Controller for supercharger-equipped internal combustion engine and control method thereof

1. A controller for an internal combustion engine equipped with a supercharger having a turbine provided in an exhaust path, a compressor that is provided at the upstream side of a throttle valve in an intake path and rotates integrally with the turbine, a wastegate valve provided in a bypass path, of the exhaust path, that bypasses the turbine, and a gate valve actuator that drives the wastegate valve, the controller comprising at least one processor configured to implement:

a driving-condition detector that detects a real rotation speed and a real intake air flow rate of the internal combustion engine and a real atmospheric pressure;

an intake air controller that calculates a target intake air flow rate and a target charging efficiency of the internal combustion engine;

a target supercharging pressure calculator that calculates a target supercharging pressure, which is a target value of a supercharging pressure that is the pressure at a position, in the intake path, that is at the downstream side of the compressor and at the upstream side of the throttle valve, based on the target charging efficiency and the real rotation speed;

a target compressor driving force calculator that calculates a target compressor driving force, which is a target value of driving force for the compressor, based on at least one of the target intake air flow rate and a target before/after-compressor pressure ratio, which is a pressure ratio of the target supercharging pressure and the real atmospheric pressure;

a target turbine flow rate calculator that calculates a target turbine flow rate, for realizing the target compressor driving force, that is the flow rate of exhaust gas that flows through the turbine;

an exhaust gas flow rate calculator that calculates an exhaust gas flow rate that is exhausted from the internal combustion engine, based on the real intake air flow rate and an air-fuel ratio of the internal combustion engine;

a target gate flow rate calculator that calculates a target wastegate flow rate, which is a target value of a flow rate of exhaust gas that flows into the bypass path through the wastegate valve, based on the exhaust gas flow rate and the target turbine flow rate;

a target before/after-turbine pressure ratio calculator that calculates a target before/after-turbine pressure ratio, for realizing the target compressor driving force or the target before/after-compressor pressure ratio, that is the ratio of a pressure before the turbine and a pressure after the turbine;

a target turbine-upstream pressure calculator that calculates a turbine-downstream pressure, based on the exhaust gas flow rate, and then calculates a target turbine-upstream pressure, which is a target value of a turbine-upstream pressure, based on said turbine-downstream pressure and the target before/after-turbine pressure ratio;

a target gate effective opening area calculator that calculates a target gate effective opening area, which is a target value of an effective opening area of the wastegate valve, based on the target wastegate flow rate, the target before/after-turbine pressure ratio, and the target turbine-upstream pressure; and

a gate valve control value calculator that calculates a gate valve control value, which is a control value for the gate valve actuator, based on the target gate effective opening area, and controls the gate valve actuator to drive the wastegate valve based on the gate valve control value.

2. The controller for the internal combustion engine equipped with the supercharger according to claim 1 ,

wherein the driving-condition detector detects a real manifold pressure, which is a pressure in an intake manifold constituting a position, in the intake path, situated at the downstream side of the throttle valve, and a real intake air temperature, and

wherein the target supercharging pressure calculator calculates a volumetric efficiency on the basis of the intake manifold, based on the real rotation speed and the real manifold pressure, calculates a target manifold pressure, which is a target value of a manifold pressure, based on the volumetric efficiency, the target charging efficiency, and the real intake air temperature, and then adds a pressure addition value to the target manifold pressure so as to calculate the target supercharging pressure.

3. The controller for the internal combustion engine equipped with the supercharger according to claim 1 ,

wherein the target turbine flow rate calculator calculates, as the target turbine flow rate, the turbine flow rate corresponding to the target compressor driving force, by use of a map in which the relationship between a turbine flow rate and a turbine output, which is driving force for the compressor, is preliminarily set,

wherein the target before/after-turbine pressure ratio calculator calculates, as the target before/after-turbine pressure ratio, the before/after-turbine pressure ratio corresponding to the target compressor driving force or the target before/after-compressor pressure ratio, by use of a map in which the relationship between driving force for the compressor or a before/after-compressor pressure ratio, which is the pressure ratio of the supercharging pressure and an atmospheric pressure, and a before/after-turbine pressure ratio, which is a pressure ratio of a pressure before the turbine and a pressure after the turbine, is preliminarily set, and

wherein the target turbine-upstream pressure calculator calculates the atmospheric-pressure pressure ratio corresponding to the exhaust gas flow rate, by use of a map in which the relationship between the exhaust gas flow rate and an atmospheric-pressure pressure ratio, which is a pressure ratio of a turbine-downstream pressure and the atmospheric pressure, is preliminarily set, calculates a turbine-downstream pressure, based on said atmospheric-pressure pressure ratio and the real atmospheric pressure, and then calculates the target turbine-upstream pressure, based on said turbine-downstream pressure and the target before/after-turbine pressure ratio.

4. The controller for the internal combustion engine equipped with the supercharger according to claim 1 , further comprising a real compressor driving force calculator that calculates a real compressor driving force, which is a detection value of driving force for the compressor, based on at least one of the real intake air flow rate and a real before/after-compressor pressure ratio, which is a pressure ratio of a real supercharging pressure detected by the driving-condition detector and the real atmospheric pressure,

wherein the gate valve control value calculator implements driving force feedback control for changing a feedback correction value that corrects the gate valve control value in order to make the real compressor driving force approach the target compressor driving force, and sets a value obtained by correcting the gate valve control value with the feedback correction value as a final value of the gate valve control value.

5. The controller for the internal combustion engine equipped with the supercharger according to claim 4 ,

wherein the gate valve control value calculator implements driving force feedback learning control for changing a feedback learning value that corrects the gate valve control value, in accordance with a deviation amount of the feedback correction value from zero, and sets a value obtained by correcting the gate valve control value with the feedback correction value and the feedback learning value as a final value of the gate valve control value.

6. A control method for an internal combustion engine equipped with a supercharger having a turbine provided in an exhaust path, a compressor that is provided at the upstream side of a throttle valve in an intake path and rotates integrally with the turbine, a wastegate valve provided in a bypass path, of the exhaust path, that bypasses the turbine, and a gate valve actuator that drives the wastegate valve, the control method comprising:

detecting a real rotation speed and a real intake air flow rate of the internal combustion engine and a real atmospheric pressure via at least one driving-condition detector; and

via a controller,

calculating a target intake air flow rate and a target charging efficiency of the internal combustion engine;

calculating a target supercharging pressure, which is a target value of a supercharging pressure that is the pressure at a position, in the intake path-portion, that is at the downstream side of the compressor and at the upstream side of the throttle valve, based on the target charging efficiency and the real rotation speed;

calculating a target compressor driving force, which is a target value of driving force for the compressor, based on at least one of the target intake air flow rate and a target before/after-compressor pressure ratio, which is a pressure ratio of the target supercharging pressure and the real atmospheric pressure;

calculating a target turbine flow rate, for realizing the target compressor driving force, that is the flow rate of exhaust gas that flows through the turbine;

calculating an exhaust gas flow rate that is exhausted from the internal combustion engine, based on the real intake air flow rate and an air-fuel ratio of the internal combustion engine;

calculating a target wastegate flow rate, which is a target value of a flow rate of exhaust gas that flows into the bypass path through the wastegate valve, based on the exhaust gas flow rate and the target turbine flow rate;

calculating a target before/after-turbine pressure ratio, for realizing the target compressor driving force or the target before/after-compressor pressure ratio, that is the ratio of a pressure before the turbine and a pressure after the turbine;

calculating a turbine-downstream pressure, based on the exhaust gas flow rate, and then calculates a target turbine-upstream pressure, which is a target value of a turbine-upstream pressure, based on said turbine-downstream pressure and the target before/after-turbine pressure ratio;

calculating a target gate effective opening area, which is a target value of an effective opening area of the wastegate valve, based on the target wastegate flow rate, the target before/after-turbine pressure ratio, and the target turbine-upstream pressure;

calculating a gate valve control value, which is a control value for the gate valve actuator, based on the target gate effective opening area; and

controlling the gate valve actuator to drive the wastegate valve based on the gate valve control value.