JP2005091890A - Fixing control device, image forming apparatus, and fixing control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly judge whether a temperature abnormality occurs in a fixing device by utilizing an induction heating system. <P>SOLUTION: In the constitution arranging a temperature sensor at a downstream side in the induction heating system by a fixing nip part, a fixing belt is enforcedly rotated with a rotation drive source (S7) and in the state, the occurrence of the temperature abnormality of the fixing device is sensed (S2, S3 and S5) again when sensing the temperature abnormality state of the fixing device during waiting (N of S3 and Y of S5). Thereby in the constitution not incorporating a rod-like heater inside of a pressure roller, the caloric value of the fixing belt is transmitted to the pressure roller, even when the fixing belt absorbs temperature with a fixing nip part, and temperature precision detected with a temperature sensor can be improved by enforcedly rotating the fixing belt and remarkably reducing a contact time between the fixing belt and the pressure roller in the fixing nip part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing control device for an induction heating type fixing device, an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile machine including such a fixing control device, and a fixing control method.

  An image forming apparatus such as a copying machine or a printer forms an image on a recording medium such as plain paper or OHP. This image forming apparatus employs an electrophotographic system in view of high speed image formation, image quality, cost, and the like. The electrophotographic method is a method in which a toner image is formed on a recording medium, and the formed toner image is fixed on the recording medium with heat and pressure. The heat roller method is currently the most widely used fixing method from the standpoint of safety. Has been.

  In the heat roller system, a heat roller heated by a heat generating member such as a halogen heater and a pressure roller disposed opposite to the heat roller are pressed to form a mutual pressure contact portion called a nip portion, and a toner image is formed in the nip portion. This is a method of heating through a recording medium to which is transferred.

  In recent years, environmental problems have become important and image forming apparatuses such as copiers and printers have been saving energy. In considering the energy saving of this image forming apparatus, what cannot be ignored is the power saving of the fixing device for fixing the toner to the recording medium.

  In order to reduce the power consumption of the fixing device during standby of the image forming apparatus, the temperature of the heating roller is maintained at a constant temperature slightly lower than the fixing temperature during standby, so that the temperature can be immediately raised to a usable temperature during use. The temperature of the fixing roller is not waited for. In this case, even when the fixing device is not used, a certain amount of power is supplied to consume extra energy.

  It is desired to save power by reducing the above-mentioned standby energy consumption, and the induction heating fixing method is adopted to shorten the heating time of the heating roller. The induction heating type fixing device has been attracting attention as a method that can contribute to environmental problems because it can dramatically shorten the heating time or the rise time and has high efficiency.

  In the induction heating type fixing device, for example, the heating roller is heated by receiving the magnetic flux generated by the exciting coil, and the heat amount of the heating roller is transmitted to the rotating fixing belt, and the heat amount and the fixing roller, Due to the nip pressure of the pressure roller, the toner on the transfer paper that travels in the rotation direction between the fixing roller and the pressure roller is fixed to the transfer paper.

  There are many patent documents relating to such an induction heating fixing method, and examples of the temperature sensor for detecting the temperature of the fixing belt and the like include the following.

  For example, according to Patent Document 1, temperature sensors for temperature control are arranged at least one of the upstream side and the downstream side in the heated material conveyance direction of the pressure nip portion between the film and the pressure member, and the temperature of the film is set. I try to detect it. In addition, temperature sensors for temperature control are arranged on the upstream side and the downstream side in the heated material conveyance direction of the pressure nip portion between the film and the pressure member, and the alternating magnetic field generating means is provided by the difference between the detected temperatures of both temperature sensors. The applied current or voltage is controlled.

  According to Patent Document 2, a roller temperature sensor for detecting the temperature of the roller and a belt temperature sensor for detecting the temperature of the belt are provided, and the control temperature of the roller is determined based on the detected temperature of the belt temperature sensor, and the determined roller control The belt heating amount is controlled from the temperature and the temperature detected by the roller temperature sensor. Further, a belt temperature sensor is arranged on the downstream side in the rotational movement direction of the belt, and the belt heating means is controlled based on the temperature detected by the belt temperature sensor.

  According to Patent Document 3, the temperature sensor is arranged in the section from the downstream in the rotation direction of the heating and fixing roller of the separation claw to the nip portion.

  According to Patent Document 4, in the induction heating fixing device, when it is determined that the toner heating medium is in a stopped state, heating by electromagnetic induction of the induction heating unit is stopped.

Japanese Patent Laid-Open No. 9-292790 Japanese Patent Laid-Open No. 11-194661 JP 2002-365965 A JP 2001-318546 A

  However, when the temperature of the pressure roller is lower than that of the fixing roller, the amount of heat generated by the heating roller is lost to the pressure roller from the fixing belt at the fixing nip portion.

  In order to avoid this, there is a method in which a heat generating member such as a halogen heater is provided inside the pressure roller. However, in this case, it is assumed that the temperature of the pressure roller is higher than the fixing belt. In other words, the fixing belt used in the induction heating type fixing device needs to be devised to increase the thermal conductivity such as a metal conductor layer structure, and the amount of heat generated by the pressure roller is pressed at the fixing nip. There is a possibility of being given to the fixing belt from the roller.

  Also, depending on the layout of the fixing device, there is a restriction on the arrangement of the temperature sensor that detects the temperature of the fixing belt. When the temperature sensor can be disposed only on the downstream side of the fixing nip portion in the conveyance direction of the fixing belt due to this restriction, for example, the temperature sensor detects the temperature after the heat is removed from the fixing belt to the pressure roller. Therefore, it may be determined that the detected temperature is lower than the expected temperature. Similarly, in a system in which a heat generating member such as a halogen heater is provided inside the pressure roller, the temperature sensor detects the local temperature after heat is applied from the pressure roller to the fixing belt, which is expected. It may be judged that the detected temperature is higher than the temperature. Therefore, it is impossible to accurately grasp whether the fixing device is in an abnormal state.

  On the other hand, when the temperature sensor is arranged on the upstream side of the fixing nip portion in the conveying direction of the fixing belt, in the process where the heat amount of the fixing belt is taken away by the pressure roller in the fixing nip portion, the amount of heat transfer, that is, the belt The temperature downstream of the fixing nip portion in the conveyance direction of the fixing belt relative to the temperature detected by the temperature sensor is unknown. Therefore, even if the detected temperature of the temperature sensor is higher than the expected temperature, there is a possibility that the heat amount of the fixing belt is taken away by the pressure roller at the fixing nip, and the fixing device is in a really abnormal state. It is not possible to accurately grasp whether there is.

  Further, for example, in Patent Document 1, temperature sensors are arranged on both the upstream side and the downstream side in the fixing belt conveyance direction of the fixing nip portion, and are applied to the alternating magnetic field generating means by the difference between the detected temperatures of the two belt temperature sensors. The current or voltage is controlled. As described above, the temperature sensor is arranged on both the upstream side and the downstream side in the fixing belt conveyance direction of the fixing nip portion, and in the process where the heat amount of the fixing belt is taken away by the pressure roller in the nip portion, fixing is performed. The detected temperature of the belt temperature sensor on the downstream side of the fixing nip portion is significantly lower than the normal temperature relative to the detected temperature of the temperature sensor on the upstream side of the nip portion. Similarly, in a method in which a heat generating member such as a halogen heater is provided inside the pressure roller, the temperature sensor on the upstream side of the fixing nip portion is detected in the process where the heat amount of the pressure roller is applied to the fixing belt in the fixing nip portion. The detected temperature of the temperature sensor on the downstream side of the nip portion with respect to the temperature becomes a significantly higher value compared to the normal time. In this configuration, it can be recognized that heat transfer occurs in the nip portion.

  However, it is difficult to accurately determine whether the fixing device is in an abnormal state from the temperatures detected by the two temperature sensors.

  An object of the present invention is to enable appropriate determination of the presence or absence of an abnormal temperature state of a fixing device when using an induction heating method.

  According to a first aspect of the present invention, there is provided a fixing control device including a fixing member to be heated that includes at least a rotating member that is rotationally driven, a rotation driving source that rotates the rotating member, and induction that heats the fixing member to be heated. A heating unit, a pressure roller facing and contacting the rotating member to form a fixing nip portion; and a downstream side of the fixing nip portion with respect to the rotation direction of the rotating member, A temperature sensor for detecting the temperature, an abnormality detecting means for detecting the presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing the fixing operation, and an abnormal temperature state by the abnormality detecting means. If detected, the abnormality detection time control means for forcibly rotating the rotating member by the rotation drive source, and the abnormality detecting means in the forced rotation state of the rotating member Comprising an abnormal re-detection means to re-detect the presence of abnormal temperature state of the fixing device based on the detection output of the temperature sensor.

  According to a second aspect of the present invention, there is provided a fixing control device including a fixing member to be heated including at least a rotating member that is driven to rotate, a rotation driving source that rotates the rotating member, and induction that heats the fixing member to be heated. A heating unit, a pressure roller facing and contacting the rotating member to form a fixing nip portion, and an upstream side of the fixing nip portion with respect to the rotation direction of the rotating member; A temperature sensor for detecting the temperature, an abnormality detecting means for detecting the presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing the fixing operation, and an abnormal temperature state by the abnormality detecting means. If detected, the abnormality detection time control means for forcibly rotating the rotating member in the direction opposite to that during the fixing operation by the rotation drive source, The abnormality detecting means and a abnormality re detection means again detecting the presence or absence of abnormal temperature state of the fixing device based on the detection output of the temperature sensor.

  According to a third aspect of the present invention, there is provided a fixing control apparatus including a fixing member to be heated including at least a rotating member that is rotationally driven, a rotation driving source that rotates the rotating member, and induction that heats the fixing member to be heated. A heating unit, a pressure roller facing and contacting the rotating member to form a fixing nip portion; and a fixing roller disposed upstream and downstream of the fixing nip portion with respect to the rotation direction of the rotating member. A temperature sensor for detecting the temperature of the member to be heated, an abnormality detection means for detecting the presence or absence of an abnormal temperature state of the fixing device based on the detection output of the temperature sensor during standby without performing the fixing operation, and the abnormality detection means When an abnormal temperature state is detected, the abnormality detection time control means for forcibly rotating the rotating member by the rotation drive source, and the abnormality detection in the forcibly rotating state of the rotating member. And a abnormality re detection means again detecting the presence or absence of abnormal temperature state of the fixing device based on the detection output of the temperature sensor by means.

  According to a fourth aspect of the present invention, in the fixing control device according to any one of the first to third aspects, the pressure roller has a built-in bar heater for heating the fixing nip portion.

  According to a fifth aspect of the present invention, in the fixing control device according to any one of the first to fourth aspects, at least a heat resistant belt as the rotating member, a heated roller inscribed in the heat resistant belt, and the heated A fixing roller that supports the heat-resistant belt so as to rotate and move between the roller and a pressure roller; and the temperature sensor contacts the heat-resistant belt. The temperature is detected.

  According to a sixth aspect of the present invention, in the fixing control device according to the fifth aspect, the temperature sensor is a thermistor.

  According to a seventh aspect of the present invention, in the fixing control device according to any one of the first to sixth aspects, an abnormality notifying unit for notifying an abnormality when the abnormal temperature detecting state is detected by the abnormality redetecting unit.

  According to an eighth aspect of the present invention, in the fixing control device according to any one of the first to seventh aspects, when an abnormal temperature state is detected by the abnormal redetection means, an image forming apparatus including the fixing device is connected. Provided with abnormal distribution means for distributing abnormal information to other terminals through the network.

  According to a ninth aspect of the present invention, there is provided an image forming apparatus comprising: a fixing device having a fixing member to be heated that is heated by an induction heating method; a printer engine including a photosensitive member; and other electrophotographic process members; and the fixing member to be heated. And a fixing control device according to any one of claims 1 to 8.

The invention according to claim 10 includes a fixing member to be heated including at least a rotating member that is rotationally driven, a rotation driving source that rotates the rotating member, and an induction heating unit that induction-heats the fixing member to be heated. A pressure roller which forms a fixing nip portion in contact with the rotating member, and a temperature downstream of the fixing nip portion with respect to the rotation direction of the rotating member to detect the temperature of the fixing member to be heated. A fixing control method for a fixing device including a temperature sensor, and an abnormality detection step of detecting presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing a fixing operation; When a temperature abnormal state is detected by the abnormality detection step, a control step at the time of abnormality detection for forcibly rotating the rotating member by the rotation drive source,
An abnormal redetection step of redetecting the presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor in the abnormal detection step in the forced rotation state of the rotating member.

  The invention according to claim 11 includes a fixing member to be heated including at least a rotating member that is rotationally driven, a rotation driving source that rotates the rotating member, and an induction heating unit that induction-heats the fixing member to be heated, A pressure roller which forms a fixing nip portion in contact with the rotating member, and a temperature upstream of the fixing nip portion with respect to the rotation direction of the rotating member to detect the temperature of the fixing member to be heated. A fixing control method for a fixing device including a temperature sensor, and an abnormality detection step of detecting presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing a fixing operation; When an abnormal temperature state is detected in the abnormality detection step, an abnormality detection control step of forcibly rotating the rotating member in a direction opposite to that during the fixing operation by the rotation drive source, and the rotation And a abnormality redetection step of re-detecting the presence or absence of abnormal temperature state of the fixing device based on the detection output of the temperature sensor by the abnormality detection process in a forced rotating state of the wood.

  The invention according to claim 12 includes a fixing member to be heated including at least a rotating member that is rotationally driven, a rotation driving source that rotates the rotating member, and an induction heating unit that induction-heats the fixing member to be heated, A pressure roller that forms a fixing nip portion in contact with the rotating member, and a heating roller for fixing that is disposed on the upstream side and the downstream side of the fixing nip portion with respect to the rotation direction of the rotating member. A fixing control method for a fixing device comprising a temperature sensor for detecting temperature, wherein the abnormality detection detects whether there is an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing a fixing operation An abnormal detection control process for forcibly rotating the rotating member by the rotation drive source when an abnormal temperature state is detected by the abnormality detecting step, And a abnormality redetection step of re-detecting the presence or absence of abnormal temperature state of the fixing device based on the detection output of the temperature sensor by the abnormality detection process in a rotating state.

  According to the first and tenth aspects of the present invention, in the configuration in which the temperature sensor is disposed downstream of the fixing nip portion by the induction heating method, when an abnormal temperature state of the fixing device is detected during standby, rotation driving is performed. The rotating member is forcibly rotated by the power source, and in this state, the operation of detecting the presence or absence of the abnormal temperature state of the fixing device is performed again. Even if the heat amount of the member is conducted to the pressure roller and the temperature of the fixing member to be heated is deprived at the fixing nip portion, the fixing member to be heated at the fixing nip portion is rotated by rotating the fixing member to be heated. The temperature accuracy detected by the temperature sensor can be improved by significantly reducing the contact time between the pressure sensor and the pressure roller. The temperature sensor may be arranged downstream of the fixing nip portion formed by the rotating member and the pressure roller in the conveyance direction, and the pressure roller may include the invention according to claim 4. Thus, even in the configuration in which the rod heater for preventing the falling is built in, the heat amount of the pressure roller using the halogen heater as a heat source is conducted to the fixing member to be heated, and the fixing member to be heated is locally at the fixing nip portion. Even if it is in a high temperature state, the fixing member to be heated is locally in a high temperature state by forcibly rotating the rotating member and moving the relative position of the fixing member to be heated detected by the temperature sensor. It can be properly judged whether the temperature is in the high temperature state.

  According to the second and eleventh aspects of the present invention, in the configuration in which the temperature sensor is arranged on the upstream side of the fixing nip portion by the induction heating method, when an abnormal temperature state of the fixing device is detected during standby, rotation driving is performed. The rotating member is forcibly rotated in the reverse direction by the power source, and in this state, the operation of detecting the presence or absence of the abnormal temperature state of the fixing device is performed again. Even if it is detected, the fixing heated member is reversely rotated, and the temperature of the fixing heated member at the position corresponding to the nip portion is detected again by the temperature sensor, so that the fixing heated member at the fixing nip portion is detected. It is possible to appropriately determine whether the amount of heat is transferred to the pressure roller and the temperature is deprived or whether the temperature is entirely high.

  According to the third and twelfth aspects of the present invention, in the configuration in which the temperature sensor is arranged on the upstream side and the fixing nip portion by the induction heating method, when the abnormal temperature state of the fixing device is detected during standby, the rotation is performed. The rotating member is forcibly rotated in the reverse direction by the drive source, and in this state, the operation of detecting the presence or absence of an abnormal temperature state of the fixing device is performed again, so that the amount of heat of the fixing heated member is transferred to the pressure roller. Even if the temperature of the fixing member to be heated is deprived at the fixing nip portion, by rotating the fixing belt, the contact time between the fixing belt and the pressure roller at the nip portion is greatly reduced, It becomes possible to improve the temperature accuracy detected by the temperature sensor.

  According to the fifth and sixth aspects of the invention, the induction heating method using a heat-resistant belt or the method using a thermistor as a temperature sensor for detecting the temperature of the heat-resistant belt is used. One aspect of the invention can be preferably applied.

  According to the invention of claim 7, when a temperature abnormality is detected by the second detection operation, the user is also notified through the notification means, so that the user can take appropriate measures such as inspection, Certain safety measures can be taken.

  According to the eighth aspect of the present invention, even when the user is located away from the image forming apparatus, the user can be notified of the temperature abnormality immediately through the network, and the user can take appropriate measures such as inspection. This is a more reliable safety measure.

  According to the ninth aspect of the invention, since the fixing control device according to any one of the first to eighth aspects is provided, the same effects as in the case of the first to eighth aspects of the invention can be achieved.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic front view showing an example of an electrophotographic image forming apparatus to which the present invention is applied. This image forming apparatus is an image forming apparatus having a copying function and other functions such as a printer function and a facsimile function. The copying function, the printer function, and the facsimile function are sequentially switched by an application switching key of the operation unit. It is possible to select. The copy mode is selected when the copy function is selected, the print mode is selected when the printer function is selected, and the facsimile mode is selected when the facsimile mode is selected.

  First, in the copy mode, the operation is as follows. In an automatic document feeder (hereinafter referred to as ADF) 101, a document bundle on which a document is placed on a document table 102 is placed on the document table 102 when the start key on the operation unit is pressed. The paper is fed to a predetermined position on a document table 105 made of contact glass by a paper feed roller 103 and a feed belt 104. The ADF 101 has a count function that counts up the number of documents every time a document is fed. The document on the document table 105 is discharged onto a sheet discharge table 108 by a feeding belt 104 and a discharge roller 107 after image information is read by an image reading device 106 as an image input unit.

  When the document set detector 109 detects that the next document is present on the document table 102, the lowermost document on the document table 102 is similarly documented by the feed roller 103 and the feeding belt 104. The sheet is fed to a predetermined position on the table 105. After the image information is read by the image reading device 106, the document on the document table 105 is discharged onto the sheet discharge table 108 by the feeding belt 104 and the discharge roller 107. Here, the paper feed roller 103, the feed belt 104, and the discharge roller 107 are driven by a carry motor.

  The first paper feeding device 110, the second paper feeding device 111, and the third paper feeding device 112 as paper feeding means were loaded on the first tray 113, the second tray 114, and the third tray 115, respectively, when selected. A transfer sheet as a transfer material is fed, and the transfer sheet is conveyed to a position where it abuts on the photoconductor 117 by the vertical conveyance unit 116. The photoconductor 117 is a drum photoconductor and is driven to rotate by a main motor.

  Image data read from the original by the image reading device 106 is converted into optical information by a writing unit 118 as writing means via an image processing means (not shown), and the photoconductor 117 is uniformly charged by a charger (not shown). After that, it is exposed with light information from the writing unit 118 to form an electrostatic latent image. The electrostatic latent image on the photoconductor 117 is developed by the developing device 119 to become a toner image.

  The conveyance belt 120 serves as a sheet conveyance unit and a transfer unit, and a transfer bias is applied from a power source. The transfer belt 120 conveys the toner image on the photoconductor 117 while conveying the transfer paper from the vertical conveyance unit 116 at the same speed as the photoconductor 117. Transfer to transfer paper. The transfer paper is fixed with a toner image by a fixing device 121 and is discharged to a paper discharge tray 123 by a paper discharge unit 122. The photoreceptor 117 is cleaned by a cleaning device (not shown) after the toner image is transferred. Here, the photoconductor 117, the charger, the writing unit 118, the developing device 119, and the transfer unit constitute a printer engine that forms an image on transfer paper based on image data.

  The above operation is an operation for copying an image on one side of a sheet in a normal mode. However, when copying an image on both sides of a transfer sheet in a duplex mode, one of the paper feed trays 113 to 115 is used. The transfer paper that has been fed and has an image formed thereon as described above is switched by the paper discharge unit 122 to the double-sided paper feed path 124 side instead of the paper discharge tray 123 side, and is switched back by the reversing unit 125. The front and back sides are reversed and conveyed to the duplex conveying unit 126.

  The transfer paper transported to the double-sided transport unit 126 is transported to the vertical transport unit 116 by the double-sided transport unit 126, transported to a position where it abuts on the photoconductor 117 by the vertical transport unit 116, and on the photoconductor 117 as described above. The toner image formed on the back surface is transferred to the back surface and the toner image is fixed by the fixing device 121, whereby double-sided copying is performed. This double-sided copy is discharged to the paper discharge tray 123 by the paper discharge unit 122.

  Further, when the transfer paper is reversed and discharged, the transfer paper that is switched back by the reversing unit 125 and turned upside down is not conveyed to the duplex conveying unit 126 but is discharged via the reverse discharge conveyance path 127. The paper is discharged to the paper discharge tray 123 by the unit 122.

  In the print mode, image data from the outside is input to the writing unit 118 instead of the image data from the image processing means, and an image is formed on the transfer paper by the printer engine. Further, in the facsimile mode, the image data from the image reading means is transmitted to the other party by a facsimile transmission / reception unit (not shown), and the image data from the other party is received by the facsimile transmission / reception unit, instead of the image data from the image processing means. By inputting the data to the writing unit 118, an image is formed on the transfer paper by the printer engine described above.

  Next, a configuration example of the fixing device 121 will be described with reference to FIG. FIG. 2 is a front view illustrating a schematic configuration example of the fixing device 121. The fixing device 121 of the present embodiment is configured as an induction heating type fixing device. First, a fixing roller 201 for heating and dissolving the toner on the transfer paper on which the toner has been transferred and fixing the toner onto the transfer paper with respect to the transfer paper transport path in the same manner as a normal halogen heater method and the like. There is provided a pressure roller 202 which is disposed opposite to form a fixing nip portion and applies pressure to the transfer paper to fix the toner. A heated roller 203 is provided at a position spaced from the fixing roller 201, and a fixing belt (heat-resistant belt) 204 is stretched between the heated roller 203 and the fixing roller 201. The fixing belt 204 is a rotating member in a fixing member to be heated that is induction-heated by an exciting coil 205, and has a multi-layer structure including a heated metal portion (metal conductor) and a non-thermally conductive portion. An exciting coil 205 as induction heating means is for inductively heating the heated roller 203 with an eddy current. In this embodiment, an external heating method is used, and the heated roller 203 portion covers the outer peripheral surface about a half circumference. A coil is wound in a spiral shape on the shaped substrate 206. Such an exciting coil 205 is energized with an electric current having an arbitrary frequency characteristic by an inverter circuit, which will be described later, and an eddy current flows through the heated roller 203 by receiving a magnetic flux generated by the electric current. The heat of the heated roller 203 is transferred to the rotating fixing belt 204, and the heat and the nip pressure between the fixing roller 201 and the pressure roller 202 cause the transfer to proceed between the fixing roller 201 and the pressure roller 202 in the rotation direction. The toner on the paper is fixed on the transfer paper.

  Further, the temperature of the fixing belt 204 is always monitored by a thermistor (temperature sensor) 207 that is close thereto, and current supply to the exciting coil 205 is continued if the temperature is lower than the control temperature, and supply is stopped if the temperature is higher. Temperature control is performed by a main body control circuit, which will be described later, but a safety device that directly shuts off the power supply by the thermostat 208 is mounted when the temperature becomes too high due to control failure. In this embodiment, the thermistor 207 is disposed downstream of the fixing nip portion between the fixing roller 201 and the pressure roller 202 in the fixing belt conveyance direction (fixing roller rotation direction).

  The fixing roller 201 is rotationally driven by a fixing motor (rotation drive source) 209, and the fixing belt 204 is moved and rotated by its power. The heated roller 203 is a driven roller that rotates by being suspended by the movement of the fixing belt 204.

  In addition, an encoder (rotation detection sensor) 210 for detecting that the fixing belt 204 is rotating is provided on the shaft of the heated roller 203, although the fixing roller 201 is rotated. When the heated roller 203 does not rotate, it is determined that the belt has run out or the belt has slipped, and the operation of the inverter circuit is interrupted to prevent burning of the exciting coil 205 due to abnormal belt temperature rise. ing.

  In this embodiment, an auxiliary halogen heater (bar heater) 211 for preventing a temperature drop in the fixing nip portion is built in the pressure roller 202.

  However, the induction heating type fixing device 121 is not limited to the external heating method using a fixing belt as shown in the figure, and may be, for example, an internal heating method of a type in which an exciting coil is built in a fixing roller. May be.

  Next, a configuration example of a control system for the fixing belt 204, the exciting coil 205, the thermistor 207, etc., that is, a fixing control device will be described with reference to a schematic block diagram shown in FIG. The fixing control board 301 is in charge of controlling the induction heating type fixing device 121 using the exciting coil 205. A CPU 302 mounted on the fixing control board 301 and responsible for the entire fixing control performs temperature control, abnormality detection, drive control, and the like by a program written in a built-in ROM. The CPU 302 also includes a RAM that stores all control data. These ROM and RAM may be external elements.

  The CPU 302 can always obtain the temperature of the fixing belt 204 by the thermistor 207 via the A / D converter 303. Further, the CPU 302 can recognize the rotation state of the heated roller 203 by acquiring a signal from the encoder 210 via the I / O driver 304. Further, the CPU 302 can perform ON / OFF control of the fixing motor 209 that rotates the fixing roller 201 via the I / O driver 305. On the other hand, the CPU 302 generates a necessary pulse through the PWM control circuit 306, and an inverter circuit 307 as an excitation drive circuit supplies a pulse current to the excitation coil 205 in conjunction with the pulse, and induces an induction phenomenon in the excitation coil 205. It can be raised and heated. That is, the inverter circuit 307 performs full-wave rectification of the AC power supply, and then supplies a current that is high-frequency switched by a switching control element such as an IGBT or FET as a coil current to the exciting coil 205 and a capacitor (not shown) to resonate. An AC magnetic field is generated and the fixing belt 204 is heated by eddy current.

  The CPU 302 controls the temperature of the fixing belt 204 by the thermistor 207, and controls the drive and stop operations of the inverter circuit 307 through the PWM control circuit 306 to perform control to maintain the necessary temperature. However, when the fixing belt 204 becomes abnormal due to an abnormal state such as a failure, the current supply is cut off by the adjacent thermostat 208. The thermostat 208 is selected so that the fixing device does not cause smoke or fire due to an abnormally high temperature.

  In such a configuration, first, FIG. 4 shows a fixing motor 209 that rotates the fixing roller 201, an encoder 210 that monitors the rotation of the heated roller 203, an inverter circuit 307 that supplies a pulse current to the exciting coil 205, and a fixing belt. The time chart of each normal signal waveform of the thermistor 207 which monitors the temperature of 204 is shown.

  At the same time as the fixing motor 209 is turned ON, the inverter circuit 307 generates a pulse current, and the thermistor 207 detects the temperature rise gradually. When the thermistor 207 reaches the target temperature, the inverter circuit 307 stops generating the pulse current, but the rotation of the fixing motor 209 and the pulse detection of the encoder 210 are continued. When it is detected that the thermistor 207 has dropped to a certain temperature, the inverter circuit 307 generates a pulse current again and supplies it to the exciting coil 205. As a result, the temperature detected by the thermistor 207 starts to rise again. By repeating this, the fixing belt 204 is always controlled at a temperature close to the target temperature. Then, at the same time as the fixing motor 209 is turned off, the generation of the pulse current of the inverter circuit 307 is also stopped, and the encoder 210 does not receive a pulse. Further, the detection output of the thermistor 207 also becomes data in which the temperature is gradually lowered.

  Under such a configuration, the present embodiment is characterized by the abnormal temperature detection operation of the fixing device 121 in the standby state (standby) of the image forming apparatus. An example of the operation control executed by the CPU 302 is shown in FIG. This will be described with reference to a schematic flowchart shown in FIG.

  First, at the time of this processing, the mode of the image forming apparatus is in a standby state. Further, the value of the abnormality flag for determining normality / abnormality of the fixing device 121 is written in the RAM, and its initial value is 0 (normal) (step S1). The CPU 302 constantly monitors the thermistor 207 (S2) and detects whether the temperature state of the fixing device 121 is normal. When it is determined that the temperature state of the fixing device 121 is normal (Y in S3), the value of the abnormality flag is updated to 0 (normal) (S4). Here, the processing of steps S2 and S3 is executed as an abnormality detection means and an abnormality detection step.

  On the other hand, when it is determined that the temperature state of the fixing device 121 is not normal (N in S3), the value of the abnormality flag on the RAM is read (S5). If the read value (previous value of the abnormality flag) is 0 (normal) (Y in S5), the value of the abnormality flag is updated to 1 (not normal) (S6). Then, the fixing motor 209 is driven to forcibly rotate the fixing roller 201, and the relative position of the fixing belt 204 detected by the thermistor 207 is moved (S7). Here, the process of step S7 is executed as an abnormality detection time control means and an abnormality detection time control process.

  In this state, the thermistor 207 is monitored again (S2), and it is detected whether the temperature state of the fixing device 121 is normal (S3). If the relative position of the fixing belt 204 detected by the thermistor 207 is moved and it is determined that the temperature state of the fixing device 121 is normal (Y in S3), the value of the abnormality flag is rewritten to 0 (normal). (S4).

  On the other hand, even if the relative position of the fixing belt 204 detected by the thermistor 207 moves, if it is determined that the temperature state of the fixing device 121 is not normal (N in S3), the value of the abnormality flag on the RAM is read (S5). If the read value (previous value of the abnormality flag) is 1 (not normal) (N in S5), the abnormal temperature state of the fixing device 121 is determined (S8). In this case, steps S2 to S4, N of S5, and S8 are executed as an abnormality redetecting means and an abnormality redetecting step.

  As described above, according to the present embodiment, the heat amount of the pressure roller 202 using the halogen heater 211 as a heat source is conducted to the fixing belt 204, and the fixing belt 204 is locally in a high temperature state at the fixing nip portion. Even if the fixing belt 204 is forcibly rotated and the relative position of the fixing belt 204 detected by the thermistor 207 is moved, whether the fixing belt 204 is locally in a high temperature state or the entire surface is hot. It can be judged whether it is in a state. That is, it is possible to accurately grasp the case where the fixing device 121 is in an abnormal temperature state.

  Further, even in a configuration in which the halogen heater 211 is not mounted inside the pressure roller 202, the heat amount of the fixing belt 204 that has been induction-heated is conducted to the pressure roller 202, and the temperature of the fixing belt 204 is deprived at the fixing nip portion. However, by forcibly rotating the fixing belt 204, the contact time between the fixing belt 204 and the pressure roller 202 in the fixing nip portion is greatly reduced, thereby improving the temperature accuracy detected by the thermistor 207. Is possible. That is, also in this case, it is possible to accurately grasp the case where the fixing device 121 is in an abnormal temperature state.

  A second embodiment of the present invention will be described with reference to FIGS. The same parts as those shown in the first embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments).

  Basically, according to the first embodiment, in this embodiment, as shown in FIG. 6, a thermistor 207 as a temperature sensor is formed by a fixing roller 201 and a pressure roller 202. The fixing nip portion is arranged upstream of the fixing belt conveyance direction (fixing roller rotation direction).

  Under such a configuration, this embodiment is also characterized by the abnormal temperature detection operation of the fixing device 121 in the standby state (standby) of the image forming apparatus, and an example of the operation control executed by the CPU 302 is shown in FIG. This will be described with reference to a schematic flowchart shown in FIG.

  First, at the time of this processing, the mode of the image forming apparatus is in a standby state. Further, the value of the abnormality flag for determining the normality / abnormality of the fixing device 121 is written in the RAM, and its initial value is 0 (normal) (S11). The CPU 302 constantly monitors the thermistor 207 (S12) and detects whether the temperature state of the fixing device 121 is normal. When it is determined that the temperature state of the fixing device 121 is normal (Y in S13), the value of the abnormality flag is updated to 0 (normal) (S14). Here, the processes of steps S12 and S13 are executed as an abnormality detection means and an abnormality detection step.

  On the other hand, when it is determined that the temperature state of the fixing device 121 is not normal (N in S13), the value of the abnormality flag on the RAM is read (S15). If the read value (previous value of the abnormality flag) is 0 (normal) (Y in S15), the value of the abnormality flag is updated to 1 (not normal) (S16). Then, the fixing motor 209 is driven in the reverse rotation mode to forcibly rotate the fixing roller 201 in the direction opposite to that during the normal fixing operation, and the relative position of the fixing belt 204 detected by the thermistor 207 is moved (S17). . Here, the process of step S17 is executed as an abnormality detection time control means and an abnormality detection time control process.

  In this state, the thermistor 207 is monitored again (S12), and it is detected whether the temperature state of the fixing device 121 is normal (S13). When the relative position of the fixing belt 204 detected by the thermistor 207 is moved, and it is determined that the temperature state of the fixing device 121 is normal (Y in S13), the value of the abnormality flag is rewritten to 0 (normal). (S14).

  On the other hand, even if the relative position of the fixing belt 204 detected by the thermistor 207 moves, if it is determined that the temperature state of the fixing device 121 is not normal (N in S13), the value of the abnormality flag on the RAM is read (S15). If the read value (previous value of the abnormality flag) is 1 (not normal) (N in S15), the abnormal temperature state of the fixing device 121 is determined (S18). In this case, the processes of steps S12 to S14 and N of S15 and S18 are executed as an abnormality redetecting means and an abnormality redetecting step.

  Therefore, according to the present embodiment, even if the high temperature state of the fixing belt 204 is detected at the position where the thermistor 207 is disposed, the fixing belt 204 is forcibly rotated in the reverse direction at a position corresponding to the fixing nip portion. The temperature of the fixing belt 204 is re-detected by the thermistor 207, so that the heat amount of the fixing belt 204 is conducted to the pressure roller 202 at the fixing nip portion, and the temperature is taken away entirely. You can determine if you are. That is, it is possible to accurately grasp the case where the fixing device 121 is in an abnormal temperature state.

  In this embodiment, it does not matter whether the halogen heater 211 is built in the pressure roller 202 or not.

  A third embodiment of the present invention will be described with reference to FIGS. Basically, it conforms to the first and second embodiments, but in this embodiment, as shown in FIG. 8, two thermistors 207a and 207b as temperature sensors are added to the fixing roller 201. The fixing nip formed by the pressure roller 202 is arranged upstream and downstream with respect to the fixing belt conveyance direction (fixing roller rotation direction).

  According to such a configuration, the temperature difference detected by the two thermistors 207a and 207b can be calculated basically across the fixing nip portion, so that the heat amount of the fixing belt 204 is conducted to the pressure roller 202, and It can be determined whether or not the temperature of the fixing belt 202 is deprived at the fixing nip portion.

  Under such a configuration, this embodiment is also characterized by the abnormal temperature detection operation of the fixing device 121 in the standby state (standby) of the image forming apparatus, and an example of the operation control executed by the CPU 302 is shown in FIG. This will be described with reference to a schematic flowchart shown in FIG.

  First, at the time of this processing, the mode of the image forming apparatus is in a standby state. Further, the value of the abnormality flag for determining the normality / abnormality of the fixing device 121 is written in the RAM, and its initial value is 0 (normal) (step S21). The CPU 302 constantly monitors both thermistors 207a and 207b (S22), calculates the difference between these thermistors 207a and 207b (S23), and detects whether the state of the fixing device 121 is normal (S24). ). When it is determined that the temperature state of the fixing device 121 is normal (Y in S24), the value of the abnormality flag is updated to 0 (normal) (S25). Here, the processing of steps S22 to S24 is executed as an abnormality detection means and an abnormality detection step.

  On the other hand, when it is determined that the temperature state of the fixing device 121 is not normal (N in S24), the value of the abnormality flag on the RAM is read (S26). If the read value (previous value of the abnormality flag) is 0 (normal) (Y in S26), the value of the abnormality flag is updated to 1 (not normal) (S27). Then, the fixing motor 209 is driven to forcibly rotate the fixing roller 201, and the relative position of the fixing belt 204 detected by the thermistors 207a and 207b is moved (S28). Here, the process of step S28 is executed as an abnormality detection time control means and an abnormality detection time control process. In this embodiment, the fixing roller 201 is rotated forward, but may be rotated backward.

  In this state, the thermistor 207 is monitored again (S22), the difference between these thermistors 207a and 207b is calculated (S23), and it is detected whether the temperature state of the fixing device 121 is normal (S24). When the relative position of the fixing belt 204 detected by the thermistor 207 is moved and the temperature state of the fixing device 121 is determined to be normal (Y in S24), the value of the abnormality flag is rewritten to 0 (normal). (S25).

  On the other hand, if it is determined that the temperature state of the fixing device 121 is not normal even if the relative position of the fixing belt 204 detected by the thermistor 207 is moved (N in S24), the value of the abnormality flag on the RAM is read (S26). If the read value (previous value of the abnormality flag) is 1 (not normal) (N in S26), the temperature abnormality state of the fixing device 121 is determined (S29). In this case, the processes of steps S22 to S25 and N of S26 and S29 are executed as an abnormality redetecting means and an abnormality redetecting step.

  Therefore, according to the present embodiment, even if the heat amount of the fixing belt 204 is conducted to the pressure roller 202 and the temperature of the fixing belt 204 is deprived at the fixing nip portion, the fixing belt 204 is forcibly rotated. Thus, the temperature accuracy detected by the thermistors 207a and 207b can be improved by significantly reducing the contact time between the fixing belt 204 and the pressure roller 202 at the fixing nip portion.

  In this embodiment, it does not matter whether the halogen heater 211 is built in the pressure roller 202 or not.

  A fourth embodiment of the present invention will be described with reference to FIG. This embodiment relates to post-processing when a temperature abnormal state is finally detected in the fixing device 121 by the above-described implementation. That is, when a temperature abnormality of the fixing device 121 is detected in the standby state (S8, S18, or S29), it has a function of notifying the user to that effect. This point will be described with reference to a schematic block diagram shown in FIG. FIG. 10 shows a schematic configuration example on the side of the main control unit 402 mounted on the main body CPU 401 that is responsible for the control of the entire image forming apparatus. The main body CPU 401 has a network I / F 407 for connection to a network environment such as a memory 403 such as a ROM and a RAM used for programs and operations, a serial communication I / F 404, an external computer 405, a network server 406, and the like. Etc. are connected. The LCD 409 functioning as a notification unit of the operation control unit 408 in the image forming apparatus is connected to the main body CPU 401 via the LCD driver 410 and the serial communication I / F 404. On the other hand, the operation control unit 408 is also provided with an LED 411 that functions as a notification unit, and is connected to the main body CPU 401 via an LED driver 412 and an I / O control unit 413. Further, in relation to the above-described fixing control board 301 side, for example, the functional part of the fixing device abnormality detecting means 309 executed by the CPU 302 is connected to the main body CPU 401, and the above-described abnormal signal is notified to the main body CPU 401. It is configured as follows.

  Therefore, in the process of step S8, S18, or S29 described above, for example, the CPU 302 (fixing device abnormality detecting means 309) notifies the main body CPU 401 of a temperature abnormality abnormality signal, thereby displaying an error display on the LCD 409, LED 411. By causing an error notification such as an error warning by blinking, the occurrence of an abnormal situation is notified to the user. This allows the user to take appropriate measures such as inspection of the fixing device 121, which is a reliable safety measure.

  For such error notification, the user may be away from the image forming apparatus. Therefore, the main body CPU 401 notifies the network server 406 of an abnormal signal through the network I / F 407, and this network server 406. Thus, it is preferable to notify the error on the screen of the computer 405 by distributing the abnormality signal to the computer 405 which is a terminal used by the user. According to this, even when the user is away from the image forming apparatus, it is possible to notify the user of the abnormality through the network and to make the user take appropriate measures such as checking the fixing device. This is a reliable safety measure.

1 is a schematic front view illustrating an example of an electrophotographic image forming apparatus to which the present invention is applied. FIG. 3 is a front view illustrating a schematic configuration example of a fixing device. 2 is a schematic block diagram illustrating a configuration example of a fixing control device. FIG. It is a time chart which shows each signal waveform example at the time of normal operation. It is a schematic flowchart which shows the example of operation control by 1st embodiment of this invention. It is a front view which shows the example of schematic structure of the fixing device in 2nd embodiment of this invention. It is a schematic flowchart which shows the example of operation control. It is a front view which shows the schematic structural example of the fixing device in 3rd embodiment of this invention. It is a schematic flowchart which shows the example of operation control. It is a schematic block diagram which shows the structural example by the side of the main control part in 4th embodiment of this invention.

Explanation of symbols

117 Photosensitive member 121 Fixing device 201 Fixing roller, fixing heated member 202 Pressing roller 203 Heated roller, fixing heated member 204 Heat resistant belt, fixing heated member, rotating member 205 Induction heating means 207, 207a, 207b Temperature sensor, thermistor 209 Rotation drive source 211 Bar heater

Claims (12)

A fixing member to be heated including at least a rotating member that is driven to rotate;
A rotation drive source for rotating the rotating member;
Induction heating means for induction heating the heated member for fixing;
A pressure roller that contacts the rotating member to form a fixing nip portion; and
A temperature sensor disposed downstream of the fixing nip portion with respect to the rotation direction of the rotating member and detecting the temperature of the fixing member to be heated;
An abnormality detection means for detecting the presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing a fixing operation;
When an abnormal temperature state is detected by the abnormality detection means, an abnormality detection time control means for forcibly rotating the rotating member by the rotation drive source;
An abnormality redetecting means for redetecting the presence or absence of a temperature abnormal state of the fixing device based on the detection output of the temperature sensor by the abnormality detecting means in the forced rotation state of the rotating member;
A fixing control device comprising: A fixing member to be heated including at least a rotating member that is driven to rotate;
A rotation drive source for rotating the rotating member;
Induction heating means for induction heating the heated member for fixing;
A pressure roller that contacts the rotating member to form a fixing nip portion; and
A temperature sensor disposed upstream of the fixing nip portion with respect to the rotation direction of the rotating member and detecting the temperature of the fixing member to be heated;
An abnormality detection means for detecting the presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing a fixing operation;
An abnormality detection time control means for forcibly rotating the rotating member in a direction opposite to the fixing operation by the rotation drive source when a temperature abnormal state is detected by the abnormality detection means;
An abnormality redetecting means for redetecting the presence or absence of a temperature abnormal state of the fixing device based on the detection output of the temperature sensor by the abnormality detecting means in the forced rotation state of the rotating member;
A fixing control device comprising: A fixing member to be heated including at least a rotating member that is driven to rotate;
A rotation drive source for rotating the rotating member;
Induction heating means for induction heating the heated member for fixing;
A pressure roller that contacts the rotating member to form a fixing nip portion; and
A temperature sensor that is disposed upstream and downstream of the fixing nip portion with respect to the rotation direction of the rotating member and detects the temperature of the fixing member to be heated;
An abnormality detection means for detecting the presence or absence of an abnormal temperature state of the fixing device based on a detection output of the temperature sensor during standby without performing a fixing operation;
When an abnormal temperature state is detected by the abnormality detection means, an abnormality detection time control means for forcibly rotating the rotating member by the rotation drive source;
An abnormality redetecting means for redetecting the presence or absence of a temperature abnormal state of the fixing device based on the detection output of the temperature sensor by the abnormality detecting means in the forced rotation state of the rotating member;
A fixing control device comprising:   4. The fixing control device according to claim 1, wherein the pressure roller has a built-in rod-shaped heater that heats the fixing nip portion. 5. At least a heat-resistant belt serving as the rotating member, a heated roller inscribed in the heat-resistant belt, and the heat-resistant belt is rotatably supported between the heated roller and opposed to the pressure roller. A fixing roller to be heated as the fixing member to be heated,
The temperature sensor is in contact with the heat-resistant belt and detects its temperature;
The fixing control device according to claim 1, wherein the fixing control device is a fixing control device.   The fixing control device according to claim 5, wherein the temperature sensor is a thermistor.   7. The fixing control device according to claim 1, further comprising an abnormality notification unit configured to notify an abnormality when a temperature abnormal state is detected by the abnormality re-detection unit.   8. An abnormality distribution unit that distributes abnormality information to other terminals through a network to which an image forming apparatus including the fixing device is connected when an abnormal temperature state is detected by the abnormality redetection unit. The fixing control device according to any one of the above. A printer including a fixing device having a heated member for fixing heated by induction heating, a photoconductor, and other electrophotographic process members;
The fixing control device according to claim 1, wherein the fixing heated member is controlled.
An image forming apparatus comprising: A heating member for fixing including at least a rotating member that is driven to rotate, a rotation driving source that rotates the rotating member, induction heating means that induction-heats the heating member for fixing, and a rotating member that faces the rotating member. A fixing device comprising: a pressure roller that forms a fixing nip portion; and a temperature sensor that is disposed downstream of the fixing nip portion with respect to the rotation direction of the rotating member and detects the temperature of the fixing member to be heated. Fixing control method,
An abnormality detection step of detecting the presence or absence of an abnormal temperature state of the fixing device based on the detection output of the temperature sensor during standby without performing a fixing operation;
When a temperature abnormal state is detected by this abnormality detection step, an abnormality detection time control step of forcibly rotating the rotating member by the rotation drive source,
An abnormal redetection step of re-detecting the presence or absence of an abnormal temperature state of the fixing device based on the detection output of the temperature sensor by the abnormality detection step in the forced rotation state of the rotating member;
A fixing control method comprising: A heating member for fixing including at least a rotating member that is driven to rotate, a rotation driving source that rotates the rotating member, induction heating means that induction-heats the heating member for fixing, and a rotating member that faces the rotating member. A fixing device comprising: a pressure roller that forms a fixing nip portion; and a temperature sensor that is disposed upstream of the fixing nip portion with respect to the rotation direction of the rotating member and detects the temperature of the fixing member to be heated. Fixing control method,
An abnormality detection step of detecting the presence or absence of an abnormal temperature state of the fixing device based on the detection output of the temperature sensor during standby without performing a fixing operation;
When an abnormal temperature state is detected by this abnormality detection step, an abnormality detection time control step of forcibly rotating the rotating member in the direction opposite to the fixing operation by the rotation drive source;
An abnormal redetection step of re-detecting the presence or absence of an abnormal temperature state of the fixing device based on the detection output of the temperature sensor by the abnormality detection step in the forced rotation state of the rotating member;
A fixing control method comprising: A heating member for fixing including at least a rotating member that is driven to rotate, a rotation driving source that rotates the rotating member, induction heating means that induction-heats the heating member for fixing, and a rotating member that faces the rotating member. A pressure roller that forms a fixing nip portion; a temperature sensor that is disposed upstream and downstream of the fixing nip portion with respect to the rotation direction of the rotating member, and detects the temperature of the fixing member to be heated; A fixing control method for a fixing device comprising:
An abnormality detection step of detecting the presence or absence of an abnormal temperature state of the fixing device based on the detection output of the temperature sensor during standby without performing a fixing operation;
When a temperature abnormal state is detected by this abnormality detection step, an abnormality detection time control step of forcibly rotating the rotating member by the rotation drive source,
An abnormal redetection step of re-detecting the presence or absence of an abnormal temperature state of the fixing device based on the detection output of the temperature sensor by the abnormality detection step in the forced rotation state of the rotating member;
A fixing control method comprising:

Images