Development of a New Clutch-to-Clutch Shift Control Technology

The non-freewheeler shift control technology (clutch-to-clutch shift) is the key enabler for a compact, low mass and low cost automatic transmission design, especially when the transmission has an extended number of speeds. For the past two decades, a variety of non-freewheeler shift control technologies have been developed. The Allison Transmission LCT, the Saturn MP7 and the Chrysler 42LE can be considered as representatives of those technologies. All of those technologies (traditional) use two independent pressure control valves to control the oncoming and the off-going clutches. The synchronization of these two clutches is accomplished by means of electronic controls. Due to the variation of the system parameters and the difficulty of detecting the oncoming clutch fill, the consistency and robustness have always been the issues, even after years of development. To improve the consistency and robustness of the control systems, the authors have developed a new non-freewheeler shift control technology. This new technology uses a hydraulic washout technique to control the synchronization of the oncoming and the off-going clutches. The test results show that this new technology greatly improves the shift quality, consistency and system robustness, and reduces the calibration work over the traditional clutch-to-clutch control technologies. The technical background, design guideline, analyses, and hardware test results will be reported.