The relay valve is a part of the automobile air brake system. In the braking system of the truck, the relay valve plays the role of shortening the reaction time and the pressure build-up time.
The air inlet of the relay valve is connected to the air storage cylinder, and the air outlet is connected to the brake air chamber. When the brake pedal is stepped on, the output air pressure of the brake valve is input as the control pressure of the relay valve. Under the action of the control pressure, the intake valve is pushed open, so the compressed air enters the brake directly from the air tank through the air inlet. The dynamic air chamber does not need to flow through the brake valve, which greatly shortens the charging pipeline of the brake air chamber and accelerates the charging process of the air chamber. Therefore, the relay valve is also called the acceleration valve.
Relay valves are used at the end of long pipelines to quickly fill the brake chamber with compressed air from the air reservoir, such as in trailer or semi-trailer braking systems.
Generally, a differential relay valve is used. To prevent the driving and parking systems from operating at the same time, the combined spring brake cylinder and the force in the spring brake chamber overlap, so as to avoid the overload of the mechanical transmission element, so that the spring brake cylinder can be quickly charged and exhausted. emergency relay valve
The emergency relay valve, also known as the three-axle synchronizing valve, is installed on the semi-trailer. At present, many vehicles have this valve in the trailer gas circuit.
At present, there are two mainstream relay valves: WABCO and Haldex. In terms of specific interfaces,
The emergency relay valve is used to control the trailer service brake. If the air supply circuit breaks, the action of the emergency relay valve will cause the trailer to brake automatically. When driving: there is always air, when pressing the brake: inflating, the piston goes down, the air pressure reaches the ABS valve, causing the brake cylinder to work, when parking: inflating, the piston goes down, the air pressure reaches the ABS valve, causing the brake cylinder to work, and stepping on the brakes The state is the same, when the air pressure of the air reservoir leaks to a certain extent, the spring in the spring cavity automatically pops up and plays a parking role.
The national standard (GB12767-1999) also has provisions on emergency relay valves. When one of the gas supply pipeline connections (or other possible connection methods) is broken or leaked, the driver must be able to use the service braking, emergency braking, etc. brakes using the trailer brakes in whole or in part by the active or parking brake controls.
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