The brake system of a modern car was invented for more than 100 years and remained the same reliable and effective.
A typical call system of the call consists of disk brakes on the front and either disk or drum brakes on the rear wheels connected by the tubes and hoses of the submitted to each wheel. The brake system also includes a parking brake, vacuum amplifier and anti -lock system.
When you press the brake pedal, you actually press on the piston of the main cylinder, which pushes the brake liquid through a series of tubes and hoses in the brake cylinder on each wheel. It is very important that there are no air bubbles in the liquid. The air can be squeezed (unlike the liquid), which leads to loot on the brake pedals and greatly reduces the efficiency of braking. If you suspect the air that there is air in the system, you need to re -pump the brakes. For this, each cylinder has a “graduation screw”.
In disc brakes, brake fluid, from the main cylinder, pushes the piston under pressure. The piston, in turn, squeezes the cakes of the cheap pads on the brake disk, which is attached to the wheel, forcing it to slow down or stop.
In the drum brakes, the liquid is pumped into the brake cylinder, which pushes the brake pads so that the friction pads are pressed to the drum that is attached to the wheel, as a result of which the wheel stops.
In any case, the progressive movement of the car is converted into heat. Heat caused by friction of the surface of the pads, wear the pads over time and require replacement.
Let’s take a closer look at each of the components of the brake system and see where problems may arise ..
The main brake cylinder.
The main cylinder is located in the engine compartment, right in front of the driver’s seat. In the typical main cylinder, in fact, two completely separate main cylinders in one case, each for two wheels. Thus, if one of the parties does not slow down, you will still be able to stop the car. The signal bulb on the dashboard will light up if both sides are not operational, warning you about the problem. The main brake cylinder in modern cars has become very reliable and rarely fails, but the most common problem is, this is internal leaks. This will lead to the fact that when you press the brake pedal, it gradually fails. Letting go and pressing the pedal again, she returns to its original position.
Brake fluid is a special oil that has certain properties. She should withstand low temperatures without expansion, and also not boil at very high temperatures. (If the brake fluid boils, this will lead to the loose brakes and the car will be difficult to stop.) The brake fluid must comply with the standards established by the Ministry of Transport (DOT). Current DOT-3 standard, which has a boiling temperature of 460 º F.
The brake fluid tank is located at the top of the main cylinder. Most cars have a transparent reservoir, so you could see the level without opening the lid. When the brake pads are worn out, the brake fluid level will slight. This is a normal state, and there is no reason to concern. If the level drops markedly over a short period of time or decreases to two -thirds of the tank, you need to check your brakes as soon as possible. Always keep the tank closed, with the exception to fill it and never leave it open. Brake fluid should have a high boiling point. The effect of air will lead to the fact that the liquid will absorb moisture and the boiling temperature will be below. Never mix brake fluid with anything. This can lead to a sudden refusal of brakes! Any other type of oil or other fluid will respond with brake fluid and very quickly destroy rubber seals in the brake system by causing a brake failure.
Brake tubes and hoses.
The brake fluid passes from the main cylinder to the wheels through a row of steel tubes and brake rubber hoses. Rubber hoses are used only in places that require flexibility, for example, on the front wheels that move up and down, and also rotate. Otherwise, non -aggressive seamless steel tubes with hermetic compounds are used. If the steel gas pipeline requires repair, it is best to replace the pipe.
Other components of the brake system.
Brake force distributor.
The distributor is installed between the main cylinder and the rear wheels. It is designed to adjust the pressure between the front and rear brakes, depending on how sharp you stop. With sharp braking, the weight of the car is more transmitted to the front wheels.
The valve of the pressure difference.
This valve is usually installed directly under the main cylinder and warns when it detects a malfunction. He measures the pressure from the two sections of the main cylinder and compares them. If he discovers the difference, this means that, probably, somewhere in the system there is a leak of brake fluid.
Electronic system distribution systems. (EBD).
New cars use electronic brake distribution systems controlled by an on -board computer (EBD). These systems use dosing valves to distribute accurate pressure on each wheel to provide a balanced brake system.
Disk brakes are the best brake system so far. Disk brakes are used to stop everything from cars to locomotives and passenger airliners. Disk brakes last longer, less exposed to water, do not require tuning, self -cleaning and more effective than any other systems. The main components of disk brakes are brake pads, brake disk and caliper.
There are two brake pads on each caliper. They are made of Metal “Bashmak” and a friction mother Ala glued on it. The pads are installed in the caliper, one on each side of the brake disk. Brake linings were once made of asbestos due to its heat-absorbing properties and noiselessness, however, due to health risk, asbestos were prohibited, therefore new materials are currently being used. Brake pads consumables and periodically should be replaced. There are many different types and qualities of the pads. The differences are associated with the brake life (how long the new pads will last) and the noise (how quiet they are). Solid linings, as a rule, last longer and are better inhibited with intense movement, but they can irritably squeal. The brake pads should periodically be checked for wear. If the pads are worn out to the metal, then this can damage the brake disk and the braking efficiency will be lost. Some brake pads are delivered with a wear sensor that will warn you about the wear of the pads.
The brake disk is made of metal processed from the pads. Over time, the brake disk wear out. It forms risks. These risks can be stuck, but to a certain residual thickness of the brake disk. If the thickness of the disk is too thin, then it will quickly heat up, losing the efficiency of braking.
The Lindrian floating calipers are the most popular, as well as the least expensive for production and maintenance. The floating caliper “floats”, constantly holding the brake disk in the center between the blocks. As soon as the pressure in the brake system occurs, the hydraulic fluid pushes the caliper in two directions. The brake fluid presses on the piston, which presses on the inner block, which in turn presses on the brake disk. It also pushes the caliper in the opposite direction in relation to the outer site, pressing it to the other side of the brake disk. Swimming calipers, on some cars, are installed with two pistons installed on one side. Double -piston floating calipers are placed on more expensive cars and they provide improved brake qualities. Four piston calipers are installed hard and cannot move. Instead, two pistons are pressed on the pads on each side. Four piston calipers are the most effective, but more expensive in production and are more expensive in maintenance. This type of caliper is usually found on more expensive luxurious cars.
If disc brakes are so good, then why do we still use cars with drum brakes? The reason is the cost. Although all cars have disk brakes in front, but still it is cheaper to produce drum brakes for rear wheels. The main reason is the parking brake system. On drum brakes, to have a parking brake, you just need to add a lever, while on disc brakes, we must completely change the parking brake mechanism should be a separate system that does not use hydraulics. It should be completely mechanical, but more about the parking brake later.
Drum brakes consist of a support disk, brake pads, brake drum, brake cylinder, return springs and a self -regulating system. When braking, the brake fluid under pressure enters the brake cylinder, which, in turn, pushes the brake pads in contact with the surface on the inside of the drum. When there is no pressure, return springs pull the pads back to its original position. With wear of brake linings, the gap between the blocks and the drum increases. When the gap reaches a certain value, the self -regulating system will automatically adjust the gap.
Drum brake pads.
Drum brake pads consist of steel shoe and an overlap of friction material glued or stained on it. In addition, as well as disk pads, the pads wear out over time and must be replaced. If the pads are worn to bare metal, they can cause serious damage to the brake drum.
The supporting disk is what holds all together. He is attached to the back beam. He rarely causes any problem.
Brake drums are made of iron and have a treated surface from the inside. Just like brake discs, brake drums wear out over time. When the brake drum reaches the maximum diameter, which is placed on the stamp on the outside of the drum, the drum should be replaced.
Wheel brake cylinders.
The brake cylinder consists of a cylinder with two pistons, one on each side. Each piston has a rubber seal and a shaft that connects the piston with the brake block. Когда создается давление в тормозной системе, поршни вытесняются толкая колодку в барабан. Brake cylinders should be restored or replaced at the first signs of leakage.
Return springs pull the brake pads back to its original position after the pressure in the brake cylinder falls. If the springs are weak and do not return the pads, this will lead to the premature wear of the drum, since the pads will remain in contact.
Self -regulating system.
The adjustment system should be clean and freely move. If the regulators themselves stop working, you will notice that you will have to press more and more on the brake pedal before you feel that the car begins to stop.
The parking brake (a lot of emergency braking) system for monitoring the rear brakes through a series of steel cables, which are connected either by a handbrake or foot pedal. The idea is that the system is completely mechanical and completely bypasses the hydraulic system in order for the vehicle to stop, even with a complete refusal of brakes.
On drum brakes, the cable is associated with the lever installed in the rear brake and is directly related to brakes. This has the effect of bypassing the brake cylinder and brake control directly. Disk brakes on the rear wheels have additional difficulties for parking brake systems. There are two main designs to add a mechanical parking brake on the rear disc brakes. The first type uses the existing rear wheel caliper and adds the lever attached to the mechanical device, the corner inside the piston of the caliper. When the parking brake cable pulls the lever, this corkscrew pushes the piston until it stops the block, thereby bypassing the hydraulic system to stop the vehicle. This type of system is used mainly with a single -piston floating caliper if the caliper has four fixed pistons, then that the type of system cannot be used. Another system uses the full mechanical design of the brake drum installed inside the rear brake disk. The brake pads are attached to the lever that pulls the parking brake cable to activate the brakes. Brake “drum” in fact the inside of the rear brake disk.
On cars with an automatic gearbox, the parking brake is rarely used.
The largest parking brake problem is that the cables of the handbrake, as a rule, are rusty and intended to the casing tightly. When trying to pull the handbrake, the cable breaks. With regular use of the parking brake, the cables remain clean and functional.
Vacuum brake amplifier.
The vacuum brake amplifier is installed behind the main cylinder and, together with the main cylinder, is directly related to the brake pedal. Its goal is to enhance the existing pressure pressure. Additional effort is provided by a vacuum that is formed in the engine during normal operation. The vacuum enters the check valve on the vacuum amplifier. The check valve is connected to the engine with a rubber hose and acts as a unilateral valve, which allows the vacuum to go into the tank and hold the vacuum inside. Tank, an empty shell, which is divided into two chambers with a rubber diaphragm. There are valves in the diaphragm that remain open if the brakes are not used, so the vacuum is filled in both cells. When you press the brake pedal, the valve is closed by a diaphragm separating two chambers, and the other valve opens, letting the air into the chamber from the side of the brake pedal. This provides additional power. Vacuum amplifier is very reliable. However, in order for the amplifier to work, the engine must be launched. If the engine stalls or turns off while driving, you will have a small power supply for two or three braking, but after that, the brake will be extremely difficult to apply.
The most effective braking takes place just before the wheel lock. With a strong press on the pedal, the brakes are blocked, causing a screech and leaving strips of rubber on the asphalt, but the braking distance will still be large.
The anti -blocking brake system solves this problem by rapid fluid pumping when the system detects a locked wheel. This effect allows you to stop blocking in the shortest possible time, while maintaining the full control of the steering even if one or more wheels on ice. The system uses a computer to control the speed of each wheel. When he discovers that one or more wheels stopped rotating or rotating much more slowly than the rest of the wheels, the computer instantly sends a signal to discard the pressure so that they can continue to rotate. These “pumping” brakes occur ten or more times per second, much faster than a person can pump the brakes manually. If you step on the brakes enough, you can feel strong vibration in the brake pedal. This is a normal state and indicates that the system works. If your car has an anti -lock brake system, check out the user guide to learn more about it.
The system consists of an electronic control unit, hydraulic drive and wheel speeds on each wheel. If the control unit detects a failure in the system, the ABS bulb on the dashboard will burn so that you know that there is a problem.