Seal device

Abstract

To provide a seal device capable of achieving both low torque and high sealability by improving grease to be applied to a seal lip and its mating member, and also provide a rotary component using the seal device.SOLUTION: A seal ring 14 is fixed to a fixing side member 2 of the rotary component, is in slide contact with a rotation side member 15, and has a seal lip in slide contact with the rotation side member 15. Grease is applied to the slide contact surface of the seal lip. The grease includes a base oil, thickening agent, and additive, and the apparent viscosity of the grease in a shear rate of 1000 s-1 at 60°C is 0.22 Pa s or higher.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Generally, a lubricant composition such as lubricating oil or grease is enclosed inside a rolling bearing. Bearings containing a lubricant composition have a long life, do not require an external lubrication unit, and are inexpensive, so they are often used for general-purpose applications such as automobiles and industrial equipment. In particular, when high sealing performance is required, a contact-type sealing device is used in which the seal lip of a seal member contacts the sliding surface of a mating member such as a raceway ring to seal the bearing space.

[0003] The intrusion of foreign matter such as water or mud from the outside can significantly reduce the durability (wear resistance and bearing life) of the bearing. Therefore, ensuring sealing performance is important in sealing devices. On the other hand, from the perspective of energy saving and carbon neutrality, low torque is required for the sliding of the seal lip.

[0004] Conventionally, it has been known to fill a hub unit bearing with a grease composition having a specific composition to prevent contamination from outside. For example, Patent Document 1 describes a grease composition containing a base oil, a thickener, three types of rust inhibitors, and an anti-wear agent, which is said to have excellent water resistance.

[0005] Also, in order to keep the sliding resistance of the seal lip low and ensure the sealing performance of the seal lip, a technique is known in which grease is applied to the seal lip or the mating member. For example, Patent Document 2 describes a rolling bearing in which grease is applied in advance to one side of the tip of the seal lip, which is in sliding contact with the surface of the hub wheel during use. Also, Patent Document 3 describes a rolling bearing in which grease is applied in advance 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 Summary of the Invention [Problem to be solved by the invention]

[0007] Conventionally, as in Patent Document 1, various grease compositions have been studied for the grease composition sealed inside the bearing, but little has been studied for the grease applied to the seal lip or its mating member. Even in cases where the grease applied to the seal lip or its mating member has been studied, the study has been insufficient.

[0008] For example, in the above-mentioned Patent Document 2, the shape of the sealing member (such as the dimensions of the seal lip) is considered to prevent the grease applied to the seal lip from peeling off in advance. This aims to increase frictional resistance and reduce sealing failure. However, the performance of the grease itself applied to the seal lip in advance in terms of frictional resistance and sealing properties is not taken into consideration. Therefore, there is a risk of increased frictional resistance and sealing failure occurring due to insufficient performance of the grease. In addition, in the above-mentioned Patent Document 3, the kinetic viscosity of the base oil of the grease is specified to reduce the rotational torque, but it is considered difficult to ensure sealing performance and reduce the rotational torque at the same time by simply specifying the kinetic viscosity of the base oil.

[0009] The present invention has been made in consideration of the above circumstances, and has an object to provide a sealing device that can achieve both low torque and high sealing performance by improving the grease applied to the seal lip and its mating member, and a rotating part that uses the sealing device. [Means for solving the problem]

[0010] The sealing device of the present invention is a sealing device that is fixed to a fixed member of a rotating component and in sliding contact with the rotating member, the sealing device has a seal lip that is in sliding contact with the rotating member, and grease is applied to the sliding surface of the seal lip, the grease containing a base oil, a thickener, and an additive, and is resistant to a shear rate of 1000 s at 60°C. -1 The grease is characterized by an apparent viscosity of 0.22 Pa s or more.

[0011] The additive is characterized by including at least one of a sulfur-phosphorus-based extreme pressure agent and a phosphorus-based extreme pressure agent, but preferably does not include an organic zinc compound or an organic molybdenum compound in the sulfur-phosphorus-based extreme pressure agent.

[0012] The additive is characterized in that it contains calcium sulfonate and other metal sulfonates, and does not contain an ester-based rust inhibitor.

[0013] The thickener is a diurea compound obtained by reacting a diisocyanate component with a monoamine component, and the monoamine component is an aliphatic monoamine and an alicyclic monoamine.

[0014] The base oil is characterized in that it consists of only a synthetic hydrocarbon oil or is a mixed oil of the synthetic hydrocarbon oil and an ester oil.

[0015] The above base oil has a kinetic viscosity of 6mm at 40°C. 2 / s~20mm 2 / s.

[0016] The additive contains a sulfur-phosphorus-based extreme pressure agent or a phosphorus-based extreme pressure agent, calcium sulfonate, and another metal sulfonate, but does not contain an ester-based rust inhibitor, the thickener is a diurea compound obtained by reacting a diisocyanate component with a monoamine component, the monoamine component being an aliphatic monoamine and an alicyclic monoamine, the base oil is composed of only a synthetic hydrocarbon oil or is a mixed oil of the synthetic hydrocarbon oil and an ester oil, and has a kinetic viscosity of 6 mm at 40°C. 2 / s~20mm 2 / s.

[0017] In the above sealing device, the seal member is formed of nitrile rubber, the seal lips include, in this order from the inner side of the bearing space, a first seal lip, a second seal lip, and a third seal lip, and the grease is applied to the sliding surfaces of these seal lips.

[0018] The rotating part of the present invention is characterized in that it uses at least one or more of the sealing devices of the present invention. The rotating part is characterized in that it is a rolling bearing. The rolling bearing is characterized in that it is a bearing that rotatably supports an axle.

[0019] The sealed rolling bearing of the present invention is a sealed rolling bearing comprising a seal member which seals a bearing space, is fixed to a fixed member, and is in sliding contact with a rotating member, the seal member having a seal lip which is in sliding contact with the rotating member, and 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 member with which the seal lip is in sliding contact, the grease containing a base oil, a thickener, and an additive, and is resistant to shear at 60° C. and a shear rate of 1000 s -1 The grease is characterized by an apparent viscosity of 0.22 Pa s or more. Effect of the Invention

[0020] In the sealing device of the present invention, grease is applied to the sliding surface of the seal lip, and the grease contains a base oil, a thickener, and an additive, and is resistant to shear at 60°C and a shear rate of 1000 s -1 Since the apparent viscosity of the grease in this case is 0.22 Pa s or more and has fluidity under the shear conditions, when the grease is applied to the sliding surface of the seal lip, the grease is supplied to the contact area between the seal lip and the rotating member (e.g., a slinger), maintaining the sealing performance and effectively preventing the intrusion of muddy water. This results in a sealing device that combines low torque with high sealing performance.

[0021] Since the additive contains at least one of a sulfur-phosphorus-based extreme pressure agent and a phosphorus-based extreme pressure agent, the sealing performance can be further improved.

[0022] The above additive contains calcium sulfonate and other metal sulfonates, but does not contain an ester-based rust inhibitor, which makes it easier to further improve the sealing performance.

[0023] The thickener is a diurea compound obtained by reacting a diisocyanate component with a monoamine component, and since the monoamine component is an aliphatic monoamine and an alicyclic monoamine, it further contributes to low torque.

[0024] The base oil is composed of only a synthetic hydrocarbon oil or is a mixed oil of the synthetic hydrocarbon oil and an ester oil, which further contributes to low torque.

[0025] The above base oil has a kinetic viscosity of 6mm at 40°C. 2 / s~20mm 2 / s, which contributes even more to low torque.

[0026] In the above sealing device, the seal member is formed of nitrile rubber and has a plurality of seal lips as seal lips, and grease is applied to the sliding surfaces of these seal lips, so that low torque is ensured while the sealing performance is further improved.

[0027] The rotating part of the present invention uses at least one sealing device of the present invention, and therefore achieves both low torque and high sealing performance. In addition, since the rotating part is a rolling bearing that rotatably supports an axle, it can contribute to improving the performance (fuel economy) of axle bearings such as hub bearings.

[0028] The sealed rolling bearing of the present invention has grease applied to at least one of the sliding contact surface of the seal lip and the sliding contact surface of the rotating member with which the seal lip slides. The grease contains a base oil, a thickener and an additive, and has a shear rate of 1000 s at 60° C. -1 Since the apparent viscosity of the grease in this case is 0.22 Pa s or more and it has fluidity under the shear conditions, when it is applied to the sliding surface of the seal lip or the sliding surface of the rotating member, the grease is supplied to the contact area between the seal lip and the rotating member (e.g., a slinger), maintaining the sealing performance and effectively preventing the intrusion of muddy water. This results in a sealed rolling bearing that combines low torque with high sealing performance. [Brief description of the drawings]

[0029] [Figure 1] 1 is a vertical cross-sectional view showing an example of a rotating part of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing the inboard side bearing sealing structure of FIG. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing the bearing sealing structure on the outboard side of FIG. 1. [Figure 4] FIG. 1 is a schematic diagram showing an example of a rotational rheometer. [Diagram 5] FIG. 4 is a vertical cross-sectional view showing another example of a rotating part of the present invention. [Figure 6] FIG. 6 is an enlarged cross-sectional view of the rotating component of FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a vertical cross-sectional view showing a hub bearing, which is an example of a sealed rolling bearing as a rotating part of the present invention. The hub bearing 1 shown in Fig. 1 is an axle bearing on the driving wheel side that rotatably supports the axle.

[0031] As shown in FIG. 1, a hub bearing 1 comprises an outer member 2 which has, integrally with it, a vehicle body mounting flange 2b which is attached to a vehicle body (not shown) on its outer periphery, and has double row outer raceway surfaces 2a, 2a formed on its inner periphery, and a wheel mounting flange 4b ​​which is integrally formed at one end thereof to which a wheel (not shown) is attached, and which has, on its outer periphery, one inner raceway surface 4a which faces the double row outer raceway surfaces 2a, 2a, and a cylindrical small diameter step 4c which extends axially from the inner raceway surface 4a, and which has serrations 6 for transmitting torque formed on its inner periphery, and an inner ring 5 which is press-fitted into the small diameter step 4c and has the other inner raceway surface 5a formed on its outer periphery.

[0032] Double row rolling elements (balls) 7 are accommodated by a cage 8 so as to roll freely between the double row outer raceway surfaces 2a, 2a and the opposing inner raceway surfaces 4a, 5a. Bearing seal structures 11, 16 are constructed in the annular space formed between the inner member 3, which is the rotating member and comprises the hub ring 4 and the inner ring 5, and the outer member 2, which is the fixed member, to prevent leakage of the grease composition sealed in the bearing space 9 and to prevent rainwater, dust, and the like from entering the bearing space 9 from the outside. Of these bearing seal structures 11, 16, the inboard side (right side in the figure) bearing seal structure 11 mounted between the outer member 2 and the inner ring 5 will be described with reference to FIG. 2.

[0033] As shown in Fig. 2, the bearing sealing structure 11 includes a seal ring 14 consisting of a core metal 12 formed with an L-shaped cross section and fitted into the outer member 2, and a seal member 13 integrally vulcanized and bonded to the core metal 12, and a slinger 15 fitted onto the inner ring 5 and similarly formed with an L-shaped cross section. In the bearing sealing structure 11, the seal ring 14 corresponds to the sealing device of the present invention. The core metal 12 of the slinger 15 and the seal ring 14 are formed by pressing an austenitic stainless steel plate (such as SUS304 of the JIS standard) or a rust-proofed cold-rolled steel plate (such as SPCC of the JIS standard).

[0034] The material of the seal member 13 may be nitrile rubber (NBR), acrylic rubber, silicone rubber, fluororubber, or the like. In Fig. 2, the seal member 13 has three seal lips 13a, 13b, and 13c, which are inner, middle, and outer, in that order from the inside of the bearing space, and the tip edge of the outer seal lip 13c is in sliding contact with the inner surface of the standing 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.

[0035] In the configuration of Fig. 2, grease is applied to the sliding surfaces of the seal lips of the seal member. Specifically, as shown in Fig. 2, grease G is applied to the sliding surfaces of the seal lips 13a, 13b, and 13c that come into sliding contact with the slinger 15. In this case, it is sufficient that the grease G is applied to at least the sliding surfaces of the seal lips, and it may be applied to the entire seal lips. Note that this grease G has a different composition from the grease composition filled in the bearing space 9 (see Fig. 1).

[0036] In the present invention, the grease G (applied grease) contains a base oil, a thickener, and additives. This grease will be described below.

[0037] The above grease was subjected to a shear rate of 1000 s at 60°C. -1The inventors assumed the fluidity of the grease near the sliding surface and set the applied grease at a shear rate of 1000 s at 60°C. -1 After careful consideration, it was discovered that by using a grease with an apparent viscosity of 0.22 Pa s or more, good sealing performance could be obtained in muddy water resistance tests while maintaining low torque properties.

[0038] The apparent viscosity of the grease is preferably 0.22 Pa·s or more and 0.30 Pa·s or less, and more preferably 0.24 Pa·s or more and 0.28 Pa·s or less.

[0039] The apparent viscosity of the grease can be calculated using a rheometer. It is preferable to use a rotational rheometer having a cone-plate type cell as the rheometer. An outline of such a rheometer is shown in FIG. 4. As shown in FIG. 4, a rotational rheometer 21 is composed of a cone-plate type cell 22 and a horizontal disk plate 23. The cell 22 and the plate 23 are arranged so that they are in contact at one point (with a small gap), and a sample, grease 24, is placed between them. In this rheometer, the shear rate applied to the grease 24 is the same at any position, regardless of the distance from the center of the cell. In the present invention, the shear rate is calculated at a temperature of 60°C and a shear rate of 1000 s -1 The shear stress when it becomes constant (steady state) is measured, and the apparent viscosity of the grease is calculated using that shear stress.

[0040] To calculate the viscosity, for example, the Herschel-Bulkley equation, which is a general flow equation for non-Newtonian fluids, is used. The Herschel-Bulkley equation is expressed by the following formula.

[0041]

number

[0042] The yield stress and each constant in the above formula can be determined based on an evaluation of the rheological properties of the grease using a rheometer.

[0043] The above greases are at least 60°C and have a shear rate of 1000 s -1 The apparent viscosity of the grease in this case must be 0.22 Pa·s or more, and an appropriate combination of base oil, thickener, and additives can be used.

[0044] The base oil used in the grease may be one generally 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 fluorine oil. These oils may be used alone or in combination of two or more.

[0045] Among the above, the base oil is preferably at least one selected from synthetic hydrocarbon oils and ester oils, and more preferably the base oil is composed of only synthetic hydrocarbon oils or is a mixed oil of synthetic hydrocarbon oils and ester oils. In the case of such a mixed oil, the synthetic hydrocarbon oil preferably accounts for 60% by mass or more of the entire base oil (mixed oil), and more preferably 65% ​​by mass to 90% by mass.

[0046] PAO oil, a synthetic hydrocarbon oil, is a mixture of α-olefins or isomerized α-olefin oligomers or polymers. Specific examples of α-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-docosene, and 1-tetradocosene, and mixtures of these are usually used.

[0047] Examples of the ester oil 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 bellargonate, and pentaerythritol ester oil, carbonate ester oils, and phosphate ester oils. Among these, pentaerythritol ester oil is preferred.

[0048] The kinetic viscosity of the base oil used in the grease at 40°C (in the case of a mixed oil, the kinetic viscosity of the mixed oil, the same applies below) is set to, for example, 6 mm 2 / s~30mm 2 / s, 6mm 2 / s~20mm 2 / s is preferred, 12mm 2 / s~19mm 2 / s is more preferable, 12 mm 2 / s~16mm 2 / s may also be used.

[0049] The thickener used in the grease is not particularly limited, and any commonly used thickener 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 benton, silica gel, diurea compounds, triurea compounds, tetraurea compounds, and urea-urethane compounds can be used. Examples of metal soaps include sodium soaps, calcium soaps, and lithium soaps, and examples of complex metal soaps include complex lithium soaps. Among these, it is preferable to use diurea compounds.

[0050] The diurea compound is obtained by reacting a diisocyanate component with a monoamine component. Examples of the diisocyanate component include phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, and hexane diisocyanate. Examples of the monoamine component include aliphatic monoamines, alicyclic monoamines, and aromatic monoamines. Examples of the aliphatic monoamines include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, and oleylamine. Examples of the alicyclic monoamines include cyclohexylamine. Examples of the aromatic monoamines include aniline and p-toluidine.

[0051] Among these diurea compounds, it is preferable to use an aromatic diisocyanate as the diisocyanate component and at least one of an aliphatic monoamine and an alicyclic monoamine as the monoamine component, because it has better low torque properties. In particular, it is more preferable to use an aliphatic / alicyclic diurea compound prepared by using an aromatic diisocyanate as the diisocyanate component and an aliphatic monoamine and an alicyclic monoamine as the monoamine component as the thickener. The ratio of the aliphatic monoamine and the alicyclic monoamine used in preparing this aliphatic / alicyclic diurea compound is not particularly limited, and is, for example, aliphatic monoamine:alicyclic monoamine=(3:1) to (1:3) in molar ratio, and the molar ratio is preferably (2:1) to (1:2). The number of moles of the aliphatic monoamine may be greater than the number of moles of the alicyclic monoamine.

[0052] The base grease using a diurea compound as a thickener is prepared by reacting the above diisocyanate component with a monoamine component in a base oil.

[0053] In the above grease, the thickener is preferably contained in an amount of 10% by mass to 30% by mass, more preferably 10% by mass to 20% by mass, and even more preferably 12% by mass to 18% by mass, based on the total amount (100% by mass) of the base oil and thickener. By making the amount of thickener relatively small, the proportion of the base oil can be increased accordingly, which tends to lead to lower torque.

[0054] The additives used in the grease are not particularly limited, and known additives can be used. However, from the viewpoint of making it easier to set the viscosity characteristics within a desired range and improving sealing properties, it is preferable that the additives include an extreme pressure agent and further a rust inhibitor.

[0055] The extreme pressure agent preferably contains at least one of a sulfur-phosphorus-based extreme pressure agent and a phosphorus-based extreme pressure agent. The sulfur-phosphorus-based extreme pressure agent contains a sulfur atom and a phosphorus atom, and examples thereof include thiophosphate, thiophosphite, zinc dialkyldithiophosphate (ZnDTP), molybdenum dialkyldithiophosphate (MoDTP), and the like, with thiophosphate and thiophosphite being preferred. The phosphorus-based extreme pressure agent contains a phosphorus atom (excluding sulfur-phosphorus-based extreme pressure agents), and examples thereof include phosphoric acid esters such as trialkyl phosphate, tricresyl phosphate, and triphenyl phosphate, acidic phosphoric acid esters such as tricresyl phosphite and triphenyl phosphite, and acidic phosphoric acid esters.

[0056] The content of the extreme pressure agent is, for example, not less than 0.5 mass % and less than 3.0 mass %, and preferably not less than 0.5 mass % and less than 1.5 mass %, relative to the total amount of the grease (100 mass %).

[0057] Examples of the rust inhibitor that can be used include sulfonate-based rust inhibitors, ester-based rust inhibitors such as sorbitan fatty acid esters, carboxylic acid-based rust inhibitors such as linear fatty acids such as lauric acid and stearic acid, succinic acid, and alkylsuccinic acid, carboxylate-based rust inhibitors such as metal salts (cobalt, manganese, zinc) of fatty acids, naphthenic acid, and the like, and amine-based rust inhibitors such as alkoxyphenylamines. Among these, it is preferable to use at least a sulfonate-based rust inhibitor as the rust inhibitor.

[0058] As the sulfonate-based rust inhibitor, various metal salts and amine salts of alkyl aromatic sulfonic acids such as alkylbenzene sulfonic acid and alkylnaphthalene sulfonic acid, and petroleum-based sulfonic acids obtained by sulfonating aromatic components of petroleum distillate components can be used. Metals constituting the metal salts include alkaline earth metals such as barium, calcium, and magnesium, alkali metals such as sodium, potassium, and lithium, and zinc. Amines constituting the amine salts include ethylamine and trimethylamine. These sulfonate-based rust inhibitors may be used alone or in combination of two or more. The sulfonate-based rust inhibitor may be a neutral sulfonate salt or a basic sulfonate salt.

[0059] In particular, it is preferable to use two kinds of sulfonate-based rust inhibitors in combination as the rust inhibitor. By combining two kinds of sulfonate-based rust inhibitors, it becomes easier to set the viscosity characteristics in the desired range than when one kind is used alone, and the rust prevention can also be improved. Specifically, calcium sulfonate is combined with another metal sulfonate. In this case, the ester-based rust inhibitor may not be included. The ester-based rust inhibitor is a partial ester of a polyhydric alcohol such as sorbitan, sorbitol, pentaerythritol, sucrose, or glycerin with a carboxylic acid such as oleic acid or lauric acid, or a succinic acid half ester.

[0060] The content of the rust inhibitor (the total amount when two or more types are included) is, for example, from 0.5 mass % to less than 3.0 mass %, and preferably from 0.5 mass % to less than 1.5 mass %, based on the total amount of the grease.

[0061] The additives may also include an antioxidant. 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, and N,N'-diisopropyl-p-phenylenediamine, and phenol-based 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.

[0062] The content of the antioxidant is, for example, not less than 0.5 mass % and less than 3.0 mass %, and preferably not less than 0.5 mass % and less than 1.5 mass %, relative to the total amount of the grease.

[0063] The grease may contain known additives other than the extreme pressure agent, rust inhibitor, and antioxidant described above, but it is preferable that the grease does not contain organic zinc compounds such as ZnDTP or organic molybdenum compounds such as MoDTP.

[0064] The worked penetration (JIS K 2220) of the grease used in the present invention is, for example, in the range of 220 or more and 300 or less, preferably in the range of more than 220 and less than 260, and more preferably in the range of 230 or more and 250 or less.

[0065] A particularly preferred embodiment of the grease is one that contains a base oil, a thickener, and additives and has a shear rate of 1000 s at 60°C. -1The grease has an apparent viscosity of 0.22 Pa s or more at 40°C, contains as additives a sulfur-phosphorus-based extreme pressure agent or a phosphorus-based extreme pressure agent, calcium sulfonate, and other metal sulfonates, and does not contain an ester-based rust inhibitor, the thickener is a diurea compound obtained by reacting a diisocyanate component with a monoamine component, the monoamine component being an aliphatic monoamine and an alicyclic monoamine, the base oil is composed of only synthetic hydrocarbon oil or a mixed oil of synthetic hydrocarbon oil and ester oil, and has a kinetic viscosity of 6 mm at 40°C. 2 / s~20mm 2 / s. Furthermore, the above-mentioned numerical ranges and configurations can be further combined with this type of grease.

[0066] Next, the bearing sealing structure 16 will be described with reference to Fig. 3. The bearing sealing structure 16 is comprised of a core metal 17 formed in an annular shape and fitted into the outer member 2, and a seal member 18 integrally vulcanized and bonded to the core metal 17. The bearing sealing structure 16 corresponds to the sealing device of the present invention. The core metal 17 is formed in the same manner as the above-mentioned slinger. The seal member 18 is made of an elastic member such as nitrile rubber, and has two side lips (dust seals) 18b, 18c and a single radial lip (grease seal) 18a, with the tip edges of each being in direct sliding contact with the surface of the hub wheel 4, specifically, with a sliding surface 19 formed in an arc shape at the inboard side base of the wheel mounting flange 4b.

[0067] 3, in the bearing sealing structure 16, grease G is applied to the surface of each seal lip 18a, 18b, 18c that comes into sliding contact with the hub wheel 4, specifically, to one side of the tip of each seal lip. This ensures both sealing performance and a reduction in rotational torque.

[0068] Fig. 5 is a longitudinal sectional view of a deep groove ball bearing, which is another example of a sealed rolling bearing as a rotating part of the present invention, and Fig. 6 is a partially enlarged view thereof. In the rolling bearing 31, an inner ring 32 having an inner ring raceway surface on its outer circumferential surface and an outer ring 33 having an outer ring raceway surface on its inner circumferential surface are concentrically arranged, and a plurality of rolling elements 34 are arranged between the inner ring raceway surface and the outer ring raceway surface. The rolling elements 34 are held by a cage 35. Sealing devices 37 are attached to the openings at both axial ends of the inner and outer rings, and a grease composition 36 is sealed at least around the rolling elements 34. The inner ring 32, the outer ring 33 and the rolling elements 34 are made of an iron-based metal material, and the grease composition 36 is interposed between the raceway surface and the rolling elements 34 to lubricate them.

[0069] As shown in FIG. 6, the sealing device 37 is composed of a disk-shaped core metal 38 formed by pressing a cold-rolled steel plate or the like, and a seal member 39 integrally vulcanized and bonded to the core metal 38. The seal member 39 has a main lip 39a formed with a bifurcated tip at the end on the inner ring 32 side, and a dust lip 39b located on the outer side of the bearing space from the main lip 39a. A part of the seal member 39 is fixed to a seal groove on the inner circumference of the end of the outer ring 33, which is a fixed member, and each seal lip slides in a seal groove having a substantially U-shaped cross section formed on the outer circumference of the end of the inner ring 32, which is a rotating member. As shown in FIG. 6, in the sealing device 37, grease G is also applied to the surfaces of each seal lip 39a, 39b that slide against the inner ring 32, specifically, to one side of the tip of each seal lip. Note that this grease G has a different composition from the grease composition 36 filled in the bearing space.

[0070] In the example of Figures 5 and 6 above, a deep groove ball bearing is shown as an example of a sealed rolling bearing, but the sealing device of the present invention can also be used for other bearings such as cylindrical roller bearings, tapered roller bearings, spherical roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, and thrust spherical roller bearings.

[0071] In the sealed rolling bearings of Figures 1 to 3 and Figures 5 to 6, the grease used in the present invention is applied in advance to the sliding surface of the seal lip of the seal member, but instead of or in addition to this, the grease may be applied in advance to the surface with which the seal lip of the rotating member slides.

[0072] The sealed rolling bearing is not particularly limited in its application, but is particularly suitable for low-speed rotation applications. -1 This applies to bearings used in the following rotational speed ranges: 2000min -1 The term "used in the following rotational speed range" means that the main rotational speed (steady-state rotational speed) of the bearing in use is 2000 min-1 -1 The rotation speed is 1500 min -1 It may be less than 1000min -1 It may be the following.

[0073] Furthermore, the rotating part of the present invention is not limited to a rolling bearing, but may be any part that uses a sealing device that requires sealing performance. EXAMPLES

[0074] First, greases were prepared to have the compositions shown in Tables 1 and 2. Note that 1) to 9) below in Table 1 are the same in Table 2.

[0075] The grease used in each test example was prepared as follows. 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 specified temperature (room temperature to 60°C). Next, oil phase B was added and mixed while stirring oil phase A, and heated at 100°C for 30 minutes (urea reaction). The completion of the reaction was confirmed by IR (infrared spectroscopy) and other methods. After that, it was heated at 130°C for 1 hour (reaction stabilization) and slowly cooled to room temperature. After that, a homogenization process was performed, and the grease was smoothed using a three-roll mill.

[0076] The resulting grease was subjected to the following physical property measurements and tests.

[0077] <Worked Penetration> The 60-stroke worked penetration of the grease was measured in accordance with JIS K2220.

[0078] <Apparent viscosity of grease> Using a cone-plate type rheometer (diameter 20 mm, cone angle 1°), each grease was subjected to a temperature of 60°C and a shear rate of 1000 s -1 The measurement was carried out for 30 minutes, and the average value for the last minute was recorded as the apparent viscosity of the grease. In this test, 0.22 Pa s or more was marked with an O, and less than 0.22 Pa s was marked with an X. These are shown together in Tables 1 and 2.

[0079] <Seal torque test> Grease was applied to one side of the tip of the three seal lips of a nitrile rubber seal member (φ60-70 mm). The above seal member was attached to a member simulating the outer ring of a hub, and a slinger made of SUS430 was attached to a member simulating the inner ring of a hub, and they were assembled so that the seal lip and the slinger were in contact. Rotation speed: 600 min -1 The torque (N m) caused by the sliding contact of the seal lip was measured for 1 minute 30 minutes after the start of the test at room temperature with the inner ring rotating. Results of this test are shown in Tables 1 and 2, with less than 0.20 N m marked with an O and 0.20 N m or more marked with an X.

[0080] <Mud water resistance test> Grease was applied to one side of the tip of three seal lips of a nitrile rubber seal member (φ60~70mm). The above seal member was attached to a member simulating the outer ring of a hub, and a slinger made of SUS430 was attached to a member simulating the inner ring of a hub, and they were assembled so that the seal lip and slinger were in contact. Furthermore, a chamber was attached to the outer surface side of the slinger, and muddy water was poured in, and the assembled seal and slinger were set up so that up to the lower half was immersed in muddy water. Rotation speed: 1100 min -1The test was conducted in a room temperature environment with the inner ring rotating, with an operating pattern of 20 hours operation + 4 hours stoppage as one cycle, and the number of cycles until muddy water penetrated the inside was regarded as the lifespan. In this test, 25 cycles or more are marked with an ◯, and less than 25 cycles are marked with an ×, and the results are shown in Tables 1 and 2.

[0081] [Table 1]

[0082] [Table 2]

[0083] As shown in Table 1, the shear rate was 1000 s at 60 °C. -1 In Examples 1 to 12, in which the apparent viscosity of the grease at 60°C is 0.22 Pa s or more, both the seal torque test and the muddy water resistance test were passed. On the other hand, in Comparative Examples 1 to 12, the seal torque test was passed, but the muddy water resistance test was -1 The apparent viscosity of the grease in this test was less than 0.22 Pa·s, and the grease failed the muddy water resistance test.

[0084] As described above, at 60°C and a shear rate of 1000 s -1 Grease with an apparent viscosity of 0.22 Pa s or more has fluidity under the shear conditions, and is supplied to the contact points between the seal lip and the slinger, etc. As a result, it is believed that the sealing performance is maintained and the intrusion of muddy water is suppressed. [Industrial Applicability]

[0085] The sealing device of the present invention is capable of achieving both low torque and high sealing performance, and therefore can be widely used in rotating parts, such as sealed rolling bearings, and is preferably used for hub bearings that are prone to ingress of muddy water, etc. [Explanation of symbols]

[0086] 1 Hub bearing (rotating part) 2 Outer member 3 Inner members 4 Hub Wheel 5. Inner Circle 6 Serrations 7 Rolling elements 8 Cage 9 Bearing space 11 Bearing seal structure 12 Core wire 13 Sealing material 14 Seal ring (sealing device) 15 Slinger 16 Bearing sealing structure (sealing device) 17 Core wire 18 Sealing material 19 Sliding surface 21 Rheometer 22 Corn-plate type cell 23 Horizontal Disc Plate 24 Grease 31 Rolling bearings (rotating parts) 32 Inner Circle 33 Outer Ring 34 Rolling elements 35 Retainer 36 Grease composition 37 Sealing device 38 Core wire 39 Sealing material Grease

Claims

1. A sealing device that is fixed to a fixed member of a rotating component and in sliding contact with a rotating member, the sealing device having a seal lip that is in sliding contact with the rotating member, and grease is applied to a sliding contact surface of the seal lip, The grease contains a base oil, a thickener, and additives, and is resistant to shear at 60° C. and a shear rate of 1000 s －１ A sealing device characterized in that the apparent viscosity of the grease is 0.22 Pa·s or more.

2. 2. The sealing device according to claim 1, wherein the additive includes at least one of a sulfur-phosphorus based extreme pressure agent and a phosphorus based extreme pressure agent.

3. 3. The sealing device according to claim 1, wherein the additive includes calcium sulfonate and other metal sulfonates, and does not include an ester-based rust inhibitor.

4. 3. The sealing device according to claim 1, wherein the thickener is a diurea compound obtained by reacting a diisocyanate component with a monoamine component, and the monoamine component is an aliphatic monoamine and an alicyclic monoamine.

5. 3. The sealing device according to claim 1, wherein the base oil is made of only a synthetic hydrocarbon oil or is a mixed oil of the synthetic hydrocarbon oil and an ester oil.

6. The base oil has a kinetic viscosity of 6 mm at 40°C. ２ / s ~ 20mm ２ 3. The sealing device according to claim 1, wherein the sealing member is a gyro.

7. The additive contains a sulfur-phosphorus-based extreme pressure agent or a phosphorus-based extreme pressure agent, a calcium sulfonate, and another metal sulfonate, and does not contain an ester-based rust inhibitor; the thickener is a diurea compound obtained by reacting a diisocyanate component with a monoamine component, the monoamine component being an aliphatic monoamine and an alicyclic monoamine; The base oil is composed of only a synthetic hydrocarbon oil or is a mixed oil of the synthetic hydrocarbon oil and an ester oil, and has a kinetic viscosity of 6 mm at 40° C. ２ / s ~ 20mm ２ 2. The sealing device according to claim 1, characterized in that:

8. 3. The sealing device according to claim 1 or 2, characterized in that in the sealing device, the seal member is formed of nitrile rubber, the seal lips include, in this order from the inner side of the bearing space, a first seal lip, a second seal lip, and a third seal lip, and the grease is applied to the sliding surfaces of these seal lips.

9. A rotating part comprising at least one sealing device according to claim 1 or 2.

10. The rotating part according to claim 9, wherein the rotating part is a rolling bearing.

11. 11. The rotating part according to claim 10, wherein the rolling bearing is a bearing for rotatably supporting an axle.

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