Some common sense to choose and use Timken bearings

1. The size, direction and nature of the Timken bearing load [bearing load capacity is expressed in terms of basic load rating, the value is shown in the bearing size table] Bearing load is rich, such as the size of the load, whether there is only radial load, shaft Whether the load is one-way or two-way, the degree of vibration or shock, and the like. After considering these factors, choose the most suitable bearing type.

In general, the radial load capacity of bearings of the same inner diameter is increased in the following order: deep groove ball bearings < angular contact ball bearings < cylindrical roller bearings < tapered roller bearings < spherical roller bearings

2. The relative inclination analysis of the inner ring and the outer ring causes the Timken bearing inner ring and the outer ring to have relative inclination factors (such as the deflection of the shaft caused by the load, the accuracy of the shaft and the casing, or the installation error), and The type of bearing that is suitable for this type of use. If the relative inclination of the inner ring and the outer ring is too large, the bearing may be damaged by internal load. Therefore, you should choose the type of bearing that can withstand this tilt.

In general, the allowable tilt angle (or centering angle) is incremented in the following order:

Cylindrical roller bearings, tapered roller bearings, deep groove ball bearings (angular contact ball bearings), spherical roller bearings (ball bearings) 3) Bearing type that meets the rigidity required for the mechanical shafting [bearing when the bearing is under load The contact portion between the body and the raceway is elastically deformed. "High rigidity" means that the amount of deformation of such elastic deformation is small.] In the machine tool spindle and the final stage of the vehicle, the rigidity of the shaft must be increased, and the rigidity of the bearing must be increased.

The roller bearing is subjected to load deformation smaller than the ball bearing. Applying a preload (negative clearance) to the bearing increases rigidity. This method is suitable for angular contact ball bearings and tapered roller bearings.

3. The bearing installation space can be accommodated in the bearing installation space. Since the design of the shaft system pays attention to the rigidity and strength of the shaft, the shaft diameter is generally determined first, that is, the inner diameter of the bearing. However, rolling bearings are available in a variety of sizes and types, and the most suitable bearing type should be selected.

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Nsk bearing common troubleshooting method

Due to the inaccurate measurement of the shaft diameter and the bearing housing hole or the roughness of the mating surface does not meet the standard requirements, an excessive interference fit is caused, so that the nsk bearing race is greatly squeezed, resulting in a decrease in the radial clearance of the bearing itself. It makes the bearing difficult to rotate, generates heat, and the wear is intensified or stuck. In severe cases, the inner and outer races of the bearing will be cracked during installation. The non-rotating seat often adopts a gap or a small interference, so that the rotation of the seat may cause a slight creep, and the contact surface of the race with the rolling element is continuously replaced, and the raceway of the race is evenly worn. At the same time, it is also possible to eliminate the axial jam of the rolling elements in the bearing due to the thermal elongation of the shaft. However, if the gap is too large, the non-rotating seat will rotate together with the rolling elements, causing severe wear of the shaft (or the bearing housing hole) and the inner race (or the outer race), and the friction causes the bearing to heat and vibrate.

B. Improper assembly method

When the interference of the nsk bearing and the shaft diameter or the bearing housing hole is small, the press-in method is often used for assembly. The easiest way is to use a copper rod and a hand hammer to symmetrically tap the bearing with an interference fit in a certain order to make the bearing smoothly pressed in. In addition, it is also possible to use a sleeve made of soft metal to be hammered in or pressed by a press. If improperly operated, the seat will be deformed and cracked, or the hammer will be hit on the non-interference fit seat, which will cause the raceway and the rolling element to be indented or the bearing to be indirectly damaged.

C. Improper temperature control during assembly

When the nsk bearing is assembled, if it has a large interference with the shaft diameter, it is usually assembled by hot charging. The bearing is placed in the oil drum filled with organic oil. The outside of the oil drum is heated by hot water or flame. The temperature of the oil required for the process is controlled at 80 ° C ~ 90 ° C, generally not more than 100 ° C, and the maximum is not more than 120 ° C. After the bearing is heated, it is quickly taken out and placed on the journal. If the temperature is not properly controlled, the heating temperature will be too high, which will cause the bearing to temper and the hardness will decrease. The bearing will be prone to wear, peeling and even cracking during operation.

D. Improper gap adjustment during assembly

The gap of the rolling bearing is divided into a radial gap and an axial gap, and its function is to ensure the normal operation and lubrication of the rolling elements and to compensate for the thermal elongation.

For bearings with adjustable clearance, because of the proportional relationship between the axial clearance and the radial clearance, the installation is to adjust the axial clearance to obtain the required radial clearance, and they are generally Used in pairs (ie at both ends or at one end of the shaft), therefore, it is only necessary to adjust the axial clearance of one bearing. Generally, the gasket is used to adjust the axial clearance, and some can also be adjusted by screws or thrust rings.

For nsk bearings whose gaps are not adjustable, the radial clearance is determined according to the standard at the time of manufacture and cannot be adjusted. After such bearings are mounted on the shaft diameter or in the bearing housing bore, the actual radial clearance is called Assemble the radial clearance, and make the radial clearance of the assembly just enough to cause the necessary working radial clearance during operation to ensure the flexible rotation of the bearing. When such a bearing is in operation, the shaft is relatively displaced due to the temperature rise when the temperature rises, so that the radial clearance of the bearing is reduced, and even the rolling elements are caught between the inner and outer races. This can be avoided by leaving an axial gap between one of the double-bearing rolling bearings (the other bearing is fixed on the shaft and in the housing) and the side cover.

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