Sealed rolling bearings

Abstract

We provide a sealed rolling bearing that achieves both low torque, torque stability, and resistance to both high and low temperatures. [Solution] The hub bearing 1 includes a sealing member 13 that seals the bearing space 9, is fixed to the stationary member 12, and slides against the rotating member 15. The sealing member 13 has a sealing lip that slides against the rotating member 15, and grease is applied to at least one of the sliding surfaces of the sealing lip and the sliding surface of the rotating member 15 that the sealing lip slides against. The grease contains a base oil, a thickener, and an antioxidant, and contains 0.1% by mass or more and less than 3% by mass of the antioxidant relative to the total amount of the base oil and thickener, and has a mixed consistency of 240 to 300 as measured in accordance with JIS K 2220.

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 Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, for example, axle bearings require minimal torque fluctuations to improve driving comfort and prevent sealing failures due to vibration. Furthermore, axle bearings are required to be usable over a wide temperature range, considering temperature increases during high-speed driving and use in cold climates.

[0008] Patent Document 2, mentioned above, prevents the grease applied to the seal lip from peeling off prematurely by considering the shape of the seal member (such as the dimensions of the seal lip). This aims to increase frictional resistance and reduce sealing failures. Patent Document 3, mentioned above, aims to reduce rotational torque by specifying the kinematic viscosity of the grease base oil. However, the grease applied in Patent Documents 2 and 3 has not been considered in any way for the characteristics required for axle bearings as described above.

[0009] 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.

[0010] 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, torque stability, and resistance to high and low temperatures by improving the grease applied to the seal lip and its mating member. [Means for solving the problem]

[0011] The sealed rolling bearing of the present invention is a sealed rolling bearing comprising a seal member that seals the bearing space, is fixed to a stationary member, and slides against a rotating member, wherein the seal member has a seal lip that slides against the rotating member, and in the sealed rolling bearing, grease is applied to at least one of the sliding surface of the seal lip and the sliding surface of the rotating member that the seal lip slides against, wherein the grease comprises a base oil, a thickener, and an antioxidant, and contains 0.1% by mass or more and less than 3% by mass of the antioxidant relative to the total amount of the base oil and the thickener, and has a mixed consistency of 240 to 300 as measured in accordance with JIS K 2220.

[0012] The thickener described above is characterized by being a urea compound obtained by reacting a polyisocyanate component with at least one monoamine component selected from aliphatic monoamines and alicyclic monoamines.

[0013] The above-mentioned base oil is characterized by consisting solely of synthetic hydrocarbon oil, or by being a mixture of the above-mentioned synthetic hydrocarbon oil and ester oil.

[0014] The above antioxidant is characterized by being an amine-based antioxidant.

[0015] The above-mentioned sealing member is made of nitrile rubber and has a first seal lip, a second seal lip, and a third seal lip arranged in order from the inside of the bearing space as the seal lip, and the above-mentioned grease is applied to the sliding surfaces of these seal lips.

[0016] The sealed roller bearing is characterized in that it is a bearing that rotatably supports a vehicle axle.

Advantages of the Invention

[0017] The sealed roller bearing of the present invention is provided with a seal member that is fixed to a fixed-side member and is in sliding contact with a rotating-side member, and 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. The grease contains a base oil, a thickener, and an antioxidant, and contains 0.1% by mass or more and less than 3% by mass of the antioxidant with respect to the total amount of the base oil and the thickener, and the consistency measured in accordance with JIS K 2220 is 240 to 300. Therefore, the seal member is excellent in low torque, torque stability, and high temperature resistance and low temperature resistance, leading to high functionality (low fuel consumption) of the sealed roller bearing sealed by the seal.

[0018] Since 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, it further contributes to reduction of torque.

[0019] The seal member is formed of nitrile rubber and has three seal lips in order from the inner side of the bearing space as seal lips, and grease is applied to the sliding contact surfaces of these seal lips, so that while ensuring low torque property, the sealing property can be further improved.

[0020] Since the sealed roller bearing is a bearing that rotatably supports a vehicle axle, it can contribute to high functionality (low fuel consumption) of bearings for vehicle axles such as hub bearings.

Brief Description of the Drawings

[0021] [Figure 1] It is a longitudinal sectional view showing an example of the sealed roller bearing of the present invention. [Figure 2] It is an enlarged sectional view showing the bearing seal device on the inboard side of FIG. 1. [Figure 3] It is an enlarged sectional view showing the bearing seal device on the outboard side of FIG. 1. [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]

[0022] 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.

[0023] 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.

[0024] 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.

[0025] As shown in Figure 2, the bearing sealing device 11 comprises a seal ring 14 consisting of a core metal 12 fitted inside the outer member 2 and formed in an L-shape in cross-section, and a seal member 13 integrally vulcanized and bonded to the core metal 12, and a slinger 15 fitted outside the inner ring 5 and also formed in an L-shape in cross-section. The core metal 12 of the slinger 15 and the seal ring 14 are formed by press working from austenitic stainless steel sheet (such as SUS304 series according to JIS standards) or cold-rolled steel sheet treated with rust prevention (such as SPCC series according to JIS standards).

[0026] The material used for the sealing member 13 is nitrile rubber (NBR), acrylic rubber, silicone rubber, or fluororubber. In Figure 2, the sealing member 13 has three sealing lips 13a, 13b, and 13c in order from the inside of the bearing space: an inner, an intermediate, and an outer one. The tip edge of the outer sealing lip 13c slides against the inner surface of the vertical plate portion 15b of the slinger 15, while the tip edges of the remaining intermediate sealing lip 13b and inner sealing lip 13a slide against 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.

[0027] In the configuration shown in Figure 2, grease is applied to the sliding surface of the seal lip of the sealing member. Specifically, as shown in Figure 2, grease G is applied to the sliding surfaces of the seal lips 13a, 13b, and 13c that slide against the slinger 15. In this case, it is sufficient that grease G is applied to at least the sliding surface of the seal lip, and it may be applied to the entire seal lip. In the present invention, grease G contains a base oil, a thickener, and an antioxidant, and is characterized by having a mixed consistency of 240 to 300. This grease will be described below.

[0028] The base oil used in grease can usually be one of the common types 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, as well as ester oils, ether oils, silicone oils, and fluorinated oils. These base oils may be used individually or in combination of two or more types.

[0029] Among the above, it is preferable that the base oil is at least one selected from synthetic hydrocarbon oil and ester oil, and more preferably that the base oil consists solely of synthetic hydrocarbon oil or is a mixture of synthetic hydrocarbon oil and ester oil. In the case of such a mixture, it is preferable that the synthetic hydrocarbon oil accounts for 60% by mass or more of the total base oil (mixture), and more preferably 65% ​​to 90% by mass.

[0030] 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.

[0031] 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.

[0032] The kinematic viscosity of the base oil used in the grease at 40°C (or the kinematic viscosity of the mixed oil in the case of a mixed oil; the same applies hereafter) is set at 6 mm from the perspective of reducing torque. 2 / s~45mm 2 / s is preferred, 6mm 2 / s~31mm 2 / s is more preferable, 6mm 2 / s~20mm 2 / s is even more preferable, 9mm 2 / s~17mm 2 / s is particularly preferred.

[0033] 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, the use of diurea compounds is preferred.

[0034] 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.

[0035] Among these diurea compounds, it is preferable to use aromatic diisocyanate as the polyisocyanate component and at least one of aliphatic monoamine and alicyclic monoamine as the monoamine component, due to its superior low torque properties. In particular, it is more preferable to use an aliphatic-alicyclic diurea compound prepared using 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.

[0036] Base greases using diurea compounds as thickeners are prepared by reacting the above-mentioned polyisocyanate component with a monoamine component in a base oil.

[0037] 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 15% to 20% by mass, relative to the total amount of the base oil and the thickener (100% by mass). By using a relatively small amount of thickener, the proportion of base oil can be increased, which makes it easier to achieve lower torque.

[0038] The grease used in this invention contains an antioxidant as an essential component. The amount of antioxidant is 0.1% by mass or more and less than 3% by mass relative to the total base grease (100% by mass) consisting of base oil and thickener. By keeping it within this range, oxidative degradation of the grease can be suppressed, and torque fluctuations during bearing rotation can be reduced. Preferably, the amount of antioxidant is 0.5% by mass or more and less than 3% by mass relative to the total base grease, and more preferably 0.5% by mass or more and 2% by mass or less.

[0039] Examples of the antioxidant include amine-based antioxidants such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, 3,7-dioctylphenothiazine, p,p'-dioctyldiphenylamine, N,N'-diisopropyl-p-phenylenediamine, and phenolic antioxidants such as 2,2'-methylenebis(6-tert-butyl-4-methylphenol). These antioxidants may be used alone or in combination of two or more. It is preferable to use an amine-based antioxidant as the antioxidant.

[0040] In addition, known additives can be added to the grease as needed. Examples of the additive include rust inhibitors such as polyhydric alcohol esters. It is preferable not to contain extreme pressure agents such as organic zinc compounds and organic molybdenum compounds.

[0041] The consistency (JIS K 2220) of the grease used in the present invention is in the range of 240 to 300, and as shown in the examples described later, it is preferably in the range of 240 to 280 because torque fluctuation can be further suppressed.

[0042] A particularly preferred form of the grease is a base oil having a kinematic viscosity at 40°C of 6 mm 2 / s to 20 mm 2 / s, 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, and an amine-based antioxidant, wherein the blending amount of the antioxidant is 0.1% by mass or more and 2% by mass or less based on the total amount of the base grease, and the consistency of the grease is in the range of 240 to 300.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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]

[0050] First, greases with the compositions shown in Tables 1 and 2 were prepared. In Tables 1 and 2, the mass percentages of base oil, thickener, and antioxidant indicate their content relative to the base grease (base oil + thickener). Also, items 1) to 4) below in Table 1 are the same in Table 2.

[0051] The grease used in the example was 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.

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

[0053] 0.6g of 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 the assembly was carried out so that the seal lips and slinger were in contact.

[0054] <Torque fluctuation test 1> Rotation speed 1000 min⁻¹ -1A component simulating the inner ring of a hub was rotated for 30 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 and 2 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 ×.

[0055] <Torque Fluctuation Test 2> 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 and 2 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] <High-temperature resistance test> The high-temperature resistance of each grease was evaluated by oxidation induction time. Oxidation induction time was measured by high-pressure differential scanning calorimetry (PDSC). PDSC is a measurement method that performs differential scanning calorimetry under pressure, and in PDSC, the oxidation induction period is measured as the time from when the sample reaches a predetermined temperature until oxidation begins. Using 3 mg of sample grease, the test temperature was set to 220°C under an oxygen atmosphere and pressurized to 3.5 MPa. The time from when the sample temperature reached 220°C until the oxidation exothermic peak (oxidation induction time) was measured. Oxidation induction times of 30 minutes or more are marked with ◎, 10 minutes or more but less than 30 minutes are marked with ○, and less than 10 minutes are marked with ×, as shown in Tables 1 and 2.

[0057] <Low-temperature resistance test> The low-temperature resistance of each grease was evaluated by its storage modulus. A parallel-plate rheometer was used for the test. The grease was placed on a φ25 mm lower plate and sandwiched between two φ25 mm upper plates, with a gap of 1 mm between the plates. The storage modulus of the grease was measured when a temperature of -40°C, a frequency of 1 Hz, and a strain of 0.001 were applied. A storage modulus of less than 200 kPa is marked with ◎, 200 kPa or more and less than 250 kPa is marked with ○, and 250 kPa or more is marked with ×, as shown in Tables 1 and 2.

[0058] [Table 1]

[0059] [Table 2]

[0060] As shown in Tables 1 and 2, Examples 1 to 10, which used grease containing a base oil, a thickener, and an antioxidant in an amount of 0.1% to less than 3% by mass relative to the total base grease, and having a mixed consistency of 240 to 300, all showed good results in the tests.

[0061] The results of the torque fluctuation test showed that the consistency of the grease had a particular influence. For example, from Examples 5-6 and Comparative Example 3, the torque decreased as the consistency decreased over 1000 min. -1 Torque fluctuations during rotation increased. On the other hand, from Examples 1, 4, and 7 and Comparative Examples 2 and 4, the consistency increased as the 50 min -1 The torque fluctuation during rotation increased. Thus, when the consistency is in the range of 240 to 300, torque fluctuations can be effectively suppressed even at different rotational speeds under low-speed rotation conditions.

[0062] Regarding high-temperature resistance, more favorable results were obtained by incorporating an antioxidant at a concentration of 0.5% by mass or more relative to the total base grease. Furthermore, regarding low-temperature resistance, the results improved as the consistency increased, with a consistency of 260 or higher yielding more favorable results.

[0063] The results in Tables 1 and 2 show that in this embodiment, by combining an appropriate consistency with an appropriate antioxidant, low torque, high torque stability, and resistance to high and low temperatures can be obtained. Furthermore, since it is easy to set the consistency within an appropriate numerical range while using a low viscosity base oil, in this embodiment, a predetermined base oil (synthetic hydrocarbon oil only, or a mixture of synthetic hydrocarbon oil and ester oil) is combined with a predetermined thickener (aliphatic / alicyclic diurea compound). [Industrial applicability]

[0064] The sealed rolling bearing of the present invention can achieve both low torque, torque stability, and resistance to high and low temperatures, making it widely applicable 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, The sealing member has a sealing lip that slides against the rotating member, and in the sealed rolling bearing, grease is applied to at least one of the sliding surfaces of the sealing lip and the sliding surface of the rotating member that the sealing lip slides against. The grease is characterized by comprising a base oil, a thickener, and an antioxidant, wherein the antioxidant is present in an amount of 0.1% by mass or more and less than 3% by mass relative to the total amount of the base oil and the thickener, and the mixed consistency, as measured in accordance with JIS K 2220, is 240 to 300.

2. The sealed rolling bearing according to claim 1, characterized in that 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.

3. The sealed rolling bearing according to claim 1 or 2, characterized in that the base oil consists solely of synthetic hydrocarbon oil or is a mixed oil of synthetic hydrocarbon oil and ester oil.

4. The sealed rolling bearing according to any one of claims 1 to 3, characterized in that the antioxidant is an amine-based antioxidant.

5. The sealing member is made of nitrile rubber, and the sealing lip has, in order from the inside of the bearing space, a first sealing lip, a second sealing lip, and a third sealing lip, and the grease is applied to the sliding surfaces of these sealing lips, as a sealed rolling bearing according to any one of claims 1 to 4.

6. The sealed rolling bearing according to any one of claims 1 to 5, characterized in that the sealed rolling bearing is a bearing that rotatably supports an axle.

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