内燃機関用弁ばねの疲れ破損防止について

抄録

It is well known that the fatigue failures of the valve springs in internal-combustion engines often give rise near both ends of them by surge in the springs in service, even though they have no defect in the material. To protect the strings against surge and to prevent fatigue failures the writer coated them with damping materials. The presence of damping causes the wave of torsional vibration of the wire of the spring to die out, and the high repeated shearing stresses in the coils of the spring are avoided. Three piano wire springs of almost the same dimensions A (uncoated), B (coated with lead) and C (coatde with copper) are compared in this experiment, and the following results are obtained. (1) Surge in the spring coated with lead is avoided and resonance in the spring coated with copper diminished considerably. (2) The ranges of repeated shearing stresses in the coated strings under repeated loading are notably smaller than those of uncoated springs and fatigue failures of springs may be avoidable by coating with damping materials. (3) As coating material, copper will stand for use in this rate of the angle of shear in the wire of the spring. (4) As for uncoated spring, maximum range of repeated shearing stress is measured about 5 times that of corresponding to the lift of cam. (5) By coating, a sping may be also protected against failures due to flaws on its surface.