JP2015127549A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing in which a protruded part on a surface becomes smooth as sliding by a favorable running-in effect of a phosphate coating, and a recessed part is hardly rusted by a sacrificial protection effect by a residual of a less noble metal than iron in the recess.SOLUTION: A rolling bearing includes an inner ring, an outer ring, a plurality of rolling elements rotatably arranged between the inner ring and outer ring, and a seal member, and comprises a coating formed by a surface processing method consisting of a first process of forming phosphate coating on the surface of at least one of the inner ring, the outer ring, and the rolling element, and a second process of forming an alloy or mixed powder of less noble metal and nobler metal than iron by shot-peening.

Description

  The present invention relates to a rolling bearing, and in particular, can be used as a rolling bearing provided with a seal member. Specifically, it can be used as a drum support bearing for indirect drum washing of a washing machine.

  When general steel is used as the material of the rolling bearing, rust may be generated on the sliding surface with which the seal member abuts in the presence of moisture. And since this rust forms an uneven shape on the sliding surface, the adhesion between the sliding surface and the seal member is lowered, and as a result, there is a problem that moisture enters the inside of the rolling bearing. It was. As a measure for preventing the occurrence of rust, the use of a corrosion-resistant metal as the material of the rolling bearing can be mentioned. However, since it is more expensive than steel, there is a problem that the manufacturing cost increases. Further, since the other end of the contact seal is always in close contact with the sliding surface, a frictional resistance is generated on the sliding surface, resulting in a problem of increasing the bearing torque.

  Therefore, in Cited Document 1, in a rolling bearing provided with a seal member whose other end abuts against the sliding surface of the seal groove, a corrosion-resistant film containing zinc and tin is formed on the sliding surface by shot peening. .

JP 2010-190282 A

  However, as the metal film formed by the shot slides, the film formed on the surface convex portion wears, and there is a problem that the base material is exposed and is easily rusted. In order to solve this problem, the present invention adopts a novel configuration in which after forming a phosphate film, a film is formed by shot peening an alloy or a mixed powder of a metal less precious than iron and a noble metal. doing. With this structure, the surface convex part becomes smooth as it slides with the good conformation effect of the phosphate coating, and the sacrificial anticorrosive effect in which a base metal remains than iron in the concave part provides a rolling bearing that is hard to rust To do.

  In order to achieve the above object, a rolling bearing according to the present invention includes an inner ring, an outer ring, a plurality of rolling elements that are freely rollable between the inner ring and the outer ring, and either the inner ring or the outer ring. A seal in which one end is fixed to an annular seal groove formed on the stationary ring side, and the other end abuts against a sliding surface of the seal groove formed on the rotating ring side of either the outer ring or the inner ring. In a rolling bearing provided with a member, a first step of forming a phosphate coating on at least one surface of an inner ring, an outer ring, or a rolling element, and an alloy or mixed powder of a base metal and a noble metal than iron It is characterized by comprising a film formed by a surface treatment method comprising a second step of forming by performing shot peening. Moreover, it is preferable that zinc content of the said film is 5 to 80 mass%, and tin content is 95 to 20 mass%. Moreover, it is preferable that the said phosphate film is a phosphoric acid Mn film and the thickness is 0.1 micrometer or more and 7 micrometers or less. Further, the metal that is lower than iron includes at least one of Al, Zn, Bi, and Mn, and the metal that is noble than iron includes at least one of Ni, Cr, Cu, Ti, and Sn. Is preferred. Moreover, it is preferable that the other end of the seal member has a plurality of lip portions separated by an annular groove. Moreover, it is preferable that one end part of the said sealing member has a collar part which covers the sealing groove | channel on the stationary wheel side. In addition, 1000 or more and 100,000 or less dimples per square millimeter are formed on at least one surface of the inner ring, outer ring, or rolling element, and the surface of the dimple is made of iron having a mass of 1 to 90% by mass. It is preferably composed of a base metal and a noble metal. Further, it is preferable that the dimple has a diameter of 0.1 μm to 20 μm and a depth of 0.1 μm to 10 μm. Further, the metal that is lower than iron includes at least one of Al, Zn, Bi, and Mn, and the metal that is noble than iron includes at least one of Ni, Cr, Cu, Ti, and Sn. Is preferred.

  The present invention employs a novel configuration in which after the phosphate coating is formed, a coating is formed by shot peening an alloy or mixed powder of a base metal and noble metal than iron. With this configuration, the surface convex part becomes smooth as it slides due to the good conformation effect of the phosphate coating, and a base metal than iron remains in the concave part and exerts a sacrificial anticorrosive effect, making it difficult to rust Has an effect.

1 is a cross-sectional view illustrating a schematic configuration of a rolling bearing according to an embodiment of the present invention using a deep groove ball bearing as an example. It is a SEM photograph of Example 2 and an analysis result. It is a figure which shows the result of having measured the uneven | corrugated state of the surface of the zinc-tin alloy film of Example 2. FIG.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a schematic configuration of a rolling bearing according to an embodiment of the present invention, taking a deep groove ball bearing as an example. In FIG. 1, a deep groove ball bearing is provided with an inner ring 1 and an outer ring 2 facing each other, and a plurality of rolling elements 3 are arranged between the inner ring 1 and the outer ring 2 so as to be freely rotatable. A cage 4 that holds the moving body 3 is installed. In addition, seal members 5 such as rubber seals are attached to both ends of the outer ring 2 and grease 6 is sealed inside the bearing. In addition, as a material of the base material of the inner ring | wheel 1, the outer ring | wheel 2, and the rolling element 3, a cold rolled steel plate can be used, for example as a material of the base material of SUJ2 material and the holder | retainer 4, for example. One end 5a is fixed to an annular seal groove 2c formed on either the inner ring 1 or the outer ring 2 on the stationary ring side, and formed on either the outer ring 3 or the inner ring 2 on the rotating wheel side. And a seal member with which the other end 5b abuts against the sliding surface of the seal groove 1c. Moreover, it is preferable that the other end of the seal member has a plurality of lip portions separated by an annular groove. Moreover, it is preferable that the one end part of the said sealing member has the collar part 5c which covers the seal groove by the side of a stationary wheel.

  In the present invention, a base metal than iron and a noble metal than iron are provided on the surface of at least one of the inner ring 1, the outer ring 2, and the rolling element 3 (all in the illustrated example) via the phosphate coatings 1 a to 3 a. Metal coatings 1b to 3b containing metal are formed. Moreover, you may form the metal film 4b on the surface of the holder | retainer 4 via the phosphate film 4a so that it may be illustrated. In addition, 1000 or more and 100,000 or less dimples per square millimeter are formed on at least one surface of the inner ring, outer ring, or rolling element, and the surface of the dimple is made of iron having a mass of 1 to 90% by mass. It is preferably composed of a base metal and a noble metal. Further, it is preferable that the dimple has a diameter of 0.1 μm to 20 μm and a depth of 0.1 μm to 10 μm.

  As the phosphate coatings 1a to 4a, a typical manganese phosphate coating can be used as a corrosion-resistant coating. For example, it can be formed as follows.

  First, the inner ring 1, the outer ring 2, the rolling element 3 and the cage 4 are ultrasonically cleaned in acetone for about 10 minutes, and then subjected to alkali degreasing treatment at 70 ° C. for about 2 minutes. Further, after washing with ion-exchanged water, pretreatment is performed in a surface conditioner at 40 ° C. for about 40 seconds. As the surface conditioner, a suspension of preparenes PM55A and PM55B manufactured by Nippon Parker Rising Co., Ltd. can be used. Then, it is immersed in a phosphoric acid aqueous solution (chemical conversion solution) in which manganese ions are dissolved, subjected to chemical conversion treatment at 95 ° C. for about 10 minutes, washed with water and dried to form a manganese phosphate coating.

  The properties of the formed manganese phosphate coating are influenced by the composition of the chemical conversion treatment solution. For example, the total acidity TA, the free acidity FA, the acid ratio AR, which is the ratio of these two acidities (TA / FA), and the manganese ion concentration. The

The free acidity FA is the amount of sodium hydroxide solution having a concentration of 0.1 mol / L necessary for neutralization of the free acid component of phosphoric acid (H ⁺ and H ₂ PO ₄ ⁻ in the following chemical formula (I)) (unit: Is mL). That is, it is necessary to titrate 10 mL of manganese phosphate solution (chemical conversion solution) with 0.1 mol / L sodium hydroxide solution using bromophenol blue as an indicator and the liquid color changes from yellow to blue yellow. The amount of sodium hydroxide solution having a concentration of 0.1 mol / L (unit: mL) is the free acidity FA.
H ⁺ + H ₂ PO ₄ ⁻ + NaOH → NaH ₂ PO ₄ + H ₂ O (I)

The total acidity TA means the free acid component of phosphoric acid (2H ⁺ and HPO ₄ ²⁻ in the following chemical formula (II)) and the total acid component (3Mn (H ₂ O ₄ ) ₂ in the following chemical formula (III)). This is the amount of sodium hydroxide solution having a concentration of 0.1 mol / L required for neutralization (unit: mL). That is, titration of 10 mL of manganese phosphate solution (chemical conversion solution) with 0.1 mol / L sodium hydroxide solution using phenolphthalein as an indicator is necessary until the liquid color changes from colorless to pink. The amount of sodium hydroxide solution having a concentration of 0.1 mol / L (unit: mL) is the total acidity TA.
2H ⁺ + HPO ₄ ²⁻ + 2NaOH → Na ₂ HPO ₄ + 2H ₂ O (II)
3Mn (H ₂ PO ₄ ) ₂ + 8NaOH → 4Na ₂ HPO ₄ + Mn ₃ (PO ₄ ) ₂ + 8H ₂ O (III)

  In the present invention, the total acidity TA is preferably 20 to 50, the free acidity FA is 2.0 to 5.0, the acid ratio AR is 5 to 15, and the manganese ion concentration is 2000 to 6000 ppm.

  The film thicknesses of the phosphate coatings 1a to 4a are preferably 7 μm or less in view of film quality and film formability. As the phosphate coatings 1a to 4a are thicker, the durability is increased. However, the crystal grains of the phosphate become too large, and the surfaces of the metal coatings 1b to 4b formed thereon become rough. Preferably, it is 4 μm or less. However, the thinner the phosphate coatings 1a to 4a, the lower the durability. Further, in the present invention, since the metal coatings 1b to 4b are formed by the shot peening method, the phosphate coatings 1a to 4a are peeled off by the collision of the metal powder. As a result, the metal coatings 1 b to 4 b may be directly formed on the surfaces of the inner ring 1, the outer ring 2, the rolling elements 3, and the cage 4. Therefore, the film thickness of the phosphate coatings 1a to 4a is preferably 0.1 μm or more, and more preferably 2 μm or more. The film thicknesses of the phosphate coatings 1a to 4a can be adjusted by the concentration of the chemical conversion solution and the immersion time.

  The average surface roughness of the phosphate coatings 1a to 4a is about 0.4 to 1 [mu] mRa, but by shot peening, the corners of the projections are removed and flattened to about 0.3 [mu] mRa. Therefore, even if the metal coatings 1b to 4b wear and the phosphate coatings 1a to 4a are exposed, the subsequent slidability is maintained well.

Moreover, in order to improve the adhesiveness of the phosphate coatings 1a to 4a, the surfaces of the inner ring 1, the outer ring 2, the rolling element 3, and the cage 4 may be roughened. For roughening, shot peening treatment using a projection material such as steel balls, SiC, SiO ₂ , Al ₂ O ₃ , glass beads, barrel treatment, or the like can be performed. The depth of the recess is preferably 0.1 to 5 μm.

  The metal coatings 1b to 4b contain a metal that is baser than iron and a metal that is noble than iron. Rust prevention performance is obtained. Al, Zn, Bi and Mn are preferred as the base metal than iron, and Ni, Cr, Ti and Sn are preferred as the noble metal than iron. In addition, both a base metal and a noble metal from iron may be used independently, and multiple types may be used.

  In addition, the mixing ratio of the metal lower than iron and the metal precious than iron in the metal coatings 1b to 4b is a weight ratio of metal lower than iron: metal precious than iron = (20:80 to 80:20). ) Is preferred, but from the phase effect of both, an equal amount (50:50) is more preferred.

  The metal coatings 1b to 4b are shot peened using a powder made of an alloy of a metal lower than iron and a metal noble than iron, or a mixed powder of a metal lower than iron and a metal noble above iron. Formed by law. Therefore, by adjusting the ratio of the base metal and the noble metal than iron in the alloy powder, or the ratio of the base metal and the noble metal powder in the mixed powder, It can be a mixing ratio.

  As for the film thickness of the metal coatings 1b-4b, 2-8 micrometers is preferable. If the film thickness is less than 2 μm, a sufficient and sustained anticorrosive effect cannot be obtained. On the other hand, if the film thickness exceeds 8 μm, not only the processing takes too much time, but it is difficult to form a thick film uniformly, the film tends to crack, and the surface becomes rough.

  Moreover, in metal coating 1b-4b, it is preferable that the total content of a base metal rather than iron and a metal noble than iron is 1-90 mass%. When the total content is less than 1% by mass, sufficient rust prevention performance cannot be obtained, and when it exceeds 90% by mass, the above film thickness is exceeded. The remainder is a mixed substance from the lower phosphate coatings 1a to 4a.

  A lot of minute irregularities are formed on the surfaces of the metal coatings 1b to 4b, but the depth of the recesses is preferably 0.1 to 10 μm. Since the metal coatings 1b to 4b are worn by sliding, if the recess is shallow, the amount of the remaining film is reduced, and the depth of the recess is preferably 0.1 μm or more. However, if the concave portion is deep, the convex portions around the concave portion are high, causing troubles in sliding and generating abnormal noise or being easily worn. Therefore, the depth of the concave portion is preferably 10 μm or less. Moreover, in order to ensure the remaining film amount of the metal coatings 1b to 4b, the diameter of the recess is preferably 0.1 to 20 μm. Furthermore, the number of concave portions or convex portions is preferably 1000 or more per square millimeter. When the number of concave portions or convex portions is small, the diameter of each concave portion or convex portion becomes larger than the above value, which is not preferable. The upper limit of the number of concave portions or convex portions is preferably 100,000 per square millimeter.

  Moreover, since the metal coatings 1b-4b slide and wear, when the surface is rough and a convex part is high, it will become easy to wear. Therefore, the average surface roughness of the metal coatings 1b to 4b is preferably 0.3 μmRa or less, and more preferably 0.2 μmRa or less. In addition, although there is no restriction | limiting in the minimum of the surface roughness of the metal coatings 1b-4b, in order to make it less than 0.1 micrometer, precise surface processing is required and it is not practical.

  In order to achieve such a surface roughness, the particle size and injection pressure of a metal powder lower than iron, a metal powder noble than iron, or an alloy powder may be adjusted. The particle diameter is preferably 10 to 50 μm as an average particle diameter according to JIS R6001, and the injection pressure is preferably 0.2 to 0.9 MPa. Moreover, what is necessary is just to make injection time into 10 to 20 minutes in order to set it as the above-mentioned film thickness.

  By forming the metal coatings 1b to 4b through the phosphate coatings 1a to 4a as described above, it is not necessary to use expensive stainless steel for the inner ring 1, outer ring 2, rolling element 3 and cage 4, Furthermore, since the metal coatings 1b to 4b are formed by the shot peening method, complicated processes such as plating and chromate are not required, and the problem of waste liquid treatment is eliminated. Therefore, it is possible to produce a rolling bearing that can maintain high antirust performance for a long period of time at a low cost.

  Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.

Example 1
Prepare the outer ring of tapered roller bearing “HR32205”, ultrasonically wash in acetone for 10 minutes, then degrease with alkali at 70 ° C. for 2 minutes, further wash with ion-exchanged water, and then in a surface conditioner at 40 ° C. Pretreatment was performed for 40 seconds. In addition, the suspension of the preparene PM55A (30g / L) and PM55B (30g / L) by Nippon Parker Rising Co., Ltd. was used for the surface conditioner. Thereafter, it was immersed in a phosphoric acid aqueous solution (chemical conversion solution) in which manganese ions were dissolved, subjected to chemical conversion treatment at 95 ° C. for 10 minutes, then washed with water and dried to form a manganese phosphate coating having a thickness of 7 μm. . In addition, the total acidity of a chemical conversion liquid is 40, and free acidity is 4.0.

  Next, a mixed powder obtained by mixing equal amounts of zinc powder with an average particle size of 30 μm and tin powder with an average particle size of 30 μm was sprayed on the outer ring on which the manganese phosphate coating was formed at an injection pressure of 0.5 MPa for 20 minutes. A zinc-tin alloy film having a thickness of 1 μm was formed.

  And the outer ring | wheel which formed the zinc-tin alloy film through the manganese phosphate film was integrated in the tapered roller bearing, and the test bearing was produced.

(Example 2)
A test bearing was prepared in the same manner as in Example 1 except that the total acidity of the chemical conversion solution was set to 35 and the free acidity was set to a low value of 3.2 and the thickness of the manganese phosphate coating was set to 4 μm.

(Comparative Example 1)
The tapered roller bearing “HR32205” was directly used as a test bearing.

(Comparative Example 2)
A test bearing was prepared by forming only a zinc-tin alloy film having a thickness of 1 μm by performing shot peening on the outer ring of the tapered roller bearing “HR32205” in the same manner as in Example 1 without forming a manganese phosphate film. Produced.

(Comparative Example 3)
In the same manner as in Example 1, a test bearing was produced by forming only a 7 μm-thickness manganese phosphate coating on the outer ring.

(Comparative Example 4)
In the same manner as in Example 2, a test bearing was manufactured by forming only a 4 μm-thickness manganese phosphate coating on the outer ring.

(Rust test)
According to ASTM D1743, the test bearing was ultrasonically cleaned with petroleum benzine for 5 minutes (twice), and then 5 g of grease was sealed. Then, after continuously rotating for 15 hours at an axial load of 1470 N and a speed of 1000 min ^−1, it was immersed in 2% by weight of salt water for 1 minute, and then placed in a constant temperature and humidity chamber at a temperature of 50 ° C. and a humidity of 95%. The occurrence of rust was observed every predetermined time. The time when rust of 1 mm or more occurred on all roller / outer ring contact surfaces was regarded as the life, and the time until that time was measured. The results are shown in Table 1, and are shown as relative values with respect to the life of Comparative Example 1.

  As shown in Table 1, when only a zinc-tin alloy film was formed as in Comparative Example 2 or when only a manganese phosphate film was formed as in Comparative Examples 3 and 4, an anticorrosion film was formed at all. Although the rust resistance performance is increased by 7 to 13 times compared with Comparative Example 1 that is not, the rust resistance performance is 20 by forming the zinc-tin alloy coating film through the manganese phosphate coating as in the examples. It is improved by ~ 31 times.

(Surface observation A of zinc-tin alloy coating A)
The test bearing of Example 2 was disassembled after continuously rotating at room temperature for 15 hours at a radial load of 0 N, an axial load of 3000 N, and a rotational speed of 1000 min ⁻¹ , and the outer ring raceway surface was observed. FIG. 2 shows the SEM photograph (1000 times) and the results of elemental analysis of the white and black portions of the SEM photograph. The white part corresponds to the original convex part and the black part corresponds to the original concave part, but as shown in the analysis results, most of the white part is iron, and the zinc-tin alloy film and the manganese phosphate coating are worn. The outer ring raceway surface is exposed. On the other hand, since a large amount of zinc and tin, oxygen, phosphorus and manganese are detected in the black portion, and the zinc-tin alloy coating and the manganese phosphate coating remain, the antirust effect due to these can be expected in the future.

  Moreover, the uneven | corrugated state of the surface of a zinc-tin alloy film was investigated about the outer ring raceway surface of the test bearing before a test. The results are shown in FIG. 3, and the diameter of the recess was about several μm to 10 μm, the depth was about 0.1 to 1 μm, and about 10,000 per square meter.

(Surface observation B of zinc-tin alloy coating)
Using the test bearings of Example 1, Example 2, and Comparative Example 2, the outer ring raceway surface was subjected to elemental analysis after being rotated under the same conditions as in the surface observation A of the zinc-tin alloy coating. The results are shown in Table 2.

  When Example 1 and Example 2 are compared, in Example 1, the amount of zinc is almost halved and the amount of tin is also reduced. From this, it can be seen that the sacrificial anticorrosive action by zinc is not particularly sufficient and seems to be related to the life ratio of the rust prevention performance shown in Table 1, and it is not preferable that the phosphate coating is too thick. .

DESCRIPTION OF SYMBOLS 1 Inner ring 1a-4a Phosphate coating 1b-4b Metal coating 2 Outer ring 3 Rolling element 4 Cage 5 Seal material 6 Grease

Claims (8)

  One of an inner ring, an outer ring, a plurality of rolling elements arranged to roll between the inner ring and the outer ring, and an annular seal groove formed on the stationary ring side of either the inner ring or the outer ring. In a rolling bearing having an end fixed, and a seal member having the other end abutting against a sliding surface of a seal groove formed on the rotating ring side of either the outer ring or the inner ring, the inner ring, the outer ring, and the rolling element A surface treatment method comprising a first step of forming a phosphate coating on at least one surface and a second step of shot peening and forming an alloy or mixed powder of a base metal and a noble metal than iron A rolling bearing comprising a coating formed by the above. 2. The rolling bearing according to claim 1, wherein the zinc content of the coating is 5 mass% or more and 80 mass% or less, and the tin content is 95 mass% or less and 20 mass% or more. The rolling bearing according to claim 1 or 2, wherein the phosphate coating is a phosphoric acid Mn coating and has a thickness of 0.1 µm or more and 7 µm or less. The metal lower than iron contains at least one of Al, Zn, Bi, and Mn, and the metal noble than iron contains at least one of Ni, Cr, Cu, Ti, and Sn. The rolling bearing according to any one of claims 1 to 3. The rolling bearing according to claim 1, wherein the other end portion of the seal member has a plurality of lip portions separated by an annular groove portion. The rolling bearing according to claim 1, wherein one end portion of the seal member has a flange portion that covers the seal groove on the stationary wheel side. At least one surface of any one of the inner ring, the outer ring, and the rolling element has 10000 or more and 100000 or less dimples per square millimeter, and the surface of the dimple is 1% by mass or more and 90% by mass or less. The rolling bearing according to claim 1, comprising a metal and a noble metal. The rolling bearing according to claim 1, wherein the dimple has a diameter of 0.1 μm to 20 μm and a depth of 0.1 μm to 10 μm.

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