JP2006342331A - Roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller bearing exhibiting excellent electroconductivity and scarcely causing leakage of a grease composition. <P>SOLUTION: The roller bearing is obtained by sealing an electroconductive grease composition 6 containing a synthetic hydrocarbon oil and three kinds of carbon black in a cavity part of a deep groove ball bearing. The first carbon black has 55 nm average primary particle diameter, 29 m<SP>2</SP>/g specific surface area and 130 mL/100 g DBP absorption. The second carbon black has 30 nm average primary particle diameter, 800 m<SP>2</SP>/g specific surface area and 360 mL/100 g DBP absorption. The third carbon black has 24 nm average primary particle diameter, 125 m<SP>2</SP>/g specific surface area and 165 mL/100g DBP absorption. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rolling bearing excellent in conductivity.

  In general office equipment and information equipment such as a copying machine, a large number of rolling bearings are used for the movable parts. An oil film is formed between the raceway surfaces of the inner and outer rings of the rolling bearing and the rolling elements during rotation, and the raceway surfaces and the rolling elements are not in contact with each other. In such a rolling bearing, static electricity is generated along with the rotation, so that there are cases where the radiation noise has an adverse effect such as distortion on a copy image of the copying machine.

  In order to prevent such inconvenience, the inner and outer races and rolling elements are made conductive by encapsulating conductive grease inside the rolling bearing, and one of the inner and outer races is grounded. Therefore, a countermeasure is taken to remove static electricity from the rolling bearing. And as conductive grease, what added carbon black as a thickener and an electroconductivity imparting additive was the mainstream (for example, the thing of patent document 1).

  However, rolling bearings filled with such conductive grease initially show excellent conductivity (the inner and outer races and rolling elements are in a conductive state), but the conductivity decreases with time. As a result, there is a problem that the electrical resistance value between the inner and outer rings of the rolling bearing (hereinafter referred to as the bearing resistance value) may increase. And, as the cause of such a phenomenon, the following was considered.

  That is, the conductive grease is initially sufficiently present on the contact surface between the raceway surface of the rolling bearing raceway and the rolling element, and the carbon black in the conductive grease causes a gap between the raceway ring and the rolling element. Conductivity is ensured, but due to the relative movement between the race and rolling elements, the conductive grease is removed from the contact surface over time, and the chain structure of carbon black particles is destroyed. A phenomenon occurs in which the conductivity decreases and the bearing resistance value increases with time.

  Further, as described in Patent Document 2, when the rolling bearing is rotated for a long time, it is said that an oxide film generated on the raceway surface of the rolling bearing increases the electric resistance value between the inner and outer rings. ing. As a countermeasure, a method using an extreme pressure additive or an anti-wear agent to protect the rolling contact surface of a rolling bearing (see Patent Document 2), a method of blending inorganic compound fine particles (see Patent Document 3). There is. However, extreme pressure additives generally have little effect at high temperatures. Further, when inorganic compound fine particles are simply added, the grease often hardens or softens with time, and the oil separation degree is not stable over time.

  Further, Patent Document 4 discloses a conductive grease that has a relatively large amount of carbon black having a small amount of dibutyl phthalate absorption (hereinafter referred to as DBP absorption amount) to stabilize the conductivity over a long period of time. Are listed. In office equipment and information equipment, resin parts that are easily deteriorated by grease and oil are frequently used. Therefore, it is preferable that grease leakage and oil separation from the rolling bearing be as small as possible. Since conductive grease has a small DBP absorption amount of carbon black, which is also a thickener, there is a possibility that the degree of oil separation will increase particularly at high temperatures.

Japanese Patent Publication No. 63-24038 JP 2002-80879 A JP 2003-42166 A JP 2002-53890 A

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a rolling bearing that exhibits excellent conductivity and is less likely to cause leakage of the grease composition.

In order to solve the above problems, the present invention has the following configuration. That is, the rolling bearing according to claim 1 of the present invention is formed between an inner ring, an outer ring, a plurality of rolling elements arranged to be freely rollable between the inner ring and the outer ring, and the inner ring and the outer ring. And a conductive grease composition enclosed in a void portion in which the rolling elements are disposed, wherein the conductive grease composition includes a base oil containing at least one of mineral oil and synthetic oil, and 2 The two types of carbon blacks include a first carbon black having a specific surface area of 20 m ² / g to 80 m ² / g and a specific surface area of 200 m ² / g to 1500 m ² / g. It is characterized by being the following second carbon black.

  If it is such a structure, it will show the outstanding electroconductivity and it will be hard to produce the leakage of a conductive grease composition. That is, excellent conductivity is imparted by the first carbon black, and oil separation of the conductive grease composition is suppressed by the second carbon black. And by containing both carbon black, aggregation of carbon black is suppressed and moderate fluidity | liquidity is provided to a conductive grease composition.

If the specific surface areas of both carbon blacks are within the above range, the above-described excellent effects can be obtained, but the specific surface area of the first carbon black is more preferably 23 m ² / g to 80 m ² / g. 23 m ² / g or more and 60 m ² / g or less is more preferable, and 27 m ² / g or more and 42 m ² / g or less is most preferable. Further, more preferably a specific surface area of the second carbon black is less than 250 meters ² / g or more 1000m ² / g, more preferably at most 320 m ² / g or more ^{1000m 2 / g, 370m 2 /} g or more 1000m Most preferably, it is ² / g or less. In addition, the numerical value of the specific surface area in this invention is a value measured by the nitrogen adsorption method.
Also, since mineral oil and synthetic oil have a small chemical attack on the resin, even if the conductive grease composition or base oil leaks from the rolling bearing and comes into contact with the surrounding resin parts, the resin parts are unlikely to deteriorate. .

  The rolling bearing according to claim 2 of the present invention is the rolling bearing according to claim 1, wherein the DBP absorption amount of the first carbon black is 30 ml / 100 g or more and 160 ml / 100 g or less, and the second carbon black The DBP absorption amount is from 80 ml / 100 g to 500 ml / 100 g.

  When the DBP absorption amount of the first carbon black is less than 30 ml / 100 g, the dispersibility of the first carbon black in the conductive grease composition tends to be insufficient, and when it exceeds 160 ml / 100 g, the carbon blacks aggregate together. The effect of preventing is reduced. In order to make such a problem less likely to occur, the DBP absorption amount of the first carbon black is more preferably 50 ml / 100 g or more and 160 ml / 100 g or less, and preferably 60 ml / 100 g or more and 150 ml / 100 g or less. More preferably, it is most preferably 67 ml / 100 g or more and 140 ml / 100 g or less.

  Further, when the DBP absorption amount of the second carbon black is less than 80 ml / 100 g, leakage of the base oil or the like is likely to occur, and when it exceeds 500 ml / 100 g, the tendency of the carbon blacks to aggregate increases. In order to make such a problem less likely to occur, the DBP absorption amount of the second carbon black is more preferably 90 ml / 100 g or more and 450 ml / 100 g or less, and preferably 100 ml / 100 g or more and 400 ml / 100 g or less. More preferably, it is 140 ml / 100 g or more and 360 ml / 100 g or less.

Furthermore, the rolling bearing according to claim 3 according to the present invention is the rolling bearing according to claim 1 or 2, wherein the mass ratio of the first carbon black to the second carbon black is 25:75 or more and 95. 5 or less, and the total content of the first carbon black and the second carbon black is 1.5% by mass or more and 20% by mass or less of the conductive grease composition.
With such a configuration, the characteristics of both carbon blacks are balanced, and the conductivity and fluidity of the conductive grease composition are improved. In addition, leakage from the rolling bearing and base oil separation are less likely to occur.

When the proportion of the first carbon black in the total amount of the first carbon black and the second carbon black is less than 25% by mass (that is, the proportion of the second carbon black exceeds 75% by mass), the thickening effect by the carbon black is Since it increases, the total carbon black content can be reduced, but oil separation at high temperatures may increase. On the other hand, if the proportion of the second carbon black is less than 5% by mass (that is, the proportion of the first carbon black exceeds 95% by mass), the retention of the base oil becomes insufficient. There is a need to do more. Further, although the initial conductivity is good, there is a possibility that good conductivity cannot be maintained over a long period of time.
In order to make such a problem less likely to occur, the mass ratio of the first carbon black to the second carbon black is more preferably 50:50 or more and 95: 5 or less, and 75:25 or more and 90:10. More preferably, it is 75:25 or more and 88:12 or less.

Further, if the total content of the first carbon black and the second carbon black is less than 1.5% by mass of the entire conductive grease composition, the conductivity may be insufficient, and the base oil There is a possibility that the oil release of the oil cannot be sufficiently suppressed. On the other hand, if it exceeds 20% by mass, the fluidity of the conductive grease composition may be reduced.
In order to make such a problem less likely to occur, the total content of the first carbon black and the second carbon black is more preferably 3% by mass or more and 17% by mass or less of the entire conductive grease composition. Preferably, it is 5 mass% or more and 15 mass% or less, More preferably, it is 7 mass% or more and 13 mass% or less.

Furthermore, the rolling bearing of Claim 4 which concerns on this invention is a rolling bearing as described in any one of Claims 1-3, The average primary particle diameter of said 1st carbon black is 40 nm or more and 200 nm or less, The average primary particle size of the second carbon black is 10 nm or more and 40 nm or less.
When the average primary particle size is less than 10 nm, there is a high possibility that carbon blacks aggregate together, and when it exceeds 200 nm, the fluidity of the conductive grease composition may be hindered. And by containing two types of carbon blacks having different average primary particle sizes, the dispersibility of the carbon black can be maintained appropriately, and as a result, the holding power of the base oil becomes sufficient. Further, even if shearing acts, the chain structure of the carbon black particles is not easily broken.

Furthermore, the rolling bearing according to claim 5 of the present invention is formed between an inner ring, an outer ring, a plurality of rolling elements arranged to be freely rollable between the inner ring and the outer ring, and the inner ring and the outer ring. And a conductive grease composition enclosed in a void portion in which the rolling elements are disposed, wherein the conductive grease composition comprises a base oil containing at least one of mineral oil and synthetic oil, and 3 The three types of carbon blacks include a first carbon black having a specific surface area of 20 m ² / g to 80 m ² / g and a specific surface area of 200 m ² / g to 1500 m ² / g. and following the second carbon black, specific surface area, characterized in that the third carbon black is less than 80 m ² / g excess 200 meters ² / g, a.

  With such a configuration, extremely excellent conductivity is exhibited, and leakage of the conductive grease composition is extremely difficult to occur. That is, excellent conductivity is imparted by the first and third carbon blacks, and oil separation of the conductive grease composition is suppressed by the second carbon black. And by containing 3 types of carbon black, aggregation of carbon blacks is suppressed and moderate fluidity | liquidity is provided to a conductive grease composition. In addition, even when shearing acts, the chain structure of the carbon black particles is not easily broken, and the holding power of the base oil is high.

If the specific surface areas of the three types of carbon black are within the above range, the above-described excellent effects can be obtained, but the specific surface area of the first carbon black is 23 m ² / g or more and 80 m ² / g or less. more preferably, more preferably at most 23m ² / g or more 60 m ² / g, and most preferably not more than 27m ² / g or more 42m ² / g. Further, more preferably a specific surface area of the second carbon black is less than 250 meters ² / g or more 1000m ² / g, more preferably at most 320 m ² / g or more ^{1000m 2 / g, 370m 2 /} g or more 1000m Most preferably, it is ² / g or less. Furthermore, the specific surface area of the third carbon black is more preferably 90 m ² / g to 180 m ² / g, further preferably 100 m ² / g to 160 m ² / g, more preferably 110 m ² / g to 140 m. Most preferably, it is ² / g or less.
Furthermore, since mineral oil and synthetic oil have a small chemical attack on the resin, even if the conductive grease composition or the base oil leaks from the rolling bearing and comes into contact with the surrounding resin parts, the resin parts are unlikely to deteriorate. .

  Furthermore, the rolling bearing according to claim 6 of the present invention is the rolling bearing according to claim 5, wherein the DBP absorption amount of the first carbon black is not less than 30 ml / 100 g and not more than 160 ml / 100 g, and the second carbon black The DBP absorption amount is from 80 ml / 100 g to 500 ml / 100 g, and the DBP absorption amount of the third carbon black is from 100 ml / 100 g to 300 ml / 100 g.

  When the DBP absorption amount of the first carbon black is less than 30 ml / 100 g, the dispersibility of the first carbon black in the conductive grease composition tends to be insufficient, and when it exceeds 160 ml / 100 g, the carbon blacks aggregate together. The effect of preventing is reduced. In order to make such a problem less likely to occur, the DBP absorption amount of the first carbon black is more preferably 50 ml / 100 g or more and 160 ml / 100 g or less, and preferably 60 ml / 100 g or more and 150 ml / 100 g or less. More preferably, it is most preferably 67 ml / 100 g or more and 140 ml / 100 g or less.

  Further, when the DBP absorption amount of the second carbon black is less than 80 ml / 100 g, leakage of the base oil or the like is likely to occur, and when it exceeds 500 ml / 100 g, the tendency of the carbon blacks to aggregate increases. In order to make such a problem less likely to occur, the DBP absorption amount of the second carbon black is more preferably 90 ml / 100 g or more and 450 ml / 100 g or less, and preferably 100 ml / 100 g or more and 400 ml / 100 g or less. More preferably, it is 140 ml / 100 g or more and 360 ml / 100 g or less.

  Furthermore, if the DBP absorption amount of the third carbon black is less than 100 ml / 100 g, the dispersibility in the conductive grease composition tends to be insufficient as in the case of the first carbon black, and if it exceeds 160 ml / 100 g. As in the case of the first carbon black, the effect of preventing the aggregation of the carbon blacks is reduced. In order to make such a problem less likely to occur, the DBP absorption amount of the third carbon black is more preferably 110 ml / 100 g or more and 250 ml / 100 g or less, and preferably 120 ml / 100 g or more and 200 ml / 100 g or less. More preferably, it is most preferably 140 ml / 100 g or more and 180 ml / 100 g or less.

Furthermore, the rolling bearing according to claim 7 according to the present invention is the rolling bearing according to claim 5 or 6, wherein the mass ratio of the first carbon black to the second carbon black is 25:75 or more and 95. : 5 or less, and the total content of the first carbon black, the second carbon black, and the third carbon black is 2% by mass or more and 25% by mass or less of the conductive grease composition. It is characterized by that.
With such a configuration, the characteristics of the three types of carbon black are balanced, and the conductivity and fluidity of the conductive grease composition are improved. In addition, leakage from the rolling bearing and base oil separation are less likely to occur.

  When the proportion of the first carbon black in the total amount of the first carbon black and the second carbon black is less than 25% by mass (that is, the proportion of the second carbon black exceeds 75% by mass), the thickening effect by the carbon black is Since it increases, the total carbon black content can be reduced, but oil separation at high temperatures may increase. On the other hand, if the proportion of the second carbon black is less than 5% by mass (that is, the proportion of the first carbon black exceeds 95% by mass), the retention of the base oil becomes insufficient. There is a need to do more. Further, although the initial conductivity is good, there is a possibility that good conductivity cannot be maintained over a long period of time.

In order to make such a problem less likely to occur, the mass ratio of the first carbon black to the second carbon black is more preferably 50:50 or more and 95: 5 or less, and 75:25 or more and 90:10. More preferably, it is 75:25 or more and 88:12 or less.
Further, if the total content of the first, second and third carbon blacks is less than 2% by mass of the conductive grease composition, the conductivity may be insufficient, and the base oil may be removed. May not be sufficiently suppressed. On the other hand, if it exceeds 25% by mass, the fluidity of the conductive grease composition may be reduced.
In order to make such problems less likely to occur, the total content of the first, second, and third carbon blacks is more preferably 5% by mass or more and 19% by mass or less of the conductive grease composition. 7 mass% or more and 22 mass% or less is more preferable, and 9 mass% or more and 20 mass% or less is most preferable.

  Furthermore, the rolling bearing of Claim 8 which concerns on this invention is a rolling bearing as described in any one of Claims 5-7, The average primary particle diameter of said 1st carbon black is 40 nm or more and 200 nm or less, The average primary particle size of the second carbon black is 10 nm or more and 40 nm or less, and the average primary particle size of the third carbon black is 10 nm or more and 40 nm or less.

  When the average primary particle size is less than 10 nm, there is a high possibility that carbon blacks aggregate together, and when it exceeds 200 nm, the fluidity of the conductive grease composition may be hindered. And by containing three types of carbon blacks having different average primary particle sizes, the dispersibility of the carbon black is maintained moderately, and as a result, the holding power of the base oil is sufficient. Further, even if shearing acts, the chain structure of the carbon black particles is not easily broken.

Furthermore, the rolling bearing of Claim 9 which concerns on this invention is a rolling bearing as described in any one of Claims 1-8. WHEREIN: The said conductive grease composition is 1 mass% or more and 10 mass% or less lithium soap. It is characterized by containing.
A thickener such as lithium soap may be added to the conductive grease composition in order to adjust the blending consistency. The average primary particle size of the lithium soap is preferably 5 nm or more and 10 μm or less. If the average primary particle size is less than 5 nm, the thickening effect is poor, and if it exceeds 10 μm, it may act as a foreign substance on the rolling bearing. is there.

Furthermore, the rolling bearing according to claim 10 according to the present invention is the rolling bearing according to any one of claims 1 to 9, wherein the conductive grease composition contains at least one of an extreme pressure agent and an oily agent. It is characterized by that.
Furthermore, the rolling bearing of Claim 11 which concerns on this invention is a rolling bearing as described in any one of Claims 1-10. WHEREIN: The penetration degree of the said conductive grease composition is 200-300. Features.
If the penetration is less than 200, the conductive grease composition is hard and the fluidity is insufficient, and if it exceeds 300, the conductive grease composition is soft and may cause leakage from the rolling bearing. is there.

  The rolling bearing of the present invention exhibits excellent electrical conductivity and is less likely to cause leakage of the grease composition.

Embodiments of a rolling bearing according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial longitudinal sectional view showing a structure of a deep groove ball bearing which is an embodiment of a rolling bearing according to the present invention. The deep groove ball bearing shown in FIG. 1 includes an inner ring 1, an outer ring 2, a plurality of balls 3 that are rotatably arranged between the inner ring 1 and the outer ring 2, and a plurality of balls 3 between the inner ring 1 and the outer ring 2. A retainer 4 to be retained, and shields 5 and 5 attached to inner peripheral surfaces of both end portions of the outer ring 2 are provided. The shield 5 is interposed between the inner ring 1 and the outer ring 2 and substantially covers the opening between the outer peripheral surface of the inner ring 1 and the inner peripheral surface of the outer ring 2.

  In addition, a conductive grease composition 6 is sealed in a gap formed between the inner ring 1 and the outer ring 2 where the balls 3 are arranged, and is sealed inside the deep groove ball bearing by a shield 5. The amount of the conductive grease composition 6 enclosed is 15% by volume or more and 35% by volume or less of the volume of the gap. A rubber seal may be used instead of the shield 5. In that case, the rubber of the rubber seal may be conductive rubber.

This conductive grease composition 6 contains a base oil and three types of carbon black and has a blending degree of 200 or more and 300 or less. Of the three types of carbon black, the first carbon black has an average primary particle size of 40 nm to 200 nm, a specific surface area of 20 m ² / g to 80 m ² / g, and a DBP absorption of 30 ml / 100 g to 160 ml / 100 g. is there. The second carbon black has an average primary particle size of 10 nm to 40 nm, a specific surface area of 200 m ² / g to 1500 m ² / g, and a DBP absorption of 80 ml / 100 g to 500 ml / 100 g. The third carbon black has an average primary particle diameter of 10nm or more 40nm or less, a specific surface area of 80 m ² / g excess 200m less than ² / g, DBP absorption is less than 100 ml / 100 g or more 300 ml / 100 g.

The mass ratio of the first carbon black and the second carbon black contained in the conductive grease composition 6 is 25:75 or more and 95: 5 or less, and the first carbon black, the second carbon black, and the third carbon. The total content with black is 2% by mass or more and 25% by mass or less of the entire conductive grease composition 6.
Such carbon black may be selected from various commercially available products based on the average primary particle size, specific surface area, and DBP absorption. For example, “Toka Black” series and “Seast” series manufactured by Tokai Carbon Co., Ltd., “Mitsubishi Carbon Black” series manufactured by Mitsubishi Chemical Corporation, “Denka Black” series manufactured by Denki Kagaku Kogyo Co., Ltd. "Ketjen Black" series can be used. Also, so-called acetylene black, fly ash and the like can be used as long as properties such as average primary particle size and specific surface area are within the scope of the present invention.

  Specifically, as the first carbon black, “Toka Black” series talker black # 7360SB, # 7350 / F, # 7270SB, # 7100F, # 7050, # 4500, # 4400, # 4300, # 3845, # 3800 or "Seast" series of seast 3, NH, N, 116HM, 116, FM, SO, V, SVH, FY, S, SP can be used. In addition, “Mitsubishi Carbon Black” series MA220, MA230, # 25, # 20, # 10, # 5, # 95, # 260, # 3030, # 3050, CF9 and “Denka Black” series Denka Black granular products , Powdery products, HS-100, etc. can be used.

Among these, Talker Black # 7050 (average primary particle size 66 nm, specific surface area 28 m ² / g, DBP absorption 66 ml / 100 g), Seest V (average primary particle size 62 nm, specific surface area 27 m ² / g, DBP absorption) 87 ml / 100 g), Siesto SVH (average primary particle size 62 nm, specific surface area 32 m ² / g, DBP absorption 140 ml / 100 g), Siesto S (average primary particle size 66 nm, specific surface area 27 m ² / g, DBP absorption 68 ml / 100 g), Denka Black HS-100 (average primary particle size 48 nm, specific surface area 39 m ² / g, DBP absorption 140 ml / 100 g) can be preferably used.

  Further, as the second carbon black, Talker Black # 8500 / F, # 8300 / F, # 5500, Mitsubishi Carbon Black # 2700, # 2650, # 2600, # 2400, # 2350, # 2300, # 2200, # 990, # 980, # 970, # 960, # 950, # 900, # 850, # 3230, Ketjen Black EC, etc. can be used.

Among these, Talker Black # 5500 (average primary particle size 25 nm, specific surface area 225 m ² / g, DBP absorption 155 ml / 100 g), Mitsubishi Carbon Black # 3230 (average primary particle size 23 nm, specific surface area 220 m ² / g, DBP absorption 140 ml / 100 g), Ketjen black EC (average primary particle size 30 nm, specific surface area 800 m ² / g, DBP absorption 360 ml / 100 g) can be preferably used.
Further, as the third carbon black, Mitsubishi carbon black # 3350 (average primary particle size 24 nm, specific surface area 125 m ² / g, DBP absorption 165 ml / 100 g) or the like can be used.

  Moreover, as base oil, mineral oil and synthetic oil are suitable. Examples of the mineral oil include paraffinic mineral oil and naphthenic mineral oil, and examples of the synthetic oil include ester oil, ether oil, polyglycol oil, silicone oil, synthetic hydrocarbon oil, fluorosilicone oil, and fluorine oil. Among these, considering the high heat resistance and the small chemical attack on the resin, fluorine oil and synthetic hydrocarbon oil are preferable, and perfluoropolyether oil and poly α-olefin oil are particularly preferable.

The kinematic viscosity at 40 ° C. of the synthetic hydrocarbon oil is preferably 10 mm ² / s to 500 mm ² / s. If the kinematic viscosity at 40 ° C. is less than 10 mm ² / s, the heat resistance may be insufficient, and if it exceeds 500 mm ² / s, the torque of the rolling bearing may be excessive. When the rolling bearing is used at a high temperature of about 200 ° C., the kinematic viscosity at 40 ° C. of the synthetic hydrocarbon oil is 20 mm ² / s or more and 200 mm ² / s or less because of the balance between torque performance and heat resistance. More preferably, it is more preferably 25 mm ² / s to 100 mm ² / s.

Further, a thickener such as lithium soap may be added to the conductive grease composition 6 in order to adjust the blending consistency.
Furthermore, various additives generally used for lubricants may be added to the conductive grease composition 6, and it is preferable to add at least one of an extreme pressure agent and an oily agent among the additives. The total content of the extreme pressure agent and the oily agent is preferably 0.1% by mass or more and 5% by mass or less of the entire conductive grease composition 6.

  Although the kind of extreme pressure agent is not particularly limited, for example, DTP metal compounds such as zinc dithiophosphate (Zn-DTP) and molybdenum dithiophosphate (Mo-DTP), nickel dithiocarbamate (Ni-DTC), Examples thereof include DTC metal compounds such as molybdenum dithiocarbamate (Mo-DTC). Also suitable are organometallic compounds containing sulfur, phosphorus, chlorine, and the like. Furthermore, solid lubricants having excellent extreme pressure properties such as molybdenum disulfide can also be used as extreme pressure agents. These extreme pressure agents may be used alone or in combination of two or more.

Examples of the oil-based agent include fatty acids such as oleic acid, fatty acid derivatives such as succinic acid ester, and organic phosphorus compounds. Examples of the organic phosphorus compounds include orthophosphoric acid esters represented by the general formula (RO) ₃ PO, phosphorous acid diesters represented by the general formula (RO) ₂ P (O) H, and the general formula (RO) _3. Examples thereof include phosphites such as phosphite triesters represented by P (R is a hydrocarbon group such as an alkyl group, an aryl group, and an alkylaryl group). Specific examples of the normal phosphate ester include tricresyl phosphate and trioctyl phosphate. These oily agents may be used alone or in combination of two or more.

Moreover, you may add additives other than an extreme pressure agent and an oil-based agent if desired. For example, antioxidants, rust inhibitors, and metal deactivators.
Examples of the rust preventive include metal rust preventives and ashless rust preventives. Specific examples of metal rust preventives include oil-soluble sulfonates such as (petroleum) sulfonic acid metal salts (barium salts, calcium salts, magnesium salts, sodium salts, zinc salts, aluminum salts, lithium salts, etc.) and phenates. , Salicylate, phosphonate and the like. Specific examples of the ashless rust preventive include succinimide, benzylamine, succinic acid ester, succinic acid half ester, polymethacrylate, polybutene, polycarboxylic acid ammonium salt and the like.

Furthermore, examples of the antioxidant include amine-based antioxidants (aliphatic amine-based and aromatic amine-based), phenol-based antioxidants, sulfur-based antioxidants, and the like.
Furthermore, examples of the metal deactivator include benzotriazole derivatives, sodium nitrite, zinc oxide and the like. Since these can form a passivating film, they have an effect of suppressing oxidation of the track surface due to wear or the like.

  In addition, this embodiment shows an example of this invention, Comprising: This invention is not limited to this embodiment. For example, in this embodiment, a deep groove ball bearing has been described as an example of a rolling bearing. However, the type of rolling bearing is not limited to a deep groove ball bearing, and the present invention is applicable to various types of rolling bearings. Can be applied. For example, radial rolling bearings such as angular contact ball bearings, self-aligning ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust types such as thrust ball bearings and thrust roller bearings This is a rolling bearing.

〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples. Conductive grease compositions having the compositions shown in Tables 1 and 2 were prepared, and various performances were evaluated.

In Tables 1 and 2, the numerical values described in the column of each component such as base oil and thickener are the mass ratio of each component when the entire conductive grease composition is 100.
The kinematic viscosity at 40 ° C. of the synthetic hydrocarbon oil described in the table is 30 mm ² / s. Carbon black A corresponding to the first carbon black, which is a constituent element of the present invention, is a seast S manufactured by Tokai Carbon Co., Ltd. (average primary particle size 66 nm, specific surface area 27 m ² / g, DBP absorption 68 ml / 100 g) Carbon black B corresponding to the first carbon black is # 3030B (average primary particle size 55 nm, specific surface area 29 m ² / g, DBP absorption 130 ml / 100 g) manufactured by Mitsubishi Chemical Corporation. Furthermore, carbon black C corresponding to the second carbon black which is a constituent element of the present invention is Ketjen black EC (average primary particle size 30 nm, specific surface area 800 m ² / g, DBP absorption 360 ml / 100 g, manufactured by Lion Akzo Co., Ltd. ), Carbon black D corresponding to the third carbon black, which is a constituent element of the present invention, is # 3350B (average primary particle size 24 nm, specific surface area 125 m ² / g, DBP absorption 165 ml / 100 g manufactured by Mitsubishi Chemical Corporation). ).

[Evaluation of conductivity]
Conductivity shown in Tables 1 and 2 in the gap formed between the inner ring and the outer ring of a deep groove ball bearing (inner diameter: 8 mm, outer diameter: 16 mm, width: 4 mm, with metal shield) with a nominal number of 688ZZ manufactured by NSK Ltd. The grease composition was sealed and rotated under the following conditions, and the bearing resistance value (maximum value) during rotation was measured.
Atmosphere temperature: Room temperature Rotational speed: 150 min ^-1
Radial load (Fr) applied to the bearing: 19.6 N for condition 1
196N for condition 2

  In the case of Condition 1, the bearing resistance value was measured after 200 hours, 400 hours, and 800 hours, and in Condition 2, after 250 hours. Note that the amount of the conductive grease composition enclosed in the gap formed between the inner ring and the outer ring of the deep groove ball bearing is 20% by volume of the volume of the gap. The test method will be described in detail below.

A deep groove ball bearing was mounted on the apparatus as shown in FIG. 2 and the electrical resistance value (maximum value) between the rotating inner and outer rings was measured. At this time, the maximum current passing through the bearing was limited to 100 μA by setting the voltage applied to the bearing to 6.2 V and the resistance to 62 kΩ.
In FIG. 2, reference numeral 11 denotes a deep groove ball bearing to be measured. The shaft member 12 attached to the inner ring 11 a is rotationally driven by a motor 13 to rotate the bearing 11. A predetermined constant voltage is applied by the constant voltage power supply 14 between the shaft member 12 and the outer ring 11b integrated with the inner ring 11a.

  The resistance measuring device 15 connected in parallel with the constant voltage power supply 14 outputs the measured voltage value (analog value) to the A / D conversion circuit 16. The A / D conversion circuit 16 converts it into a digital value at a preset sampling cycle, and outputs the converted digital signal to the arithmetic processing unit 17. In this embodiment, the sampling period is set to 50 kHz (sampling time interval = 0.02 ms).

  The arithmetic processing unit 17 includes a maximum resistance value calculating unit 17A, a threshold processing unit 17B, and a wave number counting unit 17C. The maximum resistance value calculation unit 17A calculates the maximum resistance value based on the input digital signal. The threshold processing unit 17B performs threshold processing on the input digital signal with a predetermined threshold to remove noise. The wave number counting unit 17C counts the number of fluctuations per predetermined time unit, that is, the wave number of the wave mountain, by the increase / decrease change of the pulse value with time for the pulse count from the threshold processing unit 17B, and average value of the wave number per unit time Ask for. Further, the arithmetic processing unit 17 outputs the obtained maximum resistance value and the average value of the wave number per unit time to the display unit 18. In this embodiment, the unit time for counting the wave number is set to 0.328 seconds. The display device 18 is composed of a display or the like, and displays the maximum resistance value obtained by the arithmetic processing device 17 and the average value of the wave number per unit time.

Next, a method for evaluating the bearing resistance value of the deep groove ball bearing 11 using the apparatus having the above configuration will be described.
A predetermined constant voltage is applied between the inner and outer rings 11 a and 11 b of the deep groove ball bearing 11 from the constant voltage power source 14 while the motor 13 is driven and the shaft member 12, that is, the inner ring 11 a is rotated at a predetermined rotational speed. At this time, a current flows between the inner and outer rings 11a and 11b, but the voltage fluctuates due to a spark or the like. The voltage is measured by the resistance measuring device 15, and then converted into a digital value by the A / D conversion circuit 16. Based on the digital signal, the arithmetic processing device 17 determines the maximum resistance value and the wave number per predetermined unit time. The obtained value is displayed on the display device 18.
Tables 1 and 2 collectively show the evaluation results of the bearing resistance values. In Tables 1 and 2, when the bearing resistance value is less than 10 kΩ, ◎, when it is 10 kΩ or more and less than 20 kΩ, ○, when it is 20 kΩ or more and less than 40 kΩ, Δ, or 40 kΩ or more. If there is, it is indicated by a cross.

[About evaluation of bearing torque]
Tables 1 and 2 show the electrical conductivity shown in Tables 1 and 2 in the gap formed between the inner ring and outer ring of a deep groove ball bearing (inner diameter 8 mm, outer diameter 22 mm, width 7 mm, with metal shield) of NSK 608ZZ manufactured by NSK Ltd. The functional grease composition was enclosed and rotated under the conditions described later, and the dynamic torque at the start and after 3 minutes of rotation was measured. The amount of the conductive grease composition enclosed in the gap formed between the inner ring and the outer ring of the deep groove ball bearing is 30% by volume of the volume of the gap.
Atmosphere temperature: Room temperature Rotational speed: 150 min ^-1
Axial load (Fa): 27.4N

The results are summarized in Tables 1 and 2. In addition, the numerical value of the dynamic torque of Tables 1 and 2 is shown as a relative value when the dynamic torque of the deep groove ball bearing of Example 1 is set to 1 both at the start and after 3 minutes of rotation.
From Tables 1 and 2, it can be seen that the deep groove ball bearings of Examples 1 to 7 have smaller bearing resistance values (excellent conductivity) than the deep groove ball bearings of Comparative Examples 1 to 3. Under high load conditions such as Condition 2, the conductivity may be lowered by an insulating film (for example, an oxide film) accompanying wear or the like, but the deep groove ball bearings of Examples 1 to 7 showed excellent conductivity. Moreover, the deep groove ball bearings of Comparative Examples 1 and 2 in which the content of the thickener containing carbon black was 30% by mass or more had higher torque than the deep groove ball bearings of Examples 1 to 7.

  The rolling bearing of the present invention can be used, for example, in high temperature portions (photosensitive drum (fixing portion), heat roller support portion, etc.) in office equipment and information equipment such as copying machines and laser beam printers.

It is a fragmentary longitudinal cross-section which shows the structure of the deep groove ball bearing which is one Embodiment of the rolling bearing which concerns on this invention. It is a schematic block diagram of the apparatus which measures the resistance value of a bearing.

Explanation of symbols

1 Inner ring 2 Outer ring 3 Ball 6 Conductive grease composition

Claims (11)

An inner ring, an outer ring, a plurality of rolling elements that are freely rollable between the inner ring and the outer ring, and a gap formed between the inner ring and the outer ring and enclosed with the rolling elements. In a rolling bearing comprising a conductive grease composition,
The conductive grease composition contains a base oil containing at least one of mineral oil and synthetic oil, and two types of carbon blacks,
The two types of carbon blacks are a first carbon black having a specific surface area of 20 m ² / g to 80 m ² / g and a second carbon black having a specific surface area of 200 m ² / g to 1500 m ² / g. Characteristic rolling bearing.   The DBP absorption amount of the first carbon black is 30 ml / 100 g or more and 160 ml / 100 g or less, and the DBP absorption amount of the second carbon black is 80 ml / 100 g or more and 500 ml / 100 g or less. The rolling bearing described.   The mass ratio of the first carbon black and the second carbon black is 25:75 or more and 95: 5 or less, and the total content of the first carbon black and the second carbon black is the conductive property. The rolling bearing according to claim 1 or 2, wherein the amount is from 1.5% by mass to 20% by mass of the grease composition.   The average primary particle size of the first carbon black is 40 nm or more and 200 nm or less, and the average primary particle size of the second carbon black is 10 nm or more and 40 nm or less. Rolling bearings as described in An inner ring, an outer ring, a plurality of rolling elements that are freely rollable between the inner ring and the outer ring, and a gap formed between the inner ring and the outer ring and enclosed with the rolling elements. In a rolling bearing comprising a conductive grease composition,
The conductive grease composition contains a base oil containing at least one of mineral oil and synthetic oil, and three types of carbon blacks,
The three types of carbon blacks include a first carbon black having a specific surface area of 20 m ² / g to 80 m ² / g, a second carbon black having a specific surface area of 200 m ² / g to 1500 m ² / g, and a specific surface area. rolling, characterized in that but is a tertiary carbon black of less than 80 m ² / g excess 200m ² / g.   The DBP absorption amount of the first carbon black is 30 ml / 100 g or more and 160 ml / 100 g or less, the DBP absorption amount of the second carbon black is 80 ml / 100 g or more and 500 ml / 100 g or less, and the DBP absorption of the third carbon black is The rolling bearing according to claim 5, wherein the amount is 100 ml / 100 g or more and 300 ml / 100 g or less.   The mass ratio of the first carbon black to the second carbon black is 25:75 or more and 95: 5 or less, and the total of the first carbon black, the second carbon black, and the third carbon black. The rolling bearing according to claim 5 or 6, wherein the content of is from 2% by mass to 25% by mass of the conductive grease composition.   The average primary particle size of the first carbon black is 40 nm to 200 nm, the average primary particle size of the second carbon black is 10 nm to 40 nm, and the average primary particle size of the third carbon black is 10 nm to 40 nm. It is the following, The rolling bearing as described in any one of Claims 5-7 characterized by the above-mentioned.   The rolling bearing according to any one of claims 1 to 8, wherein the conductive grease composition contains 1 to 10% by mass of lithium soap.   The rolling bearing according to any one of claims 1 to 9, wherein the conductive grease composition contains at least one of an extreme pressure agent and an oily agent.   The rolling bearing according to any one of claims 1 to 10, wherein the penetration degree of the conductive grease composition is 200 or more and 300 or less.

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