JPH0553470A - Fixing unit - Google Patents

Abstract

PURPOSE:To prevent adhesion of the non-fixed toner to the surface of a fixing thermistor, and prevent rear face soil of paper to be caused by adhesion by providing a cleaning member at a position upstream from the thermistor on a fixing roller. CONSTITUTION:In a fixing unit for an image forming device, which has a fixing roller 1 with a thermistor, a cleaning pad 7, which is positioned on the same circumference with a fixing thermistor 2 and has a width equal to or a little larger than the width of the thermistor 2, is provided upstream from the thermistor 2 on the fixing roller 1. As a result, the residual toner adhering to the fixing roller 1 among the non-fixed toner on the recording paper adheres to the cleaning pad 7, and the fixing thermistor is not soiled. Change of the fixing thermistor 2 is not required. Adhesion of the non-fixed toner to the surface of the fixing thermistor 2 is thereby prevented to prevent rear face soil of the paper due to adhesion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing unit for an image forming apparatus such as a laser printer, a copying machine or a facsimile.

[0002]

2. Description of the Related Art FIG. 3 is a schematic configuration diagram of a fixing unit.

In the image forming apparatus, the recording information on the photoreceptor which is visualized by toner is transferred onto the recording paper by the transfer charger, and the visible image which is the transferred recording information on the recording paper is fixed by the fixing thermistor 2. The image is fixed by a fixing unit including a fixing roller 1 provided with a pressure roller 3 and a pressure roller 3 that is in pressure contact with the fixing roller 1. That is, the unfixed toner 5 on the recording paper 4 after transfer is fixed by passing through the fixing unit.

[0004]

However, at this time, not all the toner on the recording paper 4 is fixed on the paper, but a small amount of toner adheres to the fixing roller 1 as the residual toner 6.

The residual toner 6 on the fixing roller 1 is reattached to the recording paper on which the toner has been sequentially fixed, and is brought along with the recording paper.
Since the fixing thermistor 2 is in contact with the fixing roller 1, the residual toner is always attached and deposited on the surface portion of the fixing thermistor 2. Since the life of the fixing unit is equivalent to tens of thousands of recording sheets, the amount of adhering and accumulating becomes very large.

If the surface of the fixing thermistor 2 becomes dirty,
When the power is turned on again, the toner adhered to the surface of the thermistor 2 in the idling state adheres to the fixing roller 1 as the fixing roller 1 rotates, moves rotationally, and further adheres to the pressure roller 3. . The toner attached to the pressure roller 3 is, as shown in FIG.
Transfers to and adheres to the back side of a sheet of paper, and stains the back side. After passing 1 to 2 sheets, the thermistor 2 is heated by the heat of the fixing roller 1.
Since the upper toner is melted and becomes difficult to separate from the thermistor 2, back stain does not occur. However, when the image forming apparatus is used, the first 1 The second sheet of paper is a problem that can always occur.

Therefore, an object of the present invention is to take measures against the above back stain.

[0008]

The present invention solves this problem by
In a fixing unit having a fixing roller with a thermistor, at a position upstream of the thermistor on the fixing roller,
The problem is solved by providing a cleaning member.

It is preferable that the cleaning member is on the same peripheral line as the thermistor and has a width at least equal to the width of the thermistor.

Further, it is more preferable that the cleaning member is integrally attached to the holder of the thermistor and can be attached to and detached from the holder.

Both the cleaning member and the thermistor are preferably pressed toward the center of the fixing roller.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments based on the drawings.

At present, there is no non-contact type thermistor with high precision, so a structure of the contact type thermistor in which toner is not adhered will be described. As shown in FIG. 1, on the upstream side of the thermistor 2 on the fixing roller 1, there is provided a cleaning pad 7 on the same peripheral line as the fixing thermistor 2 and having a width equal to or slightly larger than the width of the thermistor 2. Set up. As a result, the unfixed toner on the recording paper 4 which remains on the fixing roller 1 adheres to the cleaning pad 7 and does not stain the fixing thermistor 2.
The material of the cleaning pad is not particularly limited as long as it has heat resistance, and for example, heat resistant felt or the like can be considered. Further, an elastic means or the like is used to press the cleaning pad 7 against the fixing roller 1, but as can be recognized in FIG. It is possible to set freely by adjusting etc.

Since the cleaning pad 7 becomes soiled with time, it is preferable that the cleaning pad 7 can be easily attached and detached as shown in FIG. 2 so that it can be easily replaced. That is, by extending the member holding surface of the holder 9 of the thermistor 2,
A cleaning member is attached to the tip end portion of the cleaning unit 7 so that the cleaning unit 7 is integrated with the bending unit 10, and when the cleaning unit 7 is replaced, the engagement between the bending unit 10 and the cleaning pad 7 is released.

Cleaning pad 7 and fixing thermistor 2
Are both pressed toward the center of the fixing roller 1.

[0016]

In the fixing unit according to the first aspect of the present invention, since the cleaning member is provided on the fixing roller at a position upstream of the thermistor, the unfixed toner transferred to the fixing roller reaches the thermistor. It is removed by the cleaning member so that the thermistor does not become contaminated over its life and does not need to be replaced.

According to a second aspect, the cleaning member comprises:
Having the width on the same circumference as the thermistor and at least equal to the width of the thermistor surely prevents unfixed toner from adhering to the thermistor.

According to the third or fourth aspect, the cleaning member is integrally attached to the thermistor holder,
If the holder is detachable, the cleaning member can be easily replaced.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which the cleaning pad of FIG. 1 is held.

FIG. 3 is a schematic configuration diagram of a known fixing unit.

FIG. 4 is a diagram showing a back smear phenomenon due to unfixed toner.

[Explanation of symbols]

 1 Fixing roller 2 Thermistor 7 Cleaning pad 8 Leaf spring 9 Holder

Claims (5)

[Claims] 1. A fixing unit for an image forming apparatus having a fixing roller with a thermistor, wherein a cleaning member is provided at a position on the fixing roller upstream of the thermistor. 2. The fixing unit according to claim 1, wherein the cleaning member is on the same peripheral line as the thermistor and has a width at least equal to the width of the thermistor. 3. The fixing unit according to claim 1, wherein the cleaning member is integrally attached to the holder of the thermistor. 4. The fixing unit according to claim 3, wherein the cleaning member is attachable to and detachable from the holder. 5. The fixing unit according to claim 1, wherein the cleaning member and the thermistor are both pressed toward the center of the fixing roller.