Study on Micro Flow Behavior and Applications to Micro Systems of Electrorheological Fluids

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ER fluids are one of an exciting family of functional fluids, which show dramatic and reversible rheplogical changes in several milliseconds when the electric field is applied. Therefore, for example, in the ER fluid hydraulic circuit systems, it is possible to control the pressure and flow rate using an ER valve consisting of only electrodes with no moving parts. In this research, featuring the possibility of miniaturization of ER mechanical elements such as clutch, brake, damper and valve due to their construction using only electrodes, the following investigations have been done in order to develop micro systems utilizing electrorheological fluids as working oils.(1) The flow fields frequently used in the ER micro systems are classified into three flow modes such as a pressure flow, a shear flow and a squeeze flow. For three kinds of ER fluids, the micro flow characteristic in these three flow modes with an about 0.1-0.3mm micro gap was clarified by flow visualization observation in … More close relation to each ER characteristic, and the ER fluid suitable for the ER micro system and the optimal design concept for applications were shown.(2) As some examples of micro systems, the 3-ports micro ER valve and the micro-actuator consisting of two ER valves and a diaphragm drive part were fabricated by the photolithography method. The flow rate control characteristics for the 3-ports micro ER valve and the diaphragm response characteristics for the micro-actuator in open loop control and PID position feedback control were evaluated.(3) A piezoelectric micro pump for ER fluids actuated by a piece of PVDF piezdelectric-film diaphragm for supplying ER fluid to the above micro-actuator was developed. A normalized method for evaluating the behaviors of a circular unimorph piezoelectric diaphragm was deduced and the diaphragm deformation for the input voltage and the pumping flow rate were analyzed, and the piezoelectric diaphragm pump of 10mm diameter was actually constructed, and the pumping performance was evaluated. Less