| 摘要 |
One-way valves (30, 31) are provided in a hydraulic supply passage (28) in an advance chamber (18) and a hydraulic supply passage (29) in a retard chamber (19) respectively for preventing reverse flow of oil from each chamber (18, 19) and drain oil passages (32, 33) bypassing the one-way valves respectively disposed in the hydraulic supply passages (28, 29) of the respective hydraulic chambers (18, 19) are provided to be in parallel therewith. Drain switching valves (34, 35) are disposed in the respective drain oil passages (32, 33). A hydraulic control valve (21) for controlling a hydraulic pressure supplied to the advance chamber (18) and the retard chamber (19) includes integrally a drain switching control function (38) for controlling a hydraulic pressure supplied to the respective drain switching valves (34, 35). A point where a VCT response speed rapidly changes by switching opening/closing of the drain switching valves (34, 35) is learned to improve a control characteristic in the vicinity of the rapidly changing point of the VCT response speed. |
