JP2023020618A - Hermetic rolling bearing - Google Patents

Abstract

To provide a hermetic rolling bearing capable of suppressing occurrence of negative pressure in a bearing space without depending on a rotation direction of a bearing, and excellent in both sealability and low torque.SOLUTION: A hermetic rolling bearings comprises: an outward member 2 and a hub wheel 4 that rotate concentrically relative to each other; a rolling element 7 arranged so as to be able to roll between the outward member 2 and the hub ring 4; a lubricant enclosed in a bearing space between the outward member 2 and the hub ring 4; and a seal member 18 that is fixed to the outward member 2 and seals the bearing space, where the hub ring 4 is provided with a sliding contact surface on which the seal member 18 slides. A sliding contact surface 19 of the hub wheel 4 on which the seal member 18 slides has an axial arithmetic mean roughness of 0.45 μm or less and a circumferential arithmetic mean roughness of 0.05 μm or less.SELECTED DRAWING: Figure 3

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed rolling bearing provided with a sealing member, and more particularly to a sealed rolling bearing that supports an axle such as a hub bearing.

Generally, a grease composition is sealed inside the rolling bearing as a lubricant. A bearing containing a grease composition has a long life, does not require an external lubrication unit, etc., and is inexpensive. In particular, when high sealing performance is required, contact-type sealing is used to seal the bearing space by bringing the seal lip of the seal member (hereinafter also referred to as the lip) into contact with the sliding surface of the mating member such as the bearing ring. Type rolling bearings are used.

Here, grease leakage from the bearing may contaminate external mechanical parts. In addition, the contamination of foreign matter such as water from the outside may significantly reduce the durability (wear resistance and bearing life) of the bearing. Therefore, it is important to ensure sealing performance in sealed rolling bearings. On the other hand, from the viewpoint of energy saving and resource saving, low torque is also required for the sliding of the seal lip. In a sealed rolling bearing equipped with a seal member having multiple seal lips, if grease leaks or the temperature of the bearing rises during rotation, the internal pressure in the bearing space fluctuates and the seal lip sticks to the mating member. Adsorption state may occur and friction torque may increase.

Conventionally, various techniques are known for keeping the sliding resistance (friction torque) of the seal lip low and ensuring the sealing performance of the seal lip. For example, Patent Literature 1 discloses a technique for preventing the lip from being attracted to the sliding surface of the mating member by suppressing the shape change of the lip when the internal pressure of the bearing space changes. Specifically, in a seal having two lips, a bearing capable of suppressing deformation of the lips by providing a core metal as a reinforcing material between the lips is described. Further, in Patent Document 2, by providing minute pores in the sealing member, the air pressure difference generated between the inside and outside of the lip is suppressed, and countermeasures are taken against the generation of negative pressure that causes the lip to stick to the member to be slid. Techniques are disclosed. Patent Document 3 considers that the cause of negative pressure is the pumping action that continues to send air from the sealing side of the bearing space to the atmosphere side, and provides a threaded groove in the lip to forcibly move the air from the atmosphere side to the sealing side. A technique for suppressing the generation of negative pressure by generating a pumping action of is disclosed.

JP 2013-60975 A Japanese Patent Application Laid-Open No. 2010-230058 WO2020/012953

However, in the case of the bearing described in Patent Document 1, in order to effectively suppress the deformation of the lip, it is necessary to install the metal core up to the vicinity of the contact portion of the lip. However, according to this method, the followability of the lip to the mating member deteriorates, and there is a possibility that the sealing performance deteriorates.

In addition, in the case of the bearing described in Patent Document 2, there is a possibility that external foreign matter may enter the sealed side of the lip by providing the pores in the seal member. Although the bearing described in Patent Document 2 prevents entry of foreign matter by providing a protrusion on the atmosphere side of the pore, liquid such as muddy water may enter.

In Patent Document 3, the effect is exhibited only in the case of rotation in a specific direction, and when the lip groove wears due to long-term use, etc., the pumping action from the atmosphere side to the sealing side weakens, generating negative pressure. There is a risk that the suppressing effect of In view of the circumstances of Patent Documents 1 to 3, it is desirable to be able to take measures against lip attraction without changing the structure and surface shape of the sealing member from those of the conventional ones and regardless of the direction of rotation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. The purpose is to provide bearings.

A sealed rolling bearing according to the present invention comprises a stationary member and a rotating member that rotate relatively concentrically; rolling elements that are arranged to be able to roll between the stationary member and the rotating member; A lubricant filled in a bearing space between the side member and the rotation side member, and a seal member fixed to the fixed side member and sealing the bearing space, wherein the seal member has a sliding contact surface. In the sealed rolling bearing provided for the rotation-side member, the sliding contact surface of the rotation-side member with which the seal member is in sliding contact has an arithmetic average roughness in the axial direction of 0.45 μm or less and an arithmetic mean roughness in the circumferential direction of 0.45 μm or less. It is characterized by having an average roughness of 0.05 μm or less. Here, the arithmetic average roughness in the axial direction is a value calculated using a line segment connecting the inner and outer circumferences of the sliding contact surface as a reference length. Further, the arithmetic average roughness in the circumferential direction is a value calculated using a line segment on the circumference of the rotation side member with which the seal member is in sliding contact as a reference length. Here, "lubricant" represents a material that imparts lubricity, such as grease or oil.

The rotation-side member includes a slinger, and the slidable contact surface is provided on the slinger.

The sliding contact surface has a maximum axial height of 2.0 μm or less. Here, the maximum height in the axial direction is a value calculated using a line segment connecting the inner and outer circumferences of the sliding contact surface as a reference length.

A sealed rolling bearing according to the present invention comprises a stationary member and a rotating member that rotate relatively concentrically; rolling elements that are arranged to be able to roll between the stationary member and the rotating member; A lubricant filled in a bearing space between the side member and the rotation side member, and a seal member fixed to the fixed side member and sealing the bearing space, wherein the seal lip of the seal member is in sliding contact. A sealed rolling bearing having a contact surface on the rotation-side member, wherein the rotation-side member has a groove-shaped machining mark on the sliding contact surface, and the machining mark is formed by a longitudinal direction and a circumferential direction. The angle θ is characterized by being represented by the following formula (1).
θ<sin ^-1 (d/l) (1)
l: average length of the work marks d: average diameter of the protrusions on the surface of the seal lip that can come into contact with the grooves of the work marks Here, the angle θ formed is the major axis direction of all the work marks. The angle shall be the average of the angles formed with the above circumferential direction. Also, the average length l of the working marks is the average value of the lengths in the longitudinal direction of all the working marks.

The average length l of the machining marks is represented by the following formula (2).
l=((ΠD) ² +d ² ) ^1/2 (2)
D: Average diameter of the circular orbit drawn by the convex portion on the sliding contact surface

A sealed rolling bearing according to the present invention comprises a stationary member and a rotating member that rotate relatively concentrically; rolling elements that are arranged to be able to roll between the stationary member and the rotating member; A lubricant filled in a bearing space between the side member and the rotation side member, and a seal member fixed to the fixed side member and sealing the bearing space, wherein the seal member has a sliding contact surface. In the sealed rolling bearing provided for the rotation-side member, the rotation-side member has a groove-shaped work mark on the sliding contact surface, and the angle θ between the long axis direction and the circumferential direction of the work mark is formed by the work mark. , greater than 0° and less than 2°.

In the sealed rolling bearing of the present invention, the sliding contact surface of the rotating side member with which the seal member slides has an arithmetic average roughness in the axial direction of 0.45 μm or less and an arithmetic average roughness in the circumferential direction of 0.05 μm or less. Therefore, when the bearing rotates, grease is suppressed from being discharged from the seal lip to the outside of the bearing space regardless of the rotation direction of the bearing. As a result, generation of negative pressure in the bearing space is suppressed, and both sealing performance and low torque performance are excellent.

Since the sliding contact surface has a maximum height of 2.0 μm or less in the axial direction, discharge of grease from the seal lip to the outside of the bearing space is further suppressed.

In the sealed rolling bearing of the present invention, the sliding contact surface of the rotating side member with which the seal member slides is in sliding contact with the seal lip of the sealing member, and the rotating side member has a groove-shaped machining mark on the sliding contact surface, Since the angle θ between the long axis direction and the circumferential direction of the machined marks is expressed by the above formula (1), the grease will flow out of the bearing space from the seal lip regardless of which direction the bearing rotates. emissions are suppressed. As a result, generation of negative pressure in the bearing space is suppressed, and both sealing performance and low torque performance are excellent.

Since the average length l of the work marks is expressed by the above formula (2), each work mark has a substantially circular shape that makes one turn in the circumferential direction, making it difficult for the grease to move out of the bearing space. This further suppresses the generation of negative pressure in the bearing space.

In the sealed rolling bearing of the present invention, the sliding contact surface of the rotating side member with which the seal member slides has groove-shaped machining marks, and the angle θ between the longitudinal direction of the machining marks and the circumferential direction is 0°. Since the angle is larger and less than 2°, discharge of grease from the seal lip to the outside of the bearing space is suppressed regardless of which direction the bearing rotates. As a result, generation of negative pressure in the bearing space is suppressed, and both sealing performance and low torque performance are excellent.

1 is a longitudinal sectional view showing an example of a sealed rolling bearing of the present invention; FIG. FIG. 2 is an enlarged cross-sectional view showing an inboard-side sealing member in FIG. 1 ; FIG. 2 is an enlarged cross-sectional view showing an outboard-side sealing member in FIG. 1 ; 4 is a perspective enlarged cross-sectional view showing a contact area between a seal lip and a sliding contact surface in FIG. 3; FIG. 5 is a further enlarged view of the contact area shown in FIG. 4; FIG. FIG. 6 is an enlarged plan view of the traces of processing in FIG. 5 viewed toward the sliding contact surface; 4 is an enlarged plan view of a plurality of working marks; FIG. FIG. 4 is a longitudinal sectional view showing another example of the sealed rolling bearing of the present invention; 1 is a schematic diagram of a friction torque measuring device; FIG. It is an evaluation result of a friction torque difference.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is a longitudinal sectional view showing a hub bearing, which is an example of the sealed rolling bearing of the present invention. A hub bearing 1 shown in FIG. 1 is a driving wheel-side axle bearing that rotatably supports an axle.

As shown in FIG. 1, the hub bearing 1 integrally has a vehicle body mounting flange 2b on its outer circumference to be mounted on a vehicle body (not shown), and an outer raceway surface 2a formed on its inner circumference with double-row outer raceway surfaces 2a, 2a. The member 2 is integrally provided with a wheel mounting flange 4b to which a wheel (not shown) is mounted at one end thereof, and on the outer circumference, the double-row outer raceway surfaces 2a, one inner raceway surface 4a facing the 2a, and the inner side. A cylindrical small-diameter stepped portion 4c extending in the axial direction from the raceway surface 4a is formed. An inner ring 5 having a raceway surface 5a is provided.

The inner member 3, which is a rotating member, has inner raceway surfaces 4a, 5a, and the outer member 2, which is a stationary member, has double row outer raceway surfaces 2a, 2a. Double-row rolling elements (balls) 7 are rotatably accommodated by retainers 8 between the double-row outer raceway surfaces 2a, 2a and the opposing inner raceway surfaces 4a, 5a. Bearing sealing devices 11 and 16 are mounted in annular spaces formed between the inner member 3 consisting of the hub ring 4 and the inner ring 5 and the outer member 2, respectively, and sealed in the bearing space 9. It prevents the leakage of the grease composition, which is a lubricant, and the entry of rainwater, dust, etc. into the bearing space 9 from the outside. Of these bearing sealing devices 11 and 16, the inboard side (right side in the drawing) bearing sealing device 11 mounted between the outer member 2 and the inner ring 5 will be described with reference to FIG.

As shown in FIG. 2, the bearing sealing device 11 includes a core metal 12 fitted in the outer member and having an L-shaped cross section, and a seal member 13 integrally bonded to the core metal 12 by vulcanization. and a slinger 15 fitted on the inner ring and also formed to have an L-shaped cross section. The core metal 12 of the slinger 15 and the seal ring 14 is formed by pressing an austenitic stainless steel plate (JIS SUS304 series, etc.) or a rust-proof cold-rolled steel plate (JIS SPCC series, etc.). is formed by

Nitrile rubber (NBR), acrylic rubber, silicone rubber, fluororubber, or the like is used as the material of the seal member 13 . 2, the seal member 13 has three seal lips 13a, 13b, and 13c in order from the inner side of the bearing space. The tip edges of the remaining intermediate seal lip 13b and inner seal lip 13a are brought into sliding contact with the cylindrical portion 15a of the slinger 15. As shown in FIG. In this configuration, the cored bar 12 corresponds to a fixed side member, and the slinger 15 corresponds to a rotating side member because it is press-fitted into the inner ring and rotates integrally with the inner member.

For example, in the configuration of FIG. 2, grease is applied to the sliding contact surface of the seal lip of the seal member. Specifically, as shown in FIG. 2, grease G1 is applied to the sliding surfaces of the seal lips 13a, 13b, and 13c that slide against the slinger 15. As shown in FIG. In this case, the grease G1 should be applied at least to the sliding contact surface of the seal lip, and may be applied to the entire seal lip.

Next, the bearing sealing device 16 will be explained using FIG. The bearing sealing device 16 is fitted inside the outer member 2 and comprises an annular core metal 17 and a seal member 18 integrally bonded to the core metal 17 by vulcanization. The cored bar 17 is formed in the same manner as the above-described slinger. The seal member 18 is made of an elastic material such as nitrile rubber, and has two seal lips (side lips) 18b and 18c and a single seal lip (radial lip) 18a. Specifically, it is brought into direct sliding contact with the arc-shaped sliding contact surface 19 of the inboard side base portion of the wheel mounting flange.

As shown in FIG. 3, in the bearing sealing device 16 as well, grease G1 is applied to the surfaces of the seal lips 18a, 18b, and 18c that are in sliding contact with the hub wheel 4, specifically, to one side surface of the tip of each seal lip. is applied. This is intended to ensure both sealing performance and reduction of rotational torque.

A ferrous material can be used for at least one of the inner member and the outer member. Any material generally used as a bearing material can be used as the ferrous material. For example, high carbon chromium bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc.; JIS G 4805), carburizing steel (SCr420, SCM420, etc.; JIS G 4053), stainless steel (SUS440C, etc.; JIS G 4303), high speed Steel (such as M50), cold-rolled steel, carbon steel for machine structural use, and the like can be used. The steel materials used for each member may be different materials.

Of these, for example, as the material for the inner ring 5, it is preferable to use carbon steel for machine structural use such as S53C, which has good forgeability and is inexpensive. As will be described later, the present invention suppresses the generation of negative pressure in the bearing space and is excellent in both sealing performance and low torque performance. But you can expect it to be durable enough.

The relationship between the seal member, which is a part of the stationary member, and the sliding contact surface of the rotary member will be described with reference to FIGS. 4 to 7. FIG. In FIGS. 4 to 7, the long axis direction of the machining marks to be described later and the circumferential direction of the bearing, for example, substantially coincide, but for convenience of explanation, the angle formed by them is shown enlarged. Also, for convenience of explanation, the shape and size relationship of the convex portion of the seal lip and the groove of the processing mark, which will be described later, are also schematically shown.

FIG. 4 shows the contact area between the tip of the seal lip located on the outermost side from the bearing space in FIG. 1 is a perspective enlarged cross-sectional view viewed from the side; FIG. Here, the direction substantially perpendicular to the paper surface is the circumferential direction, and the direction substantially lateral to the paper surface is the axial direction. As shown in FIG. 4, the portion of the seal lip 18c that contacts the sliding surface 19 of the hub wheel 4 is elastically deformed and comes into surface contact with the hub wheel 4. It suppresses grease leakage to the outside in the upward direction. The sliding contact surface 19 is subjected to polishing processing, and a large number of streak-like processing marks 20 are observed. The longitudinal direction of the machined marks 20 may, for example, match the circumferential direction of the hub wheel 4 or may not match and may be inclined at a predetermined angle.

5 is a further enlarged view of the contact area shown in FIG. 4; FIG. As shown in FIG. 5, the machining marks 20 of the sliding contact surface 19 observed under magnification have grooves composed of peaks 20a and valleys 20b. Also, the seal lip 18c has a large number of protrusions 21 on its surface. Here, both the groove of the processing mark 20 and the convex portion 21 of the seal lip 18c are shown schematically in a substantially semicircular cross-sectional shape. It may be polygonal, irregular, or the like.

A possible cause of the generation of negative pressure inside the bearing space in a sealed rolling bearing having machining marks on the sliding contact surface as shown in FIG. It is considered that the discharge of grease is likely to occur when the following two phenomena overlap.
Phenomenon 1: Grease adhering to the convex part of the surface roughness of the seal lip gradually moves to the outer and inner circumferences over the ridges of the machining marks on the mating surface (sliding contact surface) due to the rotation of the rotating side member. moving phenomenon.
Phenomenon 2: Grease gathers on the sliding contact surfaces of the seal lip and the rotary member due to centrifugal force, and the grease is supplied to the sliding contact surfaces.

Phenomenon 1 will be described with reference to FIG. FIG. 6 is an enlarged plan view of the traces of machining shown in FIG. FIG. 6 shows the relationship between the convex portion of the tip of the seal lip at a position above the rotating shaft on the sliding contact surface perpendicular to the axial direction and the machining marks on the sliding contact surface. FIG. 6(a) is a view of the convex portion 21 of the seal lip before contacting the crest portion 20a of the machining mark 20 moving rightward on the paper surface, and FIG. FIG. 10 is a view after contacting the . As for the direction of the axial direction, the front side in the direction perpendicular to the paper surface is positive (vehicle side), and the back side is negative (wheel side). Since the sliding contact surface has an arcuate cross section in the axial direction, proceeding downward along the sliding contact surface coincides with the positive axial direction.

As shown in FIG. 6A, before the convex portion 21 of the seal lip contacts the peak portion 20a of the machining mark 20, the grease G2 adheres to the peak portion side of the convex portion 21, and the grease G3 adheres to the convex portion. It is attached to the side of the portion 21 opposite to the crest. In this case, when the convex portion 21 comes into contact with the peak portion 20a, as shown in FIG. direction and inside the bearing space). The greases G2 and G3 are more likely to move to the outside or inside of the bearing space as the angle θ formed by the long axis direction Dp of the machining marks and the circumferential direction (rotational direction Dr) of the bearing increases. Further, when the grease G4 adheres to the valley portion 20b of the machining mark 20 before the convex portion 21 contacts the peak portion 20a, when the hub wheel rotates and the sliding contact surface moves rightward on the paper surface, the grease G4 adheres to the convex portion 21 . When the sliding contact surface moves further rightward on the paper surface, the grease G4 moves to the outside or inside of the bearing space as the convex portion 21 contacts the peak portion 20a' adjacent to the peak portion 20a.

When the machining marks on the sliding contact surface are inclined with respect to the direction of rotation, the rotation of the rotating side member moves the grease adhering to the convex portion of the seal lip due to Phenomenon 1 to the outside or inside of the bearing space. Grease can move in the positive or negative axial direction by the number of protrusions on the seal lip surface. When Phenomenon 1 and Phenomenon 2 occur at the same time, the grease that has moved out of the bearing space moves again in the direction of the outermost seal lip due to Phenomenon 2, but is discharged out of the bearing space from the outermost seal lip. The leaked grease remains leaked. Therefore, as long as there is grease in the bearing space, the grease will gradually move out of the bearing space, and negative pressure will be generated due to the volume reduction in the bearing space. As a result, the seal lip sticks to the sliding contact surface.

The sliding contact surface of the rotating side member of the sealed rolling bearing of the present invention has, for example, an axial arithmetic mean roughness Ra(ax) of 0.45 μm or less and a circumferential arithmetic mean roughness Ra(ci). is preferably 0.05 μm or less. When the arithmetic mean roughness of the sliding contact surface is within the above range, the convex portions of the seal lip are less likely to come into contact with the ridges of the machining marks when the bearing rotates. discharge of grease from the bearing space to the outside of the bearing space is suppressed. As a result, generation of negative pressure in the bearing space is suppressed, and both sealing performance and low torque performance are excellent. From the viewpoint of sealing performance, the sliding contact surface has, for example, an axial arithmetic mean roughness Ra(ax) of 0.45 μm or less and a circumferential arithmetic mean roughness Ra(ci) of 0.03 μm or less. More preferably, the arithmetic mean roughness Ra(ax) in the axial direction is 0.25 μm or less and the arithmetic mean roughness Ra(ci) in the circumferential direction is 0.03 μm or less.

For the sliding contact surface, for example, the ratio Ra(ax)/Ra(ci) of the arithmetic mean roughness Ra(ax) in the axial direction to the arithmetic mean roughness Ra(ci) in the circumferential direction is 5 to 30. It is preferably from 5 to 25, and even more preferably from 7 to 20. When the ratio Ra(ax)/Ra(ci) is within the above range, the surface roughness of the sliding contact surface exhibits anisotropy, making it difficult for the grease to move in the axial direction during rotation of the bearing.

For example, the sliding contact surface preferably has a maximum axial height Rz(ax) of 2.0 μm or less, more preferably 1.5 μm or less. Also, the maximum height Rz(ci) in the circumferential direction is preferably 0.20 μm or less. When the maximum height is within the above range, discharge of grease from the seal lip to the outside of the bearing space is further suppressed. From the viewpoint of suppressing grease discharge, the ratio Rz(ax)/Rz(ci) of the maximum axial height Rz(ax) of the sliding contact surface to the maximum circumferential height Rz(ci) is, for example, 5 to It is preferably 30, more preferably 5-20, even more preferably 5-15. When the ratio Rz(ax)/Rz(ci) is within the above range, the surface roughness of the sliding contact surface exhibits anisotropy, making it difficult for the grease to move in the axial direction during rotation of the bearing.

The sliding contact surface preferably has, for example, an axial arithmetic mean roughness Ra(ax) of 0.45 μm or less and a maximum axial height Rz(ax) of 1.41 μm or less.

The above arithmetic mean roughness and maximum height are numerical values calculated according to JIS B 0601 (ISO 25178), and can be measured using a contact or non-contact surface roughness meter.

FIG. 7 is an enlarged plan view of a plurality of working marks. As shown in FIG. 7, the long axis direction Dp of the work mark 20 has a predetermined angle relationship with the circumferential direction (rotational direction Dr), and the angle θ between the long axis direction of the work mark and the circumferential direction. is represented, for example, by the following formula (1).
θ<sin ^-1 (d/l) (1)
l: average length of the work mark d: average diameter of the convex portion 21 on the surface of the seal lip that can contact the groove of the work mark Note that the major axis direction Dp of the work mark 20 is relative to the circumferential direction (rotational direction Dr). can be slanted, or they can be completely coincident. Further, the circumferential direction may be the arrow direction of the rotation direction Dr, or may be the opposite direction.

When the above-mentioned angle θ satisfies the above formula (1), the frequency of contact between the convex portion of the seal lip and the ridge portion of the machining mark is low. moves rightward or leftward on the paper), the convex portion of the seal lip suppresses discharge (movement) of grease from the seal lip to the outside of the bearing space. As a result, generation of negative pressure in the bearing space is suppressed, and both sealing performance and low torque performance are excellent.

The average diameter d of the protrusions on the surface of the seal lip, which is a portion (true contact surface portion) that can come into contact with the groove of the machining mark, is, for example, about 0.01 to 0.08 mm, and about 0.04 to 0.08 mm. is preferred, and about 0.06-0.08 mm is more preferred. This is because the larger the average diameter d, the larger the permissible value for the length (l×sin θ) of the axial component due to the relationship of the above formula (1). The true contact surface portion is formed by the ridges of the machining marks and the protrusions on the surface of the seal lip. When the length l from the start point to the end point of the machining mark is separated into an axial component and a circumferential component, the length of the axial component (l x sin θ) is equal to or less than the average diameter d of the protrusions. preferable.

According to the principle of grease movement shown in FIG. 6, when the formed angle θ is large, the grease is likely to be removed over the ridges of the machining marks by the protrusions of the seal lip. In order to reduce the movement of the grease in the axial direction, it is preferable to bring the angle θ formed by all the working traces on the sliding contact surface closer to 0°. The angle θ formed by the long axis direction Dp of the machining marks and the circumferential direction (rotational direction Dr) can be, for example, greater than 0° and less than 5°. The angle θ to be formed is, for example, preferably greater than 0° and less than 2°, more preferably greater than 0° and less than 1°, from the viewpoint of sealing performance and low torque. When the angle θ is within the above range, the convex portion of the seal lip is less likely to come into contact with the ridges of the machining marks, so no matter which direction the bearing rotates, the of grease is suppressed. As a result, generation of negative pressure in the bearing space is suppressed, and both sealing performance and low torque performance are excellent.

When the sliding contact surface is ground with a shaped grindstone, no feed occurs, so no spiral machining marks are formed, and each abrasive grain forms a roughly circular machining mark. In this case, the average length l of the working marks is represented by the following formula (2), for example.
l=((ΠD) ² +d ² ) ^1/2 (2)
D: Average diameter of the circular orbit drawn by the convex portion 21 on the sliding contact surface 19 Here, the substantially circular shape includes a concentric shape, an elliptical shape, and an annular shape without an end.

When the average length l of the work marks is expressed by the above formula, each work mark has no starting point and no end point and is substantially circular in the circumferential direction, so grease is less likely to move out of the bearing space. This further suppresses the generation of negative pressure in the bearing space.

It is preferable to use an iron-based material for at least one of the inner member and the outer member. As a result, machining marks on the sliding surface are less likely to disappear than in the case of using a resin material. The effect of being excellent in both torque properties is likely to last.

4 to 7, the configuration around the contact area was described using the seal lip 18c, but the present invention is not limited to this, and the seal lip 18b, the seal lip 18a, the inner seal lip 13a, the intermediate seal lip 13b, the outer seal A similar configuration can be applied to the lip 13c (see FIGS. 2 and 3). At least one seal lip among the plurality of seal lips may have the structure described above in the vicinity of the contact area. Preferably, all sealing lips are of this configuration. Further, when the fixed side member is the inner member, the rotary side member is the outer member, and the bearing sealing device is attached to the inner member, the tip of the seal lip may be in sliding contact with the outer member.

In the above, the hub bearing of the double-row rolling bearing was exemplified as the sealed rolling bearing, but the sealed rolling bearing of the present invention may be a single-row rolling bearing.

FIG. 8 is a longitudinal sectional view showing another example of the sealed rolling bearing of the present invention. This sealed rolling bearing 22 consists of a deep groove ball bearing comprising an outer ring 24 having an outer raceway surface 23 formed on its inner circumference, an inner ring 26 having an inner raceway surface 25 formed on its outer circumference, and a Balls 28 are rotatably accommodated by retainers 27, and a pair of seal rings 29, 29, which are bearing sealing devices for sealing lubricant, are mounted in annular spaces formed between inner and outer rings 24, 26. . A pair of seal rings 29, 29 prevent the leakage of the lubricant sealed inside the bearing and the entry of rainwater, dust, etc. into the bearing from the outside.

As shown in FIG. 8, the seal ring 29 includes a disk-shaped core metal 30 formed by pressing a cold-rolled steel plate (e.g., JIS SPCC type) and integrally added to the core metal 30. and a sealing member 31 that is sulfur-bonded. The seal member 31 has a main lip and a sub lip, the tip of which is bifurcated. The seal ring 29 is fixed to the outer ring 24, which is the stationary member, via the seal member 31, and the main lip and auxiliary lip of the seal member 31 are brought into sliding contact with the inner ring 26, which is the rotating member. For example, the main lip slidably contacts a seal groove 32 having a substantially U-shaped cross section formed on the outer circumference of the end portion of the inner ring 26 .

4 to 7 can be appropriately applied to the sliding contact surface of the inner ring 26 and the seal lip (main lip and auxiliary lip) in FIG. For example, the inner ring 26 may have a groove-shaped work mark on the sliding contact surface, and the angle θ between the longitudinal direction of the work mark and the circumferential direction may be expressed by the above formula (1). By applying such a configuration, the discharge of grease from the seal lip to the outside of the bearing space is suppressed regardless of which direction the bearing rotates, and the generation of negative pressure inside the bearing space is suppressed. can do.

In FIG. 8 above, a deep groove ball bearing is illustrated as the sealed rolling bearing, but the sealed rolling bearing may include cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, and thrust cylindrical roller bearings. , thrust tapered roller bearings, thrust needle roller bearings, thrust spherical roller bearings, etc.

In order to evaluate the relationship between the surface roughness of the sliding contact surface of the rotating side member with which the seal member slides and the torque characteristics during bearing rotation, three types of test pieces with different surface roughness of the sliding contact surface of the seal lip were used. (inner member), the torque properties (frictional torque difference) of two types of operation patterns were evaluated.

FIG. 9 shows a schematic diagram of the friction torque measuring device used in this evaluation. As shown in FIG. 9, in the friction torque measuring device 33, the bearing sealing device 35 fixed to the outer ring housing 34, which is the stationary member, contacts the sliding contact surface of the inner member 36, which is the rotating member, at a predetermined pressure. arranged to be in contact with each other. The XY stage 37 and Z stage 38 were adjusted so that the seal lip of the bearing sealing device 35 slidably contacts the inner member 36 with uniform pressure over the entire circumference.

Table 1 shows the surface roughness of each test piece. All the test pieces were subjected to the same conditions except for the surface roughness shown in Table 1. The minimum outer diameter of the rolling surface of the inner member was about 60 mm. The sliding surfaces of the three test pieces were polished under different conditions. Rz(ax)/Rz(ci), which is the maximum height Rz(ax) in the axial direction with respect to the maximum height Rz(ci) in the circumferential direction, was about 11.8 in Example 1 and about 5.0 in Example 2. 5, the comparative example was about 3.7. The long axis direction of the work marks formed by polishing each test piece was substantially the same as the circumferential direction.

Next, the mounting conditions of the bearing sealing device and the torque property evaluation conditions when measuring the friction torque are shown.

<Conditions for mounting the bearing sealing device>
The seal member of the bearing sealing device used in this experiment has three seal lips: a dust lip, an intermediate lip, and a grease lip. The dust lip is a seal lip located outside, the grease lip is a seal lip located inside (on the side of the bearing space), and the intermediate lip is a seal lip located between the dust lip and the grease lip. The amount of grease applied between each seal lip and the interference of each seal lip are shown below.
Amount of grease applied between dust lip and intermediate lip: 0.3 g
Amount of grease applied between intermediate lip and grease lip: 0.3 g
Dust lip interference: Aim for about 1.1 mm Intermediate lip interference: Aim for about 0.8 mm Grease lip interference: Aim for about 0.6 mm

<Torque property evaluation conditions>
In order to evaluate torqueability, friction torque was measured in two driving patterns shown in Table 2 below. Further, each operating pattern is composed of a combination of operating conditions 1 to 3 below.

Operating condition 1
Operation before measurement: None Direction of rotation: Clockwise in the positive axial direction in Fig. 9 Rotation speed: 600 min ^-1
Operating time: 30min
Measurement: Average value of friction torque from 29 minutes 30 seconds to 30 minutes from the start of operation

Operating condition 2
Operation before measurement: Insert a shim between the mating surface and the seal lip to prevent the lip from sticking. Direction of rotation: Clockwise in the positive direction of the axial direction in Fig. 9 Rotation speed: 600 min ^-1
Operating time: 30min
Measurement: Average value of friction torque from 29 minutes 30 seconds to 30 minutes from the start of operation

Operating condition 3
Operation before measurement: none Direction of rotation: counterclockwise in the positive direction of the axial direction in FIG. 9 Rotation speed: 600 min ^-1
Operating time: 30min
Measurement: Average value of friction torque from 29 minutes 30 seconds to 30 minutes from the start of operation

Here, the positive direction of the axial direction in FIG. 9 is the direction of the black arrow.

A friction torque difference for each operation pattern was calculated based on the following formula (3).
Friction torque difference = operating condition 1 - operating condition 2 or operating condition 3 (3)

As shown in Table 2, in the operation pattern 1, the friction torque was measured under the operation condition 1 and then under the operation condition 2. In operation pattern 2, the friction torque was measured under operation condition 1 and then under operation condition 3. The operation of the operation pattern 1 was performed only once, and the operation of the operation pattern 2 was performed twice continuously. For each operating pattern, under operating condition 1, a new bearing sealing device (sealing member) was used. Under the subsequent operating conditions, the friction torque was continuously measured without exchanging the sealing member. In operation pattern 1, in order to examine the influence of the seal member being attracted to the rotating member, under operation condition 2 following operation condition 1, a shim was inserted between the sliding surface of the inner ring and the seal member. Adsorption was forcibly prevented, and the difference in friction torque between Comparative Example, Example 1, and Example 2 was calculated. In addition, in order to examine the effect of the friction torque in the direction of rotation of the bearing, in operation pattern 2, the friction torque in the clockwise and counterclockwise directions was confirmed by facing the positive axial direction in FIG. , Example 1, and Example 2 were confirmed for stability of friction torque (smallness of difference in friction torque). FIG. 10 shows the evaluation results of the friction torque difference.

Regarding the friction torque difference in operation pattern 1, the friction torque differences in Examples 1 and 2 were 0.02 and -0.01 N·m, respectively. On the other hand, the comparative example has a relatively large value of 0.05 N·m, indicating that the friction torque under operating condition 1 is higher than under operating condition 2. From this result, it can be said that both Examples 1 and 2 were less affected by the adsorption of the seal lip than the comparative example.

Regarding the friction torque difference in operation pattern 2, Examples 1 and 2 were -0.04 to 0.02 N·m, respectively, and there was no large difference in friction torque between operation conditions 1 and 3. On the other hand, the comparative examples were 0.18 N·m and 0.06 N·m. In the comparative example, since condition 3 was performed after condition 1, respiration of the lip occurred during reverse rotation in condition 3, and the adsorption was released. value. From this result, in the comparative example, both operation patterns 1 and 2 showed a relatively large value of friction torque difference due to the influence of adsorption (friction torque fluctuation occurred), and in Examples 1 and 2, the influence of adsorption was small, so the friction It is thought that the torque difference showed a small value.

ADVANTAGE OF THE INVENTION According to this invention, adsorption|suction of the seal lip to the rotation side member which generate|occur|produces by grease leakage can be reduced. Since adsorption is a factor that increases frictional torque, the present invention can contribute to reducing torque during rotation of sealed rolling bearings.

INDUSTRIAL APPLICABILITY The sealed rolling bearing of the present invention can suppress generation of negative pressure in the bearing space regardless of the direction of rotation of the bearing, and is excellent in both sealing performance and low torque performance. As a result, bearings (especially outer seals of hub bearings) where grease tends to move to the sliding contact part of the seal lip during operation due to its structure, and the use of low-viscosity grease as a seal lubricant prevents grease from moving to the atmosphere side. It can be widely used for bearings that are relatively prone to leakage.

1 Hub bearing (sealed rolling bearing)
2 Outer Member 3 Inner Member 4 Hub Ring 5 Inner Ring 6 Serration 7 Rolling Element 8 Cage 9 Bearing Space 11 Bearing Seal Device 12 Core Metal 13 Seal Member 14 Seal Ring 15 Slinger 16 Bearing Seal Device 17 Core Metal 18 Seal Member 18a 18c Seal lip 19 Sliding contact surface 20 Machining mark 20a Peak 20b Valley 21 Convex 22 Sealed rolling bearing 23 Outer raceway surface 24 Outer ring 25 Inner raceway surface 26 Inner ring 27 Cage 28 Ball 29 Seal ring 30 Core metal 31 Seal Member 32 Seal groove 33 Friction torque measuring device 34 Outer ring housing 35 Bearing sealing device 36 Inner member 37 XY stage 38 Z stage G1 to G4 Grease

Claims (6)

A stationary member and a rotary member that rotate relatively concentrically; a rolling element that is rotatably disposed between the stationary member and the rotary member; and the stationary member and the rotary member. and a seal member fixed to the stationary member for sealing the bearing space, wherein the rotary member includes a sliding contact surface on which the seal member slides. a bearing,
The sliding contact surface of the rotation side member with which the seal member is in sliding contact has an arithmetic average roughness in the axial direction of 0.45 μm or less and an arithmetic average roughness in the circumferential direction of 0.05 μm or less. sealed rolling bearings. 2. The sealed rolling bearing according to claim 1, wherein said rotation-side member includes a slinger, and said sliding surface is provided on said slinger. 3. A sealed rolling bearing according to claim 1, wherein said sliding contact surface has a maximum axial height of 2.0 [mu]m or less. A stationary member and a rotary member that rotate relatively concentrically; a rolling element that is rotatably disposed between the stationary member and the rotary member; and the stationary member and the rotary member. and a seal member fixed to the stationary member for sealing the bearing space. A sealed rolling bearing,
The rotation-side member has a groove-shaped work mark on the sliding contact surface, and the angle θ formed by the long axis direction of the work mark and the circumferential direction is expressed by the following formula (1). sealed rolling bearings.
θ<sin ^-1 (d/l) (1)
l: average length of the working marks d: average diameter of the protrusions on the surface of the seal lip that can contact the grooves of the working marks 5. The sealed rolling bearing according to claim 4, wherein the average length l of the machining marks is represented by the following formula (2).
l=((ΠD) ² +d ² ) ^1/2 (2)
D: Average diameter of the circular orbit drawn by the convex portion on the sliding contact surface A stationary member and a rotary member that rotate relatively concentrically; a rolling element that is rotatably disposed between the stationary member and the rotary member; and the stationary member and the rotary member. and a seal member fixed to the stationary member for sealing the bearing space, wherein the rotary member includes a sliding contact surface on which the seal member slides. a bearing,
The rotation-side member has a groove-shaped work mark on the sliding contact surface, and an angle θ formed between a longitudinal direction of the work mark and a circumferential direction is larger than 0° and less than 2°. and sealed rolling bearings.

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