Patent Application
20120093574
Automobile parts.
In an automobile, the steering assemblage allows the driver to control the vehicle. Typically, the steering wheel is connected to the suspension and wheels via the steering knuckles. The steering knuckles, in turn, connect the steering wheel to the rest of the automobile which allows the driver to direct the vehicle. Two control arms link the chassis and the front suspension, while leaf springs connect the chassis to the rear suspension. Tie rod ends connect to the steering knuckles, which directly control the wheels.
The control arms are connected to the frame with pivoting mounts. Ball joints connect the front axle to the steering knuckle. Ball joints allow the steering knuckle to pivot during steering. As the driver turns the wheel, motion is transferred down the steering shaft to the steering gear.
Factory-installed ball joints in automobiles typically require lubricant and generally need to be replaced every two (2) years with “normal” vehicle use. Over time, ball joint replacement is often required due to poor lubrication (infrequent or insufficient) or excessive play from the soft bronze bushing contained in the assembly. Additionally, severe impacts may cause increased compressive stress on conventional ball joints thereby compromising their integrity. As a result, under extreme uses, such as off-road driving and driving at higher speeds, a ball joint pin may become loose inside the cup creating excessive play in the steering.
After-market ball joints featuring ball joint cups with a “single tier” design are available to replace factory-installed ball joints. It has been found that such ball joints are not able to withstand to the pressure created by larger tires and/or off-road vehicle use. The “single tier” design may be constructed of a small cup chamber in which the pin is surrounded by a soft bronze bushing inside the cup, which often compresses or deforms creating excessive play.
An upper ball joint assembly, comprising: (a) a ball joint cup having a cup opening extending therethrough, the cup opening comprising a first chamber, a second chamber and a stud-receiving aperture; (b) a tapered ball joint pin having a proximal portion, a medial portion and a distal portion, the proximal component comprising a head component, the head component of the pin adapted to reversibly seat within the ball joint cup; and (c) a cap having a cap opening extending therethrough, the cap adapted to reversibly engage with the ball joint cup wherein the joint assembly has a hardness of at least 56 Rockwell is herein disclosed.
From a proximal end of the ball joint cup to a distal end of the ball joint cup, the second chamber may follow the first chamber, the stud-receiving aperture may follow the second chamber. A diameter of the first chamber may be greater than a diameter of the second chamber. A diameter of the stud-receiving aperture may be less than the diameter of the second chamber. The medial and distal portions of the pin may comprise a stud, the stud may comprise a tapered portion followed by an externally-threaded portion, the externally-threaded portion may terminate in a tip portion. In an assembled configuration, the head component of the pin may be capable of vertical movement between the first chamber and the second chamber. The cap may comprise: (i) a hex portion, (ii) a medial portion and (iii) an externally-threaded distal portion.
From a proximal end of the cap to a distal end of the cap, the cap may comprise a hex-connecting component followed by a hex component followed by a flange component followed by an externally-threaded component. The hex-connecting component may be a zerk fitting. The upper ball joint assembly may further comprise a non-liquid lubricant applied to at least one inner surface of the assembly. The non-liquid lubricant may be polytetrafluroethylene. The upper ball joint assembly may be comprised of high-strength steel. The upper ball joint assembly does not include a bushing.
A process for manufacturing an upper ball joint assembly, comprising: (a) forming a ball joint cup from high-strength steel, the ball joint cup having a cup opening extending therethrough, the cup opening comprising a first chamber, a second chamber and a stud-receiving aperture; (b) forming a tapered ball joint pin from high-strength steel, the pin having a proximal portion, a medial portion and a distal portion, the proximal component comprising a head component, the head component of the pin adapted to reversibly seat within the ball joint cup; and (c) forming a portion of a cap from high-strength steel, the cap having a cap opening extending therethrough, the cap adapted to reversibly engage with the ball joint cup wherein the joint assembly has a hardness of at least 56 Rockwell is herein disclosed.
The process may further comprise applying a non-liquid lubricant to the assembly. The process may further comprise applying a heat treatment to the assembly to achieve the hardness greater than 56 Rockwell. The process may further comprise: (d) inserting the tapered ball joint pin into the ball joint cup such that at least the head component is seated within the ball joint cup; and (e) coupling the cap to the ball joint cup.
The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention.
Embodiments of the invention are directed to an upper ball joint assembly for connecting an upper axle housing to a steering knuckle of a vehicle. In one embodiment, the upper ball joint assembly comprises a plurality of components including a tapered ball joint pin (or stud), a ball joint cup and a threaded cap configured to assemble together into an upper ball joint assembly. In an assembled configuration, a proximal, or head component, of the ball joint pin may be housed within one or more chambers (or tiers) of the ball joint cup. The cap may reversibly engage with the ball joint cup to complete the assembly. The ball joint assembly may have a hardness characteristic of between forty (40) and one-hundred (100) Rockwell.
Continuing to refer to
From a proximal end 206a to a distal end 206b of the threaded cap 206, cap 206 may include a hex-connecting component 216, followed by a hex component 218 followed by a flange component 220 followed by an externally-threaded component 222. The cap 206 is configured to reversibly couple to the cup 204 when the upper ball joint assembly 200 is in an assembled configuration, i.e., with the pin 202 seated within the cup 204 (explained in more detail below).
Examples of AISI designations for these alloys include, but are not limited to 10xx, 11xx, 12xx, 13xx, 15xx, 23xx, 25xx, 29xx, 31xx, 32xx, 33xx, 34xx, 40xx, 41xx, 43xx, 44xx, 46xx, 47xx, 48xx, 50xx, 51xx, 52xx, 61xx, 72xx, 81xx, 86xx, 87xx, 88xx, 92xx, 93xx, 94xx, 97xx, and 98xx and many modifications based on these alloys. As used herein “xx” designates specific composition, i.e. grade, of the alloy. Almost all alloys also have other designations in addition to AISI designation and sometime specific alloys have names. Although high-strength low-alloy steels are preferred materials for the upper ball joint according to embodiments of the invention other alloys or their alloy hybrids may be suitable. In one embodiment, the upper ball joint assembly 200 may also be carburized and/or heat treated to achieve hardness of between (40) and one-hundred (100) Rockwell Hardness in C-scale (HRC) and tensile strengths of over 300 kilo pound per square inch (kpsi).
The “Rockwell scale” is a hardness scale based on the indentation hardness of a material. A Rockwell test determines the hardness by measuring the depth of penetration of an indenter under specific loads from 60 kilograms force (kgf) to 150 kgf and specific indenter configurations corresponding to letters A through G. Rockwell hardness C corresponds to a load of 150 kgf and 120 degree diamond cone indenter. The numerical expression of hardness in a Rockwell scale represents the load in kilograms force. In one embodiment, the upper ball joint assembly 200 has a hardness of at least fifty-six (56) HRC, in one embodiment, sixty (60) HRC. The ultimate strength of a material is a function of its composition and the heat treatment process to which is it subjected.
Ultimate strength is a measure of the ability of the material to withstand an applied stress, usually in tension, before fracture. One pound force applied to one inch square results in one psi stress. One thousand pound force applied to one inch square produces one kpsi (also known as ksi), stress. In one embodiment, the ultimate strength of the upper ball joint 200 is about 175 ksi.
In some embodiments, the upper ball joint assembly 200 may also be heat treated to achieve a hardness of between forty (40) and one-hundred (100) Rockwell. The “Rockwell scale” is a hardness scale based on the indentation hardness of a material. A Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. The numerical expression of hardness in a Rockwell scale represents the load in kilogram force. In one embodiment, the upper ball joint assembly has a hardness of at least sixty (60) Rockwell.
In an assembled configuration, a head component of a tapered ball joint pin (not shown) may be permitted to vertically move between first and second chambers 410a, 410b (see double arrow). The dual chamber (or, dual tier) design of the assembly 400 provides additional material and surface area in which the head component of the tapered ball joint pin (not shown) may be permitted to vertically move when the upper ball joint assembly is in use (i.e., when the assembly is installed between an upper axle housing to a steering knuckle of a vehicle and the vehicle is in use). Consequently, the upper ball joint assembly according to embodiments of the invention results in increased strength relative to conventional upper ball joint assemblies. These features also translate to an extended lifetime of the upper ball joint assemblies according to embodiments of the invention.
Continuing to refer to
It should be appreciated that the upper ball joint assembly according to embodiments of the invention do not include a bushing (i.e., the assembly is bushing-less). This is a significant advantage over conventional assemblies because the natural wear of assemblies having bushings (see
According to embodiments of the invention, the upper ball joint assembly as previously described may be manufactured as follows. A high-strength steel may be machined to create one or more components of the upper ball joint assembly, i.e., a tapered ball joint pin (or stud), a ball joint cup and/or a threaded cap. Then, the assembled components may be heat treated to achieve a hardness of between forty (40) and one-hundred (100) Rockwell. Then, a non-liquid lubricant (i.e., a “dry-lube”) may be applied to the assembled components to a specified thickness of between 0.05 millimeters and 0.09 millimeters. The dry-lube may be applied in one or more applications or stages to one or more surfaces of the assembly. Examples of suitable dry-lubes include, but are not limited to, polytetrafluroethylene (PTFE), graphite, molybdenum disulfide and tungsten disulfide.
According to embodiments of the invention, the upper ball joint assembly as previously described was discovered to break-in after use and, therefore, increase performance. The manufacturing process as previously described was discovered to result in a substantially smooth inner surface of the assembly, which inner surface was discovered to contain a plurality of pores generally not visible by the eye. In one embodiment, the lubrication process partially, substantially or completely fills the pores of the surface of the assembly. After a period of time and consistent use (i.e., when the assembly is installed in vehicles as previously described), it was discovered that the surface(s) of the assembly burnished. Applicant discovered that, upon removing the pin from the assembly, the inner surfaces of the assembly exhibited a luster caused by burnishing through normal use of the assembly. The burnished surfaces were discovered by Applicant to result in reduced friction and smoothed-out rotation relative to non-burnished surfaces. This discovery was unexpected in view of the conventional expectation is that such assemblies decrease in performance after repeated use. Applicant discovered that the superior performance of the assemblies according to embodiments of the invention were partially or substantially due to the design and manufacture of the ball joint cup, i.e., the additional material and surface provided by the two-tiered ball joint cup; the heating process resulting in increased hardness (Rockwell); and the two-stage lubrication process.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention is not to be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.
