Power transmission shaft

Abstract

A power transmission shaft having an improved strength and ensuring a stable torsion fatigue strength. The power transmission shaft has coupling members respectively provided on the opposite ends of an pipe part made of a steel material. The steel material includes 0.30-0.45% by weight of C, 0.05-0.35% by weight of Si, 1.0-2.0% by weight of Mn, 0.05% by weight or less of Al, 0.01% by weight or less of S, and the remainder (iron Fe and unavoidable impurities). The pipe part has an electro-unite portion that extends in the axial direction. The electro-unite portion and neighborhood thereof are hardened so as to have a Rockwell hardness HRC of 45 or more. Also, another power transmission shaft has coupling members integrally formed on opposite ends thereof. In addition, the shaft is formed from a steel element tube by a plastic working. The shaft has an inner diametrical surface which is subjected to a high-frequency induction hardening and tempering treatment to make the surface portion hardness of the inner diametrical surface to have a Rockwell hardness HRC of 35 or more.

Description

[0001] This is a Divisional Application which claims the benefit of Pending U.S. patent application Ser. No. 10 / 153,865, filed May 24, 2002 which also claims the benefit of priority from Japanese Patent Application Nos. 2001-158691 filed May 28, 2001; 2001-158766 filed May 28, 2001. The disclosures of the prior applications are hereby incorporated herein in their entirety by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a power transmission shaft to be used as, for example, a drive shaft or a propeller shaft, which constitutes a part of a power transmission system in an automobile. [0004] 2. Description of the Related Art [0005] In general, there are several kinds of transmission shafts that constitute a power transmission system of an automobile. The shafts include a drive shaft for connecting between an engine and a wheel-bearing device, a propeller shaft for transmitting power from a transmission to reduction gears,...

AI Technical Summary

Benefits of technology

The present invention provides a power transmission shaft with improved strength and stability against torsion fatigue. This is achieved by using a steel material with specific components and hardening the electro-unite portion and neighboring areas to a high level of hardness. The hardness ensures a stable torsion fatigue strength and a long useful life of the shaft. The inner diametrical surface of the shaft is also hardened to prevent wrinkle formation and breakage. Additionally, a residual compression stress can be applied to further increase the torsion fatigue strength.

Problems solved by technology

However, it will effect an increase in costs because of increasing the weight and the cutting amount of a coupling portion.

However, it will lead to an increase in costs because of increasing the number of structural components and the number of assembling steps in the manufacturing process.

Therefore, there is a possibility of a decrease in the shear strength of the hollow shaft.

Therefore, the welded portion of an electro-unite part of the welded pipe, which extends in the axial direction, tends to be broken, leading to a decrease in the strength of the power transmission shaft.

Thus, there is a tendency in which the inner radial surface of the hollow shaft become wrinkled.

Such a wrinkle may become the origin of breakage, causing a decrease in the strength of the power transmission shaft.

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