Cage structure of roller bearing

Abstract: A cage of a roller bearing including a plurality of pockets (2), formed by punching from the outside, each storing a roller (8), in the circumferential direction of a barrel comprises a first projection for preventing the roller from being disassembled to the outside of the barrel and a second projection (10) for preventing the roller (8) from being disassembled to the inside of the barrel. The first projection (7) is provided at a thin portion of the barrel which is formed between the brims of the pocket (2). The second projection (10) is provided at a thick portion of the barrel in the axial direction by knurling.

Description: 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. DE-C-1 001 550 shows a cage for a roller bearing comprising a plurality of pockets, each for storing a roller, in the circumferential direction of a cylindrical shaped barrel, an annular internal circumferential groove formed at the axial direction center of the cage, a plurality of bars between adjacent pockets comprising thick portions and a thin portion formed by said groove provided at a central and radially outermost location of said bars, first projections for preventing the roller from being disassembled to the outside of the barrel, said first projection being provided at a thin portion of the barrel which is positioned beside the brim of the pocket, and second projections, for preventing the roller from being disassembled to the inside of the barrel, whereby said second projections are oppositely disposed in the circumferentially direction at a radially innermost location of said thick portion, the distance between said oppositely disposed projections of an opening therebetween being smaller than a diameter of said roller. Such a cage is produced in many processing steps and leads to high manufacturing costs. FIG. 8 shows a conventional cage B of a roller bearing comprising a plurality of rollers. Annular circumferential grooves B₁ are formed at the center of the cage B manufactured by machining a pipe or a bar. Several roller-storage pockets B₂ are punched out. The punched-out pockets B₂ are broached and then inner faces B₃ of the pockets B₂ and inner sides of separating portions B₄ 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 B₆ inwardly projected to the pockets B₂ are disposed at a thin portion B₅ in the axial middle of the separating portion B₄. Further, small projections B₈ inwardly projected to the pockets B₂ are formed at a thick portion B₇ of the separating portion B₄ by knurling. There is the following disadvantage in the conventional cage of FIG. 8, though. In the inner faces B₃ of the punched pocket B₂, a sheared face whose surface 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 whose surface is generally rough is formed. That is, according to the construction of the cage B for a roller bearing, the projections B₆ provided at the thin portion B₅ 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 B₆ become rougher than those of the sheared face. High accuracy could not be expected of a clearance ℓ₂ between the opposing projections B₆ within the pocket. Therefore, the faces of the projections B₆ formed by breaking must be smoothly finished. For this purpose, many processing steps are needed for forming the roller-storage pocket B₂, resulting in high working cost and poor mass-production. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved cage structure for a roller bearing ensuring the face accuracy of projections for preventing rollers from being disassembled and the accuracy of a clearance between the projections, with simplified manufacturing steps. In order to accomplish the aforementioned object, a cage for a roller bearing, according to the present invention, is characterized in that the pockets are formed by punching from the outside, the second projections are formed by knurling, the roller guide surfaces of each of said bars having sheared surfaces at a radially outer side and broken surfaces at a radially inner side and the sheared surfaces includes at least the projection of the thin portion. BRIEF DECRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative to the present invention and wherein: FIG. 1 is a cross-sectional view of the essential parts of a cage of a roller bearing according to a preferred embodiment of the present invention; FIG. 2 is a partial sectional view of the cage storing a roller; FIG. 3 is a perspective view of the cage of the roller bearing; FIG. 4 is a perspective view of a punch for forming a pocket in the cage; FIG. 5 is a shematic illustration of the inner surface of the pocket after punching; FIG. 6 is a cross sectional view of an opening brim at the outer side of the pocket before a bur is removed; FIG. 7 is a cross sectional view of an opening brim at the outer side of the pocket after a bur is removed; and FIG. 8 is a cross sectional view of the conventional cage of a roller bearing. DESCRIPTION OF THE PREFERRED EMBODIMENT FIGs.1 through 5 show a cage of a roller bearing according to a preferred embodiment of the present invention. Referring to these drawings, a cage 1 of a roller bearing comprises a pocket 2 for storing a roller 8, an annular internal circumferential groove 3 having a certain width formed at the axial-directional center of the cage 1, and a bar 4 between the adjacent pockets 2. The radial-directional width of the bar 4 at the axial-directional center corresponding to the position of the internal circumferential groove 3 is thinner than the remaining portions of the bar 4. The thin portion is designated by numeral 5 while a thick portion at both sides beside the thin portion 5 is designated by numeral 6. A projection 7 is provided on the thin portion 5. The projection 7 projects slightly inwardly to the inner side of the pocket 2, from the side of the thick portion 6 at the bar 4. The projection 7 functions to prevent the roller 8 from being disassembled to the outside of the radial-direction. A streaky concavity 9 is provided along the circumferential side at the inner side of the thick portion 6. Another projection 10 is provided at the opening edge of the streaky concavity 9. The projection 10 projects slightly inwardly to the inner side of the pocket 2, from the side of the bar 4. The streaky concavity 9 and the projection 10 both are formed by knurling. The projection 10 functions to prevent the roller 8 from being disassembled to the inner side of the radial-direction. About one third of the outer portion of the side face of the thick portion 6 at the bar 4 and the side face of the projection 10 at the thin portion 5, at the inner side of the pocket 2, are formed by shearing, whereas, the remaining about two thirds at the inner portion are formed by breaking. A surface formed by shearing is designated by numeral 11 while another surface formed by breaking is designated by 12 ( In FIG.1, it is shown in spots.). The surface 12 formed by breaking is not so smooth as the surface 11 formed by shearing. The surface 12 formed by breaking is rather rough so that it is easier to keep a lubricant within the bearing. To make the pockets 2 in the cage 1 of the roller bearing, a puncher as shown in FIG.4 is used. The pockets 2 are formed by punching some circumferential portions of a cylindrical mother material forming the inner circumferential groove, from the outer radial-directional side to the inner radial-directional side as designated by an arrow in FIG.4, so that a plurality of pockets 2 are formed. Referring in detail to the inner face of the punched pocket 2, there are provided in turn a start edge 13 at the opening edge of the outer side of the pocket 2, the sheared face 11 at about one third of the radial-directional thickness by a point 21 of a sword of the puncher 20, the broken face 12 at about two-thirds of the radial-directional thickness, and finally a rear edge 14 at the opening edge of the inner side of the pocket 2, as shown in FIG. 5. The arrangement of the cage 1 of the roller bearing according to the present invention is determined as described above in view of the conditions of the punched surface formed by punching. That is, the projection 7 is provided in the cage 1 of the roller bearing of the present invention for preventing the rollers from being disassembled outwardly in the radial direction. The projection 7 is disposed at the outer side from the sheared face formed by punching, resulting that the face condition of the projection 7 is smooth, and any finishing operations for its face as required in the conventional case are eliminated. Therefore, according to the preferred embodiment of the present invention, fewer processing steps are enough to make the pocket 2 than in the conventional case. Nevertheless, the surface accuracy of the projection 7 at the pocket 2 and the required accuracy of a gap ℓ₁ between the projections 7 can be stably acquired. Since the face 12 formed by breaking during punching can function to keep a lubricant within the bearing, supply of a lubricant to the sliding portions during high speed rotation of the roller bearing can become less than in the conventional cage structure. When the puncher 20 is removed after punching the pocket 2, normally, the start edge 13 formed at the outer opening edge of the pocket 2 may be projected to the outside by the puncher 20, resulting a burr 13a, as shown in FIG.6. The burr 13a can be removed by normal burr-removing operation. According to the present invention, to remove the burr 13a, the outer face of the bar 4 is finished to be round in the circumferential direction as shown in FIG.7. As compared with the conventional case in which the burr 13a is simply removed, the cage 1 of the roller bearing having the bar 4 in this shape of FIG.7 can reduce torque loss of the cage 1 during rotation because the edge at the opening of the pocket 2 does not take off the lubricant so much. As described above, in accordance with the present invention, pockets for storing rollers are punched by a puncher. At the inner side of the pocket, there is provided the outer portions inclusive of the thin portion, preferably, the thick portion at both sides of the thin portion, the outer portions being sheared by the point of the sword of the punch, while the inner portions are broken, successive to the outer portions, by the same point. Since the outer portions inclusive of the thin portion at the inner face of the pocket are formed by shearing, the projection for preventing the roller from being disassembled does not need to be finished, the projection being provided at the thin portion. The projection is enough smooth as such. In addition, the accuracy of the gap between the adjacent projections can be assured. While the inner portions broken by the puncher remain, the rough surface of the inner portions can keep a lubricant within the bearing. This can contribute to extend the cycle of the supplying a lubricant to sliding portions, in particular, during high-speed rotation of the bearing.

Claims: A cage (1) for a roller bearing comprising a plurality of pockets (2), each for storing a roller (8), in the circumferential direction of a cylindrical shaped barrel; an annular internal circumferential groove (3) formed at the axial direction center of the cage; a plurality of bars (4) between adjacent pockets comprising thick portions and a thin portion (5), formed by said groove (3) provided at a central and radially outermost location of said bars (4); first projections (7) for preventing the roller from being disassembled to the outside of the barrel, said first projection (7) being provided at a thin portion of the barrel which is positioned beside the brim of the pocket (2); and second projections (10), for preventing the roller from being disassembled to the inside of the barrel, whereby said second projections (10) are oppositely disposed in the circumferentially direction at a radially innermost location of said thick portion, the distance between said oppositely disposed projections (10) of an opening therebetween being smaller than a diameter of said roller (8); characterized in that the pockets (2) are formed by punching from the outside, the second projections (10) are formed by knurling, the roller guide surfaces of each of said bars (4) having sheared surfaces (11) at a radially outer side and broken surfaces (12) at a radially inner side and the sheared surfaces (11) includes at least the projection (7) of the thin portion.

Inventors: KITAUCHI FUKUMITSU, MIYAWAKI NOBUYUKI, MOTOHASHI NOBUTSUNA, KITAUCHI, FUKUMITSU, MIYAWAKI, NOBUYUKI, MOTOHASHI, NOBUTSUNA
Applicants: KOYO SEIKO CO, KOYO SEIKO CO., LTD.
Application year: 1989
Main classification: F16C33
IPC codes: F16C33