JP2008158409A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration of image quality by preventing temperature rise of a device and a member or the like disposed around a fixing device due to heat radiation from the fixing device. <P>SOLUTION: The fixing device 50 is equipped with a heating roller 51, a pressure roller 55 and a duct 80 or the like. The duct 80 has a suction port 81 and an exhaust port 82 exposed to the outside of the image forming apparatus, and extends to the exhaust port 82 from the suction port 81 via at least a partial position on the periphery of the heating roller 51. The fixing device 50 is equipped with a ventilation fan 85 making outside air flow in from the suction port 81 and sending it in a direction where it is discharged from the exhaust port 82 near the suction port 81 inside the duct 80. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device that heats and fixes an unfixed developer image transferred to a sheet, and an image forming apparatus having the fixing device.

  2. Description of the Related Art In recent years, the speed of image forming processing has been increasing for electrophotographic monochrome image forming apparatuses. Specifically, an image forming apparatus that has been a high-speed machine (50 to 60 sheets / minute) a few years ago has become a medium-speed machine in the past few years, and in recent years, an image forming apparatus having a processing capacity of 100 sheets / minute or more. The device is a high-speed machine. Similarly, in color image forming apparatuses, the speed of color image forming processing has been increasing.

  For this reason, the power consumption of the fixing device disposed in the image forming apparatus tends to increase in order to cope with the high speed. The fixing device melts and fixes an unfixed developer image (hereinafter referred to as a toner image) formed on the conveyed paper by a heating roller and a pressure roller. The heating roller has a heat source such as a heater lamp inside, and heats the paper passing between the pressure roller.

  The heating roller needs to maintain a predetermined peripheral surface temperature (set temperature) in order to melt the toner. However, the heat on the peripheral surface of the heating roller is taken away by the paper every time the paper passes. Therefore, as the amount of paper passing per unit time increases, that is, as the image forming process speeds up, the amount of heat generated by a heater lamp or the like for heating the heating roller must be increased.

  However, as the amount of heat generation increases, the temperature around the fixing device also increases. The fixing device is not provided with a heat insulating structure that covers a heat generating portion such as a heating roller, and radiant heat or the like warms members, devices, and the like located around the fixing device, thereby causing various problems.

  For example, when heat is diffused around the photoconductor that forms a toner image on the surface, there is a problem that the sensitivity of the photoconductor changes due to a rise in the temperature of the photoconductor surface and the image quality varies. In addition, when heat diffuses to a developing tank that contains toner and a cleaning unit that removes and collects toner remaining on the surface of the photoconductor, the heat softens and melts the toner. Therefore, there are problems that normal charging characteristics cannot be obtained in the developing tank, and that the stirring member and the conveying member are locked due to an increase in load. Furthermore, when heat is diffused in the paper transport path from the fixing device to the discharge tray, the paper guide for paper transport is heated, and the fixing toner on the paper on the paper transport path is softened again, so that the paper guide and transport roller There is a problem in that it causes adhesion of the paper jam.

Therefore, in recent image forming apparatuses, there is a configuration in which a partition member for partitioning the fixing device and the image forming unit is arranged in order to prevent diffusion of heat from the fixing device (see, for example, Patent Document 1). ). The partition member includes a heat insulating first member that faces the image forming portion and a non-heat insulating second member that does not face the image forming member. The first member is a plate-like member and forms a hollow two-layer heat insulation structure. The hollow space is an air layer.
JP 2006-72035 A

  However, in the configuration of Patent Document 1 described above, when the first member is heated by the radiant heat from the fixing device, the hollow space (air layer) is necessarily heated. Since the air layer once warmed has a heat retaining effect, the temperature decrease rate is low, and even when heat is transmitted from the first member to the second member and radiated, In the case of continuously performing image forming processing, it is difficult to block the heat radiation of the fixing device to the image forming unit.

  An object of the present invention is to prevent a decrease in image quality by preventing a temperature rise due to heat radiation from a fixing device such as devices and members disposed around the fixing device, and image formation To provide an apparatus.

  The present invention is configured as follows to solve the above-described problems.

  The fixing device according to the present invention includes a heating member, a duct, and an air blowing unit, and is positioned on a sheet conveyance path disposed inside an image forming apparatus that forms an image on a sheet. The heating member heats an unfixed toner image transferred to a sheet from an image carrier disposed inside the image forming apparatus. The duct has an intake port and an exhaust port exposed to the outside of the image forming apparatus, and reaches from the intake port to the exhaust port via at least a part of the position around the heating member. The blower sends air in a direction in which external air flows from the intake port and is discharged from the exhaust port.

  In this configuration, the duct passes through at least a portion of the periphery of the heating member. Since the duct has air inside, the heat released from the heating member is absorbed by the air. Therefore, the heat from the heating member is blocked by the duct. Accordingly, when the duct is disposed between the heating device and the peripheral device disposed around the fixing device, the peripheral device and the like are prevented from being heated by the heating member.

  Further, since the air inside the duct is always replaced with the outside air by the blowing means, it is possible to prevent the peripheral device and the like from being heated through the air that has absorbed the heat from the heating member.

  The duct may be positioned at least between the heating member and the image carrier, and between the heating member and the paper transport path for transporting the paper that has passed through the heating member among the paper transport paths.

  As a result, it is possible to at least prevent the image carrier that is adversely affected by the heat released from the heating member and the paper conveyance path for conveying the paper on which the toner image is fixed, from being heated.

  The duct may cover the entire heating device.

  Accordingly, since the periphery of the heating member is covered by the duct except for the paper conveyance path portion, heat insulation can be performed more reliably.

  Moreover, you may make heat conductivity higher than the outer wall member which does not oppose the outer wall member which opposes a heating member among the outer wall members of a duct.

  Accordingly, the temperature of the outer wall member of the duct facing the peripheral device or the like hardly rises, and heat is transferred to the outer wall member facing the heating member even when heated, so that the heat insulation performance can be improved.

  Further, a plurality of fins may be formed on the inner surface of the outer wall member of the duct on the inner surface of the heating member side.

  As a result, the contact area between the inner wall surface of the outer wall member of the duct and the air can be increased, so that the heat from the heating member transmitted to the inner wall surface can be easily released into the air, and the heat insulation performance is further improved. be able to. Further, the air flow inside the duct can be made turbulent, and the heat insulation performance can be improved.

  In addition, the fixing device can include a control unit that adjusts the blowing amount of the blowing unit according to the processing state of the image forming apparatus.

  As a result, the amount of air blown by the air blowing unit can be adjusted according to the processing state of the image forming apparatus, so that the amount of air blown can be increased during image forming processing where the amount of heat released from the heating member is large, and the heat insulation performance is further improved. Can be improved. On the other hand, the amount of blown air can be reduced in the power saving mode where the amount of heat released from the heating member that is not subjected to image formation processing is small, and energy saving and noise reduction can be achieved.

  In addition, the control unit can set the air volume to the maximum air volume when at least the temperature of the heating member is equal to or higher than a predetermined temperature lower than the set temperature that is the target temperature.

  Accordingly, the heat insulation performance can be maximized when the amount of heat released from the heating member is higher than a predetermined temperature, and the heat insulation performance can be most improved.

  Further, the control unit can reduce the air flow rate below the maximum air flow rate when the temperature of the heating member is lower than the predetermined temperature.

  As a result, the amount of air blown can be reduced when the amount of heat released from the heating member is less than a predetermined temperature, and energy saving can be achieved.

  An image forming apparatus according to the present invention includes the fixing device according to any one of claims 1 to 8 and forms an image by transferring a toner image onto a sheet.

  In this configuration, since the toner image transferred onto the sheet by the fixing device is heated and fixed, when a duct is arranged between the heating device and the peripheral device arranged around the fixing device, It is possible to prevent the peripheral device and the like from being heated by the heating member. In addition, since the air inside the duct is constantly replaced with the outside air by the air blowing means, it is possible to prevent the peripheral devices and the like from being heated through the air that has absorbed the heat from the heating member, so that the image quality is deteriorated. Can be prevented.

  According to the present invention, it is possible to prevent the peripheral device or the like of the heating member from being heated and to prevent the image quality from being deteriorated.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 forms electrophotographic multicolor (monochrome) and monochromatic (monochrome) images on a sheet based on image information read by the scanner unit 1 and image information input via a network or the like. Selectively. The image forming apparatus 100 includes a scanner unit 1, an image forming unit 2, a paper storage unit 3, a paper conveyance unit 4, and the like.

  The scanner unit 1 includes a platen glass 11, a light source 12, reflection mirrors 13 to 15, an optical lens 16, and a CCD (Charge Coupled Device) 17. The light source 12 irradiates light on a document placed on the upper surface of the platen glass 11. The reflection mirrors 13 to 15 guide the reflected light from the document to the optical lens 16. The optical lens 16 focuses the reflected light on the CCD 17. The CCD 17 outputs an electrical signal corresponding to the reflected light.

  The image forming unit 2 includes an exposure unit 20 and a transfer device 21, and includes image forming stations 22 </ b> A to 22 </ b> D arranged in a line between the transfer device 21 and the exposure unit 20. The exposure unit 20 includes a light source such as a semiconductor laser, a polygon mirror, a reflection mirror, and the like, and irradiates image light based on image information of each hue corresponding to the photosensitive drums 221A to 221D. The transfer device 21 includes an intermediate transfer belt 211, primary transfer rollers 212A to 212D, a secondary transfer roller 213, and the like. The toner images carried on the surfaces of the photosensitive drums 221A to 221D are transferred via the intermediate transfer belt 211. Transfer to paper. Details will be described later.

  Each of the image forming stations 22 </ b> A to 22 </ b> D forms an image based on image information of each hue of a total of four colors including cyan, magenta, and yellow, which are three subtractive primary colors obtained by color separation of a color image. I do. The black image forming station 22A includes a photosensitive drum 221A, a charging charger 222A, a developing unit 223A, a cleaning unit 224A, and the like.

  The photosensitive drum 221 </ b> A is irradiated with image light based on black image information from the exposure unit 20 on the surface to form an electrostatic latent image. The charging charger 222A is a non-contact type charger that uniformly charges the entire surface of the photosensitive drum 221A to a predetermined potential. Further, in place of the charging charger 222A, a contact-type charger using a charging brush or a charging roller can be used.

  The developing unit 223A supplies black toner to the surface of the photosensitive drum 221A, and develops the electrostatic latent image into a toner image. The developing unit 223A includes two toner boxes 225A and 225A. The toner box 225A accommodates black unused toner. The stored toner is supplied to the developing unit 223A via a supply path (not shown). The cleaning unit 224A has a cleaning blade that contacts the surface of the photosensitive drum 221A, and removes and collects residual toner.

  The image forming stations 22B to 22D are configured similarly to the image forming station 22A. However, each of the image forming stations 22B, 22C, and 22D is irradiated from the exposure unit 20 with image light modulated by image information of each hue of cyan, magenta, and yellow. The developing units 223B, 223C, and 223D supply toners of cyan, magenta, and yellow hues to the photosensitive drums 221B, 221C, and 221D, respectively. To the developing units 223B, 223C, and 223D, toner boxes 225B, 225C, and 225D that store toner of each hue are connected one by one.

  As a result, toner images of hues of cyan, magenta, and yellow are formed on the photosensitive drums 221B, 221C, and 221D, respectively.

  The reason why the two toner boxes 225A and 225A are arranged like the developing unit 223A is to increase the amount of black toner used that is larger than that of other hue toners.

  Further, the black photosensitive drum 221A has a larger diameter than the photosensitive drums 221B to 221D of other hues. This is because the frequency of monochrome image formation is higher than that of color image formation, and therefore the use frequency of the black photosensitive drum 221A is higher than that of the photosensitive drums 221B to 221D used only for color image formation. Because. Increasing the diameter increases the surface area of the photosensitive drum 221A and increases the area on which the toner image can be formed. Thereby, the lifetime of the photosensitive layer forming the surface of the photosensitive drum 221A is extended.

  The image forming apparatus 100 according to the present embodiment can execute a color image forming mode in which an image is formed with four colors and a monochrome image forming mode in which an image is formed with a single black color. When an image is formed in the color image forming mode, an electrostatic latent image and a toner image are formed in all four image forming stations 22A to 22D. Yellow, magenta, cyan, and black toner images are sequentially superimposed and transferred in this order on the outer peripheral surface of the intermediate transfer belt 211.

  When an image is formed in the monochrome image forming mode, the electrostatic latent image and the toner image are formed only in the black image forming station 22A, and the black toner is formed on the outer peripheral surface of the intermediate transfer belt 11. Only the image is transferred.

  The paper storage unit 3 includes paper feed cassettes 31, 32, 33, 34 and the like that each store a plurality of sheets of a single type.

  The paper transport unit 4 includes a first paper transport path 41 from the paper feed cassettes 31 to 34 via the secondary transfer position Q to the paper discharge tray 5 positioned between the scanner unit 1 and the image forming unit 2. ing. Pickup rollers 42A, 42B, 42C, and 42D, paper feed rollers 43A, 43B, 43C, and 43D, a registration roller 44, a paper discharge roller 46, a fixing device 50, and the like are disposed on the first paper transport path 41. Yes.

  Further, the sheet conveying section 4 is connected to the upstream side of the registration roller 44 in the sheet conveying direction of the first sheet conveying path 41 between the fixing unit 45 and the paper discharge roller 46 in the first sheet conveying path 41. A two-sheet conveyance path 47 is provided. The second paper transport path 47 transports a single-sided image-formed paper that is switchback-conveyed by reversal of the paper discharge roller 46 when a double-sided image is formed on both sides of the paper.

  When the paper transported from the paper storage unit 3 on the first paper transport path 41 passes through the secondary transfer position Q, the transfer of the toner image from the intermediate transfer belt 211 is transferred. The registration roller 44 temporarily holds the leading edge of the sheet that has been conveyed in a state where the rotation is stopped. When the leading edge of the sheet that has passed through the registration roller 44 reaches the secondary transfer position Q, the registration roller 44 moves to the intermediate transfer belt 211. The rotation starts at the timing when the tip of the toner image adhering reaches the secondary transfer position Q.

  The registration roller 44 also has a function of correcting the oblique feeding of the paper by contacting the leading edge of the paper that has been transported while the rotation is stopped.

  As shown in FIG. 2, the fixing device 50 includes a heating roller 51, a pressure roller 55, a cleaning device 56, and the like, and fixes the toner image transferred to the paper at the secondary transfer position Q. FIG. 2 is a front sectional view showing a schematic configuration of the fixing device 50. The heating roller 51 has two heater lamps 51 </ b> A and 51 </ b> A inside, and heats the paper passing between the pressure roller 55 and melts the toner. The heater lamps 51A and 51A heat the peripheral surface of the heating roller 51 from the inside.

  Further, the heating belt 52 is in contact with a part of the peripheral surface of the heating roller 51. The heating belt 52 is stretched by driven rollers 53 and 54, and supplementarily heats the peripheral surface of the heating roller 51 from the outside. Further, the heating belt 52 rotates as the heating roller 51 rotates. The driven rollers 53 and 54 rotate according to the rotation of the heating belt 52, and transmit heat of the heater lamps 53 </ b> A and 54 </ b> A included therein to the heating belt 52.

  The pressure roller 55 is in contact with a part of the peripheral surface of the heating roller 51 and presses the paper passing between the pressure roller 55 and the pressure roller 55. The pressure roller 55 includes a heater lamp 55A, and supplementarily heats the toner on the passing paper, and supplementarily heats the peripheral surface of the heating roller 51 in contact therewith. The sheet is heated and pressed when passing through the nip portion between the heating roller 51 and the pressure roller 55, and the toner image is firmly fixed on the surface. Thereafter, the paper is discharged to the paper discharge tray 5. Thus, the paper image forming process is completed.

  The cleaning device 56 includes a web sheet 57, a delivery roller 58, a take-up roller 59, a pressing roller 60, tension rollers 61 and 62, and the like, and removes and collects residual toner attached to the peripheral surface of the heating roller 51.

  The web sheet 57 is a belt-like woven fabric or non-woven fabric, and removes residual toner and the like adhering to the peripheral surface when pressed against the peripheral surface of the heating roller 51. The web sheet 57 moves along a path from the feeding roller 58 to the winding roller 59 through the pressing roller 60 and the tension rollers 61 and 62 in order.

  The delivery roller 58 has a web sheet 57 before use wound around a peripheral surface. The winding roller 59 winds the used web sheet 57 around the peripheral surface. The pressing roller 60 is in pressure contact with the peripheral surface of the heating roller 51 with the web sheet 57 interposed therebetween. The tension rollers 61 and 62 apply a predetermined tension to the web sheet 57 in the path.

  The winding roller 59 rotates by a predetermined amount and winds the web sheet 57 each time a predetermined number of sheets pass between the heating roller 51 and the pressure roller 55. The winding roller 59 is rotated by driving a motor (not shown). The drive of the motor is controlled by a control unit 70 (see FIG. 1) connected via a driver. The control unit 70 controls the operation of the entire image forming apparatus.

  As shown in FIG. 2, a temperature detection sensor 65 is disposed on the peripheral surface of the heating roller 51. The temperature detection sensor 65 detects the temperature of the peripheral surface of the heating roller 51 and outputs the detection result to the control unit 70. The control unit 70 controls the operation of the heater lamps 51A, 53A, 54A, 55A and the like based on the received detection result, and maintains the peripheral surface temperature of the heating roller 51 at the set temperature. The set temperature is a target temperature of the peripheral surface temperature of the heating roller 51 and is set to a temperature (160 ° C. to 200 ° C.) higher than the melting temperature of the toner.

  The heating roller 51, the heating belt 52, the driven roller 53.54, and the pressure roller 55 are included in the heating member of the present invention.

  As shown in FIGS. 2 and 3, the fixing device 50 includes a duct 80 positioned outside the case 50 </ b> A that accommodates the heating roller 51 and the like. FIG. 3 is a top view illustrating a schematic configuration of the fixing device 50. The left side of FIG. 3 is the front side of the image forming apparatus 100, and the right side is the back side.

  The duct 80 has an intake port 81, an exhaust port 82, and the like, covers the entire periphery of the case 50, and blocks heat released from the inside of the fixing device 50. The duct 80 absorbs heat released from the heating roller 51 or the like by the air (layer) accommodated therein. Therefore, the photosensitive drum 221 </ b> A disposed around the fixing device 50, the first paper conveyance path 41 and the second paper conveyance path 47 on the downstream side of the fixing device 50 in the paper conveyance direction are heated by the fixing device 50. To prevent it.

  In the present embodiment, the entire periphery of the case 50 is covered using the duct 80, but it is only necessary to pass through the position of at least a part of a heating member such as the heating roller 51 of the fixing device 50. In particular, between the heating member and the photosensitive drum 221, and between the heating member and the paper conveyance paths 41 and 47 that convey the paper that has passed through the heating member (heating roller 51) among the paper conveyance paths 41 and 47. The duct 80 is preferably located.

  The intake port 81 and the exhaust port 82 are formed in the frame 100 </ b> A of the image forming apparatus 100, and communicate with the outside of the image forming apparatus 100 and the duct 80. A blower fan 85 is disposed in the vicinity of the air inlet 81 inside the duct 80. The blower fan 85 is rotated by the drive motor 86 and sends air from the outside of the image forming apparatus 100 in the direction from the intake port 81 to the exhaust port 82 indicated by the arrow in FIG. The operation of the drive motor 86 is controlled by the control unit 70 via the driver 87. In addition, the ventilation fan 85, the drive motor 86, and the driver 87 are contained in the ventilation means of this invention.

  As a result, the air inside the duct 80 is always replaced with the outside air by the blower fan 85, so that it is possible to prevent the peripheral devices and the like from being heated through the air that has absorbed heat from the heating member such as the heating roller 51. Therefore, it is possible to prevent the image quality from deteriorating. The arrangement position of the blower fan 85 is not limited to the vicinity of the intake port 81 as shown in FIG. 3, and may be any position in the duct 80 as long as air can be blown, and near the outside of the intake port 81 and the exhaust port 82. You may arrange in.

  A plurality of fins 90 are formed on the case 50A side of the inner surface of the outer wall member 80A of the duct 80. Since the contact area between the inner surface of the outer wall member 80A and the air can be increased by the fin 90, heat can be easily released into the air from the heating member such as the heating roller 51 transmitted to the inner wall surface of the duct 80. Insulation performance can be further improved. Further, the air flow inside the duct 80 can be made turbulent, and the heat insulation performance can be improved. Note that the fin 90 may not be provided on the inner side surface of the outer wall member 80A.

  Of the outer wall member 80A of the duct 80 of the present embodiment, the outer wall member 80A facing the case 50A has a higher thermal conductivity than the outer wall member 80A not facing the case 50A. For this reason, the temperature of the outer wall member 80A of the duct 80 facing the peripheral device such as the photosensitive drum 221A is unlikely to rise, and heat is transferred to the outer wall member 80A having the higher thermal conductivity even if heated. Further, it is possible to more reliably prevent the peripheral device and the like from being heated. In the present embodiment, Al is used for the outer wall member 80A facing the case 50A in the outer wall member 80A of the duct 80, and iron having a lower thermal conductivity than Al is used for the other outer wall member 80A. Note that the thermal conductivity of the entire outer wall member 80A may be constant.

  FIG. 4 is an explanatory diagram showing the relationship between the amount of air blown by the blower fan 85 and the processing state of the image forming apparatus 100. The blower fan 85 has a blower amount W controlled by the controller 70. The controller 85 adjusts the amount of air blown by the blower fan 85 by changing the input voltage Vm to the drive motor 86. In addition, the ventilation volume of the ventilation fan 50 may be constant.

  The processing state of the image forming apparatus 100 includes various states such as a warm-up mode, a standby mode, an image forming process, an energy saving mode, and a power saving mode. In the warm-up mode, processing at the start of energization of the image forming apparatus 100 is performed. At this time, the heating roller 51 is heated to a set temperature. Since the heating roller 51 at the start of energization is in a cold state without being used, the heating roller 51 has a large amount of heating, and thus the amount of heat released is also large. Therefore, the air volume of the blower fan 85 is also set to the maximum air volume.

  In the standby mode, power is supplied to each unit so that the image forming process can be started as soon as an image forming request is received. At this time, control is performed so that the peripheral surface temperature of the heating roller 51 that has reached the set temperature can be maintained at a predetermined temperature or higher so that it is close to the set temperature. The predetermined temperature is lower than the peripheral surface temperature, but is a temperature at which the heating roller 51 can reach the set temperature immediately after receiving an image formation request and image processing can be started. For this reason, since the amount of heat generation is smaller than that in the warm-up mode or the image forming process, the amount of air blow is also small.

  The image forming process is a process from when the image forming request is received until the paper is discharged to the paper discharge tray 5. At this time, since the heat of the peripheral surface of the heating roller 51 is taken away by the paper, a large amount of heat is generated to maintain the set temperature, and a large amount of heat is released. Therefore, similarly to the warm-up mode, the air blowing amount of the blower fan 85 is set to the maximum air amount.

  In the energy saving mode, a minimum amount of power is supplied to each unit of the image forming apparatus 100. For this reason, the peripheral surface temperature of the heating roller 51 is also lower than a predetermined temperature, and the blowing amount of the blowing fan 85 is also low. The power saving mode is a mode in which only power is supplied to the control unit 70 and power is not supplied to others when the image forming apparatus 100 is not used for a long time. At this time, since the heating roller 51 is not heated, the blowing amount of the blowing fan 85 is also zero. Thereby, it is possible to prevent the blower fan 85 from being rotated unnecessarily, and energy saving and noise reduction can be achieved.

  In this embodiment, the operation of the fixing device 50 is controlled using the control unit 70 of the image forming apparatus 100. However, the image forming apparatus 100 and the fixing device 50 may be provided with separate control units.

1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a front sectional view showing a schematic configuration of the fixing device. FIG. 2 is a top view illustrating a schematic configuration of the fixing device. It is explanatory drawing which shows the relationship between the ventilation volume of a ventilation fan, and the process state of an image forming apparatus.

Explanation of symbols

41-first sheet conveyance path 47-second sheet conveyance path 50-fixing device 51-heating roller 52-heating belt 55-pressure roller 70-control unit 80-duct 81-intake port 82-exhaust port 85-fan 100-Image forming apparatus

Claims (9)

An unfixed developer image, which is located on a sheet conveyance path disposed inside an image forming apparatus that forms an image on a sheet and is transferred to the sheet from an image carrier disposed inside the image forming apparatus, is heated. In a fixing device having a heating member,
A duct having an intake port and an exhaust port exposed to the outside of the image forming apparatus, the duct extending from the intake port to the exhaust port via at least a portion of the periphery of the heating member;
A fixing device, comprising: a blowing unit that sends the external air from the intake port and sends air in a direction of discharging from the exhaust port.   The duct is positioned at least between the heating member and the image carrier, and between the heating member and a paper conveyance path for conveying the paper that has passed through the heating member among the paper conveyance paths. The fixing device according to claim 1.   The fixing device according to claim 1, wherein the duct covers the entire heating device.   2. The fixing device according to claim 1, wherein the duct has an outer wall member that faces the heating member of the outer wall member and has a higher thermal conductivity than an outer wall member that does not face the heating member.   The fixing device according to claim 1, wherein a plurality of fins are formed on an inner side surface of the outer wall member of the duct on an inner side surface on the heating member side.   The fixing device according to claim 1, further comprising: a control unit that adjusts a blowing amount of the blowing unit according to a processing state of the image forming apparatus.   The fixing device according to claim 6, wherein the control unit sets the air flow rate to a maximum air flow rate when at least the temperature of the heating member is equal to or higher than a predetermined temperature lower than a set temperature that is a target temperature.   The fixing device according to claim 7, wherein the control unit makes the air flow rate lower than the maximum air flow rate when the temperature of the heating member is lower than the predetermined temperature. In an image forming apparatus that forms an image by transferring a developer image to paper,
An image forming apparatus comprising the fixing device according to claim 1.

Images