Family of rotary bearings designed to support axial loads

Check now

A thrust ball bearing

A thrust bearing is a particular type of rotary bearing. Like other bearings they permanently rotate between parts, but they are designed to support a predominantly axial load.[1]

Thrust bearings come in several varieties.

• Thrust ball bearings, composed of bearing balls supported in a ring, can be used in low-thrust applications where there is little axial load.
• Cylindrical thrust roller bearings consist of small cylindrical rollers arranged flat with their axes pointing to the axis of the bearing. They give very good carrying capacity and are cheap, but tend to wear due to the differences in radial speed and friction which is higher than with ball bearings.
• Tapered roller thrust bearings consist of small tapered rollers arranged so that their axes all converge at a point on the axis of the bearing. The length of the roller and the diameter of the wide and the narrow ends and the angle of rollers need to be carefully calculated to provide the correct taper so that each end of the roller rolls smoothly on the bearing face without skidding. These are the type most commonly used in automotive applications (to support the wheels of a motor car for example), where they are used in pairs to accommodate axial thrust in either direction, as well as radial loads. They can support greater thrust loads than the ball type due to the larger contact area, but are more expensive to manufacture.

A spherical roller thrust bearing

• Spherical roller thrust bearings use asymmetrical rollers of spherical shape, rolling inside a house washer with a raceway with spherical inner shape. They can accommodate combined radial and axial loads and also accommodate misalignment of the shafts. They are often used together with radial spherical roller bearings. Spherical roller thrust bearings offer the highest load rating density of all thrust bearings.

  [

  2

  ]

• Fluid bearings, where the axial thrust is supported on a thin layer of pressurized liquid&#;these give low drag.

Miba fluid film thrust bearing

• Magnetic bearings, where the axial thrust is supported on a magnetic field. This is used where very high speeds or very low drag is needed, for example the Zippe-type centrifuge.

Thrust bearings are commonly used in automotive, marine,[3] and aerospace applications. They are also used in the main and tail rotor blade grips of RC (radio controlled) helicopters.

Thrust bearings are used in cars because the forward gears in modern car gearboxes use helical gears which, while aiding in smoothness and noise reduction, cause axial forces that need to be dealt with.

Thrust bearings are also used with radio antenna masts to reduce the load on an antenna rotator.

One kind of thrust bearing in an automobile is the clutch "throw out" bearing, sometimes called the clutch release bearing.[4][clarification needed][5][6]

Fluid film thrust bearings

[

edit

]

Exploded view of a Michell type thrust bearing. Note, each sector shaped pad can pivot on the ridges on the lower plate.

Fluid-film thrust bearings were invented by Albert Kingsbury, who discovered the principle in the course of bearing and lubrication investigations commencing in while a student. His first experimental bearing was tested in . He filed for a patent in , and it was granted in .[7] The first Kingsbury bearing in hydroelectric service, one of its major applications, was installed at the Holtwood Generating Station in . It remains in full use today.

Thrust bearings were independently invented by Australian engineer George Michell (pronounced Mitchell) who patented his invention in .

Fluid thrust bearings contain a number of sector-shaped pads, arranged in a circle around the shaft, and which are free to pivot. These create wedge-shaped regions of oil inside the bearing between the pads and a rotating disk, which support the applied thrust and eliminate metal-on-metal contact.

Kingsbury and Michell's invention was notably applied to the thrust block in ships. The small size (one-tenth the size of old bearing designs), low friction and long life of Kingsbury and Michell's invention made possible the development of more powerful engines and propellers. They were used extensively in ships built during World War I, and have become the standard bearing used on turbine shafts in ships and power plants worldwide. (See also Michell/Kingsbury tilting-pad fluid bearings)

Today thrust bearings continue to play an essential role in rotating equipment like expanders, pumps, and gas or steam turbines or compressors. In addition to the traditional babbitt bearings which were used since the early 20th century, new materials for the thrust pads have come into use. For example Bronze and Copper-Chromium are commonly used to improve the bearings performance. [8]

See also

[

edit

]

Citations

[

edit

]

References

[

edit

]

• Simmons, J.E.L.; Henderson, N. (). "Developments in Naval Thrust Bearings". Journal of Naval Engineering. 32 (2):

  344&#;

  353.

An Overview of Thrust Bearings

Figure 1: Thrust bearing

Thrust bearings are used to support thrust loads, or axial loads, applied to a shaft. Thrust bearings are divided into several categories: those with ball rolling elements and those with cylindrical elements, single and double direction, and thrust bearings that can support axial and radial loads. This article covers the various types of thrust bearings, their basic design, and their general applications.

Recommended article:
How Can Thrust Ball Bearings Improve Your Machinery's Efficiency and Longevity?

With competitive price and timely delivery, Beijing SKF sincerely hope to be your supplier and partner.

Table of contents

How does a thrust bearing work?

A thrust bearing, also known as an axial thrust bearing, handles axial loads, which are loads parallel to the shaft in a mechanical system. The two main components of a thrust bearing are the bearing housing and the bearing. The housing remains stationary and attached to the machine. The bearing rotates with the shaft.

The bearing, which can be either a ball or cylinderical (roller) shape, is made of metal or plastic. When the shaft receives axial loads, the bearing distributes the load across its surface, which lets the shaft rotate smoothly without excessive friction and wear.

Thrust bearings are relatively simple to maintain due to their detachable design. This means that the individual components can be removed and replaced. Therefore, a thrust bearing can be repaired without replacing the entire bearing.

Thrust bearings are found in various mechanical systems, from automotive engines to industrial machinery and aerospace systems. They are necessary for many high-speed, high-load applications that have axial forces. Learn more about bearings by reading our complete guide to rolling bearings, which also covers the types of loads that bearings work with, including axial ones.

Thrust bearings types and applications overview

Thrust ball bearings and thrust roller bearings overlap in their suitability for applications. Therefore, it can be more complex to determine which bearing is best for an application. To help this, the following table explains different types of bearings, descriptions, and general use cases.

If replacing a bearing in a machine, look in the manufacturer's guide to determine which bearings it uses. Read beyond the table for further explanation of each bearing type.

Thrust bearing type Description General application Thrust ball bearing Ball-shaped rolling elements Higher speed but lighter loads than thrust roller bearings. Automotive and some industrial applications. Thrust roller bearing Cylindrical-shaped rolling elements Lower speed but higher loads than thrust ball bearings. Mining, construction, and paper mills. Single direction thrust bearing Basic thrust bearing washer design Applications with axial loads in a single direction. Pumps and electric motors Double direction thrust bearing Single shaft washer, but two each of housing washer and ball and cage assembly Applications with axial loads that frequently change direction. Machine tools and cranes Angular thrust ball bearing 60° contact angle between rolling elements and raceways Applications with axial and radial loads. Gearboxes and clutches Tapered roller thrust bearing Rolling element has a tapered shape Applications with axial and radial loads. Full complement thrust ball bearing No cage assembly, so more balls can fit in the washer Higher axial loads at slower speeds Thrust needle bearing No raceway in the bearing. Machine walls act as raceway Very high speeds. Machines with very limited space Spherical roller thrust bearing Barrel-shaped rollers that can self-align Heavy axial and moderate radial loads

Table 1: Thrust bearing descriptions and general applications

Thrust ball bearings

Thrust ball bearings (Figure 2) have balls as their rolling element and are primarily designed to handle axial loads. The rolling ball element allows them to handle higher rotational speeds, but they can't handle high axial loads compared to cylindrical rolling elements.

For more information about ball bearings and how bearings work read our bearing technical article. Our technical library can also help you with information about bearing lubrication, bearing maintenance, and has a wide scope of information on tribology.

Figure 2: Thrust ball bearing

Thrust roller bearings

Similar to thrust ball bearings, thrust roller bearings (Figure 3) are designed to handle axial loads. Cylindrical roller thrust bearings have cylindrical rolling elements instead of ball-shaped ones. This allows thrust roller bearings to handle heavier axial loads than thrust ball bearings can. However, thrust roller bearings cannot handle as high of speeds as thrust ball bearings.

Figure 3: Single-direction cylindrical thrust roller bearing

Single vs double direction thrust bearings

Whether ball or roller bearings, single direction thrust bearings are suitable for applications with axial loads in one direction, such as pumps and electric motors. Double direction thrust bearings are for applications with axial loads that frequently change direction, such as in machine tools and cranes.

Single direction thrust bearings have a shaft washer, a housing washer, and a ball and cage assembly. Double direction bearings have a shaft washer, and two housing washers and two ball and cage assemblies.

Angular thrust ball bearings

Angular thrust ball bearings are similar to the thrust ball bearings described above. The primary difference is that the contact angle between the balls and the raceways is 60°. This allows these bearings to not only support axial loads, but radial and combined as well. Single direction angular thrust ball bearings (Figure 4 left) handle these loads in one direction, while double direction angular thrust ball bearings (Figure 4 right) handle these loads in two directions.

Figure 4: Single direction angular thrust ball bearing (left) and double direction thrust ball bearing (right).

Tapered roller thrust bearings

Tapered roller thrust bearings (Figure 5) can be either single or double direction. They can handle medium and heavy combined radial and axial loads. They have a high carrying capacity for their small cross section, long service life. These qualities make them suitable for various industrial and automotive applications.

As a result of the rollers' tapered shape, the load is evenly distributed between the rollers. In addition, the rollers' shape and design reduce friction and heat generation.

Figure 5: Tapered roller thrust bearing

Full complement thrust ball bearings

Full complement thrust ball bearings (Figure 6) do not have a cage that contains the balls. This allows for more balls to be placed between the raceways. Therefore, full complement thrust ball bearings can handle higher axial loads, but have a lower maximum speed and more rotational torque from ball-to-ball friction.

Because they handle higher axial loads, full complement ball bearings are seen mostly in heavy-duty applications. For example, large cranes, heavy equipment, ship steering equipment, and airplane landing equipment.

Figure 6: Full complement thrust ball bearing

Thrust needle bearings

For applications with minimal space, such as gear assemblies, needle roller thrust bearings (Figure 7) are ideal. These bearings may or may not have a single raceway; adjacent machine parts can act as raceways for the rolling elements. Thrust needle bearings accommodate axial loads at high speeds.

Figure 7: Needle thrust

Spherical roller thrust bearing

Spherical thrust bearings (Figure 8) are widely used in applications involving heavy axial and simultaneous radial loads. They are self-aligning and can accommodate misalignment. Due to their low coefficient of friction, spherical roller thrust bearings require less maintenance.

Due to the cage design and conformity between rollers and washers, these bearings can operate at relatively high speeds. Learn more by reading our guide on spherical roller thrust bearings.

Figure 8: Spherical roller thrust bearing

FAQs

What does a thrust bearing do?

A thrust bearing supports axial loads on a horizontal or vertical shaft.

What's the difference between a thrust and radial bearing?

Basic thrust bearings support axial loads and radial bearings support radial loads.

For more Thrust Roller Bearings manufacturerinformation, please contact us. We will provide professional answers.