Single row four point contact ball bearing (also known as QJ/QJF series four point contact ball bearing) is a type of separated single row angular contact ball bearing. Its core feature is that the steel ball and the inner and outer raceway are in four point contact when there is no load, which can withstand radial load and bidirectional axial load. A single bearing can replace two single row angular contact ball bearings combined face-to-face (DF) or back-to-back (DB), achieving bidirectional axial load while significantly reducing the axial space occupied. Therefore, its application scope is very extensive, covering multiple high-end and general industrial fields from aerospace to warehousing and logistics.
1. Aerospace and Defense Industries (the most core traditional applications)
This is the most classic and technically demanding application field for four point contact ball bearings.
.Aircraft jet engine: used for supporting the main shaft of the engine, bearing the huge bidirectional axial thrust and radial load under high-speed rotation.
. The contact angle is usually 35 °, with high ultimate speed and strong axial rigidity, and can work stably in high-temperature and high-speed environments.Gas turbine: Similar to jet engines, it can withstand composite loads of high temperature, high speed, and large axial forces.
.Aircraft flight control system and landing gear: utilizing their high axial positioning accuracy and bi-directional limit capability to ensure precise response of the control surface.
. In terms of working temperature, models with brass retainers are suitable for temperatures ranging from -30 ℃ to+150 ℃, and for sizes with an outer diameter exceeding 240mm, the stable temperature can reach+200 ℃, fully meeting the harsh environment of aviation engines.II. Industrial Robots and Precision Equipment (the fastest growing field in recent years)
Four point contact ball bearings have become one of the core components of industrial robot joints due to their three advantages of "compactness+bidirectional load-bearing+high speed".
.Robot joint (rotary actuator): A single set of bearings can simultaneously withstand radial force, bidirectional axial force, and overturning moment, replacing complex combination bearings and simplifying the overall design.
. Million cycles of motion without failure, positioning accuracy can be maintained at ± 0.1mm.CNC machine spindle: used as an auxiliary or main support for machining centers and grinding machine spindles, bearing composite loads during cutting, with anti overturning ability to avoid spindle tilting, and tolerance fluctuations of machined parts can be reduced to ± 0.001mm.
High end humanoid robot linear joints: such as Tesla Optimus and other new generation humanoid robots have clearly adopted four point contact ball bearings in their linear actuators, combined with frameless motors, torque sensors, and harmonic reducers to form a complete rotary actuator.
.The accuracy can reach P2/P4 level, the radial runout is extremely small, the friction coefficient is about 40% lower than ordinary solutions, the maximum speed is more than 30% higher than similar bearings, and the high-speed operation noise can be less than 60dB.
Thirdly, wind power generation (large-scale batch application)
In the field of wind power, four point contact ball bearings are important core components of yaw bearings and pitch bearings.
.Yaw system: supports the rotation of the wind turbine nacelle around the tower, bearing the huge radial and bidirectional axial loads caused by wind loads.
.Variable pitch system: controls the change of blade angle and bears the composite load of blade gravity and aerodynamic force.
. Compared to cross roller bearings, four point contact ball bearings have smaller volume, lighter weight, and lower friction under the same load, making them more suitable for the lightweight and reliability requirements of large offshore wind turbines.It should be noted that for low-speed and heavy-duty yaw slewing support conditions, four point contact ball bearings are not the best choice, and the selection should be based on the specific speed and load spectrum.
.4. Transportation (automobiles and rail transit)
Automobile gearbox: used for planetary gear carriers and other parts, to withstand the bidirectional axial force generated by gear meshing. A single bearing replaces the combination of two angular contact ball bearings, saving internal space of the gearbox.
.Automotive steering gear: withstands bidirectional axial loads during steering.
. Automotive wheels: Some high-performance vehicle models use four point contact ball bearings in their wheel hub bearing units to improve axial rigidity and driving stability.Locomotive drive system and railway vehicles: used for traction motor spindles, gearboxes, and other parts to withstand composite loads under high-speed operation.
. The design with a contact angle of 35 ° results in small axial clearance and high axial positioning accuracy, making it very suitable for transmission systems that require precise axial limiting.Fifth, AGV and Intelligent Logistics (Emerging Popular Applications)
This is a rapidly growing niche market in the past two years, and the four point contact ball turntable bearing (a rotary derivative product of the four point contact ball bearing) has become a key component of AGV.
.AGV steering system: connects the chassis of the vehicle to the steering wheel mounting seat, withstands the lateral load and overturning moment caused by driving bumps, turns, and start stop, and cooperates with the steering motor to achieve stationary turning and small radius turning.
.Top lifting rotating cargo platform: installed between the chassis and the top lifting table, realizing 360 ° rotation of the table, with an ultra-thin and compact structure, and does not occupy the internal space of the AGV.
.Vehicle body rotation and floating support: used for local rotation support and floating hinge of walking wheel set for multi-directional AGV and heavy-duty AGV, balancing ground impact.
. The advantage lies in: resistance to impact and fatigue under frequent start stop and repeated reversing conditions; Under low-speed rotation conditions, the performance is superior to that of roller bearings; Single set bearings replace radial and axial combination bearings, with small thickness and light weight, meeting the needs of AGV lightweighting and miniaturization. The four point contact of steel balls reduces the friction coefficient and starting torque, effectively reducing motor power consumption and extending the battery life of lithium batteries.