the principle of hydraulics on the crane application of closed system hydraulics principle in crane

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Construction machinery hydraulic drive system, open systems and closed systems, domestic small-tonnage truck cranes normally open valve control system, to achieve the requirements of the executing agency is the opposite direction and braking. Large tonnage cranes, most of the closed system, closed system uses two-way variable hydraulic pump through the pump variable to change the hydraulic oil flow and direction of the main oil line to the executive body of the variable speed and commutation, this control method can fully reflect the advantages of the hydraulic drive.hydraulic manifold block

   Xuzhou Heavy Machinery, large tonnage cranes hydraulic device, usually a closed system swashplate axial piston variable displacement pump and fixed displacement motor. Oblique disc variable piston pump flow and drive speed and displacement is proportional to the level variables. Closed loop variable displacement pump outlet and motor oil into the port connected to the motor outlet and pump inlet connected to form a closed hydraulic circuit, without valve by adjusting the variable pump swash plate point of view to change the direction of flow and pressure oil pu mp, thus changing the motor speed and direction of rotation. Variable pump flow with the swing angle of the swash plate is increased from zero to maximum. When the swash plate placed in position, a smooth change of the direction of fluid flow, so the micro and good and steady work.

   Closed hydraulic drive system continue to work in the oil leak (high pressure oil continued to vent their inherent product of component design), in order to complement these leakage and consumption to maintain a closed system work properly, you must replenish the oil to the closed system fluid. The main pump of the closed system through the shaft attached to a small displacement to fill the pump, fill the pump displacement and pressure are very small relative to the main pump, so the additional power loss is usually only 1% to 2% of the total power of the gear. is negligible. Up the oil pressure relief valve and fill the oil check valve in the closed system hydraulic device has to make up the oil pressure relief valve limits the maximum charge pressure, charge check valve according to the level of both sides of the pipe of the hydraulic oil pressure, select direction up the oil to the low pressure side of the main oil line up the oil, to compensate for the leak flow pumps, motors, volume loss; on both sides of the main pump operates two high-pressure relief valve, the pressure peak swashplate fast swing and maximum pressure by the high pressure relief valve to protect, prevent overloading of the pump and motor; the hydraulic unit is also equipped with pressure shut-off valve, pressure shut-off valve is equivalent to a pressure regulator when the set pressure is reached, the pump displacement back transferred to the zero state. In addition, the exit of the charge pump with filter, filtration of the working medium of the hydraulic system, improve the cleanliness of the hydraulic oil.

   The closed system has the following advantages:

   (1) are integrated structure of the closed system variable pump, fill the pump and fill the oil spills, and control functions Manifolds integrated into the hydraulic pump, so that the pipe connections easier, not only reduces the installation space, and reduce the connection caused by pipeline leaks and pipeline vibration and improve system reliability, and simplify the operating process.

   (2) make up the oil system can not only change of the displacement of the main pump to ensure that the response of the volume transmission, increase the frequency of the action, but also increase at the pressure of the main pump inlet to prevent cavitation in the large flow can be effectively improve the speed of the pump and prevent the pump suction air, improve the working life; up the oil system is equipped with filters, to improve the reliability and service life of the gear; In addition, the charge pump also convenient for a number of low-voltage auxiliary bodies to provide power.

   (3) Since only a small amount of fluid drawn from the tank to reduce the loss of the tank.