osv 41 has two combinations a and b when the solenoid 43 is not energized the a combination is employed and is held in an operative position by the force of the coil spring 44 and the b combination is inoperative in this state the second oil passage 21 is disconnected from the oil pressure passage 35 when the solenoid 43 is energized the b combination is held in an operative position and the a combination is inoperative in this state the second oil passage 21 is communicated with the oil pressure passage 35 when controlling the osv 41 the ecu 38 computes the speed of the engine e based on a signal from an engine speed sensor s when the engine e is running at a low speed the ecu 38 causes the osv 41 to select the a combination to prevent oil from flowing to the second oil passage 21 in this state all the oil discharged by the pump 36 is supplied to the oil pressure passage 35 that is even if the engine is running at a low speed and the pump 36 is discharging a relatively small amount of oil the vvti 31 is provided with a sufficient amount of oil therefore the oil pressure of the oil delivered to the vvti 31 is relatively high when the engine speed increases gradually and reaches a high speed range which is equal to or higher than 5000 rpm the ecu 38 controls the osv 41 to switch to the b combination this causes oil to be supplied to the second oil passage 21 in the same manner as the oil.