# Principle of noncircular gear stepless speed regulation

As shown in Figure 1, the non-circular gear stepless speed regulation mechanism mainly includes two parts: the non-circular gear speed ratio generation part and the planetary speed ratio integration part. In Figure 1 (a), the locking mechanism not only changes the phase angle of the non-circular gear pair 1 and 2, but also realizes the split of the input speed, and transmits the input speed to the non-circular gear pair 1 and 2 respectively; Because the non-circular gear pair 1 and 2 are in different phase angles, according to Fig. 1 (b), there is a corresponding relationship between the speed ratio and the phase angle of the non-circular gear pair. At this time, the output speeds of the two non-circular gear pairs in Fig. 1 (a) are different. Therefore, the speed integration can be carried out through the differential gear train in the speed ratio integration part, and finally the selected part can output the integrated speed branch, The required continuous speed regulation output is obtained.

In Figure 1 (b), a is the radius parameter of the long shaft of non-circular gear, e is the eccentricity of non-circular gear, and N is the order of non-circular gear. It can be seen from Figure 1 (b) that the speed ratio of non-circular gear is time-varying with the change of parameters. The radius parameter a mainly affects the maximum and minimum value of speed ratio. The larger the radius parameter a is, the larger the maximum value is, and the smaller the minimum value is; Eccentricity e mainly affects the difference between the maximum and minimum values. The larger the eccentricity is, the larger the maximum value is and the smaller the minimum value is; The order n mainly affects the cycle number of speed ratio of non-circular gear pair. The higher the order is, the larger the cycle number of speed ratio is and the faster the change is. Because the non-circular gear always has a time-varying speed ratio, it can not be directly used as a CVT.

According to Fig. 1 (a), the input speed is divided into two parts by the locking mechanism, which are respectively input to the non-circular gear pair (1) and (2), and the time-varying output speed with phase difference can be obtained by setting different phase angles to the non-circular gear pair (1) and (2); The output speeds of the two groups of non-circular gear pairs are taken as the input speeds of the speed ratio integration part (3) and (4) respectively. The two input speeds are combined into a certain output speed through the differential gear train. The output speed ratios of the two groups of non-circular gear pairs (1) and (2) also have different phase differences under different phase angles. Finally, the output selection is made by selecting the gear pair (5), Under the premise of the input speed unchanged, the output speed can be continuously variable.

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