[in Japanese]

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The object of this study was to develop technology for a valve to be mounted in a disposable medical device and obtain highly robust technical information before the product planning stage. The valve had two opposing functions: to limit the amount of blood flowing backward into a needle when the needle is inserted into a blood vessel; and when medicine is administered, to allow the prescribed amount to flow forward without resistance into the subject’s body. The basic function of the valve was defined in terms of input and output, the input being fluid pressure （blood pressure or medicine pressure），the output being the differential pressure on the two sides of the valve. Experiments were performed after assignment of noise factors. To increase the efficiency and reduce the cost of the experiments, they were carried out on a scaled-up version of the contemplated product. The two opposing functions were optimized simultaneously by finding their mutual S/N ratio. The valve was thereby developed in one-fourth the time spent on previous valves, and at one-fourth the cost.

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Compressed air cannons that emit high-speed pulses of air at fixed intervals are attracting attention in manufacturing industries because of their excellent cleaning performance and reduced air consumption. Thinking that pneumatic sound might provide useful information for the design of such particulate removal systems, we compared the test results of the acoustic characteristics of pulsed air and the results of particucate removal tests. The pulsed air used in this comparative study had an ultrasonic frequency of 20 kHz. Both the air pressure and the waveform attenuation efficiency were found to be involved in the removal performance. The possibility of using the Mahalanobis-Taguchi （MT） system to discriminate the removal ratio from acoustic information was also studied. It was found that conditions yielding low removal ratios could be identified from acoustic information by use of Mahalanobis distance. It was also demonstrated that: the removal ratio fell as power-on time increased to approach continuous air blowing; ultrasonic waves created by collision played a supporting role in particulate removal; and the pressure setting affected the sounds produced by air collision with walls and ejection of air from the nozzle. We therefore propose that acoustic evaluation of pulsed air by the MT system can be an effective tool in the design of pulsed air settings.

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