JP2006200592A - Rolling bearing for machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing for a machine tool superior in reliability and durability, maintaining superior sealability in low torque over a long period, with reduced deterioration in a seal member, even if the rolling bearing is used in an environment contacting with cutting-grinding oil. <P>SOLUTION: This rolling bearing for the machine tool is used for the machine tool for cutting or grinding a workpiece under the existence of a cutting oil agent or a grinding oil agent. The rolling bearing is provided with an inner race, an outer race, a plurality of rolling bodies interposed between these inner race and outer race, and the seal member 6 for covering both end opening parts in the shaft direction of the inner race and the outer race. The seal member 6 is formed of a rubber molding contacting with at least the cutting oil agent or the grinding oil agent. The rubber molding is a vulcanizable fluororubber composition composed of a copolymer including tetrafluoroethylene, propylene, and a cross-linking monomer composed of unsaturated hydrocarbon having the carbon number of 2 to 4 with a part of a hydrogen atom substituted with a fluorine atom. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing for machine tools, and more particularly to a rolling bearing for machine tools used as a spindle or ball screw support bearing with which cutting oil or grinding oil comes into contact.

  Conventionally, in the cutting process and grinding process of work material, which is an important process when processing a metal material to manufacture a machine product, maintenance of lubricity between the tool and the work material to be cut, Cutting fluids and grinding fluids (hereinafter abbreviated as “cut grinding fluid”) are used for the purpose of cooling and cleaning of generated chips. In the past, water-insoluble cutting oils were often used as cutting oils. However, they are flammable due to frictional heat between the material to be cut and the tool rotating at high speed, and water-insoluble cutting oils are discarded. Since grinding oil has a large environmental load, in recent years, the number of cases using water-soluble cutting grinding oil has increased. Water-soluble cutting oils are prone to rot when the pH is 8 or less, so that a large amount of an amine compound such as alkanolamine is blended in order to keep the pH from being 8 or less and to suppress rot. These cutting oils come into contact with main spindles for machine tools and support bearings for ball screws. Further, the bearing is provided with a seal for preventing dust from entering from the outside and preventing leakage of the lubricating grease enclosed in the bearing. When general acrylic nitrile rubber or acrylic rubber is used as the bearing seal material, the rubber material has poor alkali resistance, so it is dissolved by the alkali component in the water-soluble cutting grinding fluid, or the strength is significantly reduced and damaged. , Durability may not be ensured. On the other hand, a fluororubber composition is an example of rubber having excellent chemical resistance. Conventionally used fluororubber compositions include binary copolymers of vinylidene fluoride and hexafluoropropylene (VDF-HFP), and terpolymers of which tetrafluoroethylene is added (VDF-HFP-). TFE) So-called FKM is common. However, even with these fluororubber compositions, when the concentration of the alkanolamine compound in the cutting grinding fluid is high, there is a problem that strength is lowered and sufficient durability cannot be obtained.

  Therefore, a vulcanizable fluororubber composition containing vinylidene fluoride-tetrafluoroethylene-propylene terpolymer or tetrafluoroethylene-propylene 2 as an elastic material used for a seal unit of a machine tool bearing. A method for suppressing deformation of a seal by employing a vulcanizable fluororubber composition containing an original copolymer is known (Patent Document 1).

However, even if the above-mentioned fluororubber composition is used, it may still deteriorate with time due to contact with the cutting grinding oil, and the sealing performance may be lowered.
JP 2002-310171 A

  The problem to be solved is that even if a rolling bearing is used in an environment where it is in contact with the cutting grinding oil, the deterioration of the seal member is small, a good seal performance is maintained at a low torque for a long time, and reliability and durability are excellent. There is no rolling bearing for machine tools.

A rolling bearing for a machine tool according to the present invention is a rolling bearing for a machine tool used in a machine tool that cuts or grinds a workpiece material in the presence of a cutting fluid or a grinding fluid, and the rolling bearing includes an inner ring and an outer ring. And a plurality of rolling elements interposed between the inner ring and the outer ring, and a seal member that covers both axial openings of the inner ring and the outer ring, and the seal member is a rubber molding that contacts at least the cutting fluid or the grinding fluid. The rubber molded body contains tetrafluoroethylene, propylene, and a crosslinking monomer composed of an unsaturated hydrocarbon having 2 to 4 carbon atoms in which some of the hydrogen atoms are substituted with fluorine atoms. It is a molded product of a vulcanizable fluororubber composition made of a copolymer.
The crosslinking monomer is trifluoroethylene, 3,3,3-trifluoropropene-1, 1,2,3,3,3-pentafluoropropene, 1,1,3,3,3-pentafluoropropylene And at least one monomer selected from 2,3,3,3-tetrafluoropropene.
The molded product of the fluororubber composition has a rubber hardness of 60 to 90 °. The rubber hardness (degree) is a value measured according to JIS K 6253.
The copolymer includes vinylidene fluoride.
The rolling bearing for a machine tool is a main shaft bearing or a ball screw support bearing.

  The rolling bearing for machine tool of the present invention includes tetrafluoroethylene, propylene, and a crosslinking monomer composed of an unsaturated hydrocarbon having 2 to 4 carbon atoms in which a part of hydrogen atoms are substituted with fluorine atoms. Since the seal member is formed of a vulcanizable fluoro rubber composition formed of a copolymer, there is little deformation or deterioration of physical properties even when immersed in a cutting grinding oil containing an alkali component. Can be effectively prevented. For this reason, the durability of the spindle of the machine tool or the ball screw support bearing can be improved.

  About normal rolling bearings for machine tools, the seal member made of fluoro rubber composition is deformed by deterioration due to contact with water-soluble cutting oil and the sealing performance is lowered. We studied diligently. As a result, a vulcanization comprising a copolymer comprising tetrafluoroethylene, propylene, and a crosslinking monomer comprising an unsaturated hydrocarbon having 2 to 4 carbon atoms in which some of the hydrogen atoms are substituted with fluorine atoms. A seal member manufactured from a molded product of a possible fluororubber composition (hereinafter abbreviated as a fluororubber molded product) has little deterioration in physical properties even when it comes into contact with a water-soluble cutting oil, and intrusion of dust from the outside. It was found that can be effectively prevented. This is presumably because the improved fluororubber molded product exhibited resistance to alkali components such as amine compounds such as alkanolamine added to the water-soluble cutting oil. The present invention is based on such knowledge.

The fluororubber composition that can be used in the present invention comprises tetrafluoroethylene, propylene, and a crosslinking monomer comprising an unsaturated hydrocarbon having 2 to 4 carbon atoms in which some of the hydrogen atoms are substituted with fluorine atoms. And a vulcanizable fluororubber composition comprising a copolymer.
Examples of the crosslinking monomer composed of an unsaturated hydrocarbon having 2 to 4 carbon atoms in which a part of hydrogen atoms are substituted with fluorine atoms include trifluoroethylene, 3, 3, 3-trifluoropropene-1, 1, 2, 3, 3, 3-pentafluoropropene, 1, 1, 3, 3, 3-pentafluoropropylene, 2, 3, 3, 3-tetrafluoropropene are mentioned. A preferred crosslinking monomer is 3,3,3-trifluoropropene-1.

  As a fourth component in the copolymer that can be used in the present invention, vinylidene fluoride, chlorotrifluoroethylene, perfluoro (alkyl vinyl) ether, perfluoro (alkoxy vinyl) ether, perfluoro (alkoxyalkyl vinyl) ether, perfluoroalkyl alkenyl ether, A perfluoroalkoxy alkenyl ether etc. can be mix | blended.

The copolymer constituting the fluororubber composition is 45 to 80% by weight, preferably 50 to 78% by weight, more preferably 65 to 78% by weight of tetrafluoroethylene, based on the whole copolymer. Is 10 to 40% by weight, preferably 12 to 30% by weight, more preferably 15 to 25% by weight, and the crosslinking monomer is 0.1 to 15% by weight, preferably 2 to 10% by weight, more preferably 3%. ~ 6% by weight.
When vinylidene fluoride is copolymerized, the vinylidene fluoride is 2 to 20% by weight, preferably 10 to 20% by weight. If it exceeds 20% by weight, the resistance to urea compounds decreases.

A method for producing this fluororubber composition is disclosed in, for example, International Publication No. WO02 / 092683, and is produced by an emulsion polymerization method or a suspension polymerization method.
In order to vulcanize these fluororubber compositions, a vulcanization accelerator selected from polyhydroxy (polyol) vulcanizing agents, quaternary ammonium salts, fourth phosphonium salts, third sulfonium salts, calcium hydroxide, Acid acceptors such as magnesium oxide, fillers such as carbon black, clay, barium sulfate, calcium carbonate and magnesium silicate, processing aids such as octadecylamine and wax, heat aging inhibitors, pigments and the like can be blended. For example, each blending amount is 0.1 to 20 parts by weight, preferably 0.5 to 3 parts by weight of the vulcanizing agent, and 0.1 to 20 parts by weight of the vulcanization accelerator, preferably 0.5 to 100 parts by weight of the copolymer. 3 parts by weight, acid acceptor 1-30 parts by weight, preferably 1-7 parts by weight, filler 5-100 parts by weight, and processing aid 0.1-20 parts by weight.

In addition to these, a second vulcanizing agent such as an organic peroxide compound may be added in an amount of 0.7 to 7 parts by weight, preferably 1 to 3 parts by weight. Furthermore, fillers and additives that can be blended in general rubber compositions can be used as appropriate within a range that does not impair the resistance to urea compounds and the sealing properties.
As a method for mixing or molding these compositions, a process used for general rubber processing can be adopted. After kneading with an open roll, a Banbury mixer, a kneader, various sealed mixers, etc., press molding (press vulcanization) ), Extrusion molding, injection molding, etc. In order to improve the characteristics, it is preferable to perform secondary vulcanization after molding, and this is performed by sufficiently heating in an oven (for example, 200 ° C. for 24 hours).

  The rubber hardness of the molded body of the fluororubber composition that can be used in the present invention is 60 to 90 °. Preferably it is 70-80 degrees. If it is less than 60 °, it becomes too soft and wear resistance decreases, and if it exceeds 90 °, the rotational torque becomes too large and the temperature of the rolling bearing rises. The rubber hardness (degree) was measured according to JIS K 6253.

  The working environment in which the rolling bearing for machine tool of the present invention can be used is an environment in which the rolling bearing for machine tool is in constant or non-stationary contact with a cutting grinding oil containing at least one alkaline substance selected from alkaline gas, alkaline solution and alkaline solid. . The rolling bearing for machine tools of the present invention is used in chemical plant equipment such as a polymer material manufacturing plant and a liquid crystal film manufacturing plant in addition to the use of a machine tool, and is also suitably used for a rolling bearing in contact with an alkaline substance. it can.

An example of a rolling bearing for machine tools of the present invention is shown in FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing.
In the deep groove ball bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a. A plurality of rolling elements 4 are arranged between the two. Sealers 6 that are fixed to the cage 5, the outer ring 3, and the like that hold the plurality of rolling elements 4 are provided in the axially opposite end openings 8a, 8b of the inner ring 2 and the outer ring 3, respectively. Grease 7 is sealed at least around the rolling element 4. In addition to deep groove ball bearings, angular ball bearings are often used as bearings for machine tools.

The seal member 6 may be a rubber molded body alone or a composite of a rubber molded body and a metal plate, a plastic plate, a ceramic plate, or the like. From the viewpoint of durability and ease of fixing, a composite of a rubber molded body and a metal plate is preferable.
An example of the sealing member 6 made of a composite of a rubber molded body and a metal plate is shown in FIG. The seal member 6 is obtained by fixing a fluororubber molded body 6b to a metal plate 6a such as a steel plate. As the fixing method, either mechanical fixing or chemical fixing may be used. As a preferable fixing method, there can be mentioned a method in which a metal plate is placed in a vulcanizing mold, and molding and vulcanization are performed and fixed at the time of vulcanization of a fluororubber molded article.

The seal member 6 can be mounted by (1) fixing one end 6c of the seal member 6 to the outer ring 3, and forming the labyrinth gap along the V groove on the seal surface of the inner ring 2 at the other end 6d. One end 6c of the member 6 is fixed to the outer ring 3, and the other end 6d is brought into contact with the V groove side surface of the seal surface of the inner ring 2. (3) One end 6c of the seal member 6 is fixed to the outer ring 3, and the other end 6d is the inner ring. 2 is contacted with the side surface of the V-groove of the sealing surface, but a low-torque structure is provided by providing a suction-preventing slit or the like in the contacting lip portion.
In any of the above mounting methods, the surrounding alkaline solution comes into contact with the rubber molded body 6 b constituting the seal member 6. The rubber molded body 6b is formed of the above-described fluororubber molded body at least at a portion in contact with the alkaline solution. For example, the rubber molded body 6b may be a single fluororubber molded body as described above, or a laminated body in which a conventional rubber molded body is laminated on the back surface of the above-described fluororubber molded body at a portion in contact with an alkaline solution.

The rubber compositions used in the respective sealing material examples, examples and comparative examples are shown below.
An unvulcanized rubber composition was obtained by kneading with the composition shown in Table 1 using an open roll at a roll temperature of 50 ° C. Each material used in Table 1 is shown below.
(1) Fluoro rubber composition 1: manufactured by DuPont Dow Elastomer Co., Ltd .; VTR8802 (containing vulcanizing agent)
(2) Fluororubber composition 2: manufactured by DuPont Dow Elastomer; A32J
(3) Magnesium oxide: manufactured by Kyowa Chemical Industry Co., Ltd .;
(4) Calcium hydroxide: manufactured by Omi Chemical Co., Ltd .; Calbit (5) Carbon: manufactured by Engineered Company; N990

実施例１は、長時間の浸漬でも劣化が軽微であり、切研削油剤に対して優れた耐性を有していた。
比較例１は、切研削油剤に浸漬された場合の硬度、機械的強度の低下および体積の膨潤が著しい。 Example 1 and Comparative Example 1
Using the unvulcanized rubber composition, a vulcanized molded product was obtained with a vulcanizing press. Primary vulcanization was performed for 12 minutes while maintaining the actual mold temperature at 170 ° C. Next, the vulcanized molded product was transferred into a thermostat and subjected to secondary vulcanization at 200 ° C. for 24 hours.
The obtained vulcanized molded product was punched into the shape of a JIS K 6251 No. 3 test piece to prepare a test piece. A test piece is immersed in a solution obtained by diluting a water-soluble cutting fluid containing 15 to 25% of triethanolamine (manufactured by Yushiro Chemical Industry Co., Ltd .: Yushiroken FGS798K) 30 times with pure water under conditions of 80 ° C. × 168 hours. The physical property values before and after were measured. The measured physical property values are hardness, tensile strength, tensile elongation, and volume, and the hardness change, the tensile strength change rate, the tensile elongation change rate, and the volume change rate after immersion with respect to the physical property values before immersion were evaluated. The measurement conditions were the same as JIS K 6253 for hardness, JIS K 6251 for tensile strength and tensile elongation, and JIS K 6258 for the volume before and after immersion. The results are shown in Table 2.

In Example 1, the deterioration was slight even when immersed for a long time, and it had excellent resistance to the cutting oil.
In Comparative Example 1, the hardness, the mechanical strength decrease, and the volume swelling are remarkable when immersed in a cutting oil.

  Since the rolling bearing for machine tools of the present invention has excellent resistance to cutting oil and alkaline solution, it is necessary to use cutting oil and alkaline in manufacturing equipment such as machine manufacturing factories, polymer material manufacturing plants, and liquid crystal film manufacturing plants. It can be suitably used for rolling bearings used in machine tools and liquid feed pumps that come into contact with the solution.

It is sectional drawing of the rolling bearing for machine tools. It is sectional drawing of the rolling bearing seal member for machine tools.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease

Claims (5)

  A rolling bearing for a machine tool used in a machine tool that cuts or grinds a work material in the presence of a cutting fluid or a grinding fluid, the rolling bearing comprising an inner ring and an outer ring, and a plurality of rollers interposed between the inner ring and the outer ring. A rolling member, and a seal member that covers both ends of the inner ring and the outer ring in the axial direction. The seal member is a rubber molded body at least in contact with the cutting fluid or the grinding fluid, and the rubber molded body Is a vulcanizable copolymer comprising tetrafluoroethylene, propylene, and a crosslinking monomer comprising an unsaturated hydrocarbon having 2 to 4 carbon atoms in which some of the hydrogen atoms are substituted with fluorine atoms A rolling bearing for machine tools, characterized by being a molded body of a fluororubber composition.   The crosslinking monomer is trifluoroethylene, 3,3,3-trifluoropropene-1, 1,2,3,3,3-pentafluoropropene, 1,1,3,3,3-pentafluoropropylene The rolling bearing for machine tools according to claim 1, wherein the rolling bearing is at least one monomer selected from 2,3,3,3-tetrafluoropropene.   The rolling bearing for machine tools according to claim 1 or 2, wherein the copolymer contains vinylidene fluoride.   4. The rolling bearing for machine tools according to claim 1, wherein the rubber hardness of the molded body of the fluororubber composition is 60 to 90 [deg.].   The rolling bearing for a machine tool according to any one of claims 1 to 4, wherein the rolling bearing for a machine tool is a main shaft bearing or a ball screw support bearing.

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