How the Trailer Control Valve and the Auxiliary Brake System Work Together to Produce a Braking Action

Several parts of the trailer brake system are involved in the braking process. The brakes are controlled by the control pistons of the trailer control valve, the auxiliary brakes, the braking circuits of the auxiliary brakes, and the pneumatic control circuit of the service brakes. It is important to know how these parts work together to produce a braking action.

The function of the control piston in the trailer control valve is to create pressure in the brake line. In addition to creating pressure, the control piston also communicates with the control chamber associated with the auxiliary brake system. This enables the control chamber to be switched over to the braking chamber for braking purposes. In the case that the auxiliary brake system is not operating, the pressure in the braking chamber of the trailer control valve is sufficient to activate the service brakes. This allows the auxiliary and service brakes to operate as a single unit. The braking actions will be performed one second apart.

The control circuit of the trailer control module includes a valve, which is connected to a pneumatic control circuit of the service brake system. This valve is used to convey a pneumatic brake pressure request signal to the trailer control module. In a further configuration, the pneumatic control circuit is able to introduce control air into a second control chamber. Typically, the directional control valve is extremely simple, but is capable of generating control pressure in the electrical control circuit. In a further embodiment, a double seat valve is used to regulate the communication between the compressed air reservoir and the control piston.

A two-way check valve is also employed in the trailer control valve. The valve has two inputs, and a single output. This allows the valve to isolate the hand and foot valves. In addition, the two-way check valve is plumbed to a double-check valve, which is used to isolate the hand and foot valves.