JP2006046668A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the life of a rolling bearing in an environment such as in a vacuum, a high temperature, corrosive gas, liquid, or molten metal in which an ordinary lubricant such as oil or grease cannot be used by improving the shift adhesiveness of a solid lubricant from a self-lubricating retainer. <P>SOLUTION: This rolling bearing is constituted of an outer ring 2, an inner ring 3, and rolling bodies 4 made of silicon nitride ceramic, and a retainer 5 made of polytetrafluoroethylene, and the surface roughness of the raceway surface of each outer ring 2 and inner ring 3 is set in a range of 0.1 μmRa-3.2 μmRa. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an improvement in a rolling bearing used in an environment where a normal lubricant such as oil or grease cannot be used, such as in vacuum, high temperature, corrosive gas, liquid, or molten metal.

Conventionally, as this type of rolling bearing used in an environment where normal lubricants such as oil and grease cannot be used, a self-lubricating cage mainly composed of polytetrafluoroethylene and a rolling bearing including a ceramic rolling element are known. It has been.
Japanese Patent Laid-Open No. 03-255224 Japanese Utility Model Publication No. 04-082431 Japanese Utility Model Publication No. 06-077620

  However, in this type of rolling bearing, since the rolling life must be relied upon by the lubrication of the solid lubricant from the cage, how to transfer the solid lubricant from the self-lubricating cage is an important technology. However, there is still room for improvement in the conventional technologies as described above.

  The present invention has been made in view of such problems of the prior art, and its object is to improve the transferability of the solid lubricant from the self-lubricating cage, in vacuum, The purpose is to extend the rolling life in an environment where normal lubricants such as oil and grease cannot be used, such as in high temperature, corrosive gas, liquid, or molten metal.

  The technical means made by the present invention to achieve the above object is that the rolling elements are made of ceramics, and the surface roughness of the raceway surfaces of the outer ring and the inner ring is in the range of 0.1 μmRa to 3.2 μmRa and held. The vessel is made of a self-lubricating material. In the present specification, “Ra” represents arithmetic average roughness.

  By the above technical means, the surface roughness of the raceway surface (outer ring and inner ring) is in the range of 0.1 μmRa or more and 3.2 μmRa or less, which is compared with the conventional rolling bearing having a surface roughness of less than 0.1 μmRa. And vibration during rotation increases.

  As a result, the opportunity for the self-lubricating cage to come into stronger contact with the rolling element is increased, so that the transfer of the solid lubricant from the self-lubricating cage to the rolling element can be increased.

Since a ceramic rolling element is used, the rolling element smoothly wears the raceway surface while maintaining the surface roughness because of its excellent wear resistance at the initial stage of rotation.
After the raceway surface becomes smooth (surface roughness is less than 0.1 μmRa), the vibration becomes low, and good lubrication is performed by the solid lubricant transferred to the rolling elements in an appropriate amount and uniformly.

  As described above, since the ceramic rolling element maintains a smooth surface that is not easily worn, the solid lubricant is transferred from the self-lubricating cage in an appropriate amount and uniformly, and good lubrication is achieved.

  Therefore, the increase in the transfer effect due to the initial vibration is controlled by the surface roughness of the raceway raceway surface, and smooth wear before the solid lubricant on the raceway raceway surface is transferred is achieved by using ceramic rolling elements. However, lubrication after smooth wear on the raceway raceway surface is carried out by transferring solid lubricant from the ceramic rolling elements to extend the rolling life in environments where normal lubricants such as oil and grease cannot be used. Can be planned.

  In the present invention, at least the rolling elements are made of ceramics, the surface roughness of the raceway surface (outer ring and inner ring) is in the range of 0.1 μmRa to 3.2 μmRa, and the self-lubricating cage is used. An environment where normal lubricants such as oil and grease cannot be used, such as in vacuum, high temperature, corrosive gas, liquid, or molten metal, by improving the transferability of solid lubricant from the lubrication cage The rolling life can be extended.

  That is, the initial vibration is increased by the surface roughness of the raceway surface, the effect of transferring the solid lubricant is increased, and after the raceway raceway surface is smoothly worn by the ceramic rolling element, Since it can be performed by transferring more solid lubricant from the rolling elements, it is possible to extend the rolling life in an environment where normal lubricants such as oil and grease cannot be used.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of the rolling bearing according to the present invention. The rolling bearing 1 is a ball bearing composed of an outer ring 2, an inner ring 3, a rolling element 4, and a cage 5, and this embodiment is hereinafter described. However, the present invention can be applied to both roller bearings and radial bearings and thrust bearings, and can be appropriately selected and applied within the scope of the present invention.

The outer ring 2 and the inner ring 3 are configured such that the surface roughness of the respective raceway surfaces 2a and 3a is in the range of 0.1 μmRa to 3.2 μmRa.
Further, since ceramics are used for the rolling elements 4 described below, the outer ring 2 and the inner ring 3 may be made of steel or ceramics.
When the surface roughness is 0.1 μmRa or less, vibration during rotation becomes too small, so there is little opportunity for the self-lubricating cage to come into contact with the rolling element, and the solid lubricant is transferred from the self-lubricating cage to the rolling element. There is little wearing. On the other hand, when the surface roughness is 3.2 μm Ra or more, the vibration becomes excessive, so that there are too many transfer or uneven transfer, which hinders lubrication.

  The rolling element 4 is made of a ceramic material with high wear resistance. Examples of the ceramic material include silicon carbide, alumina, zirconia, and the like in addition to silicon nitride.

  The cage 5 is made of a self-lubricating material such as polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). And those composed of fluorine resin, graphite, molybdenum disulfide and the like.

In order to confirm the effect of the present invention, a rotation test was performed with the test apparatus shown in FIG. 2 using several types of deep groove ball bearings shown in Examples 1 to 8 and Comparative Examples 1 to 8.
The rotation test results are shown in Table 1, and the relationship of the rolling life (h) to the surface roughness (μmRa) of the raceway raceway surface is shown in FIG.

"Examples 1-4, Comparative Examples 1-3"
Surface roughness of the raceway surface, the range of silicon nitride ceramics (Si ₃ N ₄₎ made of the bearing ring of 0.05MyumRa～9.4MyumRa (outer ring, inner ring), silicon nitride ceramics (Si ₃ N ₄₎ made rolling elements and Consists of a cage made of polytetrafluoroethylene (PTFE).
"Examples 5-8, Comparative Examples 4-6"
Stainless steel (SUS440C) race rings (outer rings, inner rings), silicon nitride ceramic (Si ₃ N ₄ ) rolling elements and polytetrafluoroethylene having a surface roughness in the range of 0.05 μm Ra to 9.4 μm Ra Consists of (PTFE) cage.
“Comparative Example 7”
Surface roughness of the raceway surface, 1.0MyumRa of silicon nitride ceramics (Si ₃ N ₄₎ made of the bearing ring (outer ring, inner ring), silicon nitride ceramics (Si ₃ N ₄₎ made rolling elements and steel (SUS304 stainless steel) Consists of made cage.
“Comparative Example 8”
Consists of a raceway surface (outer ring, inner ring) made of stainless steel (SUS440C) having a surface roughness of 1.0 μmRa, a rolling element made of stainless steel (SUS440C), and a cage made of polytetrafluoroethylene (PTFE).

  The following can be understood from the results of Table 1 and FIG.

  The surface roughness of the raceway raceway surface shown in Examples 1 to 4 is 0 with respect to the rolling life of Comparative Example 1 which shows a bearing having a surface roughness of a raceway raceway surface of less than 0.1 μmRa that has been conventionally used. In the case of bearings of .1 μm Ra to 3.2 μm Ra, it was confirmed that the rolling life was greatly extended (→ in Table 1 and FIG. 3 indicates the display time (h) or more, that is, in this test) Although it was cut off at 190h, it shows that a rolling life (h) longer than that was actually obtained.

  Moreover, when the surface roughness of the raceway raceway surface exceeded 3.2 μmRa (Comparative Examples 2 and 3), the rolling life decreased compared to the bearings of Examples 1 to 4.

  Furthermore, also from the results of Examples 5 to 8 and Comparative Examples 4 to 6, the bearings in the surface roughness range (0.1 μmRa to 3.2 μmRa) of the present invention have a longer life than bearings outside that range. A result was obtained.

  Further, in Comparative Example 7 in which the surface roughness of the raceway, the rolling element, and the raceway raceway surface is equal, and the cage material is a steel steel cage different from that of the polytetrafluoroethylene of Example 2, the cage is used. From this, it can be seen that the effective life of the solid lubricant cannot be obtained from No. 2, and the rolling life is extremely short as compared with Example 2.

The bearing ring material, the surface roughness of the bearing ring raceway surface and the cage material are the same, but the rolling element is made of stainless steel (SUS440C) different from the silicon nitride ceramics (Si ₃ N ₄ ) of Example 6. Also in Comparative Example 8, since it is a rolling element made of stainless steel, the surface of the rolling element becomes rough before transfer from the self-lubricating cage is obtained, and the rolling life is extremely short as compared with Example 6. I understand that

An embodiment of the rolling bearing of the present invention is partially omitted and shown in cross section. The outline of the testing machine for confirming the rotational performance of the rolling bearing of the present invention is shown. The relationship of the rolling life to the surface roughness of the raceway surface is shown.

Explanation of symbols

1: Rolling bearing 2: Outer ring 3: Inner ring 2a, 3a: Raceway surface 4: Rolling element 5: Cage

Claims (1)

In a rolling bearing consisting of an outer ring, an inner ring, a rolling element, and a cage, at least the rolling element is made of ceramics, the surface roughness of the raceway surface of the outer ring and the inner ring is in the range of 0.1 μmRa to 3.2 μmRa, and the cage is Rolling bearings that are self-lubricating.

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