JPH10142983A - Thermal fixing unit for electrophotographic recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the increase of the cost and to prevent the rising of the temp. of the beating part of a heating roller, at the time of consecutively printing small-width paper sheets by providing an endothermic structure which can come into contact with only both end parts of a pressure roller for exerting pressure on the heating roller and a contact control mechanism for the endothermic structure. SOLUTION: An endothermic plate 103 is supported so that it is switched to contact and noncontact states with the pressure roller 102 by an electromagnetic solenoid 104. When the endothermic plate 103 comes into contact with both end parts of the pressure roller 102, heat is absorbed and the temp. drops in both end parts of the pressure roller 102. Since this roller 102 has elastic structure, the thickness of an inserted paper sheet is absorbed by deflection and both end parts through which the paper is not inserted of the pressure roller 102 come into contact with both end parts of the heating roller 101. The rising of the temp. in both end parts of the heating roller 101 can be suppressed by the contact of both end parts of the pressure roller 102 whose temp. drops.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device for an electrophotographic recording apparatus, and more particularly, to a method for fixing a medium to which a toner image has been transferred between a heat fixing unit heated by a heat generating unit and a pressing unit. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device of an electrophotographic recording apparatus for inserting a toner image into a fixing medium by heat.

[0002]

2. Description of the Related Art In recent years, electrophotographic recording apparatuses have
A small, high-speed and excellent image quality performance has been realized as a gigaprinter, and this price has also shifted to a low-priced range that can be purchased on an individual level. However, in a conventional electrophotographic recording apparatus, a thermal fixing device provided for fixing a toner image transferred on a recording medium is used for printing a 300 W to 400 W, A3 paper or the like in a small device. A medium-sized device capable of the above required a large electric power of about 500 W to 800 W. For this reason, power consumption is too large to be used in each household at the individual level, and it is necessary to reduce this power consumption. Further, from the viewpoints of environment and earth resources in recent years, reduction of power consumption has become a condition for this type of page printer to spread on an individual level.

As shown in FIG. 5, for example, a heat fixing unit of a conventional electrophotographic recording apparatus includes a heat generating portion including a halogen lamp 501, a heater 502 having the halogen lamp 501 inside a hollow portion, and a heat roller 502 including the halogen lamp 501. A pressure roller 503 for applying pressure to the heat roller 502 constitutes a main part thereof, and a toner as a fixing medium is provided between the heat roller 502 and the pressure roller 503. The recording medium 504 on which the image was formed was inserted.

In such a conventional heat fixing device of an electrophotographic recording apparatus, the radiation of a halogen lamp 501 causes a heater 502 to be heated from the inner surface of a hollow portion. However, it is necessary to ensure sufficient rigidity and sufficient heat capacity to prevent deformation due to the pressure from the pressure roller 503 and to prevent the temperature of the roller from fluctuating due to the running of the paper. Was. Therefore, it has been considered that the thickness of the heater is required to be 1.5 mm to 2.5 mm. With this thickness, after supplying power to the halogen lamp,
It takes about 60 to 90 seconds for the temperature of the roller surface to reach the temperature required for fixing, and it takes too much time before printing becomes possible.

As is known, in order to speed up the temperature rise, the thickness of the heater 502 and the heat capacity may be reduced. However, since the heat roller 502 must receive the pressure from the pressure roller 503 as described above, it is necessary to maintain rigidity, and the heat roller 502
There was a limit to reducing the thickness of the. The limit for reducing the thickness is about 0.8 mm. Since the rigidity is reduced by reducing the thickness, the pressure of the pressure roller must be reduced. The nip width W created between the roller 502 and the pressure roller 503 (the width of the running recording medium 504 in contact with the roller 502 under pressure) is reduced.
Also, in a medium-speed printer in which the traveling speed of the recording medium 504 is high, the temperature of the
Predetermined fixing performance cannot be obtained.

When the thickness of the heat roller is reduced in this way, the rigidity is reduced, so that the pressure cannot be increased, and therefore the fixing control temperature must be increased.
This tendency increases as the paper thickness increases, as in the case of printing on postcards, and the temperature required for fixing is close to 200 ° C. On the other hand, temperature detection by a thermistor that controls the fixing temperature is performed near the center where the paper is running. Therefore, when printing is continuously performed on a narrow sheet of paper, such as a postcard, the sheet travels near the center, thereby removing heat near the center and lowering the temperature. The control replenishes this heat so that the temperature near the center recovers to the set value, so that the temperature gradually increases without decreasing at both ends where the paper is not in contact, and as a result, the heat roller The temperature at both ends is considerably higher than the control temperature at the central portion, and becomes as high as 200 ° C. or more. As a result, the temperature of the bearing that supports the rotor in a rotatable state increases, and a special material is required for the bearing.

In order to solve the problem of the temperature rise in the bearing portion caused by printing on such narrow paper, Japanese Patent Application Laid-Open No. 4-124688 discloses a heat generating portion of a halogen lamp formed in a heater. Are switched among a plurality of halogen lamps so as to differ depending on the paper width. Also, JP-A-63-2
When the sheet width is narrow as in the case of 31383, there is a method in which a waiting control is performed so as not to be in a continuous printing state. Further, in the case of using a heater having a heating resistor other than a halogen lamp formed on the surface thereof, when the paper width is narrow, the structure can be switched to the heating resistor side having the length of the paper width. is there.

However, in the former structure in which the halogen lamps are switched or the heater structure in which the heating resistors having different lengths are formed, heaters that are not used depending on the paper have to be provided. This was a significant cost increase for the department. Further, in order to select one of a plurality of heaters and supply electric power, this switching circuit is necessary. Since this switching circuit is a power line, the cost as the switching circuit has been greatly increased. On the other hand, a control structure that does not result in continuous printing like the latter,
Although it is acceptable to individual users in ordinary households, it is a printer that is completely impractical as a multi-user network printer in offices and the like, and such control is not acceptable.

[0009]

In the above-described thermal fixing device of the above-described conventional electrophotographic recording apparatus, by changing the length of the heating element itself, it is possible to prevent the temperature from increasing at both ends where the paper is not running. In addition, by controlling the printing so that continuous printing does not occur, it has been performed to prevent the temperature from increasing in portions other than the portion where the paper travels. Since such a solution involves a significant increase in cost and a significant decrease in equipment performance, as a result, a bearing made of a special bearing material, which has a considerable cost increase but is less affected, is required. The current situation was to choose. In the present invention, these conventional problems are eliminated, and (1)
It is an object of the present invention to minimize the cost increase and (2) obtain an effect of preventing a temperature rise in a bearing portion of the heat roller outside the paper running during continuous printing on a narrow paper.

[0010]

In order to achieve the above-mentioned object, according to the present invention, a heat fixing device for an electrophotographic recording apparatus according to the present invention comprises a fixing device on which a toner image is transferred. A heat fixing unit of an electrophotographic recording apparatus for fixing a toner image on a medium to be fixed by being inserted between a heat fixing unit heated by a heat generating unit and a pressing unit; (2) a heat absorbing structure that can contact only the both ends of the pressure roller or the pressure roller, which is the pressurizing section and applies pressure by contacting the heat roller; )
And a contact control mechanism for the heat absorbing structure. To achieve the above object, according to the present invention, a heat fixing device for an electrophotographic recording apparatus according to claim 2 is the heat fixing apparatus for an electrophotographic recording apparatus according to claim 1.
The heat absorbing structure includes a heat absorbing plate. According to another aspect of the present invention, there is provided a heat fixing device for an electrophotographic recording apparatus according to claim 1 or 2, wherein the heat fixing device is a heat fixing device for an electrophotographic recording apparatus according to claim 1 or 2. , The contact control mechanism of the heat absorbing structure includes an electromagnetic solenoid.

According to another aspect of the present invention, a thermal fixing device for an electrophotographic recording apparatus according to the present invention is provided. In the thermal fixing device, (1) the heat absorbing structure is made of a material having a high thermal conductivity, and a component having a large heat capacity and a flat surface in contact with the medium to be fixed is provided at a central portion in a longitudinal direction thereof; 2) The fixing medium is preheated by the contact heat generated from the component. According to another aspect of the present invention, there is provided a heat fixing unit for an electrophotographic recording apparatus according to any one of claims 1 to 3, wherein the heat fixing unit is a heat fixing unit for an electrophotographic recording apparatus according to any one of claims 1 to 3. In (1)
The heat-absorbing structure is made of a material having a high thermal conductivity, and a component having a large heat capacity and a flat surface close to the medium to be fixed is provided at a central portion in a longitudinal direction of the heat-absorbing structure. To preheat the medium to be fixed.

According to another aspect of the present invention, a heat fixing device for an electrophotographic recording apparatus according to the present invention is provided. In the heat fixing device, a housing case that houses the heat fixing device has an opening, and discharges heat absorbed by the heat absorbing structure from the opening. According to another aspect of the present invention, there is provided a heat fixing unit for an electrophotographic recording apparatus according to claim 7, wherein the heat absorbing structure is a heat fixing unit for an electrophotographic recording apparatus according to claim 6. However, a large heat capacity component having a predetermined surface area is provided near the opening.

According to another aspect of the present invention, there is provided a heat fixing device for an electrophotographic recording apparatus, wherein a fixing medium to which a toner image is transferred is heated by a heat generating portion. 8. The heat fixing device of an electrophotographic recording apparatus according to claim 1, wherein the heat fixing unit is inserted between the heat fixing unit and the pressing unit to thermally fix the toner image on the medium to be fixed. (1) The housing case has end openings for exhausting heat near both ends of the heater or near both ends of the pressure roller, respectively. (2) A shutter for opening or closing the end opening is provided. According to another aspect of the present invention, there is provided a heat fixing device for an electrophotographic recording apparatus according to claim 9, wherein the shutter is an electromagnetic fixing device. The opening is opened or closed using a solenoid.

According to another aspect of the present invention, there is provided a heat fixing device for an electrophotographic recording apparatus, wherein a medium to which a toner image is transferred is heated by a heat generating portion. The electrophotographic recording apparatus according to any one of claims 1 to 9, wherein the electrophotographic recording apparatus is a heat fixing device of an electrophotographic recording apparatus that heat-fixes a toner image to a medium to be fixed by being inserted between a heat fixing unit and a pressing unit. The heat fixing device of the apparatus includes: (1) a blocking mechanism for blocking the heat generating portion near both ends of the heat roller; and (2) a movement control mechanism of the blocking mechanism. In order to achieve the above-mentioned object, a first aspect of the present invention is described.
The thermal fixing device of the electrophotographic recording apparatus according to claim 1, wherein
Wherein the movement control mechanism of the shielding mechanism includes an electromagnetic solenoid.

[0015]

In the heat fixing device of the electrophotographic recording apparatus according to the present invention, when the mode in which the narrow paper is in the running mode, the heat is fixed.
When a heat absorbing structure is pressed against a portion of the roller or pressure roller on which the paper does not travel by a driving means such as a solenoid, the heat of the heat roller or pressure roller is released by the heat absorbing structure through a contact portion. This heat is absorbed, and this heat is conducted to a position in the center direction other than the position corresponding to the paper traveling portion of the heat absorbing structure.

Further, when the sheet is preheated by the heat absorbed by the heat absorbing structure before the heat fixing, the heat taken by the sheet from the heat roller is reduced. Furthermore, if the heat absorbed by the heat absorbing structure is discharged from the opening of the housing case, the amount of heat absorbed by the heat absorbing structure from the heat roller or the pressure roller increases. If end openings are provided near both ends of the heat roller or the pressure roller of the housing case, heat generated at both ends of the heat roller or the pressure roller of the housing case can be discharged from the end openings.

Similarly, a motor in which a narrow paper travels.
When the heat is generated, if the heat generating portion is shielded near both ends of the heat roller, heat generated from the heat generating portion in this portion is not transmitted to both ends of the heat roller. As a result, a rise in temperature at both ends of the heat roller where the paper is not running, which is caused by a reduction in the paper width, is restricted, and as a result, a rise in the temperature of the bearing portion is prevented.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a heat fixing device of an electrophotographic recording apparatus according to the present invention, a medium to which a toner or the like is transferred is inserted between a heat fixing unit heated by a heat generating unit and a pressing unit. This is a thermal fixing device of an electrophotographic recording apparatus for thermally fixing a toner image on a medium to be fixed. The heat fixing section is a heat roller. On the other hand, the pressure unit is a pressure roller, and applies pressure by contacting the heat roller. The heat absorbing structure, which can contact only both ends of the heat roller or both ends of the pressure roller, is connected to both ends of the heat roller or the pressure roller by the contact control mechanism when the width of the medium to be fixed is equal to or less than a predetermined value. When they are in contact with each other and are larger than a predetermined value, they are controlled so as to be separated from both ends. When the heat absorbing structure comes into contact with both ends of the heat roller or the pressure roller, the heat of the both ends, which are the contacted portions, is absorbed and the temperature is reduced.

The heat-absorbing structure may be a heat-absorbing plate having a plate-like protrusion at both ends, and the protrusion may be in contact only with both ends of the heat roller or both ends of the pressure roller. Further, the contact control mechanism may be configured to use an electromagnetic solenoid and move by electric control. When the power to the electromagnetic solenoid is turned off, if the heat absorbing structure is brought into contact with both ends, it is on the safe side.
The heat-absorbing structure is made of a material having high thermal conductivity, and has a part having the following width at the center in the longitudinal direction and having a large heat capacity. Or has a flat surface close to the medium to be fixed, passes through the surface of the component in contact with or close to the flat surface of the component before the medium to be fixed is inserted through the heat roller and the pressure roller, and is preheated by contact heat or radiant heat. You may do so. When the fixing medium is overheated, the amount of heat taken from the heat roller is reduced. The width of the component of the heat absorbing structure and the width of its plane may be the maximum width of the sheet when the heat absorbing structure contacts the heat roller or the pressure roller.

It is preferable that the housing case accommodating the heat fixing device has an opening, and the heat absorbed by the heat absorbing structure is discharged from the opening. The opening is sized to effectively discharge heat, and is arranged near a heat roller or a pressure roller in consideration of convection of air. The heat-absorbing structure may include a part having a predetermined surface area near the opening, and the part may have a large heat capacity. The surface area of the component should be large enough to adequately release the heat absorbed by the heat absorbing structure and exhaust it through the opening. Also, the arrangement of the components is appropriate in consideration of the flow of air when releasing heat and discharging heat from the opening. If the heat absorbed by the heat absorbing structure is discharged to the outside of the housing case, the heat absorption of the heat absorbing structure can be increased as a result.

An end opening is formed at each position corresponding to both ends of the heat roller or both ends of the pressure roller of the housing case accommodating the heat fixing device, and a heat roller or a pressure roller is formed from the end opening. It is good to discharge the heat generated from both ends. By discharging this heat, the temperature at both ends can be reduced. A shutter that opens or closes the end opening may be attached to these end openings. An electromagnetic solenoid may be used for opening and closing the shutter. It is on the safe side to open the shutter when the power to the electromagnetic solenoid is turned off. When the width of the fixing medium is equal to or smaller than a predetermined value, the shutter is opened. When the width of the fixing medium is wide, the shutter can be closed to prevent unnecessary heat release. The thermal fuser may have a heat absorbing structure and may have an end opening. Further, the electromagnetic solenoid for controlling the contact of the heat absorbing structure may also serve as the electromagnetic solenoid for opening and closing the shutter.

The heat generating portion can be disposed inside the hollow portion of the heat roller, and further, a shielding mechanism can be inserted into both ends inside the hollow portion of the heat roller so as to be located outside the heat generating portion. The shielding mechanism has a structure capable of moving to the outside in the longitudinal direction of the heat roller, so that a portion corresponding to both ends of the heat roller of the heat generating portion is covered by insertion or a state of being separated from the heat generating portion by external movement. , Can be controlled by a movement control mechanism. By covering a part of the heat generating portion with the shielding mechanism, heat generated from the heat generating portion is not transmitted to the heat roller in this portion. When the width of the fixing medium is equal to or smaller than a predetermined value, the shielding mechanism is inserted into both ends inside the heat roller as described above. Further, the movement control mechanism may use an electromagnetic solenoid. Further, the heat fixing device has a heat absorbing structure,
And you may make it have a shielding mechanism. The electromagnetic solenoid for controlling the contact of the heat absorbing structure may also serve as an electromagnetic solenoid for opening and closing the end opening and an electromagnetic solenoid for controlling the movement of the shielding mechanism of the heat generating portion. In the embodiments of FIGS. 1, 3, and 4 described above, an electric motor or the like may be used instead of the electromagnetic solenoid.

[0023]

Next, embodiments of the present invention will be described in detail with reference to the drawings. Note that the configuration of the fixing device shown in the present embodiment shows a case where a sheet traveling between a roller and a pressure roller travels with reference to a center in a roller axis direction. In the case where the sheet is used as the reference, it is possible to apply the configuration described below to the vicinity of one of the bearings on the opposite side of the sheet.

FIG. 1 is a perspective view of a basic structure of a heat fixing unit of an electrophotographic recording apparatus according to an embodiment of the present invention, in which a housing case is omitted. The paper 109 is inserted between the heat roller 101 and the pressure roller 102. The pressure roller 102 is in contact with the heat roller 101 and applies pressure to them by the action of the spring 110. A halogen lamp 108 is arranged inside the hollow portion of the heat roller 101. Thermistor 10
Reference numeral 7 is arranged such that its temperature detecting end contacts the center of the outer peripheral portion of the heat roller 101. Pressure Roller 10
There is a heat absorbing plate 103 having a "U-shape" shape that comes into contact only with both end portions of the pressure controller 2, and the heat absorbing plate 103 can be switched between a contact state and a non-contact state with the pressure controller 102 by the electromagnetic solenoid 104. Support shaft 105
Supported by. An opening 106 of the housing case is arranged immediately near the heat absorbing plate 103. Endothermic plate 10
The protrusions at both ends of the third roller 3 contact both ends of the heat roller 101 or the pressure roller 102. The heat absorbing plate 103 shown here is made of a phosphor bronze plate or the like having spring properties and heat conductivity, and heat absorbed by contact with the pressure roller 102 is transmitted from an opening 106 shown by omitting an upper portion. The structure is such that the air is discharged to the air flow outside the apparatus.

By adopting such a structure, the width of the sheet is much shorter than the length of the roller in the axial direction as in postcard printing, and the fixing temperature must be increased for continuous printing. Considering this situation, as shown in the problem of the prior art, heat is taken away by the paper near the center where the paper is running, and the taken heat is detected by the thermistor 107 as a temperature drop. Thus, the halogen lamp 108 in the hollow portion of the
The power is further replenished, and the replenishment of heat to the paper traveling unit is performed until the temperature detected by the thermistor 107 reaches a predetermined value. At this time, heat from the halogen lamp 108, which is a heat source, is uniformly generated in the entire axial direction from the inner surface of the hollow portion of the heater 101. Therefore, in the portion where the paper is not running, the heat is not taken away by the paper, and the temperature tends to be higher than the temperature of the portion where the paper is running.

However, in this embodiment, since the heat absorbing plate 103 is in contact with both ends of the pressure roller 102, heat is absorbed at both ends of the pressure roller 102, and the temperature drops. Since the pressure roller 102 has an elastic structure, the thickness of the inserted paper is absorbed by the deflection, and both ends of the pressure roller 102 where the paper is not inserted come into contact with both ends of the heat roller 101. I have. By contacting both ends of the pressure roller 102 where the temperature has dropped, the temperature rise at both ends of the roller 101 can be suppressed. As a result, even in the worst case of continuous postcard printing, the temperature distribution in the axial direction of the heater has the characteristics as shown in FIG. 2A, and the conventional characteristics without the heat drop plate 103 (b). The temperature rise occurring at the bearing portions at both ends as described above does not occur. Thermistor 1
In FIG. 2 (a), instead of setting the position where 07 contacts the heat roller 102 as the center of the heat roller as shown in FIG.
May be the position corresponding to the maximum value of the temperature distribution curve.

The structure of the heat absorbing plate shown here is a "U-shaped".
The shape is not limited to a shape having a large area near the opening for releasing heat to the outside of the device, for example, due to a fin structure, or a portion protruding to the outside from the opening. May be formed, and the material is not limited to metal. The heat absorbing plate is not a simple plate, but a belt-shaped structure that is rotated by being pressed against a pressure roller by the movement of an electromagnetic solenoid. The belt-shaped heat absorbing structure is formed at both ends. A similar effect can be obtained even in this case, and in this case, heat can be absorbed by a material such as a resin film.

FIG. 3 is a partially omitted perspective view having an opening structure showing another embodiment of the present invention. Instead of absorbing heat in the above embodiment, heat at both ends is positively released to the outside. Structure. In this embodiment, an end opening 3 is provided near a bearing 305 of a housing case 301 constituting a fixing device.
In addition, a shutter 303 for closing the end opening 302 is provided in an end opening 302 of the housing case 301, and the shutter 303 can be opened and closed by an electromagnetic solenoid 304. Also in this embodiment, the end opening 302 is opened by operating the electromagnetic solenoid 304 in the printing mode in which the paper width is small and the temperature of both ends of the heat roller is high, such as continuous printing of a postcard. By releasing the heat of the bearing portions 305 at both ends to an airflow (not shown) for discharging heat to the outside of the apparatus, it is possible to prevent the temperature of the bearing portions from rising.

As a result, the temperature distribution in the axial direction of the heat roller 101 can be made to have the same characteristics as those shown in FIG. The fixing device can be configured without using the fixing device. The opening structure is not particularly limited in the opening shape and the opening position, but may be any shape and position that can prevent the temperature of the bearings at both ends outside the paper running from rising. It is also possible to find the optimum opening shape from the simulation by the above. The end opening shown in this embodiment can be provided in the housing case of the heat fixing device having the heat absorbing plate shown in FIG.

FIG. 4 shows still another embodiment. FIG. 4 is a cross-sectional view showing only a main portion in which light-shielding shutters are provided at both ends inside the hollow portion of the heat roller, and is configured to prevent heat from a heat source from being applied to both ends of the heat roller. In this embodiment, a cylindrical shutter 401 having a taper is inserted outside both ends of a halogen lamp 108 formed inside the hollow portion of the heater 101. The shutter 401 has a reflecting surface and a taper portion so as to reflect the light emitted from the halogen lamp 108 toward the inside of the heater 101 when the shutter 401 is inserted into the inside of the heater. It has a cylindrical structure with. Also in this case, the shutter 401 has a structure that can be inserted into the heat roller or pulled out by using an electromagnetic solenoid (not shown).

Also in this embodiment, since the paper width is small as in the continuous printing of a postcard, both end bearings 3 of the heat roller are used.
At the time of the printing mode in which the temperature of 05 is high, an electromagnetic solenoid (not shown) is operated, whereby the cylindrical shutter 401 is inserted into both ends inside the hollow portion of the heat roller, so that both ends of the bearing are supported. It is possible to prevent the heat of the portion 305 from rising. As a result, the temperature distribution in the axial direction of the heat roller 101 has the same characteristics as those of the above embodiment, and the material of the heat roller bearing portion 305 has special heat resistance. This makes it possible to form a fixing device without the need.
When the sheet width is large, the light-blocking shutter 401 is pulled out of the heat roller 101, and does not cover the halogen lamp.

In this embodiment, the light-shielding shutter has a tapered cylindrical shape, but is not limited to this shape. However, since it is inserted into the hollow portion of the heat roller and directly receives the light from the halogen lamp, a structure that reflects the light so as not to be transmitted to the bearing portion is required. Further, it is desirable that the light shielding shutter is made of a heat insulating material.

FIG. 6 shows a sectional structure of another embodiment of the light-shielding shutter. As described above, the light-blocking shutter has a thin tapered cylindrical structure having two widths substantially equal to each other, and the minimum value of the inner diameter of one tapered cylinder 402A is set to the other tapered cylinder 40A.
The structure can be made slightly larger than the maximum outer diameter of 2B by the gap required for sliding. The inside of the thin-walled tapered cylinders 402A and 402B, which are light-shielding shutters, needs to have a structure in which light from the halogen lamp 108 is reflected toward the center of the halogen lamp 108, and may be made of a heat insulating material. With this structure, the light shielding shutter 4
The space in the longitudinal direction required for inserting and withdrawing the 02A and 402B into the hollow of the heat roller 101 can be reduced by the width of the thin tapered cylinder. The light-blocking shutter of this embodiment can be provided in the halogen lamp of the heat fixing device having the heat absorbing plate shown in FIG.

[0034]

As is apparent from the above description, the heat fixing device of the electrophotographic recording apparatus according to the present invention can be used as in postcard printing.
It is possible to prevent a rise in temperature near the bearing of the heat roller outside the paper running, which occurs when the paper width is significantly shorter than the axial length of the heater. Therefore, the temperature at the bearing portion can be substantially equal to or lower than the fixing temperature controlled to be a predetermined value in the paper traveling portion, and a special heat-resistant performance is required as a material of the bearing. And the cost of the apparatus can be minimized. Also, the paper may be left unheated before it is thermally fixed,
Alternatively, if heat is discharged from the end opening of the housing case formed near the bearing, the temperature of the bearing can be further reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a thermal fixing device of an electrophotographic recording apparatus according to an embodiment of the present invention.

FIG. 2 is an axial temperature distribution diagram of a heater obtained by the present invention.

FIG. 3 is a partially omitted perspective view showing another embodiment of the present invention.

FIG. 4 is a sectional view showing only a main part showing still another embodiment of the present invention.

FIG. 5 is a perspective view showing a main part of a heat fixing section of an electrophotographic recording apparatus showing a conventional roller type structure.

FIG. 6 is a cross-sectional view showing only a main part showing still another light-shielding shutter embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Heat roller 102 Pressure roller 103 Heat absorbing plate 104 Electromagnetic solenoid 105 Support shaft 106 Opening 107 Thermistor 108 Halogen lamp 109 Paper 110 Spring 301 Housing case 302 End opening 303 Shutter 304 Electromagnetic solenoid 305 Bearings 401, 402A, 402B Light-shielding shutter 501 Halogen lamp 502 Heat roller 503 Pressure roller 504 Recording medium

Claims (11)

[Claims] 1. An electronic device for fixing a toner image on a medium to be fixed by inserting the medium to which a toner image is transferred between a heating and fixing unit heated by a heating unit and a pressing unit. In a thermal fixing device of a photographic recording apparatus, (1) a pressure roller which applies pressure by contacting with both ends of a heat roller which is the heat fixing portion or the pressure roller which is the pressing portion. A heat fixing unit for an electrophotographic recording apparatus, comprising: a heat absorbing structure capable of contacting only with both ends of the heat absorbing structure; and (2) a contact control mechanism for the heat absorbing structure. 2. The thermal fixing device according to claim 1, wherein the heat absorbing structure includes a heat absorbing plate. 3. The heat fixing device of an electrophotographic recording apparatus according to claim 1, wherein the contact control mechanism of the heat absorbing structure includes an electromagnetic solenoid. (1) The heat-absorbing structure is made of a material having a high thermal conductivity, and a component having a large heat capacity and a flat surface in contact with the medium to be fixed is provided at a central portion in a longitudinal direction thereof. The heat fixing device of an electrophotographic recording apparatus according to any one of claims 1 to 3, wherein the medium to be fixed is preheated by contact heat generated from the component. (1) The heat-absorbing structure is made of a material having a high thermal conductivity, and a component having a large heat capacity and a flat surface close to the fixing medium is provided at a central portion in a longitudinal direction thereof. The thermal fixing device of the electrophotographic recording apparatus according to any one of claims 1 to 3, wherein the fixing medium is preheated by radiant heat generated from the component. 6. The electrophotographic recording apparatus according to claim 1, wherein the housing case accommodating the heat fixing device has an opening, and the heat absorbed by the heat absorbing structure is discharged from the opening. Heat fuser. 7. The heat fixing device according to claim 6, wherein the heat absorbing structure includes a large heat capacity component having a predetermined surface area near the opening. 8. An electronic device which heat-fixes a toner image onto a medium to be fixed by inserting the medium to which the toner image is transferred between a heat-fixing unit heated by a heating unit and a pressing unit. (1) The housing case has end openings for exhausting heat near both ends of the heater or near both ends of the pressure roller, respectively. 8. A heat fixing device for an electrophotographic recording apparatus according to claim 1, further comprising a shutter for opening or closing said end opening. 9. The heat fixing device according to claim 8, wherein the shutter opens or closes the opening using an electromagnetic solenoid. 10. An electrophotographic recording apparatus in which a fixing medium to which a toner image has been transferred is inserted between a heating and fixing unit heated by a heating unit and a pressing unit to thermally fix the toner image to the fixing medium. 10. The thermal fixing device of the apparatus, comprising: (1) a blocking mechanism for blocking the heat generating portion near both ends of the heat roller; and (2) a movement control mechanism of the blocking mechanism. A heat fixing device for an electrophotographic recording apparatus according to any one of the above. 11. The thermal fixing device according to claim 10, wherein the movement control mechanism of the shielding mechanism includes an electromagnetic solenoid.