Variable valve timing apparatus

A variable valve timing apparatus that is interconnected to a drive train for driving a camshaft of an internal combustion engine and varies the rotational phase of the camshaft, the apparatus comprising:

• a housing connected to either the drive side or the driven side of the drive train;
• a rotor which is connected to the other side of the drive train and is received in the housing so as to rotate relatively to the housing throughout a first angular range;
• a hydraulic chamber formed in the housing between the housing and the rotor;
• a vane which is received in the hydraulic chamber to partition the hydraulic chamber into an advance angle chamber and a delay angle chamber;
• an oil control valve for controlling the supply or discharge of hydraulic oil to or from the advance angle chamber and the delay angle chamber;
• a lock pin which has an intermediate phase position set between a largest advance angle position and a largest delay angle position of the rotor with respect to the housing and locks the rotor at the intermediate phase position;
• a delay angle restricting pin which is retractably incorporated in the vane and projects its tip end from the vane to interfere with the housing to thereby prevent the rotor from rotating to a delay angle side beyond the intermediate phase position;
• a spring for urging the delay angle restricting pin in the direction that pushes out the delay angle restricting pin from the vane;
• a control chamber into which the hydraulic oil is introduced through an exclusive oil passage provided independently of an oil passage for introducing the hydraulic oil into the hydraulic chamber to thereby push down the delay angle restricting pin into the vane;
• and
• a hydraulic control valve for controlling the hydraulic pressure of the control chamber.