Sealed rolling bearings

Abstract

To provide a sealed rolling bearing capable of achieving both low torque and high sealability.SOLUTION: A hub bearing 1 comprises a seal member 13 that seals a bearing space 9, is fixed to a fixing side member 12, and is in sliding contact with a rotary side member 15. The seal member 13 has a seal lip that is in sliding contact with the rotary side member 15. Grease is applied to at least one of the sliding contact surface of the seal lip and the sliding contact surface of the rotary side member 15 with which the seal lip is in sliding contact. The grease contains a base oil with a kinematic viscosity of 6 mm2 / s to 45 mm2 / s at 40°C and a thickener, and has a worked penetration of 220 to 320 measured in compliance with JIS K 2220.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sealed rolling bearing equipped with a sealing member, and more particularly to a sealed rolling bearing that supports an axle, such as a hub bearing. [Background technology]

[0002] Generally, rolling bearings contain a lubricating grease composition. Bearings with grease compositions are long-lasting, do not require external lubrication units, and are inexpensive, making them commonly used in general-purpose applications such as automobiles and industrial equipment. In particular, when high sealing performance is required, contact-type sealed rolling bearings are used, in which the sealing lip of the sealing member contacts the sliding surface of the mating component, such as the raceway ring, to seal the bearing space.

[0003] For example, Patent Document 1 describes a hub unit bearing in which a grease composition of a predetermined composition is sealed as a sealed rolling bearing. This grease composition is said to have excellent water resistance and other properties by containing a base oil, a thickener, three types of rust inhibitors, and an anti-wear agent.

[0004] In this context, grease leakage from bearings can contaminate external mechanical parts. Furthermore, the ingress of foreign matter such as water from the outside can significantly reduce the bearing's durability (wear resistance and bearing life). Therefore, ensuring proper sealing is crucial in sealed rolling bearings. On the other hand, from the perspective of energy and resource conservation, low torque is also required for the sliding of the seal lip.

[0005] Conventionally, a technique has been known in which grease is applied to the seal lip or its mating member in order to keep the sliding resistance of the seal lip low and to ensure the sealing performance of the seal lip. For example, Patent Document 2 describes a rolling bearing in which grease is pre-applied to one side of the tip of the seal lip, the part that slides against the surface of the hub ring during use. Patent Document 3 also describes a rolling bearing in which grease is pre-applied to the surface of the mating member with which the seal lip slides. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5110843 [Patent Document 2] Patent No. 4475055 [Patent Document 3] Patent No. 4997532 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the above-mentioned Patent Document 2, the grease applied to the seal lip is prevented from peeling off beforehand by considering the shape of the sealing member (such as the dimensions of the seal lip). This aims to increase frictional resistance and reduce sealing failures. However, the frictional resistance and sealing performance of the grease itself that is pre-applied to the seal lip are not considered. Therefore, there is a risk that increased frictional resistance or sealing failures may occur due to insufficient performance of the grease. Furthermore, in the above-mentioned Patent Document 3, rotational torque is reduced by specifying the kinematic viscosity of the base oil of the grease, but it is considered difficult to achieve both sealing performance and reduction of rotational torque by simply specifying the kinematic viscosity of the base oil.

[0008] Furthermore, while various grease compositions have been studied for greases sealed inside bearings, as described in Patent Document 1 above, very little has been studied for greases applied to seal lips and their mating components.

[0009] This invention has been made in view of the above problems, and aims to provide a sealed rolling bearing that can achieve both low torque and high sealing performance by improving the seal lip and the grease applied to its mating member. [Means for solving the problem]

[0010] The sealed rolling bearing of the present invention is a sealed rolling bearing that seals a bearing space, is fixed to a fixed-side member, and includes a seal member that slidably contacts a rotating-side member. The seal member has a seal lip that slidably contacts the rotating-side member. In the sealed rolling bearing, grease is applied to at least one of the sliding contact surface of the seal lip and the sliding contact surface of the rotating-side member with which the seal lip slidably contacts. The grease has a kinematic viscosity at 40°C of 6 mm , 2 , , , , ,

[0014] , ,

[0013] , 2 ,

[0016] , , ,

[0015] , / s to 45 mm 2 / s and contains a base oil and a thickener, and is characterized in that the consistency measured in accordance with JIS K 2220 is 220 to 320.

[0011] The thickener is a urea compound obtained by reacting a polyisocyanate component with at least one monoamine component selected from aliphatic monoamines and alicyclic monoamines, or is a complex lithium soap.

[0012] The base oil is at least one selected from synthetic hydrocarbon oils, ester oils, and ether oils.

[0013] The base oil has a kinematic viscosity at 40°C of 6 mm 2 / s to 20 mm 2 / s, and is characterized in that the consistency is 220 to 270.

[0014] The seal member is formed of nitrile rubber, and as the seal lip, it has a first seal lip, a second seal lip, and a third seal lip in order from the inner side of the bearing space, and the grease is applied to the sliding contact surfaces of these seal lips.

[0015] The sealed rolling bearing is characterized in that it is a bearing that rotatably supports an axle.

Advantages of the Invention

[0016] The sealed rolling bearing of the present invention comprises a seal member fixed to a stationary member and sliding against a rotating member, and grease is applied to at least one of the sliding surfaces of the seal lip and the sliding surface of the rotating member, wherein the kinematic viscosity of the grease at 40°C is 6 mm². 2 / s~45mm 2 Containing a base oil and thickener of / s, and with a mixed consistency of 220-320 as measured in accordance with JIS K 2220, when applied to the sliding surface of a seal lip or a rotating side member, it ensures channeling performance, prevents oil film breakdown at low speeds, results in low torque, and provides high sealing performance.

[0017] Since the above thickener is a urea compound obtained by reacting a polyisocyanate component with at least one monoamine component selected from aliphatic monoamines and alicyclic monoamines, or a complex lithium soap, it further contributes to reducing torque.

[0018] The above-mentioned sealing member is made of nitrile rubber and has three sealing lips arranged in order from the inside of the bearing space. Grease is applied to the sliding surfaces of these sealing lips, thereby ensuring low torque while further improving sealing performance.

[0019] Since the above-mentioned sealed rolling bearing is a bearing that rotatably supports the axle, it can contribute to improving the performance (fuel efficiency) of axle bearings such as hub bearings. [Brief explanation of the drawing]

[0020] [Figure 1] This is a longitudinal cross-sectional view showing an example of a sealed rolling bearing of the present invention. [Figure 2] Figure 1 is an enlarged cross-sectional view showing the inboard bearing sealing device. [Figure 3] Figure 1 is an enlarged cross-sectional view showing the bearing sealing device on the outboard side. [Figure 4] This is a longitudinal cross-sectional view showing another example of the sealed rolling bearing of the present invention. [Figure 5]Figure 4 is an enlarged cross-sectional view of a sealed rolling bearing. [Figure 6] This is a schematic diagram showing the method for producing grease. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a longitudinal cross-sectional view showing a hub bearing, which is an example of a sealed rolling bearing of the present invention. The hub bearing 1 shown in Figure 1 is a bearing for the axle on the drive wheel side that rotatably supports the axle.

[0022] As shown in Figure 1, the hub bearing 1 comprises an outer member 2 having a body mounting flange 2b on its outer circumference for attachment to the vehicle body (not shown) and having double rows of outer raceway surfaces 2a, 2a formed on its inner circumference; a hub ring 4 having a wheel mounting flange 4b ​​at one end to which a wheel (not shown) is attached, having one inner raceway surface 4a on its outer circumference opposite to the double rows of outer raceway surfaces 2a, 2a, and a cylindrical small-diameter stepped portion 4c extending axially from the inner raceway surface 4a, with torque transmission serrations 6 formed on its inner circumference; and an inner ring 5 press-fitted into the small-diameter stepped portion 4c and having the other inner raceway surface 5a formed on its outer circumference.

[0023] Between the double rows of outer raceway surfaces 2a, 2a and the opposing inner raceway surfaces 4a, 5a, a double row of rolling elements (balls) 7 are rotatably housed by a cage 8. Furthermore, bearing sealing devices 11 and 16 are installed in the annular space formed between the inner member 3, which is the rotating side member, and the outer member 2, which is the fixed side member, consisting of a hub ring 4 and an inner ring 5. These devices prevent leakage of the grease composition sealed in the bearing space 9 and prevent rainwater, dust, etc. from entering the bearing space 9 from the outside. The inboard bearing sealing device 11, which is installed between the outer member 2 and the inner ring 5 (right side in the figure), will be explained using Figure 2.

[0024] As shown in Fig. 2, the bearing seal device 11 includes a seal ring 14 composed of a core metal 12 that is fitted inside the outer member 2 and formed in an L-shaped cross-section, and a seal member 13 vulcanized and adhered integrally to the core metal 12, and a slinger 15 that is externally fitted to the inner ring 5 and also formed in an L-shaped cross-section. The core metals 12 of the slinger 15 and the seal ring 14 are formed by press working an austenitic stainless steel sheet (such as SUS304 system of JIS standard) or a rust-proof treated cold-rolled steel sheet (such as SPCC system of JIS standard).

[0025] As the material of the seal member 13, nitrile rubber (NBR), acrylic rubber, silicone rubber, fluorine rubber, etc. are used. In Fig. 2, the seal member 13 has three seal lips 13a, 13b, 13c on the inner side, middle, and outer side in order from the inner side of the bearing space. The tip edge of the outer seal lip 13c is in sliding contact with the inner surface of the upright plate portion 15b of the slinger 15, and the tip edges of the remaining middle seal lip 13b and inner seal lip 13a are in sliding contact with the cylindrical portion 15a of the slinger 15. In this configuration, the core metal 12 corresponds to the fixed-side member, and the slinger 15 corresponds to the rotating-side member.

[0026] In the configuration of Fig. 2, grease is applied to the sliding contact surfaces of the seal lips of the seal member. Specifically, as shown in Fig. 2, grease G is applied to the sliding contact surfaces of the seal lips 13a, 13b, 13c that are in sliding contact with the slinger 15. In this case, the grease G only needs to be applied to at least the sliding contact surfaces of the seal lips, and it may be applied to the entire seal lips. In the present invention, the grease G has a kinematic viscosity at 40°C of 6 mm 2 / s to 45 mm 2 / s and contains a thickener, and is characterized in that the consistency is 220 to 320. The following describes this grease.

[0027] The base oil used for the grease has a kinematic viscosity at 40°C (in the case of a mixed oil, the kinematic viscosity of the mixed oil, the same hereinafter) of 6 mm 2 / s to 45 mm 2The base oil is / s and can be any common type used in the field of grease. Examples include mineral oils such as paraffinic mineral oil and naphthenic mineral oil, synthetic hydrocarbon oils (non-polar oils) such as poly-α-olefin (PAO) oil, alkylbenzene oil, alkylnaphthalene oil, polyphenyl oil, synthetic naphthenic oil, and polybutene oil, ester oil, ether oil, silicone oil, and fluorinated oil. These base oils may be used alone or in combination of two or more types.

[0028] Among the above, it is preferable that the base oil be at least one selected from synthetic hydrocarbon oil, ester oil, and ether oil, and more preferably synthetic hydrocarbon oil alone, a mixture of synthetic hydrocarbon oil and ester oil, or a mixture of synthetic hydrocarbon oil and ether oil. Furthermore, when using a mixed oil containing synthetic hydrocarbon oil as the base oil, it is preferable that the synthetic hydrocarbon oil constitutes 60% by mass or more of the total base oil (mixed oil), and more preferably 65% ​​to 90% by mass.

[0029] PAO oil, a synthetic hydrocarbon oil, is a mixture of α-olefins or oligomers or polymers of isomerized α-olefins. 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.

[0030] Examples of ester oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, and dioctyl adipate; aromatic ester oils such as trioctyl trimellitate, tridecyl trimellitate, and tetraoctyl pyromelitate; polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane veralgonate, and pentaerythritol ester oil; carbonate ester oils; and phosphate ester oils. Among these, pentaerythritol ester oil is preferred.

[0031] The kinematic viscosity of the base oil used in the grease at 40°C is set at 6 mm from the perspective of preventing oil film breakdown at low speeds and reducing torque. 2 / s~31mm 2 / s is preferred, 6mm 2 / s~20mm 2 / s is more preferable, 7mm 2 / s~17mm 2 / s is even preferable.

[0032] Furthermore, the thickener used in the grease is not particularly limited, and general thickeners commonly used in the field of grease can be used. For example, soap-based thickeners such as metal soaps and complex metal soaps, and non-soap-based thickeners such as bentone, silica gel, diurea compounds, triurea compounds, tetraurea compounds, and urea-urethane compounds can be used. Examples of metal soaps include sodium soap, calcium soap, and lithium soap, and examples of complex metal soaps include complex lithium soap. Among these, it is preferable to use diurea compounds or complex lithium soaps.

[0033] Diurea compounds are obtained by reacting a polyisocyanate component with a monoamine component. Examples of polyisocyanate components include phenylenediisocyanate, tolylenediisocyanate, diphenyldiisocyanate, diphenylmethanediisocyanate, octadecanediisocyanate, decanediisocyanate, and hexanediisocyanate. The monoamine component can be an aliphatic monoamine, an alicyclic monoamine, or an aromatic monoamine. Examples of aliphatic monoamines include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, and oleylamine. Examples of alicyclic monoamines include cyclohexylamine. Examples of aromatic monoamines include aniline and p-toluidine.

[0034] Among these diurea compounds, it is preferable to use an aromatic diisocyanate as the polyisocyanate component and at least one of an aliphatic monoamine and an alicyclic monoamine as the monoamine component, as shown in the examples below, because of its superior low torque properties. In particular, it is more preferable to use an aliphatic-alicyclic diurea compound prepared using an aromatic diisocyanate as the polyisocyanate component and an aliphatic monoamine with 6 to 12 carbon atoms and an alicyclic monoamine as the monoamine component as a thickener. The ratio of aliphatic monoamine to alicyclic monoamine used in the preparation of this aliphatic-alicyclic diurea compound is not particularly limited, but a molar ratio of aliphatic monoamine:alicyclic monoamine = (3:1) to (1:3) is preferred, and a molar ratio of (2:1) to (1:2) is more preferred.

[0035] Base greases using diurea compounds as thickeners are prepared by reacting the above-mentioned polyisocyanate component with a monoamine component in a base oil.

[0036] Complex lithium soaps are synthesized from lithium hydroxide, aliphatic monocarboxylic acids, and dibasic acids such as aliphatic dicarboxylic acids. Examples of aliphatic monocarboxylic acids include stearic acid, 12-hydroxystearic acid, 12-hydroxylauric acid, and 16-hydroxypalmitic acid. Examples of aliphatic dicarboxylic acids include azelaic acid, sebacic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, superiic acid, undecanediic acid, and dodecanediic acid.

[0037] Among the complex lithium soaps, it is preferable to use a combination of a fatty acid monocarboxylic acid having 10 or more carbon atoms and a fatty acid dicarboxylic acid having less than 10 carbon atoms. In particular, 12-hydroxystearic acid is more preferred as the fatty acid monocarboxylic acid having 10 or more carbon atoms, and azelaic acid is more preferred as the fatty acid dicarboxylic acid having less than 10 carbon atoms.

[0038] In the grease used in the present invention, the thickener is preferably present in an amount of 10% to 30% by mass, more preferably 10% to 20% by mass, and even more preferably 12% to 18% by mass, relative to the total amount (100% by mass) of the base oil and the thickener. By relatively reducing the amount of thickener, the proportion of base oil can be increased, which tends to lead to lower torque.

[0039] Furthermore, known additives may be added to the above-mentioned grease as needed. Examples of additives include antioxidants such as amine-based, phenol-based, and sulfur-based compounds, and rust inhibitors such as polyhydric alcohol esters. It is preferable that extreme pressure agents such as organozinc compounds and organomolybdenum compounds are not included.

[0040] The consistency of the grease used in this invention (JIS K 2220) is in the range of 220 to 320. Furthermore, as shown in the examples described later, a slightly harder consistency of the grease is preferable from the viewpoint of sealing performance. Specifically, the consistency is preferably in the range of 220 to 270, and more preferably in the range of 220 to 250.

[0041] A particularly preferred form of the above grease has a kinematic viscosity of 6 mm at 40°C. 2 / s~20mm 2 The grease comprises a base oil of / s and a urea compound obtained by reacting a polyisocyanate component with at least one monoamine component selected from aliphatic monoamines and alicyclic monoamines as a thickener, wherein the base oil contains at least a synthetic hydrocarbon oil, and the miscible consistency of the grease is in the range of 220 to 270.

[0042] Next, the bearing sealing device 16 will be described using Figure 3. The bearing sealing device 16 consists of a core metal 17 that is fitted inside the outer member 2 and is formed in an annular shape, and a sealing member 18 that is integrally vulcanized and bonded to the core metal 17. The core metal 17 is formed in the same way as the slinger described above. The sealing member 18 is made of an elastic material such as nitrile rubber and has two side lips (dust seals) 18b and 18c and a single radial lip (grease seal) 18a, with the leading edge of each lip directly sliding against the surface of the hub wheel 4, specifically the arc-shaped sliding contact surface 19 at the inboard base of the wheel mounting flange 4b.

[0043] As shown in Figure 3, in the bearing sealing device 16, grease G is applied to the surfaces of each seal lip 18a, 18b, and 18c that slide against the hub ring 4, specifically to one side of the tip of each seal lip. This ensures both sealing performance and reduction of rotational torque.

[0044] Figure 4 is a longitudinal cross-sectional view showing a deep groove ball bearing, which is another example of a sealed rolling bearing of the present invention, and Figure 5 is a partially enlarged view thereof. The rolling bearing 21 has an inner ring 22 having an inner ring raceway surface on its outer circumference and an outer ring 23 having an outer ring raceway surface on its inner circumference, arranged concentrically, with a plurality of rolling elements 24 arranged between the inner ring raceway surface and the outer ring raceway surface. These rolling elements 24 are held by a cage 25. In addition, bearing sealing devices 27 are fitted to the axial openings at both ends of the inner and outer rings, and a grease composition 26 is sealed around at least the rolling elements 24. The inner ring 22, outer ring 23 and rolling elements 24 are made of an iron-based metal material, and the grease composition 26 is interposed on the raceway surface with the rolling elements 24 for lubrication.

[0045] As shown in Figure 5, the bearing sealing device 27 consists of a disc-shaped core metal 28 formed by press working from cold-rolled steel sheet and the like, and a sealing member 29 integrally vulcanized and bonded to the core metal 28. The sealing member 29 has a main lip 29a formed at the inner ring 22 side end with its tip branched into two, and a dust lip 29b located outside the bearing space relative to the main lip 29a. A portion of the sealing member 29 is fixed to a seal groove on the inner circumference of the end of the outer ring 23, which is the fixed-side member, and each seal lip slides against a seal groove with a substantially U-shaped cross-section formed on the outer circumference of the end of the inner ring 22, which is the rotating-side member. As shown in Figure 5, in the bearing sealing device 27 as well, grease G is applied to the surface of each seal lip 29a, 29b that slides against the inner ring 22, specifically to one side of the tip of each seal lip.

[0046] In the examples shown in Figures 4 and 5 above, deep groove ball bearings are used as examples of sealed rolling bearings. However, the bearing sealing device of the present invention can also be used with other types of bearings such as cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, and thrust self-aligning roller bearings.

[0047] In the sealed rolling bearings shown in Figures 1 to 5 above, the grease used in the present invention is pre-applied to the sliding surface of the seal lip of the sealing member. However, instead of this, or in addition to this, the grease may be pre-applied to the surface of the rotating member to which the seal lip slides.

[0048] The applications of the sealed rolling bearing of the present invention are not particularly limited, but as shown in the embodiments described later, it can prevent oil film breakdown even at low rotational speeds and produces low torque, making it particularly suitable for low-speed rotation applications. The sealed rolling bearing of the present invention can be used, for example, at 2000 min -1 This applies to bearings used in the following rotational speed range. Here, 2000 min -1 The term "used in the following rotational speed range" means that the main rotational speed (steady-state rotational speed) of the bearing under its operating conditions is 2000 min⁻¹. -1 The following applies: The rotational speed is 1500 min⁻¹. -1The following may also be true: 1000 min -1 The following is also acceptable. [Examples]

[0049] First, greases with the compositions shown in Tables 1 to 3 were prepared. In Tables 1 to 3, the mass percentages of base oil and thickener indicate their content relative to the base grease (base oil + thickener). Also, items 1) to 8) below in Table 1 are the same in Tables 2 and 3.

[0050] Greases using diurea compounds as thickeners (except for Example 5) were prepared as shown in Figure 6(a). First, oil phase A was prepared by mixing isocyanate (4,4'-diphenylmethane diisocyanate, MDI) and half of the base oil at 60°C, and oil phase B was prepared by mixing amine and half of the base oil at a predetermined temperature (room temperature to 60°C). Next, oil phase B was added to oil phase A while stirring and mixed, and heated at 100°C for 30 minutes (urea reaction). The completion of the reaction was confirmed by IR (infrared spectrometer). After that, it was heated at 130°C for 1 hour (reaction stabilization) and slowly cooled to room temperature. After that, a homogenization treatment was performed and the grease was smoothed using a three-roll mill. Figure 6(b) is a micrograph of the obtained grease.

[0051] A grease using a complex lithium soap as a thickener (Example 5) was prepared as follows. First, 12-hydroxystearic acid was added to half the amount of base oil and heated to 90°C. Then, lithium hydroxide diluted approximately 10 times with water was added. After that, a nonionic surfactant was added and the mixture was vigorously stirred. Next, azelaic acid was added and stirred, and then the lithium hydroxide diluted approximately 10 times with water was added in portions and stirred for about 30 minutes. The completion of the reaction was confirmed by IR (infrared spectroscopy). After that, an antioxidant was added and the mixture was heated to 180°C, then the remaining base oil was added and the mixture was allowed to cool to room temperature. After that, a homogenization treatment was performed and the grease was smoothed using a three-roll mill.

[0052] The consistency (JIS K 2220) of the obtained grease was measured.

[0053] The obtained grease was applied to one side of the tip of the three seal lips of a nitrile rubber sealing member (φ60~70mm). The sealing member was mounted on a member simulating the outer ring of the hub, and a SUS430 slinger was mounted on a member simulating the inner ring of the hub, and assembled so that the seal lips and slinger were in contact.

[0054] <Seal Torque Test> Rotation speed 600 min⁻¹ -1 Or rotation speed 50 min -1 Under room temperature conditions and with the inner ring rotating, the torque (N·m) due to the sliding contact of the seal lip was measured 15 minutes after the start of the test. In this test, the rotation speed was 600 min⁻¹. -1 In this case, a score of 0.20 or higher was considered a failure.

[0055] <Torque fluctuation test> Rotation speed 50 min -1 A component simulating the inner ring of a hub was rotated for 15 minutes at room temperature. The sealing component was brought into sliding contact with a SUS430 slinger (mating material). The torque (N·m) due to the sliding contact between the seal lip and the slinger was measured, and the difference between the maximum and minimum torque values ​​during the last 5 minutes was determined. These differences (torque fluctuations) are indicated in Tables 1 to 3 as follows: less than 0.01 N·m is marked with ◎, 0.01 N·m or more and less than 0.02 N·m is marked with ○, and 0.02 N·m or more is marked with ×.

[0056] <Grease Leakage Test> 0.4g of the grease obtained above was applied to the seal groove formed on the outer circumference of the inner ring of the deep groove ball bearing 6204, and a nitrile rubber sealing member was installed so that the seal lip contacted the seal groove. The test bearing was fixed in place and rotated at 5000 min⁻¹. -1At 80°C, an axial load of 640N and a radial load of 67N were applied to the outer ring and restrained by a load cell. The inner ring was then rotated, and the grease leakage rate was measured during 24 hours of operation. The leakage rate was calculated using the following formula. Prior to operation, 0.05g of a known grease composition (with a different composition from the greases prepared in Tables 1 to 3) was sealed into the bearing space. Leakage rate (mass %) = ((Bearing weight before operation - Bearing weight after operation) / (Bearing weight before operation)) × 100 Regarding the evaluation of the leakage rate, a ◎ mark indicates less than 8% by mass, a ○ mark indicates 8% or more but less than 13% by mass, and a × mark indicates 13% or more by mass, as shown in Tables 1 to 3.

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] As shown in Tables 1 to 3, the kinematic viscosity at 4°C is 6 mm². 2 / s~45mm 2 Examples 1 to 20, which used grease containing a base oil of / s and a thickener with a mixed consistency of 220 to 320, showed good results in all tests.

[0061] From the results in Tables 1 to 3, the kinematic viscosity of the base oil at 40°C is 6 mm². 2 / s~45mm 2 In the range of / s, a tendency was observed for lower kinematic viscosity to result in lower torque in the seal torque test (Examples 10-14, etc.). On the other hand, Comparative Example 2 (kinematic viscosity 47 mm) 2 In Comparative Example 1 (kinematic viscosity 5 mm), an increase in torque was observed. 2Although the seal torque test yielded good results, the grease leakage test showed significant grease leakage. This is thought to be due to the grease having a high consistency and being soft.

[0062] The results of the torque fluctuation test and grease leakage test revealed that the consistency of the grease had a particular influence. For example, while Examples 6-9, Examples 15-18, and Comparative Examples 3-6 had similar kinematic viscosities of base oil, Comparative Examples 4-6, with a consistency exceeding 320, showed large torque fluctuations and increased grease leakage, whereas Examples 6-9 and Examples 15-18, with a consistency of 320 or less, yielded good results. Furthermore, as the consistency decreased, the leakage rate and other parameters improved. It is thought that the increased hardness of the grease due to the decrease in consistency led to higher leak resistance. On the other hand, Comparative Example 3, with its low consistency, showed high leak resistance, but also large torque fluctuations.

[0063] From the results in Tables 1 to 3, it can be said that using a base oil with low kinematic viscosity is preferable to reduce seal torque, but on the other hand, obtaining a harder grease becomes a challenge. In this regard, in this embodiment, by combining an appropriate thickener and base oil type, it is possible to use a low viscosity base oil while maintaining a consistency within an appropriate numerical range. Specifically, by combining a low viscosity base oil (synthetic hydrocarbon oil only, a mixture of synthetic hydrocarbon oil and ester oil, or a mixture of synthetic hydrocarbon oil and ether oil) with a thickener (aliphatic diurea compound, alicyclic diurea compound, aliphatic-alicyclic diurea compound), the consistency is brought within the desired numerical range. [Industrial applicability]

[0064] The sealed rolling bearing of the present invention can achieve both low torque and high sealing performance, and therefore can be widely used as a sealed rolling bearing. [Explanation of Symbols]

[0065] 1. Hub bearing (sealed rolling bearing) 2 Outer member 3. Inner member 4 hub wheels 5. Inner Ring 6 serrations 7 Rolling element 8 Cage 9. Bearing space 11. Bearing sealing device 12 Mandrel 13. Sealing member 14 Seal rings 15 Slinger 16. Bearing sealing device 17 Mandrel 18 sealing member 19 Sliding surface 21. Rolling bearings (sealed rolling bearings) 22 Inner Ring 23 Outer ring 24 Rolling elements 25 Retainer 26 Grease Composition 27 Bearing sealing device 28 Mandrel 29. Sealing member G Grease

Claims

1. A sealed rolling bearing comprising a sealing member that seals the bearing space, is fixed to a stationary member, and slides against a rotating member, wherein a lubricating grease composition is sealed in the bearing space, The sealing member has a sealing lip that slides against the rotating member, and in the sealed rolling bearing, a grease with a different composition from the lubricating grease composition is applied to at least one of the sliding surfaces of the sealing lip and the sliding surface of the rotating member against which the sealing lip slides. The applied grease has a kinematic viscosity of 6 mm at 40°C. ２ / s ~ 45mm ２ It contains a base oil of / s and a thickener, and its mixed consistency, as measured in accordance with JIS K 2220, is 220 to 320. The thickener is limited to urea compounds obtained by reacting a polyisocyanate component with at least one monoamine component selected from aliphatic monoamines and alicyclic monoamines. The base oil comprises at least a synthetic hydrocarbon oil, and the synthetic hydrocarbon oil constitutes 65% to 90% by mass of the total base oil. The sealing member is made of nitrile rubber, and the sealing lip comprises a first sealing lip, a second sealing lip, and a third sealing lip arranged in order from the inside of the bearing space, wherein the grease is applied to the sliding surfaces of these sealing lips, characterized in that the sealing member is made of nitrile rubber, and the sealing lip comprises a first sealing lip, a second sealing lip, and a third sealing lip, in that order, and the grease is applied to the sliding surfaces of these sealing lips.

2. The base oil has a kinematic viscosity of 6 mm at 40°C. ２ / s ~ 20mm ２ The sealed rolling bearing according to claim 1, characterized in that the ratio is / s and the mixing consistency is 220 to 270.

3. The sealed rolling bearing according to claim 1 or 2, characterized in that the sealed rolling bearing is a bearing that rotatably supports an axle.

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