Abstract: The generation method, features and geometry of circle involute wrap modified with twin-circular arcs are investigated, and the existence condition of such a modified wrap is obtained. This profile modification is divided into type-Ⅰand type-Ⅱ according to the different positions of circular arc center. The general equations of these two modified wraps are derived. The mutual dependence of wrap parameters and their influence factor are analysed. In addition, the effect of profile modifica-tion on the performance of wrap profile is discussed in terms of curvature radius and meshing rotational angles. The modified wraps with minimum modification angle and minimum modi-fication expansion angle are presented. Finally, the profile modification of line segment involute and regular polygon involute is also studied, and the general modified wrap of arbitrary involute profile modification by means of twin-circular arcs is established, improving and enriching the theory of profile modification with twin-circular arcs as well as making a basis for profile modification with multi-pairs of circular arcs.

Key words: General modified wrap, Geometric theory, Involute type profile, Modification using twin-circular arcs, Scroll compressor