Patent Publication Number: US-2018038273-A1

Title: Control device for internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of Japanese Patent Application No. 2016-154643, filed on Aug. 5, 2016, which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a control device for an internal combustion engine that includes a turbocharger and an electrically driven compressor. 
     Background Art 
     An internal combustion engine that includes a turbocharger (an exhaust turbocharger) and an electrically driven compressor (an electrically driven supercharger) is known. An example of this kind of internal combustion engine is disclosed in JP 2008-274833A, for example. 
     In the internal combustion engine disclosed in JP 2008-274833A, an intake channel is connected to an internal combustion engine main body (an engine main body). An exhaust channel is connected to the internal combustion engine main body. This internal combustion engine is provided with a turbocharger that includes a compressor impeller (a compressor wheel) that is installed in the intake channel and a turbine impeller (a turbine wheel) that is installed in the exhaust channel. The compressor impeller and the turbine impeller are coupled to each other by a rotation shaft (a shaft). In a part of the intake channel on the downstream side of the compressor impeller, an electrically driven compressor is installed. 
     Furthermore, the internal combustion engine disclosed in JP 2008-274833A is provided with a first pressure sensor (a boost pressure sensor) and a second pressure sensor (an intake air pressure sensor). The first pressure sensor detects a boost pressure at a part of the intake channel between the compressor impeller and the electrically driven compressor. The second pressure sensor detects a boost pressure at a part of the intake channel on the downstream side of the electrically driven compressor. 
     JP 2008-274833A is a patent document which may be related to the present disclosure. 
     SUMMARY 
     In the internal combustion engine disclosed in JP 2008-274833A, the boost pressure detected by the first pressure sensor is not used for a control to conform this boost pressure to its target value but is used for an intake air bypass control. That is to say, in the internal combustion engine disclosed in JP 2008-274833A, a target value of the boost pressure detected by the first pressure sensor is not calculated, and, therefore, a control to rapidly conform this boost pressure to the target value is also not performed. Accordingly, in the internal combustion engine disclosed in JP 2008-274833A, a boost pressure at a part of the intake channel between the compressor impeller and the electrically driven compressor cannot be conformed to a target value thereof. 
     Furthermore, in the internal combustion engine disclosed in JP 2008-274833A, the electrically driven compressor is not controlled on the basis of the difference between the boost pressure detected by the second boost pressure and the target value thereof, but is controlled on the basis of whether it is during the time of acceleration or not. That is, in the internal combustion engine disclosed in JP 2008-274833A, the target value of the boost pressure detected by the second boost pressure is not calculated, and therefore, a control to rapidly conform this boost pressure to its target value is also not performed. Thus, in the internal combustion engine disclosed in JP 2008-274833A, the boost pressure at a part of the intake on the downstream side of the electrically driven compressor cannot be conformed to the target value thereof. 
     As described above, in the internal combustion engine disclosed in JP 2008-274833A, the electrically driven compressor is controlled without the setting of each of the target value of the boost pressure detected by the first pressure and the target value of the boost pressure detected by the second pressure. Thus, in order to achieve an acceleration according to an acceleration request from a driver, it is required to at least a process to adapt, in accordance with the degree of the acceleration, the boost pressure assisted by the electrically driven compressor and a process to detect the acceleration. As a result, there is a concern that the number of processes required to this kind of adaption may increase. 
     In view of the problem described above, an object of the present disclosure is to provide a control device for an internal combustion engine that can rapidly conform the boost pressure at a part of an intake channel between a compressor of a turbocharger and an electrically driven compressor and the boost pressure at a part of the intake channel on the downstream side of the electrically driven compressor to the respective target values, and thereby can achieve an acceleration according to an acceleration request from a driver in a simple manner. 
     A control device for an internal combustion engine according to the present disclosure is configured to control an internal combustion engine that includes: an internal combustion engine main body; an intake channel connected to the internal combustion engine main body; an exhaust channel connected to the internal combustion engine main body; a turbocharger that includes a compressor arranged in the intake channel and a turbine arranged in the exhaust channel; an electrically driven compressor arranged at a part of the intake channel on a downstream side of the compressor of the turbocharger; a first pressure sensor configured to detect a first boost pressure which is boost pressure at a part of the intake channel between the compressor of the turbocharger and the electrically driven compressor; a second pressure sensor configured to detect a second boost pressure which is boost pressure at a part of the intake channel on a downstream side of the electrically driven compressor; and an exhaust gas flow rate adjusting device configured to adjust a flow rate of exhaust gas supplied to the turbine. The control device is programmed to control the exhaust gas flow rate adjusting device based on a difference between a target value of the first boost pressure and a detection value of the first boost pressure with the first pressure sensor. The control device is programmed to control the electrically driven compressor based on a difference between a target value of the second boost pressure and a detection value of the second boost pressure with the second pressure sensor. The control device is programmed to calculate one of the target value of the first boost pressure and the target value of the second boost pressure based on an engine speed, an engine torque, and a first relationship between the engine speed, the engine torque and the one of the target value of the first boost pressure and the target value of the second boost pressure. The control device is programmed to calculate the other of the target value of the first boost pressure and the target value of the second boost pressure based on an amount of air taken into the internal combustion engine main body, the one of the target value of the first boost pressure and the target value of the second boost pressure and a second relationship between the air amount, the target value of the first boost pressure and the target value of the second boost pressure. 
     In the control device for an internal combustion engine according to the present disclosure, the exhaust gas flow rate adjusting device may be a variable nozzle device arranged in the turbine at an inlet of the exhaust gas. 
     In the control device for an internal combustion engine according to the present disclosure, the exhaust gas flow rate adjusting device may be a waste gate channel configured to bypass the turbine and a waste gate valve arranged in the waste gate channel. 
     Namely, in the control device for an internal combustion engine according to the present disclosure, the exhaust gas flow rate adjusting device for adjusting the flow rate of the exhaust gas supplied to the turbine of the turbocharger arranged in the exhaust channel is controlled on the basis of the difference between the target value of the first boost pressure that is boost pressure at the part of the intake channel between the compressor of the turbocharger and the electrically driven compressor arranged on the downstream side of the compressor, and the detection value of the first boost pressure with the first pressure sensor. 
     Thus, with the control device for an internal combustion engine according to the present disclosure, the target value of the first boost pressure and the detection value of the first boost pressure can be rapidly conformed to each other as compared with the internal combustion engine disclosed in JP 2008-274833A in which the control of the exhaust gas flow rate adjusting device based on the difference between the target value of the first boost pressure and the detection value of the first boost pressure is not performed. 
     Also, in the control device for an internal combustion engine according to the present disclosure, the electrically driven compressor is controlled on the basis of the difference between the target value of the second boost pressure that is boost pressure at the part of the intake channel on the downstream side of the electrically driven compressor and the detection value of the second boost pressure with the second pressure sensor. 
     Thus, with the control device for an internal combustion engine according to the present disclosure, the target value of the second boost pressure and the detection value of the second boost pressure can be rapidly conformed to each other as compared with the internal combustion engine disclosed in JP 2008-274833A in which the control of the electrically driven compressor based on the difference between the target value of the second boost pressure and the detection value of the second pressure is not performed. 
     Moreover, in the control device for an internal combustion engine according to the present disclosure, one of the target value of the first boost pressure and the target value of the second boost pressure is set. In more detail, in the control device for an internal combustion engine according to the present disclosure, the one of the target value of the first boost pressure and the target value of the second boost pressure is calculated on the basis of the engine speed, the engine torque and the first relationship that is a relationship between the engine speed, the engine torque and the one of the target value of the first boost pressure and the target value of the second boost pressure. 
     Furthermore, in the control device for an internal combustion engine according to the present disclosure, the other of the target value of the first boost pressure and the target value of the second boost pressure is set. In more detail, in the control device for an internal combustion engine according to the present disclosure, the other of the target value of the first boost pressure and the target value of the second boost pressure is calculated on the basis of the air amount taken into the internal combustion engine main body, the one of the target value of the first boost pressure and the target value of the second boost pressure and the second relationship that is a relationship between the air amount, the target value of the first boost pressure and the target value of the second boost pressure. 
     Thus, with the control device for an internal combustion engine according to the present disclosure, an acceleration according to an acceleration request from the driver can be achieved in a simple manner as compared with the internal combustion engine disclosed in JP 2008-274833A in which the electrically driven compressor is controlled without the setting of each of the target value of the first boost pressure and the target value of the second boost pressure. 
     In the control device for an internal combustion engine according to the present disclosure, the second relationship may be set such that, when the air amount is zero, the target value of the first boost pressure and the target value of the second boost pressure become equal to each other, and such that, when the air amount is greater than zero, the target value of the first boost pressure becomes greater than the target value of the second boost pressure. 
     Namely, in this control device for an internal combustion engine, a pressure loss is taken into consideration. This pressure loss corresponds to the difference in pressure between the part of the intake channel at which the first pressure sensor for detecting the first boost pressure is provided and the part of the intake channel at which the second pressure sensor for detecting the second boost pressure that is arranged on the downstream side of the first pressure sensor is provided. In addition, in this control device, the second relationship that is a relationship between the air amount, the target value of the first boost pressure and the target value of the second boost pressure is set such that, when the air amount that is the amount of the intake air taken into the internal combustion engine main body is zero, the target value of the first boost pressure and the target value of the second boost pressure become equal to each other, and such that, when the air amount is greater than zero, the target value of the first boost pressure becomes greater than the target value of the second boost pressure. 
     As a result, in this control device for an internal combustion engine, the target value of the first boost pressure and the target value of the second boost pressure can be appropriately set as compared with an example in which the pressure loss between the part of the intake channel at which the first pressure sensor is provided and the part thereof at which the second pressure sensor is provided is not taken into consideration. 
     In the control device for an internal combustion engine according to the present disclosure, the second relationship may he set such that, when the air amount is greater, a difference between the target value of the first boost pressure and the target value of the second boost pressure becomes greater. 
     Namely, in this control device for an internal combustion engine, it is taken into consideration that the difference between the actual boost pressure at a location at which the first pressure sensor for detecting the first boost pressure is provided and the actual boost pressure at a location at which the second pressure sensor for detecting the second boost pressure is provided becomes greater when the air amount that is the amount of the intake air taken into the internal combustion engine main body is greater. In addition, in this control device, the second relationship that is a relationship between the air amount, the target value of the first boost pressure and the target value of the second boost pressure is set such that the difference between the target value of the first boost pressure and the target value of the second boost pressure becomes greater when the air amount is greater. 
     As a result, in this control device for an internal combustion engine, the target value of the first boost pressure and the target value of the second boost pressure can be appropriately set as compared with an example in which it is not taken into consideration that the difference between the actual boost pressure at the location at which the first pressure sensor is provided and the actual boost pressure at the location at which the second pressure sensor is provided becomes greater when the air amount that is the amount of the intake air taken into the internal combustion engine main body is greater. 
     According to the control device for an internal combustion engine of the present disclosure, the boost pressure at a part of an intake channel between a compressor of a turbocharger and an electrically driven compressor and the boost pressure at a part of the intake channel on the downstream side of the electrically driven compressor can be rapidly conformed to the respective target values, and an acceleration according to an acceleration request from a driver can be thereby achieved in a simple manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing a configuration of a system in which a control device for an internal combustion engine according to a first embodiment is used; 
         FIG. 2  is a flow chart for explaining controls of a variable nozzle device and an electrically driven compressor performed by the control device for an internal combustion engine according to the first embodiment; 
         FIG. 3  is a graph showing a first relationship used for calculation of a target value P 2 trg of a second boost pressure obtained in step S 100  shown in  FIG. 2 ; 
         FIG. 4  is a graph showing a second relationship used for calculation of a target value P 1 trg of a first boost pressure in step S 103  in  FIG. 2 ; 
         FIG. 5  is a time chart for describing the first boost pressure P 1  and the second boost pressure P 2  which are changed as a result of the controls of the variable nozzle device and the electrically driven compressor performed by the control device of an internal combustion engine according to the first embodiment; and 
         FIG. 6  is a schematic diagram showing a configuration of a system in which the control device for an internal combustion engine according to a second embodiment is used. 
     
    
    
     DETAILED DESCRIPTION 
     In the following, a first embodiment concerning a control device for an internal combustion engine according to the present disclosure will be described.  FIG. 1  is a schematic diagram showing a configuration of a system in which the control device for an internal combustion engine according to the first embodiment is used. In the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, an internal combustion engine main body  1  that includes four cylinders is provided. 
     In the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, an intake channel  2  is connected to the internal combustion engine main body  1 . Also, an exhaust channel  3  is connected to the internal combustion engine main body  1 . Moreover, a turbocharger  4  that includes a compressor  4   a  arranged in the intake channel  2  and a turbine  4   b  arranged in the exhaust channel  3  is provided. A compressor impeller  4   a   1  and a turbine impeller  4   b   1  of the turbocharger  4  are coupled to each other by a rotation shaft  4   c.  Furthermore, an electrically driven compressor  6  is arranged at a part of the intake channel  2  on the downstream side of the compressor  4   a.    
     In the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, a bypass channel  7   b  configured to bypass the electrically driven compressor  6  is provided, and a bypass valve  7   a  is arranged in the bypass channel  7   b.    
     In the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, a first pressure sensor  41  configured to detect a first boost pressure which is boost pressure at a part of the intake channel  2  between the compressor  4   a  and the electrically driven compressor  6  is provided. The output signal of the first pressure sensor  41  is inputted to an electronic control unit (ECU)  50  that serves as a control device. Moreover, a second pressure sensor  42  configured to detect a second boost pressure which is boost pressure at a part of the intake channel  2  on the downstream side of the electrically driven compressor  6  is provided. The output signal of the second pressure sensor  42  is inputted to the ECU  50 . In addition, an air flow sensor  40  configured to detect an air amount taken into the internal combustion engine main body  1  is provided. The output signal of the air flow sensor  40  is inputted to the ECU  50 . 
     In the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, an exhaust gas flow rate adjusting device configured to adjust the flow rate of the exhaust gas supplied to the turbine  4  is provided. In more detail, as the exhaust gas flow rate adjusting device, a variable nozzle device  5  is provided in the turbine  4   b  at the inlet of the exhaust gas. The signal for controlling the variable nozzle device  5  is outputted from the ECU  50 . In addition, the signal for controlling the electrically driven compressor  6  and the signal for controlling the bypass valve  7   a  are outputted from the ECU  50 . 
       FIG. 2  is a flow chart for explaining controls of the variable nozzle device  5  (see  FIG. 1 ) and the electrically driven compressor  6  (see  FIG. 1 ) performed by the control device for an internal combustion engine according to the first embodiment. The processing shown in  FIG. 2  is performed during operation of the internal combustion engine. 
     When the processing shown in  FIG. 2  is started, first, in step S 100 , an air amount Ga taken into the internal combustion engine main body  1  that is detected by the air flow sensor  40  ( FIG. 1 ) is obtained by the ECU  50  (see  FIG. 1 ), for example. Also, in step S 100 , a second boost pressure P 2  that is boost pressure at a part of the intake channel  2  (see  FIG. 1 ) on the downstream side of the electrically driven compressor  6  and that is detected by the second pressure sensor  42  (see  FIG. 1 ) is obtained by the ECU  50 , for example. Moreover, in step S 100 , a target value P 2 trg of the second boost pressure is obtained by the ECU  50 , for example. 
       FIG. 3  is a graph showing a first relationship used for calculation of the target value P 2 trg of the second boost pressure obtained in step S 100  shown in  FIG. 2 . In  FIG. 3 , the vertical axis denotes an engine torque Q, and the horizontal axis denotes an engine speed NE. Each of the curves shown in  FIG. 3  represent an equal value line of the target value p 2 trg of the second boost pressure. 
     In the example shown in  FIG. 3  in which the control device for an internal combustion engine according to the first embodiment is used, the ECU  50  calculates the target value p 2 trg of the second boost pressure on the basis of the engine torque Q, the engine speed NE and the first relationship shown in  FIG. 3 . The engine torque Q is calculated by, for example, the ECU  50  on the basis of, for example, the output signal of an accelerator position sensor (not shown). The engine speed NE is calculated by, for example, the ECU  50  on the basis of, for example, a crank angle sensor (not shown). As shown in  FIG. 3 , the target value P 2 trg of the second boost pressure is higher when the engine torque Q is higher. Also, the target value P 2 trg of the second boost pressure is higher when the engine speed NE is higher. 
     Next, in step S 101  shown in  FIG. 2 , the rotational speed NC of the electrically driven compressor  6  (see  FIG. 1 ) is calculated by, for example, the ECU  50  (see  FIG. 1 ) on the basis of the target value P 2 trg of the second boost pressure obtained in step S 100 . In the example shown in  FIG. 5 , when the target value P 2 trg of the second boost pressure changes at a time point t 1  from a value P 2   a  to a value P 2   b  as shown in section (C) of  FIG. 5 , the rotational speed NC of the electrically driven compressor  6  is calculated so as to have a value shown by a curve “NC (first embodiment)” in section (D) of  FIG. 5 . 
     To be more specific, in the example shown in  FIG. 5 , the rotational speed NC of the electrically driven compressor  6  is calculated so as to be rapidly conformed to the target value P 2 trg of the second boost pressure without an overshoot of the second boost pressure P 2  as shown by a curve “P 2  (first embodiment)” in the section (C) of  FIG. 5 . 
     Next, in step S 102  shown in  FIG. 2 , the electrically driven compressor  6  is controlled by the ECU  50  so as to achieve the rotational speed NC of the electrically driven compressor  6  calculated in step S 101 . That is, in the example shown in  FIG. 5 , in step S 102 , the electrically driven compressor  6  is controlled so as to be rapidly conformed to the target value P 2 trg of the second boost pressure without an overshoot of the second boost pressure P 2  as shown by the curve “P 2  (first embodiment)” in the section (C) of  FIG. 5 . In other words, in the example shown in  FIG. 5 , in step S 102 , the electrically driven compressor  6  is controlled by the ECU  50  on the basis of the difference between the target value P 2 trg of the second boost pressure and the second boost pressure (detection value) P 2  detected by the second pressure sensor  42  (see  FIG. 1 ). In more detail, in the example shown in  FIG. 5 , if the difference between the target value P 2 trg of the second boost pressure and the second boost pressure (detection value) P 2  is zero, the rotation speed of the electrically driven compressor  6  calculated in step S 101  is zero. 
     Then, in step S 103  shown in  FIG. 2 , a target value P 1 trg of the first boost pressure is calculated by the ECU  50  (see  FIG. 1 ), for example. 
       FIG. 4  is a graph showing a second relationship used for calculation of the target value P 1 trg of the first boost pressure in step S 103  in  FIG. 2 . In  FIG. 4 , the vertical axis denotes target values of boost pressures (the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure), and the horizontal axis denotes the air amount Ga taken into the internal combustion engine main body  1  (see  FIG. 1 ). As shown in  FIG. 4 , the second relationship represents a relationship between the target value P 1 trg of the first boost pressure, the target value P 2 trg of the second boost pressure and the air amount Ga taken into the internal combustion engine main body  1 . 
     In the example shown in  FIG. 4  in which the control device for an internal combustion engine according to the first embodiment is used, a pressure loss is taken into consideration. This pressure loss corresponds to the difference in pressure between the part of the intake channel  2  (see  FIG. 1 ) at which the first pressure sensor  41  (see  FIG. 1 ) for detecting a first boost pressure P 1  is provided and the part of the intake channel  2  at which the second pressure sensor  42  for detecting the second boost pressure P 2  that is arranged on the downstream side of the first pressure sensor  41  is provided. The pressure loss may be calculated on the basis of the air amount Ga taken into the internal combustion engine main body  1  (see  FIG. 1 ) and a known arbitrary experimental equation. In more detail, the second relationship that is the relationship between the air amount Ga, the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure is set such that, when the air amount Ga is zero, the target value P 1 trg of the first boast pressure and the target value P 2 trg of the second boost pressure become equal to each other, and such that, when the air amount Ga is greater than zero, the target value P 1 trg of the first boost pressure becomes greater than the target value P 2 trg of the second boost pressure by the pressure loss. 
     As a result, in the example shown in  FIG. 4  in which the control device for an internal combustion engine according to the first embodiment is used, the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure can be appropriately set as compared with an example in which the pressure loss between the part of the intake channel  2  at which the first pressure sensor  41  is provided and the part thereof at which the second pressure sensor  42  is provided is not taken into consideration. 
     Furthermore, in the example shown in  FIG. 4  in which the control device for an internal combustion engine according to the first embodiment is used, it is taken into consideration that the difference between the actual boost pressure at a location at which the first pressure sensor  41  for detecting the first boost pressure P 1  is provided and the actual boost pressure at a location at which the second pressure sensor  42  for detecting the second boost pressure P 2  is provided becomes greater when the air amount Ga that is the amount of the intake air taken into the internal combustion engine main body  1  is greater. In more detail, the second relationship that is the relationship between the air amount Ga, the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure is set such that the difference between the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure becomes greater when the air amount Ga is greater. 
     As a result, in the example shown in  FIG. 4  in which the control device for an internal combustion engine according to the first embodiment is used, the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure can be appropriately set as compared with an example in which it is not taken into consideration that the difference between the actual boost pressure at the location at which the first pressure sensor  41  is provided and the actual boost pressure at the location at which the second pressure sensor  42  is provided becomes greater when the air amount Ga that is the amount of the intake air taken into the internal combustion engine main body  1  is greater. 
     As described above, in step S 103  in  FIG. 2 , the target value P 1 trg of the first boost pressure is calculated by, for example, the ECU  50  (see  FIG. 1 ) on the basis of the air amount Ga taken into the internal combustion engine main body  1  and the target value P 2 trg of the second boost pressure that are obtained in step S 100 , as well as the second relationship that is the relationship between the air amount Ga shown in  FIG. 4 , the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure. 
     In the example shown in  FIGS. 2, 3 and 4  in which the control device for an internal combustion engine according to the first embodiment is used, the target value P 2 trg of the second boost pressure is obtained in step S 100 , and the target value P 1 trg of the first boost pressure is calculated in step S 103  on the basis of the air amount Ga, the target value P 2 trg of the second boost pressure and the second relationship shown in  FIG. 4 . 
     Next, in step S 104  in  FIG. 2 , the opening degree of the variable nozzle device  5  (see  FIG. 1 ) that serves as the exhaust gas flow rate adjusting device for adjusting the flow rate of the exhaust gas supplied to the turbine  4   b  (see  FIG. 1 ) is calculated by, for example, the ECU  50  (see  FIG. 1 ) on the basis of the target value P 1 trg of the first boost pressure calculated in step S 103 . In the example shown in  FIG. 5 , when the target value P 1 trg of the first boost pressure changes at the time point t 1  from a value P 1   a  to a value P 1   b  as shown in section (E) of  FIG. 5 , the opening degree of the variable nozzle device  5  is calculated so as to have a value shown by a curve “First embodiment” in section (F) of  FIG. 5 . 
     To be more specific, in the example shown in  FIG. 5 , the opening degree of the variable nozzle device  5  is calculated so as to be rapidly conformed to the target valve P 1 trg of the first boost pressure without an overshoot of the first boost pressure P 1  as shown by a curve “P 1  (first embodiment)” in the section (E) of  FIG. 5 . 
     Next, in step S 105  shown in  FIG. 2 , the variable nozzle device  5  is controlled by the ECU  50  so as to achieve the opening degree of the variable nozzle device  5  calculated in step S 104 . That is, in the example shown in  FIG. 5 , in step S 105 , the variable nozzle device  5  is controlled so as to be rapidly conformed to the target value P 1 trg of the first boost pressure without an overshoot of the first boost pressure P 1  as shown by the curve “P 1  (first embodiment)” in the section (E) of  FIG. 5 . In other words, in the example shown in  FIG. 5 , in step S 105 , the variable nozzle device  5  that serves as the exhaust gas flow rate adjusting device is controlled by the ECU  50  on the basis of the difference between the target value P 1 trg of the first boost pressure and the first boost pressure (detection value) P 1  detected by the first pressure sensor  41  (see  FIG. 1 ). 
     Next, in step S 106  in  FIG. 2 , it is determined by, for example, the ECU  50  (see  FIG. 1 ) whether or not the rotational speed NC of the electrically driven compressor  6  calculated in step S 101  is higher than a threshold value TNC (see the section (D) of  FIG. 5 ). If the result of the determination in step S 106  is positive, the processing proceeds to step S 107 , and, on the other hand, if the result is negative, the processing proceeds to step S 108 . In step S 107 , the bypass valve  7   a  (see  FIG. 1 ) is closed by the ECU  50 . In step S 108 , the bypass valve  7   a  is opened by the ECU  50 . 
       FIG. 5  is a time chart for describing the first boost pressure P 1  and the second boost pressure P 2  which are changed as a result of the controls of the variable nozzle device  5  (see  FIG. 1 ) and the electrically driven compressor  6  (see  FIG. 1 ) performed by the control device of an internal combustion engine according to the first embodiment. To be more specific, section (A) of  FIG. 5  denotes the fuel injection amount, section (B) of  FIG. 5  denotes the opening degree of the bypass valve  7   a  (see  FIG. 1 ) (more specifically, whether the bypass valve  7   a  is in an open state or a closed state), and the section (C) of  FIG. 5  denotes the second boost pressure P 2 . More specifically, the section (C) of  FIG. 5  denotes the target value P 2 trg of the second boost pressure, the second boost pressure “P 2  (first embodiment)” in the example in which the control device for an internal combustion engine according to the first embodiment is used, and the second boost pressure “P 2  (comparative example)” in a comparative example. 
     The section (D) of  FIG. 5  denotes the rotational speed NC of the electrically driven compressor  6 . In more detail, the section (D) of  FIG. 5  denotes the rotational speed “NC (first embodiment)” of the electrically driven compressor  6  in the example in which the control device for an internal combustion engine according to the first embodiment is used, and the rotational speed “NC (comparative example)” of the electrically driven compressor  6  in the comparative example. The section (E) of  FIG. 5  denotes the first boost pressure P 1 . In more detail, the section (E) of  FIG. 5  denotes the target value P 1 trg of the first boost pressure, the first boost pressure “P 1  (first embodiment)” in the example in which the control device for an internal combustion engine according to the first embodiment is used, and the first boost pressure “P 1  (comparative example)” in the comparative example. 
     The section (F) of  FIG. 5  denotes the opening degree of the variable nozzle device  5  (see  FIG. 1 ). In more detail, the section (F) of  FIG. 5  denotes the opening degree of the variable nozzle device  5  (indicated by “First embodiment” in the section (F) of  FIG. 5 ) in the example in which the control device for an internal combustion engine according to the first embodiment is used, and the opening degree of the variable nozzle device  5  (indicated by “Comparative example” in the section (F) of  FIG. 5 ) in the comparative example. 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, an acceleration request from the driver is not made before the time point t 1 , but the acceleration request from the driver is made at the time point t 1 . As a result, as shown in the section (A) of  FIG. 5 , a value A 2  of the fuel injection amount required to satisfy the acceleration request is calculated at the time point t 1  by, for example, the ECU  50 . That is, at the time point t 1 , the fuel injection amount is increased in a stepwise fashion from a value A 1  to the value A 2 . 
     Also, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, at the time point t 1  at which the acceleration request is made, the engine torque Q required to satisfy the acceleration request is calculated by, for example, the ECU  50 . Moreover, the engine speed NE at the time point t 1  is calculated by, for example, the ECU  50  on the basis of, for example, the output signal of the crank angle sensor (not shown). Moreover, at the time point t 1 , the value P 2   b  (see the section (C) of  FIG. 5 ) of the target value P 2 trg of the second boost pressure is calculated by, for example, the ECU  50  on the basis of the engine torque Q, the engine speed NE and the first relationship shown in  FIG. 3 . That is, as shown in the section (C) of  FIG. 5 , at the time point t 1 , the target value P 2 trg of the second boost pressure is increased in a stepwise fashion from the value P 2   a  to the value P 2   b.    
     Furthermore, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, at the time point t 1  at which the acceleration request from the driver is made, a value Gab (see  FIG. 4 ) of the air amount Ga required to satisfy the acceleration request is calculated by, for example, the ECU  50 . In addition, at the time point t 1 , in step S 103  in  FIG. 2 , the value P 1   b  (see  FIG. 4  and the section (E) of  FIG. 5 ) of the target value P 1 trg of the first boost pressure is calculated by, for example, the ECU  50  on the basis of the value Gab of the air amount Ga, the value P 2   b  (see  FIG. 4  and the section (C) of  FIG. 5 ) of the target value P 2 trg of the second boost pressure and the second relationship shown in  FIG. 4 . That is, as shown in the section (B) of  FIG. 5 , at the time point t 1 , the target value P 1 trg of the first boost pressure is increased from the value P 1   a  to the value P 1   b  in a stepwise fashion. 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, in step S 101  in  FIG. 2 , the rotational speed NC (see the section (D) of  FIG. 5 ) of the electrically driven compressor  6  (see  FIG. 1 ) is calculated by, for example, the ECU  50  (see  FIG. 1 ) on the basis of the value P 2   b  of the target value P 2 trg of the second boost pressure obtained in step S 100  in  FIG. 2 . That is, the rotational speed NC of the electrically driven compressor  6  is calculated so as to have a value indicated by the curve “NC (first embodiment)” in the section (D) of  FIG. 5 . 
     In more detail, the rotational speed NC of the electrically driven compressor  6  is calculated so as to be rapidly conformed to the value P 2   b  of the target value P 2 trg of the second boost pressure without an overshoot of the second boost pressure P 2  as shown by the curve “P 2  (first embodiment)” in the section (C) of  FIG. 5 . 
     Furthermore, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, in step S 102  in  FIG. 2 , the electrically driven compressor  6  is controlled by the ECU  50  so as to achieve the rotational speed NC of the electrically driven compressor  6  (the value indicated by the curve “NC (first embodiment)” in the section (D) of  FIG. 5 ) calculated in step S 101  in  FIG. 2 . 
     In more detail, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, during a time period from t 1  to t 3 , since the second boost pressure P 2  (the value indicated by the curve “P 2  (first embodiment) in the section (C) of  FIG. 5 ) is smaller than the value P 2   b  of the target value P 2 trg of the second boost pressure as shown in the section (C) of  FIG. 5 , the rotational speed NC of the electrically driven compressor  6  is increased from the value NC 1  by a feedback control as shown in the section (D) of  FIG. 5 . 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, in order to reduce the overshoot of the second boost pressure P 2 , immediately before the time point t 3  at which the second boost pressure P 2  is conformed to the value P 2   b  of the target value P 2 trg of the second boost pressure as shown in the section (C) of  FIG. 5 , the increase of the rotational speed NC of the electrically driven compressor  6  is terminated and the rotational speed NC of the electrically driven compressor  6  is then decreased to the value NC 1  as shown in the section (D) of  FIG. 5 . 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, since the first boost pressure P 1  (the value indicated by the curve “P 1  (first embodiment)” in the section (B) of  FIG. 5 ) is increased as shown in the section (E) of  FIG. 5 , the second boost pressure P 2  (the value indicated by the curve “P 2  (first embodiment)” in the section (C) of  FIG. 5 ) is maintained, at or after the time point t 3 , at the value P 2   b  of the target value P 2 trg of the second boost pressure although the rotational speed NC of the electrically driven compressor  6  is decreased as shown in the section (D) of  FIG. 5 . 
     Moreover, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, in step S 104  in  FIG. 2 , the opening degree (see the section (F) of  FIG. 5 ) of the variable nozzle device  5  (see  FIG. 1 ) is calculated by, for example, the ECU  50  (see  FIG. 1 ) on the basis of the value P 1   b  (see the section (E) of  FIG. 5 ) of the target value P 1 trg of the first boost pressure calculated in step S 103  in  FIG. 2 . That is, the opening degree of the variable nozzle device  5  is calculated so as to have a value indicated by the curve “First embodiment” in the section (F) of  FIG. 5 . 
     In more detail, the opening degree of the variable nozzle device  5  is calculated so as to be rapidly conformed to the value P 1   b  of the target value P 1 trg of the first boost pressure without the overshoot of the first boost pressure P 1  as indicated by the curve “P 1  (first embodiment” in the section (E) of  FIG. 5 . 
     Moreover, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, in step S 105  in  FIG. 2 , the variable nozzle device  5  is controlled by the ECU  50  so as to achieve the opening degree of the variable nozzle device  5  (the value indicated by the curve “First embodiment” in the section (F) of  FIG. 5 ) calculated in step S 104  in  FIG. 2 . 
     In more detail, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, during a time period from t 1  to t 5 , since the first boost pressure P 1  (the value indicated by the curve “P 1  (first embodiment)” in the section (E) of  FIG. 5 ) is smaller than the value P 1   b  of the target value P 1 trg of the first boost pressure as shown in the section (B) of  FIG. 5 , the opening degree of the variable nozzle device  5  is controlled, by a feedback control, so as to be closed (that is, so as to shift to the upper side in the section (F) of  FIG. 5 ) as compared with a base opening degree (see the section (F) of  FIG. 5 ) as shown in the section (F) of  FIG. 5  in order to increase the first boost pressure P 1 . That is, the opening degree of the variable nozzle device  5  is controlled so as to fall within a range between a value F 1  (see the section (F) of  FIG. 5 ) and the base opening degree. 
     Furthermore, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, the opening degree of the variable nozzle device  5  is controlled to be the base opening degree at or after a time point t 5  at which the first boost pressure P 1  indicated by the curve “P 1  (first embodiment)” in the section (B) of  FIG. 5  is conformed to the value P 1   b  of the target value P 1 trg of the first boost pressure. 
     That is, in the example shown in  FIG. 5 , the base opening degree of the variable nozzle device  5  is set such that, if the opening degree (see the section (F) of  FIG. 5 ) of the variable nozzle device  5  is controlled to be the base opening degree (see the section (F) of  FIG. 5 ), the first boost pressure P 1  is conformed to the value P 1   b  (see the section (E) of  FIG. 5 ) of the target value P 1 trg of the first boost pressure. In other words, if the opening degree of the variable nozzle device  5  is controlled to be a value F 2  on the side of opening degrees that are greater (that is, on the lower side in the section (F) of  FIG. 5 ) as compared with the base opening degree as indicated by a curve “Comparative example” in the section (F) of  FIG. 5 , the first boost pressure P 1  does not increase so as to reach the value P 1   b  as indicated by a curve “Comparative example” in the section (E) of  FIG. 5 . 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, it is determined by, for example, the ECU  50  (see  FIG. 1 ) that the result of the determination in step S 106  in  FIG. 2  is positive during a time period from t 2  to t 4  in which the rotational speed NC (see the section (D) of  FIG. 5 ) of the electrically driven compressor  6  (see  FIG. 1 ) is greater than the threshold value TNC (see the section (D) of  FIG. 5 ), and, in step S 107  in  FIG. 2 , the bypass valve  7   a  (see  FIG. 1 ) is closed by the ECU  50  as indicated by a solid line “First embodiment” in the section (B) of  FIG. 5 . 
     Also, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, it is determined by, for example, the ECU  50  (see  FIG. 1 ) that the result of the determination in step S 106  in  FIG. 2  is negative in a time period at or before the time point t 2  and a time period at or after the time point t 4 , in each of which the rotational speed NC of the electrically driven compressor  6  is equal to or less than the threshold value TNC, and, in step S 108  in  FIG. 2 , the bypass valve  7   a  is opened by the ECU  50  as indicated by the solid line “First embodiment” in the section (B) of  FIG. 5 . 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, after the acceleration request is made by the driver (that is, at or after the time point t 1 ), the supercharging by the electrically driven compressor  6  (see  FIG. 1 ) is used to assist the supercharging by the turbocharger  4  (see  FIG. 1 ) as shown in the section (D) of  FIG. 5 . That is, at or after the time point t 5  at which the first boost pressure P 1  reaches the target value P 1 trg of the first boost pressure as shown n the section (E) of  FIG. 5 , the electrically driven compressor  6  is not driven. 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, as indicated by the “P 1  (first embodiment)” in the section (E) of  FIG. 5 , the first boost pressure P 1  can be rapidly increased as compared with the comparative example indicated by the “P 1  (comparative example)” in the section (E) of  FIG. 5 . Therefore, in the example shown in  FIG. 5 , as indicated by the “P 2  (first embodiment)” in the section (C) of  FIG. 5 , the second boost pressure P 2  can also be rapidly increased as compared with the comparative example indicated by the “P 2  (comparative example)” in the section (C) of  FIG. 5 . 
     Also, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, as indicated by the “P 1  (first embodiment)” in the section (E) of  FIG. 5 , the first boost pressure P 1  at or after the time point t 5  is higher than that in the comparative example indicated by the “P 1  (comparative example)” in the section (E) of  FIG. 5 . Therefore, in contrast to the comparative example indicated by the “NC (comparative example)” in the section (D) of  FIG. 5 , the example shown in  FIG. 5  is not required to drive the electrically driven compressor  6  at or after the time point t 5  as indicated by the “NC (first embodiment)” in the section (D) of  FIG. 5 , and the consumption of the electric power can be reduced as compared with the comparative example indicated by the “NC (comparative example)” in the section (D) of  FIG. 5 . 
     Moreover, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, the second boost pressure P 2  can be increased smoothly without a stepwise change as indicated by the “P 2  (first embodiment)” in the section (C) of  FIG. 5 . That is, the roll of supercharging can be turned over smoothly from the electrically driven compressor  6  to the turbocharger  4 . In other words, the occurrence of a stepwise change of the second boost pressure P 2  that is likely to occur when the roil of the supercharging is turned over from the electrically driven compressor  6  to the turbocharger  4  can be reduced. 
     Furthermore, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the first embodiment is used, the first boost pressure P 1  rapidly reaches the target value P 1 trg of the first boost pressure as indicated by the “P 1  (first embodiment)” in the section (E) of  FIG. 5 , and the second boost pressure P 2  also rapidly reaches the target value P 2 trg of the second boost pressure as indicated by the “P 2  (first embodiment)” in the section (C) of  FIG. 5 . In addition, the difference between the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure that corresponds to the pressure loss is set as shown in  FIG. 4 . 
     On the other hand, in the example indicated by the “Comparative example” in  FIG. 5 , a relationship as shown in, for example,  FIG. 4  is not set between the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure. Because of this, even if, as indicated by the “NC (comparative example)” in the section (D) of  FIG. 5 , the rotational speed NC of the electrically driven compressor  6  (see  FIG. 1 ) is rapidly increased as with the example indicated by the “NC (first embodiment)” in the section (D) of  FIG. 5 , the opening degree of the variable nozzle device  5  (see  FIG. 1 ) is set, as indicated by the “Comparative example” in the section (F) of  FIG. 5 , on the side of opening degrees that are greater (that is, on the lower side in the section (F) of  FIG. 5 ) as compared with the example indicated by the “First embodiment” in the section (F) FIG.  5 . Therefore, as indicated by the “P 1  (comparative example)” in the section (E) of  FIG. 5 , the rise of the first boost pressure is delayed as compared with the example indicated by the “P 1  (first embodiment)” in the section (E) of  FIG. 5 , and, as a result, as indicated by the “P 2  (comparative example)” in the section (C) of  FIG. 5 , the rise of the second boost pressure is also delayed as compared with the example indicated by the “P 2  (first embodiment)” in the section (C) of  FIG. 5 . 
     Furthermore, in the example indicated by the “Comparative example” in  FIG. 5 , since the electrically driven compressor  6  is continuously driven at or after the time point  5  as indicated by the “NC (comparative example)” in the section (D) of  FIG. 5 , the consumption of the electric power is increased as compared with the example indicated by the “NC (first embodiment)” in the section (D) of  FIG. 5 . 
     As described above, in the control device for an internal combustion engine according to the first embodiment, the variable nozzle device  5  (see  FIG. 1 ) that serves as the exhaust gas flow rate adjusting device for adjusting the flow rate of the exhaust gas supplied to the turbine  4   b  (see  FIG. 1 ) of the turbocharger  4  arranged in the exhaust channel  3  (see  FIG. 1 ) is controlled on the basis of the difference between the target value P 1 trg (see the section (E) of  FIG. 5 ) of the first boost pressure that is boost pressure at a part of the intake channel  2  (see  FIG. 1 ) between the compressor  4   a  (see  FIG. 1 ) of the turbocharger  4  (see  FIG. 1 ) and the electrically driven compressor  6  (see  FIG. 1 ) arranged on the downstream side of the compressor  4   a,  and the detection value of the first boost pressure indicated by the “P 1  (first embodiment)” in the section (E) of  FIG. 5  with the first pressure sensor  41  (see  FIG. 1 ). 
     Thus, with the control device for an internal combustion engine according to the first embodiment, the target value P 1 trg of the first boost pressure and the detection value of the first boost pressure can be rapidly conformed to each other as compared with the internal combustion engine disclosed in JP 2008-274833A in which the control of the exhaust gas flow rate adjusting device based on the difference between the target value P 1 trg of the first boost pressure and the detection value of the first boost pressure is not performed. 
     In addition, in the control device for an internal combustion engine according to the first embodiment, the electrically driven compressor  6  is controlled on the basis of the difference between the target value P 2 trg (see the section (C) of  FIG. 5 ) of the second boost pressure that is boost pressure at a part of the intake channel  2  on the downstream side of the electrically driven compressor  6  and the detection value of the second boost pressure indicated by the “P 2  (first embodiment)” in the section (C) of  FIG. 5  with the second pressure sensor  42  (see  FIG. 1 ). 
     Thus, with the control device for an internal combustion engine according to the first embodiment, the target value P 2 trg of the second boost pressure and the detection value of the second boost pressure can be rapidly conformed to each other as compared with the internal combustion engine disclosed in JP 2008-274833A in which the control of the electrically driven compressor  6  based on the difference between the target value P 2 trg of the second boost pressure and the detection value of the second pressure is not performed. 
     Moreover, as described above, in the control device for an internal combustion engine according to the first embodiment, the target value P 2 trg of the second boost pressure that is one of the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure is set. In more detail, in the control device for an internal combustion engine according to the first embodiment, the target value P 2 trg of the second boost pressure is calculated on the basis of the engine speed NE, the engine torque Q and the first relationship shown in  FIG. 3  between the engine speed NE, the engine torque Q and the target value P 2 trg of the second boost pressure. 
     In addition, in the control device for an internal combustion engine according to the first embodiment, the target value P 1 trg of the first boost pressure that is the other of the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure is set. In more detail, in the control device for an internal combustion engine according to the first embodiment, the target value P 1 trg of the first boost pressure is calculated on the basis of the air amount Ga taken into the internal combustion engine main body  1  (see  FIG. 1 ), the target value P 2 trg of the second boost pressure and the second relationship shown in  FIG. 4  between the air amount Ga, the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure. 
     Thus, with the control device for an internal combustion engine according to the first embodiment, an acceleration according to an acceleration request from the driver can be achieved in a simple manner as compared with the internal combustion engine disclosed in JP 2008-274833A in which the electrically driven compressor  6  (see  FIG. 1 ) is controlled without the setting of each of the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure. 
     In other words, in the control device for an internal combustion engine according to the first embodiment, the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure arc set such that they have the second relationship shown in  FIG. 4 . Also, the feedback control of the variable nozzle device  5  (see  FIG. 1 ) is performed on the basis of the difference between the target value P 1 trg of the first boost pressure and the detection value of the first boost pressure, and the feedback control of the electrically driven compressor  6  (see  FIG. 1 ) is performed on the basis of the difference between the target value P 2 trg of the second boost pressure and the detection value of the second boost pressure. 
     As a result, with the control device for an internal combustion engine according to the first embodiment, without the need for providing processes to adapt the control of the variable nozzle device  5  and the control of the electrically driven compressor  6  and to perform a complex model-based control, such as one disclosed in, for example, JP 5817578 B, and therefore, an acceleration according to an acceleration request from the driver can be achieved and the second boost pressure can be increased smoothly without a stepwise change. 
     To be more specific, in the control device for an internal combustion engine according to the first embodiment, in order to rapidly conform the detection value of the second boost pressure to the target value P 2 trg of the second boost pressure, the supercharging by the electrically driven compressor  6  with high responsivity is mainly used first. Then, after the detection value of the first boost pressure has risen, in order to increase the detection value of the first boost pressure, the supercharging by the electrically driven compressor  6  is not mainly used and the supercharging of the turbocharger  4  (see  FIG. 1 ) is mainly used. As a result, the detection value of the second boost pressure is increased so as to reach the target value P 2 trg of the second boost pressure. Specifically, since the feedback control for the electrically driven compressor  6  is performed on the basis of the difference between the target value P 2 trg of the second boost pressure and the detection value of the second boost pressure, the supercharging by the electrically driven compressor  6  is no longer used as the difference between the target value P 2 trg of the second boost pressure and the detection value of the second boost pressure decreases. That is, since the feedback control for the electrically driven compressor  6  is performed such that the target value P 2 trg of the second boost pressure and the detection value of the second boost pressure are conformed to each other (in other words, such that the difference therebetween decreases), the detection value of the second boost pressure is not changed in a stepwise faction, that is, the difference between the target value P 2 trg of the second boost pressure and the detection value of the second boost pressure is not increased in a stepwise fashion even when the rotational speed of the electrically driven compressor  6  is decreased. 
     In the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, since the compressor  4   a  of the turbocharger  4  is arranged at a part of the intake channel  2  on the upstream side of the electrically driven compressor  6 , the supercharging by the turbocharger  4  is mainly performed and the supercharging by the electrically driven compressor  6  that is arranged at a part of the intake channel  2  on the downstream side of the compressor  4   a  assists the supercharging by the turbocharger  4 . 
     That is, in the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, since the electrically driven compressor  6  is not used as the main supercharging, the consumption of the electric power can be reduced as compared with an example in which an electrically driven compressor is used for the main supercharging. 
     In the internal combustion engine disclosed in JP 2008-274833A, a throttle valve is arranged at a part of the intake channel on the downstream side of the electrically driven compressor, whereas, in an another example (not shown) in which the control device for an internal combustion engine according to the first embodiment is used, the electrically driven compressor  6  may be arranged at a part of the intake channel  2  (see  FIG. 1 ) on the downstream side of a throttle vale (not shown) in order to rapidly increase the pressure of the intake air taken into the internal combustion engine main body  1  (see  FIG. 1 ) by sufficiently achieving the high response of the electrically driven compressor  6  (see  FIG. 1 ). That is, in this example in which the control device for an internal combustion engine according to the first embodiment is used, the electrically driven compressor  6  is arranged at the closet possible position from the internal combustion engine main body  1  in order to sufficiently achieve the high response of the electrically driven compressor  6 . 
     In addition, in still another example in which the control device for an internal combustion engine according to the first embodiment is used, an arbitrary number of cylinders other than four cylinders may be provided in the internal combustion engine main body  1 . 
     Moreover, in yet another example in which the control device for an internal combustion engine according to the first embodiment is used, the bypass valve  7   a  and the bypass channel  7   b  may be omitted. 
     Moreover, in still another example in which the control device for an internal combustion engine according to the first embodiment is used, the target value P 1 trg of the first boost pressure may be calculated on the basis of the engine torque Q, the engine speed NE and a relationship as shown in  FIG. 3  between the engine torque Q, the engine speed NE and the target value P 1 trg of the first boost pressure. In this relationship, the target value P 1 trg of the first boost pressure is higher when the engine torque Q is greater, and the target value P 1 trg of the first boost pressure is higher when the engine speed NE is higher. 
     Furthermore, in yet example in which the control device for an internal combustion engine according to the first embodiment is used, the target value P 1 trg of the first boost pressure may be obtained in step S 100 , and the target value P 2 trg of the second boost pressure may be calculated in step S 103  on the basis of the air amount Ga, the target value P 1 trg of the first boost pressure and the second relationship shown in  FIG. 4 . 
     In the following, a second embodiment concerning the control device for an internal combustion engine according to the present disclosure will be described. 
     The control device for an internal combustion engine according to the second embodiment is configured in the same manner as the control device for an internal combustion engine described above except the points describe below. Therefore, the control device for an internal combustion engine according to the second embodiment can achieve a similar advantageous effect to the control device for an internal combustion engine according to the first embodiment described above except for the point described below. 
       FIG. 6  is a schematic diagram showing a configuration of a system in which the control device for an internal combustion engine according to the second embodiment is used. 
     In the example shown in  FIG. 1  in which the control device for an internal combustion engine according to the first embodiment is used, the variable nozzle device  5  that serves as the exhaust gas flow rate adjusting device for adjusting the flow rate of the exhaust gas supplied to the turbine  4   b  is arranged at the inlet of the exhaust gas in the turbine  4   b.  However, in the example shown in  FIG. 6  in which the control device for an internal combustion engine according to the second embodiment is used, a waste gate channel  15   a  configured to bypass the turbine  4   b  and a waste gate vale  15   b  arranged in the waste gate channel  15   a  are provided as the exhaust gas flow rate adjusting device, instead of the above. The signal for controlling the waste gate valve  15   b  is outputted from the ECU  50 . 
     In the example shown in  FIG. 2  in which the control device for an internal combustion engine according to the first embodiment is used, the controls of the variable nozzle device  5  (see  FIG. 1 ) and the electrically driven compressor  6  (see  FIG. 1 ) are performed. However, in an example shown in  FIG. 2  in which the control device for an internal combustion engine according to the second embodiment is used, a control of the waste gate valve  15   b  (see  FIG. 6 ) is performed as well as the control of the electrically driven compressor  6  (see  FIG. 6 ), instead of the above. 
     To be more specific, in the example shown in  FIG. 2  in which the control device for an internal combustion engine according to the first embodiment is used, in step S 104 , the opening degree of the variable nozzle device  5  (see  FIG. 1 ) that serves as the exhaust gas flow rate adjusting device for adjusting the flow rate of the exhaust gas supplied to the turbine  4   b  (see  FIG. 1 ) is calculated by, for example, the ECU  50  (see  FIG. 1 ) on the basis of the target value P 1 trg of the first boost pressure. However, in the example shown in  FIG. 2  in which the control device for an internal combustion engine according to the second embodiment is used, the opening degree of the waste gate valve  15   b  (see  FIG. 6 ) that serves as the exhaust gas flow rate adjusting device for adjusting the flow rate of the exhaust gas supplied to the turbine  4   b  (see  FIG. 6 ) is calculated by, for example, the ECU  50  (see  FIG. 6 ) on the basis of the target value P 1 trg of the first boost pressure. In an example shown in  FIG. 5  in which the control device for an internal combustion engine according to the second embodiment is used, the opening degree of the waste gate valve  15   b  is calculated so as to have a value indicated by the curve “First embodiment” in the section (F) of  FIG. 5  when the target value P 1 trg of the first boost pressure is changed at the time point t 1  from the value P 1   a  to the value P 1   b  as shown in the section (E) of  FIG. 5 . 
     In addition to the above, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the second embodiment is used, the opening degree of the waste gate valve  15   b  is calculated so as to be rapidly conformed to the target value P 1 trg of the first boost pressure without an overshoot of the first boost pressure P 1  as indicated by the curve “P 1  (first embodiment)” in the section (E) of  FIG. 5 . 
     In the example shown in  FIG. 2  in which the control device for an internal combustion engine according to the second embodiment is used, in step S 105 , the waste gate valve  15   b  is controlled by the ECU  50  so as to achieve the opening degree of the waste gate valve  15   b  calculated in step S 104 . That is, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the second embodiment is used, in step S 105 , the waste gate valve  15   b  is so as to be rapidly conformed to the target value P 1 trg of the first boost pressure without an overshoot of the first boost pressure P 1  as indicated by the curve “P 1  (first embodiment)” in the section (E) of  FIG. 5 . In other words, in step S 105 , the waste gate valve  15   b  that serves as the exhaust gas flow rate adjusting device is controlled by the ECU  50  on the basis of the difference between the target value P 1 trg of the first boost pressure and the first boost pressure (detection value) P 1  detected by the first pressure sensor  41  (see  FIG. 6 ). 
     In the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the second embodiment is used, during a time period from t 1  to t 5 , since the first boost pressure P 1  (the value indicated by the curve “P 1  (first embodiment)” in the section (E) of  FIG. 5 ) is smaller than the value P 1   b  of the target value P 1 trg of the first boost pressure as shown in the section (E) of  FIG. 5 , the opening degree of the waste gate valve  15   b  (see  FIG. 6 ) is controlled, by a feedback control, so as to be closed (that is, so as to shift to the upper side in the section (F) of  FIG. 5 ) as compared with the base opening degree (see the section (F) of  FIG. 5 ) as shown in the section (F) of  FIG. 5  in order to increase the first boost pressure P 1 . That is, the opening degree of the waste gate valve  15   b  is controlled so as to fall within a range between the value F 1  (see the section (F) of  FIG. 5 ) and the base opening degree. 
     Furthermore, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the second embodiment is used, the opening degree of the waste gate valve  15   b  is controlled to be the base opening degree at or after the time point t 5  at which the first boost pressure P 1  indicated by the curve “P 1  (first embodiment)” in the section (E) of  FIG. 5  is conformed to the value P 1   b  of the target value P 1 trg of the first boost pressure. 
     That is, in the example shown in  FIG. 5  in which the control device for an internal combustion engine according to the second embodiment is used, the base opening degree of the waste gate valve  15   b  is set such that, if the opening degree (see the section (F) of  FIG. 5 ) of the waste gate valve  15   b  is controlled to be the base opening degree (see the section (F) of  FIG. 5 ), the first boost pressure P 1  is conformed to the value P 1   b  (see the section (E) of  FIG. 5 ) of the target value P 1 trg of the first boost pressure. In other words, if the opening degree of the waste gate valve  15   b  is controlled to be the value F 2  on the side of opening degrees that are greater (that is, on the lower side in the section (F) of  FIG. 5 ) as compared with the base opening degree as indicated by the curve “Comparative example” in the section (F) of  FIG. 5 , the first boost pressure P 1  does not increase so as to reach the value P 1   b  as indicated by the curve “Comparative example” in the section (E) of  FIG. 5 . 
     In the control device for an internal combustion engine according to the second embodiment, the waste gate valve  15   b  (see  FIG. 6 ) that serves as the exhaust gas flow rate adjusting device for adjusting the flow rate of the exhaust gas supplied to the turbine  4   b  (see  FIG. 6 ) of the turbocharger  4  arranged in the exhaust channel  3  (see  FIG. 6 ) is controlled on the basis of the difference between the target value P 1 trg (see the section (E) of  FIG. 5 ) of the first boost pressure that is boost pressure at a part of the intake channel  2  (see  FIG. 6 ) between the compressor  4   a  (see  FIG. 6 ) of the turbocharger  4  (see  FIG. 6 ) and the electrically driven compressor  6  (see  FIG. 6 ) arranged on the downstream side of the compressor  4   a,  and the detection value of the first boost pressure indicated by the “P 1  (first embodiment)” in the section (E) of  FIG. 5  with the first pressure sensor  41  (see  FIG. 6 ). 
     Thus, with the control device for an internal combustion engine according to the second embodiment, the target value P 1 trg of the first boost pressure and the detection value of the first boost pressure can be rapidly conformed to each other as compared with the internal combustion engine disclosed in JP 2008-274833A in which the control of the exhaust gas flow rate adjusting device based on the difference between the target value P 1 trg of the first boost pressure and the detection value of the first boost pressure is not performed. 
     In other words, in the control device for an internal combustion engine according to the second embodiment, the target value P 1 trg of the first boost pressure and the target value P 2 trg of the second boost pressure are set such that they have the second relationship shown in  FIG. 4 . Also, the feedback control of the waste gate valve  15   b  (see  FIG. 6 ) is performed on the basis of the difference between the target value P 1 trg of the first boost pressure and the detection value of the first boost pressure, and the feedback control of the electrically driven compressor  6  (see  FIG. 6 ) is performed on the basis of the difference between the target value P 2 trg of the second boost pressure and the detection value of the second boost pressure. 
     As a result, with the control device for an internal combustion engine according to the second embodiment, without the need for providing processes to adapt the control of the waste gate valve  15   b  and the control of the electrically driven compressor  6  and to perform a complex model-based control, such as one disclosed in JP 5817578 B, for example, and therefore, an acceleration according to an acceleration request from the driver can be achieved and the second boost pressure can be increased smoothly without a stepwise change. 
     According to a third embodiment, any of the first and second embodiments described above and the examples described above can be appropriately combined.