Abstract: A drive shaft includes a first annular wall and a second annular wall joined together via a friction-welded portion. The first annular wall and the second annular wall have outer diameters of 30 to 50 mm and wall thicknesses of 3 to 5 mm. A burr created at the friction-welded portion has a connection radius of greater than or equal to 0.5 mm, a base radius of greater than or equal to 0.5 mm, a burr base angle of less than or equal to 40°, and a burr slope length of 0.2 to 5 mm.

Abstract: A rotational driving force transmission mechanism includes a cylindrical shaft made of fiber reinforced plastic, and a first constant velocity joint. The shaft is joined to the first constant velocity joint via a metallic intervening member which is attached to one end of the shaft in the axial direction. The intervening member includes a shaft portion and a main body portion. The shaft portion is inserted into the one end of the shaft from a distal end side thereof. The main body portion is of a bottomed tubular shape made up from a bottom part joined to a proximal end side of the shaft portion, and a tubular portion fitted over the one end of the shaft. The first constant velocity joint includes an inner ring fitted externally over the tubular portion of the intervening member.

Abstract: A drive shaft includes a first annular wall and a second annular wall joined together via a friction-welded portion. The first annular wall and the second annular wall have outer diameters of 30 to 50 mm and wall thicknesses of 3 to 5 mm. A burr created at the friction-welded portion has a connection radius of greater than or equal to 0.5 mm, a base radius of greater than or equal to 0.5 mm, a burr base angle of less than or equal to 40°, and a burr slope length of 0.2 to 5 mm.

Abstract: A drive shaft is configured by joining solid stub shafts formed of a medium carbon steel to both ends of a hollow tubular body formed of a medium carbon steel. When expressed as grain size number, the grain size of the hollow tubular body at joint parts where the hollow tubular body and the solid stub shafts are joined together ranges from #5 to #9, and the grain size of the solid stub shafts at the joint parts ranges from #10 to #12.

Abstract: A drive shaft is configured by joining solid stub shafts formed of a medium carbon steel to both ends of a hollow tubular body formed of a medium carbon steel. When expressed as grain size number, the grain size of the hollow tubular body at joint parts where the hollow tubular body and the solid stub shafts are joined together ranges from #5 to #9, and the grain size of the solid stub shafts at the joint parts ranges from #10 to #12.

Abstract: A first constant velocity joint is equipped with a cup part made of a light alloy. First ball grooves that receive a torque from torque transmitting members are formed on an inner wall of the cup part. A high hardness layer made of ceramic or cermet as a principal component thereof is formed on an inner surface of the cup part including at least inner surfaces of the first ball grooves.

Abstract: A drive shaft includes a first shaft member made of metal, a tubular member made of CFRP, and a first exterior sleeve. The first shaft member is capable of being attached on one end side thereof to a first constant velocity joint, and has a first serrated part on which serrations are formed on another end side thereof. The tubular member is formed with a first fitting part fitted externally over the first serrated part. The first exterior sleeve covers the first fitting part by being disposed to extend over outer circumferential surfaces of the first shaft member and the tubular member. A film provided with a bonding assistance region and an adhesive are interposed between the outer circumferential surface of the tubular member and the inner circumferential surface of the first exterior sleeve.

Abstract: A rotational driving force transmission mechanism includes a cylindrical shaft made of fiber reinforced plastic, and a first constant velocity joint. The shaft is joined to the first constant velocity joint via a metallic intervening member which is attached to one end of the shaft in the axial direction. The intervening member includes a shaft portion and a main body portion. The shaft portion is inserted into the one end of the shaft from a distal end side thereof. The main body portion is of a bottomed tubular shape made up from a bottom part joined to a proximal end side of the shaft portion, and a tubular portion fitted over the one end of the shaft. The first constant velocity joint includes an inner ring fitted externally over the tubular portion of the intervening member.

Abstract: A drive shaft includes a first shaft member made of metal, a tubular member made of CFRP, and a first exterior sleeve. The first shaft member is capable of being attached on one end side thereof to a first constant velocity joint, and has a first serrated part on which serrations are formed on another end side thereof. The tubular member is formed with a first fitting part fitted externally over the first serrated part. The first exterior sleeve covers the first fitting part by being disposed to extend over outer circumferential surfaces of the first shaft member and the tubular member. A film provided with a bonding assistance region and an adhesive are interposed between the outer circumferential surface of the tubular member and the inner circumferential surface of the first exterior sleeve.

Abstract: A first constant velocity joint is equipped with a cup part made of a light alloy. First ball grooves that receive a torque from torque transmitting members are formed on an inner wall of the cup part. A high hardness layer made of ceramic or cermet as a principal component thereof is formed on an inner surface of the cup part including at least inner surfaces of the first ball grooves.

Abstract: Disclosed is an efficient heat treatment method which can be performed in a short time. Specifically disclosed is a method for heat-treating a steel material wherein a plastically deformed steel work is introduced into a heat treatment furnace when the work still retains the heat applied thereto during the plastic deformation, then the work is heated preferably at a heating rate of 15-50 DEG C./min and held at a temperature between Ac1 and Ac3 for 10 minutes or less, and then the work is slowly cooled at a cooling rate of 5-45 DEG C./min. This heat treatment method enables to easily produce a steel material having a uniform metal structure by simple facilities.

Abstract: Disclosed is an efficient heat treatment method which can be performed in a short time. Specifically disclosed is a method for heat-treating a steel material wherein a plastically deformed steel work is introduced into a heat treatment furnace when the work still retains the heat applied thereto during the plastic deformation, then the work is heated preferably at a heating rate of 15-50 DEG C./min and held at a temperature between Ac1 and Ac3 for 10 minutes or less, and then the work is slowly cooled at a cooling rate of 5-45 DEG C./min. This heat treatment method enables to easily produce a steel material having a uniform metal structure by simple facilities.

Abstract: A method of manufacturing a billet for cold forging according to the present invention is characterized by the first spheroidizing annealing step of spheroidizing a carbide in a blank, the drawing step of drawing the blank at a predetermined sectional area reduction ratio after the first spheroidizing annealing step, and the second spheroidizing annealing step of promoting the dispersion of the internal carbide for an increased spheroidizing ratio after the drawing step. The drawing step has a drawing ratio of approximately 20%. The blank is cut to a desired dimension between said first spheroidizing annealing step and said second spheroidizing annealing step.

Abstract: A method of manufacturing a billet for cold forging according to the present invention is characterized by the first spheroidizing annealing step of spheroidizing a carbide in a blank, the drawing step of drawing the blank at a predetermined sectional area reduction ratio after the first spheroidizing annealing step, and the second spheroidizing annealing step of promoting the dispersion of the internal carbide for an increased spheroidizing ratio after the drawing step. The drawing step has a drawing ratio of approximately 20%. The blank is cut to a desired dimension between said first spheroidizing annealing step and said second spheroidizing annealing step.

Abstract: A method of manufacturing a billet for cold forging according to the present invention is characterized by the first spheroidizing annealing step of spheroidizing a carbide in a blank, the drawing step of drawing the blank at a predetermined sectional area reduction ratio after the first spheroidizing annealing step, and the second spheroidizing annealing step of promoting the dispersion of the internal carbide for an increased spheroidizing ratio after the drawing step. The drawing step has a drawing ratio of approximately 20%. The blank is cut to a desired dimension between said first spheroidizing annealing step and said second spheroidizing annealing step.