Abstract: The present invention provides a steel wire, for springs excellent in coiling property while having a high strength, as a heat treated steel wire for high strength springs, characterized by: comprising, in mass, C: 0.75 to 0.85%, Si: 1.5 to 2.5%, Mn: 0.5 to 1.0%, Cr: 0.3 to 1.0%, P: not more than 0.015%, S: not more than 0.015%, N: 0.001 to 0.007%, W: 0.05 to 0.3%, and the balance consisting of Fe and unavoidable impurities; having a tensile strength of not less than 2,000 MPa; spheroidal carbides, composed of mainly cementite, observed in a microscopic visual field satisfying the area percentage of the spheroidal carbides not less than 0.2 ?m in circle equivalent diameter being not more than 7%, the density of the spheroidal carbides 0.2 to 3 ?m in circle equivalent diameter being not more than 1 piece/?m2, and the density of the spheroidal carbides over 3 ?m in circle equivalent diameter being not more than 0.

Abstract: An object of the present invention is to provide an untempered free-machining steel to be nitrided, not containing Pb, capable of securing a predetermined strength and hardness and having machinability higher than steel containing Pb; and nitrided products. To be more specific, the present invention relates to a bainite-type untempered free-machining steel to be nitrided containing C: 0.05 to 0.8 wt %, Si: 0.01 to 2.5 wt %, Mn: 0.1 to 3.5 wt %, P: 0.001 to 0.2 wt %, S: 0.01 to 0.2 wt %, Cr: 1.0 to 3.5 wt %, V: 0.1 to 0.5 wt %, Al: 0.001 to 0.020 wt %, Ca: 0.0005 to 0.02 wt %, and O: 0.0005 to 0.01 wt % and the residue with an alloy composition of unavoidable impurities and Fe as its basic alloy composition, provided that a content of each of the Mn, the S and the Cr satisfy the formula: ([Mn]?55×[S]/32+[Cr])>2.0, in which an occupation area of a sulfide inclusion present in contact with an oxide inclusion containing 8 to 62 wt % of CaO and containing not less than 1.0 wt % of Ca is not less than 2.

Abstract: A valve operating system in an internal combustion engine is disclosed, wherein the operational characteristic of an engine valve which is an intake valve or an exhaust valve, can be changed in accordance with the operational state of the engine. In the valve operating system, a power transmitting means comprises an inner wheel, an outer wheel surrounding the inner wheel, and a carrier on which a planetary rotor is rotatably carried. The inner wheel is operatively connected to a cam shaft, and the outer wheel is connected to the engine valve. A rotational-amount control device is connected to the carrier for controlling the rotational amount of the carrier in accordance with the operational state of the engine. Thus, the size of the valve operating system can be reduced, and moreover, the operational characteristics of the engine valve can be finely changed.

Abstract: A valve operating system includes a connection switch-over device provided in a plurality of cam followers. The connection switch-over device has a piston moved in response to a change in hydraulic pressure in a hydraulic pressure chamber. A roller shaft is disposed on at least one of the cam followers and has a roller carried thereon to come into rolling contact with a valve operating cam. In this valve operating system, the hydraulic pressure chamber and a communication passage, which permits an oil supply passage to communicate with the hydraulic pressure chamber, are defined in a particular one of all the cam followers, which moves a smallest amount when the connection switch-over device is in its disconnecting state. The roller shaft, having the roller rotatably carried thereon, is mounted on the cam follower other than the particular one cam follower.