JP2002108127A - Fixing device for electrophotographic equipment - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To achieve stable conveyance of various types of recording materials while improving the quality of OHP images. A heat roller has a surface roughness Ra of 0.2 μm or more and 0.5 μm or less, and a backup roller surface roughness of R.
a is larger than 0.5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an electrophotographic apparatus.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device that conveys a recording material while heating and pressing an unfixed toner image on the recording material, and particularly to an improvement in image quality when an OHP film is used as a recording material and an OHP film that is difficult to convey. The present invention relates to a fixing device that realizes stable conveyance of paper having a high degree of smoothness and that can handle various types of paper.

As a prior art relating to the surface roughness of the fixing roller and the conveyance of the recording paper, for example, as described in JP-A-6-43774, the surface roughness of a roller (pressing roller) that contacts the non-printing surface side is disclosed. The recording paper is attracted to the pressure roller side by making it smaller than the surface roughness of the roller (heating roller) in contact with the printing surface side, so that the recording paper does not wind around the heating roller. Are known.

At this time, the relationship between the surface roughness values of the two rollers and the magnitude relationship is as follows: the heating roller is in the range of 1 ≦ Rz ≦ 5, the pressure roller is Rz ≦ 2, and the surface roughness of the pressure roller is Is smaller than the value of the surface roughness of the heating roller.

[0005]

In the above prior art, the surface roughness of the heating roller in pressure contact with the toner melted by heat is 1 ≦ Rz ≦ 5, which is higher than that of the pressure roller (Rz ≦ 2). ing.

From the viewpoint of image quality, the toner surface after fixing is
In order to transfer the surface state of the contacting roller surface, it is desirable that the surface of the heating roller contacting the toner is as smooth as possible. In particular, when printing is performed on an OHP film and light is transmitted, if there is fine unevenness on the toner surface, light refraction occurs on the surface and image quality deteriorates. Also, when printed on paper, a rough feeling may be observed.

Next, in terms of the transportability of a recording material such as OHP or paper, the transport force is increased by roughening the roller surface.
It can be seen that stable transportability can be obtained.

However, it is common practice to apply a release agent such as silicone oil to the surface of the heating roller that comes into contact with the toner in order to have a releasability from the molten toner. Slip occurs and stable conveyance is difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device capable of stably transporting various kinds of recording materials such as OHP films and paper without deteriorating image quality.

[0010]

An object of the present invention is to provide a fixing device for conveying an unfixed toner image held on a recording material while heating and pressing the unfixed toner image by a pair of fixing rollers. The fixing rollers each have a single silicon rubber layer coated on the outer peripheral surface of a cored bar, and the roller surface roughness on the side that comes into contact with the unfixed toner image is Ra.
This is achieved when the roller surface roughness Ra on the side in contact with the back surface of the recording material is larger than 0.5 μm.

[0011]

Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing an example of a schematic configuration of a fixing device according to this embodiment.

In FIG. 1, a heat roller 1 located on a side in contact with an unfixed toner 9 adhered to a recording material 8 by an electric force, that is, on a printing surface side,
And a backup roller 2 pressed against the heat roller 1 by applying a certain pressing force by a pressure spring (not shown). Heat roller 1
Has a structure in which a heat roller core 5 is covered with a heat roller elastic layer 3 made of a single material, and has a halogen lamp 7 serving as a heat source inside.

On the other hand, similarly to the heat roller 1, the backup roller 2 has a structure in which a backup roller core 6 is covered with a backup roller elastic layer 4 made of a single material, and a halogen lamp 7 serving as a heat source is provided therein. have.

As a material of each of the elastic layers 3 and 4, silicone rubber is used for both rollers in terms of heat resistance, toner releasability and the like, and the volume resistivity of the silicone rubber is, for example, 10 ¹³ Ω · cm or more. In this case, the amount of an additive for imparting conductivity, such as carbon, is reduced.

A single silicon rubber material is defined as a single type of rubber (containing a filler, a plasticizer, and the like) to be poured when a roller is molded. An adhesive layer is not considered. In the process of vulcanization of rubber, pure rubber and additives such as fillers spontaneously separate on the outermost surface and lower surface to form a layer, or impregnated with oil after molding to form a surface layer. A material having a concentration distribution of oil in the lower layer and the lower layer is also considered as a single silicon rubber material.

Next, FIG. 2 is an enlarged view of a nip portion (contact portion) between the heat roller 1 and the backup roller 2.

In FIG. 2, the surface of the image formed by the unfixed toner 9 before passing through the nip has fine irregularities due to the shape of the toner particles. When the unfixed image passes through the nip and is fixed by heat and pressure, the individual toner particles are melted and pressed, so that the toner particles are combined with the adjacent toner. Then, the surface shape of the heat roller 1 that is in contact with the outermost surface of the heat roller 1 is transferred by melting. Therefore, in order to smooth the surface state of the fixing toner 10 for the purpose of improving the image quality, the heat roller 1
It is desirable to make the value of the surface roughness as small as possible.

On the other hand, in order to stably convey various types of recording materials 8, it is important to generate as large a conveying force as possible. Generally, it is considered that the greater the surface roughness of the roller, the larger the transfer force.
By making it coarser than that of, a stable transport force can be obtained.

That is, the heat roller 1 can realize high image quality by reducing the surface roughness, and the backup roller 2 can realize stable conveyance of various recording materials by increasing the surface roughness.

In this embodiment, the object is achieved by setting the surface roughness of the heat roller 1 to 0.2 μm or more and 0.5 μm or less in Ra, and making the surface roughness of the backup roller 2 larger than 0.5 μm in Ra. . If the surface roughness Ra of the heat roller 1 is smaller than 0.2 μm, the recording material 8 may be wound around the heat roller 1 by electrostatic attraction of the surface when the smoothness of the recording material 8 is extremely high.

FIGS. 3 and 4 are schematic cross-sectional views of the toner surface when fixing is performed by heat rollers 1 having different surface roughnesses. The recording material 8 uses an OHP film. FIG. 3 shows a case in which a heat roller having a smooth surface is used. In the case where the outermost surface of the fixing toner 10 is smooth and light is transmitted from below the recording material 8 (OHP), light is transmitted without being refracted at the outermost surface of the toner. Is done. Therefore, the projected OHP image is also vivid.

On the other hand, FIG. 4 shows a case in which a heat roller having a rough surface is used. The outermost surface of the fixing toner 10 has fine irregularities, and light is refracted on the outermost surface of the toner, and is transmitted and projected. The OHP image becomes dark. Therefore, the color vividness cannot be expressed and the image quality is inferior.

Next, a second embodiment will be described. Second
In this embodiment, as shown in FIG. 5, a cleaning mechanism, an oil application mechanism, a peeling mechanism and the like are mounted. On the outer peripheral surface of the heat roller 1, a cleaning roller 11,
An oil felt 12 and a blade 13 are attached, and a peeling claw 15 is attached on the outer peripheral surface of the backup roller 2. The cleaning roller 11 is for cleaning minute offset toner adhered to the heat roller 1 and is configured to rotate in contact with the heat roller 1 with a certain peripheral speed difference.

The oil felt 12 is for applying a release agent such as silicon oil on the outer peripheral surface of the heat roller 1 in order to stably secure the releasability of the heat roller 1 from the toner. Is pressed against the heat roller 1. The blade 13 uniformly applies a release agent such as silicone oil applied by the oil felt 12 evenly, and scrapes off excess oil.
It works to keep the coating amount constant. By providing such a cleaning mechanism and an oil application mechanism, image quality deterioration can be prevented, and the life of the fixing device can be extended.

As for the shape of the nip portion (contact portion) between the heat roller 1 and the backup roller 2, the rubber hardness of the heat roller 1 is made softer than the rubber hardness of the backup roller 2 so that the heat roller 1 side becomes concave. Thus, a conveyance path is formed such that the recording material 8 is discharged to the backup roller 2 side. On the backup roller 2 side, a peeling nail 15 and a paper discharge guide 16
Is attached, and even when the recording material 8 is wound around the backup roller 2 and discharged,
Is reliably separated from the backup roller 2 so that the recording material can be stably conveyed.

Each of the elastic layers 3 and 4 has a volume resistance value of, for example, equal to or greater than 10 ¹³ Ω · cm, so that the charge balance is maintained. By always setting the backup roller 2
The recording material 8 can be discharged to the side.

In the second embodiment, the heat roller 1
By increasing the surface roughness of Ra to 0.2 μm or more and 0.5 μm or less and the backup roller 2 to have a surface roughness of more than 0.5 μm Ra, high image quality and stable conveyance of various types of recording materials can be realized.

According to the present invention, the surface roughness of the heat roller is represented by Ra.
By setting the thickness to 0.2 μm or more and 0.5 μm or less, the surface of the toner after fixing becomes smooth, and particularly when printing on OHP, the light transmission state becomes good and high image quality can be achieved. Further, by setting the surface roughness of the backup roller to be larger than 0.5 μm in Ra, a sufficient conveyance force for various kinds of recording media such as OHP and paper can be obtained, and stable conveyance performance can be obtained.

As described above, according to the present invention, there is provided a fixing device for conveying an unfixed toner image on a recording sheet held by an electric force while heating and pressing the unfixed toner image by a pair of fixing rollers. Heat roller surface roughness of 0.2μm or more in Ra
When the thickness is 0.5 μm or less, the toner surface after fixing becomes smooth, and particularly when printing is performed on OHP, the light transmission state becomes good, and high image quality can be achieved.

The surface roughness of the backup roller is Ra.
When the thickness is larger than 0.5 μm, a sufficient conveying force for various kinds of recording media such as OHP and paper can be obtained, and stable conveying performance can be obtained.

Further, the elastic layers of the heat roller and the backup roller are each made of a single silicon rubber having a volume resistance of 10 ¹³ Ωcm or more, and the nip portion formed by the fixing roller pair has a concave shape. By doing so, stable recording material conveyance becomes possible.

Further, by providing a peeling claw on the backup roller of the fixing roller pair that comes into contact with the back side of the recording material, it is possible to more stably convey the recording paper.

Further, by using a cleaning mechanism and an oil application mechanism together, a high-quality image output can be maintained, and a long-life fixing device in which image quality deterioration hardly occurs can be realized.

[0035]

According to the present invention, it is possible to provide a fixing device capable of stably conveying various kinds of recording materials such as OHP films and paper without deteriorating the image quality.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a first embodiment of a fixing device of the present invention.

FIG. 2 is an enlarged view of a nip portion during toner fixing.

FIG. 3 is a schematic sectional view of a fixed toner having a good surface condition.

FIG. 4 is a schematic cross-sectional view of a fixed toner having irregularities on its surface.

FIG. 5 is a sectional view showing a schematic configuration of a second embodiment of the fixing device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat roller, 2 ... Backup roller, 3 ... Heat roller elastic layer, 4 ... Backup roller elastic layer, 5 ...
Heat roller core, 6 ... Backup roller core, 7 ...
Halogen lamp, 8: recording material, 9: unfixed toner, 10
... fixing toner, 11 ... cleaning roller, 12 ... oil felt, 13 ... blade, 14 ... leaf spring, 15 ... peeling nail, 16 ... paper ejection guide.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Ogiso 502 Kandate-cho, Tsuchiura-shi, Ibaraki Pref.Mechanical Research Laboratory, Inc. Within the Machinery Research Laboratory (72) Inventor Katsuyoshi Onose 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture F-term (reference) 2H033 AA45 BB03 BB06 BB13 BB14 BB29 BB30 3J103 AA13 BA03 FA05 GA54 GA58 HA04 HA53 HA53 HA54

Claims (1)

[Claims] A fixing device for conveying the recording material while heating and pressing the unfixed toner image held on the recording material by a pair of fixing rollers; A roller having a single silicon rubber layer coated thereon, and having a surface roughness Ra of 0.2 μm to 0.5 μm in contact with the unfixed toner image and a roller surface roughness in contact with the back surface of the recording material. Is a fixing device for an electrophotographic apparatus, wherein Ra is 0.5 μm or more.