Commercial vehicles (trucks and buses) are predominantly equipped with air brakes. This unit has many differences from hydraulics. One of its distinguishing features is the operation of the parking brake. The main component of the parking system is the energy accumulator (there is a photo of the mechanism in our article). Why is it needed, how does it work and how is it arranged? Consider further.
As we said earlier, trucks and buses are equipped with an air brake system. Unlike hydraulics, it is simpler and more reliable. The drive of the brake mechanisms is carried out by means of compressed air entering through special chambers. The pressure in the circuits is from 6 to 12 atmospheres. However, this system can only work when the engine is running. And in order for the system to hold the car while parking, there is an energy accumulator in the design.
What is this mechanism? This is a pneumomechanical element that is part of the brake system of trucks and buses, which stores energy for braking the vehicle when the engine is stopped. The principle of operation of the energy accumulator is aimed at pressing the pads to the discs. At the same time, no compressed air supply is required for clamping. In addition, the energy accumulator is involved in the operation of the spare brake system. The controllability of the machine in the event of a malfunction of the main system depends on this mechanism. The element is installed on the rear axle of the car. It can be either one or several axes.
Design features of the mechanism
Regardless of the type, power accumulators have the same device. So, at the heart of the design there is a metal case. It is presented in the form of an open glass. The latter can be with conical, cylindrical or spherical walls. At the bottom of it there is a fitting. It serves to connect the brake chamber and the under-piston space through a drain tube.
There is a twisted spring inside the glass. It is closed by a piston or an elastic membrane at the top. There is a tubular pusher in the center. If a piston is provided in the design of the car's energy accumulator, then the tubular pusher acts as a rod. In the case of a diaphragm, the pusher holds the rod stem. The latter is needed to drive the membrane and the rod of the brake chamber. A bolt is screwed into the bottom of it. It is necessary to release the vehicle in the event oflack of air supply to the energy accumulator.
At the moment, modern power accumulators differ in the way they are connected to the brake chamber and in their completeness. As for the last characteristic, EAs can be represented by:
- Assembled with brake chamber.
- As separate mechanisms to connect with different types of cameras.
In the latter case, the unit is used to upgrade or repair the brake chamber. If "F has the first completeness, it can be used on the car without additional disassembly and assembly work.
Varieties by connection method
In this case, energy storage is divided into two categories:
- Flange with two clamps.
- Flange with clamp and bolted connection.
When installing a power accumulator, a flange is always used to connect the mechanism to the brake circuit. It serves not only to fix the components. It also depends on their correct location. Thus, when replacing the energy storage, the flange plays the role of centering and maintaining the distance. If you use an element of the second type, here the flange is connected to the EA using several bolts and nuts. In the first case, the connection is simpler, and is carried out using a metal clamp.
What other differences are there between power accumulators? They differ in the effective area of the diaphragm or piston. This specification is expressed in square inches.
The most common today energy storage, where the area of the membrane or piston is 20, 24 and 30 square inches. At the brake chamber, the area of the respective components ranges from 12 to 30 square inches. If the energy accumulator is sold as a set, then this value is indicated by two digits separated by a fraction. The first number always denotes the area of the chamber membrane. And the second one speaks about the area of the membrane of the energy accumulator.
This item is only used together with brake chamber. This feature eliminates unnecessary connections with wheel mechanisms. How does an energy storage device work? During the movement of the vehicle, compressed air is supplied to the energy accumulator. Due to the pressure, the coiled spring is compressed. In this case, the rod will be retracted from the diaphragm of the brake chamber. And EA does not affect the operation of the main braking system in any way. When the car is put on the handbrake, air is bled from the energy accumulator housing. The spring is no longer held under pressure and will decompress. Next, with the help of a rod, the pads are unclenched.
Thus, the principle of operation of the energy accumulator is to hold the car in place due to the compression force of the coiled springs. When the car is removed from the handbrake, air is again supplied to the mechanism. It compresses the spring and releases the wheels. It should be noted that this spring has a high rigidity. When carrying out repairs, you should use a special tool to remove and install it (but we'll talk about repairs a little later).
There are situations when you need to tow a car in which there is no way to supply compressed air to the power accumulators. In this case, manual release can be applied. To do this, there is a special bolt located on the back wall of the mechanism. If you screw it in, the spring will contract. So, the pads are gradually retracted and the car becomes movable again.
In addition, the power accumulator is involved in the operation of the spare brake system. it happens that the brake chamber cannot engage the pads. This may occur due to misalignment of the stem or destruction of the diaphragm. In this case, the energy accumulator is included in the work. Its working principle will be as follows. If it is necessary to reduce the speed, air is partially bled from the mechanism. The rod will actuate the brake mechanism. But it should be understood that such a mode of operation for a power accumulator is uncharacteristic. Therefore, you can use the vehicle on the spare system only for the purpose of driving to the place of repair.
Maintenance and repair
The mechanism is very simple, and therefore extremely reliable and requires minimal attention. What is care? During operation of the car, it is only necessary to inspect the energy accumulator for any damage. If we talk about maintenance, then the system needs periodic adjustment of the drive of wheel mechanisms.
In case of wear of the seals, diaphragm or piston, they are completely replaced. Often for energy storagereplacement kits are offered that already contain these elements. How do you determine if repairs are needed? The driver may notice that air has disappeared from the system somewhere during the parking. The brakes will also work worse.
Before you remove the energy accumulator, you need to read the safety instructions. During dismantling, a compressed spring can injure a person. The assembly of the energy accumulator is carried out by means of a special device that safely compresses the spring. It is extremely dangerous to work without this tool.
So, we have considered the principle of operation of the energy accumulator and its device. As you can see, the mechanism has a simple design, but its presence is extremely important in any air brake system. The assembly itself is quite reliable and, if timely maintenance is carried out, will function, reliably holding the vehicle both on a flat surface and on a slope.