| 摘要 |
A belt continuously variable transmission driven 22 pulley comprises forward sheave 42 and rear sheave 40 axially displacable by motor 170 and worm 171 driven axial screw 154, pressure plate 152, pins 149 and bearing plate 148. The screw reacts against split nut 158 comprising segments spring biassed apart and axially fixed within nut holder 159. In event of motor power failure, solenoid 180 releases and return spring 187 withdraws finger holder 185 and fingers 186 from surrounding the split nut which separates, releasing the screw. If the current ratio is less than a failsafe value e.g. 1:1 belt tension separates the sheaves; if greater spring 190 biasses the sheaves towards each other to achieve failsafe ratio. Driving pulley (20 Fig 3) belt tensioner has sheaves (28,30) biassed together by pivotable centrifugal arm (101) and non-linear spring (80) and cam arm arrangement.
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