Precision measurement of scroll profiles

Scroll compressors are widely used in air conditioner compressor, vacuum pump and so on. Profile measurement of a scroll compressor is important for improving compression efficiency. This paper describes the involute profile measurement of a scroll compressor by using r-θ measurement system for the manufacturing line. Involute profile measurement system consists of X-Z-θ stage and contact type scanning probe. Scanning probe draws Archimedean spiral locus by X-θ stage. Output of scanning probe includes profile error and difference of Archimedean spiral and involute. To confirm that influence of coordinate system error, simulation was carried out. It was confirmed that profile measurement error was a one tenth or less compared with the rotation setting error of work piece. From the simulation result of Y-directional offset between rotation center of θ stage and center of probe sphere, to achieve the required accuracy of profile measurement, it is necessary to reduce or measure the probe alignment error to under the required accuracy order. Fixed scroll outside-involute profile error is measured by developed measurement system. The difference from CMM result is seen in the center part. It is caused by residual Y directional alignment error of scanning probe. Excluding the center part, measurement result is corresponding to CMM result.