the process of step S41.

[0083] 3-4. Calculation of estimated piston temperature Next, the operation of calculating the estimated piston temperature in piston temperature estimator 12 will be described with reference to FIG. FIG. 14 is a flowchart showing the operation of calculating the estimated piston temperature.

[0084] 14, first, the piston temperature estimator 12 receives a temperature correction command from the temperature corrector 14. Then, the piston temperature estimator 12 determines whether the temperature correction command is ON or not (step S51). In the process of step S51, when the piston temperature estimator 12 determines that the temperature correction command is ON (to correct the estimated piston temperature) (YES determination in step S51), the piston temperature estimator 12 proceeds to a process for correcting the estimated piston temperature, that is, a process of step S52.

[0085] Furthermore, in the process of step S51, when the piston temperature estimator 12 determines that the temperature correction command is OFF (the estimated piston temperature is not corrected) (NO determination in step S51), it calculates the estimated piston temperature based on the amount of energy transmission. That is, the process proceeds to step S53.

[0086] In the process for correcting the estimated piston temperature, first, piston temperature estimator 12 replaces the current estimated piston temperature with the temperature correction value received from temperature corrector 14 (step S52). Then, the process proceeds to step S55, which will be described later.

[0087] On the other hand, in the calculation process of the estimated piston temperature based on the amount of energy transmission, first, the piston temperature estimation unit 12 calculates the amount of energy transmission to the piston 25 based on the actuator operation amount, the sensor output, and the internal combustion engine state amount (step S53). Next, the piston temperature estimation unit 12 calculates the estimated piston temperature by integrating the amount of energy transmission to the piston 25 using the above-mentioned formula 1 (step S54). Then, the process proceeds to step S55.

[0088] In the process of step S555, the piston temperature estimating unit 12 sends the calculated or replaced estimated piston temperature to the target amount calculating unit 16, and the process returns to the process of step S51.

[0089] FIG. 15 is an explanatory diagram showing an example of a time history of knock determination, temperature correction determination, estimated piston temperature, and piston temperature estimation error due to the correction operation of the estimated piston temperature. As shown in Fig. 15, according to the correction operation of the estimated piston temperature in this example, when a predetermined condition is satisfied while the knock determination is ON, the estimated piston temperature is corrected to the knock piston temperature Tk. This temperature correction suppresses the accumulation of errors in the piston temperature estimation. As a result, it is possible to prevent the accuracy of the estimated piston temperature from decreasing over time.

[0090] 3-5. Changing the piston temperature during knocking Incidentally, it is known that the likelihood of knock occurring varies depending on the fuel properties, environmental conditions, deterioration state of the internal combustion engine, and the like (hereinafter, these are abbreviated as disturbances). Therefore, even if the knock is caused by the piston temperature, the knock-time piston temperature Tk is considered to vary depending on the degree of the disturbance. For this reason, it is desirable to change the knock-time piston temperature Tk, which is the temperature correction value determined by temperature correction unit 14, depending on the degree of the disturbance.

[0091] FIG. 16 is an explanatory diagram showing an example of change in piston temperature Tk during knock with respect to changes in the octane number of the fuel, the alcohol concentration in the fuel, the latent heat of vaporization of the fuel, the rotation speed of the internal combustion engine, the humidity of the intake air, and the EGR rate (the mass ratio of recirculated gas to the intake air). The greater the octane number of the fuel, the alcohol concentration in the fuel, the latent heat of vaporization of the fuel, the rotation speed of the internal combustion engine, the humidity of the intake air, and the EGR rate, the less likely the knock will occur. Therefore, as shown in Fig. 16, the greater the octane number of the fuel, the alcohol concentration in the fuel, the latent heat of vaporization of the fuel, the rotation speed of the internal combustion engine, the humidity of the intake air, and the EGR rate, the higher the knock-time piston temperature Tk. Therefore, it is desirable for the temperature correction unit 14 to set the temperature correction value to be higher as the octane number of the fuel, the alcohol concentration in the fuel, the latent heat of vaporization of the fuel, the rotation speed of the internal combustion engine, the humidity of the intake air, and the EGR rate are greater.

[0092] FIG. 17 is an explanatory diagram showing an example of changes in knock-time piston temperature Tk with respect to changes in intake air amount, intake air pressure, intake air temperature, air-fuel ratio, compression ratio, and amount of deposits in the combustion chamber. The greater the intake air amount, intake air pressure, intake air temperature, air-fuel ratio, compression ratio, and amount of deposits in the combustion chamber, the more likely knock occurs. Therefore, as shown in Fig. 17, the greater the intake air amount, intake air pressure, intake air temperature, air-fuel ratio, compression ratio, and amount of deposits in the combustion chamber, the lower the knock-time piston temperature Tk. Therefore, it is desirable for temperature correction unit 14 to set the temperature correction value to be lower as the intake air amount, intake air pressure, intake air temperature, air-fuel ratio, compression ratio, and amount of deposits in the combustion chamber are greater.

[0093] Note that the disturbance is not limited to the examples shown in Figures 16 and 17 above, but comprehensively includes factors that affect the likelihood of knock occurring. For a factor that makes it more difficult for knock to occur as its level increases, temperature correction unit 14 sets a higher temperature correction value as the factor increases. Also, for a factor that makes it more likely for knock to occur as its level increases, temperature correction unit 14 sets a lower temperature correction value as the factor increases. By changing the temperature correction value in this way depending on the level of the disturbance, the accuracy of the corrected estimated piston temperature is further improved.

[0094] Therefore, the temperature correction unit 14 or the piston temperature / target amount calculation unit 11 acquires disturbance information from a sensor that detects disturbances. Then, the temperature correction unit 14 or the piston temperature / target amount calculation unit 11 calculates a temperature correction value (piston temperature during knock Tk) based on the acquired disturbance information by using a preset map, data table, or formula.

[0095] 3-6. Method for determining actuator control target amount Next, a method for determining the actuator control target amount in this embodiment will be described with reference to FIGS.

[0096] [How to determine the oil jet flow rate] First, a method for determining the oil jet flow rate as the actuator control target amount will be described with reference to Figs. FIG. 18 is a graph showing the relationship between the estimated piston temperature and the knock risk degree.

[0097] As described above, it is known that there is a strong linear correlation between the piston temperature and the knock intensity. In the ECU 2 of this example, the estimated piston temperature is used as a means for measuring the risk of knocking. Specifically, as shown in FIG. 18, the knock risk degree is an amount proportional to the estimated piston temperature. For example, when the estimated piston temperature is the piston temperature Tk during knocking, the knock risk degree is defined as 1, and when the estimated piston temperature is 0° C., the knock risk degree is defined as 0. The knock risk degree defined in this way is an index indicating that the risk of knocking increases as the knock risk degree approaches 1 from 0 to 1. That is, the target amount calculation unit 16 calculates the knock risk degree from the piston temperature Tk during knocking. Then, the target amount calculation unit 16 determines the control target value of the oil jet flow rate based on the knock risk degree.

[0098] FIG. 19 is an explanatory diagram showing an example of a method for determining the oil jet flow rate based on the knock risk degree, which is implemented by the target amount calculation unit 16. 19, when the knock risk degree exceeds a predetermined first threshold C1 (e.g., 0.9), the target amount calculation unit 16 increases the target oil jet flow rate from G0 to G1. Also, when the knock risk degree falls below a predetermined second threshold C2 (e.g., 0.8), the target amount calculation unit 16 decreases the target oil jet flow rate from G1 to G0.

[0099] Incidentally, by providing a gap between the first threshold C1, which is the threshold for an increase, and the second threshold C2, which is the threshold for a decrease, it is possible to prevent oscillations from occurring in the oil jet flow rate.

[0100] FIG. 20 is an explanatory diagram showing another example of the method of determining the oil jet flow rate based on the knock risk degree, which is implemented by the target amount calculation unit 16. As shown in FIG. 20, when the knock risk degree exceeds a predetermined threshold C1 (for example, 0.9), the target amount calculation unit 16 increases the target oil jet flow rate as the knock risk degree increases until the target oil jet flow rate reaches an upper limit value Gmax.

[0101] Note that the oil jet flow rate may be determined directly based on the estimated piston temperature instead of the knock risk degree. For example, the target amount calculation unit 16 may increase the target oil jet flow rate from G0 to G1 when the estimated piston temperature exceeds a predetermined first threshold (e.g., 150°C). The target amount calculation unit 16 may also decrease the target oil jet flow rate from G1 to G0 when the estimated piston temperature falls below a predetermined second threshold (e.g., 140°C).

[0102] Furthermore, when the estimated piston temperature exceeds a predetermined threshold value (e.g., 150°C), the target amount calculation unit 16 may increase the target oil jet flow rate as the estimated piston temperature increases until the target oil jet flow rate reaches an upper limit value Gmax.

[0103] However, the knock risk degree is an index normalized by the knock piston temperature Tk. Therefore, even if the knock piston temperature Tk changes due to a disturbance, the effect of this is automatically reflected in the knock risk degree. Therefore, by determining the target oil jet amount using the knock risk degree, it becomes unnecessary to change the threshold values ​​(C1, C2) for determining the change point of the oil jet flow rate even if the knock piston temperature Tk changes. As a result, there is an advantage in that the control software can be simplified.

[0104] In this way, by determining the oil jet flow rate based on the estimated piston temperature or the knock risk degree calculated from the estimated piston temperature, the oil jet flow rate is increased before the occurrence of a knock when the risk of knocking is high, and cooling of the piston 25 is promoted. This makes it possible to prevent the occurrence of a knock, or to reduce the intensity of the knock even if the knock does occur. As a result, it is possible to improve the output of the internal combustion engine 100 and reduce exhaust loss.

[0105] In addition, if the oil jet flow rate is determined based on the estimated piston temperature or the knock risk level calculated from the estimated piston temperature, the oil jet flow rate is reduced when the risk of knocking is low. This reduces friction loss associated with the load on the hydraulic pump and reduces cooling loss by suppressing cooling of the piston 25.

[0106] [Method of determining target ignition timing] Next, a method of determining a target ignition timing as an actuator control target amount will be described with reference to FIG. 21 and FIG.

[0107] Generally, in a spark ignition internal combustion engine, when knock occurs and the knock judgment is turned ON, the ignition timing is set to the retard side from the normal ignition timing (Minimum Advance for Best Torque, MBT), so-called ignition retard control is performed. Then, after the knock stops and the knock judgment is turned OFF, ignition timing recovery control is performed to advance the retarded ignition timing toward the MBT.

[0108] In the ECU 2 of this embodiment, the ignition advance angular speed (ignition advance angle per unit time dθig / dt) in the ignition timing recovery control is changed according to the magnitude of the knock risk degree, based on the estimated piston temperature. 21A and 21B are explanatory diagrams showing an example of a method for determining the ignition advance angular speed based on the knock risk degree. FIG. 22 is an explanatory diagram showing an example of a time history of knock determination, target ignition timing, piston temperature, and knock risk degree. As shown in FIG. 21A and FIG. 21B, in this example, the ignition advance angular speed when the knock risk is low is set faster than the ignition advance angular speed when the knock risk is high. In addition, the knock risk degree is calculated using the estimated piston temperature as shown in FIG. 18.

[0109] In this case, as shown in Fig. 21B, an upper limit or lower limit may be set for the ignition advance speed. By setting an upper limit for the ignition advance speed, it is possible to reduce the risk of knock reoccurring due to the advance speed becoming excessively fast when the knock risk level is low. Also, by setting a lower limit for the ignition advance speed, it is possible to reduce the risk of the ignition advance speed becoming excessively slow and the period during which the ignition timing is retarded from the MBT becoming longer when the knock risk level is high.

[0110] The spark advance speed may be determined directly based on the estimated piston temperature instead of the knock risk degree. That is, the spark advance speed when the estimated piston temperature is low may be set faster than the spark advance speed when the estimated piston temperature is high.

[0111] However, as described above, even if the knock piston temperature Tk changes due to a disturbance, the effect of this change is automatically reflected in the knock risk degree. Therefore, by using the knock risk degree to determine the ignition advance rate, there is an advantage in that the control software can be simplified.

[0112] In this way, changing the ignition advance speed in ignition timing recovery control based on the estimated piston temperature or the knock risk level has the following effects and advantages. As shown in Figure 22, immediately after a knock is determined, the ignition timing is retarded by a large amount, so the piston temperature drops and the knock risk level decreases. Therefore, a fast ignition advance speed is set and the ignition retard amount rapidly decreases. This makes it possible to reduce exhaust losses associated with retarding the ignition timing compared to when the ignition advance speed is constant (conventional example), as shown by the dotted line in Figure 22.

[0113] On the other hand, a slow ignition advance speed is set because a small spark retard amount increases the piston temperature and the knock risk. Therefore, when the ignition advance speed is slow, the rate of increase in piston temperature associated with the ignition advance is slower than when the ignition advance speed is constant (conventional example) as shown by the dotted line in Figure 22.

[0114] Furthermore, in the ignition timing recovery control, the piston temperature continues to rise due to the heat capacity of the piston 25 even after the ignition advance is stopped, and there is a risk that knock will reoccur due to piston temperature overshoot. However, according to the ECU 2 of this example, when the ignition retard amount is small, the ignition advance rate is set low. This makes it possible to suppress piston temperature overshoot and prevent knock from reoccurring. In other words, according to the method of determining ignition timing based on the estimated piston temperature or the knock risk degree of this example, in the ignition timing recovery control after knock, it is possible to reduce exhaust loss by reducing the ignition retard amount while preventing knock from reoccurring.

[0115] The present invention is not limited to the embodiment described above and shown in the drawings, and various modifications can be made without departing from the spirit of the invention as defined in the claims.

[0116] In addition, the above-mentioned components, functions, processing units, etc. may be realized in part or in whole in hardware, for example, by designing an integrated circuit. In addition, the above-mentioned components, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. Information such as the program, table, file, etc. that realizes each function can be stored in a recording device such as a memory, a hard disk, or an SSD (Solid State Drive), or in a recording medium such as an IC card, an SD card, or a DVD. [Explanation of symbols]

[0117] 2...ECU (internal combustion engine control unit), 3...input circuit, 4...input / output port, 5...RAM, 6...ROM, 7...CPU, 8...oil jet control unit, 9...ignition control unit, 10...crank angle sensor, 11...piston temperature / target amount calculation unit, 12...piston temperature estimation unit, 14...temperature correction unit, 15...temperature correction determination unit, 16...target amount calculation unit, 17...energy transmission amount estimation unit, 18...temperature calculation unit, 22...ignition coil, 23...cylinder block, 24...cylinder head, 25...piston, 26...intake valve, 27...exhaust valve, 31...electronically controlled throttle valve, 32...intake port, 33...exhaust port, 34...catalytic converter, 35...fuel injection device, 36...airflow sensor, 37...air-fuel ratio sensor, 38...knock sensor, 39...oil temperature sensor, 40... oil pan, 41... water temperature sensor, 42... water jacket, 53... oil jet, 56... oil supply passage, 62... accelerator opening sensor, 100... internal combustion engine

Claims

1. a piston temperature estimation unit that estimates a piston temperature of the internal combustion engine based on a sensor output from a sensor provided in the internal combustion engine, an actuator operation amount, and an internal combustion engine state amount; a temperature correction determination unit that determines whether or not it is a correction timing for correcting the piston estimated temperature estimated by the piston temperature estimator, based on the sensor output, an actuator operation amount, and an internal combustion engine state amount; a temperature correction unit that corrects the piston estimated temperature estimated by the piston temperature estimating unit at the correction timing determined by the temperature correction determination unit to a predetermined temperature; a target amount calculation unit that calculates a control target amount of an actuator of the internal combustion engine based on the piston estimated temperature estimated by the piston temperature estimation unit or the piston temperature corrected to the predetermined temperature by the temperature correction unit; An internal combustion engine control device comprising:

2. The temperature correction determination unit determines a timing at which a knock caused by at least the piston temperature occurs as the correction timing. The internal combustion engine control device according to claim 1.

3. The temperature correction determination unit determines, as the correction timing, at least when a deviation between the estimated piston temperature and the piston temperature at the time of knock is equal to or greater than a predetermined value and when a knock caused by the piston temperature occurs. The internal combustion engine control device according to claim 2.

4. The temperature correction determination unit determines whether or not the cause of the occurrence of the knock is the piston temperature based on a change in knock intensity when an oil jet flow rate of the internal combustion engine is changed. The internal combustion engine control device according to claim 2.

5. The temperature correction determination unit determines that the knock is caused by the piston temperature when a change in knock intensity with respect to a change in the oil jet flow rate is greater than a predetermined value while the ignition timing is constant. The internal combustion engine control device according to claim 4.

6. The temperature correction determination unit determines whether or not the cause of the occurrence of the knock is the piston temperature based on a change in ignition timing when the oil jet flow rate changes. The internal combustion engine control device according to claim 2.

7. The temperature correction determination unit determines that the knock is caused by the piston temperature when a change in ignition timing with respect to a change in the oil jet flow rate is greater than a predetermined value while the knock intensity is constant. The internal combustion engine control device according to claim 6.

8. The temperature correction determination unit determines whether or not the cause of the occurrence of a knock is a knock caused by the piston temperature, based on a temperature difference between an oil temperature and a water temperature of the internal combustion engine. The internal combustion engine control device according to claim 2.

9. The temperature correction determination unit determines that the knock is caused by the piston temperature when a temperature difference obtained by subtracting the water temperature from the oil temperature is greater than a predetermined value. The internal combustion engine control device according to claim 8.

10. The temperature correction unit sets the temperature of the piston at the time when a knock occurs to the predetermined temperature. The internal combustion engine control device according to claim 1.

11. The temperature correction unit changes the predetermined temperature based on a disturbance of the internal combustion engine. The internal combustion engine control device according to claim 10.

12. The temperature correction unit changes the predetermined temperature based on the magnitude of at least one of the disturbances, which are the octane number of the fuel, the alcohol concentration of the fuel, the latent heat of vaporization of the fuel, the rotation speed of the internal combustion engine, the humidity of the intake air, the EGR rate, the intake air amount, the intake air pressure, the intake air temperature, the air-fuel ratio, the compression ratio, and the amount of deposits. The internal combustion engine control device according to claim 11.

13. a process of estimating a piston temperature of the internal combustion engine by a piston temperature estimation unit based on a sensor output from a sensor provided in the internal combustion engine, an actuator operation amount, and an internal combustion engine state amount; a process of determining, by a temperature correction determination unit, whether or not it is a correction timing for correcting the piston estimated temperature estimated by the piston temperature estimator, based on the sensor output, an actuator operation amount, and an internal combustion engine state amount; a process of correcting, by a temperature correction unit, the piston estimated temperature estimated by the piston temperature estimating unit at the correction timing determined by the temperature correction determination unit, to a predetermined temperature; a process of calculating a control target amount of an actuator of the internal combustion engine in a target amount calculation unit based on the piston estimated temperature estimated by the piston temperature estimation unit or the piston temperature corrected to the predetermined temperature by the temperature correction unit; A method for controlling an internal combustion engine comprising:

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