Boost pressure control apparatus and boost pressure control method of internal combustion engine

A boost pressure control apparatus of an internal combustion engine, comprising:

• a turbocharger with a turbine which is rotationally driven by exhaust of an internal combustion engine and a compressor;
• an EGR device;
• a variable valve mechanism that alters opening/closure timing of at least one of an intake valve and an exhaust valve;
• a speed sensor which senses a rotation speed of the turbine;
• a pressure sensor which senses a boost pressure of the compressor;
• and
• a controller which is configured to compare a ratio of the boost pressure of the compressor from the pressure sensor to the rotation speed of the turbine from the speed sensor and a predetermined value, wherein
• EGR is performed at a time of supercharge, or an EGR amount is increased at the time of supercharge in comparison with when supercharge is not performed if the ratio of the boost pressure of the compressor to the rotation speed of the turbine is greater than the predetermined value,
• the EGR performed at the time of supercharge is an internal EGR performed by controlling opening/closure timing of the at least one of the intake valve and the exhaust valve, and
• the opening timing of the intake valve is adjusted so that an engine generated torque is within a predetermined range and an internal EGR gas amount becomes maximum.