Static And Dynamic Performance Research And Optimization On Scroll Compressor Crankshaft Components

Scroll compressor’s traits include low noise, high efficiency, compact structure,low components, smooth running and so on. Now it is widely used in all kinds of household air conditioning and car air conditioning, refrigeration, boosting the engine pressure and the vacuum pump. Scroll compressor’s main components include orbiting scroll, static scroll, crankshaft, balance iron, frame, bearings and anti-rotation mechanism. Their working force and conditions will directly affect the efficiency and reliability of the compressor. Therefore, the researches and analysis related to the mechanical properties of the core components and their optimization are very important and also the precondition to ensure the performance and reliability of the scroll compressor.In view of this situation, this paper takes crankshaft and the crankshaft’s components on scroll compressor virtual pototype as research objects. Through finite element analysis ANSYS Workbench platform, we research and analyze the dynamic and static properties of the crankshaft and the crankshaft parts during operation. At the same time, we also optimize the distance between the sliding bearings and angular contact ball bearings, the diameter of crankshaft and the length of crankshaft. The specific contents of research mainly include the following several points:(1) According to the theory of scroll profile and normal-equidistant-curve, the orbiting scroll profile of variable cross-section is designed. While according to the scroll profile equation and its basic parameters, gas forces on orbiting scroll during operation(Normal gas forcerF and tangential gas forcetF) are calculated.(2) Creating the finite element model of the crankshaft and bearing system, the bearing can be simplified into different numbers of uniform cloth springs and then explore the influences of the numbers and position of the springs on the radial stiffness of the crankshaft. Under the maximum gas force generated during the meshing process of the static and dynamic scroll plate is used as a static load, then appling to center position of crankshaft eccentric segment, the stress and deformation of the crankshaft-bearing system are simulated and analyzed while calculating the static stiffness of the crankshaft, which provide a reference for comparing with the optimization results of the crankshaft-bearing system.(3) It needs to do simulation for the dynamic characteristics of the crankshaftand the crankshaft’s components. First it is the modal analysis, which get the first six natural frequencies, modal shapes and vibration characteristics under the two structures of the crankshaft and the crankshaft and shows that the first six natural frequencies are high that indicates they are difficult to resonate under the actual excited frequency and finds factors of affecting the crankshaft’s natural frequencies.On the basis of their modal analysis, the harmonic response analysis is made on the different positions of the crankshaft and the crankshaft components. The characteristics of the stress and displacement with frequency are obtained and the comparative analysis is carried out by the characteristics.(4) By separately optimizing the span between the bearings, axial diameter, the axial length and then doing multi-objective optimization of the three parameters,thereby they can reduce the maximum deflection of the crankshaft’s eccentric section and increase the crankshaft’s radial stiffness. Optimizing and designing make the crankshaft’s components have better static and dynamic performance, which thus reduce friction between the orbiting scroll and static scroll, make them more smoothly and efficiently, and improve bearing life.