The master cylinder (Master Cylinder), also known as the brake main oil (air), its main function is to push the brake fluid (or gas) to be transmitted to each brake cylinder to push the piston.
The brake master cylinder is a one-way acting piston hydraulic cylinder, and its function is to convert the mechanical energy input by the pedal mechanism into hydraulic energy. There are two types of brake master cylinders, single-chamber and dual-chamber, which are respectively used in single-circuit and dual-circuit hydraulic braking systems.
In order to improve the driving safety of automobiles, according to the requirements of traffic regulations, the service braking system of automobiles now adopts a dual-circuit braking system, which is composed of a series of dual-chamber master cylinders (single-chamber brake master cylinders have been eliminated). dual-circuit hydraulic braking system.
At present, almost all of the dual-circuit hydraulic braking systems are servo braking systems or dynamic braking systems. However, in some miniature or light vehicles, in order to make the structure simple, and under the condition that the brake pedal force does not exceed the range of the driver's physical strength, there are also some models that use a tandem dual-chamber brake master cylinder to form a dual-circuit manual hydraulic brake. system.
Tandem double-chamber brake master cylinder structure
This type of brake master cylinder is used in a dual-circuit hydraulic brake system, which is equivalent to two single-chamber brake master cylinders connected in series.
The housing of the brake master cylinder is equipped with a front cylinder piston 7, a rear cylinder piston 12, a front cylinder spring 21 and a rear cylinder spring 18.
The front cylinder piston is sealed with a sealing ring 19; the rear cylinder piston is sealed with a sealing ring 16, and is positioned with a retaining ring 13. The two liquid reservoirs are respectively communicated with the front chamber B and the rear chamber A, and are communicated with the front and rear brake wheel cylinders through their respective oil outlet valves 3. The front cylinder piston is pushed by the hydraulic force of the rear cylinder piston, and the rear cylinder piston is directly driven by the push rod. 15 push.
When the brake master cylinder is not working, the piston head and the cup in the front and rear chambers are just located between the respective bypass holes 10 and compensation holes 11 . The elastic force of the return spring of the piston of the front cylinder is greater than that of the return spring of the piston of the rear cylinder to ensure that the two pistons are in the correct position when they are not working.
When braking, the driver steps on the brake pedal, the pedal force is transmitted to the push rod 15 through the transmission mechanism, and pushes the rear cylinder piston 12 to move forward. After the leather cup covers the bypass hole, the pressure in the rear cavity increases. Under the action of the hydraulic pressure in the rear chamber and the spring force of the rear cylinder, the piston 7 of the front cylinder moves forward, and the pressure in the front chamber also increases. When the brake pedal continues to be pressed down, the hydraulic pressure in the front and rear chambers continues to increase, making the front and rear brakes brake.
When the brake is released, the driver releases the brake pedal, under the action of the front and rear piston springs, the piston and push rod in the brake master cylinder return to the initial position, and the oil in the pipeline pushes open the oil return valve 22 and flows back The master cylinder is braked, so that the braking effect disappears.
If the circuit controlled by the front chamber fails, the front cylinder piston does not generate hydraulic pressure, but under the hydraulic force of the rear cylinder piston, the front cylinder piston is pushed to the front end, and the hydraulic pressure generated by the rear chamber can still make the rear wheel produce braking force. If the circuit controlled by the rear chamber fails, the rear chamber does not generate hydraulic pressure, but the rear cylinder piston moves forward under the action of the push rod, and contacts the front cylinder piston to push the front cylinder piston forward, and the front chamber can still generate Hydraulic pressure brakes the front wheels. It can be seen that when any set of pipelines in the dual-circuit hydraulic brake system fails, the brake master cylinder can still work, but the required pedal stroke is increased.
