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What are the technical requirements for radial deep groove ball bearings

wallpapers Tech 2020-11-20
The rolling bearing has a simple structure, a high degree of standardization, a wide variety and a wide range of applications. In micromotors, due to the limitation of structural size, basically, only single-row radial deep groove ball bearings are used. The nominal size of the bearing (NominalSize) is the inner diameter. When the inner diameter is the same, the outer diameter and width can be different. Groups of different proportions of outer diameter and width are called diameter series and width series, and diameter series and width series are collectively called size series. The micro-motor bearing structure with a double-sided dust cover or double-sided sealing ring can also use single-sided dust cover, single-sided sealing ring, or unprotected bearing when sealing is allowed.
Bearing accuracy
Bearings are divided into five levels according to basic dimensional accuracy and rotation accuracy: G, E, D, C, and B. Class B has the highest accuracy, and Class G is the lowest. The basic dimensional accuracy refers to the machining of dimensions such as inner diameter d, outer diameter D, and width B. Accuracy, rotation accuracy refers to the radial runout of the inner ring and the outer ring, the end face of the inner ring, the perpendicularity of the outer ring surface to the reference plane, and the equality of the inner and outer ring end faces.
 
One-way minimum chamfer rated dynamic load rated static load rated load is the reference value of the load when the working clearance (Play) of the bearing with G-class accuracy is zero, the limit speed is the bearing equivalent dynamic load Pr<0.1C, normal lubrication and cooling, The reference value when only subjected to radial load, the selection of the bearing should be based on the supplier's product.
Bearing clearance
Bearing clearance is divided into radial play (Radial Play) and axial play (Axial Play), which respectively indicate that when one ring (outer ring or inner ring) is fixed, the other ring is moved radially or axially. The amount of movement from one extreme position to another extreme position, the radial clearance is divided into original play (OriginalPlay), assembly play (FittingPlay) and working play (RunningPlay). Radial clearance refers to the original clearance before the bearing is installed. After assembly, the radial clearance is reduced due to interference fit, which is the assembly clearance; while the bearing is affected by temperature and load during normal operation, the radial clearance The clearance will change further, and the radial clearance at this time is the working clearance (RunningPlay). The rated dynamic load of the bearing will vary with the size of the working clearance, and the working clearance that maximizes the bearing life is a negative value slightly smaller than zero. Reasonable clearance selection should be based on the original clearance, considering the clearance changes caused by the fit, the temperature difference between the inner and outer rings during operation, and the size of the load, so that the working clearance is close to the best-installed state.
 
The temperature of each component of the bearing is different during operation. In a stable temperature state, the inner ring has a higher temperature than the outer ring, and the expansion is larger so that the radial clearance is reduced, and the radial clearance is reduced by u Estimate.
 
u = t×α×(d+D)/2
 
Where: the t temperature difference between inner and outer rings; α coefficient of linear expansion of inner and outer ring materials, usually bearing steel α 0.000011.
 
Under normal conditions, t is about 5°C~10°C. When the working temperature is high, especially the armature coil temperature is high, and the heat dissipation conditions are not good, t will exceed 10°C.
 
The radial clearance (original clearance) of standard bearings of the same model and size is divided into basic group and auxiliary group according to their size, see the table below. Under normal working conditions, the basic group should be selected first. When the temperature is high or the interference is large, when the friction needs to be reduced, the self-aligning performance is improved, and the large axial load is to be carried, the larger travel is better. Clearance auxiliary group; when the operation accuracy is high or the axial displacement of the armature needs to be strictly limited, the smaller clearance auxiliary group should be used.

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