JP2010210035A - Seal for rolling support device - Google Patents

Abstract

The present invention provides a seal for a rolling support device that has not only ozone resistance but also mechanical strength and a use temperature range necessary for a seal and has improved durability comprehensively.
A rubber composition containing at least a lip portion containing a rubber component in which a nitrile rubber and a hydrogenated nitrile rubber are mixed at a ratio (nitrile rubber: hydrogenated nitrile rubber) of 9: 1 to 4: 6 is added. A seal for a rolling support device formed of an elastic material formed by sulfur molding.
[Selection] Figure 1

Description

  The present invention relates to a seal used for a rolling support device such as a rolling bearing, a hub unit, a linear guide device, and a ball screw.

  FIG. 1 is a cross-sectional view showing an example of a rolling bearing. Between the inner ring 1 and the outer ring 2, a plurality of rolling elements (balls) 4 are arranged at substantially equal intervals in the circumferential direction by a cage 3, and further the inner ring A gap between 1 and the outer ring 2 is sealed with a seal 5. The seal 5 is formed by integrally vulcanizing and molding a metal cored bar 6 and an elastic member 7. The elastic member 7 includes a main portion 6 a outside the core metal 6, a crimping portion 7 a that is locked to a retaining groove 8 formed on the inner peripheral surface of the outer ring 2, and a receiver that is formed on the outer peripheral surface of the inner ring 1. The seal lip 7b is in contact with the groove 9.

  FIG. 2 is a cross-sectional view showing an example of a seal of a hub unit bearing of an automobile, and is composed of a cored bar 10, a slinger 11, and an elastic member 12. The metal core 10 has an outer diameter side cylindrical portion 10a that can be fitted and fixed to an inner peripheral surface of an end portion of an outer ring constituting a rolling bearing (not shown), and a diameter from an inner edge in the axial direction of the outer diameter side cylindrical portion 10a. It is formed in an annular shape with a substantially L-shaped cross section including an inner annular portion 10b bent inward in the direction. Further, the slinger 11 is bent radially outwardly from the inner diameter side cylindrical portion 11a which can be fitted and fixed to the outer peripheral surface of the outer end portion of the inner ring constituting the rolling bearing, and from the axial outer end edge of the inner diameter side cylindrical portion 11a. It is formed in an annular shape with an L-shaped cross section including an outer ring portion 11b. The elastic member 12 is made of an elastic material, and includes three seal lips 12a, 12b, and 12c on the outer side, the middle side, and the inner side. The base end portion of the core member 10 is bonded and fixed to the core bar 10 by adhesion. Then, the tip end edge of the outermost seal lip 12a located on the outermost side is brought into sliding contact with the inner surface of the outer ring portion 11b constituting the slinger 11, and the remaining two seal lips, the intermediate seal lip 12b and the inner seal lip 12c. The tip edge of this is in sliding contact with the outer peripheral surface of the inner diameter side cylindrical portion 11 a constituting the slinger 11.

  FIG. 3 is a partially cutaway plan view showing an example of a ball screw. The screw shaft 31 has a spiral thread groove 31a having a circular arc cross section on the outer peripheral surface, and is opposed to the thread groove 31a of the screw shaft 31. A cross section formed by a cylindrical ball screw nut 32 having a helical screw groove on the inner surface and screwed onto the screw shaft 31, a screw groove 31 a of the screw shaft 31, and a screw groove of the ball screw nut 32. A large number of balls (not shown) that are movably loaded in a circular spiral ball screw space. In addition, cylindrical lubricant supply members 41 and 41 made of a lubricant-containing polymer are fitted and inserted inside the both axial ends of the ball screw nut 32 while being pressed by a garter spring 33. The retained lubricant gradually exudes and lubricates. Further, seals 42, 42 made of an elastic material are mounted on the outer side in the axial direction of the lubricant supply member 41.

  The elastic material forming the above seals is appropriately mixed with additives such as nitrile rubber in order to prevent leakage of encapsulated grease and to maintain the prevention of entry of dust, water, muddy water, etc. from the outside for a long period of time. A rubber composition is used. In recent years, there is a concern that the elastic material may be deteriorated by ozone due to an increase in the ozone concentration, and an anti-aging agent is also added. However, it is difficult to say that the elastic properties and ozone resistance can be well maintained in a good balance.

  On the other hand, acrylic rubber, ethylene propylene rubber, silicone rubber, fluorine rubber, hydrogenated nitrile rubber, and the like are known as rubbers that are resistant to ozone degradation. In Patent Document 1, a mixed rubber of hydrogenated nitrile rubber and butyl rubber is used. It has been proposed. However, when grease lubrication is performed in an environment where water or dust is present, there is a problem that the mechanical strength and operating temperature range necessary for the seal cannot be obtained.

JP-A-11-286576

  The present invention has been made in view of the above problems, and in a seal for a rolling support device that is grease-lubricated in an environment where water and dust are present, in addition to ozone resistance, mechanical strength and operating temperature required for the seal The purpose is to improve durability comprehensively by adding a range.

  In order to achieve the above object, the present invention is arranged such that a first member and a second member having raceway surfaces arranged opposite to each other and a rollable surface between the raceway surfaces of the first member and the second member. A rolling support device comprising at least a plurality of rolling elements, wherein one of the first member and the second member moves relative to the other when the rolling elements roll. A seal that seals between the second member, and at least a lip portion that is in sliding contact with the first member or the second member has a ratio of nitrile rubber and hydrogenated nitrile rubber (nitrile rubber: hydrogenated nitrile rubber). A seal for a rolling support device is provided, which is formed of an elastic material obtained by vulcanizing and molding a rubber composition containing a rubber component mixed at 9: 1 to 4: 6.

  The rubber component of the seal of the present invention is a nitrile rubber and a hydrogenated nitrile rubber, and has a sealing performance equivalent or equivalent to that of a conventional nitrile rubber alone or a blend of a hydrogenated nitrile rubber and a rubber other than nitrile. In addition, ozone resistance is remarkably higher than nitrile rubber alone or a blend of hydrogenated nitrile rubber and rubber other than nitrile rubber. Nitrile rubber is a general-purpose rubber and has an advantage that it can be made inexpensive because of its high compounding ratio.

It is sectional drawing which shows an example of a rolling bearing. It is sectional drawing which shows an example of the seal | sticker used for the hub unit bearing of a motor vehicle. It is a partially notched top view which shows an example of a ball screw.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  In the present invention, there are no restrictions on the type and structure of the rolling support device and the seals used therein, and examples include rolling bearings, hub unit bearings, and seals incorporated in ball screws as shown in FIGS. can do. Further, the seal may be formed entirely of an elastic material which will be described later, or the elastic material may be bonded to the cored bar.

  The elastic material is a rubber component obtained by mixing nitrile rubber and hydrogenated nitrile rubber in a ratio (nitrile rubber: hydrogenated nitrile rubber) of 9: 1 to 4: 6, preferably 8: 2 to 6: 4. The rubber composition is obtained by vulcanization molding. If the ratio of (nitrile rubber: hydrogenated nitrile rubber) is increased, the amount of hydrogenated nitrile rubber will increase problems such as deterioration of sealing performance, deterioration of low temperature characteristics, and increase of cost. There is no improvement.

  The acrylonitrile content (AN amount) in the nitrile rubber is preferably 20 to 40%, more preferably 30 to 40%. If the amount of AN exceeds 40%, the compression set and other characteristics will be inferior, the seal lip will tend to stick, and if it is less than 20%, the wear resistance and oil resistance will become inferior. The increase in the amount and the increase in the amount of swelling due to grease etc. are not preferable because the sealing performance and followability are lowered.

  The hydrogenated nitrile rubber satisfies the above AN amount, and the double bond amount in the molecular main chain is preferably 10% or less, and more preferably 5% or less. If the amount of double bonds exceeds 10%, it is not preferable since the improvement in the resistance to osons cannot be obtained.

  The vulcanizing agent is not limited as long as it can crosslink the above rubber components, but various sulfur such as powdered sulfur, sulfur white, precipitated sulfur, highly dispersible sulfur, morpholine disulfide, alkylphenol disulfide, N, N-dithio-bis (hexahydro). -2H-azepinone-2), sulfur compounds capable of producing sulfur such as thiuram polysulfide, dicumyl peroxide, di (t-butylperoxy) diisopropylbenzene, 2,5-dimethyl-2,5-di (benzoyl) Peroxy) peroxides such as hexane and benzoyl peroxide can be used.

  When sulfur-based vulcanizing agents are used, guanidine compounds, aldehyde-ammonia compounds, thiazole compounds, thiourea compounds, sulfenamide compounds, thiuram compounds, dithiocarbamate compounds, xanthate compounds, etc. A vulcanization accelerator may be used in combination. In addition, when highly dispersible sulfur is used, tetramethylthiuram disulfide or the like or a sulfenamide-based compound such as N-cyclohexyl-2-benzothiazyl sulfenamide and 2-mercaptobenzothiazole or the like are used in combination. May be. In addition, a vulcanization accelerator may use only 1 type and may mix and use 2 or more types.

  Further, a vulcanization acceleration aid may be used in combination, and each of metal oxides such as zinc oxide, metal carbonates, metal hydroxides, organic acids such as stearic acid and derivatives thereof, amines alone, or Two or more kinds can be mixed and used.

  Various additives can be blended in the rubber composition in order to further improve the identification of the seal. For example, amine / ketone condensation products, aromatic secondary amines, monophenol derivatives, bis- or polyphenol derivatives, hydroquinone derivatives, sulfur-based anti-aging agents, phosphorus-based anti-aging agents, etc. Can be blended. Furthermore, in order to prevent thermal decomposition and improve heat resistance, a secondary anti-aging agent may be used in combination with the above-mentioned anti-aging agent, 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, and zinc thereof. You may use salt etc. together.

  Moreover, a plasticizer can be mix | blended when it is necessary to improve a moldability. For example, phthalic acid diesters such as dioctyl phthalate, adipate plasticizer, sebacate plasticizer, phosphate plasticizer, polyether plasticizer, polyester plasticizer, polyetherester plasticizer, liquid rubber, etc. Alternatively, two or more kinds can be mixed and used.

  Furthermore, carbon black, a white filler, etc. can be mix | blended as a reinforcing filler. As carbon black, SAF (Super Abrasion Furnace black), ISAF (Intermediate Super Abrasion Furnace black), HAF (High Abrasion Furnace black), MAF (Medium Abrasion Furnace black), FEF (Fast Extruding Furnace black), GPF (General Purpose Furnace black), SRF (Semi-Reinforcing Furnace black), FT (Fine Thermal Furnace black), MT (Medium Thermal Furnace black), etc. can be exemplified, but considering reinforcement and followability, HAF, FEF, SRF Is preferred. Examples of white fillers include various types of silica, basic magnesium carbonate, activated calcium carbonate, special calcium carbonate, ultrafine magnesium silicate, clay, talc, diatomaceous earth, and wollastonite. In order to improve the dispersibility of these reinforcing fillers, a silane, aluminum or titanate coupling agent may be added. Furthermore, a reinforcing filler and a white filler can be mixed and used.

  In order to seal the above rubber composition, a normal method may be used. The rubber component is blended with a vulcanizing agent and other additives and kneaded, and the resulting uncrosslinked kneaded product is mixed with a predetermined mold. It may be filled and molded. There is no restriction | limiting in the kneading | mixing method, What is necessary is just to knead | mix for about 5 to 60 minutes at 30-80 degreeC using well-known rubber kneading apparatuses, such as a rubber kneading roll, a pressure kneader, and a Banbury mixer. The molding conditions are not limited, and the kneaded product can be applied with a known rubber molding method such as compression molding, transfer molding, injection molding, etc., and is usually pressurized at 120 to 200 ° C. for about 30 seconds to 30 minutes. Vulcanization and further secondary vulcanization at 120 to 200 ° C. for about 10 minutes to 10 hours as necessary.

Since the following characteristics are usually required for a seal of a rolling support device, the amount of additives and the crosslinking conditions of the rubber composition are appropriately adjusted.
Hardness (spring hardness A scale; JIS K6301): 60-80, preferably 65-75
Tensile strength (JIS K6251): 10 to 25 MPa, preferably 15 to 25 MPa
Elongation (JIS K6251): 200 to 400%, preferably 250 to 400%

  The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

(Examples 1-4, Comparative Examples 1-3)
As shown in Table 1, a rubber component, a vulcanizing agent, and other additives are blended, and sufficiently kneaded with a rubber kneading roll, and the obtained uncrosslinked sheet-like kneaded product is obtained at 180 ° C. for 5 to 10 minutes. A crosslinked sheet was obtained through a vulcanization step by hot pressing.

Nitrile rubber: “Nipol DN3350” manufactured by Nippon Zeon Co., Ltd. (AN amount: 33%)
-Hydrogenated nitrile rubber: “Zetpol 2020” manufactured by Nippon Zeon Co., Ltd. (AN amount 36%, iodine value 28 mg / 100 mg (saturation 90%))
・ Stearic acid: “Lunac S-35” manufactured by Kao Corporation
・ Zinc flower: Sakai Chemical Co., Ltd. “France No. 1”
・ SRF carbon: "Seast SP" manufactured by Tokai Carbon Co., Ltd.
・ Calcined clay: "ST-309" (Kaolin clay) manufactured by Shiraishi Calcium Co., Ltd.
Plasticizer: “PN-350” (Adipic acid polyester) manufactured by Asahi Denka Co., Ltd.
・ Sulfur-based vulcanizing agent: “Actor R” (morpholine disulfide) manufactured by Kawaguchi Chemical Co., Ltd.
・ Vulcanization accelerator A: “Noxeller TT” (tetramethylthiuram disulfide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator B: “Noxeller TET-G” (tetraethylthiuram disulfide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator C: “Accel CZ-R” (N-cyclohexyl-2-benzothiazylsulfenamide) manufactured by Kawaguchi Chemical Co., Ltd.
・ Anti-aging agent A: “Sangite R” (selection special wax) manufactured by Seiko Chemical Co., Ltd.
Anti-aging agent B: “NOCRACK G-1” (N-phenyl-N- (3-methacryloxy-2-hydroxypropyl) -p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Anti-aging agent C: “ANTAGE RD-G” (polymer of 2,2,4-trimethyl-1,2-dihydroquinone) manufactured by Kawaguchi Chemical Co., Ltd.

  Each crosslinked sheet was subjected to (1) hardness measurement, (2) uniaxial tensile test, and (3) ozone deterioration test to evaluate mechanical properties.

(1) Hardness measurement A cross-linked sheet having a thickness of 2 mm was prepared, and a test piece having a thickness of 6 mm or more was prepared by superimposing the cross-linked sheets, and the hardness was measured with a dilometer A. The results are shown in Table 2.
(2) Uniaxial tensile test In accordance with JIS K6251, the test was performed under the conditions of a measurement temperature of 23 ° C and a tensile speed of 500 mm / min, and the strength and elongation at break were measured. The results are shown in Table 2.
(3) Ozone degradation test According to JIS K6259, the surface was observed after being left for 6 hours, 24 hours and 48 hours in an atmosphere having a static elongation of 20%, a temperature of 40 ° C., and an ozone concentration of 50 pphm or 100 pphm. “NC” indicates no crack on the surface, “A” indicates that there are few cracks, “B” indicates that there are a few cracks, and “C” indicates that there are many cracks. "1" for the case that can be confirmed with the naked eye, "2" for the case that it can be confirmed with the naked eye, "3" if the crack length is less than 1 mm, "4" if it is less than 3 mm, and "5" if it is more than 3 mm. The case where it did is evaluated on the basis of "x". For example, if the number of cracks that can be confirmed with the naked eye is slightly large, “B-2” is set. The results are shown in Tables 3 and 4.

  From Tables 2-4, it turns out that the crosslinked sheet of the Example according to this invention is equipped with the mechanical strength equivalent to or more than a nitrile rubber, and the ozone resistance is improving greatly.

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 3 Cage 4 Rolling element 5 Seal 10 Core metal 11 Slinger 12 Elastic member 31 Screw shaft 32 Ball screw nut 42 Seal

Claims (1)

A first member and a second member having raceway surfaces arranged opposite to each other; and at least a plurality of rolling elements arranged to roll between the raceway surfaces of the first member and the second member; It is a seal that blocks between the first member and the second member of a rolling support device in which one of the first member and the second member moves relative to the other when the rolling element rolls. And
At least a lip portion that is in sliding contact with the first member or the second member has a rubber component obtained by mixing nitrile rubber and hydrogenated nitrile rubber in a ratio of 9: 1 to 4: 6 (nitrile rubber: hydrogenated nitrile rubber). A seal for a rolling support device, wherein the seal is formed of an elastic material obtained by vulcanizing and molding a rubber composition.

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