Abstract: Provided are a power transmission shaft (shaft) which can achieve cost reduction by reducing a raw material diameter, and thus reducing a material cost and a lathing cost, and an assembly unit using the power transmission shaft. The power transmission shaft includes: a male spline (31) provided at an end portion of the power transmission shaft; an engagement large diameter portion (37) for preventing the power transmission shaft from being pushed in an axial direction of the power transmission shaft under a state in which the male spline (31) is fitted to a female spline (45) of another member; and a boot groove (33) for mounting a boot. When an outer dimension of the engagement large diameter portion (37) is denoted by D2, a maximum outer dimension of the male spline (45) is denoted by D1, and an outer dimension of a boot mount portion (32) provided with the boot groove (33) is denoted by D4, relationships D2<D1 and D2=D4 are established.

Abstract: A light and compact slide-type constant velocity universal joint has a maximum operating angle of 30° or more through optimization of a ball contact angle relative to ball grooves, a ball contact ratio, and a cage offset amount. In the slide-type constant velocity universal joint, a ratio of ball diameter to outer ring outer diameter is 0.21 to 0.25, a ratio of ball pitch diameter to outer ring outer diameter is 0.64 to 0.68, a contact angle of the ball groove is 30° to 35°, a contact ratio of the ball groove is 1.02 to 1.08, and a ratio of cage offset amount to ball pitch diameter is 0.07 to 0.09.

Abstract: Provided is an outer joint member for a fixed type constant velocity universal joint, the outer joint member contributing to reduction of the number of man-hours through reduction of the number of post processes after a forging process, and to an increase in yield, and reduction of manufacturing cost. The outer joint member for a fixed type constant velocity universal joint includes a cup section (16) and a shaft section (18) extending in an axial direction from a bottom portion of the cup section (16). The outer joint member is made of machine-structural carbon steel. The following portions of the outer joint member are finished by cold forging: track grooves (12); radially inner spherical-surface portions (14a); a cup-inlet chamfer (12b); track chamfers (12c); track-inlet chamfers (12a); a part except for a boot fixing portion (19) on a radially outer surface of the cup section (16); and a center hole (13) at an end surface (18a) of the shaft section (18).

Abstract: Provided is a fixed type constant velocity universal joint, including: an outer joint member having an inner spherical surface provided with a plurality of track grooves extending in an axial direction; an inner joint member having an outer spherical surface provided with a plurality of track grooves extending in the axial direction in pairs with the plurality of track grooves of the outer joint member; a plurality of balls interposed between the plurality of track grooves of the outer joint member and the plurality of track grooves of the inner joint member so as to transmit torque; and a cage interposed between the inner spherical surface of the outer joint member and the outer spherical surface of the inner joint member so as to hold the plurality of balls, at least one of the plurality of track grooves of the outer joint member and the plurality of track grooves of the inner joint member being formed by cold-forging finishing, in which components including the outer joint member, the inner joint member, t

Abstract: Provided is a fixed type constant velocity universal joint which is capable of achieving the following even at the time of an unexpected high-angle operation, in particular, even when an angle expected during use of a constant velocity universal joint is exceeded: reduction of stress generated when balls and edge portions interfere with each other, suppression of chipping of the edge portions, and prolongation of a service life of the joint as a whole.

Abstract: Provided is a fixed type constant velocity universal joint capable of securing smooth rotation and reducing a load on a cage even at a large operating angle and at a time of bearing large torque.

Abstract: An inner ring is configured to simultaneously ensure the strength thereof and the dimensional accuracy of a female spline portion of a shaft hole thereof in the case where the female spline portion is subjected to heat treatment. Also it is configured to suppress the backlash of spline fit with a shaft. The inner ring is mounted in a constant velocity universal joint for transmitting torque while the inner ring is allowed to be angularly displaced relative to an outer ring and is spline-fitted to a shaft inserted into a shaft hole formed through the inner ring. The inner ring has a hardened layer by means of heat treatment which is formed only in an axial central portion of the shaft hole, but is not formed in remaining inner diameter surface other than the axial central portion.

Abstract: The present invention provides a constant velocity universal joint having a recess-projection engagement configuration in which backlash at a shaft connecting region does not easily occur, and an inner joint component and a shaft can be firmly connected. In the constant velocity universal joint of the present invention, the inner joint component and the shaft 5 fitted into an axis hole 22 of the inner joint component are connected by the recess-projection engagement configuration. Engagement contacting regions 38 of projections 35 and recesses 36 corresponding thereto are in close contact over the whole region.

Abstract: The present invention provides a light and compact slide-type constant velocity universal joint that can have a maximum operating angle of 30° or more through optimization of a ball contact angle relative to ball grooves, a ball contact ratio, and a cage offset amount.

Abstract: A technique for improving a strength, especially a fatigue strength of a power transmission shaft provided with a serrated portion for torque transmission such as a spline shaft. A power transmission shaft is serration-fitted to an inner joint member of respective constant velocity joints. A driveshaft is provided with a serrated portion as well as a smooth portion having a cylindrical outer circumferential surface. A cut-up portion is formed at the end portion of the serrated portion. When applying an induction hardening to the smooth portion and the serrated portion, a hardening ratio of the smooth portion is set at a different value from that of the serrated portion, and such that a fatigue strength of the smooth portion becomes equal to or greater than that of the serrated portion.

Abstract: An inner ring is configured to simultaneously ensure the strength thereof and the dimensional accuracy of a female spline portion of a shaft hole thereof in the case where the female spline portion is subjected to heat treatment. Also it is configured to suppress the backlash of spline fit with a shaft. The inner ring is mounted in a constant velocity universal joint for transmitting torque while the inner ring is allowed to be angularly displaced relative to an outer ring and is spline-fitted to a shaft inserted into a shaft hole formed through the inner ring. The inner ring has a hardened layer by means of heat treatment which is formed only in an axial central portion of the shaft hole, but is not formed in remaining inner diameter surface other than the axial central portion.

Abstract: An integral hollow type power transmission shaft is proposed which is superior in the balance between the static strength and the fatigue strength. The integral hollow type shaft is induction-hardened from the outer periphery to form a hardened layer, leaving an unhardened layer at spline portions, so that at the spline portions, the hardness on the inner surface will be lower than at other portions. This increases the toughness and compressive residual stress of the shaft at the spline portions, which tend to be starting points of fatigue cracks, thus improving the balance between the static strength and the fatigue strength.

Abstract: An object of the present invention is to provide a technique for improving a strength, especially a fatigue strength of a power transmission shaft provided with a serrated portion for torque transmission such as a spline shaft. A power transmission shaft is serration-fitted to an inner joint member of respective constant velocity joints. A drive shaft is provided with a serrated portion as well as a smooth portion having a cylindrical outer circumferential surface. A cut-up portion is formed at the end portion of the serrated portion. When applying an induction hardening to the smooth portion and the serrated portion, a hardening ratio of the smooth portion is set at a different value from that of the serrated portion, and such that a fatigue strength of the smooth portion becomes equal to or greater than that of the serrated portion.

Abstract: An integral hollow type power transmission shaft is proposed which is superior in the balance between the static strength and the fatigue strength. The integral hollow type shaft is induction-hardened from the outer periphery to form a hardened layer, leaving unhardened layer at spline portions, so that at the spline portions, the hardness on the inner surface will be lower than at other portions. This increases the toughness and compressive residual stress of the shaft at the spline portions, which tend to be starting points of fatigue cracks, thus improving the balance between the static strength and the fatigue strength.