The Operation Of The Ball Of The Ball Screw

According to the ball circulation method in the nut, it can be divided into outer circulation and inner circulation.

In the form of inner circulation structure, the ball has only one circle in a circulation track. A reverser connecting two adjacent raceways is installed in the side hole of the nut, and the balls are forced to enter the adjacent raceways over the screw crest with the help of the reverser. Generally, three reversers are used on the same nut, which are staggered along the axial direction of the nut and evenly distributed on the circumference at a distance of 120°. This structure has only one circle of balls per cycle.

The external circulation is that the balls re-enter the circulation between the screw and the nut through the spiral groove or cannula on the outer surface of the nut after the end of the circulation process. For the end cap type, a longitudinal hole is machined on the nut as a return passage for the balls. The cover plates at both ends of the nut are provided with return openings for the balls, from which the balls enter the return pipe to form a circulation. Intubation type, which uses elbows as return pipes, this structure has good manufacturability, but because the pipes protrude from the outside of the nut, the radial size is large. Spiral groove type, it mills a spiral groove on the outer circle of the nut, and drills through holes at both ends of the groove and is tangent to the threaded raceway to form a return channel. This structure is smaller than the intubation structure in radial size, but Manufacturing is more complicated.

Advantages and disadvantages of inner and outer circulation ball screws:

1. The internal circulation ball screw has a small external dimension, the reverser is firmly fixed, has good rigidity and is not easy to wear;

2. The reverse channel of the ball screw is short, the number of balls is small, the fluency is good, the friction loss is small, and the transmission efficiency is high;

3. The outer diameter of the inner circulation nut with the same nominal diameter is smaller than that of the outer circulation, which is suitable for occasions where the installation space is relatively compact;

4. The ball screw shaft matched with the inner circulating nut must have one end smaller than the valley diameter;

5. Relatively speaking, the impact resistance of the inner circulation is not as good as that of the outer circulation, so the large screw and the high-load screw mostly use the outer circulation structure;

6. The inner circulation multi-purpose plastic reverser has certain requirements on the working temperature.