Supercharge control apparatus and supercharge control method for supercharged internal combustion engine

A supercharge control apparatus for an internal combustion engine, wherein the internal combustion engine includes a plurality of superchargers, and air fed from the superchargers are combined and supplied to the internal combustion engine, the apparatus comprising:

• a detecting device for detecting boost condition of each of the superchargers, the detecting device including at least two of a pressure ratio detecting unit, which detects the ratio of the pressure downstream the supercharger to the pressure upstream the supercharger, an air flow rate detecting unit, which detects the flow rate of air passing through each supercharger, and a rotational speed detecting unit, which detects the rotational speed of each supercharger;
• a determining unit, which determines whether the boost condition is within a predetermined surging area;
• and
• a control unit, when it is determined that the boost condition of only part of the superchargers is within the surging area, the control unit decreases the air flow rate of the supercharger other than the part of the superchargers the boost condition of which is determined to be in the surging area,
• wherein the engine includes intake passages each of which corresponds to one of the superchargers, the pressure ratio detecting unit comprising:
• an atmospheric pressure detecting unit, which detects the atmospheric pressure;
• a pressure detecting unit, which detects the pressure in the intake passages downstream the superchargers;
• and
• a pressure ratio computing unit, which detects the ratio of the pressure downstream the superchargers to the atmospheric pressure.

A supercharge control method for an internal combustion engine, which includes a plurality of superchargers, the method comprising:

• combining air fed from the superchargers and supplying the air to the internal combustion engine;
• detecting a parameter representing boost condition of each of the superchargers, wherein the parameter includes at least two of the ratio of the pressure downstream each supercharger to the pressure upstream each supercharger, the flow rate of air passing through each supercharger, and the rotational speed of each supercharger;
• determining whether the boost condition is within a predetermined surging area;
• and
• when it is determined that the boost condition of only part of the superchargers is within the surging area, increasing the air flow rate of the supercharger, the boost condition of which is determined to be in the surging area, the method further comprising:
• detecting the atmospheric pressure;
• detecting the pressure at a portion downstream each of the supercharger;
• and
• computing the ratio of the pressure downstream each supercharger to the atmospheric pressure.

A supercharge control method for an internal combustion engine, which includes a plurality of superchargers, the method comprising:

• combining air fed from the superchargers and supplying the air to the internal combustion engine;
• detecting a parameter representing boost condition of each of the superchargers, wherein the parameter includes at least two of the ratio of the pressure downstream each supercharger to the pressure upstream each supercharger, the flow rate of air passing through each supercharger, and the rotational speed of each supercharger;
• determining whether the boost condition is within a predetermined surging area;
• and
• when it is determined that the boost condition of only part of the superchargers is within the surging area, decreasing the air flow rate of the supercharger other than the part of the superchargers the boost condition of which is determined to be in the surging area, the method further comprising:
• detecting the atmospheric pressure;
• detecting the pressure at a portion downstream each of the superchargers;
• and
• computing the ratio of the pressure downstream each supercharger to the atmospheric pressure.