JP4434176B2 - Control device for an internal combustion engine with a supercharger - Google Patents

Description

  The present invention relates to a control device that is applied to an internal combustion engine having a supercharger such as a turbocharger and performs power assist for the supercharger.

  A turbocharger is generally known as a supercharger that supercharges intake air using exhaust power. In recent years, an electric turbocharger has been developed that attaches an electric motor or the like to the rotating shaft of a turbocharger and assists the power of the turbocharger according to the operating state of the internal combustion engine. In this case, by performing power assist control using an electric motor or the like, supercharging of the turbocharger is assisted and the supercharging effect is improved. As another method for improving the supercharging effect, an auxiliary compressor that is provided upstream or downstream of the turbocharger in the intake passage and is operated by an electric motor or the like has been developed.

  And the control method of the power assistance apparatus which assists the power of these turbochargers is proposed. For example, in Patent Document 1, a target boost pressure is corrected by obtaining an increase correction amount of the boost pressure by the power assist device according to the accelerator opening, and the target boost pressure and the actual boost pressure are calculated. The power is assisted according to the deviation. In particular, when the accelerator opening is large, a target boost pressure increase correction amount is calculated to be large, and power assist by the power assist device is reliably performed.

By the way, when the engine speed increases during acceleration, the power assist shifts from a valid state to an invalid state due to the assist performance of the power assist device. At this time, the assistable power decreases as the engine speed increases. For this reason, when a relatively large power is assisted and accelerated as in Patent Document 1, the output torque is reduced during the acceleration, which causes a problem that a so-called torque valley is formed. And when a trough arises in such torque, there is a risk that the driving feeling will be worsened such that the driver feels a lack of torque.
JP 2003-239754 A

  The present invention relates to an internal combustion engine equipped with a power assist device that assists the power of a supercharger, with a supercharger that can ensure a good driving feeling without causing the driver to feel a lack of torque during acceleration. The main object is to provide a control device for an internal combustion engine.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The control apparatus for an internal combustion engine with a supercharger according to the present invention is premised on a supercharger that supercharges intake air by exhaust power and a power that is operated by power other than the exhaust power directly or indirectly. The present invention is applied to an internal combustion engine having a power assist device that assists the vehicle. Here, the power assist device is a device that is attached to the supercharger and directly assists the power of the supercharger, or is provided upstream or downstream of the supercharger in the intake passage. A device that assists indirectly. Then, power assist control by the power assist device is performed in a predetermined low rotation range. By such power assist control, the power of the supercharger in the low rotation range is assisted, and the supercharging effect is improved.

  By the way, when the engine speed increases with acceleration, the power assist control by the power assist device shifts from a valid state to an invalid state. At this time, the power that can be assisted decreases as the engine speed increases, and the increase in the output torque by the power assist control decreases accordingly. That is, there is a case where the output torque is reduced during acceleration and a torque valley is formed. Further, the formation of such a trough of the torque may cause the driver to feel a lack of torque.

  The invention described in claim 1 is characterized by comprising means for limiting the output torque in the power assist control during acceleration. In other words, by limiting the increase in the output torque by the power assist control, the decrease in the output torque due to the decrease in assistable power is reduced, and the torque valley is suppressed. Therefore, it is avoided that the driver feels a lack of torque, and as a result, a good driving feeling is ensured.

According to the first aspect of the present invention, a minimum value of the output torque that can be generated during the transition from the assistable region to the non-assistable region is obtained in advance, and the output torque is limited based on the minimum value of the output torque.

  As described above, the torque valley is generated when the power assist control is shifted from the valid state to the invalid state. For this reason, the value of the bottom of the trough of the torque appears as the minimum value of the output torque during the transition from the assistable region where the power assist control is effective to the ineffective assistable region. Therefore, as a method of limiting the output torque, it is preferable to limit the output torque based on the minimum value of the output torque, that is, the bottom value of the torque valley. Thereby, it is possible to reduce the amount of decrease in the output torque reflecting the characteristics of the torque valley generated in accordance with the power assist control, and the torque valley can be suitably suppressed.

In the invention according to claim 2 , the output torque is limited so as not to exceed the minimum value of the output torque. That is, in the power assist control at the time of acceleration, by limiting the output torque so as not to exceed the minimum value, the output torque does not decrease, and the torque valley is not formed.

In the third aspect of the invention, the output torque is limited so that the maximum value of the output torque generated with the power assist control is reduced by a predetermined amount.

  According to the above configuration, the swell of the output torque caused by the power assist control can be suppressed. Therefore, a decrease in output torque is reduced, and torque valleys are suppressed.

Note that the minimum value or maximum value of the output torque in the invention according to any one of claims 1 to 3 is not limited to the output torque, but the power assist control is performed without limiting the output torque in the operation up to that time. You may ask.

According to the fourth aspect of the present invention, the output torque is limited based on the output torque of the internal combustion engine at the engine speed at which the power assist by the power assist device is impossible.

  As described above, when the engine speed increases, the state shifts from a state where the power assist control by the power assist device is valid to an invalid state, that is, a state where the power assist is disabled. Then, the output torque becomes minimum at the engine rotational speed at which the power assist is disabled, and becomes the bottom value of the torque valley. Therefore, by limiting the output torque based on the output torque at the engine rotation speed at which power assist is not possible, the torque valley can be suitably suppressed.

  Further, when the power assist control by the power assist device shifts from the valid state to the invalid state, the assistable power is reduced. At this time, the output torque becomes maximum at the engine rotation speed at which assistable power starts to decrease. Therefore, the output torque may be limited for the output torque at the engine rotation speed at which the assist power starts to decrease.

In the invention according to claim 5 , as a premise, in the torque control for adjusting the output torque of the internal combustion engine according to the target torque corresponding to the driver's request, the target power of the supercharger is calculated according to the target torque and the same. The actual power of the supercharger is calculated, and power assist control is performed based on the target power and the actual power. That is, so-called torque base control is performed in which various actuators such as a power assist device are operated so as to satisfy the target torque. In such a configuration, the target torque is limited and calculated in the power assist control.

  That is, in the configuration that performs the torque base control, the output torque can be controlled by adjusting the target torque. Therefore, in the power assist control, by calculating by limiting the target torque, the output torque is limited and the torque valley is suppressed.

According to the sixth aspect of the present invention, a torque map that limits the target torque during power assist control is defined in advance, and the target torque is calculated using the defined torque map.

  According to this configuration, since the output torque is controlled according to the target torque limited in advance by the torque base control, it is possible to reliably suppress the torque trough. In addition, it is difficult to calculate how much the target torque is to be limited from the viewpoint of driving feeling and the like, but it is difficult to obtain the desired torque by predefining the target torque by conformity as in the present invention. Driving feeling can be easily obtained.

Further, as a method of limiting the target torque, in addition to using a torque map as in the invention described in claim 6, as in the invention described in claim 2 , the minimum value of the torque valley is used as a guard value, and the target torque is limited. You may make it perform the upper limit guard process of a torque. Thereby, since the fall of the output torque resulting from the fall of the motive power which can be assisted by a power assist device is avoided, it can avoid that a trough of torque is formed. The method of limiting the target torque by the upper limit guard process has an advantage that it is not necessary to preliminarily define a torque map in which the target torque is limited in advance by conformance or the like.

In the seventh aspect of the invention, the output torque is limited by operating the output control means capable of adjusting the output torque of the internal combustion engine.

  According to the above configuration, the output torque can be reduced during the power assist control by operating the output control means capable of adjusting the output torque. Therefore, it is possible to suppress the torque valley, and a good driving feeling can be obtained.

In the eighth aspect of the invention, the power assisted by the power assist device is reduced as the operation of the output control means.

  That is, since the supercharging effect by the supercharger is reduced by reducing the assist power, the output torque can be reduced. As a result, a decrease in the output torque that occurs when the power assist by the power assist device shifts from a valid state to an invalid state is reduced, and a torque trough is suppressed.

  Further, when the assist power by the power assist device is reduced as in the above configuration, the energy required for driving the power assist device can be suppressed as compared with the case where the output torque is limited using other output control means. There is an advantage.

  In addition, the throttle valve may be closed as an operation of the output control means. Since the intake air amount is adjusted by adjusting the opening of the throttle valve, the output torque of the internal combustion engine can be reduced by closing the throttle valve. In a spark ignition type internal combustion engine, the output torque can be adjusted by adjusting the ignition timing, and the output torque can be reduced by correcting the ignition timing to the retard side. On the other hand, in a diesel engine, the output torque depends on the amount of fuel provided for combustion, so the output torque can be reduced by reducing the fuel supply amount.

  In order to avoid excessive supercharging by the supercharger, a wastegate valve in an internal combustion engine having a bypass passage for bypassing the supercharger and flowing exhaust and a wastegate valve for opening and closing the passage The degree of opening may be adjusted. That is, the exhaust torque of the supercharger is reduced by opening the wastegate valve, so that the output torque can be reduced. In an internal combustion engine having a variable nozzle turbo (VNT) capable of adjusting the supercharging state by adjusting the blade angle of the turbine wheel, the internal combustion engine can be adjusted by adjusting the blade angle of the turbine wheel. Output torque can be reduced.

  In an internal combustion engine equipped with a variable valve timing mechanism (VVT) that makes the intake valve opening and closing timing variable, it is preferable to adjust the closing timing of the intake valve. That is, by correcting the closing timing of the intake valve to the retard side from the bottom dead center, the charge air is blown back and the charging efficiency is reduced, so that the output torque of the internal combustion engine can be reduced.

  As described above, by operating each output control means to reduce the output torque of the internal combustion engine, it is possible to reduce the reduction in output torque that occurs when the power assisted by the power assist device decreases. . Therefore, it is possible to suppress the torque valley.

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described 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 an electric assist type turbocharger (hereinafter referred to as an electric turbocharger) is used as a supercharger for the engine of the control system. Also called charger). 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, the intake pipe 11 is provided with a throttle valve 14 as an air amount adjusting means whose opening is adjusted by a throttle actuator 15 such as a DC motor. The throttle actuator 15 incorporates a throttle opening sensor for detecting the throttle opening. An upstream side of the throttle valve 14 is provided with a boost pressure sensor 12 for detecting the pressure upstream of the throttle (a boost pressure by a turbocharger described later), and an intake air temperature sensor 13 for detecting the intake air temperature upstream of the throttle. It has been.

  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 pressure sensor 17 (intake pipe pressure detecting means) for detecting the intake pressure on the downstream side of the throttle. 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, and these are connected by a shaft 33. The shaft 33 is provided with a motor (electric motor) 34 as a power assist device, and the motor 34 is operated by electric power supplied from a battery (not shown) to assist the rotation of the shaft 33. The motor 34 is provided with a temperature sensor 35 for detecting the motor temperature.

  In the turbocharger 30, the turbine wheel 32 is rotated by the exhaust gas flowing through the exhaust pipe 24, and the rotational force is transmitted to the compressor impeller 31 via the shaft 33. The intake air flowing through the intake pipe 11 is compressed by the compressor impeller 31 to perform supercharging. The air supercharged by the turbocharger 30 is cooled by the intercooler 37 and then fed downstream. As the intake air is cooled by the intercooler 37, the charging efficiency of the intake air is increased.

  An air cleaner (not shown) is provided at the most upstream portion of the intake pipe 11, and an air flow meter 41 for detecting the intake air amount is provided downstream of the air cleaner. In addition, the present control system is provided with an accelerator opening sensor 43 that detects an accelerator pedal depression operation amount (accelerator opening) and an atmospheric pressure sensor 44 that detects atmospheric pressure.

  As is well known, the engine ECU (electronic control unit) 50 is mainly composed of a microcomputer composed of a CPU, ROM, RAM, etc., and executes various control programs stored in the ROM, so that the engine operating state in each case. Various controls of the engine 10 are performed according to the above. That is, detection signals are input to the engine ECU 50 from the various sensors described above. The engine ECU 50 calculates the fuel injection amount, 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 engine ECU 50 calculates a target torque (requested torque) based on a detection signal of the accelerator opening sensor 43 and calculates a target air amount that satisfies the target torque. The target throttle opening is calculated based on the upstream and downstream pressures and the intake air temperature. The engine ECU 50 controls the throttle actuator 15 with a control command signal based on the target throttle opening, and controls the throttle opening to the target throttle opening.

  Further, the engine ECU 50 determines the control amount of the motor 34 of the turbocharger 30 in conjunction with the torque base control. Thereby, assist power (auxiliary power) is added to the turbocharger 30 during vehicle acceleration so that a desired supercharging pressure can be obtained quickly. That is, the engine ECU 50 calculates target assist power, power assist timing, and the like based on the target air amount and target boost pressure calculated according to the target torque, and outputs the calculation results to the motor ECU 60. The motor ECU 60 receives a signal from the engine ECU 50, performs a predetermined calculation process in consideration of the motor efficiency and the like, and controls the power supplied to the motor 34.

  Next, an outline of the control of the engine ECU 50 in the present embodiment will be described with reference to FIG. FIG. 2 is a control block diagram for explaining the function of engine ECU 50.

  In the present system shown in FIG. 2, as main functions, the assist power of the motor 34 commanded to the motor ECU 60 and the torque base controller 70 that calculates the target throttle opening based on the target torque requested by the driver is calculated. An assist control unit 80. Hereinafter, the details of the control units 70 and 80 will be described.

  In the torque base controller 70, a target torque calculator 71 calculates a target torque based on the accelerator opening and the engine speed, and a target air amount calculator 72 calculates a target based on the target torque and the engine speed. Calculate the air volume. This target air amount corresponds to the air amount required for realizing the target torque required by the driver. The target intake pressure calculation unit 73 calculates a target intake pressure (target throttle downstream pressure) based on the target air amount and the engine speed, and the target boost pressure calculation unit 74 calculates the target air amount. And the target boost pressure (target throttle upstream pressure) is calculated based on the engine speed. Then, the target throttle opening calculation unit 75 calculates the target throttle opening based on the target air amount, the target intake pressure, the target boost pressure, the actual boost pressure, and the throttle passage intake air temperature. However, in this case, the target air amount [g / rev] is used for calculating the target intake pressure and the target supercharging pressure, and the target air amount [g / rev] is calculated based on the engine speed for calculating the target throttle opening. The converted target air amount [g / sec] per unit time is used.

  The actual supercharging pressure is the supercharging pressure (throttle upstream pressure) detected by the supercharging pressure sensor 12, and the throttle passing intake air temperature is the intake air temperature upstream of the throttle detected by the intake air temperature sensor 13. .

  In such a case, the target throttle opening is calculated based on the following basic formula for calculating the throttle passing air amount Ga.

Ga = f (Thr) × Pb / √T × f (Pm / Pb)
In the above equation, Thr is the throttle opening, Pb is the throttle upstream pressure, Pm is the throttle downstream pressure, and T is the intake air temperature. In the present embodiment, the basic type throttle passing air amount Ga is set as the target air amount, the throttle opening degree Thr is set as the target throttle opening degree, the throttle upstream pressure Pb is set as the actual boost pressure, and the throttle downstream pressure Pm is set as the target suction level. The target throttle opening is calculated based on the target air amount, the actual boost pressure, the target intake pressure, and the like.

  On the other hand, in the assist control unit 80, the target turbine power calculation unit 81 calculates the target turbine power based on the target air amount and the target boost pressure calculated by the torque base control unit 70. In addition, the actual turbine power calculation unit 82 calculates actual turbine power (actual turbine power) based on the exhaust information. The power difference calculation unit 83 calculates a power difference between the target turbine power and the actual turbine power. The assist power calculation unit 84 calculates assist power based on the calculated power difference and outputs the assist power to the motor ECU 60.

  In such a case, the assist power of the motor 34 is calculated as a shortage of the actual turbine power with respect to the target turbine power. That is, the shortage of turbine power is compensated by motor assist. In the assist control unit 80, the motor assist amount is also calculated by the power using the power as a unified parameter. At this time, since the command value of the motor ECU 60 of the existing electric turbo system is a motor output, it is considered desirable to calculate the motor assist amount by the power.

  When calculating the assist power, it is desirable to correct the assist power or set an upper limit guard based on the performance, operating state, engine operating state, and the like of the motor 34. In the present embodiment, the upper limit value of the assist power is set using the motor temperature (the value detected by the temperature sensor 35) as a parameter, and the upper limit value of the assist power is guarded by the upper limit value.

  Here, the outline of the assist control of the electric turbocharger will be described with reference to FIG.

  When the accelerator opening is changed and acceleration is started as shown in FIG. 3A, the target turbine power is increased according to the acceleration request as shown in FIG. 3B, and the actual turbine power (exhaust power) is the target turbine. Stand up late for power. Therefore, as shown in (d), the rise of the actual boost pressure is delayed with respect to the target boost pressure. Therefore, in the present embodiment, when the turbine power is insufficient, the assist power is added as shown in (c) to assist the turbine power. At this time, the assist power is calculated based on the difference between the target turbine power and the actual turbine power (details will be described later). In other words, in this case, assist power by the motor 34 is added to the power (actual turbine power) for turning the turbine wheel 32 by exhaust, and the compressor impeller 31 rotates via the shaft 33 by the sum of these powers (actual turbine power + assist power). Driven. Thereby, as shown in (d), the supercharging pressure is raised at an early stage.

  In the present embodiment, the calculation of turbine power (target turbine power, actual turbine power) in the assist control unit 80 is performed using an electric turbo model, and details thereof will be described below. FIG. 4 is a control block diagram showing the electric turbo model M10. In FIG. 4, the motor 34 and the intercooler 37 provided along with the turbocharger 30 are also used as the electric turbo model.

  In FIG. 4, the turbine wheel 32, the shaft 33, the compressor impeller 31, the motor 34, and the intercooler 37 are modeled as a turbine model M11, a shaft model M12, a compressor model M13, a motor model M14, and an intercooler model M15. In addition to each part model of the turbocharger, an exhaust pipe model M16 considering exhaust delay and the intake pipe model M17 considering intake delay and the like are provided.

  Incidentally, in the electric turbo model M10, the turbine model M11, the shaft model M12, the compressor model M13, and the motor model M14 are constructed with the energy (power) flow as a unified parameter based on the principle of supercharging. Therefore, convenience (reusability) when reusing the model is 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 possible to realize a highly versatile model because of its high redundancy and easy modeling of an electrified supercharger.

  In the turbine model M11, equation (1) is used from the exhaust parameters (exhaust flow rate mg, turbine upstream pressure Ptb_in, turbine downstream pressure Ptb_out, turbine upstream temperature Ttb_in, turbine adiabatic efficiency ηg) calculated in the exhaust pipe model M16. Then, the turbine power Lt is calculated.

ここで、ｃgは排気の比熱、κgは比熱比である。

Here, cg is the specific heat of the exhaust, and κg is the specific heat ratio.

  The temperature, pressure, and flow rate, which are the exhaust parameters of the engine 10, 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 actually measured value of the air flow meter 41 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.

  In an actual turbo system, there are many delay elements. For example, in a configuration in which the exhaust flow rate mg is calculated based on the actual measurement value of the air flow meter 41, the actual exhaust system is reflected in the exhaust flow rate in the turbine from the time of measuring the intake air amount. A delay occurs. For this reason, in the exhaust pipe model M16, the exhaust flow rate mg is calculated in consideration of the volume of the exhaust pipe 24 (exhaust pipe volume from the exhaust port to the turbine), the pressure, the delay factor caused by the engine speed, and the like.

  In the motor model M14, the assist power Le is calculated. The power Ltc obtained by adding the turbine power Lt calculated by the turbine model M11 and the assist power Le calculated by the motor model M14 is input to the next shaft model M12.

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

式（２）で求めたコンプレッサ動力ＬcがコンプレッサモデルＭ１３の入力とされる。

The compressor power Lc obtained by Expression (2) is used as an input to the compressor model M13.

  In the compressor model M13, supercharging energy is calculated from the compressor power Lc and the compressor efficiency ηc (formula (3)). Further, the equation (4) is obtained by modifying the equation (3), and the calculated value of the supercharging energy and the intake air parameters (intake air amount Ga, compressor upstream pressure (compressor inlet pressure) Pc_in, intake air temperature Tc_in) are used. Then, the compressor downstream pressure (compressor outlet pressure) Pc_out 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 detected from the detection signal of the air flow meter 41, the compressor upstream pressure Pc_in is detected from the detection signal of the atmospheric pressure sensor 44, and the intake air temperature Tc_in is determined from the detection signal of the intake air temperature sensor (for example, a temperature sensor attached to the air flow meter). Calculated.

なお、エンジン１０の吸気パラメータである空気量や圧力は、吸気管モデルＭ１７において、吸気管１１の体積（コンプレッサからスロットルまでの吸気管体積）や圧力等に起因する輸送遅れ等を考慮した値として算出されるようになっている。

Note that the air amount and pressure, which are the intake parameters of the engine 10, are values that take into account the transport delay caused by the volume of the intake pipe 11 (the intake pipe volume from the compressor to the throttle), the pressure, etc. in the intake pipe model M17. It is calculated.

  The efficiencies used in the above equations (1) to (3) can be 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. The power conversion efficiency ηt (see equation (2)) of the power Ltc → the compressor power Lc is calculated from the energy actually required for supercharging and the power Ltc at that time when the model is identified after obtaining each adiabatic efficiency. / Ltc is determined and determined. By using this inverse model method, it is possible to construct a model without knowing the actual turbocharger conversion efficiency (mechanical efficiency, etc.), and to reproduce the steady state value of the actual machine.

  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、コンプレッサ上流圧力Ｐc＿in、コンプレッサ下流圧Ｐc＿out、吸気温Ｔc＿inが既知であれば、式（６）からコンプレッサ下流温Ｔc＿outが算出できる。

Equation (5) can be transformed into the following equation (6). If compressor efficiency ηc, compressor upstream pressure Pc_in, compressor downstream pressure Pc_out, and intake air temperature Tc_in are known, compressor downstream temperature Tc_out can be obtained from equation (6). Can be calculated.

以上の流れにより、コンプレッサ下流圧Ｐc＿out及びコンプレッサ下流温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Ｍ１５の入力とされる。

From the above flow, the compressor downstream pressure Pc_out and the compressor downstream temperature Tc_out are calculated, and these Pc_out and Tc_out are input to the next intercooler model M15.

  The intercooler model M15 includes a pressure loss model portion that calculates a pressure loss in the intercooler 37 and a cooling effect model portion that calculates a cooling effect (temperature effect). By using these models, the supercharging pressure Pth (throttle upstream pressure) and supercharging temperature Tth (throttle upstream temperature) at the intercooler 37 outlet are calculated from the compressor downstream pressure Pc_out and the compressor downstream temperature Tc_out at the intercooler 37 inlet. To do. The pressure loss and the cooling effect in the intercooler 37 include not only the pressure at the inlet of the intercooler 37 (compressor downstream pressure Pc_out) and temperature (compressor downstream temperature Tc_out), but also the outside air temperature Ta and the wind speed passing through the intercooler 37 (that is, the vehicle speed). It changes as a parameter. Therefore, the intercooler model M15 calculates the pressure loss and the cooling effect based on these parameters.

  The target turbine power calculation unit 81 and the actual turbine power calculation unit 82 in the assist control unit 80 of FIG. 2 are constructed based on the electric turbo model M10, and an outline thereof is shown as a control block diagram in FIG. Here, the target turbine power calculation unit 81 calculates the target turbine power Lt_t by inverse calculation (inverse model) of the electric turbo model M10, and the actual turbine power calculation unit 82 performs forward calculation (forward model) of the electric turbo model M10. ) To calculate the actual turbine power Lt_r. The target turbine power Lt_t corresponds to the input of the shaft model M12 in FIG. 4 and is actually the sum of the turbine power and the assist power (that is, the target power of the turbocharger 30).

  In short, the target turbine power calculation unit 81 uses the inverse models of the shaft model M12, the compressor model M13, and the intercooler model M15 in FIG. 4, and uses the target boost pressure Pth_t (target throttle upstream pressure) and the target air amount Ga_t. The target turbine power Lt_t is calculated using as the main calculation parameters. In this case, in detail, in the intercooler inverse model, the target supercharging temperature Tth_t is calculated based on the target supercharging pressure Pth_t using a map based on actual machine data. Then, by constructing an inverse calculation formula using inverse models of the pressure loss model part and the cooling effect model part of the intercooler model M15, the target boost pressure Pth_t (target throttle upstream pressure), the target boost temperature Tth_t (target throttle upstream) Temperature), other target air amount Ga_t, outside air temperature Ta (compressor upstream temperature), and atmospheric pressure Pa (compressor upstream pressure), a target compressor downstream pressure Pc_out_t is calculated.

  Next, in the inverse model of the compressor, the following formula (7) is used to calculate the target supercharging energy Wc_t from the target compressor downstream pressure Pc_out_t, the target air amount Ga_t, the outside air temperature Ta, and the atmospheric pressure Pa. Here, ca is the specific heat of air, and κa is the specific heat ratio of air.

更に、目標過給エネルギＷc＿tをパラメータとして規定した効率マップからコンプレッサ効率ηc＿tを算出すると共に、次の式（８）により目標コンプレッサ動力Ｌc＿tを算出する。

Further, the compressor efficiency ηc_t is calculated from the efficiency map that defines the target supercharging energy Wc_t as a parameter, and the target compressor power Lc_t is calculated by the following equation (8).

また、シャフトの逆モデルでは、次の式（９）を用い、目標コンプレッサ動力Ｌc＿tを目標タービン動力Ｌt＿tに変換する。ηtは動力変換効率である。

In the inverse model of the shaft, the target compressor power Lc_t is converted into the target turbine power Lt_t using the following equation (9). ηt is power conversion efficiency.

なお、目標タービン動力算出部８１において、タービンイナーシャ逆モデル（タービンのイナーシャの１次遅れの逆モデル）を追加しても良い。このタービンイナーシャ逆モデルの追加により、目標タービン動力の算出精度向上が可能となる。

In the target turbine power calculation unit 81, a turbine inertia inverse model (an inverse model of a first-order lag of the turbine inertia) may be added. By adding this turbine inertia inverse model, the calculation accuracy of the target turbine power can be improved.

  Further, the actual turbine power calculation unit 82 calculates the actual turbine power Lt_r due to the exhaust through the exhaust pipe model and the turbine model (forward model) in the same manner as the calculation order of the turbo model described above. That is, from the exhaust parameters (exhaust flow rate mg, turbine upstream pressure Ptb_in, turbine downstream pressure Ptb_out, turbine upstream temperature Ttb_in, turbine adiabatic efficiency ηg) calculated by the exhaust pipe model, the above equation (1) is used. Turbine power Lt_r is calculated.

  The power difference calculation unit 83 calculates a power difference between the target turbine power Lt_t calculated as described above and the actual turbine power Lt_r (power difference = Lt_t−Lt_r), and calculates the required assist power Wa from the power difference. An upper limit guard or the like is appropriately applied to the required assist power Wa, and then an assist power signal (motor command value) is output to the motor ECU 60.

  Now, in the present embodiment, in the target torque calculation unit 71 of the torque base control unit 70 shown in FIG. 2, the driver does not feel a lack of torque due to the power assist performed by the motor 34. The target torque is calculated as follows.

  6 and 7 are diagrams for explaining a problem caused by the power assist performed by the motor 34 and a solution to the problem. FIG. 6 shows a torque curve when the power assist by the motor 34 is not performed with a dashed line, and a torque curve when the power assist is performed to the maximum with a broken line. The torque curve when the power assist in the present embodiment is performed is shown by a solid line. FIG. 7 shows the relationship between engine speed and assist power.

  As shown in FIG. 6, when the power assist by the motor 34 is not performed, the output torque of the engine 10 is relatively small in the low rotation range (one-dot chain line). This is because in the low speed range, the displacement is small and the turbocharging effect of the turbocharger 30 is small. Therefore, if power assist by the motor 34 is performed to the maximum in order to increase the supercharging effect in the low rotation range, the turbocharger 30 is supercharged, and a relatively large output torque can be obtained even in the low rotation range ( Dashed line).

  However, the following problems arise. That is, as shown in FIG. 7, as the engine rotation speed increases, the power assist by the motor 34 shifts from the valid state to the invalid state, and at this time, the assist power decreases according to the engine rotation speed. For this reason, a decrease in output torque occurs with an increase in engine rotation speed during acceleration, and a torque trough is formed (portion surrounded by a dotted line X in FIG. 6). The driver feels a lack of torque due to the torque valley.

  Therefore, in this embodiment, in order to avoid the formation of a torque valley, the target torque is calculated so that the output torque obtained during power assist becomes smaller than the bottom value of the torque valley as shown by the solid line. To do. Specifically, a torque map in which the target torque is limited as described above is defined in advance, and torque base control is performed according to the target torque calculated using the defined torque map.

  Next, the flow of processing for calculating the target throttle opening and assist power by the engine ECU 50 will be described based on the flowcharts of FIGS. FIG. 8 is a flowchart showing the base routine, and this routine is executed by the engine ECU 50 every 4 msec, for example. Then, in the base routine of FIG. 8, the subroutines of FIGS. 9 to 14 are appropriately executed. Note that the processing flow described below basically conforms to the control block diagram of FIG. 2, and a part of the overlapping description is simplified.

  As shown in FIG. 8, the base routine includes a torque base control routine (step S100) and an assist power calculation routine (step S200). FIG. 9 shows details of the torque base control routine, and FIG. The details of the calculation routine are shown.

  In the torque base control routine shown in FIG. 9, first, the detected values of the engine speed and the accelerator opening are read (step S110). Subsequently, a target torque is calculated based on the detected values of the accelerator opening and the engine speed (step S120). Here, the target torque is calculated using a torque map defining the torque characteristics as shown by the solid line in FIG. That is, the target torque in the low rotation range is reduced by a predetermined amount so that a torque valley does not occur. Thereafter, a target throttle opening is calculated using a subroutine of FIG. 10 described later (step S130).

  In the target throttle opening calculation routine shown in FIG. 10, the target air amount is calculated based on the target torque and the engine speed (step S131). Next, the target intake pressure (target throttle downstream pressure) is calculated based on the target air amount and the engine speed, and the target supercharging pressure (target throttle upstream pressure) is calculated (steps S132 and S133). Then, the target throttle opening is calculated based on the target air amount, the target intake pressure, the target boost pressure, the actual boost pressure, and the throttle passage intake air temperature (step S134).

  In the assist power calculation routine shown in FIG. 11, first, a target turbine power is calculated based on the inverse model of the turbo model using a subroutine shown in FIG. 12 (step S210). Using the subroutine, the actual turbine power is calculated based on the forward model of the turbo model (step S220). Further, the power difference is calculated by subtracting the actual turbine power from the target turbine power (step S230). Then, using a subroutine of FIG. 14 described later, it is determined whether or not the power assist can be performed (step S240).

  Here, in the target turbine power calculation subroutine shown in FIG. 12, the target supercharging pressure and the target air amount are read (step S211), and then, for example, the supercharging pressure-opening temperature map based on actual data is represented. A target supercharging temperature is calculated based on the used target supercharging pressure (step S212). Thereafter, using the inverse model of the intercooler, the target compressor downstream pressure is calculated in consideration of the pressure loss and the cooling effect in the intercooler (steps S213 and S214). Further, the target supercharging energy is calculated using an inverse model of the compressor, and the compressor efficiency is calculated from an efficiency map that defines the target supercharging energy Wc_t as a parameter, for example (steps S215 and S216). Then, the target compressor power is calculated from the target supercharging energy and the compressor efficiency (step S217), and further, the target turbine power is calculated using the inverse model of the shaft (step S218).

  Next, the actual turbine power calculation subroutine shown in FIG. 13 includes an exhaust pipe model portion and a turbine model portion. In the exhaust pipe model portion, the air flow rate is measured by the air flow meter 41 and reflected as the exhaust flow rate in the turbine. The exhaust flow rate is calculated in consideration of the delay until the exhaust gas is discharged (step S221), and the exhaust characteristics (pressure and temperature upstream and downstream of the turbine) are calculated based on the exhaust flow rate (step S222). The turbine model unit calculates the turbine adiabatic efficiency ηg (step S223), and calculates the actual turbine power based on the exhaust parameters such as the exhaust flow rate, the exhaust pressure, the exhaust temperature, and the turbine adiabatic efficiency ηg (step S224). ).

  Next, in the assist determination routine shown in FIG. 14, the assist power Wa is calculated based on the power difference calculated in step S230 of FIG. 11 (step S241). At this time, the upper limit guard based on the motor characteristics and the motor temperature is appropriately applied to calculate the assist power Wa. Thereafter, it is determined whether or not the assist power Wa is greater than a predetermined value Wa_th (step S242). If Wa> Wa_th, the assist permission flag Fa is set to 1, and if Wa ≦ Wa_th, the assist permission flag Fa is set to 0. Is set (steps S243 and S244). Thus, power assist by the motor 34 is executed when Wa> Wa_th (assist permission flag Fa = 1), and power assist by the motor 34 is performed when Wa ≦ Wa_th (assist permission flag Fa = 0). Stopped.

  FIG. 15 is a time chart showing various behaviors during assist control in the present embodiment. In FIG. 15, as a comparison target, the control when the power assist by the motor 34 is not performed and when the power assist is performed to the maximum are also shown.

  When the accelerator opening is changed and acceleration is started as shown in (a), the target torque is increased according to the acceleration request as shown in (c). Here, the target torque is calculated by being limited by a predetermined torque when power assist by the motor 34 is performed.

  As a result, as the engine speed increases as shown in (b), the output torque increases as shown in (c). Specifically, first, the power assist by the motor 34 is performed, so that the output torque increases rapidly and becomes larger than when the power assist is not performed. On the other hand, the output torque does not become too large in the low rotation range as in the case where the same power assist is performed to the maximum, and no torque valley is formed during the acceleration. Therefore, the driver does not feel a lack of torque during acceleration.

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

  When the power assist by the motor 34 is performed during acceleration, the output torque of the engine 10 is limited. As a result, a decrease in the output torque when the engine speed increases and the assist power decreases is reduced, and a torque trough is suppressed. Therefore, it is avoided that the driver feels a lack of torque, and as a result, a good driving feeling is ensured.

  In the present embodiment, the target torque is calculated based on the accelerator operation amount as the driver's request and the engine speed, and the torque base control is performed that calculates the target throttle opening based on the target torque. . In calculating the target torque in the torque base control, the target torque is limited when the power assist is performed. Thereby, since the output torque is limited according to the limited target torque, a trough in the torque is suppressed. In particular, since the torque map is specified in advance by conformance and the target torque is calculated using the specified torque map, torque troughs are reliably suppressed. Further, the desired driving feeling can be easily obtained by using the torque map.

(Second Embodiment)
In the first embodiment, it is assumed that a target torque according to a driver's request is calculated based on torque-based control, and power assist is performed by the power assist device based on the target torque. In such a configuration, a torque trough is prevented from being formed by limiting the target torque at the time of power assist. However, the present invention does not necessarily require torque-based control. An output capable of adjusting the output torque of the internal combustion engine in a configuration in which the target power of the turbocharger is calculated based on the operating state of the internal combustion engine and power assist is performed by the power assist device according to the target power and the actual power By operating the torque control means, it is possible to suppress the climax of torque during power assist and suppress the torque trough. Therefore, in the present embodiment, for the power assist device as the output torque control means, the output torque is limited by adjusting the assist power. Details will be described below. Note that the configuration of the engine control system shown in FIG. 1 in the first embodiment is used.

  FIG. 16 is a diagram showing the relationship between the engine rotation speed and the assist power by the motor 34. In FIG. 16, assist power obtained when the motor 34 is driven to the maximum is indicated by a broken line, and how to apply assist power in the present embodiment is indicated by a solid line. That is, the assist power by the motor 34 can be maximized up to a predetermined rotation range, but gradually decreases as the engine speed further increases (broken line). As a result, the output torque is reduced, and a torque valley is formed. Therefore, in the present embodiment, as shown by the solid line, the torque trough is suppressed by limiting the assist power in the low rotation range.

  FIG. 17 is a time chart showing various behaviors during assist control in the present embodiment. In FIG. 17, as a comparison target, conventional control in the case where power assist by the motor 34 is not performed and in the case where the power assist is performed to the maximum is also shown.

  When the accelerator opening is changed and acceleration is started as shown in (a), the output torque is increased as shown in (c) as the engine speed is increased in (b). Here, power assist by the motor 34 is performed according to assist power as shown in FIG. In other words, the assist power is reduced in the low rotation range, and is smaller than when power assist is performed to the maximum extent. Therefore, as shown in (c), the output torque does not rise as in the case where the power assist is performed to the maximum, and no torque trough is formed.

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

  By reducing the assist power by the motor 34, the output torque of the engine 10 is limited. Thereby, since the rise of the output torque in the low rotation range is suppressed, the torque valley is suppressed. Therefore, it is possible to secure a good driving feeling that does not cause the driver to feel a lack of torque.

  In addition, this invention is not limited to each embodiment demonstrated above, You may implement as follows.

  In the first embodiment, the target torque is calculated using the torque map defined in advance. However, the present invention is not limited to this. A minimum value of the output torque generated by a decrease in power that can be assisted by the motor 34 as the engine speed increases during acceleration is stored, and the minimum value of the stored output torque is used as an upper limit guard value. It is good also as a structure which performs a guard process. Even in such a configuration, the formation of a torque valley is avoided, so that a good driving feeling can be ensured. Similarly, in the second embodiment, the output torque limiting means may be operated so that the output torque does not exceed the upper guard value.

  In the second embodiment, the assist power by the motor 34 is reduced in order to reduce the increase in output torque in the low rotation range, but this is not limitative. Various output torque control means may be adjusted as in the following (1) to (6).

  (1) The output torque of the engine 10 is reduced by adjusting the throttle opening. That is, since the intake air amount is adjusted by adjusting the throttle opening, the output torque of the engine 10 can be suppressed by closing the throttle opening.

  FIG. 18 shows various behaviors when the throttle opening is adjusted. In FIG. 18, when the accelerator opening is changed and acceleration is started as shown in (a), the output torque is increased as shown in (c) as the engine rotation speed is increased (b). Here, as shown in (d), the throttle opening is largely closed immediately after the start of acceleration in order to increase the intake air amount, and then temporarily closed (the portion surrounded by the dotted line Y). As a result, the torque trough is suppressed without causing an increase in the output torque in the low rotation range.

  (2) The output torque of the engine 10 is reduced by adjusting the ignition timing. That is, the output torque of the engine 10 can be suppressed by correcting the ignition timing to the retard side.

  FIG. 19 shows various behaviors when the ignition timing is adjusted. In FIG. 19, when the accelerator opening is changed and acceleration is started as shown in (a), the output torque is increased as shown in (c) as the engine rotation speed is increased (b). Here, as shown in (d), the ignition timing is corrected to the advance side to increase the output torque immediately after the start of acceleration, and then temporarily corrected to the retard side (enclosed by the dotted line Z). Part). As a result, torque troughs are suppressed without causing torque to rise.

  (3) When applied to a diesel engine instead of a gasoline engine as an internal combustion engine, the output torque of the internal combustion engine is reduced by adjusting the fuel supply amount. In a diesel engine, since the fuel supply amount corresponds to the output torque, the output torque of the internal combustion engine can be suppressed by correcting the decrease in the fuel supply amount. Therefore, as in the above (1) and (2), by adjusting the fuel supply amount after the start of acceleration, the torque valley is suppressed without causing the output torque to rise in the low rotation range.

  (4) In an internal combustion engine having an electronically controlled wastegate valve (WGV) that adjusts the exhaust power of the supercharger, the output torque of the internal combustion engine is reduced by adjusting the opening of the wastegate valve. Since the actual power of the supercharger is reduced by opening the opening of the wastegate valve, the output torque of the internal combustion engine can be suppressed. Therefore, as described in the above (1) and (2), by adjusting the opening degree of the waste gate valve after the start of acceleration, the torque trough is suppressed without causing the output torque to rise in the low rotation range.

  (5) In an internal combustion engine equipped with a variable nozzle turbo (VNT) capable of adjusting the supercharging state by adjusting the blade angle of the turbine wheel, the internal combustion engine is adjusted by adjusting each blade of the turbine wheel. Reduce the output torque of the engine. That is, since the supercharging state changes by adjusting the blade angle of the turbine wheel, the output torque of the internal combustion engine can be suppressed. Therefore, as in the above (1) and (2), by adjusting the blade angle of the turbine wheel after the start of acceleration, the torque trough is suppressed without causing the output torque to rise in the low rotation range.

  (6) In an internal combustion engine equipped with a variable valve timing mechanism (VVT) that varies the opening / closing timing of the intake valve, the output torque of the internal combustion engine is reduced by adjusting the closing timing of the intake valve. That is, by correcting the closing timing of the intake valve to the retarded side with respect to the bottom dead center, the charging air is blown back and the charging efficiency is lowered, so that the output torque of the internal combustion engine can be suppressed. Therefore, as described in the above (1) and (2), by adjusting the opening degree of the intake valve closing timing after the start of acceleration, the torque trough is suppressed without causing the output torque to rise in the low rotation range. The

  The operation method of the output torque control means (1) to (6) described in detail above is preferably as follows. That is, the output torque control means prevents the output torque from exceeding the upper limit value by setting the minimum value of the output torque caused by the decrease in power that can be assisted by the motor 34 as the engine speed increases during acceleration. It is good to operate. This avoids the generation of torque valleys. Alternatively, it is preferable to operate the output torque control means so that the maximum value of the output torque generated when the power that can be assisted by the motor 34 decreases as the engine speed increases during acceleration decreases. Even in such a configuration, a decrease in the output torque is reduced, and a torque trough is suppressed. As a result, it is possible to obtain a good driving feeling in which the driver does not feel a lack of torque.

  In each of the above embodiments, the power assist device is configured to attach the motor 34 to the shaft 33 of the turbocharger 30 and directly assist the power of the turbocharger 30, but is not limited thereto. In the intake pipe 11, an auxiliary compressor having a motor as a power source may be provided upstream or downstream of the turbocharger 30, and the power of the turbocharger 30 may be indirectly assisted by the auxiliary compressor. However, in the first embodiment, in the case of such a configuration, as the engine control block shown in FIG. 2, as an assist control unit, an auxiliary compressor according to the difference between the target turbine power of the turbocharger 30 and the actual turbine power It is necessary to use a control model that adjusts the output supercharging pressure and to change the assist power to be calculated using the control model.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a control block diagram for demonstrating the function of engine ECU. It is a time chart which shows the outline | summary of the assist control of an electric turbocharger. It is a control block diagram which shows an electric turbo model. It is a control block diagram which shows the detail of the target turbine power calculation part in an assist control part, and an actual turbine power calculation part. It is a figure for demonstrating the setting method of a target torque. It is a figure which shows the relationship between an engine speed and assist power. It is a flowchart which shows the base routine by engine ECU. It is a flowchart which shows a torque base control routine. It is a flowchart which shows the calculation routine of target throttle opening. It is a flowchart which shows the calculation routine of assist power. It is a flowchart which shows the calculation routine of target turbine power. It is a flowchart which shows the calculation routine of real turbine power. It is a flowchart which shows an assist determination routine. It is a time chart which shows the various behavior at the time of assist control in this Embodiment. It is a figure which shows the relationship between an engine speed and assist power. It is a time chart which shows various behaviors at the time of assist control in a 2nd embodiment. It is a time chart which shows the various behavior in the case of reducing output torque by throttle opening control. It is a time chart which shows the various behavior in the case of reducing output torque by ignition control.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 30 ... Turbocharger, 34 ... Motor as power assist apparatus, 50 ... Engine ECU.

Claims (8)

Applied to an internal combustion engine having a supercharger that supercharges intake air by exhaust power and a power assist device that is operated by power other than exhaust power and assists the power of the supercharger directly or indirectly,
In the control device that performs power assist control by the power assist device in a predetermined low rotation range,
A torque limiting means for limiting the output torque of the internal combustion engine for the power assist control during acceleration ;
The minimum value of the output torque that can be generated during the transition from the assistable region to the non-assistable region is obtained in advance,
The control device for an internal combustion engine with a supercharger , wherein the torque limiting means limits the output torque based on the minimum value . The control device for an internal combustion engine with a supercharger according to claim 1, wherein the torque limiting means limits the output torque so as not to exceed the minimum value . Applied to an internal combustion engine having a supercharger that supercharges intake air by exhaust power and a power assist device that is operated by power other than exhaust power and assists the power of the supercharger directly or indirectly,
In the control device that performs power assist control by the power assist device in a predetermined low rotation range,
A torque limiting means for limiting the output torque of the internal combustion engine for the power assist control during acceleration;
The control device for an internal combustion engine with a supercharger , wherein the torque limiting means limits the output torque so that a maximum value of the output torque generated by the power assist control is reduced by a predetermined amount . Applied to an internal combustion engine having a supercharger that supercharges intake air by exhaust power and a power assist device that is operated by power other than exhaust power and assists the power of the supercharger directly or indirectly,
In the control device that performs power assist control by the power assist device in a predetermined low rotation range,
A torque limiting means for limiting the output torque of the internal combustion engine for the power assist control during acceleration;
The control of the internal combustion engine with a supercharger , wherein the torque limiting means limits the output torque on the basis of the output torque at an engine rotation speed at which power assist by the power assist device is impossible. apparatus. In the torque control for adjusting the output torque in accordance with the target torque corresponding to the driver's request, the target power of the supercharger is calculated according to the target torque and the actual power of the supercharger is calculated. In the control device that performs the power assist control based on power and the actual power,
5. The control device for an internal combustion engine with a supercharger according to claim 1, wherein the torque limiting means calculates the target torque while limiting the target torque . 6. The turbocharger according to claim 5, wherein the torque limiting means predefines a torque map that restricts the target torque, and calculates the target torque using the prescribed torque map. Control device for internal combustion engine. 5. The internal combustion engine with a supercharger according to claim 1, wherein the torque limiting means limits the output torque by operating an output control means capable of adjusting the output torque. 6. Control device. The control device for an internal combustion engine with a supercharger according to claim 7, wherein the torque limiting means reduces the power assisted by the power assist device as an operation of the output control means .

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