JP2003215965A - Fixation device, carbon lamp, and manufacture of carbon- based heat generating body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To impart emission distribution to a carbon lamp as a carbon-based heat generating body used for a fixing device for an image forming apparatus. <P>SOLUTION: The emission distribution is imparted to the carbon lamp 26 arranged as a heat generating element for the fixing roll 20 of the fixation device 6 used in the image forming apparatus by adjusting a resistance value. That is, the fixation device 6 is provided with the fixing roll 20 for heating paper Po with an unfixed image while coming in contact with the paper Po, or coming adjacent to the paper Po, and the carbon lamp 26 for heating the fixing roll 20, and the carbon lamp 26 is provided with the heat generating body constituted of carbon material having different resistance values according to areas. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to a fixing device used in an image forming apparatus such as a laser beam printer and a facsimile machine, and a carbon lamp used in these, and more specifically, to a carbon lamp whose emission distribution is adjusted.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, a facsimile, etc., an electrostatic latent image is formed on a latent image carrier such as a photoconductor belt by a potential distribution according to image information. The electrostatic latent image is developed with toner to form an unfixed toner image on a transfer material, and the toner image formed on the transfer material is heated and melted by a fixing device to be fixed on the transfer material. In such a fixing device, for example, a fixing roll having a built-in heater is provided, and energization control to the heater is performed by a built-in CPU, for example.
It is configured to maintain the temperature of the fixing roll at a predetermined temperature.

On the other hand, halogen heaters (halogen lamps) are widely used as heaters for fixing rolls. This halogen lamp is made of, for example, a tungsten resistor. For example, in the first state of the morning when power is turned on when the power is off, the tungsten is in a cold state and has a very low resistance value. Therefore, for example, 100
When V is applied, the inrush current (rush current) becomes 8
About 0 to 90 A flows at once. As a result, a voltage drop occurs, and the fluorescent lamp flickers, so-called flicker occurs.

As a countermeasure against this flicker, for example, a method has been proposed in which a halogen lamp is used as it is and a power thermistor is connected in series to the halogen lamp. However, when the power thermistor itself is at a low temperature, it works effectively as a countermeasure against flicker, but when it gets warm, the resistance value decreases, and when the temperature of the power thermistor itself rises, for example, during a normal copy sequence.
It cannot be used to control the temperature of the fixing roll during continuous feeding.

[0005]

Therefore, as a result of intensive investigations by the present inventors, a carbon-based heating element is electrically connected in series or in parallel with the halogen lamp and in the vicinity of the halogen lamp. By providing a certain carbon lamp, it has been found that the inrush current can be suppressed. That is, this carbon lamp has no inrush current when the power is turned on, and by electrically connecting the carbon lamps in series or in parallel, the inrush current when the power is turned on is reduced as in the case where the power thermistor is connected. It Also,
The power thermistor could not be used for temperature control during continuous paper feeding, but when a carbon lamp is used, this carbon lamp heats the halogen lamp as a heater. The resistance value of is secured, and it is possible to prevent the inrush current. Further, due to the excellent characteristics of this carbon lamp, it is also considered to use the carbon lamp alone as a heater for a fixing device or the like.

Here, regarding the carbon lamp itself,
Conventionally, various proposals for improvement have been made. For example, Japanese Patent Application Laid-Open No. 2
Japanese Patent Publication No. 000-223245 discloses a technique for providing a carbon-based heating element excellent in aging characteristics and thermal stability by determining a ratio of carbon as a good electric conductor and a metal (or a semimetal compound) as a conductivity inhibitor. It is shown. Also,
Japanese Unexamined Patent Publication No. 2000-323633 discloses a carbon heat radiator in which graphite powder is contained in amorphous carbon to improve thermal conductivity and thermal radiation. Furthermore, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 001-15250 discloses a technique of providing a carbon-based heating element having a temperature coefficient substantially close to zero by mixing graphite powder and boron nitride with a resin such as a chlorinated vinyl chloride resin. There is. Furthermore, JP-A-2001-72
Japanese Patent No. 469 discloses a carbon-based material having a columnar body or a cylindrical body having a rectangular or elliptical cross-section having a predetermined flatness and a longitudinal groove or wrinkle on the surface to increase the surface area and improve the heating effect. A heating element is disclosed.

On the other hand, a heating element used in, for example, a fixing device requires a heating element intentionally having a light distribution. That is, in the fixing device, if there is a temperature difference in fixing a toner image on a sheet that is a conveyed sheet, for example, if there is a low temperature portion, a fixing failure will occur at that portion. For example, when heating a fixing roll, a pressure roll, etc. provided in a direction orthogonal to the sheet conveying direction, since there are mechanical parts at both ends of the fixing roll and the pressure roll, heat radiation to this mechanical part is eliminated. The temperature is lower than in the central part. Therefore, it is desired to intentionally give the heat generating element a light distribution so that both ends of the fixing roll, the pressure roll, and the like having such a structure have a higher temperature than the central part.

However, for example, in a halogen lamp, although it is possible to intentionally change the light distribution by changing the segment length of the filament formed by the tungsten wire, a carbon lamp which is a carbon-based heating element. Then, like the halogen lamp, it is difficult to change the light distribution. This carbon lamp uses a carbon material that is a sintered body as a heating element,
It is created by cutting from a large plate-shaped body or block-shaped body. Although it is possible to change the shape of the carbon material used for the carbon lamp before sintering, it is difficult to secure the dimensional accuracy of the carbon material because the material shrinks greatly during sintering. Further, it is difficult to perform processing by surface grinding or the like after sintering, and this grinding requires a lot of time. Further, even with the carbon-based heating element manufacturing techniques described in the above-mentioned various publications, the light distribution cannot be intentionally adjusted in the longitudinal direction of the halogen lamp.

The present invention has been made to solve the above technical problems, and an object thereof is to provide a carbon lamp, which is a carbon-based heating element, with a light emission distribution. Is characterized by.

[0010]

In view of the above object, the present invention provides a resistance value adjustment for a heating member of a fixing device used in an image forming apparatus or a carbon lamp arranged as a heating element. It is characterized by having a light emission distribution. That is, the fixing device to which the present invention is applied includes a heating member that heats the sheet material in contact with or close to the sheet material having an unfixed image, and a carbon heating element that heats the heating member. The system heating element is characterized in that the heating element is a carbon material having a different resistance value depending on the region.

Here, this carbon-based heating element is a simple sintered body of ceramic and carbon, characterized in that a resistance value distribution is formed by forming holes in a predetermined region of a flat plate-shaped carbon material. It is preferable that a carbon lamp, which is a uniform light-emitting body as a flat or rod-shaped heating body, can be easily adjusted in emission distribution. Similarly, the carbon-based heating element can be characterized in that the heating element is a carbon material having regions having different compositions or cross-sectional areas in the longitudinal direction. In particular, if this carbon-based heating element is characterized in that the resistance value is adjusted so that a higher amount of heat can be obtained at both end portions in the longitudinal direction than at the central portion, for example, the temperature at both end portions of the fixing device can be controlled. This is an effective measure for raising the temperature of the sheet passing portion in an image forming apparatus that desires to set a high value.

On the other hand, the present invention is a carbon lamp comprising a heating element that emits light in the far infrared region having a peak wavelength and a quartz tube that covers the heating element and uses a carbon-based material for the heating element. This carbon-based material can be characterized in that the resistance value differs depending on the region and the emission distribution is adjusted. For example, it is effective to provide a structure in which holes are formed at predetermined locations in the longitudinal direction, or to provide regions having different compositions or cross-sectional areas in the longitudinal direction.

Further, the carbon lamp to which the present invention is applied is provided with a heating element using a carbon-based material, and is provided in a predetermined area of the heating element to define a light emitting area from the heating element, or the heating element. And a light distribution regulating member that changes the light distribution by changing the heat capacity of the light. Examples of the light distribution regulating member include heat resistant ceramics and light transmissive ceramics.

From another point of view, the method for producing a carbon-based heating element to which the present invention is applied includes a step of pelletizing a composition containing a carbon material to produce a molding composition, and the produced molding. Of the composition for molding and heating to obtain a carbon precursor wire, a step of firing the carbon precursor wire to obtain a heating element, and a hole is formed in the heating element after firing using laser light. It is characterized in that it includes an emptying step.

Furthermore, the method for producing a carbon-based heating element to which the present invention is applied includes the steps of pelletizing a composition containing a carbon material to produce a molding composition, and molding the produced molding composition. It is characterized by including a step of forming a carbon precursor wire having a different cross-sectional area or a composition depending on a region and heating the carbon precursor wire to obtain a heating element. The method of making the cross-sectional area different depending on the region includes a method of punching holes in a press before firing, and a method of forming embossing on the surface in a form of transferring a press die.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. FIG. 1 is a diagram showing an overall configuration of an image forming apparatus to which this exemplary embodiment is applied. In the image forming apparatus shown in FIG. 1, a post-processing apparatus 13 is shown together with a main body side that forms an image by an electrophotographic method. On the main body side, the photoconductor belt 1, which is a latent image carrier whose conductivity changes by irradiation with light, the charging roll 2 that charges the photoconductor belt 1, and the photoconductor belt 1 are irradiated with light reflected by the original Ps. For the exposure system member 3, the developing device 4 for supplying the charged toner to the photosensitive belt 1, the transfer roll 5 for applying the transfer voltage to the photosensitive belt 1 at the transfer position, and the sheet (sheet material) Po on which the image is formed. That is, for fixing the unfixed toner image transferred on the paper Po by fixing it by heating and pressurizing it, the cleaning device 7 for cleaning the photoconductor belt 1 after the transfer, and the charge removal for the photoconductor belt 1 after the cleaning. A static elimination lamp 8 is provided. The exposure system member 3 includes a platen glass 3a on which an original Ps is placed, an exposure lamp 3b which moves while irradiating the original Ps with light, and light reflected from the original Ps on the photosensitive belt 1.
An optical element 3c for forming an image at a predetermined position above is provided.

Further, this image forming apparatus has a document tray 9
An automatic document feeder 9 for supplying a plurality of documents Ps placed on a to the platen glass 3a, and a sheet tray 10 for stacking and accommodating sheets Po as transfer materials (sheet materials),
The paper tray 10 has different types and sizes of paper P.
Multiple stages are arranged so that o can be loaded. Also,
The paper tray 10 is provided with a manual feed tray 11 used for stacking paper Po of a size and type different from the paper tray 10, a paper feed path 12 for carrying the paper Po fed from the paper tray 10, and the manual feed tray 11. This paper transport path 12
Provides a reversing conveyance path that reverses and conveys the paper Po discharged from the fixing device 6 and enables double-sided printing. Further, in the post-processing device 13 that performs post-processing on the printed paper Po on the main body side, the top tray 13a for outputting the paper Po after fixing without performing post-processing, and performing the accumulation and sorting. At that time, a bin tray 13b that forms a sorter of 20 bins and a stapler 13c that staples the paper Po are provided. In addition, a liquid crystal display as a touch panel having a predetermined size is provided, and a user interface device 14 for setting the image forming apparatus by touching the liquid crystal display is provided.

FIG. 2 is a diagram for explaining the configuration of the fixing device 6 to which this embodiment is applied. This fixing device 6
As its main part, first, the fixing roll 20 which is heated and used, and the paper P facing the fixing roll 20.
An endless belt 21 for pressurizing o and a pressure pad 22 arranged in a state of being pressed by the fixing roll 20 via the endless belt 21 are provided. Further, in the present embodiment, as the heating member (heating element) of the fixing roll 20, a halogen lamp 25 made of tungsten and a carbon material having a rectangular shape (plate shape) or a square shape are used to emit light in the far infrared region. A carbon lamp 26, which is a carbon-based heating element that emits light, and a reflecting member 27 for actively heating the halogen lamp 25 by the carbon lamp 26 are provided. In FIG. 2, the halogen lamp 25 and the carbon lamp 26 are mechanically arranged in parallel, and are electrically connected in series or in parallel. Further, a belt running guide 23 used for the endless belt 21 to smoothly slide and rotate, a temperature sensor 24 for measuring the temperature of the surface of the fixing roll 20, and a peeling for peeling the paper Po after fixing from the fixing roll 20. The member 28 is provided.

The halogen lamp 25 is a glass tube containing an inert gas such as nitrogen or argon together with a trace amount of a halide.
It is an incandescent light bulb in which (iodine, bromine, chlorine, fluorine) is enclosed, and has a high radiation intensity characteristic in the near infrared region with a peak wavelength of, for example, about 1.7 μm. A carbon lamp 26 mechanically provided in parallel with the halogen lamp 25
, The peak wavelength is in the far infrared region (particularly 2.5 to 8 μm), and the far infrared radiation amount is increased by, for example, about 30% or more as compared with the halogen lamp 25. Further, the carbon lamp 26 has a rapid heating property that reaches the maximum temperature several seconds after the switch is turned on. The infrared ray has a lower limit of 0.76 to 0.83 μm at the long wavelength end of visible light and an upper limit of 1
Electromagnetic waves up to about mm, wavelength 2.5 μm, for example
The following can be classified as near infrared rays and far infrared rays as 2.5 μm or more. Organic substances including the human body have a property of easily absorbing heat in the far infrared wavelength region.

The fixing roll 20 comprises a metal core 20a which is a cylindrical core metal, a heat resistant heat insulating layer 20b provided around the core 20a, and the heat resistant heat insulating layer 20.
A release layer (heat resistant resin layer) 20c provided around b is provided. The core 20a, the heat resistant heat insulating layer 20b and the release layer 20c are rotated in the direction of arrow B by a motor (not shown) as a fixing rotating body. The core 20a functions as a base material of the fixing rotating body, and is made of, for example, aluminum having a thickness of about 3 mm. Besides aluminum,
A metallic cylindrical body having high thermal conductivity such as iron or stainless steel can be used. In the case of iron, for example, an outer diameter of 20 to
It is possible to use one having a thickness of about 35 mm and a wall thickness of about 0.3 to 0.5 mm. Of course, since the strength and the thermal conductivity differ depending on the material used, the optimum size can be appropriately determined. An organic substance such as polyimide can be applied to the inner surface of the core 20a in order to secure a predetermined heat generation distribution when the carbon lamp 26 is used. The surface temperature of the fixing roll 20 is measured by a temperature sensor 24, and a halogen controller 25 and a carbon lamp 26 are feedback-controlled by a temperature controller (not shown) so that the surface temperature of the fixing roll 20 becomes constant.

As the heat-resistant heat insulating layer 20b formed on the surface of the core 20a, an elastic body having high heat resistance, for example, an elastic body having a rubber strength of about 25 to 40 ° (JIS-A) such as rubber or elastomer, Specifically, silicone rubber, fluororubber, or the like can be used. In addition, the heat resistant heat insulating layer 20
As the release layer 20c formed on b, a fluororesin or a silicone resin is used in consideration of releasability and abrasion resistance. From the viewpoint of suppressing the occurrence of wrinkles on the paper Po, while suppressing the occurrence of image quality defects such as uneven gloss, the release layer 20c has a thickness of 5 to 30 μm, more preferably 10 μm.
It can be formed with a thickness of 20 μm.

The endless belt 21 is the fixing roll 20.
The nip portion is formed by making contact with each other so as to be wound at a predetermined angle. This endless belt 21
For example, it is composed of a base layer and a release layer coated on the surface thereof (the surface in contact with the fixing roll 20 or both surfaces). The base layer is selected from polyimide, polyamide, polyamideimide and the like, and has a thickness of, for example, about 50 to 125 μm. The release layer is coated with a fluororesin such as PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin) in a thickness of 5 to 20 μm.

The pressure pad 22 disposed inside the endless belt 21 is an elastic member 22a for ensuring a wide nip portion, and a low friction layer provided on the surface of the elastic member 22a that contacts the endless belt 21. Two
2b, a peeling nip member 22d arranged on the exit side of the nip portion for giving a distortion to the fixing roll 20, and is held by, for example, a metal holder 22c. The elastic member 22a is formed in a concave shape that substantially follows the outer peripheral surface of the fixing roll 20 and causes the fixing roll 20 to have a certain distortion. The endless belt 21 is driven to rotate by the rotation of the fixing roll 20.

An unfixed toner image T is transferred onto the paper Po conveyed through the transfer roll 5 shown in FIG. 1, and the paper Po is conveyed toward the nip portion in the direction of arrow A shown in FIG. It Paper Po inserted into the nip and conveyed
Is fixed by the pressure acting on the nip portion and the heat given through the fixing roll 20 by the halogen lamp 25 and the carbon lamp 26. At that time, stable fixing performance is secured by the pressure pad 22 and the endless belt 21, and the distortion of the fixing roll 20 is locally increased by the peeling nip member 22d, so that a high releasing performance is obtained with a small amount of distortion. It is possible to suppress the generation of wrinkles even when the thin film release layer 20c is provided.

Next, the heating of the fixing roll 20 will be described. As described above, inside the fixing roll 20, a plurality of types of lamp heaters, such as the halogen lamp 25 and the carbon lamp 26, having different corresponding wavelength regions as radiation intensity characteristics are arranged. When the halogen lamp 25, which has been widely used as a heating material for an image forming apparatus, is used as a single unit, it is necessary to take special measures against a rush current at the time of power input to the tungsten wire.
In the present embodiment, the carbon lamp 26 and the halogen lamp 25 are arranged inside the fixing roll 20, and the carbon lamp 26 and the halogen lamp 25 are electrically connected in series or in parallel, so that the rush No special measures against electric current are required. Here, the inrush current is, for example, a current that flows at a value several times to several tens of times the rated current value when the halogen lamp 25 is powered on. For example, the tungsten wire that is the heating element of the halogen lamp 25 is at room temperature. Occurs due to the small resistance value.

3 (a) and 3 (b) are views showing the structure of the carbon lamp 26 used in the present embodiment. FIG. 3 (a) is a perspective view of the carbon lamp 26, and FIG. FIG. 2B is a sectional view showing a state in which the carbon lamp 26 is attached inside the fixing roll 20. The carbon lamp 26 has a transparent quartz tube 31 and a heating element 33 made of a carbon material in a flat (flat) shape whose both ends are supported by tungsten coils 32.
Is provided. It is known that carbon (charcoal) which is a black body has a high emissivity for far infrared rays. In this carbon lamp 26, a carbon material is used for the heating element 33 to increase the far infrared radiation amount. . Also, this carbon lamp 26
Then, as mentioned above, the peak wavelength is in the far infrared region (especially 2.5
.About.8 .mu.m), and has a characteristic that the radiation intensity of far infrared rays is high in the absorption wavelength range of organic substances. Furthermore, after turning on the power,
It has a fast heating property that reaches the maximum temperature in a few seconds.

In the present embodiment, this carbon lamp 2
By arranging 6 to face the halogen lamp 25 and connecting them in series or in parallel, the rush current generated in the halogen lamp 25 due to the resistance of the carbon lamp 26 is suppressed by the same function as the power thermistor immediately after the power is turned on. can do. As a result, it is possible to suppress flickering of the fluorescent lamp that occurs when the power is turned on. Further, when the carbon lamp 26 is warm, the resistance value does not decrease because the heating element of the halogen lamp 25, tungsten, is warm. That is, during normal operation (during continuous paper feeding, copy sequence), the carbon lamp 2
Even if the temperature of 6 rises, the other heating source that opposes is heated, so that the rush current of the other heating source can be prevented and the flicker prevention function can be enhanced. In addition, in the present embodiment, FIG.
The reflecting member 27 shown in FIG. This reflecting member 27
Is used to increase the directivity of the carbon lamp 26. By positively warming the halogen lamp 25, the tungsten filament in the halogen lamp 25 is accelerated in heating, and the resistance value is increased to increase the inrush current. Further strengthening prevention.

Here, as shown in FIG. 3 (b), when the carbon lamp 26 is mounted on the fixing roll 20, when a flat rectangular (flat) heating element 33 is used, this heating element is used. 33 is placed vertically, that is, the heating element 33 is arranged so that the longitudinal section thereof is substantially in the same direction as the vertical direction. When the cross section of the heating element 33 is arranged in a direction orthogonal to the vertical direction, that is, when the heating element 33 is placed horizontally, the heating element 33, which is a carbon plate member, bends due to its own weight, and the center of the heating element 33 in the longitudinal direction of the tube. The part may contact the inner wall of the transparent quartz tube 31. By disposing the heating element 33 at the position shown in FIG. 3B, it is possible to prevent the bending of the heating element 33 from coming into contact with the inner wall of the transparent quartz tube 31. Further, when the heating element 33 has a rectangular shape, the heating element 33, which is a rectangular member having a wide flat surface, has directivity, and the flat surface of the heating element 33 faces the halogen lamp 25 side. It is possible to positively heat the halogen lamp 25, which is a heating element. As a result, for example, the flicker prevention function can be enhanced even during continuous paper feeding. As shown in FIG. 2, when the carbon lamps 26 are arranged side by side next to the halogen lamp 25, as shown in FIG.
By erecting a rectangular member as shown in (4), it becomes possible to secure such directivity.

In FIG. 2, one carbon lamp 26 is provided for the halogen lamp 25 and the carbon lamp 26 is arranged on the fixing roll 20. However, the number of carbon lamps 26 is increased to a plurality (for example, 2 to 3). ) Carbon lamp 26
It is also possible to arrange the halogen lamp 25 so as to surround it. As for the arrangement, in addition to the case where the lamps are arranged side by side, the lamps may be arranged in a pyramid shape or the like. That is, a plurality of lamps having different emission wavelengths can be freely combined and used as a heating member. Alternatively, the halogen lamp 25 may not be provided, and only the carbon lamp 26 may be used for heating. However, since a general carbon heating element has a negative temperature coefficient, and has the property of lowering the resistance value at room temperature than the resistance value at normal temperature, certain measures are taken against this negative temperature coefficient. It is preferable to use the carbon lamp 26.

By thus incorporating the carbon lamp 26 in the fixing roll 20, the inrush current can be reduced. However, it is difficult to cope with the temperature decrease due to heat radiation, for example, at both ends of the fixing roll 20 to which the fixing roll 20 is attached only by using the conventional carbon heating element. Further, depending on the position where the conveyed paper Po passes, for example, a specific place may radiate heat extremely. Therefore, in the present embodiment, for example, it is possible to provide the carbon lamp 26 with a heat quantity distribution corresponding to the light distribution for locally heating the fixing roll 20.

FIGS. 4A and 4B are views for explaining a state in which the light distribution in the longitudinal direction is adjusted according to this embodiment. FIG. 4A shows the structure of the heating element 33 made of a carbon material used in the carbon lamp 26.
FIG. 4B shows a light emission distribution (light distribution distribution) by the heating element 33.
Is shown. The heating element 33 of the carbon lamp 26 to which the present embodiment is applied is provided with a hole 35 having a predetermined size and number corresponding to the location where the heat capacity is desired to be increased. Before the sintering of the heating element 33, the hole 35 can be formed by forming a physically large size with a cone or the like and sintering it as it is. If the heating element 33 is produced after sintering, the heating element 33 after sintering can be processed by applying, for example, a laser beam. Here, FIG.
When forming the hole 35 as shown in (a), the desired resistance value can be obtained by processing while monitoring the resistance value. This is effective when the holes 35 are formed in the sintered heating element 33 by using laser light.

When the heating element 33 is provided with the hole 35, the resistance value of the portion provided with the hole 35 becomes larger than that of the portion not having the hole 35, and the emission level is increased at the portion having the larger resistance value. Can be higher. In FIG. 4A, since the plurality of holes 35 are provided at both ends of the heating element 33, for example, as shown in FIG. 4B, a light emission distribution having a high light emission level at both ends is obtained. It is possible to obtain a higher heat capacity at both ends than at the center.

FIGS. 5A and 5B are views for explaining another example of the carbon lamp 26 in which the light distribution in the longitudinal direction is adjusted. Here, a rectangular (flat) heating element 33
In place of, a rod-shaped heating element 40 is used. For example, when the rod-shaped heating element 40 has a circular cross section,
As shown in FIG. 5A, by making the diameters of the end region 41 and the central portion 42 different, the cross-sectional areas are made different in the longitudinal direction, and the emission distribution is adjusted to change the calorific value of the same substance. Can be made. In the example shown in FIG. 5A, the diameter d1 of the end region 41 and the diameter d2 of the central portion 42 are set to d1 <d2, thereby increasing the resistance value of the end region 41 and increasing the heat generation amount at both ends. Is up.

On the other hand, in the example shown in FIG. 5B, with respect to the rod-shaped heating element 50, an elliptical cross section 51 is provided at both ends, and a circular cross section 52 having, for example, the long side of the elliptical cross section 51 as a diameter is provided at the center. The example in which is provided is shown. In this heating element 50, the cross-sectional shape is changed in the longitudinal direction of the heating element 50 which is a carbon material, and the cross-sectional area is changed to change the resistance value for each region. In the example shown in FIG. 5B, the cross-sectional area of the elliptical cross section 51, which is both ends of the heating element 50, is smaller than that of the circular cross section 52. As a result, it is possible to increase the resistance value at both ends and obtain a high heat generation amount. The cross-sectional shape is not limited to a circle or an ellipse, and can be arbitrarily selected such as a square shape.

Here, in FIG. 4 (a) and FIGS. 5 (a) and 5 (b),
The carbon materials (heat generating elements 33, 40, 50) having different outer shapes and provided with a resistance distribution were provided, but the composition of the carbon heating element or the firing conditions were locally changed in a predetermined region in the longitudinal direction. The resistance distribution can also be formed by doing so. In addition, for example, a predetermined area in the longitudinal direction is covered with a heat-resistant ceramic before sintering to define a light emitting region by masking in advance, or a light transmissive ceramic or the like is provided on the surface of the element to determine the heat capacity. Can be changed to change the light distribution. This light transmissive ceramic is
Although light is transmitted, the rising speed becomes slower due to the increase in heat capacity. For example, when it is desired to quickly heat both ends of the carbon lamp 26, a light-transmitting ceramic is provided on the element surface in the central portion. You can

As shown in FIGS. 5 (a) and 5 (b), the heating element 4 is made of a carbon material having a different cross-sectional area in a predetermined region in the longitudinal direction.
As a method of obtaining 0,50 or another method of obtaining a carbon-based heating element in which the resistance value changes by changing the material depending on the region in the longitudinal direction, the carbon materials whose resistance values change in advance are laminated and simultaneously sintered. There are things. According to this, it is possible to manufacture the heating element having the light distribution as described above after sintering.

A basic method for producing a carbon-based heating element is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-72469. When this is cited, first, for example, 33% by weight of chlorinated vinyl chloride resin, 20% by weight of diallyl phthalate monomer as a plasticizer was added to 1% by weight of fine powder of natural graphite and 66% by weight of boron nitride, and the mixture was dispersed using a Henschel mixer. Using a mixing roll whose surface temperature was kept at 120 ° C. Kneading is sufficiently repeated to obtain a composition, which is pelletized by, for example, a pelletizer to obtain a molding composition. Next, the pellets were molded by a screw type extruder, and the pellets were molded in an air oven heated to 200 ° C. for 10 minutes.
It is treated for a time to form a breaker (carbon precursor) wire.
After that, this is fired at 1600 ° C. in a vacuum of, for example, 1 × 10 ⁻² Pa or less, whereby a plate-shaped or rod-shaped carbon-based heating element can be obtained.

In the manufacturing method for forming the carbon-based heating element to which this embodiment is applied, in the manufacturing steps described above,
For example, after making breakers with different resistance values separately, after twisting them into a coil or processing them like fibers, i.e., pasting at the stage where composition processing before heating is possible , Then treat in the oven. Thereby, depending on the plate-shaped or rod-shaped region, for example, the composition of the composition is made different or the cross-sectional area is made different between the both ends and the central portion of the carbon-based heating element having the plate-shaped or rod-shaped. As a method of changing the firing conditions, for example, there is a method of providing a shutter in the firing area and changing the vacuum degree to change the resistance value. Since it is possible to provide a temperature gradient in the firing area, the temperature distribution can be created during firing.

Here, when the holes 35 as shown in FIG. 4 (a) are provided in the heating element 33, if the holes are to be formed before sintering, the holes may be punched out by a press before sintering, or a press working die may be used. The embossing can be created on the surface in the form of transferring. Further, when making holes 35 as shown in FIG. 4A with laser light, 80 holes 35 with a diameter of 30 μm are made by a YAG laser.
You can empty it in / seconds. For example, if both ends of the heating element 33 are processed to have a width of about 50 mm and, for example, a flat plate having a width of about 10 mm is provided with a hole 35 in the center of about 5 mm, about 3000 pieces are provided in a range of 50 × 5 = 250 mm ^2. To some extent, holes 35 can be formed at both ends.

In the method of defining the light emitting region by masking with heat resistant ceramics in advance, first, before sintering, a ceramic that reflects far infrared rays on the side where far infrared rays are not to be emitted is selected. Dust and bake as it is. In general, electricity flows only in a place with low resistance, so the resistance value does not change unless the cross-sectional area changes, and when compressing in the mold, even if the cross-sectional area is small by sprinkling this heat-resistant ceramic. As the amount decreases, the resistance value increases.

As described above, according to the present embodiment, it is possible to provide a carbon material heating element in which a resistance distribution is formed for one carbon material (heating element) and a light emission distribution is formed (adjusted). You can As a method of forming this resistance distribution, there are a method of adjusting a resistance value by performing a perforating process before and after sintering of a carbon material, a method of partially changing a cross-sectional area and a resistance value, There is a method of creating a light distribution by changing the resistance value by changing the composition of the carbon-based heating element and the firing conditions.

In this embodiment, a plurality of heating elements including a carbon-based heating element are provided on the fixing roll 20 side, but they may be provided on the pressure side of the endless belt 21 or the like. Further, the fixing device 6 is not limited to the structure shown in the present embodiment, and a pressure roll may be used instead of the endless belt 21, and such a pressure roll as shown in this embodiment. It can also be configured to include a different heating element. Further, as the fixing device 6, for heating an unfixed sheet material (paper sheet Po), in addition to being in contact with this sheet material, it is not only in contact with the sheet material but also in proximity to warm the sheet material. Can also be applied. Further, it is also possible to apply the technique shown in the present embodiment to a portion other than the fixing device 6 where it is desired to suppress flicker when the power is turned on.

Further, in the present embodiment, as shown in FIG. 2, the two lamps, the halogen lamp 25 and the carbon lamp 26, are provided in parallel. However, the tungsten wire and the heat generation are provided in one glass tube. It is also possible to provide the bodies 33, 40 and 50 to form one lamp. Further, as a method of adjusting the resistance value, an example in which a high heat quantity distribution is obtained for both the front and rear sides (front side and back side) of the image forming apparatus has been described. When a side register that uses either the front side or the back side as a reference for image formation is adopted, etc., it is configured so that a higher heat quantity distribution can be obtained for either the front side or the back side. can do. Of course, it is possible to configure so as to obtain a predetermined heat quantity distribution for other reasons.

[0044]

As described above, according to the present invention, it is possible to provide a carbon lamp, which is a carbon-based heating element, with a light emission distribution.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an image forming apparatus to which this exemplary embodiment is applied.

FIG. 2 is a diagram for explaining a configuration of a fixing device to which the exemplary embodiment is applied.

3 (a) and 3 (b) are diagrams showing a configuration of a carbon lamp used in the present embodiment.

4A and 4B are diagrams for explaining a state in which the light distribution in the longitudinal direction is adjusted according to the present embodiment.

5A and 5B are diagrams for explaining another example of the carbon lamp in which the light distribution in the longitudinal direction is adjusted.

[Explanation of symbols]

1 ... Photosensitive belt, 2 ... Charging roll, 3 ... Exposure system member,
4 ... Developing device, 5 ... Transfer roll, 6 ... Fixing device, 7 ... Cleaning device, 8 ... Discharge lamp, 10 ... Paper tray,
11 ... Manual feed tray, 12 ... Paper transport path, 13 ... Post-processing device, 20 ... Fixing roll, 21 ... Endless belt, 2
2 ... Pressure pad, 23 ... Belt running guide, 24 ... Temperature sensor, 25 ... Halogen lamp, 26 ... Carbon lamp, 27 ... Reflecting member, 28 ... Peeling member, 31 ... Transparent quartz tube, 32 ... Tungsten coil, 33 ... Heat generation Body, 35 ...
Holes, 40 ... Heating element, 41 ... End region, 42 ... Central part, 5
0 ... Heating element, 51 ... Elliptical cross section, 52 ... Circular cross section

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H033 AA03 BA25 BA26 BA27 BB18                       BB21                 3K058 AA27 AA88 BA18 DA02 DA06                       GA06                 3K092 PP18 QA01 QB14 QB24 QB29                       QB32 QB39 QB74 RA03 RD11                       VV21 VV30

Claims (10)

[Claims] 1. A heating member for heating the sheet material in contact with or in proximity to a sheet material having an unfixed image, and a carbon heating element for heating the heating member, wherein the carbon heating element is a region. A fixing device characterized in that a carbon material having a different resistance value is used as a heating element. 2. The fixing device according to claim 1, wherein the carbon-based heating element forms a resistance value distribution by forming a hole in a predetermined area of a flat carbon material. 3. The fixing device according to claim 1, wherein the carbon-based heating element is made of a carbon material having regions having different compositions or cross-sectional areas in the longitudinal direction. 4. The fixing device according to claim 1, wherein the resistance value of the carbon-based heating element is adjusted so that a higher heat amount is obtained at both ends in the longitudinal direction than at the central portion. . 5. A carbon lamp using a carbon-based material for a heating element, wherein the carbon-based material has a different resistance value depending on a region, and a light emission distribution is adjusted. 6. The carbon lamp according to claim 5, wherein the carbon-based material has holes formed at predetermined locations in the longitudinal direction. 7. The carbon lamp according to claim 5, wherein the carbon-based material has regions having different compositions or cross-sectional areas in the longitudinal direction. 8. A heating element made of a carbon-based material, which is provided in a predetermined area of the heating element to define a light emitting area from the heating element, or changes the heat capacity from the heating element to change the light distribution. A carbon lamp characterized by comprising a light distribution regulating member for controlling the carbon lamp. 9. A step of pelletizing a composition containing a carbon material to produce a molding composition; a step of shaping the produced molding composition and heating to obtain a carbon precursor wire rod; A method for producing a carbon-based heating element, comprising: a step of firing a carbon precursor wire rod to obtain a heating element; and a step of forming a hole in the heating element after firing using a laser beam. 10. A step of pelletizing a composition containing a carbon material to produce a molding composition, and forming and heating the produced molding composition, and a carbon having a different cross-sectional area or composition depending on regions. A method of manufacturing a carbon-based heating element, comprising: a step of forming a precursor wire; and a step of firing the carbon precursor wire to obtain a heating element.