Installation and lubrication of motor bearing

Before installing the bearing, make sure that the mounting surface and environment are clean. If there are iron filings, burr, dust and other foreign matters in the bearing, the bearing will produce noise and vibration during operation, and even damage the raceway and rolling body. Cleanliness has a great influence on bearing life and vibration noise. When installing the bearing, do not directly hammer the bearing end face and non stressed surface, use the pressure block, sleeve or other installation tools to make the bearing evenly stressed, and do not install the bearing through the power transmission of rolling element. If the mounting surface is coated with lubricating oil, the installation will be smoother. If the fit interference is large, the bearing should be put into the mineral oil and heated to 80 ~ 90 ℃ for installation as soon as possible. The oil temperature should be strictly controlled not to exceed 100 ℃ to prevent tempering effect, hardness reduction and dimension recovery.

Radial clearance of bearing
The radial clearance of the bearing is not the smaller the better. The most suitable clearance should be selected according to the conditions. Not all bearings require the minimum working clearance. The basic radial clearance group is suitable for general operating conditions, conventional temperature and common interference fit. The bearings working under special conditions such as high temperature, high speed, low noise and low friction should use large radial clearance. The bearings for precision spindle and machine tool spindle should use small radial clearance. The roller bearings should use small radial clearance A small amount of working clearance can be maintained. In addition, there is no clearance for the separated bearing; the working clearance of the bearing after installation is smaller than the original clearance before installation, because the bearing has to bear certain load rotation, as well as the elastic deformation caused by bearing fit and load.
Lubrication of bearings
Lubrication has a very important influence on the operation and life of bearings. Lubricating grease is made of base oil, thickener and additive. The performances of different kinds and different brands of lubricating grease of the same kind vary greatly, and the allowable rotation limits are different. It is necessary to pay attention to the selection. The performance of grease is mainly determined by base oil. Generally, low viscosity base oil is suitable for low temperature and high speed, while high viscosity base oil is suitable for high temperature and high load. The water resistance of thickener determines the water resistance of lubricating wax. In principle, different brands of grease can not be mixed, and even the grease with the same thickener will have adverse effects on each other due to different additives.
When lubricating bearings, many people think that the more grease the better, which is a common misconception. Too much grease in the bearing and bearing chamber will cause excessive stirring of grease, resulting in extremely high temperature. The amount of lubricant filling in the bearing should be 1 / 2 ~ 1 / 3 of the inner space of the bearing, and it should be reduced to 1 / 3 at high speed.
Common installation methods of bearings
Generally speaking, the installation of bearings is mostly shaft rotation, so the fit between inner ring and shaft is interference fit, and the fit between outer ring and bearing chamber is clearance fit.Press fit. When the inner ring of the bearing is tightly matched with the shaft and the outer ring is loosely matched with the bearing seat hole, the bearing can be pressed onto the shaft with a press, and then the shaft and the bearing can be installed into the bearing seat hole together. When pressing, an assembly sleeve (copper or mild steel) made of soft metal material shall be padded on the end face of the bearing inner ring. The inner diameter of the assembly sleeve shall be slightly larger than the journal diameter, and the outer diameter shall be smaller than the bearing inner ring The ribs are slightly smaller to avoid pressing on the cage. When the outer ring of the bearing fits tightly with the bearing seat hole, and the inner ring fits loosely with the shaft, the bearing can be pressed into the bearing seat hole first. At this time, the outer diameter of the assembly sleeve should be slightly smaller than the diameter of the seat hole. If the bearing ring is tightly matched with the shaft and seat hole, the inner ring and outer ring in the installation chamber shall be pressed into the shaft and seat hole at the same time. The structure of the assembly sleeve shall be able to compress the end face of the inner ring and outer ring of the bearing at the same time.
Heating coordination. By heating the bearing or bearing seat, the tight fit is changed into loose fit by thermal expansion. It is a common and labor-saving installation method. This method is suitable for the installation of bearings with large interference. Before hot installation, put the rings of bearings or separable bearings into the oil tank and evenly heat them for 80-100 ℃. Then take them out of the oil and install them on the shaft as soon as possible. In order to prevent the end face of inner ring and shaft shoulder from not fitting tightly after cooling, the bearings can be tightened axially after cooling. When the outer ring of the bearing is tightly matched with the bearing seat made of light metal, the hot assembly method of heating the bearing seat can avoid the abrasion of the matching surface. When the oil tank is used to heat the bearing, there should be a grid at a certain distance from the bottom of the box, or the bearing should be hung with a hook. The bearing should not be placed on the bottom of the box to prevent impurities from entering the bearing or uneven heating. There must be a thermometer in the oil tank, and the oil temperature should not exceed 100 ℃ strictly to prevent tempering effect and reduce the hardness of the ring.Installation of tapered bore bearing. Tapered hole bearing can be directly installed on the taper journal, or loaded on the taper surface of tightening sleeve and stripping sleeve. The degree of tightness can be measured by the radial clearance reduction of bearing. Therefore, the radial clearance of bearing should be measured before installation, and the clearance should be measured frequently during installation to achieve the required clearance reduction. Generally, the lock nut is used for installation Adopt the method of heating installation.Installation of thrust bearing. The inner ring and shaft of thrust bearing are generally transitional fit, and the fit of race and bearing hole is clearance fit, so this kind of bearing is easy to install.
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