ABSTRACT The demand for better driving comfort, fuel efficiency and reduced CO2 output has been becoming increasingly stringent. In response to such needs, we developed Transmission Electro-Hydraulic Control Module (TEHCM). For Automatic Transmission, expanding the lock-up control area is necessary to improve fuel efficiency. Meanwhile, lock-up control at lower speeds aggravates shift quality. To improve shift quality, Automatic Transmission Fluid (ATF) pressure control must be precise is needed. This can be accomplished by compensating for deviation in TEHCM, which integrates Transmission Control Unit (TCU) and the pressure control actuator, Variable Force Solenoid (VFS). However, there are two problems in installing TEHCM in compact vehicle. The first problem is the miniaturization of such TEHCM. Regarding modules that require a high electrical current to operate the VFS, thermal conductivity contradicts miniaturization. We applied a half-mold structure for TCU to accomplish high thermal conductivity. However, a half-mold structure entails the problem of delamination between ceramic substrate and mold resin, and between mold resin and heat sink. Therefore, the optimization of each material and the development of a new structure are necessary to resolve this problem. The second problem is preventing an increase in calibration time. Calibration must be done at high and low temperatures. However, the bigger the product size is, the longer the setting time. Therefore, a new structure, which reduces temperature dependency of the actuator dramatically, was developed. These technical innovations enable a new TEHCM which satisfies both fuel efficiency and shift quality to be miniaturized enough for accommodate all vehicle segments.INTRODUCTION TEHCM is a module that shift gear by controlling ATF hydraulic pressure. Figure 1 is a outline drawing of TEHCM. The module involves the integration of VFS for hydraulic control, TCU for VFS control, various sensors including a rotation sensor for detecting gear rotation and a position sensor for detecting the shift range position. Compared to TCU located outside of the transmission, via integration, we were able to reduce the dozens of harnesses that connect the exterior and the interior of the transmission device. Also, by integrating the VFS and TCU, an improvement in control precision enables compensation for each error along the production line. As a result of such benefits, the demand for TEHCM is high and the transmission equipped with TEHCM is becoming more common. Simultaneously, there are new demands in regards to TEHCMas illustrated in the following two segments. Figure 1. TEHCM outline drawing Design of Transmission Electro-Hydraulic Control Module2013-01-0302 Published 04/08/2013 Eiji Sugitachi, Shinji Takeuchi, Hajime Yokoyama and Masamichi Watanabe DENSO Corp. Copyright © 2013 SAE International doi:10.4271/2013-01-0302Downloaded from SAE International by Univ of California Berkeley, Saturday, July 28, 2018Further Miniaturization of TEHCM In regards to improving passenger space, collision safety and fuel efficiency, the need for lighter/smaller components is increasing. At the same time, parallel to the increase in compact vehicle, there is a strong demand for TEHCM in small transmissions. Hence, miniaturization of TEHCM is more required. Further Improvement of Fuel Efficiency The demand for vehicle fuel efficiency is growing year by year. Engaging the lock-up clutch is widely known as a way to enhance fuel efficiency [ 1]. However, expanding the lockup range aggravates driving comfort at low speeds. Achieving a good balance between driving comfort and enhancement of fuel efficiency is necessary to realize hydraulic pressure precision for clutch control more so than ever before. Furthermore, the interior of the transmission is subject to extreme temperature changes between −40 degrees Celsius and 140 degrees Celsius. That is to say, higher pressure precision than