| 摘要 |
PURPOSE:To make a hydraulic servo small in size wherein a plurality of driving ratios are obtained between input and output axes by causig a plurality of frictional engageable apparatuses to be selectively engaged, by adopting in one of the frictionally engageable apparatuses a band brake that is operated by a hydraulic servo having a special structure. CONSTITUTION:In an automobile automatic transmission with three forward gears and one reverse gear, a desired speed change operation is obtained by selectively engaging clutches 28, 30 and brakes 42, 56. In this case, for the brake 42 the band brake 42 wherein a brake band 64 is arranged on the outer circumference of a brake drum 62 is adopted which is operated and controlled by the hydraulic servo 56. The hydraulic servo 56 includes a piston 58 of which rod 60 engages with an engaging part 66 of the brake band 64, and the piston 58 has pressure receiving surfaces 88, 94 on the brake operating side and a pressure receiving surface 68 on the brake releasing side. A hydraulic oil is suitably introduced independently into the pressure receiving surfaces 68, 88, 94 from oil paths 74, 92, 98. |
