Starting method and starting device of internal combustion engine, method and device of estimating starting energy employed for starting method and starting device

In a method of starting an internal combustion engine (1), a combustion energy is generated by combusting a fuel that has been injected into a cylinder (2) in an expansion stroke when the internal combustion engine (1) is stopped. In the aforementioned method, the combustion energy (Ec (t0)) generated by combusting the fuel is obtained based on a state of an air/fuel mixture within the cylinder (2) to which the fuel has been injected. Based on the obtained combustion energy, a kinetic energy (Ea (t1)) to be supplied to the internal combustion engine from a primary energy supply source is estimated. A difference between a predetermined target kinetic energy (Et (t1)) required for starting the internal combustion engine subsequent to the start of combustion and the estimated kinetic energy to be supplied from the primary energy supply source is obtained. The kinetic energy (Es (t1)) corresponding to the obtained difference is supplied from a secondary energy supply source in the form of a starter motor (17).