What is the working principle of the brake master valve foot brake valve?

The brake master valve foot brake valve, referred to as the foot brake valve, is one of the core components of a vehicle's hydraulic braking system. It is located inside the cab and connected to the brake pedal. By pressing the brake pedal, the driver operates the foot brake valve. The primary function of the foot brake valve is to adjust and control the hydraulic pressure in the braking system according to the driver’s braking demand, thereby controlling the braking force of the wheel brakes to achieve vehicle deceleration or stopping.

When the vehicle is not in a braking operation, the brake master valve foot brake valve is in its initial state. The seals inside the valve body isolate the brake fluid lines, and the brake fluid remains stationary, causing no braking force on the wheel brakes. When the driver presses down on the brake pedal, the pedal transmits force through the lever mechanism to the piston of the foot brake valve. Under the force, the piston moves downward, compressing the internal return spring, while simultaneously pushing the valve core downward against the spring force. As the valve core moves downward, the brake fluid lines that were initially isolated by the seals gradually open, allowing brake fluid to flow from the master cylinder to the wheel brakes.

As the brake fluid flows through the lines, it encounters resistance from the lines and friction within the wheel brakes, resulting in some pressure loss. To maintain a stable flow of brake fluid and sufficient braking force, the foot brake valve is equipped with a pressure regulating mechanism that can adjust the brake fluid pressure as needed. By adjusting the degree of opening of the brake fluid lines and the internal pressure regulating mechanism, the foot brake valve controls the braking force of the wheel brakes.

When the driver presses down on the brake pedal, the foot brake valve quickly opens the brake fluid lines, allowing brake fluid to rapidly flow into the wheel brakes and generate adequate braking force. As the brake pedal continues to be pressed, the foot brake valve further increases the flow and pressure of the brake fluid to meet greater braking demands. When the driver releases the brake pedal, the foot brake valve quickly resets under the action of the return spring. The valve core and piston return to their initial positions, the brake fluid lines are resealed by the seals, the brake fluid stops flowing, and the wheel brakes gradually release the braking force under the action of their return springs, allowing the vehicle to resume its driving state.