JP7480399B2 - Grease - Google Patents

Description

The present invention relates to grease.

Conventionally, there are rolling bearings that hold grease between a pair of raceways (inner and outer rings). In this type of rolling bearing, the resistance of the grease can be a factor in increasing the rotational resistance. However, in rolling bearings, it is desirable to reduce the rotational resistance in order to reduce the power consumption of the rotating equipment in which they are mounted. There is a strong demand for reduced rotational resistance, especially in small rolling bearings used in various motors such as fan motors.

In order to reduce the rotational resistance of a rolling bearing, it is effective to reduce the amount of grease that comes into contact with both of the components that rotate relative to each other. Therefore, grease is applied to the axial end of the fixed ring (in most cases the outer ring) of the rolling bearing, or to the seal member arranged on this end side, in order to reduce the amount of grease that comes into contact with the rolling elements (balls) and the cage that holds the rolling elements (see, for example, Patent Document 1). In the rolling bearing described in Patent Document 1, the grease adheres to the inner circumferential surface of the outer ring, avoiding the raceway surface that comes into contact with the rolling elements, and is enclosed in a ring shape biased toward the inner circumferential surface of the outer ring so as not to come into contact with the outer circumferential surface of the inner ring.

JP 2017-150615 A

However, reducing the amount of grease in contact with the rolling elements and cage can result in an insufficient supply of grease to the sliding parts, which can lead to a decrease in the long-term durability of the rolling bearing.

Therefore, the present invention provides a grease that can form rolling bearings with excellent long-term durability.

The grease according to the first aspect of the present invention is a grease filled in a rolling bearing comprising an inner ring and an outer ring arranged coaxially with each other, a rolling element arranged between the inner ring and the outer ring, and a seal member attached to one of the raceways of the inner ring and the outer ring and covering the space between the inner ring and the outer ring from the outside in the axial direction, the grease being arranged between the rolling element and the seal member, contacting at least one of the peripheral surface of the one raceway facing the other raceway of the inner ring and the outer ring, and the seal member, or being arranged in a cage that holds the rolling element rotatably, and having an unmixed penetration greater than 178 and less than 287.

According to the first aspect, the portion of the grease that is not in contact with the rolling elements and the cage is relatively soft and is easily separated from the outside. Therefore, even if the base oil in the portion of the grease that is in contact with the rolling elements or the cage becomes insufficient, the base oil seeps out from the inside of the grease that is not in contact with the rolling elements and the cage to the outside, and the base oil can be continuously supplied to the sliding part. Even if the grease is applied so as not to come into contact with the rolling elements and the cage, the base oil can be supplied to the sliding part from the surface of the grease, and the base oil can be supplied to the sliding part from the inside of the grease to the surface of the grease. Therefore, even if the grease is placed at a position away from the rolling elements and the cage to reduce the rotational resistance of the rolling bearing, the base oil can be supplied to the sliding part for a long period of time, and the durability of the rolling bearing can be improved. Therefore, a rolling bearing with excellent long-term durability can be formed.
Furthermore, by having an unmixed penetration of less than 287, excessive deformation due to sagging or dragging caused by gravity of the grease can be suppressed, and the shape of the parts of the grease that are not in contact with the rolling elements and the cage can be maintained in their initial shape. This makes it possible to suppress variations in rotational resistance caused by differences in the shape of the grease for each rolling bearing.

The grease according to the second aspect of the present invention may be the grease according to the first aspect, in which the difference between the worked and unworked penetration is less than 50.

According to the second aspect, the softness of the grease portions not in contact with the rolling elements and the cage becomes closer to the softness of the grease portions in contact with the rolling elements and the cage. This reduces the difference in the degree of base oil seepage between the portions of the grease in contact with the rolling elements or the cage and the portions not in contact with the rolling elements or the cage. Therefore, the rotational resistance of the rolling bearing can be stabilized for a long period of time.

The grease according to the third aspect of the present invention may be the grease according to the first or second aspect, in which the ratio of the difference between the mixed penetration and the unmixed penetration to the mixed penetration is less than 22.7%.

According to the third aspect, the softness of the grease portions not in contact with the rolling elements and the cage becomes closer to the softness of the grease portions in contact with the rolling elements or the cage. This reduces the difference in the degree of base oil seepage between the portions of the grease in contact with the rolling elements or the cage and the portions not in contact with the rolling elements or the cage. This makes it possible to stabilize the rotational resistance of the rolling bearing for a long period of time.

The grease according to the fourth aspect of the present invention is a grease according to any one of the first to third aspects described above, in which the thickener may contain urea.

According to the fourth aspect, the grease has high heat resistance, making it possible to form a highly durable rolling bearing.

The grease according to the fifth aspect of the present invention may be any of the greases according to the first to fourth aspects, and may have an unmixed penetration of greater than 158 after being left at 85°C for 18 hours.

According to the fifth aspect, the degree of hardening of the grease can be set to a level that allows the base oil to seep out smoothly even if the grease is exposed to high temperatures or left for a long period of time. This makes it possible to form a rolling bearing with high durability.

The grease according to the sixth aspect of the present invention is the grease according to any one of the first to fifth aspects above, wherein the seal member is enclosed in the rolling bearing having an annular seat portion that contacts the one raceway from the outside in the axial direction, an extension portion that extends outward in the axial direction from the periphery of the seat portion on the side of the other raceway, and a flat portion that extends radially from the outer edge of the extension portion in the axial direction toward the other raceway, and may be in contact with at least one of the seat portion and the extension portion.

According to the sixth aspect, after applying grease to a predetermined location, when the seal member is attached to one of the raceways, the grease may be pushed inward in the axial direction by the seat and extension of the seal member, which are located axially inward from the flat portion. Since the seat and extension are located closer to the rolling element and the cage than the flat portion, when the seal member is attached, the grease is pushed toward the rolling element and cage and is likely to come into contact with the rolling element or cage. Here, with a grease with a relatively small (hard) immiscible penetration as in the past, when the seal member pushes the grease inward in the axial direction, the entire grease may move axially inward, although there is a slight deformation, and the grease may come into contact with the rolling element or cage more than desired. According to the sixth aspect, since the immiscible penetration of the grease is relatively large (soft), the grease is easily deformed in the radial direction when it is pushed inward in the axial direction by the seal member, and the movement of the grease in the axial direction can be suppressed, and the grease can be suppressed from coming into contact with the rolling element or cage more than necessary. Therefore, the above-mentioned action and effect are effectively achieved.

The grease according to the seventh aspect of the present invention is the grease according to any one of the first to sixth aspects, wherein the seal member is enclosed in the rolling bearing having an annular seat portion that contacts the one raceway from the outside in the axial direction, an extension portion that extends from the periphery of the seat portion on the side of the other raceway to the outside in the axial direction, and a flat portion that extends radially from the outer edge of the extension portion in the axial direction toward the other raceway, and has a raceway contact portion that contacts the circumferential surface of the one raceway, and a seal member contact portion that is outside the raceway contact portion in the axial direction and contacts the flat portion on the side of the other raceway, and is arranged so that the area of the seal member contact portion is larger than the contact area of the seal member with the extension portion and the seat portion.

According to the seventh aspect, after applying grease to a predetermined location, when the seal member is attached, the grease pushed axially inward by the flat surface of the seal member can be provided with room to spread radially toward the extension and the base. This makes it possible to prevent the grease from spreading significantly toward the one raceway and the rolling element. This makes it easy to prevent the grease from directly contacting the rolling element and the one raceway.
Moreover, since the sealing member has an extension between the flat surface and the seat, the grease can be disposed at a position farther away from the rolling elements than in a configuration in which the flat surface extends radially from the seat, thereby enabling an increase in the amount of grease.
As a result, a rolling bearing can be formed that ensures durability and reduces rotational resistance.

The grease according to the eighth aspect of the present invention is the grease according to the seventh aspect, wherein the seal member contact portion may include a radial center position of the grease when viewed from the axial direction.

According to the eighth aspect, when the seal member is attached, the grease is pushed against the flat portion and spreads radially, so that the seal member contact portion includes the radial center position of the grease in a plan view, and the grease can be prevented from spreading significantly inward in the axial direction toward the rolling elements. This makes it easy to prevent the grease from coming into direct contact with the rolling elements.

The grease according to the ninth aspect of the present invention may be the grease according to the seventh or eighth aspect above, but may not be in contact with the extension portion.

According to the ninth aspect, when the seal member is attached, it is possible to provide a larger amount of room for the grease that is pushed axially inward by the flat surface of the seal member to spread radially toward the extension. This makes it possible to prevent the grease from spreading too far toward the one raceway and the rolling elements. This makes it easy to prevent the grease from coming into contact with the rolling elements, the cage, and the one raceway more than necessary.

The grease according to the tenth aspect of the present invention is the grease according to any one of the seventh to ninth aspects described above, wherein the raceway contact portion may be spaced apart in the axial direction from the contact portion between the one raceway and the base portion.

According to the tenth aspect, it is possible to prevent the grease from coming into contact with the contact portion between the raceway and the base. This makes it possible to prevent the grease from leaking out of the seal member due to capillary action through the contact portion between the raceway and the base.

The grease according to the eleventh aspect of the present invention may be a grease according to any one of the seventh to tenth aspects above, which does not contact the base portion.

According to the eleventh aspect, it is possible to prevent the grease from coming into contact with the contact portion between the raceway and the base. This makes it possible to prevent the grease from leaking out of the seal member due to capillary action through the contact portion between the raceway and the base.

The grease according to the twelfth aspect of the present invention may be the grease according to any one of the seventh to eleventh aspects described above, wherein the one raceway has a protruding portion that protrudes toward the other raceway and has a raceway surface formed thereon, the protruding portion faces outward in the axial direction and is connected to the peripheral surface at the periphery of the other raceway, has an end face that contacts the seat portion, and is filled in the rolling bearing such that the seat portion does not protrude beyond the end face toward the other raceway as viewed in the axial direction.

According to the twelfth aspect, even if the contact portion of the grease with the raceway spreads outward in the axial direction and goes over the periphery of the end face, the grease can be prevented from adhering to the base portion. This makes it possible to prevent the grease from coming into contact with the contact portion between the raceway and the base portion. This makes it possible to prevent the grease from leaking out of the seal member due to capillary action through the contact portion between the raceway and the base portion.

The present invention makes it possible to produce a rolling bearing with excellent long-term durability.

FIG. 1 is a plan view of a rolling bearing according to a first embodiment. 2 is a vertical cross-sectional view taken along line II-II in FIG. 1. 1 is a vertical cross-sectional view of a rolling bearing illustrating a method of applying grease according to a first embodiment. FIG. 1 is a vertical cross-sectional view of a rolling bearing illustrating a method of applying grease according to a first embodiment. FIG. FIG. 6 is a vertical sectional view of a rolling bearing according to a second embodiment. FIG. 11 is a vertical sectional view of a rolling bearing according to a third embodiment. FIG. 4 is a perspective view showing a cage in which grease is disposed.

The following describes an embodiment of the present invention with reference to the drawings. In the following description, components having the same or similar functions are given the same reference numerals. Furthermore, duplicate descriptions of those components may be omitted.

[First embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.
Fig. 1 is a plan view of the rolling bearing according to the first embodiment. Fig. 2 is a longitudinal sectional view taken along line II-II in Fig. 1. In Fig. 2, a rotating device 2 on which the rolling bearing 1 is mounted is shown by an imaginary line.

As shown in Figures 1 and 2, the rolling bearing 1 is a radial ball bearing that includes an inner ring 10 and an outer ring 20 that are raceways, a number of rolling elements 30, a cage 40, and a pair of seal members 50. The rolling bearing 1 is provided in a rotating device 2 such as a fan motor. The rotating device 2 includes a shaft 3 (rotating body) that is formed so as to be rotatable about a common axis O, and a housing 4 (support) that is fixedly installed and rotatably supports the shaft 3. The rolling bearing 1 is interposed between the shaft 3 and the housing 4.

The inner ring 10 and the outer ring 20 are arranged coaxially with each other so that their respective central axes coincide with the common axis O. In this embodiment, the direction in which the common axis O extends is called the axial direction, the direction extending radially from the common axis O perpendicular to the common axis O is called the radial direction, and the direction revolving around the common axis O is called the circumferential direction. In addition, of the directions parallel to the axial direction and pointing in opposite directions, one is defined as the upward direction, and the other as the downward direction.

The inner ring 10 is provided as a rotating ring. The inner ring 10 is fitted onto the shaft 3 and fixed to the shaft 3. The outer ring 20 is provided as a fixed ring. The outer ring 20 is fitted into a recess (or through hole) of the housing 4 and fixed to the housing 4. The outer ring 20 surrounds the inner ring 10 from the outside in the radial direction, with an annular space provided between the inner ring 10 and the outer ring 20. The multiple rolling elements 30 are disposed between the inner ring 10 and the outer ring 20, and are held by the retainer 40 so that they can roll. The retainer 40 holds each rolling element 30 rotatably, with the multiple rolling elements 30 evenly arranged in the circumferential direction. The seal member 50 is attached to the outer ring 20 and covers the annular space between the inner ring 10 and the outer ring 20 from the outside in the axial direction.

The outer ring 20 is formed in an annular shape from a metal material such as stainless steel or bearing steel. However, the outer ring 20 is not limited to being made of metal, and may be formed from other materials. The outer ring 20 has an outer ring body 21 whose axial width is equal to the axial width of the inner ring 10, and a protruding portion 22 that protrudes radially inward from the outer ring body 21 and extends over the entire circumferential direction. The protruding portion 22 is formed in a portion of the outer ring body 21 that is located at the center of the axial direction. The axial width of the protruding portion 22 is shorter than the axial width of the outer ring body 21 and is larger than the outer diameter of the rolling element 30.

The protrusion 22 has a pair of end faces 22a facing outward in the axial direction, and an inner peripheral surface 22b connecting the inner peripheral edges of the pair of end faces 22a. Each end face 22a extends parallel in both the radial and circumferential directions. An outer ring raceway surface 23 is formed on the inner peripheral surface 22b, recessed toward the radially outward direction. The outer ring raceway surface 23 is formed in a hemispherical shape in cross section so as to follow the outer surface of the rolling element 30, and is formed in an annular shape extending in the circumferential direction around the entire circumference of the inner peripheral surface 22b. The outer ring raceway surface 23 is formed on a portion of the inner peripheral surface 22b located at the center in the axial direction. The portion of the inner peripheral surface 22b other than the outer ring raceway surface 23 extends in the axial direction with a constant inner diameter.

The outer ring body 21 has a pair of inner peripheral surfaces 21a that extend from the outer peripheral edge of each end face 22a of the protrusion 22 to the opening edge of the outer ring 20. The axially inner portion of each inner peripheral surface 21a is located radially outward from the axially outer portion.

The inner ring 10 is formed in an annular shape from a metal material such as stainless steel or bearing steel. However, the inner ring 10 is not limited to being made of metal, and may be formed from other materials. An inner ring raceway surface 11 is formed on the outer peripheral surface of the inner ring 10, recessed radially inward. The inner ring raceway surface 11 is formed in a hemispherical shape in cross section so as to follow the outer surface of the rolling element 30, and is formed in an annular shape extending in the circumferential direction around the entire circumference of the outer peripheral surface. The inner ring raceway surface 11 is formed on a portion of the outer peripheral surface of the inner ring 10 that is located at the center in the axial direction, and is arranged so as to face the outer ring raceway surface 23 in the radial direction. The portion of the outer peripheral surface of the inner ring 10 other than the inner ring raceway surface 11 extends in the axial direction with a constant outer diameter.

As shown in FIG. 2, the rolling elements 30 are formed into a spherical shape from a metal material such as stainless steel or bearing steel. The rolling elements 30 are disposed between the outer ring raceway surface 23 and the inner ring raceway surface 11, and are supported by the outer ring raceway surface 23 and the inner ring raceway surface 11 so as to be capable of rolling. The rolling elements 30 are spaced apart in the circumferential direction by the cage 40.

The retainer 40 is formed in an annular shape as a whole from a synthetic resin or metal material. The retainer 40 is arranged around a common axis O. The retainer 40 includes an annular portion 41 formed in an annular shape and arranged below the plurality of rolling elements 30, and a plurality of column portions 42 protruding upward from the annular portion 41 and arranged at intervals in the circumferential direction. The column portions 42 are arranged evenly in the circumferential direction. A pair of column portions 42 adjacent to each other in the circumferential direction forms a ball pocket between them. The ball pocket penetrates the retainer 40 in the radial direction and opens upward at the upper end surface of the retainer 40. The ball pocket is provided in accordance with the number of the rolling elements 30 and holds each of the rolling elements 30 so that it can roll. As a result, the retainer 40 arranges the rolling elements 30 evenly at intervals in the circumferential direction. The retainer 40 is arranged with a gap from the inner ring 10 and the outer ring 20 so as not to interfere with the inner ring 10 and the outer ring 20. In this embodiment, the entire cage 40 is located axially inward of the pair of end faces 22a of the protruding portion 22 of the outer ring 20.

1 and 2, the seal member 50 is formed in a circular plate shape. The seal member 50 is arranged around the common axis O. The seal member 50 is formed uniformly around the entire circumference. The seal member 50 is fitted into the outer ring 20 from the outside in the axial direction. One seal member 50 is arranged on each side of the rolling elements 30 in the axial direction. The seal member 50 has an annular seat portion 51 that contacts the outer ring 20 from the outside in the axial direction, an extension portion 52 that extends outward in the axial direction from the inner peripheral edge of the seat portion 51, a flat portion 53 that extends radially from the outer edge of the extension portion 52 in the axial direction toward the inner ring 10, and an engagement portion 54 that extends radially outward and axially outward from the outer peripheral edge of the seat portion 51.

2, the seat 51 overlaps the end face 22a of the protruding portion 22 of the outer ring 20 from the outside in the axial direction. The seat 51 extends approximately parallel to the end face 22a of the protruding portion 22 of the outer ring 20. The seat 51 protrudes radially inward from the end face 22a of the protruding portion 22 in a plan view from the axial direction. The distance by which the seat 51 protrudes radially inward from the end face 22a of the protruding portion 22 is 10% or less of the radial distance between the inner ring 10 and the outer ring 20, and preferably 5% or less. The extension portion 52 extends from the inner peripheral edge of the seat 51 outward in the axial direction and inward in the radial direction. The flat portion 53 overlaps the center of the rolling element 30 in a plan view. The inner peripheral edge of the flat portion 53 is disposed on the outer peripheral surface of the inner ring 10 with a gap therebetween. The surface of the flat portion 53 facing inward in the axial direction is a flat surface extending in the circumferential and radial directions. The outer peripheral edge of the locking portion 54 is locked to the inner peripheral surface 21a of the outer ring body 21 from the inside in the axial direction. As a result, the seal member 50 is fixed to the outer ring 20 and rotates together with the outer ring 20 relative to the inner ring 10.

Grease 60 is sealed in the rolling bearing 1. The grease 60 contains a base oil and a thickener, and when it is stirred and sheared, the base oil held in the thickener seeps out and provides a lubricating effect to the sliding parts. The grease 60 is disposed between the rolling element 30 and the seal member 50. The grease 60 is disposed only on one side of the rolling element 30 in the axial direction in the annular space between the inner ring 10 and the outer ring 20. In this embodiment, the grease 60 is disposed on the opposite side of the rolling element 30 to the annular portion 41 of the retainer 40 in the axial direction across the rolling element 30. In other words, the grease 60 is disposed above the rolling element 30. The grease 60 is disposed along the circumferential direction. The grease 60 extends in an annular or arc shape and is disposed coaxially with the common axis O.

The grease 60 has an outer ring contact portion 61 (raceway contact portion) in contact with the inner peripheral surface 22b of the protruding portion 22 of the outer ring 20, and a seal member contact portion 62 in contact with the flat portion 53 of the seal member 50 axially outward and radially inward from the outer ring contact portion 61. The outer ring contact portion 61 and the seal member contact portion 62 extend in the circumferential direction over the entire length of the grease 60. The outer ring contact portion 61 has a width in the axial direction over the entire circumferential direction. The outer ring contact portion 61 contacts a portion of the inner peripheral surface 22b of the protruding portion 22 that is axially spaced from the outer ring raceway surface 23. The outer ring contact portion 61 contacts a portion of the inner peripheral surface 22b of the protruding portion 22 that is axially spaced from the inner peripheral edge of the upper end face 22a. That is, the outer ring contact portion 61 is provided axially spaced from the contact portion between the outer ring 20 and the seat portion 51 of the seal member 50. The seal member contact portion 62 has a radial width over the entire circumferential direction. The seal member contact portion 62 contacts the flat portion 53 at a location that is radially spaced from the connection between the extension portion 52 and the flat portion 53 of the seal member 50.

The grease 60 extends axially outward and radially inward from the outer ring contact portion 61 toward the seal member contact portion 62. The grease 60 has an inner surface 63 and an outer surface 64.
The inner surface 63 connects the axially inner edge of the outer ring contact portion 61 and the radially inner edge of the seal member contact portion 62. The inner surface 63 faces the outer peripheral surface of the inner ring 10 and the rolling elements 30. The upper half of the inner surface 63 extends axially inward and radially inward from the radially inner edge of the seal member contact portion 62. The lower half of the inner surface 63 extends axially outward and radially inward from the axially inner edge of the outer ring contact portion 61 and connects to the lower edge of the upper half. The boundary between the upper and lower halves of the inner surface 63 forms the inner peripheral edge of the grease 60 located at the innermost radial position. The inner surface 63 is separated from the inner ring 10, the rolling elements 30, and the cage 40. This prevents the grease 60 from contacting the inner ring 10, the rolling elements 30, and the cage 40.

The outer surface 64 connects the axially outer edge of the outer ring contact portion 61 and the radially outer edge of the seal member contact portion 62. The outer surface 64 faces the inner circumferential surface 22b of the protruding portion 22 of the outer ring 20 and the seal member 50. The outer surface 64 extends axially inward and radially outward from the radially outer edge of the seal member contact portion 62 and connects to the axially outer edge of the outer ring contact portion 61. The outer surface 64 is spaced apart from the seat portion 51 and the extension portion 52 of the seal member 50. As a result, the grease 60 is not in contact with the seat portion 51 and the extension portion 52 of the seal member 50, which are located closer to the outer ring 20 than the flat portion 53.

The grease 60 is formed so that the cross-sectional area of the cross section along the vertical plane of the common axis O gradually increases from the axially outer end toward the axially inner side. In this embodiment, the grease 60 is formed in a portion corresponding to the upper half of the inner surface 63 so that the cross-sectional area of the cross section along the vertical plane of the common axis O gradually increases from the axially outer end toward the axially inner side.

The grease 60 may come into contact with at least one of the rolling elements 30 and the cage 40. For example, the grease 60 may come into contact with at least one of the rolling elements 30 and the cage 40 due to changes over time, starting from an initial state in which the grease 60 is not in contact with the rolling elements 30 and the cage 40.

The composition of grease 60 will be described. Note that grease 60 may contain other components in addition to the base oil and thickener as necessary.

The base oil is not particularly limited, but examples thereof include mineral oil and synthetic oil. As the mineral oil, known mineral oils used as base oils can be used, such as naphthenic mineral oil, paraffinic mineral oil, hydrogenated mineral oil, solvent refined mineral oil, and highly refined mineral oil. One type of mineral oil may be used alone, or two or more types may be used in combination. For example, multiple types of mineral oils may be mixed and adjusted to the desired properties.

As the synthetic oil, known synthetic oils used as base oils can be used, for example, aliphatic hydrocarbon oils such as poly-alpha-olefins (PAO) and polybutene, aromatic hydrocarbon oils such as alkylbenzenes and alkylnaphthalenes, ester oils such as polyol esters and phosphate esters, ether oils such as polyphenyl ethers, polyalkylene glycol oils, silicone oils, fluorine oils, etc. These synthetic oils may be used alone or in combination of two or more types. For example, multiple types of synthetic oils may be mixed and adjusted to the desired properties.

The thickener plays a role in keeping the grease 60 in a semi-solid state. Any known thickener that is commonly used in greases for rolling bearings can be used as the thickener without any restrictions. Examples of the thickener include urea compounds, lithium soap, calcium soap, complex lithium soap, complex calcium soap, silica gel, polytetrafluoroethylene, and organo-bentonite. Urea compounds are preferred as thickeners because of their excellent heat resistance. A single type of thickener may be used alone, or two or more types may be used in combination. For example, multiple types of thickeners may be mixed to adjust the desired properties.

The unmixed penetration of the grease 60 in this embodiment is greater than 178 and less than 287. The difference between the mixed penetration and the unmixed penetration of the grease 60 is preferably less than 50. The ratio of the difference between the mixed penetration and the unmixed penetration to the mixed penetration of the grease 60 is preferably less than 22.7%. The unmixed penetration of the grease 60 after being left at 85°C for 18 hours is preferably greater than 158. In the following description, leaving at 85°C for 18 hours is referred to as leaving at high temperature.

Next, a method for manufacturing the rolling bearing 1 of this embodiment will be described.
The method for manufacturing the rolling bearing 1 of this embodiment includes a coating step and a sealing step.

3 and 4 are vertical sectional views of a rolling bearing illustrating the grease application method according to the first embodiment.
As shown in FIG. 3, the application process is performed in a state where the seal member 50 is not attached to the outer ring 20. That is, the grease 60 is applied in a state where the annular space between the inner ring 10 and the outer ring 20 is opened in the axial direction and the rolling elements 30 and the cage 40 are exposed. In the application process, the grease 60 is discharged from the nozzle A while rotating the nozzle A about the common axis O relative to the outer ring 20. At this time, the direction of the nozzle A is adjusted so that the grease 60 is discharged from the nozzle A radially outward and axially inward. Furthermore, the position of the nozzle A is adjusted so that the discharged grease 60 contacts a predetermined position of the inner circumferential surface 22b of the protruding portion 22 of the outer ring 20 and the grease 60 does not contact the rolling elements 30 and the cage 40. Since the grease 60 is discharged while rotating the nozzle A relative to the outer ring 20, the grease 60 applied to the outer ring 20 extends in a circumferential or arc shape. The grease 60 is applied in a direction parallel to the discharge direction from the nozzle A so as to protrude axially outward and radially inward from the contact portion with the outer ring 20. The axially outer end face of the applied grease 60 is formed into a convex shape that bulges outward in the axial direction.

Next, the sealing process is performed. As shown in FIG. 4, in the sealing process, the seal member 50 is brought close to the outer ring 20 from the outside in the axial direction, and the seal member 50 is attached to the outer ring 20. In the process of displacing the seal member 50 inward in the axial direction, before the seat portion 51 comes into contact with the end face 22a of the protruding portion 22 of the outer ring 20, the flat portion 53 of the seal member 50 is first brought into contact with the axially outer edge of the entire grease 60. At this time, the grease 60 is brought into contact with the radially intermediate portion of the flat portion 53. Note that the radially intermediate portion may be located radially inward from the outer peripheral edge of the flat portion 53 and radially outward from the inner peripheral edge. After that, the seal member 50 is brought even closer to the outer ring 20, and the seat portion 51 is brought into contact with the end face 22a of the protruding portion 22 of the outer ring 20 from the outside in the axial direction. At this time, the flat portion 53 of the seal member 50 pushes the grease 60 inward in the axial direction. As a result, the grease 60 is pushed against the flat surface portion 53 and spreads radially, forming a seal member contact portion 62 of the grease 60.

The rolling bearing 1 is thus formed. In the application process of this embodiment, the grease 60 is applied while the nozzle A is rotated relative to the outer ring 20, but the grease may also be applied all at once in a circumferential or arc-shaped manner by ejecting the grease from a nozzle having an ejection hole extending in the circumferential direction.

The operation of this embodiment will be described.
The grease 60 is disposed between the rolling elements 30 and the seal member 50, and most (or the entirety) of the grease 60 is not in contact with the rolling elements 30 and the cage 40. In other words, the portion of the grease 60 that is in contact with the rolling elements 30 or the cage 40 and is subjected to shear stress when the rolling bearing 1 is in operation is small, and there are cases in which the grease 60 is not in contact with the rolling elements 30 and the cage 40.

Here, the hardness of the grease differs between a state where it is not subjected to shear (a state where it is not mixed) and a state where it is subjected to shear (a state where it is mixed). Generally, grease becomes soft when it is subjected to shear. For this reason, the portion of the grease 60 that contacts the inner ring 10, the rolling element 30, or the cage 40 continues to receive shear from the rolling element 30 or the cage 40 and becomes soft, promoting the seepage of the base oil. On the other hand, the portion of the grease 60 that does not contact the rolling element 30 or the cage 40 remains hard. When only a small portion of the grease 60 contacts the rolling element 30 or the cage 40, if there is insufficient base oil seeping out from the portion that is subjected to shear by the rolling element 30 or the cage 40, most of the grease 60 remains hard without being stirred, and the supply of base oil becomes insufficient, which leads to the end of the life of the rolling bearing 1. The same applies when the entire grease 60 is not in contact with the rolling element 30 or the cage 40.

By the way, there are two indices that indicate the properties related to the hardness of grease: worked penetration and unmixed penetration. Worked penetration is an indicator of the hardness of grease immediately after it has been subjected to shear. Therefore, the state of the grease when the worked penetration is measured is close to the state of the part of the grease that is in contact with the rolling elements or cage in a rolling bearing and is subjected to shear. On the other hand, unmixed penetration is an indicator of the hardness of grease in a state that is not subjected to shear. Therefore, the state of the grease when the unmixed penetration is measured is close to the state of the part of the grease that is not in contact with the rolling elements or cage in a rolling bearing.

The grease 60 of this embodiment is in contact with the inner circumferential surface of the outer ring 20 and the seal member 50. The unmixed penetration of the grease 60 is greater than 178 and less than 287. According to this configuration, the portion of the grease 60 that is not in contact with the rolling body 30 and the retainer 40 is relatively soft and is in a state in which the oil is easily separated to the outside. Therefore, even if the base oil in the portion of the grease 60 that is in contact with the rolling body 30 or the retainer 40 is about to run short, the base oil seeps out from the inside of the grease 60 that is not in contact with the rolling body 30 and the retainer 40, and the base oil can be continuously supplied to the sliding part. In addition, even if the grease 60 is applied in a state in which it does not come into contact with the rolling body 30 and the retainer 40, the base oil can be supplied to the sliding part from the surface of the grease 60, and the base oil can be supplied to the sliding part from the inside of the grease 60 by seeping out to the surface of the grease 60. Therefore, even if the grease 60 is placed away from the rolling elements 30 and the cage 40 to reduce the rotational resistance of the rolling bearing 1, the base oil can be supplied to the sliding parts for a long period of time, improving the durability of the rolling bearing 1. Therefore, a rolling bearing 1 with excellent long-term durability can be formed.

In addition, by having an unmixed penetration of less than 287, excessive deformation of the grease 60 due to sagging or dragging caused by gravity can be suppressed, and the shape of the portion of the grease 60 that is not in contact with the rolling elements 30 and the cage 40 can be maintained in its initial shape. This prevents the shape of the grease 60 from differing for each rolling bearing 1, which causes variations in rotational resistance.

In addition, since the grease 60 is in contact with the inner peripheral surface of the outer ring 20, the grease 60 can be easily supplied to the outer ring raceway surface 23. Therefore, the base oil can be supplied to the sliding portion between the outer ring 20 and the rolling element 30 for a long period of time, and the durability of the rolling bearing 1 can be improved.

Furthermore, in this embodiment, the grease 60 is in contact with both the inner peripheral surface of the outer ring 20 and the seal member 50. In this configuration, when the grease 60 is sealed between the outer ring 20 and the inner ring 10, the grease 60 is applied to the outer ring 20, and then when the seal member 50 is attached to the outer ring 20, the grease 60 is pushed axially inward by the seal member 50. Here, in the case of a grease with a relatively small (hard) immiscible penetration as in the past, when the grease is pushed axially inward by the seal member, although there is a slight deformation, the entire grease may move axially inward and contact the rolling element 30 or the retainer 40 more than desired. In this embodiment, since the immiscible penetration of the grease 60 is relatively large (soft), the grease 60 is easily deformed in the radial direction when it is pushed axially inward by the seal member 50, and the movement of the grease 60 axially inward can be suppressed, and the grease 60 can be suppressed from contacting the rolling element 30 or the retainer 40 more than necessary. This prevents the rotational resistance of the rolling bearing 1 from increasing.

In addition, because the difference between the mixed and unmixed penetration of the grease 60 is less than 50, the softness of the portions of the grease 60 that are not in contact with the rolling elements 30 and the retainer 40 is close to the softness of the portions of the grease 60 that are in contact with the rolling elements 30 and the retainer 40. This reduces the difference in the degree of seepage of the base oil between the portions of the grease 60 that are in contact with the rolling elements 30 or the retainer 40 and the portions that are not in contact with the rolling elements 30 and the retainer 40. Therefore, the rotational resistance of the rolling bearing 1 can be stabilized for a long period of time.

In addition, since the ratio of the difference between the mixed penetration and the unmixed penetration to the mixed penetration of the grease 60 is less than 22.7%, the softness of the portions of the grease 60 that are not in contact with the rolling elements 30 and the retainer 40 is close to the softness of the portions of the grease 60 that are in contact with the rolling elements 30 or the retainer 40. This reduces the difference in the degree of seepage of the base oil between the portions of the grease 60 that are in contact with the rolling elements 30 or the retainer 40 and the portions that are not in contact with the rolling elements 30 and the retainer 40. Therefore, the rotational resistance of the rolling bearing 1 can be stabilized for a long period of time.

The thickener of the grease 60 contains urea. This configuration results in a grease with high heat resistance, which makes it possible to form a rolling bearing 1 with low rotational resistance and high durability. Generally, in greases that use urea as a thickener, the difference between the mixed and unmixed penetrations tends to be large. However, by selecting the type of urea, mixing multiple types of urea, adjusting the urea production conditions, additives, etc., it is possible to obtain a grease that satisfies the above-mentioned penetration conditions.

The unmixed penetration of the grease 60 after being left at 85°C for 18 hours is greater than 158, so the degree of hardening of the grease 60 can be set to a level that allows the base oil to seep out smoothly even if the grease 60 is exposed to high temperatures or left for long periods of time. This makes it possible to form a rolling bearing 1 with high durability.

The grease 60 has an outer ring contact portion 61 that contacts the inner circumferential surface 22b of the protruding portion 22 of the outer ring 20, and a seal member contact portion 62 that contacts the flat portion 53 of the seal member 50 on the axially outer side and the radially inner side of the outer ring contact portion 61. The area of the seal member contact portion 62 is larger than the contact area between the grease 60 and the extension portion 52 and the base portion 51 of the seal member 50. According to this configuration, after the grease 60 is applied to a predetermined location, when the seal member 50 is attached, a space can be provided for the grease 60 pushed axially inward by the flat portion 53 of the seal member 50 to spread radially toward the extension portion 52 and the base portion 51. Therefore, it is possible to prevent the grease 60 from spreading significantly toward the inner ring 10 side and the rolling element 30 side. Therefore, it is possible to easily prevent the grease 60 from directly contacting the rolling element 30 and the cage 40.
Moreover, since the sealing member 50 has the extension portion 52 between the flat portion 53 and the base portion 51, the grease 60 can be disposed at a position farther away from the rolling elements 30 than in a configuration in which the flat portion extends radially inward from the base portion. Thus, the amount of grease 60 can be increased.
As a result, it is possible to form a rolling bearing 1 that ensures durability and reduces rotational resistance.

In addition, the seal member contact portion 62 includes the radial center position of the grease 60 in plan view. With this configuration, when the seal member 50 is attached, the grease 60 is pushed against the flat portion 53 and spreads radially, so that the seal member contact portion 62 includes the radial center position of the grease 60 in plan view, which prevents the grease 60 from spreading significantly axially inward toward the rolling element 30. This makes it easy to prevent the grease 60 from directly contacting the rolling element 30.

The grease 60 is not in contact with the extension portion 52. With this configuration, when the seal member 50 is attached, the grease 60 is pushed axially inward by the flat portion 53 of the seal member 50, and has more room to spread radially toward the extension portion 52. This makes it possible to prevent the grease 60 from spreading too far toward the inner ring 10 and the rolling elements 30. This makes it easy to prevent the grease 60 from coming into contact with the rolling elements 30, the cage 40, and the inner ring 10 more than necessary.

The outer ring contact portion 61 is provided at an axial distance from the contact portion between the outer ring 20 and the base portion 51. This configuration makes it possible to prevent the grease 60 from coming into contact with the contact portion between the outer ring 20 and the base portion 51. This makes it possible to prevent the grease 60 from leaking out of the seal member 50 due to capillary action through the contact portion between the outer ring 20 and the base portion 51.

The grease 60 is not in contact with the base portion 51. This configuration makes it possible to prevent the grease 60 from coming into contact with the contact portion between the outer ring 20 and the base portion 51. This makes it possible to prevent the grease 60 from leaking out of the seal member 50 due to capillary action through the contact portion between the outer ring 20 and the base portion 51.

The rotating device 2 of this embodiment is equipped with a rolling bearing 1 that has excellent long-term durability, so the rotating device 2 can have a long life.

In the first embodiment, the seat 51 of the seal member 50 protrudes radially inward from the end face 22a of the protruding portion 22 of the outer ring 20 in a plan view, but it is preferable that the seat is arranged so as not to protrude radially inward from the end face 22a of the protruding portion 22 in a plan view. With this configuration, even if the outer ring contact portion 61 of the grease 60 spreads axially outward and overcomes the inner peripheral edge of the end face 22a, the grease 60 can be prevented from adhering to the seat. This makes it possible to prevent the grease 60 from coming into contact with the contact portion between the outer ring 20 and the seat. This makes it possible to prevent the grease 60 from leaking out of the seal member due to capillary action through the contact portion between the outer ring 20 and the seat.

In addition, in the first embodiment, the grease 60 is not in contact with the base portion 51 and the extension portion 52 of the seal member 50, but this configuration is not limited to this. The grease may be in contact with at least one of the base portion 51 and the extension portion 52 of the seal member 50. Here, the base portion 51 and the extension portion 52 are located axially inward from the flat portion 53, and are located closer to the rolling body 30 and the retainer 40 than the flat portion 53. Therefore, when the seal member 50 is attached, the grease 60 is pushed toward the rolling body 30 and the retainer 40 and is likely to come into contact with the rolling body 30 or the retainer 40, but in this embodiment, the movement of the grease 60 toward the axial inside can be suppressed, and the grease 60 can be suppressed from contacting the rolling body 30 or the retainer 40 more than necessary. Therefore, the above-mentioned action and effect are effectively achieved. However, when the grease 60 is in contact with at least one of the base portion 51 and the extension portion 52 of the seal member 50, it is desirable that the area of the seal member contact portion is larger than the area of contact between the grease and the extension portion 52 and base portion 51.

[Second embodiment]
Next, a second embodiment will be described with reference to Fig. 5. The second embodiment differs from the first embodiment in that the rolling bearing 1A includes a grease 160 instead of the grease 60 of the first embodiment. Note that the configuration other than that described below is the same as that of the first embodiment.

The grease 160 is arranged along the circumferential direction. The grease 160 extends in an annular shape and is arranged coaxially with the common axis O. The grease 160 has an outer ring contact portion 161 that contacts the inner peripheral surface 22b of the protruding portion 22 of the outer ring 20, and is not in contact with the inner ring 10, the seal member 50, the rolling element 30, and the retainer 40. The outer ring contact portion 161 extends in the circumferential direction over the entire length of the grease 160. The outer ring contact portion 161 has a width in the axial direction over the entire circumferential direction. The outer ring contact portion 161 contacts a portion of the inner peripheral surface 22b of the protruding portion 22 that is spaced in the axial direction from the outer ring raceway surface 23. The outer ring contact portion 161 contacts a portion of the inner peripheral surface 22b of the protruding portion 22 that is spaced in the axial direction from the inner peripheral edge of the upper end face 22a. That is, the outer ring contact portion 161 is spaced apart in the axial direction from the contact portion between the outer ring 20 and the seat portion 51 of the seal member 50.

The properties of the grease 160 are similar to those of the grease 60 of the first embodiment. That is, the unmixed penetration of the grease 160 is greater than 178 and less than 287. The difference between the mixed penetration and the unmixed penetration of the grease 160 is preferably less than 50. The ratio of the difference between the mixed penetration and the unmixed penetration to the mixed penetration of the grease 160 is preferably less than 22.7%.

This embodiment provides the same effects as the first embodiment. In addition, in this embodiment, since the grease 160 does not contact the seal member 50, the grease 160 is not pressed by the seal member 50 when the seal member 50 is attached to the outer ring 20. This prevents the grease 160 from moving axially inward, preventing the grease 160 from coming into contact with the rolling elements 30 or the cage 40 more than necessary. Therefore, an increase in the rotational resistance of the rolling bearing 1A can be prevented.

In the second embodiment, the grease 160 extends in an annular shape, but is not limited to this configuration. The grease may extend in an arc shape to form an intermittent portion, or may have multiple granules arranged in dots around the entire circumference. When the grease has multiple granules, the multiple granules aligned in the circumferential direction may be integrated or may be spaced apart from each other.

[Third embodiment]
Next, a third embodiment will be described with reference to Fig. 6. The rolling bearing 1B of the third embodiment differs from the rolling bearing 1A of the second embodiment in that the grease 160A is in contact with the seal member 50 and the rolling elements 30. Note that the configuration other than that described below is the same as that of the second embodiment.

The grease 160A further includes a seal member contact portion 162 that contacts the flat portion 53 of the seal member 50 axially outward and radially inward of the outer ring contact portion 161, and is not in contact with the inner ring 10. The seal member contact portion 162 contacts only the flat portion 53 of the seal member 50. As a result, the grease 160A is not in contact with the base portion 51 and the extension portion 52 of the seal member 50 that are located closer to the outer ring 20 than the flat portion 53. The grease 160A contacts the rolling element 30. The volume of the portion of the grease 160A that contacts the rolling element 30 is less than half the volume of the entire grease 160A. The grease 160A may be in contact with the cage 40.

The properties of grease 160A are similar to those of grease 60 of the first embodiment. That is, the unmixed penetration of grease 160A is greater than 178 and less than 287. The difference between the mixed penetration and the unmixed penetration of grease 160A is preferably less than 50. The ratio of the difference between the mixed penetration and the unmixed penetration to the mixed penetration of grease 160A is preferably less than 22.7%.

This embodiment has the same effects as the second embodiment. In addition, in this embodiment, since the grease 160A is in contact with the rolling element 30, the base oil of the grease 160A can be directly supplied to the rolling element 30. Therefore, an increase in the rotational resistance of the rolling bearing 1B can be suppressed.

In the third embodiment, the grease 160A extends in an annular shape, but is not limited to this configuration. The grease may extend in an arc shape to form an intermittent portion, or may have multiple granules arranged in dots around the entire circumference. When the grease has multiple granules, the multiple granules aligned in the circumferential direction may be integrated or may be spaced apart from each other.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

The viscosity of the grease in this example was measured at 40°C in accordance with JIS K2283. The consistency of the grease in this example was measured by the method specified in JIS K2220.

The greases in Examples 1 to 3 and Comparative Examples 1 to 3 were prepared as follows:

Example 1
An ester oil and a PAO were mixed at a mass ratio (ester oil/PAO) of >1 to obtain a base oil with a kinematic viscosity of 44 ^mm2 /s. Alicyclic urea was synthesized as a thickener in this base oil to obtain a grease with a worked penetration of 228, an unworked penetration of 227, and an unworked penetration of 188 after standing at high temperature.

Example 2
Using the same base oil and thickener as in Example 1, and adjusting the ratio of thickener to base oil, a grease was obtained with a worked penetration of 261, an unworked penetration of 255, and an unworked penetration of 210 after exposure to high temperatures.

Example 3
An ether oil and an ester oil were mixed at a mass ratio (ether oil/ester oil) of >1 to obtain a base oil with a kinetic viscosity of 80 ^mm2 /s. An alicyclic urea was synthesized in this base oil to obtain a grease with a worked penetration of 290, an unworked penetration of 274, and an unworked penetration after standing at high temperature of 282.

Example 4
PAO alone was used as a base oil with a kinetic viscosity of 48 mm ² /s. Alicyclic urea and aliphatic urea were synthesized in this base oil to obtain a grease with a worked penetration of 199, an unworked penetration of 197, and an unworked penetration of 200 after standing at high temperatures.

Example 5
The ester oil alone was used as a base oil with a kinetic viscosity of 100 mm ² /s. Alicyclic urea and aliphatic urea were synthesized in this base oil to obtain a grease with a worked penetration of 265, an unworked penetration of 245, and an unworked penetration of 244 after standing at high temperature.

<Comparative Example 1>
PAO alone was used as a base oil with a kinematic viscosity of 48 mm ² /s. Alicyclic urea and aliphatic urea were synthesized in this base oil as thickeners to obtain a grease with a worked penetration of 220, an unworked penetration of 170, and an unworked penetration of 158 after standing at high temperatures.

<Comparative Example 2>
PAO and ester oil were mixed at a mass ratio (PAO/ester oil) > 1 to obtain a base oil with a kinematic viscosity of 22 ^mm2 /s. Alicyclic urea and aliphatic urea were synthesized as thickeners in this base oil to obtain a grease with a worked penetration of 232, an unworked penetration of 178, and an unworked penetration of 149 after standing at high temperature.

<Comparative Example 3>
Using the same base oil and thickener as in Example 1, and adjusting the ratio of thickener to base oil, a grease was obtained with a worked penetration of 295, an unworked penetration of 287, and an unworked penetration after standing at high temperatures of 236.

<Comparative Example 4>
A base oil with a kinematic viscosity of 52 ^mm2 /s was prepared by mixing mineral oil and PAO at a mass ratio (mineral oil/PAO) of ≈1. Alicyclic urea and aliphatic urea were synthesized in this base oil as thickeners to obtain a grease with a worked penetration of 248, an unworked penetration of 164, and an unworked penetration of 155 after exposure to high temperatures.

Durability tests of rolling bearings were conducted under the following conditions for each of the greases in Examples 1 to 5 and Comparative Examples 1, 2, and 4 above. Note that when the grease in Comparative Example 3 was used in the rolling bearings listed below, the variation in the individual rolling resistance of the rolling bearings exceeded the specified required value, and fluctuations in the rolling resistance occurred over operating time. Therefore, it was determined to be unsuitable as a grease for rolling bearings and was excluded from the durability tests.

(Roller bearing shape)
A rolling bearing having an outer diameter of an outer ring of 8 mm, an inner diameter of an inner ring of 3 mm, and a height (thickness in the axial direction) of 4 mm was used.

(Grease placement)
12 mg of grease was applied in the shape of the grease 60 of the first embodiment.

(Method of evaluating durability)
Two rolling bearings using the same grease were installed in one fan motor (rated speed 25,000 rpm). Five fan motors were prepared for each of the greases in Examples 1 to 3 and Comparative Examples 1 and 2, and were operated continuously in a high-temperature chamber at 85°C. The operating conditions and the occurrence of abnormal noise were confirmed every 500 hours. The evaluation results are shown in Table 1.

When the grease of Comparative Example 1 was used, abnormal noise was confirmed in three of the five fan motors after 3000 hours of operation. When the grease of Comparative Example 2 was used, one of the five fan motors stopped after 2000 hours of operation, and two more stopped after 2500 hours of operation. On the other hand, when the greases of Examples 1 to 3 were used, the five fan motors operated stably without generating abnormal noise even after 5000 hours of operation. From the above, it is clear that if the unmixed penetration of the grease is greater than 178 and less than 287, it is possible to improve the durability of the rolling bearing while suppressing the occurrence of variations in the rotation resistance of each rolling bearing. Furthermore, it is clear that if the unmixed penetration of the grease satisfies the above conditions and the difference between the mixed penetration and the unmixed penetration is less than 50, the durability of the rolling bearing can be reliably improved. Furthermore, if the unmixed penetration of the grease satisfies the above conditions and the ratio of the difference between the mixed penetration and the unmixed penetration to the mixed penetration is less than 22.7%, it is clear that the durability of the rolling bearing can be reliably improved.

The present invention is not limited to the above-described embodiment explained with reference to the drawings, and various modifications are possible within the technical scope of the present invention.
For example, in the above embodiment, the inner ring 10 is provided as a rotating ring, and the outer ring 20 is provided as a fixed ring. And the grease 60, 160, 160A is in contact with the outer ring 20 which is a fixed ring. However, the raceway ring with which the grease is in contact does not have to be a fixed ring. That is, the inner ring may be provided as a fixed ring, the outer ring may be provided as a rotating ring, and the grease may be in contact with the inner ring which is a fixed ring. Also, the inner ring may be provided as a fixed ring, the outer ring may be provided as a rotating ring, and the grease may be in contact with the outer ring which is a rotating ring. Also, in the above embodiment, the rolling elements 30 are held by the cage 40, but the present invention may be applied to a rolling bearing that does not have a cage.

In addition, in each of the above embodiments and their modified examples, the grease is arranged approximately once around the circumference, but this configuration is not limited to this. The grease may have a first annular portion in contact with the outer ring 20 and a second annular portion connected to the first annular portion and in contact with the seal member 50. In this case, the first annular portion and the second annular portion each extend in a circular ring shape centered on the common axis O. However, at least one of the first annular portion and the second annular portion may extend less than 360° around the common axis O. Also, at least one of the first annular portion and the second annular portion may have a plurality of granules arranged in a dot pattern around the entire circumference.

In addition to the grease 60, 160, 160A, or instead of the grease 60, 160, 160A, the rolling bearing may have grease placed in the grease pocket or the lower end surface of the cage. In this case, it is desirable that the grease placed in the cage does not come into contact with the rolling elements. An example of the cage 40 in which the grease 60 is placed is shown in FIG. 7. As shown in FIG. 7, the cage 40 has the above-mentioned annular portion 41 and a plurality of column portions 42. Furthermore, a grease pocket 47 recessed downward is formed on the upper end surface 40u of the cage 40. The grease pocket 47 is formed between a pair of ball pockets B adjacent to each other in the circumferential direction. That is, the grease pocket 47 is formed in each column portion 42. The grease 60 is placed in the grease pocket 47. The grease may be placed on the lower end surface of the cage 40 in addition to the grease pocket 47 or instead of the grease pocket 47. However, when grease is placed on the cage 40, the grease placed on the cage 40 is placed separately from the grease applied so as to come into contact with the raceway and the seal member. In other words, the grease placed on the cage 40 does not come into contact with the raceway and the seal member.

In addition, in each of the above embodiments, the grease 60, 160, 160A contacts the inner peripheral surface of the outer ring 20, but this configuration is not limited to this. The grease may not contact the raceway and may only contact the seal member 50. In other words, it is sufficient that the grease contacts at least one of the peripheral surface (inner peripheral surface or outer peripheral surface) of one raceway facing the other raceway and the seal member 50.

In addition, in the above embodiment, a fan motor is exemplified as a rotating device, but the rotating device is not limited to this. For example, the present invention may be applied to a rotating device such as a dental handpiece or a spindle motor of a hard disk drive. In particular, rolling bearings applied to spindle motors of hard disk drives require low torque and have a rotation angle of less than 360°, making it preferable to place the grease in a retainer, and therefore the grease of the present invention, which allows the base oil to easily seep out even without shearing, is useful.

The present invention does not limit the size of the rolling bearing. The size of the rolling bearing used in the durability test of the above example is an example of a small bearing (outer diameter 30 mm or less) used in a small motor with a small motor torque that is easily affected by the bearing torque caused by grease, and the present invention has a significant advantage especially in rolling bearings with an outer diameter of 16 mm or less.

In addition, the components in the above-described embodiments may be replaced with well-known components as appropriate without departing from the spirit of the present invention, and the above-described embodiments and variations may be combined as appropriate.

1, 1A, 1B... bearing 10... inner ring (other raceway) 20... outer ring (one raceway) 22... protrusion 22a... end face 30... rolling element 40... retainer 50... seal member 51... pedestal 52... extension 53... flat surface 60, 160, 160A... grease 61, 161... outer ring contact portion (raceway contact portion) 62, 162... seal member contact portion

Claims (11)

An inner ring and an outer ring arranged coaxially with each other;
A rolling element disposed between the inner ring and the outer ring;
a cage that holds the rolling elements so that they can roll;
A grease to be filled in a small rolling bearing for a small motor having an outer diameter of 30 mm or less, the small rolling bearing comprising: a seal member attached to only a fixed ring of the inner ring and the outer ring and covering a gap between the inner ring and the outer ring from the outside in the axial direction,
The base oil is a synthetic oil containing at least one of poly-alpha-olefins, esters, and ethers;
It is thickened with a thickener containing alicyclic urea,
a retainer that is disposed between the rolling body and the seal member and is in contact with at least one of the circumferential surfaces of the inner ring and the outer ring that face the rotating ring and the seal member, but is not in contact with the rotating ring and the cage, or is disposed in the cage and is not in contact with any of the rolling body, the fixed ring, and the rotating ring;
The unworked penetration is 197 or more and less than 287,
A grease having a difference between worked and unworked penetration of less than 50. The ratio of the difference between the worked penetration and the unworked penetration to the worked penetration is less than 22.7%.
The grease of claim 1. The unmixed penetration after standing at 85°C for 18 hours is greater than 158.
The grease according to claim 1 or 2. The sealing member is
an annular seat portion that contacts the fixed ring from the outside in the axial direction;
an extension portion extending outward in the axial direction from a peripheral edge of the base portion on the rotating wheel side in the radial direction ;
a flat surface portion extending in the radial direction from an outer end edge of the extension portion in the axial direction toward the rotating wheel;
The rolling bearing is sealed therein,
The base portion and the extension portion are in contact with each other.
The grease according to claim 1 or 2. The thickener is used alone to thicken the composition.
The grease according to claim 1 or 2. The sealing member is
an annular seat portion that contacts the fixed ring from the outside in the axial direction;
an extension portion extending outward in the axial direction from a peripheral edge of the base portion on the rotating wheel side in the radial direction ;
a flat surface portion extending in the radial direction from an outer end edge of the extension portion in the axial direction toward the rotating wheel;
The rolling bearing is sealed therein,
a raceway contact portion in contact with the peripheral surface of the fixed ring;
a seal member contact portion that is in contact with the flat portion on the rotating ring side and is located outside the raceway contact portion in the axial direction;
having
The sealing member is disposed so that an area of the contact portion of the sealing member is larger than an area of the contact portion of the sealing member with the extension portion and the base portion.
The grease according to claim 1 or 2. The seal member contact portion includes a center position of the grease in the radial direction as viewed from the axial direction.
The grease according to claim 6. The extension portion is not in contact with the extension portion.
The grease according to claim 6. The raceway contact portion is provided at a distance in the axial direction from a contact portion between the fixed ring and the base portion.
The grease according to claim 6. Non-contact with the base portion;
The grease according to claim 6. The fixed ring has a protruding portion protruding toward the rotating ring and having a raceway surface formed thereon,
the protruding portion faces outward in the axial direction, is connected to the peripheral surface at a peripheral edge on the rotating wheel side in the radial direction , and has an end surface in contact with the base portion,
The base portion is enclosed in the rolling bearing arranged so as not to protrude toward the rotating wheel side from the end face when viewed in the axial direction.
The grease according to claim 6.

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