Generation of vibration in bearings Generally speaking, rolling bearings themselves do not generate noise. The “bearing noise” that is usually felt is actually the sound effect of the bearing directly or indirectly vibrating with the surrounding structure. This is why many times the noise problem can be regarded as a vibration problem involving the entire bearing application.
(1) Excited vibration caused by changes in the number of loaded rolling elements: When a radial load is applied to a certain bearing, the number of rolling elements carrying the load will slightly change during operation, which causes the deviation of the load direction . The resulting vibration is unavoidable, but it can be reduced by axial preloading, which is loaded on all rolling elements (not applicable to cylindrical roller bearings).
(2) Partial damage: due to operation or installation errors, a small part of the bearing raceways and rolling elements may be damaged. In operation, rolling over damaged bearing components will produce specific vibration frequencies. Vibration frequency analysis can identify damaged bearing components. This principle has been applied to condition monitoring equipment to detect bearing damage. To calculate the bearing frequency, please refer to the calculation program “Bearing Frequency”.
(3) Accuracy of related parts: In the case of a close fit between the bearing ring and the bearing seat or drive shaft, the bearing ring may be deformed by matching the shape of the adjacent part. If it is deformed, it may vibrate during operation.
(4) Pollutants: If running in a polluted environment, impurities may enter the bearing and be crushed by the rolling elements. The degree of vibration produced depends on the number, size and composition of the crushed impurity particles. Although it does not produce a typical frequency form, a disturbing noise can be heard.
The causes of noise produced by rolling bearings are more complicated. One is the wear of the mating surfaces of the inner and outer rings of the bearing. Due to this kind of wear, the matching relationship between the bearing and the housing, and the bearing and the shaft is destroyed, causing the axis to deviate from the correct position, and abnormal noise occurs when the shaft is moving at high speed. When the bearing is fatigued, the metal on its surface will peel off, which will also increase the radial clearance of the bearing and produce abnormal noise. In addition, insufficient bearing lubrication, formation of dry friction, and bearing breakage will cause abnormal noise. After the bearing is worn and loosened, the cage is loosened and damaged, and abnormal noise will also be produced.
Bearings need to be carefully used in daily life. Let us look at the nine things we need to pay attention to.
1. The riveting parts in the harvester are like the movable knife assembly. The rivets are generally made by cold extrusion and should not be heated during riveting. Heating will reduce the strength of the material. After riveting, a forming punch is used to strengthen the firmness of the blade and the knife shaft.
2. Vulnerable parts, especially pin shafts, pressing pieces, sleeves, and horns cannot be replaced and repaired with more butter during maintenance, such as long-term use of parts that are worn to the limit will cause the life of other machinery to be shortened .
3. Repair of shafts without balancing machine. When repairing various shafts that need to be balanced, a thrust bearing can be installed on one end of the shaft, clamped on the three jaws of the lathe, and the other end can be supported by the center. If the lathe is short, the center can be used. The frame clamps the SKF bearing mounted on the shaft at the other end until the balance is corrected. But when balancing the weight, use screws to tighten, and try not to use electric welding to balance the weight.
4. In the maintenance process, due to the various types of bearing materials, it is not easy to purchase, and can be processed with waste shafts. At present, most of the shafts in our country are mainly made of 45# carbon steel. If quenching and tempering is required, it can be used under bad conditions. Oxygen and earth furnace heat the required parts to red and black and place them in salt water, depending on the demand.
5. When processing sleeve parts, pull the oil groove in the sleeve hole as much as possible. Because it is very difficult to refuel some parts of the harvester, butter and heavy engine oil can be used where it is difficult to refuel, except for nylon sleeves. Where nylon sleeves are used, it is best not to replace them with cast iron, copper or aluminum, because the nylon sleeves will withstand a certain impact and will not deform.
6. The repair of the key and keyway on the belt pulley and the shaft should ensure that the size does not change in advance. Never increase the size of the key, otherwise it will affect the strength of the shaft. The keyway on the shaft can be repaired with electric welding filler and milled in the opposite direction of the old key. A keyway, the keyway on the pulley can be set with a sleeve (transition fit) method. After the setting is completed, use a countersunk screw to tap in the sleeve to tighten the key.
7. Repair the hydraulic part of the harvester. Remove the distributor and the reducing valve, and use the air pump to pressure the pipes. The hydraulic oil should be filtered and exhausted when the hydraulic oil is reloaded. The repair of the hydraulic assembly is mainly the seal. It is best to replace the seal after removing it.