To determine the intensified pressure gradient of a brake cylinder by providing a pressure intensifier determining the intensified pressure gradient of the brake cylinder based on the length of condition formation required time from starting time of a brake operation till an intensified pressure control starting condition is formed.
Time when a booster 12 reaches a boosting limit is detected by a booster pressure switch 304. Pressure-change chamber pressure to be pressure of a pressure-change chamber 12d in the booster 12 in a negative pressure state at the height which is equal to pressure of a negative pressure chamber 12c before a brake operation is started but rises according to advancing of the brake operation. When the pressure-change chamber pressure reaches atmospheric pressure, the booster 12 reaches the boosting limit. Also time from the starting time of the brake operation up to time when pressure-change chamber pressure reaches atmospheric pressure becomes shorter at a quick brake operation than that at a normal brake operation. The intensified pressure gradient at the time of starting an intensified pressure control is determined for the gradient according to the brake operation. Thus, the intensified pressure gradient can kept almost constant before and after the intensified pressure control.
SAKAMOTO SHIGERU
ISONO HIROSHI
