When the brake pedal is depressed, the push rod pushes the master cylinder piston forward. After the oil cup covers the oil return hole, the oil pressure in the front chamber of the piston increases, the oil outlet valve in the middle of the compound valve is pressed open, and the oil passes through the pipe The road flows to the wheel cylinders of each brake wheel. The oil pushes the cylinder piston to overcome the tension of the brake shoe return spring and push the brake shoe away. The shoe plate presses the brake drum to produce a braking effect.
When the driver depresses the brake pedal and stays still, the oil pressure in the front chamber of the master cylinder and the cylinder cylinder no longer increases, the oil outlet valve is closed by the spring, the oil return valve is also closed, and the compound valve is in In the double-closed state, the master cylinder no longer supplies oil to the wheel cylinder, the oil in the cylinder cannot return, the entire pipeline is at equal pressure, and the brake system maintains a certain braking intensity.
When the brake pedal is released, under the action of the pedal return spring and the piston return spring, the master cylinder piston retreats, the oil pressure in the front working chamber of the master cylinder decreases, and the high pressure oil in the cylinder cylinder opens the double valve. The oil valve flows back to the front chamber of the master cylinder. As the brake fluid flows back, the brake shoes are closed under the tension of the return spring, and the braking state is released. Since the return spring of the master cylinder piston has a certain pre-pressure in the assembled state, when the oil return pressure drops to the point where the pre-pressure cannot be overcome, the oil return valve is closed and the brake fluid stops flowing back, so the pipeline and the sub-pump The oil pressure in the cylinder is about 0.5 kg / cm2 higher than the oil pressure in the cylinder of the master cylinder. This is the so-called residual pressure in the cylinder and the pipeline. This residual pressure can provide conditions for the rapid realization of the next braking.
When the brake pedal is quickly released, the master cylinder piston quickly retreats under the action of the return spring, the volume of the front working chamber of the master cylinder expands, and the oil pressure decreases rapidly. The oil in each cylinder is affected by the resistance of the pipeline, and it is too late Back and fill the front working chamber of the piston, negative pressure will appear in the working chamber before the piston, and the oil pressure in the working chamber behind the piston is relatively high. Under the effect of this pressure difference, the oil in the liquid storage chamber will flow through the large hole of the liquid inlet, the rear chamber of the piston, and the six small holes at the top of the piston, over the edge of the leather cup, and flow into the front working chamber of the piston. At this time, when the brake pedal is depressed again, brake fluid will be supplied to the cylinder cylinders to enhance the braking efficiency. When you brake on one foot and feel the braking force is insufficient, the two-foot brake will take effect.