| 摘要 |
<p>A hydraulic power brake valve 6 controls the supply of fluid from an accumulator 58 via chamber 75 and line 76 to working chambers 52, 53 behind master cylinder pistons 23, 43. Excessive movement of the valve spool 36 is prevented by a blocking arrangement 81. This comprises a piston 72 which is moved to the left by pressure (e.g. 100 bar) in chamber 75, so raising ball 71 to obstruct the spool 36. On failure of the pressure source, this movement is not obstructed, and the pedal 51 can move to the left to operate the pistons 23, 43 without power assistance. Loss of accumulator pressure results in piston 28 moving to the right, holding valve 62 closed so creating a hydraulic lock in chamber 63, so that the piston 43 moves with the input rod 42. <IMAGE></p> |
