The relay valve is a part of the automobile air brake system. Today, let's talk about the use and working principle of differential relay valve.
When the service brake and the parking brake system are operated at the same time, the combined spring brake cylinder and the brake chamber (spring brake chamber) will be prevented from overlapping forces, so as to avoid overloading of the mechanical transmission elements, so that the spring brake cylinder can be quickly charged, exhaust.
2. Working principle
In the driving state, the hand brake valve continuously supplies air to cavity A through port 42. The piston and the piston are pressed down, close the exhaust valve, push the valve stem down, open the intake valve, the compressed air from the air reservoir through port 1 is output through port 2, and the spring brake air chamber connected to port 2 Compressed air is thus supplied, and the spring brake is released.
When the service brake system acts alone to operate the main brake, the compressed air enters the B cavity through the 41 port, and presses down the piston b. Due to the reaction force of the A cavity and the C cavity, the pressure reaching the B cavity will affect the differential relay valve The work of the tractor is not affected, and the compressed air continues to flow to the spring brake part of the spring brake chamber, thereby releasing the brake, and at the same time, the compressed air directly from the tractor brake valve makes the diaphragm part re-action.
When the parking brake system acts alone, when the hand brake valve is operated, the A cavity is completely emptied. The piston is not under pressure and is pushed up by the piston exposed to the air pressure of the C-cavity air reservoir, the exhaust valve opens, and the valve stem rises at the same time, closing the intake valve. In this way, the spring brake cylinder discharges the gas through the 2 port, the valve stem, and the exhaust valve 3 according to the position of the hand brake handle, thereby spring braking.
During partial braking, the exhaust valve is closed after exhausting, and the differential relay valve of cavity A and cavity C is in a balanced position. However, under full braking, the air intake continues to open. When the main brake and spring brake acts simultaneously A. When the service brake exhaust is the action of the spring brake cylinder, the compressed air enters the B cavity through the 41 port and acts on the piston. Since the C cavity is emptied, the piston moves down, and the exhaust valve is closed through the valve stem and the intake valve is opened simultaneously. The compressed air from port 1 reaches port 2 through cavity C and enters the spring brake chamber.
The spring brake is released according to the degree of service brake pressure rise, thus avoiding the overlapping effect of the two brakes. B. When the pressure of port B is higher than the pressure of chamber B, the pressure of chamber C pushes the piston to rise, the intake valve is closed, and the differential relay valve is in a balanced state.
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