Manufacturing method and apparatus of piston used in compressor

A method for manufacturing a hollow piston used in a compressor, wherein the compressor reciprocates the piston by a drive member, which rotates integrally with a rotary shaft, wherein the piston includes a first piece and a second piece, wherein the first piece includes a skirt, which is engaged with the drive member, and a hollow cylindrical portion, and wherein the second piece is coupled to the first piece to cover an opening formed at one end of the cylindrical portion, the method comprising:

• preparing a symmetrical work, wherein the work includes a pair of the symmetrically arranged first pieces, wherein the first pieces are coupled to each other at the skirts;
• and
• friction welding a pair of the second pieces to the ends of the work, wherein, during the friction welding, the second pieces are simultaneously pressed against the opened ends of the cylindrical portions, respectively, and are rotated in the opposite directions.

An apparatus for manufacturing a hollow piston used in a compressor, wherein the compressor reciprocates the piston by a drive member when a rotary shaft rotates, wherein the piston includes a first piece and a second piece, the second piece being coupled to the first piece, the apparatus comprising:

• a holding mechanism for holding a symmetrical work, which includes a pair of the symmetrically arranged first pieces, the first pieces being coupled to each other, wherein the holding mechanism limits rotation of the work about its axis and axial movement of the work;
• and
• a pair of support mechanisms for supporting the second pieces at the axial sides of the work, wherein the support mechanisms rotate the second pieces while simultaneously pressing the second pieces against the work, thereby friction welding the second pieces to the work.