Ball bearing

A ball bearing includes an inner ring, an outer ring, and a cage that supports balls. At least one portion of each prong of the cage overlaps with an inner ring raceway surface in an axial direction and the entirety of the prongs do not overlap with a shoulder of the inner ring in the axial direction. A pocket of the cage overlaps with virtual conical planes that are parallel to a reference virtual conical plane including an inner ring nominal contact point and an outer ring nominal contact point, and that are part, on the other axial side, of both a virtual conical plane including an edge between the inner ring raceway surface and the shoulder of the inner ring and a virtual conical plane including an edge between the outer ring raceway surface and the outer ring counter-bored portion.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2017-194354 filed on Oct. 4, 2017 including the specification, drawings and abstract, is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a ball bearing.

2. Description of the Related Art

In recent years, there are cases in which apparatuses having a rotational axis that rotates at high speed are used for automobiles. In a rolling bearing that supports such a rotational axis, a rotational speed of an inner ring is higher than that of an outer ring. When the rolling bearing supports the rotational axis, an angular contact ball bearing80as shown inFIG. 5may be used as the rolling bearing. In the ball bearing80, an outer ring81and an inner ring83are combined co-axially. An outer ring raceway surface82is formed on an inner periphery of the outer ring81. An inner ring raceway surface84is formed on an outer periphery of the inner ring83. A plurality of balls85is rollably disposed between the outer ring raceway surface82and the inner ring raceway surface84. The balls85are held by a cage86so as to be arranged at prescribed intervals in a circumferential direction. On the outer ring81, a shoulder95that supports the balls85is formed on one axial side of the outer ring raceway surface82. On the inner ring83, a shoulder96that supports the balls85is formed on the other axial side of the inner ring raceway surface84. The ball bearing80supports radial load and axial load with the shoulder95of the outer ring81, the shoulder96of the inner ring83, and the balls85.

An annular space K between the inner ring83and the outer ring81is sealed with grease. The grease lubricates the raceway surfaces82,84, the balls85, and the cage86. Sealing devices87,94are provided on opening portions of the annular space K on both axial sides. Outer peripheries of the sealing devices87,94are fitted to the inner periphery of the outer ring81with a fitting margin. Lips88,93are provided on inner peripheries of the sealing devices87,94. The lips88,93face the outer periphery of the inner ring83in the radial direction to suppress an intrusion of a foreign substance from outside (see Japanese Patent Application Publication No. 2015-86940 (JP 2015-86940 A)).

In the inner ring83of the ball bearing80, an outer diameter dimension of the other axial side portion of the inner ring83in which the shoulder96is formed is larger than that of the other axial side portion of the inner ring83which has no shoulder. Thus, when the ball bearing80rotates, the grease sealed in the annular space K flows from a small radial side (one side inFIG. 5) to a large radial side (the other side inFIG. 5) of the inner ring83, due to centrifugal force. As a result, there is a possibility that the flowing grease leaks from a clearance between the sealing device94attached on the other axial side and the inner ring83. In the ball bearing80that rotates at high speed in particular, the balls85and the cage86rotate at high speed. Thus, the grease is sheared to be softened, which makes the grease flow easily. Thus, the grease leaks more easily.

If the grease leaks from the annular space K, the service life of the bearing may decrease since the amount of grease sealed in the annular space K decreases. Additionally, there is a possibility that the usage environment will deteriorate due to the scattered grease sticking to peripheral devices.

SUMMARY OF THE INVENTION

One object of the invention is to suppress grease from softening to suppress the grease from leaking in an angular contact ball bearing used for high-speed rotation.

According to an aspect of the invention, the ball bearing includes: an inner ring that has, on an outer periphery, an inner ring raceway surface, an inner ring stepped portion that is positioned on one axial side of the inner ring raceway surface and that does not have a shoulder, and a shoulder positioned on the other axial side of the inner ring raceway surface; an outer ring that has, on an inner periphery, an outer ring raceway surface, a shoulder positioned on the one axial side of the outer ring raceway surface, and an outer ring counter-bored portion that is positioned on the other axial side of the outer ring raceway surface and that does not have a shoulder; a plurality of balls rollably disposed between the inner ring raceway surface and the outer ring raceway surface; a cage that has an annular body disposed on the one axial side of the balls, a plurality of prongs disposed on the other axial side of the annular body, and a pocket that is surrounded by two adjacent prongs and the annular body and that houses one of the balls; a first sealing member that is fixed to the one axial side of the shoulder of the outer ring while facing the inner ring in a contact or a non-contact manner at a position on the one axial side of the inner ring stepped portion and/or a position offset to the one axial side from the inner ring stepped portion, and that defines a space surrounded by the outer ring and the inner ring in the radial direction from an outside space on the one axial side; and a second sealing member that is fixed to the other axial side of the outer ring counter-bored portion while facing the inner ring in a contact or a non-contact manner at a position on the other axial side of the shoulder of the inner ring and/or a position offset to the other axial side from the shoulder of the inner ring, and that defines a space surrounded by the outer ring and the inner ring in the radial direction from an outside space on the other axial side, wherein an inner ring nominal contact point, in which the inner ring raceway surface and the balls are in contact, is positioned offset to the other axial side from an outer ring nominal contact point, in which the outer ring raceway surface and the balls are in contact, at least one portion of each of the prongs overlaps with the inner ring raceway surface in the axial direction while the entirety of each of the prongs does not overlap with the shoulder of the inner ring in the axial direction, and the pocket overlaps with virtual conical planes that are parallel to a reference virtual conical plane including the inner ring nominal contact point and the outer ring nominal contact point, and that are part, on the other axial side, of both a virtual conical plane including an edge between the inner ring raceway surface and the shoulder of the inner ring and a virtual conical plane including an edge between the outer ring raceway surface and the outer ring counter-bored portion.

DETAILED DESCRIPTION OF EMBODIMENTS

A first embodiment of the invention will be described with reference to the drawings.FIG. 1is an axial sectional view of a ball bearing10of the first embodiment. The ball bearing10is an angular contact ball bearing. The ball bearing10is used under high-speed rotation conditions. Specifically, the ball bearing10is used at a rotation speed in which a dmN value is around 1.5 million. The ball bearing10includes an inner ring11, an outer ring12, a plurality of balls13, a cage14, a first sealing device15serving as a first sealing member, and a second sealing device16serving as a second sealing member. The inner ring11and the outer ring12are annular and are combined co-axially. The inner ring11is disposed inside the outer ring12so as to be rotatable with respect to the outer ring12around a bearing axis m. For the convenience of description, a direction in which the bearing axis m extends is an axial direction in the following description. InFIG. 1, a left side of the axial direction is one axial side and a right side of the axial direction is the other axial side. A direction orthogonal to the bearing axis m is a radial direction. A direction of going around the bearing axis m is a circumferential direction.

In the inner ring11, an inner periphery is a cylindrical surface52which is annularly formed with the bearing axis m as its center. In the inner ring11, an inner ring raceway surface17is annularly formed with the bearing axis m as its center, generally at the center of an outer periphery in the axial direction. In the inner ring11, a first outer peripheral surface21is formed on the one axial side of the inner ring raceway surface17of the outer periphery. In the inner ring11, a second outer peripheral surface22is formed on the other axial side of the inner ring raceway surface17of the outer periphery. In an axial section, the inner ring raceway surface17has an arc-shape and a groove radius of the inner ring raceway surface17is slightly larger than half of a diameter of the ball13. A point of the inner ring raceway surface17, at which a dimension in the radial direction is the smallest, is an “inner ring raceway bottom” and is indicated by a point Si inFIG. 1. The first outer peripheral surface21is annularly formed with the bearing axis m as its center. An outer diameter of the first outer peripheral surface21is generally the same as a diameter of the inner ring raceway bottom Si. A retaining portion23is formed in a portion on the other axial side of the first outer peripheral surface21, which is connected to the inner ring raceway surface17. The retaining portion23has a slightly larger diameter than that of the inner ring raceway bottom Si so that the balls13do not easily fall out of the inner ring11when the ball bearing10is assembled. The second outer peripheral surface22is annularly formed with the bearing axis m as its center. An outer diameter of the second outer peripheral surface22is larger than that of the first outer peripheral surface21. An edge at which the second outer peripheral surface22and the inner ring raceway surface17are connected is indicated by a point F inFIG. 1.

A shoulder26that has a larger diameter than that of the inner ring raceway bottom Si is formed on the other axial side of the inner ring raceway surface17. The shoulder26can support the balls13in the axial direction. In order to distinguish from a shoulder35of the outer ring12described below, the shoulder of the inner ring11will be referred to as an inner ring shoulder26. In contrast, on the one axial side of the inner ring raceway surface17, a shoulder is not formed and thus, the balls13cannot be supported in the axial direction. The portion on which the first outer peripheral surface21is formed and the retaining portion23define an “inner ring stepped portion”.

A first lip groove28in which a lip18of the first sealing device15is placed is formed on the one axial side of the first outer peripheral surface21. A second lip groove29in which a lip19of the second sealing device16is placed is formed on the other axial side of the second outer peripheral surface22.

In the outer ring12, an outer periphery is a cylindrical surface53which is annularly formed with the bearing axis m as its center. In the outer ring12, an outer ring raceway surface31is annularly formed generally at the center of the inner periphery in the axial direction with the bearing axis m as its center. In the outer ring12, a first inner peripheral surface32is formed on the one axial side of the outer ring raceway surface31of the inner periphery. In the outer ring12, a second inner peripheral surface33is formed on the other axial side of the outer ring raceway surface31of the inner periphery. In an axial section, the outer ring raceway surface31has an arc-shape and a groove radius of the outer ring raceway surface31is slightly larger than half of the diameter of the ball13. A point of the outer ring raceway surface31, at which a dimension in the radial direction is the largest, is an “outer ring raceway bottom” and is indicated by a point So inFIG. 1. The second inner peripheral surface33is annularly formed with the bearing axis m as its center. An inner diameter of the second inner peripheral surface33is almost the same as the diameter of the outer ring raceway bottom So. A retaining portion24is formed on a portion on the one axial side of the second inner peripheral surface33, which connects to the outer ring raceway surface31. The retaining portion24has a diameter slightly smaller than that of the outer ring raceway bottom So so that the balls13do not easily fall out of the outer ring12when the ball bearing10is assembled. An edge at which the retaining portion24and the outer ring raceway surface31are connected is indicated by a point D inFIG. 1.

The first inner peripheral surface32is annularly formed with the bearing axis m as its center. The inner diameter of the first inner peripheral surface32is smaller than that of the second inner peripheral surface33. Thus, a shoulder with a smaller diameter than that of the outer ring raceway bottom So (hereinafter referred to as an outer ring counter-bored portion35) is formed on the one axial side of the outer ring raceway surface31. The outer ring counter-bored portion35can support the balls13in the axial direction. In contrast, on the other axial side of the outer ring raceway surface31, a shoulder is not formed and thus, the balls13cannot be supported in the axial direction. A portion on which the second inner peripheral surface33is formed and the retaining portion24define an “outer ring counter-bored portion”.

A first fixing groove36that fixes the first sealing device15is formed on the inner periphery of the outer ring12nearer to the one axial side than the first inner peripheral surface32. A second fixing groove37that fixes the second sealing device16is formed on the inner periphery of the outer ring12nearer to the other axial side than the second inner peripheral surface33.

The configuration of the cage14will be described with reference toFIG. 2. The cage14is annular as a whole.FIG. 2is an axial sectional view of the cage14. As a whole, the cage14has a configuration in which the configuration inFIG. 2is annularly connected. The cage14is formed by subjecting a synthetic resin such as polyamide (PA), polyphenylene sulfide (PPS), and polyether ether ketone (PEEK) to injection molding.

The cage14has an annular body39that continues in the circumferential direction and a plurality of “prongs”40that protrudes from the annular body39toward the other axial side. A space surrounded by two prongs40next to each other in the circumferential direction and the annular body39is a “pocket”41. One ball13is inserted in each of the pockets41. An inner peripheral surface41aof the pocket41is a portion of a single spherical surface. A diameter of the spherical surface is slightly larger than that of the outer diameter of the ball13and the ball13can be rotatably housed in the pocket41. The outer peripheral surface42and the inner peripheral surface43of the cage14have a cylindrical shape in which a center coincides with the central axis of the cage14and the shape of each prong40viewed in the circumferential direction is a generally rectangular shape. An end portion44of the prong40(seeFIG. 1) on the other axial side is formed to extend in a direction orthogonal to the bearing axis m.

A clearance b between end portions of the two prongs40that are next to each other in the circumferential direction with the pocket41therebetween is smaller than the diameter dimension of the ball13. Thus, the ball13is prevented from easily coming out of the pocket41. On the other axial side, the prong40has a cut portion45that is depressed in the axial direction. Since the end portion of the prong40has the cut portion45, the end portion can deflect in the circumferential direction and thus, contain the ball13in the pocket41. By appropriately selecting a length h of the prongs40of the cage14in the axial direction, leakage of the grease is suppressed in the ball bearing10. Since the length h of the prongs40is related to a direction in which the ball13rotates, the details thereof will be described after the configuration of each component has been described.

As shown inFIG. 1, in the ball bearing10, the inner ring11and the outer ring12are combined co-axially and the balls13are rollably contained between the inner ring raceway surface17and the outer ring raceway surface31. The balls13are held at equal intervals in the circumferential direction by being inserted in the pockets41of the cage14.

The ball13and the inner ring raceway surface17are in contact at an “inner ring nominal contact point A” that is at a position offset to the other axial side from the inner ring raceway bottom Si. The ball13and the outer ring raceway surface31are in contact at an “outer ring nominal contact point B” that is at a position offset to the one axial side from the outer ring raceway bottom So. That is, in the ball bearing10, the inner ring nominal contact point A is positioned nearer to the other axial side than the outer ring nominal contact point B. The inner ring nominal contact point A is on the opposite side of a center O of the ball13from the outer ring nominal contact point B. A line k0that connects the inner ring nominal contact point A and the outer ring nominal contact point B is inclined at an angle θ to a straight line extending in the radial direction. In this way, the inner ring nominal contact point A of the ball13and the outer ring nominal contact point B of the ball13are positioned on a single conical plane in which the bearing axis m is its center. The conical plane is a “reference virtual conical plane”. Strictly speaking, the ball13and the raceway surfaces17,31come in contact at a region (contact region) that has a prescribed expanse, such as an oval shaped region due to the contact surface being elastically deformed. In this description, the inner ring nominal contact point A and the outer ring nominal contact point B are both nominal contact points and are the center of each contact region. The angle θ formed of the straight line k0and the straight line extending in the radial direction is a contact angle. In the ball bearing10, the contact angle is about 15 degrees.

An annular space surrounded in the radial direction by the inner periphery of the outer ring12and the outer periphery of the inner ring11(hereinafter referred to as an “annular space K”) is sealed with the grease. The grease lubricates the raceway surfaces17,31, the balls13, and the cage14. Channeling-type grease such as urea grease is preferably used as the sealed grease. The first sealing device15and the second sealing device16are assembled to opening portions on both axial sides of the annular space K.

The first sealing device15includes a core metal47formed of a steel plate and an elastic body. An outer periphery end portion of the core metal47is bent at a right angle and the axial section of the core metal47has a generally L-shape. The elastic body is formed into a prescribed shape by vulcanizing and molding a material such as nitrile rubber, super nitrile rubber, and flourorubber etc. using a mold. The core metal47is inserted in the mold and the material is vulcanized in the mold and thus, the elastic body is formed integrally with the core metal47. In the elastic body, a fixed portion49is formed radially outward of the core metal47. The outer diameter of the fixed portion49is larger than that of the inner diameter of the first fixing groove36. The fixed portion49is fitted to the first fixing groove36and thus, the first sealing device15is fixed to the outer ring12. In the elastic body, the lip18is formed radially inward of the core metal47. The lip18protrudes radially inward towards the first lip groove28and faces a side surface28aof the first lip groove28in the axial direction while facing a groove bottom surface28bin the radial direction. Additionally, a portion of the lip18protrudes toward the other axial side to form a sub-lip25. The sub-lip25faces the first outer peripheral surface21in the radial direction. The lip18faces the first lip groove28and the first outer peripheral surface21with a slight clearance therebetween to form a labyrinth and thus, suppresses entry of foreign matter into the annular space K.

In this way, the first sealing device15is fixed to the one axial side of the outer ring counter-bored portion35. The first sealing device15faces the inner ring11in a non-contact manner at a position on the one axial side of the inner ring stepped portion to define the annular space K from an outside space on the one axial side.

The second sealing device16includes a core metal48formed of a steel plate and an elastic body. An outer periphery end portion of the core metal48is bent at a right angle and the axial section of the core metal48has a generally L-shape. As with the first sealing device15, the elastic body is formed integrally with the core metal48. The material of the elastic body is the same as the first sealing device15. In the elastic body, a fixed portion50is formed radially outward of the core metal48. The outer diameter of the fixed portion50is larger than that of the inner diameter of the second fixing groove37. The fixed portion50is fitted to the second fixing groove37and thus, the second sealing device16is fixed to the outer ring12. In the elastic body, the lip19is formed radially inward of the core metal48. The lip19protrudes radially inward towards the second lip groove29and faces a side surface29aof the second lip groove29in the axial direction while facing a groove bottom surface29bin the radial direction. Additionally, a portion of the lip19protrudes toward the one axial side to form a sub-lip20. The sub-lip20faces the second outer peripheral surface22in the radial direction. The lip19faces the second lip groove29and the second outer peripheral surface22with a slight clearance therebetween to form a labyrinth and thus, suppresses entry of foreign matter into the annular space K.

In this way, the second sealing device16is fixed to the other axial side of the outer ring counter-bored portion. The second sealing device16faces the inner ring11in a non-contact manner at a position on the other axial side of the inner ring shoulder26to define the annular space K from an outside space on the other axial side. In the ball bearing10, the lips18,19are not in contact with the inner ring11and thus, friction resistance of the lips18,19can be reduced. Therefore, generation of heat can be prevented and the ball bearing10can be used at a higher speed.

Effects of suppressing leakage of the grease of the ball bearing10will be described in detail with reference toFIG. 1andFIGS. 3A, 3B, and 3C.FIG. 3Ais a schematic diagram of one of the balls13of the ball bearing10when viewed in the axial direction.FIG. 3Bis a schematic diagram of the ball13shown inFIG. 3Awhen viewed from the left side of the figure (in a direction indicated by an arrow X).FIG. 3Cis a schematic diagram of the ball13shown inFIG. 3Awhen viewed from the right side of the figure (in a direction indicated by an arrow Y). Here, the case in which the inner ring11rotates in a direction indicated by an arrow R inFIG. 3Awill be described.

The description will be provided with reference toFIG. 3A. When the inner ring11rotates in the direction of the arrow R, the ball13rotates in a counter-clockwise direction as indicated by an arrow T while also revolving around the bearing axis m in the direction of the arrow R. The ball13is housed in the pocket41of the cage14. The ball13and the cage14are integrated to rotate around the bearing axis m in the direction of the arrow R.

As shown inFIGS. 3B and 3C, the ball13is in contact with the raceway surfaces17,31in the direction of the straight line k0inclined at just the contact angle θ to the straight line of the radial direction. Thus, the ball13rotates with a straight line n as its axis, in which the straight line n is orthogonal to the straight line k0and connects the ball center O and a point along the bearing axis m. InFIG. 3B, a surface of the ball13moves in a direction of an arrow G and inFIG. 3C, the surface of the ball13moves in a direction of an arrow H.

When assembling the ball bearing10, mainly a space between the ball13and the ball13in the circumferential direction is sealed with the grease. When the ball bearing10rotates, the grease sticks to surfaces of the ball13and the cage14and moves within the annular space K. Thus, the grease stuck to the ball13moves in the direction of the arrow G inFIG. 3Band moves in the direction of the arrow H inFIG. 3C.

The inner peripheral surface41aof the pocket41of the cage14is near the surface of the ball13. Thus, as shown inFIG. 3B, when viewed in the direction of the arrow X, the grease in a region in which hatching is applied, of the grease stuck to the surface of the ball13, is scraped off in an upper portion of the prong40of the cage14, that is, in regions a1to a2. In theFIG. 3A, the state of grease Q1scraped off in the upper portion of the prong40is schematically shown.

In the ball bearing10of the first embodiment, a position of a2that is an end portion of the prong40on the other axial side is positioned to be nearer to the other axial side than a straight line k1that passes through a point F (an edge at which the second outer peripheral surface22connects to the inner ring raceway surface17) and that is parallel to the straight line k0. Thus, in a moving direction of the surface of the ball13, the inner ring raceway surface17is always positioned rearward of the prong40of the cage14. Therefore, it is possible to suppress the grease stuck to the surface of the ball13from entering the inner ring raceway surface17. As a result, it is possible to suppress the grease from being severely sheared between the inner ring raceway surface17and the ball13and thus, suppress the grease from softening.

Thus, in the cage14of the ball bearing10, when considering a virtual conical plane p (the virtual conical plane p is a conical surface in which the straight line k1is a generating line) that includes the edge indicated by the point F and that is parallel to the reference virtual conical plane, at least one portion of the end portion44of the prong40on the other axial side is positioned nearer to the other axial side than the virtual conical plane p. That is, when the ball bearing10is viewed in the direction of the arrow X, the virtual conical plane p that includes the edge indicated by the point F and that is parallel to the reference virtual conical plane overlaps with the pocket41. In this way, the grease stuck to the surface of the ball13is scraped off by the prong40and thus, it is possible to suppress the grease from entering the inner ring raceway surface17.

Similarly, on the side viewed in the direction of the arrow Y, it is possible to suppress the grease from entering the outer ring raceway surface31. InFIG. 3C, the grease in the region in which hatching is applied, of the grease stuck to the surface of the ball13, is scraped off in a lower portion of the prong40of the cage14, that is, in regions b2to b3and b3to b4.FIG. 3Aschematically shows the state of grease Q2scraped off in the lower portion of the prong40.

In the ball bearing10of the first embodiment, a position of a2that is an end portion of the prong40on the other axial side is positioned to be nearer to the other axial side than a straight line k1that passes through a point F (an edge at which the second outer peripheral surface22connects to the inner ring raceway surface17) and that is parallel to the straight line k0. Thus, in the moving direction of the surface of the ball13, the outer ring raceway surface31is always positioned rearward of the prong40of the cage14. Therefore, it is possible to suppress the grease stuck to the surface of the ball13from entering the outer ring raceway surface31. As a result, it is possible to suppress the grease from being severely sheared between the outer ring raceway surface31and the ball13and thus, suppress the grease from softening.

In this way, in the cage14of the ball bearing10, when considering a virtual conical plane q (the virtual conical plane q is a conical surface in which the straight line k2is a generating line) that includes the edge indicated by the point D and that is parallel to the reference virtual conical plane, at least one portion of the end portion44of the prong40on the other axial side is positioned nearer to the other axial side than the virtual conical plane q. That is, when the ball bearing10is viewed in the direction of the arrow Y, the virtual conical plane q that includes the edge indicated by the point D and that is parallel to the reference virtual conical plane overlaps with the pocket41. In this way, the grease stuck to the surface of the ball13is scraped off by the prong40and thus, it is possible to suppress the grease from entering the outer ring raceway surface31.

In the ball bearing10of the first embodiment, the pocket41overlaps with virtual conical planes that are parallel to the reference virtual conical plane and that are part of both the virtual conical plane p and the virtual conical plane q on the other axial side. The virtual conical plane p includes the edge indicated by the point F, and the virtual conical plane q includes the edge indicated by the point D. Thus, it is possible to prevent the grease stuck to the surface of the ball13from entering the raceway surfaces17,31. As a result, it is possible to suppress the grease from being severely sheared on the raceway surfaces17,31and suppress the grease from softening.

In the ball bearing10of the first embodiment, an axial length h of the prong40is set appropriately. Thus, at least one portion of the prong40of the cage14overlaps with the inner ring raceway surface17in the axial direction and the entirety of the cage14do not overlap with the inner ring shoulder26in the axial direction. That is, the position of the end portion (a3or b3) of the prong40on the other axial side is nearer to the inner ring raceway surface17in the axial direction than the edge indicated by the point F. A clearance in which the grease can be sheared is not formed between the cage14and the inner ring11. Thus, it is possible to suppress the grease from softening.

In the first embodiment, in order to clarify the effects of appropriately setting the axial length h of the prong40, the description will be made in comparison to the movement of the grease sealed in the conventional ball bearing80, with reference toFIG. 5. In the conventional ball bearing80, a cage86has a pair of annular bodies91,91on both axial sides on the same axis, and a plurality of cage bars92that connect the annular bodies91,91in the axial direction. A pocket (not shown) is formed between the cage bars92which are adjacent to each other in the circumferential direction to support a ball85. In this way, in the conventional ball bearing80, on the other axial side, the annular body91of the cage86is positioned radially outward of an inner ring shoulder96, and the cage86and the inner ring shoulder96overlap in the axial direction. When the ball bearing80rotates, the grease sealed within flows from the one axial side to the other axial side. At this time, the grease is softened by being severely sheared between the inner periphery of the cage86and the inner ring shoulder96. Thus, the grease leaks easily on the other axial side in the conventional ball bearing80.

Since the annular body91of the cage86is provided in the conventional ball bearing80on the other axial side of the annular space K in the axial direction, the spatial volume corresponding to the annular body91decreases. Thus, at an early stage, the conventional ball bearing80is filled with the grease that flows to the other axial side due to centrifugal force, which makes it easier for the grease to leak.

In contrast, in the ball bearing10of the first embodiment, on the other axial side, the cage14and the inner ring shoulder26do not overlap in the axial direction. Even when the ball bearing10of the first embodiment rotates and the sealed grease flows to the other axial side of the ball13due to centrifugal force, the grease is not sheared between the cage14and the inner ring shoulder26on the other axial side and it is possible to suppress the grease from softening. Also, a sufficient volume can be ensured in the annular space K on the other axial side. Therefore, even if the grease flows to the other axial side due to centrifugal force, the ball bearing10is not filled with the grease at an early stage. Thus, in the ball bearing10of the first embodiment, it is possible to further effectively suppress the grease from leaking. In this way, the ball bearing10of the first embodiment can suppress the grease from softening and suppress the grease from leaking even when the ball bearing10is used for high-speed rotation.

A ball bearing60of the second embodiment will be described.FIG. 4is an axial sectional view of the ball bearing60. In the second embodiment, the configurations of an inner ring61, a first sealing device62(one sealing device), and a second sealing device63(the other sealing device) are different compared to the first embodiment. The configuration of a portion on which a lip64of the first sealing device62and an outer periphery of the inner ring61are in contact is also different. Additionally, a portion in which a lip65of the second sealing device63and an outer periphery of the inner ring61combine have a different configuration. The configurations that differ will be described below. The configurations of the second embodiment which are the same as those in the first embodiment will be described with same symbols.

In the inner ring61of the second embodiment, the inner ring raceway surface17on which the ball13rotates is formed in the generally axial center of the outer periphery. A first outer peripheral surface67is formed on the one axial side of the inner ring raceway surface17of the outer periphery. A second outer peripheral surface68is formed on the other axial side of the inner ring raceway surface17of the outer periphery.

The first outer peripheral surface67is annularly formed with the bearing axis m as its center. An outer diameter of the first outer peripheral surface67is generally the same as the diameter of the inner ring raceway bottom Si. A retaining portion69is formed in a portion on the other axial side of the first outer peripheral surface67that is connected to the inner ring raceway surface17. The retaining portion69has a slightly larger diameter than that of the inner ring raceway bottom Si, and thus the balls13do not easily fall out of the inner ring61when the ball bearing60is assembled. A lip contact surface72is formed on an outer periphery of the inner ring61nearer to the one axial side than the first outer peripheral surface67. The lip contact surface72has a smaller diameter than the first outer peripheral surface67, has a cylindrical shape, and is formed on the same axis as the first outer peripheral surface67. A lip end portion64aof an inner periphery of the lip64of the first sealing device62is in contact with the lip contact surface72.

The second outer peripheral surface68is annularly formed with the bearing axis m as its center. An outer diameter of the second outer peripheral surface68is larger than that of the first outer peripheral surface67. An edge at which the second outer peripheral surface68and the inner ring raceway surface17are connected is indicated by the point F inFIG. 4. A third outer peripheral surface75is annularly formed on the outer periphery of the inner ring61nearer to the other axial side than the second outer peripheral surface68with the bearing axis m as its center. The third outer peripheral surface75has a smaller diameter than the second outer peripheral surface68, has a cylindrical shape, and is formed on the same axis as the second outer peripheral surface68. The third outer peripheral surface75is connected to the second outer peripheral surface68through a side surface74extending in the radial direction. A second lip groove73in which the lip65of the second sealing device63is placed is formed in the third outer peripheral surface75.

On the other axial side of the inner ring raceway surface17, an inner ring shoulder70that has a larger diameter than the raceway bottom is formed and the ball13can be supported in the axial direction. In contrast, on the one axial side of the inner ring raceway surface17, a shoulder is not formed and thus, the ball13cannot be supported in the axial direction. The portion on which the first outer peripheral surface67is formed and the retaining portion69define an “inner ring stepped portion”.

The second embodiment is characterized in that the flow of the grease toward a labyrinth clearance between the second sealing device63and the inner ring61is suppressed to suppress the grease from leaking. An effect of the second embodiment is that the grease stuck to the surface of the ball13is suppressed from entering the raceway surfaces17,31and the grease is suppressed from softening, by appropriately setting the axial length h of the prong40. Additionally, an effect of the second embodiment is that the grease is suppressed from being sheared and softened, with the cage14and the inner ring shoulder70not overlapping in the axial direction. These effects are the same as those of the first embodiment. The description of the common effects will be omitted.

In the second embodiment, the first sealing device62and the second sealing device63are assembled to the opening portions on both axial sides of the annular space K.

Compared to the first sealing device15of the first embodiment, the configuration of the lip64of the first sealing device62of the second embodiment is different. In the elastic body, the lip64is formed radially inward of a metal core76. The lip64faces the lip contact surface72while the lip end portion64ais deflected in the radial direction. The lip end portion64aof the inner periphery of the lip64is in contact with the lip contact surface72throughout the entire circumference. In this way, the first sealing device62is fixed to the one axial side of the outer ring counter-bored portion35. The first sealing device62faces the inner ring61while in contact with a position on the one axial side of the inner ring stepped portion to define the annular space K from the outside space of the one axial side.

The second sealing device63of the second embodiment has the same configuration as the second sealing device16of the first embodiment. The lip65of the second sealing device63protrudes radially inward towards the second lip groove73and faces a groove side surface73aof the second lip groove73in the axial direction while facing a groove bottom surface73b. A portion of the lip65protrudes toward the one axial side to form a sub-lip66. The sub-lip66faces the third outer peripheral surface75in the radial direction with a clearance therebetween and faces the side surface74in the axial direction with a clearance s therebetween. An outer diameter of an end portion on the one axial side of the sub-lip66is generally the same size as the outer diameter of the second outer peripheral surface68. The lip65and the sub-lip66face the second lip groove73, the third outer peripheral surface75, and the side surface74with a slight clearance therebetween to form a labyrinth which suppresses entry of foreign matter into the annular space K.

In this way, the second sealing device63is fixed on the other axial side of the outer ring counter-bored portion. In this way, the second sealing device16is fixed to the other axial side of the outer ring counter-bored portion. The second sealing device16faces the inner ring11in a non-contact manner at a position on the other axial side of the inner ring shoulder26to define the annular space K from an outside space on the other axial side.

The grease flows in the annular space K in a direction indicated by a dashed line arrow inFIG. 4. In the second embodiment, the clearance s is provided between the sub-lip66and the side surface74in the radial direction, that is, in a direction generally orthogonal to the direction in which the grease flows. Thus, the grease flows towards an outer periphery of the sub-lip66, which makes it harder for the grease to flow into the clearance s that crosses with the flowing direction of the grease. Since it becomes harder for the grease to enter the labyrinth clearance between the lip65and the inner ring61in the second embodiment, it is possible to further surely suppress the grease from leaking.

As in the first embodiment, it is possible to further effectively suppress the grease form leaking since a sufficient volume can be ensured on the other axial side of the annular space K.

In this way, in the ball bearing60of the second embodiment, it is possible to suppress the grease stuck to the surfaces of the balls13from entering the inner ring raceway surface17and the outer ring raceway surface31and suppress the grease from softening even when the ball bearing60is used for high-speed rotation. In the ball bearing60of the second embodiment, it is possible to suppress the grease form being sheared and softened since the cage14and the inner ring shoulder70do not overlap in the axial direction on the other axial side. Thus, in the ball bearing60of the second embodiment, it is possible to suppress the grease from leaking from the second sealing device63even if the grease flows towards the other axial side due to centrifugal force. Additionally, in the ball bearing60of the second embodiment, it is possible to further surely suppress the grease from leaking since the flow of the grease towards the labyrinth clearance between the lip65and the inner ring61on the other axial side can be suppressed.

The invention is not limited to the embodiments described above, and may be varied in other ways. For example, the lip of the second sealing device provided on the other axial side may face the inner ring while in contact with the inner ring shoulder. Other variations are possible such as switching the corresponding configurations of the first embodiment and the second embodiment.

The ball bearing of the invention can suppress softening of the grease to suppress the grease from leaking even when the ball bearing is used for high-speed rotation.