Torque Transmission Characteristics of a Power-Split Half-Toroidal CVT Box

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Following to the actual use of half-toroidal CVT to 3L turbo passenger car in 1999, a fundamental study of torque transmission of power-split CVT has started since 2004. The power-split CVT, consisting of a variator and a planetary gear set, has features of extending the speed-ratio range and of improving the efficiency in high-speed cruising range. The purpose of this study is to examine the torque re-circulation of the PST-mode and the output-torque continuity at mode change from direct to power-split mode by using a test box with input torque capacity of 370Nm. We confirmed that the power-split CVT with a planetary gear set widen the speed-ratio range and the continuity of both the output torque and speed at mode change by using the test box of total speed-ratio ranges of 1:6.33 with a half-toroidal variator of 1:4.36 speed ratio ranges. The mode changes smoothly by controlling both the variator and clutches at the optimum point without torque surge within 0.3s.