NEGATIVE PRESSURE DOUBLING DEVICE

摘要

In the negative pressure doubling device of the invention, a threshold line is set for starting a BA operation at a pedal stepping speed not less than a set speed, and the inclination of the threshold line is set equal to that for a servo ratio (SR2) smaller than a servo ratio (SR1) for normal brake operation in a low input region (small pedal stepping force region), while in a high input region (large pedal stepping force region) it is set equal to the size of a servo ratio (SR1) during normal brake operation. That is, the threshold line for starting the BA operation is adjustable for low input and high input. And even if the brake pedal is stepped at a stepping speed not less than the set speed in spite of not being in an emergency, the BA operation is not performed; thus, unnecessary BA operation is prevented. In an emergency and when the brake pedal is stepped at a stepping speed not less than the set speed and with more than a set stepping force, the BA operation is performed.