Research On Key Issues Of Moving Coil Linear Compressor

Nowadays widely used compressor in refrigerator is reciprocating piston compressor driven by rotary motor, in which conversion mechanism (Crank) is essential. However, with this mechanism the compressor becomes cumbersome and transmission parts also increase, which not only makes efficiency lower, but also causes some other problems, such as friction loss, wear and noise. The difference between linear compressor and conventional reciprocating compressor is that linear compressor doesn't have crank and connecting rod mechanism. So relative motion parts are reduced. And the corresponding friction and noise are reduced. It is easy to regulate flow of linear compressor by adjusting the voltage. And it can keep high efficiency in the whole range of flow regulation. With these advantages linear compressor becomes an important research direction of future refrigerator compressor. This paper focuses on moving-coil linear compressor and the main contents are as follows:(1) One magnetic circuit structure composed of several silicon steel layers with different size is developed. This structure can reduce the iron loss of motor and meanwhile decrease the size of the motor structure as much as possible. One problem is that the distribution of the magnetic field made up of silicon steels with clearance can not be solved by traditional equivalent circuit method and the finite element method. So a new magnetic circuit model considering core reluctance is developed for this kind of magnetic circuit, which involves slicing the magnetic circuit into layers and each layer corresponds to one part of iron core, gas gap and magnet. Then magnetic flux of each layer is determined by the minimum of total reluctance. System equations of linear compressor are obtained by using this model and mechnical dynamics.Based on this new model a great deal of calculation is done to analyze the influence of some key parameters such as size of inner and outer yoke, size of coil, compressor clearance, piston stroke and work frequency on the performance of linear compressor Based on the analysis the optimization of these parameters is completed.(2) Based on the analysis about the existing model of flow regulation method for linear compressor, a new and more effective flow regulation method using triac control method aiming at low power loss and high efficiency is developed, which considers clearance and stroke together.Through a great deal of calculation and analysis on the relationship among flow.stoke and clearance and other factors influencing compressor efficiency, The scheme how to set the clearance and stoke at flow regulation is obtained. The new method is proved to be highly efficient and feasible by comparing it with other flow rugulation methods of chaning clearrance and storke. Besides the study on flow regulation, according to the requirement of control system, a new control method of linear compressor is designed, using MCU (Microprogrammed Control Unit) as the core control device and triac as cut-off wave device. It contains functions such as start, stop, load operation and protect of compressor. The control curcuit and relative programs are also completed.(3) A linear compressor prototype is designed and manufactureed based on the theoretical analysis. The experiment test platform of linear compressor is established. All kinds of losses in the operation of linear compressor are analyzed by the experiment test.Experiments prove that the iron core loss decreases after improvement of magnetic circuit. Control and flow regulation of linear compressor are achieved by control circuit. With the flow regulation method that considers clearance and stroke together,the efficiency of linear compressor is kept in high level during the course of flow regulation.