JP7549526B2 - Rolling bearings - Google Patents

Description

The present invention relates to rolling bearings and to technology that can reduce the amount of dust generated from inside the bearing.

In the rolling bearing 50 for a servo motor shown in FIG. 10, for models in which the encoder 52 is located near the motor 51, low dust generation from the rolling bearing 50 is required with a contact seal to prevent malfunction of the encoder 52 due to dust generation from inside the bearing and seal wear powder adhering to the encoder 52.

In the prior art rolling bearing, as shown in FIG. 11, in order to achieve low torque and high sealing performance, the main lip 53 is in contact with the outer groove wall surface of the seal groove 54, and a labyrinth seal is formed between the tip of the secondary lip 55 and the inner groove wall surface of the seal groove 54.

JP 2006-170313 A

When the inner ring of a rolling bearing rotates at high speed, the internal pressure of the rolling bearing increases. If the sealing is insufficient, grease will be expelled to the outside along with the air, causing damage to the area around the rolling bearing.
Therefore, the applicant discovered that by specifying the shape of the secondary lip and the clearance with the inner ring, the amount of grease to be filled, and the properties of the grease, it is possible to prevent grease from forming clumps from inside the rolling bearing and entering the seal groove, thereby suppressing outflow and reducing the amount of dust generated from inside the bearing.

Therefore, the object of the present invention is to provide a rolling bearing that can reduce the amount of dust generated from inside the bearing even when the internal pressure of the bearing increases during rotation of the rolling bearing.

The rolling bearing of the present invention comprises a plurality of balls interposed between an inner ring and an outer ring held in a cage, a seal member for sealing a bearing space between the inner ring and the outer ring is attached to the outer ring, a seal groove is formed in the circumferential direction on the outer peripheral surface of the inner ring, and the seal member comprises a core bar, a main lip in contact with an outer groove wall surface of the seal groove, and a secondary lip not in contact with the seal groove,
The secondary lip protrudes axially inward from a base end portion, and a labyrinth seal is formed between a tip end portion of the secondary lip and an inner groove wall surface of the seal groove,
When the maximum axial distance from a position of the core metal inside the bearing to the tip of the secondary lip is D and the plate thickness of the core metal is d, 1.90≦D/d≦2.50.

When the grease used in the present invention is relatively hard, the secondary lip must be able to withstand the movement of the grease. If the secondary lip is too long relative to the core, it may be defeated by the grease and cause dust to be generated. If the secondary lip is too short relative to the core, that is, if the core itself is too thick, the bearing space is restricted to a narrow space. If the bearing space is restricted to a narrow space, not only will it be difficult to ensure the strength of the retainer, but the amount of grease filled into the bearing space will be insufficient. In addition, because the sealing member is a contact seal, there is a concern that the torque may increase.

According to this configuration, the ratio D/d of the maximum axial distance D from the core's inner bearing position to the tip of the secondary lip to the core's plate thickness d is set to 1.90 or more and 2.50 or less, so that even if a relatively hard grease is used to fill the bearing space, the secondary lip can withstand the movement of the grease and suppress dust generation, and the core can be prevented from becoming too thick. Since the core can be prevented from becoming too thick, the strength of the cage can be ensured and the amount of grease filled into the bearing space can be sufficiently satisfied.
This prevents the grease sealed in the bearing space from forming lumps and entering the seal groove of the inner ring, and reduces the amount of dust generated from inside the bearing even when the internal bearing pressure increases during rotation of the rolling bearing.

When an axial gap between an intersection point of the outer peripheral surface of the inner ring and the inner groove wall surface and a tip end of the secondary lip is defined as A, 0.2≦A/D≦0.5 may be satisfied.
If the intersection of the outer peripheral surface of the inner ring and the inner groove wall surface is a corner (so-called an edge), that position is used as a reference to define the axial clearance A. The intersection of the outer peripheral surface of the inner ring and the inner groove wall surface may not be an edge but may be smoothly connected, in which case the axial clearance A is defined as being based on the approximate center position of the portion where the outer peripheral surface of the inner ring and the inner groove wall surface are smoothly connected.
By defining the axial gap A in this manner, it is possible to more reliably prevent the grease sealed in the bearing space from forming lumps and infiltrating into the seal groove of the inner ring.

The grease sealed in the bearing space may account for 10% or more of the volume of the internal space of the bearing.
The "bearing internal space volume" refers to the volume of the space in the bearing space between the inner and outer rings, excluding the rolling elements and the cage. When seal members are attached to both axial sides, the volume refers to the space between the seal members on both axial sides of the bearing space between the inner and outer rings.
According to this configuration, the risk of dust generation can be reduced by setting the lower limit of the amount of grease filled to 10% of the volume of the space inside the bearing. For example, if the upper limit of the amount of grease filled is set to 60% of the volume of the space inside the bearing, the risk of dust generation increases, but dust generation from grease can be suppressed by specifying the grease with a set hardness, the axial gap of the sub-lip, the degree of contact of the main lip, etc.

The grease may be a grease composition comprising a base oil and a thickener, the base oil being a mixed oil comprising a synthetic hydrocarbon oil and an ether oil and having a kinetic viscosity of 120 ^mm2 /s or more at 40°C, the thickener being a urea compound, the amount of the thickener being 10 wt% to 15 wt%, and the grease composition having a worked penetration of 200 to 240 as measured in accordance with JIS K 2220.
In order to suppress the flow of the grease, it is preferable that the grease is hard, and a worked penetration of 200 to 240 is desirable. In order to achieve a worked penetration of 200 to 240, the amount of thickener is set to 10 wt % to 15 wt %, so that the grease can be hardened, and the movement of the grease can be made insensitive and the outflow of the grease can be suppressed. By applying such a grease composition, it is possible to achieve low dust generation while suppressing the deterioration of wear resistance and life. Even if the upper limit value of the filling amount of the grease is increased, by applying this grease composition, it is possible to suppress the generation of dust from the grease.

The outer diameter dimension of the base end of the secondary lip is located on the outer diameter side of the outer peripheral surface of the inner ring, and the outer diameter portion of the secondary lip has a portion that extends in a straight line in a cross section of the rolling bearing cut along a plane including the axial direction, and has a cross-sectional straight line portion that inclines toward the outer diameter side as it moves axially outward, and the inclination angle G of the cross-sectional straight line portion of the secondary lip with respect to the axial direction may be 5° or more and 25° or less.

If the inclination angle G of the secondary lip is too large, the grease will get into the seal groove of the inner ring, which may cause dust to be generated. If the inclination angle G is too small, in other words, if the outer diameter portion of the secondary lip is close to being parallel to the axial direction, the outer diameter side end of the tip of the secondary lip will be located on the outer diameter side of the outer circumferential surface of the inner ring. This may encourage the grease to flow toward the bottom of the seal groove as it is stirred during rotation.
With this configuration, the inclination angle G of the cross-sectional straight-line portion at the outer diameter portion of the secondary lip is set to be between 5° and 25°, and the extension line of the cross-sectional straight-line portion and the extension line of the outer peripheral surface of the inner ring intersect smoothly (at a moderate angle), thereby further reducing dust generation from grease.

The outer groove wall surface of the seal groove is formed as an inclined surface that inclines toward the outer diameter as it moves axially outward, and the seal member is formed in an R-shape in which the tip of the main lip abuts on the outer groove wall surface of the seal groove in the normal direction, and the inclination angle of the outer groove wall surface with respect to the axial direction may be 53 to 68°.

With this configuration, the inclination angle of the outer groove wall surface with respect to the axial direction is set to 53 to 68°, and the tip of the main lip is rounded, resulting in a surface pressure distribution of the main lip that maintains a state in which the tip of the main lip contacts in the normal direction against the internal bearing pressure generated when the rolling bearing rotates, i.e., a so-called normal contact. Therefore, even if the internal bearing pressure increases when the rolling bearing rotates, it is possible to simultaneously suppress the outflow of grease from inside the bearing and the intrusion of foreign matter from the atmosphere side.
If the inclination angle of the outer groove wall surface is less than 53°, the seal member is likely to be turned over by the internal bearing pressure, which is not appropriate. If the inclination angle of the outer groove wall surface is more than 68°, when the internal bearing pressure is generated, the tip of the main lip hits the inclined surface too strongly, which is not appropriate because it increases the torque or generates more heat.

The tip of the main lip may be arc-shaped with a radius of 0.03 to 0.09 mm. In this case, it is possible to more reliably suppress changes in the surface pressure distribution of the main lip during rotation of the rolling bearing, and it is also possible to suppress increases in torque, heat generation, etc.
If the radius of the tip of the main lip is less than 0.03 mm, it is considered that normal contact will not be achieved when the internal bearing pressure changes during rotation of the rolling bearing, causing a slight shift in the contact position of the main lip.If the radius of the tip of the main lip is more than 0.09 mm, when the internal bearing pressure rises during rotation of the rolling bearing and the tip of the main lip hits the inclined surface hard, the contact area will increase, causing an increase in torque or heat generation, which is not appropriate.

The seal member has the core metal and a rubber material, the main lip and the sub lip are made of the rubber material, and the surface roughness of a part or the whole part located on the inner diameter side of the PCD on the inner surface of the rubber material including the inner surfaces of the main lip and the sub lip may be Ra = 0.4 to 2.5 μm. In this case, a desired dust generation suppression effect can be obtained and resistance to grease can be kept low.
If the arithmetic mean roughness Ra is less than 0.4 μm, the effect of suppressing the movement of grease is small, and the effect of suppressing dust generation is small. If the arithmetic mean roughness Ra is more than 2.5 μm, that is, if the surface is too rough, the resistance to the grease becomes too large, which is disadvantageous to rotation, and is therefore not appropriate.

The seal member may be provided with an air outlet for releasing the internal pressure. In this case, by releasing the internal bearing pressure from the air outlet when the rolling bearing rotates, it is possible to suppress excessive changes in the seal interference and the outflow of grease caused by an increase in the internal bearing pressure.

The air outlets may be provided on the outer peripheral portion of at least one of the sealing members, and may include radial air outlets formed along the radial direction and axial air outlets formed along the axial direction, with the radial air outlets and the axial air outlets being provided at different circumferential positions. By shifting the circumferential positions (circumferential phase) of the radial air outlets and the axial air outlets in this manner, the outflow of grease can be more reliably suppressed.

The main lip of the seal member may be provided with an air outlet for releasing the internal pressure of the rolling bearing. In this case, by releasing the internal bearing pressure from the air outlet when the rolling bearing rotates, it is possible to suppress excessive changes in the seal interference and the outflow of grease caused by an increase in the internal bearing pressure.

The air outlet provided in the seal member may be on one or both axial sides of the seal member.

The rolling bearing of the present invention has a plurality of balls interposed between an inner ring and an outer ring held in a cage, a seal member that seals the bearing space between the inner ring and the outer ring is attached to the outer ring, a seal groove is formed in the circumferential direction on the outer peripheral surface of the inner ring, and the seal member is a rolling bearing having a core, a main lip that contacts the outer groove wall surface of the seal groove, and a secondary lip that does not contact the seal groove, the secondary lip protruding axially inward from the base end, a labyrinth seal is formed between the tip of the secondary lip and the inner groove wall surface of the seal groove, and when the maximum axial distance from the inner bearing side position of the core to the tip of the secondary lip is D and the plate thickness of the core is d, 1.90≦D/d≦2.50 is satisfied. Therefore, even if the bearing internal pressure rises when the rolling bearing rotates, the amount of dust generated from inside the bearing can be reduced.

1 is a cross-sectional view of a rolling bearing according to a first embodiment of the present invention. 4 is an enlarged cross-sectional view of a lip and the like of a seal member of the rolling bearing. FIG. FIG. FIG. 4 is a partially enlarged cross-sectional view of the seal member taken along a radial air outlet. FIG. 4 is a partially enlarged cross-sectional view of the seal member taken along an air outlet in the axial direction. FIG. 4 is an enlarged cross-sectional view of a lip and the like of a sealing member in a rolling bearing according to another embodiment of the present invention. FIG. 11 is a cross-sectional view of a rolling bearing according to still another embodiment of the present invention. FIG. 11 is a cross-sectional view of a rolling bearing according to still another embodiment of the present invention. FIG. 2 is a perspective view of a cage of the rolling bearing. FIG. 11 is a cross-sectional view of a rolling bearing according to still another embodiment of the present invention. FIG. 2 is a schematic diagram showing a rolling bearing for a servo motor. FIG. 11 is an enlarged cross-sectional view partially showing a seal structure of a conventional rolling bearing.

[First embodiment]
A rolling bearing according to a first embodiment of the present invention will be described with reference to FIGS.
<General configuration of rolling bearing>
FIG. 1 is a cross section (longitudinal cross section) of the rolling bearing 1 cut in the axial direction, that is, in a plane including the bearing axial direction. The same applies to cross sections in other embodiments. As shown in FIG. 1, the rolling bearing 1 is a deep groove ball bearing including inner and outer rings 2 and 3, balls 4, a retainer 5, and a seal member 6. A plurality of balls 4 interposed between the raceway surfaces 2a and 3a of the inner and outer rings 2 and 3 are held at regular intervals in the circumferential direction by the retainer 5, and a seal member 6 that closes the bearing space between the inner ring 2 and the outer ring 3 is attached to the outer ring 3. In this example, seal members 6, 6 are attached to both axial sides of the inner peripheral surface of the outer ring. Grease, which will be described later, is sealed in the bearing space between the inner and outer rings 2 and 3. The retainer 5 is a so-called crown-type retainer that has pockets Pt for holding the balls 4 therein at a plurality of locations in the circumferential direction of the annular body, and is shaped such that one axial side of the pockets Pt is open.

<Seal structure>
Each seal member 6 is a contact seal in which a main lip 15 contacts a seal groove 7. Seal grooves 7 are formed in the circumferential direction on the outer peripheral surface of the inner ring 2, and seal member fixing grooves 9 are provided on the inner peripheral surface of the outer ring 3 facing each seal groove 7. As shown in Figures 1 to 3, the seal member 6 is formed by molding a rubber material 11 onto a core metal 10, and the outer peripheral edge of this seal member 6 is fitted into and fixed in the seal member fixing groove 9 of the outer ring 3. As shown in Figures 3, 4A and 4B, the outer peripheral portion of the seal member 6 is provided with an air outlet 12 for releasing the internal pressure of the rolling bearing.

1, 4A and 4B show a portion of the outer peripheral portion of the seal member 6 embedded in the seal member fixing groove 9 of the outer ring 3, but this portion is an interference and is actually fitted into the seal member fixing groove 9 in an elastically deformed state. Also, a portion of the main lip 15 of the seal member 6 is shown to be embedded in the seal groove 7 of the inner ring 2 , but this portion is an interference and is actually in contact with the seal groove 7 in an elastically deformed state. The same applies to the seal structures of the other embodiments.

As shown in Figures 3, 4A and 4B, a plurality of air outlets 12 are provided for the seal member 6. These air outlets 12 include radial air outlets 12a (Figure 4A) formed along the radial direction and axial air outlets 12b (Figure 4B) formed along the axial direction. The air outlets 12a and 12b each consist of a groove provided on the outer circumferential portion of the seal member 6. The radial air outlets 12a and the axial air outlets 12b are provided at different circumferential positions.

Specifically, two radial air outlets 12a, 12a are provided 180 degrees apart in the circumferential direction on the inner surface of the outer peripheral portion of the seal member 6 facing the inner groove wall surface 9a of the seal member fixing groove 9. The radial air outlet 12a and the inner groove wall surface 9a form a hole. In addition, one axial air outlet 12b is provided on the outer peripheral surface of the outer peripheral portion of the seal member 6 facing the outer peripheral groove wall surface 9c and the outer groove wall surface 9b of the seal member fixing groove 9. The axial air outlet 12b, the outer peripheral groove wall surface 9c, and the outer groove wall surface 9b form a hole. This axial air outlet 12b is provided at a circumferential position that is 90 degrees out of phase with the radial air outlet 12a. These radial air outlets 12a, 12a and the axial air outlet 12b communicate with each other via the outer peripheral groove wall surface 9c of the seal member fixing groove 9. Therefore, when the rolling bearing 1 rotates, the internal bearing pressure can be released from the two radial air outlets 12a, 12a via the axial air outlet 12b. Note that the circumferential positions of the axial and radial air outlets 12a, 12b are not limited to the phase described above.

As shown in Figures 1 and 2, the seal groove 7 of the inner ring 2 has, in order toward the outside in the axial direction, an inner groove wall surface 7a, a groove bottom surface 7b, and an outer groove wall surface 7c. The inner groove wall surface 7a is connected to the outer peripheral surface 2b of the inner ring 2, which is an inner ring shoulder provided on both axial sides of the raceway surface 2a, and is formed as an inclined surface that inclines toward the inner diameter as it moves axially outward. The groove bottom surface 7b, which smoothly connects to this inner groove wall surface 7a, extends approximately parallel to the axial direction. The outer groove wall surface 7c is smoothly connected to the groove bottom surface 7b, and is formed as an inclined surface that inclines toward the outer diameter as it moves axially outward. The inclination angle I of the outer groove wall surface 7c with respect to the axial direction is set to be 53 degrees or more and 68 degrees or less.

As shown in FIG. 2, the inner peripheral portion 13 of the seal member 6, which extends radially inward beyond the inner diameter of the core metal 10, is made of the rubber material 11. The rubber material 11 is typically made of nitrile rubber, but other materials such as acrylic rubber, silicone rubber, and fluororubber may be used depending on the operating temperature.

The inner peripheral portion 13 of the seal member 6 has a constricted portion 14 whose thickness decreases toward the inner diameter side, a main lip 15 connected to the constricted portion 14, and a secondary lip 16 that does not contact the seal groove 7. The constricted portion 14, main lip 15, and secondary lip 16 are integrally molded. The main lip 15 is connected to the inner diameter side end of the constricted portion 14, and the secondary lip 16 protrudes axially inward from the inner surface portion of the base end 15a of the main lip 15. As shown in FIG. 1, a labyrinth seal Rs is formed between the tip end of the secondary lip 16 and the inner groove wall surface 7a of the seal groove 7.

2, the main lip 15 has a base end 15a that slopes inward in the axial direction, a lip body 15b that extends inward from the base end 15a, and a tip end 15c that is provided on the outer surface of the lip body 15b at the tip side. The tip end 15c of the main lip 15 is formed in an R-shape that abuts the outer groove wall surface 7c of the seal groove 7 in the normal direction. The outer diameter surface 15ca of the tip end 15c of the main lip 15 slopes inward in the axial direction and smoothly connects to the R-shape. When the inclination angle I of the outer groove wall surface 7c of the seal groove 7 is 53 degrees or more and 68 degrees or less, the tip end 15c of the main lip 15 is an arc shape with a radius of 0.03 mm or more and 0.09 mm or less.

If the radius R of the tip 15c of the main lip 15 is less than 0.03 mm, it is possible that normal contact will not occur when the internal bearing pressure changes during rotation of the rolling bearing, causing a slight shift in the contact position of the main lip 15. If the radius R of the tip 15c of the main lip 15 is greater than 0.09 mm, when the internal bearing pressure rises during rotation of the rolling bearing and the tip 15c of the main lip 15 hits the inclined surface hard, the contact surface will increase, causing large torque or heat generation, which is not appropriate.

The outer diameter dimension J of the base end of the secondary lip 16 is located on the outer diameter side of the outer peripheral surface 2b of the inner ring 2. The outer diameter portion 16a of the secondary lip 16 has a portion that extends in a straight line in the longitudinal section, and has a cross-sectional straight line portion 16aa that inclines toward the outer diameter side as it moves axially outward. In this case, the cross-sectional straight line portion 16aa and the portion that extends in a straight line are the same portion. The inclination angle G of the cross-sectional straight line portion 16aa with respect to the axial direction is 5° or more and 25° or less. The inner diameter portion 16b of the secondary lip 16 extends parallel to the axial direction.

The dimensions of each part are set as follows:
Axial clearance A between the intersection of the outer peripheral surface 2b of the inner ring 2 and the inner groove wall surface 7a, and the tip of the secondary lip at the time of the initial contact angle: 0.2 mm or more and 0.5 mm or less. The initial contact angle is a state in which the axial clearance becomes zero when the outer ring is fixed and the inner ring is moved in the axial direction.
When the intersection of the outer peripheral surface 2b of the inner ring 2 and the inner groove wall surface 7a is a corner (so-called edge), the position of the corner is used as a reference to define the axial clearance A. The intersection of the outer peripheral surface 2b of the inner ring 2 and the inner groove wall surface 7a may be a smooth connection rather than an edge, in which case the axial clearance A is defined as a reference to the approximate center position of the portion where the outer peripheral surface 2b of the inner ring 2 and the inner groove wall surface 7a are smoothly connected.

Radial dimension B of the tip of the secondary lip 16: 0.3 mm ± 0.1 mm
Radial dimension C from the outer peripheral surface 2b of the inner ring 2 to the inner diameter portion 16b of the secondary lip 16: 0.2 mm ± 0.15 mm
The maximum axial distance from the bearing inner position 10a of the core 10 to the tip of the secondary lip 16 is D, and the core thickness is d. The core thickness ratio of the dimension D ( D/d ):
1.90≦D/d≦2.50 (preferably 2.05≦D/d≦2.35)

Ratio of axial clearance A to dimension D (A/D): 0.2≦A/D≦0.5
Radial dimension E from the inner diameter portion 16b of the secondary lip 16 to the inner diameter side end portion of the lip main body portion 15b: 60% ± 10% of the radial length F of the rubber portion cross section
Ratio of the radial length F of the inner circumferential portion (cross section of the rubber portion) of the seal member 6 to the core metal thickness ((F/d)×100): 400%±50%
Inclination angle G of the secondary lip 16: 15°±10°

As shown in FIG. 4A, the surface roughness of the seal member 6, covering the inner surface of the main lip 15, the inner surface, inner diameter surface and outer diameter surface of the secondary lip 16, the inner surface of the constricted portion 14, and the inner surface of the rubber material 11 connected to the inner surface of the constricted portion 14 (the portion indicated by the dotted line L1 in FIG. 4A), is 0.4 μm or more and 2.5 μm or less in arithmetic mean roughness Ra. If the arithmetic mean roughness Ra is less than 0.4 μm, the effect of suppressing the movement of grease is reduced, and the effect of suppressing dust generation is reduced. If the arithmetic mean roughness Ra is more than 2.5 μm, that is, if it is too rough, the resistance to the grease becomes too large, which is detrimental to rotation and is not appropriate.

In this example, the surface roughness is specified not only for the inner surface of the main lip 15, but also for the inner surfaces of the secondary lip 16 and the constricted portion 14, etc. However, it may also be specified that the surface roughness of at least a part or all of the inner surface of the rubber material 11, including the inner surface of the main lip 15, located on the inner diameter side of the pitch circle diameter (PCD) is 0.4 μm or more and 2.5 μm or less in arithmetic mean roughness Ra.

<About grease>
As shown in Fig. 1, the amount of grease filled in the bearing space is 10% to 60% of the volume of the bearing internal space. The "bearing internal space volume" refers to the volume of the space excluding the balls 4 and the cage 5 in the bearing space between the inner and outer rings 2 and 3, and when seal members 6 and 6 are attached on both axial sides as in this embodiment, it refers to the volume of the space between the seal members 6 and 6 on both axial sides of the bearing space between the inner and outer rings 2 and 3.

This grease is a grease composition containing a base oil and a thickener, wherein the base oil is a mixed oil containing a synthetic hydrocarbon oil and an ether oil and having a kinetic viscosity of 120 mm ² /s or more at 40° C. This kinetic viscosity is the kinetic viscosity of the mixed oil, and is preferably 120 mm ² /s to 160 mm ² /s, and more preferably 125 mm ² /s to 140 mm ² /s at 40° C. The grease composition may contain additives.

The synthetic hydrocarbon oil is preferably a poly-α-olefin oil (PAO oil). PAO oil is a mixture of α-olefins or isomerized α-olefin oligomers or polymers. Specific examples of α-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-docosene, and 1-tetradocosene, and mixtures of these are usually used.

Examples of the ether oil include polyphenyl ether oil, alkyl diphenyl ether oil, alkyl triphenyl ether oil, and alkyl tetraphenyl ether oil.

The thickener is a urea compound, and the amount of the thickener is 10 wt% to 15 wt%. The grease composition has a worked penetration of 200 to 240 as measured in accordance with JIS K 2220. From the viewpoint of suppressing the amount of dust generation, it is preferable that the worked penetration is in the range of 200 to 220.

<Action and effect>
According to the rolling bearing 1 described above, the ratio D/d of the maximum axial distance D from the position 10a inside the bearing of the core metal 10 to the tip of the secondary lip 16 to the plate thickness d of the core metal 10 is set to be 1.90 or more and 2.50 or less, so that even if a relatively hard grease is used as the grease to be sealed in the bearing space, the secondary lip 16 can withstand the movement of the grease and suppress dust generation, and it is possible to prevent the core metal 10 from becoming too thick. Since it is possible to prevent the core metal 10 from becoming too thick, the strength of the cage 5 can be ensured and the amount of grease filled in the bearing space can be sufficiently satisfied.
This makes it possible to prevent the grease sealed in the bearing space from forming lumps and infiltrating into the seal groove 7 of the inner ring 2. Even if the internal bearing pressure increases when the rolling bearing 1 rotates, the amount of dust generated from inside the bearing can be reduced.

The axial gap A between the intersection of the outer peripheral surface 2b of the inner ring 2 and the inner groove wall surface 7a and the tip of the secondary lip 16 is set to 0.2 mm or more and 0.5 mm or less. In particular, by setting 0.2≦A/D≦0.5, it is possible to more reliably prevent the grease sealed in the bearing space from forming lumps and infiltrating into the seal groove 7 of the inner ring 2. If A/D is greater than 0.5, the effect of the labyrinth is insufficient, and if A/D is less than 0.2, the tip of the secondary lip 16 is more likely to come into contact with the seal groove 7.

The risk of dust generation can be reduced by lowering the lower limit of the amount of grease to be filled to 10% of the volume of the internal space of the bearing. For example, if the upper limit of the amount of grease to be filled is increased to 60% of the volume of the internal space of the bearing, the risk of dust generation increases, but dust generation from grease can be suppressed by specifying the aforementioned specified hardness of grease, the axial gap A of the secondary lip 16, the contact condition of the primary lip 15, etc.

By using a hard grease with a worked penetration of 200 to 240 as the grease, the flow of the grease can be suppressed. By using a thickener amount of 10 wt% to 15 wt% to achieve a worked penetration of 200 to 240, the grease can be made hard, making the movement of the grease less sensitive and suppressing the outflow of the grease. By using such a grease composition, it is possible to achieve low dust generation while suppressing the decrease in wear resistance and lifespan. Even if the upper limit of the amount of grease filled is increased, by using this grease composition, dust generation from the grease can be suppressed.

If the inclination angle G of the secondary lip 16 is too large, the possibility of grease entering the seal groove 7 of the inner ring 2 and generating dust increases. If the inclination angle G is too small, in other words, if the outer diameter portion 16a of the secondary lip 16 approaches parallelism to the axial direction, the outer diameter side end of the tip portion of the secondary lip 16 is located on the outer diameter side of the outer peripheral surface 2b of the inner ring 2. For this reason, there is a possibility that the grease will be stirred during rotation and at the same time, the grease will be encouraged to flow toward the groove bottom surface 7b of the seal groove 7.
With this configuration, the inclination angle G of the cross-sectional straight-line portion 16aa at the outer diameter portion 16a of the secondary lip 16 is set to be greater than or equal to 5° and less than 25°, and the extension line of the cross-sectional straight-line portion 16aa and the extension line of the outer peripheral surface 2b of the inner ring 2 intersect smoothly (at a moderate angle), thereby further reducing the generation of dust from the grease.

By setting the inclination angle I of the outer groove wall surface 7c with respect to the axial direction to 53 to 68° and making the tip 15c of the main lip 15 round, the surface pressure distribution of the main lip 15 is such that the tip 15c of the main lip 15 can maintain a state in which it contacts in the normal direction, that is, a so-called normal contact, against the internal bearing pressure generated when the rolling bearing 1 rotates. Therefore, even if the internal bearing pressure rises when the rolling bearing 1 rotates, it is possible to simultaneously suppress the outflow of grease from inside the bearing and the intrusion of foreign matter from the atmosphere side.
If the inclination angle I of the outer groove wall surface 7c is less than 53°, the seal member 6 is likely to be turned over by the internal bearing pressure, which is not appropriate. If the inclination angle I of the outer groove wall surface 7c is more than 68°, when the internal bearing pressure is generated, the tip end 15c of the main lip 15 hits the inclined surface too strongly, which is not appropriate because the torque increases or more heat is generated.

Since the tip 15c of the main lip 15 is arc-shaped with a radius of 0.03 to 0.09 mm, changes in the surface pressure distribution of the main lip 15 when the rolling bearing 1 rotates can be more reliably suppressed, and increases in torque and heat generation can be suppressed.
If the radius of the tip 15c of the main lip 15 is less than 0.03 mm, it is considered that normal contact will not occur when the internal bearing pressure changes during rotation of the rolling bearing, causing a slight shift in the contact position of the main lip 15. If the radius of the tip 15c of the main lip 15 is more than 0.09 mm, when the internal bearing pressure rises during rotation of the rolling bearing and the tip 15c of the main lip 15 hits the inclined surface hard, the contact surface will increase, causing an increase in torque or heat generation, which is not appropriate.

The surface roughness of a portion or the entire portion located on the inner diameter side of the PCD in the portion spanning the inner surfaces, inner diameter surfaces and outer diameter surfaces of main lip 15 and secondary lip 16, the inner surface of constricted portion 14, and the inner surface of rubber material 11 connected to the inner surface of constricted portion 14 (the portion indicated by dotted line L1 in Figure 4A) is Ra = 0.4 to 2.5 μm, so that the desired dust generation suppression effect can be obtained and resistance to grease can be kept low.
If the arithmetic mean roughness Ra is less than 0.4 μm, the effect of suppressing the movement of grease is small, and the effect of suppressing dust generation is small. If the arithmetic mean roughness Ra is more than 2.5 μm, that is, if the surface is too rough, the resistance to the grease becomes too large, which is disadvantageous to rotation, and is therefore not appropriate.

A plurality of air outlets 12 are provided on the outer peripheral portion of the seal member 6, and these air outlets 12 have radial air outlets 12a formed along the radial direction and axial air outlets 12b formed along the axial direction, with the radial air outlets 12a and the axial air outlets 12b provided at different circumferential positions. By shifting the circumferential positions (circumferential phase) of the radial air outlets 12a and the axial air outlets 12b in this way, the outflow of grease can be more reliably suppressed.

<Other embodiments>
In the following description, parts corresponding to matters previously described in each embodiment are given the same reference symbols, and duplicated description is omitted. When only a part of the configuration is described, the other parts of the configuration are the same as the previously described embodiment unless otherwise specified. The same action and effect are obtained from the same configuration. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine the embodiments, provided that there is no particular problem with the combination.

As shown in Fig. 5, the main lip 15 may be provided with an air outlet 18 for releasing the internal pressure of the rolling bearing. For example, a plurality of radial air outlets 18 are provided at an equal interval in the circumferential direction in the tip portion 15c of the main lip 15. Each air outlet 18 is formed of a groove. A hole is formed by the air outlet 18 and the outer groove wall surface 7c facing the air outlet 18. Note that the number of radial air outlets 18 at the tip portion 15c of the main lip 15 may be one. Alternatively, a plurality of radial air outlets 18 may be provided at unequal intervals in the circumferential direction.
According to the configuration of FIG. 5, the internal bearing pressure is released through the air outlet 18 when the rolling bearing rotates, thereby making it possible to suppress excessive changes in the seal interference and the outflow of grease caused by an increase in the internal bearing pressure.

As shown in FIG. 6, the seal member 6 may be attached to only one axial side of the inner peripheral surface of the outer ring. In this case, it is possible to prevent the bearing internal pressure from rising excessively when the rolling bearing 1 rotates, and it is possible to reduce the number of parts and therefore costs. In addition, a seal groove and a seal member fixing groove may be provided in either or both of the inner and outer rings 2, 3.

As shown in Figs. 7 and 8, the cage 5A may be made of synthetic resin and may be a two-piece cage in which two identically shaped annular bodies 5a, 5a are engaged. This cage 5A holds the balls 4 in a pocket Pt whose axial pocket shape is cylindrical. Each annular body 5a has a plurality of semi-cylindrical pocket walls 5c and a plurality of connecting plate parts 5b. The two pocket walls 5c, 5c are combined with each other in the axial direction to form a pocket Pt. The pockets Pt are provided at equal intervals around the circumference. The cage 5 has an engagement hole Ka and an engagement claw Kb that engage with each other in the connecting plate part 5b between the pockets Pt. The cage 5 is assembled by engaging the engagement claw Kb with the engagement hole Ka and engaging the two identically shaped annular bodies 5a, 5a. The pocket shape of the cage 5 may be spherical.

As shown in FIG. 9, in a rolling bearing 1 equipped with the two-piece retainer 5A, the seal member 6 may be attached to only one axial side of the inner peripheral surface of the outer ring. In this case, it is possible to prevent the bearing internal pressure from rising excessively when the rolling bearing 1 rotates, and it is possible to reduce the number of parts and therefore the cost. In addition, a seal groove and a seal member fixing groove may be provided in either or both of the inner and outer rings 2 and 3.

In the embodiment shown in Figures 7 to 9, a resin wave-shaped retainer is used as the retainer 5A, but a general steel plate wave-shaped retainer may also be used.

The above describes the mode for carrying out the present invention based on the embodiment, but the embodiment disclosed herein is illustrative in all respects and is not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

Reference Signs List 1... rolling bearing, 2... inner ring, 3... outer ring, 4... balls, 5, 5A... cage, 6... seal member, 7... seal groove, 7c... outer groove wall surface, 10... core metal, 12... air outlet, 12a... radial air outlet, 12b... axial air outlet, 15... main lip, 16... secondary lip, 16a... outer diameter portion, 16aa... cross-sectional straight-line portion , 18 ... air outlet

Claims (13)

A rolling bearing comprising: a plurality of balls interposed between an inner ring and an outer ring held in a cage; a seal member for sealing a bearing space between the inner ring and the outer ring attached to the outer ring; a seal groove formed in the circumferential direction on an outer peripheral surface of the inner ring; the seal member including a core metal, a main lip in contact with an outer groove wall surface of the seal groove, and a secondary lip not in contact with the seal groove,
The main lip has a base end portion that is inclined toward the inner diameter side as it extends axially outward, and a lip main body portion that extends in the inner diameter direction from the base end portion,
The secondary lip protrudes axially inward from a base end portion, and a labyrinth seal is formed between a tip end portion of the secondary lip and an inner groove wall surface of the seal groove,
A rolling bearing in which 1.90≦D/d≦2.50 is satisfied, where D is the maximum axial distance from a position inside the bearing of the core metal to the tip of the secondary lip and d is the thickness of the core metal. The rolling bearing according to claim 1, in which the radial dimension E from the inner diameter portion of the secondary lip to the inner diameter side end of the lip body is 60% ± 10% of the radial length F of the cross section of the rubber portion that is the inner peripheral portion of the seal member. In the rolling bearing according to claim 1 or 2, when the axial gap between the intersection of the outer circumferential surface of the inner ring and the inner groove wall surface and the tip of the secondary lip is A, 0.2≦A/D≦0.5. A rolling bearing according to any one of claims 1 to 3, in which the grease sealed in the bearing space occupies 10% or more of the volume of the bearing internal space. 5. The rolling bearing according to claim 4, wherein the grease is a grease composition comprising a base oil and a thickener,
the base oil is a mixed oil containing a synthetic hydrocarbon oil and an ether oil and having a kinematic viscosity at 40°C of 120 ^mm2 /s or more;
The thickener is a urea compound, and the amount of the thickener is 10 wt % to 15 wt %;
The grease composition for rolling bearings has a worked penetration of 200 to 240 as measured in accordance with JIS K 2220. A rolling bearing according to any one of claims 1 to 5, in which the outer diameter dimension of the base end of the secondary lip is located on the outer diameter side of the outer peripheral surface of the inner ring, the outer diameter portion of the secondary lip has a portion that extends in a straight line in a cross section of the rolling bearing cut along a plane including the axial direction, and has a cross-sectional straight line portion that inclines toward the outer diameter side as it moves axially outward, and the inclination angle G of the cross-sectional straight line portion of the secondary lip relative to the axial direction is 5° or more and 25° or less. A rolling bearing according to any one of claims 1 to 6, in which the outer groove wall surface of the seal groove is formed as an inclined surface that inclines toward the outer diameter side as it moves axially outward, the seal member is formed in an R-shape in which the tip of the main lip abuts on the outer groove wall surface of the seal groove in the normal direction, and the inclination angle of the outer groove wall surface with respect to the axial direction is 53 to 68°. The rolling bearing according to claim 7, wherein the tip of the main lip is arc-shaped with a radius of 0.03 to 0.09 mm. A rolling bearing according to any one of claims 1 to 8, wherein the seal member has the core metal and a rubber material, the main lip and the sub lip are made of the rubber material, and the surface roughness of a part or all of the inner surface of the rubber material, including the inner surfaces of the main lip and the sub lip, located on the inner diameter side of the PCD, is Ra = 0.4 to 2.5 μm. The rolling bearing according to any one of claims 1 to 8, wherein the seal member is provided with an air outlet for releasing internal pressure. The rolling bearing according to claim 10, in which a plurality of the air outlets are provided on the outer peripheral portion of at least one of the sealing members, the air outlets having radial air outlets formed along the radial direction and axial air outlets formed along the axial direction, the radial air outlets and the axial air outlets being provided at different circumferential positions. A rolling bearing according to any one of claims 1 to 11, wherein the main lip of the seal member is provided with an air outlet for releasing the internal pressure of the rolling bearing. A rolling bearing according to any one of claims 10 to 12, wherein the air outlet provided in the seal member is located in the seal member on one or both axial sides.

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