What is the working principle of the brake pump?
3 Answers
The working principle of the brake pump is that when the brake is pressed, the piston inside the master brake cylinder is subjected to the thrust from the brake pedal, which then acts through the push rod. Depending on the vehicle type, it is divided into two types: air brake master cylinder and hydraulic brake master cylinder. The following is an introduction: 1. Hydraulic brake master cylinder: When the brake is pressed, the piston inside the master brake cylinder is subjected to the thrust from the brake pedal, which then acts through the push rod, transmitting the brake fluid through the pipes to the pistons of each brake slave cylinder. This then pushes the brake shoes to expand outward, causing the brake pads to rub against the inner surface of the brake drum, thereby achieving the braking effect. 2. Pneumatic brake master cylinder: The working principle of the pneumatic brake master cylinder is actually not much different from that of the hydraulic brake master cylinder, both serving as valves. The difference is that after braking, the hydraulic brake master cylinder controls the brake fluid to flow back into the reservoir. Vehicles using air brakes are usually equipped with several relatively large air storage tanks, and after braking, the air is directly discharged, which explains why the exhaust sound of large trucks is so loud.
After running this auto repair shop for so many years, I know brake master cylinders inside out. Simply put, when you press the brake pedal, the connecting rod pushes the piston inside the master cylinder to compress the brake fluid. You can't just use any brake fluid – it must be specifically formulated to withstand high temperatures because once pressurized, it transmits force to each wheel's brake caliper. When the caliper receives hydraulic pressure, it pushes the brake pads to clamp the rotor, slowing the vehicle. The key is that the master cylinder is designed with two independent circuits: one controls the front wheels, the other the rear. If one side fails, you can still brake. Regular maintenance must include brake fluid checks – over time it absorbs moisture, lowering its boiling point and causing spongy brakes, which is especially dangerous when descending long mountain slopes.
I remember when I last replaced the brake discs on my own car, I specifically removed the brake pump. That thing looks small, but its structure is quite ingenious: when you press the pedal, the force is transmitted to the piston inside the pump, compressing the liquid. Utilizing the incompressible nature of the liquid, the pressure is precisely delivered to all four wheels. Why use hydraulics? This thing reacts quickly, and the force transmission doesn't lose any power. Modern cars are equipped with a dual-circuit system, with one set for each side, acting as a backup for each other. Once, during a long-distance self-drive trip, I encountered abnormal brake noises. Upon inspection, I found the fluid level was low, and luckily, I topped it up in time. I recommend everyone get into the habit of checking the brake fluid reservoir; if the color turns black or bubbles appear, it's time for a replacement.
