Views: 144 Author: Site Editor Publish Time: 2019-07-23 Origin: Site
Needle roller bearings are roller bearings with cylindrical rollers that are thin and long relative to their diameter. Here we will introduce it in detail.
This thin and long roller is called a needle roller. Despite the small cross-section, the bearing still has a high load bearing capacity, and the needle bearing is equipped with a thin and long roller (roller diameter D ≤ 5 mm, L / D ≥ 2.5, L is the roller length), so The radial structure is compact, its inner diameter size and load capacity are the same as other types of bearings, the outer diameter is the smallest, and it is especially suitable for support structures with limited radial mounting dimensions.
Depending on the application, bearings or needle roller and cage assemblies without inner ring can be used. The journal surface and the housing hole surface that match the bearing directly serve as the inner and outer rolling surfaces of the bearing to ensure load capacity and running performance. As with ferrule bearings, the hardness of the raceway surface of the shaft or housing bore, the machining accuracy and surface quality should be similar to the raceway of the bearing ring. This type of bearing can only withstand radial loads.
The drawn cup needle roller bearings are needle bearings with a thin stamped outer ring. Its main features are low cross-section height and high load carrying capacity. Mainly used for bearing arrangements that are compact, inexpensive, and the bore of the bearing housing cannot be used as the raceway for the needle roller cage assembly. The bearing and bearing housing must be installed in an interference fit. If the axial positioning function such as the box shoulder and the stop ring can be omitted, the inner hole of the bearing housing can be made extremely simple and economical. The drawn cup needle roller bearings mounted on the shaft end are open on both sides and closed on one side. The base end face of the closed stamped outer ring can withstand small axial guiding forces. Drawn cup needle roller bearings generally do not have an inner ring. In the case where the journal cannot be hardened and ground, the inner ring listed in the table can be used. The hardened steel outer ring of the drawn cup needle roller bearing is inseparable from the needle roller cage assembly. The free space to store the lubricant can extend the relubrication interval.
Solid ferrule needle bearings consist of one or two ferrules and a needle set with a cage. Depending on the application, it can be divided into bearings with or without inner ring. Therefore, the physical ferrule needle roller bearing can meet the requirements of light weight, small space occupation and large transmission power. Solid ferrule needle bearings have a small volume and high load carrying capacity. Structure type outer ring double rib (or double lock ring) with cage needle roller bearings NA, NAV, NKI type can be installed inner ring and outer ring (with lock ring, full set of needle roller and cage), high speed, It is divided into single column and double column. If the shaft cannot be used as a raceway, that is, if it is impossible or uneconomical to harden the shaft, such a needle bearing with an inner ring can be used.
The combined needle roller bearing is a bearing unit composed of a combination of a radial needle bearing and a thrust bearing component. It has a compact structure, small volume, high rotation precision, and is subjected to a certain axial load while being subjected to a high radial load. And the product structure is diverse, adaptable and easy to install. Combined needle roller bearings are widely used in various mechanical equipment such as machine tools, metallurgical machinery, textile machinery and printing machinery, and can make the mechanical system design very compact and dexterous.
The thrust bearing consists of a thrust cage assembly with a needle or cylindrical roller or ball and a thrust washer. The needle roller and the cylindrical roller are held and guided by the thrust cage. When used with different series of DF thrust bearing washers, many different combinations are available for bearing configurations. Due to the high precision cylindrical needle roller, the contact length is increased, so that the bearing can obtain high load capacity and high rigidity in a small space. Another advantage is that if the surface of the adjacent part is suitable for the raceway surface, the washer can be omitted, and the design can be compact. The cylindrical surfaces of the needle roller and the cylindrical roller used for the DF thrust needle roller bearing and the thrust cylindrical roller bearing are the profiled surface reduces edge stress and increases service life.
(1) Needle bearing has large bearing capacity and is suitable for mounting support structure with limited size. The surface of the journal is hardened as a rolling surface, and the bearing is press-fitted into the seat hole without axial positioning.
(2) The bearing should be filled with proper amount of grease before installation. Under normal circumstances, the BK bearing should not be lubricated after assembly for the support of the journal without the protruding end. The end face is closed for sealing and can withstand small axial direction.