Importance

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Abstract

The present invention relates to a control device capable of estimating a compression ratio and a method for estimating a compression ratio in an internal combustion engine provided with a variable compression ratio mechanism. If an input error of a detection value of a compression ratio based on an output of a sensor occurs (S101), an engine control unit cuts off the supply of power to an actuator of the variable compression ratio mechanism (S102), and advances an ignition timing until a knock intensity reaches a set value in the process of the compression ratio decreasing due to a firing pressure (S103). Then, the engine control unit estimates the compression ratio based on the ignition timing at which the knock intensity has reached the set value (S105 and S106), and changes the variable range of the valve timing in a variable valve timing mechanism based on the estimated compression ratio.

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First Claim