| 摘要 |
PROBLEM TO BE SOLVED: To provide an engine variable valve timing device preventing increase of hunting while setting torque by a return spring of a cam shaft at an exhaust side to a smaller degree. SOLUTION: The engine variable valve timing device includes a hydraulic phase variable unit provided on the cam shaft at the exhaust side, transmitting motive power from a crank shaft to the cam shaft and capable of changing the phase of the cam shaft relative to the crank shaft; a control valve for controlling feeding/discharge of an operation oil to a spark-advance hydraulic chamber and a spark-delay hydraulic chamber of the hydraulic phase variable unit; a control means for controlling the control valve; and the return spring provided on the hydraulic phase variable unit and always urging the cam shaft in a spark-advance direction. When the cam shaft is maintained to an intermediate position between the maximum spark-advance position and the maximum spark-delay position, the control means controls the control valve such that feeding of the operation oil to the spark-advance hydraulic chamber and the spark-delay hydraulic chamber is alternately repeatedly performed. COPYRIGHT: (C)2009,JPO&INPIT
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