With the rapid development of industrial technology, people pay more attention to product quality and environmental protection. Hydraulic technology has been widely used in the national economy, the use of hydraulic transmission to measure the level of a country's industrial level is one of the important signs.

      Therefore, how to reduce the noise and vibration of hydraulic equipment, improve the working performance of hydraulic system and improve the machining accuracy of hydraulic cutting machine tools have become an urgent problem to be solved. Air into the hydraulic system is the most common factor affecting the performance of the hydraulic system. Therefore, it is necessary to study the causes of air failure on the hydraulic system and the measures to improve and eliminate the adverse effects.

     1.1 hydraulic system into the air on the impact of hydraulic oil and the consequences of 1.1 compressed air into the oil, part of the dissolved in the pressure of the oil, the part of the formation of bubbles floating in the pressure oil. Because of the compressibility of the air, so that hydraulic oil has obvious elasticity, commonly known as hydraulicSpring，Therefore, the hydraulic transmission rigidity is generally lower than that of the mechanical transmission, which is easy to cause the change of the low speed climbing straight or the working table with the change of the load.

    1.2 oxidation stability if the hydraulic oil and oxygen in the air contact, especially in high temperature prone to chemical reaction. After the oxidation of oil can produce acidic compounds, colloidal precipitate and so on, can corrode the metal, and can block the system and pipeline and valve port, which seriously affect the performance of the hydraulic system.

    The 2.1 air invasion of the hydraulic system vibration, noise hazard phenomenon and reason and analysis of 2.1 noise injustice effect of hydraulic system and performance and life, and induce a variety of fault, and give people around the cause discomfort and adverse effects in spirit and health. Air into the hydraulic system is one of the main causes of noise. Therefore, it is very important to analyze and reduce the hydraulic device and noise.

    2.2 analysis of the Henan Mechanical and Electrical Engineering College Journal of the first author: male, born in March 1969, bachelor's degree, lecturer general hydraulic oil at atmospheric pressure and room temperature, usually can absorb about 9 air. The amount of air dissolved in the liquid and the air pressure on the surface of the liquid. When the pressure is lower than the working temperature of the oil air separation pressure, dissolved in the liquid in the air will be a large number of separation, the formation of bubbles. If the formation pressure is very low, to achieve the oil saturated vaporization pressure, the oil vapor and air together with a large number of precipitation, the formation of oil boiling phenomenon. With the operation of this mixed in the oil bubble is broken with the instantaneous, local produce a high intensity of high frequency waves, and sometimes can be higher than 200M PA also accompanied by local high temperature. This high frequency hydraulic shock wave, on the one hand to the metal surface of the element damage, metal spalling, pitting the cavitation phenomenon, on the other hand pumps and other components produced only the pressure fluctuates greatly, a high frequency noise excitation. Figure 1 shows the influence of the air content of the oil on the noise, it is not difficult to see that the air content increases, the noise will increase.

     3.1 the reason and analysis of the creeping phenomenon caused by the invasion of the air to the hydraulic system 3.1 creeping and its harm to crawl is a common phenomenon in the hydraulic system. For example, in the metal cutting machine tool, the crawling injustice will affect the workpiece machining accuracy, surface roughness, but also shorten the service life of institutions or tools. Air intrusion system is the main factor of crawling. Therefore, it is very important to find the cause of crawling and eliminate the creeping phenomenon.

     3.2 the following analysis of the reasons for the hydraulic system to simulate the physical model of the 2 example, analysis of the hydraulic system in the implementation of the mechanism of the creeping mechanism.

If the hydraulic cylinder are mixed with air, Taiwan needs to overcome the static friction between the rail and the large bed table at the beginning of exercise through the pressure oil from the left chamber, then left in the cavity bubble is compressed (Figure 2a), the table does not move. When the pressure of the left chamber oil pressure increases, the bubble pressure, volume reduction, (Figure 2b) the table began to move. The movement began, the static friction between the rail and rail bed table suddenly becomes the dynamic friction force decreases, Yin, the left chamber pressure decreases the bubble expansion (Figure 2C), a sudden attack of piston is accelerated, the worktable dash speed. Because of the rapid advance of the worktable, the gas bubbles in the oil discharge chamber are suddenly compressed, on the other hand, the oil discharging force is increased, and the result is that the back pressure is increased. That is to say, with the work of the punch, on the one hand to reduce the pressure of the left cavity on the other hand to increase the pressure of the right chamber. The comprehensive effect, prompted the work table after flushing, and quickly brake, to the hydraulic cylinder pressure in the working chamber to rise again to overcome the static friction force, working table and then restart, repeat and stop suddenly, so the table will suddenly stop beating, which is constantly circulating, working table and crawling the phenomenon of.

     The main measures of 4 system structure into the hydraulic system 4.1 system structure design 1) increasing large suction tube to reduce or avoid bending pipe diameter, 2) for joint double vane pump, piping should be used the right way 3) one-way valve installed in the pump outlet, back pressure valve installed in the return line) 4 vent plug should be of the highest installed in the cylinder or pipe 5) precision hydraulic component design should meet the technical requirements of 6 tank capacity) to the right, the oil has enough time in the separation bubble tank.

     4.1 installation maintenance 1) for hydraulic pump oil height must be as small as possible (500mm) 2) hydraulic rotation should not be too high 3) seal hydraulic components and pipe head seal 4) with good oil filter properly, and to regularly check, cleaning, avoid blocking 5) high level tank tubing import and maintain a certain distance, or between the diaphragm set 6) hydraulic control valve hole inlet pressure it can not be too large (3 5Mpa) 7) to ensure that the oil tank is sufficient, the use right of not less than 8) indicating oil line oil viscosity is too high, and according to the requirements of timing replacement.

The 1 chapter Hongjia. Metal cutting machine tool hydraulic transmission. Nanjing: Jiangsu science and Technology Press, 19852 Ji Guang guo. Fault diagnosis and elimination of hydraulic system. Beijing: Ocean Press, 19923 Zhiyong. Machine tool hydraulic and lubrication equipment maintenance manual. Beijing: China Machine Press, 1998