Balance inspection apparatus, balance inspection method, balance-inspected crankshaft, arithmetic processing device, and program

A balance inspection method that calculates information on balance of a crankshaft, the method comprising:

• using a balance inspection apparatus including:
• a plurality of surface shape measuring parts that are each arranged around a rotation center axis of the crankshaft and optically measure a surface shape of the crankshaft;
• a positioning device part that moves the surface shape measuring part relative to the crankshaft in the direction of the rotation center axis of the crankshaft;
• a storage unit that stores a surface shape model, the surface shape model in which a designed surface shape of the crankshaft is defined in a coordinate system in which a designed rotation center axis of the crankshaft is an X axis;
• and
• an arithmetic processing unit that calculates information on balance of the crankshaft based on measurement results of a plurality of the surface shape measuring parts;
• a plurality of the surface shape measuring parts are arranged to measure a surface shape of the crankshaft over substantially the entire circumference and moved relative to the crankshaft by the positioning device part, to thereby measure a surface shape of the crankshaft over substantially the entire length, and
• the arithmetic processing unit
• combines measurement results of a plurality of the surface shape measuring parts, to thereby generate three-dimensional point cloud data consisting of data points corresponding to points of a surface of the crankshaft,
• aligns the three-dimensional point cloud data with the surface shape model read from the storage unit in a coordinate system of the surface shape model,
• based on the three-dimensional point cloud data that have been aligned, generates surface data represented by a collection of planes passing through three data points that constitute the three-dimensional point cloud data,
• extracts, from the surface data, evaluation object data, which are surface data of an evaluation object portion including at least an arm of the crankshaft, and calculates gravitational centers and areas of cross sections orthogonal to the X axis at a plurality of positions along the X axis of the evaluation object data,
• calculates a gravitational center and a weight of the evaluation object data based on the gravitational centers of the cross sections and predetermined weights set according to the areas of the cross sections, and
• calculates information on balance of the crankshaft based on the gravitational center and the weight of the evaluation object data.

An arithmetic processing device that calculates information on balance of a crankshaft, the device comprising:

• a computer processor including processing circuitry programmed to perform operations comprising:
• store a surface shape model in a storage unit, the surface shape model in which a designed surface shape of the crankshaft is defined in a coordinate system in which a designed rotation center axis of the crankshaft is an X axis;
• align three-dimensional point cloud data, the three-dimensional point cloud data generated based on results obtained by optically measuring a surface shape of the crankshaft and consisting of data points corresponding to points of a surface of the crankshaft, with the surface shape model read from the storage unit in a coordinate system of the surface shape model;
• generate surface data represented by a collection of planes passing through three data points that constitute the three-dimensional point cloud data, based on the three-dimensional point cloud data that have been aligned;
• extract, from the surface data evaluation object data, which are surface data of an evaluation object portion including at least an arm of the crankshaft, and calculate gravitational centers and areas of cross sections orthogonal to the X axis at a plurality of positions along the X axis of the evaluation object data;
• calculate a gravitational center and a weight of the evaluation object data based on the gravitational centers of the cross sections and predetermined weights set according to the areas of the cross sections, and
• calculate information on balance of the crankshaft based on the gravitational center and the weight of the evaluation object data.