Annular insert molded article and manufacturing method thereof

Abstract

The present invention is intended to provide an annular insert molded article that suppresses contamination of a metal mold and generation of foreign matter without increase in material costs for an adhesive or contamination of a transfer jig, and has a high adhesion strength so that, when the annular insert molded article is attached to a rotating body, the adhesive does not peel off from the insert or remain as foreign matter in the rotating body, and a manufacturing method thereof. An annular insert molded article 1 is manufactured by injection molding in a state where a thermoset resin adhesive A is applied to a joining surface of an annular insert 2 attachable to a rotating body to an annular plastic 3 and then the annular insert 2 and the annular plastic 3 are placed in a metal mold, wherein the range of the adhesive A applied to the annular insert 2 is a range not going beyond boundaries B 1 and B 2 with the annular plastic 3 by more than 3 mm, and the range does not include a portion C of the annular insert 2 to be fitted with the rotating body.

1 . An annular insert molded article manufactured by injection molding in a state where a thermoset resin adhesive is applied to a joining surface of an annular insert attachable to a rotating body to an annular plastic and then the annular insert and the annular plastic are placed in a metal mold, wherein the range of the adhesive applied to the annular insert is a range not going beyond a boundary with the annular plastic by more than 3 mm, and the range does not include a portion of the annular insert to be fitted with the rotating body. 
     
     
         2 . The annular insert molded article according to  claim 1 , wherein
 the annular insert molded article is an axial-type magnetic encoder that has the annular insert as a fixed member and the annular plastic as a plastic magnet, and   the adhesive is applied only to an axially opposed surface of the fixed member.   
     
     
         3 . The annular insert molded article according to  claim 1 , wherein
 the annular insert molded article is a radial-type magnetic encoder that has the annular insert as a fixed member and the annular plastic as a plastic magnet, and   the adhesive is applied only to a radially opposed surface of the fixed member.   
     
     
         4 . A manufacturing method of an annular insert molded article, comprising:
 an adhesive application step of applying a thermoset resin adhesive to a joining surface of an annular insert attachable to a rotating body to an annular plastic; and   an injection molding step of injecting a dissolved plastic material into a metal mold in which the annular insert having undergone the adhesive application step is placed, wherein   in the adhesive application step, the adhesive is applied to the annular insert only in a range not going beyond a boundary with the annular plastic by more than 3 mm, and   the adhesive is not applied to a portion of the annular insert to be fitted with the rotating body.   
     
     
         5 . The manufacturing method of an annular insert molded article according to  claim 4 , wherein
 the annular insert molded article is an axial-type magnetic encoder that has the annular insert as a fixed member and the annular plastic as a plastic magnet, and   the adhesive is applied only to an axially opposed surface of the fixed member in the adhesive application step.   
     
     
         6 . The manufacturing method of an annular insert molded article according to  claim 4 , wherein
 the annular insert molded article is a radial-type magnetic encoder that has the annular insert as a fixed member and the annular plastic as a plastic magnet, and   the adhesive is applied only to a radially opposed surface of the fixed member in the adhesive application step.   
     
     
         7 . The manufacturing method of an annular insert molded article according to  claim 4 , wherein the adhesive is applied to the annular insert in the adhesive application step by a pad printing process in which a pad as a transfer body with the adhesive in a predetermined region is pressed to transfer the adhesive to the annular insert, or by a screen printing process in which the adhesive is placed on a screen printing plate with pores in a predetermined range and is extruded from the pores to transfer the adhesive to the annular insert, or by a brushing process. 
     
     
         8 . The manufacturing method of an annular insert molded article according to  claim 4 , wherein
 the manufacturing method includes a drying and solidification step of volatilizing a solvent included in the adhesive under a temperature condition at a temperature lower than a cross-linking reaction starting temperature of the adhesive to dry and solidify the adhesive between the adhesive application step and the injection molding step, and   the manufacturing method does not include a heating step of heating the adhesive at a temperature equal to or higher than the cross-linking reaction starting temperature of the adhesive to bake the adhesive onto the annular insert.