JP2013246390A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To predict that a wide variety of types of recording sheets to be output possibly include wrinkles and defective images, and prevent output of unnecessary recording sheets as much as possible.SOLUTION: A fixing device includes: a heating member; and a pressure member that is provided opposite to the heating member, and applies pressure to a sheet conveyed between the heating member and the pressure member and having unfixed toner transferred thereon against the heating member, so as to fix the toner on the sheet. The fixing device further includes: detection means for detecting a shape change level of the sheet before conveyance; and notification means for notifying a user that, when the detection means detects that the shape change level of the sheet exceeds a predetermined range, image defects occur on the sheet after the toner is fixed thereon.

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In an image forming apparatus using an electrophotographic system, a fixing device for fixing an unfixed toner image transferred onto a recording sheet is mounted. The fixing device fixes the toner image on the recording paper by passing the recording paper on which the toner image is transferred through a fixing nip formed by a fixing roller and a pressure roller, for example.

  In this type of fixing device, the recording paper may be wrinkled during the fixing process. Therefore, in Patent Document 1, as shown in FIG. 9, the thickness of both ends of the elastic layer 12 of the fixing roller 11 that is rotationally driven by a drive motor (not shown) is made thicker than the central portion, and the shape of the fixing roller 11 is A fixing device having a so-called inverted crown shape with a smaller diameter at the center than at both ends is described.

  The principle of this prior art is that the fixing roller 11 has an inverted crown shape, so that the peripheral speed of the end portion having a large outer diameter becomes faster than the central portion, and the outer side in the paper width direction with respect to the recording paper in the fixing nip. The pulling force works. When the recording paper receives such a force pulling outward in the paper width direction, generation of wrinkles can be suppressed.

  However, when the fixing roller 11 is formed in an inverted crown shape, the nip pressure at the center portion is lowered, and the fixing performance at the center portion is lowered as compared with both end portions. In particular, when thick paper is used as the recording paper, there is a possibility that fixing failure may occur in the central portion. Therefore, it is also conceivable to reduce the difference between the outer diameter of the both ends of the fixing roller 11 and the outer diameter of the central portion, suppress the decrease in the nip pressure in the central portion, and suppress the decrease in the fixing performance in the central portion.

  However, in this case, the distance from the fixing nip to the center of rotation of the fixing roller 11 is substantially the same at both ends and the center of the fixing roller 11, and there is a problem that wrinkles of the recording paper cannot be suppressed over time. It was. Further, in the case of a recording paper such as thin paper that tends to cause wrinkles, there is a problem that wrinkles cannot be sufficiently suppressed.

  On the other hand, when the difference between the outer shape of the both ends of the fixing roller 11 and the outer shape of the central portion is increased to make the inverted crown shape remarkable, the effect of suppressing the generation of wrinkles can be increased, but recording during conveyance is possible. The distortion accumulated at the trailing edge of the paper increases, and a phenomenon called so-called trailing edge jumping occurs in which the trailing edge of the recording paper jumps before passing through the fixing nip. There is a problem in that an unfixed toner image comes into contact with the casing due to the trailing edge jump and a defective image such as a rubbing image is output.

  Therefore, the present invention has been made in view of the above-described conventional problems, and detects the degree of deformation of a sheet before toner fixing on various types of sheets, and the degree of deformation causes an image defect. Provided a fixing device and an image forming apparatus capable of preventing unnecessary recording paper from being output as much as possible by notifying a user in advance that a wrinkle or a defective image may be included. The purpose is to do.

  In order to solve the above-described problem, the fixing device according to the first aspect of the present invention includes a heating member and an unfixed toner that is provided opposite to the heating member and is conveyed between the heating member. A pressure member for fixing toner onto the paper by pressurizing the heated paper toward the heating member, and detecting means for detecting a shape change level of the paper before the conveyance; And a notifying means for notifying that an image defect has occurred on the paper after the toner has been fixed, when the detecting means detects that the shape change level of the paper exceeds a predetermined range. It is characterized by that.

  According to the present invention, for various types of paper, when the degree of deformation of the paper before toner fixing is detected and the degree of deformation has reached an extent that causes image defects, Thus, it is possible to provide a fixing device and an image forming apparatus that can prevent unnecessary recording paper from being output as much as possible by notifying in advance that there is a risk of including the image.

1 is a schematic block diagram illustrating an appearance of a fixing device according to an embodiment of the present invention. FIG. 4 is a view of the periphery of the fixing nip portion of the fixing device in the embodiment of the present invention as viewed from the recording paper conveyance direction. FIG. 4 is a view of the periphery of the fixing nip portion of the fixing device in the embodiment of the present invention as viewed from the recording paper width direction. FIG. 3 is a view of the periphery of a fixing nip portion of the fixing device according to the embodiment of the present invention as viewed from above the fixing device. FIG. 6 is a flowchart illustrating an operation of determining an abnormal output of the fixing device according to the embodiment of the present invention. 5A and 5B are schematic diagrams illustrating characteristics of the behavior of a sheet at the time of abnormal output of the fixing device in the embodiment of the present invention, (a) when a wave is generated on the sheet, and (b) when a jump occurs on the sheet. FIG. 7 is a diagram illustrating an example of an out-of-plane deformation shape detection result when (a) wrinkles are generated on the sheet of the fixing device according to the embodiment of the present invention, and (b) no wrinkles are generated. An out-of-plane deformation of the sheet of the fixing device according to the embodiment of the present invention when (a) a trailing edge jump occurs in the recording paper width direction, and (b) a trailing edge jump occurs in the recording sheet conveyance direction. It is a figure which shows the example of a shape detection result. It is a schematic block diagram which shows the conventional fixing roller.

  Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified thru | or abbreviate | omitted suitably.

  First, a fixing device according to an embodiment of the present invention will be described. FIG. 1 is a schematic block diagram illustrating an appearance of a fixing device according to an embodiment of the present invention. In FIG. 1, a fixing device (nip) 1 includes a heating roller 2 as a heating unit, a pressure roller 3, and a driving roller 4. A pressure roller 3 is provided on the heating roller 2 and a driving roller 4 is provided on the pressure roller 3 so as to be in pressure contact therewith. As for the heating roller 2 which is a heating means, the metal layer on the surface is heated by an electromagnetic induction heater.

  A pattern projector 9 and area sensors 10a and 10b are provided above the conveyance entrance side of the fixing nip 1. The pattern projector 9 of the fixing device 1 according to the embodiment of the present invention projects three linear patterns (LPb) in the width direction of the paper P and three linear patterns (LPa) in the recording paper conveyance direction. To do. The number of patterns may be any number as long as there are three or more patterns.

  The control unit 8 serving as a control means includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and implements the functions of each means by executing predetermined programs. Yes. As shown in FIG. 1, the control unit 8 calculates an out-of-plane deformation shape in the width direction of the sheet P on the conveyance entrance side of the fixing nip 1 from the output value of the area sensor 10a. That is, in the fixing device 1 according to the embodiment of the present invention, the control unit 8, the area sensor 10a, and the pattern projector 9 constitute an out-of-plane deformation shape detection unit in the width direction of the paper P.

  Similarly, the control unit 8 calculates an out-of-plane deformation shape in the conveyance direction of the sheet P on the conveyance entry side of the fixing nip 1 from the output value of the area sensor 10b. The control unit 8, the area sensor 10 b, and the pattern projector 9 constitute an out-of-plane deformation shape detection unit in the conveyance direction of the paper P. Further, the control unit 8 is connected to a non-volatile memory 7 as storage means, and the non-volatile memory 7 stores an out-of-plane deformation shape, a limit out-of-plane deformation shape, and the like which are obtained in advance through experiments. Has been. The non-volatile memory 7 stores the detected out-of-plane deformed shape in time series for each paper type.

  The control unit 8 controls the pressing force of the roller pressing force adjusting mechanism to control the nip width of the fixing roller 1 and the power source of a heater (not shown) to control the amount of fixing heat. Furthermore, the control unit 8 is connected to a notification unit 6 including a speaker or a display as a notification unit, and can control the notification unit 6 to notify the user of predetermined information.

  Wrinkles and trailing edge jumps may occur due to deterioration with time of the heating roller 2 and the pressure roller 3. Therefore, in the fixing device 1 according to the embodiment of the present invention, the out-of-plane deformation shape of the entire sheet P on the conveyance entering side of the fixing nip 1 is detected using the area sensors 10a and 10b. Based on the detection result, it is monitored over time whether or not there is a possibility of occurrence of wrinkles or trailing edge jumps. And when it is judged that a wrinkle and a rear end jump generate | occur | produced or generate | occur | produced, it can alert | report to a user. This will be specifically described below.

  FIG. 5 is a flowchart showing an operation of determining an abnormal output of the fixing device according to the embodiment of the present invention. First, the control unit 8 specifies a paper type for measuring the out-of-plane deformation shape (step (hereinafter referred to as “S”) 1). As for the paper type, the user inputs a paper model number using the operation unit 5, and reads storage information of past experimental values such as thickness and type corresponding to the model number from the nonvolatile memory 7 to the control unit 8. The paper type for measuring the external deformation shape is specified. Alternatively, a technique for identifying a paper type by irradiating paper with laser light or the like and detecting diffused light or transmitted light may be used. Next, the control unit 8 irradiates the sheet with a lattice pattern LP (LPa: pattern in the width direction, LPb: pattern in the transport direction) with the pattern projector 9 (S2), and the area sensors 10a, 10b The shape of the pattern being conveyed is measured to detect an out-of-plane deformed shape on the conveyance entry side of the fixing nip 1. Here, the pattern LPa in the width direction and the pattern LPb in the transport direction are orthogonal to each other.

  If a force that moves both ends in the width direction of the sheet P inward due to the occurrence of a microslip in the fixing nip 1, the detected out-of-plane deformation amount gradually increases with the conveyance amount of the sheet P. On the other hand, when the force acting on the paper P in the fixing nip 1 is the direction in which both ends in the width direction move outward, the detected out-of-plane deformation shape is flat.

  When the rear end of the sheet P is conveyed to the fixing nip 1 with the deformation amount being out of plane, the rear end of the sheet P is slightly deformed. If this is the case, wrinkles and the like will not occur in the fixing nip 1. However, when the wave at the trailing edge of the paper P is large, the probability of wrinkles occurring at the fixing nip 1 increases. Regarding the out-of-plane deformation causing wrinkles, the pattern LPa projected by the pattern projector 9 is detected by the area sensor 10a and measured (S3).

  Further, even when the force acting on the paper P in the fixing nip 1 is a direction in which both ends in the width direction move outward, if the force is large, distortion accumulates at the rear end of the paper P and the surface The amount of external deformation is detected. When distortion increases during conveyance and the amount of out-of-plane deformation continues to increase, the trailing edge of the paper P jumps up according to the conveyance status of the paper P. Regarding the out-of-plane deformation of rear end bounce, which is an out-of-plane deformation that generates a rubbing image, among the patterns LP projected by the pattern projector 9, the pattern LPb in the recording paper conveyance direction is detected by the area sensor 10b and measured. (S3).

  The non-volatile memory 7 stores, for each type of paper P, a limit out-of-plane deformation shape that is a threshold for the deformation amount of the trailing edge of the paper P. The control unit 8 detects the environment with the thermohygrometer, and reads the corresponding out-of-limit deformation shape from the nonvolatile memory 7 based on the detected environment and the paper type information. In addition, the control unit 8 determines whether the deformation feature is to generate wrinkles or a rubbing image based on the out-of-plane deformation shape detected from the two directions of the area sensors 10a and 10b. (S4), the maximum deformation amount is calculated, and it is determined whether or not the calculated maximum deformation amount exceeds the limit deformation amount (S5).

  6A and 6B are schematic views showing characteristics of the behavior of the paper when the fixing device 1 according to the embodiment of the present invention outputs abnormally, (a) when the paper is wavy, and (b) when the paper is bounced. FIG. As shown in FIG. 6A, the deformation that generates wrinkles is characterized in that one or more waves gather near the center of the paper P. On the other hand, as shown in FIG. 6B, the deformation that generates the rubbing image is characterized in that no complicated wave is seen and the entire sheet P has a gentle inclination. By identifying these by image processing, the characteristics of deformation are captured, and the type of abnormality that occurs is predicted.

  Returning to FIG. 5, it is determined whether or not the maximum deformation amount exceeds the limit deformation amount (S5). If it is determined that the maximum deformation amount exceeds the limit deformation amount (S5: Y), there is a possibility that a major problem has occurred in the fixing device, and the output paper has a wrinkled or rubbed image. May have occurred. For this reason, if the amount of deformation exceeds the limit deformation, if the paper type is used continuously, there is a high probability that a wrinkle or a rubbing image will occur. The fact that there is a possibility of a defect is displayed on the display unit (S8), and the replacement of the fixing device is urged (S9).

  When it is determined that the maximum deformation amount is equal to or less than the limit deformation amount (S5: N), the stability of the sheet conveyance is calculated based on the detected out-of-plane deformation shape (S6). The non-volatile memory 7 stores the optimal out-of-paper deformation shape, and this information has different values depending on the type and environment of the paper. Then, the control unit 8 calculates how close the detected out-of-plane deformation shape is to the limit out-of-plane deformation shape stored in the nonvolatile memory 7 or the optimum out-of-paper deformation (stability of conveyance). Sex calculation: S6). The threshold value at which the detected out-of-plane deformation shape is determined to be close to the limit out-of-plane deformation shape is set as the stable conveyance limit value of the out-of-plane deformation shape, and it is determined whether the conveyance state is stable (S7).

  During the operation of the fixing device 1 according to the embodiment of the present invention, it is determined that the calculated sheet conveyance stability continues to be closer to the limit out-of-plane deformation shape than the stable conveyance limit value of the out-of-plane deformation shape. In such a case, it is assumed that the conveyance state is unstable (S7: Y). That is, it is determined that the life of the fixing roller 1 has been reached, an alarm is transmitted by the notification unit 6, and a display to replace the fixing roller is displayed (S9).

  FIG. 1 also shows an out-of-paper deformation shape detecting means of the fixing device 1 according to the embodiment of the present invention. The sheet P is conveyed in the direction of arrow A through the nip formed by the fixing roller 1. The pattern projector 9 is installed above the nip conveyance entrance side with a predetermined angle with respect to the recording surface of the paper P, and irradiates the lattice pattern LP over the entire surface of the paper P on the nip conveyance entrance side. . The lattice pattern LP is composed of a width direction pattern LPa and a transport direction pattern LPb. 2, 3 and 4 show examples of arrangement of the pattern projector 9 and the area sensors 10a and 10b from various directions. Since the pattern LP is formed in a lattice shape this time, the area sensors 10a and 10b are arranged so as to distinguish between a shape conforming to the lattice shape, that is, a normal state and an abnormal state. In particular, it is important to provide the shape of the pattern LP so that distortion generated in either or both of the width direction of the recording medium and the conveyance direction can be detected.

  FIG. 2 is a view of the periphery of the fixing nip portion of the fixing device in the embodiment of the present invention as viewed from the recording paper conveyance direction, and FIG. 3 is a view of the periphery of the fixing nip portion of the fixing device in the embodiment of the present invention as viewed from the recording paper width direction. Figure. FIG. 4 is a view of the periphery of the fixing nip portion of the fixing device according to the embodiment of the present invention as viewed from above the fixing device.

  The area sensor 10a is disposed at a position within a plane perpendicular to the axis of the fixing roller 1 at a predetermined angle different from the pattern projector 9 with respect to the recording surface of the paper P on the pattern LP formation side of the paper P. The pattern LP formed on the paper P is photographed. If only the width direction pattern LPa is extracted from the photographed pattern LP by image processing, the pattern LPa is captured by the area sensor 10a as a straight line when the paper P is not deformed. On the other hand, when deformation occurs in the paper P, the height of the paper locally changes due to the undulation of the paper, and the pattern LPa applied to the recording surface of the paper P from the pattern projector 9 is distorted from the area sensor 10a. It can be understood as a curved line.

  It has been found that when the amount of out-of-plane deformation of the paper P increases and exceeds a predetermined value, wrinkles occur in the vicinity thereof. Therefore, by measuring the amount of out-of-plane deformation of the paper P by the area sensor 10a, it can be predicted whether or not wrinkles will occur. Further, by storing the height of the paper P and the positional relationship of the pattern LPa in advance, the out-of-plane deformation amount δa of the paper P can be obtained from the output of the area sensor 10a.

  On the other hand, the area sensor 10b is disposed at a position within a plane perpendicular to the conveyance direction of the paper P, at a predetermined angle different from the pattern projector 9 with respect to the recording surface of the paper P on the pattern LP formation side of the paper P. Then, the pattern LP formed on the paper P is photographed. If only the conveyance direction pattern LPb is extracted from the photographed pattern LP by image processing, the pattern LPb is captured by the area sensor 10b as a straight line when the paper P is not deformed. On the other hand, when a wave or splash occurs on the paper P, the deformation is regarded as a distortion of the transport direction pattern LPb.

  It is known that when the trailing edge jump of the paper increases, an abnormality such as a rubbing image occurs, and the relationship is correlated. Therefore, it is possible to predict whether or not a rubbing image is generated by measuring the amount of deformation caused by the trailing edge jump of the paper. Further, by storing in advance the positional relationship between the height of the paper and the pattern LPb, the out-of-plane deformation amount δb of the paper P can be obtained from the output of the area sensor 10b.

  FIG. 7 is a diagram illustrating an example of the out-of-plane deformation shape detection result when (a) wrinkles are generated on the sheet of the fixing device according to the embodiment of the present invention and (b) no wrinkles are generated. In FIG. 7A, the out-of-plane deformation amount of the sheet obtained from the shape of one of the width direction patterns LPa1 photographed by the area sensor 10a in the process of transporting one sheet of paper is from time t0 to time tn. It is described in time series. When a force is applied to the paper P inward in the paper width direction, a wave of the paper P is generated as the paper P is transported and grows. In the embodiment of the present invention, the difference between the maximum height and the minimum height is used as the maximum deformation amount for various determinations.

  FIG. 7B shows an out-of-plane deformed shape detection result in a state where wrinkles are not generated. When the force acting on the sheet P inward in the sheet width direction is small, no wave is generated and the sheet P is conveyed flat.

  FIGS. 8A and 8B illustrate a case where (a) a trailing edge jump occurs in the width direction of the recording sheet and (b) a trailing edge jump occurs in the recording sheet conveyance direction on the sheet of the fixing device according to the embodiment of the present invention. It is a figure which shows the example of the out-of-plane deformation shape detection result. In FIG. 8A, the amount of out-of-plane deformation of the sheet P obtained from the shape of one LPa1 of the width direction pattern photographed by the area sensor 10a in the process of transporting one sheet of paper is measured from time t0. It is described in time series until tn.

  When the force acting on the paper P outward in the paper width direction is large, the paper deforms and grows as the paper is transported. The deformation state at this time is a deformation having characteristics different from the deformation state shown in FIG. Based on the characteristics of the deformation state in the sheet width direction, it is possible to determine whether the deformation is a deformation that generates wrinkles or a trailing edge bounce that generates a rubbing image.

  FIG. 8B shows the out-of-plane deformation shape detection result when the rear end bounce occurs. This figure shows the conveyance direction imaged by the area sensor 10b in the process of conveying one sheet. The out-of-plane deformation amount of the sheet obtained from the shape of the pattern LPb1 is described in time series from time t0 to time tn. When the trailing edge of the sheet bounces, the amount of out-of-plane deformation increases at the final stage of conveyance.

  When there are a plurality of types of paper P used for image formation, an out-of-plane deformation shape is detected for each paper stored in each paper feed tray, and an abnormality occurs in the output paper P. It is determined whether or not there is a fear. Specifically, the control unit 8 specifies the paper type for measuring the out-of-plane deformation shape. For specifying the paper type, for example, when the paper P is set in the paper feed tray, the user inputs information on the thickness or type of the paper P set in the paper feed tray by the user, and the input information is And stored in the nonvolatile memory 7. The control unit 8 can specify the paper type for measuring the out-of-plane deformation shape by reading the paper type information of the paper set in the paper feed tray stored in the nonvolatile memory 7.

  Thus, when the paper type for measuring the out-of-plane deformation shape is specified, the limit out-of-plane deformation amount and the optimum out-of-plane deformation shape corresponding to the paper type stored in the nonvolatile memory 7 are read out, and the lattice Shape pattern is projected and the out-of-plane deformation shape is measured. Then, if it is determined that the life of the fixing device 1 is about the paper stored in the paper feed tray, the use of the paper feed tray is prohibited. During the image forming operation, the paper feed tray to be used is specified, and the out-of-limit deformation amount and the optimum out-of-paper deformation shape corresponding to the paper stored in the paper feed tray are read from the nonvolatile memory 7. The image forming operation is performed.

  Further, the out-of-plane deformation shape detected for each paper type is stored in the nonvolatile memory 7 in time series, and the conveyance stability corresponding to the paper stored in a certain paper feed tray reaches the stable conveyance limit. In this case, from the time-series out-of-plane deformation shape data corresponding to the paper, the time until the out-of-plane deformation shape of the paper reaches the limit out-of-plane deformation shape or the number of printed sheets is obtained in the same manner as described above.

  From the time thus obtained (or the number of printed sheets), a threshold is set at which the probability of occurrence of wrinkles and rubbing images increases. As described above, when the time or the number of printed sheets reaches the threshold value, when using the paper stored in the paper feed tray, if this paper is used before the image forming operation is started, a wrinkle or a rubbing image is generated. In addition to displaying an alarm together with an alarm to the effect that there is a high probability of performing this, a display prompting replacement of the fixing device 1 is performed. When the required time (or the number of printed sheets) is reached, use of the paper feed tray in which the paper is stored is prohibited. This eliminates the use of the fixing device 1 in which wrinkles and rubbing images are generated, thereby preventing waste of paper.

  As described above, the fixing device 1 according to the embodiment of the present invention is rotationally driven by a driving source, and between the pressure roller 3 as a driving member having at least an elastic layer and the pressure roller 3 in contact with the pressure roller 3. It has a fixing device provided with a heating roller 2 that is a facing member that forms a fixing nip and heats a sheet of recording paper that passes through the fixing nip. Then, the control unit 8 serving as a control unit performs the post-sheet deformation based on the out-of-plane deformation shape in the sheet width direction detected by the area sensor 10a or the out-of-plane deformation shape in the sheet conveyance direction detected by the area sensor 10b. The out-of-plane deformation amount due to the wave between the ends or the trailing edge splash is calculated.

  Thereby, it is possible to grasp the deformed shape of the entire area of the sheet that is about to enter the fixing nip 1. The possibility that a wrinkle or a rubbing image is generated is monitored over time, and when the probability that a wrinkle or a rubbing image is generated increases, the fact can be transmitted to the user of the fixing device 1. In addition, a non-volatile memory 7 serving as a storage unit that stores an appropriate out-of-plane deformed shape of the sheet is provided, and the stability of the sheet conveyance state is determined based on the appropriate out-of-plane deformed shape and the detected out-of-plane deformed shape data. Can be quantitatively evaluated.

  In addition, the non-volatile memory 7 stores an out-of-limit deformation shape that causes wrinkles on the sheet after fixing with respect to the deformation shape in the width direction, and a trailing edge jump occurs in the deformation shape in the conveyance direction. The limit out-of-plane deformation shape in which an abnormality such as a rubbing image occurs is stored, and if any of the detected out-of-plane deformation shapes reaches the limit out-of-plane deformation shape, the notification unit 6 (speaker And an indicator), a warning is displayed together with an alarm that there is a high probability that a wrinkle or rubbing image will occur, and a notification that the fixing device 1 is to be replaced is given. As a result, the fixing device 1 can be replaced at the stage where wrinkles or rubbing images are generated.

  Further, when the detected out-of-plane deformed shape reaches the limit out-of-plane deformed shape, the use of the fixing device 1 that generates wrinkles is prohibited by prohibiting the fixing operation, and the waste of the paper P is suppressed. can do. The detected out-of-plane deformation shape is stored in the nonvolatile memory 7 in time series, the life of the fixing device is predicted based on the out-of-plane deformation shape stored in time series, and the life of the fixing device is When predicted to be near, a warning is displayed together with an alarm that there is a high probability that a wrinkle or rubbing image will occur, and a notification that the fixing device is to be replaced is given. As a result, it is possible to prevent the downtime of the apparatus from occurring because the fixing apparatus is replaced before wrinkles or rubbing images are generated.

  Further, based on the out-of-plane deformation shape data stored in the non-volatile memory 7 in time series, a threshold for increasing the probability of occurrence of paper wrinkles and the occurrence of a rubbing image is calculated for each type of paper, and exceeds the threshold. When the paper is used, the fact that the probability that a wrinkle or a rubbing image is generated is high is notified. Accordingly, an operation such as switching the paper to be used to another one is promoted, and the generation of wrinkles and rubbing images can be suppressed.

  As described above, according to the present invention, since the shape of the recording paper before passing through the fixing nip can be measured every time the paper is passed, the recording paper passing through the fixing device has wrinkles and image defects. It can be estimated whether or not there is a possibility that wrinkles or defective images are likely to occur.

  That is, if a pulling force is applied to the recording paper in the width direction inside the fixing nip, a wave is generated behind the fixing nip of the recording paper, and the recording paper enters the fixing nip with the wave being generated. . The larger the force inward in the width direction acting in the fixing nip, the larger the wave, and the smaller the force, the smaller the generated wave.

  If the wave generated behind the fixing nip of the recording paper is large, the probability that the recording paper will wrinkle after passing through the fixing nip increases. However, if the wave is small, the probability that the recording paper is wrinkled is low. When a force in the width direction outward direction is applied in the fixing nip by using a reverse crown-shaped roller, for example, the wrinkles are suppressed. On the other hand, the outward force in the width direction is accumulated at the trailing edge of the recording paper as distortion. Accumulation of distortion causes a shape deformation at the trailing edge of the recording paper.

  That is, a wave having a characteristic different from that generated by the force inward in the width direction is generated by force in the outward direction in the width direction. Waves generated by the outward force in the width direction may jump greatly depending on the type of recording paper, the shape of the conveyance path, and the conditions of the fixing member, and this is called rear end jumping. When the recording paper comes into contact with a member such as a casing due to the trailing edge jump, an image formed on the recording paper is rubbed and an image defect occurs. Therefore, in order to know how much a wrinkle or rubbing image is likely to occur, it is only necessary to measure the out-of-plane deformation shape of the entire surface of the recording paper passing through the fixing nip.

  Further, according to the present invention, since the storage means for storing the out-of-plane deformation shape of the recording paper is provided, the limit out-of-plane deformation shape that may cause a wrinkled or rubbed image is stored in the storage means in advance. Accordingly, it is possible to monitor the shape of the recording paper that is about to pass through the fixing nip, and to compare the deformation shape of the recording paper due to the wave and the trailing edge bounce with the limit deformation shape in which wrinkles and rubbing images are generated.

  Since there is a correlation between the out-of-plane deformation shape of the recording paper before passing through the fixing nip, the wrinkle occurrence probability of the recording paper, and the occurrence probability of the rubbing image, it is based on the detection result of the out-of-plane deformation shape detecting means. In addition, it is possible to quantitatively predict whether or not wrinkles or rubbing images are generated on the recording paper.

  Thus, according to the present invention, for various types of paper, when the degree of deformation of the paper before toner fixing is detected and the degree of deformation has reached an extent that causes image defects, It is possible to provide a fixing device and an image forming apparatus that can prevent unnecessary recording paper from being output as much as possible by notifying in advance that a wrinkle or a defective image may be included.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

1 Fixing device (roller)
DESCRIPTION OF SYMBOLS 2 Heating roller 3 Pressure roller 4 Driving roller 5 Operation part 6 Notification part 7 Storage part 8 Control part 9 Pattern projector 10a Recording paper width direction pattern imaging area sensor 10b Recording paper conveyance direction pattern imaging area sensor P Recording paper A Recording Paper conveyance direction LP Lattice projection pattern LPa Recording paper width direction portion of lattice projection pattern LPb Recording paper conveyance direction portion of lattice projection pattern LPa1 One of recording paper width direction portions of lattice projection pattern LPb1 Recording paper conveyance of lattice projection pattern One of the direction parts δa Maximum deformation amount when measuring the recording paper width direction δb Maximum deformation amount when measuring the recording paper conveyance direction

Japanese Patent Laid-Open No. 05-040428

Claims (9)

A heating member;
A pressure member that is provided opposite to the heating member and presses the sheet onto which the unfixed toner conveyed between the heating member is transferred toward the heating member, thereby fixing the toner to the sheet. When,
A fixing device including:
Detection means for detecting the shape change level of the paper before the conveyance;
An informing means for informing that an image defect occurs on the paper after the toner has been fixed when the detecting means detects that the shape change level of the paper exceeds a predetermined range;
A fixing device comprising:   The detection means detects, as the shape change level of the paper before the conveyance, a shape change level in the conveyance direction of the paper and a shape change level in a direction orthogonal to the conveyance direction, respectively. Item 4. The fixing device according to Item 1. Storage means for storing a reference shape level value of the shape change level when a change in shape of the paper is not detected and an allowable limit level value of the shape change level when at least the image defect does not occur;
3. The informing means notifies that an image defect occurs when the shape change level of the sheet detected by the detecting means exceeds the allowable limit level value. Fixing device. The storage means, as a stability level when the paper is transported, a reference transport stability level value when the shape change is not detected, and at least an allowable transport stability level value when the image defect does not occur Remember
Even if the shape change level of the sheet detected by the detection means is equal to or less than the allowable limit level value, the stability level is compared with the reference conveyance stability level value, and the allowable conveyance stability level value is compared with the reference conveyance stability level value. 4. The fixing device according to claim 3, wherein when it is determined that the image is continuously present for a predetermined time, the notification unit notifies that an image defect has occurred. The storage means stores the shape change level of the paper in time series,
Control means for reading out a reference shape level value and an allowable limit level value of the shape change level of the paper based on the paper type information of the paper set in the paper feed tray from the storage means;
The control means sets a threshold value that increases the probability that the image defect will occur based on the time until the reference shape level reaches the allowable limit level value or the number of printed sheets of the paper, and the time or printing 4. The fixing device according to claim 3, wherein when it is determined that the number of sheets has reached the threshold value, the notification unit notifies that there is a high probability that an image defect will occur. The storage means stores the shape change level of the paper in time series,
Control means for predicting the life of the heating member and the pressure member based on the stored shape change level of the paper;
The fixing device according to claim 3, wherein when the control unit determines that the predicted lifetime has been reached, the notification unit notifies that the image defect has occurred.   In addition to notifying that the image defect has occurred or notifying that the probability of occurrence of the image defect is high, the notifying unit performs notifying that the heating member and the pressure member are to be replaced. The fixing device according to claim 1, wherein the fixing device is one of the fixing devices. A heating member;
A pressure member that is provided opposite to the heating member and presses the sheet onto which the unfixed toner conveyed between the heating member is transferred toward the heating member, thereby fixing the toner to the sheet. When,
Detection means for detecting the shape change level of the paper before the conveyance;
Fixing means for notifying that an image defect occurs on the paper after the toner has been fixed when the detection means detects that the shape change level of the paper exceeds a predetermined range. An image forming apparatus including the apparatus.   The detection means detects, as the shape change level of the paper before the conveyance, a shape change level in the conveyance direction of the paper and a shape change level in a direction orthogonal to the conveyance direction, respectively. Item 9. The image forming apparatus according to Item 8.

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