Outer periphery coating method of honeycomb structure

An outer periphery coating method of a honeycomb structure, having coating steps of:

• rotating a columnar honeycomb structure as an object to be coated around a central axis;
• bringing a coating member including a planar spatula and a rubber sheet into contact with a side surface of the honeycomb structure;
• and supplying a coating material slurry to the side surface of the rotating honeycomb structure, to coat the side surface of the honeycomb structure with the coating material supplied to the side surface of the honeycomb structure by the rubber sheet of the coating member,
• wherein the honeycomb structure includes an annular bulge portion formed along an outer peripheral direction on an outer periphery,
• the planar spatula has a coating surface as one surface and a back surface as the other surface, a cut portion having a shape along the shape of the annular bulge portion of the honeycomb structure is formed in one side edge portion, and the side edge portion provided with the cut portion is an inclined surface which is inclined on the side of the coating surface,
• in the rubber sheet, a cut is formed in an end portion so that an end surface of the end portion is parallel to the back surface of the spatula, when the rubber sheet is attached to the coating surface side of the spatula and the end portion of the rubber sheet is bent along the side edge portion of the spatula,
• in the step of bringing the coating member into contact with the side surface of the honeycomb structure, the side edge portion of the spatula is pressed onto the honeycomb structure via the rubber sheet, in a state where the side edge portion of the spatula is parallel to the central axis of the honeycomb structure and the end portion of the rubber sheet is bent along the side edge portion of the spatula, to bring the coating member into contact with the side surface of the honeycomb structure,
• in the step of supplying the coating material slurry to the side surface of the rotating honeycomb structure, the coating material slurry is supplied from a plurality of supply holes of a coating material supply unit disposed adjacent to the rubber sheet of the coating member, and
• an open area of supply holes corresponding in position to the annular bulge portion is 1.3 to 3.0 times greater than an open area of supply holes corresponding in position to the side surface of the honeycomb structure excluding the annular bulge portion, such that an amount of the coating material supplied to the annular bulge portion of the honeycomb structure is larger than an amount of the coating material supplied to the side surface of the honeycomb structure excluding the annular bulge portion.