How To Use The Unloading Valve For The Sequence Valve Of Small Excavator

Connect the control oil port of the external control sequence valve, namely the unloading valve, to the outlet of the hydraulic pump. When the pressure of the main oil circuit in the system reaches or exceeds the set value of the unloading valve, the valve opens to unload the low pressure large flow pump, and the high pressure small flow pump supplies oil to the system at the pressure set by the overflow valve.

What is the function of the internal control one-way sequence valve in the balance support circuit of the small excavator?

Using the balance circuit of the internal control one-way sequence valve and properly adjusting the opening pressure of the sequence valve can make the hydraulic cylinder with the back pressure generated in the rod chamber balance the dead weight of the piston when the hydraulic cylinder is lowered vertically, so as to prevent accidents and cavitation caused by the weight overspeed dropping. When the three-position four-way valve works in the left position, the pressure oil enters the upper chamber of the hydraulic cylinder and the cylinder goes down, making the oil pressure in the lower chamber of the hydraulic cylinder rise. When the lower chamber pressure exceeds the set pressure of the sequence valve, the piston of the small excavator moves downward. The balance circuit composed of the internal control one-way sequence valve plays a role in balancing the weight of the hydraulic cylinder piston.

What is the function of the externally controlled one-way sequence valve in the support circuit of the small excavator scale?

The balance circuit of externally controlled sequence valve and check valve is adopted. The opening and closing of the externally controlled sequence valve of this circuit depends on the oil pressure at the control oil port, and has nothing to do with the inlet pressure of the sequence valve. When the hydraulic cylinder goes down, the sequence valve is opened by the rod chamber pressure (i.e. the sequence valve control pressure), and the back pressure disappears, so the energy loss is small. However, in this circuit, when the rod chamber pressure of the hydraulic cylinder opens the sequence valve, the pressure will drop rapidly, which may cause the sequence valve to close again; Then the pressure in the rod chamber is opened again, the sequence valve is opened again, and the piston moves downward again, so the movement stability of the hydraulic cylinder is poor. The method to eliminate or alleviate this phenomenon is to set a throttle valve or variable hydraulic resistance in the control oil circuit to slow down the opening and closing action of the sequence valve.