Because many machines have complex structures, multiple sets of bearings are required for combined use, which is combined bearing. A rolling bearing composed of two bearing structures in a set of bearings at the same time. Such as needle roller and thrust cylindrical roller combined bearing, needle roller and thrust ball combined bearing, needle roller and angular contact ball combined bearing, etc.
The unique feature of its design is the rolling bearing with short cylindrical, conical or waist drum rollers as rolling elements. Ina bearings are mainly used in the following fields: textile machinery, printing machinery, automotive industry, household appliances, money detector.
1. Needle roller and thrust ball combined bearing without inner ring
2. Needle roller without inner ring and thrust ball combined bearing with outer cover
3. Combined thrust ball bearing with inner ring needle roller and outer cover
4. Needle roller and angular contact ball combined bearing
5. Needle roller and three-point contact ball combined bearing
6. Needle roller and thrust cylindrical roller combined bearing without inner ring
7. Combined bearing of needle roller without inner ring and thrust cylindrical roller with outer cover
8. Combined bearing with inner ring needle roller and thrust cylindrical roller
9. Thrust cylindrical roller combined bearing with inner ring needle roller and outer cover
10. Needle roller and bidirectional thrust cylindrical roller combined bearing
11. Needle roller with flange and two-way thrust cylindrical roller combined bearing
In order to ensure the normal operation of the bearing, appropriate axial and radial clearance is usually reserved in the combined bearing. The size of the clearance has a great impact on the rotation accuracy, load, service life, efficiency and noise of the bearing.
If the clearance is too large, the rotation accuracy of the bearing decreases and the noise increases; If the clearance is too small, the thermal expansion of the shaft NTN bearing increases the bearing load, shortens the service life and reduces the efficiency. Therefore, the clearance shall be properly adjusted according to the actual working conditions during bearing assembly, and the structure shall ensure that it can be adjusted conveniently.
There are three common methods to adjust the clearance:
(1) Shim adjustment
For the angular contact bearing combination shown, the clearance is adjusted by increasing or reducing the thickness of the shim pack between the bearing cover and the bearing seat. The thermal compensation clearance of deep groove ball bearing assembly is also adjusted by backing plate.
(2) Screw adjustment
Adjust the bearing clearance with screws and dished parts, and the nut plays a locking role. This method is convenient to adjust, but it can not bear large axial force.
(3) Round nut adjustment
Two tapered roller bearings are installed reversely, and the bearing clearance is adjusted by round nuts. However, the operation is inconvenient, and the thread will weaken the strength of the shaft.
The temperature of the combined bearing will rise after starting operation. After a period of time, it will be in normal state at a lower temperature than fag bearing (usually 10 ~ 40 degrees higher than room temperature). The time to normal will vary according to the bearing size, form, rotation speed and lubrication method, and the exothermic conditions around the bearing. At this time, it will take about 20 minutes to several hours.
1. Too much or too little lubricating oil
2. Poor installation of bearing
3. The internal clearance of the combined bearing is too small or the load is too large
4. Excessive friction of sealing device
5. Lubricant discrepancy
6. Creep of mating surface
In addition, in case of the above situation, shut down the machine as soon as possible and take necessary countermeasures. Temperature is very important to maintain the proper service life of the bearing and prevent the deterioration of the lubricating oil!
Secondly, check the raceway surface of the bearing, the condition of the rolling surface and joint surface, as well as the wear condition of the confrontation frame for damage and abnormal conditions. In particular, check the running track of the raceway surface. To judge whether the bearing can be used again, we should think about the damage level of the combined bearing, mechanical function, priority, operation premise, search and inspection cycle, etc.
When the combined bearing can be replaced, the new bearing shall be carefully inspected, and the shaft diameter, bearing seat hole and rotor shall be carefully inspected. When assembling and disassembling the bearing, the maintenance process shall be strictly implemented and careful operation shall be carried out to avoid bearing damage caused by improper assembly and disassembly. Refuel and change the oil on time to ensure that the NSK bearing is always in good condition; Check carefully during the operation of the combined bearing, and eliminate the hidden trouble in time if it is found.