What is the Brake Systems?


The brake system consists of the following components.

1. Brake pedal

2. Brake booster

3. Master cylinder

4. Proportioning valve (P valve)

5. Foot brake

(1) Disc brake

(2) Drum brake

6. Parking brake

The master cylinder is a device that converts the operation force applied by the brake pedal into hydraulic pressure. Currently, the tandem master cylinder, which includes two pistons, generate hydraulic pressure in two-systems brake line. The hydraulic pressure is then applied to the disc brake calipers or the wheel cylinders of the drum brakes. The reservoir serves to absorb changes in the brake fluid volume caused by changes in fluid temperature. Also, it has a separator inside that divides the tank into front and rear parts as shown in the left. The twopart design of the tank ensures that if one circuit fails due to fluid leakage, the other circuit will still be available to stop the vehicle. The fluid level sensor detects when the fluid level in the reservoir tank falls below the minimum level and then uses the brake system warning light to warn the driver.

2. Construction

The master cylinder consists of the following components.

(1) No.1 piston

(2) No.1 return spring

(3) No.2 piston

(4) No.2 return spring

(5) Rubber piston cups

(6) Reservoir tank

(7) Fluid level sensor

3. Principles

When the brake pedal is depressed, the master cylinder converts this force into hydraulic pressure. Brake pedal operation is based on the principle of the lever, and converting a small pedal force into a large force acting on the master cylinder. Based on Pascal’s law, the hydraulic force generated in the master cylinder is transmitted via brake line to individual wheel cylinders. It acts on brake linings and disc brake pads to generate a braking force. According to Pascal’s law, externally applied pressure upon a confined fluid is transmitted uniformly in all directions. Applying this principle to a hydraulic circuit in a brake system, the pressure generated in the master cylinder is transmitted equally to all wheel cylinders. The braking force varies, as shown in the left, depending on the diameter of the wheel cylinders. If a vehicle design requires a larger braking force at the front wheels, for example, the designer will specify larger wheel cylinders for the front.

4. Types of brake lines

If the brake line is cracked and the brake fluid leaks out, the brakes will no longer work. For this reason, the brake hydraulics are divided into two-systems brake line. The hydraulic pressure sent to the two systems from the master cylinder is transmitted to the disc brake calipers or wheel cylinders. The brake line layout differs between FR vehicles and FF vehicles. In FR vehicles the brake lines are divided in to a front wheel system and rear wheel system, but in FF vehicles diagonal piping is used. Because the load applied to the front in FF vehicles is large, a higher braking force is used for the front wheels than for the rear wheels. For this reason, if the same brake line systems used for FR vehicles are used in FF vehicles, the braking force will be too weak if the front wheel braking system fails, so a diagonal pipe line system for the front right wheel and rear left wheel and one for the front left wheel and rear right wheel are used so that if one system fails, the other system will maintain a certain degree of braking force.

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