ROLLING BEARING

A rolling bearing includes an outer ring and an inner ring, a rolling element disposed in a rollable manner between the outer ring and the inner ring, a cage holding the rolling element, and a shield. The outer ring includes a raceway surface supporting the rolling element in a rollable manner, recess parts formed at both direction sides in an axial direction with respect to the raceway surface, and a ridge part formed between the recess part and the raceway surface. The recess part includes a placement surface for placing a grease, and a first inclined part formed between the placement surface and the ridge part and approaching an outer peripheral surface of the outer ring toward an outer side in the axial direction.

TECHNICAL FIELD

The disclosure relates to a rolling bearing.

BACKGROUND

A motor is required to have a long life. Thus, it is known to increase the amount of grease in a rolling bearing provided with rolling elements.

SUMMARY

However, when the amount of grease increases and the grease is likely to be entrapped in the rolling elements, it causes the torque of the motor to increase.

In one aspect, an object is to provide a rolling bearing capable of suppressing the entrapment of grease.

In one aspect, a rolling bearing includes an outer ring and an inner ring, a rolling element disposed in a rollable manner between the outer ring and the inner ring, a cage holding the rolling element, and a shield. The outer ring includes a raceway surface supporting the rolling element in a rollable manner, recess parts formed at both direction sides in an axial direction with respect to the raceway surface, and a ridge part formed between the recess part and the raceway surface. The recess part includes a placement surface for placing grease, and a first inclined part formed between the placement surface and the ridge part and approaching an outer peripheral surface of the outer ring toward an outer side in the axial direction.

According to one aspect, the entrapment of grease can be suppressed.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a rolling bearing disclosed in the present application will be described in detail based on the drawings. Note that dimensional relationships between elements and scales of elements in the drawings may differ from actual configurations. The drawings may include parts having mutually different dimensional relationships and scales. For the sake of clarity of description, a coordinate system with an extension direction (or a direction parallel to a rotation axis L) of a below-described shaft99defined as an axial direction and a direction orthogonal to the shaft99(or the rotation axis L) defined as a radial direction may be illustrated in the drawings.

EMBODIMENTS

First, a rolling bearing in the present embodiment will be described usingFIGS.1to3.FIG.1is a partially cutaway plan view at the other side in the axial direction of the rolling bearing in the embodiment.FIG.2is a side cross-sectional view illustrating an example of the rolling bearing in the embodiment.FIG.3is a partially cutaway plan view at one side in the axial direction of the rolling bearing in the embodiment.FIG.2illustrates a cross section taken along line A-A inFIG.1.

A rolling bearing1in the embodiment includes a cage5as a crown-shaped cage, for example, as illustrated inFIG.4.FIG.4is a perspective view illustrating an example of the crown-shaped cage in the embodiment. As illustrated inFIG.4, the cage5in the embodiment includes a base part6and pockets7. Note that, hereinafter, the base part6side of the cage5of the rolling bearing1may be referred to as one side in the axial direction, and the pocket7side may be referred to as the other side in the axial direction.

As illustrated inFIGS.1to3, the rolling bearing1includes, in addition to the cage5illustrated inFIG.4, an outer ring2, an inner ring3disposed at an inner peripheral side of the outer ring2, and a plurality of rolling elements4ato4h, and greases G1and G2are disposed. The outer ring2includes an outer peripheral surface28located at an outer side in the radial direction. For example, the rolling bearing1rotatably pivotably supports the shaft99at an inner peripheral side of the inner ring3. The shaft99extends along the rotation axis L.

Specifically, the outer ring2is made of a metal material, such as a steel material. A raceway groove21is formed at the outer ring2so as to extend in a circumferential direction and opposes the inner ring3. The surface of the raceway groove21constitutes a raceway surface. Further, the inner ring3is made of a metal material, such as a steel material. A raceway groove31is formed at an outer peripheral surface38of the inner ring3so as to extend in the circumferential direction. The surface of the raceway groove31constitutes a raceway surface.

The outer ring2is formed with a recess part50and a ridge part60illustrated inFIG.5at each of the one side and the other side in the axial direction so as to oppose the inner ring3.FIG.5is a side cross-sectional view illustrating an example of a bearing space in the embodiment.FIG.5is an enlarged view of a portion illustrated in a frame F1inFIG.2. The grease G2is placed at the recess part50at the one side in the axial direction, and the grease G1is placed at the recess part50at the other side in the axial direction. In addition, the ridge part60is formed between the recess part50and the raceway groove21in the axial direction. Note that, inFIG.5and subsequent figures, illustration of the pockets7of the cage5may be omitted.

As illustrated inFIG.2, the plurality of rolling elements4ato4hare provided between the raceway groove21of the outer ring2and the raceway groove31of the inner ring3. Note that, hereinafter, when the rolling elements4ato4hare represented without distinction, the rolling elements4ato4hmay be simply referred to as rolling elements4. The rolling element4is made of, for example, a metal material, such as a steel material, or a ceramic material. The raceway groove21and the raceway groove31constitute raceways, and the rolling elements4roll on the raceways while coming into contact with the raceway surfaces of the raceway grooves21and31.

The cage5is a crown-shaped cage made of synthetic resin or metal, and the plurality of rolling elements4are disposed at equal intervals in the raceways. In addition, the cage5has a plurality of opening parts (pockets)7for accommodating the plurality of rolling elements4at the other side in the axial direction, and includes the base part6having an annular shape as a non-opening side of the cage5at the one side in the axial direction.

The rolling elements4are accommodated in the pockets7of the cage5illustrated inFIG.4. In this case, the one side in the axial direction of the rolling element4is supported by the base part6.

In addition, the rolling bearing1further includes one shield26closing a space between the outer ring2and the inner ring3at one end side in the axial direction and the other shield27closing a space between the outer ring2and the inner ring3at the other end side in the axial direction. The one and other shields26and27are plate members having a substantially annular shape and made of a galvanized steel sheet, a stainless steel sheet, an elastic material reinforced by a core metal, or the like. Respective outer peripheral parts of the one and other shields26and27are attached to the outer ring2. Specifically, attachment grooves8are formed at each end part of the outer ring2in the axial direction. The attachment groove8is open in a direction opposed to the inner ring3. The outer peripheral parts of the one and other shields26and27are accommodated in the respective attachment grooves8and are fixed by, for example, retaining rings9. On the other hand, inner peripheral parts of the one and other shields26and27extend to the vicinity of the inner ring3. Thus, the one and other shields26and27cover the spaces between the outer ring2and the inner ring3to protect the rolling elements4and the greases G1and G2. Note that, in the rolling bearing1, the one and other shields26and27are spaced apart from the inner ring3.

In the embodiment, as illustrated inFIG.2, the greases G1and G2are disposed at the recess parts50formed at the outer ring2. The greases G1and G2are disposed at a bearing space S obtained by subtracting the volumes of the plurality of rolling elements4and the cage5from the volume of a region surrounded by the outer ring2and the inner ring3, the shields26and27, and virtual lines L1and L2extending from an inner side in the radial direction of the shields26and27to the outer peripheral surface38.

The grease G2is sealed in the bearing space S at the one side in the axial direction across the plurality of rolling elements4, and the grease G1is sealed in the bearing space S at the other side in the axial direction across the plurality of rolling elements4, respectively. The grease G1is disposed in contact with a placement surface52of the recess part50and the shield27. Similarly, the grease G2is disposed in contact with the placement surface52of the recess part50and the shield26.

In the embodiment, as illustrated inFIGS.1to3, the volume of the grease G1is larger than the volume of the grease G2. In this case, as illustrated inFIG.2, in a stationary state, a cross-sectional area h1of the grease G1is larger than a cross-sectional area h2of the grease G2. In the embodiment, the application volumetric ratio between the grease G1and the grease G2is, for example, 9:1 to 5:5. Thus, contact between the grease G2and the cage5can be suppressed.

For example, as illustrated inFIG.1, the grease G1is applied in a ring shape along the circumferential direction of the rolling bearing1, but the grease formed in a spherical shape may be disposed along the circumferential direction. Further, the volumes of the greases G1and G2accounts for, for example, 5 to 60%, preferably 25 to 35% of the volume of the bearing space S.

The ridge part60protrudes radially inward from the raceway groove21to suppress the rolling elements4from mounting on a shoulder of the raceway groove21. The ridge part60includes, for example, a flat part61formed substantially parallel to the outer peripheral surface28of the outer ring2. Note that, as illustrated inFIG.5, the ridge part60may not include a portion other than the flat part61. Further, the cross section of the ridge part60may have a non-flat shape, for example, an arc shape.

As illustrated inFIG.5, the recess part50includes a first inclined surface51and the placement surface52. The first inclined surface51is formed continuously with the placement surface52and the ridge part60in the axial direction. The first inclined surface51in the embodiment is a surface (conical surface) inclined such that the distance from the outer peripheral surface28of the outer ring2decreases toward the placement surface52from the ridge part60. Note that the first inclined surface51is an example of a first inclined part.

A depth f in the radial direction of the recess part50is, for example, equal to or less than a depth k of the raceway groove21in the radial direction. In the embodiment, the depth f is substantially equal to the depth k of the raceway groove21in the radial direction.

The placement surface52is, for example, a flat surface formed substantially parallel to the outer peripheral surface28of the outer ring2. In the embodiment, the placement surface52is formed continuously with the first inclined surface51in the axial direction, and is in contact with the shield26or27in the axial direction. In the stationary state, the greases G1and G2are each placed at the placement surface52of the recess part50. In this case, a base oil component contained in the greases G1and G2move to the raceway groove21along the placement surface52and the first inclined surface51of the recess part50.

In this case, in order to smoothly move the base oil component contributing to the lubrication of the rolling elements4to the raceway groove21over the ridge part60having a height in the radial direction, the inclination of the first inclined surface51is desirably gradual. In the embodiment, as illustrated inFIG.6, an angle α of the first inclined surface51with respect to the flat part61is, for example, about 30°.FIG.6is an enlarged side cross-sectional view of the bearing space in the embodiment.FIG.6is an enlarged view of a portion illustrated in a frame F2inFIG.5.

On the other hand, when the greases G1and G2are entrapped in the raceway groove21, the torque increases due to stirring resistance, causing an increase in power consumption of the motor. Further, in order to suppress the entrapment of the greases G1and G2and to stably place the greases G1and G2at the placement surface52, it is preferable to ensure a sufficient size of the placement surface52. In the embodiment, a length c of the recess part50in the axial direction is desirably 40% or more of a size d of a gap in the axial direction between the central part CI in the axial direction of the outer ring2and an end part at an outer side in the axial direction of the recess part50. Further, a length g of the placement surface52in the axial direction is preferably 50% or more of the length c of the recess part50. Note that, in the embodiment, the length c of the recess part50in the axial direction is the sum of a length e of the first inclined surface51in the axial direction and the length g of the placement surface52in the axial direction.

Further, in order to make the angle α sufficiently gradual, the length e of the first inclined surface51in the length c of the recess part50is desirably 30% or more. However, since the length g of the placement surface52needs to be ensured, the length e of the first inclined surface51, the length e of the first inclined surface51in the length c of the recess part50is preferably less than 50%.

Further, the ratio between the depth f and the length c of the recess part50in the axial direction is preferably, for example, from 1:4 to 1:6. In this case, as illustrated inFIG.5, the depth f of the recess part50in the radial direction with respect to the ridge part60is, for example, substantially equal to the depth k of the raceway groove21of the outer ring2in the radial direction with respect to the ridge part60.

Note that, in order to suppress the cage5from coming into contact with the grease G2due to vibration of the motor or the like, a length a of the cage5in the radial direction is preferably small. In the embodiment, as illustrated inFIG.5, the length a of the cage5in the radial direction is, for example, 50% or less of a length b from the placement surface52of the outer ring2to the outer peripheral surface38of the inner ring3in the radial direction.

Further, at the non-opening side of the cage5, a portion for the base part6and the recess part50of the outer ring2to overlap each other in the axial direction, in other words, a portion for the base part6and the recess part50opposing in the radial direction can be increased. Thus, the grease G2is suppressed from coming into contact with the cage5, and lubricant oil can be easily supplied to the raceway groove21. In the embodiment, as illustrated inFIG.5, almost the entirety of the base part6of the cage5opposes the recess part50in the radial direction.

In addition, in the embodiment, the recess part50at the one side in the axial direction and the recess part50at the other side in the axial direction are formed so as to be substantially symmetrical with respect to the central part CI in the axial direction. In other words, the length c in the axial direction and the depth f in the radial direction of the recess part50, the length e of the first inclined surface51in the axial direction, and the length g of the placement surface52in the axial direction are all substantially the same at the one side in the axial direction and the other side in the axial direction. In this case, the ratios of the volumes of the greases G1and G2with respect to the bearing space S are also different at the one side in the axial direction than at the other side in the axial direction.

As described above, the rolling bearing1in the present embodiment includes the outer ring2and the inner ring3, the rolling elements4disposed in a rollable manner between the outer ring2and the inner ring3, the cage5holding the rolling elements4, and the shields26and27. The outer ring2includes a raceway surface21supporting the rolling elements4in a rollable manner, the recess parts50formed at both direction sides in the axial direction with respect to the raceway surface21, and the ridge part60formed between the recess part50and the raceway surface21. The recess part50includes the placement surface52to be placed with the greases G1and G2, and a first inclined part51formed between the placement surface52and the raceway surface21and approaching the outer peripheral surface28of the outer ring2toward the outer side in the axial direction. With such a configuration, the base oil component can easily move from the greases G1and G2to the raceway surface21. Accordingly, an increase in the torque of the rolling bearing I can be suppressed, and power saving of the motor can be achieved.

Modifications

Although the configurations of the present embodiment have been described above, the embodiment is not limited to such configurations. For example, the recess part50may be formed at only one side in the axial direction, in other words, at the base part6side of the cage5, rather than at both sides in the axial direction. Even in such a configuration, the grease G2can be suppressed from being entrapped in the raceway groove21.

In addition, as illustrated inFIG.7, the inclined part of the recess part formed at the outer ring may be formed to be rounded. Further, as illustrated inFIG.7, chamfers may be formed at the one side in the axial direction of the cage.FIG.7is a side cross-sectional view illustrating an example of a bearing space in a first modification. As illustrated inFIG.7, a recess part80formed at an outer ring2A of a rolling bearing1A in the first modification includes a first curved surface part81and further includes a second inclined surface83. Further, in addition to a flat part71, a ridge part70in the first modification includes a second curved surface part72having a distance in the radial direction from the outer peripheral surface28of the outer ring2A decreasing toward the raceway groove21. Note that the first curved surface part81is another example of the first inclined part.

In the first curved surface part81, the depth of the recess part80with respect to the ridge part70in the radial direction changes nonlinearly unlike the embodiment. Further, the second inclined surface83approaches the outer peripheral surface28of the outer ring2toward the outer side in the axial direction. Also in the first modification, a portion having the depth of the recess part80in the radial direction decreasing toward the outer side in the axial direction is not formed at the recess part80. In other words, also in the first modification, the depth of the recess part80in the radial direction changes only in one direction. Note that the second inclined surface83is an example of a second inclined part.

As illustrated inFIG.7, when the first curved surface part81is formed at the recess part80, the base oil component of the greases G1and G2can easily move by the raceway groove21, and processability of the recess part80can be improved.

In the first modification, the second curved surface part72is formed continuously with the raceway groove21of the outer ring2, for example. Note that, instead of the second curved surface part72in the first modification, an inclined surface having a distance from the outer peripheral surface28decreasing toward the raceway groove21may be provided. In this case, the distance in the radial direction between the inclined surface and the outer peripheral surface28changes linearly.

In addition, the recess part80includes the second inclined surface83at a position in contact with the shields26and27. The second inclined surface83is formed such that a distance in the radial direction from the outer peripheral surface28decreases toward the outer side in the axial direction. Also in the first modification, a portion with the distance from the outer peripheral surface28increasing toward the outer side in the axial direction is not formed at the recess part80. Note that, in the first modification, the length of the recess part80in the axial direction is the sum of the length of the first curved surface part81in the axial direction, the length of a placement surface82in the axial direction, and also the length of the second inclined surface83in the axial direction. In addition, instead of the second inclined surface83being substantially parallel with respect to the axial direction, a curved surface part being curved with respect to the axial direction may be provided.

Further, in the embodiment, as illustrated inFIG.5, a boundary B1between the ridge part60and the first inclined surface51is located at an inner side in the axial direction with respect to an outer edge B2of the rolling element4in the axial direction, but the embodiment is not limited to the above. For example, as illustrated inFIG.7, a boundary BIA may be located at the outer side in the axial direction with respect to the outer edge B2A, or the positions in the axial direction of the boundary BIA and an outer edge B2A may be substantially the same. Note that, in any positional relationship, ¾ or more of a length p of the base part6of the cage5in the axial direction is desirably located at a position opposing the recess part80in the radial direction.

Further, the placement surfaces52and82are not limited to flat surfaces substantially parallel to the outer peripheral surface28, and may be surfaces inclined in the axial direction, or may be curved surfaces formed to be rounded with respect to the axial direction. Also in this case, the depth in the radial direction of the placement surface52or82desirably changes only in one direction of the recess part80.

Further, in the embodiment, an angle α formed by the first inclined surface51and the flat part61is, for example, 10° to 80°, and preferably 30° to 60°. In the first modification, a maximum angle β formed by a tangent line of the first curved surface part81and the flat part61is, for example, 10° to 80°, and preferably 30° to 60°.

Note that, as illustrated inFIG.7, in a crown-shaped cage5A in the first modification, chamfers5tare formed at a base part6A. In the first modification, the chamfer5tis formed, for example, so as to have an angle of 45° with respect to the radial direction. By forming the chamfers5t, the distance between the grease G2located at the one side in the axial direction and the crown-shaped cage5A can be increased.

Further, the cage in the embodiment is not limited to a crown-shaped cage, and may be a machined cage as illustrated inFIG.8, for example.FIG.8is a perspective view illustrating an example of a machined cage in a second modification. As illustrated inFIG.8, a machined cage5B in the second modification includes a base part6B and pockets7B for accommodating the rolling elements4. In addition, similarly to the crown-shaped cage5A in the first modification, the chamfer5tmay also be formed at the machined cage5B in the second modification.

As illustrated inFIG.8, the machined cage5B is formed, for example, symmetrically with respect to the axial direction. In this case, the volumetric ratio between the greases G1and G2may be, for example, 5:5. In the case, as illustrated inFIG.8, the chamfer5tmay be formed not only at the one side in the axial direction but also at the other side in the axial direction. Thus, not only the distance between the grease G2located at the one side in the axial direction and the machined cage5B, but also the distance between the grease G1located at the other side in the axial direction and the machined cage5B can be increased.

Further, the number of the plurality of rolling elements4included in the rolling bearing1is an example, and may be seven or less or nine or more. Alternatively, the shields26and27may be fixed without using the retaining ring9.

The embodiment and respective modifications of the disclosure have been described above. However, the disclosure is not limited to the embodiment and the respective modifications and can be variously modified without departing from the gist of the disclosure. Various modifications within a scope not departing from the gist are also included in the technical scope of the disclosure, and this is obvious to a person having skill in the art from the description of the claims.