Classification and characteristics of angular contact ball bearings

- May 12, 2020-

Angular contact ball bearings have a higher limit speed and can also bear radial and axial loads at the same time.

Angular contact ball bearings are divided into:

Angular contact ball bearings

Single row angular contact ball bearings

a) Single-row angular contact ball bearings mainly include 718, 719, 70, 72, 73, and other series. The outer diameter and thickness of the bearings with the same inner diameter and different series are increased in accordance with the above order. Examples 71900 and 71800 have the same inner diameter, but the outer diameter and thickness are larger than the latter.

b) Angular contact ball bearings can withstand (unidirectional) axial and radial forces simultaneously. The contact angle is generally 15 ° (suffix C), 25 ° (suffix AC), 30 ° (suffix A) and 40 ° (suffix B). The smaller the angle, the smaller the axial load, and the faster the speed. , The greater the axial load, the slower the speed.

Double row angular contact ball bearings

Double-row angular contact ball bearings are double-row angular contact ball bearings but occupy a smaller axial space (thickness is slightly narrower than two single-row angular contact ball bearings), which can limit the axial displacement of the shaft or housing in both directions. 30 °. It can provide high rigidity bearing configuration and can withstand an overturning moment. Widely used in the front wheel hub of cars.

Four-point angular contact ball bearings

The separate bearing can bear radial load and bidirectional axial load. The thickness of the bearing of the same size is less than double row angular contact ball bearing. Mostly used for roll positioning of rolling mills. There are two types of the double half outer ring (QJF type) and double half inner ring (QJ type).

Thrust angular contact ball bearings

Bidirectional thrust angular contact ball bearings are used in conjunction with double row cylindrical roller bearings to withstand bidirectional axial loads. Divided into 2344 and 2347 series, the 2344 series is used to match the small end of the double row cylindrical roller bearing tapered hole, while 2347 is matched with the large end.

Ball screw bearing

The ball screw support bearing is a one-way thrust angular contact ball bearing with a contact angle of 60 °, which is especially suitable for the support of high-speed precision CNC machine tools. Common are 7602 (standard metric), 7603 (standard metric), BS (non-standard metric) and BSS (non-standard inch) series.

2 angular contact ball bearing selection

The selection of angular contact ball bearings should consider the working conditions and limited space. The working conditions mainly include the use environment, accuracy, rotation speed, force direction and magnitude.

Non-metal cages are generally used for high-speed and small loads; metal cages are used for low-speed and heavy loads; metal cages are used in high-temperature environments; engineering plastic cages are generally used in medium-temperature environments, and the temperature of nylon cages cannot exceed 120 degrees;

For ultra-high-speed, wear-resistant, low-temperature rise, long life, and high availability environments, hybrid ceramic ball bearings can be used, and the balls are made of silicon nitride ceramics.

If the precision of the shaft is high, for example, the spindle of the machine tool generally uses P4 or P2 bearings; the medium precision generally selects the P5 or P4 level; the general precision can select the more economical P0 or P6 level.

If high speed is required, first choose a light series bearing with a contact angle of 15 ° and a relatively high limit speed; if it is required to withstand a large axial load, choose a 2 or 3 series angular contact ball bearing with a contact angle of 40 °; if necessary Considering both speed and axial load, angular contact ball bearings with a contact angle of 25 ° can be selected.

3 Angular contact ball bearing preload and assembly

Angular contact ball bearing preload can determine the axial and radial position of the bearing, at the same time suppress the shaft runout, improve the rigidity of the bearing, prevent axial vibration, and abnormal noise or noise caused by vibration (ZYS bearings control in this regard very good).

Pre-tightening is divided into positioning pre-tightening and constant pressure pre-tightening:

1. Pre-positioning

Positioning preloading is to add preloading force along the direction of force application so that the gap is zero.

2. Constant pressure preload

The constant pressure preload is to apply a constant preload force to the bearing through the spring.

Positioning preload is suitable for improving bearing stiffness, while constant pressure preload is suitable for high-speed rotation or when it is necessary to prevent axial vibration of the shaft system.

Preload suffix: A is light preload; B is medium preload; C is heavy preload

Single-row angular contact ball bearings cannot be used alone under the condition of bearing both radial force and bidirectional axial force. Two or more single-row angular contact ball bearings are often used in combination.

Commonly used assembly methods are as follows:

There are only three kinds of DB: DB (back-to-back), DF (face-to-face), DT (tandem)

The three bearing assembly methods are TBT type, TFT type, and TT type.

The TBT type is a pair of DB type, the TFT type is a pair of DF type, and the DT type is a pair of DF type, which is a pair of DT type.

The combination of four bearings and five bearings will be explained in the paper materials.

4 angular contact ball bearing cleaning and installation

For bearings without grease, high-quality kerosene must be used for all-round cleaning. The specific method is to soak the bearings in kerosene for washing and rotating cleaning until there is no obvious resistance and vibration when rotating.

The cleaned bearings must be dried in a clean space, and then filled with grease. The amount of grease filling is generally 1/3 of the free space inside the bearing.

Angular contact ball bearings are precision bearings, and special attention must be paid to installation. At present, the commonly used installation method is to squeeze the installation. If the inner ring is tightly fitted with the shaft, use a sleeve similar to the inner ring to squeeze the inner ring. The sleeve squeezes the outer ring. If the inner and outer rings are tightly fitted with the shaft and the bearing chamber holes, you can choose a thick-walled sleeve to squeeze the inner and outer rings for installation at the same time.