POWER BRAKE UNIT CONSTRUCTION/OPERATION
id041100181100
Construction
• The construction of the brake assist (dual servo ratio) mechanism-equipped power brake unit is fundamentally the same as a conventional power brake unit except that there is a depression in the contacting surface of the plunger plate of the plunger.
Operation
During normal braking
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• During normal braking, only the flat surface area of the valve body contacts the reaction disc to transmit braking force.
During brake assist operation
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• During emergency braking when there is increased input to the brake pedal of a force greater than that during normal braking, the reaction disc deforms in accordance with the displacement of the concave ring of the valve body. When this occurs, the surface area of the valve body contacting the reaction disc increases in comparison to normal braking resulting in a larger servo ratio compared to normal braking. As a result, the dual servo ratio mechanism is actuated and transmits a greater than normal amount of brake force.
