APPARATUS FOR PROTECTING SLIPPING OF VEHICLE IN SLOPE

摘要

A roll back preventing of a vehicle is provided to operate on an uphill regardless of power transmission methods by using a variable orifice and to prevent braking pressure of a brake caliper from being suddenly released by keeping brake hydraulic pressure of a wheel cylinder as critical pressure of a relief valve. A roll back preventing device(50) of a vehicle installed at a brake hydraulic circuit(30a,30b) connecting a master cylinder(31) and a wheel cylinder(33) to apply the brake hydraulic pressure in the wheel cylinder although a brake pedal(15) is released is composed of a solenoid valve(51) for cutting off the brake hydraulic circuit; a relief valve(55) for reducing the brake hydraulic pressure of the wheel cylinder down to predetermined pressure by releasing the brake pedal, if brake hydraulic pressure over a predetermined value is generated while the brake hydraulic circuit is cut off; a variable orifice(57) for variably reducing braking power of the wheel cylinder by permitting the flow of brake fluid toward the master cylinder after releasing the brake pedal; and a fixed orifice(59) for reducing brake hydraulic pressure flowing in the relief valve. The solenoid valve, the relief valve, and the variable orifice are coupled in parallel to the brake hydraulic circuit. The fixed orifice is connected in series with the relief valve.