JPH11305578A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the nipping width and to perform the optimum design of a substrate regardless of the nipping form by providing a metal plate broader than the substrate and having a curved surface laid along a roller between the substrate of a heating element and a film. SOLUTION: A heating element H has a heating plate 13 consisting of a metal plate provided between a heater substrate 11 and a film 17, and the heating plate 13 is broader than the heater substrate 11 and has a curved surface on the side along the curved surface of a pressure roller 18. In this structure, the nipping with N formed by the heating plate 13 and the pressure roller 18 is larger than in the use of a conventional flat ceramic heater because the heating plate 13 is curved. The pressurizing force can be reduced more as the nipping width N is larger. Accordingly, the nipping width can be increased without increasing the diameter of the pressure roller 18, and it is not necessary to extend the width of the heater substrate 11, so that an optimum design can be performed advantageously for miniaturizing the device or reducing cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device provided with a heating element having a heating element provided on a substrate, and an image forming apparatus such as a copying machine, an LBP, a facsimile, etc., which employs a fixing apparatus and an electrostatic recording method. It concerns the device.

[0002]

2. Description of the Related Art For example, an image heating and fixing device of an image forming apparatus such as an electrophotographic copying machine, a print, a facsimile, etc. Indirectly (transfer) to the surface of recording material (transfer material sheet, printing paper, electrofax sheet, electrostatic recording sheet, etc.) using paint (toner)
As a heating device for heating and fixing an unfixed developer image corresponding to the target image information formed and carried by the direct or direct method on a recording material surface, recently, a heating device of a film heating type with reduced power consumption. Has been proposed and put into practical use (Japanese Patent Application Laid-Open No. 63-313182,
263679, JP-A-2-15778,
JP-A-4-44075-44083, JP-A-4-44075
204980-204984).

In this heating apparatus, a material to be heated is brought into close contact with a heating body via a heat-resistant film, and the heating body and the heat-resistant film are relatively moved to apply heat of the heating body to the material to be heated via the heat-resistant film. This configuration can be utilized as a means for performing a heat fixing process on a non-fixed toner image as a permanently fixed image on a recording material surface carrying the image.

[0004] Further, for example, it is widely used as a device for heating a recording material carrying an image to improve the surface properties such as gloss, a device for assuming deposition, and a means for heating a sheet-like material to be heated. I can do it.

[0005] In such a film heating type heating apparatus, a heating element having a low heat capacity or a thin film having a high temperature rise can be used. This eliminates the need to conduct current heating, and even if the recording material as the material to be heated is immediately passed, the heating member can be sufficiently heated to a predetermined temperature because the recording material reaches the fixing portion, thereby saving energy. This is effective because it has advantages such as reduction in power consumption and shortening of wait time (quick start property), and reduction in temperature rise in the apparatus such as an image forming apparatus.

FIG. 5 is a schematic view showing a schematic structure of a conventional film heating type heating device (image heating device, image heating fixing device). An example of a film heating type heating device (image heating fixing device) is shown. The schematic diagram of the enlarged cross section of the main part of FIG.

This heating device is a device driven by a pressure roller, and a cylindrical heat-resistant film 217 (such as PFA or PTFE is placed on a base film such as polyimide on a heating member holder 216 holding a heating member H). A film coated with a releasable heat-resistant resin) is loosely fitted over the pressure roller 218.
Is sandwiched between the film 217 and pressed against the heating element H with a predetermined pressing force, and the film 21 is
7, a fixing nip portion N is formed. Heating body H
Is printed on an alumina substrate 212 with a heating resistor 201 by screen printing and protected by a glass 203 for insulation. 22
Numeral 0 denotes a temperature detecting element for detecting the temperature of the alumina substrate. The pressure roller 218 is rotationally driven in a counterclockwise direction indicated by an arrow by a driving unit (not shown). The rotational force acts on the film 217 by the frictional force between the roller 218 and the outer surface of the film 217 by the rotation driving means of the pressure roller 218,
The cylindrical film 17 rotates clockwise as indicated by arrow A around the outer periphery of the heater holder 216 holding the heater H.

When the heating element H is heated to a predetermined temperature by energization, the recording material P carrying the unfixed toner image T is introduced between the film 217 and the pressure roller 218 in the fixing nip N. By closely adhering to the surface of the film 127 and passing through the fixing nip portion N together with the film, the heat of the heater H is applied to the recording material via the film 217, and the unfixed toner image T is transferred to the surface of the recording material P. Be established. The recording material P that has passed through the fixing nip N is conveyed after being separated from the surface of the film 217 by a curvature.

Further, there has been proposed a film heating apparatus in which a heater substrate, which is a heating element, is made of aluminum nitride having good heat conductivity to further improve the thermal efficiency (Japanese Patent Application Laid-Open No. 9-1997).
-80940).

FIG. 6 shows this.

The heating element H is obtained by screen-printing a resistance heating element 201 on an aluminum nitride substrate 211. In this case,
The resistance heating element 201 is attached to the heating element holder so that the surface of the aluminum nitride on the side opposite to the side on which the resistance heating element 201 is printed contacts the film 217. Since the thermal conductivity of aluminum nitride is good, even if the heating resistor 201 is on the surface opposite to the nip surface N, the temperature of the aluminum nitride substrate surface on the nip surface side hardly differs from the temperature on the heating element side.

The thermistor 220, which is a temperature detecting element,
It is arranged on aluminum nitride substrate 211 on the same surface as resistance heating element 201. The thermistor is chip-shaped.

[0013]

In the conventional heating apparatus, the nip portion is formed by the heater substrate. Therefore, the nip surface is a flat plate. The width of the substrate must be widened. Further, since the thermistor is disposed on a heating body opposite to the recording material passing surface (nip forming surface), the temperature of the nip portion is detected through the heating body.

For this reason, the conventional apparatus has the following problems.

To increase the nip width, it is necessary to increase the width of the heater substrate. In particular, when aluminum nitride is used, the cost is greatly increased. In addition, when an alumina substrate having a lower thermal conductivity than a metal is used, it is difficult to accurately detect the temperature in the heating device nip required to fix the toner on the recording material, and therefore, the thermal conductivity of the nip is similar to that of a metal. In the case of a heater substrate using aluminum, the cost also increases because aluminum nitride is very expensive.

[0016]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a heating element having a heating element provided on a substrate, a film, and a roller for forming a nip with the heating element via the film. A fixing device for nipping and conveying a recording material carrying an unfixed image in the nip, and fixing the unfixed image on the recording material by heat from the heating member through the film; Has a metal plate provided between the substrate and the film, wherein the metal plate is wider than the substrate in the moving direction of the recording material, and has a curved surface along the roller. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 and 2
Is a drawing showing the features of the present invention. In FIG. 1, H represents a fixed heating element.

The configuration of the heating element H will be described. 11 is a ceramic heater substrate made of aluminum nitride,
The heating resistor 101 is printed on the surface.

The heating resistor 101 is formed, for example, by printing a current-generating resistor such as silver palladium by screen printing or the like into a strip having a thickness of about 10 microns and a width of about 1 to 5 mm.
It is formed by firing. Reference numeral 102 denotes a contact for supplying power to the resistance heating element 101, which is formed of a material such as a silver paste in the same process as the resistance heating element 101.

Reference numeral 13 denotes a metal plate as a heating plate, which is made of aluminum and is heated by contacting the heater substrate 11.

The heating plate 13 is wider than the heater substrate 11 in the moving direction of the recording material, and has a curved surface on the side along the curved surface of the pressure roller 18.

N is a nip composed of a heating plate 13 and a pressure roller 18. Reference numeral 14 denotes a temperature detecting element such as a thermistor, which is provided in contact with a heating plate on the upstream side of the substrate 11 of the heating body H with respect to the moving direction of the recording material.
Detects upstream temperature.

Reference numeral 15 denotes a temperature detecting spring which functions to bring the temperature detecting element 14 into contact with the heating plate 13. Since the heating plate 13 is electrically insulated from the heating resistor 101, even if the temperature detecting element 14 comes into contact with the heating plate 13, the insulation does not break down with the heating resistor 101. Reference numeral 16 denotes a heater stay for fixedly holding the heating element H, reference numeral 17 denotes an endless fixing film, whose base is made of polyimide and whose surface is coated with fluorine, and which is loosely fitted to the heater stay 16. Part of the film is tension-free.

Reference numeral 18 denotes a nip N which is in pressure contact with the heating plate 13 via a fixing film rotatably supported by a pressure roller. Then, it is rotationally driven by a driving unit (not shown) to drive the fixing film.

FIG. 2 is a diagram showing the relationship between the heater substrate 11 and the heating plate 13 constituting the heating element H.
Is printed on the surface opposite to the heating plate 13 on the heater substrate 11. Therefore, since the heater substrate is interposed between the heating resistor 101 and the heating plate 13, the heating plate 13 is electrically insulated. Between the heater substrate 11 and the heating plate 13, a silicon adhesive or a conductive adhesive (dortite) is applied to improve heat conduction.

FIG. 3 is a schematic structural view of an image forming apparatus using the fixing device of the present invention. The image forming apparatus of this embodiment is a laser beam print utilizing a transfer type electrophotographic process.

Reference numeral 31 denotes a photosensitive member which is driven to rotate in the direction of the arrow. Reference numeral 32 denotes a charging roller as charging means for the photoconductor 31, to which a predetermined charging bias is applied, and which contacts the photoconductor 31 with a predetermined pressure. The surface of the photoconductor 31 is charged to a predetermined polarity and voltage by the charging roller 32.

Reference numeral 33 denotes a laser beam which is emitted from a laser scanner unit (not shown) and irradiates the surface of the photoreceptor 31 to form an electrostatic latent image on the surface of the photoreceptor 31.

Reference numeral 34 denotes a developing unit which stores toner therein, and attaches the toner to a latent image on the surface of the photoconductor 31. 3
A transfer roller 5 transfers the developed toner image on the surface of the photoreceptor 31 to a transfer sheet P, which is a recording material conveyed from a sheet feeding unit (not shown). Reference numeral 36 denotes a cleaner,
Clean the upper untransferred toner. The transfer paper P having the unfixed toner image is heated and pressed by the fixing unit R to fix the toner image on the transfer paper P.

In the above configuration, the nip width N formed by the heating plate 13 and the pressure roller 18 is wider than that when a conventional flat ceramic heater is used because the heating plate 13 has a curved surface. The wider the nip width, the lower the fixing temperature and pressure can be. Therefore, conventionally, when the nip is constituted by the heater substrate and the pressure roller as shown in FIGS. 5 and 6, if the nip width is to be increased, the diameter of the pressure roller is increased and the width of the heater substrate is simultaneously increased. However, according to the present embodiment, it is possible to increase the nip width without increasing the diameter of the pressure roller, and it is not necessary to increase the width of the heater substrate. This is advantageous for miniaturization and cost reduction.

In addition, the nip shape, which conventionally could only be constituted by a flat plate and a pressure roller, can be optimized because the heating plate 13 can be easily processed.

As described above, in the present embodiment, the nip surface of the heating element is formed of a metal plate, and the nip surface is curved along the pressing roller. The nip width is increased, and the fixing property can be improved without increasing the pressing force or the fixing temperature or increasing the diameter of the pressure roller, which is advantageous for speeding up and miniaturizing the printer.

As shown in FIG. 1, the temperature detecting element 14 detects the temperature on the upstream side of the nip portion N.

Since the heating plate 13 has good heat conduction, it is possible to accurately detect the surface temperature of the pressure roller before the recording material enters the nip N and the temperature of the recording material when the recording material enters the nip N. It is possible.

The thermal conductivity of the aluminum used this time is about 20
0 kcal / mhdeg. Incidentally, the thermal conductivity of the alumina substrate in the conventional configuration is about 20 kcal / mhdeg.
deg, and aluminum nitride is about 180 kcal / mhd
eg.

As shown in FIG. 4A, the temperature is detected on the downstream side of the nip (downstream of the heating pattern (resistance heating element)), and as shown in FIG. 4B, the temperature is detected on the upstream side of the nip (heating pattern). The case where the temperature is detected at the (upstream side of) and the temperature of the heating element H is controlled is described.

The temperature distribution in the nip has the lowest temperature on the upstream side and the highest temperature on the downstream side of the resistance heating element 101, and the temperature gradually decreases after the resistance heating element 101.

Here, when the recording material enters the nip portion N, the temperature on the upstream side drops greatly, but the temperature on the downstream side changes less than the upstream side (solid line). Controller (not shown) tries to keep the predetermined temperatures T ₁ in the temperature of the temperature sensing portion. When comparing the case where the temperature is detected and the temperature is controlled on the downstream side of the nip as shown in FIG. 4A and the case where the temperature is detected and the temperature is controlled on the upstream side of the nip as shown in FIG. The temperature change can be detected more accurately if it is detected.
In particular, when the temperature of the recording material is low or when the thickness of the recording material is large, it is necessary to apply a large amount of heat necessary for fixing, and since a large amount of heat can be supplied by detecting on the upstream side, the fixing property is also stable. .

As described above, according to the present embodiment, a material having good heat conductivity and a low cost is arranged in the nip portion between the heating substrate and the pressure roller, and the material on the upstream side of the nip is placed via the material having good heat conductivity. Since the temperature is detected, the temperature of the pressure roller and the temperature of the paper at the nip portion on the upstream side of the nip can be detected, so that accurate temperature control can be performed.

Further, since the nip is constituted by the heating plate 13 and the pressure roller 18, it is possible to make the width of the heater substrate narrower than the nip, thereby reducing the cost.

The material of the heating plate 13 is an aluminum plate in the present embodiment, but any material having good heat conductivity may be used, such as duralumin, copper, gold, and silver having a heat conductivity of about 100 kc.
Al / mhdeg or more may be used.

Although the present embodiment has been described using aluminum nitride for the heater substrate, the present invention is similarly applicable to the case where alumina is used for the heater substrate.

Further, the resistance heating element 101 may be arranged on the side of the heating plate, and a glass film for insulation may be formed on the surface of the heating resistance element to be electrically insulated from the heating plate 13.

[0044]

As described above, according to the present invention,
Since a metal plate having a width larger than the substrate and having a curved surface along the rollers is provided between the substrate and the film of the heating element, it is possible to make the nip shape a curved surface, and it is possible not only to increase the nip width, but also to increase the nip width. Optimum design is possible regardless of the nip shape.

Further, in the present invention, the temperature detection element is provided on the metal plate on the upstream side of the substrate, so that accurate temperature control can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fixing device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a heater and a heating plate.

FIG. 3 is a configuration diagram of a printer employing the present invention.

FIG. 4 is a diagram showing an outline of a temperature of a nip portion;

FIG. 5 is a sectional view of a conventional fixing device.

FIG. 6 is a sectional view of a conventional fixing device.

[Explanation of symbols]

 Reference Signs List 11 heater substrate 13 heating plate (metal plate) 14 temperature detecting element 16 heater stay 17 fixing film 18 pressure roller H heating element (heater)

Claims (2)

[Claims] 1. A recording apparatus comprising: a heating element having a heating element provided on a substrate; a film; and a roller for forming a nip with the heating element via the film, wherein the nip carries an unfixed image. In a fixing device that sandwiches and conveys a material and fixes an unfixed image on a recording material by heat from the heating body via the film, the heating body includes a metal plate provided between the substrate and the film. A fixing device, wherein the metal plate is wider than the substrate in the moving direction of the recording material, and has a curved surface along the roller. 2. A temperature detecting element for detecting a temperature of the heating element, wherein the temperature detecting element is provided on the metal plate upstream of a substrate of the heating element with respect to a moving direction of a recording material. The fixing device according to claim 1, wherein: