Internal combustion engine control method and control device

A control method for an internal combustion engine which is arranged to vary an engine compression ratio, and which includes a control mechanism arranged to control the engine compression ratio, and a driving source arranged to drive the control mechanism, the control method comprising:

• converting an operation amount of the driving source in accordance with a reduction ratio according to the engine compression ratio;
• transmitting the converted operation amount to the control mechanism;
• and
• controlling a cylinder pressure based on a basic ignition timing when the reduction ratio is larger than a middle reduction ratio at a predetermined middle compression ratio, and controlling the cylinder pressure based on an allowable ignition timing retarded from the basic ignition timing at the middle reduction ratio,
• wherein an ignition timing is controlled so that the cylinder pressure within the combustion chamber becomes equal to or smaller than an allowable cylinder pressure which is a limit pressure allowed within the combustion chamber of the internal combustion engine, and
• wherein an allowable advance amount of the ignition timing is calculated based on at least an engine speed and the allowable cylinder pressure.

A control device for an internal combustion engine including a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotation position of a control shaft, an actuator arranged to drive and rotate a rotation shaft, and a link mechanism mechanically connecting the control shaft and the rotation shaft, the link mechanism arranged to vary a reduction ratio which is a ratio between a rotation amount of the rotation shaft, and a rotation amount of the control shaft in accordance with the rotation position of the control shaft, the control device comprising:

• a control section configured to control a cylinder pressure based on a basic ignition timing when the reduction ratio is larger than a middle reduction ratio at a predetermined middle compression ratio, and to control the cylinder pressure based on an allowable ignition timing retarded from the basic ignition timing at the middle reduction ratio,
• wherein the control section comprises an allowable cylinder pressure setting section configured to set an allowable cylinder pressure which is a limit pressure allowed in a combustion chamber of the internal combustion engine, and
• the control section is configured to control the ignition timing so that a cylinder pressure within the combustion chamber becomes equal to or smaller than the allowable cylinder pressure,
• wherein the control section is configured to calculate an allowable advance amount of the ignition timing based on at least an engine speed and the allowable cylinder pressure.