Another popular type of braking devices is the hydraulic brake. This brake arrangement uses brake fluid to transfer pressure to the actual brake mechanism from the controlling unit. The actual brake mechanism is usually near or at the wheel of the vehicle. The controlling unit usually near the vehicle operator. The brake fluid usually contains ethylene glycol.
For passenger vehicles, the most usual arrangement of braking mechanism consists of a brake rotor or drum, a master cylinder, a slave cylinder, hydraulic lines, a brake pedal, and a vacuum assist module. In typical passenger vehicles, drum brakes on the rear wheels and disc brakes on the front wheels are employed. However, today, four wheel disc brakes are getting more and more popular.
Functionality of a Hydraulic Brake
The hydraulic brake works in an ingenious way. When the pedal is depressed, the force applied to a vacuum booster from the pedal is multiplied by leverage. The force is multiplied again this time by the booster and acts upon a booster found in the master cylinder. As this multiplied force is applied to the piston, the pressure in the hydraulic system increases. This forces the fluid to the slave cylinders through the hydraulic lines.
There are two common arrangements of slave cylinders. Disk brakes use a single piston which is forced out of its housing. Drum brakes use two opposed pistons which are forced apart by the fluid pressure.
The pistons in the slave cylinders then apply force to the linings of the brake. It is usually referred to as pads for disc brakes and shoes for drum brakes. This force applied to the brake linings cause them to be pushed against the rotors and drums. It creates friction between the rotors or drums and the linings which causes a braking torque to be generated. This makes the vehicle slow down or stop.