JP2007333172A - Bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive structure having high impedance, which has a structure wherein a ceramic insulating film 4b is formed on a raceway ring. <P>SOLUTION: The ceramic insulating film 4b mainly composed of alumina is formed on the inner circumferential surface 14 of an inner ring 3 and both axial end faces 15, 15. An interference between the inner ring 3 and a shaft is regulated so that a damage is not generated on the insulating film 4b. Since the total surface area of the inner circumferential surface 14 of the inner ring 3 and both end faces 15, 15 is smaller than the total surface area of the outer circumferential surface 12 of an outer ring 2 and axial direction both end faces 13, 13, the impedance can be heightened inexpensively without thickening the film thickness of the insulating coating 4b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement in a bearing device that constitutes a rotation support portion of a general industrial general-purpose motor, a generator generator (wind generator, etc.), a railway vehicle main motor, or a medical device (CT scanner device, etc.). In particular, the present invention is suitable as a bearing device incorporated in an inverter-controlled motor or generator.

  In the case of a rolling bearing for supporting rotating shafts of various electric devices such as an electric motor and a generator, currents such as a return current and a motor shaft current flow in the rolling bearing itself unless measures are taken. When an electric current flows through the rolling bearing, so-called electric corrosion occurs, ie, corrosion of a portion serving as a current path progresses, and the life of the rolling bearing is significantly shortened. In order to prevent the occurrence of such electric corrosion, an insulating film made of synthetic resin with excellent insulation is formed on the outer peripheral surface of the outer ring or the inner peripheral surface of the inner ring, which is the surface fitted to the housing or shaft. The technique to do is conventionally known. As such synthetic resins having excellent insulating properties, for example, polybutylene terephthalate (PBT), polyamide 66 (PA66), polyamide 6 (PA6) and the like have been proposed. However, among these, PA66 and PA6 have high water absorption, and their dimensions are likely to change by absorbing moisture in the air. For this reason, it is not preferable as a material for covering the fitting surface of the bearing device that requires accuracy. The PBT may be insufficient in heat resistance and strength, and is not preferable as a material for covering the fitting surface.

  On the other hand, for example, Patent Document 1 describes a technique using polyphenylene sulfide (PPS) containing glass fiber as a material for forming an insulating film. That is, as shown in FIG. 3, the outer peripheral surface and both end surfaces of the metal outer ring 2 constituting the rolling bearing 1 and the inner peripheral surface and both end surfaces of the metal inner ring 3 are each PPS containing glass fibers. An insulating coating 4 made of metal is formed. Note that the illustrated rolling bearing 1 is a deep groove type ball bearing, and for this reason, between the outer ring raceway 5 formed on the inner peripheral surface of the outer ring 2 and the inner ring raceway 6 formed on the outer peripheral surface of the inner ring 3. In addition, a plurality of metal balls 7 are provided. The rolling bearing 1 configured as described above has the outer ring 2 fitted and fixed to the metal housing 8 via the insulating film 4, and the inner ring 3 is fixed to the metal shaft (not shown). 4 is fixed by external fitting. As a result, electric current can be prevented from flowing through the rolling bearing 1 to prevent electrolytic corrosion.

  Further, by using PPS reinforced with glass fiber as described above as the insulating film 4, the above-described problems of dimensional change due to moisture absorption, heat resistance, and insufficient strength can be solved. However, the synthetic resin material as described above has a larger coefficient of linear expansion than a metal such as bearing steel, which is a material for rolling bearings, housings, shafts, and the like. Therefore, deformation is likely to occur due to heat generated in the rotation support portion.

  On the other hand, Patent Documents 2 to 4 describe techniques in which ceramic insulating films having a small linear expansion coefficient are formed on the outer peripheral surface and both end surfaces of the outer ring. In the case of the structure described in Patent Document 2 among these, as shown in FIG. 4, a ceramic insulating film 4a is formed on the outer peripheral surface and both end surfaces of the metal outer ring 2a, and this insulating film 4a It is covered with a metal layer 9. The illustrated rolling bearing 1a is a cylindrical roller bearing. For this purpose, the flanges 10 and 10 are formed on the inner peripheral surfaces of both ends of the outer ring 2a, and both the flanges are formed on the inner peripheral surface of the outer ring 2a. A cylindrical outer ring raceway 5 a is formed between 10 and 10. A cylindrical inner ring raceway 6a is formed on the outer peripheral surface of the intermediate portion of the metal inner ring 3a. A plurality of metal cylindrical rollers 11 are installed between the outer ring raceway 5a and the inner ring raceway 6a.

  In the case of the rolling bearing 1a configured as described above, since the insulating film 4a is made of ceramics having a small linear expansion coefficient, deformation due to heat can be suppressed. In addition, since the insulating film 4a is covered with the metal layer 9, it is possible to prevent the insulating film 4a from peeling off when the outer ring 2a is fitted and fixed to a mating member such as a housing. However, in the case of the structure described in Patent Document 2 having such a configuration, the manufacturing cost increases as the metal layer 9 is formed. In Patent Document 3, a first metal layer is provided on the outer peripheral surface and both end faces of the outer ring, an insulating film is provided on the first metal layer, and a second metal is provided on the insulating film. A structure with layers is described. In the case of such a structure described in Patent Document 3, it is inevitable that the cost is also increased.

｜Ｚ｜：インピーダンス（Ω）
Ｒ：抵抗値（Ω）
ｆ：周波数（Hz）
Ｃ：静電容量（Ｆ） Incidentally, an electric motor or a generator incorporating a rolling bearing with an insulating film as described above is generally controlled by an inverter. In recent years, there is a tendency to increase the carrier frequency of the inverter in order to reduce noise during switching. Accordingly, the current flowing through the rolling bearing becomes a high frequency. Therefore, the insulating film is required to have high impedance (high insulation resistance value). As is apparent from the following equation, this impedance decreases as the capacitance (C) increases (increases as the capacitance decreases).

| Z |: Impedance (Ω)
R: Resistance value (Ω)
f: Frequency (Hz)
C: Capacitance (F)

ε_o ：真空中の誘電率（８．８５４×１０^-12F/m）
ε_r ：比誘電率
Ａ：面積（m²）
Ｓ：距離（ｍ） Therefore, in order to increase the impedance | Z |, it is necessary to reduce the capacitance C of the insulating film. This capacitance C is proportional to the area (A), as is apparent from the following equation.

ε _o : dielectric constant in vacuum (8.854 × 10 ⁻¹² F / m)
ε _r : relative permittivity A: area (m ² )
S: Distance (m)

  For this reason, when the thickness (distance S) of the insulating film is the same, the smaller the area A, the smaller the capacitance. Therefore, when rolling bearings with different bearing sizes are coated with the same thickness of insulation film, the surface area increases, and the larger the bearing size, the larger the capacitance compared to the smaller bearing size. . Therefore, in order to increase the impedance of the insulating film applied to the rolling bearing having a large bearing size, it is necessary to increase the thickness of the insulating film. However, increasing the film thickness increases the cost of the material. In particular, when this insulating coating is made of a ceramic sprayed layer, the time required for thermal spraying is increased, which also leads to an increase in cost.

  When a ceramic insulating film is formed on a rolling bearing, it is often formed on the outer ring side. The reason for this is that when an insulating coating made of ceramic is formed by thermal spraying, the outer ring in which the surface to be sprayed is the outer peripheral surface or both end surfaces can arrange the thermal spray nozzle outside the member, and the workability is better. Further, when the rolling bearing is incorporated in the rotation support portion, the inner ring and the shaft are often fitted by an interference fit, and the outer ring and the housing are fitted by a clearance fit. However, when a brittle ceramic insulating film is formed on the inner peripheral surface of the inner ring to be fitted by interference fitting, there is a possibility that the insulating film is cracked or chipped. For this reason, in order to prevent such cracking and chipping of the insulating film, a ceramic insulating film is often formed on the outer ring side.

  However, in general, the surface area of the outer ring and the both end faces of the outer ring is larger than the surface area of the inner ring and both end faces of the inner ring, and an insulating film is formed on the outer ring side. In this case, it is necessary to increase the film thickness in order to reduce the electrostatic capacitance from the relational expression between the electrostatic capacitance and the area as described above. On the other hand, a structure in which an insulating film made of ceramic is formed on the inner peripheral surface of the inner ring, the inner ring and the shaft are fitted with a gap fit, and the shape of the fitting surface is devised, or a jig or the like is used. Although it is conceivable to prevent the fitting surface from shifting, it is not realistic because creep occurs between the inner ring and the shaft. Patent Document 4 describes a structure in which the proportion of titanium oxide contained in ceramics is regulated. In the case of the structure described in Patent Document 4, titanium oxide is regulated to 0.25 to 0.75% by weight. However, when the proportion of titanium oxide is increased in this way, sufficient impedance is ensured. It may not be possible.

  In addition, there are Patent Documents 5 to 7 as documents describing techniques related to the present invention. Of these, Patent Document 5 describes a technique for regulating the tightening allowance between the inner ring and the shaft when the inner ring is made of ceramics. Patent Documents 6 and 7 describe techniques for stabilizing the dimensions of the bearing even at high temperatures.

Japanese Patent No. 2779251 JP 2002-48145 A JP 2002-181054 A JP 2005-133876 A Japanese Patent No. 2617300 Japanese Patent No. 3475497 Japanese Patent No. 2624337

  In view of the circumstances as described above, the present invention has a structure in which a ceramic insulating film is formed on the surface of a raceway ring in contact with a metal mating member, which is inexpensive and has a high impedance (insulation resistance value). Invented to realize the above.

The bearing device of the present invention includes a rolling bearing and a metal mating member that externally fits the rolling bearing.
Of these, the rolling bearing includes an outer ring, an inner ring, and a plurality of rolling elements, each of which is made of metal.
Among these, the outer ring forms an outer ring raceway on the inner peripheral surface.
The inner ring is arranged inside the outer ring and forms an inner ring raceway on the outer peripheral surface.
The rolling elements are provided between the outer ring raceway and the inner ring raceway so as to freely roll.
The inner ring is fitted to the mating member with an interference fit.
In particular, in the bearing device of the present invention, a ceramic insulating film mainly composed of alumina (Al ₂ O ₃ ) is formed on at least an inner peripheral surface of the inner ring excluding the inner ring raceway. ing. Further, the tightening allowance between the inner ring and the mating member is regulated so that the insulating film is not damaged. The inner ring includes an insulating film that covers the inner peripheral surface, and the tightening allowance between the inner ring and the mating member (for example, the shaft) referred to in the present invention is the insulating film that covers the inner peripheral surface of the inner ring and the inner ring. This is the tightening allowance with the mating member.

Further, in order to prevent the insulating film from being damaged during use, as described in claim 2, the allowance between the inner ring and the mating member acts on the insulating film covering the inner peripheral surface of the inner ring even during use. It is preferable to regulate the hoop stress (circumferential stress) to be 200 N / mm ² or less. That is, during use, the inner ring and the mating member may thermally expand. Even in this case, the tightening allowance is determined so that the hoop stress acting on the insulating film does not exceed 200 N / mm ² . Of course, the hoop stress acting on the insulating film should not exceed 200 N / mm ² even during fitting (before the temperature rises).
When the above-described invention is carried out, preferably, the insulation film has an insulation resistance value of 1000 MΩ or more and a capacitance of 27 nF or less.
In order to regulate the insulation resistance value and capacitance of the insulating film as described above, for example, as described in claim 4, the insulating film has an alumina content of 99% by weight or more, The insulating layer contains 0.01 to 0.2% by weight of titanium oxide (titania, TiO ₂ ), and the film thickness is 0.1 to 0.7 mm.
Alternatively, as described in claim 5, the insulating film is an insulating layer having an alumina content of 97% by weight or more and zirconia (ZrO ₂ ) in an amount of 0.1 to 2.5% by weight. Is 0.1 to 0.7 mm.

  Further, in the case of carrying out each of the above-described inventions, when the insulating coating is formed by plasma spraying, preferably, as described in claim 6, of the two race rings constituting the rolling bearing, At least the inner ring that has been subjected to high-temperature dimensional stabilization treatment or that made of a high-temperature dimensional stabilizer is used. Among these, as described in the above-mentioned Patent Document 6, for example, as described in Patent Document 6, a high-temperature tempering process or a two-time tempering process is performed to reduce the residual austenite amount to 2% by volume or less. Is raised. In addition, as the high temperature dimension stabilizing material, for example, AISI M50 and M50NIL which are high speed steels for high temperature bearings, and Si and Cu contents as described in the above-mentioned Patent Document 7, ordinary bearing steels are used. (SUJ2, SUJ3, etc.) and the amount of retained austenite is 3% by volume or less.

In addition, as described in claim 7, the surface area of the outer ring surface and both end faces of the outer ring is 1.3 times or more than the surface area of the inner ring inner face and both end faces. It is preferable to apply the present invention to such a structure. More preferably, as described in claim 8, the present invention is applied to a structure in which the insulating film is composed of only one layer formed directly on the surface of the inner ring and the inner diameter of the rolling bearing is 100 mm or more.
More preferably, as described in claim 9, the bearing device of the present invention is incorporated in a rotation support portion of an inverter-controlled electric motor or generator. In this case, for example, the inner ring of the rolling bearing is externally fixed to a rotating shaft that constitutes an electric motor or the like and that has a rotor on the outer peripheral surface.

According to the bearing device of the present invention configured as described above, a structure in which a ceramic insulating film is formed on a raceway ring and a structure with low impedance and high impedance (insulation resistance value) can be realized.
That is, since the insulating film is formed on the inner ring side, the area for forming this film can be reduced. As a result, the capacitance of the insulating film can be reduced and the impedance can be increased. Further, since it is not necessary to increase the film thickness in order to reduce the capacitance, the manufacturing cost can be reduced. If the inner ring is fitted to the mating member by an interference fit, damage such as cracks may occur in the insulating coating made of brittle ceramic, but the tightening allowance between the inner ring and the mating member is Such a problem will not occur if the insulating film is regulated so that it is not damaged during use. In particular, as described in claim 2, the tightening allowance between the inner ring and the mating member is such that the hoop stress acting on the insulating film covering the inner peripheral surface of the inner ring is 200 N / mm ² or less even when in use. If it restrict | limits, it can prevent effectively that damage, such as a crack, arises in the said insulating film.

  In addition, as described in claim 3, the material and film thickness of the ceramic insulating film mainly composed of alumina are set so that the insulating resistance value of the insulating film is 1000 MΩ or more and the capacitance is 27 nF or less. By selecting, it is possible to increase the impedance of the bearing device more reliably. According to various data such as the experiment data of the present inventor, when the capacitance exceeds 27 nF, there are cases where sufficient impedance (insulation resistance value) cannot be obtained. On the other hand, if the capacitance is 27 nF or less, preferably 25 nF, more preferably 23 nF or less, the impedance of the bearing device can be increased.

  Further, the insulating film is formed by an insulating layer having an alumina content of 99% by weight or more and titanium oxide of 0.01 to 0.2% by weight as described in claim 4, for example. If the thickness is 0.1 to 0.7 mm, an insulating film having a high impedance as described above can be obtained at low cost. That is, the higher the purity of alumina, the higher the impedance can be. However, increasing the purity of alumina leads to an increase in manufacturing cost. On the other hand, if the content of titania inevitably contained is regulated to a range of 0.01 to 0.2 weight, an insulating film having a high impedance can be obtained while suppressing an increase in cost. Further, if the thickness of the insulating film is less than 0.1 mm, the insulation resistance is inferior, and even if it is thicker than 0.7 mm, the improvement in the insulation performance cannot be expected at a rate where the cost increases. Therefore, in order to secure insulation resistance and suppress an increase in manufacturing cost, the film thickness of the insulating film is set to 0.1 to 0.7 mm, preferably 0.2 to 0.5 mm.

  In addition, if the insulating film is formed of an insulating layer having an alumina content of 97% by weight or more and zirconia in an amount of 0.1 to 2.5% by weight as described in claim 5, for example, In addition to increasing the purity, the impedance can be increased, and the adhesion strength of the insulating film to the metal surface can be improved. That is, when the content of zirconia having high strength and high toughness is less than 0.1% by weight, the adhesion strength cannot be sufficiently improved. On the other hand, when the content of the zirconia is more than 2.5% by weight, the purity of alumina becomes too low and the impedance is lowered. Even when zirconia is contained as described above, the thickness of the insulating film is 0.1 to 0.7 mm, preferably 0.2 to 0.5 mm, as in the case of containing titania. If so, it is possible to achieve a balance between securing insulation resistance and reducing manufacturing costs.

  Further, when the insulating coating is formed by plasma spraying, as described in claim 6, at least the inner ring of the two bearing rings constituting the rolling bearing is subjected to high temperature dimensional stabilization treatment, or If a high temperature dimensional stabilizer is used, the dimensional accuracy of the inner ring can be ensured. That is, by performing the above high temperature dimensional stabilization treatment or using a high temperature dimensional stabilizer, the dimensional accuracy of the inner ring is maintained even when the temperature is locally increased by a high temperature plasma spray gas. The

  In addition, as described in claim 7, the surface area of the outer ring surface and both end faces of the outer ring is 1.3 times or more than the surface area of the inner ring inner face and both end faces. If the present invention is applied to the structure, the effects of the present invention can be obtained more remarkably. That is, if the difference in surface area between the outer ring and the inner ring is large, when the insulating film is formed on the inner ring side, the rate at which the capacitance can be reduced is larger than when the insulating film of the same thickness is formed on the outer ring side. Become. In addition, the impedance can be further increased and the effect of cost reduction is increased.

  Further, as described in claim 8, if the present invention is applied to a structure in which the inner diameter of the rolling bearing (inner ring) is 100 mm or more, the above-described high impedance and cost reduction can be achieved to a higher degree. Can be compatible. In the case of a large bearing having an inner diameter of more than 100 mm, 3, 2, and 0 are frequently used in the diameter series. In the case of such a diameter series rolling bearing, the surface area of the outer ring is 30 with respect to the surface area of the inner ring. % More. Further, in the case of a rolling bearing having an inner diameter of 100 mm or more, it is easy to perform thermal spraying on the inner peripheral surface, the workability is improved, and the cost can be reduced. Moreover, since the insulating film is a single layer, the manufacturing cost can be reduced as compared with the structures described in Patent Documents 2 to 3 described above. Further, as described above, if an insulating film containing zirconia is used, the adhesion between the insulating film and the inner ring is enhanced, and the insulating film can be prevented from peeling without providing a metal layer.

  Furthermore, as described in claim 9, the effect of the present invention can be obtained more effectively by incorporating the bearing device of the present invention into a rotation support portion of an electric motor or generator controlled by an inverter. That is, as described above, an inverter-controlled electric motor or the like tends to increase the carrier frequency of the inverter, so that the current flowing through the rolling bearing becomes a high frequency. Therefore, the insulating film is required to have high impedance (high insulation resistance value). On the other hand, in the case of the present invention, as described above, since a high impedance can be realized, it is suitable for the electric motor controlled by the inverter.

[Example of Embodiment]
FIG. 1 shows an example of an embodiment of the present invention. The feature of the present invention is that a ceramic insulating film is formed on the inner ring 3 side in order to realize an inexpensive and high impedance (insulation resistance value) structure, and the tightening allowance between the inner ring 3 and the mating member is regulated. In the point. The basic structure and operation of the bearing device are the same as those of conventionally known bearing devices such as Patent Documents 1 to 4 described above. For this reason, the description of the same part as the conventional structure will be omitted or simplified, and the following description will focus on the characteristic part of this example.

  Similarly to the structures described in Patent Documents 1 to 4, the bearing device of this example also includes a rolling bearing 1b and a metal shaft (not shown) that is a mating member that externally fits the rolling bearing 1b. . Examples of the material of the shaft include carbon steel such as chrome molybdenum steel, nickel chrome molybdenum steel, and medium carbon steel. In addition, the rolling bearing 1b is similar to the structure shown in FIG. 3 described above. Each of the rolling bearings 1b is made of metal such as bearing steel (for example, SUJ2, SUJ3), and the like. 7. In this example, the inner ring 3 is subjected to dimensional stabilization processing. As this dimension stabilization treatment, for example, tempering is performed at a high temperature (for example, 240 ° C.) after quenching, and the amount of retained austenite is set to 2% by volume or less.

In the case of this example, the surface area of the outer peripheral surface 12 of the outer ring 2 and the axial end faces 13 and 13 is the same as the inner peripheral surface 14 of the inner ring 3 and the axial end faces 15 and 15. 1.3 times or more of the surface area of the portion. Further, in the present example, is the inner diameter R ₃ of the rolling bearing 1b is 100mm or more.

  In particular, in the case of this example, the inner peripheral surface 14 and the axial end surfaces 15 and 15 of the inner ring 3 are covered with a ceramic insulating film 4b mainly composed of alumina. The insulating film 4b is a single layer, and no metal layer as described in Patent Documents 2 to 3 is formed. The insulating film 4b is formed by plasma spraying, and is an insulating layer having an alumina content of 99% by weight or more and a titanium oxide content of 0.01 to 0.2% by weight. Further, the insulating film 4b allows the inner peripheral surface 14 and both axial end surfaces 15 and 15 to be continuous with both axial end edges of the inner peripheral surface 14 and inner peripheral edges of the axial end surfaces 15 and 15. The surfaces of the inner-diameter side bent continuous portions 16 and 16 having a circular arc shape of a quarter of the cross section are also covered. Further, in the case of this example, the outer peripheral side bent portions 17, 17 having a quarter-circular arc-shaped cross section, in which the outer peripheral edges of the both end surfaces 15, 15 and the both axial end edges of the outer peripheral surface of the inner ring 3 are continuous. Is also covered with the insulating film 4b.

  In the case of this example, the thickness of the insulating film 4b covering the inner peripheral surface 14 and both end surfaces 15 and 15 of the inner ring 3 is set to 0.1 to 0.7 mm. Thus, in order to regulate the film thickness of the insulating film 4b, the surface is polished after the ceramic insulating layer is formed. Further, the thickness of the insulating film 4b may be at least 0.1 to 0.7 mm at a portion covering the inner peripheral surface 14 and both end surfaces 15 and 15. That is, the portion of the insulating film 4b covering the inner and outer diameter side bent continuous portions 16 and 17 is left as it is (without the ceramic solution) in order to reduce costs. It may be in a state in which droplets are ejected. In this example, as described above, the insulation resistance value of the insulating film 4b is set to 1000 MΩ or more and the capacitance is set to 27 nF or less by regulating the material and film thickness of the insulating film 4b.

  The rolling bearing 1b is incorporated in a rotation support portion of an electric motor or generator controlled by an inverter. That is, the outer ring 2 is fixed to the metal housing constituting the rotation support portion with a clearance fit, and the inner ring 3 is formed with the insulating film 4b on the inner peripheral surface 14 and both end surfaces 15, 15. Are fitted and fixed to the shaft constituting the rotation support portion by an interference fit. As described above, this shaft is made of a metal such as chromium molybdenum steel or medium carbon steel. In the case of this example, in this state, the tightening allowance between the inner ring 3 and the shaft is restricted so that the insulating coating 4b is not damaged.

For this reason, in the case of this example, the hoop stress acting on the insulating film 4b covering the inner peripheral surface 14 of the inner ring 3 is 200 N / mm ² or less even when the inner ring 3 and the shaft are tightened. It regulates like. In this way, the hoop stress acting on the insulating film 4b can be calculated from, for example, the material and dimensions of the inner ring 3 and the shaft, the material and film thickness of the insulating film 4b, and the assumed temperature during use. . Then, the tightening allowance between the inner ring 3 and the shaft is determined so that the hoop stress during use does not exceed 200 N / mm ² . Of course, the hoop stress acting on the insulating film 4b should not exceed 200 N / mm ² when the inner ring 3 and the shaft are fitted (at room temperature). In this way, in order to prevent the hoop stress from exceeding 200 N / mm ² , for example, in the case of a rolling bearing having an inner ring 3 with an inner diameter of 180 mm and the bearing grade is class 0, the fitting dimension with the shaft The tolerance is set in the range of k5 to r7 (JIS B 1566).

According to the structure of the present example configured as described above, a structure in which a ceramic insulating film is formed on the bearing ring, and a structure with low impedance and high impedance (insulation resistance) can be realized.
That is, in this example, since the insulating film 4b is formed on the inner ring 3 side, the area for forming the insulating film 4b can be reduced as compared with the case where the film is formed on the outer ring 2 side. As a result, the capacitance of the insulating film 4b can be reduced and the impedance can be increased. Further, since it is not necessary to increase the film thickness in order to reduce the capacitance, the manufacturing cost can be reduced.

Since the metal constituting the inner ring 3 and the shaft has a smaller elastic coefficient and a larger linear expansion coefficient than the ceramics constituting the insulating film 4b, the tightening allowance between the inner ring 3 and the shaft is increased as the temperature rises during use. Increases and the hoop stress acting on the insulating film 4b increases. For this reason, if the tightening allowance at the time of fitting is too large, the insulation film 4b may be damaged due to an increase in hoop stress accompanying a temperature rise. On the other hand, as in this example, if the tightening allowance between the inner ring 3 and the shaft is appropriate, the inner ring 3 and the shaft can be firmly coupled and the insulating film covering the inner peripheral surface of the inner ring 3 is also provided. Damage to 4b can be prevented. In particular, in the case of this example, the interference between the inner ring 3 and the shaft is restricted so that the hoop stress acting on the insulating film 4b covering the inner peripheral surface 14 of the inner ring 3 is 200 N / mm ² or less even during use. Therefore, it is possible to more reliably prevent the insulation film 4b from being damaged such as cracks.

  In the case of this example, the insulating film 4b is an insulating layer having an alumina content of 99% by weight or more and titanium oxide of 0.01 to 0.2% by weight. 0.7 mm, the insulation resistance value of the insulating film 4b is 1000 MΩ or more and the capacitance is 27 nF or less. For this reason, higher impedance of the bearing device can be achieved more reliably. In the case of this example, among the surfaces of the inner ring 3, the surfaces of the outer diameter side bent continuous portions 17 and 17 are also covered with the insulating film 4b, so that creeping discharge can be avoided and the impedance can be further increased. For example, when the end surface 15 of the inner ring 3 is brought into contact with a step provided on the outer peripheral surface of the shaft, the distance between the end of the outer peripheral surface of the inner ring 3 on which the insulating film 4b is not formed and the step may be reduced. is there. In this case, even if the axial end surface 15 of the inner ring 3 is covered with the insulating film 4b, a current may flow through the step along the outer peripheral surface of the inner ring 3. On the other hand, if the surface of the outer-diameter-side bent continuous portions 17 and 17 that make the both ends of the outer peripheral surface of the inner ring 3 and the outer peripheral edges of the axial end surfaces 15 and 15 continuous are covered with the insulating film 4b, It is possible to prevent a current from flowing to the shaft side along the outer peripheral surface of the inner ring 3.

  Further, the insulating film 4b is formed of an insulating layer having an alumina content of 99% by weight or more and titanium oxide of 0.01 to 0.2% by weight, and the film thickness is 0.1 to 0.7 mm. Therefore, the insulating film 4b having the high impedance as described above can be obtained at a low cost. In the case of this example, since this insulating coating 4b is formed by plasma spraying, the temperature is locally increased by the high temperature plasma spraying gas, but the inner ring 3 forming the insulating coating 4b is subjected to high temperature dimensional stabilization treatment. Therefore, the dimensions of the inner ring 3 can be maintained even when the temperature is locally increased by plasma spraying.

  In the case of this example, the surface area of the outer ring 2 on the outer ring 2 combined with the both end faces 13 and 13 is the surface area of the inner ring 14 on the inner ring 3 combined with both end faces 15 and 15. Is 1.3 times or more. Further, the inner diameter of the rolling bearing 1b is 100 mm or more. For this reason, higher impedance and cost reduction of the bearing device can be achieved at a higher level. Further, in the case of the rolling bearing 1b having an inner diameter of 100 mm or more, the inner peripheral surface 14 is easily sprayed, the workability is improved, and the cost can be reduced.

The calculation performed to confirm the effect of the present invention will be described. The purpose of this calculation is to compare the respective capacitances when a ceramic insulating film is formed on the outer ring side of the rolling bearing and when an insulating film is formed on the inner ring side. The target rolling bearing is a deep groove type ball bearing generally used in generators and electric motors, and has a nominal number 6336 (inner diameter 180 mm, outer diameter 380 mm, width 75 mm). In this ball bearing, the surface area of the portion where the outer peripheral surface and both end surfaces of the outer ring are combined is 142780 mm ² , and the surface area of the portion where the inner peripheral surface and both end surfaces of the inner ring are combined is 77200 mm ² . For this reason, the surface area on the outer ring side is 1.3 times or more (1.85 times) the surface area on the inner ring side.

  In this example, first, the capacitance per unit area of the insulating film was measured. That is, the capacitance per unit area (10 mm × 10 mm) of the ceramic insulating film containing 99.7% by weight of alumina and 0.04% by weight of titanium oxide, and having a film thickness of 0. Measurements were taken at 3 mm and 0.5 mm, respectively. In this way, straight lines (solid line and broken line) as shown in FIG. 2 were obtained, and the capacitance at each film thickness for each surface area was calculated. In addition, the thing of the thickness of 0.3 mm is shown with a continuous line, and the thing of 0.5 mm is shown with a broken line, respectively. As apparent from FIG. 2, the capacitance can be reduced by forming the insulating film on the inner ring side having a small surface area. In particular, when the thickness of the insulating film is 0.3 mm, the capacitance can be suppressed to 27 nF or less even when the insulating film is formed on the outer ring side having a large surface area. When formed, the capacitance is less than 15 nF. Further, when an insulating film having a film thickness of 0.5 mm is formed on the outer ring side, the capacitance can be reduced, but still, it is less static than when an insulating film having a film thickness of 0.3 mm is formed on the inner ring side. The electric capacity increases.

  From the results of such calculations, it can be seen that the formation of an insulating film on the inner ring side can significantly reduce the capacitance and increase the impedance. Also, from the above calculation, when an insulating film is formed on the outer ring side, it is necessary to considerably increase the film thickness of the insulating film in order to obtain the same capacitance as a rolling bearing having an insulating film formed on the inner ring side. I understand that there is. For this reason, it can be seen that the cost reduction effect by forming the insulating film on the inner ring side is very large, considering that the area for forming the insulating film on the outer ring side is large.

The fragmentary sectional view of the rolling bearing which shows one example of embodiment of this invention. The diagram which shows the result of the calculation performed in order to investigate the effect of this invention. Sectional drawing which shows the 1st example of a conventional structure. The fragmentary sectional view of the rolling bearing which shows the 2nd example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b Rolling bearing 2, 2a Outer ring 3, 3a Inner ring 4, 4a, 4b Insulation film 5, 5a Outer ring raceway 6, 6a Inner ring raceway 7 Ball 8 Housing 9 Metal layer 10 Hook 11 Cylindrical roller 12 Outer peripheral surface 13 End surface 14 Inner peripheral surface 15 End surface 16 Inner diameter side bent continuous portion 17 Outer diameter side bent continuous portion

Claims (9)

  A rolling bearing and a metal mating member that externally fits the rolling bearing, the rolling bearing of which is disposed inside the outer ring, a metal outer ring having an outer ring raceway formed on the inner peripheral surface, A metal inner ring having an inner ring raceway formed on the outer peripheral surface, and a plurality of rolling elements each made of metal and provided between the outer ring raceway and the inner ring raceway. In a bearing device in which the inner ring is fitted into the mating member by interference fit, an insulating film made of ceramics mainly composed of alumina is formed on at least the inner peripheral surface of the inner ring except for the inner ring raceway. A bearing device that is formed and restricts a tightening margin between the inner ring and the mating member so that the insulating coating is not damaged. The bearing according to claim 1, wherein the tightening allowance between the inner ring and the mating member is regulated so that the hoop stress acting on the insulating film covering the inner peripheral surface of the inner ring is 200 N / mm ² or less even during use. apparatus.   The bearing device according to claim 1 or 2, wherein the insulation film has an insulation resistance value of 1000 MΩ or more and a capacitance of 27 nF or less.   The insulating film is an insulating layer having an alumina content of 99% by weight or more, 0.01 to 0.2% by weight of titanium oxide, and a film thickness of 0.1 to 0.7 mm. The bearing device described in 1.   The insulating film has an alumina content of 97% by weight or more, an insulating layer containing 0.1 to 2.5% by weight of zirconia, and a film thickness of 0.1 to 0.7 mm. The bearing device described.   The insulating film is formed by plasma spraying, and at least the inner ring of both the bearing rings constituting the rolling bearing is subjected to high temperature dimensional stabilization treatment, or is made of a high temperature dimensional stabilizer. The bearing device according to any one of claims 1 to 5.   The surface area of the part which combined the outer peripheral surface and both end surfaces of the outer ring is 1.3 times or more with respect to the surface area of the part which combined the inner peripheral surface and both end faces of the inner ring. The bearing device described in any one item.   The bearing device according to any one of claims 1 to 7, wherein the insulating film is formed of only one layer formed directly on the surface of the inner ring, and the inner diameter of the rolling bearing is 100 mm or more. The bearing device according to any one of claims 1 to 8, wherein the bearing device is incorporated in a rotation support portion of an electric motor or a generator controlled by an inverter.

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