JPH1082426A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a sufficient durability even in a corrosive solution. SOLUTION: An outer race 3, inner race 5 and rolling body 6 are made of the seramic of silicon carbide and a retainer 7 is made of a fluorine resin. A dynamic equivalent load added at the using time is made to 5% or less of a dynamic rated load. Sufficient durability can be ensured even in a corrosive solution by that the silicon carbide seramic provides excellent anti-corrosive property and the fluorine resin provides excellent lubricant property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A rolling bearing according to the present invention constitutes a rotation support portion of a manufacturing apparatus for chemical fibers, films, etc., and is used in a corrosive aqueous solution such as an acid or an alkali or when the manufacturing apparatus is used. The present invention relates to an improvement in a rolling bearing used in a corrosive environment such as a portion to which (corrosive aqueous solution) is applied or in a corrosive gas such as steam generated by evaporation of the corrosive aqueous solution. In particular, the invention relates to oils,
It is intended to improve the durability of a rolling bearing used in an environment where conventional lubricants such as grease cannot be used.

[0002]

2. Description of the Related Art Rolling bearings having a structure as shown in FIG. The rolling bearing 1 is provided so as to be able to roll freely between an outer race 3 having an outer raceway 2 on an inner peripheral surface, an inner race 5 having an inner raceway 4 on an outer peripheral surface, and between these outer raceways 2 and the inner raceway 4. It comprises a plurality of rolling elements 6 and a retainer 7 which holds the plurality of rolling elements 6 so as to freely roll. Such a rolling bearing 1
For example, the outer ring 3 is internally fixed to a housing (not shown), and the inner ring 5 is externally fixed to a rotating shaft (not shown), so that the rotating shaft is rotatably supported with respect to the housing.

A rolling bearing used in a corrosive environment, such as in an aqueous solution of an acid or an alkali or a part to which the liquid is applied, or in steam generated by evaporation of the corrosive aqueous solution, has conventionally been disclosed in Japanese Patent Application Laid-Open (JP-A) Nos. 10-26191 and 11-213873. 62-56620
And Japanese Patent Application Laid-Open No. 7-174143 are known. Of these, Japanese Patent Application Laid-Open No. Sho 62-566
In the rolling bearing described in Japanese Patent Publication No. 20, at least one of the outer ring, the inner ring, and the rolling elements is made of a ceramic of silicon carbide, and the remaining parts are made of a ceramic of silicon nitride. On the other hand, Japanese Patent Laid-Open No. 7-174143
In the rolling bearing described in Japanese Patent Application Laid-Open Publication No. H10-209, each constituent member is made of a silicon nitride-based ceramic.

[0004]

However, in a rolling bearing made of a silicon nitride-based ceramic as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-174143, the particles of the silicon nitride-based ceramic are treated with a strong acid or a strong alkali. The field is corroded. In addition, since silicon nitride itself elutes in high-temperature and high-pressure water, the hardness and strength of the surface are reduced, and abrasion and cracks occur in components due to rolling contact. As a result, the durability of the rolling bearing cannot be sufficiently ensured. or,
The rolling bearing described in Japanese Patent Application Laid-Open No. Sho 62-56620, in which a ceramic component made of silicon carbide and a ceramic component made of silicon nitride are combined, cannot provide sufficient lubricating performance as it is, and is not suitable for actual use conditions. Below, sufficient durability cannot be ensured, for example, the progress of abrasion becomes remarkable, or cracks and peeling are likely to occur. In view of such circumstances, the rolling bearing of the present invention is intended for securing sufficient corrosion resistance even in a corrosive environment, and for securing sufficient durability by securing required lubricity. It is a thing.

[0005]

According to the present invention, there is provided a rolling bearing comprising:
Similarly to the above-described conventional rolling bearing, an outer ring having an outer ring raceway on the inner peripheral surface, an inner ring having an inner ring raceway on the outer peripheral surface, and a plurality of rollers provided rotatably between the outer ring raceway and the inner ring raceway. A rolling element; and a retainer for rotatably holding the plurality of rolling elements. Further, the rolling bearing of the present invention is used in a corrosive liquid containing water or a part to which the liquid is splashed, or in a corrosive gas containing water vapor. In particular, in the rolling bearing of the present invention, the outer ring, the inner ring, and the rolling elements are each made of silicon carbide ceramic, and at least the surface of the cage is made of a fluorine resin. And it is used under the condition that the dynamic equivalent load applied during use is 5% or less of the dynamic rated load.

[0006]

In the case of the rolling bearing of the present invention, all of the silicon carbide forming the outer ring, the inner ring and the plurality of rolling elements, and the fluororesin forming the cage have excellent corrosion resistance to acids and alkalis. Therefore, the corrosion resistance of the rolling bearing as a whole is also excellent. In addition, during operation of the rolling bearing, with the rolling of the rolling element accompanying the relative rotation between the outer ring and the inner ring, a part of the fluororesin forming the retainer is removed from the inner surface of the pocket provided in the retainer. To the rolling surface of the rolling element. Fluororesin has a low coefficient of friction and, when adhered to the rolling surface, functions as a lubricant for a rolling contact portion between the rolling surface and the outer raceway and the inner raceway. As a result, the lubrication state of the rolling contact portion can be kept good. In addition, since the dynamic equivalent load applied during use is limited to 5% or less of the dynamic rated load of the rolling bearing, excessive stress is not applied to the rolling contact portion, and the rolling contact forming the rolling contact portion is not applied. Running surface and outer ring,
Damage such as cracks can be prevented from occurring on both inner raceways. Further, the use condition of the rolling bearing is limited to the use in a corrosive liquid containing water or a part to which the liquid is splashed, or in a corrosive gas containing water vapor, that is, in a water environment. The lubrication state of the part can be kept better.
That is, during the operation of the rolling bearing, water molecules bite into the rolling contact portion, so that silicon carbide and water react at the rolling contact portion to form a reaction film. Then, the reaction film contributes to lubrication of the rolling contact portion. As a result, in combination with the transfer of the fluororesin to the rolling surface, a good lubricating state can be maintained without an oil-based lubricant such as oil or grease.

[0007]

EXAMPLES Experiments performed by the present inventors to confirm the effects of the present invention will be described. FIG. 2 shows an outline of a test machine used for the experiment. The testing machine 8 rotates the rotating shaft 11 inside the fixed housing 10 by a pair of upper and lower deep groove type ball bearings 9a and 9b (nominal number: 6002 = inner diameter 15 mm, outer diameter 32 mm, width 9 mm)}. It is freely supported. Then, of the pair of ball bearings 9a and 9b, only the lower ball bearing 9a is immersed in the corrosive aqueous solution 13 stored in the liquid storage tank 12, and the inner ring is rotated via the rotary shaft 11. Let it. Further, a predetermined axial load is applied to the lower ball bearing 9a serving as a test bearing by a spring 15 compressed by tightening of the nut 14.

That is, a spacer 16 is sandwiched between outer rings constituting the pair of ball bearings 9a and 9b, and the rotating shaft 11
The upper surface of the seat plate 17 supported on the lower end of the inner ball abuts against the lower end surface of the inner race constituting the lower ball bearing 9a. or,
The spring 15 includes a lower surface of a nut 14 screwed to a male screw portion 18 provided on an upper portion of the rotating shaft 11 and an upper ball bearing 9.
b is provided between the inner ring and the upper end surface of the inner ring. Accordingly, the spring 15 presses the inner rings of the pair of ball bearings 9a and 9b in a direction approaching each other, and these two ball bearings 9a and 9b are pressed.
The axial loads a and 9b are applied. The magnitude of the axial load is adjustable by changing the position of the nut 14 and changing the amount of compression of the spring 15. or,
A driven pulley (not shown) is supported on the upper part of the rotating shaft 11, and a belt is stretched between the driven pulley and a driving pulley also fixed to the rotating shaft of an electric motor (not shown), thereby rotating the rotating shaft 11. It is driven to rotate at a desired rotation speed. The abnormality of the lower ball bearing 9a, which is the test bearing,
It is detected by a vibration acceleration pickup 19 attached to the housing 10. When the value of the vibration acceleration detected by the vibration acceleration pickup 19 reached three times the initial value, the life of the test bearing (the ball bearing 9a) was determined.

Experiments were conducted on four types of ball bearings (Examples 1 to 4) belonging to the technical scope of the present invention as shown in Table 1 below.
The test was performed on a total of 10 types of ball bearings, including 6 types of ball bearings (Comparative Examples 1 to 6) that are out of the technical scope of the present invention. Table 1 below shows the materials of the outer ring, the inner ring, the rolling elements, and the retainers that constitute each ball bearing. still,
In each of the ball bearings, the outer ring, the inner ring, and the rolling elements were made of the same material. Groove curvature あ る = (radius of curvature of raceway / ball) where the radius of curvature of the cross section of the outer raceway and the inner raceway formed on the inner peripheral surface of the outer race or the outer peripheral surface of the inner race that constitutes each of the ball bearings is a ratio to the diameter of the ball. (Diameter) × 100%} is 53% for the outer raceway and 51% for the inner raceway for all the samples.

[0010]

[Table 1]

Rotation tests were performed on the ten types of ball bearings shown in Table 1 under the following conditions. Axial load: 98N Rotational speed: 1000 rpm Corrosion solution type: 20% sulfuric acid solution Liquid temperature: room temperature Ball bearings with the nominal number of 6002 are the outer ring, inner ring,
When the rolling elements are made of bearing steel, the dynamic load rating Cr is 5590 N
It is. The dynamic equivalent load P under the above test conditions is JIS
B1518. That is, the dynamic equivalent load P under the above test conditions corresponds to 4.6% of the dynamic rated load Cr.

The results of the rotation tests performed on each of the ten types of ball bearings shown in Table 1 above are shown in Table 2 below. Incidentally, the wear amount described in the right column of Table 2 indicates an increase amount of the axial clearance of each ball bearing.

[0013]

[Table 2]

From the results of the rotation test shown in Table 2,
You can see the following. Regarding Examples 1 to 4, which are ball bearings belonging to the technical scope of the present invention, since the outer ring, the inner ring, and the rolling elements are all made of silicon carbide ceramic and the retainer is made of fluorine resin, the sulfuric acid solution is used. No corrosion due to water.
In addition, water is interposed in the rolling contact portion, and the rolling contact caused by the rotation of the inner ring forms a reaction film on the rolling contact portion. Thus, although smooth abrasion occurred, damage such as cracks and peeling was observed. I couldn't. Such low abrasion and durability can be ensured irrespective of whether the crystal structure of silicon carbide is α-type or β-type. Further, although not particularly shown in the Examples, the type of the sintering aid is different from the boron (B) or carbon (C) type shown in the table, and is the case of BC-Al type, or the sintering method is HIP or normal pressure. Even in different cases such as sintering, the physical and chemical properties of the silicon carbide ceramic hardly change. Therefore, even when the outer ring, the inner ring, and the rolling elements are made of the silicon carbide-based ceramic made by such a sintering aid or the sintering method, it is considered that the same effects as those of the first to fourth embodiments can be expected. Further, it is not necessary that each of the outer ring, the inner ring, and the rolling elements be made entirely of the same silicon carbide ceramic. That is, these members have different crystal structures (α
It is considered that the effect is the same even if the sintering agent is of the type (β type), of different sintering aids, or of different sintering methods.

On the other hand, in Comparative Examples 1 to 3, the outer race, the inner race and the rolling elements are made of ceramics of silicon carbide. However, since the material of the cage is not a fluororesin, the corrosion resistance to the sulfuric acid solution and the rolling contact are reduced. Poor lubricity that contributes to
As a result of the corrosion and damage of the cage itself, the rotation performance of the rolling bearing was adversely affected. That is, the vibrations caused by the damage to the retainer cause the outer races, the inner races and the rolling surfaces of the balls to be roughly worn, and further cause the outer races, the inner races and the rolling surfaces of the balls to be cracked or separated. Was. However, for example, in a press type metal cage,
It is considered that an effect equivalent to that of a fluororesin retainer can be obtained even with a coating of polytetrafluoroethylene (PTFE).

In Comparative Examples 4 to 6, although the cage is made of fluorine resin, the material of the outer ring, the inner ring, and the rolling elements is silicon nitride, which has lower corrosion resistance than silicon carbide. The experimental results of the life time and the amount of wear were all poor. This is due to the intrinsic properties of the material, in that the corrosion resistance of the silicon nitride ceramic is inferior to that of the silicon carbide ceramic. That is, the sintering aid added when sintering silicon nitride into a ceramic is easily corroded by acid, and the silicon nitride ceramic eroded by the sintering aid has a reduced bonding strength, and is subjected to repetitive stress caused by rolling contact. The grains fall off.
As a result, the abrasion proceeds quickly and the durable life is shortened.

Next, regarding the corrosion resistance of the ten types of ball bearings, each of these ball bearings was subjected to an acidic aqueous solution (10% sulfuric acid aqueous solution) at 80 ° C., an alkaline aqueous solution (80% potassium hydroxide aqueous solution) at 80 ° C., and 200 ° C. After being immersed in high-pressure water for 24 hours, hardness, strength, component change, elution amount, dimensional change, and microstructure were measured. The result is
The results are shown in Table 3 below.

[0018]

[Table 3]

In Table 3, the symbol "○" indicates that no change considered to be caused by corrosion is found in any of the items of hardness, strength, component change, elution amount, dimensional change, and microstructure. Indicates that it could not be seen. On the other hand, the sign "x"
Indicates that a change attributable to corrosion was observed in at least one of the above items. From the results shown in Table 3, it can be seen that various silicon carbide ceramics have sufficient corrosion resistance to any of an acidic aqueous solution, an alkaline aqueous solution, and high-pressure water.

Next, using the test piece of Example 1, a test was conducted to confirm usable load conditions. Various conditions other than the axial load are the same as the conditions of the rotation test described above. The results are shown in Table 4 below.

[0021]

[Table 4]

From the experimental results shown in Table 4, Table 1
It was confirmed that the ball bearing described as Example 1 could obtain good rotational performance over a long period of time even in a corrosive solution if the dynamic equivalent load P was 5% or less of the dynamic rated load Cr.
On the other hand, the dynamic equivalent load P is 5 times the dynamic rated load Cr.
%, The life time decreases. The reason for this is that the strength of the silicon carbide ceramic cannot withstand the repetitive stress generated at the rolling contact surface under a use condition in which the dynamic equivalent load P exceeds 5% of the dynamic rated load Cr. Conversely, if the load is a light equivalent of a dynamic equivalent load P of 5% or less of the dynamic rated load Cr, the strength of the silicon carbide ceramic can endure. Moreover, even if the silicon carbide ceramic is in a corrosive solution, it has sufficient corrosion resistance, and since water intervenes, a reaction film is formed on the rolling contact surface and the fluorine resin is transferred from the cage to the ball rolling surface. Combined with the lubrication effect of the transfer, the outer ring, inner ring amount raceway and the rolling surface of the ball wear smoothly, crack,
Good rotation performance can be maintained in a state where damage such as peeling does not occur.

The repetitive stress generated on the rolling contact surface can be changed depending on the design content inside the bearing, that is, the radius of curvature (groove radius) of the cross section of the outer raceway and the inner raceway even if the external load is the same. it can. From this point of view, experiments were conducted on the rotational performance of a plurality of types of ball bearings having different raceway groove radii in order to examine the effect of the groove radius on the wear amount. In this case, the material of the outer ring, the inner ring, and the ball is the same as in the first embodiment,
All were made of BC silicon carbide ceramic, and the material of the retainer was PTFE. The conditions for the rotation performance test were the same as those for the rotation test. The results are shown in Table 5 below.

[0024]

[Table 5]

As a result of an experiment on rotational performance conducted to find out the influence of the groove radius on the amount of wear, all the test pieces successfully rotated for 500 hours, but a difference was observed in the amount of wear. That is, in Examples 1 to 5 to 8, the wear amount represented by the increase in the axial clearance of each ball bearing was 30 μm.
In the following, it was confirmed that the life was long. On the contrary,
For the semi-embodiments 1-4, the wear amount was 30-80 μm.
m, which was greater than in Examples 1 and 5 to 8, but less than in Comparative Examples 7 to 9 described below. On the other hand, in Comparative Examples 7 to 9, the wear amount was 80 to 1
It increased to 50 μm. In each of the nine types of ball bearings of Examples 1, 5 to 8, and Sub-Examples 1 to 4, wear progressed very smoothly, no increase in vibration acceleration was observed, and good rotation was observed. Can be obtained. From this, if the outer ring groove curvature is 55% or less and the inner ring groove curvature is 54% or less,
It can be seen that a certain long life can be expected (including the sub-embodiments). Further, when longer durability is desired, it is understood that the outer ring groove curvature is preferably 54% or less and the inner ring groove curvature is preferably 54% or less (only in the embodiment). The reason is that as the groove curvature increases, the contact surface pressure increases, and the surface pressure applied to the rolling contact portion increases. The lower limit of the groove curvature is set to 50% at which the groove curvature becomes the same as the ball diameter. Even when such a groove curvature is 50%, it is considered that the life is long in terms of the life time.

The surface roughness of the rolling surface of the outer raceway, inner raceway (including raceways for ball bearings and roller bearings) and cylindrical rollers must be regulated to 0.01 to 3.2 μmRa. Is desirable. The upper limit is set to 3.2 μmRa because, when the surface roughness exceeds 3.2 μmRa, vibrations and cracks are easily caused and the life is shortened. On the other hand, the reason why the lower limit is set to 0.01 μmRa is that even if the surface roughness is less than 0.01 μmRa, the production cost is increased and no further improvement in performance can be expected. On the other hand, when the rolling element is a ball, the shape accuracy of the ball should be better than JIS B1501 grade 100, so as not to cause vibration or shorten the life. Is desirable.

[0027]

The rolling bearing of the present invention is constructed and operated as described above, and in a corrosive environment containing water, which cannot be expected to have sufficient durability with a rolling bearing made of silicon nitride, Demonstrate excellent durability.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a rolling bearing to which the present invention is applied.

FIG. 2 is a schematic sectional view of a test apparatus used in an experiment for confirming the effect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling bearing 2 Outer raceway 3 Outer raceway 4 Inner raceway 5 Inner raceway 6 Rolling element 7 Cage 8 Testing machine 9a, 9b Ball bearing 10 Housing 11 Rotary shaft 12 Storage tank 13 Corrosive aqueous solution 14 Nut 15 Spring 16 Spacer 17 Seat plate 18 Male thread 19 Vibration acceleration pickup

Claims (1)

[Claims] 1. An outer ring having an outer raceway on an inner peripheral surface, an inner racer having an inner raceway on an outer peripheral surface, a plurality of rolling elements rotatably provided between the outer raceway and the inner raceway, A retainer that holds a plurality of rolling elements so as to freely roll,
In or on which corrosive liquids containing water
Alternatively, in a rolling bearing used in a corrosive gas containing water vapor, the outer ring, the inner ring, and the rolling elements are each made of ceramics of silicon carbide, and the retainer has at least a surface made of a fluorine resin. A rolling bearing characterized in that it is used under the condition that a dynamic equivalent load applied during use is 5% or less of a dynamic rated load.