Brief introduction of bearing knowledge

The following is the most comprehensive bearing introduction manual, which can be used as necessary information for bearing knowledge training:

1. Composition of Bearing

Bearings are generally composed of inner ring, outer ring, roller and cage. For sealed bearings, it also includes lubricant and sealing ring (or dust cover).

2. the classification of bearings

According to the direction of bearing load:

Radial bearings: can bear loads perpendicular to the shaft, some can only bear pure radial loads, and most can also bear axial loads in a certain direction.

Thrust bearing: it mainly bears the load along the axial direction. According to the design, it can support unidirectional or bidirectional pure axial load, and some can bear additional radial load.

According to the types of rolling elements:

Ball bearing: The rolling body is a ball, which has the advantages of low friction coefficient, high limit speed and insensitivity to installation error and deflection, but its bearing capacity is relatively low, its rigidity is poor, its impact resistance is weak, and it is easy to produce noise at high speed.

Roller bearing: The rolling body is a roller, which has large bearing capacity, strong impact resistance and good rigidity, but it has large friction coefficient and low limit speed, and is sensitive to installation error and deflection.

According to the number of rows of rolling bodies:

Single row bearing: there is only one row of rolling elements, such as single row deep groove ball bearing and single row cylindrical roller bearing.

Double row bearing: there are two rows of rolling elements, such as double row self-aligning ball bearing and double row tapered roller bearing.

Multi-row bearing: there are three or more rows of rolling elements, such as three rows of cylindrical roller bearings.

According to the self-aligning performance of bearings:

Self-aligning bearing: the raceway of the outer ring is spherical and can be self-aligning, such as self-aligning ball bearing and self-aligning roller bearing.

Non-self-aligning bearings: The raceway of the outer ring is cylindrical or conical, which can not be self-aligning, such as deep groove ball bearings and angular contact ball bearings.

3. the bearing model representation method

Bearing model is generally composed of pre-code, basic code and post-code, and usually only the basic model is used to represent it.

Basic code name:

Bearing inner diameter: indicated by the first digit from the right of the basic code. Generally, the inner diameter of a bearing with an inner diameter of D = 20 ~ 480 mm is a multiple of 5, and these two digits represent the quotient of the inner diameter of the bearing divided by 5, for example, 04 represents D = 20 mm; 12 means d=60mm, etc. For bearings with inner diameters of 10mm, 12mm, 15mm and 17mm, the inner diameter codes are 00, 01, 02 and 03 in turn. Bearing with inner diameter less than 10mm and greater than 500mm, the expression method of inner diameter is otherwise specified.

Diameter series of bearings: that is, the series of changes in outer diameter and width of bearings with the same structure and inner diameter, which is represented by the third digit from the right of the basic code. For example, for centripetal bearings and centripetal thrust bearings, 0 and 1 represent extra-light series; 2 stands for light series; 3 indicates medium series; 4 means heavy series. The thrust bearing is consistent with the radial bearing except that the ultra-light series is indicated by 1.

Bearing width series: that is, bearing width variation series with the same structure, inner diameter and diameter series, which is represented by the fourth digit from the right of the basic code. When the width series is 0 series (normal series), the width series code 0 may not be marked for most bearings, but it should be marked for self-aligning roller bearings and tapered roller bearings. Diameter series code and width series code are collectively called size series code.

Bearing type: it is indicated by the fifth digit from the right of the basic code (for cylindrical roller bearings and needle roller bearings, the code is a letter).

Post code: letters and numbers are used to indicate the structure, tolerance and special requirements of materials of bearings. If the internal structure code indicates different internal structures of the same type of bearing, it is indicated by letters followed by the basic code; The tolerance grades of bearings are divided into 2, 4, 5, 6, 6X and 0, with a total of 6 grades, from high to low, and their codes are/p2,/P4,/P5,/P6,/／P6X and/po respectively. Among the tolerance grades, 6X is only applicable to tapered roller bearings. Grade 0 is the ordinary grade, which is not marked in the bearing code; Commonly used bearing radial clearance series are divided into 6 groups, including 1 group, 2 group, 0 group, 3 group, 4 group and 5 group. The radial clearance is from small to large in turn. The O group is a commonly used clearance group, which is not marked in the bearing code. The rest clearance groups are represented by/C1,/C2,/C3,/C4 and/C5 in the bearing code respectively.

Pre-code: used to indicate the components of the bearing, expressed by letters. For example, l denotes a separable ring of a separable bearing; K denotes the roller and cage assembly of the bearing, etc.

4. the bearing selection method

The following factors should be considered when selecting bearings:

Load: including the size, direction and nature of radial load and axial load. If you bear pure radial load, you can choose deep groove ball bearings and cylindrical roller bearings. To bear pure axial load, thrust ball bearing and thrust roller bearing can be selected. Angular contact ball bearings and tapered roller bearings can be selected to bear combined radial and axial loads.

Speed: Different types of bearings have different limit speeds. Generally, the limit speed of ball bearings is higher than that of roller bearings. When rotating at high speed, bearings with low friction coefficient and high limit speed should be preferred, such as deep groove ball bearings and angular contact ball bearings.

Accuracy: Select the bearing with corresponding accuracy grade according to the accuracy requirements of machinery. The accuracy grades of bearings are classified into P0, P6, P5, P4, P2, etc. P0 is the ordinary grade and P2 is the highest grade.

Installation space: select the appropriate bearing type and size according to the size limitation of bearing installation position. If space is limited, you can choose a smaller bearing or choose a detachable bearing for easy installation.

Self-aligning performance: When important official's alignment is poor or skewed, bearings with self-aligning performance should be selected, such as self-aligning ball bearings and self-aligning roller bearings.

Stiffness: For parts with high rigidity requirements, bearings with large bearing capacity and good rigidity should be selected, such as cylindrical roller bearings and tapered roller bearings.

Lubrication and sealing: Select the appropriate bearing according to the working environment and lubrication conditions. In dusty, humid or corrosive gas environment, bearings with good sealing performance should be selected, and attention should be paid to the selection and addition of lubricants.

5. Installation of Bearing

Preparation before installation:

Cleaning: clean the bearing and related parts to ensure that the surface is free of oil stains and impurities, so as not to affect the installation accuracy and service life.

Check clearance: according to the bearing type and specification, check whether the bearing clearance meets the requirements to avoid excessive noise and vibration after installation.

Preparation tools: according to the bearing type and specifications, prepare appropriate installation tools, such as hammers, sleeves, presses, etc.

Installation method:

Mounting on the shaft: For bearings with tight fit or interference fit, hot mounting or cold mounting can be adopted. When hot-fitting, the bearing is heated to 80-100℃ and then quickly sleeved on the shaft; During cold installation, the bearing can be cooled with liquid nitrogen and other coolants, and then the bearing can be lightly tapped on the shaft.

Installation in the bearing seat: clean the bearing seat and apply grease on the mating surface, then gently push the bearing into the bearing seat to ensure that the bearing and the bearing seat are closely matched.

Adjustment of clearance: During installation, the clearance of bearing should be adjusted as required to ensure the normal operation of bearing.

6. bearing maintenance

Regular inspection: check the bearings regularly, including appearance, vibration and noise, so as to find potential problems in time.

Cleaning and lubrication: clean bearings regularly and replace grease or lubricating oil to ensure good lubrication of bearings.

Fastening and adjustment: check and fasten the connection of bearings and related components.