Abstract: In an emergency brake system for a vehicle having a brake booster to increase braking pressure applied to wheel brake cylinders from a master cylinder, a cut-off valve is provided within an exhaust pipe of an internal combustion engine for the vehicle and operatively connected to a manual shift lever, and a selector valve is disposed within a communication passage connecting a servo-chamber of the brake booster to an upstream of the cut-off valve in such a manner that the servo-chamber is normally communicated to a source of pneumatic pressure in response to operation of the master cylinder. The cut-off valve is normally opened when the shift lever is in a first position and is closed upon shifting the lever to a second position from the first position to create back pressure acting on the engine. The selector valve is switched-over upon shifting the lever to the second position to apply the back pressure from the exhaust pipe into the servo-chamber through the communication passage.

Abstract: A pneumatically operated brake booster comprises a hydraulic cylinder disposed within a hydraulic braking circuit connecting a master cylinder to wheel brake cylinders to increase the braking pressure trapped within the wheel brake cylinders and a servomotor for pneumatically activating the hydraulic cylinder in response to hydraulic pressure from the master cylinder. The servomotor has a spring loaded diaphgragm piston forming a negative pressure chamber and a variable pressure chamber, the former being in connection to a source of negative pressure and the latter being connected to the atmospheric pressure in response to master cylinder pressure applied to the hydraulic cylinder. The brake booster includes a control valve which is provided to selectively connect the variable pressure chamber of the servomotor to such a positive pressure source as exhaust pressure to obtain additional pressure in an emergent braking operation of the vehicle.

Abstract: Disclosed is a hydraulic brake system for vehicles having a separated-type hydraulic fluid pressure amplifier, such as a hydraulic air servo or a hydraulic vacuum servo. This hydraulic brake system includes a brake master cylinder and said fluid pressure amplifier comprises a hydraulic piston and a control piston, which are moved by the pressure of working fluid from said master cylinder, and a power piston which is moved by the air pressure introduced by the action of the control piston. This hydraulic brake system further includes means for resiliently expanding a fluid passage provided in a part of the hydraulic passage between the brake master cylinder and the portion of the hydraulic fluid pressure amplifier in which the working fluid from the master cylinder is applied to said hydraulic piston and said control piston.

Abstract: In a pneumatic brake booster, positive and variable pressure chambers on opposite sides of a spring loaded diaphragm piston both communicate with an air pressure source under inoperative condition of the booster; only the positive pressure chamber communicates with the air pressure source while the variable pressure chamber communicates with atmospheric pressure in response to activation of the booster to operate the piston.

Abstract: An engine brake control system comprises a cut-off valve disposed within an exhaust pipe of an internal combustion engine to block the exhausted gas flowing through the pipe and a vacuum motor having a spring loaded diaphragm piston operatively connected to the cut-off valve to close the valve in response to release of an accelerator pedal. In the vacuum motor, first and second chambers facing to the diaphragm piston are communicated with a vacuum source to open the valve during depression of the accelerator pedal in such a manner that only the second chamber is communicated with the atmospheric pressure in response to release of the accelerator pedal to swiftly operate the piston.

Abstract: A negative pressure generating system for an internal combustion engine powered vehicle, comprising a brake booster incorporated in the vehicle and adapted for an increase in braking power, an air cleaner for cleaning air to be supplied to the internal combustion engine, an air pump which receives air from said air cleaner and delivers the air to said internal combustion engine, and a valve disposed among said brake booster, said air cleaner and said air pump and operative in response to the booster pressure in said brake booster on receiving said pressure as an input signal, thereby interrupting air communication between said air pump and said air cleaner, with the result that the negative pressure arising on the suction side of said air pump is used as a negative pressure source for operating said brake booster.