Control device for internal combustion engine

Abstract

The present invention comprises: a temporal change reading unit that reads a temporal change in a measurement value which is correlated with an air flow rate of air sucked into a combustion chamber of an internal combustion engine; and a change trend estimation unit that estimates a change trend in a combustion chamber wall temperature on the basis of the temporal change in the measurement value. As a result, the combustion chamber wall temperature can be estimated and the reliability and certainty of the estimation result can be improved. In other words, the accuracy of the control of various actuators can be improved, and thus improvements to the performance of the internal combustion engine, such as a reduction in fuel consumption, can be more accurately achieved.

Description

Control device for internal combustion engine

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

[0002] An internal combustion engine (so-called automobile engine) such as an engine mounted on a vehicle operates according to the operation amounts of various actuators that are adapted to specific environmental conditions such as temperature, humidity, air pressure, etc. Furthermore, when driving on an actual road, the environmental conditions and the state of the internal combustion engine may deviate from the conditions assumed at the time of adaptation, and therefore the operation amounts of various actuators are corrected according to the detection results from various sensors.

[0003] An example of a condition related to the performance of an internal combustion engine is the temperature of the wall of the combustion chamber of the internal combustion engine (hereinafter referred to as the wall temperature). In order to improve the performance of the internal combustion engine, such as reducing fuel consumption, a control device for the internal combustion engine estimates the wall temperature of the combustion chamber (combustion chamber wall temperature estimation) based on an energy balance calculation, and controls various actuators based on the estimation result.

[0004] Known prior art related to such control of an internal combustion engine is, for example, that described in Patent Document 1. Patent Document 1 discloses an internal combustion engine control device including an engine state estimating unit that calculates an amount of energy transmitted from gas inside the internal combustion engine to a wall surface based on parameters related to operating conditions of the internal combustion engine, parameters related to chemical conditions of combustion, and parameters related to an operating status of the internal combustion engine, a wall surface temperature estimating unit that estimates a wall surface temperature based on the amount of energy transmitted from the gas to the wall surface calculated by the engine state estimating unit, and an operation amount calculating unit that 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 estimating unit.

[0005] Japanese Patent Application Laid-Open No. 2022-32184

[0006] Incidentally, it is conceivable that a difference will arise between the estimated value and the actual value of the combustion chamber wall temperature due to factors such as aging of the components that make up the internal combustion engine, deposits on the piston, the type of fuel (gasoline), etc. Therefore, it is necessary to provide multiple means for estimating the combustion chamber wall temperature and use these in combination to ensure the reliability and accuracy of the estimated combustion chamber wall temperature.

[0007] The present invention has been made in consideration of the above, and aims to provide a control device for an internal combustion engine that can estimate the combustion chamber wall temperature and improve the reliability and certainty of the estimation results.

[0008] The present application includes multiple means for solving the above-mentioned problems, and as one example, a control device for an internal combustion engine includes a time change reading unit that reads the time change of a measurement value that is correlated with the air flow rate taken into the combustion chamber of the internal combustion engine, and a change trend estimation unit that estimates the change trend of the combustion chamber wall temperature based on the time change of the measurement value.

[0009] According to the present invention, it is possible to estimate the combustion chamber wall temperature, and to improve the reliability and certainty of the estimation result.

[0010] FIG. 1 is a diagram schematically illustrating an example of a system configuration of an internal combustion engine mounted on an automobile, together with related configurations. FIG. 1 is a diagram schematically illustrating the hardware configuration of an ECU. FIG. 2 is a functional block diagram schematically illustrating an actuator operation amount calculation function. FIG. 3 is a functional block diagram illustrating the processing content of a combustion chamber wall temperature estimating unit. FIG. 4 is a functional block diagram illustrating the processing content of a time change reading unit. FIG. 5 is a diagram explaining the basic principle of wall temperature difference estimation processing in a combustion chamber change tendency estimating unit, and is a diagram illustrating time changes in throttle opening, air flow rate, combustion chamber wall temperature, air flow rate time change rate, and wall temperature time change rate. FIG. 6 is a diagram explaining the basic principle of wall temperature difference estimation processing in a combustion chamber change tendency estimating unit, and is a diagram illustrating time changes in throttle opening, intake pressure, combustion chamber wall temperature, intake pressure time change rate, and wall temperature time change rate. FIG. 7 is a functional block diagram illustrating the processing content of a wall temperature estimating unit. FIG. 8 is a flowchart illustrating the processing content of an operation amount correcting unit. FIG. 9 is a diagram illustrating the relationship between a wall temperature difference estimated value and an ignition timing correction amount. FIG. 10 is a diagram illustrating the relationship between a wall temperature difference estimated value and an oil pressure correction amount. FIG. 11 is a diagram illustrating the relationship between a wall temperature difference estimated value and an injection timing correction amount. 10 is a flowchart showing processing performed by a model correction unit of a wall temperature estimation unit according to the second embodiment. FIG. 11 is a diagram showing an example of time-dependent changes in piston temperature, etc.

[0011] An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, an internal combustion engine that is mounted on an automobile or the like and uses gasoline as fuel will be described as an example, but the present invention can also be applied to other internal combustion engines that use different types of fuel, specifications, or uses.

[0012] First Embodiment A first embodiment of the present invention will be described with reference to FIGS.

[0013] FIG. 1 is a diagram illustrating an example of the system configuration of an internal combustion engine mounted on an automobile, together with related components.

[0014] The internal combustion engine (engine) ENG shown in Figure 1 is a direct-injection internal combustion engine for an automobile that is driven by spark ignition combustion and includes an in-cylinder fuel injection mechanism that directly injects gasoline fuel into each of a plurality of cylinders, an intake mechanism that supplies air into the cylinders, an ignition mechanism that ignites a mixture of gasoline fuel and air injected into the cylinders, an exhaust mechanism that exhausts the air after combustion in the cylinders, etc. In this embodiment, for simplicity of illustration, only one of the plurality of cylinders is shown together with the related components.

[0015] The internal combustion engine ENG is equipped with an air flow sensor 1 (AFS: Air Flow Sensor) that measures the intake air amount (air flow rate) and intake air temperature, an intake pressure sensor 3 (MAP: Manifold Absolute Pressure sensor) that measures the intake pipe pressure (intake air pressure), a supercharger compressor 4a that supercharges the intake air, an intercooler 7 that cools the intake air, an electronically controlled throttle 2 that adjusts the intake pipe pressure (in other words, the air flow rate), and an ECU (Electronic Control Unit) 100 that is a control device that controls the overall operation of the internal combustion engine ENG. Detection results (output information) of various sensors such as the air flow sensor 1 and the intake pressure sensor 3 are sent to the ECU 100.

[0016] The internal combustion engine ENG is also provided with a fuel injection device 13 (hereinafter also referred to as an injector 13) for injecting fuel into a cylinder 14 of each cylinder, and an ignition device for each cylinder, which is composed of an ignition coil 16 and an ignition plug 17 and supplies ignition energy to the fuel injected into the cylinder 14.

[0017] The cylinder head is provided with a variable valve 5 for each cylinder that adjusts the mixture flowing into the cylinder or the exhaust gas discharged from the cylinder, and by adjusting the variable valve 5, the intake amount and internal EGR amount for all cylinders are adjusted.

[0018] A voltage sensor (not shown) is attached to the ignition coil 16 to detect the primary side voltage or the secondary side voltage, and the detection result (output information) is sent to the ECU 100 .

[0019] An oil jet system 20 for lowering the piston temperature is provided behind the piston of each cylinder. The oil jet system 20 is connected to a variable displacement (variable oil pressure) oil pump 20a, and the amount of oil injected from the oil jet system 20 toward the piston is adjusted by adjusting the output (flow rate, oil pressure) of the oil pump.

[0020] A high-pressure fuel pump (not shown) is connected to the fuel injection device 13 via a fuel pipe for supplying high-pressure fuel to the fuel injection device 13. A fuel pressure sensor for measuring the fuel injection pressure is provided in the fuel pipe. The detection result (output information) of the fuel pressure sensor is sent to the ECU 100.

[0021] The internal combustion engine ENG is equipped with a crank angle sensor 19 for detecting the piston position. The detection result (output information) of the crank angle sensor 19 is sent to the ECU 100.

[0022] The exhaust pipe 15 is provided with a turbine 4b that uses exhaust energy to provide rotational force to the turbocharger compressor 4a, an electronically controlled wastegate valve 11 that adjusts the exhaust flow rate flowing to the turbine 4b, a three-way catalyst 10 that purifies the exhaust, and an air-fuel ratio sensor 9 that detects the air-fuel ratio of the exhaust gas upstream of the three-way catalyst 10. The internal combustion engine ENG is also provided with a temperature sensor 18 that measures the temperature of coolant circulating around the internal combustion engine ENG. The detection results (output information) of the air-fuel ratio sensor 9 and the temperature sensor 18 are sent to the ECU 100.

[0023] The accelerator pedal is provided with an accelerator position sensor 12. The accelerator position sensor 12 detects the amount of depression of the accelerator pedal, i.e., the accelerator position. The detection result (output information) of the accelerator position sensor 12 is sent to the ECU 100.

[0024] The ECU 100 calculates the required torque based on the output information from the accelerator position sensor 12. In other words, the accelerator position sensor 12 can also be considered a required torque detection sensor that detects the torque required for the internal combustion engine. The ECU 100 also calculates the rotation speed of the internal combustion engine based on the output information from the crank angle sensor 19. The ECU 100 appropriately calculates the main operating variables of the internal combustion engine, such as the air flow rate, fuel injection amount, ignition timing, and fuel pressure, based on the operating state of the internal combustion engine obtained from the output information of various sensors.

[0025] The fuel injection amount calculated by the ECU 100 is converted into a valve-opening pulse signal and sent to the injector 13. An ignition signal is also sent to the ignition coil 16 so that ignition occurs at the ignition timing calculated by the ECU 100. The throttle opening calculated by the ECU 100 is also sent to the electronically controlled throttle 2 as a throttle drive signal.

[0026] An injector 13 injects fuel into air that flows into a cylinder 14 from an intake pipe through an intake valve, forming an air-fuel mixture. The air-fuel mixture is ignited (exploded) by a spark generated by a spark plug 17 at a predetermined ignition timing. The resulting combustion pressure pushes a piston downward, rotating a rotating shaft (crankshaft) connected to the piston via a connecting rod, thereby generating driving force for the internal combustion engine ENG. Exhaust gases generated after the explosion are sent through an exhaust pipe 15 to a three-way catalyst 10, where exhaust components are purified and then discharged to the outside. The internal combustion engine ENG in this embodiment employs variable valve timing control (VTC), which continuously adjusts the opening and closing timing of the intake valves according to the engine speed and load.

[0027] FIG. 2 is a diagram illustrating a schematic hardware configuration of the ECU.

[0028] 2, various output information such as the air flow rate (intake flow rate) from the air flow sensor 1, the intake manifold pressure (intake pressure) from the intake pressure sensor 3, the coil primary or secondary voltage from the voltage sensor of the ignition coil 16, the fuel injection pressure from the fuel pressure sensor of the fuel injector 13, the crank angle from the crank angle sensor 19, the exhaust gas air-fuel ratio (exhaust air-fuel ratio) from the air-fuel ratio sensor 9, the coolant temperature from the temperature sensor 18, the accelerator opening from the accelerator opening sensor 12, the rotation speed of the rotating shaft (crankshaft), and various VTC setting values ​​(VTC settings) are input to an input circuit 21 of the ECU 100, which is a control device for the internal combustion engine. However, the input information input to the ECU 100 is not limited to these.

[0029] Input information input to the input circuit 21 of the ECU 100 is sent to the input port side of the input / output port 22. The input information sent to the input / output port 22 is temporarily stored in the RAM 23c and is processed by the CPU 23a in accordance with a predetermined control program. The control program describing the contents of the processing is written in advance in the ROM 23b.

[0030] Output information indicating the amount of operation of the fuel injection valves and ignition coils that control the internal combustion engine, calculated according to the control program, is temporarily stored in RAM 23c, and then sent to the output port side of input / output port 22, and sent via each drive circuit, such as ignition control unit 24, fuel injection control unit 25, and oil jet control unit 26, to the ignition coil 16, the tumble control valve of the fuel injection device 13, and the oil pump of the oil jet system 20. Actuators other than those mentioned above are also used in the internal combustion engine ENG, but their description will be omitted here.

[0031] In this embodiment, the ECU 100 has an ignition control unit 24, a fuel injection control unit 25, and an oil jet control unit 26 as drive circuits.

[0032] The ignition control unit 24 acquires information regarding the timing and duration of energization of the ignition coil 16 as the operation amount of the associated actuator, and controls the timing and duration of energization of the ignition coil 16 based on the acquired operation amount.

[0033] The fuel injection control unit 25 acquires information regarding the valve opening timing and valve opening duration of the fuel injection device 13 as the operation amount of the associated actuator, and controls the valve opening timing and valve opening duration of the fuel injection device 13 and the opening and closing of the valve for pressure adjustment provided in the fuel pressure pump based on the acquired operation amount.

[0034] The oil jet control unit 26 acquires information regarding the output (oil flow rate, oil pressure (oil pressure)) of the oil pump 20a of the oil jet system 20 as the operation amount of the associated actuator, and controls the oil pump 20a based on the acquired information.

[0035] In this embodiment, the ECU 100 is equipped with an ignition control unit 24 for controlling the time that current is applied to the ignition coil and the amount of discharge energy, a fuel injection control unit 25 for controlling the injection timing and injection period of the fuel injection device, and an oil jet control unit 26 for manipulating the output of the oil pump 20a to control the amount of oil injected from the oil jet system 20, but this is not limited to this, and some of the control units of the ignition control unit 24, fuel injection control unit 25, and oil jet control unit 26 may be implemented in a device separate from the ECU 100.

[0036] FIG. 3 is a functional block diagram that schematically shows the actuator operation amount calculation function.

[0037] In FIG. 3 , actuator operation amount calculation function 200 is a functional section realized by a control program in ECU 100, and has an actuator steady state determination section 210 that determines whether or not actuators related to the operating state, such as the throttle opening, VTC phase, and rotation speed, are in steady states, a combustion chamber wall temperature estimation section 220 that estimates the wall surface temperature of the combustion chamber (the space defined by the cylinder 14, cylinder head, and piston) of the internal combustion engine ENG, and an operation amount correction section 230 that corrects the operation amounts of various actuators, such as the fuel injection device 13, ignition coil 16, and oil pump 20 a of the oil jet system 20, in accordance with the estimated combustion chamber wall surface temperature.

[0038] The actuator steady-state determination unit 210 determines whether each actuator is in a steady state based on the throttle opening, VTC setting, and engine speed of the internal combustion engine ENG. An actuator is in a steady state when there is no change in the position or attitude of the mechanism driven by the actuator, or when the change is within a small range. For example, when the amount of change per unit time in the detection results (output information) of each sensor that changes in response to the actuator's operation is within a predetermined small range. An actuator is not in a steady state (in other words, in a transient state) when, for example, the amount of change per unit time in the detection results (output information) of each sensor that changes in response to the actuator's operation is outside the predetermined small range. Specifically, the actuator is determined to be in a steady state when, for example, there is no change in the engine rotation speed (rpm) and the operation amount of intake system components such as the throttle opening and VTC phase (the change is within a predetermined range). In this embodiment, as necessary, the engine rotation speed (rpm) and the operation amounts of intake system components such as the throttle opening and VTC phase are fixed to constant values ​​to forcibly create a state where there is no change (a state where the change is within a predetermined value range) (i.e., the actuator is kept steady).

[0039] FIG. 4 is a functional block diagram showing the processing contents of the combustion chamber wall temperature estimation unit.

[0040] In FIG. 4 , the combustion chamber wall temperature estimation unit 220 includes a time change reading unit 221 , a combustion chamber change tendency estimation unit 222 , and a wall temperature estimation unit 223 .

[0041] FIG. 5 is a functional block diagram showing the processing contents of the time change reading unit.

[0042] 5, the time change reading unit 221 includes a unit delay calculation unit 221a that performs processing to delay the air flow rate (ma(t1)) at a certain time point (t1) by one sampling period, a calculator 221b that calculates a time change amount (Δma) of the air flow rate, which is the difference between the air flow rate and the calculation result of the unit delay calculation unit 221a, a unit delay calculation unit 221c that performs processing to delay the intake pipe pressure (pin(t1)) at the certain time point (t1) by one sampling period, and a calculator 221d that calculates a time change amount (Δpin) of the intake pipe pressure, which is the difference between the intake pipe pressure and the calculation result of the unit delay calculation unit 221c. The time change reading unit 221 outputs the time change amount (Δma) of the air flow rate, the time change amount (Δpin) of the intake pipe pressure, and the input air flow rate.

[0043] 6 and 7 are diagrams illustrating the basic principle of the wall temperature difference estimation process in the combustion chamber change tendency estimation unit.

[0044] In the present invention, when the throttle opening is constant, there is a correlation between the air flow rate (or intake manifold pressure) and the combustion chamber wall temperature, and there is also a correlation between the air flow rate (or intake manifold pressure) and the time change (rate of change) of the combustion chamber wall temperature. Based on this new finding unique to the present invention, the change in the combustion chamber wall temperature is estimated from these correlations. Note that measurement values ​​correlated with the air flow rate include the air flow rate detected by the air flow sensor 1 and the intake manifold pressure (intake pressure) detected by the intake manifold-mounted intake pressure sensor 3, as well as the fuel flow rate injected from the fuel injector 13 and the product of the fuel flow rate and the exhaust air-fuel ratio detected by the air-fuel ratio sensor 9.

[0045] Here, the combustion chamber wall temperature (combustion chamber wall temperature: hereinafter simply referred to as wall temperature) refers to the temperature of the wall formed inside the combustion chamber or on its surrounding components (in other words, the temperature of the wall near the combustion chamber). This temperature includes, for example, the temperatures of the combustion chamber head, liner, piston, etc. However, to be precise, the temperatures of the combustion chamber head, liner, and piston may differ from one another. Therefore, for example, the average of these temperatures may be used as the combustion chamber wall temperature, or the temperature of one of the components may be used as the combustion chamber wall temperature. The wall temperature is a physical quantity related to the actuator operation amount that affects fuel economy and exhaust performance. For example, under high wall temperature conditions, gas near the wall surface is heated, which makes abnormal combustion (so-called knocking) more likely to occur. Therefore, unless the actuator operation is devised, efficiency will deteriorate. On the other hand, under low wall temperature conditions, fuel adhering to the wall surface is likely to remain liquid, which may lead to the generation of unburned hydrocarbons and soot, potentially resulting in poor exhaust performance. Furthermore, under conditions where the wall surface temperature is low, it is possible to adjust the manipulated variable by utilizing the fact that the occurrence of abnormal combustion is suppressed.

[0046] The combustion chamber change tendency estimation unit 222 performs a wall temperature difference estimation process to calculate an estimated wall temperature difference (ΔT I ), which is an estimate of the temperature difference of the combustion chamber wall temperature from the steady state, based on the amount of change over time in the air flow rate (see FIG. 6 ) or the amount of change over time in the intake pipe pressure (see FIG. 7 ). Specifically, the wall temperature difference estimation process is a process that calculates and outputs, for example, a difference value from the temperature in the steady state, indicating whether the combustion chamber temperature is in the steady state or is in a state higher or lower than the steady state.

[0047] FIG. 6 shows the time changes of the throttle opening, air flow rate, combustion chamber wall temperature, air flow rate time change rate, and wall temperature time change rate.

[0048] As shown in Figure 6, similar to the correlation between the air flow rate and the combustion chamber wall temperature, there is a correlation between the air flow rate and the change over time (rate of change) of the combustion chamber wall temperature after time t1, and this relationship can be expressed by the following (Equation 1): In the following (Equation 1), the constant B can be identified from the heat capacity of the wall structure of the combustion chamber.

[0049]

[0050] On the other hand, when the throttle is fixed, the combustion chamber wall temperature changes with a first-order lag, so the following (Equation 2) holds. Furthermore, (Equation 3) can be derived from (Equation 2). The constant τ in (Equation 2) and (Equation 3) can be identified from the time it takes for the change in air flow rate to converge.

[0051]

[0052]

[0053] From the above (Equation 1) and (Equation 3), the following (Equation 4) is derived.

[0054]

[0055] Furthermore, the following (Equation 5) is derived from the time change (rate of change) of the air flow rate.

[0056]

[0057] From the above (Equation 4) and (Equation 5), the following (Equation 6) is obtained for estimating the temperature difference (ΔT) from the steady state of the combustion chamber wall surface temperature based on the air flow rate.

[0058]

[0059] FIG. 7 shows the time changes of the throttle opening, intake pressure, combustion chamber wall temperature, intake pressure time change rate, and wall temperature time change rate.

[0060] As shown in Figure 7, similar to the correlation between intake pressure and combustion chamber wall temperature, there is a correlation between the time change (rate of change) of intake pressure and combustion chamber wall temperature after time t1, and this relationship can be expressed by the following equation (7): In the following equation (7), the constant A can be identified from the heat capacity of the wall surface structure of the combustion chamber.

[0061]

[0062] On the other hand, in the case shown in Figure 7, as in Figure 6, the combustion chamber wall temperature when the throttle is fixed changes with a first-order lag, so the above (Equation 2) and (Equation 3) hold. That is, the following (Equation 8) can be derived from the above (Equation 7) and (Equation 3).

[0063]

[0064] Furthermore, the following (Equation 9) is derived from the time change (rate of change) of the intake pressure.

[0065]

[0066] From the above (Equation 8) and (Equation 9), the following (Equation 10) is obtained for estimating the temperature difference (ΔT) from the steady state of the combustion chamber wall surface temperature based on the intake pressure.

[0067]

[0068] FIG. 8 is a functional block diagram showing the processing contents of the wall temperature estimation unit.

[0069] 8, the wall temperature estimation unit 223 includes a steady-state wall temperature calculation unit 223a that calculates the steady-state combustion chamber wall temperature (steady-state wall temperature) from the air flow rate and the rotation speed, and a calculator 223b that calculates the combustion chamber wall temperature T from the steady-state wall temperature calculated by the steady-state wall temperature calculation unit 223a and the wall temperature difference estimated value (ΔT) from the combustion chamber change tendency estimation unit 222. The steady-state wall temperature calculation unit 223a calculates the steady-state wall temperature using a preset map of the combustion chamber wall temperature, which takes the air flow rate and the rotation speed as inputs and outputs the steady-state wall temperature.

[0070] FIG. 9 is a flowchart showing the processing contents of the operation amount correcting unit.

[0071] As shown in FIG. 9, the manipulated variable correction unit 230 first determines whether the combustion chamber wall temperature T estimated by the combustion chamber wall temperature estimation unit 220 is in a steady state (or a state equivalent to a steady state) (step S100).

[0072] If the determination result in step S100 is YES, that is, if the combustion chamber wall temperature is not in a steady state, the process ends.

[0073] If the determination result in step S100 is NO, it is then determined whether the combustion chamber wall temperature is higher than the steady-state wall surface temperature (step S110). The determination in step S110 can be made by checking whether the estimated wall temperature difference (ΔT I) is positive or negative. That is, if the estimated wall temperature difference (ΔT I) is positive, it can be said that the wall temperature is higher than the steady-state wall surface temperature, so the determination result in step S110 is YES. On the other hand, if the estimated wall temperature difference (ΔT I) is negative, it can be said that the wall temperature is lower than the steady-state wall surface temperature, so the determination result in step S110 is NO.

[0074] If the judgment result in step S110 is YES, as control to respond to the high wall temperature, the ignition timing is retarded by the ignition device, the oil pressure is increased by the oil jet system 20, and the injection timing is advanced by the fuel injection device 13 (step S120), and the processing is terminated.

[0075] Also, if the judgment result in step S110 is NO, as control to respond to the low wall temperature, the ignition timing is advanced by the ignition device, the oil pressure is reduced by the oil jet system 20, and the injection timing is retarded by the fuel injection device 13 (step S130), and the processing is terminated.

[0076] The details of the processes in steps S120 and S130 will now be described with reference to FIGS.

[0077] FIG. 10 is a diagram showing the relationship between the estimated wall temperature difference and the correction amount of the ignition timing.

[0078] As shown in Fig. 10, when the estimated wall temperature difference (ΔTI) is positive, there is a high possibility of knocking, so control is performed to suppress the occurrence of knocking by correcting the ignition timing of the ignition device to a retarded angle. On the other hand, when the estimated wall temperature difference (ΔTI) is negative, control is performed to reduce fuel consumption by correcting the ignition timing of the ignition device to an advanced angle.

[0079] FIG. 11 is a diagram showing the relationship between the estimated wall temperature difference and the correction amount of the oil pressure.

[0080] 11, when the estimated wall temperature difference value (ΔTI) is positive, there is a high possibility of knocking, so control is performed to suppress the occurrence of knocking by increasing the oil pressure by the oil jet system 20. On the other hand, when the estimated wall temperature difference value (ΔTI) is negative, there is no need to change the oil pressure by the oil jet system 20, so control is performed without correcting the oil pressure (however, when a low oil pressure setting is the default).

[0081] FIG. 12 is a diagram showing the relationship between the estimated wall temperature difference and the correction amount of the injection timing.

[0082] 12, when the wall temperature difference estimated value (ΔTI) is positive, fuel adhering to the piston is likely to vaporize, so the fuel injection timing by the fuel injector 13 is corrected to be advanced, that is, control is performed to prioritize the mixing time. On the other hand, when the wall temperature difference estimated value (ΔTI) is negative, fuel adhering to the piston is likely to remain, so the fuel injection timing by the fuel injector 13 is corrected to be retarded, that is, control is performed to suppress fuel adhesion to the piston.

[0083] The effects of the present embodiment configured as above will be described.

[0084] It is thought that differences may arise between the estimated value and the actual value of the combustion chamber wall temperature due to factors such as aging of the components that make up the internal combustion engine, piston deposits, the type of fuel (gasoline), etc. Therefore, it is necessary to provide multiple means for estimating the combustion chamber wall temperature and use these in combination to ensure the reliability and accuracy of the estimated combustion chamber wall temperature.

[0085] In contrast, the present embodiment is configured to include a time change reading unit that reads time changes in a measurement value that is correlated with the flow rate of air taken into the combustion chamber of the internal combustion engine, and a change trend estimation unit that estimates the change trend of the combustion chamber wall temperature based on the time changes in the measurement value, so that the combustion chamber wall temperature can be estimated and the reliability and certainty of the estimation result can be improved.In other words, the accuracy of control of various actuators can be improved, and improvement of the performance of the internal combustion engine, such as reduction in fuel consumption, can be realized with greater accuracy.

[0086] Second Embodiment A second embodiment of the present invention will be described with reference to Figures 13 and 14. In this embodiment, the same members and functional parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0087] The wall temperature estimation unit (see FIG. 4) in this embodiment includes a functional unit (estimation model unit) that calculates an estimated value of the combustion chamber wall temperature (wall temperature T) using an estimation model that inputs the control state of the internal combustion engine, and a functional unit (model correction unit) that corrects the estimation model, which is a correspondence relationship between the input of the control state of the internal combustion engine to the estimation model unit and the output of the estimated value of the combustion chamber wall temperature (wall temperature T), based on the change trend of the combustion chamber wall temperature (estimated wall temperature difference ΔTI) from the combustion chamber change trend estimation unit 222. This configuration makes it possible to maintain the accuracy of the estimation even when considering changing the fuel used in the internal combustion engine. In the following explanation, an example will be described in which the fuel used in the internal combustion engine is changed between gasoline and ethanol.

[0088] The estimation model unit of the wall temperature estimation unit in this embodiment receives the control state of the internal combustion engine as an input and calculates an estimated value of the combustion chamber wall temperature (wall temperature T) using the heat generation amount per unit amount of fuel (for example, 1 L). Note that the estimation model unit can be realized using known technology, so detailed description will be omitted.

[0089] Fig. 13 is a flowchart showing the processing contents of the model correction unit of the wall temperature estimation unit in this embodiment, and Fig. 14 is a diagram showing an example of time variation of the piston temperature, etc.

[0090] In FIG. 13 , the wall temperature estimator first records the temperature change amount (ΔTp1: see FIG. 14 ) of the piston in the physical model (step S200). Here, a physical model designed assuming the use of gasoline as fuel is used, and the temperature change amount (ΔTp1) of the piston when ethanol is used as the fuel is recorded as an example. According to this physical model (gasoline), the piston temperature when ethanol is used is expressed by the following (Equation 11). In the following (Equation 11), the piston heat input amount is (piston mass A (suitable value)) × (fuel flow rate) × (heat generation amount of fuel), and the piston heat output amount is (piston mass B (suitable value)) × ((piston temperature) − (oil temperature)).

[0091]

[0092] After the process of step S200 is completed, the amount of piston temperature change (ΔTp2: see FIG. 14) estimated by the configuration of the present invention is recorded (step S210), and the ratio of the amount of temperature change TR (=ΔTp2 / ΔTp1) is calculated (step S220). For example, as shown in FIG. 14, when ethanol is assumed to be the fuel for the internal combustion engine, the ratio TR is 0.8.

[0093] Next, it is determined whether the ratio TR is greater than a predetermined threshold value (step S230). If the determination result in step S230 is YES, the calorific value Qrc per liter of fuel is corrected based on the ratio TR of the piston temperature change amount as follows (Qrc = Qg x TR x C) (step S240), and the process ends. Note that the coefficient C is a model coefficient (e.g., 1.2), the calorific value Qrc is the calorific value per liter of the fuel used in the simulation (ethanol in this case), and the calorific value Qg is the calorific value per liter of gasoline. If the determination result in step S230 is NO, the calorific value Qrc per kg of air is set to the calorific value Qg of gasoline (step S250), and the process ends.

[0094] The other configurations are the same as those of the first embodiment.

[0095] The present embodiment configured as above can also achieve the same effects as the first embodiment.

[0096] Furthermore, in this embodiment, the estimation accuracy of the physical model is improved by correcting the calorific value of the fuel based on the ratio between the estimated value of the physical model and the estimated value in the configuration of the present invention, so that the estimation accuracy can be maintained even when the fuel for the internal combustion engine is changed, for example, from gasoline to another fuel such as ethanol.

[0097] <Notes> The present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the gist thereof. Furthermore, the present invention is not limited to those including all of the configurations described in the above-described embodiments, and also includes those in which some of the configurations are omitted. Furthermore, the above-described configurations, functions, etc. may be realized in part or in whole by designing them as, for example, integrated circuits. Furthermore, the above-described configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function.

[0098] 1...air flow sensor, 2...electronically controlled throttle, 3...intake pressure sensor, 4a...compressor, 4b...turbine, 5...variable valve, 7...intercooler, 9...air-fuel ratio sensor, 10...three-way catalyst, 11...electronically controlled wastegate valve, 12...accelerator opening sensor, 13...fuel injection device (injector), 14...cylinder, 15...exhaust pipe, 16...ignition coil, 17...spark plug, 18...temperature sensor, 19...crank angle sensor, 20...oil jet system, 20a...oil pump, 21...input circuit, 22...input Output port, 24... Ignition control unit, 25... Fuel injection control unit, 26... Oil jet control unit, 100... ECU, 200... Actuator operation amount calculation function, 210... Actuator steady state determination unit, 220... Combustion chamber wall temperature estimating unit, 221... Time change reading unit, 221a... Unit delay calculation unit, 221b... Calculator, 221c... Unit delay calculation unit, 221d... Calculator, 222... Combustion chamber change tendency estimating unit, 223... Wall temperature estimating unit, 223a... Steady state wall surface temperature calculation unit, 223b... Calculator, 230... Operation amount correcting unit, ENG... Internal combustion engine

Claims

1. A control device for an internal combustion engine, comprising: a time change reading unit that reads a time change of a measurement value correlated with an air flow rate inhaled into a combustion chamber of the internal combustion engine; and a change tendency estimation unit that estimates a change tendency of a combustion chamber wall temperature based on the time change of the measurement value.

2. The control device for an internal combustion engine according to claim 1, further comprising a wall temperature estimation unit that estimates a combustion chamber wall temperature based on the change tendency of the combustion chamber wall temperature.

3. The control device for an internal combustion engine according to claim 2, wherein the measurement value is an air flow rate value measured by an air flow rate sensor disposed in an intake passage of the internal combustion engine, and the change tendency estimation unit estimates the change tendency of the combustion chamber wall temperature based on the time change of the air flow rate value.

4. The control device for an internal combustion engine according to claim 2, wherein the measurement value is an intake pressure measured by a pressure sensor disposed in an intake passage, and the change tendency estimation unit estimates the change tendency of the combustion chamber wall temperature based on the time change of the intake pressure.

5. The control device for an internal combustion engine according to claim 1, wherein the change tendency estimation unit estimates the change tendency of the combustion chamber wall temperature when a rotational speed of the internal combustion engine and a control state of an actuator related to an operation of the internal combustion engine are stable.

6. The control device for an internal combustion engine according to claim 1, wherein the change tendency estimation unit estimates the change tendency of the combustion chamber wall temperature in a state where a control state of an actuator related to an operation of the internal combustion engine is controlled to be stable.

7. The control device for an internal combustion engine according to claim 2, wherein an ignition timing of an ignition device of the internal combustion engine is changed based on the estimated combustion chamber wall temperature.

8. The control device for an internal combustion engine according to claim 2, wherein a hydraulic pressure of a variable hydraulic oil pump that delivers cooling oil to the internal combustion engine is changed based on the estimated combustion chamber wall temperature.

9. In the control device for an internal combustion engine according to claim 2, a control device for an internal combustion engine, characterized in that the fuel injection amount and injection timing of the fuel injection device of the internal combustion engine are changed based on the estimated combustion chamber wall temperature.

10. In the control device for an internal combustion engine according to claim 2, the wall temperature estimation unit includes an estimation model unit capable of outputting an estimated value of the combustion chamber wall temperature with the control state of the internal combustion engine as an input, and a model correction unit that corrects the correspondence between the input of the control state of the internal combustion engine to the estimation model unit and the output of the estimated value based on the change tendency of the combustion chamber wall temperature. A control device for an internal combustion engine, characterized by comprising.

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