1. Boom lifting operation
When the right joystick is pushed back, the main control valve's boom spool is moved to the rising position by the pilot oil pressure from the remote control valve. The oil from the front and rear pumps flows into the main control valve and then into the large chamber of the boom cylinder. At the same time, the oil in the chamber of the boom cylinder returns to the hydraulic tank through the boom spool of the main control valve. At this time, the excessive pressure in the bottom end circuit of the boom lift boom is blocked by the overflow valve. When the boom is lifted and the joystick returns to the intermediate position, the balance pressure circuit at the bottom end of the boom cylinder is closed by the boom balance valve. This prevents the natural sinking of the boom cylinder
2. Boom lowering operation
When the right joystick is pushed forward, the boom spool in the main control valve is moved to the lowered position by the pilot oil pressure from the remote control valve. The pump oil flows into the main control valve, and then into the chamber of the boom cylinder. At the same time, the oil in the large chamber of the boom cylinder returns to the hydraulic oil tank through the boom spool in the main control valve. At this time the boom drops. When the boom lowering speed is accelerated, the return oil from the large chamber of the boom cylinder merges with the oil from the rear pump, and then flows into the small chamber of the cylinder. In this way, when the oil flow of the rear pump cannot be matched with the boom lowering speed, the cavitation phenomenon caused by the negative pressure of the oil cylinder can be prevented. And the overflow valve prevents excessive pressure in the rod end circuit of the boom cylinder.
3. Arm retraction operation
When pushed back, the arm spool in the main control valve is moved to the retracted position by the pilot oil pressure from the remote control valve.
The oil from the front and rear pumps flows into the main control valve and then into the large chamber of the arm cylinder. At the same time, the oil in the small arm cylinder chamber of the modern excavator returns to the hydraulic oil tank through the small arm spool in the main control valve. At this time, the forearm retracted.
The supplementary valve in the main control valve will prevent cavitation at the bottom of the arm cylinder
4. Arm extension operation
When the left control lever is pushed forward, the arm spool in the main control valve is moved to the extended position by the pilot oil pressure from the remote control valve.
The oil from the front and rear pumps flows into the main control valve and then into the small arm cylinder chamber.
At the same time, the oil in the large chamber of the arm cylinder returns to the hydraulic tank through the arm spool in the main control valve. At this time, the forearm stretched out.
The supplementary valve in the main control valve will prevent cavitation at the rod end of the arm cylinder.
5. Bucket retraction operation
When the right joystick is pushed to the left, the bucket spool in the main control valve is moved to the retracted position by the pilot oil pressure from the remote control valve. The pump oil flows into the main control valve and then enters the large chamber of the bucket cylinder. At the same time, the oil in the bucket cylinder of the bucket returns to the hydraulic oil tank through the boom spool in the main control valve. At this time, the bucket is retracted.
The supplementary valve in the main control valve will prevent cavitation at the bottom of the bucket cylinder.
6. Bucket extension operation
When the right joystick is pushed to the right, the bucket spool in the main control valve is moved to the retracted position by the pilot oil pressure from the remote control valve.
The oil of the rear pump flows into the main control valve and then into the small chamber of the bucket cylinder. At the same time, the oil in the large chamber of the bucket cylinder returns to the hydraulic oil tank through the bucket spool in the main control valve. At this time, the bucket came out.
The supplementary valve in the main control valve will prevent cavitation at the rod end of the bucket cylinder.
7. Swing operation
When the left joystick is pushed to the left or right, the rotary spool in the main control valve is moved to the left or right by the pilot oil pressure from the remote control valve. The oil from the rear pump flows into the main control valve and then into the rotary motor. At the same time, the return oil of the rotary motor returns to the hydraulic oil tank through the rotary valve core in the main control valve. At this time, the upper turntable can turn left or right.
Rotary motor is equipped with rotary parking brake, supplementary valve and overload relief valve. Supplementary valve prevents cavitation in rotary motors
1. Rotary circuit operation
(1) Motor brake valve The motor brake valve of the swing motor limits the buffering when starting and stopping the swing pressure.
(2) Supplementary valve The supplementary valve prevents cavitation by providing oil return to the vacuum end of the motor
(3) Parking brake If the machine needs to park on a slope, the machine's own weight may cause unintentional sliding. The parking brake prevents the machine from slipping unintentionally.
① The parking brake works “OFF”.
The parking brake is released by the pilot pressure from the pilot pump. When the left joystick is in the swing position, the pilot pressure of the shuttle valve is transferred to the brake release valve, and the brake release valve is switched. Then, the pilot pressure raises the brake plunger to release the parking brake ② The parking brake is turned ON. When the joystick is in the middle position, the pilot oil pressure drops. Then, the brake release valve returns to the intermediate position, and the return oil of the brake plunger returns to the fuel tank. The brake is set to the ON position.
(4) Bypass valve The bypass valve buffers the vibration caused by the slewing motion and reduces the machine swing caused by the slewing motion.
