Sealed rolling bearings

Abstract

To provide a sealed rolling bearing that achieves low torque, high water resistance, and corrosion resistance simultaneously. [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 has a kinematic viscosity of 6 mm at 40°C. 2 / s~45mm 2 It contains a base oil of 1 / s, a thickener, and a rust inhibitor, and its mixed consistency, measured in accordance with JIS K 2220, is 220-280.

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] Patent Document 2, mentioned above, prevents the grease applied to the seal lip 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 other characteristics of the grease itself that is pre-applied to the seal lip are not considered. Furthermore, Patent Document 3 attempts to reduce rotational torque 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. In addition, rolling bearings and hub bearings used in automotive electrical accessories are susceptible to water intrusion from rainwater and road water, so it is important to suppress water intrusion and rust formation. However, the grease applied in Patent Documents 2 and 3 does not take these characteristics into consideration at all.

[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] The present invention has been made in view of the above problems, and an object thereof is to provide a sealed rolling bearing capable of achieving both low torque characteristics, high water resistance, and rust prevention properties by improving the grease applied to the seal lip and its mating member.

Means for Solving the Problems

[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 , ,

[0015] , , ,

[0014] / s to 45 mm 2 / s of base oil, a thickener, and a rust inhibitor, and is characterized in that the consistency measured in accordance with JIS K 2220 is 220 to 280.

[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.

[0012] The base oil consists only of synthetic hydrocarbon oil or is a mixed oil of the synthetic hydrocarbon oil and ester oil.

[0013] The rust inhibitor is at least one selected from ester-based rust inhibitors and sulfonate-based rust inhibitors.

[0014] The grease contains an ester-based rust inhibitor and a sulfonate-based rust inhibitor as the rust inhibitor, and contains the rust inhibitor in an amount of 0.5 mass% or more and less than 1.5 mass% based on the total amount of the base oil and the thickener.

[0015] The above seal member is formed of nitrile rubber, and as the above 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 above sliding contact surfaces of these seal lips. It is characterized by that.

[0016] The above sealed rolling bearing is characterized by being a bearing that rotatably supports a vehicle axle.

Effect of the Invention

[0017] The sealed rolling bearing of the present invention includes a seal member that is fixed to a fixed-side member and slidably contacts 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 has a kinematic viscosity at 40°C of 6 mm 2 / s to 45 mm 2 / s base oil, a thickener, and a rust inhibitor, and the consistency measured in accordance with JIS K 2220 is 220 to 280. Therefore, when applied to the sliding contact surface of the seal lip or the sliding contact surface of the rotating-side member, channelling properties can be ensured and the torque can be reduced, and high water resistance and rust prevention properties can be obtained.

[0018] 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, it further contributes to reducing the torque.

[0019] The above grease contains an ester-based rust inhibitor and a sulfonate-based rust inhibitor as rust inhibitors, and contains 0.5% by mass or more and less than 1.5% by mass of rust inhibitors with respect to the whole grease. Therefore, excellent rust prevention properties are exhibited, and by suppressing the content of the rust inhibitor, it becomes easier to maintain the shape of the grease even when in contact with water, and the water resistance can be improved.

[0020] 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.

[0021] 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]

[0022] [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]

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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).

[0027] 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.

[0028] 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 also be applied to the entire seal lip. In this invention, grease G has a kinematic viscosity of 6 mm at 40°C. 2 / s~45mm 2 This grease contains a base oil of s, a thickener, and a rust inhibitor, and is characterized by a mixed consistency of 220-280. The following describes this grease.

[0029] The base oil used in the grease has a kinematic viscosity of 6 mm at 40°C (or the kinematic viscosity of the mixed oil in the case of a mixed oil; the same applies hereafter). 2 / s~45mm 2 The 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.

[0030] Among these, it is preferable that the base oil is at least one selected from synthetic hydrocarbon oils and ester oils. Further, it is more preferable that the base oil consists only of a synthetic hydrocarbon oil or is a mixed oil of a synthetic hydrocarbon oil and an ester oil. In the case of the mixed oil, it is preferable that the synthetic hydrocarbon oil is 60% by mass or more of the whole base oil (mixed oil), and more preferably 65% to 90% by mass.

[0031] PAO oil, which is a synthetic hydrocarbon oil, is a mixture of oligomers or polymers of α-olefins or 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, 1-tetracosene, etc. Usually, mixtures of these are used.

[0032] 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 pyromellitate; polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, and pentaerythritol ester oil; carbonate ester oils; and phosphate ester oils. Among these, pentaerythritol ester oil is preferable.

[0033] The kinematic viscosity at 40°C of the base oil used for the grease is preferably 6 mm 2 / s to 31 mm 2 / s from the viewpoint of low torque, more preferably 6 mm 2 / s to 20 mm 2 / s, and even more preferably 9 mm 2 / s to 17 mm 2 / s.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Base greases using diurea compounds as thickeners are prepared by reacting the above-mentioned polyisocyanate component with a monoamine component in a base oil.

[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 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.

[0039] The grease used in this invention contains a rust inhibitor as an essential component. The amount of rust inhibitor is preferably 0.5% by mass or more and less than 3.0% by mass relative to the total amount of the base grease (100% by mass) consisting of base oil and thickener. Keeping it within this range allows the grease to maintain its shape even when in contact with water while exhibiting rust prevention properties. More preferably, the amount of rust inhibitor is 0.5% by mass or more and less than 1.5% by mass relative to the total amount of the base grease.

[0040] The type of rust inhibitor is not particularly limited, and can be ester-based rust inhibitors; sulfonate-based rust inhibitors; linear fatty acids such as lauric acid and stearic acid, or carboxylic acid-based rust inhibitors such as succinic acid and alkyl succinic acid; carboxylic acid salt-based rust inhibitors such as fatty acids and various metal salts (cobalt, manganese, zinc) of naphthenic acid; or amine-based rust inhibitors such as alkoxyphenylamine. Among these rust inhibitors, it is preferable to use at least one selected from ester-based rust inhibitors and sulfonate-based rust inhibitors.

[0041] As ester-based rust inhibitors, partial esters of polyhydric alcohols such as sorbitan, sorbitol, pentaerythritol, sucrose, and glycerin with carboxylic acids such as oleic acid and lauric acid, or succinic acid half-esters such as alkyl succinic acid half-esters and alkenyl succinic acid half-esters can be used. These ester-based rust inhibitors may be used alone or in combination of two or more types.

[0042] Among the ester-based rust inhibitors mentioned above, sorbitan fatty acid esters are more preferred. Examples of sorbitan fatty acid esters include sorbitan monolaurate, sorbitan monostearate, sorbitan monooleate, and other sorbitan fatty acid monoesters, as well as sorbitan trioleate. When using an ester-based rust inhibitor, it is preferable that its amount is less than 1% by mass of the total base grease.

[0043] As sulfonate-based rust inhibitors, various metal salts and amine salts of alkyl aromatic sulfonic acids such as alkylbenzene sulfonic acid and alkylnaphthalene sulfonic acid, or petroleum-based sulfonic acids obtained by sulfonating aromatic components of petroleum distillates, can be used. Examples of metals that make up the metal salts include alkaline earth metals such as barium, calcium, and magnesium, alkali metals such as sodium and lithium, and zinc. Examples of amines that make up the amine salts include ethylamine and trimethylamine. These sulfonate-based rust inhibitors may be used individually or in mixtures of two or more types.

[0044] In particular, it is preferable to use a combination of ester-based and sulfonate-based rust inhibitors as rust inhibitors. By combining these two types of rust inhibitors, rust prevention can be improved compared to using one type alone.

[0045] 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. It is preferable that extreme pressure agents such as organozinc compounds and organomolybdenum compounds are not included.

[0046] The consistency of the grease used in this invention (JIS K 2220) is in the range of 220 to 280, and preferably in the range of 240 to 280.

[0047] 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, 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 ester-based rust inhibitor and a sulfonate-based rust inhibitor as rust inhibitors, wherein the consistency of the grease is in the range of 220 to 280. Furthermore, in this case, it is preferable that the amount of rust inhibitor added is 0.5% by mass or more and less than 1.5% by mass relative to the total base grease.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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. -1 The following may also be true: 1000 min -1 The following is also acceptable. [Examples]

[0055] First, greases with the compositions shown in Tables 1 to 3 were prepared. In Tables 1 to 3, the mass percentages of base oil, thickener, and rust inhibitor indicate their content relative to the base grease (base oil + thickener). Also, items 1) to 9) below in Table 1 are the same in Tables 2 and 3.

[0056] 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.

[0057] The consistency (JIS K 2220) of the obtained grease was measured.

[0058] <Seal Torque Test> A total of 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. Rotation speed 600 min⁻¹ -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 for 1 minute, 30 minutes after the start of the test. In this test, a value of 0.20 or higher was considered a failure.

[0059] <Water resistance test> A total of 0.4 g of the above grease was applied to the seal grooves formed on the outer circumference of the inner ring and the inner circumference of the outer ring of the 6204 stainless steel bearing, and a nitrile rubber seal member was installed so that the seal lip contacted the seal groove of the inner ring. 0.05 g of a known grease composition (with a different composition from the grease prepared in Tables 1 to 3) was sealed into the bearing space. Using this test bearing, the following test, a modified version of the water wash resistance test specified in JIS K 2220, was performed.

[0060] After assembling the test bearing into the housing of the water-washing water resistance tester, the test bearing was submerged in 79°C hot water. Then, with the test bearing submerged, it was rotated at a speed of 600 min⁻¹. -1 While rotating, 79°C hot water was sprayed into the test bearing from a nozzle at a rate of 6 ml / s for 120 minutes. After the test, the amount of water that entered the test bearing was calculated using the following formula. Water ingress (g) = (Bearing weight after operation - Bearing weight before operation) Regarding the evaluation of water intrusion, values ​​less than 0.5g are marked with ◎, values ​​between 0.5g and 1.0g are marked with ○, and values ​​of 1.0g or more are marked with ×, as shown in Tables 1 to 3.

[0061] <Rust Test> The tapered roller bearings coated with the above-mentioned grease were immersed in a 1% by mass salt solution for 10 seconds and left to stand in a high-humidity environment. After the test, the bearings were removed and the outer ring surface was visually inspected. The evaluation was performed by dividing the outer ring surface into 32 sections and calculating the rust occurrence rate based on how many of these sections had rust. Bearing: 4T-30204 Grease content: 2.1g Test temperature: 40℃ Test humidity: 100%RH Exam duration: 48 hours Regarding the evaluation of rust occurrence rate, a ◎ mark indicates less than 25%, a ○ mark indicates 25% or more but less than 75%, and a × mark indicates 75% or more, as shown in Tables 1 to 3.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] As shown in Tables 1 and 2, the kinematic viscosity at 4°C is 6 mm².2 / s~45mm 2 Examples 1 to 16, which used grease containing a base oil of 1 / s, a thickener, and a rust inhibitor, with a mixed consistency of 220 to 280, all showed good results in the tests.

[0066] 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 1, 14-16). On the other hand, Comparative Example 4 (kinematic viscosity 47 mm) 2 An increase in torque was observed ( / s).

[0067] The results regarding water intrusion (water resistance) showed that the consistency of the grease and the amount of rust inhibitor added were particularly influential. Comparative Examples 1 and 2, both of which had a consistency outside the range of 220-280, showed increased water intrusion. In Comparative Example 2 (concentration 300), the high consistency and softness likely caused grease to leak out from near the lip, resulting in reduced sealing performance. On the other hand, in Comparative Example 1 (concentration 200), the hard and poor fluidity likely led to gaps forming, resulting in reduced sealing performance. Furthermore, an increase in the amount of rust inhibitor was observed, which tended to increase the amount of water penetration (Examples 4-5, 9-10). While rust inhibitors are effective from the standpoint of rust prevention, this suggests that they may have a detrimental effect on the sealing ability of the grease against water penetration. It is presumed that as the amount of rust inhibitor increases, the grease becomes more compatible with water, making it more difficult to maintain the shape of the grease near the lip.

[0068] Regarding the rate of rust occurrence, the combination of ester-based and sulfonate-based rust inhibitors resulted in improved rust prevention compared to using each of them individually (Examples 3-8).

[0069] The results in Tables 1 to 3 show that in this embodiment, channeling performance can be ensured, torque can be reduced, and high water resistance and rust prevention can be obtained by combining appropriate consistency and base oil viscosity with appropriate rust inhibitors (especially a combination of ester-based and sulfonate-based rust inhibitors). Furthermore, since it is easy to set the consistency within an appropriate numerical range while using a low-viscosity base oil, the embodiment combines a predetermined base oil (synthetic hydrocarbon oil only, or a mixture of synthetic hydrocarbon oil and ester oil) with a predetermined thickener (aliphatic / alicyclic diurea compound). [Industrial applicability]

[0070] The sealed rolling bearing of the present invention can achieve low torque, high water resistance, and corrosion resistance simultaneously, making it widely applicable as a sealed rolling bearing. [Explanation of Symbols]

[0071] 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 aforementioned grease has a kinematic viscosity of 6 mm at 40°C. ２ / s ~ 45mm ２ A sealed rolling bearing characterized by containing a base oil of / s, a thickener, and a rust inhibitor, and having a mixed consistency of 220 to 280 as measured in accordance with JIS K 2220.

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. A sealed rolling bearing according to any one of claims 1 to 3, characterized in that the rust inhibitor is at least one selected from ester-based rust inhibitors and sulfonate-based rust inhibitors.

5. The sealed rolling bearing according to any one of claims 1 to 3, characterized in that the grease contains an ester-based rust inhibitor and a sulfonate-based rust inhibitor as the rust inhibitor, and the amount of the rust inhibitor is 0.5% by mass or more and less than 1.5% by mass relative to the total amount of the base oil and the thickener.

6. 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 5.

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

Images