Tractor control valve

Tractor control valve

Tractor control valve is used in trailers braking systems. A control (hydraulic) valve is responsible for the flow of refrigerant through the hydraulic system. The direction of the medium flow depends on the position of the spool. The control valve allows the hydraulic system to function properly.

The control valve's main function is to activate the trailer's brakes simultaneously with the tractor's brakes applied. In addition, in the case of unforeseen disconnection of the hose between the trailer and the tractor, the control valve automatically applies the machine's brake. The valve used has a brake release system, used when the trailer is disconnected from the tractor. After connecting the compressed air hose to the tractor, the release device automatically moves to the position enabling normal operation of the brakes.

Tractor control valve is a pressure control valve - it's a valve whose task is to control the pressure of compressed air in the system, i.e. maintaining the value or changing it according to the preset value of the input signal.

Due to the type of closing body, pressure control valves can be:

- poppet type

- diaphragm type

- piston type

Tractor control valve is used in the braking system, which works thanks to compressed atmospheric air. The mechanism maintains a constant high pressure throughout the entire system. In the event of a pressure change, braking occurs - this is caused by the pneumatic valve actuated by the tractor driver with the brake pedal.

The hydraulic functions of the machine are preselected via 2 selector valves with the aid of the hand lever and carried out via the corresponding tractor control valve. 

Pneumatic brakes can be divided into one and two-line. The single-line cable connects the tractor to the road trailer. At the same time, this brake hose supplies the trailer braking system with compressed air and is the hose that controls the brakes. In a dual-circuit system, two wires are needed to connect the tractor and trailer. One cable is responsible for supplying the system with compressed air, while the other is needed to control the brakes. These two systems have different control methods. Single-wire brakes are activated when the pressure in the hose between the tractor and trailer decreases, while in the dual-circuit system the control consists in increasing the pressure in the control line.