JPS63237084A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent the temp. drop of a heat roller so that satisfactory fixing can be carried out by providing an elastic layer to a press roller and a heat insulating layer to the outer circumference thereof. CONSTITUTION:The heat insulating layer is provided on the outer circumference of the press roller having the elastic layer and a heat insulating member enclosing said layer is provided near a fixing roller. For example, a sponge layer 18b having about 4(mm) thickness and about 10( deg.) rubber hardness and a silicone rubber layer 18c having about 1(mm) thickness are laminated around a hollow mandrel roller 18a consisting of a stainless steel and having flanges 19a, 19b on both sides and further, a fluoroplastic layer 18d having a high release property, low heat conductivity and about 15(mum) thickness is laminated on the outer circumference. An extreme drop of the surface temp. of the heat roller is thereby obviated and the sufficient fixing temp. is obtd.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a fixing method for fixing a powder toner image on an image support using a heat roller in an image forming apparatus such as an electrophotographic apparatus. Regarding equipment.

(Prior Art) In an image forming apparatus, an apparatus as shown in FIG. 3 has been conventionally used for fixing powder toner particles formed on a sheet of paper as an image support.

That is, this device includes an aluminum roller (10a) which has a built-in heater (10a) and whose surface is coated with fluororesin.
b); and a press roller (11) which is in pressure contact with the heat roller (10) and whose hollow core (lla) is covered with silicone rubber (llb).
) A sheet of paper (14) having a powder toner image (13) is inserted between a pair of fixing rollers (12) to effect thermal fixation. On the other hand, in recent years, with the diversification of image forming devices, copying is performed on both sides of a sheet of paper, or the image forming process is repeated multiple times on the same side of a sheet of paper in order to form a multicolor image. A device that performs same-sided copying has been developed. However, among such devices, in devices where the fixing process is repeated every time an image is formed, the sheet paper undergoes deterioration such as evaporation of moisture during the repetition of the fixing process, and deformation such as curling. In addition, the surface of the fixing roller (12) is relatively hard and the nip width, which is the contact width between the heat roller (10) and the press roller (11), is small. Due to various factors such as the pressure contact force of the fixing roller (12) being set high, paper wrinkles occur on the sheet paper when it passes through the fixing roller (12), which has the disadvantage that the image quality is significantly reduced. ing. For this reason, in recent years,
A sponge layer, which is an elastic layer, is provided around the press roller.
Devices have been developed that increase the nip width of the fixing rollers to improve fixing efficiency, thereby reducing the pressure contact force between the fixing rollers, and thereby preventing paper wrinkles.

However, in such devices, because the sponge layer has high thermal conductivity, the heat on the surface of the heat roller is absorbed by the sheet paper and the press roller during fusing, causing the temperature of the heat roller to drop rapidly. However, it has a new drawback, particularly when continuous copying is performed at high speeds, resulting in poor fixing.

(Problems to be Solved by the Invention) Conventionally, the sponge layer provided on the press roller to prevent paper wrinkles significantly reduces the surface temperature of the heat roller, resulting in poor fixing and deterioration of image quality. , making it impossible to apply to high-speed models.

Therefore, the present invention eliminates the above-mentioned drawbacks.Despite placing a sponge layer on the press roller, it prevents the temperature of the heat roller from dropping, provides good fixing, and provides a fixing system that can be applied to high-speed models. The purpose is to provide equipment.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a heat insulating layer around the outer periphery of a press roller having an elastic layer, and further provides a heat insulating member surrounding the vicinity of the fixing roller.

(Function) The present invention aims to prevent a drop in temperature on the surface of the heat roller, improve fixing efficiency, and expand functionality by the above-mentioned means.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. (16) is a pair of fixing rollers provided in the fixing section of an image forming apparatus (not shown), and the upper heat roller (17) is an aluminum cored roller (17a) having a fluororesin layer (17a) on its surface. A heater (17c) made of a halogen lamp is built in the center of the heater (17b). Further, (18) is a press roller that is pressed against the heat roller (17), and is made of stainless steel and has flanges (19a) and (19b) on both sides.A hollow cored roller (18a) is surrounded by an elastic layer. and has a thickness of approximately 4 (m
m), sponge layer (18b) with rubber hardness of approximately 10 [degrees]
A silicone rubber layer (18c) with a thickness of about 1 [urn] is layered, and a fluorine rubber layer (18c) such as Teflon (trademark) with a thickness of about 15 [urn], which has high mold release properties and low thermal conductivity, is layered on the outer periphery. The resin layers (18d) are layered. Furthermore, (20) surrounds the press roller (18) on three sides, and the press roller (18)
It is a heat insulating member made of an aluminum plate that shields heat from the surrounding area. In addition, (21) is a peeling device for sheet paper (not shown), and (22) is a cleaner.

(23) is a felt member to which anti-offset liquid is applied.

(24) is a conveyance plate, (26a) and (26b) are frames.

Next, we will discuss the effect. With the start of the image forming process,
The fixing process is started, and the surface of the heat roller (17) is heated to a fixable temperature, for example, 18 by the heater (17c).
The press roller (
18) is in contact with this and rotated in the direction of the arrow X. A sheet of paper (not shown) on which a toner image has been formed through an image forming process (not shown) has the toner image fixed thereon while passing between a heat roller (17) and a press roller (18). At this time, the surface of the heat roller (17) causes a temperature drop due to contact with the sheet paper and the surface of the press roller (18), but the surface of the press roller (18) is covered with a fluororesin layer (18d) with low thermal conductivity. The heat roller (18) is coated to suppress heat conduction from the heat roller (17), and the press roller (18) is surrounded by a heat insulating member (20) to prevent heat radiation to the surroundings, and the press roller (18) itself Since the temperature is maintained at a relatively high temperature, a heat roller (17
) to the press roller (18) is small, and the surface of the heat roller (17) can maintain a fixable temperature. Next, in the case of double-sided copying, since all the image forming processes have been completed once, the sheet paper, which has undergone some deformation such as curling, passes between the heat roller (17) and the press roller (18). It will be fixed, and at this time the toner image on the back side will also be somewhat melted, but the press roller (
18) Since the surface is made of a fluororesin layer (18d) and has good releasability, the toner image on the back side is transferred to the press roller (18).
There is no side offset. Also, heat roller (1
Since the nip width between the heat roller (17) and the press roller (18) is relatively large, the sheet paper can pass between the heat roller (17) and the press roller (18) while its deformation is absorbed, and the paper does not wrinkle. There is no. After the fixing is completed, the surface of the heat roller (17) is cleaned by a cleaner (22) as it rotates, and then anti-offset is applied by a felt member (23), making it ready for the next fixing process.

With this configuration, there is no sudden temperature drop in the heat roller (17) due to sheet paper passing, and fixing failure can be prevented, while paper wrinkles can be prevented even during same-sided copying, double-sided copying, etc. This does not occur and a good copy image can be obtained. Also, press roller (18) for double-sided copying at the same time.
The toner is not offset, the roller surface is not soiled, and the sheet paper is also prevented from being soiled.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, the temperature setting of the heat roller during fixing can be set arbitrarily, and the sponge layer and silicone rubber layer layered on the core of the press roller can be changed. The type and thickness of the fluororesin layer are not limited, but in order not to damage the elasticity of the sponge layer, it is preferable that the silicone rubber layer has a thickness of about 1 [I] to 2 [m]. In order to prevent heat conduction to the rollers, the thicker the fluororesin layer, the better, and preferably at least 15 ha+). The type of sponge is not limited, but the rubber hardness is between 10 [degrees] and 2 degrees.
When the temperature is as low as 0 [degrees], it is possible to effectively reduce the incidence of paper wrinkles. Further, the installation position of the heat insulating member is arbitrary, but ideally it is preferable to surround the entire fixing roller including the heat roller.

Further, the material of the heat insulating member is arbitrary, and its structure may be a hollow plate.

〔Effect of the invention〕

As explained above, according to the present invention, the outer periphery of the press roller is coated with a fluororesin layer such as Teflon (trademark), and furthermore, the vicinity of the fixing roller is surrounded by a heat insulating member, which makes it possible to pass paper such as sheet paper. Regardless, the surface temperature of the heat roller is not significantly reduced, a sufficient fixing temperature can be obtained, good images can be obtained, and the system can be applied to high-speed models, expanding its functions. Further, even in double-sided copying, there is no toner adhesion to the press roller, which prevents staining of the press roller and thus the sheet paper, and also reduces the incidence of wrinkles on one sheet, thereby improving image quality.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a partially omitted vertical cross-sectional view of the press roller, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a schematic diagram showing a conventional device. FIG. 16... Fixing roller, 17... Heat roller. 18... Press roller, 18b... Sponge layer. 18c...Silicone rubber layer, 18d...Fluororesin layer. 20...Insulating member.

Claims (1)

[Scope of Claims] 1. An image support is inserted between a heat roller and a press roller pressed against the heat roller to fix a toner image, in which the press roller has an elastic layer and a heat insulating layer on the outer periphery. A fixing device characterized by having a layer. 2. The fixing device according to claim 1, wherein the heat insulating layer is a fluororesin layer. 3. The fixing device according to claim 1 or 2, wherein at least a portion of the vicinity of the heat roller and press roller is surrounded by a heat insulating member.