Application of four point contact ball bearing

The four-point contact ball bearing is a radial single row angular contact ball. Slewing bearings have raceways designed to handle two-way axial loads. These bearings require minimal space and can withstand both pure axial loads and combined loads. These bearings are used in a variety of industries to provide greater precision and safety. This paper also analyzes the ball motion and sliding friction in the bearing, which can understand the bearing more concisely.

You will know:

• What is four point contact ball bearing

• four point contact ball bearing application

• ball motion and sliding friction in a four-contact-point ball bearing

Definition

Four point contact ball slewing bearing is a separate type of bearing. It can also be said that it is an angular contact ball bearing that can bear biaxial axial load. The inner and outer ring raceways are peach-shaped cross-sections. When there is no load or pure radial load, the steel ball and the ferrule appear as four-point contact, which is the origin of this name.

Application

• Aerial platform vehicles

Aerial work platform vehicles typically employ such a slewing ring and are compact. This type of slewing bearing is also subjected to axial force, radial force and tilting moment, and is widely used in small and medium-sized construction machinery.

• Truck crane

Truck cranes are usually using large single row four-point contact ball slewing bearing. This type of slewing bearing can bear larger axial load, radial load and tilting moment, enabling crane to lift heavy loads stably and reliably.

• Excavator

Excavator is usually using internal quenched gear single row four-point contact ball slewing bearing. This type of slewing bearing can bear axial load, radial load and tilting moment and can withstand large impact. Rotation is flexible and stable.

Ball motion and sliding friction in a four-contact-point ball bearing

When the bearing is operated with three or four contact points, the slippage and dissipation due to the increased friction within the elliptical contact increases, thereby offsetting the benefits of load sharing. This is why the concept of double arches should be carefully considered when working at high speeds. Compared with conventional ball bearings with two contact points, the load is significantly reduced, and the load of the light load ball can reach 40% or 60% in the region where the radial load is opposite. The advantage of the sphere located near the radial direction is not obvious, but it can still reach 20-40% under low thrust load.

For internal kinematics, the result and the coefficient of friction are not linear because it affects the load distribution. Compared with the traditional bearing design, the power loss caused by friction is significantly increased. However, under high thrust load, the friction loss is not obvious. It should be noted that the contribution of other dissipative sources is not considered here. At high speed power losses, oil agitation is typically significant and may mask the contribution of friction to the energy consumed at the fairway interface. The last factor that should be carefully considered at high speeds is the PV factor, which corresponds to the maximum of the product of the contact pressure and the sliding speed of the points at the contact ellipse. This PV factor is usually associated with the risk of sprains.

An analysis was performed on a double arch ball bearing that takes into account centrifugal force and gyroscopic effects. Based on the operating conditions of the five-degree-of-freedom inner ring and the Coulomb friction model, conventional bearing theory extends from two to three or four contact points. Common control standards for ball bearings for internal or external raceways are controversial and are known to be difficult to match with experimental data. In addition, when more than two contact points are involved, it becomes obsolete. A mathematical model was proposed to describe the internal kinematics of complex ball bearings under the influence of external working conditions. The lubricant thickness is considered in the geometric equation and the nonlinear system of the quasi-static model is solved by the Newton-Raphson method. It is first verified by comparison with published data from conventional or single arch ball bearings. The results were also compared to the results provided by the commercial software RBL4. Finally, the analysis of the double arch ball bearing was carried out, highlighting the complex motion of the ball.

Under normal working conditions, when the bearing is subjected to axial load in any direction, a contact angle can be formed, and the steel ball is in contact with the inner and outer races to avoid large sliding friction in the contact area. It is ideal for withstand momentary high pressure. The bearing achieves four point contact between the raceway and the steel ball. It can withstand instantaneous load and rotary axial load. Although it can also be used under light load conditions, it can withstand simple Radial load is not a substitute for radial contact ball bearings or angular contact ball bearings.