Manufacturing method for upper case of strut bearing, and strut bearing

A manufacturing method for an upper case of a strut bearing,

• the strut bearing including:
• an upper case to be fixed to an upper end portion of a strut of a vehicle strut suspension;
• a lower case to be directly or indirectly connected to a coil spring disposed on an outer side of the strut;
• an upper raceway ring held by the upper case;
• a lower raceway ring held by the lower case;
• and
• a rolling element that rolls between the upper raceway ring and the lower raceway ring;
• the upper case and the lower case being made of a synthetic resin;
• and
• the upper case including an inclined cylindrical portion inclined with respect to a central axis of the strut bearing, the inclined cylindrical portion having an inner surface having opposing flattened portions that interrupt an otherwise continuously curved inner surface of the upper case,
• the manufacturing method comprising:
• producing the upper case by injection molding using an injection molding mold that is an axial draw mold including a fixed mold and a movable mold;
• and
• providing the fixed mold with a first half body, and providing the movable mold with a second half body, wherein
• the first half body and the second half body abut against each other at respective first and second inclined planes,
• the first half body has a first flat surface and a second flat surface disposed at opposing exterior surface portions of the first half body, the first and second flat surfaces disposed at both ends of the first inclined plane,
• the second half body has a third flat surface and a fourth flat surface disposed at opposing exterior surface portions of the second half body, the third and fourth flat surfaces disposed at both ends of the second inclined plane,
• when the first inclined plane of the first half body is mated against the second inclined plane of the second half body, the first and third flat surfaces together form a first uniform flat surface and the second and fourth flat surfaces together form a second uniform flat surface, the first and second uniform flat surfaces create the opposing flattened portions that interrupt the otherwise continuously curved inner surface of the upper case, and
• the first and second uniform flat surfaces are flat surfaces that prevent occurrence of undercutting when the upper case is removed from the injection molding mold.