JP2005201327A - Rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling device with a long life in which the rolling body is hardly damaged even though it is used under the corrosive environment where a metal material can not be used and under the high load environment where a great load acts. <P>SOLUTION: An inner ring 1, an outer ring 2, and a ball 3 of a deep groove ball bearing are made of alumina made by pressure sintering. Further, the crushing load of the ball 3 is Wc or more shown by the following equation. Wc=0.05×Da<SP>1.93</SP>, wherein the unit of the Wc is kN, Da is the diameter of the ball, and the unit of the same is mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to rolling devices such as rolling bearings, linear guide devices, and ball screws.

  In a corrosive environment in which a metal material cannot be used (for example, in an environment in contact with water or a liquid having strong corrosive properties), a rolling bearing in which inner rings, outer rings, and rolling elements are made of ceramics is used. As ceramics, silicon nitride, silicon carbide, zirconia, alumina, and the like are common, but silicon carbide is often used for applications that require particularly high corrosion resistance.

For example, Patent Document 1 discloses a rolling bearing in which an inner ring, an outer ring, and a rolling element are made of silicon carbide, and a cage in which at least the surface is made of a fluororesin is incorporated.
Japanese Patent Laid-Open No. 10-82426

However, in general, brittle materials such as ceramics have many fine defects introduced in the manufacturing process, so that the fracture toughness value tends to be low and cracks tend to propagate.
Furthermore, since the size of glass substrates and the like has been increasing in recent years, rolling devices used in these production facilities are required to operate under larger loads and moments. In a rolling device with such a large load (load or moment), if the strength of the rolling element on which the load stress repeatedly acts is insufficient, there is a risk of cracking or dropping off on the surface of the rolling element or in the vicinity of the surface. Yes, the rolling element may break down.

Therefore, a rolling bearing in which the rolling member is made of silicon carbide, such as the rolling bearing described in Patent Document 1, causes damage to the rolling element when used in a high load environment where a large load acts. There was a risk that the service life would be insufficient.
Ceramics are generally roughly classified into acidic compounds, basic compounds, and amphoteric compounds having intermediate properties. Although acidic compounds are not attacked by acidic substances, their corrosion resistance to alkaline substances is inferior to basic compounds. Conversely, basic compounds exhibit excellent corrosion resistance to alkaline substances, but are easily attacked by acidic substances.

  Silicon carbide is a highly acidic compound, and exhibits extremely good corrosion resistance against acidic substances, but does not exhibit very strong corrosion resistance against alkaline substances. In particular, in rolling elements, the superiority or inferiority of the corrosion resistance to the usage atmosphere of the constituent materials significantly affects the wear and delamination, which is harmful to bearing characteristics such as abnormal wear, surface delamination, and particle dropout. May occur. Therefore, in the process in which the alkaline solution is used, there is a possibility that abnormal wear occurs on the rolling elements due to the corrosion and deterioration of silicon carbide, and that the rolling fatigue life of the rolling bearing is shortened. .

  Therefore, the present invention solves the problems of the prior art as described above, and even when used in a corrosive environment where a metal material cannot be used and in a high load environment where a large load acts, the rolling element It is an object of the present invention to provide a rolling device that is less likely to be damaged and has a long life.

  In order to solve the above problems, the present invention has the following configuration. That is, the rolling device according to claim 1 of the present invention includes a movable element capable of rotating or linearly moving, a support that supports the movable element so as to be rotatable or linearly movable, the movable element and the movable element. A rolling device comprising a plurality of rolling elements arranged so as to be freely rollable between the rolling element and the support, wherein the rolling element is made of ceramics mainly composed of alumina, and the crushing load is expressed by the following formula: It is more than Wc represented by these.

Wc = 0.05 × [diameter of rolling element] ^1.93
Here, the unit of Wc is kN, and the unit of the diameter of the rolling element is mm.
With such a configuration, even when used in a corrosive environment where a metal material cannot be used and in a high load environment where a large load acts, the rolling elements are hardly damaged and have a long life.

When the crushing load of the rolling element is less than Wc, when a large load is applied, cracks starting from the surface and internal defects are easily generated and propagated on the rolling element, and a large amount of wear powder is generated. Separation may occur and the rolling device may have a short life.
On the other hand, as corrosive substances used in liquid crystal panels and semiconductor manufacturing facilities, there are acidic substances such as hydrochloric acid, sulfuric acid and hydrofluoric acid, and alkaline substances such as ammonium hydroxide solution. In recent years, the composition of chemicals (corrosive substances) used has become complicated due to the purpose of increasing the efficiency of the manufacturing process, and it varies depending on the manufacturer of the liquid crystal panel and the semiconductor.

Therefore, the rolling devices used in these production facilities are also required to have corrosion resistance against many chemicals. In particular, rolling elements that are repeatedly subjected to load stress change their degree of wear and delamination greatly due to the superiority or inferiority of the corrosion resistance to the atmosphere used (drug), causing abnormal wear, surface delamination, particle dropping, etc. May cause harmful problems with the properties of
Alumina is an amphoteric compound having intermediate properties between an acidic compound and a basic compound and has a certain degree of corrosion resistance against both acidic and alkaline substances. Therefore, this rolling device has a long life because the rolling element is hardly damaged even in an acidic environment and an alkaline environment.

In addition, a metal oxide such as MgO and SiO ₂ is usually mixed as an additive in the sintered body of alumina, and may be slightly acidic or basic due to the influence of such an additive. Therefore, in order to obtain excellent corrosion resistance for a wide range of drugs, it is desirable to reduce the additive content as much as possible. The content of the additive is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, but unavoidably about 0.001% by mass is included.

A rolling device according to a second aspect of the present invention is the rolling device according to the first aspect, wherein the rolling element is manufactured by pressure sintering.
It is known that if a defect such as a void or a crack exists on the surface of an object, the interior is corroded by the penetration of liquid from the outside, and the corrosion resistance of the object is greatly reduced. In particular, when the load stress repeatedly acts in a corrosive environment like the rolling element used in the rolling device of the present invention, it exists on the surface because better corrosion resistance is required. It is necessary to reduce not only defects but also internal defects. Since the rolling element obtained by molding alumina raw material powder by pressure sintering has few internal defects as well as surface defects, the durability life of the rolling device in a corrosive environment is remarkably improved.

Furthermore, the rolling device according to a third aspect of the present invention is the rolling device according to the first or second aspect, wherein the center line average roughness Ra of the rolling element is 0.02 μm or more and 0.5 μm or less. It is characterized by being.
Ceramics such as silicon carbide have poor wettability compared to metal materials, and when the amount of liquid is very small, it may become partially dry and wear may increase. If the rolling element has a surface roughness of 0.02 μm or more, the liquid is easily drawn into and stays in the valley of the surface roughness, so that it is difficult to be in a dry state and wear is not likely to occur. The center line average roughness Ra is more preferably 0.1 μm or more. On the other hand, when the center line average roughness Ra exceeds 0.5 μm, a crest of the surface roughness is the starting point, and damage such as peeling or microabrasion may occur in the rolling elements.

Furthermore, the rolling device of Claim 4 which concerns on this invention is a rolling device as described in any one of Claims 1-3. WHEREIN: The said needle | mover and the said support body are ceramics which have a silicon carbide as a main component. It is characterized by comprising.
The present invention can be applied to various rolling devices. For example, a rolling bearing, a ball screw, a linear guide device, a linear motion bearing, and the like. The mover in the present invention is a rotating wheel when the rolling device is a rolling bearing, usually a nut when it is a ball screw, and usually a slider when it is a linear guide device, and also a linear bearing. In some cases, it usually means an outer cylinder. The support is a fixed ring when the rolling device is a rolling bearing, usually a screw shaft when it is a ball screw, usually a guide rail when it is a linear guide device, and also a linear bearing. In the case of, it usually means each axis.

  Even if the rolling device of the present invention is used in a corrosive environment where a metal material cannot be used and a high load environment where a large load acts, the rolling element is less likely to be damaged and has a long life.

An embodiment of a rolling device according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial longitudinal sectional view showing a structure of a rolling bearing which is an embodiment of a rolling device according to the present invention. This rolling bearing is a deep groove ball bearing having an identification number 6001 (inner diameter 12 mm, outer diameter 28 mm, width 8 mm, ball diameter 4.762 mm), facing the inner ring 1 having the raceway surface 1a on the outer peripheral surface and the raceway surface 1a. An outer ring 2 having a raceway surface 2a on the inner peripheral surface, a plurality of balls 3 disposed so as to roll between the raceway surfaces 1a and 2a, and a plurality of balls 3 between the inner ring 1 and the outer ring 2. And a retainer 4 for retaining. In the present embodiment, the outer ring 2 that is a fixed wheel corresponds to a support body that is a constituent element of the present invention, and the inner ring 1 that is a rotating wheel corresponds to a mover that is a constituent element of the present invention.

The inner ring 1, the outer ring 2, and the ball 3 are made of alumina, and the ball 3 has a crushing load equal to or greater than Wc represented by the following formula.
Wc = 0.05 × [diameter of rolling element] ^1.93
Here, the unit of Wc is kN, and the unit of the diameter of the rolling element is mm. Since the diameter of the ball is 4.762 mm as described above, Wc is 1.01 kN.

Such a rolling bearing according to the present embodiment has a long life because the ball 3 is hardly damaged even when used in a corrosive environment where a metal material cannot be used and a high load environment where a large load acts. .
In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment. For example, in this embodiment, the inner ring 1 and the outer ring 2 are made of alumina together with the balls 3, but the inner ring 1 and the outer ring 2 may be made of other types of ceramics. For example, silicon nitride (Si ₃ N ₄ ), zirconia (ZrO ₂ ), silicon carbide (SiC), aluminum nitride (AlN), boron carbide (B ₄ C), titanium boride (TiB ₂ ) Boron nitride (BN), titanium carbide (TiC), titanium nitride (TiN), or a ceramic composite material in which two or more of these are combined.

  Further, the method for producing rolling elements such as balls with alumina is not particularly limited.For example, when the rolling elements are balls, the alumina raw material powder is primarily formed into a spherical shape by a granulation molding method, After firing at a sintering temperature of 1300 to 1600 ° C., it can be produced by a method of processing with a predetermined accuracy using a lapping machine or the like. Note that primary molding may be performed by press molding using a mold having a hemispherical cavity.

  The primary particle size of the alumina raw material powder is preferably 1 μm or less, more preferably 0.5 μm or less (however, 0.05 μm is a practical lower limit). And if it sinters at low temperature, since the grain growth in a sintering process can be suppressed, the final crystal grain size can be made small. As a result, since a high-density sintered body is obtained, the strength is increased and the corrosion resistance is also improved. As a sintering condition at this time, heating at a temperature of about 1300 ° C. for about 1 to 2 hours is preferable. Furthermore, by applying a pressure exceeding normal pressure and performing pressure sintering, residual internal vacancies and abnormal growth of crystal grains can be suppressed, and a dense sintered body can be obtained. For pressure sintering, a HIP sintering method of about 1000 atm is preferable, but a hot press method of several hundred atm or a gas pressure sintering method of several tens of atm may be used. The alumina sintered body thus obtained preferably has a relative density of 98% or more, and more preferably 99% or more. Further, the average crystal grain size after sintering is preferably 5 μm or less, and more preferably 1 μm or less.

Furthermore, in the present invention, a fibrous filler may be blended with various ceramics in order to improve fracture toughness, mechanical strength, and the like. The type of fibrous filler is not particularly limited, and examples thereof include silicon carbide whiskers, silicon nitride whiskers, alumina whiskers, and aluminum nitride whiskers.
Furthermore, although the raw material which comprises the holder | retainer 4 is not specifically limited, Corrosion-resistant resin which can be melt-molded, and various fluorine-containing resin are preferable. Corrosion resistant resins that can be melt-molded include polyarylene sulfide resins represented by polyferylene sulfide resin (PPS), polyether nitrile resins (PEN), polyether ether ketone resins (PEEK), PEEK and polybenzimidazole. And a blended product (PEEK-PBI) and the like. Of these, PPS and PEEK are particularly excellent in self-lubricating properties and corrosion resistance, and are therefore suitable for use in corrosive environments such as acids and alkalis.

  Fluorine-containing resins include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), tetra Examples include fluoroethylene / hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), and the like. Among these, PTFE, PFA, ETFE, PVDF, and FEP are particularly excellent in self-lubricating properties and corrosion resistance, and are therefore suitable for use in corrosive environments such as acids and alkalis.

Further, a solid lubricant may be added to the resin constituting the cage in order to improve the lubrication characteristics. If it does so, since the frictional force which generate | occur | produces in the contact point of a needle | mover, a support body, and a rolling element is reduced, the heat_generation | fever by friction can be suppressed more. Examples of solid lubricants include PTFE powder, graphite, hexagonal boron nitride (hBN), fluorine mica, melamine cyanurate (MCA), amino acid compound having a layered crystal structure (N-lauro-L-lysine), and graphite fluoride. , Fluoride pitch, molybdenum disulfide (MoS ₂ ), and the like.

  Furthermore, in order to improve mechanical strength, heat resistance, dimensional stability, etc., a fibrous filler can be blended with the resin constituting the cage. The type of fibrous filler is not particularly limited, but aluminum borate whisker, potassium titanate whisker, carbon whisker, aramid fiber, aromatic polyimide fiber, liquid crystalline polyester fiber, graphite whisker, glass fiber, carbon fiber Boron fiber, silicon carbide whisker, silicon nitride whisker, alumina whisker, aluminum nitride whisker, wollastonite and the like. These fibrous fillers are surface treated with a silane- or titanate-based coupling agent for the purpose of improving the adhesion with the fluororesin as a base material or for the purpose of uniformly dispersing in the base material. You may give it. Moreover, you may perform the surface treatment according to the other objective.

  Furthermore, in this embodiment, a deep groove ball bearing has been described as an example of a rolling device, but the type of rolling bearing is not limited to a deep groove ball bearing, and the present invention is applicable to various types of rolling bearings. It can be applied to. For example, radial type rolling bearings such as angular contact ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings This is a rolling bearing. Furthermore, the present invention can be applied not only to rolling bearings but also to various types of various rolling devices. For example, a ball screw, a linear guide device, a linear motion bearing, or the like.

〔Example〕
Hereinafter, the present invention will be described with reference to more specific examples. In the deep groove ball bearing having substantially the same configuration as the deep groove ball bearing of the reference number 6001, the ceramics constituting the inner ring, the outer ring, and the balls are variously changed as shown in Table 1, and a rotation test is performed. Durability (life) was evaluated. In addition, about each alumina and silicon carbide of Table 1, various physical properties including purity of a raw material alumina, a sintering method, and a crushing load are shown in Table 2.

  Here, the crushing load described in Table 2 is measured by the following crushing test. That is, two balls were placed in contact with each other, a load was applied to both balls from both sides of the balls in the parallel direction, and a load causing damage to at least one ball was defined as a crushing load.

  Of the ceramics listed in Tables 1 and 2, alumina 1 was obtained by atmospheric pressure sintering, but because the internal structure was non-uniform, the crushing load was 0.7 kN, which is suitable for the present invention. Out of range. Alumina 2 is obtained by atmospheric pressure sintering, and the crushing load is 1.1 kN, which is within the preferred range in the present invention. Alumina 3 was obtained by atmospheric pressure sintering, but the relative density and purity of raw material alumina were higher than those of alumina 2, and the crushing load was 1.5 kN, which is within the preferred range of the present invention. Alumina 4 is a high-strength alumina obtained by the HIP method (hot isostatic pressing method), which is a pressure sintering method of 1000 atm or higher, and the crushing load is 2.0 kN, which is within the preferred range of the present invention. It is. Alumina 5 is a high-strength alumina obtained by the HIP method, which is a pressure sintering method at 1000 atm or higher. The relative density and purity of the raw material alumina are higher than those of alumina 4, and the crushing load is 2.5 kN. Is within a preferred range.

  Of the ceramics shown in Tables 1 and 2, silicon carbide is α-type silicon carbide produced by a sintering method using a boron and carbon-based sintering aid. The type of silicon carbide is not particularly limited, but when silicon carbide is produced by a reactive sintering method, metallic silicon may remain inside the material, which adversely affects the corrosion resistance of the material. This residual metal silicon is preferably 5% by mass or less.

Further, the center line average roughness Ra of the surface of the balls of all deep groove ball bearings is 0.1 μm. Furthermore, all the deep groove ball bearing cages are crown cages manufactured by injection molding a resin composition comprising 80% by mass of ETFE and 20% by mass of potassium titanate whiskers.
These deep groove ball bearings are immersed in a 5% hydrofluoric acid aqueous solution or 30% sodium hydroxide aqueous solution maintained at 80 ° C. for 100 hours, and then attached to a bearing rotation tester manufactured by NSK Ltd. as shown in FIG. A rotation test was performed.

  This bearing rotation tester includes a horizontal base D and a rotary shaft S that is rotationally driven by a motor (not shown). The rotary shaft S is inclined with respect to the base D. The rotating shaft S is rotatably supported by two ball bearings J1 and J2 having outer rings fixed to both end portions in the axial direction of the housing H, and a test bearing J is mounted on the tip thereof. A container 5 filled with water 51 is installed on the base D.

While the outer ring of the test bearing J was immersed in the water 51 in the container 5, a rotation test was performed by rotating the inner ring while applying a radial load (radial load) R to the test bearing J. The test conditions are radial load: 98 N, rotation speed: 1000 min ⁻¹ , and ambient temperature: normal temperature. Then, the vibration generated in the rotating test bearing J was measured, and the time until the vibration value became three times that at the start of the test was defined as the life of the test bearing J. The results are summarized in Table 1. In addition, the numerical value of the lifetime described in Table 1 is shown as a relative value when the lifetime of the deep groove ball bearing of Comparative Example 1 is 1.

  As can be seen from Table 1, the life of the deep groove ball bearings of Examples 1 to 5 was superior to the deep groove ball bearings of Comparative Examples 1 to 3. From this result, it can be said that the deep groove ball bearings of Examples 1 to 5 have excellent durability even in a corrosive environment. Moreover, since the deep groove ball bearings of Examples 3 to 5 are manufactured using high-strength alumina obtained by the pressure sintering method, the balls are manufactured using alumina obtained using the normal pressure sintering method. Compared to the deep groove ball bearings of Examples 1 and 2, the service life was longer. Furthermore, the deep groove ball bearing of Example 5 had the longest life among all the examples because the inner ring and the outer ring were also made of high-strength alumina obtained by the pressure sintering method.

  Next, deep groove ball bearings having various ball diameters and crushing loads were prepared, and the life after immersion in a 5% hydrofluoric acid aqueous solution was measured in the same manner as in the rotation test described above. The configuration of this deep groove ball bearing is almost the same as that used in the rotation test described above, except that the type of alumina constituting the ball and the size of the deep groove ball bearing were changed in order to change the ball diameter and crushing load. It is the same composition. The inner ring and the outer ring are made of silicon carbide.

The results are shown in the graph of FIG. In this graph, the life of each bearing is shown as a relative value when the life of the deep groove ball bearing of Comparative Example 1 is set to 1. When the life is 1 or less, the mark is X, and when it is less than 3 Is plotted with a circle, and when it is 3 or more, a circle is plotted. As can be seen from the graph, when the ball crushing load is greater than or equal to Wc calculated from the diameter (Da) (when plotted above the line of Wc = 0.05 × Da ^1.93 ), the deep groove ball bearing Has a long life and is less than Wc (when plotted below the Wc = 0.05 × Da ^1.93 line), the life of the deep groove ball bearing was 1 or less.

  Next, in the deep groove ball bearing of Example 4 described above, various ball surface centerline average roughness Ra were prepared, and 5% hydrofluoric acid aqueous solution was prepared in the same manner as in the rotation test described above. The life after soaking was measured, and the relationship between the surface roughness of the rolling element and the durability of the deep groove ball bearing was investigated. The result is shown in the graph of FIG. In addition, the numerical value of the lifetime in this graph is shown by the relative value when the lifetime of the deep groove ball bearing of the above-mentioned comparative example 1 is set to 1.

  As can be seen from the graph, the deep groove ball bearing in which the center line average roughness Ra of the ball surface is 0.02 to 0.5 μm had excellent durability. This is thought to be because the liquid was drawn into the valley of the surface roughness, so that it was difficult to become dry and wear was difficult to occur.

  The rolling device of the present invention is in a corrosive environment in which it is in contact with a corrosive liquid or gas such as water, acid, alkali, etc. (for example, in an environment in which it is in contact with liquid droplets or vapor or in the liquid) Can also be preferably used. For example, it is suitable as a rolling device that constitutes a rotation support portion of various cleaning devices, resist coating / peeling devices, etching devices, etc. used when manufacturing chemical fibers, films, semiconductors, liquid crystal panels, capacitors and the like.

It is a fragmentary longitudinal cross-section which shows the structure of the rolling bearing which is one Embodiment of the rolling device which concerns on this invention. It is sectional drawing which shows the structure of a bearing rotation tester. It is a graph which shows the correlation with the crushing load of a rolling element, and the lifetime of a deep groove ball bearing. It is a graph which shows the correlation with the surface roughness of a rolling element, and the lifetime of a deep groove ball bearing.

Explanation of symbols

1 Inner ring 2 Outer ring 3 Ball J Test bearing

Claims (4)

A movable element capable of rotational movement or linear movement, a support body that supports the movable element so as to be capable of rotational movement or linear movement, and a plurality of rolling elements disposed between the movable element and the support body so as to be capable of rolling. In a rolling device comprising a rolling element,
The rolling device is composed of ceramics mainly composed of alumina, and the crushing load is Wc or more represented by the following formula.
Wc = 0.05 × [diameter of rolling element] ^1.93
Here, the unit of Wc is kN, and the unit of the diameter of the rolling element is mm.   The rolling device according to claim 1, wherein the rolling element is manufactured by pressure sintering.   The rolling device according to claim 1 or 2, wherein a center line average roughness Ra of the rolling element is 0.02 µm or more and 0.5 µm or less.   The rolling device according to any one of claims 1 to 3, wherein the mover and the support are made of ceramics mainly composed of silicon carbide.

Images