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This paper studies the analysis and reduction of hydraulic power steering (PS) noise generated during its static steering operation. By an experimental analysis and a theoretical analysis, we found out that the important factors of PS noise are the bending vibrations of the pump, the pressure hose, the control valve, the power cylinder and the steering column, and the torsional vibrations of the valve and the column, which are generated by pressure pulsations of the pump. Using the theoretical model and the sensitivity analysis, we investigated a stiffness optimization analysis method and achieved the PS noise reduction of approximately 12 dB(A).

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.