JP5252290B2 - Conductive rolling bearing - Google Patents

Description

  The present invention is used for supporting rotating parts such as electrostatic transfer copying machines, and is provided with conductive rolling bearings having conductivity capable of discharging static electricity, conductive rolling bearings for electrostatic transfer copying machines, and electrostatic transfer copying machines. The present invention relates to a conductive roller bearing for a fixing roller and a method for manufacturing the conductive roller bearing.

  In general, an electrostatic transfer copying machine such as a digital PPC or a color PPC, or an electrophotographic process device such as a laser beam printer or a color LED printer, is provided with a discharge mechanism for supporting rotating parts.

  For example, in the case of an electrostatic transfer copying machine, an electrostatic latent image is formed on a photosensitive drum, toner is attached, and a visible image formed on the photosensitive drum is transferred to printing paper by charging a transfer electrode. The printing paper released from the photosensitive drum is then sent to a fixing unit roll, and the toner is fixed on the paper surface by heating and pressing. During such a printing process, static electricity is generated in parts such as a fixing unit roll through which the printing paper comes into contact.

As a means for escaping this static electricity to the outside, a mechanism for grounding and discharging the roll shaft end is generally provided.
However, since the number of parts increases when a static electricity discharge mechanism is provided at the end of the roll shaft, the number of parts can be reduced by using a conductive bearing (also referred to as a current-carrying bearing) in which the roll bearing itself is made conductive. I am trying.

  Known conventional conductive bearings include those in which conductive grease is sealed inside the bearing (Patent Document 1), or those in which a current-carrying seal or current-carrying member is attached to the bearing.

  Also known is a rolling bearing in which the shaft portion of the rotating member and the inner ring are made conductive by forming a graphite (graphite) film having electrical conductivity and low friction sliding properties on the inner diameter surface of the inner ring or the outer diameter surface of the outer ring. (Patent Document 2). As a method for forming a film on the inner ring inner diameter surface or the outer ring outer diameter surface, coating by vapor deposition, dipping using a resin dispersion, or the like is employed.

JP 2002-053890 A JP 2008-008452 A

  However, in the above-described conventional conductive rolling bearing filled with conductive grease, the change in the bearing resistance value indicating conductivity is unstable over time, and the low conductivity cannot be obtained stably over time. There is.

  For example, if a rolling bearing (small-diameter ball bearing) filled with conductive grease containing conductive carbon is used at room temperature at a bearing load of 12.3 N and 130 rpm, the resistance value becomes unstable after about 1 hour of use. (See FIG. 7).

  In addition, the conventional rolling bearing formed with the graphite (graphite) film described above has a conductive graphite film for the outer ring or inner ring to be tightly fitted. Without the use of this, sufficient conductivity could not be obtained, and as a result, the disadvantage of conductivity due to the conventional conductive grease appeared, that is, the stability with time of low bearing resistance could not be obtained.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a conductive material that can obtain a low rotational torque and sufficient conductivity with stability over time without enclosing conductive grease in a rolling bearing. It is to make a sex rolling bearing.

  In order to solve the above problems, in the present invention, in a rolling bearing in which a plurality of rolling elements are rotatably held by a cage between an inner ring and an outer ring, the surface of the cage or the rolling element or both parts is expanded. This is a conductive rolling bearing characterized by providing a conductive resin film containing graphite oxide.

  The conductive rolling bearing of the present invention configured as described above is provided with a conductive resin film containing expanded graphite on the surface of the cage, the rolling element, or both parts. By the sliding contact, a sufficient amount of finely expanded graphite is rapidly supplied between the components of the rolling bearing.

  In expanded graphite, volatile foreign molecules such as sulfuric acid and nitric acid are inserted between carbon mesh planes, and these are gasified by heating, etc., and the interlayer of the graphite is expanded in the C-axis direction by the pressure of the generated gas. It is expanded and manufactured after washing and removing residual ion components such as sulfate ions and nitrate ions by washing with water and the like, and drying. Since such expanded graphite has excellent adhesion between expanded graphite, it can be shaped by compressive force without a binder, and there is little resistance loss between expanded graphite particles, and it exhibits excellent conductivity. In addition, the solid lubricating action can be exhibited. Even when dispersed in the resin, it exhibits a solid lubricating action and excellent conductivity due to the connectivity between the expanded graphites.

  Therefore, the conductive rolling bearing of the present invention in which the conductive resin film containing expanded graphite is formed on the surface of the cage, the rolling element, or both parts has a low rotational torque without enclosing the conductive grease. It becomes an electroconductive rolling bearing from which sufficient electroconductivity is obtained with stability over time.

  A conductive rolling bearing in which a conductive resin film is provided on the surface of at least one of the plurality of rolling elements to ensure solid lubrication and conductive action by the expanded graphite is obtained. It is preferable. The surface of the rolling element is in sliding contact with the cage as the rolling bearing rotates, and the inner and outer rings are frequently in rolling frictional contact. A sufficient amount of expanded graphite powder is supplied from the start. Conductivity and solid lubricity can be exhibited.

  If such a rolling element is formed of a steel ball, the conductive resin film on the surface of the rolling element is worn, and even if the base material is exposed, the conductivity can be maintained. It becomes a conductive rolling bearing with good durability.

In addition, as described above, a conductive resin film containing expanded graphite is formed on the surface of the cage or rolling element or both parts, and the conductive material containing expanded graphite on the surface of the inner ring or outer ring or both parts. It is also preferable to use a conductive rolling bearing formed with a resin film.
This is because, when the rolling element and the cage come into contact with each other, the expanded graphite is swiftly supplied from the surface of the cage or rolling element or both parts by sliding friction to the important points in the bearing. This is because a predetermined amount of expanded graphite is stably supplied even by contact due to rolling friction between the rolling elements and the inner and outer rings, so that stable conductivity and solid lubricity for a long time can be maintained. .

  If the inner ring or outer ring or the base material of both parts is a conductive rolling bearing made of conductive polyarylene sulfide resin, it is lighter than steel inner and outer rings, and a conductive agent such as carbon black is used. Even if the surface of the rolling element or the surface of the cage is worn and the base material is exposed due to wear, the expanded graphite can be expanded by contact between the rolling element and the inner and outer rings. Powder can be generated to maintain conductivity, and the conductivity of the inner and outer rings themselves can provide a highly durable conductive rolling bearing. As a representative example of the conductive polyarylene sulfide resin as the base material of the inner ring or the outer ring or both parts, a conductive polyphenylene sulfide resin can be mentioned.

  In addition, any of the above-described conductive rolling bearings can exhibit particularly advantageous effects when used for appropriate applications, and electrostatic transfer copying that supports the shaft of a rotating part of an electrostatic transfer copying machine. Machine-use conductive rolling bearings can prevent static improper electrostatic transfer due to electrification by reliably discharging static electricity outside the rotating parts by providing sufficient conductivity with stability over time. . In particular, the conductive rolling bearing for an electrostatic transfer copying machine having the above-described configuration that supports a fixing roller as a rotating member of the electrostatic transfer copying machine is effective for stabilizing a printed image.

  As an example of the method for producing a conductive rolling bearing having such a configuration, the above-mentioned conductive rolling bearing retainer or one or more rolling elements or both components are mixed with expanded graphite, a resin binder, and a solvent. When the parts obtained are assembled by immersing them in a liquid, then taking them out of the mixed solution, and drying the coating film formed on the surface of these parts, An excellent conductive rolling bearing can be produced in which sufficient conductivity can be obtained with stability over time even without sealing.

  In addition, as an example in the above-described method of manufacturing a conductive rolling bearing, in addition to a cage or one or more rolling elements or both parts, an inner ring or an outer ring or both parts are mixed with expanded graphite, a resin binder, and a solvent mixture. After dipping, and then drying the coating film on the surface of these components taken out from the mixed solution to form a conductive resin film, and assembling the obtained conductive components, there is further excellent durability for conductivity, An excellent conductive rolling bearing can be produced in which sufficient conductivity can be obtained with stability over time without encapsulating conductive grease.

  Since this invention is a conductive rolling bearing in which a conductive resin film containing expanded graphite is formed on the surface of a cage or rolling element or both parts, the excellent conductivity and solid lubricating action of expanded graphite are achieved. Thus, the conductive rolling bearing can be obtained efficiently, and sufficient conductivity can be obtained with stability over time without enclosing conductive grease in the rolling bearing.

  In addition, the conductive rolling bearings for electrostatic transfer copiers that support the shafts of rotating parts of electrostatic transfer copiers reliably discharge static electricity to the outside of the rotating parts to prevent electrostatic transfer improperness due to charging. Can do. In particular, the conductive rolling bearing for an electrostatic transfer copying machine having the above-described configuration that supports a fixing roller as a rotating member of the electrostatic transfer copying machine is effective for stabilizing a printed image.

  Further, as an example of the manufacturing method, a conductive rolling bearing retainer or one or more rolling elements or both parts are immersed in a mixture of expanded graphite, a resin binder and a solvent, dried and fixed. By forming a conductive resin film and assembling the obtained parts, it is possible to produce an excellent conductive rolling bearing that can obtain sufficient conductivity with time-stable stability without encapsulating conductive grease. .

  Further, as an example of the manufacturing method, in addition to the cage or the one or more rolling elements or both parts, the inner ring or the outer ring or both parts are immersed in a liquid mixture of expanded graphite, a resin binder and a solvent, and the surface of these parts. If a conductive resin film is formed by drying the coating film and the conductive parts are assembled, it has excellent durability in terms of conductivity and sufficient conductivity over time without encapsulating conductive grease. An excellent conductive rolling bearing obtained with excellent stability can be manufactured.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, the embodiment is a rolling bearing having a cage 4 that rotatably holds a plurality of rolling elements 3 made of steel balls between an inner ring 1 and an outer ring 2, and the cage. 4, a conductive rolling bearing in which conductive resin films 1 a, 2 a, 3 a, 4 a containing expanded graphite are formed on the surfaces of the rolling elements 3, the inner ring 1 and the outer ring 2.

  The expanded graphite blended in the conductive resin films 1a, 2a, 3a, and 4a shown in FIG. 1 thermally decomposes a compound such as sulfuric acid intercalated between the graphite crystal layers, expands the layers, and extends in the C-axis direction. Inflated.

  Expanded graphite is also simply referred to as expanded graphite. Graphite (graphite) in which the space between hexagonal mesh planes (0.3354 nm = 3.354 mm) forming the crystal layer structure of ordinary graphite is positively expanded by thermal expansion. However, the van der Waals force due to the π-electron layer bonding the layers is weakened by the spread of the layers, the layers are easily sheared, and the composition has low friction characteristics due to the slip between the layers. And exhibits good electrical conductivity.

  Expanded graphite, for example, after processing highly crystallized graphite such as natural graphite, quiche graphite, pyrolytic graphite, etc., with a treatment solution in which hydrogen peroxide is added to sulfuric acid, nitric acid, a mixture of sulfuric acid and nitric acid, etc. It is obtained by rapid heating and expanding the C-axis direction of the graphite crystal. A specific production method is that natural graphite powder is usually wet-oxidized with a strong acid such as concentrated sulfuric acid or concentrated nitric acid, and this is rapidly heated to a high temperature of 800 ° C. or more, preferably about 1000 ° C., thereby expanding the crystal layer spacing. Can be manufactured. The expanded graphite produced in this manner usually contains residual ions such as highly corrosive sulfate ions and nitrate ions, and thus is washed and removed by washing with water. Examples of commercially available expanded graphite include EP manufactured by Nippon Graphite Co., Ltd. and KEX manufactured by Nippon Graphite Co., Ltd.

  Such expanded graphite is used in a powdered state, but the average particle diameter is 1 to 10 μm, from the viewpoint of sufficiently exhibiting uniform dispersibility in the resin and conductivity and lubricity. From this, it is preferably 3 to 7 μm.

An appropriate amount of a resin binder is blended and mixed with powdered expanded graphite as a binder, and then formed as a conductive graphite film on the surface of the bearing component. As the film formation method, dipping (dipping), coating, spray spraying, etc., and other known film formation methods can be adopted, and the film composition can be adjusted using a solvent such as water or a solvent according to the film formation method. It can be set as the mix | blended dispersion solution.
If necessary, a liquid additive such as an ionic liquid soluble in a solvent can be added to improve conductivity, improve conductivity stability, improve quietness, and the like.

  The resin binder to be used may be any of a thermoplastic resin, a thermosetting resin, a curable resin by electromagnetic waves or radiation, for example, polyurethane, vinyl chloride / vinyl acetate copolymer, polyester, polyacrylonitrile, polymethylmethacrylate. Acrylate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, cellulose acetate, ethylene / vinyl acetate copolymer, phenol resin, epoxy resin, melamine resin, polyvinylidene difluoride resin and other fluororesins, ketones and esters And polyvinylidene fluoride resin, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, which is a highly soluble fluororesin. The specific gravity of the expanded graphite particles is larger than that of ordinary organic solvents and water, and they tend to settle in these liquids. Therefore, it is particularly preferable to use a resin soluble in the solvent to expand the expanded graphite in the dispersion. / Preferable for ensuring uniform dispersibility of resin and binding property due to resin.

  As the film composition, the volume ratio of expanded graphite to resin binder is 10: 1 to 25: 1 when expanded graphite: resin binder is used. The amount of solvent can be adjusted to a viscosity suitable for the coating film forming method. For example, in the case of dip coating (dipping), it is diluted about 4 to 10 times with respect to the film component. When the volume ratio of the expanded graphite and the resin binder is less than the predetermined range, the lubricity and the conductivity are insufficient. When the volume ratio exceeds the predetermined amount, the binder resin that plays a role as a binder for the coating is relatively small. Therefore, the adhesion strength to the base material is undesirably lowered.

  As solvents for these resins, alcohols, ketones, ester solvents and the like can be selected and used depending on the resin.

The coating amount of the conductive resin film is in the range of 1 to 4 mg / cm ² is preferred. If the coating amount exceeds the above range, there is a risk of problems in rigidity, strength, accuracy, etc. as a rolling bearing. If the coating amount is less than 1 to 4 mg / cm ² , the lubricity and conductivity durability are not sufficient. Because.

  As the base material for the inner and outer rings, the cage, and the rolling element of the rolling bearing of the present invention, a well-known metal material for bearings can be used. Resin can also be employed. Specific examples of the metal material include bearing steel (high carbon chromium bearing steel JISG4805), case-hardened steel (JISG4104, etc.), high speed steel (AMS6490), stainless steel (JISG4303), induction hardened steel (JISG4051 etc.). It is done.

  The polyarylene sulfide resin is a well-known resin having a structure in which aromatic groups are connected by a thioether bond. For example, a polyphenylene sulfide resin (hereinafter abbreviated as a PPS resin) can be given as a representative example. Incidentally, the PPS resin has a repeating unit structure in which aromatic groups are connected by a thioether bond.

  As shown in FIGS. 1 and 2, the conductive rolling bearing manufactured as described above is applied to a fixing device of an electrostatic image forming apparatus. The fixing roller 5 is made of a soft metal in which a linear or rod-like heater 6 is built in a shaft center portion, and is formed in a cylindrical shape with a small-diameter shaft portion 5a protruding at both ends.

  The fixing roller 5 is made of a metal material having excellent thermal conductivity such as aluminum or aluminum alloy (A5056, A6063, etc.), and the surface is finished by turning or polishing, and the surface is non-adhesive such as fluororesin. High resin is coated. The fixing roller 5 is rotatably supported by a housing 8 via a conductive rolling bearing 7 formed of a deep groove ball bearing with small-diameter shaft portions 5a at both ends, and a gear (not shown) that receives rotational power at a separate end. Is provided.

A pressure roller (not shown) is provided in contact with the fixing roller 5 in parallel, and it is preferable that both ends of the pressure roller are rotatably supported by the housing 8 via conductive rolling bearings.
The pressure roller is typically a core metal such as iron or aluminum with a coating made of silicon rubber or the like, but like the fixing roller, a linear or rod-like heater is attached to the axial center of the pressure roller. Some are built-in and are supported by bearings at both ends with conductive rolling bearings.

The copy paper is sent between the rotationally driven fixing roller 5 and the driven pressure roller, and the toner image is fixed by heat fusion by the fixing roller 5.
Therefore, the electrostatic image forming apparatus in which the conductive rolling bearing is mounted for supporting the roller is not charged and does not disturb the image of the electrostatic image, and the fixing device including such an electrostatic image forming apparatus is The image fixing function can be exhibited stably and in good condition over time.

[Example 1]
A conductive resin film containing expanded graphite (expanded graphite: resin binder = 10: 1 to 25: 1) is applied to a cage of a small diameter ball bearing (inner diameter 30 mm × outer diameter 42 mm × width 7 mm). An amount of 2 mg / cm ^{2 was} provided.
The expanded graphite used is made by Nippon Graphite Industries Co., Ltd., and the electrical resistance value between the inner ring surface of the inner ring and the outer ring surface of the outer ring was measured over time for the obtained conductive rolling bearing. Are shown in FIG. 3 and Table 1.

[Example 2]
In Example 1, a conductive rolling bearing was manufactured in exactly the same manner except that one steel ball coated with ordinary graphite powder was used as the rolling element, and the electrical resistance value was measured in the same manner as in Example 1. The results are also shown in FIG. 4 and Table 1.

[Example 3]
In Example 1, the inner ring used was a conductive PPS resin (resin material containing 30% by weight of conductive carbon black in PPS resin, resistance value 2.2 × 10 ² Ω · cm). Except for the above, a conductive rolling bearing was produced in the same manner, and the electric resistance value was measured in the same manner as in Example 1. The results are also shown in FIG.

[Example 4]
In Example 3, a conductive rolling bearing was manufactured in exactly the same manner except that one steel ball coated with ordinary graphite powder was used as the rolling element, and the electrical resistance value was measured in the same manner as in the above example. The results are also shown in FIG.

[Comparative Example 1]
A mixture of 70% by weight of lubricating grease based on poly-α-olefin oil and 30% by weight of conductive carbon is used as a conductive grease, which is enclosed in a small-diameter ball bearing formed of bearing steel in the same type as in Example 1. The electrical resistance value between the inner diameter surface of the inner ring and the outer diameter surface of the outer ring was measured, and the result of rotating at a bearing load of 12.3 N and 130 rotations / minute at room temperature is shown in FIG.

  As is clear from the results of Comparative Example 1, the conductive rolling bearing of the comparative example using conductive grease becomes unstable after about one hour of use, and shows a maximum bearing resistance value of 30Ω. It was.

  On the other hand, as is apparent from the results of Table 1 and FIGS. 3 to 6, the conductive rolling bearings of Examples 1 to 4 have a bearing resistance value of 4.8 to 11.8 kΩ even without encapsulating conductive grease. It can be seen that good conductivity is obtained with stability over time.

Cross-sectional view of main parts of conductive rolling bearing and fixing roller of embodiment Sectional view of the fixing roller of the embodiment Chart showing the relationship between the resistance value and time of the conductive rolling bearing of Example 1 The table | surface which shows the relationship between the resistance value of the electroconductive rolling bearing of Example 2, and time The table | surface which shows the relationship between the resistance value of the electroconductive rolling bearing of Example 3, and time The table | surface which shows the relationship between the resistance value of the electroconductive rolling bearing of Example 4, and time Chart showing the relationship between resistance value and time of the conductive rolling bearing of Comparative Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 1a, 2a, 3a, 4a Conductive resin film 2 Outer ring 3 Rolling element 4 Cage 5 Fixing roller 5a Small diameter shaft part 6 Heater 7 Conductive rolling bearing 8 Housing

Claims (10)

In a rolling bearing in which a plurality of rolling elements are rotatably held by a cage between an inner ring and an outer ring,
A conductive resin film containing powdered expanded graphite on the surface of the cage or rolling element or both parts so that the volume ratio of expanded graphite: resin binder is 10: 1 to 25: 1. A conductive rolling bearing characterized by being provided.   The conductive rolling bearing according to claim 1, wherein a conductive resin film is provided on a surface of one or more of the rolling elements.   The conductive rolling bearing according to claim 1, wherein the rolling element is a steel ball. In the conductive rolling bearing according to any one of claims 1 to 3,
A conductive rolling bearing characterized in that a conductive resin film containing expanded graphite is formed on the surface of the inner ring or outer ring or both parts.   The conductive rolling bearing according to any one of claims 1 to 4, wherein the inner ring or the outer ring or the base material of both parts is a conductive polyarylene sulfide resin.   The conductive rolling bearing according to claim 5, wherein the conductive polyarylene sulfide resin is a conductive polyphenylene sulfide resin.   A conductive rolling bearing for an electrostatic transfer copying machine comprising the conductive rolling bearing according to claim 1 and supporting a shaft of a rotating part of the electrostatic transfer copying machine.   The conductive rolling bearing for an electrostatic transfer copying machine according to claim 7, wherein the rotating part of the electrostatic transfer copying machine is a fixing roller. A rolling bearing cage in which a plurality of rolling elements are rotatably held by a cage between an inner ring and an outer ring, or one or more rolling elements or both components are expanded graphite, a resin binder and a solvent mixture , The powdered expanded graphite is immersed in a mixed liquid containing a volume ratio of expanded graphite: resin binder of 10: 1 to 25: 1, and then taken out from the mixed liquid and formed on the surface of these parts. The manufacturing method of the conductive rolling bearing which dries the coated film, forms a conductive resin film, and assembles the obtained components. In conducting rolling method according to claim 9, together with the cage, or one or more rolling elements, or both parts, by immersing the inner ring or outer ring, or both parts expanded graphite, the mixture of resin binder and a solvent, Next, a method of manufacturing a conductive rolling bearing in which the coating film on the surface of the component taken out from the mixed solution is dried to form a conductive resin film, and the obtained conductive component is assembled.

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