Control device for internal combustion engine

A processor (CPU 40e) of a control device (ECU 0) of an internal combustion engine determines (s109) a first throttle valve opening degree [theta] A and a second throttle valve opening degree [theta] B at which the rate of change (differential value) of indexes (sediment thickness, the reduction ratio of the effective opening area, the flow rate reduction ratio, etc.) related to the reduction ratio of the effective opening area of a throttle valve changes. A processor (CPU 40e) estimates an index (s110) for an arbitrary throttle valve opening degree from the first throttle valve opening degree [theta] A and the second throttle valve opening degree [theta] B, and calculates an effective opening area (s112) of the throttle valve on the basis of the estimated index. 内燃机的控制装置(ECU 0)的处理器(CPU 40e)对与节流阀的有效开口面积的减少比例相关的指标(沉积物厚度、有效开口面积的减少比例、流量减少率等)的变化率(微分值)发生变化的第一节流阀开度θA和第二节流阀开度θB进行确定(s109)。处理器(CPU 40e)根据第一节流阀开度θA和第二节流阀开度θB来推定任意的节流阀开度下的指标(s110)，并根据推定出的指标来计算节流阀的有效开口面积(s112)。