Hydraulic Transmission

At present, electromechanical-hydraulic integration is the main development steering wheel of hydraulic excavators. Its purpose is to realize full automation of hydraulic excavators, that is, people's research on hydraulic excavators is gradually shifting to the direction of electromechanical-hydraulic control systems, so that excavators can be controlled by traditional levers. Control gradually developed to hydraulic control, pneumatic control, electrical control, hydraulic servo control, radio control, electro-hydraulic proportional control and computer direct control. Therefore, the research on the electromechanical-hydraulic integration of excavators mainly focuses on the control system of hydraulic excavators.

The hydraulic excavator control system is a system that controls the power system composed of the engine, hydraulic pump, multi-way reversing valve and actuator (hydraulic cylinder, hydraulic motor). According to the control function, it can be divided into position control system, speed control system and force (or pressure) control system; according to control components, it can be divided into engine control system, hydraulic pump control system, multi-way reversing valve control system, executive element control system system and the whole machine control system.

At present, the hydraulic excavator control system has developed into a composite control system.

Engine control system

From the appearance characteristic curve of the diesel engine, it can be seen that the diesel engine is an approximate constant torque adjustment, and the change of its output power is represented by the change of the speed, but the output torque basically does not change. When the throttle opening increases (or decreases), the output power of the diesel engine increases (or decreases). Since the output torque is basically unchanged, the speed of the diesel engine also increases (or decreases), that is, different throttle openings correspond to different diesel engines. Rotating speed. It can be seen that the purpose of controlling the diesel engine is to realize the adjustment of the speed of the diesel engine by controlling the opening degree of the accelerator.

At present, the control devices used in hydraulic excavator diesel engines include electronic power optimization system, automatic idle speed device, electronic governor, and electronic throttle control system.

Hydraulic valve component control system

The control of the hydraulic pump is realized by adjusting its variable swing angle. According to the different control forms, it can be divided into three categories: power control system, flow control system and combined control system. The power control systems include constant power control, total power control, pressure cut-off control and variable power control; flow control systems include manual flow control, positive flow control, negative flow control, maximum flow two-stage control, load sensing control and electrical Flow control, etc.; the combined control system is the combined control of power control and flow control, and is most widely used on hydraulic control machines.