JPH07271217A - Plate-shaped heater, fixing device and image forming device - Google Patents

Abstract

PURPOSE:To prevent or decrease curling of a paper sheet by constituting the device in such a manner that paper such as copy paper is gradually cooled as the paper leaves the resistance heating element. CONSTITUTION:The heater consists of a substrate 12 comprising a heatresistant electric insulating material, a belt-like resistance heating element 13 formed on one flat surface 12a of the substrate 12, and an overcoat layer 15 formed to cover the outer surface of the resistance heating element 13 to electrically insulate the heater on the one flat surface 12a of the substrate so that heat from the resistance heating element is transferred to paper P such as the copy paper while the paper is travelled. On the exit end (out) of the overcoat layer 15, a thickened edge part 16 is formed in such a manner that the thickness increases with the distance from the resistance heating element 13 and a rising slope 17 is formed on the one surface of the overcoating layer. The contact center 0 where the heater is directly or indirectly in contact with a pressure roller or the like is positioned at the rising part of the slope 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin plate heater to be used by being mounted on small equipment such as office automation equipment, household electric equipment and precision manufacturing equipment, and a copying machine equipped with this thin plate heater. The present invention relates to a fixing device used for fixing a toner such as a facsimile and an image forming apparatus using the fixing device.

[0002]

2. Description of the Related Art Generally, in an electronic copying machine, a copy sheet on which a toner image is formed is passed directly or indirectly between a fixing plate heater and a pressure roller while pressing the heater. The toner on the copy paper is heated, melted, and fixed.

As a conventional fixing type plate heater of this kind, one having a structure as shown in FIGS. 6 and 7 has been put into practical use. This heater H is a heat-resistant and electrically insulating substrate 1 in the form of an elongated flat plate made of alumina (Al ₂ O ₃ ) ceramics or the like.
On the surface side 1a of the glass, a paste prepared by kneading silver / palladium alloy (Ag / Pd) powder and the like with glass powder (inorganic binder) and organic binder is applied by printing, firing, and thin strip-shaped thick film. The resistance heating element 2 is formed, and silver or a silver-platinum (Ag.Pt) alloy, silver.
A film made of a good conductor such as palladium alloy (Ag · Pd) is formed to form a pair of power supply terminal portions 3a and 3b, and the outer surface of the resistance heating element 2 is covered with a vitreous overcoat layer 4. As a result, mechanical strength such as abrasion resistance and impact resistance is improved, corrosion resistance is protected from sulfidation and oxidation, and electrical insulation with a pressure roller is achieved.

As shown in FIG. 8, in the fixing device of the copying machine, the plate-shaped heater H and the pressure roller 5 are arranged in parallel so as to face each other, and the heat resistance of the surface of the pressure roller 5 having a rotating shaft is improved. The roller portion made of a flexible elastic material and the overcoat layer 4 of the plate-shaped heater H are elastically contacted directly or indirectly via the annular endless heat resistant sheet 6.

When the copy sheet P is supplied from the entrance side in between the endless heat resistant sheet 6 of the plate-shaped heater H and the pressure roller 5, the pressure roller 5 is rotated so that the copy sheet P is heated. The toner T on the copy paper P is heated and melted by the heat of the heater H during the sliding of the toner on the overcoat layer 4 of H through the heat-resistant sheet 6, and is fixed on the paper P. Is to be discharged from.

[0006]

However, in such a conventional heater H, since the upper surface of the overcoat layer 4 for moving the copy paper P through the heat-resistant sheet 6 is a flat surface in the figure, the copy paper P is Is discharged immediately after being heated to a high temperature just above the resistance heating element 2, and the discharging direction is free. Therefore, there is a problem in that the copy sheet P is curled as shown in FIG. 8 by being pressed by the pressure roller 5.

Therefore, the present invention has been made in consideration of such circumstances, and an object thereof is to provide a plate heater, a fixing device, and an image forming apparatus capable of preventing or reducing curling of paper such as copy paper. To do.

[0008]

SUMMARY OF THE INVENTION The present invention is based on the new finding that when a copy sheet P is heated, then gradually cooled while being guided in a predetermined direction and discharged, curling of the copy sheet P is prevented or reduced. It was made by the following and is structured as follows.

According to the first aspect of the present invention, a substrate made of a heat-resistant and electrically insulating material, a strip-shaped resistance heating element formed on one flat surface of the substrate, and an outer surface of the resistance heating element are provided. A coating layer formed on one flat surface of the substrate so as to cover and electrically insulate it, and to transfer the heat generated from the resistance heating element to a moving object to be heated. A thickened portion is formed at one end thereof, the thickness gradually increasing as the distance from the resistance heating element increases.

The invention according to claim 2 of the present application is characterized in that a second resistance heating element is provided on the thickened end side of the coat layer.

Furthermore, the invention according to claim 3 of the present application is a substrate made of a heat-resistant electrically insulating material, a strip-shaped resistance heating element formed on one flat surface of the substrate, and the resistance heating element. And an electrical insulating layer formed on one flat surface of the substrate along the resistance heating element, the thickness of the electrical insulating layer increasing gradually as the distance from the resistance heating element increases. It is characterized in that a thick portion is formed.

Further, the invention according to claim 4 of the present application is
A rotatable pressure roller is arranged so as to face the plate heater according to any one of claims 1 to 3 such that the thickened end side of the coat layer is on the discharge side of the heated body. It is characterized in that the center of contact between the pressure roller and the coat layer is located at the rising portion of the thickened end of the coat layer.

Further, the invention according to claim 5 of the present application is characterized by including the fixing device according to claim 4.

[0014]

Immediately after a resistance heating element heats a paper to be heated, such as copy paper, the paper is pressed by a pressure roller in a predetermined direction along the rising slope of the thickened end of the coat layer. And is gradually cooled away from the resistance heating element. Therefore, the curl of the paper can be prevented or reduced.

When the second resistance heating element is provided on the thickened end side of the coating layer, the heating temperature of the second resistance heating element is set lower than that of the first resistance heating element. This prevents quenching at the thickened end of the coat layer,
Can be slowly cooled. For this reason, since the paper is pressed for a long time, curling of the paper can be prevented or reduced.

Further, the pressure roller and the coat layer are directly
Alternatively, when the center of the contact portion that indirectly contacts is located at the rising portion of the thickened end portion of the coat layer, the paper is more reliably discharged in the predetermined direction along the rising slope of the thickened end portion. Therefore, the curl of the paper can be prevented or reduced accordingly.

[0017]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5, the same or corresponding parts are designated by the same reference numerals.

FIG. 1 is a sectional view taken along the line I--I of FIG. 2, and FIG. 2 is a plan view of an embodiment of a plate heater according to the present invention. In these figures, the plate heater 11 is a heat-resistant electric heater. An insulating material such as alumina (Al ₂ O ₃ ) ceramics having a length of about 300 mm, a width of about 8 mm, and a thickness of about 0.6 to about 1 mm is formed on the surface 12 a of the elongated flat plate-shaped substrate 12. A strip-shaped resistance heating element 13 mainly made of silver-palladium (Ag.Pd) alloy or nickel-tin (Ni.Sn) alloy having a length of about 230 mm, a width of about 2 mm and a thickness of about 10 μm along the longitudinal direction. Is formed.

The resistance heating element 13 has a length of about 1 at both ends.
Good conductor mainly composed of 5 mm wide and about 6 mm wide silver (Ag), platinum (Pt), gold (Au), silver-platinum (Ag.Pt) alloy, silver-palladium (Ag.Pd) alloy, etc. A pair of power supply terminal portions 14a and 14b made of a film are formed in layers.

On the surface 12a of the substrate 12, a layer of glass powder or the like having a thickness of 70 to 70 is formed so as to cover almost the entire surface of the substrate 12 except for the pair of power supply terminal portions 14a and 14b and both longitudinal ends. 100 μm, or 100 to 500 μm
The glassy overcoat layer 15 is formed.

As shown in FIG. 1, the overcoat layer 15 causes a paper P, such as a copy paper, which is a heated object, to slide directly or indirectly from the inlet side in to the outlet side out on the upper surface in the figure. At that time, the paper P is generated by the heat generated by the resistance heating element 13.
By heating the toner image T attached to one surface of the
The toner image T is fixed on the paper P.

As shown in FIG. 1, the overcoat layer 15 increases in thickness as it moves away from the resistance heating element 13, and its output side out end is increased in thickness end 1.
6 is formed. The rising slope 17 of the thickened end 16
A contact portion center O, which comes into direct or indirect contact with a pressure roller to be described later, is located at the rising portion of the copying paper P, and the copy paper P is surely moved along the rising slope 17 in a predetermined direction as shown by a white arrow in the figure. It is designed to be discharged.

As an example of the method of forming the slopes 17, there is a method of changing the coat pattern of each layer when the overcoat layer 15 is formed by laminating a plurality of layers by screen printing.

FIGS. 3 (A) to 3 (E) show various modifications of such a plate-shaped heater 11, and the plate-shaped heater 11A shown in FIG. 3 (A) has an outlet side of the overcoat layer 15a. ou
At the center O of the contact portion located at the rising portion of the rising slope 17a of the thickened end portion 16a formed at t, the resistance heating element 13A,
The feature is that they are arranged so that the centers in the width direction thereof are substantially the same.

In the plate-shaped heater 11B shown in FIG. 3B, the thickened end portion 16 of the exit side end portion of the overcoat layer 15b is formed.
The thickness of b is made almost the same as the thickness of the entrance end 15b1 or slightly increased, and the upper surface of the intermediate portion integrally connecting the both ends 15b1 and 16b is formed as a concave arc surface 17b. Surface 1
The contact portion center O is located at the widthwise center of 7b, that is, at the rising portion of the rising slope.

In the plate heater 11C shown in FIG. 3C, a concave arc surface 17c1 is integrally formed on the rising portion of the rising slope 17c of the thickened end portion 16c of the overcoat layer 15c, and the concave arc surface 17c1 is formed. The contact portion center O is located at the center portion in the width direction, that is, at the rising portion of the rising slope 17c.

In the plate-shaped heater 11D shown in FIG. 3D, a thickened end portion 16d, which is almost the same as the overcoat layer 15a of FIG. 3A, is formed on the overcoat layer 15d, and its rising slope 17c is formed. Although the contact portion center O is located at the rising portion, the entrance side end portion 15 of the overcoat layer 15d is located.
While the first resistance heating element 13d1 is provided on the d1 side, the second resistance heating element 13d is also provided on the thickened end portion 16d side of the output side out.
The feature is that 2 is provided.

In the plate heater 11E shown in FIG. 3E, the second resistance heating element 13e2 is embedded in the thickened end portion 16e of the overcoat layer 15e in a state of floating above the surface of the substrate 12. Other than that, the plate-shaped heater 11D is configured similarly to the plate-shaped heater 11D. That is, the overcoat layer 15e has substantially the same shape as the overcoat layer 15d of the plate-shaped heater 11D, and the first resistance heating element 13e1 is provided on the front side 12a of the substrate 12 so that the first resistance heating element 13e1 is closely attached to the entrance side in. The contact center O at the rising part of the rising slope 17e
Is located.

In each of the plate-shaped heaters 11A to 11E described above, the thicknesses and shapes are slightly different on the outgoing side out of the overcoat layers 15a to 15e, but the thickened end portions 16a to 16e.
16e is formed, and the center O of the contact portion with the pressure roller is located at the rising portions of the rising slopes 17a to 17e. Therefore, the upper surface of each of the overcoat layers 15a to 15e in FIG. Each of the rising slopes 17a to 17a ...
It can be discharged along the extension line 17e at a required angle. In addition, the copy sheet P is discharged so that the resistance heating elements 13a, 13b, 13c, 13d1 on the inlet side in.
, 13e1 gradually, so that it is gradually cooled.

That is, the copy sheet P is fed to the plate heaters 11A to 11A.
11E resistance heating elements 13a to 13c, 13d1 and 13e
After being heated at a high temperature by 1, the copy paper P is provided with rising slopes 17a to 17e of the overcoat layers 15a to 15d.
While squeezing with the pressure roller and the pressure roller, this rising slope 1
The copy paper P is discharged in a predetermined direction along 7a to 17e and gradually cooled, so that the curl of the copy paper P can be prevented or reduced.

The plate heaters 11D and 11E are the first
The second resistance heating elements 13d2, 13e2 are provided in addition to the resistance heating elements 13d1, 13e1 of FIG. By setting it low,
It is possible to prevent rapid cooling due to discharge of the copy paper P and to cool gradually.

An electrically insulating layer may be provided separately from the overcoat layers 15a to 15e, and a thickened portion corresponding to the thickened end portion 16 may be provided thereon.

FIG. 4 shows a plate-shaped heater 1 constructed as described above.
1, 11A to 11D, for example, 11 is assembled, and this is a fixing device 21 in which a heat resistant elastic material, for example, a silicone rubber layer 24 is provided on the outer surface of a cylindrical roller body 23 having rotary shafts 22 projecting from both axial end surfaces. The pressure roller 25 is formed by fitting.

The pressure roller 25 has plate heaters 11 arranged in parallel so as to face the rotary shaft 22 thereof.
1 is attached to a base not shown.

An annular endless heat-resistant sheet 26 such as a polyimide resin is wound around the base including the plate heater 11, and the outer surface of the overcoat layer 15 directly above the resistance heating element 13 is formed by this. It is in elastic contact with the silicone rubber layer 24 of the pressure roller 25 via the heat resistant sheet 26.
The pressure roller 25 is disposed so that the center O of the contact portion is located at the rising portion of the rising slope 17 of the overcoat layer 15 of the plate heater 11, and the copy paper P is moved along the rising slope 17 in a predetermined direction. It is designed to be discharged.

The plate heater 11 has a power supply terminal portion 14
Silicone rubber and the outer surface of the heat-resistant sheet 26 provided on the overcoat layer 15 of the resistance heating element 13 that is heated by being energized through an elastic connector (not shown) made of a phosphor bronze plate or the like in contact with a and 14b. By heating the copy sheet P on which the toner image T is formed with the layer 24 by the plate heater 11, the unfixed toner image T is melted and fixed on the copy sheet P.

That is, on the in-copy side P of the pressure roller 25, the unfixed toner image T on the copy sheet P is first heated and melted by the plate heater 11 via the heat resistant sheet 26, and at least the surface portion thereof is It greatly exceeds the melting point and completely softens and melts. After that, the copy paper P of the pressure roller 25
On the output side out, the copy sheet P separates from the plate-shaped heater 11, the toner image T naturally radiates heat and is cooled and solidified again, and the heat-resistant sheet 26 also separates from the copy sheet P.

As described above, since the toner image T is once completely softened and melted, the toner image T is cooled and solidified again at the paper output side out of the pressure roller 25, so that the toner image T has a very large condensing force.

Since the thickened end portion 16 of the overcoat layer 15 is formed on the paper output side out of the plate heater 11 as shown in FIG. 1, the leading end portion of the copy sheet P is the thickened end portion. It is pinched by the rising slope 17 of 16 and the pressure roller 25, is discharged in a predetermined direction while being guided by the slope 17, and is gradually cooled. That is, after the copy sheet P is heated at a high temperature by the resistance heating element 13 of the plate-shaped heater 11, the copy sheet P is squeezed by the rising slope 17 of the overcoat layer 15 and the pressure roller while the copy sheet P is pressed on the rising slope 17. The curl of the copy sheet P can be prevented or reduced because the sheet is discharged along a predetermined direction and gradually cooled.

FIG. 5 shows the fixing device 21 constructed as described above.
1 shows a configuration of an electronic copying machine 31 in which a document is placed by reciprocating an original placing table 33 made of a transparent member such as transparent glass provided on an upper surface of a housing 32 in a direction of an arrow in the figure. 34 are to be scanned.

A lamp 3 for irradiating light is provided in the upper part of the housing 32.
5 is provided, and the light rays reflected from the original 34 irradiated by the lamp 35 are arranged in the short-focus small-diameter imaging element array 3
6 exposes the photosensitive drum 37 with slits. The photosensitive drum 37 is coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and rotates in the arrow direction.

Further, the charger 38 uniformly charges the photosensitive drum 37, and the photosensitive drum 37 charged by the charger 38 is subjected to image exposure by the imaging element array 36. An electrostatic image is formed. This electrostatic image is visualized using a toner made of a resin or the like that is softened and melted by heating by the developing device 39.

On the other hand, the copy paper P stored in the cassette 40 is conveyed as a pair of rollers which are rotated in pressure contact with each other in the vertical direction at a timing so as to be synchronized with the image on the feeding roller 41 and the photosensitive drum 37. It is fed onto the photosensitive drum 37 by the roller 42. Then, the toner image T formed on the photosensitive drum 37 by the transfer discharger 43 is transferred onto the copy paper P.

After that, the copy sheet P separated from the photosensitive drum 37 is moved by the conveyance guide 44 to the fixing device 2 described above.
1 and is heated and fixed there, and then the tray 45
Is discharged to. After transferring the toner image, the photosensitive drum 3
The residual toner on 7 is removed by the cleaner 46.

The fixing device 21 has an effective length in the direction perpendicular to the moving direction of the copy paper P, which corresponds to the width (length) of the maximum size paper that can be copied by the copying machine 31, that is, the width of the maximum size paper (length). The plate-shaped heater 11 having a resistance heating element 13 (see FIGS. 1 and 2) longer than the length is disposed between the plate-shaped heater 11 and the pressure roller 25 via a heat-resistant sheet 26. The unfixed toner image T on the copy paper P, which is sent, is melted by receiving heat from the resistance heating element 13, and a copy image of characters, alphanumeric characters, drawings, etc. appears on the surface of the copy paper P.

In such a copied image by the fixing device 21, the resistance heating element 12 is continuously formed in a slender shape over the length (width) of the maximum size sheet permitted by the copying machine 31, and its extending direction. A substantially uniform temperature distribution can be obtained, and clear high-quality copying with the same contrast can be obtained on the copy paper P without uneven transfer or the like over the entire surface.

Further, the fixing device 21 can reduce or prevent the curl of the copy sheet P as described above.

The present invention is not limited to the above embodiment, and the material of the substrate 12 of the plate heater 11 is not limited to alumina (Al ₂ O ₃ ) ceramics, but may be other materials such as ceramics, glass or polyimide resin. It may be a synthetic resin member having high heat resistance.

Further, the formation of the overcoat layer 15 for covering the resistance heating element 12 and the substrate 11 is not essential, and even when this is formed, the material of the glass is not limited to that of the embodiment, and the heat generation is not necessary. It goes without saying that the temperature can be appropriately selected according to the temperature and the situation of use.

[0050]

As described above, according to the present invention, after a paper such as a copy paper as a heated object is heated at a high temperature by a resistance heating element, the paper is sandwiched between the rising slope of the overcoat layer and the pressure roller. While pressing, the paper is discharged in a predetermined direction along the rising slope and gradually cooled, so that the curling of the paper can be prevented or reduced.

When the second resistance heating element is provided on the thickened end side of the coating layer, the heating temperature of the second resistance heating element is set lower than that of the first resistance heating element. This prevents quenching at the thickened end of the coat layer,
Can be slowly cooled. Therefore, the curl of the paper can be prevented or reduced.

Further, the pressure roller and the coat layer are directly
Alternatively, when the center of the contact portion that indirectly contacts is located at the rising portion of the thickened end portion of the coat layer, the paper is more reliably discharged in the predetermined direction along the rising slope of the thickened end portion. Therefore, the curl of the paper can be prevented or reduced accordingly.

[Brief description of drawings]

FIG. 1 is a sectional view taken along line I-I of FIG.

FIG. 2 is a plan view of an embodiment of a plate heater according to the present invention.

3A to 3E are vertical cross-sectional views of various modifications of the plate heater according to the present invention.

FIG. 4 is a vertical cross-sectional view of a fixing device including the plate heater shown in FIG.

5 is a vertical sectional view of a copying machine including the fixing device shown in FIG.

FIG. 6 is a plan view of a conventional plate heater.

7 is a sectional view taken along line VII-VII of FIG.

FIG. 8 is a vertical sectional view of a fixing device including the conventional plate heater shown in FIG. 6 and the like.

[Explanation of symbols]

11, 11A to 11D Plate heater 12 Substrate 12a Substrate surface 13, 13a to 13c, 13d1, 13d2, 13e1
, 13e2 Resistance heating element 14a, 14b Power supply terminal portion 15, 15a to 15e Overcoat layer 16, 16a to 16e Thickened end portion 17, 17a to 17c Rising slope 21 Fixing device 22 Rotating shaft 23 Roller body 25 Rotating plug roller 31 Copier 35 Lamp 36 Imaging element array 37 Photosensitive drum O Center of contact area P Copy paper T Toner image

Claims (5)

[Claims] 1. A substrate made of a heat-resistant and electrically insulating material, a strip-shaped resistance heating element formed on one flat surface of the substrate, and an outer surface of the resistance heating element is covered so as to be electrically insulated. And a coating layer formed on one flat surface of the substrate for transmitting heat generated from the resistance heating element to a moving object to be heated. One end of the coating layer has a thickness of A plate-shaped heater, wherein a thickened portion is formed that gradually increases in thickness as the distance from the resistance heating element increases. 2. The plate-shaped heater according to claim 1, wherein a second resistance heating element is provided on the thickened end side of the coating layer. 3. A substrate made of a heat-resistant electrically insulating material, a strip-shaped resistance heating element formed on one flat surface of the substrate, the substrate being adjacent to the resistance heating element and along the resistance heating element. An electric insulating layer formed on one flat surface of the electric insulating layer, the electric insulating layer having a thickened portion whose thickness gradually increases as the distance from the resistance heating element increases. heater. 4. The plate-shaped heater according to claim 1, further comprising a rotatable pressure roller such that the thickened end of the coat layer is on the discharge side of the heated object. A fixing device, which is arranged so as to face each other, and a central portion of contact between the pressure roller and the coating layer is located at a rising portion of a thickened end portion of the coating layer. 5. An image forming apparatus comprising the fixing device according to claim 4.