The pressure relay is mainly used to detect the level of the liquid or gas pressure and send a switching signal to control the solenoid valve, hydraulic pump and other equipment to control the pressure level. The pressure relay is mainly composed of a pressure transmitting device and a micro switch. The liquid or gas pressure pushes the rubber membrane and the slide rod through the pressure inlet to overcome the spring reaction force and move upward. When the pressure reaches the predetermined pressure, the micro switch is triggered to send a control signal. , Rotate the pressure-adjusting nut to change the proposed pressure.
Pressure relay control circuit
1) High-pressure and low-pressure control of the system The system uses two pressure relays to control the maximum pressure and minimum pressure of the accumulator system respectively. When the accumulator is charged, YA is energized. When the pressure reaches the household level, YA is powered off and the pump is unloaded; when the accumulator pressure drops to Lu mh, YA is energized again, and the hydraulic pump recharges the accumulator.
2) Pilot control hydraulic system of electro-hydraulic directional valve The pilot control oil of electro-hydraulic directional valve can be supplied with oil by the main pump of the system. The function of the main valve of electro-hydraulic directional valve should be O-type. At this time, the control oil pressure is equal to the main system pressure, which is not good for the pilot valve;
The control principle of the pressure relay: when the system pressure exceeds the system set pressure value, the force acting on the plunger closes the micro switch through the ejector rod to send out an electrical signal, so as to achieve the role of control.
Application of pressure relay:
1. Form a holding pressure circuit. For example, when the system pressure exceeds the set value of the pressure relay, an electrical signal is sent to control the pump motor to stop. At this time, the accumulator in the hydraulic system can play the role of holding pressure. When the system pressure drops to a certain level, the pressure relay controls the pump motor again, so that the motor runs again to provide pressure for the system, and also charges the accumulator. Pressure.
2. Applied in the unloading circuit. When the system pressure exceeds the set value of the pressure relay, the pressure relay will send an electrical signal to control the solenoid of the directional valve to make the directional valve pass, thereby controlling the overflow valve to open the overflow, and the pump is unloaded.
3. Participate in the sequence circuit. In the circuit with multiple cylinders, the pressure relay can control the sequence of cylinders. For example, when the first cylinder has reached the stroke, the pressure continues to rise. Once it exceeds the set value, the relay sends a signal to control the action of the second cylinder.
4. Actuator commutation A pressure relay is used to control the circuit of hydraulic cylinder commutation. The throttle valve is arranged on the oil inlet and is used to adjust the working feed speed of the hydraulic cylinder. The two-position two-way electromagnetic directional valve provides the hydraulic cylinder return path. Two-position four-way electromagnetic directional valve is the main directional valve of the circuit. The pressure oil enters the rodless chamber of the hydraulic cylinder through the valve and the valve. When the hydraulic cylinder hits the dead iron on the right, the pressure of the hydraulic cylinder's oil inlet rises, and the pressure relay sends a signal to switch the solenoid 1YA power off valve to the right. Position, the solenoid 2YA energizing valve is switched to the left position, and the hydraulic cylinder returns quickly.