JP3243143B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fixing device used in an image forming apparatus having an electrophotographic image forming section, such as a copying machine, a printer, a facsimile machine, and the like. In a fixing device that performs hot-melt fusing, a toner or other foreign matter attached to a heating roller constituting the fixing device is positively transferred to a pressure roller side, thereby contaminating the heating roller and reducing image quality caused by the contamination. The present invention relates to a fixing device capable of preventing a decrease.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile apparatus, or the like having an electrophotographic image forming section, optical image information such as reflected light of a document is placed on a photosensitive member uniformly charged in advance. The electrostatic latent image obtained by irradiating
A toner is supplied from a developing device to form a visible image, and the toner image is transferred onto a recording sheet and then passed through a fixing device to perform heat fixing. This fixing device has a heating roller provided with a heater inside, and a pressure roller that presses against the outer peripheral surface of the heating roller, and heats the transferred recording paper passing between the two rollers while heating the recording paper while applying pressure. Fixing toner image. In the above-described conventional fixing device, in order to prevent the toner from adhering to the heating roller and the occurrence of offset (decrease in fixing ability) due to the toner, the outer peripheral surface of the heating roller is impregnated with high-viscosity silicone oil. An oil film is formed by pressing an applying means or an oil applying means for applying a small amount of oil oozing out of an oil tank provided in a roller through a felt to form an oil film. Since it is in constant contact with the heating roller, foreign substances such as toner and paper dust adhered to the peripheral surface of the heating roller are transferred to the oil application unit side, which not only reduces the ability to apply oil uniformly, but also reduces the oil. Foreign matter gradually accumulated on the coating means side flows back to the heating roller side,
Finally, there is a problem that the image quality is deteriorated by adhering to the recording paper (JP-A-61-109084, 62-5).
284, 1-120171, and 314064).

FIG. 5 is an explanatory view of the configuration of a conventional fixing device. A recording sheet P having unfixed toner T is conveyed from an image forming section located on the right side of the drawing, and heated by a heating roller 1.
01 and the nip portion of the pressure roller 102, the toner T on the recording paper P is fixed on the paper and discharged to a discharge unit (not shown) located on the left side of the fixing device. Normal,
The recording paper P holding the toner T is melted by the heat of the fixing roller 101 and fused to the recording paper. However, when the releasability of the surface of the heating roller 101 is poor, a part of the toner adheres to the surface of the heating roller 101 and causes a slight offset. As a countermeasure for this, it is necessary to press the oil application roller 105 filled with silicone oil on the heating roller 101 to constantly supply the silicone oil to the heating roller 101 to improve the releasability and prevent offset. Have been done. Reference numeral 103 denotes a heater, 104 denotes a thermistor for detecting temperature, 108 denotes a separation claw, 109 and 110 denote sheet ejection guides, 111 denotes a separation claw spring, 112 denotes a sheet ejection roller,
13 is an entrance guide, and 114 is an oil supply unit.

However, the oil application roller 10
However, it is difficult to completely prevent the offset by using No. 5, and there is a problem that a small amount of offset still remains on the heating roller 101. In other words, the result is that the roller 105 also serves as a cleaning roller, and as it is used, the oil application roller 105 becomes dirty, the amount of oil applied decreases, and the toner transferred to the cleaning roller 106 is retransferred to the heating roller 101. Occurs, causing image stains. In particular, the toner adhering to the cleaning roller 106 forms a lump by being mixed with the components in the recording paper and accumulates, and when the lump falls from the cleaning roller 106, large black stains (hereinafter, “black spots”) are formed on the recording paper. Therefore, improvement of this point has been required.

In addition to the above, as a conventional example for preventing toner contamination on the surface of a heating roller, Japanese Patent Laid-Open Publication No. Hei 3-28873 discloses a fixing unit in which a cleaning felt is brought into contact with the surface of a heating roller. A technique is disclosed in which a cleaner is provided to remove dirt due to toner or the like on the surface of a heating roller, thereby preventing dirt on the copy surface and the back surface during fixing. Generally, recording paper has a filler such as calcium carbonate adhered to the paper fiber.However, when there are many components with a large particle size such as calcium carbonate such as European paper, the adhesion between the filler and the fiber may be weak. Relatedly, the filler is likely to be offset on the surface of the heating roller together with the toner during fixing, and the cleaning means of the heating roller is also easily stained. Therefore, in order to maintain the performance of the cleaning means, it is necessary to perform maintenance at short intervals, and it becomes impossible to guarantee the performance of the cleaning member at regular inspection intervals.

Japanese Patent Application Laid-Open No. 4-107489 discloses that an outer peripheral felt portion of an anti-offset applying roller is integrally formed with a felt member and a reinforcing member, and the outer peripheral felt portion is detachable from a supporting portion. By configuring to
A configuration that simplifies the offset preventing agent supply means and reduces the cost is disclosed. In this conventional example, as in the case of the above-mentioned Japanese Patent Application Laid-Open No. 3-28873, offset occurs frequently when paper such as European paper containing a large amount of calcium carbonate as a filler is passed through, and the cleaning felt is usually used for one regular period. It has to be replaced several times during the inspection, which is unfavorable in terms of service.

Japanese Patent Application Laid-Open No. 5-53468 discloses a pair of rotators which cooperate with each other to nip and transport a transfer material on which an unfixed developer is formed, and at least one of the rotators. And a cleaning unit having a pressing roller for pressing one surface and the other surface of the web-shaped cleaning member against the rotating member, wherein the surface layer of the pressing roller is made of a layer containing a fluororesin. Thus, a technique has been disclosed in which the occurrence of image stains due to foreign matters such as developer and paper powder remaining on the heating roller is prevented beforehand. However, this apparatus requires a large cleaning mechanism, and has disadvantages such as an increase in space and an increase in cost.

Japanese Patent Application Laid-Open No. 5-119656 discloses a release agent applying means for applying a release agent to the surface of a heating roller, and a contact / separation control means for allowing the release agent applying means to be able to come and go from the heating roller. A technology has been disclosed in which a toner and paper dust are prevented from adhering to a heating roller by a release agent applying unit, and an offset is prevented from occurring on an image fixed on recording paper. However, this technique requires a contacting / separating means and its control, so that the cost is high. Further, although the cost is increased by adopting a complicated mechanism and control for separating the release agent applying means from the heating roller, there is a drawback that the effect of improving the life is small.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has a heating roller and a pressure roller which rotate while being pressed against each other on an outer peripheral surface, and at least one of the outer peripheral surface of the heating roller and the pressing roller. An oil application roller that applies oil to the roller surface in contact with the roller, and a cleaning unit that is in contact with the pressure roller surface;
A fixing device that can reliably prevent contamination of the heating roller, thereby preventing accumulation of foreign matter such as toner attached to the heating roller and occurrence of “black spots” due to transfer of the accumulated foreign matter onto recording paper. It is intended to provide.

[0010]

According to a first aspect of the present invention, there is provided a heating roller and a pressure roller which rotate while being pressed against each other on an outer peripheral surface, and at least one of the heating roller and the pressure roller. an oil application roller for applying the oil to the roller surface in contact with the outer peripheral surface, the oil coating
And Cleaning Gurora in contact with b over la surface, in the fixing device having the above cleaning roller have a surface layer
Then, the surface layer of the cleaning roller is
It is characterized by being composed of a substance having a relatively high thermal conductivity .

The invention according to claim 2 is the same as the claim 1.
The toner on the surface of the pressure roller
Set the releasability lower than the releasability of the heating roller surface
And the releasability of the pressure roller surface from the toner is
Low releasability set lower than releasability of heating roller
The portion is the whole or a part of the pressure roller surface .

The invention described in claim 3 is the first or second invention.
In the fixing device described above, the above-mentioned respective
Characterized in that have configured so as to at least intermittently idling the over La group.

[0013]

[Operation] As described above, the cleaning roller has a surface.
Having the surface layer of the cleaning roller therein.
On the other hand, it was made of a material having relatively high thermal conductivity. Paraphrase
The heat capacity of the cleaning roller for the oil application roller
Cleaning heat for a small heat capacity.
Roller surface area to increase the temperature of the cleaning roller
Cleaning roller performance.
It is possible to stabilize and prevent the above-mentioned "black spot" image from being generated.

Further, the toner on the surface of the pressure roller
The release property is set lower than the release property of the heating roller surface.
And the releasability of the pressure roller surface from the toner is
Low releasability set lower than releasability of heating roller
So that the part is all or part of the pressure roller surface
The pressure roller ensures that dirt on the surface of the heating roller
Side, and easily prevents contamination of the heating roller.
In addition, in terms of copy quality, it is also possible to prevent the generation of “black spots” due to the drop of foreign matter such as toner on the heating roller.
Kill at stop.

While waiting for the copying operation, the above roller groups are
At least intermittently idle rotation.
Cleaning roller for the application roller
Roller can always be maintained at a predetermined temperature or higher,
Cleaning such as cleaning roller for oil application roller
Toner, etc., which is likely to be generated when the temperature of the
It is possible to prevent the generation of “black spots” due to the fall of a lump of foreign matter .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1A is an explanatory diagram of a configuration of an embodiment of a fixing device of the present invention, and FIG. 1B is an enlarged view of a main part of a pressure roller. This fixing device includes a heating roller 1 having a heater 3 therein, a pressure roller 2 that is in pressure contact with the heating roller 1, and a thermistor 4 that detects the surface temperature of the heating roller 1.
An oil application roller 5 that comes into pressure contact with the surface of the heating roller 1 and rotates with the frictional force; a cleaning roller 6 for the application roller that presses and rotates with the surface of the oil application roller 5; And a pressure roller cleaning roller 8 in contact with the surface of the pressure roller 2.

The heating roller 1 is formed, for example, by subjecting a surface of an aluminum journal to a fluororesin processing as a release layer, and using PFA, PTFA, or the like as the fluororesin. As the oil applying roller 5, a roller having a surface made of PTFA resin or the like, having an oil tank inside, and having a minute oil seeping hole on the surface is used.
The cleaning roller 6 is, for example, a roller in which the surface of a metal roller is coated with fluororubber at 10 to 100 μm. The pressure roller cleaning roller 8 is made of a metal or the like, and is made of a material having lower releasability than the surface material of the pressure roller.

Next, the pressure roller 2 of this embodiment is constructed so that the surface layer is elastically deformed, and the outermost layer is made of a material whose toner release property is lower than the surface of the heating roller 1. Have been. For example, a material in which particles of carbon graphite or SiC (silicon carbide) are dispersed in a surface layer of a member made of an elastic material is used. As shown in FIG. 1B, the pressure roller 2 of this example has an elastic layer 11 made of heat-resistant silicon rubber or the like laminated on the outer periphery of a metal core 10, and further has a release property on the outer periphery of the elastic layer 11. Low release layer 12 having a low thickness. The low releasability layer 12 has a lower releasability than the surface of the heating roller 1 by mixing particles such as carbon graphite into the surface portion of the elastic layer 11, and is lower than the surface of the cleaning roller 6. The releasability is good.

When the recording paper carrying the unfixed toner is fixed by the fixing device as described above, no matter how good the releasability of the surface of the heating roller 1 is, even if the amount of toner or the like is small, the heating roller 1 Foreign matter adheres, and when it accumulates, it forms a lump and causes various problems. Therefore, in the present embodiment, the releasability of the surface of the pressure roller is intentionally reduced so that the trace offset toner does not accumulate on the heating roller 1, the oil application roller 5, and the application roller cleaning roller 6. Therefore, a very small amount of offset toner is positively transferred to the surface of the pressure roller, and further transferred to the cleaning roller 6, which has a lower toner releasability than the pressure roller 2 and has a relatively high offset toner carrying capacity. . The low releasability portion releasability against the toner is lower than the releasing of the heating roller of the pressure roller 2 surface or may be applied as a whole Ka圧Ro over la surface, as part Is also good. When a part is a low releasability part, its shape can be variously set, such as an island shape, a dot shape, and a band shape.

FIG. 2 is a timing chart showing a control method according to another embodiment of the present invention. In the standby state of the copying operation, the above-mentioned rollers provided in the fixing device are idled continuously or intermittently. It is characteristic in that it is configured. That is,
After the power supply of the image forming apparatus is turned on, even when the fixing device is not passing paper, the surface temperature of the heating roller 1 is detected by the thermistor 4 so that the heater 3 is turned on and off to keep the temperature within a predetermined temperature range. Maintains surface temperature. However, since the temperature of the cleaning roller 6 for the application roller is not controlled for heating, the temperature rapidly decreases when the heating roller is stopped. As a result, the offset toner and the detached components of the recording paper adhered to the surface of the cleaning roller 6 are easily aggregated and solidified. Because this solid is brittle,
It easily peels off and falls due to external force, which adheres to the recording paper and causes "black spots". Therefore, in the present invention, the cleaning roller 6 is intermittently rotated together with the heating roller 1 even during standby lighting. That is, the cleaning roller 6 and the heating row La 1 above a predetermined duty ratio
By rotating, the extreme temperature drop of the cleaning roller 6 can be prevented, and the occurrence of the “black spot” phenomenon can be prevented.

In FIG. 2, the heating roller 1 and the cleaning roller 6 are caused to idle by turning on the driving of the heating roller at a predetermined interval even at times other than the paper passing at the fixing nip (non-paper passing). Thus, the temperature of the cleaning roller 6 is prevented from lowering. It is sufficient if the idle rotation is performed intermittently.

Next, the offset toner and the detached components of the recording paper accumulated on the surface of the oil application roller cleaning roller 6 become brittle and easily fall when cooled, but in the third embodiment of the present invention, the cleaning roller Since the surface of No. 6 is made of a material having a high thermal conductivity and the inside is filled with a material having a low thermal conductivity, such a problem can be solved. That is, as shown in FIGS. 3 and 4, in the present embodiment, the surface layer 8a is made of a material having a good thermal conductivity such as a metal and has a very small heat capacity, while the inner layer 8a is made of a material.
b is a material having low thermal conductivity (for example, a hollow pipe having a thickness of 1 mm or less, a roller having a resin surface plated with metal, etc.)
Therefore, the temperature of the accumulated material on the surface of the cleaning roller 6 can be raised immediately after the driving of the heating roller 1 and the cleaning roller 8 is started. As a result, the accumulated material is prevented from becoming brittle and falling. As a result, it is possible to prevent "black spot" copy smear. The internal substance 8b having a low thermal conductivity includes, for example, air, vacuum, resin, foamed resin, and the like.

In the above embodiment, the cleaning roller 6 for the oil application roller has been described as an example, but this embodiment may be applied to the cleaning roller 8 for the pressing roller shown in FIG. That is, when the toner is positively transferred to the pressure roller side as in the first embodiment, the cleaning roller 8 removes the toner on the pressure roller. If a roller structure as shown in FIGS. 3 and 4 is employed in order to prevent a situation in which the upper toner becomes a lump and is reversely transferred to the pressure roller and adheres to the recording paper, the brittleness due to cooling of the lump of toner Can be prevented.

As described above, according to the present embodiment, the heat capacity of the cleaning roller 6 (8) for the oil application roller is reduced, and the surface area of the cleaning roller is increased in spite of the small heat capacity. Since the shortening is achieved, the performance of the cleaning roller can be stabilized, and the occurrence of the “black spot” image can be prevented.

The cleaning structure of the toner by the pressure roller in the first embodiment can be realized as a single embodiment. However, the cleaning structure of the second embodiment, the third embodiment, or a combination of both can be realized. It is possible. In addition, the idle rotation during the copy operation standby in the second embodiment can be established as a single embodiment, but can also be established in combination with the first and third embodiments. Further, the structure of the cleaning roller of the third embodiment can be realized as a single embodiment, but can also be realized in combination with the first and second embodiments.

[0026]

As described above, in the fixing device of the present invention, the heat roller and the pressure roller which rotate while being pressed against each other on the outer peripheral surface, and the outer periphery of at least one of the heat roller and the pressure roller an oil application roller for applying oil to the contact with the roller surface to the surface, and cleaning Gurora in contact with the oil application b over <br/> la surface, in the fixing device provided with the above-mentioned cleaning roller surface layer Have
The surface layer of the cleaning roller is
It was made of a material with high thermal conductivity. In other words, Oy
The heat capacity of the cleaning roller for the application roller
Cleaning roller surface with low heat capacity
Wider area to reduce temperature rise of cleaning roller
Stabilization of cleaning roller performance
Further, generation of the above-mentioned “black spot” image can be prevented.

Also , the toner on the surface of the pressure roller
The release property is set lower than the release property of the heating roller surface.
And the releasability of the pressure roller surface from the toner is
Low releasability set lower than releasability of heating roller
So that the part is all or part of the pressure roller surface
Configured. For this reason, the dirt on the heating roller surface is reliably pressurized.
Transfer to the roller side, and the contamination of the heating roller
Prevented the easy and wear occurs also on copy quality due to the mass of foreign matter such as toner on the heating roller from falling "black spots" dirt prevention.

During the copy operation standby, the fixing device
At least intermittently idle each roller group.
Cleaning roller for oil application roller
Always keep the cleaning roller such as above a predetermined temperature
Cleaning roller for oil application roller
Occurs when the temperature of the cleaning roller
"Black spots" dirty due to falling of foreign matter of the mass of easy toner, etc. None
This can be prevented from occurring.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are an explanatory diagram of a fixing device and an explanatory diagram of main components of an embodiment of the present invention. FIG.

FIG. 2 is a timing chart for explaining a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a third embodiment of the present invention.

FIG. 4 is an explanatory diagram of a third embodiment of the present invention.

FIG. 5 is an explanatory view of a conventional example.

[Explanation of symbols]

1 heating roller, 2 pressure roller, 3 heater, 4 thermistor, 5 oil application roller, 6 cleaning roller, 7 separation claw, 8 cleaning roller,

Claims (3)

(57) [Claims] An oil coating device for applying oil to the roller surface by contacting at least one of the heating roller and the pressure roller which rotates while being pressed against each other on the outer peripheral surface. Roller and oil above
In the fixing device and a Cleaning Gurora in contact with the coating b over la surface, the cleaning roller has a surface layer, said CLEANING
The thermal conductivity of the surface layer of the grawler relative to the inside
A fixing device characterized by comprising a material having a high density . 2. The fixing device according to claim 1, wherein
The releasability of the pressure roller surface against toner
Set lower than the releasability of the surface,
Of which, the releasability for toner is greater than the releasability of the heating roller.
The low releasability part set at a low level
A fixing device which is a whole or a part . 3. The fixing device according to claim 1, wherein :
At least, during the copy operation standby,
Fixing apparatus characterized by have configured so as to continue to idle rotation.