JP6120361B2 - Method for manufacturing rolling bearing for preventing electrical decoration - Google Patents

Description

The present invention relates to a method for manufacturing a rolling bearing, and more particularly to a method for manufacturing a rolling bearing for preventing electric corrosion in which electric corrosion caused by an electric current generated in an electric motor or the like of a railway vehicle is prevented by coating a ceramic spray coating.

  A rolling bearing provided with a metal outer ring and a metal inner ring arranged concentrically with the outer ring via a rolling element on the radially inner side of the outer ring as a bearing for a rotating shaft of an electric motor of a railway vehicle, etc. Is commonly used. In a rolling bearing that supports a rotating shaft of an electric motor, a generator, and an electric device of a railway vehicle, a current generated by the electric motor or the like flows through an outer ring, a rolling element, and an inner ring. The current flowing through the rolling bearing sparks at the contact surface between the rolling elements and the inner and outer rings, and electric corrosion occurs on the outer ring, the rolling elements, and the inner ring that form a current path. Electrical corrosion not only degrades the performance of rolling bearings, but also causes a reduction in life.

  By insulating between the outer ring of the rolling bearing, for example, and the housing that supports the rolling bearing so that no current flows through the rolling bearing, it is possible to prevent the life from being shortened by electric corrosion. For this purpose, the outer surface of the outer ring of the rolling bearing that contacts the housing may be covered with an insulating material. As the insulating material, a ceramic material is suitable, and in order to coat with the ceramic material, a ceramic film is formed on the outer surface of the outer ring of the rolling bearing by a thermal spraying method.

  Patent Document 1 and Patent Document 2 describe an electric corrosion prevention rolling bearing in which the outer surface of the outer ring of the rolling bearing is roughened and a ceramic sprayed coating of 0.15 to 0.45 mm is formed on the surface. Yes. There is also known a rolling bearing in which a ceramic sprayed coating made of gray alumina containing aluminum oxide and titanium oxide is formed on the outer surface of the outer ring with a predetermined thickness (Patent Document 3). A rolling bearing is known in which a ceramic sprayed coating containing alumina as a main component and titanium oxide content of 0.01 to 0.2% by weight is formed on the outer surface of an outer ring (Patent Document 4). In this prior art, the particle size of the ceramic powder for forming the ceramic spray coating is 10 to 50 μm.

  In the rolling bearing of Patent Document 5, a ceramic sprayed coating having a porosity of 2 to 6% is formed on the outer surface of the outer ring and further filled with an organic sealant. In the rolling bearing described in Patent Document 6, the surface of the outer ring attached to the housing is coated with a ceramic coating layer and two metal layers thereon. Patent Document 7 describes a rolling bearing in which an outer surface of an outer ring of a rolling bearing is roughened to Ra of 1.0 to 3.0 μm and a ceramic film is formed on the roughened surface.

JP 2011-117607 A JP 2007-170673 A JP 2009-299904 A JP 2007-147072 A JP 2008-50669 A JP 2002-181054 A JP 2008-32127 A

  In the rolling bearings of Patent Document 1 and Patent Document 2, the outer surface of the outer ring is roughened to form a ceramic sprayed coating having a film thickness of 0.15 mm to 0.45 mm. If the film is formed, it is not possible to obtain a sufficient manufacturing cost reduction effect. In addition, due to the influence of the film thickness, the film peels off due to the shear stress that occurs between the outer ring of the rolling bearing and the mechanical strength due to the residual stress inside the film under the environment where the temperature difference is large. There is a risk of damage such as cracks. If only the film thickness of the ceramic sprayed coating is reduced, not only the insulating property is lowered but also the coating is easily damaged. In the case of the rolling bearing of Patent Document 3 in which a ceramic spray coating made of gray alumina containing aluminum oxide and titanium oxide is formed, the film thickness of the coating is 0.1 mm to 0.8 mm. In spite of the adoption, the effect of reducing the manufacturing cost is not sufficient, and there is a problem of peeling of the ceramic sprayed coating.

  In the rolling bearings of Patent Document 4 in which the particle size of the ceramic powder is 10 to 50 μm and Patent Document 5 in which the ceramic spray coating is filled with an organic sealing agent to suppress variation in insulation resistance, ceramic spraying is performed. Since the film thickness is about 0.4 mm, the cost is high, and in addition, the adhesion between the outer ring and the ceramic spray coating is low. The rolling bearing of Patent Document 6 having a three-layer structure composed of a ceramic spray coating and a metal layer is expensive because it requires a step for providing the metal layer. In the rolling bearing of Patent Document 7 in which the outer surface of the outer ring of the rolling bearing is roughened to Ra: 1.0 to 3.0 μm, even though the adhesion can be obtained, the film thickness is large and the same as in Patent Document 1 and the like. There are problems such as high cost. In addition, there is also a drawback that insulation performance is insufficient and electrolytic corrosion occurs in an environment where a high current flows, leading to a short life.

Therefore, in view of the above-mentioned problems of the prior art, the present invention can greatly reduce the manufacturing cost, is difficult to be damaged even in various environments, and has high adhesion and sufficient insulation performance. It aims at providing the manufacturing method of the rolling bearing for prevention.

In order to achieve the above object, the following technical measures were taken. That is, a method of manufacturing a rolling bearing for preventing electrical decoration according to the present invention includes a metal outer ring, and a metal inner ring that is concentrically disposed via the outer ring and a plurality of rolling elements and is relatively rotatable. the outer ring or ceramic sprayed coating for electrolytic corrosion prevention on the inner ring of the outer surface of a production method of electrolytic corrosion prevention rolling bearing that will be formed by a plasma spraying method, the ceramic thermal sprayed coating, aluminum oxide and titanium It is made of a material having an oxide as a main component, the aluminum oxide content is 98.0 wt% to 99.5 wt%, and the titanium oxide content is 0.5 wt% to 2 wt% . A surface roughness of the outer surface of the outer ring or the inner ring formed by spraying a ceramic powder having an average particle size of 3 μm to 14 μm and coated with the ceramic spray coating is Ra: 0. Is a 5Myuemu～2.0Myuemu, the thickness of the ceramic thermal spray coating a sealing treatment with an organic resin is applied to the ceramic sprayed coating is between 50 .mu.m to 100 .mu.m, the ceramic sprayed coating having a volume resistivity of ^{10 13} [Omega] cm It is a manufacturing method of the rolling bearing for electrolytic corrosion prevention characterized by being -10 < ¹⁶ > ohm-cm.

According to the present invention, since the ceramic sprayed coating is made of a material mainly composed of aluminum oxide and titanium oxide, the film forming efficiency during the spraying is high, and the film can be formed at low cost. Since the aluminum oxide content in the ceramic spray coating is 98.0 wt% to 99.5 wt%, and the titanium oxide content is 0.5 wt% to 2 wt%, Higher insulation performance can be maintained than a material mainly composed of normal aluminum oxide and titanium oxide, and a volume resistivity of 10 ¹³ Ωcm to 10 ¹⁶ Ωcm can be achieved. Since the surface roughness of the outer surface of the outer ring or inner ring coated with the ceramic spray coating is Ra: 0.5 μm to 2.0 μm, high adhesion to the ceramic spray coating can be obtained. The film thickness of the ceramic sprayed coating is 50 μm to 100 μm, which has a great effect of reducing the manufacturing cost, and the shear stress generated between the outer ring of the rolling bearing and the residual inside the coating in a usage environment with a large temperature difference. The mechanical strength is not easily lowered by the influence of stress, and damage such as peeling or cracking of the film can be prevented. Further, the ceramic spray coating is formed by spraying ceramic powder having an average particle size of 3 μm to 14 μm. If the average particle size is too small, the fluidity of the ceramic powder during film formation is lowered and stable supply cannot be achieved, and the thickness tends to be non-uniform. When the average particle size is too large, a portion where the film is formed without being completely melted is formed, and the film is excessively porous so that it becomes difficult to fill with the sealing agent, and the insulating performance is deteriorated.

  It is preferable to adjust the surface roughness of the ceramic sprayed coating after the finishing treatment after the sealing treatment to Ra: less than 1 μm and the skewness Rsk to less than 0. The surface roughness after the finishing treatment is Ra: less than 1 μm, and the skewness Rsk, which is a rough indication of surface irregularities, is less than 0, so there are few protrusions on the surface. Therefore, the electric field concentration occurring on the surface when a current flows can be reduced, and the dielectric breakdown can be remarkably improved.

  If the dielectric breakdown voltage per unit film thickness of the above ceramic sprayed coating is adjusted to 35 kV / mm or more, even if a high current flows through the rolling bearing, the dielectric breakdown of the ceramic sprayed coating does not occur and durability Can be significantly increased.

  As described above, according to the present invention, the film formation efficiency at the time of thermal spraying is high, and the film thickness of the film is thin, so that the manufacturing cost can be greatly reduced. Since the titanium oxide content is low, high insulation performance can be maintained. Since the surface roughness of the outer surface of the outer ring or inner ring is reduced, high adhesion with the film can be obtained. Since the ceramic spray coating is thin, it is difficult for mechanical strength to decrease due to the effects of shear stress between the outer ring and inner ring or residual stress inside the coating, and damage caused by cracking or peeling of the coating should not be caused. Can be.

1 is a cross-sectional view of a rolling bearing for preventing electrolytic corrosion according to an embodiment of the present invention in which a ceramic sprayed coating is formed on an outer ring. It is sectional drawing of the rolling bearing for electrolytic corrosion prevention which concerns on other embodiment which formed the ceramic sprayed coating in the inner ring | wheel.

  Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view of a rolling bearing 1 for preventing electric corrosion according to an embodiment of the present invention. The rolling bearing 1 for preventing electric corrosion is a ball bearing using balls as rolling elements, and is a ring-shaped metal outer ring 2 and a ring-shaped metal that is arranged concentrically with the outer ring 2 and is relatively rotatable. The inner ring 3 is mainly composed of a made inner ring 3, a ring-shaped cage 4 arranged between the outer ring 2 and the inner ring 3, and a plurality of rolling elements 5 held by the cage 4. In addition, this invention is not limited to this embodiment, It applies to the rolling bearing for an electric corrosion prevention provided with another shape, a form, or another member. Examples of other electric corrosion prevention rolling bearings include a tapered roller bearing and a cylindrical roller bearing.

  An outer ring side raceway surface 2a having a circular arc shape is formed on the inner periphery of the outer ring 2, and outer ring side small diameter portions 2b and the like are formed on both sides of the outer ring side raceway surface 2a. An inner ring side raceway surface 3a having a circular arc shape is formed on the outer periphery of the inner ring 3, and inner ring side small diameter portions 3b and the like are formed on both sides of the inner ring side raceway surface 3a. The cage 4 has a plurality of pocket portions 4a in the circumferential direction, and a metallic and spherical rolling element 5 is rotatably held in each pocket portion 4a. When the inner ring 3 rotates with respect to the outer ring 2, the plurality of rolling elements 5 roll on the outer ring side raceway surface 2 a and the inner ring side raceway surface 3 a, and the rolling element 5 moves in the same direction as the rotation direction of the inner ring 3. The cage 4 that holds the plurality of rolling elements 5 also moves in the same direction as the rolling elements 5.

  The electric corrosion prevention rolling bearing 1 is mainly applied to a rolling bearing that supports a rotating shaft of an electric motor, a generator, or an electric device of a vehicle, and current generated by the electric motor or the like generates an outer ring 2, a rolling element 5, an inner ring 3. It is a rolling bearing that prevents electric corrosion from occurring in the rolling bearing 1 for preventing electric corrosion when flowing through the shaft. The outer ring 2 is fixed in contact with a housing (not shown) for attaching the rolling bearing 1 for preventing electric corrosion. An insulating function is given to the entire outer surface 21 of the outer ring 2 that is a contact portion with the housing. By making the outer surface 21 of the outer ring 2 in an insulating state, no current flows through the rolling bearing 1 for preventing electrolytic corrosion, and electrolytic corrosion can be prevented.

In order to prevent such electrolytic corrosion, a ceramic spray coating 10 as an insulating layer is formed on the outer surface 21 of the outer ring 2. In this embodiment, the ceramic sprayed coating 10 is formed on the outer ring 2, but a similar ceramic sprayed coating may be formed on the outer surface 31 of the inner ring 3 as shown in FIG. In this case, the outer surface 31 of the inner ring 3 comes into contact with a rotating shaft (not shown). As ceramic materials for forming a thermal spray coating, generally, Al ₂ O ₃ , MgO, TiO ₂ , Cr ₂ O ₃ , ZrO ₂ , HfO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ .TiO ₂ , Al ₂ O ₃ .SiO ₂ , Al ₂ O ₃ .MgO, and the like are known. Among these, as a ceramic constituting the ceramic sprayed coating 10 of the present embodiment, a material mainly composed of aluminum oxide, titanium oxide, or the like can be used. More specifically, gray alumina (Al ₂ O ₃ , TiO ₂ ), alumina yttria (3Al ₂ O ₃ · 5Y ₂ O ₃ ), alumina magnesia (Mg · Al ₂ O ₄ ), alumina · silica (3Al ₂ O ₃ · 2SiO ₂ ). In particular, gray alumina mainly composed of aluminum oxide and titanium oxide is suitable.

White alumina (Al ₂ O ₃ ), which has a high dielectric breakdown voltage and a high volume resistivity, is known as a material for a ceramic spray coating for preventing electrolytic corrosion. The gray alumina (Al ₂ O ₃ , TiO ₂ ) contains titanium oxide, which is a conductive material. Gray alumina has a volume resistivity lower than that of white alumina, and a dielectric breakdown voltage is also lower than that of white alumina. . On the other hand, film forming efficiency is an advantage of selecting gray alumina. The melting point of titanium oxide (TiO ₂ ) is lower than that of white alumina. Therefore, the titanium oxide (TiO ₂ ) is more easily adhered to the metal substrate than the case where the aluminum oxide (Al ₂ O ₃ ) is 100%, and a uniform film is formed. Cheap. Therefore, the yield is better when gray alumina is selected, and the manufacturing cost can be reduced.

  Therefore, it is necessary to select a material for the ceramic sprayed coating in consideration of the balance between the performance of dielectric breakdown voltage and volume resistivity and the cost, and in this embodiment, the main component is aluminum oxide and titanium oxide. The material, gray alumina, is most preferably used. As a compounding ratio that can realize low cost without impairing the performance aspects of dielectric breakdown voltage and volume resistivity, the content of aluminum oxide in the ceramic sprayed coating is 98.0 wt% to 99.5 wt%, and titanium oxidation The content of the product is 0.5 wt% to 2 wt%. More preferably, the content of titanium oxide in the ceramic sprayed coating is 0.5 to less than 1% by weight.

The reason why at least titanium oxide is included in the ceramic sprayed coating is to maintain a high dielectric breakdown voltage and a high volume resistivity in consideration of the manufacturing cost as described above, and to contain a large amount of aluminum oxide. is there. That is, by reducing the content of titanium oxide to 2% by weight at the maximum, a decrease in insulation performance due to titanium oxide, which is a conductive material, is suppressed. In addition, a high volume resistivity can be obtained by limiting the content of titanium oxide to such a blending ratio. Specifically, a volume resistivity of 10 ¹³ Ωcm to 10 ¹⁶ Ωcm is achieved. As a result, high insulation performance and good volume resistivity can be maintained, and at the same time, manufacturing costs can be reduced.

  It is particularly important in the present invention to adjust the film thickness of the ceramic sprayed coating. The film thickness of this embodiment is 50 μm to 100 μm, and an extremely thin ceramic spray coating is formed compared to the conventional one. A more preferable range of the film thickness is 70 μm to 85 μm. There are the following advantages by making the ceramic sprayed coating 10 formed on the outer surfaces 21 and 31 of the outer ring 2 or the inner ring 3 extremely thin. In the film-forming process of the ceramic sprayed coating 10, the longest time is required for the process of spraying the ceramic powder all over the film-forming surface of the target metal substrate, and as a matter of course, the film thickness increases. The spraying time also becomes longer. If the film thickness can be reduced to the extent of the present embodiment, the film formation time can be greatly shortened compared to the conventional case, and the effect of reducing the manufacturing cost is extremely large.

  Furthermore, in a use environment where the temperature difference is large such as an electric motor of a railway vehicle, a strong shear stress may be generated at the interface between the outer ring 2 or the inner ring 3 of the rolling bearing 1 for preventing electric corrosion and the ceramic sprayed coating 10. The shear stress acts as a force to peel the ceramic sprayed coating 10 from the outer ring 2 or the inner ring 3 and causes peeling of the coating. In addition, there is a residual stress due to thermal contraction that occurs during film formation inside the ceramic sprayed coating 10, and the mechanical strength may be reduced due to the influence of the residual stress, leading to a reduction in impact resistance.

  With respect to these points, the film thickness of the ceramic sprayed coating 10 of the present embodiment is 50 μm to 100 μm, which is a very thin coating, the shear stress is small, and peeling of the coating hardly occurs. In addition, since the residual stress at the time of film formation is small, it is difficult to cause a decrease in mechanical strength. Accordingly, damage such as peeling or cracking of the film can be prevented. The significance of setting the upper limit of the film thickness of the ceramic sprayed coating 10 to 100 μm is as described above, and the lower limit of the film thickness is set to 50 μm because the insulating performance cannot be maintained if the film thickness is smaller than this. In addition, what is necessary is just to adjust the film-forming time, for example, in order to control the film thickness of the ceramic sprayed coating 10. FIG.

  The ceramic sprayed coating 10 is subjected to sealing treatment to close the pores. The thermal spray coating generally has pores in principle, and depending on the pore structure of the thermal spray coating, gas or liquid may permeate the coated substrate. If the sealing treatment is not performed, for example, water enters the pores and the insulating performance is lowered. The sealing agent not only seals the pores of the sprayed layer, but also has a function of maintaining the adhesion of the coating after the sealing treatment. In this embodiment, the porosity of the ceramic sprayed coating 10 is set to 6% or less. When the porosity of the ceramic sprayed coating 10 is larger than 6%, the sealing agent may not be sufficiently filled, and the function of the sealing agent cannot be exhibited. The porosity can be controlled by adjusting the particle size of the ceramic powder, adjusting the distance between the spray gun and the outer surfaces 21 and 31 of the outer ring 2 or inner ring 3 to be treated, and adjusting the pressure of the spraying atmosphere. it can.

  As the organic resin for sealing treatment, any resin having fluidity that can enter the pores of the ceramic sprayed coating 10 may be used. In the selection, the average molecular weight and viscosity of the synthetic resin are taken into consideration. Synthetic resins include, for example, bisphenol F type epoxy resin, bisphenol A type epoxy resin, epoxy resin such as polyglycidyl (meth) acrylate, acrylic resin, fluorine resin, urethane resin, phenol resin, xylene resin, polyester resin, unsaturated resin Known synthetic resins such as polyester resins, polyamide resins, and melamine resins can be used. These can be used alone or in admixture of two or more.

  The ceramic spray coating 10 is formed by spraying ceramic powder having an average particle size of 3 μm to 15 μm. By spraying ceramic powder having an average particle diameter of 3 μm to 15 μm, the porosity of the sprayed layer can be controlled to 6% or less, and variation in pore size can be suppressed. By using a ceramic powder having a small particle diameter as in this embodiment, a ceramic sprayed coating 10 having small pores and uniform pore sizes can be obtained. If the pore size can be made uniform, the filling degree of the sealing agent can be improved, which is advantageous from the viewpoint of suppressing the variation in insulating performance.

  The average particle size of the ceramic powder is desirably small, but if it is too small, the fluidity of the ceramic powder may decrease during the thermal spraying process for forming a thermal spray coating, and there is a risk that stable supply cannot be achieved. If the ceramic powder can be unevenly conveyed, the strength of the film tends to vary and the thickness tends to be non-uniform. From such a viewpoint, it is preferable to use a ceramic powder having an average particle diameter in the range of 3 μm to 15 μm, more preferably 3 μm to 12 μm. When the average particle size of the ceramic powder exceeds 15 μm, a portion where the film is formed without being completely melted is formed, and the portion becomes excessively porous so that it becomes difficult to fill the sealing agent, and the insulating performance is deteriorated.

  The ceramic sprayed coating 10 is subjected to a sealing treatment with an organic resin and then subjected to a finishing process such as polishing, and the surface properties are controlled so that the surface roughness Ra is less than 1 μm and the skewness Rsk is less than 0. ing.

  Regarding the surface properties of the ceramic sprayed coating 10, the arithmetic average roughness (Ra) defined in JISB0600 and the skewness Rsk defined in JISB0601 are used as indices. The skewness Rsk is a physical quantity obtained by dividing the cube average of the height deviation in the reference length by the cube of the root mean square. The skewness Rsk is a mathematical index that expresses the difference in surface irregularities, and serves as a standard indicating the symmetry of the irregularities on the target surface. The value of the skewness Rsk is greatly influenced by the presence of a small number of protrusions and valleys remaining on the surface after polishing. The skewness Rsk has a positive value when there are sharp protrusions on the surface and the convex area of the surface roughness is large, and approaches zero when the protrusions and valleys are symmetric. When the concave area of the surface roughness is large, a negative value is shown. Therefore, the outer ring 2 or the inner ring 3 of the rolling bearing 1 for preventing electric corrosion having a surface roughness Ra of less than 1 μm and a skewness Rsk of less than 0 has a surface property with very few sharp protrusions.

  The surface properties may be controlled by adjusting the particle size of the ceramic powder during spraying. The ceramic spray coating 10 is obtained by supplying ceramic powder into a heat source, spraying the ceramic powder on the outer surfaces 21 and 31 of the outer ring 2 or the inner ring 3 while heating and melting it, and depositing molten particles. The ceramic powder is supplied in units of tens of thousands of pieces continuously into the heat source. As a result, particles having different flatness are deposited randomly. In addition to polishing, the surface roughness (Ra) and the skewness Rsk can be controlled to show the above values by using ceramic powder having an average particle diameter in the range of 3 μm to 15 μm as in this embodiment. . Furthermore, the surface roughness Ra and the skewness Rsk can easily exhibit the above values by performing a sealing treatment with an organic resin.

  If there are many protrusions on the surface of the thermal spray coating, voltage is preferentially applied to the protrusions when the electric current is about to flow to the rolling bearing 1 for preventing electric corrosion, and the electric field concentration points are scattered. By using the outer ring 2 or the inner ring 3 having a surface property with a surface roughness Ra of less than 1 μm and a skewness Rsk of less than 0 as in this embodiment, sharp and sharp protrusions on the surface of the coating are reduced, As a result, it is possible to reduce the concentration of the electric field concentration generated in the step 1, and the dielectric breakdown can be remarkably improved. Thereby, the dielectric breakdown voltage per unit film thickness of the ceramic sprayed coating 10 can be 35 kV / mm or more.

  The ceramic sprayed coating 10 is formed by any of atmospheric plasma spraying, reduced pressure plasma spraying, high-speed flame spraying, gas flame spraying, arc spraying, water plasma spraying, electric arc spraying, and explosion spraying. By using these various thermal spraying methods, it is possible to obtain a ceramic sprayed coating 10 having excellent durability and high quality. The film forming conditions by each thermal spraying method may be appropriately set according to the base material, raw material powder, film thickness, manufacturing environment, and the like.

  Among these, the plasma spraying method is a spraying method using electric energy as a heat source, and forms a film using argon or hydrogen as a plasma generation source. Since the heat source temperature is high and the frame speed is high, a high melting point ceramic material can be densely formed, which is suitable as a method for manufacturing the ceramic sprayed coating 10.

  An example of a process for obtaining the ceramic sprayed coating 10 is to clean the outer surfaces 21 and 31 of the outer ring 2 or the inner ring 3 which is a base material, roughening the outer surfaces 21 and 31 by blasting, under The coating treatment, the thermal spraying of the ceramic sprayed coating 10 as the top coat, the sealing treatment of the surface layer of the ceramic sprayed coating 10, and the surface polishing treatment are performed in this order. The undercoat process may be omitted depending on the difference in the thermal spray material, and other processes such as a preheating process may be included.

Prior to blasting, oil and fat, iron rust and the like adhering to the outer surfaces 21 and 31 of the outer ring 2 or the inner ring 3 are removed by degreasing, pickling, sand blasting, or the like. Next, the outer surfaces 21 and 31 of the cleaned outer ring 2 or inner ring 3 are blasted with hard abrasive particles such as SiC particles and Al ₂ O ₃ particles using compressed air as a driving source, and the surface roughness Ra is 0. The surface is roughened so as to be 5 μm to 2.0 μm. In the subsequent thermal spraying, the outer surface of the outer ring 2 or the inner ring 3 that has been roughened as described above, because the fine particles in the melted state physically mesh with each other along the roughened shape. 21 and 31 effectively act to increase the adhesion of the thermal spray coating. The undercoat improves the adhesion between the outer surfaces 21 and 31 of the outer ring 2 or the inner ring 3 and the ceramic sprayed coating 10 and prevents peeling or cracking of the coating.

  The undercoat is not necessarily provided, and when the ceramic powder is directly sprayed on the outer ring 2 or the inner ring 3 to form a film, a spraying condition that allows the ceramic powder to be completely melted may be employed. For this purpose, the average particle size of the ceramic powder may be set in the range of 3 μm to 15 μm as in the present embodiment, and the plasma heat source, the flight speed of the plasma particles, etc. may be optimized.

  As described above, since the ceramic sprayed coating 10 is formed on the outer surface 21 of the outer ring 2 or the outer surface 31 of the inner ring 3 of the rolling bearing 1 for preventing electric corrosion, for example, a rotating shaft of an electric motor for a railway vehicle, power generation Even if a high voltage is generated on the rotating shaft of the machine, the rolling bearing 1 that supports the rotating shaft can sufficiently exhibit the electrolytic corrosion preventing effect. In the present embodiment, the ceramic sprayed coating 10 is provided in a single layer structure on the outer ring 2 or the inner ring 3 of the rolling bearing 1 for preventing electric corrosion. However, different ceramic sprayed coatings may be formed in multiple layers, or the ceramic sprayed coating. Another metal layer may be provided on the upper layer.

According to the rolling bearing 1 for preventing electric corrosion of the present embodiment, since the ceramic sprayed coating 10 is made of a material mainly composed of aluminum oxide and titanium oxide, the film formation efficiency during spraying is high and the cost is low. It is possible to form a film. The aluminum oxide content in the ceramic sprayed coating 10 is 98.0 wt% to 99.5 wt%, and the titanium oxide content is 0.5 wt% to 2 wt%. In addition, it is possible to maintain higher insulation performance than a material mainly composed of normal aluminum oxide and titanium oxide, and to achieve a volume resistivity of 10 ¹³ Ωcm to 10 ¹⁶ Ωcm. Since the surface roughness of the outer surfaces 21 and 31 of the outer ring 2 or the inner ring 3 coated with the ceramic spray coating 10 is Ra: 0.5 μm to 2.0 μm, high adhesion to the ceramic spray coating 10 is achieved. Can be obtained. The film thickness of the ceramic sprayed coating 10 is 50 μm to 100 μm, which has a large effect of reducing the manufacturing cost, and shear stress generated between the outer ring 2 or the inner ring 3 of the rolling bearing in a use environment with a large temperature difference. Further, the mechanical strength is hardly lowered due to the influence of the residual stress inside the film, and damage such as peeling or cracking of the film can be prevented. As a result, the manufacturing cost can be greatly reduced, it is difficult to damage even in various environments, it has high adhesion, and sufficient insulation performance can be exhibited.

  Further, since the surface roughness after the finishing treatment is set to Ra: less than 1 μm and the skewness Rsk that is a rough indication of the surface roughness is set to less than 0, the surface has few protrusions. Therefore, the electric field concentration occurring on the surface when a current flows can be reduced, and the dielectric breakdown can be remarkably improved.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples. According to the above embodiment, on the surface of the metal substrate, composition, particle diameter of ceramic powder as a raw material, film thickness, sealing treatment, surface roughness of the substrate, surface roughness after film formation, and volume resistivity A test specimen with a different shape was manufactured and the dielectric breakdown property was evaluated. The dielectric breakdown property was evaluated by conducting a dielectric breakdown test and measuring the dielectric breakdown voltage.

  The dielectric breakdown test method is as follows. An 80 × 80 mm aluminum foil is placed in the center on the surface on which the test piece is formed, and a voltage is applied between the aluminum foil and the back side of the test piece. The voltage was gradually increased from 0 kV until the film was broken, and the value of the voltage immediately before breaking was read. The value obtained by dividing this by the film thickness was taken as the dielectric breakdown voltage per unit thickness. TOS-5101 manufactured by Kikusui Electronics Co., Ltd. was used as a withstand voltage tester.

The film thickness was measured using a standard outer micrometer M100 manufactured by Mitutoyo Corporation, and the surface roughness was measured using 2800G manufactured by Tokyo Seimitsu Surfcom Co., Ltd. The volume resistivity measurement method is as follows. An 80 × 80 mm aluminum foil is placed in the center on the surface on which the test piece is formed, and a voltage is applied between the aluminum foil and the back side of the test piece. The resistance value R is calculated by dividing the voltage by the current flowing at that time. The volume resistivity ρ is expressed as follows using the area S (8 × 8 cm) and the film thickness d (cm). The apparatus used for measuring the volume resistivity is a DC withstanding voltage tester IP-701G manufactured by Musashi Intec Co., Ltd.
ρ = R × (S / d) Unit: Ωcm

  One side of a SS400 flat plate of 100 x 100 x 10 mm is first roughened by blasting, then ceramic spraying is performed, the surface layer on which the film is formed is subjected to sealing treatment, and finally polishing finish is performed to obtain a test piece. Produced. In the comparative example without sealing treatment, polishing finish was performed after ceramic spraying. The roughening treatment was performed by alumina grid blasting, the sealing treatment was performed by applying an epoxy sealant and then firing, and the final polishing finish was performed using a flat polishing machine. This is because the volume resistivity and dielectric breakdown voltage of the film are hardly affected by the shape of the substrate, and a more rigorous evaluation result is obtained by comparing with a flat test piece that easily obtains uniform conditions.

  The thermal spraying conditions are as follows. Thermal spraying method: plasma spraying method, current value: 600 A, argon gas flow rate: 40 NLPM, hydrogen gas flow rate: 8.5 NLPM, spraying distance: 100 mm, ladder scan (gun feed rate: 600 mm / sec, 3 mm pitch).

  Composition of each example and comparative example (titania content), particle diameter of ceramic powder, film thickness, presence / absence of sealing treatment, surface roughness of substrate, surface roughness after film formation, volume resistivity, dielectric breakdown test The results are shown in Table 1. The result of the dielectric breakdown test is represented by a dielectric breakdown voltage (kV) and a dielectric breakdown voltage per unit thickness (kV / mm). In Table 1, the surface roughness of the base material is the roughness after one surface of the flat plate is roughened by blasting, and the surface roughness after film formation is that the surface layer formed is subjected to sealing treatment and polished. It is the surface roughness after finishing. In the case of no sealing treatment, it is the surface roughness after the film-formed surface is polished.

In all of Examples 1 to 7, the dielectric breakdown voltage per unit thickness was high. In Comparative Example 1, the dielectric breakdown voltage per unit thickness is low. In Comparative Example 2, the film thickness is thin and the dielectric breakdown voltage per unit thickness is low. In Comparative Example 3 in which the sealing treatment was not performed, there was a tendency to easily include moisture in the atmosphere and to easily cause dielectric breakdown. In Comparative Example 4 where the substrate surface roughness was small, the adhesiveness was low, and peeling occurred during film formation. In Comparative Example 5, the surface roughness of the substrate is large, and the dielectric breakdown voltage per unit thickness is low. The cause is thought to be the occurrence of electric field concentration. In Example 7 where the surface roughness after film formation was large, although the dielectric breakdown voltage per unit thickness was high, traces of electric field concentration were observed on the film surface. In Comparative Example 6 , the surface roughness after film formation is large, and the dielectric breakdown voltage per unit thickness is low. The cause is thought to be the occurrence of electric field concentration.

DESCRIPTION OF SYMBOLS 1 Rolling bearing for electric corrosion prevention 2 Outer ring 3 Inner ring 5 Rolling element 21 Outer ring outer surface 31 Outer ring outer surface

Claims (3)

A metal outer ring, and a metal inner ring concentrically disposed via the outer ring and a plurality of rolling elements to be rotatable relative to each other. The outer ring or the outer surface of the inner ring is provided for preventing electric corrosion. ceramic thermal sprayed coating method for manufacturing a galvanic corrosion preventing rolling bearing that will be formed by plasma spraying,
The ceramic spray coating is made of a material mainly composed of aluminum oxide and titanium oxide. The content of aluminum oxide is 98.0 wt% to 99.5 wt%, and the content of titanium oxide is Is formed by spraying ceramic powder having an average particle diameter of 3 μm to 14 μm ,
Surface roughness of the outer surface of the outer ring or the inner ring coated with the ceramic spray coating is Ra: 0.5 μm to 2.0 μm,
The film thickness of the ceramic spray coating is 50 μm to 100 μm,
The ceramic sprayed coating is sealed with an organic resin,
Method for producing electrolytic corrosion prevention rolling bearing, wherein the volume resistivity of the ceramic sprayed coating is ^{10 13 Ωcm~10 16 Ωcm.} 2. The electrolytic corrosion prevention according to claim 1, wherein the surface roughness of the ceramic sprayed coating after the finishing treatment after the sealing treatment is Ra: less than 1 μm and the skewness Rsk is less than 0. A manufacturing method for rolling bearings. The method for producing a rolling bearing for preventing electric corrosion according to claim 1 or 2 , wherein a dielectric breakdown voltage per unit film thickness of the ceramic sprayed coating is 35 kV / mm or more.

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