| 摘要 |
<p>An ABS modulator solenoid valve (10), having one electric solenoid (12), in which the valve control piston (14) has a passage (16) therethrough for balancing the pneumatic pressure on both ends (34, 36) of the control piston (14). One end (34) of the piston (14) is disposed in a closed piston chamber (32) while the other end (36) is positioned to contact and position a valve spool (40). The passage (16) extends between the ends (34, 36) of the piston (14). Piston (14) is biased by a spring (50) to a position within the piston chamber (32). When the solenoid (12) is de-energized, the piston (14) remains in this position and variable air pressure, from an operator controlled brake valve (126), can be supplied through the valve (10) to a brake chamber (128) for operating the vehicle service brakes. During an ABS application, the solenoid (12) is energized to overcome the inlet spring (50) bias and the piston (14) moves into engagement with the valve spool (40). The spool (40) is biased by an exhaust spring (52) to a position wherein the exhaust port (24) is isolated from the supply port (20) and the delivery port (22). When the solenoid (12) is fully energized, the piston (14) engages the spool (40) and moves it to the exhaust position. When the solenoid is energized with a selected hold current, the piston (14) engages but does not move the spool (40) and the valve (10) is then in a hold position. Since the pressure on the ends (34, 36) of the piston (14) is balanced, the force required to move the piston (14) to the hold position is relatively constant and not greatly effected by the pneumatic pressure at the supply port (20) or the delivery port (22).</p> |
