Design Of Double Circular Arc Helical Gear Hydraulic Pump And Analysis Of Its Axial Force

Gear hydraulic pump,which serves as one of the power components in hydraulic systems,has the advantages of simple structure,easy to manufacture,strong self-priming capacity,not sensitive to the pollution of the oil and so on.However,the commonly used spur gear hydraulic pump,whose tooth profile curve is involute,has the disadvantages of the phenomenon of trapping oil,high flow rate fluctuation amplitude and high noise in the working process due to structural factors.In order to improve the comprehensive performances of gear hydraulic pumps,a double arc helical gear hydraulic pump was designed,its axial force produced in the working process was analyzed and the compensation and bearing measures of the axial force were studied.The main research contents were summarized as follows:(1)In view of the phenomenon of trapping oil,high flow rate fluctuation and high noise in gear hydraulic pumps,the gears of which are spur gears and the tooth profile of the gears is involute,double arc helical gears were designed as the motion pair of the gear hydraulic pump,and the curve with the characteristics of "arc-involute-arc"was adopted as the tooth profile curve of the gears.The main structural parameters of the gears were determined and the model of active and passive gears were established.The equivalent stress and contact stress of active and passive gears generated in the meshing process were investigated by finite element method.(2)The axial force in the working process of the gear hydraulic pump was studied.It was analyzed theoretically by the theory of differential equation of curve and curved surface and thus,the calculation formula of axial force was obtained.The variation law of the output pressure and axial force of the gear hydraulic pump was analyzed by computational fluid dynamics(CFD)method.(3)The gear shaft,shaft sleeve,plunger,rear pump cover,front pump cover,pump body and other components of the gear hydraulic pump were designed and the strength of the main parts were analyzed and checked.The radial force of gear shafts of the gear hydraulic pump was analyzed and it was balanced by introducing the hydraulic oil in the high pressure area into the inside area of the shaft sleeve.The hydrostatic bearings which can bear the radial force could be formed.The axial force of gear shafts was analyzed,the plungers of floating hydrostatic bearing and the oil passages were designed.By introducing high pressure oil into the end face of the plunger,the axial force can be balanced.The assembly of the gear hydraulic pump was completed.(4)Considering the variation characteristics of output pressure of the gear hydraulic pump,the variation law of axial force under different speeds and loads was analyzed theoretically.The bearing capacity and balance performance of the hydrostatic bearings at the end of the gear shaft were analyzed.The results show that more than 83%of the axial force can be balanced and the bearing capacity is reliable.