What Are Our Concerns About Bearings（27）

Q1:Types of bearings and various kinds of applications

• A:There are many kinds of bearings.  According to the direction of the load it can bear, it can be divided into: ① Radial bearing, also known as centripetal bearing, bearing radial load.  ② Thrust bearing, also known as thrust bearing, bears axial load.  Radial thrust bearing, also known as centripetal thrust bearing, bears radial load and axial load at the same time.  According to the different friction properties of bearings, they can be divided into sliding friction bearings (referred to as sliding bearings) and rolling friction bearings (referred to as rolling bearings).  
• Angular contact bearing: rolling bearing in which the nominal contact Angle between the ball and the ring is greater than 0° and less than 90°.  Can bear radial load and axial load at the same time.  Can work at high speed.  The larger the contact Angle, the higher the axial bearing capacity.  High precision and high speed bearings usually take 15 degrees of contact Angle.  Under axial force, the contact Angle will increase.  Single row angular contact ball bearings can only bear axial load in one direction. When bearing radial load, additional axial force will be caused.  And only limit the axial displacement of the shaft or housing in one direction.  If it is installed in pairs, the outer ring of a pair of bearings is relative, that is, the wide end faces the wide end face, and the narrow end faces the narrow end face.  This avoids additional axial force and limits the shaft or housing to axial clearance in both directions.  
• Outer spherical bearing: a centripetal rolling bearing having an outer sphere and a wide inner ring with a locking element.  Mainly used for simple enclosures.  
• Inear bearing: a rolling bearing in which two raceways have relative linear motion in the rolling direction.  
• Ball bearing: The rolling body is the rolling bearing of the ball.  
• Deep groove ball bearing: each ring has a continuous groove raceway radial ball bearing with a cross section of about one-third of the circumference of the ball, suitable for precision instruments, low noise motors, cars, motorcycles and general machinery, etc, is widely used in the machinery industry.  Simple structure, easy to use and maintenance.  It is mainly used to bear radial load and also can bear certain axial load. When the radial clearance of the bearing increases, it has the performance of angular contact ball bearing and can bear larger axial load.  This kind of bearing has small friction coefficient, high limit speed and various sizes and forms.  Solid and durable, universal and low noise operation, can operate at high speed and easy to install.  Single row deep groove ball bearings have sealed design, no need for lubrication and maintenance.  Single row with ball notch and double row ball bearings, suitable for heavy duty conditions.  
• Thrust ball bearing: The rolling body is the thrust rolling bearing of the ball.  
• Roller bearing: A roller is a rolling bearing of rollers.  
• Cylindrical roller bearing: rolling body is cylindrical roller centripetal rolling bearing, a separation bearing, installation and disassembly is very convenient.  Cylindrical roller bearings are divided into single row, double row and four row.  
  Cylindrical roller bearings can be divided into single row, double row and multiple row cylindrical roller bearings according to the different number of rows of rolling body installed in bearings.  One of the most widely used is the single row cylindrical roller bearing with cage.  In addition, there are single row or double row full roller and other structures of cylindrical roller bearings.  
• Single row cylindrical roller bearings are divided into N type, NU type, NJ type, NF type and NUP type according to the different flange of the ring.  Cylindrical roller bearings bear a large radial load capacity, according to the structure of the ring flange can also bear a certain unidirectional or bidirectional axial load.  
  NN and NNU double row cylindrical roller bearings have compact structure, strong rigidity, large bearing capacity and small deformation after loading. They are mostly used for supporting machine tool spindles.  
  Type FC, FCD, FCDP four row cylindrical roller bearings can withstand a large radial load, mainly used in heavy machinery such as rolling mills.  
• Cylindrical roller bearings are mainly used in motor, machine tool, petroleum, rolling mill handling machinery and all kinds of industrial machinery.  
• Tapered roller bearing: the rolling body is a centripetal rolling bearing of tapered roller.  
• Needle roller bearing: The rolling body is a centripetal rolling bearing of needle roller.  
• Spherical roller bearing: The rolling body is a self-aligning centripetal rolling bearing with convex spherical or concave rollers.  A bearing with convex spherical rollers having a spherical raceway on the outer ring;  A bearing with concave rollers having a spherical raceway in the inner ring.  
• Thrust roller bearing: The roller is the thrust roller bearing of the roller.  
  Thrust cylindrical roller bearing: The roller is the thrust roller bearing of cylindrical roller.  
  Thrust tapered roller bearing: The rolling body is the thrust rolling bearing of tapered roller.  
  Thrust needle roller bearing: The rolling body is a thrust rolling bearing for needle rolling.  
  Thrust spherical roller bearing: the rolling body is a self-aligning thrust roller bearing with convex spherical or concave rollers.  The raceway of the bearing seat ring with convex spherical roller is spherical, and the raceway of the bearing shaft ring with concave spherical roller is spherical.  
• Seat bearing: An assembly of a centripetal bearing and seat with a base plate for mounting screws on a supporting surface parallel to the bearing axis line.  
• Joint bearing: spherical sliding contact surface, mainly suitable for swing motion, tilt motion and rotary motion spherical sliding bearing.  
• Combined bearing: a rolling bearing in a set of bearings combined by two or more of the above bearing structures at the same time.  Such as needle roller and thrust cylindrical roller combined bearings, needle roller and thrust ball combined bearings, needle roller and angular contact ball combined bearings, etc.  
  Plain bearing: plain bearing has no inner and outer rings and no rolling body. It is generally made of wear-resistant materials.  It is usually used for low speed, heavy load, lubricating oil filling and mechanical rotating parts which are difficult to maintain.  z
• Rolling mill bearings, rolling mill bearings generally only used to bear radial load, compared with the same size deep groove ball bearings, have bigger radial load capacity, limit rotational speed is close to deep groove ball bearings, but with this type of bearing shaft, shell hole processing the demand is higher, allow the axis of the inner ring and outer ring axis inclination is small (2 ° – 4 °), two axis tilted as beyond the limit,  The contact between the roller and the raceway will deteriorate, seriously affecting the bearing load capacity and reducing the service life of the bearing.  Therefore, if such bearings need to be installed in the host parts bearing axial load, they can only be used under the premise of using other types of bearings to bear axial load at the same time.  

Q2:What is the preload of rolling bearings?  Why do rolling bearings need to be preloaded?  

A:The so-called preload is to generate and maintain an axial force in the bearing in some way during installation, so as to eliminate the axial clearance in the bearing, and produce initial deformation at the contact between the rolling body and the inner and outer rings.  Through preloading can improve the bearing rotation accuracy, increase the rigidity of the bearing device, reduce the vibration of the shaft when the machine is working, often using preloading rolling bearings.  

Q3:What is the equivalent dynamic load of bearings?

A:If a rolling bearing bears combined radial and axial loads at the same time, in order to compare the bearing life under the same conditions, the actual load must be converted into the equivalent dynamic load which is consistent with the load conditions of the basic rated dynamic load, expressed by P. 

Q4:In the calculation formula of rolling bearing life, why is the ε value of ball bearing lower than that of roller bearing?  

A:Because roller bearings are theoretically linear contact, while ball bearings are point contact, the former has higher bearing capacity, so the ε value is larger, and the bearing life is higher. 

Q5:Why do rolling bearings need lubrication? What are the common lubrication methods?

A：Lubrication is of great significance to rolling bearings. Lubricants in bearings can not only reduce friction negative force, but also play a role in heat dissipation, reduce contact stress, absorb vibration, prevent corrosion and so on.  There are two common lubrication methods for bearings: oil lubrication and grease lubrication.  In addition, there are also the use of solid lubricant lubrication.  

Q6:When rolling bearings are lubricated by oil, what are the commonly used lubrication methods?

A:Oil bath lubrication, drop lubrication, splash lubrication, spray lubrication, oil mist lubrication, etc.