JP2014142426A - Fixing apparatus and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus which prevents wrinkle of a printed medium, such as paper, as well as an image defect, and to provide an image forming apparatus including the same.SOLUTION: A fixing apparatus 6 includes a fixing roller 51, an endless fixing belt 52 for conveying a printed medium and containing a magnetic body or a magnet, and a pressure roller 53 which comes into pressure contact with the fixing roller 51 across the fixing belt 52 and contains a magnet or a magnetic body. As the magnetic body, at least one kind of magnetic body selected from a group including iron oxide, chromium oxide, cobalt, and ferrite, is used. As the magnet, Al-Ni-Co magnet is used. An image forming apparatus includes the fixing apparatus 6.

Description

  The present invention relates to, for example, a belt-type fixing device and an image forming apparatus including the same.

  When the recording medium is nipped and transported by both the roller pair of the paper discharge unit and the nip part of the roller pair of the fixing unit as the image forming apparatus, the conveyance speed by the roller pair of the paper discharge unit and the temperature of the roller pair of the fixing unit Depending on the change, the conveyance speed of the roller pair of the fixing unit and the conveyance speed of the roller pair of the paper discharge unit differ, and the recording medium is pulled more than necessary to the paper discharge unit side, or the recording medium is pulled between the fixing unit and the paper discharge unit. There has been proposed an image forming apparatus that is prevented from being bent more than necessary in a conveyance path. (For example, refer to Patent Document 1.)

  The fixing roller and a pressure roller called a backup roller are pressed against each other via a fixing belt, and the pressed portion is called a hard nip portion, for example.

  In addition, in order to preheat the printing medium such as paper and the toner and ensure a wide temperature range in which the toner can be fixed to the printing medium, the pressure roller not only presses the fixing roller via the fixing belt, The pressure roller is in pressure contact with only the fixing belt portion without the fixing roller, and this portion is called, for example, a soft nip portion.

  In a fixing device having a fixing roller, a pressure roller, and a fixing belt, by providing a soft nip portion, it is possible to preheat paper and toner, and to secure a wide temperature range in which the toner can be fixed on the paper. It becomes.

JP 2012-133084 A

  However, in the soft nip portion of the conventional image forming apparatus, vibration is generated by the rotation of the fixing belt, and a gap is generated due to blurring associated therewith. Therefore, there has been a problem that wrinkles and image disturbance occur on the paper.

  For example, it is considered that a slight fluctuation of the fixing belt on the pressure roller in the soft nip portion is one of the causes of paper jam and / or image disturbance.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems, and to provide a fixing device capable of preventing the occurrence of wrinkles and image disturbance on a printing medium such as paper and an image forming apparatus including the same. And

  In order to solve the above problems, a fixing device of the present invention includes a fixing roller, an endless fixing belt that conveys a medium to be printed and includes a magnetic material or a magnet, and press-contacts the fixing roller via the fixing belt. And a pressure roller including a magnet or a magnetic material.

  According to the present invention, a wider fixing range can be obtained as compared with a state in which the fixing device does not have a soft nip portion. Further, even in a state where the soft nip portion is provided, it is possible to prevent image disturbance and / or generation of wrinkles on a printing medium such as paper.

1 is an explanatory diagram illustrating an internal configuration of an image forming apparatus according to Embodiment 1 of the present invention. 2 is an explanatory diagram illustrating an internal structure of a fixing device constituting the image forming apparatus. FIG. FIG. 4 is an explanatory diagram illustrating a state in which a fixing roller and a pressure roller are pressed against each other via a fixing belt. 2 is a cross-sectional view of a fixing belt. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram illustrating an internal configuration of an image forming apparatus (hereinafter referred to as a printer) according to Embodiment 1 of the present invention.

  The printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, a transfer belt unit 3, a toner supply unit 4, a paper feeding unit 5, and a belt type fixing device. The image forming apparatus includes a fixing device 6 serving as a unit and a transport unit 7 for duplex printing.

  The image forming unit 2 transfers the toner image onto the lower running portion surface 8a of the transfer belt 8 by a so-called back transfer method, along the lower running portion surface 8a of the transfer belt 8, from the upstream side to the downstream side in the sheet conveying direction. Up to (from right to left in the figure), four image forming units 9 (9k, 9c, 9m, 9y) are arranged in a multistage manner.

  The image forming unit 2 is held on the frame of the printer 1 so as to be movable up and down from a printing execution position shown in FIG. 1 to a maintenance position below it. Of the four image forming units 9, three image forming units 9y, 9m, and 9c on the upstream side (the left side in the figure) are subtractive mixed primary colors yellow (Y), magenta (M), cyan ( A monocolor image is formed with the color toner of C).

  The image forming unit 9k forms a monochrome image using black (K) toner mainly used for characters and dark portions of images. Each of the image forming units 9 has the same configuration except for the color of the toner for developing the image. Accordingly, the configuration of the image forming unit 9y for yellow (Y) toner will be described below as an example.

  The image forming unit 9 includes a photosensitive drum 10 at the top. The photosensitive drum 10 has a peripheral surface made of, for example, an organic photoconductive material. A cleaner 11, a charging roller 12, an optical writing head 13, and a developing roller 15 of the developing device 14 are disposed in contact with or surrounding the periphery of the photosensitive drum 10.

  The developing device 14 includes a unit housing 16 that covers the outside, a partition wall 17 provided inside, a developing roller 15, a first stirring and conveying screw 18, and a second stirring and conveying screw 19. The first and second agitating and conveying screws 18 and 19 include a screw shaft (not shown) and a fin that is integrally formed with the screw shaft and rotates.

  The developing unit 14 includes a toner supply container 20 (20y, 20m, 20c, and 20k) of the toner supply unit 4, and yellow (Y) and magenta (M) as indicated by Y, M, C, and K in FIG. ), Cyan (C), or black (K) toner is supplied.

  The transfer belt unit 3 has an endless transfer belt 8 that extends in the shape of a flat loop in the left-right direction in the figure at approximately the center of the main unit, and the transfer belt 8 is stretched over the transfer belt 8. A driving roller 21 and a driven roller 22 are provided that circulate in a counterclockwise direction indicated by an arrow a in the figure.

  A belt position control mechanism (not shown) is disposed inside the flat loop shape of the transfer belt 8. A primary transfer roller 23 is integrally incorporated in the belt position control mechanism. The primary transfer roller 23 is pressed against the photosensitive drum 10 via the transfer belt 8 and directly transfers (primary transfer) the toner image to the lower running portion surface 8a of the transfer belt 8 that circulates downward.

  The transfer belt 8 conveys the toner image to the paper secondary transfer unit 24 for further transfer (secondary transfer) to the paper. The secondary transfer unit 24 includes a transfer auxiliary roller 25 disposed on the downstream side (upward in the drawing) adjacent to the drive roller 21, and a secondary transfer roller 26 that is in pressure contact with the transfer auxiliary roller 25 via the transfer belt 8. And is configured.

  A belt cleaner 27 is disposed on the transfer belt 8. The belt cleaner 27 includes a cleaning blade 28 that contacts the surface of the transfer belt 8 that is stretched around the driven roller 22. A waste toner collection container 29 is detachably disposed adjacent to the belt cleaner 27 from the left to the bottom.

  The belt cleaner 27 scrapes off and removes the waste toner remaining on the surface of the transfer belt 8 by the cleaning blade 28, and sends the waste toner to the waste toner collection container 29 by a conveyance screw (not shown).

  The toner supply unit 4 includes four toner supply containers 20 (20y, 20m, 20c, and 20k) that are detachably disposed above the upper running unit of the transfer belt 8. As described above, the four toner supply containers 20 contain yellow (Y), magenta (M), cyan (C), and black (K) toners.

  Although these four toner replenishing containers 20 are hidden behind the transfer belt unit 3 in FIG. 1 and cannot be seen, the corresponding image forming units are respectively connected via the toner supply passages to the toner supply ports of the mounting portions. Nine developing devices 14 are connected.

  Although not particularly shown, the toner supply unit 4 is held on the frame of the printer 1 through the mounting unit so as to be able to be raised and lowered from the printing execution position shown in FIG. 1 to a maintenance position above it.

  The paper feed unit 5 includes two paper feed cassettes 30 (30a, 30b) arranged in two upper and lower stages. A paper take-out roller 31, a feed roller 32, a separating roller 33, and a standby conveyance roller pair 34 are disposed in the vicinity of the paper feed opening (right side in the figure) of the two paper feed cassettes 30, respectively.

  In the paper conveyance direction (vertical upward direction in the drawing) of the standby conveyance roller pair 34, the above-described secondary transfer portion 24 to the paper by the transfer belt 8, the transfer auxiliary roller 25, and the secondary transfer roller 26 is formed.

  The fixing device 6 is disposed downstream (upward in the drawing) of the secondary transfer unit 24, and on the further downstream side of the fixing device 6, an unloading roller pair 36 for unloading the fixed sheet from the fixing device 6, A pair of paper discharge rollers 38 is provided for discharging the conveyed paper to a paper discharge tray 37 formed on the upper surface of the apparatus.

  The conveyance unit 7 for double-sided printing also serves as, for example, an opening / closing member whose outer surface (the right outer surface in the drawing) opens or shields the inside of the printer 1 from the side surface to the outside.

  The duplex printing transport unit 7 has a return start path 39a that branches rightward in the figure from immediately before the paper discharge roller pair 38, a return intermediate path 39b that bends downward, and a left lateral direction opposite to the above. Thus, a return path 39 having a return terminal path 39c for finally inverting the return sheet is provided.

  Further, five pairs of return rollers 40 (40a, 40b, 40c, 40d, 40e) are arranged in the return path 39. The exit of the return end path 39c joins the conveyance path to the standby conveyance roller pair 34 corresponding to the sheet feeding cassette 30a below the sheet feeding section 5.

  FIG. 2 is an explanatory diagram showing the internal structure of the fixing device 6 constituting the printer 1.

  As shown in FIG. 2, the fixing device 6 includes a fixing roller 51, a fixing belt 52, a pressure roller 53, a heating roller 54, and heat sources 55a and 55b.

  More specifically, the fixing device 6 includes heat sources 55a and 55b, a heating roller 54, a fixing roller 51, a fixing belt 52 stretched between the heating roller 54 and the fixing roller 51, and a fixing belt. And a pressure roller 53 that forms a fixing nipping portion 50a by being pressed against the fixing roller 51 via 52.

  The fixing roller 51 and the pressure roller 53 are pressed against each other via the fixing belt 52, and the pressed portion is called, for example, a hard nip portion 50h.

  Further, in order to preheat the printing medium such as paper (not shown) and the toner and to ensure a wide temperature range in which the toner can be fixed to the printing medium, the pressure roller 53 is connected to the fixing roller 51 via the fixing belt 52. In addition to the pressure contact, the pressure roller 53 is also in pressure contact with only the fixing belt 52 without the fixing roller 51, and this portion is called, for example, a soft nip portion 50s.

  In the fixing device 6 having the fixing roller 51, the pressure roller 53, and the fixing belt 52, the soft nip portion 50 s is provided so that the printing medium such as paper and the toner are preheated, and the toner is covered with the paper such as paper. It is possible to ensure a wide range of temperatures that can be fixed on the print medium.

  FIG. 3 is an explanatory diagram showing a state in which the fixing roller 51 and the pressure roller 53 are pressed against each other via the fixing belt 52.

  The fixing roller 51 is formed in a cylindrical shape that is in pressure contact with the pressure roller 53 via a fixing belt 52 described later. The fixing roller 51 is configured by forming a heat-resistant smooth elastic member 51b such as cylindrical silicon rubber on the surface of a cylindrical cylindrical pipe portion 51a made of metal, for example, to a thickness of about 2 to 4 mm. .

  FIG. 4 is a cross-sectional view of the fixing belt 52.

  The fixing belt 52 is formed as an endless fixing belt 52 that conveys a printing medium such as paper and includes a magnetic material.

  Conventionally, the fixing belt 52 includes, in order from the fixing roller 51 side to the pressure roller 53 side, a metal layer 52a containing nickel (Ni), an elastic body layer 52b containing silicon rubber, and tetrafluoroethylene-perfluoroalkyl vinyl ether. The structure has three layers including a smoothing material layer 52c containing a copolymer (hereinafter abbreviated as PFA).

  However, in this example, the fixing belt 52 is moved from the fixing roller 51 side to the pressure roller 53 side, in order, a metal layer 52a containing a magnetic material, an elastic body layer 52b containing silicon rubber, and a smooth material layer containing PFA. It is assumed to have a structure having three layers 52c.

  For example, the fixing belt 52 is, in order from the fixing roller 51 side to the pressure roller 53 side, a metal layer 52a containing nickel (Ni) and a magnetic material, an elastic layer 52b containing silicon rubber, and a smooth material containing PFA. The structure is provided with three layers including the layer 52c.

  It should be noted that a magnetic material powder mixed in either one or both of the elastic body layer 52b and the smoothing material layer 52c of the fixing belt 52 can be used.

  Examples of the magnetic material included in the fixing belt 52 include iron oxide, chromium oxide, cobalt, and ferrite. As the magnetic material, for example, at least one magnetic material selected from the group consisting of iron oxide, chromium oxide, cobalt, and hard ferrite is used. A ferromagnetic material is preferably used as the magnetic material.

The magnetic material will be described in detail. Examples of ferromagnetic materials exhibiting ferromagnetism include ferric oxide (III) [Fe ₂ O ₃ ], chromium oxide (IV) [CrO ₂ ], and hexagonal close-packed cobalt. Among the ferromagnetic materials selected from the group consisting of [Co], barium ferrite, hexagonal ferrite having a hexagonal crystal structure such as barium ferrite and strontium ferrite [AFe ₁₂ O ₁₉ (A is Ba, Sr, Pb, etc.)] At least one ferromagnetic material is used.

The PFA contained in the fixing belt 52 is generally a thermoplastic resin made of a copolymer of tetrafluoroethylene (TFE / C ₂ F ₄ ) and perfluoroalkoxyethylene. Note that PFA is simply interpreted as a perfluoroalkoxy resin or the like.

  PFA is considered to have stable performance in a wide temperature range from a low temperature of −200 ° C. to 260 ° C. PFA is excellent in surface characteristics such as low friction, non-adhesion, and self-lubrication, weather resistance, and electrical insulation.

  As shown in FIGS. 2 and 3, the pressure roller 53 is formed as a cylindrical backup roller including a magnet in pressure contact with the fixing roller 51 via the fixing belt 52. The pressure roller 53 is configured, for example, by forming a heat-resistant smooth elastic member 53b such as silicon rubber on the surface of a cylindrical raw tube portion 53a to a thickness of about 1 to 4 mm.

  As shown in FIG. 2, the heating roller 54 is formed as a cylindrical heat roller heated to a high temperature of, for example, about 200 ° C. by heat sources 55a and 55b in the inside 54c. For example, the surface of the heat roller is heated to about 110 to 180 ° C.

  The heating roller 54 is formed, for example, on the surface of a cylindrical cylindrical tube portion 54a made of metal and covered with a thin layer 54b of a heat-resistant smooth member containing a fluorine resin or the like. The heating roller 54 has a hollow structure, and heat sources 55 a and 55 b are provided in a hollow interior 54 c of the heating roller 54.

  The heat sources 55a and 55b are formed as heaters 55a and 55b that heat the heating roller 54 to a high temperature of approximately 200 ° C., for example, in order to fix an unfixed toner image on a printing medium such as paper.

  Examples of magnets included in the pressure roller 53 include alloy magnets such as magnetic steel in addition to ordinary magnets. For example, as the magnet, at least one kind of magnet selected from the group consisting of an arconi magnet / alnico magnet, a samarium / cobalt magnet, a neodymium magnet, and a ferrite magnet is used.

  Examples of permanent magnets include alnico magnets that are alloy magnets of iron, aluminum, nickel, and cobalt, rare earth magnets such as samarium / cobalt magnets and neodymium magnets, and hard ferrite magnets.

  As the magnet included in the pressure roller 53, for example, an alnico magnet that hardly demagnetizes even in a high temperature environment is used for the cylindrical portion 53 a of the pressure roller 53.

  The alnico magnet (Al—Ni—Co) is a cast magnet cast from aluminum (Al), nickel (Ni), cobalt (Co), or the like as a raw material. An alnico magnet to which iron or copper is added as an additive may also be mentioned.

  The alnico magnet is a high magnetic flux density magnet. Alnico magnets are considered to be magnets that have low temperature dependence of magnetism and are less susceptible to low temperature demagnetization and thermal demagnetization.

  Since the Curie temperature of the alnico magnet is, for example, about 850 ° C., the alnico magnet is a suitable magnet as a magnetic material for a member used in a portion having a high temperature atmosphere such as the fixing device 6.

  Alnico magnets are considered to be permanent magnets that have excellent strength characteristics and are difficult to break. Thus, the alnico magnet is a permanent magnet having various excellent characteristics.

  For example, a samarium / cobalt magnet may be used instead of the alnico magnet. Since the Curie temperature of the samarium / cobalt magnet is, for example, about 700 to 800 ° C., the samarium / cobalt magnet is suitable as a magnetic material for a member used in a portion having a high temperature atmosphere such as the fixing device 6. A magnet.

  Conventionally, the cylindrical portion 53a of the pressure roller 53 is formed of a metal such as iron. On the other hand, as a material used for the cylindrical portion 53a of the pressure roller 53, a magnet is used instead of metal. The fixing belt 52 includes a magnetic material as a magnetic material.

  By doing so, as shown in FIGS. 2 and 3, the fixing belt 52 and the pressure roller 53 are brought into close contact with each other by the magnetic force b.

  By using the magnetic force b, the fixing belt 52 and the pressure roller 53 are brought into close contact with each other, thereby preventing the fixing belt 52 from moving on the pressure roller 53 and preventing image disturbance and / or paper jam.

  By forming the fixing belt 52 having a structure including a magnetic material and forming the pressure roller 53 having a structure including a magnet, the pressure roller 53 and the fixing roller 51 rotating through the fixing belt 52 are formed in contact with each other. When the printing medium is passed through the nip portions 50s and 50h and the unfixed toner image on the printing medium is fixed to the printing medium, the fixing belt 52 and the pressure roller 53 are brought into close contact with each other by the magnetic force b. it can.

  Depending on the specifications of the fixing device 6 and the like, for example, magnet powder is mixed into the heat-resistant smooth elastic member 53b such as silicon rubber formed on the outer side of the cylindrical portion 53a made of the arcuni magnet constituting the pressure roller 53. The ones that have been made can also be used.

  Depending on the specifications of the fixing device 6 and the like, for example, the cylindrical portion 53a of the pressure roller 53 is made of a metallic cylindrical portion 53a and heat resistant such as silicon rubber formed outside the cylindrical portion 53a. The smooth magnetic member 53b may be mixed with magnet powder.

  Further, depending on the specifications of the fixing device 6, for example, the outer periphery of a heat-resistant smooth elastic member 53 b such as silicon rubber constituting the pressure roller 53 is covered with a fluororesin tube such as PFA so that the surface is smooth. In addition, it is possible to use a device that improves the property and the pinching property between the fixing belt 52 and the fixing roller 51.

  Further, a tube in which magnet powder is mixed in a fluororesin tube can be used.

For example, tetrafluoroethylene (polytetrafluoroethylene / PTFE / C ₂ F ₄ ) or the like may be used as the fluororesin instead of the PFA.

  An image forming apparatus 1 shown in FIG. 1 is configured as a printer 1 including the fixing device 6.

  As described above, when the fixing device 6 having a structure in which the fixing belt 52 and the pressure roller 53 are brought into close contact with each other by the magnetic force b is configured, the fixing device 6 does not have the soft nip portion 50s. A wide fixing range can be obtained.

  Even in the state where the soft nip portion 50s is provided, it is possible to prevent image distortion and / or wrinkling of a printing medium such as paper.

  By using the magnetic force b to bring the fixing belt 52 and the pressure roller 53 into close contact with each other via the fixing belt 52, it is possible to prevent the fixing belt 52 from being out of order.

  By configuring the fixing device 6, it is possible to prevent the occurrence of image distortion and / or paper wrinkles even when the fixing device 6 has the soft nip portion 50s, and from the state where the soft nip portion 50s is not provided. Wide fixing range can be obtained.

  As a result, for example, it is possible to provide the fixing device 6 and the printer 1 including the fixing device 6 that can prevent the occurrence of wrinkles and image disturbances of a printing medium such as normal thickness paper, cardboard, and cellophane.

  Instead of the endless fixing belt 52 containing a magnetic material, an endless fixing belt 52 containing a magnet was used. As the fixing belt 52, an endless fixing belt 52 that conveys a printing medium such as paper and includes a magnet is used.

  Further, a cylindrical pressure roller 53 including a magnetic body was used instead of the cylindrical pressure roller 53 including a magnet. As the pressure roller 53, a cylindrical pressure roller 53 including a magnetic material that is in pressure contact with the fixing roller 51 via the fixing belt 52 was used.

  In these points, the fixing device 6 described in the first embodiment and the printer 1 including the fixing device 6 are different from the fixing device 6 described in the second embodiment and the printer 1 including the fixing device 6. In the same way.

  In the fixing device 6 of the second embodiment and the printer 1 including the same, the details of the fixing device 6 of the first embodiment described with reference to FIGS. The explanation was omitted.

  Examples of the magnetic material included in the pressure roller 53 include iron oxide, chromium oxide, cobalt, and ferrite. As the magnetic material, for example, at least one magnetic material selected from the group consisting of iron oxide, chromium oxide, cobalt, and hard ferrite is used. A ferromagnetic material is preferably used as the magnetic material.

  In this example, for example, the fixing belt 52 is placed from the fixing roller 51 side to the pressure roller 53 side, in order, a metal layer 52a containing nickel (Ni) and a magnet, an elastic layer 52b containing silicon rubber, and PFA. The structure includes three layers including the smoothing material layer 52c.

  It is also possible to use one in which either one or both of the elastic body layer 52b and the smoothing material layer 52c of the fixing belt 52 are mixed with magnetic powder.

  Examples of the powder magnet included in the fixing belt 52 include an alloy magnet such as magnet steel in addition to a normal magnet. For example, as the magnet, at least one kind of powder magnet selected from the group consisting of an arconi magnet / alnico magnet, a samarium-cobalt magnet, a neodymium magnet, and a ferrite magnet is used.

  As the magnet included in the fixing belt 52, for example, an alnico magnet that is difficult to demagnetize even in a high temperature environment is used for the metal layer 52a including nickel (Ni) and a magnet. Further, for example, a samarium / cobalt magnet may be used instead of the alnico magnet.

  A magnetic material is used as a material used for the cylindrical portion 53 a of the pressure roller 53. Also, the fixing belt 52 includes a magnet.

  By forming the pressure roller 53 having a structure including a magnetic body and the fixing belt 52 having a structure including a magnet, the pressure roller 53 and the fixing roller 51 rotating through the fixing belt 52 are formed in contact with each other. When the printing medium is passed through the nip portions 50s and 50h and the unfixed toner image on the printing medium is fixed to the printing medium, the fixing belt 52 and the pressure roller 53 are brought into close contact with each other by the magnetic force b. it can.

  Depending on the specifications of the fixing device 6 and the like, for example, the powder of the magnetic material is applied to the heat-resistant smooth elastic member 53b such as silicon rubber formed outside the magnetic cylindrical portion 53a constituting the pressure roller 53. The mixed material can be used.

  Depending on the specifications of the fixing device 6 and the like, for example, the cylindrical portion 53a of the pressure roller 53 is made of a metallic cylindrical portion 53a and heat resistant such as silicon rubber formed outside the cylindrical portion 53a. The magnetic smooth powder 53b may be mixed with magnetic powder.

  Further, depending on the specifications of the fixing device 6, for example, the outer periphery of a heat-resistant smooth elastic member 53 b such as silicon rubber constituting the pressure roller 53 is covered with a fluororesin tube such as PFA so that the surface is smooth. In addition, it is possible to use a device that improves the property and the pinching property between the fixing belt 52 and the fixing roller 51.

  Also, it is possible to use a fluororesin tube mixed with magnetic powder.

  The fixing device 6 including the fixing belt 52 and the pressure roller 53 configured as described above can also be used.

Although several embodiments of the present invention have been described, the present invention is included in the invention described in the claims and the equivalents thereof. Hereinafter, the invention described in the scope of claims of the present application will be appended.
[Appendix 1]

A fixing roller;
An endless fixing belt that conveys a printing medium and includes a magnetic material or a magnet;
A pressure roller in pressure contact with the fixing roller via the fixing belt and including a magnet or a magnetic material;
A fixing device comprising:
[Appendix 2]

The fixing device according to claim 1, wherein at least one magnetic material selected from the group consisting of iron oxide, chromium oxide, cobalt, and ferrite is used as the magnetic material.
[Appendix 3]

The fixing device according to appendix 1 or 2, wherein an arconi magnet is used as the magnet.
[Appendix 4]

  An image forming apparatus comprising the fixing device according to any one of appendices 1 to 3.

  INDUSTRIAL APPLICABILITY The present invention can be used for a fixing device capable of preventing occurrence of wrinkles and image disturbance on a printing medium such as paper, and an image forming apparatus including the same.

1 Printer (image forming device)
DESCRIPTION OF SYMBOLS 2 Image formation part 3 Transfer belt unit 4 Toner supply part 5 Paper feed part 6 Fixing device 7 Duplex printing conveyance unit 8 Transfer belt 8a Lower travel part surface 9 (9m, 9c, 9y, 9k) Image formation unit 10 Photosensitive drum DESCRIPTION OF SYMBOLS 11 Cleaner 12 Charging roller 13 Optical writing head 14 Developing device 15 Developing roller 16 Unit housing 17 Bulkhead 18 First agitation conveyance screw 19 Second agitation conveyance screw 20 (20y, 20m, 20c, 20k) Toner supply container 21 Drive roller 22 Driven roller 23 Primary transfer roller 24 Secondary transfer portion 25 Transfer auxiliary roller 26 Secondary transfer roller 27 Belt cleaner 28 Cleaning blade 29 Waste toner collection container 30 (30a, 30b) Paper feed cassette 31 Paper take-out roller 32 Feed Roller 33 Rolling roller 34 Standby Conveying roller pair 36 Unloading roller pair 37 Paper discharge tray 38 Paper discharge roller pair 39 Return path 39a Return start path 39b Return intermediate path 39c Return end path 40 (40a, 40b, 40c, 40d, 40e) Return roller pair 50a Fixing and clamping unit 50s Soft nip (nip)
50h Hard nip (nip)
DESCRIPTION OF SYMBOLS 51 Fixing roller 51a Element pipe part 51b Elastic member 52 Fixing belt 52a Metal layer 52b Elastic body layer 52c Smooth material layer 53 Pressure roller 53a Cylindrical part (element pipe part)
53b Elastic member 54 Heating roller 54a Elementary tube part 54b Layer 54c Hollow inside (inside)
55 (55a, 55b) Heater (heat source)

Claims (4)

A fixing roller;
An endless fixing belt that conveys a printing medium and includes a magnetic material or a magnet;
A pressure roller in pressure contact with the fixing roller via the fixing belt and including a magnet or a magnetic material;
A fixing device comprising:   2. The fixing device according to claim 1, wherein at least one magnetic material selected from the group consisting of iron oxide, chromium oxide, cobalt, and ferrite is used as the magnetic material.   The fixing device according to claim 1, wherein an arconi magnet is used as the magnet.   An image forming apparatus comprising the fixing device according to claim 1.