An insulating coating with low capacitance value and a preparation method thereof and an insulating bearing

Abstract

The present invention relates to an insulating coating with low capacitance value, a preparation method thereof and an insulating bearing, wherein the insulating coating comprises a first coating and a second coating; the first coating comprises a ceramic insulating coating, the ceramic insulating coating comprises an oxide ceramic layer with holes and a sealing resin filled in the holes, and the first coating is arranged on the outer surface of the outer ring of the bearing; the second coating comprises a resin insulating coating, the second coating is arranged in a groove on the outer surface of the outer ring of the bearing, and is arranged above the first coating. The insulating coating provided by the present invention combines the ceramic insulating coating and the resin insulating coating, and the resin insulating coating is arranged in the groove of the outer ring of the bearing, so as to achieve a lower capacitance value under the condition of satisfying the insulation, mechanical properties and breakdown resistance of the bearing, and meet the needs of high electrical insulation performance occasions.

Description

Technical Field

[0001] The invention relates to the technical field of bearings, and in particular to an insulating coating with a low capacitance value, a preparation method thereof, and an insulating bearing. Background Art

[0002] Insulated bearings are classified according to their surface treatment methods, including ceramic-coated insulating bearings and resin-coated insulating bearings. Among them, ceramic-coated insulating bearings have the widest range of uses and are mainly used in motors, generators and other fields, especially variable frequency motors. Although resin-type insulating bearings have the advantages of good insulation performance, low capacitance, high cost-effectiveness and easy processing, they may lose their insulation properties in high temperature environments and certain chemicals may damage the resin coating and affect its insulation properties, so their thermal and chemical stability are limited, and their voltage resistance is not as good as that of ceramic insulating bearings, which limits their further promotion and application.

[0003] The capacitance of an insulated bearing refers to the capacitance value of the bearing itself, which is determined by the structure, material and characteristics of the insulation layer of the bearing. The capacitance value has an important influence on the electrical performance and operating stability of the bearing. In a high-frequency or AC electrical environment, capacitance may cause current to pass through the bearing, thereby causing electrical noise, electromagnetic interference and other problems. Therefore, for occasions that require high electrical insulation performance, insulated bearings with lower capacitance values ​​should be selected.

[0004] At present, the methods commonly used to reduce the capacitance value of insulated bearings mainly include optimizing the structure of the insulation layer, selecting insulation layer materials with low dielectric constants, and reducing the size of the bearings. Among them, commonly used insulation layer materials include aluminum oxide, titanium oxide, aluminum nitride, etc. Among them, the dielectric constant of aluminum oxide is usually between 9-10, which makes it an insulating material with a medium dielectric constant, which means that aluminum oxide can effectively store electrical energy in an electric field, but it may also bring a certain capacitance value. The dielectric constant of titanium oxide ranges from 40-200. Although the use of titanium oxide may make the bearing have a higher capacitance value, the optical transparency, chemical stability and mechanical strength of titanium oxide may also be more advantageous in certain specific applications. The dielectric constant of aluminum nitride is usually in the range of 7-9, which makes it a ceramic material with a relatively low dielectric constant. It has advantages in some occasions where lower capacitance values ​​are required. It also has excellent mechanical properties, good thermal stability and chemical stability.

[0005] For example, CN112553558A discloses a method for preparing an insulating coating on the surface of a bearing, comprising: performing atmospheric plasma spraying on a mixture powder of aluminum oxide and zirconium oxide as the coating raw material, applying a sealing agent after cooling, and obtaining an insulating coating on the surface of the bearing after drying. Although the coating can achieve a certain insulating effect, it cannot achieve a lower capacitance value and is not suitable for occasions with high electrical insulation performance.

[0006] Therefore, how to reduce the capacitance value of the insulating bearing so that it meets the needs of high-frequency or AC electrical environments is a technical problem that needs to be solved in the current field. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide an insulating coating with low capacitance value, a preparation method thereof and an insulating bearing. Compared with the prior art, the insulating coating provided by the present invention combines a ceramic insulating coating and a resin insulating coating, and the resin insulating coating is arranged in the groove of the outer ring of the bearing. It can achieve a lower capacitance value while satisfying the insulation, mechanical properties and breakdown resistance of the bearing, thereby meeting the needs of high electrical insulation performance occasions.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides an insulating coating with a low capacitance value, the insulating coating comprising a first coating and a second coating;

[0010] The first coating layer comprises a ceramic insulating coating layer, the ceramic insulating coating layer comprises an oxide ceramic layer having pores and a sealing resin filled in the pores, and the first coating layer is disposed on the outer surface of the outer ring of the bearing;

[0011] The second coating layer comprises a resin insulating coating layer, and the second coating layer is arranged in a groove on the outer surface of the bearing outer ring and is arranged above the first coating layer.

[0012] In the insulating coating provided by the present invention, the capacitance value is reduced mainly from two aspects: on the one hand, by increasing the amount of resin added, compared with the existing insulating coating, the insulating coating provided by the present invention is further provided with a resin insulating coating on the basis of the ceramic insulating coating, and it is arranged in a groove on the outer surface of the outer ring of the bearing, which can effectively reduce the capacitance value on the basis of ensuring the performance of the insulating coating such as the breakdown resistance and mechanical properties; on the other hand, by increasing the thickness of the insulating coating, the capacitance value is reduced. The present invention arranges the first coating and the second coating in layers and controls their thicknesses, which can further reduce the capacitance value of the insulating coating while ensuring the insulation performance, thereby meeting the needs of high-frequency or AC electrical environments.

[0013] In the present invention, the outer surface of the insulating outer ring includes an outer diameter surface and end surfaces located on both sides of the outer diameter surface.

[0014] Preferably, the oxide ceramic layer is obtained by spraying oxide ceramic powder.

[0015] Preferably, the oxide ceramic powder contains aluminum oxide and a second compound.

[0016] Preferably, the second compound comprises aluminum nitride and / or titanium oxide.

[0017] In the present invention, the second compound is preferably controlled to be aluminum nitride or titanium oxide, which is beneficial to improving the chemical stability and mechanical strength of the insulating coating and meeting the needs of various applications. Aluminum nitride is preferred.

[0018] Preferably, the mass percentage of aluminum oxide in the oxide ceramic powder is 79.5-97.5%, for example, it can be 79.5%, 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97% or 97.5%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the mass percentage of aluminum nitride in the oxide ceramic powder is 9.5-20.5%, for example, it can be 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20% or 20.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] Preferably, the mass percentage of titanium oxide in the oxide ceramic powder is 2.5-3.5%, for example, it can be 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4% or 3.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, the particle size of the oxide ceramic powder is 10-30 μm, for example, it can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm or 30 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the thickness of the oxide ceramic layer is 0.3-0.6 mm, for example, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm or 0.6 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In the present invention, it is preferred to control the thickness of the oxide ceramic layer within a specific range. If the thickness of the oxide ceramic layer is appropriately controlled to be higher, the capacitance value can be further reduced.

[0024] Preferably, the porosity of the oxide ceramic layer is 6-10%, for example, 6%, 7%, 8%, 9% or 10%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In the present invention, when the porosity is too low, the sealing resin is difficult to penetrate, and the coating is brittle and has poor impact resistance; when the porosity is too high, the content of the sealing resin is high, but the interface between the resin and the ceramic is large, resulting in a low breakdown voltage. Therefore, the present invention preferably controls the porosity of the oxide ceramic layer within a specific range, that is, by controlling the porosity to moderately increase the content of the sealing resin, it is beneficial to further reduce the capacitance value of the insulating coating without reducing the breakdown voltage.

[0026] Preferably, the sealing resin comprises epoxy resin.

[0027] Preferably, the first coating layer further includes a metal transition layer.

[0028] Preferably, the metal transition layer is arranged between the outer surface of the bearing outer ring and the ceramic insulating coating.

[0029] In the present invention, although the capacitance value can be reduced by moderately increasing the thickness of the oxide ceramic layer, when the thickness is too high, the bonding force between the oxide ceramic layer and the outer ring of the bearing is poor. When the thickness of the oxide ceramic layer exceeds 0.5 mm, the bearing may be at risk of the entire coating falling off during use, seriously affecting the service life of the bearing. It is necessary to set a metal transition layer to enhance the bonding force between the oxide ceramic layer and the outer surface of the bearing to prevent it from falling off.

[0030] Preferably, the metal transition layer is obtained by spraying nickel-chromium alloy powder or nickel-aluminum alloy powder.

[0031] Preferably, the mass percentage of nickel in the nickel-chromium alloy powder is 75.8-80.5%, for example, it can be 75.8%, 76%, 76.2%, 76.5%, 76.8%, 77%, 77.2%, 77.5%, 77.8%, 78%, 78.2%, 78.5%, 78.8%, 79%, 79.2%, 79.5%, 79.8%, 80%, 80.2% or 80.5%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the particle size of the nickel-chromium alloy powder is 10-30 μm, for example, it can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm or 30 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the mass percentage of nickel in the nickel-aluminum alloy powder is 79.5-81.5%, 79.5%, 79.8%, 80%, 80.2%, 80.5%, 80.8%, 81%, 81.2% or 81.5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the particle size of the nickel-aluminum alloy powder is 10-30 μm, for example, it can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm or 30 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the thickness of the metal transition layer is 0.05-0.1 mm, for example, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm or 0.1 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the resin insulating coating comprises epoxy resin.

[0037] Preferably, the thickness of the resin insulation coating is 0.25-0.35 mm, for example, it can be 0.25 mm, 0.26 mm, 0.28 mm, 0.3 mm, 0.32 mm, 0.34 mm or 0.35 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In a second aspect, the present invention provides a method for preparing an insulating coating with a low capacitance value as described in the first aspect of the present invention, characterized in that the preparation method comprises the following steps:

[0039] (1) plasma spraying the outer surface of the bearing outer ring provided with the groove to prepare an oxide ceramic layer, and then performing a sealing treatment to obtain a first coating;

[0040] (2) The outer surface of the first coating layer is coated with epoxy resin slurry, which is then cured, and then the cured product outside the groove is removed by grinding to obtain a second coating layer, thereby completing the preparation of the insulating coating layer.

[0041] In the preparation method provided by the present invention, an oxide ceramic layer is first prepared by plasma spraying, and then a sealing resin is filled in the pores of the oxide ceramic layer through a sealing treatment. Thereafter, a resin insulating coating is coated on top of the first coating by a coating means such as a coating machine. After the resin is cured, the remaining cured products except those in the groove are removed to expose the ceramic insulating coating outside the groove, thereby ensuring that the insulating coating has good processing accuracy, insulation resistance and low capacitance value.

[0042] Preferably, the outer surface of the bearing outer ring includes an outer diameter surface and end surfaces located on both sides of the outer diameter surface, and the groove is arranged on the outer diameter surface of the bearing outer ring, and is further preferably arranged on the outer diameter surface and the end surfaces on both sides.

[0043] In the present invention, a groove is controlled to be opened on the outer surface of the outer ring of the bearing, and a resin insulating coating is filled in the groove. This is because when the oxide ceramic layer reaches the maximum thickness, which is generally about 1 mm, if the thickness continues to increase, the oxide ceramic layer will be at risk of falling off. The present invention can continue to reduce the overall capacitance value of the bearing by setting a groove and setting the resin insulating coating in the groove, and can achieve the desired capacitance value by adjusting the thickness of the resin insulating coating and the oxide ceramic layer. At the same time, the oxide ceramic layer still plays a supporting role, so that the bearing has good support and creep resistance.

[0044] Preferably, the depth of the groove is 0.2-0.5 mm, for example, it can be 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm or 0.5 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the opening width of the groove is 1-2 mm, for example, 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm or 2 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, two opposite side surfaces of the groove are configured as inclined surfaces.

[0047] Preferably, the angle between the inclined surface and the depth direction of the groove is 40-50°, for example, it can be 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49° or 50°, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] In the present invention, by controlling the two opposite sides of the groove to be inclined surfaces and controlling the angle between the inclined surface and the groove depth direction to be within a specific range, problems such as accumulation and line defects in the groove can be avoided, and the continuity and uniformity of the coating can be improved.

[0049] Preferably, before preparing the oxide ceramic layer in step (1), the outer surface of the bearing outer ring provided with the groove is pre-plasma sprayed to prepare a metal transition layer.

[0050] Preferably, in the preparation of the metal transition layer, plasma spraying uses argon as the main gas and hydrogen as the auxiliary gas, the current is 520-550A, for example, it can be 520A, 530A, 540A or 550A, the voltage is 69-75V, for example, it can be 69V, 70V, 71V, 72V, 73V, 74V or 75V, the spraying distance is 100-120mm, for example, it can be 100mm, 105mm, 110mm, 115mm or 120mm, the main gas flow rate is 43-45L / min, for example, it can be 43L / min, 44L / min or 45L / min, the auxiliary gas flow rate is 9-11L / min, for example, it can be 9L / min, 10L / min or 11L / min, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, in the preparation of the oxide ceramic layer, plasma spraying uses argon as the main gas and hydrogen as the auxiliary gas, the current is 550-600A, for example, it can be 550A, 560A, 570A, 580A, 590A or 600A, the voltage is 68-72V, for example, it can be 68V, 69V, 70V, 71V or 72V, the spraying distance is 100-120mm, for example, it can be 100mm, 105mm, 110mm, 115mm or 120mm, the main gas flow rate is 38-41L / min, for example, it can be 38L / min, 39L / min, 40L / min or 41L / min, the auxiliary gas flow rate is 13-15L / min, for example, it can be 13L / min, 14L / min or 15L / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, the sealing treatment in step (1) comprises placing the outer ring of the bearing in a sealed container, performing vacuuming and injecting a sealing agent in sequence, and then curing.

[0053] Preferably, the sealing agent comprises epoxy resin slurry.

[0054] Preferably, the viscosity of the epoxy resin slurry used in the sealing agent is 1000-1100cps, for example, it can be 1000cps, 1010cps, 1020cps, 1030cps, 1040cps, 1050cps, 1060cps, 1070cps, 1080cps, 1090cps or 1100cps, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] Preferably, the vacuum degree at the end point of the vacuuming is less than -0.1 MPa, for example, -0.09 MPa, -0.08 MPa or -0.07 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] Preferably, the curing temperature in the sealing treatment is 145-155°C, for example, it can be 145°C, 146°C, 148°C, 150°C, 152°C, 154°C or 155°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] Preferably, the curing time in the sealing treatment is 5-6 hours, for example, it can be 5 hours, 5.2 hours, 5.4 hours, 5.5 hours, 5.6 hours, 5.8 hours or 6 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] Preferably, the viscosity of the epoxy resin slurry used for coating in step (2) is 4000-5000cps, for example, it can be 4000cps, 4100cps, 4200cps, 4300cps, 4400cps, 4500cps, 4600cps, 4700cps, 4800cps, 4900cps or 5000cps, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0059] Preferably, the curing temperature in step (2) is 135-145°C, for example, it can be 135°C, 136°C, 138°C, 140°C, 142°C, 144°C or 145°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] Preferably, the curing time in step (2) is 5-6 hours, for example, 5 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours or 6 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] Preferably, the grinding wheel used for the grinding comprises an aluminum oxide grinding wheel.

[0062] Preferably, the particle size of the grinding wheel used for grinding is 320-400 mesh, for example, it can be 320 mesh, 330 mesh, 340 mesh, 350 mesh, 360 mesh, 370 mesh, 380 mesh, 390 mesh or 400 mesh, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] As a preferred technical solution of the second aspect of the present invention, the preparation method comprises the following steps:

[0064] (1) Plasma spraying is performed on the outer surface of a bearing outer ring with a groove to prepare an oxide ceramic layer, wherein the outer surface of the bearing outer ring includes an outer diameter surface and end surfaces located on both sides of the outer diameter surface, the groove is arranged on the outer diameter surface of the bearing outer ring, the depth of the groove is 0.2-0.5 mm, the opening width is 1-2 mm, and the two opposite side surfaces in the groove are arranged as inclined surfaces, and the angle between the inclined surface and the depth direction of the groove is 40-50°. In the preparation of the oxide ceramic layer, argon is used as the main gas for plasma spraying, and hydrogen is used as the main gas. The auxiliary gas is 550-600A, the voltage is 68-72V, the spraying distance is 100-120mm, the main gas flow rate is 38-41L / min, the auxiliary gas flow rate is 13-15L / min, and then a sealing treatment is performed, wherein the sealing treatment includes placing the outer ring of the bearing in a sealed container, evacuating to an end point vacuum degree of <-0.1MPa, and then injecting epoxy resin slurry with a viscosity of 1000-1100cps, and curing at 145-155°C for 5-6h to obtain a first coating;

[0065] Before preparing the oxide ceramic layer, the outer surface of the bearing outer ring with the groove is pre-plasma sprayed to prepare a metal transition layer. In the preparation of the metal transition layer, the plasma spraying uses argon as the main gas, hydrogen as the auxiliary gas, the current is 520-550A, the voltage is 69-75V, the spraying distance is 100-120mm, the main gas flow rate is 43-45L / min, and the auxiliary gas flow rate is 9-11L / min;

[0066] (2) The outer surface of the first coating is coated with an epoxy resin slurry with a viscosity of 4000-5000 cps, and then cured at 135-145°C for 5-6 hours. Thereafter, it is ground using an alumina grinding wheel with a particle size of 320-400 mesh to remove the cured product outside the groove to obtain a second coating, thereby completing the preparation of the insulating coating.

[0067] In a third aspect, the present invention provides an insulating bearing, which includes a bearing inner ring and a bearing outer ring, bearing balls are arranged between the bearing inner ring and the bearing outer ring, a groove is provided on the outer surface of the bearing outer ring, and an insulating coating with a low capacitance value as described in the first aspect of the present invention is arranged on the outer surface of the bearing outer ring.

[0068] In the insulating bearing provided by the present invention, by adopting the insulating coating provided by the first aspect of the present invention, not only good insulation performance can be ensured, but also a lower capacitance value can be achieved, while having breakdown resistance and impact resistance, meeting the needs of high-frequency or AC electrical environments.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) In the insulating coating provided by the present invention, by providing a resin insulating coating on the basis of the ceramic insulating coating and providing it in a groove on the outer surface of the bearing outer ring, the capacitance value can be effectively reduced while ensuring the performance of the insulating coating such as the breakdown resistance and mechanical properties; at the same time, by controlling the porosity of the ceramic insulating coating and increasing the content of the filling resin, the capacitance value can be further reduced.

[0071] (2) In the insulating coating provided by the present invention, by controlling the thickness of the insulating coating, that is, by adopting a stacked arrangement of the first coating and the second coating and controlling their thickness, the capacitance value of the insulating coating can be further reduced while ensuring the insulating performance.

[0072] (3) In the preparation method of the insulating coating provided by the present invention, an insulating coating with good insulation, high breakdown voltage and low capacitance can be prepared, and also has good mechanical strength and impact resistance. Under optimal conditions, the insulation resistance value of the insulating bearing can reach more than 200GΩ, the capacitance value can reach less than 0.44NF, the breakdown voltage can reach 10000-11000V, and the impact energy can reach 5.4J, which can meet the needs of high-frequency or AC electrical environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 This is a schematic diagram of a radial cross section of a bearing outer ring provided with an insulating coating in Example 1 of the present invention;

[0074] Figure 2 This is a partial enlarged view of the insulating coating described in Example 1 of the present invention.

[0075] Among them, 1-outer diameter surface; 2-end surface; 3-groove; 4-first coating; 5-second coating. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0077] Example 1

[0078] This embodiment provides an insulating coating with a low capacitance value, such as Figure 1 and Figure 2 As shown, the insulating coating includes a first coating 4 and a second coating 5, the first coating 4 is arranged on the outer surface of the bearing outer ring, the outer surface includes an outer diameter surface 1 and end surfaces 2 located on both sides of the outer diameter surface 1, the second coating 5 is arranged in a groove 3 on the outer surface of the bearing outer ring, and is arranged above the first coating 4, the depth of the groove 3 is 0.3mm, the opening width is 1.5mm, the two opposite side surfaces of the groove 3 are set as inclined surfaces, and the angle between the inclined surface and the depth direction of the groove 3 is 45°;

[0079] The first coating 4 is a metal transition layer and a ceramic insulating coating. The metal transition layer has a thickness of 0.07 mm and is disposed between the outer surface of the bearing outer ring and the ceramic insulating coating. The first coating 4 is obtained by spraying a nickel-chromium alloy powder. The mass percentage of nickel in the nickel-chromium alloy powder is 78%, and the particle size is 10-30 μm.

[0080] The ceramic insulating coating comprises an oxide ceramic layer with pores and a sealing resin filled in the pores, the oxide ceramic layer has a thickness of 0.6 mm, the oxide ceramic layer is obtained by spraying oxide ceramic powder, the particle size of the oxide ceramic powder is 10-30 μm, and the oxide ceramic powder comprises, by mass percentage, 20% aluminum nitride and the rest aluminum oxide, the porosity of the oxide ceramic layer is 8%, and the sealing resin comprises epoxy resin;

[0081] The second coating 5 includes a resin insulating coating, the insulating resin layer is epoxy resin, and the thickness of the resin insulating coating is 0.3 mm.

[0082] This embodiment also provides a method for preparing the above insulating coating, the preparation method comprising the following steps:

[0083] (1) Plasma spraying of an oxide ceramic powder on the outer surface of the bearing outer ring provided with the groove 3 is performed to prepare an oxide ceramic layer. In the preparation of the oxide ceramic layer, the plasma spraying uses argon as the main gas, hydrogen as the auxiliary gas, the current is 600A, the voltage is 72V, the spraying distance is 120mm, the main gas flow rate is 41L / min, and the auxiliary gas flow rate is 15L / min. Then, a sealing treatment is performed. The sealing treatment includes placing the bearing outer ring in a sealed container, evacuating to an end vacuum degree of -0.09MPa, and then injecting an epoxy resin slurry with a viscosity of 1050cps, and curing at 150°C for 5.5h to obtain a first coating 4;

[0084] Before the oxide ceramic layer is prepared, the outer surface of the bearing outer ring where the groove 3 is provided is pre-plasma sprayed with nickel-chromium alloy powder to prepare a metal transition layer. In the preparation of the metal transition layer, the plasma spraying uses argon as the main gas, hydrogen as the auxiliary gas, the current is 520A, the voltage is 69V, the spraying distance is 100mm, the main gas flow rate is 43L / min, and the auxiliary gas flow rate is 9L / min;

[0085] (2) The outer surface of the first coating 4 is coated with an epoxy resin slurry with a viscosity of 4500 cps, and then cured at 140°C for 5.5 hours. Thereafter, it is ground using an alumina grinding wheel with a particle size of 380 mesh to remove the cured product outside the groove 3 to obtain a second coating 5, thereby completing the preparation of the insulating coating.

[0086] This embodiment also provides an insulating bearing, which includes a bearing inner ring and a bearing outer ring, bearing balls are arranged between the bearing inner ring and the bearing outer ring, a groove 3 is provided on the outer surface of the bearing outer ring, and the outer surface of the bearing outer ring is provided with the above-mentioned low capacitance value insulating coating.

[0087] Example 2

[0088] This embodiment provides an insulating coating with a low capacitance value, the insulating coating comprising a first coating and a second coating, the first coating being arranged on the outer surface of the bearing outer ring, the outer surface comprising an outer diameter surface and end surfaces located on both sides of the outer diameter surface, the second coating being arranged in a groove on the outer surface of the bearing outer ring and arranged above the first coating, the depth of the groove being 0.5 mm, the opening width being 2 mm, the two opposite side surfaces in the groove being arranged as inclined surfaces, and the angle between the inclined surface and the depth direction of the groove being 50°;

[0089] The first coating is a metal transition layer and a ceramic insulating coating. The metal transition layer has a thickness of 0.1 mm and is disposed between the outer surface of the bearing outer ring and the ceramic insulating coating. The metal transition layer is obtained by spraying a nickel-chromium alloy powder. The mass percentage of nickel in the nickel-chromium alloy powder is 75.8%, and the particle size is 10-30 μm.

[0090] The ceramic insulating coating comprises an oxide ceramic layer with pores and a sealing resin filled in the pores, the oxide ceramic layer has a thickness of 1 mm, the oxide ceramic layer is obtained by spraying oxide ceramic powder, the particle size of the oxide ceramic powder is 10-30 μm, and the oxide ceramic powder comprises, by mass percentage, 15% aluminum nitride and the rest aluminum oxide, the porosity of the oxide ceramic layer is 6%, and the sealing resin comprises epoxy resin;

[0091] The second coating layer includes a resin insulating coating layer, the insulating resin layer is epoxy resin, and the thickness of the resin insulating coating layer is 0.5 mm.

[0092] This embodiment also provides a method for preparing the above insulating coating, the preparation method comprising the following steps:

[0093] (1) Plasma spraying of an oxide ceramic powder on the outer surface of the bearing outer ring with a groove to prepare an oxide ceramic layer, wherein the plasma spraying uses argon as the main gas, hydrogen as the auxiliary gas, the current is 580A, the voltage is 70V, the spraying distance is 110mm, the main gas flow rate is 40L / min, and the auxiliary gas flow rate is 14L / min, and then a sealing treatment is performed, wherein the sealing treatment includes placing the bearing outer ring in a sealed container, evacuating the container to an end vacuum degree of -0.09MPa, and then injecting an epoxy resin slurry with a viscosity of 1000cps, and curing the container at 155°C for 5h to obtain a first coating;

[0094] Before the oxide ceramic layer is prepared, the outer surface of the bearing outer ring with the groove is pre-plasma sprayed with nickel-chromium alloy powder to prepare a metal transition layer. In the preparation of the metal transition layer, argon is used as the main gas, hydrogen is used as the auxiliary gas, the current is 550A, the voltage is 75V, the spraying distance is 120mm, the main gas flow rate is 45L / min, and the auxiliary gas flow rate is 11L / min;

[0095] (2) The outer surface of the first coating is coated with an epoxy resin slurry with a viscosity of 4000 cps, and then cured at 145°C for 5 hours. Thereafter, it is ground with an alumina grinding wheel with a particle size of 320 mesh to remove the cured product outside the groove to obtain a second coating, thereby completing the preparation of the insulating coating.

[0096] This embodiment also provides an insulating bearing, which includes a bearing inner ring and a bearing outer ring, bearing balls are arranged between the bearing inner ring and the bearing outer ring, a groove is provided on the outer surface of the bearing outer ring, and the outer surface of the bearing outer ring is provided with the above-mentioned low capacitance value insulating coating.

[0097] Example 3

[0098] This embodiment provides an insulating coating with a low capacitance value, the insulating coating comprising a first coating and a second coating, the first coating being arranged on the outer surface of the outer ring of the bearing, the outer surface comprising an outer diameter surface and end surfaces located on both sides of the outer diameter surface, the second coating being arranged in a groove on the outer surface of the outer ring of the bearing and arranged above the first coating, the depth of the groove being 0.25 mm, the opening width being 1 mm, the two opposite side surfaces of the groove being arranged as inclined surfaces, and the angle between the inclined surface and the depth direction of the groove being 40°;

[0099] The first coating is a ceramic insulating coating, which includes an oxide ceramic layer with pores and a sealing resin filled in the pores, the oxide ceramic layer has a thickness of 0.3 mm, and is obtained by spraying oxide ceramic powder, the particle size of the oxide ceramic powder is 10-30 μm, and the oxide ceramic powder includes, by mass percentage, 10% aluminum nitride and the rest aluminum oxide, the porosity of the oxide ceramic layer is 10%, and the sealing resin includes epoxy resin;

[0100] The second coating layer includes a resin insulating coating layer, the insulating resin layer is epoxy resin, and the thickness of the resin insulating coating layer is 0.25 mm.

[0101] This embodiment also provides a method for preparing the above insulating coating, the preparation method comprising the following steps:

[0102] (1) Plasma spraying of oxide ceramic powder on the outer surface of the bearing outer ring with grooves to prepare an oxide ceramic layer, wherein the plasma spraying uses argon as the main gas, hydrogen as the auxiliary gas, the current is 550A, the voltage is 68V, the spraying distance is 100mm, the main gas flow rate is 38L / min, and the auxiliary gas flow rate is 13L / min, and then a sealing treatment is performed, wherein the sealing treatment includes placing the bearing outer ring in a sealed container, evacuating to an end vacuum degree of -0.09MPa, and then injecting an epoxy resin slurry with a viscosity of 1100cps, and curing at 145°C for 6h to obtain a first coating;

[0103] (2) The outer surface of the first coating is coated with an epoxy resin slurry with a viscosity of 5000 cps, and then cured at 135°C for 6 hours. Thereafter, it is ground using an alumina grinding wheel with a particle size of 400 mesh to remove the cured product outside the groove to obtain a second coating, thereby completing the preparation of the insulating coating.

[0104] This embodiment also provides an insulating bearing, which includes a bearing inner ring and a bearing outer ring, bearing balls are arranged between the bearing inner ring and the bearing outer ring, a groove is provided on the outer surface of the bearing outer ring, and the outer surface of the bearing outer ring is provided with the above-mentioned low capacitance value insulating coating.

[0105] Example 4

[0106] This embodiment provides an insulating coating with a low capacitance value. The only difference compared with the embodiment 1 is that the raw material of the oxide ceramic layer is only aluminum oxide and the thickness is 0.6 mm.

[0107] Example 5

[0108] This embodiment provides an insulating coating with a low capacitance value. The only difference compared with the embodiment 1 is that the raw material of the oxide ceramic layer is only aluminum oxide and the thickness is 1.0 mm.

[0109] Example 6

[0110] This embodiment provides an insulating coating with a low capacitance value. The only difference compared with the embodiment 3 is that the raw materials of the oxide ceramic layer are aluminum oxide and titanium oxide, wherein the mass percentage of titanium oxide is 2.5%.

[0111] Example 7

[0112] This embodiment provides an insulating coating with a low capacitance value. The only difference compared with the embodiment 3 is that the raw materials of the oxide ceramic layer are aluminum oxide and titanium oxide, wherein the mass percentage of titanium oxide is 3.5%.

[0113] Example 8

[0114] This embodiment provides an insulating coating with a low capacitance value. The only difference compared with the embodiment 3 is that the raw material of the oxide ceramic layer is only aluminum oxide.

[0115] Example 9

[0116] This embodiment provides an insulating coating with a low capacitance value, and the only difference compared with Embodiment 1 is that the thickness of the oxide ceramic layer is 0.2 mm.

[0117] Example 10

[0118] This embodiment provides an insulating coating with a low capacitance value, and the only difference compared with Embodiment 1 is that the thickness of the oxide ceramic layer is 1.5 mm.

[0119] Embodiment 11

[0120] This embodiment provides an insulating coating with a low capacitance value, and the only difference compared with the first embodiment is that the thickness of the resin insulating coating is 0.1 mm.

[0121] Example 12

[0122] This embodiment provides an insulating coating with a low capacitance value, and the only difference compared with the first embodiment is that the thickness of the resin insulating coating is 0.7 mm.

[0123] Example 13

[0124] This embodiment provides an insulating coating with a low capacitance value. The only difference compared with the embodiment 1 is that the porosity of the oxide ceramic layer is 4%.

[0125] Embodiment 14

[0126] This embodiment provides an insulating coating with a low capacitance value. The only difference compared with the embodiment 1 is that the porosity of the oxide ceramic layer is 12%.

[0127] Comparative Example 1

[0128] This comparative example provides an insulating coating, which differs from Example 1 only in that no groove is provided on the outer surface of the bearing outer ring, and the insulating coating only includes a ceramic insulating coating provided on the outer surface of the bearing outer ring, and the ceramic insulating coating is the same as Example 1.

[0129] Comparative Example 2

[0130] This comparative example provides an insulating coating, which is different from Example 3 only in that no groove is provided on the outer surface of the bearing outer ring, and the insulating coating only includes a ceramic insulating coating provided on the outer surface of the bearing outer ring, and the raw material of the ceramic insulating coating is only aluminum oxide powder.

[0131] The coating composition, thickness and porosity of the above-mentioned embodiments and comparative examples are shown in Table 1.

[0132] The electrical insulation performance of the insulating bearing with the above-mentioned insulating coating was measured by an insulation resistance tester (the coating surface was completely wrapped with conductive silicone), and the results are shown in Table 2; the capacitance value was measured by a capacitance meter (the coating surface was completely wrapped with conductive silicone), and the results are shown in Table 2; the breakdown voltage was measured by a withstand voltage tester (the coating surface was completely wrapped with conductive silicone), and the results are shown in Table 2; the impact work of the bearing was tested using a 2kg impact hammer, and the results are shown in Table 2.

[0133] Table 1

[0134]

[0135]

[0136] In Table 1, “ / ” means that the coating layer is not provided.

[0137] Table 2

[0138]

[0139]

[0140] From the contents of Table 2, we can see the following points:

[0141] (1) It can be seen from the data of Examples 1-8 that, under optimal conditions, the insulation resistance value of the insulating coating provided by the present invention for bearings can reach above 200 GΩ, the capacitance value can reach below 0.44 NF, the breakdown voltage can reach 10000-11000 V, and the impact energy can reach 5.4 J.

[0142] (2) A comprehensive comparison of the data of Example 1 and Examples 9-10 shows that the only difference between Example 9-10 and Example 1 is that the thickness of the oxide ceramic layer is not within the preferred range of the present invention. The capacitance value in Examples 9-10 is significantly higher, and the electrical insulation performance is deteriorated, and the breakdown voltage is reduced. It can be seen that the present invention can reduce the capacitance value and reduce the breakdown risk while ensuring the insulation performance of the bearing by preferentially controlling the thickness of the oxide ceramic layer.

[0143] (3) A comprehensive comparison of the data of Example 1 and Examples 11-12 shows that the only difference between Example 11-12 and Example 1 is that the thickness of the resin insulating coating is not within the preferred range of the present invention. The capacitance value in Example 11 is significantly higher, and the impact work in Example 12 is significantly reduced. It can be seen that the present invention can further reduce the bearing capacitance while ensuring the impact resistance of the coating by preferentially controlling the thickness of the resin insulating coating.

[0144] (4) A comprehensive comparison of the data of Example 1 and Examples 13-14 shows that the only difference between Examples 13-14 and Example 1 is that the porosity of the oxide ceramic layer is not within the preferred range of the present invention, the capacitance value in Example 13 is significantly higher, and the insulation resistance and breakdown voltage in Example 14 are significantly reduced. It can be seen that the present invention can avoid increasing the risk of breakdown while maintaining a lower capacitance and ensure insulation performance by preferentially controlling the porosity of the oxide ceramic layer.

[0145] (5) A comprehensive comparison of the data of Example 1 and Comparative Example 1, and Example 3 and Comparative Example 2 shows that the present invention can effectively reduce capacitance, ensure insulation performance, and improve breakdown voltage by providing grooves and filling the grooves with resin insulating coatings.

[0146] To sum up, the insulating coating provided by the present invention combines a ceramic insulating coating and a resin insulating coating, and the resin insulating coating is arranged in the groove of the outer ring of the bearing. It can achieve a lower capacitance value while satisfying the insulation, mechanical properties and breakdown resistance of the bearing, and meet the needs of high electrical insulation performance occasions.

[0147] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. An insulating coating with low capacitance, characterized in that: The insulating coating comprises a first coating and a second coating; The first coating layer comprises a ceramic insulating coating layer, the ceramic insulating coating layer comprises an oxide ceramic layer having pores and a sealing resin filled in the pores, and the first coating layer is disposed on the outer surface of the outer ring of the bearing; The thickness of the oxide ceramic layer is 0.3-1 mm, and the porosity of the oxide ceramic layer is 6-10%; the oxide ceramic layer is obtained by spraying oxide ceramic powder, and the oxide ceramic powder contains aluminum oxide and a second compound, and the second compound includes aluminum nitride and / or titanium oxide; The second coating layer comprises a resin insulating coating layer, and the second coating layer is arranged in a groove on the outer surface of the bearing outer ring and is arranged above the first coating layer; The thickness of the resin insulation coating is 0.2-0.5 mm; the resin insulation coating comprises epoxy resin; The outer surface of the bearing outer ring includes an outer diameter surface and end surfaces on both sides of the outer diameter surface. The groove is arranged on the outer diameter surface and the end surfaces on both sides of the bearing outer ring. The depth of the groove is 0.2-0.5mm, and the opening width of the groove is 1-2mm.

2. The insulating coating according to claim 1, characterized in that: The mass percentage of aluminum oxide in the oxide ceramic powder is 79.5-97.5%.

3. The insulating coating according to claim 1, characterized in that: The mass percentage of aluminum nitride in the oxide ceramic powder is 9.5-20.5%.

4. The insulating coating according to claim 1, characterized in that: The mass percentage of titanium oxide in the oxide ceramic powder is 2.5-3.5%.

5. The insulating coating according to claim 1, characterized in that: The particle size of the oxide ceramic powder is 10-30 μm.

6. The insulating coating according to claim 1, characterized in that: The sealing resin includes epoxy resin.

7. The insulating coating according to claim 1, characterized in that: The first coating layer also includes a metal transition layer.

8. The insulating coating according to claim 7, characterized in that: The metal transition layer is arranged between the outer surface of the bearing outer ring and the ceramic insulating coating.

9. The insulating coating according to claim 7, characterized in that: The metal transition layer is obtained by spraying nickel-chromium alloy powder or nickel-aluminum alloy powder.

10. The insulating coating according to claim 9, characterized in that: The mass percentage of nickel in the nickel-chromium alloy powder is 75.8-80.5%.

11. The insulating coating according to claim 9, characterized in that: The particle size of the nickel-chromium alloy powder is 10-30 μm.

12. The insulating coating according to claim 9, characterized in that The mass percentage of nickel in the nickel-aluminum alloy powder is 79.5-81.5%.

13. The insulating coating according to claim 9, characterized in that The particle size of the nickel-aluminum alloy powder is 10-30 μm.

14. The insulating coating according to claim 7, characterized in that: The thickness of the metal transition layer is 0.05-0.1 mm.

15. A method for preparing an insulating coating with low capacitance as claimed in any one of claims 1 to 14, characterized in that: The preparation method comprises the following steps: (1) Plasma spraying is performed on the outer surface of the bearing outer ring with a groove to prepare an oxide ceramic layer, and then a sealing treatment is performed to obtain a first coating; the outer surface of the bearing outer ring includes an outer diameter surface and end surfaces located on both sides of the outer diameter surface, the groove is arranged on the outer diameter surface and the end surfaces on both sides of the bearing outer ring, the depth of the groove is 0.2-0.5 mm, and the opening width of the groove is 1-2 mm; (2) The outer surface of the first coating is coated with epoxy resin slurry, which is then cured, and then the cured product outside the groove is removed by grinding to obtain a second coating, thereby completing the preparation of the insulating coating.

16. The preparation method according to claim 15, characterized in that: Two opposite side surfaces of the groove are arranged as inclined surfaces.

17. The preparation method according to claim 16, characterized in that: The angle between the inclined surface and the depth direction of the groove is 40-50°.

18. The preparation method according to claim 15, characterized in that: Before preparing the oxide ceramic layer in step (1), the outer surface of the bearing outer ring provided with the groove is pre-plasma sprayed to prepare a metal transition layer.

19. The preparation method according to claim 18, characterized in that: In the preparation of the metal transition layer, plasma spraying uses argon as the main gas, hydrogen as the auxiliary gas, the current is 520-550A, the voltage is 69-75V, the spraying distance is 100-120mm, the main gas flow rate is 43-45L / min, and the auxiliary gas flow rate is 9-11L / min.

20. The preparation method according to claim 15, characterized in that: In the preparation of the oxide ceramic layer, plasma spraying uses argon as the main gas, hydrogen as the auxiliary gas, the current is 550-600A, the voltage is 68-72V, the spraying distance is 100-120mm, the main gas flow rate is 38-41L / min, and the auxiliary gas flow rate is 13-15L / min.

21. The preparation method according to claim 15, characterized in that: The sealing process in step (1) includes placing the outer ring of the bearing in a sealed container, evacuating the container, injecting a sealing agent, and then curing the container.

22. The preparation method according to claim 21, characterized in that: The sealing agent includes epoxy resin slurry.

23. The preparation method according to claim 22, characterized in that: The viscosity of the epoxy resin slurry used in the sealing agent is 1000-1100 cps.

24. The preparation method according to claim 21, characterized in that: The curing temperature during the sealing process is 145-155°C.

25. The preparation method according to claim 21, characterized in that: The curing time in the sealing treatment is 5-6 hours.

26. The preparation method according to claim 15, characterized in that: The viscosity of the epoxy resin slurry used for coating in step (2) is 4000-5000cps.

27. The preparation method according to claim 15, characterized in that: The curing temperature in step (2) is 135-145°C.

28. The preparation method according to claim 15, characterized in that: The curing time in step (2) is 5-6 hours.

29. The preparation method according to claim 15, characterized in that: The grinding wheel used for the grinding comprises an aluminum oxide grinding wheel.

30. The preparation method according to claim 15, characterized in that: The particle size of the grinding wheel used for the grinding is 320-400 meshes.

31. An insulating bearing, characterized in that: The insulating bearing comprises a bearing inner ring and a bearing outer ring, bearing balls are arranged between the bearing inner ring and the bearing outer ring, a groove is provided on the outer surface of the bearing outer ring, and an insulating coating with a low capacitance value as described in any one of claims 1 to 14 is arranged on the outer surface of the bearing outer ring.

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