JP2015114551A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus that can equalize a conveying speed of a recording sheet by a rotary driving fixing member to a conveying speed of the recording sheet by a rotary driving transfer conveyance member as much as possible and thereby suppress trouble of an image defect such as image blurring.SOLUTION: An image formation apparatus includes a conveying speed control part which controls conveying speeds of a recording sheet so that the conveying speed of the recording sheet by a rotary driving fixing member is equal to or substantially equal to the conveying speed of the recording sheet by a rotary driving transfer conveyance member, and the conveying speed control part makes the conveying speed of the recording sheet by the rotary driving fixing member fast based upon a rise in temperature of the rotary driving transfer conveyance member when the rotary driving transfer conveyance member is heated with radiant heat from a heating and fixing part.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a multifunction machine, and a printer.

  In general, an image forming apparatus such as a copying machine, a multifunction machine, or a printer generally includes a transfer transfer roller including a transfer transfer roller that transfers a recording sheet such as a recording sheet onto which an unfixed image (specifically, a toner image) is transferred. A recording paper having a transfer conveying unit having a member and a heating fixing unit having a rotating fixing member including a fixing roller to be heated and a pressure roller disposed to face the fixing roller, onto which an unfixed image is transferred The recording sheet is conveyed to the heat fixing unit by the transfer conveying unit, and the unfixed image on the recording sheet conveyed to the heat fixing unit is heated and fixed by the heat fixing unit.

  Here, examples of the rotary transfer conveying member include a single or a plurality of transfer conveying rollers, and a single or a plurality of transfer conveying rollers arranged along the recording sheet conveying path can be exemplified. An example of the conveyance belt configuration includes a plurality of transfer conveyance rollers and a conveyance belt wound around the plurality of transfer conveyance rollers, and a part of the conveyance belt is provided along the conveyance path of the recording sheet.

  On the other hand, the rotary fixing member can be exemplified by an internal heating configuration including a fixing roller heated from the inside and a pressure roller disposed facing the fixing roller, and a fixing roller heated from the outside And an external heating configuration including a pressure roller disposed opposite to the fixing roller. The external heating structure further includes a heating roller that is heated from the inside, a fixing roller that is arranged in parallel with the heating roller, and a fixing belt that is wound around the heating roller and the fixing roller. An example of an external heating and fixing belt configuration in which the pressure roller is disposed opposite the fixing roller can be exemplified.

  For example, in the case of a conveyor belt configuration, the rotationally driven transfer conveying member that is rotationally driven in the transfer conveying unit is a transfer conveying roller located on the most downstream side in the recording sheet conveying direction. . In addition, the rotational driving fixing member that is rotationally driven among the rotational fixing members in the heat fixing unit is, for example, one of a fixing roller and a pressure roller.

  In such an image forming apparatus, the rotational drive fixing member (for example, the rotationally driven fixing roller or the rotationally driven pressure roller) changes in temperature, so that the rotationally driven fixing member is thermally expanded or contracted to have an outer diameter. If it changes, the peripheral speed of the rotational driving fixing member changes accordingly, and as a result, the recording sheet conveyance speed by the rotational driving fixing member changes.

  In this regard, Patent Document 1 determines the rotation speed of the pressure member based on information at the start or end of the fixing operation, and drives the driving unit based on the rotation speed to rotate the pressure member. The point which controls speed is indicated.

  Further, Patent Document 2 obtains the peripheral speed change rate between the fixing rotator and the transport rotator from the temperature change rate of the apparatus main body generated by the printing process, and before the printing process, the first peripheral speed of the transport rotator. The correction peripheral speed calculated from the peripheral speed change rate and the printing operation time is added to at least one of the peripheral speed and the second peripheral speed of the fixing rotator to operate the fixing rotator and the transport rotator. Is disclosed.

  Further, in Patent Document 3, when the recording material conveyance speed by the transfer roller is vt and the recording material conveyance speed by the pressure roller is vp, the transfer bias V1 when vt> vp is the transfer bias when vt <vp. It discloses that the transfer current A1 is smaller than V2, or the transfer current A1 when vt> vp is smaller than the transfer current A2 when vt <vp.

JP 2008-298877 A JP 2010-72493 A JP 2005-292549 A

  By the way, as the rotationally driven transfer conveying member (for example, the rotationally driven transfer conveying roller) in the transfer conveying unit is heated by the radiant heat from the heat fixing unit, thermal energy is supplied from the heating fixing unit to the rotationally driven transfer conveying member. Since the temperature continues, the temperature of the rotationally driven transfer conveying member gradually increases although it is moderate. Then, as the temperature of the rotational driving transfer / conveying member rises, the rotational driving transfer / conveying member (particularly the rotational driving transfer / conveying member disposed in the vicinity of the heat fixing unit) thermally expands. When the outer diameter of the rotary drive transfer conveyance member increases with the thermal expansion of the rotary drive transfer conveyance member, the peripheral speed of the rotary drive transfer conveyance member increases accordingly, and as a result, the recording sheet conveyance speed by the rotary drive transfer conveyance member increases. Get faster.

  From this point of view, as the rotational drive transfer / conveying member is heated by the radiant heat from the heating and fixing unit, the temperature of the rotational drive transfer / conveying member increases and the rotational speed of the recording sheet by the rotational drive / fixing member increases. It becomes slower than the conveyance speed of the recording sheet by the member. For this reason, the recording sheet conveyed by the rotation driving transfer conveying member and the rotation driving fixing member is loosened between the rotation driving transfer conveying member and the rotation driving fixing member. Then, for example, an unfixed image on the recording sheet comes into contact with the vicinity of the upstream side of the fixing nip portion of the rotating fixing member (for example, fixing roller) in the rotating direction of the rotating fixing member (for example, fixing roller), and the image becomes blurred. This causes inconvenience such as image defects. This is particularly noticeable for solid images (images on which toner is formed on one surface) of a relatively large size recording sheet such as A3 size or double letter size.

  However, the inventions described in Patent Documents 1 to 3 are not considered at all with respect to such inconveniences caused by the discrepancy between the recording sheet conveyance speed by the rotation driving fixing member and the recording sheet conveyance speed by the rotation driving transfer conveyance member. Not.

  Therefore, the present invention can match the recording sheet conveyance speed by the rotation driving fixing member and the recording sheet conveyance speed by the rotation driving transfer conveyance member as much as possible, thereby causing an image defect such as image fading. An object of the present invention is to provide an image forming apparatus capable of suppressing inconvenience.

  In order to solve the above problems, the present invention includes a transfer conveyance unit having a rotary transfer conveyance member and a heating fixing unit having a rotation fixing member, and the recording sheet on which an unfixed image is transferred is transferred to the transfer conveyance unit. The image forming apparatus transports the unfixed image on the recording sheet transported to the heat fixing unit by the heat fixing unit by the heat fixing unit, the rotation in the heat fixing unit The conveyance speed of the recording sheet by a rotationally driven fixing member that is rotationally driven among the fixing members, and the conveyance speed of the recording sheet by a rotationally driven transfer conveyance member that is rotationally driven among the rotational transfer conveyance members in the transfer conveyance unit, Includes a conveyance speed control unit that controls the conveyance speed of the recording sheet so that they coincide or substantially coincide with each other. An image in which the recording sheet conveyance speed by the rotation driving fixing member is increased based on an increase amount by which the temperature of the rotation driving transfer conveyance member increases when heated by radiant heat from a heat fixing unit. A forming apparatus is provided.

  In the present invention, the transport speed control unit may transport the recording sheet by the rotational driving fixing member based on a decrease amount by which the temperature of the rotational driving fixing member decreases when performing image formation on the recording sheet. An example of increasing the speed can be exemplified.

  In the present invention, a first temperature sensor for detecting the temperature of the rotational driving fixing member, and a driving device that rotationally drives the rotational driving fixing member to vary the rotational speed of the rotational driving fixing member, The first temperature sensor detects a temperature inside the outer peripheral surface of the rotational drive fixing member, and the conveyance speed control unit detects the temperature by the first temperature sensor when performing image formation on the recording sheet. A correction amount of the peripheral speed of the rotational drive fixing member is obtained based on a decrease amount in which the temperature inside the outer peripheral surface of the rotational drive fixing member decreases, and the drive device is operated with the obtained correction amount to perform the rotation. An example of increasing the recording sheet conveyance speed by the driving fixing member can be exemplified.

  In the present invention, the rotational drive fixing member is configured to include a cored bar and a resin member provided on an outer peripheral surface of the cored bar, and the first temperature sensor detects the temperature of the cored bar. The conveying speed control unit is configured to determine a peripheral speed of the rotationally driving fixing member based on a decrease amount of the core metal temperature detected by the first temperature sensor when performing image formation on the recording sheet. An example in which the correction amount is obtained and the drive device is operated with the obtained correction amount to increase the recording sheet conveyance speed by the rotationally driving fixing member can be exemplified.

  In the present invention, a heat source that heats the rotational drive fixing member from the inside is provided, and the conveyance speed control unit is configured to detect when the amount of decrease of the rotational drive fixing member exceeds a predetermined amount or exceeds the predetermined amount. A mode in which the heat source is heated to heat the rotary drive fixing member from the inside can be exemplified.

  In the present invention, the transport speed control unit is based on the rotation driving fixing member that is rotationally driven among the rotation fixing members in the heat fixing unit with reference to a predetermined state of the image forming apparatus. In a state in which the recording sheet conveyance speed coincides or substantially coincides with the recording sheet conveyance speed by the rotationally driven transfer conveyance member that is rotationally driven among the rotary transfer conveyance members in the transfer conveyance unit, the recording sheet The aspect which changes a conveyance speed can be illustrated.

  In the present invention, a second temperature sensor for detecting the temperature of the rotationally driven transfer conveying member, and a drive device that rotationally drives the rotationally driven fixing member to vary the rotational speed of the rotationally driven fixing member, The second temperature sensor detects an ambient temperature around the rotation drive transfer conveyance member, and the conveyance speed control unit is configured to heat the rotation drive transfer conveyance member by radiant heat from the heating fixing unit. A correction amount of the peripheral speed of the rotation drive fixing member is obtained based on an increase amount of the ambient temperature around the rotation drive transfer conveyance member detected by the second temperature sensor, and the correction amount is obtained based on the obtained correction amount. A mode in which the drive device is operated to increase the recording sheet conveyance speed by the rotational drive fixing member can be exemplified.

  In the present invention, a second temperature sensor for detecting the temperature of the rotationally driven transfer conveying member, and a drive device that rotationally drives the rotationally driven fixing member to vary the rotational speed of the rotationally driven fixing member, The rotary transfer conveyance member includes a plurality of transfer conveyance rollers and a conveyance belt wound around the plurality of transfer conveyance rollers, and the rotation drive transfer conveyance member is the recording sheet of the plurality of transfer conveyance rollers. The second temperature sensor detects the temperature of the conveyance belt, and the conveyance speed control unit detects that the rotation drive transfer conveyance member is the heating roller. Based on the increase amount of the temperature of the conveyor belt detected by the second temperature sensor when heated by the radiant heat from the fixing unit, the rotation driving fixing member Obtain a correction amount of the speed, can be illustrated embodiment actuates the drive device by the correction quantity obtained to increase the conveying speed of the recording sheet by the rotary drive fixing member.

  In the present invention, the rotational fixing member includes a heated fixing roller and a pressure roller disposed opposite to the fixing roller, and the rotational driving fixing member is the pressure roller. An aspect can be illustrated.

  According to the present invention, the conveyance speed of the recording sheet by the rotation driving fixing member and the conveyance speed of the recording sheet by the rotation driving transfer conveyance member can be matched as much as possible. Inconveniences such as image defects can be suppressed.

1 is a schematic front view schematically showing an overall configuration of an image forming apparatus according to an embodiment of the present invention. It is a front view which shows schematic structure of the transfer conveyance apparatus of the conveyance belt structure shown in FIG. FIG. 2 is a perspective view illustrating a schematic configuration of a transfer conveyance device having a conveyance belt configuration illustrated in FIG. 1. FIG. 2 is a front view illustrating a schematic configuration of the fixing device illustrated in FIG. 1. FIG. 2 is a perspective view illustrating a schematic configuration of the fixing device illustrated in FIG. 1. FIG. 2 is a system block diagram illustrating a schematic configuration of a control system in the image forming apparatus according to the present embodiment. FIG. 9 is an explanatory diagram for explaining inconvenience associated with a temperature increase of a transfer conveyance drive roller, and is a schematic side view showing a state in which a recording sheet is conveyed in a fixing device and a transfer conveyance device. FIG. 2 is a system block diagram mainly showing a control unit used in the image forming apparatus according to the first embodiment. It is a graph which shows the time change (upper side) of the temperature of the cored bar in a pressure roller with the time change (lower side) of the temperature of a transfer conveyance drive roller. 3 is a flowchart illustrating an example of a control operation by a control unit in the image forming apparatus according to the first embodiment. It is a system block diagram which mainly shows the control part used for the image forming apparatus which concerns on 2nd Embodiment. FIG. 10 is a schematic side view showing a state in which a heat source is provided inside a metal core in a pressure roller of a fixing device according to a third embodiment. It is a system block diagram which mainly shows the control part used for the image forming apparatus which concerns on 3rd Embodiment. 10 is a flowchart illustrating an example of a control operation by a control unit in an image forming apparatus according to a third embodiment. FIG. 10 is a schematic side view showing a state in which a heat source is provided inside a cored bar in a fixing roller of a fixing device according to a fourth embodiment. FIG. 10 is a system block diagram mainly showing a control unit used in an image forming apparatus according to a fourth embodiment. FIG. 10 is a system block diagram mainly illustrating a control unit used in an image forming apparatus according to a fifth embodiment. 14 is a flowchart illustrating an example of a control operation by a control unit in an image forming apparatus according to a fifth embodiment. It is a system block diagram which mainly shows the control part used for the image forming apparatus which concerns on 6th Embodiment.

  Embodiments according to the present invention will be described below with reference to the drawings.

(Image forming device)
FIG. 1 is a schematic front view schematically showing an overall configuration of an image forming apparatus 1 according to an embodiment of the present invention.

  An image forming apparatus 1 shown in FIG. 1 records an image of a document read by a document reading device (not shown) or an image indicated by image data received from the outside in a color or single color on a recording sheet P such as a recording sheet. A forming unit 10 is provided.

  The image forming unit 10 includes an exposure device 11, developing devices 12 to 12, photosensitive drums 13 to 13 acting as an image carrier, cleaner devices 14 to 14, chargers 15 to 15, and an intermediate transfer roller 24 acting as a transfer unit. To 24, an intermediate transfer belt device 16, a fixing device 17 (an example of a heat fixing unit), a paper feeding tray 18 that functions as a paper feeding unit, a paper discharge tray 19 that functions as a paper discharging unit, and a sheet conveying device 20 I have.

  The image data handled in the image forming unit 10 corresponds to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This corresponds to the monochrome image used. Accordingly, the developing devices 12 to 12, the photosensitive drums 13 to 13, the cleaner devices 14 to 14, the chargers 15 to 15, and the intermediate transfer rollers 24 to 24 are each four so as to form four types of images corresponding to the respective colors. It is provided one by one.

  The photoconductor drums 13 to 13 are disposed at substantially the center in the vertical direction of the main body 1 a of the image forming apparatus 1. The chargers 15 to 15 are charging means for uniformly charging the surfaces of the photosensitive drums 13 to 13 to a predetermined potential. Here, the exposure device 11 is a laser scanning unit including a laser diode and a reflection mirror, and exposes the surfaces of the charged photosensitive drums 13 to 13 according to image data, and the surface according to the image data. An electrostatic latent image is formed. The developing devices 12 to 12 develop the electrostatic latent images formed on the photosensitive drums 13 to 13 with (K, C, M, Y) toner.

  The intermediate transfer belt device 16 disposed above the photosensitive drums 13 to 13 includes an intermediate transfer belt 21, an intermediate transfer driving roller 22, a driven roller 23, and an intermediate transfer belt cleaning device in addition to the intermediate transfer rollers 24 to 24. 25 and a tension roller 26.

  The intermediate transfer driving roller 22, the driven roller 23, the intermediate transfer rollers 24 to 24, and the tension roller 26 stretch and support the intermediate transfer belt 21 and move the intermediate transfer belt 21 in a predetermined circumferential direction C. The intermediate transfer rollers 24 to 24 are rotatably supported inside the intermediate transfer belt 21 and are pressed against the photosensitive drums 13 to 13 via the intermediate transfer belt 21. The intermediate transfer belt 21 is provided so as to be in contact with each of the photosensitive drums 13 to 13, and the toner image on the surface of each of the photosensitive drums 13 to 13 is sequentially transferred to the intermediate transfer belt 21 to transfer the color. A toner image (a toner image of each color) is formed. Transfer of the toner image from the photosensitive drums 13 to 13 to the intermediate transfer belt 21 is performed by intermediate transfer rollers 24 to 24 that are in pressure contact with the inner side (back surface) of the intermediate transfer belt 21. A high-voltage transfer bias (for example, a high voltage having a polarity (+) opposite to the toner charging polarity (-)) is applied to the intermediate transfer rollers 24 to 24 in order to transfer the toner image.

  The image forming unit 10 further includes a transfer conveyance device 27 (an example of a transfer conveyance unit). The transfer conveying device 27 includes a rotary transfer conveying member including a transfer roller 27a. The transfer roller 27 a is in contact with the outside of the intermediate transfer belt 21. As described above, the toner images on the surfaces of the photosensitive drums 13 to 13 are stacked on the intermediate transfer belt 21 to become a color toner image indicated by the image data. The toner images of the respective colors stacked in this way are conveyed with the intermediate transfer belt 21 and transferred onto the recording sheet P by the transfer conveying device 27. The transfer roller 27a of the transfer conveyance device 27 has a voltage (for example, high polarity (+) opposite to the toner charge polarity (-)) for transferring the toner image of each color on the intermediate transfer belt 21 to the recording sheet P. Voltage) is applied. The transfer / conveying device 27 will be described in detail later.

  The cleaners 14 to 14 remove and collect toner remaining on the surfaces of the photosensitive drums 13 to 13 after the toner image transfer. For example, the cleaning devices 14 to 14 are provided with cleaning blades that contact the photosensitive drums 13 to 13 as cleaning members, and residual toner can be removed and collected by the cleaning blades.

  The intermediate transfer belt cleaning device 25 removes and collects residual toner on the intermediate transfer belt 21. The intermediate transfer belt cleaning device 25 is provided with, for example, a cleaning blade that contacts the intermediate transfer belt 21 as a cleaning member, and residual toner can be removed and collected by this cleaning blade.

  The paper feed tray 18 is a tray for storing the recording sheets P, and is provided below the image forming unit 10 in the main body 1 a of the image forming apparatus 1. A paper discharge tray 19 provided on the upper side of the image forming unit 10 is a tray for placing printed recording sheets P face down.

  Further, the main body 1 a of the image forming apparatus 1 is provided with a sheet conveying device 20 for sending the recording sheet P of the paper feeding tray 18 to the paper discharge tray 19 via the transfer conveying device 27 and the fixing device 17. . The sheet conveying device 20 has an S-shaped sheet conveying path S (an example of a conveying path for the recording sheet P), and along the sheet conveying path S, a pickup roller 31, a pair of separation rollers 31a and 31b, a resist A roller 32, a pre-registration roller 33, a fixing device 17, and a paper discharge roller 34 are arranged.

  The pickup roller 31 is provided at the downstream end of the sheet feeding tray 18 in the sheet conveying direction (recording sheet P conveying direction), and is called to supply the recording sheets P from the sheet feeding tray 18 one by one to the sheet conveying path S. Laura. One separation roller 31a passes the recording sheet P between the other separation roller 31b and conveys it to the sheet conveyance path S while separating the recording sheets one by one. In the stopped state, the registration roller 32 abuts the leading end of the recording sheet P that has been conveyed, aligns the leading end of the recording sheet P, and transfers the transfer nip area (transferring) between the intermediate transfer belt 21 and the transfer conveying device 27. The recording sheet P is conveyed with good timing in synchronization with the toner image formed on the intermediate transfer belt 21 so that the toner image on the intermediate transfer belt 21 is transferred to the recording sheet P at the nip portion). The pre-registration roller 33 is a small roller for promoting and assisting the conveyance of the recording sheet P.

  The fixing device 17 includes a rotary fixing member including a fixing roller 171 and a pressure roller 174. In the fixing device 17, an unfixed toner image is heated and fixed in a fixing nip region (fixing nip portion). The recording sheet P after fixing the toner images of the respective colors is discharged onto the paper discharge tray 19 by the paper discharge roller 34. The fixing device 17 will be described in detail later.

(About transfer and transfer device)
Next, as a transfer conveyance unit, a transfer conveyance device 27 provided with a rotary transfer conveyance member having a conveyance belt configuration will be described below as an example.

  2 and 3 are a front view and a perspective view, respectively, showing a schematic configuration of the transfer conveying device 27 having the conveying belt configuration shown in FIG. Note that the rear view of the transfer / conveyance device 27 is substantially the same as the front view, but the left and right sides are reversed. Therefore, only the front view is shown in FIG. 2, and the rear view is omitted.

  The transfer conveyance device 27 includes a plurality (five in this example) of transfer conveyance rollers 271 to 271 and an endless conveyance belt 272 wound around the plurality of transfer conveyance rollers 271 to 271 as rotating transfer conveyance members. A part of the conveying belt 272 is provided along the sheet conveying path S (see FIG. 2).

  Specifically, the transfer conveyance device 27 includes a plurality (four in this example) of transfer conveyance rollers 271 to 271 along the sheet conveyance path S on the side opposite to the intermediate transfer driving roller 22 with the sheet conveyance path S as a boundary. One or a plurality (one in this example) of transfer conveyance rollers 271 are arranged at positions separated from the sheet conveyance path S on the side opposite to the intermediate transfer drive roller 22 side.

  The transfer conveyance roller 271 disposed along the sheet conveyance path S and located on the most downstream side in the conveyance direction Y of the recording sheet P is a transfer conveyance drive roller 27b (an example of a rotationally driven transfer conveyance member) that is rotationally driven. ). The transfer conveyance roller 271 disposed on the most upstream side in the conveyance direction Y of the recording sheet P along the sheet conveyance path S, along with the transfer conveyance drive roller 27b, causes an upstream of a part of the conveyance belt 272 along the sheet conveyance path S. The side transfer conveyance roller 27c is used. A transfer conveying roller 271 disposed along the sheet conveying path S so as to face the intermediate transfer driving roller 22 via the intermediate transfer belt 21 transfers the toner image T on the intermediate transfer belt 21 onto the recording sheet P. The roller 27a is used. The transfer conveyance roller 271 disposed in the vicinity of the upstream side in the conveyance direction Y of the recording sheet P of the transfer roller 27a along the sheet conveyance path S, together with the transfer roller 27a, is a transfer nip area (transfer nip portion) N1 (see FIG. 2). ) To form a transfer conveyance nip roller 27d. The transfer conveyance roller 271 disposed at a position away from the sheet conveyance path S on the side opposite to the intermediate transfer drive roller 22 side is composed of a transfer conveyance drive roller 27b, a transfer roller 27a, a transfer conveyance nip roller 27d, and an upstream side. The transfer / conveyance tension roller 27e applies tension to the conveyance belt 272 wound around the transfer / conveyance roller 27c. Here, the transfer conveyance drive roller 27b, the transfer roller 27a, the transfer conveyance nip roller 27d, and the upstream transfer conveyance roller 27c are provided inside the conveyance belt 272, and the transfer conveyance tension roller 27e is inside or outside the conveyance belt 272 ( In this example, it is provided inside).

  Of the transfer conveyance drive roller 27b, transfer roller 27a, transfer conveyance nip roller 27d, upstream transfer conveyance roller 27c, and transfer conveyance tension roller 27e, the transfer conveyance drive roller 27b is disposed at a position closest to the fixing device 17. Yes.

  The transfer / conveyance device 27 is driven so that the transfer / conveyance drive roller 27b is rotated by a first drive device 20a (see FIG. 6 described later) such as a drive motor via a drive transmission member such as a gear or a pulley (not shown). It has become.

  In the transfer conveyance device 27 having such a configuration, the transfer conveyance drive roller 27b is rotationally driven by the first drive device 20a in a predetermined rotation direction E2 via a drive transmission member such as a gear or a pulley (not shown). As a result, the conveying belt 272 rotates in the conveying direction Y of the recording sheet P, and the transfer roller 27a, the transfer conveying nip roller 27d, the upstream transfer conveying roller 27c, and the transfer conveying tension roller 27e are driven to rotate in the rotational direction E2. . Further, the intermediate transfer driving roller 22 is rotated in the predetermined rotation direction E1 by a first driving device 20a via a drive transmission member such as a gear or a pulley (not shown), so that the intermediate transfer belt 21 rotates in the rotating direction C. Moving. Accordingly, the transfer conveyance device 27 can convey the recording sheet P on which the toner image T has been transferred toward the fixing device 17.

  In the present embodiment, the transfer conveyance device 27 is exemplified as having a rotation transfer conveyance member having a conveyance belt configuration. However, the transfer conveyance device 27 includes a single or plural transfer conveyance rollers, and includes a single or plural transfer conveyance rollers. May be provided with a rotary transfer conveyance member having a conveyance roller configuration arranged along the sheet conveyance path S.

(About fixing device)
Next, the fixing device 17 provided with a rotary fixing member having an external heat fixing belt configuration as the heat fixing portion will be described below as an example.

  4 and 5 are a front view and a perspective view, respectively, showing a schematic configuration of the fixing device 17 shown in FIG. Note that the rear view of the fixing device 17 is substantially the same as the front view with the left and right reversed, and therefore, only the front view is shown in FIG. 4 and the rear view is omitted.

  The fixing device 17 includes, as a rotary fixing member, a fixing roller 171 that is heated from the outside and a pressure roller 174 that is disposed to face the fixing roller 171.

  Specifically, the fixing device 17 is further wound around a heating roller 172 that is heated from the inside, a fixing roller 171 that is arranged in parallel with the heating roller 172, a heating roller 172, and a fixing belt 173 as a rotary fixing member. The endless fixing belt 173 is provided, and the pressure roller 174 is pressed against the fixing roller 171 via the fixing belt 173.

  The fixing device 17 can transfer heat from the heating roller 172 to the fixing roller 171 via the fixing belt 173 by winding the fixing belt 173 around the fixing roller 171 and the heating roller 172.

  The fixing device 17 has a fixing nip region (fixing nip portion) N2 between the fixing belt 173 and the pressure roller 174 in a state where the fixing roller 171 and the pressure roller 174 are pressed against each other with the fixing belt 173 interposed therebetween. (See FIG. 4). Although not shown, the fixing device 17 further includes a pressing device that acts as a pressing unit that presses the pressure roller 174 toward the fixing roller 171. This pressing device may have a conventionally known configuration, and the description thereof is omitted here.

  The fixing roller 171 faces the unfixed toner image T on the recording sheet P via the fixing belt 173, and the heating roller 172 heats the fixing belt 173.

  The fixing roller 171 faces the unfixed toner image T on the recording sheet P with the fixing belt 173 interposed, and is added to the fixing belt 173 with the fixing belt 173 interposed with respect to the pressure roller 174. The recording sheet P between the pressure roller 174 and the pressure roller 174 is pressed. The fixing device 17 includes a heat source 177 (specifically, a heating element such as a halogen heater lamp) that heats the heating roller 172 from the inside, and the heating roller 172 is heated by the heat source 177 to thereby fix the fixing belt 173. Is heated, and the fixing roller 171 is heated via the fixing belt 173.

  Specifically, the heating roller 172 includes a cylindrical cored bar 172a. A heat source 177 is provided inside the cored bar 172 a of the heating roller 172. As a result, the heating roller 172 is heated by the heat source 177, the heat of the heating roller 172 is transmitted to the fixing belt 173, and further transmitted to the outer peripheral surface of the fixing roller 171 via the fixing belt 173 heated by the heating roller 172. As a result, the fixing roller 171 is heated.

  The fixing roller 171 is rotatably provided on the main body (specifically, the main body frame) of the fixing device 17, and includes a cored bar 171a and a resin layer 171b (an example of a resin member) made of an elastic resin material. I have. The fixing roller 171 is provided with a resin layer 171b on the outer peripheral surface of the cored bar 171a.

  The metal core 171a in the fixing roller 171 and the metal core 172a in the heating roller 172 are made of a hollow cylindrical metal core material. As the metal cores 171a and 172a, for example, a material such as a free-cutting steel material (SUM material), a stainless steel material (SUS material), aluminum, iron, copper, or an alloy thereof can be used. Here, the core bars 171a and 172a are made of aluminum. As the resin layer 171b in the fixing roller 171, for example, a rubber member such as silicone rubber can be used.

  The pressure roller 174 is rotatably provided on the main body (specifically, the main body frame) of the fixing device 17, and includes a core metal 174a and a resin layer 174b (an example of a resin member) made of an elastic resin material. And a release layer 174c (an example of a resin member) made of a resin material having releasability. In the pressure roller 174, a resin layer 174b is provided on the outer peripheral surface of the cored bar 174a, and a release layer 174c is provided on the outer peripheral surface of the resin layer 174b.

  The metal core 174a in the pressure roller 174 is made of a hollow cylindrical metal core material. The cored bar 174a is similar to the cored bar 171a in the fixing roller 171 and the cored bar 172a in the heating roller 172. For example, a free cutting steel material (SUM material), a stainless steel material (SUS material), a metal such as aluminum, iron, copper, Materials such as those alloys can be used. Here, the cored bar 174a is made of aluminum. As the resin layer 174b in the pressure roller 174, for example, a rubber member such as silicone rubber can be used in the same manner as the resin layer 171b in the fixing roller 171. As the release layer 174c in the pressure roller 174, for example, a fluorine resin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) can be used. Here, the release layer 174c is made of PFA.

  The fixing belt 173 has a two-layer structure in which a release layer is formed on the outer peripheral surface of a flexible cylindrical substrate. As the release layer, a synthetic resin material (for example, a fluorine-based resin such as PFA or PTFE) having excellent heat resistance and release properties can be used.

  In the fixing device 17, the rotational driving fixing member (the pressure roller 174 or the fixing roller 171) is driven by a second driving device 20e (see FIG. 6) such as a driving motor via a drive transmission member such as a gear or a pulley (not shown). It is designed to rotate. The fixing temperature sensor 175 shown in FIG. 5 will be described later.

  In the fixing device 17 having such a configuration, when the rotationally driving fixing member is the pressure roller 174, driving of a gear or the like on the main body 1a side in a state where the fixing member 17 is mounted on the main body 1a of the image forming apparatus 1 (see FIG. 1). A transmission member (not shown) is meshed with a gear (not shown) provided on the metal core 174a of the pressure roller 174, and the rotational driving force from the second driving device 20e on the main body 1a side is the drive transmission of the gear or the like. The pressure is transmitted to the metal core 174a of the pressure roller 174 via the member, and the pressure roller 174 is rotationally driven in the rotation direction E2. As a result, the fixing belt 173 rotates in the rotating direction E opposite to the rotating direction E2 of the pressure roller 174, and the heating roller 172 and the fixing roller 171 are rotated in the rotating direction E1. When the rotational driving fixing member is the fixing roller 171, a drive transmission member (not shown) such as a gear on the main body 1 a side is fixed in a state where it is mounted on the main body 1 a (see FIG. 1) of the image forming apparatus 1. The roller 171 is meshed with a gear (not shown) provided on a metal core 171a, and the rotational driving force from the second driving device 20e on the main body 1a side is a metal core on the fixing roller 171 via a drive transmission member such as a gear. Then, the fixing roller 171 is driven to rotate in the rotation direction E1. As a result, the fixing belt 173 rotates in the circumferential direction E, which is the same as the rotation direction E1 of the fixing roller 171, and the heating roller 172 is rotated in the rotational direction E1 and the pressure roller 174 is rotated in the rotational direction E2.

  The recording sheet P is conveyed while being sandwiched between the fixing belt 173 and the pressure roller 174, and is heated and pressed in the fixing nip region N2. As a result, the unfixed toner image T on the recording sheet P is melted, mixed and pressed to be fixed.

  Here, the fixing device 17 may include a tension roller that applies tension to the fixing belt 173. The tension roller is arranged inside or outside the fixing belt 173 and can press the fixing belt 173 outside or inside. The fixing device 17 includes an urging member (for example, a coil spring) that applies an urging force to both ends of the rotation shaft of the heating roller 172 on the opposite side to the fixing roller 171 instead of or in addition to the tension roller. Also good. When a tension roller is provided, a heat source 177 may be provided on the tension roller. Further, when the fixing belt 173 is wound around another roller, a heat source 177 may be provided on at least one of the other rollers.

  In the present exemplary embodiment, the fixing device 17 including the rotary fixing member having an external heating configuration (specifically, an external heating fixing belt configuration) is illustrated. However, the fixing roller 171 heated from the inside and the fixing roller 171 are exemplified. The fixing device 17 may include a rotary fixing member having an internal heating configuration including a pressure roller 174 disposed opposite to the pressure roller 174. In this case, a heat source (specifically, a heating element such as a halogen heater lamp) for heating the fixing roller 171 from the inside can be provided inside the cored bar 171a of the fixing roller 171.

(Operation of image forming apparatus)
In the image forming apparatus 1 described above, as shown in FIG. 1, the recording sheet P fed from the sheet feeding tray 18 is photosensitive to the recording sheet P while it is being conveyed along the sheet conveying path S. The toner image (unfixed image) formed by the body drums 13 to 13 and conveyed to the intermediate transfer belt 21 is transferred by the transfer conveying device 27 and further fixed by the fixing device 17 to perform the printing process.

  Specifically, the photosensitive drums 13 to 13 are rotationally driven in one direction, and after the surfaces neutralized by a neutralizing device (not shown) are cleaned by the cleaner devices 14 to 14, they are uniformly charged by the chargers 15 to 15. . The exposure device 11 repeatedly scans the surfaces of the photosensitive drums 13 to 13 in the main scanning direction with laser light modulated based on the image data, and forms electrostatic latent images on the surfaces of the photosensitive drums 13 to 13. The developing devices 12 to 12 supply toner to the surfaces of the photosensitive drums 13 to 13 to develop (develop) the electrostatic latent images, and form toner images on the surfaces of the photosensitive drums 13 to 13. The intermediate transfer belt device 16 transfers the toner image formed on the photosensitive drums 13 to 13 to the intermediate transfer belt 21. The transfer conveyance device 27 transfers the toner image formed on the intermediate transfer belt 21 to the recording sheet P that passes between the intermediate transfer belt 21 and the transfer roller 27a. The fixing device 17 receives the recording sheet P on which an unfixed toner image is formed, and heats and presses the recording sheet P while sandwiching and conveying the recording sheet P between the fixing belt 173 and the pressure roller 174. The upper toner image is fixed on the recording sheet P. Thus, the image forming apparatus 1 completes a series of printing operations.

  It is also possible to form a monochrome image using at least one of the four image forming stations and transfer the monochrome image to the intermediate transfer belt 21 of the intermediate transfer belt device 16. This monochrome image is also transferred from the intermediate transfer belt 21 to the recording sheet P and fixed on the recording sheet P, similarly to the color image.

(About the control unit)
FIG. 6 is a system block diagram showing a schematic configuration of a control system in the image forming apparatus 1 according to the present embodiment.

  As shown in FIG. 6, the image forming apparatus 1 further includes a control unit 101. The control unit 101 includes a processing unit 101a such as a CPU and a storage unit 101b including various memories such as a ROM and a RAM and a writable nonvolatile memory. In the image forming apparatus 1, the processing unit 101a of the control unit 101 controls various components by loading a control program stored in advance in the ROM of the storage unit 101b onto the RAM of the storage unit 101b and executing it. It has become.

  In the present embodiment, the sheet conveying device 20 includes conveying rollers (specifically, separation rollers 31a and 31b, pre-registration rollers 33, and registration rollers 32 on the sheet conveyance path S), intermediate transfer driving rollers. 22 and the transfer conveyance drive roller 27b are rotated to rotate in the conveyance direction Y of the recording sheet P, and to the separation rollers 31a and 31b and the pickup roller 31 of the rotational drive force from the first drive device 20a. A sheet feeding clutch 20b (specifically, an electromagnetic clutch) that switches between transmission and interruption of the image and a registration that switches between transmission and interruption of the rotational driving force from the first driving device 20a to the pre-registration roller 33 and the registration roller 32, respectively. A front clutch 20c and a registration clutch 20d (specifically, an electromagnetic clutch) are provided.

  The first driving device 20a is electrically connected to the output system of the control unit 101. When an operation signal is input from the control unit 101, the separation rollers 31a and 31b, the pickup roller 31, and the pre-registration roller 33 are input. The registration roller 32, the intermediate transfer driving roller 22 and the transfer conveyance driving roller 27b are rotationally driven at a constant or substantially constant rotational speed (the number of rotations per unit time). The sheet feeding clutch 20b, the pre-registration clutch 20c, and the registration clutch 20d are each electrically connected to the output system of the control unit 101, and the first driving device is input by receiving an operation signal from the control unit 101. The rotational driving force from 20a is transmitted to or cut off from the separation rollers 31a and 31b, the pickup roller 31, the pre-registration roller 33, and the registration roller 32.

  The control unit 101 also functions as a conveyance control unit of the main body 1a of the image forming apparatus 1. Specifically, the control unit 101 controls the rotation timings of the separation rollers 31a and 31b, the pickup roller 31, the pre-registration roller 33, and the registration roller 32 by controlling the operation of the paper feed clutch 20b, the pre-registration clutch 20c, and the registration clutch 20d. It is configured to control. Accordingly, the control unit 101 can control the conveyance timing of the recording sheet P conveyed on the sheet conveyance path S to the transfer nip region N1 between the intermediate transfer belt 21 and the transfer conveyance device 27.

  The sheet conveying device 20 further includes a second driving device 20e that rotates the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) and conveys the recording sheet P in the conveyance direction Y by the rotation driving fixing member. ing.

  The second driving device 20e is electrically connected to the output system of the control unit 101, and receives an operation signal from the control unit 101, whereby a rotation driving fixing member (pressure roller 174 or fixing roller 171). Is driven to rotate.

  The fixing device 17 further includes a fixing temperature sensor 175 such as a thermistor that detects the fixing temperature Tf.

  The fixing temperature sensor 175 is electrically connected to the input system of the control unit 101, and transmits a signal corresponding to the fixing temperature Tf to the control unit 101.

  Then, the control unit 101 sets a predetermined fixing reference temperature Ts (for example, about 150 ° C.) for fixing the unfixed toner image T to the recording sheet P based on the fixing temperature Tf detected by the fixing temperature sensor 175. ) To function as a fixing temperature control means for controlling the operation (energization) to the heat source 177. Specifically, the control unit 101 energizes the heat source 177 when the fixing temperature Tf detected by the fixing temperature sensor 175 is equal to or lower than the fixing reference temperature Ts, and supplies the heat source 177 to the heat source 177 when the fixing temperature Tf is higher than the fixing reference temperature Ts. Turn off the power.

  In the present embodiment, the fixing temperature sensor 175 detects the fixing temperature Tf of the portion (in this example, the central portion in the width direction X) heated by the fixing belt 173 on the outer peripheral surface of the pressure roller 174. Yes. However, the fixing temperature sensor 175 is not limited to the fixing temperature sensor 175. The fixing temperature sensor 175 has a fixing temperature Tf of the fixing belt 173 (more specifically, a surface temperature of a portion of the fixing belt 173 around which the heating roller 172 is wound, The surface temperature of the portion around which the fixing roller 171 is wound or the surface temperature of the portion of the fixing belt 173 where the heating roller 172 and the fixing roller 171 are not wound may be detected.

  The control unit 101 also functions as a conveyance speed control unit that controls the conveyance speed of the recording sheet P.

(Control of recording sheet conveyance speed by control unit)
By the way, the rotation drive transfer conveyance member (transfer conveyance drive roller 27b which is rotationally driven in this example) in the transfer conveyance device 27 is heated by the fixing device 17 (specifically, the heat source 177 (see FIGS. 4 and 5)). As the heat is radiated from the roller 172, the fixing belt 173, the fixing roller 171 and the pressure roller 174), heat energy is continuously supplied from the fixing device 17 to the transfer conveying drive roller 27b. The temperature rises slowly but gradually. Then, as the temperature of the transfer conveyance drive roller 27b that is rotationally driven increases, the transfer conveyance drive roller 27b thermally expands. When the outer diameter of the transfer conveyance drive roller 27b increases with the thermal expansion of the transfer conveyance drive roller 27b that is rotationally driven, the peripheral speed of the transfer conveyance drive roller 27b increases accordingly, and as a result, the recording sheet by the transfer conveyance drive roller 27b increases. The conveyance speed of P becomes faster.

  This point will be further described with reference to FIG. FIG. 7 is an explanatory diagram for explaining inconvenience associated with the temperature rise of the transfer conveyance drive roller 27 b, and is a schematic side view showing a state in which the recording sheet P is conveyed in the fixing device 17 and the transfer conveyance device 27. is there.

  As the transfer / conveying drive roller 27b is heated by the radiant heat from the fixing device 17, the temperature of the transfer / conveying drive roller 27b increases, so that the recording sheet P of the recording sheet P by the rotational driving fixing member (the pressure roller 174 or the fixing roller 171) is The conveyance speed is slower than the conveyance speed of the recording sheet by the transfer conveyance drive roller 27b. Accordingly, the recording sheet P conveyed by the rotation conveyance driving roller 27b and the rotation driving fixing member (the pressure roller 174 or the fixing roller 171), which is rotationally driven, is transferred to the transfer nip area N1 and the fixing nip area. It will loosen with N2. Then, for example, the unfixed toner image T on the recording sheet P contacts the vicinity portion Na (see FIG. 7) upstream of the fixing nip region N2 of the fixing belt 173 in the circumferential direction E of the fixing belt 173, thereby fading the image. This causes inconvenience such as image defects. This is particularly noticeable in a solid image of a recording sheet P having a relatively large size such as A3 size or double letter size.

  With respect to this point, in the present embodiment, the control unit 101 performs the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) in the fixing device 17 and the rotation driving transfer in the transfer conveyance device 27. The conveyance speed of the recording sheet P is controlled such that the conveyance speed of the recording sheet P by the conveyance member (transfer conveyance driving roller 27b) matches or substantially matches. Then, the control unit 101 determines the rotation driving fixing member (pressure roller 174) based on the increase amount by which the temperature of the transfer conveying drive roller 27b increases when the transfer conveying drive roller 27b is heated by the radiant heat from the fixing device 17. Alternatively, the conveyance speed of the recording sheet P by the fixing roller 171) is increased.

  According to the present exemplary embodiment, the control unit 101 performs the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) and the recording by the rotation driving transfer conveyance member (transfer conveyance driving roller 27b). In a state in which the conveyance speed of the sheet P coincides or substantially coincides with the rotation drive transfer conveyance member (transfer conveyance drive roller 27b) by the radiant heat from the fixing device 17, even the rotation drive transfer conveyance member (transfer) Even when the outer diameter of the transport drive roller 27b) is increased, the rotational drive transfer transport member (transfer transport drive roller 27b) is heated when the rotational drive transfer transport member (transfer transport drive roller 27b) is heated by radiant heat from the fixing device 17. ) On the basis of the increasing amount of the temperature), the recording by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171). It is possible to increase the conveying speed of over preparative P. Accordingly, the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) and the conveyance speed of the recording sheet P by the rotation driving transfer conveyance member (transfer conveyance driving roller 27b) are matched as much as possible. This makes it possible to suppress inconveniences such as image defects such as image fading.

  By the way, in the standby state of the image forming apparatus in which the temperature of the rotary fixing member (in this example, the fixing belt 173, the fixing roller 171 and the pressure roller 174) in the fixing device 17 is maintained at a predetermined fixing reference temperature Ts. When a job is executed, recording that is heat-fixed as an image is formed on the recording sheet P (particularly as images are continuously formed on a plurality of recording sheets P to P in one job). Since the heat energy of the rotationally driving fixing member (the rotationally driven pressure roller 174 or rotationally driven fixing roller 171) continues to be taken away by the sheet P, the rotationally driven fixing member (the pressure roller 174 or the fixing roller 171). What is heat energy supplied from a heat source (specifically, a heat source 177 (see FIGS. 4 and 5) provided on the heating roller 172)? For example, just the temperature of the rotary drive fixing member (pressure roller 174 or the fixing roller 171) gradually decreases. Then, as the temperature of the rotationally driven fixing member (pressure roller 174 or fixing roller 171) that is rotationally driven decreases, the rotationally driven fixing member (pressure roller 174 or fixing roller 171) thermally contracts. Then, as the outer diameter of the rotation driving fixing member (pressure roller 174 or fixing roller 171) decreases with the heat shrinkage of the rotation driving fixing member (pressure roller 174 or fixing roller 171) to be rotated, the rotation driving fixing is increased accordingly. The peripheral speed of the member (the pressure roller 174 or the fixing roller 171) is decreased, and the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is decreased.

  Specifically, as the image formation is performed on the recording sheet P (particularly as the image formation is continuously performed on a plurality of recording sheets P to P in one job), the rotation driving fixing member (the pressure roller 174). Alternatively, the lower the temperature of the fixing roller 171), the lower the conveyance speed of the recording sheet P by the rotational driving fixing member (the pressure roller 174 or the fixing roller 171) is slower than the conveyance speed of the recording sheet by the transfer conveyance driving roller 27b. Therefore, the recording sheet P conveyed by the rotationally driven transfer conveying drive roller 27b and the rotationally driven rotation fixing member (the pressure roller 174 or the fixing roller 171) is transferred to the transfer nip area N1 and the fixing nip area N2. Will loosen further between.

  With respect to this point, in the present embodiment, the control unit 101 is based on the amount by which the temperature of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) decreases when performing image formation on the recording sheet P. The conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is increased.

  In this way, the control unit 101 performs the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) and the recording sheet P by the rotation driving transfer conveyance member (transfer conveyance driving roller 27b). As the image formation is performed on the recording sheet P in a state where the conveyance speed is the same or substantially the same (particularly as the image formation is continuously performed on a plurality of recording sheets P to P in one job). Even if the outer diameter of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is reduced, the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is used to form an image on the recording sheet P. The conveyance speed of the recording sheet P by the rotation drive fixing member (the pressure roller 174 or the fixing roller 171) is determined based on the decrease amount by which the temperature of the recording sheet P decreases. Can Kusuru. Accordingly, the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) and the conveyance speed of the recording sheet P by the rotation driving transfer conveyance member (transfer conveyance driving roller 27b) are matched as much as possible. This makes it possible to suppress inconveniences such as image defects such as image fading.

  In the present embodiment, the control unit 101 uses the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) to be rotationally driven on the basis of the predetermined state of the image forming apparatus 1 as a reference. Changing the conveyance speed of the recording sheet P in a state where the conveyance speed of the recording sheet P coincides with or substantially coincides with the conveyance speed of the recording sheet P by the rotationally driven transfer conveyance member (transfer conveyance driving roller 27b) that is rotationally driven. Can do.

  Here, the predetermined state of the image forming apparatus 1 is a state when the temperature of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is highest, specifically, the image forming apparatus 1. Can be exemplified by an initial state immediately after the image is activated and an image can be formed.

  In this way, the control unit 101 uses the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) based on a predetermined state of the image forming apparatus 1 (for example, the initial state of the image forming apparatus 1). In a state where the conveyance speed of the recording sheet P and the conveyance speed of the recording sheet P by the rotation drive transfer conveyance member (transfer conveyance drive roller 27b) coincide with each other or substantially coincide with each other, the rotation drive transfer conveyance member (transfer conveyance drive roller 27b). Is heated by the radiant heat from the fixing device 17, even if the outer diameter of the rotational drive transfer transport member (transfer transport drive roller 27b) increases, the rotational drive transfer transport member (transfer transport drive roller 27b) is fixed. Based on the increase amount by which the temperature of the rotary drive transfer conveyance member (transfer conveyance drive roller 27b) increases when heated by the radiant heat from the apparatus 17. In addition, the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) can be increased, and / or as the image is formed on the recording sheet P (especially once). Even if the outer diameter of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is reduced, the recording sheet P is formed even if the image is continuously formed on a plurality of recording sheets P to P in a job). On the other hand, the recording sheet P by the rotation driving fixing member (pressure roller 174 or fixing roller 171) is based on the decrease amount by which the temperature of the rotation driving fixing member (pressure roller 174 or fixing roller 171) decreases when performing image formation. The conveyance speed can be increased. Accordingly, the conveyance speed of the recording sheet P by the rotation driving fixing member (pressure roller 174 or fixing roller 171) and the conveyance speed of the recording sheet P by the rotation driving transfer conveyance member (transfer conveyance driving roller 27b) are made as much as possible. Can be matched with certainty.

  Specifically, the image forming apparatus 1 according to the present embodiment can be configured as the following first to sixth embodiments.

(About 1st Embodiment and 2nd Embodiment)
Incidentally, the rotary fixing member includes a fixing roller 171 heated from the outside or the inside (in this example, the outside) and a pressure roller 174 disposed to face the fixing roller 171, and the rotation drive fixing member is added. In the case of the pressure roller 174, or including a fixing roller 171 heated from the outside and a pressure roller 174 disposed to face the fixing roller 171, the rotation driving fixing member is the fixing roller 171. When the image is formed on the recording sheet P, the rotational drive fixing member is always the rotational drive fixing member from the outside (outer peripheral surface) regardless of whether the rotational drive fixing member is the pressure roller 174 or the fixing roller 171. The rotation driving fixing member (pressure roller 174 or fixing roller 171) is heated from the outer peripheral surface by being supplied to (pressure roller 174 or fixing roller 171). Therefore, the temperature of the outer peripheral surface of the rotation driving fixing member (pressure roller 174 or fixing roller 171) is compared with the internal temperature mainly contributing to the thermal expansion of the rotation driving fixing member (pressure roller 174 or fixing roller 171). The temperature of the outer peripheral surface of the rotation driving fixing member (pressure roller 174 or fixing roller 171) and the interior contributing to the thermal expansion of the rotation driving fixing member (pressure roller 174 or fixing roller 171) increase continuously. There is no correlation with the temperature characteristics.

  Accordingly, even if the temperature of the heated portion of the outer peripheral surface of the rotation driving fixing member (pressure roller 174 or fixing roller 171) is detected as the temperature of the rotation driving fixing member (pressure roller 174 or fixing roller 171). (In this example, even if the fixing temperature Tf is detected by the fixing temperature sensor 175), the detected temperature of the heated portion of the outer peripheral surface of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is determined as the rotation driving fixing member. It cannot be used as an internal temperature that contributes to the thermal expansion of the pressure roller 174 or the fixing roller 171. On the other hand, if a temperature inside the outer peripheral surface of the rotational driving fixing member (the pressure roller 174 or the fixing roller 171) is detected, the detected outer peripheral surface of the rotational driving fixing member (the pressure roller 174 or the fixing roller 171). The inner temperature can be used as the internal temperature that contributes to the thermal expansion of the rotary drive fixing member (the pressure roller 174 or the fixing roller 171). For example, when the rotation driving fixing member is the pressure roller 174, the pressure roller 174 has a configuration including a cored bar 174a and a resin layer 174b provided on the outer peripheral surface of the cored bar 174a. When the rotation driving fixing member is the fixing roller 171, the fixing roller 171 includes a cored bar 171 a and a resin layer 171 b provided on the outer peripheral surface of the cored bar 171 a. If the temperature inside the outer peripheral surface of the resin member (resin layer 174b or resin layer 171b) or the temperature of the core metal (core metal 174a or core metal 171a) is detected, the detected resin member (resin layer 174b or resin layer 171b). ) And the temperature of the core metal (core metal 174a or core metal 171a) contributes to the thermal expansion of the rotary drive fixing member (pressure roller 174 or fixing roller 171). It can be used as internal temperature.

  From this point of view, the image forming apparatus 1 according to the first embodiment and the second embodiment uses the first temperature for detecting the temperature (internal temperature) of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171). Sensors 181a and 181b (181) (see FIGS. 8 and 11 to be described later) and a rotation driving fixing member (pressure roller 174 or fixing roller 171) are rotationally driven to rotate the fixing member (pressure roller 174 or fixing). And a second driving device 20e (an example of a driving device) that varies the rotational speed of the roller 171). The first temperature sensors 181a and 181b (181) are configured to detect the temperature inside the outer peripheral surface of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171). The control unit 101 is inside the outer peripheral surface of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) detected by the first temperature sensors 181a and 181b (181) when performing image formation on the recording sheet P. A correction amount of the peripheral speed of the rotation drive fixing member (the pressure roller 174 or the fixing roller 171) is obtained based on the decrease amount by which the temperature of the toner decreases, and the second drive device 20e is operated by the obtained correction amount to rotate. The conveyance speed of the recording sheet P by the fixing member (the pressure roller 174 or the fixing roller 171) is increased.

  Specifically, the first temperature sensors 181a and 181b (181) are temperatures inside the outer peripheral surface of the resin member (resin layer 174b or resin layer 171b) or the temperature of the core metal (core metal 174a or core metal 171a). It is set as the structure which detects. The controller 101 detects the temperature inside the outer peripheral surface of the resin member (resin layer 174b or resin layer 171b) detected by the first temperature sensors 181a and 181b (181) when performing image formation on the recording sheet P, or Based on the amount by which the temperature of the core metal (core metal 174a or core metal 171a) decreases, the correction amount of the peripheral speed of the rotary drive fixing member (pressure roller 174 or fixing roller 171) is obtained, and the obtained correction amount is used. The second driving device 20e is operated to increase the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171).

  In the following first and second embodiments, an example will be described in which the first temperature sensors 181a and 181b (181) detect the temperature of the core metal (core metal 174a or core metal 171a). The same applies to the case where the first temperature sensors 181a and 181b (181) detect the temperature inside the outer peripheral surface of the resin member (resin layer 174b or resin layer 171b).

(First embodiment)
In the image forming apparatus 1 according to the first embodiment, the rotary fixing member is opposed to the fixing roller 171 heated from the outside or the inside (in this example, the outside) and the fixing roller 171 (in this example, the fixing belt 173 is attached). And a pressure roller 174 disposed opposite to the fixing roller 171, and the rotation driving fixing member is a pressure roller 174.

  The pressure roller 174 includes a cored bar 174a and a resin layer 174b provided on the outer peripheral surface of the cored bar 174a. The first temperature sensor 181a (181) is a cored bar in the pressure roller 174. The temperature of 174a is detected. Here, the first temperature sensor 181a (181) is in contact with the outer peripheral surface 174m (the outer peripheral surface of one end in the axial direction) (see FIG. 8) of the cored bar 174a of the pressure roller 174 (see FIG. 8). Specifically, the main body frame) is provided via a support member (not shown).

  In addition, the 1st temperature sensor 181a (181) may be provided in the both ends in the axial direction of the metal core 174a. In this case, the temperature of the cored bar 174a can be a value obtained by averaging the temperatures detected by the first temperature sensors 181a and 181a (181).

  FIG. 8 is a system block diagram mainly showing the control unit 101 used in the image forming apparatus 1 according to the first embodiment. FIG. 9 is a graph showing the temporal change α (upper side) of the temperature of the cored bar 174a in the pressure roller 174 together with the temporal change β (lower side) of the temperature of the transfer conveyance drive roller 27b.

  As shown in FIG. 8, the first temperature sensor 181 a (181) is electrically connected to the input system of the control unit 101, and sends a signal corresponding to the temperature of the core metal 174 a in the pressure roller 174 to the control unit 101. To be sent to.

  The second driving device 20e is configured to vary the rotational speed of the pressure roller 174 by rotationally driving the pressure roller 174 when an operation signal from the control unit 101 is input. As a result, the second driving device 20e can vary the conveyance speed of the recording sheet P conveyed by the pressure roller 174.

  Then, the control unit 101 performs the image formation on the recording sheet P based on the decrease amount (see T1 in FIG. 9) in which the temperature of the cored bar 174a detected by the first temperature sensor 181a (181) decreases. The correction amount of the peripheral speed of the pressure roller 174 is obtained, and the second driving device 20e is operated with the obtained correction amount to increase the conveyance speed of the recording sheet P by the pressure roller 174.

  Specifically, when the temperature of the transfer conveyance driving roller 27b is not increased, the control unit 101 is in a predetermined state of the image forming apparatus 1 (for example, the image forming apparatus 1 is activated and an image can be formed). From the amount T1 of decrease in the temperature of the cored bar 174a detected by the first temperature sensor 181a (181) on the basis of the initial state immediately after), the conveyance speed of the recording sheet P by the pressure roller 174 and the transfer conveyance drive roller 27b. The amount of correction of the peripheral speed of the pressure roller 174 is determined so that the conveyance speed of the recording sheet P is consistent with or substantially the same.

  Specifically, the correction amount of the peripheral speed of the pressure roller 174 is the initial temperature of the cored bar 174a in the pressure roller 174 when the image forming apparatus 1 is in a predetermined state (for example, the initial state of the image forming apparatus 1). For correction indicating the correction amount of the peripheral speed of the pressure roller 174 corresponding to the decrease amount T1 of the temperature of the core metal 174a in the pressure roller 174 from Ta (the correction amount that increases the peripheral speed according to the decrease amount T1). It can be determined using a table or a correction conversion formula. Such a correction table or correction conversion formula can be obtained in advance through experiments or the like, and is stored in advance in the storage unit 101b.

  FIG. 10 is a flowchart illustrating an example of a control operation by the control unit 101 in the image forming apparatus 1 according to the first embodiment. In this example, a predetermined state of the image forming apparatus 1 will be described as an initial state.

  Prior to the processing shown in FIG. 10, the initial temperature Ta of the cored bar 174a in the pressure roller 174 in the initial state immediately after the image forming apparatus 1 is activated and ready to form an image is obtained in advance by experiments or the like. , Stored in advance in the storage unit 101b.

  In the processing example illustrated in FIG. 10, first, when the image forming apparatus 1 is activated (Step S <b> 11), the control unit 101 starts the initial temperature Ta of the core metal 174 a in the pressure roller 174 when the image forming apparatus 1 is in the initial state. Is read from the storage unit 101b (step S12).

  Next, the control unit 101 determines whether or not the job (image forming operation) has started (step S13), and when the job starts (step S13: Yes), pressurization is performed by the first temperature sensor 181a (181). The temperature of the cored bar 174a in the roller 174 is detected (step S14).

  Next, the control unit 101 calculates a decrease amount T1 of the temperature of the cored bar 174a detected in step S14 from the initial temperature Ta of the cored bar 174a in the initial state read in step S12 (step S15).

  Next, the control unit 101 obtains the correction amount of the peripheral speed of the pressure roller 174 from the decrease amount T1 calculated in step S15 using a correction table or a correction conversion formula (step S16).

  Next, the control unit 101 operates the second driving device 20e with the correction amount obtained in step S16 to increase the peripheral speed of the pressure roller 174 by the correction amount, whereby the recording sheet P of the recording roller P is pressed by the pressure roller 174. The conveyance speed is increased (step S17).

  Next, the control unit 101 determines whether or not the job has ended (step S18). When the job continues (step S18: No), the process proceeds to step S14, while when the job ends (step S18). S18: Yes), the process proceeds to step S13.

  On the other hand, when the job has not started in step S13 (step S13: No), the control unit 101 repeats the process of step S13 until the processing operation ends (step S19: No) (step S19).

  According to the first embodiment, when an image is formed on the recording sheet P, heat energy is continuously supplied from the outside (outer peripheral surface) to the pressure roller 174 so that the pressure roller 174 is heated from the outer peripheral surface. The first temperature sensor 181a (181) detects the temperature inside the outer peripheral surface of the pressure roller 174 (in this example, the core metal 174a) (the internal temperature that contributes to the thermal expansion of the pressure roller 174), Correction of the peripheral speed of the pressure roller 174 based on a decrease amount T1 in which the temperature inside the outer surface of the pressure roller 174 detected by the first temperature sensor 181a (181) (in this example, the core metal 174a) decreases. The amount is obtained, and the second driving device 20e is operated with the obtained correction amount to increase the conveyance speed of the recording sheet P by the pressure roller 174. The conveying speed of the bets P to the conveying speed of the recording sheet P by the transfer conveyance driving roller 27b can be accurately approximate or match.

  The correction for the increase amount (see T3 in FIG. 9) in which the temperature of the transfer conveyance drive roller 27b increases will be described in the fifth embodiment and the sixth embodiment, so the description is omitted here. The same applies to the second to fourth embodiments described later.

(Second Embodiment)
In the image forming apparatus 1 according to the second embodiment, the rotary fixing member faces the fixing roller 171 heated from the outside and the fixing roller 171 (in this example, the fixing roller 171 faces the fixing roller 171 via the fixing belt 173). And a rotation roller fixing member is a fixing roller 171.

  The fixing roller 171 includes a cored bar 171a and a resin layer 171b provided on the outer peripheral surface of the cored bar 171a. The first temperature sensor 181b (181) It is designed to detect temperature. Here, the first temperature sensor 181b (181) is in contact with the outer peripheral surface 171m (the outer peripheral surface of one end in the axial direction) of the cored bar 171a (see FIG. 11) of the fixing roller 171 (see FIG. 11). In particular, the main body frame) is provided via a support member (not shown).

  In addition, the 1st temperature sensor 181b (181) may be provided in the both ends in the axial direction of the metal core 171a. In this case, the temperature of the cored bar 171a can be a value obtained by averaging the temperatures detected by the first temperature sensors 181b and 181b (181).

  FIG. 11 is a system block diagram mainly showing the control unit 101 used in the image forming apparatus 1 according to the second embodiment. The temporal change in the temperature of the cored bar 171a in the fixing roller 171 is the same as that in the graph shown in FIG. 9, and is not shown here.

  As shown in FIG. 11, the first temperature sensor 181 b (181) is electrically connected to the input system of the control unit 101, and a signal corresponding to the temperature of the core metal 171 a in the fixing roller 171 is sent to the control unit 101. It is supposed to send.

  The second driving device 20e is configured to vary the rotation speed of the fixing roller 171 by rotationally driving the fixing roller 171 by receiving an operation signal from the control unit 101. As a result, the second drive device 20e can vary the conveyance speed of the recording sheet P conveyed by the fixing roller 171.

  Then, the controller 101 determines the peripheral speed of the fixing roller 171 based on the decrease amount T2 in which the temperature of the cored bar 171a is detected by the first temperature sensor 181b (181) when performing image formation on the recording sheet P. The correction amount is obtained, and the second driving device 20e is operated with the obtained correction amount to increase the conveyance speed of the recording sheet P by the fixing roller 171.

  Specifically, when the temperature of the transfer conveyance driving roller 27b is not increased, the control unit 101 is in a predetermined state of the image forming apparatus 1 (for example, the image forming apparatus 1 is activated and an image can be formed). From the amount T2 of decrease in the temperature of the cored bar 171a detected by the first temperature sensor 181b (181) on the basis of the initial state immediately after), the conveyance speed of the recording sheet P by the fixing roller 171 and the transfer conveyance drive roller 27b. The correction amount of the peripheral speed of the fixing roller 171 is obtained so that the conveyance speed of the recording sheet P matches or substantially matches.

  Specifically, the correction amount of the peripheral speed of the fixing roller 171 is based on the initial temperature Tb of the cored bar 171a in the fixing roller 171 when the image forming apparatus 1 is in a predetermined state (for example, the initial state of the image forming apparatus 1). Table for correction or correction for indicating the correction amount of the peripheral speed of the fixing roller 171 corresponding to the decrease amount T2 of the temperature of the cored bar 171a in the fixing roller 171 (the correction amount that increases the peripheral speed according to the decrease amount T2). It can be determined using a conversion formula. Such a correction table or correction conversion formula can be obtained in advance through experiments or the like, and is stored in advance in the storage unit 101b.

  An example of the control operation according to the second embodiment by the control unit 101 is the same as the example of the control operation by the control unit 101 in the image forming apparatus 1 according to the first embodiment, but the pressure roller 174 is changed to the fixing roller 171. This is the same as the control operation, and the illustration and description of the flowchart are omitted here.

  According to the second embodiment, when image formation is performed on the recording sheet P, the thermal energy is constantly supplied from the outside (outer peripheral surface) to the fixing roller 171 and the fixing roller 171 is heated from the outer peripheral surface. The first temperature sensor 181b (181) detects the temperature inside the outer peripheral surface of the fixing roller 171 (in this example, the cored bar 171a) (the internal temperature that contributes to the thermal expansion of the fixing roller 171), and the first temperature sensor A correction amount of the peripheral speed of the fixing roller 171 is obtained based on a decrease amount T2 in which the temperature inside the outer surface of the fixing roller 171 detected in 181b (181) (in this example, the core metal 171a) decreases. By operating the second driving device 20e with the corrected amount to increase the conveyance speed of the recording sheet P by the fixing roller 171, the recording sheet by the fixing roller 171 is recorded. The conveying speed of the bets P to the conveying speed of the recording sheet P by the transfer conveyance driving roller 27b can be accurately approximate or match.

(About 3rd Embodiment and 4th Embodiment)
Incidentally, the rotary fixing member includes a fixing roller 171 heated from the outside or the inside (in this example, the outside) and a pressure roller 174 disposed to face the fixing roller 171, and the rotation drive fixing member is added. In the case of the pressure roller 174, or including a fixing roller 171 heated from the outside and a pressure roller 174 disposed to face the fixing roller 171, the rotation driving fixing member is the fixing roller 171. If the rotation driving fixing member is the pressure roller 174 or the fixing roller 171, the temperature of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) when performing image formation on the recording sheet P. Even if the (internal temperature) decreases, if the rotation drive fixing member (pressure roller 174 or fixing roller 171) is heated from the inside, the rotation drive fixing member (pressure application) Temperature of over La 174 or the fixing roller 171) (internal temperature) rises. Thereby, it is possible to suppress or eliminate the thermal contraction (that is, the outer diameter is reduced) of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) by the image formation.

  From this point of view, the image forming apparatus 1 according to the third embodiment and the fourth embodiment has a heat source 179 (see FIGS. 12 and 13 to be described later) that heats the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) from the inside. And FIG. 15 and FIG. 16). The controller 101 causes the heat source 179 to generate heat and rotate and fix when the decrease amounts T1 and T2 of the rotation and driving fixing member (the pressure roller 174 or the fixing roller 171) exceed a predetermined amount or exceed a predetermined amount. The member (the pressure roller 174 or the fixing roller 171) is heated from the inside.

(Third embodiment)
In the image forming apparatus 1 according to the third embodiment, the rotary fixing member is opposed to the fixing roller 171 heated from the outside or the inside (in this example, the outside) and the fixing roller 171 (in this example, the fixing belt 173 is attached). And a pressure roller 174 disposed opposite to the fixing roller 171, and the rotationally driving fixing member is a pressure roller 174.

  In the image forming apparatus 1 according to the third embodiment, the fixing device 17 includes a heat source (specifically, a heating element such as a halogen heater lamp) 179 for heating the pressure roller 174 from the inside (see FIGS. 12 and 13). ).

  Specifically, in the image forming apparatus 1 according to the third embodiment, a heat source 179 is provided inside the pressure roller 174 in the fixing device 17 in the image forming apparatus 1 according to the first embodiment.

  FIG. 12 is a schematic side view showing a state in which the heat source 179 is provided inside the cored bar 174a of the pressure roller 174 of the fixing device 17 according to the third embodiment. FIG. 13 is a system block diagram mainly showing the control unit 101 used in the image forming apparatus 1 according to the third embodiment.

  As shown in FIGS. 12 and 13, a heat source 179 that heats the pressure roller 174 from the inside is provided inside the cored bar 174 a of the pressure roller 174.

  As shown in FIG. 13, the heat source 179 is electrically connected to the output system of the control unit 101 and is energized in accordance with an instruction from the control unit 101 so as to heat the pressure roller 174 from the inside. It has become.

  When the reduction amount T1 of the pressure roller 174 exceeds a predetermined amount ta or exceeds the predetermined amount ta, the control unit 101 generates heat from the heat source 179 and moves the pressure roller 174 from the inside (specifically, Is heated (from the inside of the cored bar 174a). On the other hand, when the reduction amount T1 of the pressure roller 174 is less than the predetermined amount ta or less than the predetermined amount ta, the control unit 101 stops the heat generation of the heat source 179 and stops the heating from the inside of the pressure roller 174. It is configured.

  FIG. 14 is a flowchart illustrating an example of a control operation performed by the control unit 101 in the image forming apparatus 1 according to the third embodiment.

  The flowchart shown in FIG. 14 is different from the flowchart shown in FIG. 10 in that steps S36 to S38 are provided instead of steps S16 and S17. 14, the same processes as those shown in FIG. 10 are denoted by the same reference, and the description thereof is omitted.

  In the processing example shown in FIG. 14, the control unit 101 determines whether or not the decrease amount T1 calculated in step S15 exceeds a predetermined amount (step S36), and the decrease amount T1 is equal to or greater than the predetermined amount or exceeds the predetermined amount. Sometimes (step S36: Yes), the heat source 179 in the pressure roller 174 is caused to generate heat (step S37), and when the decrease amount T1 is less than the predetermined amount or less than the predetermined amount (step S36: No), the heat source in the pressure roller 174 The heat generation at 179 is stopped (step S38).

  According to the third embodiment, even when the temperature of the pressure roller 174 decreases when image formation is performed on the recording sheet P, the decrease amount T1 of the pressure roller 174 exceeds the predetermined amount ta or the predetermined amount ta. If the pressure exceeds, the heat source 179 generates heat and the pressure roller 174 is heated from the inside, thereby suppressing or eliminating the decrease in the temperature of the pressure roller 174, thereby suppressing the heat shrinkage of the pressure roller 174. Alternatively, the reduction in the conveyance speed of the recording sheet P by the pressure roller 174 can be suppressed or eliminated.

(Fourth embodiment)
In the image forming apparatus 1 according to the fourth embodiment, the rotary fixing member faces the fixing roller 171 heated from the outside and the fixing roller 171 (in this example, the fixing roller 171 faces the fixing roller 171 via the fixing belt 173). And the rotation driving fixing member is a fixing roller 171.

  In the image forming apparatus 1 according to the fourth embodiment, the fixing device 17 includes a heat source (specifically, a heating element such as a halogen heater lamp) 179 that heats the fixing roller 171 from the inside (see FIGS. 15 and 16). Is further provided.

  Specifically, in the image forming apparatus 1 according to the fourth embodiment, in the image forming apparatus 1 according to the second embodiment, a heat source 179 is provided inside the heating roller 172 in the fixing device 17.

  FIG. 15 is a schematic side view showing a state in which a heat source 179 is provided inside the cored bar 171a of the fixing roller 171 of the fixing device 17 according to the fourth embodiment. FIG. 16 is a system block diagram mainly showing the control unit 101 used in the image forming apparatus 1 according to the fourth embodiment.

  As shown in FIGS. 15 and 16, a heat source 179 for heating the fixing roller 171 from the inside is provided inside the cored bar 171 a of the fixing roller 171.

  As shown in FIG. 16, the heat source 179 is electrically connected to the output system of the control unit 101, and is heated by the instruction from the control unit 101 to heat the fixing roller 171 from the inside. ing.

  When the reduction amount T2 of the fixing roller 171 exceeds a predetermined amount tb or exceeds the predetermined amount tb, the control unit 101 generates heat from the heat source 179 and causes the fixing roller 171 to move from the inside (specifically, the core). It is configured to heat (from the inside of the gold 171a). On the other hand, when the reduction amount T2 of the fixing roller 171 is less than the predetermined amount tb or less than the predetermined amount tb, the control unit 101 stops the heat generation of the heat source 179 and stops the heating from the inside of the fixing roller 171. Has been.

  An example of the control operation according to the fourth embodiment by the control unit 101 is the same as the example of the control operation by the control unit 101 in the image forming apparatus 1 according to the third embodiment, but the pressure roller 174 is changed to the fixing roller 171. This is the same as the control operation, and the illustration and description of the flowchart are omitted here.

  According to the fourth embodiment, even when the temperature of the fixing roller 171 is lowered when the image is formed on the recording sheet P, the decrease amount T2 of the fixing roller 171 exceeds the predetermined amount tb or exceeds the predetermined amount tb. In addition, the heat source 179 generates heat and the fixing roller 171 is heated from the inside, whereby a decrease in the temperature of the fixing roller 171 can be suppressed or eliminated, and thereby, thermal contraction of the fixing roller 171 can be suppressed or eliminated. Therefore, it is possible to suppress or eliminate a decrease in the conveyance speed of the recording sheet P by the fixing roller 171.

(Fifth embodiment)
By the way, when the transfer conveyance drive roller 27b is heated by the radiant heat from the fixing device 17, the temperature characteristic of the ambient temperature around the transfer conveyance drive roller 27b and the temperature characteristic of the transfer conveyance drive roller 27b are substantially equal. Or there is a positive correlation.

  From this point of view, the image forming apparatus 1 according to the fifth embodiment includes a second temperature sensor 182a (182) (see FIG. 17 described later) for detecting the temperature of the transfer conveyance driving roller 27b, and a rotation driving fixing member ( A second driving device 20e (an example of a driving device) that rotationally drives the pressure roller 174 or the fixing roller 171) to vary the rotational speed of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171). Yes.

  The second temperature sensor 182a (182) is configured to detect the ambient temperature (specifically, the ambient temperature at the center in the width direction X) around (in the vicinity of) the transfer conveyance driving roller 27b. Here, the second temperature sensor 182a (182) is provided on the fixing device 17 main body (specifically, the main body frame) via a support member (not shown) while being fixed to the peripheral portion of the transfer conveyance driving roller 27b. ing.

  A plurality of second temperature sensors 182a (182) may be provided in the width direction X. In this case, the ambient temperature around the transfer conveyance driving roller 27b can be a value obtained by averaging the temperatures detected by the second temperature sensors 182a to 182a (182).

  FIG. 17 is a system block diagram mainly showing the control unit 101 used in the image forming apparatus 1 according to the fifth embodiment.

  As shown in FIG. 17, the second temperature sensor 182a (182) is electrically connected to the input system of the control unit 101, and outputs a signal corresponding to the ambient temperature around the transfer conveyance drive roller 27b to the control unit. 101 is transmitted.

  The second driving device 20e rotates the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) by receiving an operation signal from the control unit 101, and rotates the rotation driving fixing member (the pressure roller 174 or the pressure roller 174). The rotational speed of the fixing roller 171) is variable. As a result, the second driving device 20e can vary the conveyance speed of the recording sheet P conveyed by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171).

  The controller 101 increases the ambient temperature around the transfer conveyance drive roller 27b detected by the second temperature sensor 182a (182) when the transfer conveyance drive roller 27b is heated by the radiant heat from the fixing device 17. The rotational speed of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) based on the increasing amount T3a (the increasing amount substantially equal to or positively correlated with the increasing amount T3 at which the temperature of the transfer conveyance driving roller 27b increases). And the second driving device 20e is operated with the obtained correction amount to increase the conveyance speed of the recording sheet P by the rotational driving fixing member (the pressure roller 174 or the fixing roller 171). .

  Specifically, the control unit 101 activates a predetermined state (for example, the image forming apparatus 1) of the image forming apparatus 1 when the temperature of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is not decreased. Rotational drive from the increase T3a in the ambient temperature around the transfer conveyance drive roller 27b detected by the second temperature sensor 182a (182) with reference to the initial state immediately after the image can be formed. Rotation driving fixing member (pressure roller) so that the conveyance speed of the recording sheet P by the fixing member (pressure roller 174 or fixing roller 171) and the conveyance speed of the recording sheet P by the transfer conveyance driving roller 27b match or substantially match. 174 or the fixing speed of the fixing roller 171) is obtained.

  Specifically, the amount of correction of the peripheral speed of the rotationally driving fixing member (the pressure roller 174 or the fixing roller 171) is transferred when the image forming apparatus 1 is in a predetermined state (for example, the initial state of the image forming apparatus 1). Rotation drive fixing member (pressure roller 174) corresponding to an increase T3a (T3≈T3a or T3∝T3a) of the ambient temperature around the transfer transport drive roller 27b from the initial ambient temperature Tc around the transport drive roller 27b. Alternatively, it can be obtained by using a correction table or a correction conversion formula indicating a correction amount of the peripheral speed of the fixing roller 171) (a correction amount for increasing the peripheral speed in accordance with the increase amount T3a). Such a correction table or correction conversion formula can be obtained in advance through experiments or the like, and is stored in advance in the storage unit 101b.

  FIG. 18 is a flowchart illustrating an example of a control operation by the control unit 101 in the image forming apparatus 1 according to the fifth embodiment. In this example, a predetermined state of the image forming apparatus 1 will be described as an initial state.

  Prior to the processing shown in FIG. 18, the initial ambient temperature Tc around the transfer conveyance drive roller 27b in the initial state immediately after the image forming apparatus 1 is activated and ready to form an image is obtained in advance by experiments or the like. The data is stored in advance in the storage unit 101b.

  In the processing example illustrated in FIG. 18, first, when the image forming apparatus 1 is activated (Step S <b> 51), the control unit 101 starts an initial ambient temperature around the transfer conveyance driving roller 27 b when the image forming apparatus 1 is in an initial state. Tc is read from the storage unit 101b (step S52).

  Next, the control unit 101 determines whether or not the job (image forming operation) has started (step S53). When the job starts (step S53: Yes), the second temperature sensor 182a (182) performs transfer transfer. The ambient temperature around the drive roller 27b is detected (step S54).

  Next, the control unit 101 calculates an increase T3a from the initial atmospheric temperature Tc in the initial state read in step S52 of the atmospheric temperature detected in step S54 (step S55).

  Next, the control unit 101 obtains the correction amount of the peripheral speed of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) from the increase amount T3a calculated in step S55, using a correction table or a correction conversion formula. (Step S56).

  Next, the control unit 101 operates the second driving device 20e with the correction amount obtained in step S56 to increase the peripheral speed of the rotation drive fixing member (the pressure roller 174 or the fixing roller 171) by the correction amount. Thus, the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is increased (step S57).

  Next, the control unit 101 determines whether or not the job has ended (step S58). When the job continues (step S58: No), the control unit 101 proceeds to step S54 while when the job ends (step S58). (S58: Yes), the process proceeds to step S53.

  On the other hand, when the job has not started in step S53 (step S53: No), the control unit 101 repeats the process of step S53 until the processing operation ends (step S59: No) (step S59).

  According to the fifth embodiment, the second temperature sensor 182a (182) detects the ambient temperature around the transfer conveyance drive roller 27b, and the transfer conveyance drive roller 27b is heated by the radiant heat from the fixing device 17. The peripheral speed of the rotationally driving fixing member (the pressure roller 174 or the fixing roller 171) is based on the increase amount T3a in which the ambient temperature around the transfer conveyance driving roller 27b detected by the second temperature sensor 182a (182) increases. And the second driving device 20e is operated with the obtained correction amount to increase the conveyance speed of the recording sheet P by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171). The conveyance speed of the recording sheet P by the fixing member (the pressure roller 174 or the fixing roller 171) is set to the recording sheet by the transfer conveyance driving roller 27b. It can be accurately approximate or match the P conveying speed of the.

(Sixth embodiment)
By the way, as in the present embodiment, the rotary transfer conveyance member includes a plurality of transfer conveyance rollers 271 to 271 and a conveyance belt 272 wound around the plurality of transfer conveyance rollers 271. In the case where the transfer conveyance drive roller 27b is located on the most downstream side in the conveyance direction Y of the recording sheet P among the plurality of transfer conveyance rollers 271-271, the transfer conveyance drive roller 27b located on the most downstream side is the fixing device. When heated by the radiant heat from 17, the temperature characteristics of the transport belt 272 and the temperature characteristics of the transfer transport drive roller 27b are substantially equal or have a positive correlation.

  From this point of view, the image forming apparatus 1 according to the sixth embodiment includes a second temperature sensor 182b (182) (see FIG. 19 described later) for detecting the temperature of the transfer conveyance driving roller 27b, and a rotation driving fixing member (see FIG. 19). A second driving device 20e (an example of a driving device) that rotationally drives the pressure roller 174 or the fixing roller 171) to vary the rotational speed of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171). Yes.

  The rotary transfer conveyance member includes a plurality of transfer conveyance rollers 271 to 271 and a conveyance belt 272 wound around the plurality of transfer conveyance rollers 271 to 271, and the rotation drive transfer conveyance member is a plurality of transfer conveyance rollers 271 to 271. Among them, the transfer conveyance drive roller 27b is located on the most downstream side in the conveyance direction Y of the recording sheet P, and the second temperature sensor 182b (182) is a temperature of the conveyance belt 272 (specifically, surface temperature, More specifically, the surface temperature of the central portion in the width direction X is detected. Here, the second temperature sensor 182b (182) is in contact with the surface 272m (see FIG. 19) of the conveyor belt 272 via a support member (not shown) on the fixing device 17 main body (specifically, the main body frame). Is provided.

  In this example, the second temperature sensor 182b (182) detects the surface temperature of the portion of the conveyor belt 272 around which the transfer conveyance drive roller 27b is wound. However, the present invention is not limited to this, and the second temperature sensor 182b (182) detects the surface temperature of a portion around which the transfer conveyance roller 271 other than the transfer conveyance drive roller 27b of the conveyance belt 272 is wound. Alternatively, the surface temperature of a portion where the transfer conveyance rollers 271 to 272 are not wound may be detected.

  A plurality of second temperature sensors 182b (182) may be provided in the width direction X. In this case, the temperature of the conveyor belt 272 can be a value obtained by averaging the temperatures detected by the second temperature sensors 182b to 182b (182).

  FIG. 19 is a system block diagram mainly showing the control unit 101 used in the image forming apparatus 1 according to the sixth embodiment.

  As shown in FIG. 19, the second temperature sensor 182 b (182) is electrically connected to the input system of the control unit 101, and transmits a signal corresponding to the temperature of the conveyor belt 272 to the control unit 101. It has become.

  The second driving device 20e rotates the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) by receiving an operation signal from the control unit 101, and rotates the rotation driving fixing member (the pressure roller 174 or the pressure roller 174). The rotational speed of the fixing roller 171) is variable. As a result, the second driving device 20e can vary the conveyance speed of the recording sheet P conveyed by the rotation driving fixing member (the pressure roller 174 or the fixing roller 171).

  Then, the controller 101 increases the amount 3b (transfer) by which the temperature of the transport belt 272 detected by the second temperature sensor 182b (182) increases when the transfer transport drive roller 27b is heated by the radiant heat from the fixing device 17. A correction amount of the peripheral speed of the rotational drive fixing member (the pressure roller 174 or the fixing roller 171) is obtained based on an increase amount T3 that is substantially equal to or positively correlated with the increase amount T3 in which the temperature of the transport drive roller 27b increases. The second drive device 20e is operated with the obtained correction amount to increase the conveyance speed of the recording sheet P by the rotational drive fixing member (the pressure roller 174 or the fixing roller 171).

  Specifically, the control unit 101 activates a predetermined state (for example, the image forming apparatus 1) of the image forming apparatus 1 when the temperature of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is not decreased. From the amount T3b of increase in the temperature of the conveying belt 272 detected by the second temperature sensor 182b (182) with reference to the initial state immediately after the image can be formed, the rotation driving fixing member (pressure roller) 174 or the fixing roller 171) and the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) so that the conveyance speed of the recording sheet P by the transfer conveyance driving roller 27b coincides or substantially coincides with the conveyance speed of the recording sheet P. The amount of correction of the peripheral speed is calculated.

  Specifically, the correction amount of the rotational speed of the rotation driving fixing member (the pressure roller 174 or the fixing roller 171) is conveyed when the image forming apparatus 1 is in a predetermined state (for example, the initial state of the image forming apparatus 1). Correction amount of the peripheral speed of the rotational drive fixing member (pressure roller 174 or fixing roller 171) corresponding to the increase amount T3b (T3≈T3b or T3∝T3b) of the temperature of the conveying belt 272 from the initial temperature Td of the belt 272 ( It can be obtained using a correction table or a correction conversion formula indicating a correction amount that increases the peripheral speed in accordance with the increase amount T3b. Such a correction table or correction conversion formula can be obtained in advance through experiments or the like, and is stored in advance in the storage unit 101b.

  An example of the control operation according to the sixth embodiment by the control unit 101 is an example of the control operation by the control unit 101 in the image forming apparatus 1 according to the fifth embodiment, and the ambient temperature around the transfer conveyance drive roller 27b. Is the same as the control operation in which the temperature is changed to the temperature of the conveyor belt 272, and the illustration and description of the flowchart are omitted here.

  According to the sixth embodiment, the second temperature sensor 182b (182) detects the temperature of the conveyance belt 272, and the second temperature sensor 182b is heated when the transfer conveyance drive roller 27b is heated by the radiant heat from the fixing device 17. A correction amount of the peripheral speed of the rotationally driving fixing member (the pressure roller 174 or the fixing roller 171) is obtained based on the increase amount T3b in which the temperature of the conveyor belt 272 increases detected in (182), and the obtained correction amount is used. The rotation driving fixing member (pressure roller 174 or fixing roller 171) is activated by operating the second driving device 20e to increase the conveyance speed of the recording sheet P by the rotation driving fixing member (pressure roller 174 or fixing roller 171). The conveyance speed of the recording sheet P due to the recording sheet P is accurately brought close to or coincident with the conveyance speed of the recording sheet P due to the transfer conveyance driving roller 27b. Rukoto can.

  The present invention is not limited to the embodiment described above, and can be implemented in various other forms. Therefore, such an embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is shown by the scope of claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image forming part 101 Control part (an example of a conveyance speed control part)
101a processing unit 101b storage unit 11 exposure device 12 developing device 13 photoconductor drum 14 cleaner device 15 charger 16 intermediate transfer belt device 17 fixing device (an example of a heating fixing unit)
171 Fixing roller 171a Core metal 171b Resin layer (an example of a resin member)
172 Heating roller 172a Core metal 173 Fixing belt 174 Pressure roller 174a Core metal 174b Resin layer (an example of a resin member)
174c Release layer (an example of a resin member)
175 fixing temperature sensor 177 heat source 179 heat source 18 paper feed tray 181 first temperature sensor 181a first temperature sensor 181b first temperature sensor 182 second temperature sensor 182a second temperature sensor 182b second temperature sensor 19 paper discharge tray 1a main body 20 sheet Conveying device 20a First driving device 20b Feed clutch 20c Pre-registration clutch 20d Registration clutch 20e Second driving device (an example of driving device)
21 intermediate transfer belt 22 intermediate transfer driving roller 23 driven roller 24 intermediate transfer roller 25 intermediate transfer belt cleaning device 26 tension roller 27 transfer conveying device (an example of a transfer conveying unit)
271 Transfer transport roller 272 Transport belt 27a Transfer roller 27b Transfer transport drive roller 27c Upstream transfer transport roller 27d Transfer transport nip roller 27e Transfer transport tension roller 31 Pickup roller 31a Separation roller 31b Separation roller 32 Registration roller 33 Pre-registration roller 34 Discharge roller N1 transfer nip area N2 fixing nip area Na vicinity P recording sheet S sheet conveyance path T toner image X width direction Y conveyance direction

Claims (9)

A transfer conveyance unit having a rotary transfer conveyance member; and a heat fixing unit having a rotation fixing member. The recording sheet on which an unfixed image has been transferred is conveyed to the heat fixing unit by the transfer conveyance unit, and the heat fixing unit An image forming apparatus that heat-fixes the unfixed image on the recording sheet conveyed to a portion by the heat-fixing portion,
The conveyance speed of the recording sheet by a rotationally driven fixing member that is rotationally driven among the rotational fixing members in the heating and fixing unit, and the rotationally driven transfer conveying member that is rotationally driven among the rotational transfer and conveying members in the transfer and conveying unit. A transport speed control unit that controls the transport speed of the recording sheet so that the transport speed of the recording sheet matches or substantially matches,
The conveyance speed control unit is configured to control the rotation drive transfer conveyance member based on an increase amount in which the temperature of the rotation drive transfer conveyance member increases when the rotation drive transfer conveyance member is heated by radiant heat from the heating fixing unit. An image forming apparatus characterized in that the recording sheet conveyance speed is increased. The image forming apparatus according to claim 1,
The conveyance speed control unit increases the conveyance speed of the recording sheet by the rotation driving fixing member based on a decrease amount by which the temperature of the rotation driving fixing member decreases when performing image formation on the recording sheet. An image forming apparatus. The image forming apparatus according to claim 2,
A first temperature sensor for detecting the temperature of the rotational drive fixing member; and a drive device that rotationally drives the rotational drive fixing member to vary the rotational speed of the rotational drive fixing member;
The first temperature sensor detects a temperature inside the outer peripheral surface of the rotational drive fixing member,
The conveyance speed control unit performs the rotation based on a decrease amount in which the temperature inside the outer peripheral surface of the rotation driving fixing member is detected by the first temperature sensor when performing image formation on the recording sheet. An image forming apparatus characterized in that a correction amount of a peripheral speed of a driving fixing member is obtained, and the driving device is operated with the obtained correction amount to increase a conveyance speed of the recording sheet by the rotational driving fixing member. The image forming apparatus according to claim 3, wherein
The rotational drive fixing member is configured to include a cored bar and a resin member provided on an outer peripheral surface of the cored bar,
The first temperature sensor detects the temperature of the cored bar,
The conveyance speed control unit corrects the peripheral speed of the rotation driving fixing member based on a decrease amount by which the temperature of the core metal detected by the first temperature sensor is reduced when image formation is performed on the recording sheet. An image forming apparatus characterized in that an amount is obtained, and the drive device is operated with the obtained correction amount to increase the conveyance speed of the recording sheet by the rotational drive fixing member. The image forming apparatus according to claim 2,
A heat source for heating the rotational driving fixing member from the inside;
The transport speed control unit heats the rotational drive fixing member from the inside by generating heat when the amount of decrease of the rotational drive fixing member exceeds a predetermined amount or exceeds the predetermined amount. An image forming apparatus. An image forming apparatus according to any one of claims 1 to 5, wherein
The conveyance speed control unit conveys the recording sheet by a rotationally driven fixing member that is rotationally driven among the rotational fixing members in the heating and fixing unit with reference to a predetermined state of the image forming apparatus. The recording sheet conveying speed is changed in a state where the recording sheet conveying speed by the rotationally driven transfer conveying member that is rotationally driven among the rotating transfer conveying members in the transfer conveying unit is matched or substantially matched. An image forming apparatus. An image forming apparatus according to any one of claims 1 to 6, wherein
A second temperature sensor for detecting the temperature of the rotationally driven transfer conveying member; and a drive device that rotationally drives the rotationally driven fixing member to vary the rotational speed of the rotationally driven fixing member;
The second temperature sensor detects an ambient temperature around the rotary drive transfer conveying member,
The conveyance speed control unit increases an ambient temperature around the rotation drive transfer conveyance member detected by the second temperature sensor when the rotation drive transfer conveyance member is heated by radiant heat from the heat fixing unit. A correction amount of the peripheral speed of the rotational drive fixing member is obtained based on the increased amount, and the drive device is operated with the obtained correction amount to increase the conveyance speed of the recording sheet by the rotational drive fixing member. An image forming apparatus. An image forming apparatus according to any one of claims 1 to 6, wherein
A second temperature sensor for detecting the temperature of the rotationally driven transfer conveying member; and a drive device that rotationally drives the rotationally driven fixing member to vary the rotational speed of the rotationally driven fixing member;
The rotary transfer conveyance member includes a plurality of transfer conveyance rollers and a conveyance belt wound around the plurality of transfer conveyance rollers,
The rotationally driven transfer conveying member is a transfer conveying roller located on the most downstream side in the conveying direction of the recording sheet among the plurality of transfer conveying rollers,
The second temperature sensor detects the temperature of the conveyor belt,
The transport speed control unit is configured to increase the temperature of the transport belt detected by the second temperature sensor when the rotary drive transfer transport member is heated by radiant heat from the heat fixing unit. An image forming apparatus characterized in that a correction amount of a peripheral speed of a rotation driving fixing member is obtained, and the driving device is operated with the obtained correction amount to increase a conveyance speed of the recording sheet by the rotation driving fixing member. An image forming apparatus according to any one of claims 1 to 8,
The rotary fixing member includes a fixing roller to be heated, and a pressure roller disposed to face the fixing roller,
The image forming apparatus according to claim 1, wherein the rotation driving fixing member is the pressure roller.

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