JP2009210849A - Fixing device and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that achieves uniform temperature distribution of a heating member in an axial direction by the simple configuration of the device while avoiding an increase in its manufacturing cost, and to provide an image forming apparatus that has a fixing device. <P>SOLUTION: The fixing device 5 includes: an endless fixing belt 20 having a magnetic metal layer 20a; an auxiliary fixing roller 23 disposed inside the fixing belt 20; a support roller 21 disposed inside the fixing belt 20 and stretching the fixing belt 20 together with the auxiliary fixing roller 23; an endless heating belt 22 disposed in external contact with the fixing roller 21 and having a magnetic metal layer 22a; and a pressure roller 19 in pressure-contact with the auxiliary fixing roller 23 via the fixing belt 20. Further, the fixing device has an induction heating section 30 disposed on the outer periphery of the fixing belt 20 and oppositely to the support roller 21 and generating a magnetic flux, thereby induction heating the magnetic metal layers 20a and 22a. The support roller 21 has a soaking section 21a that has high heat conductivity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device for fixing an unfixed toner image on a sheet used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and an image forming apparatus including the fixing device. In particular, the present invention relates to a fixing device using an electromagnetic induction heating method using a magnetic metal, and an image forming apparatus equipped with the fixing device.

  The fixing device includes a fixing roller, a heater that heats the fixing roller, and a pressure roller that presses against the fixing roller, and the sheet onto which the toner image has been transferred passes through the fixing nip between the fixing roller and the pressure roller. The toner image is fixed on the paper by being heated and pressurized by the roller.

  In such a fixing device, it is desirable to make the temperature distribution in the longitudinal direction of the fixing roller uniform, but such control is actually difficult. For example, since both ends of the roller containing the heat source have openings, the heat tends to escape from the openings and the temperature at both ends of the roller tends to be low. For this reason, the fixability is insufficient at both ends of the roller, particularly when the fixing operation is just started from the standby state before fixing. If the size of the paper to be passed is smaller than the roller length, heat is accumulated on the roller surface (non-sheet passing portion) through which the paper does not pass, and the roller temperature rises abnormally. For this reason, the separation claw, the cleaning means and the like arranged in contact with the peripheral surface of the roller are damaged by heat at the portion where the temperature rises.

  Therefore, in Patent Document 1, two halogen lamps are provided as heaters inside the fixing roller, and the first heater has a heat distribution amount on the non-sheet passing side set smaller than other portions. On the other hand, the second heater is set so that the heat distribution amount on the non-sheet passing side is larger than the other portions. In the standby state, control is performed so that the first heater is turned off and the roller temperature is maintained only by the second heater. During printing, the second heater is turned off, and the fixing roller is heated to a predetermined temperature by the first heater. It is controlled to become. By controlling in this way, in the standby state, the temperature of the fixing roller is controlled by the second heater, so the amount of heat distribution at the end compensates for the amount of heat released from the end surface, and the temperature distribution of the roller is The end is slightly higher than the center. When printing is started with a large size paper from such a state, temperature control is started by the first heater, so that the temperature at the end portion is lower than that at the center, but the temperature at the start of printing is increased at the end portion. Therefore, no fixing failure occurs at both ends. When printing on paper of a small size, there is a tendency for excess heat to accumulate in the non-sheet passing portion, but the heat distribution of the first heater is smaller than other parts on the non-sheet passing side. Therefore, it accumulates in combination with the heat radiation from the roller end face, so that the temperature rise at the non-sheet passing portion remains within an allowable range.

  However, in the above-described prior art, the heat distribution amounts of the first and second heaters are not uniform on the sheet passing side and the non-sheet passing side, and further, the first and second heaters and the second heater do not pass the sheet passing side. Since the amount of heat distribution on the paper side must be different from each other, a special heater is manufactured, which increases the manufacturing cost. In addition, the temperature control of the first heater and the second heater must be different between the standby state for image formation and the printing start state, and the control becomes complicated, and the temperatures of the sheet passing portion and the non-sheet passing portion are increased. There is a disadvantage that it is difficult to balance each other within an allowable range.

  In recent years, as the demand for shortening the warm-up time and energy saving of an image forming apparatus is increasing, it has been proposed to adopt an electromagnetic induction heating type heat source as a heat source of a fixing device instead of a halogen heater. However, in the electromagnetic induction heating method, as in the case of a heater method such as a halogen lamp, the induction heated fixing roller generates heat transfer from the bearing supporting the end portion to the device frame, or into the air. Due to the large ratio of heat dissipation, the temperature at the end tends to be lower than the central part (paper passing part), and the temperature distribution in the axial (longitudinal) direction of the fixing roller becomes non-uniform. .

  Therefore, in Patent Document 2, an induction heating unit having an exciting coil for induction heating is provided inside the hollow fixing roller. The induction heating unit has an axial length substantially equal to that of the fixing roller, and is disposed in parallel to the central axis of the fixing roller with a predetermined interval between the inner circumferential surface of the fixing roller. A magnetic shielding plate made of a cylindrical nonmagnetic metal is inserted into the clearance between the inner peripheral surface of the fixing roller and the outer peripheral surface of the induction heating unit at both ends in the axial direction of the fixing roller so as to freely enter and exit from the end of the fixing roller. It has become so. This magnetic shielding plate can cover the induction heating part up to both sides of the paper when the paper is passed, and its axial length is the length corresponding to the minimum paper passing part. The heating temperature at the end of the fixing roller is adjusted by controlling the drive of the stepping motor to change the axial position of the magnetic shielding plate according to the paper width during warm-up, standby, printing, and printing. By doing so, the temperature distribution in the axial direction of the fixing roller is made uniform.

However, in the above-described prior art, since it is necessary to prepare a magnetic shielding plate, a stepping motor for driving the magnetic shielding plate, and a drive control means, there is a problem that the number of parts increases, and these members are fixed. If it is provided in the apparatus, the structure of the apparatus becomes complicated and there is a problem that the apparatus becomes large.
JP-A-5-134575 (paragraphs [0013]-[0019], FIG. 2) JP 2008-14966 A (paragraphs [0024]-[0026], FIG. 2)

  The present invention has been made in order to solve the above-described problems, and includes a fixing device that reduces the manufacturing cost with a simple device configuration and uniforms the temperature distribution in the axial direction of the heating member, and the fixing device. An object is to provide an image forming apparatus.

  In order to achieve the above object, the present invention provides an endless fixing belt having a magnetic metal layer, a fixing auxiliary roller included in the fixing belt, a fixing belt included in the fixing belt, and the fixing belt together with the fixing auxiliary roller. A support roller that stretches the belt, an endless heating belt that circumscribes the support roller and has a magnetic metal layer, a pressure roller that presses against the auxiliary fixing roller via the fixing belt, and a sheet that is attached to the fixing belt. A nip portion that is sandwiched between the pressure roller and melts and fixes an unfixed toner image on a sheet, and is disposed opposite to the support roller on the outer periphery of the fixing belt and generates a magnetic flux. An induction heating section for induction heating of the metal layer, and the support roller has a soaking section having a high thermal conductivity.

  According to this configuration, the magnetic metal layers of the fixing belt and the heating belt are heated by receiving the magnetic flux generated from the induction heating unit, and the fixing belt generates heat of the magnetic metal layer and the magnetic metal of the heating belt that has generated heat. When heated to a predetermined temperature by the heat received from the layer, the unfixed toner image on the conveyed paper is melted and fixed at the nip portion. During this induction heating, the support roller that circumscribes the heating belt has a soaking part with high thermal conductivity, so that part of the heat generated from the magnetic metal layer is accumulated uniformly in the axial direction of the soaking part. The accumulated heat is transmitted through the magnetic metal layer in the axial direction of the fixing belt, and the temperature distribution unevenness in the axial direction of the fixing belt is reduced.

  According to a second aspect of the present invention, the magnetic metal layer is made of iron or nickel. According to this configuration, when the magnetic metal layer is iron or nickel, the heat rise time of the magnetic metal layer is accelerated.

  According to a third aspect of the present invention, the soaking part is made of aluminum.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus equipped with the fixing device having the above configuration.

  According to the first aspect of the invention, the magnetic metal layers of the fixing belt and the heating belt are heated by receiving the magnetic flux generated from the induction heating unit, and the fixing belt generates heat and the heat of the magnetic metal layer. When heated to a predetermined temperature by being heated by heat received from the magnetic metal layer of the heating belt, the unfixed toner image on the conveyed paper is melted and fixed at the nip portion. During this induction heating, the support roller that circumscribes the heating belt has a soaking part with high thermal conductivity, so that part of the heat generated from the magnetic metal layer is accumulated uniformly in the axial direction of the soaking part. The accumulated heat is transmitted through the magnetic metal layer in the axial direction of the fixing belt, and the temperature distribution unevenness in the axial direction of the fixing belt is reduced. Accordingly, the manufacturing cost can be reduced with a simple apparatus configuration without providing a special member, and the temperature distribution in the axial direction of the fixing belt can be made uniform regardless of the sheet width during warm-up, standby, printing, and printing. be able to.

  According to the second aspect of the present invention, when the magnetic metal layer is iron or nickel, the rise time of heat generation of the magnetic metal layer is shortened, so that the warm-up time of the fixing device can be shortened.

  According to the third aspect of the present invention, when the heat equalizing portion of the support roller is formed of aluminum, it becomes possible to use both the core metal and the heat equalizing portion of the support roller, and the apparatus configuration is simplified. Become.

  According to the fourth aspect of the present invention, it is possible to provide an image forming apparatus including a fixing device that makes the temperature distribution in the axial direction of the fixing belt uniform by suppressing the manufacturing cost with a simple device configuration.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The embodiment of the present invention shows the most preferable form of the invention, and the use of the invention and the terms shown here are not limited thereto.

  FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 1 includes a sheet feeding unit 2 disposed in a lower portion thereof, a sheet conveying unit 3 disposed on the side and above the sheet feeding unit 2, and the sheet conveying unit. The image forming unit 4 disposed above the unit 3, the fixing device 5 disposed on the discharge side of the image forming unit 4, and the image forming unit 4 and the fixing device 5 are disposed above the image forming unit 4. The image reading unit 6 is provided.

  The paper feed unit 2 includes a plurality of (four in the present embodiment) paper feed cassettes 7 in which paper 9 is accommodated, and is selected from the plurality of paper feed cassettes 7 by the rotation operation of the paper feed rollers 8. The sheets 9 are surely sent out one by one from the sheet feeding cassette 7 to the sheet conveying section 3 side.

  The paper 9 sent to the paper transport unit 3 is transported toward the image forming unit 4 via the paper supply path 10. The image forming unit 4 forms a predetermined toner image on the paper 9 by an electrophotographic process, and is a photosensitive member which is an image carrier that is rotatably supported in a predetermined direction (the arrow direction in the drawing). A charging device 12, an exposure device 13, a developing device 14, a transfer device 15, a cleaning device 16, and a charge eliminating device 17 are provided around the photoconductor 11 and along the rotation direction of the photoconductor 11.

  The charging device 12 includes a charging wire to which a high voltage is applied. When a predetermined potential is applied to the surface of the photoconductor 11 by corona discharge from the charging wire, the surface of the photoconductor 11 is uniformly charged. Then, when light based on the image data of the original read by the image reading unit 6 is irradiated to the photoconductor 11 by the exposure device 13, the surface potential of the photoconductor 11 is selectively attenuated, and this photoconductor. 11 An electrostatic latent image is formed on the surface. Next, the developing device 14 attaches toner to the electrostatic latent image on the surface of the photoconductor 11 to form a toner image, and the toner image is supplied between the photoconductor 11 and the transfer device 15 by the transfer device 15. 9 is transferred.

  The sheet 9 on which the toner image has been transferred is conveyed toward the fixing device 5 disposed downstream of the image forming unit 4 in the sheet conveying direction. In the fixing device 5, the paper 9 is heated and pressed by the heating member 18 and the pressure roller 19, and the toner image is fixed on the paper 9. Next, the fixed sheet 9 is discharged onto the discharge tray 21 by the discharge roller pair 20. On the other hand, after the transfer by the transfer device 15, the toner remaining on the surface of the photoconductor 11 is removed by the cleaning device 16, and the residual charge on the surface of the photoconductor 11 is removed by the charge eliminating device 17. Then, the photoreceptor 11 is charged again by the charging device 12, and image formation is performed in the same manner.

  The fixing device 5 will be described. 2 is a cross-sectional front view showing a schematic configuration of the fixing device 5 used in the above-described image forming apparatus 1, FIG. 3 is a cross-sectional front view showing the main part of the fixing device 5, and FIG. It is a cross-sectional side view in AA.

  The fixing device 5 is a belt fixing method using a heat source of an electromagnetic induction heating method, and includes a heating member 18 and a pressure roller 19. The heating member 18 includes an endless fixing belt 20, a fixing auxiliary roller 23 included in the fixing belt 20, a support roller 21 that stretches the fixing belt 20 together with the fixing auxiliary roller 23, and a support roller 21. A circumscribed endless heating belt 22, an induction heating unit 30 disposed on the outer periphery of the fixing belt 20 and facing the support roller 21, and a temperature sensor 25 are provided. The pressure roller 19, the fixing auxiliary roller 23, and the support roller 21 are rotatably supported in the longitudinal direction of the casing (not shown) of the fixing device 5, and the induction heating unit 30 and the temperature heater 25 are the casing (not shown). Is held fixed. The temperature heater 25 detects the temperature of the surface of the fixing belt 20.

  The pressure roller 19 is a resin in which an elastic layer such as silicon rubber is formed on a cylindrical base material made of synthetic resin, metal or other material, and the surface of the elastic layer is excellent in releasability such as fluororesin. The one covered with is used. The pressure roller 19 is rotationally driven in the direction of the arrow in FIG. 2 by a driving source (not shown) such as a motor, and further presses the fixing auxiliary roller 23 in the center direction via the fixing belt 20. As a result, the pressure roller 19 is pressed against the auxiliary fixing roller 23 via the fixing belt 20, and the fixing belt 20 and the auxiliary fixing roller 23 are driven to rotate in the direction of the arrow in FIG. A nip portion N is formed at a portion that makes contact with 19 while rotating in reverse. In this nip portion N, the sheet 9 is sandwiched, and the sandwiched sheet 9 is heated and pressed to melt and fix the powdery toner on the sheet 9.

  The fixing auxiliary roller 23 is configured by arranging an elastic layer such as silicon foam rubber on a metal base material layer. The elastic layer functions as a heat insulating layer for reducing heat transfer from the fixing belt 20 to the auxiliary fixing roller 23 and as an elastic material for forming the nip portion N.

  The fixing belt 20 is formed by laminating a magnetic metal layer 20a, an elastic layer 20b, and a release layer 20c as a base material in order from the side that circumscribes the fixing auxiliary roller 23. As the magnetic metal layer 20a, a thin plate obtained by thinly rolling a magnetic metal having high permeability such as iron or nickel is used, and the thickness is set in a range of 30 to 40 μm. The magnetic metal 20a allows a magnetic flux generated from an induction heating unit 30 (described later) to pass therethrough, generates heat due to an eddy current generated around the magnetic flux, and raises the temperature of the fixing belt 20 to a predetermined temperature. The elastic layer 20b is formed of an elastic material such as silicon rubber, and gives flexibility as a belt. The release layer 20 c is formed of a resin having excellent release properties such as a fluororesin, and makes it easy to separate the melted and fixed paper 9 from the nip portion N.

  The heating belt 22 is configured by laminating a magnetic metal layer 22a and a release layer 22b as a base material in order from the side circumscribing the support roller 21. As the magnetic metal layer 22a, a thin plate obtained by thinly rolling a magnetic metal having a high magnetic permeability such as iron or nickel is used, and the thickness is set in a range of 30 to 40 μm. Further, the magnetic metal 22a penetrates a magnetic flux generated from an induction heating unit 30 described later, generates heat by an eddy current generated around the magnetic flux, and indirectly heats the fixing belt 20 by this heat generation, thereby fixing the magnetic metal 22a. The fixing belt 20 is heated to a predetermined temperature together with the magnetic metal 20a generated by the belt 20. The release layer 22b is formed of a resin having excellent release properties such as a fluororesin, and makes it easy to separate the fixing belt 20 provided on the release layer 22b from the heating belt 22.

  As shown in FIG. 3, the heating belt 22 is an endless belt that is sandwiched between the support roller 21 and the fixing belt 20 and has a peripheral length longer than the outer peripheral surface of the support roller 21 that circumscribes the fixing belt 20. When the belt 20 rotates, the belt 20 is rotated together with the fixing belt 20.

  The support roller 21 includes a soaking part 21a formed of a metal having excellent thermal conductivity such as aluminum or copper, and a release layer 21b disposed on the soaking part 21a.

  The soaking part 21a accumulates a part of heat generated from the magnetic metal 20a of the fixing belt 20 and the magnetic metal 22a of the heating belt 22, and transfers the accumulated heat to a low temperature part in the soaking part 21a. For example, if there is a temperature difference in the axial direction of the support roller 21, the temperature in the axial direction of the soaking part 21a is made uniform.

  In the present embodiment, the soaking part 21a is made of a core metal, which is a base material for the cylindrical support roller 21, made of aluminum or copper to form the soaking part 21a. Instead of forming the soaking part 21a with a cored bar, an aluminum plate or a copper plate is attached to the peripheral surface of the cored bar, and these metal plates are used as the soaking part 21a so as to contact the fixing belt 20 and the heating belt 22. Alternatively, the soaking part 21a may be configured by coating the core metal peripheral surface with copper.

  The release layer 21b is made of a fluororesin coating or a tube-covered material. The frictional resistance with the heating belt 22 is kept small, and the heating belt 22 is slid smoothly on the support roller 21.

  As shown in FIG. 4, the support roller 21 has a circumferential groove 21m on its outer peripheral surface 21n, and the heating belt 22 and the fixing belt 20 are accommodated in the circumferential groove 21m. The circumferential groove 21m is formed at such a depth that the heating belt 22 and the fixing belt 20 do not become higher than the outer peripheral surface 21n, so that the fixing belt 20 rotates between the support roller 21 and the auxiliary fixing roller 23. Prevents meandering in the moving direction. Further, the circumferential groove 21m has a width that is somewhat larger than the width of the heating belt 22 and the fixing belt 20 in the axial direction, and the heating belt 22 and the fixing belt 20 can rotate and move within the circumferential groove 21m. It is like that. The metal plate or coating of aluminum or copper as the soaking part 21a is formed on the peripheral surface of the circumferential groove 21m, and the release layer 21b is formed on the metal plate or coating. Further, the circumferential groove 21m is opposed to the induction heating unit 30 to be described later with a width substantially equal to the length. As a result, the magnetic flux generated from the induction heating unit 30 is oriented to the ends of the fixing belt 20 and the heating belt 22 in the axial direction.

  Returning to FIG. 2, the induction heating unit 30 includes an exciting coil 31, a hobbin 33, and a core 35, and heats the fixing belt 20 and the heating belt 22 by electromagnetic induction, and extends in the axial direction of the support roller 21. Thus, they are arranged to face each other through the fixing belt 20 and the heating belt 22 so as to surround a semicircle on the outer periphery of the cylindrical support roller 21.

  The copper coil 31 is wound around the hobbin 33 and is arranged in a spiral shape over a semicircle around the outer periphery of the support roller 21 so as to circulate around the central portion of the core 35 in the axial direction. The exciting coil 31 is connected to a high frequency power source (not shown), and generates a magnetic flux by a high frequency current supplied from the high frequency power source. The magnetic flux generated from the induction heating unit 30 is generated in a direction parallel to the paper surface of FIG. 2 and penetrates the magnetic metal layer 20 a of the fixing belt 20. An eddy current is generated around the magnetic flux of the magnetic metal layer 20a, and Joule heat is generated by the electric resistance in the magnetic metal layer 20a, causing the magnetic metal 20a to generate heat. Further, the magnetic flux generated from the induction heating unit 30 passes through the magnetic metal layer 22a of the heating belt 22, and an eddy current is generated around the magnetic flux, and Joule heat is generated by the electric resistance in the magnetic metal layer 22a. The magnetic metal 22a generates heat.

  From the standby state before fixing to the fixing possible temperature at which the fixing operation is possible, the induction metal heating unit 30 generates heat by the induction heating unit 30 and the magnetic metal 20a of the heating belt 22 is heated. Heat is generated and the fixing belt 20 is heated by the generated heat, and the temperature of the fixing belt 20 is increased. At this time, even if heat escapes from the end of the fixing belt 20, the heat equalizing portion 21a of the support roller 22 accumulates part of the heat generated from the magnetic metal 20a and the magnetic metal 22a uniformly in the axial direction. The accumulated heat is also conducted to the end portion of the fixing belt 20, so that the temperature at which fixing can be performed quickly reaches the end portion of the fixing belt 20. At this fixable temperature, the sheet 9 is conveyed to the nip portion N and heated and pressed by the fixing belt 20 and the pressure roller 19, whereby the powdery toner on the sheet 9 is melted and fixed. At this time, if the size of the paper to be passed is smaller than the width of the fixing belt 20, the roller temperature of the fixing belt 20 in the non-sheet passing portion is abnormally increased. 21 a accumulates heat of the fixing belt 20 in the non-sheet passing portion, and the accumulated heat is transferred to a low temperature portion (sheet passing portion side) in the temperature equalizing portion 21 a, and the heat is passed through the fixing belt 20. The temperature of the fixing belt 20 is made uniform.

  According to the embodiment, the fixing device 5 includes the endless fixing belt 20 having the magnetic metal layer 20a, the fixing auxiliary roller 23 included in the fixing belt 20, and the fixing belt 20 included in the fixing auxiliary roller. 23, a supporting roller 21 that stretches the fixing belt 20 together with the fixing belt 20, an endless heating belt 22 that circumscribes the supporting roller 21 and has a magnetic metal layer 22 a, and a pressure that presses the fixing auxiliary roller 23 via the fixing belt 20. A roller 19 and a nip portion N that sandwiches the sheet 9 between the fixing belt 20 and the pressure roller 19 and melts and fixes an unfixed toner image on the sheet 9 are provided. Further, the fixing belt 20 includes an induction heating unit 30 that is disposed on the outer periphery of the fixing belt 20 so as to be opposed to the support roller 21 and generates a magnetic flux and induction-heats the magnetic metal layers 20a and 22a by the magnetic flux. The soaking part 21a is large.

  According to this configuration, the magnetic metal layers 20a and 22a of the fixing belt 20 and the heating belt 22 are heated by receiving the magnetic flux generated from the induction heating unit 30, and the fixing belt 20 generates heat of the magnetic metal layer 20a. When the heating belt 22 is heated by the heat received from the magnetic metal layer 22a of the heating belt 22 and heated to a predetermined temperature, the unfixed toner image on the conveyed paper 9 is melted and fixed at the nip portion N. During this induction heating, the support roller 21 circumscribing the heating belt 22 has the soaking part 21a having a high thermal conductivity, so that part of the heat generated from the magnetic metal layers 20a and 22a is soaked in the soaking part 21a. The accumulated heat is transmitted to the axial direction of the fixing belt 20 through the magnetic metal layers 20a and 22a, and uneven temperature distribution in the axial direction of the fixing belt 20 is reduced. Accordingly, the manufacturing cost can be reduced with a simple device configuration without providing a special member, and the temperature distribution in the axial direction of the fixing belt 20 can be uniform regardless of the paper width during warm-up, standby, printing, and printing. can do.

  Further, according to the above embodiment, the magnetic metal layers 20a and 22a are made of iron or nickel, so that the rise time of heat generation of the magnetic metal layers 20a and 22a is shortened, so that the warm-up time of the fixing device 5 is shortened. be able to.

  Further, according to the above embodiment, the heat equalizing portion 21a of the support roller 21 is formed of aluminum, so that the core metal of the support roller 21 and the heat equalizing portion 21a can be used together, and the apparatus configuration is simplified. .

  Further, according to the above-described embodiment, if the image forming apparatus 1 includes the fixing device 5, an image in which the temperature distribution in the axial direction of the fixing belt 20 is uniform can be achieved with a simple device configuration while suppressing manufacturing costs. The forming apparatus 1 can be obtained.

  In the above embodiment, an example is shown in which the present invention is applied to an image forming apparatus that forms a monochrome image. However, the present invention is not limited to this, and may be applied to an image forming apparatus that forms a color image by a tandem method or the like. .

  The present invention relates to a fixing device for fixing an unfixed toner image on a sheet used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and an image forming apparatus including the fixing device. In particular, the present invention can be used for a fixing device using an electromagnetic induction heating method using a magnetic metal and an image forming apparatus equipped with the fixing device.

FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a front view schematically showing a configuration of a fixing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional front view schematically showing a main configuration of a fixing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional side view schematically showing a main configuration of a fixing device according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Fixing apparatus 18 Heating member 19 Pressure roller 20 Fixing belt 20a Magnetic metal layer 20b Elastic layer 20c Release layer 21 Support roller 21a Heat equalization part 21b Release layer 21m Circumferential groove 21n Outer peripheral surface 22 Heating belt 22a Magnetic metal layer 22b Release layer 23 Fixing auxiliary roller 25 Temperature detection sensor 30 Induction heating unit 31 Excitation coil

Claims (4)

An endless fixing belt having a magnetic metal layer, a fixing auxiliary roller included in the fixing belt, a supporting roller included in the fixing belt and stretching the fixing belt together with the fixing auxiliary roller, and the supporting roller An endless heating belt having a magnetic metal layer circumscribing the sheet, a pressure roller pressed against the fixing auxiliary roller via the fixing belt, and a sheet sandwiched between the fixing belt and the pressure roller. A nip portion for fusing and fixing the unfixed toner image on the top, and an induction heating portion that is disposed opposite to the support roller on the outer periphery of the fixing belt and generates a magnetic flux to inductively heat the magnetic metal layer by the magnetic flux. Prepared,
The fixing device is characterized in that the support roller has a soaking part having a high thermal conductivity.   The fixing device according to claim 1, wherein the magnetic metal layer is made of iron or nickel.   The fixing device according to claim 1, wherein the soaking part is made of aluminum.   An image forming apparatus on which the fixing device according to claim 1 is mounted.

Images