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  Grease composition conforming to vibration and guide device employing the sameUSPTO Application #: 20070265177Title: Grease composition conforming to vibration and guide device employing the same Abstract: The present invention provides a grease composition conforming to vibration, including a lubricant base oil of a mineral oil base and/or a synthetic oil base, a thickener, and an additive for improving grease performance, in which the additive includes an organomolybdenum, a metal sulfonate, and a metal phenate. The grease composition conforming to vibration exerts excellent abrasion resistance even when it is used in a guide device driven under conditions where vibration is generated. Also provided is a guide device exerting excellent abrasion resistance, including the grease composition conforming to vibration enclosed therein. (end of abstract)
Agent: Birch Stewart Kolasch & Birch - Falls Church, VA, US Inventors: Hidekazu Michioka, Yoshio Taki, Hiroshi Niwa USPTO Applicaton #: 20070265177 - Class: 508391000 (USPTO) Related Patent Categories: Solid Anti-friction Devices, Materials Therefor, Lubricant Or Separant Compositions For Moving Solid Surfaces, And Miscellaneous Mineral Oil Compositions, Lubricants Or Separants For Moving Solid Surfaces And Miscellaneous Mineral Oil Compositions (e.g., Water Containing, Etc.), Organic Sulfur Compound, Wherein The Sulfur Is Single Bonded Directly To Oxygen (e.g., Sulfites, Etc.), The Sulfur Is Part Of An -o-s(=o)(=o)- Group (i.e., Sulfonates), Overbased Or Carbonated Sulfonates The Patent Description & Claims data below is from USPTO Patent Application 20070265177. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a grease composition used for imparting lubricity to guide devices such as a bearing, a sliding part, and a connecting part for various apparatuses. In particular, the present invention relates to a grease composition conforming to vibration, which is suitable for being used in guide devices such as a linear guide device, a curve guide device, a ball screw, and a ball spline, in which a sliding member (sliding table, nut member, or the like) is engaged movably with respect to a shaft (track rail, screw shaft, or the like) via a rolling body (ball or roller) and the shaft and the sliding member are driven under conditions where vibration is generated, and to a guide device employing the grease composition. BACKGROUND ART [0002] The motion of guide devices in which a slide member is engaged movably with respect to a shaft via a rolling body while a load is applied is based on a rolling motion. Therefore, the guide devices have an advantage of low slide resistance, and thus have been used for various applications such as machine tools, conveying equipment, semiconductor equipment, and medical devices. [0003] In the guide devices, it is required to: reduce the slide resistance between a shaft and a sliding member; suppress the abrasion of a rolling body itself, abrasion of rolling surfaces of a track rail where the rolling body rolls, shaft side of a screw shaft or the like, and the like, and abrasion of load rolling surface of a sliding member side of a sliding table, a nut member, or the like; and maintain a highly precise motion between a shaft and a sliding member for a long period of time. Thus, the surface of the rolling body, the rolling surface of the shaft side, and the load rolling surface of the slide member side are required to be provided with appropriate lubricity depending on use conditions thereof. [0004] Accordingly, many lubricating methods have conventionally been adopted, and various grease compositions have been proposed as representatives used for achieving the purpose. [0005] For example, JP-A-10-169,657 proposes a rolling apparatus having improved fretting resistance performance in a swivel motion of a fine stroke, which is used in wire bonding apparatus, a machine tool, or the like, and which has enclosed with a grease composition obtained by adding a grease containing as a thickener 5 to 25 wt % of urea compound, and as a base oil 55 to 94 wt % of at least one member selected from the group consisting of an ester oil, a mineral oil, and a synthetic hydrocarbon oil having a kinematic viscosity at 40.degree. C. of 20 to 300 mm2/s with 0.5 to 10 wt % of an organomolybdenum and 0.5 to 10 wt % of calcium sulfonate and/or barium sulfonate. [0006] In addition, JP-A-2002-053,884 describes that a grease composition containing (a) a base oil, (b) a diurea-based thickener having a specific structural formula, (c) at least one metal salt compound selected from the group consisting of a basic metal sulfonate, a basic metal salicylate, and a basic metal phenate, and (d) an alkenyl succinic acid anhydride is excellent in pressure-feed ability, and in shear stability and anticorrosive properties when the composition contains water, and thus is preferable for applications of being used in bearings of continuous casting appliances in ironworks, bearings of rollers, and the like. [0007] Further, JP-A-2002-053,889 proposes a grease composition in which a grease composition containing 0.05 to 30 wt % of sodium thiosulfate is blended with 0.1 to 5 wt % of at least one additive selected from the group consisting of calcium salicylate, magnesium salicylate, calcium phenate, and calcium sulfonate. The grease composition is excellent in anticorrosive property and abrasion resistance, and thus is particularly preferably used in bearings, gears, and the like of iron and steel appliances, food manufacturing machines, and the like which are used under conditions where they are brought into contact with large amounts of water. [0008] In addition, JP-A-2003-147,378 proposes a grease composition including: as a base oil a synthetic ester oil; a Li soap-based thickener; and calcium sulfonate, in which the calcium sulfonate contains calcium in a content of 0.2 to 20 wt % and is included in a ratio of 0.5 to 10 parts by weight with respect to 100 parts by weight of the base oil and the thickener in total, whereby acoustic performance and fretting resistance of a roller bearing are improved. [0009] Further, JP-A-2004-518,014 proposes a grease composition obtained by adding a grease composition including a base oil and a thickener with 0.05 to 30 wt % of sodium thiosulfate and 0.1 wt % of at least one additive selected from the group consisting of calcium salicylate, magnesium salicylate, calcium phenate, and calcium sulfonate. The grease composition is excellent in extreme-pressure property, anticorrosive property, and abrasion resistance, and thus is preferably used in bearings and gears which are used in various industrial machinery. [0010] JP-A-2004-043,781 proposes, though it does not relate to a grease composition, a lubricant oil composition including: an oil-soluble oxymolybdenum complex obtained by reacting an acidic molybdenum compound with a specific basic nitrogen compound under the presence of a polarity accelerator (polar promotor); and a specific molybdenum dithiocarbamate. The lubricant oil composition has improved abrasion reduction performance, and thus is useful as engine oils or the like to be used in automobile production and the like. [0011] In recent years, in fields of machine tools such as machining centers, NC lathes, and drill centers, mounting apparatuses such as chip mounters and bonders, and the like, demands for improvement in production efficiency, processing/mounting at high tact, and the like have been additionally increasing. For example, ball screws, linear motors, and the like having large leads have been used for a reciprocal motion, and conditions of a speed of 90 m/min or more and an acceleration speed of 1 G or more or, sometimes, a speed of 200 m/min or more and an acceleration speed of 4 G or more are demanded instead of the conventional conditions of a speed of up to about 60 m/min and an acceleration speed of up to about 1 G. [0012] The guide devices may be used under conditions of high speeds and high acceleration speeds that the guide devices have never experienced. For example, a guide device for a withdrawal robot used in a field of an injection molding apparatus and the like (for example, LM guide device) is used at a high speed and a high acceleration speed such as a maximum speed of 480 m/min and a maximum acceleration speed of 10 G. In addition, in a conveying apparatus driven by a linear motor/belt which is used in a field of production equipment or the like, the guide device is used at a high speed and a high acceleration speed such as a maximum speed to 240 to 300 m/min and a maximum acceleration speed of 6 G. [0013] According to the investigation of the inventors of the present invention, when a guide device is used under such conditions of high speeds (120 m/min or more) and high acceleration speeds (2 G or more), there arise new types of problems in abrasion which have never been observed. [0014] That is, in a guide device in which a sliding member is moved relatively to a shaft via a rolling body, when fine slip repetitively occurs, for example, between the two surfaces being brought into contact with each other (between a rolling surface of the shaft and the rolling body, and between a rolling surface of the sliding member and the rolling body) during transfer, the absence of an oil membrane occurs between the two surfaces being brought into contact with each other, that is, a surface of a rolling body, or a rolling surface of the shaft or the sliding member (hereinafter, sometimes referred to as "lubricant surface") which require to have lubricant performance. Accordingly, the lubricant surfaces have insufficient lubricity and abnormal abrasion is generated, or, in other words, a quasi-fretting phenomenon is observed. [0015] In a conventional fretting phenomenon, it is thought that the absence of the oil membrane occurs on a lubricant surface when the relative movement between a shaft and a sliding member is absent, or if present, the movement is extremely slow, whereby abrasion and corrosion are generated. Heretofore, it has been thought that when a sliding member is moved relatively to a shaft via a rolling body, a lubricant surface thereof is supplied with a lubricant agent such as a lubricant oil or a grease from surrounding environment to form an oil membrane on the lubricant surface. Thus, it has been thought that the oil membrane is never absent and abrasion due to the fretting phenomenon does not occur. [0016] The inventors of the present invention have investigated in detail on abrasion generated when a linear guide device is subjected to a reciprocal motion under conditions of a high speed and a high acceleration speed of 90 m/min or more and 1 G or more. As a result, surprisingly, abrasion which had not been observed under the conventional conditions (speed of 60 m/min or less and acceleration speed of 1 G or less) and which was similar to that shown in the fretting phenomenon was observed not only in a stroke end, but in acceleration/deceleration regions and constant region. [0017] In addition, the inventors of the present invention have investigated in further detail on the abrasion under the conditions of the high speed and the high acceleration speed. As a result, it was found that fine vibration was generated in a stroke end or acceleration/deceleration regions in the reciprocate motion, in particular, in a stroke end, and the fine vibration has amplitudes of 5 to 20 .mu.m under the conditions of a high speed and an acceleration speed of 90 m/min or more and 1 G or more, which was larger than the amplitudes obtained under the conventional conditions (speed of 60 m/min or less and acceleration speed of 1 G or less), that was, about 5 .mu.m. The strong fine vibration causes the abrasion similar to that shown in the fretting phenomenon to be generated in the stroke end, and gradually spreads from the acceleration/deceleration regions to the constant region. In addition, it was found that abrasion powder generated by the abrasion in the stroke end was dispersed from the acceleration/deceleration regions to the constant region to promote the abrasion in the acceleration/deceleration region and the constant region. [0018] Further, it was confirmed that when vibration having amplitudes of 10 .mu.m or more is generated, even under the conventional conditions (speed of 60 m/min or less and acceleration speed of 1 G or less), the abrasion powder generated by abrasion in the stroke end disperses from the acceleration/deceleration regions to the constant region to promote abrasion in the acceleration/deceleration regions and the constant region. [0019] Patent Document 1: JP-A-10-169,657 [0020] Patent Document 2: JP-A-2002-053,884 [0021] Patent Document 3: JP-A-2002-053,889 [0022] Patent Document 4: JP-A-2003-147,378 Continue reading... 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