Truing method for grinding wheel, its truing device and grinding machine

A grinding machine for grinding a workpiece by at least one rotatably driven grinding wheel being rotatably driven about a grinding wheel axis, comprising:

• at least one grinding wheel composed of grindstones having abrasive grains bound by a conductive binding material,
• grinding wheel rotary driving means for rotating and driving the at least one grinding wheel about the grinding wheel axis,
• grinding wheel infeed driving means for moving the at least one grinding wheel in an infeed direction,
• electro-discharge truing means for truing the grindstones of the at least one grinding wheel by electro-discharge action, and
• control means for controlling the grinding wheel rotary driving means, the grinding wheel infeed driving means, and the electro-discharge truing means synchronously with each other,
• wherein said electro-discharge truing means includes an electro-discharge truing electrode disposed oppositely to the at least one grinding wheel, current feeding means for feeding current to a grindstone surface of each at least one grinding wheel and truing electrode driving means for traversing the electro-discharge truing electrode along each one of the at least one grindstone surface,
• said electro-discharge truing electrode is a disk-shaped rotary electrode being rotatably driven by electrode rotary drive means, and
• said control means controls a gap dimension between each one of the at least one grindstone surface of the at least one grinding wheel and a cylindrical in electrode surface of the rotary electrode by controlling the grinding wheel infeed driving means, according to the electrical information of a position of the rotary electrode detected either during a traversing motion or upon completion of the traversing motion of the rotary electrode.