| 摘要 |
A hydraulic brake booster is disclosed which includes an integral accumulator to provide fluid pressure source for emergency failsafe braking. The accumulator includes a bore defined within the booster housing, and a piston slidably mounted in the bore which divides the latter into a pair of fluid compartments between opposite ends of the piston and corresponding ends of the bore. One of the compartments is communicated to the booster inlet port so that the compartment is charged with fluid pressure whenever the pressure level at the inlet port is above some predetermined low value. In one embodiment of the invention, the other compartment is communicated to the fluid pressure reservoir, and a relief valve is carried within the piston which controls flow of fluid between the two compartments. In the other embodiment of the invention, the relief valve is installed in the passage communicating the inlet port to the one compartment, so that when the fluid pressure level in the one compartment reaches a predetermined value, the one compartment is vented to the inlet port. Therefore, when the pressure level in the one compartment reaches some predetermined, relaively high value, the relief valve opens to vent the one compartment, thereby limiting the pressure level in the one compartment to the predetermined level. When a failure occurs in the primary pressure source which normally operates the booster, comunication between the pressure chamber and the one compartment is opened, to use the fluid pressure content of the latter to operate the booster.
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