Variables constant pressure pump control called constant variable pump, its control principle shown in Figure 1, where 1 is the control slide valve, pressure regulator spring 2, 3 is a control cylinder, 1 and 2 are collectively referred to constant pressure valve . When the system pressure is low, there is no right of control cylinder pressure oil pump variable * Specialist, control cylinders running right under the action of the spring, pushing the variable variable pump pump mechanism * care, the pump at maximum displacement state. When the system pressure increases to the set pressure of constant pressure valves, hydraulic pressure control spool ends more than a spring force of the pressure regulator valve to the right, the right pressure oil into the control cylinder, push the control cylinder run to the left, then push the variable mechanism of the pump, the pump displacement is reduced, thus reducing the output flow, pump working with the constant pressure pump control variables to reduce the difference between editing principle of variable displacement pump 123 pumps and quantitative variable vane pump 1. the variable displacement pump, oil pressure when the blade is in the area, through the pressure of the oil at the bottom of the blade when the blade is in the suction area at the bottom of the blade through the suction chamber, so that the variable pump * refinement, the hydraulic pressure of the blade at the top and bottom of the basic balance, This avoids the fixed displacement vane pump in the suction region of the stator surface severe wear problems. If the blade is still in the bottom of the pressure oil through the suction chamber, the top of the inner surface of the stator blade will give a larger frictional force, so that the reduced pressure feedback effect. 2. The blade also has the inclination, but the tilt direction coincides with the quantitative vane pump Rather, it is because the blade down pressure variable vane pump is balanced blade movement outward centrifugal suction area rely mainly on the role of its rotation. According to mechanical analysis Such oblique direction is more conducive to the blade projecting outwardly under centrifugal effect. 3. The variable vane pump complex structure, large contour size, multiple parts in relative motion, the larger the leak, the shaft radial hydraulic pressure imbalance, noisy, volumetric and mechanical efficiency are not fixed displacement vane pump is high; However, it can automatically adjust the pressure according to the load flow, power use is reasonable, can reduce heating oil. * Variable pump hydraulic refinement _ Crystal Chong (certified) _ variable pump from Jinan Jing Chong 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.