JP2008133877A - Conductive rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain rotational torque by preventing a stain caused by grease leakage and a carbon particulate, when manufacturing a conductive rolling bearing. <P>SOLUTION: Instead of introducing conductive grease, contact parts 11a, 12a and 13 of mutually contacting raceway surfaces or rolling bodies are covered with a conductive lubricating coating film up to an outer ring from a shaft of the conductive rolling bearing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rolling bearing having conductivity, and more particularly to a rolling bearing used in a photosensitive drum.

  In general, a photosensitive drum that is rotatably supported is used in a copying machine or a printing machine using an electrophotographic apparatus such as an electrostatic transfer copying machine or a color LED type or color LBP type printing machine. An electrostatic latent image is formed on the surface of the photosensitive drum, and toner is charged and adhered to the surface. The visible image formed by the toner is transferred onto the printing paper, and the toner image is printed on the paper. .

  However, if the roller bearing for the roll used to rotatably support the photosensitive drum is charged, the charged charge affects the charge charged on the surface of the photosensitive drum and the toner adhering thereto. An electrostatic latent image or a visible image due to toner is disturbed. For this reason, it is necessary to discharge outside so that the bearing is not charged. For this reason, a conductive rolling bearing is used in which the constituent parts are made of a conductive material and the grease is conductive. As the conductive grease used here, for example, as described in Patent Documents 1 and 2, a powder obtained by mixing fine powder of conductive carbon such as graphite with grease as a conductive substance and thickener is used.

JP 2002-538901 A JP 2004-162909 A

  However, since such conductive grease uses carbon as a conductive material and a thickening agent, the base oil of the grease is poorly thickened and easily separated. The separated base oil may contaminate the periphery of the bearing and the photosensitive drum surface. In order to prevent this, when using a sealed rolling bearing in which a space for sealing grease is sealed with a sealing member as shown in FIG. 2 of Patent Document 2, there is a problem that torque during rotation increases. Also, there is a problem that the structure around the bearing is complicated and difficult to manufacture.

  In addition, if conductive grease adheres to parts other than the parts required for the bearing or workbench at the time of sealing, it is difficult to remove the dirt because the fine carbon powder contained is too fine. There was a problem that dirt was conspicuous.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive rolling bearing having a reduced possibility of contaminating the periphery of the bearing and connected components without complicating the structure of the bearing.

  The present invention solves the above problem by covering the contact surface of the bearing with a conductive lubricating film instead of introducing conductive grease.

  That is, by forming a coating film having conductivity and lubricity on the raceway surface or the surface of the rolling element having surfaces in contact with each other between the shaft and the outer ring of the bearing, a liquid is produced in the production of the conductive rolling bearing. Therefore, it is not necessary to use carbon fine powder for imparting electrical conductivity to liquid grease.

  With the conductive rolling bearing according to the present invention, it is possible to prevent the bearing from being charged due to grease leakage during use or during use, prevent charging of the bearing, and realize stable rotation over a long period of time. In addition, since it does not require a contact-type rubber seal to prevent grease leakage, it can be made simpler with an iron plate seal, making it easier to manufacture than a conductive rolling bearing using grease. . Furthermore, since there is no need for sealing, there is no rotational torque due to the contact of the seal, so the burden on the device can be reduced.

  Hereinafter, the present invention will be described in detail. As shown in FIG. 1, the present invention holds an inner ring 11 and an outer ring 12 having raceway surfaces 11 a and 12 a facing each other, a plurality of rolling elements 13 in contact with both raceway surfaces 11 a and 12 a, and the rolling elements 13. A rolling bearing provided with a cage 14 that covers at least one surface of both the raceway surfaces 11a and 12a or the rolling element 13 with a conductive lubricating film. An example of such a rolling bearing is one that rotatably holds a shaft 15 (not shown in FIG. 1) connected to the inner ring 11.

  The rolling element 13 is a cylinder or a ball that contacts the inner ring 11 and the outer ring 12 and can roll between them. The cage 14 is provided between the inner ring 11 and the outer ring 12 to fix the position of each rolling element 13.

  The raceway surface 11a and the rolling element 13 and the raceway surface 12a and the rolling element 13 are in contact with each other. In order to provide conductivity and lubricity to the contact portion, the raceway surface 11a and the rolling element 13 are covered with the conductive lubricating film. There is a need. When the conductive lubricant film is applied only to the raceway surface, it is necessary to cover both the raceway surface 11a of the inner ring 11 and the raceway surface 12a of the outer ring 12 with the conductive lubricant film.

  Further, the surface of the cage 14 may be covered with the conductive lubricating film. Since the retainer 14 is also in contact with the rolling element 13, lubricity is required for this contact portion. For this reason, in the case where the raceway surfaces 11a and 12a are covered with the conductive lubricant film without covering the rolling element 13 with the conductive lubricant film, the lubricity between the rolling element 13 and the cage 14 is ensured. The surface of the cage 14 may be covered with a lubricating film, or may be covered with the conductive lubricating film.

The conductive lubricating coating refers to a coating that has conductivity and can function as a solid lubricant. The substance constituting this film preferably has a volume resistivity of 10 ³ Ω · cm or less as a preferable conductivity value. The preferred volume resistivity of the conductive grease using fine carbon powder that has been conventionally used is 10 ³ Ω · cm. In this invention as well, if the volume resistivity is equal to or less than that, the charge of the bearing is made conductive. This is because the effect of preventing electrification is sufficiently obtained. When it exceeds 10 ³ Ω · cm, the resistivity increases, and the charge may not be negligible. In addition, volume resistivity is so preferable that it is small, and a minimum in particular is not restrict | limited.

  Further, the substance constituting the conductive lubricating film preferably has a coefficient of friction of 0.2 or less as a preferable lubricity value. If it exceeds 0.2, the force received by friction becomes strong, and the torque during rotation may become too large. In addition, it is so preferable that a friction coefficient is small, and a minimum in particular is not restrict | limited.

  Specific examples of such a substance include graphite, polytetrafluoroethylene (hereinafter abbreviated as “PTFE”)-containing nickel (hereinafter abbreviated as “Ni-PTFE”), and the like. . Among these, Ni-PTFE is a material in which fine particles of PTFE are dispersed in nickel metal to improve lubricity. When the volume mixing ratio of PTFE and nickel of this material is 5:95 to 30:70, it can be handled as a material that gives good conductivity and lubricity.

  Specifically, when the volume mixing ratio of PTFE and nickel is 5:95, the volume resistivity is 0.006 Ω · cm, and when the volume mixing ratio is 30:70, the volume resistivity is 0.010 Ω. -Cm. In addition, by providing a Ni-PTFE film having a friction coefficient of about 0.4 to 0.5 in the absence of a conductive lubricating film, the volume mixing ratio of any of the above is 0.11 to 0.00. It can be about 15. Even when a graphite film or a film made only of PTFE is provided, the friction coefficient is about 0.2 to 0.5.

  There is no particular limitation on the method for generating the conductive lubricating film using these materials on the surfaces of the bearing raceways 11a and 12a, the rolling elements 13 and the cage 14, but when graphite is used due to the properties of the materials. It is preferable to use a sputtering process or a coating process because it is easy to process. Specifically, this coating treatment includes a method in which a graphite coating liquid suspended in a solvent together with a binder resin is applied to a product by spraying and then baked. In the case of using Ni-PTFE, it is preferable to use an electroless plating process because it is easy to process. In addition, when producing | generating the electroconductive lubricating film of Ni-PTFE by electroless plating, the electroconductive lubricating film contains phosphorus other than Ni and PTFE on account of a manufacturing process.

  The thickness of these conductive lubricating coatings depends on the material, but when Ni-PTFE is used, the grease life is reduced by the influence of wear powder, so the thickness is preferably 1 to 10 μm. Although it does not specifically limit in the case of the material which does not contain a metal like graphite, It is good in manufacture to be 3-10 micrometers.

  Further, in the entire conductive rolling bearing according to the present invention, the resistance value between the metal shaft 15 connected without sandwiching the insulator to the inner ring 11 and the metal part connected to the outer ring 12 may be 50 kΩ or less. preferable. If this resistance value exceeds 50 kΩ, there is a high risk that a component connected to the shaft 15 such as a photosensitive drum used in an electrophotographic apparatus to be rotatably supported will be charged without being able to ground the outside. It is.

  In the conductive rolling bearing according to the present invention, both surfaces of the bearing raceways 11a and 12a and the rolling element 13 may be covered with the conductive lubricating film, and the surface of the cage 14 may be covered with the conductive material. It may be covered with a lubricating film.

  When a plurality of surfaces of the raceway surfaces 11a and 12a, the rolling elements 13 and the cage 14 are covered with the conductive lubricating film, all of them are covered with graphite or Ni-PTFE. Alternatively, a combination of the two materials may be used so that one of them contacting with each other is covered with graphite and the other is covered with Ni-PTFE. That is, when the two materials are used in combination, the surface of the rolling element 13 is covered with the conductive lubricating film using one of graphite or Ni-PTFE, and both the raceway surfaces 11a, 12a and At least one of the cages 14 is covered with the conductive lubricating film using the other of graphite or Ni-PTFE. As a result, when the conductive lubricating film made of graphite and the conductive lubricating film made of Ni-PTFE come into contact with each other on the contact surface, the conductive lubricating film made of softer graphite is worn first, so that Ni-PTFE is used. The conductive lubricating coating due to can be made hard to wear. Further, even if the conductive lubricating coating made of graphite is worn, the role of the lubricant can be maintained if the coating remains.

  Further, when the raceway surface 11a of the inner ring 11 and the raceway surface 12a of the outer ring 12 are covered with the conductive lubricating film, graphite may be covered on one side and Ni-PTFE on the other side, or both may be the same. May be covered with the conductive lubricating film. In addition, when the cage 14 is further covered with the conductive lubricating film, either graphite or Ni-PTFE may be selected and used.

  In order to obtain a conductive rolling bearing according to the present invention, a metal material generally used for a bearing can be used as it is as the original bearing material covered with the conductive lubricating film.

  The conductive rolling bearing according to the present invention rotatably supports the shaft of a photosensitive drum used in an electrophotographic apparatus such as an electrostatic transfer copying machine such as a PPC or a color LED type or color LBP type printing machine. Can be used. The electrophotographic apparatus in which the photosensitive drum is rotatably supported by using the conductive rolling bearing according to the present invention prevents grease leakage and contamination due to carbon fine particles, which are problems in the conductive rolling bearing using the conventional conductive grease. be able to. In addition, it is possible to support the photosensitive drum while ensuring sufficient conductivity, and it is possible to rotate the photosensitive drum with a sufficiently low torque.

The effects of the present invention will be specifically described below with reference to examples. First, the material of the conductive lubricating film used in the examples and the material of the non-conductive lubricating film used in the comparative example are shown.
・ Graphite …… Sumitomo Lubricant Co., Ltd .: Dry coat 1410
Ni-PTFE: Volume mixing ratio of PTFE and nickel = 70: 30

  NTN Co., Ltd. product: 6806 (component material: SUJ2) was used as the original bearing for forming the conductive lubricating coating. A coating having a thickness of 5 μm was formed on each bearing component using the materials shown in the following examples and comparative examples. The graphite was sputtered to produce a conductive lubricating coating, and the Ni-PTFE was electrolessly plated. PTFE was subjected to a coating treatment.

The conductivity and durability of each bearing were evaluated using the measuring instrument shown in FIG. In the figure, the arrow indicates a radial load of 49 N, the bearing 21 is set so as to receive the rotation of the shaft 15, and the resistance value is measured between the measurement terminal 31 outside the bearing and the measurement terminal 32 connected to the shaft 15. did. In the evaluation of conductivity, the measurement was performed in a state where rotation of 100 min ⁻¹ was applied by the driving pulley 33. The measurement circuit is as shown in FIG. 3, which includes a power source 51, a 300 kΩ control resistor 52, and a voltmeter 53. The resistance value between the measurement terminals 31 and 32 corresponding to the measurement circuit 54 was measured. Those having a resistance value of less than 50 kΩ were evaluated as “good”, and those having a resistance value of 50 kΩ or more were evaluated as “x”.

Further, in the durability evaluation test, the rotation given by the driving pulley 33 was set to 300 min ^−1, and the case where no abnormal noise was generated until 200 hours passed was evaluated as “good”, and abnormal noise was generated before 200 hours passed. Things were rated as x.

Examples 1 and 2 and Comparative Example 1
Table 1 shows the evaluation results of the conductivity and durability of the examples in which the raceway surfaces of the inner and outer rings and the entire surface of the cage are covered with a coating using each material.

(Examples 3 and 4, Comparative Example 2)
Table 2 shows the evaluation results of the conductivity and durability of an example in which the entire raceway surfaces of the inner ring and the outer ring are covered with a coating using each material.

(Examples 5 and 6, Comparative Example 3)
Table 3 shows the evaluation results of the conductivity and durability of an example in which the surface of the ball, which is a rolling element, is covered with a coating using each material.

(Example 7)
The results of evaluating the conductivity and durability of an example in which the entire surface of the cage is covered with a conductive lubricating film using graphite and the surface of the ball as a rolling element is covered with a conductive lubricating film using Ni-PTFE. Table 4 shows.

(Example 8)
Evaluation of conductivity and durability of an example in which the surface of a ball, which is a rolling element, is covered with a conductive lubricating film using graphite, and the raceway surfaces of the inner and outer rings are covered with a conductive lubricating film using Ni-PTFE. The results are shown in Table 4.

Example 9
The results of evaluating the conductivity and durability of an example in which the surface of a ball, which is a rolling element, is covered with a conductive lubricating film using graphite and the entire surface of the cage is covered with a conductive lubricating film using Ni-PTFE. Table 4 shows.

Schematic of the part which provides the conductive lubricating film of the conductive rolling bearing according to the present invention Schematic diagram of the measuring instrument used in the examples Conceptual diagram of the measurement circuit used in the examples

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Inner ring 11a Raceway surface 12 Outer ring 12a Raceway surface 13 Rolling body 14 Cage 15 Shaft 21 Bearing 31, 32 Measurement terminal 33 Driving pulley 34 Fixing tool 51 Power supply 52 Control resistance 53 Voltmeter 54 Measurement circuit

Claims (6)

A rolling bearing comprising an inner ring and an outer ring having raceways facing each other, a plurality of rolling elements in contact with both raceways, and a cage for holding the rolling bodies at equal intervals,
A conductive rolling bearing in which both the raceway surfaces or at least one surface of the rolling element is covered with a conductive lubricating film.   The conductive rolling bearing according to claim 1, wherein a surface of the cage is covered with a conductive lubricating film. The conductive rolling bearing according to claim 1 or 2, wherein the conductive lubricating coating is made of a material having a volume resistivity of 10 ³ Ω · cm or less and a friction coefficient of 0.2 or less.   The conductive rolling bearing according to claim 3, wherein graphite or polytetrafluoroethylene-containing nickel is used as a substance constituting the conductive lubricating coating. The surface of the rolling element is covered with the conductive lubricating film using one of graphite or nickel containing polytetrafluoroethylene,
5. The conductive material according to claim 1, wherein at least one of the both raceway surfaces and the cage is covered with the conductive lubricating film using the other of graphite or nickel containing polytetrafluoroethylene. Rolling bearing.   An electrophotographic apparatus using the conductive rolling bearing according to claim 1 for supporting a photosensitive drum.

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