JP3441889B2 - Fixing device - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a fixing device used in electrophotography, as shown in FIG. 7, a thermal fixing device is generally used in which a pair of rollers R and R'having at least one of them having a heating source 2 are pressed against each other to rotate. .

The roller is usually made of a good heat conductor such as a metal (aluminum, iron, etc. or a metal alloy), and on the core metal 1, 1 ′, the releasing property from the toner is good and the silicone rubber is excellent in heat resistance. , Perfluoroalkoxyalkane resin (PFA), polytetrafluoroethylene (PTFE)
Etc. are surface-coated as a release layer 4 having an elastic function (this release layer 4 is not a single layer structure but a two-layer structure in which the elastic function and the release layer are separated, or a structure of two or more layers). But it is possible).

A thermistor 9 as a temperature detecting means comes in close proximity to or in contact with at least one of the surfaces of the rollers R and R ', and the temperature control circuit 21 is controlled by a signal from the thermistor to control the temperature of the heating source 2. So roller R,
Keep the temperature of the R'surface constant.

The fixing device is configured to fix and fix the toner T on the transfer paper P by passing the transfer paper P having the powder toner image T obtained by electrophotography between the rollers.

[0006]

However, in the above conventional example, when the transfer paper passes through the fixing device (between fixing rollers), the heat of the surface of the fixing roller is also taken out of the fixing device, and the surface temperature of the fixing roller is lowered. Therefore, the following drawbacks have occurred.

(1) When the surface of the fixing rollers R and R'contacts the transfer paper P again after the fixing roller makes one revolution, the surface temperature of the fixing roller decreases as described above, and therefore the fixing roller 1
After the circumference, an unfixed image in which toner is not fixed and fixed on the transfer paper occurs. Further, in a color fixing device that superimposes a plurality of toners of different colors, there is an inconvenience that the first and second fixing rollers have different colors.

(2) Further, when the release layer 4 is thinned in order to improve heat conduction to the surfaces of the fixing rollers R and R ', FIG. 8 is a view as seen from the direction of arrow A in FIG. As shown in
The fixing is not sufficiently performed in the part where the image is thin (the amount of toner is small). It is considered that this is because the toner T on the transfer paper P and the surfaces of the fixing rollers R and R ′ do not sufficiently contact with each other.

In particular, it appears remarkably when there is a dark portion of the image in the periphery. In addition, it appears prominently in a color image in which a plurality of toners are superposed, particularly in color toner fixing on an OHT (recording sheet for overhead project), and when this OHT is projected by OHP, the image outline becomes dark (pseudo-image). Contour). On the other hand, the release layer may be thickened as shown in FIG. 8B, but the problem (1) occurs.

(3) In order to solve the above (1), it is necessary that the heating source 2 of the fixing rollers R and R'has a large heating capacity. When the capacity of the heating source 2 becomes large, the image forming apparatus becomes large, and every time the heating source 2 is turned on / off to control the temperature, malfunctions of surrounding electric equipment occur.

(4) Further, when the capacity of the heating source 2 is increased, the temperature of the core metal 1 rises, and the core metal 1 and the release layer 4 are separated from each other.

[0012]

The present invention has an unfixed image.
Core member for fixing member that heats and pressurizes the recording material
At the outer periphery of the core, the heat dissipation plate or heat dissipation with elasticity
A core metal for a fixing member, which is provided with a needle .

Further, according to the present invention, in a fixing device for fixing a recording material having an unfixed image by heating and pressurizing with a fixing member , at least one fixing member has elasticity on the outer circumference.
On the surface of the metal core that has a heat sink or heat sink
Even if there is at least one release layer, the heat dissipation plate or heat dissipation needle is
The fixing device has a release layer so that

In the present invention, the above-mentioned constitution improves the thermal conductivity to the surface of the fixing member.

[0015]

DETAILED DESCRIPTION OF THE INVENTION

[Embodiment 1] FIG. 1 shows a first embodiment of the present invention. The core metal 1 is made of aluminum and has an outer diameter of 36.0 mm and an inner diameter of 31.
It is a 0 mm hollow cylinder and is 230 mm wide in the longitudinal direction. A 450 W halogen heater is provided as the heating source 2 inside the hollow cylinder.

A heat radiating plate 3 is arranged outside the core metal 1. As for the heat sink 3, 500 sheets are 2m long as shown in FIG.
m, thickness 0.1 mm, using the same material as the core metal 1, diagonally arranged at a height of 1.7 mm from the outer peripheral surface of the core metal 1, and further using a silicone rubber for the release layer 4 of 2.0 mm. Form by dipping.

An image was formed by combining the fixing rollers having the above-mentioned structures with the image forming apparatus shown in FIG. 2, but the above-mentioned inconvenience was not recognized.

A detailed description will be given below with reference to FIG.

The image forming apparatus shown in FIG. 2 is a method for obtaining a color image by using toners of a plurality of colors, and an image forming apparatus of this type is described in Japanese Patent Laid-Open No. 50-50935.

The photosensitive drum 11 is constructed by applying a photoconductor 13 made of an organic photoconductor (OPC) on an aluminum cylinder 12 having a diameter of 40 mm, and in the direction of the arrow 100 per second.
Moved in mm. The above-mentioned OPC is A-Si, CdS, S
e or the like may be used. This surface layer is a conventionally known corona charger 1
4, the optical system 15 is composed of a conventionally known structure such as a laser diode, a rotary polygon mirror, and a folding mirror (not shown). An electric signal according to a yellow image pattern is input to the optical system 15, converted into light E, and irradiated on the photosensitive drum 11. An electrostatic latent image is formed on the photosensitive drum 11. Next, the yellow development 16Y visualizes the yellow toner. Further, the yellow toner image on the photosensitive drum 11 is fed with the transfer paper P from the transfer paper cassette 17 and adsorbed on the transfer roller 18. Transfer roller 18
Is an elastic layer 20 made of Inoac (manufacturer) having a resistance of 2 mm in a metal cylinder 19 having a diameter of 156 mm, and a polyvinylidene fluoride (PVdF) layer having a thickness of 100 μm as a dielectric layer in the upper layer. It is configured by winding as 21.

A transfer voltage having a polarity opposite to the toner polarity is applied to the transfer roller 18 so that the toner on the photosensitive drum 11 is transferred onto the transfer paper P (not shown), and the toner is transferred onto the transfer paper. Magenta color, cyan color, black color (developing device is magenta developing 16M, cyan developing 1 each time)
6C, black development 16Bk) is performed) to form a color image on the transfer paper P.

The transfer residual toner on the photosensitive drum 11 is a known cleaning device 2 such as a fur brush or a blade.
Cleaned by 2.

The image on the transfer paper P is pressed and heated by the fixing device having a pair of rollers in FIG. 1 to fix the toner. The fixed image has no gloss difference even on a large screen such as A4 size, and
An image having no pseudo contour can be formed even if the image is recorded on the transfer paper P such as OHT.

It is presumed that the reason is that the heat dissipation plate 3 has good heat conduction and that the heat dissipation plate 3 is thin during fixing, so that it follows the release layer 4. In addition, the heat sink 3 is formed in a thin needle shape to form a core metal 1.
Similar effects were observed even when they were arranged radially from the center of.

FIG. 3 is a diagram for concretely explaining FIGS. 1 and 2, and is a graph in which the roller surface temperature is measured in the image forming apparatus. The horizontal axis shows time (minutes) and the vertical axis shows surface temperature. (° C) is shown.

In FIG. 3, a curve a represents the roller surface temperature of FIG. 1, and a curve b represents the roller surface temperature rise of the conventional example in FIG. As a result of examination on the difference between the curves a and b, it was found that there is a difference in thermal conductivity between the heat dissipation plate 3 and the release layer 4.

In the following, silicon rubber or the like is usually used as the release layer 4, and the thermal conductivity k is 0.1 to 0.6 W.
/ M · K, whereas the thermal conductivity k of metals is 200
A difference of up to 400 W / mK and 500 to 1000 times was observed. In the present invention, the release layer 4 is a two-liquid type LTV silicone rubber (thermal conductivity: 0.13 W) supplied from IST.
/ M · K), and the core metal 1 and heat sink 3 have an industrial number:
A6063 aluminum alloy (thermal conductivity: 217W
/ M · K) was used.

As described above, a simple method of providing the heat dissipation plate 3 having elasticity on the outer periphery of the core metal 1 can reduce the gloss difference of the fixed image and reduce the false contour.

In recent years, instead of rollers, a SURF fixing method has been proposed in which a fixed heating source is combined with a thin cylindrical film made of a heat-resistant resin that moves in synchronization with the transfer paper P (Japanese Patent Publication No. 53-17061). ) And the above SUR
A method of directly heating and fixing a thin ferromagnetic cylindrical film by electromagnetic induction heating instead of the F fixing heating source has also been proposed (Japanese Patent Laid-Open No. 4-166966), which has the advantage that the heating rate is fast and the thermal efficiency is good. However, there are inconveniences such as the durability of the film and the occurrence of pseudo contours when fixing a color image in which a plurality of images are superposed.

Reference Example 1 The basic structure of FIG. 4 is the same as that of FIGS. A silicon rubber layer having a thickness of 1.8 mm in which 50% by weight of permalloy (iron-nickel alloy) having a diameter of 0.1 mm is dispersed as ferromagnetic particles 5 is formed on the outer periphery of the core metal 1 in FIG. Further, a silicon rubber layer having a film thickness of 0.1 mm is formed as a release layer 4 on the outer surface by depping, and the long electromagnet disclosed in JP-A-4-166966 is directly used as an electromagnetic induction heating source 6 from this surface side. It was found that even if the ferromagnetic particles 5 were heated, the same characteristics as in Example 1 could be obtained. Further, when the cored bar 1 is made of a resin or an inorganic substance having a low heat conductivity, a good heat efficiency result was obtained.

Reference Example 2 The basic structure of FIG. 5 is the same as that of FIGS. 1 and 4. A heating source 2 is provided inside the core metal 1 of FIG.
Even if a silicon rubber layer in which good heat conductive particles 7 such as silver, copper, aluminum or graphite carbon are dispersed, and a silicone rubber layer is formed as the release layer 4 on the outer surface,
It was found that the same effect as in Example 1 can be obtained. Also, the same effect was obtained by housing the electromagnetic induction heating source 6 of FIG. 4 in the core metal 1 and dispersing the ferromagnetic particles 5 instead of the good heat conductive particles 7.

Reference Example 3 FIG. 6 further shows Japanese Patent Publication No. 53-17061 and Japanese Patent Laid-Open No.
In a device for improving the inconvenience of Japanese Patent No. 166977, a silicone rubber layer in which good thermal conductive particles 7 are dispersed as a release layer 4 is formed by coating on the outer surface of a resin film 8 such as a belt-shaped polyimide. Even when the heating source 2 was brought into close contact with or close to the resin film 8 side, the same effect as in Example 1 was obtained. Further, the same effect was obtained by dispersing the ferromagnetic particles 5 instead of the good heat conductive particles 7 in FIG. 6 and directly heating the ferromagnetic particles 5 from the resin film 8 side by the electromagnetic induction heating source 6.

[0033]

As described above, a material having good thermal conductivity is inserted into the release layer or dispersed in the release layer, or a ferromagnetic material is inserted into the release layer or dispersed in the release layer. By a simple method, it is possible to provide a high-performance fixing device that improves thermal efficiency, shortens the temperature rising time, and can be applied to a color image forming apparatus.

Further, when the core metal 1 and the good heat conductor or the like are joined, the adhesive strength between the release layer and the core metal can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view of a fixing device for explaining the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus having the fixing device of FIG.

FIG. 3 is a temperature rise characteristic diagram of a conventional fixing device and the fixing device of the present invention.

FIG. 4 is a cross-sectional view of a fixing device according to a reference example of the invention.

FIG. 5 is a cross-sectional view of a fixing device according to another reference example of the present invention.

FIG. 6 is a cross-sectional view of a fixing device according to another reference example of the present invention.

FIG. 7 is a conventional fixing device.

8A and 8B show a state in which a transfer paper is fixed, FIG. 8A shows a thin release layer, and FIG. 8B shows a thick release layer.

[Explanation of symbols]

2 Heat dissipation source 3 Heat sink (good thermal conductor) 4 Release layer 5 Ferromagnetic particles (ferromagnetic particles) 6 Electromagnetic induction heating source 6 Good thermal conductive particles (good thermal conductor)

Claims (5)

(57) [Claims] 1. A recording material having an unfixed image is heated and pressed.
The core metal for the fixing member that is fixed by
Characterized by the provision of a heat dissipation plate or heat dissipation needle
The core metal for the fixing member. 2. The heat radiating plate or the heat radiating needle is located from the center of the core metal.
It is provided radially in view, and it is characterized by the above-mentioned.
The core metal for the fixing member described. 3. A fixing device for heating and pressurizing fixing by a fixing member of the recording material having an unfixed image, less
One of the fixing members is a heat dissipation plate or
Is at least one layer on the surface of the cored bar with the heat radiation needle.
Have the heat sink or heat sink inside the upper release layer
A fixing device having a release layer . 4. The fixing device according to claim 3 , wherein the heat conductivity of the heat radiating plate and the heat radiating needle is 500 times or more the heat conductivity of the release layer. 5. The fixing device according to claim 3, further comprising a pair of rotating bodies that are in pressure contact with each other as a fixing member, and a heating body that heats at least one of the rotating bodies.