Four row cylindrical roller bearings
The friction between the rolling element and the rib of the ring is small, which is suitable for high-speed rotation. According to whether the ring has ribs or not, it can be divided into single row bearings such as NU, NJ, NUP, N, NF, and double row bearings such as NNU and NN. The bearing is a structure in which the inner ring and the outer ring can be separated.
Cylindrical roller bearings without ribs on the inner or outer ring, the inner and outer rings can move relative to the axial direction, so they can be used as free end bearings. Cylindrical roller bearings with double ribs on one side of the inner ring and outer ring and a single rib on the other side of the ring can withstand a certain degree of axial load in one direction.
Generally, a steel stamping cage or a copper alloy turning cage is used. However, there are also part of the use of polyamide forming cage.
Four row cylindrical roller bearing application
Four-row cylindrical roller bearings mainly bear radial and axial combined loads. The bearing capacity depends on the raceway angle of the outer ring, and the larger the angle, the greater the bearing capacity. This type of bearing is a separable bearing, which is divided into single-row, double-row and four-row tapered roller bearings according to the number of rows of rolling elements in the bearing.
The clearance of single-row tapered roller bearings needs to be adjusted by the user during installation; the clearance of double-row and four-row tapered roller bearings has been given according to the user’s requirements when the product leaves the factory, and does not need to be adjusted by the user.
Four-row cylindrical roller bearings have tapered inner and outer raceways with tapered rollers arranged in between. The projected lines of all conical surfaces meet at the same point on the bearing axis. This design makes tapered roller bearings particularly suitable for combined (radial and axial) loads. The axial load capacity of the bearing is mostly determined by the contact angle α; the larger the α angle, the higher the axial load capacity. The size of the angle is represented by the calculation coefficient e; the larger the value of e, the larger the contact angle, and the greater the applicability of the bearing to bear the axial load.
Four-row cylindrical roller bearings are usually separable, that is, the tapered inner ring assembly consisting of the inner ring with the roller and cage assembly can be installed separately from the tapered outer ring (outer ring).
Four-row cylindrical roller bearings are widely used in automobiles, rolling mills, mining, metallurgy, plastic machinery and other industries.
Classification and performance of four-row cylindrical roller bearings for rolling mills
As a typical rolling mill roll bearing, four-row cylindrical roller bearings can be easily separated from each other, and their ferrules and rolling element components can be easily separated from each other. The parts can be interchanged with high precision. Installation, disassembly and cleaning are very convenient. In the space, it can provide the maximum radial bearing capacity and has a low friction coefficient.
Four-row cylindrical roller bearings mainly have three structural types, namely: FC type, FCD type, FCDP type.
FC type is a separable bearing, mainly small bearing. The integral inner ring can be separated from the whole set of bearings. The complete set of bearings consists of two outer ring assemblies and one inner ring (consisting of 1 inner ring, 2 outer rings , 4 rows of rolling elements, 2 cages), with high limit speed and interchangeability. The cage is a machined brass cage. Such bearings must first be suitable for high-speed (35m/S) rotation. Carrying capacity is secondary. Generally, the four-row cylindrical bearing with an inner diameter of 80mm~260mm is designed for this structure. Mainly used for the work rolls of cold rolling four-high, six-high and twelve-high rolling mills.
FCD type is a separable bearing, mainly medium and large bearings. The complete set of bearings consists of two outer ring assemblies and two inner rings (consisting of 2 inner rings, 2 outer rings, 4 rows of rolling elements, 2 cages composition), with high limit speed and interchangeability. Cages are machined brass or steel cages. This type of bearing is not only suitable for high speed (35m/S) but also can bear heavy load at the same time. Generally, four-row cylindrical bearings with an inner diameter of 260mm~400mm are designed for this structure. It is mostly used in profile finishing mills and high-speed wire rod rough rolling, intermediate rolling and pre-finishing rolling parts, including backup rolls, intermediate rolls and work rolls of cold-rolled non-ferrous and ferrous metal rolling mills below 950.
The FCDP type is mainly based on extra-large bearings. The rolling mill roll diameter bearing is a typical type of bearing. The parts can be separated from each other, and the positions can be exchanged with high precision. The installation, disassembly and cleaning are very convenient. In a given installation space, it can be Provides maximum radial load carrying capacity with a low coefficient of friction. Therefore, it is suitable for high-speed, heavy-duty, and harsh working environment at the rolling mill roll diameter.
In order to accommodate the maximum number of rolling elements to provide the best radial bearing capacity, the cage of the four-row cylindrical bearing with an inner diameter of more than 400mm is generally designed as a pin-type cage. It consists of two washers and a strut connecting the two washers and passing through the center of the roller, namely 2 inner rings, 2 outer rings, 4 rows of rolling elements, 1 middle retaining ring, 2 side retaining rings, 4 cages The two ends of the strut and the gasket are riveted and fixed by argon arc welding, and the cage has high strength.
This is very important for bearings subjected to frequent shocks or large acceleration and deceleration movements (eg: section steel blanking machines, high-speed reversing rolling mills).
How to properly install four row cylindrical roller bearings
Large-scale FCDP four-row cylindrical roller bearings are separable bearings. The rolling element cage is integrated with four rows, two half outer rings, one spacer ring and two ribs. Generally, the FCDP structure bearing is large in size and heavy in weight, and cannot be installed and assembled by manpower. Since the parts are scattered, they need to be loaded into the bearing box one by one, and the rolling elements and outer rings need to be hoisted by aircraft or other equipment.
Like ordinary four-row cylindrical bearings, unpacking to check the appearance, check the mating surface, etc. will not be repeated here.
Each row of rolling elements and raceways has a corresponding number and is installed in the order of the numbers. The serial number is used by the manufacturer to distinguish the raceways corresponding to each row of rolling elements of the bearing, and it also has the function of recording the usage of the bearing. (Here, it is 4 on the side of the roller body, and 1 on the side of the roller head.) Install the side retaining ring to the bottom of the bearing box first. Place the outer ring numbered 4 and 3 with the side numbered 4 facing down. A row of rolling elements numbered 4 is loaded into the outer ring first, and then the rolling elements and the outer ring are lifted.
Install the No. 4 rolling element into the bearing housing together with the outer ring.
It can effectively avoid the collision between the outer ring and the rolling body when the rolling body is installed first and then the outer ring is installed, and it is convenient and quick.