JP2012073548A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing a non-uniform image caused by degradation in fixability and, at the same time, capable of restraining deterioration of a fixing roller, a pressure roller, etc., resulting from an excessive temperature increase of a paper non-passage portion of a fixing nip part, and to provide an image forming apparatus that has the fixing device.SOLUTION: The fixing device for fixing a toner image on a target fixing body comprises: a first fixing member heated by a heat source; a second fixing member forming a fixing part extending in one direction by being brought into pressure contact with the first fixing member; and a heat homogenizing member having a shape extending to one direction and disposed in contact with a contacted fixing member, which is either one of the first and second fixing members. The heat homogenizing member can be switched between a first state in which a lengthwise central shaft of the contacted fixing member and a lengthwise central shaft of the homogenizing member are substantially parallel with respect to the contacted fixing member and a second state in which the area of the contact with the contacted fixing member is smaller than that in the first state.

Description

  The present invention relates to a fixing device including a heated body for fixing a transfer material such as toner on a recording medium by heat, and an image forming apparatus such as a copying machine, a facsimile, and various printers including the fixing device. About.

  2. Description of the Related Art Conventionally, as a fixing device used in an electrophotographic image forming apparatus or an electrostatic recording image forming apparatus, there is a heat roller fixing type fixing apparatus using a rubber roller as a heating target for fixing. In such a fixing device, a recording medium is conveyed to a fixing nip portion formed by a rubber roller and a fixing roller arranged in pressure contact with the rubber roller, and a toner image on the recording medium is fixed.

  However, the rubber roller used in the fixing device of the heat roller fixing system has a large heat capacity, so that there is a problem that a large amount of power is consumed for fixing. In addition, it takes time to raise the temperature of the rubber roller during image formation, and there is a problem that the warm-up time until the start of image formation becomes longer.

  In order to solve such problems, a fixing device using a film fixing method, in which the heat conduction efficiency is greatly improved by using a fixing belt having a heat fixing film with a low heat capacity as a heating target for fixing, is put into practical use. Has been. A film-fixing type fixing device consumes less power during fixing and can shorten the warm-up time.

  Further, as a heating unit that heats the fixing belt, a fixing device that employs an electromagnetic induction heating method having excellent heat generation efficiency has been put into practical use. In addition, by providing such a fixing device, an image forming apparatus in which warm-up time is significantly shortened and image forming productivity is improved has been put into practical use.

  However, when a toner image on a recording medium having a relatively small size is continuously fixed using such a fixing device, the temperature of the non-sheet passing portion in the fixing nip portion increases excessively, and the fixing belt Etc. had a problem that they deteriorated early.

  As a solution to such a problem, Patent Document 1 discloses that the temperature of the non-sheet passing portion of the heat roller that is a heated body is equal to or higher than the set temperature, and the entire length in the longitudinal direction of the heat roller. A fixing device having a heat transfer roller that abuts is disclosed.

  Patent Document 2 discloses a fixing device having a cooling roller that abuts only on the non-sheet passing portion of the heating roller when the temperature of the non-sheet passing portion of the heating roller that is a heated body is equal to or higher than a predetermined temperature. Has been.

Japanese Patent Laid-Open No. 10-333463 Japanese Patent Laid-Open No. 11-174897

  However, in the fixing device described in Patent Document 1, since the heat transfer roller having a relatively high heat capacity and a temperature drop contacts the entire length of the heat roller, the temperature of the sheet passing portion in the fixing nip portion is abrupt. There is a problem that image unevenness and fixing failure occur.

  Further, in the configuration of the fixing device described in Patent Document 2, since the cooling roller is brought into contact only with the non-sheet passing portion of the heating roller, less heat is radiated when fixing a large amount of recording media continuously. There was a problem that the non-sheet passing portion could not be sufficiently cooled. In such a fixing device, in order to sufficiently cool the non-sheet passing portion, it is necessary to increase the inner diameter of the cooling roller, and there is a problem that the entire device is increased in size.

  The present invention has been made to solve the above-described problems, and is a heating roller caused by excessive increase in the temperature of the non-sheet-passing portion while preventing image unevenness due to deterioration of fixability. It is another object of the present invention to provide a fixing device capable of suppressing deterioration of a pressure roller and the like and an image forming apparatus including the fixing device.

  In order to achieve the above object, a fixing device according to an aspect of the present invention includes a first fixing member heated by a heat source, and a second fixing member disposed in pressure contact with the first fixing member. The first fixing member and the second fixing member are portions where the first fixing member and the second fixing member are in pressure contact with each other. A fixing portion extending in one direction, which is a portion for fixing the toner image on the fixing body, and having a shape extending in one direction, the first fixing member or the second fixing member being A heat equalizing member that comes into contact with any one of the contacted fixing members and makes the temperature distribution of the fixing unit uniformly approach the heat fixing member; The central axis of the contact fixing member in the longitudinal direction and the longitudinal direction of the heat equalizing member A first state in which the center axis in contact substantially in parallel, said the contacted area in contact with the fixing member of the first state is smaller than the second state, may take.

  Further, in the fixing device, the fixing unit is formed of a passing part through which the fixing body passes and a non-passing part through which the fixing body does not pass. The contact fixing member is in contact with a non-excess region that is an outer peripheral surface region where the non-passing portion can be formed, and the second state is a state in which the heat equalizing member passes the contact fixing member through the passage. The state which does not contact the outer peripheral surface area | region which can form a part may be sufficient.

  Furthermore, in the fixing device according to one aspect of the present invention, the contact fixing member is a cylindrical rotating body that is rotatable in a direction in which the fixing body passes, and the fixing unit includes the fixing target. The first state is such that the heat equalizing member can form the non-passing portion of the contacted fixing member. The passage portion through which the body passes and the non-passing portion through which the fixing body does not pass are formed. The second state is a state in which the heat equalizing member can form the passage part of the contacted fixing member in a state of contacting a non-passing region which is a region on the inner peripheral surface corresponding to the outer peripheral surface region. The state which does not contact the internal peripheral surface area | region corresponding to a surface area | region may be sufficient.

  Furthermore, in the fixing device according to one aspect of the present invention, the heat equalizing member is disposed at the first position when the first state is in the first state, and is disposed at the second position when the member is in the second state. And a heat equalizing member moving means for supporting the heat equalizing member so as to be movable between the first position and the second position.

  Furthermore, in the fixing device according to one aspect of the present invention, in the first state and the second state, the soaking unit is configured so that an outer peripheral surface on one end side of the soaking member contacts the non-passing region. The heat equalizing member holding means holds the heat member, and the heat equalizing member moving means has an outer peripheral surface on the other end side of the heat equalizing member in the second state with respect to the contacted fixing member. The soaking member is moved so as to be separated, and the soaking member is moved so that the outer peripheral surface on the other end side of the soaking member is in contact with the contacted fixing member in the first state. You may let them.

  Furthermore, the fixing device according to an aspect of the present invention includes a temperature detection unit that detects a temperature on an end side of the passage portion in a direction in which the fixing portion extends, and when the temperature reaches a predetermined temperature, Control means for controlling the heat equalizing member moving means so as to move the heat equalizing member to the first position.

  In order to achieve the above object, an image forming apparatus according to an aspect of the present invention includes the fixing device.

  An image forming apparatus according to an aspect of the present invention is an image forming apparatus that includes the fixing device according to an aspect of the present invention and forms a toner image on the fixing target based on a print job including image information. A temperature detecting unit that detects a size of the fixing body that passes through the fixing unit, and the temperature equalizing member moving unit is configured to detect the size of the fixing body detected by the size detecting unit. Control means for setting a timing for moving the member to the first position and controlling the heat equalization member moving means to move the heat equalization member to the first position at the timing.

  Furthermore, in the image forming apparatus according to an aspect of the present invention, the control unit may change the timing based on a time during which the heat source is continuously operated.

  According to the fixing device and the image forming apparatus of the present invention, when the heat equalizing member is in the first state, the heat taken away from the surfaces of the first fixing member and the second fixing member corresponding to the passage portion of the fixing portion is taken. By suppressing, the temperature rise of the first fixing member and the second fixing member corresponding to the non-passing portion of the fixing portion can be suppressed while suppressing the temperature drop of the passing portion. Accordingly, it is possible to suppress the deterioration of the pressure roller and the like due to the excessive increase in the temperature of the non-passing portion while preventing image unevenness due to the deterioration of the fixing property.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus GS1 according to the present invention. FIG. 2 is a schematic diagram illustrating an example of a fixing device TS1 provided in an image forming apparatus GS1 according to the present invention. FIG. 2 is a schematic diagram illustrating an example of a fixing device TS1 according to the present invention. It is the schematic which shows an example of arrangement | positioning of the soaking | uniform-heating roller moving apparatus provided in fixing device TS1 which concerns on this invention. It is the schematic which shows an example of arrangement | positioning of the soaking | uniform-heating roller moving apparatus provided in fixing device TS1 which concerns on this invention. It is the schematic which shows an example of arrangement | positioning of the soaking | uniform-heating roller moving apparatus provided in fixing device TS1 which concerns on this invention. It is the schematic which shows an example of arrangement | positioning of the soaking | uniform-heating roller moving apparatus provided in fixing device TS1 which concerns on this invention. It is a graph which shows an example of a temperature transition at the time of fixing continuously the recording medium of the maximum size which can be fixed in fixing device TS1 which concerns on this invention. 5 is a graph showing an example of temperature transition during fixing when a recording medium is continuously fixed in a fixing device in which a temperature-uniforming roller is completely separated from a pressure roller. It is a graph which shows an example of heat_generation | fever distribution of the heating roller in fixing device TS1 which concerns on this invention. 6 is a graph showing an example of a temperature transition when performing a soaking roller moving operation 1 in the fixing device TS1 according to the present invention. 6 is a graph showing an example of a temperature transition during fixing when a small-size recording medium is continuously fixed in a fixing device in which a temperature-uniforming roller is completely separated from a pressure roller. 6 is a flowchart showing an example of a soaking roller moving operation 1 in the fixing device TS1 according to the present invention. 10 is a table showing an example of a relationship between a sheet passing size of a recording medium and a first predetermined time. It is a table which shows an example of the relationship between the energization time of a heat source, and the 2nd predetermined time. It is a table which shows an example of the relationship between the temperature of the 1st sensor at the time of restarting warm-up from the state where the heat source stopped temporarily, and the 3rd predetermined time. 6 is a graph showing an example of a temperature transition when a soaking roller moving operation 2 is performed in the fixing device TS1 according to the present invention. 6 is a graph showing an example of a temperature transition when a soaking roller moving operation 2 is performed in the fixing device TS1 according to the present invention. It is a flowchart which shows an example of the soaking | uniform-heating roller moving operation | movement 2 in fixing device TS1 which concerns on this invention. FIG. 2 is a schematic diagram illustrating an example of a fixing device TS1 according to the present invention. It is the schematic which shows an example of arrangement | positioning of the soaking | uniform-heating roller and pressure roller in fixing device TS1 which concerns on this invention. It is the schematic which shows the contact state of the soaking | uniform-heating roller and pressure roller when the elastic layer 2022 of the pressure roller in the fixing apparatus TS1 which concerns on this invention thermally expands. It is the schematic which shows the contact state of the soaking | uniform-heating roller and pressure roller when the elastic layer 2022 of the pressure roller in the fixing apparatus TS1 which concerns on this invention thermally expands. It is a graph which shows an example of the temperature transition after the warm-up completion from the warm-up start in the fixing device TS1 according to the present invention. 6 is a graph showing an example of temperature transition during fixing when a small-size recording medium is continuously fixed in the fixing device TS1 according to the present invention.

Embodiments of the present invention will be described below with reference to the drawings.
(1) Embodiment 1
FIG. 1 is a schematic configuration diagram showing a tandem color digital image forming apparatus (hereinafter referred to as “image forming apparatus GS1”) which is an image forming apparatus according to Embodiment 1 which is an example of the present invention. The image forming apparatus GS1 includes a fixing device (hereinafter, “fixing device TS1”) according to the first embodiment which is an example of the present invention. First, the image forming apparatus GS1 will be described with reference to FIG.

<Image forming apparatus GS1>
The image forming apparatus GS1 is an image forming apparatus that forms a color image, and is a so-called intermediate transfer type. That is, toner images of different colors formed on a plurality of image carriers are sequentially primary-transferred onto a common intermediate transfer belt to superimpose a single color toner image on the intermediate transfer belt. A color toner image is formed on the recording medium by collectively transferring the color toner image formed thereon onto the recording medium.

  As shown in FIG. 1, the image forming apparatus GS1 includes an intermediate transfer belt 17, and the intermediate transfer belt 17 is moved to an image forming unit arrangement region provided on the outer peripheral surface of the intermediate transfer belt 17. Four image forming units 30Y, 30M, 30C, and 30K that respectively form a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are provided along the direction. Further, a secondary transfer unit 14 is provided at a position downstream of the image forming unit 30 </ b> K at the most downstream position in the moving direction of the intermediate transfer belt 17, and further on the intermediate transfer belt 17 at a position further downstream. Intermediate transfer belt cleaning means 18T for removing the untransferred toner is provided. Further, a fixing device TS1 is provided at a position on the downstream side in the transport direction of the recording medium P (upper side in FIG. 1) in the secondary transfer unit 14. The image forming apparatus GS1 also includes a control unit 50 that controls each image forming process, a memory 501 that stores data necessary for each image forming process, and a first timer 502 that counts the execution time of each image forming process. And a second timer 503.

  For example, in the image forming unit 30Y related to a yellow toner image, the image forming unit includes an image carrier 10Y made of a rotating drum-shaped photosensitive member, a charging device 11Y for charging the image carrier 10Y, and an image forming unit. An image forming unit 13Y that performs development with a developer containing yellow toner is provided on the image carrier 10Y exposed by the external exposure device 12Y. The charging device 11Y and the image forming unit 13Y are arranged in this order along the rotation direction of the image carrier 10Y with respect to the outer peripheral surface of the image carrier 10Y. Further, an image carrier cleaning means 18Y provided with a cleaning blade is provided at a position downstream of the primary transfer means 15Y provided at a position downstream of the image forming portion 13Y in the rotation direction of the image carrier 10Y. .

  The image carrier 10Y has a photosensitive layer made of a resin containing an organic photoconductor on the outer peripheral surface of a drum-shaped metal substrate, and is arranged in a state extending in a direction perpendicular to the paper surface in FIG. Yes.

  The charging device 11Y and the exposure device 12Y constitute an electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier 10.

  The charging device 11Y is, for example, a scorotron charger having a grid electrode and a discharge electrode, and charges the surface of the image carrier 10Y.

  The exposure device 12Y is composed of, for example, a laser irradiation device, and exposes the image carrier 10Y by irradiating laser light. For example, the laser beam is irradiated based on an image signal read by a scanner (not shown) and converted into an electrical signal.

  The image forming unit 13Y includes, for example, a developer containing unit and a developing sleeve that contains a magnet and holds the developer and rotates. When an image is formed, the image forming unit 13Y is connected to a voltage applying unit (not shown). A direct current and / or alternating bias voltage is applied.

  The primary transfer unit 15Y includes a primary transfer roller 151Y disposed so as to form a primary transfer nip portion while being pressed against the surface of the image carrier 10Y via the intermediate transfer belt 17, and the primary transfer roller 151Y. For example, it is constituted by a transfer current supply device (not shown) made of a constant current power source and connected to the roller 151Y.

  For example, the primary transfer unit 15Y supplies the yellow toner image formed on the image carrier 10Y to the intermediate transfer belt 17 by supplying a primary transfer current to the primary transfer roller 151Y by a transfer current supply device. A so-called contact transfer method of transferring can be used.

  The image carrier cleaning means 18Y has a cleaning blade. The cleaning blade is made of, for example, an elastic body such as urethane rubber, and the base end portion thereof is supported by a support member, and the tip end portion is provided so as to come into contact with the surface of the image carrier 10Y. The direction extending from the base end side of the cleaning blade can be a so-called counter direction, which is the direction opposite to the moving direction due to the rotation of the image carrier 10Y at the contact portion.

  Each of the other image forming units 30M, 30C, and 30K also relates to a yellow toner image except that a developer including magenta toner, cyan toner, and black toner is used instead of the developer including yellow toner. The configuration is the same as that of the image forming unit 30Y.

  In each of the primary transfer units 15M, 15C, and 15K, the primary transfer current is supplied as in the image forming unit 30Y related to the yellow toner image. The toner images formed on the image carriers 10Y, 10M, 10C, and 10K are primarily transferred onto the intermediate transfer belt 17 that is circulated and driven in the direction of the arrow T1 at a predetermined timing. A multicolor toner image is formed by superimposing the single color toner images.

  The secondary transfer unit 14 presses the drive roller 142 via the intermediate transfer belt 17 to form a secondary transfer nip portion, and a transfer voltage application connected to the secondary transfer roller 141. And a device (not shown). The secondary transfer roller 141 can be, for example, a semiconductive rubber roller.

  The secondary transfer unit 14 is a so-called contact transfer system, and a transfer voltage is applied between the secondary transfer roller 141 and the driving roller 142 from a transfer voltage applying device (not shown), whereby the intermediate transfer belt 17. The color toner image formed above is secondarily transferred to the recording medium P that has been conveyed.

  The toner image is secondarily transferred onto the recording medium P at the secondary transfer nip, and the recording medium P on which the toner image is secondarily transferred is conveyed to the fixing device TS1.

  Although the details will be described later, the fixing device TS1 is based on an electromagnetic induction heating method including a heating roller 20 and a pressure roller 21, and heats and applies a color toner image on the recording medium P conveyed to the fixing device TS1. To fix on the recording medium P. The fixed recording medium P is discharged onto a discharge tray (not shown). Although the details will be described later, the fixing device TS1 can perform a temperature-uniforming roller moving operation for preventing excessive heating of the heating roller 20 and the pressure roller 21.

  The control unit 50 performs warm-up control for setting the temperature of the heating roller 20 to a predetermined fixing temperature so that the fixing temperature becomes an appropriate fixing temperature according to the type of the recording medium P conveyed to the fixing device TS1. Do.

  In addition, when the recording medium is fixed, the control unit 50 controls the induction coil unit 22 to perform print control for maintaining the temperature of the heating roller 20 at a predetermined fixing temperature. When completed, standby control is performed to bring the temperature of the heating roller 20 to a predetermined standby temperature lower than the fixing temperature.

  At a position downstream of the secondary transfer unit 14 in the moving direction of the intermediate transfer belt 17, a cleaning blade 181 that removes untransferred toner and the like on the intermediate transfer belt 17 and untransferred toner scraped off by the cleaning blade 181. An intermediate transfer belt cleaning means 18T provided with a recovery unit 182 for recovering the like and the like is provided. Waste toner such as untransferred toner accommodated in the collection unit 182 can be transported to a waste toner box (not shown) and discharged outside the image forming apparatus, for example.

  The cleaning blade 181 has a blade shape extending in the width direction of the intermediate transfer belt 17 and can be made of an elastic body such as urethane rubber, for example. The proximal end portion of the cleaning blade 181 is supported by a support member. Further, the direction extending from the base end side of the cleaning blade 181 can be a so-called counter direction, which is the direction opposite to the moving direction due to the rotation of the intermediate transfer belt 17 at the contact portion.

<Fixing device TS1>
Next, the fixing device TS1 will be described in more detail with reference to FIGS.

  As shown in FIGS. 2 and 3, the fixing device TS <b> 1 includes a heating roller 20 that is a heating element, a pressure roller 21 that is pressed against the heating roller 20, and an induction coil unit 22 that heats the heating roller 20. A first temperature sensor S1 for detecting the temperature of the central portion in the longitudinal direction on the outer peripheral surface of the heating roller 20, and a second temperature sensor for detecting the temperature on one end side in the longitudinal direction of the outer peripheral surface of the heating roller 20. A temperature equalizing roller moving device 24 that moves the temperature equalizing roller 23 between a temperature sensor S2, a temperature equalizing roller 23 that is in contact with the pressure roller 21, and a position that contacts the pressure roller 21 and a position that is separated from the pressure roller 21. And. The toner image transferred onto the recording medium P is fixed at a fixing nip N formed by the heating roller 20 and the pressure roller 21.

  The heating roller 20 has a fixing roller 202 extending in one direction and a fixing belt 201 provided so as to cover the outer peripheral surface of the fixing roller 202, and is provided at one end and the other end in the longitudinal direction. A bearing is rotatably supported by a fixing side plate, a heat insulating bush 204, and a bearing 205. The heating roller 20 is rotationally driven at a predetermined speed in the direction of the arrow T2 in FIG. 2 by transmitting a rotational force from the drive motor M to the drive gear G via a drive transmission mechanism (not shown). Here, the pressure roller 21 arranged in pressure contact with the heating roller 20 is driven to rotate in the direction of arrow T3 in FIG. 2 as the heating roller 20 rotates.

  The fixing roller 202 includes a cylindrical cored bar 2021 and an elastic layer 2022 formed to cover the cored bar 2021. The cored bar 2021 is made of a material such as SUS (stainless steel), and the elastic layer 2022 can be made of, for example, silicone sponge rubber.

  The fixing belt 201 includes a conductive layer 2011 that is a heat generation layer and a surface layer 2012, and is configured to be laminated on the elastic layer 2022 of the fixing roller 202 in this order. The conductive layer 2011 has a cylindrical shape with a thickness of about 0.2 mm and is made of, for example, a material such as nickel or SUS. The surface layer 2012 is a PFA (perfluoroalkoxy) tube having a thickness of about 30 μm.

  The pressure roller 21 is pressed by a pressure mechanism (not shown) so that the central axis of the pressure roller 21 and the central axis of the heating roller 20 are parallel to each other. (Downward) Here, “parallel” is a concept including substantially parallel. The pressure roller 21 presses the fixing roller 202 from the outside of the fixing belt 201 via the fixing belt 201, so that the fixing nip portion N is formed between the outer peripheral surface of the fixing belt 201 and the outer peripheral surface of the pressure roller 21. Form.

  The pressure roller 21 includes a cylindrical cored bar 211, a heat resistant elastic layer 212, and a release layer 213, and the release layer 213 is laminated around the cored bar 211 via the heat resistant elastic layer 212. Has been. The cored bar 211 is made of a material such as aluminum, and the heat-resistant elastic layer 212 can be made of, for example, silicone rubber. The release layer 213 is made of PFA, PTFE (polytetrafluoroethylene) coat or the like. The outer shape of the pressure roller 21 is about 35 mm, and the dimension in the longitudinal direction is about 300 mm.

  Here, each of the pressure roller 21 and the heating roller 20 is an area on the outer peripheral surface, and sandwiches the maximum size recording medium P (for example, A4 or A3R paper) that can be fixed by the fixing device TS1. The first area L1 is an area for fixing, and the second area L2 is an area on the outer peripheral surface and other than the first area L1.

  The fixing nip portion N has a passing portion through which the recording medium P passes and a non-passing portion that is a portion other than the passing portion. The passing portion is formed by the first region L1 of the pressure roller 21 and the first region L1 of the heating roller 20, and the non-passing portion is the second region L2 of the pressing roller 21 and the second region L2 of the heating roller 20. And formed.

  Further, when the recording medium P is conveyed to the fixing nip portion N, the central portion of the recording medium P in the direction orthogonal to the conveying direction T4 substantially serves as the conveyance reference position set at the central portion of the passing portion. It is conveyed to pass.

  In the following description, for the sake of convenience, an area within the passing portion of the fixing nip N and outside an area through which a recording medium of a predetermined size (hereinafter referred to as “small size recording medium”) passes is recorded in small size recording. The medium non-passing part. The small size recording medium is, for example, a government-made postcard or the like, and when passing through the fixing nip portion N, the width of the recording medium in the longitudinal direction of the fixing nip portion N is larger than the width in the longitudinal direction of the passing portion of the fixing nip portion N. It is a relatively narrow recording medium. For transporting a small-size recording medium to the fixing nip N, for example, when transporting A4 paper vertically, in other words, transporting A4 paper in a direction in which the long side is parallel to the transport direction. Corresponds to the conveyance of a small-size recording medium.

  The induction coil unit 22 generates heat by applying a magnetic flux to the conductive layer 2011 of the fixing belt 201, and serves as a heat source for heating the heating roller 20. The induction coil unit 22 is disposed outside the heating roller 20 on the side opposite to the pressure roller 21 so as to be separated from the outer peripheral surface of the heating roller 20 by a predetermined distance, and the fixing side plate is interposed via the blanket 221. It is fixed to. Thus, the induction coil unit 22 is provided along the outer peripheral surface of the heating roller 20.

  The induction coil unit 22 has a magnetic core 223 (magnetic core) and an induction coil 224 (electromagnetic induction heating coil). The magnetic core material 223 is formed from, for example, a ferrite core or a laminated core. The induction coil 224 is configured by winding a copper wire having a fusion layer and an insulating layer on the surface a plurality of times. For example, a litz wire can be used as the copper wire. An induction coil 224 is formed by winding a litz wire around a horizontally flat sheet-like spiral coil, and the induction coil 224 and the magnetic core material 223 covering the induction coil 224 are molded integrally with an electrically insulating resin. By doing so, the induction coil unit 22 can be configured.

  The induction coil 224 causes the heating roller 20 to generate heat by electromagnetic induction by an alternating magnetic field generated by flowing a high-frequency alternating current from a high-frequency inverter circuit IK (excitation circuit), and raises the temperature of the fixing nip portion N.

  1st temperature sensor S1 is installed in order to detect the temperature of the outer peripheral surface of the heating roller 20 which can form a passage part. In the present embodiment, the first temperature sensor S <b> 1 is a thermistor installed in a non-contact manner with respect to the heating roller 20, and detects the temperature of the central portion in the longitudinal direction on the outer peripheral surface of the heating roller 20. The thermistor is provided at a position on the outer side in the radial direction of the heating roller 20 with respect to a region on the outer peripheral surface of the heating roller 20 that can form the conveyance reference position.

  The controller 50 controls the power supplied from the high frequency inverter to the induction coil 224 based on the detection result of the first temperature sensor S1, so that the surface temperature of the heating roller 20 is fixed at a predetermined level when the recording medium P is fixed. Control to be at temperature.

  2nd temperature sensor S2 is installed in order to detect the temperature of the outer peripheral surface of the heating roller 20 which can form a non-passing part. In the present embodiment, the second temperature sensor S <b> 2 is a thermistor installed in a non-contact manner with respect to the heating roller 20, and detects the temperature on one end side in the longitudinal direction on the outer peripheral surface of the heating roller 20. It is provided at a position on the outer side in the radial direction of the heating roller 20 with respect to a region on the outer peripheral surface of the heating roller 20 that can form a non-passing portion.

  As will be described in detail later, the controller 50, based on the detection result of the second temperature sensor S2, increases the excessive temperature rise of the small size recording medium non-passing portion that occurs when the small size recording medium is continuously fixed. The soaking roller moving operation 1 and the soaking roller moving operation 2 for reduction can be performed.

  In addition, 1st temperature sensor S1 and 2nd temperature sensor S2 are respectively the temperature of the outer peripheral surface of the pressure roller 21 which can form a passage part, and the outer peripheral surface of the pressure roller 21 which can form a non-passage part. You may install so that temperature may be detected. Further, as the first temperature sensor S1 and the second temperature sensor S2, sensors that detect the temperature of the heating roller 20 by contacting the heating roller 20 may be used.

  The temperature equalizing roller 23 reduces the temperature distribution difference in the longitudinal direction of the pressure roller 21 by the outer peripheral surface of the temperature equalizing roller 23 being in contact with the pressure roller 21, and the temperature in the longitudinal direction of the fixing nip portion N. The distribution can be made uniform. As the temperature equalizing roller 23, for example, a heat pipe formed by enclosing a working fluid in a metal pipe having good heat transmission such as copper or aluminum can be used. The heat pipe can reduce the temperature distribution difference in the longitudinal direction of the pressure roller 21 in contact with the heat pipe by utilizing the latent heat of the working fluid sealed inside. Note that water can be used as the hydraulic fluid.

  As shown in FIG. 3, the temperature equalizing roller 23 has a shape extending in one direction, and the outer periphery of the temperature equalizing roller 23 with respect to the outer peripheral surface corresponding to the second region L <b> 2 of the pressure roller 21. One end of the surface is in contact. The soaking roller 23 is supported by the holding portion 231 so as to be rotatable around the central axis of the soaking roller 23, and is driven to rotate in the direction of arrow T 5 as the pressure roller 21 rotates. To do. The dimension in the longitudinal direction of the soaking roller 23 is about 300 mm.

  Although the details of the temperature-uniforming roller 23 will be described later, the leveling roller (center axis) of the pressure roller 21 and the rotation axis (center axis) of the temperature-uniforming roller 23 are substantially parallel to each other. With respect to the first state where the outer peripheral surface of the heat roller 23 is in contact with the outer peripheral surface of the pressure roller 21 and the outer peripheral surface corresponding to the second region L2 of the pressure roller 21, A second state in which the one end side contacts. In FIG. 3, the soaking roller is in the second state.

  The soaking roller 23 is in contact with the outer peripheral surface corresponding to the first region L1 and the second region L2 of the pressure roller 21 in the first state, and in the second state, the first region of the pressure roller 21 It contacts the outer peripheral surface corresponding to the second region L2 of the pressure roller 21 without contacting the outer peripheral surface corresponding to L1. Here, “substantially parallel” is a concept including substantially parallel.

  Further, the soaking roller 23 is in the first position in the first state, and is in the second position in the second state. One end of the outer peripheral surface of the temperature equalizing roller 23 is the outer peripheral surface corresponding to the second region L2 of the pressure roller 21 when the temperature equalizing roller 23 is in either the first position or the second position. It is in the position which touches against. On the other hand, the other end portion side of the outer circumferential surface of the temperature-uniforming roller 23 is located with respect to the outer circumferential surface corresponding to the second region L2 of the pressure roller 21 when the temperature-uniforming roller 23 is in the first position. When in the second position, the position is in contact with the outer peripheral surface of the pressure roller 21. When the soaking roller is in the second position, the outer peripheral surface on the other end side of the soaking roller 23 and the outer peripheral surface of the pressure roller 21 are separated by, for example, about 30 mm.

As shown in FIGS. 4 to 7, the soaking roller moving device 24 includes a first support portion 241 that supports the soaking roller 23, a support shaft 242 that supports the first support portion 241, and a support shaft 242. The soaking roller 23 is moved to the first position and the second position by moving the support shaft 242 in a direction toward the pressure roller 21 and a direction away from the pressure roller 21. A soaking roller arrangement driving gear 244 that is moved between, a driving motor for driving the soaking roller arrangement driving gear 244,
And a soaking roller arrangement sensor 246 for detecting the position of the support shaft 242.

  The first support portion 241 supports the central axis of the temperature equalizing roller 23 protruding from the end surface of the temperature equalizing roller 23.

  The support shaft 242 is provided with a concavo-convex portion that meshes with the temperature-uniforming roller arrangement drive gear 244, and is movable in a direction toward the pressure roller 21 and a direction away from the pressure roller 21. It is supported by the support portion 243. In addition, a spring is provided between the support shaft 242 and the first support portion 241, and the support shaft 242 presses the first support portion 241 via the spring so that the heat equalizing roller 23 is moved to the first position. Move from position 2 to the first position.

  The soaking roller arrangement drive gear 244 is configured to be capable of both clockwise rotation and counterclockwise rotation, and is provided with a protrusion that meshes with the uneven portion of the support shaft 242. Has a joint. When the engaging portion engages with the support shaft 242, when the temperature-uniforming roller arrangement drive gear 244 rotates in one direction by the driving force from the drive motor, the pressure roller 21 with respect to the support shaft 242. A force is applied in the direction close to. On the other hand, when the soaking roller arrangement drive gear 244 rotates in the reverse direction, a force is applied to the support shaft 242 in a direction away from the pressure roller 21.

  The soaking roller arrangement sensor 246 is a contact-type displacement sensor, and when the soaking roller 23 is in the second position, it is arranged so that the end surface of the support shaft 242 is in contact with the soaking roller. When 23 moves to the 1st position, it arrange | positions so that the end surface of the support shaft 242 may space apart. The soaking roller arrangement sensor 246 is not limited to a contact type displacement sensor, and for example, a transmissive photoelectric sensor that detects the position of the support shaft 242 without contact may be used.

<Soaking roller moving operation 1>
Next, the soaking roller moving operation 1 in the fixing device TS1 will be described with reference to FIGS. As described above, when the small-size recording medium is continuously fixed, the soaking roller moving operation is performed.

  First, the control for continuously fixing the maximum size recording medium P that can be fixed in the fixing device TS1 will be described by taking as an example the case of fixing a document composed of 55 sheets of A4 size paper. When the maximum size recording medium P is continuously fixed, the temperature equalizing roller 23 is maintained in the first state.

  When fixing in the fixing device, first, warm-up control is performed. Then, 30 seconds after energization of the inverter circuit, the temperature of the heating roller 20 reaches the warm-up completion temperature, and the process shifts to print control. After the warm-up control is finished, paper feeding is started, and after about 3 seconds, the paper reaches the fixing nip portion N and fixing is performed. After all the sheets have been printed, the control unit 50 shifts the temperature control of the fixing device to standby control.

Here, FIG. 8 shows a temperature transition from energization to the end of printing of all sheets.
The temperature detected by the first temperature sensor S1 reaches 185 ° C. when the warm-up is completed (T81). At this time, the temperature of the soaking roller 23 is 28 ° C. On the other hand, when the printing of all the sheets is completed (T82), the temperature of the soaking roller 23 is 47 ° C.

  As a comparative example, FIG. 9 shows a temperature transition in the case where the soaking roller 23 is completely separated from the pressure roller 21 from the time of energization to the end of printing of all the sheets. The temperature detected by the first temperature sensor S1 reaches 185 ° C. when the warm-up is completed (T91). At this time, the temperature of the soaking roller 23 shows a temperature transition that does not change much from 23 ° C., which is room temperature. . The temperature of the temperature equalizing roller 23 when the printing of all the sheets is completed (T92) has risen to 27 ° C., but the temperature equalizing roller 23 is relatively cooled compared to the present embodiment. It has been shown.

  Note that the heat generation distribution in the longitudinal direction of the heating roller 20 may be configured to generate heat at a higher temperature at a position where the temperature-uniforming roller 23 contacts the pressure roller 21. For example, as shown in FIG. 10, by adjusting the thickness and position of the magnetic core of the induction coil unit 22, the position where the soaking roller 23 contacts the pressure roller 21 is different from the other positions in the longitudinal direction. In comparison, it can be as high as 3%. When such a configuration is employed, temperature sagging at the time of temperature rise can be suppressed. Moreover, the dimension of the longitudinal direction of the heating roller 20 is about 300 mm, for example. In addition, in FIG. 10, the heat generation distribution is shown by the distance from the central portion in the longitudinal direction, the distance from the central portion toward one direction side in the longitudinal direction is plus, and the distance from the central portion toward the other direction side in the longitudinal direction. Is expressed as a minus.

  Next, as an example of the control for fixing a small size recording medium continuously, an operation when a document composed of 55 sheets of A4 size paper is conveyed vertically will be described. As described above, when the small size recording medium is continuously fixed, an excessive temperature rise occurs in the small size recording medium non-passing portion. Note that the flow of warm-up control, print control, and standby control is the same as when the maximum size recording medium P is continuously fixed.

  First, FIG. 11 shows a temperature transition from energization until printing of all sheets is completed. As in the case where the maximum size recording medium P is continuously fixed, the temperature detected by the first temperature sensor S1 reaches 185 ° C. when the warm-up is completed (T111). Is 28 ° C.

  When the paper feeding is started after the warm-up control is finished, the temperature detected by the second sensor rises, and as a result, the heat that moves to the soaking roller 23 increases, so the outer peripheral surface of the soaking roller 23 The temperature rises over the entire length.

  When the temperature detected by the second temperature sensor S2 reaches 220 ° C. (T112), the controller 50 moves the soaking roller 23 from the second position (FIGS. 4 and 6) to the first position (FIG. 4). 5 and FIG. 7), the soaking roller moving device 24 is controlled so that the soaking roller 23 is moved from the second state to the first state. At this time, the temperature of the soaking roller 23 has reached 80 ° C.

  When the temperature-uniforming roller 23 is in the first state, the temperature detected by the first temperature sensor S1 is 183 ° C., which is about 2 ° C., but it has been confirmed that the fixing property is not greatly affected.

  As described above, in the fixing device TS1 capable of performing the temperature-uniforming roller moving operation 1, one end side of the outer peripheral surface of the temperature-uniforming roller 23 is in relation to the outer peripheral surface corresponding to the second region L2 of the pressure roller 21. The entire soaking roller 23 is warmed in advance. For this reason, when the temperature equalizing roller 23 moves to the first position, the outer peripheral surface corresponding to the first region L1 of the pressure roller 21 is excessive from the outer peripheral surface to the temperature equalizing roller 23. Heat transfer is suppressed, and the temperature drop of the sheet passing portion can be suppressed. On the other hand, when the soaking roller 23 moves to the first position, the outer peripheral surface corresponding to the second region L2 of the pressure roller 21 is appropriately heated from the outer peripheral surface to the soaking roller 23. As a result of the movement, the temperature rise in the non-sheet passing portion can be suppressed. Accordingly, it is possible to suppress deterioration of the pressure roller 21 and the like due to excessive rise in the temperature of the non-sheet passing portion while preventing image unevenness due to deterioration in fixing performance.

  In this embodiment, when the temperature detected by the second temperature sensor S2 reaches 220 ° C., the temperature equalizing roller moving device 24 is controlled to move the temperature equalizing roller 23 to the first position. However, the detected temperature of the second temperature sensor S2, which is a threshold value for moving the soaking roller 23 to the first position, depends on the material of the pressure roller 21 and the heating roller 20, and the like. It can be set to a predetermined temperature (hereinafter referred to as “predetermined temperature”) that is set assuming that 20 or the like is deteriorated.

  Here, as a comparative example, FIG. 12 shows a temperature transition in the case where the temperature-uniforming roller 23 is in the first state from the state where it is completely separated from the pressure roller 21. As in the case of controlling the soaking roller moving device 24 in this embodiment, the temperature detected by the first temperature sensor S1 reaches 185 ° C. when the warm-up is completed (T121). The temperature of 23 is 28 ° C.

  When paper feeding is started after the warm-up control is finished, the temperature detected by the second sensor rises, but the temperature-uniforming roller 23 is completely separated from the pressure roller 21 to the extent that it is not warmed by the heat from the pressure roller 21. Therefore, the temperature of the outer peripheral surface of the temperature-uniforming roller 23 does not increase greatly from 28 ° C.

  When the temperature detected by the second temperature sensor S2 reaches 220 ° C. (T122), the controller 50 controls the soaking roller 23 to be in the first state. At this time, the temperature of the outer peripheral surface of the soaking roller 23 is 30 ° C.

  When the temperature-uniforming roller 23 is in the first state, the temperature difference between the outer peripheral surface corresponding to the first region L1 of the pressure roller 21 and the outer peripheral surface of the temperature-uniforming roller 23 is large. The detection temperature of the temperature sensor S1 decreased by 8 ° C., and it was confirmed that the fixing property was deteriorated. Moreover, it took a long time for the detected temperature of the first temperature sensor S1 to return to 185 ° C. again.

  As described above, when the temperature-uniforming roller 23 having a relatively low temperature is brought into contact with the pressure roller 21, the temperature of the sheet passing portion rapidly decreases. Further, when the power consumption is set to be low at the time of fixing, a particularly long time is required for returning to the fixing temperature. Further, for example, when the heat capacity of the temperature-uniforming roller 23 is lowered, the temperature drop of the passage portion can be suppressed to some extent, but when a large amount of small-size recording medium is continuously fixed, non-passage is performed. It becomes difficult to suppress excessive temperature rise in the part.

  Next, the flow of the soaking roller moving operation 1 in the fixing device TS1 will be described with reference to FIG.

  When the print control is started when the recording medium P is fixed, that is, when printing of the recording medium P is started, the control unit 50 starts the soaking roller moving operation 1.

  When starting the print control (step S1), the control unit 50 determines whether or not the temperature detected by the second temperature sensor S2 is equal to or higher than a predetermined temperature (step S2).

  If NO in step S2, printing is continued (step 3), and it is determined whether or not printing on the recording medium P has been completed (step S4). If YES in step S4, the soaking roller moving operation is terminated, and if NO in step S4, printing continues (returns to step S3).

  If YES in step S2, the soaking roller moving device 24 drives the drive motor KM so as to move the soaking roller 23 toward the first position, and the soaking roller 23 is moved to the first soaking roller 23. The position is held (step S5), and printing is continued (step S6). At this time, since the end surface of the support shaft 242 is separated from the temperature equalizing roller arrangement sensor 246, the detection state of the temperature equalizing roller arrangement sensor 246 is OFF.

  Next, the control unit 50 determines whether or not printing of the recording medium P has been completed, that is, determines whether or not the print control has shifted to standby control (step S7).

  In the case of YES in step S7, the control unit 50 drives the drive motor KM so that the soaking roller moving device 24 moves the soaking roller 23 toward the second position (step S8). If NO in step S7, printing on the recording medium P is continued (return to step S6).

  The control unit 50 determines whether or not the detection state of the temperature equalizing roller arrangement sensor 246 is turned ON by the end surface of the support shaft 242 contacting the temperature equalizing roller arrangement sensor 246 as the temperature equalizing roller 23 moves. Determine (step S9).

  If YES in step S9, the drive of the drive motor KM is stopped (step S10), and the soaking roller moving operation is terminated. At this time, the soaking roller 23 is held at the second position. In the case of NO in step S9, the drive motor KM is continuously driven so as to move the soaking roller 23 toward the second position (return to step S8).

  Further, for example, after the fixing of the recording medium P is completed (YES in Step S7), the control unit 50 determines whether or not the detected temperature of the second temperature sensor S2 is equal to or higher than a predetermined temperature, and the second temperature sensor If the detected temperature of S2 is equal to or higher than the predetermined temperature, the temperature equalizing roller 23 is held at the first position, and if the detected temperature of the second temperature sensor S2 is lower than the predetermined temperature, the temperature equalizing roller moving device It may be controlled that the drive motor KM is driven so that 24 moves the soaking roller 23 toward the second position. By performing such control, the excessive temperature rise of the heating roller 20 and the pressure roller 21 can be quickly reduced after the fixing of the recording medium P is completed.

<Soaking roller moving operation 2>
Next, with reference to FIGS. 14 to 18, the difference between the soaking roller moving operation 2 in the fixing device TS <b> 1 and the soaking roller moving operation 1 will be described.

  Based on the information regarding the size of the recording medium P to be fixed by the fixing device TS1 and the operation time of the heat source for heating the heating roller 20 in the temperature equalizing roller moving operation 2, the control unit performs the temperature equalizing roller 23. Control different from the soaking roller moving operation 1 is performed in that the moving timing is set.

  Note that the information regarding the size of the recording medium P can be acquired from, for example, a print job input to the control unit 50 from an information device such as a personal computer outside the image forming apparatus. Further, the user may input from the operation panel 51 provided in the image forming apparatus.

  Here, in the memory 501, as shown in FIG. 14, time for moving the soaking roller 23 from the second position to the first position for each size (CD length) of each small-size recording medium. The first predetermined time is stored as the table 1. The first predetermined time is set as an elapsed time from the time when the standby control is shifted to the print control. The first predetermined time is measured by the second timer. The CD length of the recording medium is the width of the recording medium in the direction perpendicular to the conveying direction when passing through the fixing nip N, in other words, the length of the recording medium in the longitudinal direction of the fixing nip N.

  Since the time for the non-passing portion to reach the predetermined temperature differs depending on the size of the small-size recording medium fixed in each print job, the belt regulation operation 2 includes information on the size of the small-size recording medium actually fixed, the memory Based on the first predetermined time of each small size recording medium stored in advance in 501, the movement timing of the soaking roller 23 is set.

  Further, as shown in FIG. 15, the memory 501 is a time set according to the energization time to the inverter circuit IK that supplies power to the heat source for heating the heating roller 20, and has a first predetermined value. A second predetermined time, which is a time for correcting the time, is stored as the table 2. The second predetermined time is measured by the first timer.

  When the fixing device TS1 is in a relatively cold state, the electric power for maintaining the temperature of the heating roller 20 at the fixing temperature is relatively large, so that the temperature rise per unit time of the non-passing portion is large. Further, when the fixing device TS1 is in a relatively warm state, the electric power for maintaining the temperature of the heating roller 20 at the fixing temperature is relatively small, so that the temperature rise per unit time of the non-passing portion is small. Become. By correcting the first predetermined time based on the second predetermined time, it is possible to set the movement timing of the soaking roller 23 in consideration of the power consumption related to the print control.

  Further, in the memory 501, as shown in FIG. 16, when the energization to the inverter circuit IK is interrupted due to a paper jam or the like during the print control, the energization to the inverter circuit IK is resumed. A third predetermined time, which is a time set based on the temperature detected by the first temperature sensor S1 and for correcting the first predetermined time, is stored as the table 3.

  When the fixing device TS1 is in a relatively warm state, the power for maintaining the temperature of the heating roller 20 at the fixing temperature is relatively small, so that the temperature rise per unit time of the non-passing portion is small. By correcting the first predetermined time based on the third predetermined time, the timing of movement of the temperature equalizing roller 23 is set based on the amount of heat of the fixing device in consideration of a temporary stop of the heat source during print control. be able to. Note that the third predetermined time may be set based on the elapsed time from the time when a series of print jobs are completed until the print control of the next print job is started.

  Thus, the control unit 50 sets the first predetermined time based on the information regarding the size of the recording medium P input to the image forming apparatus, and based on the second predetermined time and / or the third predetermined time, By correcting the first predetermined time, the movement timing of the soaking roller 23 is controlled.

  Next, the temperature equalizing roller moving operation 2 will be described more specifically with reference to FIG. 17 by taking as an example an operation when a document consisting of 55 sheets of A4 size paper is conveyed vertically (A4R). In this case, the CD length is about 210 mm.

  When the image forming apparatus main body is turned on, warm-up control is started. At this time, the inverter circuit IK is energized and the first timer starts counting. Three minutes after the start of energization of the inverter circuit IK, the warm-up control is shifted to the standby control, and the standby control is started so that the detected temperature of the first temperature sensor S1 becomes 150 ° C. (T171).

  When the information (A4R) relating to the print job is received from an information device such as a personal computer outside the image forming apparatus (T172), the first predetermined time is set to 45 seconds based on the table 1 stored in the memory 501. The second predetermined time is selected based on the time counted by the first timer and the table 2 stored in the memory 501, and the corrected first time is corrected based on the second predetermined time. 1 Set a predetermined time. In addition, the second timer starts counting.

  Here, since 3 minutes have passed since the time when the inverter circuit IK was energized at the time when the information about the print job was received, 12 seconds was selected as the second predetermined time, and the corrected first predetermined time Is set to 57 seconds. That is, when the second timer counts 57 seconds, that is, 57 seconds after the print start time (T173), the controller 50 causes the soaking roller 23 to move from the second position to the first position. And control to move. At this time, the temperature detected by the second temperature sensor S2 reaches 210 ° C., and the temperature of the soaking roller reaches 73 ° C.

  When the sheet feeding is started, the temperature detected by the second sensor rises, and along with this, the heat that moves to the temperature equalizing roller 23 increases. Go up across the whole direction.

  When the temperature-uniforming roller 23 is in the first state, the temperature detected by the first temperature sensor S1 is 181 ° C., which is about 4 ° C. lower, but the temperature of the temperature-uniforming roller 23 is relatively high and the first temperature sensor 23 is in the first state. It was confirmed that the temperature detected by the temperature sensor S1 rises quickly and does not significantly affect the fixability. The detected temperature of the first temperature sensor S1 returned to 185 ° C. again.

  As described above, in the fixing device TS <b> 2 that can perform the temperature-uniforming roller moving operation 2, one end portion side of the outer peripheral surface of the temperature-uniforming roller 23 is against the outer peripheral surface corresponding to the second region L <b> 2 of the pressure roller 21. The entire soaking roller 23 is warmed in advance. For this reason, when the temperature equalizing roller 23 moves to the first position, the outer peripheral surface corresponding to the first region L1 of the pressure roller 21 is excessive from the outer peripheral surface to the temperature equalizing roller 23. Heat transfer is suppressed, and the temperature drop of the sheet passing portion can be suppressed. On the other hand, when the soaking roller 23 moves to the first position, the outer peripheral surface corresponding to the second region L2 of the pressure roller 21 is appropriately heated from the outer peripheral surface to the soaking roller 23. As a result of the movement, the temperature rise in the non-sheet passing portion can be suppressed. Accordingly, it is possible to suppress deterioration of the pressure roller 21 and the like due to excessive rise in the temperature of the non-sheet passing portion while preventing image unevenness due to deterioration in fixing performance.

  In addition, the first predetermined time is set based on the information regarding the size of the recording medium P input to the image forming apparatus, and the first predetermined time is corrected based on the second predetermined time and / or the third predetermined time. In order to control the movement timing of the soaking roller 23 based on the corrected first predetermined time, the temperature detected by the second sensor is set assuming that the pressure roller 21 and the heating roller 20 are deteriorated. It is possible to shorten the time from when the predetermined temperature is reached until the soaking roller 23 moves to the first position. Therefore, it is possible to further suppress the deterioration of the pressure roller 21 and the like due to the excessive increase in the temperature of the non-sheet passing portion while preventing image unevenness due to the deterioration of the fixing property.

  Next, referring to FIG. 18, in the soaking roller moving operation 2, when the print job is printed, the power of the inverter circuit IK is temporarily shut down due to a paper jam or the like, that is, the printing is temporarily performed. An example of control when stopped will be described.

  When the image forming apparatus main body is turned on, warm-up control is started. At this time, the inverter circuit IK is energized and the first timer starts counting. Three minutes after the start of energization of the inverter circuit IK, the warm-up control is shifted to the standby control, and the standby control is started so that the detected temperature of the first temperature sensor S1 becomes 150 ° C. (T181).

  When the information (A4R) related to the print job is received from an information device such as a personal computer outside the image forming apparatus (T182), the first predetermined time is set to 45 seconds based on the table 1 stored in the memory 501. The second predetermined time is selected based on the time counted by the first timer and the table 2 stored in the memory 501, and the corrected first time is corrected based on the second predetermined time. 1 Set a predetermined time. In addition, the second timer starts counting.

  Here, since 3 minutes have passed since the time when the inverter circuit IK was energized at the time when the information about the print job was received, 12 seconds was selected as the second predetermined time, and the corrected first predetermined time Is set to 57 seconds. That is, the controller 50 causes the soaking roller 23 to move from the second position toward the first position when the second timer counts 57 seconds, that is, 57 seconds after the print start time. To control.

  When the power supply to the inverter circuit IK is temporarily interrupted after the sheet feeding is started, the control unit 50 temporarily stops the second timer while maintaining the count time so far. When the energization of the inverter circuit IK is resumed and the print job is resumed, the second timer count is resumed and the temperature detected by the second temperature sensor S2 at the time when the print job is resumed. The third predetermined time is determined based on a table stored in advance in the memory 501, and the first predetermined time is corrected based on the determined third predetermined time.

  Here, for example, if a paper jam occurs 30 seconds after the start of the print job (T183), the inverter circuit IK is deenergized and the fixing is temporarily stopped. At this time, the second timer stops counting while maintaining 30 seconds.

  Here, for example, when the temperature detected by the second sensor is 130 ° C. when energization to the inverter circuit IK is resumed by removing the paper jam and the print job is resumed (T184), 3 10 seconds is determined as the predetermined time, and the count of the second timer is restarted from a value (20 seconds) obtained by subtracting 10 seconds from the holding time of the second timer.

  Then, the control unit 50 controls the soaking roller 23 to move from the first position toward the second position when the second timer counts 57 seconds. In other words, the control unit 50 controls the soaking roller 23 to move from the second position toward the first position when 67 seconds have elapsed from the start time of the print job (T185). When the second timer reaches the corrected first predetermined time, the temperature detected by the second temperature sensor S2 is 210 ° C., and the temperature of the outer peripheral surface of the temperature equalizing roller 23 has reached 97 ° C.

  When the temperature-uniforming roller 23 is in the first state, the temperature detected by the first temperature sensor S1 is 181 ° C., which is about 4 ° C. lower, but the temperature of the temperature-uniforming roller 23 is relatively high. It was confirmed that the temperature detected by the one-temperature sensor S1 rose quickly and did not significantly affect the fixing property. The detected temperature of the first temperature sensor S1 returned to 185 ° C. again.

  According to the fixing device 2 capable of performing the soaking roller moving operation 2 as described above, in addition to the above-described effect, the heat source for heating the heating roller 20 is temporarily stopped when the print job is executed. Even so, the movement timing of the temperature-uniforming roller 23 can be set appropriately. Therefore, it is possible to further suppress the deterioration of the pressure roller 21 and the like due to the excessive increase in the temperature of the non-sheet passing portion.

Next, the flow of the soaking roller moving operation 2 in the fixing device TS1 will be described with reference to FIG.
The control unit 50 can start the soaking roller moving operation 2 when the power of the image forming apparatus main body is input.

  When the power of the image forming apparatus main body is input (step S101), the control unit 50 starts counting the first timer (step S102). At this time, the control unit 50 performs warm-up control and starts standby control after the warm-up is completed.

  The control unit 50 starts a print job (print) when image data is input from an information device such as a personal computer outside the image forming apparatus, in other words, when a print job is received, and the second timer Is started (step S103), and a first predetermined time is set based on the information regarding the size of the recording medium P included in the print job (step S104). Further, the control unit 50 determines the second predetermined time based on the elapsed time from the count start time of the first timer to the time when the print job is received (step S105), and sets the first predetermined time to the second predetermined time. The first predetermined time after the correction is set by correcting with (Step S106). At this time, the standby control is shifted to the print control.

  The control unit 50 continues to count the second timer (step S107) and determines whether the count time of the second timer has reached the corrected first predetermined time (step S108).

  When the count time of the first timer reaches the corrected first predetermined time (YES in step S108), the control unit 50 moves the soaking roller 23 from the first position to the second position. In this manner, the soaking roller moving device 24 is controlled (step S116). If the count time of the first timer has not reached the corrected first predetermined time (NO in step S108), it is determined whether or not the print job has ended (step S109).

  Here, the control related to Step S116 to Step 121 is the same as the control corresponding to Step 4 to Step 9 in the above-described soaking roller moving operation 1, and thus the description thereof is omitted.

If the print job is finished (YES in step S109), the soaking roller moving operation is finished. If the print job has not ended (NO in step S109), it is determined whether the print job is temporarily stopped for some reason (step S110).
If the print job is temporarily stopped (YES in step S110), the second timer count is temporarily stopped (step S111). If the print job is not temporarily stopped, the second timer continues counting (return to step S107).

  Hereinafter, the case where it progresses to step S111 is demonstrated. Note that the order of the determinations related to step S108 to step S110 can be arbitrarily set.

  The control unit 50 determines whether or not the print job that has been temporarily stopped has been resumed (step S112).

  If the print job has not been resumed (NO in step S112), the count of the second timer is maintained in a stopped state (return to step S111).

  When the print job is resumed (YES in step S112), a third predetermined time is determined based on the temperature detected by the first temperature sensor S1 at the time when the print job is resumed (step S113) and corrected. After the subsequent first predetermined time is further corrected by the third predetermined time (step S114), the counting of the second timer is restarted (step S115). Then, the control unit 50 determines whether or not the count time of the second timer has reached the first predetermined time corrected based on the third predetermined time (return to step S108).

  When the count time of the second timer reaches the first predetermined time corrected based on the third predetermined time (YES in step S108), the control unit 50 moves the soaking roller 23 from the second position. The soaking roller moving device 24 is controlled to move to the first position (step S116).

  And the control part 50 performs control which concerns on step S117 to step S121 which is control equivalent to step 5 to step 9 in the above-mentioned soaking | uniform-heating roller moving operation 1, and complete | finishes a soaking | uniform-heating roller moving operation.

  The fixing device TS1 and the image forming device GS1 are merely examples, and do not limit the present invention. Accordingly, the present invention can be variously improved and modified without departing from the scope of the invention. For example, the soaking roller 23 may be configured to abut against the heating roller 20. For example, as illustrated in FIG. 20, when the fixing belt 201 is stretched between at least two rollers or the like, A configuration in which the fixing belt 201 abuts on the inner peripheral surface may be adopted.

  For example, as shown in FIG. 21 to FIG. 23, the state in which the soaking roller 23 contacts the pressure roller 21 is changed by utilizing the thermal expansion of the elastic layer 2022 of the pressure roller 21. Also good.

  As shown in FIG. 21, the temperature-uniforming roller 23 and the pressure roller 21 are disposed through a slight gap that allows the temperature of the outer peripheral surface of the temperature-uniforming roller 23 to be warm at room temperature. As shown in FIGS. 22 and 23, the temperature-uniforming roller 23 comes into contact with the pressure roller 21 as the pressure roller 21 expands as the temperature rises, and the contact area gradually increases. When at least the temperature of the pressure roller 21 reaches a predetermined temperature, the soaking roller 23 is in the first state.

  When such a configuration is adopted, as shown in FIG. 24, the warm-up roller 23 comes into contact with the pressure roller 21 after a while after the start of warm-up (T241), and then the warm-up is completed (T242). ). In other words, the soaking roller 23 starts to contact the pressure roller 21 during the period from the start of warm-up to the completion of warm-up.

  Further, as shown in FIG. 25, after warm-up is completed and standby control is entered (T251), a print job is started (T252), and when the second temperature sensor S2 reaches 210 ° C., soaking is performed. The temperature of the soaking roller 23 is 76 ° C. At this time, the soaking roller 23 is in the first state (T253). When the temperature-uniforming roller 23 is in the first state, the temperature detected by the first temperature sensor S1 has decreased by 3 ° C., but it has been confirmed that the fixing property is not greatly affected.

  As described above, even when a configuration is employed in which the state in which the temperature equalizing roller 23 contacts the pressure roller 21 is changed by utilizing the thermal expansion of the elastic layer 212 of the pressure roller 21, the temperature equalization is performed in advance. Since the roller 23 is warmed, when the soaking roller 23 moves to the first position, the heat passing away from the outer peripheral surface corresponding to the first region L1 of the pressure roller 21 is suppressed, so that the paper passing portion By suppressing the temperature rise of the outer peripheral surface corresponding to the second region L2 of the pressure roller 21, the temperature rise of the non-sheet passing portion can be suppressed. Therefore, it is possible to suppress the deterioration of the pressure roller 21 and the like due to excessive increase in the temperature of the non-sheet passing portion. Note that the temperature-uniforming roller 23 and the pressure roller 21 may be arranged in a state in which a part thereof is in contact with the outer peripheral surface region corresponding to the non-passing portion of the pressure roller 21.

  Furthermore, a demagnetizing coil for canceling the magnetic flux generated from the induction coil unit 22 may be provided at a position on the end side in the longitudinal direction of the induction coil unit 22 of the fixing device TS1. When such a configuration is adopted, the temperature rise of the non-sheet passing portion can be further suppressed without increasing the size of the fixing device main body.

  Further, for example, the temperature equalizing roller 23 has a shape extending in one direction, and one end portion of the outer circumferential surface of the temperature equalizing roller 23 with respect to the outer circumferential surface corresponding to the second region L2 of the heating roller 20. The temperature equalizing roller may be arranged so that the rotation axis (center axis) of the heating roller 20 and the rotation axis (center axis) of the temperature equalizing roller 23 are substantially parallel to each other. One end side of the outer peripheral surface of the temperature equalizing roller 23 is in contact with the outer peripheral surface corresponding to the second region L2 of the heating roller 20 and the first state in which the outer peripheral surface of the heat roller 20 is in contact with the outer peripheral surface of the heating roller 20. You may have a 2nd state.

  The present invention can also be applied to tandem color copiers, monochrome copiers, printers, fax machines, and multi-function machines thereof.

10Y, 10M, 10C, 10K Image carrier 11Y, 11M, 11C, 11K Charging device 12Y, 12M, 12C, 12K Exposure device 13Y, 13M, 13C, 13K Image forming unit 14 Secondary transfer unit 141 Secondary transfer roller 142 Drive Rollers 15Y, 15M, 15C, 15K Primary transfer means 151Y, 151M, 151C, 151K Primary transfer roller 17 Intermediate transfer belts 18Y, 18M, 18C, 18K Image carrier cleaning means 18T Intermediate transfer belt cleaning means 181 Cleaning blade 182 Recovery Section 19 Tension roller 20 Heating roller 201 Fixing belt 2011 Conductive layer 2012 Surface layer 202 Fixing roller 2021 Core metal (fixing roller)
2022 Elastic layer 204 Heat insulation bush 205 Bearing 21 Pressure roller 211 Core metal (pressure roller)
212 Heat-resistant elastic layer 213 Release layer 22 Inductive coil unit 221 Blanket 223 Magnetic core material 224 Inductive coil 23 Soaking roller 231 Holding unit 24 Soaking roller moving device 241 First support unit 242 Support shaft 243 Second support unit 244 Soaking roller arrangement driving gear 245 Driving motor 246 Soaking roller arrangement sensor 30Y, 30M, 30C, 30K Image forming unit 50 Control unit 501 Memory 502 First timer 503 Second timer 51 Operation panel TS1 Fixing device P Recording medium T1 Intermediate transfer belt conveyance direction T2 Heating roller rotation direction T3 Pressure roller rotation direction T4 Recording medium PP conveyance direction T5 to the fixing nip portion Temperature equalizing roller rotation direction N Fixing nip portion L1 First region L2 Second Area K Transport reference position TB Passing part HTB Non-passing part STB Small size Recording medium non-passing portion IK inverter circuit FTS first temperature sensor STS second temperature sensor M drive motor G driven gear

Claims (9)

A fixing device for fixing a toner image on a fixing object,
A first fixing member heated by a heat source;
A second fixing member that forms a fixing portion extending in one direction by being pressed against the first fixing member;
It has a shape that extends in one direction, and has a soaking member that contacts a contacted fixing member that is either the first fixing member or the second fixing member,
The soaking member is
A first state in which the center axis in the longitudinal direction of the contact fixing member and the center axis in the longitudinal direction of the heat equalizing member are in contact with the contact fixing member, and the contact fixing; A fixing device characterized in that an area in contact with a member can be in a second state smaller than the first state. The fixing portion is formed of a passing portion through which the member to be fixed passes and a non-passing portion through which the member to be fixed does not pass,
The first state is:
The soaking member is a non-passing region which is an outer peripheral surface region where the non-passing part of the contacted fixing member can be formed, and a passing region which is an outer peripheral surface region where the passing part of the contacted fixing member can be formed. In contact with the
The second state is:
The fixing device according to claim 1, wherein the heat equalizing member is not in contact with the passage area. The contact fixing member is a cylindrical rotating body that is rotatable in a direction in which the fixing body passes,
The fixing portion is formed of a passing portion through which the member to be fixed passes and a non-passing portion through which the member to be fixed does not pass,
The first state is:
The soaking member forms a non-passing area on the inner peripheral surface corresponding to an outer peripheral surface area where the non-passing part of the contacted fixing member can be formed, and the passing part of the contacted fixing member. It is in a state in contact with a passing region that is a region on the inner peripheral surface corresponding to the outer peripheral surface region that can be,
The second state is:
The fixing device according to claim 1, wherein the heat equalizing member is not in contact with the passage area. The heat equalizing member is disposed at a first position when the first state is in the first state, and is disposed at a second position when the state is the second state;
4. The heat equalizing member moving means for supporting the heat equalizing member so as to be movable between the first position and the second position. 5. Fixing device. In the first state and the second state, there is provided a heat equalizing member holding means for holding the heat equalizing member so that an outer peripheral surface on one end side of the heat equalizing member is in contact with the non-passing region. And
The soaking member moving means includes:
Moving the heat equalizing member so that the outer peripheral surface on the other end side of the heat equalizing member is separated from the contacted fixing member in the second state;
5. The fixing according to claim 4, wherein in the first state, the heat equalizing member is moved so that an outer peripheral surface on the other end side of the heat equalizing member is in contact with the contacted fixing member. apparatus. Temperature detecting means for detecting the temperature on the end side of the passing portion in the extending direction of the fixing portion;
The control means for controlling the heat equalizing member moving means so as to move the heat equalizing member to the first position when the temperature reaches a predetermined temperature. The fixing device according to 4 or 5. An image forming apparatus comprising the fixing device according to claim 1. An image forming apparatus comprising the fixing device according to claim 4, wherein a toner image is formed on the fixed body based on a print job including image information,
Size detecting means for detecting the size of the fixing object passing through the fixing unit;
Based on the size of the fixing target detected by the size detecting means, the heat equalizing member moving means sets a timing for moving the heat equalizing member to the first position, and the heat equalizing member is moved at the timing. An image forming apparatus comprising: a control unit configured to control the heat equalizing member moving unit to move to the first position. The control means includes
The image forming apparatus according to claim 8, wherein the timing is changed based on a time when the heat source is continuously operated.

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