Research On Back Pressure Balance System Of Electric Scroll Compressor

With the increasing emphasis on energy conservation and environmental protection in China,pure electric vehicles have gradually become a hot spot in the development of automobile.The scroll compressors for pure electric vehicle air conditioners have also become the focus of research.The orbiting scroll of the electric scroll compressor generates an axial clearance between the orbiting scroll and the static scroll under the action of the axial gas force,and the refrigerant forms a radial leakage through the gap,so that the displacement of the electric scroll compressor less than the rated displacement.The back pressure which can be provided on the back of the orbiting scroll through the back pressure oil path to balance the axial gas force received by the orbiting scroll.If the back pressure is too small,the orbiting scrolls and static scrolls will be separated,the axial clearance will be increased,the refrigerant leakage will be increased.If the back pressure is too large,the orbiting scrolls and static scrolls will be tightly attached,the friction and wear will be intensify,the loss will be increase.The electric scroll compressor under the wide rotating speed range,the back pressure changes greatly,and the axial force of the movable scroll cannot be well balanced.Firstly,under the constant working condition of the electric scroll compressor,the back pressure in the back pressure balance system is not enough to balance the axial gas force of the orbiting scroll.The physical model of the back pressure oil path was established according to the prototype,the feasibility of structural optimization was analyzed.Combining theoretical calculation and Fluent numerical simulation to optimized the structure,the optimal back pressure oil path was obtained under two speed conditions,a mathematical model was established between the spindle speed and the pressure drop of the optimal back pressure oil path.Then,focusing on the balance problem of the orbiting scroll under variable working condition,the speed partitioned back pressure balance system was proposed and the structural design was carried out.It was proposed to use the electromagnetic reversing valve to control the switching of the two-way back pressure oil path to provide back pressure.The structure,drive module and drive software of the electromagnetic reversing valve were designed.The theoretical calculation and Fluent numerical simulation were combined to calculate the back pressure of the two-way back pressure oil path underdifferent speed conditions,the applicable speed range of the pressure path was zoned.The results show that the small changes in the structure and size of the back pressure oil path in the back pressure balance system will cause a large change in back pressure.The local back structure of the back pressure oil path can be changed to obtain a reasonable back pressure.Under certain condition of back pressure oil path,with the increase of the spindle speed of the electric scroll compressor,the back pressure decreased linearly.The optimal back pressure oil path under the low speed condition had insufficient back pressure at high speed,which will cause the back pressure regulating valve to flutter phenomenon,can not work normally.The optimal back pressure oil path under high speed conditions had too large back pressure when the speed was low,which will make the orbiting scrolls and static scrolls be closed,friction and wear will be intensify,friction loss will be increase;The revolving speed zone circulating oil supply model can uniformly control the back pressure in a wide range of operating conditions within a reasonable range,so that the axial gas forces of the orbiting scroll were well balanced under different speed conditions.Comparing the theoretical calculation results of back pressure drop with the numerical simulation results of Fluent,it was found that the two coincide well.The result and the proposed optimization method can provide reference for designing the back pressure balance system of the electric scroll compressor.