WO2024166524A1 - Rolling bearing elastic member and rolling bearing - Google Patents

Abstract

Provided is a rolling bearing elastic member which is a vulcanizate of a rubber composition which contains a rubber component comprising epichlorohydrin rubber and acrylic rubber, a dispersion improver, a reinforcing material, and a modified clay, wherein: the rubber component contains 50-75 wt% of the epichlorohydrin rubber and 25-50 wt% of the acrylic rubber so as to have a total for the proportions of the two rubbers in the rubber composition which equals 100 wt%; and the acrylic rubber is a rubber-like copolymer which contains a constituent unit derived from a (meth)acrylate ester, and/or a rubber-like copolymer which contains a constituent unit derived from a (meth)acrylate ester and an acrylonitrile. This rolling bearing elastic member contains an epichlorohydrin rubber as a rubber component of the rolling bearing elastic member, even when the lubricating agent is an ester oil-based lubricant which contains an ester oil as a base oil, and as a result, suppresses changes in hardness and volume caused by the lubricant, and exhibits favorable wear resistance and hardness. Further provided is a rolling bearing which has said bearing elastic member.

Description

Elastic member for rolling bearing and rolling bearing

The present invention relates to an elastic member for rolling bearings and a rolling bearing having the same, and in particular to an elastic member for rolling bearings containing epichlorohydrin rubber and a rolling bearing having the same.

Generally, rolling bearings have an inner ring, an outer ring, and rolling elements disposed between the inner and outer rings, and lubricant is sealed inside to provide lubrication to these. To prevent this lubricant from leaking out of the opening between the inner and outer rings, a member having an elastic member for sealing the opening is provided as a bearing seal. This elastic member generally comes into contact with the lubricant while sliding relative to the inner or outer ring, and is therefore required to be wear-resistant and durable against the lubricant.

In order to meet the performance requirements for such elastic members, rubber components such as nitrile rubber (NBR), acrylic rubber (ACM), ethylene acrylic rubber (AEM), fluororubber (FKM), and silicone rubber (VMQ) have traditionally been used as materials for the elastic members used in bearing seals, and these have been continuously improved according to the application of the rolling bearing and for the purpose of improving its performance.

On the other hand, epichlorohydrin rubber generally has good properties such as mechanical strength, heat resistance, low temperature resistance (cold resistance), ozone resistance, gas permeability, flame retardancy, and oil resistance, but it is known that its abrasion resistance is not necessarily sufficient. For this reason, epichlorohydrin rubber is generally used as a hose material as described in Patent Document 1, but is not actually used as a material for elastic members used to seal lubricants in rolling bearings for automobiles, for example.

Special Publication No. 60-33663

The inventors focused on the above-mentioned favorable properties of epichlorohydrin rubber and attempted to use epichlorohydrin rubber as the rubber component of elastic members for rolling bearings. However, when such elastic members for rolling bearings come into contact with ester oil-based lubricants, which are common lubricants for rolling bearings, the volume and hardness of the elastic members change significantly, and (i) the large volume change makes the seal interference unstable, and (ii) for example, the elastic member softens due to a decrease in hardness, which increases the contact area between the raceway (race) consisting of the inner and outer rings and the elastic member, which can lead to abnormal wear or a decrease in tension, and it was found that improvements were necessary to adopt epichlorohydrin rubber as the rubber component of elastic members for rolling bearings.

The object of the present invention is to provide an elastic member for rolling bearings that contains epichlorohydrin rubber as the rubber component, suppresses changes in volume and hardness due to the lubricant, and has good wear resistance and hardness, even when the lubricant is an ester oil-based lubricant that contains ester oil as the base oil, and to provide a rolling bearing having the elastic member for rolling bearings.

The present invention was developed through extensive research to solve the problems described above. As a result, it was discovered that the problems described above can be solved by using epichlorohydrin rubber and a specific acrylic rubber as the rubber components of an elastic member for a rolling bearing, mixing these in a specified ratio, and further configuring the material to contain a dispersion improver, a reinforcing material, and a modified clay. The gist of the present invention is as follows.

The first aspect of the present invention relates to an elastic member for a rolling bearing, which is a vulcanizate of a rubber composition containing a rubber component composed of epichlorohydrin rubber and acrylic rubber, a dispersion improver, a reinforcing material, and modified clay, the rubber component being 50 to 75% by weight of epichlorohydrin rubber and 25 to 50% by weight of acrylic rubber, the total ratio of both rubbers in the rubber component being 100% by weight, and the acrylic rubber being a rubber-like copolymer (ACM) containing structural units derived from a (meth)acrylic acid ester as the main component and structural units derived from a reactive group-containing monomer, and/or a rubber-like copolymer (ANM) containing structural units derived from a (meth)acrylic acid ester and acrylonitrile as the main components.

In an embodiment of the present invention, the rubber composition may contain 1.0 to 3.0 parts by weight of a dispersion improver, 25 to 35 parts by weight of a reinforcing material, and 40 to 80 parts by weight of a modified clay, per 100 parts by weight of the rubber component.

In an embodiment of the present invention, the dispersion improver may be a coupling agent.

In an embodiment of the present invention, the reinforcing material may be silica.

In an embodiment of the present invention, the modified clay may be a silane-modified clay that is a clay surface-treated with a silane coupling agent.

The second aspect of the present invention relates to a rolling bearing having an inner ring, an outer ring, rolling elements interposed between the inner ring and the outer ring, and an elastic member provided at at least one of the axial end openings of the inner ring and the outer ring for sealing a lubricant around the rolling elements, the elastic member being the aforementioned elastic member for a rolling bearing.

In addition, in the embodiments of the present invention, the configurations of the above-mentioned embodiments can be combined in any way.

According to the present invention, even if the lubricant is an ester oil-based lubricant that contains ester oil as a base oil, it is possible to provide an elastic member for a rolling bearing that contains epichlorohydrin rubber as a rubber component, suppresses changes in volume and hardness due to the lubricant, and has good wear resistance and hardness, and a rolling bearing that has the elastic member for a bearing.

1 is a cross-sectional view of a rolling bearing according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a main part of FIG. 1 . FIG. 2 is an explanatory diagram showing a method for carrying out an abrasion resistance test.

The elastic member for rolling bearings according to an embodiment of the present invention (hereinafter, sometimes simply referred to as "elastic member") is a vulcanizate of a rubber composition containing a rubber component composed of epichlorohydrin rubber and acrylic rubber, a dispersion improver, a reinforcing material, and modified clay. The rubber component is 50 to 75% by weight of epichlorohydrin rubber and 25 to 50% by weight of acrylic rubber, and the total ratio of both rubbers in the rubber component is 100% by weight. The acrylic rubber is a rubber-like copolymer (ACM) containing a structural unit derived from a (meth)acrylic acid ester as the main component and a structural unit derived from a reactive group-containing monomer, and/or a rubber-like copolymer (ANM) containing a structural unit derived from a (meth)acrylic acid ester and acrylonitrile as the main component. Here, (meth)acrylic acid ester means a general term for esters of methacrylic acid and/or acrylic acid. The main component means the component with the highest content ratio among the structural units derived from all monomers contained in ACM and ANM.

In this way, by using a rubber component with a specified blend ratio of specific acrylic rubber and epichlorohydrin rubber, even when the elastic member comes into contact with a general ester oil-based lubricant as a lubricant for rolling bearings, changes in volume and hardness are suppressed more than when epichlorohydrin rubber is used alone. Furthermore, by using a dispersion improver in combination with a reinforcing material and modified clay, the dispersibility of the reinforcing material and modified clay in the rubber component is improved. Therefore, in combination with the use of a specific rubber component, it is possible to impart good abrasion resistance and hardness to the elastic member, and to impart tensile strength at break and elongation at break applicable to bearing seals.

The rubber components contained in the rubber composition are epichlorohydrin rubber and a specific acrylic rubber. In other words, the rubber component contains both in a specified ratio, and the total ratio of both rubbers in the rubber component is 100% by weight, and the rubber component does not substantially contain any other rubber components. The content of the rubber components in the rubber composition can be appropriately determined depending on the application of the rolling bearing, and can be, for example, 35 to 75% by weight of the entire rubber composition.

Epichlorohydrin rubber may be, for example, a homopolymer of epichlorohydrin (sometimes abbreviated as CO), a copolymer of epichlorohydrin and ethylene oxide (sometimes abbreviated as ECO), a copolymer of epichlorohydrin and allyl glycidyl ether (sometimes abbreviated as GCO), or a copolymer of epichlorohydrin, ethylene oxide, and allyl glycidyl ether (sometimes abbreviated as GECO), any of which may be used. Of these, CO and ECO are preferred. As epichlorohydrin, epichlorohydrin derived from plant raw materials may be used. By using epichlorohydrin obtained from such plant-derived raw materials, epichlorohydrin rubber can be made into an environmentally friendly rubber component. From the viewpoint of environmental consideration, epichlorohydrin derived from plant raw materials is preferred, and homopolymer of epichlorohydrin derived from plant raw materials (CO) is more preferred.

The acrylic rubber is a rubber-like copolymer (ACM) whose main component is a structural unit derived from a (meth)acrylic acid ester and which contains a structural unit derived from a monomer containing a reactive group, and/or a rubber-like copolymer (ANM) whose main components are structural units derived from (meth)acrylic acid esters and acrylonitrile. In other words, it is at least one type of acrylic rubber selected from ACM and ANM.

The (meth)acrylic acid ester forming the structural unit of ACM is preferably at least one selected from (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters from the viewpoints of oil resistance, heat resistance, and cold resistance.

There are no particular limitations on the (meth)acrylic acid alkyl ester, but (meth)acrylic acid alkyl esters having an alkyl group with 1 to 12 carbon atoms are preferred, (meth)acrylic acid alkyl esters having an alkyl group with 1 to 8 carbon atoms are more preferred, and (meth)acrylic acid alkyl esters having an alkyl group with 1 to 4 carbon atoms are even more preferred. Specific examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

There are no particular limitations on the (meth)acrylic acid alkoxyalkyl ester, but (meth)acrylic acid alkoxyalkyl esters having an alkyl group with 1 to 12 carbon atoms are preferred, and (meth)acrylic acid alkoxyalkyl esters having an alkyl group with 1 to 8 carbon atoms are more preferred. Specific examples of (meth)acrylic acid alkoxyalkyl esters include methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate.

The reactive group-containing monomer forming the constituent unit of ACM is not particularly limited and can be appropriately selected depending on the application, etc., but a monomer that can crosslink with an acrylic acid ester and has at least one reactive group selected from a carboxy group, a chlorine atom, and an epoxy group is preferable. Examples of the carboxy group-containing monomer include ethylenically unsaturated carboxylic acids and ethylenically unsaturated carboxylic acid esters. Examples of the epoxy group-containing monomer include epoxy group-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate; epoxy group-containing vinyl ethers such as allyl glycidyl ether and vinyl glycidyl ether; and the like. Examples of the chlorine atom-containing monomer include unsaturated alcohol esters of chlorine atom-containing saturated carboxylic acids, chloroalkyl (meth)acrylic acid esters, chloroacyloxyalkyl (meth)acrylic acid esters, (chloroacetylcarbamoyloxy)alkyl (meth)acrylic acid esters, chlorine atom-containing unsaturated ethers, chlorine atom-containing unsaturated ketones, chloromethyl group-containing aromatic vinyl compounds, chlorine atom-containing unsaturated amides, and chloroacetyl group-containing unsaturated monomers. These reactive group-containing monomers may be used alone or in combination of two or more.

ACM can contain other monomers that are copolymerizable with these monomers. Examples of such monomers include aromatic vinyls, acrylamide monomers, and other olefin monomers. These other monomers can be used alone or in combination of two or more.

ACM may have the structural units derived from (meth)acrylic acid esters in the highest content ratio among all the structural units derived from the monomers contained in ACM, but the content ratio of the structural units derived from (meth)acrylic acid esters is preferably 50 to 99.99% by weight, more preferably 70 to 99.9% by weight, even more preferably 80 to 99.5% by weight, and particularly preferably 87 to 99% by weight. The content ratio of the structural units derived from the reactive group-containing monomer is preferably 0.01 to 20% by weight, more preferably 0.1 to 10% by weight, even more preferably 0.5 to 5% by weight, and particularly preferably 1 to 3% by weight. The content ratio of the structural units derived from other monomers is usually 0 to 30% by weight, but it is preferable that they are not included. In other words, ACM is preferably a rubber-like copolymer of (meth)acrylic acid esters and reactive group-containing monomers.

ACM can be produced according to standard methods, but commercially available products can also be used. For example, in the "Nipol" (product name) brand manufactured by Nippon Zeon Co., Ltd., examples of such products include "AR31", "AR42W", and "AR54" as polymers or copolymers of acrylic esters with epoxy groups, "AR71" and "AR72LS" as polymers or copolymers of acrylic esters with chlorine atoms (active chlorine groups), and "AR12" and "AR22" as polymers or copolymers of acrylic esters with carboxy groups.

The ANM may be a rubber-like copolymer containing as its main components structural units derived from (meth)acrylic esters and acrylonitrile. The (meth)acrylic ester may be the same as that used for ACM. The ANM may also contain reactive group-containing monomers and other monomers that are copolymerizable with these monomers. The reactive group-containing monomers and other monomers may be the same as those used for ACM. The total content ratio of the structural units derived from (meth)acrylic esters and acrylonitrile in the ANM may be the highest among all the structural units derived from all the monomers contained in the ANM, and may be 50 to 100% by weight. However, it is preferable that the total content ratio is 100% by weight, i.e., a rubber-like copolymer of (meth)acrylic esters and acrylonitrile. The ratio of the structural units derived from (meth)acrylic esters and the structural units derived from acrylonitrile may be appropriately determined depending on the application of the elastic member.

The dispersion improver is not particularly limited as long as it can improve the dispersibility of the reinforcing material and modified clay in the rubber component, and can be appropriately selected according to the type of reinforcing material and modifier. Examples of such dispersion improvers include coupling agents and surfactants. Of these, coupling agents are preferred from the viewpoint of improving dispersibility and abrasion resistance. Examples of coupling agents include silane coupling agents such as vinyl silane coupling agents, amino silane coupling agents, epoxy silane coupling agents, and mercapto silane coupling agents, zirconia coupling agents, titanate coupling agents, and aluminate coupling agents. Of these, silane coupling agents are preferred, and mercapto silane coupling agents are particularly preferred. Examples of mercapto silane coupling agents include those having 1 to 3 functional groups containing mercapto groups (-SH) or mercapto groups directly bonded to Si, and examples of functional groups containing mercapto groups include hydrocarbon groups having 1 to 6 carbon atoms substituted with mercapto groups. The hydrocarbon group may be a saturated or unsaturated hydrocarbon group, with saturated hydrocarbon groups being preferred. The structure of the hydrocarbon group may be either linear or branched, with linear being preferred. The silane coupling agent is preferably one having an alkoxy group, with alkoxy groups including methoxy and ethoxy groups being preferred, and methoxy groups being more preferred. The number of alkoxy groups may be any number from 1 to 3. The dispersion improver may be used alone or in combination of two or more.

The content of the dispersion improver in the rubber composition can be appropriately determined depending on the application of the rolling bearing, etc. From the viewpoint of dispersibility and abrasion resistance, 0.5 to 5.0 parts by weight per 100 parts by weight of the rubber component is preferable, and 1.0 to 3.0 parts by weight is more preferable.

The reinforcing material is not particularly limited as long as it can be used in combination with the modified clay to improve the abrasion resistance and hardness of the elastic member, and examples thereof include silica, calcium carbonate, barium sulfate, clay (excluding modified clay), fiber, organic reinforcing agent, organic filler, etc. As the reinforcing material, one of these may be used alone, or two or more may be used in combination. Of these specific examples, silica is particularly preferred as the reinforcing material. The silica may be silicon dioxide or a material composed of silicon dioxide, and examples thereof include wet silica, fumed silica, diatomaceous earth, and silicates such as magnesium silicate. Of these, silicon dioxide such as wet silica and fumed silica is preferred as the silica.

The content of the reinforcing material in the rubber composition can be determined appropriately depending on the application of the rolling bearing, etc. From the viewpoint of improving the hardness and abrasion resistance of the elastic member, 15 to 35 parts by weight per 100 parts by weight of the rubber component is preferable, and 25 to 35 parts by weight is more preferable.

There are no particular limitations on the modified clay, so long as it can be used in combination with a reinforcing material to improve the abrasion resistance and hardness of the elastic member. Examples of such modified clay include silane-modified clay. The silane-modified clay is preferably one obtained by surface-treating clay with a silane-based coupling agent (surface-treated product). The clay used in this treatment can be fired at, for example, 600°C. Such silane-modified clay can be commercially available, and examples include Burgess KE manufactured by Burgess.

The content of modified clay in the rubber composition can be appropriately determined depending on the application of the rolling bearing, etc. From the viewpoint of improving the hardness and abrasion resistance of the elastic member, 10 to 100 parts by weight is preferable, and 40 to 80 parts by weight is more preferable, per 100 parts by weight of the rubber component.

In addition to the above-mentioned components, other components can be blended into the rubber composition. Examples of such other components include vulcanizing agents, vulcanization accelerators, stabilizers, antioxidants, lubricants, plasticizers, softeners, colorants, processing aids, and scorch inhibitors.

Examples of vulcanizing agents include sulfur; quinoxaline-based vulcanizing agents such as 2,3-dimercaptoquinoxaline, quinoxaline-2,3-dithiocarbonate, 6-methylquinoxaline-2,3-dithiocarbonate, and 5,8-dimethylquinoxaline-2,3-dithiocarbonate; 2,4,6-trimercapto-s-triazine; thiurams such as tetramethylthiuram monosulfide (TMTS), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), and dipentamethylenethiuram tetrasulfide (DPTT); and sulfur-based vulcanizing agents such as 4,4'-dithio-dimorpholine. These may be used alone or in combination of two or more. The content of the vulcanizing agent is preferably 0.5 to 10 parts by weight per 100 parts by weight of epichlorohydrin rubber.

Examples of vulcanization accelerators include guanidine compounds, imidazole compounds, quaternary onium salts, tertiary amine compounds, tertiary phosphine compounds, and alkali metal salts of weak acids. Examples of guanidine compounds include 1,3-diphenylguanidine and 1,3-di-o-tolylguanidine. Examples of imidazole compounds include 2-methylimidazole and 2-phenylimidazole. Examples of quaternary onium salts include tetra n-butylammonium bromide and octadecyl tri n-butylammonium bromide. Examples of tertiary amine compounds include triethylenediamine and 1,8-diaza-bicyclo[5,4,0]undecene-7. Examples of tertiary phosphine compounds include triphenylphosphine and tri-p-tolylphosphine. Examples of alkali metal salts of weak acids include inorganic weak acid salts such as sodium or potassium phosphates and carbonates, and organic weak acid salts such as stearates and laurates. The content of the vulcanization accelerator is preferably 0.1 to 5 parts by weight per 100 parts by weight of the rubber component.

Stabilizers include magnesium oxide, hydrotalcites, zeolites, calcium oxide, aluminum oxide, basic silicon dioxide, magnesium hydroxide, etc. These may be used alone or in combination of two or more.

The rubber composition can be obtained by mixing the essential components described above and other components used as necessary in the desired compounding ratio and kneading them uniformly. As the kneading method, a conventionally known method can be used. For example, a method of kneading uniformly using a closed kneader such as a kneader or a Banbury mixer, or an open kneader such as a roll, etc. can be mentioned.

The elastic member according to the embodiment can be obtained as a vulcanized product (molded product) of the rubber composition in a predetermined shape by vulcanizing and molding the rubber composition obtained as described above at a predetermined temperature using a molding method such as compression molding, injection molding, transfer molding, extrusion molding, or calendar molding.

The elastic member obtained by vulcanizing the above-mentioned rubber composition contains epichlorohydrin rubber as a rubber component, but when it comes into contact with an ester oil-based lubricant commonly used as a lubricant for rolling bearings, or a lubricant containing a base oil other than ester oil, the change in volume and hardness (particularly a decrease in hardness) is suppressed, and the elastic member has good abrasion resistance and hardness. In addition, the elastic member has the tensile strength at break and elongation at break required for an elastic member for rolling bearings. Therefore, such an elastic member can be applied to various rolling bearings. For example, it is suitable for rolling bearings for automobiles, for example, for rolling bearings having an elastic member that contains a lubricant for the electrical equipment and auxiliary machinery of the automobile.

Below, an embodiment of a rolling bearing using the elastic member described above will be described with reference to the drawings. Note that, below, the axial direction of the rotating shaft is referred to as the "axial direction," and the direction of the radius of rotation is referred to as the "radial direction."

Figures 1 and 2 show a rolling bearing 1 fitted with a bearing seal 11. The rolling bearing 1 has an inner ring 2 and an outer ring 3 that rotate relative to each other via rolling elements 5, ... held by a cage 4. A lubricant 10 is sealed between the inner ring 2 and the outer ring 3. At both axial ends (left and right in the bearing width direction) of the rolling elements 5, ..., bearing seals 11, 11 that are roughly annular in front view are provided to close the annular axial end openings (annular openings) A, A between the inner ring 2 and the outer ring 3.

The lubricant may be a liquid lubricating oil or a semi-solid or solid grease, but grease is preferred. In the case of grease, the base oil is not particularly limited and can be selected appropriately depending on the application, and includes various thickeners. Any known thickener may be used, and examples of the thickener include metal soaps such as lithium soap, and urea.

The bearing seal 11 may be a single-shield type that seals only one side of the rolling bearing 1, rather than a double-shield type that seals both sides of the annular openings A, A of the rolling bearing 1 as shown in FIG. 1, depending on the location of use. In other words, the bearing seal 11 is provided in at least one of the annular openings A, A on the left and right sides in the bearing width direction between the inner ring 2 and outer ring 3 of the rolling bearing 1.

As shown in FIG. 2, the bearing seal 11 is formed by continuously covering the outer and inner peripheries of an annular metal core 12 made of steel plate or the like with the aforementioned elastic member 13, for example by vulcanization bonding, with the inner periphery end of the elastic member 13 being the seal lip 14 and the outer periphery end being the outer diameter mounting part 15. The axially inner contact lip (main lip) 14a of the seal lip 14 is pressed against the radially extending side wall surface 8 of the inner ring 2, thereby preventing leakage of the lubricant 10 filled inside the bearing 1 and preventing the intrusion of foreign matter from the outside. In addition, the axially outer non-contact lip (dust lip) 14b of the seal lip 14 faces the outer periphery of the inner ring 2 outside the circumferentially extending inner ring circumferential groove 6, also called the seal groove, formed on the outer periphery of the inner ring 2, with a small gap between them, so that the labyrinth seal effect can reduce the intrusion of foreign matter from the outside.

In the embodiment shown in FIG. 2, a constricted portion 16 is formed between the inner peripheral surface 12A of the core metal 12 of the bearing seal 11 and the seal lip 14, and when the bearing seal 11 is attached to the outer ring 3, the contact lip 14a of the seal lip 14 is pressed against the side wall surface 8 of the inner ring 2 as described above. The configuration for pressing in this way can be appropriately determined in accordance with a standard method, taking into account the balance of the lip position fluctuation due to the centrifugal force caused by the rotation of the outer ring 3, so that the centrifugal forces that the contact lip 14a and the non-contact lip 14b receive when the outer ring 3 rotates are approximately equal. By taking into account the balance in this way, the tension force of the contact lip 14a on the side wall surface 8 is reduced, widening the gap between the non-contact lip 14b and the inner ring 3 and making it easier for dust to enter, or the contact lip 14a is separated from the side wall surface 8 to create a gap, preventing the lubricant 10 from leaking and dust, water, etc. from the outside from entering. In addition, because the seal lip 14 and the constricted portion 16 are elastic members made of the cured product of the rubber composition described above, they have good hardness and abrasion resistance as well as good properties such as mechanical strength (tensile strength at break, tensile elongation at break, etc.) derived from the specified rubber components, even when various lubricants are used. This synergistic effect with the structure of the seal lip 14 ensures that good pressure contact between the contact lip 14a and the side wall surface 8 is continuously maintained, and the life of the rolling bearing can be prevented from decreasing.

As shown in FIG. 2, the bearing seal 11 has a protrusion 17 formed from the tip surface 12A of the core 12 toward the inside of the bearing, and it is preferable to provide a small gap between the protrusion 17 and the tip edge of the side wall surface 8, i.e., the edge toward the outer ring, to prevent the lubricant from flowing toward the contact lip 14a by the labyrinth effect.

As shown in Figure 2, by fitting the outer diameter mounting part 15 into the outer ring circumferential groove 7 formed on the inner surface of the outer ring 3, the bearing seal 11 is positioned and fixed to the bearing 1, and the intrusion of foreign matter from the outer diameter part of the bearing seal 11 can be prevented. Furthermore, because the outer diameter mounting part 15 is also an elastic member made of a cured product of the above-mentioned rubber composition, good adhesion can be maintained between the outer diameter mounting part 15 and the outer ring circumferential groove 7, and the intrusion of foreign matter can be effectively prevented.

In this embodiment, the elastic member described above is applied to a rolling bearing in which the contact lip 14a of the seal lip 14 is constantly pressed against the side wall surface 8 of the inner ring 2. However, the present invention is not limited to this embodiment. For example, as described in JP 2010-265968 A, when the rotation speed of the outer ring is relatively low, the elastic member functions as a contact seal to seal the rolling bearing, and when the rotation speed of the outer ring is relatively high, the elastic member that is a vulcanizate of the rubber composition described above can also be applied to an elastic member having a structure that functions as a non-contact seal even when the seal lip is separated from the inner ring, and has good hardness and good wear resistance, especially when functioning as a contact seal.

The elastic member according to an embodiment of the present invention will be described in detail below.

[Test Example 1]: Study of the composition of the rubber component (Example 1)
Epichlorohydrin rubber (Zeon Hydrin H55, CO, made by Zeon Corporation, using epichlorohydrin derived from natural products) 75.0 parts by weight, acrylic rubber (Zeon Nihon Co., Ltd., Nipol 25.0 parts by weight of AR71, ANM), 1.8 parts by weight of vulcanizing agent (Sankyo Kasei Co., Ltd., Jisnet F, 2,4,6-trimercapto-s-triazine), 0.6 parts by weight of vulcanization accelerator (Sumitomo Chemical Co., Ltd., Soxinol D-G, 1,3-diphenylguanidine), 1.0 part by weight of dispersion improver (Momentive Corp., A-189, silane coupling agent, γ-mercaptopropyltrimethoxysilane), 30.0 parts by weight of reinforcing material (Tosoh Silica Corp., Nipseal ER, silicon dioxide), and 60.0 parts by weight of modified clay (Burgess Co., Ltd., Burgess KE, silane modified clay) were mixed and kneaded with an 8-inch open roll to obtain a rubber composition. The obtained rubber composition was used and molded into a sheet through primary vulcanization (150 to 180°C, 10 to 15 minutes) and secondary vulcanization (150 to 180°C x 1 to 10 hours), to obtain a rubber sheet (rubber molded body, hereinafter referred to as "elastic member") having a thickness of 2 mm.

(Examples 2 to 3, Comparative Examples 1 and 2)
A rubber sheet (rubber molded article, hereinafter referred to as "elastic member") having a thickness of 2 mm was obtained in the same manner as in Example 1, except that the compounding ratio shown in Table 1 was used.

(evaluation)
<Tensile test>
The obtained elastic member was used to measure the tensile strength at break (strength at break) and elongation at break in accordance with JIS K 6251. The evaluation criteria were as follows.
The tensile strength at break is rated as "○" if it is 9.0 MPa or more, and "×" if it is less than 9.0 MPa. The elongation at break is rated as "○" if it is 220% or more, and "×" if it is less than 220%.

<Oil resistance test>
The obtained elastic member was used to measure the hardness (Shore A hardness) in advance according to JIS K 6253-3, and the volume was measured according to JIS K 6258. Then, it was immersed in an ester oil-based lubricant (Kyodo Yushi Co., Ltd., Multemp SRL, grease) or a silicone oil-based lubricant (Shin-Etsu Chemical Co., Ltd., G40M, grease) at 150°C for 72 hours. Thereafter, the hardness and volume were measured in the same manner, and the hardness change (ΔShore A) and volume change rate (ΔV) were measured according to the following formula to evaluate the oil resistance.
Δ Shore A = (Shore A hardness after immersion in lubricant) - (Shore A hardness before immersion in lubricant)
ΔV (%)=[(volume after immersion in lubricant/volume before immersion in lubricant)−1]×100

The evaluation criteria are as follows:
When Δ Shore A is −20 or more and 20 or less, the amount of wear can be suppressed and the material can be used practically.
When ΔV is between −5% and 20%, the amount of change in the interference of the bearing seal is small, the torque is stable, and the seal can be used practically.

The evaluation results are shown in Table 1.

[Test Example 2]: Study on the amount of dispersion improver added (Examples 4 to 7, Comparative Example 3)
A rubber sheet (rubber molded article, hereinafter referred to as "elastic member") having a thickness of 2 mm was obtained in the same manner as in Example 1, except that the compounding ratio shown in Table 2 was used.

(evaluation)
<Wear test>
A test specimen was prepared using each elastic member, and the test specimen was rotated while applying a load from above with a friction plate using an abrasion resistance tester as shown in Fig. 3, and the amount of wear (mm) of the test specimen was confirmed. The test conditions were load: 200 gf, rotation speed: 10,000 rpm, and time: 15 minutes.
The evaluation criteria are as follows, with "x" meaning that the product is not practically applicable.
○: Less than 0.10 mm △: 0.10 mm or more and 0.30 mm or less ×: More than 0.30 mm

<Dispersibility test>
Using the obtained elastic member, a JIS No. 3 dumbbell was cut out so that the length direction was the grain direction in accordance with JIS K 6251. Two faces in the range between the marked lines of the cut surface of the obtained dumbbell (both sides within a range of 20 mm between the marked lines and 2 mm in the thickness direction) were photographed with a digital microscope, and the size of the dispersed matter during the photographing was measured to confirm dispersibility.
The evaluation criteria for dispersibility are as follows, with "x" meaning that the dispersion is not practically applicable.
○: Only dispersed particles having a size of 0.029 mm or less are observed during imaging. △: One or more dispersed particles having a size of more than 0.029 mm and less than 0.049 mm are observed during imaging. ×: One or more dispersed particles having a size larger than 0.049 mm are observed during imaging.

The evaluation results are shown in Table 2.

[Test Example 3]: Examination of the amount of modified clay added (Examples 8 to 17)
A rubber sheet (rubber molded article, hereinafter referred to as "elastic member") having a thickness of 2 mm was obtained in the same manner as in Example 1, except that the compounding ratio shown in Table 3 was used.

<Wear test>
The abrasion test was carried out in the same manner as in Test Example 2 and evaluation was carried out.

<Hardness test>
The obtained elastic member was used to measure and evaluate hardness (Shore A hardness) in accordance with JIS K 6253-3. The evaluation criteria are as follows, with "x" indicating that the material is not practically applicable.
⊚: Shore A hardness is 65 or more and 75 or less; ◯: Shore A hardness is 60 or more and less than 65; Δ: Shore A hardness is more than 75 and less than 85; ×: Shore A hardness is less than 60 or more than 85

The evaluation results are shown in Table 3.

[Test Example 4]: Study on the amount of reinforcing material added (Examples 18 to 21)
A rubber sheet (rubber molded body, elastic member) having a thickness of 2 mm was obtained in the same manner as in Example 1, except that the compounding ratio shown in Table 4 was used.

<Wear test>
The abrasion test was carried out in the same manner as in Test Example 3 and evaluation was carried out.

<Hardness test>
The hardness test was carried out in the same manner as in Test Example 3 and evaluated.

The evaluation results are shown in Table 4.

Table 1 shows that when the compounding ratio of epichlorohydrin rubber and a specified acrylic rubber is specific, the material has a tensile strength and elongation at break that are applicable to bearing seals, and is applicable to bearing seals whether or not the material is an ester oil-based lubricant. Table 2 shows that the inclusion of a dispersion improver provides good dispersibility of the reinforcing material and modified clay, and provides a level of wear resistance that is practically problem-free when applied to rolling bearings. Tables 3 and 4 show that the inclusion of a reinforcing material and modified clay provides a level of wear resistance and hardness that is practically problem-free when applied to rolling bearings. Therefore, it is clear that the specified elastic member uses epichlorohydrin rubber as the rubber component, but is also applicable to rolling bearings in which a highly versatile ester oil-based lubricant is enclosed.

A Annular opening 1 Rolling bearing 2 Inner ring 3 Outer ring 4 Cage 5 Rolling element 6 Inner ring circumferential groove 7 Outer ring circumferential groove 8 Side wall surface 9 Outer peripheral surface 10 Lubricant (grease)
11 Bearing seal 12 Core metal 12A Inner peripheral surface 13 Elastic member 14 Seal lip 14a Contact lip 14b Non-contact lip (dust lip)
15: Outer diameter mounting portion 16: Narrowed portion 17: Convex portion

Claims (6)

The vulcanizate of the rubber composition includes a rubber component composed of epichlorohydrin rubber and acrylic rubber, a dispersion improver, a reinforcing material, and a modified clay,
the rubber component is 50 to 75% by weight of epichlorohydrin rubber and 25 to 50% by weight of acrylic rubber, the total ratio of both rubbers in the rubber component being 100% by weight;
The elastic member for a rolling bearing, wherein the acrylic rubber is a rubber-like copolymer (ACM) having as its main component a structural unit derived from a (meth)acrylic acid ester and including a structural unit derived from a reactive group-containing monomer, and/or a rubber-like copolymer (ANM) having as its main components a structural unit derived from a (meth)acrylic acid ester and acrylonitrile. The elastic member for rolling bearings according to claim 1, wherein the rubber composition contains 1.0 to 3.0 parts by weight of a dispersion improver, 25 to 35 parts by weight of a reinforcing material, and 40 to 80 parts by weight of a modified clay, per 100 parts by weight of the rubber component. The elastic member for a rolling bearing according to claim 1 or 2, wherein the dispersion improver is a coupling agent. The elastic member for a rolling bearing according to claim 1 or 2, wherein the reinforcing material is silica. The elastic member for a rolling bearing according to claim 1 or 2, wherein the modified clay is a silane-modified clay that has been surface-treated with a silane coupling agent. A rolling bearing comprising an inner ring, an outer ring, rolling elements interposed between the inner ring and the outer ring, and an elastic member provided at at least one of the axial end openings of the inner ring and the outer ring for sealing a lubricant around the rolling elements, the elastic member being the elastic member for a rolling bearing according to claim 1 or 2.

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