JP2006022764A - Control device of internal combustion engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of internal combustion engine with supercharger, calculating the outlet pressure and the outlet temperature of a cooling device with good accuracy by reflecting the unit characteristic of the cooling device. <P>SOLUTION: An inter cooler model M20 takes the supercharging pressure Pc-out, the supercharging temperature Tc_out, the intake air quantity and the outside air condition output from a turbo charger model M10 as input. On the basis of a unit model of an inter cooler 37, the pressure loss and the cooling effect in the inter cooler are calculated. On the basis of the supercharging pressure Pc_out and the pressure loss in the inter cooler, the inter cooler outlet pressure is calculated. The inter cooler outlet temperature is calculated on the basis of the supercharging temperature Tc_out and the cooling effect in the inter cooler. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine with a supercharger.

  As this type of prior art, for example, in Patent Document 1, in a diesel engine equipped with a turbocharger and an exhaust gas recirculation device, the engine speed, the amount of fuel, the exhaust gas recirculation rate, the power of the turbocharger compressor, and the power of the turbine are disclosed. Based on these comparisons, a control system that estimates the boost pressure and estimates the intake air amount has been proposed. In this case, the turbine rotational speed is calculated based on the comparison between the compressor power and the turbine power, and the supercharging pressure is estimated based on the turbine rotational speed. Thereby, the intake air amount is obtained as accurately as possible.

  On the other hand, in order to control the amount of intake air to the internal combustion engine as required, a method using the relationship between the pressure on the upstream side and the downstream side of the throttle valve has been proposed (for example, Patent Document 2). It is necessary to know the pressure accurately. In an internal combustion engine without a turbocharger, the throttle upstream pressure is always calculated as atmospheric pressure, whereas in an internal combustion engine with a turbocharger, the throttle upstream pressure always changes. Therefore, it is necessary to accurately estimate the throttle upstream pressure in an internal combustion engine with a turbocharger.

  By the way, in most internal combustion engines with a supercharger, an intercooler (cooler) is provided downstream of the compressor, and the amount of air supplied to the combustion chamber is increased by cooling the compressed air. This reduces the decrease in filling efficiency due to temperature rise. However, the above-described Patent Document 1 (Japanese Patent Laid-Open No. 6-26383) does not describe an intercooler. Even if the relationship between the turbine speed and the upstream pressure of the throttle is determined by a system with an intercooler, the characteristics of the intercooler change depending on the ambient outside temperature and vehicle speed. It was difficult.

In the control device of Patent Document 3, a turbocharger, an intercooler, an intake pipe, an exhaust pipe, an EGR, and a combustion chamber are modeled to construct a model of the entire system, and the amount of intake air is determined using gas energy as a parameter between the models. A method has been proposed for estimating. In the present control device, the intercooler cooling effect is calculated from the intercooler passing gas amount, the outside air temperature, and the intercooler upstream temperature as the intercooler characteristics. Further, the pressure loss of the intercooler model was not considered as being negligibly small. However, the pressure loss characteristics vary depending on the size and configuration of the intercooler alone. Therefore, it is not necessarily small enough to be ignored in all intercoolers, and the calculation accuracy of the outlet pressure of the intercooler, that is, the throttle upstream pressure may be reduced due to the influence of the pressure loss of the intercooler.
JP-A-6-26383 JP-A-10-103121 JP 2003-238221 A

  The main object of the present invention is to provide a control device for an internal combustion engine with a supercharger that can accurately calculate the outlet pressure and the outlet temperature of the cooler, reflecting the characteristics of the cooler well. It is.

  In order to achieve the above objective, the pressure loss in the cooler is calculated based on the single model of the cooler (intercooler), and the cooling effect in the cooler is also based on the single model of the cooler. Is calculated. Then, the outlet pressure of the cooler is calculated based on the supercharging pressure after supercharging by the supercharger and the pressure loss. Further, the outlet temperature of the cooler is calculated based on the supercharging temperature after supercharging by the supercharger and the cooling effect. According to this configuration, it is possible to accurately calculate the outlet pressure and the outlet temperature of the cooler, reflecting the pressure loss and the cooling effect as the single unit characteristics of the cooler satisfactorily. In the configuration where the throttle valve is provided on the outlet side of the cooler, the outlet pressure of the cooler corresponds to the throttle upstream pressure, and the outlet temperature corresponds to the throttle upstream temperature. With the above configuration, the throttle upstream pressure and throttle upstream temperature are accurately calculated. It will be possible. Here, the pressure loss of the cooler means a pressure difference between the cooler inlet and the outlet, and the cooling effect means a temperature difference between the cooler inlet and the outlet.

  The pressure loss calculating means may calculate the pressure loss using the pressure loss characteristic with respect to the amount of air flowing into the cooler under the reference operating condition. In this case, the cooler unit can be easily modeled by defining the standard operating conditions.

  The pressure loss calculating means may correct the pressure loss by using the inlet pressure of the cooler, the inlet temperature of the cooler, the outside air temperature, and the wind speed as parameters. That is, when the inlet pressure of the cooler, the inlet temperature of the cooler, the outside air temperature, or the wind speed changes, the pressure loss changes. In such a case, the outlet pressure of the cooler can be accurately calculated. Since the wind speed corresponds to the vehicle speed, the vehicle speed can be used as a wind speed parameter.

  The cooling effect calculation means may calculate the cooling effect using a cooling effect characteristic with respect to the amount of air flowing into the cooler under the reference operating condition. In this case, the cooler unit can be easily modeled by defining the standard operating conditions.

  The cooling effect calculation means may correct the cooling effect using the inlet temperature of the cooler, the outside air temperature, and the wind speed as parameters. That is, the cooling effect changes when the inlet temperature, the outside air temperature, or the wind speed of the cooler changes. In such a case, the outlet temperature of the cooler can be accurately calculated.

  As a supercharging pressure calculation means when a turbocharger is used as a supercharger, the following calculation method can be applied. That is, the turbine power is calculated based on the exhaust characteristics of the internal combustion engine, and the compressor driving force is calculated based on the turbine power. Further, the supercharging power is calculated based on the intake characteristics of the internal combustion engine and the compressor driving force, and the supercharging pressure is calculated from the supercharging power. According to this configuration, the supercharging pressure is calculated in accordance with the principle of power transmission in the turbocharger while taking into account the characteristics of exhaust and intake air, so that the supercharging pressure can be calculated with high accuracy. Even if the surrounding environment (temperature conditions and pressure conditions) changes, the actual supercharging pressure can be calculated accurately without requiring a base map or correction processing according to the surrounding environment, and an inexpensive system can be constructed as a result. .

  In such a case, a turbine model that models the turbine wheel, a shaft model that models the rotating shaft, and a compressor model that models the compressor impeller are set, and the turbine power calculation means and compressor driving force calculation means are set according to each model. The supercharging pressure calculating means may be configured respectively.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS An embodiment of the invention will be described below with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine, and the engine of the control system is provided with a turbocharger as a supercharger. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, a throttle valve 14 whose opening degree is adjusted by an actuator such as a DC motor is provided in an intake pipe 11, and each cylinder is controlled by the opening degree (throttle opening degree) of the throttle valve 14. The amount of intake air is adjusted. The throttle opening is detected by a throttle opening sensor 15. A surge tank 16 is provided on the downstream side of the throttle valve 14, and the surge tank 16 is provided with an intake pipe pressure sensor 17 (intake pipe pressure detection means) for detecting the intake pipe pressure. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. By the opening operation, the exhaust gas after combustion is discharged to the exhaust pipe 24. A spark plug 25 is attached to the cylinder head of the engine 10 for each cylinder, and a high voltage is applied to the spark plug 25 at a desired ignition timing through an ignition device (not shown) including an ignition coil. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 25, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  A crank angle sensor 26 that outputs a rectangular crank angle signal is attached to the cylinder block of the engine 10 at every predetermined crank angle (for example, at a cycle of 30 ° CA) as the engine 10 rotates.

  A turbocharger 30 is disposed between the intake pipe 11 and the exhaust pipe 24. The turbocharger 30 has a compressor impeller 31 provided in the intake pipe 11 and a turbine wheel 32 provided in the exhaust pipe 24, which are connected by a rotary shaft 33. The turbine wheel 32 is rotated by the energy of the exhaust gas flowing in the exhaust pipe 24, and the rotational energy is transmitted to the compressor impeller 31 via the rotation shaft 33. The compressor impeller 31 compresses and supercharges the intake air flowing through the intake pipe 11 using this energy. During this supercharging, the temperature of the intake air rises. An intercooler 37 that cools the compressed air is provided on the downstream side of the compressor impeller 31.

  An air cleaner (not shown) is provided at the most upstream portion of the intake pipe 11, and an intake air temperature sensor 41 for detecting the temperature of the intake air and an air flow meter 42 for detecting the intake air amount are provided on the downstream side of the air cleaner. Yes. In addition, the present control system is provided with an accelerator opening sensor 43 that detects the amount of accelerator pedal depression (accelerator opening), an atmospheric pressure sensor 44 that detects atmospheric pressure, and a vehicle speed sensor 45 that detects vehicle speed. It has been.

  As is well known, the ECU (electronic control unit) 50 is mainly composed of a microcomputer composed of a CPU, ROM, RAM, and the like, and by executing various control programs stored in the ROM, the engine operation state can be changed each time. Accordingly, various controls of the engine 10 are performed. That is, detection signals are input to the ECU 50 from the various sensors described above. The ECU 50 calculates the fuel injection amount, the ignition timing, and the like based on various detection signals that are input as needed, and controls the drive of the fuel injection valve 19 and the spark plug 25.

  In this embodiment, electronic throttle control by so-called torque base control is performed, and the throttle opening is controlled to a target value based on the torque generated in the engine 10. Briefly, the ECU 50 calculates the required torque based on the detection signal of the accelerator opening sensor 27 and calculates the required air amount that satisfies the required torque, and calculates the required air amount, the throttle upstream and downstream sides at each time. The target throttle opening is calculated based on the pressure and the intake air temperature. Then, the ECU 50 controls the throttle opening to the target throttle opening.

  Here, in order to estimate the throttle upstream pressure and the throttle upstream temperature necessary for calculating the target throttle opening, a turbocharger model constructed based on the principle of the turbocharger 30 is used. Calculate pressure and outlet temperature. Then, using a single model of the intercooler 37, pressure loss and cooling effect in the intercooler 37 are calculated, and based on the results, pressure and temperature upstream of the throttle (intercooler outlet pressure and intercooler outlet temperature) Is calculated.

  The turbocharger model M10 and the intercooler model M20 will be described in detail with reference to FIG. First, the turbocharger model M10 will be described.

  The turbocharger model M10 includes a turbine model M11 that models the turbine wheel 32 as a main part, a shaft model M12 that models the rotating shaft 33, and a compressor model M13 that models the compressor impeller 31. The turbine model M11 includes turbine power calculation means for calculating the turbine power Lt from the exhaust characteristics. The shaft model M12 includes a compressor driving force calculation unit that converts the turbine power Lt calculated by the turbine model M11 into the compressor driving force Lc using the conversion efficiency obtained in advance. The compressor model M13 includes a supercharging power calculation unit that calculates supercharging power that is actually used for supercharging from the compressor driving force Lc obtained by the shaft model M12, and a supercharging pressure calculation unit that calculates supercharging pressure from the supercharging power. Is provided.

  The turbocharger model M10 includes an exhaust pipe model M14 that takes into account exhaust delay and the like, and an intake pipe model M15 that takes into account intake delay and the like, in addition to each part model of the turbocharger 30.

  In this way, when the entire system model is constructed by combining the models for each component, and the model is combined with the unified parameters with the energy (power) flow based on the principle of supercharging, the model can be reused. Convenience (reusability) can be improved. That is, the model once constructed can be easily applied to other systems. Moreover, if this model is used as a base, it is highly redundant, and it is possible to easily model an electrified supercharger and realize a highly versatile model.

  The contents of each component of the turbocharger model M10 will be described in detail below. Since this model is constructed following the flow of energy, we will focus on the flow of energy.

  The energy that drives the turbocharger 30 is the energy that the exhaust of the engine 10 has. In the turbine model M11, the turbine power Lt is calculated from the exhaust parameters of the engine 10 (turbine upstream pressure Ptb_in, turbine downstream pressure Ptb_out, turbine upstream temperature Ttb_in, exhaust flow rate mg, turbine adiabatic efficiency ηg) using equation (1). These exhaust parameters such as temperature, pressure, and flow rate may be measured values by sensors or estimated values by models or maps. As an example, in the present embodiment, the exhaust flow rate mg is calculated from the measured value of the air flow meter 42 and the injection signal (or air-fuel ratio), and the turbine upstream / downstream pressure is calculated from the exhaust flow rate mg using a table prepared in advance. It is assumed that Ptb and turbine upstream / downstream temperature Ttb are calculated.

  FIG. 3 is a diagram showing the relationship between the exhaust flow rate mg, the turbine upstream / downstream pressure Ptb, and the turbine upstream / downstream temperature Ttb. The table created based on this relationship shows that the turbine upstream pressure Ptb_in and the turbine downstream are in accordance with the exhaust flow rate mg. The pressure Ptb_out, the turbine upstream temperature Ttb_in, and the turbine downstream temperature Ttb_out are calculated.

式（１）で求めたタービン動力Ｌtが次のシャフトモデルＭ１２の入力となる。ここで、ｃgは排気の比熱、κgは比熱比である。

The turbine power Lt obtained by the equation (1) is input to the next shaft model M12. Here, cg is the specific heat of the exhaust, and κg is the specific heat ratio.

  In the shaft model M12, the turbine power Lt is converted into the compressor driving force Lc by the equation (2) and output. ηt is power conversion efficiency.

式（２）で求めたコンプレッサ駆動力ＬcがコンプレッサモデルＭ１３の入力となる。

The compressor driving force Lc obtained by the equation (2) is input to the compressor model M13.

  In the compressor model M13, the supercharging power is calculated from the compressor driving force Lc and the efficiency ηc (Equation (3)). Further, the equation (4) is obtained by modifying the equation (3), and the supercharging pressure Pc_out is calculated using the calculated value of the supercharging power and the intake air parameters (intake air amount Ga, compressor inlet pressure Pc_in, intake air temperature Tc_in). (Compressor outlet pressure) is calculated (formula (4)). Here, ca is the specific heat of the intake air, and κa is the specific heat ratio. The intake air amount Ga is calculated from the detection signal of the air flow meter 42, the compressor inlet pressure Pc_in is calculated from the detection signal of the atmospheric pressure sensor 44, and the intake air temperature Tc_in is calculated from the detection signal of the intake air temperature sensor 41.

式（１），（２），（３）のηはそれぞれ効率である。効率はそれぞれ入力の動力（エネルギー）に対するテーブルもしくは、計算から求められる。効率ηgとηcは、温度、圧力から求められる断熱効率を用いて求めることができる。タービン動力Ｌt→コンプレッサ駆動力Ｌcの動力変換効率ηt（式（２）参照）は、各断熱効率を求めた後、モデルを同定する際に、実際に過給に必要なエネルギーとその時のタービン動力ＬtからＬc／Ｌtを求めて決定する。この逆モデル的な方法を用いることで、実際のターボチャージャの変換効率（機械効率など）が分からなくてもモデルを組むことができ、実機の定常値をモデルで再現することができる。図４にタービン動力Ｌtに対する動力変換効率ηtを示す。

In equations (1), (2), and (3), η is efficiency. Efficiency is obtained from a table or calculation for input power (energy). The efficiency ηg and ηc can be obtained using the adiabatic efficiency obtained from the temperature and pressure. Turbine power Lt → Power conversion efficiency ηt of compressor driving force Lc (refer to equation (2)) is the energy required for supercharging and the turbine power at that time when identifying the model after obtaining each adiabatic efficiency. Lc / Lt is obtained from Lt and determined. By using this inverse model method, it is possible to build a model without knowing the actual turbocharger conversion efficiency (mechanical efficiency, etc.), and to reproduce the steady state value of the actual machine. FIG. 4 shows the power conversion efficiency ηt with respect to the turbine power Lt.

  Here, the compressor efficiency ηc is expressed as shown in Equation (5).

式（５）は、次の式（６）のように変形でき、コンプレッサ効率ηc、コンプレッサ入口圧力Ｐc＿in、吸気温Ｔc＿in、過給圧Ｐc＿out（コンプレッサ出口圧力）が既知であれば、式（６）から過給温Ｔc＿out（コンプレッサ出口温）が算出できる。

Equation (5) can be transformed into the following equation (6). If compressor efficiency ηc, compressor inlet pressure Pc_in, intake air temperature Tc_in, and supercharging pressure Pc_out (compressor outlet pressure) are known, equation (6) From this, the supercharging temperature Tc_out (compressor outlet temperature) can be calculated.

以上の基本的な流れにより、ターボチャージャモデルＭ１０の出力である過給圧Ｐc＿out及び過給温Ｔc＿outが算出され、これらＰc＿out及びＴc＿outが次のインタークーラモデルＭ２０の入力とされる。

With the above basic flow, the supercharging pressure Pc_out and the supercharging temperature Tc_out, which are the outputs of the turbocharger model M10, are calculated, and these Pc_out and Tc_out are input to the next intercooler model M20.

  Next, a model such as a delay for connecting the above-described energy flow will be described. Actually, since a turbo inertia, a delay of air, and the like occur in the turbo system, a delay model for connecting the above-described models is necessary to estimate the supercharging pressure at the time of transition. The delay due to the volume of the intake pipe 11 and the exhaust pipe 24 can be expressed by equation (7) from the state equation, and is calculated according to the change in pressure in the intake pipe 11 or the exhaust pipe 24, respectively. In Expression (7), V is the volume of the intake pipe 11 or the exhaust pipe 24 (actually, the intake pipe volume from the compressor to the throttle or the exhaust pipe volume from the exhaust port to the turbine), R is the gas constant, and T is the intake air. The temperature of the pipe 11 or the exhaust pipe 24, p is the pressure of the intake pipe 11 or the exhaust pipe 24, dp / dt is a differential value thereof, min is the amount of gas flowing into the intake pipe 11 or the exhaust pipe 24, and mout is the intake pipe 11 or the exhaust. This is the amount of gas discharged from the pipe 24.

エンジン回転数によってシリンダから排出される時間が変化するため、排気流量ｍgについてはエンジン回転数によって変化する遅れも考慮する必要がある。これはエンジン回転数で変化するムダ時間で模擬した。吸入空気量Ｇaにおいても、体積の遅れのみでなく、実際にはスロットル上流に空気が到達するまでにはコンプレッサインペラ３１やインタークーラ３７により圧損の影響を受ける。そのため、ＮＡエンジン（ターボ無しエンジン）に比べてスロットルバルブ１４に到達するまでの抵抗が多く、遅れが生じる。この遅れを一次遅れで模擬した。

Since the time discharged from the cylinder varies depending on the engine speed, it is necessary to consider the delay that varies depending on the engine speed with respect to the exhaust flow rate mg. This was simulated by wasting time varying with engine speed. Also in the intake air amount Ga, not only the volume is delayed, but actually, the air is influenced by pressure loss by the compressor impeller 31 and the intercooler 37 until the air reaches the upstream side of the throttle. Therefore, the resistance until reaching the throttle valve 14 is larger than that of the NA engine (turboless engine), and a delay occurs. This delay was simulated with a first order delay.

  In addition to the delay of each pipe, there is a response delay of the turbocharger 30. This delay is simulated by the waste time + first order delay model. Considering that the coefficient of the transfer function at that time varies depending on the operating conditions, a more detailed transient model can be constructed. In this case, it can be seen from the actual measurement values that the turbocharger response time varies depending on the operating state of the engine (flow rate, rotation speed, load, etc.) (FIG. 5). Specifically, when the intake pipe pressure is small or when the engine speed is small, the response time is long, and when the intake pipe pressure or the rotational speed is increased, the response time is shortened accordingly.

  Therefore, considering the transient characteristics during acceleration, since the intake pipe pressure is small at the beginning of acceleration, the response time of the turbocharger is large and the response delay of the supercharging pressure is large, but the response time becomes small as the intake pipe pressure increases. Since the response delay of the supply pressure becomes small, it is considered that the supercharging pressure characteristic at the time of transition of the actual machine is secondary. Therefore, since it is difficult to simulate this characteristic with a delay model constructed with a first-order lag, the transmission coefficient of the first-order lag can be made variable depending on the driving condition, or logic that corrects this characteristic by adding a correction based on the driving condition can be added. By doing so, the supercharging pressure can be estimated with higher accuracy.

  Next, the intercooler model M20 will be described. The intercooler model M20 is divided into a pressure loss model portion for calculating the pressure loss in the intercooler 37 and a cooling effect model portion for calculating the cooling effect (temperature drop). The former configuration is shown in FIG. The configuration is shown in FIG. The pressure loss and cooling effect are built based on the characteristics of the intercooler, and the characteristics of the single unit are specified as follows.

  First, the reference outside temperature Ta_base, atmospheric pressure Pa_base, supercharging pressure Pb_base, and supercharging temperature Tb_base are determined. These values are standard operating condition values arbitrarily determined for the turbocharged engine in constructing the model. Under this standard operating condition, a pressure loss ΔP as a pressure loss characteristic with respect to the intercooler inflow amount and a temperature drop amount ΔT as a cooling effect characteristic (temperature drop characteristic) are obtained. The pressure loss ΔP is the difference between the intercooler inlet pressure and the outlet pressure, and the temperature drop ΔT is the difference between the intercooler inlet temperature and the outlet temperature. This is the reference model.

  Here, the pressure loss and the cooling effect in the intercooler 37 change with the pressure at the intercooler inlet (supercharging pressure Pc_out), the temperature (supercharging temperature Tc_out), the outside air temperature Ta, and the wind speed passing through the intercooler 37 as parameters. To do. Therefore, corrections are made to the calculated values under the reference conditions based on these parameters. 8 to 10 show changes in pressure loss characteristics and cooling effect characteristics with respect to changes in intercooler inlet pressure (supercharging pressure Pc_out), intercooler inlet temperature (supercharging temperature Tc_out), and wind speed.

  FIG. 8 shows the pressure loss characteristic and the cooling effect characteristic when the intercooler inlet pressure (supercharging pressure Pc_out) changes. In FIG. 8, the temperature condition and the wind speed condition are constant. In this case, since the density of the air changes as the intercooler inlet pressure (supercharging pressure Pc_out) changes, the volume flowing into the intercooler 37 changes as the pressure rises, as shown in FIG. Decrease. However, even if the intercooler inlet pressure (supercharging pressure Pc_out) changes, the mass flow rate flowing into the intercooler 37 does not change and the amount of heat released from the supercharged air does not change. Therefore, as shown in FIG. The effect (temperature drop) is unchanged.

  FIG. 9 shows pressure loss characteristics and cooling effect characteristics when the intercooler inlet temperature (supercharging temperature Tc_out) changes. In FIG. 9, the pressure condition and the wind speed condition are constant. In this case, since the density of air changes with the change of the intercooler inlet temperature (supercharging temperature Tc_out), the pressure loss decreases as the temperature rises as shown in (a). Further, since the temperature difference with the outside air changes due to the change in the intercooler inlet temperature (supercharging temperature Tc_out) and the heat radiation amount changes, as shown in (b), the cooling effect (temperature drop) as the temperature rises. Will increase.

  FIG. 10 shows the pressure loss characteristic and the cooling effect characteristic when the wind speed (that is, the vehicle speed) changes. In FIG. 10, the temperature condition and the pressure condition are constant. In this case, as shown in (a), the pressure loss decreases as the wind speed increases. Further, as shown in (b), the cooling effect increases as the wind speed increases. In the present embodiment, the intercooler model M20 is constructed reflecting the above-described intercooler single unit characteristics.

  In the pressure loss model shown in FIG. 6, a characteristic map created using the outside air temperature Ta_base, the supercharging pressure Pb_base, and the supercharging temperature Tb_base as reference values (for example, Ta_base = 25 ° C., Pb_base = 0 kPa, Tb_base = 75 ° C.) A reference pressure loss ΔPbase is calculated based on the intake air amount Ga and the vehicle speed SPD each time. FIG. 11A shows pressure loss characteristics with respect to the intake air amount Ga and the vehicle speed SPD.

  Further, the pressure correction coefficient is calculated based on the intercooler inlet pressure (supercharging pressure Pc_out) using the equation (8), and the intercooler inlet temperature (supercharging temperature Tc_out) and the outside air temperature are calculated using the equation (9). A temperature correction coefficient is calculated based on Ta. ρ (T) is the density of air at an arbitrary temperature.

なお、式（９）による温度補正は外気温と過給温の差の影響を考慮して行われ、外気温Ｔaの変化に伴う温度補正は式（９）に含まれている（後述する式（１１）による温度補正も同様）。

The temperature correction according to the equation (9) is performed in consideration of the influence of the difference between the outside air temperature and the supercharging temperature, and the temperature correction associated with the change in the outside air temperature Ta is included in the equation (9) (an expression described later). The same applies to the temperature correction by (11)).

  Then, the throttle upstream pressure Pic_out is calculated by the following equation (10).

また、図７に示す冷却効果モデルでは、前記図６の圧力損失モデルと同様、外気温Ｔa＿base、過給圧Ｐb＿base及び過給温Ｔb＿baseを基準値（例えば、Ｔa＿base＝２５℃、Ｐb＿base＝０ｋＰａ、Ｔb＿base＝７５℃）として作成した特性マップを用い、その都度の吸入空気量Ｇaと車速ＳＰＤとに基づいて基準温度降下量ΔＴbaseを算出する。図１１の（ｂ）には、吸入空気量Ｇaと車速ＳＰＤとに対する冷却効果特性を示す。

In the cooling effect model shown in FIG. 7, as in the pressure loss model of FIG. 6, the outside air temperature Ta_base, the supercharging pressure Pb_base, and the supercharging temperature Tb_base are set as reference values (for example, Ta_base = 25 ° C., Pb_base = 0 kPa, Tb_base = 75 ° C.), the reference temperature drop ΔTbase is calculated based on the intake air amount Ga and the vehicle speed SPD each time. FIG. 11B shows the cooling effect characteristics with respect to the intake air amount Ga and the vehicle speed SPD.

  Further, the temperature correction coefficient is calculated based on the intercooler inlet temperature (supercharging temperature Tc_out) and the outside air temperature Ta using the equation (11).

なお、前述したとおりインタークーラ入口圧力（過給圧Ｐc＿out）が変化しても、インタークーラ３７に流入する質量流量は変化しないため、冷却効果（温度降下）に対する圧力補正は実施しない。

As described above, even if the intercooler inlet pressure (supercharging pressure Pc_out) changes, the mass flow rate flowing into the intercooler 37 does not change, so pressure correction for the cooling effect (temperature drop) is not performed.

  Then, the throttle upstream temperature Tic_out is calculated by the following equation (12).

以上のようにして、インタークーラモデルＭ２０の出力であるスロットル上流圧Ｐic＿outとスロットル上流温Ｔic＿outとが算出できる。

As described above, the throttle upstream pressure Pic_out and the throttle upstream temperature Tic_out, which are outputs of the intercooler model M20, can be calculated.

  Next, the flow of processing for calculating the supercharging pressure by the ECU 50 will be described based on the flowcharts of FIGS. FIG. 12 is a flowchart showing the base routine. This routine is executed by the ECU 50 every 4 msec, for example. Then, in the base routine of FIG. 12, the subroutines of FIGS. 13 to 19 are appropriately executed.

  As shown in FIG. 12, the base routine includes an exhaust pipe model calculation routine (step S110), a turbine model calculation routine (step S120), a shaft model calculation routine (step S130), a compressor model calculation routine (step S140), an intercooler. A model calculation routine (step S150) is provided.

  In such a case, in the exhaust pipe model calculation routine shown in FIG. 13, the exhaust flow rate delay is calculated in step S111, and the exhaust characteristic is calculated in the subsequent step S112. Specifically, the turbine upstream pressure Ptb_in, the turbine downstream pressure Ptb_out, the turbine upstream temperature Ttb_in, and the turbine downstream temperature Ttb_out are calculated based on the exhaust flow rate mg in each case using the relationship of FIG.

  Further, in the turbine model calculation routine shown in FIG. 14, the turbine power Lt is calculated based on the exhaust characteristic calculated in the exhaust pipe model calculation routine by using the above-described equation (1) in step S121.

  In the shaft model calculation routine shown in FIG. 15, the power conversion efficiency ηt is calculated based on the turbine power Lt using the relationship shown in FIG. 4 in step S131. In the following step S132, the compressor driving force Lc is calculated from the turbine power Lt and the power conversion efficiency ηt using the above-described equation (2). In step S133, a delay due to the turbine inertia is calculated.

  In the compressor model calculation routine shown in FIG. 16, the intake air amount and the intake air temperature are read in step S141, and the intake pipe delay is calculated in step S142. In step S143, the compressor efficiency ηc is calculated, and in step S144, the supercharging pressure Pc_out is calculated using the above-described equation (4). In step S145, the supercharging temperature Tc_out is calculated using the above-described equation (6).

  Next, the intercooler model calculation routine shown in FIG. 17 includes a cooling effect calculation routine (step S210) and a pressure loss calculation routine (step S220).

  In the cooling effect calculation routine shown in FIG. 18, first, the vehicle speed SPD is read in step S211, and a ΔTbase map serving as a reference for temperature drop is selected based on the vehicle speed SPD in step S212. In step S213, the intake air amount Ga, the outside air temperature Ta, and the intercooler inlet temperature (supercharging temperature Tc_out) are read. In step S214, the reference temperature drop amount ΔTbase is calculated from the map based on the intake air amount Ga. In step S215, the temperature correction coefficient is calculated based on the outside air temperature Ta and the intercooler inlet temperature (supercharging temperature Tc_out) using the above-described equation (11). In step S216, the throttle upstream temperature Tic_out is calculated by the above equation (12).

  In the pressure loss calculation routine shown in FIG. 19, first, the vehicle speed SPD is read in step S221, and a ΔPbase map serving as a pressure loss reference is selected based on the vehicle speed SPD in step S222. In step S223, the intake air amount Ga, the outside air temperature Ta, the intercooler inlet temperature (supercharging temperature Tc_out), and the intercooler inlet pressure (supercharging pressure Pc_out) are read. In step S224, the intake air amount Ga is read from the map. A reference pressure loss ΔPbase is calculated. In step S225, the temperature correction coefficient is calculated based on the outside air temperature Ta and the intercooler inlet temperature (supercharging temperature Tc_out) using the above-described equation (9). In step S226, the pressure correction coefficient is calculated based on the intercooler inlet pressure (supercharging pressure Pc_out) using the above-described equation (8). In step S227, the throttle upstream pressure Pic_out is calculated by the above-described equation (10).

  FIG. 20 is a time chart showing various behaviors when the present embodiment is applied. FIG. 20 shows changes in intake air amount, pressure (intercooler inlet pressure, outlet pressure) and temperature (intercooler inlet temperature, outlet temperature) in order from the top. As the intake air amount increases, the intercooler inlet pressure (supercharging pressure Pc_out) and the intercooler inlet temperature (supercharging temperature Tc_out) increase accordingly. At this time, the pressure loss and the cooling effect of the intercooler 37 increase as the intake air amount increases, so that the pressure difference and temperature difference between the intercooler inlet and the outlet increase.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  Based on the single model of the intercooler 37, the pressure loss and the cooling effect in the intercooler 37 are calculated, and the outlet pressure (throttle upstream pressure Pic_out) and the outlet temperature of the intercooler 37 are calculated based on the pressure loss and the cooling effect. Since (the throttle upstream temperature Tic_out) is calculated, the outlet pressure and the outlet temperature of the intercooler 37 can be accurately calculated reflecting the pressure loss and the cooling effect as the single characteristics of the intercooler 37. .

  Since the throttle upstream pressure Pic_out and the throttle upstream temperature Tic_out can be calculated with high accuracy, electronic throttle control using these parameters as parameters can also be suitably implemented. Thereby, the accuracy of air amount control is also improved. Further, when the electronic throttle control is performed, a sensor for detecting the throttle upstream pressure and the throttle upstream temperature becomes unnecessary, and the cost can be reduced.

  Since the intercooler inlet pressure (supercharging pressure Pc_out), the intercooler inlet temperature (supercharging temperature Tc_out), the outside air temperature Ta, and the vehicle speed SPD (wind speed) were corrected as parameters, the pressure loss was changed. Also, the outlet pressure of the intercooler 37 (throttle upstream pressure Pic_out) can be calculated with high accuracy.

  Further, since the cooling effect was corrected using the intercooler inlet temperature (supercharging temperature Tc_out), the outside air temperature Ta, and the vehicle speed SPD (wind speed) as parameters, the outlet temperature of the intercooler 37 (throttle throttle) even if these parameters change. The upstream temperature Tic_out) can be calculated with high accuracy.

  The turbocharger 30 is modeled for each component, and a turbine model, a shaft model, and a compressor model are set. By each model, turbine power Lt → compressor driving force Lc → supercharging power → supercharging pressure Pc_out (compressor outlet pressure) Each parameter was calculated in order. Further, the exhaust characteristic is reflected in the calculation of the turbine power Lt, and the intake characteristic is reflected in the calculation of the supercharging power (supercharging pressure Pc_out). As a result, the supercharging pressure Pc_out (compressor outlet pressure) can be accurately calculated in accordance with the principle of power transmission in the turbocharger 30 while taking into account the exhaust and intake characteristics. Even if the surrounding environment (temperature condition or pressure condition) changes, the actual supercharging pressure Pc_out can be calculated with high accuracy. In this case, a base map corresponding to the surrounding environment, correction processing for the base map, and the like are not necessary, and an inexpensive system can be constructed.

  In the above embodiment, the turbocharger model M10 is used to calculate the supercharging pressure and supercharging temperature, and the final values of the throttle upstream pressure and upstream temperature are calculated using the calculated values as inputs to the intercooler model M20. The supercharging pressure and supercharging temperature which are input values may be estimated values or actually measured values. However, when trying to obtain the throttle upstream pressure and the upstream temperature with an inexpensive system, a model system that can omit the sensor is effective.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a figure which shows the outline of a turbocharger model and an intercooler model. It is a figure for calculating an exhaust characteristic. It is a figure which shows the relationship between turbine power and power conversion efficiency. It is a figure which shows the relationship between an engine driving | running state and a turbocharger response time. It is a figure which shows the pressure loss model of an intercooler model. It is a figure which shows the cooling effect model of an intercooler model. It is a figure which shows the pressure loss characteristic with respect to the change of supercharging pressure, and a cooling effect characteristic. It is a figure which shows the pressure loss characteristic with respect to the change of supercharging temperature, and a cooling effect characteristic. It is a figure which shows the pressure loss characteristic with respect to the change of a wind speed, and a cooling effect characteristic. It is a figure which shows the base characteristic of an intercooler. It is a flowchart which shows a base routine. It is a flowchart which shows an exhaust pipe model calculation routine. It is a flowchart which shows a turbine model calculation routine. It is a flowchart which shows a shaft model calculation routine. It is a flowchart which shows a compressor model calculation routine. It is a flowchart which shows an intercooler model calculation routine. It is a flowchart which shows a cooling effect calculation routine. It is a flowchart which shows a pressure loss calculation routine. It is a time chart which shows the behavior of the amount of intake air, pressure, and temperature.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Intake pipe, 24 ... Exhaust pipe, 30 ... Turbocharger, 31 ... Compressor impeller, 32 ... Turbine wheel, 33 ... Rotating shaft, 37 ... Intercooler, 50 ... ECU.

Claims (6)

In a control device for an internal combustion engine comprising a supercharger provided in an intake passage of the internal combustion engine, and a cooler provided downstream of the supercharger,
Based on the simple model of the cooler, pressure loss calculating means for calculating the pressure loss in the cooler;
Similarly, based on a single model of the cooler, cooling effect calculation means for calculating the cooling effect in the cooler,
Outlet pressure calculating means for calculating the outlet pressure of the cooler based on the supercharging pressure after supercharging by the supercharger and the pressure loss calculated by the pressure loss calculating means;
Outlet temperature calculating means for calculating the outlet temperature of the cooler based on the supercharging temperature after supercharging by the supercharger and the cooling effect calculated by the cooling effect calculating means;
A control device for an internal combustion engine with a supercharger.   2. The turbocharger according to claim 1, wherein the pressure loss calculation unit calculates the pressure loss using a pressure loss characteristic with respect to an amount of air flowing into the cooler under a reference operating condition. Control device for internal combustion engine.   The supercharger according to claim 1 or 2, wherein the pressure loss calculation means corrects the pressure loss by using the inlet pressure of the cooler, the inlet temperature of the cooler, the outside air temperature, and the wind speed as parameters. Control device for internal combustion engine.   The said cooling effect calculation means calculates a cooling effect using the cooling effect characteristic with respect to the inflow air quantity to the said cooler on the driving | running conditions used as a reference | standard, The Claim 1 thru | or 3 characterized by the above-mentioned. Control device for an internal combustion engine with a supercharger.   5. The internal combustion engine with a supercharger according to claim 1, wherein the cooling effect calculation unit performs correction for the cooling effect using the inlet temperature of the cooler, the outside air temperature, and the wind speed as parameters. Control device. As the supercharger, applied to an internal combustion engine having a turbocharger having a turbine wheel rotated by exhaust energy and a compressor impeller connected to the turbine wheel via a rotation shaft,
Turbine power calculating means for calculating turbine power generated in the turbine wheel based on the exhaust characteristics of the internal combustion engine;
Compressor driving force calculating means for calculating a compressor driving force for driving a compressor impeller based on the turbine power;
Based on the intake characteristics of the internal combustion engine and the compressor driving force, the supercharging power used for supercharging is calculated, and the supercharging pressure calculating means for calculating the supercharging pressure from the supercharging power;
The control device for an internal combustion engine with a supercharger according to any one of claims 1 to 5, wherein

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