JP3266428B2 - 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. The present invention relates to a fixing device capable of solving the problem that oil adhering to a roller constituting the fixing device adheres to and contaminates recording paper in a fixing device for performing heat melting and fixing.

[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 having 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 both rollers while applying pressure. And fixing of the toner image.

In the above-mentioned conventional fixing device, in order to prevent toner from adhering to the heating roller, a roller-shaped or other cleaning means is slid on the outer peripheral surface of the heating roller. The cleaning means is impregnated with oil, and at the same time as the cleaning means is in sliding contact with the heating roller, oil is applied to the heating roller to perform cleaning. The reason for applying the oil is to prevent the fixing ability of the heating roller from being reduced due to the toner fixation. 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 width of the recording paper to be fixed. However, in the conventional fixing device, when small-sized recording paper is continuously passed, oil is also applied to a non-paper passing portion,
Since the oil applied to the non-sheet passing portion does not adhere to the recording paper and is not removed, the oil accumulates in the non-sheet passing portion, and the large-size recording paper is fed 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, causing a problem that the copy quality is deteriorated.

To explain this in more detail, generally, there are two types of toner, an oilless toner and an oil-coated toner. Since oil-less toner contains a release agent in the toner itself, it is not necessary to apply oil to the heating roller in a fixing unit for oil-less toner. Not 100% of the toner is fixed on the recording paper, but a small amount of toner adheres to the heating roller side. In order to prevent such toner adhesion, a cleaning roller or a pad has been conventionally brought into sliding contact with a cleaning member for cleaning the heating roller.
In addition, instead of using a cleaning member, a self-cleaning method has been proposed in which toner adhered to a heating roller from a preceding recording sheet is cleaned by a next recording sheet. However, in the self-cleaning method, a certain degree of cleaning can be realized when the frequency of use of the copy is high. However, when the frequency of use is low and only about several tens of copies are performed a day, the heating is performed. The toner adhered to the roller will take a long time until the next recording paper passes, so if the power is left ON during that time, the toner will stick to the heating roller and will be cleaned by the next paper. Will not be done. If the toner is continuously used, the toner adheres to the heating roller, causing an offset phenomenon.

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

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above, and has been described in connection with the accompanying drawings. It is another object of the present invention to provide a fixing device having a configuration capable of solving the problem of toner sticking (offset) to a heating roller.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a pressure roller which rotates while being pressed against each other on an outer peripheral surface, and an axial direction.
Rutotomoni comprising a pressurized heat roller hourglass countercurrent central portion is small, sliding contact axial length heating roller outer peripheral surface and a shorter cleaning means than the minimum width of the recording paper, oil-less toner
In the fixing device, the contact width of a portion where the cleaning means slides on the outer peripheral surface of the heating roller is set to be shorter than the minimum width of a recording sheet passed between the rollers, and It is characterized by being in sliding contact with the paper passing reference position. In addition, a pressure roller that rotates while being pressed against each other on the outer peripheral surface, and a drum-shaped
A pressurized heat roller, sliding contact axial length heating roller peripheral surface is shorter than the minimum width of the recording paper. Cleaning means
In the fixing device using the oilless toner, a contact width of a portion where the cleaning unit slides on the outer peripheral surface of the heating roller is set to be shorter than a minimum width of recording passed between the rollers. In addition, it is characterized by being in sliding contact with the minimum outer diameter portion of the heating roller.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic structural explanatory view of a fixing device for an oilless toner to which the present invention is applied, and FIG. 2 is a side view of a main part. A 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 The toner is pressurized while being heated at the nip portion 2 and the toner T (oilless toner) on the surface is fixed. Code 5
Reference numeral denotes a claw for peeling off the recording paper wound around the outer peripheral surface of the heating roller 1, and reference numeral 6 denotes a pair of paper discharge rollers. Reference numeral 7 denotes a cleaning roller as a cleaning member that slides (co-rotates) with the outer peripheral surface of the heating roller 1. Since a release agent is mixed in the toner itself, it is not necessary to apply oil to the heating roller from the cleaning roller or the like. Absent.

The characteristic configuration of the present invention is based on the premise that a drum-shaped heating roller having a small diameter at the axial center is provided, and the axial length of the cleaning roller (or pad) slidingly contacting the heating roller is set to the minimum recording paper width. The cleaning roller is provided only at a position corresponding to a central small-diameter portion (or a paper 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 as the paper passing reference position (center reference).
However, in the paper feeding method based on the center, the same load is applied to both ends in the axial direction of the roller, so that the load at the axial end is large and the center is small at the nip portion of both rollers. Therefore, the pressure distribution shows a similar distribution. Further, the heating roller 1 has a drum shape in order to prevent wrinkles from being formed on the recording paper, and has the smallest diameter at the center in the axial direction, and has a larger diameter toward the end. . Even if the self-cleaning effect of the recording paper is expected for the heating roller having such a shape, the cleaning effect of the toner at the central portion having a small diameter is low. That is, the drum-shaped roller tries to move the recording paper in its axial direction,
The heating roller and the recording paper slip, and the portion of the heating roller contacting the end of the slipping recording paper is cleaned, but the toner in the center is hardly removed by the recording paper. The phenomenon of toner adhesion and solidification occurs on the surface.

On the other hand, in the present invention, the cleaning roller (pad) is slid only at the central portion of the small diameter, which is the paper passing reference position, and is shorter than the width of the minimum size recording paper. It is possible to prevent toner accumulation at the center of the roller. In addition, if oil is supplied to the entire length of the roller from a cleaning member or the like that slides over the entire length of the heating roller as in the related art, after the small-size recording paper is continuously fed, the oil pools outside the width of the small-size recording paper. However, in the present invention, oilless toner is assumed, and no oil is supplied outside the width from the short cleaning roller, so that this problem does not occur. Further, even in a fixing device that adopts a one-side reference paper passing mode instead of a center reference, when a drum-shaped heating roller is used, a cleaning roller (pad) having a size smaller than the minimum recording sheet width is slidably contacted with the central small diameter portion. Thereby, a similar effect can be obtained.

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

[0013]

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

[Brief description of the drawings]

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

FIG. 2 is a side view of a main part of FIG. 1;

[Explanation of symbols]

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

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (2)

(57) [Claims] 1. A pressing member which rotates while being pressed against each other on an outer peripheral surface.
Rutotomoni comprising a pressurized heat low <br/> La hourglass pressure roller and the axial center portion is small, sliding contact axial length heating roller outer peripheral surface and a shorter cleaning means than the minimum width of the recording paper ,
In the fixing device using the oilless toner, a contact width of a portion where the cleaning unit slides on the outer peripheral surface of the heating roller is set to be shorter than a minimum width of the recording paper passed between the rollers, and A fixing device, wherein the heating roller is in sliding contact with a paper passing reference position. 2. A rotary member which rotates while being pressed against each other on the outer peripheral surface.
Rutotomoni comprising a pressurized heat low <br/> La hourglass pressure roller and the axial center portion is small, sliding contact axial length heating roller outer peripheral surface and a shorter cleaning means than the minimum width of the recording paper ,
In the fixing device using the oilless toner, a contact width of a portion where the cleaning unit slides on the outer peripheral surface of the heating roller is set to be shorter than a minimum width of the recording paper passed between the rollers, and A fixing device, which is in sliding contact with a minimum outer diameter portion of the heating roller.