JPH03120572A - Fixing device - Google Patents

Abstract

PURPOSE:To reduce the curl of a transfer sheet in spite of its type by forming the outer peripherial part of a fixing roller having a heat source inside with an elastic body having surface hardness so that a press-contact part with an elastic body having surface hardness so that a press-contact part with a pressurizing roller becomes almost plane. CONSTITUTION:The diameter of the fixing roller 52 having a heater 55 inside is the same as that of the pressure roller 57, and the rubber of the same hardness is used as the surface rubber forming their outer peripheral parts. Therefore, hen the roller 57 is pressed on the roller 52 with a constant pressure by a pressurizing spring 58, the deformation of the elastic body 54 of the roller 52 is equivalent to that of the roller 57, and the press-contact surface B turns into almost plane. A carried transfer sheet P absorbs a great deal of heat on the press-contact surface B and dries, and the curl is reduced by the plane part of the press-contact surface B. Thus, the occurrence of curling is prevented in spite of the types of transfer sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device for a printer device using an electrophotographic method.

[Conventional technology]

Generally, in copiers and printers that use electrophotography, a toner image is formed on transfer paper through a series of process means including charging, exposure, development, and transfer, and is then heated by a fixing device to form a permanent image. It is fixed on the transfer paper as.

The structure of a conventional fixing device is shown in FIG.

This fixing device 1101 includes a fixing roller 102 made of stainless steel or the like whose surface is coated with fluorine, rubber, or sponge.
a pressure roller 103, a fixing lamp 104 for heating the fixing roller 102, and a separation fitting 10.
5. It is composed of a fixing pad 106.

In such a fixing device 1101, toner particles are melted and combined by heat, and the toner particles flow and permeate into the fiber spaces of the transfer paper P.

In order to provide sufficient heat to the toner particles to melt them, the pressure roller 103 is brought into pressure contact with the fixing roller 102 by a pressure spring 107 to increase the heating time of the paper and toner.

[Problem to be solved by the invention]

However, in the conventional fixing device described above, the fixing roller 102 is made of a hard material such as stainless steel, so the pressure contact portion A with the pressure roller 103 made of an elastic body has a curved surface. For this reason, there is a problem in that the transfer paper P is curled by the curved surface forming the pressure contact portion A, and it is not possible to store the paper on the paper discharge tray smoothly. Another problem is that double-sided printing is not possible. Furthermore, there are problems with the appearance of the product, which does not look good to the user.

In recent years, the types of paper used in printing devices such as printers have been increasing more and more, and the curl m of paper differs due to differences in paper thickness, properties, etc., so it is necessary to devise a technology to correct curl. That is essential.

SUMMARY OF THE INVENTION The present invention is intended to solve these conventional problems, and it is an object of the present invention to provide a fixing device that can reduce the amount of curling of all types of paper.

[Means for solving problems]

In order to solve the above problems, the present invention has been established! 41! In a fixing device including a fixing roller having an internal heat source and a pressure roller made of an elastic body that is pressed against the fixing roller, the outer peripheral portion of the fixing roller is in contact with the pressure roller. It is made of an elastic body with a surface hardness that is approximately flat.

Further, if necessary, the heat source can be provided inside the elastic body forming the outer peripheral portion of the fixing roller.

〔Example〕

FIG. 1 is a side view of an electrophotographic printer to which an embodiment of the fixing device of the present invention is applied.

The photosensitive drum 4 is rotatably supported in the direction of the arrow, and around the photosensitive drum 4 are a corona discharger 5, an exposure device 6, a developing device 7, a transfer corona discharger 8, and a cleaning device. 9 and each process means of a static eliminator 10 are provided. The photosensitive drum 4 is integrally supported by a frame as a process unit 20 along with a corona discharger 5, a developing device 7, a cleaning device 9, and a static eliminator 10. Transfer paper is supplied on the top surface of the printer device l. paper feed roller 1 from the first bin 2 and second bin 3
1.12, the transfer paper is guided by the paper guide 13 and conveyed to the transfer section by the gate roller 14.

The surface of the photoreceptor drum 4 is uniformly charged by a corona discharger 5, and the electrostatic latent image is transferred to the photoreceptor by exposing the image area to light through exposure t#6 and removing the charge in the image area. It is formed on the drum 4.

Then, a visible image is formed by causing toner, which is colored fine particles charged to the same polarity as the electrostatic latent image, to adhere to the latent image using the developing device 7. The visible image formed on the photosensitive drum 4 is transferred as a toner image onto a transfer paper by a transfer corona discharger 8 in a transfer section.

After the transfer is completed, the transfer paper is conveyed to the fixing bag W115, and the toner image on the transfer paper is heated and fixed on the transfer paper as a permanent image. Further, residual toner remaining on the photoreceptor drum 4 as an untransferred image is removed by a cleaning device 9, and latent image charges on the photoreceptor drum 4 after transfer are removed by a static eliminator 10.

The fixed transfer paper is guided by paper discharge guides 38, 39.degree. 41, and discharged by paper discharge rollers 21, 22 to a face-up tray 26 or a face-down tray 27.

FIG. 2 is an embodiment showing the structure of the fixing device of the present invention.

The fixing device 51 includes a fixing roller 52, a pressure roller 57, a pressure spring 58, a separation tab 59, and a fixing bat 60. The fixing roller 52 has an elastic body 54 such as silicone rubber on the outer periphery of a metal layer 53 such as stainless steel.
It has a double structure with The pressure roller 57 is made of an elastic material such as silicone rubber, and is integrated with a metal shaft 61 at the center of the elastic material. Also, apply pressure roller 5
The pressure spring 58 presses the bearings 62 attached to both ends of the metal shaft 61 of No. 7, so that the pressure roller 57 is pressed against the fixing roller 52 and brought into pressure contact with the fixing roller 52.

In this embodiment, the elastic body 54 of the fixing roller 52 has a surface hardness such that the pressure contact portion B with the pressurizing port 57 is substantially flat. Since the diameter of the pressure roller 57 is the same, the surface hardness of the elastic body 54 of the fixing roller 52 is set to be the same as the surface hardness of the elastic body forming the pressure roller 57. In addition, “pressure welding part B
The phrase "is substantially flat" means that the surface forming the pressure contact portion B is not curved to the extent that it causes the transfer paper P to curl.

A heater 55 made of a gold B heating element such as tungsten is embedded in the elastic body 54 of the fixing roller 52 to uniformly heat the elastic body 54 to a fixing temperature. Also,
The elastic body 54 is deformed by the pressing force from the pressure roller 57, but is made sufficiently thin so that a difference in the amount of deformation due to the embedding of the heater 55 does not occur on the surface. For this reason, 1. the heat conduction time is short, and the surface temperature of the elastic body 54 rises to the fixing temperature in a short time after the power is turned on. Further, when the transfer paper P passes between the fixing roller 52 and the pressure roller 57, the fixing roller 52.
Heat is taken away from the pressure roller 57, and even if the surface temperature decreases, the temperature can be quickly raised to the fixing temperature.

As mentioned above, the thickness of the elastic body 54 of the fixing roller 52 is thinner than that of the pressure roller 57, and when the diameters of the fixing roller 52 and the pressure roller 57 are approximately equal as shown in FIG. Since the surface rubber hardness is set to be approximately equal to the surface rubber hardness of the pressure roller 57, the pressure spring 5
8 presses the pressure roller 57 against the fixing roller 52 with a constant pressure, the elastic body 54 of the fixing roller 52
The amount of deformation is equal to the amount of deformation of the pressure roller 57, and the pressure contact surface B formed by the fixing roller 52, the pressure roller 57, and the pressure spring 58 becomes substantially flat.

The transfer paper P conveyed to the fixing device 151 described above absorbs a large amount of heat when passing through the pressure contact surface B formed by the fixing roller 52 and the pressure roller 57. In the conventional device shown in FIG. 4, the transfer paper is forcibly curled in the same direction as the bending direction of the pressing surface A, but in the fixing device 51 of this embodiment, the pressing surface B is almost Since it is a flat surface, the amount of curl of the transfer paper P immediately after passing through the fixing roller 52 is small regardless of the type of transfer paper.

The transfer paper P that has passed through the pressure contact part B is separated from the fixing roller 52 by a separating pawl 59.The tip of the one separation pawl 59 is in the immediate vicinity of the pressure contact part B, and the transfer paper P that has passed through the pressure contact part B is separated from the fixing roller 52 by a separating pawl 59. If the structure of the 0-separation stopper 59, which is formed to be conveyed as shown in FIG. The curl phenomenon in the 52 direction hardly occurs.

Further, if the fixing bat 60 is made of a conductive material.

Static electricity on the surface of the fixing roller 52 can be removed 1, and the separation of the transfer paper after passing through the pressure contact section becomes easier.

FIG. 3 shows a second embodiment of the fixing device of the present invention. A heater 55 embedded in the elastic body 54 of the fixing roller 52 described above
Instead, a lamp 56 provided at the center of the fixing roller 52
Thus, the fixing roller 52 is heated.

〔Effect of the invention〕

As described above, in the present invention, an elastic body is formed on the outer periphery of the fixing roller, and the pressure contact area formed by the fixing roller and the pressure roller is arranged in a substantially straight line. Regardless of the type of transfer paper, curling of the transfer paper, which was forced to occur in the same direction as the bending of the pressure contact part, can be prevented, making it possible to handle a wide range of paper types. Further, by providing a heat source within the elastic body around the fixing roller, heat transfer can be carried out in a short time even if an elastic material such as rubber, which has a lower thermal conductivity than metal, is used for the fixing roller. Therefore, it is possible to maintain stable fixing temperature and always obtain stable fixing performance.

4. Brief Description of WiIO FIG. 1 is a side view of an electrophotographic printer to which an embodiment of the fixing device of the present invention is applied.

FIG. 2 is a diagram showing a first embodiment of the fixing device of the present invention.

FIG. 3 shows a second embodiment of the fixing device of the present invention, and FIG. 4 is a side view showing a conventional fixing device.

51...Fuser 52...Fixing roller 54...Elastic layer 55...Heater 57...pressure roller 58...pressure spring 59...separation 60... Fixing bat B...pressure welding part Below

Claims (2)

[Claims] (1) In a fixing device equipped with a fixing roller having an internal heat source and a pressure roller made of an elastic body that is pressed against the fixing roller, the outer peripheral portion of the fixing roller is placed in pressure contact with the pressure roller. 1. A fixing device comprising an elastic body having a surface hardness that is substantially flat. (2) The fixing device according to claim 1, wherein the heat source is provided inside an elastic body forming an outer peripheral portion of the fixing roller.