BALL BEARING WITH BOTH SIDES SEALED

摘要

Disclosed is a ball bearing with both sides sealed which is capable of preventing the pressure in a bearing space from being dropped due to cooling after a plastic belt guide wheel is molded and preventing an inward lip of a rubber seal from being attached to the inner side of a seal groove due to a reduced pressure. The ball bearing includes an outer ring (2) on the outer diameter surface of which the belt guide wheel (21) is formed by plastic molding. The outer ring (2) is provided on both end portions of the inner diameter surface thereof with a pair of seal fit grooves (8), into which an outer diameter portion of the rubber seal (10) is fitted. The inward lip (12) is formed on an inner circumference portion of the rubber seal (10) and has a tip portion which is brought into resilient contact with an inner side (9a) of the seal groove (9) formed on the outer diameter surface of an inner ring (3), thereby sealing the bearing space. The inward lip (12) has a contact surface which resiliently contacts with the inner side (9a) of the seal groove (9) and is provided, at least on a circumferential part of the contact surface, with a recessed portion (18) that defines an infinitesimal gap with the inner side (9a) of the seal groove (9). The recessed portion (18) serves to leak to outside an increased pressure in the bearing space which is caused by an increase in temperature of the belt guide wheel (21) during the plastic molding. The pressure leakage is combined with cooling after the plastic molding to keep the pressure in the bearing space constant, thereby preventing the inward lip (12) of the rubber seal (10) from being attached to the inner side (9a) of the seal groove (9) of the inner ring (3) due to a reduced pressure.