Protective cover having sensor holder part, bearing device including the protective cover, and method for manufacturing protective cover having sensor holder part

2:

• A protective cover having a sensor holder part in a bearing device including:
• an inner ring with an inner ring track surface on an outer peripheral surface;
• an outer ring with an outer ring track surface on an inner peripheral surface;
• a bearing having a rolling element rolling between the inner ring track surface and the outer ring track surface;
• a magnetic encoder that is positioned at one axial end portion of the bearing, fixed to the inner ring, and has N and S poles alternately arranged at regular intervals in an circumferential direction;
• and a magnetic sensor that is opposed to the magnetic poles of the magnetic encoder to detect rotation of the magnetic encoder, wherein
• the protective cover is a cup-shaped protective cover that is press-fitted into the outer ring to seal the one axial end portion of the bearing, and has the sensor holder part holding the magnetic sensor and a division wall that is thinner than the other part to divide the magnetic encoder and the magnetic sensor,
• out of a cylindrical member and a disc-shaped member forming the cup shape, at least the disc-shaped member is a molded article formed by injection molding, and
• the disc-shaped member has a mark of a main gate of a molding die for use in the injection molding or a removal processed portion formed by removing and processing the mark in a position separated from the division wall, and has a mark of a sub gate of the molding die for use in the injection molding or a removal processed portion formed by removing and processing the mark in or near the division wall.

4:

• A method for manufacturing a protective cover having a sensor holder part in a bearing device including:
• an inner ring with an inner ring track surface on an outer peripheral surface;
• an outer ring with an outer ring track surface on an inner peripheral surface;
• a bearing having a rolling element rolling between the inner ring track surface and the outer ring track surface;
• a magnetic encoder that is positioned at one axial end portion of the bearing, fixed to the inner ring, and has N and S poles alternately arranged at regular intervals in an circumferential direction;
• and a magnetic sensor that is opposed to the magnetic poles of the magnetic encoder to detect rotation of the magnetic encoder, the protective cover being a cup-shaped protective cover that is press-fitted into the outer ring to seal the one axial end portion of the bearing, and has the sensor holder part holding the magnetic sensor and a division wall that is thinner than the other part to divide the magnetic encoder and the magnetic sensor, wherein
• the manufacturing method comprises a charging step in injection molding of charging a molten resin into a cavity of a molding die for molding, out of a cylindrical member and a disc-shaped member forming the cup shape, at least the disc-shaped member, and
• at the charging step in the injection molding, the molten resin is charged so as not to generate a charging end weld on the division wall by performing:
• forming a flow path for preferentially charging the molten resin into a thin part for forming the division wall between a gate position of the cavity and the thin part;
• using a device capable of controlling mechanically the thickness of a portion to be the division wall in the molding die to perform a control such that the portion to be the division wall becomes thick in the first half of the step and the portion to be the division wall becomes thin in the second half of the step to preferentially charge the molten resin into the portion to be the division wall when the portion is thick in the first half of the step and thin the portion to be the division wall in the second half of the step;
• or
• arranging a main gate in the cavity in a position separated from the thin part forming the division wall, arranging a sub gate in the thin part forming the division wall or near the thin part, and controlling a timing for injecting the molten resin from the sub gate relative to a timing for injecting the molten resin from the main gate to preferentially charge the molten resin from the sub gate into the thin part.