JP6479224B1 - Control device and control method for internal combustion engine - Google Patents

Abstract

An internal combustion engine control apparatus and control method capable of accurately estimating an outlet gas temperature of a combustion chamber even when an ignition timing is operated while suppressing an increase in calculation load. Based on a combustion chamber gas amount Qall, a combustion heat amount hl_b, a cooling loss rate ηc, and an indicated thermal efficiency ηi, an outlet gas temperature Tout which is an exhaust gas temperature at the outlet of the combustion chamber is calculated, and an ignition timing SA is calculated. A control device for an internal combustion engine that calculates a change amount Δηi of the indicated thermal efficiency by operation, corrects a basic value ηc0 of the cooling loss rate based on the change amount Δηi of the indicated thermal efficiency, and calculates a final cooling loss rate ηc. [Selection] Figure 5

Description

  The present disclosure relates to an internal combustion engine control device and a control method for estimating an exhaust gas temperature of an internal combustion engine.

  In order to operate the internal combustion engine suitably, it is important to accurately grasp the state quantities such as pressure and temperature of each part that change in accordance with the operation state of the internal combustion engine. In recent years, the internal combustion engine has been controlled using the state quantity of the exhaust system. The control using the state quantity of the exhaust system is, for example, when the exhaust gas temperature rises at the time of high rotation and high load operation and there is a possibility of damaging the catalyst, the air fuel ratio sensor, etc. provided in the exhaust system, the air fuel ratio is increased. Enrich control is performed to reduce the exhaust gas temperature by enrichment. The exhaust gas temperature used to perform this control may be detected using an exhaust gas temperature sensor, but there is also an estimation method in order to reduce the sensor cost. For example, a method of estimating the exhaust gas temperature with reference to map data in which the relationship between the rotation speed, the charging efficiency, and the exhaust gas temperature is set in advance based on experimental data or the like is used.

  As another example of using the exhaust gas temperature, for example, Patent Document 1 discloses a method of calculating the intake air amount and the internal EGR rate of the combustion chamber using the volume efficiency equivalent value. The exhaust gas temperature is used for the calculation. In this document, an exhaust gas temperature estimation method using map data similar to that described above is used. In addition to these, the exhaust gas temperature may be used to calculate the flow rate of the external EGR based on the opening degree of the EGR valve.

Japanese Patent No. 5409932

  As described above, there is an estimation method using map data as an estimation method of the exhaust gas temperature. However, the exhaust gas temperature is easily influenced by the ignition timing, the EGR amount, and the like. For example, the rotation speed and the charging efficiency are represented on the map axis. With only the map setting, there is a problem that it is difficult to accurately estimate when the operation conditions such as the ignition timing and the EGR amount change. Even if all the exhaust gas temperatures when the ignition timing and EGR amount change are stored as a map, the number of maps becomes enormous and the man-hours required for adaptation become enormous. There is a problem in terms of estimation accuracy and adaptation man-hours.

  If the estimation accuracy of the exhaust gas temperature is low, the estimation accuracy of the internal EGR amount and the external EGR amount is low, so that the ignition timing control based on the EGR amount is not properly performed, and the fuel consumption effect cannot be obtained sufficiently. . Even if the waste gate temperature that controls the boost pressure is not properly controlled due to the estimation error of the exhaust gas temperature, the driver cannot obtain the acceleration feeling required and the drivability deteriorates. is there. These problems can be solved if the estimation accuracy of the exhaust gas temperature can be improved.

  In order to improve the estimation accuracy of the exhaust gas temperature in the exhaust pipe, it is necessary to improve the estimation accuracy of the outlet gas temperature, which is the exhaust gas temperature at the outlet of the combustion chamber. Therefore, the inventor of the present application is examining a process for improving the estimation accuracy of the outlet gas temperature of the combustion chamber based on a heat account considering the distribution of the amount of combustion heat generated by the combustion of fuel. Specifically, the inventor of the present application uses the ratio of the amount of heat that can be taken out as work due to the cylinder pressure in the combustion chamber as the illustrated thermal efficiency, and cools the ratio of the amount of heat radiated to the wall surface of the combustion chamber during the expansion stroke. We are studying a heat account with a loss rate, and the remainder as an exhaust loss rate, which is the rate of heat used to raise the temperature of the exhaust gas. However, the ignition timing operation such as knock control changes not only the indicated thermal efficiency but also the cooling loss rate. Therefore, if the change in the cooling loss rate due to the operation of the ignition timing is not taken into account, the estimation accuracy of the outlet gas temperature deteriorates. There was a problem. Specifically, when the ignition timing is retarded, the illustrated thermal efficiency decreases, and the amount of heat corresponding to the decrease in the illustrated thermal efficiency is used to increase the outlet gas temperature, but part of the amount of heat corresponding to the decrease in the illustrated thermal efficiency is cooled. It is also used to increase the loss rate. However, it is not easy to accurately calculate the amount of change in the cooling loss rate directly from the operation of the ignition timing with a simple calculation.

  Accordingly, a control device and control method for an internal combustion engine that can accurately estimate the outlet gas temperature of the combustion chamber even when the ignition timing is manipulated while suppressing an increase in computational load and an increase in the number of man-hours for constant adaptation are desired.

A control device for an internal combustion engine according to the present disclosure includes a combustion chamber gas amount calculation unit that calculates a combustion chamber gas amount that is a gas amount flowing into the combustion chamber;
A combustion heat amount calculation unit for calculating the amount of combustion heat generated in the combustion chamber by the combustion of fuel;
A cooling loss rate calculating unit that calculates a cooling loss rate that is a ratio of the amount of heat radiated to the wall surface of the combustion chamber out of the combustion heat amount;
An illustrated thermal efficiency calculation unit that calculates an indicated thermal efficiency that is a ratio of a heat amount that can be taken out as work due to an in-cylinder pressure in the combustion chamber of the combustion heat amount,
Based on the combustion chamber gas amount, the combustion heat amount, the cooling loss rate, and the illustrated thermal efficiency, a heat bill temperature calculating unit that calculates an outlet gas temperature that is an exhaust gas temperature at the outlet of the combustion chamber;
An ignition control unit for operating the ignition timing,
The illustrated thermal efficiency calculation unit calculates the amount of change in the illustrated thermal efficiency due to the operation of the ignition timing,
The cooling loss rate calculation unit calculates a basic value of the cooling loss rate, corrects the basic value of the cooling loss rate based on the amount of change in the illustrated thermal efficiency, and calculates the final cooling loss rate. Is.

An internal combustion engine control method according to the present disclosure includes an inflow gas amount calculation step of calculating a combustion chamber gas amount that is an amount of gas flowing into the combustion chamber;
A combustion heat amount calculating step for calculating a combustion heat amount generated in the combustion chamber by combustion of fuel;
A cooling loss rate calculating step for calculating a cooling loss rate, which is a ratio of the amount of heat radiated to the wall surface of the combustion chamber out of the combustion heat amount;
An illustrated thermal efficiency calculation step of calculating an indicated thermal efficiency that is a ratio of a heat amount that can be taken out as work due to an in-cylinder pressure in the combustion chamber, among the combustion heat amount,
An outlet gas temperature calculating step for calculating an outlet gas temperature that is an exhaust gas temperature at the outlet of the combustion chamber based on the combustion chamber gas amount, the combustion heat amount, the cooling loss rate, and the illustrated thermal efficiency;
An ignition control step for operating the ignition timing,
In the illustrated thermal efficiency calculation step, the amount of change in the illustrated thermal efficiency due to the operation of the ignition timing is calculated,
In the cooling loss rate calculating step, a basic value of the cooling loss rate is calculated, and the final value of the cooling loss rate is calculated by correcting the basic value of the cooling loss rate based on the change amount of the illustrated thermal efficiency. Is.

  According to the control device and control method for an internal combustion engine according to the present disclosure, the cooling loss rate is changed based on the amount of change in the indicated thermal efficiency that is strongly correlated with the change in the cooling loss rate due to the operation of the ignition timing. It is possible to accurately calculate the cooling loss rate that changes with the operation of the time. In addition, since the calculation of the indicated thermal efficiency by the indicated thermal efficiency calculation unit can be used, the calculation load and the constant matching man-hour can be reduced as compared with the case of calculating the change in the cooling loss rate directly from the operation of the ignition timing.

1 is a schematic configuration diagram of an internal combustion engine and a control device according to Embodiment 1. FIG. 2 is a block diagram of a control device according to Embodiment 1. FIG. 2 is a hardware configuration diagram of a control device according to Embodiment 1. FIG. It is a figure which shows the idea of the heat bill which concerns on Embodiment 1. FIG. 4 is a detailed block diagram of an outlet gas temperature calculation unit according to Embodiment 1. FIG. 6 is a diagram for explaining a setting example of change amount characteristic data according to Embodiment 1. FIG. It is a figure explaining the example of a setting of the loss rate characteristic data which concerns on Embodiment 1. FIG. 1 is a diagram schematically showing a single flow heat exchanger model of an exhaust pipe according to Embodiment 1. FIG. FIG. 3 is a flowchart showing processing of a control device according to Embodiment 1.

Embodiment 1 FIG.
A control device 50 (hereinafter simply referred to as a control device 50) for an internal combustion engine according to Embodiment 1 will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an internal combustion engine 1 according to the present embodiment, and FIG. 2 is a block diagram of a control device 50 according to the present embodiment. The internal combustion engine 1 and the control device 50 are mounted on a vehicle, and the internal combustion engine 1 serves as a driving force source for the vehicle (wheel).

1. Configuration of Internal Combustion Engine 1 As shown in FIG. 1, the internal combustion engine 1 includes a combustion chamber 25 that burns an air-fuel mixture. The internal combustion engine 1 includes an intake pipe 23 that supplies air to the combustion chamber 25 and an exhaust pipe 17 that discharges the exhaust gas burned in the combustion chamber 25. The combustion chamber 25 is composed of a cylinder and a piston. Hereinafter, the combustion chamber 25 is also referred to as a cylinder. The internal combustion engine 1 is a gasoline engine. The internal combustion engine 1 includes a throttle valve 6 that opens and closes an intake pipe 23. The throttle valve 6 is an electronically controlled throttle valve that is driven to open and close by an electric motor controlled by the control device 50. The throttle valve 6 is provided with a throttle opening sensor 7 that outputs an electrical signal corresponding to the opening of the throttle valve 6.

  The intake pipe 23 on the upstream side of the throttle valve 6 has an air flow sensor 3 that outputs an electric signal corresponding to the flow rate of intake air sucked into the intake pipe 23 and an intake air that outputs an electric signal corresponding to the temperature of the intake air. And a temperature sensor 4. The temperature of the intake air detected by the intake air temperature sensor 4 can be regarded as being equal to the outside air temperature Ta.

  The internal combustion engine 1 includes an EGR passage 21 that recirculates exhaust gas from the exhaust pipe 17 to the intake manifold 12, and an EGR valve 22 that opens and closes the EGR passage 21. The intake manifold 12 is a portion of the intake pipe 23 on the downstream side of the throttle valve 6. The EGR valve 22 is an electronically controlled EGR valve that is opened and closed by an electric motor controlled by the control device 50. The EGR valve 22 is provided with an EGR opening degree sensor 27 that outputs an electrical signal corresponding to the opening degree of the EGR valve 22. EGR is an acronym for exhaust gas recirculation, that is, Exhaust Gas Recirculation. The EGR in which the exhaust gas recirculates via the EGR valve 22 is referred to as an external EGR, and the EGR in which the exhaust gas remains in the combustion chamber due to the valve overlap of the intake and exhaust valves is referred to as an internal EGR. Hereinafter, the external EGR is simply referred to as EGR.

  The intake manifold 12 has a manifold pressure sensor 8 that outputs an electric signal corresponding to the manifold pressure that is the pressure of the gas in the intake manifold 12, and an electric signal that corresponds to the manifold temperature Tin that is the temperature of the gas in the intake manifold 12. And a manifold temperature sensor 9 for outputting.

  The internal combustion engine 1 is provided with an injector 13 that supplies fuel to the combustion chamber 25. The injector 13 is provided so as to inject fuel directly into the combustion chamber 25. The injector 13 may be provided so as to inject fuel into the downstream portion of the intake manifold 12. The internal combustion engine 1 is provided with an atmospheric pressure sensor 2 that outputs an electrical signal corresponding to the atmospheric pressure.

  At the top of the combustion chamber 25, an ignition plug for igniting a mixture of air and fuel and an ignition coil 16 for supplying ignition energy to the ignition plug are provided. Further, at the top of the combustion chamber 25, an intake valve 14 for adjusting the amount of intake air taken into the combustion chamber 25 from the intake pipe 23, and an amount of exhaust gas discharged from the combustion chamber 25 to the exhaust pipe 17 are adjusted. An exhaust valve 15 is provided. The intake valve 14 is provided with an intake variable valve timing mechanism that makes the valve opening / closing timing variable. The exhaust valve 15 is provided with an exhaust variable valve timing mechanism that makes the valve opening / closing timing variable. The variable valve timing mechanisms 14 and 15 have electric actuators. The crankshaft of the internal combustion engine 1 is provided with a crank angle sensor 20 that outputs an electrical signal corresponding to the rotation angle.

  The exhaust pipe 17 is provided with an air-fuel ratio sensor 18 that outputs an electric signal corresponding to an air-fuel ratio AF (Air / Fuel) which is a ratio of air to fuel in the exhaust gas. The exhaust pipe 17 is provided with a catalyst 19 for purifying the exhaust gas.

  A knock sensor 28 is fixed to the cylinder block. Knock sensor 28 outputs a signal (vibration waveform signal) corresponding to the vibration of internal combustion engine 1. Knock sensor 28 includes a piezoelectric element or the like.

2. Next, the control device 50 will be described. The control device 50 is a control device that controls the internal combustion engine 1. As shown in the block diagram of FIG. 2, the control device 50 includes an operation state detection unit 51, an outlet gas temperature calculation unit 52, a heat release amount calculation unit 53, an exhaust temperature estimation unit 54, an exhaust temperature use control unit 55, and ignition control. A control unit such as the unit 56 is provided. Each control part 51-56 grade | etc., Of the control apparatus 50 is implement | achieved by the processing circuit with which the control apparatus 50 was provided. Specifically, as shown in FIG. 3, the control device 50 includes, as a processing circuit, an arithmetic processing device 90 (computer) such as a CPU (Central Processing Unit), and a storage device 91 that exchanges data with the arithmetic processing device 90. , An input circuit 92 for inputting an external signal to the arithmetic processing unit 90, an output circuit 93 for outputting a signal from the arithmetic processing unit 90 to the outside, and the like.

  The arithmetic processing unit 90 includes an application specific integrated circuit (ASIC), an integrated circuit (IC), a digital signal processor (DSP), a field programmable gate array (FPGA), various logic circuits, various signal processing circuits, and the like. May be. Moreover, as the arithmetic processing unit 90, a plurality of the same type or different types may be provided, and each process may be shared and executed. As the storage device 91, a RAM (Random Access Memory) configured to be able to read and write data from the arithmetic processing device 90, a ROM (Read Only Memory) configured to be able to read data from the arithmetic processing device 90, and the like. Is provided. The input circuit 92 is connected to various sensors and switches, and includes an A / D converter or the like that inputs output signals of these sensors and switches to the arithmetic processing unit 90. The output circuit 93 is connected to electric loads, and includes a drive circuit that outputs a control signal from the arithmetic processing unit 90 to these electric loads.

  The arithmetic processing device 90 executes software (programs) stored in the storage device 91 such as a ROM, and the storage device 91 and the input circuit 92 are included in each function of the control units 51 to 56 provided in the control device 50. , And in cooperation with other hardware of the control device 50 such as the output circuit 93. Note that characteristic data, setting data such as constants used by the control units 51 to 56, and the like are stored in a storage device 91 such as a ROM as a part of software (program).

  In the present embodiment, the input circuit 92 includes an atmospheric pressure sensor 2, an air flow sensor 3, an intake air temperature sensor 4, a throttle opening sensor 7, a manifold pressure sensor 8, a manifold temperature sensor 9, an air-fuel ratio sensor 18, a crank angle. A sensor 20, an accelerator position sensor 26, an EGR opening degree sensor 27, a knock sensor 28, and the like are connected. The output circuit 93 is connected to the throttle valve 6 (electric motor), the injector 13, the intake variable valve timing mechanism 14, the exhaust variable valve timing mechanism 15, the ignition coil 16, the EGR valve 22 (electric actuator), and the like. The control device 50 is connected to various sensors, switches, actuators and the like not shown.

  The operating state detection unit 51 detects the operating state of the internal combustion engine 1. The driving state detection unit 51 detects various driving states based on output signals of various sensors. Specifically, the operation state detection unit 51 detects the atmospheric pressure based on the output signal of the atmospheric pressure sensor 2, detects the intake air flow rate based on the output signal of the air flow sensor 3, and detects the intake air temperature sensor 4. The outside air temperature Ta is detected based on the output signal, the throttle opening is detected based on the output signal of the throttle opening sensor 7, the manifold pressure is detected based on the output signal of the manifold pressure sensor 8, and the manifold temperature sensor 9 The manifold temperature Tin, which is the temperature of the gas in the intake manifold 12, is detected based on the output signal and the like, the air-fuel ratio AF of the exhaust gas is detected based on the output signal of the air-fuel ratio sensor 18, and the crank angle sensor 20 The crank angle and the rotational speed Ne are detected based on the output signal, and the accelerator opening is detected based on the output signal of the accelerator position sensor 26. Detects the EGR opening degree based on the output signal of the EGR opening degree sensor 27 detects the knock intensity KNK based on the output signal of the knock sensor 28.

  The operating state detection unit 51 calculates the intake air amount Qc [g / stroke] and the charging efficiency Ec [%], which are the amount of air flowing into the combustion chamber 25 based on the intake air flow rate, the rotational speed Ne, and the like. For example, the operating state detection unit 51 uses a value obtained by performing a filter process simulating the delay of the intake manifold to a value obtained by multiplying the intake air flow rate [g / s] by a stroke cycle according to the rotational speed Ne. Calculated as the quantity Qc [g / stroke]. The stroke cycle is a cycle of 240 deg CA for a three-cylinder engine, and a cycle of 180 deg CA for a four-cylinder engine. Alternatively, the operation state detection unit 51 may calculate the intake air amount Qc [g / stroke] and the charging efficiency Ec [%] based on the manifold pressure, the rotational speed Ne, and the like.

  The operating state detection unit 51 calculates an EGR amount Qce [g / stroke], which is an exhaust gas recirculation amount flowing into the combustion chamber 25, based on the EGR opening degree and the like. For example, the operation state detection unit 51 calculates the EGR flow rate [g / s] passing through the EGR valve 22 based on the EGR opening degree, the manifold pressure, and the like, and performs filtering processing on the value obtained by multiplying the EGR flow rate by the stroke period. The value obtained by performing the calculation is calculated as the EGR amount Qce [g / stroke]. The operating state detection unit 51 calculates an EGR rate Regr [%] that is a ratio of the EGR amount Qce to the intake air amount Qc.

  The control device 50 calculates the target air-fuel ratio, fuel injection amount Qf, ignition timing SA, and the like based on the calculated rotational speed Ne, intake air amount Qc, charging efficiency Ec, EGR rate Regr, etc. The coil 16 and the like are driven and controlled. For example, the control device 50 calculates the target air-fuel ratio based on the rotational speed Ne and the charging efficiency Ec, and calculates the basic value of the fuel injection amount by dividing the intake air amount Qc by the target air-fuel ratio. When the air-fuel ratio feedback control using the air-fuel ratio sensor 18 is performed, the control device 50 corrects the basic value of the fuel injection amount, calculates the final fuel injection amount Qf, and performs the air-fuel ratio feedback control. If not, the basic value of the fuel injection amount is set to the final fuel injection amount Qf as it is.

  The control device 50 calculates the target throttle opening based on the accelerator opening and the like, and drives and controls the electric motor of the throttle valve 6 so that the throttle opening approaches the target throttle opening. The control device 50 calculates the target EGR opening degree of the EGR valve 22 based on the rotational speed Ne, the charging efficiency Ec, and the like, and drives and controls the electric actuator of the EGR valve 22 so that the EGR opening degree approaches the target EGR opening degree. To do. The control device 50 calculates target opening / closing timings (phases) of the intake valve 14 and the exhaust valve 15 based on the rotational speed Ne, the charging efficiency Ec, and the like, and the opening / closing timings of the intake valve 14 and the exhaust valve 15 are respectively determined. The electric actuators of the intake and exhaust variable valve timing mechanisms are driven and controlled so as to approach the target opening / closing timing.

  When performing torque-based control, the control device 50 requires the output torque of the internal combustion engine 1 calculated based on the accelerator opening or the like, or the internal combustion engine 1 requested by an external control device such as a transmission control device. The throttle opening, ignition timing SA, EGR opening, opening / closing timing of the intake valve 14 and the exhaust valve 15 are controlled so as to realize the required output torque. Specifically, the control device 50 calculates the target charging efficiency necessary for realizing the indicated thermal efficiency corresponding to the required output torque, based on the relationship between the charging efficiency Ec and the indicated thermal efficiency ηi preset by the adaptation. The target throttle opening, the target EGR opening, the intake valve that achieve the target charging efficiency and the target EGR rate by calculating the target EGR rate that optimizes the fuel consumption and the exhaust gas when operating at the target charging efficiency. 14 target opening / closing timing and exhaust valve 15 target opening / closing timing are calculated, and based on these target values, the electric motor of the throttle valve 6, the electric actuator of the EGR valve 22, the electric actuator of the intake and exhaust variable valve timing mechanisms Is controlled.

2-1. Ignition control unit 56
The control of the ignition timing SA will be described in more detail. The ignition control unit 56 operates the ignition timing SA. In the present embodiment, the ignition control unit 56 refers to the ignition timing characteristic data in which the relationship between the operating state such as the rotational speed Ne, the charging efficiency Ec, and the EGR rate Regr and the basic ignition timing SA0 is set in advance. A basic ignition timing SA0 corresponding to the current operating state is calculated. The basic ignition timing SA0 is basically set to an ignition timing (MBT: Minimum advance for the Best Torque) that maximizes the torque.

  The ignition control unit 56 calculates a knock retardation amount according to the knock intensity KNK detected by the knock sensor 28, and calculates an ignition timing retarded by the knock retardation amount from the basic ignition time SA0 as a final ignition timing SA. To do. Further, the ignition control unit 56 retards the ignition timing SA from the basic ignition time SA0 in order to warm up the internal combustion engine 1, to raise the temperature of the catalyst 19, and to reduce the torque of the internal combustion engine 1. The retard angle control is performed. The ignition control unit 56 performs energization control to the ignition coil 16 based on the ignition timing SA and the crank angle so that a spark is generated in the ignition plug at the ignition timing SA.

2-2. Outlet gas temperature calculation unit 52
<Calculation method of outlet gas temperature Tout>
A method for calculating the outlet gas temperature Tout will be described. What shows how the amount of combustion heat hl_b generated by combustion of the fuel supplied into the combustion chamber is distributed is called a heat account, and the concept of the heat account is shown in FIG. In the combustion heat quantity hl_b, the ratio of the heat quantity that can be taken out as work due to the cylinder pressure in the combustion chamber is shown as the thermal efficiency ηi [%], and the ratio of the heat quantity radiated to the wall surface of the combustion chamber during the expansion stroke is the cooling loss rate ηc [%]. And the remainder is the ratio of the amount of heat used to raise the temperature of the exhaust gas as the exhaust loss rate ηex [%]. Although the pumping loss and the mechanical loss are once taken out as work, they are considered to be used for purposes other than the shaft output and are included in the indicated thermal efficiency ηi. Here, if the indicated thermal efficiency ηi and the cooling loss rate ηc are known, the exhaust loss rate ηex can be expressed by the following equation.

At this time, the manifold air temperature that is the temperature of the gas introduced into the intake manifold 12 is Tin [K], the amount of combustion heat generated by the current combustion is hl_b [J / stroke], and the amount of gas in the combustion chamber in the current combustion is When Qall [g / stroke] is set and the specific heat of the combustion chamber gas (exhaust gas) is Cex [J / (g · K)], the basic value Tout0 [K] of the outlet gas temperature can be calculated by the following equation.

Here, the outlet gas temperature calculated by equation (2) is used as the basic value. When the air-fuel ratio is the stoichiometric air-fuel ratio or lean, the outlet gas temperature calculated by equation (2) can be used as it is. However, when the air-fuel ratio is rich, the outlet gas temperature decreases due to enrichment, and it is necessary to perform correction accordingly. The reason for the temperature decrease due to enrichment is thought to be due to the heat of evaporation due to the vaporization of the fuel and the energy consumed when the unburned fuel is decomposed into hydrocarbons with a low molecular weight. Eventually, if the amount of temperature decrease due to enrichment is the enrichment temperature decrease amount ΔTrich, the outlet gas temperature Tout can be calculated by the following equation. Since the outlet gas temperature Tout can be calculated as described above, the exhaust gas temperature Tex can also be calculated.

<Outlet gas temperature calculation unit 52>
The control device 50 designed based on the calculation method derived above will be described. The outlet gas temperature calculation unit 52 calculates an outlet gas temperature Tout that is the temperature of the exhaust gas at the outlet of the combustion chamber. As shown in the detailed block diagram of the outlet gas temperature calculator 52 in FIG. 5, the outlet gas temperature calculator 52 includes a combustion chamber gas amount calculator 52a, a combustion heat amount calculator 52b, a cooling loss rate calculator 52c, and the illustrated thermal efficiency. A calculation unit 52d, a heat bill temperature calculation unit 52e, and an air-fuel ratio temperature correction unit 52f are provided.

<Combustion chamber gas amount calculation unit 52a>
The combustion chamber gas amount calculation unit 52a calculates a combustion chamber gas amount Qall that is a gas amount flowing into the combustion chamber. In the present embodiment, the combustion chamber gas amount calculation unit 52a, as shown in the following equation, takes in the intake air amount Qc [g / stroke] that is the amount of air flowing into the combustion chamber and the exhaust gas recirculation that flows into the combustion chamber. The total value of the EGR amount Qce [g / stroke] and the fuel injection amount Qf [g / stroke] supplied to the combustion chamber is calculated as the combustion chamber gas amount Qall [g / stroke]. The intake air amount Qc and the EGR amount Qce are calculated by the operating state detection unit 51 as described above.

The combustion chamber gas amount calculation unit 52a calculates a value obtained by dividing the combustion chamber gas amount Qall by the stroke period ΔTsgt as an exhaust gas flow rate Qex [g / s] discharged in the exhaust stroke, as shown in the following equation. To do. The stroke period ΔTsgt is a period of 240 deg CA for a three-cylinder engine, and a period of 180 deg CA for a four-cylinder engine. Here, (n) represents a current stroke, and (n-3) represents a stroke three strokes before the current stroke. Qex (n) represents the flow rate of exhaust gas discharged from the cylinder that is currently in the exhaust stroke, and Qall (n-3) flows in when the cylinder that is currently in the exhaust stroke was in the intake stroke before the third stroke. Represents the amount of combustion chamber gas.

<Combustion heat quantity calculation unit 52b>
The combustion heat quantity calculation unit 52b calculates the combustion heat quantity hl_b generated in the combustion chamber by the combustion of the fuel. Based on the fuel injection amount Qf [g / stroke] and the air-fuel ratio AF, the combustion heat amount calculation unit 52b calculates the combustion fuel amount Qfb [g / stroke] actually burned out of the fuel injection amount Qf. When the air-fuel ratio AF is the stoichiometric air-fuel ratio or lean, it can be assumed that all of the fuel injection amount Qf burns. However, when the air-fuel ratio AF is rich, the fuel amount for the stoichiometric air-fuel ratio burns, The rich amount of fuel exceeding the air-fuel ratio does not burn. Therefore, as shown in the following equation, when the air-fuel ratio AF is the stoichiometric air-fuel ratio or lean, the combustion heat amount calculation unit 52b sets the fuel injection amount Qf to the combustion fuel amount Qfb as it is, and the air-fuel ratio AF is rich. In some cases, a value obtained by dividing the fuel injection amount Qf by the air-fuel ratio AF by the stoichiometric air-fuel ratio AF0 is calculated as the combustion fuel amount Qfb. As the air-fuel ratio AF, the target air-fuel ratio used for calculating the fuel injection amount Qf may be used, or the air-fuel ratio of the exhaust gas detected using the air-fuel ratio sensor 18 may be used.

  Then, the combustion heat amount calculation unit 52b calculates a value obtained by multiplying the combustion fuel amount Qfb [g / stroke] by the unit heat generation amount as the combustion heat amount hl_b [J / stroke]. The unit calorific value of gasoline is set to about 44000 [J / g]. The vaporization heat amount of the fuel may be subtracted from the unit calorific value, but the vaporization heat amount of gasoline is about 272 [J / g] and may be ignored.

<Indicated thermal efficiency calculator 52d>
The illustrated thermal efficiency calculation unit 52d calculates the illustrated thermal efficiency ηi, which is the ratio of the amount of heat that can be extracted as work due to the in-cylinder pressure in the combustion chamber, of the combustion heat amount hl_b. The illustrated thermal efficiency calculation unit 52d refers to the illustrated thermal efficiency characteristic data in which the relationship between the operating state such as the rotational speed Ne, the charging efficiency Ec, the EGR rate Regr, and the ignition timing SA and the illustrated thermal efficiency ηi is set in advance. The current indicated thermal efficiency ηi corresponding to the operating state is calculated. Here, as the current charging efficiency Ec and EGR rate Regr, values when the cylinder that is currently in the exhaust stroke is in the intake stroke before the third stroke are used.

  The illustrated thermal efficiency characteristic data is used for calculation of output torque in torque-based control, and is preset based on experimental data. Since the measurement of the thermal efficiency ηi shown in the figure is enormous when all operating points are measured, the measurement points are suppressed using methods such as MBC (Model Based Calibration) and DoE (Design of Experiments), and the data at the measured points are approximated. Approximate data corresponding to all operating points is created by connecting with equations. For the illustrated thermal efficiency characteristic data, a further simplified approximate expression is used. In the case where torque-based control is not performed, the illustrated thermal efficiency characteristic data may be that in which the relationship between the rotational speed Ne and the charging efficiency Ec and the illustrated thermal efficiency ηi is set. The illustrated thermal efficiency ηi is calculated using the amount of heat generated by combustion as a denominator and the amount of heat corresponding to the illustrated mean effective pressure as a numerator.

  The illustrated thermal efficiency calculation unit 52d calculates the change amount Δηi of the illustrated thermal efficiency due to the operation of the ignition timing SA. In the present embodiment, the illustrated thermal efficiency calculation unit 52d is configured to calculate the amount of change Δηi in the illustrated thermal efficiency due to the retard of the ignition timing from the preset basic ignition timing SA0. In the present embodiment, the basic ignition timing SA0 is set to an ignition timing (MBT) at which the torque becomes maximum. The illustrated thermal efficiency calculation unit 52d may use the basic ignition timing SA0 calculated by the ignition control unit 56, or may calculate the basic ignition timing SA0 based on the operating state, similarly to the ignition control unit 56.

  The indicated thermal efficiency calculation unit 52d calculates the indicated thermal efficiency ηi0 (hereinafter referred to as the basic indicated thermal efficiency ηi0) corresponding to the basic ignition timing SA0. The illustrated thermal efficiency calculation unit 52d refers to the above-described illustrated thermal efficiency characteristic data, and corresponds to the current operating state (rotational speed Ne, charging efficiency Ec, EGR rate Regr, etc.) other than the ignition timing, and the basic ignition timing SA0. The thermal efficiency is calculated as the basic illustrated thermal efficiency ηi0.

As shown in the following equation, the indicated thermal efficiency calculation unit 52d subtracts the basic indicated thermal efficiency ηi0 corresponding to the basic ignition timing SA0 from the indicated thermal efficiency ηi corresponding to the current ignition timing SA to obtain the change amount Δηi of the indicated thermal efficiency. calculate. When the ignition timing SA is retarded from the basic ignition timing SA0, the illustrated thermal efficiency ηi decreases, and the illustrated thermal efficiency change Δηi becomes a negative value.

<Cooling loss rate calculation unit 52c>
The cooling loss rate calculation unit 52c calculates a cooling loss rate ηc that is a ratio of the amount of heat radiated to the wall surface of the combustion chamber in the combustion heat amount hl_b generated by combustion.

  By the way, the operation of the ignition timing SA such as knock control changes not only the illustrated thermal efficiency but also the cooling loss rate. Therefore, if the change in the cooling loss rate due to the operation of the ignition timing SA is not taken into account, the estimated accuracy of the outlet gas temperature can be increased. There was a problem getting worse. Specifically, when the ignition timing SA is retarded, the illustrated thermal efficiency decreases, and the amount of heat corresponding to the decrease in the illustrated thermal efficiency is used to increase the outlet gas temperature. It is also used to increase the cooling loss rate.

  However, it is not easy to accurately calculate the amount of change in the cooling loss rate directly from the operation of the ignition timing SA with a simple calculation. According to the results of experiments conducted by the inventors, the change in the cooling loss rate has a strong correlation with the change in the indicated thermal efficiency. Therefore, in order to accurately calculate the change in the cooling loss rate, the change in the indicated thermal efficiency is considered. I found it necessary to do. This is because the gas temperature in the combustion chamber rises according to the amount of change in the indicated thermal efficiency due to the operation of the ignition timing SA, and the cooling loss rate at which heat is radiated to the wall surface of the combustion chamber according to the amount of increase in the gas temperature in the combustion chamber. It is thought that this is because of the rise. That is, the amount of change in the cooling loss rate is determined according to the amount of change in the indicated thermal efficiency due to the operation of the ignition timing SA. Note that the indicated thermal efficiency changes depending on a plurality of parameters such as the rotational speed Ne, the charging efficiency Ec, the EGR rate Regr, and the ignition timing SA. Therefore, in order to directly calculate the change in the cooling loss rate with high accuracy, it is complicated. It can be seen that proper calculation and constant matching are necessary.

  Therefore, in the present embodiment, the cooling loss rate calculation unit 52c calculates the basic value ηc0 of the cooling loss rate, and calculates the basic value ηc0 of the cooling loss rate based on the change amount Δηi of the indicated thermal efficiency due to the operation of the ignition timing SA. The final cooling loss rate ηc is calculated after correction.

  According to this configuration, since the cooling loss rate is changed based on the amount of change Δηi of the indicated thermal efficiency, which has a strong correlation with the change in the cooling loss rate due to the change in the ignition timing, the cooling loss rate that changes due to the operation of the ignition timing Can be calculated with high accuracy. In addition, since the calculation of the illustrated thermal efficiency by the illustrated thermal efficiency calculation unit 52d can be used, the calculation load and the constant matching man-hour can be reduced as compared with the case where the change of the cooling loss rate is directly calculated.

In the present embodiment, the cooling loss rate calculation unit 52c calculates the cooling loss rate when the ignition timing SA is set to the basic ignition timing SA0 as the basic value ηc0 of the cooling loss rate. The cooling loss rate calculation unit 52c then changes the cooling loss rate due to the retarded ignition timing from the basic ignition timing SA0 based on the variation Δηi in the illustrated thermal efficiency due to the retarded ignition timing from the basic ignition timing SA0. Δηc is calculated. Then, the cooling loss rate calculation unit 52c calculates the final cooling loss rate ηc by changing the basic value ηc0 of the cooling loss rate by the change amount Δηc of the cooling loss rate, as shown in the following equation.

  According to this configuration, since the basic ignition timing SA0 is used as a common reference, the basic value ηc0 of the cooling loss rate, the change amount Δηi of the illustrated thermal efficiency, and the change amount Δηc of the cooling loss rate are calculated. Can be simplified.

  Based on the results of experiments conducted by the inventor, the amount of change Δηi in the illustrated thermal efficiency due to the retarded ignition timing from the basic ignition timing SA0 and the amount of change Δηc in the cooling loss rate due to the retarded ignition timing from the basic ignition timing SA0 There was a strong correlation between them. Accordingly, the cooling loss rate calculation unit 52c refers to the change amount characteristic data in which the relationship between the change amount Δηi of the indicated thermal efficiency and the change amount Δηc of the cooling loss rate is set in advance, and is shown by the illustrated thermal efficiency calculation unit 52d. A change amount Δηc of the cooling loss rate corresponding to the change amount Δηi of the thermal efficiency is calculated. As shown in FIG. 6, in the change amount characteristic data, a characteristic that the change amount Δηc of the cooling loss rate increases from 0 as the indicated change in thermal efficiency Δηi decreases from 0 is set in advance based on experimental data. ing. For each characteristic data, a data map, a data table, a polynomial, a mathematical expression, or the like is used, and the setting data is stored in the storage device 91. As described above, the basic ignition timing SA0 is set to the ignition timing (MBT) at which the torque becomes maximum.

  From the results of experiments conducted by the inventors, it was found that there is a strong correlation between the exhaust gas flow rate Qex and the basic value ηc0 of the cooling loss rate calculated by back calculation, regardless of the operating conditions. Therefore, the cooling loss rate calculation unit 52c calculates a basic value ηc0 of the cooling loss rate based on the exhaust gas flow rate Qex in the exhaust pipe. Specifically, the cooling loss rate calculation unit 52c refers to loss rate characteristic data in which the relationship between the exhaust gas flow rate Qex and the basic value ηc0 of the cooling loss rate is set in advance, and corresponds to the current exhaust gas flow rate Qex. A basic value ηc0 of the cooling loss rate is calculated. As shown in FIG. 7, in the loss rate characteristic data, a characteristic that the basic value ηc0 of the cooling loss rate decreases as the exhaust gas flow rate Qex increases is set in advance based on experimental data.

<Heat balance temperature calculation unit 52e>
Based on the combustion chamber gas amount Qall [g / stroke], the combustion heat amount hl_b [J / stroke], the cooling loss rate ηc, and the indicated thermal efficiency ηi, the heat bill temperature calculation unit 52e is configured to adjust the temperature of the exhaust gas at the outlet of the combustion chamber. The outlet gas temperature Tout is calculated. Specifically, as described above using the formulas (1) and (2) based on the concept of heat billing, the heat bill temperature calculating unit 52e calculates the indicated thermal efficiency from 100 [%] as shown in the following formula. A value obtained by subtracting ηi [%] and the cooling loss rate ηc [%] is calculated as an exhaust loss rate ηex [%], which is a ratio of the amount of heat used for increasing the temperature of the exhaust gas in the combustion heat amount. Then, the heat bill temperature calculation unit 52e multiplies the combustion heat quantity hl_b [J / stroke] by the exhaust loss rate ηex [%] to calculate the temperature rise heat quantity [J / stroke] used for raising the exhaust gas temperature. The water equivalent [J / (stroke · g)] obtained by multiplying the temperature rise heat quantity [J / stroke] by the combustion chamber gas amount Qall [g / stroke] and the specific heat Cex [J / (g · K)] of the exhaust gas. ] To calculate the temperature rise amount [K], and the temperature rise amount [K] is added to the manifold temperature Tin [K] to calculate the basic value Tout0 [K] of the outlet gas temperature.

  A value of about 1.1 [J / (g · K)] is set as the specific heat Cex of the exhaust gas. Strictly speaking, the specific heat Cex of the exhaust gas changes according to the air-fuel ratio, so it may be changed according to the air-fuel ratio AF, such as correction using the specific heat of air and fuel. A fixed value may be used. As the manifold temperature temperature Tin, the gas temperature in the intake manifold 12 detected by the manifold temperature sensor 9 may be used as it is, but the gas temperature in the intake manifold 12 is adjusted so as to approach the gas temperature flowing into the combustion chamber. A temperature obtained by adding a predetermined value may be used as the manifold temperature Tin. Alternatively, a temperature obtained by correcting the gas temperature in the intake manifold 12 according to the internal EGR rate calculated based on the opening / closing timing of the intake / exhaust valves may be used as the manifold temperature Tin. As the manifold temperature temperature Tin, a gas temperature estimated based on the outside air temperature Ta may be used.

<Air-fuel ratio temperature correction unit 52f>
When the air-fuel ratio AF is richer than the stoichiometric air-fuel ratio, the air-fuel ratio temperature correction unit 52f corrects the decrease in the outlet gas temperature Tout according to the enrichment amount ΔAFr. From the experimental results conducted by the inventor of the present application, when the enrichment amount ΔAFr is increased by 1, regardless of the operating conditions, the outlet gas temperature Tout decreases by 35 to 40 ° C. The air-fuel ratio temperature correction unit 52f refers to temperature decrease characteristic data in which the relationship between the enrichment amount ΔAFr (= AF0−AF) and the enrichment temperature decrease amount ΔTrich is preset, and the enrichment temperature decrease corresponding to the current enrichment amount ΔAFr. The quantity ΔTrich is calculated. In the temperature decrease characteristic data, a characteristic that the enrichment temperature decrease amount ΔTrich having a positive value increases as the enrichment amount ΔAFr increases is set in advance based on experimental data.

As shown in the following equation, when the air-fuel ratio AF is the stoichiometric air-fuel ratio or lean, the air-fuel ratio temperature correction unit 52f sets the outlet gas temperature basic value Tout0 as it is to the outlet gas temperature Tout, and the air-fuel ratio AF is If it is rich, a value obtained by subtracting the positive enrichment temperature decrease ΔTrich from the basic value Tout0 of the outlet gas temperature is calculated as the outlet gas temperature Tout.

2-3. Exhaust gas temperature estimation calculation The controller 50 is configured to estimate the exhaust gas temperature Tex. The estimated exhaust gas temperature Tex is used for calculation of the EGR rate or the like in the exhaust gas temperature use control unit 55 described later.

<Calculation method of exhaust gas temperature using single-flow heat exchanger model>
First, an exhaust gas temperature calculation method using a single-flow heat exchanger model will be described. The single flow heat exchanger is described in detail in “University Lecture Heat Transfer Engineering” (Maruzen Co., Ltd., P224 to 226, 1983).

  FIG. 8 schematically shows a single flow heat exchanger model. At the estimated position in the figure, a suitable exhaust temperature sensor is attached and experimental data is collected. The conforming exhaust temperature sensor is attached only to the test internal combustion engine 1 and is used to adapt various constants included in the outlet gas temperature calculating unit 52, the heat radiation amount calculating unit 53, the exhaust temperature estimating unit 54, and the like. In the produced internal combustion engine 1, various controls are performed using the exhaust gas temperature Tex estimated by the outlet gas temperature calculation unit 52, the heat release amount calculation unit 53, and the exhaust temperature estimation unit 54.

Further, the combustion chamber outlet and the exhaust pipe inlet correspond to the boundary portion between the combustion chamber and the exhaust port, and correspond to the position where the exhaust valve 15 is disposed. It is assumed that the cylinder extends from the combustion chamber outlet to the estimated position (attachment position of the exhaust gas temperature sensor for adaptation). The internal surface area of the exhaust pipe from the combustion chamber outlet to the estimated position is the total heat transfer area A0 [m ² ] transferred from the exhaust gas to the exhaust pipe. In the case of a plurality of cylinders, the total internal surface area A0 from the combustion chamber outlet to the estimated position of all cylinders divided by the number of cylinders can be used. Let Qex [g / s] be the flow rate of the exhaust gas flowing through the exhaust pipe. It is assumed that the outside of the exhaust pipe is cooled by outside air (air in the vicinity of the exhaust pipe), and the outside air temperature Ta [K] is constant.

Next, the outlet gas temperature that is the temperature of the exhaust gas at the outlet of the combustion chamber is Tout [K], and the difference between the outlet gas temperature Tout and the outside air temperature Ta is θ1. The exhaust gas temperature at the estimated position is Tex [K], and the difference between the exhaust gas temperature Tex and the outside air temperature Ta is θ2. The exhaust gas temperature Tex is a temperature that is not affected by the response delay of the exhaust temperature sensor, and is an instantaneous value of the exhaust gas temperature. In addition, the total heat transfer area A0 from the combustion chamber outlet to an arbitrary position is A [m ² ], the instantaneous exhaust temperature at the arbitrary position is T [K], and the minute heat transfer area at an arbitrary position The change in the exhaust gas temperature at dA is defined as dT. If the difference between the instantaneous exhaust temperature T and the outside air temperature Ta is θ, dθ = dT. The amount of heat dQ exchanged per unit time in this minute heat transfer area dA is expressed by the following equation using the heat transmissibility (heat passage rate) Kht [W / (m ² · K)].

The product of the exhaust gas flow rate Qex [g / s] and the specific heat Cex [J / (g · K)] of the exhaust gas is referred to as water equivalent. This water equivalent exhaust gas loses the heat of dQ [J], and the temperature decreases by dT.

When dQ is deleted from the formulas (11) and (12) and arranged and integrated, the following formula is obtained. Here, Const is an integral constant.

Since A = 0 and θ = θ1 at the outlet of the combustion chamber and A = A0 and θ = θ2 at the estimated position, the following equation is obtained by applying the equation (13) and modifying the equation.

The amount of heat Q [J] taken by the outside air in this exhaust pipe is expressed by the following equation.

Further, the maximum value Qmax of the amount of heat deprived by the outside air in this exhaust pipe is expressed by the following equation because θ2 = 0 (when the exhaust gas temperature Tex is cooled to the outside temperature Ta).

From the equations (14), (15), and (16), the temperature efficiency η of the exhaust pipe is expressed by the following equation.

In equation (17), assuming that the heat transmissibility Kht, the total heat transfer area A0 from the combustion chamber outlet to the estimated position, and the specific heat Cex of the exhaust gas are constant values, the temperature efficiency η of the exhaust pipe is It can be seen that this is a function of the gas flow rate Qex. After all, if the exhaust pipe temperature efficiency η [%], the outside air temperature Ta, and the outlet gas temperature Tout corresponding to the exhaust gas flow rate Qex are known, the exhaust gas temperature Tex can be estimated by the following equation.

  The second term on the right side of the second equation of the equation (18) represents the temperature decrease amount ΔTd when the single flow heat exchanger model is applied to the exhaust system. As described above, the method for calculating the exhaust gas temperature Tex from the outlet gas temperature Tout, the outside air temperature Ta, and the exhaust pipe temperature efficiency η is shown.

<Heat dissipation calculation unit 53>
The heat release amount calculation unit 53 calculates the temperature drop amount ΔTd of the exhaust gas due to heat release from the exhaust pipe from the exit of the combustion chamber to the estimated position. As described above, from the equation (17) derived by modeling the exhaust pipe as a single flow heat exchanger, it can be seen that the temperature efficiency η of the exhaust pipe is a function of the exhaust gas flow rate Qex. It can be seen that the temperature drop amount ΔTd can be calculated based on the temperature efficiency η of the exhaust pipe. Therefore, the heat release amount calculation unit 53 is based on the exhaust gas flow rate Qex in the exhaust pipe, and the exhaust pipe as a single-flow heat exchanger uses the exhaust gas in the exhaust pipe as a heating fluid and the air outside the exhaust pipe as a heat receiving fluid. The temperature efficiency η is calculated, and the temperature drop amount ΔTd is calculated based on the temperature efficiency η of the exhaust pipe.

The heat release amount calculation unit 53 calculates the temperature efficiency η of the exhaust pipe based on the exhaust gas flow rate Qex using the following equation similar to the equation (17).

Kη is an arithmetic constant. The arithmetic constant Kη can be set by multiplying the heat transfer rate Kht of the exhaust pipe by the total heat transfer area A0 from the combustion chamber outlet to the estimated position and dividing by the specific heat Cex of the exhaust gas. Although the heat transmissivity Kht of the exhaust pipe is a suitable value, it becomes a value of about 10 to 15 [w / (m ² · K)], for example. The total heat transfer area A0 can be calculated from the structure of the exhaust pipe. The value mentioned above is used for the specific heat Cex of the exhaust gas. The calculation constant Kη may be a fixed value, but may be changed according to the specific heat Cex of the exhaust gas that changes according to the air-fuel ratio AF. In addition, the calculation constant Kη may be an experimentally adapted value.

  Alternatively, the heat release amount calculation unit 53 refers to temperature efficiency characteristic data in which the relationship between the exhaust gas flow rate Qex and the exhaust pipe temperature efficiency η is set in advance, and the exhaust pipe temperature efficiency corresponding to the current exhaust gas flow rate Qex. It may be configured to calculate η. The temperature efficiency characteristic data represents the characteristic of the equation (19), but may be adapted by experiment. For example, the measured value of the outlet gas temperature Tout using the conforming exhaust temperature sensor, the measurement of the exhaust gas temperature Tex0 at the estimated position using the conforming exhaust temperature sensor, measured at the operating points of a plurality of exhaust gas flow rates Qex. The temperature efficiency η of the exhaust pipe is calculated using the first equation (18) based on the measured value of the value and the outside air temperature Ta. Then, the temperature efficiency characteristic data is set by approximating the experimental data of the exhaust gas flow rate Qex at a plurality of operating points and the temperature efficiency η of the exhaust pipe. The operation constant Kη may be set by a similar method.

As shown in the following equation similar to the second equation of equation (18), the heat release amount calculation unit 53 reduces the exhaust gas temperature to a value obtained by subtracting the outside air temperature Ta from the outlet gas temperature Tout calculated by the outlet gas temperature calculation unit 52. A value obtained by multiplying the temperature efficiency η of the pipe is calculated as an exhaust gas temperature drop ΔTd.

<Exhaust temperature estimator 54>
As shown in the following equation, the exhaust gas temperature estimation unit 54 subtracts the temperature decrease amount ΔTd from the outlet gas temperature Tout to estimate the exhaust gas temperature Tex at the estimated position.

  The estimated position is set to the position of the exhaust gas temperature required in the exhaust gas temperature use control unit 55 described later. For example, the estimated position is the upstream position of the catalyst 19, the connection position between the exhaust pipe 17 and the EGR flow path 21, the upstream position of the turbine when a supercharger is provided in the exhaust pipe, and the exhaust gas sensor in the exhaust pipe. Is provided at the position of the exhaust gas sensor or the like. In accordance with the estimated position, an operation constant Kη or temperature efficiency characteristic data necessary for calculating the temperature efficiency η is set.

  The exhaust temperature estimation unit 54 may be configured to estimate exhaust gas temperatures at a plurality of estimated positions. In this case, the heat dissipation amount calculation unit 53 switches the calculation constant Kη or the setting value of the temperature efficiency characteristic data according to the estimated position, calculates the temperature efficiency η at each estimated position, and the temperature decrease amount ΔTd at each estimated position. Is calculated. Then, the exhaust temperature estimation unit 54 estimates the exhaust gas temperature Tex at each estimated position using the temperature decrease amount ΔTd at each estimated position. Thus, the exhaust gas temperatures at a plurality of estimated positions can be easily estimated by simply switching the operation constant Kη or the temperature efficiency characteristic data according to the estimated position.

As will be described later, when an exhaust gas temperature sensor is provided in the exhaust pipe and abnormality diagnosis of the exhaust gas temperature sensor is performed, the exhaust gas temperature detected by the exhaust gas temperature sensor is compared with the estimated exhaust gas temperature Tex. . However, the exhaust gas temperature detected by the exhaust gas temperature sensor is delayed in response due to the heat capacity of the sensor. Alternatively, a response delay due to the heat capacity of the exhaust pipe occurs in the exhaust gas temperature. Therefore, the exhaust gas temperature estimation unit 54 calculates the exhaust gas temperature Texft after the response delay process by performing a response delay process on the exhaust gas temperature Tex. For example, the exhaust gas temperature estimation unit 54 performs a first-order lag filter process represented by the following equation to calculate the exhaust gas temperature Texft after the response lag process. Here, the filter constant Kf is set from the time constant τ of the sensor and the calculation period Δt. (N) represents the value of the current computation cycle, and (n-1) represents the value of the previous computation cycle.

<Exhaust temperature use control unit 55>
The exhaust temperature utilization control unit 55 executes any one or more of exhaust temperature control, valve flow rate characteristic calculation, exhaust temperature sensor abnormality diagnosis, and turbine output calculation using the estimated value Tex of the exhaust gas temperature.

  The exhaust gas temperature control is a process for controlling the exhaust gas temperature using the estimated value Tex of the exhaust gas temperature. The exhaust gas temperature estimation unit 54 sets the position for controlling the exhaust gas temperature to the estimated position, and estimates the exhaust gas temperature. For example, the exhaust temperature utilization control unit 55 changes the enrichment amount of the fuel injection so that the estimated value Tex of the exhaust gas temperature approaches the target temperature when performing the enrichment control for reducing the temperature of the exhaust gas. Let Further, the exhaust temperature use control unit 55 changes the ignition timing SA or changes the fuel injection amount in the exhaust stroke so that the estimated value Tex of the exhaust gas temperature approaches the target temperature.

  The valve flow rate characteristic calculation is a process of calculating the flow rate characteristic of the valve through which the exhaust gas flows using the estimated value Tex of the exhaust gas temperature. The exhaust gas temperature estimation unit 54 sets the upstream position of the valve to the estimated position and estimates the exhaust gas temperature. The exhaust temperature utilization control unit 55 calculates the sound velocity and density of the exhaust gas upstream of the valve as the flow rate characteristic of the valve based on the estimated value Tex of the exhaust gas temperature. The exhaust gas flows through the EGR valve 22, a waste gate valve that bypasses the turbocharger turbine, and the like. The exhaust temperature utilization control unit 55 calculates the EGR flow rate using the flow rate characteristics of the EGR valve 22, and calculates the EGR amount Qce and the EGR rate Regr. The exhaust temperature utilization control unit 55 calculates the bypass flow rate that passes through the waste gate valve using the flow rate characteristics of the waste gate valve, subtracts the bypass flow rate from the exhaust gas flow rate, calculates the turbine passage flow rate, and passes through the turbine. Since the flow rate is proportional to the turbine output, the turbine output is calculated using the turbine passage flow rate. The turbine output is used for supercharging pressure control.

  The exhaust temperature sensor abnormality diagnosis is a process of performing an abnormality diagnosis of an exhaust gas temperature sensor provided in the exhaust pipe using the estimated value Tex of the exhaust gas temperature. The exhaust gas temperature sensor is provided to manage the temperature of the exhaust gas flowing into the exhaust gas purification device such as a catalyst and a particulate collection filter. The exhaust gas temperature estimation unit 54 sets the position of the exhaust gas temperature sensor to the estimated position and estimates the exhaust gas temperature. The exhaust temperature utilization control unit 55 compares the estimated value Texft of the exhaust gas temperature after the response delay processing with the detected value of the exhaust gas temperature by the exhaust gas temperature sensor, and if the difference between the two is large, the exhaust gas temperature sensor It is determined that an abnormality has occurred.

  The turbine output calculation is an operation for calculating the turbine output of the supercharger provided in the exhaust pipe using the estimated value Tex of the exhaust gas temperature. The exhaust gas temperature estimation unit 54 sets the upstream position of the turbine to the estimated position and estimates the exhaust gas temperature. Since the exhaust gas temperature flowing into the turbine is proportional to the turbine output, the exhaust temperature utilization control unit 55 calculates the turbine output using the estimated value Tex of the exhaust gas temperature.

2-4. Flowchart A schematic processing procedure (control method of the internal combustion engine 1) of the control device 50 according to the present embodiment will be described based on a flowchart shown in FIG. The processing of the flowchart in FIG. 9 is repeatedly executed at predetermined calculation cycles when the arithmetic processing device 90 executes software (program) stored in the storage device 91.

  In step S01, the operation state detection unit 51 performs an operation state detection process (operation state step) for detecting various operation states of the internal combustion engine 1 as described above.

  In step S02, the combustion chamber gas amount calculation unit 52a performs the combustion chamber gas amount calculation process (combustion chamber gas amount calculation step) for calculating the combustion chamber gas amount Qall, which is the amount of gas flowing into the combustion chamber, as described above. Run. In step S03, the combustion heat quantity calculation unit 52b executes the combustion heat quantity calculation process (combustion heat quantity calculation step) for calculating the combustion heat quantity hl_b generated in the combustion chamber by the combustion of the fuel as described above.

  In step S04, the illustrated thermal efficiency calculation unit 52d calculates the illustrated thermal efficiency ηi, which is the ratio of the amount of heat that can be extracted as work due to the in-cylinder pressure in the combustion chamber, of the combustion heat amount hl_b as described above (illustrated thermal efficiency calculation process). Step). Further, as shown above, the illustrated thermal efficiency calculation unit 52d calculates the change amount Δηi of the illustrated thermal efficiency due to the operation of the ignition timing SA. In the present embodiment, the illustrated thermal efficiency calculation unit 52d calculates the amount of change Δηi in the illustrated thermal efficiency due to the retard of the ignition timing from the preset basic ignition timing SA0 as described above. In the present embodiment, the basic ignition timing SA0 is set to an ignition timing (MBT) at which the torque becomes maximum.

  In step S05, the cooling loss rate calculation unit 52c calculates the cooling loss rate ηc, which is the ratio of the amount of heat radiated to the wall surface of the combustion chamber in the combustion heat amount hl_b generated by the combustion, as described above. Calculation processing (cooling loss rate calculation step) is executed. In the present embodiment, the cooling loss rate calculation unit 52c calculates the basic value ηc0 of the cooling loss rate, and corrects the basic value ηc0 of the cooling loss rate based on the change amount Δηi of the indicated thermal efficiency due to the operation of the ignition timing SA. Thus, the final cooling loss rate ηc is calculated. More specifically, the cooling loss rate calculation unit 52c calculates the cooling loss rate when the ignition timing SA is set to the basic ignition timing SA0 as the basic value ηc0 of the cooling loss rate. The cooling loss rate calculation unit 52c calculates the change amount Δηc of the cooling loss rate due to the retardation of the ignition timing from the basic ignition timing SA0 based on the change amount Δηi of the illustrated thermal efficiency due to the delay of the ignition timing from the basic ignition timing SA0. calculate. Then, the cooling loss rate calculation unit 52c calculates the final cooling loss rate ηc by changing the basic value ηc0 of the cooling loss rate by the change amount Δηc of the cooling loss rate.

  In step S06, the heat bill temperature calculation unit 52e calculates the exhaust gas temperature at the outlet of the combustion chamber based on the combustion chamber gas amount Qall, the combustion heat amount hl_b, the cooling loss rate ηc, and the indicated thermal efficiency ηi as described above. A heat bill temperature calculation process (heat bill temperature calculation step) for calculating a certain outlet gas temperature Tout is executed. In step S07, the air-fuel ratio temperature correction unit 52f performs an air-fuel ratio temperature correction for reducing the outlet gas temperature Tout according to the enrichment amount ΔAFr when the air-fuel ratio AF is richer than the stoichiometric air-fuel ratio as described above. Correction processing (air-fuel ratio temperature correction step) is executed.

  In step S08, the heat release amount calculation unit 53 calculates a heat release amount calculation process (heat release amount calculation step) for calculating the temperature decrease amount ΔTd of the exhaust gas due to heat release from the exhaust pipe from the outlet of the combustion chamber to the estimated position as described above. Execute. In the present embodiment, the heat release amount calculation unit 53 calculates the temperature efficiency η of the exhaust pipe as a single-flow heat exchanger based on the exhaust gas flow rate Qex in the exhaust pipe, and based on the temperature efficiency η of the exhaust pipe. A temperature decrease amount ΔTd is calculated. The heat release amount calculation unit 53 calculates the temperature efficiency η of the exhaust pipe based on the exhaust gas flow rate Qex using the equation (19).

  In step S09, as described above, the exhaust temperature estimation unit 54 performs the exhaust temperature estimation process (exhaust temperature estimation step) for subtracting the temperature decrease amount ΔTd from the outlet gas temperature Tout to estimate the exhaust gas temperature Tex at the estimated position. Run.

  In step S10, the exhaust temperature utilization control unit 55 performs any of exhaust temperature control, valve flow rate characteristic calculation, exhaust temperature sensor abnormality diagnosis, and turbine output calculation using the estimated value Tex of the exhaust gas temperature as described above. One or more exhaust temperature utilization control processing (exhaust temperature utilization control step) is executed.

[Other Embodiments]
Finally, other embodiments of the present disclosure will be described. Note that the configuration of each embodiment described below is not limited to being applied independently, and can be applied in combination with the configuration of other embodiments as long as no contradiction arises.

(1) In the first embodiment, the case where the internal combustion engine 1 is a gasoline engine has been described as an example. However, embodiments of the present disclosure are not limited to this. That is, the internal combustion engine 1 may be various internal combustion engines such as a diesel engine and an engine that performs HCCI combustion (Homogeneous-Charge Compression Ignition Combustion). Even in this case, the control device 50 detects the amount of change Δηi in the indicated thermal efficiency due to the operation (change) of the ignition timing in accordance with the operation (change) of the ignition timing (combustion start timing) detected by the in-cylinder pressure sensor or the vibration sensor. And the cooling loss rate ηc may be corrected.

(2) As described in the first embodiment, the internal combustion engine 1 may include a supercharger. The turbocharger includes a turbine provided in the exhaust pipe, a compressor provided upstream of the throttle valve in the intake pipe, and rotates integrally with the turbine, and a waste gate provided in a turbine bypass passage that bypasses the turbine. And a valve. The internal combustion engine 1 may include a particulate collection filter in addition to the catalyst, and may include an exhaust gas temperature sensor upstream of the catalyst and the particulate collection filter.

(3) In the first embodiment, the basic ignition timing SA0 has been described as an example in which the ignition timing (MBT) at which the torque is maximized is set. However, embodiments of the present disclosure are not limited to this. That is, the basic ignition timing SA0 may be set to an ignition timing other than MBT. For example, in an operating state where knocking occurs in MBT, basic ignition timing SA0 is set to an ignition timing retarded from MBT.

  In the present disclosure, the embodiments may be appropriately modified or omitted within the scope of the disclosure.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine, 17 Exhaust pipe, 25 Combustion chamber, 50 Control apparatus of internal combustion engine, 51 Operating state detection part, 52 Outlet gas temperature calculation part, 53 Heat release amount calculation part, 54 Exhaust temperature estimation part, 55 Exhaust temperature utilization control part 52a Combustion chamber gas amount calculation unit, 52b Combustion heat amount calculation unit, 52c Cooling loss rate calculation unit, 52d Thermal efficiency calculation unit, 52e Thermal balance temperature calculation unit, 52f Air-fuel ratio temperature correction unit, Kη calculation constant, Qall combustion chamber gas Amount, Qex exhaust gas flow rate, Regr EGR rate, SA ignition timing, SA0 basic ignition timing, Ta outside temperature, Tex exhaust gas temperature, Tout outlet gas temperature, hl_b combustion heat amount, ΔTd temperature decrease amount, η temperature efficiency, ηc cooling loss Rate, ηc0 Basic value of cooling loss rate, Δηc Change in cooling loss rate, ηex Exhaust loss rate, ηi Thermal efficiency shown, ηi0 This indicated thermal efficiency, Derutaitaai amount of change indicated thermal efficiency

Claims (13)

A combustion chamber gas amount calculation unit for calculating a combustion chamber gas amount that is an amount of gas flowing into the combustion chamber;
A combustion heat amount calculation unit for calculating the amount of combustion heat generated in the combustion chamber by the combustion of fuel;
A cooling loss rate calculating unit that calculates a cooling loss rate that is a ratio of the amount of heat radiated to the wall surface of the combustion chamber out of the combustion heat amount;
An illustrated thermal efficiency calculation unit that calculates an indicated thermal efficiency that is a ratio of a heat amount that can be taken out as work due to an in-cylinder pressure in the combustion chamber of the combustion heat amount,
Based on the combustion chamber gas amount, the combustion heat amount, the cooling loss rate, and the illustrated thermal efficiency, a heat bill temperature calculating unit that calculates an outlet gas temperature that is an exhaust gas temperature at the outlet of the combustion chamber;
An ignition control unit for operating the ignition timing,
The illustrated thermal efficiency calculation unit calculates the amount of change in the illustrated thermal efficiency due to the operation of the ignition timing,
The cooling loss rate calculation unit calculates a basic value of the cooling loss rate, corrects the basic value of the cooling loss rate based on the amount of change in the illustrated thermal efficiency, and calculates the final cooling loss rate. Control device for internal combustion engine.   The cooling loss rate calculation unit calculates the change amount of the cooling loss rate due to the operation of the ignition timing based on the change amount of the indicated thermal efficiency, and sets the basic value of the cooling loss rate as the change amount of the cooling loss rate. The control device for an internal combustion engine according to claim 1, wherein the final cooling loss rate is calculated by changing the value of the internal combustion engine. The illustrated thermal efficiency calculation unit calculates a change amount of the illustrated thermal efficiency due to a delay of the ignition timing from a preset basic ignition timing,
The cooling loss rate calculation unit calculates the cooling loss rate when the ignition timing is set to the basic ignition timing as a basic value of the cooling loss rate, and based on the amount of change in the indicated thermal efficiency, The control device for an internal combustion engine according to claim 2, wherein the amount of change in the cooling loss rate due to the retardation of the ignition timing from the basic ignition timing is calculated.   The control device for an internal combustion engine according to claim 3, wherein the basic ignition timing is set to the ignition timing at which the torque becomes maximum.   The internal combustion engine according to any one of claims 1 to 4, wherein the cooling loss rate calculation unit calculates a basic value of the cooling loss rate based on an exhaust gas flow rate discharged from the combustion chamber to an exhaust pipe. Control device.   6. The air-fuel ratio temperature correction unit according to claim 1, further comprising an air-fuel ratio temperature correction unit configured to correct the decrease in the outlet gas temperature according to the enrichment amount when the air-fuel ratio is richer than the stoichiometric air-fuel ratio. Control device for internal combustion engine. A heat release amount calculation unit for calculating a temperature drop amount of the exhaust gas due to heat release of the exhaust pipe from the exit of the combustion chamber to an estimated position;
The internal combustion engine control according to any one of claims 1 to 6, further comprising: an exhaust gas temperature estimation unit that subtracts the temperature decrease amount from the outlet gas temperature to estimate an exhaust gas temperature at the estimated position. apparatus. The heat release amount calculation unit is configured to use the exhaust pipe as a single-flow heat exchanger using the exhaust gas in the exhaust pipe as a heating fluid and the air outside the exhaust pipe as a heat receiving fluid based on the exhaust gas flow rate in the exhaust pipe. Calculate the temperature efficiency of
The control apparatus for an internal combustion engine according to claim 7, wherein the temperature decrease amount is calculated based on the temperature efficiency. The heat radiation amount calculation unit sets the temperature efficiency of the exhaust pipe as η, the exhaust gas flow rate in the exhaust pipe as Qex, and the operation constant as Kη,
η = 1-exp (−Kη / Qex)
The temperature efficiency is calculated by the following formula:
The control device for an internal combustion engine according to claim 7 or 8, wherein the temperature decrease amount is calculated based on the temperature efficiency. The heat dissipation amount calculation unit refers to temperature efficiency characteristic data in which a relationship between the exhaust gas flow rate in the exhaust pipe and the temperature efficiency of the exhaust pipe is set in advance, and calculates the temperature efficiency corresponding to the current exhaust gas flow rate. Calculate
The control device for an internal combustion engine according to claim 7 or 8, wherein the temperature decrease amount is calculated based on the temperature efficiency.   The internal combustion engine according to any one of claims 8 to 10, wherein the heat release amount calculation unit calculates a value obtained by multiplying a value obtained by subtracting an outside air temperature from the outlet gas temperature and the temperature efficiency as the temperature decrease amount. Engine control device.   Exhaust gas temperature control for controlling the exhaust gas temperature using the estimated value of the exhaust gas temperature, valve flow characteristic calculation for calculating a flow characteristic of a valve through which the exhaust gas flows using the estimated value of the exhaust gas temperature, the exhaust gas Exhaust temperature sensor abnormality diagnosis for performing abnormality diagnosis of an exhaust gas temperature sensor provided in the exhaust pipe using the estimated value of the gas temperature, and supercharging provided in the exhaust pipe using the estimated value of the exhaust gas temperature The control apparatus for an internal combustion engine according to any one of claims 7 to 11, further comprising an exhaust temperature utilization control unit that executes any one or more of turbine output calculations for calculating a turbine output of the machine. An inflow gas amount calculating step for calculating a combustion chamber gas amount that is an amount of gas flowing into the combustion chamber;
A combustion heat amount calculating step for calculating a combustion heat amount generated in the combustion chamber by combustion of fuel;
A cooling loss rate calculating step for calculating a cooling loss rate, which is a ratio of the amount of heat radiated to the wall surface of the combustion chamber out of the combustion heat amount;
An illustrated thermal efficiency calculation step of calculating an indicated thermal efficiency that is a ratio of a heat amount that can be taken out as work due to an in-cylinder pressure in the combustion chamber, among the combustion heat amount,
An outlet gas temperature calculating step for calculating an outlet gas temperature that is an exhaust gas temperature at the outlet of the combustion chamber based on the combustion chamber gas amount, the combustion heat amount, the cooling loss rate, and the illustrated thermal efficiency;
An ignition control step for operating the ignition timing,
In the illustrated thermal efficiency calculation step, the amount of change in the illustrated thermal efficiency due to the operation of the ignition timing is calculated,
In the cooling loss rate calculating step, a basic value of the cooling loss rate is calculated, and the final value of the cooling loss rate is calculated by correcting the basic value of the cooling loss rate based on the change amount of the illustrated thermal efficiency. A method for controlling an internal combustion engine.

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