What is a Universal Joint？Types and Function

Universal joint introduction:

What is a universal joint?

Universal joint, also called Cardan Joint is a mechanism for variable angle power transmission, used to change the direction of the driveline, which is an automotive drive system &#;Joint&#; parts. The universal joint combined with drive shaft is called universal joint drive. On vehicles with front-engine rear-wheel drive, a universal joint drive is installed between the transmission output shaft and the final Transaxle input shaft; on vehicles with front-engine front-wheel drive, the propeller shaft. is omitted and the universal joint is installed between the front CV Axle and the wheels, both driving and steering.

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The universal joint is subjected to a variety of forces (torsional, centrifugal, etc.) during high-speed movement. It is also in a hard-acting area and is subject to harsh working conditions. It is easily worn out and is a fragile part. In use, grease should be injected into the grease nipple after every kilometers of driving to maintain good lubrication. Under normal conditions, the universal joint has a service life of 100,000 to 120,000 km, but due to the short service life of the four needle roller bearings on the cross shaft, the bearings are normally not replaced separately, but with the complete cross universal joint. When it is sold and supplied, it is supplied as an assembly, not as a cross shaft or bearing, so the useful life of the universal joint assembly is only 50,000 to 60,000 kilometers.

Universal joint material:

The most commonly used material for manufacturing Universal joints are 20MnVB and 20 0CrMnTi alloy steel. Both materials have excellent physical properties, such as wear resistance, high strength, good flexibility, and corrosion resistance. They are also cost-effective and widely available on the market. Furthermore, these materials can be machined easily with precision to achieve the tight tolerances required for universal joints in various applications.

Universal joint function

The universal joint is the main component of the universal joint drive axles and is used to connect the angled two shafts (the output shaft of the transmission and the input shaft of the transaxle). While rotating, the driven shaft is allowed to swing at an angle that still normally transfers torque to suit the vehicle&#;s needs in bumps and vibrations.

Universal Joints Manufacturing Video In Factory

Universal joint types

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universal joint transfers power between the driving shafts, even if the rotating shafts are not inline. Universal joints that without obvious elasticity in the torsion direction could be divided into
Variable Velocity universal joint
constant velocity(CV) universal joints.
and quasi-constant velocity universal joints

Variable Velocity universal joint

The cross universal joint is the commonly seen type of variable/non-constant velocity universal joint, it consists of a universal joint yoke, a cross shaft, a needle bearing, an oil seal, a sleeve, a bearing cap, etc.

The needle rollers in the needle roller bearing rotate during the cross universal joint rotation to reduce friction. The shaft connected to the input power is called the input shaft and the shaft that delivers power through the universal joint is called the output shaft.

CV Universal Joint

The Constant Velocity Universal Joint (CVUJ) allows two shafts to rotate at a constant speed, regardless of their angle or relative position. This makes them ideal for power transmission systems where the two shafts are subject to frequent changes in orientation and distance. CVUJs are most commonly found in automotive applications, such as in the drive train of a car or truck. They can also be used for industrial machines and other heavy-duty applications.

CVUJs are typically composed of two yokes connected by a central cross-shaped piece and four needle bearings for smooth operation. The yokes are connected to shafts, allowing them to rotate independently while still maintaining the desired velocity.

Rzeppa CV Joint

The Rzeppa CV Joint consists of six circular grooves cut into the inner portion of a casing and a set of steel balls that provide constant transmission speed. This makes it an excellent choice for manufacturers wishing to create powertrains with complex mobility requirements, as its design allows for smooth pivoting between shafts without any decrease in power output.

It is also particularly suited for harsh driving conditions, given that its components are highly resistant to stress and deformations such as twists or torque.

Fixed and Plunge Joints

Fixed and Plunge Joints are a specialized form of Constant-Velocity (CV) Joints commonly used in Front-wheel drive vehicles. The plunge joint is mounted on the inside end of the drive axle enabling angular movement between the wheels and providing a smooth driving experience.

The fixed joint is located at the opposite end outside the axle. It is designed to take power from the transmission and deliver it to the wheel hub assembly, allowing for solid acceleration.

Tripod Joints and Ball-Type Joint

Tripod joints typically feature three trunnions on their base and an internal cage to contain the rolling elements; its refined shape is perfect for dynamic vehicle movement while providing strength and stability.

Ball-type joint stands out due to their simplicity and inexpensive costs; it relies on a single steel ball shaped as a spherical triangle to transmit power in tightly curved scenarios.

Fixed Tripod Joints

Found predominantly on front-wheel drive vehicles, these joints have a unique design that sets them apart from other CV joint styles. A trunnion is mounted onto the outer housing of the joint, and three steel arms, or &#;legs,&#; are connected in an arrangement reminiscent of a tripod which gives this type of joint its name. Due to their durable construction, fixed tripod joints often boast exceptional longevity compared to other CV joints making them the ideal choice for heavier-duty applications.

Useful Tips

1. On the one hand, it is objective and natural wear, because the universal joint and the drive shaft are assembled to transfer torque, in a working environment with high speed and force, and the parts are inevitably worn, which is objective
2. On the other hand, factors such as human factors, driving technique, and maintenance, failure to follow operating procedures, rude behavior, lack of timely maintenance, and increased damage to parts.
3. If the chassis makes an unbroken &#;snap&#; sound when the vehicle is moving when it suddenly increases, decelerates, or steers, the universal joints ay be running out of oil or damaged.
4. In addition to the universal joints applied to the driving system, the steering column of the steering system applies the universal joints to transfer steering forces between shafts with varying shaft lines. For ease of removal and installation, tools such as universal joints and spark plug wrenches are also applied to universal joints.

What is a Universal Joint?

A universal joint is a connection between two objects, typically shafts, that allows relative rotation in two axes. It is made up of two revolute joints with perpendicular and intersecting axes.

A universal joint (universal coupling, U-joint, Cardan joint, Spicer or Hardy Spicer joint, or Hooke&#;s joint) is a joint or coupling connecting rigid rods whose axes are inclined to each other and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90° to each other, and connected by a cross shaft. The universal joint is not a constant-velocity joint.

When shafts are connected using a universal joint, each shaft terminates in a revolute joint with its axis perpendicular to the shaft&#;s rotational axis. This allows rotary motion to be transferred between the shafts while allowing misalignment in both remaining rotational degrees of freedom.

A single rotational degree of freedom is constrained (the shaft rotation) as well as all relative translations, giving a universal joint two degrees of freedom (2-DOF).

The universal joint is not a constant-velocity joint. If the input shaft is rotating at a constant velocity, the output shaft&#;s velocity will oscillate. They will have the same average velocity but the output shaft&#;s velocity will be somewhat higher or lower than this average at any given time.

The amount of oscillation in the output shaft depends on the amount of misalignment between the shafts, if the shafts are coaxial then the output shaft will in fact have a constant velocity.

It is possible to create a constant velocity joint by combining a number of universal joints. A double Cardan joint is an arrangement of two universal joints, with a short connecting shaft between them, 90° out of phase with each other.

For more information, please visit Stainless Steel Universal Joints.

If any bend angle is shared equally between the two universal joints, then the two joints will cancel out velocity oscillations so that the final output shaft has a constant velocity. However, the oscillation of the intermediate shaft will cause vibrations, and supports are required to maintain equal angles.

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Purpose of Universal Joint

Universal joints allow drive shafts to move up and down with the suspension while the shaft is moving so power can be transmitted when the drive shaft isn&#;t in a straight line between the transmission and drive wheels.

Rear-wheel-drive vehicles have universal joints (or U-joints) at both ends of the drive shaft. U-joints connect to yokes that also allow drive shafts to move fore and aft as vehicles go over bumps or dips in the road, which effectively shortens or lengthens the shaft.

Front-drive vehicles also use two joints, called constant velocity (or CV) joints, but they are a different kind that also compensates for steering changes. On rear-drive vehicles, one sign of a worn U-join is a &#;clank&#; sound when a drive gear is engaged.

On front-drive vehicles, CV joints often make a clicking noise when they&#;re worn. CV joints are covered by protective rubber boots, and if the boots crack or are otherwise damaged, the CV joints will lose their lubrication and be damaged by dirt and moisture.

Structure of Universal joint

The universal joint consists of a spider(cross) and 4 grease-filled roller bearings. It can transmit large torque at low friction. Spider with journal pegs and bearing cases as outer rings were hot forged or cold formed and machined. They are later carburized in the furnace so that increased ruggedness and wear resistance is obtained.

Parts are finally ground to designed size under severe tolerance. Oil seals, as well as a dust cover, are also in use to protect the internal journal area from the intrusion of foreign material. A variety of grades and materials are selected to respond to extreme conditions such as very hot / very cold temperatures.

Types of Universal Joint

There are two types of universal joints, defined by their number of bending joints:

• Single joint: has only one bending aspect and is capable of operating at up to a 45-degree angle.
• Double joint: utilizes two bending joints, the double u-joint can operate at angles up to 90 degrees. Additionally, it also accommodates parallel offset between 2 shafts with an operating angle of the central section from 0 to 45 degrees.

Universal joints vary based on their material composition, hub type, and the applications for which they are designed.

Steel is the most common material used, either in stainless form; or alloyed with other metals to handle greater torque and temperature.

Plastics and thermoplastics are often used in constructing universal joints, as this lends greater rust and corrosion resistance, as well as electrical and magnetic insulation in applications where this is required.

Hub Styles

U-joints are available with two hub styles:

• Solid: solid hub universal joints are solid and have not been machined, and as a result, do not have a hole.
• Bored: bored styles of u-joints generally derive their name from the shape of the hole in their hub, as with round, hex or square styles.

The two bored styles that deviate from the convention of round, hex, or square styles are:

• Splined: has longitudinal grooves inside of the bore.
• Keyed: has keyways to prevent rotation of the u-joint on the corresponding shaft.

Application of Universal joint

Today, universal joints are used universally in many machines in which there are long rotating shafts. Most notably, such joints are found between the transmission and rear driveshafts of rear-wheel-drive cars and in old-fashioned tower clocks.

Typical applications of universal joints include aircraft, appliances, control mechanisms, electronics, Instrumentation, medical and optical devices, ordnance, radio, sewing machines, textile machinery, and tool drives.

Universal joints are available in steel or in thermoplastic body members. Universal joints made of steel have the maximum load-carrying capacity for a given size. Universal joints with thermoplastic body members are used in light industrial applications. Their self-lubricating feature, lightweight, negligible backlash, corrosion resistance, and capability for high-speed operation are significant advantages.

Universal joints of special construction, such as ball-jointed universals are also available. These are used for high-speed operation and for carrying large torques. They are available both in miniature and standard sizes.

Advantages of Universal joint

• Universal coupling is more flexible than knuckle joint.
• It facilitates torque transmission between shafts which have angular misalignment.
• It is cheap and cost-effective.
• It is simple to be assembled and dismantled.
• Torque transmission efficiency is high.
• The joint permits angular displacements.

Disadvantages of Universal Joint

• Wear may occur if the joint is not properly lubricated.
• Maintenance is often necessary to avoid wear.
• Universal joint produces fluctuating motion
• It does not support axial misalignment.

FAQs,

What is a universal joint?

Universal joints allow drive shafts to move up and down with the suspension while the shaft is moving so power can be transmitted when the drive shaft isn&#;t in a straight line between the transmission and drive wheels. Rear-wheel-drive vehicles have universal joints (or U-joints) at both ends of the drive shaft.

Where are universal joints used?

U-joints are found on the vehicle&#;s driveshaft, typically connecting the driveshaft to the transmission and differential. Additionally, some vehicles have u-joints that connect the front driveshaft to the front differential and transfer case.

What are the two types of universal joints?

There are two types of universal joints, defined by their number of bending joints:
1. Single joint: has only one bending aspect and is capable of operating at up to a 45-degree angle.
2. Double joint: utilizes two bending joints, the double u-joint can operate at angles up to 90 degrees.

What is the principle of a universal joint?

The universal joint connects two separate shafts and allows them to pivot and move independently, at relative angles of up to 45 degrees. Typical universal joints provide two degrees of freedom, meaning the two shafts are free to rotate along two axes simultaneously (commonly the X and Y axes).

Can I drive with a bad U-joint?

If you suspect that you have a bad universal joint or any other issue with your steering & suspension system, you should have your vehicle inspected by your auto technician right away. Failure to address the problem in a timely manner can cause damage to other components.

How do I know my U-joint is bad?

Vibrations, squeaking or clicking noises, and clunking sounds are telltale signs of a bad u-joint.

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