Cages and ball bearings

Abstract

The present invention provides a cage and ball bearing that can suppress the reduction in fatigue strength due to residual tensile stress caused by crimping, and the reduction in rigidity due to interference between the cage and the raceway. [Solution] The device comprises a first annular member 10 in which hemispherical first pockets 8 and first flat portions 9 are alternately formed, a second annular member 13 in which hemispherical second pockets 11 and second flat portions 12 are alternately formed, and a rivet 16 that joins the first annular member 10 and the second annular member 13 by crimping, wherein the rivet 16 has a cylindrical rivet shaft 17, a base head 18 formed on one end of the rivet shaft 17, and a finial head 19 formed on the other end of the rivet shaft 17, and the area of ​​the first flat portion 9 and the second flat portion 12 is S, and the area of ​​the orthogonal projection of the base head 18 onto a plane having a normal common to the axis of the rivet shaft 17 is S φRD When the maximum circumferential width of the first flat section 9 and the second flat section 12 is h, and the diameter of the base head 18 is φRD, then 60% ≤ S φRD The configuration is such that the relationship / S and φRD / h < 100% holds true.

Description

[Technical Field]

[0001] This invention relates to a cage and a ball bearing employing this cage. [Background technology]

[0002] Ball bearings are widely used as bearings to support rotating shafts in automobiles and industrial machinery. A ball bearing consists of an inner ring, an outer ring coaxially mounted radially outside the inner ring, a plurality of balls assembled between the inner and outer rings, and a cage that holds these balls.

[0003] As a retainer, considering the balance between cost and productivity, corrugated iron plate retainers, which are press-formed from rolled steel sheets such as cold-rolled steel sheets (SPCC), are commonly used. The corrugated iron plate retainer has a first annular member in which hemispherical first pockets and first flat sections are alternately formed at predetermined intervals along the circumferential direction, a second annular member positioned axially opposite the first annular member in which hemispherical second pockets and second flat sections are alternately formed at predetermined intervals along the circumferential direction, and rivets that are inserted from a first rivet hole formed in the first flat section toward a second rivet hole formed in the second flat section, connecting the first annular member and the second annular member.

[0004] The rivet has a cylindrical rivet shaft, a pre-formed base head at one end of the rivet shaft, and a ferrule head formed by crimping the other end of the rivet shaft. The rivet shaft is inserted from the first rivet hole to the second rivet hole with the first flat portion and the second flat portion overlapping in the axial direction. The base head and the ferrule head are positioned to sandwich the first flat portion and the second flat portion in the axial direction, with the base head locking the first flat portion in the axial direction and the ferrule head locking the second flat portion in the axial direction.

[0005] The rolled steel sheets that constitute the above-mentioned cage (first annular member, second annular member) have relatively low hardness and wear resistance. As the environment surrounding the bearing (load conditions, lubrication conditions, etc.) becomes more severe year by year, depending on the operating conditions, malfunctions may occur due to wear on the inner surface of the pocket. For example, Patent Document 1 below discloses a technique for forming a nitrided layer (e.g., an isonite treated layer) on the surface of the cage by soft nitriding treatment in order to improve the hardness and wear resistance of the cage. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6098720 [Overview of the project] [Problems that the invention aims to solve]

[0007] The above-described soft nitriding treatment is generally performed on the rivets attached to the first and second annular members, after first press-fitting rivets into the first rivet holes formed in the first flat portion of the first annular member. As a result, the masking effect of the rivet shafts of the rivets pre-press-fitted into the first rivet holes results in a lower surface hardness on the inner surface of the first rivet hole than on the inner surface of the second rivet hole.

[0008] In the manufacture of the corrugated steel plate holder described above, tensile residual stress is generated on the inner surface of the rivet hole due to the expansion of the rivet shaft during crimping. However, because the surface hardness of the inner surface of the first rivet hole is relatively low, there is a problem in that the fatigue strength decreases, particularly on the inner surface of the first rivet hole, due to residual stress. To improve fatigue strength (reduce tensile residual stress), it is conceivable to increase the diameter of the rivet head to reduce the tensile residual stress generated during crimping. However, if the diameter of the head is increased too much, the head and the R portion at the circumferential end of the pocket formed in the holder may interfere with each other, potentially causing a decrease in the rigidity of the holder due to insufficient contact between the first and second annular members.

[0009] Therefore, the object of the present invention is to provide a cage that achieves both high fatigue strength and rigidity, and a ball bearing employing the cage. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides: A first annular member having alternating hemispherical first pockets and first flat portions formed at predetermined intervals along the circumferential direction, A second annular member is positioned opposite the first annular member in the axial direction, and has alternating hemispherical second pockets and second flat portions formed at predetermined intervals along the circumferential direction, A rivet is inserted from a first rivet hole formed in the first flat portion toward a second rivet hole formed in the second flat portion, and fastens the first annular member and the second annular member together. The rivet has a cylindrical rivet shaft, a pre-formed base head on one end of the rivet shaft, and a finished head formed by crimping the other end of the rivet shaft. The area of ​​the first flat portion and the second flat portion is S, and the area of ​​the orthogonal projection of the principal head onto a plane having a normal common to the axis of the rivet shaft is S. φRD When the maximum circumferential width of the first flat portion and the second flat portion is h, and the diameter of the original head is φRD, then 60% ≤ S φRD A retainer was constructed in which the relationship / S and φRD / h < 100% was satisfied (first configuration).

[0011] This method suppresses the decrease in fatigue strength due to residual tensile stress associated with crimping, and also suppresses problems caused by a decrease in the rigidity of the retainer.

[0012] In the first configuration, nitrided layers are respectively formed on the surfaces of the first annular member and the second annular member, and on the inner surfaces of the first rivet hole and the second rivet hole, and a configuration (second configuration) can be adopted in which the surface hardness of the inner surface of the first rivet hole is lower than the surface hardness of the inner surface of the second rivet hole. Depending on the procedure of the soft nitriding treatment, as described above, the surface hardness of the inner surface of the first rivet hole may be relatively low; particularly in such cases, the configuration according to the present invention effectively acts to suppress a decrease in fatigue strength and suppress defects caused by interference between the cage and the race ring.

[0013] In the first configuration and the second configuration, a configuration (third configuration) having a smooth surface formed by removing irregularities of a fracture surface generated when forming the first rivet hole and the second rivet hole can be adopted. With this configuration, it is possible to suppress a decrease in the strength of the cage caused by concentration of tensile residual stress on the irregularities of the fracture surface.

[0014] Furthermore, the cage according to any one of the first to third configurations is can be employed in a ball bearing comprising: the inner ring; the outer ring provided coaxially on the radially outer side of the inner ring; a plurality of balls incorporated between the inner ring and the outer ring; and the cage according to any one of claims 1 to 3, which holds the balls (fourth configuration). Effects of the Invention

[0015] According to the cage of the present invention and the ball bearing employing this cage, it is possible to suppress a decrease in fatigue strength caused by tensile residual stress associated with caulking, and also suppress a decrease in cage rigidity caused by insufficient adhesion between the first annular member and the second annular member. Brief Description of the Drawings

[0016] [Figure 1] Front view showing an embodiment of the ball bearing according to the present invention [Figure 2] Cross-sectional view taken along line II-II in Fig. 1 [Figure 3] Front view showing a cage used in the ball bearing shown in Fig. 1 [Figure 4] Cross-sectional view along line IV-IV in Figure 3 [Figure 5A] Cross-sectional view showing a rivet inserted through the first rivet hole formed in the first flat portion of the first annular member. [Figure 5B] Cross-sectional view showing a rivet inserted through the second rivet hole formed in the second flat portion of the second annular member. [Figure 5C] Cross-sectional view showing the state after the rivet has been crimped and the head has been formed. [Figure 6] Cross-sectional view showing the first and second annular members on which the nitrided layer is formed. [Figure 7] Front view of the main part of the retainer according to the present invention [Figure 8] Cross-sectional view along line VIII-VIII in Figure 7 [Figure 9A] A cross-sectional view showing the first example of the retainer shown in Figure 8. [Figure 9B] A cross-sectional view showing a second example of the retainer shown in Figure 8. [Modes for carrying out the invention]

[0017] An embodiment of the ball bearing 1 according to the present invention will be described with reference to the drawings. As shown in Figures 1 and 2, the ball bearing 1 includes an inner ring 2, an outer ring 3 coaxially provided on the radially outer side of the inner ring 2, a plurality of balls 4 incorporated between the inner ring 2 and the outer ring 3, and a corrugated iron plate retainer (hereinafter abbreviated as retainer 5) shown in Figures 3 and 4 that holds the plurality of balls 4 at predetermined intervals in the circumferential direction. Hereinafter, the direction along the rotation axis of the ball bearing 1 will be referred to as the axial direction, the direction perpendicular to the rotation axis will be referred to as the radial direction, and the direction along the circumference that completes one revolution around the rotation axis will be referred to as the circumferential direction.

[0018] An inner ring raceway groove 6 is formed on the outer diameter surface of the inner ring 2, and an outer ring raceway groove 7 is formed on the inner diameter surface of the outer ring 3, and the balls 4 roll along both raceway grooves 6 and 7. The inner ring 2, outer ring 3, and balls 4 are made of high-carbon chromium bearing steel such as SUJ2. In the following, the inner ring 2 and outer ring 3 may be referred to as raceway rings 2 and 3.

[0019] As shown in Figure 5C, the retainer 5 includes a first annular member 10 in which hemispherical first pockets 8 and first flat portions 9 are alternately formed at predetermined intervals along the circumferential direction, a second annular member 13 positioned axially opposite to the first annular member 10 in which hemispherical second pockets 11 and second flat portions 12 are alternately formed at predetermined intervals along the circumferential direction, and a rivet 16 inserted from a first rivet hole 14 formed in the first flat portion 9 toward a second rivet hole 15 formed in the second flat portion 12, which connects the first annular member 10 and the second annular member 13 by crimping.

[0020] The first annular member 10 and the second annular member 13 are made from pressed strip steel formed from one of the following materials: carbon steel for machine structures (SC material, S45C, etc.), carbon steel for cold heading (SPCC, etc.), or stainless steel. The first rivet hole 14 and the second rivet hole 15 are formed by punching (piercing) using a punch. The wall thickness of each pocket 8 and 11 formed in each annular member 10 and 13 is approximately the same as the wall thickness of each flat section 9 and 12. In addition, various resins such as polyamide resin, polyetheretherketone resin, and polyphenylene sulfide resin may be used as the material for the retainer 5.

[0021] The rivet 16 has a cylindrical rivet shaft 17, a pre-formed base head 18 on one end of the rivet shaft 17, and a finial head 19 formed by crimping the other end of the rivet shaft 17. The rivet shaft 17 is inserted from the first rivet hole 14 toward the second rivet hole 15 with the first flat portion 9 and the second flat portion 12 overlapping in the axial direction. The base head 18 and the finial head 19 are positioned to sandwich the first flat portion 9 and the second flat portion 12 in the axial direction, with the base head 18 locking the first flat portion 9 in the axial direction and the finial head 19 locking the second flat portion 12 in the axial direction. The finial head 19 is formed in a hemispherical shape with a larger diameter than the rivet shaft 17. The rivet 16 is made from wire rod of either machine structural carbon steel, cold-rolled carbon steel, or stainless steel.

[0022] The above-described retainer 5 can be manufactured by the following procedure. First, by press working the steel strip, a first annular member 10 is formed, in which hemispherical first pockets 8 and first flat portions 9 are alternately formed at predetermined intervals along the circumferential direction, as shown in Figure 5A, and a second annular member 13 is formed, in which hemispherical second pockets 11 and second flat portions 12 are alternately formed at predetermined intervals along the circumferential direction. Next, by punching using a punch, a first rivet hole 14 is formed in the first flat portion 9 of the first annular member 10 and a second rivet hole 15 is formed in the second flat portion 12 of the second annular member 13. At this time, the punching is performed from the side opposite to the mating surface between the first flat portion 9 and the second flat portion 12 toward the mating surface.

[0023] Furthermore, as shown in Figure 5A, a rivet 16 is press-fitted into the first rivet hole 14 formed in the first flat portion 9 of the first annular member 10. At this time, the rivet 16 press-fitted into the first rivet hole 14 is held in place by the overlap between its rivet shaft 17 and the first rivet hole 14. The rivet shaft 17 of the rivet 16 protrudes from the mating surface between the first flat portion 9 and the second flat portion 12.

[0024] Subsequently, the first annular member 10 and the second annular member 13, into which the rivets 16 are pressed, are subjected to soft nitriding treatment. Soft nitriding treatment is a process that forms a nitride layer 20 (surface hardened layer) on the surface of the steel material. For example, it is carried out by heating the steel material at a temperature lower than its transformation point (for example, in the range of 400 to 590°C) in a mixed gas atmosphere of ammonia gas and an endothermic modification gas, thereby allowing nitrogen to penetrate the surface of the steel material. The nitride layer 20 formed by the soft nitriding treatment is an extremely thin compound layer made of iron and nitrogen, with a Vickers hardness of 400 HV or more and a thickness of 20 μm or less. This nitride layer 20 improves the durability of the retainer 5.

[0025] This soft nitriding treatment forms a nitrided layer 20 on the surfaces of the first annular member 10 and the second annular member 13, as well as on the inner surfaces of the first rivet hole 14 and the second rivet hole 15, as shown in Figure 6. Due to the masking effect of the rivet shaft 17 of the rivet 16 that is pre-press-fitted into the first rivet hole 14, the surface hardness of the inner surface of the first rivet hole 14 is lower than that of the inner surface of the second rivet hole 15. Smooth surfaces 21 are formed on the inner surfaces of the first rivet hole 14 and the second rivet hole 15 by removing the irregularities of the fracture surfaces that occurred when each rivet hole 14 and 15 was formed.

[0026] After this soft nitriding treatment, as shown in Figure 5B, the first annular member 10 and the second annular member 13 are positioned opposite each other so that the first flat portion 9 and the second flat portion 12 overlap in the axial direction. The tip of the rivet shaft 17 protruding from the first annular member 10 is inserted into the second rivet hole 15, and then protrudes from the side opposite to the mating surface of the first flat portion 9 and the second flat portion 12. At this time, the ball 4 is incorporated between the respective pockets 8 and 11 formed in both annular members 10 and 13.

[0027] Finally, as shown in Figure 5C, the tip of the rivet shaft 17 protruding from the second rivet hole 15 of the second annular member 13 is crimped in the axial direction using a crimping die (not shown) to form a shaped head 19, and the first annular member 10 and the second annular member 13 are joined together to complete the cage 5 in which the balls 4 are held. Furthermore, the ball bearing 1 can be constructed by incorporating the cage 5 in which the balls 4 are held between the inner ring 2 and the outer ring 3 which is provided coaxially on the radially outer side of the inner ring 2.

[0028] When the tip of the rivet shaft 17 is crimped to form the head 19, the crimping process causes the rivet shaft 17 to thicken, resulting in tensile residual stress on the inner surfaces of the first rivet hole 14 and the second rivet hole 15. In particular, when soft nitriding is performed using the above procedure, the surface hardness of the inner surface of the first rivet hole 14 is relatively low, so a decrease in fatigue strength due to residual stress may become a problem, especially on the inner surface of the first rivet hole 14. This decrease in strength can be reduced by increasing the diameter of the base head 18 of the rivet 16, but if the diameter of the base head 18 is increased too much, the base head 18 and the R portion at the circumferential end of the first pocket 8 formed in the retainer 5 may interfere, potentially causing a decrease in the rigidity of the retainer 5 due to insufficient contact between the first annular member 10 and the second annular member 13.

[0029] Therefore, in order to suppress the decrease in fatigue strength of the retainer 5 due to residual tensile stress, and to suppress problems caused by interference between the butt head 18 and the R portion at the circumferential end of the first pocket 8 formed in the retainer 5, as shown in Figures 7 and 8, the area of ​​the first flat portion 9 and the second flat portion 12 (shaded portion in Figure 7) is set to S, and the area of ​​the orthogonal projection of the butt head 18 onto a plane having a normal common to the axis of the rivet shaft 17 (shaded portion in Figure 7) is set to S. φRD When the maximum circumferential width of the first flat section 9 and the second flat section 12 is h, and the diameter of the head 18 is φRD, the area S of the orthogonal projection of the head 18 onto a plane having a normal common to the axis of the rivet shaft 17 is... φRD The ratio S of the area S of the first flat section 9 and the second flat section 12 φRD The safety factor when the ratio of the diameter φRD of the base head 18 to the maximum circumferential width h of the first flat section 9 and the second flat section 12, φRD / h, was changed, and the presence or absence of interference between the base head 18 and the R portion of the circumferential end of the first pocket 8 formed in the retainer 5 was evaluated. The evaluation results are shown in Table 1.

[0030] The safety factor referred to here is the value obtained by dividing the residual stress value of the commercially available (mass-produced) product by the residual stress value of the evaluated product (Examples 1 and 2, Comparative Examples 1-3). A safety factor greater than 1 means that the residual stress reduction effect is greater than that of the commercially available product, and a safety factor less than 1 means that the residual stress reduction effect is inferior to that of the commercially available product.

[0031]

Table 1

[0032] As shown in Table 1, Comparative Example 1 (S φRD / S = 40%, φRD / h = 78%) and Comparative Example 2 (S φRD / S = 50%, φRD / h = 85%), that is, when the area S of the orthogonal projection of the original head 18 φRD and the diameter φRD of the original head 18 are relatively small, the safety factor is lower than 1, which causes concerns in terms of the strength of the cage 5. On the other hand, Comparative Example 3 (S φRD / S = 80%, φRD / h = 100%), that is, when the area S of the orthogonal projection of the original head 18 φRD and the diameter φRD of the original head 18 are relatively large, the safety factor is higher than 1, and although concerns regarding the strength of the cage 5 are low, there is a problem that interference occurs between the original head 18 and the rounded portion at the circumferential end of the first pocket 8 formed in the cage 5.

[0033] In contrast to this, Example 1 (S φRD / S = 60%, φRD / h = 90%), and Example 2 (S φRD / S = 70%, φRD / h = 95%), that is, the area S of the orthogonal projection of the original head 18 φRD and the ratio S of S to the total area S of the first flat portion 9 and the second flat portion 12 φRD / S, and the ratio φRD / h of the diameter φRD of the original head 18 to the maximum circumferential width h of the first flat portion 9 and the second flat portion 12 is within a predetermined range (60% ≦ S φRD / S, and φRD / h < 100%), there is no concern regarding the strength of the cage 5, and furthermore, there is no risk of interference occurring between the original head 18 and the rounded portion at the circumferential end of the first pocket 8 formed in the cage 5.

[0034] In the above description, the shapes of the original head 18 and the formed head 19 of the rivet 16 are hemispherical in side view; however, as shown in, for example, FIGS. 9A and 9B, the shapes of the original head 18 and the formed head 19 can also be rectangular or trapezoidal in side view.

[0035] The above-mentioned retainer 5 and ball bearing 1 have an area of ​​S for the first flat portion 9 and the second flat portion 12, and an area of ​​S for the orthogonal projection of the original head 18 onto a plane having a normal common to the axis of the rivet shaft 17. φRD When the maximum circumferential width of the first flat section 9 and the second flat section 12 is h, and the diameter of the head 18 is φRD, the area S of the orthogonal projection of the head 18 onto a plane having a normal common to the axis of the rivet shaft 17 is... φRD The ratio S of the area S of the first flat section 9 and the second flat section 12 φRD / S, and the ratio of the diameter φRD of the original head 18 to the maximum circumferential width h of the first flat section 9 and the second flat section 12, φRD / h, is 60% ≤ S φRD Since the ratio is set to / S and within the range of φRD / h < 100%, the decrease in fatigue strength due to residual tensile stress associated with crimping can be suppressed, and since no interference occurs between the base head 18 and the R portion of the circumferential end of the first pocket 8 formed in the retainer 5, the decrease in rigidity of the retainer 5 due to insufficient contact between the first annular member 10 and the second annular member 13 can be suppressed.

[0036] Furthermore, due to the procedure of the soft nitriding treatment, the surface hardness of the inner surface of the first rivet hole of the cage 5 and ball bearing 1 may be relatively low. In particular, in such cases, the configuration according to the present invention is effective in suppressing a decrease in fatigue strength and suppressing problems caused by interference between the cage 5 and the raceways 2 and 3.

[0037] Furthermore, since the cage 5 and ball bearing 1 have a smooth surface 21 formed by removing the irregularities on the fracture surface that occurred when forming the first rivet hole 14 and the second rivet hole 15, it is possible to suppress the concentration of tensile residual stress on the irregularities on the fracture surface, which would reduce the strength of the cage 5.

[0038] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0039] 1 ball bearing 2. Inner ring (raceway ring) 3. Outer ring (raceway ring) 4 balls 5 Cage 8 First Pocket 9 First flat part 10 First annular member 11 Second pocket 12 Second flat part 13 Second annular member 14 First rivet hole 15 Second rivet hole 16 rivets 17 Rivet shaft 18 Head of State 19. Head of the Craftsman 20 Nitride layer 21 Smooth surface

Claims

1. A first annular member (10) having hemispherical first pockets (8) and first flat portions (9) alternately formed at predetermined intervals along the circumferential direction, A second annular member (13) is positioned opposite the first annular member (10) in the axial direction, and has hemispherical second pockets (11) and second flat portions (12) alternately formed at predetermined intervals along the circumferential direction, A rivet (16) is inserted from a first rivet hole (14) formed in the first flat portion (9) toward a second rivet hole (15) formed in the second flat portion (12), and fastens the first annular member (10) and the second annular member (13) together by crimping, The rivet (16) has a cylindrical rivet shaft (17), a base head (18) pre-formed on one end of the rivet shaft (17), and a finished head (19) formed by crimping the other end of the rivet shaft (17). The area of ​​the first flat portion (9) and the second flat portion (12) is S, and the area of ​​the orthogonal projection of the principal head (18) onto a plane having a normal common to the axis of the rivet shaft (17) is S. φＲＤ When the maximum circumferential width of the first flat portion (9) and the second flat portion (12) is h, and the diameter of the base head (18) is φRD, then 60% ≤ S φＲＤ A retainer that satisfies the relationship / S and φRD / h < 100%.

2. The retainer according to claim 1, wherein a nitride layer (20) is formed on the surfaces of the first annular member (10) and the second annular member (13), and on the inner surfaces of the first rivet hole (14) and the second rivet hole (15), and the surface hardness of the inner surface of the first rivet hole (14) is lower than the surface hardness of the inner surface of the second rivet hole (15).

3. The retainer according to claim 1, having a smooth surface (21) formed by removing the irregularities of the fracture surface that occurred when forming the first rivet hole (14) and the second rivet hole (15).

4. The inner ring (2) and, An outer ring (3) is provided coaxially on the radially outer side of the inner ring (3), A plurality of balls (4) are incorporated between the inner ring (2) and the outer ring (3), A holder (5) according to any one of claims 1 to 3 for holding the ball (4), A ball bearing having

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