林道土工建設機械の座席振動

Abstract

芦生演習林を主要な対象地として従来より林業機械作業における人間工学的研究というテーマで機械土工作業に関する労働環境の調査を行ってきた。今回は林道建設機械であるブルドーザ, ショベルドーザに関する座席振動について調べた。近年特に森林作業の機械化が進み, 林道延長も大となり, それにつれてトラクタ作業の占めるウエイトも増大し, トラクタの座席の振動について, 労働環境の面からみて改善を要する問題が起ってきた。調査及び試験は2つの部分に分けられる。まず最初に林道建設の現場作業において停止時, 走行時, 排土・路面整地作業時などの基本要素作業ごとの分析を行い, その次にシートの素材別 (D50Sシート, D6シート, スポンジ, 発泡スチロール) の振動分析を停止時について行った。トラクタの振動は停止時と走行時では全く異ったタイプを示すが, 主な振動はエンジン回転数foとその高調波によるものであり, 走行時には特にfo以下の振動が目立つ。一方素材別の振動については現在使用されているシートでも伝達率が1以上になる周波数域があり, シート素材による振動減衰をも研究していく必要がある。オペレータの心拍の増加傾向については振動と正の関係にあることは確かである。ただオペレータが通常乗り慣れている機種でない場合はレベル的に高い心拍数を示すので, この点を考慮し, 平常乗り慣れている機種についてのオペレータ集団を対象に更に詳細な検討が必要である。

We have continued the examination of the forest labour environment to accomplish the study of human-machine relations about forest operations with forest machines mainly in Ashiu forest experimental place belonged to Kyoto University since 1971. Especially, we have taken up the problem of rock borer operations which are the worst labour in the forest operations. This paper reports the vibration on the seat of forest road construction machines such as a bulldozer (Caterpillar Mitsubishi D 6) and shoveldozer (Komatsu D 50 S). Recently, the mechanization of forest operations have been promoted, and the forest road length extended and then the ratio of tractor operations increased, therefore it is the most important problem that the vibration on the seat of forest machines must be improved in the forest labour environment. This report's examination was divided into two sections. In the first, we studied the vibration analysis about each elemental operation such as conditions of stopping, moving, earth-moving and so on, and as follows, about each seat material used with a D 50 S, a D 6, sponge and stylene foam. The vibration of tractors gives the different type between on stop and on moving condition, and main vibration frequencies are engine rotation f0 and its harmonics. The vibrations which are lower than f0 are remarkable. On the other hand, even the seats used with forest machines have the frequency range that the ratio of vibration transmission is higher than 1. Therefore we have to promote the study about seat materials to decrease the vibration on the seats. On an increasing tendency of tractor operator's heart beat number, we can indeed observe the positive relation between the heart beat number and the vibration which influences human body. Speaking to the case that an operator uses the machine which he doesn't use usually, we can observe the high level of a heart beat number, and for that reason we have to study the relation between the heart beat number and the vibration on the condition that operators use the machines which they use usually. We shall have the chance to report the paper of spectrum analysis regarding to vibrations of forest machines and operator's heart beat number.