| 摘要 |
A brake fluid pressure modulator (108) for an anti-lock braking system (ABS) (100) employs a combined isolation valve/displacement cylinder (130) to effect modulation of brake fluid pressure being delivered to a vehicle's wheel brakes (110F, 110R, 111F, 111R). A control valve assembly (140) reduces and reapplies brake fluid pressure by controlling flow of hydraulic fluid to a stepped piston (1315, 1317) in the displacement cylinder to move the piston against a biasing element (1321) such as a coil die spring. Piston movement against the spring closes an isolation check valve (1307, 1309) to prevent further brake fluid from the vehicle's master cylinder from being delivered to the wheel brakes. The cylinder cavity (1312) resulting from piston movement enables brake fluid to drain from the wheel brake back into the displacement cylinder. Reapplication of brake fluid is effected by allowing flow of hydraulic fluid out of the cylinder with the biasing spring moving the piston back to its idle position, thereby forcing brake fluid back to the wheel brake. The control valve assembly is electrically driven by a control computer (120) which also monitors vehicle wheel speed and cap-off brake pressure via appropriate transducers (112, 150).
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