Insulated rolling bearing

Abstract

Provided is an insulated rolling bearing having an insulating film on the outer peripheral surface of an outer ring, and having excellent electrical corrosion resistance. An insulated rolling bearing (1) is provided with: an inner ring (2) and an outer ring (3); a raceway surface formed on the outer peripheral surface of the inner ring (2) and the inner peripheral surface of the outer ring (3); and a plurality of balls (4) interposed between the raceway surfaces, the outer peripheral surface (3a) of the outer ring (3) is provided with a resin film (6) (insulating film), and the resin film (6) in the insulating rolling bearing (1) has an insulation resistance value of 2000 megohms or more and a capacitance of 10 nF or less. The resin coating is formed from a resin composition containing a polyphenylene sulfide resin, glass fibers, an inorganic filler having a thermal conductivity of 10 W / mK or more, and a thermoplastic elastomer.

Description

Technical Field

[0001] The present invention relates to an insulating rolling bearing, and more particularly to an insulating rolling bearing used in a general-purpose motor, a generator, a main motor of a railway vehicle, or a device having a structure in which electric current may flow inside the bearing during use. Background Art

[0002] For example, in rolling bearings used in main motors of railway vehicles, discharge sometimes occurs between the rolling element and the outer ring raceway surface or between the rolling element and the inner ring raceway surface, causing electrolytic corrosion in the discharged portion. In addition, electrolytic corrosion sometimes also occurs in bearings used in other devices such as generators that may have a structure where current may flow inside the bearing.

[0003] As a means of preventing such electrolytic corrosion, it is known to form a resin coating on the outer surface of the raceway of the bearing. For example, in Patent Document 1, an insulating rolling bearing is proposed, which has a glass fiber and a resistivity of 1×10 10 A resin film formed by a resin composition of a filler material with a thermal conductivity of 10 W / m·K or more and a thermal conductivity of 10 W / m·K or more. The filler material is used to improve the heat dissipation of the resin film, and examples thereof include powders and fibers of SiC (silicon carbide), AlN (aluminum nitride), BeO (beryllium oxide), BN (boron nitride), and Al2O3 (aluminum oxide). In addition, Patent Document 1 states that the total content of glass fiber and filler material is 20% to 60% by mass, and that the content of filler material is 10% to 40% by mass.

[0004] Patent Document 2 proposes an insulating rolling bearing having an insulating coating made of ceramics containing aluminum oxide as a main component and having an insulation resistance value limited to 1000 MΩ or more and an electrostatic capacitance limited to 27 nF or less for the purpose of preventing electric corrosion.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-218846

[0008] Patent Document 2: Japanese Patent Application Publication No. 2007-333031 Summary of the invention

[0009] Problems to be solved by the invention

[0010] In general, the main motors used in railway vehicles are controlled by inverters. In recent years, in order to reduce the noise during switching, the carrier frequency tends to be increased, and high-frequency current flows inside the rolling bearings. In order to prevent electrical corrosion, it is possible to make the rolling element itself an insulator such as ceramic, but this will lead to an increase in cost.

[0011] As a method of improving the insulation of a bearing without making the bearing component itself an insulator, it is known to have a rolling bearing having an insulating coating on the surface of a metal component as in Patent Documents 1 and 2. However, as the performance of main motors continues to improve, it is desired to fully ensure the insulation performance in main motors with higher carrier frequencies.

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an insulating rolling bearing having an insulating film on the outer peripheral surface of an outer ring and the like, which has excellent anti-electrolytic corrosion properties.

[0013] Solutions to Solve Problems

[0014] The insulating rolling bearing of the present invention comprises: an inner ring and an outer ring; a raceway surface formed on the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring; and a plurality of rolling elements between the raceway surfaces, wherein at least one circumferential surface selected from the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring has an insulating coating formed of a resin coating or a ceramic coating, and is characterized in that the insulating resistance value of the insulating coating in the insulating rolling bearing is greater than 2000MΩ and the electrostatic capacitance is less than 10nF.

[0015] Here, the insulation resistance value R of the insulating film in the insulating rolling bearing can be calculated using the following formula (1).

[0016] [Mathematical formula 1]

[0017]

[0018] Z: Impedance (Ω)

[0019] R: Insulation resistance value (Ω)

[0020] f: frequency (Hz)

[0021] C: Electrostatic capacitance (F)

[0022] In the above formula (1), the frequency is equivalent to the carrier frequency of the insulating rolling bearing, that is, the frequency of the current flowing in the rolling bearing. In addition, after the outer ring of the bearing is installed in a jig for contacting the entire circumference of the outer ring of the bearing, the impedance Z is measured by using an LCR meter, for example, under the measurement condition of a load voltage of 1V, based on the phase difference between the current waveform and the voltage waveform.

[0023] In addition, the insulation resistance value R can generally be calculated using the following formula (2).

[0024] [Mathematical formula 2]

[0025]

[0026] ρ: Resistivity (Ω·m)

[0027] l: length (m)

[0028] A: Cross-sectional area (m 2 )

[0029] In the above formula (2), the resistivity ρ of the insulating film is a parameter determined by the selected material. In addition, the length l corresponds to the film thickness (the distance d in the following formula (3) described later), and the cross-sectional area A corresponds to the area S in the following formula (3).

[0030] The electrostatic capacitance C of the insulating coating in the insulating rolling bearing can be calculated using the following formula (3).

[0031] [Mathematical formula 3]

[0032]

[0033] ε0: Dielectric constant in vacuum (8.8542×10 －12 )(F / m)

[0034] ε s : Relative dielectric constant of insulating film

[0035] S: Area (m 2 )

[0036] d: distance (m)

[0037] In the above formula (3), the relative dielectric constant ε of the insulating film is s It is a parameter determined by the selected material. In addition, the area S corresponds to the surface area of ​​the insulating film formed on the raceway, and the distance d corresponds to the film thickness of the insulating film.

[0038] The insulating film is characterized in that the insulating film is composed of the resin film, and the resin film is composed of a resin composition containing polyphenylene sulfide (PPS) resin, glass fiber, an inorganic filler having a thermal conductivity of 10 W / m·K or more, and a thermoplastic elastomer.

[0039] The thermoplastic elastomer is characterized in that the content of the thermoplastic elastomer is 1% by mass to 10% by mass based on the entire resin composition.

[0040] The invention is characterized in that the total content of the glass fiber and the inorganic filler is 40% to 70% by mass relative to the entire resin composition, the resin composition contains more inorganic filler than the glass fiber, and contains 10% to 30% by mass of the glass fiber and 30% to 50% by mass of the inorganic filler relative to the entire resin composition.

[0041] The inorganic filler is characterized in that the inorganic filler is at least one selected from silicon carbide, beryllium oxide, boron nitride, silicon nitride, magnesium hydroxide, aluminum oxide, and magnesium carbonate.

[0042] The characteristic is that the above-mentioned resin coating is formed on the above-mentioned circumferential surface of the raceway ring and the axial end surfaces on both sides thereof, the film thickness on the above-mentioned circumferential surface is less than 1 mm, and the ratio of the film thickness on the above-mentioned circumferential surface to the film thickness on the above-mentioned axial end surfaces is in the range of 1:1 to 1:3.

[0043] The characteristic is that the resin in the resin coating flows in a direction from one side to the other side of the circumferential surface in the axial direction over the entire circumference of the raceway ring.

[0044] The invention is characterized in that the insulating film includes the ceramic film, and the film thickness of the insulating film is in the range of 0.1 mm to 1.0 mm.

[0045] The insulating rolling bearing is a bearing that rotatably supports a main shaft of a main electric motor of a railway vehicle.

[0046] Effects of the Invention

[0047] The insulating rolling bearing of the present invention is an insulating rolling bearing having an insulating coating composed of a resin coating or a ceramic coating on at least one of the circumferential surfaces selected from the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring, wherein the insulating coating in the insulating rolling bearing has an insulation resistance value of 2000MΩ or more and an electrostatic capacitance of 10nF or less. As shown in the above formula (1), the greater the carrier frequency, the lower the impedance. By limiting the insulation resistance value and electrostatic capacitance as described above, a high impedance (for example, 10Ω or more) can be achieved even in a main motor with a high carrier frequency (for example, 1000Hz), and excellent anti-corrosion performance.

[0048] The insulating film is a resin film, which is composed of a resin composition containing at least PPS resin, glass fiber, an inorganic filler having a thermal conductivity of 10 W / m·K or more, and a thermoplastic elastomer. Therefore, the heat dissipation of the insulating film can be improved while maintaining the insulation, and the thermoplastic elastomer can compensate for the decrease in formability caused by the addition of the above-mentioned inorganic filler (high thermal conductivity filler). In addition, by improving the heat dissipation of the resin film, the film thickness of the resin film can be increased while suppressing the increase in bearing temperature. As a result, the electrostatic capacitance can be reduced and high impedance can be achieved.

[0049] The resin coating is formed on the circumferential surface of the raceway ring and the axial end surfaces on both sides thereof, with a portion on the circumferential surface having a film thickness of less than 1 mm. The ratio of the film thickness on the circumferential surface to the film thickness on the axial end surfaces is in the range of 1:1 to 1:3. Therefore, heat dissipation is mainly borne by the resin coating on the circumferential surface, and high impedance is mainly borne by the resin coating on the axial end surfaces, thereby achieving an excellent balance between heat dissipation and insulation.

[0050] The content of the thermoplastic elastomer is 1% to 10% by mass relative to the entire resin composition, so it is possible to improve the fluidity of the resin composition during molding and the impact resistance of the resin coating while suppressing the decrease in the elastic modulus. Moreover, the total content of the glass fiber and the inorganic filler is 40% to 70% by mass relative to the entire resin composition, so the heat dissipation and mechanical strength of the resin coating are further excellent.

[0051] The flow direction of the resin in the resin coating is along the direction from one axial side of the circumference to the other side over the entire circumference of the raceway ring, that is, the orientation direction of the resin over the entire circumference of the raceway ring is limited to a specified direction (from one axial side to the other axial side). In this case, the resin coating is formed by injecting and filling the molten resin over the entire circumference of the molding cavity at the same time, so no weld portion is formed in the resin coating. As a result, the resin coating no longer has a locally low strength area, and the mechanical strength is further improved.

[0052] The insulating film is a ceramic film having aluminum oxide as a main component and a film thickness in the range of 0.1 mm to 1.0 mm. Therefore, the electrostatic capacitance is reduced and a further high impedance can be achieved.

[0053] The insulating rolling bearing of the present invention can achieve high impedance, thereby suppressing the electrical corrosion of the bearing. Therefore, it can be preferably used as a bearing for rotatably supporting the main shaft of the main motor of a railway vehicle, and can contribute to improving the reliability of the main motor for railway vehicles and reducing maintenance man-hours and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1This is an enlarged cross-sectional view showing an example of the insulating rolling bearing of the present invention.

[0055] Figure 2 Yes Figure 1 A cross-sectional view of the main parts of the molding die for insert molding of the outer ring, etc.

[0056] Figure 3 This is an enlarged cross-sectional view showing another example of the insulating rolling bearing of the present invention.

[0057] Figure 4 It is a diagram showing the structure of a bogie of a railway vehicle to which the insulating rolling bearing of the present invention is applied.

[0058] Figure 5 It is a diagram showing the structure of the main motor.

[0059] Figure 6 This is an enlarged view showing the structure around the rolling bearing on the fixed side.

[0060] Figure 7 This is an enlarged view showing the structure around the rolling bearing on the free side.

[0061] Figure 8 It is a graph showing the frequency characteristics of impedance. DETAILED DESCRIPTION

[0062] use Figure 1 An example of the insulating rolling bearing of the present invention will be described. Figure 1 This is a cross-sectional view of a deep groove ball bearing. In an insulating rolling bearing 1, an inner ring 2 having an inner ring raceway surface on the outer circumference and an outer ring 3 having an outer ring raceway surface on the inner circumference are arranged concentrically, and a plurality of balls (rolling elements) 4 are arranged between the inner ring raceway surface and the outer ring raceway surface. The balls 4 are held by a retainer 5.

[0063] Iron-based materials can be used for the inner ring 2, the outer ring 3, and the balls 4. Examples of the iron-based materials include bearing steel such as SUJ2 used in rolling bearings, etc., carburized steel, carbon steel for machine structures, cold-rolled steel, and hot-rolled steel.

[0064] exist Figure 1 In the embodiment, the outer circumferential surface 3a and the end surfaces 3b and 3b' of the outer ring 3 are covered with a resin coating 6 as an insulating coating. Two rows of circumferential grooves are formed on the outer circumferential surface 3a of the outer ring 3, and circumferential grooves are formed on the two end surfaces 3b and 3b' of the outer ring 3. Part of the resin coating 6 is immersed in these circumferential grooves. Figure 2 As shown, the resin coating 6 is formed by insert molding a resin composition described later into the outer ring 3 and is formed on the outer peripheral surface 3a of the outer ring 3 and the axial end surfaces (end surfaces 3b, 3b') on both sides thereof.

[0065] Here, the relationship among the impedance Z, the insulation resistance value R, and the electrostatic capacitance C of the insulating coating in the insulating rolling bearing can be expressed by the following formula (1) as described above.

[0066] [Formula 4]

[0067]

[0068] Z: Impedance (Ω)

[0069] R: Insulation resistance value (Ω)

[0070] f: frequency (Hz)

[0071] C: Electrostatic capacitance (F)

[0072] Therefore, in order to obtain high impedance (high resistance) in the insulated rolling bearing in a higher frequency region, it is necessary to increase the insulation resistance value R of the insulating coating or to reduce the electrostatic capacitance C of the insulating coating.

[0073] In addition, the electrostatic capacitance C can be expressed by the following formula (3).

[0074] [Mathematical formula 5]

[0075]

[0076] ε0: Dielectric constant in vacuum (8.8542×10 －12 )(F / m)

[0077] ε s : Relative dielectric constant of insulating film

[0078] S: Area (m 2 )

[0079] d: distance (m)

[0080] Therefore, in order to reduce the electrostatic capacitance C of the insulating film in the insulated rolling bearing, it is necessary to reduce the relative dielectric constant ε of the insulating film. s Or increase the thickness of the insulating film.

[0081] In the insulating rolling bearing of the present invention, the insulation resistance value of the insulating coating is greater than or equal to 2000MΩ, and the electrostatic capacitance is less than or equal to 10nF. Thus, high impedance can be achieved even in the high-frequency region, and excellent anti-corrosion properties are achieved. From the perspective of both high impedance and cost reduction, the insulation resistance value of the insulating coating is preferably greater than or equal to 2000MΩ and less than or equal to 20000MΩ, more preferably greater than or equal to 4000MΩ and less than or equal to 18000MΩ, and further preferably greater than or equal to 6000MΩ and less than or equal to 16000MΩ. In addition, the electrostatic capacitance of the insulating coating is preferably greater than or equal to 1nF and less than or equal to 10nF, more preferably greater than or equal to 1nF and less than or equal to 8nF, and further preferably greater than or equal to 1nF and less than or equal to 5nF.

[0082] As long as the electrostatic capacitance C is less than 10nF, the film thickness T of the insulating film a 、T b (Except for the circumferential groove portion, the same applies below) There is no particular limitation. For example, the insulating film may be formed so that the film thickness T of the insulating film formed on the outer peripheral surface 3a of the outer ring 3 is a and the film thickness T of the insulating film formed on the end faces 3b, 3b' b In addition, the insulating film (in Figure 1 The resin coating 6 is formed so that the film thickness T of the insulating coating formed on the outer peripheral surface 3a of the outer ring 3 is a T than the film thickness T of the insulating film formed on the end faces 3b and 3b' b Small.

[0083] In addition, when the insulating film is a resin film, it is preferred to determine the film thickness from the viewpoint of insulation and heat dissipation. That is, if the film thickness of the resin film is large, although the electrostatic capacitance becomes smaller (impedance becomes higher), the heat dissipation is likely to decrease. On the other hand, if the film thickness of the resin film is small, although the heat dissipation is improved, the electrostatic capacitance becomes larger (impedance becomes lower). In addition, the molding of the resin film tends to become difficult, and it is difficult to ensure the mechanical strength of the resin film. Therefore, if the balance of heat dissipation, insulation, and mechanical strength is considered, the film thickness of the resin film is, for example, in the range of 0.3mm to 2mm, preferably in the range of 0.3mm to 1.5mm. In particular, if heat dissipation is considered, the film thickness is preferably less than 1mm, and can also be 0.3mm to 0.9mm.

[0084] Here, if the bearing size increases, the surface area of ​​the insulating film formed on the raceway ring increases accordingly. As a result, according to the above formula (3), the electrostatic capacitance C of the insulating film increases, which may hinder the high impedance. Therefore, in the case of a large bearing size (for example, the bearing outer diameter is 70 mm or more, preferably 90 mm or more), it is preferred to reduce the film thickness T of the resin film formed on the peripheral surface (inner peripheral surface and / or outer peripheral surface) that has a large impact on the heat dissipation while ensuring the heat dissipation. a, and in order to reduce the electrostatic capacitance C, the film thickness T of the resin film formed on the axial end surface (width surface) is b Specific film thickness T a In this case, in the resin coating, the film thickness T on the peripheral surface is a The film thickness T on the axial end surface b The ratio is, for example, in the range of 1:1 to 1:3, preferably in the range of 1:1.2 to 1:3, and more preferably in the range of 1:1.2 to 1:2. In this case, the film thickness T on the peripheral surface is a Preferably it is 1 mm or less.

[0085] In the present invention, as long as the insulation resistance value and the electrostatic capacitance satisfy the above numerical range, the resin coating is not particularly limited. The resin coating is preferably composed of a resin composition containing PPS resin, and more preferably composed of a resin composition containing PPS resin, glass fiber, an inorganic filler having a thermal conductivity of 10 W / m·K or more, and a thermoplastic elastomer. The resin composition is described below.

[0086] PPS resin is a crystalline thermoplastic resin with a polymer structure in which benzene rings are linked by sulfur bonds at the para position. PPS resin has a melting point of about 280°C and a thermal conductivity of about 0.3W / m·K. It is a so-called super engineering plastic with excellent heat resistance, dimensional stability, chemical resistance, and flame retardancy.

[0087] PPS resins include cross-linked and linear types in terms of molecular structure, but can be used without being limited to these molecular structures and molecular weights. Cross-linked PPS resins are obtained, for example, by heat-treating in the presence of oxygen during the manufacturing process and increasing the molecular weight to a desired level. Cross-linked PPS resins have a two-dimensional or three-dimensional cross-linked structure in which a portion of the molecules are cross-linked via oxygen. On the other hand, linear PPS resins do not contain a cross-linked structure in the molecule because they are not heat-treated during the manufacturing process, and the molecule is a one-dimensional straight chain.

[0088] The content of PPS resin is not particularly limited. A larger content is advantageous in terms of fluidity, but on the other hand, it is easy to cause a decrease in heat dissipation. The content of PPS resin is, for example, 20% to 70% by mass, preferably 29% to 50% by mass, relative to the entire resin composition.

[0089] Glass fiber is obtained by spinning inorganic glass mainly composed of SiO2, B2O3, Al2O3, CaO, MgO, Na2O, K2O, Fe2O3, etc. Usually, alkali-free glass (E glass), alkali-containing glass (C glass, A glass), etc. can be used.

[0090] The average fiber length of the glass fiber is not particularly limited, and is preferably 0.1 mm or more, and preferably 0.2 mm or more. If the average fiber length is less than 0.1 mm, the reinforcing effect becomes smaller and the wear resistance may be reduced. In addition, the upper limit of the average fiber length is, for example, 1 mm or less, and may also be 0.8 mm or less. In addition, the average fiber length in this specification is the number average fiber length. In addition, the average fiber diameter of the glass fiber is not particularly limited, and is, for example, 5 μm to 20 μm, and preferably 10 μm to 15 μm. The average fiber diameter can be measured by an electron microscope, an atomic force microscope, etc. commonly used in the art. The average fiber diameter can be calculated as a number average fiber diameter based on the above measurement.

[0091] The content of glass fiber is not particularly limited. When the content is large, it is advantageous in mechanical strength, but on the other hand, it is easy to cause a reduction in fluidity. The content of glass fiber is, for example, 10% to 50% by mass relative to the entire resin composition, and is preferably 10% to 30% by mass. If the content of glass fiber is less than 10% by mass, it is difficult to obtain an improvement in mechanical strength, and creep resistance, etc. are likely to be reduced.

[0092] The inorganic filler with a thermal conductivity of 10 W / m·K or more is mainly used to improve the thermal conductivity of the resin coating. In addition, considering other properties (electrical insulation, water resistance, chemical resistance, heat resistance, hardness (aggression to matching parts)), availability, etc., as the above-mentioned inorganic filler, it is preferred to use at least one selected from silicon carbide, beryllium oxide, boron nitride, silicon nitride, magnesium hydroxide, aluminum oxide and magnesium carbonate. In addition, the following Table 1 shows their thermal conductivity.

[0093] [Table 1]

[0094] Inorganic filling materials SiC BeO BN <![CDATA[Si3N4]]> <![CDATA[Mg(OH)2]]> <![CDATA[Al2O3]]> <![CDATA[MgCO3]]> Thermal conductivity, w / m·K 270 250 110 60 40 20 15

[0095] The thermal conductivity of the inorganic filler is preferably 15 W / m·K or more. In addition, the inorganic filler is preferably one with high electrical insulation. For example, the resistivity is preferably 10 10 Ω·cm or more, more preferably 10 12 Ω·cm or more.

[0096] The content of the above-mentioned inorganic filler is not particularly limited. When the content is large, it is advantageous in heat dissipation, but on the other hand, it is easy to cause a decrease in mechanical strength and fluidity. The content of the above-mentioned inorganic filler is, for example, 10% to 50% by mass, preferably 30% to 50% by mass, relative to the entire resin composition. If the content of the above-mentioned inorganic filler is less than 10% by mass, it is likely to be difficult to obtain the effect of thermal conductivity.

[0097] The thermoplastic elastomer used in the resin composition is not particularly limited, but in terms of improving moldability, it is preferred to use a material having a lower melting point than the PPS resin, such as a polyolefin-based, polystyrene-based, polyvinyl chloride-based, polyurethane-based, polyester-based, polyamide-based, or polybutadiene-based material. The thermoplastic elastomer can be used in consideration of heat resistance, water resistance, chemical resistance, availability, and the like.

[0098] If the content of the thermoplastic elastomer increases, the fluidity and impact resistance of the resin composition will be improved. On the other hand, if the content of the thermoplastic elastomer is too much, the elastic modulus tends to decrease. The content of the thermoplastic elastomer is, for example, 0.5% to 30% by mass, preferably 1% to 20% by mass, and more preferably 1% to 10% by mass relative to the entire resin composition.

[0099] In addition, the resin composition may be mixed with a known resin additive to the extent that the effect of the present invention is not impaired. For example, an inorganic filler (except glass fiber) having a thermal conductivity of less than 10 W / m·K may be mixed with the resin composition.

[0100] The content of each of the above materials can be set according to formability, mechanical properties, etc. A particularly preferred embodiment of the resin composition of the present invention is to include 29% to 50% by mass of PPS resin, a total of 20% to 70% by mass (preferably 40% to 70% by mass) of glass fiber and an inorganic filler having a thermal conductivity of 10W / m·K or more, and 1% to 10% by mass of thermoplastic elastomer relative to the entire resin composition. By limiting the total amount of glass fiber and the above-mentioned inorganic filler, it is easy to achieve a balance between heat dissipation and mechanical strength. In addition, the above-mentioned resin composition preferably includes more of the above-mentioned inorganic filler than the glass fiber, and includes 10% to 30% by mass of glass fiber and 30% to 50% by mass of the above-mentioned inorganic filler relative to the entire resin composition. Furthermore, the above-mentioned glass fiber is more preferably an average fiber length of 200μm or more and an average fiber diameter of 10μm to 15μm.

[0101] According to the need, the various materials constituting the above-mentioned resin composition are mixed by a Henschel mixer, a ball mixer, a ribbon mixer, etc., and then melt-mixed by a melt extruder such as a twin-screw mixing extruder, so that pellets for molding can be obtained. Using the pellets for molding, the molten resin is injection molded on the raceway ring (for example, the outer ring). For example, the injection molding is performed at a temperature of 300°C or above.

[0102] use Figure 2 This injection molding will be described. Figure 2 (a) is a cross-sectional view of the main parts of the forming die, Figure 2 (b) indicates that Figure 2 An explanatory diagram of an insulating rolling bearing obtained by the method (a).

[0103] exist Figure 2 In (a), the forming mold is composed of a movable side mold plate 7 and a fixed side mold plate 8. A raceway ring (in Figure 2 In the state of the outer ring 3 in the middle, the fixed side mold plate 8 and the movable side mold plate 7 are butted against each other to form a cavity C. The cavity C is formed to be in contact with the resin coating 6 (refer to Figure 1 ) corresponding to the shape. Specifically, the cavity C has a cavity formed on the outer peripheral surface 3a side of the outer ring 3 and a cavity formed on the end surface 3b side and 3b' side of the outer ring 3. The cavity C is connected to the runner 9 through the gate G. In addition, Figure 2 (a) shows a partial cross-sectional view, but the cavity C is formed in an annular shape along the shape of the outer ring 3.

[0104] exist Figure 2 In (a), the gate G is arranged facing the cavity on the side of the end face 3b of the outer ring 3. When the molten resin is injected from the gate G, Figure 2 As shown by arrow (MD) in (b), the molten resin flows in the mold. Specifically, the molten resin is guided from the cavity on the end face 3b side of the outer ring 3 to the cavity on the outer peripheral face 3a side of the outer ring 3 to the cavity on the end face 3b' side of the outer ring 3.

[0105] Then, after the molten resin is filled, the resin is solidified by cooling for a certain period of time after holding the pressure. Then, the mold is opened to obtain an outer ring having a resin coating 6 formed on the outer peripheral surface and both end surfaces. In this case, a gate mark 10 is formed on one axial end surface of the resin coating 6.

[0106] exist Figure 2 In the insulating rolling bearing 1 of (b), the flow direction (MD) of the resin in the resin coating 6 is continuously along the direction from one axial end face through the outer peripheral surface to the other axial end face over the entire circumference of the outer ring 3. In this case, it can also be said that the flow direction (MD) of the resin in the resin coating 6 formed on the outer ring 3 is in a straight line from the width surface through the outer peripheral surface to the width surface on the opposite side.

[0107] exist Figure 2 The gate method is a disc gate. Unlike a pinpoint gate (dispersed on the circumference), a disc gate is continuous on the circumference. Therefore, the molten resin flows in the same direction from one axial end face to the other axial end face, so a weak weld portion is not formed.

[0108] In injection molding, the position of the gate is not particularly limited, but it is preferred that the gate be provided so as to form a Figure 2The resin flow direction (MD) is shown. As a specific gate location, for example, Figure 2 As shown in (a) of FIG. 3 , the gate G may be provided at a position facing the circumferential groove 3 d of the end surface 3 b of the outer ring 3 .

[0109] In addition, Figure 2 In (a), the gate G is arranged so that the direction of the molten resin injected from the gate G coincides with the axial direction of the cavity C, but the gate may be arranged so that these directions are different. For example, the direction of the molten resin injected from the gate G may be inclined at a predetermined angle or orthogonal to the axial direction of the cavity C.

[0110] exist Figure 2 In the process, after injection molding, the outer peripheral surface and width surface of the resin coating are subjected to grinding processing as needed, and finished to desired dimensions and accuracy, thereby obtaining an insulating rolling bearing.

[0111] use Figure 3 Another example of the insulating rolling bearing of the present invention will be described. Figure 3 The insulating rolling bearing 11 shown has a ceramic coating 16 as an insulating coating instead of the above-mentioned resin coating.

[0112] like Figure 3 As shown, in the insulating rolling bearing 11, an inner ring 12 having an inner ring raceway surface on the outer circumference and an outer ring 13 having an outer ring raceway surface on the inner circumference are arranged concentrically, and a plurality of balls 14 are arranged between the inner ring raceway surface and the outer ring raceway surface. The balls 14 are held by a cage 15. Figure 3 In the embodiment, the outer peripheral surface 13a and the two end surfaces 13b, 13b' of the outer ring 13 are covered with a ceramic coating 16. The inner diameter side portions of the two end surfaces 13b, 13b' of the outer ring 3 are formed into a tapered shape, and the ceramic coating 16 is also formed on the tapered portion. The tapered portion is formed into a tapered shape whose axial length becomes shorter as it approaches the inner diameter side.

[0113] In addition, Figure 3 In the embodiment, no circumferential groove is formed on the outer peripheral surface 13a of the outer ring 13 and the two end surfaces 13b, 13b'. In addition, the film thickness of the ceramic coating 16 is formed so that the film thickness formed on the outer peripheral surface 13a of the outer ring 13 and the film thickness formed on the end surfaces 13b, 13b' are equal to T b Roughly constant.

[0114] exist Figure 3 In the example, the ceramic coating 16 in the insulating rolling bearing 11 has an insulation resistance value of 2000 MΩ or more and an electrostatic capacitance of 10 nF or less, similar to the above-mentioned resin coating.

[0115] Here, when the film thickness of the ceramic coating is increased, the insulation resistance value is usually increased and the electrostatic capacitance is decreased. On the other hand, when the ceramic coating is, for example, a sprayed layer, in order to increase the film thickness of the ceramic coating, the spraying operation time becomes longer and the manufacturing cost is likely to increase. In addition, a thick sprayed layer may be damaged when it is fitted with the mating surface (reduced reliability).

[0116] In the present invention, from the perspective of high impedance, the thickness of the ceramic coating is preferably 0.1 mm or more, and may be greater than 0.7 mm. Furthermore, from the perspective of both high impedance and reliability, the thickness is preferably in the range of 0.1 mm to 1.0 mm, and more preferably in the range of 0.1 mm to 0.9 mm. Thus, while ensuring reliability and suppressing costs, the electrostatic capacitance can be reduced, and further high impedance can be achieved.

[0117] In addition, when the ceramic coating is a sprayed layer, the insulating coating can also be formed by combining the sealing treatment with resin. In this case, for example, the film thickness can be increased while reducing the possibility of defects during fitting, so it is easy to make the film thickness greater than 0.1 mm.

[0118] In addition, in the case of ceramic coating, heat dissipation is superior to that of resin coating, so the film thickness of the portion formed on the peripheral surface may be the same as the film thickness of the portion formed on the axial end surface (width surface). For ceramic coating, the film thickness on the peripheral surface and the film thickness on the axial end surface are preferably the same from the viewpoint of simplifying the manufacturing process.

[0119] The base material of the ceramic coating is alumina, magnesia, zirconia, metal oxides such as titanium dioxide, silicon nitride, silicon carbide, or a mixture thereof, and the main component of the ceramic coating is preferably alumina. For example, the composition of the spraying material can also be set to have an alumina content of 95.0 to 98.5% by mass and other metal oxides of 1.5 to 5.0% by mass. In addition, the alumina content can be set to be 97.0% by mass or more, and the content of metal oxides such as zirconium oxide can be set to be 1.5 to 2.5% by mass.

[0120] The ceramic coating can be formed by plasma spraying, aerosol deposition (hereinafter, referred to as AD) method, etc. In the case where the ceramic coating is formed by plasma spraying, the coating is easily formed into a porous structure, so from the viewpoint of improving insulation, it is preferred to seal the sprayed layer by resin or the like. The coating obtained by plasma spraying can fill the gaps in the porous film with a resin material having a relatively low dielectric constant, and is easy to have isolated pores, so the effective relative dielectric constant can be reduced, which is suitable for high impedance.

[0121] In this specification, the AD method is a method in which an aerosol formed by dispersing raw ceramic particles in a gas is sprayed toward a sleeve body as a substrate through an aerosol nozzle, and the aerosol collides with the surface of the substrate at a high speed to form a coating composed of the constituent material of the particles on the substrate. When the coating is formed by the AD method, the ceramic particles are maintained in a dispersed state in the aerosol. The coating obtained by the AD method is formed by the particles dispersed in the aerosol as described above, and therefore the obtained coating is easy to become a dense film and has particularly excellent heat dissipation.

[0122] The ceramic coating can also be stacked to form more than two layers of coating layers. In the case of stacking, for example, any method in plasma spraying and AD method can be repeatedly used, and the two methods can also be combined (for example, the first layer is AD method, the second layer is plasma spraying, etc.) to stack and form.

[0123] As described above, in the present invention, as the insulating film, a resin film or a ceramic film can be used. Here, for example, the relative dielectric constant of the PPS resin used in the resin film is about 4, and in the case of being composed of alumina used in the ceramic film, the relative dielectric constant is about 10. In order to increase the impedance, it is preferable to make the relative dielectric constant of the insulating film small so that the electrostatic capacitance C of the insulating film becomes small. From this point of view, PPS resin is preferred. In addition, when using a ceramic film, the film thickness can also be increased.

[0124] In particular, in the insulated rolling bearing of the present invention, it is preferred to use the most appropriate material and film thickness of the insulating film according to the intended use or need so that the electrostatic capacitance C of the insulating film is 1 nF or more and 5 nF or less.

[0125] The structure of the insulating rolling bearing of the present invention is not limited to the above Figure 1 to Figure 3 For example, the insulated rolling bearing of the present invention can also be applied to cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, thrust cylindrical roller bearings, thrust tapered roller bearings, thrust needle roller bearings, thrust self-aligning roller bearings, etc.

[0126] Above Figure 1 to Figure 3 The insulated rolling bearing adopts a structure in which the outer peripheral surface and both ends of the outer ring are coated with an insulating film, but is not limited to this. For example, a structure in which only the outer peripheral surface of the outer ring is coated with an insulating film may be adopted. In addition, the raceway ring formed with the insulating film is not limited to the outer ring, but may also be the inner ring. In this case, the insulating film is formed on at least the inner peripheral surface of the inner ring.

[0127] Next, application examples of the insulating rolling bearing of the present invention will be described. Figure 4 to Figure 7 The following is an example of application to a bearing that rotatably supports a main shaft of a main motor of a railway vehicle.

[0128] First, in Figure 4 Detailed Description of the Invention The structure of a bogie of a railway vehicle having a support structure for a main shaft for a main motor is described. Figure 4 : is a diagram showing the structure of the bogie. Figure 4 As shown, the bogie 21 is a bogie provided in a railway vehicle, and includes a bogie body 22, a main motor 30, a coupling 24, a drive device 25, an axle 26, wheels 27, and an axle bearing device 28. The main motor 30 is supported on the bogie body 22 at the main motor mounting portion 22a. In addition, the main shaft 23 of the main motor 30 is connected to the drive device 25 via the coupling 24. The drive device 25 has a pinion 25a fixed to the main shaft 23 and a gear 25b fixed to the axle 26, and the pinion 25a and the gear 25b are configured to mesh with each other. A pair of wheels 27 are fixed to the axle 26, and both ends of the wheels 27 are supported on the bogie body 22 by the axle bearing device 28. In addition, the axle bearing device 28 is supported on the bogie body 22 at the chassis 22b.

[0129] Reference Figure 4 , the operation of the wheel 27 based on the main motor 30 is described. First, the main motor 30 operates to rotate the main shaft 23. At this time, the rotation of the main shaft 23 is transmitted to the drive device 25 via the coupling 24, and the small gear 25a fixed to the main shaft 23 rotates. By the rotation of the small gear 25a, the large gear 25b meshing with the small gear 25a rotates. The axle 26 fixed to the large gear 25b rotates, so that the wheels 27 fixed to both ends of the axle 26 rotate, and the bogie 21 travels.

[0130] Figure 5 is a diagram showing the structure of the main motor 30. Figure 5 As shown, the main motor 30 mainly includes a stator 32 having a coil 32a, a rotor 33 arranged to face the stator 32, and a frame 31 arranged to surround the stator 32 and the rotor 33. The main shaft 23 is fixed to a portion including the center portion (rotation axis) of the rotor 33 in a penetrating manner. In the main motor 30, first, a three-phase alternating current is supplied to the coil 32a of the stator 32. At this time, a rotating magnetic field is formed around the rotor 33, and an induced current is generated in the rotor 33 by the rotating magnetic field. In this way, by forming a rotating magnetic field around the rotor 33 and generating an induced current in the rotor 33, an electromagnetic force is generated that acts to rotate the rotor 33 around the rotation axis, and the rotor 33 rotates. The rotation of the rotor 33 is derived to the outside via the main shaft 23.

[0131] The main motor 30 also includes a first bearing device 40 and a second bearing device 45 that support the main shaft 23 relative to a member disposed opposite to its outer peripheral surface 23a so as to be rotatable around the axis. The first bearing device 40 includes a first rolling bearing (deep groove ball bearing) 41 that supports the fixed side of the main shaft 23, and the second bearing device 45 includes a second rolling bearing (cylindrical roller bearing) 46 that supports the free side of the main shaft 23. These rolling bearings support the main shaft 23 and the rotor 33 of the main motor 30, and bear the load generated by the deadweight of the rotor 33. The first rolling bearing 41 and the second rolling bearing 46 are respectively insulating rolling bearings of the present invention. In addition, these rolling bearings are also referred to as main motor bearings.

[0132] Figure 6 FIG. 4 is an enlarged view showing the structure of the first bearing device 40. Figure 6 As shown, the first bearing device 40 includes a first rolling bearing 41, a housing 42, a stopper 43, an end cover 44, and an oil cut-off ring 44a. The inner ring 41a of the first rolling bearing 41 is clamped by the stopper 43 and the oil cut-off ring 44a, and the inner peripheral surface of the inner ring 41a contacts the outer peripheral surface 23a of the main shaft 23. In addition, the outer peripheral surface of the outer ring 41b is fixed to the housing 42 via a resin coating 41c. For example, the inner ring 41a is used with an interference fit with the main shaft 23 and the outer ring side is used with a transition fit with the housing 42. In addition, the two end surfaces of the outer ring 41b are pressed by the housing components (housing 42 and end cover 44) via the resin coating 41c and fixed in the axial direction.

[0133] in addition, Figure 7 1 is an enlarged view showing the structure of the second bearing device 45. The structure of the second bearing device 45 is the same as that of the first bearing device 40, although the type of rolling bearing is different.

[0134] exist Figure 6 In the embodiment, the first rolling bearing 41 is an open bearing in which the bearing space between the inner ring 41a and the outer ring 41b is not closed by a sealing member, and lubrication is performed by supplying a lubricant (lubricating oil or grease) to the bearing space so that the lubricant is interposed between the raceway surface and the like. Alternatively, a sealing member may be provided to seal the lubricant. When the bearing rotates, the grease and the like generate heat due to the friction between the rolling element and the raceway surface and the retaining frame, and the stirring resistance of the grease, and reach a high temperature. In addition, as for the grease and the like, as long as it is a material commonly used in the bearings for the main motor, it can be used without particular restrictions.

[0135] Normally, for the main motor bearings, maintenance such as replacement of grease and status inspection is performed in coordination with the regular inspection of railway vehicles. The required frequency of maintenance for the main motor bearings is one of the factors that determine the required frequency of maintenance for the main motor and, therefore, the railway vehicle. In addition, the required frequency of maintenance for the main motor bearings is governed by the lubrication life of the grease. Grease deteriorates due to oxidation of the base oil, etc. Therefore, generally speaking, the lubrication life of the grease is long when the bearing temperature is low. Therefore, in order to reduce the maintenance frequency of the main motor and reduce maintenance costs, it is necessary to reduce the bearing temperature. In addition, the main motor bearings sometimes suffer damage due to electrolytic corrosion due to the application of leakage voltage during use.

[0136] like Figure 4 to Figure 7 As shown, by applying the insulating rolling bearing of the present invention to the main motor bearing, even when the temperature of the bearing rises due to high-speed rotation, the heat can be dissipated through the housing component, etc. Therefore, the film thickness of the insulating coating can be increased while suppressing the increase in the bearing temperature. As a result, high impedance can be achieved, and the anti-corrosion property of preventing electric corrosion caused by power supply is particularly excellent.

[0137] Example

[0138] The frequency characteristics of impedance were measured using the outer rings of four types of insulating rolling bearings with insulating coatings of different materials and film thicknesses.

[0139] When the insulating film is a ceramic film, the film is formed by thermal spraying using a thermal spraying material having an aluminum oxide content of 95.0 to 98.5% by mass and other metal oxide content of 1.5 to 5.0% by mass. In the case of another ceramic film, a thermal spraying material having an aluminum oxide content of 97.0% or more and a metal oxide content of 1.5 to 2.5% by mass is used. The film thickness of the insulating film is 0.1 mm to 1.0 mm.

[0140] In the case where the insulating film is a resin film, the resin film is formed by injection molding using the following resin composition: the total content of glass fiber and inorganic filler with a thermal conductivity of 10W / m·K or more is 40% to 70% by mass relative to the entire resin composition of the resin film, the resin composition contains more inorganic filler than glass fiber, and contains 10% to 30% by mass of glass fiber, 30% to 50% by mass of inorganic filler relative to the entire resin composition, and also contains thermoplastic elastomer. The film thickness of the resin film is 0.3mm to 2.0mm. The insulating films in the insulating rolling bearings used for measurement all have an insulation resistance value of more than 2000MΩ and an electrostatic capacitance of less than 10nF. In addition, by meeting these conditions, electrical corrosion is prevented in actual vehicles.

[0141] After the bearing outer ring is mounted in a jig in which the entire circumference of the bearing outer ring is in contact, the impedance Z is measured using an LCR meter under the measurement condition of a load voltage of 1 V based on the phase difference between the current waveform and the voltage waveform.

[0142] The electrostatic capacitances of the above four types of insulating films are 0.5nF, 1.0nF, 5.0nF, and 10.0nF. Figure 8 The frequency characteristics of the impedance of these samples are shown. Figure 8 As shown, it was confirmed that when the electrostatic capacitance was 10.0 nF or less, the impedance was greater than 10Ω even at a high frequency such as 1000 Hz. Therefore, it is believed that the insulating rolling bearing of the present invention can fully ensure insulation performance in a main motor that operates at a high frequency due to high performance.

[0143] Industrial Applicability

[0144] The insulating rolling bearing of the present invention has electrical insulation due to the insulating film and excellent anti-corrosion property, and therefore can be applied to various rolling bearings used in devices that allow current to flow inside the bearing. In particular, it is preferably used in a rolling bearing supporting structure for a main shaft of a main motor of a railway vehicle.

[0145] Description of Reference Numerals

[0146] 1 Insulated rolling bearings

[0147] 2 Inner ring

[0148] 3 Outer ring

[0149] 4 Balls (rolling elements)

[0150] 5 Cage

[0151] 6. Resin coating

[0152] 7 Movable side plate

[0153] 8 Fixed side panels

[0154] 9 Runner

[0155] 10 Gate mark

[0156] 11 Insulated rolling bearings

[0157] 12 Inner circle

[0158] 13 Outer ring

[0159] 4 Balls (rolling elements)

[0160] 15 Cage

[0161] 16 Ceramic coating

[0162] 21 Bogie

[0163] 22 Bogie body

[0164] 23 Spindle

[0165] 24 Coupling

[0166] 25 Drive device

[0167] 26 Axles

[0168] 27 Wheels

[0169] 28 Axle bearing assembly

[0170] 30 Main motor

[0171] 31 Framework

[0172] 32 Stator

[0173] 33 Rotor

[0174] 40 First bearing device

[0175] 41 First rolling bearing

[0176] 42 Housing

[0177] 43 Stopper

[0178] 44 End cap

[0179] 45 Second bearing device

[0180] 46 Second rolling bearing

[0181] 47 Housing

[0182] 48 Stopper

[0183] 49 End cap

[0184] C-Cavity

[0185] G Gate.

Claims

1. An insulating rolling bearing, comprising: an inner ring and an outer ring; raceways formed on the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring; and a plurality of rolling elements interposed between the raceways, wherein at least one circumferential surface selected from the inner circumferential surface of the inner ring and the outer circumferential surface of the outer ring has an insulating coating including a resin coating or a ceramic coating, It is characterized in that The insulation resistance value of the insulation coating in the insulation rolling bearing is 2000 MΩ or more, and the electrostatic capacitance is 10 nF or less.

2. The insulating rolling bearing according to claim 1, characterized in that: The insulating coating is composed of the resin coating, and the resin coating is composed of a resin composition including polyphenylene sulfide resin, glass fiber, an inorganic filler having a thermal conductivity of 10 W / m·K or more, and a thermoplastic elastomer.

3. The insulating rolling bearing according to claim 2, characterized in that: The content of the thermoplastic elastomer is 1% by mass to 10% by mass based on the entire resin composition.

4. The insulating rolling bearing according to claim 2, characterized in that: The total content of the glass fiber and the inorganic filler is 40% to 70% by mass relative to the entire resin composition. The resin composition contains more inorganic filler than the glass fiber, and contains 10% to 30% by mass of the glass fiber and 30% to 50% by mass of the inorganic filler relative to the entire resin composition.

5. The insulating rolling bearing according to claim 2, characterized in that: The inorganic filler is at least one selected from silicon carbide, beryllium oxide, boron nitride, silicon nitride, magnesium hydroxide, aluminum oxide, and magnesium carbonate.

6. The insulating rolling bearing according to claim 1, characterized in that: The insulating film is composed of the resin film, which is composed of a resin composition including polyphenylene sulfide resin, glass fiber, an inorganic filler having a thermal conductivity of 10 W / m·K or more, and a thermoplastic elastomer. The content of the thermoplastic elastomer is 1% to 10% by mass based on the total mass of the resin composition. The total content of the glass fiber and the inorganic filler is 40% to 70% by mass relative to the entire resin composition, and the resin composition contains more inorganic filler than the glass fiber, and contains 10% to 30% by mass of the glass fiber and 30% to 50% by mass of the inorganic filler relative to the entire resin composition. The inorganic filler is at least one selected from silicon carbide, beryllium oxide, boron nitride, silicon nitride, magnesium hydroxide, aluminum oxide, and magnesium carbonate.

7. The insulating rolling bearing according to claim 2, characterized in that: The resin coating is formed on the circumferential surface of the raceway ring and the axial end surfaces on both sides thereof, the film thickness on the circumferential surface is less than 1 mm, and the ratio of the film thickness on the circumferential surface to the film thickness on the axial end surfaces is in the range of 1:1 to 1:

3.

8. The insulating rolling bearing according to claim 2, characterized in that: The resin in the resin coating flows in a direction from one side to the other side of the peripheral surface in the axial direction over the entire circumference of the raceway ring.

9. The insulating rolling bearing according to claim 1, characterized in that: The insulating film includes the ceramic film, and the film thickness of the insulating film is in the range of 0.1 mm to 1.0 mm.

10. The insulating rolling bearing according to claim 1, characterized in that: The insulating rolling bearing is a bearing that rotatably supports a main shaft of a main motor of a railway vehicle.

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