Experimental Research On Lubrication Characteristics Of Port Plate/Cylinder Block Frictional Pair In Axial Piston Pump

The trend of development of axial piston pump is high pressure high rotating speed and high flow. For achieving those goals, one of the key problems is optimum design of the frictional pairs in axial piston pump. The lubricating film must be formed in frictional pairs to improve the volume efficiency and working life of axial piston pump. The port plate/cylinder block friction pair is one of the most important frictional pairs in axial piston pump, and it is easiest to be worn out. So researching for lubrication mechanism is significant to design excellent performance axial piston pump having high pressure high rotating speed and high flow characteristics etc.In the paper, researching lubrication of port plate/cylinder block friction pair is the main object. The main achievements include the contents as follow. The mathematic model of lubrication of port plate/cylinder block frictional pair was established. The formation of the lubricating film thickness is described through the theory models. The formation of the lubricating film thickness was researched and simulated. The influence of working pressure, temperature, rotating speed and structure on the lubrication can be researched through simulation. When other working condition is invariable, the lubricating film thickness decreases as the oil pressure or oil temperature increases. The film forms fast as the oil pressure increases. When the oil temperature increases, the leakage of frictional pair increases. When other working condition is invariable, the supplying oil time and stopping oil time decrease, the lubricating film is difficult to form. When the rotary speed is 3000 r/min, the blind hole in port plate should be 6 and the wrap angle of blind hole should be 12° . Or the blind hole should be 12 and the wrap angle of blind hole should be 15° . When other working condition invariable, the lubricating film thickness increases as the wrap angle of blind hole increases, and the amplitude of lubricating film increase as the number of blind hole.The lubrication test system has been designed. The performance of the lubrication test system is analyzed. The functions feature and principle of the lubrication test system are summarized. The mathematic model of the micron electrohydraulic displacement feedback control system was established and simulated. The parameters of V0/B Kce and PID are selected and optimized. The controlsystem is stabilized with PID feedback controlling, otherwise the control system is not stabilized.The lubrication mechanics experiment of typical port plate /cylinder block frictional pair was finished through the lubrication test system. The loading force increases as supplying oil pressure P14 increases. If the lubricating film thickness is invariable, the leakage of port plate will increase. When the P14 increase, the pressure ripple increases, and the lubricating film is difficult to form. The lubricating film thickness decreases as the oil temperature increases. The torque of frictional pair increases as the rotary speed increases, and the frictional pair is easy to be worn out. In this time, the lubricating film is not steady. When the cylinder block vibrates, the resultant moment is not balanced. The cylinder block will sloping. So the lubricating film is variable, and the feedback force occurs. If the resultant moment is limited in certain scope, and the lubricating film rigidity is large enough, the sloping angle of the cylinder block will be small and the concentrated wear will be avoided.The key problems and research domain have been discussed in this paper. The developing process of axial piston pump and research present state of port plate/cylinder block frictional pair were summarized. In the paper, the main research contents were determined according to the difficult problems in researching lubrication of port plate/cylinder block frictional pair in axial piston pump.The mathematic models of damp groove type continuous oil supply port plate /cylinder block and semi-perimeter double oil groove type periodical oil supply port plate /cylinder block frictional pair was established in the paper. The mathematic model of the lubricating film formation was established to illustrate the lubricating film variation and pressure and flow characteristic in the damping groove and pressure groove. The relation between lubricating film thickness and force acting on port plate was described with the mathematic models and variation regularity of the lubricating film can be acquired.In the paper, the simulation model of port plate/cylinder block frictional pair in which the lubricating film forms was established according to force balance equation and flow continuity equation with SIMULINK of MATLAB. The frictional pair includes of damp groove type continuous oil supply port plate /cylinder block frictional pair and semi-perimeter double oil groove type periodical oil supply port plate /cylinder block frictional pair. The formation of the lubricating film thicknesswas researched and simulated in all kinds of different working condition.The lubrication test system has been designed in the paper. And the lubrication test system has been developed by author which consists of pump station > lubrication test apparatus and signal measure and control system. The lubrication characteristics of port plate/cylinder block in axial piston pump such as film thickness, bearing support capability and leakage can be measured through the lubrication test system. And the influence of working pressure, temperature, rotating speed and structure on the lubrication can be testec as well. The optimal matched pair of material and structure of the port plate pair of water hydraulic axial piston pump can be achieved through the lubrication test system, which can provide a good base for developing water hydraulic axial piston pump.The mathematic model of the micron electrohydraulic displacement feedback control system was established in the paper. The dynamic properties of the micron electrohydraulic displacement feedback control system were simulated. The simulation results are conformed to the experimental results. It is suggested that the value selection of vo/ -, Ka and PID coefficient is significant for the design of themicron electrohydraulic feedback control system. The measurement error was guaranteed to be less than lum by using the high-accuracy electric eddy micro-displacement sensors. The thickness of micron dimension lubricating film was feedback controlled with PID algorithm.In the paper, the lubrication mechanics experiment of typical port plate /cylinder block frictional pair was finished through the lubrication test system. From the experiment results, the lubrication parameters of port plate/cylinder block frictional pair can be acquired. The lubrication characteristics of port plate/cylinder block in axial piston pump such as film thickness, bearing support capability and leakage can be measured. And the influence of working pressure, temperature, rotating speed and structure on the lubrication can be tested as well. The experiment results were conformed to the simulation results through comparison research.