The hydraulic system of PC200-5, PC300-5, PC400-5 Komatsu excavators is an open center load sensing system (OLSS system), which controls the swash plate angle by controlling the swash plate type axial variable piston pump ( Output flow) method to reduce fuel consumption in energy-saving systems. When the excavator is working, due to the role of this system, the hydraulic loss can be reduced to enhance the fine-tuning control and control the oil supply of the oil pump. The hydraulic principle diagram of the PC200-5 excavator is shown in Figure 2-2. Features of the 1.f type central load sensing system
(1) Moment control.
Maintain the driving torque of the hydraulic pump unchanged. If the hydraulic pump load (pump pressure) increases, the hydraulic pump output flow decreases; if the hydraulic pump load (pump pressure) decreases, the hydraulic pump output flow increases. This function is controlled by a torsion control valve (TVC valve).
(2) Cut off control.
The purpose is to reduce the profit loss during operation. If the load gradually increases, the output pressure of the hydraulic pump will also increase. When the pressure is close to the overflow pressure, the oil discharge of the hydraulic pump will decrease. This function is controlled by a shut-off valve (CO valve).
(3) Oil quantity control.
When Park is in the neutral position, the output oil drum of the hydraulic pump is the least. When fine control, according to the stroke of the joystick, the hydraulic pump supplies the required amount of oil to suit. This reduces the amount of waste in neutral or fine-tuning control, thereby reducing power loss. This function is controlled by a reverse control valve (NC valve) and a jet sensor (inside the control valve).
Composition of open center load sensing system
(1) The open center load sensing system is composed of hydraulic pump system, control valve, working device cylinder and excavator walking, hydraulic motor with the same rotation and other executive components. The open center load sensing system is shown in Figure 2-3. Show.
(2) The hydraulic pump system is composed of two swash plate axial variable piston pumps (front and rear), pilot pump, torsion control valve, cut-off valve, reverse control valve, servo valve, etc. Its structure is shown in Figure 2 -4 shown
