Scroll, Wrap, Stroke Volume, Capacity Increase
In recent years, there has been demand for a large-capacity scroll compressor to reduce cost and improve performance. To increase the capacity of the scroll compressor, technology to expand the stroke volume without increasing the shell size is required. To expand the stroke volume, expanding the wrap height in the axial direction is most effective. However, the higher wrap height raises the stress on the wrap and causes the orbiting scroll to overturn. So, we started to study a new shape of wrap to expand the stroke volume in the horizontal direction. The base plate of an orbiting scroll is usually circular. However, the trajectory of the fixed scroll on the base plate of the orbiting scroll is not circular, so wasted space that is not useful for compression exists on the base plate. We devised an oval wrap to make the trajectory of the fixed scroll on the base plate circular and reduce this space. The radius of basic circle was constant regardless of the involute angle in the conventional wrap. On the other hand, we can make the wrap shape “oval” by changing the radius of the basic circle sinusoidally (every 180 degrees). In this conference, we will present the geometric theory of our new oval wrap and the experimental result of the prototype. The results are follows: (1) It is possible to increase the stroke volume by more than 20% with the oval wrap. (2) A prototype with the oval wrap operates stably, and compressor efficiency is equivalent to the conventional wrap.