JP6170886B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as a printer or a copying machine forms a toner image on a recording medium such as paper, and then records the toner image by heating and pressing the recording medium and the toner image with a fixing device. It is fixed on the medium. In recent years, with increasing demands for power saving and shortening of warm-up time, reduction of heat capacity of fixing devices has been actively studied.

  For example, as a means for realizing a low heat capacity of a fixing device, a fixing device including a fixing belt, a pressure member that presses against the fixing belt to form a fixing nip, and a heating member that heats the fixing belt (See Patent Documents 1 and 2, etc.).

JP 2010-066543 A JP 2012-002881 A

  In the fixing device having such a configuration, when the fixing belt in the rotation stop state is locally heated by the heating member, a part of the fixing belt may be excessively heated and the fixing belt may be deformed. Therefore, when the rotation of the fixing belt is stopped, the supply of electric power to the heating member is stopped, and the heating of the fixing belt by the heating member is usually stopped. However, even if the supply of power to the heating member is stopped as described above, the fixing belt may be heated by the residual heat remaining in the heating member, and the fixing belt may overshoot (overheat).

  In view of the above circumstances, an object of the present invention is to prevent the fixing belt from being heated by residual heat remaining in the heating member, and to suppress overshoot (overheating) of the fixing belt.

  The fixing device of the present invention includes a fixing belt that is rotatably provided around a rotation shaft, a pressure member that presses against the fixing belt to form a fixing nip, a heating member that heats the fixing belt, and the heating A first posture that does not block radiant heat from the member toward the fixing belt or blocks part of radiant heat from the heating member toward the fixing belt; and radiant heat from the heating member toward the fixing belt as the first position. A shutter that can be switched between a second posture that blocks more than the posture, and a shutter that moves from the first posture to the second posture in conjunction with the rotation of the fixing belt being stopped. And a switching mechanism for switching.

  By adopting such a configuration, it is possible to cause the shutter, not the fixing belt, to absorb the residual heat remaining in the heating member after the supply of power to the heating member is stopped with the rotation of the fixing belt stopped. Become. For this reason, it is possible to prevent the fixing belt from being heated by the residual heat remaining in the heating member, and to suppress overshooting (overheating) of the fixing belt.

  The switching mechanism includes a biasing member that biases the shutter to the second posture, and a holding member that holds the shutter in the first posture against the biasing force of the biasing member. In conjunction with the rotation of the fixing belt being stopped, the holding member is released from being held in the first posture, and the shutter is moved to the first posture by the urging force of the urging member. May be switched to the second posture.

  By adopting such a configuration, the shutter can be reliably switched from the first posture to the second posture in conjunction with the rotation of the fixing belt being stopped.

  The fixing device further includes a power supply unit that supplies power to the holding member, and a switch mechanism that forms a driving circuit of the shutter together with the holding member and the power supply unit, and the fixing belt stops rotating. In conjunction with this, the drive circuit is interrupted by the switch mechanism, the supply of power from the power supply unit to the holding member is stopped, and the holding of the shutter to the first posture by the holding member is released. May be.

  By adopting such a configuration, the holding of the shutter to the first posture by the holding member can be reliably released in conjunction with the rotation of the fixing belt being stopped.

  The switch mechanism includes an inner ring portion and an outer ring portion that are provided at intervals, a connection posture that connects the inner ring portion and the outer ring portion, a connection release posture that releases the connection between the inner ring portion and the outer ring portion, And a switch piece that is held in the connection posture by the centrifugal force generated by the rotation of the fixing belt, and the centrifugal force is interlocked with the rotation of the fixing belt being stopped. The switch piece may be switched from the connection posture to the connection release posture, and the drive circuit may be cut off.

  By adopting such a configuration, the switch piece can be reliably switched from the connection posture to the connection release posture in conjunction with the rotation of the fixing belt being stopped.

  The fixing device further includes a detent member that is attached to an end portion of the fixing belt and restricts the displacement of the fixing belt in the rotation axis direction, and the detent member includes the detent member at the end portion of the fixing belt. A main body portion covering the outer side in the rotational axis direction; an inner cylinder portion extending from the main body portion toward the inner side in the rotational axis direction and provided on an inner diameter side of the end portion of the fixing belt; An outer cylinder portion provided on an outer diameter side of the end portion of the fixing belt, the inner ring portion is mounted on an outer periphery of the inner cylinder portion, and the outer ring portion is the outer cylinder portion The switch piece may be provided so as to contact the inner ring portion and to be rotatable around an end portion on the inner ring portion side.

  By adopting such a configuration, it is possible to use a detent member that regulates the deviation of the fixing belt in the rotation axis direction as a mounting portion of the switch mechanism, and to suppress an increase in the number of components. .

  The heating member may be a heater provided on the inner diameter side of the fixing belt, and the shutter may include a movable portion that rotates along an inner peripheral surface of the fixing belt.

  By adopting such a configuration, it is possible to easily secure an installation space for the heater and the shutter.

  The shutter further includes a fixed portion provided on an inner diameter side of the movable portion, and the movable portion overlaps the fixed portion when viewed from the heating member in a state where the shutter is in the first posture, and the shutter In the state of being in the second posture, the fixing portion may not overlap with the heating member.

  By adopting such a configuration, the amount of radiant heat blocked by the shutter can be easily adjusted.

  The shutter does not block radiant heat from the heating member toward the portion of the fixing belt that is closest to the heating member in the state of the first posture, and the shutter in the state of the second posture. Radiant heat from the member toward the portion of the fixing belt that is closest to the heating member may be blocked.

  By adopting such a configuration, it is possible to more reliably suppress the overshoot (overheating) of the fixing belt.

  The fixing device may further include a pressing member that presses the fixing belt toward the pressing member.

  By adopting such a configuration, it is possible to reduce the heat capacity of the fixing device.

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  According to the present invention, it is possible to prevent the fixing belt from being heated by the residual heat remaining in the heating member, and to suppress overshoot (overheating) of the fixing belt.

1 is a schematic diagram illustrating an outline of a configuration of a printer according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing a front end portion of the fixing belt and its periphery in the fixing device according to the embodiment of the present invention. It is IV-IV sectional drawing of FIG. FIG. 3 is a schematic diagram illustrating a configuration of a shutter drive circuit in the fixing device according to the embodiment of the present disclosure. 1 is a block diagram illustrating a configuration of a fixing device according to an embodiment of the present invention.

  First, the overall configuration of the printer 1 (image forming apparatus) will be described with reference to FIG.

  The printer 1 includes a box-shaped printer main body 2, and a paper feed cassette 3 that stores paper (recording medium) is stored in a lower portion of the printer main body 2. 4 is provided. An upper cover 5 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray 4, and a toner container 6 is accommodated below the upper cover 5.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the paper discharge tray 4 above the printer body 2, and an image forming unit 8 is provided below the exposure unit 7. Yes. The image forming unit 8 is rotatably provided with a photosensitive drum 10 as an image carrier. Around the photosensitive drum 10, a charger 11, a developing device 12, a transfer roller 13, and a cleaning device are provided. The apparatus 14 is disposed along the rotation direction of the photosensitive drum 10 (see arrow X in FIG. 1).

  A paper transport path 15 is provided inside the printer main body 2. A paper feed unit 16 is provided at the upstream end of the conveyance path 15, and a transfer unit 17 configured by the photosensitive drum 10 and the transfer roller 13 is provided at a middle portion of the conveyance path 15. Is provided with a fixing device 18, and a paper discharge unit 19 is provided at the downstream end of the conveyance path 15. A reverse path 20 for double-sided printing is formed below the transport path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initial setting such as temperature setting of the fixing device 18 is executed. When image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  First, after the surface of the photosensitive drum 10 is charged by the charger 11, exposure corresponding to the image data is performed on the photosensitive drum 10 by laser light from the exposure device 7 (see the two-dot chain line P in FIG. 1). The electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, the electrostatic latent image is developed by the developing device 12 into a toner image with toner.

  On the other hand, the sheet taken out from the sheet cassette 3 by the sheet feeding unit 16 is conveyed to the transfer unit 17 in synchronization with the above-described image forming operation, and the toner image on the photosensitive drum 10 is transferred to the sheet by the transfer unit 17. Is transcribed. The sheet on which the toner image has been transferred is conveyed downstream in the conveyance path 15 and enters the fixing device 18 where the toner image is fixed on the sheet. The paper on which the toner image is fixed is discharged from the paper discharge unit 19 to the paper discharge tray 4. The toner remaining on the photosensitive drum 10 is collected by the cleaning device 14.

  Next, the fixing device 18 will be described.

  Hereinafter, for convenience of explanation, the front side of the sheet in FIG. 2 is the front side of the fixing device 18. Arrows Fr, Rr, L, R, U, and Lo that are appropriately attached to the drawings respectively indicate the front side, the rear side, the left side, the right side, the upper side, and the lower side of the fixing device 18. An arrow Y in FIG. 2 indicates the sheet conveyance direction. 3 indicates the inner side in the front-rear direction, and the arrow O in FIG. 3 indicates the outer side in the front-rear direction.

  As shown in FIGS. 2 and 3, the fixing device 18 includes a fixing belt 21, a pressure roller 22 (pressure member) disposed on the lower side (outer diameter side) of the fixing belt 21, and a fixing belt. A heater 23 (heating member) disposed on the inner diameter side of the fixing belt 21, a support member 24 disposed below the heater 23 on the inner diameter side of the fixing belt 21, and a lower side of the support member 24 on the inner diameter side of the fixing belt 21. A pressing pad 25 (pressing member) disposed on the inner side of the fixing belt 21, a sheet member 26 disposed on the right and lower sides of the pressing pad 25 on the inner diameter side of the fixing belt 21, and an inner periphery of the fixing belt 21 on the inner diameter side of the fixing belt 21. A shutter 27 arranged along the surface, a switching mechanism 28 connected to the shutter 27, and both front and rear end portions 21a of the fixing belt 21 (only the front end portion 21a is shown in FIG. 3). A slip stopper 29 to be mounted (see FIG. 3) is configured as a switch mechanism 30 mounted on the front side of the slip stopper 29 (see FIG. 3), the mainly. Note that the illustration of the stopper member 29 and the switch mechanism 30 is omitted in FIG.

  The fixing belt 21 is provided to be rotatable around a rotation axis A extending in the front-rear direction. That is, in the present embodiment, the front-rear direction is the rotation axis direction of the fixing belt 21. The fixing belt 21 has a long cylindrical shape in the front-rear direction, and is endless in the circumferential direction. The fixing belt 21 has flexibility. For example, the fixing belt 21 has an outer diameter of 20 mm to 50 mm.

  The fixing belt 21 includes, for example, a base material layer, an elastic layer provided around the base material layer, and a release layer that covers the elastic layer. The base material layer of the fixing belt 21 is formed of, for example, Ni (nickel) having a thickness of 30 μm to 50 μm, or formed of a polyimide resin having a thickness of 50 μm to 100 μm. When the base material layer of the fixing belt 21 is formed of a polyimide resin, a metal powder such as Cu (copper), Ag (silver), or Al (aluminum) may be mixed in the polyimide resin. The elastic layer of the fixing belt 21 is formed of, for example, silicon rubber having a thickness of 100 μm to 500 μm. The release layer of the fixing belt 21 is formed of, for example, a fluorine resin such as PFA having a thickness of 30 μm to 50 μm. In each figure, each layer (base material layer, elastic layer, release layer) of the fixing belt 21 is displayed without being particularly distinguished.

  On the inner peripheral surface of the fixing belt 21, a coating made of, for example, polyimide, polyamideimide, PTFE, or the like is applied to a portion that slides with respect to the sheet member 26. On the inner peripheral surface of the fixing belt 21, a lubricant composed of, for example, fluorine grease or silicon oil is applied to a portion that slides with respect to the sheet member 26.

  The pressure roller 22 is rotatably supported by a fixing frame (not shown). The pressure roller 22 has a long cylindrical shape in the front-rear direction. The pressure roller 22 is in pressure contact with the fixing belt 21, and a fixing nip 33 is formed between the fixing belt 21 and the pressure roller 22.

  The pressure roller 22 includes, for example, a cylindrical core material 34, an elastic layer 35 provided around the core material 34, and a release layer (not shown) that covers the elastic layer 35. ing. The core material 34 of the pressure roller 22 is formed of a metal such as stainless steel or aluminum. The elastic layer 35 of the pressure roller 22 is formed of, for example, silicon rubber or silicon sponge. The release layer (not shown) of the pressure roller 22 is made of, for example, a fluorine resin such as PFA.

  As shown in FIG. 2 and the like, the heater 23 is disposed in an upper region (region opposite to the fixing nip 33) in the space on the inner diameter side of the fixing belt 21. The heater 23 is composed of, for example, a halogen heater.

  The support member 24 extends in the front-rear direction and penetrates the fixing belt 21. The support member 24 includes a fixed portion 36 and shaft portions 37 (only the front shaft portion 37 is shown in FIG. 3) provided on both the front and rear sides of the fixed portion 36. An end portion on the inner side in the front-rear direction of each shaft portion 37 is connected to the fixed portion 36. A ring-shaped stopper 38 is fixed to the outer portion of each shaft portion 37 in the front-rear direction. The ends of the shaft portions 37 on the outer side in the front-rear direction are fixed to a fixing frame (not shown).

  The pressing pad 25 extends in the front-rear direction. The pressing pad 25 is formed of a heat resistant resin such as LCP (Liquid Crystal Polymer). An elastomer layer such as silicon rubber may be provided on the lower surface of the pressing pad 25 (the surface on the sheet member 26 side). The pressing pad 25 is supported from above by the fixing portion 36 of the support member 24. The pressing pad 25 presses the fixing belt 21 downward (the pressure roller 22 side) via the sheet member 26.

  The sheet member 26 is interposed between the fixing belt 21 and the pressing pad 25 and is in contact with the inner peripheral surface of the fixing belt 21. When the fixing belt 21 rotates, the fixing belt 21 slides with respect to the sheet member 26. The sheet member 26 is made of, for example, a fluorine resin such as PTFE, and has a smaller friction coefficient than the pressing pad 25. The sheet member 26 has a function of reducing the sliding load of the fixing belt 21.

  The shutter 27 extends in the front-rear direction. The shutter 27 is made of metal such as SUS.

  The shutter 27 includes a movable portion 31 and a fixed portion 32 provided on the inner diameter side of the movable portion 31. The movable portion 31 is provided to be rotatable along the inner peripheral surface of the fixing belt 21. Accordingly, the shutter 27 has a first posture (see the solid line in FIG. 2) in which the movable portion 31 is disposed at the lower left of the heater 23 and a second posture in which the movable portion 31 is disposed above the heater 23 (see FIG. 2) (see the two-dot chain line in FIG. 2). The movable portion 31 overlaps the fixed portion 32 when viewed from the heater 23 when the shutter 27 is in the first posture, and does not overlap the fixed portion 32 when viewed from the heater 23 when the shutter 27 is in the second posture. Are arranged as follows.

  The switching mechanism 28 includes a coil spring 40 (biasing member) and a solenoid 41 (holding member). The coil spring 40 is connected to the movable portion 31 of the shutter 27, and biases the shutter 27 to the second posture (see the two-dot chain line in FIG. 2). The solenoid 41 is connected to the movable part 31 of the shutter 27. In FIG. 2, the solenoid 41 is schematically displayed, and the position of the solenoid 41 on the drawing does not necessarily match the actual position of the solenoid 41.

  As shown in FIGS. 3 and 4, each detent member 29 includes an annular main body portion 42, an inner cylinder portion 43 extending inward in the front-rear direction from an inner diameter side end portion of the main body portion 42, and a main body And an outer tube portion 44 that extends inward in the front-rear direction from an end portion on the outer diameter side of the portion 42.

  The main body portion 42 of each detent member 29 covers the front and rear ends of the front and rear end portions 21 a of the fixing belt 21. The outer surface in the front-rear direction of the main body portion 42 is in contact with a stopper 38 fixed to each shaft portion 37 of the support member 24. With such a configuration, the front-rear direction deviation (meandering) of the fixing belt 21 is regulated.

  The inner cylinder portion 43 of each detent member 29 is provided on the inner diameter side of the front and rear end portions 21a of the fixing belt 21 and faces the inner peripheral surface of the front and rear end portions 21a of the fixing belt 21 with a gap therebetween. . Each shaft portion 37 of the support member 24 is inserted into the inner cylinder portion 43.

  The outer cylindrical portion 44 of each detent member 29 is provided on the outer diameter side of the inner cylindrical portion 43 of each detent member 29 and the front and rear end portions 21 a of the fixing belt 21. It is in contact with the outer peripheral surface.

  As shown in FIGS. 3 and 4, the switch mechanism 30 includes an inner ring part 45, an outer ring part 46 provided on the outer diameter side of the inner ring part 45, and a switch piece 47 attached to the inner ring part 45. Yes.

  The inner ring portion 45 and the outer ring portion 46 of the switch mechanism 30 are provided with a space therebetween. The inner ring portion 45 is attached to the outer periphery of the inner cylinder portion 43 of the front side detent member 29. The outer ring portion 46 is attached to the inner periphery of the outer cylinder portion 44 of the front side stopper member 29. The outer ring portion 46 is disposed on the outer side in the front-rear direction than the front and rear end portions 21 a of the fixing belt 21.

  The switch piece 47 of the switch mechanism 30 is formed of thin metal, for example. The switch piece 47 is always in contact with the inner ring portion 45. The switch piece 47 is provided so as to be rotatable around an end portion on the inner ring portion 45 side. The switch piece 47 comes into contact with the outer ring portion 46 to connect the inner ring portion 45 and the outer ring portion 46 (see the solid line in FIG. 4), and connects the inner ring portion 45 and the outer ring portion 46 without contacting the outer ring portion 46. The connection release posture (see the two-dot chain line in FIG. 4) for releasing is provided so as to be switchable.

  As shown in FIG. 5, the inner ring portion 45 of the switch mechanism 30 is connected to the solenoid 41. The outer ring portion 46 of the switch mechanism 30 is connected to the solenoid 41 via the power supply portion 48. With this configuration, the switch mechanism 30 constitutes a drive circuit 49 for the shutter 27 together with the solenoid 41 and the power supply unit 48.

  Next, a control system for the fixing device 18 will be described.

  As shown in FIG. 6, the fixing device 18 is provided with a control unit 50. The control unit 50 is connected to a storage unit 51 including a storage device such as a ROM and a RAM. The control unit 50 controls the fixing device 18 based on a control program and control data stored in the storage unit 51. It is configured to control each part.

  The control unit 50 is connected to a drive source 52 configured by a motor or the like, and the drive source 52 is connected to the pressure roller 22. The drive source 52 is configured to rotate the pressure roller 22 based on a signal from the control unit 50.

  The control unit 50 is connected to the power supply unit 53. The power supply unit 53 is connected to the heater 23 and is configured such that the heater 23 radiates radiant heat by the power supplied from the power supply unit 53 and the fixing belt 21 is heated by the radiant heat.

  The control unit 50 is connected to the rotation detection unit 54. The rotation detection unit 54 has a function of detecting the rotation of the fixing belt 21, and the detection result is output from the rotation detection unit 54 to the control unit 50.

  In the fixing device 18 configured as described above, when the toner image is fixed on the sheet, the driving source 52 rotates the pressure roller 22 based on a signal from the control unit 50 (see arrow B in FIG. 2). ). Along with this, the fixing belt 21 in pressure contact with the pressure roller 22 rotates following the rotation of the pressure roller 22 (see arrow C in FIG. 2).

  Further, when the toner image is fixed on the sheet, the power supply unit 53 supplies power to the heater 23 based on a signal from the control unit 50. Along with this, the heater 23 radiates radiant heat, and the fixing belt 21 is heated by this radiant heat. In this state, when the sheet passes through the fixing nip 33, the sheet and the toner image are heated and pressurized to fix the toner image on the sheet.

  In the fixing device 18 configured as described above, when the operation of fixing the toner image on the paper is repeated, the fixing belt 21 and the sheet member 26 are rubbed to wear the sheet member 26 and the fixing belt 21 slides. The load increases. In addition, the surface of the fixing belt 21 and the surface of the pressure roller 22 are gradually deteriorated, and the driving force of the fixing belt 21 (followability of the fixing belt 21 with respect to the pressure roller 22) is reduced. If slip occurs between the pressure roller 22 and the fixing belt 21 due to these factors, the fixing belt 21 cannot be rotated following the rotation of the pressure roller 22, and the fixing belt 21 in the rotation stopped state is heated. 23 may be locally heated. When such a situation occurs, a part of the fixing belt 21 may be overheated and the fixing belt 21 may be deformed. Therefore, in the present embodiment, when the rotation detection unit 54 detects the stop of the rotation of the fixing belt 21, the control unit 50 stops the supply of power from the power supply unit 53 to the heater 23. .

  However, for example, when the rotation of the fixing belt 21 is suddenly stopped, the time until the rotation detecting unit 54 detects the stop of the rotation of the fixing belt 21 and the communication time from the rotation detecting unit 54 to the control unit 50 are determined. After the elapse of time, the control unit 50 stops the supply of power from the power supply unit 53 to the heater 23. Therefore, the fixing belt 21 is heated until the supply of power to the heater 23 is stopped. Even if the control unit 50 stops supplying power from the power supply unit 53 to the heater 23, the fixing belt 21 is heated by the residual heat remaining in the heater 23, and the fixing belt 21 is overshooted (overheated). There is a fear. Therefore, in this embodiment, the overshoot of the fixing belt 21 is suppressed as follows.

  When the fixing belt 21 rotates, the switch piece 47 of the switch mechanism 30 is held in the connected posture by the centrifugal force generated by the rotation of the fixing belt 21 as indicated by a solid line in FIG. Along with this, as shown by a solid line in FIG. 5, the drive circuit 49 of the shutter 27 is connected, and power is supplied from the power supply unit 48 to the solenoid 41. Therefore, as indicated by a solid line in FIG. 2, the solenoid 41 holds the shutter 27 in the first posture against the urging force of the coil spring 40.

  In this state, the movable portion 31 of the shutter 27 overlaps with the fixing portion 32 of the shutter 27 when viewed from the heater 23, and only the fixing portion 32 of the shutter 27 has a function of blocking radiant heat from the heater 23. For example, radiant heat from the heater 23 toward the left side of the fixing belt 21 (see arrow D in FIG. 2) is blocked by the fixing portion 32 of the shutter 27, but from the heater 23 to the upper end portion of the fixing belt 21 (of the fixing belt 21. Thus, the radiant heat (see arrow E in FIG. 2) toward the heater 23 is not blocked by the shutter 27. Therefore, the fixing belt 21 is efficiently heated by the heater 23.

  On the other hand, when the rotation of the fixing belt 21 is stopped, the centrifugal force generated by the rotation of the fixing belt 21 disappears. Therefore, as shown by a two-dot chain line in FIG. Switch from connected posture to disconnected posture. Along with this, as indicated by a two-dot chain line in FIG. 5, the drive circuit 49 of the shutter 27 is cut off, and the supply of power from the power supply unit 48 to the solenoid 41 is stopped. Therefore, the holding of the shutter 27 in the first posture by the solenoid 41 is released, and the shutter 27 is changed from the first posture to the second posture by the urging force of the coil spring 40 as shown by a two-dot chain line in FIG. Switch.

  In this state, since the movable portion 31 of the shutter 27 does not overlap the fixed portion 32 of the shutter 27 when viewed from the heater 23, both the movable portion 31 and the fixed portion 32 of the shutter 27 function to block radiant heat from the heater 23. have. Therefore, in the state where the shutter 27 is in the second posture, the radiant heat blocked by the shutter 27 is larger than in the state where the shutter 27 is in the first posture. For example, the radiant heat (see arrow D in FIG. 2) from the heater 23 toward the left side of the fixing belt 21 is blocked by the fixing portion 32 of the shutter 27, and the upper end of the fixing belt 21 from the heater 23 (the heater of the fixing belt 21. Radiant heat (see the arrow E in FIG. 2) toward the portion 23 closest to 23) is blocked by the movable portion 31 of the shutter 27.

  When the fixing belt 21 rotates again, the switch piece 47 of the switch mechanism 30 is switched from the connection release posture to the connection posture due to the centrifugal force generated by the rotation of the fixing belt 21, and the drive circuit 49 of the shutter 27 is connected to the power supply unit. Power is again supplied from 48 to the solenoid 41. Therefore, the solenoid 41 switches the shutter 27 from the second posture to the first posture against the biasing force of the coil spring 40.

  In the present embodiment, as described above, the switching mechanism 28 switches the shutter 27 from the first posture to the second posture in conjunction with the rotation of the fixing belt 21 being stopped. By adopting such a configuration, the residual heat remaining in the heater 23 after the supply of power to the heater 23 is stopped with the rotation of the fixing belt 21 being stopped is absorbed by the shutter 27 instead of the fixing belt 21. Is possible. For this reason, it is possible to prevent the fixing belt 21 from being heated by the residual heat remaining in the heater 23, and to suppress overshooting (overheating) of the fixing belt 21.

  In conjunction with the rotation of the fixing belt 21 being stopped, the solenoid 41 is released from holding the shutter 27 in the first posture, and the biasing force of the coil spring 40 causes the shutter 27 to move from the first posture to the second posture. It is designed to switch to a posture. By adopting such a configuration, the shutter 27 can be reliably switched from the first posture to the second posture in conjunction with the rotation of the fixing belt 21 being stopped.

  In conjunction with the rotation of the fixing belt 21 being stopped, the drive circuit 49 of the shutter 27 is interrupted by the switch mechanism 30 to stop the supply of power from the power supply 48 to the solenoid 41, and the shutter 27 by the solenoid 41 is stopped. Is held in the first posture. By adopting such a configuration, it becomes possible to reliably release the holding of the shutter 27 in the first posture by the solenoid 41 in conjunction with the rotation of the fixing belt 21 being stopped.

  Further, in conjunction with the rotation of the fixing belt 21 being stopped, the centrifugal force generated by the rotation of the fixing belt 21 is eliminated, the switch piece 47 is switched from the connected posture to the disconnected posture, and the drive circuit 49 of the shutter 27 is cut off. It has come to be. By adopting such a configuration, the switch piece 47 can be reliably switched from the connection posture to the connection release posture in conjunction with the rotation of the fixing belt 21 being stopped.

  In the present embodiment, a detent member 29 that restricts the deviation of the fixing belt 21 in the front-rear direction is also used as a mounting portion of the switch mechanism 30. Therefore, it is possible to suppress an increase in the number of parts.

  The heater 23 is provided on the inner diameter side of the fixing belt 21, and the shutter 27 includes a movable portion 31 that rotates along the inner peripheral surface of the fixing belt 21. By adopting such a configuration, it is possible to easily secure an installation space for the heater 23 and the shutter 27.

  The shutter 27 further includes a fixed portion 32 provided on the inner diameter side of the movable portion 31, and the movable portion 31 overlaps the fixed portion 32 when viewed from the heater 23 in a state where the shutter 27 is in the first posture. In a state where 27 is in the second posture, it is configured not to overlap with the fixing portion 32 when viewed from the heater 23. By adopting such a configuration, the amount of radiant heat blocked by the shutter 27 can be easily adjusted.

  The movable portion 31 of the shutter 27 blocks radiant heat from the heater 23 toward the upper end portion of the fixing belt 21 (the portion of the fixing belt 21 closest to the heater 23) in a state where the shutter 27 is in the first posture. In the state where the shutter 27 is in the second posture, the radiant heat from the heater 23 toward the upper end of the fixing belt 21 is blocked. By adopting such a configuration, it is possible to more reliably suppress overshoot (overheating) of the fixing belt 21.

  Further, the fixing device 18 includes a pressing pad 25 that presses the fixing belt 21 toward the lower side (the pressure roller 22 side). By adopting such a configuration, it is possible to reduce the heat capacity of the fixing device 18.

  In the present embodiment, the case where the radiant heat from the heater 23 toward the fixing belt 21 is blocked by the fixing portion 32 of the shutter 27 has been described. On the other hand, in other different embodiments, the radiant heat from the heater 23 toward the fixing belt 21 may be reflected by the inner surface of the fixed portion 32 of the shutter 27. In other words, the inner surface of the fixing portion 32 of the shutter 27 may be a reflecting surface that reflects radiant heat from the heater 23 toward the fixing belt 21.

  In the present embodiment, the case where the shutter 27 includes the movable portion 31 and the fixed portion 32 has been described. However, in another different embodiment, the shutter 27 may include only the movable portion 31.

  In this embodiment, the case where the shutter 27 blocks a part of the radiant heat from the heater 23 toward the fixing belt 21 in the state where the shutter 27 is in the first posture has been described. On the other hand, in another different embodiment, the shutter 27 may not block the radiant heat from the heater 23 toward the fixing belt 21 in a state where the shutter 27 is in the first posture.

  In the present embodiment, the case where the heater 23 is provided on the inner diameter side of the fixing belt 21 and the movable portion 31 of the shutter 27 rotates along the inner peripheral surface of the fixing belt 21 has been described. On the other hand, in another different embodiment, the heater 23 may be provided on the outer diameter side of the fixing belt 21, and the movable portion 31 of the shutter 27 may rotate along the outer peripheral surface of the fixing belt 21.

  In the present embodiment, the case where driving is input from the driving source 52 to the pressure roller 22 has been described. On the other hand, in another different embodiment, driving may be input to the fixing belt 21 from the driving source 52, or driving may be input to both the pressure roller 22 and the fixing belt 21 from the driving source 52.

  In this embodiment, the case where the heater 23 constituted by a halogen heater is used as a heat source has been described. However, in another different embodiment, another different heater such as a ceramic heater may be used as a heat source.

  In the present embodiment, the case where the configuration of the present invention is applied to the fixing device 18 that presses the fixing belt 21 toward the lower side (the pressure roller 22 side) with the pressing pad 25 has been described. In the embodiment, the configuration of the present invention may be applied to a fixing device 18 that rotates the fixing belt 21 together with one or a plurality of rollers disposed on the inner diameter side of the fixing belt 21.

  In this embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile machine, and a multifunction machine. May be.

1 Printer (image forming device)
18 Fixing Device 21 Fixing Belt 21a Both Front and Rear Ends (of Fixing Belt) 22 Pressure Roller (Pressure Member)
23 Heater (heating member)
25 Press pad (press member)
27 Shutter 28 Switching Mechanism 29 Stopping Member 30 Switch Mechanism 31 Movable Part 32 Fixed Part 33 Fixing Nip 40 Coil Spring (Biasing Member)
41 Solenoid (holding member)
42 Main body portion 43 Inner tube portion 44 Outer tube portion 45 Inner ring portion 46 Outer ring portion 47 Switch piece 48 Power supply portion 49 Drive circuit A Rotating shaft (of fixing belt)

Claims (7)

A fixing belt provided to be rotatable around a rotation axis;
A pressure member that presses against the fixing belt to form a fixing nip; and
A heating member for heating the fixing belt;
A first posture that does not block radiant heat from the heating member toward the fixing belt or blocks a part of radiant heat from the heating member toward the fixing belt; and radiant heat from the heating member toward the fixing belt. A shutter provided so as to be switchable between a second posture that blocks more than one posture;
A switching mechanism that switches the shutter from the first position to the second position in conjunction with the rotation of the fixing belt being stopped, and biasing the biasing of the shutter to the second position A switching mechanism comprising: a member; and a holding member that holds the shutter in the first posture against a biasing force of the biasing member ;
A power supply for supplying power to the holding member;
A switch mechanism that constitutes a driving circuit for the shutter together with the holding member and the power supply unit ,
The switch mechanism is
An inner ring portion and an outer ring portion provided at intervals from each other;
A connection posture for connecting the inner ring portion and the outer ring portion and a connection release posture for releasing the connection between the inner ring portion and the outer ring portion are provided so as to be switchable, and by a centrifugal force generated by the rotation of the fixing belt. A switch piece held in the connection posture,
As the rotation of the fixing belt stops, the centrifugal force disappears and the switch piece is switched from the connection posture to the connection release posture, and the drive circuit is cut off by the switch mechanism to remove power from the power supply unit. The supply of power to the holding member is stopped, the holding of the shutter with respect to the shutter by the holding member is released, and the shutter is moved from the first position to the first by the urging force of the urging member. A fixing device that switches to a posture of 2 . A detent member that is attached to an end of the fixing belt and regulates the rotation of the fixing belt in the rotation axis direction;
The stopper member is
A main body covering the outer side in the rotational axis direction of the end of the fixing belt;
An inner cylinder portion that extends inward in the rotational axis direction from the main body portion and is provided on the inner diameter side of the end portion of the fixing belt;
An outer cylinder portion extending from the main body portion to the inner side in the rotation axis direction and provided on an outer diameter side of the end portion of the fixing belt,
The inner ring portion is attached to the outer periphery of the inner cylinder portion,
The outer ring portion is attached to the inner periphery of the outer cylinder portion,
The fixing device according to claim 1 , wherein the switch piece is provided to be in contact with the inner ring portion and to be rotatable around an end portion on the inner ring portion side. The heating member is a heater provided on the inner diameter side of the fixing belt,
The shutter fixing device according to claim 1 or 2, characterized in that it comprises a movable portion that rotates along the inner peripheral surface of the fixing belt. The shutter further includes a fixed portion provided on the inner diameter side of the movable portion,
The movable portion overlaps with the fixed portion when viewed from the heating member when the shutter is in the first posture, and the fixed portion when viewed from the heating member when the shutter is in the second posture. The fixing device according to claim 3 , wherein the fixing device does not overlap with the fixing device. The shutter does not block radiant heat from the heating member toward the portion of the fixing belt that is closest to the heating member in the state of the first posture, and the shutter in the state of the second posture. the fixing device according to any one of claims 1 to 4, characterized in that blocking the radiant heat towards the closest part to the heating member of the fixing belt from members. The fixing device according to any one of claims 1 to 5, characterized by further comprising a pressing member for pressing against the fixing belt to the pressing member side. An image forming apparatus characterized in that it comprises a fixing device according to any one of claims 1-6.

Images