JPH08106232A - Fixation device - Google Patents

Abstract

PURPOSE: To provide a fixation device having a structure capable of solving such problems as dirtying by oil of a large size paper sheet and sticking of toner (offset) on a heated roller as failures occurring due to contact of a cleaning member serving also as an oil supplying means over the entire length of the heated roller. CONSTITUTION: In a fixation device comprising a heated roller 1 and a pressuring roller 2 rotated by pressure-contacting these with each other in an outer peripheral surface and a cleaning means 7 slid and contacted with the outer peripheral surface of the heated roller 1, The contact width of a part in which the cleaning means 7 is slid and contacted with the outer peripheral surface of the heated roller 1 is set smaller than the minimum width of a recording paper sheet fed between the rollers and this is slid and contacted with the paper feeding reference position of the heated roller 1.

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, etc. The present invention relates to a fixing device for hot-melt fixing, which can solve the problem that oil adhered to a roller constituting the fixing device adheres to recording paper and stains it.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile machine, etc., which is equipped with an electrophotographic image forming section, optical image information such as reflected light from a document is preliminarily uniformly charged on a photoreceptor. The electrostatic latent image obtained by irradiation,
Toner is supplied from a developing device to form a visible image, the toner image is transferred onto a recording paper, and then the paper is passed through a fixing device for thermal fixing. This fixing device has a heating roller having a heater inside and a pressure roller that comes into pressure contact with the outer peripheral surface of the heating roller, and heats the transferred recording paper passing between both rollers while applying pressure. , Fixing the toner image.

In the conventional fixing device described above, in order to prevent toner from adhering to the heating roller, a roller-shaped or other cleaning means is brought into sliding contact with the outer peripheral surface of the heating roller. The cleaning means is impregnated with oil, and when the cleaning means slides into contact with the heating roller, the heating roller is coated with oil and cleaning is performed at the same time. The reason for applying the oil is to prevent the fixing ability of the heating roller from being deteriorated due to toner adhesion. Generally, the cleaning unit has a contact length that extends over substantially the entire length of the fixing roller in the axial direction, and is set to be at least longer than the maximum size width of the recording paper to be fixed. However, in the conventional fixing device, when a small-sized recording paper is continuously passed, oil is applied to the non-paper passing portion,
Since the oil applied to the non-paper passing portion does not adhere to the recording paper and is not removed, the oil accumulates in the non-paper passing portion, and the large size recording paper is passed after the small size continuous paper passing. When the paper is passed, a large amount of oil accumulated on the heating roller adheres to the recording paper, which causes a problem that copy quality is deteriorated.

This will be described in more detail. Generally, there are two types of toner, namely, an oilless toner and an oil-coated toner. Since the release agent is mixed in the toner itself of the oilless toner, it is not necessary to apply oil to the heating roller in the fixing device for the oilless toner, but in reality, it is not fixed on the recording paper. 100% of the toner is not fixed on the recording paper, and a small amount of toner adheres to the heating roller side. In order to prevent such toner adhesion, a cleaning roller and a pad are conventionally brought into sliding contact with each other as a cleaning member for cleaning the heating roller.
Also, instead of using a cleaning member, a self-cleaning method has been proposed in which the toner adhering to the heating roller from the preceding recording paper is cleaned by the next recording paper. However, in the self-cleaning method, although some cleaning can be realized when the frequency of use of the copy is high, when the frequency of use is low and only a few tens of copies are made per day, heating is performed. Toner that adheres to the rollers will take a long time before the next sheet of recording paper passes, so if the power is left on during that time, the toner will stick to the heating roller and be cleaned by the next sheet of paper. It will not be done. If the toner is continuously used as it is, the toner adheres to the heating roller and an offset phenomenon occurs.

Further, even in a fixing device equipped with a cleaning member, the surface of the cleaning roller or the like is soiled by the toner and the life of the cleaning roller is shortened. To extend the life of cleaning rollers,
It is effective to impregnate the cleaning roller with oil and apply a small amount of oil to the heating roller. But,
If oil is applied to the entire heating roller by bringing the cleaning roller into contact with the heating roller over the entire length in the axial direction, the oil may adhere to the recording paper due to the fluctuation of the width of the recording paper as described above. Occurs (for example,
Japanese Utility Model Publication No. 61-135357, Japanese Utility Model Publication No. 2-1428.
No. 57).

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and is a problem caused by bringing a cleaning member, which also serves as an oil supply means, into contact with the heating roller over the entire length thereof. An object of the present invention is to provide a fixing device having a configuration capable of solving the problem of toner sticking (offset) to a heating roller.

[0007]

In order to achieve the above object, the present invention provides a fixing device provided with a heating roller and a pressure roller which rotate while being in pressure contact with each other on the outer peripheral surface, and a cleaning means which is in sliding contact with the outer peripheral surface of the heating roller. In the above, the contacting width of the portion of the cleaning means that is in sliding contact with the outer peripheral surface of the heating roller is set to be smaller than the minimum width of recording to be passed between the rollers, and the paper feeding reference position of the heating roller is set. It is characterized by sliding contact. Further, in a fixing device including a heating roller and a pressure roller that rotate while being in pressure contact with each other on the outer peripheral surface, and a cleaning unit that slides on the outer peripheral surface of the heating roller, the cleaning unit slides on the outer peripheral surface of the heating roller. The contact width of the contacting portion is set to be shorter than the minimum width of the recording paper passed between the rollers, and the sliding contact is made with the minimum outer diameter portion of the heating roller.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic configuration explanatory view of a fixing device for oilless toner to which the present invention is applied, and FIG. 2 is a side view of a main part. The pressure roller 2 is in pressure contact with the outer peripheral surface of the heating roller 1 provided with the internal heater H, and the transferred recording paper P that has entered between the paper feed guides 3 and 4 on the entry side is in both rollers 1. While being heated at the nip portion of No. 2, the surface toner T (oilless toner) is fixed. Code 5
Is a nail for peeling off the recording paper wound around the outer peripheral surface of the heating roller 1, and 6 is a pair of paper discharge rollers. Reference numeral 7 denotes a cleaning roller as a cleaning member that comes into sliding contact with (corotates with) the outer peripheral surface of the heating roller 1. Since the toner itself contains a release agent, it is not necessary to apply oil from the cleaning roller or the like to the heating roller. Absent.

According to the characteristic construction of the present invention, assuming that there is a drum-shaped heating roller having a small diameter in the central portion in the axial direction, the axial length of the cleaning roller (or pad) slidingly contacting the heating roller is set to the minimum recording paper width. A characteristic is that the cleaning roller is made shorter than the above and the cleaning roller is present only at a position corresponding to the central small diameter portion (or the sheet passing reference position) of the heating roller.

In the fixing device of this embodiment, the central portion in the axial direction of both rollers is set to the sheet passing reference position (center reference).
However, in the center-based sheet passing method, since the same load is applied to both axial end portions of the rollers, the axial end portions have a large load and the central portion has a small load at the nip portion of both rollers. Therefore, the pressure distribution shows a similar distribution. In addition, the heating roller 1 has an hourglass shape in order to prevent wrinkles from being formed on the recording paper, and has the smallest diameter in the central portion in the axial direction and the larger diameter toward the end portion. . Even if the heating roller having such a shape is expected to have the self-cleaning effect by the recording paper, the toner cleaning effect at the central portion of the small diameter becomes low. That is, since the drum-shaped roller tries to move the recording paper in its axial direction,
The heating roller and the recording paper slip, and the heating roller portion that contacts the slipped recording paper edge is cleaned, but the toner in the central portion is difficult to remove by the recording paper, and as a result, the outer peripheral surface of the central portion Toner adheres and solidification occurs.

On the other hand, according to the present invention, since the cleaning roller (pad) is slidably contacted only with the central portion of the small diameter which is the paper passing reference position, and the width is shorter than the width of the minimum size recording paper, the heating is performed. It is possible to prevent the toner accumulation in the central portion of the roller. In addition, if the oil is supplied to the entire length of the roller from a cleaning member that slides in contact with the heating roller over the entire length as in the conventional case, after the small-sized recording paper is continuously fed, the oil is collected outside the width of the small-sized recording paper. However, since the present invention is premised on the oilless toner, and the oil is not supplied from the short cleaning roller to the outside of the width, this problem does not occur. Further, even in a fixing device which adopts a one-sided standard paper-passing mode instead of a center standard, when a drum-shaped heating roller is used, a cleaning roller (pad) having a size smaller than the minimum recording paper width is slidably contacted to the central small diameter portion. As a result, the same effect can be obtained.

Incidentally, Japanese Utility Model Laid-Open No. 63-47370 discloses an example in which a plurality of oil coating devices are arranged on the outer peripheral surface of a heating roller at predetermined intervals, but the purpose is different from the present invention. ing. Incidentally, in the claims, the cleaning member includes a roller shape and a pad shape, and also includes both those which also serve as oil application means and those which do not.

[0013]

According to the present invention, in a fixing device using an oilless toner and a drum-shaped heating roller having a small central portion, the cleaning member has a short structure in which only the small diameter portion of the heating roller is brought into sliding contact. Therefore, problems such as contamination of large-sized recording paper with oil and sticking of toner (offset) to the heating roller, which are problems caused by bringing the cleaning member, which also serves as an oil supply means, into contact with the heating roller over the entire length of the heating roller, Can be resolved.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view of a fixing device for oilless toner to which the present invention is applied.

FIG. 2 is a side view of a main part of FIG.

[Explanation of symbols]

1 heating roller, 2 pressure roller, 3, 4 paper feed guide, 5 claws, 6 paper discharge roller pair, 7 cleaning member.

Claims (2)

[Claims] 1. A fixing device comprising a heating roller and a pressure roller that rotate while being in pressure contact with each other on their outer peripheral surfaces, and a cleaning means that is in sliding contact with the outer peripheral surface of the heating roller, wherein the cleaning means is the outer periphery of the heating roller. The contact width of the portion that is in sliding contact with the surface is set to be shorter than the minimum width of the recording paper that is passed between the rollers, and is in sliding contact with the sheet passing reference position of the heating roller. apparatus. 2. A fixing device comprising a heating roller and a pressure roller which rotate while being in pressure contact with each other on an outer peripheral surface thereof, and a cleaning means which is in sliding contact with the outer peripheral surface of the heating roller, wherein the cleaning means is the outer peripheral surface of the heating roller. A fixing means characterized in that a contact width of a portion slidingly contacting the surface is set to be shorter than a minimum width of a recording paper which is passed between the rollers, and is in sliding contact with a minimum outer diameter portion of the heating roller. apparatus.