| 摘要 |
PROBLEM TO BE SOLVED: To achieve a stabler valve timing control that is not affected by the viscosity of operating fluid although the control structure is more simplified. SOLUTION: A first hydraulic control valve 210 and a second hydraulic control valve 220 having overlap lengths different from each other are previously prepared. The overlap lengths are lengths of zones defined by closing communication ports by valve elements. The hydraulic control valves 210, 220 are selectively used depending on the viscosity of the operating fluid in each case. Therefore, not only calculation load applied during driving control of the hydraulic control valves but also physical restriction of the hydraulic control valves are reduced, so that it is possible to realize the stabler valve timing control not affected by the viscosity of the operating fluid. COPYRIGHT: (C)2008,JPO&INPIT
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