JP7708596B2 - Bearing and manufacturing method thereof - Google Patents

Description

The present invention relates to a bearing and a manufacturing method thereof.

In recent years, the electrification of automobiles has been progressing due to global environmental issues. As a result, it has been reported that the bearings used in these vehicles suffer from electrolytic corrosion due to leakage current, resulting in damage to the bearings.
In the past, in order to prevent electrical corrosion of bearings, the mating parts of the bearing's outer ring or inner ring with other parts were often coated with a hard insulating material such as ceramic.
However, the cost of applying hard inorganic materials such as ceramics is high, and because they are hard materials, there was concern that if the bearings creep, the housing parts they fit with, such as aluminum alloys, will wear out, which could affect the function of the unit.

In addition, sintered films containing solid lubricants, which have been applied to improve creep wear resistance in the past, also have creep wear resistance, but because the coating is soft, insulation is maintained initially, but as the bearing slides, the sintered film wears away and the insulation is no longer maintained.

In light of this situation, the present invention aims to provide a bearing that is less expensive than ceramics, has insulating properties, and has a coating that is less susceptible to creep wear, and a manufacturing method for the bearing.

The present invention relates to the following (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,
A phosphate coating or a black oxide coating and a fired coating containing an anti-wear agent and an organic resin on the surface thereof,
A bearing that has insulation properties as well as creep wear resistance.
(2) In the fired film,
The content of solid lubricant is 0 to 29 mass %,
The content of the anti-wear agent is 4 to 69 mass %,
The bearing according to (1) above, wherein the organic resin content is 30 to 80 mass %.
(3) A method for manufacturing a bearing having an outer ring, an inner ring, and rolling elements sandwiched therebetween, comprising the steps of:
the 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 forming a fired film containing an anti-wear agent and an organic resin on the surface by firing at a firing temperature of 120 to 230°C,
A manufacturing method for bearings that are insulating and resistant to creep wear.
(4) In the fired film,
The content of solid lubricant is 0 to 29 mass %,
The content of the anti-wear agent is 4 to 69 mass %,
The method for producing a bearing according to (3) above, wherein the organic resin content is 30 to 80 mass %.

The present invention provides a bearing and a manufacturing method thereof that is less expensive than ceramics, has insulating properties, and has a coating that is less susceptible to creep wear.

FIG. 2 is a schematic perspective view of a bearing according to the present invention. 1 is a photograph of a friction and wear tester used in the examples.

The present invention will now be described.
The present invention is a bearing having an outer ring, an inner ring, and rolling elements sandwiched between them, and which has a phosphate coating or black oxide coating on the outer peripheral surface of the outer ring and/or the inner peripheral surface of the inner ring, and a fired film containing an anti-wear agent and an organic resin on the surface of that, giving the bearing insulation and creep wear resistance.
Such a bearing will be referred to hereinafter as the "bearing of the present invention."

The present invention also provides a method for manufacturing a bearing having an outer ring, an inner ring, and rolling elements sandwiched between them, comprising the steps of forming a phosphate film or a black oxide film on the outer peripheral surface of the outer ring and/or the inner peripheral surface of the inner ring, and then forming a sintered film containing an anti-wear agent and an organic resin on the surface by sintering at a sintering temperature of 120 to 230°C, thereby providing a bearing with insulation and creep wear resistance.
Such a manufacturing method for a bearing is hereinafter referred to as the "manufacturing method of the present invention."

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

The bearing of the present invention will now be described.
FIG. 1 is a schematic perspective view of a preferred embodiment of a bearing according to 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 between them.
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 between them. The same applies to the shapes of the outer ring 2, the inner ring 4, and the balls 6.
The materials for the outer ring 2, the inner ring 4 and the body of the ball 6 are not particularly limited, but are preferably metal, in particular steel such as bearing steel.
The balls 6 are an example of the rolling elements in the present invention. The rolling elements in the present invention are not limited to balls, and may be of the same form as the conventionally known rolling elements of a general bearing, for example.

The bearing of the present invention has two coatings, a phosphate coating or black oxide coating and a fired coating, stacked 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 have two coatings, a phosphate coating or black oxide coating and a sintered coating, stacked on top of each other on the two side surfaces 22 that are adjacent to the outer peripheral surface 20 of the outer ring 2, and on the two side surfaces 42 that are adjacent to the inner peripheral surface 40 of the inner ring 4.

Forming a phosphate film can improve the adhesion of the fired film.
Examples of the phosphate include manganese phosphate, iron phosphate, zinc phosphate, and zinc calcium phosphate, and among these, it is preferable to use manganese phosphate.
The phosphate coating can be formed on the surface of the bearing body (a 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 immersion in an aqueous phosphate solution (e.g., an aqueous manganese phosphate solution).
Here, as a surface preparation before forming the phosphate film, etching or blasting may be performed to roughen the surface.
The thickness of the phosphate coating is not particularly limited, but is preferably 1 to 15 μm, and more preferably 3 to 7 μm.

The black oxide film undergoes little dimensional change due to material elution and magnetite formation during the film formation process, forms highly adhesive magnetite aggregates, and has wear resistance and paint film adhesion. The black oxide film can be formed on the surface of the bearing body (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 immersion treatment in a strongly alkaline black oxidation treatment aqueous solution.
The thickness of the black oxide film is not particularly limited, but is preferably 0.2 to 3.0 μm, and more preferably 1.0 to 2.5 μm.

The bearings of the present invention have a fired coating over a phosphate coating or black oxide coating.
The fired film contains an anti-wear agent, and the content of the anti-wear agent in the fired film is preferably 4 to 69 mass %, and more preferably 13 to 50 mass %.
Specific examples of the anti-wear agent will be described later.

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. In other words, the fired film preferably contains a solid lubricant, but does not have to contain one.
Specific examples of the solid lubricant will be described later.

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.

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

The thickness of the phosphate coating and fired coating on the bearing of the present invention refers to values measured using a conventionally known electromagnetic coating thickness meter, with an untreated bearing as the zero point. The thickness of the black oxide coating refers to values measured using conventionally known cross-sectional magnification observation and Calotest.

Next, the production method of the present invention will be described.
First, a conventionally known bearing made of metal or the like including an outer ring, an inner ring, and rolling elements (balls, etc.) is immersed in a phosphate aqueous solution (such as a manganese phosphate aqueous solution) or a black oxide treatment aqueous solution and treated to form a phosphate coating or a black oxide coating 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 coating can also be formed on the surface of a conventionally known bearing made of metal, including an outer ring, an inner ring, and rolling elements (balls, etc.), by spraying or applying an aqueous phosphate solution thereto.

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

The black oxide film can also be formed by immersing a conventional bearing made of metal, including an outer ring, inner ring, and rolling elements (balls, etc.), in an aqueous solution (preferably adjusted to 120 to 150°C) that is primarily made of sodium hydroxide or potassium hydroxide and a reaction accelerator. The outer ring and inner ring may also be immersed separately.

Next, a fired film is formed on the surface of the resulting phosphate film or black oxide film.
A mixed solution containing an anti-wear agent and an organic resin is applied onto the surface of the phosphate film or black oxide film, and then the mixture is baked at a baking temperature of 120 to 230° C. to form a baked film.
The baking temperature is appropriately set depending on the components of the mixed solution, specifically, 120 to 230°C, and preferably within the range of 120 to 160°C.

The mixed solution containing the anti-wear agent and the organic resin in the solvent preferably further contains a solid lubricant.

Examples of solid lubricants 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 mass %, more preferably 0.2 to 5.0 mass %, even more preferably 0.25 to 2.7 mass %, and even more preferably 0.8 to 1.9 mass %.

Examples of the anti-wear 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 anti-wear agent in the mixed solution to be applied is preferably 0.5 to 24.5 mass%, more preferably 1.0 to 16.5 mass%, more preferably 12 to 21 mass%, and even more preferably 15 to 18 mass%.

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 mass%, more preferably 9.0 to 18.0 mass%, preferably 5 to 17 mass%, and more preferably 8 to 14 mass%.

Examples of the solvent that can be used in the mixed solution to be applied include 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. 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 from 60 to 90% by mass, and more preferably from 70 to 85% by mass.
The method for applying the mixed solution is not particularly limited. For example, the mixed solution can be applied using a spray, a dip coating device including electrodeposition, a spin coater, a bar coater, an inkjet, or printing, and then baked at a baking temperature of 120 to 230° C. to form a baked film.

<Experiment 1>
<Sample preparation>
A steel ring (material: AISI4620 (US standard), surface hardness: 60 HRC, outer diameter: φ35 mm) was immersed in a 3 mass % manganese phosphate aqueous solution to form a manganese phosphate coating with a thickness of 3 μm. Then, a solution having the following composition (excluding the solvent) was sprayed onto the surface of the manganese phosphate coating. It was then fired at a firing temperature of 120° C. to form a fired film with a thickness of 20 μm.
Solid lubricant (PTFE: polytetrafluoroethylene): 5% by mass
Anti-wear 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 coated steel ring thus obtained was designated "Sample 1."
The coating formed on Sample 1 had the same structure as the coating on the bearing of the present invention.

Next, similarly to the case of Sample 1, an iron ring was immersed in a 3% by mass aqueous solution of manganese phosphate to form a manganese phosphate coating with a thickness of 3 μm, and then a solution having the following composition (excluding the solvent) was sprayed onto the surface. It was then fired at a firing temperature of 120° C. to form a fired film with a thickness of 20 μm.
Polyamide-imide resin: 30 to 40% by mass
Epoxy resin 10 to 20% by mass
・Molybdenum disulfide 20-30% by mass
・Graphite mass 1-10%
Antimony trioxide 20 to 30% by mass
The coated steel ring thus obtained was designated "Sample 2."
The coating formed on Sample 2 is a coating that is provided on a conventional product, and is used as a comparison with Sample 1, which has the same configuration as the coating of the bearing of the present invention.

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

<Insulation evaluation test>
An insulation evaluation test was carried out on Samples 1, 2, 10 and 20 obtained as described above.
The insulation evaluation test was carried out using a measuring instrument TOS5301 (manufactured by Kikusui Electronics Co., Ltd.).
Specifically, for sample 1, first, a negative electrode was attached to the portion of the steel ring where no fired film was formed, and a positive electrode was attached to the portion where a fired film was formed.
For sample 10, first, a negative electrode was attached to the portion of the steel ring where no fired film was formed, and a positive electrode was attached to the sliding portion where a fired film was formed.
For sample 2, a negative electrode was first attached to the portion of the steel ring where no fired film was formed, and a positive electrode was attached to the portion where the film was formed.
For sample 20, a negative electrode was first attached to the portion of the steel ring where no fired film was formed, and a positive electrode was attached to the sliding portion where the film was formed.
Then, for each of Sample 1 and Sample 2, the voltage was increased to a set voltage (120 V, 250 V or 500 V) in 10 seconds, and the insulation was evaluated based on whether or not the limit current was exceeded (whether or not a leak 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.

As shown in Table 1, in the case of Sample 1 and Sample 10, no leakage occurred during the 60 seconds that the set voltage was maintained, regardless of whether the set voltage was 250V or 500V, and regardless of whether the voltage was AC or DC. In other words, it was confirmed that Sample 1 and Sample 10 have excellent insulation properties.

On the other hand, in the case of Sample 2 and Sample 20, when the set voltage was 120V and AC, leakage occurred during boost, and when it was DC, leakage occurred while the set voltage was being maintained. Also, when the set voltage was 250V and DC, leakage occurred during boost. In other words, it was confirmed that Sample 2 and Sample 20 have inferior insulation properties compared to Sample 1 and Sample 10.

<Wear performance evaluation test>
The amount of wear of the aluminum blocks of Samples 1, 10, 2 and 20 was measured using a contact roughness meter (Tokyo Seimitsu Co., Ltd., SURFCOM1500SP, probe: 2 μmR, 60° conical diamond).
As a result, the amount of wear obtained from a comparison (difference) between Sample 1 and Sample 10, and the amount of wear obtained from a comparison (difference) between Sample 2 and Sample 20 were both so small that they could not be measured (or were approximately 10 μm or less).
From this, it is considered that the coatings of Samples 1 and 10 have the same level of abrasion resistance of the aluminum block as the coatings of Samples 2 and 20.

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

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, a manganese phosphate coating was formed on the outer peripheral surface of this steel material, and each of the mixed solutions according to Examples 1 to 6 and Comparative Example 1 was spray-coated thereon. Each was then fired at a firing temperature of 120°C to obtain a ring steel material.
The thickness of the fired film on the ring steel material was 25 μm in all cases.
The fired film formed in Comparative Example 1 is a film that is provided on a conventional product, and is used as a comparison with Examples 1 to 6 that have the same configuration as the film provided on the bearing of the present invention.

<Sliding test>
As a test simulating the sliding environment of an aluminum housing fitted with a steel bearing, a ring-shaped steel material having a fired film of each of the compositions shown in Table 2 (Examples 1 to 6 and Comparative Example 1) was arranged as shown in Figure 2 in order to slide against the outer peripheral surface of a portion of the surface of an aluminum block, and the following evaluations were performed.
・Test equipment: Falex block-on-ring tester (LFW-1)
・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 1 Step) Step-up load control Rotation speed: 100 rpm
Test duration: 10 minutes

<Wear volume measurement>
After the sliding test, the amount of wear of the aluminum alloy block material was measured using a surface roughness meter under the following conditions.
Testing machine: Tokyo Seimitsu SURFCOM 1400G
Calculation standard: JIS-'01/'13 standard Measurement type: Cross-sectional measurement Measurement speed: 0.3 mm/s
Measurement length: 10.0 mm
Stylus shape: φ1.6 ruby Shape removal: Least squares straight line Evaluation criteria: A maximum abrasion amount of the aluminum alloy block material of 40 μm or less was considered good, and 40 μm or more was considered bad.
Since the wear pattern after the sliding test conforms to the shape of the ring, the maximum amount of wear was recorded as the measured value.

<Insulation evaluation test conditions>
For the sliding members after the sliding test for each of the compositions shown in Table 2 (Examples 1 to 6 and Comparative Example 1), a dielectric breakdown evaluation was carried out under the following measurement conditions.
Equipment used: Withstand voltage and insulation resistance tester TOS5301 (manufactured by Kikusui Electronics Co., Ltd.)
・Measurement conditions ・DC upper limit: 6.20kV
Limit: 0.5mA Stops at current value above 0.5mA Boost time: 10 seconds Start voltage: 0V
Insulation judgment: Leakage is judged at a current value of 0.5mA or more, and the voltage value at that time is measured. AC Upper limit: 5.50kV
Limit: 10mA Stops at current value above 10mA Boost time: 10 seconds Start voltage: 0V
Frequency: 50Hz
Insulation judgment: Leakage is judged at a current value of 10mA or more, and the voltage value at that time is measured. Measurement method: The alligator clip part of the high voltage test lead is attached to the positive and negative poles of the measuring device, and the ring-shaped steel material is placed on the part where the fired film is not formed (inner diameter) and the sliding part (outer diameter). The measuring device voltage is measured under the above measurement conditions. The measurement is performed three times, and the average value is used as the data.
Judgment criteria: When the limit was stopped during DC and AC measurements, it was considered to be bad, and when insulation was judged to be 0.1 kV or more, it was considered to be good.

<Evaluation Results for Examples and Comparative Examples>
Table 3 shows the amount of wear of the aluminum block and the results of the dielectric breakdown measurement after the sliding test.
In Comparative Example 1, which is a sintered film of conventional specifications, the abrasion of the aluminum block during the sliding test was suppressed, but the insulating performance was not obtained due to the abrasion of the sintered film. In contrast, in Examples 1 to 6, it was confirmed that the abrasion of the aluminum block during the sliding test was suppressed and the insulating performance after the sliding test was secured.

REFERENCE SIGNS LIST 1 Bearing of the present invention 2 Outer ring 20 Outer peripheral surface of outer ring 4 Inner ring 40 Inner peripheral surface of inner ring 6 Ball

Claims (4)

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,
A phosphate coating or a black oxide coating and a fired coating containing an anti-wear agent and an organic resin on the surface thereof,
The anti-wear agent is at least one selected from the group consisting of iron oxide, chromium oxide, aluminum oxide , and titanium dioxide;
A bearing that has insulation properties as well as creep wear resistance. In the fired film,
The content of solid lubricant is 0 to 29 mass %,
The content of the anti-wear agent is 4 to 69 mass %,
2. The bearing according to claim 1, wherein the organic resin content is 30 to 80 mass %. A manufacturing method for a bearing having an outer ring, an inner ring, and rolling elements sandwiched between them, comprising the steps of:
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 forming a fired film containing an anti-wear agent and an organic resin on the surface by firing at a firing temperature of 120 to 230°C,
The anti-wear agent is at least one selected from the group consisting of iron oxide, chromium oxide, aluminum oxide , and titanium dioxide;
A manufacturing method for bearings that are insulating and resistant to creep wear. In the fired film,
The content of solid lubricant is 0 to 29 mass %,
The content of the anti-wear agent is 4 to 69 mass %,
The method for manufacturing a bearing according to claim 3, wherein the organic resin content is 30 to 80 mass %.