JP6051815B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  2. Description of the Related Art Conventionally, as a fixing device, a fixing belt is sandwiched between an endless fixing belt that is wound around a plurality of support rolls, heated and circulated, and a single support roll, and pressed against the outer surface of the fixing belt. A fixing device including a roll is known. In this fixing device, the fixing belt is circulated and supported while being tensioned by a plurality of support rolls. The sheet holding the unfixed toner image is sandwiched between the fixing belt and the fixing roll, and at that time, is subjected to heat and pressure from the fixing belt and the fixing roll. The toner image is fixed on the paper by the heating and pressurization.

  Here, there has been proposed a fixing device having a mechanism for separating the position of a support roll sandwiching the fixing belt from the fixing roll from the fixing roll when fixing is not performed (for example, Patent Document 1 and Patent Document 2). reference.). In this fixing device, the degree of impression of the fixing belt due to the fixing belt being sandwiched between the support roll and the fixing roll for a long time is reduced by the above-described mechanism.

Japanese Patent Laid-Open No. 2001-249469 JP 2004-287131 A

  An object of the present invention is to provide a fixing device and an image forming apparatus that can relieve the tension of the fixing belt while suppressing a change in the nip state.

The fixing device according to claim 1 comprises:
A belt assembly having an endless fixing belt;
The fixing belt is circulated and moved by being pressed against the outer surface of the fixing belt, and a medium holding an unfixed toner image is sandwiched between the fixing belt and the toner image is placed on the medium in cooperation with the fixing belt. A pressure member fixed to the
The belt assembly further comprises:
A support member;
A fixing member fixed to the support member, which is assigned to a region of the inner surface of the fixing belt facing the pressure member across the fixing belt, and the inner surface of the fixing belt slides due to circulation movement of the fixing belt;
One or more support rolls that are rotatable relative to the support member, supporting the fixing belt in a tensioned state with the fixing member in cooperation with the fixing member;
A tension relaxation mechanism that relaxes the tension of the fixing belt by operating any one or more of the one or more support rolls when the fixing device is not used ;
The pressure member is separated from the fixing belt when the fixing device is not used;
The fixing member is harder than the pressing member .

The image forming apparatus according to claim 2 comprises:
An image forming unit that forms an electrostatic latent image, develops it with toner, forms a toner image, and delivers the toner image to a medium;
A fixing unit for fixing the unfixed toner image delivered to the medium on the medium,
The fixing unit is
A belt assembly having an endless fixing belt;
The fixing belt is circulated and moved by being pressed against the outer surface of the fixing belt, and a medium holding an unfixed toner image is sandwiched between the fixing belt and the toner image is placed on the medium in cooperation with the fixing belt. A pressure member fixed to the belt assembly, and the belt assembly further comprises:
A support member;
A fixing member fixed to the support member, which is assigned to a region of the inner surface of the fixing belt facing the pressure member across the fixing belt, and the inner surface of the fixing belt slides due to circulation movement of the fixing belt;
One or more support rolls that are rotatable relative to the support member, supporting the fixing belt in a tensioned state with the fixing member in cooperation with the fixing member;
A tension relaxation mechanism that relaxes the tension of the fixing belt by operating any one or more of the one or more support rolls, and
The image forming apparatus includes a tension relaxation control unit that relaxes the tension applied to the fixing belt in the tension relaxation mechanism when the fixing unit is not used .
The pressure member is separated from the fixing belt when the fixing device is not used;
The fixing member is harder than the pressing member .

According to the fixing device of the first aspect and the image forming apparatus of the second aspect , it is possible to relax the tension of the fixing belt while suppressing the change in the nip state as compared with, for example, changing the position of the fixing member. .

1 is a configuration diagram illustrating an embodiment of an image forming apparatus of the present invention. 2 is a schematic diagram illustrating an internal structure of a fixing unit. FIG. It is an enlarged view showing the shape of the outer peripheral surface corresponding to the nip region N of the fixed pad. It is a schematic diagram which shows the roll support part of a 2nd support roll including a tension relaxation mechanism.

  Embodiments of the present invention will be described below.

  FIG. 1 is a configuration diagram showing an embodiment of an image forming apparatus of the present invention.

  The image forming apparatus 1 shown in FIG. 1 includes cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y), and black (K) image units 10C and 10M. , 10HC, 10HM, 10Y, 10K. The image forming apparatus 1 is a tandem type color printer in which the six image units 10C, 10M, 10HC, 10HM, 10Y, and 10K are arranged in parallel.

  In the image forming apparatus 1, a single color image is printed, and a full color image composed of six color toner images is also printed. In addition, the image forming apparatus 1 prints an image on only one side of the paper, and also prints an image on both sides of the paper.

  The toner cartridges 18C, 18M, 18HC, 18HM, 18Y, and 18K contain toners of the above six colors. For example, the toner has an average particle diameter of 2 μm or more and 7 μm or less, and an equivalent circle diameter of 0.95 or more and 1.0 or less. The toner cartridges 18C, 18M, 18HC, 18HM, 18Y, and 18K also contain a lubricant as an external additive for the toner.

  Since the six image units 10C, 10M, 10HC, 10HM, 10Y, and 10K have substantially the same configuration, the image unit 10C corresponding to cyan will be described as a representative example. The image unit 10 </ b> C includes a photoreceptor 11, a charger 12, an exposure device 13, a developing device 14, and a primary transfer device 15. The image unit 10 </ b> C is provided with a photoconductor cleaner 16 that cleans the photoconductor 11.

  The photoconductor 11 is a drum having a photoconductor layer provided on the surface of a cylindrical substrate. The photoconductor 11 holds an image formed on the surface and rotates in the direction of arrow A around the axis of the cylinder. The charging device 12, the exposure device 13, the developing device 14, the primary transfer device 15, and the photoconductor cleaner 16 are arranged around the photoconductor 11 in the order of the arrow A.

  The charger 12 charges the surface of the photoconductor 11. The charger 12 is a charging roll that contacts the surface of the photoreceptor 11. A voltage having the same polarity as that of the toner in the developing device 14 is applied to the charger 12, and the surface of the photoreceptor 11 that is in contact is charged.

  The exposure device 13 exposes the surface of the photoconductor 11 by irradiating the photoconductor 11 with exposure light. The exposure device 13 emits a laser beam corresponding to an image signal supplied from the outside of the image forming apparatus 1 and scans the surface of the photoconductor 11 with the laser beam.

  The developing device 14 develops the surface of the photoreceptor 11 using a developer. The developer 14 is supplied with toner from a toner cartridge. The developing device 14 agitates the developer in which the magnetic carrier and the toner are mixed to charge the toner and the magnetic carrier, and develops the surface of the photoreceptor 11 with the charged toner.

  The primary transfer unit 15 is a roll facing the photoconductor 11 with the intermediate transfer belt 20 interposed therebetween. The primary transfer unit 15 transfers the toner image on the photoconductor 11 to the intermediate transfer belt 20 by applying a voltage to the photoconductor 11.

  The photoconductor cleaner 16 cleans the surface of the photoconductor 11 by removing the toner (residual toner) remaining on the portion of the surface of the photoconductor 11 that has been transferred by the primary transfer unit 15.

  The image forming apparatus 1 also includes an intermediate transfer belt 20, two paper storage units 30, a secondary transfer unit 40, a fixing unit 50, a paper transport unit 60, a paper cooling unit 70, a curl correction unit 80, and a paper stacking unit. 90, a control unit 100, and a user interface unit 110 are also provided.

  The intermediate transfer belt 20 is an endless belt that is stretched around a belt support roll 21. The intermediate transfer belt 20 circulates in the direction of the arrow B passing through the image units 10C, 10M, 10HC, 10HM, 10Y, and 10K and the secondary transfer device 40. To the intermediate transfer belt 20, toner images of respective colors are transferred from the image units 10C, 10M, 10HC, 10HM, 10Y, and 10K. The intermediate transfer belt 20 moves while holding the toner images of these colors. Further, with respect to the circulating movement, a belt cleaner 22 is disposed on the downstream side of the secondary transfer device 40 and on the upstream side of the cyan image unit 10C. Residual toner remaining on the intermediate transfer belt 20 after transfer by the secondary transfer device 40 is removed by the belt cleaner 22.

  The two sheet storage units 30 store sheets having different dimensions and the like. Each sheet storage unit 30 stores sheets corresponding to dimensions and the like stacked in the sheet storage unit 30.

  The secondary transfer device 40 is a roll that rotates with the intermediate transfer belt 20 and the paper sandwiched between one of the belt support rolls 21. The secondary transfer device 40 transfers a toner image on the intermediate transfer belt 20 to a sheet by applying a voltage having a polarity opposite to the charging polarity of the toner.

  A combination of the image units 10C, 10M, 10HC, 10HM, 10Y, and 10K, the intermediate transfer belt 20, and the secondary transfer device 40 corresponds to an example of the image forming unit referred to in the present invention.

  The fixing unit 50 is a device that fixes a toner image on a sheet. The fixing unit 50 corresponds to an embodiment of a fixing device according to the present invention. The fixing unit 50 corresponds to an example of a fixing unit included in the image forming apparatus according to the present invention. The fixing unit 50 will be described in detail later.

  The paper transport unit 60 turns over the main transport path R1 that takes out the paper stored in the paper storage unit 30 and transports it to the secondary transfer unit 40, and the paper on which printing of an image on one side has been completed during double-sided printing. A double-sided conveyance path R2 that joins the main conveyance path R1.

  The main transport path R1 includes a take-out roll 61 for picking up the paper stored in the paper storage unit 30, a scooping roll 62 for picking up the picked-up paper, and a plurality of papers that transport the paper in the direction of arrow C on the main transport path R1 A transport roll 63 is disposed. Further, a registration roll 64 that conveys the sheet to the secondary transfer device 40 and a conveyance belt 65 that conveys the sheet to the fixing unit 50 are also arranged in the main conveyance path R1.

  In the double-sided conveyance path R2, a distribution unit 66 that distributes the sheet from the curl correction unit 80 to either the sheet stacking unit 90 or the double-sided conveyance path R2, and the double-sided conveyance path R2 is indicated by an arrow D. A plurality of conveyance rolls 63 that convey the sheet in the direction are arranged. In the double-sided conveyance path R2, a temporary storage unit 67 that temporarily stores the paper to turn it over and a delivery roll 68 that sends the paper out of the temporary storage unit 67 are disposed.

  The movement of the sheet in the main transport path R1 and the duplex transport path R2 will be described later together with the basic operation of the image forming apparatus 1.

  The sheet cooling unit 70 cools the sheet that has been heated during fixing by the fixing unit 50.

  The curl correcting unit 80 corrects the bending of the sheet caused by the heating in the fixing unit 50 and the cooling in the sheet cooling unit 70.

  The paper stacking unit 90 is for stacking paper discharged after printing is completed.

  Next, the basic operation of the image forming apparatus 1 will be described.

  The basic operation of the image forming apparatus 1 shown in FIG. 1 will be described. In the cyan image unit 10 </ b> C, the photoconductor 11 rotates in the direction of arrow A, and the surface of the photoconductor 11 is charged by the charger 12. The exposure device 13 forms an electrostatic latent image on the surface of the photoconductor 11 by irradiating the surface of the photoconductor 11 with exposure light based on an image signal corresponding to cyan among image signals supplied from the outside. . The developing device 14 is supplied with cyan toner from the toner cartridge 18C, and develops the electrostatic latent image on the photoconductor 11 with toner, thereby forming a toner image. The photoconductor 11 rotates while holding a cyan toner image formed on the surface. The toner image formed on the surface of the photoreceptor 11 is transferred to the intermediate transfer belt 20 by the primary transfer unit 15. After the transfer, the residual toner remaining on the photoconductor 11 is removed by the photoconductor cleaner 16.

  The intermediate transfer belt 20 circulates in the direction of arrow B. The image units 10M, 10HC, 10HM, 10Y, and 10K corresponding to colors other than cyan form toner images corresponding to the respective colors, similarly to the cyan image unit 10C. Then, the toner images of the respective colors are transferred onto the intermediate transfer belt 20 so as to be superimposed on the cyan toner image.

The paper is taken out from the paper storage unit 30 by the take-out roll 61. The sheet is conveyed in the direction of arrow C along the main sheet conveyance path R1 toward the secondary transfer unit 40 by the conveyance roll 63 and the registration roll 64. The registration roll 64 sends the paper to the secondary transfer device 40 based on the timing at which the toner image is transferred onto the intermediate transfer belt 20. The secondary transfer device 40 transfers the toner image on the intermediate transfer belt 20 to a sheet. After the transfer, the residual toner remaining on the intermediate transfer belt 20 is removed by the belt cleaner 22. The sheet on which the toner image is transferred is conveyed to the fixing unit 50 by the conveyance belt 65. The fixing unit 50 heats and pressurizes the paper, thereby fixing the toner image on the paper. The sheet after fixing is cooled by the sheet cooling unit 70, and the curl correction unit 80 corrects the bending.

  In the image forming apparatus 1 of the present embodiment, the user interface unit 110 specifies whether to print an image on only one side of a sheet or to print an image on both sides of a sheet.

  When printing of an image on only one side is designated, the distribution unit 66 directs the paper from the curl correction unit 80 to the paper stacking unit 90 according to an instruction from the control unit 100.

  On the other hand, when printing of images on both sides is designated, the sorting unit 66 directs the sheet to the duplex conveyance path R2. In the double-side conveyance path R <b> 2, the sheet is first conveyed to the temporary storage unit 67 in the direction of arrow D by the plurality of conveyance rolls 63. Thereafter, the sheet is sent out from the temporary storage unit 67 by the sending roll 68, and further conveyed by the conveying roll 63 in the direction of the arrow D to join the main conveying path R1. After the merging, the secondary transfer is performed by the registration roll 64 in a state where the main transfer path R1 is transferred in the direction of arrow C and the surface opposite to the surface on which the toner image has been transferred is directed to the intermediate transfer belt 20. It is sent out to the transfer device 40. The toner image is transferred to the opposite surface, fixed by the fixing unit 50, cooled by the paper cooling unit 70, and further bent by the curl correction unit 80. Then, the paper is sorted by the sorting unit 66 to the paper stacking unit 90.

  As described above, the sheet on which the image is formed on only one side or both sides and discharged to the sheet stacking unit 90 is stacked on the sheet stacking unit 90.

  Next, the fixing unit 50 will be described.

  FIG. 2 is a schematic diagram showing the internal structure of the fixing unit.

  The fixing unit 50 includes a casing 51, a belt module 52 including an endless fixing belt 521, a fixing roll 53, a nip inlet guide unit 54, and a nip outlet guide unit 55. The belt module 52 includes a fixing pad 522, a first support roll 523, a second support roll 524, and a belt temperature detection sensor 525 in addition to the fixing belt 521.

  The fixed pad 522 is fixed to the casing 51, and the first support roll 523 and the second support roll 524 are supported by the casing 51 so as to be rotatable around a rotation axis extending in the longitudinal direction of each roll. . The fixing belt 521 is wound around the fixed pad 522, the first support roll 523, and the second support roll 524.

  The fixing belt 521 is formed by laminating a base layer, an elastic layer, and a release layer from the inner surface side to the outer surface side of the fixing belt 521. The base layer is made of a polyimide resin. The elastic body layer is made of silicone rubber. The release layer is made of PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin). The structure and material of the fixing belt are not limited to the structure and material in the above-described embodiment, and may be other structures and materials.

  The fixing pad 522 is not specified here, but has an outer peripheral surface formed of, for example, aluminum or SUS (Special Use Stainless Steel). In the present embodiment, one halogen heater 522a is built in the fixed pad 522. The fixing pad 522 is heated to about 150 ° C. by the halogen heater 522a at the time of fixing. Note that the number of halogen heaters in the fixed pad and the heating temperature by the halogen heater are not limited to the above number (one) and temperature (150 ° C.), but may be other numbers or temperatures.

  Although it does not specify here, the 1st support roll 523 is a roll formed, for example with aluminum or SUS. In the present embodiment, the first support roll 523 includes four halogen heaters 523a. The first support roll 523 is heated to about 190 ° C. by the halogen heater 523a at the time of fixing. The number of halogen heaters in the first support roll and the heating temperature by the halogen heater are not limited to the above number (4) and temperature (190 ° C.), but may be other numbers or temperatures. good.

  The second support roll 524 is a roll formed of, for example, aluminum or SUS. In the present embodiment, the second support roll 524 includes three halogen heaters 524a. The second support roll 524 is heated to about 190 ° C. by the halogen heater 524a at the time of fixing. The number of halogen heaters in the second support roll and the heating temperature by the halogen heater are not limited to the above number (3) and temperature (190 ° C.), but may be other numbers or temperatures. good.

  In this embodiment, the second support roll 524 is spring-biased in the direction indicated by the arrow E so as to apply a tension of about 150 kgf to the fixing belt 521 when fixing the toner image on the paper. This spring bias will be described later in detail. Note that the tension applied to the fixing belt 521 by the second support roll is not limited to about 150 kgf, and may be a tension of another magnitude.

  The second support roll 524 is supported by the casing 51 via a mechanism that controls the position of the fixing belt 521 in the width direction by twisting the circulating fixing belt 521 in the direction indicated by the arrow F. ing. A mechanism for controlling the position of the fixing belt 521 in the width direction is known and will not be described here.

  A fixing roll 53 is supported on the casing 51 so as to be rotatable about a rotation axis extending in the longitudinal direction of the fixing roll 53. Although the fixing roll 53 is not specified here, for example, a roll formed of aluminum or SUS is used as a base, and an elastic layer and a release layer are sequentially laminated from the base side. The elastic layer is made of silicone rubber, and the release layer is made of PFA. Note that the structure and material of the fixing roll are not limited to the structure and material in the above-described embodiment, and may be other structures and materials.

  The fixing roll 53 is pressed against the fixed pad 522 with the fixing belt 521 sandwiched during fixing, and is separated from the fixed pad 522 except during fixing. Although the contact and separation of the fixing roll 53 with respect to the fixed pad 522 is performed by a mechanism (not shown), since this mechanism is also known, a description thereof is omitted here. In fixing, the fixing roll 53 is driven to rotate by a motor (not shown). The fixing belt 521 is circulated and moved in accordance with the rotation of the fixing roll 53 by the rotational driving of the fixing roll 53 in a state where the fixing belt 521 is pressed against the fixing pad 522. Further, during the circulating movement, the inner surface of the fixing belt 521 slides on the surface of the fixing pad 522 on the fixing roll 53 side.

  The belt temperature detection sensor 525 is a sensor that detects the temperature of the fixing belt 521. The detection result of the belt temperature detection sensor 525 is sent to the control unit 100 shown in FIG.

  The fixing belt 521 corresponds to an example of a fixing belt according to the present invention, the belt module 52 corresponds to an example of a belt assembly according to the present invention, and the fixing roll 53 corresponds to an example of a pressure member according to the present invention. The casing 51 corresponds to an example of a support member according to the present invention, the fixing pad 522 corresponds to an example of a fixing member according to the present invention, and the first support roll 523 and the second support roll 524 refer to the present invention. It corresponds to an example of one or more support rolls.

  In the present embodiment, the halogen heaters are incorporated in each of the fixed pad 522, the first support roll 523, and the second support roll 524 as described above, and these halogen heaters are energized during fixing. Thereby, the fixing belt 521 at the time of fixing is heated by these halogen heaters. Further, as described above, at the time of fixing, the fixing roll 53 is rotationally driven and pressed against the fixed pad 522 with the fixing belt 521 interposed therebetween.

  Here, the heating of the fixed pad 522, the first support roll 523, and the second support roll 524 by the halogen heater, the pressing of the fixing roll 53 against the fixed pad 522, and the rotational driving of the fixing roll 53 are controlled as shown in FIG. This is performed under the control of the unit 100.

  An image signal representing an image to be formed is supplied to the control unit 100 from the outside of the image forming apparatus 1. When the image signal is supplied, the control unit 100 energizes the halogen heaters of the fixing pad 522, the first support roll 523, and the second support roll 524 in the fixing unit 50, and supplies the fixing pad 53 to the fixing pad 522. Executes pressing and rotation driving. At this time, the control unit 100 starts the operation of the image units 10C, 10M, 10HC, 10HM, 10Y, and 10K, the paper transport unit 60, and the like.

  On the other hand, when the image formation is completed for the supplied image signal and no new image signal is supplied, the control unit 100 stops the operation of each unit described above and stops the rotation driving of the fixing roll 53 and Perform a separation from the fixed pad 522. In addition, the control unit 100 stops energizing the halogen heaters of the fixed pad 522, the first support roll 523, and the second support roll 524.

  At the time of fixing executed under the control of the control unit 100, a sheet holding an unfixed toner image in an area (nip area N) where the fixing belt 521 and the fixed pad 522 are pressed against each other by the pressing is as follows. Feeded in the direction of arrow C by the nip inlet guide 54. The sheet is sandwiched between the fixing roll 53 and the fixing belt 521 and pressed, and is fed from the nip region N while being heated by the heat from the fixing belt 521. Then, the toner image is fixed on the paper by the pressurization and heating received while passing through the nip region N. Thereafter, the sheet is guided to the sheet cooling unit 70 (see FIG. 1) outside the fixing device 50 by the nip outlet guide unit 55.

  Here, in the present embodiment, the outer peripheral surface of the fixed pad 522 corresponding to the nip region N has the following shape.

  FIG. 3 is an enlarged view showing the shape of the outer peripheral surface corresponding to the nip region N of the fixed pad.

  The pressed portion 522b on the outer peripheral surface of the fixed pad 522 corresponding to the nip region N, to which the fixing roll 53 is pressed, has a concave shape with a curvature of 35 mm in this embodiment. Then, with respect to the sheet conveyance direction indicated by arrow C, a nip inlet portion 522c on the upstream side and a nip outlet portion 522d on the downstream side of the pressed portion 522b have a convex shape with a curvature of 4 mm. The curvatures of the pressed portion 522b and the nip outlet portion 522d are not limited to the above-described curvature, and may be other values.

  At the entrance of the nip region N, the sheet is guided between the fixing belt 521 and the fixing roll 53 by being guided by the fixing belt 521 bent at a curvature of 4 mm along the nip entrance portion 522c of the fixed pad 522.

  In the nip region N, the sheet is sandwiched between the fixing belt 521 and the fixing roll 53 and heated and pressurized over a range corresponding to the shape of the curvature 35 mm of the pressed portion 522b of the fixed pad 522. Here, in this embodiment, as described above, the outer peripheral surface of the fixed pad 522 is formed of a relatively hard material such as aluminum or SUS, and the fixing roller 53 pressed against the fixed pad 522 has silicone rubber or the like. The elastic layer is provided. Therefore, in the nip region N, the outer peripheral surface of the fixing roll 53 is deformed following the outer peripheral surface of the fixed pad 522 exclusively. Then, the fixing belt 521 wound around the fixed pad 522 without deformation passes through the nip region N while maintaining the moving speed constant during the circular movement. Thereby, wrinkles and distortion of the fixing belt 521 in the nip region N are suppressed, and a high-quality fixed image is stably provided.

  At the exit of the nip region N, a micro slip occurs between the fixing belt 521 that is bent upward with a curvature of 4 mm following the nip exit portion 522d of the fixed pad 522 and the toner image on the paper, and the fixing belt 521 and the toner image Adhesion with is weakened. As a result, at the exit of the nip region N, the sheet peels from the fixing belt 521 due to the stiffness of the sheet itself.

  Here, as described above, a tension of about 150 kgf is applied to the fixing belt 521 by the second support roll 524 shown in FIG. At the time of fixing, since the fixing belt 521 is heated to increase flexibility, the fixing belt 521 is circulated and moved in accordance with the shape of the outer peripheral surface of the fixed pad 522 under this tension.

  On the other hand, when heating of the fixing belt 521 is stopped at the time of non-fixing, if the fixing belt 521 is cooled while the above tension is applied, the following indentations are present on the fixing belt 521. There is a risk of it.

  As described above, at the entrance and exit of the nip region N, the fixing belt 521 to which tension is applied is bent with a curvature of 4 mm following the nip exit portion 522d and the nip exit portion 522d of the fixed pad 522. In the circulation path of the fixing belt 521, the curvature at the entrance and exit of the nip region N is the smallest. This curvature is smaller than the curvature at which the fixing belt 521, which has cooled and has reduced flexibility, can return to its original extended state by its own restoring force.

  For this reason, when the fixing belt 521 cools while tension is applied, the flexibility is lowered while being bent and tension is applied, and the fixing belt 521 has traces of the bent shape, that is, indentations. May occur.

  Here, in this embodiment, a tension relaxation mechanism that relaxes the tension of the fixing belt 521 is provided in accordance with an instruction from the control unit 100 illustrated in FIG. 1. When the temperature detected by the belt temperature detection sensor 525 shown in FIG. 2 is lower than 100 ° C. for the fixing belt 521 that is not heated and is not heated, the control unit 100 adjusts the tension of the fixing belt 521 to the tension relaxation mechanism. Relax.

  The case where the temperature detected by the belt temperature detection sensor 525 falls below 100 ° C. corresponds to an example of “when the fixing device is not used during the power-on period” according to the present invention.

  The “when the fixing device is not used during the power-on period” referred to in the present invention is not limited to this. In the present invention, “when the fixing device is not used during the power-on period”, for example, the control unit 100 determines that image formation has been completed for the supplied image signal and no new image signal is supplied. It may be time. Alternatively, “when the fixing device is not used during the power-on period” according to the present invention refers to a case where the next sheet is not supplied even after a predetermined time has elapsed after the sheet is fixed in the fixing apparatus. There may be.

  In this embodiment, this tension relaxation mechanism is incorporated in the roll support portion of the second support roll 524.

  FIG. 4 is a schematic diagram showing a roll support portion of a second support roll including a tension relaxation mechanism.

  The roll support portion 526 of the second support roll 524 includes a bearing 526a, a support block 526b, a first guide member 526c, a compression spring 526d, a second guide member 526e, and a cam 526f.

  The bearing 526a rotatably supports the rotation shaft 524b of the second support roll 524. The bearing 526a is fixed to the support block 526b.

  The first guide member 526c has a guide groove 526c_1 that extends in the direction in which the second support roll 524 applies tension to the fixing belt 521 (arrow E1) or the direction in which tension is relaxed (arrow E2). The support block 526b is fitted in the guide groove 526c_1 so as to be movable in both the direction indicated by the arrow E1 and the direction indicated by the arrow E2. Further, a compression spring 526d is disposed between the bottom of the guide groove 526c_1 and the support block 526b.

  The second guide member 526e sandwiches the first guide member 526c from the side, and the first guide member 526c is oriented in the direction indicated by the arrow F1 in the same direction as the arrow E1 and in the direction indicated by the arrow F2 in the same direction as the arrow E2. It is supported to move freely.

  The cam 526f is disposed at a position where the outer bottom surface of the first guide member 526c is pushed up toward the fixing belt 521 by rotation in the direction indicated by the arrow G1.

  In the roll support portion 526, when the cam 526f rotates in the direction indicated by the arrow G1, the first guide member 526c moves in the arrow F1 direction.

  Then, the support block 526b is pushed up via the compression spring 526d, and the second support roll 524 supported by the support block 526b moves in the direction indicated by the arrow E1 to apply tension to the fixing belt 521.

  In this embodiment, the urging force of the compression spring 526d causes the second support roll 524 to have a tension of about 150 kgf on the fixing belt 521 when the cam 526f pushes the outer bottom surface of the first guide member 526c toward the fixing belt 521. It is an urging force to grant.

  On the other hand, when the cam 526f rotates in the direction indicated by the arrow G2 opposite to the arrow G1, the first guide member 526c moves in the arrow F2 direction. Then, the support block 526b together with the first guide member 526c, and the second support roll 524 moves in the direction indicated by the arrow E2. Thereby, the tension on the fixing belt 521 is relieved.

  This roll support portion 526 corresponds to an example of a tension relaxation mechanism according to the present invention.

  In this embodiment, the rotation of the cam 526f in the roll support portion 526 in the direction indicated by the arrow G1 or the direction indicated by the arrow G2 is performed as follows under the control of the control unit 100 shown in FIG. The control unit 100 corresponds to an example of a tension relaxation control unit according to the present invention.

  When the image formation is completed for the image signal supplied from the outside of the image forming apparatus 1 and no new image signal is supplied, the control unit 100 stops the rotation of the fixing roller 53 and the fixed pad as described above. Perform separation from 522. Furthermore, the control unit 100 stops energization of the halogen heaters of the fixed pad 522, the first support roll 523, and the second support roll 524. Then, after stopping energization, when the temperature detected by the temperature sensor 525 shown in FIG. 2 is lower than 100 ° C., the control unit 100 rotates the cam 526f in the direction indicated by the arrow G2. As a result, the roll support portion 526 performs the above-described operation, and the tension of the fixing belt 521 is relaxed. For this reason, at the time of non-fixing, the fixing belt 521 is cooled in a relaxed state at the entrance and exit of the nip region N, and the above-described degree of indentation at the entrance and exit of the nip region N is suppressed.

  Here, unlike the present embodiment, as a method of relaxing the tension of the fixing belt 521, a method of relaxing the tension of the fixing belt 521 by moving the fixing pad 522 away from the fixing belt 521 can be considered. However, when the fixed pad 522 is moved, there is a possibility that the position of the fixed pad 522 in the moving direction of the fixing belt 521 may be shifted due to play in manufacturing of the movable part. Such misalignment of the fixed pad 522 causes instability of the nip state.

  In the present embodiment, the tension of the fixing belt 521 is relaxed by moving the second support roll 524 without moving the fixed pad 522. For this reason, in this embodiment, the tension of the fixing belt 521 is reduced while suppressing the change in the nip state as compared with the case where the tension of the fixing belt 521 is reduced by moving the fixed pad 522 as described above. .

  In the present embodiment, when the user instructs to shut off the power, if the tension of the fixing belt 521 has already been relaxed, the controller 100 performs the power shut-off process while the tension of the fixing belt 521 is relaxed. Is called. On the other hand, if the tension of the fixing belt 521 has not been relaxed when the power shutdown is instructed, the control unit 100 performs the power shutdown process after the roll support 526 has relaxed the tension of the fixing belt 521. .

  In the present embodiment, as an example of the tension relaxation mechanism and the tension relaxation control unit according to the present invention, a roll that relaxes the tension of the fixing belt both when the power is shut off and when the temperature of the fixing belt falls below 100 ° C. The support part 526 and the control part 100 are illustrated. However, the tension relaxation mechanism and the tension relaxation control unit referred to in the present invention are not limited to these. The tension relaxation mechanism and the tension relaxation control unit of the present invention may relax the tension of the fixing belt only when the power is shut off, for example.

  In this embodiment, a tandem color printer is illustrated as an example of the image forming apparatus of the present invention. However, the image forming apparatus of the present invention may be a so-called rotary color printer in which a plurality of developing devices are arranged around the rotation axis, or may be a monochrome printer. The image forming apparatus of the present invention is not limited to a printer, and may be a copying machine, a facsimile, or the like.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10C, 10M, 10HC, 10HM, 10Y, 10K Image unit 11 Photoconductor 12 Charger 13 Exposure device 14 Developer 15 Primary transfer device 16 Photoconductor cleaner 18C, 18M, 18HC, 18HM, 18Y, 18K Toner cartridge DESCRIPTION OF SYMBOLS 20 Intermediate transfer belt 21 Belt support roll 22 Belt cleaner 30 Paper storage part 40 Secondary transfer device 50 Fixing part 51 Case 52 Belt module 521 Fixing belt 522 Fixed pad 522a, 523a, 524a Halogen heater 522b Pressed part 522c Nip entrance part 522d Nip exit portion 523 First support roll 524 Second support roll 524b Rotating shaft 525 Belt temperature detection sensor 526 Roll support portion 526a Bearing 526b Support block 526c First guide portion Material 526c_1 Guide groove 526d Compression spring 526e Second guide member 526f Cam 53 Fixing roll 54 Nip inlet guide section 55 Nip outlet guide section 60 Paper transport section 61 Take-out roll 62 Rolling roll 63 Transport roll 64 Registration roll 65 Transport belt 66 Distribution Unit 67 temporary storage unit 68 delivery roll 70 sheet cooling unit 80 curl correction unit 90 sheet stacking unit 100 control unit 110 user interface unit

Claims (2)

A belt assembly having an endless fixing belt;
The fixing belt is circulated and moved by being pressed against the outer surface of the fixing belt, and a medium holding an unfixed toner image is sandwiched between the fixing belt and the toner in cooperation with the fixing belt. A pressure member for fixing the image on the medium;
A temperature detector for detecting the temperature of the fixing belt,
The belt assembly further comprises:
A support member;
A fixing member fixed to the support member, which is assigned to a region of the inner surface of the fixing belt facing the pressure member across the fixing belt, and the inner surface of the fixing belt slides due to circulation movement of the fixing belt. When,
One or more support rolls that are rotatable relative to the support member, supporting the fixing belt in a tensioned state with the fixing member in cooperation with the fixing member;
When the temperature detected by the temperature detector falls below a predetermined threshold temperature, the tension of the fixing belt is reduced by operating any one or more of the one or more support rolls. and a strain relief mechanism,
The pressure member is separated from the fixing belt when the fixing device is not used;
The fixing device , wherein the fixing member is harder than the pressure member . An image forming apparatus comprising the fixing device according to claim 1.

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