The function of the pressure holding circuit is to enable the system to maintain a stable and constant pressure when the hydraulic cylinder is not moving or when the workpiece is deformed to produce a small displacement. According to the working requirements of the bending machine, the pressure holding time needs to be about 5s, and the pressure stability is good. Then you can choose a hydraulically controlled check valve to maintain the pressure loop,
The M-type three-position four-way reversing valve is selected, and the function of the middle position slide valve is used to close the two-cylinder hydraulic cylinder, and the system is no longer unloaded. An automatic oil replenishment circuit is designed, and the pressure holding time can be controlled by the electrical component time relay. This circuit is fully qualified for high pressure systems with relatively high pressure holding performance, such as hydraulic presses.
The working principle of the system diagram of the automatic replenishing and pressure maintaining circuit: Turn on the start button, the electromagnet 1ya is energized, the right position of the reversing valve 6 is connected to the system, and a part of the pressure enters the upper cavity of the master cylinder through the fuel-saving speed control valve 8. ; Another part of the pressure oil opens the hydraulic control check valve 7 to return oil to the lower chamber of the master cylinder. The piston of the master cylinder drives the upper slider to move down quickly. The pressure in the upper chamber of the master cylinder decreases. The one-way valve 14 replenishes oil to the upper cavity of the master cylinder. When the piston of the master cylinder drives the upper sliding block to contact the pressed workpiece, the pressure in the upper cavity of the master cylinder increases, the hydraulic control check valve 14 will be closed, and the filling tank will no longer supply oil to the upper cavity of the master cylinder. The flow of the pump is also automatically reduced, the downward speed of the slider is reduced, and the slow pressurization work starts. When the oil pressure in the upper chamber of the master cylinder rises to the operating pressure point of the pressure relay 11, the pressure relay sends a signal to de-energize the solenoid valve 1ya, and the reversing valve 6 will switch to the neutral position; at this time, the hydraulic pump starts to unload and the hydraulic pressure The cylinder is pressure-maintained by the M-type neutral function of the reversing valve. At this time, the pressure relay will also send a signal to the time relay, and the time relay will start to delay power off. The holding time is adjusted by the time relay.
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