Ball Transmission

I. Core Functions of Ball Transmission

1. Motion form conversion: The rotor of the downhole motor performs a planetary motion that is both self-rotating and revolving around the center of the stator. The transmission shaft needs to drive the drill bit to rotate stably along a fixed axis. The ball transmission, through the flexible rotation angle characteristic of its own spherical hinge structure, can smoothly complete the conversion between these two motion forms, avoiding jamming during power transmission.

2. Stable power transmission: The underground drilling environment is subject to vibration and shock loads. This universal joint, through the tight fit of the ball joint with the ball seat, spherical column and other components, can smoothly transmit the torque and rotational speed generated by the rotor to the transmission shaft, reducing power loss and ensuring the drilling efficiency of the drill bit.

3. Adapted working condition protection: Its sealing structure can isolate solid particles such as sand and mud in the drilling fluid, preventing the internal transmission components from being eroded. Some models are equipped with high-temperature grease to achieve oil bath lubrication, further reducing component wear and extending the service life in the high-temperature and high-pressure underground environment.

II. Typical Structural Composition of Ball Transmission

The structures of different optimized models vary slightly, but the core components revolve around the spherical transmission and sealing design. Taking the common ball hinge type as an example, it mainly includes: the shaft, with a ball head at the end, and a concave pit for matching the rollers on the outer circumferential surface; The ball shaft assembly includes a shaft housing fitted onto the shaft rod. The shaft housing is composed of a shaft sleeve and a shaft cap, and there is a ball seat on the inner side of the shaft cap that cooperates with the ball head of the shaft rod. The rollers are fixedly connected by spherical columns and hemispherical heads. The spherical columns are installed on the inner wall of the shaft housing, and the hemispherical heads are embedded on the outer surface of the shaft rods. At least three rollers are evenly distributed to ensure balanced force distribution. Some improved models will also add components such as ball caps, rubber sleeves, and locking sleeves to enhance sealing and load-bearing capacity.

III. Common Precautions of Ball Transmission

High-temperature grease should be replenished regularly through reserved screws to prevent excessive wear of components due to insufficient lubrication. When assembling, it is necessary to ensure the fit accuracy of components such as the ball head and ball seat, rollers and pits, etc. Otherwise, local wear will be accelerated. During the drilling process, the solid content of the drilling fluid needs to be controlled to prevent mud and sand from entering the inner cavity after the sealing parts are damaged, which may cause transmission jamming or component grinding failure.