Overview of ball gear research

Ball gear is a new type of gear transmission mechanism. The flexible wrist mechanism of painting robot developed by trallfa company in Norway is its typical application. ball gear mechanism has compact structure, few transmission elements and can realize two rotational degrees of freedom. It brings new ideas for the construction of bionic mechanical joints, which has attracted great attention of scholars.

Trallfa ball crown gear mechanism (as shown in Fig. a) realizes the transmission between ball gears through the meshing of conical finger teeth with the same number and pits on the two tooth surfaces. The gear increases the joint flexibility of the mechanism and reduces the joint mass, which has been proved on the flexible wrist of the painting robot. However, this kind of gear has low machining accuracy, low bearing capacity and difficult manufacturing. Cheng Yang and others have successively proposed improved gears, such as circular arc tooth ball gear and discrete ring involute tooth ball gear. These improved gears increase the meshing area and improve the wear resistance and bearing capacity, but the principle error of discrete teeth still exists.

To solve the above problems, pan cunyun et al. Proposed the involute ring gear ball gear (as shown in Fig. b). The gear tooth profile curve is involute, and the teeth are continuously distributed along the ball surface, which overcomes the principle error of the traditional discrete tooth ball gear transmission mechanism. Involute ring gear ball gear has 360 ° omni-directional deflection function and spin motion function. It can be widely used in bionic robot joints, vector propulsion screw mechanism of underwater vehicle and walking mechanism of wheel leg composite mobile platform.

In the 40 year history of the development of ball gear transmission mechanism, generally speaking, scholars pay more attention to the meshing principle and transmission performance of transmission mechanism, but the research on the manufacturing technology of ball gear pair is relatively insufficient. Because the involute ring gear ball gear has outstanding advantages and broad application prospects in ball gear transmission, this paper first briefly reviews the development process of ball gear transmission theory, and focuses on the development trend of involute ring gear ball gear manufacturing technology and equipment, in order to promote the later research and industrial application of this kind of gear mechanism.

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