| 摘要 |
PROBLEM TO BE SOLVED: To expand an arranging space of a functional part in the center of a bore by respectively offsetting intake/exhaust camshafts to the radial directional outside of the bore relative to intake/exhaust valves, and separating these while keeping parallelism. SOLUTION: Tappets 3 respectively exist in the top parts of the respective stem parts 1a, 2a of intake/exhaust valves 1, 2, and an intake camshaft 4 and an exhaust camshaft 5 respectively exist above the tappets. An intake cam lobe 4a and an exhaust cam lobe 5a abut to the respective tappets 3. Since the intake/exhaust camshafts 4, 5 separate in parallel by being offset (A) by a prescribed distance to the radial directional outside of a bore relative to the intake/exhaust valves 1, 2, an interval L between the cam side center lines 8, 8 can be expanded by an offset A quantity more than an interval I between the valve side center lines 6, 6. Thus even if the interval I between the valve side center lines 6, 6 is set as a narrow interval corresponding to a small bore, the interval L between the cam side center lines 8, 8 can be expanded to make an occupying space of a functional part arranged in the center of the bore widely obtained.
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