| 摘要 |
A valve driving mechanism for a double overhead camshaft engine includes a camshaft drive mechanism, including a camshaft sprocket for transmitting engine output from a crankshaft of the engine to one of intake and exhaust camshafts. A valve timing varying mechanism is driven so as to vary a valve timing of, for example, a set of intake valves relative to a valve timing of a set of exhaust valves. The valve timing varying mechanism includes a first helical gear, mounted on the exhaust camshaft for rotation, a second helical gear, in mesh with the first helical gear, which is rigidly secured to the intake camshaft, and a cylindrical sliding element, mounted on the exhaust camshaft for axial displacement. The cylindrical sliding element operationally couples the exhaust camshaft to the camshaft drive mechanism so as to cause a relative rotational displacement therebetween when the cylindrical sliding element undergoes axial displacement with respect to the exhaust camshaft.
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