Patent Application
20070242912
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:
One embodiment of the present invention will be described below with reference to the accompanying drawings.
As shown in
The materials of the component parts are described below in detail. The solidified lubricating oil 1 is a semi-solid lubricative composition obtained by mixing a lubricating oil or grease with resin powder. It is applied to both axial sides of the retainer 2 (that is, both sides of portions for spacing the rolling elements 5 at equal distances, shown at 1a and 1b in
The lubricant contained in the solidified lubricating oil used in this invention may be lubricating oil or lubricating grease. As the lubricating oil, mineral oil, synthesized hydrocarbon oil, polyalkylene glycol oil, diester oil, polyolester oil, phosphate ester oil, polyphenyl ether oil, silicone oil, perfluoropolyether oil, etc. may be used. Any known lubricating oil may be used.
The perfluoropolyether oil is a compound obtained by substituting fluorine atoms for hydrogen atoms of aliphatic hydrocarbon polyether. Commercially available ones include Fomblin Y (made by Montedison), Krytox (made by DuPont), Barrierta J oil (made by Kluber), Fomblin Z (made by Montedison), Fomblin M (made by Montedison) and Demnum (made by Daikin).
The lubricating grease may be one obtained by thickening base oil by use of a soap or non-soap thickening agent. The kinds of the base oil and thickening agent are not particularly limited. Combinations of thickening agent and base oil include lithium soap-diester grease, lithium soap-mineral oil grease, potassium soap-mineral oil grease, aluminum soap-mineral oil grease, lithium soap-diester mineral oil grease, non-soap thickening agent—diester oil grease, non-soap thickening agent—mineral oil grease, non-soap thickening agent—polyol ester oil grease, lithium soap-polyol ester oil grease, and lithium soap-silicone oil grease. Also, a grease using perfluoropolyether oil as base oil and fluorine resin particles as a thickening agent may be used.
Greases or oils obtained by adding a metallic soap or non-soap (fluorine resin particles, diurea, polyurea, etc.) thickening agent to the lubricating oils described above as a base oil to adjust the viscosity may be used after adding an extreme pressure agent or other additives.
As resin material powder used to solidify a lubricating oil to obtain the solidified lubricating oil of the present invention, thermoplastic resin powder such as ultrahigh molecular weight polyolefin resin may be used.
As the thermoplastic resin powder, powder of any known thermoplastic resin may be used. Such thermoplastic resins include ultrahigh molecular weight polyolefin powder, polyamide resin (nylon), polyacetal resin, methylmetaacryl resin, acryl-styrene copolymer resin, polystyrene, ABS resin, vinyl chloride resin, polyvinylidene fluoride, polycarbonate, fluoride resin, acetate cellulose, and celluloid.
The ultrahigh molecular weight polyolefin resin powder may be a powder of ultrahigh molecular weight polyethylene, ultrahigh molecular weight polypropylene, ultrahigh molecular weight polybutene or a copolymer thereof. The molecular weight of each powder should be 1×106 to 5×106 in terms of average molecular weight as measured by viscosity method. Polyolefines in such a molecular weight range are superior to low molecular weight polyolefines in rigidity and oil retainability and hardly flow even when heated to high temperature. Also, as for average particle size of thermoplastic resin powder, favorable results have been obtained when 10 to 30 μm powder was adopted.
The content of thermoplastic resin in the solidified lubricating oil is preferably 95 to 1 weight %, though depending on the desired oil separation, toughness, and hardness of the composition. Therefore, the higher the content of thermoplastic resin such as ultrahigh molecular weight polyolefine, the harder the gel after dispersed and retained at predetermined temperature becomes.
As the resin for thermosetting resin powder used as a material of the solidified lubricating oil used in this invention, phenol resin, urea resin, melamine resin, urethane resin, polyester resin, diarylphthalate resin, and epoxy resin may be used.
As the thermosetting resin, its not-yet-cured material powder is used and mixed with a lubricating oil or grease. The mixing ratio is not limited, but they are mixed together in the range of e.g. 5 to 95 weight %. The abovesaid thermosetting resin powder or thermoplastic resin powder is mixed with a lubricating oil or grease into a uniform paste, semi-solid state with oil not separated, and the mixture is spot-packed in the bearing, or full-packed in the entire space in the bearing. In spot packing, it is preferable to apply to at least both sides of the portions of the retainer for keeping the spaces between the rolling elements, hold them wrapped and then heat.
The contact seal 7 is an annular elastic member having a core 8 covered with fluorine rubber. It is mounted in a mounting groove 9 of the outer ring 4 with its seal lip, which is a part of the elastic member and has an inclined inner periphery, in slidal contact with the sealing contact surface of the inner ring 3.
As a fluorine rubber used for the contact seal, vulcanizable fluorine rubber containing tetrafluoroethylene-propylene 2-unit copolymer, vulcanizable fluorine rubber containing vinylidene fluoride-tetrafluoroethylene-propylene 3-unit copolymer, or vulcanizable fluorine rubber containing tetrafluoroethylene-perfluoroalkylvinylether 3-unit copolymer may be used.
As tetrafluoroethylene-propylene 2-unit copolymer, AFLAS 150 series and AFLAS 100 series of Asahi Glass Co., Ltd. are commercially available.
Vinylidene fluoride-tetrafluoroethylene-propylene 3-unit copolymer is commercially available in the name of BRE LJ-298005 made by Sumitomo 3M Limited, AFLAS SP and AFLAS MZ201 of Asahi Glass Co., Ltd.
As tetrafluoroethylene-perfluoroalkylvinylether 3-unit copolymer, Kalrez made by Du Pont can be cited.
Such fluorine polymers described above are vulcanized by use of a vulcanizing assistant such as triarylisocyanurate, and triarylcyanurate and organic peroxide such as α,α-bis-t-butylperoxy-diisopropylbenzene, 2,5-dimethyl-2,5-di-t-butylperoxy hexane, and exhibit rubber elasticity.
Also, before vulcanizing the abovesaid fluorine polymers, inorganic fillers such as carbon black, silica, silicic acid, and diatomaceous earth, metallic oxides such as zinc oxide and magnesium oxide, age resistors such as octylated diphenyl amine and N-phenyl-1-naphtyl amine or other additives may be added as necessary.
Deep-groove ball bearings (inner diameter: 10 mm, outer diameter: 26 mm, width: 8 mm) with contact seals as shown in
(Durability Test)
Load Fa=10N (preload) was applied to the deep-groove ball bearing with the contact seals while showering hydrofluoric acid against them. The rotation speed was increased from 0 to 1000 rpm in 30 seconds and then decreased to zero and stopped in another 30 seconds. Assuming that this step represents one cycle, it was repeated 500000 cycles to determine the life of the bearing.
For judgment of life, the degree of wear inside the bearing was evaluated in terms of relative widening of the radial inside gap. The bearing was judged to have ended its life when the radial inside gap widened to 10 times the initial gap. The test was continued up to 500000 cycles if necessary. The results are shown in Table 1.
In addition to the radial inside gap, the bearings were evaluated for corrosion of the inner and outer rings, corrosion of the rolling elements, sealing by the contact seals, and deterioration of grease in four grades, namely best ⊚, good ◯, passable Δ, and impassable ×. The evaluation results are shown in Table 1.
A deep-groove ball bearing with non-contact seal made of soft steel (SPCC) (inner diameter: 10 mm, outer diameter: 26 mm, width: 8 mm) was made in the following manner. The inner ring, outer ring and rolling elements were made of bearing steel (SUJ2) and the retainer was made of soft steel (SPCC), and mineral oil grease (lithium soap used as thickening agent) was sealed as a lubricant. The rolling bearing obtained was tested for durability under the same conditions as described above. The results are shown in Table 1.
A deep-groove ball bearing with contact seals made of nitrile rubber (inner diameter: 10 mm, outer diameter: 26 mm, width: 8 mm) was made in the following manner. The inner ring, outer ring and rolling elements were made of bearing steel (SUJ2) and the retainer was made of soft steel (SPCC), and mineral oil grease (lithium soap used as thickening agent) was sealed as a lubricant. The rolling bearing obtained was tested for durability under the same conditions as described above. The results are shown in Table 1.
A deep-groove ball bearing with contact seals made of fluorine rubber (inner diameter: 10 mm, outer diameter: 26 mm, width: 8 mm) made in the following manner. The inner ring, outer ring and rolling elements were made of stainless steel (SUS440C) and the retainer was made of stainless steel (SUS304), and fluorine grease (PTFE powder used as thickening agent) was sealed as a lubricant. The rolling bearing obtained was tested for durability under the same conditions as described above. The results are shown in Table 1.
A deep-groove ball bearing with contact seals made of fluorine rubber (inner diameter: 10 mm, outer diameter: 26 mm, width: 8 mm) made in the following manner. The inner ring and outer ring were made of stainless steel (SUS440C) and the rolling elements were made of a ceramic material (Si3N4) and the retainer was made of stainless steel (SUS304), and fluorine grease (PTFE powder used as thickening agent) was sealed as a lubricant. The rolling bearing obtained was tested for durability under the same conditions as described above. The results are shown in Table 1.
As clearly seen from Table 1, as for Comparative Example 1, hydrofluoric acid invaded into the bearing and the radial inside gap widened ten times or over and the evaluation was impassable in all other points.
As for Comparative Example 2, the contact seal made of nitrile rubber was corroded by hydrofluoric acid, which invaded into the bearing, so that the radial inside gap widened ten times or over.
As for Comparative Example 3, the time required for the widening of the radial inside gap up to ten times was longer in comparison with the Comparative Examples 1 and 2, but corrosion and wear of the inner ring, outer ring, races, and rolling elements were observed.
As for Comparative Example 4, corrosion and wear were observed on the races of the inner ring and the outer ring. Such wear was not observed on the rolling elements, but metal powder produced by abrasion got into the rolling surface, thus making the rolling elements impossible to turn.
On the other hand, in Example 1, little increase of the radial inside gap was observed even after 500000 cycles in the durability test and good rotation condition continued.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-110858 | Apr 2006 | JP | national |
