Research On The Mechanics Properties And Gear Fatigue Life For Internal Gear Pump

Internal gear pumps are widely used in practice, the lubrication performance between stationary crescent and external gear, the force and the fatigue life of the gear play important roles for the application. But the study on these problems is still inadequate up to now.In this thesis, a calculating model was established for calculating the lubrication performance between stationary crescent and tooth surface. And based on this model and by numerical simulation, the type LL4724 internal gear pump was taken as the example to research the oil film pressure distribution and the influences of the gap between stationary crescent and external gear, rotation speed of small gear on the film pressure, friction force and the circumferential flow rate of the gear pump.Taking an involute spur gear as example, this thesis analyzed the gear meshing process to derive the computation model of tooth bending deformation and contact elastic deformation, constructed the deformation coordinate relationship to establish a precise calculation mechanical model of tooth loading. And then, by MATLAB programming, solved the precise calculation model by complex trapezoidal integral method. For a specific example, it was calculated that the change of tooth loading, tooth surface contact stress and tooth root bending stress in gear meshing. A force model was established for calculating the force on external gear shaft, obtained the force and the force angle of internal gear shaft according to the time change, and the type LL4724 internal gear pump was taken as the example to calculate the oil film pressure distribution and the influences of the gap between stationary crescent and external gear on the force and the force angle of the internal gear shaft. Determined the dangerous position of gear contact fatigue and bending fatigue, and calculated the gear meshing load spectrum, tooth contact stress spectrum and bending stress spectrum in dangerous fatigue position, and then calculated the gear fatigue life by using σ-N curve.The research results of this thesis can provide reference for the design and further research of the internal gear pump.