Patent ID: 12209613

DESCRIPTION OF EMBODIMENTS

Hereinafter, a snap cage for a ball bearing and a ball bearing according to an embodiment of the present invention will be described with reference to the drawings.

As shown inFIG.1, similar to a cage having a structure in the related art shown inFIG.12, a snap cage for a ball bearing (hereinafter, also referred to as “snap cage” or simply “cage”)10of the present embodiment is applied to a ball bearing1shown inFIG.11. That is, the snap cage10includes an annular main portion11and a plurality of bar portions12protruding axially from the main portion11at predetermined intervals in a circumferential direction. Spherical pockets13each capable of holding a ball6(seeFIG.4) are formed between the adjacent bar portions12. Further, a pair of claw portions14,14disposed at intervals from each other and forming an opening portion side of the pocket13are provided at a tip portion of the bar portion12.

The snap cage10is made of, for example, a synthetic resin material such as a polyamide resin, a polyacetal resin, polyphenylene sulfide, and polyetheretherketone, polyimide, and is manufactured by injection molding. A glass fiber, a carbon fiber, an aramid fiber, or the like may be added as a reinforcing material to the resin material.

Further, as shown inFIGS.2to4, in the snap cage10, the bar portion12includes a pair of claw portions14,14, and an outer circumferential surface12aon a tip portion side is located on an inner diameter side with respect to an outer circumferential surface11aof the main portion11. That is, as shown inFIG.2, a diameter D2of a virtual circle C connecting the outer circumferential surface12aon the tip portion side of each bar portion12is smaller than an outer diameter D1of the outer circumferential surface11aof the main portion11.

Further, as shown inFIG.4, in the bar portion12, the outer circumferential surface12aon the tip portion side extends to a main portion11side with respect to a center O of the pocket13in the axial direction, and is connected to the outer circumferential surface11aof the main portion11by a concave curved surface12b.The concave curved surface12bhas a radius of curvature of 25 to 55% of a radial thickness T of the main portion11. As described above, since the concave curved surface12bhas the radius of curvature of 55% or less of the radial thickness T of the main portion11, a volume of the bar portion12can be suppressed, and an effect of suppressing the deformation of the cage10due to centrifugal force is high.

Specifically, the outer circumferential surface12aon the tip portion side of the bar portion12is located at a position between ½ and ¾ of the radial thickness T of the main portion11from an inner circumferential surface of the cage10in a radial direction. In the present embodiment, the outer circumferential surface12aon the tip portion side is located at a position corresponding to ½ of the radial thickness T of the main portion11from the inner circumferential surface of the cage10in the radial direction, that is, on a pitch circle diameter PCD of the ball6.

Further, on an inner diameter side of the snap cage10, a plurality of lightened portions20obtained by notching in the axial direction from an axially outer surface11bof the main portion11to the respective bar portions12are formed separately at positions of the respective bar portions12in a circumferential direction. The plurality of lightened portions20are opened to the inner diameter side and an axial outer surface11bside of the main portion11, and are formed separately from a surface of the pocket13and an axially outer surface12cof the bar portion12formed between the pair of claw portions14,14. Wall portions21,22are formed between the surface of the pocket13and an inner wall surface20aof the lightened portion20, and between the axially outer surface12con the tip portion side of the bar portion12and the inner wall surface20aof the lightened portion20, respectively.

Inner circumferential surfaces of the main portion11and the bar portion12, which include the wall portions21,22and exclude the lightened portion20, constitute the inner circumferential surface of the cage10having an inner diameter D3(seeFIG.2).

Further, the lightened portion20is formed in a substantially fan shape such that a width in the circumferential direction gradually decreases from the axially outer surface11bof the main portion11to each of the bar portions12. Further, the lightened portions20are notched at the same depth such that a minimum radial thickness T3of the bar portion12defined between the inner circumferential surface of the lightened portion20and the outer circumferential surface12aon the tip portion side of the bar portion12has the same thickness dimension along the circumferential direction.

Referring toFIGS.3and4, when an axial dimension (thickness) of the wall portion22formed between the axially outer surface12con the tip portion side of the bar portion12and the inner wall surface20aof the lightened portion20is T1and an axial dimension (hereinafter, also referred to as “bottom thickness”) of the main portion11on a bottom portion of the pocket13is T2, T2>T1is designed. Accordingly, the bottom thickness T2can be sufficiently ensured, the cage stress when the centrifugal force is applied can be reduced, and the axial dimension T1of the wall portion22can be reduced to a thickness that does not cause any problem in injection molding, so that the weight reduction can be achieved, and deformation in the circumferential direction at high speed rotation can be suppressed.

In the present embodiment, the bottom thickness T2has a relationship of T2>T/4with respect to the radial thickness T of the main portion11, the bottom thickness T2can be further sufficiently ensured, and the cage stress when centrifugal force is applied can be reduced.

Further, the minimum radial thickness T3of the bar portion12in which the lightened portion20is formed is designed to be substantially equal to the axial dimension T1of the wall portion22so as not to cause any problem in injection molding. Accordingly, the minimum radial thickness T3of the bar portion12is reduced as much as possible to reduce the weight of the cage10.

In addition, since the center O of the pocket13passes through the wall portion22in the axial direction, the cage10is less likely to fall off the balls6at the high speed rotation. In particular, in the present embodiment, the center O of the pocket13coincides with the axially outer surface12cof the wall portion22in the axial direction.

Further, an entrance diameter e of the pocket13at the position of the pitch circle diameter PCD of the ball6is set to 90% to 95% of a ball diameter, and an entrance diameter e is reduced to prevent contact with the shield plate7and a seal member due to fall-off of the cage10. In general, since the thickness of the claw portion14is large, when the insertion diameter e is reduced, there is a concern about mold removal during injection molding, and whitening and breakage of the claw portion14during assembly to the ball6. However, by reducing the thickness of the claw portion14, even if the entrance diameter e is reduced, the ball6can be easily inserted into the pocket13, and the above concern is eliminated.

According to the snap cage10of the present embodiment configured as described above, since the bar portion12includes the pair of claw portions14,14, and the outer circumferential surface12aon the tip portion side is located on the inner diameter side with respect to the outer circumferential surface11aof the main portion11, the deformation due to the centrifugal force can be suppressed, and even in a case where deformation occurs due to the centrifugal force at high speed rotation, contact with other components hardly occurs.

Further, on the inner diameter side of the cage10, the plurality of lightened portions20obtained by notching in the axial direction from the axial side surface of the main portion11to the respective bar portions12are formed separately at the positions of the respective bar portions12in the circumferential direction.

Further, since the wall portion22is formed between the axially outer surface12con the tip portion side of the bar portion12and the inner wall surface20aof the lightened portion20, and an axial dimension T2of the main portion11on the bottom portion of the pocket13is made thicker than the axial dimension T1of the wall portion22, it is possible to ensure rigidity at a portion of the main portion11constituting the bottom portion of the pocket13, and to suppress the deformation at the high speed rotation. Further, since the wall portion22is left between the axially outer surface12con the tip portion side of the bar portion12and the inner wall surface20aof the lightened portion20, the deformation in the circumferential direction at the high speed rotation can be suppressed.

It should be noted that the present invention is not limited to the embodiment described above, and modifications, improvements, and the like can be made as appropriate.

For example, a snap cage10aof a modification shown inFIG.5is different from that of a first embodiment in a shape of an outer diameter side. Specifically, an axial side surface11cof the main portion11extending along the radial direction is formed between the outer circumferential surface12aon the tip portion side of the bar portion12and the outer circumferential surface11aof the main portion11, and the outer circumferential surface12aon the tip portion side of the bar portion12and the axial side surface11cof the main portion11are connected by a concave curved surface12d.In this modification, the axial side surface11cof the main portion11is provided at a position slightly on the claw portion side from a groove bottom of the pocket13in the axial direction.

In this case, the snap cage10acan be further reduced in weight as compared with the snap cage of the above embodiment.

Other configurations are similar to those of the snap cage10of the above embodiment.

Embodiment

Here, a relationship between a rotation speed and a cage stress ratio, and a relationship between the rotation speed and a cage claw portion deformation amount ratio were analyzed using the snap cage10of the embodiment having the configuration shown inFIG.1, the snap cage10aof Comparative Example 1 shown inFIGS.7A and7B, and the snap cage10bof Comparative Example 2 shown inFIGS.8A and8B.

In Comparative Example 1, the bottom thickness of the pocket13is reduced to a thickness that does not cause any problem in injection molding in order to reduce the weight of the cage10a.Compared to Comparative Example 1, Comparative Example 2 has a specification in which the bottom thickness of the pocket13is increased to a thickness that is not in contact with the seal member in order to increase rigidity of the cage10b.Further, in Comparative Examples 1 and 2, on the radially intermediate portions of the cages10a,10b, the lightened portions23notched in the axial direction from the axial side surface of the main portion11to the respective bar portions12are formed at the positions of the respective bar portions12in the circumferential direction. Table 1 shows the bottom thickness T2and the weight of each of Embodiment, and Comparative Example 1 and 2 in terms of a ratio based on the bottom thickness T2and the weight of Comparative Example 1.

FIGS.9and10show the relationship between the rotation speed and the cage stress ratio and the relationship between the rotation speed and the cage claw portion deformation amount ratio in each cage, respectively. The cage stress ratio and the cage claw portion deformation amount ratio are expressed as a ratio when each value of the cage10aof Comparative Example 1 at 10000 rpm is defined as 1.

TABLE 1ComparativeComparativeExample 1Example 2EmbodimentBottom thickness ratio11.61.6(based on ComparativeExample 1)Weight ratio (based on11.140.8Comparative Example 1)

In Comparative Example 1, since the stress of the cage at the high speed rotation is significantly increased compared to Comparative Example 2 and the embodiment, the deformation of the claw portion is also increased. As a result, it can be seen that reducing the bottom thickness for weight reduction is disadvantageous for the high speed rotation.

On the other hand, it can be seen that compared to Comparative Examples 1 and 2, both the stress and the deformation amount can be greatly reduced in the embodiment in which the weight reduction is achieved by forming the lightened portion20while leaving the wall portion22on the tip portion side of the bar portion12. Further, it can be seen that both the stress and the deformation amount can be significantly reduced by a synergistic effect of reducing the thickness T1of the wall portion22to such an extent that no problem occurs in the injection molding to achieve the weight reduction and making the bottom thickness of the pocket13thicker than the thickness T1of the wall portion22.

The present application is based on a Japanese patent application (Japanese Patent Application No. 2020-035971) filed on Mar. 3, 2020, the contents of which are incorporated herein by reference.