In the car, the ball joint is a round cushion that connects the control arm to the steering knuckles. They are used on virtually every car made and work together with the ball-and-socket design of the human hip joint.
Ball joints consist of stud pads and sockets covered in casing; all these parts are made of steel. Stud bearing tapered and threaded, and fits into a tapered hole in the steering knuckle. The protective coating prevents dirt from entering the joint assembly. Typically, this is a rubber-like boot that allows movement and lubricant expansion. Ball-ball ball connections tend to be maintained with an internal spring, which helps prevent the problem of vibration in the relationship.
The "offset" ball joint provides a means of movement in systems where thermal expansion and contraction, shock, seismic motion, and torsional movement, and power are present.
Video Ball joint
Theory
Ball joints are used to allow free rotation on two planes at the same time while preventing translation in any direction, including spinning in the field. Combining the two joints with the control arm allows movement across all three planes, allowing the front end of the car to be piloted and spring suspension and shock (damper) to make travel comfortable.
A simple kingpin suspension requires that the wishbones of the upper and lower controls have a parallel axis axis, and in tight geometric relations to the kingpin, or upper and lower trunnions, which connect the kingpin to the control arm, will be very severe. stress and cushioning will suffer severe wear. In practice, many vehicles have elastomer bearings in the horizontal pivot of the trunnion, which allows some small flexibility, but this is not sufficient to allow for a lot of caster adjustments to be made, and also introduces compliance where suspension designers may be undesirable. in its quest for optimal handling. The camber angle can generally be adjusted by moving the inner pivot from the upper or lower control arm inward or outward to an exact amount. But adherence to the inner pivot control arm, usually due to the use of elastomeric pads, will again cause trunnion to be stressful. Freedom of suspension designers is very limited, it is necessary to have some compliance where it may be undesirable, and very little where more will be useful in absorbing impact front and back loading of bumps.
The recognition of the upper and lower ball joints allows 3-axis articulation and removes all constraints on the axis of the control arm exactly parallel, so the caster can be adjusted freely, usually with asymmetric adjustment from the inner pivot control position, while the camber is adjusted by symmetric adjustment of the pivot this same.
The adjustment to adjust the toe angle does not change by introducing the ball joint in suspension, although it should be noted that the steering linkage itself should use 4 or more pivots, also usually a ball joint, and in almost every vehicle ever made, some of these have been adjusted by having threaded ends and locknut, to allow the toes to be adjusted appropriately.
The ability to fine-tune the ball-jointed suspension allows manufacturers to make the car more stable and more manageable, compared to older kingpin suspension styles. It may also be quieter and more comfortable, since lateral and front and rear compliance in the suspension can be introduced in controlled amounts on the internal pivot control arm without compromising the integrity of the shaft axis, which now is the ball joint rather than the pin and trunnion king. Smoother travel can also increase tire's tread life, as ball-joint suspension allows better control of suspension geometry so as to provide better tire-to-road contact.
Maps Ball joint
Destination
In modern vehicles, the ball joint is the axle between the wheels and the car's suspension. They are now almost universally used in front suspension, after replacing kingpin/linkpin or kingpin/trunnion settings, but also can be found in the rear suspension of some high performance cars. Ball joints play an important role in the safe operation of the steering and suspension of the car.
Many cars manufactured today around the world use MacPherson strut suspension, which uses one ball joint per side, between the lower end of the strut and the control arm, with a small amount of articulation required at the top of the stand which is normally provided by elastomeric pads, which are bearings ball to allow free rotation of the steering axis. So, usually there are only two ball joints in the suspension, but there will be at least four (the end of the track rod and the end of the rack) in the steering linkage.
In a non-MacPherson strut car suspension, the two ball joints are called "upper ball joint" and "bottom ball joint". Lower ball joints are sometimes larger and can wear out faster, because the front and back loads, especially due to braking, are higher at the bottom of the ball together. (Torsion reactions and drag add on lower joints, and partially off at the top of the joint.) Also, lateral curved loads are higher at the bottom connection. Depending on the design of the suspension, the vertical load of the suspension spring can be handled completely by the top ball connection, or entirely by the bottom ball together. The damper load, (which is low under normal conditions, is zero at stationary, but in a peak bump or rebound rate may be almost equal to the spring load) usually, but not always, taken at the same ball junction as the spring load. The loading of an anti-roll bar is often, but not always, taken at the bottom of the ball together. This can be picked up by the top ball joint, or directly from the steering knuckle with a jointed ball-drop link.
If one of the ball joints does not carry a spring load, it may be equipped with an internal anti-vibration spring to keep the ball in contact with a chair. This is the case in BMC Mini 1959 and many derivatives, where the lower control arm does not carry vertical loading, so it takes joints and anti-springs, while the top joint, consisting of identical parts, is always in compression due to spring (cone rubber) and load absorbers, and so not equipped with springs.
Other vehicles in the 1960s, including some Vauxhalls, had lower ball joints with a large enough buoy, because the joints were always in tension because the spring load and damper were applied through a lower control arm and always nonzero.
Another example is the Ford Focus, which uses MacPherson struts, and the anti-roll bar connects directly to the strut, so the lower joint ball only carries the fore and aft traction/braking and lateral cornering loads.
Front wheel drive
Unlike the kingpin, which requires assembly in the center of the wheel for the pivot, the connection is connected to the top and bottom end of the spindle (steering), to the control arm. This makes the center open to allow the use of front-wheel drive. Older kingpin designs can only be used in rear-wheel-drive configurations.
Lubrication
The sealed ball joint does not require lubrication because it is "lubricated for life". Previously most of the sphere connections had fat fittings (sometimes called grease zerk ) and were designed for the addition of lubricants on a regular basis, but almost all modern cars use sealed ball connections to minimize maintenance requirements. Lubricants are usually very high viscosity lubricants. It is generally believed that standard ball joints will last longer than sealed because eventually the seal will break, causing the connection to dry and rust. Additionally, the new lubricant action encourages old and dry lubricants, extending the life of the connection. This should be done at intervals of 1000 to 2000 miles on many vehicles, which are inconsistent with service intervals in modern cars, often 12,000 miles or more, and in any case rarely attended by the owner, resulting in severe wear and possible failure of ball connections, which may causing serious accidents. For this reason, almost all ball joints on modern European or Far Eastern cars are sealed for this type of life. The new technology is mainly applied to the internal bearing design that allows ball connections to meet these longer service intervals. This special design combines sintered metal pads that replace a sealed polymer/plastic OEM version and fix the dust boot seal that works much better in holding the grease.
Spherical rolling joint
The round ball joint is a high-precision ball consisting of an outer ball and an inner ball separated by a ball bearing. Ball bearings are placed in a round retainer and rolled along the inside and outside surfaces. This design allows the joints to have very low friction while maintaining a wide range of movement and backlash as low as 1 Ã,Âμm. SRJ is often used in parallel robotics applications such as Stewart platform, where high stiffness and low backlash are essential.
Most SRJs are designed with housing offsets, allowing for higher press loads in smaller spaces. Alternatively, the connection can be assembled backwards for higher tensile load capability but fewer range of motion.
The alternative to SRJ is a universal connection, consisting of two revolute joints. By using rounded connections instead of universal, designers can reduce the number of joints to achieve the same result. Using a rounded joint as opposed to a universal joint also eliminates the problematic possibility of kinematic singularity. Regular round bearings can be used instead of SRJ at the expense of increasing friction, but offer the opportunity to preload further connections.
Failure
Although there is no precise lifespan that can be placed on sealed joint balls, they can fail as early as 80,000 miles (130,000 km) in modern vehicles, and faster in older vehicles. Signs of a failed ball connection can begin with a sudden explosion as a result of the unloading of the ball together. Then continue by clicking, popping or bluffing sounds when the wheel is rotated and finally turns into a squeaking sound at the stop end, when the accelerator is used and/or also when hitting the mound. Another symptom is the sound of 'thud' which comes from the front suspension when it passes the mound. Dry ball joints dramatically increase friction and can cause the steering wheel to stick or become more difficult.
If the ball joint fails, the result can be dangerous because the wheel angle becomes uncontrollable, causing a loss of control. Because the tire will be at an unwanted angle, the vehicle will suddenly stop, damaging the tire. Also, during failure, flakes may damage other parts of the vehicle.
Other uses
While in automotive language the term "ball joint" usually refers to the primary sphere ball connection at the end of the control arm, this type of connection is used in other parts as well, including the tip of the tie rod. In these other applications, they are usually called end tie rods or, when they are the inner tie rod ends on a rack-and-pinion steering system, they are called inner socket assemblies. The joints are also used in a number of other non-automotive applications, ranging from puppet connections to other mechanical connections for various devices, or places where the rotational level in motion is desirable.
See also
- Rod end bearing (heim joint)
- Shaker tilting chair (one of the earliest patented technology applications)
- Head in pillow (metallurgy)
References
Source of the article : Wikipedia
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