Needle roller bearing and its manufacturing method

A connecting rod assembly comprising:

• a laminated connecting rod laminated with plate-shaped connecting rod division parts having a large end part, a small end part and a rod part individually and connected to the adjacent connecting rod division part by engaging a connecting projection formed in said rod part by a pressing process with a recess formed on a back surface of the projection or with a through hole formed separately from said projection;
• and
• a shell type roller bearing having an outer ring, a plurality of needle rollers and a retainer for retaining the plurality of needle rollers, in which said outer ring is press fitted in a bearing engagement hole in a large end or a small end of said laminated connecting rod, wherein
• said retainer of said shell type roller bearing has a sectional configuration in which its center part in a width direction is recessed toward an inner diameter side with respect to its both ends,
• said retainer comprises a plurality of pockets provided in a circumferential direction, and pillar parts positioned between said adjacent pockets;
• and
• a part positioned on a pitch circle diameter along which the needle roller is arranged in an inner surface of said pocket in a longitudinal direction consists of a sheared surface in the vicinity of the center of said pillar part in the longitudinal direction and a fractured surface at root parts thereof,
• wherein said pillar part has a configuration in which its center part is recessed toward the inside in a diameter direction from its end parts connected to said annular parts, and
• wherein said sheared surface is positioned on the outside in the diameter direction of said end parts and said center part,
• said fractured surface being positioned on the inside in the diameter direction of said end parts and said center part, and
• a length in an axial direction of said sheared surface that is positioned on a pitch circle diameter and guides the needle roller is not less than 60% of a length in the axial direction of the needle roller.

A retainer of a needle roller bearing for retaining a plurality of needle rollers, comprising:

• a pair of annular parts and pillar parts connecting said pair of annular parts so as to form pockets in which said needle rollers are housed, wherein
• said pillar part has a configuration in which its center part is recessed toward the inside in a diameter direction, and
• a sidewall surface of said pillar part has a sheared surface punched by a punching blade so that said pockets are formed, on the outside in a diameter direction, and a fractured surface fractured by a material pressed by the punching blade, on the inside in the diameter direction,
• wherein said pillar part has a configuration in which its center part is recessed toward the inside in a diameter direction from its end parts connected to said annular parts, and
• wherein said sheared surface is positioned on the outside in the diameter direction of said end parts and said center part,
• said fractured surface being positioned on the inside in the diameter direction of said end parts and said center part, and
• a length in an axial direction of said sheared surface that is positioned on a pitch control diameter and guides the needle roller is not less than 60% of a length in the axial direction of the needle roller.