JP2008008434A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing in which damage to members caused by a creep phenomenon on a fitting surface and local pulsation displacement. <P>SOLUTION: This rolling bearing comprises an inner ring and an outer ring formed of steel, and a rolling body rollingly held through a holder between the inner ring and the outer ring. In the rolling bearing, a first coating containing an oxide or a hydroxide of a predetermined metal element, and a fluorine element is overlaid on at least the fitting circumferential surface of the inner ring or the outer ring of which the fit to a housing or a shaft supporting the rolling bearing is loose fit at a predetermined thickness; a second coating of predetermined solid lubrication is overlaid on the surface of the coating; a coating containing an oxide or a hydroxide containing at least one kind of a metal element within Zr, Ti and Si, and a fluorine element is used for the first coating; and a coating formed of at least a fluorine-containing polymer-coated or molybdenum disulfide-coated coating is used for the second coating. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rolling bearing in which damage to a member due to a creep phenomenon on a mating surface and local pulsation displacement is reduced.

In general, a rolling bearing is composed of an inner ring and an outer ring as raceway rings, and a rolling element made of a ball or a roller that is movably held via a cage between the inner ring and the outer ring. The fitting with the housing or the shaft as a support member for supporting the bearing is a JIS fit on the rotating side of the race, and a JIS clearance fit on the stationary side.
Therefore, relative sliding or slight tapping vibration is likely to occur between the bearing ring (for example, outer ring) on the clearance fit side and the support member depending on the load condition, etc., and damage to the member due to creep or fretting phenomenon, etc. May occur. In order to prevent this, various means have been studied conventionally.
Recently, a thermosetting resin film, a fluoropolymer film, or the like is coated on the circumferential surface of the race ring on the clearance fit side to cope with creep between the housing and the race ring. (For example, see Patent Document 1)
Furthermore, in order to achieve adhesion of the coating with the raceway surface, a phosphate coating is applied as a base layer of the coating.
JP 2002-266870 A

As mentioned above, as a countermeasure against damage due to the creep phenomenon of rolling bearings, etc., a solid lubricant layer is basically provided on the peripheral surface of the bearing ring. In rolling bearings used for automobiles, etc., due to their longevity and maintenance, etc., the creep generation conditions are becoming stricter, and the conventional coating method is not necessarily sufficient. It is coming.
In addition, the phosphate coating as an undercoat layer of the coating is superior in terms of adhesion of the coating, but due to the more severe use conditions, the conventional creep phenomenon, etc. Stress displacement behavior (hereinafter referred to as “local pulsation displacement”) due to circumferential movement (pulsation) of local elastic deformation (mountain deformation) generated in the raceway by rolling elements such as rolling causes problems such as delamination within the coating. This may cause a problem as a bearing.

  In view of the above, the present invention provides a rolling bearing that not only copes with the creep phenomenon of the conventional rolling bearing but also has excellent durability including adhesion resistance against local pulsation displacement and damage to the coating layer. Has its purpose.

The rolling bearing of the present invention is
1) In a rolling bearing comprising an inner ring and an outer ring made of steel, and a rolling element that is movably held via a cage between the inner ring and the outer ring, the fitting with a housing or a shaft that supports the rolling bearing A predetermined thickness of a first metal oxide or hydroxide coating is coated on at least the fitting peripheral surface of the inner ring or outer ring, which is a loose fit, and a predetermined solid lubricant is formed on the surface of the coating. The second coating is coated with a predetermined thickness.

2) In the above 1), the first coating is formed on the inner peripheral surface of the inner ring or the outer peripheral surface of the outer ring when the rolling element abuts on the inner ring or the outer ring raceway due to the bearing load and revolves in the circumferential direction. Due to the elastic displacement of the raceway moving in the direction, the film strength is greater than the tensile stress generated in the first coating,
3) In the above 1) or 2), the first coating of the oxide or hydroxide of the predetermined metal comprises an oxide or hydroxide containing at least one metal element of Zr, Ti or Si, and fluorine. A coating containing an element, and the second coating of a predetermined solid lubricant is a coating comprising at least a fluorine-containing polymer coating or a molybdenum disulfide-containing coating,
4) In the above 1) to 3), the coating amount of the first coating of the predetermined metal oxide or hydroxide is 20 to 200 mg / m ² as each of the metal elements, and oxidation of the predetermined metal The molar weight ratio of the fluorine element and the metal element in the coating of the product or hydroxide is in the range of 0.1 to 0.5,
5) In the above 1) to 4), the predetermined thickness of the first coating is 0.05 to 0.1 μm, and the predetermined thickness of the second coating is 10 to 50 μm.

  In other words, the present invention basically provides a solid lubricant consisting of at least a fluorine-containing polymer coating or a molybdenum disulfide-containing coating, which has a proven track record in creeping and fretting phenomena. The material layer is applied as the outermost surface layer (second coating), and the underlying layer (first coating) is superior to the conventional surface adhesion, but has a relatively low allowable shear stress in the layer. Instead of the phosphate coating, the oxide or hydroxide coating containing at least one metal element of Zr, Ti or Si (preferably Zr or Ti) is combined.

That is, according to the present invention, in the rolling bearing, for the coating specifications under severe conditions of the first coating and the second coating, basically, at least one metal element of Zr, Ti or Si is used as the first coating. The coating of oxide or hydroxide is applied, and the optimum coating conditions for the first coating and the second coating are found and set based on the results of many experiments.
In particular, attention is paid to the local pulsation displacement due to rolling elements (balls, rollers) of a rolling bearing, and the specification is set by taking into consideration the influence on the first and second films.

  In the present invention, a film containing an oxide or hydroxide containing at least one metal element of Zr, Ti or Si (preferably Zr or Ti) and a fluorine element is used as a first film, and at least on Provided is a rolling bearing that can be expected to have an effect superior to problems due to local pulsation displacement by combining a solid lubricant layer (second coating) comprising a fluorine-containing polymer coating or a molybdenum disulfide-containing coating. Can do.

[Embodiment 1]
FIG. 1 is an explanatory view showing, in section, an example of a rolling bearing according to Embodiment 1 of the present invention.
FIG. 2 is an enlarged cross-sectional explanatory view of a part of the rolling wheel having a slip fit in FIG.
FIG. 3 is an explanatory diagram showing an outline of local pulsation displacement in a load state of the rolling bearing.
In the figure, 1 is a rolling bearing, 2 is an outer ring, 3 is an inner ring, 4 is a rolling element (ball), 5 is a cage, 6 is a coating, 61 is a first coating, 62 is a second coating, P is a load distribution, Pmax is the maximum load and ε is the maximum elastic displacement.

In the figure, the rolling bearing 1 is basically composed of a rolling element 4 that is rotatably held via an outer ring 1, an inner ring 2 and a cage 5. The outer ring and the inner ring are made of a steel material such as bearing steel. As the rolling element, for example, steel materials such as bearing steel and various materials such as ceramics can be applied.
Each of the outer ring 2 and the inner ring 3 is engaged with a housing or a shaft with an appropriate fit. In the normal rolling bearing 1, for example, the inner ring 3 is engaged with the drive shaft by an interference fit fit according to JIS, and the outer ring 2 is engaged to the housing for assembly and maintenance by a clearance fit according to JIS. Yes.

Therefore, when a rotational load is applied, there is a high possibility that the loose fit side with a loose fit will move relatively, so that a so-called bearing creep phenomenon and fretting phenomenon occur, resulting in damage to the member.
In addition, for example, as shown in FIG. 3, in the case of the inner ring rotation drive, the conventional creep phenomenon ("creep on the rotating wheel side" or "creep due to rotation"), for example, between the outer ring 1 and the housing that supports it. In addition, the above-described local pulsation displacement is generated by the rolling element 4 receiving the load.
This local pulsation displacement is generated by a local maximum load Pmax by the rolling element 4, and the maximum elastic displacement ε of the outer ring 2 due to this local movement moves in the accompanying direction of the outer ring 1. This local pulsation displacement becomes a cause of breakage in the layer of the first coating 61.

  The crystalline phosphate coating used as the conventional first coating 61 does not necessarily have sufficient durability against this local pulsation displacement, and the present applicant has found that Zr, Ti Alternatively, it has been found that Si (preferably an oxide or hydroxide film containing at least one metal element of Zr or Ti) is extremely effective against local pulsation displacement.

The following tests were carried out for the coating conditions of the first coating 61 of the rolling bearing in the present embodiment.

Test 1;
In order to consider the effects and countermeasures of the so-called local pulsation displacement generated in the bearing, the state of coating film peeling was observed by a bending test in place of the local pulsation displacement.
1) Test piece The test piece used SPCC as a steel material, and the size used the thing of 150x70x0.8mm.
2) Surface treatment (1) Zr adhesion amount 10 mg / m ² + Pallube F1457 (baking conditions 170 ° C. 180 minutes)
(2) Zr adhesion amount 20mg / m ² + Pallube F1457 (Same as above)
(3) Zr adhesion amount 200mg / m ² + Pallube F1457 (Same as above)
(4) Zr adhesion amount 300mg / m ² + Pallube F1457 (Same as above)
(5) Fine manganese phosphate coating + PALLUBE F1457 (Same as above)
The adhesion amount was controlled by changing the chemical conversion treatment time with the chemical conversion treatment liquid described below.
In addition, the film thickness of PalLube F1457 was set to 50 μm (constant).
3) Chemical conversion liquid Component name Addition method Zr Hexafluorozirconic acid (IV) aqueous solution Ti Hexafluorotitanic acid (IV) aqueous solution F Hydrofluoric acid pH Prepared with sodium hydroxide (pH = 4.0)

An aqueous solution having a zirconium concentration of 200 ppm and a total fluorine concentration of 300 ppm was prepared using a hexafluorozirconic acid (IV) aqueous solution and a hydrofluoric acid reagent. The aqueous solution was heated to 40 ° C. and further adjusted to pH 4.0 with a sodium hydroxide reagent was used as a chemical conversion treatment solution.
4) Test method A test was conducted in accordance with JISK5400.
The mandrel was subjected to a bending test using 0.8 mm due to our jig.

5) Test results

4a and 4b are diagrams in which the results of the test 1 are compared by appearance photographs.
As shown in Table 1 from the results of FIGS. 4a and 4b, partial peeling was observed at Zr deposition amounts of 10 mg / m ² and 300 mg / m ² , and the Zr deposition amount was 20 mg / m ^{2 to} 200 mg / m ^2. It has been found that a range of m ² is preferred.
In addition, the improvement with respect to peeling was recognized with respect to the manganese phosphate film.

Test 2;
An adhesion evaluation test was conducted when the molar weight ratio of the metal elements Zr and Ti and the fluorine element as a coating was changed.
1) Test piece SPCC (Cold rolled steel sheet: JIS-G-3141)
2) Surface treatment and measurement method Surface treatment is performed by the same component name and addition method as the chemical conversion treatment liquid in Test 1, and the adhesion amount is changed by changing the adhesion amount of the metal element and the molar weight ratio of (fluorine element / metal element). Compared.
In addition, the measuring method of the adhesion amount of a coating metal element was performed using the fluorescent-X-ray-analysis apparatus (System 3270 by Rigaku Corporation).
The molar weight ratio of (fluorine element / metal element) is measured using an X-ray photoelectron spectrometer (ESCA850 manufactured by Crates Co., Ltd.) to measure the molar weight ratio of fluorine element and metal element on the surface of the surface treatment coating layer. I asked for it.
Values of the adhesion amount (mg / m ² ) and (fluorine element / metal element) molar weight ratio of the metal element of each sample number are as follows.

Sample number Amount of metal element attached (mg / m ² ) (Fluorine element / Metal element)
ZrTi molar weight ratio 1 21 0 0.11
2 85 0 0.15
3 0 68 0.15
4 183 0 0.48
5 350 0 0.26
6 88 0 0.07
7 92 0 0.56

3) Adhesion evaluation method Cut 100 grids at 1 mm intervals on the surface of the test piece after coating with solid lubricant with a sharp cutter, peel the grids with adhesive tape, and count the number of remaining unstriped grids. .

4) Test results

Table 2 is a chart showing the results of Test 2.
As is apparent from Table 2, excellent adhesion is exhibited when the molar weight ratio k is in the range of about 0.1 to 0.5. However, when there is too much Zr, adhesiveness will fall (sample number 5).
When the molar weight ratio k is less than 0.1 and the molar weight ratio exceeds 0.5, the adhesion is lowered. Therefore, the molar weight ratio k is preferably in the range of about 0.1 to 0.5 for adhesion.
In addition, in the test result according to the above by the conventional phosphate coating performed as a separate test, the result almost the same as the result in the above test number 5 (adhesion about 70% with respect to the sample numbers 1 to 4) is obtained. ing.
Therefore, the first coating of the present invention can be expected to have a good degree of adhesion as compared with the conventional phosphate coating.

Moreover, the test according to the said test 1 and 2 was implemented also when the metallic element was Si compound. Compared to the case of the metal elements Zr and Ti, almost the same result was confirmed in the bending test result substituted for the local pulsation displacement. However, in the adhesion evaluation test, the variation in test data was slightly larger than in the case of the metal elements Zr and Ti.
Accordingly, the first coating 61 of the rolling bearing of the present invention is limited to an oxide or hydroxide coating containing at least one metal element of Zr, Ti or Si, but has a failure rate of ppm. For applications such as automobiles, Zr or Ti is more preferable as the metal element.

Rolling bearing; 6212 type first coating; using the chemical conversion treatment liquid in Test 1 above.
Component name Addition method Zr Hexafluorozirconic acid (IV) aqueous solution Ti Hexafluorotitanic acid (IV) aqueous solution
F Hydrofluoric acid pH Prepared with sodium hydroxide (pH = 4.0)
surface treatment;
An aqueous solution having a zirconium concentration of 200 ppm and a total fluorine concentration of 300 ppm was prepared using a hexafluorozirconic acid (IV) aqueous solution and a hydrofluoric acid reagent. The aqueous solution was heated to 40 ° C. and further adjusted to pH 4.0 with a sodium hydroxide reagent was used as a chemical conversion treatment solution.
The outer ring of the 6212 type rolling bearing that has been degreased and washed with water is immersed in the surface treatment liquid for 180 seconds to deposit a surface treatment film layer, and then washed with water, ion-exchanged water, and further dried, and the treatment liquid and Water was removed. The outer ring on which the surface-treated film layer was deposited was coated with a fluorine-based solid lubricant paint (Deflick Coat FH-70, manufactured by Kawamata Laboratories) as the second film 62 so as to have a film thickness of 50 μm. Further, after coating, baking was performed at 180 ° C. for 60 minutes to obtain a test material.

Durability test: A long-term durability test was performed under a load condition giving a local pulsation displacement ε of about 5 μm.
For comparison, a conventional test piece in which a conventional manganese phosphate coating was used as the first coating 61 and a fluorine-based solid lubricating paint similar to the above was applied as the second coating 62 under the same conditions was tested in parallel.
The fitting dimensions with the housing were the same.

In the comparative sample, blistering occurred at the circumferential center of the outer ring and the second coating and a part of the first coating were peeled off during the endurance time approximately twice the calculated life time.
Fig.5 (a) is a figure which shows the condition after completion | finish of the endurance test of a comparative sample, and FIG.5 (b) is a figure which shows the solid lubricant film peeling condition of the blister part.
In contrast, the specimen of this example maintains a stable coating state without any defects such as blistering and scuffing even after the end of the durability test that is set as the test cutoff time, which is three times the calculated life time. It was confirmed that

  In the above description, it has been described mainly for rolling bearings under severe conditions such as those for automobiles, but it can be sufficiently applied to general rolling bearings under high load and high speed conditions.

It is explanatory drawing which shows an example of the rolling bearing in Embodiment 1 of this invention in a cross section. FIG. 2 is an enlarged cross-sectional explanatory view of a part of a rolling wheel having a slip fit in FIG. 1. It is explanatory drawing which shows the outline | summary of the local pulsation displacement in the load state of a rolling bearing. It is the figure which compared the result of Test 1 with the appearance photograph. It is the figure which compared the other result of the test 1 with the external appearance photograph. It is a figure which shows the state of the blister of a comparative test sample in an endurance test, and the state of peeling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Outer ring 3 Inner ring 4 Rolling element (ball)
5 Cage 6 Coating 61 First Coating 62 Second Coating P Load Distribution Pmax Maximum Load ε Maximum Elastic Displacement

Claims (5)

  In a rolling bearing comprising an inner ring and an outer ring made of steel, and a rolling element that is movably held via a cage between the inner ring and the outer ring, the fit between the housing or the shaft that supports the rolling bearing is a clearance. A first coating of a predetermined metal oxide or hydroxide is coated on at least the fitting peripheral surface of the inner ring or outer ring, which is a fit, with a predetermined thickness, and a predetermined solid lubricant is coated on the surface of the coating. A rolling bearing characterized in that two coatings are coated to a predetermined thickness.   The first coating of the track ring that moves in the circumferential direction generated on the inner peripheral surface of the inner ring or the outer peripheral surface of the outer ring when the rolling element abuts against the race ring of the inner ring or the outer ring by a bearing load and revolves in the circumferential direction. The rolling bearing according to claim 1, wherein the rolling bearing has a film strength larger than a tensile stress generated in the first coating due to elastic displacement.   The first coating of the oxide or hydroxide of the predetermined metal is a coating containing an oxide or hydroxide containing at least one metal element of Zr, Ti, or Si and a fluorine element, The second coating of the predetermined solid lubricant is a coating comprising at least a fluorine-containing polymer coating or a molybdenum disulfide-containing coating. The rolling bearing according to claim 1 or 2. The coating amount of the first coating of the predetermined metal oxide or hydroxide is ²⁰ to 200 mg / m ² as the respective metal elements, and fluorine in the coating of the predetermined metal oxide or hydroxide The rolling bearing according to any one of claims 1 to 3, wherein a molar weight ratio between the element and the metal element is in a range of 0.1 to 0.5. The predetermined thickness of the first coating is 0.05 to 0.1 μm, and the predetermined thickness of the second coating is 10 to 50 μm. Rolling bearings as described in

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