JP2008020726A - Heat fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device applicable to an image forming apparatus of an electrophotographic system equipped with a heating roller in which the surface temperature unevenness of the heating roller of a low heat capacity is eliminated. <P>SOLUTION: A ceramic terminal 23a of a heater lamp 23 arranged within the heating roller 21 is axially movably held by a driving side heater holder 34 and a ceramic terminal 23b on a non-driving side is axially movably held by a none driving side heater holder 35 and the heater holder 35 on the non-driving side 15 is biased in an arrow (a) direction by a reset spring 36. The driving side heater holder 34 and a heater driving cam 33 come into contact with each other at all times. When the heater driving cam 33 rotates, the driving side heater holder 34 coming into contact at all times therewith moves back and forth in the arrow (a) direction and the direction opposite thereto. The heater lamp 23 held in the driving side heater holder 34 moves also back and forth in the arrow (a) direction and the direction opposite thereto and the surface temperature unevenness of the heating roller is eliminated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat fixing device used in an image forming apparatus such as an electronic copying machine, a printer, a facsimile machine, or a multifunction machine thereof.

  In an electrophotographic image forming apparatus, a laser beam modulated by an image signal is projected onto a charged photoconductor to form an electrostatic latent image of the image, and the electrostatic latent image is developed with toner. In general, the toner image is transferred onto a recording medium, and then the toner image is fixed on the recording medium by a fixing device to form an image.

  Most of the fixing devices employ a heat roller fixing type fixing device in terms of thermal efficiency and safety. In the fixing device of the heat roller fixing system, a heating roller and a pressure roller are arranged in contact with each other, a recording medium on which a toner image is transferred is passed through the nip portion, and the toner image is heated and pressed to perform recording. A configuration for fixing to a medium is provided.

  The heating roller is configured by incorporating a heater made of an infrared halogen lamp inside a metal core such as aluminum or iron whose surface is covered with a heat-resistant release layer made of a fluororesin or a silicone rubber layer. In addition, the pressure roller has a heat-resistant elastic layer composed of a sponge layer made of a silicone rubber layer on the surface of a metal core such as aluminum or iron, and a heat-resistant release layer on the surface of the heat-resistant elastic layer. It is comprised (refer patent document 1).

  The heating roller has to rapidly increase the temperature to about 180 ° C., which is the fixing temperature in order to melt the toner image, but in order to increase the temperature by energizing the heater from a state where the apparatus is cold A waiting time (warm-up time) is absolutely necessary. Further, in order to quickly raise the temperature to the fixable temperature even during standby, it is necessary to maintain a constant temperature even if the temperature is lower than the fixable temperature. Therefore, power is consumed even during standby.

  From the viewpoint of ease of use of the image forming apparatus and energy saving, the shorter the warm-up time, the better. For this purpose, it is necessary to reduce the heat capacity of the heating roller. For this purpose, it is effective to reduce the thickness of the metal core as much as possible. However, in order to form a nip portion for fixing at the facing portion between the heating roller and the pressure roller, it is necessary to press the heating roller and the pressure roller in order to elastically deform the heat-resistant elastic layer of the pressure roller. In addition, it is necessary to press the recording medium in terms of conveyance.

  When the thickness of the metal core bar is reduced to reduce the heat capacity of the heating roller, the strength of the metal core bar decreases, the heating roller bends, paper wrinkles occur, and image noise occurs. As a countermeasure, when iron or stainless steel is used as the metal core, the required strength can be secured even with a thickness of about 1 mm. However, iron and stainless steel are inferior in thermal conductivity to aluminum and have uneven temperature. There is a drawback that it tends to occur.

In addition, as the heater, an infrared halogen lamp that is relatively inexpensive and capable of quickly raising the temperature is used. The infrared halogen lamp is a heater having a feature that the quartz tube has a long life without being blackened by a circulation regeneration reaction (halogen cycle) between the halogen substance and tungsten evaporated by heating in the quartz tube. Inside the quartz tube, a plurality of filaments wound around a coil for heat quantity control are arranged along the longitudinal direction of the quartz tube, and the heat distribution characteristics and consumption of the heater depend on the number of windings and position of the filament coil. The power is determined.
JP-A-11-271232.

  The heating roller in which the infrared halogen lamp having the above-described configuration is arranged inside a metal core made of iron or stainless steel depends on the thickness of the metal core, but the surface temperature of the roller depends on the longitudinal position of the filament of the infrared halogen lamp. In some cases, temperature unevenness of about 20 ° C. may occur. Further, when aluminum is used as the metal core, if the metal core is thin, temperature unevenness may occur in the same manner.

  Such temperature unevenness is likely to occur remarkably immediately after the power is turned on, and when fixing processing is performed with a heating roller having such temperature unevenness, fixing unevenness or fixing failure occurs, and in the case of a color image, gloss unevenness occurs. It becomes. The present invention aims to solve the above problems.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the invention according to claim 1 provides a toner in a nip portion formed between a heating rotator and a pressure rotator arranged in pressure contact with the heating rotator. In a heat fixing apparatus for fixing a toner image by passing a recording medium on which an image is formed, the heating rotator includes a heating heater that reciprocates in the direction of the rotation axis of the heating rotator. A heat fixing device characterized by the above.

  The heating heater is a heater lamp including a heating element in which a large number of filaments are arranged at a predetermined interval.

  The heat fixing device includes a drive mechanism that reciprocates the heater for heating in the direction of the rotation axis of the heating rotator.

  The drive mechanism includes a drive cam mechanism that uses a drive mechanism that rotationally drives the heating rotator as a drive source.

  The drive mechanism may be a drive mechanism that reciprocates about a half of the arrangement interval of the filaments that are heating elements arranged in the heater lamp.

  The heating rotator may be a heating roller configured such that the surface of a metal core is covered with a heat-resistant elastic layer and the surface thereof is covered with a heat-resistant release layer.

  The pressure rotator may be a pressure roller configured by covering a surface of a metal core with a heat resistant elastic layer and a surface of the heat resistant release layer.

  The pressurizing rotator may be an endless belt made of a heat-resistant synthetic resin and having a surface covered with a heat-resistant release layer.

  According to the present invention, a heating lamp using a heating rotating body having a relatively thin metal core and a small heat capacity and having a heating element in which a number of filaments are arranged at predetermined intervals is used as a heat source. Even when used, it is possible to provide a heat fixing device that can reduce the temperature unevenness of the surface of the heating rotator and can warm up in a short time.

  Hereinafter, an embodiment in which the fixing device according to the present invention is applied to a tandem full-color image forming apparatus will be described.

  FIG. 1 is a diagram for explaining the configuration of a tandem full-color image forming apparatus 10. Since the tandem full-color image forming apparatus itself is a known configuration, only the outline of the configuration will be briefly described.

  In FIG. 1, image forming units 11, 12, 13, and 14 that form images of yellow (Y), magenta (M), cyan (C), and black (K) colors are a driving roller 15 and a driven roller 16. The intermediate transfer belt 17 is arranged in series under the intermediate transfer belt 17 installed between them, and the intermediate transfer belt 17 is moved at a constant speed in the direction of arrow a by a driving roller 15 driven from the main motor 10A through a driving device (not shown). Is configured to do.

  Each of the image forming units 11 to 14 is provided with a photoreceptor, a charging device, an exposure device, a developing device, and a cleaning device, but the details thereof are not the subject of the present invention, and thus the description thereof is omitted.

  The image forming units 11 to 14 are not provided with a transfer device. Instead, the primary transfer rollers 11T, 12T, 13T, and 14T are disposed on the opposite side of the image forming units 11 to 14 with the intermediate transfer belt 17 interposed therebetween. Is arranged.

  Further, a secondary transfer roller 15T is disposed at a position facing the driving roller 15 with the intermediate transfer belt 17 interposed therebetween, and cleaning is performed with the intermediate transfer belt 17 sandwiched at a position facing the driven roller 16 on the intermediate transfer belt 17. A device 18 is arranged. A fixing device 20 according to the present invention is disposed on the downstream side in the conveyance direction of the recording medium on which the driving roller 15 and the secondary transfer roller 15T are disposed with the intermediate transfer belt 17 interposed therebetween. The fixing device 20 will be described in detail later.

  The operation of the tandem full-color image forming apparatus 10 will be briefly described. When the power is turned on, the intermediate transfer belt 17 starts moving at a constant speed in the direction of arrow a. An image forming operation is started, and yellow (Y), magenta (M), cyan (C), and black (K) toner images are formed on the photoreceptors of the image forming units 11 to 14, respectively. . First, a yellow (Y) toner image is transferred onto the intermediate transfer belt 17 by the operation of the primary transfer roller 11T, and a magenta (M) toner image is superimposed and transferred thereon by the operation of the primary transfer roller 12T. Similarly, cyan (C) and black (K) color toner images are sequentially superimposed and transferred to form a full-color toner image.

  The recording medium P is fed from a paper feed unit (not shown) at the timing when the full-color toner image formed on the intermediate transfer belt 17 reaches the position of the secondary transfer roller 15T, and the secondary transfer roller 15T operates. As a result, the full-color toner image on the intermediate transfer belt 17 is transferred to the recording medium P. Thereafter, the recording medium P is conveyed to the fixing device 20, and the toner image on the recording medium P is fixed and discharged.

  Although transfer residual toner remains on the intermediate transfer belt 17, the next image formation is hindered. Therefore, the surface of the intermediate transfer belt 17 is cleaned by the cleaning blade 18 a of the cleaning device 18 and the transfer residual toner is removed.

  FIG. 2 is a cross-sectional view illustrating the configuration of the fixing device 20 according to the first embodiment. In the heating roller 21 of the fixing device 20, a silicone rubber layer is formed as a heat-resistant elastic layer on the surface of a metal core, and the surface is covered with a heat-resistant release layer composed of a fluororesin or a silicone rubber layer. An example of the dimensions of the heating roller 21 is an iron pipe having a diameter of 36 mm and a thickness of 0.6 mm for the metal core, a thickness of 1.8 mm for the silicone rubber layer, and a PFA tube having a thickness of 30 μm for the heat-resistant release layer. Consists of. The materials, numerical values, etc. shown here are merely examples, and the present invention is not limited to these.

  FIG. 3 is a cross-sectional view of the heating roller 21, and a heater lamp 23 is disposed inside the heating roller 21 and is configured to move in the axial direction. A temperature sensor 24 is disposed in contact with the surface of the heating roller 21, and energization control of the heater lamp 23 is performed by a temperature control device (not shown), so that the surface temperature of the heating roller 21 is maintained at a temperature suitable for the fixing process. To be controlled.

  Further, since the heater lamp 23 is a heater lamp in which a large number of filaments 23f are arranged in series at a predetermined interval, for example, an infrared halogen lamp, temperature unevenness occurs in the surface temperature of the heating roller 21. In order to alleviate this temperature unevenness, the heater lamp 23 is configured to reciprocate between a position indicated by a solid line and a position indicated by a chain line in FIG. The moving mechanism of the heater lamp 23 will be described in detail later.

  Returning to FIG. 2, the configuration of the fixing device 20 will be described. A pressure roller 22 is disposed in pressure contact with the heating roller 21. In the pressure roller 22, a silicone rubber layer is formed as a heat-resistant elastic layer on the surface of a metal core, and the surface is covered with a heat-resistant release layer. An example of the dimensions of the pressure roller 22 is an aluminum pipe having a diameter of 36 mm and a thickness of 1.8 mm for the metal core, a thickness of 1.8 mm for the silicone rubber layer, and a PFA having a thickness of 30 μm for the heat-resistant release layer. It consists of a tube.

  The materials, numerical values, etc. shown here are merely examples, and the present invention is not limited to these. The hardness of the heat resistant elastic layer is set higher for the pressure roller. The pressure roller 22 is pressed against the heating roller 21 by a pressure spring (not shown), and the pressure contact force is about 300 N, for example.

  Inside the pressure roller 22 is disposed a pressure heater 22a that generates less heat and consumes less power than the heater lamp 23 on the heating roller side. The pressure heater 22a is energized while the fixing device 20 is on standby and functions as a heat retaining heater. During the fixing operation, power is supplied to the heater lamp 23, and therefore the pressure heater 22a is not energized.

  The operation of the fixing device 20 will be described with reference to FIG. When energization of the heating roller 21 is started and the surface temperature reaches about 180 ° C. by the temperature sensor 24 in contact with the surface of the heating roller 21, the recording medium P on which the unfixed toner image is formed is conveyed to the conveyance guide. 25, the sheet is conveyed to the fixing nip portion between the heating roller 21 and the pressure roller 22 while being guided by the heat roller 25, and is heated and pressed while passing through the fixing nip portion to be fixed.

  The fixed recording medium P is separated from the roller surface due to the difference in the curvature of the roller peripheral surface caused by the hardness difference between the heat-resistant elastic layers of the heating roller 21 and the pressure roller 22, and is not shown while being guided by the discharge guides 26 and 27. It is discharged to the discharge tray. A heat-resistant resin separation claw 28 is disposed close to the heating roller 21 to assist the separation of the recording medium P from the heating roller.

  FIG. 4 is a view for explaining the heater lamp 23 arranged inside the heating roller 21 and the temperature distribution in the axial direction of the heating roller. FIG. 4A shows the arrangement of the filament 23 f inside the heater lamp 23. FIG. 4B shows the temperature distribution in the axial direction of the heating roller heated by the heater lamp 23. In FIG. 4B, the line X is the temperature distribution when the heater lamp is not moved, and the line Y is the temperature distribution when the heater lamp is reciprocated. The reciprocating movement of the heater lamp is 20 times per minute.

  As described above, since many filaments 23f are arranged in series at predetermined intervals in the axial direction inside the heater lamp 23, when the heater lamp 23 is fixedly arranged, the temperature distribution in the axial direction of the heating roller The temperature of the part corresponding to the part of the filament 23f becomes higher than the temperature of the part without the filament 23f, and the temperature difference reaches 20 ° C. at the maximum.

  For this reason, immediately after the heating roller is energized and the surface temperature reaches approximately 180 ° C., the surface temperature of the heating roller is uneven, and the low temperature part becomes insufficiently fixed and the gloss is lowered. In the worst case, a low temperature offset occurs. To do.

  Therefore, in the present invention, the heater lamp 23 is reciprocated in the axial direction to reduce the temperature unevenness in the axial direction of the heating roller. The temperature distribution in the axial direction of the heating roller in this case is as indicated by a line Y in FIG. 4B, which is smaller than the temperature distribution (line X) when the heater lamp 23 is fixed, and the temperature difference is 10 The temperature could be decreased below ℃.

  FIG. 5 is a conceptual diagram illustrating the configuration of the heater lamp axial movement mechanism 30. Both ends of the heating roller 21 are rotatably held by a side plate of a fixing device (not shown) via a bearing, and the driving side of the heating roller 21 is connected to a heating roller driving gear 31 and is driven by a driving source (not shown). It is configured to be. In addition, a heater driving cam 33 that is rotationally driven by a heater driving gear 32 that meshes with the heating roller driving gear 31 is disposed inside the fixing device.

  The ceramic terminal 23a on the driving side of the heater lamp 23 is held by a driving side heater holder 34 made of heat-resistant resin so as to be movable in the axial direction at the center position of the heating roller 21, and on the non-driving side of the heater lamp 23. The ceramic terminal 23b is held by a non-driving side heater holder 35 made of heat-resistant resin so as to be movable in the axial direction at the center position of the heating roller 21, and the non-driving side heater holder 35 is moved in the direction of arrow a by a return spring 36. Therefore, the drive side heater holder 34 is always in contact with the heater drive cam 33.

  With this configuration, when the heater drive cam 33 is rotated by the heater drive gear 32 that meshes with the heating roller drive gear 31, the drive side heater holder 34 that is always in contact with the heater drive cam 33 moves in the direction indicated by the arrow a (solid line position). The heater lamp 23 held by the drive side heater holder 34 also reciprocates in the direction of arrow a (solid line position) and in the opposite direction (chain line position).

  The interval between the reciprocating movements may be approximately ½ of the interval between the filaments 23 f arranged inside the heater lamp 23. Further, the reciprocating speed (number of times) of the heater lamp 23 is determined in consideration of the effect of correcting the intensity of the heater lamp and temperature unevenness, but it is appropriate to be about 10 to 60 times per minute according to experiments.

  The axial movement mechanism of the heater lamp is not limited to the above configuration, and a known movement mechanism may be adopted.

  Moreover, in the said embodiment, although one heater axial direction moving mechanism lamp | ramp is used, a several heater lamp | ramp can also be used and the same effect can be acquired.

  FIG. 6 is a cross-sectional view illustrating the configuration of the fixing device 40 according to the second embodiment. The fixing device 40 according to the second embodiment includes a heating roller 41 and a pressure belt 42.

  In the heating roller 41, a silicone rubber layer is formed as a heat-resistant elastic layer on the surface of a metal core, and the surface is covered with a heat-resistant release layer composed of a fluororesin or a silicone rubber layer. As an example of the dimensions of the heating roller 41, a metal cored bar uses an iron pipe with a diameter of 36 mm and a thickness of 0.6 mm, a silicone rubber layer has a thickness of 1.8 mm, and a heat-resistant release layer has a thickness of 30 μm. Consists of. The materials, numerical values, etc. shown here are merely examples, and the present invention is not limited to these.

  A heater lamp 43 is disposed inside the heating roller 41 and is configured to move in the axial direction. A temperature sensor 44 is disposed in contact with the surface of the heating roller 41, and energization control of the heater lamp 43 is performed by a temperature control device (not shown) to maintain the surface temperature of the heating roller 41 at a temperature suitable for the fixing process. To be controlled.

  The heater lamp 43 is the same as the heater lamp 43 described in the first embodiment, and a large number of filaments are connected in series inside. Although a configuration for reciprocating in the axial direction is provided in order to eliminate temperature unevenness, the mechanism is the same as that in the first embodiment, and the description thereof is omitted.

  The pressure belt 42 is an endless belt made of polyimide resin, and the pressure belt 42 is in pressure contact with the surface of the heating roller 41 by an elastic pad 45 disposed inside and a pressure contact pad 47.

  As an example of the dimensions of the pressure belt 42, a 30 μm PFA film is coated to prevent dirt from adhering to the surface of a polyimide resin having a thickness of 80 μm. The materials, numerical values, etc. shown here are merely examples, and the present invention is not limited to these.

  The elastic pad 45 is made of silicone rubber and is pushed up toward the heating roller 41 by a press contact spring 46 fixed to the support frame 48. The pressure contact pad 47 is disposed on the recording medium discharge side and deforms the elastic layer of the heating roller 41 to facilitate discharge of the recording medium. The pressure contact pad 47 is made of a liquid crystal polymer and is fixed to the support frame 48. .

  The support frame 48 is fixed to a pressure contact lever (not shown), and is configured to press the elastic pad 45, the pressure contact pad 47, and the like toward the pressure belt 42 by a pressure contact spring (not shown). The pressure belt 42 is rotated by the rotational driving of the heating roller 41.

  The operation of the fixing device 40 will be described with reference to FIG. When the energization of the heating roller 41 is started and the surface temperature reaches about 180 ° C. by the temperature sensor 44 in contact with the surface of the heating roller 41, the recording medium P on which the unfixed toner image is formed is conveyed to the conveyance guide. While being guided by 50, it is conveyed to the fixing nip portion between the heating roller 41 and the pressure belt 42, heated and pressurized while passing through the fixing nip portion, and subjected to a fixing process.

  The fixed recording medium P is separated from the surfaces of the heating roller 41 and the pressure belt 42 due to the hardness difference between the heating roller 41 and the pressure contact pad 47 pressing the pressure belt 42, and is guided by discharge guides 51 and 52. However, it is discharged to a discharge tray (not shown). A heat-resistant resin separation claw 53 is disposed close to the heating roller 41 to assist in separating the recording medium P from the heating roller.

  The image forming apparatus to which the fixing device described above is applied can be applied to, for example, an electrophotographic image forming apparatus, a color, a monochrome copying machine, a printer, a fax machine, and a multifunction machine of these.

  The fixing device is applied to an electrophotographic image forming apparatus having a heating roller in which a heater lamp disposed inside the heating roller is reciprocated in the axial direction to eliminate uneven surface temperature of the heating roller having a low heat capacity.

1 is a diagram illustrating a configuration of a tandem full-color image forming apparatus. FIG. FIG. 3 is a cross-sectional view illustrating the configuration of the fixing device according to the first embodiment. Sectional drawing of the heating roller of 1st Embodiment. The figure explaining the temperature distribution of the heater lamp arrange | positioned inside a heating roller, and the axial direction of a heating roller. The conceptual diagram explaining the structure of the axial direction moving mechanism of a heater lamp. Sectional drawing explaining the structure of the fixing device of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Tandem type full color image forming apparatus 10A Main motor 11, 12, 13, 14 Image forming unit 11T, 12T, 13T, 14T Primary transfer roller 15 Drive roller 15T Secondary transfer roller 16 Driven roller 17 Intermediate transfer belt 18 Cleaning device 20 Fixing device (fixing device according to the first embodiment)
DESCRIPTION OF SYMBOLS 21 Heating roller 22 Pressure roller 22a Pressure heater 23 Heater lamp 23a, 23b Ceramic terminal 23f Filament 24 Temperature sensor 25 Transport guide 26, 27 Discharge guide 28 Separation claw 30 Heater lamp axial movement mechanism 31 Heating roller drive gear 32 Heater Drive gear 33 Heater drive cam 34 Drive side heater holder 35 Non-drive side heater holder 36 Return spring 40 Fixing device (fixing device of the second embodiment)
41 Heating roller 42 Pressure belt 43 Heater lamp 44 Temperature sensor 45 Elastic pad 46 Pressure contact spring 47 Pressure contact pad 48 Support frame 50 Transport guide 51, 52 Discharge guide 53 Separation claw

Claims (8)

Heating for fixing the toner image by passing the recording medium on which the toner image is formed through a nip formed between the heating rotator and a pressure rotator arranged in pressure contact with the heating rotator. In the fixing device,
The heating fixing device is characterized in that the heating rotator includes a heating heater that reciprocates in the direction of the rotation axis of the heating rotator. 2. The heat fixing apparatus according to claim 1, wherein the heater is a heater lamp including a heating element in which a large number of filaments are arranged at a predetermined interval. The heat fixing apparatus according to claim 1, wherein the heat fixing apparatus includes a drive mechanism that reciprocates the heater for heating in the direction of the rotation axis of the heating rotator. The heating and fixing apparatus according to claim 3, wherein the driving mechanism includes a driving cam mechanism that uses a driving mechanism that rotationally drives the heating rotator as a driving source. 5. The heat fixing according to claim 3, wherein the drive mechanism is a drive mechanism that reciprocates a distance that is approximately a half of an arrangement interval of filaments that are heating elements arranged in a heater lamp. apparatus. 2. The heat fixing apparatus according to claim 1, wherein the heating rotator is a heating roller configured such that a heat resistant elastic layer is coated on a surface of a metal core and a heat resistant release layer is coated on the surface thereof. 2. The heat fixing device according to claim 1, wherein the pressure rotator is a pressure roller configured such that a heat resistant elastic layer is coated on a surface of a metal core and a heat resistant release layer is coated on the surface thereof. . 2. The heat fixing apparatus according to claim 1, wherein the pressure rotator is an endless belt made of a heat resistant synthetic resin and having a heat resistant release layer coated on a surface thereof.

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