Due to the complexity of many machine structures, multiple sets of bearings are required to be used in combination. This is a combined bearing. A set of rolling bearings composed of two bearing structures at the same time. Such as needle roller and thrust cylindrical roller combined bearings, needle roller and thrust ball combined bearings, needle roller and angular contact ball combined bearings, etc.
Among them, roller bearings are widely used. Its design is unique in its use of short cylinders, cones or waist drums
Rollers are rolling bearings used as rolling elements. Mainly used in the following fields: textile machinery, printing machinery, automotive industry, household appliances, banknote detectors.
1.Combined form of combined bearing
Several combined forms of combined bearings:
1. Needle roller and thrust ball combined bearing without inner ring
2. Thrust ball combined bearing without inner ring needle roller and housing
3. Inner ring needle roller and thrust ball combined bearing with housing
4. Needle roller and angular contact ball combined bearings
5. Needle roller and three-point contact ball combined bearings
6. Inner ring needle roller and thrust cylindrical roller combined bearings
7. Needle roller bearing without inner ring and thrust cylindrical roller with housing
8. Inner ring needle roller and thrust cylindrical roller combined bearings
9. Inner ring needle roller and thrust cylindrical roller combined bearing with housing
10. Needle roller and double thrust cylindrical roller combined bearings
11. Combined bearing with flange needle roller and double-direction thrust cylindrical roller
2.Adjustment of clearance of combined bearings
In order to ensure the normal operation of the bearing, proper axial and radial clearance is usually left inside the combined bearing. The size of the clearance has a great impact on the rotation accuracy, load, life, efficiency and noise of the bearing.
If the clearance is too large, the rotation accuracy of the bearing will be reduced, and the noise will increase; if the clearance is too small, the bearing will be increased in load due to the thermal expansion of the shaft, the life will be shortened, and the efficiency will be reduced. Therefore, when the bearing assembly is assembled, the clearance should be appropriately adjusted according to the actual working conditions, and the structure can be easily adjusted.
There are three common methods for adjusting clearance:
(1) Shim adjustment
The illustrated angular contact bearing combination adjusts the clearance by increasing or decreasing the thickness of the gasket set between the bearing cover and the bearing housing. The thermal compensation gap of the deep groove ball bearing combination is also adjusted by the gasket.
(2) Screw adjustment
The bearing clearance is adjusted with screws and dish-shaped parts, and the nut plays a locking role. This method is easy to adjust, but cannot withstand large axial forces.
(3) Round nut adjustment
Two tapered roller bearings are installed in reverse, and the bearing clearance is adjusted by a round nut. But the operation is not convenient, and the thread will weaken the strength of the shaft.
3.Effect of temperature on the efficiency of combined bearings
The combined bearing will heat up after it starts to run, and after a period of time, it will be at a lower temperature (usually 10 to 40 degrees higher than room temperature). The time to normal state varies depending on the bearing's size, form, rotation speed, lubrication method, and heat radiation conditions around the bearing. At this time, it takes approximately 20 minutes to several hours.
When the temperature of the combined bearing does not reach the normal state and abnormal heating occurs, the following main reasons can be considered:
1.Too much or too little lubricant
2.Poor bearing installation
3. The internal clearance of the combined bearing is too small, or the load is too large
4.The sealing device has too much friction
5.Lubricant does not match
6. Creep of mating surface
In addition, if the above situation occurs, stop the machine as soon as possible and take necessary countermeasures. Temperature is critical to maintaining proper bearing life and preventing deterioration of the lubricant!
Suggestion: It is best to use it under non-high temperature conditions (usually below 100 degrees).
Secondly, check the bearing's raceway surface, rolling surface and joint surface condition, as well as the wear and tear of the stern frame for damage and abnormal conditions. In particular, check the running track of the raceway surface. To determine whether the bearing can be used again, it is necessary to consider the level of damage of the combined bearing, mechanical performance, primacy, operating prerequisites, search period and so on.
By replacing the combined bearing, you must carefully check the new bearing, and at the same time carry out a careful inspection of the shaft diameter and the bearing seat hole and the rotor. When assembling and disassembling the bearing, strictly perform the maintenance process and carefully operate to avoid the improper assembly and disassembly Damaged bearings. Add oil and change oil on time to ensure that the working condition of the bearing is always in good condition; carefully check during the operation of the combined bearing to find hidden troubles and eliminate them in time.
