There are three main types of bearings commonly used in motors: rolling bearings, sliding bearings and oil bearing, which support the rotating parts of motors to rotate. Oily bearings are commonly used in micro or small motors, with fewer accessories and maintenance-free, which is conducive to simplifying the structure. Sliding bearings are mainly used in medium and large motors and are suitable for heavy load and impact-resistant occasions. Rolling bearings are the most widely used. The following topics discussed by Ms. refer mainly to this type of bearings.


How to Identify Bearings


Rolling bearing codes are composed of prefix codes, basic codes and suffix codes. The prefix codes are expressed by letters, meaning a complete set of bearing components; the basic codes represent the main characteristics of bearing types and sizes; and the suffix codes represent the characteristics of bearing accuracy and materials.


Bearing Postposition Code and Its Meaning


Examples of common internal structure code meanings


B-angular contact ball bearing with contact angle of 40 degrees


C-angular contact ball bearing with contact angle of 15 degrees


AC-Angular Contact Ball Bearing with 25 Degree Contact Angle


E-Strengthened Design


Examples of codes and meanings of sealdust proof and external shape change


Code Meaning Code Meaning


N Outer Ring Bearing with Stop Groove (2) RZ Non-contact Sealed Bearing


NR Outer Ring Bearing with Stop Groove and Stop Ring Bearing (2) Z Dust Cap Sealed Bearing


(2) RS contact seal bearing (2) LS contact seal bearing (inner ring without teeth)


Number of cage structure and material


Code Meaning Code Meaning


F steel solid cage, with figures indicating different materials J steel sheet stamping cage


Q bronze solid cage, with figures indicating different materials V full rollers


M brass solid cage E phosphating treatment cage


T-phenolic laminated pipe solid cage D carbonitriding cage


TN engineering plastic injection cage


Tolerance grade code


P 0-Dimensional Accuracy of P0 Level


P6 - Dimensional accuracy P6


P5 - Dimensional Accuracy P5


P4 - Dimensional Accuracy P4


P2-Dimension Accuracy Level P2


The accuracy of rolling bearings is improved in turn from grade 0.


Clearance code


Code Meaning


/ C1 radial clearance is a group


/ C2 radial clearance is two groups


—— Radial clearance is 0 group, that is, normal group clearance.


/ C3 radial clearance is three groups


/ Radial clearance of C4 is 4 groups


/ C5 radial clearance is 5 groups


/ Special Clearance for CM Motor Bearing


Vibration Level Code ____________


Z - the extreme value group of vibration acceleration level of bearing, from low to high, is: Z1, Z2, Z3, Z4.


V-bearing vibration speed level extreme group, in turn from low to high: V1, V2, V3, V4


Configuration code


Code Meaning


DB back-to-back installation, example: 7210C/DB


DF is installed face to face, for example: 32205/DF


DT installation in series in pairs, example: 7210C/DT


Bearing Seal Structure


2Z - bearing with dust cover is used for bearing configuration which is not polluted seriously and has no danger of contact bearing such as moisture and steam. Dust cover is also used in applications where friction reduction is important due to speed or operating temperature considerations.


2RZ - Bearings with non-contact seals are often used for less serious pollution, similar to dust caps, which have a slightly better sealing effect than dust caps.


2RS - Bearings with contact seals (hereinafter referred to as seals) are often used in bearing configurations with medium pollution, water or water splashing, which are unavoidable or require long service life without maintenance.


About Bearing Clearance of Motor


The radial (axial) clearance of a bearing is the radial (axial) distance from one radial (axial) limit position to the opposite limit position when one ring is relative to the other without external load. In reality, because of the shape error of the ring and the inconsistency of the rolling element, it should adopt the average radial (axial) displacement of the ring in different directions and different relative positions of the ring and the rolling element.


Clearance is an important technical parameter of bearings, which directly affects the load distribution, vibration, noise, friction, temperature rise, service life and mechanical operation accuracy of bearings.


A) The excessive clearance will cause the bearing internal bearing area to decrease and the contact surface stress to increase, thus shortening the service life. Excessive clearance will also reduce the accuracy of bearing operation and increase vibration and noise.


B) If the clearance is too small, the negative clearance (interference) may occur in the actual operation, which will cause the increase of friction heating and temperature rise, and then make the effective clearance smaller or the interference larger. Such a vicious cycle will lead to the bearing locking.