CONTROL DEVICE FOR HYDRAULIC VARIABLE VALVE TIMING MECHANISM

In a hydraulic variable valve timing mechanism comprising a lock pin that locks a vane rotor and a housing against relative rotation in the most retarding phase, a specified angle ± is set so that release of the lock pin is started at a time when positive cam torque acts on the vane rotor. When the crank angle reaches the specified angle ± 1 supply of hydraulic pressure to the advancing oil chamber is started to release the lock pin from the engagement with the lock hole, thereby enabling a reliable release of the lock pin prior to start of change of valve timing.