There are two main types of ball pin structures: one is a combination of a spherical pin and an integral ball seat, and the other is a combination of a hemispherical ball pin and a spherical member. In the past, helical springs were mostly used for preloading and compensating for wear. Now, synthetic resin ball seats with elasticity and lubrication are widely used, which not only reduces costs but also improves handling stability. In addition, the material and shape of the dust cover and the type of grease have been greatly improved. The grease nipple is eliminated and a maintenance-free structure is realized.
Ball head pins are mainly composed of end caps, ball pins, ball seats and dust covers.
The end caps are mostly made of steel stampings. The material is mainly carbon steel, and some also use aluminum alloy or nodular cast iron.
The machining accuracy of the ball pin surface is relatively high. Many alloy steels with good hardenability are used. The ball pin surface matched with metal balls needs to be surface hardened such as high frequency quenching to improve wear resistance. Nowadays, ball pins and non-metal tees are often used to match, so only the ball pins need to be quenched and tempered. The choice of ball pin diameter should be comprehensively considered according to tensile strength, durability and other factors.
The material of the ball seat is surface hardened steel, powder metallurgy, nylon, polyacetal resin, polyurethane and polyester elastomer. Because the material and shape of the ball seat have a greater impact on wear and fatigue life, molybdenum disulfide or oil is immersed in the material to improve wear resistance. It is also possible to add reinforcing ribs on the tee or use composite materials.
The tightness of the dust cover greatly affects the wear and fatigue life of the ball stud. Its materials are mostly polyurethane or neoprene resistant to high temperature, oil and aging. In addition, the deformation during the movement should be considered in the design to prevent dust from entering the ball pin from the mating surface after deformation. At the same time, the precision of the dust cover and related parts also has a great impact on the sealing and service life.
