Studying Self-Braking Planetary Gears with Single-Crown Satellites
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ABILITY, STRENGTH, AND WEAR RESISTANCE OF MACHINES AND STRUCTURES
Studying Self-Braking Planetary Gears with Single-Crown Satellites G. A. Timofeeva,*, V. V. Panyukhina, and D. V. Sashchenkoa a Bauman
Moscow State Technical University, Moscow, 105005 Russia *e-mail: [email protected] Received February 7, 2019; accepted March 7, 2020
Abstract—The results of studying self-braking planetary gears with single-crown satellites, as well as central and ring gears with extra-pole engagement, are outlined. The conditions of self-braking of these planetary gears are determined using the method developed for studying self-braking. The domains of existence of self-braking gearings with the highest performance are found.
Keywords: self-braking conditions, self-braking planetary gears, single-crown satellites, self-braking extra-pole engagement, domains of existence, high-performance planetary gears. DOI: 10.3103/S1052618820040147
The self-braking realization in planetary gears (mechanisms) without special braking devices is a topical theme in robotics and cargo lifting equipment. For self-braking we need to use inner and outer gearings with significant shifts. The task of the current study is to synthesize high-performance structures of self-braking planetary gear trains containing extra-pole engagements of braking profiles. The synthesis involves separating the self-braking subdomain in the domain of existence of planetary gear and searching for optimal structural parameters in this subdomain. Information on the presence or absence of self-braking in planetary gears in the literature [1–8] was obtained by analyzing the gear trains with engagements having the same values of the performance coefficients of direct and reverse runs. Therefore, they characterize only the special case where all engagements have a central position of the pole on the pressure line. It is well-known that in extra-pole cylindrical gearings it is possible to obtain a difference in the performance coefficients of the direct and reverse runs such that self-braking in the reverse run is provided at a sufficiently high performance of the direct run [9]. Study of the outer and inner cylindrical gears showed that, to achieve self-braking, we need to use gearings with a significant shift [7, 8]. Because in the spur gears we have a limited range of the shift of working gear profiles due to dangerous tapering or undercut, they are replaced with helical or herringbone gears, for which the admissible shift may be considerably larger. In helical gears the value of the working profile shift from the pitch point is determined by the difference in the helical angles of teeth during engagement. Therefore, the task of providing self-braking for a planetary gear in the given state is reduced to determination of the helical angles in the extra-pole engagements necessary for it. Here, the profile angles are chosen in the same manner as in typical gears. The schemes of single-crown planetary gears classified by V.N. Kudryavtsev [1, 12] are denoted as AH3 1 and AH1 3 (Fig. 1)
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