JP2007058119A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus which prevents poor fixing to be able to form a satisfactory image by quickly and accurately detecting a recording medium, which has been wound around a heat roll and not removed. <P>SOLUTION: The image forming apparatus includes a heater lamp 100A for locally heating a paper passage area 47A of a heat roll 46, a heater lamp 100B for locally heating the outside 47B of the paper passage area, a temperature sensor 102A for measuring the temperature of the paper passage area 47A in association with the heater lamp 100A, and a temperature sensor 102B for measuring a temperature of the outside 47B of the paper passage area, in association with the heater lamp 100B. The apparatus determines whether a paper (pre-print paper P) is abnormally wound around the heat roller 46, on the basis of a gradient difference of temperature rise between parts heated by the heater lamps 100A and 100B. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly, to an electrophotographic image forming apparatus that forms an image by passing a recording medium on which a toner image is transferred between a heating roll and a pressure roll to perform fixing processing. .

  In an electrophotographic image forming apparatus, when a sheet on which a toner image has been transferred is fixed between the heating roll and the pressure roll facing each other, the sheet may be wound around the heating roll.

  In order to prevent paper wrapping with such a heating roll, various paper peeling means have been devised and put into practical use. However, the wrapping phenomenon inevitably occurs depending on the conditions of printing content, paper type, etc. In this case, the wound paper may burn and generate a strange odor.

  In addition, since the paper once wound on the heating roll rises to almost the same temperature as the heating roll after a certain period of time, for example, if the presence or absence of the winding paper is only monitored by the temperature sensor, the winding paper is determined by the user. Printing may be resumed even if it is not removed. If the fixing process is performed while the paper is wound around the heating roll, fixing failure occurs and image smearing occurs.

On the other hand, a temperature value is calculated based on each detected temperature outside the paper passing area (paper passing area) and outside the area (outside the paper passing area) in the heating roll (fixing roll), and the temperature value and the reference temperature value are calculated. There is a technique for determining the occurrence of paper wrapping on a heating roll by comparison (see, for example, Patent Document 1). In addition, there is a technique for judging that there is no paper wound around the heating roll by temporarily stopping heating of the heating roll after occurrence of paper winding and measuring a temperature gradient when the temperature is increased by reheating. Yes (see, for example, Patent Document 2).
JP 2002-156868 A JP-A-6-89067

  However, since the technique of Patent Document 1 described above simply detects the sheet passing area and the temperature outside the area, for example, used paper that becomes equal to the roll temperature in a very short time after winding. With (backing paper), etc., there is a problem that the presence or absence of the wrapping paper cannot be accurately detected.

  Further, in the technique of Patent Document 2, since the remaining of the wound paper is judged from the temperature gradient when the heating of the heating roll is temporarily stopped and reheated, it takes time for the judgment. There is a problem that it takes time to reach a predetermined temperature and resume printing.

  In consideration of the above-described facts, the present invention provides an image forming apparatus that can quickly and accurately detect a recording medium that has not been removed by being wound around a heating roll, thereby preventing poor fixing and forming a good image. The task is to do.

  In order to achieve the above object, the invention described in claim 1 is provided with a heating roll provided with a heat source therein and a pressure roll pressed against the heating roll, and a toner image is transferred thereto. In the image forming apparatus for forming an image by passing the recording medium between the heating roll and the pressure roll and fixing the image, first heating for locally heating a passage area of the recording medium on the surface of the heating roll Means and at least one of the first cooling means for locally cooling, and at least one of the first heating means and the first cooling means, and measures the temperature of the passage region. At least one of a first temperature measuring unit, a second heating unit that locally heats the outside of the recording medium passage area on the surface of the heating roll, and a second cooling unit that locally cools, First A second temperature measuring unit that is provided corresponding to at least one of the heating unit and the second cooling unit, and that measures a temperature outside the passage region; the first temperature measuring unit and the second temperature; Based on the temperature difference of each temperature measured by the measuring means, the abnormality determining means for determining whether there is a winding abnormality of the recording medium around the heating roll, and the determination result by the abnormality determining means is notified. And notifying means.

  In the present invention, in the configuration in which the first and second heating units are provided, for example, in a printing operation (image forming operation) by the image forming apparatus, a jam including winding of the recording medium around the heating roll occurs and the operation is stopped. In this case, when the jam removal operation is performed by the user, before the printing is resumed, the passage area of the recording medium on the surface of the heating roll is locally heated by the first heating unit, for example, for a very short time. By the heating means 2, the outside of the recording medium passage area on the surface of the heating roll is locally heated, for example, for a very short time.

  Here, when the recording medium wound around the heating roll is correctly removed by the user, the heating location in the passage area of the recording medium and the heating spot outside the passage area rise in temperature almost equally, so the first temperature The gradient (temperature rise curve) of the temperature rise at the heating location in the passage area measured by the measurement means is substantially equal to the gradient of the temperature rise at the heating location outside the passage area measured by the second temperature measurement means. Thus, when there is almost no difference in the rising gradient of each temperature, the abnormality determining means determines that the recording medium wound around the heating roll has been removed. Then, the notification means notifies the determination result, that is, a message indicating that the winding abnormality of the recording medium with respect to the heating roll has been resolved. Upon receiving this notification, the user recognizes that the image forming apparatus operates normally and resumes printing.

  In addition, when the recording medium wound around the heating roll is not removed, the heating area in the passing area where the recording medium remains (the heating area of the recording medium) is more heated than the heating area outside the passing area (on the surface of the heating roll). The temperature rise gradient is less than that of the heating point), so that the temperature rise gradient of the heating point in the passing region measured by the first temperature measuring means and the outside of the passing region measured by the second temperature measuring means There is a difference in the temperature rise gradient at the heating location. Thus, when there is a difference in the rising gradient of each temperature, the abnormality determination unit determines that the recording medium wound around the heating roll has not been removed. Also, due to the temperature difference between the passing area (recording medium) and the outside of the passing area (roll surface), such as used paper that becomes equivalent to the roll temperature in a very short time after being wound around the heating roll. Even when it is difficult to detect the recording medium, the heating roll and the recording medium can be discriminated because there is a difference in the temperature rise gradient (temperature rise curve) at each heating location.

  The determination result by the abnormality determination unit, that is, an error message indicating that the winding abnormality of the recording medium with respect to the heating roll has not been eliminated is notified by the notification unit. Upon receiving this notification, the user carefully checks whether or not the recording medium is wound around the heating roll, whereby the wound recording medium is found by the user and reliably removed.

  After the removal of the recording medium, as described above, there is almost no difference in the rising gradient of each temperature measured by the first temperature measuring means and the second temperature measuring means, and the abnormality determining means It is determined that the recording medium wound around the heating roll has been removed, and the determination result is notified by the notification means. When the user resumes printing upon receiving this notification, a good image without fixing failure is obtained.

  On the other hand, in the configuration in which the first and second cooling units are provided, the recording medium on the surface of the heating roll is removed by the first cooling unit before the jam is cleared by the user and printing is resumed. The passing area is locally cooled, for example, for a very short time, and the second cooling means locally cools the outside of the recording medium on the surface of the heating roll, for example, for a very short time.

  Here, when the recording medium wound around the heating roll is correctly removed by the user, the cooling section in the passage area of the recording medium and the cooling section outside the passage area drop in temperature approximately equally, so the first temperature The temperature decrease gradient (temperature decrease curve) of the cooling part in the passing region measured by the measuring means is substantially equal to the temperature decrease gradient of the cooling part outside the passing region measured by the second temperature measuring means. As described above, when there is almost no difference in the temperature decrease gradient, the abnormality determination unit determines that the recording medium wound around the heating roll has been removed, and the determination result (the recording medium winding abnormality with respect to the heating roll is resolved). Is notified by the notification means.

  In addition, when the recording medium wound around the heating roll is not removed, the temperature of the cooling section outside the passing area (heating roll surface) is higher than the cooling section of the passing area (recording medium) where the recording medium remains. Since the gradient of the decrease becomes gentle, the gradient of the temperature drop of the cooling part in the passing region measured by the first temperature measuring means and the temperature drop of the cooling part outside the passing region measured by the second temperature measuring means There is a difference in slope. As described above, when there is a difference between the temperature decrease gradients, the abnormality determination unit determines that the recording medium wound around the heating roll has not been removed. In addition, even for used paper that is difficult to detect due to the temperature difference between the passing area (recording medium) and outside the passing area (roll surface), there is a difference in the temperature drop gradient (temperature drop curve) at each cooling point. By exiting, the heating roll and the recording medium can be discriminated also in this case.

  The determination result by the abnormality determination means (that the winding abnormality of the recording medium with respect to the heating roll has not been eliminated) is notified by the notification means, whereby the user reconfirms the presence or absence of the recording medium wound around the heating roll. , Surely removed after discovery.

  After the winding recording medium is removed, as described above, there is almost no difference in the temperature decrease gradient measured by the first temperature measuring means and the second temperature measuring means. It is determined that the recording medium wound around is removed, and the determination result is notified by the notification means. When printing is resumed in response to this notification, a good image without fixing failure is obtained.

  In addition, the first heating unit and the first cooling unit are provided as one set, and the passage area of the recording medium on the surface of the heating roll is locally heated and cooled, and the second heating unit and the second heating unit are heated and cooled. The cooling means may be provided as one set and configured to locally heat and cool the outside of the recording medium passage area on the surface of the heating roll.

  For example, when the cooling means is arranged on the downstream side in the rotation direction of the heating roll with respect to the heating means, the cooling can be performed after locally heating the outside of the passing area / passing area, and the upstream side. When it arrange | positions, it can heat after cooling.

  As a result, the distinction between the heating roll and the recording medium can be determined from both the temperature increase gradient and the temperature decrease gradient (curve that decreases after the temperature increase or curve that increases after the temperature decrease). The detection accuracy of the medium can be improved.

  In this way, by locally heating / cooling the passing area / outside the passing area, it is possible to accurately detect the presence or absence of the winding recording medium on the heating roll, and the roll temperature is equivalent to the roll temperature in a very short time after winding. Even if it is a used paper or the like that would become an error, the presence or absence thereof can be accurately detected. Further, unlike the prior art, since heating of the heating roll is not temporarily stopped and reheated, the time required for detection determination of the recording medium and the time until printing can be resumed are reduced. Therefore, the recording medium that is wound around the heating roll and not removed is detected quickly and accurately, so that fixing failure is prevented, and good image formation without image contamination due to fixing failure is possible.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the length of the recording medium is longer or shorter than the circumferential length of the heating roll, the heating by the first heating means or the Cooling by the first cooling unit is not performed, and the abnormality determination unit winds the recording medium around the heating roll based on the temperature change in the circumferential direction of the rotating heating roll measured by the first temperature measuring unit. It is characterized by determining the presence or absence of abnormality.

  According to a third aspect of the present invention, there is provided a heating roll provided with a heat source therein, and a pressure roll that is in pressure contact with the heating roll, and a recording medium on which a toner image is transferred is the heating roll. In the image forming apparatus for forming an image by passing between the pressure rolls and fixing, temperature measuring means for measuring the temperature of the passage area of the recording medium on the surface of the heating roll, and the length of the recording medium When the circumference of the heating roll is longer or shorter than the circumference of the heating roll, the presence / absence of winding abnormality of the recording medium around the heating roll is determined based on the temperature change in the circumferential direction of the rotating heating roll measured by the temperature measuring means. It has an abnormality determining means and a notifying means for notifying the determination result by the abnormality determining means.

  According to the second and third aspects of the present invention, when the length of the recording medium is longer or shorter than the circumferential length of the heating roll, a jam including winding of the recording medium around the heating roll occurs, and the jam by the user occurs. Before the printing is resumed after the elimination operation is performed, the temperature of the passage region of the recording medium on the surface of the rotating heating roll is measured by the first temperature measuring unit or the temperature measuring unit.

  Here, when the recording medium wound around the heating roll is correctly removed by the user, there is almost no temperature change in the circumferential direction of the rotating heating roll, and the temperature becomes substantially constant.

  As described above, when there is almost no temperature change in the circumferential direction of the rotating heating roll, the abnormality determining unit determines that the recording medium wound around the heating roll has been removed, and the determination result (an abnormal winding of the recording medium on the heating roll). Is notified by the notification means.

  Further, if the recording medium wound around the heating roll is not removed, the recording medium is warmed by the heating roll, but if the length is longer than the circumference of the heating roll, both ends in the length direction of the recording medium Since the portions overlap each other, the temperature at the overlapping portion is lower than that at the other portions (the temperature rise is delayed), so that the low temperature portion appears at a constant cycle in the temperature in the circumferential direction of the rotating heating roll.

  On the other hand, when the length of the recording medium is shorter than the circumferential length of the heating roll, a gap is formed at both ends in the length direction of the recording medium, and the surface of the heating roll is exposed in the gap portion than the recording medium. Since temperature becomes high, a high temperature part appears with a fixed period in the temperature in the circumferential direction of the rotating heating roll.

  Here, when the low temperature part or the high temperature part is detected, the abnormality determination unit determines that the recording medium wound around the heating roll has not been removed.

  The determination result by the abnormality determination means (that the winding abnormality of the recording medium with respect to the heating roll has not been eliminated) is notified by the notification means, whereby the user reconfirms the presence or absence of the recording medium wound around the heating roll. , Surely removed after discovery.

  After the winding recording medium is removed, as described above, the temperature measured by the first temperature measuring means or the temperature measuring means does not appear to be a periodic change and becomes almost constant, and the abnormality determining means winds around the heating roll. It is determined that the recording medium has been removed, and the determination result is notified by the notification means. When printing is resumed in response to this notification, a good image without fixing failure is obtained.

  As described above, for a recording medium having a length longer or shorter than the circumference of the heating roll, it is detected whether the winding recording medium has been removed by rotating the heating roll and measuring the roll surface temperature. Therefore, the wrapping recording medium can be detected quickly.

  According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the second or third aspect, further comprising recording medium detecting means for detecting a recording medium wound around the heating roll, wherein the length of the recording medium is the heating roll. And when the wound recording medium is detected by the recording medium detecting means, the recording medium to be fixed next to the recording medium is accelerated to wind the recording medium in the middle of winding. It is characterized by being wound around a heating roll while being sandwiched between the heating rolls.

  According to the fourth aspect of the present invention, when a recording medium having a shorter length than the circumference of the heating roll is wound around the heating roll, the winding recording medium is detected by the recording medium detecting means, so that the recording medium is detected. Next, the recording medium to be fixed is accelerated, and the leading end of the recording medium is sandwiched between the rear part of the recording medium in the middle of winding and the heating roll. Wound around a roll.

  Thereby, even if the recording medium has a shorter length than the circumference of the heating roll, an overlapping portion of the recording medium can be formed, and the surface of the heating roll as in the inventions of claims 2 and 3. When the temperature change in the circumferential direction is monitored to detect the recording medium, it can be detected more reliably.

  In particular, in a recording medium having a length shorter than the circumference of the heating roll, it is recorded that the surface of the heating roll is exposed when the user opens the image forming apparatus and confirms the heating roll. It may be recognized that there is no medium and the device may be blocked as it is. However, here, it is easy to find the recording medium when the heating roll is confirmed, and it is possible to prevent the recording medium from being left unattended.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the invention, the recording medium detecting unit is disposed opposite to the surface of the heating roll by a predetermined distance and is provided with a protrusion on the outer peripheral surface. And a rotation detecting means for detecting the recording medium by rotating the rotating member when the projection is pushed on the tip of the wound recording medium.

  According to the fifth aspect of the present invention, the tip of the recording medium wound around the heating roll comes into contact with the protrusion provided on the outer peripheral surface of the rotating member provided in the rotation detecting means, and the rotating member rotates as it is pushed against the tip of the recording medium. By doing so, the recording medium is detected.

  With the rotation detection means provided with such a rotating member, the recording medium wound around the heating roll can be quickly detected.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the heating roll is disposed opposite to the surface of the heating roll by a predetermined distance, and a protrusion is provided on the outer peripheral surface so as to rotate in a direction opposite to the heating roll. It has a rotary peeling member that is driven and hooks the tip of the wound recording medium on the projection to peel it from the heating roll.

  The invention according to claim 7 comprises: a heating roll provided with a heat source therein; and a pressure roll that is pressed against and opposed to the heating roll, and the recording medium on which the toner image is transferred is said heating roll. In an image forming apparatus that forms an image by passing between the pressure rolls and fixing the image, the face is spaced apart from the surface of the heating roll by a predetermined distance, and is provided with protrusions on the outer peripheral surface, which is opposite to the heating roll. And a rotary peeling member that is driven to rotate in the direction and that peels off the heating roll by hooking the leading end of the recording medium wound around the heating roll to the protrusion.

  In the invention according to claim 6 and claim 7, the tip of the recording medium wound around the heating roll is hooked on the protrusion provided on the outer peripheral surface of the rotary peeling member that rotates in the direction opposite to the heating roll, and the heating roll Is peeled off and jammed. If it is such a rotation peeling member, peelability will be improved with respect to the peeling nail etc. which were fixedly provided, for example.

  In this way, the recording medium wound around the heating roll is peeled off, so that the burning of the recording medium can be suppressed. Further, by jamming the recording medium, when the user opens the image forming apparatus and confirms the heating roll, the possibility that the recording medium is overlooked is reduced, and the effect of preventing the recording medium from being left is enhanced.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the fifth to seventh aspects, an interval is maintained to keep a distance between the rotating member or the rotating peeling member and the heating roll substantially constant. It has the means.

  In the invention according to claim 8, for example, even when the surface of the heating roll is uneven due to a manufacturing error or the roll is eccentric, the spacing member holds the rotating member or the rotating peeling member. The interval between the heating rolls is kept substantially constant. This prevents the rotating member or the rotating peeling member from coming into contact with the roll surface and scratching the roll surface, or being separated from the roll surface more than necessary to prevent the wound recording medium from slipping through the rotating member or the rotating peeling member. In addition, the detection accuracy or peelability of the wound recording medium can be improved.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the interval holding means is arranged coaxially with the rotary member or the rotary peeling member and has a larger diameter than those, and The rotating rolls can be rotated independently from each other and are in contact with the outside of the recording medium passage area on the surface of the heating roll.

  In the ninth aspect of the present invention, the rotating roll that is coaxially disposed with the rotating member or the rotating peeling member and has a larger diameter than that of the rotating member or the rotating peeling member and is rotatable independently of the rotating member is a heating roll. By contacting the outside of the recording medium passage area on the surface of the recording medium, the distance between the rotating member or the rotating peeling member and the heating roll is kept substantially constant. With such a rotating roll, it is possible to realize an interval holding means that can maintain an interval substantially constant with high accuracy with a simple configuration.

  According to the image forming apparatus of the present invention, it is possible to quickly and accurately detect a recording medium that is wound around a heating roll and is not removed, thereby preventing a fixing failure and forming a good image.

  An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, an image forming apparatus 10 according to this embodiment is a color laser printer using an electrophotographic method, and performs so-called + N color printing in which N colors are added to black and no overcoating is performed. The image forming apparatus 10 is provided with a display unit 62 such as a liquid crystal display panel on the upper surface. Inside the image forming apparatus 10, a paper feed cassette 20 loaded with a preprinted paper P, which is a recording medium of the present embodiment, is provided. An image forming unit 14 for forming a desired image on the print paper P, a fixing device 12 for fixing the image formed on the preprint paper P, and a transport roll 18 for transporting the preprint paper P are provided. And a control unit 80 that controls the operation of the entire image forming apparatus 10 is provided.

  In this image forming apparatus 10, first, a toner image is formed on the photosensitive belt 16 by the image forming unit 14, and this toner image is transported from the paper feed cassette 20 to the transfer unit 22 by the transport roll 18. Transferred to P. Then, the preprint paper P to which the toner image has been transferred is pressurized and heated by the fixing device 12 on the downstream side in the transport direction of the transfer unit 22 to fix the toner image on the preprint paper P. 26 is discharged. When images are formed on both the front and back sides of the preprinted paper P, the preprinted paper P with the toner image fixed on the front and back surfaces is switched by switching the transport path downstream in the transport direction of the fixing device 12. It is conveyed to the back surface conveyance path 28 for reversing. Then, the preprinted paper P with the front and back reversed is transported to the upstream side in the transport direction of the transfer unit 22 by the transport belt 29, transported again to the transfer unit 22 by the transport roll 18, and the toner image from the photoreceptor belt 16 to the back surface. Is transcribed. Then, the preprinted paper P passes through the fixing device 12, the toner image is fixed on the back surface, and is discharged to the stacker 26 by the paper discharge roll 24.

  The image forming unit 14 includes a belt driving device 60. The belt driving device 60 includes a photosensitive belt 16 that is an endless belt, a driving roll 32 on which the photosensitive belt 16 is rotatably stretched, and a driven roll 34. The drive roll 32 is disposed along the conveyance path 30 extending in the up-down direction, the driven roll 34 is disposed in the horizontal direction of the drive roll 32, and the photosensitive belt 16 is stretched in the horizontal direction. ing.

  In the image forming unit 14, a plurality of print engines 36 for forming toner images of different colors such as red and black on the surface of the photoreceptor belt 16 are arranged along the lower flat surface 16B. Each print engine 36 includes a charger 37, an exposure head 38, and a developing device 39 that are sequentially arranged in the rotation direction of the photosensitive belt 16 (the direction of arrow A in the figure). The charger 37 uniformly charges the photosensitive belt 16 with a charging corotron, a charging roll, or the like. Further, the exposure head 38 exposes the charged surface of the photosensitive belt 16 with an LED array, an optical scanning device (Raster Optical Scanner), or the like to form an electrostatic latent image on the photosensitive belt 16 based on image data. . The developing device 39 contains a one-component developer made of toner or a two-component developer made of toner or carrier, and transports the developer to the developing roll 39A while stirring the developer in the developing device 39. The developing device 39 applies a developing bias to the developing roll 39A, and moves the toner from the developing roll 39A onto the electrostatic latent image on the photosensitive belt 16. As a result, the electrostatic latent image on the photoreceptor belt 16 is visualized with toner. Here, the toner of each color is not superimposed on the same dot, and each dot is formed with the toner of each color.

  A transfer corotron 42 is disposed facing the photoreceptor belt 16 with the conveyance path interposed therebetween. The transfer corotron 42 discharges toward the back surface of the preprinted paper P and gives a charge opposite in polarity to the toner charge in a non-contact manner on the back surface of the preprinted paper P to preprint the toner image on the photoreceptor belt 16. Transfer to paper P.

  A cleaning mechanism 44 including a cleaning blade 100 and a blade bracket for holding the cleaning blade 100 is disposed facing the flat surface 16A on the upper side of the photosensitive belt 16. The cleaning mechanism 44 removes untransferred residual toner remaining on the photosensitive belt 16 without being transferred to the preprinted paper P by the transfer unit 22 from the photosensitive belt 16.

  The fixing device 12 disposed on the downstream side in the transport direction of the transfer unit 22 is in contact with the heat roll 46 that rotates in contact with the transfer surface of the preprint paper P, and press-contacts the heat roll 46 between the preprint paper P. The pressure roll 48 rotates in contact with the back surface of the preprinted paper P, and a fixing nip N is formed by the heat roll 46 and the pressure roll 48. A heater lamp 50 such as a halogen lamp is disposed inside the heat roll 46, and the surface of the heat roll 46 is heated. Therefore, when the preprinted paper P to which the toner image is transferred passes through the fixing nip N, the preprinted paper P is heated and pressurized, and the toner on the preprinted paper P is melted to form the preprinted paper P. It is fixed.

  Here, the fixing device 12 is provided with a release agent supply device 13. The release agent supply device 13 includes a donor roll 52 that is in contact with the surface of the heat roll 46, a tank 54 that stores a release agent such as silicon oil, a sponge and the like in the release roll in the donor roll 52 and the tank 54. And a metering roll 56 in contact with each other through the absorber.

  A metering blade (not shown) is in contact with the surface of the metering roll 56. The metalling blade contacts the surface of the metalling roll 56 with a predetermined pressure, and regulates (measures) the release agent on the surface of the metalling roll 56 to a predetermined thickness with micron order accuracy.

  A release agent having a predetermined thickness on the surface of the metalling roll 56 is conveyed to the surface of the heat roll 46 by the donor roll 52, and a layer of the release agent having a predetermined thickness is formed on the surface of the heat roll 46. Is formed. As a result, the releasability of the toner on the preprinted paper P from the surface of the heat roll 46 in the fixing nip N is improved, so that fixing failure and toner fixing offset can be prevented.

  In addition, as described above, depending on the printing content, the paper type, and the like, the paper may be wound around the heat roll 46. Regarding the configuration for preventing paper scorching and fixing failure when the wrapped paper is left unattended. It will be described later.

  A purge tray 27 is disposed on the downstream side of the fixing device 12 in the conveyance direction, and some trouble occurs during the conveyance, an appropriate printing process cannot be performed, and the unnecessary preprint paper P is discharged. Loaded.

  As shown in FIG. 2, the control unit 80 drives the display unit 62, the image forming unit 14, the fixing device 12, the belt driving device 60 that drives the photosensitive belt 16, and the paper conveyance system. A transport system driving unit 78 is connected. The control unit 80 sends control signals to these units to control the overall operation of the image forming apparatus 10.

(First embodiment)
Next, the fixing device 12 according to the first embodiment of the present invention will be described.

  As shown in FIGS. 3A and 3B, the fixing device 12 includes a sheet on the surface (outer peripheral surface) 47 of the heat roll 46 that is located downstream from the fixing nip N in the rotation direction of the heat roll 46. A heater lamp 100A that locally heats the passage region 47A and a heater lamp 100B that locally heats the outside 47B of the paper roll region on the surface 47 of the heat roll 46 are provided. The two heater lamps 100A and 100B are both composed of a halogen lamp or the like.

  A temperature sensor 102A for measuring the temperature of the paper passage area 47A is provided corresponding to the heater lamp 100A further downstream of the heater lamps 100A and 100B in the rotation direction of the heat roll 46. Correspondingly, a temperature sensor 102B for measuring the temperature outside the paper passage area 47B is provided. Both of these two temperature sensors 102A and 102B are constituted by a non-contact type radiation thermometer or the like.

  The heater lamps 100A and 100B and the temperature sensors 102A and 102B are connected to the control unit 80. The heater lamps 100A and 100B have their heating timing and heating temperature controlled by the control unit 80, and the temperature sensor 102A. , 102B outputs the measured temperature of the surface 47 of the heat roll 46 (paper passage area 47A / outside paper passage area 47B) to the control unit 80 as temperature data based on electrical signals.

  Next, in the printing operation (image forming operation) by the image forming apparatus 10, when a sheet (preprint sheet P) is wound around the heat roll 46, a series of operations from the sheet winding to recovery is shown in the flowchart of FIG. It explains using.

  As shown in FIG. 4, when printing by the image forming apparatus 10 is started (step 110) and a paper jam occurs in the paper conveyance system, including paper winding around the heat roll 46 in the fixing process (step 112), Printing is paused and an error message notifying that a jam has occurred is displayed on the display unit 62 (step 114).

  Here, when a predetermined opening / closing panel of the image forming apparatus 10 is opened by the user and a jam clearing operation is performed to close the opening / closing panel (step 116), the control unit 80 that has detected the opening / closing panel closes the heater lamp 100A. , 100B is controlled, and the heating operation is performed at the same temperature for the same time (for example, several seconds). As a result, the sheet passage area 47A and the sheet passage area outside 47B are locally heated under the same conditions (step 118), and the control unit 80 fixes the fixing device so that these heating points are located in the vicinity of the temperature sensors 102A and 102B. 12 drive motors are controlled to rotate the heat roll 46 by a predetermined angle. As a result, the temperature of the heating location in the paper passage area 47A on the surface of the heat roll 46 is measured by the temperature sensor 102A, the temperature of the heating location outside the paper passage area 47B is measured by the temperature sensor 102B, and each temperature data is controlled. Input to the unit 80 (step 120). Then, the control unit 80 monitors the temperature rise gradient (temperature rise curve) for a predetermined time for each measured temperature.

  Here, when the paper (pre-printed paper P) wound around the heat roll 46 is correctly removed by the user, the heating place in the paper passage area 47A and the heating place outside the paper passage area 47B rise in temperature almost equally. For this reason, the gradient of the temperature rise at the heating point in the paper passage area 47A measured by the temperature sensor 102A and the gradient of the temperature rise at the heating spot outside the paper passage area 47B measured by the temperature sensor 102B are substantially equal.

  Thus, when there is almost no difference in the rising gradient of each temperature, the control unit 80 determines that the paper wound around the heat roll 46 has been removed (No determination in step 122). Then, a message indicating that the paper winding abnormality with respect to the heat roll 46 has been resolved is displayed on the display unit 62, or an error indicating that the paper winding abnormality displayed on the display unit 62 has occurred. By deleting the message, it is notified that the winding abnormality has been resolved (step 124). Upon receiving this notification, the user recognizes that the image forming apparatus 10 operates normally and resumes printing (step 126).

  In addition, if the user overlooks and does not remove the paper wound around the heat roll 46, the heating location (paper heating location) in the paper passage area 47A where the paper remains is heated outside the paper passage area 47B. Since the temperature increase gradient becomes gentler than the position (the heating position on the surface of the heat roll 46), the temperature increase gradient of the heating position of the paper passage area 47A measured by the temperature sensor 102A and the paper measured by the temperature sensor 102B are measured. There is a difference between the temperature rise gradient of the heated portion 47B outside the passage region. Thus, when there is a difference in the rising gradient of each temperature, the control unit 80 determines that the paper wound around the heat roll 46 has not been removed (Yes determination in step 122). Further, like used paper that becomes equivalent to the roll temperature in a very short time after being wound around the heat roll 46, the paper passage area 47A (paper) and the outside of the paper passage area 47B (roll surface) Even when it is difficult to detect the paper due to the temperature difference, the temperature rise gradient (temperature rise curve) at each heating point is different, so that the heat roll 46 and the paper can be discriminated.

  As a result of the determination by the control unit 80, that is, an error message indicating that the paper winding abnormality with respect to the heat roll 46 has not been eliminated is displayed on the display unit 62 (step 128). The user who has received the notification by the error message opens a predetermined opening / closing panel of the image forming apparatus 10 and carefully checks whether or not the sheet is wound around the heat roll 46, whereby the wound sheet is notified to the user. Discovered and reliably removed (step 116).

  After the wrapping paper is removed, the surface of the heat roll 46 is locally heated again by the heater lamps 100A and 100B (step 118), and each heating point is measured by the temperature sensors 102A and 102B (steps). 120), there is almost no difference in the rising gradient of each temperature. Thereby, the control unit 80 determines that the paper wound around the heat roll 46 has been removed (No determination in step 124), and notifies that the winding abnormality has been eliminated through the display unit 62 (step 124). When the user resumes printing by the image forming apparatus 10 in response to this notification, a print on which a good image without fixing failure is formed is output.

  As described above, in the image forming apparatus 10 according to the present embodiment, the sheet passing area 47A and the sheet passing area outside 47B on the surface 47 of the heat roll 46 are locally heated, so The presence / absence can be accurately detected, and the presence / absence of a used paper or the like that becomes equal to the roll temperature in a very short time after winding can be accurately detected. Further, unlike the prior art, heating of the heat roll 46 is not temporarily stopped and re-heated, so that the time required for paper detection determination and the time until printing can be resumed are reduced. Therefore, detection of the paper that is wound around the heat roll 46 and has not been removed is performed quickly and accurately to prevent fixing failure, and good image formation without image contamination due to fixing failure can be achieved.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  As shown in FIGS. 5A and 5B, in the fixing device according to the present embodiment, cooling is performed toward the surface 47 of the heat roll 46 instead of the heater lamps 100A and 100B described in the first embodiment. By blowing air (arrow CA), a blower unit 104A for locally cooling the paper passage area 47A and a blower unit 104B for locally cooling the outside 47B of the paper passage area are provided. The two air blowing units 104A and 104B are connected to the control unit 80, and the control unit 80 controls the temperature of the cooling air, the injection timing, and the injection amount.

  Next, in the image forming apparatus 10 of the present embodiment including the fixing device having the above-described configuration, a series of operations from winding of the paper around the heat roll 46 to recovery thereof in the printing operation will be described with reference to the flowchart of FIG.

  In steps 130 to 136 of the flowchart shown in FIG. 6, the same operations as those in steps 110 to 116 of the flowchart shown in FIG. 4 described in the first embodiment are performed.

  After the jam clearing operation by the user, the control unit 80 controls the air blowing units 104A and 104B to equalize the temperature and the injection amount of the cooling air, and the cooling air injection operation (cooling operation) for the same time (for example, several seconds). To do. As a result, the sheet passage area 47A and the sheet passage area outside 47B are locally cooled under the same conditions (step 138), and the control unit 80 fixes the fixing device so that the cooling points are positioned in the vicinity of the temperature sensors 102A and 102B. 12 drive motors are controlled to rotate the heat roll 46 by a predetermined angle. Thereby, the temperature of the cooling part in the paper passage area 47A on the surface of the heat roll 46 is measured by the temperature sensor 102A, the temperature of the cooling part outside the paper passage area 47B is measured by the temperature sensor 102B, and each temperature data is controlled. Input to unit 80 (step 140). Then, the control unit 80 monitors a temperature decrease gradient (temperature decrease curve) for a predetermined time for each measured temperature.

  Here, when the paper (preprint paper P) wound around the heat roll 46 is correctly removed by the user, the cooling point in the paper passage region 47A and the cooling point outside the paper passage region 47B are approximately equal in temperature drop. Therefore, the gradient of the temperature drop at the cooling point in the paper passage area 47A measured by the temperature sensor 102A and the gradient of the temperature drop at the cooling point outside the paper passage area 47B measured by the temperature sensor 102B are substantially equal.

  As described above, when there is almost no difference in the temperature decrease gradient, the control unit 80 determines that the paper wound around the heat roll 46 has been removed (No determination in step 142). Then, it is notified through the display unit 62 that the paper winding abnormality in the heat roll 46 has been resolved (step 144), and printing can be resumed (step 146).

  Further, when the paper wound around the heat roll 46 remains, the cooling location outside the paper passage region 47B (cooling location on the surface of the heat roll 46) is the cooling location (paper cooling location) in the paper passage region 47A. Therefore, the gradient of the temperature drop at the cooling point in the paper passage region 47A measured by the temperature sensor 102A and the temperature drop at the cooling point outside the paper passage region 47B measured by the temperature sensor 102B are obtained. There is a difference in the slope of As described above, when there is a difference between the temperature decrease gradients, the control unit 80 determines that the paper wound around the heat roll 46 has not been removed (Yes determination in step 142). Further, even for used paper that is difficult to detect due to a temperature difference between the paper passage area 47A (paper) and outside the paper passage area 47B (roll surface), the temperature drop gradient (temperature drop curve) at each cooling point In this case, the heat roll 46 and the paper can be discriminated.

  The determination result by the control unit 80 (that the paper winding abnormality with respect to the heat roll 46 has not been eliminated) is notified through the display unit 62 (step 148). As a result, the user reconfirms the presence or absence of the paper wound around the heat roll 46 and reliably removes it after discovery (step 136).

  Then, after the removal of the wrapping paper, the surface of the heat roll 46 is locally cooled again by the blower units 104A and 104B (step 138), and each cooling point is measured by the temperature sensors 102A and 102B (step 138). 140), there is almost no difference in the decreasing gradient of each temperature. Thereby, the control unit 80 determines that the paper wound around the heat roll 46 has been removed (No determination in step 142), and notifies that the winding abnormality has been eliminated through the display unit 62 (step 144). When the user receives the notification and resumes printing by the image forming apparatus 10 (step 146), a print on which a good image without fixing failure is formed is output.

  As described above, even in the configuration of the present embodiment in which the sheet passage area 47A and the sheet passage area outside 47B on the surface 47 of the heat roll 46 are locally cooled, it is possible to accurately detect the presence or absence of the wrapping paper around the heat roll 46. As a result, it is possible to accurately detect the presence or absence of used paper or the like. In addition, as in the first embodiment, the time required for paper detection determination and the time required to resume printing are reduced. Therefore, according to the present embodiment, the detection of the paper that has not been removed by being wound around the heat roll 46 is performed quickly and accurately, and fixing failure is prevented. Is possible.

(Third embodiment)
Next, a third embodiment of the present invention will be described.

  As shown in FIGS. 7A and 7B, in the fixing device according to the present embodiment, the heater lamp 100 </ b> A described in the first embodiment and the second corresponding to the paper passage region 47 </ b> A of the heat roll 46. The blower unit 104A described in the embodiment is provided as a set, and the heater lamp 100B and the blower unit 104B are also provided as a set corresponding to the outside 47B of the heat roll 46 in the sheet passage area. ing. In addition, here, the air blowing units 104A and 104B are arranged on the upstream side in the rotation direction of the heat roll 46 with respect to the heater lamps 100A and 100B, whereby the paper passage area 47A / outside the paper passage area 47B are localized. It is configured to be heated after being cooled.

  Next, in the image forming apparatus 10 of the present embodiment including the fixing device having the above-described configuration, a series of operations from winding of the paper around the heat roll 46 to recovery thereof in the printing operation will be described with reference to the flowchart of FIG.

  In steps 150 to 156 of the flowchart shown in FIG. 8, the same operations as steps 110 to 116 of the flowchart shown in FIG. 4 described in the first embodiment are performed.

  After the user clears the jam, the control unit 80 operates the air blowing units 104A and 104B to locally cool the surface 47 of the heat roll 46 (paper passage area 47A / outside passage area 47B). The heater lamps 100A and 100B are operated to locally heat the cooling part (step 158). Subsequently, the temperature of each portion heated once after being cooled in this way is measured by the temperature sensors 102A and 102B (step 160), and the difference in the curve that rises after the temperature of the paper passage area 47A and the outside of the passage area 47B decreases. From this, the presence or absence of the wrapping paper with respect to the heat roll 46 is determined (step 162). In steps 164 to 168 after this determination, the same operations as steps 124 to 128 of the flowchart shown in FIG. 4 described in the first embodiment are performed.

  As described above, in this embodiment, the winding between the heat roll 46 and the paper is determined by both the temperature decrease gradient and the temperature increase gradient (curve that increases after the temperature decrease). The paper detection accuracy can be increased.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, when a paper having a length longer or shorter than the circumferential length of the heat roll 46 is wound, the presence / absence (remaining) of the wound paper is determined by a method different from the first to third embodiments. It is something to detect.

  In the fixing device of this embodiment shown in FIGS. 9A and 10A, the heater lamps 100A and 100B, the air blowing units 104A and 104B, and the temperature sensors 102A and 102B described in the first to third embodiments. Of these, at least the temperature sensor 102A is provided.

  Next, in the image forming apparatus 10 of the present embodiment including the fixing device having the above-described configuration, a series of operations from winding of the paper around the heat roll 46 to recovery thereof in the printing operation will be described with reference to the flowchart of FIG.

  In steps 170 to 176 in the flowchart shown in FIG. 11, the same operations as those in steps 110 to 116 in the flowchart shown in FIG. 4 described in the first embodiment are performed.

  When the length of paper to be printed is longer than the circumference of the heating roll (see the preprinted paper PL in FIG. 9A) or shorter (see the preprinted paper PS in FIG. 10A), the heat roll In the present embodiment, a paper passage area described in the first to third embodiments is described before a jam including a winding of the paper around 46 occurs and the user clears the jam and resumes printing. The control unit 80 operates the fixing device drive motor to rotate the heat roll 46 at a constant speed (step 178) and does not rotate the temperature sensor 102A. The temperature of the sheet passage area 47A on the surface 47 of the heat roll 46 is measured (step 180).

  Here, when the paper wound around the heat roll 46 is correctly removed by the user, there is almost no temperature change in the circumferential direction of the rotating heat roll 46 and the temperature is almost constant.

  As described above, when there is almost no temperature change in the circumferential direction of the rotating heat roll 46, the control unit 80 determines that the paper wound around the heat roll 46 has been removed (No determination in step 182). Then, it is notified through the display section 62 that the paper winding abnormality in the heat roll 46 has been resolved (step 184), and printing can be resumed (step 186).

  If the paper wound around the heat roll 46 is not removed, the paper is heated by the heat roll 46, but the length of the paper is longer than the circumference of the heat roll 46 as shown in FIG. In this case (pre-printed paper PL), both end portions in the length direction of the paper overlap, and the temperature at the overlapping portion (C portion) is lower than that at the other portions (temperature rise is delayed). Therefore, as shown in FIG. 9B, the low temperature part LT appears at a constant cycle in the temperature in the circumferential direction of the rotating heat roll 46.

  On the other hand, as shown in FIG. 10A, when the length of the paper is shorter than the circumference of the heat roll 46 (preprint paper PS), a gap is formed at both ends in the paper length direction, In the gap portion (D portion), the surface 47 of the heat roll 46 (outside the paper passage region 47B) is exposed and the temperature becomes higher than that of the paper. Therefore, as shown in FIG. 10 (B), the high temperature part HT appears at a constant period in the temperature in the circumferential direction of the rotating heat roll 46.

  Here, when the low temperature part LT or the high temperature part HT is detected, the control unit 80 determines that the paper wound around the heat roll 46 has not been removed (Yes determination in step 182).

  The result of determination by the control unit 80 (that the paper winding abnormality with respect to the heat roll 46 has not been eliminated) is notified through the display unit 62 (step 188), whereby the user determines the paper wound around the heat roll 46. Presence / absence is reconfirmed and reliably removed after discovery (step 176).

  After the removal of the wrapping paper, the temperature of the surface of the rotating heat roll 46 is measured again by the temperature sensor 102A (steps 178 and 180). Here, no periodic change appears in the measured temperature, It becomes almost constant. Accordingly, the control unit 80 determines that the paper wound around the heat roll 46 has been removed (No determination in step 182), and notifies that the winding abnormality has been eliminated through the display unit 62 (step 184). When the user resumes printing by the image forming apparatus 10 in response to this notification (step 186), a print on which a good image without fixing failure is formed is output.

  As described above, whether or not the wrapping paper is removed by rotating the heat roll 46 and measuring the roll surface temperature for the paper having a length longer or shorter than the circumference of the heat roll 46. Therefore, the wrapping paper can be detected quickly.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. The fifth embodiment is a modification of the fourth embodiment that detects the presence (remaining) of a wound paper when a paper having a shorter length than the circumference of the heat roll 46 is wound.

  In the fixing device of this embodiment shown in FIGS. 12A and 12B, the heater lamps 100A and 100B, the air blowing units 104A and 104B described in the first to third embodiments, as in the fourth embodiment. Among the temperature sensors 102A and 102B, at least the temperature sensor 102A is provided. Further, a non-contact type wrapping paper detection sensor 106 that detects paper wrapping around the paper passage area 47A on the surface of the heat roll 46 is provided upstream of the temperature sensor 102A in the rotation direction of the heat roll 46. . The wrapping paper detection sensor 106 is connected to the control unit 80 and outputs a detection signal to the control unit 80 at the timing when the leading edge of the paper wrapping around the heat roll 46 is detected.

  Next, in the image forming apparatus 10 of the present embodiment including the fixing device having the above-described configuration, a series of operations from winding a sheet around the heat roll 46 to recovery in the printing operation will be described with reference to a flowchart of FIG.

  As shown in FIG. 13, printing by the image forming apparatus 10 is started (step 190), and in the fixing process, a paper (preprint paper P <b> 1) having a shorter length than the circumference of the heat roll 46 is wound around the heat roll 46. If this occurs (see step 192 / FIG. 12A), the wrapping paper (preprint paper PS1) is detected by the wrapping paper detection sensor 106 (step 194), the control unit 80 then fixes. The paper conveyance system 108 is driven and controlled to increase the conveyance speed for the paper to be processed (preprint paper PS2). As a result, the accelerated next paper (preprint paper PS2) is sandwiched between the rear portion of the paper (preprint paper PS1) and the heat roll 46 in the middle of winding (see FIG. 12A). ) With the rotation of the heat roll 46, the paper is wound around the heat roll 46 so as to overlap the paper that has been wound first (see step 198 / FIG. 12B). Here, printing (fixing processing) is temporarily stopped, and an error message notifying that a jam (paper winding around the heat roll 46) has occurred is displayed on the display unit 62 (step 198). Subsequently, in steps 200 to 212 in the flowchart shown in FIG. 13, the same operations as those in steps 176 to 188 in the flowchart shown in FIG. 11 described in the fourth embodiment are performed.

  As described above, in the present embodiment, it is possible to form the overlapping portion of the sheets with respect to the sheet whose length is shorter than the circumferential length of the heat roll 46, and thereby the heat described in the fourth embodiment. When detecting a sheet by monitoring a temperature change in the circumferential direction of the surface of the roll 46, it can be detected more reliably.

  In particular, for a sheet having a length shorter than the circumference of the heat roll 46, when the user opens the open / close panel of the image forming apparatus 10 and confirms the heat roll 46, the surface 47 of the heat roll 46. If it is exposed, it may be recognized that there is no paper, and the open / close panel may be closed as it is. However, here, when the heat roll 46 is confirmed, it is easy to find the wrapping paper, and the wrapping paper can be prevented from being left unattended.

(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described.

  As shown in FIG. 14, in the fixing device according to the present embodiment, a contact-type wrapping paper detection sensor 220 is provided in place of the non-contact wrapping paper detection sensor 106 described in the fifth embodiment. . The wrapping paper detection sensor 220 includes a paddle roll 222 that rotates with a light load, and a rotary encoder (not shown) that outputs the rotational displacement amount of the paddle roll 222 to the control unit 80 as an electrical pulse signal. A plurality of protrusions 224 are provided along the circumferential direction on the outer peripheral surface of the paddle roll 222, and the tip of the protrusion 224 of the paddle roll 222 extends from the surface 47 (paper passage area 47 </ b> A) of the heat roll 46. The heat roll 46 is disposed so as to be slightly separated from the heat roll 46. The paddle roll 222 may be replaced with, for example, a star wheel (star gear) provided with a plurality of teeth (projections) on the outer peripheral surface along the circumferential direction.

  As a result, in this embodiment, the leading edge of the paper (preprint paper P) wound around the heat roll 46 hits the protrusion 224 of the paddle roll 222 provided in the wound paper detection sensor 220 (see FIG. 14), and the paper is left as it is. When the paddle roll 222 is rotated by being pushed by the leading end of the sheet, a pulse signal is output from the rotary encoder to the control unit 80 to detect the paper. Even if the leading edge of the sheet passes through the protrusion 224 of the paddle roll 222, the sheet is detected by the paddle roll 222 rotating while the floating part of the sheet contacts the protrusion 224.

  By using the contact type wrapping paper detection sensor 220 provided with such a paddle roll 222, it becomes possible to quickly detect the paper wrapping around the heat roll 46.

(Seventh embodiment)
Next, a seventh embodiment of the present invention will be described.

  As shown in FIG. 15, in the fixing device according to the present embodiment, a paddle roll 230 having a plurality of protrusions 234 provided on the outer peripheral surface is provided as a rotary peeling member that peels off the paper wound around the heat roll 46. ing. The paddle roll 230 is disposed to face the surface 47 (paper passage area 47A) of the heat roll 46 slightly apart from the paddle roll 230, and is rotated by a drive motor (not shown) driven and controlled by the control unit 80. It is rotated at high speed in the opposite direction. As the drive motor, a drive motor that rotationally drives the heat roll 46 may be used to transmit the rotational driving force to the paddle roll 230 by a gear mechanism.

  In addition, the wrapping paper detection sensor 106 described in the fifth embodiment is provided in the vicinity of the upstream side in the rotation direction of the heat roll 46 with respect to the paddle roll 230.

  As a result, in the present embodiment, the leading end of the paper (preprint paper P) wound around the heat roll 46 is hooked on the protrusion 232 of the paddle roll 230 that is driven to rotate in the opposite direction to the heat roll 46, and the heat roll 46 Peeled and jammed. When the jammed paper is detected by the wrapping paper detection sensor 106, printing is temporarily stopped.

  By using such a rotary peeling member composed of the paddle roll 230, for example, peelability can be improved with respect to a peeling claw or the like provided in a fixed manner. Further, even if the paddle roll 230 is rotated with the pressing force of the paper, it is possible to detect the wrapping paper itself unlike a normal peeling claw or the like.

  In this way, by peeling the paper wound around the heat roll 46, the occurrence of scorching of the paper can be suppressed. Further, by jamming the paper, when the user opens the open / close panel of the image forming apparatus 10 and confirms the heat roll 46, the possibility of the paper being overlooked is reduced, and the effect of preventing the paper from being left is enhanced. It is done.

(Eighth embodiment)
Next, an eighth embodiment of the present invention will be described.

  As shown in FIG. 16, in the present embodiment, the paddle roll 222 of the wrapping paper detection sensor 220 described in the sixth embodiment, or the paddle roll 230 as the rotation peeling member described in the sixth embodiment, A rotating roll 240 is provided as an interval holding means for keeping the interval between the heat rolls 46 substantially constant. The rotary roll 240 is arranged coaxially with the paddle roll 222 or the paddle roll 230 via a shaft 242 and has a slightly larger diameter than them, and is rotatable independently of them. In other words, the surface 47 of the heat roll 46 is in contact with the outside 47B of the sheet passage area.

  Thereby, in this embodiment, for example, even when the surface 47 of the heat roll 46 is uneven due to a manufacturing error or the roll is eccentric, the paddle roll 222 or the paddle roll 230 is rotated by the rotating roll 240. And the space | interval of the heat roll 46 is kept substantially constant. Accordingly, the paddle roll 222 or the paddle roll 230 comes into contact with the surface 47 (paper passage area 47A) of the heat roll 46 to damage the roll surface, or is separated from the roll surface more than necessary. It is possible to prevent the paddle roll 230 from slipping through, and to improve the detection accuracy or peelability of the wound paper. Further, by using such a rotating roll 240, it is possible to realize an interval holding means that can maintain an interval substantially constant with high accuracy with a simple configuration.

  The present invention has been described in detail with reference to the first to eighth embodiments. However, the present invention is not limited to these embodiments, and various other modes can be implemented within the scope of the present invention. is there.

1 is a configuration diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a schematic configuration of a control system of an image forming apparatus according to an embodiment of the present invention. (A) is a front view showing the main part of the fixing device according to the first embodiment of the present invention, (B) is a side view seen from the direction of arrow 3B of (A). 6 is a flowchart showing a flow of a series of operations from winding of a sheet to a heat roll to recovery thereof in the fixing device according to the first embodiment of the present invention. (A) is a front view showing a main part of a fixing device according to a second embodiment of the present invention, and (B) is a side view seen from the direction of arrow 5B in (A). 7 is a flowchart showing a flow of a series of operations from winding a sheet to a heat roll to recovering the heat roll of a fixing device according to a second embodiment of the present invention. (A) is a front view showing a main part of a fixing device according to a third embodiment of the present invention, and (B) is a side view seen from the direction of arrow 7B of (A). 10 is a flowchart showing a flow of a series of operations from winding a sheet to a heat roll to recovering the heat roll of a fixing device according to a third embodiment of the present invention. (A) is a front view showing a main part of a fixing device according to a fourth embodiment of the present invention and a state in which a sheet having a length longer than the circumference is wound around a heat roll, and (B) is (A). It is a graph which shows the temperature change in the circumferential direction of the heat roll which rotates in the state. (A) is a front view showing a main part of a fixing device according to a fourth embodiment of the present invention and a state in which a paper having a shorter length than the circumference is wound around a heat roll, and (B) is (A). It is a graph which shows the temperature change in the circumferential direction of the heat roll which rotates in the state. 10 is a flowchart showing a flow of a series of operations from winding of a sheet around a heat roll to recovery thereof in a fixing device according to a fourth embodiment of the present invention. (A) shows the main part of the fixing device according to the fifth embodiment of the present invention, and a sheet of paper shorter than the circumference around the heat roll, and the second sheet following the sheet. FIG. 5B is a front view showing a state in which two sheets of paper shorter than the circumference are wound around the heat roll of FIG. 10 is a flowchart showing a flow of a series of operations from winding of a sheet to a heat roll to recovery thereof in a fixing device according to a fifth embodiment of the present invention. It is a front view which shows the principal part of the fixing device which concerns on the 6th Embodiment of this invention. It is a front view which shows the principal part of the fixing device which concerns on the 7th Embodiment of this invention. It is a partial side view which shows a part of heat roll vicinity of the fixing device which concerns on the 8th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Fixing apparatus 46 Heat roll (heating roll)
47 Front 47A Paper passage area (passage area of recording medium)
47B Out of paper passage area 48 Pressure roll 50 Heater lamp (heat source)
62 Display section (notification means)
80 Control unit (abnormality judgment means)
100A heater lamp (first heating means)
100B heater lamp (second heating means)
102A Temperature sensor (first temperature measuring means / temperature measuring means)
102B Temperature sensor (second temperature measuring means)
104A Blower unit (first cooling means)
104B Blower unit (second cooling means)
106 Wound paper detection sensor (recording medium detection means)
220 Wrapping paper detection sensor (rotation detection means)
222 Paddle roll (rotating member)
224 Protrusion 230 Paddle roll (Rotary peeling member)
232 Protrusion 240 Rotating roll (Interval holding means / Rotating roll)
P Preprinted paper (recording medium)

Claims (9)

A heating roll provided with a heat source therein and a pressure roll pressed against the heating roll, and the recording medium on which the toner image is transferred is passed between the heating roll and the pressure roll. In the image forming apparatus for fixing and forming an image,
At least one of first heating means for locally heating a passage region of the recording medium on the surface of the heating roll, and first cooling means for locally cooling;
First temperature measuring means provided corresponding to at least one of the first heating means and the first cooling means and measuring the temperature of the passage region;
At least one of a second heating means for locally heating the outside of the recording medium passage area on the surface of the heating roll, and a second cooling means for locally cooling;
A second temperature measuring unit provided corresponding to at least one of the second heating unit and the second cooling unit, and measuring a temperature outside the passage region;
Abnormality determination for determining whether or not there is a winding abnormality of the recording medium around the heating roll, based on the temperature difference of each temperature measured by the first temperature measuring unit and the second temperature measuring unit. Means,
Informing means for informing the determination result by the abnormality determining means;
An image forming apparatus comprising:   When the length of the recording medium is longer or shorter than the circumference of the heating roll, heating by the first heating unit or cooling by the first cooling unit is not performed, and the abnormality determination unit is 2. The image forming apparatus according to claim 1, wherein the presence or absence of a winding abnormality of the recording medium with respect to the heating roll is determined based on a temperature change in the circumferential direction of the rotating heating roll measured by one temperature measuring means. . A heating roll provided with a heat source therein and a pressure roll pressed against the heating roll, and the recording medium on which the toner image is transferred is passed between the heating roll and the pressure roll. In the image forming apparatus for fixing and forming an image,
Temperature measuring means for measuring the temperature of the passage region of the recording medium on the surface of the heating roll;
When the length of the recording medium is longer or shorter than the circumferential length of the heating roll, based on the temperature change in the circumferential direction of the rotating heating roll measured by the temperature measuring means, An abnormality determination means for determining presence or absence of winding abnormality;
Informing means for informing the determination result by the abnormality determining means;
An image forming apparatus comprising:   A recording medium detecting means for detecting a recording medium wound around the heating roll; a length of the recording medium is shorter than a circumferential length of the heating roll; and the wound recording medium is detected by the recording medium detecting means. The recording medium to be fixed next to the recording medium is accelerated and wound around the heating roll while being sandwiched between the rear part of the recording medium in the middle of winding and the heating roll. 3. The image forming apparatus according to 3.   The recording medium detection means includes a rotatable rotating member that is opposed to the surface of the heating roll by a predetermined distance and is provided with a protrusion on an outer peripheral surface, and the protrusion presses the leading end of the wound recording medium. The image forming apparatus according to claim 4, wherein the rotation member is a rotation detection unit that detects the recording medium when the rotation member rotates.   Oppositely arranged with a predetermined distance away from the surface of the heating roll and provided with a protrusion on the outer peripheral surface and driven to rotate in the opposite direction to the heating roll, the front end of the wound recording medium is hooked on the protrusion and the protrusion The image forming apparatus according to claim 1, further comprising a rotary peeling member that peels from the heating roll. A heating roll provided with a heat source therein and a pressure roll pressed against the heating roll, and the recording medium on which the toner image is transferred is passed between the heating roll and the pressure roll. In the image forming apparatus for fixing and forming an image,
Oppositely arranged at a predetermined distance from the surface of the heating roll and provided with protrusions on the outer peripheral surface, the rotation is driven in the opposite direction to the heating roll, and the tip of the recording medium wound around the heating roll is hooked on the protrusion. An image forming apparatus comprising a rotary peeling member that peels from the heating roll.   The image forming apparatus according to claim 5, further comprising an interval holding unit that maintains an interval between the rotating member or the rotating peeling member and the heating roll substantially constant.   The interval holding means is arranged coaxially with the rotating member or the rotating peeling member and has a larger diameter than them, and is rotatable independently of them, and is recorded on the surface of the heating roll. The image forming apparatus according to claim 8, wherein the image forming apparatus is a rotating roll that is in contact with the outside of a medium passage region.

Images