一、前 言昭和48（1973）年后半期石油危机以后,世界上突然对资源保护、珍视物资、有效使用的舆论高涨起来。但是,有史以来,不论在运行成本方面或维修费用方面,都在为制造低成本、高效率的机器而努力。当然,目前世界舆论中的资源保护,节约能源也是为了机器的高效应用,纠正那种浪费、滥用的呼声是很强烈的。 I. Introduction Since the oil crisis of the second half of the Showa 48 (1973) year, there has been a sudden rise in public opinion in the world of resource conservation, precious materials, and effective use. However, historically, efforts have been made to create low-cost, high-efficiency machines both in terms of operating costs and maintenance costs. Of course, resource conservation and energy conservation in the current world public opinion are also for the efficient application of machinery. It is very strong to correct such waste and abuse.