JP2013044961A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress or prevent an excessive temperature rise of a fixing member.SOLUTION: An image forming apparatus 10 comprises: an image forming part 12 including image forming means 14 which forms an image to be transferred to a recording medium P which is conveyed; a pair of fixing members 72, 74 which are disposed in the downstream side of the conveyance direction of the recording medium P from the image forming part 12 and fix the image formed by the image forming means 14 on the recording medium P while sandwiching and conveying the recording medium P by rotating in a state of being in pressure-contact with each other with at least one of them being heated by a heat source 80; and a control part 60 including calculation means 61 which calculates a reference conveyance interval time for the recording media P which are continuously conveyed on the basis of an image forming reference signal generated when an image is formed by the image forming means 14, and performing control so as to lower the temperature of the heat source 80 when the image forming reference signal is not generated within the reference conveyance interval time.

Description

  The present invention relates to an image forming apparatus.

  Image formation configured to control a heater for heating a fixing roller so that the temperature of the fixing roller is lower than a target temperature when the sheet interval exceeds a preset threshold during continuous printing. The apparatus is conventionally known (for example, refer to Patent Document 1).

JP 2011-2511 A

  An object of the present invention is to obtain an image forming apparatus capable of suppressing or preventing an excessive temperature rise of a fixing member.

  In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention includes an image forming unit including an image forming unit that forms an image to be transferred onto a transported recording medium, and the image forming unit. The recording medium is disposed downstream of the recording medium in the conveyance direction, and at least one of the recording medium is heated by a heating source and is rotated in a state of being pressed against each other while the recording medium is nipped and conveyed by the image forming unit. A pair of fixing members for fixing the formed image to the recording medium, and an image forming reference signal generated when the image is formed by the image forming unit. A calculation means for calculating a reference conveyance interval time, and when the image formation reference signal is not generated within the reference conveyance interval time, the temperature of the heating source is lowered; It is characterized by having a Gosuru control unit.

  The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1, wherein the control unit controls the temperature of the heating source to be lowered, and then the image forming reference signal is If generated, the temperature of the heating source is controlled to be once higher than the target temperature.

  The image forming apparatus according to claim 3 is the image forming apparatus according to claim 1, wherein the control unit controls the temperature of the heating source to decrease, and then is set for a predetermined time. If the image formation reference signal is not generated even after elapse of time, control is performed to raise the temperature of the heating source to a target temperature or a temperature higher than the target temperature, and then the image formation reference signal is generated. In such a case, the temperature of the heating source is controlled to be raised once.

  An image forming apparatus according to a fourth aspect is the image forming apparatus according to any one of the first to third aspects, wherein the calculating means continuously conveys a preset number of sheets. The reference transport interval time is calculated by calculating the maximum value or the average value of the transport interval time of the recording medium.

  According to the first aspect of the present invention, it is possible to suppress or prevent an excessive temperature rise of the fixing member as compared with a case where the control unit configured as described above is not provided.

  According to the second aspect of the present invention, it is possible to suppress or prevent the occurrence of fixing failure due to insufficient temperature as compared with the case where the control unit configured as described above is not provided.

  According to the third aspect of the present invention, it is possible to suppress or prevent the occurrence of fixing failure due to insufficient temperature as compared with the case where the control unit configured as described above is not provided.

  According to the fourth aspect of the present invention, it is possible to appropriately suppress or prevent an excessive temperature rise of the fixing member as compared with a case where the control unit configured as described above is not provided.

Schematic diagram showing schematic configuration of image forming apparatus Schematic diagram showing the schematic configuration of the fixing device Graph showing temperature change over time of heating roll Chart showing the timing to control the temperature of the heating roll Chart showing the timing to control the temperature of the heating roll Graph showing the conditions that determine the timing for controlling the temperature of the heating roll

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment is a so-called tandem full-color printer. An image forming unit 14Y provided as an example of an image forming unit for each color of yellow (Y), magenta (M), cyan (C), and black (K) is provided in the image forming unit 12 provided in the apparatus main body. , 14M, 14C, and 14K. Note that the image forming units 14 are arranged in series at predetermined intervals along the horizontal direction.

  Each image forming unit 14 is basically configured in the same manner, and a photosensitive drum 16 as an example of an image carrier that is rotationally driven at a predetermined speed along the direction of arrow A, and the photosensitive drum 16. A charging device 18 comprising a scorotron or a charging roll for uniformly charging the surface of the photosensitive drum 16, an exposure device 20 for exposing an image corresponding to each color on the surface of the photosensitive drum 16 to form an electrostatic latent image, and a photosensitive drum A developing device 22 that develops the electrostatic latent image formed on the toner 16 with corresponding color toners and a cleaning device 24 that removes the toner remaining on the photosensitive drum 16 are provided.

  The photoconductive drum 16 is formed by coating a photoconductive layer such as an organic photoconductor on the surface of a conductive cylindrical member, for example, in the direction of arrow A at a predetermined rotation speed by a driving source (not shown). It is designed to be rotated along.

  Further, in the exposure apparatus 20, a laser beam LB modulated according to image data is emitted from the semiconductor laser, and the laser beam LB emitted from the semiconductor laser is irradiated to the rotary polygon mirror via the mirror, and the rotation thereof. After being deflected and scanned by a polygon mirror, the surface of the photosensitive drum 16 is scanned and exposed through an fθ lens and a mirror. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of each photosensitive drum 16.

  The electrostatic latent image formed on the surface of each photoconductor drum 16 is converted into yellow (Y) and magenta (magenta) by a two-component developing type developing device 26 containing a two-component developer composed of toner and carrier, for example. M), cyan (C), and black (K) toner images are developed. As the developing device 26, a one-component developing type developing device using a one-component developer composed only of toner may be used.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drums 16 of the image forming units 14 are located below the image forming units 14. Are transferred onto an intermediate transfer belt 30 as an example of an intermediate transfer member disposed in the state of being sequentially superposed by a primary transfer roll 28.

  The primary transfer roll 28 is disposed to face the photosensitive drum 16 with the intermediate transfer belt 30 interposed therebetween, and constitutes a primary transfer portion T1. The intermediate transfer belt 30 is wound around a drive roll 32, a tension roll 34, a steering roll 36, a backup roll 40 in contact with the power supply roll 38, and an idler roll 42 with a predetermined tension. A drive roll 32 that is rotationally driven by a drive motor (not shown) is circulated and driven at a predetermined speed substantially equal to that of the photosensitive drum 16 along the arrow B direction.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred onto the intermediate transfer belt 30 in multiple contact are pressed against the backup roll 40 via the intermediate transfer belt 30. Secondary transfer is performed on a recording sheet P as an example of a recording medium by the pressing force and electrostatic force of the secondary transfer roll 44. The recording paper P on which the toner images of the respective colors are transferred is conveyed to the fixing device 70 by the conveyance belt 46 and the conveyance guide 48.

  The secondary transfer portion T2 includes a secondary transfer roll 44 disposed on the toner image holding surface side of the intermediate transfer belt 30 and a backup roll 40. The recording paper P on which the toner images of the respective colors are transferred is subjected to a fixing process by heat and pressure by the fixing device 70, and then a discharge tray (see FIG. 2) provided outside the apparatus main body by the discharge roll 100 (see FIG. 2). (Not shown in the figure).

  Further, the recording paper P having a desired size and material from a paper feed tray 52 disposed inside the apparatus main body passes through a paper transport path 50 including a paper feed roll 54 and a pair of transport rolls 56 for paper transport. And is conveyed to the secondary transfer portion T2 of the intermediate transfer belt 30 through the conveyance guide 64 by the registration roll 58.

  Further, the transfer residual toner remaining on the intermediate transfer belt 30 is removed by a belt cleaning device 62 disposed at a position facing the idler roll 42. Further, the image forming unit 12 is provided with a reference sensor 66 for detecting the reference position of the intermediate transfer belt 30 and a detection sensor 68 for detecting a pattern for registration registration formed on the surface of the intermediate transfer belt 30. Yes.

  Further, the image forming apparatus 10 is provided with a control unit 60 that controls the operation of each unit. Then, as will be described later, the control unit 60 informs the image forming unit 12 of the sheet passing interval time of a plurality of recording papers P that continuously pass through the nip N in the fixing device 70 (the image forming unit 14). Is incorporated (provided) with calculation means 61 for calculating the image formation timing (image formation reference signal).

  Here, the fixing device 70 will be described in detail. As shown in FIG. 2, the fixing device 70 includes a heating roll 72 as an example of a fixing member (heating member) having a halogen lamp 80 as an example of a heating source, and an endless belt-like fixing member (pressure). A fixing belt 74 as an example of a member), a pressure contact member 76 that is disposed inside the fixing belt 74 and presses the fixing belt 74 against the surface of the heating roll 72, and an oil supply that supplies oil to the inner surface of the fixing belt 74. And a felt member 78 as a member.

  The heating roll 72 is made of a thin cylindrical cored bar made of iron, stainless steel, aluminum or the like, an elastic layer made of silicon rubber coated on the surface of the cored bar, PFA coated on the surface of the elastic layer, or the like. It consists of a release layer. And the temperature sensor 82 is arrange | positioned on the surface of the heating roll 72 so that it may contact (non-paper passing part) or non-contact (paper passing part).

  The fixing belt 74 is formed in an endless belt shape using a synthetic resin such as a polyimide resin or a polyamide-imide resin, and a release layer made of PFA or the like is provided on the surface as necessary. A portion (range) where the heating roll 72 and the fixing belt 74 are in contact (pressure contact) with each other is defined as a nip portion N.

  The pressure contact member 76 is a belt housing 84 made of a synthetic resin, a metal belt frame 86 having a rectangular cross section mounted in a state of being fitted to the belt housing 84, and a pressure belt 76 for pressing the fixing belt 74 against the heating roll 72. The nip head member 88 and a pad member 90 attached to the nip head member 88 are mainly configured. The pressing member 76 is urged so that the fixing belt 74 is pressed against the heating roll 72 by a compression spring (not shown) as an urging means.

  A synthetic resin film-like sheet member 92 is interposed between the fixing belt 74 and the pressure contact member 76, and the sheet member 92 is a frictional force between the fixing belt 74 and the pressure contact member 76. Is to be reduced. The felt member 78 is impregnated with an oil made of amino Si oil or the like, and the felt member 78 is attached to the back side of the belt frame 86 by a fixing means such as adhesion. Yes.

  Further, the fixing device 70 is provided with a peeling auxiliary member 94 that assists in peeling the recording paper P from the heating roll 72. The peeling auxiliary member 94 includes a peeling baffle 96, and the peeling baffle 96 is in a direction (counter direction) opposite to the rotation direction of the heating roll 72 and close to the heating roll 72. Is held by.

  In the fixing device 70 having the above-described configuration, a control unit that can suppress or prevent a phenomenon (excessive temperature rise) in which the surface temperature of the heating roll 72 exceeds a predetermined upper limit temperature, and further, at the time of fixing, A control means capable of suppressing or preventing the occurrence of fixing failure due to the insufficient (decreased) surface temperature of the heating roll 72 will be described with reference to FIGS.

  The “upper limit temperature” referred to here is a predetermined temperature that is higher than the target temperature at the time of fixing the surface of the heating roll 72. In this embodiment, the surface temperature of the heating roll 72 is The phenomenon exceeding the upper limit temperature is regarded as an overshoot.

  In the fixing device 70, when the recording paper P passes through the nip portion N between the heating roll 72 and the fixing belt 74, the surface temperature of the heating roll 72 is lowered due to the recording paper P being deprived of heat. As shown in FIG. 3, the surface temperature of the heating roll 72 is constantly monitored by a temperature sensor 82.

  Here, if the image forming apparatus 10 is set with an image quality setup cycle operation or a finisher operation such as a finisher, during continuous printing, during the operation, a sheet passing interval time passing through the nip portion N of the recording sheet P is set. The (conveyance interval time) becomes longer (longer) than the normal sheet passing interval time when the image quality setup cycle operation and the post-processing operation are not executed.

  When such an interval (see FIG. 4) of the sheet passing interval occurs, at that time, the time during which the recording paper P does not take heat from the surface of the heating roll 72 (sheet passing interval time) is longer than usual. Therefore, an overshoot occurs in which the surface temperature of the heating roll 72 exceeds a predetermined upper limit temperature.

  Therefore, in the present embodiment, the control unit 60 constantly monitors the image formation reference signal (see FIG. 4) generated by the image forming unit 12, and the time difference at which the image formation reference signal is generated is used during continuous printing. When a sheet passing interval time (conveyance interval time) serving as a reference for the recording paper P is calculated and the image forming reference signal is not generated within the reference sheet passing interval time, the energization to the halogen lamp 80 is performed. Is controlled to lower the surface temperature (control temperature) of the heating roll 72.

  Specifically, when an image is formed by the image forming unit 14 (for example, the laser beam LB is emitted by the exposure device 20), an image forming reference signal is generated in the image forming unit 12 and sent to the control unit 60. Then, the calculation means 61 (see FIG. 1) provided in the control unit 60 calculates the timing at which the recording paper P passes through the nip N in the fixing device 70 based on the image formation reference signal.

  In other words, the calculation means 61 provided in the control unit 60 uses each recording sheet P based on the image formation reference signal generated for each image transferred to each recording sheet P that is continuously conveyed. Is calculated as an interval time (sheet passing interval time) through which the sheet passes through the nip portion N. Here, the paper passing interval time may vary.

  Therefore, the control unit 60 (calculating means 61) has a preset value, for example, the maximum value or average value of the sheet passing interval time of the recording paper P between the first sheet and the Nth sheet (N ≧ 3). The maximum value or the average value is stored (set) as a normal sheet passing interval time that is a reference of the recording sheet P that passes through the nip portion N. For example, the sheet passing interval time between the first sheet and the second sheet may be stored, and may be set as a normal sheet passing interval time as a reference.

  If an image quality setup cycle operation or a post-processing operation is executed during continuous printing, the image formation reference signal is not generated within the normal normal paper passing interval time. Then, the control unit 60 recognizes that the paper passing interval time of the next recording paper P that passes through the nip portion N is longer than the normal normal paper passing interval time (arrow R1 shown in FIG. 4). Position), the energization of the halogen lamp 80 is controlled to lower the control temperature of the surface of the heating roll 72 below the target temperature.

  Here, the timing (time lag) D (see FIG. 4) for the control unit 60 to lower (change) the control temperature of the surface of the heating roll 72 is the printing operation time during continuous printing or the continuous lighting time of the halogen lamp 80. It is decided accordingly. That is, the printing operation time during continuous printing in the image forming apparatus 10 and the continuous lighting time of the halogen lamp 80 during the printing operation are constantly monitored by the control unit 60.

  Therefore, for example, as shown in FIG. 6, when the printing operation time during continuous printing is 20 seconds or more (long time) and the continuous lighting time of the halogen lamp 80 is 7 seconds or more (long time), the heating roll The timing D for lowering the control temperature of the surface 72 (see FIG. 4) is after the control unit 60 recognizes that the image formation reference signal has not been generated within the standard normal paper passing interval time (see FIG. 4). Within 0.5 seconds from the position of arrow R1 shown in FIG.

  On the other hand, for example, when the printing operation time during continuous printing is 10 seconds or less (short time) and the continuous lighting time of the halogen lamp 80 is 10 seconds or less (short time), the control temperature of the surface of the heating roll 72 is set to At the lowering timing D (see FIG. 4), the control unit 60 recognizes that the image formation reference signal has not been generated within the reference normal paper passing interval time (the position of the arrow R1 shown in FIG. 4). From), after 3.0 seconds.

  The timing D for lowering the control temperature of the surface of the heating roll 72 is not limited to the case where it is determined by both the printing operation time during continuous printing and the continuous lighting time of the halogen lamp 80. It may be determined by the printing operation time or the continuous lighting time of the halogen lamp 80.

  Thereafter, when an image is formed again by the image forming unit 14, the control unit 60 (calculating means 61) determines the timing at which the recording paper P passes through the nip portion N based on the image forming reference signal generated thereby. calculate. Then, in accordance with the timing, the control unit 60 controls energization of the halogen lamp 80 so that the control temperature of the surface of the heating roll 72 is once higher than the target temperature.

  Specifically, when an image is formed again by the image forming unit 14, the control unit 60 recognizes that the recording paper P is resumed based on the image forming reference signal generated thereby (FIG. Arrow R2 position shown by 4). Then, the control unit 60 controls energization to the halogen lamp 80 to once raise the control temperature of the surface of the heating roll 72 from the target temperature.

  Here, when the control unit 60 temporarily raises (changes) the control temperature of the surface of the heating roll 72 from the target temperature (time lag) U (see FIG. 4), the recording paper P enters the nip portion N. It is just before coming. That is, even if the surface temperature of the heating roll 72 is once raised from the target temperature, the heat is immediately taken away by the recording paper P. Therefore, overshoot does not occur in the heating roll 72.

  Further, immediately before the recording paper P enters the nip portion N, the control temperature of the surface of the heating roll 72 is controlled so as to be temporarily raised above the target temperature instead of the target temperature. ) Is resumed and the heat is taken away by the recording paper P that first passes through the nip portion N, the fixing is caused by the surface temperature of the heating roll 72 being significantly lower than the target temperature (due to insufficient temperature). There is no defect.

  As shown in FIG. 4, when the continuous printing is continued at the normal sheet passing interval time (time difference Δt at which the image formation reference signal is generated in the normal time) as shown in FIG. 60 controls the energization of the halogen lamp 80 so that the control temperature of the surface of the heating roll 72 becomes the target temperature.

  Further, as shown in FIG. 5, even if a predetermined time H elapses after the control temperature of the surface of the heating roll 72 is controlled to be lower than the target temperature, an image formation reference signal is not generated. In this case, that is, when the control unit 60 does not recognize that the passing of the recording paper P is resumed (arrow R3 position), the control unit 60 determines that the surface temperature (control temperature) of the heating roll 72 is the target temperature or The energization of the halogen lamp 80 is controlled so that the temperature is higher than the target temperature (FIG. 5 shows an example of returning to the target temperature).

  Then, when the image forming unit 14 forms an image again, an image forming reference signal is generated, and the control unit 60 recognizes that the recording paper P is resumed based on the image forming reference signal. (Arrow R2 position), the control unit 60 (calculation means 61) has a control temperature (target temperature or target temperature) of the surface of the heating roll 72 at a timing immediately before the recording paper P enters the nip portion N. The energization of the halogen lamp 80 is controlled so as to rise once more (than a higher temperature).

  Therefore, also in this case, overshoot does not occur in the heating roll 72. Then, when printing (conveyance) is resumed and heat is first taken away by the recording paper P that passes through the nip portion N, the surface temperature of the heating roll 72 is greatly reduced below the target temperature ( Fixing failure (due to insufficient temperature) does not occur.

  As shown in FIG. 5, when continuous printing is continued at a normal sheet passing interval time (a time difference Δt at which an image formation reference signal is generated in the normal time), as described above, Similarly, the control unit 60 controls energization to the halogen lamp 80 so that the control temperature of the surface of the heating roll 72 becomes the target temperature.

  The image forming apparatus 10 according to the present embodiment has been described with reference to the drawings. However, the image forming apparatus 10 according to the present embodiment is not limited to the illustrated one, and various modifications, changes, and improvements can be made. Is possible. For example, the heating source may be provided on the fixing belt 74 side or may be provided outside the heating roll 72.

  Further, the sheet passing interval time is not limited to an aspect calculated based on the time difference at which the image formation reference signal is generated. For example, by a sensor (detection unit) (not shown) provided in the sheet conveyance path 50, A configuration may be adopted in which the conveyance of the recording paper P is directly detected.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming part 14 Image forming unit (an example of image forming means)
60 Control Unit 61 Calculation Unit 70 Fixing Device 72 Heating Roll (Example of Fixing Member)
74 Fixing belt (an example of a fixing member)
80 Halogen lamp (an example of a heating source)
P Recording paper (an example of a recording medium)

Claims (4)

An image forming unit including an image forming unit that forms an image to be transferred to a recording medium to be conveyed;
The image forming unit is disposed downstream of the image forming unit in the conveyance direction of the recording medium, and at least one of the recording medium is heated by a heating source and rotates in a state of being pressed against each other while nipping and conveying the recording medium. A pair of fixing members for fixing the image formed by the forming means to the recording medium;
A calculation unit that calculates a conveyance interval time serving as a reference of the recording medium continuously conveyed based on an image formation reference signal generated by forming an image by the image forming unit; A control unit that controls to lower the temperature of the heating source when the image formation reference signal is not generated within the conveyance interval time,
An image forming apparatus comprising: The controller is
2. The control according to claim 1, wherein when the image forming reference signal is generated after controlling to lower the temperature of the heating source, the temperature of the heating source is controlled to be temporarily raised above a target temperature. The image forming apparatus described in 1. The controller is
After the control to lower the temperature of the heating source, if the image formation reference signal is not generated even after a predetermined time has elapsed, the temperature of the heating source is set to a target temperature or a target temperature. 2. The image forming apparatus according to claim 1, wherein control is performed to raise the temperature to a high temperature, and when the image formation reference signal is generated thereafter, the temperature of the heating source is controlled to be raised once. .   The calculating means calculates the reference transport interval time by calculating a maximum value or an average value of the transport interval time of the recording medium that is continuously transported in a preset number of sheets. The image forming apparatus according to any one of claims 1 to 3.

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