SPOOL VALVE FOR HYDRAULIC BRAKE BOOSTER

摘要

A hydraulic brake booster is disclosed for use in a vehicle hydraulic braking system. The booster provides a spool valve having spaced lands and grooves cooperating with corresponding lands and grooves on the booster housing to control communication between an inlet port, an outlet port, an exhaust port, and the booster pressure chamber. The spool valve has an internal passage which communicates the booster pressure chamber to one of the aforementioned ports depending upon the position of the spool valve. A check valve is provided in a branch passage communicating with the groove communicated with the booster inlet port so that the pressure level in the pressure chamber never exceeds the pressure level at the inlet regardless of the position of the spool valve. This feature enhances spool stability.