JP2006131762A - Conductive grease composition and rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive grease composition which exhibits excellent conductivity and hardly causes oil separation even at high temperatures, hardly exerts bad influences on a resin and hardly leaks when used for a rolling device such as a rolling bearing. <P>SOLUTION: The conductive grease composition G, comprising a synthetic hydrocarbon oil, two kinds of carbon blacks and an additive containing at least either one of an extreme pressure agent and an oily agent, is sealed in a void space of a deep groove ball bearing. The total content of the extreme pressure agent and the oily agent is at least 0.1 mass% and at most 5 mass% based on the whole conductive grease composition G. One of the two kinds of carbon blacks has an average primary particle size of 30 nm, a specific surface area of 800 m<SP>2</SP>/g and a DBP absorption of 360 ml/100 g, while the other carbon black has an average primary particle size of 66 nm, a specific surface area of 27 m<SP>2</SP>/g and a DBP absorption of 68 ml/100 g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a grease composition and a rolling device 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 measures against this, there are a method using an extreme pressure agent and an antiwear agent to protect the rolling contact surface of the rolling bearing (see Patent Document 2), and a method of blending inorganic compound fine particles (see Patent Document 3). is there. However, extreme pressure agents 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.

  On the other hand, Patent Document 4 discloses a conductive grease in which carbon black having a small amount of dibutyl phthalate absorption (hereinafter referred to as DBP absorption amount) is blended in a relatively large amount to stabilize the conductivity over a long period of time. Are listed. Since office equipment and information equipment use many resin parts that are easily deteriorated by grease and oil, it is preferable that leakage of grease from rolling bearings and separation of oil from grease be as small as possible. Since the conductive grease described in Document 4 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 be high particularly at high temperatures.

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

  Therefore, the present invention solves the problems of the prior art as described above, exhibits excellent conductivity even at high temperatures, hardly releases oil, does not adversely affect the resin, and further has a rolling bearing. It is an object of the present invention to provide a conductive grease composition that hardly leaks when used in a rolling device such as the above. Another object of the present invention is to provide a rolling device that exhibits excellent conductivity even at high temperatures 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 conductive grease composition of claim 1 according to the present invention is a conductive grease composition containing a base oil, carbon black, and an additive, wherein the base oil contains at least one of mineral oil and synthetic oil. The carbon black has a first primary carbon black having an average primary particle size of 10 nm to 200 nm and a specific surface area of 20 m ² / g to 80 m ² / g, an average primary particle size of 10 nm to 200 nm and a specific surface area. A second carbon black of 200 m ² / g or more and 1500 m ² / g or less, the additive contains at least one of an extreme pressure agent and an oily agent, and a total of the extreme pressure agent and the oily agent The content of is not less than 0.1% by mass and not more than 5% by mass of the whole composition.

  With such a configuration, excellent conductivity is exhibited even at a high temperature, and oil separation is difficult even at a high temperature. Moreover, it is hard to have a bad influence with respect to resin. Furthermore, even when used in a rolling device such as a rolling bearing, it is difficult to leak from the rolling device to the outside. That is, excellent conductivity is imparted by the first carbon black, and oil separation 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 1000 m ² / g, more preferably at most 320 m ² / g or more ^{1000m 2 / g, 370m 2 /} g or more 800m 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.

  Further, when the average primary particle size is less than 10 nm, there is a high possibility that the carbon blacks aggregate, and when it exceeds 200 nm, the fluidity of the conductive grease composition may be hindered. In order to make such problems less likely to occur, the average primary particle size of both carbon blacks is more preferably 10 nm or more and 100 nm or less, further preferably 10 nm or more and 80 nm or less, and 13 nm or more and 70 nm or less. Most preferably it is.

  Furthermore, since the conductive grease composition contains an extreme pressure agent or an oily agent, an oxide film that may occur on the raceway surface of the rolling device when the surface pressure is high is suppressed. Therefore, the electrical conductivity of the rolling device is dramatically improved. If the total content of the extreme pressure agent and the oily agent is less than 0.1% by mass of the entire conductive grease composition, the effect of addition may be insufficient. On the other hand, if it exceeds 5% by mass, the properties of the conductive grease composition become unstable, and for example, there is a risk that large hardening or softening may occur over time or oil separation may occur.

  The conductive grease composition of claim 2 according to the present invention is the conductive grease composition of 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. The DBP absorption amount of the second carbon black is 80 ml / 100 g or more and 500 ml / 100 g or less.

  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 150 ml / 100 g or more and 360 ml / 100 g or less.

Furthermore, the conductive grease composition of claim 3 according to the present invention is the conductive grease composition of 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 entire composition. And
With such a configuration, the characteristics of both carbon blacks are balanced, and the conductivity and fluidity of the conductive grease composition are improved. Further, leakage from the rolling device 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. As a result, an insulating oil film is formed on the rolling contact surface of the rolling device, and the conductivity of the rolling device may be reduced.

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. Furthermore, the durability of the rolling device may be insufficient.
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 60:40 or more and 90:10. More preferably, it is 70:30 or more and 85:15 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 5% by mass or more and 20% by mass or less of the entire conductive grease composition. preferable.

Furthermore, the conductive grease composition according to claim 4 of the present invention is the conductive grease composition according to any one of claims 1 to 3, wherein the synthetic oil has a kinematic viscosity at 40 ° C. of 10 mm ^2. It is a synthetic hydrocarbon oil of / s or more and 500 mm ² / s or less.
Synthetic hydrocarbon oil has a small chemical attack on the resin, so even if the conductive grease composition or base oil leaks from a rolling device such as a rolling bearing and contacts the surrounding resin parts, the resin parts deteriorate. Is unlikely to occur.

If the kinematic viscosity at 40 ° C. of the synthetic hydrocarbon oil is less than 10 mm ² / s, heat resistance may be insufficient, and if it exceeds 500 mm ² / s, the torque when used in a rolling device is May be excessive. When sealed in a rolling device used in a high temperature of about 200 ° C., from the balance between the torque performance and heat resistance, kinematic viscosity at 40 ° C. of synthetic hydrocarbon oil is 20 mm ² / s or more 200 mm ² / S or less is more preferable, and 25 mm ² / s or more and 100 mm ² / s or less is further preferable.

  Furthermore, the conductive grease composition of claim 5 according to the present invention is the conductive grease composition according to any one of claims 1 to 4, wherein the metal oxide has an average primary particle size of 5 nm to 10 μm. It is characterized by containing 0.05% by mass or more and 5% by mass or less of one or more powders among a material, metal nitride, metal carbide, clay mineral, cluster diamond, and fullerene.

  If it is such a structure, it can suppress that an oxide film produces | generates on the track surface and rolling element surface of a rolling device. If the average primary particle size of each powder is less than 5 nm, the effect of preventing the formation of an oxide film is insufficient, and if it exceeds 10 μm, it acts as a foreign substance when used in a rolling device such as a rolling bearing. There is a risk. In order to make such a problem less likely to occur, the average primary particle size is more preferably 5 nm or more and 2 μm or less, further preferably 10 nm or more and 500 nm or less, and most preferably 10 nm or more and 200 nm or less. .

  Further, if the content of the powder is less than 0.05% by mass of the entire conductive grease composition, the effect of preventing the formation of an oxide film is poor, and if it exceeds 5% by mass, the flow of the conductive grease composition There is a risk that the performance will deteriorate, or the raceway surface and the rolling element surface will be excessively scraped off. In order to make such a problem less likely to occur, the content of the powder is more preferably 0.1% by mass or more and 3% by mass or less of the entire conductive grease composition.

  Furthermore, the conductive grease composition of Claim 6 which concerns on this invention is a conductive grease composition as described in any one of Claims 1-5, A fiber length is 5 nm or more and 10 micrometers or less, and an aspect-ratio is. One or more carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon fibers, and metal oxide whiskers that are 5 or more and 1000 or less are contained in an amount of 0.05% by mass or more and 5% by mass or less of the entire composition. To do.

  The conductive grease composition containing such a fibrous material is more excellent in conductivity. If the fiber length of each of the above-mentioned fibrous materials is less than 5 nm, the effect of improving the conductivity is poor, and if it is more than 10 μm, it may act as a foreign substance when used in a rolling device such as a rolling bearing. is there. Further, if the content of the fibrous material is less than 0.05% by mass of the entire conductive grease composition, the effect of improving the conductivity is poor, and if it is more than 5% by mass, the flow of the conductive grease composition May decrease.

Furthermore, the conductive grease composition of Claim 7 which concerns on this invention is a conductive grease composition as described in any one of Claims 1-6, The miscibility is 200-300, It is characterized by the above-mentioned. And
If the penetration is less than 200, the conductive grease composition is hard and the fluidity is insufficient. If it exceeds 300, the conductive grease composition is soft and may leak from the rolling device. There is.

  A thickener may be added to adjust the blending degree. The type of thickener is not particularly limited, and metal soaps such as lithium 12-hydroxystearate and urea compounds such as diurea can be used. However, the average primary particle size of the thickener is preferably 5 nm or more and 10 μm or less. When the average primary particle size is less than 5 nm, the effect of increasing is poor, and when it exceeds 10 μm, it may act as a foreign substance when used in a rolling device such as a rolling bearing.

Furthermore, the conductive grease composition according to claim 8 of the present invention is the conductive grease composition according to any one of claims 1 to 7, wherein the conductive grease composition is for a rolling bearing.
Furthermore, the rolling device according to claim 9 of the present invention includes an inner member having a raceway surface on the outer surface, and a raceway surface facing the raceway surface of the inner member, and is disposed outward of the inner member. A gap formed between the inner member and the outer member, in a rolling device comprising: an outer member formed and a plurality of rolling elements arranged to roll between the raceway surfaces. The conductive grease composition according to any one of claims 1 to 7 is arranged in the section.

  The conductive grease composition as described above is suitable for a rolling device such as a rolling bearing, and particularly suitable for a deep groove ball bearing having a seal or a shield. The rolling device of the present invention is excellent in electrical conductivity, heat resistance, and durability, and hardly leaks the conductive grease composition. In the case of a deep groove ball bearing, the filling amount of the conductive grease composition is preferably 15% by volume to 35% by volume of the volume of the gap formed between the inner ring and the outer ring. If the amount is less than 15% by volume, the amount of the conductive grease composition may be too small to cause poor lubrication at an early stage. If the amount is more than 35% by volume, the conductive grease composition tends to leak.

  The present invention can be applied to various rolling devices. For example, a rolling bearing, a ball screw, a linear guide device, a linear motion bearing, and the like. Here, the inner member in the present invention refers to an inner ring when the rolling device is a rolling bearing, a screw shaft when the ball screw is also used, a guide rail when the linear guide device is used, and a linear bearing. In the case, each means an axis. The outer member is the outer ring when the rolling device is a rolling bearing, the nut when it is a ball screw, the slider when it is a linear guide device, and the outer cylinder when it is also a linear bearing. Each means.

  The conductive grease composition of the present invention exhibits excellent conductivity even at high temperatures, hardly releases oil, and does not easily adversely affect the resin. Further, when used in a rolling device such as a rolling bearing, leakage hardly occurs. In addition, the rolling device of the present invention exhibits excellent conductivity even at high temperatures, and the grease composition is unlikely to leak.

DESCRIPTION OF EMBODIMENTS Embodiments of a conductive grease composition and a rolling device according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a structure of a deep groove ball bearing which is an embodiment of a rolling device according to the present invention. This deep groove ball bearing has an inner ring 1 having a raceway surface 1a on the outer peripheral surface, an outer ring 2 having a raceway surface 2a facing the raceway surface 1a on the inner peripheral surface, and a raceway between the raceway surfaces 1a and 2a. A plurality of rolling elements (balls) 3, a cage 4 that holds the plurality of rolling elements 3 between the inner ring 1 and the outer ring 2, and seals 5 and 5 that cover the openings of the gaps between the inner ring 1 and the outer ring 2. And. A gap formed between the inner ring 1 and the outer ring 2 is filled with a conductive grease composition G and sealed inside the deep groove ball bearing by seals 5 and 5. The amount of the conductive grease composition G filled is preferably 15% by volume or more and 35% by volume or less of the volume of the gap. The cage 4 and the seal 5 may not be provided.

This conductive grease composition G comprises a base oil containing at least one of mineral oil and synthetic oil, two types of carbon black, and an additive containing at least one of an extreme pressure agent and an oily agent. The penetration is 200 or more and 300 or less.
The total content of the extreme pressure agent and the oily agent is 0.1% by mass or more and 5% by mass or less of the entire conductive grease composition G. 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.

Of the two types of carbon black, the first carbon black has an average primary particle size of 10 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. The second carbon black has an average primary particle size of 10 nm to 200 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 mass ratio of the first carbon black and the second carbon black contained in the conductive grease composition G is 25:75 or more and 95: 5 or less, and the total of the first carbon black and the second carbon black is Content is 1.5 to 20 mass% of the whole conductive grease composition G.
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.

As the base oil, mineral oil or synthetic oil is 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 with respect to the resin, fluorine oil and synthetic hydrocarbon oil are preferable, and poly α-olefin oil is particularly preferable. The kinematic viscosity at 40 ° C. of the synthetic hydrocarbon oil is preferably 10 mm ² / s or more and 500 mm ² / s or less.

In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment.
For example, a thickener may be added to the conductive grease composition G in order to adjust the penetration. The type of thickener is not particularly limited, but metal soap, metal composite soap, urea compound and the like are preferable.
Moreover, you may add additives other than an extreme pressure agent and an oil-based agent if desired. For example, an oxide film formation inhibitor, a conductivity improver, a commonly used antioxidant, rust inhibitor, and the like.

The oxide film formation inhibitor added as desired to the conductive grease composition G includes metal oxides, metal nitrides, metal carbides, clay minerals, cluster diamonds, and fullerenes having an average primary particle size of 5 nm to 10 μm. Of these, one or more powders are preferred. Specific examples include silica (silicon oxide), alumina (aluminum oxide), titanium oxide, zinc oxide, zirconium oxide, barium titanate, zirconium titanate, silicon nitride, zirconium nitride, chromium nitride, silicon carbide, titanium carbide, carbonized. tungsten, smectite, bentonite, boron nitride, carbon nitride, C ₆₀ fullerene, C ₇₂ fullerene, C ₈₄ fullerene, and the like. Among these, metal oxides such as magnesium oxide, zinc oxide and zirconium oxide are particularly suitable, and magnesium oxide is most suitable. The addition amount of the oxide film formation inhibitor is preferably 0.05% by mass or more and 5% by mass or less of the entire conductive grease composition G.

  The conductivity improver optionally added to the conductive grease composition G includes carbon nanotubes, carbon nanofibers, carbon nanohorns having a fiber length of 5 nm to 10 μm and an aspect ratio of 5 to 1000, One or more of carbon fibers and metal oxide whiskers are preferred. Among these, carbon nanotubes are particularly suitable. The addition amount of the conductivity improver is preferably 0.05% by mass or more and 5% by mass or less of the entire conductive grease composition G.

Furthermore, 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, in this embodiment, the deep groove ball bearing has been described as an example of the rolling device, but the type of the rolling bearing is not limited to the deep groove ball bearing, and the present invention is applicable to various types of rolling bearings. It can be applied to. For example, radial type 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.
Furthermore, the present invention can be applied not only to rolling bearings but also to various types of various rolling devices. For example, a ball screw, a linear guide device, a linear motion bearing, or the like.
〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples. 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 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, and carbon black B is Denka black manufactured by Denki Kagaku Kogyo Co., Ltd. HS-100 (average primary particle size 48 nm, specific surface area 39 m ² / g, DBP absorption 140 ml / 100 g), carbon black C is Tokai Carbon Co., Ltd. Seast S (average primary particle size 66 nm, specific surface area 27 m ² / g) The carbon black D 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.

[Evaluation of conductivity]
Grease shown in Tables 1 and 2 in the gap formed between the inner ring and outer ring of NSK 6806ZZ deep groove ball bearing (inner diameter 30 mm, outer diameter 42 mm, width 7 mm, with metal shield) The composition was sealed and rotated under the conditions described later, and the bearing resistance value (maximum value) during rotation was measured. The bearing resistance value was measured after 200 hours of rotation, 400 hours of rotation, and 800 hours of rotation. The amount of the grease composition enclosed in the gap formed between the inner ring and the outer ring of the deep groove ball bearing is 25% 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. 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.

The measurement conditions are shown below.
Rotational speed of the shaft member 12: 120 min ⁻¹
Radial load (Fr) applied to the bearing 11: 27.4N
Applied voltage: 30V
Resistance: 300kΩ
Maximum current: 100 μA
Atmospheric temperature: 60 ° C
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]
Grease shown in Tables 1 and 2 in the gap formed between the inner and outer rings of a deep groove ball bearing (inner diameter 8mm, outer diameter 22mm, width 7mm, with metal shield) No. 608ZZ made by NSK Ltd. The composition was sealed 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 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.
Rotational speed: 150 min ^-1
Axial load (Fa): 27.4N
Atmospheric temperature: Normal temperature

The results are summarized in Tables 1 and 2. In addition, the numerical value of the torque of Table 1, 2 is shown by the relative value when the torque of the deep groove ball bearing of Example 1 is set to 1 both at the time of starting 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 8 have smaller bearing resistance values (excellent conductivity) even at high temperatures than the deep groove ball bearings of Comparative Examples 1 and 2. . Moreover, the deep groove ball bearings of Comparative Examples 1 and 2 having a carbon black content of 30% by mass or more had higher torque than the deep groove ball bearings of Examples 1 to 8.

  The present invention is applicable to, for example, 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 longitudinal cross-sectional view explaining the structure of the deep groove ball bearing which is one Embodiment of the rolling device which concerns on this invention. It is a schematic block diagram of the apparatus which measures a bearing resistance value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 1a Raceway surface 2 Outer ring 2a Raceway surface 3 Rolling element G Conductive grease composition

Claims (9)

In a conductive grease composition containing a base oil, carbon black and an additive,
The base oil contains at least one of mineral oil and synthetic oil,
The carbon black has a primary carbon black having an average primary particle size of 10 nm to 200 nm and a specific surface area of 20 m ² / g to 80 m ² / g, an average primary particle size of 10 nm to 200 nm, and a specific surface area. Containing 200 m ² / g or more and 1500 m ² / g or less of second carbon black,
The additive contains at least one of an extreme pressure agent and an oily agent, and the total content of the extreme pressure agent and the oily agent is 0.1% by mass or more and 5% by mass or less of the entire composition. A conductive grease composition.   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 conductive grease composition as 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 whole composition The conductive grease composition according to claim 1 or 2, wherein the conductive grease composition is 1.5 mass% or more and 20 mass% or less. The conductive grease composition according to any one of claims 1 to 3, wherein the synthetic oil is a synthetic hydrocarbon oil having a kinematic viscosity at 40 ° C of 10 mm ² / s to 500 mm ² / s. object.   One or more powders of metal oxides, metal nitrides, metal carbides, clay minerals, cluster diamonds, and fullerenes having an average primary particle size of 5 nm or more and 10 μm or less are 0.05% by mass or more and 5% by mass of the entire composition. The conductive grease composition according to any one of claims 1 to 4, which is contained in an amount of not more than%.   One or more carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon fibers, and metal oxide whiskers having a fiber length of 5 nm to 10 μm and an aspect ratio of 5 to 1000 are added to 0.05% of the total composition. The conductive grease composition according to claim 1, wherein the conductive grease composition is contained in an amount of 5% by mass or more and 5% by mass or less.   The conductive grease composition according to any one of claims 1 to 6, wherein the blending penetration is 200 or more and 300 or less.   It is an object for rolling bearings, The electrically conductive grease composition as described in any one of Claims 1-7 characterized by the above-mentioned.   An inner member having a raceway surface on the outer surface, an outer member having a raceway surface opposite to the raceway surface of the inner member, and arranged on the outer side of the inner member, and rolling between the both raceway surfaces In a rolling device provided with a plurality of rolling elements arranged freely, in a crevice formed between the inner member and the outer member, The rolling device according to any one of claims 1 to 7 A rolling device characterized by comprising a conductive grease composition of

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