| 摘要 |
PROBLEM TO BE SOLVED: To provide a bicycle provided with an automatic elastic change type crank mechanism wherein the turning radius of a pedal is small in a cruising operation mode, and the turning radius of the pedal is automatically expanded corresponding to drag, and large angular moment is obtained in an operation mode with a heavy load. SOLUTION: A crankshaft 10 is inserted in a hollow shaft 30, and a double shaft structure is rotatably supported to a frame 40 of a bicycle 1. An elastic change type crank A is fixed to the crankshaft 10, and a sprocket gear 31 is fixed to the hollow shaft 30. A spring member 11 is provided between the crankshaft 10 and the sprocket gear 31 directly or indirectly and energized in a direction in which the linear dimension of the crank A, i.e., the turning radius of a pedal 12 is reduced. The length of the crank A is elongated when the pedal 12 is stepped on with a force overcoming a load and contracted when a stepping force disappears. COPYRIGHT: (C)2004,JPO
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