| 1.Servise Brake Systems |
Q: What is the toxic substances in exhaust gas? |
| A1: There are two ways of braking wheel rotation, and three types of systems for transmitting braking power. |
 |
Drum brakes
When the brakes are applied, frictional material attached to the brake shoe is pressed against the drum. The resulting friction acts as a braking force that stops wheel rotation. |
 |
Disc brakes
The wheel has a disc attached to it that rotates with the wheel. Brake pads are mounted on both sides of the disc. These pads press against the disc to stop wheel rotation. |
| Three Systems for Transmitting Braking Power |
 |
Hydraulic Brakes
The force of pressing the brake pedal goes through the booster to the master cylinder. The transmitted force presses a piston against brake fluid in the master cylinder, raising the fluid's pressure (hydraulic pressure). This pressure is transmitted through brake lines to each wheel, where it acts to press the brake shoe against the drum. Light- and medium-duty trucks and small buses generally use hydraulic brakes. |
 |
Air-Over Hydraulic Brakes
A brake valve connected directly to the brake pedal releases compressed air stored in an air tank. This air is controlled by an air master. The rest of the mechanism is the same as that of hydraulic brakes. Medium- to heavy-duty trucks and medium buses generally use air-over hydraulic brakes. |
 |
Full Air Brakes
Pressing the brake pedal opens the brake valve, sending compressed air from the air tank into the brake chamber, where it presses a piston. The piston then presses the brake shoe against the drum. Heavy-duty trucks and tractors, and large busses generally employ full air brakes. |
| Full air brakes provide the most powerful braking. |
| With full air brakes, even an extremely light touch on the brake pedal provides strong braking power. |
| Full air brakes feature a simple line configuration because they do not use hydraulic power. |
|
|
|
