JP2000187410A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent residual toner from slipping through, to surely restrain back staining offset and to prevent a cleaning web from being needlessly fed by changing the feeding amount of the cleaning web in accordance with the surface temperature of a fixing rotating body. SOLUTION: Plain paper P to which toner is transferred is carried to a fixing device 15 by a carrying belt 25 after electrostatic attractive force between a drum and the paper P is removed by a separation electrifier 34. A CPU 16 controls an image forming means such as a laser 27 and also the fixing device 15. A thermistor functioning as a temperature detection means is arranged in a contact state on the outer peripheral surface of a fixing roller 1 and a detection signal therefrom is transmitted to a control means. After starting copying, a take-up shaft is actuated and the web performs cleaning by executing winding operation once. When the surface temperature of the roller 1 is lowered and the temperature detected by the thermistor is equal to or under a specified value, the take-up shaft is actuated to wind up the web twice so as to control the web feeding amount per one copy to be a specified amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller type toner image fixing device most commonly used in an electrostatic recording device such as an electrophotographic copying machine or a facsimile, that is, a toner image fixing device formed on a recording material. More specifically, the present invention relates to a toner image fixing device including a fixing roller that heats and melts toner in contact with a toner image, and a pressing roller that presses and feeds a recording material between the fixing roller and the toner roller. The present invention relates to a cleaning device of a fixing device for cleaning.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a web cleaning apparatus for cleaning with a cleaning web made of a nonwoven fabric or the like in order to clean and remove residual toner on an object to be cleaned such as a fixing roller is widely used. It is used.

FIG. 2 shows a toner image T formed by electrophotography.
1 shows an apparatus for fixing a sheet P to plain paper P by heating.
In FIG. 2, reference numeral 1 denotes a fixing roller, which is a fixing rotating body having a heating heater 3 such as a halogen heater therein, and is adapted to rotate in a direction indicated by an arrow upon receiving a driving force from a driving motor (not shown).

Below the fixing roller 1, a pressure roller 2 is supported by a bearing, and is disposed so as to be in pressure contact with the fixing roller 1 at least at the time of fixing by a known pressing means. The roller 1 rotates with the rotation of the roller 1.

Further, a temperature sensing element 4 such as a thermistor or a heat conductor is arranged in contact with the outer peripheral surface of the fixing roller 1 and transmits a detection signal thereof to a known control means.
By controlling the output of the heater 3 or the voltage applied thereto by the control means, the temperature of the outer peripheral surface of the fixing roller 1 is maintained at the toner image melting temperature.

[0006] Separating claws 51 and 52 for reliably separating the fixed plain paper P from the fixing roller 1 and the pressing roller 2 are in contact with the fixing roller 1 and the pressing roller 2. It is formed by coating a polyimide or polyamide resin with a fluororesin.

On the other hand, a cleaning device 6 for removing foreign matters such as offset toner and paper powder attached to the surface of the fixing roller 1 from the roller surface is disposed above the fixing roller 1. A cleaning web 60 made of a heat-resistant nonwoven fabric is used.

The web pressure roller 65 is rotatably supported at both ends by bearings 72, and presses against the fixing roller 1 to remove foreign matters, such as offset toner and paper powder, adhering to the surface of the fixing roller 1 from the roller surface. Prevents offset.

The web is wound up by a predetermined amount per copy in synchronization with the copy operation, irrespective of one copy or a plurality of continuous copies by a driving means (not shown).

[0010]

However, in the above-mentioned prior art, when a predetermined number or more of sheets are continuously copied, paused, and then re-copied, toner remaining between the cleaning web and the fixing roller slips through, and the fixing roller is removed. There is a possibility that the residual toner transferred from the roller to the pressure roller is retransferred to the back side of the copy paper, causing a back-stain offset.

The reason why the back stain offset is remarkable at the time of re-copying after a pause after a large amount of continuous copying is as follows.

During continuous copying, the web is wound up in synchronization with the copying operation, and an unused surface is always supplied with the rotation of the fixing roller.

Further, a small amount of toner that cannot be completely collected by the cleaning web is dispersed on the surface of both the fixing roller and the pressure roller, and flows out evenly in small amounts on both the front and back surfaces of the transfer material. Almost inconspicuous as image stains.

On the other hand, when copying is started again after pausing, the toner accumulated between the fixing roller and the cleaning web strongly adheres to the fixing roller due to the heat during pausing. When the toner passing through the fixing roller comes into contact with the pressure roller, the toner solidifies and adheres on the pressure roller having a low temperature, so that most of the toner passing through is transferred to the pressure roller side.

When the transfer material is fed here, most of the toner on the pressure roller is retransferred to the back surface of the transfer material, which is less releasable than the pressure roller, and a back-stain offset occurs.

In particular, when the wattage of the fixing heater is not sufficiently large, the temperature of the fixing roller gradually decreases in continuous copying, whereby the amount of residual toner not fixed to the transfer material increases due to a decrease in fixing property, The occurrence of the offset becomes more significant.

It has been confirmed that increasing the web feed amount is effective in preventing back-stain offset, but when only a small amount of copying is performed, the amount of decrease in the fixing roller temperature is small, so Since the amount of residual toner due to the deterioration of the toner property is also reduced, wasteful web feed occurs by uniformly increasing the web feed amount, leading to an increase in running cost.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a fixing device which can prevent the occurrence of a back-stain offset and can appropriately feed the cleaning web.

[0019]

Means for Solving the Problems To achieve the above object, a first invention according to the present application is to provide a fixing rotator that contacts a toner image formed on a recording material and heats and fixes the toner image. A fixing rotator cleaning unit for pressing the fed cleaning web against the fixing rotator to remove foreign matter containing at least toner adhered to the fixing rotator. Temperature detection means for detecting the surface temperature, cleaning means control means for controlling the fixing rotating body cleaning means,
Wherein the cleaning unit control unit controls the feed amount of the cleaning web in accordance with the surface temperature of the fixing unit detected by the temperature detection unit.

With this arrangement, when the surface temperature of the fixing rotator drops below a predetermined temperature, the amount of residual toner becomes larger than when the surface temperature exceeds the predetermined temperature. The toner remaining between the cleaning web and the fixing rotator is reliably collected, so that the back-stain offset due to the slippage of the remaining toner is prevented.

When the surface temperature of the fixing rotating body is equal to or higher than a predetermined density, the amount of residual toner is small, so that offset can be prevented even if the web feed amount is small, so that wasteful web feed is also prevented.

According to a second aspect of the present invention, there is provided a fixing rotator for heating and fixing a toner image by contacting the toner image formed on a recording material, and pressing a fed cleaning web against the fixing rotator. A fixing device including a fixing rotator cleaning unit configured to remove foreign matters including at least toner adhered to the fixing rotator; a temperature detecting unit configured to detect a surface temperature of the fixing unit; Cleaning means control means for controlling the body cleaning means, the cleaning means control means,
The number of times the cleaning web is fed is controlled according to the surface temperature of the fixing unit detected by the temperature detecting unit.

With this arrangement, when the surface temperature of the fixing rotator drops below a predetermined temperature, the amount of residual toner becomes larger than when the surface temperature becomes higher than a predetermined temperature. The toner remaining between the cleaning web and the fixing rotator is reliably collected, so that the back-stain offset due to the slippage of the remaining toner is prevented.

When the surface temperature of the fixing rotating body is equal to or higher than a predetermined temperature, the amount of residual toner is small, so that offset can be prevented even if the number of web feeds is small, so that wasteful web feed is also prevented.

According to a third aspect of the present invention, there is provided an image forming means for forming a toner image on a recording material, and a fixing means for fixing the toner image on the recording material on which the toner image has been formed by the image forming means. Wherein the fixing device according to the first or second invention is provided as the fixing unit.

In this way, even when re-image is formed after a pause after continuous image formation, contamination of the recording material due to back-stain offset is prevented, and the feed amount of the cleaning web of the fixing rotating body cleaning means is made appropriate. Accordingly, it is possible to provide an image forming apparatus capable of forming a high quality image at a low running cost.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a fixing device according to this embodiment will be described below with reference to FIG.

First, a fixing roller 1 as a fixing rotating body
Is a heat-resistant elastic layer 12 of 0.1 to 1 m on the outer peripheral surface of a hollow core 1 of a metal such as aluminum, stainless steel or iron.
m, and a resin layer 13 as a release layer is further formed thereon with a thickness of about 1.0 to 40 μm.

The pressure roller 2 has a relatively thick (for example, 5 to 10 m) elastic layer 22 made of silicone rubber, fluorine rubber, fluorosilicone rubber or the like on the outer peripheral surface of the metal roller core 1.
m) and a fluororesin layer 2 serving as a release layer thereon
8 is provided with a thickness of about 30 to 50 μm.

The cleaning device (fixing rotating body cleaning means) 6 includes a cleaning web 6 made of a heat-resistant nonwoven fabric.
0 is used. The web 60 is usually made by mixing a high-temperature soft polyester fiber with an aromatic polyamide fiber to form a nonwoven fabric having appropriate softness and strength, and adding a silicone oil having a viscosity of about 10,000 centistokes to the nonwoven fabric. It is impregnated at high temperature and wound.

The web pressing roller 65 is formed by coating a metal core with a heat-resistant rubber layer such as silicone rubber, and in order to obtain sufficient softness, a foaming agent is put in the rubber to form a sponge. . Rubber hardness is 10 to 2
0 ° (Asker-C) is used.

Next, the configuration of an image forming apparatus having the fixing device of the present embodiment will be described with reference to FIG.

In FIG. 3, the original placed on the platen glass of the reader section is illuminated by an illumination lamp 10, and the reflected light is guided to a CCD by an optical system including a reflecting mirror and a lens (not shown), whereby image information is obtained. Converted to electrical signals.

In the printer section 80, the CPU 16 is a CCD
The laser 27 emits light and irradiates the photosensitive drum 26 on the basis of the image signal from. The electrostatic latent image formed by irradiating the uniformly charged photosensitive drum 26 with the laser beam by the primary charger 20 is visualized by the toner supplied from the developing device 28 to become a toner image.

On the other hand, the plain paper P as a recording material stored in the cassettes 29 to 31 is fed by a pickup roller, synchronized with the above-described toner image by a registration roller, and rotated by the registration roller to form a printer unit. Sent to 80.

In the printer section 80, the toner image is transferred onto the plain paper P by electrostatically attracting the toner on the photosensitive drum 26 from the back side of the plain paper P by the corona charger 35 or the like. The toner remaining on the photosensitive drum 26 is removed by the cleaning unit 24. Here, the image forming means includes the primary charger 20, the photosensitive drum 2
6, a laser 27, a developing device 28, a corona charger 35 and the like.

The plain paper P to which the toner has been transferred is removed from the electrostatic attraction force with the drum by the separation charger 34.
The sheet is conveyed to the fixing device 15 by the conveyance belt 25. The CPU 16 controls the image forming means such as the laser 27 and also controls the fixing device 15.

In this embodiment, the cleaning device of the fixing device 15 is the same as that described in the prior art shown in FIG. 2, but the web winding is controlled by a CPU 16 as a cleaning means control means shown in FIG. Only the method of controlling the shaft 61 is different.

Hereinafter, the control method according to this embodiment will be described with reference to FIG.
This will be described with reference to FIG.

A thermistor 4 as a temperature detecting means is disposed in contact with the outer peripheral surface of the fixing roller 1 and transmits a detection signal to a known control means. , The temperature of the outer peripheral surface of the fixing roller 1 is maintained at 200 ° C.

When the number of copies is set on the operation panel 9 and the start button is pressed, copying is started. After the start of copying, the take-up shaft 61 is operated, and the web 60 is fed by one sheet of 0.02 mm / A4 for cleaning by one winding operation. However, the surface temperature of the fixing roller 1 decreases, When the temperature detected by the thermistor 4 becomes 180 ° C. or lower, the take-up shaft 61 operates so as to wind the web 60 twice, and the web feed amount per copy is 0.04.
mm.

FIG. 1 is a diagram showing a rotation sequence of the web winding shaft of the present embodiment.

The experimental results of this embodiment and the conventional example will be described below.

In the conventional example 1, the web feed amount is 0.02 m
m / A4 is set to one, and in the conventional example 2, the web feed amount is set to 0.04 mm / A4.

With each of these devices, A4 size paper is printed at a rate of 50 sheets / min.
After continuous copying of 0 sheets, after a 1-minute pause, the presence or absence of back-stain offset when five sheets were continuously passed was checked.

Table 1 shows the results.

[0047]

[Table 1] As shown in Table 1, in Conventional Example 1, a back-stain offset occurs after continuous copying, whereas in the present embodiment, the back-stain offset can be prevented.

When a 10 m roll web is used, the life of the web is 250,000 sheets in Conventional Example 2, but in this embodiment, the fixing roller temperature is 180 ° C. by continuous copying.
If the ratio is less than 10% of all copies, the web life is 450,000 sheets, and if it is 30% of all copies, the web life is 380,000 sheets, greatly extending the web replacement time. I was able to.

In the present embodiment, the case where the fixing roller is a fixing roller is described, but a fixing film may be used, and the present invention is not limited to this.

[0050]

As described above, according to the first aspect of the present invention, the remaining toner is prevented from slipping through by changing the feeding amount of the cleaning web in accordance with the surface temperature of the fixing rotating body. In addition, the back dirt offset can be surely suppressed, and at the same time, the wasteful feeding of the cleaning web can be prevented, and the cleaning web replacement time can be extended.

According to the second invention of the present application,
By changing the number of times the cleaning web is fed according to the surface temperature of the fixing rotator, it is possible to prevent the residual toner from slipping through and to surely prevent the back dirt offset, and at the same time, to prevent unnecessary feeding of the cleaning web and replace the cleaning web. The time can be extended.

According to the third invention of the present application,
Even during re-image formation after a pause after continuous image formation, contamination of the recording material due to back surface stain offset can be prevented, and the amount of cleaning web feeding of the fixing rotating body cleaning means can be adjusted to an appropriate amount. An image forming apparatus capable of forming a high quality image can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a rotation sequence of a web winding shaft according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a fixing device according to an embodiment of the present invention and a conventional example.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus including a fixing device according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 fixing roller 4 thermistor 6 cleaning device 9 operation panel 16 CPU 20 primary charger 26 photosensitive drum 27 laser 28 developing device 35 corona charger 60 cleaning web 61 web take-up shaft 65 web pressure roller 66 web feed shaft P plain paper T toner

Claims (3)

[Claims] A fixing rotator that heats and fixes the toner image by contacting the toner image formed on the recording material; and a cleaning web that is sent is pressed against the fixing rotator to contact the fixing rotator. A fixing device including a fixing rotator cleaning unit for removing foreign matters including at least toner adhered thereto; a temperature detecting unit for detecting a surface temperature of the fixing unit; and a cleaning unit for controlling the fixing rotator cleaning unit. A fixing unit, wherein the cleaning unit control unit controls a feed amount of the cleaning web in accordance with a surface temperature of the fixing unit detected by the temperature detecting unit. 2. A fixing rotator for heating and fixing a toner image in contact with a toner image formed on a recording material, and a cleaning web sent out is pressed against the fixing rotator to contact the fixing rotator. A fixing device including a fixing rotator cleaning unit for removing foreign matters including at least toner adhered thereto; a temperature detecting unit for detecting a surface temperature of the fixing unit; and a cleaning unit for controlling the fixing rotator cleaning unit. A fixing unit, wherein the cleaning unit control unit controls the number of times the cleaning web is fed according to the surface temperature of the fixing unit detected by the temperature detecting unit. 3. An image forming apparatus comprising: an image forming unit that forms a toner image on a recording material; and a fixing unit that fixes the toner image on the recording material on which the toner image has been formed by the image forming unit. An image forming apparatus comprising the fixing device according to claim 1 or 2 as the fixing unit.