four point contact bearing design details and force methods

four point contact bearing design details and force methods
The standard four point contact bearing (also known as QJ series bearings) consists of an integral outer ring, a radially split inner ring, a ball group, and an outer ring guided cage.
The design details of the four point contact bearing collar are shown in the following figure. The outer ring is designed similar to a deep groove ball bearing, but the raceway geometry and cross-section are slightly different. The raceway of the deep groove ball bearing is circular, while the outer ring of the four point contact bearing is composed of two symmetrical raceways. Each raceway is a circular ring shape, intersecting at a point in the middle of the outer ring raceway of the bearing. The centers of the two raceway arcs have a small offset in the axial direction. The inner ring is divided into two halves, and the design principle is basically the same as the outer ring.

A bearing with a 35 degree contact angle requires a high raceway shoulder. The number of rolling elements that can be assembled in the overall inner ring bearing is relatively small, so the four point contact bearing adopts a double half inner ring design, which can accommodate the maximum number of rolling elements. The number of rolling elements is only limited by the width of the cage beam.
In theory, a ball has four different contact points with the bearing ring. This only occurs when pure radial loads are applied, but this load situation may not necessarily occur in real applications.
The most meaningful case of four point contact bearing is for pure axial load applications, in which only two contact points located diagonally transmit the load. If the axial load changes direction, these two contact points will move to opposite positions. This explains why this type of bearing can withstand axial loads in two directions.

There are also some applications that have both radial and axial loads but mainly axial loads. If single row angular contact ball bearings are required to achieve the same function, two identical bearings are required in a back-to-back or face-to-face configuration. This means that it can be achieved with a four point contact bearing, which is a space saving layout design.

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