Sugitachi, E., Takeuchi, S., Yokoyama, H., and Watanabe, M., "Design of Transmission Electro-Hydraulic Control Module," SAE Technical Paper 2013-01-0302, 2013, doi:10.4271/2013-01-0302.
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.