| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a valve operation characteristics variable system configured so as not to deteriorate responsiveness or stability during control of a cam phase advance angle. SOLUTION: A valve operation characteristics variable system (a second valve operation characteristics variable system 6 in the embodiment) is configured such that an intake camshaft phase with respect to a rotation angle of a crankshaft 9 is made variable by hydrostatic transmission according to engine operating condition. In this system, a control valve (a second hydraulic control valve 66 in the embodiment) that controls hydraulic fluid pressure of the valve operation characteristics variable system is provided on a side wall of a cylinder head 61, and an oil passage through which the hydraulic fluid pressure is supplied is formed inside the cylinder head. An orifice whose opening faces upward when installed in a vehicle is provided in an air release passage 98 which branches off from the oil passage. Consequently, air can be removed from the hydraulic fluid flowing though the oil passage.</p> |
