Research And Optimization Of Flow Passage And Motor Control Circuit Opening And Closing Characteristics Of Axial Piston

With the rapid development of construction machinery industry,the performance of axial piston motor has been paid more and more attention by main engine manufacturers.At present,there are two main problems in the application of domestic high-end axial piston motor in construction machinery,one is the high noise,the other is the "Deviation" caused by the asynchronous opening and closing of the motor.These two problems seriously hinder the localization of high-end axial piston motors.It is urgent to solve the problems of noise and "run-off" of axial piston motors used in construction machinery.This paper takes 125 cc axial piston motor displacement for excavator as the research object and carries out the following work:(1)The composition and control principle of axial piston motor are introduced.Based on the control schematic diagram of axial piston motor,Reynolds number criterion,fluid mechanics theory and pipe design theory,the control principle of axial piston motor is presented,The goal is to minimize turbulence,reduce flow shock and noise,and reduce pressure loss.The section of main inlet circuit is 13.7mm ×39mm rectangular,buffer circuit section 12mm×12mm rectangular,speed control circuit runner diameter is φ4.5mm,balancing valve movable flow path diameter isφ4.2mm;According to the pressure loss along the bend,the bend angle of the main intake circuit is determined to be 33 degrees,the cushion circuit angle is 45 degrees and the balance valve moving circuit is 33 degrees.The structural design of the flow path of the control circuit of the axial piston motor is completed.(2)CFD simulation is carried out with Fluent software to analyze the pressure and speed characteristics on the critical flow section of flow channel of axial piston motor control circuit,obtain the pressure cloud and velocity vector diagram,determine that the pressure and speed are within the wall bearing range,and verify the rationality of flow channel.Find the structure where the design defect locates at the annular window,optimize the defect location structure and change the convex structure at the annular window to horizontal structure.Comparing the CFD simulation post-processing results of flow path of axial piston motor control circuit before and after optimization,it is found that the maximum speed before vortex formation is reduced by 10% after optimization.Random sampling points show that the optimized pressure and speed decrease.It is confirmed that the flow path structure of control circuit of axial piston motor is basically reasonable except for some defects in structure.It is reasonable to determine the optimum scheme by comparing the results before and after optimization.(3)The structure of balancing spool and the control mechanism of spool motion are analyzed.The mathematical model of balancing spool throttle groove is built and analyzed.The functional relationship between the orifice area of the throttle valve controlling spool motion and the starting characteristics of axial piston motor is obtained.The relation curve between the throttle groove shape of balancing spool and the overflow area is plotted.(4)The noise test platform of axial piston motor is built.The noise test of axial piston motor is carried out by using the comprehensive performance test stand and noise tester of axial piston motor.After optimization,the mean sound pressure is reduced by 3.1d B.The comprehensive performance test determines the influence of the improvement scheme on the performance of axial piston motor.The mechanical efficiency,volumetric efficiency and total efficiency of the axial piston motor are 74%,92.9% and 69.8% respectively.The mechanical efficiency,volumetric efficiency and total efficiency of the optimized axial piston motor are 75.3%,93.0% and 70.7%respectively.It can be seen from the numerical value that the optimized scheme affects the mechanical efficiency,volumetric efficiency and total efficiency of the axial piston motor.The total efficiency is about 1% and has a certain improvement.The rationality of the optimization scheme is further determined by comparing the simulation results with the test results.