JP5684668B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for controlling an internal combustion engine in accordance with the pressure of exhaust gas discharged from the internal combustion engine.

  2. Description of the Related Art Conventionally, a control technique for controlling an internal combustion engine based on the flow rate and pressure of intake and exhaust gas of the internal combustion engine is known. For example, in order to control the combustion temperature in the combustion chamber of the internal combustion engine, control called exhaust gas recirculation (EGR) is performed to return a part of the exhaust discharged from the internal combustion engine to the intake side. A target value (hereinafter referred to as a target EGR rate) is set for the mixing ratio of recirculated exhaust in the intake air (hereinafter referred to as the EGR rate). In order to set the EGR rate of the intake air as the target EGR rate. Adjust the recirculation displacement.

Generally, the recirculation exhaust amount Q _EGR is the difference between the difference between the exhaust pressure P _EXH and the intake pressure P _IN (P _EXH −P _IN ) and the opening degree A _{EGR of the} EGR valve provided on the flow path of the recirculated exhaust gas. It is proportional to the product. That is, these parameters have a relationship as shown in Equation 1 below.

Here, the opening degree A _EGR of the EGR valve can be obtained from an EGR valve position sensor that detects the opening degree of the EGR valve, and the intake pressure _PIN is obtained from an intake pressure sensor provided in the intake pipe. Is possible. That is, the opening degree A _EGR and the intake pressure _PIN of the EGR valve can be obtained by actual measurement.

On the other hand, acquisition of the exhaust pressure P _EXH by actual measurement may be difficult. For example, when the exhaust pressure P _EXH is measured by an exhaust pressure sensor, a part of the exhaust is taken in by connecting a bypass pipe (narrow pipe) of the exhaust pressure sensor to the exhaust pipe. Here, the exhaust gas contains particulate matter (soot), and this particulate matter may adhere to the bypass pipe and cause clogging of the bypass pipe. When the bypass pipe is clogged, it is difficult to obtain the exhaust pressure.

Therefore, for example, in Patent Document 1, instead of obtaining the exhaust pressure P _EXH by actual measurement, a model formula is established and the exhaust pressure P _EXH is estimated by the model formula. Specifically, an estimated value of the exhaust pressure P _EXH is obtained using a relational expression of the exhaust pressure P _EXH , the exhaust amount Q _EXH and the exhaust temperature T _EXH as expressed by the following formula 2.

Here, Q _{EGR — n−1} represents the recirculation exhaust amount in the previous control step. Further, the exhaust temperature T _EXH is obtained as a product of the basic exhaust temperature T _EXHB obtained from the fuel injection amount and the correction coefficient k2 (T _EXH = T _EXHB × k2). Further, the correction coefficient k2 is obtained based on P _{EXH_n-1} in the previous control step (k2∝P _{EXH_n-1} ). Thus, according to Patent Document 1, the estimated value of the exhaust pressure is calculated using the values Q _{EGR_n-1} and P _{EXH_n-1} of the previous control step.

JP 2004-251288 A

  By the way, in the repetitive calculation for estimating the exhaust pressure in the current control step n using the value of the previous control step n-1, the time interval between the previous control step n-1 and the current control step n. If the distance between the control steps is too large, the error becomes large. Therefore, it is necessary to shorten the interval between the control steps. However, when the interval between the control steps is shortened, another problem arises that the calculation load increases. Accordingly, an object of the present invention is to provide means capable of obtaining the exhaust pressure without repeatedly performing calculations in order to reduce the calculation load.

The present invention relates to a control device for an internal combustion engine. The control device includes a turbocharger having a compressor wheel that pressurizes intake air sucked into an internal combustion engine, and a turbine wheel that is connected to the compressor wheel and is driven to rotate by exhaust gas discharged from the internal combustion engine, Intake flow rate acquisition means for acquiring the intake flow rate after passing through the compressor wheel, and a control unit for controlling the internal combustion engine. Further, the control unit is characterized in that a characteristic of a change in the exhaust flow rate before passing through the turbine wheel with respect to a change in an expansion ratio representing a ratio of the exhaust pressure before passing through the turbine wheel and after passing through the turbine wheel is determined, A turbine wheel characteristic equation approximated to a plurality of primary equations divided for each section is stored. Further, the control unit, based on the intake flow rate acquired by the intake flow rate acquisition means and the respective coefficients of the plurality of linear expressions, exhaust pressure candidates before passing through the turbine wheel according to the respective coefficients Calculate the value. Further, the control unit calculates an expansion ratio candidate value based on the exhaust pressure candidate value calculated as the exhaust pressure before passing through the turbine wheel, and among the calculated expansion ratio candidate values, the expansion ratio candidate The expansion ratio candidate value that is included in the expansion ratio section of the primary expression corresponding to the value is extracted, and the exhaust pressure candidate value used when calculating the extracted expansion ratio candidate value is used as the turbine. The exhaust pressure before passing through the wheel is determined, and the internal combustion engine is controlled based on the determined exhaust pressure.

In the above invention, the control unit calculates the exhaust pressure candidate value based on an exhaust gas temperature before passing through the turbine wheel in addition to the intake air flow rate and the plurality of linear coefficients, and the exhaust gas temperature is 800 It is preferable that the temperature is set to a temperature not lower than 900C and not higher than 900C.

  According to the present invention, it is possible to obtain the exhaust pressure without repeatedly performing calculations.

It is a figure which illustrates the control apparatus of the internal combustion engine which concerns on this embodiment. It is a figure which illustrates a turbine characteristic figure. It is a figure explaining the linear approximation process with respect to a turbine characteristic line. It is a figure explaining the calculation flow of exhaust pressure. It is a figure explaining the calculation flow of exhaust pressure. It is a figure explaining preset exhaust temperature.

  FIG. 1 illustrates a control device 10 for an internal combustion engine according to this embodiment. The control device 10 includes a turbocharger 12, a turbine wheel rotational speed sensor 13, an intake flow rate sensor 14, an intake pressure sensor 16, an atmospheric pressure sensor 17, and a control unit 20. Further, the control device 10 includes an EGR valve 22, an EGR valve position sensor 24, a throttle valve 26, a throttle valve position sensor 28, a waste gate valve 30, and a waste gate valve position sensor 32. Note that the control device 10 according to the present embodiment is mounted on a vehicle using, for example, the internal combustion engine 33 as a drive source.

  The turbocharger 12 is a so-called supercharger and has a function of compressing intake air sent to the internal combustion engine 33. The turbocharger 12 includes a compressor wheel 34, a turbine wheel 36, and a shaft 38 that connects the two. The intake air is pressurized by rotating the compressor wheel 34. For example, in this embodiment, the compressor wheel 34 is provided between the air cleaner 40 and the intercooler 42 in the intake pipe 39.

  The turbine wheel 36 is driven to rotate by exhaust. Rotational motion of the turbine wheel 36 is transmitted to the compressor wheel 34 via the shaft 38, whereby the compressor wheel 34 rotates. The compressor wheel 34 is provided on the exhaust passage. For example, in this embodiment, the compressor wheel 34 is provided between the exhaust recirculation pipe 46 and the catalyst 48 in the exhaust pipe 44.

  The turbine wheel rotational speed sensor 13 can measure the rotational speed of the turbine wheel 36. The turbine wheel rotational speed sensor 13 can measure the rotational speed Nt of the turbine wheel 36 in a contact or non-contact manner. For example, in this embodiment, the rotational speed of the turbine wheel 36 is determined in a non-contact manner by an optical sensor. Measuring. The rotational speed Nt of the turbine wheel 36 measured by the turbine wheel rotational speed sensor 13 is transmitted to the control unit 20.

The intake air flow rate sensor 14 functions as an intake air flow rate measuring unit that measures the flow rate Q _{I2 of} the intake air that has passed through the compressor wheel 34 and is pressurized. The intake flow sensor 14 is provided on the flow path of the pressurized intake air. For example, in this embodiment, the intake flow sensor 14 is provided between the intercooler 42 and the intake pressure sensor 16. The intake flow rate sensor 14 is constituted by, for example, a hot wire type air flow meter, and measures the intake flow rate by connecting a bypass pipe to the intake pipe 39 and taking a part of the intake air. The measured intake air flow rate Q _I2 is transmitted to the control unit 20.

The intake pressure sensor 16 can measure the pressure P _{I2 of} the intake air that has passed through the compressor wheel 34 and is pressurized. The intake pressure sensor 16 is provided on the flow path of the pressurized intake air. For example, in this embodiment, the intake pressure sensor 16 is provided between the intake flow sensor 14 and the throttle valve 26. The intake flow sensor 14 is composed of, for example, a vacuum sensor, and measures intake pressure by connecting a bypass pipe to the intake pipe 39 and taking in part of the intake air. The measured intake pressure _PI2 is transmitted to the control unit 20.

The EGR valve 22 includes a valve body that can adjust a recirculation exhaust amount that recirculates a part of the exhaust discharged from the internal combustion engine 33 to the intake side, and includes, for example, a needle valve. The EGR valve 22 is driven by driving means such as a motor 50, and the opening degree A _{EGR of the} EGR valve 22 changes according to this driving. The recirculation exhaust amount Q _EGR passing through the EGR valve 22 is adjusted in accordance with the opening degree change. The EGR valve 22 is provided on the flow path of the recirculation exhaust. For example, in the present embodiment, the EGR valve 22 is provided on the downstream side (intake pipe side) of the exhaust recirculation pipe 46 from the EGR cooler 43.

  The exhaust gas recirculation pipe 46 connects the exhaust pipe 44 and the intake pipe 39. For example, in this embodiment, the exhaust gas recirculation pipe 46 is connected upstream of the turbine wheel 36 of the exhaust pipe 44 and is connected downstream of the throttle valve 26 of the intake pipe 39.

The EGR valve position sensor 24 measures the opening degree A _EGR of the EGR valve 22 and transmits it to the control unit 20. For example, the EGR valve position sensor 24 measures the rotational speed of the motor 50, calculates the opening degree of the EGR valve 22 from the rotational speed, and transmits the opening degree A _EGR to the control unit 20.

  The throttle valve 26 includes a valve body capable of adjusting the flow rate of intake air (fresh air) supplied to the internal combustion engine 33, and is configured by, for example, a butterfly valve. The throttle valve 26 is driven by driving means such as a motor 52, and the opening degree of the throttle valve 26 changes in accordance with this driving. The amount of intake air that passes through the throttle valve 26 is adjusted in accordance with this change in opening. Further, the throttle valve 26 is provided on the intake air flow path. For example, in this embodiment, the throttle valve 26 is provided downstream of the intake pressure sensor 16 in the intake pipe 39.

  Further, the throttle valve position sensor 28 measures the opening degree of the throttle valve 26 and transmits it to the control unit 20. The throttle valve position sensor 28 measures, for example, the rotational speed of the motor 52, calculates the opening degree of the throttle valve 26 from the rotational speed, and transmits the opening degree to the control unit 20.

The waste gate valve 30 is configured to include a valve body capable of adjusting the flow rate Q _{O3 of the} bypass exhaust, for example, a needle valve. Bypass exhaust refers to exhaust that is partly discharged and discharged to the atmosphere without passing through the turbine wheel 36. It is possible to adjust the expansion ratio P _r is the ratio of the exhaust pressure P _O2 after passing through the exhaust pressure P _O1 before passing through the turbine wheel 36 by passing the bypass exhaust. As will be described later by adjusting the expansion ratio P _r becomes possible to high level maintaining efficiency of the turbocharger 12.

The waste gate valve 30 is driven by driving means such as a motor 54, and the opening degree of the waste gate valve 30 changes in accordance with this drive. The bypass exhaust amount Q _O3 passing through the waste gate valve 30 is adjusted in accordance with the opening degree change. Further, the waste gate valve 30 is provided on the bypass exhaust passage, and is provided, for example, in the bypass pipe 56 in the present embodiment.

  The waste gate valve position sensor 32 measures the opening degree of the waste gate valve 30 and transmits it to the control unit 20. The waste gate valve position sensor 32 measures, for example, the rotation speed of the motor 54, calculates the opening degree of the waste gate valve 30 from the rotation speed, and transmits the opening degree to the control unit 20.

The atmospheric pressure sensor 17 can measure the atmospheric pressure outside the vehicle, and is provided, for example, near the front grill of the vehicle. Atmospheric pressure P _A measured by the atmospheric pressure sensor 17 is transmitted to the control unit 20.

  The control unit 20 includes a calculation unit for calculating information and a storage unit for storing information. The control unit 20 is composed of a device capable of calculating information, storing and reading information, and includes, for example, a microcomputer in the present embodiment. This microcomputer can be composed of, for example, an electronic control unit (ECU) mounted on a vehicle.

  The control unit 20 determines the opening of the EGR valve 22, the throttle valve 26, and the waste gate valve 30 based on the calculation result of the calculation unit, and the motors 50, 52, and 54 for operating the valves according to the opening commands corresponding thereto. Send to. The combustion temperature and output of the internal combustion engine 33 are controlled by controlling the opening of each valve.

Further, the intake flow rate Q _I2 , the intake pressure P _I2 , and the atmospheric pressure P _A are transmitted to the control unit 20 from the intake flow rate sensor 14, the intake pressure sensor 16, and the atmospheric pressure sensor 17, respectively. Further, the opening degree of each valve is transmitted from the EGR valve position sensor 24, the throttle valve position sensor 28, and the waste gate valve position sensor 32. Further, the rotational speed N _t of the turbine wheel 36 is transmitted from the turbine wheel rotational speed sensor 13. Further, the depression amount is transmitted from the accelerator position sensor 60 that measures the depression amount of the accelerator pedal 58 to the control unit 20.

Further, the calculation unit of the control unit 20 calculates the exhaust pressure _PO1 before passing through the turbine wheel 36 based on various measurement values received by the control unit 20 and an exhaust pressure calculation formula described later.

The storage unit of the control unit 20 stores an exhaust pressure calculation formula, turbine characteristics, a corrected flow rate calculation formula, which will be described later, and the like. The turbine characteristic is also called a turbine map or a turbine performance diagram, and is a function, a table, or a map representing the efficiency of the turbocharger 12, and is used for controlling the turbocharger 12 and for estimating the exhaust pressure PO ₁ in this embodiment. It is used.

Turbine characteristics are illustrated in FIG. The turbine characteristics are based on the expansion rate P _r (= P _O1 / P _O2 ), which is the ratio of the exhaust pressure P _O1 before passing through the turbine wheel and the pressure P _O2 after passing through, and the exhaust flow rate Q _O1 before passing through the turbine wheel. a diagram taken, the characteristic line 70A~70D is defined for each rotational speed _{N t} of the turbine wheel 36. A choke line CL indicating the upper limit of the operating range of the turbine wheel 36 and a surge line SL indicating the lower limit of the operating range are defined. Further, the efficiency B1% to B4% is determined as indicated by broken lines on the coordinate plane on which the characteristic lines 70A to 70D are plotted. This efficiency is also called adiabatic efficiency, and is an index indicating how much the enthalpy of the exhaust can be recovered as the motive energy of the turbine wheel 36 when the exhaust expands.

This turbine characteristic is used to operate the turbocharger 12 with high efficiency. For example, the expansion ratio _Pr is adjusted so that the efficiency is B1% of the high efficiency region. Specifically adjusting the expansion ratio P _r by adjusting the flow rate Q _O3 bypass exhaust by adjusting the opening degree of the waste gate valve 30. The turbine characteristics are obtained in advance by actual measurement. For example, an experimental apparatus having a flow rate sensor and a pressure sensor for measuring the exhaust flow rate Q _O1 and the exhaust pressure P _O1 before passing through the turbine wheel and the exhaust pressure P _O2 after passing through the turbine wheel is configured and obtained from each sensor. The relationship between the obtained value and the efficiency of the turbine wheel 36 is plotted. Determining characteristics line of each rotation speed with divide this plot for each rotation speed N _t of the turbine wheel 36.

The storage unit stores each of the characteristic lines 70A to 70D as a set of a plurality of linear functions by piecewise linear processing as shown in FIG. That is, a characteristic line having a curved locus is divided into a plurality of expansion ratio sections (expansion ratio sections), and the locus in each section is approximated to a linear function. In FIG. 3, the measured values of the expansion ratio _Pr and the exhaust flow rate _QO1 acquired when obtaining the characteristic line are plotted, and [1 ≦ P _r <1.1] and [1.1 ≦ P _r <1. 3] and [1.3 ≦ P _r <1.6] are divided into three expansion ratio sections to perform linear approximation. When the characteristic lines 70A to 70D are each divided into k sections and the threshold value of the section is represented by c, the characteristic lines 70A to 70D can be expressed as the following (Formula 1) as a turbine characteristic formula.

  Furthermore, the opening degree of the throttle valve 26 corresponding to the intake air amount, the opening degree of the EGR valve 22 corresponding to the recirculated exhaust gas amount, and the like are stored in the storage unit as a map (table). Further, the storage unit stores an air-fuel ratio α and a target EGR rate corresponding to a drive mode (eco-mode, power mode, etc.) for the internal combustion engine 33, a mathematical expression for executing output control of the internal combustion engine, which will be described later, and the like. Yes. The storage unit may be any device capable of storing such information, and may be configured by one or a combination of a ROM, a RAM, an EPROM, a hard disk device, and the like.

Next, control of the EGR valve 22 by the control unit 20 will be described. The control unit 20 adjusts the opening degree A _EGR of the EGR valve 22 based on the intake pressure P _I2 after passing through the compressor wheel 34, the exhaust pressure P _O1 before passing through the turbine wheel, and the target return exhaust amount. The relationship among the intake pressure P _I2 , the exhaust pressure P _O1 , the recirculation exhaust amount Q _EGR , and the opening degree A _EGR can be expressed as (Equation 2) below.

That is, the recirculation exhaust amount Q _EGR can be expressed as a function of the EGR valve opening degree A _EGR , the intake pressure P _I2 , and the exhaust pressure P _O1 . Further, (Expression 2) can be divided into a plurality of sets of linear functions as shown in Expression 3 below by the piecewise linear processing described above.

Here, d ₁ , f ₁ , and γ are arbitrary coefficients, and can be obtained in advance by actual measurement or the like.

The control unit 20 adjusts the opening degree of the EGR valve 22 based on (Equation 2) or (Equation 3). First, the control unit 20 obtains the intake air flow rate Q _I2 after passing through the compressor wheel 34 from the intake air flow rate sensor 14. Furthermore, the control part 20 calls the target EGR rate according to the driving state of the vehicle from the storage part. The control unit 20 obtains a target recirculation exhaust amount Q _EGR from the intake flow rate Q _I2 and the target EGR rate.

Furthermore, the control unit 20 acquires the intake pressure _PI2 after passing through the compressor wheel 34 from the intake pressure sensor 16. Further, the control unit 20 calculates an exhaust pressure _PO1 before passing through the turbine wheel, as will be described later. The target EGR valve opening A _EGR-REF is obtained by inputting the target recirculation exhaust amount Q _EGR , the intake pressure P _I2 , and the exhaust pressure P _O1 into (Equation 2) or (Equation 3). Further, the opening degree A _EGR-t of the EGR valve 22 at the current time _t is acquired from the EGR valve position sensor 24. A difference ΔA _EGR between the current opening degree A _EGR-t and the target opening degree A _EGR-REF is set as an operation amount for the EGR valve 22. By opening and closing the EGR valve 22 along the operation amount, it is possible to obtain a recirculation exhaust amount corresponding to the target EGR rate. Thereby, the combustion temperature, output, etc. of the internal combustion engine 33 can be controlled.

Next, the process of calculating the exhaust pressure _PO1 by the control unit 20 will be described. 4 and 5 exemplify flowcharts showing the calculation process of the exhaust pressure _PO1 . First, the control unit 20 acquires the turbine speed _{N t} from the turbine wheel rotation speed sensor 13 (S1). Further, the control unit 20 of the stored in the storage unit characteristic lines 7OA to 7OD, call a characteristic line corresponding to the obtained from the rotational speed sensor 13 the turbine speed N _t (S2).

Next, the control unit 20 calls up the air-fuel ratio α based on the running state of the vehicle from the storage unit, and acquires the intake flow rate Q _I2 from the intake flow rate sensor 14 (S3). Further, the control unit 20 obtains the fuel injection amount and the flow rate Q _I3 of the air-fuel mixture in which the intake air and the fuel flow are mixed from the intake flow rate Q _I2 and the air-fuel ratio α (S4). Specifically, the air-fuel mixture flow rate Q _I3 is calculated based on the following (Equation 4) stored in the storage unit.

Then the control unit 20 of the air-fuel mixture flow rate Q _I3, is input to the exhaust pressure estimation formula for estimating the exhaust pressure P _O1. The exhaust pressure estimation formula will be described. In this embodiment, the exhaust pressure estimation formula is derived based on the above-described turbine characteristic formula (Formula 1) and the formula for _obtaining the exhaust flow rate Q _O1 before passing through the turbine wheel.

The exhaust flow rate Q _O1 before passing through the turbine wheel is also called a corrected flow rate, and can be obtained from the following (Formula 5) based on the mixture flow rate Q _I3 , the exhaust pressure P _O1 before passing through the turbine wheel 36 and the exhaust temperature T _O1. .

Furthermore, the following (Expression 6) can be derived as an exhaust pressure estimation expression for calculating the exhaust pressure _PO1 before passing through the turbine wheel from (Expression 1) and (Expression 5).

Here, the exhaust pressure P _O2 after passing through the turbine wheel can be approximated to the atmospheric pressure P _A (P _O2 ≈P _A ). Where the control unit 20 inputs the atmospheric pressure _{P A} of the atmospheric pressure sensor 17 is acquired as the exhaust pressure _{P O2} in (Equation 6). Further, the air-fuel mixture flow rate Q _I3 obtained by (Expression 4) is input to (Expression 6). Further, inputs setting the exhaust temperature _{T OS,} which will be described later, as the turbine wheel 36 before passing through exhaust temperature _{T O1.} Next, the coefficients a _i and b _i are sequentially substituted from a ₁ , b ₁ to a _k , b _k and exhaust gas candidate values P _{O1 — 1} ... P _{O1 — k} before passing through the turbine wheel corresponding to the respective coefficients are obtained. Obtain (S5 in FIG. 5).

Next, the control unit 20 determines which of the exhaust pressure candidate values P _{O1 — 1} ... P _{O1 — k} is appropriate as the exhaust pressure. First, the control unit 20 is the atmospheric pressure _{P A} (≒ _{P O2)} and the expansion ratio candidate value from the exhaust pressure candidate values _P O1_1 ··· _{P O1_k} obtained from (Equation 6) _{P r_1} · the atmospheric pressure sensor 17 acquired _{..Pr_k} is calculated. (S6). Next, the control unit 20 calls a primary expression of the turbine characteristics corresponding to the expansion ratio candidate values P _{r — 1} ... P _{r — k} . That is, based on the exhaust pressure candidate values _{P O1_i} used to calculate the expansion ratio candidate value _{P r_i,} a linear expression _{Q 01 = a i P r +} b i of the turbine characteristics used for the calculation of the exhaust pressure candidate values _{P O1_i} call.

Further, the control unit 20 calls the expansion ratio section [c _i-1 ≦ P _r <c _i ] defined for the primary expression Q ₀₁ = a _i P _r + b _i , and the expansion ratio candidate value P _{r_i} is the expansion ratio. It is determined whether it is included in the section (c _i−1 ≦ P _{r — i} <c _i ) (S7). For example, the determination is started from i = 1, and it is determined whether or not the expansion ratio candidate value P _{r — 1} is included in the expansion ratio section [c ₀ , c ₁ ) (c ₀ ≦ P _{r — 1} <c ₁ ). If not, i = 2 (increment) and make the above determination. Thereafter, the process is repeated until the expansion ratio candidate value _{Pr_i} included in the expansion ratio section is obtained.

Further, the control unit 20 extracts the expansion ratio candidate value P _{r_i} included in the expansion ratio section, _obtains the exhaust pressure candidate value P _{O1_i} used for calculating the extracted expansion ratio candidate value P _{r_i} , and finalizes this. The exhaust pressure P _O1 before passing through a typical turbine wheel is set (S8).

Thus, according to the present embodiment, when estimating the exhaust pressure P _O1 before passing through the turbine wheel, basically, the estimation of the exhaust pressure P _O1 can be executed without using the value of the previous control step. It becomes possible.

Next, (Equation 5), described set exhaust temperature _{T OS} in (Equation 6). Just as it is difficult to actually measure the exhaust pressure, it is also difficult to actually measure the exhaust temperature T _O1 because, for example, the particulate matter (soot) of the exhaust may adhere to the detection surface. . Therefore, in the present embodiment, an appropriate value is obtained in advance as the exhaust temperature T _O1 through an experiment or the like, and this is input to (Equation 5) and (Equation 6).

The graph shown in Figure 6, a variety of value as the exhaust gas temperature T _O1 and exhaust pressure P _O1 of the calculated when the input to (Equation 6), an error between the exhaust pressure P _O1 actually measured for each expansion ratio P _r The appearance is shown. Here, the hollowed white circle plots (○) is representative of the error between the exhaust pressure P _O1 actually measured and the exhaust pressure P _O1 obtained when inputting this by determined by actually measuring the exhaust gas temperature T _O1 in (Equation 6) Yes. In the actual measurement of the exhaust temperature T _O1 and the exhaust pressure P _O1 , for example, the experimental apparatus is periodically stopped and the detection surface and the bypass pipe connected to the exhaust pipe 44 are washed to perform measurement processing accuracy. Is maintained.

In Figure 6, respectively 700 ° C. The set exhaust temperature _{T OS} to enter, 800 ° C., the error between the exhaust pressure _{P O1} actually measured and the exhaust pressure _{P O1} of the calculation of when the 900 ° C. is shown as the exhaust temperature _{T O1} ing. According to this, an error between 800 ° C. (downward filled triangles ▼) and 900 ° C. (filled squares ■) exhaust pressure P _O1 by the exhaust pressure P _O1 and measured on calculations when the was set exhaust temperature, the exhaust gas by the measured It is smaller than the equivalent to or the error between the exhaust pressure P _O1 by the exhaust pressure P _O1 and measured on calculations when the temperature T _O1 was set exhaust temperature. For this reason, it is preferable to set the temperature of 800 ° C. or more and 900 ° C. or less that ensures at least the same accuracy as when using the actual measurement value of the exhaust temperature T _O1 as the set exhaust temperature T _OS .

  DESCRIPTION OF SYMBOLS 10 Control apparatus, 12 Turbocharger, 13 Turbine wheel rotation speed sensor, 14 Intake flow sensor, 16 Intake pressure sensor, 17 Atmospheric pressure sensor, 20 Control part, 22 EGR valve, 24 EGR valve position sensor, 26 Throttle valve, 28 Throttle Valve position sensor, 30 waste gate valve, 32 waste gate valve position sensor, 33 internal combustion engine, 34 compressor wheel, 36 turbine wheel, 38 shaft, 39 intake pipe, 40 air cleaner, 42 intercooler, 43 EGR cooler, 44 exhaust pipe, 46 Exhaust gas recirculation pipe, 48 Catalyzer, 50 EGR valve motor, 52 Throttle valve motor, 54 Wastegate valve motor, 56 Bypass pipe, 58 Cell pedal, 60 accelerator position sensor, 70A-70D characteristic line.

Claims (3)

A turbocharger having a compressor wheel that pressurizes intake air sucked into the internal combustion engine, and a turbine wheel that is coupled to the compressor wheel and that is driven to rotate by exhaust gas discharged from the internal combustion engine;
An intake flow rate acquisition means for acquiring an intake flow rate after passing through the compressor wheel;
A control unit for controlling the internal combustion engine;
With
The controller is
The characteristics of the change in the exhaust flow rate before passing through the turbine wheel with respect to the change in the expansion ratio representing the ratio of the exhaust pressure before and after passing through the turbine wheel are determined, and the characteristics are divided into a plurality of expansion ratio sections. A turbine wheel characteristic equation approximated to a plurality of linear equations is stored,
Based on the intake flow rate acquired by the intake flow rate acquisition means and the respective coefficients of the plurality of linear equations, the exhaust pressure candidate value before passing through the turbine wheel according to the respective coefficients is calculated,
Calculating an expansion ratio candidate value based on the exhaust pressure candidate value calculated as the exhaust pressure before passing through the turbine wheel;
Among the calculated expansion ratio candidate values, the expansion ratio candidate values that are included in the expansion ratio section of the linear expression corresponding to the expansion ratio candidate values are extracted, and the extracted expansion ratio candidate values are extracted. Determining the exhaust pressure candidate value used when calculating the exhaust pressure before passing through the turbine wheel,
A control apparatus for an internal combustion engine, which controls the internal combustion engine based on the determined exhaust pressure. The control apparatus for an internal combustion engine according to claim 1,
It has an atmospheric pressure sensor that measures atmospheric pressure,
The control unit of the internal combustion engine, wherein the control unit calculates the expansion ratio candidate value based on the calculated exhaust pressure candidate value and a measured value of atmospheric pressure acquired from the atmospheric pressure sensor. A control apparatus for an internal combustion engine according to claim 1 or claim 2,
The control unit calculates the exhaust pressure candidate value based on an exhaust gas temperature before passing through the turbine wheel in addition to the intake air flow rate and the plurality of linear equations.
The control apparatus for an internal combustion engine, wherein the exhaust temperature is set to a temperature of 800 ° C or higher and 900 ° C or lower.