JPH07244444A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device capable of stably fixing over a long period without soiling the surface of a heating roll with toner. CONSTITUTION:In the fixing device provided with a pair of fixing rolls composed of the heating roll 1 and a pressure roll 5 rotated while presscontacting with the heating roll 1 and a cleaning member 8 wiping off the toner stuck to the surface of the heating roll 1, when the rotations of pair of the fixing rolls are stopped, the cleaning member 8 is retracted retracted from the heating roll 1, to prevent the toner 14 stuck to the cleaning member 8 from coming into contact with the heating roll 1 by the wiping off and prevent the soiling of the surface of the heating roll caused by the retransfer of the toner as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an electrophotographic apparatus or
The present invention relates to a fixing device used in an electrostatic recording device, and more particularly to a fixing device having an improved ability to wipe off residual toner on a heating roll.

[0002]

2. Description of the Related Art Conventionally, various types of fixing devices have been proposed, but at present, from the viewpoint of thermal efficiency, a so-called hot roller fixing device composed of a roller pair having at least one heat source is the mainstream. .

FIG. 3 shows a conventional technique. Reference numeral 1 denotes a heating roll, which is a fluororesin (for example, PFA, P
A coating 2 of TFE) is formed and has a heating source 4 such as a heater or a halogen lamp inside. Further, 5 is a pressure roll, and silicon rubber is formed on the surface of the metal roll base material 7 such as aluminum. Reference numeral 17 is a cleaning roll slidably provided on the surface of the heating roll 1, and 18 is an oil application roll slidably provided on the surface of the heating roll 1. Composed. Dimethyl silicone oil is usually used as the silicone oil.

Recently, also in the fixing device, due to the problems of reducing the fixing energy and extending the life of the heat fixing roller,
Hard materials having excellent high heat resistance have been demanded. In the case of a fluororesin, it becomes soft (B class in pencil hardness) at a temperature of 190 ° C. or higher, so that a decrease in the film thickness of the coating film inevitably results in a decrease in life. Further, there is also a drawback that when it is continuously used under a high voltage application, the wear resistance is substantially lost, the surface becomes rough due to contact with a paper or the like, releasability is remarkably lowered, and offset occurs.

Therefore, recently, a polysiloxane resin having a ladder structure as a hard material excellent in high heat resistance as a heating roll coating (Japanese Patent Laid-Open No. 5-197304)
Or using thermosetting resin as a binder, molybdenum disulfide,
A resin containing a solid lubricant such as graphite or a fluororesin (Japanese Patent Laid-Open No. 2-289877) has come to the spotlight.

[0006]

However, when fixing is performed using the heating roll using the above new coating and the fixing device configuration shown in FIG. 3, the surface of the heating roll is cleaned by the cleaning member. However, it was found that the surface of the heating roll was contaminated with the toner after printing a large number of times, which caused problems such as transfer to the paper and the occurrence of jams.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a fixing device capable of performing stable fixing for a long period of time.

[0008]

[Means for Solving the Problems] The cause of the generation of stains on a heating roll having a polysiloxane resin coating formed thereon was examined.

[0009]

[Table 1]

Conventional fluororesins (eg PFA, PT
Table 1 shows the molecular structures of dimethyl silicone oil and polysiloxane resin used in the FE) coating. As can be seen, the molecular structures of the two are almost the same, and thus the wettability with each other is good. Therefore, at the time of fixing, the above-mentioned silicone oil is uniformly applied to the surface of the heating roll and the offset toner on the surface of the heating roll is ensured to have good cleanability by mechanical rubbing with the cleaning roll. 4 is stopped, the toner 14 wiped off by the cleaning roll 16 and dispersed in the oil 17 is retransferred to the surface of the heating roll coating 2 together with the oil, as shown in FIG. I found out. Therefore, when the rotation of the fixing roll pair is stopped, the cleaning roll is retracted from the heating roll, and when the cleaning member is the cleaning felt, a new felt is fed before the rotation of the fixing roll pair is stopped. did.

In the case of a heating roll using a polyimide resin coating containing a solid lubricant such as fluororesin (PTFE) or molybdenum disulfide, the fluororesin functions as the releasability and the molybdenum disulfide functions as the wear resistance. The film structure is a so-called "sea-island structure" in which the plurality of solid lubricants are mixed in the polyimide resin. Since the releasability is secured by the fluororesin part, the releasability is inferior to that of the film made of the fluororesin alone. Furthermore, when used under a high pressure for a long period of time and the fluorine-based solid lubricant is worn, the releasability is deteriorated.

While the fixing roll is rotating, it is slid by the cleaning member and the adhered toner is wiped off, so there is no problem. However, when the heating roll is stopped, it comes into contact with a constituent material such as a polyimide resin, which has insufficient releasability as compared with a fluororesin, and therefore, like the heating roll having a polysiloxane resin coating, rotation of the pair of fixing rolls does not occur. When stopped, retract the cleaning member from the heating roll,
When the cleaning member is an oil-impregnated cleaning felt, feeding out new felt before the rotation of the pair of fixing rolls is effective in preventing surface contamination of the heating roll coating. In addition to improving the cleaning means, silicone oil suitable for a polysiloxane resin coating having a ladder structure was investigated, and it was found that the methylphenyl silicone oil shown in Table 1 is preferable.

Methylphenyl silicone oil was selected for the polysiloxane resin coating, and dimethylpolysiloxane oil was selected for the polyimide resin coating containing the fluororesin solid lubricant.

[0014]

A heating roll having a surface layer of a polyimide resin coating containing a polysiloxane resin having a ladder structure and a solid lubricant having high heat resistance (heat resistance temperature: 250 to 300 ° C.) and hardness (pencil hardness: H). In the fixing device using the heating roller, when the rotation of the fixing roll is stopped, the toner adhered to the cleaning member of the cleaning device does not come into contact with the heating roller. It is possible to prevent surface contamination of the coating.

Further, by using methylphenyl silicone oil suitable for the polysiloxane resin having a ladder structure, the wiping performance can be improved.

[0016]

【Example】

(Embodiment 1) FIG. 1 is a diagram for explaining an embodiment of the present invention. Reference numeral 1 is a heating roll, on which a polysiloxane resin having a ladder structure or a polyimide resin coating 2 containing a fluororesin solid lubricant is formed on the surface of a metal roll base material 3 such as aluminum, and a heater, a halogen lamp, or the like is provided inside. Heating source 4. Further, 5 is a pressure roll, and silicon rubber is formed on the surface of the metal roll base material 7 such as aluminum. Reference numeral 8 is a cleaning member. Reference numeral 9 denotes a cleaning felt that can be wound up, 11 is a member that presses the cleaning felt against a heating roll, and has an oil port 10 that applies silicone oil for mold release to the felt. Dimethyl silicone oil was used as the oil.

Reference numeral 13 denotes a cam which rotates by a rotary shaft,
During printing, the cleaning felt 9 is pressed against the heating roll to wipe off the toner 14 adhering to the surface of the heating roll. When the fixing roll is stopped, such as when waiting for printing, the cam rotates,
Since the pressing member 11 is retracted by the spring 12, the cleaning felt is separated from the heating roll. As a result,
The toner 14 adhering to the cleaning felt did not come into contact with the heating roll, and it was possible to prevent surface contamination of the heating roll coating due to retransfer of the toner.

Although FIG. 1 shows the case where the cleaning member is the cleaning felt, in the case of the cleaning roll used in FIG. 3, the toner attached to the cleaning roll comes into contact with the surface of the heating roll by providing the retract mechanism. It is possible to prevent surface contamination of the heating roll coating due to retransfer of toner.

As a result, high heat resistance (heat resistant temperature: 250 to 3)
Using a heating roll having a surface layer of a polyimide resin coating containing a polysiloxane resin having a ladder structure having a hardness (pencil hardness: H) at 00 ° C) and a solid lubricant, and removing the surface contamination of the heating roll. It was possible to realize a fixing device that does not have a fixing device.

(Embodiment 2) FIG. 2 is a view showing another embodiment. Reference numeral 1 is a heating roll, and 5 is a pressure roll. The cleaning felt 9 is pressed against the heating roll, and at the time of printing, the toner 14 adhering to the surface of the heating roll is wiped off.
When fixing is stopped and the fixing roll is stopped until the next fixing is started, a signal indicating this is sent from the control section 16 of the electrophotographic apparatus or the electrostatic recording apparatus to the felt winding mechanism section 15. The winding mechanism unit 15 draws out an appropriate amount of the cleaning felt, and brings a new felt without toner attached to the surface of the heating roll. As a result, the toner 14 adhering to the cleaning felt did not come into contact with the heating roll, and the surface contamination of the heating roll due to retransfer of the toner was prevented. In addition, it is desirable that the feeding of the new felt is performed before the fixing roll is stopped.

(Embodiment 3) FIG. 5 shows the results of examining the relationship between the contact angle of silicon oil on the heating roll coating surface and the stain on the heating roll coating surface in the conventional configuration of FIG. As can be seen from this, when the oil contact angle on the heating roll coating surface is approximately 5 to 20 degrees, it was found that the heating roll coating surface was less contaminated. In a fixing device using a heating roll with a polysiloxane resin coating, the silicone oil was changed from the conventional dimethyl silicone oil to methylphenyl silicone oil.

[0022]

[Table 2]

Table 2 shows an example of measuring the contact angle of each silicone oil on the heating roll surface. In the case of dimethyl silicone oil, the contact angle of PFA coating is 12 degrees,
The contact angle of the polysiloxane resin is 2 degrees, which is a very small value. Therefore, in the case of a heating roll coated with a polysiloxane resin, the toner dispersed in dimethyl silicone oil is retransferred to the surface of the heating roll coating 2 together with the oil when the fixing roll is stopped, and the surface contamination of the heating roll is not generated. Cause. However, when the methylphenyl silicone oil was used, the contact angle became 12 degrees, retransfer of the toner to the heating roll coating surface was stopped when the fixing roll was stopped, and it was possible to prevent surface contamination of the thermal fixing roll.
Further, the viscosity of methylphenyl silicone oil is 11CS at the surface temperature of the heating roll (about 200 ° C.), which is the same as that of dimethyl silicone oil, but is about 4 times at room temperature. So, from the oil tank (not shown),
When supplying to the cleaning felt or the cleaning roll, it is desirable to heat the oil tank so that the viscosity becomes 100 cs. Further, in the case of a heating roll having a polyimide resin coating containing a solid lubricant, either dimethyl silicone oil or methylphenyl silicone oil can be used.

Needless to say, further effects can be achieved by applying oil to the fixing device shown in FIGS.

[0025]

As described above, according to the present invention, in the fixing device, the toner adhered to the cleaning member does not contact the surface of the heating roll when the rotation of the pair of fixing rolls is stopped. It is possible to prevent the surface contamination of the heating roll due to retransfer. Further, with respect to the heating roll using the polysiloxane resin coating, the oil type can be optimized to further improve the prevention of the surface contamination of the heating roll.

As a result of the above, high heat resistance (heat resistance temperature: 250 to
Uses a heating roll having a surface layer of a polyimide resin coating containing a polysiloxane resin having a ladder structure having a hardness (pencil hardness: H) at 300 ° C.) and a solid lubricant, and is free from surface contamination of the heating roll. A fixing device can be realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a fixing device according to the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a conventional fixing device.

FIG. 4 is an explanatory diagram showing a conventional technique.

FIG. 5 is an explanatory diagram showing the relationship between the contact angle of silicone oil on the heating roll coating surface and the stain on the heating roll coating surface.

[Explanation of symbols]

1 is a heating roll, 2 is a surface coating, 5 is a pressure roll, 9 is a cleaning felt, 13 is a cam, 14 is toner, 2
0 is silicone oil.

Claims (7)

[Claims] 1. A fixing device comprising: a heating roll; a fixing roll pair including a pressure roll that rotates while being in pressure contact with the heating roll; and a cleaning member that wipes off toner adhered to the surface of the heating roll. A fixing device, wherein the cleaning member retracts from the heating roll when the rotation of the pair of fixing rolls is stopped. 2. The fixing device according to claim 1, wherein the cleaning member is a cleaning roll slidably provided on the surface of the heating roll. 3. The fixing device according to claim 1, wherein the cleaning member is a cleaning felt that is slidably and wound around the surface of the heating roll. 4. The fixing device according to claim 3, wherein the cleaning member is controlled so that a new cleaning felt is fed before the rotation of the pair of fixing rolls is stopped. 5. The fixing device according to claim 1, wherein the heating roll has a film of a polysiloxane resin or a film of a thermosetting resin containing a solid lubricant formed on the surface of the base material. . 6. The fixing device according to claim 1, wherein the releasing oil supplied to the cleaning member has a contact angle of about 5 to 20 degrees on the heating roll coating. 7. The heating roll has a coating film formed from a polysiloxane resin as a binder resin on the surface of a base material, and the oil supplied to the cleaning member is methylphenyl silicone oil. The fixing device according to item 1.