Insulated rolling bearing with nano calcium fluoride coating and preparation method thereof

Abstract

The present invention discloses an insulating rolling bearing with a nano-calcium fluoride coating and a preparation method thereof. The rolling bearing comprises a bearing inner ring, a bearing outer ring and a rolling element, wherein the rolling element is installed between the bearing inner ring and the bearing outer ring, the raceway surfaces of the bearing inner ring and the bearing outer ring are coated with a layer of nano-calcium fluoride coating or the outer surface of the rolling element is coated with a layer of nano-calcium fluoride coating, and the contact portion between the bearing inner ring and the rolling element and the contact portion between the bearing outer ring and the rolling element are filled with bearing grease. The method is used to prepare an insulating rolling bearing. Compared with a conventional bearing, the insulating rolling bearing of the present invention has the advantages of strong insulation performance, high resistivity, high temperature resistance, strong load-bearing capacity and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of rolling bearings and is an insulating rolling bearing, in particular to an insulating rolling bearing with a nano calcium fluoride coating and a preparation method thereof. Background Art

[0002] The performance of rolling bearings directly affects the quality, performance and reliability of urban subway traction motors, high-power motors for construction machinery, and electrified railway traction motors. They are important core components in mechanical equipment. With the continuous development and improvement of inverter drive technology, AC variable frequency motors are increasingly used in the industrial field, among which the most frequently used type is the variable frequency speed regulation induction motor. However, for these high-power, variable frequency, high-voltage explosion-proof AC variable frequency motors, water conservancy, thermal power, wind turbines, high-speed rail train traction motors and other equipment, in most cases, the main failure form of the motor bearings inside is electrolytic corrosion. Electrolytic corrosion is one of the common forms of bearing damage. When current passes through the bearing, it will damage the bearing, greatly reducing the bearing life, and causing the bearing to fail in just a few days or even hours.

[0003] The inner ring of the bearing moving at high speed cuts the magnetic lines of force, generating eddy currents. At the same time, the moving rolling steel balls or cylindrical rollers cut the magnetic lines of force, generating eddy currents. In AC motors, the magnetic field is changing, and it will interact with the inner ring, outer ring and rolling elements of the bearing, generating eddy currents in the rolling bearing. The current will flow through the inside of the bearing, and even generate tiny electric sparks, causing local melting damage on the contact surface. At this time, densely packed small pits will appear on the surface of the bearing, that is, electrical corrosion has occurred. If the bearing continues to operate, its vibration and temperature rise will increase rapidly, the bearing will soon fail, and cause unexpected damage to the motor and related equipment. In addition, electrical corrosion will cause the deterioration of lubricating grease, causing it to lose its proper lubrication ability. In severe cases, the shaft and bearing will be stuck, leading to safety accidents.

[0004] The hybrid ceramic insulated bearings currently in use are a type of ceramic bearings. Unlike full ceramic bearings, this type of bearings only use ceramic materials to replace the commonly used bearing steel materials in one or both of the inner and outer rings or rolling elements. They have the advantages of light weight, good rigidity, high temperature resistance, corrosion resistance and good insulation performance. However, since ceramic materials are brittle and hard, they are difficult to process and the process is also complex. However, the bearing processing accuracy requirements are high, the production cost is high, and it is difficult to maintain the bearing size accuracy. At present, large-scale and stable production of this type of bearings cannot be achieved in China.

[0005] The resin-coated insulating bearings currently used generally have a layer of PPS (polyphenylene sulfide) resin insulation layer injected on the surface of the bearing ring to cut off the current circulation path and prevent the occurrence of electrical corrosion. PPS resin has the characteristics of high temperature resistance and weak water absorption. It still has good insulation even in high temperature and high humidity environments. However, due to the low thermal conductivity and large thermal expansion coefficient of the material, when the large amount of heat generated by the bearing during operation is not easy to dissipate, it will cause internal high temperature and cause dimensional changes. In addition, the material also has shortcomings such as high brittleness and low impact strength. This type of insulating bearing is prone to edge damage when repeatedly disassembled or collided. Therefore, this type of insulating bearing is not suitable for occasions with large working temperature rise, frequent disassembly or high requirements for dimensional changes.

[0006] The ceramic spray-coated insulating bearings currently in use are the most common type of insulating bearings. A highly insulating ceramic coating is usually prepared on the outer surface and side end face of the inner and outer rings of the bearings using a plasma spraying method to achieve bearing insulation and prevent electrical corrosion. This type of insulating bearing has good insulation and wear resistance and corrosion resistance at high temperatures, but this type of insulating bearing can only block low-frequency shaft currents caused by magnetic asymmetry. For high-frequency shaft currents caused by the common-mode voltage of the inverter, the insulation layer capacitance can still form a low-impedance path and cannot play an isolating role. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an insulating rolling bearing with a nano calcium fluoride coating and a preparation method thereof. The bearing has strong insulation performance, high resistivity, high temperature resistance, strong load-bearing capacity, and can simultaneously suppress low-frequency shaft current and high-frequency shaft current.

[0008] The technical solution of the present invention is as follows:

[0009] 1. An insulating rolling bearing with a nano-calcium fluoride coating

[0010] The rolling bearing comprises a bearing inner ring, a bearing outer ring and a rolling element, wherein the rolling element is installed between the bearing inner ring and the bearing outer ring, and is characterized in that the raceway surfaces of the bearing inner ring and the bearing outer ring are coated with a layer of nano-calcium fluoride coating or the outer surface of the rolling element is coated with a layer of nano-calcium fluoride coating, and the contact portion between the bearing inner ring and the rolling element and the contact portion between the bearing outer ring and the rolling element are filled with bearing grease.

[0011] The bearing inner ring, bearing outer ring and rolling elements are all made of GCr15 high-carbon chromium bearing steel.

[0012] The nano calcium fluoride coating is prepared from nano calcium fluoride particles with a particle size of 100 nm or less.

[0013] The nano calcium fluoride coating is prepared by immersing the bearing inner ring and the bearing outer ring or the rolling element in a calcium fluoride solution.

[0014] The nano calcium fluoride insulating layer uniformly covers the entire raceway surface of the bearing inner ring and the bearing outer ring or the outer surface of the rolling body.

[0015] The thickness of the nano calcium fluoride insulating layer is 25-50 μm.

[0016] 2. Preparation method of insulating rolling bearing with nano calcium fluoride coating

[0017] The method comprises the following steps:

[0018] A) Preparation of nano calcium fluoride powder by chemical method: taking equal amounts of 0.4 mol / L calcium chloride solution and 0.8 mol / L ammonium fluoride solution, stirring at 1000 rpm for 2 h until the reaction is complete, centrifuging, washing and drying to obtain nano calcium fluoride powder;

[0019] B) Dip coating, using nano calcium fluoride powder to prepare a nano calcium fluoride solution, subjecting the nano calcium fluoride solution to ultrasonic treatment to make the nano calcium fluoride molecules evenly distributed in the solution, subjecting the rolling element to surface dipping treatment, or subjecting the entire raceway surface of the bearing inner ring and the bearing outer ring to single-sided dipping treatment to form a nano calcium fluoride coating;

[0020] C) Drying: bake the bearing inner ring and bearing outer ring or rolling element at 60°C for 8 hours;

[0021] D) Heat treatment: The nano calcium fluoride coating is heat treated at 800°C.

[0022] E) filling bearing grease, the contact part between the inner ring of the bearing and the rolling element and the contact part between the outer ring of the bearing and the rolling element are filled with bearing grease to obtain an insulating rolling bearing coated with a nano calcium fluoride coating.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Compared with the existing alumina coating, the present invention adopts the method of adding nano calcium fluoride coating between the inner and outer rings of the bearing and the rolling element, which effectively isolates the eddy current between the inner and outer rings of the bearing and the rolling element. Even in a high-frequency magnetic field environment, there will be no tiny electric sparks that break through the lubricating oil film between the inner and outer rings of the rolling bearing and the rolling element, thus preventing the occurrence of electrical erosion;

[0025] 2. Compared with the existing aluminum oxide coating, the nano calcium chloride coating used in the present invention has a load-bearing capacity increased by 50% to 80%.

[0026] 3. The insulated rolling bearing in the present invention has the advantages of strong insulation performance and high resistivity, and can withstand high temperatures. Usually, the operating temperature of the bearing in the power locomotive motor is below 150°C. Within this temperature range, the structure is stable, the resistivity fluctuation is small, the load-bearing capacity is strong, and it can simultaneously suppress low-frequency shaft current and high-frequency shaft current, thereby reducing electrical corrosion; 4. The preparation method of the insulated rolling bearing with nano-calcium fluoride insulating coating provided by the present invention has simple process steps and low preparation cost, which can not only ensure the technical effect of the insulated bearing, but also is suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of eddy currents generated by the high-speed rotating inner ring and rolling elements of a bearing cutting magnetic flux lines.

[0028] Figure 2 This is a schematic diagram of an embodiment of the nano-calcium fluoride coated insulating rolling bearing of the present invention.

[0029] Figure 3 This is a schematic diagram of another embodiment of the nano-calcium fluoride coated insulating rolling bearing of the present invention.

[0030] Figure 4 This is the bearing voltage change diagram of ordinary bearing under high-frequency motor.

[0031] Figure 5 This is a graph showing the bearing current changes of ordinary bearings under high-frequency motors.

[0032] Figure 6 This is a graph showing the bearing voltage changes of ceramic insulated bearings under high-frequency motors.

[0033] Figure 7 This is a graph showing the bearing current changes of ceramic insulated bearings under high-frequency motors.

[0034] Figure 8 This is a graph showing the bearing voltage changes of nano-calcium fluoride insulated bearings under high-frequency motors.

[0035] Fig. 9 This is a graph showing the bearing current changes of nano-calcium fluoride insulated bearings under high-frequency motors.

[0036] In the figure: 1. Bearing inner ring, 2. Nano calcium fluoride coating, 3. Bearing grease, 4. Rolling element, 5. Bearing outer ring. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods, but the description of the embodiments is not a limitation of the scheme of the present invention, and any equivalent changes made based on the concept of the present invention that are merely formal but not substantial should be regarded as within the scope of the technical scheme of the present invention.

[0038] Embodiment 1:

[0039] This embodiment provides an insulating bearing product with a nano calcium fluoride coating that has reliable insulation performance, can simultaneously suppress low-frequency shaft current and high-frequency shaft current, and is economically feasible, such as Figure 2 As shown, the rolling bearing includes a bearing inner ring 1, a bearing outer ring 5 and a rolling element 4. The rolling element 4 is installed between the bearing inner ring 1 and the bearing outer ring 5. The raceway surfaces of the bearing inner ring 1 and the bearing outer ring 5 are coated with a layer of nano calcium fluoride coating 2. The contact portion between the bearing inner ring 1 and the rolling element 3 and the contact portion between the bearing outer ring 5 and the rolling element 3 are filled with bearing grease 3.

[0040] The bearing inner ring 1, the bearing outer ring 5 and the rolling element 4 are all made of GCr15 high carbon chromium bearing steel.

[0041] The nano calcium fluoride coating 2 is made of nano calcium fluoride particles with a particle size of 100 nm or less.

[0042] The nano calcium fluoride coating is prepared by immersing the bearing inner ring 1 and the bearing outer ring 5 or the rolling element 4 in a calcium fluoride solution.

[0043] The nano calcium fluoride insulating layer uniformly covers the entire raceway surface of the bearing inner ring 1 and the bearing outer ring 5 or the outer surface of the rolling element 4 .

[0044] The greater the thickness of the nano calcium fluoride coating 2, the higher the porosity of the coating surface, and the insulation performance of the coating will decrease accordingly; the greater the thickness of the coating, the greater the internal stress of the coating, and the bonding force between the coating and the raceway surface of the bearing inner ring 1 and the bearing outer ring 5 will decrease accordingly. The coating thickness is 25 to 50 μm, the insulation performance of the coating is good, and the bonding with the raceway surface is strong.

[0045] Embodiment 2:

[0046] This embodiment provides an insulating bearing product with a polytetrafluoroethylene coating having reliable insulation performance, capable of suppressing both low-frequency shaft current and high-frequency shaft current, and being economically feasible, such as Figure 3 As shown, the rolling bearing includes a bearing inner ring 1, a bearing outer ring 5 and a rolling body 4, the rolling body 4 is installed between the bearing inner ring 1 and the bearing outer ring 5, the outer surface of the rolling body 3 is coated with a layer of nano calcium fluoride coating 2, and the contact part between the bearing inner ring 1 and the rolling body 3 and the contact part between the bearing outer ring 5 and the rolling body 3 are filled with bearing grease 3.

[0047] The bearing inner ring 1, the bearing outer ring 5 and the rolling element 4 are all made of GCr15 high carbon chromium bearing steel.

[0048] The nano calcium fluoride coating 2 is made of nano calcium fluoride particles with a particle size of 100 nm or less.

[0049] The nano calcium fluoride coating is prepared by immersing the bearing inner ring 1 and the bearing outer ring 5 or the rolling element 4 in a calcium fluoride solution.

[0050] The nano calcium fluoride insulating layer uniformly covers the entire raceway surface of the bearing inner ring 1 and the bearing outer ring 5 or the outer surface of the rolling element 4 .

[0051] The greater the thickness of the nano-calcium fluoride coating 2, the higher the porosity of the coating surface, and the insulation performance of the coating will decrease accordingly; the greater the thickness of the coating, the greater the internal stress of the coating, and the bonding force between the coating and the surface of the rolling element 4 will decrease accordingly. When the coating thickness is 25 to 50 μm, the insulation performance of the coating is good and the bonding with the rolling element surface is strong.

[0052] The preparation method of the insulating rolling bearing is to use a nano calcium fluoride solution to immerse the entire raceway surface of the bearing inner ring 1 and the bearing outer ring 5 or the outer surface of the rolling element 4 in an immersion method to form a uniform and dense nano calcium fluoride coating on the surface, which specifically includes the following steps:

[0053] A) Preparation of nano calcium fluoride powder by chemical method: taking equal amounts of 0.4 mol / L calcium chloride solution and 0.8 mol / L ammonium fluoride solution, stirring at 1000 rpm for 2 h until the reaction is complete, centrifuging, washing and drying to obtain nano calcium fluoride powder;

[0054] B) Dip coating, using nano calcium fluoride powder to prepare a nano calcium fluoride solution, subjecting the nano calcium fluoride solution to ultrasonic treatment to make the nano calcium fluoride molecules evenly distributed in the solution, subjecting the rolling element 4 to surface dipping treatment, or subjecting the entire raceway surface of the bearing inner ring 1 and the bearing outer ring 5 to single-sided dipping treatment to form a nano calcium fluoride coating;

[0055] C) Drying: bake the bearing inner ring 1 and the bearing outer ring 5 or the rolling element 4 at 60° C. for 8 hours to remove moisture from the coating surface;

[0056] D) Heat treatment: heat treatment of the nano calcium fluoride coating at 800° C. makes the surface nano calcium fluoride coating more dense and uniform, and effectively fills and covers cracks and holes.

[0057] E) Filling bearing grease, the contact part between the bearing inner ring 1 and the rolling element 3 and the contact part between the bearing outer ring 5 and the rolling element 3 are filled with bearing grease 3 to obtain an insulating rolling bearing coated with a nano calcium fluoride coating.

[0058] Using a YQ190 three-phase induction motor as the bearing working motor, the voltage between the inner and outer rings of ordinary bearings, ceramic insulation bearings, and nano calcium fluoride insulation bearings under high-frequency changing magnetic fields and the current between the bearing rolling elements and the inner and outer rings of the bearings are measured. The measurement results are as follows: Figure 4-9As shown, the key values ​​are shown in the following Table 1.

[0059] Table 1 Comparison of bearing voltage and bearing current of the present invention and existing bearings

[0060] Bearing Type Maximum bearing voltage (V) Maximum bearing current (A) Remark Ordinary bearings 0.17 0.16 Comparative Example 1 Ceramic insulated bearings 21 0.013 Comparative Example 2 Nano calcium fluoride insulating bearing 5 0 Invention Example 1

[0061] According to Table 1, compared with ordinary bearings and ceramic insulating bearings, the inventive example directly arranges the nano calcium fluoride insulating layer on the contact surface between the bearing rolling element and the inner and outer rings of the bearing, which directly eliminates the tiny electric sparks passing through the lubricating oil; at the same time, compared with ceramic insulating bearings, the voltage across the insulating layer is lower, which can reduce the risk of the insulating layer being broken down and reduce the electrical corrosion damage of the bearing.

[0062] The above are only preferred feasible embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Various modifications or applications made according to the above embodiments are within the protection scope of the present invention.

Claims

1. An insulating rolling bearing with a nano-calcium fluoride coating, the rolling bearing comprising a bearing inner ring (1), a bearing outer ring (5) and a rolling element (4), wherein the rolling element (4) is installed between the bearing inner ring (1) and the bearing outer ring (5), and characterized in that: The raceway surfaces of the bearing inner ring (1) and the bearing outer ring (5) are coated with a layer of nano calcium fluoride coating (2), or the outer surface of the rolling element (3) is coated with a layer of nano calcium fluoride coating (2), and the contact portion between the bearing inner ring (1) and the rolling element (3) and the contact portion between the bearing outer ring (5) and the rolling element (3) are filled with bearing grease (3); The bearing inner ring (1), the bearing outer ring (5) and the rolling element (4) are all made of GCr15 high carbon chromium bearing steel; The nano calcium fluoride coating (2) is prepared using nano calcium fluoride particles with a particle size of 100 nm or less; The nano calcium fluoride coating is prepared by immersing the bearing inner ring (1) and the bearing outer ring (5) or the rolling element (4) in a calcium fluoride solution; The thickness of the nano calcium fluoride insulating layer is 25-50 μm; The insulating rolling bearing is applied to an AC motor.

2. The insulating rolling bearing with nano calcium fluoride coating according to claim 1, characterized in that: The nano calcium fluoride insulation layer uniformly covers the entire raceway surface of the bearing inner ring (1) and the bearing outer ring (5) or the outer surface of the rolling body (4).

3. A method for preparing an insulating rolling bearing with a nano-calcium fluoride coating according to any one of claims 1 to 2, characterized in that: The steps include: A) Preparation of nano calcium fluoride powder by chemical method: taking equal amounts of 0.4 mol / L calcium chloride solution and 0.8 mol / L ammonium fluoride solution, stirring at 1000 rpm for 2 h until the reaction is complete, centrifuging, washing and drying to obtain nano calcium fluoride powder; B) dipping coating, using nano calcium fluoride powder to prepare a nano calcium fluoride solution, subjecting the nano calcium fluoride solution to ultrasonic treatment so that the nano calcium fluoride molecules are evenly distributed in the solution, subjecting the rolling element (4) to surface dipping treatment, or subjecting the entire raceway surface of the bearing inner ring (1) and the bearing outer ring (5) to single-sided dipping treatment to form a nano calcium fluoride coating; C) drying: baking the bearing inner ring (1) and the bearing outer ring (5) or the rolling element (4) at 60° C. for 8 h; D) Heat treatment: heat treatment of the nano calcium fluoride coating at 800°C. E) filling bearing grease, the contact part between the bearing inner ring (1) and the rolling element (3) and the contact part between the bearing outer ring (5) and the rolling element (3) are filled with bearing grease (3), so as to obtain an insulating rolling bearing coated with a nano calcium fluoride coating.

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