Ball joint assembly for vehicle and manufacturing method thereof

A method of manufacturing a ball joint assembly for a vehicle comprising a ball stud having a ball on a shaft, a bearing member roll-contacted with the ball of the ball stud, wherein the bearing member presents a plurality of protrusions at the exterior circumference thereof along a circumferential direction, a seat member supporting an exterior circumference of the bearing member, wherein the seat member is made of a synthetic resin material, and wherein the seat member presents grooves corresponding to the protrusions at an interior circumference thereof, and an outer case enclosing the seat member, wherein the outer case and the bearing member are separately provided, wherein the seat member is formed of a molded portion that is insert-molded between the outer case and the bearing member, wherein the bearing member consists of a pair of bearing members, wherein each bearing member is made of a synthetic resin material, wherein the outer case is made of a metal material, and wherein the outer case presents a knurled portion at an interior circumference thereof, the method comprising:

• mounting the pair of bearing members on the ball;
• setting the outer case at an exterior circumferential side of the bearing members;
• and
• forming the seat member by insert-molding, in a state in which a predetermined molding region is set between the bearing members and the outer case apart from the bearing members, a molten synthetic resin material into the predetermined molding region.