Nhk Spring Co., Ltd.

Suzuki-Sumiden Stainless Steel Wire Co., Ltd.

Mitsutoshi Kaneyasu

Kazuo Iwata

Noritoshi Takamura

Michihiko Ayada

Nobuharu Kato

Takeshi Yabushita

Toshiaki Sudo

Hiroyuki Enokida

A damper spring device is provided with a first spring and a second spring retained by a stopper in such a manner that the second spring is compressed by a preload. The preload on the second spring is greater than a preload on the first spring. The first spring and the second spring have load-deflection characteristics such that the first spring deforms when an axial load acting in the direction of compression of the first spring is not greater than a load at which a strand of the first spring is at least partially compacted and that the first spring and the second spring deform when the axial load is greater than the load at which the strand of the first spring is at least partially compacted.

Damper spring device, flywheel, clutch disk, and clutch disk for lockup mechanism

By controlling the thickness of the nitrization layer formed on the surface, the coil spring made of spring steel may be made highly resistant to permanent set and fatigue. By carbonitriding the material of the coil spring to a depth of 20 to 50 .mu.m from the surface thereof so as to have an internal hardness of Hv 540 or higher, the coil spring can be made to endure 10.sup.7 cycles of repeated high stress without suffering any significant permanent set.

Coil spring resistant to permanent set and fatigue

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Kamiina-gun, Japan

Mitsutoshi Kaneyasu