JPS59149385A - Heat fixing device - Google Patents

Abstract

PURPOSE:To shorten considerably a preheating time and attain a uniform heating temperature throughout the overall length of a heat roll by constituting both end parts of a resistance heating body layer of a material having a higher calorific value than that of material in the center part. CONSTITUTION:Electrodes 9 and 9a brought into contact with the resistance heating body layer 8, where the material in both end parts 8b and 8c have a calorific value larger than that of the material in the center part 8a, are provided on a heat roll 1 where said resistance heating body layer 8 is formed on the outside circumference of a metallic hollow core 5 through a coupling layer 6 and an insulating layer 7. If the layer 8 is formed with a TiO2 ceramic, a surface temperature of about 200 deg.C is attained in a short time with low power consumption. When the roll 1 and a pressure roll 2 are rotated and a voltage is impressed to a feeding brush, a current is flowed to the layer 8 through the electrodes 9 and 9a to heat the heat roll 1. Since the materials in both end parts 8b and 8c of the layer 8 have a calorific value larger than that of the material in the center part 8a, the temperature distribution on the surface of the heat roll 1 is kept uniform practically.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat fixing device, and particularly to a heat fixing device for fixing a toner image formed on a support such as paper in an image forming device such as an electrophotographic copying machine, a facsimile machine, or a printer. The present invention relates to a heat fixing device that performs fixing by applying pressure using a heat roll.

As one of the constant @ devices in J3 image forming apparatus, a heat-resistant elastic layer such as silicone rubber or Teflon is coated on the surface of a metal core with good thermal conductivity that has a heat source such as an infrared lamp, halogen lamp, or nichrome wire inside. A so-called hot roll type heating chamber @ device is known, which is equipped with a heating roll coated with a releasable layer such as (trade name) and a pressure roll.

In this type of heat fixing device, the roll main body is indirectly heated through the air by the radiant heat from the heat source inside the heating roll, so thermal efficiency is poor, and the heating roll surface is kept at a predetermined temperature (usually 150~150°C). There was a drawback that the preheating time to reach the temperature (approximately 180°C) was long (3 to 5 minutes).

In order to shorten this preheating time, for example, JP-A IN? b 6-123581 and JP-A-56-1
It has been proposed to directly heat the roll body using a resistance heating element such as a ceramic heater as described in Japanese Patent No. 3B 766 and the like.

Although this direct heating type fixing device can shorten the preheating time compared to the conventional radiation heating type, it still
A preheating time of about 2 minutes was required.

Furthermore, as a resistance heating element, a ceramic heating element having a positive temperature coefficient of resistance, or so-called PTC characteristic, is known. Ceramic heating elements with PTC characteristics are characterized by the fact that a predetermined heat generation temperature can be obtained by selecting a Curie temperature, that the temperature rise time is fast, and that the resistance increases rapidly at a constant temperature, so that the It has advantages such as having a hot stone control function.

However, the generally known Ba Ti 03 series +7
The 7T ramic heating element has not been put into practical use because it takes a lot of effort to manufacture and it is extremely difficult to obtain one with high dimensional accuracy.

Furthermore, improvements to this type of lamic heating element have been proposed in various publications such as JP-A-55-164859, JP-A-56-138766, and JP-A-56-123581, but they are not sufficient. Yes, it is (2).

The present invention solves the problems of the prior art described in +, +, and j, and makes it possible to significantly shorten the distance between preheating surfaces, and to achieve a uniform heating temperature over the entire length of the heating LTI-ru. The purpose of this invention is to provide a heat fixing device that can be used.

The characteristics of the present invention include a heating roll having a resistance heating layer,
In a fixing device having a structure in which a support holding a toner image is passed between a pressure roll that is in pressure contact with the heating roll, the material of both ends of the resistance heating layer is changed to 4A of the central part. The heat fixing device is designed to generate more heat than the heat fixing device.

An embodiment of the present invention will be explained below based on the drawings.

Here, FIG. 1 is a partially vertical front view of a heat fixing device according to an embodiment, and FIG. 2 is a sectional view taken along the line Δ-Δ in FIG.

In the figure, 1 is a heating roll, 2 is a pressure roll, 3,
3aJ'i, 3b, 3c are bearings, 4.4
The heating roll 1 is rotatably supported by the side plates 4, 4a via bearings 3.3a, and the pressure roll 2 is rotatably supported by the side plates 4.4a via bearings 3b, 3c.

5 is a metal hollow 21A, 6 which constitutes the heating roll 1;
is a bonding layer, 7 is an uninsulated layer, and 8 is a resistance heating layer. The material of the central portion 8a is, for example, T'i02. The material of both end portions 8b and 8c is l'!02-x (0(X < 1 ), and the 4.J quality at both ends generates 1 more heat than the material in the medium heat part.
It is made by one person and is formed around the outer periphery of the hollow core 5 with a bonding layer 6 J5 and an insulating layer 7 interposed therebetween. 9°9a4,1:
, (: A ring-shaped electrode made of a conductive material such as a u-alloy, which is attached near both ends of the outer peripheral surface of the resistance heating layer 8 with a gap slightly larger than a predetermined width.

The ring cutting dies 4fj9, 9a are in contact with a power supply brush (not shown) such as a J-bon (which is connected to a power source through a wire connection). 10 is a length corresponding to the above-mentioned fixing width on the outer circumferential surface of the resistance heating layer 8 (J formed release f
It is one layer.

11 is a metallic hollow core constituting the pressurization 1''-rule 2;
Reference numeral 12 denotes a heat-resistant elastic layer formed to cover the outer peripheral surface of the hollow core 11.

Next, the details of each component of the heating roll 1 are as follows.

The resistance heating element layer 8 is made of Rio2 ceramic.
By doing so, it becomes possible to put it into practical use. ]-102 series ceramics are represented by the chemical formula 1-102-x (0≦x<1), and as X becomes larger, the specific resistance becomes smaller. In this case, by controlling the production atmosphere,
o2-x a) It is possible to adjust X; for example, the stronger the reducing nature of the atmosphere, the louder X becomes. This 1-io? The characteristics of this type of ceramic are that it has good corrosion resistance and
It is possible to obtain a surface temperature of about 200°C in a short time (several seconds to tens of seconds) with low power consumption (40V x 5Δ to 50V One example is that it can be formed. ? In other words, with -l iO2-based ceramics, plasma spraying can be applied as the method for forming the resistive film, so manufacturing costs are significantly reduced compared to 3a7'i03-based ceramics. This makes it possible to manufacture heating rolls with a cost equal to or lower than when using conventional heat sources for width. However, the resistance of RTO2 type lamic decreases as the temperature increases. Since it has a negative temperature coefficient of resistance, it is necessary to incorporate a control circuit between the resistance heating layer and the input power source to stop the current supply to the heating layer when a predetermined temperature is reached.

The insulating layer 7 is for electrically insulating the resistive heating element layer 8 and the hollow core 5 by 1q, and various materials can be used. In the case of 02 series ceramic, Δ1203·MgO is suitable.

The bonding layer 6 is for securely fixing the insulating layer 7 to the hollow core 5, and may be omitted depending on the materials of the hollow core 5 and the insulating layer 7.

The thicknesses of the above resistance heating layer, insulating layer, and bonding layer may be set as appropriate depending on the fixing temperature, material (composition), method (length, outer diameter, inner diameter) of the hollow core, etc. . For example, the hollow core is 27Qmm (length) x 34.5mmφ (outer diameter) 3
When the diameter is 2 mmφ (inner diameter) and the fixing temperature is 190 to 210°C, the resistance heating layer (Ti 02 ) is 50 H-70
About um, the insulating layer (△1203 ・Mg0) is 15
0□-・200IIIll, and the bonding layer (Ni
-Ai-Mo) is suitably about 50μIII.

At the ends 8b and 8c of the resistance heating layer 8, Ti02-X
If A31=jru× is shifted by a smaller value than the central portion 8a, the specific resistance becomes human and the calorific value becomes human.

Next, the fixing operation of the heat fixing device configured as described above will be explained.

First, the heating roll 1 and pressurizing roll 2, which are in pressure contact with each other, are rotated by a drive mechanism (not shown), and at the same time, a commercial liquid is applied to the power supply brush. , 1ζ is applied, a current flows through the ring-shaped electrodes 9 and 9a to the resistance heating layer 8 and heats the resistance heating layer 8, thereby heating the ring 1.

During this heating, the resistance heating element layer 8 has both ends 8b, 8
Since the material of C has a larger amount of light heat than the material Jζ of the central portion 8a, the temperature distribution on the surface of the heating roll 1 is kept substantially uniform, and the temperature drop at both ends is compensated for.

Therefore, when the support holding the hener is passed between the heating roll 1 and the pressure roll 2, a high-quality fixed image without defective fixing at both ends can be obtained.

In the heating roll 1, a heat-resistant elastic layer such as silicone rubber may be formed on the resistance heating layer 8, and a 1-layer 1-layer such as Teflon may be formed thereon.

On the other hand, in addition to the above, the pressure roll 2 may be one in which a heat-resistant elastic layer is formed on a solid metal horn.

In the heat fixing device according to the present embodiment, the material 41 at both end portions 8b and 8c is attached to the outer periphery of the metal hollow core 5 via the bonding layer 6 and the insulating layer 7 in the central portion. Ring-shaped electrodes 9, 9a are attached to the heating roll 1 on which the resistance heating element layer 8 is formed, which has a larger heat generation value than the material of 8a, in contact with the resistance heating element layer 8.
It is equipped with Iζ.

Therefore, if power is supplied from the power supply to the ring-shaped electrodes 9, 9a through the power supply brush, the wear amount 4i on the surface of the heating roll 1 can be reduced by keeping the temperature 1 at both ends uniform. , a high-quality fixed image with no fixing defects at both ends is 1.
be qed.

As described above, the present invention can be expected to provide a heat fixing device that can significantly shorten the preheating time and maintain a uniform heating temperature over the entire length of the heating roll.-C1 Practical Effects It can be said that this is an excellent invention.

[Brief explanation of the drawing]

FIG. 1 is a partially vertical front view of a heat fixing device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line Δ--Δ in FIG. 1...Heat roll, 2...Pressure 1-roll, 8...
Resistive photothermal layer, 8a...center portion, 8b, 8'C...
Both ends. Patent applicant Hitachi Metals, Ltd.

Claims (1)

[Claims] In a constant weight device configured to pass a support holding a toner image between a heating roll having a resistance heating layer and a pressure roll that is in pressure contact with the heating roll, both ends of the resistance heating layer are A heat fixing device characterized in that the material of the central portion has a higher calorific value than the material of the central portion.