Slip ring, rotation sensor device having slip ring, and method of manufacturing slip ring

A method of manufacturing a slip ring for use in a slip ring brush type rotation sensor device, comprising the steps of:

• forming a central groove part parallel to long sides of an approximately rectangular metal plate and dented from a first surface at a central part of short sides of the approximately rectangular metal plate by a joggling process, and forming n elongated holes that penetrate to a second surface opposite to the first surface intermittently in the central groove part, and (n×2−1) projecting parts that project together from a predetermined region with respect to an edge part of one of the long sides, by a die-blanking process, where n is a positive number greater than or equal to 2;
• bending the (n×2−1) projecting parts toward the second surface to form projecting bent parts by a bending process;
• rounding the long sides of the approximately rectangular metal plate to join the short sides to each other to form a cylindrical or approximately cylindrical shape by a rounding process;
• molding the rounded metal plate having the cylindrical or approximately cylindrical shape after the rounding process with a resin by a molding process;
• and
• forming (n×2) slits in an outer peripheral surface of the rounded metal sheet having the cylindrical or approximately cylindrical shape and in an outer peripheral surface of the molded resin by a slitting process,
• wherein the step of forming the slits includes
• forming a common part at a metal part on an end provided with the projecting bent parts, to include (n×2) common regions segmented by the slits, and
• forming a detection part at a metal part on another end not provided with the projecting bent parts, to include n conducting regions that are electrically connectable to the common regions at a part of the metal part on the other end where the elongated holes are interrupted, and n isolated regions that are isolated from and not electrically connectable to the common regions at a part of the metal part on the other end where the elongated holes extend,
• wherein the conducting regions and the isolated regions are alternately provided with the slit interposed between adjacent conducting region and isolated region.