JPH10221988A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the blur of a character by eliminating the flapping of a recording paper caused by forward winding executed for increasing the quantity of heat supplied to toner, in a fixing device for dealing with high-speed successive sheets. SOLUTION: In the fixing device, a recording paper carrying plate 4 having a heat source 4a and a recording paper holding sucking port 5 is arranged in the front stages of a heating roller 1 and a pressure roller 2 for attaining fixation and the recording paper 3 passes on the recording paper carrying plate 4, to be wound on a part of the heating roller 1 and then, through the nipping part 8 between the heating roller 1 and the pressure roller 2, to fix an unfixed image on the recording paper 3. Further, the sucking pressure of the recording paper holding sucking port 5 can be changed according to the thickness of the recording paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to a fixing device of an electrophotographic recording device such as a facsimile, and more particularly, to a high-speed conveyance technology of a recording sheet in a fixing unit.

[0002]

2. Description of the Related Art A recording apparatus using an electrophotographic method records a toner through a process of developing (transferring) toner as an image on a recording paper surface and a process of fixing the visualized toner image on recording paper. Print on paper.

[0003] The toner is melted by heating, and is fused to the recording paper by passing the recording paper through a nip formed between a heat roller (fixing roller) for fixing and a pressure roller.
It is fixed, that is, fixed by cooling.

In a high-speed machine in which the printing speed exceeds 300 ppm, the time required for the recording paper to pass through the nip becomes short, so that the energy (amount of heat) required for fixing is insufficient, and a fixing defect occurs. In order to compensate for this shortage of heat, a forward winding method has been proposed in which the recording paper is wound around a part of the fixing roller before being inserted into the nip portion (DE2717).
260C3).

However, when adopting the front winding method,
The recording paper flutters near the winding area,
Character blur occurs. In the conveyance of the recording paper, bending, which is a so-called buckling, occurs due to hardness which is one of the characteristics of the recording paper, which causes fluttering. As the thickness of the recording paper increases, the flapping of the recording paper increases, and the image of the recording paper is disturbed in the fixing unit.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-speed printing copier or printer which can prevent fluttering during conveyance of recording paper and provide high-quality images.

[0007]

In order to achieve the above-mentioned object, the following problem solving means is proposed.

(1) One is that a recording paper transport plate having a heat source and a recording paper holding suction port is disposed in front of a heating roller and a pressure roller for fixing, and the recording paper is moved on the recording paper transport plate. A fixing device for fixing an unfixed image on recording paper through a nip portion between the heating roller and the pressure roller after passing and winding around a part of the heating roller records the suction pressure of the recording paper holding suction port. It is characterized by comprising means for changing according to the thickness of the paper.

As described above, when the recording paper is conveyed,
The hardness, which is one of the characteristics of the recording paper, causes breakage, so-called buckling, which causes fluttering. This is more likely to occur as the thickness of the paper is larger. In particular, when a recording paper having a paper thickness of 150 μm or more is used, flutter is likely to occur and the image quality is significantly degraded.

In consideration of the above, for example, in order to reduce flutter, the suction pressure at the recording paper transport plate is specified to be 1.86 kPa or more when the paper thickness is 125 μm or more. However, the paper thickness 1
When a recording sheet having a size of 00 μm or less is conveyed, the recording sheet is cut at a perforation. Therefore, when the sheet thickness is 100 μm or less, the suction pressure is specified to be 1.86 kPa or less.

That is, the boundary pressure of the suction pressure of the recording paper holding suction port provided on the recording paper transport plate is determined so as to satisfy both requirements of suppressing the flutter of the recording paper during the transport of the recording paper and preventing the cutting of the recording paper. When the recording paper thickness is 100 μm or less, the boundary pressure is lower than the boundary pressure, and when the recording paper thickness is 125 μm or more, the boundary pressure is higher than the boundary pressure. To this end, the suction pressure of the recording paper holding suction port is changed according to the thickness of the recording paper by the suction pressure changing means of the recording paper conveyance plate. And character blurring can be prevented.

(2) The other is a heating roller for fixing,
In a fixing device in which a recording paper transport plate having a heat source and a recording paper holding suction port is arranged at a stage preceding the pressure roller,
According to another feature of the present invention, there is provided means for changing the suction pressure of only the leading end of the recording paper transport plate, in which the recording paper tends to flutter, in accordance with the thickness of the recording paper.

According to this structure, in addition to preventing the recording paper from fluttering, the suction pressure changing means for that purpose can be minimized.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the fixing device of the present invention, and is a sectional side view of a front winding type fixing device in an electrophotographic recording system.

A nip 8 is formed between the heating roller 1 and the pressure roller 2 by pressing the pressure roller 2 against the fixing heating roller 1 with a constant load. The fixing roller 1 is formed by coating an aluminum cylinder with a releasable resin such as a fluororesin, and includes a heater 1a serving as a heat source inside.

A recording paper transport plate 4 having a heater 4a and a recording paper holding suction port 5 is disposed in front of the heating roller 1 and the pressure roller 2.

The recording paper 3 is a continuous folding paper, and an unfixed image is formed on the upper surface before fixing. Recording paper 3
Is heated (preheated) by being transported on a recording paper transport plate 4 having a heat source. At this time, in order to hold the recording paper 3 on the recording paper transport plate 4, the recording paper 3 is sucked by the suction device 6 from the plurality of recording paper holding suction ports 5 provided on the recording paper transport plate 4.

In high-speed printing, a sufficient amount of heat cannot be obtained with the recording paper transport plate 4 alone. Therefore, before the nip portion is inserted, a portion (front winding portion) 7 around which the recording paper 3 is wound around a part of the heating roller 1 is required. Form. However, the formation of the winding portion 7 causes the recording paper 3 to flutter near the winding portion 7.

Therefore, when the thickness of the recording paper 3 is 100 μm or less, the suction pressure from the recording paper holding suction port 5 is 1.86.
When the thickness of the recording paper 3 is 125 μm or more, the suction device 6 is set so as to be 1.86 kPa or more, preferably about 5 kPa, so that the recording paper 3 is effectively stretched and the recording paper 3 is conveyed. Eliminating fluttering can prevent character blurring.

FIG. 2 shows a second embodiment of the present invention.

In this embodiment, the suction device 6 is divided into two parts 6a and 6b, and the other parts are the same as in the first embodiment. In this embodiment, a means for changing the suction pressure is provided on the suction device 6b side, and the suction device 6b is connected to the recording paper holding suction port 5 provided at the tip end of the recording paper transport plate 4,
The remaining recording paper holding suction port 5 is connected to a suction device 6a.

The flapping of the recording paper occurs in the vicinity of the front winding portion 7 from the leading end of the recording paper transport plate 4. Therefore, by changing only the suction pressure at the leading end of the recording paper transport plate 4 by the suction device 6b and the recording paper holding suction port 5 connected thereto according to the thickness of the recording paper, the necessary minimum The recording paper can be effectively stretched by the suction pressure changing means, and flapping at the time of transporting the recording paper can be eliminated and character blur can be prevented.

[0024]

As described above, according to the present invention, by regulating the suction pressure by the recording paper, it is possible to eliminate fluttering during conveyance of the recording paper, and to provide a high-quality fixed image stably and at high speed. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional side view showing a first embodiment of the present invention.

FIG. 2 is a sectional side view showing a second embodiment of the present invention.

[Explanation of symbols]

1. Heating roller (fixing roller) 2. Pressurizing roller 3.
Recording paper, 4 ... Recording paper transport plate, 5 ... Suction port for holding recording paper, 6 ... Suction device, 7 ... Winding part, 8 ... Nip part.

Claims (4)

[Claims] A recording paper transport plate having a heat source and a recording paper holding suction port is disposed in front of a heating roller and a pressure roller for fixing, and the recording paper is passed over the recording paper transport plate to heat the recording paper. In a fixing device for fixing an unfixed image on recording paper through a nip portion between the heating roller and the pressure roller after being wound around a part of a roller, the suction pressure of the recording paper holding suction port is adjusted to a thickness of the recording paper. A fixing device, comprising: means for changing according to the condition. 2. The suction pressure of the recording paper holding suction port is:
The boundary pressure is determined so as to satisfy the requirements of both suppressing the flapping of the recording paper during recording paper conveyance and preventing the cutting of the recording paper. When the recording paper thickness is 100 μm or less, the boundary pressure is less than the boundary pressure. 2. The fixing device according to claim 1, wherein the pressure is equal to or higher than the boundary pressure. 3. The fixing device according to claim 2, wherein the boundary pressure is 1.86 kPa. 4. A fixing device in which a recording paper transport plate having a heat source and a recording paper holding suction port is disposed in front of a heating roller and a pressure roller for fixing, wherein the recording is performed in accordance with the thickness of the recording paper. A fixing device comprising means for changing a suction pressure of only a leading end portion of a recording paper transport plate, in which a recording paper is likely to flutter, in a paper holding suction opening.