| 摘要 |
<p>A modulator piston assembly (6) is of generally dumb-bell shape, consisting of a first modulator piston (7) and a second modulator piston (9) having an integral stem (10) carrying an isolation valve member (14) engageable with a seat (16) carried by the first piston (7). First, second and third modulator chambers (23, 24 and 41) respectively are bounded by the modulator piston assembly, such that on movement of the modulator piston assembly from its normal position the volumes of first and third chambers (23, 41) increase, and that of second chamber (24) decreases. A master cylinder (28) is connected permanently to the second chamber (24), and a wheel brake (25) to the first chamber (23), and a normally closed solenoid controlled dump valve (35, 36) is interposed between the master cylinder inlet (31) and the third chamber (41). On a skid signal the dump valve (35, 36) opens, and fluid flows from the second chamber (24) to the third chamber (41), isolation valve (14, 16) closes, and the first chamber (23) is expanded to relieve the wheel brake pressure. A pump piston (51) is arranged in association with one-way seals (42, 43) to pump fluid from the third chamber (41) back to the inlet of the dump valve (35, 36), and on cancellation of the skid signal thereby returns fluid from the third chamber (24). The pump piston on the Fig. 2 construction is remote from the modulator assembly and is connected thereto by only a single hydraulic line (56). <IMAGE></p> |
