Optimization design of structural parameters of duplex geared pump in hydraulic automatic transmission

Gear pumps often bear unbalanced radial hydraulic pressure, which is easy to cause serious wear of bearings, and the improvement of working pressure will be limited by many aspects. The built-in double gear pump of hydraulic mechanical automatic transmission is designed, and the structural composition and characteristics are analyzed; the basic parameters of gear pump are designed, and the working process and instantaneous flow characteristics are analyzed; the radial force generated by the hydraulic pressure along the gear circumference, the radial force generated by the gear meshing transmission torque and the synthetic force are analyzed; the structural parameters of gear pump are designed. According to the analysis results, the gear strength is checked by using the finite element model. Based on the gear pump test bench, the characteristics of the gear pump are analyzed under two working conditions: fixed speed (1,500 rpm), regulated pressure (1 MPa - 5 MPa), fixed pressure (2 MPa) and regulated speed (600 rpm – 1,800 rpm) to test the reliability of the design. The results show that the radial force generated by the liquid pressure of the center wheel of the double gear pump is balanced, and the meshing force of the center wheel is also balanced. The maximum stress on the center gear of gear pump occurs at the tooth root, which is 98.453 MPa, far less than the yield limit of gear material. When the pump speed is constant, the total efficiency, mechanical efficiency and volumetric efficiency of the pump show a decreasing trend with the increase of pressure, but the range is small. When the pressure remains unchanged, the flow of the pump increases gradually with the increase of rotating speed. The torque increase shows a downward trend, but the range is small. The mechanical efficiency shows an increasing trend, but the range is small. The volumetric efficiency increases first and then decrease. When the rotating speed is 1,000 rpm ~ 1,500 rpm, the volumetric efficiency of the pump is high. The analysis contents and results provide a reference for the design of this kind of gear pump.