JP2005099104A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device for shortening the warm-up time by suppressing power consumption to be low. <P>SOLUTION: The fixing device includes an endless fixing belt 45, stretched in between the fixing roller 41 and a support roller 44, a heating roller 47 incorporating a heat source, a pressure roller 42 contacting on the fixing roller 41 by pressure the fixing belt 45. The fixing device conducts fixing via a recording material K, carrying a toner image t of non-fixing on a nip part N in between the fixing belt 45 and the pressure roller 42. The heating roller 47 is contacted and arranged on an outer peripheral face 45a of the upstream-side fixing belt 45 farther in the belt-running direction A than from the nip part N. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a belt-fixing type fixing device for fixing an unfixed image, and an image forming apparatus such as a copying machine, a printer, and a facsimile machine including the fixing device.

  In an image forming apparatus that creates recording paper using an electrophotographic system, such as an electrophotographic copying machine or a laser beam printer, a toner image is formed on an image carrier such as a photosensitive drum, and the toner image is formed on a sheet. After the transfer, means for fixing through a fixing device is used. As the fixing device, a heat roller type device is often used because of its simple structure and easy miniaturization. In the heat roller type fixing device, the heating roller and the pressure roller are arranged so as to face each other and can be heated using a heating lamp or the like disposed inside the heat roller. Therefore, it can be easily incorporated into a small image forming apparatus.

  However, in the case of a heat roller type fixing device as described above, there is a concern that a device that requires a large amount of heat for heating, such as a color copying device, cannot perform sufficient heating. There are many. Accordingly, in order to solve the above-described problems, it has been proposed to configure a fixing device using a fixing belt as disclosed in, for example, Japanese Patent Laid-Open No. 5-273766. In the conventional example, the sheet is run while pressing the toner image carrying surface of the sheet against the endless fixing belt, and a means for heating from the back surface of the fixing belt is provided. The fixing operation is performed while pressing the fixing belt.

  As a fixing device using a fixing belt, for example, a device disclosed in Japanese Patent Laid-Open No. 2000-66541 is known. The fixing device is detachably attached to the printer main body. This fixing device is assembled by attaching a heating roller having a built-in heater and a unit in which an endless fixing belt is wound around the fixing roller and incorporated into a cover to be detachably attached to the apparatus main body including the pressure roller. . The fixing belt is heated by a heater built in the heating roller. Then, the sheet on which the toner image is transferred is conveyed between the fixing roller around which the fixing belt is wound and the pressure roller, and the toner image is melted and fixed on the sheet by heat applied from the fixing belt. In this fixing device, a unit in which members such as a fixing belt having a relatively short service life are integrated can be attached to and detached from the fixing device body, thereby facilitating replacement of the unit and improving maintainability.

Further, as another fixing device using a fixing belt, a device disclosed in Japanese Patent Application Laid-Open No. 8-292669 is known. In this fixing device, an endless fixing belt is wound and stretched around three rollers including a driving roller, a heater is disposed inside the fixing belt, and a pressure roller is attached to the driving roller via the fixing belt. It is configured by pressing. The fixing belt is heated from the back side by a heater. Then, the paper on which the toner image is transferred is conveyed between the driving roller and the pressure roller around which the fixing belt is wound, and the toner image is melted and fixed on the paper by heat applied from the fixing belt.
Japanese Patent Laid-Open No. 5-273766 JP 2000-66541 A JP-A-8-292669

  However, in the above-described fixing device disclosed in Japanese Patent Application Laid-Open No. 2000-66541, the fixing belt is heated by a heater built in the heating roller, so that the heat from the heater is heated to the heating roller, the fixing belt back surface, the fixing belt. There is a problem that a large amount of time is required until the temperature of the fixing belt surface is raised to a desired temperature, and it takes a long time to warm up the fixing device. In addition, for example, heat escapes to the cover via the rotating shaft of the heating roller, so that there is a problem that more heat energy is required than necessary to bring the surface of the fixing belt to a desired temperature and power consumption increases. .

  In the fixing device disclosed in Japanese Patent Laid-Open No. 5-273766 or Japanese Patent Laid-Open No. 8-292669, the belt itself is directly heated by a heater disposed inside the fixing belt. Since heat is transferred to the fixing belt surface after being transferred to the back surface of the fixing belt, for example, the heat escapes through the rotation shafts of three rollers in contact with the back surface of the fixing belt, and the temperature of the fixing belt surface is raised to a desired temperature. There has been a problem that much time and heat energy are required.

  Accordingly, the present invention has been made in view of the above points, and an object of the present invention is to provide a fixing device capable of suppressing power consumption and shortening the warm-up time, and an image forming apparatus including the fixing device. It is in.

  According to the first aspect of the present invention, an endless fixing belt stretched between a fixing roller and a support roller, a heating roller having a built-in heat source, and pressure applied to the fixing roller via the fixing belt. A fixing device that performs fixing through a recording material carrying an unfixed toner image in a nip portion between the fixing belt and the pressure roller, wherein the heating roller is located upstream of the nip portion in the belt traveling direction. The fixing device is disposed in contact with an outer peripheral surface of the fixing belt. In this configuration, since the belt surface is directly heated on the upstream side of the nip portion between the fixing belt and the pressure roller, heat necessary for melting the toner at the nip portion between the fixing belt and the pressure roller is generated. It can supply efficiently, increase energy efficiency, and shorten the time required for warming up the fixing device.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the heating roller applies a tension to the fixing belt. In this configuration, the tensioning roller is not added as a separate member to apply tension to the fixing belt, and the running of the fixing belt is stabilized, speed unevenness due to slip or the like is eliminated, and a recording material carrying an unfixed image ( Paper) can be stably conveyed. In addition, when a tension roller is added as another member for applying tension to the fixing belt, heat that escapes to the tension roller is prevented, so that energy efficiency can be improved and the time required for warming up the fixing device can be shortened.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the fixing belt includes a heat-resistant heat-insulating elastic layer. In this configuration, the heat insulating layer prevents heat from escaping to the back side of the belt, increases energy efficiency, and shortens the time required for warming up the fixing device. Further, since the fixing belt has elasticity in the layer direction, pressure unevenness at the nip between the fixing belt and the pressure roller is reduced, and a uniform gloss can be obtained in a fixed image.

  According to a fourth aspect of the present invention, in the fixing device according to the third aspect, the fixing belt includes a release layer made of a fluororesin around a heat-resistant heat-insulating elastic layer. It is. In this configuration, since offset can be suppressed without applying silicone oil as a release agent to the belt surface, an inexpensive fixing device can be provided without adding a complicated oil application mechanism. In addition, energy efficiency can be improved by preventing heat escaping to the oil application mechanism, and the time required for warming up the fixing device can be shortened.

  Further, according to the present invention, the electrostatic latent image formed on the image carrier is visualized as a toner image by a developing means, and the toner image is transferred onto a recording material. An image forming apparatus for fixing a transferred recording material through a fixing device, wherein the fixing device is the one described in any one of claims 1 to 4. With this configuration, the energy efficiency of the image forming apparatus can be increased, and the time required for warming up the fixing apparatus can be shortened.

  According to the first aspect of the present invention, since the fixing belt surface is directly heated on the upstream side of the nip portion between the fixing belt and the pressure roller, the toner is formed at the nip portion between the fixing belt and the pressure roller. The heat required to melt the toner can be efficiently supplied, energy efficiency can be improved, and the time required for warming up the fixing device can be shortened.

  According to the second aspect of the present invention, since the heating roller applies tension to the fixing belt, the belt travels without adding a tension roller as a separate member for applying tension to the fixing belt. Is stabilized, speed unevenness due to slip or the like is eliminated, and a recording material (paper) carrying an unfixed image can be stably conveyed. Further, when another member is added, the heat that escapes to the tension roller is prevented, so that energy efficiency can be improved and the time required for warming up the fixing device can be shortened.

  According to the third aspect of the present invention, it is possible to prevent heat from escaping to the back side of the belt by having the heat insulating layer, increase energy efficiency, and shorten the time required for warming up the fixing device. In addition, since the belt has elasticity in the layer direction, pressure unevenness at the fixing nip is reduced, and a uniform gloss can be obtained in a fixed image.

  Further, according to the present invention, since the offset can be suppressed without applying silicone oil as a release agent to the belt surface, an inexpensive fixing device can be provided without adding a complicated oil application mechanism. Can be provided. In addition, energy efficiency can be improved by preventing heat escaping to the oil application mechanism, and the time required for warming up the fixing device can be shortened.

  According to the present invention described in claim 5, it is possible to obtain an image forming apparatus having high energy efficiency and short warm-up time.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a color printer according to an embodiment of the present invention. FIG. 1 schematically shows a configuration of a four-tandem full-color printer as an image forming apparatus according to an embodiment of the present invention.

  This full-color printer is an electrophotographic type 4 for forming toner images of four colors of yellow, magenta, cyan, and black on the surfaces of the corresponding photosensitive drums 1Y, 1M, 1C, and 1Bk (image carrier). A set of image forming units 10Y, 10M, 10C, and 10Bk (image forming means) is provided.

  Below these image forming units 10Y, 10M, 10C, and 10Bk, a conveying belt 20 is stretched to convey a sheet (recording material) through each image forming unit. The photosensitive drums 1Y, 1M, 1C, and 1Bk of the image forming units 10Y, 10M, 10C, and 10Bk are respectively arranged in contact with the conveyance belt 20, and the sheet (recording material) is electrostatically applied to the surface of the conveyance belt 20. Adsorbed.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk have substantially the same structure. Therefore, here, the yellow image forming unit 10Y disposed on the most upstream side in the sheet conveyance direction will be described as a representative, and the other color image forming units 10M, 10C, and 10Bk are denoted by the same reference numerals. Detailed description is omitted.

  The image forming unit 10Y has a photosensitive drum 1Y that is in contact with the conveyance belt 20 at a substantially central position. Around the photosensitive drum 1Y, a charging device 2Y for charging the surface of the photosensitive drum 1Y to a predetermined potential, the charged drum surface is exposed based on the color-separated image signal, and the surface of the drum is electrostatically charged. An exposure device 3Y that forms a latent image, a developing device 4Y that supplies yellow toner to the electrostatic latent image formed on the drum surface and develops it, and a developed toner image on a sheet that is conveyed via the conveyance belt 20 A transfer roller 5Y (transfer device) for transferring, a cleaner 6Y for removing residual toner remaining on the drum surface without being transferred, and a charge eliminating lamp for removing electric charge remaining on the drum surface (not shown) are provided in the rotational direction of the photosensitive drum 1Y. Are disposed in order.

  A paper feed mechanism 30 for feeding paper onto the transport belt 20 is disposed on the lower right side of the transport belt 20 in the drawing. A fixing device 40 according to an embodiment of the present invention, which will be described in detail later, is disposed on the left side of the conveyance belt 20 in the drawing. The paper transported by the transport belt 20 is transported through a transport path continuously extending from the transport belt 20 through the fixing device 40 and passes through the fixing device 40.

  The fixing device 40 heats and pressurizes the conveyed paper, that is, the paper on which the toner images of the respective colors are transferred. Then, the toner images of the respective colors are melted and permeated into the paper to be fixed. In addition, the paper is discharged to the downstream side of the conveyance path of the fixing device 40 via a paper discharge roller.

  Next, the fixing device 40 according to the embodiment of the present invention described above will be described in detail with reference to FIG. FIG. 2 is a schematic view of a fixing device according to an embodiment of the present invention. As shown in FIG. 2, the fixing device 40 includes a fixing roller 41 and a pressure roller 42 that are disposed in a positional relationship that sandwiches the sheet conveyance path vertically. The fixing roller 41 is formed by forming a heat-resistant sponge rubber layer on the outer periphery of a metal core. A sheet as an example of the recording material K is conveyed at a constant speed on the conveyance path in a posture with the surface onto which the toner image t is transferred facing up. The sheet is conveyed in a posture in which the front surface faces the fixing roller 41 and the back surface faces the pressure roller 42. In this embodiment, the pressure roller 42 is pressed upward in the figure by the spring 43, and the pressure roller 42 is pressed toward the fixing roller 41. However, since the pressing force is generated between the two, the fixing roller 42 is fixed. The roller 41 may be pressed toward the pressure roller 42.

  In the present embodiment, a rotational driving force is transmitted to the pressure roller 42 via a gear (not shown), and the fixing roller 41 is driven to rotate. Instead of rotationally driving the pressure roller 42, the fixing roller 41 may be rotationally driven. Alternatively, the pressure roller 42 and the fixing roller 41 may be engaged with each other by a gear so that both the pressure roller 42 and the fixing roller 41 are rotationally driven.

  The fixing device 40 includes an endless fixing belt 45 stretched between a fixing roller 41 and a support roller 44 having a heat-resistant sponge rubber layer formed on the outer periphery of a metal core. The structure of the fixing belt 45 will be described in detail later.

  In this way, the fixing belt 45 stretched between the fixing roller 41 and the support roller 44 travels endlessly in a state where the outer peripheral surface is in contact with the surface of the sheet conveyed on the conveyance path. The outer peripheral surface of the pressure roller 42 is in contact with the back surface of the conveyed paper P. In other words, the conveyed sheet passes through the nip portion N between the outer peripheral surface 45 a of the fixing belt 45 and the outer peripheral surface of the pressure roller 42 and is pressed.

  A heating roller 47 incorporating a halogen lamp (heater) 46 is disposed in contact with the outer peripheral surface of the fixing belt 45 upstream of the nip portion N between the fixing belt 45 and the pressure 42 roller in the belt running direction A, and the fixing belt 45 45 is heated from its outer peripheral surface 45a over its entire width. The heating roller 47 is a hollow pipe made of a metal having good heat conductivity, and a halogen lamp 46 (heater) is disposed in the hollow portion. A heat resistant black paint is applied to the inner peripheral surface of the heating roller 47 in order to efficiently absorb the heat energy radiated from the halogen lamp 46.

  The heating roller 47 is pressed by the spring 48 in the left direction in the figure. Tension is applied to the fixing belt 45 by pressurizing the outer peripheral surface 45 a of the fixing belt 45. Further, a nip is formed between the heating roller 47 and the outer peripheral surface 45a of the fixing belt 45, and the heat radiated from the halogen lamp 46 is transferred to the surface of the heating roller and is transmitted to the fixing belt 45 through this nip.

  The first thermistor 49b has a detection end at a position facing the position upstream of the nip portion N between the fixing belt 45 and the pressure roller 42 in the belt traveling direction A and downstream of the heating roller 47. The fixing belt 45 is disposed so as to contact the outer peripheral surface. In this manner, the first thermistor 49b is brought into contact with the outer peripheral surface of the fixing belt 45 at the portion wound around the fixing roller 41, so that the contact state between the two is stabilized and variation in temperature detection is prevented. did. Further, a second thermistor 49a is disposed on the outer periphery of the heating roller so that the temperature of the outer surface of the heating roller can be monitored.

  Here, the operation of the fixing device 40 described above will be described. First, when the printer is turned on, the warm-up operation of the fixing device 40 is started. In the warm-up operation, the halogen lamp 46 is turned on and heating of the heating roller 47 is started. The temperature of the outer peripheral surface of the heating roller 47 is monitored via the second thermistor 49a, and when the predetermined temperature is reached, the belt travel (followed by the pressure roller rotation drive) is started. The temperature of the outer peripheral surface 45a of the fixing belt 45 is monitored via the first thermistor 49b, and when the temperature reaches a predetermined set temperature, the warm-up operation is finished. That is, by the warm-up operation, the outer peripheral surface 45a of the fixing belt 45 is heated to a set temperature necessary for fixing.

  In the warming-up operation described above, heat from the halogen lamp 46 is transmitted to each member as follows. The heat from the halogen lamp 46 is effectively absorbed by the black paint on the inner surface of the heating roller 47 and transmitted to the outer peripheral surface of the heating roller 47. The heat transmitted to the outer peripheral surface of the heating roller 47 is transmitted to the outer peripheral surface 45 a of the fixing belt 45 through the nip with the fixing belt 45.

  The heat transmitted to the outer peripheral surface 45 a of the fixing belt 45 is transmitted in the thickness direction toward the inner surface thereof and reaches the inner surface of the fixing belt 45. The heat transmitted to the inner surface of the fixing belt 45 is transmitted to the outer peripheral surface of the fixing roller 41 and the outer peripheral surface of the support roller 44 that are in contact with the inner surface. The heat transmitted to the outer peripheral surfaces of the fixing roller 41 and the support roller 44 is transmitted so as to escape to the printer casing via the respective rotation shafts.

  Further, the heat transmitted to the outer peripheral surface 45 a of the fixing belt 45 is transmitted to the outer peripheral surface 42 a of the pressure roller 42 through the nip portion N as the fixing belt 45 travels, and the outer peripheral surface of the fixing belt 45. It is transmitted to the first thermistor 49b arranged in contact with 45a. The heat transmitted to the pressure roller 42 is transferred through the rotating shaft and the spring 43 so as to escape to the printer casing.

  Of the heat transmitted between the members in this way, the heat directly related to the fixing of the toner image is the heat transmitted from the outer peripheral surface 45a of the fixing belt 45 to the surface of the sheet. The heat transferred to the other members is wasted without being used for fixing. For fixing the toner image, a constant pressure at the nip portion N is required in addition to the heat.

  In other words, the conditions under which the toner image can be fixed on the paper are slightly different depending on the physical properties of the toner, the paper material / thickness, the paper conveyance speed, etc., but the fixing belt 45 and the pressure roller 42 are pressed with a constant pressing force. Thus, it is necessary to form a nip portion N having a predetermined width between them and to raise the temperature of the outer peripheral surface 45a of the fixing belt 45 to a set temperature. If these conditions are not satisfied, for example, insufficient heating of the outer peripheral surface 45a of the fixing belt 45 causes fixing failure and cold offset.

  By the way, in order to suppress the power consumption required for the warming-up operation as low as possible and to shorten the time required for the warming-up operation as much as possible as the object of the present invention, the temperature is efficiently increased to the set temperature of the outer peripheral surface 45a of the fixing belt 45. It is desirable to warm.

  In the present embodiment, a heating roller 47 incorporating a heater is disposed in contact with the outer peripheral surface 45a of the fixing belt 45 on the upstream side of the nip portion N in the belt traveling direction A, and the outer peripheral surface 45a of the fixing belt 45 is By directly heating, the heat to escape was minimized. As a result, for example, compared with the conventional apparatus disclosed in the above-mentioned JP-A-2000-66541 and JP-A-8-292669, that is, an apparatus of a type in which an endless fixing belt is wound around a plurality of rollers. Thus, the “escape path” through which heat escapes from the fixing belt can be reduced, and the temperature of the fixing belt 45 can be increased efficiently in a short time with less heat energy. Therefore, as a result, it is possible to reduce power consumption and shorten the time required for warming up.

  Further, in this embodiment, in order to reduce the “escape path” of heat, a configuration having a heat insulating elastic layer is employed as the configuration of the fixing belt 45. FIG. 3 is a cross-sectional view of a fixing belt according to an embodiment of the present invention. As shown in FIG. 3, in the fixing belt 45 of this embodiment, a heat insulating elastic layer 452 is formed by coating silicone rubber with a thickness of 200 μm on the outside of a base film 451 having a thickness of 90 μm made of a resin material such as polyimide. A release layer 453 made of a fluororesin is formed outside the heat insulating elastic layer 452.

  The base film 451 is required to have heat resistance and mechanical strength. For example, a metal such as Ni or SUS may be employed as the base film 451. The heat insulating elastic layer 452 of the fixing belt 45 may be formed of a material that can uniformly apply heat and pressure to toner and paper, can exhibit stable fixing performance, and has excellent heat insulating properties. Not limited to rubber.

  Thus, by forming the heat insulating elastic layer 452 on the inner surface side of the fixing belt 45, it is possible to suppress heat from escaping to the fixing roller 41 and the support roller 44 that are members disposed in contact with the inner surface of the fixing belt 45. The temperature of the fixing belt 45 can be increased more efficiently, the power consumption can be kept lower, and the warm-up time can be further shortened.

  Further, a release layer 453 made of a fluororesin was formed on the outer peripheral surface 45 a of the fixing belt 45. In order to prevent toner offset in the conventional fixing device, a method of applying and impregnating silicone oil as a release agent to the silicone rubber layer is known, but the oil application mechanism is complicated and expensive, and the oil application mechanism There is a problem that heat loss due to contact of the toner with the outer peripheral surface of the fixing belt 45 is large. The release layer 453 (fluororesin layer) is a heat insulating elastic layer made of a known fluororesin such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl), FEP (fluorinated ethylene propylene) or a blended material thereof. It is obtained by coating and baking on 452 via a primer. Or you may wear a fluororesin tube.

  As described above, the release layer 453 made of fluororesin is formed on the outer peripheral surface 45 a of the fixing belt 45 to suppress offset without adding a complicated oil application mechanism. Since it does not contact the outer peripheral surface, it is possible to suppress the escape of heat to the oil application mechanism, the temperature of the fixing belt 45 can be raised more efficiently, the power consumption can be kept lower, and the warm-up time can be further shortened. In addition, this invention is not limited to the said Example. That is, various modifications can be made without departing from the scope of the present invention.

1 is a schematic diagram of a color printer according to an embodiment of the present invention. 1 is a schematic view of a fixing device according to an embodiment of the present invention. 1 is a cross-sectional view of a fixing belt according to an embodiment of the present invention.

Explanation of symbols

1Y, 1M, 1C, 1Bk photoconductor drum (image carrier)
4Y, 4M, 4C, 4Bk developing device (developing means)
10Y, 10M, 10C, 10Bk Image forming unit 40 Fixing device 41 Fixing roller 42 Pressure roller 44 Support roller 45 Fixing belt 45a Outer peripheral surface 46 Halogen lamp (heat source)
47 Heating roller 48 Spring 452 Thermal insulation elastic layer 453 Release layer A Belt running direction K Recording material N Nip part

Claims (5)

  An endless fixing belt stretched between a fixing roller and a support roller, a heating roller having a built-in heat source, and a pressure roller in pressure contact with the fixing roller via the fixing belt; In a fixing device for fixing through a recording material carrying an unfixed toner image in a nip portion with the pressure roller, the heating roller is disposed in contact with the outer peripheral surface of the fixing belt upstream of the nip portion in the belt running direction. A fixing device.   The fixing device according to claim 1, wherein the heating roller applies tension to the fixing belt.   3. The fixing device according to claim 1, wherein the fixing belt includes a heat-resistant heat-insulating elastic layer.   4. The fixing device according to claim 3, wherein the fixing belt includes a release layer made of a fluororesin around a heat-resistant heat-insulating elastic layer.   The electrostatic latent image formed on the image carrier is visualized as a toner image by developing means, the toner image is transferred onto a recording material, and the recording material on which the toner image is transferred is passed through a fixing device and fixed. 5. The image forming apparatus according to claim 1, wherein the fixing device is the one according to claim 1.

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