Vibration reduction, Natural frequency, Reciprocating Compressor, Refrigerator, Support structure
In household refrigerators, the rotational speed of a reciprocating compressor can be appropriately adjusted according to the temperature inside of the refrigerator. The lower rotational speed reduces the power consumption of the compressor. However, several natural frequencies of the compressor exist in the low rotation region, and besides, the unbalance force arising from the piston motion acts on the internal drive unit. Thereby the vibrations of the compressor are likely to be larger due to the resonance in the low rotation region. Although the compressor on the refrigerator is supported by vibration-proofing materials, such as rubber bushes, it is difficult to fully suppress the vibration transmission from the compressor to the refrigerator. In this study, therefore, a method for supporting the drive unit inside the shell, which is called “the self-standing support” is newly proposed in order to reduce the vibration of the compressor drastically. In the proposed method, a spherical support element is utilized instead of coil springs to support the drive unit. And the drive unit can maintain a stable self-standing state by acting restoring moment due to the gravity while it is directly placed on the shell. The natural frequencies of the compressor can be greatly reduced by decreasing the support stiffness for the drive unit in comparison with the support method using coil springs. Furthermore, in designing the drive unit, the application point of the exciting force is matched with the center of percussion to the contact point on the spherical support. As a consequence, the periodic restraining force acting on the contact point can be minimized. By these two features, it is possible to considerably reduce the vibration transmission from the drive unit to the shell. In the present study, a simplified model for a reciprocating compressor is treated, and the effectiveness of the self-standing support is investigated analytically and experimentally.