Abstract: Abrasion resistance is further enhanced in a sliding member used in an internal combustion engine. With respect to a valve lifter 6 used in an internal combustion engine 100, hard particles having higher hardness than the valve lifter 6 are dispersed onto the top face 61 of the valve lifter 6, and a nitriding treatment is conducted on the top face 61 dispersed with the hard particles.

Abstract: Abrasion resistance is further enhanced in a sliding member used in an internal combustion engine. With respect to a valve lifter 6 used in an internal combustion engine 100, hard particles having higher hardness than the valve lifter 6 are dispersed onto the top face 61 of the valve lifter 6, and a nitriding treatment is conducted on the top face 61 dispersed with the hard particles.

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: The present invention provides a valve operating system for internal combustion engines, having a roller rolling contacting a valve operating cam, the system being provided with an oil supply passage capable of reducing a pressure loss to a low level even when a flow rate of lubricating oil entering the oil supply passage increases in accordance with a heightened engine speed, improving the lubricating ability with respect to the roller, and attaining a long lifetime of a rocker arm.

Abstract: The present invention provides a valve operating system for internal combustion engines, having a roller rolling contacting a valve operating cam, the system being provided with an oil supply passage capable of reducing a pressure loss to a low level even when a flow rate of lubricating oil entering the oil supply passage increases in accordance with a heightened engine speed, improving the lubricating ability with respect to the roller, and attaining a long lifetime of a rocker arm.