JPS60207170A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent recording paper from curling without using any separating member by specifying the diameter of a roller member which contacts the toner image formation surface of the recording paper below 20mm.. CONSTITUTION:A heat generating conductor 1b is embedded in a core body 1a made of a ceramic material and its surface is covered with an offset preventing layer 1c of silicone rubber having superior heat resistance and separability to decrease the diameter of a heat fixing roller 1 which is rotated by a driving device. Further, the roller 1 is provided with a silicone oil coating member 3 to improve the offset prevention effect. A pressure roller 2 is provided in press contact with the heat fixing roller 1 and the surface is covered with an offset preventing layer 2a. Then, the diameter of the pressure roller 2 is set to 20mm. and the diameter of the heat fixing roller 1 is also at set to 20mm. to prevent the recording paper 4 from being wound around the rollers 1 and 2.

Description

[Detailed description of the invention] The present invention is a facsimile machine using electrophotography.

The present invention relates to a fixing device used in image forming apparatuses such as printers and copying machines.

Conventionally, a fixing device that fixes the toner image on the recording paper by passing the recording paper with a toner image formed on the surface between roller members disposed facing each other to melt the toner is well known. A fixing roller incorporating a heating element is generally used as the roller member that comes into contact with the toner image forming surface. Such an apparatus has a problem in that when the recording paper is passed between the rollers, an offset phenomenon occurs due to the adhesiveness of the melted toner, and the recording paper winds around the fixing roller.

For this reason, in a conventionally known image forming machine using the fixing device, a separating member such as a blade or a separating claw is arranged near the roller or in light pressure contact with the roller surface.
A configuration is adopted in which the recording paper stuck to the surface of the roller is forcibly peeled off.

However, in a structure in which the separating member is lightly pressed against the roller surface, the roller surface is easily damaged, and in a structure in which the separating member is placed near the roller, it is difficult to set the distance between the roller and the separating member, which only increases the number of assembly steps by 1. First, if the distance is increased, defects such as edge folding and jamming of the recording paper are likely to occur.

In addition, the presence of such a separation member requires extra space for arranging the separation member within the image forming machine, which impedes the request for miniaturization and increases costs due to an increase in the number of parts.
In addition to various drawbacks, such as obstructing the removal of paper jammed between the rollers, especially when the separation member is formed of separation claws.

Since the tip of the separating claw is a free end, there is a risk that the handler may injure himself by accidentally touching the separating claw.

In view of the drawbacks of the prior art, it is an object of the present invention to provide a fixing device that can completely prevent the recording paper from being rolled up without using the separation member.

As a result, the drawbacks of the conventional techniques described above can be solved at once, and an image forming apparatus that can be downsized and significantly reduced in cost can be provided.

The present invention will be explained below.

The present invention provides a fixing device that fixes a toner image on a recording paper by inserting a recording paper on which an I/toner image is formed between roller members arranged to face each other, in which the toner image is brought into contact with the toner image forming surface of the recording paper. The diameter of the roller member to be
Particularly in the case where the roller member that contacts the toner image forming surface is a heating fixing roller, the fixing roller has a diameter of 10 to 20 mm.
This is because I set it to .

Generally, the paper used for recording paper has a certain thickness so that it is conveyed without bending when it is inserted through the transfer conveyance path in an image forming machine, and therefore it is difficult to roll up the recording paper. Then, a certain repulsive force is generated due to the thickness,
If the repulsive force is greater than the adhesive force of the toner, the recording paper is reliably separated from the roller by its own elastic force without using the separating member. Therefore, among the roller members.

In particular, the smaller the diameter of the roller member that contacts the toner image forming surface of the recording paper, the more reliably the above effect will be achieved.
No special separation member is required.

However, in a heat fixing roller that has a heat generating element inside or embedded inside, not only a certain diameter is required to accommodate the heat generating element inside or embedded, but especially when the diameter of the fixing roller is set to 10 mm or less. Since the heat storage effect is greatly reduced, a uniform temperature distribution cannot be obtained on the outer peripheral surface of the roller, leading to a decrease in fixing efficiency.

Therefore, it is extremely difficult to set a diameter that can reliably achieve the above-mentioned separation effect without causing a decrease in the fixing efficiency, and the inventors of the present invention have finally set the range after many years of intensive research efforts. Obtained.

Incidentally, as a technique seemingly similar to the present invention, in order to prevent the recording paper from being wrapped when a visible image formed on an image carrier such as a photosensitive drum is transferred to recording paper, the image carrier is A technique in which the diameter is set to 40 mm or less has been disclosed (Japanese Patent Application Laid-Open No. 196574/1983), but this technique sets the diameter of the image carrier in relation to the electrostatic attraction force during transfer. Yes, the fixing roller invention sets the diameter of the roller in relation to the adhesive force of the toner, and not only is the technical idea completely different, but especially when the diameter of the fixing roller is set to 25 to 40 mm. Since the adhesive force of the toner is greater than the elastic force of the recording paper, the recording paper does not separate from the fixing roller and winds up, making it impossible to achieve the effects of the present invention at all.

Therefore, setting this diameter is particularly important in the present invention.

The experimental results of the present invention will be explained in detail below.

The drawing is a schematic explanatory diagram of the fixing device used in this experiment.

1 is a heat-fixing roller rotated by a drive device (not shown); in order to make the diameter smaller, a heat-generating conductor is inserted into a core body 1a made of a ceramic material without having to insert an infrared heater or the like into the hollow cylindrical body. 1b is buried, and its surface is coated with an offset prevention layer 1c made of silicone rubber or the like having excellent heat resistance and peelability. Further, a silicone oil coating member 3 is attached to the heating fixing roller 1 to enhance the offset prevention effect.

Reference numeral 2 denotes a pressure roller configured to be brought into pressure contact with the heat fixing roller 1 and rotate in synchronization with the heat fixing roller 1, and similarly to the heat fixing roller 1, the surface is coated with an anti-offset layer 2a. ing.

Using such a fixing device, the diameter of the pressure roller 2 is set to 20), and the diameter of the heat fixing roller l is set to 30).
011116.25+1111,2011111,15
11111.1°0 m11, the fixing device was installed in a copying machine, and the presence or absence of wrapping of the recording paper 4 was checked. The results are shown in Table 1 below.

The surface temperature of the heat fixing roller 1 is 180°C, the recording paper feeding speed is 200 mm/sec, the toner used is a monocomponent toner, and the recording paper is plain paper (45 kg paper, below) with a wall thickness of about 0.0611111 mm. ) and 0.
Using A4 size tracing paper (hereinafter referred to as B paper) with a wall thickness of 0.05 mm, the original presser plate of the copying machine was opened, and the toner adhered to almost the entire surface of the recording paper under the worst conditions. The test was repeated 1000 times for each roller diameter.

In addition, all the numbers in the table indicate the defective rate in which wrapping has occurred, and are expressed in percentage. The wrapping of the recording paper 4 can be prevented to the extent that there is no practical problem with the following, and about 0.0
In the case of plain paper having a wall thickness of 8 mm, the winding of the recording paper 4 could be prevented to such an extent that there would be no practical problem at a thickness of 25 mm or less. In particular, since this experiment was conducted under the worst conditions in which toner adheres to almost the entire surface of the recording paper 4, it is presumed that wrapping of the recording paper 4 can be completely prevented under normal copying conditions.

Furthermore, plain paper used in copying machines and the like has a wall thickness of Q, Q7 mm or more, and therefore it is estimated that ordinary copying machines will have effects greater than the above results.

On the other hand, when the toner fixation state was compared for each diameter of the recording paper 4 on which the experiment was conducted, no significant difference was found for any of the diameters.

Furthermore, although the diameter of the pressure roller 2 was similarly fixed at 20 mm, no occurrence of four rolls of recording paper occurred even when the diameter of the heat-fixing roller 1 was varied.

In this experiment, a heat fixing type fixing device was used, but it is presumed that similar results can be obtained with a pressure fixing type fixing device. In addition, in a pressure fixing type fixing device, there is no need to consider uniform temperature distribution on the outer circumferential surface of the roller during fixing, so the pressure is applied between the pressure roller and the pressure roller disposed on the opposite side of the toner forming surface. It is also possible to create a wheel with a smaller roller diameter as long as the roller has a diameter that can withstand pressure.

As described above, according to the present invention, the diameter of the roller member in contact with the toner image forming surface of the recording paper is set to be 20 mm or less, and in particular, the roller member in contact with the toner image forming surface is a heat fixing roller. In this case, since the diameter of the fixing roller is set to 10 to 20 mm, wrapping of the recording paper can be completely prevented without using a special separation member, and heat fixing can be performed within the diameter range. A book that avoids a reduction in the heat storage effect of the rollers can be created, and a decrease in fixing efficiency can be prevented.

As a result, the drawbacks of the prior art described above can be solved all at once, and there are various advantages such as being able to provide an image forming apparatus that can be downsized and significantly reduced in cost.

[Brief explanation of drawings]

The drawing shows a schematic explanatory diagram of a fixing device used in experiments of the present invention.

Claims (1)

[Scope of Claims] 1) In a fixing device that fixes the toner image to the recording paper by inserting the recording paper on which the toner image is formed between roller members arranged to face each other, the toner image forming surface of the recording paper 2) When the roller member that contacts the toner image forming surface is a heated fixing roller, the diameter of the fixing roller is set to 20 mm or less. 1
A fixing device for an image forming machine according to claim 1, wherein the fixing device is set to 0 to 20 mm.