The present invention relates to a cage for a roller bearing and, more particularly, to a cage for a needle roller bearing which is suitable for an internal combustion engine.
FIG. 8 shows a conventional cage B of a roller bearing comprising a plurality of rollers. Annular circumferential grooves B.sub.1 are formed at the center of the cage B manufactured by machining a pipe or a bar. Several roller-storage pockets B.sub.2 are punched out. The punched-out pockets B.sub.2 are broached and then inner faces B.sub.3 of the pockets B.sub.2 and inner sides of separating portions B.sub.4 are finished. In the above-described cage B of FIG. 8, to facilitate its assembling operation, the cage B has such a structure that the rollers aren't disassembled when being handled. Projections B.sub.6 inwardly projected to the pockets B.sub.2 are disposed at a thin portion B.sub.5 in the axial middle of the separating portion B.sub.4. Further, small projections B.sub.8 inwardly projected to the pockets B.sub.2 are formed at a thick portion B.sub.7 of the separating portion B.sub.4 by knurling.
There is, however the following disadvantage in the conventional cage B of FIG. 8. In the inner faces B.sub.3 of the punched pocket B.sub.2, a sheared face the surface of which is generally smooth is formed and, successively, in the direction of punching, namely, from the radial outer side to the radial inner side and, successively, a breaking face the surface of which is generally rough is formed. That is, according to the construction of the cage B for a roller bearing, the projections B.sub.6 provided at the thin portion B.sub.5 for preventing the rollers from being disassembled in the inner radial direction are formed by breaking during punching. Accordingly, the face conditions of the projections B.sub.6 become rougher than those of the sheared face. High accuracy can not be expected of a clearance l.sub.2 between the opposing projections B.sub.6 within the pocket.
Therefore, the faces of the projections B.sub.6 formed by breaking must be smoothly finished. For this purpose, many processing steps are needed for forming the roller-storage pocket B.sub.2, resulting in high working cost and poor mass-production.