Bearing and method for manufacturing the same

Abstract

To provide a bearing more inexpensive than ceramic, having insulation quality, and less likely to generate abrasion due to creep.SOLUTION: A bearing has an outer ring, an inner ring, and rolling elements sandwiched therebetween. An outer peripheral surface of the outer ring and / or an inner peripheral surface of the inner ring have a phosphate film or a black oxide film, and a calcination film containing an anti-abrasion agent and an organic resin on a surface of the phosphate film or the black oxide film. The bearing has insulation quality and creep wear resistance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bearing and a method for manufacturing the same.

Background Art

[0002] In recent years, due to global environmental problems, the electrification of automobiles has been progressing. Along with this, it has been reported that electric corrosion due to leakage current occurs in the bearings used, and the bearings are damaged. Conventionally, in order to prevent electric corrosion of bearings, a hard insulating substance such as ceramic has often been coated on the fitting portion of the outer ring or the inner ring of the bearing with other parts. However, inorganic hard substances such as ceramics are expensive to apply, and because they are hard substances, if the bearing creeps, the housing parts such as aluminum alloy on the mating side will wear, which may affect the unit function.

[0003] Also, conventionally, although the fired film containing a solid lubricant substance or the like applied to improve anti-creep wear resistance has anti-creep wear resistance, since the coating film is soft, the insulation property is maintained initially, but there is a problem that the fired film wears as the bearing slides and the insulation property cannot be maintained.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In view of such a situation, an object of the present invention is to provide a bearing having a film that is cheaper than ceramic, has insulation properties, and is less likely to wear due to creep, and a method for manufacturing the same.

Means for Solving the Problems

[0005] The present invention is as follows: (1) to (4). (1) A bearing having an outer ring, an inner ring, and rolling elements sandwiched between them, on the outer peripheral surface of the outer ring and / or the inner peripheral surface of the inner ring, It has a phosphate film or black oxide film, and a fired film containing an antiwear agent and an organic resin on its surface, A bearing having creep wear resistance in addition to insulation. (2) In the fired film, The content of the solid lubricant is 0 to 29% by mass, The content of the antiwear agent is 4 to 69% by mass, The bearing according to (1) above, wherein the content of the organic resin is 30 to 80% by mass. (3) A method for manufacturing a bearing having an outer ring, an inner ring, and rolling elements sandwiched therebetween, After forming a phosphate film or black oxide film on the outer peripheral surface of the outer ring and / or the inner peripheral surface of the inner ring, a fired film containing an antiwear agent and an organic resin is fired at a firing temperature of 120 to 230°C on its surface, and a step of forming is provided. A method for manufacturing a bearing having creep wear resistance in addition to insulation. (4) In the fired film, The content of the solid lubricant is 0 to 29% by mass, The content of the antiwear agent is 4 to 69% by mass, The method for manufacturing a bearing according to (3) above, wherein the content of the organic resin is 30 to 80% by mass.

Advantages of the Invention

[0006] According to the present invention, it is possible to provide a bearing having a film that is cheaper than ceramic, has insulation, and is less likely to cause wear due to creep, and a method for manufacturing the same.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0008] The present invention will be described. The present invention relates to a bearing having an outer ring, an inner ring, and rolling elements sandwiched therebetween, wherein the outer peripheral surface of the outer ring and / or the inner peripheral surface of the inner ring has a phosphate coating or a black oxide coating, and a fired film containing an antiwear agent and an organic resin on the surface thereof, and is a bearing having creep wear resistance in addition to insulation. Such a bearing is also referred to as "the bearing of the present invention" hereinafter.

[0009] Further, the present invention relates to a method for manufacturing a bearing having an outer ring, an inner ring, and rolling elements sandwiched therebetween, wherein after forming a phosphate coating or a black oxide coating on the outer peripheral surface of the outer ring and / or the inner peripheral surface of the inner ring, a fired film containing an antiwear agent and an organic resin is fired at a firing temperature of 120 to 230°C on the surface thereof to form a step, and is a method for manufacturing a bearing having creep wear resistance in addition to insulation. Such a method for manufacturing a bearing is also referred to as "the manufacturing method of the present invention" hereinafter.

[0010] The bearing of the present invention is preferably manufactured by the manufacturing method of the present invention.

[0011] The bearing of the present invention will be described. FIG. 1 shows a schematic perspective view of a preferred embodiment of the bearing of the present invention. The bearing 1 of the present invention shown in FIG. 1 has an outer ring 2, an inner ring 4, and balls 6 sandwiched therebetween. The shape of the bearing is not particularly limited as long as it has an outer ring 2, an inner ring 4, and balls 6 arranged at positions sandwiched therebetween. The same applies to the shapes of the outer ring 2, the inner ring 4, and the balls 6. The materials of the main bodies of the outer ring 2, the inner ring 4, and the balls 6 are not particularly limited, and are preferably metals, particularly steel materials such as bearing steel. Note that the ball 6 is an example of the rolling element in the present invention. In the present invention, the rolling element is not limited to a ball, and may be of the same type as a conventionally known rolling element of a general bearing, for example.

[0012] Furthermore, the bearing of the present invention has two coatings, namely a phosphate coating or a black oxide coating and a fired coating, on the outer peripheral surface 20 of the outer ring 2 and / or the inner peripheral surface 40 of the inner ring 4. The bearing of the present invention may also have two coatings, namely a phosphate coating or a black oxide coating and a fired coating, on two side surfaces 22 which are surfaces adjacent to the outer peripheral surface 20 of the outer ring 2 and on two side surfaces 42 which are surfaces adjacent to the inner peripheral surface 40 of the inner ring 4.

[0013] The adhesion of the fired coating can be improved by forming a phosphate coating. Examples of phosphates include manganese phosphate, iron phosphate, zinc phosphate, calcium zinc phosphate, etc. Among these, it is preferable to use manganese phosphate. The phosphate coating can be formed on the surface of the bearing body (the surface including at least the outer peripheral surface 20 of the outer ring 2 and / or the inner peripheral surface 40 of the inner ring 4) by dipping it in a phosphate aqueous solution (for example, a manganese phosphate aqueous solution). Here, as a pretreatment before forming the phosphate coating, etching or blasting may be performed to roughen the surface. The thickness of the phosphate coating is not particularly limited, but it is preferably 1 to 15 μm, and more preferably 3 to 7 μm.

[0014] The black oxide coating has little dimensional change due to material elution and magnetite generation during the film formation process, generates a magnetite aggregate with high adhesion, and has wear resistance performance and coating adhesion performance. The black oxide coating can be formed on the surface of the bearing body (the surface including at least the outer peripheral surface 20 of the outer ring 2 and / or the inner peripheral surface 40 of the inner ring 4) by dipping it in a strongly alkaline black oxide treatment aqueous solution. The thickness of the black oxide coating is not particularly limited, but it is preferably 0.2 to 3.0 μm, and more preferably 1.0 to 2.5 μm.

[0015] The bearing of the present invention has a fired coating on the phosphate coating or the black oxide coating. The fired film contains an antiwear agent, and the content of the antiwear agent in the fired film is preferably 4 to 69% by mass, more preferably 13 to 50% by mass. Specific examples of the antiwear agent will be described later.

[0016] Also, the content of the solid lubricant in the fired film is preferably 0 to 29% by mass, more preferably 1 to 15% by mass, and even more preferably 1 to 10% by mass. That is, the fired film preferably contains a solid lubricant, but it may not contain it. Specific examples of the solid lubricant will be described later.

[0017] Also, the content of the organic resin in the fired film is preferably 30 to 80% by mass, more preferably 49 to 80% by mass, and even more preferably 49 to 60% by mass. Specific examples of the organic resin will be described later.

[0018] The thickness of the fired film is not particularly limited, but is preferably 10 to 60 μm, more preferably 20 to 40 μm.

[0019] The thicknesses of the phosphate film and the fired film of the bearing of the present invention are defined as the values measured using a conventionally known electromagnetic film thickness gauge with the untreated bearing as the zero point. Note that the film thickness of the black oxide film is defined as the value measured by conventionally known cross-sectional magnification observation and calorimetry.

[0020] Next, the manufacturing method of the present invention will be described. First, a bearing made of metal including a conventionally known outer ring, inner ring, and rolling elements (such as balls) is immersed in an aqueous phosphate solution (such as an aqueous manganese phosphate solution) or an aqueous black oxide treatment solution and treated to form a phosphate film or a black oxide film on the surface (the outer peripheral surface 20 of the outer ring 2 and / or the inner peripheral surface 40 of the inner ring 4). In addition to immersion, a phosphate film can also be formed on the surface of a bearing made of metal including a conventionally known outer ring, inner ring, and rolling elements (such as balls) by spraying or applying an aqueous phosphate solution thereto.

[0021] The concentration of the phosphate in the aqueous phosphate solution is not particularly limited, but it is preferably 3 to 5% by mass.

[0022] Also, the black oxide film can be formed by immersing a bearing made of metal including a conventionally known outer ring, inner ring, and rolling elements (such as balls) in an aqueous solution mainly composed of sodium hydroxide or potassium hydroxide and a reaction accelerator (preferably an aqueous solution adjusted to 120 to 150°C). Further, the outer ring and the inner ring may be immersed separately.

[0023] Next, a fired film is formed on the surface of the obtained phosphate film or black oxide film. A fired film can be formed by applying a mixed solution containing an antiwear agent and an organic resin onto the surface of the phosphate film or black oxide film, and then firing at a firing temperature of 120 to 230°C. The firing temperature is appropriately set according to the components of the mixed solution. Specifically, it is 120 to 230°C, but preferably within the range of 120 to 160°C.

[0024] The mixed solution containing the antiwear agent and the organic resin in the solvent preferably further contains a solid lubricant.

[0025] Examples of the solid lubricant include fluororesins such as PTFE (polytetrafluoroethylene) and FEP (copolymer of tetrafluoroethylene and hexafluoropropylene), molybdenum disulfide, graphite, graphene, polyethylene, and tungsten disulfide. The content of the solid lubricant in the mixed solution to be applied is preferably 0.1 to 10% by mass, more preferably 0.2 to 5.0% by mass, still more preferably 0.25 to 2.7% by mass, and even more preferably 0.8 to 1.9% by mass.

[0026] Examples of the antiwear agent include iron oxide, chromium oxide, aluminum oxide, aluminum hydroxide, alumina white, zirconia, tungsten carbide, titanium carbide, titanium dioxide, silicon carbide, iridium, beryllium oxide, zirconium oxide, boron carbide, tungsten carbide, silicon carbide, and diamond. The content of the antiwear agent in the mixed solution to be applied is preferably 0.5 to 24.5% by mass, more preferably 1.0 to 16.5% by mass, still more preferably 12 to 21% by mass, and even more preferably 15 to 18% by mass.

[0027] It is preferable to use an organic binder and a curing agent as the organic resin. Examples of the organic binder include polyamideimide resin, polyamide resin, polyimide resin, fluororesin, isocyanate resin, and elastomer resin. Examples of the curing agent include epoxy resin, phenol resin, urea resin, amino resin, and isocyanate resin. The content of the organic resin (organic binder + curing agent) in the mixed solution to be applied is preferably 4.5 to 18.0% by mass, more preferably 9.0 to 18.0% by mass, preferably 5 to 17% by mass, and more preferably 8 to 14% by mass.

[0028] As the solvent in the mixed solution to be applied, for example, aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as toluene and xylene, alcohols such as ethanol and isopropyl alcohol, ketones such as acetone and methyl isobutyl ketone, esters such as methyl acetate, ethyl acetate, and γ-butyrolactone, amides such as N,N-dimethylformamide and N-methyl-2-pyrrolidone (NMP), etc. can be used. Specific preferred examples of the solvent include N-methyl-2-pyrrolidone (NMP), xylene, etc. The content of the mixed solvent in the solution to be applied is preferably 60 to 90% by mass, and more preferably 70 to 85% by mass. The method of applying the mixed solution is not particularly limited. For example, after applying using spraying, dipping coating equipment including electrodeposition, spin coater, bar coater, inkjet, printing, baking can be performed at a baking temperature of 120 to 230 °C to form a baked film.

Example

[0029] <Experiment 1> <Preparation of Samples> A steel ring (material: AISI4620 (US standard), surface hardness: 60 HRC, outer diameter: φ35 mm) was immersed in a 3% by mass manganese phosphate aqueous solution to form a manganese phosphate film with a thickness of 3 μm. Then, a solution with the following composition (excluding the solvent component) was sprayed onto the surface of the manganese phosphate film. And it was baked at a baking temperature of 120 °C to form a baked film with a thickness of 20 μm. · Solid lubricant (PTFE: polytetrafluoroethylene): 5% by mass · Abrasion-resistant agent (iron oxide: chromium oxide = 100 parts by mass: 90 to 110 parts by mass): total 35% by mass · Organic resin (polyamide-imide resin: epoxy resin = 100 parts by mass: 20 to 30 parts by mass): total 60% by mass The steel ring with the film thus obtained was designated as "Sample 1". Note that the film formed on this Sample 1 has the same configuration as the film of the bearing of the present invention.

[0030] Next, in the same manner as in the case of Sample 1, an iron ring was immersed in a 3% by mass manganese phosphate aqueous solution to form a manganese phosphate film with a thickness of 3 μm. Then, a solution with the following composition (excluding the solvent component) was sprayed onto the surface. And it was baked at a baking temperature of 120 °C to form a baked film with a thickness of 20 μm. · Polyamide-imide resin: 30 to 40% by mass · Epoxy resin 10 to 20% by mass · Molybdenum disulfide 20 to 30% by mass · Graphite mass 1 to 10% · Antimony trioxide 20 to 30% by mass The steel ring with the film thus obtained is designated as "Sample 2". The film formed on this Sample 2 is the same film as that of the conventional product, and is used as a comparison target for Sample 1 having the same configuration as the film of the bearing of the present invention.

[0031] <Sliding test> Next, Samples 1 and 2 obtained as described above were subjected to a sliding test. The sliding test is the following test. Samples 1 and 2 were each set on a block-on-ring type LFW-1 friction and wear tester (manufactured by Falex Corporation, USA) shown in Figure 2, a load of 65 LBS was applied to an aluminum block (material: ADC12), and while sliding this block on the surface of the sample, the rings of Samples 1 and 2 were rotated at a rotational speed of 55 rpm for 30 minutes. During the test, lubricating oil (Nissan genuine CVT oil) was added to the sliding part. Samples 1 and 2 after being subjected to such a sliding test are hereinafter referred to as Sample 10 and Sample 20.

[0032] <Insulation evaluation test> An insulation evaluation test was conducted on Samples 1, 2, 10, and 20 obtained as described above. The insulation evaluation test was conducted using TOS5301 (manufactured by Kikusui Electronics Industry Co., Ltd.) as a measuring instrument. Specifically, for Sample 1, first, a negative electrode was attached to a portion where the fired film was not formed on the steel ring, and a positive electrode was attached to a portion where the fired film was formed. Also, for Sample 10, first, a negative electrode was attached to a portion where the fired film was not formed on the steel ring, and a positive electrode was attached to the sliding portion where the fired film was formed. Also, for Sample 2, first, a negative electrode was attached to a portion where the fired film was not formed on the steel ring, and a positive electrode was attached to the portion where the film was formed. For sample 20, first, the negative electrode was attached to a location on the steel ring where the fired film was not formed, and the positive electrode was attached to the sliding location where the film was formed. For each of samples 1 and 2, the voltage was increased to the set voltage (120 V, 250 V, or 500 V) in 10 seconds, and the insulation performance was evaluated based on whether the limit current was exceeded (whether leakage occurred) while the set voltage was maintained for 60 seconds. In this test, the limit current was set to 10 mA (AC) and 500 mA (DC). The results are shown in Table 1.

[0033]

Table 1

[0034] As shown in Table 1, in the cases of samples 1 and 10, regardless of whether the set voltage was 250 V or 500 V, and regardless of whether it was AC or DC, no leakage occurred during the 60 seconds of maintaining the set voltage. That is, it was confirmed that samples 1 and 10 were excellent in insulation performance.

[0035] On the other hand, in the cases of samples 2 and 20, leakage occurred during the voltage increase when the set voltage was 120 V and AC, and leakage occurred during the holding at the set voltage when it was DC. Also, leakage occurred during the voltage increase when the set voltage was 250 V and DC. That is, it was confirmed that samples 2 and 20 were inferior in insulation performance compared to samples 1 and 10.

[0036] <Wear Performance Evaluation Test> The wear amounts of the aluminum blocks of samples 1, 10, 2, and 20 were measured using a contact roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., SURFCOM1500SP, probe: 2 μmR, 60° conical diamond). As a result, both the wear amount obtained from the comparison (difference) between Sample 1 and Sample 10 and the wear amount obtained from the comparison (difference) between Sample 2 and Sample 20 were at an unmeasurable level (or about 10 μm or less). From this, it is considered that the films of Sample 1 and Sample 10 have the same wear resistance of the aluminum block as the films of Sample 2 and Sample 20.

[0037] <Experiment 2> <Preparation of Sliding Member> A polyamideimide resin as an organic binder and an epoxy resin hardener as a hardener were put in a solvent containing N-methyl-2-pyrrolidone at a predetermined ratio, and a solid lubricant and an anti-wear agent were also added, and these were mixed to obtain a mixed solution. Here, as the solid lubricant, PTFE was used in Examples 1 to 5, and molybdenum disulfide and graphite were used in Examples 6 and Comparative Example 1. Also, as the anti-wear agent, a mixture of iron oxide and chromium oxide and aluminum oxide were used in Examples 1 to 5, and chromium oxide, aluminum oxide, and titanium dioxide were used in Example 6. Also, no anti-wear agent was used in Comparative Example 1. However, in Comparative Example 1, antimony trioxide, which is a sliding auxiliary agent generally used as an antioxidant for molybdenum disulfide, was added to the mixed solution. Table 2 shows the composition of the mixture in the mixed solution (excluding the solvent portion). The composition shown in Table 2 is considered to be almost the same as the composition of each component in the fired film.

[0038]

Table 2

[0039] Next, a ring-shaped steel material (material AISI4620: US military standard; surface hardness HRC60; outer diameter φ35 mm) was prepared as a sliding test piece. Then, after forming a manganese phosphate film on the outer peripheral surface of this steel material, each of the mixed solutions according to Examples 1 to 6 and Comparative Example 1 was spray-coated thereon. And each was fired at a firing temperature of 120°C to obtain a ring steel material. Incidentally, the thickness of the fired film on the ring steel material was 25 μm in all cases. Incidentally, the fired film formed in Comparative Example 1 is a film provided in a conventional product, and is used as a comparison target for Examples 1 to 6 having the same configuration as the film of the bearing of the present invention.

[0040] <Sliding test> As a test simulating the sliding environment of an aluminum material housing that fits with a bearing made of steel, in order to slide the outer peripheral surface of a ring-shaped steel material having a fired film of various compositions (Examples 1 to 6 and Comparative Example 1) shown in Table 2 and a part of the surface of an aluminum material block, it was arranged as shown in Fig. 2, and the following evaluations were carried out. ·Test apparatus Block-on-ring tester (LFW-1) manufactured by Falex ·Test piece Ring (material: AISI 4620; surface hardness: HRC60; outer diameter φ = 35 mm) Block (material: ADC12) ·Test conditions Atmosphere: AT Fluid DW-1 Load: 100 to 1000 lbs (100 lbs / min 1Step) Step-up load control Rotation speed: 100 rpm Test time: 10 minutes

[0041] <Measurement of wear amount> The wear amount of the aluminum alloy block material after the sliding test was measured under the following conditions using a surface roughness meter. Testing machine: SURFCOM 1400G manufactured by Tokyo Seimitsu Co., Ltd. Calculation standard: JIS-'01 / '13 standard Measurement type: Cross-section measurement Measurement speed: 0.3 mm / s Measurement length: 10.0 mm Stylus shape: φ1.6 ruby Shape removal: Least squares straight line Judgment criterion: The maximum wear amount of the aluminum alloy block material was considered good if it was 40 μm or less and bad if it was 40 μm or more. In addition, since the wear morphology after the sliding test becomes a shape conforming to the ring shape, the maximum wear amount was used as the measured value.

[0042] <Insulation Evaluation Test Conditions> Regarding the sliding members after the sliding test for various compositions (Examples 1 to 6 and Comparative Example 1) shown in Table 2, an insulation breakdown evaluation was carried out under the following measurement conditions. Equipment used: Dielectric Withstand and Insulation Resistance Tester TOS5301 (manufactured by Kikusui Electronics Industry Co., Ltd.) · Measurement conditions · DC Upper limit: 6.20 kV Limit: 0.5 mA Stop at a current value of 0.5 mA or more Voltage rise time: 10 seconds Starting voltage: 0 V Insulation determination: Leakage determination is made at a current value of 0.5 mA or more, and the voltage value at that time is measured. · AC Upper limit: 5.50 kV Limit: 10 mA Stop at a current value of 10 mA or more Voltage rise time: 10 seconds Starting voltage: 0 V Frequency: 50 Hz Insulation determination: Leakage determination is made at a current value of 10 mA or more, and the voltage value at that time is measured. · Measurement method: The alligator clip parts on the high-voltage test leads of the measuring instrument are installed at the part (inner diameter) where the fired film of the ring-shaped steel material is not formed and the sliding part (outer diameter). The voltage of the measuring instrument is measured according to the above measurement conditions. The measurement is carried out 3 times, and the average value is used as the data. · Judgment criteria: In the DC and AC measurements, when the limit stops, it is judged as defective, and when the insulation is judged, 0.1 kV or more is judged as good.

[0043] <Evaluation Results for Examples and Comparative Examples> The wear amount of the aluminum block after the sliding test and the insulation breakdown measurement results are shown in Table 3. In Comparative Example 1, which is a fired film of the conventional specification, the wear of the aluminum block by the sliding test is suppressed, but the insulating performance cannot be obtained because the fired film wears. On the other hand, in Examples 1 to 6, in addition to suppressing the wear of the aluminum block by the sliding test, it was confirmed that the insulation after the sliding test was ensured.

[0044]

Table 3

Explanation of Signs

[0045] 1 Bearing of the present invention 2 Outer ring 20 Outer peripheral surface of the outer ring 4 Inner ring 40 Inner peripheral surface of the inner ring 6 Ball

Claims

1. A bearing having an outer ring, an inner ring, and rolling elements sandwiched therebetween, wherein on the outer peripheral surface of the outer ring and / or the inner peripheral surface of the inner ring, there is provided a phosphate coating or a black oxide coating, and a fired film containing an antiwear agent and an organic resin on the surface thereof, the antiwear agent being at least one selected from the group consisting of iron oxide, chromium oxide, aluminum oxide, and titanium dioxide, a bearing having creep wear resistance in addition to insulation properties.

2. In the fired film, the content of the solid lubricant is 0 to 29% by mass, the content of the antiwear agent is 4 to 69% by mass, and the content of the organic resin is 30 to 80% by mass. The bearing according to claim 1.

3. A method for manufacturing a bearing having an outer ring, an inner ring, and rolling elements sandwiched therebetween, the method comprising a step of forming a phosphate coating or a black oxide coating on the outer peripheral surface of the outer ring and / or the inner peripheral surface of the inner ring, and then firing a fired film containing an antiwear agent and an organic resin on the surface thereof at a firing temperature of 120 to 230°C, the antiwear agent being at least one selected from the group consisting of iron oxide, chromium oxide, aluminum oxide, and titanium dioxide, a method for manufacturing a bearing having creep wear resistance in addition to insulation properties.

4. In the fired film, the content of the solid lubricant is 0 to 29% by mass, the content of the antiwear agent is 4 to 69% by mass, and the content of the organic resin is 30 to 80% by mass. The method for manufacturing a bearing according to claim 3.

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