CN1770040A - Fixing device and image forming apparatus including the same - Google Patents

Abstract

A fixing device and an image forming apparatus are provided that shorten warming-up time, reduce power consumption and deviation of a belt, and surely fix a toner image onto a sheet. Support members and a pressurizing member contact each other with pressure at an upstream side and a downstream side in a carrying direction of a recording medium. A first interposing portion of the belt disposed between the support members is inserted between the support members and the pressurizing member and is installed in a tensed state. A second interposing portion of the belt is installed in a non-tensed state, the pressurizing member contacts the outside of the first interposing portion to form the fixing nip portion. The support members contact the pressurizing member with different pressures at the upstream side and the downstream side in the carrying direction of the recording medium.

Description

Fixing device and image forming apparatus including same

technical field

The present invention relates to a fixing device installed in an electrophotographic image forming apparatus, such as a laser printer or a laser facsimile, and an image forming apparatus including the same.

Background technique

In an electrophotographic image forming apparatus, a photosensitive drum is uniformly charged and exposed by a laser scanning device to form an electronic latent image thereon according to an image signal. The charged toner is supplied to the photosensitive drum to develop the electrostatic latent image with a developer and form a toner image. The toner image is transferred onto a sheet (a type of recording medium). Since the toner image transferred onto the page is not fixed, the toner image is heated and pressed by the fixing device included in the image forming apparatus, so that the toner image is melted by the heat, thereby forming a fixed image on the page. Image.

A conventional fixing device generally includes a cylindrical metal heating roller (electrical heating element), a pressure roller (pressing element) that is in contact with the heating roller (pressing element), and is installed on the heating roller and heats the heating roller by radiant heat. halogen lamp (heat source). In a fixing device (two-roller type), a sheet with a toner image is inserted and conveyed into a fixing nip formed by a heat roller and a pressure roller. The toner image is then heated by the heat in the heated roller and fused to the sheet by squeeze-type contact between the heated roller and the pressure roller.

In a conventional fixing device, it takes a long time to heat the heating roller from room temperature to a fixing temperature between 160°C and 200°C. Therefore, the warm-up time from the application of power to the start of the printing operation is considerably long. Furthermore, in order to shorten the period from the print preparation time to the print start time, the fixing device should be kept at a high temperature. However, in order to keep the fixing device at a high temperature, the fixing device needs to be heated by a halogen lamp, thus increasing power consumption.

Therefore, fixing devices capable of shortening warm-up time and reducing power consumption have been proposed.

For example, an electromagnetic induction heating type fixing device includes a cylindrical or semicircular holder. A cylindrical thin film is formed on a stent by laminating conductive layers and resistive layers. The magnetic field generating device is composed of an excitation coil and a magnetic core and is installed on a support. The pressure roller presses and contacts the outer peripheral surface of the film to form a fixing nip. According to the fixing device of the electromagnetic induction heating type, the magnetic flux generated by the magnetic field generating device generates an eddy current. The eddy current generates Joule heat in the conductive layer, and the Joule heat increases the temperature of the fixing nip. When the electromagnetic induction heating type fixing device heats the fixing nip to the fixing temperature, the temperature of the fixing nip can be increased to the fixing temperature in a short time, and the preheating temperature can also be shortened. In addition, since the thin film has a low heat capacity, power consumption can be reduced. This type of fixing device has been disclosed, for example, in Japanese Unexamined Published Patent Application No. 2004-126274. However, since the fixing device requires a magnetic field generating device, the component cost increases compared to the two-roller type fixing device. In addition, since the inner peripheral surface of the film slides on the holder, the film wears out quickly, so that the service life of the film is shortened. Therefore, the range of material selection is narrowed.

In addition, the fixing device of the pressure belt type that performs pressure has a tubular pressure belt that replaces the pressure roller in the two-roller type fixing device and presses a part of it toward the heating roller. The belt applies pressure to form the fixing nip. A pressure-belt-type fixing device that performs pressure includes a heat roller that is heated by a heat source and rotates about an axis, such as a halogen lamp. The chain pressure belt is in contact with the heating roller and moves in the direction of the heating roller. The pressure member applies pressure to the surface of the pressure belt inside the heating roller in the direction of the heating roller. A pressure belt type fixing device that performs pressure is disclosed in Japanese Examined Laid-Open Patent Application No. 2004-12682. According to this fixing device, since the surface-pressurized pressure belt contacts the heating roller with pressure, a wide fixing nip is formed. Therefore, compared with the fixing device of the electromagnetic induction heating type, the warm-up time is shortened, the power consumption is reduced, and the component cost is also reduced. However, since the inner peripheral surface of the pressure belt is surface-pressed and slidable, the pressure belt is easily worn. Therefore, the use time of the pressure belt or the pressure element is shortened. Therefore, the range of material selection is narrowed.

Further, a heating belt type fixing device employs a heating belt unit using a heating belt instead of a heating roller in a two roller type fixing device, and brings a pressure roller and a heating roller into contact with pressure to form a fixing nip. The heating belt unit is composed of a chain heating belt on a supporting roller and a cylindrical heating roller winding. The cylindrical pressure roller is in contact with the inserted portion of the heating roller installed between the backup roller and the heating roller. Halogen lamps are installed in heated or pressure rollers. According to the fixing device of the heating belt type, since a wide fixing nip is formed, it is possible to shorten warm-up time and reduce power consumption. Also, since there are no sliding parts, there is no component loss and a variety of materials can be used. In addition, the component cost is also reduced more than that of the electromagnetic induction heating type fixing device. This fixing device is disclosed in Japanese Examined Laid-Open Patent Application No. 2004-205877.

However, in the conventional heating belt type fixing device, since the heating belt is stretched by the supporting roller and the heating roller and inserted under tension, if the heating roller rotates, the heating belt moves in the axial direction of the heating roller or the supporting roller, and Due to the manufacturing error or assembly error of each roller, the fluctuation of the heating belt in the width direction deviates from the predetermined track.

Therefore, for an image forming apparatus having an improved fixing device, it is necessary to securely fix a toner image on a recording medium while shortening warm-up time, reducing power consumption, and reducing belt deviation.

Contents of the invention

The present invention provides a fixing device and an image forming apparatus capable of shortening warm-up time, reducing power consumption and belt deviation, and fixing a toner image on a sheet.

According to an aspect of the present invention, the fixing device includes at least two support members, a chain belt wound around the support members and movably supported in the circumferential direction of the support members, a heat source for heating the belts, and Pressurized elements with contacts. The toner image is heated and fused on the recording medium by transferring the recording medium, and the toner image is electrostatically formed on the recording medium by the fixing nip between the belt and the pressing member. The supporting member and the pressing member are in contact with each other by the pressure on the upstream side and the downstream side in the recording medium transport direction. A first insertion portion of the strap arranged between the supporting elements is inserted between the supporting elements and the pressing element and mounted under tension. The second inserted portion of the strap is installed in a non-tensioned state. The pressing member contacts the outside of the first insertion portion to form a fixing nip. The supporting member contacts the pressing member with different pressures on the upstream side and the downstream side in the recording medium conveyance direction.

The pressure between the pressing member and the supporting member on the downstream side may be greater than the pressure between the pressing member and the supporting member on the upstream side.

According to another aspect of the present invention, an image forming device for transferring a toner image onto a recording medium to form an image has the above-mentioned fixing device.

Other objects, advantages and salient features of the present invention will become apparent from the detailed description disclosing preferred exemplary embodiments of the present invention in conjunction with the accompanying drawings.

Description of drawings

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments with reference to the accompanying drawings.

1 is a schematic diagram of an image forming apparatus including a fixing device according to an exemplary embodiment of the present invention;

FIG. 2 is a schematic diagram of a fixing device according to an exemplary embodiment of the present invention.

Throughout the drawings, the same reference numerals will be understood to refer to the same parts, elements and components.

Detailed ways

Hereinafter, a fixing device and an image forming apparatus according to exemplary embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 illustrates a schematic structure of a main part of an image forming apparatus 1 .

Referring to FIG. 1, an image forming apparatus 1 according to an exemplary embodiment includes a transfer unit 2, a plurality of image forming units (image forming units) mounted on the transfer unit 2 and electrostatically transferring a toner image onto a sheet (recording medium) X. Apparatus) 3M, 3Y, 3C, and 3BK, and a fixing device 4 for conveying a sheet X on which a toner image has been formed and fixing (fusing) the toner image to the sheet X.

First, the imaging units 3M, 3Y, 3C, and 3BK are described.

The image forming units 3M, 3Y, 3C and 3BK charge the photosensitive drum 6 . Laser light 11 is irradiated on the surface of the charged photosensitive drum 6 to perform an exposure operation. The latent image formed by the exposure operation is developed to form an image (toner image). The image is transferred onto the sheet X conveyed by the transfer belt 10 . A plurality of image forming units 3M, 3Y, 3C, and 3BK are sequentially arranged in the conveyance direction of the transfer belt 10 and form magenta, yellow, cyan, and black tones on the most upstream side in the conveyance direction of the transfer belt 10, respectively. Toner image. Each image forming unit 3M, 3Y, 3C, and 3BK includes a photosensitive drum 6 , an exposing member (exposure device) 7 , a developer (developing device) 8 , a charging roller 9 , and a cleaning unit 19 .

The photosensitive drum 6 is an example of an image forming portion, which rotates about an axis in a direction indicated by an arrow in FIG.

The exposure unit 7 scans the laser light 11 in a direction parallel to the rotation axis of the photosensitive drum 6 at the exposure position of the photosensitive drum 6 .

The developer 8 develops the latent image to form a toner image. The developer 8 charges toner powder of a predetermined color with a negative voltage, supplies the toner to the exposed portion of the photosensitive drum 6 which has a positive potential with respect to the non-exposed portion of the developing voltage, and The toner adheres to the surface of the photosensitive drum 6 . The developer 8 includes an agitator 12d for agitating and charging the toner, and a supply roller 12c for conveying the charged toner to the developing roller 12a. The developing roller 12 a supplies the toner supplied from the supply roller 12 c to the surface of the photosensitive drum 6 by electrostatic charge adsorption according to Coulomb force. The developing blade 12b controls the thickness of the developer on the developing roller 12a to a predetermined thickness.

The cleaning unit 19 includes a drum cleaning roller 19 a for contacting the photosensitive drum 6 and removing toner from the surface of the photosensitive drum 6 . A container (not shown) is disposed near the cleaning roller 19a, and serves to collect the toner removed by the cleaning roller 19a.

The charging roller 9 charges the surface of the photosensitive drum 6 to a predetermined voltage when an image is formed. The charge roller 9 includes an elastic conductor formed on a metal shaft, and is in contact with the photosensitive drum 6 at a downstream electrostatic position of the photosensitive drum cleaning roller 19a. A nip portion in which the charging roller 9 is in contact with the photosensitive roller 6 in the circumferential direction with a predetermined width is formed by the pressure relationship of elastic pressing means such as a spring. When a DC voltage is supplied to the charge roller 9, the surface of the photosensitive drum 6 is charged to a predetermined voltage. In addition, the charging roller 9 is in contact with an electrostatic roller cleaning roller 20 responsible for removing dirt on the surface of the charging roller 9 .

The transfer unit 2 is described below.

The conveying unit 2 includes roller followers 13b and 13c installed at inner peripheral portions. The chain transfer belt 10 is looped in the direction of the tension roller 14, the drive roller 13a, and the transfer roller 16a that enable the transfer belt 10 to contact the photosensitive drum 6 at the transfer position. The belt cleaning unit 17 brings the cleaning blade into contact with the transfer belt 10 so as to remove materials attached to the surface of the transfer belt 10 and has a space for collecting the attached materials.

The transfer belt 10 is made of a material that absorbs the toner on the photosensitive drum 6 by means of a transfer voltage applied to a transfer roller 16a that passes a sheet X such as a dielectric sheet while facing the photosensitive drum 6 Instead, it is in contact with the rear surface of the transfer belt 10 . In addition, the transfer belt 10 has light reflective properties.

The transfer belt 16 a includes, for example, a conductor or semiconductive synthetic rubber formed on a metal rotary shaft. A high-voltage power source (not shown) is connected to the rotation shaft of the transfer roller 16a so as to control the surface potential of the roller.

The transfer unit 18 electrostatically transfers the toner images formed by the image forming units 3M, 3Y, 3C, and 3BK onto the sheet X conveyed by the transfer belt 10 . The transfer unit 18 is composed of a transfer roller 16a and a control device 16 that controls the roller surface potential.

The fixing device 4 will be described below.

FIG. 2 is a schematic diagram showing the structure of the fixing device 4 . As shown in FIG. 2 , the fixing device 4 includes a plurality of supporting members 21 (two are shown in FIG. 2 ), and the fixing belt 22 is wound around the two supporting members and movably supported in the circumferential direction thereof. Preferably, the fixing belt 22 is a chain belt. The heating source 23 is provided in the fixing belt 22 together with the supporting member 21 and heats the inside of the fixing belt 22 . The pressing member 24 is in contact with the supporting members 21 and the fixing belt 22 interposed between the supporting members 21 by pressure.

The two supporting members 21 are cylindrical members rotating in a predetermined direction and are arranged on the upstream side (the right side of FIG. The pressing member 24 inside the fixing belt 22 (left side of FIG. 2 ) is in contact. At this time, the pressure P1 of the support member 21 provided on the downstream side (downstream support member) is greater than the pressure P2 of the support member 21 on the upstream side (upstream support member). The supporting element 21 on the downstream side is preferably a drive roller 25 rotatable about an axis by a drive mechanism (not shown). The upstream supporting member 21 is a guide roller 26 which has rotational resistance and presses against the circumferential movement of the fixing belt 22 .

The fixing belt 22 is a thin member having a length longer than the width of the sheet X and having a cylindrical shape without receiving external force. In addition, an elastic layer having a thickness of several hundreds of micrometers made of neoprene rubber such as silicon rubber is laminated on the peripheral surface of the basic coating layer comprising a metal or heat-resistant resin film and having a thickness of several tens of micrometers to 150 micrometers, and The fixing belt 22 is formed by laminating a toner release layer including a fluorocarbon resin or a modification of a fluorocarbon resin such as polymethyl methacrylate having good heat resistance and a thickness of several tens of micrometers on the elastic layer.

The fixing belt 22 is inserted and supported between the driving roller 25 and the pressing member 24 and the guiding roller 26 and the pressing roller 24 by bringing the driving roller 25 and the guiding roller 26 into contact with the pressing member 24 by pressure. Therefore, the inner surface of the fixing belt 22 is brought into contact with the driving roller 25 and the guide roller 26 by pressure and moved in the circumferential direction by the rotation of the driving roller 25 .

In this configuration, the fixing belt is fitted between the driving roller 25 and the guiding roller 26 by inserting both ends of the fixing belt between the driving roller 25 and the pressing member 24 and between the guiding roller 26 and the pressing roller 24 and applying tension. The first insertion portion 27 of the fixing belt 22 between them is fitted, while the second insertion portion 28 is assembled in a non-tensioned state.

The heating source 23 may be, for example, a halogen lamp, and its main body is disposed in the fixing belt 22 to heat the fixing belt 22 . The heat source 23 is assembled such that the main body is disposed in the vicinity of the fixing nip 29 formed by bringing the outside of the first insertion portion 27 into contact with the pressing member 24 .

The pressing member 24 is a cylindrical member that rotates about an axis in a predetermined direction, and has a metal shaft core 24a and an elastic layer 24b made of silicon rubber and wound around the metal shaft core 24a. The pressing member 24 is in contact with the first insertion portion 27 , both ends of which are inserted in the driving roller 25 and the guide roller 26 , and the outside of the first insertion portion 27 and the pressing member 24 form a fixing nip 29 . Normal pressure is applied to the fixing nip portion 29 by tension applied to the first insertion portion 27 . Since the first insertion part 27 is inserted such that the pressure P1 of the drive roller 25 is greater than the pressure P2 of the guide roller 26, the pressure between the pressing element 24 and the first insertion part 27 causes an increasing pressure gradient from the guide roller 26 to the drive roller 25. . The toner image formed on the sheet X conveyed through the fixing nip 29 is gradually pressed with a larger pressure as the sheet X is conveyed toward the drive roller 25 . That is, the toner image is pressed at the drive roller 25 with greater pressure. Further, the pressing member 24 , which is brought into contact with the outer peripheral surface of the fixing belt 22 by pressure, rotates about an axis and follows the circumferential movement of the fixing belt 22 .

The operation of the image forming apparatus 1 will now be described. Since the operation of the image forming apparatus 1 is similar to that of a typical multi-color printer, the description of the components of the image forming apparatus 1 is omitted and the operation of the fixing device 4 is described in detail.

First, when the image forming apparatus 1 is operated, the heating source 23 performs a heating step by a heating operation. Specifically, the heating operation is performed until the temperature of the fixing device 4 reaches a predetermined fixing temperature. At this time, the driving roller 25 is rotated around the axis due to a driving mechanism (not shown) and the fixing belt 22 is moved in the circumferential direction due to the rotation of the driving roller 25 . In addition, the guide roller 26 and the pressing member 24 are rotated about their respective axes by the movement of the fixing belt 22 . Furthermore, since the internal temperature of the image forming apparatus 1 increases due to heat emitted from the fixing device 4 , a fan (not shown) generates forced heat convection in the vicinity of the fixing device 4 to lower the internal temperature of the image forming apparatus 1 .

Next, when the temperature of the fixing device 4 reaches a predetermined fixing temperature, the image forming units 3M, 3Y, 3C, and 3BK form an image on the sheet X conveyed by the transfer belt 10 . That is, laser light 11 is irradiated on the surface of photosensitive roller 6 charged by charging roller 9 to form a latent image. The latent image is developed by the developer 8 to form a toner image. The toner image formed on the surface of the photosensitive drum 6 is transferred onto the sheet X conveyed by the transfer belt 10 .

Next, the sheet X on which the toner image is formed is conveyed to the fixing device 4 and the toner image is fixed on the sheet X by the fixing belt 22 and the pressing member 24 as the sheet X moves. That is, the fixing belt 22 moves in the circumferential direction and the sheet X on which the toner image is formed is inserted between the fixing belt 22 and the pressing member 24 from the starting point of the fixing nip 29 (fixed in FIG. 2 ). right side of the fixing nip 29 ) where the fixing belt 22 passes the guide roller 26 so that the pressure roller 24 comes into contact with the inside of the fixing nip 29 . The toner image formed on the sheet X is gradually melted due to the heat of the heated fixing belt 22 and fixed on the sheet X by the pressing member 24 in the fixing nip 29 . Further, the sheet X on which the toner image is fixed is conveyed from one end point (the left side of the fixing nip 29 in FIG. twenty four.

At this time, since the pressure P1 of the driving roller 25 is greater than the pressure P2 of the guide roller 26, the toner image gradually melted in the fixing nip 29 is gradually formed by a larger pressure as the sheet X moves toward the driving roller 25. Squeeze. Since a greater pressure is applied to the toner image at the driving roller 25, the toner image is fixed on the sheet X in a sufficiently fused state.

According to the fixing device 4 described above, since the pressing member 24 presses the first insertion portion 27 in the tensioned state of the fixing belt 22, which moves in the circumferential direction to form the wide fixing nip portion 29, the fixing time is made longer. And sufficient fixing can be realized. Since the heated fixing belt 22 has a low heat capacity, the heating time is shortened and energy consumption is reduced. Furthermore, since the upstream and downstream sides of the fixing nip 29 contact the supporting member 21 and the pressing member 24, respectively, the fixing nip 29 is not affected by fluctuations of the fixing belt 22 and surely maintains its length and pressure. Since the second insertion portion 28 not in contact with the pressing member 24 is installed in a non-tensioned state, the second insertion portion 28 absorbs the movement of the fixing belt 22 due to twisting of the support member 21 portion or deformation of the fixing belt 22 , and reduce the movement of the fixing belt 21 in the axial direction of the supporting member 21 . Furthermore, since the fixing device 3 does not use expensive components, it is less expensive.

Also, since the pressure P1 between the downstream supporting member 21 and the pressing member 24 is greater than the pressure between the upstream supporting member 21 and the pressing member 24, the pressure increases from the upstream side to the downstream side, whereby pressure pinching portion 29 A pressure gradient is formed in the middle so that a larger pressure is applied to the end of the fixing nip 29 . Therefore, since the toner image that gradually melts when the sheet X is conveyed to the fixing nip 29 is fixed using a pressure gradually increased from the upstream side to the downstream side of the fixing nip 29, the toner image can be fixed with certainty. on page X.

Therefore, since the heating time is shortened, the power consumption is reduced, and the deviation of the belt is reduced, and since the fixing device 4 has inexpensive components, it is possible to provide an inexpensive and reliable image forming apparatus.

Because the two support members 21 for supporting the fixing belt 22 include a drive roller 25 and a guide roller 26 that rotate about their respective axes, and a shaft-rotating roller that is in contact with the first insertion portion 27 of the fixing belt 22 by pressure. There is no sliding portion in the fixing belt 22, and thus the fixing belt 22 is not damaged due to abrasion.

Although the fixing device and the image forming apparatus have been described above according to the exemplary embodiments of the present invention, the present invention is not limited to these exemplary embodiments and modifications can be made without departing from the scope of the present invention. For example, although in the typical embodiment the pressure P1 of the downstream support element 21 in the sheet X transport direction is greater than the pressure P2 of the upstream support element 21 , the pressure of the upstream support element may be greater than the pressure of the downstream support element. In addition, although the heating source 23 is separated from the inner peripheral surface of the chain fixing belt 22, the heating source may be provided on the upstream supporting member so that the supporting member is heated with radiant heat from the heating source and the fixing is heated with the heat of the heated supporting member. bring. Alternatively, the heat source may be placed outside the chain belt or the heat source may be in contact with the electric heating element to directly heat the electric heating element.

Although in the typical embodiment, two support members 21 are provided on the upstream and downstream sides, three support members may be provided, and the upstream and downstream support members may serve as guide rollers and the other support member may serve as a driving roller.

In the typical embodiment, the guide roller 26 (upstream support member 21 ) has rotation resistance against the fixing belt 22 . Tension is applied to one insertion portion 27 by applying resistance against circumferential movement to the fixing belt 22, and the other insertion portion 28 is in a non-tensioned state, by including drive means for rotating the upstream support and the downstream support, respectively, Setting the linear velocity of the downstream support member greater than the linear velocity of the upstream support member, and setting the coefficient of friction between the fixing belt 22 and the driving roller 25 greater than the coefficient of friction between the fixing belt 22 and the guide roller 26, can be performed on an inserted portion Tension is applied while the other inserted parts are in a non-tensioned state.

Furthermore, although in the exemplary embodiment, the multicolor image forming apparatus 1 includes a plurality of image forming units 3M, 3Y, 3C, and 3BK, the exemplary embodiment of the present invention is applicable to a monochrome image forming apparatus including only one image forming unit. Also, since typical embodiments of the present invention have a wider fixing nip and a longer fusing time, the present invention is particularly suitable for a multi-color image forming apparatus for fixing unfused color toner images.

In addition, the recording medium may be a sheet-shaped recording medium that replaces the page X, and the shape and material of the recording medium may be appropriately changed.

According to the first aspect of an exemplary embodiment of the present invention, since the pressing member contacts at least two support members at the upstream side and the downstream side of the direction in which the recording medium is conveyed with different pressures, and contacts the at least two support members installed between the at least two support members The insertion portion of the belt thus forms a wide-angle fixing nip. Therefore, the fixing time is longer, thereby obtaining sufficient image fixing. In addition, due to the high heat capacity of the heating belt, the heating time is shortened and the energy consumption is reduced. In addition, since the upstream side and the downstream side of the fixing nip contact the supporting member and the pressing member, respectively, its length and pressure range can be surely maintained and not affected by belt fluctuations. Since different pressures are applied on the upstream side and the downstream side, a pressure gradient is formed in the fixing nip and the toner image is surely fixed on the sheet. In addition, since the insertion portion not in contact with the pressure member is installed in an untensioned state, the insertion portion in the untensioned state absorbs movement of the belt due to twisting of the portion of the supporting member or the deformation of the belt, and reduces tension. Movement of the belt in the axial direction of the support element is reduced. In addition, since the present invention does not use expensive components, component costs are reduced.

According to the second aspect of an exemplary embodiment of the present invention, the pressure increases from the upstream side to the downstream side, so that by setting the pressure between the downstream support and the pressing member to be greater than the pressure between the upstream support and the pressing member, Instead, a pressure gradient is formed in the fixing nip. Therefore, a large pressure is generated at the end of the fixing nip. Thus, since the gradually melted toner fixes the toner image by the pressure increasing from the upstream side to the downstream side of the fixing nip while the sheet is being transferred, the toner image can be surely fixed on the sheet.

According to the third aspect of the exemplary embodiments of the present invention, since the width of the fixing nip between the support members is large, the fixing time is long and sufficient fixing is achieved.

According to the fourth aspect of the exemplary embodiments of the present invention, since warm-up time is shortened, power consumption is reduced, belt deviation is reduced, and since the fixing device uses inexpensive components, an inexpensive and reliable image forming apparatus can be provided.

While the invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the spirit and scope of the invention as defined by the following claims. Various changes.

This application claims the benefit of Japanese Patent Application No. 2004-319700 filed in Japan Intellectual Property Office on November 2, 2004 and Korean Patent Application No. 10-2005-0096493 filed in Korean Intellectual Property Office on October 13, 2005 priority, the entire disclosure of which is incorporated herein by reference.

Claims (13)

1. A fixing device, comprising: at least two support elements; a belt wrapped around said at least two support elements and movably supported in the circumferential direction of the at least two support elements; a heat source for heating the belt; a pressing element in contact with the belt by means of pressure; and wherein the toner image is heated and fused on the recording medium by passing the recording medium on which the toner image is electrostatically formed through a fixing nip formed between the belt and the pressing member; The supporting member and the pressing member are in contact with each other on upstream and downstream sides in the recording medium conveyance direction by pressure; The first insertion portion of the belt disposed between the supports is inserted between the support member and the pressing member and installed in a tensioned state, the second insertion portion of the belt is installed in a non-tensioned state, and the pressing member is connected to the first tensioning state. outer surfaces of an insert portion are in contact to form a fixing nip; and The supporting member is in contact with the pressing member with different pressures on the upstream side and the downstream side in the recording medium conveyance direction. 2. The fixing device according to claim 1, wherein A first pressure between the pressing member and the supporting member on the downstream side is greater than a second pressure between the pressing member and the supporting member on the upstream side. 3. The fixing device according to claim 1, wherein A fixing nip is formed in the first insertion portion of the belt, which is disposed between the supporting members in a tensioned state. 4. The fixing device according to claim 2, wherein A fixing nip is formed in the first insertion portion of the belt, which is disposed between the supporting members in a tensioned state. 5. The fixing device according to claim 2, wherein The downstream support elements are drive rollers and the upstream support elements are guide rollers. 6. The fixing device according to claim 1, wherein The belt is a chain belt. 7. An image forming apparatus for transferring a toner image onto a recording medium to form an image, comprising: A fixing device placed in an image forming device, the fixing device comprising: at least two support elements; a belt wrapped around the at least two support elements and movably supported in the circumferential direction of the at least two support elements; and a heat source for heating the belt; and a pressing element in contact with said belt by means of pressure; wherein the toner image is heated and fused on the recording medium by passing the recording medium on which the toner image is electrostatically formed through a fixing nip formed between the belt and the pressing member; The supporting member and the pressing member are in contact with each other on upstream and downstream sides in the recording medium conveyance direction by pressure; The first insertion portion of the belt disposed between the supports is inserted between the support member and the pressing member and installed in a tensioned state, the second insertion portion of the belt is installed in a non-tensioned state, and the pressing member and the first pressing member are installed in a tensioned state. outer surfaces of an insert portion are in contact to form a fixing nip; and The supporting member is in contact with the pressing member with different pressures on the upstream side and the downstream side in the recording medium conveyance direction. 8. The image forming apparatus for transferring a toner image onto a recording medium to form an image according to claim 7, wherein A first pressure between the pressing member and the supporting member on the downstream side is greater than a second pressure between the pressing member and the supporting member on the upstream side. 9. The image forming apparatus for transferring a toner image onto a recording medium to form an image according to claim 7 or 8, wherein A fixing nip is formed in the first insertion portion of the belt, which is disposed between the supporting members in a tensioned state. 10. The image forming apparatus for transferring a toner image onto a recording medium to form an image according to claim 7 or 8, wherein The downstream support elements are drive rollers and the upstream support elements are guide rollers. 11. A method of transferring a toner image onto a recording medium to form an image, comprising the steps of: pressing a chain belt wound around at least two support members in the fixing device with a pressing member, the belt being movable along the circumferential direction of the at least two support members; heating the belt; forming a fixing nip between the belt and the pressing member with at least two support members so as to form a pressure gradient between the at least two support members; and The recording medium on which the toner image is formed is conveyed through the fixing nip to heat and fuse the toner image on the recording medium. 12. The method of transferring a toner image onto a recording medium to form an image according to claim 11 , further comprising applying a first pressure to the pressurizing element with a downstream support element; and A second pressure is applied to the pressurizing element with the upstream support element. 13. The method of transferring a toner image onto a recording medium to form an image according to claim 11 or 12, wherein The first pressure is greater than the second pressure.

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