JP4989128B2 - Rolling bearing - Google Patents

Description

  The present invention relates to a rolling bearing that supports a rotating member such as a fixing roller of a fixing device for office equipment, and more particularly to a rolling bearing in which a shaft portion of the rotating member is fitted to one of the inner and outer rings by a clearance fit.

Rotating members such as fixing rollers and pressure rollers incorporated in office machines such as copiers and printers have their shaft parts (shafts) of the inner and outer rings of rolling bearings due to problems of assembly due to downsizing and simplification of the structure. Many of them are fitted to one of the race rings by a clearance fit (loose fit). For this reason, depending on use conditions, there is a possibility that creep may occur between the shaft portion fitted by clearance fitting and the race. Conventionally, in order to prevent wear of the fitting portion due to creep, there is a rolling bearing in which an oxide film is formed on the fitting portion of the race (see, for example, Patent Document 1). In what is described in Patent Document 1, when applied to a rolling bearing that supports a fixing roller that receives a thermal cycle, the oxide film also has an effect of preventing rusting due to condensation.
In addition, due to the clearance fit between the shaft portion of the rotating member and the bearing, there is a problem that abnormal noise such as a squealing sound is generated at the fitting portion during printing. Conventionally, the generation of abnormal noise is prevented by applying grease to the fitting portion or press-fitting the shaft.

  On the other hand, the fixing roller of a copying machine or printer that fixes toner on printing paper with heat and pressure is formed in a hollow with a metal material such as steel or aluminum, and heated by electromagnetic induction heating from the inside. ) Method. In such a fixing roller, since the roller is charged by the internal current (electromagnetic noise) generated by electromagnetic induction and the quality of the printed matter is deteriorated, the charged portion is released by grounding the roller. A bearing having conductivity is adopted as the supporting bearing, and the roller is grounded through the bearing.

  In recent years, the fixing unit of the fixing device is required to have a function of fixing toner to paper and high-quality printing faster as printing speed increases and image quality increases. As the speed increases, the temperature is raised to increase the fixing speed to the paper, which inevitably increases the ambient temperature (including the bearing). In addition, since the service life of the device has been extended, the bearing used for this purpose is required to have a high temperature and a long life. With such a rise in the temperature of the fixing portion and the bearing, abnormal noise at the fitting portion described above is more likely to occur.

However, in the case where the shaft portion of the rotating member is press-fitted into the bearing in order to prevent abnormal noise, it is effective in preventing abnormal noise due to the interference fit, but there is a problem that the assembly workability is remarkably lowered.
On the other hand, when grease is applied to the mating part, the assembly workability does not decrease so much, but the fixing part becomes hot, so abnormal noise and creep over time due to deterioration of grease over time (decrease in oil content and depletion) There is a problem that occurs. In addition, the applied grease may be scattered to the surrounding area and contaminate the surrounding area.
When electrical conductivity is required, conductive grease is sealed in the bearing, and conductive grease is also applied between the bearing inner surface and the shaft. Causes abnormal noise and creep, and further deteriorates the grounding performance, resulting in a problem that the quality of printed matter is lowered.

In addition, the rolling bearing in which an oxide film is formed on the fitting portion of the bearing ring described in Patent Document 1 can prevent wear at the fitting portion, but can support a charging rotating member such as the fixing roller described above. If it is used, the oxide film is not conductive, so that there is a problem that the rotating member cannot be grounded via the bearing and a separate grounding means is required.
JP 2001-140901 A

  The present invention has been made to cope with such problems, and supports a rotating member that is charged in a fixing device, and a shaft portion of the rotating member is fitted into one of the inner and outer race rings by a clearance fit. An object of the present invention is to provide a rolling bearing that can prevent creep and noise over a long period of time and does not require a separate grounding means.

  In the rolling bearing of the present invention, a plurality of rolling elements are arranged between the raceways of the inner ring and the outer ring, and a rotating member that is charged in the fixing device is rotatably supported, and a shaft portion of the rotating member is an inner diameter surface of the inner ring or A rolling bearing fitted with a clearance fit on the outer diameter surface of the outer ring, and at least the inner diameter surface of the inner ring or the outer diameter surface of the outer ring where the shaft portion of the rotating member is fitted with the clearance fit A film having a low friction sliding property is formed, the film has a thickness of 2 to 10 μm, and a dynamic friction coefficient between the film and the shaft portion of the rotating member is 0.2 or less.

  The film is a nickel-polytetrafluoroethylene composite film. Further, the film is a graphite film.

  The dynamic friction coefficient between the coating and the shaft of the rotating member when the rotating member is rotated at 130 rpm for 500 hours while applying a radial load of 220 N to the rolling bearing is 0.2 or less. .

  The rotating member is a fixing roller having a built-in heater for fixing toner onto printing paper in a fixing device.

The rolling bearing of the present invention has a thickness of 2 to 10 μm as a coating having conductivity and low friction sliding property on the inner diameter surface of the inner ring or the outer diameter surface of the outer ring to which the shaft portion of the rotating member is fitted. Since the film having a dynamic friction coefficient of 0.2 or less between the film and the shaft portion of the rotating member is formed, the dynamic friction coefficient on the mating surface is stabilized at a low level over a long period (for example, 500 hours), and creep and noise can be prevented. Further, since the application of grease on the mating surfaces can be avoided by forming a film, contamination due to grease scattering to the surroundings can be prevented.
Since the coating is a conductive coating such as a nickel-polytetrafluoroethylene composite coating or a graphite coating, the bearing itself can serve as a ground mechanism by encapsulating conductive grease in the bearing. Separate grounding means can be dispensed with.
In addition, it can contribute to the miniaturization of the fixing device and the abolition of anti-noise and creep prevention measures such as grease application and press-fitting to the shaft, which have been conventionally performed.

The structure of the fixing device is photosensitive → conveyance → development → fixing → discharge. The fixing unit consists of two hollow rubber rollers (aluminum or steel is used for the core metal), temperature (about 200 ° C) and a bearing that supports it. And a heater. Usually, since the roller is hollow, it is directly heated from inside the roller through a heater. In order to fix the toner on the paper that has come out of the developing unit, in addition to the above temperature, pressure (about 98 N) is applied to fix the toner on the paper.
A mechanism for generating abnormal noise such as squealing between the shaft portion of the rotating member and the bearing, that is, the fitting portion, during operation of the fixing device will be described with reference to FIG. FIG. 3 is a cross-sectional view when the shaft of the fixing roller is fitted to the inner ring inner surface of the rolling bearing with a clearance fit. 3A shows a case where only the temperature is applied to the fitting portion, and FIGS. 3B and 3C show a case where temperature and load (pressure) are applied to the fitting portion.
As shown in FIG. 3A, the shaft thermally expands due to the temperature rise, and the bearing inner ring moves together with the shaft (because the dynamic friction coefficient of the contact surface is large).
As shown in FIG. 3B, the shaft bends (curves) due to the radial load. In the figure, Fr represents the radial force applied to the bearing, and Fa represents the axial force applied to the bearing. Here, when Fr <Fa, the posture of the bearing inner ring is maintained.
As shown in FIG. 3C, Fr changes due to misalignment (eccentricity) between the shaft and the outer diameter of the fixing roller. When Fr> Fa, the inner ring posture of the bearing is broken. When the bearing posture returns to the original position, a squeak noise is generated.
In the above mechanism, when the dynamic friction coefficient on the fitting surface between the shaft and the bearing is sufficiently small, Fr <Fa, and the bearing posture can be maintained.
In the present invention, a coating film having predetermined characteristics is formed on the inner ring inner surface of the bearing, and the squeal noise is reduced by maintaining a low coefficient of dynamic friction on the mating surface over the service life required for the fixing device. It was found that it can be prevented over the durability period. The present invention is based on such knowledge.

A rolling bearing according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing in which lubricating grease is enclosed.
As shown in FIG. 1, in the deep groove ball bearing 1, an inner ring 2 having an inner ring rolling surface 2a on an outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on an inner peripheral surface are arranged concentrically, and an inner ring rolling surface is obtained. A plurality of rolling elements 4 are arranged between 2a and the outer ring rolling surface 3a. Sealing members 6 that are fixed to the cage 5 that holds the plurality of rolling elements 4, the outer ring 3, and the like are provided at openings in the axial ends of the inner ring 2 and the outer ring 3, respectively. Lubricating grease 7 is sealed at least around the rolling element 4.
A coating 8 having conductivity and low friction sliding property is formed on the inner diameter surface 2b of the inner ring 2 into which the shaft portion of a rotating member such as a fixing roller or a pressure roller is fitted by clearance fitting.

The structure of the fixing member using the rolling bearing of the present invention will be described with reference to FIG. FIG. 2 shows the fixing roller 9 of the fixing device in which the shaft portion 9a is supported by the deep groove ball bearing 1 described above.
The fixing roller 9 is made of aluminum and is hollow, and is heated to about 200 ° C. by an electromagnetic induction heater 10 disposed in the hollow portion. The fixing roller 9 is charged by an internal current generated by electromagnetic induction. The shaft portions 9 a at both ends of the fixing roller 9 are fitted to the inner diameter surface of the inner ring 2 by clearance fitting, the outer ring 3 is fixed to the frame 11 of the fixing device, and each shaft portion 9 a is framed via the deep groove ball bearing 1. 11 is grounded, and the electricity charged in the fixing roller 9 is released.
In the present invention, since the coating 8 is formed on the inner diameter surface of the inner ring 2, it is not necessary to apply grease on the fitting surface.

In the embodiment described above, the deep groove ball bearing in which the shaft portion of the rotating member to be charged is fitted to the inner diameter surface 2 b of the inner ring 2 is used. However, in the rolling bearing of the present invention, the shaft portion is formed on the outer diameter surface 3 b of the outer ring 3. It can also be applied to fittings and is not limited to deep groove ball bearings.
The rolling bearing of the present invention can also be used to support rotating members other than the fixing roller that is charged by static electricity or the like.

The film having conductivity and low friction sliding property in the present invention has conductivity, and the coefficient of dynamic friction between the film and the shaft portion of the fixing roller, that is, the coefficient of dynamic friction on the mating surface is 0.2 or less. If there is, it can be adopted. When the dynamic friction coefficient on the mating surface exceeds 0.2, the inner ring posture of the bearing collapses (see FIG. 3C), and abnormal noise (squeal noise) is likely to occur.
Examples of such a film include a composite film in which a metal powder is blended with a fluororesin, and a graphite film. Moreover, as a composite film which mix | blended the metal powder with the fluororesin, the Ni-PTFE composite film which mix | blended the metal nickel (henceforth PT) powder with the polytetrafluoroethylene (henceforth PTFE) resin is mentioned.

As a method of forming a coating on the inner ring inner surface or outer ring outer surface, electroplating, electroless plating, vacuum deposition, ion plating, sputtering, etc., physical vapor deposition (PVD), chemical vapor deposition (CVD), etc., or resin Dipping using a dispersion, coating, coating by spraying, etc., and other known film forming methods can be employed.
In the rolling bearing of the present invention, the film thickness of the coating can be adjusted uniformly, and it has excellent dimensional accuracy, heat resistance, wear resistance, and slidability. Therefore, by electroless plating, the Ni-PTFE composite coating Is preferably formed.

The thickness of the film having conductivity and low friction sliding property in the present invention is 2 to 10 μm. Preferably, it is 2-5 μm. By setting the film thickness to 2 μm or more, as a practical use condition in office equipment such as copiers and printers, the fixing roller was rotated at 130 rpm for 500 hours while applying a radial load of 220 N to the rolling bearing. Even at the time, the dynamic friction coefficient on the mating surface can be maintained at 0.2 or less, and abnormal noise can be prevented.
When the thickness of the coating is less than 2 μm, sliding of metals at the fitting portion cannot be sufficiently prevented, and abnormal noise may be generated. When the thickness exceeds 10 μm, the fitting accuracy with the shaft portion is lowered, and the film formation cost is increased.

  The thickness of the coating adhering to the raceway surface of the inner ring or outer ring is preferably 10 μm or less, preferably 5 μm or less. It is preferable that the coating is not attached to the raceway surface. However, in order to simplify the work, the coating is also attached to the raceway surface depending on the coating formation method such as performing a coating formation process without masking. If the thickness of the coating film adhering to the raceway surface exceeds 10 μm, the coating film is peeled off by rolling of the rolling element, and the peeled film is caught in the rolling element as a foreign substance, thereby shortening the bearing life.

  As a material of the inner and outer rings used in the rolling bearing of the present invention, a well-known metal material for bearings can be used, and there is no particular limitation as long as it is a material capable of forming the above-described plating film. Specific examples include bearing steel (high carbon chromium bearing steel JIS G 4805), case hardening steel (JIS G 4104, etc.), high speed steel (AMS 6490), stainless steel (JIS G 4303), induction hardening steel (JIS). G 4051). Also, other bearing alloys can be employed. The fixing roller is usually formed of a lightweight aluminum alloy such as A5056 or A6063.

  The grease to be sealed in the rolling bearing of the present invention is not particularly limited as long as it is a grease generally used for a bearing. When the bearing needs to be conductive, conductive grease containing a conductive agent such as carbon black, charged microgel particles, and graphite can be enclosed.

  As an example and a comparative example, a deep groove ball bearing having a coating formed on the inner diameter surface of the inner ring shown in FIG. 1 was prepared. Table 1 shows the coating type, film thickness, and the like in each example and comparative example. The Ni-PTFE composite coating was formed by electroless nickel plating, and the graphite coating was formed by sputtering. The composition of the Ni-PTFE composite coating is 82 to 86% by weight of Ni, 7 to 9% by weight of phosphorus, and 7 to 9% by weight of PTFE (particle diameter of 1 μm or less).

The inner ring of the deep groove ball bearings of each of these examples and comparative examples was fitted to the shaft of an aluminum rotating member with a clearance fit (clearance of 100 μm), and the rotating member was tested for 1000 hours. The initial investigation (immediately after the start of operation) of the dynamic friction coefficient, the timing of noise generation, and the current-carrying performance between the shaft and the bearing were investigated. Test conditions and energization conditions are as follows. The results are shown in Table 1. In the investigation of energization performance, the energization performance was good when the resistance between the shaft and the bearing was maintained at 200 kΩ or less for a test time of 1000 hours, and the resistance exceeding 200 kΩ was judged as poor even once. .
[Test conditions]
・ Bearing dimensions: Inner diameter 25 mm, Outer diameter 37 mm, Width 7 mm
-Shaft temperature: 200 ° C
・ Bearing load: 220 N (radial load)
・ Rotation speed: 130 rpm
-Partner material: Aluminum [energization condition]
・ Charge voltage: 30 V
・ Control resistance: 300 kΩ (connected in parallel with the current measurement unit)
・ Sampling interval: 1 μs

  Further, with respect to Example 2, Example 6, and Comparative Examples 1 to 3, the change over time in the dynamic friction coefficient on the mating surfaces under the same test conditions was measured. The results are shown in FIG. In FIG. 4, the horizontal axis represents elapsed time (h), and the vertical axis represents the dynamic friction coefficient.

  As shown in Table 1, the bearing with the coating film of each example can prevent the generation of abnormal noise over a practically sufficient durability time (500 hours) in office equipment, etc., and has good current-carrying performance. It was. As shown in FIG. 4, in Example 2 and Example 6 in which the thickness of the coating was 5 μm, the dynamic friction coefficient could be kept low for a long time, and the generation of abnormal noise could be prevented.

  The rolling bearing according to the present invention can prevent abnormal noise such as squeal noise over a long period of time when the shaft portion of the rotating member is fitted to one of the inner and outer races by clearance fitting. It can be suitably used as a bearing for supporting a rotating member such as a fixing roller used in a fixing device for office equipment.

It is sectional drawing of a deep groove ball bearing (rolling bearing). FIG. 2 is a longitudinal sectional view showing a fixing roller of a copying machine using the rolling bearing of FIG. 1. It is a figure explaining the mechanism which abnormal noise generate | occur | produces. It is a figure which shows a time-dependent change of the dynamic friction coefficient in a fitting surface.

Explanation of symbols

1 Deep groove ball bearing (rolling bearing)
2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease 8 Coating 9 Fixing roller 9a Shaft 10 Electromagnetic induction heater 11 Frame

Claims (2)

A plurality of rolling elements are arranged between the raceway surfaces of the inner ring and the outer ring, and a rotating member that is charged in the fixing device is rotatably supported, and a shaft portion of the rotating member is provided on the inner diameter surface of the inner ring or the outer diameter surface of the outer ring. A rolling bearing fitted with a clearance fit,
The rotating member is a fixing roller with a built-in heater for fixing the toner on the printing paper;
On the inner diameter surface of the inner ring or the outer diameter surface of the outer ring where at least the shaft portion of the rotating member is fitted with a clearance fit, a film having conductivity and low friction sliding property is formed,
Said coating of nickel is formed by electroless plating - polytetrafluoroethylene composite coating or, a graphite coating formed by sputtering process,
The coating is thick 2 to 10 [mu] m, the dynamic friction coefficient between the shaft portion of the coating film and the rotary member is Ri der 0.2,
A rolling bearing characterized by preventing an abnormal noise generated by hitting the shaft portion when the bearing posture collapses at a fitting portion between the rolling bearing and the shaft portion of the rotating member .   The dynamic friction coefficient between the coating and the shaft portion of the rotating member when the rotating member is rotated at 130 rpm for 500 hours while applying a radial load of 220 N to the rolling bearing is 0.2 or less. The rolling bearing according to claim 1.