Abstract: A tripod type constant velocity universal joint includes an outer joint member having track grooves formed at trisected positions thereon in a circumferential direction to extend in an axial direction of the tripod type constant velocity universal joint, a tripod member having a trunnion barrel spline-fitted to a shaft and trunnion journals radially projecting from trisected positions on the trunnion barrel in the circumferential direction, and rollers fitted to the trunnion journals, respectively, that are received in the track grooves, respectively. Each of the rollers is guided by roller guide surfaces formed on both side walls of each of the track grooves. The tripod member has quench-hardened layers formed by carburizing, quenching, and tempering, and a depth of a quench-hardened layer of a radially outer surface of the trunnion journal is larger than a depth of a quench-hardened layer of a root portion of the trunnion journal.

Abstract: A method of generating a free-form surface model includes the steps of applying linear transformation to a lattice polygon model to generate vertices of a free-form surface model corresponding to respective vertices of the lattice polygon model, and generating control points of cubic Bezier curves that connect the vertices of the free-form surface model, and that correspond to respective edges of the lattice polygon model.

Abstract: A shaft member 1 and an outer peripheral member 2 disposed on the outer periphery of the shaft member 1 are joined together by splines 3 through which the teeth 31 of the shaft member 1 and the teeth 32 of the outer peripheral member 2 are fitted together. At one axial end of each spline 3, a trough 31 in the tooth 31 of the shaft member 1 is diametrically increased to provide a diametrically increased region S1. In this diametrically increased region S1, there is defined a fit region F for the tooth 31 of the shaft member 1 and the tooth 32 of the outer peripheral member 2.

Abstract: The power transmission shaft 12 is made by applying induction hardening to carbon steel with hardening ratio in a range from 0.25 to 0.50. For the carbon steel, one containing 0.39 to 0.49% of C, 0.4 to 1.5% of Si, 0.4 to 1.0% of Mn, 0.025% or less S, 0.02% or less P and 0.01 to 0.1% of Al by weight as the basic components, with the rest comprising Fe and inevitable impurities is used. This makes it possible to achieve higher strength and lighter weight of the power transmission shaft.

Abstract: A shaft member 1 and an outer peripheral member 2 disposed on the outer periphery of the shaft member 1 are joined together by splines 3 through which the teeth 31 of the shaft member 1 and the teeth 32 of the outer peripheral member 2 are fitted together. At one axial end of each spline 3, a trough 31 in the tooth 31 of the shaft member 1 is diametrically increased to provide a diametrically increased region S1. In this diametrically increased region S1, there is defined a fit region F for the tooth 31 of the shaft member 1 and the tooth 32 of the outer peripheral member 2.

Abstract: A power transmission shaft using the constant velocity joint is manufactured by applying induction hardening to graphite steel thereby to harden the surface layer and form a 2-phase structure of ferrite and martensite in the core thereof. The graphite steel contains 0.35 to 0.70% of C, 0.4 to 2.0% of Si, 0.3 to 1.5% of Mn, 0.025% or less S, 0.02% or less P, 0.01 to 0.1% of Al, 0.001 to 0.004% of B and 0.002 to 0.008% of N by weight as the basic components, with the rest comprising Fe and inevitable impurities.

Abstract: The power transmission shaft 12 is made by applying induction hardening to carbon steel with hardening ratio in a range from 0.25 to 0.50. For the carbon steel, one containing 0.39 to 0.49% of C, 0.4 to 1.5% of Si, 0.4 to 1.0% of Mn, 0.025% or less S, 0.02% or less P and 0.01 to 0.1% of Al by weight as the basic components, with the rest comprising Fe and inevitable impurities is used. This makes it possible to achieve higher strength and lighter weight of the power transmission shaft.

Abstract: The power transmission shaft 12 is made by applying induction hardening to carbon steel with hardening ratio in a range from 0.25 to 0.50. For the carbon steel, one containing 0.39 to 0.49% of C, 0.4 to 1.5% of Si, 0.4 to 1.0% of Mn, 0.025% or less S, 0.02% or less P and 0.01 to 0.1% of Al by weight as the basic components, with the rest comprising Fe and inevitable impurities is used. This makes it possible to achieve higher strength and lighter weight of the power transmission shaft.

Abstract: A hub unit includes an axle hub, a brake rotor, an axle bearing, and a constant velocity universal joint and transmits power of an engine of an automobile to drive wheels via a drive shaft. The axle hub takes the role as a bearing inner ring of the axle bearing and an outer joint member of the constant velocity universal joint. The axle hub, brake rotor, axel bearing, and constant velocity universal joint are compactly assembled. The ratio r2 (=Douter/PCDserr) between the outer diameter Douter of the axle hub (outer joint member) and the pitch circle diameter (PCDserr) of the tooth profile (serrations or splines) of the fitting portion of the inner joint member is set in a range of 2.5≦r2<3.2.

Abstract: A constant velocity universal joint is disclosed in which the end of a track groove 24 which opens to the open end surface 26 of the outer joint member 2 is formed with a cut portion 28a, 28b for the incorporation of a ball, thereby making the incorporation of balls possible without shifting the position of the open end surface 26. Therefore, the strength of the inlet portion of the outer joint member 2 is increased. Furthermore, since the ball incorporating angle .alpha. of the cage 5 can be decreased, it is possible to increase the width of the pocket column portion 58 of the cage 5 and increase the strength of the cage 5.

Abstract: A carburizing steel having the following chemical composition:C: 0.1 to 0.25%,Si: 0.2 to 0.4%,Mn: 0.3 to 0.9%,P: 0.02% or less,S: 0.001 to 0.15%,Cr: 0.5 to 0.9%,Mo: 0.15 to 1%,Al: 0.01 to 0.1%,B: 0.0005 to 0.009%,N: less than 0.006%, andthe balance of Fe and incidental impurities, wherein % is on a weight basis. Also disclosed are a method for the manufacture of the carburizing steel, parts of constant velocity universal joints for drive shafts made of the carburizing steel, as well as a method for the manufacture of such parts. The carburizing steel may further contain Ni: 0.3-4.0%, and one or more elements selected from the group consisting of Ti, Nb, V and Zr: 0.01-0.3% for each. The parts of constant velocity universal joints for drive shafts are manufactured using the carburizing steel of the present invention as a material. When they are carburized and quenched, they exhibit a surface hardness (Hv) of 650-800, core hardness (Hv) of 250-450, and carburized case depth of 0.2-1.2 mm.

Abstract: A carburizing steel having the following chemical composition:C: 0.1 to 0.25%,Si: 0.2 to 0.4%,Mn: 0.3 to 0.9%,P: 0.02% or less,S: 0.001 to 0.15%,Cr: 0.5 to 0.9%,Mo: 0.15 to 1%,Al: 0.01 to 0.1%,B: 0.0005 to 0.009%,N: less than 0.006%, andthe balance of Fe and incidental impurities, wherein % is on a weight basis. Also disclosed are a method for the manufacture of the carburizing steel, parts of constant velocity universal joints for drive shafts made of the carburizing steel, as well as a method for the manufacture of such parts. The carburizing steel may further contain Ni: 0.3-4.0%, and one or more elements selected from the group consisting of Ti, Nb, V and Zr: 0.01-0.3% for each.

Abstract: The present invention provides an outer ring for a high strength constant velocity joint which has an excellent torsional strength and torsional fatigue strength and can provide an improved processability, and a process for producing the same. An outer ring used for a high strength constant velocity joint having an involute serration part and a screw part, the outer ring made of a steel containing:C: 0.45 to 0.53%, Si: 0.05 to 0.25%, Mn: 0.7 to 1.0%, Al: 0.01 to 0.05%, Mo: 0.2 to 0.4%, N: 0.003 to 0.012%, the remainder being Fe and inevitable impurities, the inevitable impurities including:Cr: 0.05% or less than 0.05%, P: 0.015% or less than0.015%, S: 0.01% or less than 0.01%, and O: 0.002% orless than 0.002%,wherein an old austenite crystal grain at the involute serration end is 8 or more in JIS grain size classification; a surface hardness at the end is 720 or more in Hv; and a ratio (CD/R) is 0.35 to 0.