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1、Automobile Brake System The braking system is the most important system in cars. If the brakes fail, the result can be disastrous. Brakes are actually energy conversion devices, which convert the kinetic energy (momentum) of the vehicle into thermal energy ( stepping on the brakes, the driver comman
2、ds a stopping force ten times as powerful as the force that puts the car in motion. The braking system can exert thousands of pounds of pressure on each of the four brakes. Two complete independent braking systems are used on the car. They are the service brake and the parking brake. The service bra
3、ke acts to slow, stop, or a separate parking brake foot pedal or extreme conditions, fills the system. “Shoes ” and “pads” are pushed by the slave cylinders to contact the “drums ” and “rotors ” thus causing drag, which ( front and either disk or drum brakes in the rear connected by a system of tube
4、s and brakes. When the driver applies the brake, the control device forces brake shoes, or pads, against the rotating brake drum or disks at wheel. Friction between the shoes or pads and the drums or disks then slows or stops the wheel so that the car is braked. In most modern brake systems (see Fig
5、ure 15.1), there is a fluid-filled cylinder, called master cylinder, which contains two separate sections, there is a piston in each section and both pistons are connected to a brake pedal in the drivers compartment. When the brake is pushed down, brake fluid is sent from the master cylinder to the
6、wheels. At the wheels, the fluid pushes shoes, or pads, against revolving drums or disks. The friction between the stationary shoes, or pads, and the revolving drums or disks slows and stops them. This slows or stops the revolving wheels, which, in turn, slow or stop the car. The brake fluid reservo
7、ir is on top of the master cylinder. Most cars today see the level without opening the cover. The brake fluid level will drop slightly as the brake pads wear. This is a normal condition and no cause for concern. If the level drops noticeably over ashort period of time or goes down to about two third
8、s full, as possible. Keep the reservoir covered except for the amount of time you need to fill it and never leave a cam of brake fluid uncovered. Brake fluid must maintain a very places that require flexibility, such as at the front wheels, which move up and down as well as steer. The rest of the sy
9、stem uses non-corrosive seamless steel tubing with special fittings at all attachment points. If a steel line requires a repair, the best procedure is to replace the compete line. If this is not practical, a line can be repaired using special splice fittings that are made for brake system repair. Yo
10、u must never use copper tubing to repair a brake system. They are dangerous and illegal. Drum brakes, it consists of the brake drum, an expander, pull back springs, a stationary back plate, two shoes with friction linings, and anchor pins. The stationary back plate is secured to the flange of the ax
11、le the wheel the inner surface of the drum and the shoe lining. To apply brakes, the driver pushes pedal, the expander expands the shoes and presses them to the drum. Friction between the brake drum and the friction linings brakes the wheels and the vehicle stops. To release brakes, the driver relea
12、se the pedal, the pull back spring retracts the shoes thus permitting free rotation of the wheels. Disk brakes, it each side of the disk. The shoes squeeze the rotatin g disk to stop the car. Fluid from the master cylinder forces the pistons to move in, toward the disk. This action pushes the fricti
13、on pads tightly against the disk. The friction between the shoes and disk slows and stops it. This provides the braking action. Pistons are made of either plastic or metal. There are three general types of disk brakes. They are the floating-caliper type, the fixed-caliper type, and the sliding-calip
14、er type. Floating-caliper and sliding-caliper disk brakes use a single piston. Fixed-caliper disk brakes the parking brakes fitted in all automobile. When the brake pedal is depressed, the rod pushes the piston of brake master cylinder which presses the fluid. The fluid flows through the pipelines t
15、o the power brake unit and then to the wheel cylinder. The fluid pressure expands the cylinder pistons thus pressing the shoes to the drum or disk. If the pedal is released, the piston returns to the initialposition, the pull back springs retract the shoes, the fluid is forced back to the master cyl
16、inder and braking ceases. The primary purpose of the parking brake is to a separate parking braking the car the “on” position. The car may now be left without fear of its rolling away. When the driver wants to move the car again, before the lever can be released. The the event of the foot brake failing. For this reason, it is separate from the foot brake uses cable or rods instead of the slippery pavement or during a panic
