JP2012189153A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing having improved water resistance and wear resistance under a water environment.SOLUTION: The rolling bearing includes, to improve a bearing life and bearing performance, namely, water resistance and wear resistance, an outer ring having a raceway in an inner peripheral surface, an inner ring having a raceway in an outer peripheral surface, and a plurality of rolling elements arranged to freely roll between the pair of raceways. At least one of the outer ring and the inner ring is made of corrosion-resistant steel, and the plurality of rolling elements is made of ceramics mainly containing zirconium but no alumina.

Description

  The present invention relates to a rolling bearing used in a water environment such as a semiconductor cleaning device or a submersible pump.

In general, a bearing used for a semiconductor cleaning device, a submersible pump, or the like is provided with a rolling bearing in a space into which a cleaning liquid or water enters. Therefore, high corrosion resistance is required for bearings used in such a water environment. As an example of measures against corrosion of a bearing, it is considered to enclose grease having excellent water resistance inside the bearing. For example, as disclosed in Non-Patent Document 1, it is disclosed that the rolling strength of steel is reduced by 32 to 48% when only 100 ppm of water is mixed in the lubricating oil.
Such a decrease in the life is considered that hydrogen generated from the mixed water acts on the bearing material and causes metal peeling called white tissue peeling.

  In order to suppress this exfoliation, many improvements have been proposed in the past in the enclosed grease. For example, the following Patent Documents 1 to 3 include greases to which an oxidizing agent that forms a passive state such as sodium nitrite is added. In addition, greases to which organic antimony compounds and organic molybdenum compounds are added, greases to which inorganic compounds having a particle diameter of 2 μm or less are added, and the like have been proposed.

P.Schatzberg, I.M.Felsen: Effects of water and oxygen during rollingcontact lubrication, wear 12, pp.331-342,1968 Japanese Patent No. 2878749 Japanese Patent No. 3512183 Japanese Patent Laid-Open No. 9-169989

  However, as described in Patent Documents 1 to 3, simply by improving the water resistance of the bearing by improving the grease composition, the progress of corrosion due to long-term use of the bearing in an aqueous environment is unavoidable, and it is drastic as a corrosion-resistant means. Measures were required. Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a bearing having improved bearing life, that is, water resistance and wear resistance.

  According to a first aspect of the present invention, there is provided a plurality of outer rings having a raceway surface on an inner peripheral surface, an inner ring having a raceway surface on an outer peripheral surface, and a plurality of rolls provided between the pair of raceway surfaces. A rolling bearing provided with a rolling element is characterized in that at least one of the outer ring and the inner ring is made of corrosion-resistant steel, and the plurality of rolling elements are ceramics containing zirconia as a main component and not containing alumina.

  In the rolling bearing according to the present invention, the bearing life in a water environment, that is, water resistance and wear resistance is obtained by using a corrosion-resistant steel for the outer ring and the inner ring, a ceramic containing zirconia as a main component and no alumina for the rolling element. It is possible to improve the bearing performance.

It is a schematic sectional drawing which shows the rolling bearing corresponded to one Embodiment of this invention.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a rolling bearing 10 according to the present invention. As shown in the figure, the rolling bearing 10 has a configuration in which a plurality of rolling elements 3 held by a retainer 4 are provided between an outer ring 1 and an inner ring 2 so as to have a predetermined interval.

(Examples and comparative examples)
Here, as shown in Table 1, the rolling element 3 containing yttria containing zirconia as the main component was used in Example 1, and yttria containing alumina as the main component and alumina containing the comparative example 1, alumina. Comparative Example 2 was used as a main component.

The specifications and test conditions of the test bearing were set as follows.
Bearing used: Thrust bearing inner ring, outer ring material: Corrosion resistant steel (SUSC440 equivalent)
Rolling element diameter: 3/8 inch Number of rolling elements: 6 Cage material: Fluororesin (Polytetrafluoroethylene)
Test load: 1666N (bearing axial direction)
Test rotation speed: 1000 min ⁻¹
Lubricant: None Seals and rolling bearings without lubricant were immersed in water, and bearing life and wear tests were performed under the above conditions.

(Test results)
Table 2 shows the measurement results of Example 1 and Comparative Examples 1 and 2. According to this, it was found that Example 1 in which the main component of the rolling element is zirconia has the longest bearing life, and the outer ring, the raceway surface of the inner ring and the wear of the rolling element are less than those of Comparative Examples 1 and 2. Compared to Comparative Example 1 in which silicon nitride was used as the main component of the rolling element, the bearing life was improved 1.5 times, the wear of the rolling surface was reduced to 3/4, and the wear of the rolling element was reduced to 1/6. The reason why the wear amount of Example 1 is reduced compared to Comparative Examples 1 and 2 is considered that Example 1 does not contain an alumina component that easily wears the mating material. As a result, the rolling element component of the bearing in the water environment is to make the ceramics containing zirconia as the main component and not containing alumina, and to make the outer ring and inner ring corrosion-resistant steel. I found it good.

  The raceway wear rate shown in Table 2 is calculated by dividing the sum of the maximum wear depths of the inner ring and outer ring by the test time. The rolling element wear rate is the change in diameter of the rolling element. Calculated by dividing by test time.

DESCRIPTION OF SYMBOLS 1 ... Outer ring 2 ... Inner ring 3 ... Rolling element 4 ... Cage
10 ... Bearing

Claims (1)

  A rolling bearing comprising: an outer ring having a raceway surface on an inner peripheral surface; an inner ring having a raceway surface on an outer peripheral surface; and a plurality of rolling elements provided between the pair of raceway surfaces so as to be freely rollable. A rolling bearing, wherein at least one of the inner rings is made of corrosion-resistant steel, and the plurality of rolling elements are ceramics containing zirconia as a main component and not containing alumina.

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