Basic knowledge of rolling bearings

A rolling bearing is a precision mechanical component that changes the sliding friction between the running shaft and the shaft seat into rolling friction, thereby reducing friction losses. Rolling bearings generally consist of four parts: inner ring, outer ring, rolling elements and cage. The function of the inner ring is to cooperate with the shaft and rotate with the shaft; the function of the outer ring is to cooperate with the bearing seat and play a supporting role; the rolling element is The cage evenly distributes the rolling elements between the inner ring and the outer ring. Its shape, size and number directly affect the performance and life of the rolling bearing; the cage can evenly distribute the rolling elements, prevent the rolling elements from falling off, and guide the rolling elements. Rotation provides lubrication.

According to the structure, rolling bearings can be divided into: deep groove ball bearings, needle roller bearings, angular contact bearings, aligning ball bearings, spherical roller bearings, thrust ball bearings, thrust spherical roller bearings, cylindrical roller bearings, tapered rollers Bearings, seated spherical ball bearings, etc.

Deep groove ball bearings have a simple structure and are easy to use. They are the type of bearings with the largest production volume and the widest application range. It is mainly used to bear radial load and can also bear certain axial load. When the radial clearance of the bearing increases, it functions as an angular contact bearing and can withstand larger axial loads. Used in automobiles, tractors, machine tools, motors, water pumps, agricultural machinery, textile machinery, etc.

Needle roller bearings are equipped with thin and long rollers (the roller length is 3 to 10 times the diameter, and the diameter is generally not larger than 5mm). Therefore, the radial structure is compact. When its inner diameter size and load capacity are the same as other types of bearings, the outer diameter The smallest diameter, especially suitable for support structures with limited radial installation dimensions. Depending on the application, you can choose a bearing without an inner ring or a needle roller and cage assembly. At this time, the journal surface and shell hole surface matching the bearing directly serve as the inner and outer rolling surfaces of the bearing to maintain the load capacity and operating performance. As with ring bearings, the hardness, machining accuracy and surface quality of the raceway surface of the shaft or housing hole should be similar to the raceway of the bearing ring. This kind of bearing can only bear radial load. For example: universal joint shafts, hydraulic pumps, sheet rolling mills, rock drills, machine tool gearboxes, automobile and tractor gearboxes, etc.

Angular contact ball bearings have a high limit speed and can bear both meridional and axial loads, as well as pure axial loads. Their axial load capacity is determined by the contact angle and increases as the contact angle increases. Mostly used in: oil pumps, air compressors, various transmissions, fuel injection pumps, printing machinery.

The self-aligning ball bearing has two rows of steel balls, the inner ring has two raceways, and the outer ring raceway is an inner spherical shape and has automatic self-aligning performance. It can automatically compensate for the coaxiality error caused by the deflection of the shaft and the deformation of the housing. It is suitable for components where the support hole cannot guarantee strict coaxiality. This type of bearing mainly bears radial load. While bearing radial load, it can also bear a small amount of axial load. It is usually not used to bear pure axial load. If it bears pure axial load, only one row of steel balls will be stressed. Mainly used in combine harvesters and other agricultural machinery, blowers, paper machines, textile machinery, woodworking machinery, bridge crane wheels and transmission shafts.

Spherical roller bearings have two rows of rollers, which are mainly used to bear radial loads and can also bear axial loads in any direction. This kind of bearing has high radial load capacity and is especially suitable for working under heavy load or vibration load, but it cannot bear pure axial load. It has good alignment performance and can compensate for the same bearing error. Main uses: papermaking machinery, reduction devices, railway vehicle axles, rolling mill gearbox seats, crushers, various industrial reducers, etc.

Thrust ball bearings are a separable bearing. The shaft ring and seat ring can be separated from the cage and steel ball components. The shaft ring is a ferrule that matches the shaft, and the seat ring is a ferrule that matches the bearing seat hole, with a gap between it and the shaft. Thrust ball bearings can only handle axial loads, one-way thrust ball bearings can only bear axial loads in one room, and two-way thrust ball bearings can bear axial loads in both directions. The thrust ball bearing cannot limit the meridional movement of the shaft, and the limit speed is very low. One-way thrust ball bearings can limit the axial displacement of the shaft and housing in one direction, and two-way bearings can limit the axial displacement in both directions. Mainly used in automobile steering mechanisms and machine tool spindles.

Thrust roller bearings are used to bear mainly axial loads on shafts and combined meridional loads, but the meridional load shall not exceed 55% of the axial load. Compared with other thrust roller bearings, this kind of bearing has a lower friction coefficient, higher rotation speed, and has the ability to adjust. The rollers of the 29000 bearing are asymmetric spherical rollers, which can reduce the relative sliding between the stick and the raceway during operation. The rollers are long and have a large diameter. They have a large number of rollers and a large load capacity. They are usually lubricated with oil. Grease lubrication can be used at low speeds. When designing and selecting, it should be given priority. Mainly used in hydraulic generators, crane hooks, etc.

The rollers of cylindrical roller bearings are usually guided by two ribs of a bearing ring, and the cage, roller and guide ring form an assembly that can be separated from another bearing ring and is a separable bearing. This kind of bearing is more convenient to install and disassemble, especially when the interference fit between the inner and outer rings and the shaft and casing is required. This type of bearing is generally only used to bear radial loads. Only single-row bearings with ribs on both the inner and outer rings can bear small steady axial loads or large intermittent axial loads. It is mainly used for large motors, machine tool spindles, axle boxes, diesel engine crankshafts, automobiles, and gearboxes with bearings in mind.

Tapered roller bearings are mainly suitable for bearing combined radial and axial loads, which are mainly radial loads, while large taper angle tapered roller bearings can be used to bear combined radial and axial loads, which are mainly axial loads. This type of bearing is a separable bearing, and its inner ring (including tapered rollers and cage) and outer ring can be installed separately. During the installation and use process, the meridional clearance and axial clearance of the bearing can be adjusted, and it can also be pre-interference installed for automobile rear axle hubs, large machine tool spindles, high-power reducers, axle bearing boxes, and rollers of conveying devices. .

The seated spherical ball bearing is composed of an spherical ball bearing with seals on both sides and a cast (or steel plate stamped) bearing seat. The internal structure of the outer spherical ball bearing is the same as that of the deep groove ball bearing, but the inner ring of this bearing is wider than the outer ring. The outer ring has a truncated spherical outer surface, which can be automatically aligned with the concave spherical surface of the bearing seat. Usually there is a gap between the inner hole of this kind of bearing and the shaft. The inner ring of the bearing is fixed on the shaft with a jackscrew, eccentric sleeve or adapter sleeve, and rotates with the shaft. Mounted bearings have compact structure, easy loading and unloading, and perfect sealing. They are suitable for simple support and are commonly used in mining, metallurgy, agriculture, chemical industry, textile, printing and dyeing, conveying machinery, etc.