Abstract: In a vehicle brake system including a pneumatic force multiplier apparatus in which a power piston moves by virtue of a pressure difference between atmospheric and negative pressure, a manual brake switch is provided to apply braking force without need for depressing the brake pedal. A controller includes a deceleration calculating circuit reading vehicle speed for every specified number of seconds and calculating the amount of deceleration. The deceleration is compared with a predetermined value and braking force is increased, maintained, or decreased depending on whether the vehicle is running on a downwardly sloping, level, or unwardly sloping road.

Abstract: A pneumatic servo booster including a housing, a power piston unit partitioning the interior of the housing into front and rear chambers and having therein a first passage with one end opening to the front chamber and the other end opening to the interior of the power piston unit and a second passage with one end opening to the rear chamber and the other end opening to the interior of the power piston unit, and a valve mechanism provided in the interior of the power piston unit and being associated with an input rod to control the communication between first and second passages and between the second passage and another passage which is communicated with a source of a first reference pressure. A plurality of diversion channels are provided in at least one of the first and second passages to decrease the speed of the air flow in the passage and to rectify the air flow thereby suppressing noise.

Abstract: A pneumatic booster includes a housing, a power piston and flexible diaphragm assembly partitioning the interior of the housing into two chambers, a poppet valve mechanism for selectively connecting or disconnecting communication between the two chambers and disconnecting or connecting communication between one of the chambers and a reference pressure, an input rod for actuating the poppet valve mechanism and an output rod connected to the power piston. The poppet valve mechanism includes a plunger connected to the inner end of the input rod, a valve member, a valve body having an axial bore therein for slidably receiving the plunger, and a restricting member mounted on the plunger for restricting the relative axial displacement of the plunger and the valve body. A resilient member is interposed between the restricting member and the valve body to avoid impacting abutment between the restricting member and the valve body.

Abstract: A pneumatic servo booster includes a shell housing consisting of front and rear shells, a valve body slidably extending through an opening formed in the rear shell, a flexible diaphragm connected to the valve body and to the inner circumference of the shell housing to divide the interior of the housing into front and rear chambers, a valve mechanism incorporated in the valve body for controlling the pressure difference between the two chambers, and at least one reinforcing rod extending between front and rear shells and through the two chambers. The valve mechanism comprises a plunger slidably received in the valve body and connected to an input rod, a valve seat formed on the valve body, another valve seat formed on the plunger, and a poppet valve cooperating with the valve seats. A return movement restricting member is slidably mounted on the reinforcing rod and restricts the return movement of the plunger, thereby establishing the rearmost position of the plunger.