Abstract: A constant velocity universal unit includes an outer joint member whose inner peripheral face is formed with three guide grooves, an inner joint member including three tripod shafts each formed with a tripod spherical face, three roller units each including an outer peripheral face and an inner peripheral face coaxially formed with each other. The guide groove includes a pair of strip-shaped inner side faces formed with a pair of guide projections having a substantially half arc shape in cross section whose diameter is smaller than a height of the inner side face of the guide groove. The constant velocity universal joint further includes an annular recess formed on a substantially center portion in a height direction of the outer peripheral face of the roller unit and engaging with the pair of guide projections in a rolling manner and rotatable relative to a central axis of the guide projection.

Abstract: A power transmission shaft which can be evaluated on torsional fatigue strength based on a management indicator different from compressive residual stress in an outer surface. In a power transmission shaft having outer circumferential serrations 1a, 1b, torsional fatigue strength is evaluated by using compressive residual stress at a depth of 30 ?m (and 50 ?m) from an outer surface of a rising portion of each concave of the outer circumferential serrations 1a, 1b as a management indicator. A high torsional fatigue strength can be secured by having a compressive residual stress of 1150 MPa or more at a depth of 30 ?m (and 50 ?m) from the outer surface.

Abstract: A steel material for a high strength constant velocity joint intermediate shaft is provided. The steal material may preferably contain C: 0.46 to 0.52%, Si: 0.6 to 0.8%, Mn: 0.7 to 0.9%, S: 0.01 to 0.05%, Mo: 0.3 to 0.5%, B: 0.0005 to 0.005%, Al: 0.002 to 0.05%, and Ti: 0.02 to 0.09%, restricting N to 0.007% or less, Cr to 0.15% or less, and P to 0.02% or less. A structural percentage of bainite+martensite may be provided which is 40% or more. The steal material may have a hardness of 250 HV to 340 HV. A high strength constant velocity joint intermediate shaft made of that steel material may be provided which has a spline-vanishing part with a surface hardness of about 610 HV to 750 HV, and a ratio t/r of an effective hardened layer depth t and radius r of 0.35 to 0.55, having a flat part with a surface hardness of about 630 HV to 770 HV and a ratio t/r of 0.55 to 1.0, and having a core hardness of about 250 HV to 340 HV.

Abstract: In a tripod-type constant velocity joint having an inner joint member, an outer joint member, and three roller units, the radius R1, outer width W1, and inner width W2 of the outer periphery cylindrical surface of each roller unit, and the radius R3 of the center hole of each roller unit are determined to satisfy the following two inequalities: 0.5Rtc(1/cos0.3??1)+(R1?R3)?<W1 1.5Rtc(1?cos0.3?)+(R1?R3)?<W2 where Rtc: the radius of a circle passing through the respective centers of tripod spherical surfaces of the inner joint member, ?: the maximum joint angle between the outer joint member and the inner joint member, and ?: coefficient of friction between each tripod spherical surface and the wall surface of the center hole of the corresponding roller unit.

Abstract: A grease composition for use in ball type constant velocity joints, which comprises the following components a base oil; a diurea thickener of the formula: R1—NH—CO—NH—C6H4-p-CH2—C6H4-p-NH—CO—NHR2 wherein R1 and R2 are alkyl groups having 8 carbon atoms, molybdenum disulfide; molybdenum dithiocarbamate of the formula: (R3R4N—CS—S)2—Mo2OmSn wherein R3 and R4 independently represent an alkyl group having 1 to 24 carbon atoms, m is 0 to 3, n is 4 to 1 and m+n=4, calcium salts or overbasic calcium salts of petroleum sulfonates, sulfur-phosphorus extreme pressure agent, and castor oil. The grease composition exhibits excellent wear-resistance and pitting-inhibitory effect.

Abstract: A boot structure fitting into an axial component to protect from wrong environment including outside dust. Said boot has a pair of annular grooves and an annular lip between said pair of annular grooves on inner surface of said boot. Said annular lip is formed so that the annular lip top is not projected from inner surface to centerline of the boot. An annular protuberance means between said boot and clamping means, through which clamping force from said clamping means is exerted in concentration to said annular lip so that said annular lip is elastically deformed and pushed to outside of said axial component. Therefore, the axial component enables to be inserted into the boot without interference between the annular lip and the axial component. Furthermore, the annular lip becomes to be free from damage by interference between the annular lip and the axial component.