| 摘要 |
<p>PROBLEM TO BE SOLVED: To easily form a thick-wall portion of a hollow cylindrical portion of a compressor piston. SOLUTION: A piston raw material 160 for manufacturing the compressor piston is manufactured by forging. An inner peripheral surface 200 and a bottom surface 202 of a bottomed hollow cylindrical portion 164 are molded by side punching. Center holes 210, 212 are respectively formed on the bottom surface 202 and a projecting portion 172 of the piston raw material 160. A mandrel 310 of a spinning device is engaged in the center hole 210, and a center 318 is engaged in the center hole 212. While the piston raw material 160 is centered and supported from both sides, three spinning rollers 224 synchronize and approach each other, thereby reducing the diameter of an opening side end portion of a hollow cylindrical portion 166. After forming a diameter-reducing portion 130 and a non-diameter-reducing portion 132 on the hollow cylindrical portion 166, by cutting machining of an outer peripheral surface 328, the outer diameter of the non-diameter-reducing portion 132 is made to be same as the outer diameter of the diameter-reducing portion 130, and a thick-wall portion 130 is formed on an opening side end portion of the hollow cylindrical portion 166. An annular piston ring groove is formed on an outer peripheral surface of the thick-wall portion 130.</p> |
