Introduction

Spherical roller bearings have double row rollers, the outer ring has a shared spherical raceway, and the inner ring has two raceways that are inclined at an angle relative to the bearing axis. This ingenious structure enables it to have self-aligning performance, so it is not easily affected by the angle between the shaft and the bearing box seat on the error or the shaft bending, and is suitable for the occasions where the installation error or the shaft deflection causes the angle error. In addition to radial loads, the bearings can also withstand axial loads acting in both directions.

Spherical roller bearings have two types of inner holes: cylindrical and conical, and the taper of the conical taper hole is 1:30 and 1:12. This conical inner hole bearing is equipped with an adapter sleeve or a withdrawal sleeve. The tapered inner hole self-aligning ball bearing can be easily and quickly assembled on the optical shaft or the stepped machine shaft.

The models of spherical roller bearings are: spherical roller bearing (type 20000CC); spherical roller bearing with tapered hole (type 20000CCK); spherical roller bearing (type 20000CC/W33); spherical roller bearing with tapered hole (Type 20000CCK/W33); Spherical roller bearing mounted on the adapter sleeve (Type 20000CCK+H); Spherical roller bearing mounted on the adapter sleeve (Type 20000CCK/W33+H) There are 6 types in total.

Specific introduction

Spherical roller bearings have two rows of rollers, which mainly bear radial loads, as well as axial loads in either direction. It has high radial load capacity, especially suitable for working under heavy load or vibration load, but cannot bear pure axial load. The outer ring raceway of this type of bearing is spherical, so its self-aligning performance is good, and it can compensate for the coaxiality error.

There are two rows of symmetrical spherical rollers, the outer ring has a common spherical raceway, and the inner ring has two raceways inclined at an angle to the bearing axis, which has good self-aligning performance. The bearing can still be used normally, and the centering performance varies with the bearing size series. Generally, the allowable centering angle is 1~2.5 degrees. The load capacity of this type of bearing is large, and the bearing can withstand radial load in addition to radial load The axial load acting in both directions has good impact resistance. Generally speaking, the allowable working speed of spherical roller bearings is low.

Spherical roller bearings are divided into two different structures: symmetrical spherical rollers and asymmetric spherical rollers according to the cross-sectional shape of the rollers. Asymmetric spherical roller bearings are early products, mainly for main engine maintenance services, newly designed main engine Symmetrical spherical roller bearings are rarely used at this time. The internal structure has been comprehensively improved and designed and parameters are optimized. Compared with the early production spherical roller bearings, it can withstand greater axial load. The operating temperature of this bearing is The bearing is relatively low, so it can meet the requirements of higher speed. According to whether the inner ring has ribs and the cage used, it can be divided into C type and CA type. The characteristics of C type bearings are that the inner ring has no ribs and adopts steel plates. Stamping cage, CA type Trien bearing is characterized by ribs on both sides of the inner ring and the use of car-made solid cage. In order to improve the lubrication of the bearing, the spherical roller bearing with an annular oil groove and three oil holes in the outer ring can be provided to the user, which is represented by the bearing rear code /W33. Spherical roller bearings with inner ring oil holes can also be supplied according to the user's requirements. In order to facilitate customer loading, unloading and replacement of bearings, spherical roller bearings with tapered inner holes can also be provided. The taper taper is 1:12 , It is represented by the post code K. In order to meet the requirements of special users, bearings with an inner hole taper of 1:30 can also be provided, and the post code is K30. Bearings with a tapered inner hole can be directly mounted on the tapered journal with a lock nut, or mounted on a cylindrical journal with the help of an adapter sleeve or a withdrawal sleeve. In order to ensure that the bearing prevents harmful slippage between the raceway and the roller due to centrifugal action when the bearing is running at high speed, the bearing should bear a certain minimum radial load, which can be estimated as follows:

Fr =0.02C

where:

Fr -- minimum radial load N

C—the basic dynamic load rating N of the bearing

Equivalent Dynamic Load

P=Fr+Y1Fa when Fa/F e

P=0.67Fr+Y2Fa when Fa/F e

where:

P—equivalent dynamic load N

Y1 Y2—axial dynamic load factor

Equivalent static load

P0=Fr+Y0Fa

where:

P0—equivalent static load N

Y0—Axial static load factor

SKF manufactures rod ends requiring maintenance with a steel/steel or a steel/bronze sliding contact surface combination.

Steel/steel rod ends consist of a rod end housing and a steel/steel radial spherical plain bearing from the standard assortment, where the outer ring is secured in the housing. These rod ends are available with:

• a female (fig. 1) or male (fig. 2) thread (table 1)

• a female thread with a slotted shank (fig. 3) (special series for hydraulic cylinders) (table 2)

• a welding shank with cylindrical (fig. 4) or rectangular (fig. 5) section (table 3)

Steel/bronze rod ends are available with a female (fig. 6) or male (fig. 7) thread. They consist of a rod end housing and a steel/bronze spherical plain bearing (table 4). These bearings have an inner ring made of steel and an outer ring made of bronze. The bearing is held in position by staking the housing on both sides of the outer ring. These rod ends are available with a male or female thread.

Relubrication facilities

SKF rod ends requiring maintenance are provided with a grease fitting or a lubrication hole in the rod end housing. Relubrication via the pin is also possible. Exceptions are steel/steel rod ends in the SA .. E and SI .. E series and a few smaller rod ends as indicated in the product tables. The type and design of relubrication facilities in the rod end housing are listed in table 5.

SKF Explorer steel/steel rod ends (table 6) in the SI(A) (fig. 8) and SA(A) (fig. 9) series can be equipped with SKF Explorer steel/steel plain bearings in the GE series, which makes them virtually maintenance-free (SKF Explorer steel/steel plain bearings). Their sliding surfaces are treated further to improve wear and corrosion resistance.

The rod end housings are equipped with lubrication holes due to manufacturing reasons, which are plugged to avoid contamination and relubrication.

SKF manufactures maintenance-free rod ends with three different sliding contact surface combinations in different series (table 7).

Rod ends with either a steel/PTFE sintered bronze (fig. 10 and fig. 11 or steel/PTFE fabric (fig. 12 and fig. 13) sliding contact surface combination contain a bearing from the standard assortment. The outer ring is staked in place in the housing.

Rod ends with a steel/PTFE FRP sliding contact surface combination (fig. 14 and fig. 15) consist of a rod end housing and a spherical plain bearing inner ring. Between the housing and the inner ring, a sliding layer of fibre reinforced polymer, containing PTFE, is moulded to the housing.

Dimension standardsISO 12240-:1998

Male and female threads:

• rod ends without suffix VZ019: ISO 965-1:2013

• rod ends with suffix VZ019: ISO 8139:2018

TolerancesInner rings: ISO 12240-4:1998 (table 6)

Radial internal clearance, preload

For additional information → Internal clearance

Depending on their design, maintenance-free rod ends either have a radial internal clearance or a light preload. Tables list maximum values for the radial internal clearance as well as for the frictional moment in the circumferential direction caused by preload:

• Sliding surface steel/PTFE sintered bronze (suffix C) (table 7)

• Sliding surface steel/PTFE fabric (suffix TXE-2LS) (table 8)

• Sliding surface steel/PTFE FRP (suffix F) (table 9)

MaterialsIncorporated bearings:

• steel/PTFE sintered bronze and steel PTFE fabric rod ends (table 10)

• steel/PTFE FRP rod ends: inner ring made of through-hardened and ground bearing steel, hard chromium plated sliding contact surface; sliding layer consists of a fibre reinforced polymer, containing PTFE

LS-seals: acrylonitrile butadiene rubber (NBR) (table 3)

Housing materials (table 11)Permissible operating temperature rangeDepends on the rod end housing, the bearing, the bearing seals and the grease (table 12)

The load carrying capacity of the rod end is reduced at temperatures above 100 °C (210 °F). For temperatures below 0 °C (30 °F), check to be sure that the fracture toughness of the rod end housing is adequate for the intended application.
Permissible operating temperature range of the grease must be considered too.

Pay attention to the problem

The preloading force of the spherical roller bearing is carried out at room temperature, but in the working state, the drive shaft caused by the micro-stretching temperature of the system will change the bearing preloading force. Therefore, the set preloading force should be considered. to this factor.

It requires the ability of size, speed, and other conditions to set the reasonable use of spherical roller bearing preload to ensure the life of the transmission. If the preload is too large, the power consumption may even lead to overheating. If the preload is too small, under the action of the body load, the shaft rolling, and the gap between the outer rings, there will be beating, running, and the transmission accuracy will increase to reduce noise, affect the gear meshing, and severely damage the teeth and bearings.

According to different spherical roller bearing assemblies, such as: directly by the axial compression of the inner bearing inner ring, the bearing preload nut is rotated, and the inner and outer rings are rotated to eliminate the gap and achieve the purpose of bearing preload. Achieving common use: first, well over the preloaded bearing, last of the nut, then back 1/4 turn. Assembly method, the advantages of this method are less investment, simple, practical, and consistent with the premise of good quality tapered roller bearings, it can be used.

1. Electric heating plate heating method Put the bearing on the electric heating plate with a temperature of 100 ℃ for a few minutes. This method is the most simple. If it is turned several times, the bearing can be heated evenly, and the efficiency is also high. This method can be used.

2. Electric furnace heating method Put the bearing in a closed automatic temperature-controlled electric furnace for heating, the heating is uniform, the temperature control is accurate, the heating is fast, and it is suitable for heating many bearings in a batch.

3. Induction heating method The use of induction heaters can quickly, reliably and cleanly heat the spherical roller bearing to the required temperature, which is especially suitable for occasions where the inner ring is tightly fitted, because only the inner ring is heated, and the outer ring is heated. The ring is less heated, which makes it easier to install on the shaft and into the seat hole.

4. The light bulb heating method uses a 50W light bulb to heat the spherical roller bearing, which can ensure that the heating temperature is about 100 ° C. The smaller bearing can be placed directly on the bulb, and the larger bearing can be placed in the cone of the bulb. The cover can prevent the heat loss of the bulb, and make the heating uniform. The conical cover can be adjusted up and down, and can be adapted to heat bearings of different sizes within a certain range. If far-infrared light bulbs are used, pay attention to the direction of the light bulbs, so as to avoid infrared rays being harmful to people. This kind of light bulb can be used for energy-saving light bulb heating method, which is suitable for a small number and is not often needed; where the bearing needs to be heated, the light bulb can also be used for lighting at ordinary times, and no other equipment is required.

5. Oil tank heating method This is a widely used traditional heating method. A metal mesh is installed at a distance of 50~70mm from the bottom of the oil tank, and the bearing is placed on the mesh. The large bearing should be lifted by hooks and should not be placed directly at the bottom of the tank to prevent contact with the tank. The bearing parts at the bottom are locally heated too high, or the dirt deposited at the bottom of the tank enters the bearing oil tank. The points to be noted in the heating method are as follows. Non-corrosive mineral oil with good thermal stability should be used, preferably transformer oil. Both the oil and the container should be used. The capacity of the oil tank to keep clean should be determined by the size and oil volume of the heated spherical roller bearing. If the container is too small, the temperature of the oil will drop quickly once the bearing is put in during continuous operation, and the effect will not be good.