Do you know the ball cage type universal joint?

Update:15-04-2022
Summary:

The ball cage joint is the most widely used constant ve […]

The ball cage joint is the most widely used constant velocity joint. The early Rzeppa type ball cage universal joint is with indexing rod. There are six concentric arc raceways evenly distributed along the circumference on the inner surface of the spherical shell and the spherical surface of the star-shaped sleeve, between them. Equipped with six force-transmitting steel balls, these steel balls are kept in the same plane by the ball cage. When the angle between the two shafts of the universal joint changes, the guide plate is moved by the indexing rod with appropriate proportion, and the ball cage is driven to make the six steel balls lie on the bisector of the angle between the shafts. Experience shows that when the included angle between the shafts is small, the indexing rod is necessary; when the included angle between the shafts is greater than 11°, the steel ball can also be fixed by the intersection of the spherical cyan and the radial raceway on the star sleeve. in the correct location. No matter what the direction of rotation of this constant velocity joint, all six steel balls transmit torque, and it can work when the angle between the two shafts reaches 35°~37°.

At present, the Birfield-type ball cage universal joint is relatively simple in structure and widely used. It cancels the indexing rod, and the raceways of the spherical shell and the star-shaped sleeve are not concentric, so that the center of the circle deviates from the center of the universal joint symmetrically. In this way, even if the angle between the shafts is 0°, the intersection of the inner and outer radial raceways can fix the steel ball in the correct position. When the included angle between the shafts is 0', the included angle of the center track of the steel ball determined by the inner and outer raceways is slightly greater than 11°, which is the minimum angle that can reliably determine the correct position of the steel ball. The cross-section of the raceway is elliptical, and the line connecting the contact point and the center of the sphere forms an angle of 45' with the radial line passing through the center of the sphere. When loaded, the contact point of the steel ball with the raceway is actually an elliptical contact area. Since each direction of the ball has an opportunity to transmit torque during operation, and since the ball and cage are spherical in shape, sufficient attention should be paid to the lubrication of this universal joint. The use of lubricants mainly depends on the speed and angle of the transmission. When the speed is up to 1500r/min, anti-rust grease is generally used. If the speed and angle are large, use lubricating oil. A better method is to use oil bath and circulating oil lubrication. In addition, the sealing device of the universal joint should ensure that the lubricant does not leak, and different forms of sealing devices should be adopted according to the size of the transmission angle. This universal joint allows working angles up to 42°. Since all six steel balls work at the same time when transmitting torque, it has strong bearing capacity and impact resistance, high efficiency, compact structure and convenient installation. However, the manufacturing precision of the raceway is high, and the cost is high.

The structure of the telescopic ball cage universal joint is similar to the general ball cage type, only the outer raceway is a straight groove. When transmitting torque, the star-shaped sleeve and the cylindrical shell can move relative to each other in the axial direction, so the sliding splines in other universal transmission devices can be omitted. This not only makes the structure simple, but also has lower rolling resistance and higher transmission efficiency than sliding splines because the relative axial movement is achieved by rolling the steel balls along the inner and outer raceways. The maximum working angle allowed by this universal joint is 20°. Rzeppa-type ball cage universal joints were mainly used in steering drive axles before, but they are rarely used at present. Birfield type ball cage universal joints and telescopic type ball cage universal joints are widely used in steering drive axles with independent suspension. On the side, a telescopic ball cage universal joint is used to compensate for the change of the wheel track caused by the jump of the front wheel and the change of the load. Telescopic universal joints are also widely used in disconnected drive axles.

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