JPH02173779A - Thermal fixing roll device for electrophotographic device - Google Patents

Abstract

PURPOSE:To improve durability by forming a wrinkle for absorbing the thermal expansion of a heat insulating layer laminated on the surface of a rotary shaft in a heat generating layer. CONSTITUTION:A heating roll 11 is obtained by laminating the heat insulating layer 15 consisting of a foaming elastomer material as which silicone foaming rubber is good, the heat generating layer 17 connected to an outside power source at the end part in an axial direction and a protective layer 20 consisting of fluororesin on the metallic rotary shaft 13 in this order from the center to the outer periphery of the roll 11. Many wrinkles 19 extending in the axial direction are provided in the heat generating layer 17. Therefore, in the case that the heat insulating layer 15 consisting of the foaming elastomer material is thermally expanded with the temperature of the heating roll 11 rises, the heat generating layer 17 deforms corresponding to the thermal expansion, so that the heat insulating layer 15 is prevented from being pressed. Thus, the durability of the heating roll 11 is improved.

Description

Detailed Description of the Invention [Object of the Invention] <Industrial Field of Application> The present invention relates to a heat fixing method for an electrophotographic apparatus in which a transfer means is heated and pressurized using a pair of rolls in order to fix a mapped image. Relating to a roll device.

<Prior Art> In a heat fixing roll device that transfers toner to a transfer medium such as paper and then fixes it in an electrophotographic device using an electrophotographic process such as a copying machine, a heating roll and a pressure roll are used. They are placed in close contact with each other, and the transfer means is passed through the nip where both rolls touch each other, and the toner is heated and pressed onto the transfer means at the same time, but conventionally it takes a relatively long time for the heated rolls to heat up. Therefore, for example, in Japanese Patent Application No. 63-57279 filed by the same applicant, a heating roll is provided with a heat insulating/elastic layer made of an elastic material such as silicone foam rubber. A structure has been proposed in which a heat generating layer made of a resistor which may be made of metal is formed over the entire surface of the layer. According to this structure, the above-described fixing operation can be performed by raising the temperature of only the heat generating layer, so that the time required to raise the temperature of the heating roll is shortened.

However, since the heat-insulating/resilient layer has a higher coefficient of thermal expansion than the heat-generating layer and is sealed between the rotating shaft and the heat-generating layer, when the temperature of the heating roll increases, it is suppressed by the heat-generating layer. In some cases, the core layer partially deflates when the temperature drops due to the gas inside the heat insulating/resilient layer being pushed out. Furthermore, if the air in the heat insulating/resilient layer is repeatedly expanded and contracted due to temperature changes in a sealed state, the durability of the silicone foam rubber, etc. of the heat insulating/resilient layer is likely to decrease.

<Problems to be Solved by the Invention> In view of the problems of the prior art, the main object of the present invention is to improve the thermal insulation of the thermal insulation layer in a heating roll that has an internal thermal insulation layer and a heat-generating layer on the surface. It is an object of the present invention to provide a heat fixing roll device for an electrophotographic device that does not impair its effects, does not cause deformation or deterioration of its core layer, and has improved durability.

[Structure of the Invention] <Means for Solving the Problems> According to the present invention, the object is to pass a transfer means between a heating roll and a pressure roll that rotate in close contact with each other, and to A heat fixing roll device of an electrophotographic apparatus for fixing a mapped image on the transfer target means, the heating roll comprising a rotating shaft, a heat insulating layer laminated on the surface of the rotating shaft, and a heat insulating layer laminated on the surface of the heat insulating layer. and a heat generating layer,
This is achieved by providing a heat fixing roll device for an electrophotographic apparatus, characterized in that the heat generating layer is formed with pleats for absorbing thermal expansion of the heat insulating layer.

<Function> With this arrangement, the heat generating layer deforms as the heat insulating layer thermally expands when the temperature of the heating roll increases.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the configuration of an electrophotographic apparatus to which the present invention is applied.

The rotatable photosensitive drum 1 has an outer peripheral surface plated with selenium. A charging section 2, a photosensitive section 3, a developing section 4, a transfer section 5, a cleaning section 6, and a static eliminating section 7 are provided along the outer peripheral surface of the photosensitive drum 1 in this order. Further, a fixing section 8 is provided downstream in the direction in which the transfer paper 9 is carried out from the transfer section 5, that is, in the direction of arrow A.

When the photosensitive drum 1 rotates in the direction of arrow B in FIG. 1, the surface of the drum passes through a charging section 2 consisting of corona charging means and is charged to a uniform potential of about 700 volts. be done. Next, photosensitive drum 1
The surface portion of the image passes through the exposure section 3, and a latent image corresponding to the shape of the subject is formed by exposure. Then, toner conveyed to a carrier (not shown) in the developing section 4 adheres to the surface of the photosensitive drum 1 in correspondence with the latent image. Furthermore, the transfer section 5
At this time, the transfer paper 9 conveyed from the right side in the direction of arrow A in FIG.
At the same time as the drum 1 is charged, the toner attached to the surface of the drum 1 is transferred to the paper 9. The surface portion of the photosensitive drum 1 after the toner has been transferred passes through a cleaning section 6, and residual toner is cleaned off. Then, in the static eliminator 7 consisting of an exposure lamp, the static electricity is removed to approximately a negative potential in the axial direction, and the above process is repeated again. On the other hand, the toner transferred to the paper 9 is heated and pressed onto the paper 9 at the same time in the fixing section 8, so that the image is fixed on the paper 9.

FIG. 2 is an enlarged sectional view of the fixing section 8 of FIG. 1.

The fixing unit 8 includes a pressure roll 10 that is rotationally driven by a driving means (not shown) and a heating roll 11 that is driven by being in close contact with the pressure roll at a contact portion 12. The heating roll 11 extends from its center to its outer periphery and has a rotating shaft 13 made of metal, a heat insulating layer 15 made of a foamed elastomer material which may be silicone foamed rubber, and an external power source (not shown) connected at its axial end. The connected heat generating layer 17 and the protective layer 20 made of fluororesin are laminated in this order.

On the other hand, the pressure roll 10 is made of a metal tube. In fact, a core material made of metal and a resilient layer made of foamed rubber or hard rubber layered thereon may be used for the pressure roll.

As shown in FIG. 3 when the heating roll 11 is viewed from the side, the heating layer 17 has a width of 5 mm to 15 mm and a thickness of 20 μm.
It is wrapped with nichrome foil of m to 80 μm. A spiral slit-shaped void 18 is formed between adjacent portions of the nichrome foil of the heat generating layer 17 in the axial direction.

The adhesive layer between the heat generating layer 17 and the protective layer 20 is made of a heat resistant resin with high thermal conductivity, and the void 18 is also filled with this heat resistant resin.

Here, the heat generating layer 17 is provided with a large number of folds 19 extending in the axial direction. Therefore, when the heat insulating layer 15 made of foamed elastomer expands thermally when the temperature of the heating roll 11 rises, the heat generating layer 17 also deforms accordingly.
is not under pressure. Furthermore, the base resin layer, which was conventionally provided integrally with the core layer to reinforce the heat generating layer, becomes unnecessary.

In this embodiment, the heat generating layer 17 is provided with folds 19 extending in the axial direction, but the folds 19 may have any shape as long as it acts as a relief during thermal expansion of the heat insulating layer. For example, the shape may extend in the circumferential direction of the rotating shaft.

[Effects of the Invention] As described above, according to the present invention, since the heat generating layer is deformed due to thermal expansion of the heat insulating layer when the temperature of the heating roll increases, deformation and deterioration of the heat insulating layer due to temperature changes of the heating roll can be prevented. This improves the durability of the heating roll. From the following two points, the effects of the present invention are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus based on the present invention. FIG. 2 is an enlarged sectional view of the main part of FIG. 1. FIG. 3 is a partially cutaway side view of only the heating roll shown in FIG. 2. 1... Photosensitive drum 2... Charging section 3... Exposure section 4... Developing section 5... Transfer section
5a...Charging section 6...Cleaning section 7...Static elimination section 8...Fixing section 9...Transfer paper 10
...Crimping roll 11...Heating roll 12...
Contact portion 13... Rotating shaft 15... Heat insulation layer
17...Heating layer 18...Void 19.
...Fold 20...Protective layer

Claims (1)

[Scope of Claims] A heat fixing roll device of an electrophotographic apparatus for fixing an image of a subject on the transfer means by passing a transfer means between a heating roll and a pressure roll that rotate in close contact with each other. The heating roll has a rotating shaft, a heat insulating layer laminated on the surface of the rotating shaft, and a heat generating layer laminated on the surface of the heat insulating layer, and the heat generating layer has thermal expansion of the heat insulating layer. A heat fixing roll device for an electrophotographic device, characterized in that it has pleats for absorbing.