Koyo Seiko Company, Ltd.

Koyo Machine Industries, Ltd.

Motohiro Morita

Kenichi Aota

A power transmission shaft in a steering unit shortens in an axial direction when an impact load, over a specified impact load, is applied thereto, and thereby absorbs impact. The power transmission shaft includes a hollow shaft having a female serration on the inner circumference thereof. An insertion shaft has a male serration on the outer circumference thereof that engages with the female serration of the hollow shaft when inserted into the hollow shaft. The hollow shaft and the insertion shaft are connected with each other so that they can transmit power in the circumferential direction, yet they are displaceable in the axial direction . An inward depressed portion is formed on the hollow shaft to establish the impact absorption of the power transmission shaft. A concave portion, formed on the insertion shaft aids in the uniform formation of the depressed portion and thereby simplifies the assembly process.

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Kashiwara, Japan

Motohiro Morita