Hydraulic Control Valve Control System

1) Pilot type control system The control forms of the reversing control valve are direct-acting type (the main spool of the reversing valve is directly controlled by the handle, which is rarely used at present) and the pilot type. The latter is to use the pilot valve to control the pilot oil, and then use the pilot oil to control the main spool of the reversing valve. It is divided into two types: the hydraulic pilot type and the electro-hydraulic pilot type.

2) Load sensing control system hydraulic valve control system is essentially a throttle system. On the hydraulic excavator, the general three-position six-way multi-way valve is commonly used at present, and the fine-tuning performance and compound operation performance of the spool valve are poor. Since the 1990s, the load sensing control system has been used in hydraulic excavators, and the control system is equipped with a pressure compensation valve regardless of whether it is a neutral open type or a neutral closed type. Compared with the traditional hydraulic system, the hydraulic excavator hydraulic system using electronic control pressure compensation, the main advantages of the load sensing control system are:

(1) Save energy consumption. Ordinary three-position, six-way reversing valve, whether using a quantitative pump or a variable pump, always has a part of the oil overflowing through the overflow valve, wasting energy. With the load sensing variable system, the flow of the pump is all used for the load, and the pressure of the pump is only 1-3MPa larger than the load pressure.

(2) The flow control has high precision and is not affected by changes in load pressure sensor.

(3) Several actuators can move synchronously or at a certain speed ratio without interfering with each other. The ordinary three-position six-way valve system uses parallel oil circuits. When several actuators act at the same time, the oil output by the pump first flows to the actuator with low pressure, which cannot be synchronized.

The load-sensing control system includes a load-sensing control valve and a load-sensing control pump (or quantitative pump).

3) Complete load sensing control system Complete load sensing control system consists of load sensing control valve and load sensing control variable pump.

The above-mentioned load sensing control valve only solves the fine-tuning performance and compound operation performance of the spool valve, but does not solve the problem of energy saving. The system of fixed pump and load sensing control valve also does not save energy consumption, because when the output flow of the pump exceeds the flow required by the actuator (hydraulic cylinder and hydraulic motor), the excess oil flows back to the tank through the pressure compensation valve ( to keep the differential pressure constant) into heat energy. Only a full load sensing control system can solve the energy saving problem.

4) Load sensing system with secondary pressure compensation valve A load sensing diverter LUOV (Last Unabhangige Durchfluss Vereilung) system is set on the produced hydraulic excavator. Its main function is: when multiple actuators work at the same time, the required When the flow rate of the hydraulic pump is greater than that of the hydraulic pump, the phenomenon of insufficient oil supply occurs, which cannot ensure the control of the actuators on the workbench independent of the load pressure. The LUDV system can ensure that the working speed of all actuators is proportionally reduced in the event of insufficient oil supply to obtain control independent of load pressure.