Engine

1. An engine in which intake air guided by one intake path is distributed to cylinders, and exhaust gas collected from the cylinders is discharged through one exhaust path, comprising:

a variable series supercharging system comprising a high-pressure supercharger and a low-pressure supercharger each comprising a turbine rotated by receiving the exhaust gas flowing in the exhaust path and a compressor driven by the turbine so as to compress the intake air flowing in the intake path;

a supercharging pressure sensor configured to detect a pressure of the intake air compressed by the variable series supercharging system;

a high-pressure supercharger rotation sensor configured to detect a high-pressure supercharger rotation speed of the high-pressure supercharger;

a high-pressure supercharger variable actuator configured to control a capacity of the high-pressure supercharger; and

a control device configured to calculate a target high-pressure supercharger rotation speed and a target pressure of the intake air compressed by the variable series supercharging system, the control device being configured to control the high-pressure supercharger variable actuator based on the detected pressure of the intake air compressed by the variable series supercharging system, the detected high-pressure supercharger rotation speed of the high-pressure supercharger, the target high-pressure supercharger rotation speed, and the target pressure of the intake air compressed by the variable series supercharging system.

2. The engine according to claim 1 , further comprising:

a bypass path bypassing exhaust gas from an upstream side of the turbine of the high-pressure supercharger to a downstream side of the turbine; and

a bypasses flow rate control valve configured to control a flow rate of the exhaust gas flowing in the bypass path,

wherein the control device is configured to control the bypasses flow rate control valve,

wherein the control device is configured to control the high-pressure supercharger variable actuator and the bypasses flow rate control valve based on the detected pressure of the intake air compressed by the variable series supercharging system, the detected high-pressure supercharger rotation speed of the high-pressure supercharger, the target high-pressure supercharger rotation speed, and the target pressure of the intake air compressed by the variable series supercharging system.

3. The engine according to claim 1 , further comprising:

a low-pressure supercharger rotation sensor configured to detect a low-pressure supercharger rotation speed of the low-pressure supercharger; and

a low-pressure supercharger variable actuator configured to control a capacity of the low-pressure supercharger,

wherein the control device is configured to control the low-pressure supercharger variable actuator,

wherein the control device is configured to control the low-pressure supercharger variable actuator based on the detected pressure of the intake air compressed by the variable series supercharging system, the detected low-pressure supercharger rotation speed of the low-pressure supercharger, the target low-pressure supercharger rotation speed, and the target pressure of the intake air compressed by the variable series supercharging system.

4. The engine according to claim 3 , further comprising:

a bypass path bypassing exhaust gas from an upstream side of the turbine of the high-pressure supercharger to a downstream side of the turbine; and

a bypasses flow rate control valve configured to control a flow rate of the exhaust gas flowing in the bypass path,

wherein the control device is configured to control the bypasses flow rate control valve,

wherein the control device is configured to control the low-pressure supercharger variable actuator and the bypasses flow rate control valve based on the detected pressure of the intake air compressed by the variable series supercharging system, the detected low-pressure supercharger rotation speed of the low-pressure supercharger, the target low-pressure supercharger rotation speed, and the target pressure of the intake air compressed by the variable series supercharging system.

5. The engine according to claim 3 , further comprising:

a bypass path bypassing exhaust gas from an upstream side of the turbine of the high-pressure supercharger to a downstream side of the turbine;

a bypasses flow rate control valve configured to control a flow rate of the exhaust gas flowing in the bypass path;

an EGR path guiding a part of the exhaust gas flowing in the exhaust path to the intake path; and

an EGR valve configured to control a flow rate of the exhaust gas flowing in the EGR path,

wherein the control device is configured to calculate the flow rate of the exhaust gas flowing in the EGR path based on the detected pressure of the intake air compressed by the variable series supercharging system, the detected high-pressure supercharger rotation speed of the high-pressure supercharger, and the detected low-pressure supercharger rotation speed of the low-pressure supercharger, and

wherein the control device is configured to control the EGR valve based on the calculated flow rate of the exhaust gas flowing in the EGR path.

6. The engine according to claim 1 , wherein the target high-pressure supercharger rotation speed is based on the target pressure of the intake air compressed by the variable series supercharging system.

7. The engine according to claim 1 , wherein the control device is further configured to control the high-pressure supercharger variable actuator so as to make an absolute value of a difference between the detected high-pressure supercharger rotation speed and the target high-pressure supercharger rotation speed smaller than a predetermined value.

8. The engine according to claim 1 , wherein the control device is further configured to control the high-pressure supercharger variable actuator so as to make an absolute value of a difference between the detected pressure of the intake air compressed by the variable series supercharging system and the target pressure of the intake air compressed by the variable series supercharging system smaller than a predetermined value.

9. The engine according to claim 1 , wherein:

the control device is configured to control the high-pressure supercharger variable actuator so as to make a first absolute value of a difference between the detected high-pressure supercharger rotation speed and the target high-pressure supercharger rotation speed smaller than a first predetermined value;

the control device is configured to control the high-pressure supercharger variable actuator so as to make a second absolute value of a difference between the detected pressure of the intake air compressed by the variable series supercharging system and the target pressure of the intake air compressed by the variable series supercharging system smaller than a second predetermined value; and

the control device is configured to control the high-pressure supercharger variable actuator such that first absolute value is made smaller than the first predetermined value before the second absolute value is made smaller than the second predetermined value.

10. An engine in which intake air guided by one intake path is distributed to cylinders, and exhaust gas collected from the cylinders is discharged through one exhaust path, comprising:

a variable series supercharging system comprising a high-pressure supercharger and a low-pressure supercharger each comprising a turbine rotated by receiving the exhaust gas flowing in the exhaust path and a compressor driven by the turbine so as to compress the intake air flowing in the intake path;

a supercharging pressure sensor configured to detect a pressure of the intake air compressed by the variable series supercharging system;

a low-pressure supercharger rotation sensor configured to detect a low-pressure supercharger rotation speed of the low-pressure supercharger;

a low-pressure supercharger variable actuator configured to control a capacity of the low-pressure supercharger; and

a control device configured to calculate a target low-pressure supercharger rotation speed and a target pressure of the intake air compressed by the variable series supercharging system, the control device being further configured to control the low-pressure supercharger variable actuator based on the detected pressure of the intake air compressed by the variable series supercharging system, the detected low-pressure supercharger rotation speed of the low-pressure supercharger, the target low-pressure supercharger rotation speed, and the target pressure of the intake air compressed by the variable series supercharging system.

11. The engine according to claim 10 , further comprising:

a bypass path bypassing exhaust gas from an upstream side of the turbine of the high-pressure supercharger to a downstream side of the turbine; and

a bypasses flow rate control valve configured to control a flow rate of the exhaust gas flowing in the bypass path,

wherein the control device is configured to control the bypasses flow rate control valve,

wherein the control device is configured to control the low-pressure supercharger variable actuator and the bypasses flow rate control valve based on the detected pressure of the intake air compressed by the variable series supercharging system, the detected high-pressure supercharger rotation speed of the high-pressure supercharger, the target high-pressure supercharger rotation speed, and the target pressure of the intake air compressed by the variable series supercharging system.

12. The engine according to claim 10 , wherein the control device is configured to control the low-pressure supercharger variable actuator so as to make an absolute value of a difference between the detected low-pressure supercharger rotation speed and the target low-pressure supercharger rotation speed smaller than a predetermined value.

13. The engine according to claim 10 , wherein the control device is configured to control the low-pressure supercharger variable actuator so as to make an absolute value of a difference between the detected pressure of the intake air compressed by the variable series supercharging system and the target pressure of the intake air compressed by the variable series supercharging system smaller than a predetermined value.