Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2002-02-21
2004-12-07
La Villa, Michael (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S627000, C428S632000, C428S687000, C428S336000, C384S206000, C384S492000, C384S564000, C384S527000, C384S023000
Reexamination Certificate
active
06828041
ABSTRACT:
TECHNICAL FIELD
This invention concerns a rolling device such as a rolling bearing, a ball screw and a linear guide and, more in particular, it relates to a rolling device suitable to use, for example, in semiconductor production apparatus, chemical fiber production machines, liquid crystal panel production apparatus, and equipments using electron beams or X-rays.
BACKGROUND ART
In rolling bearings such as ball bearings, bearing rings and rolling elements thereof are generally formed of iron and steel materials such as high carbon chromium bearing steels and case hardening steels and rolling bearings are used in various working circumstances. Accordingly, in machines that use water or sea water such as food machines or chemical fiber production machines, since rust is formed on the surfaces of bearing rings and rolling elements due to water or sea water intruding into the inside of bearings making them no more usable, rolling bearings in which bearing rings or rolling elements are formed of austenitic stainless steels such as SUS 440C are mainly used.
While such rolling bearings have good corrosion resistance to water or sea water, corrosion resistance to chemicals, for example, acidic solutions such as sulfuric acid or alkaline solutions can not be said favorable. In view of the above, rolling bearings in which bearing rings are formed of titanium alloys have often been used in machines that use chemicals, for example, acidic solutions such as sulfuric acid or alkaline solutions, for example, semiconductor production apparatus and liquid crystal panel production apparatus. However, titanium alloys lack in the surface hardness when merely applied with usual solution treatment or aging treatment and can not be used as they are as the material for the bearing ring of the rolling bearing. Accordingly, when titanium alloy is used as the material for the bearing ring of the rolling bearing, it is necessary to increase the surface hardness of the titanium alloy by some or other methods.
As a method of increasing the surface hardness of the titanium alloys, a method of increasing the surface hardness of &bgr;-titanium alloy to the surface hardness of Hv 600 or more is disclosed in Japanese Published Unexamined Patent Application No. Hei 11-22221. However, according to the method disclosed in this publication, &agr;-phase has to be precipitated in excess in the &bgr; type titanium alloy and since the &agr;-phase is poor in the corrosion resistance compared with the &bgr;-phase, the corrosion resistance is sometimes insufficient depending on the working circumstance. Further, in the method disclosed in this publication, it is necessary to apply shot peening after cold working to result in a problem of increasing the cost by the increase in the number of steps such as cold working or shot peening.
Further, in equipments used in semiconductor production steps, for example, an electron beam lithography system or a wafer inspection apparatus, laser beams have been used so far as a means for writing circuit patterns on a wafer but along with the micro-miniaturization of the circuit patterns, electron beams having shorter wavelength and higher resolution power than the laser beams have been used in recent years. In the electron beam lithography system or the wafer inspection equipment using the electron beams, the electron beams are deflected easily when disturbance is present in peripheral magnetic fields to sometimes lower the writing accuracy or inspection accuracy. Accordingly, in a case of using rolling bearings to such apparatus, it requires such a rolling bearing that does not disturb the peripheral magnetic fields by the rotation of the bearing ring and, in order to satisfy such a demand, use of non-magnetic stainless steel or beryllium copper as the material for the bearing ring of the rolling bearing has been investigated.
However, since the permeability of the non-magnetic stainless steel is about 1.04 to 1.002, when the non-magnetic stainless steel is used as the material for the bearing ring of the rolling bearing, it has a possibility of causing disturbance in the peripheral magnetic fields when the bearing ring is magnetized even slightly. On the other hand, beryllium copper has a permeability of 1.001 or less and has less possibility of causing disturbance in the peripheral magnetic fields as in the non-magnetic stainless steel. However, since a portion of elements or compounds thereof constituting beryllium copper is considered as environmental load substances, its use may sometimes suffer from restriction. Further, since it is expected that the environmental problem will be considered more important in the future, use of beryllium copper itself may possibly be limited. Further, since beryllium copper has a highest hardness of about Hv 400, it involves a problem of tending to cause early wear during use under large load.
OBJECT OF THE INVENTION
A first object of the present invention is to provide a rolling device that can be used favorably over an extended period of time even in a highly corrosive circumstance.
A second object of the present invention is to provide a rolling device suitable to use in machines that use strongly acidic solutions such as sulfuric acid or strongly alkaline solutions.
A third object of the present invention is to provide a rolling device that can be used favorably over an extended period of time also in a circumstance where non-magnetic property is required.
A fourth object of the present invention is to provide a rolling device suitable to use in equipments using electron beams or X-rays such as a wafer inspection apparatus or nuclear magnetic resonance diagnostic apparatus.
A fifth object of the present invention is to provide a rolling device that can be used favorably over an extended period of time also in a circumstance where a lubricant such as grease can not be used.
SUMMARY OF THE INVENTION
A rolling device according to this invention comprises an outer member and an inner member each having a raceway surface and rolling elements rolling on the raceway surface by rotational or linear movement of the outer member or the inner member in which the outer member and/or the inner member is constituted with at least one kind of titanium alloys of &bgr; type titanium alloys, near &bgr; type titanium alloys and &agr;+&bgr; type titanium alloys.
In a preferred embodiment of the present invention, the titanium alloy has a surface hardness of Hv 400 or more and less than Hv 600. Further, the titanium alloy has a core hardness of Hv 420 or more, preferably, Hv 450 or more and has an oxygen compound layer on the surface in which the oxygen compound layer comprises a titanium oxide containing rutile type TiO
2
and has a thickness of 20 nm or more and, preferably, 50 nm or more.
In a preferred embodiment of the present invention, the rolling element is constituted with at least one kind of materials of titanium alloys, silicon nitride, silicon carbide, zirconia series ceramics, alumina series ceramics and SIALON series ceramics.
In another preferred embodiment of the present invention, the rolling device further comprises a cage for holding the rolling elements and the cage has a heat conductivity of 20 W/(m·K) or more. Further, the cage is constituted, preferably, with one kind of materials of copper, tellurium copper, brass, aluminum bronze, phosphorus bronze, nickel silver, cupro nickel and beryllium copper.
In a further preferred embodiment of the present invention, at least one of the outer member, the inner member and the rolling elements is constituted with a titanium alloy and the titanium alloy has a &ohgr; phase with the size of the crystal particles of 1 &mgr;m or less, preferably, 800 nm or less and, further preferably, 10 nm or less.
In a further preferred embodiment of the present invention, the outer member and/or the inner member has a hard film on the raceway surface. The hard film is constituted with at least one kind of materials of TiN, TiC, TiCN, TiAlN, CrN, SiC and diamond-like carbon, and the raceway surface formed with th
Saito Tsuyoshi
Ueda Koji
Uyama Hideyuki
La Villa Michael
NSK Ltd.
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