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Rolling-element bearings are used to ensure smooth, efficient operation in many machines with rotary motion—from car wheels, engines and turbines to medical equipment. A ball bearing is a type of rolling-element bearing that serves three main functions while it facilitates motion: it carries loads, reduces friction and positions moving machine parts.
Ball bearings use balls to separate two “races,” or bearing rings, to reduce surface contact and friction across moving planes. The rotation of the balls causes a reduced coefficient of friction when compared with flat surfaces rubbing against each other. Because there is little surface contact between the balls and races, ball bearings typically have a lower load capacity for their size than other rolling-element bearings.
There are a variety of different designs and applications for ball bearings, and their design is specific to their industrial application and load type. Some common designs of ball bearings include:
Angular Contact Bearings: designed to work under combined radial and axial loads.
Axial Bearings: also called thrust ball bearings, these are designed to work under force applied parallel to the bearing’s axis, or thrust loads.
Deep-Groove Bearings: designed to carry both radial and light axial loads.
Linear Bearings: designed to allow movement in one direction along a linear axis.
Self-aligning Ball Bearings: bearings with two sets of balls that are self-aligning and to carry both radial and light axial loads.
High-Speed Angular Contact Bearings: another type of precision ball bearing is a high-speed angular contact bearing. As the name implies, high-speed bearings are designed to handle high RPMs with precision and accuracy.
Ball bearing sizes vary according to their use. The width of the bearing also depends on the application. For example, thin section bearings are used in situations where space is at a premium. The difference between the diameter of the outside and inside races and width is minimized, allowing for compact designs.
The materials used in ball bearings depend on their application. The vast majority of ball bearings are made from steel. Other material types include stainless steel bearings for improved corrosion resistance and hybrid ball bearings for which ceramic balls are the moving parts of the bearing between the inner and outer races to reach high rotational speeds.
Roller Bearings Information
Roller bearings are used to replace sliding movement with low friction, rolling motion in rotary applications. The principal types of roller bearings are cylindrical, spherical, and tapered. In general, roller bearings offer higher load capacities than ball bearings of the same size.
There are five main types of roller bearings:
Cylindrical Roller Bearings have high radial-load capacity and moderate thrust loads. They contain rollers which are cylindrically-shaped, but crowned or end-relieved to reduce stress concentrations. Cylindrical roller bearings are similar in design to needle roller bearings but the dimensions of diameter and roller length are closer in magnitude.
Spherical Roller Bearings are self-aligning, double row, combination radial and thrust bearings. They use a spherical or crowned roller as the rolling element.
how to select roller bearingsTapered Roller Bearings consist of an inner ring (cone), an outer ring (cup), a cage and rollers, which are profiled to distribute the load evenly across the roller. During operation, tapered roller bearings create a line contact between the raceway and rolling element, distributing loads across a larger area.
Needle Roller Bearings are a type of cylindrical roller bearing where the length of the roller is much larger than then the diameter. Needle roller bearings are designed for radial load applications where a low profile is desired.
Thrust Bearings are designed for pure thrust loads, and can handle little or no radial load. Roller thrust bearings use rollers similar to other types of roller bearings
Radial type roller bearings (cylindrical, tapered, spherical, and needle) consist of four basic components, an inner ring, an outer ring, rollers, and a cage (roller retainer). Under normal operating conditions, bearing rings and rollers carry the load while the cage spaces and retains the rollers on the cone.
how to select roller bearings
Comparison of Cylindrical Roller Bearing and Ball Bearing Components
Image Credit: bridgat
Roller thrust bearings are designed to carry pure thrust loads. Like radial roller bearings, roller thrust bearings also consist of two rings, rollers, and a cage (roller retainer). However, instead of an inner and outer ring concentric to the axis of rotation, they have two rings or thrust washers on either side of the roller.
How To Install A Pillow Block Bearing
A Pillow Block Bearing is a mounted anti-friction bearing that is contained within a solid cast iron, ductile iron or cast steel housing unit. Also referred to as a housed bearing unit, meaning they are self-contained, greased, sealed and ready for installation on the equipment. Pillow Block bearings are typically bolted to a surface, so that the attached shaft runs parallel with the surface. There are two types of housings used for pillow block bearings, solid and split housings. Solid housed bearings are single-piece housings, while split housed bearings are two-piece housings. Pillow block bearings can contain several types of bearings, including ball, roller and tapered. Shaft attachment devices can be set screw, eccentric lock, single or double set collar, concentric lock or tapered adapter. Each device has their own positive and negatives. Seals vary as well, including clearance seals, light contact, heavy contact and auxiliary type seals. Pillow Block Bearings, in most cases, also come in a fixed or expansion version. The expansion bearings allow for shaft growth and can reduce the risk of loading one bearing against the other. Choosing the best shaft mount device and seal will prolong bearing life. When installed properly, pillow block bearings can last years without needing to be replaced. Follow these steps to ensure minimal downtime and a longer service life.
*This procedure is for the most common shaft locking device set screw or set collar, utilizing a fixed and expansion unit, but the general guidelines apply to all bearing installs.
1) Check and Clean the Shaft
First, check your shafting to ensure it is clean, round, straight, free of burrs and nicks and is not undersized or oversized, per the manufacturers specification. Use fine sandpaper or scotch bright to clean the shaft of any rust. Then use a light coat of oil to remove any debris.
2) Position the Bearings on the Shaft
When placing the bearing on the shaft, if it is necessary to tap the bearing into place, use a mallet and a hardwood block or soft steel tube against the inner ring. DO NOT strike or exert pressure on the housing or seals.
3) Lightly Bolt the Housing to the Mounting Structure
Locate the shaft in position by lightly bolting the housing to the mounting structure. Bridge over the housing mounting bolt slots with heavy washers, or heavy spring lock washers. This may help prevent loosening.
What are the characteristics of joint bearing?
The structure of the joint bearing is simpler than that of the rolling bearing. It is mainly composed of an inner ring with an outer spherical surface and an outer ring with an inner spherical surface.Joint bearing is generally used for low-speed swing motion (that is, angular motion). Since the sliding surface is spherical, it can also be tilted within a certain angle range (that is, self-aligning motion), and the support shaft and the shaft shell hole are not concentric When the degree is large, it can still work normally.
Features of joint bearing, the joint bearing can bear larger loads. According to its different types and structures, it can bear radial load, axial load or combined load of radial and axial.Since the outer spherical surface of the inner ring is embedded with composite material, the bearing can generate self-lubrication during operation. Generally used for low-speed swing movement and low-speed rotation, it can also be used for tilting movement within a certain angle range, and it can still work normally when the support shaft and the shaft shell hole are not centered. Self-lubricating joint bearing is used in water conservancy, professional machinery and other industries.
Application of joint bearing, elf-lubricating joint bearingJoint bearings are widely used in engineering hydraulic cylinders, forging machine tools, engineering machinery, automation equipment, automotive shock absorbers, water conservancy machinery and other industries.The joint bearing is a spherical sliding bearing. The basic type is composed of an inner and outer ring with a spherical sliding spherical contact surface.Depending on its structure and type, it can withstand radial loads, axial loads, or combined loads acting simultaneously in the radial and axial directions.
What Is the Purpose of Bearings?
The main purpose of bearings is to prevent direct metal to metal contact between two elements that are in relative motion. This prevents friction, heat generation and ultimately, the wear and tear of parts. It also reduces energy consumption as sliding motion is replaced with low friction rolling.
Rolling element bearings contain rolling elements in the shape of balls or cylinders. We know that it is easier to roll a wheel than slide it on the ground as the magnitude of rolling friction is lower than sliding friction. The same principle is in work here. Rolling element bearings are used to facilitate the free movement of parts in rotational motion.
Even when we need linear motion in applications, it is easy to convert rotational motion to sliding motion. Consider an escalator or a conveyor. Even though the motion is linear, it is powered by rollers that are driven by motors.
Another example is a reciprocating pump that can convert rotational energy from a motor into translational motion with the help of linkages. In each of these applications, ball bearings are used to support motor shafts as well as shafts of other rollers in the assembly.
Rolling elements carry the load without much friction as the sliding friction is replaced with rolling friction. Rolling element bearings can be subdivided into two major types: ball bearings and roller bearings.
Ball bearings are one of the most common types of bearing classes used. It consists of a row of balls as rolling elements. They are trapped between two annulus shaped metal pieces. These metal pieces are known as races. The inner race is free to rotate while the outer race is stationary.
Ball bearings provide very low friction during rolling but have limited load-carrying capacity. This is because of the small area of contact between the balls and the races. They can support axial loads in two directions besides radial loads.
Ball bearings are used for controlling oscillatory and rotational motion. For example, in electrical motors where the shaft is free to rotate but the motor housing is not, ball bearings are used to connect the shaft to the motor housing.
Depending on the application, different types of ball bearings are available to choose from.