JPH09329136A - Rolling bearing - Google Patents

Abstract

(57) [Summary] [Object] To prevent fretting wear from occurring in the outer ring raceway 11 and the inner ring raceway 13 irrespective of the impact load repeatedly applied during transportation or the minute rocking displacement repeatedly performed. [Structure] An outer race 12 having an outer raceway 11 on an inner peripheral surface and an inner race 14 having an inner raceway 13 on an outer peripheral surface are made of steel. The plurality of rolling elements 15 provided between the outer ring raceway 11 and the inner ring raceway 13 so as to be rollable are made of ceramic. In addition, the surface porosity of the rolling surface of each rolling element 15 is 0.20.
˜14.0%. The frictional state between the rolling surface of each rolling element 15 and the outer ring raceway 11 and the inner ring raceway 13 is improved, and fretting wear is less likely to occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION A rolling bearing according to the present invention is used as a rolling bearing for an electric motor or an HDD for rotatably supporting a rotor shaft inside a housing constituting the electric motor.
It is used as a rocking support rolling bearing for rockably supporting the base end portion of a swing arm that supports a magnetic head that constitutes a magnetic recording device such as an FDD.

[0002]

2. Description of the Related Art An electric motor used as a drive source for various electric machines is constructed, for example, as shown in FIG. A rotor shaft 2 is rotatably supported by a pair of rolling bearings 3a, 3a that are concentrically arranged at a distance from each other in the center of the inside of the casing 1. A rotor 4 is fixed to a portion of the rotor shaft 2 located between the two rolling bearings 3a, 3a, and a stator is provided on a portion of the inner peripheral surface of the casing 1 facing the outer peripheral surface of the rotor 4. 5 is fixed. When the electric motor is used, the stator 5 is energized to rotate the rotor shaft 2 via the rotor 4.

Further, FIG. 2 shows a swing for swingably supporting a base end portion of a swing arm which supports a magnetic head constituting a magnetic recording device disclosed in Japanese Patent Laid-Open No. 61-151881. The structure of a dynamic support part is shown. In this swinging support portion, the base end portions of the swinging shafts 8 are arranged concentrically with each other on a support block 7 fixed in a hermetically sealed case 1.
The pair of rolling bearings 3b and 3b are supported so as to be swingable. The base ends of swing arms 10 and 10 supporting the magnetic heads 9 at their tip parts are fixedly coupled to the swing shaft 8. When the magnetic recording apparatus provided with such a swing support portion is used, the swing shaft 8 swings as the magnetic head 9 traces the magnetic recording plates 18, 18 such as HD and FD. To do.

Each of the above-mentioned components is incorporated for supporting the swing of the electric motor or the swing arm as described above, and for supporting the swing or rotation of the crankshaft of a stepping motor or various mechanical devices (not shown). The rolling bearing 3a (3b) is configured as shown in detail in FIG. That is, the rolling bearing 3a (3b) is the outer ring 1 having the outer ring raceway 11 on the inner peripheral surface.
2, an inner race 14 having an inner raceway 13 on the outer peripheral surface, and a plurality of rolling elements 15 rotatably provided between the outer raceway 11 and the inner raceway 13. The outer ring 12, the inner ring 14, and the plurality of rolling elements 15 are all made of a steel material such as high carbon chromium bearing steel. Further, the plurality of rolling elements 15 are rotatably held by a retainer 16 while being circumferentially spaced from each other. Further, the outer peripheral edges of the sealing plates 17, 17, which are seals or shields, are locked to the inner peripheral surfaces of both ends of the outer ring 12 to close both end openings of the space portion in which the plurality of rolling elements 15 are installed. . The sealing plates 17, 17 prevent the grease filled in the space from leaking to the outside.

Among such rolling bearings 3a (3b),
In the case of the rolling bearing 3a incorporated in the motor for electric motor as shown in FIG. 1, there is a minute gap between the rolling surfaces of the plurality of rolling elements 15 and the outer ring raceway 11 and the inner ring raceway 13 in which grease can enter. The size of each part is regulated so that it is formed. That is, a so-called positive gap is provided inside the rolling bearing 3a. Therefore, the outer ring 12, the inner ring 14, and the plurality of rolling elements 15 are arranged in the axial direction (left and right direction in FIG. 3) and the diametrical direction (up and down direction in FIG. 3) of the outer ring 12 and the inner ring 14.
However, relative displacement is possible, albeit slightly. On the other hand, in the case of the rolling bearing 3b for swingably supporting the base end portions of the swing arms 10 and 10 as shown in FIG. 2, the rolling surfaces of the plurality of rolling elements 15 and the outer ring. A so-called preload is applied to elastically abut the raceway 11 and the inner ring raceway 13. That is, a so-called negative gap is provided inside the rolling bearing 3b. However, even when such a negative gap is provided, the rolling surfaces of the plurality of rolling elements 15 and the outer ring raceway 1 are
It is prevented that grease enters between the inner raceway 13 and the inner raceway 13 and the rolling surfaces directly contact with the outer raceway 11 and the inner raceway 13 (metal contact).

[0006]

In the case of the rolling bearings 3a, 3a incorporated in the electric motor, the outer ring 12, the inner ring 14, and the plurality of rolling elements 15 are relatively displaceable, but the electric motor or the electric motor can be replaced. If vertical vibration or lateral wobbling is applied during transportation of the incorporated mechanical device, a shocking load is repeatedly applied to the rolling surfaces of the outer ring raceway 11, the inner ring raceway 13, and the rolling elements 15. Further, at the moment when this impact load is applied, the outer ring raceway 11 and the inner ring raceway 13 and the rolling element 15
A slight slip occurs at the contact portion with the rolling surface. Moreover, at the moment when this slight slippage occurs, the grease present in the abutting portion is pushed away by the impact load, resulting in a so-called metal contact state in which steels come into contact with each other. Therefore, due to the slight slip, the outer ring raceway 11, the inner ring raceway 13,
Local damage occurs on the rolling surface of the rolling element 15, and so-called fretting wear occurs based on this damage. Such fretting wear is not preferable because it may cause abnormal noise or vibration during operation of the electric motor or shorten the life of the rolling bearings 3a, 3a.

Particularly in the case of the rolling bearing 3a for electric motor,
The outer ring 12 is internally fitted and fixed to the casing 1, and the inner ring 14 is externally fitted and fixed to the rotor shaft 2.
2 and the inertial mass applied to the inner ring 14 are large. For this reason, the impact load applied repeatedly becomes large, and the fretting wear is likely to occur. In particular, in a large electric motor such as a fan motor for an air conditioner for a building, the above fretting wear becomes remarkable.

In order to suppress the above fretting wear, it is effective to use a stronger grease as the grease to be filled in the rolling bearing 3a. If strong grease is used, the outer ring raceway 11, the inner ring raceway 13 and the rolling elements 15
The mechanical strength of the oil film formed between the rolling surface and the rolling surface is increased, and it is possible to suppress the occurrence of minute slip (metal contact) between the metal surfaces, which leads to fretting wear. However, when a firm grease is used, the fluidity of the grease decreases, the lubricity deteriorates during operation of the electric motor, or the rotational torque of the rolling bearing 3a increases, and the fluctuation of this rotational torque It is not preferable because it becomes large.

In view of such circumstances, conventionally, the packing of an electric motor or a mechanical device incorporating the electric motor is strengthened so as to have vibration resistance and the impact load applied to the rolling bearing 3a is alleviated. It is not always an effective measure because it is difficult to completely suppress fretting wear and increase costs.

On the other hand, in the case of the rolling bearing 3b for swingably supporting the base ends of the swing arms 10 and 10,
When the magnetic recording plates 18, 18 are traced by the magnetic heads 9, 9, one raceway ring of the inner ring 14 and the outer raceway 12 with respect to the other raceway ring (in the case of the structure shown in FIG. The inner ring 14 repeatedly swings at a small angle with respect to the outer ring 12. As a result of the repeated swing displacement of such a small angle, the contact position between the rolling surface of the rolling element 15 and the outer ring raceway 11 and the inner ring raceway 13 becomes localized. Moreover,
When the rocking direction is reversed, the relative speed between the rolling surface and the outer ring raceway 11 and the inner ring raceway 13 becomes zero. Thus, when the contact position between the rolling surface and the outer ring raceway 11 and the inner ring raceway 13 becomes local or the relative speed becomes zero, the contact between the rolling surface and the outer ring raceway 11 and the inner ring raceway 13 occurs. It becomes difficult to form an oil film for lubrication on the part. If the oil film is not formed, metal contact occurs at the contact portion, wear (fretting wear) occurs, the bearing performance deteriorates, and the bearing life decreases. The present invention was made in view of the above circumstances, and has excellent bearing characteristics, and in addition, a rolling bearing for an electric motor that exhibits excellent fretting resistance regardless of the impact load repeatedly applied during transportation, Alternatively, the present invention provides a rolling bearing or the like for rocking support that exhibits anti-fretting properties.

[0011]

The rolling bearing of the present invention comprises:
Similar to the conventional rolling bearing described above, 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 rollablely provided between the outer ring raceway and the inner ring raceway. And a rolling element. Particularly, in the rolling bearing of the present invention, the outer ring and the inner ring are made of steel, and the plurality of rolling elements are made of ceramic. The surface porosity of these rolling elements is 0.20 to 14.0%. The material of the steel forming the outer ring and the inner ring is not particularly limited, but bearing steel, high carbon steel, stainless steel, carburized steel and the like can be used. The steel material forming the outer ring and the steel material forming the inner ring may be of the same type or of different types. Further, the material of the ceramic constituting the rolling element is not particularly limited, but silicon nitride, alumina, zirconia or the like can be used.

Further, between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, both ends are closed by sealing plates, and the space in which the plurality of rolling elements are installed is filled with a lubricant. But
As the lubricant, grease containing 5% by weight or more and less than 20% by weight of a thickening agent made of urea resin is preferably used. Further, synthetic hydrocarbon oil, ester oil, mineral oil, ether oil or the like is used as the base oil for constituting this grease. In addition, an antioxidant,
Additives such as a rust inhibitor, an antiwear agent, and an extreme pressure agent may be contained within a range that does not deteriorate the function of the rolling bearing.

[0013]

In the case of the rolling bearing of the present invention configured as described above, unlike the case of the conventional rolling bearing described above,
The contact state of the abutting portions of the outer ring raceway and the inner ring raceway and the rolling surfaces of the plurality of rolling elements is not the contact between steels but the contact between steel and ceramics. If steel and ceramic come into contact,
Friction and wear characteristics are better than when steels contact each other.

The friction and wear characteristics of the outer ring raceway and inner raceway race of the steel outer race and the inner raceway and the contact surface of the rolling surface of the ceramic rolling element can be determined by the combination of these steels and ceramics. Even in this case, the frictional characteristics are improved (the frictional force becomes smaller) as compared with the frictional characteristics when the steels contact each other. Among them, in particular, each combination of bearing steel and silicon nitride, stainless steel and silicon nitride, and bearing steel and zirconia can obtain excellent friction and wear characteristics (low friction characteristics) and cause damages such as the above-mentioned fretting wear. Since it is less likely to occur, it can be preferably used.

Further, by restricting the surface porosity of the plurality of ceramic rolling elements within the range of 0.20 to 14.0%, the frictional force acting on the abutting portion is further reduced. As a result, it is possible to further reduce the occurrence of damage such as the above-mentioned fretting wear. That is, if the surface porosity is regulated within the above range, the grease retained in the pores on the surface of the rolling element exudes to the abutting portion when the impact load that causes the damage is applied, Lower the friction of the contact part. Therefore, it is possible to further reduce the occurrence of damage such as the above-mentioned fretting wear. If the surface porosity is less than 0.20%, the effect of the oil sump in the pores cannot be expected, and wear is likely to occur. Further, when the surface porosity exceeds 14.0%, the surface roughness of the rolling surface is deteriorated and abrasion is likely to occur.

The grease containing urea resin as a thickener in an amount of 5% by weight or more and less than 20% by weight is a grease which uses lithium soap, sodium soap or the like as a thickening agent in terms of fluidity, shear stability and lubricity. Is superior to. Therefore, when such a grease is used as a lubricant for filling the space in which the plurality of rolling elements are installed, excellent friction and wear characteristics can be obtained. When the proportion of the thickener of urea resin is less than 5% by weight, the obtained grease is too soft (viscosity is too low), this grease leaks out from the space, and the grease existing in this space is insufficient. The fretting wear is likely to occur. On the other hand, when the thickening agent of urea resin is 20% by weight or more, the obtained grease becomes hard (viscosity is high) and the fluidity is deteriorated, so that the fretting wear cannot be sufficiently reduced.

[0017]

EXAMPLES Next, in order to confirm the effects of the present invention, an experiment conducted by the present inventor will be described. In the first experiment, the rolling bearing 3 incorporated in the electric motor as shown in FIG.
a and 3a, a fretting test to measure the extent to which fretting wear occurs due to the impact load repeatedly applied during transportation of this electric motor, and a durability test to measure the durability of the rolling bearing in use, and a use condition Four types of tests were performed: a torque test for measuring the rotational torque acting on the rolling bearing and a grease noise test for measuring the noise of the grease enclosed in the rolling bearing. The method of performing each test and the results thereof will be described below. The conditions common to each test and the specific contents of terms described in Tables 1 and 2 described later are as follows. Bearing steel: SUJ2 (JIS G 4805) Stainless steel: SUS440C (JIS G 4303) Grease type: "Multemp SRL" made by Kyodo Yushi Co., Ltd. Amount of grease filled: 35% (volume ratio to the bearing space)

Fretting test The fretting test was carried out by using a test apparatus as shown in FIG. Rolling bearings 3a, 3a which are articles under test
Is pre-loaded by a spring 21 while being installed between the outer peripheral surface of the spindle 19 and the inner peripheral surface of the housing 20,
Further, a weight 22 applies a downward load to the spindle 19. After placing the spindle 19 on the vibrator 23 and applying vibration under predetermined conditions, the rolling bearings 3a and 3a are disassembled and generated in the outer ring raceway 11 and the inner ring raceway 13 (see FIG. 3). Fretting wear was observed under a microscope. The test conditions are as follows. Specifications of rolling bearing 3a: Deep groove ball bearing (Nominal number = 608ZZ) Inner diameter = 8mm Outer diameter = 22mm Width = 7mm Load by spring 21: 6kgf Load by weight 22: 0.5kgf Vibration frequency by vibrator 23: Excitation acceleration by 30 Hz shaker 23: 5G Temperature: 25 ° C Excitation duration: 5 hours The results of this fretting test are shown in Tables 1 and 2 together with the results of the durability test, torque test, and grease noise test. Regarding the results of this fretting test, ∘ indicates that there was neither fretting wear nor running marks of rolling elements, and ○ indicates that there was almost no fretting wear even if there were running marks of rolling elements. A mark indicating slight fretting wear is indicated by a triangle, and a mark indicating large fretting wear is indicated by a cross. The ◎ and ○ marks are passed.

Endurance Test This endurance test was carried out using a general bearing endurance rotation tester, and the test was terminated after 2000 hours had elapsed or when seizure occurred. The test conditions are as follows. Specifications of rolling bearing 3a: Deep groove type ball bearing (Nominal number = 6200VV) Inner diameter = 10mm Outer diameter = 30mm Width = 9mm Axial load: 3kgf Radial load: 1kgf Rotation speed: 6000r.pm Temperature: 140 ° C Results of this durability test Are shown in Tables 1 and 2 together with the results of the fretting test, the torque test, and the grease noise test. Regarding the results of this durability test, the bearing life time (time until seizure occurs) of 2000 hours or more is marked with a circle, and that of 1500 to 2000 hours is marked with a triangle.
The mark indicates that less than 1500 hours is indicated by x, respectively. The ○ mark is passed.

Torque Test This torque test was carried out using a general bearing torque measuring tester to measure the dynamic torque of the rolling bearing 3a. The test conditions are as follows. Specifications of rolling bearing 3a: Deep groove type ball bearing (Nominal number = 6202VV) Inner diameter = 15mm Outer diameter = 35mm Width = 11mm Axial load: 3kgf Radial load: 1kgf Rotation speed: 1800r.pm Temperature: 25 ° C Result of this torque test Are shown in Tables 1 and 2 together with the results of the fretting test, the durability test and the grease noise test. Regarding the results of this torque test, those with a dynamic torque of 50 gf · cm or less are marked with ⊚, those with 50 to 70 gf · cm are marked with ○, and those with 70-100 gf · cm are marked with Δ. 1
Those with a value of 00 gf · cm or more are indicated by a cross. The ◎ and ○ marks are passed.

Grease Noise Test This grease noise test was conducted by acoustically evaluating the grease enclosed in the rolling bearing 3a by measuring the grease noise with a grease noise tester. The rolling bearing 3a used is 6200 VV as in the case of the durability test. The results of this grease noise test are shown in Tables 1 and 2 together with the results of the fretting test, the durability test and the torque test.
Described in. Regarding the results of the grease noise test, those with almost no irregular sound and excellent acoustic characteristics are marked with a circle, those with a little irregular sound and slightly poor acoustic characteristics are marked with a Δ. Those with a lot of irregular sounds and bad acoustic characteristics are indicated by crosses. The ○ mark is passed.

[0022]

[Table 1]

[0023]

[Table 2]

In these Tables 1 and 2, the symbols ⋄ indicate that the materials described in the corresponding positions in the left column were used. As is clear from the descriptions in Tables 1 and 2, the rolling bearing of the present invention has excellent bearing characteristics in terms of durability, low torque, and grease noise, and is not affected by repeated impact loads during transportation. Demonstrates excellent fretting resistance.

Next, a description will be given of an experiment conducted to know the influence of the surface porosity of the ceramic rolling element 15 on the fretting resistance. The experiment was performed on a plurality of samples having different surface porosities under the same conditions as the above-mentioned fretting test. However, the vibration duration is 5, 1
Three kinds of tests, 0 and 15 hours, were carried out, and the same evaluation as in the above fretting test was carried out. The results are shown in Tables 3 and 4 below. The surface porosity was determined by the following equation after the surface of the rolling element 15 was photographed with an optical microscope and the photographed data was image-processed. (Total area of pores in visual field) / (total area of visual field) x 100

[0026]

[Table 3]

[0027]

[Table 4]

From the results of the fretting durability test shown in Tables 3 and 4, a plurality of ceramic rolling elements 15
If the surface porosity of the above is regulated within the range of 0.20 to 14.0%, the frictional force acting on the abutting portions between the rolling surfaces of the plurality of rolling elements 15 and the outer ring raceway 11 and the inner ring raceway 13 is further increased. It can be seen that the amount of damage can be further reduced and the occurrence of damage such as fretting wear can be reduced over a longer period of time. On the other hand, for example, Comparative Examples 4, 6, and 8 show good fretting resistance at the initial stage (for 5 hours or 10 hours after the start of the experiment) because the surface porosity is small (0.1%). However, fretting wear was observed when the vibration duration was long. This is considered to be because Comparative Examples 4, 6, and 8 have a small surface porosity and a small amount of grease retained in the pores existing on the surface of the rolling element 15. On the contrary, Comparative Examples 5, 7, and 9 have large surface porosity (> 14.0).
%), Good fretting resistance was exhibited when the vibration duration was up to 5 hours or 10 hours, but when the vibration duration was long, occurrence of fretting wear was observed.
The reason for this is considered to be that the surface porosity is excessively large, the surface roughness is deteriorated, and the edge portions of the pores locally have a high surface pressure, causing grease to run out at the portions.

Next, as shown in FIG. 2 described above, the rolling bearings 3b and 3b constituting the swing support portion of the magnetic recording apparatus are
A second experiment conducted to confirm the effect obtained when the present invention is applied will be described. In this second experiment, a rolling bearing 3b, 3b incorporated in a magnetic recording device as shown in FIG. 2 was subjected to a fretting durability test for measuring the extent to which fretting wear occurred during use of the magnetic recording device. The test was performed using a test apparatus as shown in FIG.

This test apparatus is equipped with the above-mentioned rolling bearings 3b, 3
A rotary cylinder 24 that fits and supports the outer rings 12, 12 of b and a fixed shaft 25 that fits and supports the inner rings 14, 14 of the rolling bearings 3b, 3b. And these rotary cylinders 24
A plurality of rolling bearings 3b, 3b are mounted between the inner peripheral surface of the above and the outer peripheral surface of the fixed shaft 25. Each of these rolling bearings 3b, 3b has an outer ring 12, 12 adjacent in the axial direction.
Preload is applied by the sleeves 26a, 26b and the springs 21 provided between the inner rings 14, 14 or between the inner rings 14, 14. The rotary cylinder 24 is repeatedly swingable by a drive motor 27 such as an AC servomotor at a predetermined small angle (swing angle). Therefore, during the test, the outer rings 12, 12 of the rolling bearings 3b, 3b are repeatedly oscillated and displaced at a small oscillating angle. The axial load applied to the rolling bearings 3b, 3b by the spring 21 was 10 kgf, the swing angle of the outer rings 12, 12 was 8 degrees, and the number of times of swinging was 2 million times.
The rolling bearings 3b and 3b used have a nominal number of 69.
5 (inner diameter = 5 mm, outer diameter = 13 mm, width = 4 mm).

After conducting the test under the above-mentioned conditions, the rolling bearings 3b, 3b are disassembled, and the inner ring raceways 13, 13 provided on the outer peripheral surfaces of the inner rings 14, 14 of the rolling bearings 3b, 3b are disassembled. The wear state and the wear depth were observed. Then, the case where the wear depth of the running trace was less than 0.2 μm was regarded as a pass, and the case where the wear depth was 0.2 μm or more was also judged as a failure. The test was conducted on the material of the rolling elements 15, 15 as well as the surface porosity of the rolling surface, the material of the lubricant filled in the space in which the plurality of rolling elements are installed, and the thickener constituting the lubricant. This was done by changing the ratio variously. The results are shown in FIGS.

First, FIG. 6 shows the result of an experiment carried out to find out the influence of the material of the rolling element and the surface porosity of the rolling surface on the fretting wear of the inner ring raceway 13. The horizontal axis of FIG. 6 represents the surface porosity, and the vertical axis represents the depth of fretting wear generated in the inner ring raceway 13. The depth of fretting wear was measured by a shape measuring machine. In addition, ∘ indicates the result when the rolling elements 15 and 15 are made of silicon nitride, Δ indicates the result when the same is made of alumina, and □ indicates the result when the same is made of zirconia. In either case, the material of the inner ring 14 was bearing steel {SUJ-2 subjected to a predetermined heat treatment (quenching and tempering)}. Further, as a lubricant, the content of urea resin, which is a thickener, is 10% by weight.
The urea resin-ester oil type grease described above, in which the viscosity of the ester oil is 100 mm ² / s, was used.

As is clear from FIG. 6 showing the results of the test conducted under such conditions, if the surface porosity of the rolling surfaces of the rolling elements 15, 15 is regulated within the range of 0.2 to 14.0%. Therefore, it is possible to satisfy the acceptance criterion that the fretting wear depth of the inner ring raceway 13 is 0.2 μm or less. Also, as is clear from FIG. 6, the surface porosity is 0.25 to
When the content is regulated within the range of 13%, the depth of fretting wear can be suppressed to 0.1 μm or less, and the rolling bearings 3b and 3b having more excellent durability can be obtained.

That is, as is clear from FIG. 6, there is a critical point for fretting wear (of the inner ring running trace) in the portions where the surface porosity is 0.20% and 14.0%. When the surface porosity is less than 0.20%, the contact portion between the raceway surface (the inner ring raceway 13 in the case of the second experiment) and the rolling surface of the rolling element 15 is as described above. In this case, the ratio of the pores existing in the cylinder and functioning as an oil reservoir to the contact portion (so-called contact ellipse) becomes insufficient, and fretting wear increases. On the contrary, when the surface porosity exceeds 14.0%,
Again, as described above, it can be seen that the surface roughness of the rolling element 15 is deteriorated, and the fretting wear is similarly increased and the wear is remarkable. The surface porosity is 0.25
When it is set to 13%, fretting wear can be further reduced.

When the surface porosity is within the range of the present invention (0.20 to 14.0%), the rolling element 15
If silicon nitride or zirconia is used as the material, the fretting resistance superior to that in the case where the material of the rolling element 15 is alumina is obtained. However, regarding the degree of fretting wear, rather than such a difference in the material of the rolling elements 15,
The difference in surface porosity has a greater effect. Therefore, the present invention does not limit the ceramic material forming the rolling element 15.

Next, FIG. 7 shows the material of the lubricant filled in the space in which the plurality of rolling elements 15 are installed, and the material of the lubricant by changing the ratio of the thickener constituting the lubricant. And the results of an experiment conducted to find out the effect of the proportion of the thickener on the fretting wear.
The test conditions and the judgment conditions are the same as in the case of the test whose results are shown in FIG. However, the ceramic forming the rolling element 15 was silicon nitride (Si ₃ N ₄ ) having a surface porosity of 2%. The horizontal axis of FIG. 7 represents the content of the urea resin or lithium soap that is a thickener, and the vertical axis represents the depth of fretting wear generated in the inner ring raceway 13. Also, △ mark indicates the case where a grease prepared by mixing a thickener composed of lithium soap and mineral oil having a viscosity of 100 mm ² / s is used, and ○ mark indicates a thickener made of urea resin and ester oil. The test results are shown when the greases used are used.

As is apparent from FIG. 7, according to the present invention, excellent wear resistance can be obtained regardless of which grease is used, but especially urea resin as a thickener is 5% by weight or more and 20% by weight or more. It can be seen that excellent wear resistance can be obtained when a grease containing less than less than is used.

[0038]

Since the rolling bearing of the present invention is constructed and operates as described above, it has excellent bearing characteristics in terms of durability, low torque, and grease noise, and the impact applied repeatedly during transportation. Exhibits excellent fretting resistance regardless of load. Therefore, the acoustic characteristics, vibration characteristics, and durability of the electric motor and various mechanical devices incorporating the electric motor can be improved. Further, when it is incorporated in a swinging support portion that is slightly displaced, such as a magnetic recording device, it can exhibit excellent fretting resistance.

[Brief description of drawings]

FIG. 1 is a half cutaway side view of an electric motor incorporating a rolling bearing as an object of the present invention.

FIG. 2 is a sectional view of the magnetic recording device.

FIG. 3 is a partial cross-sectional view showing an example of a rolling bearing which is an object of the present invention.

FIG. 4 is a schematic vertical sectional front view showing a test device used for a fretting test of a rolling bearing used for an electric motor.

FIG. 5 is a schematic vertical sectional front view showing a test device used for a fretting test of a rolling bearing used for a magnetic recording device.

FIG. 6 is a diagram showing the results of an experiment conducted to know the influence of the material of the rolling elements and the surface porosity of the rolling surfaces on the fretting wear of the inner ring raceway.

FIG. 7 is a diagram showing the results of an experiment carried out in order to know the influence of the material of the lubricant and the ratio of the thickener on the fretting wear in the space in which a plurality of rolling elements are installed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 Rotor shafts 3a, 3b Rolling bearings 4 Rotor 5 Stator 6 Sealing case 7 Support block 8 Swing shaft 9 Magnetic head 10 Swing arm 11 Outer ring raceway 12 Outer ring 13 Inner ring raceway 14 Inner ring 15 Rolling body 16 Cage 17 Sealing plate 18 Magnetic recording plate 19 Spindle 20 Housing 21 Spring 22 Weight 23 Vibrator 24 Rotating cylinder 25 Fixed shaft 26a, 26b Sleeve 27 Drive motor

Claims (1)

[Claims] 1. An outer ring having an outer ring raceway on an inner peripheral surface, an inner ring having an inner ring raceway on an outer peripheral surface, and a plurality of rolling elements rotatably provided between the outer ring raceway and the inner ring raceway. ,
In a rolling bearing that rotatably supports a shaft inside a casing, the outer ring and the inner ring are made of steel, the plurality of rolling elements are made of ceramic, and the surface porosity of the plurality of rolling elements is 0. A rolling bearing characterized by being 20 to 14.0%.