Lathe-cutting apparatus for crankshaft and lathe-cutting method thereof

A lathe-cutting apparatus which performs lathe-cutting of an eccentric part of a crankshaft, comprising:

• supporting devices which support both end portions of said crankshaft;
• rotational drive devices which rotate said crankshaft from at least one end side of said supporting devices with a main journal of said crankshaft as a center, and rotationally drive said eccentric part;
• tools which perform lathe-cutting of said eccentric part;
• two cutting tool driving main shafts each having an axis parallel with an axial direction of said crankshaft;
• eccentric pins which are provided to be protruded by the same eccentricity amount on the end surface of said cutting tool driving main shafts;
• tool stands each including said tool at a tip end portion thereof, and including two eccentric pin bearings for fitting said eccentric pins which are provided with the same space between them as the space between the axes of said two cutting tool drive main shafts;
• driving devices which rotationally drives at least any one shaft of said two cutting tool driving main shafts;
• and
• synchronization means which synchronizes crank rotation of the cutting edge position of said tools via said tool stands by said driving devices with rotation of said eccentric part with said main journal as a center.

A lathe-cutting method of performing lathe-cutting of an eccentric part of a crankshaft, comprising the steps of:

• on performing lathe-cutting of said eccentric part, supporting both end portions of said crankshaft;
• rotating said crankshaft from at least one end side of said both end portions with a main journal as a center;
• and
• rotating two cutting tool driving main shafts which are provided in parallel with an axial direction of said crankshaft synchronously with the rotation of said eccentric part with said main journal as the center, and rotationally driving a tool stand via respective eccentric pins which are provided at one end surfaces of said cutting tool driving main shafts, thereby making a cutting edge position of the tool provided at said tool stand perform crank rotation synchronously with the rotation of said eccentric part.