| 摘要 |
PURPOSE:To efficiently etch a cylinder bore surface and to reduce oil consumption by holding an etching liquid in a hermetic state between an electrode and the bore surface and moving the electrode at varied moving speeds while the quantity of the electricity to be supplied is maintained constant. CONSTITUTION:The electrode 4 is freely slidably inserted into the cylinder bore 2 of a cylinder block to form a hermetic space 8 between flanges 5, 6 having a seal ring 7 and the bore surface 3. While the etching liquid 9 supplied from a pipe 10 is maintained in the above-mentioned hermetic space 8, the above-mentioned electrode 4 is moved and the surface 3 is electrically etched. The moving speed of the electrode 4 is made higher toward the lower side than the upper side of the cylinder bore 2 while the quantity of the electricity to be supplied is maintained constant. The surface in the range of about 20mm downward from the top dead point of the cylinder bore surface 3 is thereby formed to 2.5-3.5muRz surface roughness, the range B from the lower part thereof to the part near the bottom dead point to 1.5-2.5muRz surface roughness and the part C below the bottom dead point to <=1.5muRz surface roughness. |
