Patent ID: 8253362

Claim:
An apparatus, comprising: a motor controller configured to control supply current to a motor within a predetermined upper limit value; a heat generation amount calculation section configured to calculate a heat generation amount of said motor based on the supply current; an integration section configured to integrate the heat generation amount to obtain an integrated temperature; an addition section configured to add an initial temperature to the integrated temperature to calculate a temperature estimated value; a current upper limit map having a current upper limit value set therein corresponding to the temperature estimated value; a ratio map having a current limitation ratio of said motor set therein corresponding to the temperature estimated value; and a selection section configured to select a lower one of limited current values determined using said current upper limit map and said ratio map to limit energization to said motor, wherein said heat generation amount calculation section is configured to use a heat generation amount calculation expression that includes a heat generation correction term and a heat radiation correction term for calculating, as a subtraction term, a value by multiplying the difference between the integrated temperature and a motor ambient temperature by a heat radiation coefficient, and wherein said heat generation amount calculation section is configured such that, in a first case wherein the motor ambient temperature is equal to or higher than a first comparison temperature set in advance, the heat generation amount is calculated with a calculation expression equivalent to the heat generation amount calculation expression from which the heat radiation correction term is deleted so that the limitation to energization of said motor may be increased.