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Design methods of flexible bearings

time:2024-02-06   pv:3

Since the shaft that matches the flexible bearing is elliptical, and the inner ring is also elliptical after the bearing is installed, bearings designed using conventional methods are prone to falling apart due to elliptical deformation during assembly, and may become stuck during operation. In order to solve this problem, an extra large filling angle design method can be used, that is, increasing the filling angle to 263° to increase the number of filling steel balls. Flexible bearings are special thin-walled ball bearings. Part of the design can refer to the design method of thin-walled ball bearings, such as the selection and calculation of the main parameters steel ball diameter (Dw), groove curvature coefficient (fe, fi), groove diameter (D-d), and material selection. , heat treatment and turning, grinding processing technology, etc. However, due to its special use requirements, its main parameters such as the number of steel balls (z), ball group pitch circle diameter (D), rib diameter, ball filling angle, cage ball pocket diameter and shape, and clearance selection and calculation The formula needs to be changed accordingly.

1. Calculation of basic parameters

The flexible bearing model is 456109, the inner diameter is 45mm, the outer diameter is 61mm, the outer ring width is 9mm, the inner ring width is 6mm, the ball group pitch circle diameter is 53mm, the number of steel balls is 23, the steel ball diameter is 5.556mm, theoretically The fill angle is 263°.

2. Selection of materials and heat treatment

The ferrule and steel ball (G10) are made of high-carbon chromium bearing steel GCrl5; the cage material is PA66+25%GF; the heat treatment is vacuum heat treatment and freezing treatment. The hardness of the inner ring is 57~61HRC, and the hardness of the outer ring is 59-63HRC. The heat treatment hardness of the steel ball is 61-66HRC, and the structure is grade 2-4.

3. Assembly of flexible bearings

Conventional ball filling method:

The last steel ball filling method is traditionally to apply a radial force to the outer ring between 186-195° ball filling angle, causing it to elastically deform to fill the last ball. Although this method is very common, there are also steel ball filling methods. The ball is pinched and the ferrule undergoes plastic deformation.

Arc filling ball slot method:

When the ball filling angle is greater than 195°, an arc-shaped groove slightly larger than the diameter of the steel ball is opened from the inner and outer ring ribs to the groove bottom diameter. During assembly, the steel balls are filled into the groove one by one. , this method has low assembly efficiency, high production cost, and difficult to control quality. If the ball-filling slot is too deep, the ferrule will be scrapped; if it is too shallow, the steel ball cannot be filled in. Grooving also has a certain impact on the performance of the bearing, mainly by significantly reducing high-speed performance and limiting axial movement.

Fracture method:

When the ball filling angle is greater than 195°, and the bearing operating condition requirements are low, and the speed and vibration requirements are not high, the fracture ball filling method is used. It is necessary to open a small groove on the inner diameter before the heat treatment of the outer ring. The heat treatment will produce stress concentration. After the outer ring grinding process is completed, the outer ring will be cracked. When filling the ball, the outer ring will be expanded to fill in the steel balls that need to be filled. This is a method to increase the number of balls filled at the expense of bearing performance.

The elastic filling principle of the special ball filling method of flexible bearings:

The so-called elastic filling principle is a method of radially stretching, deforming and expanding the bearing ring within the allowable range of the tensile stress of the bearing ring, and then filling the steel ball into the channel. The force applied is mainly to press the end face of the outer ring. When the outer ring is pressed downward, the steel ball will continue to expand the outer ring and become the tension of the steel ball on the outer ring in the radial direction. As the pressing distance increases, the participating steel The number of balls also continues to increase, and the tension on the outer ring also continues to increase until the steel balls are fully opened and enter the channel. The stress process is shown in Figure 3. This method can theoretically meet the filling requirements of 360° ball filling angle.


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