Installing the motor bearing properly and preventing it from rusting will directly affect the accuracy, life and performance of the bearing

Time：2020.03.17  Source：Roller Bearings Suppliers

Motor bearing is a special type of bearing specially used in motors. The bearing used in the motor is a part that supports the shaft. It can guide the rotation of the shaft and can also withstand idle parts on the shaft. The concept of a bearing is very broad. There are four types of bearings commonly used in electric motors, namely rolling bearings, plain bearings, articulated bearings and oil-containing bearings. The most common motor bearing is a rolling bearing, that is, a bearing with rolling elements. Sliding bearings generally refer to bearings without rolling elements, that is, bearings for sliding motion.

Motor bearings use smooth metal balls or rollers and lubricated inner and outer metal surfaces to reduce friction. These balls or rollers "load" the load and support the main shaft of the motor so that the rotor of the motor can rotate smoothly. Most small and medium-sized motors use rolling bearings. Large and medium motors also use rolling bearings.

Ball bearings (deep groove ball bearings) are used for bearings at both ends of small motors. Medium motor use roller bearings at the load end (usually used in high-load conditions), and ball bearings at the non-load end (but the opposite is true, such as 1050kW motors). Rolling bearings are lubricated with grease, but lubricated with oil.

Installation of motor bearings

The quality of the motor bearing installation will directly affect the accuracy, life and performance of the bearing. Therefore, please study bearing installation thoroughly, and perform bearing installation according to the operating standards including the following items.

1. Clean the bearings and related parts. (For grease-lubricated bearings and oil seals or dust covers on both sides, seal bearings need not be cleaned before installation.)

2. Check the dimensions and finishing of the relevant parts of the motor bearing

3. Installation method

The installation of the bearing should be determined according to the bearing structure, size and the matching nature of the bearing components. The pressure should be directly applied to the end face of the tight-fitting ferrule, and the pressure should not be transmitted through the rolling elements.

a. Press fit

The inner ring of the bearing and the shaft are tightly fitted. When the outer ring and the bearing seat hole are loosely fitted, the bearing can be press-fitted on the shaft with a press, and then the shaft and the bearing are inserted into the bearing seat hole. On the end face of the bearing inner ring, a mounting sleeve (copper or soft steel) made of soft metal material is cushioned.

The outer ring of the bearing fits tightly with the bearing seat hole. When the inner ring and the shaft are loosely fitted, the bearing can be pressed into the bearing seat hole first. At this time, the outer diameter of the mounting sleeve should be slightly smaller than the diameter of the seat hole.

If the bearing ring is tightly fitted with the shaft and the seat hole, the inner and outer rings of the installation must be pressed into the shaft and the seat hole at the same time. The structure of the mounting sleeve should be able to tighten the end faces of the bearing inner ring and outer ring at the same time.

b. Heating fit

By heating the bearing or bearing seat, the thermal expansion is used to transform the tight fit into a loose fit installation method. It is a common and labor-saving installation method. This method is suitable for the installation of bearings with a large amount of interference. Before the hot-loading, the bearing or separable bearing ring is put into the oil tank and heated evenly at 80-100 ° C. Then it is taken out of the oil and installed on the shaft as soon as possible. Prevent the inner ring end face from abutting tightly with the shoulder after cooling, and then axially tighten the bearing after cooling. When the outer ring of the bearing is tightly matched with a light metal bearing seat, the hot mounting method of heating the bearing seat can be used to prevent the mating surface from being scratched.

When heating the bearing with the fuel tank, there should be a grid at a certain distance from the bottom of the tank, or the bearing should be suspended by a hook. The bearing cannot be placed on the bottom of the tank to prevent sinking impurities from entering the bearing or uneven heating. Strictly control the oil temperature not to exceed 100 ℃ to prevent the tempering effect and reduce the hardness of the ferrule.

How to prevent motor bearings from rusting?

1. Try to use solvent-free paint.

2. If possible, use impregnating paints that do not contain oxidizing ingredients, such as Epoxy-urethane-based or Epoxy-based impregnating paints.

3. When using melamine dipping paint, the curing temperature and curing time should be adjusted. The curing temperature should be slightly higher than 130 ℃ (such as 135 ℃) and the curing time should be greater than 180min. The process must be strictly implemented, especially at high temperature. In the wet season, from the perspective of rust prevention, the paint drying (curing) time specified in the samples of the paint factory is not necessarily sufficient, and the motor has a specific internal shape.

4. Use volatile acid-free paint.

5. Select paint with good hydrolysis resistance.

6. Try to choose mineral oil bearing grease.

7. When the motor factory injects grease by itself, in order to prevent water vapor and dust from entering the bearing to generate noise and another rust factor that may be caused, the grease container should be sealed, even when it is being greased, and The amount of grease injection should be constant according to the standard. If 6202 bearings are used, the reference value is in the range of 0.60 to 0.80g. The grease injection process should be kept clean and dry.

8. Use micro-hole plastic film packaging to allow some ventilation before the motor is activated. When using a plastic film to seal the package, paint gas will remain in the bearing and moisture will condense, and you should try to avoid it.

9. Grease may deteriorate under the influence of high temperature when the motor cover is sprayed with powder or solidified after painting.

10. Negotiate with bearing manufacturers to use more effective rust preventives in bearing production.

11. In order to completely solve the paint rust, it can be considered by the motor manufacturer, the bearing manufacturer and the paint production unit to discuss the capabilities of all aspects to solve the bearing rust.