Design And Characteristic Study Of Multi-rotor Hydraulic Pump

Many modern intelligent machinery requires multiple actuators synchronized action in the course of operation.The accuracy of the hydraulic synchronization control especially the high-speed action of these systems is a difficult problem of research.The commonly used synchronous control methods at present have their own advantages and disadvantages.Aiming at the synchronous hydraulic system with multiple terminal executive components,it is of great practical significance and application value to reduce the difficulty and cost of control and improve the control precision of hydraulic system by studying the multi-rotor pump with multiple working units and low breakdown rate.A flow pulsation instantaneous synchronization principle of parallel multi-rotor hydraulic pump was put forward in this paper.The parallel multi-rotor hydraulic pump was divided into two categories:parallel gear pump and parallel cam pump.Then the research emphasis was on the parallel gear pump.According to the working condition of the parallel gear pump,it was used as synchronous pump and synchronous shunt.On the basis of the flow characteristic study,parameter design and characteristic research were carried out,and the test prototype was developed.Using the prototype,variable control test for the parallel gear pump and constant flow control test for the parallel synchronous shunt were done.(1)The flow pulsation instantaneous synchronization principle of parallel multi-rotor pump was studied.According to the relationship between the number of center rotor teeth and planetary rotors,the pump can be divided into three classes.The flow pulsation instantaneous states of each working unit of the Class Ⅰ pump are fully synchronous,and of the Class Ⅱ pump are packets synchronous but be independent control among groups,and of the Class Ⅲ pump are different but average synchronous among working units.(2)The flow characteristics of three classes of parallel gear pumps were studied.By analyzing the meshing point position and trajectory of the center gear and the planetary gear,the instantaneous flow rate and theoretical displacement expressions of each working unit of the three classes of pumps were derived by finite volume method.The effect of trapped oil on the parallel gear pump was analyzed.The research results show that the volumetric efficiency can be effectively improved by designing unload groove to eliminate trapped oil,and the more center gear teeth number,the more obvious consequent.(3)The parallel gear pump was designed.The mathematic models of radial leakage and face leakage were established by using the clearance flow theory.Combined with the fluid analysis module of the ANSYS software,the influence rules of various factors on the leakage and volumetric efficiency of the parallel gear pump were analyzed when it was working in pumping state.Based on this,the key design parameters such as center gear teeth number,radial clearance,face clearance and planetary gear teeth number were determined.The research results show that,by properly selecting the center gear teeth number and using the design method of the center gear radial clearance greater than the planetary gear,the performance of the parallel gear pump can be achieved or higher than the common gear pump.(4)The characteristics of parallel gear pump were studied by simulation experiment.The research results show that,the common characteristics of the I,II and III parallel gear pumps are as the outlet pressure increases,the flow rate decreases linearly,and the local amplitude of the instantaneous velocity curve increases.The local fluctuation is cyclical at the time axis.The outlet flow velocity of each working unit is only related to its own pressure value but not the other units.Work units synchronous variable control can be achieved through controlling the gear rotating speed by an adjustable-speed motor.(5)The design and characteristics study of the parallel synchronous shunt were done.A parallel synchronous shunt is a Class I parallel gear pump applied as a shunt.The working states of shunt units are instantaneously synchronized.The working condition is the center gear teeth number can be divided by uniformly distributed planetary gears number N.The influence rules of various factors on the leakage and volumetric efficiency were analyzed,and the key design parameters were determined.The research results show that,when the parallel gear pump is used as a synchronous shunt,the volume efficiency is higher than used as a synchronous pump.When the load pressure is constant,the mean flow rate decreases linearly with the gear speed reducing,and synchronous variable control can be realized by adjusting the center gear rotating speed by a servo motor.When the load pressure changes,the mean flow rate varies linearly with the same direction,and the synchronous constant control can be realized through increasing or decreasing the gear rotating speed by a servo motor.(6)A three-gear pump prototype was developed.Using the prototype,variable control test for the parallel gear pump and constant flow control test for the parallel synchronous shunt were completed,and the results of the tests were analyzed.The problems of large leakage and disparity among the three outlet flow in tests were dissected,and solutions were put forward.