Nsk Corporation

Other

Sanyo Special Steel Co., Ltd.

Tomonobu Yoshikawa

Yasuo Murakami

Nobuaki Mitamura

Shigeru Okita

Hiromichi Takemura

Yoichi Matsumoto

Takashi Nagato

Takashi Imanishi

Hiroyuki Itoh

Susumu Tanaka

Nobuo Goto

Akihiro Kiuchi

Shuhei Kitano

Yutaka Ishii

Kazuhiko Hiraoka

A power roller bearing of a toroidal-type continuously variable transmission unit that is used for a transmission of an automobile or the like comprises a power roller, an outer race, balls, a retainer, etc. Annular raceway grooves are formed individually on the respective opposite end faces of the outer race and the power roller. Treated-surface layers for enhancing the endurance of the power roller bearing are formed individually on the respective surfaces of the raceway grooves. The treated-surface layers include super-finished surfaces with the surface roughness of 0.05 Rad or less, formed individually on the raceway grooves, and low-friction layers formed individually on the super-finished surfaces. Alternatively, the treated-surface layers include residual compression stress layers formed on the respective surface layer portions of the raceway grooves by shot-preening.

Power roller bearing of toroidal-type continuously variable transmission unit

The present invention provides a rolling bearing having high wear resistance at high temperature and with reduced manufacturing cost. At least one of an inner ring, an outer ring and rolling elements is formed of the following steel material into a predetermined shape, then applied with hardening and tempering at a temperature of 240&deg; C. or higher or 350&deg; C. or lower to make the Vickers hardness (Hv) on the raceway surface and/or rolling surface to 720 or more. The steel material contains, as the alloy ingredient, 0.8% by weight or more and 1.2% by weight or less of C, 0.5% by weight or more and 2.5% by weight or less of Si, 0.7% by weight or more and 1.5% by weight or less of Cr, 0.8% by weight or more and 2.0% by weight or less of Mo and 0.3% by weight or more and 1.2% by weight or less of Mn, with a ratio of Mo to Cr (Mo/Cr: weight ratio) of 1.1 or more.

Rolling bearing

The toroidal-type continuously variable transmission comprises an input shaft rotatably supported, an input side disk, an output side disk, a plurality of trunnions, a plurality of power rollers, and a plurality of thrust rolling bearings , in which the mutually opposed inner surfaces of the input side and output side disks are respectively formed as concave surfaces each having an arc-shaped section, the peripheral surfaces of the power rollers are formed as spherical-shaped convex surfaces, and the peripheral surfaces of the power rollers are contacted with the inner surfaces of the input side and output side disks. In the thus structured toroidal-type continuously variable transmission, each of the thrust rolling bearings is made of high carbon chromium bearing steel and is also carbonitrided.

Toroidal-type continuously variable transmission

A toroidal continuously variable transmission is characterized by comprising an input disk, an output disk, trunnions, power rollers, and thrust rolling-element bearing, in which at least one of the input disk, output disk and power rollers of a power roller bearing is formed of an alloy steel and subjected to either carburizing processing and polishing or carbonitriding processing and polishing, and at least one of the input disk, output disk and the inner ring of the power roller bearing has an efficient hardened layer of Hv 653, which has a depth of 2.0 mm or more and 4.00 mm or less from the surface.

Toroidal continuously variable transmission

A toroidal continuously variable transmission system of the present invention is provided with an input disk, an output disk and power rollers. The input and output disks have traction surfaces defined between a small-diameter portion and a large-diameter portion and having an arc-shaped concave section. The input and output disks are coaxially arranged in such a manner that the traction surfaces face each other. The power roller are frictionally engagement with the traction surfaces of the input and output disks and transmit a driving force. At least one of the input disk, the output disk and the power rollers is formed of an alloy steel which contains 0.15 to 2.0% by weight of Mo. The alloy steel is subjected first to carburization or carbonitriding processing executed at a temperature not lower than 1,000&deg; C., and then to hardening and tempering. The alloy steel has a surface carbon content of 0.8 to 1.4%.

Toroidal continuously variable transmission and manufacturing method thereof

The toroidal-type continuously variable transmission comprises an input shaft, an input disk, an output disk, a plurality of trunnions, a plurality of power rollers, and power roller bearings, wherein the mutually opposed inner surfaces of the input and output disks are respectively formed as concave surfaces each having an arc-shaped section, the peripheral surfaces of the power rollers are respectively formed as spherical-shaped convex surfaces, and these peripheral surfaces are contacted with the above-mentioned inner surfaces. The retainer of the power roller bearing is formed of high strength brass, and the high strength brass has a micro structure in which the &agr; phase thereof is 40% or more in the area ratio thereof, and the hardness of said retainer is set at HB80 or higher.

In the thus structured toroidal-type continuously variable transmission, at least one of the concave surface of the input side disk, the concave surface of the output side disk, the convex surfaces of the power rollers, the raceway surfaces of the inner races of the power roller bearings, and the raceway surfaces of the outer races of the power roller bearings is, after heat treatment, subjected to grinding, superfinishing and shot-peening and then surperfinishing again, and the resultant surface residual compression stress is in the range from &minus;780 to &minus;1800 MPa.

The present toroidal-type continuously variable transmission comprises input and output disks coaxially disposed so as to be opposed to each other, and a pair of power roller bearings, each power roller bearing including an inner race, an outer race, and power rollers disposed so as to roll on the toroidal surfaces of the input and output disks. At least one of the input and output disks and power rollers are made of medium-carbon steel containing carbon in an amount ranging from 0.3 wt %-0.5 wt %, to thereby have a very long life.

An induction-hardened rolling bearing device used by disposing rolling elements in a raceway track member, with excellent cold drawability and improved wear resistance and extended service life, in which ingredients of an alloy for the raceway track member contain, from 0.40 to 0.90% of C, from 0.05 to 0.80% of Si, from 0.10 to 2.0% of Mn, from 0.05 to 0.50% of Ti and 0.03% or less of N, on the weight basis, induction hardening is applied at least to the raceway surface of the raceway track member, and Ti carbide and Ti carbonitride each having an average particle diameter of from 5 to 100 nm are dispersed on the surface and in the steels of the raceway track member to make the hardness of the raceway surface to HRC 59 or more.

Induction-hardened rolling bearing device

A linear guide bearing device includes a rail, a bearing supported by the rail and rectilinearly movable along the axial direction of the rail, and rolling members interposed between the rail and the bearing to roll along with motion of the bearing. At least one of the rail and the bearing is made of induction-hardened steel including 0.6 to 0.9 wt % of carbon, 0.05 to 0.25 wt % of silicon, 0.3 to 0.9 wt % of manganese, 0.1 to 0.5 wt % of chromium, 0.2 to 1.0 wt % of molybdenum, and residual portion as iron and unavoidable impurities, and the induction-hardened steel has a total content of carbon, manganese, and molybdenum, which satisfies predetermined inequalities.

Linear guide bearing device

At least one of input/output disks, a power roller and a cam disk of a toroidal type continuously variable transmission is formed of a high-cleanness steel in which a size of a maximum inclusion is estimated by the following extremum statistical process. In step S1, a plane including a central line of the high-cleanness steel is cut out in a direction of rolling of the high-cleanness steel. In step S2, a portion d of the cut-out cross-section, which is defined by 40% of a diameter D in the vicinity of the central line, is used as a to-be-tested surface. In step S3, a test reference area S.sub.0 is set at an area not less than 300 mm.sup.2 within the to-be-tested surface, and a root of an area of the maximum inclusion is measured five times or more. In step S4, a maximum inclusion distribution straight line is obtained. In step S5, the root, that is, the size of the area of the maximum inclusion within an estimation area S is estimated.

High-cleanness steel and toroidal type continuously variable

A water-resistant and long-life rolling bearing used in an environment involving water's seeping in the lubricant thereof, wherein at least one of the inner race, the outer race, and the rolling member is formed of alloy steel containing 0.05 to 0.60% by weight of Cu, 0.10 to 1.10% by weight of C, and 0 to 0.2% by weight of Nb or V. The alloy steel has functions of reducing hydrogen evolution on the surface thereof and of forming a film hardly permeable to hydrogen thereby to retard occurrence of flaking due to hydrogen-induced brittleness.

Growing community of inventors

Kanagawa, Japan

Tomonobu Yoshikawa