JP6657736B2 - Fixing device and image forming device - Google Patents

Description

  The present invention relates to a fixing device for fixing a toner image carried on a recording material and an image forming apparatus including the fixing device. The image forming apparatus includes various types such as a copier, a printer, a facsimile, and a multifunction peripheral having a combination of these functions.

  Conventionally, in an image forming apparatus employing an electrophotographic method, a recording material on which an unfixed toner image has been transferred is conveyed to a fixing nip portion between a fixing roller heated by a heat source and a pressing roller pressed against the fixing roller, and heated. And a fixing device for fixing the toner image to the recording material by applying pressure.

  When the fixing device is left for a long time in the pressure contact state, the belt and the roller member are deformed at the fixing nip position (so-called C set). When the fixing device is restarted in the deformed state, abnormal noise is generated, and the distance between various sensors and the distance between the separation claws are changed from the normal position. When the amount of change in the distance between the sensor and the separation claw becomes large, there has been a problem that erroneous detection, a decrease in separation performance due to the separation claw, and a gloss level difference that causes image noise occur. In order to solve such a problem, a method has been proposed in which a roller member is heated in a press-contact state during image formation to perform a recovery operation (for example, see Patent Document 1).

JP 2012-032502 A

  However, if the temperature of the fixing nip in the recovery mode is set higher than the temperature in the fixing operation as in the method disclosed in Patent Document 1, the temperature immediately after the temperature rise when the recovery operation is started overshoots. There was a problem.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device and an image forming apparatus in which the temperature of a fixing nip is not excessively increased when recovering the shape distortion of a rotating member.

The invention according to claim 1, wherein the first rotating member, the second rotating member pressed against the first rotating member to form a fixing nip between the first rotating member and the first rotating member, A heat source for heating the nip portion, a pressure setting mechanism for pressing the second rotating member toward the first rotating member so as to change a load applied to the fixing nip portion, and the first rotating member A control unit for controlling operations of the second rotating member, the heat source, and the pressure setting mechanism, wherein the control unit is carried on the recording material while passing the recording material through the fixing nip. An image forming mode in which the heated toner image is fixed by heating, wherein the first rotating member and the second rotating member are rotated without passing the recording material through the fixing nip, and A recovery mode for recovering the shape distortion of the second rotating member. The recovery mode is performed at a temperature setting where the amount of heat per unit area in the fixing nip portion is smaller than that in the image forming mode, and at least a part of the recovery mode period The second rotating member is pressed toward the first rotating member at a pressure setting where the amount of deformation generated in the first rotating member and the second rotating member is larger than in the image forming mode. Things.

  According to a second aspect of the present invention, in the first aspect, the load applied to the fixing nip portion is changed from a relatively small first pressure setting to a relatively large second pressure setting during execution of the recovery mode. That's what I did.

  According to a third aspect of the present invention, in the second aspect of the present invention, the load applied to the fixing nip portion at the time of the first pressure setting is smaller than the load in the image forming mode.

  According to a fourth aspect of the present invention, in the second aspect, a load applied to the fixing nip portion at the time of setting the second pressure is larger than a load in the image forming mode.

According to a fifth aspect of the present invention, in the first aspect of the present invention, during execution of the recovery mode, the first rotating member and the second rotating member rotate at a speed equal to or lower than a rotating speed in the image forming mode. It is like that.

According to a sixth aspect of the present invention, in the invention of the fifth aspect, a comparison is made from a first speed setting that makes the rotation speeds of the first rotating member and the second rotating member relatively low during execution of the recovery mode. The second speed setting is changed to a high speed.

  According to a seventh aspect of the present invention, in the first aspect, the temperature setting of the fixing nip is changed from a relatively low first temperature setting to a relatively high second temperature setting during execution of the recovery mode. It is like that.

According to an eighth aspect of the present invention, in the first aspect of the present invention, the control unit is configured to control the idle time information, the idle temperature information, the continuous print number information, the paper size information, the heating temperature setting information, the paper jam occurrence information, and the main power OFF. The temperature setting of the fixing nip portion in the recovery mode, the pressurization setting of the load applied to the fixing nip portion, and the first rotating member , based on the use history information including at least one of the information. At least one of the rotation speed settings of the second rotating member is determined.

  According to a ninth aspect of the present invention, in the first aspect of the present invention, there is further provided a detecting member for detecting a position of the second rotating member, wherein the pressure setting mechanism is manually operated. The unit is configured to detect a pressurized state of the second rotating member with respect to the first rotating member based on detection information of the detecting member.

  According to a tenth aspect, there is provided an image forming apparatus including the fixing device according to any one of the first to ninth aspects.

  The fixing device and the image forming apparatus of the present invention can prevent the temperature of the fixing nip from excessively increasing when the distortion of the shape of the rotating member is recovered.

FIG. 2 is a schematic explanatory view of a printer. FIG. 4 is a side sectional view of the fixing device. FIG. 3 is a schematic perspective view of a fixing device. It is a functional block diagram of a controller. 5 is a graph for explaining an example of a temperature setting and a rotation speed in the first embodiment of the recovery mode control. It is a graph for explaining the example of temperature setting and rotation speed in a 2nd embodiment of recovery mode control. It is a flow chart for explaining a 3rd embodiment of recovery mode control. 9 is a chart for explaining table information showing an example of temperature setting, pressurization setting, rotation speed setting, and driving time setting in a recovery mode according to pre-use history information. 11 is a chart for explaining table information showing another example of temperature setting, pressurization setting, rotation speed setting, and drive time setting in the recovery mode according to the history information before use. It is a flow chart for explaining a 4th embodiment of recovery mode control.

  An embodiment embodying the present invention will be described below with reference to the drawings when applied to a tandem-type color digital printer (hereinafter, referred to as a printer) as an example of an image forming apparatus. In the following description, when a term indicating a specific direction or position (for example, “left / right”, “up / down”, or the like) is used as needed, a direction perpendicular to the paper of FIG. ing. These terms are used for convenience of description and do not limit the technical scope of the present invention.

(1). Overview of Printer First, an overview of the printer 1 will be described with reference to FIG. As shown in FIG. 1, the printer 1 includes a transfer device 3 (which may be referred to as an image processing device), a paper feed device 4, a fixing device 5, and the like in a housing 2 thereof. The printer 1 is connected to a network such as a LAN, for example. When receiving a print command from an operation panel 57 (see FIG. 4) as an operation display unit or an external terminal (not shown), the printer 1 performs printing based on the command. Is configured to execute. The printer 1 is a so-called A3-compatible machine, and the sheet feeding device 4 can accommodate a recording material P having a maximum size of A3 in a vertical feeding position in which the recording material P enters the transfer device 3 from the short side. In this case, the long side dimension (transport direction dimension) of the A3 longitudinal recording material P is 420 mm (millimeter), and the short side dimension (width dimension) is 297 mm.

  A sheet feeding device 4 located at a lower portion in the housing 2 includes a sheet feeding cassette 21 as a recording material storage unit that stores the recording material P, and a sheet feeding roller 22 that feeds out the recording material P in the sheet feeding cassette 21 from the uppermost layer. A separating roller 23 for separating the fed recording material P one by one; and a pair of timing rollers 24 for transporting the separated recording material P to the transfer device 3 at a predetermined timing. . The paper feed cassette 21 is detachably disposed at a lower portion of the housing 2. The recording material P in the paper feed cassette 21 is sent to the transport path 30 one by one from the uppermost layer by the rotation of the paper feed roller 22 and the separating roller 23. The transport path 30 is provided from the paper feed cassette 21 of the paper feed device 4, the nip portion of the timing roller pair 24, the secondary transfer nip portion 11 of the transfer device 3, the fixing nip portion 35 of the fixing device 5, and the upper part of the housing 2. Through the discharge roller pair 26, the paper reaches the paper discharge tray 27 on the upper surface of the housing 2.

  The recording material P in the paper feed cassette 21 is set on the basis of the center where the recording material P is conveyed in the conveyance direction S toward the conveyance path 30 with reference to the center of the paper passing width (width dimension orthogonal to the conveyance direction S). The paper feed cassette 21 is provided with a pair of side regulating plates 25 for shifting the recording material P before the paper feed from the center. The pair of side regulating plates 25 are configured to move in the paper passing width direction (a direction orthogonal to the transport direction S) in an interlocked manner. By sandwiching the recording material P in the sheet cassette 21 from both sides in the sheet passing width direction by the pair of side regulating plates 25, the recording material P in the sheet cassette 21 is set on the basis of the center regardless of the standard. Therefore, the transfer process in the transfer device 3 and the fixing process in the fixing device 5 are also executed on the basis of the center.

  In the paper feed cassette 21, a paper feed sensor 58 (see FIG. 4) for detecting the presence or absence of the internal recording material P is arranged. In addition, a paper passing width detection sensor 59 for detecting the position of the side regulating plate 25 is attached to at least one of the side regulating plates 25. The paper passing width of the recording material P is detected from detection information of the paper passing width detection sensor 59, that is, position information of the side regulating plate 25.

  The transfer device 3 located above the sheet feeding device 4 plays a role of transferring the toner image formed on the photosensitive drum 13 as an example of the image carrier to the recording material P. The transfer device 3 includes an intermediate transfer belt 6, and a total of four image forming units 7 corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K).

  The intermediate transfer belt 6 is an endless belt made of a conductive material. The intermediate transfer belt 6 is wound around a driving roller 8 located on the right side of the center in the housing 2 and a driven roller 9 also located on the left side of the center. By rotating the driving roller 8 in the counterclockwise direction in FIG. 1 by the main motor (not shown), the intermediate transfer belt 6 rotates in the counterclockwise direction in FIG. A secondary transfer roller 10 is disposed on the outer peripheral side of a portion of the intermediate transfer belt 6 that is wound around the drive roller 8. The secondary transfer roller 10 is in contact with the intermediate transfer belt 6, and a portion (contact portion) between the intermediate transfer belt 6 and the secondary transfer roller 10 is a secondary transfer nip 11 which is a secondary transfer area. I have. The secondary transfer roller 10 rotates clockwise in FIG. 1 with the rotation of the intermediate transfer belt 6 or the movement of the recording material P nipped and conveyed by the secondary transfer nip 11. A transfer belt cleaner 12 that removes untransferred toner on the intermediate transfer belt 6 is disposed on an outer peripheral side of a portion of the intermediate transfer belt 6 that is wound around the driven roller 9. The transfer belt cleaner 12 is in contact with the intermediate transfer belt 6.

  The four image forming units 7 are arranged below the intermediate transfer belt 6 along the intermediate transfer belt 6 in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the left in FIG. They are arranged side by side. In FIG. 1, for convenience of description, reference characters Y, M, C, and K are attached to the respective image forming units 7 according to reproduced colors. Each image forming unit 7 includes a photosensitive drum 13 that rotates clockwise in FIG. Around the photosensitive drum 13, a charging device 14, a developing device 15, a primary transfer roller 16, and a photosensitive member cleaner 17 are arranged in this order along the clockwise rotation direction in FIG. 1.

  The photoconductor drum 13 is negatively charged, and is configured to be driven to rotate clockwise in FIG. 1 by a main motor (not shown). The charging device 14 is of a roller charging type that uniformly charges the surface of the photosensitive drum 13. A voltage for charging the photosensitive member is applied to the charging device 14 at a predetermined timing from a charging power supply (not shown). The developing device 15 makes the electrostatic latent image formed on the photoconductor drum 13 visible by reversal development using a toner having a negative polarity.

  The primary transfer roller 16 is located on the inner peripheral side of the intermediate transfer belt 6, and faces the corresponding photosensitive drum 13 of the image forming unit 7 with the intermediate transfer belt 6 interposed therebetween. The primary transfer roller 16 also rotates counterclockwise in FIG. 1 with the rotation of the intermediate transfer belt 6. Between the intermediate transfer belt 6 and the primary transfer roller 16 (contact portion) is a primary transfer nip 18 which is a primary transfer area. The photoconductor cleaner 17 is for removing untransferred toner remaining on the photoconductor drum 13, and is in contact with the photoconductor drum 13. An exposure device 19 is arranged below the four image forming units 7. The exposure device 19 forms an electrostatic latent image on each photosensitive drum 13 by laser light based on image information from an external terminal or the like. Above the intermediate transfer belt 6, a hopper 20 that accommodates toner supplied to each developing device 15 is arranged. In FIG. 1, for convenience, reference characters Y, M, C, and K are added to the respective hoppers 20 according to the reproduced colors.

  In each image forming section 7, when a laser beam corresponding to an image signal is projected from the exposure device 19 to the photosensitive drum 13 charged by the charging device 14, an electrostatic latent image is formed. The electrostatic latent image is reversely developed with toner supplied from the developing device 15 to be a toner image of each color. The toner images on each photoconductor drum 13 are primarily transferred from the photoconductor drum 13 to the outer peripheral surface of the intermediate transfer belt 6 in the order of yellow, magenta, cyan, and black in the corresponding primary transfer nip portions 18 and overlapped. Can be The untransferred toner remaining on the photoconductor drum 13 is scraped off by the photoconductor cleaner 17 and removed from the photoconductor drum 13. Then, when the recording material P passes through the secondary transfer nip portion 11, the superimposed toner images of four colors are collectively and secondarily transferred onto the recording material P. The untransferred toner remaining on the intermediate transfer belt 6 is scraped off by the transfer belt cleaner 12 and removed from the intermediate transfer belt 6.

  The fixing device 5 located above the secondary transfer roller 10 includes a fixing roller 31 (first rotating member), a heating roller 32, and a fixing belt 33 wound around these rollers 31, 32. . A pressure roller 34 (second rotating member) is arranged on the outer peripheral side of the portion of the fixing belt 33 that is wound around the fixing roller 31.

  The pressure roller 34 is in contact with the fixing belt 33, and a portion (contact portion) between the fixing belt 33 and the pressure roller 34 is a fixing nip 35 which is a fixing area. When the pressing roller 34 is driven to rotate clockwise in FIG. 1 by a sub motor (not shown), the fixing roller 31 rotates counterclockwise in FIG. 1 together with the fixing belt 33. The fixing roller 31 and the fixing belt 33 rotate in a direction opposite to the rotation direction of the pressure roller 34. Inside the heating roller 32, a heater 36 (heat source) such as a halogen lamp for heating the fixing belt 33 is accommodated. The power supply to the heating element 36 is controlled by the control unit 28 described later, and the heating element 36 and thus the fixing belt 33 are maintained at a temperature required for fixing. The recording material P on which the unfixed toner image is placed after passing through the secondary transfer nip 11 is heated and pressed when passing through the fixing nip 35, and the toner image is fixed on the recording material P. Thereafter, the recording material P is discharged onto the discharge tray 27 by the rotation of the discharge roller pair 26.

  A control unit 28 (see FIG. 4) that controls the overall control of the printer 1 is disposed inside the housing 2. The controller 28 has a built-in controller 50 (see FIG. 4) for executing various arithmetic processing, storage, and control.

(2). Next, a detailed structure of the fixing device 5 and its surroundings will be described with reference to FIGS. 2 and 3. As described above, the fixing device 5 includes the fixing roller 31 and the pressure roller 34 that extend in the paper passing width direction and are rotatable in a state of being pressed against each other with the fixing belt 33 interposed therebetween. On the inner peripheral side of the fixing belt 33, a heating roller 32 is arranged in addition to the fixing roller 31. Both the fixing roller 31 and the heating roller 32 have a cylindrical shape that is long in the paper passing width direction. Both ends in the paper passing width direction of each of the rollers 31 and 32 are rotatably supported by a frame in the housing 2. A heating member 36 such as a halogen lamp for heating the fixing belt 33 is housed on the inner peripheral side of the heating roller 32. The fixing belt 33 that is in pressure contact with the pressure roller 34 has a cylindrical shape that is long in the paper passing width direction, and holds the cylindrical shape by the tension applied to the fixing roller 31 and the heating roller 32 and the own tension.

  A pressure roller 34 is located on the opposite side of the heating roller 32 across the fixing roller 31. The pressure roller 34 is pressed by the pressure setting mechanism 39 toward the fixing roller 31 and the fixing belt 33 to form a fixing nip 35 with the fixing roller 31. The pressure roller 34 and the fixing roller 31 hold the fixing belt 33 therebetween. The pressure roller 34 is pressed against the fixing roller 31 and the fixing belt 33.

  The pressure setting mechanism 39 includes, for example, a nip adjustment shaft 40, a shaft support plate 41, a connection arm 42, a tension spring 43, a movable frame 44, and the like. The nip adjustment shaft 40 is arranged near the pressure roller 34 in parallel with the axis of each of the rollers 31, 32, 34. Both ends in the paper passing width direction of the nip adjustment shaft 40 are rotatably supported by a frame in the housing 2. A shaft support plate 41 that supports each end of the nip adjustment shaft 40 in the paper passing width direction is fixed to both ends in the paper passing width direction. The front ends of the pair of support plates 41 project in the same direction, and each end of the pressure roller 34 in the paper passing width direction is fitted into a U-shaped groove 41 a formed on the front end of each support plate 41. In. One end of a tension spring 43 is connected to a connection arm 42 fixed to a middle part in the longitudinal direction of the nip adjustment shaft 40. The other end of the tension spring 43 is connected to the movable frame 44.

  The movable frame 44 is moved to any of the movable frame positions 44a to 44d by, for example, an actuator (not shown). In accordance with the movable frame positions 44 a to 44 d of the movable frame 44, the pressure roller 34 rotates around the nip adjustment shaft 40 and moves in a direction of coming into contact with and separating from the outer peripheral surface of the fixing belt 33. As a result, the pressing state of the pressing roller 34 against the fixing roller 31 and the fixing belt 33 is changed stepwise (in this case, four steps of light pressure contact, medium pressure contact, high pressure contact, and separation state).

  A roller position sensor 61, which is an example of a detection member that detects the position of the pressure roller 34, is disposed at a position facing at least one end of the pressure roller 34 in the paper passing width direction. Based on the detection information of the roller position sensor 61, the pressing state of the pressing roller 34 against the fixing roller 31 and the fixing belt 33 is detected. The detection member for detecting the position of the pressure roller 34 is not limited to the roller position sensor 61 for directly detecting the position of the pressure roller 34. For example, the detection member may be, for example, a shaft support plate 41, a connection arm 42, or a movable frame 44. The position of the pressure roller 34 may be detected indirectly by detecting the position of the pressure roller 34.

  Further, the pressing state of the pressing roller 34 against the fixing roller 31 and the fixing belt 33 can be detected based on the arrangement position information of the movable frame 44. When the arrangement position of the movable frame 44 is controlled by the controller 50, the pressing state and the position of the pressing roller 34 can be detected even without the roller position sensor 61.

  As described above, the pressing state of the pressing roller 34 against the fixing roller 31 and the fixing belt 33 (the load applied to the fixing nip 35) is changed stepwise according to the movable frame positions 44a to 44d of the movable frame 44. . When the movable frame 44 is located at the movable frame position 44a, the fixing belt 33 and the pressure roller 34 are separated from each other. When the movable frame 44 is located at the movable frame position 44b, the fixing belt 33 and the pressure roller 34 are in a light pressure contact state. When the movable frame 44 is located at the movable frame position 44c, the fixing belt 33 and the pressure roller 34 are in a medium pressure contact state. When the movable frame 44 is located at the movable frame position 44c, the fixing belt 33 and the pressure roller 34 are in a high pressure contact state. The amount of deformation of the fixing roller 31 and the pressure roller 34 when the movable frame 44 is disposed at the movable frame positions 44b to 44d is, for example, about 5 to 40%.

(3). Next, a structure of the control unit 28 and a first embodiment of the recovery mode control performed by the control unit 28 will be described with reference to FIGS. 4 and 5. The control unit 28 basically receives an image signal transmitted from the operation panel 57, the external terminal 70, or the like, converts the image signal into digitized YK color image data, The printing is executed by controlling the apparatus 4 and the like.

  As shown in FIG. 4, a controller 50 of the control unit 28 includes a CPU 51 for executing various arithmetic processing and control, a communication interface (I / F) unit 52 for connection to an external terminal 70 and the like, an EEPROM and a flash memory. And the like, a RAM 54 for temporarily storing control programs and data, a counter 55 for measuring the number of conveyed recording materials P, and a timer 56 for measuring time.

  The controller 50 includes a heating element 36 such as a halogen lamp for heating the fixing belt 33, an operation panel 57 mounted on the outer surface of the housing 2, and a paper feed sensor 58 for detecting the presence or absence of the recording material P in the paper feed cassette 21. A paper width detection sensor 59 for detecting the position of the side regulating plate 25, a roller position sensor 61 as an example of a detection member for detecting the position of the pressure roller 34, and a temperature sensor 62 for measuring the temperature of the fixing belt 33. Are electrically connected.

  After the operator selects the recovery mode on the operation panel 57, the movable frame 44 is movable so as to change the pressure setting “medium pressure” to the pressure setting “high pressure” in the image forming mode for fixing the unfixed toner image. It is moved from the frame position 44c to the movable frame position 44d.

FIG. 5 is a graph for explaining an example of the temperature setting and the rotation speed in the recovery mode. In FIG. 5, the left vertical axis indicates the temperature setting, the right vertical axis indicates the rotation speed, and the horizontal axis indicates the time. As shown in FIG. 5, the pressure roller 34 starts normal rotation (rotation in the same rotation direction as in the image forming mode) at a low speed (relatively low speed) which is the first speed setting. After the drive start t ₀ the predetermined time t ₁ has elapsed, the pressure roller 34 is rotated forward in until driving end time t _2, medium speed is the second speed setting (relatively fast). At this time, the temperature setting of the fixing nip portion 35 is set to a lower temperature setting T ₁ than the temperature setting T ₀ of the image forming mode. During the recovery mode, the pressure setting is set to “high pressure”, so that the amount of deformation of the fixing roller 31 and the pressure roller 34 in the fixing nip 35 increases, and the deformed portion generated in the elastic layer is corrected. . In addition, during the time t ₁ to t2 and it does not accept the print instruction button of the operation panel 57.

After the drive-end from the drive start t ₀ time t ₂ has elapsed, the movable frame 44 so that the pressure setting of the image forming mode (medium pressure) is moved from the movable frame position 44d to the movable frame position 44c, recovery mode To end. Then, a warm-up operation is started, and a print instruction can be accepted.

(4). Second Embodiment of Recovery Mode Control Next, a second embodiment of the recovery mode control by the control unit 28 will be described with reference to FIG. FIG. 6 is a graph for explaining an example of the temperature setting and the rotation speed in the recovery mode. In FIG. 6, the left vertical axis indicates the temperature setting, the right vertical axis indicates the rotational speed, and the horizontal axis indicates the time.

The second embodiment of the recovery mode control is different from the first embodiment of the recovery mode control described above in that the temperature setting of the fixing nip 35 is changed from the relatively low first temperature setting to the relatively high second temperature setting. The difference is that it is changed to The fixing nip 35 is heated at a relatively low first temperature setting (temperature setting T ₂ ) from the start of driving t ₀ to a predetermined time t ₃ . Transition from the time t ₃ is the relatively high temperature of the second temperature setting in the rotation axis direction after the predetermined period of time in which the temperature distribution is stabilized (time t ₄₎ of the fixing roller 31 and the pressure roller 34 (temperature setting T ₃₎ The operation of the heating element 36 is controlled so as to perform the heating. The fixing nip 35 is heated at a relatively high second temperature setting (temperature setting T ₃ ) from the time t ₄ to the drive end time t ₅ . Incidentally, the period from the time t ₄ until t ₅ and does not accept the print instruction button of the operation panel 57.

After the driving end time t ₅ since the drive start t ₀ has elapsed, as in the first embodiment of the recovery mode control described above, to start the warm-up operation to exit the recovery mode, and can accept print instruction .

(5). Third Embodiment of Recovery Mode Control A second embodiment of the recovery mode control by the control unit 28 will be described with reference to FIG. FIG. 6 shows a third embodiment of the recovery mode control by the control unit 28. The algorithm shown in the following flowchart is stored in the storage device 53 of the controller 50 as a program in advance, and is read by the RAM 54 and executed by the CPU 51. Before use, the storage device 53 includes, for example, leaving time information, leaving temperature information, continuous printing number information, paper size information, heating temperature setting information, JAM (paper jam) occurrence / non-occurrence information, and main power OFF information. Table information showing the setting of the temperature of the fixing nip 35 in the recovery mode, the setting of the pressure applied to the load applied to the fixing nip 35, the setting of the rotation speed of the pressing roller 34, and the setting of the driving time according to the history information (FIG. 8 and FIG. 9).

  Regarding the previous history information shown in FIGS. 8 and 9, for example, the leaving time St is about 500 to 800 hours, the leaving temperature Lt is about 20 to 30 ° C., the continuous print number S is about 300 to 600 sheets, and the heating temperature setting. T0 (the temperature of the fixing nip 35 in the image forming mode) is about 160 to 180 ° C.

  Regarding the pressure setting (the load applied to the fixing nip portion 35), for example, the “medium pressure” is the same as the load in the image forming mode and is about 150 to 250 N (Newton), and the “light pressure” is the “medium pressure”. ”Is about 100 to 150N, and“ high pressure ”is larger than“ medium pressure ”and about 300 to 500N.

  Regarding the speed setting, "low speed", "medium speed", and "high speed" are all lower than the rotation speed in the image forming mode. For example, "low speed" is about 20 to 50 mm / s (millimeter per second), "medium speed" is about 60 to 100 mm / s, and "high speed" is about 150 to 180 mm / s.

  Regarding the temperature setting (temperature setting of the fixing nip 35 in the recovery mode), the temperature settings T1, T2, and T3 are all lower than the heating temperature setting T0 in the image forming mode. Therefore, the amount of heat per unit area in the fixing nip 35 in the recovery mode is equal to or less than the amount of heat in the image forming mode. For example, the temperature setting T1 is about 80 to 120 ° C., the temperature setting T2 is about 100 to 150 ° C. higher than the temperature setting T1, and the temperature setting T3 is about 150 to 170 ° C. higher than the temperature setting T2.

  Regarding the drive time in the recovery mode, for example, the drive time Dt1 is about 5 to 20 seconds, the drive time Dt2 is longer than the drive time Dt1 and about 20 to 40 seconds, and the drive time Dt3 is longer than the drive time Dt2. It is about 40 to 80 seconds long.

  Note that the numerical values described with reference to FIGS. 8 and 9 are examples, and the embodiments of the present invention are not limited to these numerical values.

  In the recovery mode control shown in FIG. 7, it is determined whether or not the operator has selected the recovery mode on the operation panel 57 (step S1). If the recovery mode is selected (YES), the previous history information (leaving time, leaving temperature, continuous printing number, paper size information, heating setting temperature information, presence / absence of paper jam, The power OFF information is read into the CPU 51 (step S2). The CPU 51 selects one of the recovery mode conditions 1 to 64 from the table information (see FIGS. 8 and 9) according to the read history information (step S3).

  The recovery mode is executed based on the selected recovery mode condition (step S4). After a lapse of a predetermined time from the start of the recovery mode, it is assumed that the print instruction button on the operation panel 57 is not accepted, as in the above-described second and third embodiments of the recovery mode control.

  An example of the recovery mode condition will be described with reference to FIGS. For example, when the leaving time is relatively long (conditions 33 to 64), or when the JAM history and the main power OFF information are included in the previous history information even if the leaving time is relatively short (conditions 16 and 32, etc.), the fixing roller 31 is used. It is expected that the deformation amount of the pressure roller 34 is large. In such a case, if the fixing roller 31 and the pressure roller 34 are rotated with the pressure setting “high pressure” from the beginning, the load on the motor and the like increases. Therefore, at the start of the recovery mode, the pressure setting is set to “light pressure”, and the fixing roller 31 and the pressure roller 34 are rotated for a predetermined time to correct the deformation of the roller to some extent. It is preferable to change to. Thereby, the motor load can be reduced.

  In addition, except when it is expected that the deformation amount of the fixing roller 31 and the pressure roller 34 is small (conditions 1, 3, 5, and 7), the speed setting may be set to “low” at the start of the recovery mode. preferable. If the amount of deformation is expected to be large, it is preferable to set the speed setting to "low speed" from the start to the end of the recovery mode. Thereby, the motor load can be reduced.

  If the amount of deformation of the fixing roller 31 and the pressure roller 34 is expected to be small, the speed setting is set to “medium speed” at the start of the recovery mode, and the speed setting is set to “high speed” after a predetermined time has elapsed. Is preferred. As a result, the recovery mode can be ended quickly.

  After a predetermined drive time has elapsed from the start of the recovery mode, a warm-up operation is started as in the second and third embodiments of the recovery mode control described above, and a print instruction can be accepted. If the operator does not select the recovery mode in step S1 (NO), the process shifts to the warm-up control.

(6). Fourth Embodiment of Recovery Mode Control Next, a fourth embodiment of the recovery mode control by the control unit 28 will be described with reference to FIG. In this embodiment, the movable frame 44 is manually moved to any of the movable frame positions 44a to 44d using, for example, a lever member (not shown).

  In the recovery mode control shown in FIG. 10, it is determined whether or not the operator has selected the recovery mode on the operation panel 57 (step S11). If the recovery mode is selected (YES), it is determined whether or not the movable frame 44 is located at the movable frame position 44d and the pressure setting is “high” (step S12).

  If the pressurization setting is “high pressure” (YES), the recovery mode is executed under preset conditions (step S13). For example, the temperature setting is lower than that in the image forming mode, about 150 to 170 ° C., the speed setting is smaller than that in the image forming mode, about 120 to 140 mm / s in forward rotation, and the driving time is 20 to It is about 50 seconds. Since the movable frame 44 is manually moved, the pressurization setting cannot be automatically changed in the recovery mode. However, similar to the third embodiment of the recovery mode control described above, the recovery mode condition according to the previous history information is set. It is possible to prepare a table and automatically select the recovery mode conditions (temperature setting, speed setting, driving time) according to the history information.

  After the end of the recovery mode, an instruction to change the pressurization setting to “light pressure” or “medium pressure” is displayed on the operation panel 57 (step S14). When the pressurization setting is manually changed to “light pressure” or “medium pressure” by the operator, the process shifts to warm-up control. If the operator does not select the recovery mode in step S11 (NO), or if the pressure setting is not “high pressure” in step S12 (NO), the process shifts to the warm-up control.

(7). Conclusion As is evident from the above description, according to the embodiment, in the recovery mode, fixing is performed at a temperature setting at which the amount of heat per unit area in the fixing nip 35 is equal to or less than the amount of heat per unit area in the image forming mode. Since the nip 35 is heated, it is possible to prevent the temperature of the fixing nip 35 from excessively increasing when the shape distortion of the fixing roller 31 and the pressure roller 34 is recovered.

  For example, in the case where the excessive temperature rise prevention device of the fixing nip 35 is provided in the fixing device 5, if the temperature of the fixing nip 35 is set higher than that in the image forming mode as in the related art, the recovery mode is started. In this case, the temperature immediately after the temperature rise is overshot, and an unnecessary break of the excessive temperature rise prevention device occurs. In particular, this problem becomes conspicuous in a fixing device having a small heat capacity and improved energy saving performance in recent years. The above embodiment can prevent such a problem.

  Further, since it is not necessary to set the temperature of the fixing nip portion 35 higher than that in the image forming mode, a single-layer rotating member forming the fixing nip portion can be formed, or a material having relatively low heat resistance such as a silicone sponge material can be used. Adoption becomes feasible.

(8). Others The present invention is not limited to the above embodiments, but can be embodied in various forms. For example, although a printer has been described as an example of an image forming apparatus, the present invention is not limited to this, and may be a copying machine, a facsimile, or a multifunction machine having a combination of these functions. In addition, the configuration of each unit is not limited to the illustrated embodiment, and various changes can be made without departing from the spirit of the present invention.

  Further, the recovery mode executed by the fixing device and the image forming apparatus according to the embodiment of the present invention is not limited to the setting conditions shown in FIGS. 8 and 9, but may be variously set within the scope described in the claims. Changes are possible.

  Although the above embodiment employs a heat belt fixing system for heating the fixing belt, the fixing device of the present invention can be applied to other contact heating fixing systems such as a heat roller fixing system.

P Recording material 1 Printer (image forming device)
5 Fixing device 28 Control unit 31 Fixing roller (first rotating member)
34 pressure roller (second rotating member)
35 Fixing nip 36 Heating element (heat source)
39 Pressure setting mechanism

Claims (10)

A first rotating member;
A second rotating member that is pressed toward the first rotating member and forms a fixing nip between the first rotating member and the first rotating member;
A heat source for heating the fixing nip,
A pressure setting mechanism for pressing the second rotating member toward the first rotating member so as to change a load applied to the fixing nip portion;
A control unit that controls operations of the first rotating member, the second rotating member, the heat source, and the pressure setting mechanism,
The control unit includes:
An image forming mode for heating and fixing a toner image carried on the recording material while passing the recording material through the fixing nip portion;
Recovery for rotating the first rotating member and the second rotating member without allowing the recording material to pass through the fixing nip portion to recover the distortion of the shapes of the first rotating member and the second rotating member. Mode and
The recovery mode is performed at a temperature setting where the amount of heat per unit area in the fixing nip portion is smaller than that in the image forming mode, and
The second rotation is performed under a pressure setting in which the amount of deformation generated in the first rotating member and the second rotating member in at least a part of the period of the recovery mode is larger than that in the image forming mode. A fixing device in which a member is pressed toward the first rotating member;   2. The fixing device according to claim 1, wherein a load applied to the fixing nip is changed from a relatively small first pressure setting to a relatively large second pressure setting during execution of the recovery mode.   The fixing device according to claim 2, wherein a load applied to the fixing nip when the first pressure is set is smaller than a load in the image forming mode.   The fixing device according to claim 2, wherein a load applied to the fixing nip when the second pressure is set is larger than a load in the image forming mode. The fixing device according to claim 1, wherein the first rotation member and the second rotation member rotate at a speed equal to or lower than a rotation speed in the image forming mode during execution of the recovery mode. 6. The method according to claim 5, wherein during the execution of the recovery mode, the rotation speed of the first rotating member and the second rotating member is changed from a first speed setting at a relatively low speed to a second speed setting at a relatively high speed. 3. The fixing device according to claim 1.   2. The fixing device according to claim 1, wherein a temperature setting of the fixing nip is changed from a relatively low first temperature setting to a relatively high second temperature setting during execution of the recovery mode. The control unit includes pre-use history information including at least one of leaving time information, leaving temperature information, continuous printing number information, paper size information, heating temperature setting information, paper jam occurrence information, and main power OFF information. At least one of a temperature setting of the fixing nip in the recovery mode, a pressure setting of a load applied to the fixing nip, and a rotation speed setting of the first rotating member and the second rotating member. The fixing device according to claim 1, wherein one of the fixing devices is determined. A detecting member for detecting a position of the second rotating member,
The pressure setting mechanism is manually operated,
2. The fixing device according to claim 1, wherein the control unit detects a pressing state of the second rotating member with respect to the first rotating member based on detection information of the detection member. 3. An image forming apparatus comprising the fixing device according to claim 1.

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