チェインソーの評価法 (II) : 防振性能について (1)

Abstract

近年, チェインソーの振動対策としてエンジンの改良・開発がなされてきたが, その振動を評価する術を我々は持っていない。今回はエンジンより発生する振動起源力, 防振構造の特性, ハンドル把持部の振動加速度値よりチェインソーの振動についての物理的評価法を組み立てるための研究を行ない, あわせて防振構造の改良点を示した。西ドイツ・S社の一機種について4台のチェインソーを金属製脚立より弾性抵抗係数 (0. 185kg/cm) のバネを介して吊り, 前後ハンドル把持部の振動を測定した。この測定値を本体, ハンドルそれぞれの重心変位, 重心まわりの2つづつの回転角を変数とする6自由度系の振動モデルを用いて解析した。今回の研究を通して得られた結論は, まずある程度, この振動モデルによって防振構造の特性を表現できたが, 防振材の特性の吟味が不十分なためか, 測定値の説明等が完全に行なえなかった。一方, 評価法の吟味の中から防振構造の改良点として, ハンドルの重心まわりの回転角によって, ハンドル把持部の防振性を向上できる事が推測された。

There are many hand-hold tools that are improved on the vibration in Japan. In the case of CHAIN-SAW, one is the ROTARY-CHAIN-SAW that is driven by ROTARY engine, one is the PNEUMATIC-CHAIN-SAW that is driven by air-compressor, etc. But, we cannot decide which is better, because we have not a fixed way to evaluate the CHAIN-SAW. This time, we measured four CHAIN-SAW (STIHL-041AV) on the vibration, and got many data, (TABLE-2). And then, we compared those data with the calculated one that was gotten from six-degree-freedom anti-vibration system. After that, we could indicate how to isolate the vibration of CHAIN-SAW. Many types of AV system are used of the CHAIN-SAW, but this report is only about THREE-POINTS SUSPENDED AV system. On the situation of measurement, each CHAIN-SAW is hanged down by a spring, (modulus of elasticity is 0.185 kg/cm) and this set is suspended by a steal stepladder. We have simulated AV system of CHAIN-SAW to the two-degree freedom system till now. These two degree freedom are the fluctuations of the center of gravity (c. g.) about the handle and the body of CHAIN-SAW. But we cannot simulate the vibration of CHAIN-SAW to the two degree freedom system, since the handle and the body of CHAIN-SAW are not mass points. So in this study, we simulated it to the six degree freedom system added each two rotary angles around two centers of gravity. (FIG. 1) By this study, we reached the following conclusions. The relation between fore and after handle obtained from the measurements was obedient to the simulation to a certain extent. (FIG. 5) Then the AV capacity at c. g. of the handle obeid only the fluctuations of c. g., but the AV capacity at the gripped points obeid the fluctuations and the rotary angles. (FIG. 6) Finally, we shall investigate this simulation for the modulus of elasticity and the coffiecient of viscosity on AV system. Then on the improvement of AV system, we may isolate the vibration at the gripped point by means of the rotary angles.