1. Technical Field
This invention relates generally to joints for linking relatively movable vehicle steering components to one another, such as ball joints, tie rod ends, and sway bar links.
2. Related Art
Vehicle suspension systems and steering systems typically include joints, such as tie rod end ball-type joints for operable attachment of a tie rod end to a steering knuckle and a ball joint for coupling the steering knuckle to a control arm. In addition, other applications, such as carnival rides or any other mechanism with relatively movable joints, typically have ball joints to facilitate the relative movement between linked components. Such ball joints typically include one or more bearings that are received in a housing and a ball stud that slidably contacts the bearing or bearings to allow the housing and ball stud to articulate relative to one another during use.
Upon assembly of ball joints, it is generally desirable to build in a frictional resistance between the ball stud and housing that is within a predetermined torque tolerance. In addition, it is essential that the ball joints exhibit a long and useful life, and of additional importance, it is important that the ball joints be economical in manufacture. If the frictional resistance or torque is too high, it may impede the motion of the mechanism and/or make installation difficult. If the frictional resistance is too low, it may result in an undesirable “out-of-box feel” to which the installer of the joint will believe the socket to have excessive looseness, and therefore, shorter operating life.
It is known to construct ball joints from metal, including coated metal bearings against which the metal ball stud pivots. However, although the coated metal bearings can provide a desirable “out-of-box” feel and exhibit a long and useful life, they typically come at a high cost in manufacture.
In an effort to reduce costs associated with manufacture, it is known to construct tie rod end ball joints with glass-filled nylon or fiber-reinforced nylon bearings against which a metal ball stud pivots. Although the cost of manufacture is greatly reduced, the glass-filled nylon bearings provide a reduced useful life as compared to metal bearings.
During manufacture of such socket assemblies, prior to molding a nylon bearing, the nylon resin must be sufficiently dried to remove any water from the nylon resin and minimize water in the socket assembly that could corrode the metal ball stud. Even with this drying operation, the metal ball studs of socket assemblies with nylon bearings are coated with a corrosion resistant material for further corrosion protection as water often inevitably finds its way into the socket assembly, if not during assembly, then during use.