Single row four point angular contact ball bearing (four point contact ball bearing) is a specially designed single row angular contact ball bearing. Its core characteristics are reflected in structure, load capacity, space occupation, speed performance, and installation and maintenance, as follows:
1. Structural features: Double half inner ring and four point contact design
Separated structure
The inner ring is composed of two independent half rings (shoulder rings), and the outer ring is an integral structure. This design allows the bearing to be installed by first installing the outer ring and cage components, and then installing two inner half rings separately, greatly improving installation flexibility.
Four point contact principle
The inner and outer raceway adopts a special groove shape (such as Gothic arc or angled elliptical arc), which theoretically forms four contact points between each steel ball and the inner and outer raceway.
. When subjected to axial load, the steel ball contacts the inner and outer raceway at two points, achieving bidirectional axial bearing; Under pure radial load, it exhibits a four point contact state (but in practical applications, axial load is predominant).2. Load Capacity: Bi directional Axial Load and Radial Supplement
Bi directional Axial Load
It can withstand axial loads in two directions simultaneously, without the need for back-to-back or face-to-face combination installation like single row angular contact ball bearings, simplifying the structure and saving space.
. Radial load supplementCan withstand a certain degree of radial load, but the design priority is axial load.
. It is usually recommended that the axial to radial load ratio (Fa/Fr) be greater than 1.27 to ensure stable operation.High load-bearing efficiency
The double half inner ring design allows for the installation of more steel balls, significantly improving the bearing's load-bearing capacity.
. For example, SKF QJ series four point contact ball bearings achieve a rated load similar to double row angular contact ball bearings by increasing the number of steel balls.III. Space occupancy: Compact design replaces double row bearings
Axial space optimization
Compared with double row angular contact ball bearings, the axial size of four point contact ball bearings is reduced by about 50%, making them suitable for applications with limited axial space (such as industrial gearboxes, compressors, wind power deviation systems, etc.).
. Lightweight design reduces material usage and overall weight while maintaining high rigidity, making it suitable for weight sensitive applications such as aviation engines and robot joints.Fourth, Speed Performance: High Limit Speed and Stable Operation
High Speed Adaptability
The contact angle is small (usually 35 °), reducing the centrifugal force during high-speed operation. Combined with high-quality retainers (such as brass or PEEK material) and outer ring guide design, the maximum speed ratio of double row angular contact ball bearings of the same specification is about 70% higher.
.Low friction and smoothness
The four point contact design disperses the load, avoids local stress concentration, and the contact points between the steel ball and the raceway are evenly distributed, reducing vibration and noise. The running smoothness is better than traditional deep groove ball bearings.
.Fifth, Installation and Maintenance: Balancing Flexibility and Professionalism
Installation Flexibility
The separated structure supports step-by-step installation, making it easy to operate in small spaces.
. The outer ring can be equipped with a positioning groove (such as the suffix N2 of FAG bearings), which is fixed to the bearing seat through a positioning pin to prevent rotation.During installation, it is necessary to ensure that the height of the shaft shoulder is adapted to avoid radial forces acting on the outer ring, and to reserve a radial gap (1-2mm) in the outer ring to compensate for thermal expansion.
.Maintenance points
Regularly check the lubrication status, and it is recommended to use thin oil lubrication (because the clearance between the cage and the inner and outer rings is small, the lubricating grease is not easy to enter the raceway).
. When disassembling, the puller can be fixed with a deep concave inner ring to avoid damaging the bearing.Monitor the operating temperature, and the working temperature of the bearings after heat treatment can reach 150 ℃ (some models even reach 200 ℃), but attention should be paid to the temperature limitations of the cage material (such as polyamide cages).
VI. Typical Application Scenarios
High axial load scenarios
Industrial gearboxes, screw compressors, turbine retarders, and other equipment that require bi-directional axial force.
. The wind turbine gearbox is combined with cylindrical roller bearings to bear axial and radial loads respectively.High speed rotation scenes
Fields with high requirements for speed and rigidity, such as aircraft engines, machine tool spindles, and robot joints.
. Replace double row bearings in traction motors and pump equipment to achieve a compact layout.Space limited environment
For applications with limited axial space such as automobile transmissions and railway traction motors, single bearings are used instead of double bearing combinations.
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