JP2008057602A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing with superior insulation, capable of preventing early peeling caused by energization or the like even when it is used in a high load condition or the like. <P>SOLUTION: The rolling bearing 1 comprises an inner ring 2, an outer ring 3, and a plurality of rolling elements interposed between the inner ring and the outer ring. Insulating oxide film is formed by a basic treatment liquid on an outer ring inner diameter face (including a rolling face) 3b, an outer ring outer diameter face 3a, and an outer ring end face 3c, and the insulating oxide film is formed by using the basic treatment liquid formed by diluting a treatment agent containing at least sodium nitrite and sodium hydroxide with water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rolling bearing, and more particularly to a rolling bearing having excellent insulating properties.

In recent years, as automobiles become smaller, lighter, and more efficient, electrical components and auxiliary machines are required to have higher performance and higher output without exception. For example, an alternator is required to be used under high-speed rotation conditions in order to compensate for a decrease in output due to downsizing. For this reason, in order to reduce the diameter of the pulley to be used and prevent the transmission efficiency from being reduced, the belt tension is increased. That is, the bearing used for the pulley is required to have a performance that can withstand severe conditions such as high speed rotation and high load.
There have been reports of cases where bearings reach the end of their service life due to the peeling that occurs on the rolling surface when used under such severe conditions. This is because the electric current caused by electromagnetic induction and static electricity caused by friction between the pulley and the belt cause current to flow through the bearing, electrolyzes the grease (lubricant), and the hydrogen generated by this decomposition penetrates the steel, making the metal structure brittle. It has been considered that the mechanism leads to early peeling.
A case has been reported in which a bearing life is successfully improved by forming a chemically stable insulating oxide film on the rolling element surface and inner and outer ring rolling surfaces against this unique early peeling (see Patent Document 1). ).

However, although the insulating oxide film functions effectively for the above-mentioned unique early peeling, from the viewpoint of maintaining the insulating property, the insulating oxide film is formed on the surface of the rolling element or inside and outside. The rolling surface alone is not always sufficient. For example, under a use condition with a large load, the oxide film may become thin due to wear, and the insulation may be deteriorated, and there is a possibility that the insulation performance over a long period cannot be guaranteed. In addition, in order to maintain insulation, in the case where an oxide film is formed only on the inner ring inner surface other than the rolling surface, there is a problem in that the above-described unique early peeling on the rolling surface cannot be prevented.
Japanese Patent Laid-Open No. 4-160225

  The present invention has been made to cope with such a problem, and an object thereof is to provide a rolling bearing excellent in insulation that can prevent early peeling due to energization even when used under high load conditions. .

The rolling bearing of the present invention is a rolling bearing comprising an inner ring and an outer ring, and a plurality of rolling elements interposed between the inner and outer rings, and an insulating oxide film formed on a predetermined portion with a basic treatment liquid, The insulating oxide film is formed on at least one surface selected from a rolling element surface, an inner ring rolling surface and an outer ring rolling surface, and at least one surface selected from an inner ring inner diameter surface and an outer ring outer diameter surface. It is characterized by that.
The insulating oxide film is formed on at least one bearing end surface selected from an inner ring end surface and an outer ring end surface.
The inner ring rolling surface is a sliding surface with the rolling element on the inner ring outer diameter surface, and the outer ring rolling surface is a sliding surface with the rolling element on the inner ring inner diameter surface.

The insulating oxide film is formed by using a basic treatment liquid obtained by diluting a treatment agent containing at least sodium nitrite and sodium hydroxide with water.
The sodium nitrite is mixed in an amount of 10 to 30 parts by weight with respect to 100 parts by weight of the treatment agent.

  The rolling bearing of the present invention is basic on at least one surface selected from the rolling element surface, the inner ring rolling surface and the outer ring rolling surface, and at least one surface selected from the inner ring inner surface and the outer ring outer surface. Since the chemically stable insulating oxide film is formed using the treatment liquid, the insulating property can be maintained even if the insulating oxide film on the rolling contact surface becomes thin due to wear under a heavy load. For this reason, it has the effect of preventing energization from a generator such as an alternator, and can prevent the decomposition of the lubricant / grease that causes generation of hydrogen. As a result, early peeling due to energization can be prevented. Further, by preventing the intrusion of hydrogen generated by the coating itself, the bearing life can be improved as compared with the untreated bearing.

Provide a bearing that can maintain sufficient insulation, that is, insulation that can prevent premature delamination due to energization, even if the insulating oxide film on the rolling surface becomes thin due to wear under heavy load conditions We studied as much as possible. As a result, it was found that a bearing having an insulating oxide film formed not only on the rolling element surface and the bearing rolling surface but also on the inner ring inner diameter surface or the outer ring outer diameter surface has improved insulation performance and bearing life. Furthermore, it has been found that insulating performance and bearing life are improved by forming an insulating oxide film on the inner or outer diameter end face.
In addition to the rolling element surface and bearing rolling surface, an insulating oxide film is also formed on the inner ring inner diameter surface or outer ring outer diameter surface to prevent energization between the shaft and bearing inner ring or between the outer ring and housing. It is considered that surface treatment is also applied to the inner or outer diameter end surface, so that the current supply to the contact surface with the shaft or housing is completely cut off, so that early peeling due to current supply can be prevented. Conceivable. The present invention is based on such knowledge.

The rolling bearing of the present invention is a rolling bearing comprising an inner ring and an outer ring, and a plurality of rolling elements interposed between the inner and outer rings, and having an insulating oxide film formed on a predetermined portion with a basic treatment liquid, The insulating oxide film is formed on at least one surface selected from an inner ring rolling surface and an outer ring rolling surface and at least one surface selected from an inner ring inner surface and an outer ring outer surface.
The insulating oxide film formed by the above-mentioned basic treatment liquid is a chemically stable triiron tetroxide film, which prevents the catalytic decomposition of grease caused by the generation of a new surface and prevents the steel from becoming brittle by hydrogen. It is for prevention. This triiron tetroxide has high insulation properties and has an effect of preventing energization from a generator such as an alternator, and can prevent decomposition of a lubricant and grease that cause hydrogen generation. Further, by preventing the intrusion of hydrogen generated by the triiron tetraoxide coating itself, the bearing life can be improved as compared with a non-treated bearing.

Embodiments of the rolling bearing of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a deep groove ball bearing showing an embodiment of the present invention. 2 to 4 are sectional views of deep groove ball bearings showing other embodiments of the present invention.
A rolling bearing 1 shown in FIG. 1 includes an inner ring 2 and an outer ring 3 arranged concentrically, a rolling element 4 interposed between the inner ring 2 and the outer ring 3, a cage 5 that holds the rolling element 4, and inner and outer rings. The seal member 6 that seals the opening portions at both ends in the axial direction and the lubricating grease 7 sealed in the bearing space. An insulating oxide film is formed on the outer ring inner surface (including the rolling surface) 3b, the outer ring outer surface 3a, and the outer ring end surface 3c with a basic treatment liquid.

  The rolling bearing 11 shown in FIG. 2 includes an inner ring 12 and an outer ring 13 arranged concentrically, a rolling element 14 interposed between the inner ring 12 and the outer ring 13, a cage 15 that holds the rolling element 14, and inner and outer rings. The seal member 16 seals the opening portions at both ends in the axial direction, and the lubricating grease 17 sealed in the bearing space. An insulating oxide film is formed on the inner ring outer diameter surface (including the rolling surface) 12b, the inner ring inner diameter surface 12a, and the inner ring end surface 12c with a basic treatment liquid.

  The rolling bearing 21 shown in FIG. 3 includes an inner ring 22 and an outer ring 23 arranged concentrically, a rolling element 24 interposed between the inner ring 22 and the outer ring 23, a cage 25 that holds the rolling element 24, and inner and outer rings. The seal member 26 seals the opening portions at both ends in the axial direction, and the lubricating grease 27 sealed in the bearing space. An insulating oxide film is formed on the outer ring inner diameter surface (including the rolling surface) 23b and the outer ring outer diameter surface 23a with a basic treatment liquid.

  A rolling bearing 31 shown in FIG. 4 includes an inner ring 32 and an outer ring 33 arranged concentrically, a rolling element 34 interposed between the inner ring 32 and the outer ring 33, a cage 35 that holds the rolling element 34, and inner and outer rings. The seal member 36 that seals the opening portions at both ends in the axial direction and the lubricating grease 37 sealed in the bearing space. An insulating oxide film is formed by a basic treatment liquid on the outer ring outer diameter surface 33a and the rolling element surface 34a.

  The rolling bearing 41 shown in FIG. 5 includes an inner ring 42 and an outer ring 43 arranged concentrically, a rolling element 44 interposed between the inner ring 42 and the outer ring 43, a retainer 45 that holds the rolling element 44, and inner and outer rings. The seal member 46 seals both axial end openings and the lubricating grease 47 sealed in the bearing space. Inner ring outer diameter surface (including rolling surface) 42b, outer ring inner diameter surface (including rolling surface) 43b, inner ring inner diameter surface 42a, outer ring outer diameter surface 43a, inner ring end surface 42c, outer ring end surface 43c, and rolling element An insulating oxide film is formed on the surface 44a with a basic treatment liquid.

A method for forming an insulating oxide film with a basic treatment liquid will be described below. A high-concentration sodium hydroxide aqueous solution (basic treatment solution) is heated, and base materials such as inner rings, outer rings, and rolling elements, which have been subjected to degreasing, cleaning, and temperature adjustment, are formed. In the case where a film is formed only on a predetermined part, a masking tape is applied in advance to a part of the base material that does not require a film, and then it is introduced. After a predetermined treatment time has elapsed, the substrate is taken out and neutralized and washed with hot water.
By this treatment, an insulating oxide film of black triiron tetraoxide Fe ₃ O ₄ is formed on the substrate surface.

The typical reaction mechanism at this time is considered to proceed in the following three stages (see Metal Surface Technology Handbook (new edition), Nikkan Kogyo Shimbun, p. 818, edited by Metal Surface Technology Association).

4 Fe + 3 O ₂ → 2 Fe ₂ O ₃ --- (1)
2 Fe ₂ O ₃ + 8 NaOH + O ₂ → 4 Na ₂ FeO ₄ + 4 H ₂ --- (2)
3 Na ₂ FeO ₄ + 5 H ₂ → Fe ₃ O ₄ + 6 NaOH + 2 H ₂ O --- (3)

Here, as a treatment condition, the temperature of the treatment liquid is preferably 125 ° C. or higher and lower than 150 ° C., and more preferably 130 ° C. or higher and lower than 145 ° C. When the processing temperature is less than 125 ° C., the reaction proceeds slowly and the oxide film formed by the processing is thin, so that sufficient insulation cannot be maintained. In addition, when the processing temperature is 150 ° C. or higher, the reaction proceeds remarkably and becomes the main cause of increasing the surface roughness, leading to a decrease in bearing life.
The processing time is preferably over 5 minutes. When the treatment time is 5 minutes or less, the oxide film formed by the treatment is very thin, and sufficient insulation cannot be maintained, and hydrogen embrittlement cannot be prevented.

In the present invention, it is preferable to use a basic treatment liquid in which sodium nitrite is blended as a reducing agent in a high concentration aqueous sodium hydroxide solution. Sodium nitrite acts as a reducing agent, adjusts the reaction rate of the above formulas (1) and (2) and rapidly reduces Na ₂ FeO ₄ produced by formula (2) using formula (3). Generation of ferric trioxide Fe ₂ O ₃ can be suppressed by generating triiron tetraoxide Fe ₃ O ₄ . As a result, it is formed as an oxide film whose surface roughness is not increased. This eliminates the need for the conventional grinding treatment for finishing the surface roughness of the oxide film, and can be used with the thickness of the formed oxide film, so that sufficient insulation can be maintained and hydrogen embrittlement can be maintained. It is possible to effectively prevent the surface of the bearing sliding surface from peeling off.

Example 1
Sodium hydroxide (Wako Pure Chemical Industries, Ltd.) 60 parts by weight, sodium nitrite (Wako Pure Chemical Industries, Ltd.) 25 parts by weight, sodium nitrate (Wako Pure Chemicals Co., Ltd.) 15 parts by weight Reagents were mixed in a commercially available juicer mixer. The resulting solution was diluted with water to a concentration of 1.0 kg / 1.0 L to obtain a basic treatment solution. A bearing outer ring (Model No. 6203, steel type SUJ2 manufactured by NTN) was used as a test piece, heat-treated at 140 ° C., washed, and the corresponding inner ring, steel ball, and cage were assembled into a ball bearing. And the electrical resistance value between an outer ring | wheel / inner ring | wheel was measured using the commercially available tester. In addition, 1.9 g of lubricating grease (aromatic urea grease manufactured by Kyodo Yushi Co., Ltd., trade name: Multemp ET130) is sealed in the above bearing, a non-contact seal member is assembled, and a test bearing for a rapid acceleration / deceleration test (see Fig. 1) It was. This test bearing was subjected to the following rapid acceleration / deceleration test, and the bearing life time was measured. The results are also shown in Table 1.

<Rapid acceleration / deceleration test>
A rapid acceleration / deceleration test of a rolling bearing that supports a rotating shaft that supports a pulley around which a rotating belt of an alternator, which is an example of an electrical auxiliary machine, is wound with an inner ring using a test bearing was performed. The rapid acceleration / deceleration test conditions were set at 1960 N for the load applied to the test bearing attached to the tip of the rotating shaft, the operating speed was set to 0 rpm to 18000 rpm, and a current of 0.1 A flows through the test bearing. The test was carried out in the state. Then, the bearing life time (h) was defined as the time during which abnormal peeling occurred in the test bearing, the vibration of the vibration detector exceeded 3 times the initial test value, and the generator stopped. The test was terminated in 500 hours.

Example 2
The test obtained in the same manner as in Example 1 except that the surface treatment location in Example 1 was changed from the bearing outer ring to the bearing inner ring (model number 6203, steel type SUJ2 manufactured by NTN) and presented in the electrical resistance test. The bearing (see FIG. 2) was subjected to a rapid acceleration / deceleration test. The results are also shown in Table 1.

Example 3
The bearing in which the masking tape is pasted on the outer ring end face of the bearing in the first embodiment is treated in the same manner as in the first embodiment, and after washing and drying, the tape is removed and the other sections are assembled. The test bearing (see FIG. 3) obtained was subjected to a rapid acceleration / deceleration test. The results are also shown in Table 1.

Example 4
In Example 1, the masking tape was applied to the outer ring inner diameter surface and the outer ring end surface of the bearing, and the surface treatment locations were changed to the outer ring outer diameter surface and the rolling element surface. The tape was removed and the other sections were assembled and subjected to an electrical resistance test as an untreated outer ring inner surface and outer ring end face bearing, and the obtained test bearing (see FIG. 4) was subjected to a rapid acceleration / deceleration test. The results are also shown in Table 1.

Comparative Example 1
The bearing (model number 6203, steel type SUJ2 manufactured by NTN) was directly subjected to the electrical resistance test without surface treatment, and the obtained test bearing (see FIG. 6) was subjected to a rapid acceleration / deceleration test. The results are also shown in Table 1.

Comparative Example 2
In Example 1, the outer ring outer diameter surface and the outer ring end surface with masking tape attached were treated in the same manner as in Example 1, and after washing and drying, the tape was removed and the other sections were assembled. The surface and outer ring end face untreated bearings were subjected to an electrical resistance test, and the obtained test bearings (see FIG. 7) were subjected to a rapid acceleration / deceleration test. The results are also shown in Table 1.

In each example and each comparative example, the electrical resistance value increases with the lapse of processing time, but Example 1 in which an insulating oxide film was formed on the entire outer ring surface and Example in which an insulating oxide film was formed on the entire inner ring surface 2 is larger in electrical resistance value than Comparative Example 1 in which an insulating oxide film was not formed on the inner and outer rings and Comparative Example 2 in which an insulating oxide film was formed only on the inner surface of the outer ring, and an insulating film was formed. I found out. When the influence of the portion of the outer ring surface on which the insulating oxide film is formed is seen, Example 3 having an insulating oxide film on the outer ring outer diameter surface and the outer ring inner diameter surface has an insulating oxide film on the entire outer ring surface. The bearing life was inferior to that of Example 1, but it was clearly longer than that of the outer ring inner diameter surface (including rolling surface) shown in Comparative Example 2.
It was found that Example 1 and Example 2 showed a longer bearing life than Comparative Example 1 and Comparative Example 2 in the rapid acceleration / deceleration test (energization amount 0.1 A). Together with the electrical resistance test, it was possible to prevent energization by forming an insulating oxide film on the end surface of the outer ring in addition to the raceway surface, thereby preventing premature delamination.
In Example 4, the outer ring outer diameter surface and the rolling element were subjected to surface treatment, but it was found that, as in Examples 1 to 3, there is an effect of preventing energization and premature delamination associated therewith. It was.

  Since the rolling bearing of the present invention is excellent in insulation, it is suitable as a bearing used in various industrial machines that receive both high-speed rotation and high load, particularly as a bearing used in automotive electrical equipment and auxiliary equipment that requires electrical insulation, such as an alternator. Available to:

It is sectional drawing of the deep groove ball bearing which shows one Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other Example of this invention. It is sectional drawing of the deep groove ball bearing which shows the comparative example of this invention. It is sectional drawing of the deep groove ball bearing which shows the other comparative example of this invention.

Explanation of symbols

1, 11, 21, 31, 41 Rolling bearings 2, 12, 22, 32, 42 Inner ring 3, 13, 23, 33, 43 Outer ring 3a, 23a, 33a, 43a Outer ring outer diameter surface 3b, 23b, 43b Outer ring inner diameter surface 3c, 43c Outer ring end face 4, 14, 24, 34, 44 Rolling element 5, 15, 25, 35, 45 Cage 6, 16, 26, 36, 46 Seal member 7, 17, 27, 37, 47 Lubricating grease 12a 42a Inner ring inner surface 12b, 42b Inner ring outer surface 12c, 42c Inner ring end surface 34a, 44a Rolling element surface

Claims (4)

A rolling bearing comprising an inner ring and an outer ring, and a plurality of rolling elements interposed between the inner and outer rings, wherein an insulating oxide film is formed with a basic treatment liquid at a predetermined site,
The insulating oxide film is formed on at least one surface selected from a rolling element surface, an inner ring rolling surface and an outer ring rolling surface, and at least one surface selected from an inner ring inner diameter surface and an outer ring outer diameter surface. A rolling bearing characterized by that.   The rolling bearing according to claim 1, wherein the insulating oxide film is formed on at least one bearing end surface selected from an inner ring end surface and an outer ring end surface.   3. The rolling according to claim 1, wherein the insulating oxide film is formed by using a basic treatment liquid in which a treatment agent containing at least sodium nitrite and sodium hydroxide is diluted with water. bearing.   The rolling bearing according to claim 3, wherein the sodium nitrite is blended in an amount of 10 to 30 parts by weight with respect to 100 parts by weight of the treatment agent.

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