Excavator PC120-6 main gun main relief valve 723-30-90400

According to the characteristics of hydraulic pump, the hydraulic system used by hydraulic excavator is roughly divided into three types: quantitative system, variable system, and quantitative and variable system.
(1) Quantitative system
In the quantitative system used by hydraulic excavators, the flow is constant, that is, the flow does not change with the load, and the speed is usually adjusted by throttling. According to the quantity and combination form of oil pumps and circuits in the quantitative system, it can be divided into single pump single loop, double pump single loop quantitative system, double pump double loop quantitative system and multi-pump multi-loop quantitative system.
(2) Variable system
In the variable system used in hydraulic excavator, stepless speed regulation is realized by volume variable, and there are three adjustment methods: variable pump-quantitative motor speed regulation, quantitative pump-variable motor speed regulation, and variable pump-variable motor speed regulation. The variable system adopted by hydraulic excavator mostly adopts the combination of variable pump and quantitative motor to realize stepless variable, and all of them are double pumps and double circuits. According to whether the variables of the two circuits are related, they can be divided into two kinds: sub-power variable system and total power variable system. Each oil pump of the sub-power variable system has a power regulating machinery, and the flow change of the oil pump is only affected by the pressure change of the circuit in which it is located, which has nothing to do with the pressure change of the other circuit, that is, the oil pumps of the two circuits independently carry out constant power regulating variables, and the two oil pumps each have a bucket of engine output power; The two oil pumps in the full power variable system are balanced by a total power regulating mechanism, so that the swing Angle of the two oil pumps is always the same
The synchronization variables and traffic are the same. What determines the flow rate change is the total pressure of the system, and the power of the two oil pumps is not the same in the range of variables. The regulating mechanism has two forms of mechanical linkage and hydraulic linkage.