Manufacturing method for slinger used in rotary seal, and rotary seal

A manufacturing method of a slinger to be used in a rotary seal that includes the slinger, a core metal, and a seal member,

• the slinger including a cylindrical sleeve and a flange extending outward in a radial direction from one end of the sleeve in an axial direction,
• the core metal including a core metal cylinder having a cylindrical shape, and a core metal flange extending inward in the radial direction from one end of the core metal cylinder in the axial direction,
• the seal member including a base portion joined to the core metal, and a seal lip portion extending from the base portion,
• the seal lip portion including an axial lip in slidable contact with a first slide-contact surface which is an inner surface of the flange of the slinger, and a radial lip in slidable contact with a second slide-contact surface which is an outer circumferential surface of the sleeve of the slinger,
• the manufacturing method comprising:
• molding an annular blank material from a dull-finished steel sheet material through sheet metal press working, laser cutting machining, or wire cut electric discharge machining;
• burring the annular blank material, so as to mold the slinger;
• and
• pressing a mold against the first slide-contact surface of the molded slinger, wherein
• the burring is performed using a mold having a face that has an arithmetical mean roughness Ra set to 0.03 μm≤Ra≤0.07 μm, the face coming into contact with the second slide-contact surface,
• a clearance for the mold used for the burring is set to T×(0.9 to 0.7) where “T” represents a sheet thickness of the annular blank material,
• the pressing is performed using a mold having a face with an arithmetical mean roughness Ra set to 0.03 μm≤Ra≤0.07 μm, the face coming into contact with the first slide-contact surface,
• a ratio of pressing force for pressing the mold in the pressing to a 0.2% proof stress of the dull-finished material is set to 1.0 or more and 1.53 or less, and,
• with these conditions, an arithmetical mean roughness Ra of each of the first slide-contact surface and the second slide-contact surface of the slinger falls within a predetermined range of 0.25 μm≤Ra≤0.5 μm.