1) Structure of overflow valve
2) The role of relief valve
Relief valve uses the balance of inlet oil pressure and spring force to achieve pressure control.
Overflow valve is used for hydraulic excavator. There are four main functions. 1) In the quantitative pump (gear pump) hydraulic system, it is used to overflow excess oil back to the oil tank to maintain the hydraulic system pressure constant (approximately constant).
2) In the variable pump hydraulic system, only when the pressure exceeds a certain preset pressure value, the overflow is opened, so that the system pressure no longer rises, and plays a role in safety protection. At this time, the overflow valve is often called a safety valve.
3) In the system, it is used to protect the actuator (such as the cylinder) or structural parts from being damaged under the strong external force. In this case, the overflow valve is called an overload valve.
4) As a pressure limiting valve, it buffers and limits the pressure of the rotary mechanism.
3) Working principle of relief valve
①Pump pressure PP rises
②When it exceeds 21.6MP
③The pump pressure pushes the poppet (2) against the force of the spring (1) and pushes upward
④ The plunger (3) small hole (φ0.5 only) starts to have oil flow
⑤The plunger (3) is pushed upwards due to the pressure difference between the front and back (the bottom is larger, the top becomes smaller)
⑥Pressure oil return tank
⑦ Pump pressure drops until 21.6
