Abstract: Disclosed is a steel wire rod for hard-drawn springs capable of exhibiting fatigue strength and sag resistance equivalent to or higher than springs made of an oil-tempered wire. The steel wire rod contains carbon in a range from 0.5 to less than 0.7 mass %, silicon in a range from 1.4 to 2.5 mass %, manganese in a range from 0.5 to 1.5 mass %, chromium in a range from 0.05 to 2.0 mass %, and vanadium in a range from 0.05 to 0.

Abstract: This tensioner comprises a casing, a first shaft member rotatably stored in the casing so as to be restrained from moving in its axial direction, a second shaft member in screwed engagement with the first shaft member, and a spring for applying a turning force to the first shaft member. The second shaft member is restrained from rotating relatively to the casing and allowed to move in the axial direction. An axial load from a force transmitting member, such as a chain or belt, acts on the first shaft member. An end face of the first shaft member touches a receiving surface of the casing across a washer. The end face receives the axial load that acts on the second shaft member. The flatness of at least the end face of the first shaft member is adjusted to 15 &mgr;m or less.

Abstract: This tensioner comprises a casing, a first shaft member rotatably stored in the casing so as to be restrained from moving in its axial direction, a second shaft member in screwed engagement with the first shaft member, and a spring for applying a turning force to the first shaft member. The second shaft member is restrained from rotating relatively to the casing and allowed to move in the axial direction. An axial load from a force transmitting member, such as a chain or belt, acts on the first shaft member. An end face of the first shaft member touches a receiving surface of the casing across a washer. The end face receives the axial load that acts on the second shaft member. The flatness of at least the end face of the first shaft member is adjusted to 15 &mgr;m or less.

Abstract: 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.

Abstract: A spring system for applying an elastic restoring force to a moveable member undergoing a reciprocating movement. This spring system includes a coil spring made of steel and having a moveable end engaged to a moveable member and a fixed end engaged to a fixed member. The moveable end is formed as an open end. A spring seat member is interposed between the moveable end of the coil spring and the moveable member. The spring seat member has a receiving surface contoured to snugly receive the moveable end of the coil spring.

Abstract: A spring system for applying a restoring force to a reciprocating member such as an exhaust or intake valve of an internal combustion engine, comprising: a helical spring having open ends and consisting of titanium or an alloy thereof; and a spring seat supporting one of the two ends of the helical spring. Since this helical spring is provided with open ends, mutual striking of the coil wire can be avoided and, thereby, the durability of the helical spring can be ensured in addition to the advantage obtained from the low-mass and high transverse elastic modulus of titanium or its alloy.

Abstract: A high strength spring is made of steel of which composition consists of 0.6 to 0.7 wt % of C, 1.2 to 1.6 wt % of Si, 0.5 to 0.8 wt % of Mn, 0.5 to 0.8 wt % of Cr, 0.05 to 0.2 wt % in total of one or more than one of V, Mo, Nb and Ta and the balance of Fe and inevitable impurities. The steel is limited in particle size of non-metallic inclusions in such a way that the maximum particle size of the non-metallic inclusions is equal to or smaller than 15 .mu.m. The spring is applied at a portion adjacent the outer surface thereof with a residual compression stress in such a way that the maximum of the residual compression stress ranges from 85 to 110 Kgf/mm.sup.2. The spring is further process so as to have such a surface roughness that is equal to or smaller than 15 .mu.m.