JPS5838786B2 - Contact type fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact fixing device for an electrophotographic copying machine.

In electrophotography, a powder image on a support, such as a toner image on a sheet, must be fixed to become a permanent image.

As shown in FIG. 1, the most efficient and quickest fixing means for this toner image has conventionally been a method in which a sheet is fed between rollers rotating in pressure contact with each other.

In the figure, reference numeral 1 indicates a fixing roller, and reference numeral 2 indicates a pressure roller.

The fixing roller 1 has PT on the outer periphery of a hollow cored roller 3.
FE (Polytetra F'1uoro Eth
ylene) layer, such as a Teflon layer 4, and has a heater 5 inside.

Although the fixing roller 1 is polished to reduce its surface roughness to prevent toner offset, the surface condition of Teflon itself causes offset or sheet wrapping.

For this purpose, an anti-offset liquid application roller 6 is in contact with the fixing roller 1 and is coated with a material having good releasability, such as silicone oil, to supply the anti-offset liquid to the roller surface.

On the other hand, the pressure roller 2 is composed of a hollow metal roller 8 having a heater 7 therein, and is brought into pressure contact with the fixing roller 1 by appropriate means (not shown).

When the sheet S on which the toner image A is formed is fed between the rollers 1 and 2 rotating in the direction of the arrow, the toner image A is melted by the heat of the heaters 5 and 7, and the sheet S
will be established.

However, the heater 7 is not necessarily required.

However, since the surface of the fixing roller 1 is made of Teflon, which has oil repellency, the better the surface properties are, the more the anti-offset liquid applied there will be able to prevent objects in close proximity to each other due to surface tension. I stopped by,
A liquid film is no longer formed around the entire circumference of the roller.

Therefore, when fixing the toner image, the toner partially adheres to the fixing roller 1 and is transferred to the next sheet as an offset phenomenon, staining the image.

Although a cleaning member (not shown) is in contact with the fixing roller 1 and cleans the surface thereof, it becomes useless if a large amount of toner adheres to the fixing roller 1.

Further, when the anti-offset liquid gathers in one place, it tends to form droplets, so that the excess liquid tends to adhere to the sheet.

The above offset phenomenon occurs because the surface of the fixing roller 1 is made of Teflon, which has excellent releasability.
This property has the disadvantage that a uniform liquid film cannot be formed.

In the present invention, of a pair of rollers that draw the sheet through, the outermost layer of the roller in contact with the toner image is made of continuous porous tetrafluoroethylene resin, and this roller is brought into contact with a roller coated with an anti-offset liquid. It is an object of the present invention to provide a fixing device which eliminates the above-mentioned drawbacks, improves retention of an anti-offset liquid, and is excellent in preventing offset.

The present invention will be explained below with reference to illustrated embodiments.

In FIG. 2, reference numeral 10 indicates a fixing roller.

The fixing roller 10 is made up of a core roller 11 and an elastic layer 12 formed around the outer periphery of the core roller 11 and made of open-pore polytetrafluoroethylene resin, and has a heater 1 inside.
It has 3.

The tetrafluoroethylene resin forming the elastic layer 12 is commercially available under the trade name GORE-TEX, and has a porosity of 25 to 95% and an average surface pore diameter of 0.2 to 8 μm. It is porous with open pores.

The fixing roller 10 is brought into contact with the application roller 6 that supplies an anti-offset liquid, such as silicone oil, in the same way as described above, and the pressure opening/roller 2 is brought into pressure contact with the fixing roller 10.

Therefore, the pores of the elastic layer 12 of the fixing roller 100 are impregnated with silicone oil, and its retention is extremely high.

Further, since the outermost layer of the fixing roller 10 is made of an elastic material, the contact surface with the pressure roller sheath 2 increases as shown in FIG.

Further, the surface layer of the pressure roller 20 is applied to the fixing roller 1.
If it is made of a material with a rubber hardness lower than 0, for example soft silicone rubber with a rubber hardness of about 25°, the amount of deformation of the roller surface that comes into contact with the image surface can be reduced, and image distortion can be prevented. However, it is advantageous that the contact area can be increased.

According to the fixing device of the present invention, since the outermost layer of the fixing roller is formed of open-cell porous tetrafluoroethylene resin,
The retention of anti-offset liquid is improved.

Therefore, it is possible to obtain a fixing device that has good fixing properties and does not cause an offset phenomenon.

Furthermore, by increasing the contact area with the pressure roller, the efficiency of heat conduction to the toner image and sheet is improved.

The fixing roller 10 has the best durability when manufactured by directly corrugating a tube made of tetrafluoroethylene resin onto the core roller 11 to form the outermost layer.

This is because the resin does not have oil resistance, and when the fixing roller is manufactured by a press-fitting method in which an adhesive layer is provided between it and the core roller, the adhesive layer has the disadvantage of being eroded by the anti-offset liquid.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional example of the present invention, FIG. 2 is a sectional view showing an embodiment of the invention, and FIG. 3 is an enlarged sectional view of the same. A...Powder image, S...Support, 1o.
...Fixed loaf -0

Claims (1)

[Claims] 1. In a fixing device that heats and fuses the powder image to the support by drawing the powder image support on which the powder image has been formed between rollers that rotate in pressure contact with each other, the pair of rollers comprising:
A contact type fixing device characterized in that the outermost layer of the roller that contacts the powder image is made of a continuous porous polytetrafluoroethylene resin, and an anti-offset liquid coating roller is brought into contact with this roller. .