Constant pressure valve is turned on, the pressure on the oil into the variable chamber piston, variable piston pressure in the lowest position, full displacement pump output pressure oil; it is set when the pump is constant pressure of work, the role of the constant pressure hydraulic spool it is set equal to the spring force of the thrust, constant pressure into the oil discharge port of the valve is turned on at the same time, the variable hydraulic thrust of the piston is equal to the upper and lower chambers, a variable balanced position in the piston, when hydraulic damping (load) increase, oil instantaneous pressure increase, constant drain port valve to open big, oil inlet off small, relatively lower chamber pressure variable piston upper chamber reduced variable piston moves upward, the pump flow is reduced until the pressure drops to the constant pressure it is set, Then variable piston working in the new equilibrium position. Conversely variable pump, if the hydraulic damping (load) decreases, hydraulic transient decrease variable vane pump, constant pressure to open the inlet valve large drain port off small, variable on relatively lower chamber hydraulic piston chamber increases, variable piston move down, pump flow increases, the pressure rises until it is set to a constant pressure. One revolution each plunger and its amount of oil discharged to go stroke related to the larger stroke of the larger amount of oil is discharged, and the stroke of the plunger depends on the angle of the swash plate when the swash plate angle A greater the plunger the greater the pump stroke the greater the amount of oil discharged. So changing the swash plate angle can change the pump displacement. In the swash plate angle of the variable displacement pump is controlled by the servo piston, when the big end of the servo piston oil pressure servo piston moves to the left to walk variable pump, push the swash plate moves to the left, so that the angle A smaller mixer variable pump, Travel smaller displacement smaller. Control of critical control servo piston pump displacement becomes, currently there are many factors to control it, such as system pressure, back to the oil pressure valve and electronic control devices. Domestic variable pump, hydraulic Jing Chong (certified), Weifang, Jinan crystal by creating variable pump hydraulic machinery Limited. Jinan Jing Chong Hydraulic Machinery Co., Ltd. (www.jnjcyy.com) (www.jnjcyy.com) Shandong Jinan, mining machinery leaders, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, the maximum meet customer needs. In the crystal to create a hydraulic leadership with the staff warmly welcome all inquiries negotiations to create the crystal to create a better future for the hydraulic.