JP2016118735A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device 14 that heats, while holding and conveying, a recording material S carrying a toner image t at a nip part N formed by a first rotor 140 and a second rotor 141 at least one of which is an endless belt to fix the toner image, and make it possible to detect that the belt is damaged in a wide area in a generatrix direction and a circumferential direction of the belt without being affected by scratches generated on and foreign substances adhered to a surface irrespective of the presence/absence of a conductive layer.SOLUTION: A fixing device comprises: a moving member 150 that is approximate to a belt and can move between a first position on an end of the belt and a second position on the center part in a generatrix direction of the belt; and a control part that executes, at a predetermined control timing, a control sequence including a first step of moving the moving member to a second position from a first position as a starting point or to the first position from the second position as a starting point, and a second step of notifying a user of an error when arrival of the moving member moved from the first or second position to the second or first position cannot be detected within a predetermined period.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device mounted on an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine of these.

  Conventionally, a belt-type fixing device has been put to practical use as a fixing device that heats and fixes a toner image formed and supported on a recording material by image forming means such as an electrophotographic process or an electrostatic recording process on the surface of the recording material. Has been.

  In this fixing device, for example, a ceramic heater is used as a heating member, a pressure roller as a pressure member is disposed on the opposite side, and a flexible thin endless film (hereinafter referred to as a heat transfer member) The fixing nip portion is formed by sandwiching a belt). A recording material (hereinafter referred to as paper) on which an unfixed toner image is formed and supported is introduced between a belt and a pressure roller, and is nipped and conveyed together with the belt. At that time, the unfixed toner image is fixed on the paper surface by the heat of the ceramic heater transferred through the belt and the pressure applied to the fixing nip portion.

  In addition, for example, using an induction heating unit disposed as a heating member facing the outer peripheral surface of the belt, a magnetic flux is formed around the heat generation layer of the belt, and the heat generation layer is heated by electromagnetic induction heating to heat the belt. A fixing device configuration has been put to practical use.

  As described above, the belt-type fixing device has a thin belt as a fixing member, has a small heat capacity, and has a good thermal response. Therefore, the thermal response of the heating member can be efficiently reflected in the fixing nip portion. Accordingly, the fixing temperature can be reached in a short time after the power is turned on, which greatly contributes to power saving of the image forming apparatus.

  However, the thin belt may be damaged due to deformation or scratches caused by a strong external force. When the belt is broken, not only does the image become defective, but there is a possibility that the other parts of the fixing device and other units such as a paper discharge device may come into contact with each other and be damaged. Therefore, when the belt is damaged, it is necessary to immediately grasp the fact and take measures such as replacing the belt.

  As a method for detecting damage to a belt, Patent Document 1 discloses an image forming apparatus having a sensor that detects a mark on a belt (film) having a mark formed on a surface with reflected light or the like. When the sensor cannot detect the mark for a certain period, it can be determined that the belt is broken.

  On the other hand, Patent Document 2 discloses an image forming apparatus in which a resistance value detection circuit for detecting a resistance value of a conductive layer is connected to a belt (sleeve layer, fixing sleeve) having a conductive layer. According to Patent Document 2, when the conductive layer is damaged, the resistance value of the conductive layer increases. When the resistance value detection circuit detects an increase in the resistance value above a certain level, it can be determined that the belt is damaged.

JP 2002-287541 A JP 2011-197060 A

  The present invention is a further development of the above prior art. The purpose is not to be affected by scratches on the surface or adhering foreign matter, and regardless of the presence or absence of a conductive layer, it detects that the belt has been damaged in a wide area in the busbar direction and circumferential direction. It is an object of the present invention to provide a belt-type fixing device that can perform the above-described operation. As a result, it is possible to detect belt breakage at an early stage and prevent the damaged belt from coming into contact with other parts of the fixing device and other units such as the paper discharge device to damage them. To do.

  In order to achieve the above object, a typical configuration of the fixing device according to the present invention is such that at least one of the toners is in a nip portion formed by a first rotating body and a second rotating body, which are endless belts. A fixing device that fixes a toner image by heating while nipping and conveying a recording material carrying an image, the fixing device being disposed in the vicinity of the belt, and a first position on the belt end side in the direction of the bus line of the belt And a movable member movable between the belt and the second position on the center side of the belt, and at a predetermined control timing, the movable member is moved to the second position starting from the first position, or the second position is A first step of moving to the first position as a starting point, and the arrival of the moving member moved from the first position or the second position to the second position or the first position within a predetermined time; If you can't And having a control unit for executing control sequences with a second step of notifying the error, the will.

  According to the present invention, it is possible to detect that the belt is damaged in a wide area in the busbar direction and the circumferential direction of the belt regardless of the presence or absence of the conductive layer, regardless of the presence or absence of the conductive layer. Is possible. As a result, it is possible to detect damage to the belt at an early stage, and to prevent the damaged belt from coming into contact with other parts of the fixing device or other units such as a paper discharge device and damage them. is there.

FIG. 3 is a schematic external perspective view of the fixing device according to the first exemplary embodiment when viewed from the paper exit side. Cross-sectional left side view of the device Explanatory drawing of movement control of the moving member of the apparatus Block diagram of the control system of the device Flowchart illustrating an example of movement control of a moving member during printing Flowchart showing an example of a fixing belt breakage detection sequence 1 performed before jam processing The perspective schematic diagram which looked at the fixing device of Example 2 from the induction heating device side Cross-sectional left side view of the main part of the device Perspective view of moving member Explanatory drawing of movement control of a moving member (the 1) Explanatory drawing of the movement control of a moving member (the 2) Explanatory drawing of the movement control of a moving member (the 3) Block diagram of the control system of the device Flowchart illustrating an example of movement control of a moving member during printing 7 is a flowchart illustrating an example of a fixing belt breakage detection sequence 2 performed after jam processing in the third and fourth embodiments. Schematic configuration diagram of an example of an image forming apparatus

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

Example 1
[Image forming apparatus]
FIG. 14 is a schematic diagram of an example of an image forming apparatus 100 equipped with a belt-type fixing device (fixing device) 14 according to the present invention. The image forming apparatus 100 is an intermediate transfer type, tandem four-color full-color electrophotographic laser printer, which can form a full-color toner image on the recording material S and print it out. The recording material S is a sheet-like recording medium on which a toner image can be formed, and examples thereof include plain paper, glossy paper, resin sheet, cardboard, postcard, envelope, OHP sheet, printing paper / format paper, and the like. Hereinafter referred to as paper. Since the printer configuration other than the fixing device 14 is well-known, the following description of the printer configuration will be simplified.

  Reference numeral 2 denotes an image forming unit. The process cartridge 3 (3Y, 3M, 3C, 3K) as four image forming units arranged in parallel, a laser scanner unit 4 as an exposure unit, and an intermediate transfer belt unit 5 are arranged. Have. Each cartridge 3 includes a rotating drum type photoreceptor 6, a charging roller 7, a developing device 8, a primary transfer roller 9, a cleaning member 10, and the like as electrophotographic image forming process means. A yellow (Y), magenta (M), cyan (C), and black (K) toner image (developer image) is formed on the photoreceptor 6 of each cartridge 3.

  Then, the toner images of the four colors are sequentially superimposed on the intermediate transfer belt 11 from the photosensitive member 6 of each cartridge 3 and are primarily transferred to form a full-color toner image on the intermediate transfer belt 11. The The full-color toner image is secondarily transferred onto the sheet S at a secondary transfer nip portion 17 which is a pressure contact portion between the intermediate transfer belt 11 and the secondary transfer roller 16.

  The sheet S is separated and fed from the sheet cassette 12 and is introduced into the secondary transfer nip portion 17 through the conveyance path 15 including the registration roller pair 13 at a predetermined control timing. Then, the sheet S that has undergone the secondary transfer of the toner image is introduced into the fixing device 14 and undergoes hot-pressure fixing of the toner image.

  The sheet S exiting the fixing device 14 is discharged by a discharge roller 18 onto a tray 19 on the upper surface of the apparatus as a full color image formed product. Reference numerals 155A and 155B denote a fixing inlet sensor and a fixing outlet sensor as recording material detecting means. The fixing entrance sensor 155 </ b> A detects the sheet S introduced into the fixing device 14. The fixing exit sensor 155B detects the sheet S that exits the fixing device 14. Each sheet detection information of the sensors 155A and 115B is input to the control unit 101 (FIG. 4).

  In the monochromatic image forming mode such as monochrome, only the cartridge necessary for the image forming operation is performed, and the other cartridges are merely rotated idly and the image forming operation is not performed.

  In the image forming apparatus 100 of the present example, the conveyance of the paper S in the apparatus is performed by so-called central reference conveyance. This paper transport is a form in which the center line in the width direction of the paper is aligned with the center in the width direction of the paper transport path regardless of the width of the paper that can be used (passable) in the apparatus. That is.

[Configuration of Fixing Device]
The belt fixing device heats a toner image while nipping and conveying a sheet carrying a toner image at a nip formed by a first rotating body and a second rotating body, at least one of which is an endless belt. It is a fixing device.

  The fixing device 14 of this example uses an endless fixing belt as the first rotating body, an elastic pressure roller as the second rotating body, and a belt using a ceramic heater as the heating means (heat source, heating body). It is a heating type, pressure roller drive type (tensionless type) device.

  FIG. 1 is a schematic external perspective view of the fixing device 14 as viewed from the paper exit side, and FIG. 2 is a schematic left side view of the fixing device 14. FIG. 3 is an explanatory diagram of movement control of the moving member in accordance with the width of the paper used, and the fixing device 14 is viewed from the paper exit side. FIG. 4 is a block diagram of the control system.

  In this example, regarding the fixing device 14 or its constituent members, the front side is a surface viewed from the paper inlet side, the back surface is the opposite side (paper outlet side), and the left and right sides are the devices viewed from the front side. Left (one end side) or right (the other end side). Up and down is up or down in the direction of gravity. The upstream side and the downstream side are the upstream side and the downstream side in the paper transport direction a. The longitudinal direction (or the width direction) and the paper width direction are directions substantially parallel to the direction orthogonal to the paper transport direction a on the paper transport path surface. The short direction is a direction substantially parallel to the paper transport direction a on the paper transport path.

  In this example, the fixing device 14 is disposed with the front side, which is the paper entrance side, facing downward with respect to the image forming apparatus main body. Then, the sheet S conveyed upward from the secondary transfer nip portion 17 is guided by a sheet back surface guide member (not shown) and introduced into the fixing device 14 from the bottom to the top (FIG. 2).

  The fixing device 14 is a cylindrical fixing belt (heat transfer member) as a rotatable endless belt that heats an unfixed toner image t on a sheet (on a recording material) at a nip portion (fixing nip portion) N. A belt unit (fixing member) 140U having 140 is provided. Further, a pressure roller (pressure member) 141 is provided as a nip forming member that forms and forms a nip portion N between the fixing belt 140 and nipping and conveying the paper S carrying a toner image. Further, the image forming apparatus includes a fixing frame (housing) 160 that accommodates the belt unit 140U and the pressure roller 141.

  In addition, as a blower section that blows and cools one end side and the other end side in the width direction (longitudinal direction) of the fixing belt 140 outside the belt for countermeasures against temperature rise at the end (non-sheet-passing temperature rise countermeasure). The ventilation cooling unit 180 is provided.

(1) Belt unit 140U
The belt unit 140U has the cylindrical fixing belt 140 as described above. The fixing belt 140 includes a ceramic heater 142 as a heating unit, a guide member 143, a stay 144 as a reinforcing member, and left and right fixing flanges 145 (F · R). The fixing belt 140, the heater 142, the guide member 143, and the stay 144 are members that are long in the left-right direction.

  The fixing belt 140 is a thin-walled hollow endless belt, and exhibits a substantially cylindrical shape due to its elasticity in a free state. The base layer is formed of a heat-resistant resin such as polyimide, polyamideimide, or PEEK, or a pure metal or alloy such as SUS, Al, Ni, Cu, or Zn having heat resistance and high thermal conductivity. In the case of the resin base layer, in order to improve the thermal conductivity, a high thermal conductive powder such as BN, alumina, Al or the like may be mixed.

  Furthermore, in order to prevent offset and ensure separation of paper, the surface layer is coated with a heat-resistant resin with good releasability, such as PTFE, PFA, FEP, ETFE, CTFE, PVDF, and other fluororesins, and silicone resin. Thus, a releasable layer is formed.

  The heater 142 is basically composed of an elongated thin plate-like ceramic substrate and a resistance heating element that generates heat when energized, and has a steep rise characteristic over the entire effective heat generation length region due to energization of the heating element. It is a low heat capacity heater that raises the temperature. In this example, a heating element is formed by printing a thick film of Ag / Pd paste on an AlN substrate having good thermal conductivity and baking it. And the ceramic heater by which the glass coating layer about 50-60 micrometers thick was integrally provided as a sliding member on the heat generating body is comprised.

  The heater 142 is fitted and supported in a heater fitting groove formed along the length on the outer surface side of the guide member 143. The heater 142 has a central thermistor TH1 for detecting the temperature of the central portion and the end portion of the effective heat generation length region on the substrate opposite to the side on which the heating element is provided across the AlN substrate (see FIG. 4) and an end thermistor TH2. These thermistors are pressed against the substrate at a predetermined pressure by a pressing means (not shown) such as a spring. The central thermistor TH1 is a temperature detecting element for controlling temperature control of the fixing device, and the end thermistor TH2 is a temperature detecting element for detecting temperature rise at the end of the fixing device.

  The guide member 143 is a molded member made of a heat-resistant and heat-insulating material having a substantially semicircular cross section, and the outer surface side that supports the heater 142 is in sliding contact with the inner peripheral surface of the fixing belt 140. The guide member 143 is made of a material having good insulation and heat resistance such as phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, and LCP resin.

  The guide member 143 guides the rotation of the fixing belt 140 to improve the conveyance stability, and holds the heater 142, backs up the fixing belt 140, and presses the pressure roller 141 to form a nip portion N. It plays the role of trying to pressurize.

  The stay 144 is a rigid member for imparting longitudinal strength to the guide member 143 and correcting the guide member 143 by being pressed against the inner surface side of the relatively flexible guide member 143 made of resin. In this example, it is a metal mold such as iron or aluminum having a U-shaped cross section.

  The fixing belt 140 is loosely fitted to the assembly of the guide member 143 holding the heater 142 and the stay 144. The left end portion (one end side end portion) and the right end portion (the other end side end portion) of the guide member 143 and the stay 144 are extended and protruded outward from the left end portion and the right end portion of the fixing belt 140, respectively. .

  The left and right fixing flanges 145 (F · R) are fitted to the left and right extended ends of the stay 144 that protrude outward from the left and right ends of the fixing belt 140, respectively. The left and right fixing flanges 145 (F · R) each include a saddle portion that regulates an end portion of the fixing belt 140, a guide portion that guides an inner peripheral surface of the end portion of the fixing belt 140, a pressure receiving portion, and the like.

(2-2) Pressure roller 141
The pressure roller 141 has a columnar (or cylindrical) metal core 141a made of metal such as iron or aluminum as a core material, an elastic layer 141b such as sponge or silicon rubber on the outer peripheral side of the metal core 141a, and a surface layer. Includes a PFA layer as a release layer 141c.

  In this embodiment, the surface of the cored bar 141a such as iron or aluminum is subjected to surface roughening treatment such as blasting, and then washed, and then the cored bar 141a is inserted into a cylindrical mold, and liquid silicon rubber is placed in the mold. Pour into and heat cure. At this time, in order to form a resin tube layer such as a PFA tube as a release layer 141c on the surface layer, a tube with a primer applied on the inner surface in advance is inserted into the mold, so that the tube is heated simultaneously with the heat curing of the rubber. Glue the rubber layer. The pressure roller 141 thus molded is demolded and then subjected to secondary vulcanization.

  In the pressure roller 141, the left and right shaft portions 141 d can rotate between the left and right side plates 160 (F · R) of the fixing frame 160 via bearing members 161 made of heat-resistant resin such as PEEK, PPS, and liquid crystal polymer. It is held and arranged. A drive gear G is integrally disposed substantially concentrically at the end of the left shaft portion 141d.

  The left and right side plates 160F and 160R of the fixing frame 160 are formed with slit portions 160a that are engaged with the engaged portions of the left and right fixing flanges 145 (F and R) on the mirror surface. The slit portion 160 a is a guide portion that holds the fixing flange 145 (F · R) so as to be slidable in a direction approaching and separating from the pressure roller 141.

  The belt unit 140U is arranged substantially parallel to the pressure roller 141 with the heater 142 facing the pressure roller 141, and the left and right fixing flanges 145 (F · R) are fitted into the slit portions 160a, respectively. It is engaged. Then, predetermined pressure is applied to the pressure receiving portions of the left and right fixing flanges 145 (F · R) by the right and left pressure mechanisms 170 (F · R), respectively. In FIG. 3, for the sake of convenience, the writing of the pressurizing mechanism 170 (F · R) is omitted.

  In this example, the right and left pressure mechanisms 170 (F · R) are mechanisms having a pressure lever 146, a compression spring 147, a cam 171 and the like, respectively. The compression reaction force of the compression spring 147 is applied to the pressure receiving portion of the fixing flange 145 (F · R) through the pressure lever 146 as a pressing force. With this applied pressure, the stay 144, the guide member 143, the heater 142, and the fixing belt 140 are pressed against the pressure roller 141 against the elasticity of the elastic material layer 141b. As a result, a nip portion N having a predetermined width is formed between the fixing belt 140 and the pressure roller 141 in the short direction.

  The cams 171 and 171 of the left and right pressurizing mechanisms 170 (F and R) are fixed to the common cam shaft 172 that is rotatably supported between the left and right side plates 160F and 160R of the fixing frame 160 with the same phase. Has been. The cam shaft 172 is rotationally driven by a third motor M3 (FIG. 4). The control unit 100 drives the cam shaft 172 by the third motor M3 at a predetermined control timing and controls the rotation of the cam 171 to the first rotation angle posture separated from the pressure lever 146. Further, the cam 171 is controlled to rotate to the second rotation angle position in which the pressure lever 146 is swung in the direction of escaping from the pressure receiving portions of the fixing flanges 145F and 145R against the compression spring 147.

  By controlling the cam 171 to the first rotation angle posture, the belt unit 140U is held in a state of being pressed against the pressure roller 141. Further, the cam 171 is controlled to the second rotation angle posture, so that the pressure on the pressure roller 141 of the belt unit 140U is released.

  In the present example, the control unit 101 pressurizes the pressure mechanism 170 (F · R) so that the belt unit 140U is kept pressed against the pressure roller 141 during the image forming operation of the image forming apparatus 100. To control. When the image forming operation of the image forming apparatus 100 is stopped, the pressure mechanism 170 (F · R) is controlled so that the pressure applied to the pressure roller 141 of the belt unit 140U is released.

  The left and right electrical connectors 173 (F · R) are fitted to the left and right extension ends of the guide member 143 holding the heater 142, respectively. As a result, the heater 142 and the power supply unit (power supply unit) 103 are electrically connected to each other so that power can be supplied from the power supply unit 103 to the heater 142. In this example, the electrical information on the detected temperatures of the center thermistor TH1 and the end thermistor TH2 of the heater 142 is fed back to the control unit 101 via the electrical connector 173 (F · R). It is also.

(2-3) Blower Cooling Unit A blower cooling unit 180 serving as a blower unit is configured such that one end side and the other end of the fixing belt 140 are introduced when a small size sheet having a width smaller than the maximum width sheet usable in the apparatus is introduced. This is a mechanism that relaxes the temperature rise (edge temperature rise) of the non-sheet passing portion (recording material non-passing portion) on the side by air cooling. That is, when a small amount of paper is continuously passed through the fixing device 14 and a large amount of fixing processing is performed, the paper passing area of the nip portion N is deprived of heat by the paper S, whereas the non-paper passing area is Heat is not taken away. Therefore, the non-sheet passing portion temperature rises at the non-sheet passing portion. The air blowing / cooling unit 180 is a mechanism that cools the non-sheet-passing portion temperature rising regions at both ends of the fixing belt 140.

  The ventilation cooling unit 180 of this example is disposed on the side opposite to the pressure roller 141 side of the belt unit 140U. The air-cooling unit 180 has a unit substrate 181 attached between the left and right side plates 160F and 160R of the fixing frame 160. Openings (air blowing ports) 149 (F · R) are formed on the left end side and the right end side of the unit substrate 181, respectively.

  In addition, two fans 148 (F · R) (FIG. 3) serving as blowing means are arranged outside the unit substrate 181 so as to correspond to the blowing ports at positions corresponding to the openings 149 (F · R). Has been. The fan 148 (F · R) is on / off controlled by the control unit 101. In FIG. 1 and FIG. 2, the writing of the fan 148 (F · R) is omitted for convenience.

  Further, on the inner side of the unit substrate 181, on the left end side and the right end side of the unit substrate 181, there are two moving members 150 (F · R) in the directions of arrows U1 and U2, which are the bus direction of the fixing belt 140, respectively. It is installed so that it can move.

  Each moving member 150 (F · R) is a fan shielding portion that shields the opening 149 (F · R) (shutter portion: a movable adjustment member that adjusts the opening width of the opening 149 (F · R)). 150a. Further, the moving member 150 (F · R) is formed with a hooking portion 150 b and is disposed close to the fixing belt 140 with a gap.

  Each of the left and right moving members 150 (F · R) has a rack portion (not shown), and these rack portions mesh with the pinion 151. The pinion 151 is rotated forward or reverse in the direction of the arrow V1 or V2 by the second motor M2 controlled by the control unit 101. As a result, the left and right moving members 150 (F · R) move symmetrically around the central reference line for paper conveyance in synchronization (interlocking) in the direction of the arrow U1 or U2 in FIG. In other words, the opening width of the opening 149 (F · R) is controlled to be narrow and wide about the central reference line of the sheet conveyance by the fan shielding part 150a of the moving member 150 (F · R) controlled to be symmetrically moved.

  The moving direction U1 of the left and right moving members 150 (F · R) respectively narrows the opening width of the opening 149 (F · R) symmetrically, and finally the opening 149 (F · R) is fully closed. Direction of movement. The moving directions U2 of the left and right moving members 150 (F · R) each symmetrically widen the opening width of the opening 149 (F · R), and finally open the opening 149 (F · R) fully. The direction of movement.

  The unit substrate 181 is provided with photosensors 152 to 154 as position detecting means for detecting the moving position of the moving member 150 (F · R). And it is the structure which detects the movement position of the moving member 150 (F * R) in combination with the comb-shaped sensor light-shielding part 150c currently formed in the left moving member 150F.

  FIG. 3A shows a state where the moving member 150 (F · R) is in the first position when the fixing device 14 fixes the paper S having the maximum width size Wa that can be used in the apparatus 100.

  The photo sensor 152 is shielded from light by the sensor light shielding part 150c, and the opening 149 (F · R) is sufficiently shielded by the shielding part 150a. The heat generation area in the longitudinal direction of the ceramic heater 142 corresponds to the maximum width size Wa of the paper S, and suppresses the temperature rise of the non-sheet passing portion generated in the nip portion N without using the fan 148 (F · R). doing.

  Next, when the fixing device 14 fixes the minimum width size Wb that can be used in the apparatus 100, corresponding to the cooling by the fan 148 (F · R), the moving member 150 (F · R) is in the second position. The state in FIG. 3 is shown in FIG.

  The photosensor 153 is shielded by the sensor light-shielding part 150c, and the opening part 149 (F · R) is sufficiently opened by sufficiently retracting the shielding part 150a from the opening part 149 (F · R). Then, by blowing air from the fan 148 (F · R), the region Xb of the fixing belt 140 (the fixing belt region corresponding to the non-sheet passing portion of the paper having the minimum width size Wb) is cooled, and the non-passage at the nip portion N is not detected. The temperature increase (edge temperature increase) of the paper passing part can be suppressed.

  When the width Wc of the paper used in the apparatus 100 corresponds to Wa> Wc> Wb, the moving state of the moving member 150 (F · R) when the fixing process is performed by the fixing device 14 is shown in FIG. Shown in A part of the opening 149 (F · R) is opened by detecting the comb-teeth shape of the sensor light-shielding part 150c by the photo sensor 154 and retracting the shielding part 150a from the opening 149 (F · R) by a predetermined distance. Has been. Then, by blowing air from the fan 148 (F · R), the region Xc of the fixing belt 140 (the fixing belt region corresponding to the non-sheet passing portion of the paper of the width size Wc) is cooled, and the non-passing in the nip portion N is performed. The paper portion temperature rise can be suppressed.

  As described above, the moving member (F · R) is disposed in the vicinity of the fixing belt 140, and in the bus direction U1 and U2 of the fixing belt, a first position on the belt end side and a second position on the belt center side are provided. It is possible to move between.

(2-4) Fixing Operation The control unit 101 starts a print job based on an input of a print job start signal. When starting this print job, the control unit 101 receives a paper size input unit from an operation unit (not shown) installed in the image forming apparatus 100 or an external terminal such as a personal computer connected to the image forming apparatus 100. (Recording material size input unit) 102 signal is read. That is, the input value of the size of the paper used in the print job is read.

  The control unit 101 controls the rotation of the motors M1, M2, M3, the electric power supplied to the ceramic heater 142, the fan in response to signals from the photosensors 152 to 154, the fixing inlet sensor 155A, the outlet sensor 155B, etc. ON / OFF control is performed. Note that the control unit 101 may perform not only these controls but also control of the entire image forming apparatus 100.

  A fixing operation including movement control of the moving member 150 (F · R) of the fixing device 14 will be described based on the control flowchart of FIG.

  S1: A print job is started.

  S2: The control unit 101 reads the size input value of the paper S used for the print job from the paper size input unit 102.

  S3: The control unit 101 reads the signal of the photosensor 152 and confirms whether or not the moving member 150 (F · R) is in the first position (fully closed state: home position) in FIG. .

  S4: If it is not detected in S3 that the moving member 150 (F · R) is in the first position, the control unit 101 moves the moving member 150 (F · R) in the direction of the arrow U1. To drive the second motor M2. Thereafter, S3 is executed again.

  S5: When it is detected in S3 that the moving member 150 (F · R) is in the first position, the size input value of the paper S corresponds to the comb-tooth shape of the sensor light-shielding portion 150c and the photosensor 154. Check if it is.

  S6: When the size input value of the paper S corresponds in S5, the control unit 101 moves the moving member 150 (F · R) to the target position according to the size input value of the paper S. The second motor M2 is driven so as to move in the direction of arrow U2.

  S7: The control unit 101 reads the comb-tooth shape of the sensor light-shielding unit 150c by the photo sensor 154, and confirms whether the moving member 150 (F · R) has reached the target position. If it cannot be confirmed, S6 is executed again.

  S8: If the size input value of the paper S does not correspond in S5, or if it is confirmed in S7 that the moving member 150 (F · R) has reached the target position, printing is started.

  As a result, when the paper S to be used is a small size paper, the open area of the opening 149 (F · R) is limited to a desired area by the shielding part 150a. That is, it is possible to apply cooling air from the fan 148 (F · R) to the non-sheet passing regions Xb and Xc of the fixing belt 140 corresponding to the width size of the small size paper S to be used. Therefore, the heat generation distribution of the nip portion N can be formed without causing the fixing belt 140 to raise the temperature of the non-sheet passing portion or to cause poor fixing of the end portion.

  Note that the movement of the moving member 150 (F · R) to the target position is not necessarily performed before the start of printing. For example, when the paper S is continuously passed and the temperature distribution difference between the paper passing area and the non-paper passing area in the nip portion N detected by the center thermistor TH1 and the end thermistor TH2 exceeds a threshold value. You may move.

  In addition, the start-up and fixing operations other than the above-described movement control of the moving member 150 (F · R) of the fixing device 14 at the start of printing in S8 are as follows.

  The control unit 101 changes the pressurization mechanism 170 (F · R) from the pressurization release state to the pressurization state. The first motor M1 is activated to start the rotational driving of the pressure roller 141. The pressure roller 141 is driven as a driving rotary body at a predetermined peripheral speed in the clockwise direction of an arrow R141 in FIG. A rotational force (rotational torque) acts on the fixing belt 140 by a frictional force in the fixing nip N between the pressure roller 141 and the outer surface of the fixing belt 140 driven by the pressure roller 141.

  As a result, while the fixing belt 140 slides in close contact with the outer surface of the guide member 143 including the heater 142 in the nip portion N, the rotational peripheral speed of the pressure roller 141 in the counterclockwise direction indicated by the arrow R140 in FIG. It is driven to rotate at a peripheral speed almost corresponding to.

  In order to make the driven rotation of the fixing belt 140 smooth, it is preferable that a lubricant is interposed between the sliding portions of the outer surfaces of the guide member 143 including the fixing belt 140 and the heater 142.

  Further, the control unit 101 starts power supply from the power supply unit 103 to the heater 142. As a result, the heater 142 is heated rapidly, and the fixing belt 140 that rotates while the inner peripheral surface slides on the heater 142 is heated. The control unit 101 raises the heater temperature to a predetermined fixing temperature based on the detection information of the heater center temperature input from the center thermistor TH1. Then, the temperature of the heater 140 is controlled by controlling the power supplied to the heater 140 so that the fixing temperature is maintained.

  In this fixing device state, the sheet S carrying the unfixed toner image t is introduced from the secondary transfer nip 17 side of the image forming unit 2 and is nipped and conveyed by the nip N. As a result, the toner image t and the paper S are heated and pressed, whereby the toner image t is fixed to the paper S as a fixed image. The sheet S nipped and conveyed by the nip N is separated from the surface of the fixing belt 140 at the sheet exit of the nip N and is discharged and conveyed from the fixing device 14.

  When the paper to be used is a small size paper, as described above, the temperature rise of the non-sheet passing portion is mitigated by the movement control of the moving member 150 (F · R) and the turning on of the fan 148 (F · R).

[Fixing belt breakage detection sequence 1]
Next, the breakage detection sequence 1 of the fixing belt 140 in this example will be described. When the fixing belt is broken, the sheet S is caught on the broken fixing belt 140 or the fixing belt 140 cannot be rotated, and the jamming of the sheet S is likely to occur in the fixing device 14. Therefore, in this example, when the jam of the paper S is detected by the fixing entrance sensor 155A as the paper detection means disposed upstream of the fixing device 14 in the transport direction of the paper S, and after the jam processing is performed. The fixing belt breakage detection sequence 1 is performed before resuming printing.

  The fixing inlet sensor 155A is arranged on the image forming apparatus main body side in this example, but may be arranged on the fixing apparatus 14. Further, the detection of a jam in the fixing device 14 may use a fixing exit sensor 155B on the downstream side in the transport direction of the paper S. The fixing outlet sensor 155B may be disposed on the image forming apparatus main body side or may be disposed on the fixing device 14. The control unit 101 determines that a paper jam has occurred in the fixing device 14 in the following case.

1) The trailing edge passage detection signal of the sheet S is not input from the sensor 155A even if a predetermined time has elapsed after the leading edge arrival detection signal of the sheet S sent to the fixing device 14 is input from the fixing inlet sensor 155A. Case 2) Even if the trailing edge passage detection signal of the paper S is input from the fixing entrance sensor 155A within the predetermined time, the predetermined time has elapsed since the leading edge arrival detection signal of the paper S is input from the sensor 155A. Even if the leading edge arrival detection signal of the sheet S is not input from the fixing outlet sensor 155B, 3) Even if a predetermined time elapses after the leading edge arrival detection signal of the sheet S is input from the fixing outlet sensor 155B. When the paper S does not receive the trailing edge detection signal from the paper S, the control unit 101 urgently stops the printing operation of the image forming apparatus when paper jam is detected. When the printing operation is urgently stopped, the control unit 101 controls the pressure mechanism 170 (F · R) so that the pressure applied to the pressure roller 141 of the belt unit 140U is released. The release of the pressurization facilitates the removal of the jammed paper that is nipped in the nip portion N.

  FIG. 6 shows an example of a failure detection sequence 1 of the fixing belt 140 that is performed before the jam processing when the paper S is jammed by the fixing entrance sensor 155A. This sequence detects the fixing belt breakage before the fixing belt 140 breaks down due to jam processing, so that the damaged fixing belt 140 contacts other parts of the fixing device 14 or other units such as a paper discharge device. Thus, these are also prevented from being damaged.

  When the control unit 101 detects a paper jam in the fixing device 14, it detects the breakage of the fixing belt 140 by moving the moving member 150 (F · R) in the directions U 1 and U 2 in FIG. That is, when the fixing belt 140 is damaged, the hooking portion 150b of the moved moving member 150 (F · R) is caught by the damaged fixing belt 140, and the movement of the moving member 150 (F · R) is prevented. . When the hindrance to the movement of the moving member 150 (F · R) is detected, it is determined that the fixing belt 140 is damaged.

  S10: The fixing entrance sensor 155A detects the occurrence of a jam of the paper S.

  S11: The control unit 101 reads the signal of the photosensor 153 and confirms whether or not the moving member 150 (F · R) is in the second position (full open state) in FIG.

  S12: If it is not detected in S11 that the moving member 150 is in the second position, the control unit 101 moves the moving member 150 (F · R) in the direction of the arrow U2 in FIG. The motor M2 is driven.

  S13: The control unit 101 reads the signal of the photosensor 153 and confirms whether or not the moving member 150 (F · R) is in the second position.

  S14: If it is detected in S11 or S13 that the moving member 150 (F · R) is in the second position, the moving member 150 (F · R) is moved to the first position in FIG. Let That is, the control unit 101 drives the motor M2 to move the moving member 150 (F · R) in the direction of the arrow U1.

  S15: The control unit 101 reads the signal from the photosensor 152 and checks whether or not the moving member 150 (F · R) is in the first position (fully closed state).

  S16: If it is confirmed in S15 that the moving member 150 (F · R) has reached the first position, it is determined that the fixing belt 140 is not damaged, the occurrence of the jam is notified, and the jam processing is executed. Announcement is made by the alarm unit 104 (FIG. 4) such as an alarm or operation screen.

  S17: In S13, if it is not detected that the moving member 150 is in the second position even after a predetermined time has elapsed since the moving member 150 (F · R) was moved, the movement of the moving member 150 is determined to be the fixing belt. It is thought that it is hindered by 140 damage. In S16, the moving member is also detected when it is not detected that the moving member 150 (F · R) is in the first position even after a predetermined time has elapsed since the moving member 150 (F · R) was moved. It is considered that the movement of 150 is hindered by breakage of the fixing belt 140.

  That is, since there is a high possibility that the fixing belt 140 has been damaged, the notifying section 104 announces the inspection of the fixing belt 140 by notifying the occurrence of a jam and the occurrence of an error.

  The damage detection sequence 1 (control sequence) executed by the control unit 101 based on a paper jam detection signal as a predetermined control timing as described above is summarized as follows.

  That is, the breakage detection sequence 1 includes a first step of moving the moving member 150 (F · R) from the second position to the first position. In addition, there is a second step of notifying an error when the movement member 150 (F · R) moved from the second position cannot be detected within a predetermined time. The first step includes a step of moving the moving member 150 (F · R) to the second position when the moving member 150 (F · R) is between the first position and the second position at the time of execution.

  Further, the following operation control may be performed. That is, the breakage detection sequence 1 includes a first step of moving the moving member 150 (F · R) from the first position to the second position. In addition, there is a second step of notifying an error when the movement member 150 (F · R) moved from the first position cannot be detected within a predetermined time. The first step includes a step of moving the moving member 150 (F · R) to the first position when the moving member 150 (F · R) is between the first position and the second position at the time of execution.

Example 2
[Image forming apparatus]
In the second embodiment, the configuration of the image forming apparatus is the same as that of the first embodiment (FIG. 14), and the description thereof is omitted.

[Configuration of Fixing Device]
7 is a schematic perspective view of the fixing device 14 in this example as viewed from the side of the induction heating device 142 as a heating means, FIG. 8 is a schematic diagram of the transverse left side of the main part of the device 14, and FIG. It is a perspective view. 10A to 10C are explanatory diagrams of movement control of the moving member in accordance with the width of the paper to be used. FIG. 11 is a block diagram of the control system.

  The fixing device 14 of this example is a belt heating type, pressure roller driving type (tensionless type) device using an induction heating device 142 as a heating means. Constituent members and portions common to the fixing device 14 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  Similar to the fixing device 14 of the first embodiment, the fixing device 14 of this example includes a fixing belt unit 140U, a pressure roller 141, a fixing frame 160, and a pressure mechanism 170 (F · R) (not shown). Yes. Further, an induction heating device 142 is provided instead of the heater 142 and the air blowing / cooling unit 180 included in the fixing device 14 of the first embodiment.

  The fixing belt 140 is formed using a pure metal or alloy such as Ni, Cu, Ag, or Fe having heat resistance and high thermal conductivity as a base layer. Moreover, when using heat resistant resins, such as a polyimide, a polyamideimide, and PEEK, for the base layer, the structure of laminating | stacking those metals may be sufficient. The thickness of the base layer is adjusted according to the frequency of the high-frequency current flowing in the exciting coil 142a of the induction heating device 142, which will be described later, the permeability and conductivity of the base layer material, and is preferably set to a value of about 5 to 200 μm. Note that a release layer may be formed on the surface of the base layer in the same manner as the fixing belt 140 of the first embodiment.

  The induction heating device 142 is a heating unit that induction heats the fixing belt 140. The induction heating device 142 includes an exciting coil 142a and an outer magnetic shielding member 142b.

  The exciting coil 142a uses, for example, a litz wire as an electric wire, and is wound horizontally so as to face part of the surface and the side surface of the fixing belt 140 in a horizontally long and bottom shape.

  The outer magnetic shielding member 142b is disposed so as to cover the exciting coil 142a so that the magnetic flux generated by the exciting coil 142a does not leak to other than the fixing belt 140. The outer magnetic shielding member 142b is composed of a plurality of core elements, and is divided and arranged in the generatrix direction of the fixing belt 140. The outer magnetic shielding member 142b may be configured by integrating a plurality of core elements.

  Such an excitation coil 142a and the outer magnetic shielding member 142b are supported by a coil support member 142c made of an electrically insulating resin. The magnetic flux generated by the exciting coil 142a is guided to the fixing belt 140 by the outer magnetic shielding member 142b, and the base layer of the fixing belt 140 generates heat due to the passage of the magnetic flux.

  The induction heating device 142 is disposed close to the surface of the fixing belt 140 with a gap. The gap between the surface of the fixing belt 140 and the induction heating device 142 is, for example, about 2 mm.

  In addition, as shown in FIGS. 10A to 10C, the outer magnetic shielding member 142 b has a plurality of core elements arranged so as to be movable relative to the fixing belt 140. A moving mechanism for moving a plurality of core elements to and from the fixing belt 140 is well known, and is omitted from the drawing in order to avoid complication of the drawing. In FIG. 11, M <b> 3 is a drive motor for the moving mechanism, and is controlled by the control unit 101.

  Passing the fixing belt 140 by widening the gap between the fixing belt 140 and the outer magnetic shielding member 142b at the non-sheet passing portion in the nip portion N when a small size sheet is passed as shown in FIGS. 10B and 10C. The magnetic flux density is weakened, and the heat generation amount of the fixing belt 140 is reduced. Thereby, the non-sheet passing portion temperature rise in the nip portion N can be suppressed.

  The excitation coil 142 a is induction-heated to the base layer of the fixing belt 140 when a high frequency current of 20 to 60 kHz is applied from the power supply unit 103. Then, the control unit 101 uses the detected temperature information of the central thermistor TH1 (FIGS. 8 and 11) that detects the temperature of the central portion in the width direction of the fixing belt 140 so that the fixing belt 140 has a predetermined constant temperature. Based on this, the power supply unit 103 is controlled. That is, the frequency of the high-frequency current flowing from the power supply unit 103 to the exciting coil 142a is changed. Thereby, the temperature of the fixing belt 140 is controlled by controlling the power input to the exciting coil 142a.

  An inner magnetic shielding member 156 that shields the magnetic flux generated by the exciting coil 142a is provided in the longitudinal direction on the induction heating device 142 side of the stay 144 in order to prevent the temperature of the guide member 143 from increasing due to induction heating. .

[Configuration of moving member]
At both ends of the gap between the fixing belt 140 and the induction heating device 142, moving members 150 (F · R) that are movable in the direction of the generatrix of the fixing belt 140 are provided. That is, in the fixing device 14 of this example, as the magnetic flux shielding member for suppressing the temperature rise of the non-sheet passing portion in addition to the distance movement of the outer magnetic shielding member 142b in the induction heating device 142 with respect to the fixing belt 140 described above. Moving member 150 (F · R).

  The moving member 150 (F · R) is provided between the exciting coil 142 a and the fixing belt 140 so as to freely enter, and adjusts the magnetic flux flowing from the exciting coil 142 a to the fixing belt 140. Such a moving member 150 (F · R) is made of a nonmagnetic metal such as Al, Cu, Ag, Au, or brass, or an alloy thereof, or a material such as ferrite or permalloy that is a high magnetic permeability member.

  Two moving members 150 (F · R) are movably disposed at both ends of the fixing belt 140 in the generatrix direction. The length in the bus-line direction of the fixing belt 140 of each moving member 150 (F · R) is set to be equal to or shorter than the length that can be arranged at the difference position between the end portion of the fixing belt 140 and the end portion of the outer magnetic shielding member 142b. With such a length, the heat generation area of the maximum width size Wa of the paper S corresponding to the image forming apparatus 100 has a sufficient width to exert the magnetic flux shielding effect and is not reduced.

  Further, in order to sufficiently exhibit the magnetic flux shielding effect, the length of the moving member 150 (F · R) in the bus-bar direction of the fixing belt 140 is made larger than the length of the core element of the outer magnetic shielding member 142b. With such a length, the effect of reducing the temperature rise of the non-sheet passing portion at the end of the sheet passing portion by the moving member 150 (F · R) is narrower than the width of the core element of the outer magnetic shielding member 142b. It is trying not to decline.

  The moving member 150 (F · R) is moved by rotating the lead screw member 157 by driving the second motor M2 as the driving means in the forward or reverse direction. Screw portions 157a are formed at both ends of the lead screw member 157, and the moving member 150 (F · R) is engaged with each.

  The screw portion 157a is formed so that the moving member 150 (F · R) can move from the first position shown in FIG. 10A to the second position shown in FIG. 10B. Each screw portion 157a is threaded in the opposite direction with respect to the other end, and the moving member 150 (F · R) moves symmetrically around the sheet passing area.

  FIG. 10A shows a state where the moving member 150 (F · R) is in the first position when the image forming apparatus 100 fixes the maximum width size Wa of the corresponding paper S by the fixing device 14. It is detected that the moving member 150 (F · R) is in the first position when the photosensor 152 is shielded by the sensor shading unit 150c.

  All of the plurality of core elements of the outer magnetic shielding member 142b are moved toward the fixing belt 140 to maximize the amount of heat generated by the fixing belt 140. The moving member 150 (F · R) is disposed outside the region of the maximum width size Wa, and secures a heat generation distribution corresponding to the maximum width size Wa.

  Next, FIG. 10B shows a state in which the moving member 150 (F · R) is in the second position when the image forming apparatus 100 fixes the minimum width size Wb of the corresponding paper S by the fixing device 14. It is detected that the moving member 150 (F · R) is at the second position by the photosensor 153 being shielded by the sensor shading unit 150c.

  The core elements at both ends in the longitudinal direction of the outer magnetic shielding member 142b are kept away from the fixing belt 140 to minimize the heat generation area of the fixing belt 140. The moving member 150 (F · R) is moved to the center of the nip portion N and inserted inside the exciting coil 142a. As a result, the magnetic flux passing through the fixing belt 140 is weakened, and by ensuring the heat generation distribution corresponding to the minimum width size Wb, it is possible to suppress the temperature rise of the non-sheet passing portion at the nip portion N.

  Next, FIG. 10C shows the state of the moving member 150 (F · R) when the fixing device 14 performs the fixing process when the relationship of the width size Wc of the paper S corresponds to Wa> Wc> Wb. The core element outside the Wc region of the outer magnetic shielding member 142b is moved away from the fixing belt 140, and the heat generation region of the fixing belt 140 is limited to a substantially paper passing region.

  The moving member 150 (F · R) that has been moved to the first position in advance is moved to an arbitrary position by being moved at a constant speed for a predetermined time, and is inserted inside the exciting coil 142a. Here, the end portion of the moving member 150 (F · R) in the U1 direction substantially coincides with the end portion of Wc. As a result, the magnetic flux passing through the fixing belt 140 is weakened, and a heat generation distribution corresponding to the width size Wc is secured, so that the temperature rise of the non-sheet passing portion in the nip portion N can be suppressed.

[Movement of moving member during image formation]
Next, movement control of the moving member 150 (F · R) in the fixing device 14 of this example will be described with reference to FIGS. 10A to 10C, 11, and 12. FIG. 12 is an example of an operation control flow of the moving member 150 (F · R) during printing.

  S18: The print job is started.

  S 19: The control unit 101 reads the size input value of the paper S used for the print job from the paper size input unit 102.

  S20: The control unit 101 determines the number C1 of input pulses to the motor M2 necessary for moving the moving member 150 (F · R) from the first position to the target position that matches the size input value of the paper S. .

  S21: The control unit 101 reads the signal from the photosensor 152 and confirms whether or not the moving member 150 (F · R) is in the first position in FIG. 10A.

  S22: When it is not detected in S21 that the moving member 150 (F · R) is in the first position in FIG. 10A, the control unit 101 moves the moving member 150 (F · R) in the direction of the arrow U1. The motor M2 is driven so as to move. Thereafter, S21 is executed again.

  S23: The control unit 101 moves the moving member 150 (F · R) in the direction of the arrow U2 in order to move the moving member 150 (F · R) to the target position according to the size input value of the paper S. The pulse C1 is input to the motor M2.

  S24: Printing is started.

  The fixing operation is the same as that of the fixing device 14 of the first embodiment except that the fixing belt 140 is heated by the induction heating device 142 in the fixing device 14 of this example. The description will not be repeated.

[Fixing belt breakage detection sequence 1]
Since the fixing belt damage detection sequence 1 in the fixing device of this example is the same as the fixing belt damage detection sequence 1 (FIG. 6) in the fixing device of the first embodiment, a repetitive description is omitted.

Example 3
In the third embodiment, the configuration of the image forming apparatus, the configuration of the fixing device, the configuration of the moving member, the movement of the moving member at the time of image formation, and the fixing belt breakage detection sequence 1 are the same as those in the first embodiment. Omitted.

[Fixing belt breakage detection sequence 2]
In this example, the fixing belt breakage detection sequence 2 will be described with reference to FIGS. 3, 4, and 13.

  FIG. 13 shows an example of a failure detection sequence 2 of the fixing belt 140 that is performed after the jam processing when the jamming of the sheet S occurs at the fixing inlet sensor 155A. This sequence 2 is the fixing belt 140 when the breakage detection sequence 1 (FIG. 6) before the jam processing in the first embodiment fails to detect the breakage or when a breakage occurs due to an erroneous operation during the jam treatment. It is for detecting the damage in detail.

  Similar to the breakage detection sequence 1, the movement of the moving member 150 (F · R) is used, but the control unit 101 drives the pressure roller 141 when the moving member 150 (F · R) moves. Then, the fixing belt 140 is rotated. Thereby, the damage which may have occurred on the opposite side of the proximity surface of the fixing belt 140 to the hooking portion 150b of the moving member 150 (F · R) is also detected.

  In the breakage detection sequence 1 before jam processing in FIG. 6, the user performs jam processing based on the announcement of S16. In the jam processing, by opening an opening / closing door (not shown) of the image forming apparatus 100, the sheet conveyance path including the fixing device 14 of the apparatus main body is opened. Further, when the opening / closing door is opened, a kill switch (not shown) is turned off, and the power supply circuit of the image forming apparatus main body is opened. The user performs an operation (jam processing) for removing jammed paper from the fixing device 14.

  The user closes the open / close door with respect to the image forming apparatus main body after the jam processing. When the open / close door is closed, the kill switch is turned on, and the power supply circuit of the image forming apparatus main body is closed. Based on the closing of the power supply circuit, the control unit 101 executes an initialization operation of the image forming apparatus. In this initialization operation, the control unit 101 executes a failure detection sequence 2 for the fixing belt 140 performed after the jam processing, as shown in FIG.

  S26: The control unit 101 detects the jam processing of the paper S in the fixing entrance sensor 155A.

  S27: The control unit 101 operates the pressure mechanism 170 (F · R) from the pressure release state to the pressure state, and drives the motor M1 so as to rotate the pressure roller 141 in the direction of the arrow R141. As a result, the fixing belt 140 also rotates in the arrow R140 direction.

  S28: The control unit 101 reads the signal from the photosensor 153 and confirms whether or not the moving member 150 (F · R) is in the second position in FIG.

  S29: If it is not detected in S28 that the moving member 150 (F · R) is in the second position in FIG. 3B, the control unit 101 moves the moving member 150 (F · R) to the arrow U2. The motor M2 is driven so as to move in the direction of.

  S30: The control unit 101 reads the signal of the photosensor 153 and confirms whether or not the moving member 150 (F · R) is in the second position.

  S31: If it is detected in S28 or S30 that the moving member 150 (F · R) is in the second position, the moving member 150 (F · R) is moved to the first position in FIG. Let That is, the control unit 101 drives the motor M2 to move the moving member 150 (F · R) in the direction of the arrow U1.

  S32: The control unit 101 reads the signal from the photosensor 152 and confirms whether or not the moving member 150 (F · R) is in the first position.

  S33: If it is confirmed in S32 that the moving member 150 has reached the first position in FIG. 4A, printing before the occurrence of jam is resumed.

  S34: When it is not detected in S30 that the moving member 150 (F · R) is in the second position, or in S32, it is not possible to detect that the moving member 150 (F · R) is in the first position. In such a case, it is highly likely that the fixing belt 140 has been damaged. Therefore, the occurrence of an error is notified and the inspection of the film 140 is announced by the notification unit 104.

  The above damage detection sequence 2 (control sequence) is summarized as follows. The breakage detection sequence 2 includes a first step of moving the moving member 150 (F · R) from the second position to the first position. In addition, there is a second step of notifying an error when the movement member 150 (F · R) moved from the second position cannot be detected within a predetermined time. The first step includes a step of moving the moving member 150 (F · R) to the second position when the moving member 150 (F · R) is between the first position and the second position at the time of execution.

  Further, the following operation control may be performed. That is, the breakage detection sequence 2 includes a first step of moving the moving member 150 (F · R) from the first position to the second position. In addition, there is a second step of notifying an error when the movement member 150 (F · R) moved from the first position cannot be detected within a predetermined time. The first step includes a step of moving the moving member 150 (F · R) to the first position when the moving member 150 (F · R) is between the first position and the second position at the time of execution.

  With this damage detection sequence 2, it is possible to detect in detail the damage to the fixing belt 140 when damage is not detected in the damage detection sequence 1 before jam processing or when damage is caused by an erroneous operation during jam processing.

Example 4
For the image forming apparatus 100 and the fixing device 14 according to the second embodiment, the same fixing belt 140 breakage detection sequence 2 as in the third embodiment can be applied. As a result, as in the third embodiment, the damage to the fixing belt 140 is detailed when the breakage detection sequence 1 before the jam processing cannot detect the breakage or when the breakage occurs due to an erroneous operation during the jam processing. Can be detected.

  As described above, according to the first to fourth embodiments, when a paper jam is detected in the fixing device having the moving member that is movable between the end portion and the central portion of the belt in the vicinity of the fixing belt surface. After the jam processing, the moving member is moved. As a result, it is possible to detect damage to the fixing belt by hooking the damaged fixing belt on the moving member. In addition, by rotating the fixing belt while moving the moving member, it is possible to detect damage that has occurred on the surface of the fixing belt adjacent to the moving member and on the opposite surface in the circumferential direction.

  As a result, regardless of the presence or absence of the conductive layer, it is possible to detect the failure of the fixing belt in a wide area in the busbar direction and the circumferential direction of the fixing belt at an early stage without being affected by scratches on the surface or attached foreign matter. . For this reason, it is possible to prevent the damaged fixing belt from coming into contact with other parts of the fixing device and other units such as a paper discharge device to damage them. When damage is detected, it is possible to take quick measures such as replacing the fixing belt.

Example 5
The above-described breakage detection sequences 1 and 2 are executed in a timely manner as required by the user in addition to the case where the breakage detection sequences 1 and 2 are executed based on a paper jam detection signal as a predetermined control timing as in the first to fourth embodiments. It can also be made.

  In this example, the control unit 101 is based on an execution instruction signal input by a user from an operation unit installed in the image forming apparatus or a manual operation unit 105 such as an external terminal connected to the image forming apparatus. The damage detection sequences 1 and 2 are executed.

<< Other Embodiments >>
(1) In each of the above embodiments, as the best mode, the fixing entrance sensor 155A is used as the paper detection means, the damage detection sequence 1 is performed when the paper S is jammed in the fixing device 14, and the damage detection sequence 2 is processed after the jam processing. Executed.

  However, when a sheet detection unit other than the fixing entrance sensor 155A is provided, these breakage detection sequences may be executed when a jam occurs in another conveyance path.

  (2) In each of the above embodiments, the moving member 150 (F · R) and the photosensors 152 to 154 as position detecting means are arranged in the fixing device 14, but these are arranged on the image forming apparatus main body side. May be installed.

  (3) In the first and third embodiments, the fan 148 (F · R) as the cooling unit is disposed on the image forming apparatus main body side, but may be disposed on the fixing device 14. A single fan 148 may be used to distribute the air flow to the left and right openings 149 (F · R) through a branch duct.

  (4) In the second and fourth embodiments, the induction heating device 142 as the heating unit is disposed in the fixing device 14, but all or part of the induction heating device 142 may be disposed in the image forming apparatus main body.

  (5) In the first and third embodiments, the three photosensors 152 to 154 are used as the position detecting means of the moving member 150 (F · R). However, the first photo sensor shown in FIG. Only one or two sensors that can detect both the position and the second position of (b) may be used.

  (6) In the second embodiment and the fourth embodiment, the two photosensors 152 and 153 are used as the position detection means of the moving member 150 (F · R), but the first position in FIG. Only one sensor capable of detecting both of the second positions may be used.

  (7) In the breakage detection sequence 1 and the breakage detection sequence 2 in the embodiment, the movement of the moving member 150 (F · R) starts from the first position, passes through the second position, and then moves to the first position. Although the returning operation sequence is used, the present invention is not limited to this.

  In order to detect damage in more detail, after returning to the first position, it may be moved again to the second position, or the movement may be repeated. Alternatively, an operation sequence may be used in which the movement of the moving member 150 (F · R) starts from the second position, passes through the first position, and then returns to the second position.

  In the embodiment, the fixing belt 140 is driven by the rotation of the pressure roller 141. Therefore, when the fixing belt 140 is rotated before the paper S is jammed in the fixing device 14, there is a possibility that the paper S is forcibly conveyed in the jam state. However, if the fixing belt 140 and the pressure roller 141 are sufficiently separated when a jam occurs and only the fixing belt 140 can be driven, the fixing belt 140 may be rotated simultaneously during the breakage detection sequence 1.

  (8) In the third and fourth embodiments, the pressure roller 141 is driven and the fixing belt 140 is rotated during execution of the damage detection sequence 2, but the damage detection sequence is performed with the fixing belt 140 stopped. 2 may be executed.

  (9) In the embodiment, the ceramic heater 142 or the induction heating device 142 is used as the heating unit. However, the fixing belt 140 may be heated using a halogen lamp as the heating unit.

  (10) The moving member 150 (F · R) may not be configured to shield the cooling air from the fan 148 (F · R) and the magnetic flux from the exciting coil 142b. For example, the moving member 150 (F · R) is between the halogen lamp and the fixing belt 140 (F · R), and the temperature distribution of the fixing belt 140 (F · R) is adjusted by blocking the halogen lamp to block the passage. The structure which suppresses paper part temperature rising may be sufficient.

  (11) In the embodiment, the moving member 150 (F · R) also functions to shield the cooling air from the fan 148 (F · R) and the magnetic flux from the exciting coil 142b. The moving member 150 (F · R) may be used.

  (12) In the embodiment, the fixing belt 140 of the fixing device 14 that is in contact with the side on which the unfixed toner image t of the paper S is placed is used as a belt body that is a damage detection target. However, when the pressure member 141 that contacts the side opposite to the surface where the unfixed toner image is carried on the paper S is not a pressure roller but a belt body, this may be detected.

  (13) The fixing device is not limited to a so-called tension-free type (tensionless) device like the device of the embodiment. It also includes a device configuration in which an endless belt is rotated by being tensioned (tensioned) by applying tension between a plurality of support members.

  (14) In the embodiments, the fixing device that fixes an unfixed toner image to the recording material has been described as an example. The present invention is similarly applicable to a device that heats and presses a toner image (also called a fixing device in this case).

  (15) The control unit 101 is not limited to the case where the control related to image formation and the control related to fixing are combined, and may be a control unit that exclusively performs control related to fixing. The fixing device 14 is not limited to the one fixed inside the image forming apparatus main body, and may be a unit that can be removed and replaced outside the image forming apparatus main body. In this case, it may be removed and replaced including the control unit, or may be removed and replaced except for the control unit. The fixing device of the present invention may be used independently of the image forming apparatus and independently of the fixing device.

  (16) The image forming unit 2 of the image forming apparatus is not limited to the electrophotographic system. The image forming unit may be an electrostatic recording system or a magnetic recording system. Further, the toner image is not limited to the transfer method, and a toner image may be formed directly on the recording material.

  (17) The image forming apparatus and the fixing apparatus are not limited to the apparatus configuration that conveys the sheet S by the central reference conveyance, and may be an apparatus configuration that conveys the sheet S by a so-called one-side reference.

14 .. Fixing device 140... First rotating body 141... Second rotating body N.. Nip part S S. Recording material t toner image 150.・ Control unit

Claims (8)

A fixing device that fixes a toner image by heating while nipping and conveying a recording material carrying a toner image at a nip formed by a first rotating body and a second rotating body, at least one of which is an endless belt Because
A moving member that is disposed close to the belt and is movable between a first position on the belt end side and a second position on the belt center side in the direction of the bus of the belt;
A first step of moving the moving member to the second position starting from the first position or moving to the first position starting from the second position at a predetermined control timing; and Or a second step of notifying an error when the movement member moved from the second position cannot reach the second position or the first position within a predetermined time. A control unit for executing
A fixing device.   The first step includes a step of moving the moving member to the first position or the second position when the moving member is between the first position and the second position at the time of execution. The fixing device according to claim 1.   The fixing device according to claim 1, wherein the predetermined control timing is based on a jam detection signal of the recording material.   The fixing device according to claim 3, wherein the control unit re-executes the control sequence when it is detected that jam processing has been performed.   The fixing device according to claim 1, wherein the predetermined control timing is based on an execution instruction signal of the control sequence from a manual operation unit.   6. The fixing device according to claim 1, wherein the control sequence is executed in a state where the belt is rotated.   A blower that blows air to the recording material non-passing portion of the belt, the fan for blowing air, an opening for guiding the blow to the recording material non-passing portion, and an opening width of the opening is adjusted The fixing device according to claim 1, further comprising: a blower unit including a movable adjustment member configured to function as the moving member.   An excitation coil for inductively heating the belt; a movable magnetic flux shielding member disposed between the excitation coil and the belt for suppressing temperature rise of the recording material non-passing portion of the belt; The fixing device according to claim 1, wherein the magnetic flux shielding member functions as the moving member.