| 摘要 |
PURPOSE:To make a device compact, by press-contacting displaceable adjust pulleys against tight and loose sides of a timing belt for transmitting rotation of one cam shaft receiving rotation of a crank shaft to the other cam shaft. CONSTITUTION:A first timing belt 6 is wound around a sprocket 3 on a crank shaft 2 and a large diameter sprocket 5 on an over head type cam shaft 4 for driving an exhaust valve. A sprocket 11 having a diameter smaller than that of the sprocket 5 is fixed to the cam shaft 4, and a second timing belt 14 is wound around the sprocket 11 and a sprocket 13 on a cam shaft 12 for driving a suction valve. A pair of adjust pulleys 15 and 16 functioning as a valve timing adjusting pulley are press-contacted with outer surfaces of a tight side (a) and a loose side (b) of the belt 14, respectively. The pulleys 15 and 16 are displaceable by a driving device including adjust levers 17 and 18 to which power of a step motor 23 is transmitted through a wire 22.
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